SPEED-INDEPENDENT GAIT IDENTIFICATION FOR MOBILE DEVICES Due to the intensive use of mobile phones for different purposes, these devices usually contain confidential information which must not be accessed by another person apart from the owner of the device. Furthermore, the new generation phones commonly incorporate an accelerometer which may be used to capture the acceleration signals produced as a result of owner's gait. Nowadays, gait identification in basis of acceleration signals is being considered as a new biometric technique which allows blocking the device when another person is carrying it. Although distance based approaches as Euclidean distance or dynamic time warping have been applied to solve this identification problem, they show difficulties when dealing with gaits at different speeds. For this reason, in this paper, a method to extract an average template from instances of the gait at different velocities is presented. This method has been tested with the gait signals of 34 subjects while walking at different motion speeds (slow, normal and fast) and it has shown to improve the performance of Euclidean distance and classical dynamic time warping. In biometrics, the term "gait" is used to describe a particular manner or style of walking which is distinctive for each individual. 1 Although gait shows a common pattern for everybody, it also presents some interpersonal differences which make possible individual identification. This fact may be observed in our ability to recognize a person only by observing his/her gait.. In previous literature, different sensors have been used to capture the human gait. Many works [2] [3] [4] proposed to extract the movement of lower limbs from images recorded by a camera. In other works, the authors 5 ' 6 extracted the movement of the legs by using some pressure sensors incorporated to the floor of the room. However, both approaches limit the acquisition to specific indoor environments. In order to alleviate this restriction, some authors used some wearable sensors which allow the subject to move freely. 7 Due to the miniaturization of inertial sensors, some works have also proposed to use gyroscopes and accelerometers to measure these body movements. 8 ' 9 In particular for this paper, the human gait is captured by means of a tri-axial accelerometer.. In former works, the authors have placed an accelerometer on the back 10 ' 11 or on the chest 12 in order to classify the different activities performed by a subject.. Although these positions make it possible to differentiate between several activities, they are not adequate to identify subjects, as the movements captured in these positions are similar among most individuals. The first work that analyzed the acceleration of the gait as a biometric technique was performed by Ailisto and Mántjárvi et al. in Ref. 8 . They performed an experiment over 36 subjects by placing the accelerometer at their waists. This is an interesting position since the accelerometer can be incorporated easily in the buckle of the belt. Another place that could be comfortable for users is their hip; however, signals captured at this place are not well-balanced since the sensor is closer to one leg in relation to the other one. Although other authors 9 ' 13 have tried to identify subjects from the accelerations of their ankles, capturing the movement of only one leg is a bit restricted since the movement of other body parts are also specific for each subject. The work presented in Ref. 14 shows that measuring the accelerations at several body parts considerably increases the identification performance, however this implies that the user must wear many sensors which could be uncomfortable. In our proposal, only one accelerometer was placed near the sacral vertebra since the center of gravity (COG) is close to this position. Therefore, the accelerations measured at this place represent a summary of the accelerations of the whole body. The COG is approximately at the same height of the waist so the sensor was attached to the belt of the subject.. Several techniques have been proposed to discriminate among gait acceleration signals of different individuals. In Ref. 9 , the authors extracted the walking cycle length and some histogram statistics from the gait accelerations of each subject to perform this discrimination. The work presented in Ref. 8 compared the identification results obtained by these histogram statistics with two other features: the coefficients of Fast Fourier Transform calculated over a window of the acceleration signal and the correlation between the walking cycles and a template obtained during the enrolling time. This work concluded that the best result -an equal error rate of 7% -is achieved by the correlation method. Other works have also generated templates of the gait cycles from the data captured during the enrolment phase. In Refs. 13 and 15, the authors divided the enrolment signal into steps averaging all these steps to create a gait template. The amplitude and length of each step were normalized using linear interpolation in order to produce a template independent of the variations on speed and amplitude of the signals. Other authors have proposed to use a normalization based on dynamic time warping (DTW) since it is able to deal with nonlinear time variability. 16 Nevertheless, in this paper they did not evaluate the system performance with gaits at different speeds. Recent works in human gait 17 ' 18 have shown the high intra-variability present in the gait. In these studies, the authors affirm that the gait of the same person at different speeds can be as different as other person's gait. Furthermore, they also remark on the great differences in the gait of the same individual when using different kind of shoes.. In this paper, an experiment has been conducted to analyze the differences in gait identification performance when the walking speed varies considerably. In an initial phase, Euclidean distance and classical DTW algorithm were used to calculate the distances among gaits of different individuals at several speeds. Due to the fact that these algorithms have shown to be insufficient to deal with this speed variability, we have generated a gait template which summarizes the signals of gaits at different speeds. This template generation is based on the work presented in Ref. 19 where the authors generate templates for the recognition of upper limb gestures at different speeds.. The rest of the paper is structured as follows. First, we describe the acquisition of the acceleration signals and the preprocessing applied to them. After that we present how the experiments were performed to analyze the variability produced by the speed. Before describing the method which extracts the template from the gait at different speeds, we present the results obtained by Euclidean distance and classical DTW. Then, the results obtained by our template extraction technique are shown. Finally, we conclude the paper stating our final conclusions. In this paper, we have concluded that Euclidean distance and dynamic time warping are not able to deal properly with changes in the gait signal caused by different walking speeds. Nevertheless, the extraction of a template from gaits at different speeds has shown to improve the identification overall performance from 19.31% to 7.81% which makes this technique appropriate to noncritical security problems. Furthermore, the use of only one template for modeling the individual gait supposes to perform only one comparison when identifying the gait signal of a user saving a considerable amount of time. Therefore, the identification process has not a high computational cost which makes it suitable to devices with low computational power as smartphones or other mobile devices. This feature is specially interesting since one of the main applications of the gait identification based on acceleronieter signals is to detect whether a mobile device has been stolen by detecting changes in the gait signals.

