bluuebunny/crossref_metadata_2025 huggingface dataset:
Strategies for Product Structure Management in Manufacturing Firms
Authors: Svensson Daniel , Malmqvist Johan
Published: December 2020

Product structure management (PSM) is a process that affects many different disciplines in a company. Different disciplines have different demands on the decomposition of the product structure and the functionality of the information systems used. Different disciplines therefore often work in different information systems. If several information systems to some extent contain the same information, it is important that the information is updated in all systems if it is changed. Since PSM is a change intensive activity, it is difficult to perform PSM in an environment consisting of several different information systems.

There is a need for strategies for PSM that considers all relevant aspects of an information system, such as the process it supports, the information handled, the information systems used and the organisation.

This paper discusses different disciplines requirements on the product structure based on a case study at an automotive manufacturing firm. The paper proposes strategies for PSM that can be used as a guide and for categorisation when analysing the information system before restructuring and/or introduction of new systems.
Representing an Artifact Transport System in a Design Repository: A Case Study
Authors: Allen R. H. , Fijol R. J. , Syzkman S. , Sriram R. D.
Published: December 2020

This paper describes a case study representing the design essence of a prototype ultra-high vacuum artifact transport system (ATS) in an existing design repository (DR). Specifically designed for the purpose of transporting nanometer-scale dimensional artifacts at pressures near 10−8 Pa, the ATS consists of a transport cart and an ultra-high vacuum (UHV) system. The artifacts are the result of nanomanufacturing efforts to create atom-based dimensional standards for the semiconductor industry. To populate the design repository, we represent engineering geometry, function and associated behavior, as well as taxonomies of generic functions and flows of the transport system. We model geometry with digital photographs and Virtual Reality Markup Language (VRML) images of actual Computer-aided Design (CAD) drawings, represent function with linked textual descriptions, and capture behavior with mathematical expressions. Through an evolving user interface, this representation serves to capture the more than 50 parts and systems of the ATS in such a way that the information relating to form, function and behavior is accessible and browsable to subsequent designers. We conclude that such a representation, or ones similar to it, can provide the basis for a generic database in which specific information — including design rationale — can be easily retrieved by future design teams.
Corba Based System Integration of Product Development Process Management for Concurrent Engineering
Authors: Zhao Jinmin , Wu Junjun , Liu Jihong , Jin Guodong , Wang Jibin
Published: December 2020

The product development process management for concurrent engineering (CE) is the emerging technology to reduce the time to market for new product. The product development environment for CE is remarkably characterized by the heterogeneity and distribution. So, it is highly important to build a robust, object-oriented information infrastructure to allow the interoperability between the distributed application systems for realizing system integration of product development process management for CE (CEPDPM). CORBA provides the best technical solution for building such an infrastructure.

In this paper, a CORBA based architecture of CEPDPMS integration is described. Herein, a set of interoperable objects includes process management, product data management, and resource management, organization management systems and some design tools. How these objects are encapsulated into CORB A/ORB bus and provided as shared services is detailed by analyzing their granularity wrapped and defining their interfaces in DDL. A prototype implementation of CEPDPMS is outlined.
A Foundation for Interoperability in Next-Generation Product Development Systems
Authors: Szykman Simon , Fenves Steven J. , Keirouz Walid , Shooter Steven B.
Published: December 2020

U.S. industry spends billions of dollars as a result of poor interoperability between computer-aided engineering software tools. While ongoing standards development efforts are attempting to address this problem in today’s tools, the more significant demand in next-generation tools will be for representations that allow information used or generated during various product development activities to feed forward and backward into others by way of direct electronic interchange. Although the next generation of tools has the potential for greatly increased benefits, there is also a potential for the cost of poor interoperability to multiply. The goal of this work is to develop representations of information that are unavailable in traditional CAD/CAM/CAE tools to support the exchange of product information in a distributed product development environment. This paper develops a vision of next-generation product development systems and provides a core representation for product development information on which future systems can be built.
“Thin” vs. “Fat” Client of Web-Based CAD Tools
Authors: Wang Charlie C. L. , Yuen Matthew M. F. , Wang Yu
Published: December 2020

Internet technology in particular opens up another domain for building future CAD/CAM environment. This environment will be a global, network-centric environment with various members providing different software tools, manufacturing facilities, and analysis services for distributed design and fabrication. Web-based CAD tools play a prominent role in the environment. Two kinds of clients can be used to develop a web-based CAD tool now, one is “thin” client, and another is “fat” client. This paper compares the advantage of “thin” and “fat” client, and explains the advantage of using low-cost, configurable, CAD components.
An E-Documenting Approach to Conceptual Design
Authors: Benami Oren , Jin Yan
Published: December 2020

