• Journal of Korean Port Research
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• v.13 no.1
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• pp.113-122
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• 1999

Congestion and traffic accidents occur on the merge and diverge sections in the interchange of the freeway. Studies have been conducted to reduce the traffic delay and accidents on the merge section in the freeway since 1960s. but a study was not conducted to estimate the speed variation on the merge section construct models estimated for the speed variation and suggest the appropriate measures. The purpose of this study was to identify the traffic flow characteristics on the merge section in the freeway construct the models estimated for the speed variation on the merge section in the freeway and finally establish the appropriate measure for reduction of traffic delay and accidents on the merge section in the freeway. The following results were obtained: I) Speed variations in the urban freeway appeared to be about 3.2mph, 6.5mph and 7.4mph based on the morning peak period, afternoon peak period and 24-hours period but those in the suburban freeway appeared to be about 8.0mph, 11.1mph and 10.1mph based on the same periods respectively. So different speed reduction signs need be installed to reduce delay and accidents on the merge section in the freeway based on the areas and periods as the freeway traffic management system(FTMS). ii) These models estimated for speed variation need to be studied with the changeable message sign(CMS) technique based on the real-time data so that the traffic flow could be maximized and the traffic delay and accidents be on the merge section in the freeway as more efficient freeway traffic management system(FTMS) in the near future.

• Solar Energy
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• v.18 no.3
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• pp.217-228
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• 1998

The purpose of this research is to investigate the characteristics of static and total pressure distribution in the upward free water jet system impinged on a downward flat plate. The rectangular nozzle was used and its contraction and aspect ratio was five and about seven respectively. Experimental conditions considered were jet velocity, distance between nozzle and flat plate, height of supplementary water. It was founded that pressure distribution on the flat plate had the Gaussian curve when the pressure at stagnation point and impinging half width were chosen as the scaling parameters. The maximum pressure was shown at the stagnation point. The central impingement velocity decreased with the increment of distance between nozzle and flat plate, and its slop of decay was similar to that of chracteristics decay region in the three-dimensional free jet.

• Journal of the Korean Society of Industry Convergence
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• v.7 no.1
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• pp.47-53
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• 2004

양방향 2차로 도로에서는 보다 효율적으로 운영하고 도로의 안전성을 도모하기 위하여 오르막 차로 및 양보차로 추월차로 등의 부가차로를 설치하고 있다. 이러한 부가차로 효율성의 비교 분석을 통한 연구에 의하여 기존의 도로를 효율적으로 운영하는 방안이 제시되어야 된다. 본 연구에서는 이러한 부가차로 중 추월차로 및 양보차로가 포함된 구간을 조사하여 기하구조에 따른 교통류 특성을 분석하고 각 구간별로 서비스 수준분석을 실시하였다. 그 결과는 다음과 같다. (1) 각 기하구조별로 지점속도와 통행속도를 분석한 결과 지점속도는 통행속도보다 조사지점의 기하구조에 의한 영향을 많이 받아 변동이 심한 것을 알 수 있었으며, 통행속도는 그 기하구조에 따른 교통류의 특성을 잘 반영하고 있음을 알 수 있었다. (2) 차량별 지점속도의 비교 분석에서는 현재 차량성능의 진보로 인하여 조사구간의 설계속도에 반해 중차량 및 버스-트럭, 승용에 대한 차량별 속도차이가 거의 없는 것으로 분석되었다. 기존의 중차량에 대한 보정은 현장제한속도에 대하여 감안되어야 된다고 판단된다. (3) 모의실험모형과 현장조사에 의한 교통류특성을 비교해 보았을 때, 시뮬레이션은 도로의 전구간에 대한 결과는 잘 반영하고 있으나 짧은 구간에 대하여 교통류의 연속성을 파악하기에는 부족하다고 판단된다. (4) 추월가능 구간과 양보차로구간의 효율성을 비교해 보면, 추월율에서 양보차로구간이 추월가능구간보다 22.5%나 높게 나왔으며 총지체비교에서는 추월가능구간보다 5.56sec/h의 지체감소를 보이고 있다. 서비스 수준분석에서는 같은 C의 수준을 보이고 있으나 양보차로의 영향으로 양보차로 후구간의 서비스 수준이 A까지 상향되었다. 따라서 대향교통류의 영향을 받는 추월차로의 확보보다는 효율성이 좋은 양보차로구간의 보급이 많아야 되겠다.

