A CVD diamond film detector for pulsed proton detection

A chemical vapour deposition （CVD） diamond film detector was prepared and the main characteristics for pulsed proton detection were studied at Beijing Tandem Accelerator. The result shows that the charge collection efficiency of the detector increases with increasing electric field intensity and reaches to 9.44% at 5 V/μm with the charge collection distance of 15.9 μm. The relationship between the sensitivity of the detector and proton energy is consistent with the Monte Carlo （MC） simulation result. Its plasma time for a pulse with 4.85×10^5 protons is 1l.2ns. The dose threshold for onset of damage under 9MeV proton irradiation in the detector is about 10^13 cm^-2. All of the results show that a CVD diamond detector has fast time response and high radiation hardness, and can be used in pulsed proton detection.

Determination of neomycin in water samples by high performance anion chromatography with pulsed amperometric detection

A simple, fast and reliable method, using high performance anion chromatography with pulsed amperometric detection, had been developed for the analysis of neomycin in water samples. The elution and separation were carried out with an isocratic mobile phase, containing 10 mmol/L NaOH. The influence of the concentration and pH of the mobile phase on the separation and detection was investigated. A quadruple-potential waveform used for the detection was optimized. The detection limit of neomycin was down to 0.027 μg/mL. The linearity of neomycin calibration curve ranged from 0.050 to 0.505 μg/mL with correlation coefficient of 0.9997. R.S.D. (n = 11) was 4.0%.

Deterministic Quantum Key Distribution with Pulsed Homodyne Detection

In this paper, we propose a deterministic quantum communication protocol using weak coherent states and pulsed homodyne detection. In this protocol, the communication parties exchange their secret information deterministicaJly in two rounds. The devices and efficiency of the protocol are discussed respectively. We also show the security of the protocol against intercept-resend and Trojan-Horse eavesdropping attacks.

Simultaneous determination of flavonoids and anthraquinones in chrysanthemum by capillary electrophoresis with amperometry detection

A high-performance capillary electrophoresis with amperometry detection method （CE-AD） has been developed for the analysis of flavonoids and anthraquinones （emodin, kaempferol, apigenin, luteolin and rhein） in chrysanthemum. Under optimum conditions, these five analytes were base-line separated within 17 min using a borate-phosphate running buffer （1.5 ×10^-2 mol/L borate-3× 10^-2 mol/L phosphate running buffer, pH 9.0） at a working potential of ＋0.90 V （vs. SCE） and a separation voltage of 19 kV. The linear relationship between concentration and current response was obtained with detection limits （S/N = 3） ranging from 1.0 × 10^-7 to 2.1 × 10^-7 g/mL for all analytes. This proposed method was successfully used in the analysis of four kinds of chrysanthemum with relatively simple extraction procedures, the assay results were satisfactory.

Digital coherent detection research on Brillouin optical time domain reflectometry with simplex pulse codes

The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry （BOTDR）, where the simplex pulse codes are applied in the sensing system. The time domain signal of every code sequence is collected by the data acquisition card （DAQ）. A shift-averaging technique is applied in the frequency domain for the reason that the local oscillator （LO） in the coherent detection is fix-frequency deviated from the primary source. With the 31-bit simplex code, the signal-to-noise ratio （SNR） has 3.5-dB enhancement with the same single pulse traces, accordant with the theoretical analysis. The frequency fluctuation for simplex codes is 14.01 MHz less than that for a single pulse as to 4-m spatial resolution. The results are believed to be beneficial for the BOTDR performance improvement.

Realizing precision pulse TIG welding with arc length control and visual image sensing based weld detection

Methods of arc length control and visual image based weld detection for precision pulse TIG welding were investigated. With a particular all hardware circuit, arc voltage during peak current stage is sampled and integrated to indicate arc length, deviation of arc length and adjusting parameters are calculated and output to drive a step motor directly. According to the features of welding image grabbed with CCD camera, a special algorithm was developed to detect the central line of weld fast and accurately. Then an application system were established, whose static arc length error is ±0.1 mm with 20 A average current and 1 mm given arc length, static detection precision of weld is 0.01 mm , processing time of each image is less than 120 ms . Precision pulse TIG welding of some given thin stainless steel components with complicated curved surface was successfully realized.

