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The numerical and experimental examinations in the behavior of ARMOX 500 T steel plates of a standard thickness under blast loading are presented in this study. Furthermore, the dynamic reaction of the steel plate is crucial, particularly when subjected to blast loads produced by various explosive forms and at a certain stand-off distance (SoD). This study conducted experimental and numerical simulation tests on steel plates under the close-range air blast loads generated by 150 g TNT cylindrical explosives, which are the most widely used explosives in the military and engineering fields. In order to investigate the failure modes of steel plates, close-range air blast load experiments were conducted at a 400 mm SoD. Pressure gauges were positioned at equal distances, and the impact of these tests on the failure deformation and dynamic response of the steel plate was quantitatively examined. Ultimately, the properties of shock waves produced by cylindrical explosives were examined in order to ascertain how SoD and charge quantity affected the shock waves' spatial dispersion. • The stand-off distance has a great impact on the loading conditions of a structure. • Shock waves have a key influence on the detonation action. • Numerical simulations carried out to learn more about the deformation modes of plates. [ABSTRACT FROM AUTHOR]

This study addresses the critical need for optimizing heat transfer and fluid flow in porous ring structures, which are essential for various thermal management applications. The aim is to investigate how different parameters such as obstacle length(B), heat source position(D), heat generation coefficient(Q), Hartmann coefficient (Ha), porosity(ε), and Rayleigh coefficient (Ra) affect heat transfer and fluid flow characteristics in a porous ring structure with multiple heat sources. The modeling assumes steady-state conditions, isotropic and homogeneous porous media, and uniform heat generation within the obstacles. Finite Element Method (FEM) simulations were employed to analyze the effects of the aforementioned parameters on streamline distributions, temperature profiles, and heat transfer rates. Remarkably, increasing obstacle length and higher porosity generally enhance heat transfer efficiency, while positioning heat sources closer to the outer boundary and higher Rayleigh numbers lead to reduced heat transfer. The study reveals that, contrary to conventional expectations, various parametric changes consistently result in decreased heat transfer, making the porous ring structure suitable for applications requiring thermal isolation or minimized heat leakage. [ABSTRACT FROM AUTHOR]

Metal cutting processes contribute significant share of the added value of industrial products. The need for machining has grown exponentially with increasing demands for quality and accuracy, and despite of more than a century of research in the field, there are no reliable and accurate models that describe all the physical phenomena needed to optimize the machining processes. The scientific community has begun to explore hybrid methods instead of expanding the capabilities of individual modelling schemes, which has been more efficient than efficacious direction. Following this trend, we propose a hybrid finite element — machine learning method (FEML) for modelling metal cutting. The advantages of the FEML method are reduced need for experimental data, reduced computational time and improved prediction accuracy. This paper describes the FEML model, which uses a Coupled Eulerian Lagrangian (CEL) formulation and deep neural networks (DNN) from the TensorFlow Python library. The machining experiments include forces, chip morphology and surface roughness. The experimental data was divided into training dataset and validation dataset to confirm the model predictions outside the experimental data range. The hybrid FEML model outperformed the DNN and FEM models independently, by reducing the computational time, improving the average prediction error from 23% to 13% and reduced the need for experimental data by half. [Display omitted] • A Novel Hybrid FEML model based on Deep Neural Networks (DDN) and Finite Element Method (FEM) is proposed for predicting metal cutting process outcomes. • Hybrid FEML model outperforms DNN and FEM models independently regarding prediction accuracy, computational time and need for experimental data. • FEM model with CEL formulation has advantages in 3D machining simulations over ALE methods because CEL does not require remeshing. [ABSTRACT FROM AUTHOR]

The micro electrical discharge machining (µ-EDM) process is one of the most widely used techniques to produce miniaturized components in micro-electro mechanical system (MEMS) applications due to its inherent advantages. This work investigates the wear phenomena and the morphology of the copper electrodes during the micro-die sinking process. A numerical model of a single spark is developed assuming the Gaussian distribution of heat flux to estimate the crater dimensions formed in the copper tool electrode (tool wear) used as a result of electric discharge. The crater dimension attained from the ABAQUS finite element model is validated with experimental results using a single spark test setup. Moreover, the effect of input parameters namely capacitance and voltage on the electrode wear rate and surface roughness is also studied. The crater dimensions from the single discharge study are used to formulate the wear model for different possibilities of crater distribution, such as non-overlapping craters, craters with less than 30 % overlap, and 50 % overlap. The electrode wear rate (EWR) also displayed a decline from 20.4 % to 11.6 % and further to 8 % when the overlap was permitted up to 30 % and up to 50 % for the wear model respectively. The developed model results are further compared with experimental results in terms of the electrode wear rate and depth of erosion and the deviations are found to be 20.33 % and 20.55 % respectively [ABSTRACT FROM AUTHOR]

The heat transfer analysis and time dependent magneto hydrodynamics boundary layer flow of three dimensional viscous incompressible Newtonian fluid in rotating frame across the extending surface subject to microgravity g ∗ (t) (= g o [ 1 + ϵ cos (π ω t) ] k) is investigated. The gravity modulation and gradient of fluid temperature typically generate buoyant convective flows in case of various situation, most likely in environment of low gravity or microgravity, the systems can operate under purely diffusive conditions in this environment since buoyancy-driven fluid flows and sedimentations are significantly diminished. Recent years have seen a growing interest of researchers in mixed convection that is regulated by microgravity environment due to highly extensive modern technological applications. The innovative aspect of the current study is the consideration of the impacts of gravity jitters (g-jitter) in rotating Newtonian fluid. The leading governing equations of elaborated fluid flow problem transformed into form of non dimensional coupled non-linear PDEs (partial differential equations) by the help of appropriate similarity functions. For seek of numerical solution, a very powerful technique, finite element method is used via MATLAB. The flexibility, robustness, and exactness of this technique make it a strong tool for solving fluid flow problems. The magnitude of average Nusselt number exhibits 16% & 17% decline against 46.31% increment in Coriolis and magnetic forces. Rising the amplitude of modulation results in proportional rise and decline in skin friction and heat transfer. By increasing strength of rotating parameter, magnetic parameter and frequency modulation parameter, the velocity profile declined while, temperature field has opposite trend against these parameters. The comparison of current results with existing results is given and found a very good agreement between them. [ABSTRACT FROM AUTHOR]

