KJ2007C监控分站模入口的隐患及改造

KJ2 0 0 7C监控分站在使用中模入口电阻烧毁、高电压误入等造成的危害很常见。通过重新设计 ,加强和优化了模入口的适应性 ,使故障率大为减少 。

浅球形零件拉伸凹模入口尺寸的确定

在对浅球形零件拉伸过程中凹模入口处切向压应力以及临界起皱切向压应力分析的基础上 ,针对不同凹模结构进行了内皱校核 ,证明了凹模入口尺寸对消除内皱的重要性 。

KJF23B分站模入口的扩展与使用

我矿与1999年采用现代化的核子秤计产方式取代了落后人工计产方式,原有的KJ66系统中所用KJF23B型分站的8个模拟量输入接口中核子秤占用2个口,按《煤矿安全规程》规定:KJF23B分站模拟量输入接口显得不能满足现场安全监控的需求,如装两套分站:一是造成设备浪费,二是事故点增加;在原有的分站基础上将模入口进行扩展,既能满足核子秤的需求,又能满足8个模拟量需求;经实际改用效果良好,即节约了资金,又保障了安全生产。

花键冷挤压成形过程凹模入口半角优化数值模拟

以花键挤压成形过程为研究对象,利用DEFORM-3D软件对花键的冷挤压成形过程进行模拟;以金属流动、变形程度、成形载荷和模具磨损等作为花键成形过程中的衡量指标,分别设定15°、20°、22.5°、25°和30°的不同凹模入口半角,模拟分析对花键冷挤压成形过程的影响。模拟结果表明,凹模入口半角为20°时,花键的整体成形质量最好。

拉丝模入口锥和定径带对拉拔高碳钢丝力学性能的影响

拉丝模入口锥和定径带对高碳钢丝拉拔过程中长度方向上的残余应力和力学性能都有影响。拉丝模类型主要有凹面、凸面和圆锥形的3种，定径带有圆柱形和圆锥形2种，经过对长度方向上的应力进行测试，钢丝拉拔过程中表面残余应力的最小值发生在带有网锥形定径带的凹形托丝模内。

Absorption of Sulphur Dioxide with Sodium Citrate Buffer Solution in a Rotating Packed Bed

Absorption of SO2 from a SO2/air mixture with sodium citrate buffer solution was investigated using a rotating packed bed(RPB) in laboratory scale.The effects of operating parameters,such as the rotation speed of RPB,liquid-gas ratio,inlet gas flow rate,inlet concentration of SO2 in flue gas,sodium citrate buffer concentration and initial pH of absorption solution,on the SO2 concentration in the absorption solution or removal efficiency of SO2 were examined.Incremental rate of sulfate radical ions in the absorption solution was also examined.Experimental results indicate that the efficiency of this regenerative process will be improved by using RPB under appropriate operating conditions,and the generation of SO2-4 will be restrained in the process in RPB.

Effect of auxiliary ventilations on diesel particulate matter dispersion inside a dead-end entry

Diesel particulate matter(DPM) is considered carcinogenic after prolonged exposure. This paper used computational fluid dynamics(CFD) method to study the effect of four auxiliary ventilation systems on DPM distribution in a dead-end entry with loading operation. The auxiliary ventilation systems considered include: blower fan and tubing; exhaust fan and tubing, jet fan, and push–pull system. A species transport model with buoyancy effect was used to examine the DPM dispersion pattern with unsteady state analysis. During the 200 s of the loading operation, high DPM levels were identified in the face and dead-end entry regions. This study can be used for mining engineer as guidance to design and setup of local ventilation. It can also be used for selection of DPM control strategies and DPM annual training for underground miners.

