• 동력기계공학회지
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• 제2권2호
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• pp.55-59
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• 1998

In practice, the property of nonlinearity is contained in all physical systems. In other word, all physical systems are nonlinear to some degree. Therefore it is important that we acquires a facility for analyzing feedback control systems with varying degrees of nonlinearity. To operate the system linearly over wide range of variation of signal amplitude and frequency, the system requires components of an extremely high quality. Such a system would probably be impractical in the view points of cost, space and weight. In this context of view, it is worth noting that the nonlinearities may be intentionally introduced into a system in order to compensate for the effects of other undesirable nonlinearities or to obtain better performance than what could be achieved using linear element only. A simple example of an intentional nonlinearity is the use of a nonlinear damped system to optimize response in accordance with the magnitude of error. In this paper, an on-off type nonlinear controller is introduced and the applicability and validity of a simple on-off controller are presented by the experimental result.

• 무역상무연구
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• 제59권
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• pp.137-157
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• 2013

The Electronic Trade Finance not only has with the trait which is simple procedures, low cost but also easier access to using statistics compare to formerly paper based system. In Korea, all of trade finance system will be changed to electronic base by February 2014. The purpose of this research finds the using status and problems of the electronic local L/C and electronic purchase certificate, and suggests several improvements. First, the whole trade finance system should improve in terms of simple procedures, especially small and medium companies can use the system sufficient maximum limit. Second, the organizers, KTNET, KITA etc, need to the new electronic trade finance system promote to customers and training program for early settlement. It also has to manage at an unified system between IT and tex authorities. Third, small and medium size companies still think the charge for using high, so it need to make a resonable charge for using the electronic system to persuasive extent reasonable about it.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.249-254
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• 2001

Abstract In this paper, we propose a method of cooperative control based on artifical intelligent system in distributed autonomous robotic system. In general, multi-agent behavior algorithm is simple and effective for small number of robots. And multi-robot behavior control is a simple reactive navigation strategy by combining repulsion from obstacles with attraction to a goal. However when the number of robot goes on increasing, this becomes difficult to be realized because multi-robot behavior algorithm provide on multiple constraints and goals in mobile robot navigation problems. As the solution of above problem, we propose an architecture of fuzzy system for each multi-robot speed control and fuzzy-neural network for obstacle avoidance. Here, we propose an architecture of fuzzy system for each multi-robot speed control and fuzzy-neural network for their direction to avoid obstacle. Our focus is on system of cooperative autonomous robots in environment with obstacle. For simulation, we divide experiment into two method. One method is motor schema-based formation control in previous and the other method is proposed by this paper. Simulation results are given in an obstacle environment and in an dynamic environment.

• 전력전자학회논문지
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• 제18권1호
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• pp.26-36
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• 2013

This paper presents a simple and cost-effective stand-alone rapid battery charging system of 30kW for electric vehicles. The proposed system mainly consists of active front-end rectifier of neutral point clamped 3-level type and non-isolated bi-directional dc-dc converter of multi-phase interleaved half-bridge topology. The charging system is designed to operate for both lithium-polymer and lithium-ion batteries. The complete charging sequence is made up of three sub-interval operating modes; pre-charge mode, constant-current mode, and constant-voltage mode. The pre-charge mode employs the stair-case shaped current profile to accomplish shorter charging time while maintaining the reliable operation of the battery. The proposed system is specified to reach the full-charge state within less than 16min for the battery capacity of 8kWh by supplying the charging current of 78A. Owing to the simple and compact power conversion scheme, the proposed solution has superior module-friendly mechanical structure which is absolutely required to realize flexible power expansion capability in a very high-current rapid charging system.

• Korean Chemical Engineering Research
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• 제55권6호
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• pp.767-770
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• 2017

Quadruple tank liquid level systems are popular in testing multivariable control systems for multivariable processes with positive or negative zeros. The liquid level system is nonlinear and it will help to illustrate the robustness of control systems. However, due to nonlinearity, it can be cumbersome to obtain process parameters for testing linear control systems. Perturbation sizes are limited for valid linearized process models, requiring level sensors with high precision. A simple method where the outlet orifice is replaced to a long tube is proposed here. The effluent flow rate becomes proportional to the liquid level due to the friction loss of long tube and the liquid level system shows near linear dynamics. It is applied to the quadruple tank system for easier experiments.

