bluuebunny/crossref_metadata_2025_split huggingface dataset:
User Interactive Flexible Fixturing System
Authors: Kwasny D. M. , Cipra R. J. 
Published: March 2021

Abstract
The focus of this work is on developing a user interactive flexible fixturing system which is used for synthesizing and testing fixture layouts for use in assembly operations. The system is designed to develop fixtures that utilize a specific type of three-point frictional constraint The first component of the system is the synthesis program which employs an analysis strategy that uses graphical techniques to characterize the stability of given fixture configurations. A stability threshold based on fixture element contact friction is identified to provide an indicator for the stability of layouts, and on-screen graphical displays are available to compare the stabilities of multiple configurations. A synthesis strategy is introduced to provide a guide to aid in the selection of constraining element arrangements on part surfaces. The second component of the system is the verification phase which allows arbitrary polygonal objects to be constrained with newly synthesized fixture layouts in a flexible test cell so that experimental results can be compared to analysis results. The entire system is demonstrated through examples and comparisons are made between the analytical results and experimental verification data.
Generalized Topology Optimization of Linear Elastic Structures Subjected to Thermal Loads
Authors: Rodrigues Helder C. , Fernandes Paulo A. 
Published: March 2021

Abstract
This paper presents the development of a computational model for the generalized topology optimization problem, using a material distribution approach, of 2-D linear elastic solids subjected to thermal loads, with compliance objective function and an isoperimetric constraint on volume.
The model relies on homogenization asymptotic methods to characterize the influence of the material periodic microstructure and a finite element displacement formulation is used to approximate the homogenized equilibrium equations obtained.
The computational model developed is tested in several examples considering different finite element approximations and the influence of the design variables (material density and orientation) is analyzed.
Derivation of Generalized Datum Reference Frames for Geometric Tolerance Analysis
Authors: Nigam Swami D. , Guilford James D. , Turner Joshua U. 
Published: March 2021

Abstract
Datum reference frames define coordinate systems for use in determining part compliance with geometric tolerances. A datum reference frame is specified based on the perfect nominal geometry of the part features called out as datums. However, the actual computation of a coordinate system frame of reference from the datum callouts becomes quite challenging when the features depart from nominal location, orientation, size, and form. We present a general method for representing datum reference frames (both partial and complete), and for computing a coordinate system from a simulated varianced part and a datum reference frame specification. The method makes use of built-in construction procedures, and derived or “virtual” geometry, in conjunction with a powerful parts positioning module that simulates the placement of the varianced part in a fixture represented by the datum surfaces. The reliance on virtual geometry as an intermediate representation, permits the concise representation of not only the datum reference frame types defined in the standard, but also allows for any arbitrary datum reference frames constructed by the user.
Some New Developments in Tolerance Design in CAD
Authors: Zhang Genbao , Porchet Michel 
Published: March 2021

Abstract
This paper presents some recent developments in tolerance design in CAD. An Oriented Functional Relationship Graph (OFRG) is developed to identify all the relevant functional components which have an impact on the (evaluated) performance of a product. It is proposed to use expert system technique to determine all the functional surfaces and necessary relational tolerance types on functional surfaces. Using an OFRG, it is easy to determine dimensional chains, error transmission chains, functional dimension trees and the functional dimensioning mode of a component. We propose to use a transformation matrix technique to determine the sensitivity of each tolerance. A new practical cost model, serving as the criterion for tolerance allocation, is presented. In contrast to empiric data (they are nearly uncollectible) based cost model, the cost model presented in this paper is a process data (they are collectable) based one. The discussion on optimal tolerance shows that optimal functional tolerances can not be obtained without considering the method in machining the workpieces. Hence, the concept of concurrent engineering must be introduced into tolerance design. Finally a mathematic model for tolerance design, called simultaneous tolerancing, in the context of concurrent engineering is proposed.
Validity Check for a Function-Oriented Modeler
Authors: Zhang K. F. , ElMaraghy Hoda H. 
Published: March 2021

