The intersection of a Loxodrome with a great circle

The intersections of a loxodrome (rhumb line) and a great circle are of interest for some navigational problems, but a closed-form solution cannot be formulated. An algorithm is given for computing approximations to any desired degree of accuracy using Newton's method. By using the equatorial angle φ as an independent variable all solutions can be found rapidly using the modest computational capabilities of a personal computer     

某任务计算机调试设备配套软件的设计与实现

简介了任务计算机调试设备配套软件在任务计算机仿真环境中的重要作用 ,对该软件设计方法和流程进行了详细的说明 ,主要介绍了VC ++6 .0环境下串行通信和显示控制软件的设计技术 ,并讨论了如何提高应用程序性能的途径。     

Analysis of a redshifted plasma flow over a sunspot

The ultraviolet spectrum of a redshifted plasma flow appearing over a sunspot observed during the first flight of the High Resolution Telescope Spectrograph (HRTS I) is analysed, and interpreted as a radiatively cooling plasma. For most of the lines emitted from this plasma, the assumption of ionization equilibrium during the cooling is good. However for He II (and other ions with a single electron outside of closed shells), this is not the case. Integrating differential equations for the various ionization fractions of helium and the temperature allows an approximate determination of the abundance of helium relative to other elements whose lines appear in the spectrum of the plasma flow.     

从科技论文的特点看科技论文的选题

本文论述了科技文的特点及选师原则。在特点方面主要就科技论文的科学性,创造性,理论性进行了阐述,在选题方面科技论文选题的客观需要与主条件进行阐述,旨在揭示科技论文的特点与课题选择之间的关系,从而了解其特点,并据此选题,写出符合要求的科技论文。     

Flow about a jet source with a deflector

We suggest a method to solve one of the model problems of aerohydrodynamics, namely, a problem of a flow about a point source, from which a fluid with density and total pressure, different from the corresponding values in the incoming flow enters. The calculations are carried out for various values of the determining parameter; and the data are compared with the known results. We revealed the advantages of the suggested method in comparison with the known ones.     

Asymptotically Stable Motions of a Gyro in a Spinning Vehicle

An analysis of the motion of a single-axis rate gyroscope mounted in a space vehicle which is spinning with uncertain constant angular velocity xz about the spin axis of the gyro is presented. The nonlinearity in the equation of motion of the gimbal is retained. Using the Lyapunov approach, regions are obtained in the k-xz plane where k is the torsional spring constant, for asymptotic stability and for global asymptotic stability, and an estimate of the region of stability in state space is presented. Analytical relations for the selection of the gyro parameters are derived.     

Excitation control of a synchronous generator using a lookup table

A scheme involving the use of a lookup table is developed for the excitation control of a synchronous generator. The proposed control scheme, generator speed deviation, and acceleration deviation are taken as the input signals. These input signals are sampled and converted to linguistic terms before they are fed into the controller. The controller generates the desired output (control) signal by using a set of production rules (if-then rules) that are based on previous experience to relate the input signals to the output. The output signal is converted from linguistic terms to a numerical value before it is sent to the excitation system of the synchronous machine. To demonstrate the effectiveness of the proposed control scheme, digital simulations of a synchronous generator subject to a three-phase fault under different operating conditions were performed. It was found that the controller can improve the dynamic performance of a synchronous generator over a wide range of operating conditions. Since the controller does not require model identification, it is computationally efficient and is suitable for online excitation control, using a microcomputer     

Closed-Form Solution of a Recursive Tracking Filter with a Priori Velocity Initialization

A closed-form solution is presented for the transient gains and covariances of a two-state tracking filter which is initialized with a finite a priori velocity error variance. The formulas are applied to long-range tracking and fire control problems, and are shown to agree (in the limit) with classical formulas for a least-squares line estimator and a bias-in-noise estimator.     

A door-opening system using a low-cost fingerprint scanner and a PC

Biometrics can offer improved security for access control. Several biometric devices can be adapted to our special requirements and some criterion is needed to choose the best solution for us. On the one hand, it is possible to use a standalone embedded system. On the other hand, a low-cost PC-based system can be better fitted to our special requirements, by means of special purpose software. With the actual reduction on the price of informatic components, it can be a good alternative. This describes one of these systems for door-opening with the user's fingerprint. Special emphasis is given on the design, advantages, and inconveniences with respect to embedded systems.     

燃气轮机多微机监控系统通讯协议的制订与实现

对舰用燃气轮机组的多微机实时控制系统提出了多微机实时控制通讯协议。该协议为面向字符的数据链路层协议,能实现全双工通讯。通讯全部采用中断方式,为保证各通信互不干扰可靠畅通进行,该协议对通信管理设计为四大模块：通信数据组织模块、通信启动发送模块、通信中断模块和通信Watchdog模块。以监测机为例,根据监测机在通信中的地位,将通讯分为监测机主动发送方式、主动接收方式、被动发送方式和被动接收方式,并对各种方式下的通信过程进行了详细的论述。     

Towards a new paradigm: from a quasi-steady description to a dynamical description of the magnetosphere

A great deal of the research done on the dynamical process of the solar wind- magnetosphere interaction is based on large-scale, quasi-steady theoretical models, such as the classical reconnection model. However, it can be argued that the theoretical and observational foundations of these commonly believed paradigms are not always strong, and support for these models is sometimes weak, controversial or inconsistent. This paper discusses the need for a transition from an oversimplified quasi-steady paradigm towards a more realistic one including the dynamics of MHD waves and wave packets. The effects of localized wave packets may be most important in active plasma regions, where ideal MHD breaks down and localized, time-dependent processes become dominant. New insights into the theories of field-aligned current generation, auroral particle acceleration and the concept of reconnection may be found by including MHD wave propagation and wave packet dynamics.     

