bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of Part Families for Shared Setups Generation in Sheet Metal Bending
Authors: Gupta Satyandra K.
Published: February 2021

Sheet metal bending press-brakes can be setup to produce more than one type of parts without requiring a setup change. To exploit this flexibility, we need setup planning techniques to generate press-brake setups that can be shared among many different parts. In this paper, we describe an algorithm which partitions a given set of parts into setup compatible part families which can be produced on the same setup. Our algorithm is based on a two step approach. The first step is to identify setup constraints for each individual part. The second step is to form setup-compatible part families based on the compatibility of setup constraints. We expect that by producing many different types of parts on the same setup, we can significantly reduce the required number of setups and enable cost effective small batch manufacturing.
Multi Disciplinary Early Performance Evaluation via Logical Description of Mechanisms: DVD Pick up Head Example
Authors: Ozawa Masanori , Iwasaki Yumi , Cutkosky Mark R.
Published: February 2021

This paper describes an approach developed to support the early stages of designing multidisciplinary products. In the design of such products it is important for various specialists to share representations of the engineering models they use in making trade-off studies. Sharing information among diverse engineering tools at the data level is notoriously difficult and inflexible. When any of the modeling details, assumptions or constraints change, the translation must usually be rewritten. Our solution to this problem is to formalize the exchange of information among engineering specialists and their tools as a problem in communication among agents. The agents share a common ontology and a compositional modeling language (CML) in which models can be created such that conventions, constraints, and assumptions are defined formally and ultimately grounded in logic.

We have applied CML in the context of a pick-up head design problem for DVD (digital versatile disc / digital video disc) players. We describe the pick-up head design problem, the CML models we have created to address early stages of pick-up head design, and the use of the CML models by a team of specialists, each participating as an agent in a concurrent engineering exercise.
Finite Element Analysis Used to Optimize Welding Patterns for Marine Structure
Authors: Ischenko Dmitry , Ibrahim Raafat
Published: February 2021

The development of optimum welding patterns which can reduce the adverse effects of welding is important for industry, and particularly, for shipbuilding. In this investigation, a finite element simulation was employed in order to optimize the design of the weldment and reduce residual stresses and distortions. A gusset plate, which was used to increase the stiffness of marine structures, was subjected to thermal loads to simulate the effect of the welding process. Temperature distributions were obtained as a solution of the nonlinear transient problem of thermal conductivity. These distributions were then used to calculate residual stresses and distortion by solving thermo-elastic-plastic problems. The results indicated a significant reduction in the distortion when a plate with circular slots and interrupted welding was used instead of a continuously welded solid plate.
Optimal Layout of Bogie Frames Considering Fatigue Strength
Authors: Rottler Andreas , Eschenauer Hans A.
Published: February 2021

Bogie frames are an important component within the entire system “train”. Currently, a layout of these frames with respect to durability is only carried out on the basis of substantially reduced load assumptions. By a more precise consideration of the states of operation an improved layout can be achieved with an optimal exploitation of the material properties. This concept is realized by calculating the forces acting on the bogie frame, by a dynamic simulation of the entire system “train”, by an FE-analysis of the bogie frame, and finally by evaluating the transient stresses by means of the rainflow-counting procedure. A computation of the damage is carried out at the critical points. The total concept has been integrated into the SAPOP optimization procedure by means of which better designs can be found considering the given requirements.
Spherical Mechanism Synthesis in Virtual Reality
Authors: Furlong Todd J. , Vance Judy M. , Larochelle Pierre M.
Published: February 2021

This paper presents a new approach to using virtual reality (VR) to design spherical mechanisms. VR provides a three dimensional design space where a designer can input design positions using a combination of hand gestures and motions and view the resultant mechanism in stereo using natural head movement to change the viewpoint. Because of the three dimensional nature of the design and verification of spherical mechanisms, VR is examined as a new design interface in this research. In addition to providing a VR environment for design, the research presented in this paper has focused on developing a “design in context” approach to spherical mechanism design. Previous design methods have involved placing coordinate frames along the surface of a constraint sphere. The new “design in context” approach allows a designer to freely place geometric models of movable objects inside an environment consisting of fixed objects. The fixed objects could either act as a base for a mechanism or be potential sources of interference with the motion of the mechanism. This approach allows a designer to perform kinematic synthesis of a mechanism while giving consideration to the interaction of that mechanism with its application environment.
The Robust Concept Exploration Method With Enhanced Model Approximation Capabilities
Authors: Varadarajan Sriram , Chen Wei , Pelka Chester J.
Published: February 2021

