基于半导体激光器的乙炔气体光声光谱检测及其定量分析

油中溶解乙炔是变压器等油浸式电气设备早期放电性故障的重要特征气体。基于半导体激光器的光声光谱传感技术具有灵敏度高,选择性好等优点,能很好地应用于微弱气体检测中。论文构建了基于分布反馈半导体激光器光声光谱检测装置,并分析了光声池的特性参数;实验研究了光声信号与激光功率、乙炔气体浓度之间的关系;并借助激光器的波长调制特性,研究了乙炔分子在近红外区第一泛音带1.5μm附近的光声光谱;提出了一种基于最小二乘回归的光声光谱定量分析方法。理论和实验结果为乙炔的光声光谱在线检测及高灵敏度可调谐光声光谱仪的设计提供了参考。     

变压器油中气体拉曼光谱检测及信号处理方法

准确检测变压器油中溶解故障特征气体是诊断变压器运行状态的重要技术手段之一。论文基于拉曼光谱和腔长调制频率锁定原理,搭建了变压器故障特征气体频率锁定腔增强拉曼光检测平台,实现了H_2、CH_4、C_2H_2、C_2H_4、C_2H_6、CO、CO_2等七种故障特征气体的同时检测;1atm时,H_2、CH_4、C_2H_2、C_2H_4、C_2H_6、CO、CO_2的最小检测浓度实验值分别达到106、25、45、73、41、170、126(ppm)。频率锁定增强腔技术使最小检测浓度提高了约68倍。运用小波模极大值法对H_2的拉曼光谱检测信号进行了去噪处理,提出了基于包络线迭代法的光谱基线校正方法,校正后的光谱荧光背景残留减少,使气体拉曼光谱检测准确度提高了约2.95%,为变压器油中溶解故障气体同时准确检测提出了一种新方法。     

Ferrographic and spectrometer oil analysis from a failed gas turbine engine

An experimental gas turbine engine was destroyed as a result of the combustion of its titanium components. It was concluded that a severe surge may have caused interference between rotating and stationary compressor parts that either directly or indirectly ignited the titanium components. Several engine oil samples (before and after the failure) were analyzed with a Ferrograph and with plasma, atomic absorption and emission spectrometers to see whether this information would aid in the engine failure diagnosis. The analyses indicated that a lubrication system failure was not a contributory factor in the engine failure. Neither an abnormal wear mechanism nor a high level of wear debris was detected in the engine oil sample taken just prior to the test in which the failure occurred. However, low concentrations (0.2–0.5 ppm) of titanium were evident in this sample and samples taken earlier. After the failure, higher titanium concentrations (more than 2 ppm) were detected in oil samples taken from different engine locations. Ferrographic analysis indicated that most of the titanium was contained in spherical metallic debris after the failure. Attempts to pinpoint the failure initiation site were inconclusive, but the oil analyses did eliminate a lubrication system bearing or shaft seal failure as the cause of the engine failure.     

用改装的HP5890型GC作变压器油中溶解气的一次进样全分析

通过对HP5890型GC的改装，使其满足了新电力行标DL／T 722-2000的技术要求，实现了对变压器油中溶解气的一次进样全分析。     

用于光合作用的光声光谱仪数据采集系统的改进

对本室研制的用于光合作用研空的光声不义的数据采集系统作了改进。采用计算机采样,提高了采样频率和锁相放大器的时间常数,实验应用了基于最小二乘法的数字滤波技术、多通道采样技术、变要样技术。列举的实例证明,改进了数据采集系统的光声光谱仪,在性能上有了很大的提高。     

用于光合作用研究的光声光谱仪数据采集系统的改进

对本室研制的用于光合作用研究的光声光谱仪的数据采集系统作了改进.采用计算机采样,提高了采样频率和锁相放大器的时间常数.实验应用了基于最小二乘法的数字滤波技术、多通道采样技术、变频率采样技术.列举的实例证明,改进了数据采集系统的光声光谱仪,在性能上有了很大的提高.     

Production of a transformer oil from paraffinic basestocks

The work described in this paper is concerned with the production of a high quality transformer oil from local Egyptian paraffinic basestocks. Analysis showed that a neutral base oil 70N was most suitable for producing transformer oils. This neutral base oil was chemically treated with a sulphonation process. Optimum sulphonation conditions were achieved by using oleum or SO₃ at a concentration of 6 wt. %. The sulphonation reaction was carried out in three stages, each with an equal portion of the sulphonating agent. The acidic oil was then neutralised with an alkaline solution. Oil colour improvement was effected using activated clay as an absorbent. Laboratory results and field trials indicated that such a treated neutral paraffinic oil meets the IEC 296 international specifications for transformer oils, with the exception of pour point (−12°C). However, such a pour point is not relevant in certain hot climatic conditions. Comparative evaluation of the treated oil with commercial transformer oils has shown its suitability.     

