• Journal of The Korean Association For Science Education
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• v.17 no.1
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• pp.45-53
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• 1997

The purpose of this study was to investigate the instructional effects of a problem solving model on students' achievement, science process skills, and perceptions of science activities. The problem solving model was developed on the basis of the SSCS (Search, Solve, Create, Share) problem solving model while considering Korean educational situations under a national curriculum. The model developed is composed of 4 stages; identify, solve, create, and share. In this research, the treatment and control groups (6 classes) were selected from a middle school in Seoul and taught about the separation of mixture for four weeks. Prior to instruction, the Group Assessment of Logical Thinking and the Learning Approach Questionnaire were administered, and their scores were used as covariate and blocking variable, respectively. During instruction, classroom observations for each group were conducted with a researcher-made checklist. Immediately following the instructions, students' achievement, science process skills, and perceptions of science activities were measured by a researcher-made achievement test, the Middle Grades Integrated Science Process Skills Test(MIPT), and the Perceptions of Science Activities Questionnaire, respectively. The results indicated that students in the treatment group achieved significantly better than those in the control group. Although students in the treatment group were found to use more science process skills correctly during their science activities, the MIPT scores of the treatment group were not significantly higher than those of the control group. No interaction with students' learning approach was found for both students' achievement and science process skills. On the questionnaire of students' perceptions of science activities, the treatment group showed more positive perceptions and interest than the control group. Educational implications are discussed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.11
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• pp.1477-1485
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• 2018

There are two major issues for activated sludge process in sewage treatment plant. One is how to make sewage be more clean and the other is the energy saving in sewage treatment process. The major monitoring sewage qualities are chemical oxygen demand, phosphorus, nitrogen, suspended solid in effluent. These are transmitted to the national TMS(Telemetry Monitoring System) at every hour. If these exceed the environmental standard, the environmental charges imposed. So, these water qualities are to be controlled below the environmental standard in operation of sewage treatment plant. And recently, the energy saving is also important in process operation. Over 50% energy is consumed in blowers and motors for injection oxygen into aeration tank. So, with the water qualities to be controlled below the environmental standard, the energy saving also is to be accomplished for efficient plant management. Almost researches are aimed to control water quality without considering energy saving. AI techniques have been used for control water quality. AI modeling simulator provided the optimal control inputs(blower speed, waste sludge, return sludge) for control water quality. Blower speed is the main control input for activated sludge process. To make sewage be more clean, the excessive blower speed is supplied, but water quality is not better than the previous. In results, non necessary energy is consumed. In this paper we propose a new method that the energy saving also is to be accomplished with the water qualities to be controlled below the environmental standard for efficient plant management. Water qualities in only aeration tank are used the inputs of fuzzy models. Outputs of these models are chemical oxygen demand, phosphorus, nitrogen, suspended solid in effluent and have the environmental standards. In test, we found this method could save 10% energy than the previous methods.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.843-849
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• 2007

Monitoring of NOM characteristics is important for improving removal efficiency of natural organic matter (NOM) in water treatment processes. In this study, several NOM characteristics, which include specific UV absorbance (SUVA), total carbonate content, molecular weight distribution, and fluorescence properties, were measured using samples collected from a pilot-scale water treatment plant consisting of coagulation/flocculation (C/F), filtration, ozonation and granular activated carbon (GAC) processes. The highest removal of NOM was observed in C/F and filtration processes as demonstrated by the reduction of dissolved organic carbon (DOC) by 25% and 21%, respectively. Despite nearly no change in DOC, however, the lowest SUVA value and the highest total carbohydrate content were observed in the sample from ozonation process. This indicates that non-degradable aromatic compounds become depleted and biodegradable organic compounds are enriched during the process. Comparison of synchronous fluorescence spectra of the samples showed that ozoation process increased protein-like fluorescence while it decreased fulvic-like and terrestrial humic-like fluorescence. Consistently, a slight peak of protein-like fluorescence was observed in the sample from ozonation process. The greatest change in molecular weight distributions of the samples was observed in C/F process. Comparison of size exclusion chromatogram of the samples revealed that NOM fractions with the molecular weight greater than 2000 Da were reduced by over 90% after C/F process. SUVA values and total carbohydrate content of the samples were well correlated with a ratio of protein-like fluorescence and terrestrial humic-like fluorescence intensities with the correlation coefficients of 0.99 and 0.91, respectively. This suggests that synchronous fluorescence properties of NOM could be used as useful tolls for monitoring changes of some NOM characteristics during water treatment processes.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.105-112
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• 2005

