• Water for future
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• v.29 no.2
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• pp.167-178
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• 1996

In designing automatic water quality monitoring networks for a river basin, determination of measurement locations and items is critical to the effectiveness of the total system. In this paper we studied how to decide these two design factors when a monitoring network is designed for the purposse of water quality surveillance and emergency alarm. For measurement locations, candidate sites are chosen based on the intake amount for water supply and the point sources of contamination. Then, detailed locations are decided according to the contaminant flow distance. As for measurement items, characteristics and the accident history of water pollution in the basin must be taken into account. Considering economic aspects, we proposed a two-stage measurement plan: basic components for all locations and selective ones variable for different locations. Proposed methodology is demonstrated through a case study for Nak-dong River Basin.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.1
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• pp.119-125
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• 2005

The current automotive is seeking the improvement of performance, the prevention of environmental pollution and the saving of energy resources according to miniaturization and lightweight of the components. And the variance analysis on the basis of structure analysis and DOE is applied to the lower control am. We have proposed a statistical design model to evaluate the effect of structural modification by performing the practical multi-objective optimization considering weight, stress and fatigue lift. The lower control arm is performed the fatigue analysis using the load history of real road test. The design model is determined using the optimization of acquired load history with the fatigue characteristic. The characteristic function is made use of the optimization according to fatigue characteristics to consider constrained function in the optimization of DOE. The structure optimization of a lower control arm according to fatigue characteristics is performed. And the optimized design variable is D=47 m, T=36mm, W=12 mm. In the real engineering problem of considering many objective functions, the multi-objective optimization process using the mathematical programming and the characteristic function is derived an useful design solution.

• Journal of Korea Society of Digital Industry and Information Management
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• v.15 no.4
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• pp.9-17
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• 2019

Sun power generation systems which use large capacity centralized inverters have loss of power generation due to cloud and building shadows, pollution, cell deterioration, etc. To minimize loss of power generation, decentralized solar power systems using multiple micro-inverters are being proposed as an alternative. A distributed solar power system consisting of a system-connected system uses power line communication to collect data from the micro-inverters. Power line communication has the advantage of using power lines without separate lines for data transmission, but in distributed solar power generation systems that use a large number of micro-inverters, the bit error rate is less reliable due to the phenomenon caused by limited transmission power, high load interference and noise, variable signal attenuation, and impedance characteristics. So we proposed wireless intelligent controller for micro-inverter that is used to build distributed solar power systems. and we design and implement that. Further, the proposed wireless intelligent controller for micro-inverter was used to establish a small-volume solar power plant to check its function and operation.

• Journal of Microbiology
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• v.45 no.5
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• pp.379-387
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• 2007

A hundred and seventeen antibiotic-resistant Escherichia coli strains were isolated from public tap and spring waters which were polluted by fecal coliforms. There were no significant differences between two water sources as to the coliform pollution level (p> 0.05). All E. coli isolates were detected to be resistant to one or more antibiotics tested. Nearly 42% of the isolates showed multiresistant phenotype. Three (2.5%) of these isolates contained class 1 integron. Sequencing analysis of variable regions of the class 1 integrons showed two gene cassette arrays, dfr1-aadA1 and dhfrA17-aadA5. Resistance to ampicillin, tetracycline or trimethoprim-sulfamethoxazole was transferable according to the results of conjugation experiments. The rate of tetracycline resistance was 15%. tet(A)-mediated tetracycline resistance was widespread among tetracycline-resistant E. coli isolates. Genotyping by BOX-polymerase chain reaction (BOX-PCR) showed that some of the strains were epidemiologically related. This is the first report on the prevalence and characterization of class 1 integron-containing E. coli isolates of environmental origin in Turkey.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.2
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• pp.165-173
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• 2004

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. Experiments are performed for 304 stainless steel plates changing several process parameters such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar plates, etc. The following conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/ aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1154-1159
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• 2004

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. Experiments are performed for Inconel 600 plates changing several process parameter such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between plate and plate, etc. The follow conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/ aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power . Welding characteristics of austienite Inconel 600 using a continuous wave Nd:YAG laser are experimentally investigated. This paper describes the weld ability of inconel 600 for machine structural use by Nd:YAG laser.

