Linear theory of a large-orbit electron cyclotron maser

By using of the perturbation approach, a large-orbit electron cyclotron maser is investigated in this paper. The perturbed motion of a relativistic electron and dispersion equation for both gyrotron and gyro-peniotron are obtained, then some discussions are carried out.     

Calculation of electron drift velocity at Si avalanche

In evaluating the electron drift velocity at Si avalanche, the electron distribution is obtained by solving the Boltzmann transport equation in the maximum anisotropy truncation (MAT) approximation of Baraff. Improvements are made to the MAT procedure so that the symmetrical part of the distribution function can be obtained in a straightforward manner. The temperature dependence of electron drift velocity is studied by including both optical phonon emission and absorption rather than emission alone. The calculated electron drift velocity varies from1 times 10^{7}to2.9 times 10^{7}cm/s at Si avalanche.     

Single electron motion sensor

Researchers from the University of California at Santa Barbara have combined a single electron transistor and a nano-mechanical beam, which is a microscopic, vibrating cantilever. The SET, is very sensitive to electrical charge. The researchers put the SET very close to the nano-mechanical beam and put voltage through the resonator. The voltage made the beam vibrate, and the vibrations affected the way single electrons passed through the transistor. Displacement, or how much an object has moved, can be inferred from this measurement. The researchers are currently working on making a higher frequency resonator.Visit www.three-fives.com for the latest advanced semiconductor industry news     

Linear motor motion control using a learning feedforward controller

The design and realization of an online learning motion controller for a linear motor is presented, and its usefulness is evaluated. The controller consists of two components: (1) a model-based feedback component, and (2) a learning feedforward component. The feedback component is designed on the basis of a simple second-order linear model, which is known to have structural errors. In the design, an emphasis is placed on robustness. The learning feedforward component is a neural-network-based controller, comprised of a one-hidden-layer structure with second-order B-spline basis functions. Simulations and experimental evaluations show that, with little effort, a high-performance motion system can be obtained with this approach     

Analytic modeling of transit-time device drift regions with field-dependent transport coefficients

An iterative procedure for obtaining two-carrier d.c. solutions in regions of rapidly varying carrier concentration is presented. The procedure uses an analytic solution for the carrier concentrations in a region of linear spatial electric field variation. Field-dependent diffusion and field-dependent velocities are assumed. A single-carrier small-signal model for a drift region with a spatially varying field and field-dependent transport properties is presented. When applied to a BARITT device, results consistent with published experimental data are obtained. The importance of momentum relaxation effects in Si BARITT drift regions is discussed.     

捷联陀螺漂移误差系数预测方法研究

针对目前通用的均值估计法和AR（P）模型直接预测法对捷联陀螺漂移误差系数预测精度不高的情况,对AR（P）模型直接预测法进行了改进,建立了基于误差系数漂移量的AR（P）模型,首先预测漂移量,进而预测出漂移误差系数值。通过仿真实例对3种方法的预测效果进行比较分析,结果证明本文提出的预测方法优于目前通用的两种预测方法。     

Diocotron instability of the electron beam in the drift tube of a gyrotron

A cold fluid model is used to investigate instabilities associated with a velocity shear due to the self fields of a relativistic electron beam inside the beam tunnel of a gyrotron. General statements concerning the stability of an electron beam like the frequency and the growth rate are possible. The growth is expressed as a length that can be compared with the geometry in the gun-tube-resonator system.     

Waveguide modes of a warm drifting uniaxial electron plasma for large drift velocities

The dispersion relation for guided waves in a warm drifting uniaxial electron plasma is derived for the case of large drift velocities using relativistic transformations. The phase characteristics of the "fast," "slow," and "waveguide" waves are presented and compared with the results of the nonrelativistic treatment. Significant differences are noted for small values of the normalized empty guide cutoff frequency and large drift velocities.     

