• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.191-198
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• 2009

There are almost no studies on verification of requirements for high speed rolling stocks by means of RAM goals and on setting RAM goals by means of verification on practical reliability, availability and maintainability for high speed rolling stocks though they are covered in specification of an order that RAM goals asked of rolling stocks are shown for gaining high quality of them and availability when they are in operation. This study is for estimating number of high speed train-sets that would be supplementarily placed an order through verification of RAM goals of a project for the introduction of KTX-II 100 cars. It verify that optimized requirements for high speed rolling stocks by relatively comparison with between requirements for train-sets through setting RAM goals and requirements for train-sets through analysis of prospects for management balance with high speed rolling stocks.

• Communications for Statistical Applications and Methods
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• 제29권2호
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• pp.151-160
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• 2022

The total system is composed of the main system (MS) and the failure detection equipment (FDE) which detects failures of MS. The analysis of system reliability is performed when the failure of FDE is possible. Several repair policies are considered to determine the order of repair of failed systems, which are sequential repair (SQ), priority repair (PR), independent repair (ID), and simultaneous repair (SM). The states of MS-FDE systems are represented by Markov models according to repair policies and the main purpose of this paper is to derive the system availabilities of the Markov models. Analytical solutions of the stationary equations are derived for the Markov models and the system availabilities are immediately determined using the stationary solutions. A simple illustrative example is discussed for the comparison of availability values of the repair policies considered in this paper.

• 국제학술발표논문집
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• The 5th International Conference on Construction Engineering and Project Management
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• pp.412-418
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• 2013

With the increasing demand for public housing, the Singapore government decided to reduce the waiting time of future public housing owners, which requires these projects to be completed on time. As a result, this study aims to identify the frequent and impactful factors affecting schedule performance of public housing projects in Singapore. The survey conducted with 36 industry experts revealed that "site management", "coordination among various parties", "design changes by owner during construction", "availability of laborers on site", "availability of material", and "availability of staff to manage projects" were the six factors that should be emphasized to assure the schedule performance of public housing projects. In addition, there was statistically significant agreement between public housing projects and other building projects on both the frequency and impact ranks of the factors. The findings from this study will help practitioners involving public housing projects to take measures to assure the achievement of project schedule objectives.

• 제어로봇시스템학회논문지
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• 제5권5호
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• pp.614-621
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• 1999

In this paper, the analytical appproaches are presented for jointly determining the profit-miximizing configuration of the fault-tolerance real time modular cell manufacturing system. The transient(time-dependent) analysis of Markovian models is firstly applied to modular cell manufacturing system from a performability viewpoint whose modeling advantage lies in its ability to express the performance that truly matters - the user's perception of it - as well as various performance measures compositely in the context of application. The modular cells are modeled with hybrid decomposition method and then availability measures such as instantaneous availability, interval availability, expected cumulative operational time are evaluated as special cases of performability. In addition to this evaluation, sensitivity analysis of the entire manufacturing system as well as each machining cell is performed, from which the time of a major repair policy and the optimal configuration among the alternative configurations of the system can be determined. Secondly, the recovery policies from the machine failures by computing the minimal number of redundant machines and also from the task failures by computing the minimum number of tasks equipped with detection schemes of task failure and reworked upon failure detection, to meet the timing requirements are optimized. Some numerical examples are presented to demonstrate the effectiveness of the work.

• 한국시뮬레이션학회논문지
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• 제16권1호
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• pp.59-68
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• 2007

침입감내 기술은 기존의 정보보호 기술이 방어하지 못하는 공격들이 있는 상황에서 일정 시간 동안 일정 수준의 서비스 품질을 유지시키기 위해 사용되는 기술을 일컫는 말이다. 침입감내 기술을 통해서, 서비스 혹은 이를 제공하는 시스템의 가용성 및 신뢰성을 높여 줄 수 있고, 공격으로 인한 피해를 줄일 수 있게 된다. 침입감내 기술의 핵심 기술 중 하나가 그룹관리 프로토콜 (GMP : Group Management Protocol) 및 투표 기능(Voting) 이다. 본 논문은 이 두 요소기술이 갖는 신뢰성을 수학적으로 검증하고 또한, 시뮬레이션을 통한 검증을 수행하였다. 이러한 분석이 갖는 의미는, 분석 결과를 활용한 보안 정책을 만들 수 있다는 것과, 다수개의 시스템의 결과를 기반으로 의사결정을 해야 하는 경우에 어떠한 분석 절차를 가져야 하는 지에 대한 방법론을 제시한다는 것이다.

• 유통과학연구
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• 제21권9호
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• pp.103-114
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• 2023

Purpose: This paper aims to assess psychological heuristics' effectiveness on cumulative returns after significant stock price changes. Specifically, it compares availability and anchoring heuristics' empirical validity due to conflicting stock return predictions. Research Design, Data, and Methodology: This paper analyzes stock price changes of Korean distribution industry stocks in the KOSPI market from January 2004 to July 2022, where daily fluctuations exceed 10%. It evaluates availability heuristics using daily KOSPI index changes and tests anchoring heuristics using 52-week high and low stock prices as reference points. Results: As a result of the empirical analysis, stock price reversals did not consistently appear alongside changes in the daily KOSPI index. By contrast, stock price drifts consistently appeared around the 52-week highest stock price and 52-week lowest stock price. The result of the multiple regression analysis which controlled for both company-specific and event-specific variables supported the anchoring heuristics. Conclusions: For stocks related to the Korean distribution industry in the KOSPI market, the anchoring heuristics theory provides a consistent explanation for stock returns after large-scale stock price fluctuations that initially appear to be random movements.

