单元式空调机采用替代工质的热力性能分析

编制了单元式空调机制冷循环的热的热力性能计算程序,并对采用环境可接受的ＨＦＣ类替代工质的单元式空调机的热力性能作了分析,结果表明采用ＨＦＣ－１３４ａ作为制冷工质的单元式空调机其制冷性能会达到 或超过采用Ｒ２２的单元式空气调节机。     

环保型发泡剂HFC-365mfc在硬质聚氨酯泡沫塑料中的应用研究

对HFC-365m fc发泡剂在硬质聚氨酯泡沫塑料中的应用作了较为系统研究,研究结果表明HFC-365m fc作为环保型的发泡剂其泡体的综合力学性能与HCFC-141b比较接近,泡体的力学性能达到了国家＂喷涂聚氨酯泡体保温材料＂标准（JC/T998-2006）标准,可作为HCFC-141b发泡剂的替代品用于市场。     

A new environment-friendly refrigerant

CFCs and HCFCs, widely used in refrigeration and air-conditioning equipment, have been or will be phased out according to the revisions of the Montreal Protocol because they deplete the ozone layer. Many substitutes have been proposed, but no one has perfectly replaced the CFC end HCFC refrigerants. New generation alternatives are being investigated worldwide. According to the industrial and environmental requirements, many factors should be considered in the screening and evaluation of refrigerant alternatives. A new method is proposed using the soft algebra method——fuzzy multiple evaluation. The weights for different factors are determined mathematically and criteria values for all the objects are made dimensionless to quantitatively compare the different alternatives. A new long-term drop-in mixture alternative THR02 is developed and evaluated in a series of theoretical and experimental evaluations.THR02 is proved to be an environment-friendly, nontoxic, inflammable, drop-in alternative to CFC-12 a     

GeV伽玛射线噪blazar天体观测特性的统计分析

收集了35个GeV伽玛射线噪blazar天体的从光学到伽玛射线波段观测数据,计算了αzγ,αzxx,αγxγ,分析了Гγ和logvpeak时,Гx和logvpeak以及Гx和Гy的相关性,得出FSRQs具有较大的B光子谱指数,对应的谱较陡,而HBLs具有较小的t光子谱指数,其谱较平．BL-Lacs和FSRQs的αxγ与αxγ,αxnx与αγxγ存在明显的负相关．     

绸型裙装面料的分类研究

裙装的外观形态与面料种类有着密切的关系.利用KES织物风格仪测量了40种绸型裙装面料的拉伸、剪切、弯曲等力学性能,提出运用最短距离系统聚类法、多元方差分析确定最佳聚类域的绸型裙装面料分类方法,并借鉴手感评价二级指标探讨了分类后各类面料手感的差异.结果表明,该方法具有一定的可行性,所选面料最佳分类数为5类,且5类面料的手感具有明显差异.     

华南籼稻早造稻米品质特性与米粉凝胶质构的相关性研究

研究了用27个华南籼稻早造稻米为原料制作的米粉凝胶质构特性与大米淀粉热特性、晶体特性之间的相关性.结果表明：上述米粉凝胶主要呈现中等硬度（4000～5000g）、低粘性（〈300g.s）、中等剪切力（1000～2000g）的特点;凝胶最大剪切力和米粉直链淀粉含量极显著正相关,而和硬度不显著相关;米粉凝胶抗剪切特性受到大米淀粉热特性的显著影响,其中米粉凝胶最大剪切力与DSC峰面积显著相关,与热焓值极显著负相关;剪切功与米粉糊化起始温度显著相关,与峰面积极显著负相关,与热焓值极显著正相关;米粉凝胶粘性与大米淀粉亚微晶相相对结晶度显著相关.     

