bluuebunny/crossref_metadata_2025 huggingface dataset:
A c/μ‐Rule for Job Assignment in Heterogeneous Group‐Server Queues
Authors: Xia Li , Zhang Zhe George , Li Quan‐Lin
Published: November 2021

We study a dynamic job assignment problem in queueing systems with one class of Poisson arrivals and K groups of heterogeneous servers. A scheduling policy prescribes the job assignment among servers in each group at every state n (number of jobs in the system). Our goal is to obtain the optimal policy to minimize the long‐run average cost, which involves the increasingly convex holding cost for jobs and the operating cost for working servers. This problem has wide application scenarios in operations management, such as job scheduling in manufacturing systems, packet routing in communication systems, and staffing in service systems. We prove that the optimal policy has monotone structures and quasi bang–bang control forms. Specifically, we discover that the optimal policy is governed by the marginal cost rate c −  μG( n), where c is the operating cost rate, μ is the service rate, and G( n) is called the perturbation realization factor at state n. Under the condition of scale economies which can be guaranteed by any increasingly concave operating cost in μ, we prove that the optimal policy obeys a so‐called c/ μ‐ rule: Servers with a smaller c/ μ should be occupied by jobs with higher priority. Optimality of multi‐threshold type policies is further proved when the c/ μ‐rule is applied. Our c/ μ‐rule in group‐server queues can be viewed as a counterpart of the famous cμ‐rule in polling queues, which both significantly reduce the complexity of optimization problems. By utilizing these optimality structures, we also develop computational‐efficient algorithms to determine the optimal policy numerically. Simulation experiments demonstrate the good scalability and robustness of the c/ μ‐rule, which are important for managerial practice.
Optimal Trade‐in Return Policies: Is it Wise to be Generous?
Authors: Cao Kaiying , Choi Tsan‐Ming
Published: November 2021

To retain old customers and promote sales, firms offer trade‐in programs in which consumers bring in an old product and receive a trade‐in rebate when buying a new one. However, after buying the new product, the consumer who has traded in (the “trade‐in consumer”) may return the new product and claim a refund for it if she/he is not satisfied with it. In this situation, under a full‐trade‐in‐return (FTR) policy, trade‐in consumers receive a generous refund that includes a trade‐in‐rebate for them to redeem if they purchase again in future. Alternatively, some firms have a partial‐trade‐in‐return (PTR) policy under which trade‐in consumers who return a newly purchased product only receive a refund for the amount of money they paid (without including the trade‐in‐rebate). In this study, we build stylized analytical models to explore the optimal choice of a trade‐in‐return policy. We find that there is no difference to the firm between an FTR and a PTR policy when no trade‐in consumers keep unsatisfactory new products. In the case of a relatively medium residual value of the used product, FTR is always the better choice for the firm. When some trade‐in consumers keep unsatisfactory new products, we show that FTR (PTR) is the better choice when the used product's durability is sufficiently low (high). We also show that the firm may not reduce its trade‐in rebate when the “average new product satisfaction rate” of trade‐in consumers increases. In the extended models, we find that, the firm is more likely to prefer PTR to FTR under the online–offline dual‐channel retailing mode, but tends to prefer FTR to PTR when there is a competitive secondhand market, and should make the same optimal trade‐in return policy when there are two selling periods.
De novo transcriptome sequencing, assembly, and gene expression profiling of a salt‐stressed halophyte (Salsola drummondii) from a saline habitat
Authors: Elnaggar Attiat , Mosa Kareem A. , Ramamoorthy Kalidoss , El‐Keblawy Ali , Navarro Teresa , Soliman Sameh S. M.
Published: November 2021

Salsola drummondii is a perennial habitat‐indifferent halophyte growing in saline and nonsaline habitats of the Arabian hyperarid deserts. It offers an invaluable opportunity to examine the molecular mechanisms of salt tolerance. The present study was conducted to elucidate these mechanisms through transcriptome profiling of seedlings grown from seeds collected in a saline habitat. The Illumina Hiseq 2500 platform was employed to sequence cDNA libraries prepared from shoots and roots of nonsaline‐treated plants (controls) and plants treated with 1200 mM NaCl. Transcriptomic comparison between salt‐treated and control samples resulted in 17,363 differentially expressed genes (DEGs), including 12,000 upregulated genes (7870 in roots, 4130 in shoots) and 5363 downregulated genes (4258 in roots and 1105 in shoots). The majority of identified DEGs are known to be involved in transcription regulation (79), signal transduction (82), defense metabolism (101), transportation (410), cell wall metabolism (27), regulatory processes (392), respiration (85), chaperoning (9), and ubiquitination (98) during salt tolerance. This study identified potential genes associated with the salt tolerance of S. drummondii and demonstrated that this tolerance may depend on the induction of certain genes in shoot and root tissues. These gene expressions were validated using reverse‐transcription quantitative PCR, the results of which were consistent with transcriptomics results. To the best of our knowledge, this is the first study providing genetic information on salt tolerance mechanisms in S. drummondii.
The role of player mass and contact speed on head kinematics and neck dynamics in rugby union tackling
Authors: Tierney Gregory J. , Tucker Ross
Published: November 2021

