~(87)Y核素生产方法研究

~(87)Y/~(87m)Sr是辐射医学中很有用的同位素发生器,但~(87)Y生产的可能途径没有全面探索和比较。我们认为具有生产意义的方法是利用(p,xn)(d,xn)和(α,xn)三种核反应。在收集国际全部有关数据以后,国际原子能委员会医用核数据科指出的数据不能满足需要,我们用理论计算补充了(p,xn)的部分反应道激发函数,实验测量了(d,xn)反应激发函数。在此基础上对三种反应可能达到的最大产额和杂质含量进行了估算和比较。     

Ba原子6pnd自电离态实验研究

采用三步孤立实激发与偏振光激发相结合的技术将 Ba原子分别从中间态6snp1 D2 (n=7～ 41 )和 6snp3D2 (n=7～ 2 9)激发到 6p1 / 2 nd以及 6p3/ 2 nd自电离态 ,从而获得了这 4个系列的自电离光谱。采用 Lorentz线型拟和的方法对这 4个系列的光谱所展现的不同的光谱特性及其所反映的物理意义做了详细的分析     

联网燃气轮机的动态特性分析

介绍了燃气轮机发电机组及其励磁系统和调速系统的数学模型,并在MATLAB中建立了燃气轮机励磁系统的仿真模型,对其动态特性进行了仿真计算.利用电力系统分析综合程序(PSASP 6.1版)建立了燃气轮机励磁系统及调速系统的用户自定义模型,并结合典型配电网,对并网后的燃气轮机进行了暂态分析和小干扰稳定分析计算,分析了励磁系统及调速系统的有关参数对燃气轮机动态特性的影响,为研究分布式电源对电力系统暂态特性的影响奠定了基础.     

一种低速率语音编码技术在测量船语音通信中的应用

从分析测量船对语音通信的需求开始,主要探讨了测量船在执行载人航天任务时,如何在应急情况下做好航天员与指挥中心之间的话音通信的保障工作。为实现低速率语音通信,将混合激励线性预测(MELP)声码器这种全新的语音编解码器引入到测量船话音通信中,并为这一些新技术与原有系统的融合作了探讨。     

Speech separation algorithm for auditory scene analysis

A simple and efficient algorithm is presented to separate concurrent speeches. The parameters of mixed speeches are estimated by searching in the neighbor area of given pitches to minimize the error between the original and the synthetic spectrums. The effectiveness of the proposed algorithm to separate close frequencies is demonstrated.     

基于Matlab的发电机励磁系统参数测试的研究

根据发电机空载试验数据计算了励磁系统的参数,并对励磁系统数学模型进行了仿真。结合仿真获得的参数,进行了发电机空载电压阶跃试验。仿真和试验结果表明,该方法优化了励磁系统的参数配置,减少了现场工作量,是一种有效的励磁系统参数测试方法。     

Excitation of hypersound in n-GaN films

The aim of this paper is the analysis of hypersound excitation in GaN films. Simulation of process is presented for a case of a thin film geometry on a non-piezoelectric substrate. The frequency range considered is from 50 GHz up to 200 GHz. The excitation is due to coupling with space charge waves (SCWs) in GaN film. The amplification of SCWs is related with negative differential conductivity in GaN films. Possible spatial increments are obtained. The amplified SCWs can excite hypersonic waves at the same frequency due to piezoeffect and deformation potential mechanisms. The first effect is stronger and causes an effective resonant excitation of hypersonic waves in the case of full mechanic contact of GaN film and non-piezoelectric substrate.     

Experimental evaluation of the luminescence performance of fired clay brick coated with SrAl2O4:Eu/Dy phosphor

This study evaluates the luminescence performance of fired clay bricks coated with SrAl₂O₄:Eu/Dy phosphor. To do so, SrAl₂O₄:Eu/Dy phosphor was first produced using the traditional solid-state reaction synthesis technique. The prepared phosphor was then used for coating fired clay bricks to analyze the luminescence performance via spectral analysis, decay characteristics, and microstructure of the bricks. The results reveal that excitation and emission spectra of the phosphor coated bricks range from 200 to 480 nm and 455 to 650 nm, respectively, suggesting that the phosphor coated bricks have the capacity of absorbing light with a wide range of wavelengths. The peak wavelength projected at 511 nm in the emission spectrum is achieved, which indicates 4f⁶5 d¹-4f⁷ transition of Europium (Eu²⁺). The repeated excitation and deexcitation of Eu²⁺ by using hole traps and trap levels offered by Dysprosium (Dy³⁺), exist between the ground and the excited state of Eu²⁺ leads to luminescent phenomenon. Moreover, the decay characteristics has revealed that phosphor coated bricks can emit light for a considerable amount of time (>8.5 min) upon the removal of the excitation source. The results reveal that phosphor coated bricks has the potential of increasing energy efficiency of residential and commercial buildings.     

热激励硅谐振式压力传感器的研制

介绍了基于表面微加工工艺和多孔硅牺牲层技术，设计并制作出梁膜一体化的热激励硅谐振梁压力传感器，给出了制作的工艺过程和参数，测试了传感器在真空中开环状态下的谐振频率一压力特性及幅频特性，其灵敏度达到54．89Hz／kPa，Q值大于20000，0～300kPa范围内线性相关系数为0．9997。     

An adaptive algorithm applied to a design of robust observer

Primary goal of adaptive observers would be to estimate the true states of a plant. Identification of unknown parameters is of secondary interest and is achieved frequently with the persistent excitation condition of some regressors. Nevertheless, two problems are linked to each other in the classical approaches to adaptive observers; as a result, we get a good state estimate once after a good parameter estimate is obtained. This paper focuses on the state estimation without parameter identification so that the state is estimated regardless of persistent excitation. In this direction of research, Besancon (2000) recently summarized that most of adaptive observers in the literature share one common canonical form, in which unknown parameters do not affect the unmeasured states. We enlarge the class of linear systems from the canonical form of (Besancon. 2000) by proposing an adaptive observer (with additional dynamics) that allows unknown parameters to affect those unmeasured states. A recursive algorithm is presented to design the proposed dynamic observer systematically. An example confirms the design procedure with a simulation result.