Abstract
This paper presents a method for validity check for a feature-oriented modeler which is developed at the center for flexible manufacturing at McMaster University. Maintaining feature validity after feature deletion or modification is, an important issue in product modelling. Among the current commercial modelling systems, it is the designers’ responsibility to create a valid product model. The graphical display of the model provides an auxiliary means for feature verification. However such visual checking is incomplete, unreliable and time-consuming. In the case of invalid internal features, such as, holes and pockets, the visual check usually fails. The approach proposed by authors intends to maintain a valid model by the system automatically. Any interference between features which occurs after an addition, deletion or edition operation will be detected by the system and is resolved by either built-in rules or user’s assistance.
Kinematic Synthesis of Tendon-Driven Manipulators With Isotropic Transmission Characteristics
Authors: Ou Yeong-Jeong , Tsai Lung-Wen 
Published: March 2021

Abstract
This paper presents a methodology for kinematic synthesis of tendon-driven manipulators with isotropic transmission characteristics. The force transmission characteristics, from the end-effector space to the actuator space, has been investigated. It is shown that tendon forces required to act against externally applied forces are functions of the structure matrix, its null vector, and the manipulator Jacobian matrix. Design equations for synthesizing a manipulator to possess isotropic transmission characteristics are derived. It is shown that manipulators which possess isotropic transmission characteristics do have much better force distribution among their tendons.
A Free-Form Mesh Generator for Three-Dimensional Surfaces
Authors: Hua Tienyong , Zeid Ibrahim 
Published: March 2021

Abstract
A fully automatic 3D free-form mesh generation method is developed in this paper. The method is capable of meshing 3D parametric surfaces, both analytic and synthetic. Surfaces may have holes and may be composite, i.e. consisting of more than one patch. In addition to being fully automatic, the method produces quadrilateral or triangular elements with aspect ratio near one. The input to this method includes surface definition points, the element size, and mesh grading information. The method begins by calculating patch boundary curve lengths so that boundary nodes are determined. Utilizing these boundary nodes, the 3D surface patch is mapped from its Cartesian space into its parametric space where it becomes a 2D region. In this parametric region, a 2D mesh generator is utilized to mesh the region. The final mesh is transformed back to the Cartesian space via transforming the coordinates of its nodal points based upon the surface equation. The free-form generator and its related method have been tested extensively and applied to a wide number of surfaces. Sample examples are presented.
Scallop Elimination Based on Precise 5-Axis Tool Placement, Orientation, and Step-Over Calculations
Authors: Mullins S. H. , Jensen C. G. , Anderson D. C. 
Published: March 2021

Abstract
This paper presents algorithms for computing precise 5-axis placement, orientation, and step-over calculations for end mill cutters at a single point on a sculptured surface. Present methods leave irregular scallops between finishing tool passes that require manual grinding to prepare the machined surface for polishing. The relationship between scallop height and step-over is well known for 3-axis movement of a ball end mill across a planar surface but no such relationship exists for 5-axis movement of end mills of other types. Manual grinding of machined surfaces is a time consuming process that generally results in a significant difference between the surface as designed and the actual machined surface. The goal of this approach is the elimination of rough grinding by eliminating scallops between adjacent points on consecutive finish machining passes. An example of a computer implementation of the method using a filleted end mill is also presented.
Optimizaton-Based Design of Hub-and-Shaft Assemblies for Dual-Wheel Excavators
Authors: Wilson L. A. , Azarm S. , Kotras T. V. 
Published: March 2021

Abstract
In this paper, optimization-based design for a minimum weight hub-and-shaft assembly for dual-wheel excavators is presented. Two optimization models are developed: one is based on a keyed hub-to-shaft connection, and the other based on a threaded hub-to-shaft connection. The optimization models are tested and compared with test designs for dual-wheel excavators that are currently in use in industry. It is found that for the test designs: (1) both optimization models generated weight reductions averaging 17%, with reductions ranging from 3% to 30%, (2) both optimization models exhibit significant increases in their weight when subjected to an increasing transverse load on the hub, and (3) hub width is the most influential design variable in determining the weight of the hub-and-shaft assembly.
Heterogeneous Distributed Data Storage for an Object-Oriented Engineering Design Environment
Authors: Brintle Lee P. , Koppes Elizabeth A. , Wu J. K. 
Published: March 2021

