适用于液氮温度工作的硅双极晶体管

硅双极晶体管电流增益具有正温度系数，这使得普通硅双极器件电流增益在液氮温度下严重退化，失去了放大能力。本文分析了多晶硅发射极晶体管电流增益的温度相关性，优化设计和选取了发射区掺杂浓度和发射区宽度，成功地研制了液氮温度下电流增益高达２００的硅双极晶体管。     

High Temperature Superconductor THz Thermal Sensors and Coolers

High temperature Superconductors (HTSCs) are a good candidate for developing THz radiation sensors. They are easy to manufacture and operate in the convenient temperature range of 80–140 K. The speed of operation of a THz sensor need to be controlled by a fast dissipation of heat, by the electrons which act as the sensing element. There is recently a surge in the development of fast and efficient low dimensional thermoelectric, temperature control devices. They would be ideal for cooling of the sensor, over the temperature interval of operation of the HTSCs. Status of these cooling devices towards achieving low temperature self cooling is discussed in the paper. Some results of the modeling study, carried out by the author, in an HTSC hot electron thermal sensor (HETS) are presented.     

High Temperature Superconductor THz Thermal Sensors and Coolers

High temperature Superconductors (HTSCs) are a good candidate for developing THz radiation sensors. They are easy to manufacture and operate in the convenient temperature range of 80–140 K. The speed of operation of a THz sensor need to be controlled by a fast dissipation of heat, by the electrons which act as the sensing element. There is recently a surge in the development of fast and efficient low dimensional thermoelectric, temperature control devices. They would be ideal for cooling of the sensor, over the temperature interval of operation of the HTSCs. Status of these cooling devices towards achieving low temperature self cooling is discussed in the paper. Some results of the modeling study, carried out by the author, in an HTSC hot electron thermal sensor (HETS) are presented.     

The Specific Load Capacity of Radial-Flux Radial Magnetic Bearings

This paper addresses the specific load capacity of radial-flux radial magnetic bearings and provides some insight into what values are achievable and how these values depend on various parameters such as air-gap thickness, allowable temperature rise in the coils, certain heat-transfer coefficients, and certain de-rating factors associated with the distribution of the bearing load in time and space. We define the specific load capacity of a radial magnetic bearing as the ratio of the largest sustainable root-mean-square radial force to the total self-weight of all parts necessary for the electromagnetic function of the bearing. We show that it is possible to push the limit of the specific load capacity of naturally cooled bearings up to around 35:1 with present-day materials, for a wide range of practical bearing sizes. This figure is still very small compared with the capacity of mechanical bearings.     

径向磁悬浮轴承铁损特性研究

为了准确计算主动式磁悬浮轴承的铁损值,首先采用电磁仿真软件Ansoft Maxwell对在交变磁通条件下的径向磁悬浮轴承的铁损耗进行计算与分析,探究了铁损耗的构成和影响因素,揭示了铁损耗、磁滞损耗和涡流损耗随频率及磁感应强度的变化规律.然后通过实验获取了定转子铁芯所用硅钢片的损耗特性,采用最小二乘法拟合各项损耗系数并分析得到损耗系数随频率的分布规律.最后将实验结果和经典的Bertotti铁损分离理论相结合对磁悬浮轴承铁损耗进行分析,验证了有限元法对磁悬浮轴承铁损规律分析的正确性,研究结果可以为磁悬浮轴承损耗问题的分析提供指导.     

钢水连续测温传感器的准确度提高和结构优化

为提高钢水连续测温传感器的准确度和灵敏度,以传感器所形成的在线黑体空腔的实际结构模型、带盖半球-圆筒形腔体为研究对象,建立了结构参数为二次关系的积分发射率的计算公式,并推导出全照区、半照区和不可见区域的自动划分计算公式.详细分析了传感器结构,即黑体空腔的长度、半径、孔径、腔口与探测器之间的距离,以及探测器接收面半径对积分发射率的影响,并在此基础上给出了传感器的优化参数.     

液氮温区金属钆（Gd）热导率研究

详细介绍小样品热导率测量装置，用该装置测定了沪产９９．９％纯钆的热导率。发现在２３０Ｋ附近轧热导率反常，趋向极小。证实了除电子以外，磁机制对钆电导和热导有较大贡献。     

实验室中液氮和液氧的提纯

阐述了以液态空气为冷源、用“重蒸馏”和冷凝的方法获得更纯的液氮和液氧。所得液氧和液氮的正常沸点之差值Ｔ。＿ｎ＝１２．７５Ｋ；与标准值相差＜０．１Ｋ。     

液氮温度下分子筛的真空吸附特性试验研究

为探究低温容器夹层所用分子筛吸附剂的吸附特性,采用静态膨胀法进行试验,获得了平衡压力为10-3Pa～103Pa范围内4A、5A和13X分子筛对N2、O2单一组分以及空气的吸附等温线,比较了不同分子筛对气体的吸附能力差异,探究了分子筛的吸附机理.研究结果表明:液氮温度下,5A和13X分子筛在真空条件下对N2及O2的吸附性...     

