• 대한기계학회논문집A
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• 제27권6호
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• pp.890-897
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• 2003

This paper compares engineering estimation schemes of C＊ and creep COD for circumferential and axial through-wall cracked pipes at elevated temperatures with detailed 3-D elastic-creep finite element results. Engineering estimation schemes included the GE/EPRI method, the reference stress method where reference stress is defined based on the plastic limit load and the enhanced reference stress method where the reference stress is defined based on the optimized reference load. Systematic investigations are made not only on the effect of creep-deformation behaviour on C＊ and creep COD, but also on effects of the crack location, the pipe geometry, the crack length and the loading mode. Comparison of the FE results with engineering estimations provides that for idealized power law creep, estimated C＊ and COD rate results from the GE/EPRI method agree best with FE results. For general creep-deformation laws where either primary or tertiary creep is important and thus the GE/EPRI method is hard to apply, on the other hand, the enhanced reference stress method provides more accurate and robust estimations for C* and COD rate than the reference stress method.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2010년도 한국우주과학회보 제19권1호
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• pp.25.3-25.3
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• 2010

Our previous study used a bar-type reference mirror to measure the relative distance to the target surface. The target measurement accuracy was required to $1{\mu}m$ PV for aspheric optical surface up to 1m in diameter. Earlier system suffers from the reference surface deformation when the measuring part moves. In order to reduce the deformation, measuring part and the reference part separated from each order in the new design. This system utilizes a kinematic support assembly using invar flexure to minimize the reference surface deformation under gravity and vibration. The surface deformation requirement of reference mirror is defined as of $0.2{\mu}m$ under gravity and 40Hz vibration. The finite element results, shows reference mirror deformation of $0.164{\mu}m$. The first resonance mode was computed to analysis 46.05Hz for reference part and 43.44Hz for measuring part. Thesis satisfies the frequency requirement.

• 한국측량학회지
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• 제39권5호
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• pp.313-319
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• 2021

The national geodetic reference frame of Korea was adopted in 2003, which is referenced to ITRF (International Terrestrial Reference Frame) 2000 at the epoch of January 1, 2002. For precise positioning based on the satellites, it should be thoroughly maintained to the newest global reference frame. Other than plate tectonic motion, there are significant events or changes such as earthquakes, antenna replacement, PSD (Post-Seismic Deformation), seasonal variation etc. We processed three years of GNSS (Global Navigation Satellite System) data(60 NGII CORS stations, 51 IGS core stations) to produce daily solutions minimally constrained to ITRF. From the time series of daily solutions, the sites with unexpected discontinuity were identified to set up an event(mostly antenna replacement). The combined solution with minimum constraints was estimated along with the velocity, the offsets, and the periodic signals. The residuals show that the surrounding environment also affects the time series to a certain degree, thus it should be improved eventually. The transformation parameters to ITRF2014 were calculated with stability and consistency, which means the national geodetic reference frame is properly aligned to the global reference frame.

• 한국ITS학회 논문지
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• 제5권1호
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• pp.45-54
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• 2006

주파수 선택적 채널에서의 신호왜곡은 수신기에서의 채널추정을 어렵게 하여 펄스 타입의 UWB 시스템의 경우 동기 회로의 구현이 어렵다는 단점이 있다. 본 논문에서는 구현상 난점인 채널추정과 동기회로 설계를 간단히 기준 펄스를 함께 전송함으로써 해결하는 TR(Transmitted Reference), DTR(Differential TR) UWB을 분석하고 FSK 변조방법을 이용한 새로운 형태의 PRM(Pulse Repetition Modulation) UWB 방식을 제안한다. 기준 펄스를 이용한 통신의 수신기 구조인 Auto-correlation(AcR) 수신기가 잡음이 섞인 기준펄스를 이용하는 경우 성능저하 정도를 확률적으로 분석한다. 또한 SNR에 영향을 미치는 AcR 적분기의 적분구간에 대한 분석을 시뮬레이션을 통하여 분석한다.

• Imaging Science in Dentistry
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• 제41권2호
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• pp.53-57
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• 2011

Purpose : The purpose of this study was to evaluate the diagnostic performance of dental students in detection of mandibular condyle fractures and the effectiveness of reference panoramic images. Materials and Methods : Forty-six undergraduates evaluated 25 panoramic radiographs for condylar fractures and the data were analyzed through receiver operating characteristic (ROC) analysis. After a month, they were divided into two homogeneous groups based on the first results and re-evaluated the images with (group A) or without (group B) reference images. Eight reference images included indications showing either typical condylar fractures or anatomic structures which could be confused with fractures. Paired t-test was used for statistical analysis of the difference between the first and the second evaluations for each group, and student�fs t-test was used between the two groups in the second evaluation. The intra- and inter-observer agreements were evaluated with Kappa statistics. Results : Intra- and inter-observer agreements were substantial (k=0.66) and moderate (k=0.53), respectively. The area under the ROC curve (Az) in the first evaluation was 0.802. In the second evaluation, it was increased to 0.823 for group A and 0.814 for group B. The difference between the first and second evaluations for group A was statistically significant (p<0.05), however there was no statistically significant difference between the two groups in the second evaluation. Conclusion : Providing reference images to less experienced clinicians would be a good way to improve the diagnostic ability in detecting condylar fracture.

