• Transactions of the Korean hydrogen and new energy society
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• v.23 no.4
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• pp.293-299
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• 2012

The serpentine flow channel is widely used in polymer electrolyte membrane fuel cells (PEMFCs) to prevent flooding phenomena because it effectively removes liquid water in the flow channel. The pressure drop between inlet and outlet increases as compared with straight channels due to minor losses associated with the corners of the turning configurations. This results in a strong pressure gradient between adjacent channels in specific regions, where some amount of reactant gas can be delivered to catalyst layers by convection through a gas diffusion layer (GDL). The enhancement of the convective flow in the GDL, so-called bypass flow, affects fuel cell performance since the bypass flow influences the reactant transport and thus its concentration over the active area. In the present paper, for the bipolar plate design, a simple analytic model has been proposed to predict the bypass flow in the serpentine type flow channels and validated with three-dimensional numerical simulation results.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.1
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• pp.41-55
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• 2018

General polymer electrolyte fuel cell (PEMFC) operates at less than $80^{\circ}C$. Therefore liquid phase water resulting from electrochemical reaction accumulates and floods the cell which in turn increases the mass transfer loss. To prevent the flooding, it is common to employ serpentine flow channel, which can efficiently export liquid phase water to the outlet. The major drawback of utilizing serpentine flow channel is the large pressure drop that happens between the inlet and outlet. On the other hand, in the high temperature polymer electrolyte fuel cell (HT-PEMFC), since the operating temperature is 130 to $180^{\circ}C$, the generated water is in the state of gas, so the flooding phenomenon is not taken into consideration. In HT-PEMFCs parallel flow channel with lower pressure drop between the inlet and outlet is employed therefore, in order to circulate hydrogen and air in the cell less pumping power is required. In this study we analyzed HT-PEMFC's different flow channels by parallel computation using previously developed 3-D isothermal model. All the flow channels had an active area of $25cm^2$. Also, we numerically compared the performance of HT-PEMFC parallel flow channel with different manifold area and Rib interval against the original serpentine flow channel. Results of the analysis are shown in the form of three-dimensional contour polarization curves, flow characteristics in the channel, current density distribution in the Membrane, overpotential distribution in the catalyst layer, and hydrogen and oxygen concentration distribution. As a result, the performance of a real area fuel cell was predicted.

• Korean Journal of Environment and Ecology
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• v.12 no.1
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• pp.22-29
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• 1998

This study is investigated for the trace element concentration in the soils derived from different parent rocks, which are serpentinites, metamorphic rocks and black shales, and the absorption of the trace element by Pinus rigida in Hongseong and Keumsan, Chungnam, respectively. The concentrations of nickel, chrominium and cobalt are high in the serpentinites, whereas the concentrations of zinc, molybdenium and iron are high in the metamorphic rocks. These elements in black shale are lower than those in serpentinites and metamorphic rocks. The serpentine soils show high nickel, chrominium and cobalt content, while zinc and iron content are high in the mixed soils(serpentinites + metamorphic rocks) and black shales. Comparing with parent rocks, all of trace elements in their weathered soils are low. The pH of serpentine soil is high, 7.73~9.55 and that of black shale soil in 5.61. In serpentine area, the absorptions of chrominium by P. rigida is lower than its in the soils. The absorption of zinc by P. rigida is high relative to zinc concentration in soils. The Co/Ni and Fe/Ni quotient in P. rigida over serpentine soils are considerably lower than those growing over other soils tpes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.8
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• pp.689-698
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• 2021

The development of modern warfare detection technology is increasingly threatening the survivability of aircraft. Among them, IR-seeking missiles greatly affect the survivability of aircraft and are a main factor that reduces the success rate of aircraft missions. In order to increase aircraft survivability, studies on shape-modifying nozzles with added curvature are being actively conducted. In this study, we selected a double serpentine nozzle among shape-modifying nozzles to increase aircraft survivability. We then investigated the effects of the location of the maximum area change rate of the nozzle. It was confirmed that the location of the change rate of area affects the thrust and exit temperature of the nozzle. In addition, it was shown that the thrust penalty was reduced as the position of the change rate of the maximum area was located at the rear of the nozzle.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.181-182
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• 2008

In this paper, we present the design of an electromagnetic scanning mirror with rotated serpentine springs. We considered three types of torsional springs: simple beam springs (SBS), classic serpentine springs (CSS), and rotated serpentine springs (RSS). The analysis was done for an electrical resistance, differences in the mode-frequency, and resonances regarding to spring thickness. Electromagnetic coils under the mirror plate were also analyzed for power consumption and the mechanical deflection. From the analysis result, RSS and electromagnetic coils were designed for the silicon scanning mirror.