Tackling is the most common cause of general injuries in rugby union, with player speed and mass identified as risk factors. This study aimed to use multibody modeling simulations to examine how tackler and ball carrier mass and contact speed affect inertial head kinematics and neck dynamics. Simulations were run by independently varying the ball carrier and tackler mass (from 60 to 110kg) and speed (from 0 to 10 m/s). Peak resultant inertial neck dynamics (force and moment) and head kinematics (linear acceleration, angular acceleration, and angular velocity) were extracted from each simulation. The greatest inertial head kinematics and neck dynamics sustained by a player was when there was the greatest mass disparity in the tackle, with the lighter player experiencing greatest inertial neck dynamics and head kinematics by up to 24% in comparison with the scenario when both players were the lightest mass (60 kg). As a player's mass increased, the magnitude of their head kinematics and neck dynamics diminished, but increased for their direct opponent, irrespective of whether they were the tackler or ball carrier. For speed, the greatest inertial head kinematics and neck dynamics sustained by the ball carrier and tackler were when they were both traveling at the highest speed. In theory, large discrepancies in mass of players, and high speeds into a tackle should be avoided.
The Localist Turn in Populism Studies
Authors: Chou Mark , Moffitt Benjamin , Busbridge Rachel
Published: November 2021

While the study of populism has typically focused on the national level, recent years have seen a growing body of research on populism’s local dimensions. Despite making important scholarly advances, this ‘localist turn’ has yet to develop a systematic account of how populism intersects with localism. In this research note, we broach this gap. By exploring how right‐ and left‐wing populisms conceptualize the ‘local’, as well as how localist sentiments can heighten or diminish the appeal of right and left populist politics, we establish a general framework to guide future inquiry into local manifestations of populist politics.
Recognition of the HLA‐A*11:85 allele in a Taiwanese bone marrow donor
Authors: Yang Kuo‐Liang , Li Chi‐Cheng , Lin Py‐Yu
Published: November 2021

One nucleotide substitution in codon 47 of HLA‐A*11:01:01:01 results in a novel allele, HLA‐A*11:85.
Identification of the Damping Matrix
Authors: Baruch Menahem
Published: November 2021

Only experiments can provide the data necessary to obtain the damping matrix of a dynamic structural system. In the method proposed here the damping matrix can be separated from the mass and stiffness matrices and obtained in an independent of them way. Two methods are presented. In the first method it is assumed that all the degrees of freedom can be loaded and measured. Several methods for calculation of the damping, mass and stiffness matrices, using the experimental data are presented. In the second method the load is employed only in some chosen points. However, it is assumed again that all the degrees of freedom are measured.

In order to identify the damping, stiffness and mass matrices of the structure the measured quantities are forced to comply with the general laws for a linear structure.

The structure is idealized to be a linear dynamic structure with viscous damping. The measured quantities are measured during the tests at discrete points of the Frequency Response Function.
Impact Behavior of Sandwich Beams With Various Composite Facesheets and Balsa Wood Core
Authors: Abot J. L. , Yasmin A. , Daniel I. M.
Published: November 2021

This study presents a combined experimental and theoretical analysis of both unidirectional and woven fabric composite sandwich beams under low velocity impact loading. The sandwich beams were fabricated by bonding carbon/epoxy facesheets to a balsa wood core. All constituent materials including facesheets, cores and adhesives were fully characterized separately under stress conditions similar to those encountered in the sandwich structures. A comprehensive study that includes fabrication, mechanical testing and analysis of these structures under both quasi-static and impact loading was performed. The failure mechanisms were also analyzed. Existing models developed by the authors for sandwich beams with PVC foam cores were extended to predict impact loads for sandwich beams with balsa wood core.
The New Approach to the Analysis of Elasto-Plastic Deformation of Solids Within the Bounds of Theory of Processes by A. A. Ilyushin
Authors: Babamuratov Kamal Sh. , Abirov Rustam A.
Published: November 2021

In this report results of systematic researches of the experimental-theoretical CL-computer (complex loading) method, offered by Ilyushin for solving of problem of strength and strains of elastic-plastic bodies at an incomplete theoretical information about the equations of relation between stresses and strains and the method of appraisal of reliability of plasticity problems’ solution are given.

