基于多核处理器的程序性能优化方法

多核处理器即在一个处理器芯片上集成多个处理器核心,可同时执行多个线程。虽然多核处理器中每个核的时钟频率没有增加,但多个核的并行处理提供了远比单核强大的计算能力,同时,也大大提高了CPU的设计复杂性,基于现代处理器的设计技术,结合程序的实现过程,探讨优化程序性能的几种方法,提升程序编写质量,提高执行效率。     

用表面活性剂提高生物滴滤床净化废气中氯苯的性能

A laboratory-scale trickling biofilter column,filled with Raschig rings and inoculated with Pseudomonas putida (ATCC 1785)was used to purify chlorobenzene contained waste gases.Sodium dodecyl sulfonate(SDS)was used to enhance the performance of trickling biofllter.Purification performance of the trickling biofilter was examined for chlorobenzene inlet concentration of 1.20～5.04 g/m~3 at different EBRTs between 76～153 s.Without SDS addition,with simultaneous increase in chlorobenzene inlet loading rate and gas flow rate,100% removal efficiency was achieved at EBRT of 109 s and inlet loadings below 5120 mg/m~3.Addition of SDS to nutrient solution led to improvement of trickling biofilter purification performance. By introducing 25 mg/L SDS,the removal efficiency was increased by 21% and elimination capacity up to 234 g/(m~3.h)was achieved at chlorobenzene inlet loading of 241 g/(m~3.h).Although SDS concentration experienced a low rate reduction after continuous nutrient solution recirculation,this result has little influence on trickling biofilter's removal efficiency in monitoring period.     

空调表冷器热工性能测试的实现及分析

介绍了一种自行研制的空调表冷器热工性能测试系统,该系统是通过对实验室现有空气调节处理过程实验台进行改造制得。在压缩机和节流阀之间装设套管式蒸发器,制得冷冻水,经水泵送入表冷器中,与空气进行换热后重新返回套管式蒸发器中。通过温控器实现表冷器入口冷冻水温度的控制,表冷器进出口冷冻水温通过布置热电偶进行测量,冷冻水流量通过转子流量计进行测量,利用原有干湿球温度计测量空气进出口干湿球温度,进而在不同工况下实现表冷器析湿系数、热交换效率、接触系数和换热量的测试。依据测试结果分析风量、风速、冷冻水流量对表冷器热工性能的影响。     

高压管式反应器夹套跨管泄漏失效的数值分析

为了探究高压管式反应器夹套跨管失效机理,在进行表观分析的基础上,采用数值计算的方法,对跨管内脱盐水流动进行了分析。结果表明,由于水流的90°转向,在跨管入口产生严重的偏流效应,而偏流又导致水流的局部增速和集中冲刷,致使跨管入口部分冲刷严重,在弯管入口处内侧产生剪切应力极值区,导致泄漏失效。     

Investigation of Separated Flow around a Curved Air Intake

Nomenclaturex,y,g,11Cartcsiatlandcurvilinearcoordinatesif,v,U.j,'physicalvelocitycomponentsandcontl'avat7ian[velocitycomponCntsk,eturbulen[bineticcnet'gyanditsdissipationA)nl,nctlturbulent,lanlinarandof'l'ectivcviscositiesfdin\lsioncoel'tlcientRe.,Reynold…     

Numerical study on viscosity reduction in mining heavy oil by circulating hot water

Viscosity reduction is an important process in mining heavy oil.To predict the temperature variation and viscosity variation of heavy oil in flow direction,computational fluid dynamics(CFD) was adopted to simulate the process of heat transfer and flow in this paper.Moreover,an objective function,namely viscosity reduction efficiency,was established to analyze the effect of viscosity reduction.The results indicate that circulating hot water can reduce viscosity significantly,and that the effect of viscosity reduction depends on the inlet temperature and inlet volumetric flow rate of hot water.There is a maximum temperature of heavy oil in flow direction.With the inlet volumetric flow rate of 2.0m3/h and the inlet temperatures of 60,℃,70,℃ and 80,℃,viscosity reduction efficiencies are 94.6%,96.7% and 97.3%,respectively.With the inlet temperature of 70,℃ and the volumetric flow rates of 1.5m3 /h,2.0 m3/h and 2.5m3/h,viscosity reduction efficiencies are 94.4%,96.7% and 97.2%,respectively.     

