• Journal of Environmental Science International
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• v.19 no.6
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• pp.665-670
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• 2010

Pollutants from urban pavement consists various kinds of substances which are originated from dry deposition, a grind out tire, corrosive action of rain to pavement and facilities and raw materials of the road etc.. These are major pollutants of urban NPS (Non-point source) during rainfall period. However there is not enough information to control such pollutants for appropriate management of natural water quality. In this study of transportation areas, three monitoring stations were set up at trunk road, urban highway and national road in Gyeongnam province. Runoff flow rate was measured at every 15minutes by automatic flow meters installed at the end of storm sewer pipe within the road catchment area for water quality analysis. Data was collected every 15 minutes for initial two hours of rainfall. Additional samples were collected 1-4 hours interval till the end of rainfall. The monitoring parameters were $COD_{Mn}$, SS, T-N & T-P and heavy metals. The average EMCs of TSS and $COD_{Mn}$ were 62.0 mg/L and 24.2 mg/L on the city trunk road, which were higher than those of urban highway and national road, indicating higher pollutant loads due to activities in the city downtown area beside the vehicle. On the other hand, the average EMC of T-N and T-P were in the range of 2.67-3.23 mg/L and 0.19-3.21 mg/L for all the sampling sites. Heavy metals from the roads were mainly Fe, Zn, Cu and Mn, showing variable EMCs by the type of road. From the TSS wash-off analysis in terms of FF(first flush) index, first flush phenomenon was clearly observed in the trunk road(FF : 0.89-1.43). However, such mass delivery behavior was not apparently shown in urban highway(FF : 0.90-1.11) and national road(FF : 0.81-1.41).

• Journal of the Korean Society of Safety
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• v.24 no.1
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• pp.31-36
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• 2009

This paper focuses on techniques of improving refinery reliability, availability, and profitability. Our team developed a corrosion control document(CCD) for processing of the crude distillation unit(CDU). Recent study shows the loss due to corrosion in US is around $276 billion. It's a big concern for both managers and engineers of refinery industry. The CCD consists of numerous parts namely damage mechanism(DM), design data, critical reliability variable(CRV), guidelines, etc. The first step in the development of CCD is to build material selection diagram(MSD). Damage mechanisms affecting equipments and process need to be chosen carefully based on API 571. The selected nine DM from API 571 are (1) creep/stress rupture, (2) fuel ash corrosion, (3) oxidation, (4) high temperature sulfidation, (5) naphthenic acid corrosion, (6) hydrochloric acid(HCL) corrosion, (7) ammonium chloride(salt) corrosion, (8) wet $H_2S$ corrosion, and (9) ammonia stress corrosion cracking. Each DM related to corrosion of CDU process was selected by design data, P&ID, PFD, corrosion loop, flow of process, equipment's history, and experience. Operating variables affecting severity of DM are selected in initial stage of CRV. We propose the guidelines for reliability of equipments based on CRV. The CCD has been developed on the basis of the corrosion control in refinery industry. It also improves the safety of refinery process and reduces the cost of corrosion greatly.

• Korean Journal of Food Science and Technology
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• v.21 no.5
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• pp.676-685
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• 1989

Optimal operating conditions of on-farm red pepper dryer were searched by using the simulation-optimization algorithm combining the drying and quality deterioration models of red pepper with Box's complex method. Determination of control variables such as air temperature, air recycle ratio and air flow rate was based on a criterion of minimizing energy consumption under the constrainst conditions that satisfied the specified color retention of carotenoids. As quality constraint was stricter, energy consumption increased and total drying time decreased with lower recycle ratio and higher air flow rate Product mixing during drying was found to be able to improve the energy efficiency and product quality. Currently used air flow rate was assessed to be increased for the optimal operation. Two stage drying at the fixed optimal air flow rate was proven to be useful means for further saying of energy consumption. In the optimal bistaged drying, the second stage began at about one third of the total drying time and low air temperature in the first stage Increased to a high value and air recycle ratio increased slightly in the second stage. Optimal control variable scheme could be explained by the dryer performance and the carotenoids destruction kinetics in red pepper drying.

