Research on fast detection method of infrared small targets under resourceconstrained conditions

Infrared small target detection is a common task in infrared image processing.Under limited computa⁃tional resources.Traditional methods for infrared small target detection face a trade-off between the detection rate and the accuracy.A fast infrared small target detection method tailored for resource-constrained conditions is pro⁃posed for the YOLOv5s model.This method introduces an additional small target detection head and replaces the original Intersection over Union(IoU)metric with Normalized Wasserstein Distance(NWD),while considering both the detection accuracy and the detection speed of infrared small targets.Experimental results demonstrate that the proposed algorithm achieves a maximum effective detection speed of 95 FPS on a 15 W TPU,while reach⁃ing a maximum effective detection accuracy of 91.9 AP@0.5,effectively improving the efficiency of infrared small target detection under resource-constrained conditions.

High Impedance Fault Detection of Distribution Network by Phasor Measurement Units

This paper proposes a new algorithm for High Impedance Fault (HIF) detection using Phasor Measurement Unit (PMU). This type of faults is difficult to detect by over current protection relays because of low fault current. In this paper, an index based on phasors change is proposed for HIF detection. The phasors are measured by PMU to obtain the square summation of errors. Two types of data are used for error calculation. The first one is sampled data and the second one is estimated data. But this index is not enough to declare presence of a HIF. Therefore another index introduces in order to distinguish the load switching from HIF. Second index utilizes 3rd harmonic current angle because this number of harmonic has a special behaviour during HIF. The verification of the proposed method is done by different simulation cases in EMTP/MATLAB.

Improvement Design of Biochip Towards High Stable Bioparticle Detection Utilizing Dielectrophoresis Impedance Measurement

Dielectrophoresis impedance measurement(DEPIM)is a powerful tool for bioparticle detection due to its advantages of high efficiency,label-free and low costs.However,the strong electric field may decrease the viability of the bioparticle,thus leading to instability of impedance measurement.A new design of biochip is presented with high stable bioparticle detection capabilities by using both negative dielectrophoresis(nDEP)and traveling wave dielectrophoresis(twDEP).In the biochip,a spiral electrode is arranged on the top of channel,while a detector is arranged on the bottom of the channel.The influence factors on the DEP force and twDEP force are investigated by using the basic principle of DEP,based on which,the relationship between Clausius-Mossotti(CM)factor and the frequency of electric field is obtained.The two-dimensional model of the biochip is built by using Comsol Multiphysics.Electric potential distribution,force distribution and particle trajectory in the channel are then obtained by using the simulation model.Finally,both the simulations and experiments are performed to demonstrate that the new biochip can enhance the detection efficiency and reduce the negative effects of electric field on the bioparticles.

AN IMPEDANCE ANALYSIS FOR CRACK DETECTION IN THE TIMOSHENKO BEAM BASED ON THE ANTI-RESONANCE TECHNIQUE

An alternative technique for crack detection in a Timoshenko beam based on the first anti-resonant frequency is presented in this paper. Unlike the natural frequency, the anti-resonant frequency is a local parameter rather than a global parameter of structures, thus the proposed technique can be used to locate the structural defects. An impedance analysis of a cracked beam stimulated by a harmonic force based on the Timoshenko beam formulation is investigated. In order to characterize the local discontinuity due to cracks, a rotational spring model based on fracture mechanics is proposed to model the crack. Subsequently, the proposed method is verified by a numerical example of a simply-supported beam with a crack. The effect of the crack size on the anti-resonant frequency is investigated. The position of the crack of the simply-supported beam is also determined by the anti-resonance technique. The proposed technique is further applied to the ＂contaminated＂ anti-resonant frequency to detect crack damage, which is obtained by adding 1-3% noise to the calculated data. It is found that the proposed technique is effective and free from the environment noise. Finally, an experimental study is performed, which further verifies the validity of the proposed crack identification technique.

An interdigitated impedance microsensor for detection of moisture content in engine oil

To address the need for the on-site measurement of aging oil, in this paper, we propose an impedance-based microsensor for analyzing the moisture content in engine oil. Using a microfabrication process, we fabricated an interdigitated microelectrode and integrated it with a 3 D-printed microcontainer to produce a microsensor that can detect changes in the permittivity of oil. When the moisture content in oil increases, this sensor can detect the resulting change in the oil impedance, which is related to its permittivity, and then determine the degree to which the oil has aged. The test results show that the proposed microsensor has the advantages of being small and having high sensitivity, good accuracy, and the ability to be combined with hand-held instruments.The proposed method is expected to be used for the rapid, low cost, on-site determination of oil aging.

