bluuebunny/crossref_metadata_2025 huggingface dataset:
A Prior and Data Validation and Adjustment Scheme for Bayesian Reliability Analysis in Engineering Design
Authors: Huang Zhaofeng , Jin Yan
Published: March 2011

Bayesian reliability analysis (BRA) technique has been actively used in reliability assessment for engineered systems. However, there are two key controversies surrounding the BRA, that is, the reasonableness of the prior, and the consistency among all data sets. These issues have been debated in Bayesian analysis for many years, and as we observed, they have not been resolved satisfactorily. These controversies have seriously hindered the applications of BRA as a useful reliability analysis tool to support engineering design. In this paper, a Bayesian reliability analysis methodology with a prior and data validation and adjustment scheme (PDVAS) is developed to address these issues. In order to do that, a consistency measure is defined first that judges the level of consistency among all data sets including the prior. The consistency measure is then used to adjust either the prior or the data or both to the extent that the prior and the data are statistically consistent. This prior and data validation and adjustment scheme is developed for Binomial sampling with Beta prior, called Beta-Binomial Bayesian model. The properties of the scheme are presented and discussed. Various forms of the adjustment formulas are shown and a selection framework of a specific formula, based on engineering design and analysis knowledge, is established. Several illustrative examples are presented which show the reasonableness, effectiveness and usefulness of PDVAS. General discussion of the scheme is offered to enhance the Bayesian Reliability Analysis in engineering design for reliability assessment.
Design of Energy Harvesting Technology: Feasibility for Low-Power Wireless Sensor Networks
Authors: Weaver Jason M. , Wood Kristin L. , Crawford Richard H. , Jensen Dan
Published: March 2011

In designing for a system’s lifecycle considerations, long-term energy needs often become an important limiting factor. Shifting from conventional energy sources (e.g. fossil fuels) toward renewable sources (e.g. wind and solar) has become a popular means for focusing on the lifecycle of large-scale systems like automobiles and the national electrical grid. This same shift in small, low-power systems such as sensors has the additional advantage of potentially increasing the operational life of the systems. This paper introduces a methodology for determining the feasibility of in situ energy harvesting as a viable power source for a given low-power system. The method is demonstrated by considering a wireless sensor node and the specific application of monitoring the fatigue life of highway bridges, with a target operational life of ten years for the sensor node. Peak and average power requirements for wireless sensor nodes are calculated and compared to the power density available from solar, wind, and vibration energy. Energy storage is also discussed, including both disposable batteries (as the status quo with which to compare energy harvesting) and rechargeable systems (as a necessary component of the energy harvesting system). Solar, wind, and vibration energy are all found to be feasible sources of power for this particular application. Vibration harvesting has lower power density than solar and wind harvesting, but has the advantage of being less dependent on location, more self-contained, and largely maintenance free. Energy harvesting in general only becomes attractive for projected life cycles exceeding the life of disposable batteries, which for this particular application is estimated at 4–6 years. Thus, energy harvesting is an excellent way to extend the lifespan of low-power systems where power availability is the limiting factor.
A Cable-Actuated Robotic Lumbar Spine for Palpatory Training of Medical Students
Authors: Karadogan Ernur , Williams Robert L.
Published: March 2011

This paper presents the kinematic and pseudostatic analyses of a fully cable-actuated robotic lumbar spine (RLS) which can mimic in vivo human lumbar spine movements to provide better hands-on training for medical students. The design incorporates five active lumbar vertebrae between the first lumbar vertebra and the sacrum, with dimensions of an average adult human spine. Medical schools can benefit from a tool, system, or method that will help instructors train students and assess their tactile proficiency throughout their education. The robotic lumbar spine has the potential to satisfy these needs in palpatory diagnosis. Medical students will be given the opportunity to examine their own patient that can be programmed with many dysfunctions related to the lumbar spine before they start their professional lives as doctors. The robotic lumbar spine can be used to teach and test medical students in their capacity to be able to recognize normal and abnormal movement patterns of the human lumbar spine under flexion-extension and lateral bending. This project focus is on palpation, but the spine robot could also benefit surgery training/planning and other related biomedical applications.
Control of an Underwater Biomimetic Vehicle Using Floquet Theory
Authors: Plamondon Nicolas , Nahon Meyer
Published: March 2011

