改进型Henke超软X光源的研究

本文介绍了改进型Henke超软X光源的结构特点及电子光学特性。新研制的改进型Henke X光源在原型基础上作了许多改进。首次采用了双阴极四焦线的结构。通过四条焦线的合理分布,有效地改善了辐射强度的空间分布,使原Henke型软X光源的驼峰形辐射强度分布变平坦了。同时,在改进的Henke源中采用了新型六硼化镧(LaB₆)高效阴极取代了原来的钨阴极,从而降低了灯丝功率,提高了阴极发射效率。同时本文还推导了当电子垂直入射靶面时的辐射强度最大值所对应之靶电压的计算公式:U_0m=3.77×10⁵(μ/ρ)^-1/2。利用该公式计算了Al-k_α、Cu-l_α1α2、B-k_α以及Be-k_α等特征谱线辐射强度的峰值靶压,计算结果与Henke等学者发表的实验结果完全符合。     

光热敏微晶玻璃的制备及其特性研究

研究了SiO₂-R₂O-Al₂O₃-ZnO-B₂O₃(R=Li、Na、K)系统的玻璃组成及光敏、热敏组分对敏化、成核及受控结晶的影响。在1320～1420℃熔化制备了原始透明玻璃。用=2537Å光源进行光刻,经400～560℃及2～5h热处理工艺,获得了性能良好的光热敏微晶玻璃。测定了玻璃中微晶相的密度变化,证明了体积效应。由x射线粉末衍射分析鉴定其微晶相为Li₂O·SiO₂,晶粒尺寸为23.8nm.     

表征漫射体反射特性的一个重要物理参数——双向反射分布函数

本文着重介绍了双向反射分布函数f_b(θ_i,φ_i,θ_r,φ_r)及其在漫射测量中的主要作用,给出了f_b(θ_i,φ_i,θ_r,φ_r)与九种反射比和九种反射比系数之间的关系,同时介绍了f_b(θ_i,φ_i,θ_r,φ_r)的几种测试方法,有关测试仪器的设计准则以及我所研制和使用这种仪器的简单情况.     

柔性制造系统切削稳定性在线监测技术的研究

主要讨论柔性制造系统(FMS)切削稳定性的在线监测方法,在研究FMS切削过程中振动信号变化规律的基础上^[1],提出了用μ_a=E(a)/F(a)作为FMS切削稳定性的监测参数,并进行了理论分析和试验验证.     

铌硼酸盐玻璃网络结构的研究

用径向分布函数和红外光谱分析方法研究了2Nb₂O₅·4B₂O₃·4K₂O和1.5Nb₂O₅·45B₂O₃·3.5K₂O·0.5TiO₂等玻璃的网络结构.得出了铌原子和硼原子的配位数分别为5.8～5.6及3或4.在原子分布函数g(r)和径向分布函数RDF(r)曲线中得出了Nb-O键平均键长为1.92～1.88Å.位于3.11,3.17和3.85Å的其它峰分别是Nb-B,O-O,和Nb-Nb原子对间的距离.红外光谱表明每种玻璃对应的各吸收峰,归结为=B-O(1440和1220cm^-1),≡B-O(1040或920cm^-1),Nb-O(870、730cm^-1)及Nb-O-B(1330cm^-1)的键振动.也就是说,在网络结构中六配位的铌原子与四配位和三配位的硼原子是共存的.这里,四配位的硼分数N₄决定于K₂O和Nb₂O₅的含量.而且与布雷用核磁共振法在B₂O₃-K₂O系统玻璃中的研究结果相符.最后,在对实验数据的分析和计算的基础上提出了NBK玻璃网络结构的一个可能的模型.认为铌硼酸盐玻璃的网络结构是由NbO₅、BO₄和BO₂共同组成的六节和四节环状结构单位元所构成的.     

毫米级微型机器人操作手的研制和操作特性

采用单晶片型压电悬臂梁制作了一种双悬臂梁结构的微型夹持器,用作毫米级微型机器人的微操作手.该微夹持器整体尺寸为15mm×2mm×2mm,重量为100mg.在分析该悬臂梁操作原理的基础上,选用PbNi_1/3Nb_2/3-PbZrO₃-PbTiO₃三元系压电陶瓷准同型相界的配方作为悬臂梁压电驱动材料,这种压电陶瓷具有高压电常数 (d₃₁) 和机电耦合系数 (K_p).进一步研究了压电微夹持器的操作特性.结果表明:50V电场下,其最大张口距离可以达到40μm,最大夹持力为25.7×10^-3N.     