• International Journal of Knowledge Content Development & Technology
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• 제13권4호
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• pp.39-49
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• 2023

This research investigates the availability of information resources for visually impaired students in University libraries in Nigeria; a tool for inclusive University education. A Descriptive survey research design was adopted for the study and a total number of 20 University libraries took parts in the study. A self-constructed online questionnaire was designed and distributed to collect the data from respondents (librarians) using a simple random sampling technique. A total of 45 respondents filled out the online questionnaire, but 40 were valid and useful for analysis. The use of frequency count and percentages method of data analysis was adopted for this research work. The study reveals that most of the University libraries lacked information resources for visually impaired students, it was found that the inclusion of information resources for visually impaired persons will promote inclusive education and librarians' skills. The challenges hindering the availability of information resources to the visually impaired students are insufficient funds for maintenance, erratic power supply and inadequate skills by users, among others. Recommendations were made for the campaign for inclusive education and the provision of information resources for visually impaired students.

• 한국가스학회지
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• 제24권6호
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• pp.18-27
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• 2020

본 연구에서는 LNG-FPSO 상부구조물의 시스템 가용도를 고려한 해저 유동관내 유동안정성 연구를 수행하였다. 이를 위해 PVCap 억제 성능 평가 실험, LNG-FPSO 상부구조물 가용도 분석, 유동관내 하이드레이트 위험도 평가, PVCap 주입 농도 산출로 구성된 하이드레이트 관리 전략을 수립하였다. 과냉각 온도 6.1, 9.2, 12.1℃에 따라 PVCap의 하이드레이트 지연시간을 측정함으로써 PVCap 주입 농도 결정에 필요한 실험 기준을 확보하였다. 시스템 가용도 분석을 통해 산출된 20년 동안의 LNG-FPSO 상부구조물의 가용도는 89.3%이며, 50시간의 최장 고장 시간이 연간 2.9회 발생하였다. 현장 자료를 이용하여 다상 유동 시뮬레이션을 위한 유동관 모델을 구축하였다. 다상 유동 시뮬레이션을 통해 하이드레이트 플러깅 위험도를 예측한 결과, 50시간의 생산 중단 조건에서는 23.2시간 만에 유동관 끝단에서 하이드레이트가 발생하는 것을 확인하였다. 하이드레이트 방지를 위해 PVCap 실험 결과를 기반으로 PVCap 주입 농도를 산출하였으며, 0.25 wt%의 PVCap을 연간 2.9회 주입하면 하이드레이트 플러깅을 방지할 수 있을 것으로 판단된다.

• International Journal of Computer Science & Network Security
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• 제24권1호
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• pp.23-30
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• 2024

This study tries clarify the process of making decisions with geographic information systems and how to choose the best place for Khartoum State displaced people to relocate to in order to be closer to cheaper places with access to commodities and services. For network analysis, use a unique model. The network analysis tool was dependent on the following information: availability of goods and services, cheap cost, and proximity to the state of Khartoum.in choosing the best state. The study came to the conclusion that, in terms of accessibility, affordability, and availability of products and services, Gezira State is the best state for people who have been displaced from Khartoum State.When developing a new model, we recommend that all GIS users apply the theories of spatial analysis.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.655-658
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• 2016

고성능 디지털 회로 구현에 매우 많이 사용되는 Xilinx사의 7-Series FPGA(Field Programmable Gate Array)는 configuration memory가 SRAM 기반으로 제작되어 configuration memory에 소프트 에러(soft error)가 발생하는 경우 FPGA는 오동작하게 된다. Xilinx사에서 제공하는 SEM(Soft Error Mitigation) Controller를 이용하면 configuration memory에서 발생하는 소프트 에러의 영향을 줄일 수 있다. SEM Controller는 FPGA의 configuration memory 영역에 추가된 ECC(Error Correction Code)와 CRC(Cyclic Redundancy Code) 기능을 이용하여 configuration memory에 발생한 소프트 에러를 감지하여 필요시 partial reconfiguration 과정을 수행하여 FPGA의 기능을 소프트 에러 발생 이전으로 복구한다. 본 논문에서는 Xilinx사의 7-Series FPGA에서 SEM Controller를 이용하여 configuration memory의 소프트 에러를 검출하고 정정할 때 FPGA의 신뢰도를 가용성(availability) 관점에서 분석한다. 이를 위해 SEM Controller의 소프트 에러 정정 성능에 따른 가용성 함수를 유도하고 그 효과를 검토한다. 연구 결과는 소프트 에러가 발생하는 환경에서 동작하는 SRAM 기반 FPGA의 신뢰성 예측에 사용할 수 있을 것으로 기대된다.