Aqua is an underwater biomimetic vehicle designed and built at McGill University that uses six paddles to produce control and propulsion forces. It has the particularity of having time-periodic thrust due to its oscillating paddles. Using an existing model of the vehicle, two types of controller were developed: a PD controller and a Floquet controller. The Floquet controller has the advantage of explicitly addressing the time-periodicity of the system. The performance of the controllers was assessed experimentally in the Caribbean Sea. We find that the vehicle was able to follow the prescribed trajectories with relative accuracy using both controllers. However, the Floquet controller slightly outperforms the PD controller. Furthermore, a key advantage of the Floquet controller is that it requires no tuning while the PD controller had to be tuned by trial and error.
Applied Tests of Design Skills: Divergent Thinking Data Analysis and Reliability Studies
Authors: Shah Jami J. , Millsap Roger E. , Woodward Jay , Smith S. M.
Published: March 2011

A number of cognitive skills relevant to conceptual design were identified. They include Divergent Thinking, Visual Thinking, Spatial Reasoning, Qualitative Reasoning and Problem Formulation. A battery of standardized tests have been developed for these skills. We have previously reported on the contents and rationale for divergent thinking and visual thinking tests. This paper focuses on data collection and detailed statistical analysis of one test, namely the divergent thinking test. This particular test has been given to over 500 engineering students and a smaller number of practicing engineers. It is designed to evaluate four direct measures (fluency, flexibility, originality, quality) and four indirect measures (abstractability, afixability, detailability, decomplexability). The eight questions on the test overlap in some measures and the responses can be used to evaluate several measures independently (e.g., fluency and originality can be evaluated separately from the same idea set). The data on the 23 measured variables were factor analyzed using both exploratory and confirmatory procedures. Two variables were dropped from these exploratory analyses for reasons explained in the paper. For the remaining 21 variables, a four-factor solution with correlated (oblique) factors was deemed the best available solution after examining solutions with more factors. Five of the 21 variables did not load meaningfully on any of the four factors. These indirect measures did not appear to correlate strongly either among themselves, or with the other direct measures. The remaining 16 variables loaded on four factors as follows: The four factors correspond to the different measures belonging to each of the four questions. In other words, the different fluency, flexibility, or originality variables did not form factors limited to these forms of creative thinking. Instead the analyses showed factors associated with the questions themselves (with the exception of questions corresponding to indirect measures). The above four-factor structure was then taken into a confirmatory factor analytic procedure that adjusted for the missing data. After making some adjustments, the above four-factor solution was found to provide a reasonable fit to the data. Estimated correlations among the four factors (F) ranged from a high of .32 for F1 and F2 to a low of .06 for F3 and F4. All factor loadings were statistically significant.
A Nonlinear Electromechanical Model of a Scalable Self-Excited Wind Energy Harvester
Authors: Bibo Amin , St. Clair Daniel , Sennakesavababu Venkata R. , Li Gang , Daqaq Mohammed F.
Published: March 2011

We present and validate a nonlinear aero-electro-mechanical model that describes the response of a scalable self-excited wind energy harvester. Similar to music-playing harmonica that create tones via oscillations of reeds when subjected to air blow, the proposed device uses flow-induced self-excited oscillations of a piezoelectric beam embedded within a cavity to generate electric power. Specifically, when the volumetric flow rate of air past the beam exceeds a certain threshold, the energy pumped into the structure via nonlinear pressure forces offsets the intrinsic damping in the system setting the beam into self-sustained limit-cycle oscillations. The vibratory energy is then converted into electricity through principles of piezoelectricity.
Probability Tolerance Maps: A New Statistical Model for Non-Linear Tolerance Analysis Applied to Rectangular Faces
Authors: Khan Nadeem S. , Shah Jami J. , Davidson Joseph K.
Published: March 2011

A new statistical model for the tolerance analysis based upon joint probability distribution of the trivariate normal distributed variables involved in the construction of Tolerance-maps (T-Maps) for rectangular face is presented. Central to the new model is a Tolerance-Map (T-Map) (Patent No. 69638242). It is the range of points resulting from a one-to-one mapping from all the variational possibilities of a perfect-form feature, within its tolerance-zone, to a specially designed Euclidean point-space. The model is fully compatible with the ASME/ANSI/ISO Standard for geometric tolerances. In this research, 4D probability T-Maps (prob T-Maps) have been developed in which the probability value of a point in space is represented by the size of the marker and the associated color. Additionally, 3D prob T-Maps (3D cross sections of the 4D prob T-Maps at pre specified values) are used to represent the probability values of two variables at a time for a constant value of the third variable on a plane. Superposition of the probability point cloud with the T-Map clearly identifies which points are inside and which are outside the T-Map. This represents the pass percentage for parts manufactured with the statistical parameters such as mean and standard deviation as of the assumed trivariate probability distribution. The effect of refinement with form and orientation tolerance is highlighted by calculating the change in pass percentage with the pass percentage for size only. Delaunay triangulation and ray tracing algorithms have been used to automate the process of identifying the points inside and outside the T-Map. Proof of concept software has been implemented to demonstrate this model and to determine pass percentages for various cases. The model is further extended to assemblies by employing convolution algorithms on two trivariate statistical distributions to arrive at the statistical distribution of the assembly. Accumulation T-Maps generated by using Minkowski Sum techniques on the T-Maps of the individual parts is superimposed on the probability point cloud resulting from convolution. Delaunay triangulation and ray tracing algorithms are employed to determine the assemleability percentages for the assembly.
Simulation and Experimental Studies of Electrothermal Behaviors of Microwire Initiators for Fusing Applications
Authors: Jang Seongjin , Du Sarah , Pochiraju Kishore , Manoochehri Souran
Published: March 2011

