M－矩阵的行列式不等式

我们首先把文献［２］的结果：ｄｅｔＡｄｅｔＢ≤ｄｅｔｍ（Ａ＊Ｂ）改进为（ｂ１１…ｂｎｎ）ｄｅｔＡ＋（ａ１１…ａｎｎ）ｄｅｔＢ－（ｄｅｔＡ）（ｄｅｔＢ）≤ｄｅｔｍ（Ａ＊Ｂ），其中Ａ，Ｂ为ｎ阶Ｍ－矩阵，“＊”记Ｈａｄａｍａｒｄ积，“ｍ”记比较矩阵。其次，把关于Ｍ－矩阵的Ｈａｄａｍａｒｄ不等式改进为ｄｅｔＡ≤ａ１１…ａｎｎ－｜ａ１σ（１）…ａｎσ（ｎ）｜，其中σ是１，２…ｎ的任一个置换，当ｎ为奇数时，它为偶置换，否则为奇置换。最后，对Ｂ为非奇异的情形给出下列估计式：ｄｅｔＡ≤ｄｅｔ（Ａ＊Ｂ－１）／（β１１…βｎｎ）≤ａ１１…ａｎｎ，和ｄｅｔＡ／ｄｅｔＢ≤ｄｅｔ（Ａ＊Ｂ－１），其中，βｉｉ为Ｂ－１的主对角元     

波前传感器子孔径数和信标亮度的匹配

针对云南天文台１．２ｍ望远镜上的６１单元高分辨率自自应光学系统，进行了微光工作环境下波前传感器子孔径数和信标亮度匹配的实验研究。在Ｈａｒｔｍａｎｎ－Ｓｈａｃｋ波前传感器前的平行光路加入一个变倍光学系统，进行了８＊８、６＊６、４＊４和２＊２子孔径阵列在不同信标亮下波前感器对波前的探测实验。     

气相反应法合成超细粉末过程中的r~＊叶和晶型的研究

本文以ＳｉＣｌ４－ＮＨ３、ＳｉＣｌ４－Ｏ２、ＳｉＣｌ４－Ｎ２－Ｈ２、ＴｉＣｌ４－ＮＨ３－Ｈ２、ＴｉＣｌ４－Ｎ２－Ｈ２、ＴｉＣｌ４－Ｏ２、ＡｌＣｌ３－Ｏ２等为体系，运用均匀成核理论，研究了平衡常数Ｋｐ、过饱和比Ｓ及临界核半径，ｒ＊等因素对气相反应法中超细粉末的形成及粉末结构状态的影响．结果表明，当２ｒ＊大于某物质的晶格常数时，用气相反应法得到的该物质的超细粉末一般为晶体粉末，反之则得到无定形粉末．     

磁控反应溅射TaN薄膜的结构和性能

采用磁控溅射仪制备了ＴａＮ薄膜,研究了不同氮分压条件下ＴａＮ薄膜的成份、结构和力学性能。结果表明,氮分压在０．２＊１０＾－１Ｐａ时镀层由两相混合物正方的β－Ｔａ和面心立方结构的δ－ＴａＮ组成。而氮分压在０．４＊１０＾－１－０．８＊１０＾－１Ｐａ时,得到单相六方ＴａＮ结构。     

弥漫激光抽运铯束频标实施研究

对本北京大学铯束频标实验室所提出的一种光抽运铯束频标的新结构弥漫激光抽运斜入射光检测铯束频标进行了首次实验。本论述了这种新抽运检测机制的工作原理及其主要特点，对弥漫激光场的光强分布作了计算和测量，并实验检测了弥漫激光场的光抽过性能。实现了弥漫激光抽运铯束频标实验系统的闭环工作，与ＨＰ－５０７１Ａ商品小铯钟比对，此频标实验系统频率短期稳定度为２＊１０＾－１１／√τ，天稳定度为３．５＊１０＾－１３。     

高纯CO2制备的研究：催化燃烧法脱除CO2中微量甲烷,乙烷

分析了比较了提纯ＣＯ２的工艺方法，研制了以脱除ＣＯ２中微量ＣＨ４和Ｃ２Ｈ６的贵金属体系催化燃烧剂，筛选出４＃催化剂在氧过量一倍，空速１４００ｈ＾－１条件下，将ＣＨ４和Ｃ２Ｈ６脱除至１＊１０＾－６的最低温度，分别为３３１℃和３８０℃，在３９０℃，　ｈ＾－１条件下长期考察，ＣＨ４〈１＊１０＾－６的时间长达３１７ｈ。催化剂的最高使用温度不宜超过８００℃，且可能和于惰性气体中微量ＣＨ４和Ｃ２Ｈ６的脱除。     

