• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.241-248
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• 2006

Mobile computing has such characteristics as portability, wireless network, mobility, etc. These characteristics cause various problems to mobile terminals like frequent disconnection, high error rate, and varying network status. These problems motivate us to develop an adaptive error control mechanism for supporting multimedia service in mobile computing environment. In this paper, we propose the Adaptive Error Control(AEC) scheme using client's buffer size and current error rate. After categorizing the status into four groups according to client's buffer size and current error rate, this scheme applies an appropriate error control scheme to each status. In this scheme, thresholds of buffer size and error rate are determined by the data transmission time, play rate and average VOP size, and by the probability of error for a sequence of packets. The performance of proposed scheme is evaluated by flaying MPEG-4 files on an experimental client/server environment, respectively. The results show that error correcting rate is similar to other schemes while the time for correcting error reduce a little. In addition, the size of data for correcting error is decreased by 23% compared with FEC and Hybrid FEC, respectively. Theses results demonstrate that the proposed scheme is more suitable in mobile computing environment with small bandwidth and varying environment than existing schemes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.8-14
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• 2005

Understanding of the flow past a bluff body close to a moving ground is very important in automobile and aeronautical fields because of aerodynamic characteristic and instability induced by unsteady vortex shedding. The passive control method that mounted the vertical and horizontal plates at the lower surface of the cylinder is studied to suppress the unsteady oscillation motion. When the grounds moves, the diminish of the shear layer on the ground promotes the interaction between the lower and the upper separated shear layers of the cylinder, hence vortex shedding occurs at the lower gap height than the stationary ground.

• JOURNAL OF ELECTRICAL WORLD
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• s.307
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• pp.68-73
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• 2002

감전보호$\cdot$누전화재보호로서 누전차단기가 일반적으로 사용되고 있는데 이 누전차단기가 누전으로 트립되었을 경우 (1) 누전트립이 재현되지 않는다. (2) 누설전류치가 고조파의 영향 때문에 측정이 곤란하다는 등의 이유로 원인조사가 어려운 경우가 많다. 그래서 누전차단기의 동작원인조사를 지원하는 기기로서 WS시리즈의 노퓨즈차단기 및 누전차단기에 각종 누설전류치의 액정표시유닛을 탑재한 $''$누설전류표시부 노퓨즈차단기$\cdot$누전차단기$''$를 제품화하였다. 이에 의하여 전로에 영상변류기(ZCT)와 계측기 등을 설치하지 않고 전로의 절연열화상태나 누전사고 상황을 간단하게 파악할 수가 있다. 또 액정표시유닛의 제어전원은 차단기 내부에 포함하고 있기 때문에 특별배선작업은 불필요하다. 이 제어전원은 차단기가 오프상태 또는 트립상태에서는 끊어지나 내부에 전기이중충 콘덴서를 내장하고 있기 때문에 각종 누설전류 정보를 표시할 수가 있다(정전보상시간 100시간). 주요특징은 다음과 같다. (1)각종 누설전류의 계측과 표시(현재치, 최대치, 이동평균치, 이동평균의 최대치, 각 최대치의 발생경과시간) (2) 누전경보의 설정 감도를 세분화하여 설정가능 또한 접점경보출력 표준탑재 (3) 누전트립 발생시의 누전사고전류치 및 누전사고 발생으로부터의 경과시간 표시(누전차단기만) (4) 미쓰비시전기 누전차단기의 액티브필터와 같은 특성의 필터를 내장하고 있으며 누전차단기의 동작특성에 맞는 누설전류치 표시가능 (5) 누전경보만으로 누전트립 동작을 하지 않는 누설전류표시부 노퓨즈차단기 라인업

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2715-2720
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• 2009

Supporting Quality of Service (QoS) for multimedia services in heterogeneous mobile networks is a part of key issue for Three Generation Evolution (3GE) development. A QoS management structure needs to guarantee the QoS of moving users based on an end-to-end negotiation to support the seamless service when MT is moving between the heterogeneous networks. We propose an end-to-end negotiation method based on SLA(Service Level Agreement). For this aim, the SLA control and algorithm for supporting MT's QoS is considered. Simulation is focused on the average delay and packet loss rate, and the results show that our proposed method provides mobile terminals with the optimal performance.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.7
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• pp.127-132
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• 2017

In this paper, we propose a controller gain based on model based design and implement the two-wheel inverted pendulum type robot using NXT Lego and RobotC language. Two-wheel inverted pendulum robot consists of NXT mindstorm, servo DC motor with encoder, gyro sensor, and accelerometer sensor. We measurement wheel angle using bulit-in encoder and calculate wheel angle speed using moving average method. Gyro measures body angular velocity and accelerometer measures body pitch angle. We calculate body angle with complementary filter using gyro and accelerometer sensor. The control gain is a weighted value for wheel angle, wheel angular velocity, body pitch angle, and body pich angular velocity, respectively. We experiment and observe the effect of two-wheel inverted pendulum with respect to change of control gains.