Conceptual design is the most creative, most informal, most ambiguous, and least understood phase of design. During conceptual design, ideas are in a state of transformation and relationships between concepts are often unclear or not well developed. This paper presents our view of conceptual design as an information transformation process and proposes an approach to support conceptual design. The basic idea is the following. Limitations in human information processing capability frequently prevents designers from being effective in retaining, managing, and applying the large amount of information generated during the conceptual design phase. Therefore, if one can provide a system that receives the flow of ideas generated, and arranges the ideas in a way that can be effectively retained, managed, and applied, then fewer ideas will be lost, connections between ideas can be easily identified, and consequently the overall design will be more effective and efficient.
Simulated Annealing for the Optimal Trajectory Planning of an Automated Crack Sealing Machine
Authors: Mathurin R. , Velinsky S. A.
Published: December 2020

A Simulated Annealing algorithm is employed to optimally plan the trajectory of the manipulator of an Automated Crack Sealing machine. This paper presents the semi-automatic image processing based method that is first used to identify the cracks to be sealed. Because of frequent morphological complexity of pavement cracks, an optimization approach is necessary to best plan the trajectory. The developed algorithm provides a complete path including crack coordinates, and the optimal shortest path to allow sealing of all cracks. Actual pavement images are processed to show the efficacy of the approach.
Product Knowledge Management Within Knowledge-Based Engineering Systems
Authors: Sainter P. , Oldham K. , Larkin A. , Murton A. , Brimble R.
Published: December 2020

Knowledge-based engineering systems are now becoming more commonplace in engineering industry. There is a need to ensure the technology is used correctly and to provide the user with all the possible benefits that the system can offer.

This paper looks at how product knowledge can be managed within knowledge-based engineering systems to ensure that the knowledge retains its value and usefulness during the product lifecycle. Presently, the use of these systems has been for the short-term benefit of the company. However, it is believed that it is important to consider longer-term issues also, since knowledge normally has a half-life of around 20 years.

The main aim of this paper is to demonstrate the need for product knowledge management within knowledge-based engineering systems by looking at key issues that are related to the longer-term use of these systems. This paper will also provide a product knowledge management scheme for the development and management of product knowledge within knowledge-based engineering systems, thereby extending the benefits of knowledge-based engineering systems into the longer-term.
Automatic Determination of Tolerance Chains in Unidirectional Tolerancing
Authors: Forster Charles , Boufflet Jean-Paul , Lecouvreur Fabien
Published: December 2020

Herein is proposed an automatic method by which the all-tolerance chains of a mechanical assembly may be constructed. The method, implementable in a CAD system, is divided into two main steps.

In the first step, we model the mechanical assembly with a graph, of which the vertices represent the parts and the edges, the contact between the parts. By « sliding » the parts, we may determine all the configurations of the mechanical assembly. The proposed model, which uses classical algorithms of the graph theory, allows control of the coherence of the mechanical assembly.

In the second step, we introduce an extended syntax by which the functional constraints may be decoded without ambiguity. Then, using the syntax and the model, we show how to construct the tolerance chain for each functional constraint.
Fluid Simulation on the World Wide Web: Transient Natural Convection in a Cavity
Authors: Wang Charlie C. L. , Yuen Matthew M. F. , Wang Yu
Published: December 2020

The primary objective of this research work is the methodology about the development of a fluid simulation package integrated with the Internet, which will allow the user to perform fluid simulation on the World Wide Web (WWW). The web-based software package is developed using tools like Java, ActiveX and HTML and is accessible over the Internet from anywhere in the work. This work is a part of a project on framework of web-based CAE system, which includes the creation of software packages for other CAE issues such as Computer Aided Design (CAD), Computer Aided Geometry Design (CAGD), Computer Aided Manufacturing (CAM). The framework of web-based CAE system is a set of CAE packages that can be accessed from all over the world. The simulation package is stored on a powerful server located at the Hong Kong University of Science and Technology, and the input/output (text, graphics, and animation) can be viewed and accessed by any computer supporting a web browser.

In this paper, the traditional Computational Fluid Dynamics (CFD) problem — Transient Natural Convection in a Cavity is used as the example to show how to build a fluid simulation package integrated with the Internet. At first, we will introduce the prospect of such a research work; then, the transient natural convection problem in a cavity is analyzed based on the stream-function and vorticity-function; at last, two solution of web-based fluid simulation will be compared using the example of transient natural convection in a cavity. Experiments on Transient Natural Convection in a Cavity have shown the feasibility for a networked fluid simulation service via the Internet.
Developing Theoretical Foundations of DfM
Authors: Shah Jami J. , Wright Paul K.
Published: December 2020