Second Law of Thermodynamics Analysis of TranscriticalCarbon Dioxide Refrigeration Cycle

In order to identify the locations of irreversible loss within the transcritical carbon dioxide refrigeration cycle with an expansion turbine, a method with respect to the second law of thermodynamics based on exergy analysis model is applied. The effects of heat rejection pressures, outlet temperatures of gas cooler and evaporating temperatures on the exergy loss, exergy efficiency and the coefficient of performance (COP) of the expansion turbine cycle are analyzed. It is found that the great percentages of exergy losses take place in the gas cooler and compressor. Moreover, heat rejection pressures, outlet temperatures of gas cooler and evaporating temperatures have strong influence on the exergy efficiency, COP and the exergy loss of each component. The analysis shows that there exists an optimal heat rejection pressure corresponding to the maximum exergy efficiency and COP, respectively. The results are of significance in providing theoretical basis for optimal design and the control of the transcritical carbon dioxide system with an expansion turbine.     

逆流降膜除湿器除湿过程的数值研究

建立了模拟逆流降膜除湿过程传热传质的数学模型,给出了传热传质的控制方程和适当的边界条件和气液界面条件.采用氯化钙作为除湿剂,运用控制容积法对降膜除湿溶液与被处理空气之间的除湿过程进行了分析和计算.获得了相应的除湿溶液与被处理空气的速度场、温度分布和出口参数.计算结果表明:沿着除湿器高度方向溶液和空气的温度、溶液的浓度、空气的湿度在入口区域变化较快而在出口区域变化较慢.可分别通过增加竖壁的高度、溶液的入口浓度和溶液的流速来改善除湿过程;同样,也可通过降低空气的流速或空气入口湿度达到改善除湿过程的目的.研究结果有利于改进除湿器的性能,为太阳能液体除湿、空调系统的优化设计和运行调节提供了理论依据.     

Mental computation performance in Australia,Japan and the United States

The study was conducted to explore performance on a variety of mental computation tasks using two presentation formats (visual and oral). Students at four grade levels between grades 2 and 9 in three countries (Australia, Japan, United States) were given a group administered mental computation test consisting of two parts (oral presentation format, visual presentation format).The sample of nearly 2000 students represents 6 classes at each of four grade levels in each country. Results indicate a wide variation in performance within the sample of each country at each grade level. Differences in performance between countries are also apparent and may reflect variations in instructional focus on mental computation. In particular, Japanese students perform at a higher level at the early grades than do students in either of the other countries sampled. However, by grade 8 this difference narrows in the American sample, and vanishes for the Australian sample. Differences in performance related to presentation format were dramatic for particular items and non-existent for other items. The most consistent effect was found in the Japanese sample where the visual presentation format resulted in higher performance levels on most items.It is hypothesised that superior results on visually presented items are attributable to a greater reliance on use of the standard written algorithm, while superior results on orally presented items indicate a greater tendency to use invented mental algorithms.     

Computational fluid dynamic simulation of an inter-phasing pulse tube cooler

An inter-phasing pulse tube cooler （IPPTC） consists of two pulse tube units, which are connected to each other at hot ends of the pulse tubes through a needle valve. This paper presents the computational fluid dynamic （CFD） results of an IPPTC using a 2D axis-symmetrical model. General results such as the phase difference between pressure and velocity at cold end and hot end, the temperature profiles along the wall, the available lowest temperature as well as its oscillations and the coefficient of performance （COP） for IPPTC are presented. The formation of DC flow and its effects on the performance of the cooler are investigated and analyzed in detail. Turbulence, which is partially responsible for the poor overall performance of a single orifice pulse tube cooler （OPTC）, is found to be much reduced in IPPTC and its performance is improved significantly compared with the single OPTC.     