This study aims at evaluating the environmental impacts stemmed from the End-of-Life Vehicle(ELV) treatment systems in Korea, using Life Cycle Assessment(LCA) method. In this study, both environmental burden from the ELV dismantling process & recycling processes and environmental benefit which were derived from the avoided environmental impacts by substituting recycled materials for virgin materials were considered. First of all, the key issues which were defined as the environmental aspects that account for more than $1\%$ out of the total environmental impacts were identified from the Life Cycle Impact Assessment(LCIA). $CO_2$, crude oil, natural gas, coal, etc. were found out to be the key issue parameters. From the LCI Analysis and LCIA studies, it was shown that the significant environmental aspects were related with the recycling process of ferro scrap, the shredding process of compressed car bodies and the dismantling process of end-of-life engines. In particular, the recycling process of ferro scrap has the most significant effects on the environmental impacts of the ELV treatment systems. Based on these results, it is recommended to improve the recycling process of ferro scrap in order to make the ELV treatment systems more environmentally sound.

• Journal of Powder Materials
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• v.11 no.1
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• pp.22-27
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• 2004

The Indium Tin Oxide(ITO) nano powders were prepared by spray drying and heat treatment process. The liquid solution dissolved Indium and Tin salts was first spray dried to prepare chemically homogeneous recursor powders at the optimum spray drying conditions. Subsequently, the precursor powders were subjected to eat treatment process. The nano size ITO powders was synthesized from the previous precursor powders and the npuities also were decreased with increasing heat treatment temperature. Furthermore, the lattice parameter of TO nano powders was increased by doping Tin into Indium with increasing heat treatment temperature. The par icle size of the resultant ITO powders was about 20∼50nm and chemical composition was composed of In:Sn =86:10 wt.％ at 80$0^{\circ}C$.

• Journal of Industrial Technology
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• v.26 no.A
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• pp.69-73
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• 2006

Mach peening treatment is one of the various kinds of techniques to improve the fatigue properties. The mach peening process gives high-level work hardening and compressive residual stress near the surface layer, improving the fatigue strength. In addition, this treatment reduces slip bands that initiate the fatigue cracks near the surface. During impingement, a plastic indentation surrounded by a plastic zone is formed. Mach peening treatment characteristic is less energy consumption and is an environmental friendly processing methods that is not accompanied by pollution. It is machining process that can prevent fatigue fracture beforehand in structure using already as well as process of production. The test results showed that fatigue crack propagation delay appeared by drilling type 43%, mach peening type 110%.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.3
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• pp.137-141
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• 2010

The Co-Cr alloys have clinical histories in dental and orthopaedic implants, and recently in cardiovascular stent applications because the alloys exhibit a high elastic modulus and radiopacity. In order to improve mechanical property of the Co-Cr alloys, electropolishing is employed as the final process. Electropolishing, an anodic dissolution process in the transpassive state, is sensitively affected by process conditions such as current density, machining time, electrode gap. In this study, the effect of heat treatment conditions on surface roughness and inclusion analysis is investigated in Co-Cr alloy (L605). The most smooth surface of Co-Cr alloy is obtained when electropolishing is performed at 15-20 V for 15-30 sec with a electrode gap of 3.5 mm.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.102-106
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• 2009

Thermal energy control is a important factor in a large size casting and forging. Good control of thermal energy makes characteristics and defect of large cast-forged part, such as large sized forged shell. We have studied about not only large size ring forging process and after heat treatment by FEM simulation. Also, changes of temperature and microstructure for forged shell were predicted. Therefore, we can choose the proper heat treatment condition by FEA. The sectional properties confirmed by practical experiment and evaluation have presented possibilities of process design by computational analysis.

• Clean Technology
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• v.18 no.4
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• pp.341-346
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• 2012

Many researchers have studied that many processes to effectively remove heavy metals in water/wastewater. Especially, among many processes, physical and chemical processes are relatively simple and obtain high treatment efficiency for removal heavy metals compared with biological treatment. Recently, interests in physical and chemical methods are sharply increasing again because of dangerousness for radioactive element. In this study, various physical and chemical processes such as chemical precipitation, ion-exchange, electrodialysis, and membrane separation are introduced.

• Proceedings of the KIEE Conference
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• 2007.04b
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• pp.61-63
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• 2007

In these days there are many troubles - system data error, control malfunctions, cable overheating - in water treatment plant. Specially DAF(Dissolved Air Floation Process) plant has high frequency than previous water treatment process. DAF plant has diverse equipment, nonlinear loads for the precise control. But there is no sufficient overall study about harmonics condition of water treatment plant just taking a following partial action without a fundamental solution. On designing of power system, designer should have regard to harmonics condition, but there is no guide reflected harmonics condition on DAF plant This study says what is the result of guideless design about harmonics. With the result of diagnosis and analysis in DAF plant, economical efficiency and safety of plant will be upgraded in the next design.