• Transactions of Materials Processing
• /
• v.18 no.5
• /
• pp.410-415
• /
• 2009

Experimental and numerical studies were performed to examine the effect of material temperature and reduction ratio on friction coefficient during hot flat rolling. We carried out a single pass pilot hot flat rolling test at the temperatures range of $900{\sim}1200^{\circ}C$ and measured the spread of deformed material while reduction ratio varied from 20% to 40%. Materials used in this study were a high carbon steel and two alloy steels. The dimension of specimen used in hot rolling experiment was $50mm{\times}50mm{\times}300mm$. We performed a series of finite element simulation of the hot rolling process to compute the friction coefficient change in terms of steel grade and reduction ratio. Results showed that temperature dependency of friction coefficient is not noteworthy but the effect of reduction ratio on friction coefficient is quite large. For high carbon steel, friction coefficient at reduction ratio of 30% is lower than that at that of 20%. Meanwhile friction coefficient at reduction ratio of 40% was one and half times large compared with that at that of 20%. The effect of steel grade on friction coefficient was significant when reduction ration was large, e.g., 40%.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.43 no.1
• /
• pp.65-73
• /
• 2011

The fibrous raw materials in packaging-grade paper production in Korea were mainly obtained from waste paper. The use of recycled paper has both positive and negative impacts in papermaking process. The primary positive impacts are the environmental protection and manufacturing cost reduction, and the negative impacts are the quality reduction in paper quality and the accumulation of heavy metals and other pollutants in wet- and dry-end process. This study was carried out to consider the optimum acid decomposition system with the highest recovery rate for the analysis of heavy metals in packaging-grade paper. The open digestion system using Kjeldahl apparatus and the closed digestion system using microwave oven for decomposing the organic materials in paper were compared. In both open and closed digestion method, the combination of nitric acid, hydrochloric acid and hydrogen peroxide showed higher recovery rate than using only nitric acid alone because the presence of Cl- ions in hydrochloric acid stabilizes ligand formation with metal ions. KOCC was observed to have the highest heavy metal content among the recycled paper samples. The heavy metal contents decomposed with the closed digestion system were relatively higher than with open digestion system.

• Transactions of the Korean hydrogen and new energy society
• /
• v.31 no.6
• /
• pp.637-645
• /
• 2020

In this paper, entransy analysis is carried out for combined heat and power (CHP) generation system driven by low-grade heat source compared with energy and exergy analyses. The system consists of a regenerative organic rankine cycle (ORC) and an additional process heater in a series circuit. Special attention is paid to the effects of the turbine inlet pressure, source temperature, and the working fluid on the thermodynamic performance of the system. Results showed that the work efficiency of entransy is higher than that of energy but lower than that of exergy, wheress the process heat efficiency of entransy is lower than that of energy but higher than that of exergy. Entrance analysis showed the potential to complement the exergy analysis in the optimal design of the energy system.

• Transactions of the Korean hydrogen and new energy society
• /
• v.32 no.1
• /
• pp.77-85
• /
• 2021

In this paper, entransy analysis is carried out for combined heat and power (CHP) generation system driven by low-grade heat source compared with energy and exergy analyses. The system consists of an organic Rankine cycle (ORC) and an additional process heater in a parallel circuit. Special attention is paid to the effects of the source temperature, turbine inlet pressure, and the working fluid on the thermodynamic performance of the system. Results showed that the work efficiency of entransy is higher than that of energy but lower than that of exergy, wheress the process heat efficiency of entransy is lower than that of energy but higher than that of exergy. Entrancy analysis showed the potential to complement the exergy analysis in the optimal design of the energy system.

• Journal of Korean Elementary Science Education
• /
• v.28 no.2
• /
• pp.178-186
• /
• 2009

The science writing is recognized for useful learning method to boost up scientific thinking for all class course as well as traditional lecture and experiment. Many researches say that science writing is helpful to extend students' science knowledge and scientific attitude. By the way, the researchers thought that science writing can also improve the science process skill if students participate in delicately organized learning program. In this study, we had contrived the teaching & learning strategy of science writing to improve science process skills. The learning program covers all field of Klopfer's process skills with various forms of writing; explaining writing, logical writing, critical writing, and creative writing. The learning program has been developed for 5th grade students in the regular classes in order to enhance science process skills as well as knowledge and scientific attitude. Not to miss any process skill or various kinds of writing, we used 3 dimensional frame. The axes of the frames are science process skills, forms of writing, and science curriculum contents. The students are given the final writing theme at the beginning of each chapter. They drill science process skills step by step during the classes, and have a chance to talk each other before the final writing. They practice writing skills from one sentence to full article by degrees. The effect of the program was examined by students' work and TSPS (Test of Science Process Skill). The result showed that 5th grade students had a meaningful progress in science process skills as well as knowledge and scientific attitude. we could confirm it with examining students' work in the class.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.14 no.2
• /
• pp.19-24
• /
• 2015

Gears are produced through a variety of methods. In general, a metal piece is formed into the general shape of a gear through rough cuts. The gear then moves on to a more precise machine that removes more material. Grinders work via abrasion, rubbing a rough surface against a work piece at such high speeds that it literally scrapes unwanted material away from the item. Since the grinder is spinning so fast, the material is removed very quickly. This allows a grinder to remove a very small amount without taking any unwanted material with it. This study investigates the effect of grinding process parameters like grinding spindle speed and table transfer speed on the gear grade and grinding efficiency.