Microwire initiators enhance the output pressure and reduce the required input voltage for the explosives initiation in fusing applications due to large surface areas and high electrical and thermal conductivities. We investigated electrothermal behavior of Cu and Au microwires with diameters in the range of 25∼100 μm. Microwires with smaller diameter ignited quickly and required the lower input voltage to be ignited. A low impedance circuit was used in order to apply relatively low voltages but high current density to the initiator wire. We investigated the ignition process theoretically by combining an electric circuit model and a specific current action model related to phase changes. The theoretical calculations are in good agreement with the experimental observations in terms of the burst time and voltage rise profile.
Development of a Five-Bar Parallel Robot With Large Workspace
Authors: Campos Lucas , Bourbonnais Francis , Bonev Ilian A. , Bigras Pascal
Published: March 2011

Five-bar planar parallel robots for pick and place operations are always designed so that their singularity loci are significantly reduced. In these robots, the length of the proximal links is different from the length of the distal links. As a consequence, the workspace of the robot is significantly limited, since there are holes in it. In contrast, we propose a design in which all four links have equal lengths. Since such a design leads to more parallel singularities, a strategy for avoiding them by switching working modes is proposed. As a result, the usable workspace of the robot is significantly increased. The idea has been implemented on an industrial-grade prototype and the latter is described in detail.
Tetrahedral Mesh-Based Embodiment Design
Authors: Serna Sebastian Pena , Stork Andre , Fellner Dieter W.
Published: March 2011

The engineering design is a systematic approach implemented in the product development process, which is composed of several phases and supported by different tools. Computer-Aided Design (CAD) and Computer-Aided Engineering (CAE) tools are particularly dedicated to the embodiment phase and these enable engineers to design and analyze a potential solution. Nonetheless, the lack of integration between CAD and CAE restricts the exploration of design variations. Hence, we aim at incorporating functionalities of a CAD system within a CAE environment, by means of building a high level representation of the mesh and allowing the engineer to handle and manipulate semantic features, avoiding the direct manipulation of single elements. Thus, the engineer will be able to perform extruding, rounding or dragging operations regardless of geometrical and topological limitations. We present in this paper, the intelligence that a simulating mesh needs to support, in order to enable such operations.
Requirement Modeling Systems for Mechanical Design: A Systematic Method for Evaluating Requirement Management Tools and Languages
Authors: McLellan James Michael , Morkos Beshoy , Mocko Gregory G. , Summers Joshua D.
Published: March 2011

Requirements engineering has received increased attention in mechanical design as systems have become increasingly complex. Requirements engineering involves several key activities including eliciting, modeling, and analyzing requirements. Problems with requirements engineering include addressing requirements generated from multiple design perspectives, communicating requirements across the design team, and understanding how requirements affect other product design information. Several requirement management tools have been developed to address these issues. However, evaluating the capabilities of current and next generation tools has not been systematically addressed. In this paper, a systematic approach and example problem are developed to evaluate the capability of modern requirements management tools. First, eight capabilities are identified from existing literature and industry design problems. Next, a baseline example problem is developed and implemented in two requirement management tools, namely IBM DOORS and NoMagic MagicDraw+SysML. The evaluation results show that each software tool addresses seven of the eight capabilities to a varying degree, with the exception of input validation of an individual requirement. Further, SysML offers a robust and descriptive set of relationships for modeling complex engineering systems that are useful for requirements analysis. Finally, the research is not intended to be a complete survey of all requirements management tools, but rather to provide a repeatable and systematic method for evaluating and developing requirements management tools.
Role of Automated Symbolic Generation of Equations of Motion in Mechanism and Robotics Education
Authors: Shah Hrishi , Tripathi Sumit , Lee Leng-Feng , Krovi Venkat
Published: March 2011

