• Korean Journal of Applied Biomechanics
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• v.20 no.3
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• pp.319-325
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• 2010

The purpose of this research was to investigate the differences in the ski carving turn motion according to level of expertise. The posture and movement of 6 skiers nearby the fall-line was evaluated with a biomechanical approach focusing the rotational mechanics. The slope was at an angle of $9^{\circ}$ and the following variables were measured and calculated: tangential velocity, change of COM height after passing fall-line, width between feet, angle between upper body and thigh, trunk angle, average radius of curvature and average centripetal force. The expert skiers minimized their center of mass height movement and maintained the width of between their feet after the passing the fall-line in comparison with the beginners and intermediate skiers. The experts restrained themselves from pushing their upper body downward after the turn to maximize the centripetal force. The experts in comparison with the beginners and intermediate skiers during the turn didn't have to reduce their radius of curvature to maintain a high centripetal force. It was concluded, that the most important factor affecting the centripetal force, was for the beginners and intermediate skiers, to minimize their movement while using the appropriate amount of edging.

• Journal of the Korean Institute of Navigation
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• v.17 no.3
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• pp.49-55
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• 1993

This study describes the accuracies of position fixes observed by the DGPS systems for the purpose of obtaining the utility basic data in the fishery and oceanography observation field. The circling sail experiments around a reterence point using the DGPS were made in water level point of National Fisheries University of Pusan and on the sea in Yongho day located on the southeast of that university. The main results are as follows ; 1) The number of the usable satellites in position fixing were all eighteen, SV 2, 3, 11-21, 23-26 and SV 28 etc. Each satellites could be observed for average seven hours a day, and position fixing was found to be always possible except about thirty minutes a day. 2) In the standard fixed position, the radius of 95% probability circle and the shifted distance between the position fixes by the DGPS and true position were respectively 5.7m, 0.9m. In the above case those of ordinary GPS was respectively 48.8, 54.2m. Therefore, the accuracy of the position fixes by DGPS was shown much higher the ordinary GPS. 3) At land, the shifted distance between the center of traces in the circling sail experiment of 15m ra-dius by DGPS and the reference position amounted to 5.5m and observed radius of circling traces was 17.5m. other than 15m. At sea, that distance the center of traces in circling experiment of 20m radius by the DGPS and the reference position amounted to 3.6m and observed radius of circling traces was 19.7m, other than 20m. Therefore, the utility of the circling experiment to obtain the accurate position fixes by the DGPS was found to be very high.

• Composites Research
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• v.14 no.2
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• pp.22-32
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• 2001

Damage induced by low-velocity impact on the curved composite laminates was experimentally evaluated for CFRP cylindrical shells with the radius of curvatures of 50, 150, 300, and 500 mm. The result was then compared with that of flat laminates and with the results by nonlinear finite-element analysis. The radius of curvatures and the effective shell stiffness appeared to considerably affect the dynamic impact response of curved shells. Under the same impact energy level, the maximum contact force increased with the decreasing radius of curvatures, with reaching 1.5 times that for plates at the radius of curvature of 50 mm. Since the maximum contact farce is directly related to the impact damage, curved laminates can be more susceptible to delamination and less resistant to the low-velocity impact damage. Delamination was distributed rather evenly at each interface along the thickness direction of curved laminates on the contrary to the case of flat laminates, where delamination is typically concentrated at the interfaces away from the impact point. This implies that the effect of curvatures has to be considered for the design of a curved composite laminate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.1957-1967
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• 1997

Adaptive channel equlization accomplished without resorting to a training sequence is known as blind equalization. In this paper, in order to reduce the speed of the convergence and the steady-state mean squared error simultaneously, we propose the multi-stage RD(radius-directed) algorithm derived from the combination of the constant modulus algorithm and the radius-directed algorithm. In the starting stage, multi-stage RD algorithm are identical to the constant modulus algorithm which guarantees the convergence of the equalizer. As the blind identical to the constant modulus algorithm which guarantees the convergence of the equalizer. As the blind equalizer converges, the number of the level of the quantizers is increased gradually, so that the proposed algorithm operate identical to the radius-directed algorithm which leads to the low error power after the covnergence. Therefore, the multi-stage RD algorithm obtains fast convergence rage and low steady stage mean square error.

• Journal of KSNVE
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• v.10 no.2
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• pp.240-246
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• 2000

One of the widely accepted methods for evaluating the interior sound quality of automobiles is Articulation Index(AI). The AI actually measures the articulation level of the sound in the vehicle cabin as passengers talk to one another. In this study, the effect of two different absorption materials inside the cabin on AI has been investigated by ray-tracing method : one is firewall, the other is celling. It turns out that the back seat location is found to be strongly dependent on the type of absorption materials treated at the celling, since the sound absorbing area is different due to the location and the firewall is situated in the "Reverberation Radius". The proposed methdo could be used to improve the sound quality of automobiles at the design stge.sign stge.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.5
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• pp.63-71
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• 2005

