• Molecules and Cells
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• 제37권8호
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• pp.575-584
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• 2014

Potassium is a macronutrient that is crucial for healthy plant growth. Potassium availability, however, is often limited in agricultural fields and thus crop yields and quality are reduced. Therefore, improving the efficiency of potassium uptake and transport, as well as its utilization, in plants is important for agricultural sustainability. This review summarizes the current knowledge on the molecular mechanisms involved in potassium uptake and transport in plants, and the molecular response of plants to different levels of potassium availability. Based on this information, four strategies for improving potassium use efficiency in plants are proposed; 1) increased root volume, 2) increasing efficiency of potassium uptake from the soil and translocation in planta, 3) increasing mobility of potassium in soil, and 4) molecular breeding new varieties with greater potassium efficiency through marker assisted selection which will require identification and utilization of potassium associated quantitative trait loci.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.739-745
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• 2004

In reference to conventional line speed-up and improvement railway, accurate assembly of turnout affects traveling quality of turnout area and running safety. Because of heavy weight and a large volume of the long sleepers and car limit, transport and construction of the P.C(prestress concrete) sleeper turnout is the most difficult process. the prerequisite for trouble-free transport of the factory pre-assembled major turnout components is achieved through division of long sleepers. So, in this paper we investigate structural safety of segmented sleeper which is adopted for the first time to improve performance of turnout and, new construction method.

• 대한안전경영과학회지
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• 제13권2호
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• pp.267-273
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• 2011

Since 'The Act on Private Investment of The Infrastructure' was established in 1994, private investment as well as government's investment in transport infrastructure has been active. However investment in transport infrastructure has more risks than others' due to uncertainty both in traffic volume and in construction cost. In the current appraisal procedure of deciding transportation infrastructure investment, instead of risk management, the sensitivity analysis considering only the changes of benefit, cost and social discount rate which are main factor affecting economic feasibility is carried out. Therefore the uncertainty of various factors affecting demand, cost and benefit are not considered in feasibility study. In this study the problems in current investment appraisal system were reviewed. Using Delphi technique the major factors which have high uncertainty in feasibility study were surveyed and then improvement plan was suggested in the respective of classic 4 step demand forecasting method. The range estimation technique was also mentioned to deal with the uncertainty of the future.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2010년도 학술발표회
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• pp.546-550
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• 2010

흐름과 장파에 의하여 발생되는 난류의 subgrid scale mixing effects를 고려할 수 있는 수심적분형 모형(depth-integrated model)을 제시하였다. 완전비선형의 수심적분형 모형은 약분산(weakly dispersive) 환경에서 흐름의 회전성(rotational)을 고려하도록 perturbation approach를 이용하여 유도되었다. 동일한 방법을 이용하여 수심적분형 이송확산방정식(depth-integrated scalar transport equation)을 유도하였다. 방정식은 4차정확도의 유한체적기법을 이용하여 해석하였으며, 다양한 혼합양상을 보이는 흐름에 대한 수치모의를 수행하였다.

• 한국미생물·생명공학회지
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• 제13권3호
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• pp.209-212
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• 1985

산소 투과율이 좋은 silicone tube안쪽에 nutrient 공급을 위한 3개의 isotropic polypropylene hollow fiber 3개를 넣어 제작된 이중 실관 반응기에서 E. coli cell을 immobilization 하여 cell density와 packing characteristics를 조사해 보았다. E. coli cell들은 거의 100% Packing되어 동물조직에서 처럼 층을 이루면서 자랐고 ceil density를 측정해 본 결과 약 550g/$\ell$고농도 세포배양이 가능하였다.

• Bulletin of the Korean Chemical Society
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• 제6권3호
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• pp.128-131
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• 1985

A series of copolymer membranes of 2-hydroxyethylmethacrylate (HEMA) with selected hydrophobic monomers were prepared without crosslinking agents. The equilibrium water content, the partition coefficient, and the permeability of the solutes such as urea, methylurea, 1,3-di-methylurea, and acetamide via these membranes were measured. The partition coefficient data show that as the hydrophobicity of solutes increased, the partition of solutes were dictated by hydrophobic interaction between solute and polymer matrix. Diffusion coefficients obtained in these experiments decrease as the water content of polymer membrane decreases. This decrease is blunt as the excess heat capacities, ${\phi}C^0_p$ (excess) in aqueous solution at infinite dilution of solute increases. To investigate the relationship between water content and diffusion coefficient, the results of the diffusion experiments were examined in light of a free-volume model of diffusive transport. The remarkable increase of urea mobility in the polymer network containing relatively larger bulk water can be considered as water structure breaking effect.

• International Journal of Computer Science & Network Security
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• 제22권1호
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• pp.276-282
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• 2022

One of the most essential foundations upon which big institutions rely in delivering cloud computing and hosting services, as well as other kinds of multiple digital services, is the security of infrastructures for digital and information services throughout the world. Distributed denial-of-service (DDoS) assaults are one of the most common types of threats to networks and data centers. Denial of service attacks of all types operates on the premise of flooding the target with a massive volume of requests and data until it reaches a size bigger than the target's energy, at which point it collapses or goes out of service. where it takes advantage of a flaw in the Transport Control Protocol's transmitting and receiving (3-way Handshake) (TCP). The current study's major focus is on an architecture that stops DDoS attacks assaults by producing code for DDoS attacks using a cloud controller and calculating Round-Tripe Time (RTT).

