• International Journal of Concrete Structures and Materials
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• 제11권2호
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• pp.199-213
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• 2017

Chloride penetration is among the main causes of corrosion initiation in reinforced concrete (RC) structures producing premature degradations. Weather and exposure conditions directly affect chloride ingress mechanisms and therefore the operational service life and safety of RC structures. Consequently, comprehensive chloride ingress models are useful tools to estimate corrosion initiation risks and minimize maintenance costs for RC structures placed under chloride-contaminated environments. This paper first presents a coupled thermo-hydro-chemical model for predicting chloride penetration into concrete that accounts for realistic weather conditions. This complete numerical model takes into account multiple factors affecting chloride ingress such as diffusion, convection, chloride binding, ionic interaction, and concrete aging. Since the complete model could be computationally expensive for long-term assessment, this study also proposes model simplifications in order to reduce the computational cost. Long-term chloride assessments of complete and reduced models are compared for three locations in France (Brest, Strasbourg and Nice) characterized by different weather and exposure conditions (tidal zone, de-icing salts and salt spray). The comparative study indicates that the reduced model is computationally efficient and accurate for long-term chloride ingress modeling in comparison to the complete one. Given that long-term assessment requires larger climate databases, this research also studies how climate models may affect chloride ingress assessment. The results indicate that the selection of climate models as well as the considered training periods introduce significant errors for mid- and long- term chloride ingress assessment.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.993-1000
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• 2009

In general, a drilled shaft embedded in weathered rock has a large load bearing capacity. Therefore, most of the load tests are performed only up to the load level that confirms the pile design load capacity, and stopped much before the failure load of the pile is attained. If a reliable failure load value can be extracted from the premature load test data, it will be possible to greatly improve economic efficiency as well as pile design quality. The main purpose of this study is to propose a standard for judging the reliability of the failure load of piles that is obtained from extrapolated load test data. To this aim, eleven static load test data of load-displacement curves were obtained from testing of piles to their failures from 3 different field sites. For each load-displacement curve, loading was assumed as 25%, 50%, 60%, 70%, 80%, and 90% of the actual pile bearing capacity. The limited known data were then extrapolated using the hyperbolic function, and the failure load was re-determined for each extrapolated data by the ASCE 20-96 method (1997). Statistical analysis was performed on the reliability of the re-evaluated failure loads. The results showed that if the ratio of the maximum-available displacement to the failure-load displacement exceeds 0.6, the extrapolated failure load may be regarded as reliable, having less than a conservative 20% error on average. The applicability of the proposed standard of judgment was also verified with static load test data of driven piles.

• 한국정보통신학회논문지
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• 제18권7호
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• pp.1531-1539
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• 2014

조기심실수축(PVC)은 가장 보편적인 부정맥으로 심실세동, 심실빈맥 등과 같은 위험한 상황을 유발할 수 있는 가능성을 가지고 있기 때문에 이의 조기 검출은 매우 중요하다. 하지만 ECG 신호의 개인 차이가 있음에도 불구하고, 일반적인 신호의 판단 규칙에 따라 진단을 수행함으로써 성능하락이 나타날 수 밖에 없다. 이러한 문제점을 극복하기 위해서는 개인에 따른 이상 신호를 검출한 후 다양한 QRS 패턴을 고려하여 PVC를 분류할 수 있는 알고리즘이 필요하다. 본 연구에서는 개인별 이상신호 검출과 QRS 패턴 변화에 따른 PVC 분류 기법을 제안한다. 이를 위해 전 처리 과정과 차감기법을 통해 R파를 검출하였으며, 개인별 이상신호를 검출하였다. 이후 QRS 패턴에 따른 QS 간격과 R파의 진폭 변화율에 따라 PVC를 분류하였다. 제안한 알고리즘의 이상 신호 검출 및 PVC 분류 성능을 평가하기 위해서 MIT-BIH 부정맥 데이터베이스를 사용하였다. 성능평가 결과, 이상 신호 검출률은 98.33%, PVC는 각각 94.46%의 평균 분류율을 나타내었다.