Numerical Simulation of Seaplane Wave Ground Effect with Crosswind

Under the absolute coordinate system, the unsteady Reynolds averaged Navier-Stokes(URANS)equations and the k-ω SST turbulence model are solved using the finite volume method to simulate the aerodynamic characteristics of large seaplane flying with the ground-effect above wavy surface. The velocity inlet wave-making method and the volume of fluid model are used to accurately simulate the linear regular waves and to precisely capture the free surface. This paper studies the influence of the sideslip angle on the aerodynamic characteristics of large seaplane when it is cruising above wavy water. The results show that the wave surface mainly affects the pressure distribution on the lower surface of the wing. When the sideslip angle varies from 0° to 8°,the varying of frequency of aerodynamic forces is consistent with the wave encounter frequency,and both periods are 0.6 s. With the increase of the sideslip angle,the lift coefficient and the pitching moment coefficient decrease. However,when the sideslip angle is smaller than 4°,the decrease amplitude is small,and the significant decrease occurs above 4° and during the whole process of the change of sideslip angle,the aerodynamic fluctuation amplitude is almost unchanged. As the drag coefficient increases with the increase of sideslip angle,significant increase also occurs when the value is greater than4°,and the fluctuation amplitude does not show any correlations. The rolling moment coefficient and yaw moment coefficient increase with the increase of the sideslip angle,and the fluctuation amplitudes of both increase linearly with the increase of the sideslip angle.

CFD simulation of an industrial hydrocyclone with Eulerian-Eulerian approach: A case study

In the present study, a three-dimensional computational fluid dynamics simulation together with experimental field measurements was applied to optimize the performance of an industrial hydrocyclone at Sarcheshmeh copper complex. In the simulation, the Eulerian–Eulerian approach was used for solid and liquid phases, the latter being water. In this approach, nine continuous phases were considered for the solid particles with different sizes and one continuous phase for water. The continuity and momentum equations with inclusion of buoyancy and drag forces were solved by the finite volume method. The k–e RNG turbulence model was used for modeling of turbulency. There was a good agreement between the simulation results and the experimental data. After validation of the model accuracy, the effect of inlet solid percentage, pulp inlet velocity, rod inserting in the middle of the hydrocyclone and apex diameter on hydrocyclone performance was investigated. The results showed that by decreasing the inlet solid percentage and increasing the pulp inlet velocity, the efficiency of hydrocyclone increased. Decreasing the apex diameter caused an increase in the hydrocyclone efficiency.

DPM simulation in an underground entry: Comparison between particle and species models

The diesel particulate matter(DPM) emission from diesel powered equipment in underground mines can cause health hazards including cancer to the miners. The understanding of the DPM propagation pattern under realistic mining condition is required for selecting proper DPM control strategies and to improve working practices in underground mines. In this paper, three dimensional simulations of DPM emission from the exhaust tail pipe of a load-haul-dump(LHD) vehicle and its subsequent distribution inside an isolated zone in the typical underground mine are carried out using two different solution models available in Ansys Fluent. The incoming fresh air into the isolated zone is treated as a continuous phase and DPM is treated either as a continuous phase(gas) or as a secondary discrete phase(particle). Species transport model is used when DPM is treated as gas and discrete phase model is used when DPM is assumed to behave like a particle. The distributions of DPM concentration inside the isolated zone obtained from each method are presented and compared. From the comparison results, an accurate and economical solution technique for DPM evaluation can be selected.

Ruin Probability of One Kind of Entrance Processes Based Insurance Risk Models

In this note,one kind of insurance risk models with the policies having multiple validity times are investigated.Explicit expressions for the ruin probabilities are obtained by using the martingale method.As a consequence,the obtained probability serves as an upper bound for the ruin probability of a newly developed entrance processes based risk model.

