Structure of Cu-Sn Melt at High Temperature

The temperature-dependent viscosity and X-ray diffraction (XRD) patterns of a Cu₆₅Sn₃₅ melt were investigated at high temperatures. The viscosity of the melt changed discontinuously at about 1283?K (1010?°C). An XRD analysis of the Cu₆₅Sn₃₅ melt revealed no obvious changes in the correlation radius, whereas the coordination number increased abruptly at a similar temperature with that mentioned previously, i.e., 1283?K (1010?°C) during the cooling process. The results indicate a redistribution of atoms in the nearest environment. The structural transition at the higher temperature was attributed to a change of combination mode of nearest atoms in the short-range order cluster of the Cu₆₅Sn₃₅ melt.     

Synthesis of Plastic Mg-Based Bulk-Metallic-Glass Matrix Composites by Bridgman Solidification

The microstructures of the in-situ Mg-based bulk-metallic-glass (BMG) matrix composites synthesized by the copper-mold casting are inhomogeneous, and the optimized mechanical properties are usually realized through alloy composition design. In this article, Mg-based BMG matrix composites containing uniform flake-shaped precipitates with a fixed composition of Mg₇₀Cu_8.33Ni_8.33Gd_8.33Zn₅ were synthesized by the Bridgman solidification. Adjusting the withdrawal velocities controlled the size and volume fractions of the precipitates in the composites, and large plasticity was obtained by controlling the cooling condition only. Thus, the Bridgman solidification is an effective way not only to fabricate the homogeneous BMG matrix composites but also to tailor and optimize their mechanical properties.     

Processing of graded anode-supported micro-tubular SOFCs based on samaria-doped ceria via gel-casting and spray-coating

A simple gel-casting method was successfully combined with the spray-coating technique to manufacture graded anode-supported micro-tubular solid oxide fuel cells (MT-SOFCs) based on samaria-doped ceria (SDC) as an electrolyte. Micro-tubular anodes were shaped by a gel-casting method based on a new and simple forming technique that operates as a syringe. The aqueous slurry formulation of the NiO–SDC substrate using agarose as a gelling agent, and the effect of spray-coating parameters used to deposit the anode functional layers (AFLs) and electrolyte were investigated. Furthermore, pre-sintering temperature of anode substrates was systematically studied to avoid the anode–electrolyte delamination and obtain a dense electrolyte without cracks, after co-sintering process at 1450 °C. Despite the high shrinkage of substrate (～70%), an anode porosity of ～37% was achieved. MT-SOFCs with ～2.5 mm of outer diameter, 370 μm thick substrate, 20 μm thick AFLs and 15 μm thick electrolyte were successfully obtained. The use of AFLs with 30:70 and 50:50 wt% NiO–SDC allowed to obtain a continuous gradation of composition and porosity in the anode–electrolyte interface.     

Flexible diamond-like carbon films on rubber: Friction and the effect of viscoelastic deformation of rubber substrates

This paper focuses on the frictional behavior of flexible diamond-like carbon (DLC) film-coated hydrogenated nitrile butadiene rubber. By making use of the substantial thermal mismatch between DLC film and rubber substrate, a dense network of cracks forms in the DLC films and contributes to flexibility. The influence of the size of DLC film microsegments on the frictional performance is studied. The effect of viscoelasticity of the rubber substrate on the frictional behavior of the DLC film-coated system is scrutinized by tribo-tests and theoretical analysis. The importance of adhesive and hysteresis contributions to friction is revealed, and an overarching model is presented.     

Fracture and impulse based finite-discrete element modeling of fragmentation

A numerical method for fragmentation is presented that combines the finite element method with the impulse-based discrete element method (impulse-based FDEM). In contrast to existing methods, fragments are not represented as a conglomeration of spheres; instead, their shapes are represented using solid modeling techniques, and are the result of multiple fracture growth. Fracture growth within each three-dimensional fragment is controlled by stress intensity factors computed using the finite element method and the reduced virtual integration technique. Non-convex fragment interaction and movement is modeled using impulse dynamics, rather than a penalty-based method. Collisions leading to fracture are handled individually by propagating pre-existing internal flaws and cracks. The method utilizes decoupled geometry and mesh representation, and local failure and propagation criteria. Fractures that reach volume boundaries lead to further fragmentation. The approach is demonstrated by the fragmentation of a sphere, which exhibits a velocity-dependent fragment size distribution. The distribution is characterized by a two-parameter Weibull distribution, an emergent property of the simulation. Results are in good agreement with experimental data.     

