• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.4
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• pp.351-359
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• 2007

Multi-axial compression tests have been frequently conducted to evaluate the in situ properties of rock masses and the mechanical behaviors of rock strata through the model tests. Without the proper boundary condition for the model tests, the mechanical behavior of rock mass would deviate, as can be expected, from the in situ conditions. The boundary condition will affect the internal stress distribution of the specimens and cause some distortion on the measurement. In this study, a design process regarding the steel brush, which has been employed for multi-axial compression test to reduce the frictional restraint along the specimen/loading platen interface, is introduced. The individual brushes are regarded as a simple column and beam to calculate the cross-sectional size and length of the brushes in consideration of the buckling capacity and the allowable deflection.

• Journal of the Korean Professional Engineers Association
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• v.18 no.3
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• pp.28-35
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• 1985

As the paper industry consumes much water in process and discharge wastewater containing suspended solid and COD(chemical oxygen demand), relevant law against this discharge has been set up to limit the total containment of COD in discharge. This study has been carried out to improve the treatment method for the soluble COD in wastewater produced during the process of paste-board production, which is made of semichemical pulp and waste paper. Applicated methods are, O$_2$AS : O$_2$ activated sludge process DAS : Deep well activated sludge process SAS : standard activated sludge process and proper combination of DAS and SAS 1) As a result of this experiment, we get the following conclusion between in COD sludge loading "X" and COD removable rate in the process of treating waste-water. COD removable rate(％)=(0.778+0.0146/X)${\times}$100(％)……(7) 2) In case that the COD sludge loading is high, it has been cleared out that the COD removable rate shall become low due to unknown unsoluble substances contained in the process. Meanwhile, to increase the efficiency rate of treatment, it is thought to be necessary, to provide long-time contacts with activated sludge. 3) Once the COD of original waste-water and the target COD of treated water are decided, COD sludge loading is obtained from equation(7), and capacity of aeration tank in the effective systems such as O$_2$AS, DAS, to bet the required COD removable rate can be decided. Therefore the choice among SAS, O$_2$AS, DAS methods is made in consideration of required COD removable rate and allowable installation area. 4) In the sedimentation tank with sludge bulking, it is possible to increase the COD removable rate by 3～7％ but still there exist many obstacles to manage this operation.

• Journal of the Korea Society for Simulation
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• v.27 no.2
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• pp.71-81
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• 2018

Forklifts in a shipyard lift and transport heavy objects. Tasks occur dynamically and the rate of the task occurrence changes over time. Especially, the rate of the task occurrence is high immediately after morning and afternoon business hours. The weight of objects varies according to task characteristic, and a forklift also has the workable or allowable weight limit. In this study, we propose an online forklift dispatching algorithm based on nearest-neighbor dispatching rule using minimal cost assignment approach in order to attain the efficient operations. The proposed algorithm considers various types of forklift and multiple jobs at the same time to determine the dispatch plan. We generate dummy forklifts and dummy tasks to handle unbalance in the numbers of forklifts and tasks by taking their capacity limits and weights. In addition, a method of systematic forklift selection is also devised considering the condition of the forklift. The performance indicator is the total travel distance and the average task waiting time. We validate our approach against the priority rule-based method of the previous study by discrete-event simulation.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.379-389
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• 2010

It is very important to determine a target probability of failure in reliability based design such as an allowable factor of safety in working stress design because they are indices to judge the stability of structures. We have carried out reliability analyses of nationwide gravity type quay walls and found that sliding and foundation failures of quay walls were dominant failure modes for every case of loads. And a target probability of failure for bearing capacity of foundation of quay wall was also determined in this study. Of several approaches which have been suggested until now, a couple of reasonable approaches were used. Firstly, in order to consider the safety margin of structures which have been executed so far, the reliability levels of existing structures were assessed. And then a mean probability of failure for the quay walls was estimated. In addition, life cycle cost(LCC) analyses for representative structures were performed. Probabilities of failure for several quay walls were calculated with changing the width of each quay wall section. LCC of quay wall which is requiring case by case during the service life was evaluated, and also the optimum probability of failure of quay wall which minimizes LCC was found. Finally, reasonable target probabilities of failure were suggested by comparing with mean probability of failure of existing structures.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.653-657
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• 2005

This study applied the NDS method to the creek levee and the foundation of a building, for the purpose of ground improvement and cut-off. The conclusions are shown in the following. (1) The results of the field tests in the creek levee are as follows; the N value of the standard penetration test is $2{\sim}3$ before NDS grout and $9{\sim}21$ after NDS grout; in the alluvial layer, $7{\sim}11$ before NDS grout and $14{\sim}23$ after NDS grout. This confirms increasing ground strength with consistency ranging from stiff to very stiff. (2) The result of the permeability test in the creek levee shows that the ground had a great hydraulic conductivity with complete leakage before ground improvement but that the hydraulic conductivity has significantly increased to $3.17{\times}10^{-5}{\sim}4.65{\times}10^{-5}cm/sec$ after ground improvement by the NDS method. (3) The result from the field test of the foundation of the building confirms great reinforcing effects, showing that the allowable bearing capacity has increased from Pa = 5.0 $t/m^2$ before reinforcement to Pa = 25.0 $t/m^2$ after reinforcement.

