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We have obtained the interfacial properties of short rigid-linear chains formed from tangentially bonded Lennard-Jones monomeric units from direct simulation of the vapour-liquid interface. The full long-range tails of the potential are accounted for by means of an improved version of the inhomogeneous long-range corrections of Janecˇek [J. Phys. Chem. B 110, 6264-6269 (2006)] proposed recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] valid for spherical as well as for rigid and flexible molecular systems. Three different model systems comprising of 3, 4, and 5 monomers per molecule are considered. The simulations are performed in the canonical ensemble, and the vapor-liquid interfacial tension is evaluated using the test-area method. In addition to the surface tension, we also obtain density profiles, coexistence densities, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the chain length and rigidity on these properties. According to our results, the main effect of increasing the chain length (at fixed temperature) is to sharpen the vapor-liquid interface and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases and the surface tension increases as the molecular chains get longer. The surface tension has been scaled by critical properties and represented as a function of the difference between coexistence densities relative to the critical density. [ABSTRACT FROM AUTHOR]

Density functional molecular dynamics simulations have been performed in the NVT ensemble (moles (N), volume (V) and temperature (T)) on a system formed by ten acetone molecules at a temperature of 2000 K and density ρ = 1.322 g cm-3. These conditions resemble closely those realized at the interface of an acetone vapor bubble in the early stages of supercompression experiments and result in an average pressure of 5 GPa. Two relevant reactive events occur during the simulation: the condensation of two acetone molecules to give hexane-2,5-dione and dihydrogen and the isomerization to the enolic propen-2-ol form. The mechanisms of these events are discussed in detail. [ABSTRACT FROM AUTHOR]

We report the simulation of current–voltage (I–V) and capacitance–voltage (C–V) characteristics of Au/n-InP Schottky contact in the temperature range of 200–400 K by steps of 20 K with and without interface states, traps and tunnelling current. The simulation was carried out using Atlas-Silvaco-Tcad device simulator. The simulation is performed using the appropriate physical models to explain the behaviour of the physical phenomena of the Schottky diode. The simulation results ofI–V–TandC–V–Twithout native oxide, tunnelling current and traps are far away from experimental data. Thus, native oxide, tunnelling current and traps should be considered. Our results strongly suggest that the spatial inhomogeneities at the MS interface did not affect theI–VandC–Vcharacteristics in the simulated temperature range. In addition, the extracted parameters, zero-bias barrier height, capacitance barrier heightand the ideality factorwere found to be strongly temperature-dependent due to the deviation of the transport mechanism from thermionic emission current. Moreover, the obtained results lead to a coherent explanation of the discrepancy betweenand. Good agreement of simulatedI–V–TandC–V–Tresults with existing experimental data are obtained by considering a thin native oxide layer at the interface, traps and tunnelling current. [ABSTRACT FROM PUBLISHER]

Hot stamping tools with cooling systems are key facilities for hot stamping processes in the automotive industry. In hot stamping, the tools are heated by workpieces and rapidly cooled by cooling water. The thermal deformation of the tools has a significant influence on the properties of the hot stamped parts and the useful life of the tools. In this paper, a multi-field simulation method is proposed for analysis of deformation in the tools. Based on a mesh based parallel code coupling interface, a thermal-fluid-mechanical coupled model is established to analyse the cooling effect and the deformation of the tools. The experimental set-up was built to verify the multi-field coupling model. It is shown that the cooling rate of the hot stamped part was 217°C s−1, higher than the critical cooling rate of 30°C s−1. The temperature history of the hot formed part was in good agreement with the experimental result. The cooling ducts were deformed because of the thermal expansion of the hot tools. This led to stress concentration at the rectangular corner of the ducts. The speed of cooling water flow increased by 112% through the bottom ducts, while at the corners of the ducts, the speed was very low and a 'hot spot' appeared. [ABSTRACT FROM AUTHOR]

Abstract: The interface thickness is the most crucial parameter in the phase field model (PFM) for the accuracy and the computability. However, the Gibbs–Thomson equation can be satisfied only when the interface thickness is sufficiently small, especially with a large undercooling, but this greatly limits the applications of PFM to a realistic problem. The temperature correction in the thin-interface model partially resolves the problem, but the range is rather limited. In this report, we propose a new formulation of PFM by adding extra terms stabilizing the hyperbolic tangent profile of the phase-field, and this allows us to use a much larger interface thickness for simulation, even with a large undercooling. Several benchmark comparisons with analytical solutions are carried out and discussed. [Copyright &y& Elsevier]