• International Journal of Highway Engineering
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• v.11 no.1
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• pp.145-151
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• 2009

Current highway design standards is based on the safety under the free flow condition. The length of deceleration lane is also determined in terms of the deceleration distance which is necessary for the driers to adjust the vehicle speed from the speed limit on the main road to that on the exit ramp of the interchange. However, the queues are frequently developed on the deceleration, and the following vehicles to exit must decelerate on the main road. It may cause delay on the main road and traffic accidents. This study is to suggest a methodology to minimize such problems with the shock-wave theory. The queue length of exiting vehicles can be estimated by the design speeds, traffic volumes of main road and the exiting ramp, and the countermeasures to the operational problems. According to the results, the queue length can be shortened to 80% by upgrading the design speed of exit ramp as the amount of 10km/h. Fifty percent of queue length can be shortened by adding an additional lane on the ramp to two lanes.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.5
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• pp.40-51
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• 2020

Much time has passed since Korea's expressway congestion-threshold speed was revised in 2011. In the meantime, various expressway environments have changed owing to improved performance of vehicles, expanded operations of transport competition (i.e., the KTX), and increased speed limits along some expressway sections. In addition, the speed that expressway users expect to travel at is also increasing. Therefore, through a survey, this study investigates expressway users' perceptions of congestion, and reviews the adjustment of the expressway speed congestion threshold by analyzing expressway traffic flow. One result of the survey confirms that the threshold speed expressway users consider to be congestion has slightly increased. Analyzing traffic and speed data through a K-means algorithm found that the threshold speed for congestion is 60 km/h. In addition, assuming the congestion threshold speed increase from 40 km/h to 50 km/h and 60 km/h, frequently congested expressway sections are identified, determining that 50 km/h is appropriate as a congestion threshold for proper expressway mobility management.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.4
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• pp.339-345
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• 2008

The stratified flow can be seen in the oil and gas pipelines as well as pipelines related to ship's fluid machineries. Numerous theories and correlations have also been proposed in the past for the prediction of stratified flow in horizontal or slightly inclined pipe. The previous researches are mostly about the effects of physical properties, viscosity, phases densities and pipe geometries on the stratified flow. Very few study outcomes exist on the effect of gravity magnitude and large slop angle of pipe inclinations on the occurring condition of stratified flow. In this study, therefore, analytical procedures were conducted about the effect of both the change in the gravity magnitude and pipe inclinations on the stratified flow occurring conditions. From the analytical results, it was found that stratified flow occurred at the vertical upward inclination and at very low liquid phase flowrates in 0.17g and 0.33g conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.3
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• pp.129-138
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• 1988

In order to develop the design and operational criteria in sewage treatment by indirect aerating submerged biofilter, experimental investigations were performed for the reasonable oxygen supply and effecting factors of treatment efficiency. The experiments were executed for the up-flowing synthetic wastewater and aerated water in the submerged biofilter at $20^{\circ}C$. The obtained results are as follows: 1) Appropriate mean diameter of gravels was about 11mm. 2) $BOD_5$ loading rate based on biofilter volume was more reasonable than that on surface area of gravel for operational criteria. 3) To remove the influent $BOD_5$ more than 90%, $BOD_5$ loading rate must be less than $1.0kg-BOD_5/m^3{\cdot}d$ and circulating flowrate must be more than $189m^3/m^3{\cdot}d$. 4) Reaction rate coefficient $K_1$ is related to diameter of gravel and circulating flow rate based on biofilter volume.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.3
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• pp.405-415
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• 2000

