We present an implementation of a GPU based FFT routine (Graphics Processing Unit based Fast Fourier Transformation) into a CPU based ab initio periodic DFT (Density Functional Theory) calculation code. The FFT calculation in the CPU based DFT codes is the most time-consuming part; for the 128 silicon system, the fraction of time of a CPU FFT calculation amounts to 0.64 of the whole periodic DFT calculation. The replacement of a double precision FFT in the periodic PWscf code with a single precision FFT gives no appreciable differences in both the numerical total energies and the interatomic forces, guaranteeing the use of a single precision GPU based FFT, CUFFT, for the code. The use of the CUFFT reduces the fraction to 0.20 of the whole PWscf code; the replacement speedups a factor of 2.2 for single CPU system. The use of the multi-CPU system with the GPU FFT accelerates by 2.2f, where f is the acceleration factor of the multi-CPU system. The single precision GPU calculation is implementable in any self-consistent electronic structure code, except for the eigensolver part in the DFT codes.
This paper presents a wet etching simulation method for sacrifice layer of MEMS (micro electro mechanical system) that considers physical phenomenon including flow, diffusion and chemical reaction. In this method, a partial differential equation with implicit parameterization of etching properties was studied that was solvable by any commercial CFD code. Two parameters for flow and reaction were determined by fitting the numerical result to experimental one obtained using a test device. For automatic calibration of parameters, an error function was proposed considering the position of etching front, averaged etching rate and shape of etching front. The distribution of the error (response surface) was predicted by second order Lagrange interpolation. The iteration algorithm for this automatic calibration contributed to reduce the computational cost. Once the parameters were determined, the etching simulation of real MEMS device could be practically carried out.
Tablets are the most common dosage forms found in the market today. They come in many different shapes, colors and flavors. People sometimes find it difficult to swallow tablets, and we have reported that tablets with a smaller radius of curvature are easier to swallow. However, a small radius of curvature tends to result in decreased tablet hardness. On the other hand, a lot of stress occurring on the tablet press may break the punch head. There are simple design manuals of punch strength, however no computational method has been described in detail. We performed an FEM analysis of tablet hardness and punch strength using ANSYS software. The punch reaction force was then transcribed as the tablet Young's modulus (the transcription model). The result of ANSYS simulation in a tablet made from dry yeast was consistent with the experimental result. In addition, the relation between punch shape and allowable load was studied employing the Response Surface Method and the punch shape contribution for allowable load was calculated.
Multi-objective design optimization for a steam turbine stator blade was implemented using three-dimensional large eddy simulation (LES) and a genetic algorithm (GA). The GA used here was assisted by the Kriging response surface model for global and efficient optimization. The aim of the optimization described here was to reduce overall pressure loss and local pressure loss due to end walls simultaneously. The optimization results revealed the blade design candidates that overcame the baseline design in terms of overall loss and local loss, and the trade-off relation between them. In addition, these results provided a specific design concept and corresponding flow mechanism to realize a highly efficient stator blade.
During car frontal crash, crush energy is absorbed by the parts of front bumper, front side member, front panel member and so on. Previous research has indicated that front side member plays major role in energy absorption. For protecting the passengers, the front side member is expected to absorb crush energy as much as possible. In this study, we adopt cylindrical thin-walled structure using origami engineering as front side member instead of structure with rectangular cross section which is generally used. We develop an optimization system of the cylindrical thin-walled origami structure, in which the objective function is to maximize the energy absorption of origami structure; the design variables are structural parameter, number of divisional sections along axis, number of edges of polygonal cross section and number of subdivision levels; the weight and initial peak load of optimal structure must be less than those of structure with rectangular cross section. We then discuss the optimization results that the optimal structure is capable of absorbing energy 91% more than that of original rectangular cross sectional structure which is usually bended on the way of being crushed, 37% more than that of original structure which is ideally crushed to 70% length without bending.
In this paper, a Trans-mesh method is presented for simulating three-dimensional incompressible fluid-rigid body interaction with collisions. In the Trans-mesh method, the bodies can move freely in a main mesh that covers the entire flow field. The method is constructed based on the four-dimensional control volume in space-time unified domain such that the method assures to be divergence-free in the space-time unified domain and thus satisfies both the physical and geometrical conservation laws simultaneously. First of all, it is confirmed that the present method satisfies the geometric conservation law. Next, we did calculations for a single sphere settling under gravity in the stationary fluid to evaluate the present method. The method was applied to a flow around bodies driven by a flow in a square duct and the unsteady behavior of the flow is shown. The results indicate that this method is promising in such simulations.
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