bluuebunny/crossref_metadata_2025 huggingface dataset:
Accurate Stress Analysis on Steel Box Girder of Long Span Suspension Bridges Based on Multi-Scale Submodeling Method
Authors: Wang Hao , Li Aiqun , Hu Ruomei , Li Jian
Published: August 2010

The streamline flat steel box girder is broadly used in long span cable-supported bridges all over the world. As one of the most important part of the bridges, its stress level and distribution under various dynamic loads are especially concerned. However, it is difficult to obtain the accurate stress of the steel box girder by common finite element (FE) calculation. The Runyang Suspension Bridge (RSB) is taken as an example. To increase the accuracy of results, a 3-dimensional FE full model for the RSB is created by ANSYS and a spatial submodel of the steel box girder is particularly built with greater detail. Submodeling method is then employed as a connection technique to link different scale models. After the global analysis and connecting process, the local stress of the steel box girder under various vehicle loads is obtained by submodel analysis. The composite action between the full model and the submodel is analyzed, and the reasonable mesh size for the submodel is specially investigated. The numerical results are proved to be accurate by the field test results. This study demonstrates the reliability and efficiency of the submodeling method; and can provide references for accurately analyzing and designing the steel box girders of other long span bridges.
Using Phased Array Beamforming to Identify Broadband Noise Sources in a Turbofan Engine
Authors: Sijtsma Pieter
Published: August 2010

Fan broadband noise is a major component of the total noise emitted by turbofan engines, especially at lower shaft speeds. It is generated in the rotor/stator region, but the exact origin is not always known. This article discusses the application of phased array beamforming techniques for a better understanding of the source mechanisms of fan broadband noise. The Conventional Beamforming technique was applied, as well as the deconvolution technique CLEAN-SC and the beamforming technique ROSI for rotating sources. Beamforming was applied to acoustic data measured by two circular microphone arrays that were mounted in the intake and in the bypass of a Rolls-Royce fan rig. These arrays are normally used for the detection of azimuthal modes. The merits of beamforming are discussed by considering a number of typical low shaft speed cases. Using the intake array, in one of the cases forward radiating broadband noise sources were found that were coherent over a large area. These could have been due to a rotor instability. In an other case, the forward radiating broadband noise seemed to have its origin at the stator vanes. This could be made plausible with the help of the intake mode detection results. Using the bypass array, stator bound noise sources were found that seemed to be distributed along the span of the vanes. In other words, tip sources seemed to be of minor importance for aft radiating fan broadband noise. The bypass mode detection results seemed to indicate that the spanwise distributed noise sources were located at the trailing edges of the stator vanes.
Relation between the Generalized Acoustic Analogy and Lilley's Contributions to Aeroacoustics
Authors: Goldstein M.E.
Published: August 2010

This paper reviews Lilley's reformulation of Lighthill's equation and shows that it can be obtained as a special case of a much more general acoustic analogy. It also shows how this generalized analogy can be used to eliminate some of the difficulties that arise when more conventional parallel flow analogies are applied to high speed jets. And, finally, some recent applications of these ideas are discussed.
Distributions of Noise Sources in Heated and Cold Jets: Are They Different?
Authors: Viswanathan K.
Published: August 2010

The axial extent of the high-speed flow region in a heated jet is much longer than its counterpart in an unheated jet at fixed Mach number. This trend has led some to believe that the source distributions would be different. Two specific questions are addressed in this study: (1) is the noise source distribution different for heated jets? and (2) is the distance to the true farfield longer for heated jets? The second question has practical significance as it impacts the measurement and processing of spectra. The assumption of a point source located at the nozzle exit plane is invoked in many tests – the condition for its validity is established for heated jets. Source distributions for heated and unheated jets have been measured with an elliptic mirror, for jets with a Mach number range of 0.5 to 1.9. The effect of jet temperature on the peak source location for the noise radiated to all the inlet angles in the range of 90° to 150° is negligible, both for the overall sound pressure level and individual frequencies. The effect of jet mach number is pronounced, with the peak source location moving downstream with increasing Mach number. Different approaches have been adopted for the establishment of the minimum distance to the true farfield for heated and unheated jets: microphone arrays at different distances together with nozzles of various diameters, microphones set at normal and grazing incidence, and the elliptic mirror. Both subsonic and supersonic jets have been considered. It is shown from detailed analyses that the distance to the true acoustic and geometric farfield is the same for heated and unheated subsonic jets, and is ∼37D (D is the jet diameter). The polar response characteristics of condenser microphones are examined to explain the observed good agreement of spectra between microphones located at ∼37D and larger distances. Finally, a minimum distance of ∼40D and a desirable distance of 50D or longer are recommended for true farfield measurements for subsonic jets. The minimum distance for supersonic jets is more nuanced: for unheated jets, a distance of 45D has been shown to represent the farfield. For highly heated supersonic jets, 45D again represents the farfield for the lower polar angles ≤∼100°. Rapid change in source directivity in the angular range of ∼100° to ∼125° dictates that a minimum distance of ∼70D for angles ≥∼100° might be prudent even though a shorter distance might be adequate for angles ≥∼130°. A good understanding of the source distributions and the radiation characteristics for different jet operating conditions, coupled with prudent test planning should help eliminate the nearfield effects in acoustic measurements.
Experimental Assessment of Low Noise Landing Gear Component Design
Authors: Dobrzynski Werner , Chow Leung Choi , Smith Malcolm , Boillot Antoine , Dereure Olivier , Molin Nicolas
Published: August 2010