Acoustic wave detection of laser shock peening

In order to overcome the existing disadvantages of offline laser shock peening detection methods, an online detection method based on acoustic wave signals energy is provided. During the laser shock peening, an acoustic emission sen- sor at a defined position is used to collect the acoustic wave signals that propagate in the air. The acoustic wave signal is sampled, stored, digitally filtered and analyzed by the online laser shock peening detection system. Then the system gets the acoustic wave signal energy to measure the quality of the laser shock peening by establishing the correspondence between the acoustic wave signal energy and the laser pulse energy. The surface residual stresses of the samples are measured by X-ray stress analysis instrument to verify the reliability. The results show that both the surface residual stress and acoustic wave signal energy are increased with the laser pulse energy, and their growth trends are consistent. Finally, the empirical formula between the surface residual stress and the acoustic wave signal energy is established by the cubic equation fitting, which will provide a theoretical basis for the real-time online detection of laser shock peening.

Bistable Stochastic Resonance Enhanced 4-ary PAM Signal Detection under Low SNR

To boost the performance of 4-ary pulse amplitude modulated(PAM) at low signal-to-noise ratio(SNR), bistable stochastic resonance(BSR) system is introduced into digital communications system and get a reliable signal detection scheme. In this paper, we first analyse BSR system for different amplitudes of 4-ary PAM signals. The steadystate of the bistable system will be statistically distinct, and the feasibility of the proposed detection scheme is confirmed. On this basis, we present a detailed study on steady-state transitions of the BSR system, and an explicit expression of the bistable system parameters is derived. By setting the bistable system parameters, bistable system, 4-ary PAM signal, and noise reach the resonance state, and the BSR-based detection scheme is implemented. Moreover, we derive an analytical expression to calculate the symbol error rate(SER) of 4-ary PAM signals with the BSR-based detection under additive white Gaussian noise(AWGN). Finally, the simulation results validate that BSR-based detection scheme can improve the detection performance while efficiently reducing the symbol error rate.

High photon detection efficiency InGaAs/InP single photon avalanche diode at 250 K

Planar semiconductor InGaAs/InP single photon avalanche diodes with high responsivity and low dark count rate are preferred single photon detectors in near-infrared communication.However,even with well-designed structures and well-con-trolled operational conditions,the performance of InGaAs/InP SPADs is limited by the inherent characteristics of avalanche pro-cess and the growth quality of InGaAs/InP materials.It is difficult to ensure high detection efficiency while the dark count rate is controlled within a certain range at present.In this paper,we fabricated a device with a thick InGaAs absorption region and an anti-reflection layer.The quantum efficiency of this device reaches 83.2%.We characterized the single-photon performance of the device by a quenching circuit consisting of parallel-balanced InGaAs/InP single photon detectors and single-period sinus-oidal pulse gating.The spike pulse caused by the capacitance effect of the device is eliminated by using the characteristics of parallel balanced common mode signal elimination,and the detection of small avalanche pulse amplitude signal is realized.The maximum detection efficiency is 55.4%with a dark count rate of 43.8 kHz and a noise equivalent power of 6.96×10^(−17 )W/Hz^(1/2) at 247 K.Compared with other reported detectors,this SPAD exhibits higher SPDE and lower noise-equivalent power at a higher cooling temperature.

STUDY OF PULSED DOPPLER SIGNAL PROCESSING AND VELOCITY TRACKING TECHNIQUE

This paper describes a signal processing system in a Pulsed Doppler (PD) radar. It mainly consists of a velocity tracking loop and a digital signal processing auxiliary channel. With many signal processing techniques, the system successfully solves the signal detection and tracking at low SNR and the interference identification and rejection. The idea of system design is introduced in detail. Finally, some simulation and experimental results are presented.

