• Structural Engineering and Mechanics
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• 제55권3호
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• pp.473-494
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• 2015

A graded harmonic finite element formulation based on three-dimensional elasticity theory is developed for the structural analysis of 2D functionally graded axisymmetric structures. The mechanical properties of the axisymmetric solid structures composed of two different metals and ceramics are assumed to vary in radial and axial directions according to power law variations as a function of the volume fractions of the constituents. The material properties of the graded element are calculated at the integration points. Effects of material distribution profile on the static deformation, natural frequency and dynamic response analyses of particular axisymmetric solid structures are investigated by changing the power law exponents. It is observed that the displacements, stresses and natural frequencies are severely affected by the variation of axial and radial power law exponents. Good accuracy is obtained with fewer elements in the present study since Fourier series expansion eliminates the need of finite element mesh in circumferential direction and continuous material property distribution within the elements improves accuracy without refining the mesh size in axial and radial directions.

• 무역학회지
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• 제42권6호
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• pp.111-129
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• 2017

세계은행 통계에 따르면 2013~2016년 기간 중 세계 경제 성장에 대한 중국의 기여도는 31.6%인 것으로 나타났다. 이는 미국, EU 및 일본의 기여도를 합한 29.0%에 비해 높은 수치로서 중국 경제가 세계 경제에 미치는 영향력이 상당히 크다고 볼 수 있다. 본 연구는 중국의 주요 품목별(화학제품, 곡물, 철재, 원유, 컨테이너) 연도별 수출입 해상물동량이 세계 경제성장에 미치는 영향을 시계열 데이터 분석 모형을 적용하여 분석하였다. 총 분석기간은 1999~2016년이며, 제1기(1999~2007년)와 제2기(2008~2016년)의 시기별 분석을 수행함으로써 중국 무역이 세계 경제에 미치는 영향력 측면에서 시기별로 어떠한 구조적 변화가 발생했는지 조명하였다. 특히 대다수 선행연구들이 세계 무역이 세계 경제에 미치는 영향력을 분석하였다면, 본 연구는 중국 무역의 영향력을 분석하여 세계 무역 대국으로 부상하고 있는 중국을 집중적으로 분석하였다는 데 의의가 있다.

• 한국농공학회지
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• 제38권3호
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• pp.70-81
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• 1996

Solutions of geotechnical engineering problems require predictions of deformation and stresses during various stages of loading. Powerful numerical methods are available to make such predictions even for complicated problems. To get accurate results, realistic stress-strain relationships of soils are dependent on a number of factors such as soil type, density, stress level and stress path. Attempts are continuously being made to develope analytical models for soils incorporating all such factors. Isotropic compression-expansion test and a series of drained conventional triaxial tests with several stress path for Baekma river sand were performed to investigate stress-strain and volume change characteristics of Lade's single work hardening model dependant on the stress path. In order to predicted of stress-strain and volumetric strain behavior were determined the values of parameters for the mode by the computer program based on the regression analysis. Predicted stress-strain behavior of triaxial compression tests and optional stress path tests for increasing confining pressure with parameters obtained conventional triaxial compression tests agreed with several test results but the prediction results for decreasing confining pressure reduced triaxial compression tests make a little difference with test results.

• 소성∙가공
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• 제18권8호
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• pp.625-632
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• 2009

The influence of the subsequent-annealing(SA) temperature on the plasma electrolytic oxidation(PEO)-treated Mgbased alloy was investigated in terms of surface properties associated with hardness and corrosion. For this purpose, a series of the SA treatments were performed on the PEO-treated samples at four different temperatures, i.e., 100, 150, 200, and $250^{\circ}C$ for 10 hrs. When compared to the sample without SA, the samples annealed at temperatures higher than $200^{\circ}C$ showed a difference in surface morphology due to the volume expansion accompanied by the dehydration reaction where the part of $Mg(OH)_2$ changed into MgO, working as harder phase. From the results of nano-indentation tests, the applied loads of the samples were seen to increase with increasing SA temperatures. However, the electro-chemical and corrosion properties of the sample annealed at $150^{\circ}C$ were higher than those of the samples annealed at three temperatures.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2022년도 춘계학술대회
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• pp.391-393
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• 2022

