• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.49-59
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• 2011

In order to understand evaluation of the seismic stability of a reinforced earth retaining, we made chambers of 1:10 (the ratio of the miniature), considering the law of similarity based on drawings of representative cross sections. And we measured an increase in acceleration, earth pressure, and displacement after applying Hachinohe wave (long period), Ofunato wave (short period), and artificial wave, complying with the domestic standards, in order to evaluate the external stability of the reinforced earth retaining wall during earthquake based on the measurements. As a result, the unreinforced earth retaining wall collapsed at 2 g of seismic acceleration. But the reinforced earth retaining wall was evaluated to ensure proper stability as well, with respect to the earth pressure gauge, the increments of earth pressure tend to be raised significantly in the upper than the lower and showed a similar characteristic of behavior in previous theory.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.1-7
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• 2015

The environmental regulations for CO2 emissions from the ship have been established recently, and fuel oil price has been increased continuously. In order to overcome these circumstances, Energy Saving Devices (ESDs) have been developed continuously to reduce the fuel oil consumption and improve the propulsive efficiency. This paper describes the trial performance of PBCF (Propeller Boss Cap Fins), SCHNEEKLUTH duct, Asymmetric rudder bulb and Mewis duct applied to handy-size bulk carriers. As a result, SCHNEEKLUTH duct is more effective than other energy saving devices at the reducing the fuel oil consumption and the improvement of the propulsive efficiency. In addition, it is confirmed that SCHNEEKLUTH duct is really effective in the vibration of the deck house. And the fuel oil consumption can also be reduced through main engine de-rating.

• 한국해양학회지
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• v.21 no.4
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• pp.245-258
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• 1986

A two-dimensional numerical model is developed to investigate the phenomenon of forced seiche caused by the incident long waves. This model is applied to Young-il Bay and Pohang New Harbor, where the seiche is most frequently observed and the damage of the seiche is serious compared with the other harbors in Korea. Some results on this study are as follows; 1. The natural periods of the first two modes obtained from the present model are about 70 and 25 minutes respectively for Young-il Bay, and about 25 and 7.5 minutes for Pohang New Harbor. These results are well consistent with those obtained by the theoretical formula, the spectral analysis, and the statistical investigation of the recorded data. 2. Since the fundamental natural period of Pohang New Harbor is almost the same as the second natural period of Young-il Bay, the seiche in Pohang New Harbor can be strongly amplified by the Oscillation in Young-il Bay. Therefore, the most strong seiche in Pohang New Harbor can occur when the long wave of about 25-minute period come into Young-il Bay.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.86-93
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• 2010

The wear of railway track affects loss of rough ride, noise or vibration of train and traveling safety. Moreover as the track is worn away, this promotes destruction of structural mechanism of rail track which can bring about increasing of rail track maintenance cost drastically. For this reason, it is very important and interested research subject to design railway track structure and to analyse train movement mechanism based on systematic analysis of the reasons causing rail wear possible in real field. In this research, for the efficient maintenance, Life Cycle Performance of rail track and maintenance characteristics are computed considering some track components such as track type, contracting type, sleeper type and roadbed type. Time - Wear probabilistic distribution relationship as well as multiple regression analysis based on time, curvature and wear data are computed to predict the service life remainder of railway track and to be adapted to safety assessment.

• Korean Journal of Agricultural Science
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• v.34 no.1
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• pp.61-65
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• 2007

This study was conducted to evaluate the response of CIDR-S on estrus synchronization of dairy goats and the effect of artificial insemination on conception rate. Estrus synchronization of sexually matured Saanen goats was induced with insertion of CIDR-S into vagina for 15 days and injection of 500 IU PMSG before removal of CIDR-S. Artificial insemination was conducted using liquid or frozen semen by intra-cervical insemination with synchronized does. Estrus synchronization was 90% using CIDR-S insertion for 15 days. Conception rate of inseminated does was 20% - 25%, while that of natural mated does was 100%. These results suggested that synchronization of dairy goats can be successfully induced and artificial insemination method has to be improved for the practical use in dairy goats.

• Journal of the Korean Geosynthetics Society
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• v.19 no.1
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• pp.55-63
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• 2020

In this study, a scaled model test of the shaking table and a seismic analysis considering effective stresses were performed to reveal the dynamic behavior characteristics of box structures deep located in multi-layered soils upon seismic loading. The input seismic wave was operated below the ground using five seismic waves, including long period wave (Hachinohe), short period wave (Ofunato), artificial wave and real earthquakes that occurred in Gyeong-ju and Po-hang. As a result of model test and numerical analysis, the vertical displacement of box structures upon seismic loading was greater than that of horizontal direction, and it was confirmed that an increase of excess pore water pressure below the foundation ground caused a displacement. In addition, behavior of the ground and structures during artificial seismic wave appeared to be larger than real earthquake wave.

• Journal of the Korean Geotechnical Society
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• v.34 no.1
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• pp.25-35
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• 2018

Geocentrifuge tests are performed to investigate the structure-soil-structure interaction of shallow foundations that have various sizes. The soil specimen is prepared by using the air-pluviation, and the dynamic responses of the foundation are monitored with separation distances between the two foundations and the embedment. During the centrifugal test, the measured ground acceleration shows a tendency to increase with the increase of the input seismic amplitude, and maximum acceleration is measured at the surface due to the ground amplification. As the separation distance between the two foundations decreases, the ratio of the response spectral acceleration (RRS) increases and the period at the peak RRS decreases due to the structure-soil-structure interaction (SSSI). The RRS of the two foundations tends to decrease when the foundations are buried in the ground at the same separation distance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.325-331
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• 2010

Three-cup anemometers are popular devices for measuring wind speeds in automated weather stations, environmental monitoring systems, and wind turbines. Cup anemometers usually suffer from lack of long-term stability owing to the wear of the bearing systems that support the rotational parts. The bearing systems are susceptible to external pollutants, vibrations, and gusts. Therefore, these anemometers have to be calibrated regularly to maintain the desired characteristics for measuring wind speed. In the present study, a new in-situ calibration system to help reduce cost and save time by calibrating the cup anemometers at the installation site is proposed. A portable in-situ calibrator was fabricated. After the characteristics of this calibrator were verified, it was used to calibrate cup anemometers. Some of the calibration results were compared with the data obtained by wind tunnel testing.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.6
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• pp.40-52
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• 2011

This paper develops a traffic condition decision algorithm to improve the reliability of traffic information on urban streets. This research is reestablished the criteria of qualitative traffic condition categorization and proposed a new qualitative traffic condition decision types and decision measures. The developed algorithm can be classified into 9 types for qualitative traffic condition in consideration of historical time series of speed changes and traffic patterns. The performance of the algorithm is verified through individual matching analysis using the radar detector data in Ansan city. The results of this paper is expected to help promotion of the traffic information processing system, real-time traffic flow monitoring and management, use of historical traffic information, etc.

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.845-852
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• 2007

An OWC-type Wave Energy Conversion passes through 3 steps energy conversion process. This paper deal with the impulse turbine with staggered blade to improved performance by numerical analysis using commercial CFD code, FLUENT Maximum value of axial airflow velocity during exhalation is higher than that during inhalation This paper deal with special-type of Impulse Turbine so-called "Staggered Blade" for more efficiency to making air flow direct to on pressure side. Also, this paper has proposed special-type turbine with self-pitched blade more efficient.