• Structural Engineering and Mechanics
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• 제65권2호
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• pp.129-139
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• 2018

Post-tensioning (PT) tendons are commonly used for the assembly of modularized concrete members, and tension is applied to the tendons during construction to facilitate the integrated behavior of the members. However, the tension in a PT tendon decreases over time due to steel corrosion and concrete creep, and consequently, the stress on the anchor head that secures the PT tendon also diminishes. This study proposes an automatic detection system to identify tension reduction in a PT tendon using pulsed-eddy-current (PEC) measurement. An eddy-current sensor is installed on the surface of the steel anchor head. The sensor creates a pulsed excitation to the driving coil and measures the resulting PEC response using the pick-up coil. The basic premise is that the tension reduction of a PT tendon results in stress reduction on the anchor head surface and a change in the PEC intensity measured by the pick-up coil. Thus, PEC measurement is used to detect the reduction of the anchor head stress and consequently the reduction of the PT tendon force below a certain threshold value. The advantages of the proposed PEC-based tension-reduction-detection (PTRD) system are (1) a low-cost (< $ 30), low-power (< 2 Watts) sensor, (2) a short inspection time (< 10 seconds), (3) high reliability and (4) the potential for embedded sensing. A 3.3 m long full-scale monostrand PT tendon was used to evaluate the performance of the proposed PTRD system. The PT tendon was tensioned to 180 kN using a custom universal tensile machine, and the tension was decreased to 0 kN at 20 kN intervals. At each tension, the PEC responses were measured, and tension reduction was successfully detected.

• 한국항행학회논문지
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• 제18권4호
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• pp.304-311
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• 2014

본 논문에서는 항공기 복합재료 내부의 결함을 자동으로 검출하고 분류하는 초음파 검사 방식을 제안한다. 결함 검출을 위해서 초음파의 국부 최대값을 이용해 피크(peak) 값을 추출해낸다. 피크의 거리정보를 이용해 히스토그램화 하며 시편의 표면과 바닥의 백월에코(back-wall echo)를 결정한다. 이를 통해 C-scan 영상을 생성한다. 검출된 피크의 평균과 분산을 이용해 임계값을 정하고 그 값으로 결함여부를 판단한다. 결함의 종류를 구분하기 위해서는 주성분 분석(PCA; principal component analysis)와 이차 판별 분석(QDA; quadratic discriminant analysis)를 수행하였다. PCA를 통한 512개의 차원은 주성분으로 변환 시 30개의 주성분에 99% 이상의 분산이 포함되었다. 주성분 개수를 한정시킴으로써 차원 축소를 통해 계산량을 크게 줄였고 오분류를 최소화하였다. 이차 판별 분석을 적용해 결정경계(decision boundary)의 방정식을 얻었고 이를 통해 결함을 분류할 수 있음을 실험을 통해 보였다.

• Asian Pacific Journal of Cancer Prevention
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• 제14권9호
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• pp.5101-5105
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• 2013

The incidence and mortality of cervical cancer remains high in India even after sixty years of introduction of the Pap smear (cervical cytology) which is an effective means of identifying preinvasive lesions of carcinoma cervix. The morbidity and mortality due to cervical cancer has come down drastically in countries with well established screening programmes at national level. This study aims at screening women for cervical cancer opportunistically during their visit to hospital and to study various types of neoplastic and non-neoplastic lesions of the cervix by cervical smear study (Pap smear study). In the present study, a total of 350 cervical smears were studied. The age of patients ranged from 19 years to 80 years with mean age being 37.5 years. Out of 350 cases, the diagnosis of neoplasia was given in 43 cases and 258 cases were diagnosed as inflammatory smears. Forty-cases were normal and 9 cases were inadequate to evaluate. Forty-three patients who were found to have neoplastic lesions on cytology were referred for further investigations like colposcopy and biopsy to confirm the diagnosis and avail proper treatment. Limitation of the present study was small sample size as all female patients aged between 20 and 60 years visiting hospital were not included in the screening, other screening tests like VIA (visual inspection with acetic acid test) and HPV DNA (human papilloma virus) tests were not done. Until the time centrally organised screening programmes for cervical cancer are established in India, arrangements should be made for hospital based opportunistic screening for all women attending hospital. The cost effectiveness of different screening tests for cervical cancer should be evaluated.

