bluuebunny/crossref_metadata_2025 huggingface dataset:
How Well Do They Manage a Crisis? The Government's Effectiveness During the COVID‐19 Pandemic
Authors: Mizrahi Shlomo , Vigoda‐Gadot Eran , Cohen Nissim
Published: February 2021

The COVID‐19 pandemic clearly highlighted the importance of effective crisis management and its relationship with citizens’ willingness to cooperate with the government in such turbulent times. We develop a theory and hypotheses about the impact of citizens' experiences on their perceptions of the government's effectiveness during times of crisis. We do so with data collected at two points in time: in late March 2020 during the first peak of the COVID‐19 crisis in Israel, and in October 2020 when Israel was exiting from a second lockdown. The findings demonstrate that during crises citizens focus on the short term and seek immediate results in terms of readiness and preparedness. During such times, the government's responsiveness and transparency, as well as the public's participation in decisions, seem even more important than their trust in the government. Implications and practical recommendations follow.
The role of patent expiration in acquisition decision and target selection in the pharmaceutical industry
Authors: Arroyabe Marta F.
Published: February 2021

This paper addresses the calls for greater research on the antecedents of technological acquisitions by exploring a mechanism that drives both acquisition decision and target selection. Drawing from the RBV, this paper presents patent expiration as a driver behind pharmaceutical firms’ acquisition decisions and target selection. This paper argues that patent expiration constitutes a disruption to pharmaceutical firms’ pipelines and a threat to revenue and profit streams and that acquisitions represent a possible short‐term solution for firms to replenish their patent portfolios and to ensure a continuous flow of revenues. Using a sample of US pharmaceutical firms, this paper shows that pharmaceutical firms engage in acquisitions when they face large amounts of patent expiration and when they are unable to internally replenish their patent portfolios. The results also show that acquiring firms have a preference for targets with resources similar to their existing portfolio of patents, which is explained by firms’ desire to minimize post‐integration problems and possible disruptions derived from the difficulties in assimilation and commercial exploitation of distant knowledge. This is in contrast with previous studies indicating that acquiring firms benefit from knowledge bases that are more distant.
Asymptotic theory for statistics based on cumulant vectors with applications
Authors: Rao Jammalamadaka Sreenivasa , Taufer Emanuele , Terdik György H.
Published: February 2021

For any given multivariate distribution, explicit formulae for the asymptotic covariances of cumulant vectors of the third and the fourth order are provided here. General expressions for cumulants of elliptically symmetric multivariate distributions are also provided. Utilizing these formulae one can extend several results currently available in the literature, as well as obtain practically useful expressions in terms of population cumulants, and computational formulae in terms of commutator matrices. Results are provided for both symmetric and asymmetric distributions, when the required moments exist. New measures of skewness and kurtosis based on distinct elements are discussed, and other applications to independent component analysis and testing are considered.
What do we know about LGBQ+ college student academic experiences and outcomes?
Authors: Beattie Irenee R. , Van Dyke Nella , Hagaman Natasha
Published: February 2021

In spite of recognition that lesbian, gay, bisexual, and queer+ (LGBQ+) young adults face challenges associated with their sexual identities, research on inequality in education has only recently begun examining their academic experiences and outcomes in college. Prior work has mainly focused on social and extracurricular experiences during college or academic outcomes among LGBQ+ students in K‐12 settings. In this article, we review the growing body of social science literature on LGBQ+ college students' academic outcomes. A strength of our review is our integration of research on individual, interpersonal, and institutional characteristics and experiences that influence LGBQ+ student outcomes. In reviewing the literature, we identify a number of methodological and theoretical limitations, such as a lack of precision and consistency in defining and conceptualizing LGBQ+ identities and experiences and limited attention to intersections with race, class, and gender. We offer some solutions to these limitations and present a theoretical framework that promises to add clarity and further reliability to future research on LGBQ+ college student outcomes. We conclude by suggesting directions for future research.
Recent pension reforms in Europe: More challenges, new directions. An overview
Authors: Hinrichs Karl
Published: February 2021

During the last 30 years, all European Union member states have reformed their pension systems. In view of ongoing and intensifying population aging, efforts have aimed at containing the future rise of the contribution rate, improving the system dependency ratio, lowering the benefit ratio and/or infusing tax money or other financial resources into the system. Moreover, since about the early 2000s, we can observe a move towards a multi‐pillar pension system in countries hitherto running a dominant‐pillar system: private pre‐funded occupational pensions and individual provision for old age are given larger roles within the public–private mix of retirement income. An analysis of reforms shows a finite menu of adjustment options, and concrete measures have to be adapted to nation‐specific institutional contexts. Finally, we can conclude that pension reforms focusing on long‐term financial sustainability may increase the risk of old‐age poverty and, thus, violate a central objective of pension schemes.
Inclusive citizenship and degenderization: A comparison of state support in 22 European countries
Authors: Finch Naomi
Published: February 2021

