• Structural Engineering and Mechanics
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• 제81권1호
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• pp.59-68
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• 2022

Prestressed prefabricated hollow core concrete slabs with spans of 5 m and 10 m are commonly used since last century and still in service due to the advantage of construction convenience and durability. However, the end slabs are regularly subjected to cracks at the top and fail with brittleness due to the asymmetric boundary conditions. To better maintain such widely used type of hollow core slabs, the effect of asymmetric constraint in the end slabs are systematically studied through detailed nonlinear finite element analyses and experimental data. Experimental tests of slabs with four prestressed tendons and seven prestressed tendons with different boundary conditions were conducted. Results observe three failure modes of the slabs: the bending failure mode, shear and torsion failure mode, and transverse failure mode. Detailed nonlinear finite element models are developed to well match the failure modes and to reveal potential damage scenarios with asymmetric boundary conditions. Recommendations regarding ultimate capacity of the slabs with asymmetric boundary conditions are made to ensure a safe and rational design of prestressed concrete hollow slabs for short span bridges.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2002년도 제7차 학술대회 초록집
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• pp.47-49
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• 2002

At present, the trend of magnetic field strength in MRI system is dramatically changing. In early 70, the only low field (<0.5T) was developed. It was technically difficult to develop the high field system. At that time, people believed that the fine MR imaging could not be obtained in the high field MR system due to the magnetic susceptibility effect. However, 1.5T system was evolved at the end of 80, and used for clinical usage. Thus, it was proved that the signal to noise ratio (SNR) could be greatly contribute to enhance the image quality. And, the results of functional MRI and MR spectroscopy could be improved in the higher field MR system. So, 8T system was eventually developed in Ohio State University Hospital at the end of 90. Therefore, there is no doubt that the system with the ultra high magnetic field strength will be developed near future in 21 century.

• 한국수학사학회지
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• 제11권1호
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• pp.1-9
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• 1998

This article explores what is the genuine Koreanness in Korean arithmetic by examining what kind of influence the Chinese arithmetic had on the Korean arithmetic and how the Korean arithmetic scholars had accepted and utilized it. Because the main stream of Korean culture before the end of Chosun dynasty was located under the umbrella of the Chinese philosophy, technique, and culture, it is necessary to make researches on the historical documents and materials in order to establish the milestone in the Korean arithmetic history for the Korean arithmetic scholars. For this research, the arithmetic books published in between the sixteenth century and the end of Chosun dynasty are mainly consulted and discussed, dealing with the bibliographical introduction in the arithmetic Part in Re Outline History of the Korean Science & Technology written by Prof. Yong-Woon Kim.

• Parasites, Hosts and Diseases
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• 제51권1호
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• pp.43-49
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• 2013

Three species of tapeworms infect humans in their adult stage (Taenia solium, Taenia saginata and Taenia asiatica). The 3 are flat, opaque white or yellowish, and exceptional long segmented parasites, measuring 1 to 12 m in their adult stage. In this review, the development of the knowledge regarding the first species, mainly focused on understanding how the larval stage or cysticercus is transmitted to humans, is described. The second species is a cosmopolitan parasite that only causes taeniosis and not cysticercosis; therefore, it will not be included. Information on the third species, which is presently being produced, since this species was recognized as such only at the end of the 20th century, will be discussed at the end of this review.

• Tribology and Lubricants
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• 제31권4호
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• pp.177-182
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• 2015

Tapered roller bearings are widely used in equipment where high combined thrust and radial loads are experienced. A certain amount of tilting between the tapered rollers and the races always occurs because of bending moment load conditions and shaft deflection. It is now well understood that a coherent elastohydrodynamic lubrication (EHL) film separates the rollers and races. In spite of extensive study on EHL problems for over half a century, relatively few studies have focused on the finite line contacts problem. This study presents a complete numerical analysis of the effects of roller tilting on the EHL characteristics in a tapered roller bearing. We systematically analyze this highly nonlinear problem using finite differences with fully non-uniform grids and the Newton-Raphson method. Detailed EHL pressure distributions and film shapes are presented under moderate loads and material parameters. A very small roller tilting significantly affects the pressure distributions and film shapes near both ends of the roller. Moreover, the effect of tilting on the EHL characteristics at the small end is much greater than that at the large end. Therefore, in designing optimum profiles for tapered roller bearings, the profile radius should be larger at the small end.

