• Journal of Power System Engineering
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• v.13 no.3
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• pp.11-19
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• 2009

This paper introduces a conceptual design of a combined scroll expander-compressor unit for a fuel cell. Since air discharged out of the fuel cell stack has still high pressure energy, some power can be extracted from the air by directing it to pass through an expanding device. Such extracted power can be used to drive an auxiliary compressor. For this purpose, a scroll type expander coupled to a scroll type compressor was designed for a 1kW-class fuel cell. The orbiting scroll members of the expander and the compressor were made to share three of common drive shafts installed in the mid frame plate. Performance analysis for the combined expander-compressor unit showed that the installation of this unit could reduce the auxiliary power consumption in the fuel cell by about 42%.

• The Plant Pathology Journal
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• v.15 no.1
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• pp.8-13
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• 1999

Hypersensitive cell death of plants during incompatible plant-pathogen interactions is one of the efficient defense mechanisms of plants against pathogen infections. For better understanding of the molecular mechanisms involved in the plant hypersensitive response (HR), TMV-induced biotic plant cell death and CuSO4-induced abiotic plant cell death were compared in terms of expression patterns of ten different defense-related genes as molecular markers. The genes include five pathogenesis-related protein genes, two plant secondary metabolite-associated genes, two oxidative stress-related genes and one wound-inducible gene isolated from tobacco. Northern blot analyses revealed that a same set of defense-related genes was induced during both biotic and abiotic cell death but with different time and magnitude. The expression of defense-related genes in tobacco plants was temporarily coincided with the time of cell death. However, when suspension cell cultures was used to monitor the expression of defense-related genes, different patterns of the gene expression were detected. This result implies that three are common and, in addition, also different branches of signaling pathways leading to the induced expression of defense-related genes in tobacco during the pathogen- and heavy metal-induced cell death.

• Proceedings of the Microbiological Society of Korea Conference
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• 1998.04a
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• pp.49.1-49.1
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• 1998

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.227-235
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• 2000

Agricultural products are easily deformable its shape because of some external forces. However, these force behavior is difficult to measure quantitatively. Until now, many researches on the mechanical property was performed with various methods such as material testing, chemical analysis and non-destructive methods. In order to investigate force behavior on the cellular unit of agricultural products, electro-microscope based 3D image processing method will contribute to analysis of plant cells behavior. Before image measurement of plant cells, plant sample was cut off cross-sectioned area in a size of almost 300-400 ${\mu}$ m units using the micron thickness device, and some of preprocessing procedure was performed with fixing and dyeing. However, the wall structure of plant cell is closely neighbor each other, it is necessary to separate its boundary pixel. Therefore, image merging and shrinking algorithm was adopted to avoid disconnection. After then, boundary pixel was traced through thinning algorithm. Each image from the electro-microscope has a information of x,y position and its height along the z axis cross sectioned image plane. 3D image was constructed using the continuous image combination. Major feature was acquired from a fault image and measured area, thickness of cell wall, shape and unit cell volume. The shape of plant cell was consist of multiple facet shape. Through this measured information, it is possible to construct for structure shape of unit plant cell. This micro unit image processing techniques will contribute to the filed of agricultural mechanical property and will use to construct unit cell model of each agricultural products and information of boundary will use for finite element analysis on unit cell image.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.98-102
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• 2002

The structure of a single crystal, grown by a slow cooling a melt of $Ca_{1.29}Bi_{0.14}VO_4$ composition, was analyzed. The crystals belong to the rhombohedral space group R3c and the dimensions of the unit cells are a = 10.848(1)${\AA}$, c = 38.048(6)${\AA}$, V = 3877.6(8)${\AA}^3$ for the pale yellow crystal, and a = 10.857(1), c = 38.063(6)${\AA}$, V = 3885.6(8)${\AA}^3$ for the yellow crystal, respectively. Unit cell dimensions of the crystal were larger than those of the host crystal, $Ca_3(VO_4)_2$, owing to the Bi that replaced Ca in the unit cell. Ca in the unit cell formed six, eight and nine coordinated polyhedra with O atoms and Bi replacing Ca entered the eight or nine coordinated Ca sites with different crystallographic environments in the unit cell. All the V in the unit cell formed four coordinated tetrahedra with O atoms, however V-O bond lengths in the tetrahedra were different from one another.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1950-1957
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• 2004

Analysis for structures composed of materials containing regularly spaced in-homogeneities is usually executed by using averaged material properties. In order to evaluate the effective properties, a unit cell is defined and loaded somehow, and its response is investigated. The imposed loading, however, should accord to the status of unit cells immersed in the macroscopic structure to secure the accuracy of the properties. In this study, mathematical description for the periodicity of the displacement field is derived and its direct implementation into FE models of unit cell is attempted. Conventional finite element code needs no modification, and only the boundary of unit cell should be constrained in a way that the periodicity is preserved. The proposed method is applicable to skew arrayed in-homogeneity problems. Homogenized in-plane elastic properties are evaluated for a few representative cases and the accuracy is examined.

• International Journal of Contents
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• v.11 no.3
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• pp.34-38
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• 2015

A band stop filter is proposed with cascading unit cells that are based on a dual composite right/left-handed (D-CRLH) conductorbacked coplanar waveguide. The parameters of the unit cell have been analyzed to confirm the behavior of each component for the equivalent circuit of the cell. We simulated the dispersion characteristics and energy distribution and have determined that the unit cell has a D-CRLH property. The band stop filter was implemented by symmetrically cascading two of the proposed unit cells. The experimental results for the band stop filter revealed a band rejection performance of 32 dB and a return loss of 0.35 dB in the stopband frequency range from 869MHz to 954MHz. Finally, we show that there is a good agreement in the experimental results and those obtained through the simulations.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.6-10
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• 2016

Until a recent day, degradation of PEMFC (Proton Exchange Membrane Fuel Cells) has been mainly studied in unit cell. But operation and degradation of real PEMFC going along in stack instead of unit cell. Therefore in this work, ADT (Accelerated Degradation Test) of PEMFC was done in stack and the result from stack's test was compared with that of unit cell. The polymer electrolyte membrane was degraded by repeated electrochemical and mechanical degradation method among several ADT methods. Current densities of MEA at 0.6V decreased in stack and unit cell, 28.4% and 27.8% respectively after ADT for 312 hours. Hydrogen crossover current densities of membrane increased in stack and unit cell, 16.8% and 15.2% respectively after ADT for 312 hours. The result of ADT in stack was similar that of ADT in unit cell, which showed that ADT method of unit cell was available to the stack.

• Korean Journal of Crystallography
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• v.11 no.1
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• pp.6-9
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• 2000

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.317-323
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• 2017

Due to the unique characteristic of auxetic material, negative poisson's ratio, it has a variety of distinctive properties compared to conventional materials. Numerous researches have been conducted on the auxetic material in order to find out how to make auxetics. In this study, we analyzed triangular and rectangular patterned rotating rigid units using finite element method. Our purpose is to investigate the mechanical properties of the rotating rigid units and to show their auxetic behaviors. We studied the Poisson's ratio and the bulk modulus of the rotating rigid units depending on their unit cell sizes. The Poisson's ratio and the bulk modulus decreased as the number of unit cells increased. Also, when the geometry of the unit cell was changed, the tendency of the Poisson's ratio and the bulk modulus was also different from the previous case. The results of the Poisson's ratio and the bulk modulus referred that they were critically affected by the number of unit cells and the shape of unit cell.