• Journal of Drive and Control
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• v.18 no.2
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• pp.9-19
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• 2021

The spool displacement signal of a directional control valve, including the servo valve, can be considered as the standard signal to measure dynamic characteristics. When the spool displacement signal is not available, the velocity signal of a metering cylinder piston can be used. In this study, the frequency response characteristics of the metering cylinder are investigated for the spool displacement input. The transfer functions of the servo valve-metering system are derived taking into consideration the oil inertia effect in the transmission lines. The theoretical results of the transfer functions are verified through computer simulations and experiments. The oil inertia effect in the transmission lines was found to have a very significant effect on the bandwidth frequency of the servo valve-metering cylinder system. In order to more precisely measure the dynamic characteristics of a servo valve, the metering cylinder should be set up to minimize the oil inertia effect by increasing the inner diameters of the transmission lines or shortening their lengths.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.5
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• pp.159-166
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• 2010

From public insecurity, access of wealth, alteration of population structure, and changes of security recognition, physical security has been continuously developed and changed. In these days, typical systems for physical security are unmanned security system using telephone network and security equipment, image recognition system using DVR and camera, and access control system by finger print recognition and RFID cards. However, physical security system is broadening its domain towards ICT based convergence with networked camera, biometrics, individual authentication, and LBS services. This paper proposes main technical trends and various security convergences for future physical security services by classifying the security categories into 3 parts; Individual security for personal protection, IT Convergence for large buildings, and Homeland Security for omni-directional security.

• Journal of Drive and Control
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• v.19 no.1
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• pp.69-75
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• 2022

This study aimed to develop solutions for the intermittent performance deterioration of self-propelled spinach harvesters through analysis model. The study was conducted in the following manner. First, changes in performance deterioration and surplus flow, which result from oil temperature changes, were analyzed by simulating actual sequential harvesting movements, which involve driving with actuators operated simultaneously, by analysis model developed in a previous study. Second, fundamental solutions for surplus flow problems were presented. Third, the solutions were applied to a virtual environment to present their practicality and quantitative effects. The two solutions based on the study results were as follows. First, a closed center-type directional control valve was applied to the hydraulic circuit. Second, an unloading system was set up through an on-off solenoid valve.

• Journal of Navigation and Port Research
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• v.40 no.1
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• pp.43-50
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• 2016

Amid of the logistics hub center competition is going to intensifying between the world major port, it is essential to pre-occupied the base in the logistics hub world take advantage of advanced technology of logistics equipment than other ports. In existing container terminal, when container moves the terminal use the omnidirectional and directional antenna in order to exchange data information on the basis of 802.11 wireless network system. Case of loading height of exceeding, the blind sport will occur and a limited frequency channel can't help using in the area. A limited frequency channel usage and nested areas happen to use the closed terminal, it has a great influence to operate the terminal working. In this paper, LTE network is configured provided by the specified company ('L' Corp,.Ltd) and terminal data extracted through LBO (Local Breakout) in the cell site which is configured directly with container terminal operation server. Using this method, container terminal yard equipment operate without overlapping arises with uninterrupted data presented for ways to efficiently. I would suggest both the existing wireless AP LAN configuration of container terminal and new LTE system and applied to the real yard operating devices situations. Through these methods presented comparative the existing network traffic with new constructed LTE configuration. I admired to suggest that wireless network LTE introduction is fundamental factors to get rid of the blind spot, the problem of limited frequency channel and overlapping arises. These essential points can be a continual improving terminal services and more efficient terminal operational management.

• Journal of Navigation and Port Research
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• v.43 no.3
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• pp.172-178
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• 2019

Although the needs for providing resilient PNT information are increasing, threats due to the intentional RFI or space weather change are challenging to resolve. eLoran, which is a terrestrial navigation system that use a high-power signal is considered as a best back-up navigation system. Depending on the user's environment in the eLoran system, the user may use one of E-field or H-field antennas. H-field antenna, which has no restriction on setting stable ground and is relatively resistant to noise of general electronic equipment, is composed of two loops, and shows anisotropic gain pattern due to the different measurement at the two loops. Therefore, the H-field antenna's phase estimation value of signal varies depending on its direction even at the static environment. The error due to the direction of the signal should be eliminated if the user want to estimate the own position more precisely. In this paper, a method to compensate the error according to the geometric distribution between the H-field antenna and the transmitting station is proposed. A model was developed to compensate the directional error of H-field antenna based on the signal generated from the eLoran signal simulator. The model is then used to the survey measurement performed in the land area and verify its performance.

• Journal of Intelligence and Information Systems
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• v.29 no.1
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• pp.233-247
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• 2023

Recently, research on detecting objects in hidden spaces beyond the direct line-of-sight of observers has received attention. Most studies use optical equipment that utilizes the directional of light, but sound that has both diffraction and directional is also suitable for non-line-of-sight(NLOS) research. In this paper, we propose a novel method of detecting objects in non-line-of-sight (NLOS) areas using acoustic signals in the audible frequency range. We developed a deep learning model that extracts information from the NLOS area by inputting only acoustic signals and predicts the properties and location of hidden objects. Additionally, for the training and evaluation of the deep learning model, we collected data by varying the signal transmission and reception location for a total of 11 objects. We show that the deep learning model demonstrates outstanding performance in detecting objects in the NLOS area using acoustic signals. We observed that the performance decreases as the distance between the signal collection location and the reflecting wall, and the performance improves through the combination of signals collected from multiple locations. Finally, we propose the optimal conditions for detecting objects in the NLOS area using acoustic signals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.427-436
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• 2016