This work is motivated by a desire to put DfM on solid theoretical foundations. The paper evaluates measures of manufacturability and classes of DfM methods and frameworks independent of the specific manufacturing processes. Criteria used in evaluation include theoretical foundation, accuracy, flexibility in choosing utility/objective function, domain independence, ease of use, level and extent of information required, computational cost, ability to incorporate uncertainty and market factors. We introduce a DfM approach based on Benefit/Cost analysis. All design utilities are lumped into a single “Design Benefit (RD)”, all manufacturability factors into another parameter “Manufacturing Rating (RM)”, and then techniques of benefit-cost analysis and value engineering are used to make decisions about design improvements. Use of overall and marginal DfM ratings allows trade-offs to be made. Any set of desired objectives can be used for computing the ratings. It is also possible to incorporate design or manufacturing constraints.
A Function-Based Approach to Design for Manufacturing
Authors: Verma Manish , Wood William H.
Published: December 2020

Internet-enabled design and manufacturing requires more than just replacing physical walls with virtual ones in the old ‘over the wall’ design/manufacturing process. By emphasizing the functional requirements of a design, we propose to delay commitment to a manufacturing process, providing a larger design space for the designer and more flexibility to the manufacturer. A function-based approach is being developed which not only utilizes the increased understanding of both design and manufacturing but also exploits the benefits of the Internet to free the team of designers of time, space and organizational constraints. A design/manufacturing interface based on function is proposed and a scenario provided to demonstrate its potential impact.
An Aggregated Value Model for Collaborative Engineering Decisions
Authors: Danesh Mohammad Reza , Jin Yan
Published: December 2020

In recent years, considerable attentions have been given to collaboration and teamwork for product development in engineering communities. Engineering collaboration involves sharing and exchanging design objectives and information with other team members, detecting and resolving design conflicts, and integrating results of sub-tasks into overall solution. Our research views the collaborative product development process as a distributed decision-making process executed by an engineering team with members from different disciplines. Distribution of design activities among team members, on the one hand, reduces knowledge requirement for designers to carry out their sub-tasks, and, on the other hand, poses demand for smooth coordination among team members to deal with dependencies between the sub-tasks. We argue that to achieve efficient engineering collaboration, team members should share their objectives and values from the early stages of the product development. Our aggregated value model is an attempt to formalize collaborative engineering process. In this paper, we introduce three modes of collaboration, namely total distribution, partial aggregation, and total aggregation as different collaboration schemes and compared their advantages and disadvantages. After that, we present a formal aggregated value model of engineering decision-making process. Finally, an example is discussed to illustrate some of the interesting features of the proposed model in engineering practice.
On Optimization Methods in the House of Quality: Facilitating the Early Stages of Product Design
Authors: Gauthier Benoit , Sodhi Manbir , Dewhurst Peter
Published: December 2020

During a conceptual design effort we find we are making the most far-reaching decisions on product and process form and robustness, while under great pressure to quickly definitize the product. Success is a function of how well we optimize to market needs and producibility, among other constraints. In this paper we focus on implementation of optimization early in the design process, within the structured environment of the House of Quality. Using a normalized weighting format for parameter correlations and relationships, several formulations are presented and discussed, each with its own appropriate use. Using mathematical programming techniques, opportunities exist to greatly reduce the rank of the matrix, facilitating early design iteration and optimization. We present several new roles for the correlation matrix, or roof of the house of quality, which to date has been underutilized in product optimization. Formulations are proposed to employ design information contained in the roof to facilitate concurrent design optimization and management of complexity at the early stages of design.
A Survey of Concurrent Engineering Design Practice in the Australian Automotive and Maritime Industries
Authors: Smith Warren F. , Anforth Troy M. , Crane Andrew M.
Published: December 2020

It is our contention that engineering design in the 21st century requires a holistic systems approach that is flexible, adaptable and able to cope with change. Such an approach would draw on integrative design philosophies such as concurrent engineering. This paper presents a review of current design practice within two major Australian engineering sectors in an effort to benchmark the “state of practice” and allow for some assessment of the paradigm shift perceived to be required to take it to the “state of research” with respect to concurrent engineering.
On Properties of the Screw Geometry of Contact Wrenches in Multiple Grasping Agents
Authors: Chevallier Dominique , Payandeh Shahram
Published: December 2020

Establishing a force-closure contact configuration between multiple contacting agents such as dexterous fingers and an object is one of the main requirements for further object manipulation. Various tools and methods have been proposed in the literature for such analysis and modelling. This paper extends the previous results by the authors and by using basic notions from screw geometry present some preliminary tools for a) locating the next contact wrench given any first two contact wrenches; b) computing the grasping wrenches as a function of the external wrench (force) and c) computing the local friction wrenches between the agents and object as a function of the external wrench. The main contribution of the paper is the application of basic tools from screw geometry and the associated algebra to the problem of planning and analysis of forces in multiple contacting agents.
A Study of Vibration in Caliper-Disc Brake Systems With Surface Roughness Effects: Part A — Contact Stiffness Characterization
Authors: Meinhardt Glenn , Farhang Kambiz , Abdo Jamil
Published: December 2020

Vibration in mechanical systems with friction depends on the physical characteristics of the frictional contact. The elastic characteristic of contact is considered in this paper for the interaction of pad and rotor surfaces in caliper-disc brake systems. Mathematical formulation of contact stiffness is obtained by using the theory of rough surfaces. It is shown that surface roughness results in nonlinear contact stiffnesses and these are approximated as polynomials in terms of the relative movement of the pad and rotor along their common normal.