• 한국유통학회지:유통연구
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• 제15권5호
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• pp.273-285
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• 2010

이 논문은 소매업체의 청과물 구입실태와 농산물 도매시장 구매의 문제점을 조사 분석하여 소매업체와 도매시장간 연계성 강화 방안을 모색하고 있다. 대형유통업체는 구매채널이 비교적 골고루 분산되어 효율적인 구매방식을 모색하고 있으나 중소 유통업체는 산지직거래 능력이 미약하여 주로 중도매인(방문구매)에 의존하고 있다. 업태별로 향후 도매시장 구입 의향을 보면, 대형유통업체와 외식/급식업체의 경우 도매시장 구입을 유지 내지 감축하려는 비율이 높고, 중소유통업체는 도매시장 구입을 확대 내지 유지하려는 경향을 보였다. 소매업체가 도매시장 구입 시 느끼는 문제점으로는 상품의 균질성 미흡과 속박이, 저온저장고 부족, 장소협소로 물류미비, 유통비용과다, 가격안정성 미흡 등이 있다. 농산물 도매시장이 시급히 개선해야 할 사항으로는 시장면적 확대로 물류효율화, 저온저장고 확충 등 시설 개선, 품질관리시스템 확립, 소분 포장 등 가공시설 확충 등인 것으로 조사되었다. 소매업체와 농산물 도매시장간 연계를 강화시키기 위해서는 도매시장 공간 확보를 통한 물류 원활화, 도매시장내 국가 검품제도 도입, 경락가격 안정화 방안 모색, 하역비 절감 방안, 소매업태별 차별화 마케팅 추진, 중도매인의 규모화 등이 필요하다. 거래제도 측면에서는 단기적으로 선취매매, 정가수의매매 등을 활성화시키고 중장기적으로는 도매상제도의 확대가 필요하다.

• 한국생산제조학회지
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• 제22권3_1spc호
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• pp.518-524
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• 2013

Recently, probabilistic assessments of nuclear power plant components have generated interest in the nuclear industries, either for the efficient inspection and maintenance of older nuclear plants or for improving the safety and cost-effective design of newly constructed nuclear plants. In the present paper, the partial safety factor (PSF) of wall-thinned nuclear piping is evaluated based on a reliability index method, from which the effect of each statistical variable (assessment parameter) on a certain target probability is evaluated. In order to calculate the PSF of a wall-thinned pipe, a limit state function based on the load and resistance factor design (LRFD) concept is first constructed. As for the reliability assessment method, both the advanced first-order second moment (AFOSM) method and second-order reliability method (SORM) are employed to determine the PSF of each probabilistic variable. The present results can be used for developing maintenance strategies considering the priorities of input variables for structural integrity assessments of wall-thinned piping, and this PSF concept can also be applied to the optimal design of the components of newly constructed plants considering the target reliability levels.

• Smart Structures and Systems
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• 제6권3호
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• pp.277-290
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• 2010

Internationally the load carrying capacity of bridges is decreasing due to material deterioration while at the same time increasing live loads mean that they are often exposed to stresses for which they were not designed. However there are limited resources available to ensure that these bridges are fit for purpose, meaning that new approaches to bridge maintenance are required that optimize both their service lives as well as maintenance costs. Wireless sensor networks (WSNs) provide a tool that could support such an optimized maintenance program. In many situations WSNs have advantages over conventional wired monitoring systems in terms of installation time and cost. In order to evaluate the potential of these systems two WSNs were installed starting in July 2007 on the Humber Bridge and on a nearby approach bridge. As part of a corrosion prevention strategy, a relative humidity and temperature monitoring system was installed in the north anchorage chambers of the main suspension bridge where the main cables of the bridge are anchored into the foundation. This system allows the Bridgemaster to check whether the maximum relative humidity threshold, above which corrosion of the steel wires might occur, is not crossed. A second WSN which monitors aspects of deterioration on a reinforced concrete bridge located on the approach to the main suspension bridge was also installed. Though both systems have provided useful data to the owners, there are still challenges that must be overcome in terms of monitoring corrosion of steel, measuring live loading and data management before WSNs can become an effective tool for bridge managers.

• 한국광학회지
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• 제20권4호
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• pp.241-248
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• 2009

액정 디스플레이에서 시야각 향상을 위해 사용하는 보상판과 편광판을 접합한 복합판의 광축 틀어짐 오차와 보상판의 $R_{in}$(in-plane retardation), $R_{th}$(out-of-plane retardation)를 동시에 결정하는 새로운 방법을 제시하였다. 보상판은 광축이 임의의 기울임각과 방위각을 갖는 o-판으로 하였으며, 확장된 존스 행렬법에 기반한 광학모델을 도입하여 복합판의 편광특성을 분석하였다. 입사각 0도와 50도에서 시료의 방위각을 360도 회전시키며 투과된 빛의 편광상태를 각각 계산한 후, 타원법의 모델링 분석기법을 적용하여 광축 틀어짐과 복합판의 기울임각과 방위각들을 역방계산하였다. 이 방법은 편광판과 보상판을 접합한 후에도 복합판의 성능평가를 할 수 있어 제조공정단계를 줄여 제조 원가를 절감하는데 기여할 수 있을 것으로 기대된다.

