新型半桥逆变电流源控制器设计

在中小功率逆变应用中,半桥电路使用的功率器件少,结构简单,因此得到广泛应用.针对半桥逆变电路建立等效模型,用交流电源等效代替开关器件,根据叠加原理得到电路传递函数,并给出设计PID调节器的方法,通过实验验证其有效性,实现50～750 Hz正弦电流输出.     

A flexible curvilinear electromagnetic filter for direct current cathodic arc source

Widespread applications of direct current (dc) cathodic arc deposition are hampered by macroparticle (MP) contamination, although a cathodic arc offers many unique merits such as high ionization rate, high deposition rate, etc. In this work, a flexible curvilinear electromagnetic filter is described to eliminate MPs from a dc cathodic arc source. The filter which has a relatively large size with a minor radius of about 85 mm is suitable for large cathodes. The filter is open and so the MPs do not rebound inside the filter. The flexible design allows the ions to be transported from the cathode to the sample surface optimally. Our measurements with a saturated ion current probe show that the efficiency of this flexible filter reaches about 2.0% (aluminum cathode) when the filter current is about 250 A. The MP density measured from TiN films deposited using this filter is two to three orders of magnitude less than that from films deposited with a 90 degrees duct magnetic filter and three to four orders of magnitude smaller than those deposited without a filter. Furthermore, our experiments reveal that the potential of the filter coil and the magnetic field on the surface of the cathode are two important factors affecting the efficacy of the filter. Different biasing potentials can enhance the efficiency to up to 12-fold, and a magnetic field at about 4.0 mT can improve it by a factor of 2 compared to 5.4 mT.     

一种可驱动多路发光二级管的精密镜象恒流源

在对普通恒流源加以变形的基础上,设计了一种可以驱动多路发光二级管的镜象电流源。利用D／A转换器和精密运放实现V／I转换及恒流连续可调。采用晶体管扩流,ULN2003进行多路电流切换。测试表明,V／I转换电路的输入电压和镜象输出电流之间具有良好的线性关系,恒流精度达0．05％。     

A source of short electron bunches for injection into accelerators

A pulse electron current source with an oxide-coated cathode is designed and manufactured. When the pulse duration is 0.5 ns, the regulated average current varies from zero to 110 mA. The pulse charge is regulated from zero to 1.5 nC.     

A current source for supporting discharges in pumping lamps of solid-state lasers

A circuit for supporting discharges in pumping lamps of solid-state lasers with the galvanic decoupling is presented. The mathematical model of processes in the circuit is designed. Based on the analysis results of this circuit, the calculation procedure for circuit parameters is given and its volt-ampere characteristic is plotted. The condition for obtaining the maximal switching frequency in the circuit is formulated. The simulation results are experimentally checked.     

A novel method for effective sodium ion implantation into silicon

Although sodium ion implantation is useful to the surface modification of biomaterials and nano-electronic materials, it is a challenging to conduct effective sodium implantation by traditional implantation methods due to its high chemical reactivity. In this paper, we present a novel method by coupling a Na dispenser with plasma immersion ion implantation and radio frequency discharge. X-ray photoelectron spectroscopy (XPS) depth profiling reveals that sodium is effectively implanted into a silicon wafer using this apparatus. The Na 1s XPS spectra disclose Na(2)O-SiO(2) bonds and the implantation effects are confirmed by tapping mode atomic force microscopy. Our setup provides a feasible way to conduct sodium ion implantation effectively.     

A current source with an inductive energy storage for measuring pulse impedances of grounding connections

A pulse generator with an inductive energy storage for measuring pulse impedances of grounding connections is developed. The generator produces current pulses with a rise time of 200–300 ns and an amplitude of up to 8 A. In contrast to the capacitive storage sources, it is fully controllable, allows one to adjust the amplitude, and ensures a constant current-pulse shape regardless of the load parameters. The different operation modes of the source are described. The experimental load-current waveforms are presented.     

高感电磁阀驱动恒流源的设计

电磁阀在核工业中应用广泛,安全稳定地运行是核工业发展的要求,对电磁阀的稳定驱动是电磁阀长期运行的保障.针对供电电压、温度、负载变化等因素造成电磁阀驱动电流稳定度低、可靠性差、功耗大等问题,设计一款基于STM32的可调节DC/DC恒流源驱动.该恒流源主要包括全桥DC/DC变换器电路、串联负反馈式稳流电路和STM32控制系...     