Special features of electron drift in submicrometer GaAs structures

A quasi-hydrodynamic model of a submicrometer field-effect transistor was used to study the effect of the drift-velocity overshoot on the characteristics of drain-current saturation. It is shown that, in submicrometer transistor structures based on many-valley semiconductors, the current saturation is controlled by levelling off of the electron-drift velocity in the channel, with this levelling off being caused by the effective intervalley scattering. It is also shown that the highest electron-drift velocity in the channel is inversely proportional to the transistor gate length.     

Measurement of the electron drift velocity in avalanching GaAs diodes

The scattering-limited drift velocity vsnof electrons in an avalanching GaAs diode is estimated by measuring the space-charge resistance. The result shows a lower value of vsn(5.7 ± 0.3) × 10⁶cm/s than the generally accepted value 8 × 10⁶cm/s at room temperature. The temperature dependence of vsnis also measured.     

A method of determining impurity diffusion coefficients and surface concentrations of drift transistors

In order to control the electrical parameters of drift transistors, it was found necessary to control the impurity concentration gradient in the base. An extension of the space charge widening theory provides a method of calculating this gradient, the surface concentration, and the diffusion coefficient. By this method, the diffusion coefficient of arsenic into germanium at 725°C was found to be 3.1 × 10^-12cm²/second and the initial surface concentration was of the order of 10²⁰atoms/cm³. Universal graphs for design calculations and rapid reference are presented.     

广义变系数Kuramoto-Sivashinsky方程的显式解

应用修正的CK直接约化方法,得到了广义变系数Kuramoto-Sivashinsky方程与其对应的常系数方程解之间的关系,利用李群方法得到了常系数Kuramoto-Sivashinsky方程的一些显式解,从而获得了广义变系数Kuramoto-Sivashinsky方程的新解.     

Determination of electron drift velocity in a gaseous discharge from Doppler shifts of plasma waves

Measurements of Doppler shifts of plamsa waves in a low-pressure mercury-vapour discharge have been made, in order to determine the electron drift velocity in the positive column. It is concluded that, within the accuracy of the expenments, there is no radial variaton of the electron drift velocity in the discharge.     

A lucky drift model,including a soft threshold energy,fitted to experimental measurements of ionization coefficients

We have fitted the lucky drift model of impact ionization due to Burt to experimental data for GaAs, InP, Si and In_0.53Ga_0.47As. The agreement is surprisingly good considering the simplicity of that model. The lucky drift model has been further extended to include the effects of a soft threshold energy where carriers do not necessarily ionize immediately on achieving the threshold energy. This new lucky drift model is found to fit the same experimental data better than the model due to Burt in all cases but one.     

The probability for ballistic electron motion in n-GaAs

By choosing the value of P = e⁺¹as a probability criterion, ballistic electron motion in n-GaAs devices is investigated. The scattering processes due to optical phonons, intervalley phonons of Γ &rarr L and Γ → X and acoustic phonons are included in the calculations. The relation between the length of the active region and the applied voltage at 77°K and 300°K is discussed. This provides a guide to ballistic electron device design.     

Linear time-invariant space-variant filters and the parabolic equation approximation

Wave propagation in a random, inhomogeneous ocean is treated as transmission through a linear, time-invariant, space-variant, random communication channel. Using the parabolic equation approximation of the Helmholtz wave equation, a random transfer function of the ocean volume is derived. The ocean volume is characterized by a three-dimensional random index of refraction which is decomposed into deterministic and random components. Two additional calculations are performed using the transfer function. The first involves the derivation of the equations for the random, output electrical signals at each element in a receive planar array of complex weighted point sources in terms of the frequency spectrum of the transmitted electrical signal, the transmit and receive arrays, and the transfer function of the ocean medium. The second involves the derivation of the coherence function.     

类锂硅离子电子碰撞激发速率系数

本文在Z标度类氢模型下,计算了SiXII的电子碰撞激发速率系数。