Landing gear related airframe noise is one of the dominant aircraft noise components at approach, so continued research efforts to reduce landing gear noise are essential. This paper describes further development of an advanced low noise main landing gear that was previously designed and tested in the European SILENCER project. The work was carried out under the current European co-financed TIMPAN project (Technologies to IMProve Airframe Noise) using a ¼ scaled landing gear model that was tested in the German-Dutch Wind Tunnel. A variety of gear configurations were tested including a new side-stay design and various modifications to the bogie inclination, wheel spacing, bogie fairings with different flow transparency, leg-door configurations and brake fairings. The farfield noise data from the tests are compared with results from a landing gear noise prediction model, transposed to full scale flight conditions and compared with the full scale test data obtained for the original SILENCER advanced A340 style 4-wheel main landing gear. An optimal combination of tested gear modifications led to a further noise reduction of up to 8 dB(A) in terms of overall A-weighted noise levels relative to the original advanced gear configuration.
Digital Architectural Design as Exploration of Computable Functions
Authors: Kotnik Toni
Published: August 2010

In recent decades, new methodologies have emerged in architectural design that exploit the computer as a design tool. This has generated a varied set of digital skills and a new type of architectural knowledge. However, up to now, a theoretical framework is missing that would allow for a comprehensive pedagogical agenda for the teaching of digital design in architecture. The present paper offers an attempt towards such a theoretical grounding based on the concept of computable functions. This approach results in an abstract and formal perspective on digital design that enables a grouping of contemporary digital design methods and an understanding of their logical relationship. On a theoretical level, it opens a path for the study of the mechanism that facilitates the transfer of concepts from various scientific disciplines into architecture.
Automated 3D Reconstruction of Interiors from Point Clouds
Authors: Budroni Angela , Boehm Jan
Published: August 2010

We present a new technique for the fully automated 3D modelling of indoor environments from a point cloud. The point cloud is acquired with several scans and is afterwards processed in order to segment planar structures, which have a noticeable architectural meaning (floor, ceiling and walls) in the interior. The basic approach to data segmentation is plane sweeping based on a hypothesis-and-test strategy. From the segmentation results, the ground plan is created through cell decomposition by trimming the two-dimensional ground space using half-space primitives. An extension in height of the ground contours makes the generation of the 3D model possible. The so-reconstructed indoor model is saved in CAD format for analysis and further applications or, simply, as a record of the interior geometry.
Augmented Reality-Based Education and Fire Protection for Traditional Korean Buildings
Authors: Phan Viet Toan , Choo Seung Yeon
Published: August 2010

This study examines an application of Augmented Reality technology (AR) for Korean Cultural Traditional Buildings, specifically, the Namdaemun Gate, “National Treasure No 1” of the Republic of Korea. Unfortunately, in February 2008, the Namdaemun Gate burned down, despite the efforts of many firemen, as the main difficulty was getting the fire under control without any structural knowledge of the wooden building. Hence, with the great advances in digital technology, an application of virtual technical information to traditional buildings is needed, and the new technology of AR offers many such advantages for digital architectural design and construction fields. While AR is already being considered as new design approach for architecture, outdoor AR is another practical application that can take advantage of new wearable computer equipment (Head-mounted display also know as HMD, position and orientation sensors, and mobile computing) to superimpose virtual graphics of traditional buildings (in this case, Namdaemun Gate) in a real outdoor scene. Plus, outdoor AR also allows the user to move freely around and inside a 3D virtual construction, thereby offering important training opportunities, for example, specific structural information in the case of firemen and mission planning in the case of a real-life emergency. In this example, the proposed outdoor AR system is expected to provide important educational information on traditional wooden building for architects, archaeologists, and engineers, while also assisting firemen to protect such special buildings.
Tackling in Rugby: Coaching Strategies for Effective Technique and Injury Prevention
Authors: Hendricks Sharief , Lambert Michael
Published: August 2010

