• Journal of information and communication convergence engineering
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• 제15권2호
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• pp.97-103
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• 2017

Implementation of faster pairing calculation is the basis of efficient pairing-based cryptographic protocol implementation. Generally, pairing is a costly operation carried out over the extension field of degree $k{\geq}12$. But the twist property of the pairing friendly curve allows us to calculate pairing over the sub-field twisted curve, where the extension degree becomes k/d and twist degree d = 2, 3, 4, 6. The calculation cost is reduced substantially by twisting but it makes the discrete logarithm problem easier if the curve parameters are not carefully chosen. Therefore, this paper considers the most recent parameters setting presented by Barbulescu and Duquesne [1] for pairing-based cryptography; that are secure enough for 128-bit security level; to explicitly show the quartic twist (d = 4) and sextic twist (d = 6) mapping between the isomorphic rational point groups for KSS (Kachisa-Schaefer-Scott) curve of embedding degree k = 16 and k = 18, receptively. This paper also evaluates the performance enhancement of the obtained twisted mapping by comparing the elliptic curve scalar multiplications.

• 한국환경과학회지
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• 제16권5호
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• pp.561-569
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• 2007

This study used SCS-CN method to estimate the real recharge of the study area which is one of the most reasonable techniques to estimate groundwater recharge when there is no available runoff data in a watershed. From the results of tile real recharge analysis for the study area using SCS-CN method, it was analyzed that the year 1994 when the drought was severe shotted the lowest recharge of 106.3mm with recharge rate of 12.4%, and the highest recharge of 285.6mm with recharge rate of 21.8% occurred in 1990. Yearly average recharge of 213.2mm was obtained, and tile average recharge rate was 16.9%/year. KOG-FLOW model which has powerful post process functions consists of setting environments for input parameters in Korean language, and help function is added to each input data. Detailed information for each parameter is displayed when the icon is placed on the input parameters, and geologic boundaries or initial head data for each layer can be set easily on work sheet. The relative errors (R. E.) for each model's observed values and calculated values are $0.156{\sim}0.432$ in case of KOG-FLOW, and $0.451{\sim}1.175$ in case of WINFLOW, therefore it is known that KOG-FLOW model developed in this study produced results compared to observed head values.

• 전자공학회논문지SC
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• 제42권3호
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• pp.11-16
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• 2005

본 논문에서는 루프 형성 기법을 이용한 새로운 IMC-PID 제어기 설계 방법을 제안하였다. 내부 안정성이 보장되고 동조 파라미터가 1개 뿐 인 IMC-PID 제어기의 동조 규칙에 루프 형성 기법을 적용함으로 이득 여유, 위상 여유, 감도함수 등의 설계 사양을 고려할 뿐 아니라 이러한 설계 사양과 설계 파라미터 사이의 관계를 유도하여 루프 이득을 얻을 수 있게 되었다. 원하는 설계 사양을 만족 시키도록 IMC-PID 제어기의 설계 파라미터 값을 선정하는 조직적 방법을 제시하고 그 유용성을 사례 연구와 분석을 통해 검토했다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.453-460
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• 2000

A test rig is developed for performance test of 1 stage axial-type turbine which is designed by meanline analysis, streamline curvature method, and blade design method using configuration parameters. The purpose of this study is to find the best configuration parameters for designing a high efficiency axial-type turbine blade. To measure the efficiency of turbine stage, a dynamo-meter is installed. Two different stators which are manufactured as an integrated type are developed, and a rotor blade and 5 sets disc are developed for setting different stagger angle. The tip and hub diameters of the test turbine are 300 and 206.4mm, respectively. The rotating speed is 1800RPM, and the extracted power is 2.5kW. Flow coefficient is 1.68 and the reaction factor at meanline is 0.373. The number of stator and rotor of test turbine are 31 and 41, respectively. The Mach number of stator exit flow near hub is 0.164.

• 한국CDE학회논문집
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• 제4권4호
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• pp.327-338
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• 1999

In this paper, we propose the framework of an integrated design system as a CAD system of a new concept that can incorporate the design information. Current CAD systems are powerful in representing the shape of a product with solid models but cannot provide the design information that is used or created in designing the product. Therefore an integrated design system is proposed to enable the storage and usage of the design information in addition to the shape manipulation. In order to represent the design information, we define element object that represents design element such as a part, a sub-assembly or an assembly by using object-oriented methodology. The element object carries various design information such as design parameters, documents, catalogues, functions, and behaviors as well as shapes. By using the stored information, the system can provide a designer with some functions to assist design activity such as interrogating necessary information, setting design parameters and goals, and constructing constraints among design elements. A mailing system is also constructed among element objects to assist a collaborative design. In addition, an evolutionary design method using genetic algorithms is realized within the proposed framework.

