• Journal of Mechanical Science and Technology
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• v.16 no.9
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• pp.1102-1111
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• 2002

The study focuses on the heat transfer performance of two-phase closed thermosyphons with plain copper tube and tubes having 50, 60, 70, 80, 90 internal grooves. Three different working fluids(distilled water, methanol, ethanol) are used with various volumetric liquid fill charge ratio from 10 to 40%. Additional experimental parameters such as operating temperature and inclination angle of zero to 90 degrees are used for the comparison of heat transfer performance of the thermosyphon. Condensation and boiling heat transfer coefficients, heat flux are obtained using experimental data for each case of specific parameter. The experimental results are assessed and compared with existing correlations. The results show that working fluids, liquid fill charge ratio, number of grooves and inclination angle are very important factors for the operation of thermosyphons. The relatively high rate of heat transfer is achieved when the thermosyphon with internal grooves is used compared to that with plain tube. The optimum liquid fill charge ratio for the best heat transfer performance lies between 25% and 30%. The range of the optimum inclination angle for this study is 20$^{\circ}$～30$^{\circ}$ from the horizontal position.

• Magazine of the Korean Society of Agricultural Engineers
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• v.21 no.3
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• pp.92-103
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• 1979

The compaction of core zone of the fill dam is very important foe increasing of the Strength of soil mass and reduction of permeability of the core. The principal objects of this study are to give the construction criteria of tamping rollers and to find out the relationships between density and permeability of soil after compaction. The results in this study are summarized as follows. 1. The core zone of fill dam should be compacted more than 8 passed because the compaction effects of clayey soil increase sharply in about 8 passes of roller. 2. The coefficient of permeability (K) increases with the thickness of compaction of soil even though the density is same. 3. The effect of compaction increases with the quantity of coarse materials such as coarse sand and gravel. 4. If D values change from 100 percent to 98 percent and from 100 percent to 95 percent, K values become 2 times and 5 times of initial K value respectively. 5. The coefficient of permeability in the field soil is very high comparing with the result of laboratory test at the same 100 percent compaction ratio, but differences between both results decrease with the decrease of compaction ratio. 6. Thickness of soil layer for the compaction should be increased for heavier compaction machine. 7. In order to get the compaction ratio of 98 percent or more, 10 to 12 passes of roller is generally required with the thickness of soil from 20cm to 30cm.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.667-675
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• 2008

As a large construction such as highway, dam, reclaimed land etc. increase in number more and more, large amount of fill materials are required. However, it's difficult to obtain it because of environmental problems and economical efficiency. A alternative plan is to utilize a gypsum which is a by-product yielded from chemical plants and verify suitability to use gypsum as fill materials. Therefore, a characteristic of compaction for gypsum is analyzed and construction methods are given regard to this characteristic from construction of dike using gypsum. Based on the results obtained, it is found that moisture of gypsum in compaction should to be more dry side of O.M.C(optimal moisture content) because of sponge phenomenon. When gypsum is used to fill materials, standards of compaction should be decided from laboratory test.

• Journal of Drive and Control
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• v.17 no.3
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• pp.47-56
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• 2020

As a shift control of automatic transmission was managed with the electronic control unit (ECU), shift quality which is a measure of shift shock during gear change has markedly improved. However, the initial clutch pressure control of the clutch filling phase should continue to rely on the predetermined control input since the input and output speeds are unchanged until the shifting process attains the inertia phase. It is critical to minimize the clutch response time and control the clutch pressure accurately at the end of clutch fill to achieve quick shift response and smoothness. Advanced transmission companies have adopted an auto calibration method which establishes the databases for the clutch piston fill-up attributes and the frictional characteristics of the disks. In this study, a distinctive auto calibration algorithm for forklift transmission under development is proposed and verified with the real-vehicle test. The experimental calibration results showed consistent turbine dynamics at the initial stage of shifts with the properly calibrated clutch-fill control parameters. By using this technique, it is necessary to finalize the shift control for the various operation conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.9
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• pp.725-733
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• 2002

In this study, the heat transport limitations of a two-phase closed thermosyphon were investigated. For the test, a two-phase closed thermosyphon ($L_t/: 600 mm,\;L_e:105mm,\;L_a:75mm,\;L_c:420mm,\;D_o:22.2mm,$ container: copper (inner grooved surface), working fluid: PFC ($C_6F_14$) was fabricated with a reservoir that can change the fill charge ratio. The following was imposed as the factors on the heat transport limitations of a two-phase closed thermosyphon. 1) Fill charge ratio of the working fluid. 2) Tilt angle of the longitudinal axis. From tile experimental data, some results were obtained as follows. When the fill charge ratio was relatively small ($\psi$20%), the heat transport limitation occurred about 100W by dry-out limitation. However over 40%, it shelved nearly constant value (500 W) by flooding limitation. The heat transport limitation according to the tilt angle increased smoothly until the tilt angle was $60^{\circ}$,/TEX>, after then decreased slowly.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.8
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• pp.90-97
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• 2015