Improvements in industrial productivity require the creation of a reliable design in the shortest possible time. This is especially significant for designs that involve computer intensive analyses. The Robust Concept Exploration Method (RCEM) embodies a systematic approach to configuring complex engineering systems in the early stages of product design by introducing quality considerations based on the robust design principle. Approximation techniques are employed in the RCEM to replace intensive analysis programs for saving the computational time and cost, thereby increasing the efficiency of a design process. In this paper, the applicability of the RCEM for facilitating multiobjective complex systems design is examined by applying it to the propulsion system conceptual design process at Pratt & Whitney. Various approximation techniques are studied and a new strategy is proposed to enhance the existing model approximation techniques embodied in the RCEM.
Integrating DFX Tools With Computer-Aided Design Systems
Authors: Kalyan-Seshu Uma-Sankar , Bras Bert
Published: February 2021

The growing emphasis on environmentally conscious design and manufacturing approaches has placed new burdens on designers. The amount of information available to designers is of great significance in making life cycle assessments on a product. However, well-established commercial CAD systems do not provide means for evaluating most of the different life cycle aspects of the product being modeled. Hence there is a need to have a CAD-environment where the life cycle tools (DFX tools in this work) are integrated with these systems so that life cycle design is made possible. In the research discussed in this paper, the specific focus is to enable the quantification and enhancement of product assemblability, serviceability, recyclability, remanufacturability, de-manufacturability, and life cycle impact during product design. Guidelines for integrating some of the commercially available CAD packages (I-DEAS and Pro/ENGINEER) to these assessment models, and ways to use the input information to some these assessments for making other assessments are developed. A case study is given to illustrate the approach.
Robust Activity Analysis: Partitioning Non-Monotonic Design Spaces Into Robust Optimal Regions
Authors: Agarwal Manish , Cagan Jonathan
Published: February 2021

This paper introduces a new symbolic optimization technique called robust activity analysis that partitions non-monotonic design spaces into non-optimal and potentially optimal regions. The constraint activity in the potentially optimal regions can be examined to obtain insight into the design space. The algorithm works by filtering out the unnecessary non-linearities in the design space and the ranges returned by the algorithm are guaranteed to be sufficiently robust (insensitive to parameter variations), i.e. as robust as the designer specifies. The algorithm is applied to solve a photoconductor-developer design problem and the results generated are examined to obtain insight into the solution that traditional numerical methods typically miss. The advantages of the algorithm over current numerical and symbolic optimization algorithms as well as the advantages over standard robust design techniques are discussed.
A Genetic Algorithm for Path Planning in Rapid Prototyping
Authors: Joneja Ajay , Wah Pang King , Murty Katta G. , Lam David , Yuen Matthew
Published: February 2021

In several applications of Rapid Prototyping (RP), the tool must travel along a set of curves in the plane to generate each layer of the part. The total processing time for a layer is the sum of the times for the movements of the tool, which can be in one of two modes: when it is switched on (machining time), and when it is switched off (non-machining time). Typically, the machining velocity, at which the tool travels along each curve is decided by technological factors. However, for any reasonably complex shape, there is a significant portion of the tool motion while jumping from the end of one curve to the beginning of the next curve, during which time the tool is not machining. It is therefore interesting to see if we can reduce the non-machining time in RP, and this paper proposes a genetic algorithm attempting to do so. Results of a test case are also presented.
A Design Methodology for Attachment Concept Development in Integral Snap-Fit Assemblies
Authors: Genc Suat , Messler Robert W. , Gabriele Gary A.
Published: February 2021

The importance and foundation for conceptual-level design of integral snap-fit assemblies was first pointed out by Bonenberger at General Motors. Based on that work, a design methodology is presented to identify and address important issues at the conceptual-level in a systematic way and generate alternative attachment concepts. The methodology starts by exploring the design space to generate as many concepts as possible. Alternative concepts are generated by considering variation in interface geometry, assembly procedure, snap-fit features, and options for fully constraining all parts in the assembly. At the last step, alternatives are evaluated by using a quantitative tool, and the “best” attachment concept is selected based on design objectives for a particular application. Applying the design methodology to case studies confirms that it is a useful design aid for efficiently generating, evaluating, or simply checking attachment concepts.
An Introduction to the Consensus Model of Engineering Design Decision Making
Authors: Ullman David G. , D’Ambrosio Bruce
Published: February 2021

This paper presents an introduction1 to a model of a collaborative working environment which supports distributed team argumentation, negotiation, consensus building and rationale capture. Based on a natural model of team deliberation, this model is the basis for the development of a system that enables team support and the capture of the design rationale in value added activities. The consensus model is the result of over fifteen years of studying and modeling design engineers by the authors and the integration of research results from the fields of negotiation and argumentation modeling, design rationale capture, decision theoretics, and engineering best practices.
Quantitative Selection of Variation Reduction Plans
Authors: Thornton Anna C.
Published: February 2021

Quality has been a rallying call in the design and manufacturing world for the last two decades. One way to improve quality is to reduce the impact of manufacturing variation. Variation risk mitigation is challenging especially when a product has multiple quality characteristics and complex production and assembly. It is common wisdom that companies should identify and mitigate the risk associated with variation throughout the design process. As yield problems are identified, they should be mitigated using the most cost effective approach.

