• 전력전자학회논문지
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• 제18권5호
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• pp.448-457
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• 2013

This paper proposes a control method under stand-alone operating mode for distributed-module type photovoltaic power conditioners. In conventional schemes, there are some problems of a controller saturation in the DC-link (or load) voltage controller when overly-heavy load, light load, and the generated PV power reduction occurs, as well as when a transition occurs from an overly-loaded to normal conditions. To overcome these problems, the proposed controller method switches the main control target from DC-link voltage to the maximum power point, which is closer to the stable operating point when it returns to normal operating conditions. For the analysis, a state-plane trajectory was given and the circuit analysis by PSIM simulation was done. For the verification, a prototype hardware with 110[W] and 50[W] dual photovoltaic modules has been implemented. From the results, it can be seen that PV power tracking is successfully done with the proposed method even under a stand-alone operation mode.

• 한국초전도ㆍ저온공학회논문지
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• 제20권4호
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• pp.55-59
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• 2018

Currently, the development of industry makes needs larger electric supply. Providers must consider the efficiency about losses and reliability of the system. In this case, DC power system can save electrical energy; long-distance transmission line losses. Relevance to switch technology with a voltage-source converter (VSC) in AC-DC conversion system have been researched. But, protection device of DC-link against fault current is still needed to study much. VSC DC power system is vulnerable to DC-cable short-circuit and ground faults, because DC-link has a huge size of capacitor filter which releases extremely large current during DC faults. Furthermore, DC has a fatal flaw that current zero crossing is nonexistence. To interrupt the DC, several methods which make a zero crossing is used; parallel connecting self-excited series LC circuit with main switch, LC circuit with power electronic device called hybrid DC circuit breaker. Meanwhile, self-excited oscillator needs a huge size capacitor that produces big oscillation current which makes zero crossing. This capacitor has a quite effective on the price of DCCB. In this paper, hybrid self-excited type superconducting DCCB which are using AC circuit breaker system is studied by simulation tool PSCAD/EMTDC.

• Steel and Composite Structures
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• 제38권4호
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• pp.381-397
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• 2021

Based on the spatial substructure hybrid simulation test (SHST) method, the seismic performance of a high-strength steel composite K-eccentrically braced frame (K-HSS-EBF) structure system is studied. First, on the basis of the existing pseudostatic experiments, a numerical model corresponding to the experimental model was established using OpenSees, which mainly simulated the shear effect of the shear links. A three-story and five-span spatial K-HSS-EBF was taken as the prototype, and SHST was performed with a half-scale SHST model. According to the test results, the validity of the SHST model was verified, and the main seismic performance indexes of the experimental substructure under different seismic waves were studied. The results show that the hybrid simulation results are basically consistent with the numerical simulation results of the global structure. The deformation of each story is mainly concentrated in the web of the shear link owing to shear deformation. The maximum interstory drifts of the model structure during Strength Level Earthquake (SLE) and Maximum Considered Earthquake (MCE) meet the demands of interstory limitations in the Chinese seismic design code of buildings. In conclusion, the seismic response characteristics of the K-HSS-EBFs are successfully simulated using the spatial SHST, which shows that the K-HSS-EBFs have good seismic performance.

• 한국기계가공학회지
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• 제20권7호
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• pp.41-47
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• 2021

In this study, the hinges of heavy weight doors were designed and analyzed in line with the trend that built-in appliances are becoming larger and the weight of doors is also increasing. The main specification of the heavy weight door hinge is to allow the deflection at the end of the door to be less than 2 mm when opening and closing, including the automatic closing, slow closing, and closing force control functions. The structural analysis of the design mechanism, component design, and methods for improving the deflection are as follows: 1) Mechanism of the automatic closing function should sense automatically using the spring compression force at a specific angle by the contact between the cam and the cam module roller. 2) Through structural analysis, the maximum stress of the door was found in the link pin hole connected to the pin at each link. 3) Consequently, the pin holder was designed and applied, with little variance, but up to 93% of the specification limit.

