bluuebunny/crossref_metadata_2025 huggingface dataset:
Intimate partner violence, prenatal stress, and substance use among pregnant Black women
Authors: Zhang Liying , Dailey Rhonda K. , Price Mercedes , Misra Dawn P. , Giurgescu Carmen
Published: February 2021

Objectives

We examine the mediation effects of prenatal stress on the associations between intimate partner violence (IPV) experience and the most common forms of substance use (i.e., cigarette smoking, alcohol drinking, and marijuana use) among pregnant Black women.

Design

Cross‐sectional.

Sample

Black women (N = 203) from metropolitan Detroit, Michigan and Columbus, Ohio, were recruited between 8 and 29 weeks of gestation.

Measurements

Women were asked about IPV experience during 12 months prior to the start of the pregnancy, perceived stress during pregnancy, and substance use during pregnancy.

Results

Intimate partner violence prior to pregnancy was positively associated with cigarette smoking and marijuana use but not with alcohol use during pregnancy. IPV prior to pregnancy was also positively associated with higher levels of perceived stress during pregnancy after controlling for covariates. Path analysis indicated that IPV had an indirect effect on marijuana use through perceived stress (standardized indirect effect = 0.026, SE = 0.020, 95% CI = 0.005–0.064, p =.017).

Conclusions

Perceived stress during pregnancy partially mediated the association between previous experience of IPV and marijuana use among pregnant Black women. Interventions are needed to reduce IPV that would lower stress during pregnancy and consequently substance abuse to improve pregnancy outcomes and maternal and newborn health.
The Random Walk Presidency
Authors: Mayer Kenneth R.
Published: February 2021

Donald Trump's erratic and unpredictable behavior as president was, metaphorically at least, a Random Walk. Combined with an inexperienced White House staff and a near total absence of any meaningful decision‐making processes, the result was, routinely, unforced errors that both impeded the president’s ability to see his policy goals implemented effectively, led to poor congressional relations and, in several key cases, failures of leadership that played a role in his defeat in the 2020 election. The worst policy outcome was his catastrophic response to the COVID‐19 pandemic, which laid bare the pathologies of poor decision‐making processes. As president, Trump’s record exposed institutional weaknesses that a more skilled populist or authoritarian successor may be able to exploit.
High‐throughput genotyping of HLA‐G, HLA‐F, MICA, and MICB and analysis of frequency distributions in healthy blood donors from Catalonia
Authors: Closa Laia , Vidal Francisco , Herrero Maria J. , Caro Jose L.
Published: February 2021

Similarly to HLA class I molecules, certain non‐classical HLA class I genes and MHC class I polypeptide‐related sequences A and B (MICA and MICB) act as ligands for KIR and NKG2D natural killer receptors. Although these genes are less polymorphic than HLA class I, few studies have analyzed their association with diseases. Information on allele frequencies in healthy donors is needed to map their distribution worldwide. This study is the first to analyze high‐resolution HLA‐G, HLA‐F, MICA, and MICB allele frequencies using a novel high‐throughput next generation‐sequencing method. We analyzed DNA samples from 96 unrelated blood donors resident in Catalonia, Spain, and registered in the Barcelona Blood and Tissue Bank. Using the first two fields of the HLA nomenclature, we detected six HLA‐G and two HLA‐F alleles. The most frequent alleles were HLA‐G*01:01 (77.08%) and HLA‐F*01:01(84.90%). When the four fields were analyzed, we detected 16 and 10 alleles, respectively. Nineteen alleles were detected for MICA and 10 for MICB. The most frequent alleles in these cases were MICA*008:01 (16.15%) and MICB*005:02 (46.84%). All frequencies were in Hardy Weinberg equilibrium except MICA. We also estimated maximum‐likelihood haplotype frequencies and calculated corresponding linkage disequilibrium (LD) values and found that few allele pairs were in disequilibrium. Strong LD between MICA and HLA‐B (using data from a previous study) was observed. Our findings will be useful for guiding further research evaluating the functional role of these genes in different diseases and populations.
Formality conjecture for minimal surfaces of Kodaira dimension 0
Authors: Bandiera Ruggero , Manetti Marco , Meazzini Francesco
Published: February 2021

Let $\mathcal {F}$ be a polystable sheaf on a smooth minimal projective surface of Kodaira dimension 0. Then the differential graded (DG) Lie algebra $R\operatorname {Hom}(\mathcal {F},\mathcal {F})$ of derived endomorphisms of $\mathcal {F}$ is formal. The proof is based on the study of equivariant $L_{\infty }$ minimal models of DG Lie algebras equipped with a cyclic structure of degree 2 which is non-degenerate in cohomology, and does not rely (even for K3 surfaces) on previous results on the same subject.
Effect of high‐intensity interval training on cardiometabolic component risks in persons with paraplegia: Protocol for a randomized controlled trial
Authors: Farrow Matthew T. , Maher Jennifer , Thompson Dylan , Bilzon James L. J.
Published: February 2021