Homogeneous and nonhomogeneous problems for element of construction in form of the rods, plates, shell are accomplished. The results of numerical and CL experiments indicate on perspectivity of considered methods for calculations and projection of responsible designs in an engineering and building.
Intelligent Image Correlation Using Genetic Algorithms for Measuring Surface Displacements and Strain Profiles
Authors: Pilch Alan , Maudlin Jay , Mahajan Ajay , Chu Tsuchin
Published: November 2021

This paper presents an intelligent digital image correlation technique that uses genetic algorithms to estimate surface displacements and strains. Speckle patterns are spray painted on the surface of interest and pictures taken before and during loading. Subpixel resolution, required for measuring displacements and strains accurately, is obtained by using interpolation methods. An innovative procedure based on genetic algorithms (GAs) is used that directly gives two displacements and four deformation gradients for a subset being investigated. The genetic algorithms guarantee a solution based on an innovative calibration procedure. The focus of this paper is the description of the GA routine used for the search process as well as the calibration scheme. Results are presented for measuring rigid-body displacement and uniform normal strain as proof of concept. Some potential applications for this work are to extract surface displacements and strains on aircraft, spacecraft and reusable launch vehicles, submarine and ship hulls, civil infrastructures such as bridges, dams and buildings, and biomedical imaging applications.
Intelligent Modeling of Drilling Process: A Knowledge-Based Neural Strategy With Fuzzy Switches
Authors: Sheng Ye , Nelles Oliver , Tomizuka Masayoshi
Published: November 2021

In this paper, an intelligent modeling strategy for thrust force in drilling process is developed. Neural network models and a fuzzy switching strategy are presented to deal with the gain variation problem due to transitions from one drilling stage to another. Gain variation due to drill wear and the related modeling strategy are studied. Simulation and experimental results show that the proposed model works well over a wide operating range.
Some Key Issues in Using Bond Graphs and Genetic Programming for Mechatronic System Design
Authors: Rosenberg R. C. , Goodman E. D. , Seo Kisung
Published: November 2021

Mechatronic system design differs from design of single-domain systems, such as electronic circuits, mechanisms, and fluid power systems, in part because of the need to integrate the several distinct domain characteristics in predicting system behavior. The goal of our work is to develop an automated procedure that can explore mechatronic design space in a topologically open-ended manner, yet still find appropriate configurations efficiently enough to be useful.

Our approach combines bond graphs for model representation with genetic programming for generating suitable design candidates as a means of exploring the design space. Bond graphs allow us to capture the common energy behavior underlying the several physical domains of mechatronic systems in a uniform notation. Genetic programming is an effective way to generate design candidates in an open-ended, but statistically structured, manner.

Our initial goal is to identify the key issues in merging the bond graph modeling tool with genetic programming for searching. The first design problem we chose is that of finding a model that has a specified set of eigenvalues. The problem can be studied using a restricted set of bond graph elements to represent suitable topologies. We present the initial results of our studies and identify key issues in advancing the approach toward becoming an effective and efficient open-ended design tool for mechatronic systems.
A Lyapunov Function Approach to Energy Based Model Reduction
Authors: Chang Samuel Y. , Carlson Christopher R. , Gerdes J. Christian
Published: November 2021

Model reduction based upon the idea of eliminating coordinates with low levels of associated power, energy or activity has been proposed by a number of researchers. None of these results, however, produce the sort of computable bounds on the neglected dynamics that would be useful in the design of controllers with guaranteed robustness properties. This paper outlines an approach to model reduction based upon Lyapunov functions that represent a modified version of the system energy of Lagrangian subsystems. The Lyapunov functions are used to bound the states of subsystems to be removed, enabling these states to be treated as time-varying perturbations in a simplified set of dynamic equations. In contrast to other results in energy-based model reduction, this approach provides bounds on the disturbances caused by the unmodeled dynamics though at the cost of the implementation ease associated with other methods.
An Approach to Acoustic Noise Control via Passivity Techniques
Authors: Kelkar A. G. , Joshi Suresh M.
Published: November 2021

This paper presents a passivity-based robust controller design methodology for broad-band control of acoustic noise in ducts. A brief review of passivity-based control using passification techniques is given for non-passive dynamic systems. An application of this design technique to the acoustic duct system is presented. The acoustic duct model being inherently non-passive, passification techniques are necessary to render the system passive. The controller design is based on finite-dimensional approximation and is shown to be robust to unmodeled dynamics and parametric uncertainties. The control design methodology exploits inherent robustness of passivity-based controllers and selective mode attenuation capability of resonant mode controllers. The resulting controller is low-order, robust, broadband, and has guaranteed stability.
Position and Orientation Identification of Platform Manipulators
Authors: Ji Zhiming , Rodriguez Maximilian
Published: November 2021

A novel approach is developed for identifying both the position and orientation of the base joints of modular platform manipulators. This new approach first establishes a spherical triangle to isolate and solve for one of the unknown placement parameters. With the reduced complexity, a closed-form formulation is then developed for the remaining unknown parameters through Dialytic Elimination for two identification poses. The identification process with the presented method is illustrated with a numerical example.
Enhancement of Vibration Suppression for Multi-Link Flexible Robots Using Direct Parameter Adaptation
Authors: Cheong Joono , Chung Wan Kyun , Youm Youngil
Published: November 2021