Photon detection efficiency of a germanium semiconductor spectrometer

A mathematical model of a detector has been constructed using the comparison of calculated and experimental values of the photon detection efficiency of a gamma-spectrometer based on a high-purity germanium detector. The method and program for calculating the correction for coincidences in low-activity measurements for radionuclides with complex decay schemes have been created. This study makes it possible to calculate the photon detection efficiency in the cases, where the working standards for the considered measurement conditions are absent, and to take the correction of the experimental data for the cascade summation into account.     

SF 3208型原子吸收分光光度计乙炔气路检修一例

故障现象：本单位一台SF3280型原子吸收分光光度计（上分厂产品）在使用中出现了原子化器火焰不能点燃,同时乙炔气体压力表和流量表均无指示,但乙炔钢瓶低压表正常的现象。为此,关闭了乙炔气钢瓶总阀,过段时间再打开,可以正常点火使用。但第二天又重复出现上述现象,在调换了新钢瓶后,仍不见好。原认为乙炔输气管路漏气,经查气路正常。再查仪器气路控制阀门开关,空气气路通断正常,但乙炔压力表和流量表无反应,有电磁阔的断合声。故障分析：从以上现象可以判断故障出在仪器内的乙炔气路上。将仪器后部乙炔进口气路接管拆下,换上…     

一种新型变压器油中溶解气体在线监测仪的研究

研究提出了一种基于固体氧化物燃料电池(SOFC)技术的微量可燃气体检测新方法,该方法只需要一种载气就能够完成变压器油中溶解气体的检测.利用从四大守恒定律出发建立的管式SOFC数学模型,得到了可燃气体含量与SOFC输出电压的关系,进而通过优化参数并结合色谱分析技术设计了一套变压器油中气体在线监测仪.该测量仪以嵌入式PC104为核心,具有油中气体含量的实时LCD显示,并通过与上位机的串行通信实现气体含量数据的后台存储.实验与现场投运的结果表明该技术满足电力变压器在线监测与故障诊断的需求,具有线性度好、精度高、方便、清洁和自动化程度高等优点.     

光声成像反射伪影的机理分析和控制

在光声成像中,重建图像经常会受到图像伪影的影响而降低图像质量.为了解决图像伪影的问题,从超声波在水中的传播特性出发,分析了光声图像中伪影的产生机理.分析表明:伪影的产生是由超声信号在水面的反射延迟造成的.进而提出了通过延迟相减来控制反射伪影的方法,并给出了在实际应用中控制水面高度的依据.通过构建的光声成像平台进行实验验证,结果表明:提出的方法能有效地消除重建图像中的伪影,提高了重建图像的质量.     

Note: Observation and analysis of the aberration in a photoacoustic imaging system

Acoustic lens is applied in the research of photoacoustic imaging. The aberration is always inevitable due to the existence of the acoustic lens, and it influences the resolution of the imaging system severely. However, the imaging system based on an acoustic lens also provides a new method for observing the aberration of a system and testing the quality of the acoustic lens. In this paper, a method of observing the aberration of photoacoustic imaging system is reported, and the causes of aberrations are discussed based on the theory of lens aberration. All these would be helpful to correct the aberration and improve the resolving power of acoustic lens.     

基于模糊粗糙集的变压器油纸绝缘状态评估

回复电压法(RVM)是一种研究电力变压器绝缘老化状态的检测方法,基于大量回复电压测试数据,提出运用模糊粗糙集理论评估变压器油纸绝缘状态,并构建变压器油纸绝缘状态评估系统。首先,基于回复电压特征量建立变压器油纸绝缘状态评估指标;其次,采用模糊C均值聚类算法获得变压器测试数据对于特征量模糊划分的隶属度函数;然后,根据可辨识矩阵对油纸绝缘状态评估表的模糊属性进行约简,并提取油纸绝缘状态评估规则;最后,在历史数据库的基础上构建油纸绝缘状态评估系统。通过实例演绎论证提出的评估系统能有效、准确地评估电力变压器绝缘状态,为变压器油纸绝缘状态评估提供了新思路,且在工程应用中具有实际价值。     

Investigation of iron content of lubricating oil using a Ferrograph and an emission spectrometer

An investigation was carried out into the discrepancies in iron content of used oils as assessed by density readings of Ferrograms and determined by several emission spectrometers of the rotating disc type. It was concluded that used jet engine oil contains a significant number of iron particles so large that the spectrometer is not responsive to them and also contains a large total fraction of iron content in the form of non-magnetic compounds which are not precipitated on the Ferrobgram.     