Restaurant emissions removal by a biofilter with immobilized bacteria

INTRODUCTION Restaurant emission is a pollutant to atmosphereand human body. Polycyclic aromatic hydrocarboncontained in oil smoke directly induces lung andbladder cancer (Chen and Ye, 1991; Gupta et al.,2001; Lutz, 1982). According to former researches(Kleinerman et al., 1999; Liu et al., 1987), oil smokecontains many harmful substances that can induce notonly general diseases but also gene mutation, DNAdamage and immune function impairment, and manyingredients such as fatty ac…     

Numerical investigation on the flow and power of small-sized multi-bladed straight Darrieus wind turbine

Straight Darrieus wind turbine has attractive characteristics such as the ability to accept wind from random direction and easy installation and maintenance. But its aerodynamic performance is very complicated,especially for the existence of dynamic stall. How to get better aerodynamic performance arouses lots of interests in the design procedure of a straight Darrieus wind turbine. In this paper,mainly the effects of number of blades and tip speed ratio are discussed. Based on the numerical investigation,an assumed asymmetric straight Darrieus wind turbine is proposed to improve the averaged power coefficient. As to the numerical method,the flow around the turbine is simulated by solving the 2D unsteady Navier-Stokes equation combined with continuous equation. The time marching method on a body-fitted coordinate system based on MAC (Marker-and-Cell) method is used. O-type grid is generated for the whole calculation domain. The characteristics of tangential and normal force are discussed related with dynamic stall of the blade. Averaged power coefficient per period of rotating is calculated to evaluate the eligibility of the turbine.     

Experimental evaluation of the effect of an internal heat exchanger on a transcritical CO2 ejector system

This study presents experimental results focused on a performance comparison of a transcritical CO₂ ejector system without an internal heat exchanger (IHX) (EJE-S) to a transcritical CO₂ ejector system with an IHX (EJE-IHX-S). The comparison includes the effects of changes in operating conditions such as cooling water flow rate and inlet temperature. Experiments are conducted to assess the influence of the IHX on the heating coefficient of performance (COP_r), heating capacity, entrainment ratio, pressure lift, and other parameters. The primary flow rate of the EJE-IHX-S is higher than that of the EJE-S. The pressure lift and actual ejector work recovery are reduced when the IHX is added to the transcritical CO₂ ejector system. Using a more practical performance calculation, the compression ratio in the EJE-S is reduced by 10.0%–12.1%, while that of EJE-IHX-S is reduced only by 5.6%–6.7% compared to that of a conventional transcritical CO₂ system. Experimental results are used to validate the findings that the IHX weakens the contribution of the ejector to the system performance.     

Predictive control of a direct internal reforming SOFC using a self recurrent wavelet network model

In this paper, an application of a nonlinear predictive controller based on a self recurrent wavelet network （SRWN） model for a direct internal reforming solid oxide fuel cell （DIR-SOFC） is presented. As operating temperature and fuel utilization are two important parameters, the SOFC is identified using an SRWN with inlet fuel flow rate, inlet air flow rate and current as inputs, and temperature and fuel utilization as outputs. To improve the operating performance of the DIR-SOFC and guarantee proper operating conditions, the nonlinear predictive control is implemented using the off-line trained and on-line modified SRWN model, to manipulate the inlet flow rates to keep the temperature and the fuel utilization at desired levels. Simulation results show satisfactory predictive accuracy of the SRWN model, and demonstrate the excellence of the SRWN-based predictive controller for the DIR-SOFC.     

