• 한국환경복원기술학회지
• /
• 제15권4호
• /
• pp.97-109
• /
• 2012

In this study this writer carried out survey and analysis on paving materials of children's playground for 40 apartment buildings with each of such apartment containing 100 households or more and which were built within last 15 years in Jeonju. As a result of analysis of such questionnaires this author could draw following conclusion. In the second half of 1990s pavement materials which were used mainly were sand and during first half of 2000s they were mixture of sand and rubber block and around 2010 they were rubber block or rubber chip pavements. Such change seemed to be a result of consideration of convenience for management and safety rather than in deference to diversity of children's outing places. Survey on the current status of pavement materials revealed need for directives by the main entity for management and their firm resolve for its implementation. And there was need for their coping with problems such as pressure of treading or lack of it or poor condition of drainage in case of sand and phenomena of pitting or dipping down, discoloring and poor drainage in case of rubber chips and rubber blocks and loosening of gaps between rubber blocks etc. Result of analysing status of usage disclosed that 50.4% of the respondents to questionnaires stated that they had experience of accidents. With regard to cause of such accident it was found that 47.5% of accidents were attributable to play facilities and 19.5% were due to paving (floor) materials thus it was disclosed that not only play facilities but also pavement materials had impact on safety for the children. Result of analysing level of satisfaction with pavement materials showed that pavement by rubber chips and blocks had higher level of satisfaction which was reflection of fear on cleanness of sand. In terms of preference rubber chip and rubber block pavements were highest and the next one was sand. Reason for such preference was based on concern with safety.

• 한국자동차공학회논문집
• /
• 제17권1호
• /
• pp.105-113
• /
• 2009

The performance of a direct-injection type diesel engine often depends on the strength of swirl or squish, shape of combustion chamber, the number of nozzle holes, etc. This is of course because the combustion in the cylinder was affected by the mixture formation process. In this paper, combustion process of biodiesel fuel was studied by employing the piston which has several grooves with inclined plane on the piston crown to generate swirl during the compression stroke in the cylinder in order to improve the atomization of high viscosity fuel such as biodiesel fuel and toroidal type piston generally used in high speed diesel engine. To take a photograph of flame, single cylinder, four stroke diesel engine was remodeled into two stroke visible engine and high speed video camera was used. The results obtained are summarized as follows; (1) In the case of toroidal piston, when biodiesel fuel was supplied to plunger type injection system which has very low injection pressure as compared with common-rail injection system, the flame propagation speed was slowed and the maximum combustion pressure became lower. These phenomena became further aggravated as the fuel viscosity gets higher. (2) In the case of swirl groove piston, early stage of combustion such as rapid ignition timing and flame propagation was activated by intensifying the air flow in the cylinder. (3) Combustion process of biodiesel fuel was improved by the reason mentioned in paragraph (2) above. Consequently, the swirl grooves would also function to improve the combustion of high viscosity fuel.

• 한국건축시공학회지
• /
• 제11권4호
• /
• pp.371-378
• /
• 2011

콘크리트는 다공질로서 수분이 접하게 되면 시간경과에 따라 흡수가 일어난다. 다양한 배합의 콘크리트에서 어느 정도 수분 흡수가 빨리 일어나는가는 흡수수분 확산계수 산출을 통하여 가능하며, 본 연구에서는 길이가 다른 시험체의 질량 경시변화를 통하여 깊이별 흡수 수분량을 산출하였다. 흡수 수분 확산계수는 시간과 깊이의 함수로 이뤄진 볼츠만 변수를 사용하여 실험값과의 회귀분석을 통하여 구하였으며, 그 정확도는 비선형 유한요소 과도해석을 통하여 검증하였다.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제13권1호
• /
• pp.51-60
• /
• 2005

