• Journal of Industrial Technology
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• v.22 no.B
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• pp.27-34
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• 2002

3-D numerical studies are performed to investigate the effect of the air dam height and approaching air velocities on the pressure distribution of notchback road vehicle. For this purpose, the models of test vehicle with four different air dam heights are introduced and PHOENICS, a commercial CFD code, is used to simulate the flow phenomena and to estimate the values of pressure coefficients along the surface of vehicle. The standard $k-{\varepsilon}$ model is adopted for the simulation of turbulence. The numerical results show that the height variation of air dam makes almost no influence on the distribution of the value of pressure coefficient along upper and rear surface but makes strong effects on the bottom surface. That is, the value of pressure coefficient becomes smaller as the height is increased along the bottom surface. Approaching air velocity makes no differences on pressure coefficients. Through the analysis of pressure coefficient on the vehicle surface, one tries to assess aerodynamic drag and lift of vehicle. The pressure distribution on the bottom surface affects more on lift than the pressure distribution on the upper surface of the vehicle does. The increase of air dam height makes positive effects on the lift decrease but no effects on drag reduction.

• Journal of the Korean Institute of Navigation
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• v.20 no.3
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• pp.127-135
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• 1996

This study investigated the correlation of physique factor( standing height, body weight, chest girth, body surface ) and vital capacity upon records of swimming discipline at sea water. The subjects are 194 sophomore students of Korea Maritime University who participated in the swimming discipline. The swimming records were divided into three groups - higher, middle and lower group. The results from this investigation are as follow ; 1. The standing height was above the average on the A, B+ record, body weight was above on the A+, A record, and vital capacity was above on the A+, A, B+, C record respectively. 2. The standing height, body weight, chest girth, body surface, vital capacity was significantly correlated between record P < 0.05 and P < 0.01. Therefore the higher record group has better physique factor and vital capacity than the middle or lower record group. 3. The standing higher of the higher record group was significantly correlated with body weight(0.514), body surface(0.768) and vital capacity(0.427), and body weight was significantly correlated with chest girth(0.525), body surface(0.940) and vital capacity. This standing heiht of the middle record group was sigificantly correlated with body weight(0.509) and body surface(0.779), and body weight was significantly orrelated with chest grith(0.618) and body surface(0.927). The standing height of the lower record group was significantly correlated with body weight(0.595), chest grith(0.363), body surface(0.802) and vital capacity(0.250), and body weight was significantly correlated with chest grith(0.678) and body surface(0.952).

• Journal of Environmental Science International
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• v.3 no.4
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• pp.305-315
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• 1994

The field observation was carried out to investigate the characteristics of surface inversion layer at Kimhae using the feild observed date and upper layer meteorological data during 4-5 February 1993. The results of the study can be summarized as follows : The maximum height of surface inversion layer observed at Kimhae is 193m and the height of upper level inversion layer ranges from 2nm to 300m. The surface weather elements was influenced the formation of surface inversion layer. According to the pasquill stability and time variation of temperature with height, both the surface heating from insolation and the disturbance of upper level of inversion layer was influenced the disappearance of inversion layer. And the stability of surface temperature inversion layer generally belongs to the class of F, that of upper level temperature inversion layer commonly to the class of E.

• Bulletin of the Korean Chemical Society
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• v.18 no.2
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• pp.149-151
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• 1997

Barrier height on the surface was monitored at 77 K by observing the inflection of V-I characteristics of ZnO(1010)-ZnO(1010) contact in the surface reaction of oxygen species with carbon monoxide. The contact showed inflections at 10-20 mV and 10-50 mV for the sample adsorbed oxygen at 298 K and 573 K, respectively. When the sample adsorbed oxygen at 573 K was exposed to carbon monoxide at 298 K and 573 K, inflections were observed at 10-40 mV and 10-30 mV, respectively. The results indicated that the adsorption of oxygen on ZnO increased the surface barrier height, and the reaction of carbon monoxide with the oxygen-preadsorbed (at 573 K) ZnO decreased the surface barrier height.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.16 no.1
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• pp.18-29
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• 1990

In this report, the variation of skin surface between before treatment and after treatment was investigated by skin image analyzer. The 30 volunteers were applied cream and lotion on the forearm Inside for 4 weeks, and the measurement parameter of skirl surface was adopted peak, length, height, and width. The results were as follows ; 1. variation trends of parameters was showed that number of peaks were increased, but length, height and width were decreased. 2. The order of improvement for skin surface are as follow ; height > length > peak > width. 3. And also disclosed that the number of peak has a correlation with width, and length has a correlation with height.