• Textile Coloration and Finishing
• /
• v.29 no.4
• /
• pp.276-283
• /
• 2017

The aim of this study is to develop an effective dyeing process for black color on the silk fabrics, using natural Indigo, Madder, Amur cork tree, Alder, Logwood, and Gallnut. All natural dye materials were water-extracted, concentrated, and freeze-dried. Seven different processes were carried out and the color differences(${\Delta}E$) of black color with each process from the chemical black dyed fabric were compared. The light, washing, and rubbing fastness were evaluated. The black dyeing of the silk fabrics was well carried and excellent black color was obtained in every methods. The profound black color could be obtained by the subtractive mixture of the three primary colors of red, yellow, and blue in the order of indigo(blue) - amur cork tree(yellow) - madder or lac(red). Black color was efficiently obtained by iron mordant when logwood or alder fruit was used. The color difference(${\Delta}E$) from the black color with chemical dyestuff was the lowest in the indigo - amur cork tree - lac - iron method. Light fastness and washing fastness were excellent in all dyeing processes, showing grade 5. The fastness to rubbing was excellent as shown grade 5 in the dry samples of logwood - iron process and alder fruit - iron process.

• Journal of Gifted/Talented Education
• /
• v.7 no.2
• /
• pp.69-92
• /
• 1997

The purpose of the study was to evaluate the effects of the enrichment program for the gifted on gifted childrens development of the logical thinking and science process skills. The enrichment program consists of 200 enrichment courses in language arts, mathematics, sciences, social sciences and thinking for children at the age of 30 months to Grade 8. Enrichment programs are characterized as process-oriented, student-choice available, activities-oriented, open-ended, and interdisciplined. Subjects were 123 gifted children from Grade 1 to 3 at the Korean Academy of Gifted Education (KAGE), whose IQ scores were above 130 at their entry point to KAGE. Children were divided into two groups depending the duration of the program participation. Older Group participated in the program for longer than 13 months, while Newer Group did for shorter than 12 months. Mean of IQs of the two groups were not significantly different. They were tested on Logical Thinking Test and Integrated Process Skills Test revised by KEDI into Korean version in 1991. Descriptive statistics were calculated and group differences were analyzed with t-test, and scheffe test. The main finding were as follows: There were not significant differences between gender. Children in higher grades showed higher level of development. Older groups showed significantly higher level of logical thinking level of development. Older group showed significantly higher level of logical thinking and process skills than the Newer group inspite of the similar IQ levels to each other. The longer the gifted child participate in the enrichment program, the higher the development of childrens thinking skills.

• The Mathematical Education
• /
• v.53 no.4
• /
• pp.493-507
• /
• 2014

The purpose of this study is to analyze how high school students form and interpret the mental image in the process of solving regular polyhedron problems. For this purpose, a set of problems about the regular polyhedron's vertex is developed on the base of the regular polyhedron's duality and circulation. and applied to 2 students of the 12th graders in D high school. After 2 hours of teaching and learning and another 2 hours of mental image-analysis process, the following research findings are obtained. Fisrt, a student who recorded medium high-level grade in the national scholastic test can build the dynamic image or the patten image in the process of solving regular polyhedron's vertex problems by utilizing the 3D geometry program. However, the other student who recorded low-level grade can build the concrete-pictorial image. Second, pattern image or dynamic image can help students solve the regular polyhedron's vertex problems by proper transformation of informations and the mental images while the concrete-pictorial image does not help. Hence, it is recommended that the mathematics teachers should develop teaching and learning materials about the regular polyhedron's duality and circulation and also give students suitable questions to build the various mental images.

• Journal of Environmental Science International
• /
• v.29 no.12
• /
• pp.1185-1198
• /
• 2020

This study aimed to suggest a framework for biotope classification and evaluation based on habitat values to rationally establish management areas of national parks. The factors and indicators related to the biotope classification and evaluation were established based on integration from those of previous studies. The decision tree evaluation process was applied to the classification and evaluation of the biotope type level. The evaluation of the biotope group level was carried out to determine the weight and the AUEM (Adding Up Estimation Matrix) was applied for the final grades. As a result, the biotope type of Seolaksan National Park was classified into 43 types and Odaesan National Park was classified into 41 types. Bukhansan National Park, which is located in a metropolitan city, was classified into 49 types. In terms of biotope evaluation, grade III had a ratio of 50.6%, the highest in Seolaksan national park. The ratios of grade I and grade II, which have great ecological-value, were respectively 12.0% and 36.5%. Grade II was 48.2%, the highest ratio in Odaesan National Park. The ratios of grades I and II were 10.8% and 37.9%, respectively. Grade III was 54.8%, the highest ratio in Bukhansan national park, and the ratios of grade I and grade II, which have great ecological-value were, respectively, 11.4% and 25.7%. The biotope values of major national parks were evaluated according to the type focusing on the actual vegetation. This framework can be considered for application to the spatial management of other types of protected areas.