HL-2M 装置供电系统研制

为满足 HL-2M 装置的供电需求,须配套建设相应的供电系统。通过仿真计算 HL-2M 装置的总体供 电需求,考虑到 HL-2A 装置现有的供电系统设备,提出了兼顾 HL-2A 和 HL-2M 装置供电需求的总体配置方案。介绍了国内首台 300MVA 立式交流脉冲发电机组、磁体电源、高压电源和电源控制系统的研制情况。     

磁场电源在 HL-2M 装置初始等离子体放电中的应用

磁场电源是 HL-2M 装置初始等离子体放电的重要组成部分,它关系到 HL-2M 装置零场的建立,等 离子体的击穿和维持及位形控制。为实现初始等离子体放电所需的供电电压和电流,对磁场电源从主回路、控制、 测量和保护分别作了相应的调整。在此基础上进行了大量的工程调试,确保了磁场电源的控制和保护等性能达到 初始等离子体放电的需求。在磁场电源运行中,电源控制性能和输出参数的一致性、纹波质量等都有显著提高。 介绍了磁场电源在调试及 HL-2M 装置初始放电中的应用。     

Continuous production of glass-coated microwires and the applications for broadband noise suppression composite sheets

A system and a method were developed for continuous production of glass-coated microwires with controllable glass thickness and metallic core diameter. Fe-Si-Al flakes were fabricated by planetary ball milling using ethanol as a dispersant. A composite noise suppression sheet was prepared with glass-coated microwires combined with Fe-Si-Al flakes. The characteristics of the conduction noise suppression of the composite sheet were evaluated on a microstrip line in gigahertz frequencies. The conduction electromagnetic noise was effectively suppressed by the composite sheet in broad-band frequency region; the power loss is greater than 70% in the frequency range from 0.7 to 8.5 GHz.     

Temperature dependent energy relaxation time in AlGaN/AlN/GaN heterostructures

The two-dimensional (2D) electron energy relaxation in Al_0.25Ga_0.75N/AlN/GaN heterostructures was investigated experimentally by using two experimental techniques; Shubnikov-de Haas (SdH) effect and classical Hall Effect. The electron temperature (T_e) of hot electrons was obtained from the lattice temperature (T_L) and the applied electric field dependencies of the amplitude of SdH oscillations and Hall mobility. The experimental results for the electron temperature dependence of power loss are also compared with the current theoretical models for power loss in 2D semiconductors. The power loss that was determined from the SdH measurements indicates that the energy relaxation of electrons is due to acoustic phonon emission via unscreened piezoelectric interaction. In addition, the power loss from the electrons obtained from Hall mobility for electron temperatures in the range T_e > 100 K is associated with optical phonon emission. The temperature dependent energy relaxation time in Al_0.25Ga_0.75N/AlN/GaN heterostructures that was determined from the power loss data indicates that hot electrons relax spontaneously with MHz to THz emission with increasing temperatures.     

关于激光模谱分析实验模式图的讨论

对近代物理实验中激光模谱分析实验激光模式图的具体表示形式及所表达的物理含义进行了分析及讨论.     

微波场中Josephson结的微波发射与吸收研究

采用数值仿真方法,研究微波场中约瑟夫森结微波感应台阶处的功率特性。发现微波场中约瑟夫森结不止吸收辐射,也发射辐射的情况。得到微波辐照和结电阻对功率吸收和发射的影响规律。结果表明,处于发射功率的状态对应的偏置电流范围占整个台阶总电流范围的比例可以趋于50%。这一发现对约瑟夫森结理论和应用研究具有重要的意义。     

Long-term correlations in hourly wind speed records in Pernambuco, Brazil

We study the statistical properties of hourly wind speed time series detected at four weather stations in the state of Pernambuco, Brazil, in the period 2008-2009. We find that the average and maximum hourly wind speeds deviate from a mutual linear relationship, and that they may be well explained individually by a Weibull distribution, however, with different shape parameter values. On the other hand, the long-term correlations of both of these observables obey the same power-law behavior, with two distinct scaling regimes. Our results agree with previous studies on wind speed series correlations in other regions of the world, which is suggestive of universal behavior.     

Evaluation of relative importance of ultrasound reactor parameters for the removal of estrogen hormones in water

The growing interest in sonochemistry as a tool for environmental remediation leads to the need for process optimization. Sonochemistry is a complex process, which depends on physical parameters and also on the process conditions. Physical parameters are interrelated and therefore a systematic approach has to be taken to optimize the process. The effect of physical parameters on the destruction of seven estrogen hormones (17α-estradiol, 17β-estradiol, estriol, 17α-ethinylestradiol, 17α-dihydroequilin, estrone and equilin) is reported in this study. Artificial neural networks (ANN) was used as a tool to identify the correlations between these process parameters. ANN enabled the establishment of relationship between sonication parameters such as power density, power intensity, ultrasound amplitude, as well as the reactor design parameters. The major significance was attributed to the area-specific power density and the volume-specific power intensity. The results of this work provide a sound basis to design pilot and full-scale ultrasound treatment systems. Process optimization lead to a 5-fold decrease in energy consumption as compared to the commercially available reactors, thereby making the process attractive for field applications.     

Tempered stable Lévy motion and transient super-diffusion

The space-fractional diffusion equation models anomalous super-diffusion. Its solutions are transition densities of a stable Lévy motion, representing the accumulation of power-law jumps. The tempered stable Lévy motion uses exponential tempering to cool these jumps. A tempered fractional diffusion equation governs the transition densities, which progress from super-diffusive early-time to diffusive late-time behavior. This article provides finite difference and particle tracking methods for solving the tempered fractional diffusion equation with drift. A temporal and spatial second-order Crank-Nicolson method is developed, based on a finite difference formula for tempered fractional derivatives. A new exponential rejection method for simulating tempered Lévy stables is presented to facilitate particle tracking codes.     

Power Spectrum in Krein Space Quantization

The power spectrum of scalar field and space-time metric perturbations produced in the process of inflation of universe, have been presented in this paper by an alternative approach to field quantization namely, Krein space quantization (Gazeau et al. in Class. Quantum Gravity 17:1415, 2000; Takook in Int. J. Mod. Phys. E 11:509, 2002; Rouhani and Takook in ). Auxiliary negative norm states, the modes of which do not interact with the physical world, have been utilized in this method. Presence of negative norm states play the role of an automatic renormalization device for the theory.