增光子压缩真空态的压缩特性

利用玻色湮没算符的逆算符-a∧1及玻色产生算符a∧ 分别作用于压缩真空态来构造增光子压缩真空态,并对它们的压缩特性进行了讨论.结果表明,a-∧1作用于压缩真空态所得到的增光子压缩真空态不产生压缩效应,而a∧ 作用于压缩真空态所得到的增光子压缩真空态则产生压缩效应,其压缩区间与压缩参数的取值有关.从而显示了增光子压缩真空态的压缩特性与算符a-∧1及a∧ 之间的密切关系.     

基于CFD的洁净手术室速度场的数值模拟

合理的气流组织是医院洁净手术室空调系统设计的重要内容。文章以RNGK-ε湍流双方程模型为基础,采用CFD技术,建立了相应的物理和数学模型,对上送——相对单侧墙底部回风洁净手术室内速度场进行了数值模拟,得到了洁净手术室内工作面三维速度场与二维流场的分布。     

RH精炼钢中全氧量变化与操作改进

为了使钢中全氧量控制在一个适当的水平,在武钢炼钢总厂RH真空脱气装置对低碳、超低碳钢进行了脱氧净化试验.结果表明,影响全氧去除的因素按作用高低依次是出钢溶解氧水平,溶解氧与钢包渣的交互作用,钢包渣,和真空处理净化时间.通过改进工艺生产了全氧量≤10×10-6,非金属夹杂物尺寸<10μm的清洁钢水,建立了一个钢包内钢水全氧浓度随时间变化的新方程,该方程考虑了全氧的表观平衡含量及环流、扩散传质对去除氧化物夹杂速率的影响.     

长株潭地区运输车船推广LNG清洁能源应用研究

通过对湖南省新能源和清洁能源推广应用情况分析,并结合实际,总结了LNG在长株潭地区推广的有利条件和障碍,提出了LNG清洁能源推广的实施目标和步骤,并从政府政策扶持、行业部门支持及企业服务保障三个方面给出了推广应用建议.     

SiCl_4制备正硅酸乙酯的工艺研究

为寻找一条工序简单、耗价低、易于工业放大路线,实现多晶硅副产物四氯化硅(SiCl4)废物资源化制备正硅酸乙酯(TEOS),本文以多晶硅副产物SiCl4和无水乙醇为原料制备TEOS,在半连续化生产工艺的基础上研究了SiCl4与乙醇的摩尔比、反应温度、反应时间等因素对TEOS产率及纯度的影响。正交实验优化结果表明:15℃下,以恒定速率滴加14.21 g无水乙醇于15 g四氯化硅中,反应35 min,补加8.12 g无水乙醇;55℃下恒温40 min,经减压蒸馏,除去低沸点的乙醇和氯化氢,TEOS产率达到86.61%。对正交实验优水平下制得的产物进行红外光谱(IR)和气相色谱(GC)分析,结果表明:产物中TEOS结构正确,其纯度大于99.0%,达到市售分析纯纯度。     

Magnetoresistance of the thin film ferromagnetic nanoconstrictions

The magnetoresistance and I-V characteristics at different temperatures of the thin film ferromagnetic nanoconstrictions of variable width (from 20 to 250 nm) and 10 nm thicknesses, fabricated by electron beam lithography and vacuum thin film deposition are compared. The magnetoresistance and resistance of the thin film ferromagnetic nanoconstrictions are not related to the width of the nanoconstrictions. Instead the resistance of the local nano-region in the middle of the thin film ferromagnetic nanoconstriction has only a minor role compared to that of the two microscale thin film ferromagnetic electrodes, which contribute the majority of the measured resistance. The magnetoresistances of the thin film ferromagnetic nanoconstrictions and a 0.2 cm × 0.8 cm thin ferromagnetic film deposited under the same conditions were also compared; the thin film ferromagnetic nanoconstrictions have higher magnetoresistances than the thin ferromagnetic film, which implies that the measured magnetoresistance of the thin film ferromagnetic nanoconstrictions comes mainly from the local nano-region in their centers. In conclusion, the measured magnetoresistance of the whole sample is similar to the anisotropic magnetoresistance, because the resistance of the two microscale thin film ferromagnetic electrodes is much higher than that of the local nano-region in the middle of the samples. Comparing the experimental results for the thin film ferromagnetic nanoconstrictions and the thin ferromagnetic film reveals that the magnetoresistance of the local nano-region in the middle of the sample is much higher than that of the two microscale thin film ferromagnetic electrodes attached to it.     

Deep levels,transport and THz emission properties of SiGe/Si quantum-well structures

In coal mines in such countries as China and Russia,most of the coal mine methane(CMM) generated during mining is emitted to the atmosphere without any effective usage,because the methane concentration of CMM is relatively low and not allowed to be used as fuel for safety reasons.Methane is one of the greenhouse gases.Therefore,if it becomes possible to concentrate CMM to an acceptable level for use as fuel,this will greatly contribute to reduction of greenhouse gas emissions.With the aim of gaining approva...     

晶粒尺寸和热处理对Sm2Fe17N3/Fe3N/BN软磁/硬磁复合材料的合成及磁性能影响

采用高能球磨和真空热处理方法制备Sm2Fe17N3/Fe3N/BN复合材料, 并研究球磨过程中晶粒尺寸变化对固态相变和磁性能的影响.  结果表明: Sm2Fe17N3和Fe3N相产生的条件是Fe的晶粒尺寸达到纳米量级（D＜80 nm）并形成Fe(Sm)固溶体; 随着退火时间的增加, 300 ℃真空退火的球磨样品中Sm2Fe17N3的结晶物增多, 矫顽力提高, 表明样品的磁性能与Sm2Fe17N3的结晶程度有关.     

Enhancing site style tree construction algorithm

The World Wide Web has become a global information service center with a vast amount of news, advertisements, product and service information, and disparate information from diversified sources. However, only a small portion of information is truly relevant and useful to the users who are seeking information on specific topics. In this paper, common relations among nodes are taken into consideration when constructing site style tree, and a new node type is introduced. Experimental results show that the proposed algorithm has higher precision and recall.      

太阳能在公路交通领域中的应用

太阳能以其节能、清洁、零排放、来源广泛、安全等特点,成为目前各种新能源中越来越受重视的一种绿色能源。通过对太阳能设施在公路交通各领域中的应用分析,提出了缓解交通能源危机及交通环境问题的新思路。