Movable contactless-conductivity detector for microchip capillary electrophoresis

A new movable contactless-conductivity detection system for microchip capillary electrophoresis is introduced. Such a versatile system relies on positioning the detector at different points along the separation channel via "sliding" the electrode holder. The new movable microchip detection system offers distinct improvements compared to common fixed-location conductivity detectors. For example, placing the detector at different locations along the microchannel offers useful insights into the separation process. Three-dimensional plots of resolution/channel length/separation voltage can be used for optimizing the separation process and selecting the analysis time. The system enables rapid switching between "total" (unresolved) and "individual" (resolved/fingerprint) signals on the basis of placing the detector at the beginning and end of the separation channel, respectively. By moving the detector to a shorter effective separation length, after eluting fast-migrating ions, shorter analysis times can be achieved (through faster detection of late-eluting analytes). These and other improvements in the analytical performance and insights into the separation process are illustrated in connection with the detection of low-energy ionic explosives and nerve agent degradation products.     

基于分数阶功率谱熵的未知水声脉冲信号检测方法

水声侦察的核心问题是在无先验知识条件下捕获其他平台发射的脉冲信号,单频(Continuous Wave,CW)信号和调频(Frequency Modulation,FM)信号是常用的水声探测脉冲.功率谱熵算法能有效检测低信噪比的CW信号,但对FM信号性能不佳,分数阶傅里叶变换(Fractional Fourier Tr...     

基于深度学习检测器的多角度人脸关键点检测

针对人脸关键点检测(人脸对齐)在应用场景下的速度和精度需求,首先在SSD基础之上融合更多分布均匀的特征层,对人脸框坐标进行级联预测,形成对于多尺度人脸信息均具有更加鲁棒响应的深度学习检测器MR-SSD。其次在局部二值特征LBF的级联形状回归方法基础上,提出了基于面部像素差值的多角度初始化算法。采用端正人脸正负90°倾斜范围内的五组特征点形状进行初始化,求取每组回归后形状的眼部特征点像素均方差值并以最大者对应方案作为最终回归形状,从而实现对多角度倾斜人脸优异的拟合效果。本文所提出的最优架构可以实时获得极具鲁棒性的人脸框坐标并且可实现对于多角度倾斜人脸的关键点检测。     

Dielectric barrier discharge-induced chemiluminescence: potential application as GC detector

Atmospheric pressure dielectric barrier discharge (DBD) plasma can be used to split low molecular weight organic compounds, and the DBD-split/excited species can be swept into luminol solution to induce chemiluminescence (CL) emission. Based on this observation, a novel optical detector was proposed and preliminarily tested as a potential gas chromatographic (GC) detector in this work. The advantages of this new type of detector include the following: direct detection, fast response, high sensitivity, versatility (sensitive to a broad range of volatile organic compounds), simple and easy instrumentation, compactness (3.0 mm i.d. x 4.0 mm o.d. x 20 mm length of the DBD device), and low power (less than 5 W). Twelve volatile organic compounds, including methanol, ethanol, propanol, formaldehyde, acetaldehyde, benzene, dichloromethane, trichloromethane, tetrachloromethane, tetrahydrofuran, carbon bisulfide, and ethyl ether, were tested with this detector, and each of them produced a large signal. It was found that the CL signal was proportional to the analyte concentration and affected by the DBD parameters. Under the optimized experimental conditions, the limits of detection down to the tens of nanogram level were achieved for methanol, ethanol, propanol, formaldehyde, and acetaldehyde. It was then preliminarily tested as a GC detector for the separation of formaldehyde, ethanol, and propanol. This is the new application of DBD in analytical chemistry, and CL was for the first time generated in this way. The new detector can be a potential GC detector suitable for a wide range of volatile organic compounds.     

基于环形光电探测器的多目标探测与跟踪研究

提出并研究了基于环形光电探测器的多目标探测与跟踪技术.首先提出了一种基于6片线阵CCD的环形探测器设计.该探测器中的每一线阵CCD光学系统的光轴均通过探测器中心点,且任意两光轴之间的夹角为60°,形成具有360°视场的环形探测结构;提出了基于目标信号脉宽判据、基于目标信号水平尺度比率的复合判据,研究了适用于环形探测器的多目标快速识别与跟踪算法;建立了硬件实验系统,并进行了功能验证实验,实验结果表明:所提出的环形光电探测器及算法设计可实现多个运动目标的探测与跟踪,在目标机器视觉、虚拟现实等领域具有潜在的应用前景.     