Polymer-metal hybrids are a lightweight solution for many industrial applications, especially in the automotive or aircraft sector. However, due to their poor chemical bonding the manufacturing of such compounds requires the use of adhesive layers or the conditioning of the metallic surface to achieve form closure and high joint strength. Ultrasonic Vibration Assisted Deformational Machining (UVADM) is a novel process that generates functional microstructures with high production rates, aiming to form defined burr structures with undercuts, that have a significant impact on the interlaminar strength of polymer-metal hybrids (PMH). A 3D FEM simulation using Abaqus/Explicit software was applied to design and analyze process conditions including tool geometry. Material deformation was described by the Johnson-Cook model. Simulation results were validated experimentally using two different MCD tools. For the UVADM experiments, specimens of the aluminum alloy EN AW-6082 were used. In the tests, a constant ultrasonic frequency (20.42 kHz), machining speed (100 m/min and 200 m/min), and peak-to-peak amplitude (7 µm) were used. Geometrical surface properties were analyzed by optical methods and SEM. The study demonstrates a conformity between simulated and experimental results, highlighting the potential of UVADM for an increased productivity in the surface conditioning for polymer-metal hybrids. [ABSTRACT FROM AUTHOR]

Efficient manoeuvrability of off-road tracked vehicles such as military tanks and rovers is essential in ensuring the success of military/extra-terrestrial operations. To achieve this, in-depth research on vehicle-terrain interaction is crucial. This manuscript deals with reviewing the ways to study terramechanics viz. theoretical, empirical, and field tests, and proposing the merits and demerits of each method. Under the theoretical approach, empirical, numerical, and semi-empirical methods are discussed. Under the empirical approach, the method based onthe vehicle cone index for tracked and wheeled vehicles is discussed. Under the numerical approach, advantages and disadvantages of Finite Element Method (FEM) and Discrete Element Method (DEM) are discussed. Semi-empirical method, based upon a combination of the best features of numerical and empirical approaches discusses terrain response to normal repetitive loads and shear repetitive loads for tracked as well as wheeled vehicles. Pressure sinkage relationship for terrains at various loading conditions and shear stress displacement relationship for different terrains obtained through penetration and shear tests are discussed to determine the vehicle's mobility parameters under a semi-empirical approach. Further, the Super element model, multi-body simulation model, and ride and cornering vibration model are discussed under computer simulation models. A detailed review of various models customized towards tracked vehicle-terrain interaction discussed in this manuscript helps the authors set up a laboratory for terramechanics at DIAT. Preliminary analysis along with conceptual design of the experimental setup is also discussed. In a nutshell, this paper attempts to summarize the research that has been carried out in the field of tracked vehicle-terrain inter action comprising of VCI, MMP, FEM, DEM, Super element model, Multibody technique, and Semi-empirical methods helping the authors to establish a laboratory of terramechanics for their M. Tech. program on Armament and Combat Vehicles at DIAT Pune. [ABSTRACT FROM AUTHOR]

Lapped column transition is a novel structural form. In lapped column transition structures, the reinforcement at the lapped column nodes is generally dense, which is highly unfavorable for construction operations. Even if construction operations are carried out, it is difficult to guarantee the construction quality and mechanical performance of the nodes. To address this issue, taking a practical engineering project as an example, a comprehensive optimization of the reinforcement layout in lapped columns is conducted using BIM (Building Information Modeling) and FEM (Finite Element Method) technologies. The research results demonstrate that BIM technology can effectively and rapidly optimize the reinforcement layout in lapped columns, resulting in a layout that is more conducive to on-site construction and can effectively ensure construction quality. FEM technology can effectively perform mechanical performance calculations on the optimized lapped columns, with the mechanical performance of the optimized lapped columns being basically unchanged and still meeting the requirements of engineering structural mechanics. [ABSTRACT FROM AUTHOR]

This work deals with the investigation of the effect of porosity on the natural frequencies of the rotating pre twisted sandwich blade with a functionally graded core in the thermal environment. The top metallic and the bottom ceramic surfaces are exposed to ambient temperature and high inlet temperature, respectively. A finite element approach using a layer wise theory is developed. Two different porosity distributions are assumed here. The effect of the volume fraction index, rotational velocity, porosity model and temperature gradient on the natural frequencies of the pre twisted sandwich blade is studied. [ABSTRACT FROM AUTHOR]

Business Process LifeCycle (BPLC) is a topic never disappearing from the discussions in the Business Process Management (BPM) research. Nevertheless, most graphical models of BPLC are simple and need extended textual explanations to clarify them. What is more, to the best of our knowledge, these models are separated from the target process that is being changed in the BPLC. The paper investigates a possibility to have a model where lifecycle activities are connected to the elements of the target process, and assess the practical usefulness of such a model. The research uses the Fractal Enterprise Modeling (FEM) technique for building the model. The paper presents a generic model of BPLC and its extension for one step, and discusses potential usefulness of the results achieved so far. [ABSTRACT FROM AUTHOR]

• The finite element method is a valuable method for understanding the biomechanics of aligners. • Trimming line design of orthodontic aligners has a key role in force transmission. • Extended straight aligner trimming line improves control of tooth movement. • Properly designed thin aligners offer enhanced efficiency and comfort. • Aligners present a higher likelihood of uncontrolled tipping than bodily movement. A finite element model was used to investigate the effect of different designs and thicknesses of orthodontic aligner margins on their biomechanical behavior. A three-dimensional data set of an upper jaw was imported into the 3-matic software. The upper right central incisor tooth (Tooth 11) was separated from the remaining model, and its periodontal ligament and surrounding bone were designed. Aligners were designed with four different trimming lines (scalloped, straight, scalloped extended, straight extended), each with four different thicknesses (0.3, 0.4, 0.5, and 0.6 mm). The models were imported into a finite element package (Marc/Mentat). A linear elastic constitutive material model was applied. A facial 0.2 mm bodily malalignment of tooth 11 was simulated. The maximum resultant force was in the range of 1.0 N to 2.2 N. The straight trimming designs deliver higher resultant forces compared with scalloped trimming designs. Increasing the aligner thickness and/or extending the aligner edge beyond the gingival line leads to an increase in the resultant force. All designs showed an uneven distribution of the normal contact forces over the tooth surface with a predominant concentration toward the cervical third and distal third, particularly with the extended trimming designs. All designs showed uncontrolled tipping of the tooth. Based on the current model outcomes, the use of a straight extended trimming line design for aligners is favored because of its positive impact on force distribution and, consequently, the control of tooth movement. These findings provide aligner companies and orthodontists a valuable biomechanical evidence and guidance to enhance control over tooth movement and therefore optimize treatment outcomes. This can be achieved by trimming the edges of aligners with a straight extended design and selecting the appropriate aligner thickness. [ABSTRACT FROM AUTHOR]