Thermodynamic Properties of a d-Wave Superconductor Near Zero Temperature

On the basis of Fermi liquid theory, we study the thermodynamic properties near zero temperature of a d-wave superconductor assuming the BCS pairing model. The temperature dependence of the order parameter is derived. We then obtain an analytical expression for the free energy difference between the normal and superconducting states in the vicinity of zero temperature from the coupling constant integral. New expressions for the critical field and the specific heat in the superconducting state are given as functions of temperature. We compare our expressions with previous formulas due to others.     

填炭纸在高真空多层绝热中液氮温度下的吸气性能测试

通过实验获得了填炭纸在液氮温度下对N2和H2两种气体的等温吸附线,结果表明:填炭纸对N2的吸附效果非常好,对H2的吸附效果较差,相同平衡压力下对N2的吸附量比对H2的吸附量高出1～2个数量级,且在填炭纸外包上绝热材料能大大提高其对气体的吸附能力,尤其是对N2的吸附量能提高1～2个数量级,对H2的吸附量也能提高1倍以上,填炭纸对H2的吸附效果是活性炭的3～15倍.用Temkin吸附式对等温吸附线进行拟合,得到了填炭纸在10-4～10 Pa范围内适用的对N2和H2两种气体的等温吸附方程式.     

Effects of Temperature and [S] on the Kinetics of Nitrogen Removal from Liquid Steel

The kinetics of denitrogenation from liquid steel was studied by using an oxygen-nitrogen analysis system(LECO TC-436) under 1600℃ similar to 2813℃ conditions. The results show that when [S]=0.005%, nitrogen removal was controlled by nitrogen transfer in liquid diffusion layer, when [S]=0.012% and 0.140%, it was controlled by both nitrogen transfer in liquid diffusion layer and the chemical reaction at the liquid-gas interface below 2250℃, and by nitrogen transfer in liquid diffusion layer under 2250℃ similar to 2813 degreesC conditions. The activation energy E-a was 57 kJ/mol for 0.0050%[S], 95 kJ/mol for 0.012%[S], 165 kJ/mol for 0.140%[S]. The resistance of sulphur on nitrogen removal decreased with the temperature rose, and disappeared at 2630℃. Based on the results obtained, it has been answered why the nitrogen in liquid steel can be decreased rapidly by carbon-oxygen reaction under very high oxygen and sulphur content conditions during the BOF, EAF, VOD and AOD steelmaking processes.     

高温高湿生产厂房除湿降温技术研究与应用

由于厂房内部非常潮湿,加之水蒸气碱性较大,对设备腐蚀性非常严重,严重影响了设备的正常使用,增加了维修的难度。在投产几年内,部分设备已经严重腐蚀。作业人员长时间在厂房内工作,将严重危害身体健康。     

磁悬浮转子径向位置精度的实验研究

以实际涡轮膨胀机为对象，研究了径向控制电流、工作载荷、轴承及转子的温度变化、磁场干扰等因素与转子径向位置精度的关系。提出了估计转子实际静态工作点变化的方法。实验数据表明，估计结果符合实际情况。采用该方法可监测磁悬浮轴承转子系统长期运行的安全性。     

Improvement of YBCO Superconductor Magnetic Shielding by Using Multiple Bulks

HTS bulks present a high critical current density which can be used as magnetic shields. Previous works showed that BSCCO bulks can screen magnetic fields up to 0.1 T. For large scale applications like electrical machines, stronger magnetic field is usually needed. In so doing, (RE)BCO materials are more suitable since they can shield much higher magnetic fields. Another key issue concerns the size of the bulks. Nowadays, it is possible to manufacture 150-mm diameter class cylindrical YBCO bulk. In order to get larger magnetic shielding areas, multiple bulk superconductors should be arrayed and stacked in layers. This paper presents experimental results on screening performances of layered YBCO pellets. These results are compared with 2D simulations. The experiments are carried out at 77 K under external magnetic fields of 150 mT. Different topologies are considered: single-layer configuration with 9 square pellets and double-layer configuration with respectively 9 and 4 square pellets. Experimental and simulation results show that a checkerboard of one layer configuration does not fully shield the external magnetic field. Improved shielding properties are obtained when the double-layer configuration is used.     

高温热泵在我国的应用及研究进展

综述了近年来高温热泵技术在我国的应用和研究进展.列举了高温热泵的应用实例和效果,并提供了多种公开发表的有关高温热泵技术的研究成果,如高温热泵循环工质、高温热泵循环系统的优化等.在此基础上,指出了现有研究内容的不足和高温热泵未来几年的研究方向.     

Bi-Sr-Ca-Cu-O系高温超导体结构的电子显微镜研究

本文用透射电子显微术和 EDAX 对 Bi 系超导体的成份和晶体结构进行了分析研究。结果表明该 Bi 系超导体中存在 a=b=5.41(?)c=24.21(?)四方结构超导相,为改进成份、热处理工艺提供了依据。