• Journal of Power Electronics
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• v.5 no.4
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• pp.312-318
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• 2005

This paper presents a compensator for reduction of the reactive lateral current in multiple autonomously controlled uninterruptible power supplies (UPS) connected in parallel. This compensator acts directly on the control equation for voltage amplitude and it provides an improved current distribution especially in the case of parallel connection of UPSs with different output power ratings. Observations show that the original control equation for output voltage amplitude is efficient for voltage regulation but it causes great variation of voltage levels. A compensator with the same structure is added to counterbalance the variation caused by the original control equation. Simulations show promising results with the employment of the proposed compensator. Our simulations are confirmed by experimental results using three UPSs with different output ratings and voltage limiters ($1\%$) connected in parallel under various conditions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.77-80
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• 2017

One of the fundamental limits of Bluetooth Low Energy(BLE) is that the data transmission is available via singlehop connection. In this research, we suggested the stable multihop transmission method to overcome this limitation. In multihop connection situation, multiple singlehop connection should be made and disconnected dynamically. Therefore, we stored the data within the GATT layer and tried to send it dynamically. We divided whole process as 4 states, and let each nodes transfers around each states to make data connection safely. Also, we set the transfer policy between each states during the transmission to make a robust system. From the experiment in real-time environment, we proved that our method showed high rate of packet delivery in a multihop network, which consists of more than 3 nodes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3440-3446
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• 2015

One of technologies that make it possible for users to enjoy always-on Internet service using potable devices does be Wifi. However, users frequently feel its connection is not stable or its speed becomes slow. On the other hand, users see multiple available Wifi access points exist often. In this paper, we present a smartphone application, called to WiSMax, that periodically changes its Wifi connection to the best one among available Wifi access points to maximize its speed. Experimental results show that WiSMax presents faster Internet connection than IEEE802.11 as much as about fifteen percent and higher signal strength than IEEE802.11 as much as about five dBm.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.5
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• pp.67-77
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• 2022

Recently, the trend in structural analysis and design is moving towards the development of reliable system. The reliability-based method defines various limit states related to usability and failure, thereby enabling multiple levels of design according to the importance of a structure. Meanwhile, an actual structure is composed of a set of several elements, and particularly, a frame type is composed of a system in which the members are connected each other. At this time, the actual connection between members is in a semi-rigid condition, not in complete rigid or hinged. This semi-rigid is found in several structures, especially in agricultural facilities designed with lightweight materials. In this study, a system reliability analysis technique for frame structure was established, and applied to an analysis of the semi-rigid connection. Various conditions of correlation were applied to reflect the connectivity between members, and through this, the limitations of existing structural analysis method and the behavioral characteristics of structure were analyzed. The failure probability of the frame member component and the overall structure system was significantly different in consideration of the semi-rigid connection. In addition, it was evaluated that the behavior of structure can be more accurately analyzed if the correlation according to the position of members in a system is further investigated.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.395-397
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• 1999

디지털 카메라에 의해 획득된 RGB 칼라 신호는 디지털 카메라의 하드웨어적인 특성에 따라 서로 다른 값을 가지는 장비 의존적(Device Dependent) 특성을 가지며, 칼라 운영 시스템(CMS; Color Management System)이 프로파일 연결 칼라 공간(PCS:Profile Connection Space)으로 사용하는 CIE XYZ 칼라 공간에 대해 비선형적인 특성을 가진다. 본 논문에서는 디지털 카메라의 RGB 칼라 신호를 장비 독립적(Device Independent)인 CIE XYZ 칼라 공간으로 변환하는 변환 행렬을 구하는 방법을 제안한다. 변환 행렬은 비선형 다항식을 이용하여 3$\times$m의 변환 행렬을 구하고, 실험에 사용되는 칼라 샘플의 수에 따른 일반화(Generalization) 성능을 평가한다.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.273-276
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• 2004

Home networking is the collection of elements that process, manage, transport, and store information, enabling the connection and integration of multiple computing, control, monitoring, and communication devices in the home. In this paper, we review the state of the home networking technologies and analyse the trends of the patent information.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.261-264
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• 1999

This paper presents a circuit-level method to deal with transistor nonuniformity In this method, which is called transistor slicing, a transistor is implemented as a parallel connection of multiple smaller transistors. The paper analyzes the method and demonstrates that transistor slicing can effectively reduce the nonuniformity in TFT mobility and threshold voltage. The method is particularly useful in Implementing analog functions using poly-silicon TFTs which show a significant level of nonuniformity.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2705-2708
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• 2003

In this paper, we propose a method that applies matrix decomposition technique to the connection of actuator capabilities of each robot to object acceleration limits for multiple cooperative robot systems. The robot systems under consideration are composed of several robot manipulators and each robot contacts a single object to carry the object while satisfying the constraints described in kinematics as well as dynamics. By manipulating kinematic and dynamic equations of both robots and objects, we at first derive a matrix relating joint torques with object acceleration, manipulate the null space of the matrix, and then we decompose the matrix into three parts representing indeterminancy, connectivity, and redundancy. With the decomposed matrix we derive the boundaries of object accelerations from given joint actuators. To show the validity of the proposed method some examples are given in which the results can be expected by intuitive observation.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.256-259
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• 2007

Multicast and Broadcast Service (MBS) provides flexible and efficient transmission of the same information to multiple users using shared radio resources on WiBro network. The advantage of this service is to achieve the most efficient use of radio and network resources as well as to lessen sender's processing load when sending the same information to multiple users. Though radio resources are saved since a multicast or broadcast transport connection is associated with a service flow, it is hard to change MBS service channel dynamically. In this paper, we propose a Radio Resource Management System (RRMS) for supporting dynamic scheduling of MBS service channels. Results show that our proposed scheme using Radio Resource Allocation Table (RRAT) can efficiently support MBS services by providing dynamic schedule for MBS service channels.

• ETRI Journal
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• v.19 no.1
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• pp.13-25
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• 1997

In this paper, we propose a new queuing model, MMDP/MMDP/1/K, for an asynchronous transfer mode(ATM) multiplexer with multiple quality of service(QoS) variable bit rate (VBR) traffic in broadband-integrated services digital network (B-ISDN). We use the Markov Modulated Deterministic Process(MMDP) to approximate the actual arrival process and another MMDP for service process Using queuing analysis, we derive a formula for the cell loss probability of the ATM multiplexer in terms of the limiting probabilities of a Markov chain. The cell loss probability can be used for connection admission control in ATM multiplexer and the calculation of equivalent bandwidth for arrival traffic, The major advantages of this approach are simplicity in analysis, accuracy of analysis by comparison of simulation, and numerical stability.