• 한국군사과학기술학회지
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• 제3권1호
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• pp.218-230
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• 2000

In the weapon system development/operation stage, the goals of RAM activities are to support the cost effective performance optimization in design and operation supports. In the study, the main contents are as follows; 1) To establish the operational concept and circumstance of the subsequent tank, the combat/operation scenario, the operational mode summary and mission profile for subsequent tank development are analyzed. 2) To evaluate the administrative and logistics down time for subsequent tank, the prefigured logistics circumstance and maintenance system are analyzed. 3) To calculate the RAM object values, a mathematical model for the user are developed. 4) To examinate the propriety of the RAM object values, the combat readiness are reviewed. The obtained RAM object values are provided to predict and analyze for the combat readiness, staying power, mission reliability, equipment availability and the logistic support capability.

• 전기의세계
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• 제28권7호
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• pp.60-66
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• 1979

In this paper we deal with a hardware redundency, using the replications of an original module to enhance the reliability of the system in view of static and dynamic redundancy. As results of the study the following facts have been proved that (1) if the mission time is small (T .neq. 0.5), the effect of spare modules cannot be expected significantly, (2) for the small mission time (0.1 .neq. T .neq. 0.3) the SPR system is more reliable than the other redundant systems. In addition to above facts, it is also proved that for the large mission time (T=1), the dynamic redundant system is more reliable than the static redundant system, and that the SR system is more reliable than the HR system in the dynamic redundant system.

• 항공우주시스템공학회지
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• 제9권2호
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• pp.41-46
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• 2015

The various risk factors that affected schedule, costs and mission success, etc. in development of the satellite. This paper derives the considerable "Cost of Quality" factors in the satellite development phase through the survey of practical techniques in respect of measurement of quality cost in the commercial products manufacturing, and proposes mitigation strategy of quality cost using the approach that can be minimized it.

• International Journal of Reliability and Applications
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• 제17권1호
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• pp.51-63
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• 2016

Stress function of ball bearing is function of multiple stochastic factors and this system is so complex that analytical expression for reliability is difficult to obtain. To address this pressing problem, in this article, we have made an attempt to approximate system reliability of this important item based on reliability bounds under the stress strength setup. This article also provides level of error of this item. Numerical analysis has been adopted to show the closeness between the upper and lower bounds of this item.

• Journal of Information Technology Applications and Management
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• 제25권2호
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• pp.109-116
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• 2018

In this study, we was compared the reliability performance of the software reliability model, which applied the Goel-Okumoto model developed using the exponential distribution, to the logarithmic function modifying the intensity function and the Rayleigh form. As a result, the log-type model is relatively smaller in the mean squared error compared to the Rayleigh model and the Goel-Okumoto model. The logarithmic model is more efficient because of the determination coefficient is relatively higher than the Goel-Okumoto model. The estimated determination coefficient of the proposed model was estimated to be more than 80% which is a useful model in the field of software reliability. Reliability has been shown to be relatively higher in the log-type model than the Rayleigh model and the Goel-Okumoto model as the mission time has elapsed. Through this study, software designer and users can identify the software failure characteristics using mean square error, decision coefficient. The confidence interval can be used as a basic guideline when applying the intensity function that reflects the characteristics of the lifetime distribution.

• 반도체디스플레이기술학회지
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• 제19권1호
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• pp.11-16
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• 2020

In this paper, system that includes multiple unmanned aerial vehicles (UAVs) are considered. The vehicles are equipped with a mission computer for a specific mission and equipment. The mission equipment operates based on the time of mission computer. Also, data collected by flight computer and mission computer is saved with the time of each operating system. Generally, time offset between multiple computers always exists, though the computers are connected to the Internet. When the data collected by multiple computers is combined, the time offset causes damage on reliability of the combined data. Computers that connected to the Internet are synchronized by network time protocol (NTP). This paper proposes a system that the time of multiple mission computers are synchronized by the same NTP server to minimize the time offset. In the results of the measurement, the system time offset of multiple mission computer is maintained within 10ms from the system time of the server computer.