The high impact and physical nature of the tackle during a rugby match places the tackler(s) and ball-carrier at risk of injury. Injuries as a result of the tackle account for up to 61% of all injuries that occur during a rugby match. The purpose of this paper is to: i) review the literature on tackle injury mechanisms and events associated with increased risk of injury during the tackle; and ii) identify strategies that can be coached during training and executed by players during a match to reduce the risk of injury. Coaches equipped with a better understanding of injury mechanisms and a thorough knowledge of a safe and effective technique in the tackle have a major role in preventing or reducing tackle injuries.
The Assessment of Athletic Ability at the Junior College Level
Authors: Solomon Gloria B.
Published: August 2010

The means by which coaches select, develop, and evaluate their athletes is a topic of interest among sport scholars. Expectancy theory is one framework implemented to further understand the leadership behaviors of coaches. Results from previous research suggest that coaches use a wide variety of sources to develop and evaluate their players. Unfortunately, junior (also called community) college coaches have been omitted from this important work. The purpose of the present study was to query junior college coaches and their athletes regarding impression cues utilized to judge athlete ability. Thirty-four coaches and 210 athletes completed the Solomon Expectancy Sources Scale (SESS). Results determined that head and assistant coaches are consistent in their prioritization of expectancy sources. Coaches and athletes are also congruent; however, coaches rated Coachability significantly higher than athletes. These results are discussed in light of the unique position of the junior college coach.
Looking the other Way: Athletes' Perceptions of Coaches' Responses to Hazing
Authors: Kowalski Christopher , Waldron Jennifer
Published: August 2010

Framed within the psychosocial context of the sport ethic and social-approval goal orientation, this study qualitatively investigated athletes' perceptions of their coaches' involvement in hazing, as well as the role coaches should assume if hazing occurs. Twenty-one athletes volunteered from a number of classes associated with a Midwestern university's health, physical education, and leisure services division. The athletes participated in interviews regarding their involvement in hazing. Data analysis identified a variety of perceptions by participants associated with the coaches' role and actual involvement in team hazing experiences, including taking a proactive stance against hazing and accepting hazing. Implications of these findings to future research relate to the sport ethic, team building, social cohesion, and leadership in the athletic setting.
Training Characteristics of Male Junior Cross Country and Track Runners on European Top Level
Authors: Tjelta Leif Inge , Enoksen Eystein
Published: August 2010

The purpose of the present study was to describe training characteristics of distance junior runners at European top level. The athletes' training diaries for the 2008 season were analysed. The total training volume (km/week) performed over the different training periods was registered on five differentiated intensities. The results showed that during the building-up period for the season the junior runners ran an average of 132.5 ± 25.9 km/week. 78.3 ± 4.7 % of their weekly training distance (km/week) was continuous running with a heart rate (HR) between 62–82 % of maximum. During the track competition season the total weekly running distance was 115 ± 22.9 km/week. The training in the three last months before the European Cross Country Championship was very similar to the training in the building up period. In 2008, three of four tested V̇O2max, and the average was 79.2 ± 4.8 ml · kg-1 · min-1.
A Markov Chain Model of Elite Table Tennis Competition
Authors: Pfeiffer Mark , Zhang Hui , Hohmann Andreas
Published: August 2010

The evaluation of the structure of sports performance is one of the important functions of diagnostics in competitive sport. Especially in game sports, it is important to obtain diagnostic information on competition because of the interactive process between the two teams or players. This interaction cannot be simulated or replicated in training or test situations. When it comes to table tennis, performance diagnostics offers many different techniques and methods to analyze a game. In this context, problems mostly occur in adequately modelling the game. Moreover, the approaches lack a scope of uniform performance criteria. According to a stochastic performance diagnostic concept (Markov Chain) for game sports, we developed four different state-transition-models to describe tactical behaviour in table tennis: (1) game action, (2) stroke position, (3) stroke direction and (4) stroke technique. Afterwards we formalized these models by means of finite Markov Chain (stochastic modelling) to determine the relevance of tactical behaviour to performance by simulation. In this study, 152 games of the top 50 ranked male players in the world were analyzed. The results suggest that in international-level table tennis, the diagonal game from backhand to backhand (“stroke position”), strokes into the long backhand zone (“stroke direction”), and especially the topspin stroke for shake-hand players in general (“stroke technique”), are the most important winning tactical strategies. In comparison with traditional methods used in elite table tennis the approach described here is valuable in quantifying and comparing the relevance of various tactical behaviours to performance.
Changes in Stress and Recovery as a Result of Participating in a Premier Rugby League Representative Competition
Authors: King Doug , Clark Trevor , Kellmann Michael
Published: August 2010

