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A numerical study of turbulent combustion characteristics in a combustion chamber of a scramjet engine

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Science China(Technological Sciences) 2010年第8期53卷 2111-2121页

作者： lee ChunHian School of Aeronautical Sciences and Engineering Beihang University

3D numerical simulation of flow fields in a combustion chamber of a scramjet engine using an SST turbulence model with an explicit compressibility correction was performed and the results were compared to the experimental *** characteristics of the turbulent combustion flow fields were analyzed via the numerical results and *** order to identify the mechanisms of turbulent combustion in supersonic flows,the evolutions of governing dimensionless parameters in the flow fields were investigated based on the theory of combustion and the available numerical *** was found that the supersonic combustion takes place in the region of fully developed turbulence and that the strongest effects of turbulence and combustion processes appear in the vicinity of the *** unsteady effects and the local flame extinction phenomenon induced by turbulent flows were found to be negligibly small,and the steady flamelet approximation will hold for practical applications.

关键词： scramjet turbulent combustion flamelet approximation numerical simulation

Characterization of the three-dimensional supersonic flow for the MHD generator

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Science China(Physics,Mechanics & Astronomy) 2009年第4期52卷 534-545页

作者： lee ChunHian National Laboratory for Computational Fluid Dynamics Beihang University

A numerical procedure based on a five-wave MHD model associated with non-ideal,low magnetic Reynolds number MHD flows was developed in the present study for analyzing the flow fields in the MHD generator of a MHD bypass scramjet. The numerical procedure is composed of an entropy conditioned scheme for solving the non-homogeneous Navier-Stokes equations,in conjunction with an SOR method for solving the elliptic equation governing the electrical potential. It was found that a separation would take place near the downstream edge of the second electrode,where the local adverse pressure gradient is large,and the core of the flow field is characterized as a 2-D flow due to the Hartmann effects along the direction of the magnetic field. The electric current lines would be increasingly distorted as the magnetic interactive parameter increases,and even induce an eddy current. Induced eddy current was also found in the different cross-sections along the axial direction,all of these would definitely deteriorate the performance of the MHD generator. The cross-sectional M-shape velocity profile found along the axial direction between the insulating walls is responsible for the formation of the vortex flow at the corner of the insulator cross-section,which,in turn,induces the corner eddy current at the corner. A numerical parametric study was also performed,and the computed performance parameters for the MHD generator suggest that,in order to enhance the performance of MHD generator,the magnetic interaction parameter should be elevated.

关键词： MHD generator entropy conditioned scheme SOR numerical simulation

A study on neural mechanism of face processing based on fMRI

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Progress in Natural Science:Materials International 2008年第2期18卷 201-207页

作者： Kang lee Canada Institute of Child Study University of Toronto

Recently,there were debates about the specificity of lateral middle fusiform in face processing. The debates focused on whether these areas were specialized in face processing or involved in processing of visual expertise and categorization at individual level. The present study aims to investigate the neural mechanism of face processing,using Chinese characters as comparison stimuli. Chinese characters are greatly similar to faces on a variety of dimensions,among which the most significant one is that both faces and Chinese characters not only are extremely familiar to literate Chinese adults but also are processed at individual level. In the present study,faces and Chinese characters activated bilateral middle fusiform with great correlation. Greater activities were observed in the right fusiform face area (FFA) for faces than for Chinese characters. These results demonstrate that FFA is specialized in face processing per se rather than the processing of visual expertise and categorization at individual level.

关键词： Face processing Chinese characters Fusiform gyrus fMRI

A Fast Quantitative Analysis and Performance Estimation Method of SoC Bus Architectures

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Chinese Journal of Electronics 2014年第4期23卷 682-687页

作者： Jaesung lee Department of Electronic Engineering Korea National University of Transportation

Various multi-layered bus architectures are now being used in the So C industry. Reckless use of bus layers may result in low utilization of communication resource and waste silicon area. This paper introduces a quantitative analysis at the initial stage of So C *** time complexity is examined and it is found that their scale is the order of n to the power of n, or combinatorial,and thus the problem is NP-complete. The paper proposes some heuristic methods through in-depth investigation and applies them to each step of the exploration to reduce the time complexity. The exploration processes and the proposed methods are implemented as a software program and several experiments are performed. From the results, the performance of SNP turns out to be significantly enhanced and achieves 25% enhancement in comparison with a defacto standard bus, AXI. For time complexity, the reduction ratio goes down to 3.7 × 10-6.