In recent years there has been a significant increase in the variety and complexity of Articulated-Multi-Body-Systems (AMBS) used in various applications. There is also increased interest in the model-based design-refinement and controller-development, which is critically dependent upon availability of underlying plant-models. Kinematic and dynamic plant-models for AMBSs can be formulated by systematic application of physics postulates. This process, in its various variants, forms the basis of various mechanisms/robotics courses. However, the type and complexity of the example systems is often limited by the tractability of first generating and subsequently analyzing complex equations-of-motion. Nevertheless, using simpler examples alone may sometimes fail to capture important physical phenomena (e.g. gyroscopic, coriolis). Hence, we examine the use of some contemporary symbolic- and numeric-computation tools to assist with the automated symbolic equation generation and subsequent analysis. We examine a host of examples beginning with simple pendulum, double pendulum; building up to intermediate examples like the four-bar mechanism and finally examine the implementation of 3-PRR and 3-RRR planar parallel platform mechanisms. The principal underlying philosophy of our effort is to establish linkage between traditional modeling approaches and use of these contemporary tools. We also try to make a case for use of automatic symbolic computation and manipulation as a means for enhancing understanding of both basic and advanced AMBS concepts. Lastly, we document our efforts towards creation of self-paced tutorials and case-studies that serve to showcase the benefits.
Suppression of String Vibration Using a Constraint Actuator at One Boundary
Authors: AlSahlani Assaad , Mukherjee Ranjan
Published: March 2011

The problem of a vibrating string subjected to a sudden constraint at one boundary is investigated in this paper. The constraint is imposed by a sleeve that axially moves along the mean position of the string with a small distance. The constraint is applied instantaneously such that the geometry of the string outside the sleeve, immediately after application of the constraint, remains unchanged whereas the length of string covered by the sleeve remains at rest. The change in energy of the string after application and removal of the sleeve is investigated for different values of sleeve travel distance and time of application of the constraint. Analytical and numerical simulation results are first provided for the string vibrating in the first mode, and then for a more general case where the string has arbitrary initial conditions. The results show that the energy content can decrease or increase depending on the time of application of the constraint and sleeve travel distance. This provides the opportunity for active control of string vibration through direct physical interaction with a small portion of the string by using the sleeve as an actuator.
External Disturbances and Coupling Mechanisms in Underactuated Hands
Authors: Balasubramanian Ravi , Belter Joseph T. , Dollar Aaron M.
Published: March 2011

With the goal of improving the performance of underactuated robotic hands in grasping, we investigate the influence of the underlying coupling mechanism on the robustness of underactuated hands to external disturbance. This paper identifies unique behaviors in the hand’s response as a function of the coupling mechanism and the actuation mode the hand is operated in. Specifically, we show that in conditions when the actuator position is fixed, hands with single-acting mechanisms exhibit a bimodal behavior in contrast to hands with double-acting mechanisms that exhibit a unimodal behavior. We then present an analysis of how these behaviors influence grasping capability of the hand and then discuss implications for underactuated hand design and operation.
Extraction and Transfer of Biological Analogies for Creative Concept Generation
Authors: Cheong Hyunmin , Chiu Ivey , Shu L. H.
Published: March 2011

Biomimetic design, which borrows ideas from nature to solve engineering problems, has been identified as a promising method of concept generation. However, there are still many challenges. Previous research has revealed that novice designers have difficulties in extracting the analogical strategy present in biological phenomena and mapping the strategy even if the strategy is provided. This research, therefore, attempts to develop tools that could assist novice designers to execute effective biomimetic design and ultimately generate creative concepts. In particular, we investigated the use of tools developed by the authors: 1) a causal relation template that helps retrieve relevant strategies from biological descriptions and 2) instructional mapping rules that aid structural mapping of the strategies to design concepts and abstraction of the enabling functions of the strategies. We found that the participants who used both tools generated concepts with significant correlation between the correctness of analogical transfer and creativity of the concepts. This effect was not observed for the participants who only used the first tool, mainly because of the participants’ inability to explore enabling solutions for the applied biological strategy and generate concepts that are wholly developed. To encourage generation of creative ideas in biomimetic design, the tools must be devised to facilitate abstraction of biological strategies, enable effective mapping of strategies from biology to engineering, and discourage design fixation.
A Comparison of Formal Methods for Evaluating the Language of Preference in Engineering Design
Authors: Honda Tomonori , Yang Maria C. , Dong Andy , Ji Haifeng
Published: March 2011

In design, as with many fields, the bases of decisions are generally not formally modeled but only talked or written about. The research problem addressed in this paper revolves around the problem of modeling the direct evaluation of design alternatives and their attributes as they are realized in linguistic communication. The question is what types of linguistic data provide the most reliable linguistic displays of preference and utility. The paper compares two formal methods for assessing a design team’s preferences for alternatives based on the team’s discussion: APPRAISAL and Preferential Probabilities from Transcripts (PPT). Results suggest that the two methods are comparable in their assessment of preferences. This paper also examines the nature of consistency in the way design teams consider the attributes of a design. Findings suggest that assessment of an attribute can change substantially over time.
Teaching Multiple Approaches to Engineering Design Within a Unified Curriculum
Authors: Nagel Robert L. , Poppa Kerry , Stone Robert B.
Published: March 2011