Correlation-sensitive adaptive sequence detection

In high density magnetic recording, noise samples corresponding to adjacent signal samples are heavily correlated as a result of front-end equalizers, media noise, and signal nonlinearities combined with nonlinear filters to cancel them. This correlation significantly deteriorates the performance of detectors at high densities. In this paper, we propose a novel sequence detector that is correlation sensitive and adaptive to the nonstationary signal sample statistics. We derive the correlation-sensitive maximum likelihood detector. It can be used with any Viterbi-like receiver (e.g., partial response maximum likelihood, fixed delay tree search, multilevel decision feedback equalization) that relies on a tree/trellis structure. Our detector adjusts the metric computation to the noise correlation statistics. Because these statistics are nonstationary, we develop an adaptive algorithm that tracks the data correlation matrices. Simulation results are presented that show the applicability of the new correlation-sensitive adaptive sequence detector     

采用色彩相似性约束的立体匹配

在立体匹配算法中引入色彩相似性约束条件.首先加入权值模板来对用于灰度空间匹配的SSD算法进行改进,在抑制噪声的同时,可以最大程度的保持景物的细节信息,从而有效的解决SSD算法对于噪声比较敏感的问题.然后引入色彩相似性约束将灰度空间的匹配和彩色空间的匹配有机的结合起来,大大提高了匹配的精度.实验结果表明,该算法能够合理利用彩色立体像对中的色彩信息,从而生成准确度较高的视差图,是一种有效的立体匹配方法.     

General differential modulation scheme for quasi-orthogonal space?time block codes with partial or full transmit diversity

A general and simple differential modulation scheme that can be applied to both partial-diversity quasi-orthogonal space-time block codes and full-diversity quasi-orthogonal space-time block codes is reported. A new class of quasi-orthogonal coding structures is presented for various number of transmit antennas. Differential encoding and decoding can be simplified to differential Alamouti codes by grouping the signals in the transmitted matrix and decoupling the detection of data symbols, respectively. For the codes with partial transmit diversity, the new scheme can achieve constant amplitude of transmitted signals, and avoid signal constellation expansion; in addition, it has a linear signal detector with very low complexity. Simulation results show that these partial-diversity codes can provide very useful results at low signal-to-nose ratio for current communication systems. For codes with full transmit diversity achieved by constellation rotation, the proposed scheme has performance equal to the best full-rate quasi-orthogonal schemes previously described in the literature with the benefit of a simpler detector. Moreover, a simple linear detector is also presented for the case when two orthogonal ASK constellations are used. Extension to more than four transmit antennas is also considered.     

机动小目标的时空联合检测技术

主动声呐信号处理中一般采用匹配滤波和背景均衡等算法检测回波信号,为提高信号的检测性能,还需利用信号与混响和环境噪声在时间、空间上的统计特征差异。文章在对信号的时、空特征算法进行简单描述的基础上,提出了频率能量统计特征和方位能量统计特征,将两种特征检测器的输出进行融合处理构成时、空联合检测器。仿真和试验数据处理结果证明,此方法可有效提高机动小目标在混响及环境噪声中的检测性能。     

环境扫描电子显微镜的成像特点

环境扫描电子显微镜(ESEM)中所指的环境并非真正意义上的大气环境(760 Torr),与传统扫描电子显微镜(SEM)样品室高真空度相比,ESEM样品室的真空度可以很低(约达20 Torr)。ESEM是在传统的SEM样品室中多一个GSED探头,因此,它在传统的SEM基础上增添了新的功能。其主要的特点是,可以观察含适量水分的样品和非导体材料样品,比如植物的叶片、动物中的昆虫、作物的籽粒、含结晶水的固体材料等。     

Development and application of CVD diamond detectors to 14 MeV neutron flux monitoring

