Time-Resolved Laser Doppler Measurements in the Underexpanded Jet of a Model Gas-Blast Circuit Breaker under Arcing Conditions

A differential laser Doppler system has been used in conjunction with a self-triggered oscillographic raster display system for measuring particle concentrations and flow velocities in a model gas-blast circuit breaker. The flow velocities have been correlated with particle size to enable extrapolation to be made to determine the true plasma flow velocity. The results have been deconvoluted to take account of lateral movements of the arc column. The measurements have been taken with air as the host arcing medium and a flow through a 25-mm-diameter orifice sustained by an upstream pressure of about 7 bar (downstream pressure 1 bar). The arc was sustained by sinusoidal cuffents of peak values 3 and 8 kA and a frequency of 85 Hz. These two currents corresponded to conditions when the model circuit breaker successfully and unsuccessfully interrupted the arc-sustaining current, respectively. The results show that in the case of the 8-kA arc, the flow pattern is severely distorted from that under nonarcing conditions, suggesting that this is a contributory reason for the poorer perfonnance of the model circuit breaker at this higher current level.     

Frequencies Rotation at High Sound Pressure Levels Toward Low Frequencies

Today, analyzing of sound pressure level and frequency is considered as an important index in human society. Sound experts believe that analyzing of these parameters can help us to better understanding of work environments. Sound measurements and frequency analysis did to fix the harmful frequency in all sections in Shiraz gas power plant with sound analyzer model BSWA 308. The sound pressure levels (L_P) and the one and one-third octave band were continuously measured in A and C weighting networks and slow mode for time response. Excel 2013 and Minitab 18.1 software used for statistical calculations. Results analyzed by Minitab 18.1 software. The highest harmful frequency in Shiraz Gas Power Plant (SGPP) was 50 Hz with 115 dB. The sound pressure level (SPL) ranged from 45 dB to 120 dB in one-third octave band and weighting network C. The maximum sound pressure level was in Craft electricity generator with 105.3 dB and 67 Hz. Sound pressure level in surrounded environment was 120 dB. According to the results, in this industry the sound pressure level exceeded the Occupational Exposure Level of Iran (OEL). The value of sound pressure level were higher than the Standard of occupational health. SGPP consumes 47000 cubic meters of natural gas per hour to produce 100 MW (Mega Watt) of electricity. It is very high and it is not economical and cost effective. These numbers indicate that the power plant’s efficiency is low. It could be concluded that the noise pollution is an important issue in these industries. Moreover, SGPP produce noise with loss energy. Frequencies rotation at high sound pressure levels toward low frequencies were happened.     

Inertial Attached Length of an Orifice at High Sound Pressure Levels

Effect of sound pressure level on acoustic impedance of an orifice in a baffle is investigated based on the measurements performed in an impedance tube by the two-microphone method. Dependences of imaginary and real parts of impedance on the orifice diameter are obtained in nonlinear conditions. Special attention is paid to the attached length (the end correction) of the orifice. Dependence of the attached length of an orifice on the oscillating velocity in it is approximated by analytic functions.     

A Model for Diffuse Breakdown in High Pressure Gases at Homogeneous Electric Field Strengs

A model of the breakdown in high pressure gases is presented taking into consideration the finite voltage rise time at the discharge electrodes and a finite initial charge carrier density in the gap. Several types of breakdown could be distinguished important for several applications. Thus, the range of existence of high pressure laser discharges at a given preionization density and circuit parameters can be calculated. Moreover, the change in the breakdown characteristics of high pressure gases at high temperatures is explained. This behaviour seems to be important for understanding the physical processes in circuit breaker chambers.     

Some Aspects of Current Interruption Physics in High Voltage Circuit Breakers

Recent results of experimental and theoretical investigations on current interruption processes are presented with a focus on SF₆ high voltage circuit breakers. Various aspects of thermal interruption at the zero crossing of the current are shown, including the scatter and the distribution of arc voltage shortly before CZ and the role of turbulence. The thermal interruption capability of air and CO₂ are compared to that of SF₆. Investigations on the dielectric recovery are shown for SF₆ and CO₂. The breakdown voltage during the dielectric recovery can be described by simple streamer and leader inception models. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Superconductivity Observed in Tantalum Polyhydride at High Pressure

We report experimental discovery of tantalum polyhydride superconductor.It was synthesized under highpressure and high-temperature conditions using diamond anvil cell combined with in situ high-pressure laser heating techniques.The superconductivity was investigated via resistance measurements at pressures.The highest superconducting transition temperature T_c was found to be ～30 K at 197 GPa in the sample that was synthesized at the same pressure with ～2000 K heating.The transitions a...     

