• Nuclear Engineering and Technology
• /
• 제49권4호
• /
• pp.710-720
• /
• 2017

In Korea, many nuclear power plants operate at a single site based on geographical characteristics, but the population density near the sites is higher than that in other countries. Thus, multiunit accidents are a more important consideration than in other countries and should be addressed appropriately. Currently, there are many issues related to a multiunit probabilistic safety assessment (PSA). One of them is the quantification of a multiunit PSA model. A traditional PSA uses a Boolean manipulation of the fault tree in terms of the minimal cut set. However, such methods have some limitations when rare event approximations cannot be used effectively or a very small truncation limit should be applied to identify accident sequence combinations for a multiunit site. In particular, it is well known that seismic risk in terms of core damage frequency can be overestimated because there are many events that have a high failure probability. In this study, we propose a quantification method based on a Monte Carlo approach for a multiunit PSA model. This method can consider all possible accident sequence combinations in a multiunit site and calculate a more exact value for events that have a high failure probability. An example model for six identical units at a site was also developed and quantified to confirm the applicability of the proposed method.

• 한국문헌정보학회지
• /
• 제32권4호
• /
• pp.209-225
• /
• 1998

본 연구는 이용자들이 온라인목록을 주제탐색용으로 사용할 때 어떠한 탐색행태특성을 나타내는지를 조사하고자 하였다. 101명에게 한 건의 주제탐색문제를 제시하고 그들의 탐색수행 과정을 관찰하였다. 주요 연구결과는 다음과 같다. 1) 주제탐색을 위해 사용한 주요 탐색의 접근점은 주제필드$(55.2\%)$와 서명필드$(42.2\%)$로서 그 차이는 크지 않았다. 2)주제탐색에서의 탐색실패율은 $59.3\%$로 나타났다. 3)탐색실패의 원인은 부적절한 탐색어사용$(0.5\%)$과 불리안논리자를 기용하지 않은$(42.5\%)$ 결과로 들어났다. 4) 탐색실패에 대처하는 방안으로 탐색어변경$(42.0\%)$이나 탐색 대상필드 변경$(33.8\%)$ 방법이 가장 많이 시도되었다.

• 한국정밀공학회지
• /
• 제23권6호
• /
• pp.151-159
• /
• 2006

This paper describes a design process of end-milling cutters: solid model of the designed cutter is constructed along with computation of cutter geometry, and the wheel geometry as well as wheel positioning data f3r fabricating end-mills with required cutter geometry is calculated. In the process, the main idea is to use the cutting simulation method by which the machined shape of an end-milling cutter is obtained via Boolean operation between a given grinding wheel and a cylindrical workpiece (raw stock). Major design parameters of a cutter such as rake angle, inner radius can be verified by interrogating the section profile of its solid model. We studied relations between various dimensional parameters and proposed an iterative approach to obtain the required geometry of a grinding wheel and the CL data for machining an end-milling cutter satisfying the design parameters. This research has been implemented on a commercial CAD system by use of the API function programming, and is currently used by a tool maker in Korea. It can eliminate producing a physical prototype during the design stage, and it can be used for virtual cutting test and analysis as well.

• 전자공학회논문지B
• /
• 제33B권1호
• /
• pp.128-132
• /
• 1996

[1]에서 extended threshold Boolean filter(ETBF)의 부분 군인 self-dual ETBF가 중앙값 부여파기 출력의 가중 평균으로 표현되어짐을 보였다. 이 논문에서는 이 결과를 일반적인 ETBF로 확장한다. 특히, 모든 ETBF를 최솟값(또는 최댓값) 부여파기 출력의 가중 평균으로 표현할 수 있음을 보였다. 이 표현은 자연스럽게 윈도우(window)의 크기가 K보다 작거나 같은 부여파기만을 사용하는 K차 ETBF(K-ETBF)라 불리는 ETBF의 부분 군(subclass)을 제시한다. 여러 가지 K 값에 대하여 평균 제곱 오차(mean square error)를 최소화하는 K-ETBF를 설계한 후 이들을 오염된 신호의 복구에 적용함으로써 여파기의 성능과 복잡도간의 호환작용(tradeoff)을 고찰하였다.

• Spatial Information Research
• /
• 제7권2호
• /
• pp.223-236
• /
• 1999

본 연구는 최근 시설의 확충이 절실히 요구됨에서 불구하고 사회적 기피시설로 인식되어 그 입지를 둘러싸고 많은 사회적 문제를 일으키고 있는 쓰레기 소각장의 후보입지를 선정하는데 있어서 보다 유연성있고 객관적인 방법론을 도입하여 의사결정을 위한 지원시스템으로의 GIS 기능을 높이려는데 목적을 두었다. 본 연구에서는 종전의 입지분석시에 주로 많이 활동된 부울 논리에 의한 단순 도면중첩기능의 문제점을 제시하고 쓰레기 소각장의 입지를 선정하는데 있어서 퍼지집합(Fuzzy Set) 과 계층분석과정(AHP : Anlaystic Hierarchy Process) 이론을 활용하여 후보 입지들에 대한 적합도 수준을 평가하는데 보다 유연성을 l할수 있는 방법론을 모색하였다. 특히 본 연구는 쓰레기 소각장의 후보입지들을 선정하는데 있어서 어떠한 요인을 기회요인으로 하였는가, 또한 각 요인들에 대한 상대적 중요성, 즉 가중치를 어떻게 설정하였는가에 따라서 다양한 결과들이 추출될 수 있음을 제시하려는데 초점을 두었다.

