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1.
We present a simple analytical nonlinear theory for quantum diodes in a dense Fermi magnetoplasma. By using the steady-state quantum hydrodynamical equations for a dense Fermi magnetoplasma, we derive coupled nonlinear Schr?dinger and Poisson equations. The latter are numerically solved to show the effects of the quantum statistical pressure, the quantum tunneling (or the quantum diffraction), and the external magnetic field strength on the potential and electron density profiles in a quantum diode at nanometer scales. It is found that the quantum statistical pressure introduces a lower bound on the steady electron flow in the quantum diode, while the quantum diffraction effect allows the electron tunneling at low flow speeds. The magnetic field acts as a barrier, and larger potentials are needed to drive currents through the quantum diode. 相似文献
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文中介绍了制冷机驱动控制器中,基于dsPIC6015实现的SPWM数字化逆变控制信号的高效生成方法。阐述了SPWM逆变的基本概念和原理,及基于dsPIC实现下的发生方法和硬件原理、配置方法,以及软件的编写。利用近似值查表法和C语言与汇编混编的方式,对程序进行了优化设计,大大减少了PWM的实时计算量,极大的提高了程序运行速度。采用此种方法设计的程序拥有极高的运行效率和极低的CPU占用率。采用DSP芯片数字化生成SPWM驱动信号,以代替模拟器件的方法具有空间紧凑、可靠性高、波形精度高、编程调整易等特点,对实现红外、超导制冷应用中高温控精度要求和小型化具有较好的工程实用价值。 相似文献
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A mathematical model for the spectra of monocolor light-emitting diodes (LEDs) and phosphor-coated white LEDs at different drive currents is established.The simulation program of the color rendering of a white light LED cluster is developed based on this model.The program can predict not only the spectral power distribution and color rendering index (CRI),but also the number of LEDs,drive currents,input power,and luminous efficacy of a white light LED cluster at a given color temperature according to the requirement of the luminous flux.The experimental results show that the relative spectral power distributions (SPDs) and chromaticity coordinates of the model LED are very close to that of the real LED at different drive currents.Moreover,the correlated color temperature (CCT),CRI,special color rendering index (R9) luminous flux,input power,and luminous efficacy of the white light LED cluster predicted by simulation are also very close to the measured values.Furthermore,a white/red cluster with high rendering (CCT=2903 K,CRI=91.3,R9=85) and a color temperature tunable warm-white/red/green/blule LED cluster with high rendering (CCT=2700 6500 K,CRI 〉 90,R9 〉 96) are created. 相似文献
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Effect of interface roughness on the carrier transport in germanium MOSFETs investigated by Monte Carlo method
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Interface roughness strongly influences the performance
of germanium metal--organic--semiconductor field effect transistors
(MOSFETs). In this paper, a 2D full-band Monte Carlo simulator is
used to study the impact of interface roughness scattering on
electron and hole transport properties in long- and short- channel
Ge MOSFETs inversion layers. The carrier effective mobility in the
channel of Ge MOSFETs and the in non-equilibrium transport
properties are investigated. Results show that both electron and
hole mobility are strongly influenced by interface roughness
scattering. The output curves for 50~nm channel-length double gate n
and p Ge MOSFET show that the drive currents of n- and p-Ge MOSFETs
have significant improvement compared with that of Si n- and
p-MOSFETs with smooth interface between channel and gate dielectric.
The $82\%$ and $96\%$ drive current enhancement are obtained for the
n- and p-MOSFETs with the completely smooth interface. However, the
enhancement decreases sharply with the increase of interface
roughness. With the very rough interface, the drive currents of Ge
MOSFETs are even less than that of Si MOSFETs. Moreover, the
significant velocity overshoot also has been found in Ge MOSFETs. 相似文献
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针对等离子体特定领域的应用需求,研制了一种基于上位机监控且具有手动/自动控制功能的脉冲电源。详细介绍了脉冲电源主电路、检测电路、驱动电路、数字脉宽调制(DPWM)产生模块以及脉冲变压器的设计方法。该电源采用现场可编程门阵列(FPGA)作为主控芯片,产生DPWM信号及继电器控制信号,经驱动电路放大后驱动逆变全桥及继电器。设计了过温和短路保护电路,通过DS18B20温度传感器和QBC10PS5霍尔电流传感器对电源模块的工作温度和电流进行实时采样。实际应用测试表明,该电源满足设计指标要求。 相似文献
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针对等离子体特定领域的应用需求,研制了一种基于上位机监控且具有手动/自动控制功能的脉冲电源。详细介绍了脉冲电源主电路、检测电路、驱动电路、数字脉宽调制(DPWM)产生模块以及脉冲变压器的设计方法。该电源采用现场可编程门阵列(FPGA)作为主控芯片,产生DPWM信号及继电器控制信号,经驱动电路放大后驱动逆变全桥及继电器。设计了过温和短路保护电路,通过DS18B20温度传感器和QBC10PS5霍尔电流传感器对电源模块的工作温度和电流进行实时采样。实际应用测试表明,该电源满足设计指标要求。 相似文献
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A. I. Harris K. -F. Schuster L. J. Tacconi 《International Journal of Infrared and Millimeter Waves》1993,14(3):715-728
Everyone recognizes the need to drive symmetric quasioptical antennas in a symmetric way to maintain clean antenna patterns; in this note we report on the advantages of bringing out the IF in a symmetric (balanced) way as well. The main difference in IF circuits between waveguide and open structure mixers is that the quasioptical mixers are usually also open at IF wavelengths, so IF currents can flow on the outside of the mixer mounting structures. We measured these surface currents and their associated resonances on a scale model of our mixer block for a 690 GHz SIS mixer. Bringing the IF off the mixer with a balanced circuit solves the surface current problems, yielding a broad bandwidth with predictable impedances. We successfully tested an octave bandwidth IF matching circuit for open structure mixers that incorporates a commercial 180° hybrid at cryogenic temperatures. We also found that surface currents are not significant for corner cube mixers because they generate their own balancing currents. 相似文献