One approach to variation risk mitigation is variation reduction (VR). VR targets reduction of variation introduced by existing manufacturing processes using tools such as Design of Experiments (DOE) and robust design. Many companies have specialized groups that specialize in these methods. VR teams have the role of improving manufacturing performance; however, these teams are limited in their resources. In addition, no tools exist to quantitatively determine where a VR team’s efforts are most effectively deployed. This paper provides a mathematical and optimization model to best allocate VR resources in a complex product.
An Implementation of Expected Utility Theory in Decision Based Design
Authors: Marston Matthew , Mistree Farrokh
Published: February 2021

The development of a design science rests on the ideal that design is anchored in a set of fundamental axioms similar to the more ‘traditional’ sciences of mathematics and physics. However, the axioms upon which a design science is constructed must reflect that design is a science of the artificial. It is our contention that such axioms may exist in Decision-Based Design as those formulated by von-Neumann and Morgenstern for developing utilities under conditions of risk. In this paper we have a very narrow focus: evaluating a proposed framework for applying these axioms in the context of a simple design problem through the use of Monte Carlo simulation and expected utility theory.
Experimental Investigation of Progressive Idea Generation Techniques in Engineering Design
Authors: Shah Jami J.
Published: February 2021

Three idea generation methods for engineering design have been studied over a period of several years. They are Method 6-3-5, Collaborative Sketching (C-Sketch), and the Gallery Method. Common features of all three methods are that they are team based and ideas are generated and developed in progressive stages. Differences between them include the medium for recording and communication allowed between team members. Experiments have been conducted on the influence of these factors on the idea generation process and results. Data from idea generation methods from 3 sets of experiments has been collected and partially analyzed. Specific issues examined are (a) overcoming design fixation (b) sentential vs. diagrammatic recording of ideas (c) misinterpretation of idea description as a provocative stimulus (d) identification of creative exploratory processes during design sessions. Results of work in progress are presented based on over 200 hours of data from roughly 44 subjects over nearly 3 years.
Product Architecture Definition Based Upon Customer Demands
Authors: Yu Janet S. , Gonzalez-Zugasti Javier P. , Otto Kevin N.
Published: February 2021

The product architecture developed by a design team will have a tremendous impact upon customer satisfaction and market acceptance of a product. Yet most work in product architecture centers around configuring them for cost savings, manufacturability, and other production-driven concerns. Here, we propose a customer need basis for defining a product architecture. Customer needs analysis can provide a list of requirements for a product to sell. At any moment in time, one can assess a market population to establish target values for product features and represent those targets as probability distributions. Alternatively, one can also trace a few products through their use in time, and establish desired target values as a set of different distributions. Comparing these two distribution sets for every important customer need can point to the type of architecture a market population desires. When population and time distributions match, feature adjustability is required. When these distributions are different but constant in time, a family of product variants is more appropriate. When the population distribution changes over time, the feature must be isolated so it can be upgraded over time. If the distributions across both time and population are narrow, a single offering will supply the needs of the market. An instant film camera product is used as an example of the relationship between customer need distributions and appropriate product architecture.
A Concurrent Function Deployment Process for Product Life-Cycle Management
Authors: Prasad Biren
Published: February 2021

In this paper, an alternate framework for deployment called Concurrent Function Deployment (CFD) for managing a product’s life-cycle process is described. The framework considers parallel deployment of several value characteristics as opposed to a single value such as Quality. The American Supplier Institute’s (ASI’s) quality function deployment (QFD) concept [Sullivan, 1988] is a typical case of a conventional four-phased deployment process, where quality is the prime consideration for deploying life cycle functions. CFD is not based on using a single measurement, such as “Quality“ as in ASI’s QFD. Six concurrent values, namely Functionality (Quality), Performance (X-ability), Tools & Technology (innovation), Cost, Responsiveness, and Infrastructure (delivery) are considered simultaneously in CFD rather than serially in QFD. Three-dimensional Value Characteristics Matrices (VCM) are employed to ensure that both the company and the customers’ goals are optimally met. In the present setting, ASI’s deployment scenario emerges as a special case of Concurrent Function Deployment. CFD enables the planners and strategic decision-makers — early on during a design process — to deal with tradeoffs among the crucial factors of artifact values.
The Topological Representation and Detection of Isomorphism Among Geared Linkage Kinematic Chains
Authors: Li Tuan-Jie , Cao Wei-Qing , Chu Jin-Kui
Published: February 2021

Proceeded from the topological characteristics of Geared Linkage Mechanisms (GLM) structure, a fully new graph, combinatorial graph, which can be used to describe the topological relationship in a Geared Linkage Kinematic Chain (GLKC), is firstly proposed. Then the corresponding matrix, combinatorial matrix, and the structural invariants of GLKC are presented. Based on the structural invariants, this paper establishes a systematic procedure for detecting isomorphism among GLKCs using the powers of combinatorial matrix. A computer program based on the procedure has been applied successfully for detecting isomorphism among both the planar kinematic chains as well as GLKCs.
A Compliant, Over-Running Ratchet and Pawl Clutch With Centrifugal Throw-Out
Authors: Roach Gregory M. , Lyon Scott M. , Howell Larry L.
Published: February 2021

