Two-dimensional position sensitive neutron detector

Pramana - A two-dimensional position sensitive neutron detector has been developed. The detector is a3He + Kr filled multiwire proportional counter with charge division position readout and has a...     

An eye behavior measuring device for VR system

This work presents an eye-tracking and pupil size-measuring device that interfaces with a computer for applications useful in psychometry, ophthalmology, physiology and virtual reality (VR) systems. This system utilizes a change-coupled device (CCD) camera, appropriate lenses, PC with frame grabber and a DSP unit with various types of VR equipment, i.e., HMD, simulator or LCD projection device. The digital signal processing unit is used to calculate the average brightness and contrast of the VR video image. A CCD camera with various attachments can be mounted on various VR systems to capture the human eye image for testing. An image capture card and a personal computer are used to analyze the test image. From the eye digital image, the computer obtains data on the pupil size and a trace of the tested eye. A pattern recognition computer program and five measurement parameters are used to distinguish the position of the pupil, calculate the pupil location coordinate and analyze the physical conditions of the user. These data can be plotted against the average brightness and contrast of the VR video image in real time. This information is shown on the screen of a personal computer and used for cross-link analysis. This eye-tracking interface can determine the position of a subject's pupil and map that position into a display point on a computer screen. The pupil size and location data versus the average brightness and contrast of a VR video image are computed in real time.     

The effect of head position on glottic closure in patients with unilateral vocal fold paralysis

The present study was designed to assess the effect of head position on glottic closure as reflected in airflow rates (open quotient and maximum flow declination rate), in patients with unilateral vocal fold paralysis. Ten patients, 2 males and 8 females ranging in age from 40 to 75, with a mean age of 57.3, served as subjects. Airflow measures were taken during sustained phonation of two vowels (/i/ and /a/) in 3 head positions (center, right, left). Vowels /i/ and /a/ were produced at subject's comfortable pitch and loudness, with random ordering of both vowel order and head orientation. Subjects were trained to focus eye gaze on right and left markers (70-degree angle) and a central marker at eye level directly in front of the subject. Theoretically, if turning the head during phonation alters the laryngeal anatomic relationship by bringing the vocal folds in closer proximity to one another, then airflow rate should lessen. Our results indicate that head position does not improve glottic closure in these patients, which is in contrast to previously published research.(1) Our results question the utility and underlying theoretical construct for the use of head turning as a therapeutic technique for improvement of voice in patients with unilateral vocal fold paralysis.     

应用振幅矢量法讨论夫琅和费单缝衍射光强分布

本文提供了夫琅和费单缝衍射（简称衍射，下同）光强计算公式，与一般文献中的理论公式相比，不但完全等效，而且计算简便精确，对衍射光强分布的实际应用及实验测量￣［３］具有一事实上的参考价值。     

植物研究用γ射线成像系统设计

为了利用正电子发射断层成像技术在植物生理功能研究中的优势,正在开发由两个探测器相向放置构成的γ射线成像系统.系统中采用的探测器是由10×10的氧正硅酸镥(LSO)晶体阵列与滨松R5900-C12耦合组成.单个LSO尺寸为1.8mm×1.8mm×10mm.根据PET应用的特点,测试了该探测器的性能.所有闪烁晶体的图像在位置图谱中清楚可见;511keV全能峰处的能量分辨率位于14.5%—22%之间;符合时间分辨率随着位置灵敏光电倍增管的供给电压的增加而得到改善.这些实验结果表明,该LSO探测器适于构造高分辨率的双探测器成像系统.     

反馈抑制HLS注入过程中β振荡的尝试

为了提高注入束流的积累,抑制由于注入系统误差所引起较大的β残余振荡是非常有必要的.本文较系统地介绍了合肥光源(HLS)抑制注入β振荡反馈系统的设计思想、原理和线路,并提供了它的初步实验结果.作为原理论证和预研,我们使用了一个相对简单的模拟滤波器和移相器对Kicker过程激发的β振荡进行反馈,看到了明显的抑制作用.为以后研制低频和高频反馈系统,研究抑制束流的横向和纵向不稳定性打下基础.     

北斗双星/SINS组合导航系统滤波模型的一致性研究

北斗双星定位系统（简称双星定位）是我国自行建立的一种定位系统.根据北斗双星定位系统采用有源定位的特点,介绍了北斗双星与SINS组合的最优预测模型,该方法利用了双星定位系统提供的滞后定位信息对组合系统进行最优预测,进而校正惯导;同时为验证该滤波方法对状态估计的一致性,文中重点研究了滤波器一致性的准则,并给出了检验的统计量.理论研究和试验仿真证明,文中介绍的滤波器与系统是匹配的,具有较高的滤波性能和精度.     

Optimization of support positions to minimize the maximal deflection of structures

In this paper, the design sensitivity analysis for the deflection of a beam or plate structure is first investigated with respect to the position of a simple support using the discrete method. Both elastic and rigid supports are taken into account, and closed-form formulae for the deflection sensitivity are developed straightforwardly. Then, on the basis of the design sensitivity analysis, a heuristic optimization algorithm, called the evolutionary shift method, is presented for support position optimization to minimize the maximal deflection of a structure with a fixed grid mesh scheme. In each iterative loop, the support with the highest efficiency is shifted in priority. To facilitate the convergence of the process, a polynomial interpolation technique is employed to evaluate the solution more accurately. The optimal solution is achieved gradually with a minimum modification of the support layout design. Finally, three numerical examples are presented to demonstrate the validities of the sensitivity analysis and the optimization method. Results show that support optimization can improve the structural behavior significantly.     

临界空穴扩张比准则的适用性

用新研制成的DE36平台钢制的轴对称和平面应变试样,进一步考察了临界空穴扩张比V_(Gi)准则[1]、[2]、[3]的适用性。实验和大应变有限元理论计算结果表明,V_(Gi)准则适用于所研究材料。文中指出,按V_(Gi)准则可根据试样或构件材料中V_G的发展变化来预起裂位置。     

基于多功能数据采集卡和变速PID的转台控制系统设计

为了提高采用转台对惯导系统和惯性仪表进行误差模型标定时的可靠性和精度,对角位置转台的控制系统进行了研究。首先借助NI公司PXI-8101控制器和功能强大的数据采集卡PXIe-6363对转台控制系统进行了硬件设计。随后在对转台常规PID控制方法研究的基础上提出了一种能随系统调节偏差自动改变积分项累加速度的变速PID控制方法。接着又对基于软件实现的双通道旋转变压器轴角解调算法进行了研究并提出了一种粗精组合角纠错方法。最后对本文设计的转台控制系统进行了测试实验,结果表明提出的轴角解调算法具有较好的解码速度和精度,并且变速PID控制方法大大提高了转台控制系统的自学习能力和鲁棒性,显著地改善了转台控制过程的稳定性。