• Earthquakes and Structures
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• 제16권2호
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• pp.177-183
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• 2019

In this paper, a new refined hyperbolic shear deformation beam theory for the bending analysis of functionally graded beam is presented. The theory accounts for hyperbolic distribution of the transverse shear strains and satisfies the zero traction boundary conditions on the surfaces of the functionally graded beam without using shear correction factors. In addition, the effect of different micromechanical models on the bending response of these beams is studied. Various micromechanical models are used to evaluate the mechanical characteristics of the FG beams whose properties vary continuously across the thickness according to a simple power law. Based on the present theory, the equilibrium equations are derived from the principle of virtual work. Navier type solution method was used to obtain displacement and stresses, and the numerical results are compared with those available in the literature. A detailed parametric study is presented to show the effect of different micromechanical models on the flexural response of a simply supported FG beams.

• Earthquakes and Structures
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• 제17권3호
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• pp.329-336
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• 2019

An efficient shear deformation beam theory is developed for thermo-elastic vibration of FGM beams. The theory accounts for parabolic distribution of the transverse shear strains and satisfies the zero traction boundary conditions on the on the surfaces of the beam without using shear correction factors. The material properties of the FGM beam are assumed to be temperature dependent, and change gradually in the thickness direction. Three cases of temperature distribution in the form of uniformity, linearity, and nonlinearity are considered through the beam thickness. Based on the present refined beam theory, the equations of motion are derived from Hamilton's principle. The closed-form solutions of functionally graded beams are obtained using Navier solution. Numerical results are presented to investigate the effects of temperature distributions, material parameters, thermal moments and slenderness ratios on the natural frequencies. The accuracy of the present solutions is verified by comparing the obtained results with the existing solutions.

• Steel and Composite Structures
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• 제48권6호
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• pp.709-725
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• 2023

This paper uses a new type of deformation theory to establish the free vibration and static buckling equations of nanoplates resting on two-parameter elastic foundations, in which the flexoelectric effect is taken into account. The proposed approach used in this work is not only simpler than other higher-order shear deformation theories but also does not need any shear correction coefficients to describe exactly the mechanical responses of structures. The reliability of the theory is verified by comparing the numerical results of this work with those of analytical solutions. The results show that the flexoelectric effect significantly changes the natural frequency and the critical buckling load of the nanoplate compared with the case of neglecting this effect, especially when the plate thickness changes and with some different boundary conditions. These are new results that have not been mentioned in any publications but are meaningful in engineering practice.

• Journal of Astronomy and Space Sciences
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• 제22권4호
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• pp.451-462
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• 2005

향후 우리나라의 화성 탐사선 개발을 대비하여 B-평면 조준법(B-plane targeting method)을 이용한 최적 궤적 보정 기동(Optimal Trajectory Correction Maneuver, TCM)의 설계에 대한 연구를 수행하였다. 궤적 보정 기동을 설계하기 위하여 요구되는 화성 탐사 임무의 각 단계별 비행 궤적 및 궤도 정보 역시 이 연구를 통해 개발된 알고리즘을 이용하여 산출 할 수 있으며, 관련 정보는 임무 설계시 필요로 하는 최소의 섭동력들을 고려한 상황에서 산출되었다. 항행 단계에서의 탐사선은 다양한 섭동력에 의한 영향 또는 순간 기동의 오차로 기인된 비행 궤적의 오차로 인하여 목표한 위치에 도달하지 못할 수 있다. 따라서 탐사선의 적절한 비행 궤적을 유지하고 목표하고자 한 지점에 정확하게 도달시키기 위하여 도착 행성의 위치에 대하여 설정된 B-평면 좌표계를 이용하여 탐사선의 방향을 조준하여 줄 필요가 있다. NPSOL 소프트웨어를 사용하여 관련 최적해를 도출하였으며 임무동안 수행되는 기동의 총 크기를 최소화 시키도록 목적함수를 설정하였다. 수행되는 기동의 횟수는 설계자가 임의로 설정($1\~5$회)할 수 있도록 하였으며 그 시기 역시 조정 변수로 설정 할 수 있다. 마지막으로 화성 도착시 설정된 B-평면 좌표의 위치가 최종 구속조건으로 적용되어 최적화 문제를 완성하게 된다. 이 연구를 통하여 지구 출발에서부터 화성 도착, 그리고 임무 수행을 위한 포획궤도에 이르기까지 전반적인 임무 설계 및 해석이 가능하게 되었으며, 항행 단계에서 이루어지는 궤적 보정 기동의 최적 시기 및 크기 또한 분석이 가능하게 되었다. 이 연구를 통하여 개발된 알고리즘을 이용하여 향후 우리나라의 화성 탐사 임무의 설계, 분석이 가능하다.