Since the machining of complex aerospace components, like integral compressor-rotors (blade integrated disks), is very cost-intensive, optimizing the process by means of process simulations is an active field of research. With the rise of Quantum Computing, a new instrument with high optimization potential is moving into focus. In this paper, a possible application of Quantum Computing for the machining simulation of multiaxis milling of thin-walled aerospace components is discussed. For this reason, a simulation framework used for the milling simulation is analyzed and each component is evaluated separately in relation to Quantum Computing. Parts of the Harrow, Hassidim, and Lloyd algorithm are proposed to enhance the Finite-Element simulation-based component, like the modal analysis for dynamics simulation. This algorithm can solve linear system problems with exponential speed-up over the classical method. The paper presents a roadmap on how the classical steps of a modal analysis for dynamics simulation could be replaced by quantum algorithms based on quantum phase estimation. The implementation of the first working steps is presented to validate this approach. The linear system problem, arising from the dynamics simulation, is analyzed in detail and a minimal value problem of linear coupled oscillators is derived. [ABSTRACT FROM AUTHOR]

The structural analysis of a road foldable prefabricated steel Baileytype bridge located over the Tuga River in Żelichowo, Poland is performed in this paper. Interesting and untypical bridge redevelopment performed made it possible to lift the middle foldable bridge span by approximately 4.0 m concerning the existing state. The paper begins with a survey of literature carried out on the investigations of foldable Bailey-type bridge subject matter. A description of the numerical modelling of foldable prefabricated bridges is performed. The comparison of the proof load test results with the FEM numerical model results has shown very good compatibility. This paper can provide scientists, engineers, and designers the basis for structural analysis in the field of foldable Bailey-type bridge constructions and numerical simulations. [ABSTRACT FROM AUTHOR]

Harmonic oscillations of piezoceramic functional-gradient sectioned hollow cylinders are studied, taking into account energy dissipation. A cylinder of finite length is considered. Cylinder consists of an even number of sections polarized in the circular direction, which are connected to each other by similar sides. The material is considered to be functionally heterogeneous in the direction of the previous polarization. The cylinder is loaded by the potential difference applied to the flat faces of the sections. The calculation is performed by the finite element method. Damping matrices forming and determining of coefficients corresponding to methods of introducing frequency-independent damping and Rayleigh damping is described. Electric losses are taken into account by entering the dielectric loss tangent or dielectric loss tangent matrix. The result of calculations is compared with the result obtained with the help of complex elastic and dielectric moduli. Amplitudefrequency characteristics are constructed for movements, charge on the electrodes, electrical admittance and its logarithm, taking into account damping. Energy dissipation consideration is related to the experimental data due to the mechanical quality factor of the piezo element. The frequencies of electrical resonances, anti-resonances and corresponding electromechanical coupling coefficients for functionally inhomogeneous and homogeneous cylinders are determined. For the functional-gradient piezoelectric element of the considered configuration, the maximum CEMC occurs at the frequency of the second electrical resonance. At this frequency, the dynamic stress-strain state of the cylinder is investigated. Forms of oscillations and distribution of stress amplitude values are constructed. The largest normal stresses according to the Coulomb-Mohr strength theory are determined and compared with the von Mises strength theory. FEA allows three-dimensional calculation of harmonic oscillations of functional-gradient piezo elements of complicated geometry. The determined frequencies of electrical resonance and anti-resonance and the corresponding CEMC make it possible to choose the most effective operating mode of the piezo element. The FEM mathematical apparatus makes it possible to quickly and qualitatively evaluate the strength, determine the charge on the electrodes, the current in the circuit, build the amplitude-frequency characteristics of admittance and impedance, and evaluate the efficiency of energy conversion. [ABSTRACT FROM AUTHOR]

The present paper focuses on an elastic properties analysis of new and depreciated tires. The research was carried out using two different methods, field and numerical, respectively. The purpose of the study is to check whether there is a change in the elastic properties of a tire during its depreciation and to what extent the process affects the comfort of driving and riding. The experimental tests were conducted on a hydraulic test stand and by applying strength and deformation analysis the effect of its structure deformation was additionally considered. The investigation was performed on a vehicle-based tire test stand to find out stress-strain and tire deformation was with different vertical loading according to FEM. The numerical solution was reached by implementing SolidWorks - Simulation and Abaqus. The obtained results are graphically compared, and the average value of the elastic constant for a new and depreciated tire has been determined. [ABSTRACT FROM AUTHOR]

Black cotton soil is highly susceptible to volume change due to moisture fluctuations. This leads to the deformation of structures built on such soil. Therefore, the aim of this study is to improve the soil-bearing capacity and deformation analysis of black cotton soil. The laboratory tests were done according to the American Association State of highway and Transport Official (AASHTO) and the American Society for Testing and Materials (ASTM). These tests were natural moisture content, grain size distribution, X-ray diffraction test, Atterberg limit test, modified compaction, California bearing ratio, and triaxial test. Soil sample was stabilized with a ratio of 0%, 4%, 8%, 12%, and 16% of brick dust and 0%, 1%, 3%, 5%, and 7% of lime, respectively. The result of the laboratory test at the optimum percentage of 12% brick dust and 5% lime shows that the liquid limit improved from 93.2% to 67.5%, plastic limit improved from 48.71%, to 58.2%. The optimum moisture content improved from 26.76 to18.5% and Maximum dry density improved from 1.42 g/cm3 to 1.58 g/cm3. The California bearing ratio improved from 1.29%, to 13.6%. The deformation analysis result shows that at optimum percentage of stabilizing agent, the deformation reduced from 2.087 mm to 0.973 mm. Therefore, brick dust-lime soil stabilization shows the promising improvement of weak subgrade soil. [ABSTRACT FROM AUTHOR]

