• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.1
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• pp.25-33
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• 2010

The matching condition at a perforated wall with vertical slits involves the permeability parameter, which can be calculated by two different methods. One expresses the permeability parameter in terms of energy dissipation coefficient and jet length at the perforated wall, being advantageous in that all the related variables are known, but it gives wrong result in the limit of long waves. The other expresses the permeability parameter in terms of friction coefficient and inertia coefficient, giving correct result from short to long waves, but the friction coefficient should be determined on the basis of a best fit between measured and predicted values of such hydrodynamic coefficients as reflection and transmission coefficients. In the present study, an empirical formula for the friction coefficient is proposed in terms of known variables, i.e., the porosity and thickness of the perforated wall and the water depth. This enables direct estimation of the friction coefficient without invoking a best fit procedure. To obtain the empirical formula, hydraulic experiments are carried out, the results of which are used along with other researchers' results. The proposed formula is used to predict the reflection and transmission coefficients of a curtain-wall-pile breakwater, the upper part of which is a curtain wall and the lower part consisting of a perforated wall with vertical slits. The concurrence between the experimental data and calculated results is good, verifying the appropriateness of the proposed formula.

• The Journal of Engineering Geology
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• v.30 no.2
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• pp.147-160
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• 2020

Unsaturated hydraulic conductivity of near-surface unconsolidated layers depends on the physical properties and water content of the unconsolidated layers. So far, many studies have been conducted on the unsaturated hydraulic conductivity of near-surface unconsolidated layers. However, researches on hydraulic conductivity of unsaturated fractured rocks have been relatively rare. In relation to the construction of a low/intermediate level radioactive waste surface-disposal facility, this study compared and analyzed van Genuchten parameters (α, n) in the laboratory and the hydraulic conductivity obtained in field tests for fractured hornfels at a radioactive-waste disposal site of Korea. The relationship between the field hydraulic conductivity and van Genuchten parameters using data from the ten depth intervals of three boreholes resulted in that the correlation coefficient (R) between the hydraulic conductivity and the van Genuchten parameter α was 0.7607, showing positive correlation whereas the R between the hydraulic conductivity and the van Genuchten shape-defining parameter n was -0.8720, showing negative correlation. Hence, this study confirmed the relationship between the field hydraulic conductivity and the van Genuchten unsaturated functions for the unsaturated fractured hornfels.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.16 no.1
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• pp.27-35
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• 1980

The purpose of the present study is to find the light intensity which induces maximum gathering rate and to observe the variation of the gathering rate both in' daytime and at night by using two species of commercial fishes: rock bream, Oplegnathus fasciatus(Temminet et Schlegel) and glass-puffer,\ulcorner Fugu.niphobles (Jordan \ulcorneret. Snyder). An experimental tank($360L{\times}50W{\times}55H cm$) was set up in a dark room. An illumination system was attached to one end of the tank to control horizontal light intensity. Six artificial light sources were prepared by combination of two light bulbs (5W, 150W) and seven filters. During the. experiment water depth was maintained 50 em level in the tank. The tank was marked into six longitudinal sections each, being 60 cm long to observe the distribution of fish. The fish were acclimatized in dark condition for 40 minutes prior to the main experiment. Upon turning on the light, the number of fish in each section was counted40 times every 30 seconds, and the gathering rates were obtain from th~ average number of. fish' in each section. The light intensity inducing maximum gathering rate is as follows: rock bream: 162.0 lux (104,3--238, 1 lux) (day), 162.0 lux (104.3--238.1 lux) (night). grass puffer: 16.6 lux (10.6--24.5 lux) (day), 1. 9 lux (1. 2-2. 9 lUX) (night). Trend .of the gathering rate in illumination time revealed different results in two fish species. Gathering rate of rock bream showed the increasing trend fluctuately with the lapse of ' illumination time. However, that of grass puffer showed the increasing trend gradually at the early period of the illumination time and the uniform trend at the latter period with little distictive fluctuation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.83-90
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• 2017