Abstract: The present study concerns the feedback stabilisation of the unstable equilibria of a two-dimensional nonlinear pool-boiling system with essentially heterogeneous temperature distributions in the fluid–heater interface. Regulation of such equilibria has great potential for application in, for instance, micro-electronics cooling. Here, as a first step, stabilisation of these equilibria is considered. To this end, a control law is designed that regulates the heat supply to the heater as a function of the Fourier–Chebyshev modes of its internal temperature distribution. These modes are intimately related to the physical eigenmodes of the system and thus admit robust and efficient regulation on the basis of the natural composition of the temperature field. Key to this modal-control strategy and its application for controller design are an interchangeable PDE form and state-space form of the linearised model. Derivation of these forms is a central theme of this study. Performance of modal controllers thus designed is demonstrated and analysed by simulations of the nonlinear closed-loop system. [Copyright &y& Elsevier]

It is shown that initially sharp interface in AB diffusion couple, above the ordering temperature, can shift with anomalous kinetics, i.e. deviations from the parabolic growth kinetics are possible. The initial slopes of the shift versus time functions can be even unity for large diffusion asymmetry (the ratio of diffusion coefficients of the parent materials in orders of magnitude) and gradually decrease to 0.5 at larger distances (longer times). This is in accordance with earlier results obtained in phase separating systems. It is shown that from the results of simulations the crossover thickness, X*, between the linear and parabolic regimes can also be calculated, and the applicability of the linear–parabolic law is confirmed. Furthermore, it is illustrated that the crossover thickness depends exponentially on the diffusion asymmetry parameter, with the exponent close to the value obtained from analytical estimations. [ABSTRACT FROM AUTHOR]

Abstract: The influence of the ambient temperature on the stress, deformation and temperature of a dump truck tire has been predicted with the virtual tire model established in this work by employing the finite element method (FEM) and Algor software. The nonlinear stress–strain relationship of tire rubber material has been given by Mooney–Rivlin material model. The hysteresis and loss strain energy density have been related to give the heat generation rate. A two-dimensional (2D) FE model of rolling radial tire has been built in Algor environment according to the actual construction of bridgestone 24.00R35 tire adopted for Caterpillar Earth Mover 775E Model. The model consists of the tread, belt, carcass, air filled volume and tire–rim interface. The material properties of the components and boundary conditions from tire–rim contact and tire–road contact are considered. The mechanical event simulation (MES) with nonlinear material model and the steady-state heat transfer analysis have been performed. The analysis results of the tire stress, deformation and temperature are presented under the ambient temperatures ranging from −40 to 40°C conditions at the Syncrude mine in Canada. The results show that the effect of the ambient temperature on the tire deformation is larger than on the tire stress. The increase of ambient temperature will cause the tire temperature rise. This study provides a comprehensive modeling and analysis that provide key to avoid tire temperature related failure. [Copyright &y& Elsevier]

Abstract: Considering the mismatch of coefficient of thermal expansion (CTE) of Cu and W phase and temperature gradient, internal and external thermal load are applied on meso-scale 2D representative volume element (RVE) of CuW alloys under thermal shock, respectively. Void volume fraction (VVF) and VVF induced crack are determined by finite element method (FEM) utilizing Gurson–Tvergaard–Needleman (GTN) model, and the driving forces for damage nucleation and growth are analyzed with normal and shear stress as well. The simulation results show that damage and damage induced crack initiate from the vertex of W grain and grow along W/Cu interface, then propagate into Cu phase. After thermal shock experiment on CuW specimen by high voltage arc, micro cracks present along W/Cu interfaces and inside Cu phase, which is in good agreement with simulation results. [Copyright &y& Elsevier]

Abstract: We recently performed constant energy molecular dynamics simulations of the endothermic decomposition of methane hydrate in contact with water to study phenomenologically the role of mass and heat transfer in the decomposition rate [S. Alavi, J.A. Ripmeester, J. Chem. Phys. 132 (2010) 144703]. We observed that with the progress of the decomposition front temperature gradients are established between the remaining solid hydrate and the solution phases. In this work, we provide further quantitative macroscopic and molecular level analysis of the methane hydrate decomposition process with an emphasis on elucidating microscopic details and how they affect the predicted rate of methane hydrate decomposition in natural methane hydrate reservoirs. A quantitative criterion is used to characterize the decomposition of the hydrate phase at different times. Hydrate dissociation occurs in a stepwise fashion with rows of sI cages parallel to the interface decomposing simultaneously. The correlations between decomposition times of subsequent layers of the hydrate phase are discussed. [Copyright &y& Elsevier]