• 한국CDE학회논문집
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• 제13권2호
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• pp.139-152
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• 2008

In order to survive worldwide competition, today's industries are experiencing strong pressure to introduce higher quality products with lower cost and shorter lead-time. Therefore, the role of design in the process of product development is increasing in significance. In this research, two methods for improving the design capability are proposed: construction of design environment and design automation using 3D CAD system. The designers and design process are the core of product design using 3D CAD system. In order to maximize the design performance, construction of the design environment including selection of a suitable system, designer training for best use of the system, establishment of an efficient design process, and stabilization of the environment are required. A method is suggested to construct design environment by systematizing the contents of the projects and consulting experiences carried out for various categories of business such as electronic devices, motorcycles, electricity parts, sanitary wares, injection molds, and die casing molds. Design automation helps reduce tedious and time-consuming jobs, simplify complicated and error-prone modeling and drawing works to shorten the lead time and improve the product quality. To develop a design automation system, understanding the process and the related knowledge on design are very important before implementing the system using API provided by 3D CAD system. In this research, an eight-step procedure is proposed for the development of a design automation system. These eight steps are analysis of needs, determination of specification, verification of specification using 3D CAD system, inspection of related API functions, programming, field test, application in practice, and maintenance. A case study in which five design automation systems in the design of turbine generators using the proposed method is introduced in detail. These systems play important roles in the generation of various output items including 3D models, drafts, material information, and NC data. The case study shows how effectively the design time is reduced and the quality improved using those systems.

• 대한토목학회논문집
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• 제32권5D호
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• pp.463-472
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• 2012

국내 대다수의 토목 CM을 포함해 특히 도로부문 CM은 근 10여 년 간 다양한 시범 사업을 수행하고 있으나, 현재 건설시장의 안착에 상당한 어려움을 겪고 있으며 감독, 감리, CM이 과도기적으로 운영되는 여건 속에서 다양한 문제점에 노출되어 있다. 이러한 상황 속에서 부실시공 및 안전문제 등으로 대변되어 온 건설 산업에 대한 부정적인 시각을 극복하고 건설 산업 전반에 걸친 비용절감 및 품질향상을 이룩하여야 하는 당면과제는 필수적이다. 이를 위해 각 주체와 효율적으로 융화될 수 있는 CM의 정착은 매우 중요하다고 볼 수 있으며, 현재까지 다양한 분야에서 토목 CM의 정착화 방안에 대한 검증을 추진 중에 있다. 하지만 아직까지 수행성과에 대한 정확한 측정이 이루어지지 않고 있는 실정이며, 발주자를 위해 CM에 대한 객관적인 이해를 돕는 문헌이 매우 부족하다고 판단된다. 본 연구는 이러한 문제를 해결하고 발주처의 관점에서 바라본 CM 제도 활성화를 추진하기 위해 현재 수행되고 있는 다양한 CM의 업무 및 제도분석을 실시하였으며, 이를 통해 빈번하게 발생되는 문제점의 해결방안을 다각도로 제시하였다. 또한 발주처를 대상으로 설문조사를 실시하여 발주처의 관점에서 바라본 CM 제도 활성화 방안을 다양한 측면에서 제시 하였다. 이를 통해 얻어진 연구 결과는 향후 CM의 제도적 정립에 있어 중요한 기여를 할 것으로 판단된다.

• Strategy21
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• 통권46호
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• pp.29-56
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• 2020

Despite the deep concerns against the DPRK and the harsh sanctions imposed on it, the country renders the sanctions futile by facilitating various illegal trades such as the ship-to-ship transfers of petroleum or coal. Recently, the international community went into paying attention to solve this matter. Among the measures the community can take, "reinforcing the search and inspection of the DPRK related vessels transiting in the high and territorial seas" is the best policy approach to reduce the sanction evasion and provide the international community with considerable bargaining advantages. This measure requires the forceful action by legal enforcement agencies, also known as VBSS. (Visit, Board, Search, and Seizure) It would make the deals prohibited by the UNSCRs (United Nation Security Council Resolutions) less profitable by reducing the expected return on the deals and increasing the cost for them. So, it would make the illegal deals under the table less attractive. The DPRK has been able to render the sanctions futile by exploiting the limitations of the current maritime sanctions. The resolutions are short of being specific about law enforcement, and the PSI (Proliferation Security Initiative) is legally nonbinding. However, if the UNSCRs and the PSI are combined, they can generate a new source of power and exploit the weakness of the DPRK. Noting that the recent UNSCRs stipulated all the legal discussions in the resolutions are confined and applied only to the DPRK, the PSI can target the commercial trade as well as the WMD-related materials in the case of the DPRK's illegal maritime practices. Therefore, the PSI endorsing partners should go beyond mere commitments. They should discuss action plans to implement the maritime interdictions to the extent that they discourage the DPRK and its business partners continuing the illegal activities.