Individuals with a spinal cord injury (SCI) are at an increased risk of developing cardiovascular disease and present with a multitude of elevated cardiometabolic component risks. Although upper‐body exercise appears an effective strategy to improve some of these outcomes, the effectiveness of high‐intensity interval training (HIIT) has yet to be determined for this population. Therefore, a randomized controlled trial will be conducted to determine the effectiveness of a 6 week home‐based upper‐body HIIT intervention on biomarkers of cardiometabolic health in persons with spinal cord injury, in comparison to a control (CON) group. We will recruit 40 individuals with chronic (>1 year post‐injury) paraplegia (spinal cord lesion between the second thoracic and second lumbar vertebrae), aged between 18 and 65 years. After baseline testing, participants will be assigned randomly, using a 2:1 allocation, to the home‐based exercise intervention (HIIT, n = 26) or control group (CON, n = 14). The HIIT intervention will consist of 30 min of arm crank‐based HIIT (60 s intervals at 80–90% peak heart rate) four times per week. Participants in the CON group will be asked to maintain their habitual diet and physical activity patterns over the study period. Baseline and follow‐up assessments will be made for determination of body composition, postprandial glycaemic control, fasting blood lipids and systemic inflammation, aerobic capacity, physical activity and energy intake, resting metabolic rate, resting blood pressure, and subjective measures of health and well‐being. ClinicalTrials.gov, ID: NCT04397250. Registered on 21 May 2020.
BDS: A Knowledge-Based Bumper Design System
Authors: Becker Beverly J. , Kaepp Gregory A.
Published: February 2021

A knowledge-based Bumper Design System (BDS) has been developed which automatically generates optimized conceptual bumper beams which meet manufacturing and product performance requirement.

The BDS has captured and refined the corporate design knowledge of the product design engineer, the CAD designer, the CAE analyst and manufacturer. The BDS enables the bumper design engineers to evaluate multiple design alternatives quickly and early in the design process. It also automates repetitive bumper analysis tasks.

The purpose of the paper is to describe the BDS. A description of the Knowledge Based Engineering (KBE) methodology used to create the BDS is given, as well as an overview of bumper designs and design requirements. An overview of the BDS software design, user interface, and a sample run are also presented.
Automatic Recognition of Interacting Machining Features Based on Minimal Condition Sub-Graph
Authors: Gao Shuming , Shah Jami J.
Published: February 2021

This paper presents a new approach for automatic recognition of machining features from the B-Reps of the part. In this approach we combine the conventional graph based recognition method with the hint based feature recognition idea so as to efficiently handle feature interactions and provide alternative interpretations of interacting features. A Manufacturing Face Adjacency Graph proposed here is useful for improving the recognition of isolated features and effectively reducing the search space for virtual links, unifiable faces and features. Isolated (non-intersecting) features are recognized first based on the Manufacturing Face Adjacency Graph. Then, interacting features are recognized based on the Feature’s Minimal Condition Sub-Graph (MCSG) which is proposed as feature hint. The MCSGs for all types of features are defined, generated and completed in a uniform way, independent of feature type. Feature definitions are based on an extended Attributed Adjacency Graph, generated by graph decomposition and completed by adding related virtual links. An efficient algorithm for generating virtual links is developed. A new feature interaction classification and a virtual link classification are also described. Our approach can produce alternative interpretations of intersecting features. The main contribution of this paper is a methodology for recognizing interacting features in a uniform way.
An Integrated, Computer-Based Method for Rapid-Prototyping Weapons-Scale Marine Propulsors Using Stereolithography
Authors: Koch Robert M.
Published: February 2021

The present work describes an integrated, two-phase computer-based method for fabricating marine propulsors using stereolithography. This new methodology seamlessly integrates stereolithography rapid prototyping techniques with the hydrodynamic design, structural design, and prototype testing of advanced marine propulsors in order to greatly increase the design process efficiency and reduce development time. Its use as applied to the design, fabrication, and testing of advanced propulsor prototypes for small weapon’s-scale undersea vehicles (e.g., Unmanned Underwater Vehicles (UUVs), lightweight and heavyweight torpedoes, etc.) is described in order to demonstrate specific strengths of the new method.
Group Technology Code Generation Over the Internet
Authors: Kalyanapasupathy Venkatraman , Lin Edward , Minis Ioannis
Published: February 2021

This paper discusses the use of the Internet to support the generation of Group Technology codes for mechanical parts. In our approach, we use a STEP-based product information model as a medium for the exchange of product information between designers and manufacturing service providers through an Internet broker. The designer uses a commercial CAD tool to create a feature-based mechanical design. The CAD design file is automatically translated into a standard STEP file. The latter is the input to the automated GT code generation tool which has been implemented as a manufacturing service available to the designer over the Internet. An Internet broker facilitates the entire exchange of product information between the designer and the service provider through the World Wide Web. We have found that automated GT code generation is a prime candidate for a distributed manufacturing service.
A Supply Chain Configuration Tool
Authors: Graser Thomas J. , McGiverin Brian J. , Barber K. Suzanne
Published: February 2021

The manufacturing of complex products often involves the assembly of other products, or sub-assemblies. Furthermore, these sub-assemblies may be manufactured by different suppliers. As a result, the specification of the assembly process for the final product contains relationships between multiple supply chain components, including business entities, manufacturing processes, products, and parts. This specification, involving the coordination and arrangement of supply chain components to support final product assembly, is referred to as a supply chain configuration.