This paper presents a comparison on four different, yet complimentary, design methods: (1) Pahl and Beitz’s Systematic Approach to Design, (2) Suh’s Axiomatic Design, (3) Altshuller’s Theory of Inventive Problem Solving and (4) Ulwick’s Outcome-Driven Method. To compare these approaches to design, a general definition and process for design is first derived from common engineering design texts. After a general description of each of these design approaches is presented, a comparison is made between each design approach and the general design method. The paper is concluded with the proposal of an integrated curriculum for teaching the methods within the scope of a single design course.
Querying and Reasoning With Product Engineering Ontologies: Moving Past Modeling
Authors: Zhu Lijuan , Jayaram Uma , Jayaram Sankar , Kim OkJoon
Published: March 2011

Much of the work in ontologies for product engineering has focused on the modeling of these ontologies. A key characteristic of an ontology model is that it uses a logic-based and formal specification to represent the information model, thus allowing querying and reasoning. In order to take advantage of this, we seek to move past ontology modeling and focus on developing meaningful reasoning mechanisms that are applicable for the domain of product engineering — a) to allow the user to make basic inferences such as checking consistency for definitions of concepts, b) to query and retrieve existing product data information, and c) to derive new product data information not explicitly expressed in knowledge bases. A typical semantic application architecture consisting of knowledge base layer, logic reasoning layer, and application interface layer is adopted. Reasoning units are deployed in the logic reasoning layer of this architecture. These reasoning units act on the knowledge base for product engineering, specifically, the domain of product assembly constraint. SWRL & SQWRL are used to define the retrieval specifications and inference rules. User interfaces are also developed to help users submit the reasoning tasks, view the results, and thus assess the knowledge base indirectly and transparently. It is concluded that the reasoning mechanism exploits and extends the semantic representation made possible through ontology and holds promise for improved knowledge discovery and understanding.
Augmented Reality Visualization of Automobile Air Conditioning Using Optical Tracking Tools
Authors: Willmann Rita T. , Woessner Uwe
Published: March 2011

Virtual prototyping allows us to reduce the expensive production of real prototypes to a minimum and shorten vehicle development phases. Augmented Reality (AR) visualization is a demonstrative and intuitive tool in order to overlay physical prototypes with virtual content and thus comprehend complex relationships quickly. Further, AR technologies can intensify the collaboration between specialists with different expert knowledge and support common decision making during reviews meetings. However, the existing work processes, software tools and predefined regulations do not permit the use of AR tools in all automotive areas. In this work, a prototypical AR application, based on optical tracking tools, was set up in a real automotive environment and evaluated in terms of its applicability for CFD simulation data in the passenger compartment. The examination provides valuable information about environmental conditions, requirements from end users as well as the integration in existing work processes. The results are a basis for future improvements in order to offer a seamless and automated workflow in an early state of the development process and for maintenance.
Parallel Ellipsoid Collision Detection With Applications in Contact Dynamics
Authors: Pazouki Arman , Mazhar Hammad , Negrut Dan
Published: March 2011

This work concentrates on the contact detection of ellipsoids, an enhancement to collision detection which can be used to study the dynamics of multibody systems with frictional contact. A first method for contact detection is posed as an unconstrained optimization problem. This method, while computationally demanding, can find the contact parameters as well as determine the state of the contact of two ellipsoids. Next, a method is presented that is approximately two orders of magnitudes more efficient in finding the contact state of two ellipsoids. However, it cannot find the contact parameters such as contact normal, depth of penetration, etc. Finally, a parallel algorithm for the ellipsoid contact detection problem is presented. The algorithm is implemented on a ubiquitous Graphics Processing Unit (GPU) card and shown to achieve a speedup of up to 70× over a Central Processing Unit (CPU) based method. The proposed methodology is expected to have an impact in granular flow dynamics applications.
An Exploration of Buckling Modes and Deflection of a Fixed-Guided Beam
Authors: Holst Gregory L. , Teichert Gregory H. , Jensen Brian D.
Published: March 2011

