• 대한수학회지
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• 제33권1호
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• pp.145-154
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• 1996

In the study of manifold decompositions, a central theme is to understand the source manifold taking advantage of the informations of a base space and a decomposition. The concepts of both Hurewicz fibrations and cell-like maps have played very important roles for investigating the mutual relations of three objects. But it is somewhat restrictive for a decomposition map to be cell-like because its inverse images must have trivial shapes.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2003년도 연료전지심포지움 2003논문집
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• pp.151-154
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• 2003

The lap-top with a integrated fuel cell system presented here proves that these solutions have a great potential. Though, there are things that have to be improved before they are introduced to the marked. In this system, heat and water management as well as dead end operation are critical issues which must be directly addressed in further research. Both modified stack design and other new cooling techniques are possible ways to continue the work.

• 대한임상검사과학회지
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• 제47권1호
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• pp.51-58
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• 2015

Ethanol has long been implicated in triggering apoptotic neurodegeneration. Alcohol also may indirectly harm the fetus by imparing the mother's physiology. We examined the effects of ethanol on immature brain of mice. Three-weeks-old female ICR strain mice daily intraperitoneally injected with ethanol at the concentration of 4 and 20% in saline for 0, 6, and 24 hours and 1 and 4 weeks. The mice were weighted and sacrificed, and the brains were ectomized for the present histological, immunohistochemical and TUNEL assays. Based on the histologic hematoxylin and eosin stain, immunohistochemical expression of glutamate receptor protein and neuronal cell adhesion molecule (NCAM) were evaluated. The cerebral cortex of the ethanol-treated group showed few typical symptoms of apoptosis such as chromosome condensation and disintegration of the cell bodies. TUNEL staining revealed DNA fragmentation in the 6 and 24 hours. This results demonstrated that acute ethanol administration causes neuronal cell death. I found that either glutamate receptor inhibition or activation could induce cerebellar degeneration as ethanol effect. Neuronal death also can be induced by excess activity of certain neurotransmitter, including glutamate. Neurons must establish cell-to-cell contact during growth and development in order to survive, migrate to their final destination, and develop appropriate connections with neighboring cell. Purkinje cell in cerebellar are especially vulnerable to the cell death and degeneration. After ethanol treatment in cerebellar, NCAM had decreased by 4 weeks. This result suggest that apoptosis seems to be involved in the slow elimination of neuron and cerebellar degeneration.

• Journal of Oral Medicine and Pain
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• 제20권2호
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• pp.449-459
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• 1995

To investigate the relationship between recurrent aphthous ulcer and oral mucosal keratinization, exfoliative cytology in buccal mucosa, lip mucosa, tongue mucosa were performed on 25 recurrent aphthous ulcer patients and 25 controls whose age ranged from 10 to 65. Keratinization cell ratio was then measured. The results were as follows : 1. Yellow cell ratio in the control group was more than that in the patient group in buccal mucosa, lip mucosa, tongue mucosa. Red cell ratio in the control group was more than that in the patient group in lip mucosa. Blue cell ratio in the patient group was more than that in control group in all regions( p(0.01) 2. In the comparison by sex, the patient group showed no significant difference in all site but, the control group showed different results according to the site; males were more than females in yellow cell, but less than females in red cell Females were more than males in yellow cell, but less than males in red cell. 3. In the comparison by age, patient group showed no significant difference in all site, but the control group showed significantly high yellow cell ratio in buccal and tongue mucosa over the age of 50. In conclusion, there was close relationship between recurrent aphthous ulcer and decreased oral mucosal keratinization. In other words, reduced oral mucosal keratinization must be recommended for prevention of recurrent aphthous ulcer.

• Journal of Korean Dental Science
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• 제7권2호
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• pp.80-86
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• 2014

Purpose: Current common method of cytotoxicity evaluation for elastomeric impression materials use animal based cell lines, which the clinical relevance has been often questioned. Hence, the purpose of this study was to examine the difference in results with both human based and animal based fibroblast cell line. Materials and Methods: Three types of fibroblast cells were used in this study; conventional mouse fibroblasts of L929, human gingival fibroblasts (HGF-1), and immortalized human oral fibrobalsts (hTERT-hNOF). Test on extract and test by direct contact using different commercially available elastomeric impression materials were carried out according to the international standards. Result: There was significant difference in cell viability between types of fibroblasts cell used, where HGF-1 showed highest cell viability and L929 the lowest. Conclusion: Within the limitation of this study, careful consideration must be given when selecting the cells and interpreting the results for cytotoxicity evaluation of elastomeric impression materials, where use of human based cell lines such as hTERT-hNOF would be appropriate for both ease of cytotoxicity test and clinical relevance.