O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O B O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O


ATTACK PATTERN ANALYSIS FRAMEWORK FOR MULTIAGENT INTRUSION DETECTION SYSTEM The paper proposes the use of attack pattern ontology and formal framework for network traffic anomalies detection within a distributed multiagent Intrusion Detection System architecture. Our framework assumes ontology-based attack definition and distributed processing scheme with exchange of communicates between agents. The role of traffic anomalies detection was presented then it has been discussed how some specific values characterizing network communication can be used to detect network anomalies caused by security incidents (worm attack, virus spreading). Finally, it has been defined how to use the proposed techniques in distributed IDS using attack pattern ontology. In order to process intrinsically distributed information, most of modern IDS systems are organized in a hierarchical architecture 4 , consisting of low level nodes which collect information and management nodes which aim to detect large-scale phenomena. The task of management nodes is to reduce the amount of the data processed, identify attack situations as well as make decisions about responses 10 .. In our approach it is assumed that the network system consists of the set of nodes. There are also two types of agents in our multiagent system: monitoring agents (MoA) and managing agents (MA) 7, 8, 9 . Monitoring agents observe the nodes, process captured information and draw conclusions that are necessary to evaluate the current state of system security within their areas of responsibility. Managing agents are responsible for gathering information from MoA agents and generating reports about global threats and ongoing attacks. Each agent MoA monitors its own area of responsibility consisting of the set of network nodes. It is commonly known that in the case of worm attack there occur at least two kinds of anomalies: in observed traffic characteristics and in communication scheme which tends to be constant under normal conditions. In this context the system properties observed by the agent MoA in the proposed architecture will fall into two basic (and physically different) categories: traffic measurement, communication pattern measurement. The attack recognition is being made on the basis of them.. The MoA agent's algorithm for decision making process is invoked periodically and uses observed values as input data. MoA also stores acquired values thus creating the history of system behavior.. Our approach assumes the use of attack pattern ontology which allows to define known attack schemes. Typical attack definition consists of a combination of attack symptoms which are abnormal values of the network variables being observed by the MoAs. The information about attack symptoms is exchanged between the agents in the form of communicates which associate an attack probability value with each variable. The entire framework is extensible -the attack pattern ontology and the set of observed variables may be easily extended in order to incorporate new concepts and variables needed to define new attack types.. The rest of the paper is structured as follows. After short introduction (sec. 2) we present a basic set of network variables which are observed by the agents (sec. 3). The statistics used to determine the probability of abnormal values of any given variable are defined in sec. 4. Also, the concept of observation of network traffic structure in order to reason about abnormal situations is presented in sec. 5 along with appropriate variables. Sec. 6 introduces attack pattern ontology which is used to define exemplary attack in sec. 7. Sec. 8 explains the reasoning procedure for attack detection. In the paper we presented a new method for traffic anomalies detection based on Mark Burges statistics, observation of network traffic variables and the attack pattern ontology. As Mark Burgess technique has quite good ability to tolerate seasonal changes, do not require regularized data and requires relatively small set of data and utilizes CPU only on low level we hope that all this features will characterize also our proposal. These features are especially interesting in a context of real time identification performed on a single host and within mobile agent environments. Another important outcome of our work is the application of attack pattern ontology within a process of intrusion detection. The attack ontology allows us to efficiently combine observation coming from different sources (MoAs) and to draw final conclusion about current network security level. Additionally, a technique for observation of network communication patterns was proposed in order to reason about probability of unknown types of attacks and as an additional heuristic for tuning system parameters. All the above features were integrated within distributed multiagent infrastructure which is now under development and will be subject of further investigations.

O O O O O O B I O O O O O O O O O B O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O B I O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Intra Prediction for the Hardware H.264/AVC High Profile Encoder Abstract The hardware implementation of the intra prediction described in this paper allows the H.264/AVC encoder to achieve optimal compression efficiency in real-time conditions. The architecture has some features that distinguish it from other solutions described in literature. Firstly, the architecture supports all intra prediction modes defined in High Profile of the H.264/AVC standard for all chroma formats. Secondly, the architecture can generate predictions for several quantization parameters. Thirdly, the hardware cost is reduced as the same resources are used to compute prediction samples for all the modes. Fourthly, the high sample-generation rate enables the encoder to achieve high throughputs. Fifthly, 4×4 block reordering and interleaving with other modes minimize the impact of the long-delay reconstruction loop on the encoder throughput. The architecture is verified against the JM.12 reference model and within the real-time FPGA hardware encoder. The synthesis results show that the design can operate at 100 MHz and 200 MHz for FPGA Aria II and 0.13 μm TSMC technology, respectively. These frequencies allow the encoder to support 720p and 1080p video at 30 fps. The H.264/AVC standard [1] allows more compressionefficient coding compared to its predecessors. The main coding improvement stems from the advanced prediction techniques. Particularly, some intra prediction methods are introduced. They apply the extrapolation of reconstructed pixel samples from neighboring blocks to approximate actual pixel samples from a given block. Architectures of H.264/AVC encoders must support at least the DC intra prediction for both luma and chroma. However, the best compression efficiency can be achieved when all predictions are checked in terms of the rate-distortion (RD) criterion. This leads to a high computational burden of video encoders. As many multimedia applications require real-time coding, hardware acceleration of video encoders is indispensible, especially for High Definition Television (HDTV).. There are some challenges in design of intra prediction architectures. Firstly, the selected prediction mode should be optimal or near optimal. Secondly, the consumption of hardware resources must be as small as possible. Thirdly, the latency between processing of successive blocks must be minimized to achieve high-speed encoding. The last problem addresses the throughput of both the intra predictor and the encoder reconstruction loop. In particular, prediction samples within a block can be computed only when reconstructed samples of blocks adjacent to the left and top side are ready for the reference.. In literature, there are some architectures of the H.264/AVC encoder intra prediction [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] . However, none of them supports all intra prediction modes available in High Profile. Particularly, they do not support either 8×8 or Plane predictions, and some designs are dedicated only for a selected block size [10, 11] . The architectures apply separate design units to generate prediction for blocks of different sizes, which increases resource consumption. Although view-parallel MBinterleaved scheduling and open-closed loop intra prediction decomposed into two pipeline stages [14] enable a high processing speed, they have some limitations. Particularly, the first method is dedicated for multi-view or B frames, whereas the second involves quality losses for blocks predicted from original pixels. Intra-frame encoder chips described in [2-4, 6-8, 10, 12, 14] achieve high processing speed. However, they apply basic cost functions based on transformed residuals for mode selection, and their dataflow is optimized only for intra modes. The advanced mode selection based on actual rates (estimated according to binarization schemas of quantized coefficients and associated control data) and distortions (estimated as squared errors of reconstructed samples) would deteriorate significantly the throughput, especially when the reconstruction loop is shared with Inter modes. This limitation is caused by the fact that all prediction modes must be processed by the long-delay path including transformations, the (de)quantization, the reconstruction, the error estimation, and the cost evaluation.. In this paper, the hardware architecture of intra predictor for the encoder is proposed. The design supports all prediction modes for all chroma formats. 4×4 and 8×8 modes can be computed for several quantization parameters. This feature allows more efficient compression when the advanced mode selection based on the rate-distortion criterion is used. The same logic is used for the generation of all prediction modes, leading to the reduction of hardware resources. The architecture applies three main techniques in order to maximize the processing speed. Firstly, the 16 prediction samples can be generated in one clock cycle. Secondly, predictions for 4×4 blocks are interleaved with remaining intra modes. Thirdly, the generation order of 4×4 blocks is modified to decrease the impact of their prediction dependencies on the latency. The obtained throughput allows the encoder to support 1080p 30 fps video at 200 MHz when intra and inter modes are checked based on the rate-distortion analysis. The following sections describe the proposed architecture, and the last one provides implementations results.