• Asia pacific journal of information systems
• /
• 제1권1호
• /
• pp.87-101
• /
• 1991

The primary purpose of this study was to investigate a robust search methodology that could be used in full-text information retrieval systems. A robust search methodology is one that can be easily used by a variety of users (particularly naive users) and it will give them comparable search performance regardless of their different expertise or interests In order to develop a possibly robust search methodology, a fully functional prototype of a fuzzy knowledge based information retrieval system was developed. Also, an experiment that used this prototype information retreival system was designed to investigate the performance of that search methodology over a small exploratory sample of user queries To probe the relatonships between the possibly robust search performance and the query organization using fuzzy inference logic, the search performance of a shallow query structure was analyzes. Consequently the following several noteworthy findings were obtained: 1) the hierachical(tree type) query structure might be a better query organization than the linear type query structure 2) comparing with the complex tree query structure, the simple tree query structure that has at most three levels of query might provide better search performance 3) the fuzzy search methodology that employs a proper levels of cut-off value might provide more efficient search performance than the boolean search methodology. Even though findings could not be statistically verified because the experiments were done using a single replication, it is worth noting however, that the research findings provided valuable information for developing a possibly robust search methodology in full-text information retrieval.

• International Journal of Computer Science & Network Security
• /
• 제21권7호
• /
• pp.267-272
• /
• 2021

The current study aimed at measuring the rate of loss in search results of the actual number of publications in journals indexed by Web of Science when not using the accurate official authority name as indicated by the Ministry of Education. Conducting a search using the authority name does not always yield complete results of all existing publications. Researchers in Saudi universities tend to use up to 10 different random names of universities when searching. This interesting fact has prompted the authors of this paper to conduct a study on the search results of 30 Saudi universities using the authority name as indicated by the Ministry of Education. The statistical analyses revealed that there is a high tendency for the wrong use of authority names. Results show that 8 universities were not found in the search results. Furthermore, other universities are losing between 10 and 30% of search results that reflect the actual number of publications. Consequently, the rank of each university, as well as the general rank of Saudi universities in the Web of Science, will be affected.

• 한국콘텐츠학회논문지
• /
• 제9권11호
• /
• pp.54-62
• /
• 2009

국가적으로 그리고 각 연구기관에서는 투자의 효율성을 기하기 위하여 연구사업 선정과정에서 데이터베이스로부터 중복과제 혹은 유사과제를 검색하는 과정을 거친다. 최근 부얼리언 기반의 키워드 매칭 검색알고리즘의 발전 및 이를 채택한 검색엔진의 개발로 인하여 검색의 정확도가 많이 향상되었지만, 사용자가 입력하는 제한된 수의 키워드들에 의한 검색은 유사과제 파악과 우선순위의 결정에 어려움이 있다. 본 연구에서는 제안된 과제의 문서를 분석하여 다수의 색인어들을 추출하고, 이들에게 가중치를 부여한 후, 기존의 문서들과 비교하여 유사과제를 찾아내는 문서단위의 검색 알고리즘을 제안한다. 구체적으로 벡터공간검색(Vector-Space Retrieval)모델의 한 종류인 TFIDF(Term Frequency Inverse document Frequency)를 기본 구조로 채택한다. 또한 개발되는 알고리즘에는 연구과제 제안문서의 구조에 적합한 속성별 가중치(feature weighting)를 반영하고 검색속도의 향상을 위하여 K-최근접 문서(KNN: K-Nearest Neighbors) 기법도 반영한 알고리즘을 제시한다. 실험을 위하여 실제 연구제안 문서와 구조가 동일한 기존의 보고서를 사용하였는데, KISTI에서 운영하는 과학기술정보포털서비스인 NDSL에서 이미 분류해 놓은 4분야의 1,000 개 연구 보고서 문서를 발췌하여 실험을 하였다.

• 한국안전학회지
• /
• 제31권5호
• /
• pp.187-194
• /
• 2016

A single fire event within a fire area can cause multiple initiating events considered in internal events probabilistic safety assessment (PSA). For an example, a fire event in turbine building fire area can cause a loss of the main feed-water and loss of off-site power initiating events. This fire initiating event could result in special plant responses beyond the scope of the internal events PSA model. One approach to address a fire initiating event is to develop a specific fire event tree. However, the development of a specific fire event tree is difficult since the number of fire event trees may be several hundreds or more. Thus, internal fire events PSA model has been generally constructed by modifications of the pre-developed internal events PSA model. New accident sequence logics not covered in the internal events PSA model are separately developed to incorporate them into the fire PSA model. Recently, many fire PSA models have fire induced initiating event fault trees not shown in an internal event PSA model. Up to now, there has been no analytical comparative study on the constructions of fire events PSA model using internal events PSA model with and without fault trees of initiating events. In this study, the changing process of internal events PSA model to fire events PSA model is analytically presented and discussed.

• Journal of Microbiology and Biotechnology
• /
• 제16권6호
• /
• pp.993-998
• /
• 2006

We earlier suggested a hierarchical regulatory network using defined modeling symbols and weights in order to improve the flux balance analysis (FBA) with regulatory events that were represented by if-then rules and Boolean logic. In the present study, the simulation results of the models, which were developed and improved from the previou model by incorporating a hierarchical regulatory network into the FBA, were compared with the experimental outcome of an aerobic batch growth of E. coli on glucose and tryptophan. From the experimental result, a diauxic growth curve was observed, reflecting growth resumption, when tryptophan was used as an alternativee after the supply of glucose was exhausted. The model parameters, the initial concentration of substrates (0.92 mM glucose and 1 mM tryptophan), cell density (0.0086 g biomass/1), the maximal uptake rates of substrates (5.4 mmol glucose/g DCW h and 1.32 mmol tryptophan/g DCW h), and lag time (0.32 h) were derived from the experimental data for more accurate prediction. The simulation results agreed with the experimental outcome of the temporal profiles of cell density and glucose, and tryptophan concentrations.