The surface roughness of a brake pad is shown to lead to fifth and sixth-order polynomial functions, in terms of the relative displacements, for compressive and shear contact stiffnesses respectively. In a companion paper, the contact stiffness is incorporated into a vibration model of the caliper-disc brake system.
Kinematic Analysis and Design of Planar Parallel Mechanisms Actuated With Cables
Authors: Barrette Guillaume , Gosselin Clément M.
Published: December 2020

In this paper, we present a general and systematic analysis of planar parallel mechanisms actuated with cables. The equations for the velocities are derived, and the forces in the cables are obtained by the principle of virtual work. Then, a detailed analysis of the workspace is performed and an analytical method for the determination of the boundaries of an x-y two-dimensional subset is proposed. The new notion of dynamic workspace is denned, as its shape depends on the accelerations of the end-effector. We demonstrate that any subset of the workspace can be considered as a combination of three-cable sub-workspaces, with boundaries being of two kinds: two-cable equilibrium loci and three-cable singularity loci. By using a parametric representation, we see that for the x-y workspace of a simple no-spring mechanism, the two-cable equilibrium loci represent a hyperbolic section, degenerating, in some particular cases, to one or two linear segments. Examples of such loci are presented. We use quadratic programming to choose which sections of the curves constitute the boundaries of the workspace for any particular dynamic state. A detailed example of workspace determination is included for a six-cable mechanism.
Evaluation and Optimum Design of Parallel Manipulators Having Defined Workspace
Authors: Schönherr Jürgen
Published: December 2020

The condition of the Jacobian characterizes the transmission quality of manipulators and is used in this paper for the determination of the dimensions of manipulators having best mobility for a defined workspace. Typical planar and spatial manipulators of parallel structure and having 3 or 6 degrees of freedom are used to demonstrate the method of design used. Manipulators having identical degrees of freedom and workspaces and different structures, including those having fixed or variable leg lengths, are compared with respect to their mobility. The computing program developed for the purpose of optimum design performs the kinematic optimization of machines and manipulators of any structure.
Some Implications for Parallel Kinematic Machine Design Based on Kinetostatic Model
Authors: Gosselin Clément M. , Zhang Dan
Published: December 2020

In this paper, a new method — named lumped kinetostatic modeling — to analyze the effect of the link flexibility on the mechanism’s stiffness is provided. A new type of mechanism whose degree of freedom (dof) is dependent on a passive constraining leg connecting the base and the platform is introduced and analyzed. With the proposed kinetostatic model, a significant effect of the link flexibility on the mechanism’s precision has been demonstrated. The influence of the changement of structure parameters, including material properties, on the system behavior is discussed. In the paper, the geometric model of this kind of mechanism is first introduced. Then, a lumped kinetostatic model is proposed in order to account for joint and link compliances; some results and design guidelines are obtained. Finally, the optimization of the precision is addressed using a genetic algorithm.
Grasp Stiffness Matrix for Soft Finger Contact Model in Robotic Applications
Authors: Ghafoor Abdul , Dai Jian S. , Duffy Joseph
Published: December 2020

This paper proposes a practical and analytical model for soft finger grasp. It presents a contact stiffness matrix by applying congruence transformation and mapping stiffnesses from a line spring model onto translational and rotational stiffnesses. The contact that is realised in this paper is in the form of a patch contact with evenly distributed finite number of equivalent point contacts. An analytical approach is hence proposed based on line springs and screw representation of the frictional elastic point contacts that provides a direct correlation between the equivalent point contact and soft finger contact of a rigid object and gives a procedure to complete the analysis. The grasp achieved with the analysis provides both translational and rotational restraint. The approach and its use for finite manipulation are supported by a case study.
Gait Programming for Multi-Legged Robot Climbing on Walls and Ceilings
Authors: Qian Jinwu , Gong Zhenbang , Zhang Qixian
Published: December 2020

Wall-climbing gait programming is one of the basic issues for the multi-legged robot working on vertical walls and ceilings. In this paper, the authors propose geometric measurements related to support patterns to describe the overturn-resistance capability for multi-legged robots climbing on vertical walls and on ceilings. Employing optimization approaches, optimal regular periodic wall gaits are computed for a six-legged robot climbing vertically or horizontally, and optimal ceiling gaits are also obtained. Comparisons are made for crab-type and insect-type leg-stroke layouts.
Investigation of the Parameters Governing Linkage-Based Rocking Chairs
Authors: Canfield Stephen L. , Beard James W. , Soper R. Randall
Published: December 2020

