Tunable supercurrent through semiconductor nanowires

Nanoscale superconductor/semiconductor hybrid devices are assembled from indium arsenide semiconductor nanowires individually contacted by aluminum-based superconductor electrodes. Below 1 kelvin, the high transparency of the contacts gives rise to proximity-induced superconductivity. The nanowires form superconducting weak links operating as mesoscopic Josephson junctions with electrically tunable coupling. The supercurrent can be switched on/off by a gate voltage acting on the electron density in the nanowire. A variation in gate voltage induces universal fluctuations in the normal-state conductance, which are clearly correlated to critical current fluctuations. The alternating-current Josephson effect gives rise to Shapiro steps in the voltage-current characteristic under microwave irradiation.     

Spin Hall effect transistor

The field of semiconductor spintronics explores spin-related quantum relativistic phenomena in solid-state systems. Spin transistors and spin Hall effects have been two separate leading directions of research in this field. We have combined the two directions by realizing an all-semiconductor spin Hall effect transistor. The device uses diffusive transport and operates without electrical current in the active part of the transistor. We demonstrate a spin AND logic function in a semiconductor channel with two gates. Our study shows the utility of the spin Hall effect in a microelectronic device geometry, realizes the spin transistor with electrical detection directly along the gated semiconductor channel, and provides an experimental tool for exploring spin Hall and spin precession phenomena in an electrically tunable semiconductor layer.     

基于GIS的农村配电网用电管理系统的设计与实现

本文阐述一种基于GIS的农村配电网用电管理系统的设计方法。该系统将GIS与配电网用电管理相结合，用于管理与其地理位置相关的农村配电网设备信息和供电用户信息。系统以SuperMap、VB和SQL Server为软件开发工具，所开发的应用管理信息系统含有农村配电网中的各种运行数据的浏览、查询、分析、统计、汇总及综合报表等功能。     

强渗水大型河流管道开挖穿越降水系统的构建

在强渗水大型河流管道大开挖穿越施工中,降水控水是确保安全顺利施工的关键。以水源地沙河大开挖穿越工程为例,科学、合理地构建了一种改进的降水系统,其主要由发电系统、电气控制系统、水泵组系统及附件系统组成。发电系统采用冗余硬件配置,利用N模冗余系统模型构建,提高了降水系统的可靠度;电气控制系统中的自耦降压启动方式,可以通过分阶段启动降低电机的启动电压,进而减小启动电流;水泵组系统及附件系统可以有效辅助大型深水位的降水。该降水系统应用于西气东输二线水源地沙河大开挖穿越工程,取得了良好的降水效果,可为其他大型类似工程降水系统的构建提供参考。     

Electrical manipulation of magnetization reversal in a ferromagnetic semiconductor

We report electrical manipulation of magnetization processes in a ferromagnetic semiconductor, in which low-density carriers are responsible for the ferromagnetic interaction. The coercive force HC at which magnetization reversal occurs can be manipulated by modifying the carrier density through application of electric fields in a gated structure. Electrically assisted magnetization reversal, as well as electrical demagnetization, has been demonstrated through the effect. This electrical manipulation offers a functionality not previously accessible in magnetic materials and may become useful for reversing magnetization of nanoscale bits for ultrahigh-density information storage.     

Cooling, heating, generating power, and recovering waste heat with thermoelectric systems

Thermoelectric materials are solid-state energy converters whose combination of thermal, electrical, and semiconducting properties allows them to be used to convert waste heat into electricity or electrical power directly into cooling and heating. These materials can be competitive with fluid-based systems, such as two-phase air-conditioning compressors or heat pumps, or used in smaller-scale applications such as in automobile seats, night-vision systems, and electrical-enclosure cooling. More widespread use of thermoelectrics requires not only improving the intrinsic energy-conversion efficiency of the materials but also implementing recent advancements in system architecture. These principles are illustrated with several proven and potential applications of thermoelectrics.     