Abstract: A novel lubrication generator combing piezoelectric drop-on-demand (DOD) oil-jet technology is proposed for space mechanisms. A finite difference numerical model was established to analyze the design parameters of droplet ejection. The volume-of-fluid piecewise linear-interface construction (VOF-PLIC) interface-capturing method was adopted to represent the fluid domain and to track the evolution of its free boundaries whereas the continuous surface force (CSF) mode was chosen to model the interfacial physics. To explore the practicability of the proposed new lubrication generator, the flow behavior during the stages of fluid ejection and droplet formation are examined with Krytox 143AB lubricant as the baseline test fluid for a ejection cycle of 100μs. To improve the droplet ejecting performance of lubricant, the characters of inject flow part have been investigated with the variation of the pulse voltage for different spatial temperature. Injection process in the extra-low pressure is also investigated. The developed model helps to understand the drop formation process and this approach can be applied in various inject head designs. [Copyright &y& Elsevier]

Short-channel zinc oxide (ZnO) thin-film transistors (TFTs) are investigated in a wide range of temperatures and bias conditions. Scaling down the channel length, the TFT performance is seriously affected by contact resistances, which depend on gate voltage and temperature. To account for the contact resistances, the transistor is ideally split in three parts. The contact regions are modeled as two separate transistors with a fixed channel length and an exponential distribution of localized states, whereas the channel is treated as reported in Part I. The overall model reproduces the measured characteristics at different channel length, with a single set of physical and geometrical parameters. It can be readily implemented in a circuit simulator. Numerical simulations confirm the validity of the model approach and are used to evaluate the impact of nonidealities at the electrode/semiconductor interface. [ABSTRACT FROM PUBLISHER]

Abstract: We investigated structures derived from and ZSM-5-crystallites in different orientations and combinations. Gaps are introduced into the configurations in order to produce surfaces. However, interfaces can be formed by coalescence of surfaces. The structural and thermal properties of the thus generated interfaces and of the remaining surfaces are qualitatively discussed. Applying different sizes of the gaps between the structures allowed the monitoring of structural changes, partial pair-correlation functions and bond-angle distributions. Furthermore, we discuss the influence of the thermal or temperature distribution in the thus constructed materials. We report about the qualitative differences using both constant temperatures and temperature gradients. [Copyright &y& Elsevier]

Abstract: Vanadium oxide undergoes a sharp metal-insulator transition in the vicinity of room temperature and there is considerable interest in exploring novel device applications that utilize this phase transition. Using experimentally determined values of the thermal conductivity across the metal-insulator transition in VO2 thin films, we estimate the switching characteristics of two-terminal VO2 devices. The minimum switching time for both heating (“on” state) and cooling (“off” state) processes is explored using a simple resistance-capacitance thermal circuit model. The estimated minimum switching time is on the order of ∼1ns for 20nm VO2 films which is comparable to experimentally observed switching times. Optimal operating temperatures to maximize switching times are estimated. Methods to further enhance the switching kinetics by device thickness, carrier doping/strain, interfacial thermal resistance and input thermal energy are discussed. The simulations are compared with a 3-D model for VO2 devices on Si substrates utilizing COMSOL. The results are of potential relevance to the emerging field of correlated oxide electronics with fast phase transitions. [Copyright &y& Elsevier]

The current experimental methods are not able to reveal the actual processes of atomic movements during twinning and thus are incapable of clarifying the underlying mechanisms of annealing twinning, which are still not clear at present. We developed a method of molecular dynamics simulation to study the mechanism of annealing twinning in copper at an atomic-level. The simulation revealed that a annealing twin can be developed quickly from a pair of grains with Σ3 misorientation interfaced by a (5̅1̅1̅)/(1̅11) asymmetric boundary. The twinning proceeds by a mechanism in which every three adjacent (5̅1̅1̅) atomic layers merge into a (1̅1̅1̅) layer in the (5̅1̅1̅) side, while the atomic arrangement in the (1̅11) side remains unchanged. Such twinning takes place readily upon annealing at temperatures ranging from 700 to 1300 K, without requiring any extra driving force, indicating that annealing twinning in copper is indeed a thermally activated process with an activation energy estimated to be 0.1 eV. Similar annealing twinning is also observed in another two pairs of grains with Σ3 misorientation interfaced by (8̅22)/(022) and (2̅44)/(2̅00) asymmetric boundaries, respectively, yet their twinning rates are much slower than that of the (5̅1̅1̅)/(1̅11) grain pair, suggesting a different mechanism governing the process. The simulation also suggested that annealing twinning may involve two separate steps of which one is the formation of grain pairs with Σ3 misorientation and the other is the fine-tuning through which the grain pairs with Σ3 misorientation are converted into ideal annealing twins, which can grow larger with grain growth. [ABSTRACT FROM AUTHOR]