The precise modeling of multi-link flexible robot is hard to obtain and even if we can get it, it is difficult to use in on-line control tasks. Due to these reasons, a simplified model is often used to describe the robot dynamics instead of using complex dynamic model. In the simplified model, however, parameter mismatch and structural modeling error are inevitable. To compensate these uncertainties, an adaptive control is formulated in this paper after separating the system into rigid and flexible subsystems. A simple direct parameter update rule is presented considering the flexible subsystem. Different from most of adaptive control schemes in multi-link flexible robots, which is indirect model-independent approach, the proposed adaptive control is a direct one and good for fast suppression of vibration of uncertain and untuned systems. We verify the effectiveness of the proposed algorithm through experiments.
PDE Modeling of a Flexible Two-Link Manipulator
Authors: Zhang X. , Nair S. S. , Chellaboina V.
Published: November 2021

The partial differential equations of a flexible two-link manipulator are derived using the Hamilton’s Principle. The model is validated by simulation as well as experimental studies using a two-link setup in the laboratory.
Lower Limb Human Muscle Enhancer
Authors: Misuraca Joseph J. , Mavroidis Constantinos
Published: November 2021

This paper describes the design, control, and testing of a Human Muscle Enhancer (HME) system that will augment the muscle capabilities of subjects requiring partial lower-limb weight-bearing gait support. The HME described in this paper is a pneumatically actuated quick connecting exoskeleton system that attaches to the foot and hip area of the body, thus “closing” the lower body kinematic chain. Control of the system is achieved by using encoders at the knee joints and Myo-Pneumatic (MP) Sensors implanted into the shoes and outer garments of the human. To test this design concept, a lower body exoskeleton test fixture has been fabricated. The test fixture mimics the human leg with the top cylinder providing the body weight on the leg. Another cylinder acts as leg muscles to provide the adjustable human reaction of the leg. Preliminary open and closed loop control tests have been performed that demonstate the capability of controlling the HME using the MP sensors.
Design Features of Compliant Packages and Their Impact on Reliability
Authors: Mohammed Ilyas , Kim Young-Gon
Published: November 2021

It is well-known that the main cause of mechanical failure in electronic packages is due to the difference in the Coefficients of Thermal Expansion (CTE) of the silicon and the organic board. There are many packaging technologies that try to overcome this limitation; ranging from making curved connection pins (gull-wing leads) from the package to the board, as in the case of Thin Small Outline Package (TSOP), to using hard epoxy to rigidly adhere the die to the board as in the case of flip-chip packages. This paper illustrates a compliant packaging concept that minimizes the effect of the CTE mismatch between the silicon die and the board.

A summary of different packaging techniques that address the CTE mismatch problem is presented. From this summary, it is apparent that many of these techniques do not provide as high reliability as the compliant packages do, especially when the electrical connections from the package to the board (solder balls) are present directly under the silicon die as in the case of chip scale packages. As the compliant package isolates the effect of the silicon die from the substrate, the silicon has some motion relative to the substrate. This means that the interconnections from the silicon to the substrate must be designed to withstand this motion. Hence the design of these interconnections is key to maximizing the reliability of the compliant packages.

A detailed design and reliability analysis of compliant packages for different applications is presented. The design highlights the main parameters that have an effect on reliability of the package. Reliability simulation and analysis using finite element techniques is presented for different designs to highlight the key parameters that govern the reliability of compliant packages. Finally, reliability testing data is presented for different packages.
Failure Mechanisms and Modeling in High Power Optical Device Packaging: Semiconductor Laser Diodes — A Case Study
Authors: Dhamdhere Ajit R. , Schmidt W. F. , Malshe Ajay P. , Brown W. D. , Yedave S. N.
Published: November 2021

High power semiconductor laser diodes are finding increasing applications in diverse areas such as the biomedical field, materials processing, cosmetics, etc. Dissimilar materials integration and thermal management are some of the primary challenges in the fabrication and packaging of reliable laser diode systems. For example, in a specific case, a high power diode must be mounted with its epitaxy-side down, so as to achieve efficient heat transfer. The device and package junction, particularly the die attach interface, is desired to be void-free (i.e., micro-defect free), stress-managed, and contamination-free for uniform optical delivery and reliable optical alignment. Soft solders used in optoelectronic applications are typically subjected to extreme service conditions that may exceed two-thirds of the melting point. As a result, it is expected that the solder microstructure will be metastable and subjected to nearly constant modification during processing and device operation. In this study, we investigated high power laser diode packages aged under various conditions. Die attach interface, device stress, and microscopic defect analyses were carried out using primarily metallography, scanning electron microscopy (SEM), scanning acoustic microscopy, and micro-Raman spectroscopy. It was observed that the intermetallic compounds and microscopic physical defects at the die attach interface are detrimental to transient heat transfer, and thus, overall package reliability. Further, accurate device modeling can be used to assist in the overall understanding of the effect of packaging-induced stress on the performance and reliability of semiconductor lasers. The purpose of this modeling work was to better understand the interplay between electrical, optical, mechanical, and thermal effects in the operation of laser diodes. Micro-Raman spectroscopy was employed to explore the degradation of high power lasers due to mechanical stresses that appear in an active region of the diode during its growth, packaging, and operation. Using micro-Raman spectroscopy, we found that, although stress increases with aging, the shape of the stress profile and the strength changes randomly from one active region of the diode to another.
Creep Behavior of PB-Free Solders
Authors: Hua F. , Garner C. M. , Song H. G. , Morris J. W.
Published: November 2021