Due to disasters such as earthquakes and landslides in urban areas, persons have been buried inside collapsed buildings and structures. Rescuers have mainly utilized detection equipment by applying sound, video and electric waves, but these are expensive and due to the directional approaches onto the collapsed site, secondary collapse risk can arise. In addition, due to poor utilization of such equipment, new human detection technology with quick and high reliability has not been utilized. To address these issues, this study develops a wireless signal-based human detection module that can be loaded into an Unmanned Aerial Vehicle (UAV). The human detection module searches for the 3D location for buried persons by collecting Wi-Fi signal and barometer sensors data transmitted from the mobile phones. This module can gain diverse information from mobile phones for buried persons in real time. We present a development framework of the module that provides 3D location data with more reliable information by delivering the collected data into a local computer in the ground. This study verified the application feasibility of the developed module in a real collapsed area. Therefore, it is expected that these results can be used as a core technology for the quick detection of buried persons' location and for relieving them after disasters that induce building collapses.

• Journal of Digital Convergence
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• v.11 no.2
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• pp.43-50
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• 2013

Recently, Cyber threats that is doing intelligence and sophistication from the organization's information assets to secure order technical disciplines, as well as managerial and environmental sectors, such as mind-response system is must established. In this paper, possible to analyze the case for the theory in network security, such as the logical network and physical network separation suitable for the corporate environment and constantly respond and manage the Information Security Management Model A secure network design is proposed. In particular, the proposed model improvements derived from the existing network, network improvements have been made in order to design improved ability to respond to real-time security and central manageability, security threats, pre-emptive detection and proactive coping, critical equipment in the event of a dual hwalreu through applied features such as high-availability, high-performance, high-reliability, ensuring separation of individual network security policy integrated management of individual network, network security directional.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2007.04a
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• pp.271-271
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• 2007

본 내용은 첨단 정보통신 기술을 이용하여 강의자 중심의 단방향 교육(Teaching) 환경을 학생 중심의 양방향 교육(Learning) 환경으로 개선하여 보다 창의적인 인재를 양성할 수 있는 교육환경 구축에 관한 내용이다. 우리나라를 포함한 OECD 국가들은 ICT활용 수업에 대한 필요성을 공감하고 교단 선진화를 위한 연구 및 지원을 다양하게 진행하고 있다. 학생들에게 지급하는 교과서를 인쇄매체 대신에 메모리 스틱, CD-ROM 및 인터넷을 통한 전자 매체로 대체하는 방안 등이 그 예이다. 따라서 학생들이 강의실에서 멀티미디어를 이용해 강의를 듣고, 과제를 풀며 정리된 내용을 발표하고 토론할 수 있는 양방향 수업환경이 요구된다. 그러나 컴퓨터를 활용한 수업을 진행할 때의 문제점이 강의내용을 학생들에게 효율적으로 전달하기가 어렵고, 학생들의 컴퓨터를 통제할 수 없기 때문에 수업을 이탈하는 경우가 발생되는 등 교육에 역효과가 초래된다. 본 내용에서 소개하는 양방향 수업진행 장비(드림랩)는 강의자가 학생들의 컴퓨터 모니터, 키보드 및 마우스를 자유로이 통제할 수 있어서 강의자의 화면과 음성을 실시간으로 선명하게 학생들에게 전달하고, 학생들의 내용을 모니터하고 제어할 수 있으며, 개인지도 및 수준별 그룹지도가 가능하다. 또한 강의자에게 개인적으로 질문을 할 수 있고, 학생들의 내용을 자신의 자리에서 전체 학생들에게 발표할 수도 있다. 드림랩은 순수 하드웨어로 구성되어 컴퓨터 기종이나 운영체제에 영향을 받지 않으며, 컴퓨터 자원과 네트워크 자원을 사용하지 않기 때문에 컴퓨터나 네트워크의 성능을 저하시키지 않는다. 또한 사용법이 간단하고 유지관리가 쉬운 장점 등이 있다. 따라서 컴퓨터를 활용한 수업진행이 원활하여 다양한 과목에 활용 가능하고, 학생들의 자발적인 수업 참여로 강의 중심 교육에서 자기 주도적 수업환경(T2L, Teaching to Learning)으로 자연스럽게 전환되어 교육의 질적 향상과 함께 창의적인 인재를 양성할 수 있을 것으로 기대된다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.297-302
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• 2007

Vibrating test of vehicle component can be possible in lab-based simulators instead of field testing owing to the development of technology in control algorithm as well as computational process. Currently, Multi-Axial Simulation Table(MAST) is recommended as a vibrating equipment, which excites a target component for 3-directional translation and rotation motion simultaneously and hence, vibrational condition can be fully approximated to that of real road test. But, the vibration-free performance of target component is not guaranteed with MAST system, which is only simulator subjective to the operator. Rather, the reliability of multi-axial vibration test is dependent on the quality of input profile which should cover the required severity of vibrating condition on target component. In this paper, multi-axial vibration testing methodology of vehicle component is presented here, from data acquisition of vehicle accelerations to the obtaining the input profile of MAST using severe data at proving ground. To compare the severity of vibration condition, between real road test and proving ground one, energy principle of equivalent damage is proposed to calculate energy matrices of acceleration data and then, it is determined the optimal combination of special events on proving ground which is equivalent to real road test at the aspects of vibration fatigue using sequential searching optimal algorithm. To explain the vibration methodology clearly, seat and door component of vehicle are selected as a example.