• Journal of Hydrogen and New Energy
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• v.33 no.6
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• pp.684-691
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• 2022

Hydrogen fuel cell electric vehicles are typically refueled at a wide range of temperatures (-40℃ to 85℃) in the hydrogen refueling station in accordance with the worldwide accepted standard. Currently, there is no traceable method by which to verify and calibrate the hydrogen flowmeters to be used at hydrogen refueling stations except for a water calibration process as a conventional method. KRISS hydrogen field test standard based on the gravimetric principle was developed to verify the measurement accuracy of the mass flowmeter to be used at hydrogen refueling stations for the first time in Korea.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.4
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• pp.84-91
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• 2010

Owing to revolutionary developments in automobile technologies, a variety of advanced vehicles - hybrid vehicle, hydrogen fuel-cell vehicle, electric vehicle, etc. - emerges recently. The safety is getting more important for developing automobiles. The electro-magnetic compatibility has to be assured, since those advanced vehicles are equipped with various new electronic systems. Electro-magnetic compatibility tests, in general, consist of an EMI(electro-magnetic interference) test and an EMS (electro-magnetic susceptibility) test. We investigated the susceptibility test method suggested in KMVSS (Korean Motor Vehicle Safety Standard) as the EMS test method. A series of experiments results that the above test method should be partially revised to comply with a Korean governmental standard method. In this paper, the some directions of modifications are presented to enhance the quality of the above EMS test method.

• Corrosion Science and Technology
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• v.2 no.6
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• pp.266-271
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• 2003

Safety diagnosis of various structural components and facilities is indispensable for preventing catastrophic failure of material by time-dependent and environment accelerating degradation. Also, this diagnosis of operating components should be done periodically for safe maintenance and economical repair. However, conventional standard methods for mechanical properties have the problems of bulky specimen, destructive procedure and complex procedure of specimen sampling. So, a non-destructive and simple mechanical testing method using small specimen is needed. Therefore, an advanced indentation technique was developed as a potential method for non-destructive testing of in-field structures. This technique measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation such as yield strength, tensile strength and work-hardening index. In this paper, we characterized the tensile properties including yield and tensile strengths of the V-modified Cr-Mo steels in petro-chemical and thermo-electrical plants. And also, the effects of hydrogen-assisted degradation of the V-modified Cr-Mo steels were analyzed in terms of work-hardening index and yield ratio.

• Corrosion Science and Technology
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• v.20 no.4
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• pp.175-182
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• 2021

Magnesium alloy is limited in the industrial field because its standard electrode potential is -2.363 V vs. NHE (Normal Hydrogen Electrode) at 25 ℃. This high electrochemical activity causes magnesium to quickly corrode with oxygen in air; chemical conversion coating prevents corrosion but causes surface defects like cracks and pores. We have examined the anti-corrosion effect of sol-gel coating sealed on the defected conversion coating layer. Sol-gel coatings produced higher voltage current and smaller pore than the chemical conversion coating layer. The conversion coating on magnesium alloy AZ31 was prepared using phosphate-permanganate solution. The sol-gel coating was designed using trimethoxymethylsilane (MTMS) and (3-Glycidyloxypropyl) trimethoxysilane (GPTMS) as precursors, and aluminum acetylacetonate as a ring-opening agent. The thermal shock resistance was tested by exposing specimens at 140 ℃ in a convection oven; the results showed changes in the magnesium alloy AZ31 surface, such as oxidization and cracking. Scanning electron microscope (FE-SEM) analysis confirmed a sealed sol-gel coating layer on magnesium alloy AZ31. Electrochemical impedance spectroscopy (EIS) measured the differences in corrosion protection properties by sol-gel and conversion coatings in 0.35 wt% NaCl solution, and the potentiodynamic polarization test and confirmed conversion coating with the sol-gel coating show significantly improved resistance by crack sealing.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.1
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• pp.1-8
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• 2002

The high frequency ultrasonic transducers using polyvinyliden fluoride(PVDF) and polyvinylidene fluoride trifluorethyylene(P(VDF-TrFE)) were developed. The characteristics of fabricated high frequency ultrasonic transducer such as beam diameter, high frequency ultrasonic detection field and amplitude of the first pulse echo signal from the test target in the water were analyzed. The high frequency ultrasonic detection field was affected by the length of coaxial cable between high frequency transducer and ultrasonic pulser/receiver. As the size of the test target increased, the high frequency detection field decreased and the amplitude of a reflection signal increased. The peak amplitude of the first pulse echo signal of P(VDF-TrFE) transducer was higher than that of PVDF transducer. The high frequency ultrasonic detection field of PVDF transducer was wider than that of P(VDF-TrFE) transducer. With C-scan testing, the developed high frequency ultrasonic transducer could detect the 30 to $100{\mu}m$ of hydrogen induced crack of steel specimen by C-scan testing.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.121-131
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• 2006

This study is performed to examine the ground reinforcement effect and the environmental impact of LW injection, which is widely used during the excavation of high-rise apartment buildings. In addition, it proved that by conducting field exploration and laboratory test the engineering ground reinforcement effect of LW injection in the ground has low coefficient of permeability. The environmentally friendly aspect was evaluated through an assessment of environmental impact. The results of laboratory test shows that LW coagulating material with SC type soil structure has significant improvement of uniaxial compressive strength, increasing by three times and the shear strength increasing by twice, coefficient of permeability decreasing six to seven times. And the result of environmental impact tests show that from 6 hour after where the pH increases until 7.96 to initially it diminished, it started and to 80 hour after it recovered a pH 7.25 initially with 7.30. The chemical composition analysis test result that unpolluted water and polluted water hydrogen ion concentration (pH) show that the unpolluted water pH 7.36, polluted water pH 7.85, which is inside the Ministry of Environment standard of drinking water (the pH 5.8~8.5). The assessment of environmental impact and chemical analysis test also demonstrate that the LW coagulating material is environmentally friendly. In the $Cr^{6+}$ and the salinity detection test, it was proven that the salinity is slight and the $Cr^{6+}$ is not detected.

• Korean Journal of Soil Science and Fertilizer
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• v.1 no.1
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• pp.117-123
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• 1968

A simplest and best method to find out lime requirement for Korean soils is described. Twenty six top soil samples were collected from various localities and chemical characteristics were dertermined. Three different buffer curve methods were employed as the standard to find out the most reliable test for lime requirement. In addition, the lime requirement test by the Shoemaker's and Woodruff's as well as the O.R.D. kit method were compared with the most reliable buffer curve method. The results may be summarized as follows. 1. The regression equation of the most reliable lime requirement by buffer curve method, y, on percent base saturation of various soils, X, was y=9.69-0.106 X and the negative correlation coefficient r=-0.84 was statistically significant at 5% level. 2. Lime requirement test by the best, buffer curve, method was more well correlated with the sum of exchangeable hydrogen and exchangeable aluminum contents of the soil samples than the exchangeable hydrogen content only. 3. The ordinary buffer curve method for lime requirement is more reasonable than the lime requirement test by the buffer curve prepared after addition of 1 normal potassium chloride or calcium chloride solutions. 4. The lime requirement tests by the most reasonable buffer curve method, X, and by the Woodruff's, the Shoemaker's and O.R.D. kit were compared. The best method for laboratory lime requirement test was the Shoemaker's method and the O.R.D. kit method also was good enough for the field test and these two method are recommended as the unified method of lime requirement test in each soil testing laboratories throughout Korea.