• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.199-205
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• 1998

Butt fusions were practiced with butt fusion in the various conditions of fusion temperatures, pressure and time, and the tests of tesile strength, breaking water pressure and fusion features were also practiced so that the reliability of the butt fusion and the fittets fusion condition may be closely examined. And the width, height and thickness of the beads were also closely measured. The fittest fusion result was achieved in the condition of the temperature of $210^{\circ}C$, heating time hight pressure of 14 seconds on the pressure of $1.5kg/cm^2$, heating time hight pressure of 100 seconds and pressure buid-up time of 11 seconds. And in case of the temperature of $250^{\circ}C$, the fittest fusion result was showed in the condition of the heating time hight pressure of 3 seconds on the pressure of 1.0$kg/cm^2$, the heating time low pressure variable of 100 seconds. heating time hight pressure of 14 seconds and the heating maintenance of around 60 seconds. The result of breaking water pressure test of a test piece fusion in the fittest fusion condition was that the fusion condition of the PE pipe showed a good stability and hight reliance. Through this test, it is proved that the temperature of fusion PE pipes can be increased to $250^{\circ}C$ from $210^{\circ}C$. And it can be expected that the above fusion method greatly helps to reduce the fusion time.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.3
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• pp.331-338
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• 2008

Coal-tar enamel, blown asphalt and polyethylene have been used as wrapping materials of steel pipe in Korea. Currently, every manufacturer produces wrapped steel pipes with different materials and methods, and little research has been performed to get on wrapping methods and materials. In this research, properties of wrapping material of steel pipe used for water supply have been evaluated. All of the materials tested in this work were found to meet the standard. Among the wrapping materials of steel pipe tested, blown asphalt and coal-tar enamel were reasonable in price, and their mechanical properties were excellent. The quality of the wrapped steel pipes was being melted easily in organic solvent. When coated thick, the load of the steel pipes was higher than necessary. Tensile strength of cathode exfoliation and PE 3-layer wrapping method was excellent. The pulling intensity of T-Die PE 3-layer was stronger than PE fluidized in PE wrapping method. Cathode exfoliation area was smaller than PE fluidized. Mechanical property and thermo-property of T-Die PE 3-layer were excellent and its anti-chemical property was great. Liquid epoxy can change the property of coating materials depending on the hardening condition and resin selection. Polyurethane used in this test showed a less adhesive strength with steel pipes than epoxy. Moisture absorbance rate was higher than Epoxy's, however. To utilize polyurethane as wrapping materials, basic property of the matter should be improved followed by finding the best suited coating condition. The method of PE 3-layer by extrude method appeared to be the best in this study. However, identification of other wrapping materials requires further additional tests.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.524-536
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• 1994

Chitosan is known to be a good biocompatible natural polymer. Polyethyleneglycol monomethacrylates(PEGM) were grafted onto chitosan and their reaction conditions and properties of the graft polymers obtained were estimated. Using ceric ammonium nitrate(CAN) as the initiator, the optimum condition for graft polymerization was determined amount of the initiator and monomer concentrations and reaction time. Grafting yields such as total conversion, the percentage of grafting and the efficiency of grafting were calculated and examined the optimum reaction condition for high grafting yields. The percentage of grafting and total conversion were maximum at condition that the concentration of initiator was $4{\sim}5{\times}10^{-3}M$, the concentration of monomer was 0.5~0.6M, the reaction time was 2~3 hours and the reaction temperature was about $40^{\circ}C$. Thermal characteristics, solubility for chitosan solvents and inherent viscosity of synthesized graft copolymers were investigated. In high initiator concentration, characteristics of chitosan were greatly diminshed. In case of inherent viscosities, chitosan-g-PE-90 was 2.81 dl/g, chitosan-g-PE-200, 3.01dl/g and chitosan-g-PE-350, 4.93dl/g. And a tendency of viscosity increase depending on the length of ethylene oxide residue was confirmed. Degree of swelling, tensile strength, elongation of membrane prepared from graft copolymers were determined. Properties of graft copolymers were affected by percentage of grafting and length of ethylene oxides residue in polyethylene glycol monomethacrylates. Tensile strength, elongation and degree of swelling of graft copolymers were remarkably improved than chitosan. As percentage of grafting increased, the amount of drug permeation was also increased.

