冷弯型钢垂直尖角成形方法研究

开发带有垂直尖角的新型冷弯型钢,对垂直尖角的成型,采用在转角处凸出圆弧、预留出多余材料的方法来补偿外圆角,然后精整成垂直尖角.本文对试验结果进行了分析和总结,为其他异形断面冷弯型钢在垂直尖角冷弯成型方面积累了经验.     

Rain induced cross polarization at millimeter waves in a Xi'an environment

The rainfall intensity accumulative distribution, raindrop size and canting angle distributions in Xi'an(108.9 E, 34.3 N) have been obtained from data measured over a long period of time. Rain induced crose polarization in this environment has been studied. The crose polarization discrimination, XPD, was compu ted over a frequency range of 19.3 to 300 GHz for non spherical drops. The variations of XPD with frequency, rainfall rate and copolar attenuation, CPA, were investigated. The computational resulte are in good agreement with experimental data. A mathematical relationship was established between the XPD and CPA, raindrop canting angle, which result is in good agreement with experimental data. The cumulative distribution of rain induced cross polarization for eleven years and in month have been ob tained with the cumulative distribution of the rain rate from the data measured from 1975 to 1985. The role of multiple scattering also has been discussed, it is shown that the multiple scattering play an important part in short millimeter wave.     

增压泵用机械密封稳态分析及改进

针对机械密封在核电厂增压泵的使用情况欠佳问题,对机械密封端面、两平行面问、微间隙流的压力稳态特性进行了分析,并应用柱坐标系Reynolds方程及有限差分法进行求解,得到密封端面压力的分布。根据此分析,说明了增压泵失效的原因,并提出了一些改进措施,从而使机械密封在核电厂增压泵的使用中更为可靠。     

余热回收换热器最佳传热面积计算

分析了余热回收换热器的经济性,根据效能-传热单元数法(ε-NTU法),对换热器进行最佳传热面积的计算与讨论.     

厚试样层析图像重构的研究

从激光在厚试样中入射和受激发荧光在试样中出射时光能的吸收与散射损耗的基本原理获得了光学系统接收荧光的归一化光强表达式。给出了迭代法、ＦＦＴ方法的数学模型，进行了计算模拟，并分析比较了ＦＦＴ方法和迭代法的计算量和计算精度。给出了用ＦＦＴ法层析恢复后的图像     

Computation of the Backscattering Power Density for Rainfall in Millimeter Waves Band

The size distribution and canting angle distribution for non-spherical rain drops are taken into account. Utilizing the Muller matrix, the backscattering power densities are computed at different rain rate and different polarization in millimeter waves band, according the rainfall condition in Xi'an, China. Finally the results obtained are discussed.     

互联网化趋势下的信息安全之路——访北京瑞星科技股份有限公司高级技术经理刘宏伟

2008年,全球范围内的金融危机对中国每一个大型企业都提出了更高的要求.企业面临的诸多挑战接踵而来,这些挑战包括全球化竞争、不断增长的劳动力成本和高能源成本,以及人民币升值等.在这种情况下,企业迫切需要改变经济和业务增长方式,而信息技术则是帮助企业应对挑战的重要手段,信息化和工业化的融合势在必行.企业将自己越来越多的业务架构在了IT系统之上,而一旦信息系统出现安全问题,后果就难以想象.     

The Effects Induced by Turbulence and Dust Storms on Millimeter Waves

Dust storms and turbulence consist of a random medium system, its effects on milimeter waves propagation are studied. Attenuation of millimeter waves, its phase shift and cross- polar discrimination are presented. Results show that dust storms mainly effects XPD and phase shift of millimeter waves, turbulence chiefly produces attenuation, in mediocre fluctuation.     

Hydrogeochemical Characteristics and Formation Mechanisms of the Geothermal Water in the Qingdong Coal Mine,Northern Anhui Province,China

Mine Water and the Environment - The hydrogeochemistry of geothermal fluids provides insight into the occurrence, formation, and circulation of geothermal resources. We collected 13 geothermal...     

Effect of high oxygen modified atmosphere on post‐harvest physiology and sensorial qualities of mushroom

The changes in physiology and sensorial qualities of mushroom stored at 2 °C for 12 days under high oxygen (100% O₂, 80% O₂) atmosphere and air had been investigated. Respiration rate was suppressed in mushroom in 80% O₂ and 100% O₂. No significant differences were found between 80% O₂ and 100% O₂. Weight loss was not more than 1.5% in all treatments. Weight loss and firmness of mushroom held in high oxygen were significantly (P < 0.05) higher than in air. Total soluble solid (TSS) was only slightly affected by high oxygen treatment. High oxygen, especially 100% O₂ treatment was effective at reducing browning degree and electrolyte leakage of mushroom. The surface colour of mushroom changed slightly before tenth day under high oxygen treatment. From day 2 the L‐value of mushroom flesh was significantly (P < 0.05) lower under air atmosphere compared with high oxygen treated mushroom. High oxygen, especially 100% O₂ was effective at inhibiting discoloration. The PPO activity of mushroom was significantly (P < 0.05) higher in 100% O₂ compared with air treatment. The POD activity was highest in high oxygen at eighth day, then reduced. High oxygen, especially 100% O₂ was effective at maintaining the quality of mushroom.