Eigenspace-based source number estimation for direction-of-arrival estimation

A eigenspace-based source number estimation was presented.It projects the estimated covariance matrix of array signal into signal eigen-subspace and noise eigen-subspace, respectively.Using the orthogonality between signal eigen-subspace and noise eigen-subspace, it is easy to differentiate the contribution of signal and noise by using the criterion value,or the magnitude of projection.Like the Direction-of-Arrival(DOA) estimation algorithm,the estimator uses the eigenvalue decomposition of covariance matrix with order M×M,where M is the number of elements,and hence can save much computational burden.To reduce more computational burden,the estimation can be implemented by the decomposition in the real-value space.Computer simulation demonstrates the distribution of criterion value and the performance of the estimation method.The estimation method was also tested with the sonar data,which shows good performances.     

Investigation on nonlinear thermo-acoustic characteristics of Rijke tube

Based on the energy conservation relationship,nonlinear thermo-acoustic effects of Rijke tube including instability range,saturation processes and higher harmonics modes were investigated.With coupling between the external flow and the inner space of a Rijke tube, the acoustic characteristics of self-excited oscillation were simulated.The experimental study was also carried out and the results were compared with those from simulation.The nonlinear factors which distort the acoustic waveform distortion were analyzed.From the results,it is seen that varying size of the nozzle outlet changes the acoustic impedance in the boundary, and leads to reduction of the nonlinear effects.The results show that the modes of self-excited oscillation could be influenced by the position of higher harmonics.In the large amplitude oscillation,the distortion of pressure wave within Rijke tube could be induced by the acoustic losses due to vortices on nozzle.It is found that the waveform distortion could be avoided by the shrinkage of nozzle.     

肾脏热物性测量及低温下细胞形态分析

肾脏热物性参数获取和微观结构的观察,对研究冰温延时保存器官的机理非常重要。采用差示扫描量热仪测量了离体肾脏导热系数、冰点和器官保存液冰点;利用低温显微系统对肾脏组织不同保存温度及不同降温速率等状态条件,做了细胞形态的观察与分析。研究结果认为,鲜活肾脏导热系数值对肾脏冷却速率影响较大,同时发现在实验条件范围内较小的降温速率对细胞的损伤较轻。     

HL-2M装置放电管理平台研制

HL-2M装置放电管理平台的主要功能是为装置运行人员提供一个运行时序系、PLC逻辑保护系统和反馈控制系统的平台.在放电间歇,它在历史数据的基础上预置下一次放电的各种控制波形、配置各个技术子系统的运行模式和运行参数.其基于反射内存的通讯机制主要负责将控制参数和预设波形以有效的、可靠的方式传递到其它子系统中.与各相关子系统...     

Preparation and mechanism of magnetic carbonaceous polysaccharide microspheres by low-temperature hydrothermal method

In this study, the preparation method for magnetic carbonaceous polysaccharide (Fe₃O₄@CP) microspheres was developed to increase the yield and encapsulation efficiency using a suitable quantity of NaOH as the catalysis. The optimum fabrication condition was identified through a series of experiment, under which the resulting Fe₃O₄@CP microspheres show good magnetic properties. The saturation magnetization was 60.629 emu/g and the magnetite content increased up to 81.7%. The shell of the microspheres was carbonaceous polysaccharide with rich hydroxyl and carbonyl groups located on the surface, and the mean size was less than 300 nm. The formation mechanism of Fe₃O₄@CP was also discussed in this paper.     

Diffusion interaction between Al and Mg controlled by a high magnetic field

The effects of an 11.5 T high magnetic field on the growth behavior of compounds layers during reactive diffusion in solid Al/solid Mg diffusion couples have been investigated. After annealing with and without a magnetic field, the interfacial zone was still composed of two layers of stable compounds β (Mg₂Al₃) and γ (Mg₁₇Al₁₂), but the thicknesses of the layers were increased by the magnetic field. Data analysis of the thicknesses of compound layers showed that the growth of the γ layer was controlled by grain boundary diffusion as well as volume diffusion at B=0 T, but only controlled by volume diffusion when an 11.5 T high magnetic field was applied. The interdiffusion coefficients for the samples annealed at 643–693 K were calculated from the parabolic relationship between the migration of the interface and the annealing time. The results show that the diffusion constant increased due to the high magnetic field, increasing the chemical potential gradient, and in turn it caused the interdiffusion coefficient to increase.     

钢液中多元素的LIBS实时定量分析

将激光诱导击穿光谱(LIBS)技术直接应用于钢液成分的检测.研究结果表明,氩气作为保护气不仅可以避免钢液表面的氧化,同时可以增强等离子体信号强度.在氩气氛围下,钢液表面被聚焦成高功率密度的脉冲激光击穿形成等离子体,利用耦合CCD的多通道光纤光谱仪探测等离子体在冷却过程中发射的光谱信号,得到钢液组分的相关信息.根据分析谱线选取原则,确定了主要合金元素Mn,Si和Cr的特征谱线,并建立了相应元素的定标曲线,曲线的线性拟合度均在0.925以上,对应的质量浓度检测限分别为75.7,23.8和724.5 μg·g-1.