The implementation of the wind turbine is a major issue in the wind engineering sector. However, the presence of wind turbines in the lower part of the atmospheric boundary layer (ABL) requires an appropriate study for the simulation of turbulent airflow in the wind farm situated on hilly terrain. The use of precise Computational Fluid Dynamics (CFD) simulations for the ABL flow is vital for numerous applications, such as wind energy, building, urban planning, etc. To achieve accurate results, it is imperative that the inlet boundary conditions produce vertical profiles that keep a uniform horizontal distribution (with no streamwise gradients) in the upstream region of the computational domain for all important parameters. A development approach is proposed herein, focused on the imposition of two different inlet profiles when used in combination with the rough z0-type scalable wall function. The horizontal homogeneity of these profiles has been verified by 2D Reynolds averaged Navier-Stokes (RANS) through the examination of a neutral ABL in an empty computational domain using the k-ε turbulence model. The findings indicate that the use of this modeling approach can yield relatively consistent homogeneity of neutral ABL for both inlet boundary conditions. Subsequently, sensitivity analyses were performed on the inflow profiles to forecast the evolution of the bottom half of an idealized truly-neutral ABL and to accurately capture the complex dynamics of atmospheric flows over hilly terrain. This study compares the results with the CRIACIV (Inter-University Research Centre on Building Aerodynamics and Wind Engineering) boundary layer wind tunnel experimental data, showing that the inflow profiles and the presence of topographic complex have a significant impact on air velocity, turbulent kinetic energy and turbulence intensity in the x-direction. The results obtained are in good correlation with published experimental data in the presence of the hill surface. [ABSTRACT FROM AUTHOR]

A dynamic finite element methodology (FEM) was developed to simulate an entire dynamic replacement (DR) program of clay with sand involving multiple poundings. The main objective of this research was to employ FEM and geotechnical test data such as cone penetration test (CPT) data at the site to predict the maximum achievable sand column (SC) depth and the corresponding optimum levels of attributing parameters such as number and height of pounder drops. Another goal was to predict the pore pressure generated in clay due to pounding. A full-scale ground improvement project was used to guide the analytical process. Comparison of FEM predictions and field measurements showed the potential of using FEM to achieve the above objectives in advance of the field work. Finally, a step – by-step procedure for using a FEM procedure to predict the optimum field setup and hence improve the efficacy of DR field implementation is illustrated. [ABSTRACT FROM AUTHOR]

The planet on which we are living is currently under an imminent threat. Population growth, massive digitalization, environmental pollution, increased scarcity of resources, and the greenhouse effect are putting our future and the future of generations to come at risk. As more and more governmental reforms are aiming to diversify the sources of energy production and many international players are working on market coupling to enhance cross-border cooperation, the question that arises is what developing countries can do in light of an energy crisis. Such so-called transition economies are working hard to promote growth, sustainable development and increase competitiveness in the European arena. Said that, it becomes important to know how market dynamics shape the energy demand, and thus the energy consumption in these countries. To answer this question, this paper employs secondary data from 2007-2021. The empirical analysis builds on unbalanced panel data and studies the main statistically significant determinants steering energy consumption across Balkan region, by examining the case of Albania, Serbia, Bulgaria, Republic of North Macedonia, and Bosnia & Herzegovina through a Fixed Effects model. A wide pool of variables related to innovation, political climate, economy, and finance were chosen to explain the energy consumption in the region. Using a general-to-specific approach, we were able to obtain a model with three regressors, all of them critical in capturing the variability in energy consumption. The results showed that in developing countries the main drivers of energy consumption are HDI, FDI and Innovation Index. This research provides an up-to-date picture on the dynamics of the energy markets in the region by providing a comprehensive analysis, which accounts for a variety of factors and adequate methodology. It is especially useful for policy makers to have a forward-looking approach and embed the results of such a study in their projections, analysis, and future decisions. [ABSTRACT FROM AUTHOR]

The structural analysis of an old steel riveted railway truss bridge located over the Maruska River on the Działdowo - Olsztyn, Poland railway line is performed in this paper to check its behaviour under today's railway loads. The mechanical properties of construction steel extracted from the old steel bridge are investigated by tensile tests, impact tests through the Charpy pendulum impact V-notch, and an optical emission spectrometer. Structural analysis exhibits that the steel bridge requires proper structural bridge improvements to meet today's load requirements in terms of bearing capacity and serviceability state. The paper begins with a wide survey of literature carried out on the investigation of steel riveted railway bridge subject matter. This paper can provide scientists, engineers, and designers with an experimental and structural basis in the field of old steel riveted railway truss bridge construction. [ABSTRACT FROM AUTHOR]

The rapid development of modern science, technology, and industrialization has promoted the birth of more large and complex engineering structures. When the finite element (FE) method is used for dynamic analysis of these structures, such as high-rise buildings, aircraft, and ships, the structural FE models often contain millions of degrees of freedom. This will lead to great hardware and computing costs, which is often unacceptable in the engineering field. Therefore, many FE model reduction technologies have been developed, among which dynamic condensation and component mode synthesis are the most widely used methods. This paper reviews the historical processes and general theoretical framework of these two main categories of FE model reduction technologies and briefly summarizes the latest applications of these methods in the engineering field. Current bottlenecks in dynamic condensation and component mode synthesis methods, as well as solutions found in literature, are also briefly discussed. Finally, this paper gives a conclusion and brief prospects for future research. This review aims to comprehensively introduce the two most widely used methods of FE model reduction technologies and hopes to provide suggestions and guidance for developing new model reduction technologies. [ABSTRACT FROM AUTHOR]

To analyze the effects of maxillary tooth distalization by clear aligner (CA) treatment with variations in the angular direction of the distalization force, presence of attachments, and force-application method used. A finite element model containing alveolar bone, dentition, and periodontal ligament was constructed. Analytical model groups were as follows: (1) distalization with buttons (without attachments), (2) buttons on canines (with attachments), (3) precision cuts on the canines (without attachments), and (4) precision cuts on the canines (with attachments). A distalization force of 1.5 N was applied to the button or precision cut at −30°, −20°, −10°, 0°, 10°, 20°, and 30° to the occlusal plane. As the direction of force approached +30°, the dentition inclined posteriorly. The posterior movement pattern was significantly influenced by the presence of an attachment and the direction of force, rather than the area where the force was applied. Distal inclination was dramatically reduced with attachments. A disengagement or deformation of the CA may reduce the distalization efficiency of the dentition or move the dentition in an inappropriate direction. Attachments for efficient distalization by the CA are necessary. The use of miniscrews in the direction of force parallel to the occlusal plane is more advantageous than the use of Class II elastics. Due to CA deformation, distalization with the button on the canines can be more effective for distal movement of the maxillary dentition. [ABSTRACT FROM AUTHOR]

