International Insurance Seminar 12 참석보고(參席報告)

유호선 한국보험학회 1977 保險學會誌 Vol.13 No.-

한국의 재벌형성 과정

유호선 한국보험학회 1984 保險學會誌 Vol.23 No.-

Engineering Branching Point of Side Chain in Naphthalene Diimide-Based Polymers for Enhancing Electron Mobility and All-PSCs Performance

유호선,김범준 한국고분자학회 2019 한국고분자학회 학술대회 연구논문 초록집 Vol.44 No.2

단열실린더내에서 톱날파형 피스톤운동을 하는 스터링기관에 대한 해석적인 해

유호선 대한기계학회 1988 대한기계학회논문집 Vol.12 No.5

본 연구에서는 피스톤운동을 톱날파로 근사하였을 때 단열된 실린더를 갖는 스터링기관에 대한 해석적인 해를 구하고자 한다. 실제기관에서 피스톤운동은 기구 학적 구동기구에 따라 상이하지만 대략적으로 정현파가 되며, 이 경우에는 해석적인 해가 존재하지 않으므로 수학적으로 구간선형적인 톱날파로 근사하였다. 비록 이러 한 근사를 도입한 단열해석이라 하더라도 해석적인 해가 존재한다면 등온해석보다는 기관성능의 예측에 더욱 적합함은 당연하다. An analytical method to predict qualitative performance characteristics of the Stirling Engines in the preliminary design stages is investigated. Both the expansion and the compression cylinder are treated as adiabatic and piston motions are approximated as saw-toothed waves. Basic equations which were originally proposed by Finkelstein consist of mass conservation and energy balances for each adiabatic cylinder. The approximation on piston motions and physical conditions make it possible to divide an engine cycle into four fundamental processes. In each process, first, pressure can be expressed as a function of the crank angle by solving a nonlinear first order ordinary differential equation and other thermodynamic variables are determined in turn. Application of the cyclic steady condition to the whole processes can complete a cycle. Also, further analysis results in analytic expressions for cyclic work and heat transfer in terms of the engine parameters and thermodynamic variables at boundary points. The results are expected useful as a quick reference for the engine performances. Finally, the present method can be applied to the other adiabatic analyses on the Stirling Engines with piece wise linear piston motions, if mass variations are predictable.

대한설비공학회 학회상의 위상 제고를 위하여

유호선 대한설비공학회 2014 설비저널 Vol.43 No.12

경제운영 (經濟運營)의 사상구조의 변천 - 통제와 자유 -

유호선 한국보험학회 1982 保險學會誌 Vol.20 No.-

N/A

시멘트-모래-파라핀 왁스 혼합물을 이용한 축열에 관한 연구

유호선,노승탁,Yoo, Ho-Seon,Ro, Sung-Tack 대한설비공학회 1980 설비저널 Vol.9 No.3

In order to enhance the thermal energy storage capacity of cement mortar and to improve the effective thermal conductivity of paraffin waxes, cement- sand- paraffin wax mixture was investigated. By means of finite difference method, the transient temperature distribution in a hollow cylinder with phase change using average composite properties was obtained, and compared with experimental results. It was shown that the heat absorbed by mixture with $25\%$ paraffin fraction was as much as $50\%$ more than either a concrete mortar or pure paraffin wax in the case of ${\Delta}T=\;18.25^{\circ}C$.

등온가열에 의한 접촉융해의 초기 과도과정에 대한 근사적 해석해

유호선,Yu, Ho-Seon 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.12

An approximate analytical solution for the initial transient process of close-contact melting occurring between a phase change material kept at its melting temperature and an isothermally heated flat surface is derived. The model is so developed that it can cover both rectangular and circular cross-sectional solid blocks. Normalization of simplified model equations in reference to the steady solution enables the solution to be expressed in a generalized form depending on the liquid-to-solid density ratio only. A selected result shows an excellent agreement with the previously reported numerical data, which justifies the present approach. The solution appears to be capable of describing all the fundamental characteristics of the transient process. In particular, dependence of the solid descending velocity oft the density ratio at the early stage of melting is successfully resolved. The effects of other parameters except the density ratio on the transient behaviors are efficiently represented via the steady solution implied in the normalized result. A simple approximate method for estimating the effect of convection on heat transfer across the liquid film is also proposed.

