高速光测装置的价值函数

本文提出一个价值函数,作为高速光测装置的评价准则。此函数建立在装置可能获得的信息容量和质量的基础上,例如,数据锐度和装置的多功能性等。     

A new instrument for measuring the viscoelastic properties of dilute polymer solutions

A new oscillating capillary viscometer has been developed and used for measuring viscoelastic flow properties of dilute polymer solutions. These flow properties are determined from measurements of the pressure to volume flow relationships for sinusoidal flow in cylindrical glass capillaries. The theory for this measurement procedure is based upon the known theory for oscillatory flow of a viscoelastic fluid in circular tubes and which is presented with a few supplementations in this paper.The oscillatory flow is generated by a piezoelectric driver which is dipped directly into the aqueous solution. The advantage of this driver is that the excitation voltage for the piston is a direct measure of the motion of the piston. Changes in pressure are measured with a sensitive low-pressure quartz tranducer.The viscometer was tested with aqueous glycerol solutions and a gelatin gel. The viscoelastic flow properties of dilute polymer solutions (gelatin, gelatin/color-coupler, polyacrylamide) were then investigated in the frequency range 5 Hz to 150 Hz at very small volume flow amplitudes. The results presented illustrate the suitability of the method. The results are also evaluated with regard to the stabilizing action of slightly viscoelastic gelatinous coating liquids in the high-speed coating process in the manufacture of photographic materials.     

CHARACTERISTICS OF 30--60 DAY OSCILLATION OF GENERAL CIRCULATION IN NORTHERN HEMISPHERE

Some characteristics of the 30- 60 day oscillation in general circulation are investigatedin this paper. In the tropical atmosphere, besides some results consisting with the knownfacts, we still find that the 30- 60 day atmospheric oscillations are very obvious in theequatorial eastern Pacific, and the zonal scale of the vorticity and divergence for the30- 60 day oscillation in the tropics is much smaller than wavenumber 1. There are the strongest 30- 60 day oscillations at the high latitudes in the Northern Hemi-sphere, but weaker at 20°-40°N latitudes. The 30- 60 day oscillations have an obviousbarotropic structure at mid-high latitudes and their zonal scales are smaller than those in thetropics. The 30- 60 day oscillations at the mid-latitudes propagate westwards and fast in thewintertime. At the high latitudes, 30- 60 day oscillations propagate westwards in the win-tertime but eastwards in the summertime. Meridional propagations of the oscillation arerather different in various regions.     

On the output characteristics of a semiconductor optical amplifier driven by an ultrafast optical time division multiplexing pulse train

A comprehensive theoretical analysis of a semiconductor optical amplifier (SOA) that is subject to an ultrafast optical time division multiplexing pulse stream is presented with the help of a simple but efficient model developed for this purpose. The model combines the necessary set of mathematical equations with the appropriate simplifying assumptions to describe in the time domain gain saturation and recovery for the case of multiple incoming pulses. In this manner, analytical expressions can be obtained for the power and chirp profile of the amplified pulses, essentially extending the work that has been performed for a single pulse only. This allows to identify the critical operational parameters and to investigate and evaluate their effect on these two output characteristics. The derived simulation curves are thoroughly studied to specify the limitations imposed on the SOA small signal gain and carrier lifetime as well as on the full-width at half-maximum (FWHM) and energy of the input pulses and, based on a series of logical arguments, to extract useful rules concerning their selection so as to achieve improved performance with respect to the practical applications of all-optical switching and pulse compression. The obtained results indicate that due to the continuous insertion of pulses, the requirements for the SOA small signal gain and the input pulse energy are stringent than those for the case of isolated pulse amplification. The combination of these two parameters determines also the regime in which the amplifier must be biased to operate in order to ensure distortionless pulse amplification and enhanced chirp for efficient pulse compression and it has been found that low saturation is necessary for the former case whilst heavy saturation for the latter. The scopes of the corresponding requirements for the carrier lifetime and the FWHM are also tight but to a less extent and can be simply satisfied with the available photonics technology. These results are in good agreement with the available experimental data essentially proving the validity and robustness of the model. The model can be thus applied to predict the behavior of more complex all-optical circuits of enhanced functionality in which the SOA is the basic functional device.     

