Applied Mechanics and Materials Vols. 411-414

Abstract: A rapid real-time polarization measurement system was designed and implemented in this paper. The system is centered round a laptop running application developed for the purpose. The paper illustrates how to build such an excellent application with National Instruments graphical programming language LabVIEW, a synchronized high speed multi-channels data acquisition card and some photoelectric conversion module in detail. With simple and friendly user interface, the experimental result shows that the measurement system has high computational efficiency, high precision calibration matrix, which can be efficiently utilized in experiments relating to the measurement of polarization.

Abstract: In this paper, we proposed a mobile security system based on IP camera network video surveillance by improving the traditional monitoring methods. This system includes three parts: Android mobile client, cloud server, IP camera monitoring terminals. By setting IP cameras at 24 fps but only sending one frame each second, we can infer the situation by analyzing of the single image and reduce the amount of data transmission. User can check the live scenes and send control commands to monitoring terminal or receive the push information from the server to freely give alarm signal to users anytime, anywhere. And users can also select any regions or any specific objects to monitor, the server will real-time monitor each scene according to the specific requirements by using the algorithms of image contrast and depth estimation. The experiment results show that the system can greatly improve the accuracy of the alarm.

Abstract: This paper focuses on the research of weak signal acquisition based on time-division CDMA-OFDM (TC-OFDM) system by using long PN sequence with low power. An enhanced weak signal acquisition algorithm is proposed to improve the ability of weak signal acquisition compared with regular algorithm which uses short PN sequence with high power. Simulation shows that the ability of resistance to white noise in weak signal acquisition is enhanced by 12dB. Further, because of the good correlation of long PN sequence, the performance of resistance to strong signal interference has also improved 6dB.

Abstract: We demonstrate a new multiple-junction photodetector incorporating concentric circular subwavelength gratings as a broadband reflector. A quantum efficiency of 81% and a 3dB bandwidth of 121 GHz are simultaneously obtained due to the suitable design of junction number and absorption layer thickness.

Abstract: In this paper, we investigate the features of energy detection and cyclostationary feature detection for spectrum sensing. In order to combine their advantages, we propose an adaptive two-stage sensing scheme which performs spectrum sensing using an energy detector first in cognitive radio networks. Then in the second stage, this scheme decides whether or not to implement cyclostationary feature detection based on the sensing results of the first stage. On the premise of meeting a given constraint on the probability of false alarm, the goal of our proposed scheme is to optimize the probability of detection and sensing speed at the same time. In order to obtain the optimal detection thresholds, we can formulate the detection model as a nonlinear optimization problem. Furthermore, the simulation results show that the proposed scheme improves the performance of spectrum sensing compared with the ones where only energy detection or cyclostationary feature detection is performed.

Abstract: We have designed a photoelectric yarn signal acquisition system, which is based on the STM32 processor, having a sample rate up to 270kHz, and uploading data collection through synchronous parallel communication mode; Owing to the large noise of yarn signal and the unobviousness of yarn defect, we respectively adopting wiener filter and mean filter to filter this signal; The simulation result of matlab has manifested that both the wiener filter and mean filter can effectively decrease the noise level of the yarn signal and make the nep defects easier to identify, and that the wiener filter applies to application where the yarn speed is higher , while the mean filter is appropriate to the lower speed spinner.

Abstract: As a novel biometric identification technology, human gait recognition has wide applications in public security and other fields. Aiming to solving problems of conventional Time-Frequency analysis of human gait signal, the paper presented a processing method that adopts time-frequency distribution with complex-lag. Firstly, the human walking Doppler signal model and the principle of time-frequency distribution with complex-lag were introduced. Then the signal based on the model was generated and was analyzed utilizing Spectrogram, WVD and time-frequency distribution with complex-lag. The results show that the presented method has the best performance since its high time-frequency concentration and less cross-terms disturbances.

Abstract: Infrared biosensor has been a hot area of research for several years in infrared field. This paper proposes a method to test infrared biosensor array which is not bonding with ROIC. The presented ROIC-less infrared biosensor is encapsulated in a vacuum chip scale packaging, and we design the off-chip “ROIC” in order to read out signal of infrared biosensor. It is necessary to apply bias voltage on pixels when infrared biosensor works, we gave a simulation of infrared biosensor in pulsed bias votage mode according to the infrared biosensor heat balance equation. Based on the simulation result, we have implemented the test system for ROIC-less and small-scale infrared biosensor array. We use FPGA as main controller to readout the infrared signal and transfer the data to PC via USB interface.

Abstract: In image digitization and transmission, images often suffer contamination inevitably. The noises in images often consist of Gaussian noise and impulse noise. The common denoising algorithms are capable of removing single one of them. In order to remove those two types of noise, a composite algorithm is proposed. Firstly, based on median filter, an impulse noise detection algorithm is used to filter impulse noise. Secondly, adaptive directional lifting wavelet (ADL) and normal lifting wavelet is combined to suppress noise from image signal and protect the texture edge from loss simultaneously. Meanwhile an improved half-soft threshold is used for normal lifting wavelet. At last, simulations show that this technology can suppress Gaussian and impulse noise in image efficiently．

Abstract: This paper presents the design and simulation of a piezoresistive pressure sensor with wide operation range (up to the pressure of 1000 m-deep water). Structural and electrical simulations were carried out using COMSOL Multiphysics 4.3. The dimension of the membrane, and the geometry and placement of piezoresistors, were optimized through structural simulations. Electrical simulations were used to evaluate the performance of selected sensors. The output characteristics revealed good linearity throughout the measurement range with sensitivities of 0.4500~0.8964 mV/V/MPa. The optimum design of sensor was determined according to the simulation results.