加倍地做好自己的事情

改革开放以来,中国经济的高速发展引起全世界的高度关注,也一路伴随着西方发达国家对逆差、汇率、质量、环保、人权等方面的不断施压.而近来,随着部分别有用心之人利用火炬接力把北京奥运肆无忌惮地政治化,使双方的情绪也达到了对立新高潮.     

论网络时代医药企业的营销决策

传统的营销方式在网络时代已经不再占有优势,网络时代的营销也不仅仅是做个网站来展示自己的商品,而是通过人性化的服务来进一步推销自己的产品.传统意义上的市场营销,是指个人和群体通过创造并同他人交换产品和价值,以满足需求和欲望的一种社会和管理过程.     

三地路演,带来一路震撼——记2007年世冠AMESim车辆行业技术研讨会

在路演上海专场,笔者有幸与IMAGINE市场及销售总监Olivier DATRY、特种热动力应用事业部经理Cedric ROMAN、区域技术经理David MARAND及世冠公司总经理李京燕女士进行了深层次的交流.     

本地化,服务于中国用户——SolidWorks"老兵"写"新传"

作为SolidWorks在中国华南的增值软件经销商,智诚科技(ICT)公司一直以推动整个制造韭技术发展为己任,以先进的设诗理念引导中国的制造业紧跟世界最新潮流为目标.     

A hybrid time-delay prediction method for networked control system

This paper presents an Ethernet based hybrid method for predicting random time-delay in the networked control system.First,db3 wavelet is used to decompose and reconstruct time-delay sequence,and the approximation component and detail components of time-delay sequences are fgured out.Next,one step prediction of time-delay is obtained through echo state network(ESN)model and auto-regressive integrated moving average model(ARIMA)according to the diferent characteristics of approximate component and detail components.Then,the fnal predictive value of time-delay is obtained by summation.Meanwhile,the parameters of echo state network is optimized by genetic algorithm.The simulation results indicate that higher accuracy can be achieved through this prediction method.     

多起典型网络安全事件被成功处理——CNCERT/CC2007年网络安全事件处理部分案例介绍

恶意代码事件处理"Nimaya(熊猫烧香)"病毒事件处理"Nimaya(熊猫烧香)"病毒在2007年初出现流行趋势。该病毒具有感染、传播、网络更新、发起分布式拒绝服务攻击(DDoS)等功能。     

知识资本:中国参与全球创新网络的关键

对于当前世界发达经济实体中的领袖而言,中国到底是威胁还是机遇?在全球商业、工业、政府和学术观察人士中间,这一争论仍在延续.中国在全球工业中的显著作用已经无庸讳言.今天,中国制造了世界上50%的照相机、30%的空调和电视机、25%的洗衣机及接近23%的冰箱.制造业占中国GDP的53%,出口额的90%,进口额的85%以及吸引投资额的70%.中国是世界上(继美国、日本和德国之后)的第四大生产国,并正以惊人的增长速度向前发展.     

整合江湖谁称霸 AMD 780G对决NVIDIA MCP78

AMD 780G 作为超威派7系列整合芯片组掌门人,AMD 780G算得上乱世英雄,因为它是首款正式上市的DirectX 10整合主板,引领着整合江湖进入到另一个新"视"界.这款芯片组全面支持新一代K10处理器,支持Hyper Transport 3.0总线与PCI-E2.0显卡插槽,并且内建了性能等效于Radeon HD2400 PRO的显示核心,从而全面支持UVD高清解码引擎.另外,这款整合芯片组还特别对混合交火技术提供支持,从而让AMD 780G这位独行侠行走江湖一段时间后,便获得了众多派别的鼎立相助,江湖地位日渐攀升.     

单位局域网中ARP攻击的故障处理

1故障现象公安部上海消防研究所11台接入层交换机通过一台交换机和路由器进行级联,接入层交换机类型为ZXR102826(以下简称2826)。设备自开通两年以来一直运行正常,用户上网和下载上传均正常,但是在某个时刻该11台交换机上的40%用户无法上网,表现为打开网页出现"Internet Explorer不能链接到您请求的网页。此页可能暂时不可用。",但其余用户能正常上网,但表现为上网速度大幅度下降。     

中国Linux软件产业生机勃勃2008年Q1中国Linux软件市场销售额同比增长22.6%

根据赛迪顾问发布的<2008年第一季度中国Linux软件市场分析报告>数据显示,2008年一季度,中国Linux软件市场销售额达3800万元,较去年同期增长22.6%,在整个操作系统市场中继续保持快速增长势头.与Unix在整个非嵌入式操作系统中比重下滑相比,Linux则小幅上升0.2个百分点,显示出Linux产业的勃勃生机.这既得益于国家宏观经济的良好走势,同时也与近年来Linux市场产业链生态环境的改善密切相关.     