B I O O O B O O O O O O O O O B I O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B I O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


The effect of a lower extremity kinematic constraint on lifting biomechanics Leaning against a stationary barrier during manual materials handling tasks is observed in many industrial environments, but the effects of this kinematic constraint on low back mechanics are unknown. Thirteen participants performed two-handed lifting tasks using both a leaning posture and no leaning posture while trunk kinematics, muscle activity and ground reaction force were monitored. Results revealed that lifting with the leaning posture required significantly less activity in erector spinae (26% vs. 36% MVC) and latissimus dorsi (8% vs. 14% MVC), and less passive tissue moment compared with the no leaning posture. Peak sagittal accelerations were lower when leaning, but the leaning posture also had significantly higher slip potential as measured by required coefficient of friction (0.05 vs. 0.36). The results suggested that the leaning lifting strategy provides reduced low back stress, but does so at the cost of increased slip potential. Industrial manual materials handling tasks often require lifting a load over a static barrier such as a railing or the side of a storage bin. The constraint that this barrier places on the kinematics of the lower extremities has a direct impact on the postures of the torso and it is believed that this will influence lifting biomechanics and lumbar stress. A review of the literature revealed that prior studies on this topic have focused on an alternative strategy wherein lifters used their off hand to support the weight of the upper body on the barrier while the dominant hand lifts the load (Ferguson et al., 2002; Kingma and van Dieën, 2004) . Both studies illustrated the superiority of this strategy in terms of reduced trunk moment, reduced spine compression and reduced anterior-posterior shear force on low back. While this approach is shown to be effective at reducing spinal loads, this option is not available during two-handed lifts and so the uncertainty of the biomechanical effects of two-handed lifting over a barrier persists.. The two-handed lifting over a barrier are commonly observed in lifting task of crab fishermen in North Carolina wherein the LBP was shown as the highest cause of work impairment, holding 17.7% (Lipscomb et al., 2004) . Mirka et al. (2005) evaluated biomechanical stresses placed on lumbar spine during the work activities of crab fishing by employing continuous assessment of back stress (CABS) methodology, which characterizes the stress on the low back throughout the workday, expressed in terms of time-weighted histograms (Mirka et al., 2000) . The results of this study showed that the workers pulling the crab pots from the water or side of the boat up into the sorting table (using two hands) deserve attention in terms of a risk of LBP (Kucera and McDonald, In Review; Mirka et al., 2005) . The crab pots used by fishermen in the estuary waters of North Carolina are big and heavy, 60cm × 60cm × 60cm cages made of chicken wire and framed with rebar, weighing between 3 and 12 kgf (depending on catch) and are lifted at a rate of one lift per minute. These pots are typically pulled up to the side of the boat by a mechanised "pot-puller" and then the fishermen reach over the side of the boat and lift the pot into the boat. A common lifting strategy observed in small-boat crab fishing operations is to lean against the side of the boat (washboard) with one or both thighs to handle big and heavy crab pots when lifting the crab pots from the water. If the fishermen choose not to lean against the washboard, hyper-flexion of trunk and/or asymmetric lifting are typically observed. If the fishermen choose to lean against the washboard, they are not able to use their legs to help with the lifting motion because the knee and ankle degrees of freedom in the kinematic chain have been lost. In addition, the horizontal external force provided by the interaction between the thighs and the washboard generates additional anterior-posterior ground reaction forces that can increase the slip potential on the slippery deck surface. However, from the opposite point of view, the leaning on a barrier could increase the stability of the entire body by providing additional contact points between body and stationary objects where the support provided by additional contact could reduce the rocking motion on the boat. These observations make the exploration of the biomechanics of these kinematically constrained leaning postures worthy of further exploration.. One previous study considered the effect of a shin-level kinematic constraint on low back biomechanics during lifting. Shu et al. (2007) evaluated the differences in activation levels of trunk extensor muscles while kneeling on a knee support (i.e. loss of the degree of freedom of the ankle joint). In this study the participants were asked to maintain a designated trunk flexion angle and then receive and hold a weight that was released into their hands by the experimenter.. The kinematic constraint eliminated the motion of the ankle joint but allowed participation of the knee joint in supporting this load. Their results showed that the loss of the degree of freedom at the ankle joint had little effect on the activation level of latissimus dorsi and multifidus muscles during this task. While this previous study provided some information regarding the effect of a kinematic constraint, it was somewhat limited in that it only considered the constraint on the ankle joint -a joint with relatively limited direct impact on low back function. It was felt that limiting the participation of the knee joints through a kinematic constraint may be much more impactful on the function of the low back. The goal of current study was to investigate the effect of a thigh-level kinematic constraint by leaning against the barrier on trunk muscle activation and lifting kinematics. This study considered the effects of a leaning posture on spine biomechanics and lower extremity slip potential. Our results showed that the leaning lifting strategy provides some biomechanical benefits over the no leaning lifting strategy (lower muscle activations levels, more controlled lifting motions, reduced passive tissue forces) but at a cost of increased required coefficient of friction. In some work environments where the coefficient of friction between the lifter and the floor is high this may not be an issues, however in the commercial fishing industry, the low coefficient of friction deck surface highlights the leaning posture as problematic. Understanding the impact of a leaning posture on low back biomechanics can provide valuable insight into possible ergonomic interventions for lifting in many scenarios. The particular scenario considered in the current study was lifting heavy loads from over the side of a small commercial fishing vessel. Quantifying the trunk kinematics through motion analysis, the muscle activation level through electromyography, and slip risk through required coefficient of friction can provide the type of quantitative data that will indicate whether this would be effective intervention in this particular work environment.. Normalized EMG results showed that the no leaning condition requires significantly greater trunk muscle activities (both agonist and antagonist) than did the leaning condition. The first thing that one notes in evaluating the postures assumed during these static contractions