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A novel ultrasonic method is presented for assessing the movement of a screw-driven assembly in a direction perpendicular to the direction of drive, which thus provides a quantitative assessment of the mechanical precision of the drive and its bearing. The principle and limitations of the method are discussed in some detail and measurement results from one specific practical arrangement are shown. 相似文献
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An analysis is made of the geometric and morphological properties of YBCO superconducting films and of their effect on the
magnetic and transport phenomena. A study is presented of the statistical characteristics of critical currents derived from
the variation of trapped magnetic flux induced by passing a pulsed transport current. It is shown that the critical currents
in the materials under study have a specific statistical distribution, whose main properties are due to the morphology of
their structure and can be determined by geometric-probability analysis. The superconducting film is considered as a percolation
system. An empirical normal-phase cluster-area distribution function was used to derive the distribution function of magnetic
critical currents, which describes adequately the experimental data on how transport current affects trapped magnetic flux.
The critical current for transition of a film to the resistive state has been calculated.
Fiz. Tverd. Tela (St. Petersburg) 41, 1739–1742 (October 1999) 相似文献
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研究了高k栅介质对肖特基源漏超薄体SOI MOSFET性能的影响.随着栅介质介电常数增大,肖特基源漏(SBSD) SOI MOSFET的开态电流减小,这表明边缘感应势垒降低效应(FIBL)并不是对势垒产生影响的主要机理.源端附近边缘感应势垒屏蔽效应(FIBS)是SBSD SOI MOSFET开态电流减小的主要原因.同时还发现,源漏与栅是否对准,高k栅介质对器件性能的影响也不相同.如果源漏与栅交叠,高k栅介质与硅衬底之间加入过渡层可以有效地抑制FIBS效应.如果源漏偏离栅,采用高k侧墙并结合堆叠栅结构,可以提高驱动电流.分析结果表明,来自栅极的电力线在介电常数不同的材料界面发生两次折射.根据结构参数的不同可以调节电力线的疏密,从而达到改变势垒高度,调节驱动电流的目的.
关键词:
k栅介质')" href="#">高k栅介质
肖特基源漏(SBSD)
边缘感应势垒屏蔽(FIBS)
绝缘衬底上的硅(SOI) 相似文献
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《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2009,37(11):2234-2240
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We study the fluctuation theorem formulated in terms of the currents present in a Hamiltonian system with coupled mass and energy transport. To drive the system out of equilibrium, we assume it to be connected to two ideal thermodynamical baths. The fluctuation symmetry is, thus, expressed in terms of the joint probability distribution of energy and particle currents in the system. This relation is verified numerically for the stationary state in the Spinning Lorentz Gas (SLG), driven out of equilibrium by temperature and/or chemical potential differences between the baths, as well as in the presence of an applied field. 相似文献
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Mesa stripe geometry double heterostructure lasers have been made with cavity widths down to 16 μm. The lowest threshold current
values are down to 75 mA but more typical values are 110 mA, and the slope efficiencies are typically 40%. Measurements of
near- and far-field distributions have shown that the problem of high order mode structure parallel to the junction is not
as serious as expected although emission is normally in the lowest order only for very low drive currents. Improved mode control
is demonstrated by a hybrid mesa-contact stripe geometry device which gave a pulse power output of 30 mW in the lowest order
mode at a drive current of 310 mA. 相似文献
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Mabrouk Benhamou 《Contemporary Physics》2013,54(2):135-136
It has recently been realized that there is more than one kind of superconductor, and we now recognize superconducting metals and alloys as being either ‘type-1’ or ‘type-2’. The ‘new’ type-2 superconductors can exist in a state which allows them to carry isrestanceless currents even in very strong magnetic fields, and they are used to construct very powerful electromagnets. This article describes the properties of type-2 superconductors, why very strong magnetic fields are required to drive them normal and why under certain circumstances they can carry large lossless currents. 相似文献
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Victor BS Jarboe TR Hossack AC Ennis DA Nelson BA Smith RJ Akcay C Hansen CJ Marklin GJ Hicks NK Wrobel JS 《Physical review letters》2011,107(16):165005
The first sustainment of toroidal plasma current of 50 kA at up to 3 times the injected currents, added in quadrature, using steady inductive helicity injection is described. Separatrix currents-currents not linking the helicity injectors-are sustained up to 40 kA. Decreases in the n=1 toroidal mode of the poloidal magnetic field at higher current amplifications indicate more quiescent, direct toroidal current drive. Results are achieved in HIT-SI (with a spheromak of major radius 0.3 m) during deuterium operations immediately after helium operation. These results represent a breakthrough in the development of this new current drive method for magnetic confinement fusion. 相似文献