This paper argues that welfare state progress needs to be based upon support for “inclusive citizenship” – the right to care, work and earn. Comparative analyses of welfare have often focused on defamilization to capture these dimensions. But inclusive citizenship requires challenging gender roles in both work (public sphere)andcare (private sphere), and thus the paper argues that the concept of degenderization is a more suitable analytical tool. This paper adds to our understanding by operationalizing the concept of degenderization to compare how (far) 22 European countries degenderize. Indeed, it goes further to examine not just howmuchwelfare states degenderize buthow– whether they focus on degenderingbothwork and care, crucial for “inclusive citizenship”. To examine how states degenderize, it uses a new way of classifying welfare states by examining policy packages using radar charts. It examines how much they degenderize against a yardstick, using the Surface Measure of Overall Performance approach. Seven welfare types were identified, but none fully supported inclusive citizenship. Indeed, the country clusters identified in this study differ from those found by previous studies, challenging commonly held views about which countries ought to be seen as key exemplars. This reflects the paper's distinctive focus on inclusive citizenship – capturing support for degendering care and work – and that it compares countries on the basis of their policy packages. It also examines how approach to and generosity of degenderization are related to gender equality outcomes.
Biochar combined with nitrogen fertilizer affects soil properties and wheat yield in medium‐low‐yield farmland
Authors: Dong Linlin , Wang Jidong , Shen Mingxing , Zhang Haidong , Wang Lingqing , Li Chuanzhe , Lu Changying
Published: February 2021

Biochar combined with fertilizer as a soil amendment benefits to improving soil fertility, especially soil organic carbon and crop yield. However, the effect of biochar on the improvement of soil properties and crop yield was varied from soil properties and limited for medium–low‐yield farmland in the North China. During the completely randomized field experiment, SIX treatments (biochar applied as 0, 15 and 30 t·ha‐1, under 240 and 300 kg N ha‐1 nitrogen fertilizer) were applied in wheat season and examined to reveal changes in the SOC and other properties of 0‐ to 10‐cm and 10‐ to 20‐cm soil layers. The results showed that two years after the application of biochar, a significant increase in the SOC was observed, ranging from 19.52% to 97.50% (p < 0.05) in the 0‐ to 20‐cm soil layer. Wheat yield and SOC content increased with increasing amount of biochar applied under the same amount of nitrogen fertilizer. The content of soil available potassium increased significantly under 30 t·ha‐1 biochar application (p < 0.05). Both biochar and nitrogen fertilizer application could increase wheat yield, and the effect of biochar application for increasing wheat yield was better than that of nitrogen fertilizer. Wheat yield and SOC content increased with increasing nitrogen fertilizer at the same amount of biochar application. The principal component analysis results showed that biochar input, SOC, available potassium and total nitrogen were the key factors affecting wheat yield. Biochar application is a fast and effective measure to improve SOC and wheat yield in medium‐ and low‐yield farmlands.
The Creep of Metals—II
Authors: Nadai A. , Davis E. A.
Published: February 2021

In the following a few simpler cases of the slow flow of solids with particular reference to the creep of metals in the strain-hardening range are treated. These means should permit considering the effect of strain hardening when discussing observations on creep. Creep tests with soft and strain-hardened copper at room temperature are included.
The Rate of Growth of Fatigue Cracks
Authors: deForest A. V.
Published: February 2021

The author discusses the resistance of metal to the propagation of cracks, and points out that in the accepted method of fatigue testing the results are not conclusive because there is no distinction between (1) the load and the number of repeated stresses required to start cracks and (2) the load and the number of reversals needed to propagate the cracks to failure. The investigation reported in the paper was undertaken to determine (a) the stress and number of reversals required to start a fatigue crack, and (b) the resistance of the material to the effect of a fatigue crack once it had been formed. The tests reported were conducted on annealed cold-rolled low-carbon steel bars with various finishes. The author presents data on the rate of progress of the cracks and on the size of the cracks, the latter of which was determined by magnetizing the bars and inspecting them with finely divided iron oxide in a bath of kerosene.
Fatigue Failure From Stress Cycles of Varying Amplitude
Authors: Langer B. F.
Published: February 2021

A method is proposed for estimating the life of a machine part which is subjected to repeated applications of various stresses, some of which are above the fatigue limit.
Recent Investigations in Plastic Torsion
Authors: MacGregor C. W. , Hrones J. A.
Published: February 2021

Tension, double-shear, and torsion tests on cast iron, S.A.E. 1045 annealed steel, and S.A.E. 1112 annealed steel are described in which the quantitative relations between the so-called modulus of rupture, double shear strength, and actual maximum shear stress in the bar at fracture are given for each material. The shear stress distribution over the cross section of each bar at fracture is also determined. Further, the data obtained from tension and torsion tests on the two steels are plotted on a single set of coordinates, namely the octahedral shearing stress τn and the octahedral shearing strain γn. A reasonable check is obtained between the two curves when the shear strain is less than that corresponding to the tensile strength.

