• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.2
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• pp.173-182
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• 1994

A numerical experiment on the effective discharge of waste materials caused in recirculating aquaculture basins was performed. The numerical model used in this study was a 4-level hydrodynamic and advection-diffusion model. Flow structures and settling processes of ss in the various mathematical model basins are discussed. The calculated flow fields of the numerical basin corresponded well with the measured velocity in field basin. In the cases of steep bottom slopes in 4/30, the non-dimensional tractive force($U{\ast}/U{\ast}_c$) which is all important parameter for the deposition pattern of waste materials was stronger than with the mild slope one. The settling pattern of ss depended considerably on the degree of bottom slope of basin. To concentrate deposited waste materials into the center discharge pipe, it is useful to design a cylindrical basin with a steeply conical bottom. In addition, to prevent movement of the deposit area away from the center, it is necessary to locate the circulating ducts at diametrically opposed points on the basin sides.

• Journal of the Korean Society of Combustion
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• v.16 no.4
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• pp.8-15
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• 2011

The present study investigates the combustion phenomena in a sludge incinerator using experimental and numerical method. The temperature and gas concentration were measured at 33 points during operation of the incinerator in order to assess the mixing and combustion characteristics. Numerical simulation was also carried out using a commercial CFD code. Simplified inlet conditions were introduced in oder to predict the bulk solid combustion and the diffusion of the volatile matter released by pyrolysis of sludge. The experimental results showed that the combustion process is extremely inhomogeneous. Large variations were observed in the temperature and gas concentrations in the freeboard of the incinerator due to poor mixing performance between the air and the combustibles, which is caused by massive and bulk generation of volatile matter by fast pyrolysis of sludge particles. The boundary condition of the CFD simulation was found effective in predicting the poor mixing and combustion performance of the reactor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.16-19
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• 1997

We have investigated the optical properties of a Ti:LiNbO$_3$ optical waveguide which was fabricated by Ti-diffusion in a alto atmosphere, and propose an effective method of polishing waveguide. This method was regarded to be applicable to waveguide fabrications.

• Advances in environmental research
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• v.1 no.2
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• pp.143-151
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• 2012

Nitrate removal from aqueous solution was investigated using $ZnCl_2$ and phosphoric acid activated carbon developed from pomegranate peel with particle size 0.4 mm. Potassium nitrate solution was used in batch adsorption experiments for nitrate removal from water. The effects of activated carbon dosage, time of contact, and pH were studied. The equilibrium time was fond to be 45 min. Two theoretical adsorption isotherms namely Langmuir and Freundlich were used to describe the experimental results. The Langmuir fit the isotherm with the theoretical adsorption capacity ($q_t$) was fond 78.125 mg g-1. Adsorption kinetics data were modeled using the pseudo-first, pseudo-second order, and intraparticle diffusion models. The results indicate that the second-order model best describes adsorption kinetic data. Results show activated carbon produced from pomegranate is effective for removal of nitrate from aqueous solution.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.09a
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• pp.51-54
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• 2001

This research was carried out to evaluate feasibility of using an Electrokinetic-Fenton(EK-Fenton) technique to treat hydrophobic organic pollutant(phenanthrene) from soils. Experiment examined the effect by introducing a continuous flow of a 3.5% hydrogen peroxide solution at the anode. An electric gradient of 1V/cm was applied to enhance the saturated flow in the soil cell for a period of 11 days. After 11 days or 1 pore volume, overall concentration of residual phenanthrene in the soil cell was 11% and residual phenanathrene concentration in the soil was found to increase with toward the cathode. This results indicated that Fenton-like reaction catalyzed by mineral surface was effective in oxidizing phenanthrene. This results also showed that hydrogen peroxide was effectively transported into the soil by electroosmotic flow as well as by diffusion.

• International Commerce and Information Review
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• v.4 no.2
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• pp.279-301
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• 2002

Lately, one of the most representative phases on business world is the diffusion of internet business. This change has been making new port business model called 'e-Port' in maritime transport. The focus of this article is to suggest some strategies on the implementation of e-Port in Korea. To research and analyze the e-Port realities, we first reviewed the previous study on Internet Marketing and e-Business. Six strategies that are critical on e-Port model were classified: (1) contents, (2) community, (3) commerce, (4) connection, (5) communication, (6) customization. Secondly, we chose and evaluated website of eight ports: Hongkong, Singapore, Antwerp, Hamburg, as successful e-port models. And then, we investigated actual conditions of e-Port in Pusan, Inchon, K wangwang, and Gusan. And then we try to find effective plan on the operation of e-Port.

• Asia pacific journal of information systems
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• v.16 no.2
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• pp.69-84
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• 2006

Importance of Today's diffusion of integrated hospital information systems is that various and huge amount of data is being accumulated in their database systems. Many researchers have studied utilizing such hospital data. While most researches were conducted mainly for medical diagnosis, there have been insufficient studies to develop medical care cost prediction model, especially using machine learning techniques. In this research, therefore, we built a medical care cost prediction model for cancer patients using CBR (Case-Based Reasoning), one of the machine learning techniques. Its performance was compared with those of Neural Networks and Decision Tree models. As a result of the experiment, the CBR prediction model was shown to be the best in general with respect to error rate and linearity between real values and predicted values. It is believed that the medical care cost prediction model can be utilized for the effective management of limited resources in hospitals.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.12 s.243
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• pp.1369-1376
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• 2005

Effective mixing gives strong advantageous impact on microfluidic applications since mixing is in general very slow process motivated by molecular diffusion transport only on the micro-scale. In this work, the mixing characteristics are analyzed in a Y-channel micromixer with obstacles. For the through analysis, our laboratory in-house unstructured grid CFD code is validated through solving a concentration transport in a uniform microchannel. The solutions well correspond to both exact solutions and those from MemCFD. Mixing in a Y-channel micromixer with obstacles is numerically investigated by the in-house code to search the optimal radius and layout of obstacles. From the simulations, the mixing efficiency appears to be proportional to the magnitude of the formation of lateral velocity component. It is also shown that the asymmetric layout and radius enlargement of obstacles greatly improves mixing efficiency.

• Journal of Mechanical Science and Technology
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• v.14 no.4
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• pp.426-432
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• 2000

The development of a low-pollution burner is important for saving energy and preserving the environment. A low-pollution burner can be produced by lean-mixture combustion and general combustion technology. The flammable limit of premixed flame is narrower than that of diffusion flame. Producing a lean mixture of fuel results in an effective combustion condition, which in turn produces high load and low pollution. In this study, it was found that the influx of $Q_2$ had an effect on extending the lean flammable limits and flame stabilization in a doubled jet burner. And the flame, consisting of small eddies, can be stabilized by the nozzle neck phenomena.

• Fire Science and Engineering
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• v.11 no.3
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• pp.3-14
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• 1997

An experimental investigation of smoke spread in a corridor is made using thermocouples and visualization technique with a laser beam sheet. A speed of smoke front under a ceiling is measured by thermocouple trees. Visualization of the ceiling jet formation and of smoke filling process is carried out to observe lowering of the smoke layer. From the results, a large-scale convective motion the corridor plays dominant roles for smoke spread from visualized photos together with temperature records. A circulating motion of fluid transports some smokes to some regions where its momentum is effective. It is therefore showed that the conventional concept of lowering smoke with two-layer zone model has some restrictions for the corridor because the lowering of smoke layer has been thought to be mass transport due to relatively small scale motion such as decrease of buoyancy, mass diffusion and momentum exchange.