A rail noise prediction model for the Tehran-Karaj commuter train

Rail noise prediction models enable consideration of different scenarios for the optimal management of noise prevention and mitigation. This project is aimed at developing an equation that enables computation of L_A,max for the Tehran-Karaj commuter train, a type of Diesel-Electric Locomotive. The form of the proposed model is derived from equations for predicting L_A,max for a single locomotive pass-by, proposed in the manual prepared by Harris Miller Miller & Hanson Inc. for the US Federal Transit Administration, and in the French rail noise prediction model. The algorithm for predicting L_A,max for the Tehran-Karaj commuter train has been developed on the basis of the 50 measurements from 5 locations at distances of 25 m, 35 m, 45 m, 55 m, and 65 m from the centre of the track and at a height of 1.5 m. In the field measurements, the reference distance and the reference vehicle speed have respectively been set equal to 25 m and 80 km per hour. The reference L_A,max, length and the speed correction coefficients have been estimated from the field measurements and have been found to be 86.2 dB(A), 11.3, and 18.4 respectively. The fitness test (Kolmogorov-Smirnov) and regression analysis indicate satisfactory results.     

非线性掺铒光纤环镜中超短光孤子串的产生及放大

利用数值模拟方法证明了,双频弱连续波的拍频信号在分布增益的非线性掺铒光纤环镜内传输,能产生超短光孤子串.数值计算表明,当输入信号为重复率<20 GHz的拍频弱信号时,可在较短的环镜长度内产生占空比大且高质量的光孤子串.研究同时发现,输入信号的平均功率越大,所需环镜长度越短.与其他方法相比,该方法不仅能克服传统方法所产生的脉冲重复率受限的困难,而且在无需采用特种光纤的情况下,将弱信号转化为超短光孤子串.     

A study of daily variation in cosmic ray intensity during high/low amplitude days

A detailed study has been conducted on the long-term changes in the diurnal, semi-diurnal and tri-diurnal anisotropies of cosmic rays in terms of the high/low amplitude anisotropic wave train events (HAE/LAE) during the period 1981–94 using the neutron monitor data from Deep River Neutron Monitoring Station. In all, 38 HAE and 28 LAE cases have been studied. An inter-comparison of the first three harmonics during these events has been made so as to understand the basic reason for the occurrence of these types of events. It has been observed that the phase of diurnal anisotropy shifts towards earlier hours for HAEs and it shifts towards earlier hour as compared to 18-h direction for LAEs. For semi-diurnal anisotropy, phase remains statistically the same for both HAE and LAE. In the case of tri-diurnal anisotropy, phase is evenly distributed for both types of events. The interplanetary magnetic field (IMF) and solar wind plasma (SWP) parameters during these events are also investigated. It has also been observed that HAE/LAEs are weakly dependent on high-speed solar wind velocity. The two types of solar wind streams (corotating streams and flare-generated streams) produce significant deviations in cosmic ray intensity during HAE/LAE.      

A material design of a new high-performance ferroelectric. I. SrTiO2C perovskite

At room temperature, cubic SrTiO₃ perovskite exhibits only paraelectric property, although ferroeletric properties appear in tetragonal BaTiO₃ and PbTiO₃. In this study, the new high-performance ferroelectric such as SrTiO₂C perovskite was theoretically designed. Cluster model calculations based on hybrid density functional theory were performed to clarify a ferroelectric mechanism of SrTiO₂C. It has been concluded that SrTiO₂C can be utilised for a ferroelectric material of a high-speed memory, due to the extremely small polarisation-inversion energy.     

水下爆炸气泡脉动测量及分析

水下爆炸气泡破坏效应是水中兵器的重要毁伤模式之一。为研究水下爆炸气泡脉动现象,建立了小当量水下爆炸实验系统,并进行了爆炸当量分别为0.125g、1.0g、3.375g和8g TNT的水下爆炸实验。采用球形PETN装药并中心起爆,产生球形对称的气泡和冲击波载荷,并利用高速摄像系统记录水下爆炸气泡脉动过程,以及布置压力传感器测量水中冲击波压力。实验获得了清晰的水下爆炸气泡脉动过程图像,得到了冲击波和气泡脉动压力曲线。对数字化图像进行判读,得到气泡脉动直径和周期。另外根据冲击波曲线测量了气泡脉动周期,对比分析了气泡脉动相关参数。结果表明,高速摄像数据测量的气泡直径与经验公式较接近,高速摄像测量的气泡周期与冲击波曲线测量的气泡脉动周期以及经验公式结果具有较好的一致性。本文提出的实验技术安全、经济、可靠,气泡脉动参数判读精确,满足水下爆炸气泡脉动研究需求。