Abstract:Trace is the important composition structure of printed circuit board, which connects the devices, it is also the module that taking up the highest proportion, thus, it is the major testing target of quality assurance. The sunken defects proposed in this paper is a width abnormity defect on the FPC trace, which would cause the latent open circuit defect and affect the electrical function of circuit. The problem of flexible deformation and width difference make the FPC trace detection harder. Therefore, this paper proposed a detection scheme combined with linear masks and circle distribution characteristic. Firstly, this scheme preprocessed the acquired FPC image, divided the trace into several sub-regions and obtained the line width values of each trace transverse section. Then the line width sequences were searched with the linear difference template of gray scale. Thus, the sunken defects alternative positions were located. Lastly, the circle distribution characteristic is defined to identify the real defect areas from the alternative regions acquired from the previous step. Thus, the detection of sunken defects on the FPC trace was accomplished. The algorithm was tested in the self-built image database, which shows the better detection performance than the other typical algorithms.

Abstract:Mammography x-rays standard is required to improve the quality of mammary machine and reduce the dose for women and staff. The molybdenum target x-rays machine is used as the radiation source and free-air cylindrical chamber is designed for detecting photon. Four standard radiation qualities are established with international standard documents as references. The Correction factors including air attenuation, scattered radiation, fluorescence, wall transmission, electron loss are studied in the four radiation quality. The uncertainty in absolute measurement of air-kerma includes air volume measurement of ionization chambers, current measurement, measurement of temperature and pressure, measurement of correction factors, physical constants and orientation of the reference distance. The relative combined standard uncertainty is 0.24%.

Abstract:This paper addresses the principle and control topology of active power filter (APF). The control strategy of direct power control based on DC side is introduced, and the control output is implemented by using the principle of hysteresis control. The active power filter can effectively control the power system harmonics, improve the quality of electricity and purify power grid. The experimental results are provided to illustrate that the direct power control based on DC side has the advantages of simple structure, stable DC output voltage and fast dynamic response.

Abstract:In view of the problem that the packet information preempted network resources in the process of transmission in the CAN bus, which leads to the low utilization of network resources and the low accuracy of information transmission. Thus, a hybrid scheduling algorithm NMTS based on CAN bus is proposed, in the NMTS hybrid scheduling algorithm, the dynamic scheduling algorithm EDF is used to schedule hard real-time messages to solve the problem of low utilization of network resources; the static scheduling algorithm RMS is used to schedule soft real-time messages and non real-time messages, so as to solve the problem of low accuracy of information transmission. By using MATLAB software, the CAN network model can be built, the EDF algorithm, RMS algorithm and NMTS algorithm are simulated. The experimental results show that the network resources utilization is 90%, the packet loss rate is 0% of the NMTS algorithm. Therefore, The hybrid scheduling algorithm based on CAN bus NMTS has the characteristics of high network resource utilization and high accuracy of information transmission, which will be very helpful for further research of CAN bus.

Abstract:With the development of intelligent and networking technology in automobile, the malicious attacks against in-vehicle CAN networks are increasing day by day, and the problem of information safety in automobile is aggravated. In this regard, this paper analyzes the security loopholes and threats which the CAN bus faced, put forward a kind of anomaly detection algorithm for vehicle CAN bus. The method uses support vector machine algorithm to distinguish between normal message and abnormal message, so as to realize the CAN bus anomaly detection. Theoretical and experimental studies show that this method can effectively detect abnormal packets in the CAN bus with a detection rate of over 90%, which can effectively resist malicious attacks such as tampering and cheating on the vehicle CAN bus.

Abstract:Chirp signals show energy aggregation in the fractional Fourier domain (FrFD) which can be used to estimate the parameter of the signals. In this paper, a parameter estimation method for multi-component chirp signal which corrupted by white Gaussian noise is proposed based on the discrete fractional Fourier transform (DFrFT) and the differential evolution (DE) algorithm. The proposed algorithm uses the DE algorithm instead of the conventional fine search algorithm to detect the peak of the signals in the FrFD. The paper simulated the influence of the noise and the resolution of the proposed algorithm. The results of the simulation show the proposed method does not only improve the estimation accuracy of the peak coordinate, but also reduces time consuming.

Abstract:Despite of the small amount in the atmosphere, ozone is one of the most critical atmospheric component as it protects human beings and any other life on the earth from the sun's high frequency ultraviolet radiation. In recent decades, the global ozone depletion caused by human activities is well known and produces an "ozone hole", the most direct consequence of which is the increase in ultraviolet radiation, which will affect human survival, climatic environment, ecological environment and other important adverse impacts. Due to the implementation of the Montreal protocol and other agreement, the total amount of ozone depleting substance in the atmosphere has been prominent reduced, which will lead to a new round of regional climate change. Therefore, predicting the changes of the total ozone in the future will have an important guiding significance for predicting the future climate change and making reasonable measures to deal with the climate change. In this paper, based on the ozone data of 1979 to 2016 in the southern hemisphere and ARIMA model algorithm, using time series analysis, we obtain prediction effect of ARIMA model is good by Ljung-Box Q-test and , and the model can be used to predict the future ozone change. With the help of SPSS software, the future trend of the total ozone can be predicted in the future 50 years. Based on the above experiment results, the global ozone change in the future 50 years can be forecasted, namely the atmospheric ozone layer will return to its 1980's standard by the middle of this century at the global scale.

Abstract:A low-phase-noise CMOS voltage-controlled oscillator (VCO) with zero-bias scheme and multi-stage filtering is presented. Sharing ground with fully integrated loop filter, the PMOS-only VCO achieves a zero-bias scheme, which prevents tuning line noise from disturbing VCO output common-mode voltage and hence minimizes phase noise caused by nonlinear C-V characteristic of varactors. Top-biased current source is optimized by multi-stage filtering to reduce 1/f flicker and thermal noise. Fabricated in TSMC 180 nm CMOS process, the proposed VCO exhibits a measured oscillation frequency of 0.85~1.45 GHz, with a phase noise of -121.8~-131.3 dBc/Hz @1MHz offset over the whole band. Power consumption is 3.8~6.3mW from a 1.8V supply.

Abstract:In order to improve the performance of the antenna at low frequency, short circuit branch and coupling feed structure are introduced into the folded broadband single antenna in this paper, then resonant frequency is merged into the antenna using method of stagger tuning, finally, a UWB antenna is designed to work between 800MHz～2700MHz. Analysis are conducted to determine the antenna’s properties. The short-circuit wire location, feeding point location and the length of folded strip are discussed in detail. The SAR is calculated by HFSS simulation software while the antenna is close to a 3D human head model. The research results show that the antenna can cover eight commonly used commercial frequency bands at present, and electromagnetic radiation of the antenna has tiny influence on the human head model.