• 전기학회논문지
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• 제58권2호
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• pp.391-398
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• 2009

In this study, we introduce the design methodology of an optimized fuzzy cascade controller with the aid of hierarchical fair competition-based genetic algorithm(HFCGA) for ball & beam system. The ball & beam system consists of servo motor, beam and ball, and remains mutually connected in line in itself. The ball & beam system determines the position of ball through the control of a servo motor. The displacement change the position of ball leads to the change of the angle of the beam which determines the position angle of a servo motor. Consequently the displacement change of the position of the moving ball and its ensuing change of the angle of the beam results in the change of the position angle of a servo motor. We introduce the fuzzy cascade controller scheme which consists of the outer(1st) controller and the inner(2nd) controller as two cascaded fuzzy controllers, and auto-tune the control parameters(scaling factors) of each fuzzy controller using HFCGA. The inner controller controls the position of lever arm which corresponds to the position angle of a servo motor and the outer controller decides the set-point value of the inner controller. HFCGA is a kind of parallel genetic algorithms(PGAs), and helps alleviate the premature convergence being generated in conventional genetic algorithms (GAs). For a detailed comparative analysis from the viewpoint of the performance results and the design methodology, the proposed method for the ball & beam system which is realized by the fuzzy cascade controller based on HFCGA, is presented in comparison with the conventional PD cascade controller based on serial genetic algorithms.

• 농업과학연구
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• 제39권4호
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• pp.467-471
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• 2012

In this study, we investigated the antioxidative and antiaging activity of Perilla frutescens using LLC-$PK_1$ porcine renal epithelial cell and WI-38 human diploid fibroblast cell. The extract from Perilla frutescens showed strong protective effect against nitric oxide (NO) and superoxide ($O_2{^-}$)-induced oxidative stress generated by sodium nitroprusside (SNP) and pyrogallol, respectively. The result showed that P. frutescens increased the cell viability and showed scavenging activity of NO and $O_2{^-}$. In addition, the extract of P. frutescens exerted the protective effect against peroxynitrite ($ONOO^-$) induced by 3-morpholinosydnonimine. It suggests that P. frutescens would have the protective role against $ONOO^-$ itself and its precursors, NO and $O_2{^-}$. Furthermore, the aging model of hydrogen peroxide ($H_2O_2$)-treated WI-38 human diploid fibroblast was employed to investigate the anti-aging effect of P. frutescens. $H_2O_2$-treated WI-38 cells showed the loss of cell viability, however before-treatment with P. frutescens to WI-38 cells under premature senescence could delay the cellular aging process. The present study suggests the antioxidative and antiaging potential against free radical-induced oxidative damage of P. frutescens.

• 한국전산구조공학회논문집
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• 제19권1호
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• pp.27-37
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• 2006

모사풀림(SA)의 특징적인 Metropolis 규준을 단순 유전자 알고리즘(SGA)의 재생산 연산과정에 도입함으로써 Metropolis 유전자 알고리즘(MGA)이 개발되고, 구조 설계 최적화에 응용되었다. 이러한 결합을 통하여 MGA는 개체의 다양성을 유지하며, 초기 세대에서 나타날 수 있는 유용한 유전자 정보가 보존될 수 있다. 따라서 이 연구에서 제안된 MGA는, 국부적 최적해로 조기 수렴하게 되는 SGA의 단점과 정밀한 전역적 최적해를 찾기 위해 수없이 많은 계산을 해야 하는 SA의 단점을 극복하게 되었다 수치예를 통하여 MGA의 성능과 적용성을 재래의 알고리즘들과 비교하고 평가하였다. 특히 MGA의 성능 신뢰성과 강건성을 평가하는 데는 집단 크기와 최대 반복세대수의 효과를 인용하였다. 이론적 고찰과 수치예의 결과로부터, 이 연구에서 개발된 MGA가 효율성과 신뢰성을 갖춘 구조 설계 최적화의 도구로서 평가되었다.

• 한국전산구조공학회논문집
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• 제21권5호
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• pp.483-491
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• 2008

철근콘크리트 보에 대한 섬유-강판 복합플레이트의 보강효과를 연구하였다. 합계 12개 철근콘크리트 보 중, 7개는 탄소 섬유-강판 복합플레이트(CSP)로 보강되었으며, 4개는 유리섬유-강판 복합플레이트(GSP)로 보강되었고, 나머지 1개는 비교를 목적으로 보강되지 않았다. 보강보 실험결과, 새로 개발된 섬유-강판 복합플레이트 보강시스템은 보강재의 조기탈락을 제어하여 연성파괴를 유도하는 것으로 나타났다. 본 연구에 사용된 CSP 보강보의 연성지수는 $3.01\sim3.81$, GSP 보강보의 연성지수는 $3.55\sim4.95$로 측정되었다. ESP 보강보 및 GSP 보강보의 최대하중은 보강하지 않은 기준보에 비해 각각 115%, 107% 향상된 것으로 측정되었다. 또한, 보강보 실험과 해석 결과들은 잘 일치하는 것으로 나타났다.