• 한국항공우주학회지
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• 제44권2호
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• pp.172-180
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• 2016

극초소형 위성으로 분류되는 큐브위성의 경우, 저가/단기간 개발목표 충족을 위해 일반적으로 진동 및 열 환경 규격을 만족하는 상용부품을 선정하여 제작하고 최소한의 검증시험을 통해 발사 및 궤도 운용을 실시한다. 하지만 제한된 회수로 지상에서 실시된 환경시험만으로 장시간에 걸친 궤도상 열진공과 같은 물리적 부하 환경에 노출된 임무보드의 신뢰성을 보장할 수 없다. 본 논문에서는 현재 자동차 분야에서 탑재 전자기기 신뢰도 예측에 폭넓게 활용중인 신뢰성 수명예측 상용도구인 Sherlock을 적용하여 큐브위성용으로 제작된 전자보드를 대상으로 발사 및 궤도환경에서의 고장 메커니즘 별 수명예측 및 임무기간동안의 신뢰도를 분석하였다.

• 항공우주시스템공학회지
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• 제17권6호
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• pp.108-117
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• 2023

지금까지 해외 수출용 KT-1 군용 고정익 항공기에 통합된 임무 소프트웨어는 해외업체와 국제 공동개발을 통하여 개발이 되었으며, 감항인증을 위해 DO-178B를 기반으로 하는 해외업체의 개발 환경과 절차를 준수함으로써 소프트웨어의 신뢰성을 인정받을 수 있었다. 하지만, 최근에는 해외 수출 시 DO-178C 인증을 요구하고 있으며, 국내 소요군에 납품 시 방사청 무기체계 소프트웨어 개발 및 관리 매뉴얼 준수를 위해 신뢰성 시험을 필수적으로 요구하고 있다. 본 논문은 기 개발된 KT-1 수출형 항공기 체계통합 사업의 국제 공동개발에 있어 국내 감항인증을 받기 위한 문제점을 기술하고 DO-178C와 무기체계 소프트웨어 개발 및 관리 매뉴얼을 모두 준수하기 위한 해결방안을 찾아서 최적의 소프트웨어 신뢰성 시험 방안을 제시한다.

• Journal of Astronomy and Space Sciences
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• 제15권2호
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• pp.459-473
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• 1998

인공위성이 더욱 복잡해 감에 따라 예측할 수 없는 실패의 발생은 설계의 부적당성, 경험 부족, 문제인식 부족, 빈약한 품질제어 능력, 부적당한 시험 또는 작업자의 실수 등 때문에 늘어나고 이들은 위성의 임무 수명을 단축시킬 수 있다. 본 고에서는 위성의 일반적인 실패유형과 임무수명 인자에 대해 검토하고, 지구 및 해양관측 임무를 갖고 있는 태양동기 저궤도위성인 다목적 실용위성에 대한 임무수명인자를 조사하고 실제 예상되는 위성의 임무수명을 예측하였다. 임무수명의 예측 시 랜덤하게 발생하는 실패에 의한 수명의 중단은 예측할 수 없는 것이기 때문에, 여기서는 주로 예측이 가능한 마모에 의한 대표적인 임무수명 인자 예를 들어, 전력 버짓, 추진제 버짓, 배터리 충 방전 사이클, 복사환경의 영향, 탑재체의 신뢰도, 단일 점 실패, 위성 여유 분을 등을 조사하고 개략적인 수명을 예측하였다.

• International Journal of Reliability and Applications
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• 제6권2호
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• pp.117-133
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• 2005

Estimations of the parameters included in a two-component system are derived based on masked system life test data, when the probability of masking depends upon the exact cause of system failure. Also estimations of reliability for the individual components at a specified mission time are derived. Maximum likelihood and Bayes methods are used to derive these estimators. The problem is explained on a series system consisting of two independent components each of which has a Pareto distributed lifetime. Further we present numerical studies using simulation.