• 상하수도학회지
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• 제29권3호
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• pp.305-317
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• 2015

The function failure of present major facilities is likely to lead to failure of related systems and/or whole facilities, increasing the necessity for protection of infrastructures, main structures, and major industrial facilities. In addition, safe and efficient management for urban infrastructure (waterworks and sewerage facilities, electricity, telecommunications, roads, etc) installed in the basement or on large cities grounds at various public areas is required. Recently in response to this demand, efforts for vitalizing asset management are being made such as enacting related laws and developing asset management system in the U.S., Australia, Europe and other advanced countries with the concept for a new maintenance. In our county, identifying maintenance system problems such as aging and rapid increasing of existing infrastructures and decision-making about updating maintenance is required for systematic and organizational maintenance. In this study, by comparing and observing the LOS(Level of Service) of each countries' waterworks and risk-based LOS, we suggest the direction of future urban water infrastructure management systems for more effective management.

• 제어로봇시스템학회논문지
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• 제20권10호
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• pp.1014-1022
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• 2014

In mechatronic systems using electric signals to drive control systems, driving signals including the frequency band of the unwanted signals, such as resonant frequencies and noise frequencies, can affect the accuracy of the controlled system and can cause serious damage to the system due to the resonance phenomenon of the mechatronic system. An LOS (Line of Sight) control unit is used to automatically rotate the gimbal system with a video imaging system generally mounted on modern aerial vehicles. However, it still suffers from natural frequency variation problems due to variations of operational temperature. To prevent degradation in performance, this paper proposes an adaptive filtering technique based on real-time noise analysis and adaptive notch-filtering for LOS control systems, and verifies how our proposed method maintains the LOS stabilization performance. Additionally, this filtering technique can be applied to the image noise filtering of the video imaging system. It is designed to reduce image noises generated by switching circuits or power sources. The details of design procedures of the proposed filtering technique and the experiments for the performance verification are described in this paper.

• Steel and Composite Structures
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• 제2권1호
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• pp.21-34
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• 2002

A model of the process of local buckling in tubular steel structural elements is presented. It is assumed that this degrading phenomenon can be lumped at plastic hinges. The model is therefore based on the concept of plastic hinge combined with the methods of continuum damage mechanics. The state of this new kind of inelastic hinge is characterized by two internal variables: the plastic rotation and the damage. The model is valid if only one local buckling appears in the plastic hinge region; for instance, in the case of framed structures subjected to monotonic loadings. Based on this damage model, a new finite element that can describe the development of local buckling is proposed. The element is the assemblage of an elastic beamcolumn and two inelastic hinges at its ends. The stiffness matrix, that depends on the level of damage, the yielding function and the damage evolution law of the two hinges define the new finite element. In order to verify model and finite element, several small-scale frames were tested in laboratory under monotonic loading. A lateral load at the top of the frame was applied in a stroke-controlled mode until local buckling appears and develops in several locations of the frame and its ultimate capacity was reached. These tests were simulated with the new finite element and comparison between model and test is presented and discussed.

• 대한교통학회지
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• 제26권4호
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• pp.161-172
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• 2008

국토해양부는 신호교차로 서비스수준 분석에 도로용량편람이 제시하는 방법의 적용을 장려하고 있으며 실시간신호제어교차로는 지능형교통체계 구축사업으로 그 숫자가 현장에서 꾸준히 증가하고 있다. 도로용량편람은 정주기식 신호교차로 서비스수준 분석방법에 국한하여 제시하고 있어 현장 실무자들은 실시간신호제어교차로 서비스수준 분석에 어려움을 경험하고 있다. 본 연구는 도로용량편람 수준에서 실시간신호제어교차로 서비스수준 분석의 기초가 되는 방법론을 제안하며 향후 추가로 수행되어야 하는 개발방향을 검토한다. 한 개의 신호교차로를 표본으로 세부 요소모형들을 간이 개발하여 검증한 결과 제안된 방법은 실제 현장 자료와 유사한 수준의 서비스 수준을 추정할 수 있음을 확인하였다.

• 국제물리치료학회지
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• 제10권3호
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• pp.1823-1829
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• 2019

Background: Stroke patients have leg muscle weakness and impaired balance resulting in compensatory changes. To restore balance in these patients, functional training using postural strategy is needed. Objective: To examine the effects of ankle and hip strategy training on the center of pressure (COP) movement and limits of stability (LOS) in standing posture in stroke patients. Design: The study was an assessor-blinded and randomized-controlled clinical trial. Methods: Thirty patients were randomly assigned to an ankle strategy training group and a ankle/ hip strategy training group. Patients in the ankle strategy training group underwent ankle strategy exercise for 30 min, and those in the ankle/ hip strategy training group underwent 15 min of ankle strategy exercise and 15 min of hip strategy exercise. Both groups underwent training thrice a week for four weeks. Forward, backward, paretic side, and non-paretic side COP movements and LOS were measured using BioRescue. Results: After the intervention, except for the backward area in the ankle strategy training group, the COP movement area and the LOS were significantly improved in both the groups. In addition, these improvements were significantly higher in ankle/ hip strategy training group than that in the ankle strategy training group. Conclusions: Ankle strategy training in addition to hip strategy training improves COP movement (forward-backward, paretic side area, and non-paretic side area) and LOS in stroke patients.