• Journal of Environmental Science International
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• v.7 no.5
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• pp.639-645
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• 1998

A Jump model was evaluated for the calculation of hourly mixing height and mean potential temperature within the height. The Sump model was modified for estimation of downward heat fluxes by mechanical convections and surface heat fluxes. The surface heat fluxes were estimated from routine weather data such as solar radiation and air temperature. Total of 8 upper-air data observed at 0000UTC and 0600UTC in Osan station during April 23 to 26, 1996 were analyzed, and compared to the model results in detail. The calculated mixing heights and potential temperatures within the height were comparable to the observations, but some differences were showed. The calculated mixing heights were generally higher than observations. And, when variations of wind directions were large, the large difference of potential temperature was occurred. From the results, it was important to note that vortical motions and advections of air masses would affect to the growth of the mixing height.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.107-112
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• 2016

In this paper, the hydrophobic rough surfaces were prepared by employing a conventional nano-imprint lithography technique, and the effects of surface parameter, ratio of the top surface to the flat unit cell, on the impingement behaviors of liquid droplet were investigated to improve robustness of hydrophobic functionality. The critical height defined for the transition from rebound to fragmentation is measured by droplet impingement test in order to study dynamic behavior of an impinged droplet. It showed the critical height decreased with high surface parameter while it increased with low surface parameter. However, the critical height decreased again as surface parameter decreased further. Observed results suggest that the optimized surface pattern should be designed for the increased critical height.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.127-128
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• 2006

We introduce a novel approach for generating constant scallop height tool paths. We derive a Riemannian metric tensor from curvature tensors of a part surface and a tool surface. Then, we construct geodesic parallels from the newly constructed metric. Those geodesic parallels constitute an asymptotically-correct family of constant scallop height tool paths.

• Atmosphere
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• v.31 no.1
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• pp.101-112
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• 2021

The long-term trend of surface wind speed in Korea is examined for 31 KMA weather stations from 1985 to 2019. Most stations, except Daegwallyeong, have several times of anemometer height changes from tens of centimeters to several meters. To minimize such height change effect on long-term wind trend, the present study adjusts anemometer height in each station to the standard height of 10 m using the power-law wind profile. This adjustment results in non-negligible trend change. For instance, the increasing surface wind speed at Suwon station, which has six times of anemometer height changes in a range of 0.8 m to 20 m, is weakened up to 67% and becomes statistically insignificant. Likewise, the decreasing trend at Andong station, with three times of anemometer height changes in a range of 10 m to 15.5 m, is weakened up to 66%. A similar weakening in long-term trend is observed in most stations regardless of positive and negative trends. However, due to the cancellation between weakened negative trends and weakened positive trends, the station-averaged wind speed trend in Korea does not change much. This result suggests that anemometer height adjustment is crucial for evaluating local wind speed trend but its impact on nation-wide wind speed trend is rather minor.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1483-1495
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• 1994

A quantitative analysis of a surface roughness for a precision machining of a sculptured surface in milling process is treated under superposition theory in this paper. The geometrical surface rouhgness is calculated as a function of feed per tooth, path interval, radii of tool and cutting edge, and radii of curvatures of workiece. Through machining experiments in a 3-axis machining center, we confirmed the adequacy of the adequacy of the analysis. While cutter mark is neglegible in ball endmilling, it is significant in flat endmilling. When feed per tooth is very small, flat endmilling gives superior finish to ball endmilling. In flat endmilling, cutting condition and cutter path should be strategically chosen to balance the cutter mark height and cusp height.