bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of biological maturity status on ground reaction force production during sprinting
Authors: Colyer Steffi L. , Nagahara Ryu , Takai Yohei , Salo Aki I.T. 
Published: April 2020

Sprint ability develops nonlinearly across childhood and adolescence. However, the underpinning ground reaction force (GRF) production is not fully understood. This study aimed to uncover the kinetic factors that explain these maturation‐related sprint performance differences in Japanese boys and girls. A total of 153 untrained schoolchildren (80 boys, 73 girls) performed two 50‐m maximal effort sprints over a 52‐force‐platform system embedded in an indoor track. Maturity offset (years from peak height velocity; PHV) was estimated using anthropometric data and used to categorise the children into six‐year‐long maturation groups (from group 1 [5.5‐4.5 years before PHV] to group 6 [0.5 years before to 0.5 years after PHV). Maximum and mean step‐averaged velocities across 26 steps were compared across consecutive maturation groups, with further GRF analysis (means and waveforms [statistical parametric mapping]) performed when velocity differences were observed. For boys, higher maximum velocities (effect size ± 90% CI = 1.63 ± 0.69) were observed in maturation group 2 (4.5‐3.5 years before PHV) compared to group 1 (5.5‐4.5 years before PHV), primarily attributable to higher antero‐posterior GRFs across shorter ground contacts. Maximum velocities increased from maturation group 4 (2.5‐1.5 years before PHV) to group 5 (1.5‐0.5 years before PHV) in the girls (effect size ± 90% CI = 1.00 ± 0.78), due to longer ground contacts rather than higher GRFs per se. Waveform analyses revealed more effective reversal of braking forces and higher propulsive forces (e.g. 14%‐77% of stance 4), particularly for comparisons involving boys, which suggested potentially enhanced stretch‐shortening ability. Youth sport practitioners should consider these maturation‐specific alterations when evaluating young athletes’ sprint abilities.
Solution of Biharmonic Equation in Complicated Geometries With Physics Informed Extreme Learning Machine
Authors: Dwivedi Vikas , Srinivasan Balaji 
Published: April 2020

Abstract
Recently, physics informed neural networks (PINNs) have produced excellent results in solving a series of linear and nonlinear partial differential equations (PDEs) without using any prior data. However, due to slow training speed, PINNs are not directly competitive with existing numerical methods. To overcome this issue, the authors developed Physics Informed Extreme Learning Machine (PIELM), a rapid version of PINN, and tested it on a range of linear PDEs of first and second order. In this paper, we evaluate the effectiveness of PIELM on higher-order PDEs with practical engineering applications. Specifically, we demonstrate the efficacy of PIELM to the biharmonic equation. Biharmonic equations have numerous applications in solid and fluid mechanics, but they are hard to solve due to the presence of fourth-order derivative terms, especially in complicated geometries. Our numerical experiments show that PIELM is much faster than the original PINN on both regular and irregular domains. On irregular domains, it also offers an excellent alternative to traditional methods due to its meshless nature.
Modeling of Flexible Beam Networks and Morphing Structures by Geometrically Exact Discrete Beams
Authors: Lestringant Claire , Kochmann Dennis M. 
Published: April 2020

Abstract
We demonstrate how a geometrically exact formulation of discrete slender beams can be generalized for the efficient simulation of complex networks of flexible beams by introducing rigid connections through special junction elements. The numerical framework, which is based on discrete differential geometry of framed curves in a time-discrete setting for time- and history-dependent constitutive models, is applicable to elastic and inelastic beams undergoing large rotations with and without natural curvature and actuation. Especially, the latter two aspects make our approach a versatile and efficient alternative to higher-dimensional finite element techniques frequently used, e.g., for the simulation of active, shape-morphing, and reconfigurable structures, as demonstrated by a suite of examples.
Effect of Homogenization on the Microstructure and Magnetic Properties of Direct Laser-Deposited Magnetocaloric Ni43Co7Mn39Sn11
Authors: Stevens Erica , Kimes Katerina , Chernenko Volodymyr , Lázpita Patricia , Wojcik Anna , Maziarz Wojciech , Toman Jakub , Chmielus Markus 
Published: April 2020

