• 전력전자학회논문지
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• 제27권6호
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• pp.535-540
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• 2022

DC-link capacitors are reliability-critical components in a photovoltaic (PV) inverter. Typically, the lifetime of a DC-link capacitor is evaluated by considering the voltage and hot-spot temperature of the capacitor under the specific operating condition of the PV inverter. However, the output of the PV inverter is determined by solar irradiation and ambient temperature, which vary with the seasons; accordingly, the hot-spot temperature of the capacitor also changes. Therefore, the mission profile of the PV system should be considered to effectively evaluate the reliability of the DC-link capacitor. In this study, the reliability of the DC-link capacitor of a three-level NPC inverter is comparatively analyzed with and without considering the mission profiles of the PV system, where two mission profiles recorded in Arizona and Iza are considered. The accumulated damage of the DC-link capacitor is calculated based on the lifetime model by analyzing its thermal loading. Afterward, a reliability evaluation of the DC-link capacitor is performed at the component level and then at the system level by considering all capacitors by means of Monte Carlo analysis. Results reveal the importance of performing a mission-profile-based reliability evaluation during the design of high-reliability PV inverters to achieve the target reliability performance.

• ETRI Journal
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• 제40권1호
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• pp.101-110
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• 2018

In wireless positioning systems using range measurements non-line-of-sight (NLOS) links cause estimation errors. Several studies have attempted to improve the positioning performance by mitigating these NLOS errors. These studies, however, have focused on the performance of a dataset consisting of three or more links. Therefore, measurement errors induced by links are averaged, and a reliable link is not fully utilized in the dataset. This paper proposes a Link Reliability based on Range Measurement (LRRM) scheme, which specifies the relative reliability of each link using residuals. The link reliability becomes the input to a Link Residual Weighting (LRW) scheme, which is also proposed as a weighted positioning scheme. Moreover, LRRM and LRW constitute new turbo positioning, where the estimation errors are reduced considerably by iterative updates.

• 한국신뢰성학회지:신뢰성응용연구
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• 제14권2호
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• pp.103-107
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• 2014

An algorithm to get network reliability, where each link has probability of fuzzy number, is proposed. Decomposition method and fuzzy numbers arithmetic are applied to the algorithm. Pivot link is chosen one by one from start node recursively at time of decomposition, and arithmetic of fuzzy complementary numbers is included at the same time. No criteria of pivot link selection and the recursive calculation make the algorithm simple.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2001년도 정기학술대회
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• pp.455-462
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• 2001

We propose a new method to evaluate the network reliability which greatly reduces the intermediate steps toward calculations of maximum capacity flow by excluding unnecessary simple paths contained in the set of failure simple paths. By using signed simple paths and signed flow, we show that our method is more efficient than that of Lee and Park (2001a) in the number of generated composite paths and in the procedure for obtaining minimal success composite paths. Numerical examples are given to illustrate the use and the efficiency of the method.

• International Journal of Reliability and Applications
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• 제2권1호
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• pp.73-80
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• 2001

A network, where links have different capacities, is considered to be in functioning state if a specified amount of flow can be transmitted through the network. In this paper, we consider the measures of importance of a link in such networks. We define the structural importance and reliability importance of a link when the required amount of flow is given. We also present the performability importance, which can be used to determine which links should be improved first in order to make the greatest improvement in the expected maximum flow of network. Numerical examples are presented as well for illustrative purpose.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2000년도 추계학술대회
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• pp.405-409
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• 2000

The flow network is considered to be in a functioning state if it can transmit a maximum flow which is greater than or equal to a specified amount of flow. In this paper we consider the measures of importance of a link in the flow network. We define the structural importance and reliability importance of link when the required amount of flow is given. Also, we present the performance importance of link in a flow network. The performance importance can be used to determine which links should be improved first in order to make the greatest improvement in performance of the network. Numerical examples are presented for illustrative purpose.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.249-252
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• 1998

ETSI(European Telecommunications Standards Institute) 300 34701, ITU-T(International Telecommunication Union) G.965 recommended PSTN, CONTROL, LINK CONTROL, BCC, PROTECTION protocols on V-Interfaces. But it is possible to occur misalignment between LE(Local Exchange) and AN(Access Network), especially in link identification procedure because there isn't any comment about V5.2 system management. In this paper we propose S/W guard timer to improve reliability in V5.2 link identification procedure in scope of Recommendation.

• 한국정보통신학회논문지
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• 제24권7호
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• pp.891-897
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• 2020

비행종단시스템은 지상국과 탑재체로 구성되며, 발사체가 계속 비행하는 것이 위험하다고 판단할 경우 강제로 비행을 종단시키는 역할을 한다. 이를 위해서는 비행 구간 내내 일정 수준 이상의 통신 신뢰도를 유지하여야 하나, 국내 유도무기 시험장에서는 점차 요구 성능이 늘어남에 따라 해당 조건을 일부 충족하지 못했다. 본 논문에서는 비행종단시스템의 링크 버짓을 분석하였고, 필요한 링크 마진을 확보할 수 있도록 지상국에 해당하는 비상종료 명령 송신시스템을 설계 및 개발하였다. 이후 탑재체에서의 수신 신호세기를 측정하여 기존 송신시스템과의 성능을 비교하였으며, 이로써 비행종단시스템의 통신 신뢰도가 향상되었음을 확인하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.578-580
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• 2009

무선 센서 네트워크는 다양한 분야에 응용하여 사용하고 있다. 배터리를 사용하는 센서노드는 전원이 제한적이기 때문에 다양한 기능과 전송의 신뢰성보다 저전력을 사용하는 동작에 더 최적화 되어있다. 하지만 더욱 다양한 목적으로 정확한 데이터를 사용하기 위해서는 전송의 신뢰성이 보장되어야 한다. 멀티홉 환경으로 구성되어 있는 센서 네트워크에서 종단간 전송 신뢰성을 보장하기 위해서는 링크(홉)간의 전송 신뢰성이 바탕이 되어야 하지만, IEEE 802.15.4 표준은 링크계층의 전송 신뢰성을 고려하지 않고 있다. 본 논문에서는 에너지를 효율적으로 사용하면서 링크(홉)간 전송 신뢰성을 제공하기 위한 링크계층 프로토콜을 제안한다.

• 대한기계학회논문집
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• 제18권9호
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• pp.2257-2264
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• 1994

A method to evaluate the position performance for a stochastically defined planar robot manipulator is presented. Performance is defined as the operational reliability based upon the positional errors of the manipulator tip. An analytical method is developed and applied to a two-link robot manipulator through forward kinematics. This study includes uncertainties in the link length, pin center location and radial clearance. By virtue of the effective link length model, only the nominal manipulator model and statistical information on the uncertainties are required. The results from the analytical method is compared to those from the Monte Carlo simulation.