卧式螺旋管临界热流密度的流体模化

为检验经典的临界热流密度(critical heat flux, CHF)流体模化方法对于卧式螺旋管的应用效果,采用大功率直流电加热的方法对制冷剂HFC-134a在卧式螺旋管内的流动沸腾CHF进行了实验测试。通过运用Ahmad和Katto模型对实验测试数据和已有数据源进行模化计算发现:Ahmad和Katto模型确定的流量模化因子对于卧式螺旋管CHF的流体模化会产生较大的偏差,导致预测的CHF值高于实验结果。在实验数据分析的基础上提出了卧式螺旋管CHF流量模化因子的经验关联式。计算结果表明:应用该关联式对实验条件下卧式螺旋管CHF的预测偏差在±20%以内,其流体模化精度明显优于Ahmad和Katto模型。     

两种管长单管中水临界热流密度（CHF）实验比较

介绍了在常压下，竖直环形通道内水强迫循环流动的临界热流密度实验。先后做了两种不同管长的单管ＣＨＦ实验。根据实验结果拟合了适用于本实验参数范围的ＣＨＦ关系式，计算值与实验值吻合良好，给出了这两种不同管长单管ＣＨＦ的结果并进行了比较。     

Effect of sintering time on the electrochemical properties of spinel LiMn2O4 synthesized by solid-state reaction

LiMn2O4 powder as a cathode materials for rechargeable lithium-ion batteries was prepared by solid-state reaction from LitCO3 and electrolytic MnOz at different sintering periods （2, 6, 18, and 32 h）. X-ray diffraction （XRD） patterns of the prepared samples are identified as the spinel structure with a space group of Fd3 m. The lattice parameters almost remain the same as the sintering periods increase. The sample with a sintering period of 32 h shows good cycling performance at both low and nigh current densities, and also elevated temperature. It is believed that the excellent electrochemical behavior of this sample results from its good crystallinity and large grain size compared with other samples. Different electrochemical measurements were conducted to investigate the electrochemical properties of spinel LiMn204. 2008 University of Science and Technology Beijing. All rights reserved.     

Effect of sintering time on the electrochemical properties of spinel LiMn_2O_4 synthesized by solid-state reaction

LiMn_2O_4 powder as a cathode materials for rechargeable lithium-ion batteries was prepared by solid-state reaction from Li_2CO_3 and electrolytic MnO_2 at different sintering periods(2,6,18,and 32 h).X-ray diffraction(XRD)patterns of the prepared samples are identified as the spinel structure with a space group of Fd(?)m.The lattice parameters almost remain the same as the sin- tering periods increase.The sample with a sintering period of 32 h shows good cycling performance at both low and high current densities,and also elevated temperature.It is believed that the excellent electrochemical behavior of this sample results from its good crystallinity and large grain size compared with other samples.Different electrochemical measurements were conducted to investi- gate the electrochemical properties of spinel LiMn_2O_4.     

固态物料升华干燥过程传输特性的测定

本文建立固态物料升华干燥过程中干燥层传输特性的数学模型，利用由实验测得的牛肉干燥速率，计算出牛肉干燥层的有效导热系数和有效质扩散系数．把两个传输特性参数与文献值进行比较，证明传输特性模型合理，所得传输特性数据基本可靠．分析发现有效导热系数主要受真空空压力的影响；有效质扩散系数不仅受真空室压力的影响，也受物料表面温度的影响．     

芯子开槽工艺对蜂窝纸板缓冲性能的影响

为解决蜂窝纸板初始缓冲性能差、干燥速度慢、易发霉等问题,对蜂窝纸芯采用开槽工艺处理,在不显著降低蜂窝纸板平压强度的前提下,尽可能地改善其缓冲性能。采用正交试验方法对30 mm厚蜂窝纸板进行静态压缩试验,以考察芯子槽形的宽度、深度和槽间距3个工艺参数对蜂窝纸板性能的影响。实验结果表明:当采用槽宽2.5 mm、槽深3 mm、槽间距32 mm的开槽方式时,蜂窝纸板具有较优的抗压与缓冲综合性能。     

不同种类颗粒射流流化床的射流深度

对Geldart B、D类颗粒进行了射流深度计算关联式的研究。对前人的实验数据进行多元线性回归分析,建立了射流流化床中Geldart B、D类颗粒射流深度的计算关联式,关联式计算值与实验值吻合较好。将关联式与其他研究者得到的关联式进行比较,本关联式误差相对较小。     

基于数字信号处理器(DSP)的小波变换视音频数据压缩系统开发

利用小波变换对视音频数据压缩系统进行了研究与开发,该系统基于ＴＭＳ３２Ｃ８０的数字信号处理器（ＤＳＰ）芯片,着重对系统总体结构、系统硬件设计与软件总体设计进行了研究．     