• Economic and Environmental Geology
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• v.26 no.1
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• pp.1-10
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• 1993

The Andong serpentinite body is distributed along the Andong fault, and shows an elliptical shape. The serpentinite is composed of serpentine minerals and other various minerals such as forsterite, pyroxene, talc, tremolite, chlorite, prehnite, calcite and dolomite. The serpentine minerals consist primarily of lizardite with minor chrysotile. Antigorite rarely occurs in some veins. The serpentinite is largely divided into two alteration zones by the occurrence and mineral assemblages. One of the alteration zones is composed of a large amount of serpentine minerals. The other is characterized by tremolite and chlorite. The alteration zone composed of tremolite and chlorite seems to have been formed by hydrothermal alteration after the formation of serpentinite. It is considered that the serpentinite have been formed by alteration of the ultramafic rock such as peridotite.

• Applied Chemistry for Engineering
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• v.19 no.5
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• pp.526-532
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• 2008

The proposed $CO_2$ storage technology in the present study is a one-step sequestration process that stabilizes $CO_2$ in a reactor with Serpentine. The advantage of this technology is associated with its high stability of final product so that the entire system is recognized as permanent environment-friendly $CO_2$ removal method. Since the sequestration reaction mechanisms are generally understood that carbonation reaction proceeds with very slow rate, so that pretreatment method to increases reaction rate of $CO_2$ carbonation reaction should be developed. To increase the reactivity of Serpentine with $CO_2$, two different methods of pretreatment are carried out in the present investigation. One is heat-treatment, the other is chemical pretreatment. In this study, only chemical pretreatment is considered leaching method of magnesium from Serpentine using sulfuric acid at the various reaction temperatures, times, and acid concentrations. Experimental results illustrated that pretreatment by sulfuric acid increases surface area of serpentine from $11.1209m^2/g$ to $98.7903m^2/g$ and extracts magnesium compounds. Single variable experiment demonstrated the enhancements of magnesium extraction with increased reaction temperature and time. Amount of magnesium extraction is obtained by using the data of ICP-AES as maximum extraction condition of magnesium is 2 M acid solution, $75^{\circ}C$ and 1hr. After performing chemical pretreatment, carbonation yield increased from 23.24% to 46.30% of weight.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.485-497
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• 2019

The Jade Investiture Books in Joseon Dynasty shows diverse facies with various petrographic characteristics to green and white based on color. In lithologically, the green rocks are jade composed of calcite and serpentine, and the white ones are marbles consisting mainly in crystalline calcite. As a result of X-ray diffraction of jade rocks, the more green in color, the more increased intensity of serpentine appears. Therefore, the grade of jade is correlated with contents of serpentine. The Jade Investiture Books owned by the National Palace Museum of Korea are subdivided with 104 (41.3%) books made by only jade rocks, 98 (38.9%) books made by only marbles, and 50 (19.8%) books mixed with jade rocks and marbles. Among the mixed ones, 47 (18.6%) books consisted mainly of the marbles. This result shows the superior marble books occupy more than half of the total books. The Jade Investiture Books made in early Joseon Dynasty are composed of high grade jade. However, the grade of jade had decreased as the kings changed in process of time, and the composition of marble had increased in reverse proportion of jade. The quality of letter pigments, metal accessories and fabrics also had decreased with jade. These trends are reflected in the aspect of society such as weakening royal authority, national power and finance with the course of time. The jade of the books has different mineralogical characteristics from some modern jade produced in Chuncheon nephrite and Buyeo precious serpentine in Korea. Meanwhile, there is ancient literature that described quarries from Namyang in Hwaseong of Gyeonggi province. This area has a wide distribution of gneiss, limestone and limesilicate rocks are interbedded between muscovite schist. The limesilicate rocks contain diopside, which produced serpentine through alteration. It has possibility to make the Jade Investiture Books using these small amounts of jade through mining activity.

• Journal of the Korean Professional Engineers Association
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• v.34 no.1
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• pp.59-65
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• 2001

Imported China Jades are mostly talc and serpentine groups, and that's occured troubles for our health and life of living organism. Serpentine is a group of common rock-forming minerals having the formula:(Mg$.$Fe)$^3$Si$_2$O$\_$5/(OH)$_4$. Sometime, simulated by nephrite or jade and translucent varieties we used for ornamental and decorative purposes. But it's forbid by heating materials for sauna and heating mats etc. that reason are it's occured asbestos dusts(chrysotile dusts) easily by the beating operations.

• Journal of the Korean Professional Engineers Association
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• v.34 no.1
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• pp.66-73
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• 2001

Imported China Jades are mostly talc and serpentine groups, and that's occured troubles for our health and life of living organism. Serpentine is a group of common rock-forming minerals having the formula : (Mg$.$Fe)$_3$Si$_2$O$\_$5/(OH)$_4$. Sometime, simulated by nephrite or jade and translucent varieties are used for ornamental and decorative purposes. But it's forbid by beating materials for sauna and heating mats etc. that reason are it's occured asbestos dusts (chrysotile dusts) easily by the heating operations.