测量范围为100MPa的PTB标准压力平衡器

简要介绍了ＰＴＢ压力范围为１００ＭＰａ的压力平衡器,叙述了低压时使用标准仪器进行比对测量的结果。对用作描述活塞系统有效面积压力关系的不确定度系数测定范围作了讨论。１００ＭＰａ压力平衡标准测量的相对不稳定度为△Ｐｅ／Ｐｅ＝３＊１０＾－５＋３＊１０＾－７ＭＰａ＾－１．Ｐｅ。     

TN－LG钢结构防火隔热涂料

ＴＮ－ＬＧ钢结构防火隔热涂料＊Ｎ＊Ｇ钢结构防火隔热涂料是以改性无机高温粘接剂配以膨胀经石、膨胀珍珠岩等吸热、隔热及增强材料和化学助剂合成的一种钢结构防火保护喷涂涂料。ＴＮ－ＬＧ涂料性能优良，在国内外享有很高的信誉。在北京中国国际贸易中，Ｇ３９层钢框架...     

我为初哥选功放

呀！冬天怎么还打雷？"发烧初哥李惊讶地问。"雷打在喇叭里却响在天上！"我给老友解释。"听了几年音响，还从未听过这么真的呢！"初哥道。接着我播放了几段优美动听的音乐络初哥赏鲜，初哥频频点头赞扬。急问："＊＊＊？多少钱？""三件，不到两千元。""给我买一套！"老友求机心切，我只得将ONE说给他听。激光唱机和前后级分体式功放都是ONE牌国货。A－931前后级功放从93年5月就停产了，开始生产新一代威马（REMER）牌P－934O／M－9340前后级分体式功放。据资料介绍，新型号从电路、选料、外观到工艺等各方面都有很大的改进与提高。选…     

CCD光标式微电流计

介绍了一种使用ＣＣＤ线阵光敏器件的数字化微电流测量仪器，其灵敏度：１＊１０＾－１１Ａ／字，测量范围：２０００字，精度：±１字。对仪器的光机电结构作了扼要介绍，并阐述了电路工作原理。     

Performance analysis of air cycle refrigerator integrated desiccant system for cooling and dehumidifying warehouse

In this paper, the performance of air cycle refrigerator integrated desiccant system used to cool and dehumidify warehouse is analyzed theoretically. Simulation analysis is carried out to calculate the system coefficient of performance, cooling effects and the humidity change under different values of pressure ratio, storage zone temperature inside dock and outdoor air conditions. Also, the effect of the air cycle and the rotor parameters on the system performance is evaluated. From the simulation result it is found that, the desiccant system has the ability to supply air to the dock area at very low humidity. The system coefficient of performance increases due to the exhaust heat recovery on the desiccant system, and this enhancement can be more than 100%. The coefficient of performance of the proposed system is greater than that of a conventional system under the same operating conditions.     

极端气候下家用空调器性能测试分析

对极端气候下家用空调器的性能进行了测试分析。房间空调器的制冷（热）量采用空气焓差法进行测量和计算,并用评价指标EER对其性能进行评价。最后给出典型家用空调在不同室内外温度特别是夏季高温和冬季低温下的制冷／制热量、耗功率、性能系数,评价其在极端气温下的性能。     

冷却装置嵌入式数据中心机柜供冷效果研究

针对目前数据中心空调系统在冷量供应环节普遍存在的能耗大、冷却效果差等问题,本文提出将冷却装置嵌入机柜内部以实现对服务器的定量化精确供冷,利用已通过实验验证的CFD仿真平台,研究了冷却装置的排布方式和运行参数对供冷效果的影响.结果表明:当冷却装置位于两排服务器中间时冷却效果最好,温度合格系数为100％,相比于冷却装置位于...     

Determination and verification of the gap dependent heat transfer coefficient during permanent mold casting of A356 aluminum alloy

In complex castings, the heat transfer across the casting / mold interface depends on the local gap size and contact pressure. Thus, an experimental setup is constructed to measure and evaluate the air‐gap dependent heat transfer coefficient during solidification of an A356 permanent mold casting. In order to evaluate the heat transfer coefficient, the temperature gradient and air gap development is measured at the casting / mold interface. This allows the interface temperatures and the time‐dependent heat flux across the gap to be calculated as a function of the measured gap size. Furthermore, the heat transfer coefficient and gap size are correlated to the interface temperature of the casting. The experimental setup and the evaluation procedure provide consistent and reproducible results. The heat transfer coefficient thus evaluated is employed to simulate the experimental setup. The temperatures measured are well reproduced. The results of the present work are compared to simulations using two heat transfer coefficient functions found in literature. This comparison shows a substantial improvement over the state of the art. This improvement is due to the exact knowledge of gap formation and the corresponding values of the heat transfer coefficient.     

