• Earthquakes and Structures
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• v.14 no.1
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• pp.85-94
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• 2018

The paper focuses on the seismic responses of a hyperbolic cooling tower resting on soil foundation represented by the three-parameter Vlasov elastic soil model. The three-parameter soil model eliminates the necessity of field testing to determine soil parameters such as reaction modulus and shear parameter. These parameters are calculated using an iterative procedure depending on the soil surface vertical deformation profile in the model. The soil and tower system are modeled in SAP2000 structural analysis program using a computing tool coded in MATLAB. The tool provides a two-way data transfer between SAP2000 and MATLAB with the help of Open Application Programming Interface (OAPI) feature of SAP2000. The response spectrum analyses of the tower system with circular V-shaped supporting columns and annular raft foundation on elastic soil are conducted thanks to the coded tool. The shell and column forces and displacements are presented for different soil conditions and fixed raft base condition to investigate the effects of soil-structure interaction. Numerical results indicate that the flexibility of soil foundation leads to an increase in displacements but a decrease in shell membrane and column forces. Therefore, it can be stated that the consideration of soil-structure interaction in the seismic response analysis of the cooling tower system provides an economical design process.

• Journal of KSNVE
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• v.5 no.4
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• pp.493-501
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• 1995

Optimum design of a viscoelastic damping layer which is unconstrainedly cohered on a steel plate is discussed from the viewpoint of the modal loss factor. Themodal loss factor is analyzed by using the energy method to the base steel plate and cohered damping layer. Optimum distributions of the viscoelastic damping layer for modes are obtained by sequentially changing the position of a piece of damping layer to another position which contributes to maximizing the modal loss factors. Analytical procedure performed by using this method simulated for 3 fundamental modes of an edge-fixed plate. Simulated results indicate that the modal loss factor ratios can be increase by as much as 210%, or more, by optimizing the thickness distribution of the damping layer to two times of the initial condition which is entirely covered. Optimum configurations for the modes are revealed by positions where added damping treatments become most effective. The calculated results by this method are validated by comparison with the experimental results and the calculated results obtained by the Ross-Ungar-Kerwin's model in the case of the layer is uniformly treated over the steel plate.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1221-1226
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• 2007

The subway with the initial constructive expense which is enormous together is the public transportation means where the many expense is expended in the operation and maintenance civil official. Seoul Metro until initial opening to traffic after present time cannot escape every year deficit to be, the cause is a possibility of seeking from the fare system which is short in transportation prime cost. Currently Seoul Metro is operating with the distance proportional fare system the passenger ticket system which is simple (usual volume, group volume and fixed amount volume, affection renunciation, charge free volume). When the biased characteristic of the user it plans considering from the goods development side for the variety for and a deficit solution, against the fare system systematic it researches and solution plan politically. Financial of the subway operation agency young the investigation against the present condition of the hazard subway fare system which is solved the bud with problem point a fare system from the research which it sees consequently and improvement program under analyzing the man with underdeveloped genital organ. Base on the reporter to analyze the introduction plan which with the character which will reach it follows with the necessity of introduction of the 1st passenger ticket (24 hour volume).

• Journal of Korean Foot and Ankle Society
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• v.4 no.1
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• pp.44-47
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• 2000

Freiberg's infarction involving the fifth metatarsal head is very rare condition. The authors experienced a case of avascular necrosis of the fifth metatarsal head and base of the proximal phalanx in a 27-year-old female patient. Involved bones were excised and internally fixed with 2 K-wires after autogenous cancellous bone grafting. Pain was relieved, and an excellent clinical result was obtained at the follow-up examination six months after the surgery.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.3
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• pp.127-133
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• 2017

Performance analysis has been carried out on a high side scroll compressor that had a fixed scroll equipped with a circular oil groove on its thrust surface. Oil was supplied to the oil groove through an intermittent opening from a high pressure oil reservoir formed inside the orbiting scroll hub. Oil in the groove was then delivered to both suction and back pressure chambers by pressure differentials and viscous pumping action of the orbiting scroll base plate. Mathematical modeling of this oil groove system was incorporated into a main compressor performance simulation program for an optimum oil groove design. The study findings were as follows. Pressure in the oil groove can be controlled by changing its configuration and the oil passage area. With an enlarged oil passage, the pressure in the oil groove heightens due to an increased flow rate, but the pressure elevation in the back pressure chamber is small, resulting in reduced friction loss at the thrust surface between the two scrolls. On the other hand, by increasing the oil passage area, the oil content in the refrigerant flow increases. Considering all these factors, the energy efficiency ratio could be improved by about 3.6% under the ARI condition by an optimal oil groove design.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.6
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• pp.601-607
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• 2015

The friction material for automobile is manufactured by mixing several composites to stop the running vehicles. Friction characteristics are changed significantly according to the relative amount of the base materials. However, difference of friction coefficient is sometimes measured at the test for the same friction material. Nevertheless, the study for solving these problems is insufficient. In this paper, the friction tests were carried out by changing the external environment and processing condition when the main ingredients are fixed and also evaluated how the friction coefficient changes. The variables are cooling air speed, humidity (Relative humidity and Absolute humidity), scorching time, soaking time and pad area. And it is analytically considered which environmental factor mainly affects the characteristic of friction coefficient variation by experiment. It is expected that the results from this study can be very useful as a database for development of the friction material.