Abstract
Transitioning current cooling and refrigeration technologies to solid-state cooling leveraging the magnetocaloric effect would improve efficiency and eliminate a harmful influence on the environment. Employing additive manufacturing as a production method would increase geometrical freedom and allow designed channels and porosity in heat exchangers made from magnetocaloric materials, to increase surface area for heat transfer via a fluid. This study is the first to demonstrate a successful deposition of the Ni43Co7Mn39Sn11 magnetocaloric material by direct laser deposition. Samples were defined as either properly- or overbuilt, and representative ones were characterized for microstructural features before and after homogenization heat treatment, as well as magnetic behavior and constituent phases. As-built microstructures consisted of dendrites, columnar grains, and elongated cells, with a mix of both austenite and 7M martensite phases. Homogenization increased the fraction of 7M martensite, and encouraged distinct equiaxed and columnar grains, eliminating dendrites and cellular structures. The increased fraction of the weak magnetic martensitic phase also resulted in a strong reduction of the saturation magnetization. Some differences in structure and performance may be related to an energy density difference causing higher Mn loss in the properly built sample, with a lower powder-to-energy input ratio. As a whole, it is found that direct laser deposition (DLD) additive manufacturing of Ni-Mn-based magnetocaloric material is very promising, since representative transformation, phase state, and magnetic properties have been achieved in this study.
Surface Modification of Additively Manufactured 18% Nickel Maraging Steel by Ultrasonic Vibration-Assisted Ball Burnishing
Authors: Ituarte Iñigo Flores , Salmi Mika , Papula Suvi , Huuki Juha , Hemming Björn , Coatanea Eric , Nurmi Seppo , Virkkunen Iikka 
Published: April 2020

Abstract
The scope of this research is to characterize and optimize the vibration-assisted ball burnishing of additively manufactured 18% Nickel Maraging steel for tooling applications. We evaluate the suitability of vibration-assisted ball burnishing as an alternative method to post-process additively manufactured tool steel. To do so, we assessed a single pass post-processing technique to enhance surface roughness, surface micro-hardness, and residual stress state. Results show that ultrasonic burnishing after age hardening functionalizes additively manufactured surfaces for tooling applications creating a beneficial compressive residual stress state on the surface. The surface micro-hardness (HV1) varied between 503 and 630 HV1, and the average surface roughness (Ra) varied between 1.31 and 0.14 µm, depending on process parameters with a maximum productivity rate of 41.66 cm2/min making it an alternative approach to functionalize additively manufactured tool components.
Numerical Optimization of an Ejector for Waste Heat Recovery Used to Cool Down the Intake Air in an Internal Combustion Engine
Authors: Galindo José , Gil Antonio , Dolz Vicente , Ponce-Mora Alberto 
Published: April 2020

Abstract
In the present paper, a numerical investigation of a jet-ejector is carried out using a real gas model of R1234yf. The prototype under investigation works with specific operating conditions of a jet-ejector refrigeration system intended for waste heat recovery in an internal combustion engine (ICE). In the first instance, the geometry optimization involving nozzle exit diameter, mixing chamber diameter, and nozzle exit position (NXP) is performed. Once the optimum geometry has been obtained, the jet-ejector prototype is tested with different operating pressure ratios to determine its off-design performance. The flow structure in relevant cases has been examined with an emphasis on critical and subcritical modes. The flow phenomena occurring during expansion, entrainment, and mixing processes are discussed so performance degradation can be directly related to physical processes. The analysis has been completed fitting simulated points to critical and subcritical planar surfaces. The results in terms of goodness of fit are satisfactory so the jet-ejector performance in off-design operating conditions can be reflected through simple mathematic models. When the overall cycle is assessed by using previous computational fluid dynamics (CFD) maps, it is observed that the achievable cooling drops significantly when an ambient temperature of 31 °C is exceeded.
Unsteady Heat Transfer Between Gas and Tube in a Wave Rotor Refrigerator
Authors: Hu Dapeng , Wang Jingxian , Wu Mei , Liu Tingjiang , Zhao Yiming , Yu Yang 
Published: April 2020

Abstract
The performance of a wave rotor refrigerator (WRR) is strongly affected by unsteady heat transfer between gas and tubes. In this work, the mechanism of the heat transfer and its effects on WRR were investigated numerically and experimentally. Results show that the heat absorption of wave rotor occurs in the process of shock wave propagation, and heat release happens in other processes. The unsteady heat transfer causes an uneven wall temperature. The temperature varies along the longitudinal direction, while the time variation can be neglected. Furthermore, the position of the bolts, which link the wave rotor and the shaft, has a great influence on WRR gaps. The closer the position of bolts to the high-pressure (HP) nozzle is, the less effect of gaps would be. The research is an important guiding significance to the improvement of WRR refrigeration performance and WRR design.
Steam Condensation Heat Transfer During Initial Blow-Down Period of a Severe Nuclear Accident
Authors: Yadav Mahesh Kumar , Punetha Maneesh , Bhanawat Abhinav , Khandekar Sameer , Sharma Pavan K. 
Published: April 2020