is that the leaning posture allows the pelvis to move anteriorly (Figure 1) , thereby moving the fulcrum of the biomechanical system closer to the load and reducing the moment generated by the external load. This observation is consistent with the results of Kingma and van Dieën (2004) which showed a reduction in the distance between L5/S1 and external loads by supporting the upper body with the free hand during lifting. Second, the passive components of the low back also suggested the benefit of the leaning posture by showing that the moment generated by the passive tissues of the low back were greater under the no leaning condition. As the trunk flexion is deeper the passive tissues are in tension and begin to offset the external torque instead of the active tissues. Consequently, the active tissue captured by EMG shows no activity (i.e., FRP), and the passive tissue moment provides additional information predicting spinal loading.. Considering that the passive mechanism initiated over 60 degree trunk flexion and enhanced with more trunk flexion, the participants tended to keep a more upright trunk posture during the leaning condition, instead of the hyper trunk flexion observed during the no leaning condition for reaching an object (Figure 1 ). In line with this, the lumbar flexion angle during the leaning condition was significantly smaller than that observed in the no leaning condition resulting in a lower passive tissue moment. With regard to low back loading, it is clear that the leaning posture is superior.. Less clear are the impacts of the leaning posture on lower extremity biomechanics and the resulting slip potential from this technique. The EMG results of gastrocnemius showed a significant (~15%) reduction suggesting a decrease in the necessary plantar flexion moment during the leaning condition as compared to the no leaning condition, indicating a positive effect of leaning. However, the nature of the leaning posture generated significantly higher RCOF than the no leaning condition. The nature of the leaning posture required that the participants push against the barrier with the thighs. With this pushing force comes an equal and opposite ground reaction force that could result in greater RCOF. In the current study the RCOF was shown to vary significantly as a function of load height during the leaning condition with the lower load heights generating the greater RCOF. While our laboratory simulation of the process of lifting the load from three different heights had high fidelity in some characteristics, the realistic working conditions (wet surface, oil and other particles) will reduce this coefficient of friction and may alter the strategies employed by workers performing this constrained lifting task. For the best results, the working condition with dried floor (solids) and wearing shoes (rubber) could be satisfactory because the coefficient of friction between solids and rubber is between 1 and 4 (RCOF in the leaning posture: 0.35). Also, regarding the coefficient of friction between rubbers (1.16) a rubber mat on the working place may lower the slip potential.. Regarding the trunk kinematics, the result also showed slower peak angular acceleration of the leaning posture in sagittal plane than no leaning posture during a concentric lifting motion, except at the lowest level of height (i.e., 65 cm). It is well known that increased trunk acceleration have a significant impact on spinal force and moment because of the increased inertial force and moment (Marras et al., 1993; Marras and Davis, 1998) . On this basis, slower lifting acceleration may be another benefit of the leaning posture.. Expanding the results of the current study to a more general recommendation for broader industry applications should be done with care. It is clear that leaning against a solid barrier will move the lifter closer to the load and thereby reduce the external moment of the load. Caution should be taken, however, when considering the slip potential that this leaning posture generates.. Our results indicate that the RCOF is significantly greater with the leaning posture and it is also increased as the load height decreased. The RCOF can be counteracted by providing high friction floor surface (e.g., rubber mat) or vertical stabilizers in the floor against which the lifters feet can push to accomplish the lift in a safe manner. Therefore as one considers the effectiveness of a leaning strategy to reduce low back injury risk, one should consider environmental factors when developing the leaning strategy as an effective ergonomic intervention strategy.. There are several limitations to the generalizability of the results of the current study.. First, participants in this study were physically fit, male college students with relatively limited experience in manual materials handling tasks and no experience in crab pot lifting on the boat.. Previous studies found that inexperienced subjects generally demonstrated greater spinal loading than experienced manual material handlers when the moment exposure was the same (Marras et al., 2006) . Future study with experts in crab pot lifting could result in different low back biomechanical responses. Second, the current study controlled variables such as lifting technique (two hand, symmetric lifting), load size and load weight and these variables might influence the strategy and the biomechanical response of the lifters under the leaning and no leaning conditions. Future research should provide insight into the interaction between these factors and the POSTURE. The results of MANOVA for average NEMG showed significant effects of POSTURE and HEIGHT, but there was no significant interaction effect between POSTURE and HEIGHT (See Table 1 ). Accordingly, the interaction effect was not considered in subsequent data analysis.. Univariate ANOVAs were conducted on each of the five muscles and revealed a significant effect of POSTURE on all five selected muscle activities. The results showed that a leaning posture requires significantly lower muscle activation as compared to no leaning posture in the erector spinae, latissimus dorsi, rectus abdominis, external oblique and the gastrocnemius ( Figure 2 ). However, the magnitude of difference in rectus abdominis (1.05%) and external oblique (0.64%) was quiet small, suggesting minimal or no significant effect in a biomechanical view point. The effect of HEIGHT was to have ~5 % reduction in gastrocnemius activity at the highest load position (85 cm) as compared to the others (55 and 70 cm). Simple effects analysis confirmed that both main effects were significant. Regarding lifting kinematics, the result of ANOVA for angular acceleration in sagittal plane during a concentric lifting motion showed significant effects of POSTURE (p < 0.0001), HEIGHT (p < 0.0001) and its interaction (p < 0.0001) (Figure 4) . Simple effects analysis, however, revealed that there is no difference between leaning and no leaning conditions at the height of 55 cm (p < 0.4319) when it was sliced by each HEIGHT (other two levels of HEIGHT showed significant effects of POSTURE (p=0.0424 (70 cm) and p<0.0001 (85 cm)). Also, the effect of HEIGHT was significant in both leaning and no leaning when it was sliced by POSTURE (p<0.0001) ( Figure 5 ).. In regards to the RCOF, the results of ANOVA for RCOF also showed significant effects of POSUTRE (p < 0.0001), HEIGHT (p = 0.0032) and its interaction (p = 0.0018). Simple effects analysis revealed that HEIGHT was not significant in the no lean condition, but confirmed POSTURE as a significant main effect.