The mechanical behavior of a magnesium alloy E-form under bending was investigated using the elasto-visco-plastic polycrystal model (ΔEVPSC) and its finite element (FE) implementation (ΔEVPSC-FE) developed in Jeong et al. and Jeong and Tomé. The crystallographic orientation distribution (COD) obtained from X-ray diffraction was used to represent the initial texture, and the Voce hardening parameters were calibrated by fitting the uniaxial tension and the compression flow stress curves. A quasi-static FE analysis of a miniaturized V-bending operation was conducted using the ΔEVPSC-FE model. The bending induced an inhomogeneous stress response along the through-thickness and the lateral directions, which was well captured by the model. Moreover, the predictive capability of the model was validated by comparing with various experimental results such as (1) force vs. displacement curves; (2) the through-thickness variations in the twin volume fraction; and (3) the changes in crystallographic texture as a function of displacement. Additional bending simulation was performed using an isotropic texture, the result of which suggests that the potential improvement in bendability of the magnesium alloy is attainable by weakening the initial texture. Moreover, the simulation results imply that the crystallographic texture, which may affect the twin activation across the thickness direction, plays a significant role in the shifting direction of the neutral layer. [ABSTRACT FROM AUTHOR]

In aerospace industry, turbine engine blades made of nickel-based superalloys are commonly machined by creep-feed grinding processes. In order to pre-design grinding processes and avoid grinding burn, a method for calibrating a thermal finite element model was developed. For this purpose, the heat flux distribution and heat partition were evaluated by solving an optimization problem with the BOBYQA algorithm. A heat flux distribution differing from the frequently used triangular distribution was found and, further, a regression model estimating the heat partition was calibrated. The findings were compared to the experimental results, which showed a good agreement of the transient temperatures and maximum temperature rise. Subsequently, the findings were transferred to the grinding process of a fir tree profile. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid Smoothed Particle Hydrodynamics (SPH) – Finite Element Method (FEM) solver for metal cutting simulations on Graphics Processing Units (GPU). For the first time in chip formation simulation, the heat transfer between an SPH model of the workpiece, and a transient FEM temperature model for the cutting tool, is established. For validation, the performance of the modeled thermal contact between two numerical domains is compared with a commercial FEM software. The sensitivity of the implemented SPH-FEM contact parameters is investigated for the first time and further insights into the thermal modeling of cutting simulations are generated. Overall, the newly developed hybrid model saves the computational time on the cutting tool side in the pure SPH method and enables more efficient high-fidelity cutting simulations. By clearly defining the thermal contact at the tool-chip interface, the simulated tool surface temperature agrees well with the experimental measurements in the literature. [ABSTRACT FROM AUTHOR]

The current study has investigated the influence of a non-uniform magnetic field on heat transfer and entropy generation through the convection flow of ferrofluid filled inside the cavity in the presence of thermal radiation. Consider that magnetohydrodynamics is the result of the applied magnetic field, induced by the Lorentz force, while ferrohydrodynamics is the effect of the Kelvin force, which is associated with the applied magnetic field that affects the magnetized liquid. The highly coupled non-linear governing system of partial differential equations are transformed into the set of non-linear algebraic equations by utilizing the Galerkin finite element method, and the Newton-Raphson method has been used to solve them. Results show that the fluid velocity and entropy generation are decreased via increasing Magnetic number. Intensity of streamlines decreases from 12.407 to 1.004 by increasing Hartmann number from 0 to 5. Velocity and temperature profiles increases 31.25 % and 48 % respectively, by increases concentration of ferroparticles up to 0.05 %. The applications of this problem can be found in various heat transfer phenomena through fluid flow and their optimizations, such as in cooling processes of devices, advanced oxidation processes for dye removal from textile wastewater, solar collectors, chemical reactors, and heat exchangers. [ABSTRACT FROM AUTHOR]

A significant portion of the wheel assembly's safety is determined by the performance of the spindle and hub. In conventional designs, weight-to-strength ratio, connection configuration, etc., have barely been optimized. The purpose of this paper is to apply an optimization process through the design of experiments (DoE) concept to hub and spindle designs. To achieve better efficiency, lighter materials are targeted for use in a 3-wheel solar-powered vehicle. Using FEM analysis, both designs were statically analysed. Using Taguchi method, experiments were designed for both maximum safety and minimum weight, subjected to geometrical boundary constraints with regard to maximum safety and minimum weight. Each part was evaluated based on its impact on performance and safety. Both spindle and hub have been optimized to provide a reliable factor of safety and light weight. [ABSTRACT FROM AUTHOR]

This paper describes research on the effect of structural form on hydration-heat-related changes in large-scale precast concrete lining segments. These segments of mass concrete were used in the construction of an underground metro transit station in Changchun, China, a location where conventional cast-in-place construction is interrupted for months by cold winter weather. Heat of hydration analysis of closed-cavity and solid lining segments was conducted using the finite element method (FEM). Two ambient temperatures of 25°C and 10°C (77°F and 50°F) were selected to simulate segment manufacturing conditions in summer and winter, respectively. The FEM and selected parameters were found to be reasonable because the numerical predictions and experimental observations from the closed-cavity segment were consistent. At both of the ambient temperatures, the maximum internal concrete temperature of the closed-cavity segment was much lower than that in the solid one and the temperature distribution in the closed-cavity segment was more uniform. As a result, thermal stress was lower in the closed-cavity segment than in the solid segment, which reduced the risk for cracking. The closed-cavity form of the lining segments enhanced the structural integrity and durability, and the ability to prefabricate these segments in cold ambient temperatures effectively accelerated construction on this project. [ABSTRACT FROM AUTHOR]

The current study proposes an eficient numerical method to evaluate the effects of the variable heat ux, viscous dissipation, and slip velocity on the viscous Casson Heat Transfer (CHT), considering the unsteady stretching sheet that took into account the effect of heat generation or absorption. In this respect, Finite Element Method (FEM) was employed to solve the resulting ODEs that described the problem. The effects of the factors governing the HT such as unsteadiness parameter, slip velocity parameter, Casson parameter, local Eckert number, heat generation parameter, and Prandtl number were studied. In addition, the local skin friction coeficient and local Nusselt number on the stretching sheet were also computed. Finally, the obtained solutions confirmed that the proposed procedure could be an easy and eficient tool for finding a solution to such uid models. [ABSTRACT FROM AUTHOR]

