• Journal of the Korea Institute of Information Security & Cryptology
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• v.9 no.2
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• pp.25-36
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• 1999

In this paper we propose a one-time password mechanism that solves the problems of the S/KEY: the limitation of a usage and the need of storage for keys. because of using a cryptographic algorithm the proposed mechanism has no the limitation of a usage. Also because of producing the key for an authentication from a user's password it is easy to manage the authentication key and is possible to share the session key between a client and a server after the authentication process. In addition the proposed mechanism is easy to protect and manage the authentication information because of using a smart card and is adopted by the system that needs a noe-way authentication from a client to a server without the challenge of a server.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.911-912
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• 2013

• Journal of Applied Reliability
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• v.2 no.2
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• pp.85-97
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• 2002

In this paper, partially repairable concurrent spare parts requirement determination problem of newly procured equipment systems is considered. “partially repairable” means that a portion of damaged parts can be recover their function and reused after repairs. A mathematical model is derived for making an CSP requirement determination subject to the constraint of satisfying any given operational availability limitation. We assume that the failure of a part follows a Poisson process and the repair time has an exponential distribution. Using the generalized Lagrange multipliers method, the solution procedure is derived.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.5
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• pp.264-268
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• 2000

In discuss how the existing study results that decide optimum release time are rational and reasonable, considering the cost and reliability simultaneously in this paper. As a study method this paper examines the proposed results and their methodologies centering around the existing related papers for the general cost-reliability optimal release policies, especially their limitation for the derived results.

• The Journal of Information Systems
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• v.7 no.1
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• pp.55-76
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• 1998

Various trials to overcome the limitation of current accounting which fails in synchronizing business activities and their information have failed to make satisfactory result merely showing a little saving of processing time. This is because such trials have been done within the boundary of double-entry bookkeeping system. Without consolidating business activities and their information, reformation efforts such as BPR(business process re-engineering), ABC(activity-based costing), CALS(commerce at light speed) etc to fit the business organization to the changing business environment could not be achieved. Overcoming the limitation of accounting takes precedence of any other attempt to construct the management information systems. Activity Information Accounting System(AIAS) proposes the way of overcoming the limitation of current accounting by using the new accounting methodology and unique solution to real time accounting information. AIAS produces accounting and management information directly of activity information without bookkeeping process of activity information. AIAS adopts method of transforming the details of corporation activities directly into accounting information rather than method of double-entry bookkeeping system. The purpose of this paper is to prove AIAS to be very flexible system by using flexibility concepts. Flexibilities are defined as three aspects, namely ① timeliness (rapid accounting information generations and presentations) ② easy systems modificabilities according to environment changes ③ adaptabilities to all industries.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.59
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• pp.53-67
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• 2000

In this paper we consider the CSP requirements determination problem of new equipment(machine) system. For the newly procured equipment systems, mathematical analyses are made for the system which is constructed with the consumable parts and the repairable parts to derive the associated CSP requirement determination model in mathematical expression. Based on these analyses, a mathematical model Is derived for making an optimal CSP requirement determination subject to the constraint of satisfying any given operational availability limitation. We assume that the failure of a part follows a Poisson process and the repair time has an exponential distribution. Firstly, the operational availability concept in CSP is defined and the relation between the general system availability and the operational availability is established. Secondly, the problem is formulated as the cost minimization problem that should satisfy the operational availability limitation, and then, using the generalized Lagrange multipliers method, the optimal solution procedure Is derived.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2284-2293
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• 2016

With the rapid development of clean energy, photovoltaic (PV) generation has been utilized in the harmonic compensation of power systems. This paper presents a novel multi-function PV micro-inverter with three stages (pseudo-two-stage). It can inject active power and compensate harmonic currents in the power grid at the same time. In order to keep the micro-inverter working under the maximum allowable output power, an optimized capacity limitation strategy is presented. Moreover, the harmonic compensation can be adjusted according to the customized requirements of power quality. Additionally, a phase shedding strategy in the DC/DC stage is introduced to improve the efficiency of parallel Boost converters in a wide range. Compared with existing capacity limitation methods, the proposed strategy shows better performance and energy efficiency. Simulations and experiments verify the feasibility of the micro-inverter and the effectiveness of the strategy.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.13 no.4
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• pp.324-335
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• 2013

This article presents the design, control, and implementation of a small quad-rotor system under the practical limitation of being cost effective for private use, such as in the cases of control education or hobbies involving radio-controlled systems. Several practical problems associated with implementing a small quad-rotor system had to be taken into account to satisfy this cost constraint. First, the size was reduced to attain better maneuverability. Second, the main control hardware was limited to an 8-bit processor such as an AVR to reduce cost. Third, the algorithms related to the control and sensing tasks were optimized to be within the computational capabilities of the available processor within one sampling time. A small quad-rotor system was ultimately implemented after satisfying all of the above practical limitations. Experimental studies were conducted to confirm the control performance and the operational abilities of the system.

• Journal of the military operations research society of Korea
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• v.36 no.2
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• pp.11-24
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• 2010

Quick precision-strike capability of the artillery will be an important factor in modern and future war and it's represented by NCW and EBO. This study is based on artillery which has time limitation of firing, such as artillery which hides when not firing, and modeling various situations to decide firing order and who to shoot. The main purpose of this study is to suggest a mathematical programming model and a genetic algorithm which satisfies the limitation of firing time. The objective function is to minimize the total firing time to spend. The results of the suggested algorithm quickly gives a best solution for a large scale field artillery targeting problems.

• Journal of the military operations research society of Korea
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• v.24 no.1
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• pp.41-57
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• 1998

Since the aircraft has a property of moving in the three-dimensional space, it may cause personally and financially critical damage in the case of an accident. Among the causes of aircraft accident, human factor has occupied about 70% of all accidents. Specially, fatigue among human's problems has been studied earlier than any other factor. Fatigue has been the cause of 75% of accidents that are related to human factor. So many studies have been conducted. But the direction of these studies mainly attach importance to the sleep loss and circadian rhythm. Limitation for flight time of ICAO is 8 hours per day, civil airlines in domestic line also adopt the limitation. But this rule is not based on human's performance but compromise between labor and management. The long-haul flight brings about a mental block to pilot. This mental block decreases performance of pilot and loses a lot of important information. So this may cause many accidents. This paper is to offer optimal flight time according to the amount of fatigue due to increasing flight time. The optimal flight time is searched through the field experiment. The experiment has adopted two methods. One is to examine pilot's objective fatigue accumulation rate through the critical fusion frequency, and another is to investigate pilot's subjective fatigue feeling through the fatigue subjective symptoms investigation table.