Fail-safe Function Research Articles

인터넷 환경에서 서버간 부하 분산을 위한 새로운 웹 클러스터 기법

This paper presents a new web cluster scheme based on dispatcher which does not depend on operating system for server and can examine server`s status interactively. Two principal functions are proposed for new web cluster technique. The one is self-controlled load distribution and the other is transaction fail-safe. Self-controlled load distribution function checks response time and status of servers periodically, then it decides where the traffic goes to guarantee rapid response for every query. Transaction fail-safe function can recover lost queries including broken transaction immediately from server errors. Proposed new web cluster scheme is implemented by C language on Unix operating system and compared with legacy web cluster products. On the comparison with broadcast based web cluster, proposed new web cluster results higher performance as more traffic comes. And on the comparison with a round-robin DNS based web cluster, it results similar performance at the case of traffic processing. But when the situation of one server crashed, proposed web cluster processed traffics more reliably without lost queries. So, new web cluster scheme Proposed on this dissertation can give alternative plan about highly increasing traffics and server load due to heavy traffics to build more reliable and utilized services.

Clinical application of a blood pressure autoregulation system during hypotensive anesthesia.

A blood pressure autoregulation system based on the state-predictive control method was developed to minimize intraoperative blood loss and hence avoid blood transfusion. In this report, the system is further improved by incorporating fuzzy logic with a fail-safe function and an individual parameter-identifying function. The safety and stability of this system had been confirmed by preclinical experiments with dogs. Thereafter clinical application with 17 patients was conducted to maintain their mean arterial pressure at around 60 mmHg during major surgery. The use of this system resulted in decreased blood loss and more speedy and accurate surgery due to a clearer surgical field. Unwanted effects of hypotension were not observed clinically or in laboratory tests. This system is therefore safe, stable, and effective in reducing the blood loss during major surgery that otherwise might cause substantial blood loss.

皿ばねを用いた摩擦ダンパーを有する免震建物の振動台上の実証試験

This report describes the static and dynamic characteristics of the friction damper with coned disc springs for base-isolation system. The friction damper is constructed by keeping coned disc springs against a horrizontally placed stainless steel plate on the sliding surface by making use of the rebound from deformation of vertical compression. The friction damper has not only damping mechanism but also a function that it supports a part of upper structural load and a fail-safe function. These characteristics were verified by shaking table tests and analyses of base-isolated model using the friction dampers with coned disc springs and laminated rubber bearings.

１０２６．マイクロプロセッサ化原子炉保護系のフェイルセーフ構成とオンライン診断法の開発

The microprocessor-based reactor protection system (RPS) combining a fail-safe configuration and an on-line diagnosis is presented. This combination further enhances the maintainability and reliability. The signal processing unit which judges the scram action has fail-safe and diagnosis functions. The load driver which drives the scram pilot valves is diagnosed in an on-line state. A failure in any component of the RPS which is insured a majority voting function is by-passed. The failed component is repaired based on the results of an on-line diagnosis and a fail-safe action. A latch circuit is needed to hold a scram action. A configuration of the latch circuit which can fulfill the fail-safe function and its quick response has been proposed. An on-line diagnosis method for the load driver has been developed in which the RPS functions are not interfered with, even if a single failure occurs in the diagnosis circuits. A diagnosis circuit checks a switching element which is a component of the load driver. The test pulse that is outputted from the diagnosis circuit forces the switching element to the open-state rapidly without activating the scram pilot valves. The rapid execution of the fail-safe function and the on-line diagnosis of the load driver was validated by experiments that simulated failures.

Evolution of automatic devices in conjunction with signalling on the SNCF

Computerised installations linked to the signalling in French Railways bring computer techniques to signal boxes as operational aids. The first installation, in 1977, was that in the Versailles Chantiers signal box, near Paris. This signal box manages many routes in a complicated area. The second installation, at about the same time, was that involving the traffic management on two 50 km double track sections with sidings and cross-overs. The third installation was at the Paris Invalides signal box, in 1979, on heavily used suburban lines. These three installations used mini computers. But now, with microprocessors and microcomputers, French manufacturers and French Railways (SNCF) have studied new structures with a modular approach. The main differ ence between the systems now being built and the former ones is that it is easier, with the `modules?, to have decentralised systems, and thus, less development for each installation and a larger facility for building the systems. Moreover, systems managing functions which are not strictly involved in safety in signal boxes have been studied, and fail-safe signalling function design is now in progress. The first French solid-state interlocking signal box put into service has been at Chateauroux.