• Plant Journal
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• v.4 no.3
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• pp.54-59
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• 2008

The resonance of boiler is caused by exciting force in the gas path and it generates the vibration by the harmony of boiler's dimensional factor. According to trending toward the boiler of increasing capacity and a bigger size, it has a problem of the vibration at back-pass heating surfaces. We can predict such vibrations as comparison between vortex frequency and gas column's natural frequency. We can't rely on the method for the past decades because of changing parameters, such as an allowable error, gas temperature, gas velocity, Strouhal number. We can reduce the vibration to use the seasoning effect and change the operating condition in coal fired boiler but it's not essential solution. When the vibration occurred in the model boiler, we must measures the acoustic pressure and frequency of places for considering the means. So far, we confirmed the problem from field measures and theoretical analysis about the acoustic vibration of boiler. We installed anti-acoustic baffle in a existing boiler to change the acoustic natural frequency at the cavity, which results in reducing the acoustic vibration. The first, we prove that the acoustic resonance is caused by harmonizing vortex shedding frequency of tube heat surface with acoustic natural frequency of cavity in the range of 650~750 MW loads. The second, the acoustic resonance at the back-pass heating surface has the third order of acoustic natural frequency at the second economizer. We install five anti-acoustic baffles at the second economizer to reducing the resonance. We confirm considerably reducing the acoustic vibration of boiler during the commercial boiler.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.6
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• pp.749-757
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• 2005

The present study analyzed actual cases of designed flow estimation method and designed flow rate of sewage pipe lines. In order to examine the effects of peak-hour demand factor estimation with given daily highest peak loading, we analyzed its effects on designed flow rate with changing the peak-hour demand factor from 2.0 to 10.0. The results of this study are as follows. When reviewing the recent designs, we found that 59.4% of pipe line with 250mm and 300mm diameter, which fall under minimum allowable pipeline did not meet the minimum velocity which is specified as 0.6m/sec in design standards. The pipe line that have minimal access population or have very low slope did not satisfy the minimum velocity. In estimating the designed sewage flow, the applied daily highest peak loading and hourly highest peaking loading were the load factor for the entire population of the planned area, and for the peak loading of the initial pipes connected to a very small population, we applied the same factor as that applied to the entire area and, as a result, the hourly highest flow was underestimated. Because, in case of the initial pipes, the method of applying the same peak loading to all subject areas is highly possible to produce underestimated design flow, when estimating the designed flow of the initial pipes connected to a small population need to adopt a rational flow factor according to the size of population. For this, it is considered to investigate and analyze raw data on daily and hourly variation of sewage flow.

• Journal of the Korean Geotechnical Society
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• v.33 no.8
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• pp.29-40
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• 2017

In this study, the dynamic compaction method was selected by analyzing field situation, soil condition data and compaction test characteristics of the special selected soils, and the compaction method for using the selected soils as the site restoration soil of the ${\bigcirc}{\bigcirc}$ city non-sanitary landfill maintenance project. The N value in the standard penetration test (SPT) before and after dynamic compaction increased by an average of 89% over the range 12~18, and the allowable bearing capacity of the plate bearing test (PBT) was ranged $150{\sim}227kN/m^2$, at least 80% higher than that before test. As a result, it can be seen that the same tendency as the dynamic compaction effect applied to the existing dredging and waste landfill is shown.

• Journal of the Korean GEO-environmental Society
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• v.10 no.5
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• pp.33-39
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• 2009

This study was conducted to evaluate production of complex odor and 12 specific odorous compounds in a pilot-scale (capacity : $100m^3$) ultra thermophilic aerobic composting. There were three types input: municipal wasted sludge, livestock manure and slurry, and food waste produced in Jung-Eb city. Each raw material was mixed with seed material and operated for two periods (1st : 50 days, 2nd : 60days). During composting, the temperature hit $90{\sim}95^{\circ}C$ after every mixing in both periods. Therefore, it was concluded that increasing temperature also saves the time which required for composting and high reduction of organics and water contents. The primary odorous compounds were ammonia, methyl mercaltan, dimethyl disulfide and trimethylamine. The concentration of the primary compounds and complex odor during the operation were higher than those on final day and most compounds did not exceed the allowable exhaust standard for odor. Also, it was found that optimal mixing time and control of high temperature are the most important parameters for odor control in ultra thermophilic aerobic composting.

• Proceedings of the Korea Contents Association Conference
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• 2005.11a
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• pp.533-538
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• 2005

Due to rapidly inc Due to rapidly Increase the number of vehicles, the number of vehicle passed over the traffic capacity which is allowable on each road. In order to disperse the traffic in the congestion area, ITS related techniques have been studied advancing. However, the cost of setting up and managing In is considerable to recently improve the problem or In, various traffic analysis technique are problem using low cost RFID. In this paper, the method of RFID-Reader location selection, which is a core technique to analyze traffic amount and traffic context is proposal. In order to systematically utilize traffic related road information, GIS is used for the proposal method. In addition, a rule-based model using O/D data that is the important information for selection the location of traffic observation.