• 한국항해항만학회지
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• 제30권9호
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• pp.741-748
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• 2006

Number of researches on efficient terminal operation system applying RFID(Radio Frequency Identification) are in progress. However, RFID has limitations on tracking and providing accurate positions of containers. In this paper, to enhance the performance of the integrated terminal operation system, an efficient loading management of yard is proposed by applying RFID based RTLS(Real Time Locating System) that provides real time accurate positions of containers. It was found that a group based sequence system is more efficient than the existing individual sequence number system in the container yard In the group based sequence system, the containers in the same group should have similar characteristics such as port of destination(POD), size, weight, etc. In order to run this system, we proposed the parameters to the unspecified N bytes of RFID tag which are specified in ISO 18000 7. And then, we developed an integrated operation system of container terminal using RFID. The proposed system reduces the ship turnaround time in ubiquitous port environments.

• Journal of Power Electronics
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• 제19권1호
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• pp.234-243
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• 2019

Studying the control strategy of a microgrid under the load unbalanced state helps to improve the stability of the system. The magnitude of the power fluctuation, which occurs between the power supply and the load, is generated in a microgrid under the load unbalanced state is called negative sequence reactive power $Q^-$. Traditional power distribution methods such as P-f, Q-E droop control can only distribute power with positive sequence current information. However, they have no effect on $Q^-$ with negative sequence current information. In this paper, a stationary-frame control method for power sharing and voltage unbalance compensation in islanded microgrids is proposed. This method is based on the proper output impedance control of distributed generation unit (DG unit) interface converters. The control system of a DG unit mainly consists of an active-power-frequency and reactive-power-voltage droop controller, an output impedance controller, and voltage and current controllers. The proposed method allows for the sharing of imbalance current among the DG unit and it can compensate voltage unbalance at the same time. The design approach of the control system is discussed in detail. Simulation and experimental results are presented. These results demonstrate that the proposed method is effective in the compensation of voltage unbalance and the power distribution.

• 센서학회지
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• 제32권6호
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• pp.481-486
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• 2023

Anomaly detection holds paramount significance across diverse fields, encompassing fraud detection, risk mitigation, and sensor evaluation tests. Its pertinence extends notably to the military, particularly within the Warrior Platform, a comprehensive combat equipment system with wearable sensors. Hence, we propose a data-compression-based anomaly detection approach tailored to unlabeled time series and sequence data. This method entailed the construction of two distinctive features, typicality and atypicality, to discern anomalies effectively. The typicality of a test sequence was determined by evaluating the compression efficacy achieved through the pattern dictionary. This dictionary was established based on the frequency of all patterns identified in a training sequence generated for each sensor within Warrior Platform. The resulting typicality served as an anomaly score, facilitating the identification of anomalous data using a predetermined threshold. To improve the performance of the pattern dictionary method, we leveraged atypicality to discern sequences that could undergo compression independently without relying on the pattern dictionary. Consequently, our refined approach integrated both typicality and atypicality, augmenting the effectiveness of the pattern dictionary method. Our proposed method exhibited heightened capability in detecting a spectrum of unpredictable anomalies, fortifying the stability of wearable sensors prevalent in military equipment, including the Army TIGER 4.0 system.

• Journal of Power Electronics
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• 제13권3호
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• pp.469-478
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• 2013

This paper proposes a novel scheme for the current controller for the grid-side converter (GSC) of permanent-magnet synchronous generator (PMSG) wind turbines to eliminate the high-order harmonics in the grid currents under grid voltage disturbances. The voltage unbalance and harmonics in three-phase systems cause grid current distortions. In order to mitigate the input current distortions, multi-loop current controllers are applied, where the positive-sequence component is regulated by proportional-integral (PI) controllers, and the negative-sequence and high-order harmonic components are regulated by proportional-resonance (PR) controllers. For extracting the positive/negative-sequence and harmonic components of the grid voltages and currents without a phase delay or magnitude reduction, composite observers are applied, which give faster and more precise estimation results. In addition, an active damping method using PR controllers to damp the grid current component of the resonant frequency is employed to improve the operating stability of VSCs with inductor-capacitor-inductor (LCL) filters. The validity of the proposed method is verified by simulation and experimental results.

• 정보과학회 컴퓨팅의 실제 논문지
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• 제21권11호
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• pp.713-720
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• 2015

컴퓨팅 기술과 네트워크의 발달로 인해, 정보 기기가 소형화되고 이동성이 강조되고 있다. 이에 따라 모바일 환경에서 작동 가능한 음성 인식 시스템에 대한 수요가 최근 급격히 증대되고 있다. 본 논문은 음소 기반 한국어 음성 인식 시스템의 일부로서, 한국어 모음 'ㅐ'에 대한 새로운 인식 방식을 제안한다. 제안하는 방식은 주파수 영역에서의 분석을 배제하고, 시간 영역에서의 시퀀스 패턴에 기반하여 인식을 수행함으로써, 계산 비용을 현저히 절감할 수 있다. 'ㅐ'의 전형적인 시퀀스 패턴들을 탐지하기 위한 세 가지 알고리즘이 제시되며, 이를 결합하여 최종 판별을 수행한다. 실험 결과를 통해, 제안하는 방식이 89.1%의 정확도로 모음 'ㅐ'를 인식할 수 있음을 확인하였다.