Abstract
The Tracked Vehicle Workstation (TVWS) is a distributed, object-oriented design environment that stores the large amounts of data associated with mechanical system’s design and analysis across heterogeneous UNIX† machines on a network. A Distributed ASCII File Storage (DAFS) server was developed to provide an easy to port, easy to modify means of retrieving and updating files on remote machines. This paper describes the different techniques and difficulties of methods the TVWS environment has used previously, including commercial solutions, single-node storage and the Network File System (NFS)‡, as well as a description of the current method utilizing DAFS.
Stability of Heart Rate at Physiological Thresholds Between Temperate and Heat Stress Environments in Endurance-Trained Males
Authors: Maunder Ed , Plews Daniel J. , Merien Fabrice , Kilding Andrew E. 
Published: March 2021

Many endurance athletes perform specific blocks of training in hot environments in “heat stress training camps.” It is not known if physiological threshold heart rates measured in temperate conditions are reflective of those under moderate environmental heat stress. A total of 16 endurance-trained cyclists and triathletes performed incremental exercise assessments in 18°C and 35°C (both 60% relative humidity) to determine heart rates at absolute blood lactate and ventilatory thresholds. Heart rate at fixed blood lactate concentrations of 2, 3, and 4 mmol·L−1 and ventilatory thresholds were not significantly different between environments (P > .05), despite significant heat stress-induced reductions in power output of approximately 10% to 17% (P < .05, effect size = 0.65–1.15). The coefficient of variation for heart rate at these blood lactate concentrations (1.4%−2.9%) and ventilatory thresholds (2.3%−2.7%) between conditions was low, with significant strong positive correlations between measurements in the 2 environments (r = .92–.95, P < .05). These data indicate heart rates measured at physiological thresholds in temperate environments are reflective of measurements taken under moderate environmental heat stress. Therefore, endurance athletes embarking on heat stress training camps can use heart rate–based thresholds ascertained in temperate environments to prescribe training under moderate environmental heat stress.
Reappraisal of the Mesozoic tectonic transition from the Paleo-Tethyan to Paleo-Pacific domains in South China
Authors: Gan Chengshi , Zhang Yuzhi , Wang Yuejun , Qian Xin , Wang Yang 
Published: March 2021

Abstract
The southeastern (SE) South China Block was mainly influenced by the Paleo-Tethyan and Paleo-Pacific dynamic domains during the Mesozoic. The initial timing of the tectonic transition between these two domains in the SE South China Block still remains debated. The transition would affect the nature of the lithosphere and material provenance of sediments, and, therefore, igneous and sedimentary rocks in the area could record such dynamic processes. In this study, published geochronological and geochemical data of the Triassic and Jurassic igneous rocks and detrital zircon data of contemporaneous sedimentary rocks in the SE South China Block were compiled, aiming to provide constraints on the tectonic transition via tracing the spatial-temporal variations in the nature of the lithosphere and sedimentary provenance signals. The compiled results suggest that the magmatic intensity and volume decreased significantly from the Late Triassic to Early–Middle Jurassic, with an obvious magmatic quiescence between them, and increased from the Early–Middle Jurassic to Late Jurassic. The εNd(t) and zircon εHf(t) values of mafic rocks, granitoids, and shoshonitic rocks remarkably increased from the Late Triassic to Early–Middle Jurassic, indicative of variations in the lithospheric mantle and continental crust. Such variations suggest that the initial tectonic transition occurred at the earliest Early Jurassic. Based on the southward paleocurrents from Early Jurassic sandstone, E-W–trending extension of Early–Middle Jurassic mafic and shoshonitic rocks, and similar sedimentary provenances of Late Triassic and Early–Middle Jurassic sedimentary rocks, these features imply that the SE South China Block was not immediately influenced by the Paleo-Pacific domain during the Early–Middle Jurassic. However, from the Early–Middle Jurassic to Late Jurassic and Early Cretaceous, the spatial distribution, geochemical signatures, magmatic intensity, and magmatic volume of igneous rocks and provenance of sedimentary rocks exhibit obvious variations, and the regional fold hinge direction changed from E-W–trending to NE-trending, suggesting significant effects from Paleo-Pacific subduction on the SE South China Block. Thus, the Mesozoic tectonic transition from the Paleo-Tethyan to the Paleo-Pacific dynamic domain in the SE South China Block likely occurred during the Early–Middle Jurassic.
High-dose electronic media use in five-year-olds and its association with their psychosocial symptoms: a cohort study
Authors: Niiranen Janette , Kiviruusu Olli , Vornanen Riitta , Saarenpää-Heikkilä Outi , Paavonen E Juulia 
Published: March 2021