Abstract: A profound description of friction in wheel–rail contact plays an essential role for optimization of traction control strategies, as input quantity for railway simulations in general and for the estimation of wear and rolling contact fatigue. A multitude of wheel–rail contact models exists, however, traction–creepage curves obtained from measurements show quantitative and qualitative deviations. There are several phenomena which influence the traction–creepage characteristics: Mechanisms resulting from surface roughness, frictional heating or the presence of interfacial fluids can have a dominating influence on friction. In this paper, a new wheel–rail contact model, accounting for these influential parameters, will be presented. The presented model accounts for the interaction of an interfacial fluid model for combined boundary and mixed lubrication of rough surfaces with a wheel–rail contact model that additionally accounts for frictional heating. A quantitative comparison with measurements found in the literature is not conducted, since the exact conditions of the measurements are mostly unknown and parameters can easily be adjusted to fit the measurements. Emphasis is placed on the qualitative behavior of the model with respect to the measurements and good agreement is found. The dependence of the maximum traction coefficient on rolling velocity, surface roughness and normal load is studied under dry and water lubricated conditions. [Copyright &y& Elsevier]

Abstract: The detailed knowledge of the fine atomic structure of epitaxial interface is of fundamental importance for design and fabrication of electronic devices with exotic physical properties. Recently, it has been shown that accounting for diffusion energy barriers at specific sites on the epitaxial interface (atomic terraces, steps, kinks and imperfections), allows fine tuning of the adatom thermal energy which opens up a way for specific nanoscale surface design. Hence, through simple temperature variation, the surface migration of foreign atoms and clusters leads to formation of a variety of alloyed or pure terraces, alloyed islands and alloyed atomic stripes thus forming nanoscale surface patterns. A key role in this scenario plays the density of steps and kinks at the epitaxial interface. On that physical background, in the present paper we discuss the structure, stability and rupture of alloyed terraces as a first step towards the formation of alloyed two-dimensional islands on pure, non-alloyed substrate. The atomistic simulational model reveals a temperature-dependent critical terrace width for rupture and specifies criteria for thermodynamic stability. In the case of incomplete alloying we analyze the competition and overlapping of the elastic strain fields generated by opposite terrace edges. The specific atomic ordering in alloyed islands is also discussed. The simulation results frame the limits of incomplete surface-confined intermixing and point to a path to nanoscale surface design. [Copyright &y& Elsevier]

Abstract: Surface nucleation of poly(l/d-lactide) at the interface with aluminum was studied by performing isothermal DSC analysis of amorphous samples of varying thickness between 100 °C and 130 °C. To ensure complete wetting of the aluminum surface, a hot melt laminating process was used to prepare the samples. Theoretical aspects of surface crystallization kinetics were explored and the resulting model was compared with the results of Monte-Carlo simulations. Three stages of surface crystallization were identified depending on the growth geometry: (1) impingement-free growth, (2) increasingly laterally-constrained transverse growth, and (3) interstitial growth. By fitting the Monte-Carlo simulation to the experimental half-times of crystallization the surface nucleation concentration and the bulk nucleation rate was estimated at 4 different temperatures. It was found that both surface nucleation concentration and the bulk nucleation concentration decrease with increasing crystallization temperature. [Copyright &y& Elsevier]

The structural evolution of misfit dislocation networks at γ/γ' phase interfaces in Ni-based single crystal superalloys under tensile loading and temperatures is simulated by molecular dynamics. From the simulation, we find that, with increasing load or temperature, the patterns of dislocation networks on the (100), (110) and (111) phase interfaces change from regular to irregular or disappear. Under the same load and temperature, the dislocation networks of the different phase interfaces show different degrees and patterns of damage. The density and stability of the dislocation networks decrease with increasing temperature. When the interfacial dislocation networks become more regular, the γ/γ' interfaces become more stable. The simulated results are supported by related experimental findings. Moreover, based on MD simulations, the averaged stress-strain responses for different phase interfaces under loading are presented. The results indicate that the combined influences of temperature and load play an important role for the structure evolution of misfit dislocation networks at γ/γ' phase interfaces of Ni-based superalloys. [ABSTRACT FROM AUTHOR]

Abstract: We analyze the processes of thermal softening, melting and subsequent melt lubrication that occur during the high speed sliding of a metal piece on another metal block. The temperature rise in the slider arising from both high speed interface friction and from the energy dissipated during plastic deformations is computed using simple analysis and the finite element method. Subsequently, we propose a mathematical model for the transient lubrication problem that describes the behavior of the molten film at the slider–rail interface. This model successfully predicts the evolution process of the melt thickness and the melt front velocity of the liquid film; these predictions agree with the experimentally observed dynamics of molten film better than those from other existing models. [ABSTRACT FROM AUTHOR]