Experiments for autotrophic denitrification were performed using an upf10w reac1.or packed with sulfur particles as an electron donor. The influent $NO_3{^-}$-N concentration was kept almost constant, but the hydraulic retention time(HRT) and temperature varied. Results of the research showed that the denitrification efficiency and gas generation rate decreased as the HRT and temperature were reduced. During the HRT effect experiment, alkalinities of 3.44~5.71g, with an average of 4.67 g which is close to the theoretical value of 4.57g were consumed for each gram of $NO_3{^-}$-N removed. During the temperature effect experiment, however, the values were 6.58~13.41 g with an average of 9.12 g which is almost twice the theoretical value Denitrification along the length of the reactor appeared to be a first-order reaction with a reaction rate constant of 0.1648/hr. On the other hand, the sulfate generation showed a zero-order reaction with a reaction rate constant of 241/hr. There was some discrepancy in the nitrogen mass balance between the theoretical and measured values, requiring further researches.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.8
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• pp.866-871
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• 2006

The nutrient recovery in phosphate crystallization process was investigated by using laboratory scale uptlow reactors, adopting sequencing batch type configuration. The industrial waste lime was used as potential cation source with magnesium salt($MgCl_2$) as control. The research was focused on its successful application in a novel integrated sludge treatment process, which is comprised of a high performance fermenter followed by a crystallization reactor. In the struvite precipitation test using synthetic wastewater first, which has the similar characteristics with the real fermentation effluent, the considerable nutrient removal(about 60%) in both ammonia and phosphate was observed within $0.5{\sim}1$ hr of retention time. The results also revealed that a minor amount(<5%) of ammonia stripping naturally occurred due to the alkaline(pH 9) characteristic in feed substrate. Stripping of $CO_2$ by air did not increase the struvite precipitation rate but it led to increased ammonia removal. In the second experiment using the fermentation effluent, the optimal dosage of magnesium salt for struvite precipitation was 0.86 g Mg $g^{-1}$ P, similar to the mass ratio of the struvite. The optimal dosage of waste lime was 0.3 g $L^{-1}$, resulting in 80% of $NH_4-N$ and 41% of $PO_4-P$ removal, at about 3 hrs of retention time. In the microscopic analysis, amorphous crystals were mainly observed in the settled solids with waste lime but prism-like crystals were observed with magnesium salt. Based on mass balance analysis for an integrated sludge treatment process(fermenter followed by crystallization reactor) for full-scale application(treatment capacity Q=158,880 $m^3\;d^{-1}$), nutrient recycle loading from the crystallization reactor effluent to the main liquid stream would be significantly reduced(0.13 g N and 0.19 g P per $m^3$ of wastewater, respectively). The results of the experiment reveal therefore that the reuse of waste lime, already an industrial waste, in a nutrient recovery system has various advantages such as higher economical benefits and sustainable treatment of the industrial waste.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.5
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• pp.282-287
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• 2017

The purpose of this study was predicted the effects of mixing and diffusion due to the operation of the apparatus before the development of the mixed diffusion device for the decontamination absorbent to minimize the influence of contaminant inflow due to radiation accident. The tracer used for the flow characteristics was $^{68}Ga$, $^{99m}Tc$, which is a radioactive isotope, and 2 inch NaI radiation detector was used to detect it. The impeller of the decontamination mixed diffusion system applied to this study was made into three types and the mixing diffusion effect was compared. As a result of analyzing the flow characteristics of the radio-isotope with decontamination mixed diffusion device, mixing, diffusion and flow pattern were obtained. The radial mixing type impeller was able to diffuse to the water surface by the upflow flow, and the fin structure was adjusted for finding optimal conditions. The model 3 type consists of a fin guiding part and an auxiliary fin so that the diffusion speed is higher than that of other types of impellers. It also showed a short time to reach complete mixing.