Empirical relationship between communication costs and the channel bit rate for large computer networks

The primary trade-off in a large computer-communication network (CCN) is the balance between computation processing capability and communication capability. Essentially, a CCN model should utilize operational optimization (rather than mathematical optimization) allowing the user (mostly a non-programme network expert) to call upon his experience and insight in dealing with real-life networks to decide upon proper direction for modifications. We propose, in this paper, a unified approach which will hopefully allow an on-line user to make real-time modifications to CCNs to obtain operationally optimal system trade-offs in such areas as network overall reliability, communication response, computation response, and optimum channel capacities etc.     

Surface and interfacial tension measurement by drainage methods

The drainage of a liquid from a narrow vertical tube which is open at the bottom but closed at the top is prevented when the capillary forces exceed the gravitational forces acting on the liquid meniscus. The critical tube diameter for prevention of drainage is a function of surface or interfacial tension, and this effect forms the basis of three techniques for measuring surface or interfacial tension. Results are given for various liquid/air and liquid/liquid systems in (a) a tapered tube, (b) a rotating uniform tube and (c) a tilted uniform tube. Methods (a) and (b) appear capable of measuring surface or interfacial tension within about ± 1%.     

On program testing issues in software reliability—A survey

On account of various difficulties encountered with establishing the proof of correctness for software systems; the program testing seems to be the only sure way to prevent malfunctions from occurrence and thus to improve the software reliability. Whereas program proving is a reductive process; program testing is an affirmative process since everything done in testing can potentially contribute information about the quality of program being tested. Testing is the process of executing programs with representative input data or conditions, for which the correct results are known to determine whether incorrect results occur. This paper makes an attempt to provide a cross-section of current program testing technology—ranging from philosophical issues to research and development concepts to the extent that the known literature permits.     

A copper-base brazing alloy for electronics industries

A copper-based alloy with suitable additives has been developed. Major applications are envisioned in the electronics and vacuum-tube industries. The developed alloy with only half the quantity of silver is less expensive than the standard Ag-Cu eutectic alloy and possesses comparable brazing characteristics.     

Dynamic detection of subgraphs in computer networks

Most distributed algorithms for computer networks are designed to work with arbitrary graph structures. Most networks, however, can usually be decomposed into subgraphs with a specific structure. Detecting and exploiting these subgraphs can considerably reduce the storage and communication cost of the algorithm. In this paper we propose a distributed algorithm for detecting and exploiting tree subgraphs. In a network with fixed topology, the algorithm is optimal in terms of communication complexity. The algorithm also dynamically adapts to changes in network topology caused by link failure and recovery. The dynamic operation of the algorithm is incremental as only nodes that may be affected by the change reinitiate the algorithm. Another important property of our algorithm is that it requires no node identities or sequence numbers. We examine how this idea can be extended to other subgraph structures.     

Software complexity: An aid to software maintainability

Recent estimates that 40–70% of software cost is being spent after the software has been tested and delivered by the development contractor, makes the area of post-delivery maintenance of software a prime candidate for major technological effort with potentially high return on investment. Maintenance is most affected by software complexity, and if complexities could somehow be identified, then maintenance procedures could be adjusted accordingly. What is needed is some method of pin-pointing the characteristics of a computer program that are difficult to maintain and measuring the degree of their presence (or lack of it). This paper discusses a number of software complexity metrics reported in the last few years and examines the applicability of these complexity metrics to form a software maintainability point of view.     

Paris: An approach to integrated high-speed private networks

This paper describes a design of a high-speed packet switching system for integrated voice, video and data communications. The system makes use of a simplified network architecture in order to achieve the low packet delay and high nodal throughput necessary for the transport of voice and video. A prototype of this system has been implemented and is now being tested under a variety of packet traffic loads. We have demonstrated that this system provides a cost-effective solution for private integrated networks.     

Hardware vs software maintainability: A comparative study

The rapid technological advances in microelectronics, microprocessors and computer science, accompanied by the increasing use of digital techniques in system designs, have resulted in a transition of system problems from hardware to software. Software costs now generally exceed hardware costs. The use of the words reliability and maintainability for software are taken in a completely different context than for hardware. Significant differences exist between hardware R & M (reliability and maintainability) and software R & M in the basic concepts, understanding, principles, analytic models and design techniques used. Some recent papers 1., 5., 9. point out some of these differences with respect to reliability. This paper discusses hardware and software with respect to maintainability, to point out their similarities and differences in both conceptual and practical terms.     

Preparation, characterization and thermolysis of phenylenediammonium dinitrate salts

Four phenylenediammonium dinitrate salts were prepared and characterized by elemental, Infrared spectroscopy (IR), Ultraviolet spectroscopy (UV) and gravimetric methods. These dinitrates find application in propellant, explosives and pyrotechnics. Their thermal decomposition has been studied using thermogravimetry (TG) and simultaneous thermogravimetry-differential scanning calorimetry (TG–DSC). Kinetics parameters were evaluated by model fitting and isoconversional methods. Their thermolytic pathways have also been suggested, which involves decomposition followed by ignition.