A new compliant, over-running ratchet and pawl clutch with centrifugal throw-out has been developed that drastically reduces the overall part count as compared to traditional ratchet and pawl clutches. Part count for the pawl hub assembly was virtually eliminated by making the hub a single compliant mechanism. This results in large savings in manufacturing, assembly and maintenance costs. Peak torque output for a polypropylene clutch was measured at over 66.2 N-m with an over-running torque measured at < 0.01 N-m. A mathematical model has been developed to predict the rotational speed at which the pawls disengage from the ratchet when free-wheeling. This model was verified experimentally to be accurate within 5.2%. This clutch also demonstrates the advantage of compliant mechanisms to reduce assembly and manufacturing costs.
Pitch Cone Design of Face-Hobbed Hypoid Gears
Authors: Chen Ningxin
Published: February 2021

In the present paper, the principle of pitch cone design of hypoid gears by Mr. E. Wildhaber is studied first. Then, three equations are derived for calculation of the radii of curvatures of tooth lengthwise lines of the imaginary crown gear, the generated gear and the non-generated gears. And finally, an improved algorithm for pitch cone design of face-hobbed hypoid gears is proposed, in which two design equations in two variables are used, and hence the trial-and-error procedure is avoided.
A Deviation-Function Method for the Design of New Conjugate Kinematic Pairs
Authors: Yang Daniel C. H. , Tong Shih-Hsi
Published: February 2021

In this paper a method for generating new conjugate kinematic pairs is developed. This method, called the “Deviation-Function” method, is to use deviation functions to reshape the original pitch pairs so that the desired profiles of generated pairs can be obtained. A deviation function is defined as the distance between contacts and their corresponding instant centers of two conjugate pairs. In other words, a deviation function measures the amount of deviation of a point on the generated profile from its corresponding point on the original pitch profile. As demonstrated, this new method is superior to the existing methods for conjugate pair generation in three ways: 1. it is applicable to any pitch pairs including circular or noncircular, identical or non-identical; 2. it enables the design of geometric intuition into the generated profiles; and 3. it enables the design of special analytical properties to the generated profiles.
Evolutionary Techniques in MEMS Synthesis
Authors: Li Hui , Antonsson Erik K.
Published: February 2021

Initial results have been obtained for automatic synthesis of MEMS mask-layouts using a genetic algorithm. An initial random population of geometrically valid mask-layouts (non-self intersecting 2D polygons) is produced. The fabrication of each layout is simulated using a 3-D simulation of etching. The 3-D results of the fabrication simulation are compared to a desired 3-D shape specified by users. A genetic algorithm is applied to this initial population to iteratively search for a global optimum mask-layout whose fabricated 3-D shape is sufficiently close to the desired shape. During each iteration of the genetic algorithm, the mask-layouts with fabricated 3-D shapes close to the desired shape are more likely to survive. Random shape variations with ensured geometrical validity are applied to the surviving mask-layouts to produce the mask-layouts for the next iteration. The procedure is then repeated until one or more simulated shape is sufficiently close to the desired shape to stop the iteration. Initial results demonstrate the feasibility of this approach to mask-layout synthesis.
Next Generation Machine Design Requirements for a Punch Press Machine
Authors: Kirchner Ned C.
Published: February 2021

Current designs of punch press machines have evolved over time to produce a well constructed high speed machine. But as customer needs have increased the overall demands on speeds and forces, the present use of mechanisms and dynamic considerations has reached a limit. New designs of possible machine types are needed to achieve the higher performance. This paper outlines the evolution of the punch press machine, and poses the problem as a challenge to the greater design community.
Research on the Normal Damping of Machine Joints
Authors: Xueliang Zhang , Yumei Huang , Weiping Fu , Xiaoyue Wang , Yongchao Liu
Published: February 2021

In order to master the regularity of the normal damping of machine joints, a new experimental research setup and a testing system are designed, the greatest characteristic of which is that the normal dynamic relative displacement of machine joints is measured with eddy-current displacement sensors directly. Having analyzed the experimental data, some important conclusions are given out.
On the Differential Forms of Coordinate and Metric Independent Object Norms
Authors: Kazerounian Kazem , Rastegar Jahangir
Published: February 2021

“Object norms” are measures of distance for rigid body displacement in the plane or space. These norms are independent of the coordinate systems or metrics used. Since their introduction in 1992, they have been effectively used in several applications including computational kinematics, precision design, and robotics. This paper deals with the formulation and study of the time differential form and properties of these norms. A local linearization based on the differential forms of object norms is also independant from coordinate systems or their metrics.
K-L Expansion of a Random Process in Wavelet Bases
Authors: Agrawal Om P. , Pai Shantaram S.
Published: February 2021

