Controlling of crystal size and optical band gap of CdO nanopowder semiconductors by low and high Fe contents

The CdO:Fe nanopowder semiconductors were synthesized by the sol?Cgel calcination for the first time. The structural properties of Fe doped CdO samples were analyzed by AFM and XRD measurements. XRD patterns of the pure and Fe-doped CdO samples reveal that the pure and Fe doped CdO nanopowders are polycrystalline of cubic CdO structure. The crystallite size of undoped and Fe-doped CdO samples is changed unsystematically with a regular increase of Fe content. The optical band gaps of Fe doped CdO samples were determined for the first time by diffused reflectance measurements. The optical band gap of the samples is increased with the increase of Fe dopant inside the host matrix (CdO) up to 15?% followed by a decrease in its value. It is evaluated that Fe doped CdO nanopowder semiconductors can be producted by sol?Cgel calcination for advanced technological applications     

Tribocharging Characteristics of the Mars Dust Simulant (JSC Mars-1)

The determination of triboelectric properties of the Martian dust would be critical for future human and robotic missions to Mars. Several major studies relating to future missions to Mars have highlighted the significance of electrostatic charge accumulation and its impact on various aspects of the mission due to tribocharging of the Mars dust. The tribocharging properties of the Mars dust simulant (JSC Mars-1) against stainless steel and Teflon were characterized. An electronic single particle aerodynamic relaxation time (ESPART) analyzer was used to measure the aerodynamic size and charge distributions of the dust particles. Faraday cup measurements were used for calculating average charge-to-mass ratio. The average charge-to-mass ratio of dust tribocharged against stainless steel (SS) was -1.19 muC/g, whereas it was found to be +1.21 muC/g against Teflon (PTFE). These results indicated that the work function of the JSC Mars-1 lies between that of the SS and Teflon.     

Optical constants of vacuum evaporated SiO film and an application

Silicon monoxide films were deposited on silver films on glass substrates and studied by infrared ellipsometry to determine the optical properties in the infrared wavelength range from 1.3 to 40 micrometers. The thicknesses of silicon monoxide and aluminum films were designed to 1 micrometer and 200 nanometers, respectively. The ellipsometric measurements were carried out by using a spectro-ellipsometer attached with an FT-IR. The imaginary part of the refractive index shows a high absorption region which is centered at 10 micrometers, whereas in other wavelength regions it shows rather low absorption. The resultant optical properties of silicon monoxide film are compared with published data. As an application, the spectral reflectance of spectral selective panel heating surface is calculated.     

Constructions and characteristics of a tiny piezoelectric linear motor using radial mode vibrations

A tiny ultrasonic linear motor with a structure has been developed, and various shaft materials were tested in the motor in order to improve its dynamic properties. We found that the shaft material has direct influence on efficiency, reliability and quality of the motors and their dynamic properties and is crucial to the achievement of high motor performance. The use of shafts of various materials such as stainless steel, stainless steels coated with DLC (Diamond Like Carbon) and PTFE (Teflon), a Pyrex, and a graphite, can make it possible to improve dynamic properties of the motors over a wide range of tribological conditions. In a motor with a stainless steel shaft coated with DLC driven at 44 kHz, its velocity was 4 mm/s with a force of 75 mN. When a motor used the Pyrex shaft was used a force of 110 mN was attained at 51 kHz. Thus the maximum force produced by a motor with a graphite shaft is estimated to be 120 mN with a velocity of 8 mm/s. We found that graphite has the appropriate surface conditions and directional texture to promote the linear motion of the moving element. Finally, the use of a cap resulted in significant improvements in the stability of the motor’s operation. Motor with graphite and Pyrex shafts were found to exhibit very stable operation and improved dynamic characteristics.     

玻璃陶瓷表面浅陷阱分布对其真空沿面闪络特性的影响

长期以来沿面闪络现象一直制约着真空绝缘系统的整体性能,极大地限制了高压电真空设备的发展进程。针对一种具有良好加工性能及表面耐电特性的低熔点可加工微晶玻璃陶瓷引入真空绝缘的背景,研究了不同制备工艺的可加工陶瓷试品在进行表面氢氟酸处理前后其电学特性的变化。利用表面电位衰减法测量了材料表层陷阱分布,分析了表面酸处理对其陷阱分布的影响;采用光电结合的方法,测量了不同表面处理的材料在真空中的表面耐电情况,分析了材料表面陷阱的密度和能级对闪络特性的影响。发现玻璃陶瓷材料表面存在的玻璃相结构是造成存在大量浅陷阱的重要原因,而浅陷阱对沿面闪络特性造成不利影响。得知通过氢氟酸处理可以腐蚀掉材料表面的玻璃相结构,从而降低浅陷阱密度,进而明显提高材料表面闪络的稳定性和降低分散性。     

