• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.480-488
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• 2010

The CGS method is non-discharge replacement method improving ground stiffness by the effect of static compaction with injecting very low slump mortar into ground, and is applied for increasing bearing capacity and filling ground cavity by lifting or restoring differential settled structures and preventing differential settlement. This paper suggests design of ground improvement and construction case history for civil engineering structures by CGS method. This method can be used for reinforcing soft ground and liquefaction of loose sandy soil. This method was used in SongDo area in Incheon Economic Free Zone due to its low vibration of ground while it can improve the soft soil where underground structures(subway and box culvert) are already existed.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.629-636
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• 2003

The purpose of this study is localization of safety relief valves for Nuclear Service through technical development with overall design, fabrication, inspection, capacity certification test and functional qualification test of safety relief valves in accordance with ASME Section III and KEPIC Code. Safety relief valve is the important equipment used to protect the pressure vessel, the steam generator and the other pressure facility from overpressure by discharging the operating medium when the pressure of system is reaching the design pressure of the system. But we're depending on technology of the other country up to the present time. Because we don‘ have our own technologies, we have been spent the great time and money on installing and repairing safety relief valve at nuclear power plant. Therefore we have to achieve the development of safety relief valves for Nuclear Service with our own technologies.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.129-139
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• 2016

Cast-in-place concrete-filled hollow PC (HPC) columns are used to reduce lifting load of heavy-weight PC columns and to improve the structural integrity of joints. In the present study, a new type of HPC column was proposed to improve the productivity and structural integrity of the concrete. To form the hollow PC columns, a permanent inner form was prefabricated using structural deck plates and penetrated lateral bars. Half-scale specimens of four HPC columns were tested under combined axial compression and lateral cyclic loading to evaluate the seismic resistance. In the design of test specimens, various parameters such as the spacing of lateral re-bars, the use of steel fiber, and the thickness of PC cover were considered. The test results showed that the proposed HPC columns generally exhibited satisfactory load-carrying capacity and deformation capacity without brittle failure of PC. If closely spaced hoops or fiber reinforcements are used for PC, the deformation capacity can be improved further by restraining PC spalling.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.1
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• pp.29-36
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• 2016

Lifting lugs are frequently used to transport and to turn over blocks of ship and offshore structures in a shipyard. As the shipbuilding technology has been developed, blocks has become bigger and bigger, and block management technology takes a more important role in shipbuilding to enhance the productivity. For the sake of economy as well as safety in design of lug structure, needed is a more rational design procedure based on the ultimate strength derived through the rigorous non-linear structural analysis considering both the material and geometric non-linearity. This study is aimed at deriving the optimum design of T type lug structure which is frequently used in a shipyard. The optimum thickness of lug's main body is to be determined based on the results of non-linear strength analysis. As far as the present results for T type lugs having various capacity are concerned, it can be said that the present optimum design result can guarantee both safety and economy. From the fact that any regular trend cannot be found in weight reduction to the capacity of lugs, it seems to be necessary to review the current design procedure of lug structure. The present design procedure can be extensively used in design of various types of lug structures used in shipyard.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.3
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• pp.288-294
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• 2005

This study was conducted to evaluate the grit removal efficiency of tornado block-type vortex grit separator. Vortex grit separator was manufactured for this study, and it was characterized by the impeller and tornado block installed in separator. Impeller was installed to increase water velocity in the separator and tornado block was installed to increase the grit lifting efficiency. Pilot study was also conducted in A sewage treatment plant (STP) in Gyeonggi province from November 2003 to May 2004 (64 days). Major findings are as follows. 1. Impeller was proven to increase water velocity in the grit separator, especially in low flow rate. This influence will increase separation ratio of organics from grits, preventing those organics from sedimentation. 2. Sand (with 0.2~0.3mm size) removal efficiency was over 98 % and 96 %, at the flow rate of $500m^3/day$ and $750m^3/day$ under the condition that impeller rotation velocity kept at 15 rpm. Originally that grit separator was designed to have the capacity of $500m^3/day$. $750m^3/day$ was tried to investigate the performance of this type of grit separator under overload condition. Stable grit removal was still available to the extent of 150% of designed capacity. 3. It took less than 3 minutes for the grit separator to completely lift out 3 kgs of 0.2-0.3 mm sized, settled sand at the bottom to 2,060 mm high above water surface. But it showed the tendency to spend a little more time on lifting the grit as the grit size and the vertical height of the lift increased. 4. During experimental duration in A STP, it was found that the average amount of inlet grit was about 981 g/day (160~1,685 g/day) under $500m^3/day$ of operation condition, but it varied so severely during the experimental duration. After classification of discharged grit according to its size, grit with 0.3-0.42 mm size was found as largest part of output.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.3
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• pp.163-173
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• 2001

