基于DSP的航天器压力变化检漏仪的设计

航天器的密封性能是极其重要的指标之一,利用压力变化方法进行舱体密封性检漏是保障其密封性的重要技术手段;设计研制小型压力变化检漏仪对满足航天器检漏设备小型集成化、高精度的迫切需求是十分重要的;以DSP为数据的核心处理器,分析绝压和差压具有温度补偿方法,设计基于485通信接口实现数字绝压传感器的数据采集,采用250Ω的高精度电阻接入电流环的方法实现差压传感器的信号调理,通过ADS1247高精度24位数模转换器实现差压信号的采集;并采用恒流供电和电阻比测量原理实现对两路热敏电阻温度传感器的测量;各信号经DSP中固化的压力变化检漏算法集中处理,得到被测物体的漏率值,检测结果通过LCD显示。所研制集绝压、差压和温度多参量监测于一体的检漏仪,经过温度、压力、检漏试验等测试,验证了其精度和检漏能力满足要求;研究结果表明：所研制的检漏仪小巧,精度高,可靠性高,可实现压力、温度、漏率等多参量的同时监测,漏率检测的最大相对误差为19.3%,相对不确定度小于2%,可有效地解决航天器泄漏检测的问题。     

用于长城等古建筑探测的NMR探测器的磁体设计

以万里长城为代表的古建筑是世界瑰宝,更是中华民族的象征和骄傲.本文提出利用便携式核磁共振（NMR）装置来探测研究这类古建筑的建筑材料,在不对其造成损伤的基础上,发掘其隐含的科学、技术和工程相关的丰富信息.为此,作为第一步,设计了适合于探测这类古建筑的便携式单边NMR探测器组合式磁体.该探测器的磁体结构以semi-Halbach为基础,通过不同磁体模块间的组合得到对应移动探测模式、长距离探测模式和均匀磁场探测模式的磁体结构.随后根据优化结果,设计加工了磁体组件,并采用该磁体进行了流体、长城城砖和现代红砖的NMR实验,实测结果与模拟一致.该组合式磁体的优点在于通过不同磁体模块组合,实现了多种探测方式,适用于探测长城等这类古建筑物需要多种探测模式的科学研究.     

杜仲的核磁共振指纹图谱研究

核磁共振氢谱（Proton Nuclear Magnetic Resonance,¹H NMR）是中药指纹图谱中一种鉴定和控制植物中药质量的新方法．本文采用CPMG（Carr-Purcell-Meiboom-Gill）脉冲序列采集了杜仲提取物的¹H NMR谱,通过完整还原振幅频率表（Complete Reduction to Amplitude-Frequency Table,CRAFT）分析技术对杜仲指纹图谱进行特征指纹分析,将待目标合物的信号从混合物图谱中剥离出来,实现了不分离样品而分析目标化合物信息的目的,从而对杜仲的特征化合物——松脂醇二葡萄糖苷（Pinoresinol Glucoside,PDG）进行了定性和定量分析．结果显示贵阳药用植物园所得杜仲的PDG含量为0.275 6%,相对标准偏差（Relative Standard Deviation,RSD）为1.69%,与高效液相色谱（High Performance Liquid Chromatography,HPLC）定量分析结果（含量为0.269 6%,RSD为0.65%）基本一致．另外,通过NMR检测与多变量数据建模相结合分析了杜仲提取物的全指纹图谱,结果显示同一采收期不同产地的杜仲药材有显著差异,这表明该方法可用于鉴定不同产地的药材,具有一定的实用意义．     

间歇式高速电视CCD视频图像实时存储系统

针对间歇式高速电视系统中CCD数字图像需要实时无压缩存储的需求,提出一种基于SCSI磁盘阵列的视频图像实时采集存储方案.在磁盘存储速度可行性论证测试的基础上,利用软件技术实现图像数据硬盘实时存储,并将存入硬盘的数据流转换为BMP文件格式加以显示.实验验证了该方案的可行性.     

