• Korean Management Science Review
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• v.27 no.2
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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.

• Korean Management Science Review
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• v.24 no.2
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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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• v.10 no.1
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• pp.74-85
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• 1985

The four new operational quantities for the practical determination of dose equivalents from external radiation sources, defined in the ICRU report 39, are reviewed from the viewpoint of the underlying concept, the relationship to the existing quantities, and the expected role in the radiation protection practice and in the radiation measurements.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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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.

• Journal of Korean Society for Quality Management
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• v.27 no.2
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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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• v.14 no.2
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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.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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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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• v.18 no.1
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• pp.1-7
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• 1993

In its recent recommendation No. 60(1990), ICRP has newly introduced several terminology which had not existed in its prior recommendation No. 26(1977). Of these, a newly defined quantity 'Equivalent Dose' replacing the 'Dose Equivalent' of the ICRU concept has been recommended to be adopted in the radiation protection programme. However, since the committee still uses the 'Dose Equivalent' and 'Equivalent Dose' in its several publications, it is likely to provoke unnecessary confusions and misuses in applying these two quantities. In this paper were described the definition and difference between these two quantities to help in understanding of these two quantitites among the person involved in the radiation protection activities.

• Wind and Structures
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• v.26 no.4
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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.

• Journal of The Korean Association For Science Education
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• v.21 no.1
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• pp.76-88
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• 2001

This study explored people's accuracy and methods of estimating some base physical quantities, i.e. length, mass, time and temperature. A total of 40 members, ranging from freshmen to professors, of a physics education department of a local university were asked to make two different kinds of estimations, intuitive and operational, on two sets of objects. For intuitive estimation, they were asked to make estimations on four given objects (length - wood chopsticks, mass - rubber eraser, time electric fan, temperature - water in a cup) as soon as they faced with the objects, usually within a few seconds of seeing. For operational estimation, they were allowed to make estimations on a different set of objects (length - plastic rod, mass - lock, time - simple pendulum, temperature - water in a cup) with enough time and they could apply various available methods (e.g. using pencil to estimate the object's length, counting their own pulse rate to estimate time) for the estimation. The findings of this study can be summarized as follows: (1) for length, mass and temperature the intuitive estimations were better performed while for the time estimation the result was the reverse; (2) there was no positive relationship between the amount of physics experience and the accuracy of the estimation; (3) in general, people's accuracy of the length estimation was best performed while their mass estimation was worst performed; (4) people used their own various methods for estimation, esp. using nearby objects around them and applying mental units which have convenient values (e.g. 30cm, 50cm, 1kg, 1 Keun, 1 second).