Abstract: Shrink fit is an important method used to connect mechanical parts but less studied by three-dimensional finite element method. Through a finite element method study, here we have simulated the crankshaft shrink fitting process by focusing on four main aspects: the optimization of heating method before shrink fit, the contact behavior on the interface in shrink fit process, and the structural distortion after shrink fit, as well as the evaluation of the bonding strength. Our results have demonstrated: (1) an extended bore with a satisfied radius can be obtained by imposing temperature gradient around the bore during the heating process. (2) In the beginning of the shrink fit, the journal tends to be absorbed into the shrink fit bore until the interfaces are fully contacted. The journal is then squeezed in radius and extended in axial as the heat transfer becomes stable through the interface. (3) The upper crankweb bends upward when heated, while downward after shrink fitted. The shrink fit distortion leads to the journal’ offset and rotation in an individual shrink fit process, and the stacking offset of each journal aggregates the distortion in an integrated crankshaft as compared with the expected shape in an ideal state. (4) The interfacial bonding strength reaches a relative constant in a time that much shorter than expected. The final distribution of the contact pressure on the interface is not uniform but the maximum transmitted torque evaluated by finite element method agrees with that obtained via the proposed analytical method. In terms of these simulated results, a series of practical measurements have been performed with an aim of efficiently enhancing the bonding strength and preventing the shrink fit distortion. [Copyright &y& Elsevier]

nonequilibrium molecular dynamics study of the cross-plane thermal conductivity and interfacial thermal resistance of nanoscale bilayered films is presented. The films under study are composed of argon and another material that is identical to argon except for its atomic mass. The results show that a large temperature jump occurs at the interface and that the interfacial thermal resistance plays an important role in heat conduction for the whole films. The cross-plane thermal conductivity is dependent on the average temperature. The interfacial thermal resistance is found to be dependent apparently on the atomic mass ratio of the two materials and the temperature, but to be independent of the film thickness. A linear relationship is observed between the reciprocal of the cross-plane thermal conductivity and that of the film thickness with the film thickness between 5.4 nm and 64.9 nm, which is in good agreement with results in the literature for a single film. [ABSTRACT FROM AUTHOR]

Abstract: A two-dimensional finite element model is created to investigate the effects of temperature and residual stress on transverse tensile behaviors for SiC/Ti–6Al–4V composites with square fiber array. The spring elements are used to simulate interfacial debonding when interfacial radial stress, composed of residual radial stress and radial stress introduced by the applied transverse tensile stress, reaches interfacial bonding strength. The results indicate that temperature has an obvious influence on the collapse stress of composites due to the change of matrix strength with temperature. And the higher temperature is, the lower collapse stress is. Residual radial stress can increase the applied stress required to cause interfacial debonding, but has a little influence on the collapse stress of the composites. [Copyright &y& Elsevier]

Abstract: Transport mechanisms through SiO2/HfO2 gate stacks have been investigated by means of Capacitance–Voltage (C–V), Current–Voltage (I–V) in a large range of temperature (80–400K) and Transmission Electron Microscopy (TEM) measurements, on several nMOS transistors featuring different interfacial layer and HfO2 thicknesses. The temperature dependency of experimental gate leakage currents have been found to be very weak when plotted versus total charge, except on thicker stacks, in inversion regime, between 300 and 400K. Experiments have been compared with Direct Tunneling current (DT) simulations in inversion regime, using as few as possible arbitrary assumptions and fitting parameters. This comparison has shown that ultra-thin interfacial layer differs from pure SiO2 only below 1nm thickness, confirming previous theoretical works. [Copyright &y& Elsevier]

Abstract: A Monte Carlo simulation has been used to study the magnetic properties and the critical behaviors of a single spherical nanoparticle, consisting of a ferromagnetic core of spins surrounded by a ferromagnetic shell of , 0 or , spins with antiferromagnetic interface coupling, located on a simple cubic lattice. A number of characteristic phenomena has been found. In particular, the effects of the shell coupling and the interface coupling on both the critical and compensation temperatures are investigated. We have found that, for appropriate values of the system parameters, two compensation temperatures may occur in the present system. [Copyright &y& Elsevier]