Joint optimization of preventive maintenance and inventory control in a production line using simulation

This paper proposes an integrated method for preventive maintenance and inventory control of a production line, composed of n machines (n?≥?1) without intermediate buffers. The machines are subject to failures and an age-dependent preventive maintenance policy is used. Approximate analytical results are proposed for the one machine case. Simulation software is used to model and simulate the behaviour of the production line of n machines under various maintenance and inventory control strategies. A methodology combining the simulation and genetic algorithms is proposed jointly to optimize maintenance and inventory control policies. Results are compared with the analytical solutions.     

Metallic glass-based chiral nanolattice: Light weight,auxeticity, and superior mechanical properties

Metallic glasses (MGs) possess large elastic limit and high strength, but unfortunately they are of limited commercial utility due to their macroscopic brittle nature. Here, we report that a chiral nanolattice can be used to design large-scale MGs with negative Poisson’s ratio, large elastic deformation capability, extensive hardening, and large ductility. Furthermore, the mechanical behaviors of the metallic glass chiral nanolattice (MGCN) can be significantly altered through changing the thickness and length of the ligaments in the nanolattice. An exceptional combination of high strength and ductility is observed for MGCN with thin and long ligaments, wherein the sample density is only twice that of water. The deformation mechanism that characterizes the chiral topology is a combination of rotation of the nodes with bending and extension of the ligaments, leading to the extraordinary mechanical behaviors. The present study not only offers a potential solution to mitigating the brittleness of MGs, but also provides some guidelines in designing large-scale MG meta-materials for prospective applications in the fields of acoustics and energy absorption.     

Effects of monensin on glucose metabolism in transition dairy cows

Eight multiparous periparturient Holstein cows fitted with ruminal cannula were used in a split plot design to evaluate the effects of monensin on plasma glucose metabolism. Diets were top-dressed daily with 0 mg/cow of monensin (control) or 300 mg/cow of monensin (MON) both pre- and postpartum. Plasma glucose kinetic parameters on d ?13 ± 2.0 and 19 ± 1.6 relative to parturition were determined by using stable isotopes. Na-1-¹³C₃-Propionate (labeled propionate) was infused into the rumen to measure glucose synthesis originating from ruminal propionate, and U-¹³C-glucose (labeled glucose) was injected into the jugular vein to determine total glucose kinetics. A sampling period of 480 min following labeled glucose injection was implemented. A compartmental analysis was employed to determine steady state glucose kinetic parameters. To develop a steady state glucose model, the Windows version of SAAM software (WinSAAM) was used. A 4-compartment model was adequate to comprehensively describe plasma glucose metabolism. The main model compartments consisted of propionate and plasma glucose. The time frame of the 480-min sampling period post-tracer glucose infusion allowed accurate quantification of glucose metabolism. The model estimated that glucose input from sources other than ruminal propionate decreased with MON, from 2.26 to 1.09 g/min postpartum. Gluconeogenesis, expressed as the propionate contribution to the plasma glucose pool, increased in cows fed MON (22 vs. 31%), whereas glucose oxidation, expressed as the glucose disposal rate, significantly decreased (1.67 vs. 0.92 g/min). In conclusion, MON may improve the energy status of transition cows by (1) improving the efficiency of propionate to produce glucose and (2) decreasing glucose oxidation in body tissues.     

Coherent precipitation in a high-temperature Cr–Ni–Al–Ti Alloy

Chromium alloys present a potential for development of new high-temperature materials. Precipitation characteristics of a Cr–5Ni–5Al–0.5Ti (at.%) alloy were investigated utilizing a series of heat treatments. XRD, SEM, and analytical TEM were used to characterize the microstructure. This study has shown that the small spherical B2-NiAl precipitates forming below 1345 °C are highly coherent and have a well-defined orientation relationship with the Cr-matrix. Also, some evidence has been presented for the formation of L2₁-Ni₂AlTi phase within the B2-NiAl phase.