掺Cr,Ni对S在Fe(100)面吸附的第一性原理研究

基于密度泛函理论(DFT)的第一性原理方法,在广义梯度近似下计算了Fe中掺Cr或Ni时S原子在Fe(100)面吸附的结构和电子性质,并计算了其分子轨道和吸附能。结果表明:S原子均是吸附在H位最稳定;纯铁时S在Fe(100)面H位的吸附能为-7.70 eV,掺Ni时S原子在H位的吸附能为-7.35 eV,吸附能的相对变化为4.5%;掺Cr时S原子在H位的吸附能为-5.79 eV,吸附能相对纯铁时变化为24.8%,表明掺Cr对S原子在Fe表面的吸附抑制作用更大。对比分析了每种吸附情况下的分波态密度,结果发现掺Cr时具有较高的局域电子云重叠,从而产生的排斥作用抑制了S原子的吸附。     

河北省中央节目地面数字电视覆盖网优化研究

本文所述工作是中央广播电视节目无线数字化覆盖工程的一部分。本文概括介绍了河北省频率规划方案,逐一确定了网络优化工作所需的技术参数,重点分析了网络优化工作的原理和方法。通过区域单频网和多频网实例,解决了存在的干扰问题,提出了河北省中央节目地面数字电视覆盖网组网的优化参数和方案,为其他省份开展类似工作提供了技术参考。     

Image Processing of Biological Liquids Films for Medical Diagnostics

In this paper, the development of smart medical autonomous technology is considered. An example of a smart medical autonomous distributed system for diagnostics is also discussed. To develop this system for medical image analysis we review several processing methods. The use of the cuneiform dehydration method for medical diagnosis is considered. The experimental results obtained for blood serum dehydrated films are presented. The author proposes an algorithm for the primary identification of structures formed in the films and their use for automated detection of various structures for diagnostic purposes. The paper describes the first stage of image processing, i.e. the selection of filtering types for the correct identification of structural features and characteristics of the images. The results of filtering and some computational results of various types of structures in the films are presented.     

Volterra series representation of a forward-biased p-i-n diode

A nonlinear model is proposed for a forward-biased p-in diode controlled by an ac signal consisting of a group of sinusoidal signals. The model is applicable to these phases of diode operation where linearized basic physical equations are valid. Current-voltage relations have been obtained for junctions and the "i" region in the form of a Taylor series with frequency-dependent coefficients. The new model is valid for signal levels considerably exceeding those admissible for the known linear model [3], [4]. A new form of signal limiting condition, suitable for measurement verification and calculations, has been obtained. The Volterra series for the equations representing the diode has been found which correspond to the Taylor series obtained. The convergency condition for this series is identical to that for thel Taylor series. The conformability of measurement and calculation results fully testifies to the usefulness of the proposed model for nonlinear distortion analysis.     

Supercomputers-perspectives on visualization

The role of visualization and its capabilities are discussed. The loss of information incurred in translating a three-dimensional scene into a two-dimensional image plane and ways of compensating for it are considered. The need for interactive capability is stressed. The dichotomy between the use of visualization for analysis and for communication is traced to the way the technology evolved. That is, historically, computer graphics has been used in two separate and quite different industries: for science and engineering, and for entertainment. The emergence of cross-fertilization between the two is examined. Future trends and challenges are discussed     

Spatially Adaptive Estimation via Fitted Local Likelihood Techniques

This paper offers a new technique for spatially adaptive estimation. The local likelihood is exploited for nonparametric modeling of observations and estimated signals. The approach is based on the assumption of a local homogeneity of the signal: for every point there exists a neighborhood in which the signal can be well approximated by a constant. The fitted local likelihood statistics are used for selection of an adaptive size and shape of this neighborhood. The algorithm is developed for a quite general class of observations subject to the exponential distribution. The estimated signal can be uni- and multivariable. We demonstrate a good performance of the new algorithm for image denoising and compare the new method versus the intersection of confidence interval (ICI) technique that also exploits a selection of an adaptive neighborhood for estimation.     

