• 대한기계학회논문집A
• /
• 제29권11호
• /
• pp.1455-1462
• /
• 2005

In this paper, we intend to introduce a nonlinear finite element method based on the fully nonlinear potential flow theory in order to simulate the large amplitude sloshing flow in two-dimensional baffled tank subject to horizontally forced excitation. The free surface is tracked by a direct time differentiation scheme with the four-step predictor-corrector time integration method. The flow velocity is accurately recovered from the velocity potential by second-order least square method. In order to maintain the finite element mesh regularity and total mass, the semi-Lagrangian surface tracking method with area conservation is applied. According to the numerical formulae, we perform the parametric experiments by varying the installation height and the opening width of baffles, in order to examine the effects of baffle on the nonlinear liquid sloshing. From the numerical results, the hydrodynamic characteristics of the large amplitude sloshing are investigated.

• International Journal of Korean Welding Society
• /
• 제3권2호
• /
• pp.15-23
• /
• 2003

A genetic algorithm was applied to an arc welding process to determine near optimal settings of welding process parameters which produce good weld quality. This method searches for optimal settings of welding parameters through systematic experiments without a model between input and output variables. It has an advantage of being able to find optimal conditions with a fewer number of experiments than conventional full factorial design. A genetic algorithm was applied to optimization of weld bead geometry. In the optimization problem, the input variables were wire feed rate, welding voltage, and welding speed, root opening and the output variables were bead height, bead width, penetration and back bead width. The number of level for each input variable is 8, 16, 8 and 3, respectively. Therefore, according to the conventional full factorial design, in order to find the optimal welding conditions, 3,072 experiments must be performed. The genetic algorithm, however, found the near optimal welding conditions from less than 48 experiments.

• 대한소아치과학회지
• /
• 제31권4호
• /
• pp.569-578
• /
• 2004

본 연구는 유치열과 영구치열에서 구개의 길이, 폭, 깊이 및 치열궁의 형태 등을 조사하여 남녀간의 차이와 유치열과 영구치열간의 변화양상을 파악하는 것이다. 유치열기 아동 100명과 영구치열기 성인 100명 총 200명을 대상으로 하여 상악 석고 모형을 채득하고 3차원 laser scanner(SD Scanner, DS4060, LDI, U.S.A.)를 통한 석고 모델의 측정을 통해 cloud data, polygonization, section curve and loft surface, fit and horizontal plane (Surfacer 10.0. Imageware, U.S.A.)을 기초로 하여 구개의 폭, 길이, 높이 및 치열궁의 형태 등을 계측하였다. 통계학적 분석을 위해 t-tests가 사용되었다. 이에 다음과 같은 결론을 얻었다. 1. 구개의 계측항목에서 유치열 전방부 구개높이를 제외한 나머지 항목에서 남자가 여자보다 크게 나왔으며, 유치열은 전구개폭(p<0.05)과 후구개폭(p<0.01), 영구치열은 구개폭(p<0.05)과 전구개길이(p<0.01), 중구개, 후구개길이(p<0.05)에서 남녀간에 유의한 차이가 있었다. 2. 남녀의 구개지수에서 유치열에서는 구개장고지수(p<0.05)와 구개장폭지수(p<0.01)가 남녀간에 통계학적으로 유의한 차이가 있었다. 영구치열의 구개지수에서는 남녀간에 유의한 차이가 없었다. 3. 유치열과 영구치열의 계측항목 비교에서 후방부 구개폭이 가장 많이 증가하였으며, 다음으로 후방부 구개높이, 전방부 구개폭, 전방부 구개길이 순이었다. 전방부 구개높이와 후방부 구개길이는 오히려 감소하였다. 4. 유치열과 영구치열의 구개지수 비교에서 구개장고지수와 구개장폭지수, 후구개폭고지수는 영구치열에서 증가하였고, 나머지 지수는 감소하였다.보아 Er:YAG 레이저와 Chinese ink로 photosensitization을 시행한 후의 Nd:YAG 레이저 조사는 일정시간 동안 S. mutans의 증식과 산 생성능을 억제시키므로써 치아우식증 예방효과를 얻을 수 있다고 사료되나 억제효과가 오래가지 않아 임상적으로 효과를 얻기 위해서는 자주 조사를 해주어야 한다는 문제점을 안고 있어 임상적으로 치아우식증 예방이란 단독 목적으로 사용하기에는 실용성이 크지 않다고 사료된다.전자현미경 관찰에서 초음파 진동을 가한 군에서 resin tag의 길이가 길었고, lateral branch의 수도 많이 관찰되었다.TEX>$1\rightarrow6$ 결합이 주된 결합인 수용성 글루캔이었다. 이상의 결과를 종합하면 구강에서 분리된 Streptococcus salivarius 119에 의한 Streptococcus mutans의 인공치태 형성 억제작용은 수용성 글루캔 형성에 의한 것으로 사료되었다.동을 유도할 수 있다고 사료된다. 또한 이유식을 통한 다양한 식품의 경험 및 식품 섭취방법 등을 연습하는 과정을 통해 앞으로의 식생활 및 성장 발달에 영향을 미칠 것으로 사료된다. 따라서 영유아의 성장발달에 따른 적절한 영양교육의 실시가 보다 체계적으로 활성화 되어야 하겠으며 이를 위해 실제로 도움이 될 수 있는 구체적인 교육내용, 방법 및 도구의 개발이 요구된다.어서, B군은 A군,C군,D군과 비교하여 통계학적으로 유의성 있는 차이를 보였고(p<0.05), E군은 F군,G군과 비교하여 통계학적으로 유의성 있는 차이를 보였다(p<0.05). 3. 광중합형 및 자가중합형 교정용 전색제는 법랑질탈회 예방효과가 있었다. 4. 광중합형 및 자가중합형 교정용 전색제는 법랑질탈회 진행억제효과가 있었다. 5. 광중합형 및 자가중합형 교정용 전색제 표본에