Analysis and Improvement of the Real-Time Segmented Pulse Compression-Detection Algorithm

Real-Time segmented pulse compression-detection is one of the key technologies of space-borne tracking receiver. Its implementation requires an optimized and dedicated hardware. The real-time processing places several constraints such as area occupied, power comumption, and speed. A number of segmented compression techniques have been proposed to overcome these limitations and decrease the processing latency. However, relatively high power loss in the partial field could limit their implementation in many current real-time systems. A good theoretical model was designed with intersection signal accumulation to enhance signal- noise-ratio （SNR） gain of detecting signal in the paper. From the experimental results it is known that this approach works well for pulse compression-detection, which is better suited for implementation in the high performance of current field programmable gate array （FPGA） with dedicated hardware multipliers.

Shadow detection combining characters of human vision

A shadow detection method using pulse couple neural network inspired by the characters of human visual system is proposed.More precisely,lateral inhibition of human vision and coefficient of variation are combined together to improve the pulse couple neural network.Shadow detection is considered to be a shadow region segmentation problem.Experiment shows that the presented method is consistent with human vision compared to shadow detection methods based on HSV and pulse couple neural network(PCNN) by both subjective and objective assessments.

Research and Application of Log Defect Detection and Visualization System Based on Dry Coupling Ultrasonic Method

In order to optimize the wood internal quality detection and evaluation system and improve the comprehensive utilization rate of wood,this paper invented a set of log internal defect detection and visualization system by using the ultrasonic dry coupling agent method.The detection and visualization analysis of internal log defects were realized through log specimen test.The main conclusions show that the accuracy,reliability and practicability of the system for detecting the internal defects of log specimens have been effectively verified.The system can make the edge of the detected image smooth by interpolation algorithm,and the edge detection algorithm can be used to detect and reflect the location of internal defects of logs accurately.The content mentioned above has good application value for meeting the requirement of increasing demand for wood resources and improving the automation level of wood nondestructive testing instruments.

Image Edge Detection Based on Oscillation

A new method for image edge detection based on a pulse neural network is proposed in this paper. The network is locally connected. The external input of each neuron of the network is gray value of the corresponding pixel. The synchrony of the neuron and its neighbors is detected by detection neurons. The edge of the image can be read off at minima of the total activity of the detection neurons.

Test Method of Laser Detection Sensitivity Based on Every Pulse Measurement and Rearrangement

It is very important to accurately measure the detection sensitivity of laser receiving equipment. Based on the traditional test method of detection probability curve, a new test method is proposed which works through measuring laser pulse one by one. Accurate measurement systems were constructed to improve the accuracy of laser energy measurement and energy regulation. A new data processing method of detection probability curve is put forward, which based on subsection statistics. The new data processing method in effect reduces the light source instability from 6.57% to 0.67%. These works improve the test accuracy of laser receiving detection sensitivity. It is a great support for the accurate evaluation of key technical indices of laser receiving equipment, which subsequently are done by models and simulation.

Frequency response range of terahertz pulse coherent detection based on THz-induced time-resolved luminescence quenching

It has been proposed previously that the coherent detection of a terahertz（THz） pulse can be achieved based on the time-resolved luminescence quenching. In this paper, we investigate the frequency response range of this novel detection technology by simulating the motion of carriers in gallium arsenide（GaAs） by the ensemble Monte Carlo method. At room temperature, for a direct-current（DC） voltage of 20 kV/cm applied to the semiconductor（GaAs） and sampling time o140 fs, the luminescence quenching phenomena induced by terahertz pulses with different center frequencies are studied The results show that the quenching efficiency is independent of the THz frequency when the frequency is in a range o0.1 THz–4 THz. However, when the frequency exceeds 4 THz, the efficiency decreases with the increase of frequency Therefore, the frequency response range is 0.1 THz–4 THz. Moreover, when the sampling time is changed to 100 fs the frequency response range is extended to be approximately 0.1 THz–5.6 THz. This study of the frequency-dependen characteristics of the luminescence response to the THz pulse can provide a theoretical basis for the exploration of THz detection technology.