A magnetocumulative energy source for reproduction of lightning current pulses on a branched protective grounding system

An energy source based on two magnetocumulative generators with a transformer energy output for reproducing positive-polarity lightning current pulses with amplitudes of up to 200 kA on the protective grounding is described. Results of a full-scale experiment on reproducing a current pulse with an amplitude of about 190 kA on the protective grounding model with a direct-current ohmic resistance value of 4 Ω are presented.     

A comparison of techniques for identifying the configuration state of statically indeterminate rotor bearing systems

Turbomachinery rotors are frequently supported on several hydrodynamic bearings and so are statically indeterminate. In such cases, the relative locations of the bearing centres (viz. the system configuration state) affect the bearing reaction forces and hence their stiffness and damping properties, thereby significantly influencing the vibration behaviour of the rotor bearing system. Since this configuration state may differ from its value at time of installation, due to thermal effects and/or foundation settlement, it would be useful to identify its value under operating conditions. This paper illustrates how this can be done in principle, regardless of the unbalance, by measuring the locations of the rotor journals relative to their respective bearing housings at any speed at which the system has reached steady state operating conditions, provided one has good models of the rotor and the foundation. Two identification procedures are compared. Both methods rely, to varying degrees, on using the Reynolds equation for hydrodynamic lubrication to obtain the bearing reaction forces. The first procedure uses the Reynolds equation to evaluate both the magnitudes and directions of the forces (the ‘magnitude and direction’ or MAD method), whereas the second procedure uses the Reynolds equation to evaluate only the directions of the forces (the ‘direction only’ or DO method). Numerical experiments on a flexibly supported statically indeterminate four bearing flexible rotor prove that both the MAD and DO identification procedures are sound in principle, being able to identify the locations of the two inboard bearings relative to the two outboard bearings to within 0.1 μm assuming seven-digit accuracy in journal orbit eccentricity measurements. On the other hand, three-digit measurement accuracy, felt to be the best accuracy practically achievable, restricts identification of the bearing locations to within 10 μm, with somewhat better identification being achieved with the MAD procedure. Such identification accuracy presupposes that the Reynolds equation correctly predicts the bearing reaction forces and could be in error owing to the temperature dependence of the bearing clearance, the assumption of a mean lubricant viscosity and the uncertainty of the cavitation boundaries. It is shown that error in lubricant viscosity may introduce significant errors into the identification achievable with the MAD procedure, but has no effect on that achievable with the DO procedure; and error in clearance introduces more error into the identification achievable with the MAD procedure than the DO procedure. Identification errors due to assumed cavitation conditions still need to be addressed.     

A comparison of techniques and images obtained using SEAM and SPAM

Images of a circuit have been obtained with similar techniques. Using two scanning acoustic microscopes—a SEAM (scanning electron acoustic microscope) and a SPAM (scanning photoacoustic microscope)—an examination of the surface and subsurface images has shown varied details while highlighting the differences between the above techniques. This paper presents in the first instance the experimental arrangements with the recorded results, followed by a comparison between them.     

Absorbed current: A source of information about voltage relations on measured specimen

It is shown that a change in the SE current is opposite and equal in magnitude to a change in the absorbed current. Thus using the effect of potential contrast, allows measurement of voltage changes on a specimen by means of changes in the absorbed current. The present method offers a new possibility to complementary information, which can be helpful in various cases.     

Concentrated dyes as a source of two-dimensional fluorescent field for characterization of a confocal microscope

The axial spread function is a useful tool for evaluation of a confocal microscope. It can be obtained experimentally by scanning a uniform fluorescent layer whose thickness is significantly below the resolution limit. Previous researchers have created thin fluorescent films by chemical synthesis. We show here that concentrated fluorescent dyes with a strong absorption at the excitation wavelength can serve as a good approximation of thin fluorescent films. The vertical intensity profiles of such dyes are symmetrical and represent the true axial resolution of a microscope. Solutions of dyes sufficiently opaque to test confocal microscopes with high‐NA objectives can be prepared from sodium fluorescein, acid fuchsin and acid blue 9 for excitation at 488 nm, 543 nm and 633 nm, respectively.     

A comparison of techniques for obtaining convergent beam electron diffraction patterns with a JEOL 200CX

Three different techniques for obtaining convergent beam electron diffraction (CBED) patterns using a JEOL 200CX transmission electron microscope will be described and compared. The first technique, described by Goodman, will be shown to yield clear, undistorted patterns, but only with relatively large camera length, and a limited field of view. A second technique, which is a modification of Goodman's technique, will be shown to yield CBED patterns of both large camera length and small camera length with a much larger angular coverage, but the magnitude of the beam convergence is limited by distortion in the pattern. A third technique will then be presented which permits the formation of small camera length, relatively undistorted CBED patterns with large angular coverage and greatly increased beam convergence; high quality large camera length CBED patterns can also be obtained by simply increasing the strengths of the diffraction lenses.     