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.735-740
• /
• 2003

In this study, a numerical optimization to find the optimal shape of streamwise periodic ribs mounted on both of the principal walls is performed to enhance turbulent heat transfer in a rectangular channel. The optimization is based on Navier-Stokes analysis of flow and heat transfer with $k-{\varepsilon}$ turbulence model and is implemented using response surface method. The width-to-height ratio of a rib, rib height-to-channel height ratio, rib pitch to rib height ratio and distance between opposite ribs to rib height ratio are chosen as design variables. The object function is defined as a function of heat transfer coefficient and friction drag coefficient with weighting factor. Optimum shapes of the rib have been investigated for the range of 0.0 to 0.1 of weighting factor.

• 대한기계학회논문집A
• /
• 제24권4호
• /
• pp.955-962
• /
• 2000

Scanning Probe Microscope (SPM) such as Scanning Tunneling Microscope (STM) and Atomic Force Microscope (AFM) was shown to be the powerful tool for nano-scale characterization of a fracture surface . AFM was used to study cross sectional profiles and dimensions of fatigue striations in 2017-T351 aluminum alloy. Their widths (SW) and heights (SH) were measured from the cross sectional profiles of three-dimension AFM images. The following results that will be helpful to understand the fatigue crack growth mechanism were obtained. (1) Coincidence of the crack growth rate with the striation width was found down to the growth rate of 10-5 mm/cycle. (2) The relation of SH=0.085(SW)1.2 was obtained. (3) The ratio of the striation height to its width SH/SW did not depend on the stress intensity factor range K and the stress ratio R. (4) Not only the SW but also the SH changed linearly with the crack tip opening displacement (CTOD) when plotted in log-log scale. From these results, the applicability of the AFM to nano-fractography is discussed.

• 전자공학회논문지B
• /
• 제32B권10호
• /
• pp.1269-1279
• /
• 1995

A mobile robot in a nuclear power plant is usually needed to equip the ability of going up and down stairs for a some kind of inspection. For this purpose, it is necessary for the mobile robot to figure out the size of stairs laid on a navigation path to gurantee robot's moving freely. In this paper, to measure the size of stairs existing in front of a mobile robot we designed the stair size recognition unit which can measure the stair's height and width using an ultrasonic sensor and/or a CCD camera. Also to obtain higher reliability of ultrasonic sensing data we proposed the horizontal sensing method. On the assupmtions that the mobile robot generates a trajectory while ascending stairs, we simulated it on a IBM compatible computer. The result showed that the suggested method satisfied our purpose. In a stair size estimation, the detected stair's height error was about .+-.3mm, and width was about .+-.5mm.