Abstract: The spatiotemporal behavior of an initially corrugated interface in the two-dimensional driven lattice gas (DLG) model with attractive nearest-neighbors interactions is investigated via Monte Carlo simulations. By setting the system in the ordered phase, with periodic boundary conditions along the external field axis. i.e. horizontal, and open along the vertical directions respectively, an initial interface was imposed, that consists in a series of sinusoidal profiles with amplitude and wavelength set parallel to the applied driving field axis. We studied the dynamic behavior of its statistical width or roughness , defined as the root mean square of the interface position. We found that decays exponentially for all and lattice longitudinal sizes , i.e., the lattice side that runs along the axis of the external field. We determined its relaxation time , and found that depends on as a power law , where depends on the temperature and . At low ’s () and large , approaches to . At intermediate ’s (), decreases up to , and is free of finite effects. This indicates that the interface stabilizes faster than in the equilibrium model, i. e. the Ising lattice gas where . At higher ’s increases for , and the finite size dependence is recovered. Also, if is fixed, increases with until it saturates at large values of it, while this regime is vanishing at . In this way, the dynamic relaxation process of a sinusoidal interface is improved by the external driving field with respect to its equilibrium counterpart, if the system is set in an intermediate temperature stage far from and in a lattice with a sufficiently large longitudinal side. The behavior of was also investigated as a function of and in the intermediate stage . It was found that decreases exponentially with in the interval , while for higher fields it remains constant. The exponential decay depends on the wavelength of the initial profile. In order to study the spatial evolution of the profiles, we evaluated the structure factor of the interface, and the Fourier coefficients corresponding to the same wave vector of the initial profile. The obtained results allowed us to conclude that the spatial evolution of the profile maintains its initial wavelength, does not travel along the external field axis, and its shape is preserved over all the relaxation process. [Copyright &y& Elsevier]

The effects of several growth parameters in cylindrical and spherical Czochralski crystal process are studied numerically and particularly, we focus on the influence of the pressure field. We present a set of threedimensional computational simulations using the finite volume package Fluent in two different geometries, a new geometry as cylindrospherical and the traditional configuration as cylindrocylindrical. We found that the evolution of pressure which is has not been studied before; this important function is strongly related to the vorticity in the bulk flow, the free surface and the growth interface. It seems that the pressure is more sensitive to the breaking of symmetry than the other properties that characterize the crystal growth as temperature or velocity fields. © 2010 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim [ABSTRACT FROM AUTHOR]

Extensive molecular dynamics simulations at room temperature were carried out for model films of two dissimilar lipids (DPPC and dicaprin) at the air/water interface. To study the peculiarities of the organization patterns at different average areas per molecule, surface concentrations corresponding to five almost equally spaced points along the isotherms of the two surfactants were considered. A variable of prime interest was the density distribution in a direction normal to the interface of the monolayer components: interfacial water and surfactant on one hand and the separate moieties of the lipids on the other hand. The packing pattern and cluster size dispersion were studied by means of Voronoi tessellation and radial distribution functions. Speculations regarding structural changes upon phase-state changes during film compression were made. Individual characteristics for surfactant heads and tails as well as for interfacial water were outlined and related to the available experimental data. An analysis of the diffusion coefficients revealed the limiting factors for lipid lateral and normal diffusion. Structural arguments in support of changes in monolayer dielectric properties with the area per molecule were provided. [ABSTRACT FROM AUTHOR]

Abstract: We present phase-field simulations of isothermal phase transformations in the peritectic system below and above the peritectic temperature. The physical processes involved are of different natures, involving either a triple junction or a liquid-film-migration (LFM) mechanism. Below the peritectic temperature, one of the solid phases steadily grows along the other. Above the peritectic temperature the phase transformation proceeds via the LFM mechanism. To the best of our knowledge, this mechanism has not been discussed in the literature as a generic process of phase transitions in peritectic systems. In addition to the LFM process, we also simulate melting along the solid–solid interface. Finally, we make a simplified linear stability analysis of the liquid film, supporting our simulation results. [Copyright &y& Elsevier]

Abstract: Numerical modeling of linear friction welding (LFW) of TC4 titanium alloy was conducted using ABAQUS/Explicit with a 2D model. The coupled thermo-mechanical analysis was performed with the Johnson–Cook material model. The effects of processing parameters on the temperature evolution and axial shortening of LFW joints were numerically investigated. It is shown that the temperature at the interface can first increase quickly to about 1000°C within 1s, then increases slowly, and finally tends to become uniform across the interface under certain processing conditions. The temperature gradient across the joint from the interface is very high during the friction process. Consequently, significant axial shortening and fast formation of flash start to happen as the interface temperature becomes more uniform. During cooling, the interface temperature decreases steeply at a rate of several hundred degrees per second because of the fast heat conduction to the cold end of the specimen. The temperature distribution appears to be uniform in the joint after about 30s. At a higher oscillation frequency, the interface temperature rises more quickly and the axial dimension shortens more and at a faster rate. The same phenomena are observed for the amplitude and friction pressure. The effects of these three factors can be integrated into one parameter of heat input. The axial shortening increases with increasing heat input almost linearly as the heat input exceeds a critical value. [Copyright &y& Elsevier]