关键词： System-on-chip On-chip bus Design automation Multi-layered architecture

Impacts of optimization strategies on performance,power/energy consumption of a GPU based parallel reduction

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Journal of Central South University 2017年第11期24卷 2624-2637页

作者： Phuong Thi Yen lee Deok-Young lee Jeong-Gun Smart Computing Lab. Department of Computer EngineeringHallym UniversityChuncheon 24252Korea College of General Education Hallym UniversityChuncheon 24252Korea

In the era of modern high performance computing, GPUs have been considered an excellent accelerator for general purpose data-intensive parallel applications. To achieve application speedup from GPUs, many of performance-oriented optimization techniques have been proposed. However, in order to satisfy the recent trend of power and energy consumptions, power/energy-aware optimization of GPUs needs to be investigated with detailed analysis in addition to the performance-oriented optimization. In this work, in order to explore the impact of various optimization strategies on GPU performance, power and energy consumptions, we evaluate performance and power/energy consumption of a well-known application running on different commercial GPU devices with the different optimization strategies. In particular, in order to see the more generalized performance and power consumption patterns of GPU based accelerations, our evaluations are performed with three different Nvdia GPU generations(Fermi, Kepler and Maxwell architectures), various core clock frequencies and memory clock frequencies. We analyze how a GPU kernel execution is affected by optimization and what GPU architectural factors have much impact on its performance and power/energy consumption. This paper also categorizes which optimization technique primarily improves which metric(i.e., performance, power or energy efficiency). Furthermore, voltage frequency scaling(VFS) is also applied to examine the effect of changing a clock frequency on these metrics. In general, our work shows that effective GPU optimization strategies can improve the application performance significantly without increasing power and energy consumption.

关键词： parallel reduction GPU code optimization power energy voltage frequency scaling

Characteristics of bifurcation and buckling load of space truss in consideration of initial imperfection and load mode

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第3期14卷 206-218页

作者： Su-deok SHON Seung-jae lee Kang-guk lee School of Architectural Engineering Korea University of Technology and Education1800 ChungjeolroCheonan ChungnamRepublic of Korea Research Center for Urban Affair Kyungil UniversityGyeongsan-city GyeongbukRepublic of Korea

This study investigated characteristics of bifurcation and critical buckling load by shape imperfection of space truss,which were sensitive to initial *** critical point and buckling load were computed by the analysis of the eigenvalues and determinants of the tangential stiffness *** two-free-nodes example and star dome were selected for the case study in order to examine the nodal buckling and global buckling by the sensitivity to the eigen buckling mode and the analyses of the influence,and characteristics of the parameters as defined by the load ratio of the center node and surrounding node,as well as rise-span ratio were *** sensitivity to the imperfection of the initial shape of the two-free-nodes example,which occurs due to snapping at the critical point,resulted in bifurcation before the limit point due to the buckling mode,and the buckling load was reduced by the increase in the amount of *** two sensitive buckling patterns of the numerical model are established by investigating the displaced position of the free nodes,and the asymmetric eigenmode greatly influenced the behavior of the imperfection shape whether it was at limit point or ***,the sensitive mode of the two-free-nodes example was similar to the in-extensional basis mechanism of a simplified *** star dome,which was used to examine the influence among several nodes,indicated that the influence of nodal buckling was greater than that of global buckling as the rise-span ratio was ***,global buckling is occurred with reaching bifurcation point as the value of load ratio was higher,and the buckling load level was about 50%-70% of load level at limit point.

关键词： Space truss Geometric nonlinearity Initial imperfection Snap-through Bifurcation Global buckling

Densification simulation of compacted Al powders using multi-particle finite element method

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中国有色金属学会会刊：英文版 2009年第B09期19卷 68-75页

作者： Kyung-Hun lee Jung-Min lee Byung-Min KIM School of Mechanical Engineering Pu san National University

The powder compaction simulations were performed to demonstrate deformation behavior of particles and estimate the effect of different punch speeds and particle diameters on the relative density of powder by a multi-particle finite element model(MPFEM). Individual particle discretized with a finite element mesh allows for a full description of the contact mechanics. In order to verify the reliability of compaction simulation by MPFEM, the compaction tests of porous aluminum with average particle size of 20 μm and 3 μm were performed at different ram speeds of 5, 15, 30 and 60 mm/min by MTS servo-hydraulic tester. The results show that the slow ram speed is of great advantage for powder densification in low compaction force due to sufficient particle rearrangement and compaction force increases with decrease in average particle size of aluminum.

