毕业设计英文翻译.docx

1、毕业设计英文翻译外文文献：Estimates of the Operational Reliability of Fire Protection SystemsFor the past three years，the National Institute of Standards and Technology (NIST) has been working to develop a new encryption standard to keep government information secureThe organization is in the final stages of an

2、open process of selecting one or more algorithms，or data-scrambling formulas，for the new Advanced Encryption Standard (AES) and plans to make adecision by late summer or early fallThe standard is slated to go into effect next year INTRODUCTION Background Fire protection strategies are designed and i

3、nstalled to perform specific functions. For example, a fire sprinkler system is expected to control or extinguish fires: To accomplish this, the system sprinklers must open, and the required amount of water to achieve control or extinguishment must be delivered to the fire location. A fire detection

4、 system is intended to provide sufficient early warning of a fire to permit occupant notification and escape, and in some cases activation of other fire protection features (e.g., special extinguishing systems, smoke management systems). Both system activation (detection) and notification (alarm) mu

5、st occur to achieve early warning. Construction compartmentation is generally designed to limit the extent of fire spread as well as to maintain the buildings structural integrity as well as tenability along escape routes for some specified period of time. In order to accomplish this, the constructi

6、on features must be fire “rated” (based on standard tests) and the integrity of the features maintained. The reliability of individual fire protection strategies such as detection, automatic suppression, and construction compartmentation is important input to detailed engineering analyses associated

7、 with performance based design. In the context of safety systems, there are several elements of reliability, including both operational andperfornzance reliability. Operational reliability provides a measure of the probability that a fire protection system will operate as intended when needed. Perfo

8、rmance reliability is a measure of the adequacy of the feature to successfully perform its intended hnction under specific fire exposure conditions. The former is a measure of component or system operability while the latter is a measure of the adequacy of the system design. The scope of this study

9、was limited to evaluation of operational reliability due primarily to the form of the reported data in the literature. In addition to this distinction between operational and performance reliability, the scope focused on unconditional estimates of reliability and failure estimates in terms offail-da

10、ngerous outcomes. A discussion of these terms is provided later in the paper. Scop This paper provides a review of reported operational reliability and performance estimates for (1) fire detection, (2) automatic suppression, and to a limited extent ，(3) construction compartmentation. In general, the

11、 reported estimates for fire detection are largely for smoke detectiodfire alarm systems; automatic sprinklers comprise most of the data for automatic suppression, and compartmentation includes compartment fire resistance and enclosure integrity. It should be noted that in some cases the literature

12、did not delineate beyond the general categories of “fire detection” or “automatic suppression,” requiring assumptions regarding the specific type of fire protection system. Several studies reported estimates of reliability for both fire detection and automatic sprinkler system strategies. However, v

13、ery little information was found detailing reliability estimates for passive fire protection strategies such as compartmentation. A limited statistical based analysis was performed to provide generalized information on the ranges of such estimates and related uncertainties. This latter effort was li

14、mited to evaluation of reported data on detection and suppression. Insufficient data were identified on compartmentation reliability to be included. This paper addresses elements of reliability as they relate to fire safety systems. The literature search that was performed for this analysis is revie

15、wed and important findings and data summarized. The data found in the literature that were applicable to sprinkler and smoke detection systems reliability were analyzed, with descriptive estimates of the mean values and 95 percent confidence intervals for the operational reliability of these in situ

16、 systems reported. ELEMENTS OF RELIABILITY ANALYSIS There is considerabIe variation in reliability data and associated anaIysesreported in the literature. Basically, reliability is an estimate of the probability that a system or component will operate as designed over some time period. During the us

17、eful or expected life of a component, this time period is “reset” each time a component is tested and found to be in working order. Therefore, the more often systems and components are tested and maintained, the more reliable they are. This form of reliability is referred to as unconditional. Uncond

18、itional reliability is an estimate of the probability that a system will operate “on demand.” A conditional reliability is an estimate that two events of concern, i.e., a fire and successful operation of a fire safety system occur at the same time.Reliability estimates that do not consider a fire ev

19、ent probability are unconditional estimates. Two other important concepts applied to operational reliability arefuiled-safe andfailed- dangerous.when a fire safety system fails safe, it operates when no fire event has occurred. A common example is the false alarming of a smoke detector. A fire safet

20、y system fails dangerous when it does not function during a fire event. In this study, thefailed-dangerous event defines the Operational probability of failure (1-reliability estimate). A sprinkler system not operating during a fire event or an operating system that does not control or extinguish a

21、fire are examples of this type of failure. The overall reliability of a system depends on the reliability of individual components and their corresponding failure rates, the interdependencies of the individual components that compose the system, and the maintenance and testing of components and syst

22、ems once installed to veri operability. All of these factors are of concern in estimating operationaz reliability. Fire safety system performance is also of concern when dealing with the overall concept of reliability. System performance is defined as the ability of a particular system to accomplish

23、 the task for which it was designed and installed. For example, the performance of a fire rated separation is based on the construction components ability to remain intact and provide fire separation during a fire. The degree to which these components prevent fire spread across their intended bounda

24、ries defines system performance. Performance reliability estimates require data on how well systems accomplish their design task under actual fire events or full scale tests. Information on performance reliability could not be discerned directly from many of the data sources reviewed as part of this

25、 effort due to the form of the presented data, and therefore, it is not addressed as a separate effect. The cause of failure for any type of system is typically classified into several general categories: installation errors, design mistakes, manufacturing/equipment defects, lack of maintenance, exc

26、eeding design limits, and environmental factors. There are several approaches that can be utilized to minimize the probability of failure. Such methods include (1) design redundancy, (2) active monitoring for faults, (3) providing the simplest system (i.e., the least number of components) to address

27、 the hazard, and (4)a well designed inspection, testing, and maintenance program. These reliability engineering concepts are important when evaluating reliability estimates reported in the literature. Depending on the data used in a given analysis, the reliability estimate may relate to one or more

28、of the concepts presented above. The literature review conducted under the scope of this effort addresses these concepts where appropriate. Most of the information that was obtained from the literature in support of this paper were reported in terms of unconditional operationaZ reliability, i.e., in

29、 terms of the probability that a fire protection strategy will not faiZ dangerous. LITERATURE REVIEW A literature search was conducted to gather reliability data of all types for fire safety systems relevant to the protection strategies considered: automatic suppression, automatic detection, and com

30、partmentation. The objective of the literature search was to obtain system-specific reliability estimates for the performance of each type of fire safety system as a function of generic occupancy type (e.g., residential, commercial, and institutional). Sources of information included national fire i

31、ncident database reports, US Department of Defense safety records, industry and occupancy specific studies, insurance industry historical records and inspection reports documented in the open literature, and experimental data. Reports on experimental work and fire testing results were utilized only

32、when fire detection, automatic suppression, or compartmentation strategies were explicitly evaluated. Tests of systems used for qualification, approval, or listing were also reviewed for information on failure modes. Published data from the United Kingdom, Japan, Australia, and New Zealand were included. General Studies The Warrington Fire Research study addressed the reliability of fire safety systems and the interaction of their components. A Delphi methodology was used to develop discrete estimates of the reliability of detection and alarm systems, fire