Evaluation of Sonic Toothbrush on the Reduction of Clinical Parameters, Interleukin-1, MMP-8 and Periodontal Pathogens in Incipient to Moderate Periodontitis

유호선,채경준,홍지연,최성호,김종관 대한치과의사협회 2008 대한치과의사협회지 Vol.46 No.12

Daily plaque removal with toothbrush is an important component of oral hygiene program to prevent and treat periodontal diseases.1-4) Although it has been reported that both manual and electric toothbrushes are effective in removing supragingival plaque and reducing clinical signs of gingival inflammation, several recent studies reported that electric toothbrushes show superiority to manual brushes.5-11) The Sonicare® toothbrush utilizes solid-state electronics to create sonic-frequency bristle movement with 520 brush strokes per second. This rapid bristle movement creates dynamic activities in surrounding fluids in addition to its scrubbing plaque-removing activity. It has been suggested that these fluid forces lift and disperse plaque bacteria from tooth surfaces about 2-3 mm beyond the physical reach of the bristles.12-15) Furthermore, in vitro experiments have shown that low-amplitude acoustic energy such as that generated by the Sonicare® brush has structural and metabolic effects on oral bacteria, which may retard their ability to form plaque by disrupting bacterial adherence properties.16) Increased levels of bacterial pathogens common in periodontal pockets are known to be associated with an elevated biochemical inflammatory response that promotes bone resorption. Understanding the process of periodontal pathogenesis in terms of the biochemical pathway prompted by greater than normal levels of bacteria and mitigating the subsequent effects is a primary component of periodontal therapy.17-20) The most potent pro-inflammatory cytokine stimulating bone resorption is interleukin-1 (IL-1).21,22) IL-1 is a pleiotropic cytokine having multiple biological activities including stimulation of osteoclast recruitment and activation. IL-1 also stimulates fibroblast to produce matrix metalloproteinases (MMPs) important for the degradation of non-mineralized extracellular tissue. Several studies have reported increased levels of inflammatory mediators, such as IL-1 and prostaglandin E2 (PGE2), in gingival crevicular fluids (GCFs) from diseased sites exhibiting periodontal bone loss when compared with healthy sites. Furthermore, GCF from diseased sites has been shown to stimulate bone resorption in vitro to a higher degree than GCF from healthy sites. One important factor responsible for this bone resorbing activity seems to be IL-1.21-24) Matrix metalloproteinases (MMPs) are enzymes activated by IL-1 and are involved in tissue destruction and regeneration.15) A complex cascade involving both host and microbial derived proteinases mediates extracellular matrix degradation during periodontal disease. In this regard, the host-derived MMPs are thought to play a key role. Enhanced activity of these enzymes is a consequence of microbial induced inflammation in the periodontal tissues. Polymorphonuclear leukocyte (PMN)-derived MMPs (MMP-8, MMP-9) are the main proteinases related to tissue destruction and remodeling events in periodontal diseases.23) Traditional clinical measurements such as assessments of probing pocket depth, attachment level, gingival inflammation and microbial plaque yield only historic information about periodontal status. By directly analyzing the changes in the levels of MMPs and IL-1 in GCF, we can associate parameters of inflammation with clinical parameters of tissue destruction. Among several methods that have been applied to detect periodontopathogenic microorganisms, nucleic acid-based methods using DNA probes can give insight on changes in bacterial counts in the periodontal pocket.24) Objectives of this study were to assess the effects of the Sonicare® toothbrush on clinical parameters [Probing Pocket Depth (PPD), Plaque index (PI), Gingival index (GI), Bleeding on probing (BOP), Clinical attachment level (CAL)] and to evaluate the changes in MMP-8, IL-1 and the reduction of 4 bacterial species (PG, TF, SS, AV) testing 