This paper explored the deflection and buckling of fixed-guided beams. It uses an analytical model for predicting the reaction forces, moments, and buckling modes of a fixed-guided beam undergoing large deflections. One of the strengths of the model is its ability to accurately predict buckling behavior and the buckled beam shape. The model for the bending behavior of the beam is found using elliptic integrals. A model for the axial deflection of the buckling beam is also developed based on the equations for stress and strain and the buckling profile of the beam calculated with the elliptic integral solution. These two models are combined to predict the performance of a beam undergoing large deflections including higher order buckling modes. The force vs. displacement predictions of the model are compared to the experimental force vs. deflection data of a bistable mechanism and a thermomechanical in-plane microactuator (TIM). The combined models show good agreement with the force vs. deflection data for each device. The paper’s main contributions include the addition of the axial buckling model to existing beam bending models, the exploration of the deflection domain of a fixed-guided beam, and the demonstration that nonlinear finite element models may incorrectly predict a beam’s buckling mode unless unrealistic constraints are placed on the beam.
A Distance-Based Multi-Criteria Decision Making Approach to Problem of Supplier Involvement in New Product Development
Authors: Akman Gu¨ls¸en , O¨tku¨r F. Mine , Okudan Gu¨l E.
Published: March 2011

Because of rising global competition and more rapid technological changes, the need for faster development of products with higher quality and reliability has increased, also elevating the importance of supplier involvement. Accordingly, companies give high priority to development of relationships with their suppliers, including collaborative product development. This paper focuses on evaluating current suppliers, which are to be involved in design decisions and product development processes. First, an overview of the supplier involvement in product development process is described. Then, a questionnaire form is introduced, which was administered to 40 automotive suppliers to determine the supplier selection criteria’s importance levels. Survey results were evaluated using statistical means for reliability and suitability. Finally, in order to select the best supplier, results were evaluated using a method integrating Analytical Network Process (ANP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). The evaluation criteria were weighted with ANP, and then supplier companies were ranked using TOPSIS methodology.
The Design, Fabrication, and Performance of the East African Trial Leveraged Freedom Chair
Authors: Winter Amos G. , Bollini Mario A. , DeLatte Danielle H. , Judge Benjamin M. , O’Hanley Harrison F. , Pearlman Jonathan L. , Scolnik Natasha K.
Published: March 2011

The Leveraged Freedom Chair (LFC) is a lever-powered, wheelchair-based mobility aid designed specifically for use in the developing world. Its drivetrain optimally converts upper body power in a wide range of terrains, giving the LFC operational capabilities that extend beyond those of currently available mobility products. In this work we present the design and analysis process used to create an LFC for trial in East Africa. All of the moving parts in the LFC are made from bicycle components and the entire chair can be fabricated without any machining processes. This allows the LFC to be manufactured for the same price as existing mobility aids and repaired anywhere in the developing world. Eight prototypes were produced in Kenya during August 2009, with six distributed to mobility aid users throughout East Africa. After four months of testing, the subject-averaged propulsion efficiency using the LFC was 20% greater than that of existing mobility products. Performance results and feedback from the subjects indicate that the LFC is ideally suited for active wheelchair users who require the seating and postural support of a wheelchair, and who desire to travel on rough terrain under their own power. Test subjects’ input was also used to codify future improvements to the LFC design, including narrowing the stance of the chair and lowering the rider’s center of gravity.
On the Criteria for Choice of the Best Solution From a Generated Set of Partially Compliant Linkages
Authors: Naik Sujitkumar V. , Saxena Anupam , Rai Ashok Kumar
Published: March 2011

Linkages are broadly classified as rigid-body, partially and fully compliant, capable of accomplishing a specified kine(tostatic)matic task. Path generating partially compliant linkages can generate prescribed non-smooth paths with high fidelity. Kempe’s linkages too can trace the non-smooth paths. But their complexity makes partially compliant linkages superior in terms of compactness and connectivity. A unified procedure to synthesize a solution set of all path generating linkage kinds is implemented in [1]. While there can be many solutions that can satisfy a given kinematic objective, choosing one may not be straightforward. This work proposes a set of criteria to choose the best linkage design. The proposed criteria are categorized as General and Specific. General criteria are applied to evaluate the solutions for any application whereas Specific criteria pertain to the application at hand. As an example, the solutions are generated for the displacement delimited gripper using the unified procedure. The solutions are then evaluated by the user with respect to these criteria. The solution appraisal is performed using a variant of the Pugh’s decision matrix and thereafter, the best solution is identified.
Investigation of Stall Events of a Modern Aircraft Engine
Authors: Zeid Abe , Kamarthi Sagar , Leary Steve , Mooney Thomas , Millar Richard C.
Published: March 2011

