Modeling of the calculation of the atmospheric chlorine monoxide content from the data of ground-based observations at millimeter waves

Computer modeling of the calculation of the content of chlorine monoxide in the atmosphere is performed. Radiation spectra of the substance that are measured at 204 GHz with an optimized ground-based spectroradiometer, currently under development at the Lebedev Institute of Physics, are used in the calculation procedure. It is shown that these spectra can be used to determine the average chlorine monoxide content in atmospheric layers and to reconstruct the vertical profile of this content by means of an algorithm based on the Tikhonov regularization method. The accuracy of determination of the content is estimated for different heights, including the heights of the layers that are most sensitive to atmospheric pollution.     

Influence of the organic pollution on the reliability of HE9 connectors

Edge connectors are very commonly used in instrumentation and control (I&C). Failures are difficult to explain and to predict. As a consequence the long-term reliability is difficult to demonstrate. We present in this paper the results of studies we carried out on the influence of the organic pollution in the reliability of HE9 connectors that have been used for more than 25 years. We demonstrate that organic pollution is one of the main important factor that influences the reliability and give an analysis method to evaluate its impact.     

On the interaction of the MMIC and its packaging

The software package WATMIC-EMsim is used to simulate the interaction of an MMIC circuit and its packaging. The circuit used is the spiral transformer, and the packaging is the surrounding ground ring used to interface the transformer to its coplanar probes. It is found that the resonant frequencies of the transformer are affected greatly with the introduction of the ring but, with its introduction, only slightly by the width of the ring. It is pointed out that this interaction mimics a well-known phenomenon in electrostatic capacitance. The results show that in the field-theoretic analysis of an MIC/MMIC circuit the influence of the packaging must be considered     

Generalization of the ECCS method to the multihour case

The classical ECCS method for dimensioning hierarchical telephone networks is extended to the multihour case. The problem is reformulated as a nonlinear optimization method, and the Kuhn-Tucker equations are derived. It is shown why the ECCS method cannot solve this multihour case. The ECCS method is presented as a solution technique for the Lagrangian relaxation of the multihour problem in which subgradient techniques are used for the solution of the dual. A numerical algorithm implementing these ideas is described that can handle networks with arbitrary hierarchies and allows time-of-day routing changes. Preliminary numerical results of the method are presented, showing that the multihour algorithm can reduce a network's cost when compared to currently used methods     

Radiation power loss in the output unit of the multiwave Cherenkov generator

The power loss of the multiwave Cherenkov generator is estimated for the output unit when gigawatt pulses are emitted to atmosphere. A simplified model of the output unit that represents a series of multimode circular waveguides, couplers, and a horn with a relatively large opening angle and a thick dielectric window is used in the analysis. The transforming properties of couplers and the passage of radiation through the window are studied. The results of numerical calculations are presented for the output unit that was used in experiments.     

Refractive index profiling-state of the art

Problems associated with different calibration techniques and some instrumental effects that can determine instrumental accuracy are discussed. It is shown how transmission effects can be observed and used to generate a correction curve for refracted near-field instruments. High-quality fiber slices needed for axial interferometry were used to obtain refractive index differences on suitable fibers to ±1% with the measurements traceable to national standards. Interferometry was used to calibrate a multiple-step fiber which is available in 10-m lengths with a certificate of calibration. The limitations of the technique are discussed, and preliminary results of a study on the effects of residual stress and stress relief on measurements are given. Comparisons are made between measurements made by axial interferometry and refracted near field on a range of fibers. It is shown that commercial profilers can produce reliable measurements of refractive index difference, absolute refractive index, profile shape, and numerical aperture that agree well with measurements by other techniques     

An efficient numerical technique for the solution of the monodomain and bidomain equations

Most numerical schemes for solving the monodomain or bidomain equations use a forward approximation to some or all of the time derivatives. This approach, however, constrains the maximum timestep that may be used by stability considerations as well as accuracy considerations. Stability may be ensured by using a backward approximation to all time derivatives, although this approach requires the solution of a very large system of nonlinear equations at each timestep which is computationally prohibitive. In this paper we propose a semi-implicit algorithm that ensures stability. A linear system is solved on each timestep to update the transmembrane potential and, if the bidomain equations are being used, the extracellular potential. The remainder of the equations to be solved uncouple into small systems of ordinary differential equations. The backward Euler method may be used to solve these systems and guarantee numerical stability: as these systems are small, only the solution of small nonlinear systems are required. Simulations are carried out to show that the use of this algorithm allows much larger timesteps to be used with only a minimal loss of accuracy. As a result of using these longer timesteps the computation time may be reduced substantially.     