热泵相变储热器动态特性分析及强化传热研究

热泵相变储热器传输过程具有动态性,提出基于四阶动态响应特性分析的热泵相变储热器动态特性分析及强化传热模型。构建热泵相变储热器的欠阻尼振荡输出特征分析模型,以系统功率突变为控制状态约束对象进行热泵相变储热器动态驱动响应模拟,采用二项单调衰减分量、二项欠阻尼振荡分量作为控制约束变量进行热泵相变储热器动态强化传输控制,建立热泵相变储热器的输出功率调制模型,结合热泵相变储热器动态状态量初始值及变化值进行强化传热过程控制,提高热泵相变储热器的输出性能。仿真结果表明,采用该模型进行热泵相变储热器的输出动态控制能力较好,强化传输的输出增益较高,提高了热泵相变储热器的输出响应能力。     

压电风扇与散热器组合系统的散热性能及其改进

为提高散热器的散热性能,将压电风扇分别与直肋和针肋式散热器组合进行散热,利用FLUENT软件仿真其散热流场并计算其协同角,分析2种散热器的散热性能特点。考虑压电风扇的振动特性,将直肋式散热器的肋片改为扇形布置,并根据仿真结果进一步将该散热器扇形肋片的后端改为针肋,设计新型散热器。根据散热器温度和协同角分布对散热器的散热性能进行评价分析,结果表明：自然散热时,针肋散热器的散热性能最好,且协同角相对较小;当压电风扇工作时,新型散热器散热性能最好,可比原直肋散热器组合温度降低4 K,比原针肋散热器组合温度降低2 K。新型散热器仅通过改变散热器的肋片布置即可明显改善散热器的散热性能。     

Optimal Configuration and Performance of Heat Engines with Heat Leak and Finite Heat Capacity

The optimal configuration of a class of two-heat-reservoir heat engine cycles in which the maximum work output can be obtained under a given cycle time is determined with the considerations of heat leak, finite heat capacity high-temperature source and infinite heat capacity low-temperature heat sink. The heat engine cycles considered in this paper include: (1) infinite low- and high-temperature reservoirs without heat leak, (2) infinite low- and high-temperature reservoirs with heat leak, (3) finite high-temperature source and infinite low-temperature sink without heat leak, and (4) finite high-temperature source and infinite low-temperature sink with heat leak. It is assumed that the heat transfer between the working fluid and the reservoirs obeys Newton's law. It is shown that the existence of heat leak doesn't affect the configuration of a cycle with an infinite high-temperature source. The finite heat capacity of a high temperature source without heat leak makes the cycle a generalized Carnot heat engine cycle. There exists a great difference of the cycle configurations for the finite high-temperature source with heat leak and the former three cases. Moreover, the relations between the optimal power output and the efficiency of the former three configurations are derived, and they show that the heat leak affects the power versus efficiency characteristics of the heat engine cycles.     

微通道换热器的数值模拟和结构优化

为提高微通道换热器的换热效率,利用COMSOL耦合求解流动和传热方程,对微通道换热器换热特征进行数值模拟.通过分析微通道换热器的温度、微通道的入口与出口的压差以及微通道换热器的总热阻等参数,对其换热性能进行评估.优化微换热器的几何结构可以有效提高换热性能.数值模拟结果表明：当微通道的高宽比为0.8、微通道与间隔的宽度比为0.6、微通道数为71时热阻最小,换热性能最佳.     

基于聚四氟乙烯表面滴状冷凝的传热分析

表面材料对滴状冷凝传热影响很大,本文建立聚四氟乙烯复合材料表面传热的数学物理模型,分析滴状冷凝的传热机理,计算表面液滴和液膜的冷凝传热,获得冷凝面的总传热系数.应用ANSYS软件模拟液滴,液膜传热,液膜区换热对整体滴状冷凝影响很大.     

