Evolution Of Density Distribution Research Articles

Application of Video-to-Video Translation Networks to Computational Fluid Dynamics

In recent years, the evolution of artificial intelligence, especially deep learning, has been remarkable, and its application to various fields has been growing rapidly. In this paper, I report the results of the application of generative adversarial networks (GANs), specifically video-to-video translation networks, to computational fluid dynamics (CFD) simulations. The purpose of this research is to reduce the computational cost of CFD simulations with GANs. The architecture of GANs in this research is a combination of the image-to-image translation networks (the so-called “pix2pix”) and Long Short-Term Memory (LSTM). It is shown that the results of high-cost and high-accuracy simulations (with high-resolution computational grids) can be estimated from those of low-cost and low-accuracy simulations (with low-resolution grids). In particular, the time evolution of density distributions in the cases of a high-resolution grid is reproduced from that in the cases of a low-resolution grid through GANs, and the density inhomogeneity estimated from the image generated by GANs recovers the ground truth with good accuracy. Qualitative and quantitative comparisons of the results of the proposed method with those of several super-resolution algorithms are also presented.

Influence of the inicial porous preform shape on the deformed state evolution and force parameters of the forging process in a semi-closed die

Abstract. The results of simulation of hot forging process for porous powder preforms of two initial configurations (cylindrical shape and in the form of a cut cone) in a die with detachable matrix are presented. Numerical assessment of the effect of the boundary conditions of the deformation scheme on the evolution of the stress-strain state of the forged piece was performed using the model of rigidly plastic porous body. The evolution of the relative density distribution, the deformed state along the cross section of the workpiece at different stages of deformation and the overall effort of deforming the process were studied. The fundamentally different nature of the evolution of density distribution and components of deformation tensor in the forged pieces volume is shown in deformation of the preforms of different initial configuration, which is manifested in a substantially higher level of deformations intensity in the volume for the initial preforms, which are made in the form of a cut cone in a cut cylindrical shape. The maximum value of the forging force for the initial preforms of both configurations is practically the same, but the intensity of the deformation force increase is much higher for the cylindrical blanks.

Ground-state properties of interacting two-component Bose gases in a one-dimensional harmonic trap

We study ground-state properties of interacting two-component boson gases in a one-dimensional harmonic trap by using the exact numerical diagonalization method. Based on numerical solutions of many-body Hamiltonians, we calculate the ground-state density distributions in the whole interaction regime for different atomic number ratio, intra- and inter-atomic interactions. For the case with equal intra- and inter-atomic interactions, our results clearly display the evolution of density distributions from a Bose condensate distribution to a Fermi-like distribution with the increase of the repulsive interaction. Particularly, we compare our result in the strong interaction regime to the exact result in the infinitely repulsive limit which can be obtained by a generalized Bose-Fermi mapping. We also discuss the general case with different intra- and inter-atomic interactions and show the rich configurations of the density profiles.

NMR imaging of density distributions in tablets

This paper describes the use of 1H nuclear magnetic resonance (NMR) for 3D mapping of the relative density distribution in pharmaceutical tablets manufactured under controlled conditions. The tablets are impregnated with a compatible liquid. The technique involves imaging of the presence of liquid which occupies the open pore space. The method does not require special calibration as the signal is directly proportional to the porosity for the imaging conditions used. The NMR imaging method is validated using uniform density flat faced tablets and also by direct comparison with X-ray computed tomography. The results illustrate (1) the effect of die wall friction on density distribution by compressing round, curved faced tablets using clean and pre-lubricated tooling, (2) the evolution of density distribution during compaction for both clean and pre-lubricated die wall conditions, by imaging tablets compressed to different compaction forces, and (3) the effect of tablet image on density distribution by compressing two complex shape tablets in identical dies to the same average density using punches with different geometries.

