Dual-band reflector-feed element for frequency-reuse applications

Proposed frequency-reuse systems have created a need for reflector-feed elements that generate symmetrical primary patterns with low crosspolar content. The letter describes a horn radiator of only 1? diameter that meets these requirements over two discrete frequency bands.     

A note on hybrid finite element method for solving scatteringproblems

The hybrid finite-element formulation (HFEM) originated by P. Silvester and M.S. Hsieh (1971) is modified in such a way that it results in a sparse or uniformly banded matrix, rather than a partly full and partly sparse nonuniform matrix. The modification is accomplished by changing the sequence of matrix substitutions and substantially improves the computational efficiency and enhances the capability of the method, which is demonstrated by numerical examples. A comparison with other numerical techniques is presented     

On stability and realizability of derived FDNR networks

A proof is given for the empirical fact that resistance-capacitance-supercapacitance networks, as well as superinductanceinductance-resistance networks are unconditionally stable. This is in spite of the second degree poles at zero and at infinity. Realizability conditions are given for a function of frequency to be the driving point immittance of such networks.     

A note on heterojunction discontinuities

Recently, an analytic proof has been advanced to the effect that the intrinsic Fermi level of a heterojuntion is by necessity continuous across the interface joining two different semiconductors. Here we wish to show that the proof given is incorrect and that the solution of Poisson's equation for an intrinsic heterojunction on which the proof was based, does not yield any information on possible continuities or discontinuities of the intrinsic Fermi level.     

A note on minimal repair

The cumulative function for the number of failures for a unit which is subjected to minimal repair after each failure is a nonstationary Poisson process. In this note, a simple method for obtaining this result is presented. A conditional probability approach is used for the derivation     

A note on reflector arrays

A Van Atta antenna array, which has a major lobe of the reradiated field in a direction retrograde to that of the incident wave for arbitrary directions of incidence, is analyzed in terms of the scattering matrix of the network interconnecting the antennas.     

A note on IC-yield statistics

Expressions given by Moore and by Dingwall for relating integrated-circuit yield to area are compared and are given a common interpretation in terms of the composite model. The issue of large-chip yield projection is discussed, a subject that is still unclear because of the concave-up projections of the empirical curves, the linear projection of the composite model, and the concave-down projections of recent analytical models.     

A note on asymmetric turbo-codes

Little attention has been devoted in the literature to turbo-codes with nonidentical component codes. However, in order to optimize the performance of parallel concatenated schemes with respect to both the so called “error-floor” and the “waterfall” regions, the idea has certain advantages     

A note on volume holograms

A model describing the operation of volume phase holograms is studied. It is shown that due to hitherto disregarded effects the Bragg conditions are not automatically satisfied, and high efficiency of wave conversion may only be achieved under special circumstances.     

韩永飞的三次"上山下乡"

密安公司总经理韩永飞,话说草原当年——出国——回国,他所经历的三次“上山下乡”……     

A note on resistor loops

Methods to directly measure the element values of a resistor loop without opening it are presented.     

A note on microprocessor typology

Our intentions is to simply show the usefulness of certain classic statistical tools in domains where such tools are rarely used. Certain of these tools bring about a new vision of a set of complex objects or systems: we have chosen, as a first step, to illustrate their potential on a simple set of micro-processors. It would be possible, in a further step, to apply those same techniques in other domains of computer science, in particular in the field of software metrics.The paper is divided in two parts: (1) Illustation of the techniques, through a practical example, which permit to reveal the essential characteristics of a family of micro-processors. (2) A short theorical summary of the statistical tools used.     

A note on antennas: Definitions and methods

Definitions of scattered and diffracted fields, originally given by R. F. Millar, are reviewed and supplemented. The definitions are used to discuss relations between results obtained by commonly used pattern prediction methods for reflector antennas.     

A note on computing environments and network reliability

Interest has increased during recent years in using microcomputers for implementation of network reliability algorithms. There are indications that some implementations suffer severe restrictions imposed by such a computing environment, whereas some other results indicate otherwise. This brief note attempts to clarify the apparently contradictory conclusions that would be naturally drawn from recent papers that treat this subject.     

A note on determining component reliability and redundancy

The computer program listed in a paper published in this journal was used to solve the two numerical examples in a substantial article published in 1977. Each of these two examples has five positive-integer variables and five continuous variables. The solutions presented here are better than the solutions in the 1977 article. Specifically, for the first example, the system reliability presented here is .9316741721437588 while the system reliability presented in the 1977 article is 0.91494. For the second example, the system reliability presented here is slightly better than that of the 1977 article: these are .9955247245296241 and 0.994767, respectively.The complete computer program for the first example and the computer outputs for the two examples are presented here. These computational results suggest that this computer program can be useful as a model to determine simultaneously both component reliability and redundancy.     

A note on sorting sparse matrices

The problem of sorting all the rows of a sparse matrix according to increasing or decreasing column indices is considered. An algorithm for doing the sort in order τ operations (where τ is the number of nonzeroes in the matrix) is given.     

A note on Gilbert burst-correcting codes

The codes discussed here, due to E. N. Gilbert, are capable of detecting and correcting certain bursts, i.e., errors which occur in clusters. In particular, it is shown that Gilbert's burst-correcting cedes have capabilities beyond those previously recognized. D. A. Huffman's graph-code formulation is used, which greatly facilitates the appreciation of the results. A cyclic code formulation is also given, and certain Gilbert codes are seen to be Fire codes.