Present work focuses on analysis of the stress and strain fields inside and around the individual {10–12} twin in magnesium alloy. The 3D crystal plasticity model represents twin as an ellipsoidal inclusion surrounded by the matrix. Five different twin thicknesses and three different lateral twin lengths are used for stress/strain analysis. The simulations are complemented with experimental observations using high-resolution electron backscattered diffraction. The simulations and experiments show a similar distribution of the shear stress and the spatial activity of individual slip systems (basal, prismatic, pyramidal). Plasticity induced inside the twin is dominantly caused by the prismatic dislocations slip and does not influence twin back stress which is identical to pure elastic twin. The twin with larger lateral dimension requires lower equilibrium stress which suggests anisotropic twin propagation and increased thickness of such twins. The lateral twin propagation is mostly influenced by prismatic and pyramidal slip in the twin vicinity. The twin thickness can reach a maximal level that is driven by the critical resolved shear stress values for dislocation slip with the significant influence of basal slip. [ABSTRACT FROM AUTHOR]

This paper presents a new coupled approach to incorporate the effect of vertical load on lateral response of pile in clay, by considering both the lateral and vertical strain of the soil-pile system. Experimental and numerical studies on pile subjected to combined loading carried out by different researchers showed that coupling behaviour cannot be modelled using Beams on Winkler foundation or subgrade reaction approach and use of continuum modelling is essential. However, in this present study an is made to develop a method using FEM by utilizing both the lateral and vertical strain of soil-pile system. The proposed coupled method is capable of simulating the influence of vertical load on lateral response of pile in clayey deposit much more realistically compared to uncoupled method. However, this coupling effect is more prominent for pile subjected to a vertical load equal to ultimate pile capacity (Vu), compared to pile under a load equal to allowable pile capacity (Vall). [ABSTRACT FROM AUTHOR]

In recent years, the use of composite materials in the nautical sector has grown significantly due to the demand for lightweight products with high mechanical properties. In particular, Carbon Fiber Reinforced Polymers (CFRP) represent a valuable choice in sports equipment and structural applications. In this context, the present study focuses on a simplified model for structural analysis of hydrofoil and moth masts realized with composite laminates. A Finite Element Simulation software was employed to investigate the flexural strength of different laminations and reinforcement configurations for cantilever beams subjected to a transversal force. In this way, it was possible to determine which solution guarantees the best mechanical properties with the minimum weight. This study provides a useful tool for the design of mast-like structure and for the optimization of the stacking sequence of CFRP laminates. [ABSTRACT FROM AUTHOR]

For an optimized design of gear soft machining processes, detailed knowledge of the thermomechanical tool load is essential, which is often obtained by finite element method (FEM). For this purpose, validated material models are required. In this paper, the Johnson-Cook material model was calibrated for a 20MnCr5 soft state case-hardening steel based on linear-orthogonal machining experiments. The calibrated model was validated by comparing 3D FE simulations of a gear machining process to respective trials. It could be shown that the simulated machining forces as well as the simulated chip geometries are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

The X30CrMoN-15-1 steel is one of the most important steels in the rolling bearing production, which generates considerable interest with regard to machining. In this work, the orthogonal cutting of X30CrMoN-15-1 steel with CBN tools was studied. The thermomechanical loads in the cutting zone were experimentally investigated with different cutting parameters. Based on the empirical results, two numerical simulation models, friction and material models were developed, inverse calibrated and verified by comparing cutting forces and workpiece temperature. The simulation results revealed a good agreement with the experimental results and provided a theoretical basis for predicting the workpiece quality. [ABSTRACT FROM AUTHOR]

In response to growing environmental concerns regarding the presence of per- and polyfluoroalkyl substances (PFAS) in landfills, this study explores PFAS permeation through pinhole defects of high-density polyethylene (HDPE) geomembranes (GMs) experimentally. Specifically, this study aims to: (i) investigate the adsorption of PFAS onto HDPE GMs, (ii) evaluate the effectiveness of GMs experimentally in retaining PFAS-laden leachate in the event of a puncture failure, (iii) assess the critical conditions leading to puncture failure of GM using mechanical characterization testing with complementary finite element method (FEM) analyses with the input data from mechanical characterization. Our findings show limited intermolecular attractive interactions between PFAS and GMs, and surfactant properties of PFAS contribute to higher leachate permeation through pinholes. In general, highly fluorinated, short chain PFAS exhibit increased permeation rates, which was attributed to their size and greater propensity to align at the water-air interface. This study underlines the environmental implications of PFAS-laden leachates especially when there are no proper liner systems or leachate collection systems in place underscoring the necessity for modern landfill design and management practices to mitigate environmental risks associated with PFAS. [Display omitted] • PFAS increase the permeation rate due to their surfactant properties. • Intact geomembranes can contain PFAS-laden leachate in landfills for over 30 years. • The diameter of sharp objects is the most sensitive parameter for punctures. • Changes in pH, temperature, and ionic strength in landfills impact PFAS permeation. [ABSTRACT FROM AUTHOR]

• Introduced a unique wavy lid-driven cavity with an embedded cylinder and non-uniformly heated wall for studying hybrid nanofluid flow. • Found that an inclined magnetic field at γ = 60 ° optimizes heat transfer, while the Hartmann number (Ha) reduces flow strength. • Number of wall undulations and cylinder radius strongly affect flow patterns and entropy generation, with N = 4 best performance. • Heat transfer enhancement with a 5.4 times increase in the average Nusselt number at high Reynolds and Grashof numbers. • Findings aid in optimizing heat transfer and entropy in hybrid nanofluids, relevant to solar energy, microelectronics, and medical devices. This study investigates entropy generation, mixed convection, and magnetohydrodynamic (MHD) effects in hybrid nanofluid flow within a wavy lid-driven cavity with non-uniform heated wall. This research addresses a significant problem in heat transfer system efficiency which is essential for uses such as solar energy collection, medical devices, and microelectronics cooling. The nondimensional governing equations are solved using the Finite Element Method (FEM) for various key parameters including Hartmann number (Ha), Grashof number (Gr), Reynolds number (R e), volume fraction (ϕ), number of undulations (N), wave amplitude (A), radius of cylinder (r) and inclined magnetic field (γ). Findings show that the enhancement of Grashof number , inclined angle, volume fraction and Reynolds number depict increasing flow magnitude but the number of undulations, radius of cylinder and Hartmann number cause a decay in flow strength. Increasing R e and Gr enhances heat transfer, with an average Nusselt number increase of 5.4 times when R e = 300 and Gr = 10 6 compared to R e = 10 and Gr = 10 3. Entropy generation is significantly influenced by N with the highest total entropy observed at N = 4. In contrast to previous studies, the novelty of this investigation lies in the unique geometric configuration featuring a wavy lid-driven cavity with an embedded cylinder and non-uniformly heated walls. This study of hybrid nanofluids and an angled magnetic field provides new paths for improving heat transfer and decreasing entropy generation. This study enhances previous literature by providing comprehensive quantitative insights into how they interact between those parameters opening the way for more efficient heat management in modern technological systems. [ABSTRACT FROM AUTHOR]