ObjectivesThis study investigated the frequency of electronic media (e-media) usage by preschool children and the risks of high-dose e-media use on young children’s psychosocial well-being.DesignLongitudinal associations between e-media use at 18 months and psychosocial symptoms at 5 years of age were studied, as well as cross-sectional associations between e-media use and psychosocial symptoms at 5 years.SettingBetween 2011 and 2017 in Finland.ParticipantsChildren aged 5 years (n=699).Primary and secondary outcome measuresChildren’s psychosocial symptoms were determined at the age of 5 years using the parent-reported questionnaires Five-to-Fifteen (FTF) and the Strengths and Difficulties Questionnaire (SDQ).ResultsBased on our results, 95% of the preschool children exceeded the daily recommended use of e-media set by health professionals. Our results indicate that increased screen time at 5 years of age is associated with a risk of multiple psychosocial symptoms (OR 1.53–2.18, 95% CI 1.05 to 3.34, p<0.05), while increased levels of e-media use at 18 months was only associated with FTF peer problems (OR 1.59, 95% CI 1.04 to 2.41, p=0.03). Moreover, high-dose use of electronic games at the age of 5 years seems to be associated with fewer risks for psychosocial well-being than programme viewing, as it was only associated with SDQ hyperactivity (OR 1.65, 95% CI 1.08 to 2.51, p=0.02).ConclusionIncreased screen time has multiple risks for children’s psychosocial well-being. These risk factors seem to be significant in the long term, and are related to problems in children’s socio-emotional development later on. Health professionals and paediatricians have an important role as communicators of the current research results on the safe usage time of e-media for families, and enhancing parents’ skills as regulators of children’s safe e-media use. More research is needed on the family conditions of high-dose e-media users.
What are parents’ perceptions related to barriers in diagnosing swallowing dysfunction in children? A grounded theory approach
Authors: Baqays Abdulsalam , Rashid Marghalara , Johannsen Wendy , Seikaly Hadi , El-Hakim Hamdy 
Published: March 2021

