• Journal of the Korean Society of Safety
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• v.28 no.1
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• pp.12-17
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• 2013

Considering the wind power system and the rotor blades which are composed of much technology, the wind power blade would be the most dangerous part because it revolves at high speed and weighs about dozens of tons, if the accident happens. Therefore, the light weight composite materials have been replacing as substitutional materials. The object of this study is to examine the delamination and damage for CFRP/GFRP hybrid composite that is used for strength improvement of a wind power blade. The influence of the initial crack length and fiber orientation for the interlaminar delamination was exposed for the blade safety. Plain woven CFRP instead of GFRP was inserted into the layer of the box spar for improving the strength and blade life. DCB(Double Cantilever Beam) specimen was used for evaluating fracture toughness and damage evaluation of interlaminar delamination. The material used in the experiment is a commercial material known as CF 3327 EPC in plain woven carbon prepreg(Hankuk Carbon Co.) and UD glass fiber prepreg(Hyundai Fiber Co.). From the results, crack growth rate is not so different according to the variation of the initial crack length. Mode I interlamainar fracture toughness of fiber direction $0^{\circ}$ is higher than that of $45^{\circ}$. Interlaminar fracture has an effect on fiber direction and K decreased with lower value according to increasing initial crack length. Also energy release rate fracture toughness was evaluated because CFRP/GFRP hybrid composite with a different thickness is under the mixed mode loading condition. The interlaminar fracture was almost governed by mode I fracture even though the mixed mode.

• Journal of the Korean Vacuum Society
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• v.22 no.3
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• pp.111-118
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• 2013

The influence of gas flow on the plasma generation in the atmospheric plasma jet is described with the theory of hydrodynamics. The plasma discharge is affected by the gas-flow streams with Reynolds number (Re) as well as the gas pressure with Bernoulli's theorem according to the gas flow rate inserted into the glass tube. The length of plasma column is varied with the flow types such as the laminar flow of Re<2,000 and the turbulent flow of Re>4,000 as it has been known in a general fluid experiments. In the laminar flow, the plasma column length is increased as the increase of flow rate. Since the pressure in the glass tube becomes low as the increase of flow velocity by the Bernoulli's theorem, the breakdown voltage of plasma discharge is reduced by the Paschen's law. Therefore, the plasma length is increased as the increasing flow rate with the fixed operation voltage. In the transition of laminar and turbulent flows, the plasma length is decreased. When the flow becomes turbulent as the flow rate is increasing, the plasma length becomes short and the discharge is shut down ultimately. In the discharge of laminar flow, the diameter of plasma beam exposed on the substrate surface is kept less than the glass diameter, since the gas flow is kept to the distinct distance from the nozzle of glass tube.

• Korean Journal of Human Ecology
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• v.7 no.3
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• pp.35-48
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• 2004

In this study, by determining lower limb movements which cause significant changes in body surface lines, body parts with the greatest maximum expansion and contraction rate respectively were illustrated in descending order. Using unmarried female university students aged 18 - 24 as subjects, a total of 32 body surface categories (15 body surface lines and 17 body surface segment lines) were measured in one static and 9 movement poses. In particular, expansion and contraction levels and rates were measured and used in the analysis. The analysis first involved the calculation of the average measurement per body part in body surface line in static pose as well as of the average expansion and contraction levels and rates in 9 lower limb movements. Two-way MANOVA and multiple comparison analysis (Tukey) were conducted on movements and individual somatotypes regarding measurement per body part and expansion and contraction rates. Movements which cause measurements of body surface lines differed significantly in body surface line in static pose versus in movement were then identified. Among average expansion and contraction rates in such movements, maximum average expansion and contraction levels, maximum average expansion and contraction rate, and classes of expansion and contraction rate were determined per body part. The results of this study are as follows. First, 5 lower limb movements; F2, F5, F6, F7, F8, which caused significant changes in body surface lines were determined and illustrated in table 4. Second, the levels, rates, and classes of expansion and contraction rate per body part are illustrated in Tables 5 and 6. Body parts with the greatest maximum expansion rate were, in descending order: upper segment of center back leg line, upper segment of inner leg line, middle segment of center front leg line, posterior crotch length, anterior knee girth, anterior thigh girth, center back leg line, girth at crotch height, anterior midway thigh girth, hip girth, anterior crotch length, knee girth, waist girth, inner leg line, thigh girth, and crotch length. Those with the greatest maximum contraction rate were, in descending order: anterior crotch length, upper segment of center front leg line, lower segment of center back leg line, center front leg line, and posterior thigh girth. The maximum expansion rates and maximum contraction rates, which ranged from 2.05 to $35.95\%$ and from -0.20 to $-30.16\%$ respectively, were classified per body part into 4 ABCD classes. The body part with maximum expansion was the upper segment of the center back leg line at vertical body surface line, expanding by $35.95\%$ or 16.03cm in F5 flexion movement. In contrast, the body part with maximum contraction was the anterior crotch length at vertical body surface line, contracting by $-30.16\%$ or -10.54cm in F5 flexion movement. Both, however, were the body parts to expand or contract the most among all horizontal and vertical body surface lines.

• Current Research on Agriculture and Life Sciences
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• v.20
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• pp.99-105
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• 2002

To develop good soybean varieties for sprouts. 285 indigenous lines and 16 recommending varieties were evaluated by the sprout and agronomic characteristics. The range of whole length, hypocotyl length, root length, and yield rate of sprouts was 9.5~23.0cm, 5.9~15.1cm, 3.2~9.2cm, and 121~695%, respectively. Yield rate of sprouts was the highest, 409%, in the lines of mixed seed coat color. At the same time, it was reversely proportional to seed weight : the smaller the seed weight, the higher the yield rate as in all other reports. The number of roots was significantly fewer in the lines of the black and the green seed coat color than others. Based on whole length, rate of root length, and yield rate of sprouts, many indigenous lines were evaluated much better than recommending varieties. In the hypocotyl color of sprouts, the brightness was higher in improved variety than indigenous lines but vice versa in redness and yellowness in general.

