• 한국산림과학회지
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• 제97권5호
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• pp.485-491
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• 2008

This study was performed in 14 unthinned Mongolian pine (Pinus sylvestris L. var. mongolica Litvin) plantations in northeast China. Data were collected on 70 sample trees of different canopy position with diameter at breast height (DBH) ranging from 6.9 cm to 34.5 cm. Diameter and length of knots per whorl below the living crown were studied by different vertical levels divided by relative knot height (RHK) in this paper. Models taking DBH and height to the crown base (HCB) as independent variables were developed to predict knot diameter (KD) in a sample whorl. According to the vertical distribution tendency and range of sound knot length (KLsound), KLsound was modeled as multiple linear function of DBH, KD and relative knot height (RHK). The loose knot length (KLloose) was described as a function of DBH, KD and height above the ground for knots (HK) in a mixed log-linear model. Results from this study can provide abundant knot information so as to describe the knot size and vertical distribution tendency of Mongolian pine plantation.

• 한국유체기계학회 논문집
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• 제10권2호
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• pp.7-15
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• 2007

A numerical procedure for optimizing the shape of three-dimensional channel with V-shaped ribs extruded on both walls has been carried out to enhance the turbulent heat transfer. The response surface based optimization is used as an optimization technique with Reynolds-averaged Wavier-stoked analysis. Shear stress transport (SST) turbulence model is used as a turbulence closure. Computational results for average heat transfer rate show good agreements with experimental data. The objective function is defined as a linear combination of heat transfer and friction loss-related terms with a weighting factor. Three dimensionless variables such as, rib pitch-to-rib height ratio, rib height-to-channel height ratio, and the attack angle of the rib are chosen as design variables. Nineteen training points obtained by D-optimal designs for three design variables construct a reliable response surface. In the sensitivity analysis, it is found that the objective function is most sensitive to the ratio of rib height-to-channel height ratio. And, optimal values of design variables have been obtained in a range of the weighting factor.

• 대한인간공학회지
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• 제29권5호
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• pp.789-795
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• 2010

This study aimed to investigate the effect of differing heel height on static balance and muscle activation of ankle joint during standing. Twenty-one young females volunteered to participate in this study. To measure balance function and EMG activity of tibialis anterior and gastrocnemius muscles, the subjects were asked to perform 1-min standing with eyes open and closed state under 3 different heel heights: barefoot, 3cm, and 7cm each. During the standing, postural sway distance and area, and EMG activity of tibialis anterior and gastrocnemius muscles were significantly augmented with increasing heel height (p<0.05). For comparison between eyes open and closed in terms of postural sway area and EMG activity of tibialis anterior muscle, barefoot and 7cm height conditions respectively showed significant differences as well. The findings indicate that high-heeled shoes may have disadvantages in maintaining balance function because of extra-muscular effort of ankle joint. This study provides useful information that will inform future studies on how heel height affects muscle activity around the ankle joint in aspects of static and dynamic balance.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.568-572
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• 2000

A numerical investigation was performed to determine the effect of airfoil thickness on the optimum Gurney flap height using NACA 00XX series airfoils. Seven airfoils which have 3% chord thickness difference were used. These were NACA 0006, 0009, 0012, 0015, 0018, 0021, and 0024. A Navier-Stokes code, FLUENT, was used to calculate the flow field about airfoil. The fully turbulent results were obtained using the standard $k-{\varepsilon}$ two-equation turbulence model. To provide a check case fur our computational method, numerical studies for NACA 4412 airfoil were made and compared with already existing experimental data for this airfoil by Wadcock. For every NACA 00XX airfoil, Gurney flap heights ranging from 0.5% to 2.0% chord were changed by 0.5% chord interval and their effects were studied. With the numerical solutions, the relationship between $(L/D)_{max}$ and airfoil thickness as a function of flap height and the relationship between $(L/D)_{max}$ and flap height as a function of airfoil thickness were investigated. The same relationship for $(C_l)_{max}$ also were shown. From these results, the optimum flap size for each airfoil thickness can be determined and vice versa.

• 대한조선학회논문집
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• 제33권1호
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• pp.145-152
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• 1996

본 연구에서는 해상 구조물에 작용하는 설계 파랑 하중을 산정하기 위하여 해상에서 관측되거나 또는 예측된 파랑 자료를 사용하여 해상 구조물의 설계 생존 기간 동안 만나게 될 극한 설계파를 산정하는 기법을 개발하였다. 주어진 파랑 자료에 Order Statistics와 Monte Carlo Simulation 기법을 적용하여 가장 알맞은 파랑 자료의 극한 분포식을 선택하여 이 분포식으로부터 원하는 회귀 주기에 해당하는 극한 설계파를 결정하고 결정된 극한 설계 파고의 불확실성에 대한 범위를 설정함으로서 설계 파고의 여유를 줄 수 있다. 이와 같은 기법을 우리나라 남해안의 1938년부터 1987년까지 태풍에 의한 파랑 자료에 적용하여 극한 설계파를 산정하는 예를 보였다. 이상과 같은 방법을 이용함으로서 대형 해양 구조물을 설계함에 있어 극한 하중 상태를 산정할 수 있는 정보를 설계 초기 단계에 제공할 수 있으며 해당 구조물의 주요 요목, 구조 등의 설계 인자들을 산정할 수 있다.

