• 전기의세계
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• 제29권3호
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• pp.179-184
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• 1980

This paper presents in some detail a discussion of the design of the digital control system without nonlinear elements to exhibit deadbeat performance in response to step inputs. The transfer function of digital dontroller is obtained by calculating the sequence of inputs and outputs of the digital controller for deadbeat performance. Digital controllers are designed for unity feedback multivariable systems by this method, which is well adapted for obtaining a solution by a digital computer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.900-902
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• 1997

Stabilization of Power systems is investigated using a proportional-integral power system stabilizer(PI PSS). Time division PI PSS is examined in this paper. Two approaches are presented for determining the optimal stabilizer gains of the proposed PI PSS. Simulation results show that the proposed PI PSS yields better system dynamic performance and stability than the sub-optimal stabilizer in the sense of having greater damping in response to a step disturbance.

• 한국철도학회논문집
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• 제2권4호
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• pp.32-39
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• 1999

A flywheel system which can compensate electric power is presented. The designed system has a capability of providing real and imaginary power instantaneously as well as storing energy. In this paper, a control algorithm is designed. The designed algorithm is to control the secondary side current of the wound rotor induction motor using voltage-based PWM inverter. The flywheel system has advantages in converter size and power quality improvement comparing to the conventional system.

• 대한전기학회논문지
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• 제43권3호
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• pp.485-492
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• 1994

Trajectory tracking control porblems are described for a two-link robot manipulator with artificial rubber muscle actuators. Under the assumption that the so-called independent joint control is applied to the control system, the dynamic model for each link is identified as a linear second-order system with time-lag by the step response. Two control laws such as the feedforward and the computed torque control methods, are experimentally applied for controlling the circular trajectory of an actual robot mainpulator.

• 전기의세계
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• 제17권1호
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• pp.11-20
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• 1968

A typical type-1 positioning servomechanism is theoretically analyzed as a multirate sampled-data system which contains two or more signals sampled at different rates by the Z-transform method. And also it is analyzed as a continuous system by using the Younsei 101 Electronic Analog Computer. Comparing the solution of the multirate sampled data system with that of the continuous system to a step input, it is concluded that the response time of the output of the multirate sampled-data system is reduced by a multirate controller, the ripple between samples is lessened and all the transients are diminished within one period.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1744-1746
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• 2003

This paper represents the development of national standard (NS) for lightning impulse (LI) voltage measuring system rated 400 kV. A traceability of the NS to the international standard could be achieved by the intercomparison test with Helsinki University. According to the IEC 60060-2, a measurement uncertainty was assessed. As a result of the tests, a measurement uncertainty and step response characteristics were satisfied with the requisite for NS.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1492-1493
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• 2007

This paper represents the development of national standard(NS) for switching impulse(SI) voltage measuring system rated 500 kV. A traceability of the NS to the international standard could be achieved by the intercomparison test with PTB(Physikalisch-Technische Bundesansalt). According to the IEC 60060-2, a measurement uncertainty was assessed. As a result of the tests, the measurement uncertainty and the characteristics of step response were satisfied with the requisite for NS.

• 융합보안논문지
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• 제12권1호
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• pp.17-25
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• 2012

SQL Injection 기법은 공개된지 수년이 지났지만 웹해킹 공격중 가장 위험한 공격으로 분류되어 있다. 웹 프로그래밍은 자료의 효율적인 저장 및 검색을 위해 DBMS를 필수적으로 사용하고 있다. 주로 PHP,JSP,ASP 등의 스크립트 언어를 이용하여 DBMS와 연동한다. 이러한 웹 어플리케이션에서 클라이언트의 잘못된 입력값을 검증하지 않으므로 비정상적인 SQL 쿼리가 발생할 수 있다. 이러한 비정상적 쿼리는 사용자 인증을 우회하거나 데이터베이스에 저장된 데이터를 노출시킬 수 있다. 공격자는 SQL Injection 취약점을 이용하여 아이디와 암호를 몰라도 웹기반 인증을 통과할 수 있고 데이터베이스에 저장된 데이터를 열람해 볼 수 있다. SQL Injection에 대한 대책으로 다수의 방법이 발표되었다. 그러나 어느 한 가지 방법에 의존할 경우 많은 보안 공백이 발생할 수 있다. 단계적 대응모델은 사고 예방적 측면에서 소스코드 작성 단계, 서버 운용단계, 데이터베이스 핸드링 단계, 사용자 입력값 검증 활용 단계 등 대책을 프레임워크로 구성하여 적용하는 방법이다. 이 대응모델 을 적용할 경우 운용과정을 통해 존재하는 SQL Injection의 공격가능성을 보다 효과적으로 차단이 가능하다.

