• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.181-183
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• 2003

본 연구에서는 현재 국내-외 논문을 참조하여 배전계통에 적용된 조류계산 알고리즘의 적용사례를 조사하였다. 배전계통에 적용된 조류계산알고리즘은 Power Summation Method와 Current Summation Method가 있다. 배전계통은 선로의 구조가 거의 대부분 방사상으로 성되어 있기 때문에 Newton Raphson, Gauss Seidel, Fast Decoupled 방법을 그대로 사용하기는 문제가 있다. 그래서 DistFlow, Forward/Backward sweeping 법 등이 주로 사용되어 왔다. 그러나 미래의 계통은 현재와는 또 다른 Topology로 방사상과 루프가 혼합된 형태로 다르게 구성되어야 할 것이다. 이러한 상황에서 미래의 배전계통에 대하여 적용 가능한 알고리즘을 전망하고져 한다.

• Journal of information and communication convergence engineering
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• v.11 no.1
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• pp.45-49
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• 2013

A compact radio frequency (RF) bandpass filter (BPF) in low temperature co-fired ceramic (LTCC) is suggested for WiMAX applications. The center frequency ($f_0$) of the BPF is 5.5 GHz and its pass band or 3-dB bandwidth is 700 MHz to cover all the three major bands, low and middle unlicensed national information infrastructure (U-NII; 5.15-5.35 GHz), World Radiocommunication Conference (5.47-5.725 GHz), and upper U-NII/industrial, scientific, and medical (ISM) (5.725-5.85 GHz), for the WiMAX frequency band. A lumped circuit element design-the 5th order capacitively coupled Chebyshev BPF topology-is adopted. In order to design a compact RF BPF, a very thin ($43.18{\mu}m$) ceramic layer is used in LTCC substrate. An interdigital BPF is also designed in silicon substrate to compare the size and performance of the lumped circuit element BPF. Due to the high relative dielectric constant (${\varepsilon}_r$ = 11.9) of the silicon substrate, the quarter-wavelength resonator of the interdigital BPF can be reduced. In comparison to the 5th order interdigital BPF at $f_0$ = 5.5 GHz, the lumped element design is 24% smaller in volume and has 17 and 7 dB better attenuation characteristics at $f_0{\pm}0.75$ GHz.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.205-208
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• 2008

Generally, there are several types in rear suspension. The rear suspension of subframe type consisting of side member and front/rear cross member is widely used in a medium car and full car. In the small car case, the beam of tubular type without independent suspension system is used to reduce manufacturing cost. The optimized rear suspension of subframe type using hydroforming method has been developed in this study. In designing suspension, the driving stability and durability performance should be considered as an important factor. The stability is related to dynamic frequency and durability is connected with stress analysis of structure. We focus on increasing the stiffness of suspension and decreasing the maximum stress relating to durability cycle life. For making use of the merits of hydroforming which is possible to make the bead, tube expansion, and feeding in desiring position, several optimization design techniques such as shape, size, and topology optimization are proposed. This optimization scheme based on the sensitivity can provide distinguished performance improvement in using hydroforming. Through commercial software based on the finite element, the superiority of this design method is demonstrated.

• Journal of Power Electronics
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• v.19 no.1
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• pp.254-264
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• 2019

This paper proposes an indirect current control technique based on a proportional resonant (PR) approach for the seamless mode transfer of utility interactive inverters. Direct-current and voltage hybrid control methods have been used for inverter control under grid-connected and islanded modes. A large bandwidth can be selected due to the structure of single-loop control. However, this results in poor dynamic transients due to sudden changes of the controller during mode changes. Therefore, inverter control based on indirect current is proposed to improve the dynamic transients by consistently controlling the output voltage under all of the operation modes. A PR-based indirect current control topology is used in this study to maintain the load voltage quality under all of the modes. The design processes of the PR-based triple loop are analyzed in detail while considering the system stability and dynamic transients. The mode transfer techniques are described in detail for both sudden unintentional islanding and islanded mode voltage quality improvements. In addition, they are described using the proposed indirect control structure. The proposed method is verified by the PSiM simulations and laboratory-scale VDER-HILS experiments.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1388-1391
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• 2010

In this paper, we present a design and implementation of U-learning system using pen based augmented reality approach. Student has been given a smart pen and a smart study book, which is similar to the printed material already serviced. However, we print the study book using CMY inks, and embed perceptually invisible dot patterns using K ink. Smart pen includes (1) IR LED for illumination, IR pass filter for extracting the dot patterns, and (3) camera for image captures. From the image sequences, we perform topology analysis which determines the topological distance between dot pixels, and perform error correction decoding using four position symbols and five CRC symbols. When a student touches a smart study books with our smart pen, we show him/her multimedia (visual/audio) information which is exactly related with the selected region. Our scheme can embed 16 bit information, which is more than 200% larger than previous scheme, which supports 7 bits or 8 bits information.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.547-548
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• 2009

The development of USN(Ubiquitous Sensor Network) technology is creating numerous application areas. Although a network configuration with fixed sensors was the norm in the past, the coexistence of mobile and fixed sensor nodes is a new trend. Fixed sensor networks focused on the energy efficiency of nodes, but the latest studies consider guaranteeing the mobility of nodes and maintaining their connectivity, while remaining energy efficient at the same time. This paper proposes a routing protocol for a mobile ad-hoc sensor network that improves the mobility, connectivity and energy efficiency of nodes while allowing for the management and maintenance of a large number of nodes even in a complex communication environment where mobile and fixed nodes coexist. An algorithm for multi-hop multi-paths, a technique for topology reconfiguration by node movement prediction and vibration sensors, path setting for a large number of nodes, and efficient data transfer technology have been introduced to implement the modified LEAHC-AOMDV protocol. Furthermore, the excellence of this protocol was verified through a comparative experiment with the conventional LEACH protocol.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.05a
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• pp.374-376
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• 2023