The aim of this study is to monitor changes in stress and recovery of amateur rugby league players competing in a premier representative competition. A prospective observational cohort design was used in a rugby league match environment over the 2009 representative competition season with 30 registered members in the regional representative rugby league team. Members of the team completed the Recovery-Stress Questionnaire for Athletes (RESTQ-Sport) on the first training session following every scheduled match throughout the representative competition season. Injuries were reported as rate per 1,000 match hours. A repeated measure of analysis was used to evaluate differences in the RESTQ-Sport scale scores among the different measure taken. Significant changes were observed in Social Stress between weeks 1 and 4; Fatigue between pre-competition and week 5; and Lack of Energy between week 3 and week 4. The statistical differences observed in the Social Stress scale between weeks 4 and 5 may be related to the programming of the competition. Although the RESTQ-Sport did not predict any future performance or injury of the players, it did reflect how the players were dealing with the effects of amateur participation and the other requirements of life (work, relationships, etc.).
The Team-Mate Identification (TM-ID) Test: Effect of Participant and Situation Familiarity on Response Accuracy and Latency
Authors: Steel Kylie , Adams Roger , Canning Colleen , Eisenhuth John
Published: August 2010

In field and pool sports, players' running or swimming motor patterns appear to characterise them, and these ‘gait signatures' may aid in identifying players as team-mates. If this identification process was sufficiently brief to be relevant in ball sports, training to improve familiarity with team-mates' movement patterns may improve team performance. We examined time for Team-Mate Identification (TM-ID) decisions under different circumstances. 6 water-polo players (team-mate participants) and 6 club swimmers (unknown distractors) were filmed sprint swimming past two video cameras, one above and one below the water surface. The resulting footage was edited into two randomised series of video-clips. The water-polo players then viewed the clips and determined whether each observed swimmer was a team-mate or not, in the fastest possible time. Participants were faster with an overwater than an underwater view, significantly better than chance at identifying their team-mates, and did so in a mean time of 381 ms, which is within the normal window of time where expert sports people might be required to make time-stressed decisions.
Exploring High School Coaches' Implicit Theories of Motivation from a Self-Determination Theory Perspective
Authors: Iachini Aidyn , Amorose Anthony , Anderson-Butcher Dawn
Published: August 2010

According to Self-Determination theory, coaches' fulfillment of their athletes' psychological needs for competence, relatedness, and autonomy has strong implications for motivation in the sporting context. Given this, the purpose of the study was to understand whether coaches' implicit theories of motivation mirror Self-Determination theory and thus incorporate satisfaction of athletes' three psychological needs. Eleven high-school coaches were interviewed using a semi-structured interview guide. Data were analyzed through both inductive and deductive analytic procedures. Content analyses of the data found that these coaches use a variety of strategies to address the need for competence, but implement fewer strategies to support relatedness. Autonomy strategies were only discussed when specifically guided by the researchers. Two other findings also emerged from the data, including perceived barriers to implementing motivational strategies and differences in strategy utilization based on specific demographic indicators. Overall, findings from this study suggest that these coaches' implicit theories of motivation primarily focused on two of the three key tenets of Self-Determination theory. Implications of these findings for both research and practice are discussed.
Coaching Philosophies: Perceptions from Professional Cricket, Rugby League and Rugby Union Players and Coaches in Australia
Authors: Bennie Andrew , O'Connor Donna
Published: August 2010

This paper reports on the perceptions of effective coaching based on interviews with male professional coaches and players from cricket, rugby league, and rugby union in Australia. It is part of a larger research project into effective coaching in professional sport where the coach's philosophy reflected a key ingredient of a coach's perceived effectiveness. The findings from the current study show that coaches in these professional settings develop programs to assist players in acquiring on- and off-field skills. In addition to this, there is a tendency to focus on learning and improvement as opposed to a win-at-all-costs attitude. These philosophies highlight elements of a Humanistic approach to coaching which focuses on the total development of the person.
Towards a Theory of the Interactive Factors Implicated in Successful Individual Performance in Cricket
Authors: Sanctuary Colin , Smith Andrew , Thombs Barry
Published: August 2010

A longitudinal study, where qualitative data was grounded in the experiences of professional County Cricket players, suggests that it is an interaction of tactical, technical, psychological and environmental factors that determines good performance in cricket.

For coaches, it would appear important to help their players to understand how to reflect accurately on the determinants of their own performance. For players, it seems important that they understand the impact of technical and tactical factors on their psychological state, and the interaction of these variables. In addition, players need to reflect on how attributions to environmental factors may lead to either an appropriate or inappropriate evaluation of their performance.
Computing High-Frequency Scattered Fields by Beam Propagation Methods: A Prospective Study
Authors: Antoine Xavier , Huang Yuexia , Lu Ya Yan
Published: August 2010

This paper presents some theoretical and numerical investigations concerning the fast computation of an exterior wave field to a scatterer by the Beam Propagation Method (BPM). Different models are presented and compared. It appears that the approach is able to correctly model the propagation of the propagative modes of the wave field while inaccuracies still remain for the evanescent and transition modes.
Hash Functions Using Chaotic Iterations
Authors: Bahi Jacques M. , Guyeux Christophe
Published: August 2010

