• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.343-349
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• 2011

A loosely coupling method is adopted to combine a computational fluid dynamics (CFD) solver and the comprehensive structural dynamics (CSD) code, CAMRAD II, in a systematic manner to correlate the airloads, vortex trajectories, blade motions, and structural loads of the HART I rotor in descending flight condition. A three-dimensional compressible Navier-Stokes solver, KFLOW, using chimera overlapped grids has been used to simulate unsteady flow phenomena over helicopter rotor blades. The number of grids used in the CFD computation is about 24 million for the isolated rotor and about 37.6 million for the rotor-fuselage configuration while keeping the background grid spacing identical as 10% blade chord length. The prediction of blade airloads is compared with the experimental data. The current method predicts reasonably well the BVI phenomena of blade airloads. The vortices generated from the fuselage have an influence on airloads in the 1st and 4th quadrants of rotor disk. It appeared that presence of the pylon cylinder resulted in complex turbulent flow field behind the hub center.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.2
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• pp.184-188
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• 2001

In a summer study during May to July, involving 12 young Murrah buffalo bulls at forty months of average age, the effects of multiple shower vs single shower body cooling and vitamin A, D and E supplementation on the sexual behaviour, semen quality and freezability were investigated. The animals were divided into two groups (6 animals in each group) and housed in a half-walled shed with proper spacing, the feeding management being identical. The bulls in the control group were given a single shower at 1000 h, whereas the experimental bulls were given four showers at 10,12,14 and 16 h. In addition, the experimental bulls were given vitamin A, D and E injections at fifteen day intervals. The sexual behaviour of bulls was observed in terms of reaction time, sexual aggressiveness and ejaculatory thrust. Semen quality of all the bulls was assessed in terms of volume, mass activity, live-dead sperm and sperm concentration, sperm motility and morphology, and acrosomal abnormality. The sexual behaviour did not vary significantly between the groups, whereas semen quality differed significantly for volume, per cent live sperms, total sperms per ejaculate and total live sperm per ejaculate between groups. It can be concluded that sexual behaviour was not influenced by the thermal comfort treatment coupled with periodic vitamin A, D and E injections. But the treatments improved most of the seminal traits in the experimental group of bulls. However, benefit of treatment was not reflected in the freezability traits of the semen.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.181-186
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• 2003

An experimental study has been conducted to measure the temperature fields for two and three staggered rows of the rectangular shaped-holes with high turbulence intensity. 10 % turbulence intensity is obtained by installation of two kinds of grids which have different shapes. One grid which is installed at 30d upstream from center of 1st row of holes is composed of vertical cylinders of which diameter is 10 mm and center to center distance is 18 mm. The other installed 15d apart to upstream from center of 1st row of holes which has square pattern is constructed of 3 rum square bars and bar spacing is 25 mm. Temperature fields are measured by using a thermocouple rake which is attached on three-axis traversing system. The results show that the overall values are decreased and the thicker film of coolant is fanned downstream of rows of holes for high mainstream turbulence intensity.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.24 no.2
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• pp.83-88
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• 1979

Competitive relationships between soybean cultivars and weeds were determined at different plant spacings and weed competition times. Soybean yields did not differ significantly between plant spacings. Annual weed competition more signficantly reduced yields and yield components of 'Williams' soybeans than those of 'Dongbuktae' and 'Suweon 83'. 'Suweon 83' and 'Dongbuktae' were more competitive to weeds than 'Williams'.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.5
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• pp.249-256
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• 2010

Water jet impingement cooling has been widely used in a various engineering applications; especially in cooling of hot steel plate of steelmaking processes and heat treatment in hot metals as an effective method of removing high heat flux. The effects of cooling water temperature on water jet impingement cooling are primarily investigated for hot steel plate cooling applications in this study. The local heat flux measurements are introduced by a novel experimental technique that has a function of high-temperature heat flux gauge in which test block assemblies are used to measure the heat flux distribution during water jet impingement cooling. The experiments are performed at fixed flow rate and fixed nozzle-to-target spacing. The results show that effects of cooling water temperature on the characteristics of jet impingement heat transfer are presented for five different water temperatures ranged from 5 to $45^{\circ}C$. The local heat flux curves and heat transfer coefficients are also provided with respect to different boiling regimes.