Random processes play a significant role in stochastic analysis of mechanical systems, structures, fluid mechanics, and other engineering systems. In this paper, a numerical method for series representation of random processes, with specified mean and correlation functions, in wavelet bases is presented. In this method, the Karhunen-Loeve expansion approach is used to represent a process as a linear sum of orthonormal eigenfunctions with uncorrelated random coefficients. The correlation and the eigenfunctions are approximated as truncated linear sums of compactly supported orthogonal wavelets. The eigenfunctions satisfy an integral eigenvalue problem. Using the above approximations, the integral eigenvalue problem is converted to a matrix (finite dimensional) eigenvalue problem. Numerical algorithms are discussed to compute one- and two-dimensional wavelet transforms of certain functions, and the resulting equations are solved to obtain the eigenvalues and the eigenfunctions. The scheme provides an improvement over other existing schemes. Two examples are considered to show the feasibility and effectiveness of this method. Numerical studies show that the results obtained using this method compare well with analytical techniques.
Modified Methods for Dynamic Modelling of Robot Manipulators
Authors: Sallam Mohamed M. , Abo-Shanab Roshdy F. , Nassr Abo-Bakr A.
Published: February 2021

Control analysis and design for robot manipulators require the knowledge of their dynamic model. In the first part of this paper, the Lagrange-Euler (L-E) formulaion has been developed to separate the generalized forces/torques due to rotational motion from that due to the translational motion. Therefore a new form for the dynamic equations of the robot manipulators has been obtained. In the second part, the generalized d’Alembert (GD) method has been used to develop the equations of motion for robot manipulators with revolute and/or prismatic joints. Also, the rotational effect and the translational effect in the new form of the GD method are separated. The develpoed equations, by both methods, when applied to robot manipulators result in an efficient and explicit set of closed form second order nonlinear differential equations. They give fairly well structured equations of motion suitable for control analysis and manipulator design. Using the proposed models, the rotational effects and translational effects have been studied separately and a simplified model has been obtained, a computational algorithm has been established and a computer software has been developed to perform the necessary calculations to obtain the generalized force required for each joint to follow any pre-specified trajectory. As an application of the proposed methods, a simplified model for a Stanford manipulator has been obtained and it is found that the results of the normal and the simplified models are very close and the simplified model can be accepted even with end-effector load variation and with different trajectories. The simplified model has the advantage of less computational time which is more appropriate for control purposes. Also, the results obtained by the developed L-E and GD methods are the same.
Modeling and Simulation of Dynamic Mass Capture by Robot Manipulators Considering Structural Flexiblity
Authors: Kövecses J. , Cleghorn W. L. , Fenton R. G.
Published: February 2021

In this paper we investigate the dynamics of the process when a robot intercepts and captures a moving object. This operation is called dynamic mass capture. The effects of structural flexibility of the robot is taken into consideration. In terms of time the analysis is divided into three phases: before interception (finite motion), at the vicinity of interception and capture (impulsive motion), and after interception (finite motion). Special attention is paid to the modeling of the second phase when the robot intercepts and captures a target and it becomes part of the end effector, thus, the system’s degrees of freedom and topology suddenly change. To describe this event, an alternative approach is proposed. This is based on the use of a class of impulsive constraints, the so-called inert constraints. Jourdain’s principle is employed to derive the dynamic equations for both finite and impulsive motions. Based on the proposed approach, simulation results are presented for a flexible slewing link capturing a moving target. These results are compared with the observations of an experiment. Good agreement is found between the experimental and simulation results, which suggests that the analysis presented in this paper can be used with confidence in investigations of robots intercepting and capturing moving objects.
A Framework for Closed-Form Displacement Analysis of 10-Link 1-DOF Mechanisms
Authors: Dhingra A. K. , Almadi A. N. , Kohli D.
Published: February 2021

This paper presents a closed-form approach, based on the theory of resultants, to the displacement analysis problem of planar 10-link 1-DOF mechanisms. Since each 10-link mechanism has 4 independent loops, its displacement analysis problem can be written as a system of 4 reduced loop-closure equations in 4 unknowns. This system of 4 reduced loop closure equations, for all non-trivial mechanisms resulting from 230 10-link kinematic chains, can be classified into 22 distinct structures. Using the successive and repeated elimination procedures presented herein, it is shown how each of these structures can be reduced into a univariate polynomial devoid of any extraneous roots. This univariate polynomial corresponds to the input-output (I/O) polynomial of the mechanism. Based on the results presented, it can be seen that the displacement analysis problem for all 10-link 1-DOF mechanisms is completely solvable, in closed-form, devoid of any extraneous roots.
Knotting Mechanisms and a Knotting Theory
Authors: Payandeh Shahram , Lomax Alan J.
Published: February 2021