Train Safety Control System for SHINKANSEN—CPU System With Priority on Safety

For 10 years since its opening SHINKANSEN, Japan’s 210 km/hr railway line, has carried 700 million passengers with a perfect safety record. Train operation safety depends on the working of local devices, while overall traffic control is maintained by a centralized system with a computer to aid the dispatchers. The local devices for safety control have an extremely high failsafe function which rejects any mistaken order from the center, when it judges that said order conflicts with the safety. The present paper describes the fundamental idea behind this highly reliable train operation control system.

Digital Data Processing of Oilfield Production Data

Abstract This paper is primarily concerned with relating time-proven digital data-processing techniques with a modern-day automatic lease production-control system. The system described is one recently installed in southeastern New Mexico. It is comprised of three remote batteries involving 150 producing wells (both flowing and pumping), 7 LACT units, 8 separate pay zones and 77 alarms, located 20 to 30 miles away from the central office. The connecting link between the central office and the three remote batteries is a leased two-wire telephone system. Several supervisory control functions are handled with this system in addition to transmitting and recording production data, e.g., individual-well test data, LACT data, tank gauge readings, various alarm conditions and other pertinent information. Application of Communications Equipment for Digital Data Processing Extensive use of communications equipment is providing oil producers with an efficient means for handling production data. Manufacturers are offering equipment with higher reliability, greater flexibility and lower over-all cost, which affords the application of such equipment for operation of lease systems. Frequency-shift tone equipment was selected as the communications medium for the system described in this paper. In this method of tone transmission a non-keyed or non-information condition represents a "space", or low-frequency tone, while an information pulse keys the transmitter to a "mark", or high-frequency tone. Either a "space" or "mark" signal is present on the transmission line at all times. Lack of either condition or a "no carrier" signal provides a fail-safe supervisory control function which causes the remote batteries to switch into "local control". The "no carrier" condition is indicated in the central office as an "error transmit" signal. Supervisory control or interrogation data are transmitted over the two-wire telephone system from the central office to the remote batteries by the use of a basic sequential-pulse-code system, wherein each control function is assigned a particular pulse-code arrangement. A "remote data selector" with selection of automatic or manual operation generates the DC-pulse code bits to key the frequency-shift tone transmitter for transmission of the proper supervisory control function. The frequency-shift receiving equipment at each remote location has matching frequencies to correspond with the transmitter frequency at the central office. Telemetering information or information on the measurement of quantitative variables is transmitted from each of the three remote batteries to the central office using tone transmitters of identical frequencies to match the receiving frequency of the frequency-shift tone receiver located in the central office. The telemetered data arrive in the central office in the form of an eight-channel coded paper tape. The ability to transmit the standard eight-channel code over a single tone channel is made possible by use of an eight-channel tape transmission machine which sends each bit of the eight-bit binary code in a determined sequence. In addition to regular tape transmission, this machine also has the ability to read and punch paper tapes. The supervisory control system of the communications link is so designed that a transmission failure at any one of the remote batteries, at the central office or of the actual two-wire line causes the batteries to switch into "local control". This feature provides a tremendous advantage for a data-processing system of this description, in that information is retained at the battery in the event of equipment or line failure of the communication link. Operation of Field Installations A system utilizing the equipment just described has recently been installed in Lea County, N. M. The system is made up of one central control and recording point located in Hobbs, N. M., with information telemetered from the separate battery installations located from 20 to 30 miles away. The batteries have different characteristics and, for purposes of description, will be referred to as Batteries A, B and C. Battery A Battery A is comprised of 106 producing wells, some flowing and some pumping, divided among nine different leases. JPT P. 1191^