CVD diamond is an interesting material for radiation detection, its atomic number (Z = 6) is close to that of soft tissues (Z = 7.1) and it can also work in harsh environments. Since many years CVD diamond films have been grown at the Faculty of Engineering, Rome 'Tor Vergata' University, and in 1998 a collaboration with ENEA Fusion Division was established to develop fast neutron monitors to be used in fusion tokamak environment. In this paper the first test of a 120 microm thick polycrystalline CVD diamond detector used for monitoring 14.7 MeV neutrons emission produced with the Frascati Neutron Generator (FNG) is reported. The detector operates in air and in pulse mode. The time irradiation profiles recorded with the CVD diamond detector were compared with those recorded by the standard monitors available at FNG (SSD, fission chamber, NE-213). Good stability and capability to operate in neutron flux up to 1.5 x 10(8) n cm(-2) s(-1) was observed. The radiation hardness property was also investigated using a 460 microm thick film and these results are also reported.     

Photon Fluctuations,Equivalent Quantum Efficiency,and the Information Capacity of Photographic Images

The equivalent quantum efficiency (EQE) enables the signol-to-noise ratio of a detector to be compared with that attainable by an ideal noiseless detector working under the some conditions. It thus provides a scientific basis for the measurement of photographic speed-to-grain ratios. The limitations of an ideal detector are only those imposed by photon fluctuations in the signal. The signal itself may also be measured in terms of these inherent photon fluctuations, and this enables the information capacity of the detector to be expressed in terms only of the EQE and the ratio of the power spectrum of the signal to that of the photon fluctuations. There are several advantages when the information capaCity is expressed in this manner. Not only is the signal specified in a basic farm, but also, since the EQE is the most fundamental of imaging properties, the information capacity of the photographic process can be rapidly compared with that of any other type of detector by substitution of the appropriate value of the EQE. In this way the information capacity can also be compared with the ultimate capacity, which is that of the signal itself and corresponds to an EQE of 100 per cent. Examples are given of the information capacity for a range of values of the EQE and signal size, and its spatial frequency dependence is demonstrated in terms of the transfer function.     

Laser ranging and mapping with a photon-counting detector

We propose a new technique for remote sensing: photon-counting laser mapping. MicroChannel plate detectors with a crossed delay-line (MCP/CDL) readout combine high position accuracy and subnanosecond photon timing, at event rates of 10(6) detected photons per second and more. A mapping system would combine an MCP/CDL detector with a fast-pulse, high-repetition-rate laser illuminator. The system would map solid targets with exceptional in-range and cross-range resolution. The resulting images would be intrinsically three dimensional, without resorting to multiple viewing angles, so that objects of identical albedo could be discriminated. For a detector time resolution and pulse width of the order of 10(-10) s, the in-range resolution would be a few centimeters, permitting the discrimination of surfaces by their textures. Images could be taken at night, at illumination levels up to full moonlight, from ground, airborne, or space platforms. We discuss signal to noise as a function of laser flux and background level and present simulated images.     

Status of the High density Projection Chamber

The High density Projection Chamber (HPC) for the Delphi detector is a lead gas sampling electromagnetic calorimeter constructed using the lead wire technique which is well adapted for mass production. The HPC offers good energy resolution and superb space resolution and may consequently serve as a tracking device.     

A nonvolatile plasmonic switch employing photochromic molecules

We demonstrate a surface plasmon-polariton (SPP) waveguide all-optical switch that combines the unique physical properties of small molecules and metallic (plasmonic) nanostructures. The switch consists of a pair of gratings defined in an aluminum film coated with a 65 nm thick layer of photochromic (PC) molecules. The first grating couples a signal beam consisting of free space photons to SPPs that interact effectively with the PC molecules. These molecules can reversibly be switched between transparent and absorbing states using a free space optical pump. In the transparent (signal "on") state, the SPPs freely propagate through the molecular layer, and in the absorbing (signal "off") state, the SPPs are strongly attenuated. The second grating serves to decouple the SPPs back into a free space optical beam, enabling measurement of the modulated signal with a far-field detector. In a preliminary study, the switching behavior of the PC molecules themselves was confirmed and quantified by surface plasmon resonance spectroscopy. The excellent (16%) overlap of the SPP mode profile with the thin layer of switching molecules enabled efficient switching with power densities of approximately 6.0 mW/cm2 in 1.5 microm x 8 microm devices, resulting in plasmonic switching powers of 0.72 nW per device. Calculations further showed that modulation depths in access of 20 dB can easily be attained in optimized designs. The quantitative experimental and theoretical analysis of the nonvolatile switching behavior in this letter guides the design of future nanoscale optically or electrically pumped optical switches.     