• Solar Energy
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• v.8 no.2
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• pp.3-11
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• 1988

To suppress the natural convection within enclosure spacing it has been shown theoretically and experimentally that the introduction of cell walls will effectively raise the critical Rayleigh number by providing more shear surfaces within the fluid. For a solar collector, a useful solar thermal converter requires effective control of heat losses. It has been reported that the natural convection can be suppressed and the heat performances of the solar collector increased by placing thin, poorly conducting material honeycomb between the absorber plate and the coverglass. The heat performances were measured and compared directly throughout the simultaneous installation of two solar collectors, one with honeycomb structures fabricated from thin poly carbonate sheet and the other without honeycomb structures. Various tilt angles of 30, 45 and 60 deg. from the horizontal and the honeycomb sizes ($W{\times}H$) of $10{\times}10,\;10{\times}20$ and $10{\times}40mm$ were utilized in the present investigation. It is found that the larger the tilt angle are, the greater the heat losses are, and that the smaller the honeycomb size is, the larger suppression effect of heat losses are. Especially, at tilt angles of 30 degree, the heat use ratio of solar collector with the honeycomb sizes of $10{\times}10mm$ improved approximately 29.5% more than that without honeycomb structures.

• Korean Journal of Human Ecology
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• v.1 no.2
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• pp.113-118
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• 1998

Clothing shape is principally described in seven factors that are composed of clothing design, clothing material, clothing size, pattern design, sewing method and body motion etc.. The aims of this study was to measurement out-line space-shape variation of clothing fitness with somato type by using the image processing. The subjects for direct anthropometric measurements were 248 female college students aged from 19 to 22. The data were statistically analyzed by principal analysis and cluster analysis. The results were obtained three somato type. Also I made skirts in order to analyzed to the out-line space-shape variation of clothing fitness with body. The effect of somato type on the shape of flare skirts was determined by the out-line space-shape variation of clothing fitness with body. The out-line space-shape variation of clothing fitness with body was observed between the node number and amplitudes of clothing wave form and node number was determined at the maxim of space-shape amplitude, and the space-shape amplitudes have related with aspect ratio of cross-sectional shape. Results for flare skirts show changes in amplitude and mean with fabrics, somato type. therefore gray-level histogram are correlated with changes out-line space-shape, differences in drape spacing and related fabric properties and their somato type. (Korean J Human Ecology 1(2):113∼110 1998)

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.2
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• pp.175-182
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• 2002

The cement injection technology on the purpose of ground reinforcement and cut-off has been used in construction sites until now. However, recently it is applied to prevent leakage of underground structure. In this study, applicability of the back side waterproof grouting method was verified through performing field model tests and reviewing case histories. From the results of this study, injection shape of the back side waterproof grouting method was appeared to be root type, and waterproof effect by injection of cement grout material was excellent because grout material infiltrated into boundary between wall of structure and back side ground to be waterproof layer. Components influencing infiltration of injection material are type of soil and degree of compaction. For effective injection, injection pressure has to vary gradually from high pressure to low pessure and small quantity of injection material has to be injected for long times. Also, spacing of injection hole must be designed considering condition of back side ground, injection area, W/C ratio, the number of injection and injection pattern properly.

• International Journal of Concrete Structures and Materials
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• v.3 no.1
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• pp.39-45
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• 2009

The purpose of this study is to establish flexural behavior of high-strength concrete beams confined in the pure bending zone with stirrups. The experiment was carried out on full-scale high-strength reinforced concrete beams, of which the compressive strengths were 40 MPa and 70 MPa. The beams were confined with rectangular closed stirrups. Test results are reviewed in terms of flexural capacity and ductility. The effect of web reinforcement ratio, longitudinal reinforcement ratio and shear span to beam depth ratio on ductility are investigated. The analytic method is based on finite element method using fiber-section model, which is known to define the behavior of reinforced concrete structures well up to the ultimate state and is proven to be valid by the verification with the experimental results above. It is found that confinement of concrete compressive regions with closed stirrups does not affect the flexural strength but results in a significantly increased ductility. Moreover, the ductility tends to increase as the quantity of stirrups increases by reducing the spacing of stirrups.

• Carbon letters
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• v.21
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• pp.51-60
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• 2017

Isotropic pitch-based fibers produced from coal tar pitch with the melt-blowing method were carbonized at temperatures ranging from 800 to $1600^{\circ}C$ to investigate their crystalline structure and physical properties as a function of the carbonization temperature. The in-plane crystallite size ($L_a$) of the carbonized pitch fiber from X-ray diffraction increased monotonously by increasing the carbonization temperature resulting in a gradual increase in the electrical conductivity from 169 to 3800 S/cm. However, the variation in the $d_{002}$ spacing and stacking height of the crystallite ($L_c$) showed that the structural order perpendicular to the graphene planes got worse in carbonization temperatures from 800 to $1200^{\circ}C$ probably due to randomization through the process of gas evolution; however, structural ordering eventually occurred at around $1400^{\circ}C$. For the carbonized pitch powder without stabilization, structural ordering perpendicular to the graphene planes occurred at around $800-900^{\circ}C$ indicating that oxygen was inserted during the stabilization process. Additionally, the shear stress that occurred during the melt-blowing process might interfere with the crystallization of the CPF.