O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Expression Detection Based on a Novel Emotion Recognition Method As facial expression is an essential way to convey human's feelings, in this paper, a dynamic selection ensemble learning method is proposed to analyze their emotion automatically. A feature selection algorithm is proposed at first based on rough set and the domain oriented data driven data mining theory, which can get multiple reducts and candidate classifiers. Then the nearest neighborhood of each unseen sample is found in a validation subset and the most accurate classifier is extracted from the candidate classifiers. Finally, the selected classifier is used to recognize unseen samples. Experimental results show that the proposed method is effective and suitable for emotion recognition. Even there have been some commercial products, such as the amazing robots in Japan, it still takes a long time to make a computer act as a human to recognize human emotions since there are many problems remain unsolved in psychology and cognitive fields. Currently, emotion recognition is studied with such methods as ANN, fuzzy set, SVM, HMM and rough set, where the recognition rate often ranges from 64% to 98% [1] [2] . To achieve a better result based on existing classification methods, ensemble learning is proposed in 1990s' 3 , which construct a set of candidate classifiers and then classify new objects by integrating the prediction of the candidate classifiers. Experiments have validated that an ensemble system is much more accurate than any separate classifier. Ditterrich proved the effectiveness of ensemble methods from the viewpoint of statistic, computation and representation in Ref. 4 . Currently, ensemble methods have been applied widely over a variety of areas, e.g., pattern recognition, network security and medical diagnosis [4] [5] [6] [7] . Ensemble strategies are commonly used to gain a different subset of the original dataset by multi-sampling the training set, like bagging 6 , boosting 7 and cross-validation. These methods work well especially for unstable learning algorithms, such as decision trees and neural network. Some other methods are also studied, such as manipulating the output targets 8 and injecting randomness into classifiers 9 . In addition, the ensemble feature selection (EFS) 10 is another effective approach for ensemble, which is also a classical ensemble method. It uses different feature subset as input feature to construct a candidate classifier.. In this work, we propose a novel emotion recognition method based on EFS and rough set theory. At first, a feature selection algorithm is proposed based on rough set and domain oriented data driven data mining (3DM) theory [11] [12] , which can obtain multiple reducts and candidate classifiers. The nearest neighborhood of each unseen sample is then found in a validation subset and the most accurate classifier is selected from the candidates. At last, the selected classifier is used to classify the unseen samples. The proposed method is proved to be effective by extensive experiments.. The remainder of this paper is structured as follows. In Section 2, the tolerance relation model for continuous value information system is introduced. The proposed emotion recognition method based on dynamic selection ensemble learning is then discussed. Simulation experiments and discussions are presented in Section 3. Finally, conclusion is drawn in Section 4. In this paper, a novel emotion recognition method is proposed based on the ensemble learning. First, a feature selection method is proposed based on RS and domain oriented data driven data mining theory. It can get multiple reductions and candidate classifiers. For each unseen sample, a nearest neighborhood is found and the most accurate classifier is then selected from the candidates. Finally, the selected classifier is used for recognizing the unseen samples. The comparative experiments have validated the proposed method is suitable for emotion recognition.

O O O O O O B I O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O B I O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O B I O O O O O O O O O O O B I O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O B I O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I


Modeling and systematic analysis of biomarker validation using selected reaction monitoring Background: Discovery and validation of protein biomarkers with high specificity is the main challenge of current proteomics studies. Different mass spectrometry models are used as shotgun tools for the discovery of biomarkers. Validation of a set of selected biomarkers from a list of candidates is an important stage in the biomarker identification pipeline. Validation is typically done by triple quadrupole (QQQ) mass spectrometry (MS) running in selected reaction monitoring (SRM) mode. Although the individual modules of this pipeline have been studied, there is little work on integrating the components from a systematic point of view. Results: This paper analyzes the SRM experiment pipeline in a systematic fashion, by modeling the main stages of the biomarker validation process. The proposed models for SRM and protein mixture are then used to study the effect of different parameters on the final performance of biomarker validation. Sample complexity, purification, peptide ionization, and peptide specificity are among the parameters of the SRM experiment that are studied. We focus on the sensitivity of the SRM pipeline to the working parameters, in order to identify the bottlenecks where time and energy should be spent in designing the experiment. Conclusions: The model presented in this paper can be utilized to observe the effect of different instrument and experimental settings on biomarker validation by SRM. On the other hand, the model would be beneficial for optimization of the work flow as well as identification of the bottlenecks of the pipeline. Also, it creates the required infrastructure for predicting the performance of the SRM pipeline for a specific setting of the parameters. General facts can be gleaned from the results reported above in the paper on the relative importance of each http://bsb.eurasipjournals. parameter to the sensitivity of biomarker validation performance using the QQQ-based SRM system.. • Purification critically increases the efficiency of the whole pipeline by reducing the background high-abundance proteins.. • On the other hand, peptide ionization efficiency also plays an important role in the success of biomarker validation experiment.. • A high value of modification noise can greatly compromise the performance of the system, as measured by the decreases of the TPR and ranking power value.. • Likewise, a decrease of peptide specificity reduces the TPR and ranking power to a great extent.. The results emphasize the importance of the correct selection of peptides in an SRM experiment. If the selected peptides are not unique to the targeted protein, it is hard to have high-precision quantification of the abundance of the targeted peptides, which will show itself in the unsuccessful protein validation results. An additional factor is of course sample size, which not surprisingly showed a clear effect on the performance of the biomarker discovery pipeline. In this paper, the key components of the typical SRMbased biomarker validation workflow were reviewed, modeled, and analyzed. Based on the synthetic data, the process was simulated and the effect of different parameter setting on the performance was studied. Ranking power and the TPR were used as two different metrics to assess the performance of the biomarker validation process as a function of the parameters of the model. The goal of this study was not the determination of the exact value of each parameter for reaching a given performance value but rather to investigate the effect of the different parameters, namely, sample purification, peptide ionization efficiency, peptide specificity, modification noise, and sample size, on the overall performance of the SRM experiment utilized for biomarker validation.. The model presented here can not only be utilized to observe the effect of different instrument and experimental settings on biomarker validation by SRM but also could be useful for experimental design, providing an insight on the working range of the important parameters of the SRM pipeline. It creates the required infrastructure for studying the inverse problem, where one can use the model to set the parameters of the entire experiment to reach the highest performance considering technical, experimental and financial constraints. Also, the model has the advantage of being flexible to future possible extension in order to include more detailed modules of the SRM pipeline. In spite of the widespread application of SRM in the protein biomarker validation process, there is little work on the integration of the different modules in SRM workflow, and their systematic study to assess the impact of different parameters on the overall biomarker validation pipeline. A model-based approach toward the SRM experiment will help us to have a better understanding of the characteristics of the different modules of the SRM-based biomarker validation process. Here, the SRM pipeline is modeled as a noisy channel affecting the underlying protein abundance signal; a model for the noise channel is proposed and used to analyze the effect of different parameters and experimental settings on the final performance of the SRM-based biomarker validation pipeline and the ability of SRM to detect true biomarkers among a set of candidate ones. Although the aim of the SRM model proposed here is not to determine the exact value of each parameter, it will be useful in providing a systematic view towards studying the individual components of the SRM experiment. We perform a total of 5,000 Monte Carlo runs in this experimental study, using the parameter settings given in Table 1 , and compute average performance metrics over all the runs.. The performance metrics used to evaluate SRM performance are the percentage of peptides correctly identified and the ranking power [27] . The former is computed by applying the t-test as a feature selection method to find the best discriminant set of features, and computing the ratio of true biomarkers detected in that list. The latter defines a measure of goodness based on how close the estimate-based feature sets are to optimality. Let A best be the best feature set relative to the feature-label distribution, ε 0 be the true error of the classifier for A best designed on the sample, and A (1) , A (2) sorted from lowest to highest. The ranking power of the list is defined by n,r. for r > 0. The ranking power gives the probability that at least one feature set in the list has error within r of the best feature set. The closer n,r D,d is to 1, the better the performance is (as long as m is small; here, m = 10 is used).. The pseudocode for computing the power rank is described in Algorithm 1.