变频技术在长输管道输油泵机组上的应用

传统工频定速电机在管道输量较低时,既浪费电能,又缩短了输油泵机组的维护周期和使用寿命。针对该问题,提出了对泵机组采用变频调速改造的方法进行节能控制。输油泵节能原理：保持离心泵输送流量不变,减小离心泵扬程。以某实际运行长输管道为例,详细介绍了高压变频改造项目在长输管道输油泵机组上的节能测试过程,对比分析了输油泵机组加装变频装置前后的节能效果。结果表明：加装变频装置后,节流率、功率因数和机组效率均满足评价标准SY/T 6275-2007限定值和节能评价值的要求,管道2008-2009年度节省电费304.5×104元。     

Electrical System for Home Conversion and Storage of Solar Energy

Energy storage has long been a problem in connection with home utilization of solar energy. A solution which utilizes solar semiconductor cells for conversion to d-c power is proposed. The d-c power is used to drive an alternator which is connected directly across the residential power lines. Thus a-c power is delivered to the power lines when a surplus of power is available in the home and is used in other parts of the power distribution system. At latitude 42 degrees N there is 3 times more yearly energy recoverable than is used by an average residence on the basis of a 10-by-10-m collection area. At the present state of technical development the cost of such a large-area semiconductor solar cell would be prohibitive.     

Selective growth of metal tips onto semiconductor quantum rods and tetrapods

We show the anisotropic selective growth of gold tips onto semiconductor (cadmium selenide) nanorods and tetrapods by a simple reaction. The size of the gold tips can be controlled by the concentration of the starting materials. The new nanostructures display modified optical properties caused by the strong coupling between the gold and semiconductor parts. The gold tips show increased conductivity as well as selective chemical affinity for forming self-assembled chains of rods. Such gold-tipped nanostructures provide natural contact points for self-assembly and for electrical devices and can solve the difficult problem of contacting colloidal nanorods and tetrapods to the external world.     

Profiling the thermoelectric power of semiconductor junctions with nanometer resolution

We have probed the local thermoelectric power of semiconductor nanostructures with the use of ultrahigh-vacuum scanning thermoelectric microscopy. When applied to a p-n junction, this method reveals that the thermoelectric power changes its sign abruptly within 2 nanometers across the junction. Because thermoelectric power correlates with electronic structure, we can profile with nanometer spatial resolution the thermoelectric power, band structures, and carrier concentrations of semiconductor junctions that constitute the building blocks of thermoelectric, electronic, and optoelectronic devices.     

Quantum cascade surface-emitting photonic crystal laser

We combine photonic and electronic band structure engineering to create a surface-emitting quantum cascade microcavity laser. A high-index contrast two-dimensional photonic crystal is used to form a micro-resonator that simultaneously provides feedback for laser action and diffracts light vertically from the surface of the semiconductor surface. A top metallic contact allows electrical current injection and provides vertical optical confinement through a bound surface plasmon wave. The miniaturization and tailorable emission properties of this design are potentially important for sensing applications, while electrical pumping can allow new studies of photonic crystal and surface plasmon structures in nonlinear and near-field optics.     

Hydrogen-evolving solar cells

Sunlight is directly converted to chemical energy in hydrogen-evolving photoelectrochemical cells with semiconductor electrodes. Their Gibbs free energy efficiency of solar-to-hydrogen conversion, 13.3 percent, exceeds the solar-to-fuel conversion efficiency of green plants and approaches the solar-to-electrical conversion efficiency of the best p-n junction cells. In hydrogen-evolving photoelectrodes, electron-hole pairs photogenerated in the semiconductor are separated at electrical microcontacts between the semiconductor and group VIII metal catalyst islands. Conversion is efficient when the island diameters are small relative to the wave-lengths of sunlight exciting the semiconductor; when the island spacings are smaller than the diffusion length of electrons at the semiconductor surface; when the height of the potential energy barriers that separate the photogenerated electrons from holes at the semiconductor surface is raised by hydrogen alloying of the islands; when radiationless recombination of electron-hole pairs at the semiconductor-solution interface between the islands is suppressed by controlling the semiconductor surface chemistry; and when the semiconductor has an appropriate band gap (1.0 to 1.8 electron volts) for efficient solar conversion.     