The dynamic behavior characteristics of a small fishing crane for inshore and coastal fishing vessels was experimentally analyzed in order to improve the fishing operation and to reduce considerably manual work of fisherman. The small fishing crane was designed to be controlled electro-hydraulically by means of proportional valves and solenoid valves, and also to be controlled the speed of each operation. The dynamic behavior characteristics was investigated by measuring the changes of parameters such as oil pressure, swing angle of load, load tension, the lifting angle and the swing angle of crane arm when the arms extended in a side way was given a test load. The results obtained are summarized as follows: 1. The designed small fishing crane can be proportionally controlled by means of proportional valves and rapidly by operating the solenoid valves, respectively. The capacity, turning angle, maximum reach of crane were 2 T-M, $180^\circ$, 3.7m, respectively. 2. The vertical change of crane arm on the extension of lifting cylinder was $1.2^\circ$/cm, and the swing speed of crane arm due to the extension of swing cylinder by on/off operations of solenoid valves was $15^\circ$/sec, with the swing period of 1.4 sec and the angle fluctuation of $\pm$11.0$^{\circ}$. 3. When changing simultaneously the horizontal and vertical positions of the lifting load by on/off operations of solenoid valves, the swing and lifting speeds of crane arm were $4.46^\circ$/sec and $6.4^\circ$/sec, respectively. 4. The movements of the designed crane were particularly smooth as they are controlled with the aid of proportional valves than by means of solenoid valves.

• Journal of Biosystems Engineering
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• v.35 no.1
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• pp.31-36
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• 2010

A small unmanned helicopter was suggested to replace the conventional spray system. Aerial application using an agricultural helicopter helps precise and timely spraying, and reduces labor intensity and environmental pollution. In this research, a rotor system (SW05) was developed and its lift capability was evaluated. Lift force for the dead weight of the helicopter was obtained at the grip pitch angle of $12^{\circ}$. As the pitch angle increased to $14^{\circ}$ and $16^{\circ}$, the payload increased to 176 N and 216 N, respectively. Compared with SW04 airfoil performance in the total lift, the SW05 airfoil showed nearly the same capacity, but the payload of the SW05 was reduced because of the increased dead weight. A rated flight condition was defined as lifting mean payload of 294 N with the grip pitch angles of $16{\sim}17^{\circ}$ at the rotor rotating speed of 850~950 rpm for the adjusted engine power. The fuel consumption would be 4.8~6.0 L/hr, and the air temperature of cooling fan should be kept below $160^{\circ}C$.

• Journal of Ocean Engineering and Technology
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• v.22 no.4
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• pp.78-83
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• 2008

In recent years, small boats used for marine leisure have been steadily increasing because of the increase in national income and the desire for marine leisure. But the repair of such small boats in dry dock has pointed out many faults in small FRP-shipbuilding in terms if workspace and manpower. Lifting a boat from the water to land is done with a crane or by hand using a sling around the bottom of the boat. But dry dock work is limited by the scale of the boat, which corresponds to the crane capacity, with carelessness making it possible to capsize a boat and endanger life. The purpose of this study was the development of a marine docking system that would improve economical efficiency and safety, for which we carried out concept design, model tests, structural analysis, etc.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.4
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• pp.335-342
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• 2007

A propulsion and lift shafting system in an air cushion vehicle is flexible multi-elements system which consists of two aeroderivative gas turbines with own bevel gears, four stage lift fan reduction gear, two stage propulsion reduction gear air propellers and high capacity of lifting fans. In addition, the system includes the multi-branched shafting with multi-gas turbine engines and thin walled shaft with flexible coupling. Such a branched shafting system has very intricate vibrating characteristics and especially, the thin walled shaft with flexible couplings can lower the torsional natural frequencies of shafting system to the extent that causes a resonance in the range of operating revolution. In this study, to evaluate vibrational characteristics some analytical methods for the propulsion and lift shafting system are studied. The analysis, including natural frequencies and mode shapes, for five operation cases of the system is conducted using ANSYS code with a equivalent mass-elastic model.

• Biomaterials and Biomechanics in Bioengineering
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• v.4 no.1
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• pp.9-20
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• 2019

Living beings are formed of advanced biological and mechanical systems which exist for millions of years. It is known that various animals and insects right from small ants to huge whales have different weight carrying capacities, which is generally expressed as a ratio of their own bodyweights i.e., Strength to Bodyweight Ratio (SBR). The puzzle is that when a rhinoceros beetle (scientific name: Dynastinae) can carry 850 times its own bodyweight, why a man cannot accomplish the same feat. There are intrinsic biological and mechanical reasons related to their capacities, as per biomechanics. Yet, there are underlining principles of engineering and structural mechanics which tend to solve this puzzle. The paper attempts to give a plausible answer for this puzzle through structural mechanics and experimental modeling techniques. It is based on the fact that smaller an animal or creature, it has larger value of weight lifting by self-weight ratio. The simple example of steel prism model discussed in this paper, show that smaller the physical model size, larger is its SBR value. To normalize this, the basic length of the model need to be considered and when multiplied with SBR, a constant is arrived. Hence, the aim of the research presented is to derive this constant on a pan-living being spectrum through size/scaling effect.