A supply chain configuration tool is used to recognize and modify the relationships between these components. Users of this tool may be engineers, purchasing agents, program managers, or other personnel concerned with the configuration’s dependencies. The focus of this paper is on the development of such a tool and its use from the perspective of a purchasing agent.
Real-Time and Exact Collision Detection for Interactive Virtual Prototyping
Authors: Zachmann Gabriel
Published: February 2021

Many companies have started to investigate Virtual Reality as a tool for evaluating digital mock-ups. One of the key functions needed for interactive evaluation is real-time collision detection.

An algorithm for exact collision detection is presented which can handle arbitrary non-convex polyhedra efficiently. The approach attains its speed by a hierarchical adaptive space subdivision scheme, the BoxTree, and an associated divide-and-conquer traversal algorithm, which exploits the very special geometry of boxes.

The traversal algorithm is generic, so it can be endowed with other semantics operating on polyhedra, e.g., distance computations.

The algorithm is fairly simple to implement and it is described in great detail in an “ftp-able” appendix to facilitate easy implementation. Pre-computation of auxiliary data structures is very simple and fast.

The efficiency of the approach is shown by timing results and two real-world digital mock-up scenarios.
Generic Modular Operations for Virtual Manufacturing Process Engineering
Authors: Lee David E. , Hahn H. Thomas
Published: February 2021

In order to address the computational costs of modeling and analyzing manufacturing processes, a novel approach to virtual manufacturing process engineering using generic modular operations is presented. Relying on a state based representation of operation control for a simplified virtual manufacturing workcell, the valid states for each sequence of generic modular operations are aggregated and both operation state and processing constraints applied to specify the subtasks required to complete each step in a product’s process plan. By adopting this state based control approach, virtual process engineering provides a direct mechanism to map virtual process representations onto actualized processes. Using these generic modular operations and their temporal and processing dependencies, the computationally complex elements of virtual manufacturing process simulation can be directly identified and an architecture for virtual process development specified. Examples from both machining and assembly processes are provided.
A Differential Equation of the First Law of Thermodynamics for Modeling the Indicator Process of a Diesel Engine
Authors: Danov Stanislav N.
Published: February 2021

Several improvements to the mathematical model of the indicator process taking place at a diesel engine cylinder are proposed. The thermodynamic behavior of working medium is described by the equation of state, valid for real gases. Mathematical dependencies between thermal parameters (P, T, v) and caloric parameters (u, h, cv, cp) have been obtained. An improved mathematical model, based on the first law of thermodynamics, has been developed, taking into account working medium imperfections. The numerical solution of the simultaneous differential equations is made by a method of Runge-Kutta type. The computing procedure is iterative. Calculations in respect to the caloric parameters (u, h, cv and cp) for various gases under pressure up to 25 MPa and temperature up to 3000°C have been carried out. The results show, that there are significant differences between the values, calculated by equations for ideal gases, and the proposed equations for real gases under high pressure and temperature. Actual applied problems for two-stroke turbocharged engines Sulzer-RLB66 and 8DKRN 74/160 have been solved. The comparison between the experimental data and numerical results show very good agreement. The numerical experiments show that if the pressure is above 8–9 MPa, the working medium imperfections must be taken into consideration.
Estimation and Improvement of Case Retrieval System for Finite Element Analysis Modeling
Authors: Nagasawa Shigeru , Hasegawa Hiroshi , Miyata Yasunori , Fukuzawa Yasushi , Sakuta Hiroshi
Published: February 2021

This paper deals with performance of support system for finite element modeling and with a methodology for case retrieval. A support system was developed with the hypertext markup language and the common gateway interface facilities. The query response of proposed case retrieving method, based on the hamming distance with a vectorized attribute coding, was verified experimentally through an usage examples for a general purpose finite element program.
Hysteretic Mapping of Structural Wood Systems
Authors: Foliente G. C. , Ma F.
Published: February 2021