This paper will discuss several of the kinematic and dynamic issues in developing a linkage-based rocking chair or recliner. To create the gentle oscillating motion desired in such a chair, a number of mechanical systems could be used. The most common mechanisms historically have consisted of three types: a pendulum type (e.g., a porch swing), a traditional cam-based rocking chair and a linkage-based design in which the suspended coupler is free to swing with a single degree of freedom. A number of factors effect the desirability of the motion of these chairs including the range of linear displacement, range of angular displacement, peak accelerations and acceleration profile, period, ease of generating and maintaining the oscillatory motion, and stability. One of the primary factors is the period; a longer period in the net usually indicates slower, gentler motion in any isolated segment of the oscillation.

The intrinsic advantages of linkage-based rocking chairs have motivated progressive companies within the industry to choose glider rockers as a significant part of or signature product in their product lines. Based on the criteria desired in a rocking chair, an approach to the design of linkage-based rockers is being developed. While many analytical, graphical, and optimal synthesis techniques are available which consider all possible factors in linkage design, simpler, single parameter or reduced-parameter-set approaches to the development of candidate linkages are highly desirable. This paper will present an investigation of a reduced-parameter-set approach to the synthesis of linkage-type rockers. The investigation will proceed with a simple theoretical and numerical analysis of simple rocking chairs, i.e., swing and circular-cam-based rockers, and then establish a means to extend the reduced-parameter-set design approach to the more complicated four-bar rockers. The paper will conclude with a discussion of the synthesis procedure as applied to the creation of a prototype linkage-based rocker.
The Combined Influence of Helix Angle and Total Contact Ratio on the p-FEM Calculated Tooth Root Stress in Cylindrical Gears
Authors: Piazza Andrea , Uberti Maurizio
Published: December 2020

Many parametrical studies about the effect of the helix angle on the maximum tooth root stress on cylindrical gears were conducted by means of a p-FEM (polynomial Finite Element Method) analysis, using models that comprehend all the contacting teeth and the adjacent ones. The studies were conducted in a way that the helix angle was varied from 0 to 35 degrees, keeping the transverse section constant (i.e. twisting the gears). Many non-HCR existing spur and helical gearsets, with different transverse contact ratio εα, transmission ratio, pressure angle, correction factor, and facewidth to module ratio were examined. Neither profile modification, nor crowning were considered. For each gearset the maximum p-FEM-calculated tooth root stress in both pinion and gear drops considerably when the total contact ratio εγ reaches the value of 2, with a minimum noticed around εγ = 2.1 ÷ 2.4; then the stress rises monotonically except for a non-remarkable drop when εγ reaches the value of 3. The p-FEM results were also compared with those based on ISO 6336-3 method B and AGMA 2001, showing noticeable differences.
Determination of the Tooth Surface Friction Coefficient of a Pair of Mating Gears Based on the Distribution Along the Tooth Profile Precisely Measured With the Gravity Pendulum Method
Authors: Hori Kohei , Hayashi Iwao , Iwatsuki Nobuyuki
Published: December 2020

A new gravity pendulum method has been proposed in order to precisely measure the tooth surface friction coefficient of a pair of mating gears excluding the bearing loss. In this method, one of the mating gears, which is fixed on a gravity pendulum, is put on the other gear, which is fixed on the ground, and is freely oscillated. The center-to-center distance between the mating gears is kept constant with a flexure hinge mechanism in order to accurately reproduce the relative motion, including rolling and sliding, between the tooth surfaces of practical rotating gears. This method has a great advantage, in that the tooth surface friction co-efficient can be measured in a very small region of the tooth profile, because the initial oscillation amplitude can be set approximately one arc-degree. The distribution of the friction coefficients along the tooth surface has been precisely measured for the exact one pair-, inexact one pair-, and two pair-tooth engagements of an internal gear pair and an external gear pair. Also, the mean values of the distributed tooth surface friction coefficients are calculated by taking the specific sliding between the tooth surfaces into account, and are compared with each other.
Surface Temperature Calculation and its Application for the Surface Fatigue Strength Evaluation of Rollers
Authors: Deng Gang , Nakanishi Tsutomu , Ikeda Hironori
Published: December 2020