改性氮化碳/铜基MOF纳米复合材料修饰电极对草甘膦的电化学检测研究

使用铜基MOF材料(Cu-BTC)和含羰基杂环的介孔氮化碳(CN)合成的纳米复合材料修饰电极构建了电化学传感器,采用差分脉冲伏安法检测水环境中的草甘膦。该传感器的检测机理是通过Cu^(2+)与草甘膦发生络合反应,使得响应电流发生降低。所制备的材料通过扫描电子显微镜、透射电子显微镜、X射线衍射技术、X射线光电子能谱和傅立叶变换红外光谱等进行表征,确认了其形貌与结构。实验结果表明,该传感器具有高的灵敏度,检出限为0.1576 pg/L,线性范围为10^(-6)~10^(-12)g/L,对草甘膦具有良好的选择性。当评估该传感器以检测实际水样中的草甘膦时,回收率达到94%~107%,表现出很高的准确性和实用性。

一种窄脉冲信号峰值电压检测电路设计

SiCMOSFET器件栅极峰值电流可以表征器件结温,但是栅极峰值电流信号上升下降速度快、维持时间短,给峰值电压信号检测电路设计带来了挑战。此处提出了一种基于两级峰值采样保持电路的窄脉冲峰值电压检测电路,其具有采集精度高、保持时间长等优点。首先介绍了峰值检测原理以及两级峰值检测原理,然后给出了详细的电路参数选型,最后,利用仿真和实验对此处所提峰值电流检测电路进行了验证。结果表明,所提峰值检测电路检测误差小于1.1%,电压下垂速率为0.55μV/μs。

基于柔性压电薄膜的可穿戴脉搏传感器设计

针对传统脉搏传感器存在的穿戴不适、携带不便以及精度不高等问题,本文设计一种基于P(VDF-TrFE)柔性压电薄膜的可穿戴脉搏传感器,旨在实现人体脉搏信号的连续检测,为心血管疾病的预防和治疗提供有力支持。首先,采用溶液流延法制备P(VDF-TrFE)柔性压电薄膜作为传感器基底,并利用丝网印刷技术在制备好的压电薄膜表面印刷导电电极,结合网状屏蔽层的设计制备方形传感器和圆形阵列传感器,用于脉搏信号采集性能的实验对比。其次,为了解决脉搏信号低频微弱且容易受到各种噪声干扰的问题,设计包含信号放大和信号滤波功能的精密信号调理电路,用于获取高保真和高清晰度的低噪声脉搏波信号。实验结果表明,所制备的P(VDF-TrFE)薄膜具有良好的介电、压电和铁电性能,其中d_(33)值达到-25 pC·N^(-1),能够提升传感器快速准确捕捉低频脉搏信号的能力,设计的柔性脉搏传感器相较于传统刚性传感器能够较好地贴合人体皮肤,提升无感佩戴体验,符合可穿戴性以及舒适性的要求。其中,圆形阵列式传感器能够检测到包含大部分生理特征点的连续脉搏波信号,相比于方形传感器具备更高的灵敏度和清晰度,检测性能更好。除此之外,设计的信号调理电路能够缓解50 Hz工频干扰和高频噪声干扰,成功将平均峰值电压从0.069 V放大至5.467 V,显示出清晰稳定的脉搏波形并保留脉搏信号的主要特征,抑制噪声干扰的同时实现了对人体脉搏信号的高灵敏度、高稳定性和高准确性的采集。因此,本文设计的基于柔性压电薄膜的可穿戴脉搏传感器能够有效检测和采集人体脉搏波信号,可用于医疗健康监测和可穿戴设备研究领域,具有广阔的应用前景。

关于脉搏波谐波产生机理、分布特性及相关心率检测方法的研究

传统中医认为人体特定的脉搏波频率特性与其脏腑的功能有关。为了研究和阐明脉搏波谐波的产生机理和分布特征,通过对理想脉搏波的离散傅里叶变换进行理论研究,并将真实脉搏波的频谱与理想脉搏波频谱进行比较和分析,验证了真实脉搏波谐波现象存在的合理性。在此基础上,文章提出了一种基于脉搏波谐波特性的更为稳定的心率计算方法。该研究为脉搏波的频域分析奠定了理论基础,对各种类似的准周期信号的分析也具有一定的应用和参考价值。