Security assessment for intentional island operation in modern power system

There has been a high penetration level of Distributed Generations (DGs) in distribution systems in Denmark. Even more DGs are expected to be installed in the coming years. With that, to utilize them in maintaining the security of power supply is of great concern for Danish utilities. During the emergency in the power system, some distribution networks may be intentionally separated from the main grid to avoid complete system collapse. If DGs in those networks could continuously run instead of immediately being shut down, the blackout could be avoided and the reliability of supply could be increased. However, when to island or how to ensure the islanded systems can survive the islanding transition is uncertain. This article proposes an Islanding Security Region (ISR) concept to provide security assessment of island operation. By comparing the system operating state with the ISR, the system operator can clearly know if it is suitable to conduct island operation at one specific moment. Besides, in order to improve the computation efficiency, the Artificial Neural Network (ANN) is applied for fast ISR formation. Thus, online application of ISR based islanding security assessment could be realized.     

Measurements of Reflectance and Thermal Emissivity of a Black Surface Created by Electrostatic Flocking with Carbon-Fiber Piles

A black surface was created using electrostatic flocking with polyacrylonitrile (PAN) carbon flock fibers. Reflectance of diffused reflection for ultraviolet, visible, and near-infrared rays was measured using the created flocked surfaces. The resultant surface exhibits extremely low reflectance values. Furthermore, the authors measured thermal emissivity of carbon-fiber flocked surfaces. A sample used for emissivity measurements was fabricated by pasting two pieces of flocked surface samples together, into which a heater and a thermocouple had been embedded. Using a space chamber of 1,050 mm diameter and 1,206 mm depth, emissivity measurements were carried out using calorimetry. The authors obtained 0.98 as the highest thermal emissivity of the flocked surface, demonstrating that the surface emissivity is almost equivalent to the value of a black body. Results of both measurements were discussed.     

Study of porous dielectrics as electret materials

A special class of nano-porous inorganic dielectrics, the silicon dioxide aerogels, with porosities >70% were prepared using single and two-step sol-gel processing and a supercritical drying method. Samples, pretreated at temperatures ⩽800°C for several hours, and with chemical surface modification by HMDS (hexamethyldisilazane), were subjected to microstructure analysis. Electret properties of these samples, corona charged at temperatures ranging from room temperature to 200°C, were studied. Isothermal surface potential decay and thermally stimulated discharge measurements were made. The relationship between the microstructure of these samples and their electret properties was discussed. The electret properties of one of the most important fluoropolymeric electret materials, porous PTFE (polytetrafluoroethylene), also were studied. Our results show that porous dielectrics can be good electret materials     

Synthesis,and measurement of structural and magnetic properties,of La<Subscript>1−x</Subscript>Cd<Subscript>x</Subscript>CoO<Subscript>3</Subscript> perovskite ceramic oxides

Perovskite-type Cd-doped LaCoO₃ materials were synthesized by a simple solution-based combustion process. The synthesized materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance (DR) in the UV-VIS, and magnetic property measurements. The parent LaCoO₃ compound showed spin-glass transition at low temperatures, and with progressive Cd doping, showed transition to paramagnetic ordering. The changes in magnetic properties of the materials are correlated to the changes in structural features resulting from the Rietveld structural refinement of the materials.     

稀土贮氢合金织构生长特性的研究

用Ｘ射线衍射（ＸＲＤ）分析方法,探讨了ＡＢ５ 型稀土贮氢合金在不同冷却速度下织构生长特性及其对电极性能的影响。研究结果表明：在普通快冷条件下,具有不同成分的贮氢合金锭呈不同的织构生长特性,一般具有（１０１）＋ （００２）晶面择优取向,平行于冷却面也即柱状晶生长方向,并可获得较高的放电容量;在快速凝固下制得的贮氢合金,其表面呈强的（０００２）基极织构也即ｃ轴织构。这与不含Ｍｎ 的稀土贮氢合金即Ｍｍ Ｎｉ３．５Ｃｏ０．７ Ａｌ０．８合金锭的柱状晶结构具有强的ｃ轴织构取向以及定向凝固合金在不同冷却速率下的织构取向相一致     

