• 경영과학
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• 제27권2호
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• pp.31-44
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• 2010

It is very important to forecast demand and determine the optimal procurement quantities of spare parts. The Army has been forecasting demand not with actual usage of spare parts but with request quantities. However, the Army could not purchase all of forecasted demand quantities due to budget limit. Thus, the procurement quantities depend on the item managers' intuition and their meetings. The system currently used contains many problems. This study suggests a new determination procedure; 1) forecasting demand method based on actual usage, 2) determining procurement method through LP model with budge and other constraints. The newly determined quantities of spare parts is verified in the simulation model, that represents the real operational and maintenance situation to measure the operational availability. The result shows that the new forecasting method with actual usage improves the operational availability. Also, the procurement determination with LP improves the operational availability as well.

• 경영과학
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• 제24권2호
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• pp.81-93
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• 2007

Achieving a target operational availability is more economical and efficient than having many quantities of the weapon system, since the cost of weapon system becomes expensive. The intent of this study is twofold; first, we develop the simulation model to determine the optimal inventory level of the maintenance float while achieving a target operational availability of the Korean-made helicopter. The quantity decision model considers following factors such as a reliability. a turn around time(TAT). a protection level for inventory, and so on. Second, we analyze whether the existence of a lateral transshipment among bases and the reduction of TAT relate to an inventory level and the operational availability. The research result shows that both TAT and lateral transshipment have an effect on reducing the inventory level of the maintenance float and improving an operational availability.

• Journal of Radiation Protection and Research
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• 제10권1호
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• pp.74-85
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• 1985

ICRU 보고서 39에서 새로이 정의된 의부방사선피폭에 의한 선량당량평가 목적의 네 가지 실용량에 대하여 그 도입의 배경과 기존량과의 관계, 그리고 방사선 방어 및 측정에서의 전망에 대하여 기술하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
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• pp.162-163
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• 2016

This paper presents a mathematical model for optimizing earthwork allocation plan that minimizes earthwork cost. The model takes into account operational constraints in the real-world earthwork such as material-type (i.e., quality level of material) and quantities excavated from cut-sections, required quality of material and quantities for each embankment layer, top-down cutting and bottom-up filling constraints, and allocation orders. These constraints are successfully handled by assuming the rock-earth material as the three dimensional (3D) blocks. The study is of value to project scheduler because the model identifies the optimal earth allocation plan (i.e., haul direction (cut and fill pairs), quantities of soil, type of material, and order of allocations) expeditiously and is developed as an automated system for usability. It is also relevant to estimator in that it computes more realistic earthworks costs estimation. The economic impact and validity of the mathematical model was confirmed by performing test cases.

• 품질경영학회지
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• 제27권2호
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• pp.251-262
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• 1999

In the automated manufacturing systems, the problem regarding how to make production activities flexible is even more important and critical than that regarding how to product large quantities, and the more flexible, if possible, the manufacturing system is, the more competitiveness and profitable factors it gets. This research, therefore, concentrated on establishing the flexibility and evaluating performance on the manufacturing system, operational flexibility is considered because of enabling the manufacturing system to get both the improvement of production rate and the adaptive ability of environment changes. For it, we used the analytical tool, GSPNs, which is a kind of timed Petri-Nets. GSPNs is competent enough to consider practical situations just like operation priorities, machine failure, randomness, concurrency and so on. Through the GSPNs analysis, it is confirmed that in the manufacturing system with operational flexibility is compatible with the traditional performances such as production rate or mean waiting time.

• International Journal of Reliability and Applications
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• 제14권2호
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• pp.55-70
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• 2013

This paper deals with the Bayesian analysis of the failure data of a repairable mechanical system subject to minimal repairs and periodic overhauls. The effect of overhauls on the reliability of the system is modeled by a proportional age reduction model and the failure process between two successive overhauls is assumed to be 2-parameter Engelhardt-Bain process (2-EBP). Power Law Process (PLP) model has a disadvantage which 2-EBP can overcome. On the basis of the observed data and of a number of suitable prior densities, point and interval estimation of model parameters, as well as quantities of relevant interest are found. Also hypothesis tests on the effectiveness of performed overhauls have been developed using Bayes factor. Sensitivity analysis of improvement parameter is carried out. Finally, a numerical application is used to illustrate the proposed method.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.3-6
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• 2005

In this thesis, We researched on the characteristics of optical tunable filter that selects the channel by the wavelength changes of transmission spectrum when we apply outer physical quantities on a fiber bragg grating by using Fabry-Perot Interformer's operational principle.

