A three-dimensional computational model of two CRH2 trains passing by each other in a tunnel was developed using finite volume method with moving mesh, to investigate the characteristics of air wave and flow field around high-speed trains. Two meeting scenarios (i.e. meeting at the same train speeds and at different train speeds) and five train speeds (i.e. 200, 250, 300, 350, and 400 km/h) were examined. The computational model is demonstrated to be qualified to investigate the characteristics of air wave for two trains meeting in a tunnel. The pressure distribution and velocity vectors of two trains meeting in a tunnel were revealed, and the typical features of the corresponding air wave curve were discussed. Furthermore, the variation regularity of pressure amplitudes and the relationship between pressure wave amplitude and train speed were also analyzed. The results indicate that two trains with a large speed difference should be avoided when they pass by each other in a tunnel. These findings are helpful to guide the design of trains and tunnel structures and the dispatching management of rail transit.

This paper presents the design of low noise CMOS pre-amplifiers based on photoelectric detection systems, which can directly affect the detecting precision of the whole systems. The design of pre-amplifier circuit from photoelectric detector was introduced. The photoelectric conversion circuit, amplifier circuit bandwidth, amplifier circuit noise, amplifier circuit stabilization and other questions were mainly discussed, and an amplifier circuit capable of effectively decreasing the noise, the temperature drift and a large dynamic range was designed. This paper analyzes the sources of photoelectric detection circuit internal noise, and gives the formulas of internal noise, designs a variable equivalent load photoelectric conversion circuit, and is verified by experiments. Then the result is used to reduce the noise of CMOS based operational amplifiers and finally implement the design work of pre-amp using 0.5μm CMOS Technology.

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This paper presents a photoelectric detection circuit for microfluidics chip. The proposed photoelectric detection system can reduce noise and increase sensitivity. It is consist of pre-amplifier, ac-amplifier and band-pass filter. The transfer function of photoelectric detection circuit is introduced. The circuit implementations and simulation results are given. The proposed photoelectric detection circuit is suitable for integrated microfluidics chip.

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This paper presents a low-power multistage amplifier with a novel capacitor-multiplier frequency compensation (CMFC) technique. The proposed compensation strategy can allow the circuit to occupy less silicon area and to drive large capacitive loads more effectively. Moreover, smaller physical capacitance results in higher gain-bandwidth product (GBW) and improved transient responses. Furthermore, the capacitor multiplier stage (CMS) embedded in CMFC creates a left-half plane (LHP) zero, which boosts the phase margin and enhances the stability of the amplifier. Implemented in a commercial 0.5-μm CMOS technology and driving 500pF capacitive load, a three-stage CMFC amplifier achieves over 120dB gain, 1.699MHz GBW and 1.625V/μS average slew rate, while only dissipating 330μW under 3.3V supply.

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In this paper, the statistical characteristics of the multi-cascade κ-μ shadowed fading channels are investigated and analyzed under the classic Wyner’s eavesdropping model. In particular, the general accurate expressions of the probability density function and the cumulative distribution function for amplitude and signal-to-noise ratio (SNR) are derived for the first time. Moreover, we further utilize the two performance evaluation metrics including outage probability and intercept probability to investigate the impacts of cascade number and channel parameters on reliability and security. Finally, the theoretical results are consistent with the simulations, proving the correctness of the derivation. The interesting conclusion is that when the average SNR is greater than 2 dB, the reliability of the multi-cascade model will decrease as the number of cascade increases; on the contrary, more cascading can lead to stronger anti-eavesdropping ability.