U型真空管集热器温度场的模拟分析

建立和分析了U型真空管集热器的热效率的表达式,并在FLUENT中建立动态仿真模型,利用模型分析了U型管的入口流速和结构尺寸、太阳辐照度对真空管内温度场的影响.结果表明:减小入口流速和U型管内径、增加太阳辐射量和U型管的长度都可以使真空管的出口平均温度增高.该分析结果可对U型玻璃真空管的优化设计、参数匹配等方面提供理论支撑.     

Dynamic Distribution Model with Prime Granularity for Parallel Computing

Dynamic distribution model is one of the best schemes for parallel volume rendering. However, in homogeneous cluster system, since the granularity is traditionally identical, all processors communicate almost simultaneously and computation load may lose balance. Due to problems above, a dynamic distribution model with prime granularity for parallel computing is presented. Granularities of each processor are relatively prime, and related theories are introduced, A high parallel performance can be achieved by minimizing network competition and using a load balancing strategy that ensures all processors finish almost simultaneously, Based on Master-Slave-Gleaner （ MSG） scheme, the parallel Splatting Algorithm for volume rendering is used to test the model on IBM Cluster 1350 system. The experimental results show that the model can bring a considerable improvement in performance, including computation efficiency, total execution time, speed, and load balancing.     

混流式水轮机主要过流部件设计概要

设计性能优良的过流部件是水轮机设计的一项重要内容.本文以混流式水轮机为例,概述了主要过流部件基本设计思想,并说明在过流部件设计方案中引入CFD进行分析,能较快地实现设计目标,并可以从CFD给出的分析结果中拓展设计思路,探索新的设计方法.     

Study on performance of a packed bed latent heat thermal energy storage unit integrated with solar water heating system

INTRODUCTION Efforts of rational and effective energy man-agement, as well as environmental considerations, increase the interest in using renewable energy sources, especially solar energy. Because of discrep-ancy between the energy supply and demand in solar heating applications, a thermal energy storage (TES) device has to be used for the most effective utilization of the energy source. Energy storage combined with solar collectors and photovoltaic systems have been developed over the…     

Free-Interface Dual-Compatibility Modal Synthesis Substructure Method in Large-Scale Structures

Free-interface dual-compatibility modal synthesis method(compatibility of both force and displacement on interfaces)is introduced to large-scale civil engineering structure to enhance computation efficiency. The basic equations of the method are first set up, and then the mode cut-off principle and the dividing principle are proposed. MATLAB is used for simulation in different frame structures. The simulation results demonstrate the applicability of this substructure method to civil engineering structures and the correctness of the proposed mode cut-off principle. Studies are also conducted on how to divide the whole structure for better computation efficiency while maintaining better precision. It is observed that the geometry and material properties should be considered, and the synthesis results would be more precise when the inflection points of the mode shapes are taken into consideration. Furthermore, the simulation performed on a large-scale high-rise connected structure further proves the feasibility and efficiency of this modal synthesis method compared with the traditional global method. It is also concluded from the simulation results that the fewer number of DOFs in each substructure will result in better computation efficiency, but too many substructures will be time-consuming due to the tedious synthesis procedures. Moreover, the substructures with free interface will introduce errors and reduce the precision dramatically, which should be avoided.     

Regulation law of turbine and generator in organic Rankine cycle power generation experimental system

In the performance experiment of organic Rankine cycle power generation experimental system, the loadresistance-regulation method is one of the most important regulation methods. However, the regulation law has not been clear enough to guide the experiment, which is unfavorable to the experimental research on organic Rankine cycle. In this paper the regulation law of turbine and generator by the load-resistance-regulation method is studied theo- retically and experimentally. The results show that when the thermal cycle parameters keep constant, the turbine speed increases with the increase of load resistance and there is a maximum value of transmission-generator efficiency with the variation of the turbine speed; when the turbine speed and generator speed keep constant, the transmissiongenerator efficiency decreases and gradually tends to zero with the increase of load resistance.