In the filed of remote manipulation, it is generally required to manipulate objects through elongated tools or through a tele-operation system. In the field of EndoSurgery, one of the challenging tasks for the surgeons is the notion of knotting a suture. This is done by using long graspers and needle drivers which have constrained degrees of freedom caused by the ports of entry to the surgical area. In general, this task is the most time consuming one and requires degree of dexterity which is not available. The objective of this paper is to present an overview of the patented design features of various knotting assisting mechanisms which have been invented for automating aspect of knotting and discussion on a novel and practical design concept. Then this paper presents how the notion of the Knot Theory which is mathematical abstraction can be extended to develop a Graphical Surgeon Interface (GSI) in order to guide the operator during the remote manipulation of the suture during the knotting task and also during the training phases using a haptic interface device.
A Closed-Form Approach to Coupler-Curves of Multi-Loop Mechanisms
Authors: Dhingra A. K. , Almadi A. N. , Kohli D.
Published: February 2021

This paper presents a closed-form approach, based on the theory of resultants, for deriving the coupler curve equation of 16 8-link mechanisms. The solution approach entails successive elimination of problem unknowns to reduce a multivariate system of 8 equations into a single bivariate equation. This bivariate equation is the coupler curve of the mechanism under consideration. Three theorems which summarize key coupler curve characteristics are presented. The computational procedure is illustrated through two numerical examples. These examples address in detail some of the problems associated with the conversion of transcendental loop equations into an algebraic form using tangent half-angle substitutions. An extension of the proposed approach to the determination of degrees of input-output (I/O) polynomials and coupler curves for general n-link mechanisms is also presented.
A New Method of Dimensional Synthesis for Planar 4-Bar Path Generation With Prescribed Timing
Authors: Xin Wu , Jinkui Chu , Chen Wu , Weiqing Cao
Published: February 2021

Mathematical equations for 4-bar path generation on an arbitrarily arranged mechanism are set up by using complex number and Fourier series theory in this paper. The harmonic components of path generation on the coupler are carried out by systematic study. According to the conception of Coupler Rotation-Angle Operator (in short CRAO) about coupler’s rotation-angle function, a new method of determining the position for a coupler point, real dimensions and installing dimensions of the linkage is established for the first time. Based on this thinking, the concrete steps of dimension synthesis for path generation with prescribed timing are formed, and the method of path synthesis by using harmonic characteristic parameters is developed and further prefect is made.
Design and Stress Analysis of Gears Using the Boundary Element Method
Authors: Dippery Richard E. , Echempati Raghu , Ellis John
Published: February 2021

Basic design and stress analysis of gears can be, for the most part, accomplished through the use of the American Gear Manufacturers’ Association (AGMA) criterion or use of a machine design text book such as Norton[1]. Real life questions as to the effect of undercut, misalignment, notches or grooves, and so on are not answered quite so quickly or with reasonable accuracy. The boundary element method (BEM) provides a relatively quick modeling method for assessing stresses and a means to accurately predict crack propagation in components. Lubricated bodies in contact, such as gears, cams and bearings, provide an application for which BEM can be applied. This paper has been written to provide an assessment of the use of BEM to evaluate the effect of undercut on the stresses in a gear, the propagation of a notch in the root of a gear, with and without undercut. Future work will be expanded to include contact analysis using a second gear and three dimensional analysis, possibly providing a means for assessing misalignment of gears and load distribution effects on gears.
Pacing and Hazard Score of Elite Open Water Swimmers During a 5-km Indoor Pool Race
Authors: Baldassarre Roberto , Ieno Cristian , Bonifazi Marco , Piacentini Maria Francesca
Published: February 2021

Purpose: The sensation of fatigue experienced at a certain point of the race is an important factor in the regulation of pacing. The rating of perceived exertion (RPE) is considered one of the main mediators utilized by athletes to modify pacing. The aim was to analyze the relationship between pacing and RPE of elite open water swimmers during national indoor pool championships. Methods: A total of 17 elite open water swimmers (males, n = 9; females, n = 8) agreed to provide RPE every 500 m during the finals of the national championships 5-km indoor pool race. Time splits, stroke rate, and RPE were collected every 500 m. The Hazard score was calculated by multiplying the momentary RPE by the remaining fraction of the race. Athletes were placed in one of two categories: medalists or nonmedalists. For all variables, separate mixed analysis of variances (P ≤ .05) with repeated measures were used considering the splits (ie, every 500 m) as within-subjects factor and the groups (ie, medalists and nonmedalists) as between-subjects factor. Results: Average swimming speed showed a significant main effect for split for both males and females (P < .001). A significant interaction was observed between average swimming speed and groups for females (P = .032). RPE increased in both groups (P < .001) with no difference observed between groups. However, the female nonmedalists showed a disproportionate nonlinear increase in RPE (5.20 [2.31]) halfway through the event that corresponded to the point where they started significantly decreasing speed. Conclusions: The results of the present study show different pacing strategies adopted by medalists and nonmedalists despite a similar RPE.
The Educational Project in the Context of High-Performance Sports
Authors: Burlot Fabrice , Desenfant Mathilde , Joncheray Helene
Published: February 2021

