Papers by Keyword: Detector

Abstract: Today, to respond to the increase of development of accurate, precise and relevant experiments in nuclear research reactors and tokamaks with their severe and intense operating conditions, there is a major need of innovative sensors that can accurately measure key parameters such as neutron and photon fluxes or nuclear heating rates. Thus, innovation in the field of nuclear instrumentation and measurements is a privileged research topic. It is crucial to develop optimized devices for accurate on-line in-core measurements, and scientific/technological requirements for various applications such as ageing of materials, safety applications, beam monitoring or nuclear physics. Nowadays, more and more semiconductors are used as sensor materials in nuclear instrumentation to measure various kinds of nuclear radiations. Silicon Carbide (SiC) is among them. In fact, SiC detectors could be used for the on-line measurement of key quantities such as neutron (thermal and fast) and photon fluxes. One main challenge is to enlarge the measurement range of this detector type. The work presented in this paper deals with this aim. Firstly, an introduction dedicated to the use of SiC versus other wide bandgap semiconductors and the characteristics of the studied sensor is shown. Secondly, this paper presents 3D numerical results obtained with a parametrical thermal study of the SiC detector using COMSOL Multiphysics code for a nuclear heating range corresponding to TRIGA nuclear research reactor conditions (integral neutron flux ~2.0 x10¹³ n·cm^‑2·s^-1 leading to a nuclear heating rate of 0.25 W·g^-1 in Tungsten). The main objective is to adapt and optimize the design and the housing of the detector by determining its temperature field for different configurations. The influence of various parameters is presented such as that of the housing material nature, the gas nature around the diode, the gas-gap height and the housing thickness.

Abstract: The combination of carbon nanotubes (CNT) and conducting polymers offers an attractive route for the production of novel compounds that can be used in a variety of applications such as sensors, actuators, and molecular scale electronic devices. In this work, functionalized multiwall carbon nanotubes (f-MWCNTs) were added in different load ratios (3 wt%, 5 wt% and 10 wt%) to thiophen (PTh) polymer to procedure PTh/CNTs nanocomposite and deposited on porous silicon substrate by electropolarization. Photoconductive detectors were fabricated using PTh/f-MWCNTs matrix to work in the near region and middle IR regions. These detectors were illuminated by semiconductor laser diode wavelength of 808(nm) and Nd-YAG laser of wavelength 1064 (nm) to study the I-V characteristics and figures of merit. FTIR spectra assignments verify that the thiophene groups were successfully introduced into the carbon nanotubes. SEM images reflect that the electro polymerization process gives well coating for the CNTs by PTh. The conductivity of PTh as a function of temperature increased about 30 times due to addition of f-MWCNTs. Figures of merit reflect a good IR radiation sensitivity and photo response. The specific detectivity was in order of 10⁸ (cm.Hz^1/2/W) for both IR regions. The rise and fall times of the output signal are about of 192 (μs) and 121 (μs) respectively for load ratio 5wt% of CNT, which consider good values for these types of detectors.

Abstract: Electrical systems and devices suffer from unexpected failures due to various reasons such as input voltage fluctuation and low or high voltages. This paper discussedabout the development of a device for detecting imminent failure of electric products such as refrigerators, ovens, Air-conditions and etc. The main objective of this developed preventive device is todetect voltage drop or rise and produce an alarmsignal to enable and activates other protection circuitry.The mechanismof the detector/sensing circuit is based on differentiating the voltage level using dualcomparator; this makes the system more considerate. The method enables real-time monitoring of stability boundaries and the corresponding margin to the observed operating point, which is used to provide an early warning for emerging stability problems.

Abstract: 4H-SiC ultraviolet photodetectors based on Schottky barriers have been formed on lightly doped n-type epitaxial layers grown by chemical vapor deposition method on industrial substrates. The diode structures were irradiated at 25°C with 167 MeV Xe ions at a fluence of 6x10⁹ cm^-2. Comparative studies of the optical and electrical properties of initial and irradiated structures with Schottky barriers were carried out in temperature range 23-180°C. Swift heavy ion stimulated changes in photosensitivity and electrical characteristics of the initial and irradiated detectors are explained in terms of the fluctuation traps model with the subsequent thermal dissociation.

Abstract: Traditional anomaly detection algorithm has improved to some degree the mechanism of negative selection. However, there still remain many problems such as the randomness of detector generation, incompleteness of self-set and the generalization ability of detectors, which would cause a lot of loopholes in non-self-space. This paper proposes a heuristic algorithm based on the second distribution of real value detectors for the remains of loopholes of the non-self-space in the first distribution. The algorithm proposed can distribute real value detectors through omission data based on the methods of partition and movement. A method is then proposed to solve the problem on how to get the optimal solution to the parameters related in the algorithm. Theoretical analysis and experimental results prove the universality and effectiveness of the method. It is found that the algorithm can effectively avoid the generation of loopholes and thus reduce the omission rate of detector sets.

Abstract: Pin structure GaN-based alpha particle detector with epitaxial growth on c-plane sapphire substrate through metal organic chemical vapor deposition (MOCVD) method, uses electron beam evaporation and photoetching machine to produce the ohmic contact electrodes of device. The electrical properties of device which were tested by I-V and C-V show that the device’s reverse leakage current is 9.9μA at 100V reverse bias voltage is at; and the detector’s junction capacitance is 19pF at 20V reverse bias voltage.

Abstract: Focusing on the disturbance of moving cast shadow, a Bagging-ensemble-based moving cast shadow removal method is proposed. Collecting shadow discrimination features from multiple shadow discrimination models, a shadow detector is trained by employing Bagging ensemble based learning framework. The shadow detector can automatically select effective shadow discrimination features and be updated online adaptively. Experimental results demonstrate the effectiveness of the proposed method.

Abstract: As the primary technique to offer safety and productivity improvement s for under- ground project s , rock bolt s have been widely used in t he construction of t raffic and hydro- power stations. The quality of the rock bolt s is of great importance and has been paid a lot of at tention to. This paper reviewed the history of some techniques used for the inspection of rock bolt s and analyzed their t heory and application. It point sout that the t heoretic p roblem is t he primary problem existed in t hese techniques.Nondestructive testing of bolt develops quickly with plenteous accomplishments and experiences.And we state these accomplishments mainly and look into the future.

Abstract: This paper analyzes the factors that cause axial fatigue testing machine not coaxiality and influence on test results, put forward the axial fatigue testing machine alignment inspection, and designed a new type concentric structure to adjust not coaxiality.

Abstract: ^{This paper puts forward a visual method of detecting pop-cans based on AdaBoost Algorithm. This method, is basing on the idea of AdaBoost Algorithm, and we use Haar Feature and LBP Feature to extract pop-can characteristics respectively. Finally we compare the differences of the training processes and the experiment results between these two detectors. It shows that these pop-can detectors that are trained by this visual method have high detection rate and speed.}