Parallel algorithm of solidification process simulation for large-sized system of liquid metal atoms

A parallel arithmetic program for the molecular dynamics (MD) simulation study of a large sized system consisting of 50 000100 000 atoms of liquid metals is reformed, based on the cascade arithmetic program used for the molecular dynamics simulation study of a small sized system consisting of 5001 000 atoms. The program is used to simulate the rapid solidification processes of liquid metal Al system. Some new results, such as larger clusters composed of more than 36 smaller clusters (icosahedra or defect icosahedra) obtained in the system of 50 000 atoms, however, the larger clusters can not be seen in the small sized system of 5001 000 atoms. On the other hand, the results from this simulation study would be more closed to the real situation of the system under consideration because the influence of boundary conditions is decreased remarkably. It can be expected that from the parallel algorithm combined with the higher performance super computer, the total number of atoms in simulation system can be enlarged again up to tens, even hundreds times in the near future.

ON THE EXTINCTION OF POPULATION-SIZE-DEPENDENT BISEXUAL GALTON-WATSON PROCESSES

In this article, the population-size-dependent bisexual Galton-Watson processes are considered. Under some suitable conditions on the mating functions and the offspring distribution, existence of the limit of mean growth rate per mating unit is proved. And based on the limit, a criterion to identify whether the process admits ultimate extinct with probability one is obtained.

Refinement of packet size in low carbon bainitic steel by special thermo-mechanical control process

The packet size of bainitic steel can be refined by a specialrelaxation-precipitation-control phase transformation (RFC) technology. When processed by RPCprocess, the low carbon bainitic steel composes of two kinds of main intermediate transformationphases. One is ultra-fine lath-like bainitic ferrite and the lath is less than 1μm in width andabout 6 μm in length; the alignment of laths forms a refined packet, and the size of packets isabout 5-7 μm in length and about 3-4μm in width. The other is acicular structure. The morphologyand distribution of these acicular structures are influenced by relaxation process, the thin andshort acicular structures cut the prior austenite grain and refine the bainitic packet size. For theoptimum relaxation time, the packet size can be refined to the finest. The mechanical propertiesare influenced by relaxation time and the 800 MPa grade low carbon bainitic steel with excellenttoughness can be obtained by RPC process.

Relationship between Microcellular Foaming Injection Molding Process Parameters and Cell Size

In order to study the relationship between the main process parameters and the cell size,the mathematical model of cell growth of microcellular foaming injection process is built.Then numeric simulation is employed as experimental method,and the Taguchi method is used to analyze significance of effect of process parameters on the cell size.At last the process parameters are focused on melt temperature,injection time,mold temperature and pre-filled volume.The significance order from big to small of the effect of each process parameters on cell size is melt temperature,pre-filled volume,injection time,and mold temperature.On the basis of above research,the effect of each process parameter on cell size is further researched.Appropriate reduction of the melt temperature and increase of the pre-filled volume can optimize the cell size effectively,while the effects of injection time and mold temperature on cell size are less significant.

EFFECT OF PARTICLE SIZE ON THE FILMING PROCESS OF POLYSTYRENE LATEX STUDIED BY AFM

The film formation process of micro-PS particles (diameter 742 nm) and nano-PS particles (diameter 29 nm) was studied by atomic force microscopy and differential scanning calorimetry. During a step heating process, the particles were annealed for 0.5 h at each selected temperature. It was found that the deformation and interdiffusion temperatures of the micro-PS particles are ca. 120-130degreesC and 140-150degreesC, that of the nano-PS particles are 90degreesC and 100-110degreesC respectively. The DSC traces of nano-PS particles showed that there was an exothermic peak near T-g after annealing for 0.5 h at the selected temperatures below 90degreesC; otherwise, the exothermic peak disappeared after annealing at 100degreesC or above. Compared with the micro-PS particles, the sintering process of nano-PS particles occurs at much lower temperature determined by the confined state of polymer chains with higher conformational energy in nano-particles, and completes in a much narrower temperature range driven mainly by the larger total surface energy.

FLOWING FILM JIGGING FUNCTION IN THE NEW″IFFC″PROCESS FOR SEPARATING MINERALS OF ULTRAFINE SIZES

The concept of the flowing film jigging was first applied to the flowing film concentration area.The flowingfilm jigging function is an important element of the new process,in jection-flowing film centrifugation(IFFC),for separating and recovering minerals of ultrafine sizes.

