• 한국자동차공학회논문집
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• 제23권2호
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• pp.169-177
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• 2015

In this study we investigated the regeneration methods for the lean $NO_x$ trap (LNT) catalyst in a 2.2L direct injection diesel engine. The regeneration methods were 1) in-cylinder post fuel injection and 2) external fuel injection strategy. The in-cylinder post fuel injection method uses in-cylinder injectors with the addition of the post fuel injection to supply enough reductants such as CO, $H_2$, THC. The external fuel injection method was enabled by installing a fuel injector with a wide spray angle before the LNT catalyst. Through the engine experiment, the $NO_x$ conversion efficiency, the amount of reductant exhaust gases, fuel consumption, and temperature behavior in the LNT catalyst were evaluated and compared for the two regeneration methods.

• 대한토목학회논문집
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• 제43권4호
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• pp.449-458
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• 2023

용존 유기물을 흡착 제거하는 기술로서, 흡착능이 우수한 입상활성탄을 우선적으로 적용할 수 있지만, 흡착탑의 운전기간에 따라 GAC의 흡착능이 현저히 저하되어 파과되는 한계가 있으며 파과된 활성탄인 spent-GAC는 교체나 재생이 불가피하다. 활성탄 교체는 비용의 경제성 때문에 기피되며 상업적으로 열재생법을 사용하고 있으나, 800℃ 이상의 고온 조건으로 인한 높은 에너지 비용과 활성탄의 질량 손실이 발생하는 단점이 있다. 본 연구에서는 CSOs내의 용존 유기물 처리에 사용된 spent-GAC의 재생효율을 제고하기 위해, Fenton 산화법과 초음파 산화를 융합한 다중산화기술인 Sono-Fenton 방법을 적용하였고, 산화제 주입농도와 초음파 주파수별 spent-GAC의 재생효율을 조사하였다. 적용된 Sono-Fenton 처리에서 Fe²⁺ 10 mmol/L, H₂O₂ 농도 1,000 mmol/L, 120분 초음파 주사시간, 초음파 주파수 40 kHz 재생처리 조건에서 68.5%의 가장 높은 재생효율을 얻을 수 있었고, 750 kHz에서도 유사한 효율을 얻을 수 있었으며, 다른 주파수의 초음파는 재생효율이 불량했고 주파수의 크기와 GAC 재생효율은 선형 관계를 나타내지 않았다. 실 하수를 희석하여 제조한 CSOs로 GAC 흡착탑을 연속운전 한 경우, 재생없이 700시간 내외의 운전이 가능했고 1회의 Sono-Fenton 처리를 적용한 결과, 총 1,000시간의 GAC 흡착 운전 기간 동안 40~70%의 COD_cr 제거 효율이 확보하였다.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.199-199
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• 2017

This study investigated the aspects of damage due to low temperature treatment in order to establish the damage criterion according to low temperature invasion during regeneration period in wheat after regeneration period in the early spring. We cultivated wheat cultivar 'Geumgang' in Wagner pots and treated them with three types of low temperature, and the gradual temperature change program was set in a low temperature incubator for 12.5 h per day for 5 days during the night time when the length of young spikes was about 1 mm. All treatments except for the control were treated in 5 steps for each temperature. Treatment 1 was treated at the lowest temperature $-5^{\circ}C$ for 5 h, treatment 2 for 7 h at $-5^{\circ}C$, and treatment 3 for 9 h at $-5^{\circ}C$. The most common type of damage was partial infertility, and there were some discolored spikes. The damage rate of wheat spikes treated at $-5^{\circ}C$ for 9 h was the highest, while the damage rates of wheat sprouts treated at 5h and 7h were not different from each other. It was found that the damage of wheat spikes exposed to low temperatures for a long time was large. It is necessary to investigate the aspects of spike damage by duration days of low temperature.