• Journal of the Korean Solar Energy Society
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• v.27 no.4
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• pp.167-173
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• 2007

This study analyzed by simulation using TRNSYS as well as by experiment on the solar district heating system installed for the first time for the district heating system in Bundang. Simulation analysis using TRNSYS focused on the thermal behavior and long-term thermal efficiency of solar system. Experiment carried out for the reliability of simulation system. This solar system where the circuits of two different collectors, flat plate and vacuum tube collector, are connected in series by a collector heat exchanger, and the collection characteristics of each circuit varies. Therefore, these differences must be considered for the system's control. This system uses variable flow rate control in order to obtain always setting temperature of hot water by solar system. Specifically, this is a system that heats returning district heating water (DHW) at approximately $60^{\circ}C$ using a solar collector without a storage tank, up to the setting temperature of approximately $85{\sim}95^{\circ}C$ To realize this, a flat plate collector and a vacuum tube collector are used as separate collector loops. The first heating is performed by a flat plate collector loop and the second by a vacuum tube collector loop. In a gross collector area basis, the mean system efficiency, for 4 years, of a flat plate collector is 33.4% and a vacuum tube collector is 41.2%. The yearly total collection energy is 2,342GJ and really collection energy per unit area ($m^2$) is 1.92GJ and 2.37GJ respectively for the flat plate vacuum tube collector. This result is very important on the share of each collector area in this type of solar district heating system.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1511-1519
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• 2014

The objective of this paper is to propose a modelling of a small compressed air energy storage system, which drives an induction generator based on a field-oriented control (FOC) principle for a renewable power generation. The proposed system is a hybrid technology of energy storage and electrification, which is developed to use as a small scale of renewable energy power plant. The energy will be transferred from the renewable energy resource to the compressed air energy by reciprocating air compressor to be stored in a pressurized vessel. The energy storage system uses a small compressed air energy storage system, developed as a small unit and installed above ground to avoid site limitation as same as the conventional CAES does. Therefore, it is suitable to be placed at any location. The system is operated in low pressure not more than 15 bar, so, it easy to available component in country and inexpensive. The power generation uses a variable speed induction generator (IG). The relationship of pressure and air flow of the compressed air, which varies continuously during the discharge of compressed air to drive the generator, is considered as a control command. As a result, the generator generates power in wide speed range. Unlike the conventional CAES that used gas turbine, this system does not have any combustion units. Thus, the system does not burn fuel and exhaust pollution. This paper expresses the modelling, thermodynamic analysis simulation and experiment to obtain the characteristic and performance of a new concept of a small compressed air energy storage power plant, which can be helpful in system designing of renewable energy electrification. The system was tested under a range of expansion pressure ratios in order to determine its characteristics and performance. The efficiency of expansion air of 49.34% is calculated, while the efficiency of generator of 60.85% is examined. The overall efficiency of system of approximately 30% is also investigated.

• Geomechanics and Engineering
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• v.9 no.5
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• pp.619-629
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• 2015

Influenced by various mining activities, fractures in rock masses have different densities, set numbers and lengths, which induce different mechanical properties and failure modes of rock masses. Therefore, precisely expressing the failure criterion of the fractured rock influenced by coal mining is significant for the support design, safety assessment and disaster prevention of underground mining engineering subjected to multiple mining activities. By adopting PFC2D particle flow simulation software, this study investigated the propagation and fractal evolution laws of the micro cracks occurring in two typical kinds of rocks under uniaxial compressive condition. Furthermore, it calculated compressive strengths of the rocks with different confining pressures and box-counting dimensions. Moreover, the quantitative relation between the box-counting dimension of the rocks and the empirical parameters m and s in Hoek-Brown strength criterion was established. Results showed that with the increase of the strain, the box-counting dimension of the rocks first increased slowly at the beginning and then exhibited an exponential increase approximately. In the case of small strains of same value, the box-counting dimensions of hard rocks were smaller than those of weak rocks, while the former increased rapidly and were larger than the latter under large strain. The results also presented that there was a negative correlation between the parameters m and s in Hoek-Brown strength criterion and the box-counting dimension of the rocks suffering from variable mining activities. In other words, as the box-counting dimensions increased, the parameters m and s decreased linearly, and their relationship could be described using first order polynomial function.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.5
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• pp.136-144
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• 2010