Spatial Variations in Particle Size and Magnetite Concentration on Cedar Beach:Implications for Grain-Sorting Processes,Western Lake Erie,Canada

This study examined spatial variations in the concentration,grain size and heavy mineral assemblages on Cedar Beach（Lake Erie,Canada）.Magnetic studies of heavy mineral-enriched,dark-reddish sands present on the beach showed that magnetite（～150μm） is the dominant magnetic mineral.Surficial magnetic susceptibility values defined three zones：a lakeward region close to the water line（Zone 1）,the upper swash zone（Zone 2） and the region landwards of the upper swash zone （Zone 3）.Zone 2 showed the highest bulk and mass susceptibility（κ,χ） and the highest mass percentage of smaller grain-size（250μm） fractions in the bulk sand sample.Susceptibility（i.e.κandχ） values decreased and grain size coarsened from Zone 2 lakewards（into Zone 1） and landwards （into Zone 3）,and correlated with the distribution of the heavy mineral assemblage,most probably reflecting preferential separation of large,less dense particles by waves and currents both along and across the beach.The eroded western section of Cedar Beach showed much higher concentrations of heavy minerals including magnetite,and finer sand grain sizes than the accreting eastern section, suggesting that magnetic techniques could be used as a rapid,cost-effective way of examining erosion along sensitive coastline areas.

Successive defects asymmetric simple exclusion processes with particles of arbitrary size

This paper uses various mean-field approaches and the Monte Carlo simulation to calculate asymmetric simple exclusion processes with particles of arbitrary size in the successive defects system. In this system, the hopping probability p （p 〈 1） and the size d of particles are not constant, Through theoretical calculation and computer simulation, it obtains the exact theoretical results and finds that the theoretical results are in agreement with the computer simulation. These results are helpful in analysing the effect of traffic with different hopping probabilities p and sizes d of particle.

A method of manufacturing process modeling based on activity network for large-sized and complex products

Simulation technique is an efficient approach to realize the planning and scheduling of manufacturing process of products. An appropriate and efficient manufacturing process model is the basis and key of manufacturing process simulation. By analyzing the features of large-sized and complex products, a method of manufacturing process modeling based on activity network is presented and a mapping algorithm of translating BOM/BOP into the manufacturing process model is designed in detail.

Optimal Size for Maximal Energy Efficiency in Information Processing of Biological Systems Due to Bistability

Energy efficiency is closely related to the evolution of biological systems and is important to their information processing. In this work, we calculate the excitation probability of a simple model of a bistable biological unit in response to pulsatile inputs, and its spontaneous excitation rate due to noise perturbation. Then we analytically calculate the mutual information, energy cost, and energy efficiency of an array of these bistable units. We find that the optimal number of units could maximize this array＇s energy efficiency in encoding pulse inputs, which depends on the fixed energy cost. We conclude that demand for energy efficiency in biological systems may strongly influence the size of these systems under the pressure of natural selection.

Simulation of fluid-structure interaction in a microchannel using the lattice Boltzmann method and size-dependent beam element on a graphics processing unit

Fluid-structure interaction （FSI） problems in microchannels play a prominent role in many engineering applications. The present study is an effort toward the simulation of flow in microchannel considering FSI. The bottom boundary of the microchannel is simulated by size-dependent beam elements for the finite element method （FEM） based on a modified cou- ple stress theory. The lattice Boltzmann method （LBM） using the D2Q13 LB model is coupled to the FEM in order to solve the fluid part of the FSI problem. Because of the fact that the LBM generally needs only nearest neighbor information, the algorithm is an ideal candidate for parallel computing. The simulations are carried out on graphics processing units （GPUs） using computed unified device architecture （CUDA）. In the present study, the governing equations are non-dimensionalized and the set of dimensionless groups is exhibited to show their effects on micro-beam displacement. The numerical results show that the displacements of the micro-beam predicted by the size-dependent beam element are smaller than those by the classical beam element.