Any realistic model of structural wood systems must account for the equivalent hysteresis, which is the principal source of internal energy dissipation. Thus, determination of model parameters for hysteresis should be a first step in dynamic analysis. This paper presents a plan to use system identification techniques to estimate hysteresis model parameters for wood joints and structural systems from the extensive base of experimental data on cyclic tests that have been collected over the years around the world. A smoothly varying hysteresis loop, which represents an extension of the Bouc-Wen model, can be generated to bring about pinching as well as stiffness and strength degradation. The identified models will be used to study the dynamic response of single and multi-degree-of-freedom wood structures subjected to both deterministic and stochastic loads.
Dynamic Elasto-Plastic Response of a Generic Vehicle Floor Model to Coupled Transient Loads
Authors: Gupta Aaron D.
Published: February 2021

A dynamic elasto-plastic large displacement response analysis of the bottom floor of a generic vehicle hull model subjected to empirically obtained coupled blast and impact loads has been conducted using 3-D shell elements in the ADINA nonlinear dynamic finite-element analysis code. Although several simplifying assumptions are made regarding the structural model, material properties, and forcing functions, the investigation gives valuable insight into the nonlinear dynamic response behavior of a generic hull bottom floor to externally applied coupled blast and impact loads and provides an inexpensive method of evaluation of the structural integrity of modern vehicles subjected to spatially varying transient loads.
Normalization of Different Viewpoints on Product Development
Authors: Ghodous Parisa , Vandorpe Denis
Published: February 2021

One of the major problems for communication of information in a collaborative environment is how to transform the different experts’ viewpoints on the same application to a normalized view point. This paper presents our approach for transformation and unification of different experts’ viewpoints on product and process data models. Until now, the research works in this domain have considered only the mapping between the different product data models. In this paper, firstly we analyze the problems related to these works and then we present our approach which considers not only the unification between the product data models but also the unification between different process data models.
Dynamic Analysis of Spatial Four-Degree-of-Freedom Parallel Manipulators
Authors: Wang Jiegao , Gosselin Clément M.
Published: February 2021

The dynamic analysis of spatial four-degree-of-freedom parallel manipulators is presented in this article. First, expressions for the position, velocity and acceleration of each link constituting the manipulators are obtained. Then, the principle of virtual work is used to derive the generalized input forces of the manipulators. The corresponding algorithm is implemented and numerical examples are given in order to illustrate the results. The results obtained are verified using the classical Newton-Euler approach.
Multiobjective Collaborative Optimization
Authors: Tappeta Ravindra V. , Renaud John E.
Published: February 2021

This investigation focuses on the development of modifications to the Collaborative Optimization (CO) approach to multidisciplinary systems design, that will provide solution capabilities for multiobjective problems. The primary goal of this research is to provide a comprehensive overview and development of mathematically rigorous optimization strategies for MultiObjective Collaborative Optimization (MOCO). Collaborative Optimization strategies provide design optimization capabilities to discipline designers within a multidisciplinary design environment. To date these CO strategies have primarily been applied to system design problems which have a single objective function. Recent investigations involving multidisciplinary design simulators have reported success in applying CO to multiobjective system design problems. In this research three MultiObjective Collaborative Optimization (MOCO) strategies are developed, reviewed and implemented in a comparative study. The goal of this effort is to provide an in depth comparison of different MOCO strategies available to system designers. Each of the three strategies makes use of parameter sensitivities within multilevel solution strategies. In implementation studies, each of the three MOCO strategies is effective in solving two multiobjective multidisciplinary systems design problems. Results indicate that these MOCO strategies require an accurate estimation of parameter sensitivities for successful implementation. In each of the three MOCO strategies these parameter sensitivities are obtained using post-optimality analysis techniques.
An Analytical Model for Spur Gear Dynamics
Authors: Kuang Jao-Hwa , Lin Ah-Der
Published: February 2021

A mathematical model for a spur gear pair with two-step mesh stiffness is proposed. Two constant values of mesh stiffness are used to approximate the complicated compliance alternation of contact tooth pairs between one and two during meshing. Analytical solutions of the dynamic loads are derived. The method has been employed to calculate the dynamic contact load, transmitted torque and the bearing forces. The results compared favorably with a more detailed model found in the literature.
Kinematics of Two Wheels Joined by a Variable-Length Axle on Uneven Terrain
Authors: Davis P. W. , Sreenivasan S. V. , Choi B. J.
Published: February 2021

If two thin wheels independently joined by a fixed-length axle are placed on a flat surface, the wheels can roll on the surface without slipping, regardless of the speed at which the wheels are driven. However, if the same system is placed on an uneven surface, such that the line joining the wheel contact points is not coplanar with the axle, rolling without slip is possible only if the wheels are driven at the same speed. Otherwise, the wheels must slip against the terrain due to kinematic constraints. One method to prevent slip on uneven terrain is to use a variable-length axle. This research explores the instantaneous and gross motion of two wheels joined by a variable-length axle on uneven terrain. The end result is an algorithm to simulate this vehicle rolling on two arbitrarily oriented planes.
Assembly Configurations of Planar Non-Single-Input-Dyadic Mechanisms
Authors: Foster David E. , Cipra Raymond J.
Published: February 2021