全光谱配色的匀色空间权重因子方法

在CIE 1976(L^*a^*b^*)匀色颜色空间中,本文为全光谱匹配方法提供一种权重因子。这种权重因子使∑_j[ΔE(λ_j)]²→min.实验结果表明,使用这种色差型权重因子进行计算机配色比Schmid和Strockash设计的两种权重因子效果好。     

微通道板对软X射线响应的实验研究

在X光成像望远镜中微通道板(MCP)作为焦平面上的成像接收器,探测天体的软X射线辐射图像。本文实验研究在软X射线波段MCP的成像性能以及与此有关的其他性能。作者没计了实验装置,测量了在碳K_a(4.47nm)线下微通道板——荧光屏组件的分辨率,与计算结果进行了比较。提出了一种用软X射线光电发射作为初电流测量MCP电流增益的新方法,具有可反复多次测量、重复性良好及测量方便等优点。测量了在两个波长下微通道板的量子效率及随X射线入射角的变化。     

硅靶摄象管靶面的击穿

本文讨论了靶面的厚薄对硅靶摄象管电特性的影响.由于靶面减薄的不均匀,局部过薄区域在监视器上会出现与此相对应的白区.推导了当耗尽层穿透n区时p⁺⁺—n—n⁺结耗尽层的宽度,最大场强和击穿电压的表达式.用此公式对监视器上出现的白区进行了分析,明确了白区的出现是由于靶面局部过薄区域p⁺⁺—n—n⁺二极管击穿的结果.     

软X射线电离室

软 X 射线稀有气体电离室作为软 X 射线波段绝对探测器,是通过测量光电离子流得出光谱辐射强度.并详细介绍我们研制1米软 X 射线稀有气体电离室的工作原理及结构,测出空阴极光源辐射出的HeⅡ25.6nm 离子线及 Henke 光源辐射出的 CK_α 4.47nm 线的强度随电离室工作气压的变化,外推出零气压下谱线光谱辐射强度,最终得出谱线的绝对光谱辐射强度.     

高强度脉冲软X光源

本文介绍清华大学电机工程系研制的一种高强度软X光源,这种光源是由喷气式Z箍缩等离子体产生的。阐述了Z箍缩装置的工作原理,研究了装置的运行参数(如充电电压、充气密度等)对软X射线发射的影响。用热电堆测量了X射线的产额。并介绍了用无窗XRD(X射线二极管)测量脉冲x射线的初步结果:光源处的X射线总能量超过100J,发射时间约100ns,其功率达10⁹W以上。     

An extra-bright X-ray source

A bremsstrahlung X-ray source based on deceleration of electrons in the target is described. Its overall dimensions and cost are typical of bremsstrahlung sources, and the main parameters of its X-ray beam are similar to those of synchrotron sources. In a range of Δλ/λ = 10⁻³, the spectral radiant power of CuKα is at least 100 mW/mrad with a divergence angle of 1 mrad. The direction of the X-ray beam at the outlet is arbitrary, depending on the source head holder design. The source can be embedded into existing nanolithography systems and used in medical and industrial introscopes and tomographs, in scientific instruments, etc.     

An Efficient High-Voltage Power Supply for a Photomultiplier Tube

An adjustable power supply for a photomultiplier tube operating in the pulsed spectrometric mode with a wide range of linearity is described. The power consumed by the source is 50 mW. The output voltage is varied from 800 to 2000 V. The maximum ripple amplitude is 2.5 mV.     

Effect of thermal decomposition products of coal on anodic reactions in direct carbon fuel cells

The effect of inherent volatile matter in fuels on anodic electrochemical reactions was investigated in a direct carbon fuel cell (DCFC). Through thermal decomposition, raw coals, which are used as power source in the DCFC system, release gases under an operating temperature of 700°C. These exhaust gases change the gas composition around the anode and affect the system’s electrochemical reaction. To investigate the effect of produced gases, a comparative study was conducted between Indonesian sub-bituminous coal and char obtained through thermal treatment. The open circuit voltage of raw coal increased to 0.23 V compared with that of char. The maximum power density of raw coal (52 mW/cm²) was also higher than that of char (37 mW/cm²) because of the enhanced electron transport caused by the additional reaction of hydrogen, methane, and carbon monoxide. The influence of volatile matter on the anodic electrolyte-electrode interface was analyzed with the use of the equivalent circuit induced from fitting the impedance data.     