Surface temperature is resulted by not only the load and dimension at the contact point but also the sliding velocity, rolling velocity, surface roughness, lubrication condition and etc. So, the surface fatigue strength of such as roller and gear may be evaluated more exactly and simply by use of the surface temperature or an index including the surface temperature than the Hertzian stress. In this research, the surface temperatures of rollers in different rolling and sliding conditions were measured with a thermocouple. The effects of the load P, mean velocity Vm and sliding velocity Vs on the surface temperature are clarified. An experimental formula, which expresses a linear relationship between the surface temperature and the P0.86Vs1.31Vm−0.83 value, is presented to calculate the surface temperature. This formula is also confirmed available for the gear tooth surface temperature calculation by comparison of calculated temperature and the measured temperature on the gear tooth surface. The relationship between the surface temperature and the number of load cycles of rollers are investigated, the necessity and rationality of the surface fatigue strength evaluation considering the surface temperature are discussed.
Consideration of Moving Tooth Load in Gear Crack Propagation Predictions
Authors: Lewicki David G. , Spievak Lisa E. , Wawrzynek Paul A. , Ingraffea Anthony R. , Handschuh Robert F.
Published: December 2020

Robust gear designs consider not only crack initiation, but crack propagation trajectories for a fail-safe design. In actual gear operation, the magnitude as well as the position of the force changes as the gear rotates through the mesh. A study to determine the effect of moving gear tooth load on crack propagation predictions was performed. Two-dimensional analysis of an involute spur gear and three-dimensional analysis of a spiral-bevel pinion gear using the finite element method and boundary element method were studied and compared to experiments. A modified theory for predicting gear crack propagation paths based on the criteria of Erdogan and Sih was investigated. Crack simulation based on calculated stress intensity factors and mixed mode crack angle prediction techniques using a simple static analysis in which the tooth load was located at the highest point of single tooth contact was validated. For three-dimensional analysis, however, the analysis was valid only as long as the crack did not approach the contact region on the tooth.
A Novel Approach of Obtaining Localized Tooth Contact for Spiroid Gear Drives
Authors: Su Daizhong , Song Yongle , Gentle Richard C.
Published: December 2020

A novel approach to obtaining localized bearing contact of spiroid gear drives has been developed. The localized contact is achieved by modifying the pinion tooth surface. With this approach, only the pinion cutter’s geometrical angles and mounting position need to be adjusted, and, hence, it is simpler and more economical than other methods. In this paper the following are presented: overview of the approach, equations for modified spiroid gear tooth geometry, and computer simulation results. The results confirm that the proposed modification of the tooth geometry pennits localized bearing contact.
Design of a Self-Actuating, Traction Drive Speed Reducer
Authors: Flugrad Donald R. , Qamhiyah Abir Z.
Published: December 2020

Traction drive speed reducers offer certain advantages over geared speed reducers. In particular, they generally run quieter than geared units, and they provide an opportunity for higher efficiency by eliminating sliding motion between contacting elements.

In order to generate a sufficiently high output torque, some means must be provided to create a normal force between the rolling elements. This normal force, along with the friction coefficient, enables the device to transmit torque from one rolling member to the next. The speed reducer proposed here is designed so that the configuration of the rolling elements creates the needed normal force in response to the torque exerted back on the system by the downstream loading. Thus the device is self-actuating.

Since the normal force is only present when needed, the rolling elements of the device can readily be disengaged. This eliminates the need for a separate clutch in the drive system. This feature can be exploited to design a transmission with several distinct speed ratios which can be engaged and disengaged in response to changing speed requirements.
Modeling the Nonlinear Vibration of a Spur Gear Pair
Authors: Parker R. G. , Vijayakar S. M. , Imajou T.
Published: December 2020

The dynamic response of a spur gear pair is investigated using a finite element/contact mechanics model that offers significant advantages for dynamic gear analyses. The gear pair is analyzed across a wide range of operating speeds and torques. Comparisons are made to other researchers’ published experiments that reveal complex nonlinear phenomena. The nonlinearity source is contact loss of the meshing teeth, which, in contrast to the prevailing understanding, occurs even for large torques despite use of high-precision gears. A primary feature of the modeling is that dynamic mesh forces are calculated using detailed contact analysis at each time step as the gears roll through mesh; there is no need to externally specify the excitation in the form of time-varying mesh stiffness, static transmission error input, or the like. A semi-analytical model near the tooth surface is matched to a finite element solution away from the tooth surface, and the computational efficiency that results permits dynamic analysis. Two single degree of freedom models are discussed briefly. While one gives encouragingly good results, the second, which appears to have better mesh stiffness modeling, gives poor comparisons with experiments. The results indicate the sensitivity of such models to changing mesh stiffness representations.
Dynamics of a Transmission System Having a Cracked Gear Tooth
Authors: Berri Sidi M. , Klosner J. M.
Published: December 2020