Self-capacitance of inductors

A new method for predicting the stray capacitance of inductors is presented. The method is based on an analytical approach and the physical structure of inductors. The inductor winding is partitioned into basic cells-many of which are identical. An expression for the equivalent capacitance of the basic cell is derived. Using this expression, the stray capacitance is found for both single- and multiple-layer coils, including the presence of the core. The method was tested with experimental measurements. The accuracy of the results is good. The derived expressions are useful for designing inductors and can be used for simulation purposes     

Performance of an Echo Canceller and Channel Estimator for On-Channel Repeaters in DVB-T/H Networks

This paper investigates the design and performance of an FIR echo canceller for on-channel repeaters in DVB-T/H network within the framework of the PLUTO project. The possible approaches for echo cancellation are briefly reviewed and the main guidelines for the design of such systems are presented. The main system parameters are discussed. The performance of an FIR echo canceller based on an open loop feedforward approach for channel estimation is tested for different radio channel conditions and for different number of taps of the FIR filter. It is shown that a minimum number of taps is recommended to achieve a certain mean rejection ratio or isolation depending on the type of channel. The expected degradation in performance due to the use of fixed point rather than floating point arithmetic in hardware implementation is presented for different number of bits. Channel estimation based on training sequences is investigated. The performance of maximum length sequences and constant amplitude zero autocorrelation (CAZAC) sequences is compared for different channels. Recommendations are given for training sequence type, length and level for DVB-T/H on-channel repeater deployment.     

An operational amplifier model for evaluating test strategies at behavioural level

This paper proposes a new operational amplifier model for evaluating test strategies at behavioural level. Major modifications on a previously reported model for improving its performance and for allowing reliable fault simulations are presented here. The new model presents a set of very appealing characteristics for behavioural-level fault injection and simulation.The matching between the behavioural-level model and a transistor-level one is evaluated for validating the model. We suggest the use of the model early in the design process, when the schematic of the circuit is not available for the test engineer and only the specifications are given. The model is also useful for evaluating different test alternatives for commercial operational amplifiers or standard cells designed by others vendors. The paper addresses two application examples and shows the usefulness of the model for evaluating test strategies when only the specifications of the circuit are available.     

基于泰勒分布线阵特殊旁瓣技术的研究

提出了基于泰勒加权分布线阵特殊旁瓣要求的设计方法,其波束图是由给定的旁瓣级要求来设计的泰勒分布波束图,在实际需要的特殊旁瓣要求上,设计满足了要求的最窄波束宽度波束图。给出了相应的参数设计,并证明该设计能在要求的最大旁瓣级上获得最大阵增益。借助计算机对线阵进行波束图设计。结果表明,使用该方法设计的波束图能满足特殊旁瓣要求和最大阵增益。     

Spectrum of incorrectly decoded bursts for cyclic burst error codes

The enumeration of the incorrectly decoded bursts for cyclic burst error-correcting codes is reported here. The enumeration yields closed formulas for long bursts, whereas an efficient algorithm for the enumeration is given for the short bursts. The enumeration is carried out for two different decoding rules. Under the first rule, the cyclic code is a full length code, and split decodable patterns are decoded by the decoder in spite of the fact that a split decodable pattern can be a burst that exceeds the decoding capability of the decoder. The analysis for the second rule assumes split patterns are not decoded. This analysis is valid for the class of shortened cyclic codes.     

A type-II censored, log test time based, component-testingprocedure for a parallel system

The authors consider the problem of acceptance testing for a parallel (1-out-of-n:G) system of different components with constant failure rates. The components are individually tested and the tests are terminated as soon as a preassigned number of each component fails. The authors provide a criterion for accepting or rejecting the system based on the sum of the logarithms of the total times on test for each component. The critical level for the test statistic is chosen so as to guarantee that the specified consumer and producer risks on the system reliability are not exceeded. The use of this statistic makes the computation of these critical values much simpler as compared with that of a previously used statistic based on the product of the total times on test for each component. Several approximate procedures are considered for deriving these critical values. The authors also formulate the optimization problem for deriving the minimum-cost component-testing plans when a type-II censored component-test procedure is used for a parallel system     

Diagnostic-strategy selection for series systems

The selection of efficient testing strategies for repairable systems composed of components arranged in series is considered. Two cost models (for perfect and imperfect testing) represent the consequences of possible test realizations. The probability that any particular component is responsible for the failure is derived and used as a basis for the two models. The model for perfect testing is solved exactly. In the optimal perfect-test sequence the components are tested in decreasing order of the ratio of: [probability that the component is responsible for the system failure] to [component test cost]. For imperfect testing, possible diagnostic errors are included in a model for which two heuristic solution strategies are provided. The model represents the consequences of both false-positive and false-negative component-test outcomes. The heuristic strategies yield efficient test sequences. Under reasonable assumptions, the second heuristic strategy is guaranteed to locate the optimal test sequence. The model can quantitatively evaluate the benefits of test-accuracy enhancement plans. These models and algorithms provide convenient methods for selecting efficient test-sequences. This is illustrated by representative examples     

A recursive T-matrix approach for the solution of electromagneticscattering by many spheres

The generalized recursive aggregate T-matrix algorithm (RATMA) is used to solve for the multiple scattering solution for over 6000 spheres. The solution is valid for all angles of incidence. An efficient method is used to calculate the coefficients for the vector addition theorem. This, together with the use of the generalized RATMA, makes calculation possible for many-particle scattering. The theory can be used for Monte Carlo simulation in remote sensing and geophysics applications     