Finally, there is described a series of plastic-torsion tests on bars of mild steel with various new cross sections of practical interest, namely, the splined shaft, the circular shaft with two shallow rectangular keyways, double- and four-lipped drills, and I-beams. In these tests, the regions of initial yielding are determined by means of the Fry etching method.
Analysis of Bolted Joints at High Temperature
Authors: Waters E. O.
Published: February 2021

A preliminary study shows that the flanges in a typical bolted joint for piping have a more nearly uniform, and hence more favorable, stress distribution after creep has occurred than when the joint is first tightened up. However, the tightness of the joint depends on the initial elastic stretch of bolts and flanges; hence an estimation of its durability at high temperature is really a compound relaxation problem, and the advantage to be gained by the quasi-uniform stress distribution is apt to be illusory.
Creep of Metals at High Temperature in Bending
Authors: Davis E. A.
Published: February 2021

The author develops a theory for plastic bending and obtains equations for the creep due to bending. Results of tests on a chromium-nickel composition are given to show the agreement between the experimental and theoretical results.
Heat Dissipation Through an Annular Disk or Fin of Uniform Thickness
Authors: Murray William MacGregor
Published: February 2021

The subject matter considered in this paper deals with the mathematical investigation of heat flow in an annular disk of uniform thickness. Originally, the investigation was carried on in connection with the design of fins for increasing the heat transfer in various kinds of heat exchangers and engines. The results of the study, however, might easily be applied to a number of other problems, since by altering the boundary conditions slightly one may use the same basic equations for calculating the temperature distribution and heat transmission in grinding wheels and disk clutches.

The study of the problem in connection with fin design has brought forth other solutions for special cases of the general proposition considered here. The particular results obtained by previous investigators can be readily found from the general equations given in this paper. In order to assist in the numerical solution of the somewhat complicated equations a chart for evaluating the mathematical expressions has been included.
Convective and Absolute Instabilities Induced by Viscous Dissipation in the Thermocapillary Convection With Through-Flow
Authors: Reis Eduardo V. M. , Alves Leonardo S. de B.
Published: February 2021

The mixed convection in a thin liquid film flow over a horizontal plate is investigated under finite Prandtl numbers. The gas–liquid interface is considered free, nondeformable and subject to surface tension gradients and convection, while gravity is assumed negligible. Therefore, thermocapillary instead of buoyancy effects appears due to the unstable temperature stratification induced by the internal heating generated by viscous dissipation. A linear and modal stability analysis of this model is then performed to identify its convective/absolute nature. This is achieved by solving the resulting differential eigenvalue problem with a shooting method. Longitudinal rolls are the most unstable at the onset of instability for most parametric conditions. Otherwise, transverse rolls are the first to become convectively unstable. Finally, longitudinal rolls are absolutely stable. A transition to absolute instability occurs through transverse rolls, but only within a limited region in parametric space.
Numerical Simulation of Heat Transfer in Laminar Natural Convection of Mixed Newtonian-Non-Newtonian and Pure Non-Newtonian Nanofluids in a Square Enclosure
Authors: Vallabh Ajay , Ghoshdastidar P. S.
Published: February 2021

This paper presents a steady-state heat transfer model for the natural convection of mixed Newtonian-Non-Newtonian (Alumina-water) and pure non-Newtonian (Alumina-0.5 wt% Carboxymethyl Cellulose (CMC)/water) nanofluids in a square enclosure with adiabatic horizontal walls and isothermal vertical walls, the left wall being hot and the right wall cold. In the first case, the nanofluid changes its Newtonian character to non-Newtonian past 2.78% volume fraction of the nanoparticles. In the second case, the base fluid itself is non-Newtonian and the nanofluid behaves as a pure non-Newtonian fluid. The power-law viscosity model has been adopted for the non-Newtonian nanofluids. A finite-difference based numerical study with the Stream function-Vorticity-Temperature formulation has been carried out. The homogeneous flow model has been used for modeling the nanofluids. The present results have been extensively validated with earlier works. In Case I, the results indicate that Alumina-water nanofluid shows 4% enhancement in heat transfer at 2.78% nanoparticle concentration. Following that there is a sharp decline in heat transfer with respect to that in base fluid for nanoparticle volume fractions equal to and greater than 3%. In Case II, Alumina-CMC/water nanofluid shows 17% deterioration in heat transfer with respect to that in base fluid at 1.5% nanoparticle concentration. An enhancement in heat transfer is observed for increase in hot wall temperature at a fixed volume fraction of nanoparticles, for both types of nanofluid.
Thermal Performance Comparison and Augmentation of Two Identical Box-Type Solar Cookers Operating in Tropical Climatic Conditions
Authors: Arif Md. Reyaz , Khan Mohammad Athar , Azhar Md. , Akhtar Naiem , Meraj Md.
Published: February 2021