The present study is a combined experimental/analytical investigation of the effect of a cracked pinion tooth on the vibrational characteristics of a power transmission system. It is part of an ongoing effort to develop strategies for locating and quantifying local defects by properly processing and interpreting the output signals. Presented, is a system of nonlinear equations representing the analytical model of an experimental test rig. The model includes the effect of crack size on the time-varying gear mesh stiffness, and the equations are solved by using a Newmark-Beta numerical integration scheme. The numerically and experimentally obtained signals, processed by using the wavelet transform, show excellent agreement over a range of crack sizes and running speeds, thus suggesting that mathematical simulation can provide a useful tool for quantifying cracks.
Introducing Fuzzy Logic Analysis in the Life Cycle of Mechanical Systems
Authors: Drakatos P. A. , Kallaras M. , Karakassis K.
Published: December 2020

During an operation a mechanical system cost is a function of the time operation. Until now, we have taken into account the variation of economical factors as a function of time. The present work tries to import fuzzy logic in order to determine a variable model of economical factors as a reference to stillness, lubrication, repair of the mechanical systems and the variation of the operation tensions as for time. Which important levels are the mechanical systems so time operation affects the equivalent cost. The fuzzy logic model which was established, have data which was measured in the past and these data make a model with polynomial method, which doesn’t gives trustworthily results. The use of computer software is important because this method is variable as a function of cost and time.
Rapid generation of durable B cell memory to SARS-CoV-2 spike and nucleocapsid proteins in COVID-19 and convalescence
Authors: Hartley Gemma E. , Edwards Emily S.J. , Aui Pei M. , Varese Nirupama , Stojanovic Stephanie , McMahon James , Peleg Anton Y. , Boo Irene , Drummer Heidi E. , Hogarth P. Mark , O’Hehir Robyn E. , van Zelm Menno C.
Published: December 2020

Memory B cells specific for SARS-CoV-2 spike and nucleocapsid proteins persist in peripheral blood after recovery from COVID-19.
Modelling the COVID-19 pandemic in context: an international participatory approach
Authors: Aguas Ricardo , White Lisa , Hupert Nathaniel , Shretta Rima , Pan-Ngum Wirichada , Celhay Olivier , Moldokmatova Ainura , Arifi Fatima , Mirzazadeh Ali , Sharifi Hamid , Adib Keyrellous , Sahak Mohammad Nadir , Franco Caroline , Coutinho Renato
Published: December 2020

The SARS-CoV-2 pandemic has had an unprecedented impact on multiple levels of society. Not only has the pandemic completely overwhelmed some health systems but it has also changed how scientific evidence is shared and increased the pace at which such evidence is published and consumed, by scientists, policymakers and the wider public. More significantly, the pandemic has created tremendous challenges for decision-makers, who have had to implement highly disruptive containment measures with very little empirical scientific evidence to support their decision-making process. Given this lack of data, predictive mathematical models have played an increasingly prominent role. In high-income countries, there is a long-standing history of established research groups advising policymakers, whereas a general lack of translational capacity has meant that mathematical models frequently remain inaccessible to policymakers in low-income and middle-income countries. Here, we describe a participatory approach to modelling that aims to circumvent this gap. Our approach involved the creation of an international group of infectious disease modellers and other public health experts, which culminated in the establishment of the COVID-19 Modelling (CoMo) Consortium. Here, we describe how the consortium was formed, the way it functions, the mathematical model used and, crucially, the high degree of engagement fostered between CoMo Consortium members and their respective local policymakers and ministries of health.
Implementation of C-reactive protein point of care testing to improve antibiotic targeting in respiratory illness in Vietnamese primary care (ICAT): a study protocol for a cluster randomised controlled trial
Authors: Thi Thuy Do Nga , Greer Rachel Claire , Lubell Yoel , Dittrich Sabine , Vandendorpe Maida , Nguyen Van Anh , Ngoc Thach Pham , Thi Dieu Ngan Ta , Van Kinh Nguyen , Hung Thai Cao , Dung Le Thi Kim , Nguyen Thi Cam Tu , Nguyen Thanh Ha , Nadjm Behzad , van Doorn H Rogier , Lewycka Sonia
Published: December 2020

Introduction

C-reactive protein (CRP), a biomarker of infection, has been used widely in high-income settings to guide antibiotic treatment in patients presenting with respiratory illnesses in primary care. Recent trials in low- and middle-income countries showed that CRP testing could safely reduce antibiotic use in patients with non-severe acute respiratory infections (ARIs) and fever in primary care. The studies, however, were conducted in a research-oriented context, with research staff closely monitoring healthcare behaviour thus potentially influencing healthcare workers’ prescribing practices. For policy-makers to consider wide-scale roll-out, a pragmatic implementation study of the impact of CRP point of care (POC) testing in routine care is needed.