• The Korean Journal of Malacology
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• v.22 no.2
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• pp.175-182
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• 2006

Artificial induction of maturation by heating of the ark shell, Scapharca broughtonii (Schrenck) broodstock was investigated from 10th March to 21th May in 2004. Maturity at the fixed water temperature group of $23^{\circ}C$ was 60.5％, and it was the highest in maturity among experimental groups cultured for seven weeks. The proportions of organism surviving to start of S. broughtonii in the raised water temperature experimental groups (20 and $23^{\circ}C$) were over 90.5％, as similar to the control group (natural water temperature, 84.8％). But, the proportions of organism surviving to start of S. broughtonii in the fixed water temperature experimental groups (20, 23, and $26^{\circ}C$) were decreased with the increasing of the water temperature. In the fixed water temperature experimental groups of $26^{\circ}C$, the survival was 18.1％. Base on these results, the fixed water temperature of $20^{\circ}C$ (accumulated water temperature; $1,295^{\circ}C$) was the best condition for artificial induction of sexual maturation.

• Journal of Ocean Engineering and Technology
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• v.35 no.5
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• pp.347-359
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• 2021

This study aims to evaluate the dynamic responses of the jacket-type offshore wind turbine using FAST software (Fatigue, Aerodynamics, Structures, and Turbulence). A systematic series of simulation cases of a 5 MW jacket-type offshore wind turbine, including wind-only, wave-only, wind & wave load cases are conducted. The dynamic responses of the wind turbine structure are obtained, including the structure displacement, rotor speed, thrust force, nacelle acceleration, bending moment at the tower bottom, and shear force on the jacket leg. The calculated time-domain results are transformed to frequency domain results using FFT and the environmental load with more impact on each dynamic response is identified. It is confirmed that the dynamic displacements of the wind turbine are dominant in the wave frequency under the incident wave alone condition, and the rotor thrust, nacelle acceleration, and bending moment at the bottom of the tower exhibit high responses in the natural frequency band of the wind turbine. In the wind only condition, all responses except the vertical displacement of the wind turbine are dominant at three times the rotor rotation frequency (considering the number of blades) generated by the wind. In a combined external force with wind and waves, it was observed that the horizontal displacement is dominant by the wind load. Additionally, the bending moment on the tower base is highly affected by the wind. The shear force of the jacket leg is basically influenced by the wave loads, but it can be affected by both the wind and wave loads especially under the turbulent wind and irregular wave conditions.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.253-258
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• 2010

In the field of the $CO_2$ absorption process using aqueous ammonia, the effects of regeneration pressure and temperature on $CO_2$ absorption performances of the aqueous ammonia were investigated. The absorbents were prepared by dissolving ammonium carbonate solid in water to grant the resulted solution 0.5 $CO_2$ loading ($mol\;CO_2/mol\;NH_3$) and various ammonia concentration (14, 20, 26 and 32 wt%). As-prepared absorbents were regenerated at high pressure and temperature (over $120^{\circ}C$ and 6 bar) before the absorption test. The absorption test was carried out by injecting the simulated gas that contains 12 vol% of $CO_2$ into a bubbling reactor. The introduction of 26 wt% of the ammonia concentration for $CO_2$ absorption test resulted in the higher absorption capacities than other experimental conditions. In particular, when the absorbents with 26 wt% of the ammonia were regenerated at $150^{\circ}C$ and 14 bar, the highest absorption capacity, $45ml\;CO_2/g$, was obtained. According to the analysis of absorbents using acid-base titration, the ammonia loss during the regeneration of the absorbents with a fixed ammonia concentration decreased as the regeneration pressure increased, while it increased as the regeneration temperature increased. In the condition of fixed regeneration pressure and temperature, as expected, the ammonia loss increased as the ammonia concentration increased. The measured $CO_2$ loadings and ammonia concentrations of absorbents were compared to the values calculated by Electrolyte NRTL model in Aspen Plus.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.706-713
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• 2016

In this study, the welding characteristics of friction stir welding were investigated in accordance with the tool plunge position and cooling to the base materials for the joining of dissimilar materials (A6005-AZ61). Other different welding conditions, such as the tool rotation speed and welding speed, were fixed to 500rpm-30mm/min, respectively, and welding was then carried out by placing the Mg alloy (AZ61) on the advancing side and Al alloy(A6005) on the retreating side. Welding was conducted under six different conditions. To investigate the welding characteristic, tensile test and microstructure observations using an optical microscope were carried out. As the tensile test result, the maximum strength appeared under the condition in which the tool is moved 1 mm to the Mg alloy direction and cooling to the base materials. Under the same welding conditions, the strength with cooling was approximately two times higher than that without cooling. The tool was located in each direction of 1.7 mm from the weld line. Therefore, in the excessive off-set of tool position, the welding integrity was in an extremely poor condition due to the lack of stirring. This study was confirmed by the A6005-AZ61 dissimilar friction stir welding the welding speed and the tool rotation speed. In addition, the temperature control and tool plunge position are important welding parameters.