• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.645-654
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• 1989

Specimens of WC-Co were indented to measure the resulting crack size and unindented samples were fractured in 3-point flexure to obtain the strength and to measure characteristic features on the fracture surface. Fracture toughness was determined using fractography and compared to those determined using identation techniques. We show that principles of fracture mechanics can be applied WC-Co composites and can be used to analyze the fracture process. The fracture surfaces were examined by scanning electron microscopy and optical microscopy. Characteristic feature observed in glasses, single crystals and polycrystalline materials known as mirror, mist, hackle, and crack branching were identified for these composites. We discuss the importance of fracture surface analysis in determining the failure-initiating sources and the failure behaviorof WC-Co composites.

• Journal of Environmental Health Sciences
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• v.24 no.3
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• pp.48-53
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• 1998

Chitin is known as biodegradable natural polymer. But, in spite of various application of chitin from waste marine sources, commercial use of chitin has been limited due to highly resistance to chemicals and the absense of proper solvents. We made various viscosity of chitosan from chitin by change of Mima's method through the deacetylation which is various condition of NaOH concentration, reaction time and temperature. Also, Polyvinyl alcohol/chitosan blend films were prepared by different solution blends containing the ratio of 5, 10, 15 and 20% chitosan and low, medium, high molecular weight of chitosan to find a more useful biodegradable polymer. Thermal and mechanical properties of PVA/chitosan blend films such as DSC, impact strength, tensile strength and morphological changes by SEM were determined. The 10-15% PVA/chitosan(low, medium) blend films were similar to PVA. Also, PVA/chitosan blend films at the laboratory soil test(Pot Test) were completely degraded in month with four kinds of soils by microorganisms.

• Culinary science and hospitality research
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• v.3
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• pp.327-341
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• 1997

Food materials usually contain much water, and thus are susceptible to decay be enzyme and microorganism. Cereals are usually consumed as staple food, but they have low protein content. Protein is a major component of body, and should be consumed as a nutrient for all ages. Animal protein like chicken and vegetable protein such as bean curd and soybean and good sources of high quality protein. Bean curd is a traditional food which have good nutrients, and so various cooking methods are needed to be developed for the supplement of high quality food. 1) Cereals such as rice, barley, and bean curd, soybean, green vegetables, tangle and brown seaweed are known as food for long life. 2) Soybean is able to suppress the formation of hydroperoxide by saponin and lecithin. 3) Curd in bean curd means soft in Chinese character, and bean curd may be the mother of cheese. 4) Bean curd have high nutrition and digestibility. As soybean is dipped longer in water for bean curd, the production rate is higher. 5) There are many kinds of bean curd products, and can be purchased inexpensively.

• Journal of Marine Bioscience and Biotechnology
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• v.1 no.1
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• pp.9-21
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• 2006

Foods and related substances from diverse sources known to have a potential for disease risk reduction are called functional foods, while nutraceuticals are bioactive compounds isolated from food and sold in dosage form. Nutraceutical and functional food industries are rapidly growing in recent years and most of the cases development of these functional materials involves certain biotransformation processes. A number of bioactive compounds has been identified up to date and isolated from seafood related products through enzyme-mediated hydrolysis. The enzymatic bioconversion process require suitable biocatalysts and appropriate bioreactor systems to incubate byproducts with digestive enzymes. Membrane bioreactor technology is recently emerging for the development of bioactive compounds from seafood processing byproducts.

• Communications of the Korean Mathematical Society
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• v.12 no.1
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• pp.193-201
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• 1997

The paper presens results on the perturbation problem of invariant manifolds of differential equations. It is well-known that if there is a pseudohyperbollic structure on an invariant manifold then one is strongly indestructible. The set of strongly inderstructible invariant manifolds is wider than the set of persistent (normally hyperbolic) manifolds. The following theorem is main result of the paper: if the condition of transversality holds on an invariant manifold, except, possibly, for the non-degenerate strong sources and non-degenerate strong sinks, then there is the pseudohyperbolic structure on the invariant manifold. From this it follows the conditions for the indestructibility of locally non-unique invariant manifolds. An example is considered.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1187-1190
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• 2007

This study aims to induce acoustic environmental characteristics which could be used for soundscape design by carrying out factor analysis on sound source image and cognition analysis on subjects' responses on selective questions due to class differences. The results of this study are as follows ; Satisfaction rate differences on exterior acoustic environment due to sensitivity and residence year were revealed. After factor analysis of living sound sources' image, it is known that natural sound, traditional sound, socials traffic sound, rural sound, religious sound and the others are main factors. Social traffic sound is the most one that should be eliminated and traditional sound is selected as a most Korean-like sound. Natural sound is evaluated as the most one that should be preserved and the most retrospectively one.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.802-805
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• 2007

The exhaust system, including a muffler, is one of the major sources to generate the radiated noise of construction equipment. The muffler is generally known that it reduces the exhaust noise level, but it sometimes increases the noise level because of the flow effect inside a muffler. So, it is required to consider the flow effect inside a muffler to reduce the exhaust noise level of construction equipment. In this paper, an experimental method to consider a quantitative flow effect inside a muffler was set up through a series of tests. Finally, the experimental result was verified through the flow noise analysis using CFD analysis result. These results make it possible to understand the dynamic characteristics of the flow noise and to design the low noise muffler for the construction equipment.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.354-356
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• 2011

Renewable energy resources such as wind, wave, solar, micro hydro, tidal and biomass etc. are becoming importance stage by stage because of considering effect of the environment. Solar energy is one of the most successful sources of renewable energy for the production of electrical energy following solar energy. And, the solar/photovoltaic cell generators depend on the solar radiation, which is a random variable so this poses difficulty in the system scheduling and energy dispatching, as the schedule of the photovoltaic cell generators availability is not known in advance. This paper proposes to use the two-layered artificial neural networks for predicting the actual solar radiation from the previous values of the same variable.

• Journal of Preventive Medicine and Public Health
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• v.12 no.1
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• pp.99-106
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• 1979

Accessibility to medical facilities and personnels has been known as one of important determinants of medical care utilization. This study attempted to identify the effects of medical accessibility in terms of geographical distance and occupational opportunity to the medical utilizations. Two-year-experiences of Yonsei University Health Insurance Cooperatives were used as the sources of data. Out patient utilization patterns of 713 members sampled from 4,352 members of Health Insurance Cooperatives were analyzed in order to identify the effects of medical accessibilities. Findings: 1 Average clinic visit rate of Yonsei Health Insurance is 1.66 per person per year. 2. The utilization rates of geographically more accessible group were 33% higher than that of less accessible group. 3. No marked difference in clinic visit rate were observed between medical and non-medical personnel and their family members. 4. Clinic visit rates among occupationally accessible group were slightly higher than those of less accessible. The utilization rate was more sensitively changed by the insurance policy changes in occupationally accessible group.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.346-351
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• 2002

Noise of the VVVF inverter and DC/DC converter, which are the most dominant noise sources of maglev train at low speed, is studied, The coils inside inverter and converter are excited by electro-magnetic forces, which results in core vibration and generations of the noise. It is found that the spectra of the noise show many harmonics, where there exist several different fundamental frequencies. Some noise reducing techniques are known for the transformer noise such as changing stiffness and using different core materials, which make less electrostatic responses, and consequently less noise. In this study, it is shown that the most effective and feasible noise reducing method is to increase the switching frequencies of the inverter and converter, where peaks in higher frequency are significantly reduced.