16S rRNA at 3 sites of selected teeth with moderate chronic periodont... Daily plaque removal with toothbrush is an important component of oral hygiene program to prevent and treat periodontal diseases.1-4) Although it has been reported that both manual and electric toothbrushes are effective in removing supragingival plaque and reducing clinical signs of gingival inflammation, several recent studies reported that electric toothbrushes show superiority to manual brushes.5-11) The Sonicare® toothbrush utilizes solid-state electronics to create sonic-frequency bristle movement with 520 brush strokes per second. This rapid bristle movement creates dynamic activities in surrounding fluids in addition to its scrubbing plaque-removing activity. It has been suggested that these fluid forces lift and disperse plaque bacteria from tooth surfaces about 2-3 mm beyond the physical reach of the bristles.12-15) Furthermore, in vitro experiments have shown that low-amplitude acoustic energy such as that generated by the Sonicare® brush has structural and metabolic effects on oral bacteria, which may retard their ability to form plaque by disrupting bacterial adherence properties.16) Increased levels of bacterial pathogens common in periodontal pockets are known to be associated with an elevated biochemical inflammatory response that promotes bone resorption. Understanding the process of periodontal pathogenesis in terms of the biochemical pathway prompted by greater than normal levels of bacteria and mitigating the subsequent effects is a primary component of periodontal therapy.17-20) The most potent pro-inflammatory cytokine stimulating bone resorption is interleukin-1 (IL-1).21,22) IL-1 is a pleiotropic cytokine having multiple biological activities including stimulation of osteoclast recruitment and activation. IL-1 also stimulates fibroblast to produce matrix metalloproteinases (MMPs) important for the degradation of non-mineralized extracellular tissue. Several studies have reported increased levels of inflammatory mediators, such as IL-1 and prostaglandin E2 (PGE2), in gingival crevicular fluids (GCFs) from diseased sites exhibiting periodontal bone loss when compared with healthy sites. Furthermore, GCF from diseased sites has been shown to stimulate bone resorption in vitro to a higher degree than GCF from healthy sites. One important factor responsible for this bone resorbing activity seems to be IL-1.21-24) Matrix metalloproteinases (MMPs) are enzymes activated by IL-1 and are involved in tissue destruction and regeneration.15) A complex cascade involving both host and microbial derived proteinases mediates extracellular matrix degradation during periodontal disease. In this regard, the host-derived MMPs are thought to play a key role. Enhanced activity of these enzymes is a consequence of microbial induced inflammation in the periodontal tissues. Polymorphonuclear leukocyte (PMN)-derived MMPs (MMP-8, MMP-9) are the main proteinases related to tissue destruction and remodeling events in periodontal diseases.23) Traditional clinical measurements such as assessments of probing pocket depth, attachment level, gingival inflammation and microbial plaque yield only historic information about periodontal status. By directly analyzing the changes in the levels of MMPs and IL-1 in GCF, we can associate parameters of inflammation with clinical parameters of tissue destruction. Among several methods that have been applied to detect periodontopathogenic microorganisms, nucleic acid-based methods using DNA probes can give insight on changes in bacterial counts in the periodontal pocket.24) Objectives of this study were to assess the effects of the Sonicare® toothbrush on clinical parameters [Probing Pocket Depth (PPD), Plaque index (PI), Gingival index (GI), Bleeding on probing (BOP), Clinical attachment level (CAL)] and to evaluate the changes in MMP-8, IL-1 and the reduction of 4 bacterial species (PG, TF, SS, AV) testing 16S rRNA at 3 sites of selected teeth with moderate chronic periodontitis follo...

회원의 소리 : 세상을 보는 여유

유호선 대한기계학회 1999 기계저널 Vol.39 No.9