• 유통과학연구
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• 제16권4호
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• pp.67-74
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• 2018

Purpose - Most of the amendments to the law on the improvement of the distribution structure of mobile communication terminal equipment, the fully self-sufficient system of terminals, and the separated disclosure system on the terminals are aimed at securing transparency of the distribution structure by eliminating or reducing handset subsidies. This study investigates what items are important for the purchase of mobile phones in various and rapidly changing mobile phone markets from the consumer's point of view and tries to make a strategic suggestion for future mobile distribution strategies. Research design, data, and methodology - The procedure of this study takes place in four steps. In step 1, only the SF type respondents selected for this study were extracted through MBTI analysis. In step 2, they were divided into three hierarchies for the AHP analysis and each element was arranged. In step 3, the AHP analysis was converted to a Fuzzy-AHP number using the trigonometric centroid method. This was to eliminate the ambiguity of the response by converting into a fuzzy number even if data consistency was maintained with CI value below 0.1. In step 4, the number of converted 2-layer and 3-layer was combined to derive the priority when the final handset is selected. Results - First, the highest importance among the four items in the second tier was the terminal function item, followed by brand, price, and design item. Second, in the third tier, the highest importance was level of after-sales service, followed by device price, processing speed, ease of use, usefulness, and rate system. Third, the arithmetic average of the determinant of the fuzzy function showed that processing speed, ease of use and usefulness in the function item, level of after-sales service in the brand item, and device price in the price item were the five most important factors among 16 choice factors. Conclusions - First, there will be a change in the consumption patterns of consumers who have compared distributors and dealers to purchase handsets with more subsidies. Second, it is highly likely that people will purchase new handsets only when they need to change their devices because they can not receive subsidies by switching phone brands any more.

• 전산구조공학
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• 제8권2호
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• pp.153-161
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• 1995

세계적으로 대공간 구조물의 건설은 점점 늘어나고 있으며, 이러한 증가 추세와 함께 붕괴 사고 또한 점차 늘어나고 있다. 보다 안전하고 경제적인 구조물의 구축을 위해서는 사고 및 붕괴의 원인이 정확히 규명되어야 한다. 따라서 이러한 규명을 위하여 대공간 구조물의 붕괴 메커니즘의 정확한 규명이 필요하며, 많은 연구자들에 의한 연구가 보고되고 있다. Step 하중 하에서의 동적 파괴 메커니즘은 비교적 많은 연구가 진행되어 왔으나, 주기성을 가진 동적 외력에 의한 파괴 메커니즘에 관한 연구는 거의 없는 실정이며, Step 하중하에서의 메커니즘과는 매우 다르리라 예상된다. 본 연구는 주기성을 가진 동적 외력에 의한 얕은 EP 쉘(Elliptic Paraboloidal Shell)의 동적 불안정 현상을 Fourier 스펙트럼을 이용하여 분석한다. 즉 1 자유도의 얕은 EP 쉘의 동적 좌굴 현상과 파라메트릭 공진 현상과의 상호 작용을 파악하기 위하여 비선형 응답의 연속 스펙트럼(runing spectrum)을 이용한다. 연구 결과, 동적 불안정 현상은 외력의 성질에 따라 크게 다른 메커니즘을 나타내는 것을 알 수 있다.