• Journal of Korean Society of Forest Science
• /
• v.97 no.5
• /
• pp.485-491
• /
• 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.

• The KSFM Journal of Fluid Machinery
• /
• v.10 no.2 s.41
• /
• pp.7-15
• /
• 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.

• Journal of the Ergonomics Society of Korea
• /
• v.29 no.5
• /
• pp.789-795
• /
• 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.

• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.568-572
• /
• 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.

• Journal of the Society of Naval Architects of Korea
• /
• v.33 no.1
• /
• pp.145-152
• /
• 1996

In this study, the technique to evaluate the extreme design wave height of certain return period is developed from the given measured or hindcasted sea state data of concerned area for limited period. By using the order statistics and Monte Carlo Simulation method, the best fit probability distribution function with proper parameters describing the given wave height data is chosen, from which extreme design wave height can be predicted by extrapolation to the desired return period. The fitness and the confidence limit of the chosen probability function are also discussed. Application calculation is carried out for the wave height data given by applying the Wilson wave model theory to major 50 typhoon wind data affecting Korean South coast during the year from 1938 to 1987.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.6 no.1
• /
• pp.88-93
• /
• 1994

This study is concerned with an analytic derivation of the probability density function applicable for wave heights in finite water depth using two different methods. As the first method of the study, a probability density function is developed by applying a series of polynomials which is orthogonal with respect to Rayleigh probability density function. The newly derived probability density function is compared with the histogram constructed from wave data obtained in finite water depth which indicate strong non-Gaussian characteristics. Although the probability density represents the histogram very well. it has negative density at large values. Although the magnitude of the negative density is small. it negates the use of the distribution function fer estimating extreme values. As the second method of the study, a probability density function of wave height is developed by applying the maximum entropy method. The probability density function thusly derived agrees very well with the wave height distribution in shallow water, and appears to be useful in estimating extreme values and statistical properties of wave heights in finite water depth. However, a functional relationship between the probability distribution and the non-Gaussian characteristics of the data cannot be obtained by applying the maximum entropy method.

• Journal of the Ergonomics Society of Korea
• /
• v.34 no.4
• /
• pp.303-312
• /
• 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
• /
• v.18 no.6
• /
• pp.43-49
• /
• 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.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.24 no.2
• /
• pp.205-213
• /
• 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
• /
• 2000.05a
• /
• pp.1-8
• /
• 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.