• Journal of Preventive Medicine and Public Health
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• 제55권4호
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• pp.398-406
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• 2022

Objectives: While the risk of depression is expected to substantially increase among older adults receiving community care, leisure life satisfaction can be regarded as a key component in enhancing the mental health of those receiving community care. However, it is not yet known whether community care utilization increases the risk of depression, or what role is played by leisure life satisfaction in these settings. This study investigated the relationship between community care utilization and depression, as well as the main effect and the moderating role of leisure life satisfaction on the link between community care utilization and depression among older adults. Methods: This study, using the 2019 Korean Welfare Panel Survey, conducted multiple regression analysis on data from 4494 elderly people aged 65 years or older. Results: After controlling for potential covariates, older community care recipients were more likely to report symptoms of depression than those who did not receive community care. Meanwhile, leisure life satisfaction was negatively associated with depression in older adults. The test for interaction between community care utilization and leisure life satisfaction revealed that leisure life satisfaction significantly attenuated the link between depression and community care utilization. Conclusions: The findings of this study imply that leisure life satisfaction could play a meaningful role in improving the mental health of older adults receiving community care. Welfare policies affecting older adults should consider leisure life satisfaction as an important resource for reducing depression in community care settings.

• 대한교통학회지
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• 제24권2호
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• pp.19-30
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• 2006

본 연구는 일반국도의 통행특성을 고려한 지점검지기의 적정설치지점 선정을 다루고 있다. 일반국도에서의 ITS 구축은 활발히 진행되고 있으나. 자료수집 구간에서의 통행시간 추정 신뢰도에 가장 큰 영향을 미치고 있는 지점검지기의 설치지점에 관해 적절한 기준이 제시되지 못하고 있는 실정이다. 따라서 본 연구에서는 일반국도의 구간 통행시간의 추정을 위해 대표성을 확보할 수 있는 지점검지기의 적정설치지점을 선정하여 제시하고자 한다 이를 위하여 GPS 프로브 차량과 지점검지기를 이용하여 대상지역의 통행특성을 수집하고, 지점속도와 구간통행시간의 상관분석을 통하여 적정설치지점을 선택한다. 분석결과 일반국도의 구간별 적정설치지점의 특성은 다음과 같다. 첫째. 구간 통행시간과 지점 속도와의 상관관계는 구간의 시점에서부터 높아지다가 일정시점이 지나서는 낮아지는 U자형 형태를 보이고 있다. 둘째. 최적설치지점은 분석구간마다 상이하게 존재하나, 대부분 구간연장을 기준으로 중류부 및 중 하류부에 존재한다. 셋째, 구간의 적정설치지점은 구간의 중류부에서 하류부로 넘어가는 지점이 적절하며, 일반적으로 자료수집 구간 연장을 기준으로 시점부로부터 $55{\sim}60%$가 되는 지점이다. 넷째, 종단경사는 적정설치지점과 관련하여 중요한 결정인자가 되며, 종단경사가 큰 경우에 있어서 검지기의 설치는 배제되어야 한다. 끝으로, 본 연구의 결과를 토대로 한 지점검지기의 현장적용을 통해, 정보제공 구간내 통행시간 추정 및 예측력의 개선을 기대한다.

• 한국측량학회지
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• 제31권5호
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• pp.385-391
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• 2013

증가하고 있는 자동차로 인하여 발생하는 환경 문제의 해결방안으로 친환경 교통수단으로서의 자전거 이용이 권장되고 있다. 자전거 이용의 활성화를 위해서는 자전거 사용자의 이용목적을 반영할 수 있는 연결성과 안전성을 확보한 자전거 전용도로의 구축이 요구된다. 본 연구에서는 자전거 도로 이용자에 대한 설문조사 결과를 바탕으로 자전거의 주요 이용목적을 통학용 및 레저용으로 설정하고, 이와 관련된 시설물들을 Dijkstra 알고리즘을 활용하여 기 구축된 자전거 도로와 최단거리로 연계할 수 있는 방안을 도출하였다. 또한 탐색된 네트워크에 RTK DGPS 측량을 실시하여 3차원 좌표를 획득하고 이를 바탕으로 자전거 전용도로의 링크별 경사를 측정하였다. 측량된 경사를 활용하여 일정 경사 이상의 링크를 배제하고 우회도로를 탐색하는 방안을 적용하여 사용자의 편의와 안전을 확보하였다. 전라남도 목포시를 대상으로 제안된 방법을 적용하여 결과를 분석하였다.