Evaluation of the design requirements for the electrical part oftransmission-type optical smoke detector to improve its thresholdstability to slowly varying influences

The output signal sensitivity to optical component contamination and other slowly varying parasitic influences in the transmission-type smoke detector is analyzed. The analysis carried out the new topology characterized by the selective feedback loop incorporating the optical part of the detector. Depending on the loop gain frequency shaping in the electrical part of the loop, dual-stability enhancement of the input threshold level can be achieved. The stable dc output signal can be preserved by the high dc loop gain value, as an option to the standard serial filter dc rejection. The detector passband gain stability is achieved by the high loop gain selectivity, eliminating feedback at very low or passband frequencies. The proposed topology can be easily adopted to both digital and low-cost analog detector designs. The special case of the threshold sensitivity neutralization through the cancellation of the output dc signal sensitivity and passband gain sensitivity is considered, too, as an option suitable for low-cost detectors. In addition to the described linear settlement, two nonlinear solutions are presented, the first of them based on the foregoing linear circuit analysis. Despite its nonlinear nature, this alternative solution is not troublesome for analog implementation, since the nonlinear function required is realized by the standard variable gain amplifier. Another nonlinear method requires logarithmic function implementation, so that its suitability depends on the particular design requirements     

遮挡和光照变化下的单鱼目标跟踪

鱼类跟踪是对鱼类行为分析的基础,在对水中的鱼类跟踪时,目标鱼会由于姿势的变化、受到周围鱼或者物体的遮挡或者光照的影响变得难以追踪.针对这种情况,提出一种利用MobileNet-SSD(SSD,single shot multibox detector)与Dlib关联跟踪器相结合对鱼体进行跟踪的方法,通过SSD算法精准地...     

A digital X-ray imaging system based on silicon strip detectors working in edge-on configuration

We present the energy resolution and imaging performance of a digital X-ray imaging system based on a 512-strip silicon strip detector (SSD) working in the edge-on configuration. The SSDs tested in the system are 300 μm thick with 1 or 2-cm-long strips and 100 μm pitch. To ensure a very small dead area of the SSD working in edge-on configuration, the detector is cut perpendicular to the strips at a distance of only 20 μm from the end of the strips. The 512-strip silicon detector is read out by eight 64-channel integrated circuits called DEDIX [Grybos et al., IEEE Trans. Nucl. Sci. NS-54 (2007) 1207]. The DEDIX IC operates in a single photon counting mode with two independent amplitude discriminators per channel. The readout electronic channel connected to a detector with effective input capacitance of about 2 pF has an average equivalent noise charge (ENC) of about 163 el. rms and is able to count 1 Mcps of average rate of input pulses. The system consisting of 512 channels has an excellent channel-to-channel uniformity—the effective threshold spread calculated to the charge-sensitive amplifier inputs is 12 el. rms (at one sigma level). With this system a few test images of a phantom have been taken in the 10–30 keV energy range.     

Implementation of a likelihood ratio test for laser Doppler velocimeter burst detection

A likelihood ratio test for laser Doppler velocimeter burst detection is derived and implemented with the appropriate photon detection statistics. This detector utilizes the first point of the autocorrelation function of the laser Doppler velocimeter photodetector signal and relies on a simple identity for this point. The detector looks at the ratio of two probability functions of the data (burst and no burst) to make its decision. Because the detector does not depend on the absolute strength of the signal, detection down to very low (-10-dB) signal-to-noise levels can be achieved. Because the autocorrelation function is insensitive to the phase of the signal, the detector will operate reliably with signals containing multiple overlapping bursts.     

Predicting range performance of sampled imagers by treating aliased signal as target-dependent noise

This paper presents a new theory to predict the impact of sampling on target acquisition. The aliased signal that results from sampling is treated as noise. The aliased signal is different from detector noise in two ways. First, aliasing disappears as the target contrast decreases. Second, the image corruption due to aliasing gets worse with increased range. This is because sampling is constant in angle space, and targets become poorly sampled as range increases. The theory is presented, along with the results of three experiments. The match between model and experiment is excellent.