Design and fabrication of a cross flow micro heat exchanger

A cross flow micro heat exchanger was designed to maximize heat transfer from a liquid (water-glycol) to a gas (air) for a given frontal area while holding pressure drop across the heat exchanger of each fluid to values characteristic of conventional scale heat exchangers. The predicted performance for these plastic, ceramic, and aluminum micro heat exchangers are compared with each other and to current innovative car radiators. The cross flow micro heat exchanger can transfer more heat/volume or mass than existing heat exchangers within the context of the design constraints specified. This can be important in a wide range of applications (automotive, home heating, and aerospace). The heat exchanger was fabricated by aligning and then bonding together two identical plastic parts that had been molded using the LIGA process. After the heat exchanger was assembled, liquid was pumped through the heat exchanger, and minimal leakage was observed     

Optimal Allocation of Heat Exchanger Investment

The optimal allocation of a given investment capital to the heat exchanging inventory is studied for heat engines, refrigerators and heat pumps. The study is based on an endoreversible model operating between two constant temperature heat reservoirs at optimal thermodynamic performance, which is either minimal entropy production or maximum power production. The analysis accounts for the fact that the actual costs of heat exchangers equipment is subject to the material, design and operating conditions of the heat exchangers so that the dependence between the costs and heat transfer coefficients generally needs to be considered as nonlinear and different for the hot and cold side of the system. Contrary to existing results showing no difference between cyclic and stationary operation for Newtonian heat transfer we find one. This result also pertains to non-Newtonian heat transfer.     

MPTL板翅式换热器性能的数值分析

研究机械泵驱动的两相冷却回路(MPTL)换热器传热效能优化问题,由于换热器的应用环境极为复杂,目前的实验数据极度匮乏,而且结构特殊,现有的标准叉流板式换热器的设计方法并不适用。为了提出可行的设计优化方法,针对某典型MPTL板翅式换热器,建立一种简化的三维物理数学模型,采用有限体积法及流固耦合方法深入研究该换热器在典型结构及设计工况下的流场特性,随后研究其在不同翅高及进口雷诺数时的换热性能变化规律。数值仿真结果表明,换热器换热效率较高,压力损失较小,且随着翅高的降低、进口雷诺数的增加,换热性能逐渐提高。结果证明,可为换热器的进一步设计与优化提供有益的参考。     

Spatial–temporal patterns of urban anthropogenic heat discharge in Fuzhou,China, observed from sensible heat flux using Landsat TM/ETM+ data

The urban heat island (UHI) effect is the phenomenon of increased surface temperatures in urban environments compared to their surroundings. It is linked to decreased vegetation cover, high proportions of artificial impervious surfaces, and high proportions of anthropogenic heat discharge. We evaluated the surface heat balance to clarify the contribution of anthropogenic heat discharges into the urban thermal environment. We used a heat balance model and satellite images (Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) images acquired in 1989 and 2001), together with meteorological station data to assess the urban thermal environment in the city of Fuzhou, China. The objective of this study was to estimate the anthropogenic heat discharge in the form of sensible heat flux in complex urban environments. In order to increase the accuracy of the anthropogenic heat flux analysis, the sub-pixel fractional vegetation cover (FVC) was calculated by linear spectral unmixing. The results were then used to estimate latent heat flux in urban areas and to separate anthropogenic heat discharge from heat radiation due to insolation. Spatial and temporal distributions of anthropogenic heat flux were analysed as a function of land-cover type, percentage of impervious surface area, and FVC. The accuracy of heat fluxes was assessed using the ratios of sensible heat flux (H), latent heat flux (L), and ground heat flux (G) to net radiation (R _n), which were compared to the results from other studies. It is apparent that the contribution of anthropogenic heat is smaller in suburban areas and larger in high-density urban areas. However, seasonal disparities of anthropogenic heat discharge are small, and the variance of anthropogenic heat discharge is influenced by urban expansion, land-cover change, and increasing energy consumption. The results suggest that anthropogenic heat release probably plays a significant role in the UHI effect, and must be considered in urban climate change adaptation strategies. Remote sensing can play a role in mapping the spatial and temporal patterns of UHIs and can differentiate the anthropogenic heat from the solar radiative fluxes. The findings presented here have important implications for urban development planning.     

Numerical analysis of heat transfer in a manifold microchannel heat sink with high efficient copper heat spreader

A manifold microchannel heat sink integrated with a high efficient copper heat spreader is presented. A series analysis of three-dimensional fluid flow and heat transfer performance in this mirochannel heat sink and conventional structure are performed by CFX commercial software package. The temperature difference along the flow direction in the new microchannel heat sink is less than that of the conventional microchannel heat sink due to effect of the transverse channel arrays. The maximum heat flux input of the new microchannel heat sink increases 75% more than the conventional structure with the flow rate of 1 m/s. The new design has better heat transfer characteristics than conventional one for the full range of flow rates considered.