ObjectivesSwallowing dysfunction (SwD) is under-reported in otherwise healthy infants and toddlers (OHITs). The identification of parental perceptions of factors that may hinder the diagnosis could help clinicians manage these children in a more expeditious manner. This study investigated the barriers to diagnosing SwD, as reported by the families.DesignGrounded theory study.SettingThis study was performed in a tertiary care paediatric centre in Canada.ParticipantsParents of OHITs were recruited using purposeful sampling.InterventionWe used detailed, semistructured, in-person interviews and the audiotapes and transcriptions were thematically analysed. From the parental insights, we built a framework composed of three themes of barriers.ResultTen parents of OHITs with SwD were interviewed. The children presented with recurrent coughing, choking, cold-like symptoms, recurring/consistent illnesses and feeding difficulties. They were managed with multiple rounds of antibiotics and diagnosed with allergies, asthma or recurrent viral infections before considering SwD. The three emerging themes are false beliefs about SwD among parents and some physicians, parent-related barriers and physician-related barriers. These barriers had severely impacted the parents, impairing work productivity and leading to work-related reprimands and changes in the family dynamics.ConclusionThis study suggests that there are several barriers that face the parents of OHITs when seeking a diagnosis of SwD and initiating appropriate management. These barriers likely interact with one another and amplify their effects on the family and the child. A common denominator is a lack of education regarding SwD, its clinical manifestations and the available expertise to manage this condition.
Breastfeeding education, early skin-to-skin contact and other strong determinants of exclusive breastfeeding in an urban population: a prospective study
Authors: Dueñas-Espín Iván , León Cáceres Ángela , Álava Angelica , Ayala Juan , Figueroa Karina , Loor Vanesa , Loor Wilmer , Menéndez Mónica , Menéndez David , Moreira Eddy , Segovia René , Vinces Johanna 
Published: March 2021

ObjectiveThe current study aims to demonstrate independent associations between social, educational and health practice interventions as determinants of exclusive breastfeeding in an urban Ecuadorian population.DesignProspective survival analyses.SettingEcuadorian mother–child dyads in urban settings.ParticipantsWe followed-up 363 mother–baby dyads who attended healthcare centres in Portoviejo, province of Manabi, for a median time (P25–P75) of 125 days (121–130 days).Main outcome measuresWe performed a survival analysis, by setting the time-to-abandonment of exclusive breastfeeding measured in days of life, that is, duration of exclusive breastfeeding, periodically assessed by phone, as the primary outcome. Crude and adjusted mixed-effects Cox proportional hazards model were performed to estimate HRs for each explanatory variable.ResultsThe incidence rate of abandonment of breastfeeding was 8.9 per 1000 person-days in the whole sample. Multivariate analysis indicated the three most significant protective determinants of exclusive breastfeeding were (a) sessions of prenatal breastfeeding education with an HR of 0.7 (95% CI: 0.5 to 0.9) per each extra session, (b) self-perception of milk production, with an HR of 0.4 (95% CI: 0.3 to 0.6) per each increase in the perceived quantity of milk production and (c) receiving early skin-to-skin contact with an HR of 0.1 (95% CI: <0.1 to 0.3) compared with those not receiving such contact, immediately after birth.ConclusionsPrenatal education on breastfeeding, self-perception of sufficient breast-milk production and early skin-to-skin contact appear to be strong protectors of exclusive breastfeeding among urban Ecuadorian mother–baby dyads.
Potential impact of physical distancing on physical and mental health: a rapid narrative umbrella review of meta-analyses on the link between social connection and health
Authors: Morina Nexhmedin , Kip Ahlke , Hoppen Thole Hilko , Priebe Stefan , Meyer Thomas 
Published: March 2021

BackgroundThe imperative for physical distancing (mostly referred to as social distancing) during COVID-19 pandemic may deteriorate physical and mental health. We aimed at summarising the strength of evidence in the published literature on the association of physical and mental health with social connection via social isolation, living alone and loneliness.MethodsWe conducted a systematic search in April 2020 to identify meta-analyses using the Medline, PsycINFO and Web of Science databases. The search strategy included terms of social isolation, loneliness, living alone and meta-analysis. Eligible meta-analyses needed to report any sort of association between an indicator of social connection and any physical or mental health outcome. The findings were summarised in a narrative synthesis.ResultsTwenty-five meta-analyses met our criteria, of which 10 focused on physical health and 15 on mental health outcomes. The results suggest that lack of social connection is associated with chronic physical symptoms, frailty, coronary heart disease, malnutrition, hospital readmission, reduced vaccine uptake, early mortality, depression, social anxiety, psychosis, cognitive impairment in later life and suicidal ideation.ConclusionsThe existing evidence clearly indicates that social connection is associated with a range of poor physical and mental health outcomes. A potential negative impact on these outcomes needs to be considered in future decisions on physical distancing measures.