• Journal of Power Electronics
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• 제17권6호
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• pp.1587-1599
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• 2017

This paper proposes a real-time implementation of an optimal operation of a double stage grid connected wind power system incorporating an active power filter (APF). The system is used to supply the nonlinear loads with harmonics and reactive power compensation. On the generator side, a new adaptive neuro fuzzy inference system (ANFIS) based maximum power point tracking (MPPT) control is proposed to track the maximum wind power point regardless of wind speed fluctuations. Whereas on the grid side, a modified predictive current control (PCC) algorithm is used to control the APF, and allow to ensure both compensating harmonic currents and injecting the generated power into the grid. Also a type 2 fuzzy logic controller is used to control the DC-link capacitor in order to improve the dynamic response of the APF, and to ensure a well-smoothed DC-Link capacitor voltage. The gained benefits from these proposed control algorithms are the main contribution in this work. The proposed control scheme is implemented on a small-scale wind energy conversion system (WECS) controlled by a dSPACE 1104 card. Experimental results show that the proposed T2FLC maintains the DC-Link capacitor voltage within the limit for injecting the power into the grid. In addition, the PCC of the APF guarantees a flexible settlement of real power exchanges from the WECS to the grid with a high power factor operation.

• Journal of Power Electronics
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• 제19권4호
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• pp.881-893
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• 2019

This paper proposes a practical sliding-mode controller design for shaping the impedances of cascaded boost-converter power decoupling circuits for reducing the second order harmonic ripple in photovoltaic (PV) current. The cascaded double-boost converter, when used as power decoupling circuit, has some advantages in terms of a high step-up voltage-ratio, a small number of switches and a better efficiency when compared to conventional topologies. From these features, it can be seen that this topology is suitable for residential (PV) rooftop systems. However, a robust controller design capable of rejecting double frequency inverter ripple from passing to the (PV) source is a challenge. The design constraints are related to the principle of the impedance-shaping technique to maximize the output impedance of the input-side boost converter, to block the double frequency PV current ripple component, and to prevent it from passing to the source without degrading the system dynamic responses. The design has a small recovery time in the presence of transients with a low overshoot or undershoot. Moreover, the proposed controller ensures that the ripple component swings freely within a voltage-gap between the (PV) and the DC-link voltages by the small capacitance of the auxiliary DC-link for electrolytic-capacitor elimination. The second boost controls the main DC-link voltage tightly within a satisfactory ripple range. The inverter controller performs maximum power point tracking (MPPT) for the input voltage source using ripple correlation control (RCC). The robustness of the proposed control was verified by varying system parameters under different load conditions. Finally, the proposed controller was verified by simulation and experimental results.

• 한국ITS학회 논문지
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• 제19권6호
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• pp.134-143
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• 2020

아프리카 돼지 열병의 세계적인 확산과 함께 가축전염병에 대한 관심이 증가하고 있다. 가축관련 운송차량은 가축전염병 확산의 주요 원인으로 제기되고 있으나 국내에서는 가축관련 운송차량의 이동성과 관련한 실증적인 방역절차와 기준이 마련되지 않고 있는 실정이다. 이에 본 연구는 국가가축방역시스템의 축산시설 방문이력 데이터와 한국교통안전공단의 DTG(Digital Tachograph) 데이터를 활용하여 가축관련 운송차량이 이용한 도로이용정보를 추출하고, 각 차량의 링크별 점유시간을 집계하여 노출도 지표로 제시하였다. 총 274,519행의 가축관련 운송차량의 통행궤적이 추출되었으며 링크별, 존별 노출도를 정량적으로 도출하였다. 본 연구를 통해 가축관련 운송차량의 사전 모니터링 및 사후 방역방침 수립이 가능할 것으로 기대된다.