O O O O O B I O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O B I I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


SLurtles: Supporting constructionist learning in Second Life Constructionism places an emphasis on the process of constructing shareable artefacts. Many virtual worlds, such as Second Life, provide learners with tools for the construction of objects and hence may facilitate in-world constructionist learning experiences. However, the construction tools available present learners with a significant barrier (or 'high-floor') for the novice to first master. To address this problem, this paper presents the design concepts, first implementation and analysis of SLurtles (programmable turtles in Second Life), easy-to-use, programmable construction tools for use in Second Life. During a pilot study 24 postgraduate learners in pairs and working at distance from one another, programmed SLurtles to create interactive installations in Second Life over four weeks. Open interviews were conducted, chat logs recorded and learners artefacts and reflections were collected and analysed using qualitative methods. Findings show that SLurtles provide learners with a programmable, low-floor, high-ceiling and wide-wall construction tool, which supported their construction of a wide range of complex artefacts as part of a constructionist learning experience in Second Life. Underpinning constructionist learning experiences is the learner's engagement with programming and the construction of personally meaningful and shareable artefacts (Hoyles, Noss, & Adamson, 2002) . On first glance virtual worlds appear to provide an exciting new environment to engage in constructionist learning experiences. However the inbuilt tools of virtual worlds such as Second Life and Active Worlds present the novice with a high-floor (steep learning curve) barrier to overcome (Dickey, 2005; Sanchez, 2009) .. While Scratch for Second Life (S4SL) provides a low-floor and high-ceiling (powerfully expressive) programming environment for the virtual world Second Life, it does not support the construction of artefacts. Learners must first learn how to use the relatively complex 3D object modelling tools before they can engage in exploring, testing and extending their understanding. Thus to enable constructionist approaches to learning within virtual worlds, it is first necessary to lower the barriers to engagement.. To address the need for a low-floor construction tool in virtual worlds, this paper presents the design and implementation of SLurtles (programmable turtles in Second Life). Borrowing design concepts from Lego and Turtle graphics, SLurtles build upon S4SL and are designed to provide learners in Second Life and OpenSim with programmable tools with which to create personally meaningful and shareable artefacts. To guide research into the use of SLurtles by learners, the following question is posed: Do SLurtles provide learners with a pedagogical tool with which to engage in constructionist learning in virtual worlds?. Underpinning the design of SLurtles are the concepts of a low-floor (easy to use), high-ceiling (powerfully expressive) and wide-walls (support the creation of a variety of artefacts), concepts central in the design of constructionist tools for learning. Considering Norman's (1999) distinction between designed and perceived affordances, while designed for, these affordances may not emerge when SLurtles are used by learners. While a block programmed to be persistent, will be persistent, SLurtles may not be easy to use. The complexity of constructions may be constrained. Similarly, while aiming not to limit the types of constructions which learners could make, this may not be perceived to be true by the learner. Thus, these design concepts are examined through a pilot study of SLurtles with learners, which also provides an opportunity to engage in an open exploration of learners' use of SLurtles. Thus the following sub-questions are:. B Do SLurtles provide learners with a low-floor construction tool? B Do SLurtles provide learners with a high-ceiling construction tool? B Do SLurtles provide learners with a wide-wall construction tool? B How do learners use SLurtles as part of a constructionist learning experience?. To pilot the use of SLurtles by learners, an exploratory case study approach is employed. 24 learners took part in a four week constructionist learning experience in Second Life, as part of a postgraduate course in teaching and learning. Through qualitative analysis of participant interviews, chat logs, the artefacts they created using SLurtles and their personal reflections, SLurtles are found to provide learners with an empowering low-floor, high-ceiling and wide-wall construction tool with which learners were able to engage in the construction of personally meaningful and shareable 3D artefacts as part of a constructionist learning experience in the virtual world. The initial motivation for creating SLurtles was due to the high-floor object construction tools currently available in virtual worlds (Dickey, 2005; Sanchez, 2009 ) which may limit learners' engagement with constructionist learning experiences in-world. This paper has presented the design and pilot study of SLurtles as low-floor, programmable construction tools for use in the virtual world of Second Life.. The findings demonstrate that SLurtles provided learners with a low-floor programmable construction tool with which they were able to create a variety of complex artefacts. While initial constructions were easy, more complex constructions required more complex programmes and with this came a sense of challenge, hard fun and achievement. Although most learners had little or no previous programming or virtual world experience, they were able to collaborate at distance to create complex artefacts with SLurtles.. The intention of this study was to pilot SLurtles, considering the floors, ceilings and walls which may constrain learners. While they are shown to provide a low-floor, high-ceiling and wide-wall construction tool, much of the data is drawn from learners' perceptions. Further research is needed to understand the points at which the floor, ceiling and walls stop and begin to limit what learners may achieve. This may undertaken in comparison to other in-world tools or other constructionist environments such as Scratch. However the need for such research also highlights a potential limitation in the discourse surrounding constructionist tools, that is how to measure floors, ceiling and walls and whether these are comparable between tools. Within this paper it is not possible to engage in such a debate, however it is an issue which needs to be clearly addressed by the field.. While SLurtles and S4SL may under-go further development to address the concerns highlighted in Section 5 and the barriers described in Section 4, they have been found to provide a low-floor tool for the construction of objects in Second Life. Although designed for Second Life, SLurtles have the potential to be used in a number of other virtual worlds developed through the OpenSim project. Although presented in terms of Second Life, the design concepts behind SLurtles could also be implemented for the development of similar tools in other virtual worlds such as Active Worlds.. With a low-floor programmable construction tool, SLurtles are currently being implemented in further work which aims to develop