• 한국해양환경ㆍ에너지학회지
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• 제17권2호
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• pp.116-121
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• 2014

지열수를 온열원으로 사용하고, 해양심층수를 열침으로 사용하는 바이너리(binary) 지열 발전시스템은 기존 지열 발전시스템의 효율을 증대하기 위한 재열과정과 터빈출력을 향상시키기 위한 다단과정을 각각 또는 복합적으로 적용하여 다단재열재생사이클의 성능개선을 검토하였다. 사이클종류는 다단재열사이클(Multi Stage reheater cycle; MS), 다단재열재생사이클(Multi stage reheater regeneration cycle; MSR)이 있다. 작동유체는 R134a, R245fa를 적용하였으며 온열원의 온도가 $65^{\circ}C$, $75^{\circ}C$, $85^{\circ}C$ 열침은 $5^{\circ}C$를 적용하여 기본해석을 수행하였다. 본 논문에서는 온열원변화, 작동유체의 종류, 사이클의 종류에 따른 해양지열발전용 다단재열재생사이클의 출력 및 효율을 높이기 위한 해석을 수행하였다. 이를 열역학적 사이클로 모사하기 위한 상용 프로그램인 Aspen HYSYS(V8.0)를 이용하여 해석을 진행 하였다. 작동유체는 R245fa가 R134a보다 우수한 성능을 보였으며, 온열원의 변화와 각각의 사이클 종류에 따라 적절한 작동유체가 있음을 확인 할 수 있었다. 사이클의 출력 및 효율은 각각 MS사이클과 MSR사이클에서 좋은 성능을 나타냈다.

• 한국환경과학회지
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• 제18권5호
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• pp.501-508
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• 2009

In this study, the characteristics of granular activated carbon (GAC) supported metal was investigated in an area influenced by flame discharge and temperature variation during irradiating microwave. The modified GAC was formulated by impregnating metal hydroxides of nickel (Ni/GAC), barium (Ba/GAC), copper (Cu/GAC), zinc (Zn/GAC), cobalt (Co/GAC) and lanthanum (La/GAC). Ba/GAC was selected as it showed lack of spark discharge and temperature increasing aspects. Comparison of adsorption and desorption amount of GAC and Ba/GAC showed that adsorption and desorption rate of the GAC were higher than those of Ba/GAC. The results show that the presence of barium can decrease adsorption/desorption rate because of plugging pore of GAC. Toluene regeneration rate of Ba/GAC was better than that of GAC due to barium loading. Finally, GAC with barium can be controled a rapid increasing temperature and spark discharge, increased the regeneration rate of toluene during desorption by irradiating microwave.

• 대한기계학회논문집B
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• 제33권5호
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• pp.358-364
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• 2009

This paper is to investigate the influence of driving patterns of slow and high speed vehicles on the performance of continuously regenerating diesel particulate filter(DPF) system matched with operating conditions in field application. The DPF performance test for field application was carried out for two identical DPFs installed to slow and high speed vehicles. A slow speed vehicle was selected among local buses which have driving patterns to repeat running and stop frequently, while a high speed vehicle was prepared to have long route of high speed over 60km/h like inter-city buses. In this test, the regeneration performance on the DPF of slow speed vehicle deteriorated because of high soot load index(SLI) in spite of same balance point temperature(BPT) distribution for high speed vehicle. The DPF of slow speed vehicle melted in the end because the rapid increase of back pressure caused high temperature over $1200^{\circ}C$ in the ceramic wall of DPF. The PM components like ash collected to the filter in the DPF were analyzed in order to investigate the cause of the defect and provide an operation performance of DPF system. In the result of the analysis, high levels of lubrication oil ash(Ca, Mg, P, Zn) were detected.

• International Journal of Industrial Entomology and Biomaterials
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• 제20권2호
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• pp.99-105
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• 2010

In this paper, the regenerated silk fibroins were dissolved in LiBr aqueous solution with different dissolution temperature and time, and the effects of the dissolution condition on the regeneration yield, molecular weight, wet spinnability, and electrospinnability of regenerated silk fibroin were investigated. The regeneration yield, molecular weight distribution, and wet spinnability of regenerated silk fibroin were nearly affected by the dissolution temperature and time. However, the electrospinning performance of silk fibroin was influenced by the dissolution condition implying the electrospinning of silk fibroin is more sensitive process than the wet spinning in the range tested in this study. While $25^{\circ}C$ of dissolution temperature resulted in a good electrospinnability of regenerated silk fibroin, the electrospinnability was slightly deteriorated when silk fibroin was dissolved at $60^{\circ}C$ for 6 hours. Also, though the fiber diameters of electrospun silk fibroin produced by the dissolution at $25^{\circ}C$ for 6 hours and 24 hours were 443 and 451 nm, respectively, that at $60^{\circ}C$ for 5 min was reduced to 411 nm. The fiber diameter was more decreased to 393 nm when the dissolution time increased up to 6 hours at $60^{\circ}C$.