In the present study, experimental studies have been performed to compare the thermal performance of two geometrically identical box type solar (B-T-S) cookers. To carry out this aim, the thermal performance of BTS cooker in terms of figure of merits, namely, first figure of merit (F1) and second figure of merit (F2) are calculated for both cookers as specified by the Bureau of Indian Standards (BIS). At no-load condition (i.e., stagnation test), it is found that first figure of merit for both cookers that is cooker 1 and cooker 2 is around 0.12. This implies that both the cookers are identical in thermal performance. In addition to this, the effect of lugs height, reflector, number of pots, and load on B-T-S cooker performance have also been investigated. From the results and discussion, it is concluded that the use of lugs reduced the heat transfer rate between cooking pot and absorber plate. Further, it is found that the pot content temperature is enhanced by 25.5% and 23.4% by using mirror and aluminum reflector with cooker, respectively. However, it is observed that the performance parameters of B-T-S cooker in terms of F2 increases linearly with the increase of number of cooking pot (with correlation F2 = 0.0316n + 0.2238, where n is the number of pots) and load (correlation as F2 = 0.0451 m + 0.1844, where m is the mass of water in cooking pot) on the pot.
Assessment of Heat Exchanger Degradation in a Boeing 737-800 Environmental Control System
Authors: Jennions Ian , Ali Fakhre
Published: February 2021

There are a number of systems on an aircraft working together, in harmony, to produce safe and trouble free flight. The environmental control system (ECS) is one of these systems, and its failure is a major contributor to unscheduled maintenance, particularly in older aircraft. The ECS is composed of several complex sub-systems and components, but at its heart is the passenger air conditioner (PACK). The PACK is prone to degradation, which can lead to the functional failure of the ECS. Often its degradation is masked by the overall ECS control system and this can, ultimately, result in the ECS shutting down and extensive maintenance being required. There are a number of critical fault modes associated with the PACK, and in this paper, those modes associated with the primary and secondary heat exchangers (SHX) are explored. A robust ECS simulation framework called Simscape ECS simulation under all conditions (SESAC) has previously been implemented, calibrated, and tested against data from healthy systems. Here the simulations are extended to cover degraded components in a representative Boeing 737-800 aircraft PACK model. Fault modes such as blockage and fouling are assessed for the primary and secondary heat exchangers of the PACK. Simulation results, in terms of temperature, pressure, and mass flow at various degradation severities, are presented and discussed. The results highlight the interdependency between the PACK components and the strong association between the primary and secondary heat exchangers performance. The reported simulation methodology and findings serve as a further step towards the goal of formulating a cost-effective ECS fault isolation and diagnostic solution.
Sub-Channel Analysis of a Hexagonal Sub-Assembly: Influence of Blockage and Axial Power Distribution on Critical Heat Flux
Authors: Pothukuchi Harish , Patnaik B. S. V. , Prasad B. V. S. S. S.
Published: February 2021

The study of thermal hydraulics of a hexagonal sub-assembly is essential to ensure the safe operation of liquid metal cooled fast reactors. Identifying the dryout location in fuel sub-assembly (FSA) is a precursor to the determination of safe Critical Heat Flux (CHF) margins. In this study, a sub-channel analysis code coupled with a film thickness model is employed to predict the CHF location in a hexagonal sub-assembly. A simple post-CHF heat transfer model is proposed and validated against the experimental data. The nature of flow resistance changes and operating conditions would significantly influence the occurrence of CHF. To this end, the effect of blockage (0.0 ≤ b ≤ 0.3) and axial power distribution (APD) on CHF is systematically investigated in a hexagonal sub-assembly. It was observed that the presence of blockage causes coolant flow maldistribution which results in an early occurrence of CHF for higher mass flux (G > 1500 kgm−2s−1) and lower inlet subcooling (ΔTsub ≤ 30 K) conditions for b = 0.3. Furthermore, a comparative study of uniform and sinusoidal heat flux distributions is performed. It was noticed that sinusoidal APD causes the early occurrence of CHF compared to uniform APD.
Conjugate Heat Transfer Simulations to Evaluate the Effect of Anisotropic Thermal Conductivity on Overall Cooling Effectiveness
Authors: Bryant Carol E. , Rutledge James L.
Published: February 2021