On the Accuracy of the Beam-Wave Theory of the Open Resonator (Letters)

In an interesting paper Erickson has demonstrated how perturbation theory can be used to improve the accuracy of the beam-wave theory of the open resonator. Specifically, two defects of beam-wave theory are considered. The first is that the equiphase surfaces of beam-wave theory are not spherical, the second is that the wave function employed is only an approximate solution to the wave equation.     

Performance Analysis of DS Signal Code Acquisition Using the Matched Filter and the Median Filter

The theoretical analysis and simulation of the performance of a matched filter code acquisition structure with a median filter as the aiding device to cancel CW jamming in the AWGN channel is described. Both coherent and noncoherent structures are considered. As performance measures, the probability of detection and of a false alarm and mean acquisition times are used. Two kinds of analysis for coherent acquisition structure are presented. At first, the approximation for the pdf of the input signal to the comparator is used. Next, the probabilities are calculated directly. This is called the direct form. For the analysis of noncoherent acquisition, the pdf approximation of the coherent case is used. The performance of the median filter structure is compared to the performance of a simple linear interference cancellation method. The effect of CW jamming can be eliminated by both methods. Fixed thresholds of the comparator and the constant false alarm probability (CFAR) criteria are used. It is concluded that the median filter has a better performance, especially when fixed thresholds are used.     

Techniques for Estimating the Bit Error Rate in the Simulation of Digital Communication Systems

Computer simulation is often used to estimate the bit error rate (BER) performance of digital communication systems. There are a number of distinct techniques in the simulation context that can be used to construct this estimate. A tutorial exposition of such techniques is provided, with particular reference to five specific methods which can be implemented in a simulation. These methods range from the traditional Monte Carlo trials to assumption of definite forms for the noise statistics. An attempt is made to show how these methods are related, and the specific assumptions that are invoked in order to apply them.     

On the approximation of the output process of multiuserrandom-access communication networks

Bernoulli and first-order Markov processes are used to approximate the output process of a class of slotted multiuser random-access communication networks. The output process is defined as the process of the successfully transmitted packets within the network. The parameters of the approximating processes are analytically calculated for a network operating under a specific random access algorithm. The applied methods are general and can be used to calculate these parameters in the case of any random access algorithm within a class. To evaluate the accuracy of the approximations, a star topology of interconnected multiuser random-access communication networks is considered. The mean time that a packet spends in the central node of the star topology is calculated under the proposed approximations of the output processes of the interconnected networks. The results are compared to simulation results of the actual system. It turns out that the memoryless approximation gives satisfactory results up to a certain per network traffic load. Beyond that per network traffic load, the first-order Markov process performs better     

A reflection coefficient derivation for the Q of a reverberationchamber

Reverberation chambers (also called mode-stirred chambers) are multimoded cavities that are used for radiated emissions or immunity measurements. A reflection coefficient method is used to derive the quality factor (Q) of reverberation chambers of arbitrary shape. The results are applicable to walls of general materials, but reduce to the previous result for highly conducting walls with small skin depth. The reflection coefficient method is also used to derive the decay time of reverberation chambers     

An application of the WKBJ technique to the on-surface radiationcondition

The on-surface radiation condition method and the WKBJ method for approximating solutions to differential equations are used to derive an analytic formula for the surface currents on a two-dimensional perfectly conducting convex target. The currents are induced by an incident TE-polarized plane wave. The case of a circular cylinder is used to demonstrate the usefulness of the combined methods. It is shown that a two-term expansion yields good results for the surface currents and excellent results for the ensuing bistatic radar cross section     

Isolated-word segmentation based on the dynamics of the parameters of short correlation functions

The theoretical and experimental results obtained in an investigation of the dynamic behavior of short-correlation-function parameters and applied to the problem of speech-signal segmentation are described. The side maxima of the correlation functions of various quasi-periodic signals are investigated theoretically. Their dependences on the characteristics that determine the degree of signal quasi-periodicity are presented. These dependences are used to construct instrumental estimates of the degree of such parameters as the quasiperiodicity, the duration of quasi-periodicity segments, and the fundamental-tone period. The obtained estimates are interpreted for the case of voice signals, and it is shown that many important procedures used in speech technologies can be implemented on the basis of these estimates.     