Improved algorithm for calculations of Rayleigh-scattering optical depth in standard atmospheres

Precise calculations of the total Rayleigh-scattering optical depth have been performed at 88 wavelengths ranging from 0.20 to 4.00 microm for the six well-known standard atmosphere models by integrating the volume Rayleigh-scattering coefficient along the vertical atmospheric path from sea level to a 120-km height. The coefficient was determined by use of an improved algorithm based on the Ciddor algorithm [Appl. Opt. 35, 1566 (1996)], extended by us over the 0.20-0.23-microm wavelength range to evaluate the moist air refractive index as a function of wavelength, air pressure, temperature, water-vapor partial pressure, and CO2 volume concentration. The King depolarization factor was also defined taking into account the moisture conditions of air. The results indicate that the influence of water vapor on Rayleigh scattering cannot be neglected at tropospheric altitudes: for standard atmospheric conditions represented in terms of the U.S. Standard Atmosphere (1976) model, the relative variations produced by water vapor in the Rayleigh scattering parameters at a 0.50-microm wavelength turn out to be equal to -0.10% in the moist air refractivity at sea level (where the water-vapor partial pressure is equal to approximately 7.8 hPa), -0.04% in the sea-level King factor, -0.24% in the sea-level Rayleigh-scattering cross section, and -0.06% in the Rayleigh-scattering optical depth.     

Effect of melt superheat on heat transfer coefficient for aluminium solidifying against copper chill

Solidification of metal castings inside moulds is mainly dependent on the heat flow from the metal to the mould which is in turn proportional to an overall heat transfer coefficient h which includes all resistances to heat flow such as the presence of an air gap. In the present work the heat transfer coefficient is determined using a directional solidification set-up with end chill for solidifying commercial-purity aluminium with different superheats (40 K and 115 K) against copper chill. A computer program solving the heat conduction and convection in the solidifying metal is used together with the experimental temperature history in order to determine the heat transfer coefficient at the interface. The variation of h as a function of time, surface temperature and gap temperature for each melt superheat is found. The results indicate that h reaches a maximum value for surface temperature close to the liquidus. The analysis of heat flux from the metal to the mould indicates that it is mainly by conduction. The air gap size is evaluated with time, surface temperature and with melt superheat. It is found that higher h values and smaller gap sizes are obtained with higher superheats.     

Water-vapor continuum CO2 laser absorption spectra between 27 degrees C and -10 degrees C

Water continuum CO2 laser absorption spectra are reported for temperatures between 27 and -10 degrees C. The continuum is found to possess a negative temperature coefficient. The results obtained suggest that the magnitude of this temperature coefficient increases with increasing water pressure and decreasing temperature. The temperature coefficients between 27 and 10 degrees C for air mixtures containing 3.0- and 7.5-Torr water vapor are -2.0 +/- 0.4 and -2.9 +/- 0.5%/ degrees C, respectively. For mixtures with 3.0-Torr water the 10-0 degrees C temperature coefficient is -7.7 +/- 0.2%/degrees C. The temperature and water pressure dependencies observed for the continuum suggest that while both collisional broadening and water dimer mechanisms contribute to the continuum, the dimer mechanism is more important over this temperature range.     

热处理对聚乙烯/炭黑复合材料PTC性能的影响

为提高聚乙烯/炭黑导电复合材料的PTC性能,将高分子PTC复合材料热处理一定时间后,再分别通过淬火、慢火、空气冷却等方式进行处理,室温放置一定时间后进行电气性能测试.结果表明:慢火处理比淬火和空气冷却处理更能降低样品的电阻;在低于基体熔融温度下处理,可以使样品电阻降低;而在高于熔融温度下处理时,可以使电阻增大,但却缩短了样品的动作时间.在170℃加热后的样品经淬火冷却后,其动作时间缩短为28 s.     

Method for measuring small optical absorption coefficients with use of a Shack-Hartmann wave-front detector

We present a method for measuring absorption at the 1 x 10(-5) cm(-1) level in high-quality optical materials. Using a Shack-Hartmann wave-front detector, thermal lensing in these materials may be measured. Then, the absorption coefficient may be estimated by fitting the observed deformation to a thermal lensing model based on the temperature dependences of the refractive index and the thermal expansion coefficient. For a particular sample of fused silica, the absorption coefficient was determined to be 1.8 +/- 0.4 x 10(-5) cm(-1). Obtaining this result requires a resolution in the optical path length better than +/- 0.1 nm.     

电动客车用余热回收型热泵的换热器优化及性能实验研究

本文针对热泵空调系统在冬季低温工况下制热能力衰减问题,通过换热器设计优化,研发出基于喷射补气的余热回收型热泵空调系统,并进行了性能实验研究.结果表明:研制的准二级压缩电动客车热泵空调系统在低温条件下具有较好的制热性能.在环境温度为-20℃,车内温度为20℃,余热量为1.8 kW的制热工况下,相比于无余热回收工况,系统制...