Research on Magnetically Coupled Resonant Detection Method for Breakpoint of Four Mesh Grounding Grid

Magnetically coupled resonant technology is a novel method for solving the breakpoint locating of power grounding grid.But the method can only detect breakpoints of a single mesh grounding grid at present.In this paper,a magnetically coupled resonant detection method for four-hole grounding grid breakpoint is proposed.Firstly,the equivalent circuit model of the four mesh grounding grid with two types of breakpoints,namely edge branch and intermediate branch,is established.The input impedance and phase angle of the system are obtained by analyzing the equivalent capacitance and equivalent resistance in the model.Secondly,the magnetically coupled resonant physical process of grounding grid faults is solved via HFSS software.The magnetic field intensity and phase frequency characteristic curves of four mesh holes with different branches and positions of breakpoints and different corrosion degrees are studied,and an experimental system is built to verify the feasibility.The results show that under the condition of grounding grid buried depth of 0.5 m and input frequency of 1~15MHz,and there is an inverse relationship between equivalent capacitance and distortion frequency,the phase angle is positively correlated with the degree of corrosion of grounding grid,and the error of signal distortion frequency can be positioned at 5%.This paper provides some ideas for the application of magnetic coupling grounding grid detection technology.

High Impedance Fault Detection Based on Attention Mechanism and Object Identification

Detection of high impedance faults(HIFs)has been traditionally a main challenge in the protection of distribution systems,since they do not generate enough current to be reliably detected by conventional over-current relays.Data-based methods are alternative HIF detection methods which avoid threshold settings by training a classification or regression model.However,most of them lack interpretability and are not compatible with various distribution networks.This paper proposes an object detection-based HIF detection method,which has higher visualization and can be easily applied to different scenarios.First,based on the analysis of HIFs,a Butterworth band-pass filter is designed for HIF harmonic feature extraction.Subsequently,based on the synchronized data provided by distribution-level phasor measurement units,global HIF feature gray-scale images are formed through combining the topology information of the distribution network.To further enhance the feature information,a locally excitatory globally inhibitory oscillator region attention mechanism(LEGIO-RAM)is proposed to highlight the critical feature regions and inhibit useless and fake information.Finally,an object detection network based You Only Look Once(YOLO)v2 is established to achieve fast HIF detection and section location.The obtained results from the simulation of the proposed approach on three different distribution networks and one realistic distribution network verify that the proposed method is highly effective in terms of reliability and generalization.

Cycle life prediction and match detection in retired electric vehicle batteries

The lifespan models of commercial 18650-type lithium ion batteries （nominal capacity of 1150 mA-h） were presented. The lifespan was extrapolated based on this model. The results indicate that the relationship of capacity retention and cycle number can be expressed by Gaussian function. The selecting function and optimal precision were verified through actual match detection and a range of alternating current impedance testing. The cycle life model with high precision （〉99%） is beneficial to shortening the orediction time and cutting the prediction cost.

Impedance characteristics for solid Ag/AgCl electrode used as recording electric field generated by vessels in seawater

Ag/AgCl electrode has been prepared using pressed powder techniques. In order to verify the feasibility of this type of electrode used as detecting electric field generated by vessels in seawater, its characteristics of DC resistance, low frequency AC impedance, and receiving impedance in artificial seawater have been studied by polarization measurements, low frequency electrochemical impedance spectra, the open and short circuit cell conditions. The results show that the electrode can keep a low resistance when it responses the weak electrostatic field in seawater. The AC impedance of the electrode decreases as the frequency of the signal increasing. The receiving impedance decreases when the frequency of external field increases too. The valid detection bandwidth is determined by the properties of the impedance and the reactions occurring on the surface of the electrode.

One Step Quick Detection of Cancer Cell Surface Marker by Integrated NiFe-based Magnetic Biosensing Cell Cultural Chip

RGD peptides has been used to detect cell surface integrin and direct clinical effective therapeutic drug selection. Herein we report that a quick one step detection of cell surface marker that was realized by a specially designed NiF e-based magnetic biosensing cell chip combined with functionalized magnetic nanoparticles. Magnetic nanoparticles with 20-30 nm in diameter were prepared by coprecipitation and modified with RGD-4C, and the resultant RGD-functionalized magnetic nanoparticles were used for targeting cancer cells cultured on the NiF e-based magnetic biosensing chip and distinguish the amount of cell surface receptor-integrin.Cell lines such as Calu3, Hela, A549, CaF br, HEK293 and HUVEC exhibiting different integrin expression were chosen as test samples. Calu3, Hela, HEK293 and HUVEC cells were successfully identified. This approach has advantages in the qualitative screening test. Compared with traditional method, it is fast, sensitive, low cost,easy-operative, and needs very little human intervention. The novel method has great potential in applications such as fast clinical cell surface marker detection, and diagnosis of early cancer, and can be easily extended to other biomedical applications based on molecular recognition.

