Based on the continuum hypothesis, problem of compressing wave was studied analytically. By exploring the temperature distribution, the propagation velocity, and the thickness of the transition region, the developing process of compressing wave turning into shock wave was revealed, and the following conclusions were reached: (1) the governing equations of compressing wave can be turned into two autonomous equations, and the phase diagram can be used as an effective tool for the analysis of the compressing wave; (2) the solution of compressing wave was composed of two parts: the inner solution and the outer solution; when Pr = 3/4, the analytical inner solution can be obtained; (3) as the disturbance velocity increases, the thickness of compressing wave will decrease, and the propagation velocity of the compressing wave will increase, and the compressing wave will become shock wave when the disturbance velocity is large enough; (4) velocity and temperature across compressing wave change monotonically and continuously, but the entropy generation changing tendency is closely related to Pr; therefore, the inner solution reveals the mechanism of irreversibility happening in compressing waves.

：The pump-controlled technology has wide application in engineering machinery, heavy machinery and other fields.However, there are few analyses on its output characteristics at present. To explore the effect of the critical parameters of the pump control system on the output characteristics of the system, based on the state equations of open circuit pump-controlled asymmetric cylinder systems, the first-order trajectory sensitivity equations are derived and the sensitivity function curves of each parameter are obtained. Two measures of peak sensitivity and mean sensitivity are proposed to analyze the influence degree of each parameter variation on the displacement output characteristics. Based on 0.6MN pump-controlled hydraulic forging test bench, the accuracy of sensitivity theory analysis is verified. Experimental results indicate that in no-load time, servo variable pump 2 pilot servo valve gain, servo variable pump 2 and servo variable pump 1 pilot stage servo valve time constant has great influence. In load, that value of the sensitivity indexes of two parameter of each parameter is similar, in which the gain of pilot stage servo valve of servo variable pump 2, time constant and oil cylinder area and flow gain and system ratio gain are greatly affected. All the research above can provide theoretical basis for pump-controlled asymmetric cylinder systems performance optimization. Key words：pump-controlled system；asymmetric cylinder；sensitivity analysis；state equations

Wireless laser pointer is widely used in multimedia teaching. Due to the usage of professional high speed USB interface chips and USB2.0 protocol, the price of a wireless laser pointer in the market with the only function of changing PPT pages is about 50 dollar.This paper completes a very low price design of wireless laser pointer for multimedia teaching use based on STC89C52RC MCU and nRF905 single-chip radio transceivers,which can complete not only PPT page turning forward or backward but also black screen, drawing lines with fluorescent pen or needlepoint.