Ceramic matrix composites (CMCs) show promise as higher temperature capable alternatives to traditional metallic components in gas turbine engine hot gas paths. However, CMC components will still require both internal and external cooling, such as film cooling. The overall cooling effectiveness is determined not only by the design of coolant flow, but also by the conduction through the materiel itself. CMCs have anisotropic thermal conductivity, giving rise to heat flow that differs somewhat relative to what we have come to expect from experience with traditional metallic components. Conjugate heat transfer computational fluid dynamics (CFD) simulations were performed in order to isolate the effect anisotropic thermal conductivity has on a cooling architecture consisting of both internal and external cooling. Results show the specific locations and unique effects of anisotropic thermal conduction on overall effectiveness. Thermal conductivity anisotropy is shown to have a significant effect on the resulting overall effectiveness. As CMCs begin to make their way into gas turbine engines, care must be taken to ensure that anisotropy is characterized properly and considered in the thermal analysis.
A Generalized Method for the Classification and Extraction of Form Features
Authors: Qamhiyah A. Z. , Venter R. D. , Benhabib B.
Published: February 2021

Feature-extraction techniques address the primary limitation of feature-recognition approaches, namely their lack of generalization. This paper presents a boundary-based procedure for the classification and sequential extraction of form features from the CAD models of objects with planar surfaces. Form features are first classified based on their effect on the boundary elements of a basic shape. Geometric reasoning is then used to obtain generalized properties of the form-features’ classes. Finally, form-features’ classes are sequentially extracted based on the recognized properties. At the onset of each extraction stage, the object is viewed as an initial basic shape that has been iteratively altered through the introduction of form features.
A Computer Environment for Realistic Assembly Design
Authors: Beach D. A. , Anderson D. C.
Published: February 2021

Described is an object-oriented assembly model that is formulated based on the needs of 3D graphical interaction, information needed for assemblability analysis, and principles of kinematics. The user interface provides real-time interaction with dual part representations, consisting of both feature and solid models, for building and modifying an assembly. Parts are moved and assembled in a realistic 3D environment. The system assists the user in creating attachments between parts in a “drag and drop” manner by dynamically displaying potential mating conditions based on location and alignment proximity.
Computer Controlled Integrated Steering / Drive System for Vehicles
Authors: Blair D. B. , Spark I. J.
Published: February 2021

This paper discusses how a computer controlled four-wheel-steering (4WS) system can be used to increase the ability, namely low speed stability and traction as well as increased manoeuvrability of four-wheel-drive (4WD) vehicles.

The essential feature of the integrated 4WS/4WD vehicle is that the path of the vehicle is selected via a joy stick or steering wheel, and a computer then controls the drive system of the two right hand wheels independently of the two left hand wheels, along with the positive rotation of the four wheels about vertical axes to the appropriate angles.

Previous work by Spark and Besselink (1994a) relating to two wheel steering (2WS) / two wheel drive (2WD) systems will also be discussed briefly and expanded.
Solution of Geometrically Nonlinear Problems Using Spatial Reference and the p-Version of the FEM
Authors: Noël Andre T. , Szabó Barna A.
Published: February 2021

This paper presents a new formulation for geometrically nonlinear problems and their numerical treatment by the p-version of the finite element method. The formulation is characterized by a weak form based on the spatial representation of the equilibrium equations, a deformed geometry mapped by the displacement field, a natural description for non-conservative loads that keeps the symmetry of the equations, and a direct (non-incremental) iterative algorithm for solving the equations. The paper is concerned only with problems for which the solution is unique, i.e. the load-displacement curves are single-valued. Examples are presented.
Finite Element Analysis of Automotive Structures Based on Simplified Models
Authors: Tang Xiaodong D. , Lu Chiming
Published: February 2021

This paper presents finite element analysis (FEA) of simplified automotive structures using beam-like elements. The concept is to perform FEA quickly or at early product development stage in order to guide the design process. Two types of finite element models are studied: 1) simplified models which use beam elements to model beam-like components and use other elements for the rest of the vehicle parts such as joints, engines and roofs; 2) thin-walled beam models which purely use thin-walled beam elements. The static stiffness, modal and crash analyses are conducted and the correlation of the results with those from conventional methods are provided.
The Geometry and Generation of NC Tool Paths
Authors: Sarma Radha , Dutta Debashish
Published: February 2021

Numerically controlled milling is the primary method for generating complex die surfaces. These complex surfaces are generated by a milling cutter which removes, material as it traces out pre-specified tool paths. The accuracy of generation of tool paths directly affects the accuracy of the manufactured part. For a given machine and cutting tool the cost of manufacture is directly dependent on the tool paths.