Methods and analysis

A pragmatic, cluster-randomised controlled trial, with two study arms, consisting of 24 commune health centres (CHC) in the intervention arm (provision of CRP tests with additional healthcare worker guidance) and 24 facilities acting as controls (routine care). Comparison between the treatment arms will be through logistic regression, with the treatment assignment as a fixed effect, and the CHC as a random effect. With 48 clusters, an average of 10 consultations per facility per week will result in approximately 520 over 1 year, and 24 960 in total (12 480 per arm). We will be able to detect a reduction of 12% to 23% or more in immediate antibiotic prescription as a result of the CRP POC intervention. The primary endpoint is the proportion of patient consultations for ARI resulting in immediate antibiotic prescription. Secondary endpoints include the proportion of all patients receiving an antibiotic prescription regardless of ARI diagnosis, frequency of re-consultation, subsequent antibiotic use when antibiotics are not prescribed, referral and hospitalisation.

Ethics and dissemination

The study protocol was approved by the Oxford University Tropical Research Ethics Committee (OxTREC, Reference: 53–18), and the ethical committee of the National Hospital for Tropical Diseases in Vietnam (Reference:07/HDDD-NDTW/2019). Results from this study will be disseminated via meetings with stakeholders, conferences and publications in peer-reviewed journals. Authorship and reporting of this work will follow international guidelines.

Trial registration details

NCT03855215; Pre-results.
Early prediction of in-hospital mortality in acute pancreatitis: a retrospective observational cohort study based on a large multicentre critical care database
Authors: Li Caifeng , Ren Qian , Wang Zhiqiang , Wang Guolin
Published: December 2020

Objective

To develop and validate a prediction model for predicting in-hospital mortality in patients with acute pancreatitis (AP).

Design

A retrospective observational cohort study based on a large multicentre critical care database.

Setting

All subject data were collected from the eICU Collaborative Research Database (eICU-CRD), which covers 200 859 intensive care unit admissions of 139 367 patients in 208 US hospitals between 2014 and 2015.

Participants

A total of 746 patients with AP were drawn from eICU-CRD. Due to loss to follow-up (four patients) or incomplete data (364 patients), 378 patients were enrolled in the primary cohort to establish a nomogram model and to conduct internal validation.

Primary and secondary outcome measures

The outcome of the prediction model was in-hospital mortality. All risk factors found significant in the univariate analysis were considered for multivariate analysis to adjust for confounding factors. Then a nomogram model was established. The performance of the nomogram model was evaluated by the concordance index (C-index) and the calibration plot. The nomogram model was internally validated using the bootstrap resampling method. The predictive accuracy of the nomogram model was compared with that of Acute Physiology, Age, and Chronic Health Evaluation (APACHE) IV. Decision curve analysis (DCA) was performed to evaluate and compare the potential net benefit using of different predictive models.

Results

The overall in-hospital mortality rate is 4.447%. Age, BUN (blood urea nitrogen) and lactate (ABL) were the independent risk factors determined by multivariate analysis. The C-index of nomogram model ABL (0.896 (95% CI 0.825 to 0.967)) was similar to that of APACHE IV (p=0.086), showing a comparable discriminating power. Calibration plot demonstrated good agreement between the predicted and the actual in-hospital mortality. DCA showed that the nomogram model ABL was clinically useful.

Conclusions

Nomogram model ABL, which used readily available data, exhibited high predictive value for predicting in-hospital mortality in AP.
Combination of InnoSEAL plus TR band compared with TR band alone for radial artery outcomes in patients undergoing transradial coronary intervention (InnoSEAL-II): an open-label randomised controlled trial (protocol)
Authors: Aijaz Saba , Sheikh Sana , Pathan Asad
Published: December 2020

Introduction

About 2%–30% of cardiac catheterisation procedures get complicated by radial artery occlusion (RAO). Ensuring patent haemostasis appears to be an important factor in reducing RAO. Currently employed method is a radial compression device (RCD) such as transradial band (TRB) that take hours to achieve haemostasis and cause discomfort to the patients. Haemostatic pads offer an alternative to RCD with reduced time to achieve haemostasis. Our trial aims to determine the non-inferiority of the catecholamine chitosan-based pad (InnoSEAL haemostatic pad) used in conjunction with TRB (InnoSEAL +TRB) when compared with the TRB alone in reducing composite adverse access site outcomes.

Methods and analysis

It will be an open-label, parallel, randomised controlled trial on 714 adult patients (325 in each arm) undergoing coronary procedure using transradial approach at a cardiac health facility over 7 months duration. InnoSEAL patch along with TRB will be used to control bleeding in intervention arm and TRB alone in control arm, which is the standard practice. Study primary outcomes include RAO and haematoma; secondary outcomes are compression time, patient discomfort, time to discharge and ease of use of the intervention technique by the healthcare staff. χ2 test will be used to compare the categorical outcomes between two arms and student’s t-test for continuous outcomes. A p value of <0.05 will be considered significant.

Ethics and dissemination

Ethical approval for the study has been obtained from the Institutional Review Board of Tabba Heart Institute number IORG0007863. Findings will be disseminated through seminars and scientific publications.

Trial registration number

NCT04380883; Pre-results.