Abstract
Heat transfer coefficient (HTC) relations developed using steady-state experimental data are used for capturing the complete heat transport characteristic in a severe nuclear accident. It is important to verify the applicability of these correlation(s) at an early stage of the accident where heat transfer is transient in nature. In this paper, an experimental study is executed for this purpose. High-pressure steam (at 0.26 MPa (2.6 bar) and 0.41 MPa (4.1 bar) absolute pressure) is leaked into the closed containment initially filled with atmospheric air, and filmwise condensation is studied on an isothermally maintained vertical stainless steel test plate. During the experiment, temperature variation across the test plate at specified locations and inside the containment are recorded using the microthermocouples. The steam–air mixture composition is also examined using an online mass-spectrometry system. An inverse heat conduction (IHC) technique, validated using air-jet impingement heat transfer data, is used to estimate the time-varying condensation heat flux. It is found that the existing correlations based on the steady-state experimental data predict the transient condensation flux quite well, except in very early transient situation with a time scale of ∼20 s.
Energy distribution in Dual-UAV collaborative transportation through load sharing
Authors: Mohiuddin Abdullah , Zweiri Yahya , Almadhoun Randa , Taha Tarek , Gan Dongming 
Published: April 2020

Abstract
In this paper, a novel dual-UAV collaborative aerial transport strategy based on energy distribution and load sharing is proposed. This paper presents the first experimental demonstration of dual-UAV collaborative aerial transport while distributing power consumption. The demonstration is performed while distributing the power consumption between two drones sharing a load based on their battery state of charge. A numerical model of the dual-hex-rotor-payload is used to validate the proposed strategy. Numerical and hardware tests were conducted to demonstrate the load distribution using multiple UAV with certain spatial configurations. Finally, collaborative aerial transport test scenarios are performed numerically and experimentally. The simulation and experimental results show the effectiveness and applicability of the proposed strategy.
Dead Center Identification of Two-Degrees-of-Freedom Planar Parallel Manipulator Using Graph Theory and Transmission Angle
Authors: Nie Liangyi , Ding Huafeng 
Published: April 2020

Abstract
Parallel manipulators are widely applied for their advantages of high stiffness, load-bearing, operation speed, and precision positioning capabilities, which are required in many industrial applications. However, dead center identification is a challenging task and fundamental problem during design stage of parallel manipulators, and becomes more intractable for two-degrees-of-freedom (DOF) complex planar parallel manipulators (PPMs) design. This paper proposes a method to identify the dead center positions of two-DOF PPMs based on graph theory and transmission angle. First, these PPMs are denoted by a set of independent loops using a topological structural analysis of the kinematic chains and structural decomposition. Then, the relationship between the mobility factor and the loop factor in the same independent loop is utilized to obtain the folded or stretched operation to form the new PPMs containing the corresponding instantaneous virtual loop. Subsequently, the dead center positions can be located since the corresponding transmission angle of the new PPMs is equal to 0 deg or 180 deg. As a result, the solved dead center positions of the two-DOF three types seven-bar, nine-bar, and 11-bar PPMs will provide guidance for the proper design of these PPMs. Finally, the Jacobian method for identifying the dead center position is then used to verify the proposed method. The proposed method is systematic and programmable and can be applied to any two-DOF PPM regardless of the number of independent loops or types of joints.
Multi-Objective Redundancy Allocation for Multi-State System Design Under Epistemic Uncertainty of Component States
Authors: Xiahou Tangfan , Liu Yu , Zhang Qin 
Published: April 2020

AbstractMulti-state is a typical characteristic of engineered systems. Most existing studies of redundancy allocation problems (RAPs) for multi-state system (MSS) design assume that the state probabilities of redundant components are precisely known. However, due to lack of knowledge and/or ambiguous judgements from engineers/experts, the epistemic uncertainty associated with component states cannot be completely avoided and it is befitting to be represented as belief quantities. In this paper, a multi-objective RAP is developed for MSS design under the belief function theory. To address the epistemic uncertainty propagation from components to system reliability evaluation, an evidential network (EN) model is introduced to evaluate the reliability bounds of an MSS. The resulting multi-objective design optimization problem is resolved via a modified non-dominated sorting genetic algorithm II (NSGA-II), in which a set of new Pareto dominance criteria is put forth to compare any pair of feasible solutions under the belief function theory. A numerical case along with a SCADA system design is exemplified to demonstrate the efficiency of the EN model and the modified NSGA-II. As observed in our study, the EN model can properly handle the uncertainty propagation and achieve narrower reliability bounds than that of the existing methods. More importantly, the original nested design optimization formulation can be simplified into a one-stage optimization model by the proposed method.
Study on Building Digital-Twin of Face-Milled Hypoid Gear From Measured Tooth Surface Topographical Data
Authors: Lee Yi-Hui , Fong Zhang-Hua 
Published: April 2020