Numerical simulation for separation of multi-phase immiscible fluids in porous media

Based on a lattice Boltzmann method and general principles of porous flow, a numerical technique is presented for analysing the separation of multi-phase immiscible fluids in porous media. The total body force acting on fluid particles is modified by adding relative permeability in Nithiarasu's expression with an additional surface tension term. As a test of this model, we simulate the phase separation for the case of two immiscible fluids. The numerical results show that the two coupling relative permeability coefficients K12 and K21 have the same magnitude, so the linear flux-forcing relationships satisfy Onsager reciprocity. Phase separation phenomenon is shown with the time evolution of density distribution and bears a strong similarity to the results obtained from other numerical models and the flows in sands. At the same time, the dynamical rules in this model are local, therefore it can be run on massively parallel computers with well computational efficiency.

In situ 타원법을 사용한 광기록매체용 Ge-Sb-Te 박막의 최적성장조건 연구

타원법(ellipsometry)을 사용하여 광기록 매체용 Ge<TEX>$_2$</TEX> Sb<TEX>$_2$</TEX> Te<TEX>$^{5}$</TEX> (GST) 박막의 성장과정에 따른 타원상수 Ψ와 <TEX>$\Delta$</TEX>를 측정하여. GST 박막의 최적성장조건을 연구하였다. 아르곤기체압력과 DC 출력 그리고 기판의 온도를 변화시키면서 GST 박막을 성장시켰다. 제작된 시료들의 분광타원 데이터를 모델링 분석하여 GST박막의 밀도분포를 구하고 한편으로는 GST 박막이 성장하는 동안 측정한 in situ 타원 성장곡선을 분석하여 박막의 밀도분포의 변화를 추적하였다. 아르곤기체압력이 7 mTorr일 때 박막의 상대적인 밀도분포가 고르게 되었고 DC출력이 증가함에 따라 그리고 기판의 온도가 증가함에 따라 GST 박막의 밀도 균일성은 크게 향상되었다. 주사형전자현미경(SEM)을 사용하여 최적 밀도 균일성을 가지는 성장조건(7 mTorr, 45 W, 15<TEX>$0^{\circ}C$</TEX>)에서 제작된 GST 시료가 가장 균일한 구조를 보여줌을 확인하였다. 균일한 밀도 분포를 가지는 GST 박막의 성장조건 확립을 통하여 여러번 기록/재생할 때 광기록 박막의 안정성을 유지하는데 크게 기여할 것이다. The spectroe-ellipsometric constant <TEX>$\Delta$</TEX>, Ψ and the ellipsometric growth curves at the wavelength of 632.8 nm are collected. These are critically examined to find out the optimum growth condition of phase change <TEX>$Ge_2Sb_2Te_5(GST)$</TEX> thin films as an optical recording medium. GST films are prepared using DC magnetron sputtering technique, under the selected experimental conditions of Ar gas pressure (5 mTorr, 7 mTorr and 10 mTorr), DC power of sputtering gun (15 W, 30 W and 45 W), and substrate temperature (from room temperature to 18<TEX>$0^{\circ}C$</TEX>). Based on the three film model, the density distribution of deposited GST films are obtained versus Ar gas pressure and DC power by analyzing spectro-ellipsometric data. The calculated evolution curves at the wavelength of 632.8 nm, are fit into the in situ observed ones to get information about the evolution of density distribution during film growth. The density distribution showed different evolution curves depending on deposition conditions. The GST films fabricated at DC power of 30 W or 45 W, and at Ar gas pressure of 7 mTorr turned out to be the most homogeneous one out of those prepared at room temperature, even though the maximum density difference between the dense region and the dilute region of the GST film was still significant (~50%). Finally, in order to find the optimum growth condition of homogeneous GST thin films, the substrate temperature is varied while Ar gas pressure is fixed at 7 mTorr and DC power at 30 W and 45 W respectively. A monotonic decrease of void fraction except for a slight increase at 18<TEX>$0^{\circ}C$</TEX> is observed as the substrate temperature increases. Decrease of void fraction indicates an increase of film density and hence an improvement of film homogeneity. The optimum condition of the most homogeneous GST film growth turned out to be 7 mTorr of Ar gas pressure, 15<TEX>$0^{\circ}C$</TEX> of substrate temperature. and 45 W of DC power. The microscopic images obtained using scanning electron microscope, of the samples prepared at the optimum growth condition, confirmed this conclusion. It is believed that the fabrication of homogeneous GST films will be quite beneficial to provide a reliable optical recording medium compatible with repeated write/erase cycles.