• The costs associated ANN with CFD simulations. • Heat transfer under periodic conditions is analyzed. • These results from training, validation, and testing data against a visual representation of the problem. • The histograms demonstrate that the actual error levels are quite minimal. Predicting precise results for the quantities of interest in time-dependent Computational Fluid Dynamics (CFD) simulations requires a significant investment of computational resources and time. To get around these issues, CFD simulations have been joined with Artificial Neural Networks (ANN). An optimally configured artificial neural network (ANN) is given the training and validation data sets produced by computational fluid dynamics (CFD). The flow around a cylinder, which is a well-known benchmark problem for incompressible flows, has been taken into consideration by the hybrid-CFD system. The mathematical model is based on the non-stationary Navier-Stokes and energy equations with viscosity. The basic architecture of the ANN model consists of 10 hidden layers, three output levels, and five input layers. Fast second-order LMA, a top-tier approach, was used to train the network. Both the Mean Square Error (MSE) and the coefficient of determination (R) provide statistical evidence that the ANN projected values for the drag and lift coefficients and average Nusselt number obtained from the finite element analysis are accurate. This analysis suggests that ANNs have the potential to significantly cut down on the amount of time and energy needed to run time-dependent simulations. [ABSTRACT FROM AUTHOR]

Currently, cutting-edge Additive Manufacturing techniques, such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM), offer manufacturers a valuable avenue, especially in biomedical devices. These techniques produce intricate porous structures that draw inspiration from nature, boast biocompatibility, and effectively counter the adverse issues tied to solid implants, including stress shielding, cortical hypertrophy, and micromotions. Within the domain of such porous structures, Triply Periodic Minimal Surface (TPMS) configurations, specifically the Gyroid, Diamond, and Primitive designs, exhibit exceptional performance due to their bioinspired forms and remarkable mechanical and fatigue properties, outshining other porous counterparts. Consequently, they emerge as strong contenders for biomedical implants. However, assessing the mechanical properties and manufacturability of TPMS structures within the appropriate ranges of pore size, unit cell size, and porosity tailored for biomedical applications remains paramount. This study aims to scrutinize the mechanical behavior of Gyroid, Diamond, and Primitive structures in solid and sheet network iterations within the morphological parameter ranges suitable for tasks like cell seeding, vascularization, and osseointegration. A comparison with the mechanical characteristics of host bones is also undertaken. The methodology revolves around Finite Element Method (FEM) analysis. The six structures are originally modeled with unit cell sizes of 1, 1.5, 2, and 2.5 mm, and porosity levels ranging from 50% to 85%. Subsequently, mechanical properties, such as elasticity modulus and yield strength, are quantified through numerical analysis. The results underscore that implementing TPMS designs enables unit cell sizes between 1 and 2.5 mm, facilitating pore sizes within the suitable range of approximately 300–1500 μm for biomedical implants. Elasticity modulus spans from 1.5 to 33.8 GPa, while yield strength ranges around 20–304.5 MPa across the 50%–85% porosity spectrum. Generally, altering the unit cell size exhibits minimal impact on mechanical properties within the range above; however, it's noteworthy that smaller porosities correspond to heightened defects in additively manufactured structures. Thus, for an acceptable pore size range of 500–1000 μm and a minimum wall thickness of 150 μm, a prudent choice would involve adopting a 2.5 mm unit cell size. [Display omitted] • Conducted a comprehensive study on porous structures for biomedical application. • Numerically, unit size changes from 1 to 2.5 mm do not affect the mechanical properties. • Gyroid and Diamond sheets with 2.5 mm units and 50–85% porosity meet biological needs. • Solid network designs with different unit sizes and porosity meet manufacturing needs. • Gyroid and Diamond sheets are the best morphologies for biomedical applications. [ABSTRACT FROM AUTHOR]

In this study, convective heat transfer and phase change process are analyzed for an L-shaped vented cavity equipped with an inner rotating cylinder and phase change material-packed bed (PCM-PB) system under magnetic field during hybrid nanofluid convection. The numerical work is performed for different values of Reynolds number (Re between 200–1000), rotational Reynolds number (Rew between −1000–1000), size of the cylinder (R between 0.05H-0.15H) and Hartmann number (Ha between 0–40) while hybrid Ag/MgO nanoparticle loading amount in water is 2 %. It is observed that the vortex size and their distributions in the cavity and within the PCM-PB system can be controlled by varying rotating cylinder size and rotational speed along with the magnetic field. With higher cylinder size, phase change becomes fast while complete phase transition time (tP) is reduced by about 22 % and average Nusselt number (Nu) rises by about 86 % at Rew = −1000. Rotational direction of the cylinder is effective for phase transition dynamics while at Rew = −1000, tP rises up to 27 % when compared to non-rotating cylinder case. Magnetic field strength is a good parameter for vortex suppression. At the highest strength, phase change becomes fast and average Nu rises up to 26.5 % at Rew = −1000. ANFIS based modeling approach is used for impacts of rotating cylinder on the phase change dynamics in the L-shaped vented cavity. [ABSTRACT FROM AUTHOR]

Today, simulation of cutting processes still relies, in most cases, on the phenomenological representation of flow stress properties of workpiece materials. This investigation presents a physics-based (dislocation-based) constitutive model to simulate the flow stress properties of Ti6Al4V titanium alloy at elevated temperatures and a large range of strain rates. The Split Hopkinson Pressure Bar (SHPB) data and inverse modelling of orthogonal cutting tests are combined using a novel approach to obtain flow stress properties and to calibrate the damage and friction models. The applicability of the presented model for cutting simulation is critically discussed. [ABSTRACT FROM AUTHOR]