Numerical simulation on the process of saltwater intrusion and its impact on the suspended sediment concentration in the Changjiang(Yangtze)estuary

To study the relationship between sediment transportation and saltwater intrusion in the Changjiang (Yangtze) estuary, a three-dimensional numerical model for temperature, salinity, velocity field, and suspended sediment concentration was established based on the ECOMSED model. Using this model, sediment transportation in the flood season of 2005 was simulated for the Changjiang estuary. A comparison between simulated results and observation data for the tidal level, flow velocity and direction, salinity and suspended sediment concentration indicated that they were consistent in overall. Based on model verification, the simulation of saltwater intrusion and its effect on sediment in the Changjiang estuary was analyzed in detail. The saltwater intrusion in the estuary including the formation, evolution, and disappearance of saltwater wedge and the induced vertical circulation were reproduced, and the crucial impact of the wedge on cohesive and non-cohesive suspended sediment distribution and transportation were successfully simulated. The result shows that near the salinity front, the simulated concentrations of both cohesive and non-cohesive suspended sediment at the surface layer had a strong relationship with the simulated velocity, especially when considering a 1-hour lag. However, in the bottom layer, there was no obvious correlation between them, because the saltwater wedge and its inducing vertical circulation may have resuspended loose sediment on the bed, thus forming a high-concentration area near the bottom even if the velocity near the bottom was very low during the transition phase from flood to ebb.

Experiment and simulation of diffusion of micron-particle in porous ceramic vessel

The general behavior of micron-particles in the inner domain of porous ceramic vessel was simulated by computational fluid dynamics software in terms of sampling experimental data.The results show that there is an optimum porosity of 0.32 to get a higher efficiency and lower pressure drop during filtration.According to the results of simulation and experiment,it is evident that lower inlet velocity can maintain lower pressure drop and obtain higher collection efficiency and inlet concentration also has a crucial influence on the collection efficiency.The collection efficiency of equipment increases significantly with the increase of inlet concentration when the inlet concentration is less than 6.3 g/m3,but it gradually tends to be stable in the range of 97.3%-99.7%when the inlet concentration is over this concentration.

DPM dispersion inside a single straight entry using dynamic mesh model

Three-dimensional simulations of diesel particulate matter （DPM） distribution inside a single straight entry for the Load-Haul-Dump loader （LHD）-truck loading and truck hauling operations were conducted by using ANSYS FLUENT computational fluid dynamics software. The loading operation was performed for a fixed period of 3 min. The dynamic mesh technique in FLUENT was used to study the impact of truck motion on DPM distribution. The resultant DPM distributions are presented for the cases when the truck were driving upstream and downstream of the loading face. Interesting phenomena were revealed in the study including the piston effect, layering of DPM in the roof region, and backflow of diesel exhaust against ventilation. The results from the simulation can be used to determine if the areas inside the face area and straight entry exceed the current U.S. regulatory requirement for DPM concentration （〉160 pg/m3）. This research can guide the selection of DPM reduction strategies and improve the working practices for the underground miners.

The Dual Effects of Global Value Chain Embeddedness on Chinese Exports’ Technological Sophistication

This paper develops a framework for the assessment of global value chain embeddedness based on the dual structure of product embeddedness and functional embeddedness and provides a theoretical demonstration of the dual effects of the level, structure and the value sources of global value chain embeddedness on export technology sophistication. From there, the paper carries out an estimation of non-competitive input- output table using quadratic optimized algorithm with differentiation between processing trade and general trade to arrive at various indicators of foreign value-added ratio that reflect the level of global value chain embeddedness. On this basis, the panel econometric model for 27 manufacturing sectors of China between 2001 and 2010 is employed to test the effect of foreign value-added ratio on the technology sophistication of manufacturing export. Our research indicates that by taking part in division of labor in the global value chain and acquiring foreign intermediate inputs, China＇s manufacturing sector has increased its export technology sophistication. It also indicates that, compared with such inputs as raw materials and parts and components, service input has great contributions to technology improvement. With the direct contributions of foreign value-added under control, the foreign value-added from developed countries has a restrictive effect on the R＆D activities of export manufacturing, which gives rise to the one-way technology reliance on dominant enterprises of the value chain and the ＂low-end lock-up＂ effect; meanwhile, the method of embeddedness that takes advantage of the foreign value-added of other countries is more dependent on the indigenous R＆D capacity of export enterprises and thus more favorable to the improvement of export technology sophistication.