• Korean Journal of Poultry Science
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• v.31 no.3
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• pp.157-164
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• 2004

The objective of this study was to investigate the association of growth rate with body weight or shank length at birth in broiler chickens. Cobb and Ross breeds were used as experimental stocks and four groups were assigned in each breed; thirteen-male and twelve-female chicks(25 birds) were allocated in each group. The heavier body weight group(HBW) and the lighter body weight group(LBW) were established by birth weight. Whereas, the longer shank length group(LSL) and the shorter shank length group(SSL) were established by shank length at birth. The heavier group chicks in birth weight were significantly(P < 0.05) the longer in shank length at birth. The differences between HBW and LSL or between LBW and SSL in the mean 5-wk body weight of Cobb were not significantly different in each other; however, HBW and LSL were significantly(P < 0.05) heavier than LBW or SSL. Whereas, there were no significant differences in the mean 5-wk body weight of Ross although HBW was heavier by 13.1 g than LBW and LSL was heavier by 68.0 g than SSL. In the mean 5-wk shank length, the LSL of Cobb and Ross was longer by 2.9 mm and 1.3 mm than SSL, respectively; however, the significant(P < 0.05) difference was showed in Cobb only. In both breeds, the differences in the mean 5-wk shank length between HBW and LBW were not great. By the results of correlation analysis, the associations of the overall mean birth weights with the overall mean shank length at birth or the association of the 0～5 wk growth rate with the change of shank length during 0～5 wk showed highly significant(P < 0.01～0.001) in both breeds. The present study suggested that the selection based on birth weight could be at advantage due to easier and more accurate tool in using for the improvement growth rate in broiler chickens because the measurement of shank length takes individually longer and less accurate than the measurement of body weight.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.421-426
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• 2010

With hydraulic noise test facility, a variety of tests were performed to investigate the pulsation pressure generation mechanism and its transmission characteristics and to derive the noise control methodology. Many experiments were carried out by changing average pressure, flow rate, pump speed, hose length and MCV spool condition. From the test results, the correlations between pulsation pressure and other design parameters, such as static pressure, flow rate and MCV spool opening area and length of hose, were found out. And also each contribution factors were evaluated from the regression analysis. By changing hose length, the pulsation pressure resonance phenomenon was investigated. In order to find out the pulsation pressure reduction measures pulsation pressure analysis, such as pulsation pressure of hydraulic pump itself and pulsation pressure of hydraulic system, by using AMESim were studied. In addition hydraulic silencer was developed based on the Helmholtz resonator. And its performance was evaluated by installing the silencer at the excavator.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.159-162
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• 2005

Random Early Detection (RED), one of the most well-known Active Queue Management (AQM), has been designed to substitute Tail Drop and is nowadays widely implemented in commercially available routers. RED algorithm provides high throughput and low delay as well as a solution of global synchronization. However RED is sensitive to parameters setting, so the performance of RED, significantly depends on the fixed parameters. To solve this problem, the Adaptive RED (ARED) algorithm is suggested by S. Floyd. But, ARED also uses fixed parameters like target-queue length; it is hard to respond to bursty traffic actively. In this paper, we proposed AQM algorithm based on the variation of current queue length in order to improve adaptability about burst traffic. We measured performance of proposed algorithm through a throughput, marking-drop rate and bias phenomenon. In experimentation, we raised a packet throughput as reduced packet drop rate, and we confirmed to reduce a bias phenomenon about bursty traffic.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.107-112
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• 2001

The effect of ambient gas (steam) condensation on swirl spray characteristics were studied experimentally for low subcooling condition of the liquid. The configuration of the liquid(water) sheet and the breakup modes were examined. Also variation of the discharge coefficient, breakup length, local and the cross-sectional area-averaged SMD of droplets with the liquid flow(injection) rate were obtained. The perforation breakup mode appears dominant with condensation while the aerodynamic wave breakup mode is dominant without condensation(in the air environment). The discharge coefficient, breakup length and the mean drop sizes decrease in a same manner with increasing of the liquid flow rate for both cases(with and without condensation). The condensation effects are insignificant with the discharge coefficient. However, the local and cross-sectional area-averaged SMD are larger and the breakup length becomes shorter in the steam environment. The spray angle predicted from the volumetric flux distribution along the radial direction of the sprays in the steam environment becomes larger with condensation.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2203-2208
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• 2006

Both 1-D and 2-D analytic methods are used for a rectangular fin optimization. Optimum heat loss is taken as 98% of the maximum heat loss. Temperature profile using 2-D analytic method and relative error of temperature along the fin length between 1-D and 2-D analytic methods are presented. Increasing rate of the optimum heat loss with the variation of Biot number and decreasing rate of that with the variation of the fin base length are listed. Optimum fin tip length using 2-D analytic method and relative error of that between 1-D and 2-D analytic methods are presented as a function of Biot numbers ratio.

• Electrical & Electronic Materials
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• v.9 no.3
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• pp.246-250
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• 1996

In optical soliton transmission systems with nonlinear dispersive materials, which is utilized for ultra-long and high bit rate transmission, it is shown that the value of initial time difference between adjacent solitons is analyzed for optimum bit rate. The method is inducted by uncorrelation condition with minimum interaction forces in initial covariance coefficient between adjacent solitons. When the initial time difference is 6 times of soliton pulse width by the results, it is shown that the reliability is maintained with more than 90% within transmission length of soliton period. multiplied by 93.