In-situ soil remediation mechanism through the vertical drains (VDs) is analyzed with numerical model as the error and complementary error function. Results from in-situ test and analysis indicate that the contaminant concentration ratio as initial one ( C/$C_0$) increases as the radius ratio ( r/R) increases from the injection well, and also increases as the depth ratio ( z/ H) increases from the top of contaminated area. The elapse time needed to attain $50\%$ and $90\%$ clean up level ($ t_{50},\;t_{90}$) increases as the radius ratio ( r/R) and the depth ratio ( z/ H) increase. As above results, the procedure of soil flushing in contaminated area using vertical drains makes progress from the top of injection well to the bottom of extraction well.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.20 no.43
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• pp.47-57
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• 1997

As a general index in surface quality of machined products, surface roughness is to measure worker's skill level, a ground product quality and machining accuracy, etc. The surface roughness is defined by a function of rotational speed and radius of a grinding wheel, distances of active grains composed of the wheel, and feed of a grinder's worktable. To predict surface roughness in horizontal surface grinding operations, probability distributions were used. Probability distribution functions(p.d.f.) of surface roughness were found as results when the size of active grains(=the radius of a grinding wheel) is given as uniform, exponential distribution, and the distance between active grains follows the distributions of uniform, exponential. For each pdf case, probabilistic features of surface roughness were also analyzed and presented. This study is a substantial step for determining mathematically the surface roughness instead of using empirical approaches. More works should be presented to develop a general model by which an accurate roughness value can be obtained in horizontal surface grinding operations.

• Communications for Statistical Applications and Methods
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• v.17 no.4
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• pp.611-624
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• 2010

Several methods were suggested for constructing a fuzzy relationship between fuzzy independent and dependent variables. This paper reviews the use of the method by minimizing the square of the difference between an observed and a predicted fuzzy number in an ${\alpha}$-level linear regression model. We introduce a new distance between fuzzy numbers on the basis of a mode, a core point and a radius of an ${\alpha}$-level set of a fuzzy number an construct the fuzzy regression model using the proposed fuzzy distance. We also investigate sufficient condition for an equivalence in the ${\alpha}$-level regression model.

• Journal of Nutrition and Health
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• v.31 no.1
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• pp.46-61
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• 1998

This study was carried out to evaluate the effects of vitamin D nutritional status on bone mineral density of adults (21-49 years). To attain the aim, we measured bone mineral density (BMD) of the subjects at distal radius by single-photon absorptiometry (SPA). Serum level of 25-hydroxyvitamin D(25-(OH)D) , known to be the best indicator of indicator of vitamin D status in humans was analyzed . The factors affecting this vitamin D level were also investigated in autumn in 122 young adults. Serum level of 25-(OH)D was measured by high pressure liquid chromatography(HPLC) and biochemical variables, general health status, time spent outdoors, and dietary intakes of the subjects. BMD of the male subjects was significantly greater than that of female subjects. Weight, activity and total energy expediture (TEE) showed a positive correlation with distal BMD. The mean level of serum 25-(OH)D was 24.4$\pm$11.0 ng./ml and by sex, 26.0$\pm$6.8ng/ml for males and 23.3$\pm$12.3ng/ml for females , the level was significantly higher in male (p<0.01). there was significant correlation between BMD at distal-radius and s-25(OH)D levels (p<0.001). The serum level fo parathyroid hormone (PTH) showed a negative correlation with BMD(p<0.05), with the more obvious correlation in females. Vitamin D intake was estimated to be 3.75$\pm$2.19ug/day in average. Among the nutrients studied, protein ,fat, calcium , and vitamin D intake were positively correlated with distal BMD. When food frequencies were concerned , milk and dairy products showed a significant positive correlation with the BMD level, and driedfoods, eggs , fats and oils, and cereals also showed a positive correlation. Time spent outdoors was estimated to be about 70 minutes in average and positively correlated with the distal BMD level(p<0.01). During the day, the specific time between 12 :00pm and 2:00pm showed the most significant correlation with BMD (p<0.001). Multiple regression analysis with the variables showed that distal BMD could be fit 31.9% by the time spent outdoors a day, intake of Ca and vitamin D, and TEE. The standardized estimates were 0.344 for vitamin D intake, 0.284 for Ca intake 0.179 for the time spent outdoors a day and 0.273 for TEE. For males, s-25*OH)D level, TEE and time spent outdoors during a day showed a significant correlation. For females, intake of Ca and vitamin D could fit about 27.1% of the distal BMD.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.907-910
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• 2008

The wheel radiation noise characteristic of Korean tilting train(Hanvit 200) on curved rail under the field test conditions is analyzed in this paper. The test railroad track was selected from Seodaejon to Songjeongri in Honam line. $5^{th}$ and $6^{th}$ car are decided to measure radiation noise level among a train of six cars. The test subject curve radius executed from R400, R500, R600, R700 and R800 segments. The speed of test trains when from R600 and R800 curves existing operation speed and speed up 20% of existing speed. On curved rail at the time of operation speed of Hanvit 200 trains from below 95km/h wheel radiation noise level at $94dBA{\sim}99dBA$, the operation speed from between $100km/h{\sim}144km/h$ wheel radiation noise level at $100dBA{\sim}106dBA$.