• Journal of Periodontal and Implant Science
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• 제32권1호
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• pp.13-23
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• 2002

The ultimate goal of periodontal therapy is directed to arresting the progression of the disease, and regenerating the fibrous attachment. In order to achieve such treatment aim, the plaque and calculus must be eliminated and the physiological conditions of the root surface must be changed to facilitate the attachment and migration of the new fibroblasts, The method of changing the proper root surface conditions to promote the healing of periodontal tissue involves mechanical procedures, such as scaling and root planing, and chemical procedures such as tetracycline-HCl. However, the formation of a long junctional epithelium was most frequently observed type of healing. Thus, the aim of this study was to examine in vitro the influence of surface conditioning of dentin by TC-HCl on human gingival epithelial cell attachment. Human gingival epithelial cells were obtained from healthy retromolar pad area(under the age 23 years). Seventy two teeth extracted from severe periodontitis were used as study material. To evaluate the epithelial cell attachment to dentin, the prepared specimen was divided to four groups. For the control group, only scaling and root planing were carried out, and for the test group, 1 to 3, the concentration of the TC-HCl was 50, 125 and 250mg/ml respectively. After cell cultivation time of 1-, 3-. 24 hour, for the indirect quantitative assessment of gingival epithelial cell attached to dentin sample, the absorbance of epithelial cell unattached to dentin was measured. The results were as follows; 1. There was no statistically significant difference between scaling and root planing group and TC-HCl 50mg/ml 125mg/ml and 250mg/ml group about absorbance of unattached epithelial cell to dentin sample(p>0.5). 2. As time passes, the absorbance of unattached gingival epithelial cell to dentin sample was decreased statistically significant(p<0.05). 3. There was no statistically significant difference among the TC-HCl group(p>0.05) We concluded that there was similar effect on gingival epithelial cell attachment between TC-HCl conditioning on root surface and only scaling and root planing treatment

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 추계학술대회 논문집
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• pp.279-285
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• 2007

Since the residential load is an AC load and the output of solar cell is a DC power, the photovoltaic system needs the DC/AC converter to utilize solar cell. In case of driving to interact with utility line, in order to operate at unity power factor, converter must provide the sinusoidal wave current and voltage with same phase of utility line. Since output of solar cell is greatly fluctuated by insolation, it is necessary that the operation of solar cell output in the range of the vicinity of maximum power point. In this paper, DC/AC converter is three phase PWM converter with smoothing reactor. And then, feedforward control used to obtain a superior characteristic for current control and digital PLL circuit used to detect the phase of utility line.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1627-1632
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• 1991

A compact type LDPE autoclave reactor is analyzed with respect to the effects of the initiator feed concentration and the rate of heat transfer by employing the mixing-cell model with backflow. Singularity theory is applied for the single-cell model so that one can construct all the possible bifurcation diagrams. Since the single-cell model may not be adequate for the actual reactor, a two-cell model is also treated to predict the dynamic behavior of the reactor. As the rate of heat transfer increases, various multiplicity patterns and oscillatory motions are found. Apparently, the monomer conversion can be substantially increased with proper he-at removal and initiator supplement scheme. For this, however, the complex dynamic features accompanied must be taken into consideration in the reactor design.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.65-68
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• 2008

This paper proposes the parallel operation control algorithm of a power conditioning system (PCS) for a distributed Fuel Cell power generation system. A proposed control algorithm is made good a drawback of the conventional control algorithm. The controller must also supervise the total PCS operation while communicating with the fuel cell system controller. Simulation results are presented to performance of a proposed control algorithm for the PCS.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.496-499
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• 1991

Photovoltaic system has very low energy conversion efficiency and the output characteristics of solar cell is varied by the Insolation quantity and the temperature. In order to improve the efficiency of photovoltaic system, the energy which has got from solar cell must be use maximum. In this paper, it was stimultaneous executed both MPPT control and instrumentation in order that the operating point of solar cell is located maximum power point, using the PWM inverter and micro-computer, which is for the purpose of acquiring maximum power from the solar cell. As a result, maximum power point tracking had carried out and the efficiency of photovoltaic system improved, even if insolation quantity and the temperature are varied.