• 한국농림기상학회지
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• 제23권4호
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• pp.415-423
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• 2021

NCAM-LAMP 중기예측 자료의 통계적 후처리와 개선을 위하여 R 기반의 지점 시계열 자료 검증 체계를 구축하였다. 이 시계열 검증체계를 이용하여 기상청 AWS 관측 자료와 NCAM-LAMP, KMA GDAPS 중기예측 모델 자료를 비교하였다. 이를 위해 관측 지점에 가장 근접한 모델 위도 및 경도 자료를 추출하여 총 9개 지점을 선정하였다. 각 지점에 대해 NCAM-LAMP, GDAPS 모델의 기온, 강수량, 풍속 일평균 예측 자료를 관측과 비교한 결과, 모델들은 풍속의 과대예측 경향을 뚜렷이 보였으며, 기온과 강수의 경우에는 두 모델의 예측력이 월별 및 변수별로 다르게 나타났다. 이를 바탕으로 본 연구에서는 통계적 기법을 개발하여 NCAM-LAMP가 가지고 있는 오차를 줄이고자 하였다. 모델 오차를 줄이기 위해 일반적으로 쓰이는 MOS(Model Output Statistics)기법 중에 인공지능 SVM(Support vector machine) 방식을 8~10월 기간에 적용한 결과, 8월에 비해서 10월이, 기온 변수에 비해서 바람과 강수 변수가 개선된 효과를 보여주었다. 이러한 결과는 풍속의 과대예측을 줄이고, 농림 가뭄지수와 산사태 예측 등을 개선시키며, 지역 수치예보 모델이 시간 적분됨에 따라 영역 내 예측가능성이 점점 저하되는 현상을 완화시키는데 SVM 방법이 일정 부분 기여할 수 있음을 가리키며, 현업 표출 중인 NCAM Agro-Meteogram 개선에도 도움을 줄 것으로 기대된다.

• 패션비즈니스
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• 제14권1호
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• pp.43-56
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• 2010

In the modern 21st century society, the personal image is considered to be very important. As a result, the importance of presenting one's personal image through personal color in fashion and beauty related fields are increasing, and is the most realistic and practical field of color. When the color of the wardrobe and the skin color are in disharmony, that disharmony becomes the source of the lines and wrinkles that appear on one's face, resulting in shades. The boundary that is created when the color of the wardrobe and the skin color are in disharmony, it works negatively on one's image. When color arrangements are close or similar (in harmony) or are in complementary color arrangements or in strong contrasting state (contrasting harmony), it is generally believed to be beautifully harmonious. Personal color assessment is finding colors, through systematic and scientific methods, that improve the personal image by reaching harmony with skin colors that each and every individual are uniquely born with. In this study, one was able to learn the improved visual effects of the face image through creating harmony with the wardrobe and color shade make up and complementary colors that were selected based on personal colors. The base make up, through using the contrasting effects of the complementary colors which represents the supplementing, correcting, and complementing of the face image by contrasting with complementary colors, brings positive changes through correcting the base skin color. It is believed that this study finds its importance in that the improved image that is created by the overall harmony of the wardrobe and body can be used as valuable data in marketing and new product development efforts in the related industries.

• 한국석유지질학회지
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• 제13권1호
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• pp.17-23
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• 2007

ArcGP 중력자료를 이용하여 다산과학기지가 위치한 북극 스발바드 군도의 중력특성을 파악하였다. 지형자료와 유사한 형태로 분포하는 free-air 중력이상에서 보이던 대륙 연변부의 가장자리 효과는 부게보정 후 보이지 않고, 육상지역의 CTOPO30 지형자료를 이용한 지형보정을 거친 완전 부게 중력이상에서 육상지역에서 해양지역으로 갈수록 중력이상이 증가하는 즉, 모호면의 상승과 관련이 깊은 특성이 관찰된다. 파워스펙트럼 분석을 통해 결정된 절단파수를 이용할 필터링 후 계산된 고주파 영역의 잔여이상에서 육상지역의 단층대를 따라 발달하는 특징적인 고이상대와 두꺼운 퇴적층에서 기인한 저이상대가 나타나며 해양지역 대륙사면의 최하부에서 기반 함몰 내지는 기반암 상부의 두꺼운 퇴적층과 관련이 있는 저이상대가 발달하고 있다. 역산 모델링을 통해 저주파 영역 성분에서 계산된 모호면의 기복은 스발바드 군도에서 유라시안 판 경계인 Knipovich ridge쪽으로 갈수록 상승하는 즉, 대륙주변부에서의 전형적인 특성을 보여준다.