In this paper we propose a new method for generating NC tool paths. This method gives the part programmer direct control over the accuracy (scallop height) of the final surface and is capable of yielding a uniform surface finish. We also propose a new method for step-over calculations which is robust and accurate. The method also provides the part programmer options to generate a variety of tool paths.
Design of Modular Product Architectures in Discrete Design Spaces Subject to Life Cycle Issues
Authors: Rosen David W.
Published: February 2021

A product’s architecture affects the ability of a company to customize, assemble, service, and recycle the product. Much of the flexibility to address these issues is locked into the product’s design during the configuration design stage when the architecture is determined. The concepts of modules and modularity are central to the description of an architecture, where a module is a set of components that share some characteristic. Modularity is a measure of the correspondence between the modules of a product from different viewpoints, such as functionality and physical structure. The purpose of this paper is to investigate formal foundations for configuration design. Since product architectures are discrete structures, discrete mathematics, including set theory and combinatorics, is used for the investigation. A Product Module Reasoning System (PMRS) is developed to reason about sets of product architectures, to translate design requirements into constraints on these sets, to compare architecture modules from different viewpoints, and to directly enumerate all feasible modules without generate-and-test or heuristic search approaches. The PMRS is described mathematically and applied to the design of architectures for a hand-held tape recorder. Life cycle requirements are used as design criteria.
Augmented Reality Based Interaction: Application to Design and Manufacturing
Authors: Kesavadas T.
Published: February 2021

This paper presents applications of augmented reality-based interaction that allow new ways of interaction with manufacturing and design environments. The first example shows a design verification system in which a prototype virtual model of a template is blended into a manufacturing environment. The second part describes an interactive system for specifying robotic tasks using virtual tools that allow an operator to reach into a live video scene and direct robots to use corresponding real tools in complex scenarios. Such an interwoven AR system will allow easy and intuitive control of manufacturing tasks and will help designers to preempt design defects or faults and reduce the prototype development time.
Virtual Prototyping of Product Structure in Product Data Management
Authors: Menon Jai , Horn William
Published: February 2021

Product Data Management (PDM) systems are beginning to be deployed for organizing, accessing, and controlling data about products throughout their life cycle. In general, these systems lack integrated tools for prototyping PDM data, such as the Product Structure. Product Structure (PS) encompasses broadly the hierarchical organization of parts, typically denned by the bill of material, that describes the product from a variety of (e.g. design, manufacturing) views. Consistent maintenance and constant evaluation of the evolving PS is vital during iterative design, particularly when parts are shared across different products. The first contribution of this paper is a framework for understanding how PS/PDM fits within the broad context of mechanical design, leading to the identification of key desirables of PS prototypes. The second contribution is a system architecture for PS prototyping that satisfies these desirables. The system conveniently accesses different versions of the PS stored in the IBM ProductManager PDM system, and supports virtual prototyping of the PS using real-time interactive visualization in the IBM 3D Interaction Accelerator (3DIX) environment.
Virtual Prototyping: New Information Techniques in Product Design
Authors: Flaig Thomas , Thrainsson Magnus Thor
Published: February 2021

International competition is characterised by the reduce of the innovation time. Therefore the success of new products strongly depends on the necessary time for their development. Virtual Reality, a new 3D human-computer interface accelerates significantly the processes of creating and handling 3D data in 3D space for design and evaluation purposes. The paper outlines required system tools for the design and evaluation of new products based on Virtual Reality techniques. The goal of these tools is to enable interaction in an intuitive and easy way with a virtual product. Furthermore tools have been developed for the support of co-operative work in a virtual environment.
On the Design of Rapidly Deployable Field Robotic Systems
Authors: Farritor Shane , Dubowsky Steven , Rutman Nathan
Published: February 2021

Long development times and high costs limit the practical use of robots for many important field missions. Here the underlying hypotheses of a modular design approach to producing rapidly deployable, low cost field robotic systems are presented and their validity explored. An inventory of physical modules and software modules are assembled into a field robotic system for a specified task. The proposed design method uses a hierarchical selection process combined with a genetic algorithm to select a robot configuration and action plan for a given task. The method is applied to an inspection task required for the preservation of an historic ship.
Constraint Management Methodology for Conceptual Design Tradeoff Studies
Authors: Reddy Sudhakar Y. , Fertig Kenneth W. , Smith David E.
Published: February 2021

This paper presents a constraint management methodology, which facilitates tradeoff studies during conceptual design. This approach represents design models as constraints between variables, and uses the resulting constraint network to automatically derive computational procedures for performing user-specified tradeoff studies. By decomposing large constraint networks into smaller pieces that can be solved robustly, this approach can solve extremely large systems of non-linear equations present in practical system models. Design Sheet is a software implementation of this methodology; it allows the designer to interactively develop models, flexibly define tradeoff studies, and quickly explore large areas of design space to study how the different performance and cost criteria tradeoff with respect to one another. Design Sheet has been used on practical applications ranging from the system-level design of spacecraft using combined performance and cost models to the preliminary design of automotive bearings. This paper demonstrates the unique capabilities of Design Sheet in performing design tradeoff studies, using a thermal imaging system performance model developed for the DARPA MADE program.
Implications of Modularity on Product Design for the Life Cycle
Authors: Newcomb Patrick J. , Bras Bert , Rosen David W.
Published: February 2021