This paper discusses to the capability improvement of the 1/4 HP compressor. And, for efficiency improvement of the single phase induction motor, this paper has proposed a casting method to improving the fill factor of the rotor of the single phase induction motor. First, by using FEM, it was analyzed the magnetic flux distribution and the fill factor to the SPIM rotor by the conventional method and the proposed method. And, based on the FEM analysis results, SPIMs are manufactured by the each casting process. Through experiments using dynamometer, they were compared and measured to their efficiencies. In addition, through experiments using Calorimeter, we have analyzed the refrigerating capacity of the compressor of which they were applied. Based on the results of the previous two experiments, they are to verify the validity of the proposed method.

• Journal of Mechanical Science and Technology
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• v.19 no.12
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• pp.2296-2302
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• 2005

This study is focused on the comparison of heat transfer performance of two thermosyphons having 60 straight and helical internal grooves. Distilled water has been used as working fluid. Liquid fill charge ratio defined by the ratio of working fluid volume to total internal volume of thermosyphon, the inclination angle and operating temperature were used as experimental parameters. The heat flux and heat transfer coefficient are estimated from experimental results. The conclusions of this study may be summarized as follows; Liquid fill charge ratio, inclination angle and geometric shape of grooves were very important factors for the operation of thermosyphon. The optimum liquid fill charge ratio for the best heat flux were $30\%$. The heat transfer performance of helically grooved tube was higher than that of straight grooved tube in low inclination angle (less than $30^{\circ}$), but the results were opposite in high inclination angle (more than $30^{\circ}$). As far as optimum inclination angle concerns, range of $25^{\circ}\~30^{\circ}$ for a helically grooved tube and about $40^{\circ}$ for a straight grooved tube are suggested angles for the best results.

• Geomechanics and Engineering
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• v.34 no.4
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• pp.341-380
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• 2023

This study evaluates the seismic fragilities in fill slopes in South Korea through parametric finite element analyses that have been barely investigated thus far. We consider three slope geometries for a slope of height 10 m and three slope angles, and two soil types, namely frictional and frictionless, associated with two soil states, loose and dense for frictional soils and soft and stiff for frictionless soils. The input ground motions accounting for four site conditions in South Korea are obtained from one-dimensional site response analyses. By comparing the numerical modeling of slopes using PLAXIS^2D against the previous studies, we compiled suites of the maximum permanent slope displacement (D_max) against two ground motion parameters, namely, peak ground acceleration (PGA) and Arias Intensity (I_A). A probabilistic seismic demand model is adopted to compute the probabilities of exceeding three limit states (minor, moderate, and extensive). We propose multiple seismic fragility curves as functions of a single ground motion parameter and numerous seismic fragility surfaces as functions of two ground motion parameters. The results show that soil type, slope angle, and input ground motion influence these probabilities, and are expected to help regional authorities and engineers assess the seismic fragility of fill slopes in the road systems in South Korea.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.132-137
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• 2015

A modular construction method includes factory-prefabricated room-sized volumetric units. Although low-rise buildings have been constructed worldwide using this method for more than 30 years, it is a relatively new technology in high-rise construction. There are three basic methods of constructing high-rise buildings using modular construction: the core method, the core-and-podium combination method, and the modular in-fill method. While the first two have been used in the USA and in several European countries, the third method, introduced in 2011 by an international cruise ship development firm, is a rather new approach for which there are few case histories. Therefore, its applicability and construction feasibility should be verified. As a pilot study to test the applicability of the modular in-fill method, a 12-story residential building was built in Korea. This paper describes a case study of the pilot project. The advantages and disadvantages of the method and its applicability in terms of cost effectiveness and construction schedule management were evaluated.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.43-46
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• 2013

Active use of images in the same place as the religion according to the height of the screen is determined by the height of the main speakers. This causes the 'sound image mismatch' and 'bass boost' sound like a failure occurs. Front seats are good seats in visual acoustics is a bad place. To minimize these obstacles acoustical speakers to actively apply the front fill needed. Higher sound pressure difference between the main speaker and the distance must be determined in accordance with the appropriate capacity. Actively using the front speakers to the sound image field by implementing the agreement to increase the concentration of sound. The relatively high inflow enhance alto lacking the front seat can be implemented evenly in the frequency response. Column in front of the main seat of the main speakers to supplement the deficiencies can be implemented more comfortable acoustic environment. Front fill speaker needs to be actively introduced, thereby presenting a detailed estimate, is needed.