正交法设计分析制膜条件对纤维素膜力学性能的影响

选择气隙高度、凝固浴温度、拉伸速度3种工艺参数作为研究对象,并设计3因素4水平的正交实验来分析制膜条件对纤维素膜力学性能的影v向．通过结果分析得出：影响纤维素膜力学性能的主要因素为凝固浴温度,其次为拉伸速度以及气隙高度．最优的制膜条件为：气隙高度32mm,凝固浴温度20℃、拉伸速度500mm／min．最优组合所得纤维素膜拉伸强度为13．68MPa、断裂伸长率为79．37％．对最优组合、正交表中综合评分最高值与最低值3种试样进行结晶度与断面结构的对比,结晶度分别为63．27％、72．7％、54．74％,在膜断面结构方面,最优组合膜较另外两者呈现出更均匀且致密的断面结构．     

电子陶瓷材料的现状与展望

概括了电子陶瓷材料的发展与现状，详细介绍了主要电子陶瓷的研究热点和发展前景，对近几年出现的新型电子陶瓷及其器件作了讨论．根据目前信息技术的发展状况及其应用需求，开发高性能多功能电子陶瓷及器件具有广阔的市场前景和经济效益．从具体材料发展到材料体系的研究以及单一性能向多功能复合器件的转换是目前电子陶瓷十分活跃的研究领域．     

微电极阵列神经元锋电位信号的去噪方法

为了去除神经细胞外单细胞动作电位(即锋电位)记录信号中的各种噪声,提高幅值很小的单细胞锋电位信号检测的正确性,根据多通道微电极阵列记录信号中各个通道之间噪声空间相关性较强的特点,提出主成分分析(PCA)去噪与小波阈值去噪相结合的联合去噪方法.采用PCA方法提取并去除多通道记录信号中相关噪声的第一主成分,然后将信号进行小波多尺度分解,采用软阈值法去除各尺度下的噪声.仿真数据和测试结果表明,联合去噪方法可以同时去除有色噪声和白噪声,在各通道锋电位序列相互独立而噪声相关性较强的情况下,可以显著提高锋电位信号的信噪比.联合去噪方法的性能明显优于PCA去噪方法和小波阈值去噪方法单独使用时的性能,是一种有效的多通道锋电位信号去噪新方法.     

聚甲基丙烯酸甲酯强制点燃过程的实验与模拟

采用锥形量热仪对典型热塑性高分子材料聚甲基丙烯酸甲酯在不同外部入射热通量下进行了强制点燃的实验研究。建立了PMMA强制点燃过程的数学模型，通过数值分析的方法将点燃数据相关联，得到了PMMA强制点燃的点燃时间与临界表面温度的表达式。并计算了PMMA不同外部入射热通量下强制点燃的点燃时间及点燃的临界表面温度。模拟计算结果与实验结果比较表明，在高入射热通量下二者基本吻合。     

Optimization of spectroscopic properties of ytterbium-doped laser glasses

Four laser glasses with high emission cross sections are experimentally obtained. The laser performance parameters are determined from the spectroscopic parameters of these glasses and compared with those of developing laser glasses abroad. It is shown that Yb~(3-)-doped telluorogermanate, Yb~(3 )-doped niobosilicate glasses have the highest emission cross section and gain coefficient, the smallest minimum pumping intensity and saturation pumping intensity, and the lowest minimum fraction of excited ions. Yb~(3 )-doped borate glass follows just behind them. These glasses have some spectroscopic advantages over laser glasses developed recently elsewhere. Yb~(3 )-doped phosphate glass is comparable to phosphate laser glass which had high emission cross section and was developed recently by HOYA Corporation in Japan.The domestic glasses with optimum spectroscopic properties may be promising candidates for applications in high-average power and high-peak power solid state lasers, especially laser for the ne     

水和水蒸汽热力性质计算程序的研究及应用

根据火力发电厂热力计算中经常查用水和水蒸汽的各项热力性质的需要,以IFC公式为基础,利用VisualBasic6 0编制了一套水和水蒸汽热力性质计算程序,该程序可用任意2个已知参数算出其他参数.着重讨论了编程过程中的一些方法、技巧以及计算精度,并在此基础上编制了汽轮机热力特性计算程序,程序经试用效果良好.