三级复叠式制冷系统性能的实验研究

实验系统为三级复叠制冷循环,制冷系统制冷剂为R404A/R23/R14,最低温度可达到-110℃以下。实验时测量系统运行的温度、压力以及压缩机的压比、耗功等参数。结果表明:库温从-60℃降低到-110℃的过程中,三级复叠式制冷循环制冷量先升高后降低,在-80℃左右时达到最大值,并且在整个降温降温过程中,压缩机的耗功一直减小;由三台压缩机的吸、排气压力变化图以及压比变化图和排气温度变化图分析可知,系统有不匹配的地方,还需进一步改进。     

Influence of GaAsP Insertion Layers on Performance of InGaAsP/InGaP/A1GaAs Quantum-Well Laser

We report on the use of very thin GaAsP insertion layers to improve the performance of an In GaAsP/InGaP/AIGaAs single quantum-well laser structure grown by metal organic chemical vapour deposition. Compared to the noninsertion structure, the full width at half maximum of photoluminescence spectrum of the insertion structure measured at room temperature is decreased from 47 to 38 nm indicating sharper interfaces. X-ray diffraction shows that the GaAsP insertion layers between AIGaAs and InGaP compensates for the compressive strain to improve the total interface. The laser performance of the insertion structure is significantly improved as compared with the counterpart without the insertion layers. The threshold current is decreased from 560 to 450 mA while the slope efficiency is increased from 0.61 to 0.7W/A and the output power is increased from 370 to 940mW. The slope efficiency improved is very high for the devices without coated facets. The improved laser performance is attributed to the suppression of indium carry-over due to the use of the GaAsP insertion layers.     

Optimization of the Loading Process of the QUIC Magnetic Trap for the Experiment of Bose-Einstein Condensation

The magnetic quadrupole-Ioffe configuration (QUIC) trap in our Bose-Einstein condensation experiment is introduced. The magnetic trap loading process after laser cooling is ana/ysed and the optimization of the loading process is studied experimentally, Calculation of the magnetic field explains the loss of the atoms during the loading process of the QUIC trap. The number of atoms loaded in the QUIC trap is increased by 40% after optimization in comparison with the normal loading process.     

软代数的同余理想

本文以软代数Ｆ的真积分解为工具，得到的主要结果是，如果软代数Ｆ的每信满足条件Ｉ∩Ｉ’＝Φ的理想Ｉ都是同余理想。则Ｆ是既约软代数，在既约的情况下，给出了软代数Ｆ的每个满足条件Ｉ∩Ｉ‘＝Φ的理想Ｉ都是同余理想的一个充分条件。从而初步解决了文「１」的结尾提出的一个问题。     

Interactions of a Projectile Charge with Two-Dimensional Dusty Plasmas

The interactions of a moving charge (namely, one additional dust particle) with a two-dimensional dusty plasma in gas discharge experiment are studied by means of the linearized hydrodynamic theory for the dusty plasma. Expressions are derived for the induced potential and the stopping power of the moving charge, when the charge flights parallel to and over the dust layer. The numerical results are obtained for different discharge pressures and different distances from the moving charge to the dust layer. The results show that the moving charge excites a V-shaped disturbance of induced potential or the so-called Mach cone in the dust layer, while the charge itself loses its energy.     

穿孔板在切向流条件下非线性效应的理论与实验研究

流过声衬表面的切向流和高声压级的声场对于穿孔板共振结构的声学特性有这非常显著的影响。本文从波涡相互作用机制出发,发展了一种旨在研究矩形穿孔板在切向流条件下非线性效应的离散涡模型。同时用双传声器法测量了不同几何参数的穿孔板的声阻抗随偏流速度及声压级的变化情况。将本文的实验与理论结果进行了对比分析,对比的结果表明本文的实验与理论结果符合良好。     

弹性接触问题的形状优化设计方法

设计模型复杂和结构的高度非线性等问题使得目前结构优化技术中很少涉及接触问题。面向对象的有限元法利用了面向对象编程的优点，有效地提高了编程的效率，并便于程序的扩充。在Visual C 软件平台上，开发编制了面向对象的有限元法程序，并对含接触问题的结构进行形状优化设计，重点推导并给出了含接触问题有限元法的灵敏度全解析分析的表达式，包括位移和应力的灵敏度分析、接触条件的灵敏度分析及相应的边界支配方程等。最后通过算例，验证了所提出的优化方法的正确性。     

基于声涡转化对穿孔板切向流效应的研究

建立了一种有关切向流对小孔声阻抗影响的小扰动势流模型,其要点是使用法向质点速度连续而非广为采用的质点位移连续边界条件来匹配小孔剪切层两侧的声场,并在小孔前缘施加 Kutta条件以反映切向流效应的机理——锐缘处的声涡转化;模型中还考虑了实际应用中经常遇到的小孔形状和穿孔板厚度两个重要因素.理论预测的声阻和声抗与实验结果吻合良好.     

珊瑚礁工程地质初论──新的研究领域珊瑚礁工程地质

珊瑚礁是一种特殊的岩土类型。珊瑚礁工程地质是工程地质学的一个新领域。本文概述了珊瑚礁的工程建设简史和二战后期以来珊瑚礁工程地质研究的兴起, 提出了必须加强我国珊瑚礁工程地质的研究。