A circuit scheme to control current surge for RFID-NVM pumps

This paper presents a new circuit scheme to control the current surge in the boosting phase of an radio frequency identification-nonvolative memory pump. By introducing a circuit block consisting of a current reference and a current mirror, the new circuit scheme can keep the period-average current of the pump constantly below the desired level, for example, 2.5μA. Therefore, it can prevent the rectified supply of the RFID tag IC from collapsing in the boosting phase of the pump. The presented scheme could effectively reduce the voltage drop on the rectified supply from more than 50% to even zero, but could cost less area. Moreover, an analytical expression to calculate the boosting time of a pump in the new scheme is developed.     

用于控制RFID－NVM中电荷泵电流冲击的电路结构

本文提出了一种新的电路结构用于控制RFID非挥发存储器中电荷泵启动阶段的电流冲击。通过引入一个由参考电流源和电流镜组成的电路模块,此结构可以把电荷泵的周期平均电流恒定控制在任何想要的值之下,例如2.5微安。因此它可以防止RFID标签芯片的整流输出电压在电荷泵的启动阶段不被破坏。此结构可以有效地把整流输出上多于50％的压降减小到几乎为0,然而却占用更少的芯片面积。另外,用于计算此结构中电荷泵启动时间的理论公式也一并被提出。     

On the detection of load active currents for active filter control

The control of current source converters used as active filters can be based on either the current active components detection or the instantaneous imaginary power detection from which all or only a part can be used. The authors study the conditions in which this second method is equivalent to the first one and propose an improvement for the cases when it is not so     

simultaneous feedback control of bias and modulation currents for injection lasers

A feedback circuit is described which regulates the light output from an injection laser through simultaneous independent control of bias current and modulation current. The circuit is capable of preserving a large extinction ratio and it is independent of the duty cycle of the modulating signal. Experiments were performed on simulated `lasers? and the results are discussed.     

Nanodroplets for Stretchable Superconducting Circuits

The prospective utilization of nanoscale superconductors as micro/nanocoils or circuits with superior current density and no electrical resistance loss in next‐generation electronics or electromagnetic equipment represents a fascinating opportunity for new microsystem technologies. Here, a family of superconducting liquid metals (Ga–In–Sn alloys) and their nanodroplets toward printable and stretchable superconducting micro/nanoelectronics is developed. By tuning the composition of liquid metals the highest superconducting critical temperature (T_c) in this family can be modulated and achieved as high as 6.6 K. The liquid metal nanodroplets retain their bulk superconducting properties and can be easily dispersed in different solvents as inks. The printable and stretchable superconducting micro/nano coils, circuits and electrodes have been fabricated by inkjet printer or laser etching by using superconducting nanodroplets inks. This novel superconducting system greatly promotes the commercial utilization of superconductors into advanced flexible micro/nanoelectronic devices and offers a new platform for developing more application with superconductors.     

Superconducting magnets for LHC insertions

The LHC comprises eight insertions, four of which are dedicated to the experiments while the others are used for major collider systems. The various functions of the insertions are fulfilled by a variety of magnet systems, most of them based on the technology of NbTi superconductors cooled by superfluid helium at 1.9 K. In this paper, we review the concepts underlying the design of the LHC insertions, and describe the corresponding design of the various specialized magnet systems. A status of the procurement of the magnets is given, and plans for their installation and commissioning reviewed.     

Quantum interference control of electrical currents in GaAs

In an earlier publication, preliminary observations of the generation of electrical currents were reported in GaAs and low-temperature-grown GaAs (LT-GaAs) at 295 K using quantum interference control of single- and two-photon band-band absorption of 1.55- and 0.775-μm ultrashort optical pulses. Time-integrated currents were measured via charge collection in a metal-semiconductor-metal (MSM) electrode structure. Here we present detailed characteristics of this novel effect in terms of a simple circuit model for the MSM device and show how the injected current depends on MSM parameters as well as optical coherence, power, and polarization. For picosecond pulse excitation with peak irradiance of only 30 MW/cm^-2 (1.55 μm) and 9 kW/cm^-2 (0.775 μm), peak current densities of ~10 A/cm^-2 at peak carrier densities of 10¹⁵ cm ^-3 are inferred from the steady-state signals. This compares with 50 A/cm^-2 predicted theoretically; the discrepancy mainly reflects inefficient charge collection at the MSM electrodes     