• Journal of Radiation Protection and Research
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• 제18권1호
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• pp.1-7
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• 1993

국제방사선방어위원회(ICRP)는 최근의 권고 60(1990)에서 이전의 권고 26(1976)에는 없었던 새로운 용어들을 도입하였다. 이중에서도 동 위원회는 지금까지 사용되어 왔던 국제 방사선단위 및 측정위원회(ICRU) 개념의 '션량당량(dose equivalent)'을 대체하는 용어로 '등가선량(equivalent dose)'을 새로 정의하여 방사선방어 프로그램에의 적용을 권고하고 있다. 그러나 한편 동 위원회는 선량 당량이라는 용어도 여전히 채택하고 있기 때문에 경우에 따라 두 양의 사용시 불필요한 혼동을 불러일으킬 수가 있다. 따라서 본 해설문에서는 방사선 방어, 관리 및 측정분야 종사자들의 이해를 돕기 위하여 두 양의 정의와 사용상의 차이점에 대하여 정리하였다.

• Wind and Structures
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• 제26권4호
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• pp.231-251
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• 2018

The objective of the investigation is the analysis of wind-tunnel experimental errors, associated with the measurement of aeroelastic coefficients of bridge decks (Scanlan flutter derivatives). A two-degree-of-freedom experimental apparatus is used for the measurement of flutter derivatives. A section model of a closed-box bridge deck is considered in this investigation. Identification is based on free-vibration aeroelastic tests and the Iterative Least Squares method. Experimental error investigation is carried out by repeating the measurements and acquisitions thirty times for each wind tunnel speed and configuration of the model. This operational procedure is proposed for analyzing the experimental variability of flutter derivatives. Several statistical quantities are examined; these quantities include the standard deviation and the empirical probability density function of the flutter derivatives at each wind speed. Moreover, the critical flutter speed of the setup is evaluated according to standard flutter theory by accounting for experimental variability. Since the probability distribution of flutter derivatives and critical flutter speed does not seem to obey a standard theoretical model, polynomial chaos expansion is proposed and used to represent the experimental variability.

• 한국과학교육학회지
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• 제21권1호
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• pp.76-88
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• 2001

본 연구는 길이, 질량, 시간, 온도와 같은 일부 기본 물리량에 대한 사람들의 어림의 정확성과 방법에 대해 탐색하였다. 대학 물리교육과의 구성원(학부 1학년부터 교수까지) 중 임의로 선정된 총 40명이 2종류의 대상물 세트에 대해 직관적 어림과 조작적 어림 활동을 수행하였다. 직관적 어림에서는 참여자들이 각 대상물을 직면하자마자 해당 물리량의 값을 어림하였으며, 조작적 어림에서는 별도의 대상물에 대해서 충분한 시간을 두고 다양한 가용한 방법들을 (예컨대, 길이를 어림하기 위해 연필을 활용하거나 시간을 어림하기 위해 맥박을 세거나) 동원하여 어림하였다. 연구의 결과는 다음과 같이 요약될 수 있겠다: (1) 길이, 질량, 온도에 대해서는 직관적 어림이 더 정확하였으나 시간에 대해서는 조작적 어림이 더 정확하였다. (2) 물리학에 대한 경험의 정도와 어림의 정확성 사이에는 정적인 상관관계가 존재하지 않았다. (3)일반적으로 길이에 대한 어림이 가장 정확하였으며 질량에 대한 어림은 가장 부정확하였다. (4) 사람들은 조작적 어림을 위해서 스스로의 다양한 방법을 사용하였는데, 예컨대 대상물 주변의 각종 사물들을 활용하거나 특정한 값을 갖는 마음 속의 측정 단위(즉, 30cm, 50cm, 1kg, 1근, 1초 등)들을 적용하였다.