弹性蛋白酶发酵过程中发酵液紫外吸收光谱的研究

研究了弹性蛋白酶发酵过程中发酵液紫外吸收光谱的变化,分析比较了发酵液吸收光谱的变化与细菌生长以及发酵产酶过程之间的联系.结果表明,弹性蛋白酶发酵液紫外吸收光谱的变化与菌体生长以及弹性蛋白产酶过程存在密切联系.紫外吸收光谱技术可以用于检测发酵液中有机氮源消耗以及弹性蛋白酶的产生等动态变化,研究为检测弹性蛋白酶发酵的动态过程提供一种比较新颖的方法,为建立紫外光谱技术在线检测发酵过程奠定了基础.     

微振动振幅的精密测量

本文给出一种微振动振幅的精密测量方法.此方法采用光拍相位检测、伺服锁定干涉仪光程差和窄带检测技术,大大提高了信噪比.微振动振幅检测灵敏度达2.2×10~(-2)(?)/Hz~(1/2)(2kHz信号).     

Energy Index technique for detection of Acoustic Emissions associated with incipient bearing failures

The application of Acoustic Emission (AE) technique to condition monitoring of gears and bearings is gaining significance as it can detect early symptoms of defects such as pitting, wear and flaking of surfaces. Such early detection of defects is of vital importance so as to avoid major failures with catastrophic consequences. This article presents results on the Energy Index (EI) technique, used in detecting masked AE signatures associated with the loss of mechanical integrity in bearings. Both simulated and real experimentally generated AE signatures were used to investigate the efficiency and applicability of the technique at signal-to-noise ratios as low as 0.25. In conclusion it is shown that the EI technique is effective in detecting AE burst buried in random noise thereby offering a complementary tool for the diagnostician.     

Bivariate empirical mode decomposition and its contribution to wind turbine condition monitoring

Accessing difficulties and harsh environments require more advanced condition monitoring techniques to ensure the high availability of offshore wind turbines. Empirical mode decomposition (EMD) has been shown to be a promising technique for meeting this need. However, EMD was developed for one-dimensional signals, unable to carry out an information fusion function which is of importance to reach a reliable condition monitoring conclusion. Therefore, bivariate empirical mode decomposition (BEMD) is investigated in this paper to assess whether it could be a better solution for wind turbine condition monitoring. The effectiveness of the proposed technique in detecting machine incipient fault is compared with EMD and a recently developed wavelet-based ‘energy tracking’ technique. Experiments have shown that the proposed BEMD-based technique is more convenient than EMD for processing shaft vibration signals, and more powerful than EMD and wavelet-based techniques in terms of processing the non-stationary and nonlinear wind turbine condition monitoring signals and detecting incipient mechanical and electrical faults.     

Intracavity sensing via compliance voltage in an external cavity quantum cascade laser

We demonstrate a technique for gas phase spectroscopy and sensing by detecting changes in compliance voltage of an external cavity quantum cascade laser due to intracavity absorption. The technique is characterized and used to measure the absorption spectrum of water vapor and Freon-134a.     

适用于化学动力学研究的激光纹影系统

激光纹影技术特别适合检测激波后高温快速反应的反应速率。本文建立的激光纹影系统能很好地从事化学动力学研究。并对Kiefer的激光纹影系统进行了改进,改进后的激光纹影系统测定结果稳定,操作简便。     

Damage localisation in plate like-structures using the two-dimensional polynomial annihilation edge detection method

The topic of non-destructively detecting localised damage in plates is addressed in this article. Since the presence of a crack or a delamination causes a discontinuity in the mode shape first derivatives, a numerical method for detecting discontinuities in smooth piecewise functions and their derivatives, based on a polynomial-annihilation technique is presented. The method, already proposed for beam-type structures, has been extended to enable the detection and localisation of damage in plate-like structures for which only post-damage mode shapes are available. Applying finite element analysis, the mode shapes of an isotropic plate with a saw-cut and a multi-layered composite plate with a delamination have been calculated and the performance of the approach evaluated for increasing amounts of noise. Encouraging results indicate that further development of the technique for non-destructive testing of plate-like structures would be highly worthwhile.     

Technique for detecting a direct signal pulse from an underwater explosive source in a waveguide

A technique for detecting direct signal pulses based on steep rising edges of acoustic pressure is developed. The technique consists in calculating the mirror derivative of the received signal and normalizing it in a specific manner. This makes it possible to amplify weak direct signals and suppress strong reflected ones. A key feature of this technique is that it ensures a high probability of detection of direct signal pulses while keeping the number of false detections at a minimum.     

Probabilistic characteristics of detection of short light pulses and single photons

One of the most important problems of detecting weak light pulses is the determination of the accurate signal transit time. In this case, photodetectors capable of detecting single photons are characterized by two main parameters: the photon detection efficiency and transit time spread. A unified technique for measuring these parameters is proposed. The technique is based on the probabilistic distribution of transit times, which allows separation of characteristics of single-photon processes as multiphoton light pulses are fed and under conditions of high dark noises, which seems important, in particular, when operating with solid-state photomultipliers.     

应用于高性能光学薄膜表征的光热光声检测技术

本文介绍了光热与光声探测技术的基本原理,结合光学薄膜的吸收测试、光学薄膜的激光辐照特性表征、激光损伤特性表征以及光学薄膜的机械性质表征等各种具体应用,对激光量热法、光热偏转法、表面声波法等典型的光热、光声检测方法进行了分析;阐述了这些方法的测试原理以及各自优势与不足。介绍了该领域利用这些方法取得的一些成果,并就光声光热检测技术的发展趋势做了展望。     

MR knee imaging: axial 3DFT GRASS pulse sequence versus spin-echo imaging for detecting meniscal tears.