Characteristics of the system of polarization-optical detection of a pulsed terahertz spectrometer

Characteristics of a system of polarization-optical detection of a pulsed terahertz spectrometer in nonlinear crystals of zinc telluride (ZnTe) are considered. The influence of the ZnTe crystal thickness (0.5, 1, and 2 mm) on the detection system sensitivity is studied experimentally; a comparison with model calculations is performed. The effect of the time step and the interval of scanning of the terahertz pulse on the spectral resolution and range of the spectrometer is demonstrated experimentally and theoretically. Terahertz transmission spectra of typical container materials are measured.     

A portable mass spectrometer for direct monitoring of gases and volatile compounds in air and water samples

A portable automated mass-spectrometric system allows direct testing of gases and volatile substances in both air and water samples in in situ and on-line modes and is intended for studies in ecology, oceanology, and for testing technological processes. The parameters, the instrument design and operating modes, and the units included in it are described. The choice of the design of the membrane input system, which ensures low threshold levels of detecting goal compounds (down to a few ppb for toluene and benzene) and the dependence of this choice on the measurement mode and the state and composition of the investigated sample are considered. The results of tests of the mass-spectrometer in the mode of direct selective and total inspection are presented.     

Signal-to-noise analysis of biomedical photoacoustic measurements in time and frequency domains

Sensitivity analysis of photoacoustic measurements is conducted using estimates of the signal-to-noise ratio (SNR) achieved under two different modes of optical excitation. The standard pulsed time-domain photoacoustic imaging is compared to the frequency-domain counterpart with a modulated optical source. The feasibility of high-SNR continuous wave depth-resolved photoacoustics with frequency-swept (chirp) modulation pattern has been demonstrated. Utilization of chirped modulation waveforms achieves dramatic SNR increase of the periodic signals and preserves axial resolution comparable to the time-domain method. Estimates of the signal-to-noise ratio were obtained using typical parameters of piezoelectric transducers and optical properties of tissue.     

A precise scheme for detection of current transformer saturation based on time frequency analysis

Current Transformers (CTs) are prone to saturation due to large amplitude of fault current and existence of decaying Direct Current (DC) offset. Since the CT saturation leads to mal-operation of protective relays, detection and correction of saturated currents is one of the most important challenges in the power systems protection. In this paper, a new algorithm is presented for detection of CT saturation time interval by using the Improved S-Transform (IST). Simultaneously, IST can yield a complete visualization of signal in both time and frequency domains. An index based on instantaneous power of the CT secondary current is calculated using the IST output matrix. Then, the saturation region is estimated by determining the maximum and minimum values of the proposed index in the time domain. Comprehensive simulations are implemented using PSCAD/EMTDC software. Main parameters which have direct effect on the saturation levels are considered in simulation studies. As extremum points of the proposed index are determined for detection of saturation regions, the proposed method is not affected by CT parameters. The obtained results show that the proposed algorithm can precisely detect CT saturation time intervals even in noisy conditions.     

Precise measurements of collision parameters of spectral lines with a spectrometer with radioacoustic detection of absorption in the millimeter and submillimeter ranges

The factors influencing the accuracy of determining the parameters of molecular lines with the use of a spectrometer with radioacoustic detection of absorption are analyzed. In addition, the following instrumental features of the spectrometer that were not studied earlier are analyzed: the dependence of the sensitivity of the radioacoustic cell on the pressure of the cell-filling gas and the frequency dependence of the radiation power in the cell at gas pressures lower than 10 Torr. Methods of mathematical simulation of the spectrometer’s output signal at various gas pressures are considered. A technique for calibrating the dependence of the cell’s sensitivity on the pressure based on measurements of the integrated absorption coefficient of molecular spectral lines is presented. With allowance for the considered features of the spectrometer, the parameters of the lines of rotational multiplet J = 9 of fluoroform in the ground vibrational state are studied at gas pressures of 0.01–10 Torr.     

近红外光谱分析快速测定柴油氧化安定性

采用红外光谱方法建立快速测定柴油氧化安定性方法。并对方法的合理性和准确度进行验证。与传统方法比较,该方法具有分析速度快和重现性好的特点。