Electrical Communication Systems Research Articles

RELIABILITY AND DURABILITY PROBLEMS OF LOAD BEARING CONCRETE STRUCTURES FOR ELECTRIC POWER TRANSMISSION LINES

Summary Experimental and theoretical investigations associated with reliability and durability problems of concrete structures of electric power and communication systems have been carried out by scientists of Vilnius Gediminas Technical University since 1959. An attempt to generalise the accumulated statistical data enabling to evaluate reliability and durability of such structures is presented in this article. It has been determined that concrete pylons of supports of electric power overhead lines under long-term service (over 30 years) are with defects and damages, and the most characteristic of these are vertical cracks close to the longitudinal reinforcing bars, delaminated or fallen down concrete protective cover, naked longitudinal reinforcement which is corroded along 0,5-2 m intervals (not along the whole its length). Cross-sectional area of corroded reinforcement is reduced not substantially, because corrosion becomes slower due to ventilation after opening of a wide crack. Technical state of sp...

Mie University, Faculty of Engineering, Hori Research Laboratory

The Faculty of Engineering, Mie University was established in April 1969. Therefore, it has a rather short history. The Department of Electrical and Electronic Engineering with full enrollment of 110 students was initiated in April 1991 by the merger and reorganization of the Department of Electrical Engineering, established in 1969, and the Department of Electronic Engineering, established in 1975. Over 30% of the graduate students continue on to the masters course each year. In the 1995 academic year, the doctoral course was established in the Faculty of Engineering. With this reorganization, the conventional minor professorial chair system (9 minor chairs) was changed to 3 major professorial chair system. The major chairs are: the Laboratories of Electrical Systems Engineering, the Information and Communication Systems, and the Electronic Material Science and Technology. Hori Research Laboratory is part of the Laboratories of Electrical System Engineering. The Laboratory consists of Professor Takamasa Hori, Associate Professor Muneaki Ishida, Assistant Professor Satoshi Komada, Engineer Masaru Nakamura, 2 doctoral students, 9 masters course students, 12 undergraduates, and one researcher. T. Hori joined the lab from Hitachi Research Lab. of Hitachi, Ltd. in January 1987, M. Ishida from Nagoya University in June 1987, and S. Komada from Keio University in April 1989. Major research themes of the lab are as follows:

Regulation of gap junction coupling in the developing neocortex.

In the developing mammalian, neocortex gap junctions represent a transient, metabolic, and electrical communication system. These gap junctions may play a crucial role during the formation and refinement of neocortical synaptic circuitries. This article focuses on two major points. First, the influence of gap junctions on electrotonic cell properties will be considered. Both the time-course and the amplitude of synaptic potentials depend, inter alia, on the integration capabilities of the postsynaptic neurons. These capabilities are, to a considerable extent, determined by the electrotonic characteristics of the postsynaptic cell. As a consequence, the efficacy of chemical synaptic inputs may be crucially affected by the presence of gap junctions. The second major topic is the regulation of gap junctional communication by neurotransmitters via second messenger pathways. The monoaminergic neuromodulators dopamine, noradrenaline, and serotonin reduce gap junction coupling via activation of two different intracellular signaling cascades--the cAMP/protein kinase A pathway and the IP3/Ca2+/protein kinase C pathway, respectively. In addition, gap junctional communication seems to be modulated by the nitric oxide (NO)/cGMP system. Since NO production can be stimulated by glutamate-induced calcium influx, the NO/cGMP-dependent modulation of gap junctions might represent a functional link between developing glutamatergic synaptic transmission and the gap junctional network. Thus, it might be of particular importance in view of a role of gap junctions during the process of circuit formation.

A hormone-sensitive communication system in an electric fish.

The electric communication system includes both special muscle-derived cells or electrocytes that produce species-typical electric signals, or electric organ discharges (EODs), and specialized sensory receptors, or electroreceptors, that encode the electric fields set up by EODs. Steroid hormones can influence the characteristic properties of both EODs and electroreceptors. Steroids appear to directly effect the anatomy and physiology of the electrocytes that generate an EOD. In contrast, the steroid effect on electroreceptors may be predominantly via an indirect mechanism whereby changes in the spectral characteristics of the EOD appear to induce changes in the spectral sensitivity of electroreceptors. Continued studies of electrosensory and electromotor systems will offer insights into the cellular bases for the development and evolution of steroid-sensitive pathways in the vertebrate nervous system.

