• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.3
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• pp.189-202
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• 2012

An Oscillating Water Column (OWC) wave generation system uses the air flow induced by the vertical motion of water column in the air chamber as a driving force of turbine. It is well known that OWC is one of the most efficient devices to harness wave power. This study estimated the air flow velocity from the time variation of the water level fluctuation in the air chamber under regular wave conditions using 3-dimensional numerical irregular wave tank (3D-NIT) model that can simulate the 3-dimensional irregular wave field. The applicability of the 3D-NIT model was validated by comparing numerically predicted air flow velocities with hydraulic experimental results. In addition, the characteristics of air flow frequency spectrum variation due to the incident frequency spectrum change, and the variations of frequency spectrum and wave reflection due to the existence of converter inside the air chamber were discussed. It is found that the phase difference exists in between the air flow velocity and the water level fluctuation inside the air chamber, and the peak frequency of the spectrum in water level fluctuation is amplified by the resonance in the air chamber.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.3
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• pp.173-182
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• 1997

This study is a basic research in purse seine fishery : on the behaviour of fish schools of tilapia Tilapia mossambica in the process of catch of the purse seine fishing method. The experiment was carried out for the mackerel purse seine which using of power block by fishing fleet system in the near sea of Cheju Island and as a forecast in the near future on the purse seine fishing, using of triplex net winch by one boat system in the near sea of Norway. These model purse seines were made of the scale of 1/180 of its full scale. The model purse seine test on the escaping behaviour of fish school by gap, area reducing of gap and tension of purse line was carried out in the stagnant water of experimental water tank. Designing and testing for the model purse seines were based on the Tauti's law. The results obtained were as follows : 1. When the time for the completing of pursing was 20 minutes, average swimming speed of fish school through a gap was 9.71cm/sec for powerblock seine and 9.97cm/sec for triplex seine. 2. In the case of pursing time in actual value was 20minutes, at 50 percent of the pursing, swimming behaviour of fish school in purse seine was 10% to I section, 80% to II section, 10% to III sectional direction for powerblock seine and a similar tendency for triplex seine. 3. In the case of pursing time in actual value was 20 minutes, at the time of 10 minutes have proceeded since then, area reducing rate of gap of the seine in projected front view was 63.5% for powerblock seine and 67.5% for triplex seine. 4. In the case of pursing time in actual value was 20 minutes, escaping rate of fish school by gap in projected front view was 70% for powerblock seine and 30% for triplex seine. Maximum tension of purse line was about 8.1 tons for powerblock seine and about 8.3 tons for triplex seine.

• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.87-94
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• 2002

Recently, there have been numerous attempts to expand the traditional temporary soil nailing system into a permanent wall. Two reasons for this include the soil nailed system's advantage of efficient and economic use of subgrade space and its ability to decrease the total construction cost. However, the systematic and logical design approach has not been proposed yet. The permanent soil nailing wall system, which utilizes precast concrete from soil nailing system, is already used in many countries, but the study of cast-in-place concrete lacing or rigid walls in bottom-up construction of traditional soil nailing walls is imperfect and insufficient. In this paper, various laboratory model tests have been carried out to investigate the influence of parameters, including stiffness of the rigid wall to the soil nailing structure with respect to failure mode, displacement patterns and tensile forces at the nail head in several levels of load. Then, the variation of earth pressure distribution on the soil nailing wall, built with a rigid front plate, is sought through different levels of surcharge load and tensile forces at the nail head.

• Journal of the Korean Geotechnical Society
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• v.20 no.2
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• pp.87-96
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• 2004

Application of the soil nailing method is continuously extending in maintaining stable excavations and slopes. However, ground anchor support system occasionally may not be used because of space limitations in urban excavation sites nearby the existing structures. In this case, soil nailing system with relatively short length of nails could be efficiently adopted as an alternative method. The general soil nailing support system, however, may result in excessive deformations particularly in an excavation zone of the existing weak subsoils. Pretensioning the soil nails then could play important roles to reduce deformations mainly in an upper part of the nailed-soil excavation system as well as to improve local stability. In this study, a newly modified soil nailing technology named as the PSN (Pretension Soil Nailing) is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the PSN system has been investigated mainly focusing on an establishment of the design procedure. In the present study, laboratory model tests are carried out to investigate the failure mechanism and behavior characteristics of the PSN system. Various results of model tests are also analyzed to provide a fundamental basis for the efficient design.

• Journal of the Society of Disaster Information
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• v.8 no.3
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• pp.297-303
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• 2012

This study examines the isolation-heat performance of fire proof fabric that is equipped over ceiling board in order to secure the capability of arresting the spread of a fire at roof 'Jucsim' structure of Wooden Cultural Properties. For this examination, I conduct experiments with the model and compare two construction methods of fire proof fabric, or flat-type, folding-type. The experiments show the following results. In case of installing the fire proof fabric in flat-type, when the temperature under the ceiling board is $750^{\circ}C$, the temperatures over the ceiling board is $50^{\circ}C$; the difference is $700^{\circ}C$. Compared with the case of removing fire proof fabric, the temperature over the ceiling board is lower by approximately $580^{\circ}C{\sim}600^{\circ}C$. Therefore it can be said that the construction of fire proof fabric enhances the isolation-heat performance. In case of installing the fire proof fabric in folding-type, when the temperature under the ceiling board is $600^{\circ}C$, the temperatures over the ceiling board is $65^{\circ}C$; the difference is approximately $530^{\circ}C$. Thus its isolation-heat performance is a little inferior to the flat-type equipment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3469-3476
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• 2015