• 한국해안해양공학회지
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• 제6권1호
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• pp.88-93
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• 1994

유한수심에서의 불규칙파에 적용할 수 있는 파고의 확률분포함수를 2가지 해석적 방법으로 유도하였다. 첫번째 방법으로 새로이 유도된 확률분포함수는 Rayleigh 확률분포함수에 대한 직교 다항식을 유도함으로써 급수형태로 표시된다. 유도된 확률밀도함수를 비정규성이 강한 천해에서 측정한 파랑자료와 비교하였다. 확률밀도함수가 자료의 막대그래프와 잘 일치하였으나, 확률밀도함수가 급수로 표시되어 있기 때문에 파고가 큰 부분에서 음의 확률값이 된다. 비록 음의 확률값의 크기가 작다 하더라도 파고의 극치분포함수를 구하기에 부적절하다고 판단된다. 두번째 방법은 최대 엔트로피 법(maximum entropy method)을 적용하여 파고 분포와 매우 잘 일치하며, 극치파고분포와 파고의 통계적인 특성 등을 추정하는 데 매우 유용함을 알 수 있다. 그러나 최대 엔트로피 법을 사용했을 경우, 비정규분포 특성을 나타내는 변위의 분포함수와 파고의 분포함수 사이의 함수관계를 구할 수 없었다.

• 대한인간공학회지
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• 제34권4호
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• pp.303-312
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• 2015

Objective: The aim of this study is to investigate the effect of insole height change in the lumbosacral angle and physical functions in healthy males. Background: In order to release male's dissatisfaction with his height and to increase satisfaction with his body, using insole is generalized. There have been researches on female's body change in accordance with function of insole and heel height, whereas there are few researches on males. Method: Participants were divided into three groups. A control group had 10 participants who wore 0cm insole. Experimental group I had 10 participants who wore 2cm insole. Experimental group II had 10 participants who wore 4cm insole. All participants wore insoles during their daily lives for a trial period of 8 weeks. The results were evaluated before and after comparison, and we measured lumbosacral angle, balance (dynamic balance, agility, quickness) and lumbar pain (LBP). Results: This study showed that insole height affected lumbosacral angle and dynamic balance and pain. In particular, there were significant differences in the 4cm group among the three groups (p<.05). The 2cm group did show a significant difference in lumbosacral angle and pain (p<.05). Furthermore, no significant difference was observed within the control group. Conclusion: The 4cm insole height suggests that the increase of lumbosacral angle contributes to some changes in LBP, balance, pain and physical functions, probably leading to negative effects on variety of activities of daily life. Application: The results of wearing insoles with proper height will help to prevent musculoskeletal disorders.

• The Journal of Korean Physical Therapy
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• 제18권6호
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• pp.43-49
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• 2006

Purpose: Changes of degenerative disc have been analyzed or with the Magnetic Resonance Imaging (MRI) to assign appropriate meaning, and the relationship between the degenerative changes of the discs and its living function has been evaluated through the living function evaluation scores collected by functional rating index. Methods: in April, 2006, a physical examination was conducted for physical laborers to be employed as on-site laborer in a steel industrial complex located at a region. A month later, these 20 laborers who participated in lumbar vertebra MRI tests have been investigated for one-to-one mobile phone functional rating index test. Excluding 3 of 14 respondents whom scored 0 in functional rating index, the rest of respondents' degenerative disc grade changes shown in MRI and its relationship to living functional rating index have been performed. Results: The Dabbs method of measuring disc height resulted to show significant increase as the disc height changes from L1-2 level to L5-S1 level (p<0.01). However, there was no statistical significance with a relationship between disc height and functional rating index, and disc height average. The Magnetic Resonance Imaging analysis regard on the degree of disc degeneration and its relationship to living functional rating proved to have significant relationship (p<0.05). Conclusion: The degenerative changes monitored by Magnetic Resonance Imaging show significant relationship (p<0.05) to living function. However, this relationship could vary depend upon the characteristics of study population. So, it suggested that the future studies should be performed by considering population's age and job career.

• 한국자동차공학회논문집
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• 제24권2호
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• pp.205-213
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• 2016

Heat loss and fin efficiency of symmetric and asymmetric trapezoidal fins with variable slope of fin's top surface are obtained by using a two-dimensional analytic method. Shapes of symmetric and asymmetric fins are changed from rectangular through trapezoidal to triangular by adjusting the fin shape factor. The ratio of symmetric trapezoidal fin length to asymmetric trapezoidal fin length is presented as a function of fin base height and convection characteristic number. The ratio of symmetric trapezoidal fin efficiency to asymmetric trapezoidal fin efficiency is presented as a function of the fin base height and fin shape factor. One of results shows that asymmetric trapezoidal fin length is shorter than symmetric trapezoidal fin length (i.e., asymmetric trapezoidal fin volume is smaller than symmetric trapezoidal fin volume) for the same heat loss when the fin base height and fin shape factor are the same.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2000년도 제20회 KOSCO SYMPOSIUM 논문집
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• pp.1-8
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• 2000

The effects of nozzle arrangements, nozzle distances and fuel flowrates on the flame stabilities such as flame length, liftoff height and blowout characteristics are investigated experimentally. Three nozzle arrangements - diamond 4 nozzle, linear 5 nozzle, cross 5 nozzle- are used. Flame interactions result in the increase of the blowout flowrates and constant turbulent liftoff heights. The flames separated about 10 nozzle diameters are sustained as nozzle attached flames to the higher fuel flowrates than the other separation cases. Normally flames are extinguished at the lifted states. Blowout flowrates are affected by the nozzle configuration, nozzle seperation distance. Blowout flowrates for the diamond- or cross- shaped nozzle arrangements are parabolic function of nozzle distances. Maximum blowout flowrates for the 5 nozzle configuration case except linear one is about 2.9 times that of single equivalent nozzle case. Turbulent liftoff heights are not function of flowrates for the interacting flames.