an understanding of constructionism in virtual worlds. In particular this work explores the public nature of construction, the role of avatars and barriers to engagement.. In Mindstorms, Papert (1980) advocated "the construction of educationally powerful computational environments that will provide alternatives to traditional classrooms and traditional instruction" (p. 182). With SLurtles providing the low-floor programmable construction tool with which learners can engage in constructionist learning activities, virtual worlds may provide such an educationally powerful computational environment. S4SL was created to lower the floor and allow learners to engage in programming in virtual worlds. However to engage in constructionist learning experiences, learners also require a low-floor construction tool. Following the design of SLurtles, the pilot study reported in this paper aims to answer the question: Do SLurtles provide learners with a pedagogical tool with which to engage in constructionist learning in virtual worlds?. In order to answer this question, four sub-questions were posed. The first sub-question focuses on whether or not SLurtles provided the learners with a low-floor construction tool, which was the initial motivation behind the construction of SLurtles. The findings demonstrate that SLurtles are easy-to-use construction tools without which learners stated they would not have been able to achieve such complex artefacts. There was, however, an initial skill barrier described by some participants when transferring a script from S4SL to SLurtle and this limited their initial engagement with SLurtles. Although there was only evidence of this from two interviews, it is unclear how many other participants may also have experienced this barrier but not reported it. While this may raise the floor for initial engagement with SLurtles, the creation of objects using the 3D object modelling tools in Second Life would, for novices, be a much higher barrier to entry.. Generic Second Life skills and tools were also identified as barriers, in particular avatar movement, camera controls, permissions and communication tools. It is unclear from the findings as to what extent these limited engagement with SLurtles, however once learners engaged in the use of SLurtles these barriers were quickly overcome or became irrelevant. These barriers suggest that there may be some inworld skills that learners need to successfully master in order to initially or fully engage with SLurtles, however there is insufficient data to draw any firm conclusions on this.. The second and third sub-questions consider the high-ceiling and wide-wall concepts of constructionist tools in relation to SLurtles. Each of the groups created very different installations, suggesting that SLurtles do support the wide-wall concept. There were mixed views on the complexity of the artefacts that could be created using SLurtles. While some considered S4SL or the type of SLurtle blocks limited what could be created, others viewed these aspects of SLurtles as enabling them to create complex artefacts.. The fourth sub-question explores the learners' use of SLurtles as part of a constructionist learning experience. The SLurtle character, its clear position and heading together with the blocks it created, provided learners with a focal point through which they were able to gain feedback and reflect on their programmes. Learners were able to quickly engage in using the SLurtles to create objects and explore and test their understanding through concrete constructions.. The limited variety of simple blocks was used to create a wide variety of artefacts of varying complexity, identified as personally meaningful constructions. There was evidence that as constructions became more complex so did the programmes used for the constructions. It is also interesting to note that there was no evidence of the experienced programmers using the in-world programming tool, suggesting that S4SL provided a suitably high-ceiling programming environment with which to programme SLurtles. Due to the persistent nature of the blocks, learners were able to share their artefacts during and after construction. This supported collaboration with their partner and the wider class group.. Within the category 'Thinking' there is evidence of learners engaging in an experiential learning cycle (Kolb, 1984) . Although Kolb's model is often critiqued, it provides a useful frame of reference to which the findings in the category of 'thinking' can be discussed. The SLurtle's movement, indicated by its clear position and heading, as well as the SLurtle blocks created, provided the learners with a concrete experience which they could observe and reflect upon. This provided learners with an opportunity to reassess their code asking questions of themselves and their partner including "why didn't it work, or why did it work?" and comparing the outcome to the original plan. This was followed by the redesign of the programme which was exported from S4SL into Second Life and implemented by the SLurtle to provide the learner with a concrete experience. The full stages of this process, mapped onto Kolb's model, are illustrated in Fig. 16 .. While Hoyles and Noss (2003) may argue that as the learners in this context are not engaged in a microworld they will lose the psychological connection between the abstract code and the concrete output, the findings show that the learners described using SLurtles as supporting the exploration and testing of their abstract understanding of programming through concrete constructions. However as S4SL is currently unavailable within Second Life, the disconnect that may result from moving between two programmes could reduce the effectiveness of SLurtles in supporting learners' concrete experience. In addition it has the potential to diminish the sense of immersion experienced by learners and the tools with which learners engage may not become 'invisible', an important feature of constructionist learning experiences (Papert, 1980s, 1991 .. The process of exporting the code from S4SL into the SLurtle was also identified as an initial skill barrier and demonstrates the lack of 'bidirectionality' (Hoyles et al., 2002) between code and SLurtle. While this lack of bidirectionality also supports the notion that this learning context does not provide a microworld for learners, it is important to note that this was not the aim when developing SLurtles, but rather to create a low-floor construction tool. To address these issues, further development of S4SL to provide a representation of the S4SL environment in Second Life may be necessary.. Despite some limitations, SLurtles clearly supported learners' creation of artefacts as they engaged in the constructionist learning experience. While not easily achieved, learners began to explore more complex constructions over time. Exploring, testing and extending their understanding they gained a high sense of satisfaction when they were able to programme the SLurtles accurately. SLurtles engaged learners in thinking about programming by providing them with a programmable low-floor tool for the construction of a wide variety of personally meaningful and shareable artefacts within the virtual world Second Life. Therefore the answer to the main research question is yes, SLurtles provide learners with a pedagogical tool with which to engage in constructionist learning in virtual worlds.