The requirements of performance sport are becoming more and more time-consuming for athletes. Based on the work of Rosa, the article looks into the ability of athletes to reconcile their training project and the increasing requirements of practice at a high level. To address this issue, we interviewed 63 high-level French athletes who train at the French Institute of Sport. The results show that although the training project appears to be time-consuming, it is nonetheless a source of social balance and a reassuring choice for their future professional retraining. In order to preserve this educational project in the time-consuming context of high-performance sports, athletes on the one hand implement strategies of arrangement in order to produce an acceptable timetable, and on the other hand use this temporality as an adjustment variable allowing them to better manage temporal emergencies. By giving athletes a voice, this work deconstructs the idea of the incompatibility of educational and sports projects and offers recommendations to sports institutions.
Fun and games and ecosystems
Playing Nature: Ecology in Video Games
Alenda Y. Chang
University of Minnesota Press, 2019. 320 pp.
Authors: LeMenager Stephanie
Published: February 2021

Video games—even those without explicit educational goals—can offer insights into ecology
People-powered discovery
The Crowd and the Cosmos
Chris Lintott
Oxford University Press, 2020. 288 pp.
Authors: Shanley Lea A.
Published: February 2021

A physicist reveals how citizen science is reshaping research
Evaluation of the MAST PAcE Colorimetric Test for Rapid Detection of Carbapenemase Activity in Gram-Negative Bacilli
Authors: Rezzoug Inès , Emeraud Cécile , Sauvadet Aimie , Cotellon Garance , Naas Thierry , Dortet Laurent
Published: February 2021

The MAST Carba PAcE test is a colorimetric test used to detect carbapenemase-producing Gram-negative bacilli from cultured colonies. The performances of this test were compared with those of β-CARBA, Carba NP, and RAPIDEC Carba NP tests using a collection of 280 characterized isolates.
Comparison of 16 Serological SARS-CoV-2 Immunoassays in 16 Clinical Laboratories
Authors: Harritshøj Lene H. , Gybel-Brask Mikkel , Afzal Shoaib , Kamstrup Pia R. , Jørgensen Charlotte S. , Thomsen Marianne Kragh , Hilsted Linda , Friis-Hansen Lennart , Szecsi Pal B. , Pedersen Lise , Nielsen Lene , Hansen Cecilie B. , Garred Peter , Korsholm Trine-Line , Mikkelsen Susan , Nielsen Kirstine O. , Møller Bjarne K. , Hansen Anne T. , Iversen Kasper K. , Nielsen Pernille B. , Hasselbalch Rasmus B. , Fogh Kamille , Norsk Jakob B. , Kristensen Jonas Henrik , Schønning Kristian , Kirkby Nikolai S. , Nielsen Alex C. Y. , Landsy Lone H. , Loftager Mette , Holm Dorte K. , Nilsson Anna C. , Sækmose Susanne G. , Grum-Schwensen Birgitte , Aagaard Bitten , Jensen Thøger G. , Nielsen Dorte M. , Ullum Henrik , Dessau Ram B.
Published: February 2021

Serological assays for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are needed to support clinical diagnosis and epidemiological investigations. Recently, assays for large-scale detection of total antibodies (Ab), immunoglobulin G (IgG), and IgM against SARS-CoV-2 antigens have been developed, but there are limited data on the diagnostic accuracy of these assays.
End-of-life outcomes with or without early palliative care: a propensity score matched, population-based cancer cohort study
Authors: Seow Hsien , Sutradhar Rinku , Burge Fred , McGrail Kimberlyn , Guthrie Dawn M , Lawson Beverley , Oz Urun Erbas , Chan Kelvin , Peacock Stuart , Barbera Lisa
Published: February 2021

Objectives

To investigate whether cancer decedents who received palliative care early (ie, >6 months before death) and not-early had different risk of using hospital care and supportive home care in the last month of life.

Design/setting

We identified a population-based cohort of cancer decedents between 2004 and 2014 in Ontario, Canada using linked administrative data. Analysis occurred between August 2017 to March 2019.

Participants

We propensity-score matched decedents on receiving early or not-early palliative care using billing claims. We created two groups of matched pairs: one that had Resident Assessment Instrument (RAI) home care assessments in the exposure period (Yes-RAI group) and one that did not (No-RAI group) to control for confounders uniquely available in the assessment, such as health instability and pain. The outcomes were the absolute risk difference between matched pairs in receiving hospital care, supportive home care or hospital death.

Results

In the No-RAI group, we identified 36 238 pairs who received early and not-early palliative care. Those in the early palliative care group versus not-early group had a lower absolute risk difference of dying in hospital (−10.0%) and receiving hospital care (−10.4%) and a higher absolute risk difference of receiving supportive home care (23.3%). In the Yes-RAI group, we identified 3586 pairs, where results were similar in magnitude and direction.