• Journal of Welding and Joining
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• v.16 no.3
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• pp.55-63
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• 1998

Among the position sensing methods available, the arc sensor which utilizes the electrical signal obtained from the welding arc itself is one of the most prevalently used methods, because it has an advantage that no particular sensing device is necessary and real-time sensing of a groove position is possible directly under the arc. The authors have already developed a seam tracking system that contains a new arc sensor algorithm, which uses the relative welding current variation according to the tip-to-workpiece distance in GMA welding. In this study a torch height control algorithm for automatic weld seam tracking was proposed for completing the previous system, which uses an on-off control technique. To implement the torch height control algorithm during weld seam tracking the system parameters which include 2nd averaging range, weighting factor for 2nd moving averaging, and Z-directional basic compensation distance were determined by experimental analysis. Finally the two different height control methods, one is simple on-off control and the other on-off control using a reference current value , were compared in their tracking abilities.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.755-761
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• 2017

In railways powered by AC power, the main circuit breaker (MCB) is used for supplying the electric power to the catenary of the vehicle. Generally, the main circuit breaker is located between the pantograph and the main transformer, and the phase of the power applied to the vehicle changes according to the operation timing of the main circuit breaker. The operation of the main circuit breaker should be actively controlled according to the phase of the power source, since the phase of the power causes unintended transient states in the vehicle's electrical system in the form of an inrush current and surge voltage. However, the MCB has a delay time when it operates which is not constant. Therefore, an intelligent controller is needed to predict the operation delay time and control the opening and closing of the MCB.

• Proceedings of the KAIS Fall Conference
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• 2008.11a
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• pp.290-293
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• 2008

본 논문은 이종의 이동통신 시스템에서 멀티미디어 서비스의 QoS를 보장하기 위한 D-ISHO(Degradation reason Intra-System Handover)를 다룬다. 이를 위하여 D-ISHO 시, QoS 보장하기 위한 제어 모듈을 제시한다. 이를 위하여, 각 모듈간의 상관 관계를 갖는 순서도를 기술하고, D-ISHO 시나리오가 고려된다. 시뮬레이션을 위하여 평균 지연과 패킷 손실율을 평가한다. 제안된 QGRM(QoS Guaranteed Resource Management)를 적용한 시스템이 각각의 서로 다른 이동통신 망보다 더 좋은 성능을 보인다.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.118-121
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• 2018

끊김 없는 이동성은 멀티미디어가 풍부한 실시간 서비스를 지원하는 미래의 무선 네트워크에서 필수적이다. SDN (Software Defined Networking)은 중앙 집중식 컨트롤러를 통해 무선 네트워크에서 세밀한 플로우 수준의 이동성 관리를 제공할 수 있지만 핸드오버 지연의 새로운 네트워킹 패러다임이다. 스플릿 포인트 방식은 SDN 무선 네트워크에서 핸드오버 및 종단 간 전송 지연을 줄이는 효과적인 방법이다. 스플릿 포인트는 트래픽이 새로운 AP (Access Point)를 향하여 핸드오버 한 후에 기존 플로우 경로상에 존재하는 스위치이다. 본 논문에서는 MN-CN (Corresponding Node) 경로의 각 스위치의 가중치를 스위치와 후보 AP 사이의 평균 고리(홉)로 계산하고 최소 가중치를 갖는 스위치가 스플릿 포인트로 선택된다. 스플릿 포인트 선택 외에도 이 논문은 SDN 에서 제공하는 제어 및 데이터 플레인 분리를 이용하여 핸드오버 후 플로우에 대한 최적의 경로를 복원한다. 제안 아이디어의 수치 해석은 이전 솔루션과 비교하여 총 비용이 9.6 % ~ 13 % 향상되었음을 보여준다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.92-96
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• 2004

In this paper, polishing method using bonded magnetic abrasive particle has been applied to the micro mold polishing. Through process control using the Run-to-Run control, it tried to form the surface roughness In order to grasp the influence of the surface roughness which is reached by selection of control factor and the factor, a design of experiment was been processed. The study is processed with a purpose of to embody and to maintain the surface roughness of nano scale by the basis of an influence between a control factor and the factors which has been selected in this way. As a result, the result of the process control converged at a target value of surface roughness Ra 10nm and Rmax 50nm