• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.1
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• pp.55-62
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• 2008

This study investigated the status and problems of marine-related environmental impact assessment and a utilization-consultation system in Korea and suggested improvement of the review organization. Also, it conducted SWOT analysis based on evaluation of functions, roles and performance of the marine environmental impact assessment center and proposed development strategies of the center through introduction of expert opinions and advanced systems. The performance statement-review by the center in 2007 included 358 cases in total; 165 (46.1%) for consultation on utilization of sea area, 104 for environmental impact assessment (29.0%), and 89 (24.9%) for prior environmental review. The consultation on utilization of sea area can be divided into that for public water surface-use (41%) and reclamation (32%), and sea aggregate extraction process (21%). Although bad impacts on marine environment are reducing under the current system, there are some limits and problems to supplement it in terms of content, system and operation. Review system on sea area utilization-impact(marine environmental impact assessment center) by marine environmental management law needs to obtain expertise, fairness and efficiency and, to do so, have operational supports and institutional improvement to maximize its own functions and roles. At the same time, it is necessary for the center to establish identity and the status as a professional review organization by setting active development strategies inside the center. Finally, it should strengthen an consultation system of marine environmental impact assessment led by the related ministry to achieve effective coastal management.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.334-341
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• 2020

The optimum solutions of the instability of the target velocity were studied to solve the case of the target velocity of the ship approaching at a speed of ◯◯knots and deviated by more than ± 10knots, while the surveillance radar rotating speed was varied, while the maximum search range of the radar was evaluated during the operational test & evaluation. The instability of the target velocity did not enable the radar to calculate the information of the target precisely and to degrade the probability of hit and the quality of the target management. The improvement to handle the deviation of the target velocity was optimally determined by using a fishbone diagram to find 9 reasons based on 4M1E, and the algorithm of the target management was identified as the crucial reason. In this study, the improvement was applied to the filter algorithm to stabilize the target velocity in the target tracking management SW by reviewing the current algorithm to find the velocity of the target and recognizing that the problem does not apply to different 𝜶, 𝞫 values when the antenna changed the rotating speed. The ability of the improvement to work was tested on board.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.588-595
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• 2020

Prediction and control of nitrogen oxides (NO_x) emission is of great interest in industry due to stricter environmental regulations. Herein, we propose an artificial intelligence (AI)-based framework for prediction of NO_x emission. The framework includes pre-processing of data for training of neural networks and evaluation of the AI-based models. In this work, Long-Short-Term Memory (LSTM), one of the recurrent neural networks, was adopted to reflect the time series characteristics of NO_x emissions. A decision tree was used to determine a time window of LSTM prior to training of the network. The neural network was trained with operational data from a heating furnace. The optimal model was obtained by optimizing hyper-parameters. The LSTM model provided a reliable prediction of NO_x emission for both training and test data, showing an accuracy of 93% or more. The application of the proposed AI-based framework will provide new opportunities for predicting the emission of various air pollutants with time series characteristics.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.40-46
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• 2013

Based on Korean railway design standards, the thicknesses of the reinforced roadbeds of conventional and high speed railways are different, and so too, for the size distribution of the ballast particles. Accordingly, considerable cost would be required to increase operating speeds of conventional lines, in particular related to changing from a ballasted track system to a ballastless one. In this study, applicability of a roadbed which supports conventional ballasted track, for use as a ballastless track for a high speed rail line was examined. A reinforced roadbed for a conventional railway is 20cm thick, and the type of material used for a conventional reinforced roadbed is M-40 (crushed gravel for road embankments). A dynamics test was conducted to evaluate the occurrence of the permanent settlement of the track substructure. These results suggest that, without changes to the track substructure, an operational speed of 400km/h is feasible with a ballastless track. This result; however, is from laboratory experiments. Further studies, such as numerical analyses or field validation, are required.

• Journal of Korean Society on Water Environment
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• v.32 no.1
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• pp.36-45
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• 2016

Sand filters are widely used in infiltration systems to manage polluted urban runoff. Clogging, which is mainly caused by the deposition of sediments on the filter media, reduces the filter system's infiltration capacity, which further limits its lifespan and function. The physical, chemical and biological clogging characteristics of sand filter, therefore, need to be known for effective design and maintenance. Physical clogging behavior and variations in the characteristics of sand filters according to different media depths are examined in this paper. The variations were observed from laboratory column infiltration tests conducted in a vertical flow and fluctuating head condition. It can be seen that an increase in filter media depth results in a high sediment removal performance; however, it leads to a shorter lifespan due to clogging. In the choice of filter media depth to be used in field applications, therefore, the purpose of facilities as well as maintenance costs need to be considered. At all filter media depth configurations, premature clogging occurred because sediments of 100~250 μm clogged the top 15% of filter media depth. Thus, scrapping the top 15% of filter media may be suggested as the first operational maintenance process for the infiltration system.