Abstract: In this article, we have investigated the anisotropic nature of thermal transport in molybdenum disulphide using molecular dynamics simulations. At first, a force field has been validated with respect to crystal structure and experimental vibrational spectra of MoS2. Thereafter, non-equilibrium MD simulations have been performed in two perpendicular directions (along as well as across the basal planes) to study thermal transport behavior. At room temperature, our results show an anisotropic factor of ∼4 in the values of thermal conductivity along two studied directions, which is in good agreement with recent experiments on MoS2 thin films. However, the predicted values of thermal conductivity are about an order of magnitude higher with respect to experiments. The reasoning behind these differences has been discussed in terms of layer disorder and the large number of grain boundary interfaces in experimental thin films, which consisted of nano-crystalline MoS2 grains with a predominant parallel or perpendicular basal plane orientation. Incorporation of phonon scattering via structure disorder and boundary interfaces were identified as further directions for the model refinement. [Copyright &y& Elsevier]

Abstract: The evolution of interfacial phenomena during CO2 corrosion of C1018 carbon steel was characterized by EIS (Electrochemical Spectroscopy Impedance) and LPR (Linear Polarization Resistance). Turbulent conditions were simulated by a channel flow cell with deoxygenated 3wt.% NaCl solution at 80°C and pH 6 during 158h. EIS helped in the characterization of the dynamic mechanism during the formation of the unprotective porous Fe3C layer, and subsequent precipitation of the protective FeCO3 layer inside the cementite. The experimental response of the active states at the interface was characterized by electrical passive elements with constant phase parameter analogs showing good agreement with the experimental results. [Copyright &y& Elsevier]

Abstract: Non-equilibrium molecular dynamics (NEMD) simulations were performed on Au–SAM (self-assembly monolayer)–Au junctions to study the thermal energy transport across the junctions. Thermal conductance of the Au–SAM interfaces was calculated. Temperature effects, simulated external pressure effects, SAM molecule coverage effects and Au–SAM bond strength effects on the interfacial thermal conductance were studied. It was found that the interfacial thermal conductance increased with temperature increase at temperatures lower than 250K, but it did not have large changes at temperatures from 250 to 400K. Such a trend was found to be similar to experimental observations on similar junctions. The simulated external pressure did not affect the interfacial thermal conductance. SAM molecule coverage and Au–SAM bond strength were found to significantly affect on the thermal conductance. The vibration densities of state (VDOS) were calculated to explore the mechanism of thermal energy transport. Interfacial thermal resistance was found mainly due to the limited population of low-frequency vibration modes of the SAM molecule. Ballistic energy transport inside the SAM molecules was confirmed, and the anharmonicity played an important role in energy transport across the junctions. A heat pulse was imposed on the junction substrate, and heat dissipation inside the junction was studied. Analysis of the junction response to the heat pulse showed that the Au–SAM interfacial thermal resistance was much larger than the Au substrate and SAM resistances separately. This work showed that both the Au substrate and SAM molecules transported thermal energy efficiently, and it was the Au–SAM interfaces that dominated the thermal energy transport across the Au–SAM–Au junctions. [Copyright &y& Elsevier]

Abstract: Accurately predicting the physical cutting process variables, e.g. temperature, velocity, strain and stress fields, plays a pivotal role for predictive process engineering for machining processes. These predicted field variables, however, are highly influenced by workpiece constitutive material model (i.e. flow stress), thermo-mechanical properties and contact friction law at the tool–chip–workpiece interfaces. This paper aims to investigate effects of friction modeling at the tool–chip–workpiece interfaces on chip formation process in predicting forces, temperatures and other field variables such as normal stress and shear stress on the tool by using advanced finite element (FE) simulation techniques. For this purpose, two distinct FE models with Arbitrary Lagrangian Eulerian (ALE) fully coupled thermal-stress analyses are employed to study not only the effects of FE modeling with different ALE techniques but also to investigate the influence of limiting shear stress at the tool–chip contact on frictional conditions, which was never done before. A detailed friction modeling at the tool–chip and tool–work interfaces is also carried by coupling sticking and sliding frictions. Experiments and simulations have been performed for machining of AISI 4340 steel using tungsten carbide tooling and the simulation results under increasing limit shear stress have been compared to experiments. The influence of limiting shear stress on the tool–chip contact friction was explored and validity of friction modeling approaches was examined. The results presented in this work not only provide a clear understanding of friction in FEM modeling of machining but also advance the process knowledge in machining. [Copyright &y& Elsevier]

