• 열처리공학회지
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• 제13권1호
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• pp.10-15
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• 2000

Evaluation of long term stability of the Brinell standard hardness tester was carried out to secure its application as a national standard in Brinell hardness. Accuracy and repeatability in load application were tested through evaluating errors in hardness measurement of certified reference blocks. All of those requirements in KS as well as ISO specifications were satisfied by this standard hardness tester. In addition to this, long term stability test of automatic indentation measurement system was carried out. The scattering range was almost the same with its error range. To figure out an optimum test condition for better repeatability and long term stability, the effect of load variation, load application speed and time have been studied using orthogonal array experimental plan. It was found that the best combination is $30{\mu}m/s$ of load application speed and 25 seconds of load application time.

• 한국태양에너지학회 논문집
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• 제33권5호
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• pp.1-8
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• 2013

Wind resource data of short-term period has to be corrected a long-term period by using MCP method that Is a statistical method to predict the long-term wind resource at target site data with a reference site data. Because the field measurement for wind assessment is limited to a short period by various constraints. In this study, 2 different MCP methods such as Linear regression and Matrix method were chosen to compare the predictive accuracy between the methods. Finally long-term wind speed, wind power density and capacity factor at the target site for 20 years were estimated for the variability of wind and wind energy. As a result, for 20 years annual average wind speed, Yellow sea off shore wind farm was estimated to have 4.29% for coefficient of variation, CV, and -9.57%~9.53% for range of variation, RV. It was predicted that the annual wind speed at Yellow sea offshore wind farm varied within ${\pm}10%$.

• 아태비즈니스연구
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• 제11권4호
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• pp.255-269
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• 2020

Purpose - This paper analyzes the market efficiency focusing on the long memory properties of the domestic futures market. By decomposing futures prices into yield and volatility and looking at the long memory properties of the time series, this study aims to understand the futures market pricing and change behavior and risks, specifically and in detail. Design/methodology/approach - This study analyzes KOSPI 200 futures, KOSDAQ 150 futures, 3 and 10-year government bond futures, US dollar futures, yen futures, and euro futures, which are among the most actively traded on the Korea Exchange. To analyze the long memory and market efficiency, we used the Variance Ratio, Rescaled-Range(R/S), Geweke and Porter-Hudak(GPH) tests as semi- parametric methods, and ARFIMA-FIGARCH model as the parametric method. Findings - It was found that all seven futures supported the efficiency market hypothesis because the property of long memory turned out not to exist in their yield curves. On the other hand, in futures volatility, all 7 futures showed long memory properties in the analysis, which means that if new information is generated in the domestic futures market and the market volatility once expanded due to the impact, it does not decrease or shrink for a long period of time, but continues to affect the volatility. Research implications or Originality - The results of this paper suggest that it can be useful information for predicting changes and risks of volatility in the domestic futures market. In particular, it was found that the long memory properties would be further strengthened in the currency futures and bond rate futures markets after the global financial crisis if the regime changes of the domestic financial market are taken into account in the analysis.

• 한국정보통신학회논문지
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• 제21권1호
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• pp.53-60
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• 2017

본 연구는 해상 인명구조를 위한 장거리, 광대역 멀티미디어 통신을 지원하는 드론을 설계하고 구현하는 것이다. 드론은 사람이 기계의 본체에 탑승하지 않고 무선전파의 유도에 의해서 조종이 가능한 무인항공기(UAV : Unmanned Aerial Vehicle)이다. 최근 증가하는 선박사고에 신속하게 대응하기 위하여 드론을 이용하고자 한다. 선박사고에 대응하기 위한 해상 장거리, 고속 영상 전송이 가능한 스마트 드론을 개발하기 위해서는 드론을 구조적으로 설계하는 하드웨어 설계부분과 개발된 드론을 동작시키기 위한 제어기술 그리고 원격지에서 드론을 제어하기 위한 통신기술등이 필요하다. 본 논문은 해상 장거리, 광대역 멀티미디어 통신을 지원하는 드론 구조를 설계하기 위한 제한사항과 요소기술을 정리하고 이를 위한 드론 구조를 설계 및 구현한다. 이러한 통신용 드론을 드론 네트워크로 확장함으로써 드론의 활용성을 확장하고자 한다.

• 한국인터넷방송통신학회논문지
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• 제18권6호
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• pp.83-90
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• 2018

LoRa(Long Range)는 장거리, 저 전력 통신 기술이다. 근거리 무선 통신 기술보다 통신 범위가 넓어 다수의 AP를 설치하지 않고도 통신할 수 있으며, 초기 인프라 구축비용을 줄일 수 있다. MQTT(Message, Queuing, Telemetry, Transport) 프로토콜 또한 저 전력, 경량 프로토콜로 LoRa와 함께 사용 시 모듈의 지속성을 증가시키고, 유지보수 비용을 줄일 수 있다. 본 논문에서는 이러한 LoRa와 MQTT를 활용해 공장 안의 다양한 환경 정보를 취합하는 시스템을 개발하였다. 먼 거리에 위치한 작업장들의 환경 센서 데이터를 관리 시스템에서 모니터링 할 수 있고, 각 작업장에 있는 설비들을 제어할 수 있다. 또한, 성능 실험을 통해 LoRa와 MQTT 활용이 장거리, 전력소모 측면에서 효과적임을 확인했다.