Instrument for insulation conditions detection of roof insulator on high-speed-train

With the rapid development of high-speed-railway,environment around high voltage device on train roof becomes very complicated. Most train accidents happened due to occurrence of flashover on roof insulator,but the insulation condition estimation of insulator in such environment is much difficult. To ensure the insulation property of electric equipment,and guarantee the operation safety of high-speed-train,here established an instrument with high reliability which can on-line monitor insulation condition of roof insulator and give out advanced alarm before the incipient insulator flashover. The instrument consists of three parts,Data Acquisition & Sensor,Data Processing and Back Processing. Anti-interference and protection methods are processed to Rogowski coil sensor for better leakage current signal. To avoid the fluctuation from railway power supply,four modules are set to filter the power supply waveform. Through laboratory measurement,it is shown that the leakage current and the impedance angle can be detected by the instrument accurately. From the comparison of leakage current and impedance angle results under different moisture condition and the alarm operation when leakage current value reached threshold,this instrument can give out enough information for staff to understand the insulation condition of insulator.

A New Micro-magnetism Sensor Based on Giant Magneto-impedance Effect and Multivibrator Bridge

A novel sensor for micro-magnetic field detection is proposed based on the physical characteristics and giant magneto-impedance (GMI) effect of Fe-Co-Si-B amorphous wires. The sensor circuit ensures high sensitivity,high detection precision,fast response and small power consumption. The signal processing circuit taking complex programmable logic device (CPLD) as core chip not only improves the identification ability for pseudo ferromagnetic objects,but also ensures the real-rime response. It is the foundation for the proposed sensor to serve widely in military and civil. By using its high sensitivity for geomagnetism variation,as an application example,the sensor is used to compare and analyze different cars.

A New Sensorless Technique for the Speed Detection of an Induction Motor

This paper presents a new sensorless method, the so-called harmonic impedance / admittance, for detecting speed of induction motors, which is based on the impedance measurement, harmonic analysis and digital signal processing. The method improves theperformance of conventional voltage-based and current-based techniques, because the impedance or admittance harmonics is independent of input or output of motor system due to the system-inherent nature of impedance. It has been used successfully in detecting the rotor speed of three-phase induction motors. A comparison between the proposed method and the conventionalcurrent-based method is also demonstrated.

基于SSTDR的光伏连接器故障检测

随着运行时间的增长,光伏连接器会出现氧化、老化、松动等现象,易导致接触不良、发热等问题,最终可能引起断路、电弧等故障,对光伏系统的高效、安全运行造成不良影响。由于光伏连接器故障会引起其等效阻抗的变化,该文采用扩频时域反射法(spread spectrum time domain reflectometry,SSTDR)来进行检测:通过向光伏连接器所在的光伏组件串注入正弦高频信号调制的伪随机序列序列测试信号,分析入射信号与反射信号的相关特性,再与健康状态下的特性进行比较,来实现光伏连接器故障在线诊断。对此进行仿真计算并在4块光伏板组成的光伏组串中进行实验,发现开路故障时包络面积最大可达到5×10^(5),而脱离故障时包络面积最小为0.8×10^(5),二者皆远大于健康时的包络面积0.07×10^(5),可有效诊断光伏连接器是否发生故障。

基于XGBoost的配电网高阻接地故障检测方法

配电网高阻接地故障具有电气量微弱、与正常运行工况相似等特点,因此难以检测。针对传统指标阈值法常由经验整定,在复杂环境下适应性较差、灵敏性不足等问题,提出一种基于极端梯度提升(extremegradient boosting, XGBoost)的配电网高阻接地故障检测方法,以避免复杂的阈值整定。首先,通过建立10 kV中压配电系统高阻接地故障的等效模型,获取高阻接地故障和正常运行工况的零序电流数据。然后,在对数据进行归一化处理的基础上,利用XGBoost直接从原始量测信息中学习其与高阻接地故障的映射关系,构建高阻接地故障检测模型,以降低因特征提取产生的误差。最后,大量仿真结果表明,所提方法对高阻接地故障检测具有较好的灵敏性和速动性,并且在噪声和数据缺失等情况下表现出较强的泛化能力。