• 대한기계학회논문집B
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• 제40권9호
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• pp.589-596
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• 2016

최근 들어 작동유체가 액체 상태를 유지하며 흡열 과정이 일어나는 증기동력사이클인 유기플래시 사이클이 제안되었다. 본 연구에서는 재생을 이용한 수정 유기플래시 사이클을 제안하고 현열 형태의 저온 열원을 사용하는 시스템의 열역학적 성능 해석을 수행하였으며 작동유체나 플래시 온도가 순생산 동력이나 열효율 등 시스템의 성능에 미치는 영향을 체계적으로 분석하고 논의하였다. 해석 결과는 시스템의 순생산동력은 플래시 온도에 대해 최대값을 갖지만 열효율은 플래시 온도에 따라 상승함을 보여준다. 재생 사이클은 기존의 유기플래시 사이클에 비해 시스템 열효율이 높고 저온 열원의 동력 변환에 있어 성능 개선을 위한 잠재성을 보여준다.

• Journal of Microbiology and Biotechnology
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• 제13권4호
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• pp.501-508
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• 2003

Artificial coupling of one enzyme with another can provide an efficient means for the production of industrially important chemicals. Xylose reductase has been recently discovered to be useful in the reductive production of xylitol. However, a limitation of its in vitro or in vivo use is the regeneration of the cofactor NAD(P)H in the enzyme activity. In the present study, an efficient process for the production of xylitol from D-xylose was established by coupling two enzymes. A NADH-dependent xylose reductase (XR) from Pichia stipitis catalyzed the reduction of xylose with a stoichiometric consumption of NADH, and the resulting cofactor $NAD^+$ was continuously re-reduced by formate dehydrogenase (FDH) for regeneration. Using simple kinetic analyses as tools for process optimization, suitable conditions for the performance and yield of the coupled reaction were established. The optimal reaction temperature and pH were determined to be about $30^{\circ}C$ and 7.0, respectively. Formate, as a substrate of FDH, affected the yield and cofactor regeneration, and was, therefore, adjusted to a concentration of 20 mM. When the total activity of FDH was about 1.8-fold higher than that of XR, the performance was better than that by any other activity ratios. As expected, there were no distinct differences in the conversion yields of reactions, when supplied with the oxidized form $NAD^+$ instead of the reduced form NADH, as a starting cofactor for regeneration. Under these conditions, a complete conversion (>99%) could be readily obtained from a small-scale batch reaction.

• Journal of Ecology and Environment
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• 제48권2호
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• pp.152-162
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• 2024

Background: Plant species of the alpine treeline ecotone are highly sensitive to climate change and may adjust their population dynamics, and functional traits in response to changing climate. This study examined regeneration patterns and leaf traits variations in an important treeline ecotone element Rhododendron campanulatum along the elevation gradient in western Nepal to assess its potential adaptive responses to climate change. The distribution range of R. campanulatum (3,400-3,800 m above sea level [a.s.l.]) was divided into five horizontal bands, each with a 100 m elevational range. Eight plots (10 m × 10 m) were sampled in each band, resulting into a total of 40 plots. In each plot, all R. campanulatum individuals and co-occurring tree species were counted. From each elevation, R. campanulatum leaf samples were collected to determine leaf dimensions, leaf density, specific leaf area (SLA), and stomatal density (SD). Results: The density-diameter curve indicated that R. campanulatum was regenerating well, with enhanced regeneration at higher elevation (3,800 m a.s.l.) than at lower. Tree canopy cover appeared to be the major determinant of R. campanulatum regeneration, as indicated by a higher number of seedlings in treeless stands. With increasing elevation, the leaf length, width, SLA, and stomata length decreased but leaf thickness and SD increased. Conclusions: Overall, a higher regeneration and lower SLA with the high SD in the leaves at the upper limit of the species distribution suggested that R. campanulatum is well adapted at its upper distribution range with the possibility of upslope range shift as temperature increases.