• Journal of Positioning, Navigation, and Timing
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• 제11권4호
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• pp.361-368
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• 2022

An indoor navigation system that utilizes long-term evolution (LTE) signals has the benefit of no additional infrastructure installation expenses and low base station database management costs. Among the LTE signal measurements, received signal strength (RSS) is particularly appealing because it can be easily obtained with mobile devices. Propagation channel models can be used to estimate the position of mobile devices with RSS. However, conventional channel models have a shortcoming in that they do not discriminate between line-of-sight (LOS) and non-line-of-sight (NLOS) conditions of the received signal. Accordingly, a previous study has suggested separated LOS and NLOS channel models. However, a method for determining LOS and NLOS conditions was not devised. In this study, a machine learning-based LOS/NLOS classification method using RSS measurements is developed. We suggest several machine-learning features and evaluate various machine-learning algorithms. As an indoor experimental result, up to 87.5% classification accuracy was achieved with an ensemble algorithm. Furthermore, the range estimation accuracy with an average error of 13.54 m was demonstrated, which is a 25.3% improvement over the conventional channel model.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2023년도 추계학술대회
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• pp.100-102
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• 2023

항로추종성능은 자율운항선박(MASS)의 중요한 자율제어기능 중 하나이다. 이는 선박의 안전성을 보장하기 위해 중요하며, 자율운항선박의 설계 단계에서 사전 평가가 필수적이다. 본 연구는 자율운항선박의 항로추종성능 평가를 위한 전산유체역학(CFD) 모델과 LOS 알고리즘 연계 방안을 제안한다. 먼저, 자율운항선박의 정수 중 거리 이탈 편차를 이용한 항로 추종 성능 평가 모델 개발에 관하여 기술했다. 먼저, 항로 추종을 수행하는 선박 주변의 난류 흐름은 비압축성 뉴턴 유체의 가정하에 비정상 RANS(Reynolds Averaged Navier-Stokes) 법을 이용하여 수치적으로 계산되었다. 중첩격자계법을 CFD 모델에 적용함으로써 거리 이탈 편차를 이용하는 LOS(Line-of-Sight) 가이던스 알고리즘에 의한 타의 회전 및 이에 따른 선체의 6 자유도 움직임을 CFD 환경에서 구현하였다. 개발된 자유 항주 선박 CFD 모델을 이용하여 항로 추종 시뮬레이션 평가 결과, 설정된 항로에서 선박의 정수 중 항로 추종 제어는 파도, 조류, 및 바람과 같은 외부 교란의 부재로 LOS 알고리즘에 의한 우현/좌현 측 변침뿐만 아니라 직진 경로의 추종도 성공적으로 수행됨을 확인하였다. 선체, 프로펠러, 타의 복잡한 상호작용을 정도 높게 해석할 수 있는 자유 항주 선박 CFD 모델과 LOS 알고리즘의 결합은 자율운항선박의 항로 추종 성능 평가를 정량적으로 평가하는 데 기여할 것으로 기대된다.

• Journal of Korean Biological Nursing Science
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• 제26권2호
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• pp.136-143
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• 2024

Purpose: The purpose of this study was to investigate the associations of obesity and clinical characteristics including interleukin-6 (IL-6) with hospital length of stay (LOS) in coronavirus disease-2019 (COVID-19) patients in Korea. Methods: A retrospective descriptive study design was employed to analyze medical data from a government-designated hospital in a city of Korea. Clinical data were collected from 256 patients with COVID-19 in negative-pressure isolation wards in 2021. The following parameters were analyzed: body mass index (BMI), IL-6 levels, age, sex, comorbidities, healthy habitsat the time ofadmission, and LOS. The statistical package SPSS 26.0 was used for descriptive statistics, the independent t-test, the chi-square test, and partial correlation coefficients. Results: The age of COVID-19 patients was positively correlated with BMI (r = -.16, p = .012), IL-6 levels (r = .14, p = .022) and LOS (r = .26, p < .001). Obesity, non-drinking, hypertension, and older age were associated with longer LOS. Conclusion: These results suggest that age, obesity, and hypertension in COVID-19 patients are related to LOS. Studies investigating other factors that can affect long-term hospitalization in COVID-19 patients are suggested.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.268-273
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• 1991

Missile and target closing velocity is used in the proportional navigation(PN) missile guidance loop. But it is difficult to estimate the closing velocity when passive seeker is used and only the Line-of-Sight(LOS) rate is available in the guidance loop. In this study, new closing velocity estimation method is developed. This method uses LOS rate measurement only and uses some characteristics of PN guidance law. The Lyapunov method is used to analyze the stability of the developed estimation method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
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• pp.201-203
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• 2006

This paper describes a new LOS(Line-of-Sight) estimator for BTT missiles. The dynamic models of LOS rate and a seeker are derived. Based on these dynamic models, we design a nonlinear estimator, which takes into account roll motion of BTT missiles and sensor noises. Simulation results show that the LOS rate estimates of the proposed estimator are more accurate than those of the conventional estimator.