正序电压电流补偿的方向元件

提出了一种基于正序电压电流补偿的方向元件,可用于高压输电线路纵联方向主保护。给出了补偿阻抗的确定方法,在经过合适的阻抗补偿后,该方向元件能够反应系统全相及非全相状态下各种不对称故障,不受系统振荡的影响,在启动元件启动后整个过程能长期投入运行。对于线路发生三相短路的解决办法是补偿加入电压电流的正序故障分量。用电力系统动态模拟试验的故障录波数据对该方向元件进行验证,结果表明,该方向元件能有效、可靠地判断出故障方向。     

Intraoperative application of optical spectroscopy in the presenceof blood

A simple but effective method of spectral processing was developed to minimize or remove the effects of the presence of superficial blood on tissue optical spectra and, hence, enhance the performance of optical-spectroscopic-based in vivo tissue diagnosis and surgical guidance. This spectral-processing algorithm was developed using the principles of absorption-induced light attenuation wherein the ratio of fluorescence intensity (F) and the hth power of diffuse reflectance intensity (Rd) at a given emission wavelength λ_m is immune to spectral distortions induced by the presence of blood on the tissue surface. Here, the exponent h is determined by the absorption coefficients of whole blood at the excitation and emission wavelengths. The theoretical basis of this spectral processing was verified using simulations and was experimentally validated. Furthermore, the optical spectra of brain tissues collected in vivo was processed using this algorithm to evaluate its impact on brain tissue differentiation using combined fluorescence and diffuse reflectance spectroscopy. Based on the simulation, as well as experimental results, it was observed that using F/Rd^h h can effectively reduce or remove spectral distortions induced by superficial blood contamination on tissue optical spectra. Thus, optical spectroscopy can also be used intraoperatively for applications such as surgical guidance of tumor resection     

微机型发电机变压器保护投运试验及检查

发电机组在投运前及投运试验过程中,有必要对其继电保护装置及二次回路进行试验和检查。机组启动前应进行远方通流试验、远方加压试验及操作试验;机组启动过程中应进行机组短路试验时各种测量以及发电机空载升压过程中的测量和检查;在负荷工况下应进行发电机定子匝间保护负序功率方向元件正确性检查、机端及中性点三次谐波电压的测量、各差动保护差流的测量;另外还需要进行变压器零序方向过电流保护动作方向正确性的检查。给出了各种检查中的情况分析．提高了继电保护动作可靠性。     

利用TracePro模拟分析导光管的传输效率

基于光线追踪法,利用光学模拟软件TracePro,可模拟各种导光管采光系统的采光性能。通过模拟多种不同类型导光管的传输效率,分析其变化规律,并与相关规程的实验参考值比较,研究发现:内壁光反射比越高、有效长度越小时,直管的传输效率就越高,模拟值也越接近规程中实验参考值;弯头的传输效率仅与弯曲角度和内壁光反射比有关,与管径无关,这与规程的实验结果相悖。     

Directional relays without voltage sensors for distribution networks with distributed generation: Use of symmetrical components

This paper presents two local algorithms using only currents measurements that could be used as a back-up protection (after the loss of the voltage sensors) in directional relays for distribution networks with distributed generation (DG), or as additional directional relay dispatched along the feeders. These algorithms are based on the symmetrical components (0-zero, 1-positive and 2-negative sequences) of the 3-phases currents. Due to the power flows generated by the DG the positive sequence current argument is unforeseeable, thus it is not possible to use only the positive sequence. Then, we first propose in this paper an algorithm using the I₂/I₀ ratio to locate a phase-to-ground fault upstream or downstream the detector. The second algorithm measures the zero and positive sequence components of the fifth harmonic of the current and calculates the I_{0_5}/I_{1_5} ratio. The performances of these algorithms are analysed for several DG power, fault resistance, capacitive current and neutral grounding (resistive and compensative grounding). The fluctuations of the phasors measurements is also taken into account in the range ±5% for the modulus and ±5° for the argument. The present paper shows that these algorithms can be reliable in the major part of the studied cases.     

Understanding surface partial discharges in HV coils and the role of semi-conductive protection

An electrical insulating system in high voltage rotating machines is subjected to several stresses that cause changes of material properties during its lifetime. This phenomenon reduces progressively ability of the insulation to withstand the service stresses. Internal partial discharges can be located inside the high voltage insulation and usually they are dangerous for life-cycle duration. Surface discharges are generated at the solid/air interface in the gaps of machine stator slots or at the slot exits. Surface discharges can cause more intensive deterioration of the insulation, accelerate aging processes and definitively take aim toward premature failure of the machine. The application of conductive or semi-conductive protection layer provides certain protection for solid insulation from these discharges. Semi-conductive corona protection tapes are used on the coils at the slot exit region to electrical field control and prevent surface discharges. Laboratory measurements of the surface partial discharge quantities in specimens of high voltage coils with mica insulation were performed. The aim of the paper is to describe theoretically the development of surface discharges in rotating machines and to present surface partial discharge development in HV motors when semi-conductive layer protection is missing. The results can be found useful to understand better the surface discharge development and importance of high-quality semi-conductive protection technology.     