In this paper, a novel formulation of discrete chaotic iterations in the field of dynamical systems is given. Their topological properties are studied: it is mathematically proven that, under some conditions, these iterations have a chaotic behavior as defined by Devaney. This chaotic behavior allows us to propose a way to generate new hash functions. An illustrative example is detailed in order to show how to use our theoretical study in practice.
Implementing and Optimizing Multiple Group by Query in a MapReduce Approach
Authors: Pan Jie , Magoulès Frédéric , Le Biannic Yann
Published: August 2010

MapReduce model is a new parallel programming model initially developed for large-scale web content processing. Data analysis meets the issue of how to do calculation over extremely large dataset. The arrival of MapReduce provides a chance to utilize commodity hardware for massively parallel data analysis applications. The translation and optimization from relational algebra operators to MapReduce programs is still an open and dynamic research field. In this paper, we focus on a special type of data analysis query, namely, multiple group by query. We first study the communication cost of MapReduce model, then we give an initial implementation of multiple group by query. We then propose an optimized version which addresses and improves the communication cost issues. Our optimized version shows a better accelerating ability and a better scalability than the other version.
Distributed Computational Method for Coupled Fluid Structure Thermal Interaction Applications
Authors: Aulisa E. , Manservisi S. , Seshaiyer P. , Idesman A.
Published: August 2010

The problem of effcient modeling and computation of the nonlinear interaction of fluid with a solid undergoing nonlinear deformation has remained a challenging problem in computational science and engineering. Direct numerical simulation of the non-linear equations, governing even the most simplified fluid-structure interaction model depends on the convergence of iterative solvers which in turn relies heavily on the properties of the coupled system. The purpose of this paper is to introduce a distributed multilevel algorithm with finite elements that offers the flexibility and efficiency to study coupled problems involving fluid-structure interaction. Our numerical results suggest that the proposed computational methodology for solving coupled problems involving fluid-structure interaction is reliable and robust.
An Improvement of the Gibbs-Poole-Stockmeyer Algorithm
Authors: Feng GU
Published: August 2010

A pseudo-peripheral node was found by the Gibbs-Poole-Stockmeyer algorithm as the staring node for reducing bandwidth of a sparse matrix. This influences algorithm's performance because it is shown in this paper that eccentric distance of a pseudo-peripheral node may much less than diameter of the graph. The best selection of the staring node is a peripheral node whose eccentric distance is equal to diameter of the graph. A peripheral node finding algorithm was proposed in this paper. This algorithm can be applied to improvement of sparse matrix bandwidth reducing algorithms' performance. Correctness and efficiency of it were proved. Some computing experiments were done.
Identifying the Mesophilic and Thermophilic Proteins from Their Amino Acid Composition with ν-Support Vector Machines
Authors: Ding Y. R. , Cai Y. J. , Sun J. , Xu B. W.
Published: August 2010

Many researchers had proved that both single amino acid composition and dipeptide composition can influence protein thermostability. We use ν-support vector machines approach to predict hyperthermophilic protein, thermophilic protein and mesophilic protein from single amino acid composition, dipeptide composition and the combination of the two factors. For the prediction accuracies, we conclude that, single amino acid composition is suitable for prediction of mesophilic protein; dipeptide composition is suitable for prediction of hyperthermophilic protein and thermophilic protein; when considering the combination of the two factors, the prediction accuracy of hyperthermophilic protein is 84.1%, thermophilic protein is 83.4%, mesophilic protein is 84.4%, average accuracy is 84.0%. It shows that the protein thermostability can be predicted properly based on the combination of single amino acid composition and dipeptide composition. Obviously, dipeptide composition is correlative significantly to protein thermostability based on the prediction accuracies.
Parallel Solution Algorithm for the Multi-Group Particle Transport Equations on the Unstructured Meshes
Authors: Jie Liu , Li-Hua Chi , Jing Chen , Hongbin Zhuo , Han Xu , Jie Jiang , Qing-Feng Hu
Published: August 2010

The numerical simulations for solving the transport equations lead to the large computation and need to implement parallel calculation. On the unstructured grids, the communicating delays, sorting algorithms and inserting algorithms limit the performance of current algorithms, which decrease the scalable parallel performance. This paper presents an effective way to implement the scalable parallel numerical simulation on the clusters by combining the energy groups and the space domain decomposition. Based on the list schedule, we first design a multi-group parallel method to solve the load unbalance problem which is brought about by the energy group parallel decomposition. After we describe the priority algorithm to arrange the orders for all meshes, we present a parallel algorithm based on geometry domain decomposition. A parallel code combining those two algorithms was designed. Using the code, we solved a two dimension particle transport equations on a cluster, performance results show the algorithms have well scalability.
A Numerical Comparison of Spray Combustion between Raw and Water-in-Oil Emulsified Fuel
Authors: Tarlet D. , Bellettre J. , Tazerout M. , Rahmouni C.
Published: August 2010