Use of the X-ray projection microscope in the examination of bone and cartilage sections

The conditions of use of the X-ray projection microscope for the investigation of bone and cartilage sections have been examined. For the non-calcified tissues an aluminium target operating at 6 kV has been found the most satisfactory. Aluminium at 15 kV and a copper target at 6 kV are also useful. The instrument is not so satisfactory as conventional microradiography for examination of fully calcified bone, but provides useful information about the softer tissues. In the X-ray projection microscope a beam of X-rays produced as nearly as possible from a point is used as a source of illumination, and objects to be photographed are placed between, but not in contact with, the source of X-rays and the photographic plate. All parts of the specimen or section are equally in focus, so that details from one surface to the other are recorded on the plate with equal sharpness. Because of this depth of focus stereoscopic photographs can be taken to give additional information. The X-ray microscope is capable of giving useful information where density differences between tissue components are of importance. The resolving power is governed by the size of the X-ray source, while another factor that influences resolution is the X-ray scattering factor of the tissue components. The microscope is designed to give X-rays of different wavelength by change of target material, and of different penetrating power by altering the voltage. At the time this work started, there was insufficient information available about the conditions required for obtaining useful photographs of longitudinal and cross-sections of bone, so that the first need was to investigate the effect of variations in the experimental method. These will be considered under three main headings: the instrument, preparation and photography of specimens, target material and voltage. An attempt will also be made to give a preliminary assessment of the areas of investigation where the instrument is likely to prove of greatest use in bone research.     

一种高稳定性多功能氘灯恒流电源的研制

本文介绍了一种高稳定性多功能的氘灯恒流电源,其电流调整率达到6.5×10~(-6),漂移达到5.0×10~(-5)/hr。它具有多功能的特点,既可满足各类氚灯使用的供电要求,又可满足各类氘灯科研和生产工作中测试工作的要求;既可与使用氘灯(或氢灯)作光源的各类光学式分析仪器(如紫外光谱仪、HPLC、FIA等仪器)配套,又可单独使用在需要50～450mA直流恒流电源的各类仪器装置中。文中简单介绍了该恒流电源的电路结构、工作原理、主要技术指标。并对几个有关的问题进行了初步探讨。     

弱激光对神经元瞬时外向钾通道电流特性的影响

应用全细胞膜片钳技术,研究了急性分离的大鼠海马CA3区锥体神经细胞在波长670 nm、功率5 mW的半导体激光器照射时,其瞬时外向钾通道电流特性。实验发现:弱激光对瞬时外向钾电流I_A有抑制作用,5 min激光抑制作用达到稳定,去极化至+50 mV时抑制百分比为(40.13±5.19)%(n=10);弱激光对I_A的抑制作用呈现电压依赖性和可逆性,对照组、照射组和恢复组的最大激活电流密度分别为(398.55±36.49)pA/pF、(238.62±30.78)pA/pF(n=10,P<0.01)和(354.08±35.16)pA/pF(n=10,P>0.05);激光作用可显著地影响瞬时外向钾通道电流的稳态激活和失活过程,对照组和激光照射组通道的半数激活电压分别为(-27.05±4.53) mV和(-2.10±3.14) mV(n=10, P<0.01),斜率因子分别为(-26.71±6.15) mV和(-20.70±4.38) mV(n=10,P<0.05),半数失活电压分别为(-70.49±7.21) mV和(-81.27±6.26) mV(n=10, P<0.01),斜率因子分别为(9.47±3.54) mV和(9.58±3.02) mV(n=10,P>0.05)。结果表明:弱激光作用海马神经元可以改变其瞬时外向钾通道特性,从而影响动作电位的形成和发放,调节神经元的生理功能,有利于受损神经元的恢复和再生。     

The flight test and power simulations of an UAV powered by solar cells,a fuel cell and batteries

The target mid-class UAV system used in this study consists of three types of power sources operating simultaneously. These power sources are designed and constructed to share the same operation voltage range and connect to the power bus without additional converters or controllers. The flight test of the target UAV system was conducted for 22.13 hours after the take-off at 20:53 on June 21, 2012. The power sources successfully supplied the propulsion power required during the test flight. In addition, the power simulation was conducted and validated against the flight test results proving that the dynamic behavior of each power source can be properly predicted.     

Soft X-ray microscopy with a cryo scanning transmission X-ray microscope: I. Instrumentation, imaging and spectroscopy

We have developed a cryo scanning transmission X-ray microscope which uses soft X-rays from the National Synchrotron Light Source. The system is capable of imaging frozen hydrated specimens with a thickness of up to 10 μm at temperatures of around 100 K. We show images and spectra from frozen hydrated eukaryotic cells, and a demonstration that biological specimens do not suffer mass loss or morphological changes at radiation doses up to about 10¹⁰ Gray. This makes possible studies where multiple images of the same specimen area are needed, such as tomography ( Wang et al. (2000 ) Soft X-ray microscopy with a cryo scanning transmission X-ray microscope: II. Tomography. J. Microsc . 197, 80–93) or spectroscopic analysis.