The prediction of the tool wear progression using numerical methods has been widely studied in recent years, and various wear models considering different wear mechanisms have been implemented in the simulation work. Typically, these wear models take the physical fields such as contact pressure, sliding velocity and temperature at the tool-workpiece interface into account and are applied either individually or in combinations into the wear simulation. However, how and to what extent the physical parameters in these models affect the generated wear profiles have not been explored in detail in the simulation. In this paper, the behaviors of several typical wear models are studied by simulating the tool wear of cutting Ti6Al4V using a hybrid SPH-FEM method. Considering different combinations of physical contact parameters in the wear model, the simulated wear progression is discussed, and the resulting worn tool geometry is qualitatively compared to the experimental result. Furthermore, insights into the calibration of wear models are proposed. [ABSTRACT FROM AUTHOR]

Bi-metallic design concept has been introduced in automotive industries to meet the increasingly tighter standards on carbon emission. Yet, machining of bi-metallic engine blocks is accompanied by several challenges like short tool life and long cycle times. This study presents a novel methodology that combines the concept of experimental design with Finite Element (FE) to optimise the tool performance and enhance the productivity when finish face milling of aluminium-grey cast iron engine blocks. This simulation-assisted approach led to an approximately 32% decrease in machining cycle time as compared to that of a reference cutting condition. [ABSTRACT FROM AUTHOR]

Severe plastic deformation is not desired in machining as it adversely affects surface integrity. In this study, the performance of finite element formulations on subsurface plastic deformation is studied. Finite element models of orthogonal milling of Ti6Al4V have been developed using Update Lagrangian with element deletion as well as continuous remeshing algorithms. The models are validated not only by the measured cutting forces, but quantitative measurements of the subsurface plastic deformation. The results showed that continuous remeshing strategy generate smooth milling forces and predicted the plastic deformation of the machined subsurface with higher accuracy compared to the element deletion method. [ABSTRACT FROM AUTHOR]

The development of an optimized discontinuous drilling process of Inconel 718 with reduced thermal loads is supported by a CFD simulation, whose application already resulted in improvements of coolant flow. To consider the heat flow from the chip formation into the tool and the fluid, the numerical model must be expanded by a FEM chip formation simulation. Thus, its modulation and results validated by experimental work on thermal and mechanical loads are presented and discussed. In the following, the export of an optimized number of process interruptions will be enabled in favor of heat-related tool wear due to temperature monitoring. [ABSTRACT FROM AUTHOR]

The current state-of-the-art for the simulation of machining process is the application of the FEM (finite element method). Nevertheless, the cost of FEM analyses for such problems is high due to their complex multi-physics nature, mesh regeneration issues, and small time-length scales. In contrast, particle methods are an alternative numerical approach well-suited for large deformations as in material's chip formation. In this work, the key features and simulation capabilities of iMFREE are presented, which is a massively parallel and robust particle-based code for machining simulations developed at the ETH Zürich. Various applications of iMFREE are shown, where the efficiency is demonstrated in orthogonal cutting simulations for the optimisation of material removal rates, a chip formation study, the inverse identifications of friction law parameters and material constitutive law parameters. Further, the applicability to single and multiple grain grinding simulations of Ti6Al4V and silicon is shown. [ABSTRACT FROM AUTHOR]

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The current numerical investigation focuses on the power-law nanofluids behaviors in slant wavy enclosures in the presence of thermal radiation. The entropy of the system together with the flow and thermal features are examined for several patterns of the side wavy walls, namely, Out-Out, In-In and In-out. The components of the suspension are multi-wall carbon nanotubes and ethylene glycol. The magnetic field is considered in the current study to be inclined and its components are expressed in terms of the enclosure inclination angle. The solution scheme is based on the Characteristic-Based Split (CBS) scheme and the resulting system is discretized using the finite element method (FEM). It is noted that the flow structures, temperature, and entropy features have strong responses for changing the patterns of the side walls. Also, for the non-inclined domain, an augmentation in the non-Newtonian fluid flow up to 44.2% is given as the radiation coefficient is altered from 0 to 5. [ABSTRACT FROM AUTHOR]

Hindrance to weld metal shrinkage by the adjacent base material introduces inevitable residual stress and distortion in welded components. Nevertheless, proper choice of welding process can reduce the magnitude of tensile residual stress and distortion. Here hybrid laser MIG and Hotwire-TIG welding processes are used, which provides sound 316L(N) stainless-steel weld joint at reduced heat input. The numerical modeling and experimental result shows that tensile residual stress distribution is substantially narrower in hybrid laser MIG than in Hotwire-TIG weld joint. Furthermore, the degree of external restraint significantly influences the magnitude of residual stress distribution and distortion. The numerical and experimental results exhibited reasonable agreement. [Display omitted] • 11 mm thick Type 316L(N) weld joints were fabricated using HLM and HW-TIG welding techniques. • The IHM and MHM accurately predicted residual stress and distortion in HLM and HW-TIG weld joints. • Residual stress distribution was narrower in HLM (∼22 mm) than HW-TIG weld joint (∼46 mm). [ABSTRACT FROM AUTHOR]

The present study investigates the efficiency of using sand crumb rubber mixture for vibration isolation and its prediction using machine learning. Safe disposal of waste rubber from tire industries is a matter of concern due to its detrimental effects. A two-dimensional finite element (FE) analysis was performed in ABAQUS, considering a strip foundation as the source of vibration. The effectiveness of the screening was evaluated by calculating the Amplitude Reduction Factor (Arf) for open and infilled trench (OT and IFT) for different trench geometry (distance from the source, depth and width). In previous studies, modelling such screening problems has mostly been accomplished through regression models. The present study explored the Support Vector Regression (SVR) model since machine learning excels in modelling complex behaviours. The SVR model's optimum parameters were successfully determined by performing a grid search and selecting the best model using the Preferential Ranking Organization Method for Enrichment Evaluation (PROMETHEE) technique. [ABSTRACT FROM AUTHOR]

Copyright of Industria Textila is the property of Institutul National de Cercetare-Dezvoltare pentru Textile si Pielarie and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)