• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.03b
• /
• pp.623-630
• /
• 2000

In this study, it was to investigate the possibility to use the converts slag, by product in producing steel as a substitute material with sand that is used fur a civil construction materials, in developing techniques to use converts slag to improve soft clay ground. To do this, it was investigated the physical and mechanical properties of the converts slag as a civil construction material. For this, cylindrical cell consolidation with a single vertical drains and large scale soil box test were performed. Through large scale soil box test, the applicability of the converts slag to the present vertical drain techniques which is dependent on sand and plastic drains was studied. As a result of that, it was found that the shape of inserted drains was maintained after completing a consolidation process of a soft clay with slag drains. In addition, we could find that the slag drains showed the similar results with sand drains in soft clay by analyzing the effect of acceleration of consolidation.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.5
• /
• pp.59-66
• /
• 2004

This study compared the reinforcing effect of sand by Geocell to those of newly devised Tirecell$^{\circledR}$ made by waste tires, tire mat by sidewalls of tires. Plate loading tests in a large chamber were conducted for different reinforcing materials at the same conditions of relative density, embedded depth of sand. The combination of Tirecell and sidewall gives the highest increase of bearing capacity and reduction of settlement. The Geocell with the same height of Tirecell gives similar reinforcement effect to the tire mat made by sidewalls.

• The Journal of the Korean dental association
• /
• v.56 no.8
• /
• pp.424-431
• /
• 2018

Silver diamine fluoride (SDF) is an alkaline topical solution and it derives from the conjunction of silver nitrate and fluoride. It reduces the growth of cariogenic bacteria, inhibits degradation of dentinal collagen, impedes demineralization and enhances remineralization. It is inexpensive due to the low cost of materials and its application to dental surface is very simple and requires relatively short chair time. Previous studies have shown that the dental caries prevention effect of SDF is superior or similar to topical fluoride application. The main disadvantage of SDF is its esthetic result, and it permanently blacken carious enamel and dentin. The use of SDF has not yet been approved in Korea, but it may be helpful to prevent and treat dental caries in patients with special health care needs and uncooperative young patients.

• Korean Journal of Health Education and Promotion
• /
• v.10 no.2
• /
• pp.22-31
• /
• 1993

Presently, in the countries, such as America and Japan which are better in socio-economical conditions than Korea, in Taiwan which is similar in them to us, and even in Thailand and Philippine which are thought lower in them, health education is taught as one of curricular subjects in elementary and secondary school levels. In Korea, however, the importance of teaching health education as a curricular subject has been recognized among many professionals of health since a long time ago. Along with current rapid development of polytechnique and industry, various kinds of serious health hazard have appeared even in our daily life, so it has been urgently needed that people have comprehensive knowledge and skills to resolve one's own health problems. Among various conditions needed to resolve the health problems in our society, it is one of the most effective precedures that health education is taught as a curricular subject at least in elementary and secondary school levels. For this, the followings are inevitable ; reformation of school health organization and laws involving health, development of teaching materials in health and training of health educators.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2002.04a
• /
• pp.223-238
• /
• 2002

This paper presented on an environment estimation of cutting fluid which is a mouse model of acute bacterial rhinosinusitis using cutting fluid in grinding and cutting. Above results will be remarked the necessity of friendly environmental cutting skill when it had used in workshop. The results of a mouse experimental using cutting fluid showed that it are occurred to the respiratory organs sickness. Also cutting fluid are occurred to hurtfulness a person when it used to grinding and cutting in workshop. Also, the results of grinding experiments in avitation materials showed that surface roughness are superior to more emulsion type oil than vegetable type oil according to increase of the depth of cut. Grinding force are similar to both emulsion type oil and vegetable type oil.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2004.04a
• /
• pp.124-128
• /
• 2004

By the use of a similar numerical method as that in the previous paper, the forming limit strain by coaling method of clad sheet metals is investigated, in which the FEM is applied and J2G(J$_2$-Gotoh's corner theory) is utilized as the plasticity constitutive equation. Declined Multilayer Metals Materials are stretched in a plane-strain state, with various work-hardening exponent n-values and thicknesses of each layer. Processes of shear-band formation in such composite sheets are clearly illustrated. It is concluded that, in the bonded state, the higher limiting strain of one layer is reduced due to the lower limiting strain of the other layer and vice versa, and does not necessarily obey the rule of linear combination of the limiting strain of each layer weighted according thickness.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2004.04a
• /
• pp.48-52
• /
• 2004

Ultrasonic machining is effective for machining of extreme hard and brittle materials, including glass, ceramic, carbide, graphite. The major machining principle involves the direct hammering as well as the impact of abrasive panicles on the workpiece. Also, it involve cavitation erosion. The general workpiece is flat side. This study attempted micro hole machining of a curved surface of glass tube. Ultrasonic machining is fault of the slow machining speed. An experiment does and got 16 seconds validity machining time as increasing the processing speed. Moreover, entrance crack and surface roughness was similar both machining speed is slow and fast. Several micro hole of glass tube machined using one micro tool, but tool wear is infinitesimal.

• Research in Mathematical Education
• /
• v.15 no.3
• /
• pp.251-259
• /
• 2011

Metaphor is the main representations of teachers' practical knowledge, which can help students to understand mathematics better. Through the recording and quantitative analysis of video cases of expert teachers in mathematics classroom, there are some results after analysis: 1) Teachers use many metaphors in the classroom and most of that are structural-ontological metaphors, which takes a certain period of time. 2) Teachers use the metaphors mainly in the teaching process of introduce and explore by the form of question-answer. 3) During the process of concept teaching, the metaphors from the real-world examples can promote the students have more motivation to study. During the process of procedure teaching, the metaphors from similar materials can promote the students to understand the operational skill better.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.18 no.1
• /
• pp.120-126
• /
• 2010

It was known that the excellent wear resistance of hyper eutectic aluminum alloy is based on the primary Si particles which are distributed in the base metal. When the primary Si volume fraction increases, the smaller size have excellent wear resistance characteristics. However, this trend always does not match. There is no investigation result based on the materials and methods for real using parts. In this study, using the automotive parts manufacturer currently in use hyper eutectic Al alloy tensile test specimen type sample was fabricated by 350Ton high pressure die-casting machine. Then, fluidity, tensile, impact and wear resistance properties were evaluated. If the casting quality, primary Si size, fraction and distribution are similar, mechanical properties and wear resistance are equivalent.

• Analytical Science and Technology
• /
• v.25 no.6
• /
• pp.345-349
• /
• 2012

Polysilane black powders were synthesized by sonochemical methods from silicon tetrachloride with sodium metal with 37.0% yield. Those black powder materials were found to have fibrous or irregular shapes with round surface. It was found that thermal behaviors of those polysilane black powders were similar to that of hydropolysilanes which was reported earlier. After thermal treatment, black polysilicon was obtained with 57.1% residue yield, and those fibrous or irregular shapes with round surface were intact but lots of small cavities were formed indicating porous structure, and found to be an amorphous state from XRD analysis.