The knees of 17 patients (34 menisci) referred for magnetic resonance (MR) imaging to evaluate knee pain were examined using thin axial three-dimensional Fourier transform (3DFT) gradient-refocused acquisition in a steady state (GRASS) images through the menisci, to determine if this method is sensitive and specific for detecting meniscal tears. Results were compared with spin-echo images with long TR and double-echo TE in both coronal and sagittal planes. Arthroscopy results, available in each case, were used as the "gold standard." Twelve meniscal tears were identified at arthroscopy. Axial 3DFT GRASS technique detected 10 of the 12 meniscal tears compared to 9 or 12 using spin-echo technique. With axial 3DFT GRASS technique one false-positive meniscal tear was reported, compared with two false-positive tears on spin-echo images. Axial 3DFT GRASS images were very useful in detecting peripheral tears, showing displaced meniscal fragments, and evaluating complex tears. In this small study, thin axial 3DFT GRASS images were comparable to spin-echo images for detecting meniscal tears, and were helpful in complicated cases in which they provided complementary information to that obtained from spin-echo images.     

Detection of small laser gains in a helium-selenium discharge using dye laser assisted oscillation

We describe a new technique for detecting extremely small gains on atomic transitions. The use of this technique has enabled us to detect gain on nine transitions in Se II, with total gains as low as 0.03%.     

Applying the photonuclear technique to fissile materials detection

Application of a photonuclear technique is considered as a nondestructive method for detecting the unauthorized transporting of camouflaged fissile nuclear material in cargo containers. The advantages of the technique (the use of time selection and the analysis of energy distributions of delayed neutrons) are demonstrated. The operating modes of the accelerator were optimized by modeling. A version of a neutron scintillation spectrometer based on a stylbene monocrystal is presented along with its schematic and main parameters.     

The use of a metal-insulator-metal system for the study of structural transitions in metals

The conductivity of a low-melting metal-polymer-metal system as a function of temperature is studied. A new technique for detecting structural modifications in metals is suggested. Experimental results are discussed within a model of charge instability, which occurs in thin polymer films when boundary conditions are changed.     

微波介电谱应用于低碳醇化合物的分析

研究了甲醇、乙醇等低碳醇类化合物在微波传输过程中对传输散射参数(又称S参数)的影响,利用微波透射法测定了S参数,根据其变化探讨了微波介电谱应用于低碳醇化合物分析的可能性,建立了一种基于散射参数的微波介电化学分析法。实验数据表明,微波的S参数与甲醇、乙醇等低碳醇化合物的浓度在一定范围内呈现良好的线性关系。     

融合散斑干涉技术的阵列式洛伦兹力微颗粒探测方法

提出了一种阵列式洛伦兹力微颗粒探测法,该方法结合了散斑干涉技术的全场位移测量、分辨率高等特性与洛伦兹力微颗粒探测法中探测量为矢量、可探测内部缺陷等优势,探索了一种实时、在线、原位的缺陷检测方法.针对阵列式洛伦兹力微颗粒探测法中阵列式排布的多个悬臂梁位移测量问题,设计了大剪切数字散斑干涉系统,使来自于被测悬臂梁和安装悬臂梁的横梁的反射光发生干涉,形成剪切干涉,通过对相位差进行分析获得悬臂梁的绝对位移,并且以洛伦兹力及悬臂梁末端的位移量为中间量建立了散斑干涉相位差与缺陷体积之间的关系.本文通过实验成功获得了悬臂梁全场位移量以及缺陷的体积,通过散斑干涉的方法测量悬臂梁位移量理论分辨率可达30 nm,这使洛伦兹力微颗粒探测法具备了微米级缺陷的探测能力.     

Low-noise detection of ultracold atoms

We have demonstrated a new technique for detecting ultracold atoms. A balanced detection technique was used to reduce laser-induced detection noise in conjunction with modulation-transfer spectroscopy to distinguish cold atoms from a thermal cloud. Using this technique, we have achieved signal-to-noise ratios in excess of 2000:1.     

探测结构材料应力的频率谐振技术

设计和建造大型磁体系统(包括常温和低温超导磁体)是目前核聚变工程中重要的问题之一。而磁体研制的核心问题都与强大机械力的存在有关。因此开展对磁体及结构材料应力的研究工作就显得特别重要。 近年来开始应用声学方法研究磁体中与力有关的问题(例如用声发射技术探测超导磁体的工作情况),已取得了有希望的结果。我们对低温与超导磁体中常用结构材料进行过声发射实验研究,也对目前尚存在争论的“磁体猝灭的声发射预测”问题进行了实验研     

Study on the Phase Detecting Laser Interferometric System with Computer Generated Hologram

ＳｔｕｄｙｏｎｔｈｅＰｈａｓｅＤｅｔｅｃｔｉｎｇＬａｓｅｒＩｎｔｅｒｆｅｒｏｍｅｔｒｉｃＳｙｓｔｅｍｗｉｔｈＣｏｍｐｕｔｅｒＧｅｎｅｒａｔｅｄＨｏｌｏｇｒａｍ￥ＤＡＩＸｉａｏｆａｎｇ；ＣＨＥＮＸｉｎｇｗｕ；ＷＥＩＹａｏｌｉｎ；ＣＨＥＮＢｅｎｚｈｉ；Ｗ...     

Multiplexed time-correlated single-photon counting

We review the technique of multiplexed time-correlated single-photon counting whereby multiple fluorescence decay curves are recorded in parallel by statistically time-sharing a single time-to-amplitude converter. Application of the multiplexing technique to measuring the fluorescence lifetime topography of a self-absorbing sample is demonstrated. Further possibilities are discussed for multiplexed optical fiber sensor networks with built-in intelligence for detecting and discriminating between different metal ions in solution.