• 산업경영시스템학회지
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• 제42권2호
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• pp.94-103
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• 2019

Self Organizing Map (SOM) is a neural network that is effective in classifying patterns that form the feature map by extracting characteristics of the input data. In this study, we propose an algorithm to determine the cell formation and the machine layout within the cell for the cell formation problem with operation sequence using the SOM. In the proposed algorithm, the output layer of the SOM is a one-dimensional structure, and the SOM is applied to the parts and the machine in two steps. The initial cell is formed when the formed clusters is grouped largely by the utilization of the machine within the cell. At this stage, machine cell are formed. The next step is to create a flow matrix of the all machine that calculates the frequency of consecutive forward movement for the machine. The machine layout order in each machine cell is determined based on this flow matrix so that the machine operation sequence is most reflected. The final step is to optimize the overall machine and parts to increase machine layout efficiency. As a result, the final cell is formed and the machine layout within the cell is determined. The proposed algorithm was tested on well-known cell formation problems with operation sequence shown in previous papers. The proposed algorithm has better performance than the other algorithms.

• 한국자기공명학회논문지
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• 제26권4호
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• pp.51-58
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• 2022

The baseline flattened NMR spectrum has been achieved by several methodologies including pulse manipulation with a series of phase cycling. The background signal inherent in the probe is also main source of baseline distortion both in solution and solid NMR. The simple direct polarization with 90° pulse flipping the magnetization from the z-axis onto the receiver coil requires the strong rf pulse enough to encompass the wide frequency range to excite the resonance of interest nuclei. Albeit the perfect polarization 90° pulse, the signal from the unwanted magnetic fields such as background signal can not be completely suppressed by suitable phase cycling. Moreover, slowly baseline wiggling signal from the low 𝛾 nuclei is not easy to eliminate with multiple pulse manipulation. So there is still need to contrive the new scheme for that purpose in an adroit manner. In this article new triple pulse excitation schemes for TIP and modified DEPTH pulse sequence are analytically examined in terms of arbitrary phase and flip angle of pulse. The suitable phase cycling for these pulse trains is necessary for the good sensitivity and resolution of the spectrum. It is observed that the ¹³C sensitivity TIP experiment is almost equal to the CP/MAS with modified DEPTH sequence, both of which are applicable to both solid and solution state NMR.

• 전력전자학회논문지
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• 제10권5호
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• pp.501-507
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• 2005

본 연구에서는 유도 전동기의 파워 스펙트럼 확산을 위한 LF2407 DSP기반 하이브리드 랜덤 PWM(HRPWM)을 제안하였다. 제안된 방법은 Lead-Lag 랜덤 비트를 갖는 PRBS (Pseudo-Random Binary Sequence)와 논리적으로 비교를 하기 위한 랜덤 삼각파 캐리어로 구성된다. 또한 DSP에 의하여 랜덤 수 및 PRBS 그리고 3상 기준 정현파를 실시간으로 발생하며, DSP외부의 주파수 변조기 MAX038에 의하여 랜덤 주파수의 캐리어를 발생한다. 본 연구의 타당성 검증을 위하여 제안된 기법을 3상 가변속 구동장치에 적용하였으며, 종전의 방법과 전압 및 전류 그리고 전동기 소음의 파워 스펙트럼을 비교 검토하였다.

• Nuclear Engineering and Technology
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• 제49권2호
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• pp.306-312
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• 2017

The purpose of this research is to introduce the technical standard of accident sequence precursor (ASP) analysis, and to propose a case study using the dynamic-probabilistic safety assessment (D-PSA) approach. The D-PSA approach can aid in the determination of high-risk/low-frequency accident scenarios from all potential scenarios. It can also be used to investigate the dynamic interaction between the physical state and the actions of the operator in an accident situation for risk quantification. This approach lends significant potential for safety analysis. Furthermore, the D-PSA approach provides a more realistic risk assessment by minimizing assumptions used in the conventional PSA model so-called the static-PSA model, which are relatively static in comparison. We performed risk quantification of a steam generator tube rupture (SGTR) accident using the dynamic event tree (DET) methodology, which is the most widely used methodology in D-PSA. The risk quantification results of D-PSA and S-PSA are compared and evaluated. Suggestions and recommendations for using D-PSA are described in order to provide a technical perspective.

• 대한전자공학회논문지TC
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• 제48권9호
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• pp.27-34
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• 2011

무선 통신 시스템의 효율을 높이기 위해 제안된 무선인지 (Cognitive Radio) 시스템은 2차 사용자가 주사용자 (primary user)의 스펙트럼을 서로 공유하는 시스템이다. 2차 사용자가 주사용자에게 간섭을 일으키지 않으면서 효율적으로 데이터를 전송하기 위해서 NC-OFDM (Non-contiguous Orthogonal Frequency Division Multiplexing)을 사용한다. 하지만 NC-OFDM은 기존 OFDM과 마찬가지로 높은 PAPR (Peak-to-Average Power Ratio)을 발생시켜 시스템 성능을 저하시킨다. 본 논문에서는 첫 번째로 NC-OFDM에서 부반송파의 분포에 따른 PAPR에 대해 분석하였다. 두 번째로 기존 OFDM의 PAPR 감소기법인 PTS (Partial Transmit Sequence)와 SLM (Selective Mapping)을 NC-OFDM에 적용하여 PAPR 감소성능을 확인하였다. 마지막으로 pruned-FFT가 적용된 PAPR 감소기법을 NC-OFDM에 적용할 경우 계산복잡도를 기존 OFDM과 비교하였다. 시뮬레이션을 통해 pruned-FFT가 적용된 NC-OFDM이 기존 OFDM보다 PAPR 감소성능 및 계산복잡도 측면에서 보다 효율적임을 검증하였다.