Autonomous terrain-following for unmanned air vehicles

This paper presents an integrated guidance and control design scheme for an unmanned air vehicle (UAV), and its flight test results. The paper focuses on the longitudinal control and guidance aspects, with particular emphasis on the terrain-following problem. An introduction to the mission, and the terrain-following problem is given first. Waypoints for climb and descent are defined. Computation of the reference trajectory in the vertical plane is discussed, including a terrain-following (TF) algorithm for real-time calculation of climb/descent points and altitudes. The algorithm is particularly suited for online computation and is therefore useful for autonomous flight. The algorithm computes the height at which the vehicle should fly so that a specified clearance from the underlying terrain is always maintained, while ensuring that the vehicle’s rate of climb and rate of descent constraints are not violated. The output of the terrain-following algorithm is used to construct a smooth reference trajectory for the vehicle to track. The design of a robust controller for altitude tracking and stability augmentation of the vehicle is then presented. The controller uses elevators for pitch control in the inner loop, while the reference pitch commands are generated by the outer altitude control loop. The controller tracks the reference trajectory computed by the terrain-following algorithm. The design of an electromechanical actuator for actuating the control surfaces of the vehicle during flight is also discussed. The entire guidance and control scheme is implemented on an actual experimental vehicle and flight test results are presented and discussed.     

Moving window detection for discrete data (Corresp.)

The moving window detection procedure for discrete data is studied. Bounds for the probabilities and expected values of the waiting time for a detection are derived. The bounds are evaluated for independent identically distributed zero-one Bernoulli trials, binomial, and Poisson random variables, and also for the two-state stationary Markov chain. The results are applicable to the theory of radar detection, time sharing systems, and quality control.     

Exact image theory for the Sommerfeld half-space problem, part II: Vertical electrical dipole

The exact image theory, introduced earlier by the present authors for the Sommerfeld problem with a vertical magnetic dipole above a planar interface of two dielectric media, is now extended to the more complicated problem of a vertical electric dipole. The image source is seen to be a line current which lies in complex space for best convergence. The image current function is expressable as an integral expression, easily adapted for numerical calculations and unlike for the vertical magnetic dipole, its form is dependent on the dielectric factor ratio of the two half-spaces. Series expansions are given for an easy calculation of the image current. The reflection coefficient method and Sommerfeld surface-wave expressions are obtained as limit cases of the exact image theory. The method is tested for a large grid of field points and good accuracy for a modest calculation algorithm is observed.     

Reduction of motion artifacts using a two-frequency impedanceplethysmograph and adaptive filtering

The authors measured transthoracic impedance in nine presumed healthy adult subjects with a two-frequency plethysmograph at 57 kHz and 185 kHz. The measurement protocol included periods of normal breathing without motion and periods of motion without breathing. The authors analyzed the cross-correlation and the ratio between the signals at both frequencies for all the different maneuvers. The correlation coefficient was between 0.97 and 1 for breathing, the minimal cross-correlation (0.81) was for simulated obstructive apnea. The authors found that the amplitude ratio between the two-frequency signals was different for normal breathing and for motion. Based on these results, the authors designed and tested an adaptive filter to increase the signal-to-artifact ratio (SAR). The increase in SAR (mean±standard deviation) compared with the signal at 57 kHz was: 183%±117% for arm movement, 133%±93% for leg movement, and 34%±62% for simulated obstructive apnea     

Temperature control for food in pots on cooking hobs

A control system for the temperature of food in a cooking pot is introduced. The cooking pot is heated on a consumer cooking hob. The temperature of the pot side is used as input for the controller. It is measured by an infrared detector. The infrared detector is a thermopile. The sensor signal is evaluated by a rule-based control algorithm. The system is simple, reliable, and very user friendly. An exact temperature settlement in a consumer hob is available for the first time. The system is used for automatic cooking     

Phased Mission Analysis: A Review of New Developments and An Application

Both exact and approximate methods for obtaining the unreliability of a nonrepairable system undergoing a phased mission are presented. The techniques are applied to an emergency core cooling system for a boiling water reactor. The estimates for the example agree well with the exact solution. The accuracy and ease of implementation are compared for both methods. The approximation techniques for unavailability estimates for phased missions contained in this paper are useful for industrial applications. The techniques are implementable and existing computer programs such as MOCUS, PREP, and KITT can be used for the analysis although such use is not efficient at this time. These programs are currently being modified, for efficient use in phased mission problems, at the Idaho National Engineering Laboratory. MOCUS, PREP, and KITT are obtainable from the Argonne Code Center; 9700 South Cass Avenue; Argonne, IL 60439 USA.