• Journal of Environmental Policy
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• v.11 no.4
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• pp.85-105
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• 2012

In this paper, the energy efficiency of wastewater utilities was evaluated to explore ways to save energy via operational measures. The correlation of each wastewater characteristic parameter to energy was assessed to find a set of parameters that explained most of the variations in energy use among utilities. The results show that increases in inflow, influent COD concentration, and ratio of advanced treatment generally increased the energy use. On the other hand, increases in load factor (influentaverage flow/design flow) reduced the energy use. In the regression analysis, the energy efficiency was highest in the A2O advanced process. On the other hand, the membrane process (among the advanced processes) and the contacted aeration process (among the secondary processes) require more efforts in saving energy. However, the data base system related to energy use must be supplemented in order for more accurate analysis of energy consumption in wastewater treatment facilities. In particular, i) electricity consumption of relay pumps and, ii) energy usage per unit process, iii) pump power usage to discharge treated wastewater in a long distance, if necessary, and iv) alternative energy production and utilization status must be recorded. By utilizing the results of the analysis conducted in this study, it is possible to quantify a level of energy savings needed and establish customized energy saving measures to achieve a certain target level for benchmarking a successful case of wastewater utilities.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.610-618
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• 2008

It is not easy to compare the treatment processes and find an optimum operating condition by the experiments due to influent conditions, treatment processes, various operational conditions and complex factors in real wastewater treatment system and also need a lot of time and costs. In this paper, the activated sludge models are applied to four principal biological wastewater treatment processes, $A_2O$(anaerobic/anoxic/oxic process), Bardenpho(4 steps), VIP(Virginia Initiative Plant) and UCT(University of Cape Town), and are used to compare their environmental and economic assessment for four key processes. In order to evaluate each processes, a new assessment index which can compare the efficiency of treatment performances in various processes is proposed, which considers both environmental and economic cost. It shows that the proposed index can be used to select the optimum processes among the candidate treatment processes as well as to find the optimum condition in each process. And it can find the change of economic and environmental index under the changes of influent flowrate and aerobic reaction size and predict the optimum index under various operation conditions.

• International Commerce and Information Review
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• v.16 no.3
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• pp.431-463
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• 2014

This paper analyzed the effect of the alliance capabilities needed for each stage of alliance lifecycle(search & negociation, contract, operation, evaluation/termination) according to the alliance life cycle of SMEs consulting firms on the performance, and the moderating effect of the partnership & entrepreneurship between the process capabilities and performance using the multi-group analysis The result shows that searching & operational capabilities have a positive impact on the customer & learning performance, not contracting and termination capabilities, and the partnership & entrepreneurship moderated between the process capabilities and alliance performance. This study shows that the operation stage in the alliance life cycle is the most important, in this process alliance partners show the higher partnership & entrepreneurship than any other stages.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.4
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• pp.491-498
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• 2018

The cost evaluation for voyage route planning in an ice-covered sea is one of the major topics among ship owners. Information of the ice properties, such as ice type, concentration of ice, ice thickness, strength of ice, and speed-power relation under ice conditions are important for determining the optimal route in ice and low operational cost perspective. To determine achievable speed at any designated pack ice condition, a model test of resistance, self-propulsion, and overload test in ice and ice-free water were carried out in a KRISO ice tank and towing tank. The available net thrust for ice and an estimation of the ice resistance under any pack ice condition were also performed by I-RES. The in-house code called 'I-RES', which is an ice resistance estimation tool that applies an empirical formula, was modified for the pack ice module in this study. Careful observations of underwater videos of the ice model test made it possible to understand the physical phenomena of underneath of the hull bottom surface and determine the coverage of buoyancy. The clearing resistance of ice can be calculated by subtracting the buoyance and open water resistance form the pre-sawn ice resistance. The model test results in pack ice were compared with the calculation results to obtain a correlation factor among the pack ice resistance, ice concentration, and ship speed. The resulting correlation factors were applied to the calculation results to determine the pack ice resistance under any pack ice condition. The pack ice resistance under the arbitrary pack ice condition could be estimated because software I-RES could control all the ice properties. The available net thrust in ice, which is the over thrust that overcomes the pack ice resistance, will change the speed of a ship according to the bollard pull test results and thruster characteristics (engine & propulsion combination). The attainable speed at a certain ice concentration of pack ice was determined using the interpolation method. This paper reports a procedure to determine the attainable speed in pack ice and the sample calculation using the Araon vessel was performed to confirm the entire process. A more detailed description of the determination of the attainable speed is described. The attainable speed in 1.0 m, 90% pack ice and 540 kPa strength was 13.3 knots.

• Journal of Korean Society of Transportation
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• v.29 no.2
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• pp.111-121
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• 2011

This paper discusses a method for optimizing the semi-actuated traffic signal control system by adjusting the initial interval according to the number of vehicles waiting for the green light in the actuated phase. We also present a Left-Turn actuated traffic signal control strategy that examines the vehicular noise in the detection area and determines the phase extension and the gap-out. In order to detect the vehicles in real-time, an image detector's Video Image Tracking technology was adopted. A 'Zone in Zone'method was implemented, and the image detection area is segmented into three zones: 1) Zone1 for verifying a vehicles obligatory presence, 2) Zone2 for counting the standby vehicles, and 3) Zone3 for examining the number of vehicles that have passed. The on-site assessment of the Left Turn Actuated Control is carried out using CORSIM, and the results show that the Control Delay decreased by 23.10%, 15.06%, and 4.34% compared to the delays resulted from pre-timed control, semi-actuated control-1 and semi-actuated control-2 traffic signal control systems respectively. The Queue Time also decreased by 36.24%, 20.10% and the Total Time by 14.36%, 7.02% for the same scenario. Which clearly demonstrates the operational efficiency. A sensitivity analysis reveals that the improvement from the propose traffic control strategy tends to increase as the through traffic volume reaches a saturated condition and the left-turn traffic volume decreases.