This paper examines the problem of enumerating the assembly configurations (ACs), also called circuits, of planar non-single-input-dyadic (NSID) mechanisms. An SID mechanism is a multi-loop mechanism which can be defined by adding one loop at a time such that the mechanism has one degree of freedom (DOF) after each loop is added. An NSID mechanism is any mechanism that does not meet the SID criterion, i.e. it does not have one DOF after each loop is added. This includes all multi-DOF mechanisms, as well as some complex single-DOF mechanisms. The number of ACs of an NSID mechanism may be determined by defining the mechanism one loop at a time. The emphasis in this paper is on using graphical interpretation to determine the mobility regions of the mechanism which are preserved when each new loop is added to the mechanism. Several examples are given to demonstrate the use of this method, spanning the simpler NSID mechanisms, up to the three-loop, eight-bar linkage. The scope of this method includes mechanisms for which there are never more than 2 DOF when any loop is added. Only mechanisms with pin joints are considered in this paper.
Camera Placement Evaluation for Visual Servo Controlled Robotics
Authors: Rognvaldsson Magnus H. , McMurray Gary , Daley Wayne , Griffin Paul M.
Published: February 2021

The performance of a vision system for a robot using visual servo control is very dependent upon the placement of the camera. The placement on robot attached positions other than at the end-effector of the robot manipulator has generally not been considered. In this paper we examine the practical issues for different placements of the camera on the robot manipulator for the purpose of visual servo control. An animated computer model was developed to aid in the evaluation of various vision sensor placements. We present the results of the analysis and make recommendations.
Uniformity As the Guide to Evaluation of Dexterous Manipulator Workspaces
Authors: Canfield Stephen L. , Soper R. Randall , Reinholtz Charles F.
Published: February 2021

While robotic dexterity is the common measure of a manipulator’s ability to adequately and effectively position and orient a tool, it is position and direction dependent and therefore variable throughout the manipulator’s workspace. Since the ability to pose (position and orient) is the robot’s fundamental task, a parameter for evaluating this ability over all the workspace, proposed and referred to in this paper as the “dexterous measure,” is extremely important for use in selecting and evaluating manipulators. This work demonstrates that uniformity in dexterity is the essential feature of a dexterous manipulator and thus provides a correct basis for comparison of manipulators, all other factors being equal. Uniformity of dexterity is of tantamount importance because of the ability to select the relative magnitude of dexterity at the actuator level, for example by means of transmission gearing or in actuator selection. Arguments are presented for a holistic evaluation of the dexterous properties of manipulators based on the variation of dexterity over the workspace for a specific task. Application of the new measure is demonstrated by the analysis of three mechanical pointing devices for two common tasks over a hemispherical workspace.
Topology Design of Structures Subjected to Thermal Loading by Evolutionary Optimization Procedure
Authors: Li Qing , Steven Grant P. , Querin Osvaldo M. , Xie Y. M.
Published: February 2021

This paper extends the algorithm of Evolutionary Structural Optimization (ESO) developed by Xie and Steven to the optimal design problems of thermoelastic structures. This extension simply incorporates an evolutionary iterative process into thermoelastic finite element analysis. During each iteration two basic steps are included. Firstly, a finite element thermoelastic analysis is carried out throughout the structure at current iterative step; secondly, a small part of the lowly stressed material is gradually removed from the structure by an evolving rejection criterion. Using such an evolution process, some existing solutions for 2D thermoelasticity optimization can be easily reproduced. The work presented in this paper demonstrates the capability of this approach in solving thermoelastic problems.
Prediction of Optimal Orientation of Orthotropic Materials Using Energy Based Method
Authors: Luo Jian Hui , Gea Hae Chang
Published: February 2021

In this paper, an analytical energy based method is proposed to determine the optimal orientation of orthotropic materials under static loading. Instead of assuming the strain or stress is fixed with respect to orientational variables, the dependency of strain and stress fields on material orientation is explored by introducing an energy factor in the inclusion model. From the derivations, the strain based method and the stress based method can be recovered and their limitations are discussed. Numerical examples from these methods are presented and compared.
Probabilistic Tolerance Allocation for the Dynamics of an Internal Combustion Engine With a Flexible Connecting Rod
Authors: Zhang F. , Gilmore B. J. , Sinha A.
Published: February 2021