Concrete structure for nuclear power plant is mass concrete structure with large wall depth and easily permits cracking in early age due to hydration heat and drying shrinkage. It always needs cooling water so that usually located near to sea shore. The crack on concrete surface permits rapid chloride intrusion and also causes more rapid corrosion in the steel. In the study, the effect of age and crack width on chloride diffusion is evaluated for the concrete for nuclear power plant with 6000 psi strength. For the work, various crack widths with 0.0~1.4 mm are induced and accelerated diffusion test is performed for concrete with 56 days, 180days, and 365 days. With increasing crack width over 1.0mm, diffusion coefficient is enlarged to 2.7~3.1 times and significant reduction of diffusion is evaluated due to age effect. Furthermore, apparent diffusion coefficient and surface chloride content are evaluated for the concrete with various crack width exposed to atmospheric zone with salt spraying at the age of 180 days. The results are also analyzed with those from accelerated diffusion test.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.6
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• pp.561-567
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• 1987

The purpose of this study was to find out the removal capacity of harmful ammonia by different filter media in the submerged biological filters in a given space of chamber. Four materials, pile cloth, corrugated skylight roofing plate, embossed plastic plate, and gravel, were used as the experimental filter media. Each filter medium was placed in two aquariums, each aquarium measuring $90cm\times60cm\times60cm\;(depth)$. Under the normal operating condition, the average of mean ammonia removal rates during the first and second functioning periods by each filter material which occupied tile space in the filter chamber (aquarium) was as follows: 1. Pile cloth: $8.381\;g{\cdot}m^{-3}.\;day^{-1}$ 2. Corrugated skylight roofing plate: $7.834\;g{\cdot}m^{-3}.\;day^{-1}$ 3. Embossed plastic plate: $7.797\;g{\cdot}m^{-3}.\;day^{-1}$ 4. Gravel: $7.051\;g{\cdot}m^{-3}.\;day^{-1}$ Thus, there were no significant differences between the media, but at the time of practical application of these materials, some other factors such as investment cost, easiness for the removal of excess detritus accumulated in tile interstices of filter media, etc. should be fallen into consideration. When large units are required, in particular, removal of excess detritus from tile gravel bed is extremely difficult, and in case of pile cloth filters the installation work is much complicated and a problem in supporting the structure when drained also exists. In these respects, corrugated skylight roofing plate and embossed plastic plate seem to be more optimal, but again in practice the local situation for the availability and the price of the materials should be rechecked and the fitness of tile materials in the particular filter chambers under use or under consideration for construction must be taken into account.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.101-111
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• 2006

In case of drilled shafts installed by drilling through soft overburden onto a strong rock, the piles can be regarded as end-bearing elements and their working load is determined by the safe working stress on the pile shaft at the point of minimum cross-section or by code of practice requirements. Drilled shafts drilled down for some depth into weak or weathered rocks and terminated within these rocks act partly as friction and partly as end-bearing piles. The base resistance component can contribute significantly to the ultimate capacity of the pile. However, the shaft resistance is typically mobilized at considerably smaller pile movements than that of the base. In addition, the base response can be adversely affected by any debris that is left in the bottom of the socket. The reliability of base response therefore depends on the use of a construction and inspection technique which leaves the socket free of debris. This may be difficult and costly to achieve, particularly in deep sockets, which are often drilled under water or drilling slurry. As a consequence of these factors, shaft resistance generally dominates pile performance at working loads. The efforts to improve the prediction of drilled shaft pile performance are therefore primarily concerned with the complex mechanisms of shaft resistance development. In this study, the numerical analyses are carried out to investigate the behavior characteristics of side of rock socketed drilled shafts varying the loading condition at the pile head. The difference of behavior characteristics of side resistance is also evaluated with the effects of modelling of asperity.

• Progress in Medical Physics
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• v.12 no.2
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• pp.125-131
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• 2001

We was investigate the dosimetric characteristics of the virtual wedge and it compared to the conventional fixed wedge. Also we was evaluate the quality factor of the experimental multi-channel dosimetry system for virtual wedge. Recently virtual wedge technique and wedge fraction methods are available through the computer controlled asymmetric collimator or the independent jaw in medical linear accelerator for radiation therapy. The dosimetric characteristics are interpreted by radiation field analyzer RFA-7 system and PTW-UNIDOS system. Experimental multi-channel dosimetry system for virtual wedge was consists of the electrometer, the solid detector and array phantom. The solid detectors were constructed using commercially diodes for the assessment of quality assurance in radiotherapy. And it was used for the point dose measuring and field size scanning. The semiconductor detector and ion chamber were positioned at a dmax, 5 cm, 10 cm, 20 cm depth and its specific ratio was determined using a scanning data. Wedge angles in fixed and virtual type are compared with measurements in water phantom and it is shown that the wedge angle 15$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$were agree within 1$^{\circ}$ degree in 6, 10 MV photon beams. In PDD and beam flatness, experimental multi-channel disimetry system was capable of reproduceing the measured values usually to within $\pm$2.1% the statistical uncertainties of the data. It was used to describe dosimetric characteristics of virtual wedge in clinical photon beams. Also we was evaluate optimal use of the virtual wedge and improve the quality factor of the experimental multi-channel dosimetry system for virtual wedge.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.36 no.3
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• pp.215-219
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• 2010