최근 환율 예측에 관한 다양한 연구가 진행되어 왔다. 이러한 추세에 대응하여 본 연구에서는 Pearson 상관 계수 및 상호 정보를 사용하여 외환 시장의 환율 변동을 분석하는 다중 연결 네트워크를 구축하였다. 본 연구에서는 이러한 구성된 환율 변화에 대한 시공간 의존성 네트워크를 만들고 그래프 기계 학습의 잠재력을 조사하여 예측 정확도를 향상시키려고 노력하였다. 본 연구 결과는 선형 및 비선형 종속 네트워크 모두에 대해 그래프 신경망을 활용한 임베딩을 활용하여 기존의 기계 학습 알고리즘과 결합시킬 경우 환율 변화의 예측력이 향상될 수 있음을 경험적으로 확인하였다. 특히, 이러한 결과는 통화 간 상호 의존성에만 의존하여 추가 데이터 없이 달성되었다. 이 접근 방식은 데이터 효율성을 강화하고 그래프 시각화를 통해 설명력 있는 통찰력을 제공하며 주어진 데이터 세트 내에서 효과적인 데이터를 생성하여 예측력을 높이는 결과로 해석할 수 있다.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.149-152
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• 2007

본 논문에서는 대규모 네트워크 상에서 발생되는 시뮬레이션 결과를 효과적으로 보여주기 위한 Visualization Tool 을 제안한다. 복잡하고 다양한 시뮬레이션 결과를 얻기 위해, 생태계 모방형 플랫폼을 이용한 Bio-IDS (Intrusion Detection System) 시뮬레이터의 실험 데이터를 이용하였다. 대규모 네트워크를 모두 보이기에는 화면이 너무 작기 때문에, Visualization Tool 은 화면의 확대 및 축소를 위한 Zoom In/Out 기능, 화면의 Panning 을 위한 Scroll Bar 및 현재 영역의 위치를 알려주는 Mini Map 이 필요하였다. 또한, 사용자가 쉽게 시뮬레이션의 속도를 조절할 수 있도록 Simulation Speed Control 기능을 구현하였으며, 각 노드의 효과적인 정상 및 침입 상태 표시를 위한 Icon, 각 노드의 진화 정도와 침입 탐지 정확도를 알려주는 Evolution Number와 Accuracy Gauge, 해당 시뮬레이션의 결과를 도시하기 위한 Simulation Graph 도 추가하였다. 네트워크 Off-line 환경도 대비하여, DB 로부터의 데이터 입력뿐만 아니라 Log File 을 통한 데이터 입력도 가능하게 하였다. 끝으로, 전체 Node 들의 다양한 상태변화를 확인할 수 있는 Topology Window 와 Simulation Demo Window 간의 Synchronization 을 위한 Socket 통신 등 다양한 기능들이 통합된 Visualization Tool 을 개발함으로써, 대규모 네트워크 시뮬레이션의 효과적인 시뮬레이션이 가능하게 되었다. 이로 인해 대규모 네트워크 상의 복잡한 시뮬레이션 결과도 사용자가 매우 쉽게 파악할 수 있 매우 효과적으로 사용자가 파악할 수 있게 되었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.787-790
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• 2015

Recently, M2M (Machine to Machine) communication is possible the development of MTC (Machine Type Communication) devices becomes active. MCT devices in the form of home appliances have a low power consumption, low cost, short-range wireless communication in wireless home network. For purpose, MTC devices based on IEEE 802.15.4/Zigbee are composed in the form of cluster-tree topology, which consists of one PAN (Personal Area Network), one or other router and end of nodes. It happens that transmission delay, packet drop, and lacking data resulted from collision originated by a competition for allocating channels among MTC devices that greatly increased. At last performance of entire network can be degradated. This paper proposes that the beacon frame-based grouping algorithm using multiple channels in a MTC devices in the presence of wireless home network interference. The proposed algorithm decreases the transmission delay, dropped packet and throughput is more increase, so the proposal algorithm is more efficient than the IEEE 802.15.4/ Zigbee standard.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.484-488
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• 2001

The grid voltage of commercial utility power source hi Japan and USA is 100rms, but in China and European countries, it is 200rms. In recent years, In Japan 200Vrms out putted single phase three wire system begins to be used for high power applications. In 100Vrms utility AC power applications and systems, an active voltage clamped quasi-resonant Inverter circuit topology using IGBTs has been effectively used so far for the consumer microwave oven. In this paper, presented is a half bridge type voltage-clamped high-frequency Inverter type AC-DC converter using which is designed for consumer magnetron drive used as the consumer microwave oven in 200V utility AC power system. This zero voltage soft switching Inverter can use the same power rated switching semiconductor devices and three-winding high frequency transformer as those of the active voltage clamped quasi-resonant Inverter using the IGBTs that has already been used for 100V utility AC power source. The operating performances of the voltage source single ended push pull type Inverter are evaluated and discussed for consumer microwave oven. The harmonic line current components In the utility AC power side of the AC-DC power converter operating at ZVS­PWM strategy reduced and improved on the basis of sine wave like pulse frequency modulation and sine wave like pulse width modulation for the utility AC voltage source.