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It is very difficult to identify Shadowsocks (SS) traffic, most of which stay in the laboratory environment, and there are very few published research results in this field at home and abroad. ShadowsocksR (SSR) is an enhanced version of SS. It can disguise the traffic of SS as that of conventional protocol, such as HTTP traffic, TLS traffic, etc., which makes it more difficult to identify SSR traffic. Based on Xgboost algorithm, this paper proposes a method to identify SSR traffic for the first time. The experimental results show that this method has a good recognition effect on SSR traffic, and the precision, the recall, the accuracy is all above 95.3%.

Bipolar current sources with a stability better than 0.1% in the temperature range of -30 to +70 °C are demanded for driving voice coil motors applied in a new ultra-quiet satellite platform, but almost none of the existing designs satisfy the harsh requirements. This paper presents a possible solution, which is essentially a floating-load, bipolar current source circuit with a dual feedback path. The key circuit is a composite amplifier (co-amp) composed of a high precision amplifier for error correction and a high power amplifier for load driving. The first feedback path comprises a specially designed four-wire current-sense resistor for current-to-voltage conversion and a discrete instrumentation amplifier for amplifying the converted voltage and closing the loop. The second feedback path is a proposed compensation network for loop stability. Error budgets for evaluating current stability and choosing key components of the circuit are comprehensively studied based on a derived rigorous current equation. Loop-stability problems attributable to the inductive load and the high open-loop gain of the co-amp are analyzed, and the proposed dual feedback compensation method is verified by theory, simulation, and measurement. All these contributions are demonstrated by three implemented prototypes with an output of up to ±2 A. The measured results agree well with theoretical predictions. The best and the worst stability performances of the three prototypes at +2 and -2 A are, respectively, 394 and 986 ppm in the temperature range of -30 to +70 °C, which are close to the theoretical value of 776 ppm.

In diffusion processes of solid materials, such as in the classical thermal shock problem and the recent lithium ion battery, the maximum diffusion induced stress (DIS) is a very important quantity. However a widely accepted, accurate and easy-to-use quantitative formula on it still lacks. In this paper, by normalizing the governing equations, an almost analytical model is developed, except a single-variable function of the dimensionless Biot number which cannot be determined analytically and is then given by a curve. Formulae for various typical geometries and working conditions are presented. If the stress and the diffusion process are fully coupled (i.e. stress-dependent diffusion), as in lithium ion diffusion, the normalized maximum DIS can be characterized by a two-variable function of a dimensionless coupling parameter and the Biot number, which is obtained numerically and presented in contour plots. Moreover, it is interesting to note that these two parameters, within a wide range, can be further approximately combined into a single dimensionless parameter to characterize the maximum DIS. These formulae together with curves/contours provide engineers and materialists a simple and easy way to quickly obtain the stress and verify the reliability of materials under various typical diffusion conditions. Via energy balance analysis, the model of diffusion induced fracture is also developed. It interestingly predicts that the spacing of diffusion induced cracks is constant, independent of the thickness of specimen and the concentration difference. Our thermal shock experiments on alumina plates validate these qualitative and quantitative theoretical predictions, such as the constant crack spacing and the predicted critical temperature difference at which the cracks initiate. Furthermore, the proposed model can interpret the observed hierarchical crack patterns.

A fast algorithm of extracting laser line is proposed for real-time image processing in 3DLCS and is compared with the former algorithm. First of all, the threshold S(T) of the laser stripe is computed by host computer unnecessarily in real time. Second the laser stripe is determined in real time. At last the central line of the laser stripe is detected by templates in real time. The fast algorithm was successfully implemented using VC6.0, then simulated successfully programming with Verilog HDL on the “Verilog XL” software which is developed by CANDENCE corporation. The fast algorithm is implemented by FPGA designed as pipelined architecture. The average time of processing every pixel in each step is less than 74ns. The results of emulation and synthesis show that extracting laser line from a frame of standard PAL video image is completed within 40ms. The advantages of the fast algorithm include easy computing, less data throughput, and fast implementation, etc. It reduces greatly information redundancy.