• 한국시조학회지:시조학논총
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• 제26집
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• pp.151-185
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• 2007

사대부 계층이 중심이 되어 이루어진 시조에 삶의 물적 토대인 구체적 생산의 현실이 어떻게 투영되어 있는가를 살피는 것이 이 글의 목적이다. 생산 관련 생활은 사회 체제의 필연적 근거인데, 생산 활동과 무관한 것으로 보이는 시조를 이런 관점에서 논의하는 일은 시조 작품과 작가를 이해하는 또 다른 방법이다. 생활을 다룬 시조의 작가는 크게 유명씨와 무명씨로 나누어진다. 유명씨는 사대부와 평민 가객, 무명씨는 사대부와 평민 가객, 시정인으로 구성되어 있다. 시대적으로 14-17세기에는 사대부 작가가 중심이고 18-19세기에는 평민 가객이 새로운 작가층으로 부상하여 사대부 작가와 같은 비중을 차지하다가 평민 가객이 우위를 점하고 무명씨가 대거 참여한다. 다음으로 시적 자아의 입장에서 유명씨의 14-17세기 작품에 나타난 시적 자아는 촌부, 일을 함께 하려는 농부, 일을 시키는 상전, 실제 일하는 농부 등으로 되어 있고 18-19세기 작품에는 전원인, 구경꾼, 일을 하거나 원망하는 농민 등이 중심이다. 이는 구체적 생산 활동이 점차 사실적으로 표현돼 가던 추세의 반영이다. 무명씨의 작품은 유명씨와 유사한 점이 있으면서도 상업 활동을 하는 시적 자아의 등장이 특이하다. 생활의 내용과 그 표현 방식에서 14-17세기 작품에는 논밭갈이, 산나물 캐기, 벼베기, 풀베기 등 여러 생활을 한 작품 안에 포괄하여 표현하는 작품이 많이 나타나며 관념적 용어에서 구체적 생활을 구어로 표현하는 작품이 나타나기 시작한다. 문장은 평서문, 의문문, 감탄문, 명령문, 청유문의 순서로 많이 사용된다. 18-19세기 작품에 나타난 생활은 물건 매매. 산전과 수전의 개간, 베짜기, 물푸기, 가렴주구 등 매우 구체적인 일들을, 하나씩 각각 한 작품 내에 집중적으로 구체적 생활에서 쓰는 구어를 더 많이 사용하여 주로 평서문과 의문문으로 표현한다. 무명씨 작품에 표현된 생활의 종류 유명씨 작품의 경우와 비슷하나 논밭갈이, 김매기, 벼 베기 등의 전통적 일반 생활에 옷 만들기, 물건 장수와 같은 구체적 생활이 부가적으로 더 표현된 점이 다르다. 표현 방법은 유명씨 작품의 전대 선례에서 점차 후대의 선례를 더 많이 수용하는 방향으로 바뀌며 문장 형태에서는 명령문, 명령문이 가장 많이 사용된다.

• 복식
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• 제42권
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• pp.207-222
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• 1999

This study is a thesis based on the fact that at the end of eighteenth century similar change in hair style appeared in Chosun and France which are located very far almost the opposite side of the earth. We can see that very exaggerated and big hair styles of those days in both countries became exceptionally reduced and changed to practical shapes through (an order prohibiting to make large hair style using wigs) is case of Chosun and through the France Revolution in case of France. Outwardly the abobe mentioned change may seem to be caused by such brave and outward convention as the prohibition order and the revolution. however I think that more basic cause of such change from big and splendid hair styles of those days to simple styles was because of many people's sympathy with the necessity of improving various social and economical problems caused by the luxurious and even prodigal situation of those days before the change and additionally because of such pragmatic thought as Positivism of chosun and illuminism of france. In case of france the change in hair style occurred for such a short period of time around the France Revolution(1789) that we can even that the change occurred in a day. However in case of Chosun such change became fixed at the time of king Suncho prohibiting to make large hair style using wigs (1756-1788) was announced. in case of France such change in hair style was mainly because of change of thought caused by people's self-consciousness. But in case of Chosun under the situation where common people's way of thinking about sumptuous moods and beauty was not changed unvoluntary and compulsory change was asked by the King's order so a lot of time seemed to have been necessary for the change in hair style to become fixed as a nationwide common and general custom.