TCSC对平行双回线上方向继电器的影响

分析了TCSC（晶闸管控制串联补偿装置）对平行双回线上的方向继电器的影响。文中指出：由于TCSC与固定串补不同，健全回线上的TCSC的运行方式对故障回线上的方向继电器有很大影响；而当健全回线上的TCSC被可靠旁路后，平行双回线中的方向高频保护装置均能正确动作。与固定串补相比，TCSC具有一定的优势，只要健全回线上的TCSC被可靠旁路，双回线上的方向高频保护装置均能正确动作。     

In situ monitoring and control for MBE growth of optoelectronicdevices

Improved control over layer thickness has been realized using optical interference techniques such as reflectance spectroscopy. It is now common to observe spectra of distributed-Bragg-reflector (DBR) mirrors during growth to make corrections for growth rate drifts. Real-time optical flux monitoring (OFM) by atomic absorption allows precise layer control by measuring group III fluxes continuously during growth. The flux information can be used to operate growth shutters and to control effusion cell heaters in a feedback loop. Improved substrate temperature measurement by diffuse reflectance spectroscopy (DRS) allows precise measurement of substrate temperature. DRS is not subject to the same errors encountered in pyrometer or thermocouple measurements of substrate temperature     

Inverse method 3-D reconstruction of localized in vivofluorescence-application to Sjogren syndrome

The development of specific fluorescently labeled cell surface markers have opened the possibility of specific and quantitative noninvasive diagnosis of tissue changes. We are developing a fluorescence scanning imaging system that can perform a “noninvasive optical biopsy” of the Sjogren syndrome (SS) which may replace the currently used histological biopsy. The diagnosis of SS is based on the quantification of the number of topical preadministered fluorescent antibodies which specifically bind to the lymphocytes infiltrating the minor salivary glands. We intend to scan the lower lip, and for each position of the scan, generate a two-dimensional (2-D) image of fluorescence using a charge-coupled device (CCD) camera. We have shown previously that our diffuse fluorescent photon migration theory predicts adequately the positions and strengths of one and two fluorescent targets embedded at different depths in tissue-like phantoms. An inverse reconstruction algorithm based on our theoretical findings has been written in C⁺⁺ and uses 2-D images to predict the strength and location of embedded fluorophores. However, due to large numbers of variables, which include the optical properties of the tissue at the excitation and emission wavelengths, and the positions and strengths of an unknown number of fluorophore targets, the validity of the final result depends on assumptions (such as the number of targets) and the input values for the optical parameters. Our results show that the number of fluorophore targets reconstructed for each scan is limited to two, and at least the scattering coefficient at the excitation wavelength is needed a priori to obtain good results. The latter can be obtained by measurements of spatially resolved diffuse reflectance at the excitation wavelength that provides the product of the absorption and scattering coefficients     

Fluorescence Anisotropy of Cellular NADH as a Tool to Study Different Metabolic Properties of Human Melanocytes and Melanoma Cells

In this study, we wanted to see if fluorescence anisotropy could be used to detect changes in metabolism in cells with significant light scattering and absorption properties. Fluorescence anisotropy measurements of nicotinamide adenine dinucleotide (NADH) were performed with human melanocytes and melanoma cell lines. To demonstrate the feasibility of using fluorescence anisotropy for detecting metabolic changes, the electron transport chain was blocked using rotenone, inducing an accumulation of intracellular NADH. Total fluorescence increased in all cells as a result of rotenone treatment. Fluorescence anisotropy decreased in the rotenone-treated cells relative to the controls, suggesting an increased ratio of free to protein-bound NADH in the treated cells. In general, the fluorescence anisotropy of the melanocytes was significantly higher than that of the melanoma cell lines. Reflectance spectroscopy showed that the differences in fluorescence anisotropy between the cell types were not due to differences in scattering and absorption properties. Intrinsic cellular NADH fluorescence was experimentally extracted by ratioing polarized fluorescence to polarized reflectance. NADH binding, measured as the ratio of fluorescence intensity at 430 and 465 nm, showed more protein-bound NADH in the melanocytes than in the melanoma cells, consistent with the fluorescence anisotropy measurements.