• 한국지진공학회논문집
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• 제8권3호
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• pp.87-96
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• 2004

최근에 수행된 보 플랜지 절취형 (Reduced Beam Section, RBS) 내진 철골모멘트접합부의 실험 결과에 의하면, 보 웨브를 볼트 접합한 시험체는 보 웨브를 용접 접합한 시험체에 비해서 조기에 스캘럽을 가로지르는 취성파단이 발생하는 열등한 내진성능을 보였다. 실험결과에 의할 때, 이러한 접합부 취성파괴가 발생하는 주요 원인은 웨브 볼트의 슬립과 고전 휨이론에 의한 예측과는 전혀 다른 응력 전달메카니즘에 의한 스캘럽 부근의 응력집중 때문으로 사료된다. 이는 고전 휨이론에 기초한 전통적 보 웨브 볼트접합부의 설계법을 재검토할 필요가 있음을 시사하는 것이다. 본 연구를 통하여 고전 휨이론에 기초한 현행의 보 웨브 설계법에 문제가 있음을 지적하였다. 실험 및 해석결과를 바탕으로 RBS 접합부의 실제 응력전달경로에 부합되는 새로운 보 웨브 볼트접합 설계법을 제안하였다.

• Clinical and Experimental Reproductive Medicine
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• 제41권1호
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• pp.29-32
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• 2014

Objective: To investigate the causes of amenorrhea in Korean women. Methods: Medical records from 1,212 women with amenorrhea who visited the Department of Obstetrics and Gynecology, Asan Medical Center, between January 1989 and December 2011 were retrospectively reviewed. Amenorrhea was categorized as either primary or secondary. Results: Primary amenorrhea was identified in 132 of the patients (10.9%) and secondary amenorrhea in 1,080 (89.1%). The most frequent causes of primary amenorrhea were gonadal dysgenesis (28.0%, 37/132); Mayer-Rokitansky-K$\ddot{u}$ster-Hauser syndrome (20.0%, 27/132); and constitutional delay and androgen insensitivity syndrome (8.3%, 11/132; 8.3%, 11/132, respectively). Secondary amenorrhea was due to polycystic ovary syndrome (48.4%, 523/1,080); premature ovarian insufficiency (14.0%, 151/1,080); and nutrition-related hypogonadotropic hypogonadism (8.3%, 90/1,080). Conclusion: In this retrospective study, gonadal dysgenesis was the most common cause of primary amenorrhea and polycystic ovary syndrome was the most common cause of secondary amenorrhea in Korean women.

• STI Policy Review
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• 제7권2호
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• pp.60-84
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• 2016

What impact does the sharing economy have on existing businesses? This paper empirically examines how Uber transformed the taxi industry in New York City. Using a regression model controlling various potential influencing factors, we find no direct evidence that daily trips or revenue per taxi driver decreased since Uber entered the taxi industry. However, a closer investigation into other dimensions of taxi trips reveals that taxi drivers were forced to change their way of doing businesses to retain existing daily trips and revenue. Since Uber crowded out yellow taxis from the central area of Manhattan, yellow taxis responded by serving customers outside of the Manhattan borough. From enlarging their geographical coverage and serving customers that were previously ignored, yellow taxis were able to retain their previous level of taxi trips and market share. We also find that yellow taxis responded by improving their service quality to better serve customers' needs. Our result suggests that incumbents actively responded to Uber's entry and provided substantial benefit to consumers. Combined with the incumbent's response, the sharing economy transformed the existing market in a welfare-enhancing way. This paper provides managerial and policy implication on how incumbents affected by the disruptions of the sharing economy should respond. Even though it might be yet premature to examine the impact of Uber, results suggest that incumbents have effectively defended against Uber's entry so far. We conclude that the sharing economy and the existing economy can create positive value in our society through well-intentioned competition, complementing each other's weaknesses and strengths.