The Ising--Sherrington-Kirpatrick Model in a Magnetic Field at High Temperature

We study a spin system on a large box with both Ising interaction and Sherrington-Kirpatrick couplings, in the presence of an external field. Our results are: (i) existence of the pressure in the limit of an infinite box. When both Ising and Sherrington-Kirpatrick temperatures are high enough, we prove that: (ii) the value of the pressure is given by a suitable replica symmetric solution, and (iii) the fluctuations of the pressure are of order of the inverse of the square of the volume with a normal distribution in the limit. In this regime, the pressure can be expressed in terms of random field Ising models.     

高温高压下绿辉石成因研究

在3 GPa,1 200 ℃条件下,分别以碱性玄武岩粉末和等化学计量光谱纯试剂为原料进行高温高压熔融结晶实验,对实验产物进行了电子探针测试和拉曼光谱分析,确定结晶产物为绿辉石,其拉曼谱峰的半高宽较窄且形态尖锐,表明绿辉石晶体中Si—O四面体结构稳定,矿物内部有序度高。结合前人研究成果探讨了绿辉石成因的影响因素及其原始岩浆,结果表明绿辉石的形成可能受母岩成分、体系流体含量和温压条件等多种因素影响。本实验结果为绿辉石和榴辉岩成因学研究提供可能的实验依据。     

Associated Productions of HZZ and HHZ at Linear Colliders in Large Extra Dimension Model

In this paper we investigate the effects of the large extra dimensions on the two processes e⁺e^-→ H⁰Z⁰Z⁰ and e⁺e^-→ H⁰Z⁰Z⁰ at linear colliders in both unpolarized and polarized collision modes. We find that the virtual Kaluza-Klein graviton exchange can significantly enhance the cross section from their standard model expectations for these two processes. The results show that the LED effect on the process e⁺e^-→ H⁰Z⁰Z⁰ allows the observation limits on the effective scale M_S to be probed up to 9.75 TeV and 10.1 TeV in the unpolarized and +-(λ_e⁺=1/2, λ_e^-=-1/2) polarized beam collision modes (with P_e⁺=0.6, P_e^-=0.8), respectively. For the process e⁺e^-→ H⁰Z⁰Z⁰, these limits on M_S can be probed up to 6.06 TeV and 6.38 TeV in the unpolarized and polarized collision modes separately. We find that the λ_e⁺=1/2, λ_e^-=-1/2 polarization collision mode in both process e⁺e^-→ H⁰Z⁰Z⁰ and e⁺e^-→ H⁰Z⁰Z⁰ may provide a possibility to improve the sensitivity in probing the LED effects.     

Measurement of the Dynamic Displacement Current as a New Method of Study of the Dynamics of Formation of a Streamer at a Breakdown of Gases at a High Pressure

The dynamics of formation of streamers in a “needle–plane” gap filled with air at atmospheric pressure has been studied. It has been shown that the time dependence of the dynamic displacement current measured by either a current shunt or a collector placed behind a grid electrode is determined by the rate of variation of the shape and dimensions of a streamer. The presence of a single peak on oscillograms of the dynamic displacement current means that a ball streamer is formed in the gap and does not cross the gap during the time of voltage application. The presence of two peaks on oscillograms of the dynamic displacement current means that the ball streamer crosses the gap and reaches the opposite electrode. In this case, the ball streamer is usually transformed to a cylindrical one. It has been shown that the measurement of the dynamic displacement current makes it possible to determine the time dependence of the electric field strength near the planar electrode.     

常温高压下水的拉曼谱峰标定压力的研究

 利用金刚石压腔测定了26 ℃高压下水的O—H伸缩振动拉曼谱峰的变化,并对其进行分峰处理,初步确定了水的拉曼拟合峰ν_{3 244}的峰位置与体系压力的关系,且论证了利用水的拉曼拟合峰ν_{3 244}的变化标定金刚石压腔压力的优点以及应用上的局限性。实验结果表明：26 ℃时,在实验的压力范围内,由水的拉曼谱峰拟合得到的ν_{3 244}峰位置随着体系压力的增加呈线性减小。其关系式为p (MPa)=32.9(ν_p)_{3 244}+200.7（3 215 cm^-1< ν_{3 244}<3 244 cm^-1）。     