This paper reviews the studies on the pressure drop and the heat transfer in microchannels. Although a lot of studies about the single-phase flow have been done until now, conflicting results are occasionally reported about flow transition from laminar flow to turbulent flow, friction factor, and Nusselt number. Some studies reported the early flow transition due to relatively greater wall effect like surface roughness, but the other studies showed that the flow transition occurred at the Reynolds number of about 2300 and the early flow transition might be due to less accurate measurement of the channel geometry. Also, there have been arguments whether the conventional relation based upon continuum theory can be applied to the fluid flow and the heat transfer in microchannels without modification or not. The studies about the two-phase flow in microchannels have been mostly about investigating the flow pattern and the pressure drop in rectangular channels using two-component, two-phase flow like air/water mixture. Some studies proposed correlations to predict two-phase flow pressure drop in microchannels. They were mostly based on Lockhart-Martinelli model with modification on C-coefficient, which was dependent on channel geometry, Reynolds number, surface tension, and so on. Others investigated the characteristics of flow boiling heat transfer in microchannels with respect to test parameters such as mass flux, heat flux, system pressure, and so on. The existing studies have not been fully satisfactory in providing consistent results about the pressure drop and the heat transfer in microchannels. Therefore, more in-depth studies should be done for understanding the fundamentals of the transport phenomena in the microchannels and giving the basic guidelines to design the micro devices.

• 한국분무공학회지
• /
• 제17권3호
• /
• pp.113-120
• /
• 2012

It is being more serious problems that the pollutant and the greenhouse gas emitted from the internal combustion engines due to the increasing demand of automobiles. To counteract this, as one of the ways has been studied, GDI type engine, which is directly injected into the combustion chamber and burns by a spark ignition that chose the merits of both gasoline engine and diesel engine, was appeared. The combustion phenomena in this GDI engine is known to contribute to combustion stability, fuel consumption reduction and reductions of harmful substances of exhaust gas emission, when the fuel spray of atomization being favorable and the mixture formation being promoted. Accordingly, this study analyzed the affection of ambient temperature and fuel injection pressure to the fuel by investigate the visualization of combustion, combustion pressure and the characteristic of emission, by applying GDI system on the constant combustion chamber. As a result, as the fuel injection pressure increases, the fuel distribution in the combustion chamber becomes uniform due to the increase of penetration and atomization. And when ambient temperatures in the combustion chamber become increase, the fuel evaporation rate being high but the penetration was reduced due to the reduction of volume flux, and confirmed that the optimized fuel injection strategy is highly needed.

• 대한화학회지
• /
• 제37권10호
• /
• pp.855-860
• /
• 1993

SDS(sodium dodecyl sulfate) 존재하에서 NP-40EO[nonylphenol-(ethylene oxide)40]와 요오드와의 상호작용에 따른 $Ca^{2+}$의 영향을 UV-visible spectrophotometer를 이용하여 수용액 중에서 조사하였다. SDS 부재시보다 상호작용 피크의 흡광도는 줄어들었으며, CMC 이상에서 $Ca^{2+}$ 첨가에 따른 상호작용 피크의 강도는 크게 증가하였다. 상호작용 피크의 감소는 SDS 삽입에 따른 혼합미셀 단위 표면적당 요오드와 상호작용할 수 있는 EO 수의 감소에 기인하며, 상호작용 피크 강도의 증가는 $Ca^{2+}$ 존재하에서 미셀 구조가 더욱 조밀해진데 따른 전자주게-받게 겹침 증가로 불 수 있다. 이러한 현상들은 수용액 중에서 상대적으로 자유로운 배향을 갖는 선형 EO 사슬이 유사 크라운 에테르 구조를 형성하여 $Ca^{2+}$ 이온과 착물을 형성할 수 있는 가능성을 보여준다.

• Corrosion Science and Technology
• /
• 제7권6호
• /
• pp.350-361
• /
• 2008

Canada's oil sands contain one of the largest reserves of oil in the world. According to recent estimates, there are nearly 180 billion barrels of oil in the Canadian oil sands trapped in a complex mixture of sand, water and clay. More than 40 companies have been currently operating or developing oil sands facilities since the first production in 1967. The process of oil sands upgrading is similar with down stream refinery, but the corrosion environment in upgrading refinery is often more severe than in the refinery because of high chlorides, mineral contents, carbonic acid, heavy viscosity and fouling, higher naphthenic acid [$NA-R(CH_{2})nCOOH$], and greater sulfur contents. Naphthenic acid corrosion (NAC) which is one of the most critical corrosion issues in up & downstream refinery plants was observed for the first time in 1920's in refinery distillation processes of Rumania, Azerbaizan (Baku), Venezuela, and California. As a first API report, the 11th annual meeting stated sources and mechanism of NAC in early 1930's. API has been developing the risk base standards, such as API RP580, 571, and Publication 581 which are based on the worst NAC damage in the world since 2000. Nevertheless not only the NAC phenomena and control in Canadian sands oil process are not much widely known but also there are still no engineering guidances for the Canadian sands oil in API standards. This paper will give NAC phenomina and materials selection guidance against NA environment in Canadian oil sands upgrading processes.