基于频变衰减弹性阻抗的纵、横波品质因子反演方法

地层品质因子在页岩气储层、致密气和水合物等勘探领域具有较大的应用潜力。文中,首先,基于近似常数地层品质因子模型和弱黏弹性近似假设推导了黏弹性介质PP波弹性阻抗方程,有效反映了地层纵、横波速度、密度、纵波品质因子和横波品质因子的频变特征;其次,使用回溯快速迭代软阈值算法,实现了衰减弹性阻抗反演,为进一步提高多参数反演的稳定性,提出了基于对数域不同频率衰减弹性阻抗差异的纵、横波品质因子直接提取方法;最后,使用Marmousi2模型合成含噪声数据验证了反演方法的适用性和稳定性,并将该方法应用到实际工区。结果与已钻井解释结果一致,说明该方法在油气分布预测应用中具有一定的效果和潜力。

基于Q弹性阻抗流体因子反演研究

流体因子反演的难题在于地层介质的正问题从弹性过渡到非弹性介质后如何建立非弹性介质的反射系数表达式,从而更精确地描述传播介质。针对地震波在非弹性介质中的衰减问题,建立了基于Q弹性流体因子理论,结合衰减系数对弹性流体因子项进行扰动获得Q弹性流体因子,在相似介质和弱衰减假设条件下推导了Q弹性流体因子在介质分界面上的散射方程,该表达式与复数条件下的纵、横波速度项及密度项有较高的相关度;进一步通过Q弹性流体因子推导了与纵横波速度的关系,获得了近似条件下Q弹性流体因子纵波反射系数表达式,并分析了该表达式与完全弹性介质反射系数表达式的联系,该方法消除了反演剖面中存在的虚假亮点干扰,从而对衰减弹性介质假设下的储层流体响应进行了更准确的描述。在胜利油田某实际工区的应用结果表明:对流体和围岩进行了区分,获得了相比于常规流体因子反演结果更准确的储层流体响应特征,该流体检测方法在一定程度上降低了流体检测的多解性,消除了仅考虑振幅影响的识别假象。

考虑电容投切扰动的配电网高阻接地故障检测方法

高阻接地故障的准确、可靠检测是配电网故障处理的难点,正常的电容投切操作可对其产生干扰。针对这一问题,文中提出了一种基于零序李萨如曲线分析的高阻接地故障抗扰检测方法。首先,理论推导了高阻接地故障与电容投切扰动的零序电气量,二者在传统时频域特征角度无规律性差异,从而明确了干扰原因;进一步,将零序电流、电压波形重构为零序李萨如曲线,提出了基于数学形态学理论的李萨如曲线轨迹形状畸变复杂度量化指标,并结合零序李萨如曲线面积概率分布规律设计自适应启动判据,给出了噪声场景下高阻接地故障的抗扰检测方法;最后,利用配电网电磁暂态仿真算例和真型故障试验验证了所提方法的有效性和可靠性。

温变下基于奇异谱分析的机电阻抗损伤识别法

为消除温度变化对损伤识别的影响,采用奇异谱分析(singular spectrum analysis,简称SSA)方法处理阻抗信号以分离不受温度变化影响的信号分量,提出结合t-分布随机邻域嵌入(t-distribution stochastic neighbor embedding,简称t-SNE)与K均值聚类算法的无监督机器学习方法,进一步处理信号分量实现损伤识别。为验证该方法的可行性,以螺栓组连接的铝板结构作为实验对象进行温度变化工况下螺栓松动机电阻抗损伤识别实验。结果表明,应用SSA方法得到的信号分量能在温度变化影响下有效识别螺栓松动状态,各工况识别准确率均达到98%以上,证明了所提出方法对消除温度变化影响的有效性。

用于土壤温湿度检测的声表面波标签设计

针对土壤温湿度的并行检测提出了基于声表面波标签的解决方案。采用耦合模理论对阻抗负载型声表面波标签进行建模与仿真,得到负载反射栅回波幅值和相位随电容值变化规律。在此基础上,根据声表面波标签对土壤温湿度不同的敏感机理,设计了一种双通道双边带标签结构,采用时分多址的方法解决了对不同深度层级土壤同时检测时存在的回波信号混叠问题。通过回波信号的相位和幅值比实现了土壤温湿度检测,结合矢量网络分析仪和阅读器对标签进行测试,测试结果表明了标签的有效性。