液压支架立柱防冲吸能构件优化仿真及压溃实验研究

液压支架作为煤炭开采主要支护设备,经常受到冲击地压影响,防冲吸能构件起到保护液压支架作用,为获得更大的初始支反力峰值与吸能量、更小的支反力分散度,对吸能构件参数细化并通过ABAQUS有限元软件进行吸能构件的建模与压溃冲击仿真,获取吸能构件的吸能性能及屈曲变形形态,验证最优尺寸的吸能性能;对比吸能构件平均支反力的预测数据与有限元仿真数据,误差在15%以内,最优尺寸构件的平均支反力模型预测误差为−3.40%,验证吸能构件预测模型所预测数据较为准确;搭建吸能构件压溃实验台,选择5种加载速度,以准静态压溃方式对定制加工的吸能构件进行轴向加载压溃实验,实验结果表明:不同加载速度轴向压溃实验,支反力波动基本一致,最大初始支反力峰值为2253.52 kN,最大支反力标准差为206.23 kN,最小初始支反力峰值为2096.26 kN,最小支反力标准差为189.83 kN,初始支反力峰值的平均值为2149.32 kN,支反力标准差平均值为196.77 kN;不同压溃速度下的轴向压溃实验数据与吸能构件有限元仿真数据对比,初始支反力峰值、支反力标准差的相对误差分别为5.6%、11.07%;对最优尺寸吸能构件通过预测模型法、有限元仿真法、压溃实验法三种方法进行吸能性能分析,预测模型法的平均支反力为1879.7 kN,有限元仿真法的平均支反力为1945.9 kN,压溃实验法平均支反力为1919.8 kN,预测模型误差3.41%,压溃实验误差−1.3%,通过3种方法的数据验证结果,证明了吸能构件分析方法的可靠性和可行性。

激光熔化沉积Al-Mg-Sc-Zr合金晶粒尺寸预测及成形工艺优化

通过激光熔化沉积试验分析了工艺条件(送粉速度、扫描速度和激光功率)对Al-Mg-Sc-Zr合金晶粒尺寸的影响,构建了晶粒尺寸预测模型,优化了成形工艺参数,给出了工艺参数最佳区间。结果表明,相较于激光功率和扫描速度,送粉速度对晶粒尺寸的影响最为显著;随着成形能量密度的增加,合金晶粒尺寸呈现出先减小后增大的演变趋势;采用回归方程构建的晶粒尺寸-工艺参数关系模型能准确预测不同工艺条件下激光熔化沉积Al-Mg-Sc-Zr合金的平均晶粒尺寸,相对误差小于2%;通过响应面分析得到工艺参数最佳区间为:送粉速度2.8~3 g·min^(-1)、激光功率1000~1050 W、扫描速度4~5 mm·s^(-1)。

PERFORMANCE-DRIVEN BUSINESS PROCESS MANAGEMENT METHODOLOGY FOR SMALL AND MEDIUM SIZED-ENTERPRISES

Based on the analysis of the common limitations of business processmanagement (BPM) methodologies and the requirements of small and medium sized-enterprises (SMEs),the importance of a 'performance construct' of BPM methodologies is identified, a six-phaseperformance-driven BPM methodology for the production and operation processes of Chinese SMEs isdeveloped. A case study on the process management of a medium-sized enterprise shows a successfulexample of running the methodology.

南芬选矿厂综合尾矿工艺矿物学研究

南芬选矿厂为实现综合尾矿的回收利用及为合理选择选矿工艺及参数提供参考,以综合尾矿为研究对象,采用MLA矿物自动分析系统进行了尾矿矿物学特性研究。研究结果表明:综合尾矿全铁品位为9.64%,铁主要以赤、褐铁矿的形式存在,分布率为63.49%;其次以磁铁矿的形式存在,分布率为12.20%;主要脉石矿物为石英、镁铁闪石、绿泥石和透闪石,其他矿物含量少。磁、赤铁矿的嵌布粒度-75μm含量占85.71%,单体解离度为63.88%;其中,单体的磁、赤铁矿包裹少量石英,被包裹的磁、赤铁矿则主要被石英等矿物包裹,富连生体中含有较多的石英和少量的菱铁矿。

稀缺主焦煤高效重介分选工艺在吕家坨矿选煤厂的应用

针对吕家坨矿选煤厂原生产工艺存在的问题,分析了入选原煤煤质特性,采用超宽粒级原煤三产品重介质旋流器选煤工艺、新型煤泥重介质旋流器选煤技术-反分流分选工艺、粗精煤泥两段弧形筛组合脱泥回收技术进行技术改造。改造后工艺系统指标检测结果表明,改造可提高综合精煤产率1.78%,增加税前利润10573.2万元。