春运问题正在改善

改革开放以来，中国发生的大规模入口迁移，背后是制度变迁和经济转型的共同推动。每年的春运郜能让我们看到中国的进步与变化，但它也同时是诸多社会矛盾的集中反映，

The Net Flow of Carbon Emissions Embodied in Trade of China

Based on the most current GTAP8 database, we analyzed flow, structure and change in trade- embodied carbon emissions between China and the developed world and the developing world from 2004 to 2007 using input-output model. We found that China was always a net embodied emissions exporting country over this period. Based on the LMDI decomposition method, we found that factors influencing net embodied emissions exported from China to developed countries and developing countries differ. Trade surpluses and differences in emissions factors were vital in determining net embodied emissions exported from China to the developed world. Differences in export structures and emissions factors were key factors influencing net emissions between China and developing countries. These were closely related to respective divisions amongst developed countries, China and other developing countries in the global industrial chain. From 2004 to 2007, the export structure of China was transformed to high-end manufacturing with domestic producing technology gradually approaching the level of developed countries. With further technological improvement, industrial upgrades and export structure optimization in China, the net export of embodied carbon emissions will decrease and the driving forces of trade for China＇s domestic carbon emissions will decline.

Effects of Inlet Circumferential Fluctuation on the Sweep Aerodynamic Performance of Axial Fans/Compressors

Swept blades have been widely used in the transonic fan/compressor of aircraft engines with the aids of 3D CFD simulation since the design concept of controlling the shock structure was firstly proposed and successfully tested by Dr.Wennerstrom in the 1980s.However,some disadvantage phenomenon has also been induced by excessively 3D blade geometries on the structure stress insufficiency,vibration and reliability.Much confusion in the procedure of design practice leading us to recognize a new view on the flow mechanism of sweep aerodynamical induction: the new radial equilibrium established by the influence of inlet circumferential fluctuation(CF) changes the inlet flows of blading and induces the performance modification of axial fans/compressors blade.The view is verified by simplified models through numerical simulation and circumferentially averaged analysis in the present paper.The results show that the CF source items which originate from design parameters,such as the spanwise distributions of the loading and blading geometries,contribute to the changing of averaged incidence spanwise distribution,and further more affect the performance of axial fans/compressors with swept blades.

Numerical and experimental research on different inlet configurations of high speed centrifugal compressor

Three different inlet configurations,including a original straight pipe and two bend pipes with different axial length,for a high speed low mass flow centrifugal compressor were modeled with whole blade passages and simulated unsteadily by 3D viscous Navier-Stokes equations.The performance disparities of compressor stage were tested and verified by experiments in which dynamic pressure data acquisition of internal flow field was performed.As the result shows,the choke point decreases to lower mass flow rate due to the distortion caused by bend-pipe inlet and is aggravated as the rotation speed increases.The distortion effect spreads circumferentially in impeller and makes the flow structure varied.The longer axial distance bent inlet leads to larger radial distortion and heavy blockage at mid-span under large mass flow mainly causes compressor choke margin nar-rowed.Bend pipe distortion brings an impact up to diffuser on unsteady pressure pulsation caused by blades sweep and the impact appears more powerful when it is closer to volute tongue.

Modeling and Experimental Validation on Pressure Drop in a Reverse-flow Cyclone Separator at High Inlet Solid Loading

High inlet solid loading is one of the most important features of cyclone separators in high density circulating fluidized beds （CFB）. In this work, the effect of high solid loading on pressure drop in a reverse-flow cyclone was experimentally studied. The particles used were sand and 2zAl203. Art extended range of inlet solid loadings （M）, up to 30 kg of solids/kg of air was tested at different inlet air velocities （Vin=16~24 m/s）, well beyond the solid loading range reported before. The experiments showed that, in the tested range of solid loadings, the cyclone pressure drop decreased dramatically with increasing solid loading when M〈7.5 kg/kg and then almost remained constant. A new semi-empirical model for predicting cyclone pressure drop was also developed. The calculated and experimental results showed good agreement for particle free flow and particle laden flow.