Heavy fuel-oils, used engine oils and animal fat can be used as dense, viscous combustibles within industrial boilers. Burning these combustibles in the form of an emulsion with water enables to decrease the flame length and the formation of carbonaceous residue, in comparison with raw combustibles. These effects are due to the secondary atomization among the spray, which is a consequence of the micro-explosion phenomenon. This phenomenon acts in a single emulsion droplet by the fast (< 0.1 ms) vaporization of the inside water droplets, leading to complete disintegration of the whole emulsion droplet. First, the present work demonstrates a model of spray combustion of raw fuel. Secondly, the spray combustion of water-in-oil emulsified fuel is exposed to the same burning conditions, taking into account the micro-explosion phenomenon. Finally, the comparison between the results with and without second atomization shows some similar qualitative tendencies with experimental measurements from the literature.
Critical Review of Phenomenological Models for Studying Transient Combustion of Solid Propellants
Authors: Zarko V.E. , Gusachenko L.K.
Published: August 2010

A brief review of the existing generalizations of phenomenological model of solid propellants combustion, originally formulated by Ya. B. Zel'dovich in 1942, is presented. The model still remains valid and allows the description of different patterns of solid propellant transient combustion. However, over the years after this formulation was published, several publications appeared in the literature with assumptions that are not justified. Shortcomings of different model options and their limits of applicability are discussed. In fact, in some cases the attempts of model generalization are based on rather strong additional assumptions that lead to narrowing the applicability range of the model.
Reviewing and Investigating the Use of Co-Axial Rotor Systems in Small UAVs
Authors: Prior Stephen D.
Published: August 2010

Co-axial propeller systems have been used successfully in fixed-wing aircraft for many years due to their inherently good performance. Likewise, several pioneering rotary-winged aircraft projects used co-axial rotors, such as the Westland WG-25 Mote, Gyrodyne DASH, and a range of rotorcraft from Kamov in Russia. There has been much debate over the years about whether the co-axial rotor arrangement is more efficient than traditional layouts. Our findings point to the fact that although the co-axial arrangement has a reduced power output of up to 15% when compared to an equivalent single rotor system, this can be offset by the elimination of the need for a tail rotor, which could save up to 20% of the required power. It is only recently that this type of technology has reached the small UAV market in the form of a series of semi-autonomous and autonomous rotorcraft which are starting to make their mark in the military, homeland security and civilian fields. This paper investigates the use of such systems and discusses their advantages, disadvantages and performance metrics.
Simulation of the Steam-Bitumen Jet in the Fluidized Bed of Coke Particles Using the Eulerian-Lagrangian Splitting Method
Authors: Nowak Paul , Pougatch Konstantin , Salcudean Martha
Published: August 2010

Simulation of the steam-bitumen jet injected into the steam-coke fluidized bed is presented. The computational method is based on the Eulerian-Lagrangian splitting. The Eulerian two-fluid model is used for the steam and the coke phases; the latter is composed of dry and wet coke particles. The Lagrangian model is applied to the bitumen droplets and the primary bitumen-coke agglomerates, generated by the random collisions of the droplets with the coke particles. A simple primary agglomeration-breakup model based on the experimental evidence is used. The gravity and the fluidizing cross-flow are neglected. Consequently, the computational problem is led to the axisymmetric form. Realistic results were obtained for the steam parameters at the end of the nozzle, the jet half-angle, and the location of the areas with the predominant agglomerations and breakups. The composition and stability of the agglomerates, and the mass transfer between the agglomerates and the coke phase are investigated.
Ringing Response of Offshore Compliant Structures
Authors: Chandrasekaran Srinivasan , Gaurav Srinivasan , Jain A.K.
Published: August 2010

Ringing involves excitation of transient structural deflections at (or close to) structural frequency arising at the third-harmonic of incident wave field. Ringing waves are highly nonlinear containing strongly asymmetric transient waves and hence the shape of such waves becomes critical. This study develops mathematical formulation of impact waves responsible for ringing and examines their influence on offshore tension leg platforms (TLPs) with different geometric configurations located at different water depths. Based on the numerical studies conducted, it is found that the ringing response seen in pitch degree-of-freedom poses threat to platform stability. Also, undesirable response seen in stiff degree-of-freedom, like heave, emphasizes the necessity of the study for offshore compliant structures in deep waters, in particular.
Preparatory Tests with an Explorer Class Autonomous Underwater Vehicle for Missions under Sea Ice
Authors: Bose Neil , Lewis Ron S. , Adams Sara
Published: August 2010