关键词：粉末压实粉末粒子多孔铝有限元法模拟致密化平均粒径有限元模型

Zircon U-Pb dating and geochemical study of the Xianggou granite in the Ma'anqiao gold deposit and its relationship with gold mineralization

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Science China Earth Sciences 2010年第2期53卷 220-240页

作者： lee Ben State Key Laboratory of Continental Dynamics Department of GeologyNorthwest University

Single zircon LA-ICP-MS U-Pb dating and lithogeochemical studies have been performed on the Xianggou monzonitic granitic porphyry outcropped in the Ma’anqiao gold deposit.A weighted average U-Pb age of 242.0±0.8 Ma for Xianggou monzonitic porphyry has been *** corresponds with the conclusions of previous studies indicating a syn-orogenic age (242±21 Ma) of the Qinling Orogenic Belt,suggesting that the formation of the Xianggou granite should be associated with the collisional event of the North China Plate and the Yangtze Plate in the Indosinian *** Xianggou granite is characterized by the high silicon and alkali of high K calc-alkaline series *** is rich in Al (Al2O3=14.49%-15.61%) and Sr (457.10-630.82 ppm),poor in Y (<16 ppm) and HREE (Yb<0.45 ppm),and exhibits high ratios of Sr/Y (76.24-97.34) and (La/Yb)N (29.65-46.10),as well as strongly fractionated REE *** geochemical characteristics suggest the Xianggou granite can be classified as C-type adakitic *** initial Sr isotope ratios for the Xianggou granite vary from 0.70642 to 0.70668,εNd(t) values from -4.54 to -3.98,and TDM values from 1152 Ma to 1220 *** low εNd(t) and ISr and high TDM values,as well as Na2O/K2O ratios of the Xianggou granite are close to 1 (Na2O/K2O=0.95-1.10),indicating that it is not an I-type adakite formed by partial melting of the subducting oceanic crust,nor adakitic rock formed by melting of the underplated basaltic lower crust,but the product of partial melting of the nonunderplated basaltic thickened lower *** from the Xianggou pluton have a homogeneous Hf isotopic composition with negative εHf(t) values (between -9.7 and -5.9,with an average of -6.9),indicating that the rock-forming materials were mostly extracted from the ancient crust,not from the depleted *** Xianggou monzonitic granitic porphyry is rich in LILE and LREE and depleted in HSFE,HREE and Y;the composition of trace element and REE are similar to those

关键词： zircon U-Pb dating Xianggou monzonitic granitic porphyry Carlin type and Carlin-like type gold deposits petrologenic and metallogenic dynamic background

Numerical investigation of compressibility effects in turbulent channel flows using large eddy simulation

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Science China(Physics,Mechanics & Astronomy) 2012年第2期55卷 305-315页

作者： lee ChunHian School of Aeronautic Sciences and Engineering Beihang UniversityBeijing 100191 China

The large eddy simulation (LES) of compressible turbulent channel flows at three different Mach numbers is performed in the present work,by extending the dynamic mixed subgrid-scale (SGS) model to compressible *** turbulent statistics agree well with those from the existing direct numerical simulation (DNS) results,indicating that the LES method established in the present work is *** analysis of the turbulent fluctuations computed by the present LES reveals that the flows considered in this work follow the Morkovin's ***,the compressibility effects are dominated by the mean field properties,and the relevant statistical ratios are invariant to the variation of Mach *** near-wall streamwise streaks are more coherent and the spacing between streaks is wider as the Mach number *** can be regarded as a direct feature characterized by the compressibility *** restrained influences of compressibility effects on the production and dissipation of the turbulence kinetic energy are also identified based on the present LES results.

关键词： compressibility channel flow large eddy simulation subgrid-scale model