Exhaust gas recirculation (EGR) is an emission control technology allowing significant NOx emission reduction from light-and heavy duty diesel engines. The future EGR type, dual loop EGR, combining features of high pressure loop EGR and low pressure loop EGR, was developed and optimized by using a commercial engine simulation program, GT-POWER. Some variables were selected to control dual loop EGR system such as VGT (Variable Geometry Turbocharger)performance, especially turbo speed, flap valve opening diameter at the exhaust tail pipe, and EGR valve opening diameter. Applying the dual loop EGR system in the light-duty diesel engine might cause some problems, such as decrease of engine performance and increase of brake specific fuel consumption (BSFC). So proper EGR rate (or mass flow) control would be needed because there are trade-offs of two types of the EGR (HPL and LPL) features. In this study, a diesel engine under dual loop EGR system was optimized by using design of experiment (DoE). Some dominant variables were determined which had effects on torque, BSFC, NOx, and EGR rate. As a result, optimization was performed to compensate the torque and BSFC by controlling start of injection (SOI), injection mass and EGR valves, etc.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.181-191
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• 1997

Before cables are constructed, tower of suspension bridge is behaved as a cantilever type. Buffeting occured by unsteady loading of the tower due to velocity fluctuation in the oncoming flow has a wind velocity consistent with fundamental frequency of the tower and may give rise to large response by the tower resonance. To reduce the dynamic response by buffeting, the behavior of tower with TMD(Tuned Mass Damper) has studied using finite element method in time domain. The buffeting was obtained by transforming the velocity spectrum in frequency domain to random variable in certain time domain. The most probable maximum displacement which can be occured during the time interval was obtained using peak factor. The optimum location for TMD installation and TMD specification were decided by parametric study. Also, the effect of vibration control about various wind velocity was studied by the TMD which has optimum specification and location.

• The Journal of the Korea Contents Association
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• v.8 no.2
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• pp.116-124
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• 2008

The foods served in festivals only affect attractiveness on visitors in itself. Because residents, tourists and vendor flow into the site in opening periods. In this case, there are always the possibility to happen to accident in site unprecedently. Therefore, The purpose of the study is to examine how visitors perceive the foods vendors served in festivals and how the factors influence among the casual relationship to applying the planned behavior theory. The Results is following up. Behavior Intention is affected the variables of belief, subjective norm and perceived behavior control. Final varialbe Food buying is affected the variable of behavior intention positive, but perceived behavior contro is not significant(p<0.05). Festivals make for the depar from the life, the attractiveness of the food happen to buy it stronger than the control ability of visitors. The health control for the food is needed systemically on the focus of the risk management

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.6
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• pp.307-315
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• 2003

This paper proposes a novel simulation method of WPGS (Wind Power Generation System). The rotation speed control method of turbine under variable wind speed using the pitch control is proposed. Moreover, when wind speed exceeds the cut-out wind speed, the turbine will be stopped by controlling pitch angle to 90$^{\circ}$, otherwise it will be controlled to steady-state operation. For the purpose of effective simulation, the SWRW (Simulation method for WPGS using Real Weather condition) is used for the utility interactive WPGS simulation in this paper, in which those of three topics for the WPGS simulation: user-friendly method, applicability to grid-connection and the utilization of the real weather conditions, are satisfied. It is impossible to consider the real weather conditions in the WPGS simulation using the EMTP type of simulators and PSPICE, etc. External parameter of the real weather conditions is necessary to ensure the simulation accuracy. The simulation of the WPGS using the real weather conditions including components modeling of wind turbine system is achieved by introducing the interface method of a non-linear external parameter and FORTRAN using PSCAD/EMTDC in this paper. The simulation of long-term, short-term, over cut-out and under cut-out wind speeds will be peformed by the proposed simulation method effectively. The efficiency of wind power generator, power converter and flow of energy are analyzed by wind speed of the long-term simulation. The generator output and current supplied into utility can be obtained by the short-term simulation. Finally, transient-state of the WPGS can be analyzed by the simulation results of over cut-out and under cut-out wind speeds, respectively.