• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.135-148
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• 2001

In this study, an assessment method was proposed to evaluate the pullout resistance between geosynthetic and backill soil by using a stress-strain relationship of the orthotropic composite material subjected to both longitudinal and vertical loadings. For this analysis friction characteristics of geosynthetic-soil and stress-strain relationships subjected to soil confined pressure were investigated by performing the laboratory pullout tests for three types of geosynthetics and performing the confined extension tests far seven types of geosynthetics having geotextiles, composite geosynthetics and geogrids. A comparison was made between unconfined an confined moduli far each geosynthetic material to quantify the soil confinement effect on stress-strain properties. A comparison was also made between the relative increase of moduli at the same strain level among the seven geosynthetic materials to demonstrate the different responses of these geosynthetic materials under soil confinement. Based on the proposed procedure, it was shown that values of the increased tensile force are applicable fur the evaluation of friction strengths between five types of geosynthetics and sands in light of the soil confinement effect.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1857-1863
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• 2010

We present the fabrication and characterization of transparent carbon nanotube film (CNF) piezoresistors. CNFs were fabricated by vacuum filtration methods with 65?92% transmittance and patterned on Au-deposited silicon wafer by photolithography and dry etching. The patterned CNFs were transferred onto poly-dimethysiloxane (PDMS) using the weak adhesion property between the silicon wafer and the Au layer. The transferred CNFs were confirmed to be piezoresistors using the equation of concentrated-force-derived resistance change. The gauge factor of the CNFs was measured to range from 10 to 20 as the resistance of the CNFs increased with applied pressure. In polymer microelectromechanical systems, CNF piezoresistors are the promising materials because of their high sensitivity and low-temperature process.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.5
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• pp.365-372
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• 2017

Finger electrodes on a crystalline silicon solar cell are required to be constructed as narrow and thick as possible in order to minimize shading losses and electrical resistance. The most common means to construct high-aspect ratio finger electrodes has been screen-printing, but it has difficulty achieving fine finger electrodes because the as-printed finger width is generally wider by 1.3-2.2 times the screen opening width. Consequently, it requires an extremely small screen opening (below $30{\mu}m$) in order to achieve a finger width below $40{\mu}m$. However, the use of such a small screen opening could result in various problems, such as high printing pressure, defective transport of silver paste, and high electrical resistance due to unfavorable mesh marks left on the finger electrodes. In this study, dispensing printing with a screw pump is introduced as an alternative to conventional screen-printing and its unique traits in the front side metallization of crystalline silicon solar cells is discussed.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.11
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• pp.2067-2076
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• 2000

The experiments have been made to develop manganese-based sorbent(MT, MFT) for the removal of hydrogen sulfide from simulated hot coal gases. Manganese-based sorbents were tested in an ambient-pressure fixed-bed reactor to calculate H2S removal efficiency. and a three hole jet attrition tester to characterize the sorbent physical properties. According to the experimental results of attrition test. the attrition resistance of 5% bentonite containing sorbent was higher than that of 2% bentonite. The attrition resistances of both sorbents increased with induration temperature. Effects of sulfidation temperature. space velocity. and $H_2S$ concentrations on the $H_2S$ removal efficiency were investigated. Experimental results showed that $H_2S$ could be removed from 5,100ppmv to 20ppmv at $450^{\circ}C$, and to 30~65ppmv at $550{\sim}650^{\circ}C$ for both MT/MFT sorbents. As for the change of space velocity, the breakthrough time was decreased with space velocity.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.2
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• pp.87-93
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• 2004

Nitrocarburizing was carried out with various $CH_4$ gas composition with 4 torr gas pressure at $570^{\circ}C$ for 3 hours and post oxidation was carried out with 100% $O_2$ gas atmosphere with 4 torr at different temperatures for various time. In the case of plasma nitrocarburizing, It is that the ratio of ${\varepsilon}-Fe_{2-3}$(N, C) and ${\gamma}^{\prime}-Fe_4$(C, N), which comprise the compound layer phase, depend on concentrations of $N_2$ gas and $CH_4$ such that when the concentration of $N_2$ and $CH_4$ increased, the ratio of ${\gamma}^{\prime}-Fe_4$(C, N) decreased, but the ratio of ${\varepsilon}-Fe_{2-3}$(N, C) increased. The thickness of compound layer consistently increased as gas concentration increased regardless of $N_2$ and $CH_4$ expect when the concentration of $CH_4$ was 3.5 volume%, it decreased insignificantly. When oxidizing for 15min in the temperature range of $460{\sim}570{^\circ}C$, the study found small amount of $Fe_3O_4$ at the temperature of $460{^\circ}C$ and also found that amounts of $Fe_2O_3$. and $Fe_3O_4$ on the surface and amount of ${\gamma}^{\prime}-Fe_4$(C, N) in the compound layer increased as the increased over $460^{\circ}C$, but the thickness of the compound layer decreased. Corrosion resistance was influenced by oxidation times and temperature.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.6
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• pp.2093-2098
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• 2010