Growing concern for the environment has spurred interest in environmentally conscious design and manufacturing. The concept of Design for the Life Cycle encompasses all aspects of a product’s life cycle from initial conceptual design, through normal product use, to the eventual disposal of the product. A product’s architecture, determined during the configuration design stage, plays a large role in determining the product’s life cycle characteristics. In this paper, modularity of product architectures with respect to life cycle concerns, not just product functionality and structure, is defined and applied in the analysis of architecture characteristics. A principal hypothesis underlying this work is that high degree of life cycle modularity can be beneficial across all viewpoints of interest because all interested people will view the product similarly and consistently. An architecture decomposition algorithm from the literature is adopted for partitioning architectures into modules from each life cycle viewpoint. Two measures of modularity are proposed: one that measures module correspondence between several viewpoints, and another that measures coupling between modules. The algorithm and measures are applied to the analysis and redesign of an automotive center console. Results of applying the algorithm and measures accurately reflected our intuitive understanding of the original center console design and predicted the results of our redesign. Furthermore, these measures incorporate only configuration information of the product; hence, can be used before detailed design stages.
Integration Infrastructure to Support Concurrence and Collaboration in Engineering Design
Authors: Bliznakov Plamen I. , Shah Jami J. , Urban Susan D.
Published: February 2021

Traditionally, CAD tools have provided limited possibilities for interaction between different participants in a design project. This paper describes an environment for information integration of CAD systems and other application programs referred to as meta-level design information system. Taxonomies of CAD and other application programs with regards to their “integration friendliness” and possibilities for remote access by the enduser are developed. These taxonomies can be used by CAD vendors as a guidance for development of software which can be integrated easier in a higher-level design information system. In this work the taxonomies are used to catalogue the applications and their data.

The information integration infrastructure is based on an object-oriented multidatabase using the WWW to transfer the transactions. An information broker provides a global conceptual view of data and knowledge stored in a metadatabase including description of product data and design constraints, design process, organizational information, etc. It processes user queries and dynamically accesses the information from CAD tools (which act as objects on the WWW) if needed. The CAD tools interface is provided by software network adapters. They export parts of the local application models needed for maintaining intertool constraints and supporting remote queries by participants in the design process who do not have direct access to the CAD systems.
Topological Synthesis of Geared Robotic Mechanism
Authors: Chen Dar-Zen , Shieu Shuen-Chen
Published: February 2021

An efficient and systematic methodology for the topological synthesis of geared robotic mechanisms is developed. The approach is based on the idea that the kinematic structure of a geared robotic mechanism can be described by an equivalent open-loop chain (EOLC) and mechanical transmission lines (MTLs) which drive the joints of the EOLC. It is shown that an MTL can be decomposed as an input unit and several transmission units connected in series. The characteristics of the input and transmission units are laid out and a systematic methodology is developed to enumerate all admissible input and transmission units from the existing atlas of non-fractionated geared kinematic chains. The atlas of admissible MTLs are then generated accordingly. Thus, all admissible geared robotic mechanisms can be enumerated efficiently with the atlas of admissible MTLs and a preferred form of the EOLC. With this new methodology, some novel structures of geared robotic mechanisms are obtained and it is believed that new areas of application can be further explored.
Design and Implementation of Metamorphic Robots
Authors: Pamecha Amit , Chiang Chih-Jung , Stein David , Chirikjian Gregory
Published: February 2021

This paper discusses issues in the design and implementation of metamorphic robotic systems. A metamorphic robotic system is a collection of independently controlled mechatronic modules, each of which has the ability to connect, disconnect, and climb over adjacent modules. A metamorphic system can dynamically reconfigure by the locomotion of modules over their neighbors. Thus they can be viewed as a collection of connected modular robots which act together to perform the given task. The planar metamorphic robots described in this paper consist of hexagonal or square modules. Because of their shape, the modules completely fill the plane without any gaps, their centers forming a regular lattice. Both the hexagonal and square modules are provided with electromechanical coupling mechanisms actuated by D.C. motors. These connectors help to couple and uncouple modules as they move around each other to form different configurations. The modules are currently controlled by an external processor.
Spatial Motion Interpolation in an Image Space of SO(4)
Authors: Etzel Karl R. , McCarthy J. Michael
Published: February 2021

Many applications in robotics, spatial mechanism design, and mechanical systems animation require the specification of the movement of a rigid body through space. In this paper, we apply Shoemake’s quaternion interpolation formula to pairs of quaternions, known as biquaternions, to obtain an interpolation procedure for spatial motion. A biquaternion represents a rotation in four dimensional space, an element of SO(4). Because a spatial displacement can be viewed as special case of a four dimensional rotation, we can use a biquaternion as an image point of a spatial configuration and a biquaternion curve to represent spatial movement. We present an example of biquaternion interpolation using four key configurations. The result is a smooth movement in SO(4), which we then map to a spatial movement. A comparison with a similar technique based on dual quaternions is provided.
Elastodynamics of Horizontally Body-Guiding Cam-Driven Linkages Interacting With Robots, and Elastic Error Compensation for Robot Positioning
Authors: Kurnool Sirihari , Bagci Cemil
Published: February 2021