几种半导体在高压下的金属化相变

 在金刚石压砧装置上，采用我们建立的电阻测量方法，研究了半导体InP_0.97As_0.03、InP_0.5As_0.5、Ga_0.76In_0.24As和Ga_0.24In_0.76As在室温下、16 GPa内的电阻与压力的关系。工作中，对测量技术进行了一些改进，采用微机进行测量控制和数据记录。实验结果表明，这些样品在测量的压力范围内，均发生了金属化相变。它们的相变压力分别为：10.3、9.7、13.5~14.6和10~10.4 GPa左右。这些实验结果在过去发表的文章中未见报导过。     

Observation of the Cinnabar Phase in ZnSe at High Pressure

In this paper we describe the results of an energy dispersive X-ray diffraction experiment carried out in the ZnSe 1 m x Te x alloy and pure ZnSe under high pressure. In the downstroke the cinnabar phase is observed between the rocksalt and the zincblende phases. The analysis of the whole series of compositions ( x =0, 0.05, 0.1 and 0.2) enables us to establish its lattice parameters in ZnSe ( a =3.785 + and c =8.844 + at 10.5 GPa). The X-ray diffraction pattern simulation suggests that the internal parameters u and v are close to 0.5, indicating that the cinnabar phase in ZnSe is similar to that observed in GaAs and ZnTe. The cinnabar's stability range decreases as the Te content is reduced.     

高温高压下文石和方解石的拉曼光谱研究

利用金刚石压腔结合拉曼光谱分析技术,研究了文石在18～388 ℃,71～2 014 MPa,以及方解石在19～351 ℃,96～1 823 MPa条件下的拉曼光谱特征,并得到文石和方解石的拉曼位移与温度、 压力三者之间的关系式。研究结果表明,文石和方解石的拉曼位移随温度压力的变化规律相似,都随压力升高向高频移动,除文石的704 cm-1外均随温度升高向低频移动。二者的晶格振动ν_i/T值均大于[CO₃]基团内振动的值,说明CaO₆八面体的热膨胀性大于[CO₃]基团的热膨胀性。二者的对称伸缩振动ν/T及ν/P值不同,由于该振动拉曼位移和C—O键的键长有关,方解石的C—O键的热膨胀性比文石小而可压缩性比文石大。另外升温升压过程中文石和方解石可以相互转化,伴随该过程发生的[CO₃]基团旋转变形等动力学因素也可以造成二者ν_i/T和ν_i/P值差异。     

Transformation of Carbon Nanotubes to Diamond at High Pressure and High Temperature

The synthesis of diamond at high pressure and high temperature and the discovery of fullerenes and carbon nanotubes are among the most important achievements in carbon science. In the present work, we report the synthesis of diamond from carbon nanotubes at 4.5 GPa and 1300°C. Under these conditions, no diamond crystals were obtained when graphite was used as the starting material. The detailed investigation shows that at high pressure and high temperature carbon nanotubes first transform into quasi-spherical onion-like structures and then into diamond crystals. Our work suggests that carbon nanotubes can be used for the synthesis of high-quality diamond crystals at lower pressure and temperature.     

常温高压下碳酸根离子的拉曼谱峰标定压力初探

在准静水压的条件下,利用碳化硅压腔和显微拉曼光谱原位测量技术,在0～1.7 GPa压力范围测定22 ℃高压下三种不同的H₂O-Na₂CO₃体系(1.5,2.0,2.5 mol·L-1)中CO2-₃的对称伸缩振动ν_{1 066}拉曼谱峰的变化。结果表明,在室温条件下,碳酸根的ν_{1 066}峰的拉曼位移随着压力的增大而线性增加。三种浓度下ν_{1 066}峰的拉曼位移与压力的拟合直线彼此接近,斜率误差小于1%,偏差小于系统误差,因此在实验误差范围内碳酸根浓度对ν_{1 066}峰随压力变化的行为不存在影响。经过数据拟合得到公式：p/MPa=174.13 Δν_{1 066}/cm-1—59.03(Δν_{1 066}=ν_{1 066}-ν_{1 066}0,ν_{1 066}0为体系零压时碳酸根离子ν_{1 066}峰的拉曼位移)。此公式可以用于常温下在含有纯碳酸钠体系中的压力标定。     

Transients in switching a diode with a thin base

An analytical expression is obtained for the duration of the shelf which is observed when a diode with a limited base is switched from the forward to the reverse direction. The problem is solved for an arbitrary value of the recombination velocity at the nonrectifying contact.