Insulin resistance plays a central role in fatty liver, a part of the metabolic syndrome. This study examined the relationship between fatty liver, metabolic abnormalities and mitochondrial DNA [mtDNA] copy number in peripheral blood that is correlated with diabetes or metabolic markers. Fatty liver was assessed by questionnaire on alcohol consumption and abdominal ultrasonography. MtDNA copy number in peripheral leukocytes was measured by a real-time quantitative polymerase chain reaction [PCR]. Among 445 subjects, 148 subjects had hepatic steatosis and 297 were controls. mtDNA copy number was significantly lower in fatty liver group in comparison with that of normal finding group. This result is similar in both groups, alcoholic or non-alcoholic fatty liver group. MtDNA copy number was inversely correlated with alanine aminotransferase [ALT], aspartate aminotransferase [AST], gamma-glutamyltransferase [$\gamma$-GTP], body mass index [BMI], waist circumference, diastolic blood pressure, and free fatty acid. MtDNA copy number in peripheral leukocytes was associated with fatty liver and insulin resistance related factors.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.600-602
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• 2006

Some abnormal signals diagnostics and analysis through an important equivalent circuits modeling for passive elements under severe accident conditions have been performed. Unlike the design basis accidents, there are inherently some uncertainties in the instrumentation capabilities under the accident conditions. So, the circuit simulation analysis and diagnosis methods are used to assess instruments in detail when they give apparently abnormal readings as an accident alternative method. The simulations can be useful to investigate what the signal and circuit characteristics would be when similar to a variety of symptoms that can result from the environmental conditions such as high temperature, humidity, and pressure condition. In this paper, a new simulator through an analysis of the important equivalent circuits modeling under temperature accident conditions has been designed, the designed simulator is composed of the LabVIEW code as a main tool and the out-put file of the Multi-SIM code as an engine tool is exported to in-put file of the LabVIEW code. The procedure for the simulator design was divided into two design steps, of which the first step was the diagnosis method, the second step was the circuit simulator for the signal processing tool. It has three main functions which are a signal processing tool, an accident management tool, and an additional guide from the initial screen. This simulator should be possible that it could be applied a output signal analysis to some transient signal by variation of the resistance passive elements in the R-L-C equivalent circuit modeling under various degraded conditions in NPPs.

• Elastomers and Composites
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• v.34 no.3
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• pp.229-238
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• 1999

In this study, double bond, unsaturated group was introduced to the main chain of EVA by chemically treating EVA, nondiene polymer. Benzene sulfonic acid, ENB and DCPD were used as a third element. Also, from blending CR and SBR, conventional synthetic rubber we prepared vulcanizates and examined their physical properties. The datum lead to the following conclusion that some problems were modified; limited temperature in use and mechanical properties like hardness, tensile strength, tensile stress, and elongation rate of thermoplastic EVA, keeping the following advantages of original EVA; green strength, injection molding by Pressure, adhesion, tackiness, dimensional stability, and ozone resistance, etc. It is expected that continuous research of the modification between nondiene and diene polymer will improve what were shown disadvantages in synthetic polymer; processing, oxidation resistance, and adhesion. In addition, it will be possible to continue process of rubber products by utilizing possible fluidity for fusion of EVA.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.3
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• pp.1-7
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• 1999

This paper describes the modification of hull bottom for the air lubrication technique to the passenger boat in service at the Chung-Ju lake, which has a large beam-draft ratio. From numerical analysis of 2-D cavity problem by potential theory, the cavity shape, length and the pressure in cavity are estimated for the simplified geometry of hull bottom, and the non-dimensional parameters affecting air cavity phenomena are investigated. Extensive resistance tests for the model ship which has variation of step height and side strip have been performed to investigate the formation of air cavity and the drag reduction effectiveness. And also, the development of attached cavity to the bottom were observed from the flat bottom made by transparent acrylic plate. From this survey on the modification of bottom shape and the air lubrication technique, the total resistance of model ship could be reduced by about 25% at the design speed compared to the proto type hull form.

• Geotechnical Engineering
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• v.3 no.2
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• pp.17-28
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• 1987

Reliability of the cone penetration test (CPT) for estimating shear strength of marine soils is investigated in this paper. For sands, the uncertainty about the angle of internal friction is analyzed. It includes the spatial variation of the soil and the model error in the equation used for interpretation. The most serious uncertainty encountered was the error in the interpretative models. Different methods of interpretation gave quite different values. Subjective opinion was introduced to combine all the interpretative models in a systematic manner. For clays, the undrained Shear Strength from the CPT results is usually =derived by empirical correlations between cone resistance and untrained shear strength from laboratory tests or field vane tests, expressed in terms of cone factor and function of overburden pressure. The uncertainty of the undrained shear strength is caused by data scatter of the cone factor in the correlation, model error of the cone factor, effect of anisotropy, and spatial variability of cone resistance. Among these uncertainties, the most serious one was the data scatter of the cone factor in the .correlation. Between the laboratory test and the field vane test used for correlation, the field vane test was more reliable.