This study reports results of shear creep behavior of four Pb-free solders, Sn-3Ag-0.5Cu, Sn-3.5Ag, Sn-0.7Cu and Sn-10In-3.1Ag at 95θC and 130θC. At the stress levels tested, all the four solders showed the stress components close or larger than 5, typical for matrix creep. The calculated activation energies for Sn-0.7Cu, Sn-3.5Ag and Sn-3Ag-0.5Cu are from 103kJ/mol to 117kJ/mol, which are very close to the pure Sn self-diffusion activation energy (107kJ/mol). It suggested that the creep process is controlled by Sn bulk self-diffusion rate. The creep activation energy for Sn-10In-3.1Ag is higher in the range of 173–193kJ/mol.

The Sn-0.7Cu, Sn-3Ag-0.5Cu and Sn-10In-3.1Ag solder joints were also prepared with two different cooling rates, 3.5θC/min. (furnace-cooling) and 2.7θC/S (air-cooling) and tested at 130θC. It was observed that faster cooled solder joints have faster creep strain rates than slower cooled solder joints at the stress levels tested for all three solders, due to the fine and even distribution of intermetallic particles.
Viscoelastic Effects in Helical Flows of Polymer Fluids
Authors: Jeong Jae-Hyeuk , Leonov Arkady I.
Published: November 2021

The paper shows that detailed viscoelastic properties of helical flow can be exactly determined from those known for simple shearing as soon as a constitutive equation is specified. This paper also demonstrates the calculated characteristics of helical flow compared with experimental data.
PIV Measurements of Recirculation Patterns in a Stirred Tank
Authors: Hammad Khaled J. , Papadopoulos George
Published: November 2021

Phase-resolved PIV measurements were performed to reveal the detailed flow features within a triple impeller stirredtank. Two tests were performed: low and high rotational speeds, 175 and 575 RPM, respectively. The tests used an optically transparent mixing vessel to measure the 2D flow field characteristics along a vertical plane passing through the tank center. The measurements disclosed interesting in-plane vortical behavior that when measured at two angular positions with respect to the blade passage further indicated the three-dimensional flow behavior. For the low RPM case, a laminar flow nature was apparent, whereby vortical toroidal structures spanned around the stirrer vertical axis. Six such structures were dominant. For the high RPM case and for θ = 0° six dominant vortical structures were apparent. Their r-z plane location and size were different from that for the low RPM case. With blade passage four of these vortical structures appeared to merge into two, suggesting that constant toroidal vortical structures spanning around the stirrer axis were absent from the high RPM case. A switch between six distinct and four distinct in-plane vortical structures as the blades pass through the measurement plane further suggested a transitional flow field at 575 RPM.
Parameter Estimation in a Hydrostatic System Using Extended Kalman Filter
Authors: Chinniah Yuvin A. , Burton Richard , Habibi Saeid
Published: November 2021

In this paper, the Extended Kalman Filter (EKF) estimation technique is applied to a novel hydrostatic actuation system referred to as the Electrohydraulic Actuator (EHA). A state space model of the EHA is developed and the effective bulk modulus is estimated in simulation. The EHA is a high performance actuation system capable of moving large loads with very high accuracy and precision. In a practical situation, this parameter is very difficult to measure directly as it depends on entrained air which cannot be known at a particular point of time. The bulk modulus is critical for system response and a low bulk modulus as a result of air in the system can seriously hinder the performance of EHA and cause safety problems.
Correlations of Fin-Tube Heat Exchanger Performance Data Using Genetic Algorithms, Simulated Annealing and Interval Methods
Authors: Pacheco-Vega Arturo , Sen Mihir , Yang K. T. , McClain Rodney L.
Published: November 2021

We consider the prediction of the performance of an air-water fin-tube compact heat exchanger using correlations of the power-law type. Measurements of the in-tube and over-tube mass flow rates, inlet temperatures and heat transfer rates, with water as the in-tube fluid and air as the over-tube fluid, are used to show that a regression analysis for the best-fit correlation of a prescribed form does not provide a unique answer in the heat rate predictions and that a global, rather than a local, search for the best correlation should be conducted. To this end, we propose the application of three different global optimization techniques to find the constants in a prescribed correlating function which can then be used to predict the performance of this heat exchanger under different operating conditions. Comparisons of the different results are then made to determine the relative advantages and disadvantages among the methods in terms of efficiency, accuracy and certainty of the results. Every method is found to have advantages over the others, and the results demonstrate that all three techniques are able to predict well the performance of this heat exchanger.
An Advanced Multiblock Solution Procedure and its Application to Silicon Tube Growth by EFG Technique
Authors: Sun D. , Zhang H. , Prasad V. , Mackintosh B. , Kalejs J. P.
Published: November 2021