超导计算机及超导武器装备

超导技术的发展前景广阔,在国外军事领域受到极大重视。超导计算机具有很高的运算速度和巨大的运算能力,是21世纪超级计算机的发展方向。超导技术将使武器装备发生重大变革。军事C3I系统由于有了超导计算机,能快速、有效地把各种武器系统、各军兵种和各战场连结成一个有机整体。概略介绍超导磁性水雷、超导发动机和超导飞机、超导装甲车和超导导弹、超导电磁推进系统和超导舰艇、超导太空发射器等武器装备的发展前景。     

Superconducting joints for silver-clad BSCCO tapes

The advent of high-T_c superconducting tapes for a variety of applications has resulted in the need for superconducting joints. Although long-length tapes can be custom-made for some applications, interconnections between subcoils of a magnet or shorter-length conductors for coil winding and current leads, make the development of such joints imperative. Additionally, high-quality short-or medium-length conductors, which are easier to make, can be joined for improved performance. Employing a novel chemical etching technique, we have fabricated lap joints between short lengths of silver-clad BSCCO tapes. Each joint was formed by etching the silver away and bringing together the exposed superconductor cores of two tapes together. The joined tapes were then subjected to a series of thermomechanical treatments. Detailed microstructural and electrical characterization within and across the joint was performed. Critical currents of up to 37 A within the joint region and 10 A through the joint region(at 77K) have been achieved.     

Superconducting materials for large scale applications

Since the 1960s, Nb-Ti (superconducting transition temperature T/sub c/=9 K) and Nb/sub 3/Sn (T/sub c/=18 K) have been the materials of choice for virtually all superconducting magnets. However, the prospects for the future changed dramatically in 1987 with the discovery of layered cuprate superconductors with T/sub c/ values that now extend up to about 135 K. Fabrication of useful conductors out of the cuprates has been difficult, but a first generation of silver-sheathed composite conductors based on (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ (T/sub c//spl sim/110 K) has already been commercialized. Recent progress on a second generation of biaxially aligned coated conductors using the less anisotropic YBa/sub 2/Cu/sub 3/O/sub 7/ structure has been rapid, suggesting that it too might enter service in the near future. The discovery of superconductivity in MgB/sub 2/ below 39 K in 2001 has brought yet another candidate material to the large-scale applications mix. Two distinct markets for superconductor wires exist-the more classical low-temperature magnet applications such as particle accelerators, nuclear magnetic resonance and magnetic resonance imaging magnets, and plasma-containment magnets for fusion power, and the newer and potentially much larger market for electric power equipment, such as motors, generators, synchronous condensers, power transmission cables, transformers, and fault-current limiters for the electric utility grid. We review key properties and recent progress in these materials and assess their prospects for further development and application.     

复杂涌流下水下自主航行器横滚抑制控制仿真

在复杂的海洋涌流背景下,水下自主推进航行器受到扰动较大,出现横滚导致控制稳定性下降,提出一种基于模糊PID扰动抑制的复杂涌流下水下自主航行器横滚抑制算法.构建在复杂涌流下的水下自主航行器运动状态模型,在航行器的纵向运动全包线内对横舵角、横滚角、回旋角等运动约束参量进行定常运动分析,采用模糊PID神经网络控制模型进行控制律的改进设计,结合Lyapunov稳定性原理进行横滚抑制和误差修正,实现控制算法改进.仿真结果表明,采用该控制算法进行复杂涌流下水下自主航行器横滚抑制控制,具有较好的输出响应跟踪性能,有效抑制横滚,提高了水下自主航行器的稳定控制能力,鲁棒性较好.     

