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排序方式: 共有193条查询结果,搜索用时 15 毫秒
1.
介绍了耐浓硝酸介质腐蚀的新型低铬高硅铸造不锈钢的化学成分,着重研究了含镍量对其组织、冲击韧性与腐蚀行为的影响。试验结果表明,含有7%Ni的超低碳Cr13Ni7Si4Nb双相铸造不锈钢,在浓硝酸介质中具有优良的耐蚀性能,并具有良好的冲击韧性和铸造性能。  相似文献   
2.
大连马栏河污水处理厂二期工程采用水解酸化/前置反硝化BIOFOR生物滤池工艺,处理后出水水质达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)的一级A排放标准。结合马栏河污水厂实际工程,系统地介绍了水解酸化/前置反硝化BIOFOR生物滤池工艺中各个工艺单元功能及设计情况,并着重分析了该工艺的优劣点。  相似文献   
3.
Natural diamond tool is quickly worn out while cutting a workpiece made of a tungsten-based alloy. This paper presents a new approach to reduce tool wear: ultrasonic vibration cutting of a workpiece made of a tungsten-based alloy based on gas–liquid atomization cooling. An atomizer is a device which mixes carbon dioxide gas with vegetable oil and changes the liquid into minute droplets, which are carried by a stream of gas. Atomizer is also a device that incorporates a venture device to translate liquid into a gas stream. The atomized minute droplets act as the cooling and lubricating medium to protect the tools. The system is designed to ensure that droplets can spread all over the surface of a work piece. At a constant spindle speed, feed rate, and cutting depth, the experiments were carried out for investigating the effects of the tool vibration parameters, carbon tetrachloride liquid flow rate, carbon dioxide gas flow, and gas–liquid mass ratio on the tool wear. The experiments showed that the technology of ultrasonic vibration with gas–liquid atomization cooling effectively prolongs the tool life in cutting tungsten-based alloy.  相似文献   
4.
利用ANSYS有限元分析软件的APDL语言进行二次开发,完成臂架参数化建模,分析不同截面参数的变化对臂架刚度、强度及稳定性的影响程度,确定了影响臂架结构整体性能的主要因素和相对次要因素,并对其截面尺寸进行优化.分别以臂架的刚度、强度及稳定性作为性能指标,对伸缩臂结构模型进行性能参数优化,得出不同条件下的最优截面形式.  相似文献   
5.
顺次及交叉加载方案下螺栓弹性交互作用规律   总被引:4,自引:0,他引:4  
由于螺栓之间存在弹性交互作用,采用力矩方法逐个加载螺栓难以获得均匀一致的预紧载荷。试验研究了顺次及交叉多轮加载方案下螺栓的弹性交互作用规律。螺栓采用8根M20×1.5双头螺柱,材料35CrMoA。采用应变片和应变仪实时监控螺栓载荷,采用力矩扳手加载。结果表明,在螺栓加载过程中存在两种弹性交互作用:正作用和负作用。弹性交互作用使交叉加载和顺次加载的最终载荷分布分别呈现W形和N形。分析了正作用和负作用的规律,依据规律提出了优化的加载方案,可将弹性交互作用系数方阵[A]m×n简化为三对角阵,提高了弹性交互作用系数法的实用性。  相似文献   
6.
气瓶安全泄放量计算方法探讨   总被引:1,自引:0,他引:1  
基于目前国内外标准中对气瓶安全泄放量的计算存在诸多差异的现状,对国内原气瓶用爆破片标准GB16918--1997、美国压缩气体协会标准CGAS-1.1-2005、美国石油学会标准API521q007中气瓶泄放量的计算方法进行了分析。将CGAS-1.1安全泄放量公式中空气的当量体积排放量推导转化为实际介质的安全泄放质量流量,该成果有助于正确理解和应用CGAS~1.1标准。分析比较认为:CGAS公式计算结果较API相比,爆破片计算面积差别不大,但泄放阀结果明显偏大,API521中对受火引起超压的气瓶泄放面积计算,具有扎实的理论基础,但对因其他原因导致的超压,适用性有待考证。GB16918中气瓶安全泄放量公式采用的是CGAS-1.1中适用于单一压力泄放阀的泄放量公式,因此当泄放装置采用爆破片时,不能采用GB16918进行计算,建议补充完善GB16918中安全泄放相关内容。  相似文献   
7.
竞争优势作为企业生存和发展的基础,在特定的经营环境中为其提供竞争能力和竞争优势基础的多种技能、互补性资产和运行机制的有机结合。通过对企业竞争优势来源和相关理论的综述,从不同的角度对集团公司加强内部管理、寻找外部扩张、战略联盟的竞争优势进行了分析与评述。  相似文献   
8.
《Building and Environment》2002,37(3):241-255
The primary functions of mechanical ventilation systems include the delivery of outdoor air to the occupants, the removal of indoor contaminants and the maintenance of thermal comfort conditions in the occupied zones. Air exchange effectiveness can be employed to characterise the ventilation air mixing within a room. This paper presents our findings pertaining to air exchange effectiveness values in a seven-storey office building. Tracer gas analysis, based on concentration decay method, is employed to determine these values. The results indicate air flow patterns in the occupied zones which approximate “perfect mixing”. The measured concentration levels of indoor air pollutants are also found to be within reasonable limits.  相似文献   
9.
A systematic study of liquid phase axial dispersion was conducted in glass columns (inner diameters, 1 cm and 1.6 cm), packed randomly with granular sand, by varying the fluid flow rate, particle size and bed height. Pulse and step response techniques, with KCl as an inert tracer, were used. The resultant data, covering the Reynolds number range from 1 to 50, are presented as plots of the Peclet number based on particle diameter against Reynolds number.Inert tracer experiments were also carried out in a column (inner diameter, 1.6 cm) packed with activated carbon granules, using different particle sizes, fluid flow rates and bed heights, in order to estimate the effective intraparticle diffusivity. We show that flow maldistribution produces pulse response curves with sharp, narrow peaks which, when compared with theoretical curves, result in small intraparticle diffusivities.We illustrate how the outer-phase transfer function can be obtained from the overall transfer function of the activated carbon bed and we compare it with the transfer function obtained directly using impermeable particles similar to the activated carbon granules.  相似文献   
10.
In most priority scheduling algorithms, the number of priority levels is assumed to be unlimited. However, if a task set requires more priority levels than the system can support, several jobs must in practice be assigned the same priority level. To solve this problem, a novel group priority earliest deadline first (GPEDF) scheduling algorithm is presented. In this algorithm, a schedulability test is given to form a job group, in which the jobs can arbitrarily change their order without reducing the schedulability. We consider jobs in the group having the same priority level and use shortest job first (SJF) to schedule the jobs in the group to improve the performance of the system. Compared with earliest deadline first (EDF), best effort (BE), and group-EDF (gEDF), simulation results show that the new algorithm exhibits the least switching, the shortest average response time, and the fewest required priority levels. It also has a higher success ratio than both EDF and gEDF.  相似文献   
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