• 전기학회논문지P
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• 제66권4호
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• pp.213-218
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• 2017

The DC electrolytic capacitor for DC-link of power converter is widely used in various power electronic circuits and system application. Its functions include, DC Bus voltage stabilization, conduction of ripple current due to switching events, voltage smoothing, etc. Unfortunately, DC electrolytic capacitors are some of the weakest components in power electronics converters. Many papers have proposed different algorithms or diagnosis method to determinate the ESR and tan ${\delta}$ capacitance C for fault alarm system of the electrolytic capacitor. However, both ESR vary with frequency and temperature. Accurate knowledge of both parameters at the capacitors operating conditions is essential to achieve the best reference data of fault alarm. According to parameter analysis, the capacitance increases with temperature and the initial ESR decreases. Higher frequencies make the reference ESR with the initial ESRo value to decrease. Analysis results show that the proposed DC Bus electrolytic capacitor reference ESR model setting technique can be applied to advanced reference signal of capacitor diagnosis systems successfully.

• Industrial Engineering and Management Systems
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• 제11권1호
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• pp.30-38
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• 2012

This paper discusses a clearance pricing on daily perishable products considering a reference price of consumers. The daily perishable products are sometimes sold at a discount price before closing time to stimulate demand when the number of unsold products is more than initially envisioned. The discount pricing results both in an increase of the revenue of the day and in a decrease of the disposal cost. The discounting, however, also declines a reference price of consumers which is a mental price and serves as an anchor price to judge if a current sales price is loss or gain for the consumers. An excess discounting decreases the demand for the products sold at a regular price in the future and diminishes long-term profit. This study conducts a mathematical analysis on the clearance pricing problem for a single period with stochastic variations both on demand and on the inventory level at clearance time. The expected profit function especially depends on the response of consumers to the clearing price against their reference prices. A procedure is proposed to derive an optimal clearance price when consumers are loss-neutral. A sufficient condition is shown to obtain an optimal price for loss-averse and loss-seeking consumers by an analogous procedure.

• 한국정보통신학회논문지
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• 제25권4호
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• pp.530-536
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• 2021

LBP 알고리즘은 지역적 질감표현이라는 특성을 가지고 있기 때문에 기준영상과 샘플 영상의 추출 위치와 크기에 따라 전혀 다른 결과를 얻을 수 있다. 이러한 단점을 해결하기 위하여 본 논문에서는 먼저 LBP 기본특성을 조사하고, 기준영상(100×100)의 크기를 영상내의 대부분의 특성을 포함할 수 있도록 하고, 임의의 지점에서 추출된 샘플영상(40×40)을 선택한다. 기준영상의 LBP와 샘플영상의 LBP 간의 상관관계를 이용하여 기준영상의 LBP에서의 매칭위치를 찾은 후, 카이분석 방법을 사용하여 샘플영상과 가장 일치하는 기준영상을 찾는 방법을 제시한다.

• Journal of Electrical Engineering and information Science
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• 제1권1호
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• pp.45-50
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• 1996

This paper mainly describes the wind load assumption of 765kV transmission towers. We analyzed wind velocity data a meteorological observatories to get the wind velocity of 50 years return period by using Gumbel I type extreme value distribution. By multi-correlative regression analysis method, wind velocity at no observation site was obtained. Reference dynamics wind pressure map was obtained from above analysis and the wind pressure was classified as three regio in high temperature season.

• 융합보안논문지
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• 제6권4호
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• pp.91-99
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• 2006

그 동안 이루어진 웹 캐싱에 대한 연구주제는 캐시에 대한 구조적인 접근을 통한 성능의 향상과, 캐싱 기법 자체에 대한 연구, 이들 기법을 혼합적으로 결합한 기법에 대한 연구가 주로 이루어져 왔다. 또한 기존의 웹 객체 참조특성 분석은 웹 로그를 통한 히스토리 분석, 사용자선호도, 데이터마이닝 관점에서의 사용자 특성을 위주로 이루어져왔다. 본 연구에서는 웹 객체참조특성을 확률분포적인 특성 관점에서 분석하며, 이를 통해 객체의 평균수명을 분석하고 이를 웹 캐싱 성능 향상에 도입하는 새로운 연구 방법을 제시한다. 본 연구는 다양한 연구로 발전할 수 있으며, 전자상거래시스템의 성능향상, 지연시간 계산을 통한 고객 만족도의 향상, 웹 로그분석을 통한 데이터마이닝 분야 등 다양한 분야에 대해 연구의 파급 효과가 기대된다.