• 한국ITS학회 논문지
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• 제10권5호
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• pp.124-134
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• 2011

전기자동차의 보급 활성화를 촉진시키기 위해서는 전기자동차를 위한 교통기반시설의 공급과 효율적인 정책결정이 필요하다. 하지만 이를 뒷받침할 수 있는 전기자동차의 시설표준화 및 지침구축은 미비한 상태이다. 시설표준화 및 지침 구축을 위해서는 다양한 연구를 통한 기준지표와 자료가 마련되어야 한다. 본 연구에서는 2차로도로 시뮬레이션모형(TWOPAS)을 이용하여 이상적인 조건에서 저속전기자동차가 혼입되었을 때의 교통특성을 평균통행속도, 추종시간백분율, 총지체를 통해 분석하고 교통류에 미치는 영향을 검토하였다. 시나리오는 교통량을 기준으로 설정하였으며, 저속전기자동차 혼입율을 1%~30%로 적용하여 분석하였다. 각 시나리오 별로 분석한 결과, 교통량이 650대/시인 시나리오 1의 경우와 교통량이 2,600대/시인 시나리오4가 교통량이 1,300대/시, 1,950대/시인 시나리오2, 시나리오3보다 교통영향이 작게 받는 것으로 나타났다. 이는 교통량이 적은 경우 추월이 비교적 원활해 영향이 작게 나타나며, 교통량이 많은 경우는 기존의 교통류가 전기자동차 주행특성과 비슷하기 때문에 영향이 작은 것으로 나타났다. 반면 비교적 원활한 교통소통을 보이는 시나리오2와 시나리오3은 저속전기자동차의 혼입에 따른 영향을 크게 받는 것으로 나타났다. 따라서 도시내 도로와 같이 교통량이 많은 도로와 교통량이 비교적 한산한 지방부 2차로 도로의 경우는 저속전기차동차에 대한 친화도가 높은 반면 교통량이 1,300대/시~1,950대/시인 도로는 저속전기자동차에 대한 친화도가 낮아 기하구조의 개선 등이 필요한 것으로 나타났다.

• 한국ITS학회 논문지
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• 제21권5호
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• pp.149-161
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• 2022

제한속도는 주행속도에 영향을 주기 때문에 교통흐름은 물론 교통사고와도 밀접한 관계에 있다. 기존 제한속도 산정 방법은 공학적 판단요소로 차로수, 교차로 간격, 진출입로 수, 횡단보도 수, 85백분위 속도, 토지이용 형태, 도로기하 특성 등 다양한 요소들을 고려하지만 대부분이 교통시설에 해당되고 교통량을 고려한 교통영향분석이 이루어지지 않고 있어 공학적 분석이 미흡하다고 할 수 있다. 또한 지점속도인 85%속도만으로는 도로 전체의 교통류 특성을 잘 반영해주지 못한다. 따라서 본 논문에서는 교차로 간격과 교통량 조건에서 제한속도 변화가 순행속도와 통행속도의 크기와 그 차이에 미치는 영향을 상세하게 분석하였다. 그리고 그 결과를 활용하여 제한속도 변경 전과 동일한 서비스수준을 유지토록 하여 속도개선효과를 높이고 순행속도와 통행속도의 차이를 줄이는 제한속도 산정방안을 제안하였다. 그리고 교통량 변화에 따른 가변적 제한속도 운영방안도 제시하였다. 본 방안은 속도개선효과를 확보하면서 교통사고 심각도에 영향을 주는 속도 차이를 줄이고 교통량 변화에 따른 주행속도 변화를 반영한 제한속도 운영으로 운전자들의 제한속도 준수율을 높여 안전측면에서도 효과가 기대된다.

• 한국대기환경학회지
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• 제28권3호
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• pp.233-248
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• 2012

The national emission from energy sector accounted for 84.7% of all domestic emissions in 2007. Of the energy-use emissions, the emission from mobile source as one of key categories accounted for 19.4% and further the road transport emission occupied the most dominant portion in the category. The road transport emissions can be estimated on the basis of either the fuel consumed (Tier 1) or the distance travelled by the vehicle types and road types (higher Tiers). The latter approach must be suitable for simultaneously estimating $CO_2$, $CH_4$, and $N_2O$ emissions in local administrative districts. The objective of this study was to estimate 31 municipal GHG emissions from road transportation in Gyeonggi Province, Korea. In 2008, the municipalities were consisted of 2,014 towns expressed as Dong and Ri, the smallest administrative district unit. Since mobile sources are moving across other city and province borders, the emission estimated by fuel sold is in fact impossible to ensure consistency between neighbouring cities and provinces. On the other hand, the emission estimated by distance travelled is also impossible to acquire key activity data such as traffic volume, vehicle type and model, and road type in small towns. To solve the problem, we applied a hierarchical cluster analysis to separate town-by-town road patterns (clusters) based on a priori activity information including traffic volume, population, area, and branch road length obtained from small 151 towns. After identifying 10 road patterns, a rule building expert system was developed by visual basic application (VBA) to assort various unknown road patterns into one of 10 known patterns. The expert system was self-verified with original reference information and then objects in each homogeneous pattern were used to regress traffic volume based on the variables of population, area, and branch road length. The program was then applied to assign all the unknown towns into a known pattern and to automatically estimate traffic volumes by regression equations for each town. Further VKT (vehicle kilometer travelled) for each vehicle type in each town was calculated to be mapped by GIS (geological information system) and road transport emission on the corresponding road section was estimated by multiplying emission factors for each vehicle type. Finally all emissions from local branch roads in Gyeonggi Province could be estimated by summing up emissions from 1,902 towns where road information was registered. As a result of the study, the GHG average emission rate by the branch road transport was 6,101 kilotons of $CO_2$ equivalent per year (kt-$CO_2$ Eq/yr) and the total emissions from both main and branch roads was 24,152 kt-$CO_2$ Eq/yr in Gyeonggi Province. The ratio of branch roads emission to the total was 0.28 in 2008.