• Korean Journal of Environmental Agriculture
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• v.16 no.1
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• pp.31-36
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• 1997

This study was carried out to analyze the composition of landfill generation gas using vertical pipe wells installed at landfill. The characteristics of composed waste were examined by the open-cut test at H. landfill in Pusan. The waste compositions of landfill layer by Open-cut test indicated that organic matter was average $4.6{\sim}8.78%$ in each landfill. $CH_4$ compositions of gas in each landfill were $49.71{\sim}50.45%$(A-point), $50.39{\sim}53.74%$(B-point), and $58.76{\sim}61.62%(C-point), respectively. The chemical formula of organic matter left in the underground was $C_{36.3}H_{76}O_{30}N_{0.3}S_{0.1}$ Underground temperatures were changed to $18.8{\sim}25.8^{\circ}C$ when the ambient temperature was about $13.4^{\circ}C$. Temperatures with passed times in A, B and C-lysimeter were about $21.1{\sim}22.5^{\circ}C,\;30{\sim}32.5^{\circ}C$ and $35{\sim}38.5^{\circ}C$, respectively. After about 65 day, decomposition rates of organic matter in A, B and C-lysimeter were 9.9%, 14.9% and 22.3%, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.78-85
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• 2020

The scaffolding system, which is a construction workbench of the cargo containment for a membrane LNG carrier, is a large truss structure composed of various members. To shorten the installation period and process of the scaffolding system, it is effective to enlarge the mounting unit from the existing two stages to eight stages. Owing to the increase in lifting load according to the large size of the module, the stresses around the pin and hole will be increased significantly. In this study, a tensile strength test and contact stress analysis were performed to confirm the structural safety. The relatively large hole deformation was observed visually near the average load generated in the vertical pipe at the top through tensile strength tests. A contact stress calculation confirmed the stress distribution around the hole. The contact problem was dealt with in terms of the Herzian contact stress. The possibility of 8-stage loading was examined by comparing the yield strength and contact stresses of failure critical locations. As a result, the 8-stage loading method of the existing scaffolding material was inadequate, and a new loading method with proper safety is proposed.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.303-312
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• 2006

The main objective of this experimental study is to examine the feasibilities of each testing method with various kinds of grip systems for the analysis of tensile strength of GFRP(glass fiber reinforced polymer) reinforcing bars. Three types of grip systems were examined such as resin-sleeved pipe-type grip proposed by CSA(Canadian Standard Association), frictional resistance type metal grip by ASTM(American Standard for Testing and Materials) and wedge-inserted cone-type grip normally used in prestressing tendons. Also, mechanical properties of GFRP rebars with different surface deformations were investigated for each different type of testing grip used in this study. All testing procedures including specimens preparation, set-up of test equipments and measuring devices were made according to the CSA S806-02 recommendations. From the test results, it was found that the highest tensile strengths of GFRP rebars were observed when tested by resin-sleeved grip system regardless of their different surface deformations. But tensile strengths of GFRP rebars by ASTM grip system are only 10% less than those by CSA grip system. On the other hand, CSA grip is not only difficult to prepare but also not disposable. Therefore, ASTM grip system is recommended as a practical alternative to estimate the tensile strength of GFRP rebars.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.509-516
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• 2012

The aims of this research is to develop a fire resistant admixture to enhance high-pressured pumping of high-strength concrete (HSC) with a compressive strength of 60~80 MPa. Generally, the efficiency of HSC high-pressured pumping is dramatically reduced due to entanglement of short fibers added to prevent fire spalling. Therefore, the fire resistant admixture that can facilitate pumping of fire resistant HSC is urgently needed presently. The fire resistant HSC mix is comprised of Polypropylene fiber, Nylon fiber and Polymer powder. The test results showed that the slump-flow was improved by approximately 70% of the HSC without fire resistant admixture. However, the air void content was increased slightly due to the addition. The standard design compressive strength at 28-days was satisfied, while its flexural strength was similar to the concrete without the admixture. Since the flexural strength was 12~15% of its compressive strength, the general trend of flexural to compressive strength ratio in normal concrete was maintained. Even though its elastic modulus was decreased by adding the admixture, the study results showed that the concrete can be used for construction since all of the test results exceeded the code requirements.

• Journal of the Korean Institute of Gas
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• v.5 no.3 s.15
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• pp.45-50
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• 2001

Open rack vaporizer (ORV) has been used in liquefied natural gas (LNG) receiving terminal in order to vaporize LNG into natural gas (NG) by heat exchange with seawater The U-type ORV which had been operated with seawater for 14 years is one of the important utilities of the gas production and the weld part of tube connected with header_ pipe had experienced many corrosion problems. To elucidate the cause of corrosion at weld part of vaporizer tube, corrosion potentials were compared by parts. This study concerns on the measurement of corrosion pit depth using non-destructive method and the evaluation of stress distribution in an aspect of safety with finite element analysis. In order to confirm the reliability of galvanic corrosion between weld parts and base metal, the measurement of corrosion potential by parts was conducted for 20 minutes in 3.5$\%$(wt.) NaCl solution. Many non-destructive methods were tried to measure the remaining thickness of vaporizer tube at fields. For general corrosion, tangential radiography test was confirmed as an effective method. In case of a fine corrosion pit, the shape of corrosion pit was reproduced using surface replication method. From collected data, stress distributions were quantitatively evaluated with 2-dimensional finite element method and the diagnostic evaluation on internal pressure of the U-type vaporizer could be made.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2008.03a
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• pp.79-88
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• 2008