• 한국농공학회논문집
• /
• 제54권4호
• /
• pp.73-81
• /
• 2012

In this study, the settlement data of 32 center cored rockfill dams (total 39 monitored data) were collected and analyzed to develop the method to predict the crest settlement of a CCRD after impounding by using the internal settlement data occurred during construction. An artificial neural network (ANN) modeling was used in developing the method, which was considered to be a more reliable approach since in the ANN model dam height, core width, and core type were all considered as input variables in deriving the crest settlement, whereas in conventional methods, such as Clements's method, only dam height is used as a variable. The ANN analysis results showed a good agreement with the measured data, compared to those by the conventional methods using regression analysis. In addition, a simple procedure to use the ANN model for engineers in practice was provided by proposing the equations used for given input values.

• International journal of advanced smart convergence
• /
• 제9권2호
• /
• pp.123-128
• /
• 2020

We constructed a cooling system for solar cells using convection phenomena and investigated its cooling performance. The cooling system didn't need any driving power or water resources. The convection cooler manufactured with a right-triangle shape of an air duct was attached to the rear of the solar cell to confirm that cooling was performed using convection phenomena. When the ratio of duct width to attachment surface width was 3:7, and the ratio of entrance height and exit height of duct was 5:1, it showed the best cooling performance. Comparative experiments with solar cells without convection cooler showed that cooling effects from 16.5℃ to 20.9℃ occurred after 40 minutes exposed to the 1300W Xenon lamp condition.

• 한국연초학회지
• /
• 제4권2호
• /
• pp.23-30
• /
• 1982

Six flue- cured cultivars of Nicotiana tabacum L., 15 possible $F_1$ hybrids and $F_2$ Populations among them, and 15 haploid Populations from Fl hybrids and haploids from Parents, were evaluated. Comparisons of the $F_1$, hybrids and $F_2$ Populations with the Parents indicated that heterosis values were small but significant for yield, plant height, days to flower, leaf length and width and total alkaloids from-6.0% to 5.4% in $F_1$ hybrids, and from -3.4% to 3.6% for Plant height days to flower leaves per plant in $F_2$ populations, respectively. There were positive correlations for yield, plant height, days to flower, leaves per plant and total alkaloids between diploid and haploid populations. Increase or decrease ratio of haploids to diploids of total alkaloids was appeared to 30.3%. Those for yield, leaf length and width, value arid reducing sugar were ranged from -4.1% to -27.6%.

• 대한치과보철학회지
• /
• 제36권1호
• /
• pp.166-182
• /
• 1998

The purposes of this study are to evaluate the Korean mandibular dental arch and classify the mandibular dental arch shape and size based on the incisal angle, canine angle, inter second molar width and height. In this study the mandibular study models were fabricated using irreversible hydrocolloid impression material from 225 volunteers with a mean age 23.62 (range 19-29). And the study models were measured with 3-dimensional measuring device and the mandibular dental arch was classified by means of K-means clustering method and visual inspection, then obtained data were analyzed with t-test for the statistical analysis. The results were as follows ; 1. The average canine height was 5.19mm(s.d. 1.17) in both sex, 5.34mm in male, and 4.95mnm in female. And the sexual difference was significant($0). 2. The average second molar height was 39.81mm(s.d. 2.44) in both sex, 40.19mm in male, and 39.21mm in female. And the sexual difference was significant($0). 3. The average inter-canine width was 27.16mm(s.d. 1.78) in both sex, 27.41mm in male, and 26.77mm in female. And the sexual difference was significant($0). 4. The average inter-first molar width was 46.93mm(s.d. 2.67) in both sex, 47.72mm in male, and 45.7mm in female. And the sexual difference was significant($0). 5. The inter-second molar width was average 56.09mm(s.d. 3.01) in both sex, 57.24mm in male, and 54.32mn in woma. And the sexual difference was significant($0). 6. The arch form was classified into three shapes based on the incisal and canine angle. V-shape showed $124.88^{\circ}$ of incisal angle and $141.64^{\circ}$ of canine angle, U-shape showed $152.76^{\circ}\;and\;125.35^{\circ}$, and O-shape showed $138.03^{\circ}\;and \;33.66^{\circ}$ respectively. Each shape distribution was that the V-shape was 14.2%, the U-Shape was 14.7%, and the O-shape was 71.1% of the 225 study models. 7. It was thought that the use of second molar width is more reasonable than height for classifying the dental arch size. The arch size was classified into four sizes based on the second molar width. Size 1 showed range of 42.24-48.23mm, size 2 showed 48.24-54.23mm, size 3 showed 54.24-60.23mm, and size 4 showed 60.24-66.23mm respectively. Each arch size distribution was that the size 1 was 1.3%, the size 2 was 27.1%, the size 3 was 63.6%, and the size 4 was 8.0% of the 225 study models.