Common industrial applications of body-guiding linkages occur with robot (or CNC machine) interaction at workstations in automated production and assembly lines in industry. A linkage in such cases is generally operated horizontally where large deflections at the body location occur creating positioning and orientation errors of the body. These errors must be delivered to the interacting robot to program its motions and operating geometries to eliminate effects of errors on the performed tasks at the workstations. Driving the linkage at high speed, generating dwells at workstations, experiencing efficient dynamic behaviors is an important phase of its design. In this article, a four-bar linkage guides the body. A disk cam with translating roller follower drives a slider-crank loop driving the body guiding linkage providing dynamically efficient motion of the guided-body along its path and the mechanism. Processes of programming motion of the rigid-body along its path, obtaining the corresponding motions of the links of the mechanism, designing the cam-follower mechanism, determnine elastic errors and their correction and minimization, and performing the elastodynamics of the system are offered. A three-dimensional isoparametric beam element and matrix exponential method are used to perform the elastodynamics of the cam-link mechanism, determining dynamic stresses, elastic errors, bearing forces, frequencies, and response with and without vibratory motion effects, and furnishing data for the interacting robot. Numerical results for a system are given.
Modified Standard Codes in Enumeration and Automatic Sketching of Mechanisms
Authors: Jonnalagadda Srinath , Krishnamurty Sundar
Published: February 2021

This paper presents the application of modified standard codes in the systematic enumeration and graphical display of non-isomorphic mechanisms. A two-stage enumeration procedure is presented that involves the identification and generation of contracted graphs using modified standard codes. In this scheme, unique numbering reflecting the symmetry properties of the higher order links deduced from these contracted graphs is propagated to the second stage in which all the non-isomorphic kinematic chains corresponding to each contracted graph are enumerated. The integration of the resulting numerical code values with a robust automatic sketching algorithm provides the basis for the systematic enumeration and pictorial displays of basic kinematic chains. Illustrative examples from the enumeration of basic kinematic chains with up to 12 bar 3 degree of freedom system are presented, and the results are discussed.
Parametric Deflection Approximations for Initially Curved, Large-Deflection Beams in Compliant Mechanisms
Authors: Howell Larry L. , Midha Ashok
Published: February 2021

The analysis of systems containing highly flexible members is made difficult by the nonlineararities caused by large deflections of the flexible members. The analysis and design of many such systems may be simplified by using pseudo-rigid-body approximations in modeling the flexible members. The pseudo-rigid-body model represents flexible members as rigid links, joined at pin joints with torsional springs. Appropriate values for link lengths and torsional spring stiffnesses are determined such that the deflection path and force-deflection relationships are modeled accurately. Pseudo-rigid-body approximations have been developed for initially straight beams with externally applied forces at the beam end. This work develops approximations for another fundamental type of flexible member, the initially curved beam with applied force at the beam end. This type of flexible member is commonly used in compliant mechanisms. An example of the use of the resulting pseudo-rigid-body approximations in compliant mechanisms is included.
On the Complete Balancing of the Inertia-Caused Input Torque for Plane Mechanisms
Authors: Funk Wolfram , Han Jianyou
Published: February 2021

This paper presents a new method for complete balancing inertia-caused input torque. This method transforms the balancing problem into a displacement curve synthesis for a plate cam. The method is simple and convenient to be used. The planar four-bar linkage and a six-bar linkage are cited as two examples. The fluctuating torques in the driving shaft caused by the inertia forces are completely balanced.
Longitudinal Locomotor Competence and Body Mass Index Across Self-Reported Gender and Vision Level for Youth With Visual Impairments: A 3-Year Investigation
Authors: Brian Ali , Starrett Angela , Pennell Adam , Haibach-Beach Pamela , Gilbert Emily , Stribing Alexandra , Miedema Sally Taunton , Lieberman Lauren
Published: February 2021

Youth with visual impairments are more likely to be overweight than peers without visual impairments and often struggle with their locomotor skills. Locomotor development can combat unhealthy body weight statuses by supporting physical activity behaviors. There are no longitudinal investigations concerning the locomotor skill and body mass index (BMI) developmental trajectories of youth with visual impairments. The purpose of this study was to examine the 3-year developmental trajectory of the locomotor skills and BMI of youth with visual impairments including differential effects of self-reported gender and degree of vision. Participants (N = 34, Mage = 11.75 years, 47% female) showed severely delayed and arrested locomotor development with increases in BMI across 3 years regardless of self-reported gender or degree of vision. Participants failed to breech a proficiency barrier of motor competence to combat against increases in BMI across time. Additional longitudinal inquiries are needed.