• 한국정밀공학회지
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• 제3권3호
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• pp.40-71
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• 1986

By developing a computer program for the systematic design of worm gears, the design formulae and tables of AGMA, JGMA, BS and DIN are analized and compared. The computer program can be used on micro-computers. According to the input data of the reduction ratio, the center distance. the driving torque and the material as design parameters, the program calculate the most efficient worm gear dimension. The variation of the design parameters and other empirical coefficients in case of resulting an inadequate design gear dimension can be easily modified throuth the way of interactive method between the user and the monitoring system of computer. A proposal of the standardization of worm gears was made in which a standard module according to the DIN 323 standard series number was applied. For the more exact and effective calculation of the stress concentration and the deformation of gear teeth, a computer program using the boundary element method is also developed. Even the strength of the special gear shape such as Niemann's "Cavex" gear can be calculated in a short CPU-time. The most effort of this study has been layed on the developing a computer program for the correction of a tooth profile and face width which is most important design factor for an exact and wide teeth contacts under loads, especially by great and wide gears. For this purpose were investigated the tooth stiffness, the mesh interferences and the kinematics and the dynamics of gear mesh. The deflection and the deformation of the gear shaft due to the loads acting on gear and shaft were aslo considered. Some examples have shown the sufficient good status of teeth contact in which the correction of the tooth profile and face width were accomplished due to the calculated results.d results.

• 대한의용생체공학회:의공학회지
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• 제26권2호
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• pp.73-86
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• 2005

We need to flatten the brain cortex to smooth surface, sphere, or 2D plane in order to view the buried sulci. The rendered 3D surface of the segmented white matter and gray matter does not have the topology of a sphere due to the partial volume effect and segmentation error. A surface without correct topology may lead to incorrect interpretation of local structural relationships and prevent cortical unfolding. Although some algorithms try to correct topology, they require heavy computation and fail to follow the deep and narrow sulci. This paper proposes a method that corrects topology of the rendered surface fast, accurately, and automatically. The proposed method removes fractions beside the main surface, fills cavities in the inside of the main surface, and removes handles in the surface. The proposed method to remove handles has three-step approach. Step 1 performs smoothing operation on the rendered surface. In Step 2, vertices of sphere are gradually deformed to the smoothed surfaces and finally to the boundary of the segmented white matter and gray matter. The Step 2 uses multi-resolutional approach to prevent the deep sulci from geometrical intersection. In Step 3, 3D binary image is constructed from the deformed sphere of Step 2 and 3D surface is regenerated from the 3D binary image to remove intersection that may happen. The experimental results show that the topology is corrected while principle sulci and gyri are preserved and the computation amount is acceptable.

• 한국한의학연구원논문집
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• 제10권1호
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• pp.49-61
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• 2004

The Standardization of terms in The Pulse studies(脈學) is a need for development of learning. This study, for the correction of existing misused terms in The Pulse studies, we study on modernly and objectively the terms in The Pulse studies. By a focus of ${\ulcorner}$The Pulse Studies of Bin-Ho(瀕湖脈學)${\lrcorner}$, we studies on the new classification of pulse condition. The error of a existing technical books on Pulse studies begin that the classification of pulse condition is not establish a Standardization. For the correction of existing misused terms in The Pulse studies, we study on the pulse condition is expressed objectively a blood vessel that it is a subject of pulse condition. The expression of blood vessel contain a depth of blood vessel, a speed of pulsation, a curve of blood vessel, thickness of blood vessel, a diameter of blood vessel in expand and contract of blood vessel, a interval in expand and contract of blood vessel, a distinctness on a boundary of blood vessel, a speed of blood flow in blood vessel, a volume of blood flow in blood vessel, a condition of blood in blood vessel, a propelling power of blood vessel. These is standard of the new classification of pulse condition.