• 대기
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• 제26권4호
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• pp.553-563
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• 2016

Land evaporation contribution to precipitation over East Asia is studied to understand terrestrial moisture source of continental precipitation. Moisture recycling of precipitation relying on terrestrial evaporation is estimated based on the analysis method of Van der Ent et al. (2010). We utilize HadGEM2-AO simulations for the period of 1970~1999 and 2070~2099 from RCP8.5. Globally, 46% of terrestrial precipitation is depending from continental evaporation. 58% of terrestrial evaporation returns as continental precipitation. Over East Asia, precipitation has been affected by local evaporation and transported moisture. The advection of upwind continental evaporation results from the prevailing westerlies from the midwestern of Eurasian continent. For the present-day period, about 66% of the precipitation over the land of East Asia originates from land evaporation. Regionally, the ratios change and the ratios of precipitation terrestrial origin over the Northern inland and Southern coast of East Asia are 82% and 48%, respectively. Seasonally, the continental moisture recycling ratio is larger during summer (JJA) than winter (DJF). According to RCP8.5, moisture recycling ratio is expected to change. At the end of the 21st century, the impact of continental moisture sources for precipitation over East Asia is projected to be reduced by about 5% compared to at the end of 20th century. To understand the future changes, moisture residence time change is investigated using depletion and replenishment time.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2018년도 학술발표회
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• pp.145-145
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• 2018

Small islands rely heavily on groundwater resources in addition to rainwater as the source of freshwater since surface water bodies are often absent. The groundwater resources are vulnerable to sea level rise, coastal flooding, saltwater intrusion, irregular pattern of precipitation resulting in long droughts and flash floods. Increase in population increases the demand for the limited groundwater resources, thus aggravating the problem. In this study, the effects of climate change on Tongatapu Island, Kingdom of Tonga, a small island in Pacific Ocean, are investigated using a sharp interface transient groundwater flow model. Twenty nine downscaled General Circulation Model(GCM) predictions are input to a water balance model to estimate the groundwater recharge. The temporal variation in recharge is predicted over the period of 2010 to 2099. A set of GCM models are selected to represent the ensemble of 29 models based on cumulative recharge at the end of the century. This set of GCM model predictions are then used to simulate a total of six climate scenarios, three each (2010-2039, 2040-2069, and 2070-2099) under RCP 4.5 and RCP 8.5. The impacts of predicted climate change on groundwater resources is evaluated in terms of freshwater volume changes and saltwater ratios in pumping wells compared to present conditions. Though the cumulative recharge at the end of the century indicates a wetter climate compared to the present conditions the large variability in rainfall pattern results in frequent periods of groundwater drought leading to saltwater intrusion in pumping wells. Thus for sustaining the limited groundwater resources in small islands, implementation of timely assessment and management practices are of utmost importance.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2019년도 학술발표회
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• pp.407-407
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• 2019

According to Asian Development Bank report Pakistan is among water scarce countries. Climate scenario on the basis IPCC fifth assessment report (AR5) revealed that annual mean temperature of Pakistan from year 2010-2019 was $17C^o$ which will rise up to $21C^o$ at the end of this century, similarly almost 10% decrease of annual rainfall is expected at the end of the century. It is a changing task in underdeveloped countries like Pakistan to meet the water demands of rapidly increasing population in a changing climate. While many studies have tackled scarcity and stream flow forecasting of the Upper Indus Basin (UIB) Pakistan, very few of them are related to socio-economic and climate change impact on sustainable water management of UIB. This study investigates the pattern of current and future surface water availability for various demand sites (e.g. domestic, agriculture and industrial) under different socio-economic and climate change scenarios in Upper Indus Basin (UIB) Pakistan for a period of 2010 to 2050. A state-of-the-art planning tool Water Evaluation and Planning (WEAP) is used to analyze the dynamics of current and future water demand. The stream flow data of five sub catchment (Astore, Gilgit, Hunza, Shigar and Shoyke) and entire UIB were calibrated and validated for the year of 2006 to 2011 using WEAP. The Nash Sutcliffe coefficient and coefficient of determination is achieved ranging from 0.63 to 0.92. The results indicate that unmet water demand is likely to increase severe threshold and the external driving forces e.g. socio-economic and climate change will create a gap between supply and demand of water.