Solving a radiation problem with forward speed using a lifting surface method with a Green''s function

The progress of seakeeping computations requires development of computating codes for unsteady flows around a ship or its elements. In this paper, we present a method of calculation concerning waves radiated by an oscillating surface-piercing flat plate with forward speed, with a yaw angle. By use of Green's third identity, the problem is transformed into the resolution of a Fredholm integral equation of the first kind by a panel method using Green's function. The Green's diffraction-radiation function with forward speed is used. Its numerical values are calculated by an adaptative integration procedure to reduce the computation time. The present method permits determination of the pressure jump distribution across the plate, the total forces and moments. The results obtained are compared with other numerical methods in hydrodynamics and in aerodynamics, and with experimental data obtained in a water tank.     

共轴式直升机线性系统建模

应用小扰动理论和数值法,对共轴式直升机飞行动力学非线性数学模型进行线性化,获得了用于操稳特性分析和控制系统设计的共轴式直升机线性化模型.以某型共轴式直升机为研究对象,计算其稳定性导数和控制导数,结果与俄罗斯计算结果基本一致,并对研究对象的稳定性进行了初步分析.     

Angular Accuracy of a Scanning Radar Employing a Two-Pole Filter

A two-pole filter is proposed as a detector for a scanning radar. The optimum values of the filter coefficients are found and are approximated by a simple expression. The optimum two-pole filter requires a 0.15-dB increase in signal-to-noise ratio in order to provide the same detection capability as the optimum detector, and yields azimuth estimates whose standard deviation are within 15 percent of the Cramér-Rao lower bound. The estimator is simple to implement, avoiding the storage requirements of the moving window detector and the bias complications of the feedback integrator.     

科学实验卫星高速上行链路设计

为保障在卫星与地面之间开展空间量子科学实验的条件,必须为科学实验载荷建立一条星—地高速数据双向传输链路.通过跟踪CCSDS-SLS-NGU（空间数据系统咨询委员会-空间链路业务-下一代上行链路）工作组对NGU的研究进展,结合科学实验卫星有效载荷建立高速上行链路的需求,采用高带宽利用率调制技术、高效信道编码方式及适用的链路数据传输协议,设计了一种传输速率为1Mbit/s、误码率优于1×10-9的高速上行链路方案,并给出星载设备实现方案和地面初步测试结果.该方案在技术体制上兼容已有CCSDS规范,便于地面站及星载接收机实现,完全满足开展空间量子科学实验的需要.     

A technique for selecting a rational variant of a multifunctional aircraft system

A technique for selecting a rational variant of a multifunctional aircraft system using the analytic hierarchy process is proposed and a solution of a practical problem is presented.     

Analysis of a Class of Nonlinear Sampled-Data Systems with a Gaussian Input Signal

The problem treated here is the analysis of a class of nonlinear sampled-data systems with a Gaussian input signal. The nonlinear element is a symmetrical limiter (memoryless device) that feeds the linear element. Preceding the limiter is a sampler and zero-order hold unit for data reconstruction. The analysis is predicated on finding an equivalent gain for the nonlinear element such that the mean-square error is a minimum. The nonlinearity is thus replaced by a linear component and the system is then analyzed by conventional techniques. It is also shown that for appropriate sampling rates the sampled-data system is equivalent to a continuous system due to the action of the sampler-hold combination. All calculations pertaining to the limiter input signal require the use of a transfer function that is interior to the feedback loop. However, in developing this transfer function, the overall system is considered so that the system output may be evaluated after the value of equivalent gain has been found.     

Developing a visual component library for a graphical programmingplatform using object orientation

The development of virtual instruments (VIs) is bringing a great revolution to the fields of automated testing and measurement. It is accelerating the integration of measurement systems and is promoting instrument standardization, modularization and generalization. A graphical programming platform for automated testing is one of the most important applications of VI technology, and it provides users with an intuitive and friendly programming environment. The visual component library (VCL) is the key part of such graphical programming platforms. The research reported in this paper makes full use of the advantages of the object-oriented methodology to develop the visual VI components for a graphical programming platform. By setting up two base classes for all the VI components, various VIs can be efficiently developed     

Output of a Balanced Frequency Discriminator Driven by a Sine Wave and Gaussian Noise

The output of a realizable balanced frequency discriminator is calculated for an input consisting of a sine wave plus Gaussian noise. Explicit autocorrelation and power spectra are found for one practical embodiment of the discriminator for various input carrier-to-noise ratios, with the carrier tuned to center frequency and also off-center. The formulas also permit the calculation of the output for the case of a spectrum of noise slowly swept through the discriminator. Although qualitatively similar to results previously obtained with an ideal discriminator, substantial differences are also found. Measurements are made that closely verified the theoretical results. No limiting is assumed.     

Oscillations of a viscous liquid in a cylindrical container

The natural damped frequencies of a viscous liquid in a circular cylindrical container are obtained for slipping and anchored contact line at the container wall r = a. In addition the response to translational forced excitation has been determined. The results may also be applied to viscous liquid in a micro-gravity environment, as long as the contact angle of the liquid surface to the cylindrical container wall is in the vicinity of π/2, indicating, that the free liquid surface equilibrium position remains a plane surface. It could be found that there exists in contrast to frictionless liquid a small filling range, in which the liquid performs only an aperiodic motion. The adherence condition at the side wall was replaced by the somewhat weaker condition of an anchored contact line.