최근에는 딥러닝과 빅데이터를 기반으로 한 수요예측 기술이 전자상거래, 물류, 유통 분야의 스마트화를 가속화하고 있다. 특히, 글로벌 운송 네트워크와 현대적인 지능형 물류의 중심인 항만은 4차 산업혁명으로 인한 세계 경제 및 항만 환경의 변화에 발 빠르게 대응하고 있습니다. 항만물동량 예측은 신항만 건설, 항만확장, 터미널 운영 등 다양한 분야에서 중요한 영향을 담당하고 있다. 따라서 본 연구의 목적은 항만 물동량 예측에 자주 쓰이는 시계열 분석과 타 산업에서 좋은 결과를 도출해내고 있는 딥러닝 분석을 비교하여 부산항의 미래 컨테이너 예측에 적합한 예측모델을 제시하는 것이다. 부산항 컨테이너 물동량을 이용하여 학습시키고 그 이후 물동량 예측을 진행하였다. 또한, 상관관계 분석을 통해 물동량 변화와 관련된 외부변수를 선정하여 다변량 딥러닝 예측모델에 적용하였다. 그 결과 부산항 컨테이너 물동량만 이용한 단일변수 예측모델에서 LSTM의 오차가 가장 낮았고, 외부변수를 이용한 다변수 예측모델에서도 LSTM의 성능이 가장 우수하였다.

• 수산경영론집
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• 제37권3호
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• pp.1-24
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• 2006

In terms of the size of aquaculture farms and production volume, inland freshwater aquaculture is much smaller than marine aquaculture in Korea. However, freshwater aquaculture provides fish which is not produced in the sea. Freshwater aquaculture plays an important role in the efficient use of resources, development of local areas and economy vitalization in under - developed areas. freshwater aquaculture also helps ecosystem recovery by stocking farmed fry. As addressed above, inland freshwater aquaculture plays various roles and can not be ignored. However, freshwater aquaculture has been off the interest of fisheries authority. Considering a series of changes in the circumstances such as the government's disapproval of pen - raised aquaculture, higher standard for discharged water from aquaculture farms and a rapid increase in import of low price fish from other countries, it is difficult to expect the quantitative expansion of the freshwater aquaculture any more. Furthermore, freshwater aquaculture lost the trust of people because of the use of Malachite green, and the consumption of farmed product plummeted last year. Even though it would be difficult to expect the quantitative expansion, we could expect qualitative growth and let the inland freshwater aquaculture keep playing the own roles. In order to achieve competitive advantage and regain the trust by providing safer farmed product, the government's support and freshwater aquaculture industry's active and voluntary efforts are very important. This paper suggests several points for the future oriented inland freshwater aquaculture in Korea such as strategic intensive development of selected species, the technical improvement and its diffusion, increased cooperation among the government authority, industry and scientists.

• Structural Engineering and Mechanics
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• 제71권5호
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• pp.469-483
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• 2019

In this paper, an improved mathematical model is presented for the bending analysis of doubly curved functionally graded material (FGM) sandwich rhombic conoids. The mathematical model includes expansion of Taylor's series up to the third degree in thickness coordinate and normal curvatures in in-plane displacement fields. The condition of zero-transverse shear strain at upper and lower surface of rhombic conoids is implemented in the present model. The newly introduced feature in the present mathematical model is the simultaneous inclusion of normal curvatures in deformation field and twist curvature in strain-displacement equations. This unique introduction permits the new 2D mathematical model to solve problems of moderately thick and deep doubly curved FGM sandwich rhombic conoids. The distinguishing feature of present shell from the other shells is that maximum transverse deflection does not occur at its center. The proposed new mathematical model is implemented in finite element code written in FORTRAN. The obtained numerical results are compared with the results available in the literature. Once validated, the current model was employed to solve numerous bending problems by varying different parameters like volume fraction indices, skew angles, boundary conditions, thickness scheme, and several geometric parameters.

• 한국지반공학회논문집
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• 제32권2호
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• pp.53-62
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• 2016

흙의 다짐 특성에 영향을 주는 주요인자 중 하나인 온도는 지역과 계절에 따라 다양하게 변화하는 특성을 가진다. 최근 동토지방에서 많은 토목공사가 시행되고 있지만, 온도와 관련된 흙의 다짐기준 및 지침을 정량화할 수 있는 문헌은 미비한 실정이다. 따라서 본 연구는 온도에 따른 흙의 다짐특성을 시험을 통해 평가하고자 하였다. 시험을 위해 러시아 시베리아, 캐나다 앨버타 주 오일 샌드 지역 등에서 자주 쓰이는 성토재료인 모래의 온도별 다짐특성을 나타낼 수 있는 주문진 모래를 사용하였으며, 표준다짐시험을 흙의 다양한 온도조건($-10^{\circ}C$에서 $17^{\circ}C$)에서 수행하였다. 시험 결과 영상 온도에서는 다짐 시 벌킹 효과로 인해 흙 공시체의 부피 팽창이 발생하였으며, 그 범위는 0%~6%이였다. $0^{\circ}C$에서 $17^{\circ}C$까지 온도가 증가하면서 최대 부피(최소 건조단위중량)에 해당하는 함수비는 감소하였고, 최소 부피(최대 건조단위중량)에 해당하는 함수비는 온도가 증가함에 따라 약간 증가하였다. 영하 온도의 경우 함수비가 추가됨에 따라 건조단위중량은 지속적으로 감소하였다. 영하 온도에서는 벌킹이 발생하지 않았으며 물의 단위부피보다 얼음의 단위부피가 더 크기 때문에 흙 공시체의 부피가 증가하였다.

