Temperature Effects on Photoluminescence Properties of Porous Silicon

The temperature effects on the photoluminescence(PL) properties of porous silicon(PS) have been observed in the early stage. However, the obtained results are different. Through repeated experiments, some different and useful information are got, which benefits us in that PL properties of porous silicon can be fully made use of. Firstly, samples with porosity of 76% and 49% were chosen to study the exciting temperature effects on the PL spectrum. For the samples with low porosity, the decreasing temperature causes the peak wavelength to be red-shifting and that of the samples with high porosity to present the blue-shifting trend. The light intensity of both reaches the maximum at -10℃. These experimental results can be well explained with the synthesized center PL model based on the quantum confinement model, other than the PL efficiency function σ(λ). Thereafter, PL properties of PS samples fabricated separately under the temperature of -10℃, 0℃, 10℃, 20℃ and 30℃ were studied. The results indicate that with the decrease of the etching temperature, the PL intensity increases from 406.7 to 716.6 and the peak wavelength blue-shifts from 698.9nm to 671.8nm. The WHFM of the PL spectrum dramatically narrows. At the same time, the images observed by AFM show that with the decreasing temperature, the holes are becoming deeper and the porosity is higher, which suggests that the decreasing temperature accelerates the etching rate.

Approach of Synthesizing Model Predictive Control and Its Applications for Rotary Kiln Calcination Process

An actual control demand of rotary kiln is taken as background. By analyzing and improving approach of MPC （synthesizing model predictive control）, an effective strategy which applies complex S-MPC in actual industrial process is designed. Firstly, after analyzing the main components technology and calcination reaction mechanism in detail, the calcining belt state-space model of rotary kiln is built using PO-Moesp （past-output multivariable output error state space model identification） method. Then, calcining belt temperature predictive control system is de signed. The control system combines time-delay gain scheduled, output-tracking, recursive subspace adaptive and other methods, and forms the off-line/on-line predictive controller of rotary kiln. At last, MATLAB is applied for simulation, experiments run in constant value tracking and servo tracking situation. Simulation results show its ef- fectiveness and feasibility.

A head-related transfer function model for fast synthesizing multiple virtual sound sources

A head-related transfer function （HRTF） model for fast and real-time synthesizing multiple virtual sound sources is proposed. A head-related impulse response （HRIR, time- domain version of HRTF） is first decomposed by a two-level wavelet packet and then represented by a model composed of subband filters and reconstruction filters. The coefficients of the subband filters are the zero interpolation of the wavelet coefficients of the HRIR. The coefficients of the reconstruction filters can be calculated from the wavelet function. The model is simplified by applying a threshold method to reduce the wavelet coefficients. The calculated results indicate that for a model with 30 wavelet coefficients, the error of reconstructed HRIR is about 1%. And the result of a psychoacoustic test shows that a model with 35 wavelet coefficients is perceptually indistinguishable from the original HRIR. When multiple virtual sound sources are synthesized simultaneously, the computational cost of the proposed model is much less than the traditional HRTF filters.