• 한국컴퓨터정보학회논문지
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• 제5권4호
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• pp.120-125
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• 2000

기존의 인터넷 망 관리에 사용되는 SNMP(Simple Network Management Protocol)는 망 관리 정보 수집을 위한 폴링과 이에 대한 응답 트래픽으로 관리자 시스템(Management System)이 관리하는 피관리 시스템(Agent System)이 많아지면 망의 과부하를 가져올 수 있다. 본 논문에서는 기존의 SNMP에서 사용하는 폴링 방법을 개선하여 피관리 시스템이 많은 경우에 망의 과부하를 줄일 수 있는 그룹 폴링 방법을 제안하였다. 제안한 방법은 피관리 시스템들을 그룹으로 나누어 정보를 수집하는 방식으로, 기존의 방식에 비해 응답 지연시간과 통신 부하가 줄어서 피관리 시스템의 수가 많은 경우나 폴링 횟수가 많은 경우, 제안된 그룹 폴링 방법을 이용하는 것이 효율적이었다.

• 한국산업정보학회논문지
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• 제20권6호
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• pp.1-10
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• 2015

본 논문에서는 음영 지역을 위한 다중 중계기 기반의 주파수 효율적인 OFDMA(orthogonal frequency division multiple access) 전송 시스템을 제안한다. 본 논문에서는 다중 중계기를 통해 확보된 다중 경로에 주파수 공간 블록 부호를 적용하여 음영 지역의 시스템 성능을 향상시킨다. 또한, 주기적 프리픽스 부족으로 인해 발생하는 채널 주기성 손실을 복원하는 과정이 포함된 주기적 프리픽스를 사용하지 않는 OFDMA 시스템을 제안한다. 본 논문에서 제안된 주기적 프리픽스를 사용하지 않는 OFDMA 시스템의 성능이 충분한 주기적 프리픽스를 사용하는 기존 OFDMA 시스템의 성능과 거의 동일하여, 기존 시스템 대비 주파수 효율이 향상되는 것을 실험을 통해서 확인할 수 있다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.201-202
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• 2012

This paper presents a simple and cost-effective stand-alone rapid battery charging system of 30kW for electric vehicles. The proposed system mainly consists of active front-end rectifier of neutral point clamped 3-level type and non-isolated bi-directional dc-dc converter of multi-phase interleaved half-bridge topology. The charging system is designed to operate for both lithium-polymer and lithium-ion batteries. The complete charging sequence is made up of three sub-interval operating modes; pre-charging mode, constant-current mode, and constant-voltage mode. Each mode is operated according to battery states: voltage, current and State of Charging (SOC). The proposed system is able to reach the full-charge state within less than 16min for the battery capacity of 8kWh by supplying the charging current of 67A. The optimal discharging algorithm for Vehicle to the Grid (V2G) operation has been adopted to maintain the discharging current of 1C. Owing to the simple and compact power conversion scheme, the proposed solution has superior module-friendly mechanical structure which is absolutely required to realize flexible power expansion capability in a very high-current rapid charging system. Experiment waveforms confirm the proposed functionality of the charging system.

• Journal of Multimedia Information System
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• 제8권3호
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• pp.159-166
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• 2021

COVID-19 has dramatically changed people's daily life. Wearing masks is considered as a simple but effective way to defend the spread of the epidemic. Hence, a real-time and accurate mask wearing detection system is important. In this paper, a deep learning-based mask wearing detection system is developed to help people defend against the terrible epidemic. The system consists of three important functions, which are image detection, video detection and real-time detection. To keep a high detection rate, a deep learning-based method is adopted to detect masks. Unfortunately, according to the suddenness of the epidemic, the mask wearing dataset is scarce, so a mask wearing dataset is collected in this paper. Besides, to reduce the computational cost and runtime, a simple online and real-time tracking method is adopted to achieve video detection and monitoring. Furthermore, a function is implemented to call the camera to real-time achieve mask wearing detection. The sufficient results have shown that the developed system can perform well in the mask wearing detection task. The precision, recall, mAP and F1 can achieve 86.6%, 96.7%, 96.2% and 91.4%, respectively.

• International Journal of Internet, Broadcasting and Communication
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• 제16권3호
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• pp.212-220
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• 2024

A recently the advancement of society, AI technology has made significant strides, especially in the fields of computer vision and voice recognition. This study introduces a system that leverages these technologies to recognize users through a camera and relay commands within a vehicle based on voice commands. The system uses the YOLO (You Only Look Once) machine learning algorithm, widely used for object and entity recognition, to identify specific users. For voice command recognition, a machine learning model based on spectrogram voice analysis is employed to identify specific commands. This design aims to enhance security and convenience by preventing unauthorized access to vehicles and IoT devices by anyone other than registered users. We converts camera input data into YOLO system inputs to determine if it is a person, Additionally, it collects voice data through a microphone embedded in the device or computer, converting it into time-domain spectrogram data to be used as input for the voice recognition machine learning system. The input camera image data and voice data undergo inference tasks through pre-trained models, enabling the recognition of simple commands within a limited space based on the inference results. This study demonstrates the feasibility of constructing a device management system within a confined space that enhances security and user convenience through a simple real-time system model. Finally our work aims to provide practical solutions in various application fields, such as smart homes and autonomous vehicles.