Secret ballot systems using cryptography

AbstractSeveral problems arise when an electrical communication system is utilized to realize a secret ballot. For example, double voting is easy. Even if cryptography is used, the content can be deciphered by voters who know the key to the cryptography. This paper proposes and discusses a system which can solve those problems and can realize a secure secret ballot by electrical communication. The divided‐vote secret ballot system is considered first. In this system, the individual votes represented by integers are divided into several sets and are distributed to ballot managers who process the subsets and announce the total. Deciphering and counterfeiting are impossible. Then the sum‐round‐opening secret ballot is discussed. In this system, the vote is enciphered using the GS public‐key system, and are totaled in the enciphered form. The separate‐round‐opening secret ballot is also discussed in this paper. The system is a modification of the sum‐round‐opening type so that the individual votes can be opened separately. Deciphering, counterfeiting and impeding are impossible in this system.

Photographic System as a Communication Channel

The light spread function, the density variations due to granularity, and the shape of the density-vs-log-exposure curve are basic properties of a black-and-white photographic system that determine its effectiveness as a communication channel. The amount of information stored per unit area on a photographic material is analogous to the amount of information transmitted per unit time by an electrical communication system. Simple formulas, involving in one instance only the resolving power and in the other a cross-sectional area of the point spread function, the standard deviation of the density variations, and the density range, have been used with considerable success to predict experimentally determined information storage capacities for a variety of black-and-white photographic systems. The upper limit of storage capacity, attainable only if the input information is efficiently coded, can be calculated by the use of a two-dimensional version of Shannon's formula for channel capacity. This method takes into account the shape of the modulation transfer function and also the shape of the granularity Wiener spectrum of the system. The contribution of color to information storage capacity is considered by D. L. MacAdam (in an appendix at the end of this paper), who finds that color photographs can provide a capacity approximately three times as great as that obtainable with corresponding black-and-white photographs.

New means of communication

In the past, men viewed different modes of communication, such as telegraphy and telephony, as being fundamentally different in kind, a view that has been dispelled by technological advances and especially by the communications theory of Shannon. The way is now open to achieve a universality in electrical communications systems analogous to that of the human nervous system in which different sensory functions-vision, hearing, taste, etc.-are served by uniform nervous transmission lines that differ only in the different types of sensory transducers in which they terminate. There are technical problems and challenges in achieving a future universal communication system that will serve all man's needs, but there are also other obstacles rooted in obsolete social and legal concepts.

A New Electrical Research Laboratory

The outstanding features of this laboratory are the power and surge testing facilities. Power laboratory energy for testing is supplied at 138 kv from a high-capacity utility system. A main transformer designed for short-circuit testing duty provides test voltages ranging from 1.5 kv for 18 kv and currents up to 25,000 amperes rms. Use of additional transformers widens this range. Test initiation can be timed accurately for any desired point on the 60-cycle voltage wave. The power test bus is so arranged that connections can be extended to energize and test full-scale line construction on the unimproved acreage of the laboratory site. The surge laboratory is equipped with five surge generators capable of producing high-voltage surges up to 3,000,000 volts and high-current surges of over 100,000 amperes. The surge generators can be used individually or together for multiple surge phenomena. For combined power and surge testing of lightning protective equipment, surges of predetermined characteristics are applied to equipment energized from the power laboratory test bus. The mechanical laboratory includes universal testing machines equipped with load-deflection graphic recorders, and facilities for full-scale testing of line hardware and structures. Created for the development of electrical and mechanical products for both electric power utility and wire communication systems, the laboratory is an integrated operation, with research, development, building of prototypes, and testing, all at one location.

Communication Sciences in a University Environment

Information processes and information processing systems are the principal concerns of investigators in many fields, including electrical engineering, neurophysiology, psychology, linguistics, genetics and mathematics. Studies in each of these fields contribute to understanding in the others, and each has a need for mathematical models and mathematical methods for describing and analyzing these processes. Studies of electrical communication and computational systems have provided the mathematical tools and understanding which are useful to the other fields. The related interests of this diverse group of scientists are examined and the activities of several groups in the Communication Sciences Center at M.I.T. are described.

