• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.911-920
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• 2005

The present study investigates heat/mass transfer and flow characteristics in a ribbed rotating passage with turning region. The duct has an aspect ratio (W/H) of 0.5 and a hydraulic diameter ($D_h$) of 26.67 mm. Rib turbulators are attached in the parallel arrangement on the leading and trailing surfaces of the passage. The ribs have a rectangular cross section of 2 m (e) $\times$ 3 m (w) and an attack angle of $70^{\circ}$. The pitch-to-rib height ratio (p/e) is 7.5, and the rib height-to-hydraulic diameter ratio (e/$D_h$) is 0.075. The rotation number ranges from 0.0 to 0.20 while the Reynolds number is constant at 10,000. To verify the heat/mass transfer augmentation, internal flow structures are calculated for the same conditions using a commercial code FLUENT 6.1. The results show that a pair of vortex cells are generated due to the symmetric geometry of the rib arrangement, and heat/mass transfer is augmented up to $Sh/Sh_0=2.9$ averagely, which is higher than that of the cross-ribbed case presented in the previous study for the stationary case. With the passage rotation, the main flow in the first-pass deflects toward the trailing surface and the heat transfer is enhanced on the trailing surface. In the second-pass, the flow enlarges the vortex cell close to the leading surface, and the small vortex cell on the trailing surface side contracts to disappear as the passage rotates faster. At the highest rotation number ($R_O=0.20$), the turn-induced single vortex cell becomes identical regardless of the rib configuration so that similar local heat/mass transfer distributions are observed in the fuming region for the cross- and parallel-ribbed case.

• Clinical and Experimental Reproductive Medicine
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• v.49 no.4
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• pp.259-269
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• 2022

Objective: Animal-free scaffolds have emerged as a potential foundation for consistent, chemically defined, and low-cost materials. Because of its good potential for high biocompatibility with reproductive tissues and well-characterized scaffold design, we investigated whether polyglycolic acid (PGA) could be used as an animal-free scaffold instead of natural fibrin-agarose, which has been used successfully for three-dimensional human endometrial cell culture. Methods: Isolated primary endometrial cells was cultured on fibrin-agarose and PGA polymers and evaluated various design parameters, such as scaffold porosity and mean fiber diameter. Cytotoxicity, scanning electron microscopy (SEM), and immunostaining experiments were conducted to examine cell activity on fabricated scaffolds. Results: The MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay and SEM results showed that endometrial cells grew and proliferated on both scaffolds. Immunostaining showed cytokeratin and vimentin expression in seeded cells after 7 days of culture. On both scaffolds, an epithelial arrangement of cultured cells was found on the top layer and stromal arrangement matrix on the bottom layer of the scaffolds. Therefore, fibrin-agarose and PGA scaffolds successfully mimicked the human endometrium in a way suitable for in vitro analysis. Conclusion: Both fibrin-agarose and PGA scaffolds could be used to simulate endometrial structures. However, because of environmental and ethical concerns and the low cost of synthetic polymers, we recommend using PGA as a synthetic polymer for scaffolding in research instead of natural biomaterials.

• Korean Journal of Veterinary Pathology
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• v.3 no.1
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• pp.65-68
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• 1999

Clinically, three holstein dairy cattle showed the inappetence and decrease of milk production with severe lameness and pain. Grossly, strawberry-like proliferation of the skin between the heel bulbs were observed 4${\times}$5${\times}$1.5cm in size. Histopathologically, severe hyperplasia of epidermis, parakeratotic hyperkeratosis and multifocal ulceration of cornified cell layer, acanthosis, spongiosis of prickle cell layer and irregular arrangement of basal cell layer were seen. And focally observed the lesions of necrotic vasculitis, infiltration of inflammatory cells, congestion and hemorrhage. Spirochete bacteria were found in necrotic and outer proliferated epidermal cells by Levaditi's silver stain. Clinical and pathological findings were consistent with dermatitis verrucosa.

• Applied Microscopy
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• v.15 no.2
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• pp.69-79
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• 1985

Ultrastructural and cytochemical studies of the root hair cell and the trichoblast were undertaken with light and electron microscopes to clarify the type of root hair, fine structure and the activities of acid phosphatase and ATPase. The root hair was differentiated from the middle portion of the cell, and perpendicularly to the long axis of the cell. Consequently, the type of root hair comes under the panicoid type. In the trichoblast, nucleus and cytoplasm are located in the vicinity of cortex. On the contrary, after the root hair is formed, they migrate to the apical region of the root hair, and the basal region of the root hair is filled with numerous vacuoles. Cell walls of actively growing root hairs are subdivided into two layers on the basis of the arrangement of cellulose microfibrils. New cell wall of the root hair is presumptively formed from Golgi complex-derived vesicles. Activity of acid phosphatase appeared on tonoplast, plasma membrane, and nuclear envelope, whereas ATPase activity appeared on the plasma membrane, heterochromatin, and mitochondrial cristae.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1568-1569
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• 2005

This paper presents a method to optimize train radio communication network for train control(CBTC) or multimedia services. To determine the optimized distance between wayside radio stations in a radio communication network constructed along railway, radio frequency allocation and hand-over capability is studied in terms of radio communication cell coverage and roaming feasibility.