Abstract: We determine the interface tension for the 100, 110 and 111 interface of the simple cubic Ising model with nearest-neighbour interaction using novel simulation methods. To overcome the droplet/strip transition and the droplet nucleation barrier we use a newly developed combination of the multimagnetic algorithm with the parallel tempering method. We investigate a large range of inverse temperatures to study the anisotropy of the interface tension in detail. [Copyright &y& Elsevier]

Abstract: Dynamic behavior of superheated He II–superheated He I interface as a result of heating in a narrow channel between parallel walls that simulates cooling channels of superconducting magnets was investigated using a shadowgraph visualization method. It was confirmed that a superheated state could be created in the narrow channel without preparing a special calm environment. A superheated He II–superheated He I interface transiently appeared between 2.0K and lambda temperature when applying a small heat flux. The boiling state accompanying the superheated He II–superheated He I interface was repeatedly generated and collapsed. This boiling mode was anticipated to have a high heat transfer coefficient. [Copyright &y& Elsevier]

Abstract: The dynamical and thermal performances of molten salt pipe during the filling process are numerically investigated using volume of fluid model. The whole filling process has three main stages, or the developing stage with the interface width quickly increasing, the fluctuating stage with the interface width fluctuating and the fully developed stage with stable interface, and then associated interface structures, flow and temperature fields are described in detail. Before the molten salt flows through a certain position, the fluid temperature will jump within a short time, while the wall temperature only linearly increases after that. The heat transport during the filling process is mainly dependent upon the pipe wall and molten salt flow, while natural convection outside can almost be ignored. The dimensionless interface temperature has similar evolution process under different surrounding temperatures, but it will apparently increase with the flow velocity rising. In addition, the pipe will be blocked when the interface temperature drops below the freezing point, so a model of penetration distance is derived by correlating the interface temperature evolution process, and it has a good agreement with available experimental results. [Copyright &y& Elsevier]

Abstract: The characterization of frictional phenomena at the tool–chip–workpiece interface remains an issue. This paper aims to identify a friction model able to describe the friction coefficient at this interface during the dry cutting of a AISI4142 treated steel with TiN coated carbide tools. A new tribometer has been designed in order to reach relevant values of pressures, temperatures and sliding velocities. This set-up is based on a modified pin-on-ring system. Additionally a numerical model simulating the frictional test has been associated in order to identify local phenomena around the spherical pin, from the standard macroscopic data provided by the experimental system. A range of cutting speeds and pressures has been investigated. It has been shown that the friction coefficient is mainly dependant on the sliding velocity, whereas the pressure has a secondary importance. Moreover a new key parameter has been revealed, i.e. the average local sliding velocity at the contact. Finally a new friction model has been identified based on this local sliding velocity. [Copyright &y& Elsevier]

In this paper molecular dynamics simulations are performed to study the accumulation behaviour of N2 and H2 at water/graphite interface under ambient temperature and pressure. It finds that both N2 and H2 molecules can accumulate at the interface and form one of two states according to the ratio of gas molecules number to square of graphite surface from our simulation results: gas films (pancake-like) for a larger ratio and nanobubbles for a smaller ratio. In addition, we discuss the stabilities of nanobubbles at different environment temperatures. Surprisingly, it is found that the density of both kinds of gas states can be greatly increased, even comparable with that of the liquid N2 and liquid H2. The present results are expected to be helpful for the understanding of the stable existence of gas film (pancake-like) and nanobubbles. [ABSTRACT FROM AUTHOR]

We have used molecular dynamics simulations to calculate the interfacial tension of hydroxylated SiO2 nanoparticles under different temperatures and solutions (helium and brine with monovalent and divalent salts). In order to benchmark the atomistic model, quartz SiO2 interfacial tension was measured based on inverse gas chromatography under He atmosphere. The experimental interfacial tension values for quartz were found between 0.512 and 0.617 N/m. Our calculated results for the interfacial tension of silica nanoparticles within helium atmosphere was 0.676 N/m, which is higher than the value found for the system containing He/α-quartz (0.478 N/m), but it is similar to the one found for amorphous silica surface. We have also studied the interfacial tension of the nanoparticles in electrolyte aqueous solution for different types and salts concentrations (NaCl, CaCl2, and MgCl2). Our calculations indicate that adsorption properties and salt solutions greatly influence the interfacial tension in an order of CaCl2 > MgCl2 > NaCl. This effect is due to the difference in distribution of ions in solution, which modifies the hydration and electrostatic potential of those ions near the nanoparticle. [ABSTRACT FROM AUTHOR]