农业网格建设势在必行

网格是因特网的发展和升级,其实质就是实现真正的资源共享。网格将把人类带入理想的“三元世界”,就像拿起电话能通话、插上电源能用电一样,用户一旦接入网格就能根据需要取用各种IT资源。本文介绍网格的特性、国内外应用状况、农业上的应用及可能的应用,指出建设农业网格的迫切性,并提出以农业数据网格建设为突破点等几点建议。     

一种柔性集鱼灯的探讨

将具有节能环保、响应速度快等优点的半导体照明技术作为集鱼灯的光源,可达到节能减排、安全环保、科学捕捞的目的。基于OLED是面发光、柔性半导体光源,设计了一款OLED柔性集鱼灯。该集鱼灯采用彩色OLED模块作为光源、用单片机与数字电路控制、用集成电路驱动、用非接触供电系统对锂电池充电来提供电能,能制成条形、带形、网形、圆形、甚至鱼的形状,安装于船上、船底、渔网上、钢缆上等,能根据诱集目标鱼类的视觉特性调节出彩色的图像来诱集、驱集鱼群进行捕捞。     

电力载波在电器设备监控中的应用

以低压电力线作为传输媒质,以电力载波技术为基础,通过电力载波信号来监控电器设备的运行状态,达到维护电器设备的目的。基于电力载波技术的智能管理系统可以很好地维护管理大型医疗设备,从而节约财力物力、提高经济效益。     

双电机同轴驱动系统功率追踪算法研究

测算股权制衡度时不考虑股东间的关联关系可能引致偏差。鉴此,重新测算了股权制衡度,以2003~2013年927家A股主板上市公司为样本研究其与公司绩效的关系。结果表明：“新股权制衡度”与公司绩效为非线性的U型关系,而“旧股权制衡度”与公司绩效为线性关系;［1,2］为股权制衡度对公司绩效影响的灰色区间;股权制衡度与公司绩效的关系受股东持股模式和外部环境影响。研究结果支持条件有效论,适度的股权制衡才能发挥积极作用。     

The principle and Application of the Multiple and Partial Coherence Analysis

The basic principles of the partial and multiple coherence ananlysis and their utilization on vibration source idenfification are discussed in detail in this paper,The partial coherence analysis is the effective method of vibration source identification in multiple input-single output systems.Formerly,there was not any this kind of unction in the signal processor,and there was not and special software too.The software which we developed and used in the 7T 17S signal processor has this function.This software can be used not only for the parial and multiple coherence analysis of signal,but also for the correlation analysis,power spectrum analysis,transfer function analysis et al.We used this software to make the identifcation of the vibration source of the car floor board of electrical measuring vehicle,and to find the main factors which effect the vibration of the ear board.The excellent result was obtained.This method can also be used for making the identifications of noise source and other sources.     

Photon number squeezed States in semiconductor lasers

Electromagnetic fields, with the noise on one quadrature component reduced to below the quantum mechanical zero-point fluctuation level and the noise on the other quadrature component enhanced to above it, are currently of great interest in quantum optics because of their potential applications to various precision measurements. Such squeezed states of light are usually produced by imposing nonlinear unitary evolution on coherent (or vacuum) states. On the other hand, squeezed states with reduced photon number noise and enhanced phase noise are generated directly by a constant current-driven semiconductor laser. This is the simplest scheme for the generation of nonclassical light, and so far it has yielded the largest quantum noise reduction. The mutual coupling between a lasing junction and an external electrical circuit provides opportunities for exploring the macroscopic and microscopic quantum effects in open systems.     

马铃薯播种器自动补偿系统的设计

为减少马铃薯播种机在播种过程中出现的漏播现象,设计了马铃薯播种器自动补偿系统,该系统由红外光电传感器、单片机、步进电机3个部分组成.工作时由红外光电传感器对取种勺上有无薯块的情况进行监测,当监测到取种勺上无薯块时,传感器将监测到的信号输送给单片机,然后单片机系统对步进电机的转动方向和转角的大小进行控制,驱动步进电机带动补偿排种器进行转动,实现补种.结果表明:该系统能最大限度地降低漏播率,进而提高播种质量.     

Computational neuroscience

The ultimate aim of computational neuroscience is to explain how electrical and chemical signals are used in the brain to represent and process information. This goal is not new, but much has changed in the last decade. More is known now about the brain because of advances in neuroscience, more computing power is available for performing realistic simulations of neural systems, and new insights are available from the study of simplifying models of large networks of neurons. Brain models are being used to connect the microscopic level accessible by molecular and cellular techniques with the systems level accessible by the study of behavior.