The Edge-defined Film-fed Growth (EFG) is a widely used technique for the growth of polycrystalline silicon from its melt in the form of ribbon and hollow cylinders. The current octagonal tube growth technique has been modified successfully to produce 50 cm diameter circular tube for photovoltaic application by ASE Americas, Inc. A comprehensive growth model has been developed that accounts for conduction, convection and radiation heat transfer in the growth system, electromagnetic heating, and solidification. To improve the efficiency and accuracy of the model, two sets of grid system have been employed. A single structured grid system is used to calculate the magnetic potential field generated by radio-frequency induction heater, and a non-matching multi-block grid system to solve the temperature field with fine grids in the vicinity of the die-tip and silicon tube. Two sets of grid system overlap each other. A multi-block solution procedure has been developed satisfying the flux conservation at the block interfaces. The new solution procedure is used to simulate the existing octagonal silicon tube growth. The results obtained by different solvers, e.g., TDMA, CGSTAB, BiCGSTAB, SIP solver, are compared. It is evident that the CPU time is reduced dramatically if a fast solver, such as SIP or multigrid method, is used in the multi-block system.
Comparison of Sharp Interface Dendritic Growth Simulation With Microscopic Solvability Theory
Authors: Udaykumar H. S. , Mittal R. , Mao L.
Published: November 2021

We present and validate a numerical technique for computing dendritic growth of crystals from pure melts. The solidification process is computed in the diffusion-driven limit. The mixed Eulerian-Lagrangian framework treats the immersed phase boundary as a sharp solid-fluid interface and a conservative finite volume formulation allows boundary conditions at the moving surface to be exactly applied. The case of discontinuous material properties is also computed. The results from our calculations are compared with two-dimensional microscopic solvability theory. It is shown that the method predicts dendrite tip details in good agreement with solvability theory. The ability of the method to treat the front as a sharp entity and therefore to respect discontinuous material property variation at the solid-liquid interface is also shown to produce results in agreement with solvability and with other sharp interface simulations.
Thermally Optimum Natural Convection Cooled Longitudinal-Plate Heat Sinks With Horizontal Base Plates
Authors: Sikka K. K. , George C.
Published: November 2021

Longitudinal-plate fin heat sinks are optimized under natural convection conditions for the horizontal orientation of the heat sink base plate. The thermal performance of the heat sinks is numerically modeled. The fin height, thickness and spacing and heat sink width are systematically varied. The numerical results are validated by experimentation.

Results show that the thermal resistance of a heat sink minimizes for a certain number of fins on the base plate. The fin spacing-to-length ratio at which the minimum occurs is weakly dependent on the fin height and thickness and heat sink width. The flow fields reveal that the minimum occurs for the heat sink geometry in which the number of fins are maximized such that the flow velocity as the air exits the fins is fully developed. A correlation of the heat transfer with the heat sink geometrical parameters is also developed.
Non-Equilibrium Thermal Effects in Power Transistors
Authors: Raman Ashok , Walker D. G. , Fisher T. S.
Published: November 2021

The present work considers electro-thermal simulation of LDMOS devices and associated non-equilibrium effects. Simulations have been performed on three kinds of LDMOS i.e. bulk Si, partial SOI and full SOI. From the analysis, the extent of thermal non-equilibrium is determined from phonon temperature contours and electron energies in each case. The results indicate that, under similar operating conditions, non-equilibrium is more significant in the case of full SOI devices. Time development of acoustic phonon and lattice temperatures, obtained using two different heat source terms, was studied. This study provided insight into the difference between localized device heating in the electrically active region. The variation of optical and acoustic phonon temperatures with time is presented, and is used to identify time scales where thermal non-equilibrium would be significant.
Comparative Analysis of Implant Effectiveness in Maintaining the Stability of the Reverse Obliquity Hip Fracture
Authors: Kerr Kevin A. , Hashemi Javad , Post Jordan , Ngo Khai , Dabezies Eugene
Published: November 2021

The reverse obliquity hip fracture is an unstable intertrochanteric fracture. The existing treatments of the reverse obliquity hip fracture have a high failure rate leading to re-operation. The objective of this study was to design an experimental setup to systematically evaluate and quantitatively document the effectiveness of various fixation devices used to treat the reverse obliquity hip fracture.

The fixation devices tested and analyzed were 1) the 135 Degree Dynamic Hip Screw with a Trochanteric Stabilizing Plate (DHS/TSP)®, 2) the 95 Degree Condylar Hip Screw (CHS)®, and 3) the Recon Nail®. These devices were implanted in composite sawbone specimens with material properties close to that of human bone. All devices were tested under identical cyclic loading conditions. Based on a quantitative stability analysis, the 95 Degree CHS® showed the most promise for treatment of non-comminuted reverse obliquity hip fractures. The Recon nail® caused the bone to fracture at areas of high stress concentration and the 135 Degree DHS/TSP® was associated with high values of stress shielding. In this paper, the experimental set-up will be presented, the generated data will be discussed, and the performance of each fixation device will be analyzed.
Relationship Between Body Segment Mass and Running Performance in Well-Trained Endurance Runners
Authors: Ueno Hiromasa , Suga Tadashi , Takao Kenji , Terada Masafumi , Nagano Akinori , Isaka Tadao
Published: November 2021