In this study, we investigated effects of Monegy (mixture of Sophorae Radix, Panax ginseng, Salvia miltiorrhiza BUNGE) on epilate-induced hair-loss in dorsal region of C57/BL6 mice and external structure of human hair. For morphological and histological analysis in scalp of epilate-induced hair-loss animal model, we utilized several microscopic techniques, such as confocal laser scanning microscopy (CLSM) and LAS 4000. Confocal analysis showed the distribution of FITC-conjugated Monegy and penetration depth compared with normal and control group. Furthermore, when Monegy was topically administrated onto a C57BL6 mouse, it penetrated very well. The fluorescence intensity was increased upto 205 and 113 folds compared to normal and control group, respectively. Also, area of fluorescence was increased to upto 255 to 127 folds compared to normal and control group. Broad scale area of fluorescence in dermis region was observed in the Monegy-treated mice. Furthermore, Monegy induced upto 75% hair repair against depilation. It might be promoted via the induction of growth factors in hair follicle.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.670-679
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• 1997

The pH changes in 4 small cavities prepared at the facial inner dentin and lingual outer dentin of the cervical and apical portion of root filled with calcium hydroxide pastes were investigated. Forty extracted permanent teeth with single canal were instrumented with step-back method, and then 4 small cavities were prepared. Two inner dentin cavities were cut a distance of about 1.0mm from the canal wall and two outer dentin cavities were cut to a depth of about 0.5mm from the root surface. Root canals and prepared cavities were flushed with 17% EDTA, and then irrigated with 5% NaOCl to remove smear layer. Teeth were randomly divided into four groups. Control group was not filled and the remaining other groups were filled with mixture of calcium hydroxide and distilled water, Vitapex$^{(R)}$ paste and Pulpdent$^{(R)}$ paste respectively. The pH change of the dentin in each cavity was measured at 0, 1, 3, 7, 14, 21, 28, 60, 90 days with pH microelectrode(WPI Co., USA). The results were as follows : 1. The groups obturated with Pulpdent$^{(R)}$ paste and Aqueous calcium hydroxide produced the increased pH level at 1 day and maintained plateau over next 3weeks and decreased after 3weeks. 2. The group obturated with Vitapex$^{(R)}$ paste observed no significant pH change until 2weeks and slight increased pH at 3weeks and sequential increasing after 3weeks. But, the pH in the group obturated with Vitapex$^{(R)}$ paste remained significantly below the pH measured in the other two experimental groups(P<0.05). 3. All experimental groups showed pH level similar to control group after 28 days. 4. The pH of outer dentin is slightly higher than that of inner dentin. There is no significant difference in pH level between apical and cervical dentin throughout the duration of the experiment, though apical dentin showed slightly higher pH than cervical dentin at 1 day(P<0.05).

• Korean Journal of Weed Science
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• v.15 no.3
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• pp.175-182
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• 1995

The experiment was conducted to obtain basic information on weed ecology and effective weed control in direct-seeded rice Gelds at National Yeongnam Agricultural Experiment Station in 1994. Double cropping system of rice-barley reduced weed occurrence about 30% as compared with rice single cropping due to allelopathic effect of barley residue or stubble. Occurrences of red rice (weedy rice), barnyard grass and water foxtail were closely related with tillage method; the greatest occurred in no tillage plot followed by rotavation only and plow plus rotavation. Period of seed germination of barnyard grass and carbgrass varied with temperature and soil depth. In the same environmental condition, the germination period of barnyard grass shortened 3 to 5 days as compared with that of carbgrass. Two systematic applications of herbicides, that is, the first application at 10 to 15 days after seeding and the second at just after flooding, were the most recommendable system in dry-seeded rice field in terms of weed suppression and yield capacity.