Conclusions

Cancer decedents who received palliative care earlier than 6 months before death compared with those who did not had a lower absolute risk difference of receiving hospital care and dying in hospital, and an increased absolute risk difference of receiving supportive home care in the last month of life.
Comparative efficacy and side-effect profile of ketamine and esketamine in the treatment of unipolar and bipolar depression: protocol for a systematic review and network meta-analysis
Authors: Zhan Zhiqing , Wang Xichao , Chen Qing , Xiao Zhidai , Zhang Bin
Published: February 2021

Introduction

Despite a range of antidepressant drugs and therapies, approximately one-third of patients fail to achieve meaningful recovery, prompting the urgent need for more effective treatment for depression. Several open-label studies randomised controlled trials (RCTs) and meta-analyses have been conducted to confirm the therapeutic efficacy and side effects of ketamine and esketamine. Esketamine is (S)- enantiomer of ketamine; however, there is limited evidence comparing esketamine and ketamine in treating unipolar and bipolar depression have been published so far.

Methods and analysis

We will include all double-blind RCTs comparing efficacy and side-effect profile of ketamine and esketamine in the treatment of unipolar and bipolar depression. Our primary outcomes will be study-defined response at endpoint assessment; dropouts due to adverse events and other adverse drug reactions. Published studies will be retrieved through relevant database searches. Reference selection and data extraction will be independently completed by two investigators, resolving inconsistencies by consensus or a discussion with the third investigator. For each outcome, we will undertake a network meta-analysis to synthesise all evidence. Local and global methods will be used to evaluate consistency. We will assess the quality of evidence contributing to network estimates with the Confidence in Network Meta-Analysis web application.

Ethics and dissemination

This work does not require ethics approval as it will be based on published studies. This review will be published in peer-reviewed journals.

PROSPERO registration number

CRD42020201559.
Effects of general versus regional anaesthesia on circadian melatonin rhythm and its association with postoperative delirium in elderly patients undergoing hip fracture surgery: study protocol for a prospective cohort clinical trial
Authors: Yuan Yi , Song Yanan , Wang Geng , Jia Yunyang , Zhou Yang , Mi Xinning , Jia Xixi , Wang Xiaoxiao , Liu Chang , Li Yue , Shi Chengmei , Han Yongzheng , Guo Xiangyang , Zhang Wenchao , Li Zhengqian
Published: February 2021

Introduction

Postoperative delirium (POD) is a common neurological complication after hip fracture surgery and is associated with high morbidity and mortality in elderly patients. Although the specific mechanism of POD remains unclear, circadian rhythm disruptions have recently drawn increased attention. To date, only limited postoperative time points of plasma melatonin level measurements were recorded in previous studies, and such data cannot represent a comprehensive melatonin rhythm. The process of anaesthesia (either general anaesthesia (GA) or regional anaesthesia (RA)) is known to influence the melatonin rhythm. However, how these two anaesthesia methods differently affect the postoperative melatonin rhythm is still unknown. Therefore, we hypothesise that RA may attenuate the disruption of the melatonin rhythm, which might decrease the incidence of POD in elderly patients undergoing hip surgery.

Methods and analysis

In this prospective cohort clinical trial, 138 patients scheduled for hip fracture surgery will be divided into two groups to receive either GA or RA. The primary aim is to compare the circadian rhythm of melatonin secretion between the two groups and explore its association with the incidence of POD.

Ethics and dissemination

The study has been approved by the Medical Science Research Ethics Committees of Beijing Jishuitan Hospital (JLKS201901-04). The results of the study will be published in peer-reviewed international journals.

Trial registration number

ChiCTR1900027393.
Cross-disciplinary perspectives on the transition to remote education
Authors: Houghton Natasha , Houstoun Will , Yates Sophie , Badley Bill , Kneebone Roger
Published: February 2021

The COVID-19 pandemic has prompted the cancellation of clinical attachments and face-to-face teaching at medical schools across the world. Experiential learning—through simulation or direct patient contact—is essential for the development of clinical skills and procedural knowledge. Adapting this type of teaching for remote delivery is a major challenge for undergraduate medical education. It is also an opportunity for innovation in technology enhanced learning and prompts educators to embrace new ways of thinking. In this article, the authors explored how educators from different disciplines (medicine, music and performing arts) are using technology to enhance practical skills-based learning remotely.

The authors, five experienced educators from different fields (surgery, medicine, music and magic), jointly documented the transition to technology enhanced remote teaching through a series of five structured conversations. Drawing from literature on distance learning in medicine and professional experience in education, the authors identified seven practice-enhancing recommendations for optimising teaching of procedural knowledge and skills. These are: (1) make a virtue out of necessity; (2) actively manage your environment; (3) make expectations clear; (4) embrace purposeful communication; (5) use digital resources; (6) be prepared for things to go wrong and (7) personalise the approach. The authors argue that widening the discourse in technology enhanced learning to include cross-disciplinary perspectives adds richness and depth to discussions. This article demonstrates a cross-disciplinary approach to addressing challenges in technology-enhanced medical education.