Tolerance allocation standards do not exist for mechanical systems with flexibility and whose response are time varying, subjected to discontinuous forcing functions. Previous approaches based on optimization and numerical integration of the dynamic equations of motion encounter difficulty with determining sensitivities around the force discontinuity. The Alternating Frequency/Time approach is applied here to capture the effect of the discontinuity. The effective link length model is used to model the system and to account for the uncertainties in the link length, radial clearance and pin location. Since the effective link length model is applied, the equations of motion for the nominal system can be applied for the entire analysis. Optimization procedure is applied to the problem where the objective is to minimize the manufacturing costs and satisfy the constraints imposed on mechanical errors and design variables. Examples of tolerance allocation are presented for a single cylinder internal combustion engine with a flexible connecting rod.
GAPRUS: Three-Dimensional Pipe Routing Using Genetic Algorithms and Tessellated Objects
Authors: Sandurkar Sunand , Chen Wei , Fadel Georges M.
Published: February 2021

Pipe routing is the technique of developing collision-free routes for pipes between two locations in an environment scattered with obstacles. In the past, research has been primarily focused on the use of deterministic optimization techniques to derive the optimal route. Computational efficiency of deterministic techniques is low for highly nonlinear and sometimes discontinuous problems like the pipe routing problem. Besides, due to limitations in the representation of 3-dimensional geometry, the shapes of obstacles have been restricted to primitives. In this paper we present a novel approach to overcome these limitations.

A non-deterministic optimization approach based on Genetic Algorithms is proposed to generate pipe routing solution sets with a high computational efficiency. Representation of the objects and pipes in the tessellated format offers huge benefits in computation as well as adaptability. We demonstrate the versatility of our approach and its ability to accommodate and solve problems involving 3-D freeform obstacles.
Fine Tuning of Rational B-Splines Motions
Authors: Srinivasan Lakshmi N. , Ge Q. Jeffrey
Published: February 2021

This paper presents two algorithms for fine-tuning rational spatial motions suitable for Computer Aided Design. The rational motions are represented by rational B-spline curves in a projective dual three-space known as the Image Space of Spatial Kinematics. The problem of fine-tuning of rational motions is studied as that of fine-tuning the corresponding rational curves in the Image Space called the image curves. The path-smoothing algorithm automatically detects and smoothes out the third order geometric discontinuities in the path of a cubic rational Bspline image curve. The speed-smoothing algorithm uses a quintic rational spline image curve to obtain a second-order geometric approximation of the path of a cubic rational B-spline image curve while allowing specification of the speed and the rate of change of speed at the key points to obtain a near constant kinetic energy parametrization. The notion of kinetic energy is used in the paper as a natural way of combining the rotational and translational speed of a spatial motion. The results have applications in trajectory generation in robotics, planing of camera movement, spatial navigation in visualization and virtual reality systems, as well as mechanical system simulation.
Tolerance Analysis in System Design Based on Multiobjective Optimization
Authors: Rai Sudhendu , Jackson Mark
Published: February 2021

This paper addresses the problem of robustness in the design of engineering systems in which design parameters and multiple performance criteria are coupled with each other. The problem of analyzing the robustness of such systems that simultaneously involve multiple performance criteria is formulated and solved.

The inverse problem of allocating optimal variabilities on design parameters that will yield acceptable robustness in performance is formulated as a multi-objective optimization problem. A direct approach of generating solutions is described and applied to the xerographic problem of allocating to functional parameters such that the performance variability in print output is within acceptable limits.
Survey of Process Planning Techniques for Layered Manufacturing
Authors: Marsan Anne , Dutta Debasish
Published: February 2021

This paper focuses on process planning for LM and provides a survey of techniques developed to date. Process planning is performed to generate the tool paths and process parameters for an object that is to be built by a particular LM process. The steps required are: part orientation, support structure generation, slicing, path planning, and process parameter selection. STL files, solid models, and image and reverse engineering data are all considered as possible input to the process planning system. The techniques reviewed can be used for a variety of LM systems.
Integrating I-DEAS With Remanufacturing and Assemblability Assessments
Authors: Kalyan-Seshu Uma-Sankar , Bras Bert
Published: February 2021

A growing concern about the environment, and especially about waste and landfill, has motivated research into environmentally conscious design and manufacturing approaches. This has placed new burdens on designers. In order to aid designers in their new tasks, one of our objectives is to minimize the gathering of information and maximize the utility of existing design information. In the research discussed in this paper, the specific objective is to enable the quantification and enhancement of product remanufacturability. Guidelines for integrating some of the commercially available CAD packages (like I-DEAS, Pro/ENGINEER, CATIA) to remanufacturing assessments, and ways to use the input information to these assessments for making other assessments (like assemblability) are developed. A number of case studies are given to illustrate the approach. Our long term goal is to identify the minimum amount of information needed to do effective design for the life-cycle.
Ruled Surfaces, Lie Groups, and Mesh Generation
Authors: Sprott Kenneth , Ravani Bahram
Published: February 2021

This paper develops a method for design of Beziér and B-spline ruled surfaces taking advantage of the Lie group structure associated with the displacement of lines. The result is a computational method which is independent of the choice of coordinate system. The method is unique in that it can be used on a set of intersecting lines and in this way is applied to automatic mesh generation for finite element analysis.
Robust Design for Mechanism Balancing
Authors: Li Zhe
Published: February 2021