• 한국분무공학회지
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• 제15권4호
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• pp.177-181
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• 2010

This paper has designed a mixing enhancement apparatus called Lobed-plate and Step-plate and comparatively calculated desulfurization efficiency of when its shape was changed. The parameters used at this time were the shape, SR ratio and the number of nozzles of the mixing enhancement apparatus and comparatively analyzed desulfurization efficiency according to these parameters. As a result, the Step-plate appeared as more highly by around 4% than Lobed-plate in desulfurization efficiency according to the shape of the mixing promotion apparatus, and when the desulfurization efficiency as a SR ratio is considered, it appeared highly by an average of 5% when the SR ratio is 3 rather than 2. As a result of comparing desulfurization efficiency by fixing the SR ratio and setting the number of nozzles as 4 pieces and 6 pieces, there was no big change in desulfurization efficiency when the SR ratio is 2, but it could be confirmed to improve by around 5% when the SR ratio is 3 when time passed 8 seconds.

• 설비공학논문집
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• 제8권3호
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• pp.386-396
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• 1996

The dynamic characteristics of a condenser are numerically studied for the control of air-conditioning systems. The important factors, such as the refrigerant flow rate and refrigerant temperature, air velocity and air temperature at the condenser inlet, are incorporated into the analysis. This study was focused on the analysis of dynamic responses by transfer function method in the condenser. Block diagrams were made through analytic transfer function, and dynamic responses are evaluated on Bode diagrams in the frequency response. These results may be used for determining an optimum design parameters in an actual component and total systems. Also, the mathematical models, frequency response and steady state response may be used to increase understanding, to obtain useful information for its commercialization, to evaluate the hardware and the optimum design parameters, the design control system and to determine the best controller setting for the refrigeration and air conditioning systems.

• Journal of Electrical Engineering and Technology
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• 제7권1호
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• pp.109-114
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• 2012

In this paper, we utilize training strategy of hidden Markov model (HMM) to use in versatile issues such as classification of time-series sequential data such as electric transient disturbance problem in power system. For this, an automatic means of optimizing HMMs would be highly desirable, but it raises important issues: model interpretation and complexity control. With this in mind, we explore the possibility of using genetic algorithm (GA) and harmony search (HS) algorithm for optimizing the HMM. GA is flexible to allow incorporating other methods, such as Baum-Welch, within their cycle. Furthermore, operators that alter the structure of HMMs can be designed to simple structures. HS algorithm with parameter-setting free technique is proper for optimizing the parameters of HMM. HS algorithm is flexible so as to allow the elimination of requiring tedious parameter assigning efforts. In this paper, a sequential data analysis simulation is illustrated, and the optimized-HMMs are evaluated. The optimized HMM was capable of classifying a sequential data set for testing compared with the normal HMM.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권6호
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• pp.2838-2858
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• 2019

Traditional channel models for vehicle-to-vehicle (V2V) communication usually assume fixed velocity in static scattering environment. In the realistic scenarios, however, time-variant velocity for V2V results in non-stationary statistical properties of wireless channels. Dynamic scatterers with random velocities and directions have been always utilized to depict the non-stationary statistical properties of the channel. In this paper, a non-stationary geometry-based cooperative scattering channel model is proposed for multiple-input multiple-output (MIMO) V2V communication systems, where a birth-death process is used to capture the appearance and disappearance dynamic properties of moving scatterers that reflect the time-variant time correlation and Doppler spectrum characteristics. Moreover, our model has more straight and concise to study the impact of the vehicular traffic density on channel characteristics and thus avoid complicated procedure in deriving the analytical expressions of the channel parameters and functions. The numerical results validate our analysis and demonstrate that setting important parameters of our model can appropriately build up more purposeful measurement campaigns in the future.

• 한국시뮬레이션학회논문지
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• 제31권1호
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• pp.19-27
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• 2022

본 연구는 하나의 공급자와 하나의 소매자가 구성된 분산화된 공급사슬에서 도매가 계약과 수익공유 계약, 수량유연 계약, 판매환급 계약을 비교·분석한다. 선행 연구의 결과에 따라 공급사슬 조정(coordination)이 이루어지는 각 조정 계약의 모수를 설정하였다. 이들 모수의 조합에 대해 @RISK를 활용하여 시뮬레이션을 수행하고 공급사슬 조정을 이루는 상태 하에서 계약의 성사율과 각 계약에 유리한 참여자를 평가한다. 결과적으로 수량 유연 계약은 소매자 쪽에 가장 유리하고 판매환급 계약은 공급자 쪽에 가장 유리하다. 수익공유 계약은 공급자와 소매자의 이익 재배분에 가장 넓은 범위에서 선택할 수 있어 더 유연하게 사용할 수 있음을 밝혔다.