• 한국한의학연구원논문집
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• 제17권3호
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• pp.1-8
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• 2011

In the late Joseon Dynasty, a bulky volume of books, which had rarely been seen, poured out including "Imwongyeongjeji", "Japdongsani", "Songnamjapsik" and "Ohjuyeonmunjaangjeonsango". such sorts of books have a characteristic that an author collected various pieces of information, which were scatter away at that time, in one's own way and compiled them into a book rather than an author's own remarks or ideas. Most authors of such books were known to have made not a few book beside bulky books. Such a trend of the times doubled its revitalization with the influx of that books in a series that were popular especially in the period of Ming State & Ching State in China. The research work on such a trend once showed not a little progress by a few faithful researchers even under the circumstances where they were overwhelmed by the bulkiness of a book in a series itself and its target volume. However, in spite of not a little fruition of such studies, there has been no comments at all on the new factors of change faced by Oriental medicine in the climate of the intellect history in the late Joseon Dynasty. Thus, this study aimed at looking at the significance of medical-history-based studies on this matter on the basis of Park, Jiwon's "Keumryosocho", and Lee, Deokmu's "Iemokgushimseo", and suggesting the further task. The conclusions obtained from the analysis of "Keumryosocho" and "Iemokgusimseo" are as follows: 1.The prescriptions cited from the sorts of writings excluded entirely the medical theories on the principles of prescription, and they are composed of a single-medicine prescription or so, which made it easier even for those who lacked a special knowledge of medicine to use it; in addition, it was easy to get medicinal ingredients in most cases. It's presumed that such a composition of medicinal ingredients had a close relation with the difficulty in the supply of medicinal ingredients, which issue became a serious issue in the late Joseon Dynasty. 2. The prescriptions originating from the sorts of writings sometimes are mixed with the ones whose medical efficiency are doubted. This means the inherence of obstacles to delivering accurate medical knowledge couldn't be avoided because the initial purpose of such sorts of writings lay in popularity than practicality. 3. In spite of such problems, the prescriptions originating from writings seems to have not a few influences on the intellectuals in the late Joseon Dynasty, and it's possible for us to take a glance on the traces of their use of these prescriptions in an actual daily life. This fact is fully confirmed by the contents in the preface of "Keumryosocho" that Park-jiwon personally tried to write a prescription. Moreover, such facts can be also confirmed from the fact that the writings of China or our country are seen quite often among the writings which were incited by Seo, Yugu's "Injeji." Like this, the fact that the information of orthodox medicine and the one originating from general books other than medicine books were integrated at one place is plainly showing a phase of the intellect history in the late Joseon Dynasty deluged with information; because of such a characteristic, we can say that Oriental medicine became plentiful in the aspect of diversity with its expansion of denotation, but Oriental medicine could not but additionally assume the problem of having to distinguish good from bad in the midst of such a situation.

• 한국ITS학회 논문지
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• 제20권5호
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• pp.113-129
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• 2021

최근 수도권 중심의 생활권역 확장과 대도시로의 인구 집중으로 도시 내의 교통 혼잡이 지속적으로 증가하고 있다. 도심지의 땅값 상승과 한정된 부지로 인해 새로운 도로 건설은 불가능하게 되었고, 데이터 기반의 효율적인 도로 운영의 중요성이 점점 부각되고 있다. 효율적인 도로 운영을 위해서는 교통상황의 변화에 따른 적절한 TOD 시간분할과 TOD 시간분할을 통한 최적의 신호 운영 방안이 필수적이다. 본 연구에서는 최적의 TOD 시간 분할을 위해 연속된 교차로에서 수집된 교통량과 속도 데이터에 시계열 데이터의 군집 분석을 위한 동적 타임 워핑 모델을 적용하였다. 시간 분할을 위해 활용된 데이터별 군집의 특성을 분석하여 최적의 신호 운영 시나리오를 구성하기 위한 시간 분할 방법론을 제안하고자 한다.