• Journal of Energy Engineering
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• v.17 no.4
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• pp.204-211
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• 2008

Polyethylene(PE) pipes have been widely used as they are easy to construct and suitable for economical efficient when they are compared with metal pipelines. This paper studied the effect of various external loadings on stress and deflection of the buried PE pipes using Finite Element Method(FEM). For this purpose, stresses of buried PE pipes were calculated according to the loading condition such as pipe types(pipe diameter $50{\sim}400mm$), burial depths($0.6{\sim}1.2m$) and internal pressures($0.4{\sim}4bar$). As a result, it was founded the effect and relation with each of loading conditions under the buried condition.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.6
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• pp.871-881
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• 2012

This study suggested a model that can predict a degradation condition over time of two plastic pipes, PE and PVC, which are currently used in the country. This study was analyzed physical characteristics change of plastic pipes by comparison with initial physical characteristics (on the case of new pipes). Since this is dependent on accidents that already occurred, there are limitations that it only decides a priority on improvement based on relative corrosion status rather than precautionary aspects. The comparison results between physical degradation by the deducted performance rating and a conventional numerical scoring method showed that correlation coefficient was 0.67 for PE pipes and 0.86 for PVC pipes, indicating a high correlation. According to this result, it has been decided that the performance rating suggested herein can be applied naturally to the criterion of an improvement decision, which was based on Scoring System. From results of the research, it is expected that a reliable result can be provided to an improvement decision process related to degradation of plastic pipes by comprehensively comparing and evaluating a condition of pipe materials(direct factors) and an environmental impact(indirect factors).

• Journal of the Korea Safety Management & Science
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• v.9 no.5
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• pp.157-165
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• 2007

Currently, there are two major problems in professional engineer(PE) licensure system in Korea to be accredited internationally. One is a incompleteness of system connecting the licensure and the accredited engineering education program and the other one is a insufficient working experience condition required for achieving PE license. Therefore, these two problems are setbacks hindering Korea's PE license accredited internationally. In this study, international tendency stream on mutual accreditation of PE license are reviewed first, and the PE licensure system of the major countries are compared and analyzed. Based on the results, requirements improvement plan are suggested and the gradual implementation method are suggested also.

• The Journal of the Acoustical Society of Korea
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• v.25 no.3E
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• pp.131-136
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• 2006

The PML developed for the radio wave propagation is a powerful numerical domain truncation technique. We perform an analytic study on the reflection from the PML inserted in the ocean bottom. In the ocean bottom, we show the PML to have the improved performance but simultaneously the degeneration below the critical angle of the fast ocean bottom. The degeneration of the PML can be simply relaxed by stretching the thickness of the PML or putting the attenuation coefficient to the ocean bottom. As a better solution, we propose the improved truncation technique based on the PML and the non-local boundary condition. Finally, we apply the PML to the acoustic wave propagation using split-step Pade PE solver. For the problems of the ocean waveguide, the numerical efficiency of the PML is examined and the usefulness of the PML is confirmed.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.532-535
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• 2000

Optical microscope, SEM and fluorescent microscope were used for qualitative and morphological studies of the attachment bacteria on PE substratum under anaerobic condition. The observation of optical microscopic has demonstrated that the initial attachment of bacteria began in crevices of surface. In SEM photographs, shape and structure of biofilm could be observed, but bacteria species and methanogens was not identified. A large number of methanogenic bacteria were showed on the surface of PE substratum by fluorescence under 480nm of radiation. It was estimated that methanogenic bacteria was related to initial attachment of bacteria under anaerobic condition.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.10
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• pp.740-747
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• 1988

This paper describes the parameter convergence property for an adaptive identifier and deals with the stability of the adaptive system in terms of the general error model. The Persistent Excitation (PE) condition to guarantee parameter convergence is derived using the Power Spectrum Analysis. In the adaptive identifier designed under the assumptions that the plant has not unmodelled dynamics, it can be shown that the equilibrium points of adjustable parameters are independent on the position or the number of input spectrums, if the adaptive signal is PE. When the plant contains unmodelled dynamics and the same controller is used, the PE condition can still hold but the parameter tuned values are changed with the spectrum.

• Resources Recycling
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• v.10 no.6
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• pp.35-42
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• 2001

A study was conducted in order to remove Poly vinyl chloride (PVC) from granular plastic mixture by using Air Table. The motion of plastic particle on Air Table was investigated, and separation test on the plastic mixture with the mixing ratio of PVC 10% and PE 90% was conducted. At the optimum condition obtained from this study, that is frequency of 9.2Hz, air velocity of 1.05 m/sec, End-slope of $7.5 ^{\circ}$, Side-slope of $1^{\circ}$, Feeding speed of 450 g/min, etc., we could separate the PE-PVC mixture to PE (99.96% grade and 98.9% yield) and PVC (88.7% grade and 99.6% yield).