激光二极管相对于铯饱和吸收D2线的无调制扰动三次谐波锁频

将频率调制加在声光调制器上 ,用三次谐波探测法获得了铯原子D2 线的三阶微分饱和光谱。采用这种激光器无调制扰动方案结合三次谐波锁频技术 ,实现了 85 2nm的分布布拉格反射器半导体激光器相对于 6S1/2 F =4- 6P3 /2 F′ =5超精细跃线的频率锁定。由锁定后的频率误差信号估算 ,10s内激光频率起伏小于± 35 0kHz ,相对频率稳定度约 1× 10 -9。这种无调制扰动方案可以消除一般的饱和吸收稳频方法中由于直接对激光器进行频率调制而带来的额外频率噪声 ;三次谐波锁频技术的应用 ,还可有效地降低铯原子饱和吸收谱中剩余多普勒背景的影响     

The influence of crystalline grain size on the thermal stability of the Er<Subscript>0.45</Subscript>Ho<Subscript>0.55</Subscript>Fe<Subscript>2</Subscript> compound

The phase composition and the temperature dependence of the magnetization of the Er_0.45Ho_0.55Fe₂ compound in coarse-grained, microcrystalline, and submicrocrystalline states are investigated experimentally. It is found that, upon heating under vacuum, the Er_0.45Ho_0.55Fe₂ microcrystalline powder with a crystalline grain size of ∼1 μm undergoes decomposition into pure iron and rare-earth (erbium and holmium) oxides and nitrides at a temperature of 500 K. The changes observed in the phase composition of the microcrystalline powder due to annealing are confirmed by x-ray diffraction analysis. Heating of the Er_0.45Ho_0.55Fe₂ submicrocrystalline sample leads to a partial change in the phase composition. The phase composition of a large crystal (∼1 mm in size) remains unchanged upon heating to 1080 K. It is shown that the thermal stability of the Er_0.45Ho_0.55Fe₂ compound depends on the crystalline grain size. __________ Translated from Fizika Tverdogo Tela, Vol. 44, No. 6, 2002, pp. 1060–1063. Original Russian Text Copyright ? 2002 by Mulyukov, Sharipov, Korznikova.     

The orientation-selective growth of LaNiO3 films on Si(100) by pulsed laser deposition using a MgO buffer

Highly (100)-oriented, (110)-oriented and polycrystalline LaNiO₃ (LNO) films were successfully prepared on Si(100) using an oriented MgO film as a buffer. It was somewhat surprising to find that that the orientation relation between the LNO film and the corresponding MgO buffer was: LNO(100)\MgO(110), LNO(110)\MgO(111) and LNO(polycrystalline)\MgO(100). The crystalline quality of the LNO films was shown to be sensitive to the preparation conditions of the MgO buffer. The film surface was very smooth, without micrometer-sized droplets being observed. All LNO films were of metallic conductivity, with a room-temperature resistivities of approximately 250, 280 and 420 μΩ cm for the (110)-oriented, (100)-oriented and polycrystalline LNO, respectively. Received: 2 April 2001 / Accepted: 23 October 2001 / Published online: 3 June 2002     

On the interaction of two beating electrostatic waves with plasma electrons

This paper is devoted to the study of the interaction of particles with two beating plasma waves. We follow the instructional article by Ott and Dum. According to them, the sum of wave actions during the interaction is constant, supposing the effect of trapped particles on the beat can be neglected. In the present paper, this problem is solved more generally, just for the case of trapped and also untrapped particles in the wave. Our study shows that the sum of wave actions is constant also in the case when the influence of the trapped particles on the amplitudes of two waves was considered. On the contrary this conclusion is not valid if it is supposed that two original waves are amplitude modulated e.g. by the influence of the interaction of the beat with particles. The author is deeply indebted to Dr. Ladislav Krlín for guidance and encouragement throughout the course of this work.     

Raman characteristics of carbon nitride synthesized by nitrogen-ion-beam-assisted pulsed laser deposition

Raman characteristics of carbon nitride films synthesized by nitrogen-ion-beam-assisted pulsed laser deposition were investigated. In addition to the D (disorder) band and G (graphitic) band commonly observed in carbon nitride films, two Raman bands located at 1080–1100 and 1465–1480 cm^-1 were found from our carbon nitride films. These two bands were well matched with the predicted Raman frequencies for βC₃N₄ and the observed Raman bands reported for carbon nitride films, indicating their relation to carbon-nitrogen stretching vibrations. Furthermore, the relative intensity ratio of the two Raman bands to the D and G bands increased linearly with increasing nitrogen content of the carbon nitride films. Received: 30 October 2000 / Accepted: 5 February 2001 / Published online: 2 October 2001     

CP violation and extra dimensions

It is shown that new sources of CP violation can be generated in models with more than one extra dimension. In the supersymmetric models on the space-time , where the radius moduli have auxiliary vacuum expectation values and the supersymmetry breaking is mediated by the Kaluza–Klein states of the gauge supermultiplets, we analyze the gaugino masses and trilinear couplings for two scenarios and obtain the result that there exist relative CP violating phases among the gaugino masses and trilinear couplings. Received: 10 October 2001 / Published online: 20 December 2001