This study examined the relationship between body segment mass and running performance in endurance runners. The total (muscle, fat, and bone masses), lean (muscle mass), and fat masses of the leg, arm, and trunk segments in 37 well-trained endurance runners were measured using dual-energy X-ray absorptiometer. The relative segment mass was calculated by normalizing the absolute mass to body mass. There were no significant correlations between absolute total, lean, and fat masses of all 3 segments and personal best 5000-m race time. No significant correlations were also observed between all 3 relative masses of the arm segment and personal best 5000-m race time. In contrast, medium positive correlations were observed between the relative total and lean masses of the leg segment and personal best 5000-m race time (r = .387 and .335, respectively, bothP ≤ .031). Furthermore, large negative correlations were observed between the relative total and lean masses of the trunk segment and personal best 5000-m race time (r = −.500 and −.548, respectively, bothP ≤ .002). These findings suggest that a mass distribution with smaller leg mass and greater trunk mass may be advantageous for achieving better running performance in endurance runners.
Valued Insight or Act of Insubordination? How Context Shapes Coaches’ Perceptions of Challenge-Oriented Followership
Authors: Gottlieb Marcus , Eys Mark , Hardy James , Benson Alex J.
Published: November 2021

Effective leadership is a collaborative effort, requiring a degree of complementarity in how people enact roles of leadership and followership. Using a novel online vignette methodology, we experimentally tested how three contextual factors influenced coaches’ responses to challenge-oriented acts of followership, as well as investigated two potential mechanisms. Coaches (N = 232) watched videos of an athlete provided unsolicited challenge-oriented feedback to a coach. Videos varied by the (a) athlete’s status, (b) presence of third-party observers, and (c) stage of the decision-making process. Following the video, we assessed coaches’ evaluations of the athlete. Challenge-oriented followership was perceived more favorably when enacted by an athlete in one-on-one (vs. in a group) and before a decision has been reached (vs. after a decision is reached). Coaches may appreciate proactivity from athletes in positions of followership, but challenge-oriented followership behaviors enacted at the wrong time and place can elicit negative reactions.
Effective actions for loop quantum cosmology in fourth-order gravity
Authors: Miranda Marcello , Vernieri Daniele , Capozziello Salvatore , Lobo Francisco S. N.
Published: November 2021

Loop quantum cosmology (LQC) is a theory which renders the Big Bang initial singularity into a quantum bounce, by means of short-range repulsive quantum effects at the Planck scale. In this work, we are interested in reproducing the effective Friedmann equation of LQC, by considering a generic f(R, P, Q) theory of gravity, where $$R=g^{\mu \nu }R_{\mu \nu }$$

R
=

g

μ
ν

R

μ
ν

is the Ricci scalar, $$P=R_{\mu \nu }R^{\mu \nu }$$

P
=

R

μ
ν

R

μ
ν

, and $$Q=R_{\alpha \beta \mu \nu }R^{\alpha \beta \mu \nu }$$

Q
=

R

α
β
μ
ν

R

α
β
μ
ν

is the Kretschmann scalar. An order reduction technique allows us to work in f(R, P, Q) theories which are perturbatively close to General Relativity, and to deduce a modified Friedmann equation in the reduced theory. Requiring that the modified Friedmann equation mimics the effective Friedmann equation of LQC, we are able to derive several functional forms of f(R, P, Q). We discuss the necessary conditions to obtain viable bouncing cosmologies for the proposed effective actions of f(R, P, Q) theory of gravity.
Modeling Analysis and 3D Force Prediction of a Novel Piezoelectric Tactile Sensor
Authors: Wang Feilu , Ye Rungen , Song Yang , Chen Yufeng , Jiang Yanan , Lv Shanna , Li Mingkun
Published: November 2021

To measure three‐dimensional (3D) forces efficiently and improve the sensitivity of tactile sensors, a novel piezoelectric tactile sensor with a “sandwich” structure is proposed in this paper. An array of circular truncated cone‐shaped sensitive units made of polyvinylidene fluoride (PVDF) is sandwiched between two flexible substrates of polydimethylsiloxane (PDMS). Based on the piezoelectric properties of the PVD F sensitive units, finite element modelling and analysis are carried out for the sensor. The relation between the force and the voltage of the sensitive unit is obtained, and a tactile perception model is established. The model can distinguish the sliding direction and identify the material of the slider loaded on the sensor. A backpropagation neural network (BPNN) algorithm is built to predict the 3D forces applied on the tactile sensor model, and the 3D forces are decoupled from the voltages of the sensitive units. The BPNN is further optimized by a genetic algorithm (GA) to improve the accuracy of the 3D force prediction, and fairly good prediction results are obtained. The experimental results show that the novel tactile sensor model can effectively predict the 3D forces, and the BPNN model optimized by the GA can predict the 3D forces with much higher precision, which also improves the intelligence of the sensor. All the prediction results indicate that the BPNN algorithm has very efficient performance in 3D force prediction for the piezoelectric tactile sensor.
Impact of Fusion Temperature on Hydrothermal Features of Flow within an Annulus Loaded with Nanoencapsulated Phase Change Materials (NEPCMs) during Natural Convection Process
Authors: Seyyedi Seyyed Masoud , Hashemi-Tilehnoee M. , Sharifpur M.
Published: November 2021