The sensitivity formulae of the shaking force and shaking moment of general planar articulating mechanisms are derived. A planar four-bar mechanism is taken as a numerical example. The sensitivity and robustness of the complete force balancing result and the optimum force and moment balancing result to the link mass parameters are analyzed separately. A new robust balancing method that is insensitive to the processing errors is presented.
Goal-Based Configuration Design of Fluid Power Systems Using Neural Networks
Authors: Potter Stephen , Chawdhry Pravir , Culley Stephen , Burrows Cliff
Published: February 2021

In this paper, we present a machine learning goal-based methodology for producing configuration designs of fluid power systems. The goal is to produce solution(s) that provide the functionality desired by the user. This methodology allows the construction of an automated tool for producing the designs based on machine learning techniques, specifically artificial neural networks. In order to do this, the set of functional elements that constitute the user requirements must be recognised, as must the elements of the solution space. These sets are described in what is a necessarily context-sensitive method of producing valid mappings from the requirements set to the solution space.

The neural networks are applied to extract and encapsulate the necessary design knowledge from examples of good designs, and in doing so, overcome one of the principal problems associated with previous attempts to build automated configuration design tools, namely that of knowledge acquisition. The problem of specifying the time-varying functional requirements was addressed by the adoption of a Time Delay Neural Network algorithm.

Two examples are presented as design test cases. The results show that it is possible to construct a configuration design tool based on the methodology and incorporating domain-specific design knowledge in the form of trained neural networks.
Information Requirements for the Support of Assembly Mating Conditions
Authors: Henson Brian W. , Juster Neal P.
Published: February 2021

This paper presents an analysis of the requirement to be able to exchange or share data about assembly mating conditions between different computer systems. The challenge is that although drawing and solid model data can be exchanged between different systems, there are currently no methods of exchanging data about assembly mating conditions. A brief assessment of existing data exchange technologies is presented, the benefits of a canonical representation for mating conditions are discussed, and some of the information requirements that need to be satisfied are detailed. The requirement for a canonical representation is illustrated with a data model that satisfies the information requirements. An example of the use of the data model to describe a mating condition is presented.
Direct Manipulation of Planar Geometry
Authors: Fukuda Shuichi , Asano Tatsuya
Published: February 2021

Most of the presently available CAD systems are oriented toward generating the geometry of a whole product. But if we consider the problem of manufacturing, we sometimes wish to have such a CAD system that permits us to decompose the geometry of a final product so that we may make adequate decisions how to assemble pieces into the final shape.

For example, if we consider welding, the decision where to weld does not necessarily reflect the welding engineers’ knowledge and experience. Rather, it is determined from other considerations such as design, mechanical machining, etc. But if we could take some portion of welding engineer’s knowledge and experience at the earlier stages of design, designers might change this design to make welding much easier to perform or to permit larger degree of allowances for mechanical machining, since large amount of heat will be inputted there later on by welding. Thus, a CAD system that permits such a decomposition of geometry is desired in order to integrate design and manufacturing and to achieve true concurrent engineering.

In this work, a preliminary system has been developed which allows direct manipulation of only planer geomtry. But to consider that we do not have adequate systems which allow such decomposition for planer geometries and we still use CAD systems to work on a final geometry and different systems to determine the optimum plate cutting out of a large plate and further some other different systems to verify that the section to be welded will have enough strength, such a system would provide a first step toward realizing real concurrent engineering. Because there are many cases in welding where only planer geometries are used and if a final geometry can be decomposed into planer geometries, we would know that where it would be better to weld or how we can put them together.
Shape Grammars and Their Languages: A Methodology for Product Design and Product Representation
Authors: Agarwal Manish , Cagan Jonathan
Published: February 2021

This paper argues that shape grammars and the languages they define are an ideal means to generate and represent products where basic functionality can be decomposed into discrete processes, forms can be created to fulfill those functional processes, and variation in those forms differentiates between competitive products. A shape grammar for the design of coffee makers is highlighted and used to illustrate how an infinite set of a class of products can be articulated through a concise shape grammar. Novel coffee makers and coffee makers in the market today are generated from the grammar.
Customer Metrics for the Selection of Generic Forms at the Conceptual Stage of Mechanical Design
Authors: Kirschman C. F. , Fadel G. M.
Published: February 2021

Customer satisfaction is critical to product success. Yet evaluation methods that directly consider the customer’s wants and that are applicable at various stages of the design process are few. This paper proposes three metrics that provide the designer with a means to evaluate designs based on customer attributes: Pleasure, Protection, and Inverse Cost (Icost). These metrics are general enough to be used in conceptual design but broad enough to evaluate finished products. In addition to describing the metrics in detail, this work describes how they are used to provide a selection technique for choosing generic forms to fulfill functions at the conceptual stage of mechanical design. At this stage, there are often many alternatives to select from based on a large number of attributes. This technique uses the new metrics in combination with an adaptation of the utility theory to provide a means for the designer to organize the information and choose between alternatives while maintaining a customer viewpoint.
A Probabilistic-Based Design Model for Achieving Flexibility in Design
Authors: Chen Wei , Yuan Chenhao
Published: February 2021