烟丝加工过程中的破碎规律研究

为探索烟丝在加工过程中的破碎规律,设计不同切丝宽度和尺寸的烟丝,研究滚筒、流态化、机械输送等关键加工环节前后烟丝的结构变化规律。结果表明,随着烟丝加工进行,各规格烟丝不断破碎,烟丝的特征尺寸降低,破碎度升高,主要表现在>7.10 mm和4.50~7.10 mm等尺寸较长的烟丝质量分数不断降低,<2.00 mm的烟丝质量分数不断升高,不同处理间3.35~4.50 mm的烟丝质量分数变化差异最大。滚筒加工过程中烟丝质量分数的变化率整体较大,其中滚筒干燥过程最大,其次是振动输送、干燥后的提升输送和风送过程,风选和干燥前的提升等过程较小。加工后1.0 mm宽度烟丝、1.0 mm宽度断丝的烟丝、0.8 mm宽度烟丝和0.8 mm宽度断丝的烟丝特征尺寸变幅分别达到1.86 mm、1.09 mm、1.65 mm和1.08 mm,其破碎度分别达到33.51%、26.35%、33.39%和27.43%。综上,>7.10 mm和4.50~7.10 mm等特征尺寸较大及同一断丝或未断丝处理下宽度较窄的烟丝在加工过程中更易破碎,应根据加工的需求,关注特定尺寸的烟丝质量变化规律,在原料消耗允许的范围内,开展烟丝结构调控和工艺优化。

热处理工艺对大规格TC17钛合金棒材组织与力学性能的影响

研究了固溶温度、冷却方式、保温时间及取样方向对两相区锻造的大规格TC17钛合金棒材显微组织和力学性能的影响,并根据实验结果选择最佳热处理制度。结果表明:TC17钛合金棒材的最佳热处理工艺为800℃/2h/WQ+630℃/8h/AC;固溶温度在两相区时,随着固溶温度的升高,合金强度升高,塑性降低;固溶空冷+时效的合金较相同温度固溶水冷+时效的合金强度高、塑性低;在相同温度固溶水冷条件下,缩短固溶保温时间,可改善合金的塑性;锻造后的TC17钛合金大规格棒材存在各向异性。

微生物去除加工晶体铜的表面质量实验研究

通过跟踪微生物去除加工两类不同晶粒尺寸纯铜的表面粗糙度和表面形貌的变化规律,研究了微生物去除加工表面的形成机理。结果表明,纯铜加工表面质量会随着微生物去除加工时间的增加而变差,晶粒粒度会对其微生物加工表面质量产生影响;不同的工件原始表面质量对微生物去除加工初始阶段的表面质量有明显影响;前期机械加工所形成的划痕会随着微生物去除加工而逐渐变小,当机械作用表面被去除后,影响微生物加工表面质量的主要因素是工件的晶界及亚晶界。

骨料粒径对混凝土Ⅰ型断裂裂缝扩展影响研究

为研究不同骨料粒径混凝土Ⅰ型断裂裂缝扩展特性,开展了骨料粒径为10、20、30、40 mm的混凝土三点弯曲梁断裂试验;结合数字图像相关技术(digital image correlation, DIC)测得试件表面计算区域全场位移变化数据;对不同骨料粒径混凝土断裂能、断裂韧度、断裂过程区(fracture process zones, FPZ)变化和发展进行研究,探讨了FPZ扩展过程与峰后荷载之间的关系。结果表明:随着骨料粒径增大,试件峰值荷载和断裂参数均呈现先增大后减小的趋势,M20试件FPZ长度的变化与峰后荷载的变化有很强的关联性,其骨料对微裂缝扩展的约束效果最好;此外,通过分析不同骨料粒径混凝土试件FPZ的发展规律,可知,骨料粒径为20 mm的混凝土试件,其峰后局部变形能力得到了改善,断裂能及断裂韧度得到了提高,在断裂过程中具有比其他骨料粒径混凝土更高的承载力和更小的FPZ,因此,合适的骨料粒径为20 mm。