AbstractA highly accurate digital-twin spiral bevel gear or hypoid gear is often required for dynamic analysis or stress analysis for gear transmission. However, a highly accurate digital-twin solid model is not always available because the final hypoid gear is completed by the gear manufacturer. This study constructs a digital-twin from a sample hypoid gear. The tooth surface of sample gear is digitized as topographical grids using a coordinate measuring machine (CMM) or a gear measurement center. The geometric parameters (the surface position vector, the normal vector, the principal curvatures, and the corresponding principal directions) for the measured tooth surface (MTS) are then extracted using numerical differential geometry (NDG). The machine settings and the cutter parameters for the sample hypoid gear are obtained by minimizing the topographical error between the replicated digital-twin and the sample gear using optimization software. The initial estimation for the machine settings and the cutter parameters is calculated using an explicit form of the modified-roll motion (MRM), which decreases numerical divergence and time that is required for calculation. The machine settings, the cutting tool parameters, and the auxiliary flank modification (AFM) motion are used as the design variables. A numerical example is presented to verify the proposed methodology. The numerical results show that the replicated digital-twin that is developed using the proposed method is sufficiently accurate for industrial applications.
Investigation of a Voronoi Diagram Representation for the Computational Design of Additively Manufactured Discrete Lattice Structures
Authors: Stanković Tino , Shea Kristina 
Published: April 2020

Abstract
A lattice structure is defined by a network of interconnected structural members whose architecture exhibits some degree of regularity. Although the overall architecture of a lattice may contain many members, its generation can be a simple process in which a unit cell composed of a small amount of members, in comparison to the overall structure, is mapped throughout the Euclidean space. However, finding the right lattice architecture in a vast search space that customizes the behavior of a design for a given purpose, subject to mechanical and manufacturing constraints, is a challenging task. In response to this challenge, this work investigates a Voronoi diagram-based tessellation of a body-centered cubic cell for applications in structural synthesis and computational design of 3D lattice structures. This work contributes by exploring how the Voronoi tessellation can be utilized to parametrically represent the architecture of a lattice structure and what the implications of the parametrization are on the optimization, for which a global direct search method is used. The work considers two benchmark studies, a cubic and a cantilever lattice structure, as well as the effect of isotropic and anisotropic material property models, stemming from applications to additive manufacturing. The results show that the proposed parameterization generates complex search spaces using only four variables and includes four different lattice structure types, a Kelvin cell, a hexagonal lattice, a diamond-core lattice structure, and a box-boom type lattice structure. The global direct search method applied is shown to be effective considering two different material property models from an additive manufacturing (AM) process.
Computational Study on Machine Settings for Face-Milled Hypoid Gears With Low Shaft Angles
Authors: Yang Xingyu , Song Chaosheng , Zhu Caichao , Liu Siyuan , Liang Chengcheng 
Published: April 2020

Abstract
Hypoid gear with small cone angle and large pitch cone distance can be directed at the transmission with low shaft angle (LSA). The manufacturing process has more freedoms of motion to control the tooth surface and ensure higher mesh performance. However, it is difficult to adjust the machine settings due to the extreme geometry. This paper focused on the manufacturing process and machine settings calculation of hypoid gear with low shaft angle (LSA hypoid gear). Based on the generating process, nongenerated gear, and generated pinion manufactured by circular cutter blade, the mathematic model of tooth surface of LSA hypoid gear was developed, and the expressions of principal directions and curvatures of LSA hypoid gear were derived. The relationship of curvatures between pinion and gear was also proposed. Then based on the basic relationships of two mating surfaces, an approach to determinate machine settings for LSA hypoid gear was proposed. Finally, the tooth contact analysis (TCA) and loaded tooth contact analysis (LTCA) were directed at the validation of machine settings’ derivation. TCA contact pattern results highly coincide with the preset values. And the LTCA contact pattern also highly coincides with TCA results, it can be considered that the determination approach of machine settings is valid. The TCA transmission error result also shows that the ratio of contact is quite large, which is a little bigger than 2. Thus, the load bearing ability and stability of LSA hypoid gear may be superior.
Asymptotic of the electric structure function and the deuteron wave function
Authors: Zhaba V. I. 
Published: April 2020

The main features of obtaining the asymptotic behavior of the electric structure function [Formula: see text] at large values of the transmitted momentum are analyzed. The asymptotic behavior of the structure function [Formula: see text] was determined to take into account the asymptotic behavior of the deuteron form factors and the original dipole approximation for the nucleon form factors. Asymptotic values of [Formula: see text] were obtained for the nucleon–nucleon potential Reid93 and compared with the calculations for different nucleon form factor models and their approximations. In the broad momentum range up to 12.5 fm[Formula: see text], the basic forms of the asymptotic behavior of the electric structure function are demonstrated and compared with the experimental data of the modern collaborations. As the analysis shows in most cases considered, the asymptotic for [Formula: see text] is represented in the form of the power function [Formula: see text].