Based on the structure platform of the gas turbine engine, the components of variable cycle engine were simulated by using the component method. The mathematical model of nonlinear equations correspondeing to each component of the gas turbine engine was established. Based on Matlab programming, the nonlinear equations were solved by using Newton-Raphson steady-state algorithm, and the performance of the components for engine was calculated. The numerical simulation results showed that the model bulit can describe the basic performance of the gas turbine engine, which verified the validity of the model.
The medium-low orbit satellite is used as observation satellite to make parameters estimation and error analysis of the spacecraft orbit. Based on the variable mass particle dynamics, the simplified motion equation of observation satellite was numerically solved by the Runge-Kutta method, and the position of the observation satellite at any time was calculated more accurately. Based on the variable mass particle dynamics, the orbit estimation equation of the spacecraft was given, and the position and the velocity data of the spacecraft at any time were numerically solved by the Runge- Kutta method, and then the fitting curves of these data were obtained. The residual analysis was made to test the output from the model, which indicated that this model is acceptable and valid.
Heat dissipation is a crucial issue for development and applications of high power LEDs. In this paper, heat conductions
of various light sources are compared, and the necessity of heat dissipation of high-power LEDs was further pointed out.
The packaging structure of high power LEDs is introduced, and the heat transfer procedure is analyzed. Finally, some
considerations to dissipate heat effectively to keep good performance of high-power LEDs are given.
Junction temperature is a critically important parameter for high-power white LED applications. It has directly influence
upon light output, device life time, reliability, and emitting wavelength of an LED. In this paper, the principle and
common types of LED is introduced. The effects of the junction temperature on performance of high-power LED are
discussed. The influencing factors of the junction temperature are analyzed, and some general guidelines to maintain a
low junction temperature to keep good performance of an LED are given.
The architectures of CCD and CMOS image sensors are introduced briefly, followed by comparison of their
performances in detail. At last, the future development trends of CCD and CMOS image sensors are prospected. It is
pointed out that CCD and CMOS image sensors will remain complementary and competition, and flourish the image
sensor market together in predictable future.
In the design of Erbium Doped Fiber Amplifier (EDFA), improving flat-gain has great important significance. The
working principle and gain characteristics of EDFA are introduced briefly, the influence of the factors such as Erbium doped
fiber (EDF) length and pump power on the gain of EDFA is analyzed in detail, and the simulation experiments
were carried out with Optisystem software. The result shows that, when pump power is constant, with EDF length
departing the optimal value, the gain of each channel decreases at different degrees; when EDF length is constant, with
pump power departing the optimal value, the gain of each channel changes at different degrees. Moreover, Er<sup>3+</sup>
concentration has significant effect on the gain, and there is an optimal Er<sup>3+</sup> concentration to get the largest gain.
Since the 1990s, with the development of technology of VLSI, CMOS image sensors have been developed increasingly.
The architecture and working principle of CMOS image sensors are introduced. The main advantages of CMOS image
sensors with respect to CCD are analyzed. The key technical problems of CMOS image sensor are discussed, and the
related solving ways are given. The research status of CMOS image sensors is reviewed. At last, the development trends
of CMOS image sensor are prospected.