Measurement of effective source distribution and its importance for quantitative interpretation of STEM images

We review the manner in which lens aberrations, partial spatial coherence, and partial temporal coherence affect the formation of a sub-Å electron probe in an aberration-corrected transmission electron microscope. Simulations are used to examine the effect of each of these factors on a STEM image. It is found that the effects of partial spatial coherence (resulting from finite effective source size) are dominant, while the effects of residual lens aberrations and partial temporal coherence produce only subtle changes from an ideal image. We also review the way in which partial spatial and temporal coherence effects are manifest in a Ronchigram. Finally, we provide a demonstration of the Ronchigram method for measuring the effective source distribution in a probe aberration-corrected 300 kV field-emission gun transmission electron microscope.     

A comparison of some condition monitoring techniques for the detection of defect in induction motor ball bearings

Rolling element bearings are critical components in induction motors and monitoring their condition is important to avoid failures. Several condition monitoring techniques for the bearings are available. Out of these stator current monitoring is a relatively new technique. Vibration, stator current, acoustic emission and shock pulse methods (SPMs) for the detection of a defect in the outer race of induction motor ball bearing have been compared. The measurements were performed at different loads. The defect in the bearing could be detected by all the methods. Acoustic emission monitoring proved to be the best method followed by SPM when the increase in the levels of the measured parameters were compared with respect to those of healthy bearings.     

A quantitative method of effective soft tissue management for varus knees in total knee replacement surgery using navigational techniques

Total knee replacement (TKR) has become the standard procedure in management of degenerative joint disease with its success depending mainly on two factors: three-dimensional alignment and soft-tissue balancing. The aim of this work was to develop and validate an algorithm to indicate appropriate medial soft tissue release during TKR for varus knees using initial kinematics quantified via navigation techniques. Kinematic data were collected intraoperatively for 46 patients with primary end-stage osteoarthritis undergoing TKR surgery using a computer-tomography-free navigation system. All patients had preoperative varus knees and medial release was made using the surgeon's experience. Based on these data an algorithm was developed. This algorithm was validated on a further set of 35 patients where it was used to define the medial release based on the kinematic data. The post-operative valgus stress angles for the two groups were compared. These results showed that the algorithm was a suitable tool to indicate the type of medial release required in varus knees based on intra-operatively measured pre-implant valgus stress and extension deficit angles. It reduced the percentage of releases made and the results were more appropriate than the decisions made by an experienced surgeon.     

兆瓦级强流离子源地电极的热应力计算与分析

在设计用于高能中性束注入装置的强流离子源时,最关键的环节是对用于产生兆瓦级离子束的引出电极进行热-应力分析。以EAST-NBI强流离子源地电极为模型,考虑受均匀热流载荷作用下电极在主动冷却过程中的耦合传热问题,利用CFD和有限元联合求解的方法进行了热应力分析,得到了固体结构和流场的瞬态温度场、结构应力分布及变形情况。结果表明在热流载荷密度不超过2MW.m-2、冷却水质流速率为(0.125～0.25)kg.s-1时,电极温度场在4s内达到稳态,而且最大Von-Mises等效应力值小于材料屈服强度,不会发生塑性变形。     

A superconducting magnetic-energy storage system as a source of high-power current pulses with constant amplitude

A facility is described that allows generation of long current pulses with a virtually constant amplitude by a superconducting inductive (magnetic) energy storage with a 5-MJ energy content. The design of this facility ensures the possibility of changing the parameters of an output current pulse by varying the inductances of the magnetic-system’s sections and their electromagnet coupling. This approach allows not only the stabilization of the current pulse but also a severalfold increase in the initial current value. The electric insulation of the storage’s coil can withstand a voltage higher than 200 kV, and a special system of multielectrode current leads can transfer a power of up to 250 MW at a 1.3-kA current from the cold zone (4.2 K) into the warm (300 K) zone almost without energy losses. The current can be increased to 10 kA by changing the connection of the facility’s sections. The facility has been tested in six full-scale experiments and is ready for further tests as a component of electrophysical facilities of various purposes.     

VFW图像获取技术在磁光/涡流成像系统中的应用

介绍了一种根据电涡流效应和法拉第磁光效应设计出的磁光／涡流显微成像检测系统，实现了亚表面下细小缺陷的可视化。本系统选用执行效率高的VC作为开发工具来设计图像处理软件，并采用VFW技术实现了对该缺陷图像的实时获取。试验结果进一步验证了系统设计的正确性。