• International Journal of Highway Engineering
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• v.15 no.1
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• pp.163-169
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• 2013

PURPOSES: The urban traffic problems can be defined as general problems for smooth traffic flow including maintenance of mass transportation system according to suddenly increased population, traffic regulations for vehicles and pollution problem. As a method for solving traffic jams, one of the traffic problems of late, interest in Intelligent Traffic System(ITS) is increasing sharply, which is a system managing traffic demand by providing passers with information on traffic state of path and road conditions before they pass the road through ATIS, a field of ITS. METHODS: Variable message signs(VMS) is used on the roads as a method for providing information to promote smooth traffic flow and safety and prevent traffic accidents in advance by providing drivers with various information while driving. RESULTS: Recently, as ITS industry has been vitalized and technical factors of VMS have developed, various kinds of information is provided but the effect of VMS has not been maximized due to its limited type. CONCLUSIONS: Therefore, this study intends to provide methods for effective information transfer by analyzing driver's visual behavior characteristics for VMS and presenting a basis for maximizing VMS effect after considering read by expression type.

• KCID journal
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• v.18 no.1
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• pp.4-17
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• 2011

The standard design methodology was suggested to construct wetland system for reducing non-point source pollution from Saemangeum reclaimed paddy land. To set for the design flow and concentrations, runoff and water quality survey were conducted during the irrigation period in 2008 at Gyehwa reclaimed paddy land located at near Saemangeum lake. It is rational that 1ha is the optimum constructed wetland size. To meet this size, the moderate drainage area of reclaimed paddy field was 50ha under the conditions that rainfall is 30mm, average runoff coefficient is 0.83, and runoff capture ratio is 0.6. At these condition, the runoff volume from 50ha was 10,520 $m^3/d$ including base flow during irrigation period. To select the optimum wetland system, several case studies were conducted by focusing on the tidal reclaimed land areas having wetland systems in Seokmun. Pond-Wetland system was selected as the standard model because of showing the highest reduction efficiency. Single variable regression equation were delivered to estimate effluent water concentrations from the designed wetland by using long-term monitoring data from the Seokmun experiment site. The effluent concentration from the designed wetland using these equation were showed moderately range.

• International journal of advanced smart convergence
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• v.11 no.3
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• pp.206-214
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• 2022

Automobile manufacturers in each country are spurring the development of electric vehicles that use electric energy, an eco-friendly energy, as a futuristic vehicle. Electric vehicles have the advantage of no harmful gas or environmental pollution and low noise. Unlike automobiles using existing internal combustion engines using fossil fuels, electric vehicles use the electricity of batteries to cause rotational motion of motors. In the electric vehicle driven by the motor, it is indispensable to develop a controller for controlling the motor. One of the areas where automobile manufacturers are concentrating is the development of small electric vehicles as a personal transportation means. Small electric vehicles such as electric motorcycles, one-seat electric vehicles and two-seat electric vehicles are expanding the market as a means of operating throughout the city. In the domestic road conditions with many hills, it is effective to have a separate transmission system for small electric vehicles to drive smoothly. In this study, we propose a new type of continuously variable transmission(CVT) system to ensure that small electric vehicles can be driven smoothly in hilly domestic terrain. The proposed CVT system is equipped with a basic disk and a rotational disk in the driving pulley and the driven pulley, respectively, and is applied with a sloping spline to rotate the rotational disk. To commercialize the proposed CVT system, an experimental device was developed to examine the power transmission efficiency and the configuration of the CVT system was proposed.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.1
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• pp.36-44
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• 2015

The spatial and temporal distribution of dissolved trace metals has been studied to identify trends in space and time and to evaluate the pollution status in a semi-closed bay (Gohyun bay), Korea. Surface seawater samples were collected over four seasons at 18 stations in the bay between 2003 and 2004 and once at 7 stations around a large shipyard in May 2004. The concentration of Cd, Co, Cu, Ni, Pb, and Zn in seawater in February and May were highly variable in space, showing the higher value relative to other season. Those metals concentrations were decreased from inner-to outer-stations. In around the shipyard, Cu, Pb and Zn showed the higher variability depending on time. Cu and Zn concentrations at the sites around the shipyard had 2 times higher values compared with the average of inner stations in Gohyun bay. The very high correlations between salinity and either Cu and Zn has been showed. Especially, there was a significant relationship between Cu and Zn. We recognize that the shipyard is major source of Cu and Zn in seawater. Therefore, marine environment management policy such as the prevention and control of heavy metal input from a shipyard is required.