Determination of the spatial variation of interface trapped charge using short-channel MOSFET's

Previous measurements of interface trapped charge (ITC) by charge pumping used long-channel metal gate transistors. In this paper charge pumping is extended to short-channel Self-aligned polysilicon gate transistors and used to determine the spatial variation of ITC on wafers. Only the MOSFET gate area and a pulse frequency are required to calculate ITC density from the charge pumping current. In previous work, with long-channel devices, it appears that some investigators used the design dimension of metal gate devices and others used the metallurgical channel length of the transistors to calculate gate area. Two-dimensional simulation of the charge pumping measurement showed that, for a sufficient applied pulse height voltage, the correct area is obtained if the polysilicon gate length and width asmeasured are used. When the process-induced variation of the polysilicon gate length is included in the measurement analysis, no systematic variation of ITC is observed across 5 cm wafers. The charge pumping measurement technique on short-channel MOSFET's can be used to resolve the spatial variation of ITC if the area variations are correctly handled. The measurement of ITC is linear with frequency from 1 kHz to 1 MHz, indicating that the emission time constant of the fast states measured using this method is ≤10^-6s. A variation of ITC with channel lengths is also observed. This variation could not be detected using large area devices such as capacitors, but will have important consequences for short-channel MOSFET's.     

Broad-band array design using the asymptotic theory of unequallyspaced arrays

The problem of designing broadband linear arrays of omnidirectional sensors is addressed. Attention is restricted to the case of shaded delay-and-sum beamforming. Broadbanding is here defined to mean that the beam-pattern function has little or no frequency dependence of peak response, main-lobe width, plateau sidelobe level, and sinespace separation between the main lobe and the plateau sidelobe. The asymptotic theory of unequally spaced arrays is used to derive relationships between beam-pattern properties and array properties. These relationships are used to translate beam-pattern requirements into functional requirements on sensor spacings and amplitude shadings. The functional requirements are then used to derive a broadband array design. In addition to the design equations, the asymptotic theory is used to derive equations for main-lobe level, sidelobe level, beamwidth, and signal-to-noise ratio (SNR) gain in isotropic noise. A specific example is presented to clarify the concepts and verify that the design procedure actually works     

浅谈电极对平行缝焊质量的影响

伴随着现代微电子技术的高速发展,对温度较敏感的电子元器件在设计中被普遍采用,为了满足这种电子元器件的封装要求,平行缝焊技术应运而生。平行缝焊是一种温升小、气密性高的高可靠性封装方式,普遍用于对水汽含量和气密性要求较高的集成电路封装中。影响平行缝焊质量的有诸多因素,如盖板和管壳之间的匹配、工艺参数的设置、电极表面的状态等。我们通过在SSEC(Solid State Equipment Company)M-2300型平行缝焊机上进行实验,总结出电极的状态对于平行缝焊的成品率有着直接的影响。     

Smoothing of discontinuous signals: the competitive approach

Discontinuous signals buried in noise cannot be recovered by linear filtering methods. This paper presents a new class of nonlinear filters in which sets of forward and backward linear predictors and smoothers compete with each other at each timestep. The winner of each competition is granted the right to produce the smoothed estimate at that timestep. This conceptually simple approach to nonlinear filtering, called the competitive smoothing approach, is justified by considering sets of Kalman filters (corresponding to the hypotheses used in the Bayesian framework) which are used to derive model credibility coefficients. These are shown to essentially “switch” between the various models. We argue that the concept of competitive smoothing is considerably more general than just the Kalman setting, and can be used with almost any predictors and/or smoothers. Several examples are presented which demonstrate the efficacy of the approach at both smoothing and preserving jump discontinuities. Comparisons are made with the other main nonlinear filtering approach, the median filter     

A study of the properties of the structures with Al nanoclusters incorporated into the GaAs matrix

It is shown that organometallic vapor-phase epitaxy can be used to form an artificial medium that constitutes a matrix of single-crystal GaAs with incorporated Al nanoparticles. Electrical and optical properties of this medium are studied.     

On the coefficient quantization of the Fourier basis

A family of function bases is devised from a superposition of unit characteristic functions. It is shown that these simple bases can be used to perform a quantized Fourier transform. Furthermore, the transform can be implemented in an iterative scheme such that system resources are balanced in accordance with performance.