O O O O O O O B O O O O O O O O O O O B I O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O B O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O B O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O B O O O O O O O O O O O O O O O O B O B I O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O B O B I O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I


Social networks and information retrieval, how are they converging? A survey, a taxonomy and an analysis of social information retrieval approaches and platforms There is currently a number of research work performed in the area of bridging the gap between Information Retrieval (IR) and Online Social Networks (OSN). This is mainly done by enhancing the IR process with information coming from social networks, a process called Social Information Retrieval (SIR). The main question one might ask is: What would be the benefits of using social information (no matter whether it is content or structure) into the Information Retrieval process and how is this currently done?With the growing number of efforts towards the combination of IR and social networks, it is necessary to build a clearer picture of the domain and synthesize the efforts in a structured and meaningful way. This paper reviews different efforts in this domain. It intends to provide a clear understanding of the issues as well as a clear structure of the contributions. More precisely, we propose: (i) to review some of the most important contributions in this domain to understand the principles of SIR, (ii) a taxonomy to categorize these contributions, and finally, (iii) an analysis of some of these contributions and tools with respect to several criteria, which we believe are crucial to design an effective SIR approach. This paper is expected to serve researchers and practitioners as a reference to help them structuring the domain, position themselves and, ultimately, help them to propose new contributions or improve existing ones. With the emergence of the social Web, the Web has evolved from a static Web, where users were only able to consume information, to a Web where users are also able to produce information. This evolution is commonly known as Social Web or Web 2.0. Thus, the Web 2.0 has introduced a new freedom for the user in his relation with the Web by facilitating his interactions with other users who have similar tastes or share similar resources. Social platforms and networks (such as MySpace, 1 certainly the most adopted technologies in this new era. These platforms are commonly used as ameans to communicate with other users, exchange messages, share resources (photos and videos), comment news, create and update profiles, interact and play online games, etc. In addition to dedicated social platforms, traditional content providers sites like newspapers, tend to be more social since they provide to users means for sharing, commenting, constructing, and linking documents together [1, 2] , e.g., through the buttons "share on social networks". This has been also facilitated by initiatives like OpenID 9 and OpenSocial. 10 These collaborative tasks that make users more active in generating content are among the most important factors for the increasingly growing quantity of available data. In such a context, a crucial problem is to enable users to find relevant information with respect to their interests and needs. This task is commonly referred to as Information Retrieval (IR). IR is performed every day in an obvious way over the Web [3] , typically using a search engine. However, classic models of IR do not consider the social dimension of the Web. They model web pages 11 as a mixture of static homogeneous terms generated by the same creators, i.e., the authors of the web pages. Then, the ranking algorithms are often based on (i) a query and document text similarity (e.g., the cosine measure and the Okapi BM25 [4] ), and (ii) the existing hypertext links that connect these web pages (e.g., PageRank [5] , and HITS [6] ). Therefore, classic models of IR and even the IR paradigm have to be adapted to the socialization of the Web in order to fully leverage the social context that surrounds web pages and users. Indeed, exploiting social information has a number of advantages (for IR in particular): first, feedback information in social networks is provided directly by the user, so users' interests accurate information can be harvested as people actively express their opinions on social platforms. Second, a huge amount of social information is published and available with the agreement of the publishers. Exploiting this information should not violate user privacy, in particular social tagging information, which does not contain sensitive information about users. Finally, social resources are often accessible, as most of social networks provide APIs to access their data (even if often, a monetized contract must be established before any large scale use).. There is currently a number of research works undertaken to improve the IR process with information coming from social networks. This is commonly known as "Social Information Retrieval" (SIR). This paper intends to provide a clear understanding of the various efforts performed in the domain of SIR, and in this perspective, we propose. 1. An objective review of some of the most representative research contributions and existing tools in this domain to understand the principles of SIR as they are currently formulated.. 2. A taxonomy to categorize these contributions in order to structure this wide domain. 3. An analysis of some of these contributions and tools with respect to several criteria considered as crucial to design an effective SIR approach or to appreciate one.. This study is useful for researchers, engineers, and practitioners in this domain to help in understanding trends, challenges and expectations of a SIR approach. The rest of this paper is organized as follows: in Section 2, we discuss the main concepts used throughout this paper. In Section 3, we introduce our taxonomy of SIR approaches and tools, while describing each of these categories in Sections 4-6. In Section 7, we elaborate on an analysis of some of these contributions and tools based on several dimensions. Finally, we give some future directions in Section 8 and we conclude in Section 9. In this paper, we proposed a deep review of the topic of Social Information Retrieval (SIR). Especially, we proposed a taxonomy to classify and categorize SIR approaches into three main categories, namely: (i) social Web search, (ii) social search, and (iii) social recommendation. We showed that these three sub-categories are fundamentally different in the way they leverage and use social information. Many methods have been proposed to improve the classic IR process, while others proposed new search paradigms based on the socialization between users.. Social platforms represent valuable sources of information and knowledge that can be reused to improve many services (especially search services). On one hand, initiatives like OpenID, and the Mashup concept are promoting the possibility to social platforms to share their data with other applications, e.g., the full user name, the profile's picture, the gender, the username and user id (account number), and even the list of friends and contacts. On the other hand, users are encouraged to share and publish content on social platforms, and make their social information publicly accessible. Therefore, this social dimension of the Web attracted the attention of many researchers in the IR community.. We discussed many SIR methods with respect to some dimensions that we judge to be essential in order to assess the robustness and the effectiveness of a SIR approach. We consider these dimensions, as factors that indicate the extent to which a SIR approach can be applicable, and in what context, i.e. size of the data and sparsity of the data. Finally, we discussed some interesting improvement for some SIR categories for a research perspective. Information Retrieval is the process of recovering stored information from large datasets to satisfy users' information needs. Salton [7] and Baeza et al. [3] defined IR as follows:. Definition 1 (Information Retrieval). Information Retrieval (IR) is the science that deals with the representation, storage, organization of, and access to information items in order to satisfy the user requirements concerning this information.. Example 3 (Online social network). Facebook is certainly the most popular social network that handles relationships between individuals. There are many social network sites that manage in addition to users, objects. These include documents on CiteULike, images on Flickr, videos on YouTube, etc.. The structure of a social network can be constructed in two ways: (i) either explicitly declared by the user, e.g., friendship links in Facebook, or (ii) implicitly inferred from the behavior and the common interests of users, e.g., Social Network of Web services [8] . To understand the underlying social structures and phenomena, a set of techniques and methods exist, which are known as Social Networks Analysis (SNA) techniques [9] . SNA introduces methods and metrics (e.g., centrality and influence) for analyzing a Social Network, e.g., measuring the role of individuals and groups of individuals in a social network.. Each social network might be characterized by the relationships that link its users, e.g., friend relationships, follower-following relationships, and publisher-subscriber relationships. Hence, we distinguish mainly three models of social relationships that we describe hereafter. 13

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