In this paper we present a neural network-based approach to predict engine stall events 2 seconds prior to their occurrence. The objective of this effort is to use engine and aircraft data to investigate stall events that have occurred on a modern gas turbine engine and to use that data to develop methods to predict stall events probabilistically. Engine data included pre-stall event data for multiple stall events, take-off trend data for the flights when the stalls occurred, and flight data for dozens of flights. The results indicate that neural network-based approach is able predict 99 out of 100 the stall events with a false alarm rate of 12%. The insights gained through this research can be used for developing an elaborate probabilistic model for predicting stall events.
Synthesis and Analysis of Slider-Crank Mechanism Motions
Authors: Chen Hsin-Pao , Tsay Der-Min , Huey Cecil O.
Published: March 2011

Slider-crank mechanisms used in open/close motion from toggle positions can be driven at the crank by many devices. Usually, the slider motion is defined first to synthesize crank motion. When slider motion has acceleration continuity only, crank acceleration is discontinuous causing shock loading at high speeds. To avoid such behavior, motion constraints must be assigned up to ping continuity at the limiting positions. This paper presents kinematic motion equations of slider-crank mechanisms with input from both the slider and crank. Toggle and limiting positions having required transmission angles at varied link ratios are determined. Motion functions that yield continuous crank acceleration are demonstrated.
Design and Application of Chattering-Free Sliding Mode Controller to Cable-Driven Parallel Robot Manipulator: Theory and Experiment
Authors: Zeinali Meysar , Khajepour Amir
Published: March 2011

High-performance robust controller design for nonlinear uncertain dynamical systems such as cable-driven parallel robot manipulators is a challenging work. In this paper, a new and systematic approach to combine sliding mode control, adaptive control design techniques and PID control for tracking control of cable-driven parallel robot manipulators, in the presence of model uncertainties is presented. In the proposed method, structured (parametric) and unstructured (un-modeled) uncertainties are lumped into one term and one uncertain parameter (term) is considered corresponding to each degrees of freedom of robot manipulator. Therefore, the problem of computation burden and large number of parameters, which are not addressed in the literature, is solved to a large extent. The global uniform ultimate boundedness stability is obtained in the presence of fast time-varying uncertainties. The simulation and experimental results revealed that the proposed method is robust against uncertainties and its simplicity makes the approach attractive for industrial applications.
Safety of Spur Gear Design Under Non-Ideal Conditions With Uncertainty
Authors: Stoker Kyle , Chaudhuri Anirban , Kim Nam Ho
Published: March 2011

The current practice of gear design is based on the Lewis bending and Hertzian contact models. The former provides the maximum stress on the gear base, while the latter calculates the contact pressure at the contact point between the gear and pinion. Both calculations are obtained at the reference configuration with ideal conditions; i.e., no tolerances and clearances. The first purpose of this paper is to compare these two analytical models with the numerical results, in particular, using finite element analysis. It turns out that the estimations from the two analytical equations are closely matched with those of the numerical analysis. The numerical analysis also yields the variation of contact pressures and bending stresses according to the change in the relative position between gear and pinion. It has been shown that both the maximum bending stress and contact pressure occur at non-reference configurations, which should be considered in the calculation of a safety factor. In reality, the pinion-gear assembly is under the tolerance of each part and clearance between the parts. The second purpose of this report is to estimate the effect of these uncertain parameters on the maximum bending stress and contact pressure. For the case of the selected gear-pinion assembly, it turns out that due to a 0.57% increase of clearance, the maximum bending stress is increased by 4.4%. Due to a 0.57% increase of clearance, the maximum contact pressure is increased by 17.9%.
Guiding Strategies for the Assembly of Micro-Components Subjected to Planar Pull-Off Force
Authors: Rabenorosoa Kanty , Cle´vy Ce´dric , Rakotondrabe Micky , Lutz Philippe
Published: March 2011

During micro-assembly processes, planar contacts often appear (between two manipulated components, one manipulated component and its gripping tool or substrate). Adhesion forces being predominant at the microscale, such contacts have important consequences on assembly strategies. One of these adhesion forces is the pull-off force which is the necessary force to break a contact. This article focuses on the measurement of pull-off force of micrometric planar contacts (50×50 μm2) and shows that it can be in the range of several hundreds of microNewtons. Consequences of this pull-off force on assembly strategy, especially guiding tasks, are then introduced. A strategy based on a force study is applied on teleoperated assembly sequences and validates the proposed guiding strategy. The study also enables to establish design rules that are specific for the microscale and that can be applied to the field of MOEMS assembly.
Moment-Dependent Pseudo-Rigid-Body Models for Straight Beams
Authors: Espinosa Diego A. , Lusk Craig P.
Published: March 2011