• Journal of the Semiconductor & Display Technology
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• v.21 no.1
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• pp.127-131
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• 2022

The effect of bypass diodes on the output energy of solar cells was investigated under the condition of partial shading. The maximum power point was estimated using the perturbation & observation algorithm, taking into account the correlation effect between the arrangement and number of bypass diodes. The performance of the bypass diode was tested under the consideration of the partial shading effect and simulated using a Matlab/Simulink.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.158-163
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• 1998

This paper is our first attempt to construct a information processing system such as the living creatures' brain based on artificial life technique. In this paper, we propose a method of constructing neural networks using bio-inspired emergent and evolutionary concept, Ontogeny of living things is realized by cellular automata model and Phylogeny that is living things adaptation ability themselves to given environment, are realized by evolutionary algorithms. Proposing evolving cellular automata neural systems are calledin a word ECANS. A basic component of ECANS is 'cell' which is modeled on chaotic neuron with complex characteristics, In our system, the states of cell are classified into eight by method of connection neighborhood cells. When a problem is given, ECANS adapt itself to the problem by evolutionary method. For fixed cells transition rule, the structure of neural network is adapted by change of initial cell' arrangement. This initial cell is to become a network b developmental process. The effectiveness and the capability of proposed scheme are verified by applying it to pattern classification and robot control problem.

• Journal of radiological science and technology
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• v.13 no.2
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• pp.51-51
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• 1990

This study was undertaken to observe the effects of $^{60}Co\;{\gamma}-irradiation$ on the cell of spermatogenic epithelium in the testis of the chicken. 16-week-old chicken were provided as an experimental group and compared with control group. The experimental group was divided into a single irradiation (800, 1000, 1200 rads) and into three partial irradiation group (800/3, 1000/3, 1200/3 rads). The morphological changes of epithelial cell of the testis were observed by means of hematoxyline and eosin stain. Microstructure of spermatocyte and sperm was observed by means of semithin section of electron microscopic specimen. The results obstained are summerized as follows. 1. Spermatogonia and sertoli cells were found to be isolated from the basal membrane of seminiferous tubules as dose of $^{60}Co\;{\gamma}-irradiation$ was increased. 2. Spermatocytes of pachytene stage were seperated from the cytotplasmic process of sertoil cell in case of 1000 rads of $^{60}Co\;{\gamma}-irradiation$. 3. Normal arrangement of the cell of spermatogenic epithelium was found in control group and only the partial irradiation group of 800 rads. Vaculation in the seminiferous was pronounced in case of a single irradiation group of 800 rads, but the irradiation group of 1000 rads and 1200 rads were found to be damaged severely in both a single and a partial dose.

• Applied Microscopy
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• v.15 no.2
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• pp.1-9
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• 1985

The portion of Cuscuta japonica haustorium which lies internal to the host tissues, the endophyte, was examined at the ultrastructural level. The endophyte consisted of mainly small parenchymatous cells and large, slightly elongate cells at the tip. The tip cells were characterized by the presence of large and lobed nucleus, several small vacuoles, dense cytoplasm, abundant rough endoplasmic reticulum, dictyosomes, and mitochondria, and thus suggested to have a high metabolic activity. The shape, arrangement, and cytological characteristics of the parenchymatous and tip cells consisting the endophyte were very similar to those of the dividing cells and idioblasts, respectively, which appeared in the endophyte primordium of the upper haustorium. The tip cells with the thickened-apical wall were observed to grow intrusively through the host cell walls and to engulf the remnants of the degenerated host cells. In the former case intrusive growing cell was regarded to develop into the filamentous cell, the hypha. Plasmodesmata through the cell wall were not observed between host and parasite cells. Some host cells that in contact with the penetrating tip cells of the endophyte, showed the degenerating features such as a loss of cytoplasm, a beaded fashion of small vesicles, and deformation of chloroplasts.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.4
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• pp.236-244
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• 2021

Fuel cell systems for medium duty truck require high power demands under driving. Since high power demands results in significant heat generation, thermal management is crucial for the performance and durability of medium duty truck. Therefore, various configurations of dual stacks with cooling systems are investigated to understand appropriate thermal management conditions. The simulation model consists of a dynamic fuel cell stack model, a cooling system model equipped with a controller, and the mounted controller applies a feedback controller to control the operating temperature. Also, In order to minimize parasitic power, the comparison of the cooling systems involved in the arrangement was divided into three case. As a result, this study compares the reaction of fuel cells to the placement of the cooling system under a variety of load conditions to find the best placement method.