In the early stages of product development, the transformation between design requirements and design solutions often involves uncertainties when specifying the desired target value for the performance expressed in design requirements. Additionally, to provide flexibility for later development, the design solution obtained is desired to be a range rather than a single solution. Our primary focus in this paper is on developing a probabilistic-based design model as a basis for providing the flexibility that allows designs to be readily adapted to changing conditions. This is obtained by developing a range of design solutions which meet a ranged set of design requirements. Meanwhile, designers are allowed to specify the varying degree of desirability of a ranged set of design requirements based on their preferences. The Design Preference Index (DPI) is introduced as a design metric to measure the goodness of flexible designs. Providing the foundation to our work are the probabilistic representations of design performance, the application of robust design concept, and the utilization of the compromise Decision Support Problem (DSP) as a multi-objective decision model. A two-bar structural design is used as an example to demonstrate our approach. Our focus in this paper is on introducing the probabilistic-based design model and not on the results of the example problem, per se.
Multiobjective Optimization and Quantitative Trade-Off Analysis in Xerographic System Design
Authors: Rai Sudhendu
Published: February 2021

A complex engineering system such as a xerographic marking engine is an aggregate of interacting subsystems that are coupled through a large number of constraints and design variables. The traditional way of designing these systems is to decouple the overall design into smaller subsystems and assign teams to work on these subsystems. This approach is critical to making the project manageable and enabling concurrent development. However, if the goal is to design systems that can deliver best possible performance, i.e. if the performance limits are being pushed to the extreme, characterizing the interactions becomes critical.

Multiobjective optimization is a design methodology that addresses the issue of designing large systems where the goal is to simultaneously optimize a finite number of performance criteria that come from one or more disciplines and are coupled through a set of design variables and constraints. This approach to design makes explicit and quantitative the inherent tradeoffs that need to be made in doing coupled system design. It also enables the determination of the attainable limits of performance from a given system.

This paper will discuss the multiobjective optimization methodology and optimal methods of performing quantitative trade-off analysis. These design methods will be applied to problems from the xerographic design domain and results will be presented.
Design for Purchasing: A Methodology for Reducing the Materials Cost of Engineered Products
Authors: Bradley Stephen , Calice Matthias , Fischer Marc , Harmening Michael
Published: February 2021

This paper gives an overview of a methodology for reducing the cost of purchased materials for engineered products. The methodology has been successfully employed for a wide range of applications, ranging from low value-added products, such as simple processed materials (e.g., steel sheet or profiles), to high value-added equipment, such as machine tools and major components of industrial plants. We have applied the methodology in some 80 projects, achieving cost savings averaging 17% on top of the 10% savings achieved using traditional purchasing optimization approaches. The key distinguishing features of the methodology are a product-oriented as opposed to materials group-driven approach, the establishment of interdisciplinary teams that include engineers and purchasing professionals, and a well-defined, systematic method for addressing the most important drivers of materials cost together with key suppliers. The methodology is introduced by performing pilot projects, then anchored in the enterprise through organizational and procedural changes.
Using Student Preferences to Guide Design Team Composition
Authors: Wilde Douglass J.
Published: February 2021

For five years now Stanford’s Mechanical Engineering Design Division has experimented with restrictions on how students choose the members of their design teams. The constraints are based on voluntary student responses to a short questionnaire, essentially a sampling of questions from the Myers-Briggs Type Indicator widely used for vocational and educational counseling. This has produced teams performing qualitatively and quantitatively better, as measured by prizes won in the nationwide Lincoln Foundation Design Competition, than did teams of the thirteen years preceding. In 1995, Stanford teams won all but two of the twelve prizes awarded. This article describes these experiments, lists the results, describes how to construct a suitable questionnaire, reviews pertinent psychological theory, and gives mathematically precise instructions for constraining construction of the teams. The current procedure also incorporates information obtained from a recent survey on team satisfaction in a different project design course. This modified method seeks to generate satisfied teams without sacrificing prize-winning ability.
To Injection Mold, to Stamp, or to Assemble? Part I — A DFM Cost Perspective
Authors: Hu Weiyi , Poli Corrado
Published: February 2021

This paper presents a DFM cost comparison of injection molding and stamping, the processes most commonly used in the production of consumer oriented special purpose components. The general guidelines obtained and conclusions drawn in order to determine if a component should be injection molded or stamped, and/or if several components should be combined into a single component or not, are discussed. The cost evaluation and comparison are primarily in terms of the functional equivalence of feature, component, and assembly.