The Korea Academia-Industrial cooperation Society. The Korea Academia-Industrial cooperation Society. In Korea, the territory has east high west low type and the rainfall is concentrated in the summer season. A nation having these topography and precipitation condition like Korea has to basically needs support of hardware alternatives. However, the right places decrease gradually and the resistance of the public opinion for national water resources policy stiffens gradually. The climate change has an effect in water resources fields and has a close relation. In the present study, therefore, future inflow of Miryang multipurpose dam basin is estimated by using SWAT model applied RCP 4.5 and 8.5 scenarios of "Korea Meteorological Administration" and considering the results, the future direction is purposed to operate the dam. As a result, the rainfall pattern is changed from traditional peak form to flat form. The dam operation rule in accordance with changing precipitation pattern has to be modified from the conventional operation rule and a new plan has to be established to meet a situation.

• Journal of agriculture & life science
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• v.45 no.6
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• pp.109-114
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• 2011

The objective of this study was to investigate the effects of environments (farms born, testing groups, age at the tests, date at slaughter, ages at slaughter) on body weights at 6, 12, 18 and 24 months of ages, body type measurements at 18 months of age and carcass characteristics in Hanwoo steer populations that were collected from commercial farms and reared in a progeny testing station. Performances of a total of 1,838 steer calves set for tests from 2004 to 2008 were recorded. Carcass characteristics were the carcass grading results evaluated and data collected slaughter scores at 24 months of age. For growth traits of all age classes and body type traits measured at 18 months of age, farms born, test group and linear covariate of age at test were fit in the models. For carcass traits, date at slaughter and linear covariate of ages at slaughter were fit in the models. Effect of farm at birth was not significant for body weight at 24 months of age. Carcass weight, eye muscle area, yield score and back fat thickness were affected by dates at slaughter but not by the ages at slaughter. Marbling score, however, was affected by these two effects. Farms at birth did not seem to affect body type measures greatly. This study will be utilized for Hanwoo Steers genetic evaluation.

• Proceedings of KOSOMES biannual meeting
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• 2008.05a
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• pp.61-67
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• 2008

This study analyzes the characteristics of material transportation between Busan new-port and Nakdong river estuary. Measurements of water temperate, salinity, turbidity, and tide is also analyzed to determine the characteristics of sea water and described the tidal current between two regions. For the purpose of indicating characteristics of tidal current numerical modeling is used. From the observed results, the total volume transport of sea water calculations revealed $184.71m^3/sec$ and residual volume transport was $(+)59.74m^3/sec$ during the 1st field measurement, and the total volume transport was $331.15m^3/sec$ and residual volume transport was $(-)28.88m^3/sec$ during the 2nd. The numerical simulation for three different topography cases are calculated. The results are summarized as follows: 1) The volume of material transportation about $0.7\sim18.4%$ is decreased as the depth of Busan new-port decrease (10 m). 2) The volume of material transportation about $3.5\sim21.9%$ is increased, as channel(water depth is 5 m) constructed to the Nakdong river estuary direction.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.384-395
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• 2020

Breaking waves generated by wave shoaling in coastal areas have a close relationship with various physical phenomena in coastal regions, such as sediment transport, longshore currents, and shock wave pressure. Therefore, it is crucial to accurately predict breaker index such as breaking wave height and breaking depth, when designing coastal structures. Numerous scientific efforts have been made in the past by many researchers to identify and predict the breaking phenomenon. Representative studies on wave breaking provide many empirical formulas for the prediction of breaking index, mainly through hydraulic model experiments. However, the existing empirical formulas for breaking index determine the coefficients of the assumed equation through statistical analysis of data under the assumption of a specific equation. In this paper, we applied a representative linear-based supervised machine learning algorithms that show high predictive performance in various research fields related to regression or classification problems. Based on the used machine learning methods, a model for prediction of the breaking index is developed from previously published experimental data on the breaking wave, and a new linear equation for prediction of breaker index is presented from the trained model. The newly proposed breaker index formula showed similar predictive performance compared to the existing empirical formula, although it was a simple linear equation.

• Geophysics and Geophysical Exploration
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• v.24 no.4
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• pp.180-193
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• 2021

The complex resistivity method is an exploration technique that can obtain various characteristic information of underground media by measuring resistivity and phase in the frequency domain, and its utilization has recently increased. In this paper, a three-dimensional inversion algorithm for the CR data was developed to increase the utilization of this method. The Poisson equation, which can be applied when the electromagnetic coupling effect is ignored, was applied to the modeling, and the inversion algorithm was developed by modifying the existing algorithm by adopting comlex variables. In order to increase the stability of the inversion, a technique was introduced to automatically adjust the Lagrangian multiplier according to the ratio of the error vector and the model update vector. Furthermore, to compensate for the loss of data due to noisy phase data, a two-step inversion method that conducts inversion iterations using only resistivity data in the beginning and both of resistivity and phase data in the second half was developed. As a result of the experiment for the synthetic data, stable inversion results were obtained, and the validity to real data was also confirmed by applying the developed 3D inversion algorithm to the analysis of field data acquired near a hydrothermal mine.