A new type of nanofluids is nanoencapsulated phase change materials (NEPCMs), where nanoparticles are made of a shell and a core. In the current study, characteristics of free convection flow, entropy generation, and heat transfer of NEPCMs in an enclosure are investigated. The enclosure is an annulus between concentric horizontal circular and square cylinders with a porous medium. The governing equations (i.e., continuity, energy, and momentum) are written in the nondimensional form and then numerically solved by the control volume finite element method (CVFEM). The results of the validation are in good agreement with those of the literature. The effects of decision variables on the entropy generation number and the average Nusselt number are investigated. The outcomes discovered that there is a maximum for

Nu

ave

and a minimum for

N

gen

at

θ

f

=
0.4

for each value of the Stefan number. Also,

Nu

ave

and ECOP increase by 8.8% and 24.8%, respectively, while

N

gen

decreases by 12.8% when

ϕ

increases from 0 (pure fluid) to 0.05 at

θ

f

=
0.4

.
Relieving the Congestion around a School via Automatic Vehicle Identification Technology-Based Traffic Measures
Authors: Li Bo , Yu Zhi , Sun Weiwei , Chen Kaiying , Zhang Teng
Published: November 2021

Recently, many parents drive their children to and from schools, leading to serious road congestion around the school gate. The school-related congestion is a special type of congestion caused by periodic impulsive aggregation of specific travellers for certain events. In this study, the individual long short-term traffic behaviours were reconstructed based on automatic vehicle identification (AVI) technologies. The cause and countermeasure of congestion around the service centers were identified through the individual behavioural properties. The vehicles that were primarily responsible for periodic impulsive aggregation congestion (PIAC) around the school gate were precisely targeted via a proposed vehicle grading clustering framework. The road management objectives were updated in the AVI data environment and it was found that only 3%–5% of the total number of vehicles passing by the school gate require specific management such as traffic enforcement activities. A series of traffic measures were formulated based on the results of vehicle grading clustering and achieved positive effects in a periodic impulsive aggregation area. It is an effective way to solve the PIAC by formulating management with different activity levels and resolutions for specific travellers. The methodologies and experience presented in this study may provide a useful tool for relieving such special type of congestion around other service centers faced with similar scenarios.
Use of Extracorporeal Membrane Oxygenation in Patients with Refractory Cardiac Arrest due to Severe Persistent Hypothermia: About 2 Case Reports and a Review of the Literature
Authors: Attou Rachid , Redant Sébastien , Preseau Thierry , Mottart Kevin , Chebli Louis , Honore Patrick M. , De Bels David , Gallerani Andrea
Published: November 2021

We report the cases of two patients experiencing persistent severe hypothermia. They were 45 and 30 years old and had a witnessed cardiac arrest managed with mechanized cardiopulmonary resuscitation (CPR) for 4 and 2.5 hours, respectively. Extracorporeal membrane oxygenation was used in both patients who fully recovered without any neurological sequelae. These two cases illustrate the important role of extracorporeal CPR (eCPR) in persistent severe hypothermia leading to cardiac arrest.
BPSK Modulation‐Based Local Oscillator‐Free IQ Demodulation for Millimeter Wave Imaging
Authors: Zheng Qibin , Jian Yanpeng , Wang Lei , Ma Ziyue , Li Xinyu , Song Chaofan , Li Ping , Ding Li
Published: November 2021

The precision of local oscillator (LO) signal in in‐phase and quadrature (IQ) demodulation strongly affects the imaging performance of millimeter wave (mmWave) radars. Therefore, to eliminate the requirement for high‐precision LO, a simple yet effective digital IQ demodulation method has been proposed with the aid of a specified sampling scheme in order to eliminate the demand for LO. Based on the bandpass sampling theorem, the characteristic of the intermediate frequency signal of mmWave imaging indicates that the LO is unrequired if the sampling rate is twice of the frequency of the carrier of the intermediate signal. In this way, the in‐phase signal would be directly and accurately obtained by performing the Binary‐Phase‐Shift‐Keying (BPSK) modulation on the samples, based on which the IQ demodulation would be completed by using the Hilbert transform. The proposed method does not employ LO and thus simplifies the demodulation process and is suitable for implementation in a Field‐Programmable Gate Array (FPGA) with fewer hardware resources. To verify the method, a three‐dimensional mmWave radar imaging is carried out at the 30‐34 GHz bandwidth, where the sampling and digital IQ demodulation are realized by an ADC (AD9250) and FPGA (XC7K325T), respectively. The results show a simplified transceiver with lower requirements and the prospect of the proposed method being applied in radar imaging and other related fields.