Corrosion Mitigation in a Metropolitan Area

The corrosion mitigation of cable sheaths and other underground metallic structures in a metropolitan area involves many problems not encountered in the protection of cross-country cables and pipe lines. It is difficult for any one operator to apply protection to small section of his system or the entire system without increasing corrosion on other systems in the same area.A description is given of how Miami utility companies participated jointly in the designing and installation of a cathodic protection system. Purpose of the project was to provide protection to all metallic structures in a certain downtown area. Eleven 50-ampere rectifiers were installed at selected locations throughout the area.The selecting of reference electrode locations is discussed in detail. Other topics considered include cathodic protection design factors, tests made to determine need for resistance bonds, changes in construction practice, use of magnesium anodes and cost of installing cathodic protection.After eight years time the Miami cooperative corrosion control program was found to have provided good protection to electric and gas and communication systems. Corrosion failures on protected communication system cables were found to be almost nonexistent. Corrosion failures on electric cable sheaths were found to have dropped to one per year.

Electrical pulse communication systems. Part 3: Transmission and reception problems in pulse systems

Pulse systems offer the advantage of time-division multiplexing. Synchronous and asynchronous systems are compared and many further methods are mentioned. A novel method of reducing redundancy by functional multiplexing (CODEP) is disclosed. Special signals like synchronization pulses, channel markers, code switching signals, etc., have to be added to the combined pulse train prior to the final carrier modulation process. When comparing the various possible combinations of pulse modulation, multiplexing and carrier modulation to find the most efficient system, the limitations in power radiation have to be considered, average power or peak power limitation being the most usual specifications.Noise and disturbance characterize the transmission medium. Passive and active interceptions may also influence the selection of an optimum system. Passive interceptions include the typical radar reflections, but also ionospheric recording, fault location, etc. Active interceptions comprise all types of repeaters. Regenerative repeating is the most important method for the elimination of cumulative disturbances over long distance communication systems.Important problems arise at the receiver where noise and information carrying signals arrive in a closely mixed form. Apart from special detection methods there are several operations which may be adopted in the frequency domain (comb filter) and time domain (gating, integration, correlation) to improve the separation of signals from noise. Error detection and correction systems, together with prediction methods, may further improve the system quality.Brief reference is made to the various destinations terminating any pulse communication system. Future possibilities are mentioned.

Electrical pulse communication systems. Part 2: Message encoding and signal formation in pulse systems

Five specifications should be known of an information source: dimensionality; maximum information content and peak rate of information production; average rate of information production auto-correlation function; and statistical fine structure of the source. Various sources are discussed with reference to the specifications. Message encoding is split into two distinct operations : space matching and entropy matching. The former process has to reduce the dimensionality of the message space to match the three-dimensional signal space, the latter has to remove redundancy. Signal formation involves sampling, quantization and pulse modulation. The typical pulse waveforms are compared and their frequency spectra are listed. Signal encoding is considered as a linear transformation of the signal space into the channel space for the sole purpose of matching it to the requirements of a noisy channel of limited bandwidth.

Electrical pulse communication systems. Part 1: Information theory and pulse systems

Information theory and its more specialized branch, communication theory, are based on the statistical definition for the information content of messages. Statistics deals with discrete elements and is therefore directly applicable to pulse systems. The ‘system engineer’ has to use results of this theory for designing o communication systems.Four classes of systems are distinguished: communication—data transmission—location—computers. The main sections in each system are: source—message encoding—signal formation—multiplexing (train formation)—wave formation (carrier modulation)—transmission over the medium—reception Some sections may be omitted in particular systems.Information is defined and its transmission over all the sections of a system is discussed in the light of modern theory. Message encoding has to transform the multi-dimensional message space into the three-dimensional signal space at the same time allowing for sufficient reduction of redundancy. Signal encoding will reshape the signal space for matching a given channel. Authenticity examination at the receiving end will assure reliable service by error detection. Error correction methods may be employed to reduce equivocation (error expectancy).

Sun-spot disturbances of terrestrial magnetism

For many years magnetic storms at irregular intervals have been known to interfere seriously with the operation of electrical communication systems. The storm of March 24, 1940, however, considered to be possibly the greatest magnetic storm that has ever been recorded, not only interfered widely with communication systems, but also caused numerous interruptions in electric-power systems. The latter experiences are reviewed here, followed by some notes on current theories concerning magnetic storms.

Electrical features of the Texas Centennial central exposition

The one-hundredth birthday of the state of Texas has been the occasion for the construction of a great exposition at Dallas. The success of such an exposition is dependent upon the electrical illumination, power, sound equipment, and signal and communication systems. This paper outlines the electrical features of the Dallas exposition.

Electrical Features of the Texas Centennial Central Exposition

The one-hundredth birthday of the state of Texas has been the occasion for the construction of a great exposition at Dallas. The success of such an exposition is dependent upon the electrical illumination, power, sound equipment, and signal and communication systems. This paper outlines the electrical features of the Dallas exposition.