The autonomous underwater vehicle (AUV) operations described here are preparatory missions to enable operation of an AUV under sea ice in polar regions. The proposed polar projects include operations under land fast ice in the Arctic through an ice moon pool and a planned project to assess sea ice mass balance and habitat assessment in the Southern Ocean in East Antarctica. This paper focuses on the preparatory missions, done in open water, and the planned Southern Ocean project. The plan is to use an autonomous underwater vehicle (AUV) for the under ice component of measurements. The ultimate goals are to quantify the size and shape of ridge keel structures and their contribution to the sea ice mass balance over a study region; to understand the processes that link sea ice with the distribution of ice algae and krill; to provide the necessary field measurements, over sufficiently large areas, for the calibration/validation of satellite and aircraft-based measurements of the sea ice and snow cover thickness; and to provide baseline measurements of sea ice thickness for future climate monitoring.
Estimation of Sway Velocity-Dependent Hydrodynamic Derivatives in Surface Ship Manoeuvring Using Ranse Based CFD
Authors: Janardhanan Sheeja , Krishnankutty P.
Published: August 2010

The hydrodynamic derivatives appearing in the manoeuvring equations of motion are the primary parameters in the prediction of the trajectory of a vessel. Determination of these derivatives poses major challenge in ship manoeuvring related problems. This paper deals with one such problem in which an attempt has been made to numerically simulate the conventional straight line test in a towing tank using computational fluid dynamics (CFD). Free-surface effects have been neglected here. The domain size has been fixed as per ITTC guide lines. The grid size has been fixed after a thorough grid independency analysis and an optimum grid size has been chosen in order to ensure the insensitivity of the flow parameters to grid size and also to have reduced computational effort. The model has been oriented to wider range of drift angles to capture the non-linear effects and subsequently the forces and moments acting on the model in each angle have been estimated. The sway velocity dependent derivatives have been obtained through plots and curve-fits. The effect of finite water depth on the derivatives has also been looked into. The results have been compared with the available experimental and empirical values and the method was found to be promising.
Hydro-Elastic Simulation of Stern Slamming and Whipping
Authors: Oberhagemann J. , Moctar O. El , Holtmann M. , Schellin T. , Bertram V. , Kim D.W.
Published: August 2010

Rational assessment of stern slamming of a large twin-screw LNG carrier comprised prediction of hydrodynamic impact loads and their effects on the dynamic global structural behaviour of the hull girder. Linear theory obtained regular equivalent waves that caused maximum relative normal velocities at critical locations underneath the ship's stern. Reynolds-averaged Navier-Stokes equation (RANSE) computations based on the volume of fluid (VOF) method yielded transient (nonlinear) hydrodynamic impact (slamming) loads that were one-way coupled to a nonlinear motion analysis of the ship in waves. Hydrodynamic loads acting on the hull were converted to nodal forces for a finite element model of the ship structure. Shape and duration of computed slamming pressures agreed well with full-scale measurements carried out on other ships, indicating that computed results captured all essential physical phenomena. Maximum slamming pressures were close to, but did not exceed classification society rule values. Hull girder whipping was analyzed to investigate dynamic amplification of structural stresses. The analyses indicated a significant amplification (up to 25%) of bending moments due to whipping.
Simulation of Propeller – Hull Interaction Using Ranse Solver
Authors: Prakash M.N. Senthil , Subramanian V. Anantha
Published: August 2010

This work simulates propeller-hull interaction effects by a novel method namely, coupling a Vortex Lattice Method (VLM) with a RANSE solver. The VLM generates the propeller forces based on the inputs of blade geometry, wake at propeller inlet, the required thrust and the propeller revolutions. The propeller forces thus obtained are distributed in the fluid domain at the propeller disk region at specific cells. These cells lie close to the blade coordinates and the forces are assigned to the centroids of cells by means of a user-defined function (UDF). The introduction of the body forces into the fluid domain, emulates the propeller action in the field of flow with consequent influences on the flow kinematics. Therefore the interaction effect between propeller and ship hull is simulated successfully by coupling the two methods. Thereby the kinematical aspects such as effective wake conditions are obtained. The results based on the methodology have been verified by comparison with data from the KCS ship available in recent published literature. The method establishes a successful numerical tank approach in understanding the ship hull-propeller interaction problem.
Spectral Fatigue Analysis of Jacket Stuctures in Mumbai High Field
Authors: Nallayarasu S. , Goswami S. , Manral J.S. , Kotresh R.M.
Published: August 2010