This paper introduces a parametric beam model for describing the kinematics and elastic properties of ortho-planar compliant beams subject to specific buckling loads. This model uses an approach similar to the Pseudo-Rigid-Body Model but differs that in a key parameter, the characteristic radius factor, is not a constant, but a rational function of the moment. The rational function coefficients are determined by least squares, along with the statistical significance of the coefficients. Results are calculated for straight beams for two cases: a vertical displacement and a horizontal displacement.
Science Translational Medicine
Podcast: 23 March 2011
Authors: Chan Timothy , Colmone Angela
Published: March 2011

A conversation with Timothy Chan about a new way to predict breast cancer metastasis.
Two Peas in a Pod
Authors: Farrell Ruth M.
Published: March 2011

Eclampsia and preeclampsia may be branches off a common event that takes place at the utero-placenta junction.
Genetic Tug of War in the Immune System
Authors: Niewold Timothy B.
Published: March 2011

A genome-wide association study uncovers loci that confer risk for an immune-mediated kidney disease.
Population attributable risk for chlamydia infection in a cohort of young international travellers (backpackers) and residents in Australia
Authors: Wand Handan , Guy Rebecca , Donovan Basil , McNulty Anna
Published: March 2011

Aim

To estimate the population attributable risk (PAR) forChlamydia trachomatisinfection in young men and women in Sydney, Australia.

Method

Multivariate logistic regression was used to examine the association between demographic, sexual behaviour and other potential risk factors and chlamydia positivity in young (≤30 years) heterosexual international travellers (backpackers) and Australian residents attending a sexual health clinic. Point and interval estimates of PAR were calculated to quantify the proportion of chlamydia infections that can theoretically be prevented if a combination of risk factors is eliminated from a target population.

Results

In males, the PAR associated with inconsistent condom use in the past 3 months was 65% (95% CI 56% to 71%) in backpackers compared to 50% (95% CI 41% to 56%) in non-backpackers and the PAR associated with reporting three or more female sexual partners in the past 3 months was similar between male backpackers and non-backpackers (33% (95% CI 28% to 40%) and 36% (95% CI 32% to 41%), respectively). In females, the PAR associated with inconsistent condom use in the past 3 months was 51% (95% CI 42% to 59%) in backpackers compared to 41% (95% CI 31% to 51%) in non-backpackers, and the PAR associated with reporting three or more male sexual partners in the past 3 months was 14% (95% CI 11% to 18%) in backpackers compared to 30% (95% CI 25% to 37%) in non-backpackers.

Conclusion

These findings suggest that the largest number of chlamydia infections could be avoided by increasing condom use, particularly in backpackers. Reporting multiple partners was also associated with a large proportion of infections and the risk associated with this behaviour should be considered in health promotion strategies.
The NOTA study: non-operative treatment for acute appendicitis: prospective study on the efficacy and safety of antibiotic treatment (amoxicillin and clavulanic acid) in patients with right sided lower abdominal pain
Authors: Tugnoli Gregorio , Giorgini Eleonora , Biscardi Andrea , Villani Silvia , Clemente Nicola , Senatore Gianluca , Filicori Filippo , Antonacci Nicola , Baldoni Franco , De Werra Carlo , Di Saverio Salomone
Published: March 2011

Background

Case control studies that randomly assign patients with diagnosis of acute appendicitis to either surgical or non-surgical treatment yield a relapse rate of approximately 14% at one year. It would be useful to know the relapse rate of patients who have, instead, been selected for a given treatment based on a thorough clinical evaluation, including physical examination and laboratory results (Alvarado Score) as well as radiological exams if needed or deemed helpful. If this clinical evaluation is useful, the investigators would expect patient selection to be better than chance, and relapse rate to be lower than 14%. Once the investigators have established the utility of this evaluation, the investigators can begin to identify those components that have predictive value (such as blood analysis, or US/CT findings). This is the first step toward developing an accurate diagnostic-therapeutic algorithm which will avoid risks and costs of needless surgery.

Methods/design

This will be a single-cohort prospective observational study. It will not interfere with the usual pathway, consisting of clinical examination in the Emergency Department (ED) and execution of the following exams at the physician's discretion: full blood count with differential, C reactive protein, abdominal ultrasound, abdominal CT. Patients admitted to an ED with lower abdominal pain and suspicion of acute appendicitis and not needing immediate surgery, are requested by informed consent to undergo observation and non operative treatment with antibiotic therapy (Amoxicillin and Clavulanic Acid). The patients by protocol should not have received any previous antibiotic treatment during the same clinical episode. Patients not undergoing surgery will be physically examined 5 days later. Further follow-up will be conducted at 7, 15 days, 6 months and 12 months. The study will conform to clinical practice guidelines and will follow the recommendations of the Declaration of Helsinki. The protocol was approved on November 2009 by Maggiore Hospital Ethical Review Board (ID CE09079).

Trial Registration

ClinicalTrials.gov identifier:NCT01096927.