• 산업경영시스템학회지
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• 제37권2호
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• pp.27-34
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• 2014

In this paper, we investigate the statistical correlation of the time series for temperature measured at the heat box in the automobile drying process. We show, in terms of the sample variance, that a significant non-linear correlation exists in the time series that consist of absolute temperature changes. To investigate further the non-linear correlation, we utilize the volatility, an important concept in the financial market, and induce volatility time series from absolute temperature changes. We analyze the time series of volatilities in terms of the de-trended fluctuation analysis (DFA), a method especially suitable for testing the long-range correlation of non-stationary data, from the correlation perspective. We uncover that the volatility exhibits a long-range correlation regardless of the window size. We also analyze the cross correlation between two (inlet and outlet) volatility time series to characterize any correlation between the two, and disclose the dependence of the correlation strength on the time lag. These results can contribute as important factors to the modeling of forecasting and management of the heat box's temperature.

• 대한물리의학회지
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• 제8권4호
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• pp.573-582
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• 2013

PURPOSE: The purpose of this study was to establish the reliability and validity of the Wheelchair User's Shoulder Pain Index (WUSPI), which was translated into Korean for long-term wheelchair users. This index measured 15 functional activities, including transfer, self-care, wheelchair mobility and general activities. METHODS: To assess test-retest reliability, 23 long-term wheelchair users completed this self-administered index twice within the same day. Reliability was determined by the intraclass correlation coefficient (ICC), and Cronbach's alpha was used to measure internal consistency. To examine concurrent validity, 21 long-term wheelchair users completed the questionnaire, and we examined the correlation between the index score and the shoulder range of motion measurements. RESULT: The results showed that the intraclass correlation for test-retest reliability of the total index score ranging from .88 to .99 was good to excellent. Additionally, Cronbach's alpha was .96. The internal consistency indicated excellent. Concurrent validity showed negative correlations of total index score to range of motion measurements of shoulder flexion (rho=-.58), extension (rho=-.09), abduction (rho=-.59), external rotation (rho=-.07) and internal rotation (rho=-.3), suggesting a relationship of total index score to loss of shoulder range of motion. CONCLUSION: The Korean WUSPI shows not only high reliability and internal consistency, but also concurrent validity with loss of shoulder flexion and abduction.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.2179-2183
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• 2009

As urbanization is progressed, the network for distributing water in a basin become complex due to the spatial expansion and parameter uncertainties of water supply systems. When a long range water supply plan is determined, the total construction and operation cost has to be evaluated with the system components and parameter uncertainties as many as possible. In this paper, the robust optimization approach of Bertsimas and Sim is applied in a hypothetical system to find a solution which remains feasible under the possible parameter uncertainties having the correlation effect between the uncertain coefficients. The system components to supply, treatment, and transport water are included in the developed water supply system and construction and expansion of the system is allowed for a long-range period. In this approach, the tradeoff between system robustness and total cost of the system is evaluated in terms of the degree of conservatism which can be converted to the probability of constraint violation. As a result, the degree of conservatism increases, the total cost is increased due to the installation of large capacity of treatment and transportation systems. The applied robust optimization technique can be used to determine a long-range water supply plan with the consideration of system failure.

• BMB Reports
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• 제31권4호
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• pp.307-327
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• 1998

Cytochrome c peroxidase (CcP) is a yeast mitochondrial enzyme which catalyzes the reduction of hydrogen peroxide to water using two equivalents of ferrocytochrome c. The CcP/cytochrome c system has many features which make it a very useful model for detailed investigation of heme protein structure/function relationships including activation of hydrogen peroxide, protein-protein interactions, and long-range electron transfer. Both CcP and cytochrome c are single heme, single subunit proteins of modest size. High-resolution crystallographic structures of both proteins, of one-to-one complexes of the two proteins, and a number of active-site mutants are available. Site-directed mutagenesis studies indicate that the distal histidine in CcP is primarily responsible for rapid utilization of hydrogen peroxide implying significantly different properties of the distal histidine in the peroxidases compared to the globins. CcP and cytochrome c bind to form a dynamic one-to-one complex. The binding is largely electrostatic in nature with a small, unfavorable enthalpy of binding and a large positive entropy change upon complex formation. The cytochrome c-binding site on CcP has been mapped in solution by measuring the binding affinities between cytochrome c and a number of CcP surface mutations. The binding site for cytochrome c in solution is consistent with the crystallographic structure of the one-to-one complex. Evidence for the involvement of a second, low-affinity cytochrome c-binding site on CcP in long-range electron transfer between the two proteins is reviewed.

• 비파괴검사학회지
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• 제28권5호
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• pp.416-420
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• 2008

전자기음향변환기 분야에서는 나선형 RF 코일이 솔레노이드 코일보다 훨씬 널리 사용되고 있다. 그러나 실린더 구조물의 원거리 초음파검사용 자왜 스트립 도파변환기 분야에서는 솔레노이드 코일이 주로 사용되어왔다. 이는 아마도 낮은 주파수의(즉, 치수가 큰) 나선형 코일의 제작의 어려움에 기인하는 것 같다. 본 논문에서는 FFC(flexible flat cable)로 나선형 코일 자왜 스트립 도파변환기를 제작하는 방법을 기술한다. 기존의 솔레노이드 코일 변환기와의 비교실험을 통하여 나선형 코일 변환기가 훨씬 우수한 성능(감도, 신호-대-잡음 비, 도파방향조정능력)을 갖는다는 것을 실증한다.