Fatigue analysis of offshore structures is an integral part of design of offshore structures and shall be carried out with suitable method of discretising the seastate. Historically, for most of the fixed offshore structures, deterministic fatigue analysis found to predict the fatigue damage reasonably well and has been in use for several decades. Fixed structures with small topsides, mostly exhibit a static response characteristics and the natural period may be in the order of less than 2 seconds. Offshore platforms with larger production capacity and deeper water depths may require specialised treatment of seastate due to their dynamic characteristics more vulnerable for fatigue damage. A spectral fatigue analysis has been performed for two different platforms in Mumbai high field (MNP and RS14) and a comparison is made with deterministic analysis. The spectral fatigue analysis indicates that the predicted fatigue life is lower than the deterministic analysis since the dynamic amplification of wave loads are treated approximately in deterministic analysis. Hence for large structures, it recommended to use spectral methods to assess the fatigue life of tubular joints.
Wave Height Distributions of Laboratory Generated Bimodal Seas with Abnormal Waves
Authors: Petrova P. G. , Soares C. Guedes
Published: August 2010

The study analyses bimodal data recorded in an offshore basin. The measured sea states represent two wave systems propagating at an angle of 60°, 90° and 120°, respectively, from each other. The wave spectra are separated into swell and wind sea components and the energy ratio between the areas under the associated curves (SSER) is estimated. The sea states are grouped into three classes with respect to SSER.

Abnormal waves are identified in the three classes of SSER, although the majority of the cases pertain to wind-sea dominated wave fields. The probabilities of exceedance of the individual wave heights for the sea states with abnormal waves are estimated and approximated with probabilistic models, which take into account either the spectral bandwidth or the wave nonlinearities. Strong correlation is found between SSER and the fourth order normalized cumulant of the surface elevation, Λ40.

The distributions for the maximum wave heights are constructed and compared with theoretical predictions depending only on the number of waves in the sample and Λ40. Furthermore, the probability of a wave to exceed a given threshold level conditional on Λ40 is compared with the theoretical estimates.
Low‐Power Implantable Device for Onset Detection and Subsequent Treatment of Epileptic Seizures: A Review
Authors: Salam Muhammad Tariqus , Sawan Mohamad , Nguyen Dang Khoa
Published: August 2010

Over the past few years, there has been growing interest in neuro‐responsive intracerebral local treatments of seizures, such as focal drug delivery, focal cooling, or electrical stimulation. This mode of treatment requires an effective intracerebral electroencephalographic acquisition system, seizure detector, brain stimulator, and wireless system that consume ultra‐low power. This review focuses on alternative brain stimulation treatments for medically intractable epilepsy patients. We mainly discuss clinical studies of long‐term responsive stimulation and suggest safer optimized therapeutic options for epilepsy. Finally, we conclude our study with the proposed low‐power, implantable fully integrated device that automatically detects low‐voltage fast activity ictal onsets and triggers focal treatment to disrupt seizure progression. The detection performance was verified using intracerebral electroencephalographic recordings from two patients with epilepsy. Further experimental validation of this prototype is underway.
Locomotor Training in Subjects with Sensori‐Motor Deficits: An Overview of the Robotic Gait Orthosis Lokomat
Authors: Riener R. , Lünenburger L. , Maier I. C. , Colombo G. , Dietz V.
Published: August 2010

It is known that improvement in walking function can be achieved in patients suffering a movement disorder after stroke or spinal cord injury by providing intensive locomotor training. Rehabilitation robots allow for a longer and more intensive training than that achieved by conventional therapies. Robot assisted treadmill training also offers the ability to provide objective feedback within one training session and to monitor functional improvements over time. This article provides an overview of the technical features and reports the clinical data available for one of these systems known as "Lokomat". First, background information is given for the neural mechanisms of gait recovery. The basic technical approach of the Lokomat system is then described. Furthermore, new features are introduced including cooperative control strategies, assessment tools and augmented feedback. These features may be capable of further enhancing training intensity and patient participation. Findings from clinical studies are presented covering the feasibility as well as efficacy of Lokomat assisted treadmill training.
Lying Posture Classification for Pressure Ulcer Prevention
Authors: Wai Aung Phyo , Foo Siang Fook , Huang Weimin , Biswas Jit , Hsia Chi-Chun , Liou Koujuch , Yap Philip
Published: August 2010

Pressure ulcers are a common problem among patients with limited mobility, such as those bed‐bound and wheelchair‐bound. Constant and prolonged applied pressure is one of the extrinsic factors contributing to the development of pressure ulcers. Analyzing lying postures together with interface pressure measurements from a pressure sensitive bed helps revealing pressure hot spots that can potentially lead to pressure ulcer development. We propose an intelligent system that features lying posture classification with pressure hot spots identification based on interface pressure measurements to possibly identify potential pressure ulcer risk and to provide effective preventive measures. Experimental outcomes correctly classify different lying postures with an accuracy of up to 93%. The proposed system is expected to assist caregivers to detect risk evidence and to provide timely and appropriate interventions for effective pressure ulcer prevention.