• 혜화의학회지
• /
• 제16권2호
• /
• pp.251-265
• /
• 2007

Yanhyeoljeseuptang(YHJST) is a traditional herbal medicine used for the treatment of dermatitis. The aim of this study was to confirm whether or not YHJST has a preventive effect on development of atopic dermatitis in dinitrochlorobenzene(DNCB)-applied Nc/Nga mouse. This study was undertaken to develop a reliable mouse model demonstrating similar immunologic phenomena as human atopic dermatitis characterized with predominance of type-2 immune response. NC/Nga mouse were sensitized with $200\;{\mu\ell}$ of 1% 2,4-dinitrochlorobenzene(DNCB) (acetone : olive oil = 3 : 1 mixture) and challenged twice or three times with $150\;{\mu\ell}$ of 0.2% DNCB in a week for the following 4 weeks. YHJST was administered orally to Nc/Nga mouse for 8 weeks, which led to the remarkable suppression on the development of dermatitis, as determined by various immune factors related to pathogenesis of atopic dermatitis in splenocytes and DLN cells. In this study, YHJST selectively suppressed T ce11 (CD4+, CD3+/CD69+, CD4+/CD25+) activation, which may be essential for ratio of IL-4 versus INF-$\gamma$ produced in the splenic T cell culture supernatants was approximately 3-fold higher in the mouse treated with DNCB than their control mouse respectively. Immunologic studies showed down-regulated that the capacity of spleen T cells to produce IL-4, but IFN-$\gamma$ was up-regulated by means of oral intake of these YHJST. These results strongly suggest that YHJST is a promising candidate for treatment of human atopic dermatitis.

• 혜화의학회지
• /
• 제16권2호
• /
• pp.267-280
• /
• 2007

Gupoongjeseuptang(GPJST) is a traditional herbal medicine used for the treatment of dermatitis. The aim of this study was to confirm whether or not GPJST has a preventive effect on development of atopic dermatitis in dinitrochlorobenzene(DNCB)-applied Nc/Nga mouse. This study was undertaken to develop a reliable mouse model demonstrating similar immunologic phenomena as human atopic dermatitis characterized with predominance of type-2 immune response. NC/Nga mouse were sensitized with $200\;{\mu\ell}$ of 1% 2,4-dinitrochlorobenzene(DNCB) (acetone : olive oil = 3 : 1 mixture) and challenged twice or three times with $150\;{\mu\ell}$ of 0.2% DNCB in a week for the following 4 weeks. GPJST was administered orally to Nc/Nga mouse for 6 weeks, which led to the remarkable suppression on the development of dermatitis, as determined by various immune factors related to pathogenesis of atopic dermatitis in splenocytes and DLN cells. In this study, GPJST selectively suppressed T ce11 (CD4+, CD3+CD69+, CD4+CD25+) activation, which may be essential for ratio of IL-4 versus INF-$\gamma$ produced in the splenic T cell culture supernatants was approximately 3-fold higher in the mouse treated with DNCB than their control mouse respectively. Immunologic studies showed down-regulated that the capacity of spleen T cells to produce IL-4, but IFN-$\gamma$ was up-regulated by means of oral intake of these GPJST. These results strongly suggest that GPJST is a promising candidate for treatment of human atopic dermatitis.

• Bulletin of the Korean Chemical Society
• /
• 제30권11호
• /
• pp.2589-2594
• /
• 2009

Aging phenomena of plasma polymer films were studied by using the surface analysis techniques of contact angle measurement, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOFSIMS), and atomic force microscopy (AFM). The polymer films were grown on an aluminum substrate by using a plasma polymerization method from a gas mixture of acetylene and helium, and the films were subsequently modified to have a hydrophilic surface by oxygen plasma treatment. Aging of the polymer films was examined by exposing the samples to water and air environments. The aging process increased the hydrophobicity of the surface, as revealed by an increase in the advancing contact angle of water. XPS analysis showed that the population of oxygen-containing polar groups increased due to the uptake of oxygen during the aging, whereas TOF-SIMS analysis revealed a decrease in the polar group population in the uppermost surface layer. The results suggest that the change in surface property from hydrophilic to hydrophobic nature results from the restructuring of polymer chains near the surface, rather than compositional change of the surface. Oxidative degradation may enhance the mobility and the restructuring process of polymer chains.