Fast extraction of positive-sequence current from harmonicallycorrupted three-phase currents for TCR compensator control systems

The authors discuss a practical scheme for extracting the magnitude of the positive-sequence component from harmonically corrupted three-phase currents found in modern energy systems. The scheme is cost-effective, fast, and simple in design, with the novel combination of software processing and digital and analog circuits. The scheme has been successfully applied to a microprocessor-based thyristor-controlled reactor (TCR) control system and is suitable for similar real-time applications that already include one or more processing units. It is demonstrated that the scheme is adequately fast for the TCR control system because the extraction delay is typically less than half a cycle. The scheme is especially suitable for microprocessor-based control systems because the averaging function can be advantageously performed by software     

Superconducting contacts

The microscopic size of the contact between two crossed superconducting wires offers a practical way to make a class of superconducting devices which are operated at high speed by very small currents. The critical current through the contact can be modulated by a current flowing along one or both of the crossed superconductors. Several device possibilities are presented.     

超导亚毫米波阵列振荡器的扰动模拟

本文系统地研究了超导亚毫米波阵列振荡器。首先介绍了约瑟夫森结阵列振荡器的基本原理 ,然后根据原理引出超导亚毫米波阵列振荡器的模型 ,最后 ,根据约瑟夫森原理 ,对超导亚毫米波阵列振荡器的模型进行了模拟和分析 ,仿真得出了振荡器各项参数值 ,并给出了相位锁定的条件     

Superconducting magnets for the LHC main lattice

The main lattice of the Large Hadron Collider (LHC) employs about 1600 main magnets and more than 4000 corrector magnets. All superconducting and working in pressurized superfluid helium bath, these impressive line of magnets fills more than 20 km of the underground tunnel. With almost 70 main dipoles already delivered and 10 main quadrupoles almost completed, we passed the 5% of the production and now all manufacturers have fully entered into series production. In this paper the most critical issues encountered in the ramping up in such a real large scale fabrication is addressed; uniformity of the coil size and of prestress, special welding technique, tolerances on curvature (dipoles) or straightness (quadrupoles) and of the cold mass extremities, harmonic content and, most important, the integrated field uniformity among magnets. The actual limits and the solution for improvements are discussed. Finally a realistic schedule based on actual achievements is presented.     

Superconducting receiver coils for sodium magnetic resonanceimaging

Presents the results from sodium magnetic resonance imaging (MRI) experiments using high-temperature superconducting (HTS) receiver coils. Sodium imaging has been shown to have great potential for the assessment of cell integrity but suffers from substantially lower signal-to-noise ratio (SNR) than that of hydrogen imaging. The use of an HTS receiver coil was found to significantly increase the SNR relative to an equivalent copper receiver coil at room temperature. The SNR gains afforded by HTS coils can also be used to decrease the imaging time     

Superconducting instrument systems

Some recently developed superconducting instrument systems which are based upon the use of a highly reliable thin-film superconducting quantum interference device (SQUID) are discussed in detail. These SQUID's, which are shown to have a noise temperature of less than 2 × 10^-4K, are capable of measuring: 1) magnetic flux with a sensitivity of 10^-11Gċcm²rms/√Hz; 2) magnetic field with a sensitivity of 10^-11G rms/√Hz; 3) magnetic field gradient with a sensitivity of 10^-11(G/cm) rms/√Hz. We present construction details and performance data on systems capable of making the above measurements.     

Superconducting electrical machinery

Recent developments in superconductors have made possible the application of superconductivity in the windings of electric machinery. Extensive studies have been made, and several experimental superconducting machines have been built and tested. In synchronous machines, the higher currents and flux densities in a superconducting field winding offer savings in size, weight, and cost. In homopolar machines, the greater flux densities make possible higher terminal voltages. This, with the development of liquid-metal current collection, makes homopolar machines a feasible alternative to conventional dc machines for high-power applications.     

Superconducting quantum electronics

The quantum electronic properties of superconductors have been vividly demonstrated by means of experiments on Josephson tunneling junctions and small area superconducting contacts. Emphasis is placed on ring configurations where quantum state transitions corresponding to changes of magnetic flux of2.07 times 10^{15}webers are directly observed. Such systems can be used to make ultrasensitive measurements of magnetic fields, electric currents and voltages, cryogenic temperatures, and electro-magnetic radiation.