Since the hydraulic fracturing field testing method was introduced first to Korean geotechnical engineers in 1994, there have been lots of progresses in a hardware system as well as an interpretation tool. The hydrofracturing system of first generation was the pipe-line type, so it was not easy to handle. It had been modified to a wire-line system at their second generation. It was more compact one but it also needed an additional air-compressor. Our current system is much more compact and operated by all-in-one system, so it doesn't need an additional air-compressor. With a progress in a hardware system, the software for analyzing the in-situ stress regime has also been progressed. For example, the shut-in pressure, which is the most ambiguous parameter to be obtained from hydrofracturing pressure curves, can now be acquired automatically from the various methods. While the hardware and software for hydrofracturing tests are being developed during the last decade, the author could accumulate the field test results which can cover the almost whole area of South Korea. Currently these field data are used widely in a feasibility study or a preliminary design step for tunnel construction in Korea. Regarding the difficulties in a site selection and a test performance for the in-situ stress measurement at an off-shore area, the in-situ stress regime obtained from the field experiences in the land area can be used indirectly for the design of a sub-sea tunnel. From the hydrofracturing stress measurements, the trend of magnitude and direction of in-situ stress field was shown identically with the geological information in Korea.

• Journal of Korean Society of Disaster and Security
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• v.10 no.1
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• pp.1-10
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• 2017

Recently, increasing cases of ground subsidence in the urban area has become social issue, and related bill has been passed. Ground subsidence occurs through complex combination of various factors, and numerical analysis of this problem is limited thereby. This is why verification of ground subsidence mechanism has been conducted through physical modelling. Previous researches has been focused on modelling ground subsidence caused by utility pipe defects, and there has been insufficient physical modelling study on ground subsidence caused by various reasons such as groundwater flow and excavation activity. Also, most previous physical modelling studies were performed in 1g condition, which cannot take the in-situ stress condition into the evaluation of the ground subsidence mechanism. Therefore, in this study, physical modelling techniques to simulate various conditions is discussed by studying the previous researches on the ground subsidence mechanism through physical modelling. Also, centrifuge modelling test is suggested in this study as the technique to perform more reliable evaluation of ground subsidence mechanism. Lastly, this study suggests to apply the techniques used in the evaluation of ground subsidence mechanism into Ground Stability Assessment.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.2
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• pp.96-103
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• 2009

The biodegradability in water of the artificial baits for blue crab pots which were made of intestines of mackerel, tuna and grinded krill were studied. The biodegradability of artificial bait was evaluated with the effective capacity of 10L water tank which was made of acryl pipe at the velocity of 1m/d and hydraulic retention time of 12 hours. For the 23 days operation time, all artificial baits were degraded fast at the early stage of operation time and stabilized within 5 days after start up. The rates of biodegradation were different depending on the raw materials of artificial baits. In terms of degradation rate of organic matter which can be expressed as COD, artificial bait made of tunas intestine showed the fastest degradation rate. On the other hand, in terms of degradation rate of nitrogenous matter which can be expressed as ammonia nitrogen, artificial bait made of mackerels intestine showed the fastest degradation rate. In order to evaluate the effect of artificial bait on marine ecosystem, seawater qualities including SS, COD, DO, nitrogen, phosphorus were determined depending on depth and location during 2 days test operation period. It is apparent that the effect of artificial bait on seawater quality was negligible when comparing seawater quality of test operation area with control area.

• Fire Science and Engineering
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• v.29 no.2
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• pp.84-91
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• 2015

The purpose of this study is to suggest the reasonable model of the caliber in suction nozzle, the pressure of suction nozzle, and the flow rate about foam system of line proportioner type using in the pumpcar. To test this, the experimental study was accomplished on the ground of the standards for the Performance Certification and Product Inspection of Foam Fire-extinguishing Chemical Mixing Machine. Aqueous Film Forming Foam in 3% and pipe type air foam nozzle with line proportioner FE 40 type were used. Test result showed that the pressure of suction nozzle within the limits between 0.25 MPa and 0.35 MPa was appropriate when the caliber in suction nozzle is 4 mm. Also, the pressure of suction nozzle within the limits between 0.45 MPa and 0.60 MPa was appropriate in the higher pressure than 4 mm when the caliber in suction nozzle is 5 mm.

• Journal of Biosystems Engineering
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• v.25 no.3
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• pp.221-226
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• 2000

Hot air heater with light oil burner is the most common heater for greenhouse heating in the winter season in Korea. However, since the thermal efficiency of the heater is about 80∼85%, considerable unused heat amount in the form of exhaust gas heat discharges to atmosphere. In order to capture this exhaust heat a heat recovery system for plant bed heating in the greenhouse was built and tested in the hot air heating system of greenhouse. The heat recovery system is made for plant bed or soil heating in the greenhouse. The system consisted of a heat exchanger made of copper pipes, ${\Phi}12.7{\times}0.7t$ located in the rectangular column of $330{\times}330{\times}900mm$, a water circulation pump, circulation plastic pipe and a water tank. The total heat exchanger area is 1.5$m^2$, calculated considering the heat exchange amount between flue gas and water circulated in the copper pipes. The system was attached to the exhaust gas path. The heat recovery system was designed as to even recapture the latent heat of flue gas when exposing to low temperature water in the heat exchanger. According to the performance test it could recover 45,200 to 51,000kJ/hr depending on the water circulation rates of 330 to $690\ell$/hr from the waste heat discharged. The exhaust gas temperature left the heat exchanger dropped to $100^{\circ}C$ from $270^{\circ}C$ by the heat exchange between the water and the flue gas, while water gained the difference and temperature increased to $38^{\circ}C$ from $21^{\circ}C$ at the water flow rate of $690\ell$/hr. By the feasibility test conducted in the greenhouse, the system did not encounter any difficulty in operations. And, the system could recover 220,235kJ of exhaust gas heat in a day, which is equivalent of 34% of the fuel consumption by the water boiler for plant bed heating of 0.2ha in the greenhouse.