• Journal of the Korean Society for Precision Engineering
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• v.13 no.1
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• pp.78-83
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• 1996

This paper presents the characteristics of surface roughness and cutting force in ultraprecision cutting of aluminium alloy using natural diamond tools whose edge radii are smaller than those of tools made of other materials. The feed rate and depth of engagement were set to be a micrometer order. After measuring the surface roughness of machined surface and cutting force for each cutting condition, the relations between the surface quality and its condition were investigated qualitatively. If the feed rate was under a certain limit, the machined surface quality was deteriorated unexpectedly. This is supposed to have happened due to vibration leading its condition to abnormal one. In a certain situation the machined surface roughness by a natural diamond tool was inferior to that made by a carbide tool whose cutting edge radius is larger. This is supposed to be caused by not normal machining but burnishing effect.

• Journal of Korean Society of Rural Planning
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• v.7 no.2 s.14
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• pp.55-64
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• 2001

The objectives of this study were 1) to evaluate the environmental and social cultural public benefits but a food supply, 2) to revalue the importance of rural and rural living, This study was carried out through review of literature, a delphi technique, a case study. It was mainly used the delphi technique by expert group. Major findings were as follows ; 1. The public benefits in rural were classified into three categories:(1) social culture (2) natural environment (3) economic & etc. 2. To evaluate the values for public benefits, questionaries were developed by expert group, and the total number of items were 30. 3. There were picked out 12 items on social culture, 10 items on natural environment, and 8 items on economic & etc of public benefits in rural. 4. In the public benefits, a food supply was highest in total 30 items, and water resources contain, emotional-psychological rest, place of environment education, beautiful view, etc were followed in order.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.176-180
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• 2006

When the vibration troubles occur on the ship structure during the sea trial, the rectification work is very restricted because of in-situ limitation. Usually, the finite element method is used to improve vibration characteristics of the structure, but it takes lots of time and effort in modeling the structure and adjusting the finite element model in order to consider appropriate boundary conditions of a complex ship structure. Therefore, experimental methods have been in general suggested to obtain proper countermeasures without time-consuming in modeling. In this paper, FRE(frequency response function) synthesis method is applied to estimate natural frequency of the modified ship structure, which is obtained from experimental and numerical methods.

• Steel and Composite Structures
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• v.34 no.4
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• pp.615-623
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• 2020

In this paper, free vibration analysis of a functionally graded cylindrical nanoshell resting on Pasternak foundation is presented based on the nonlocal elasticity theory. A two-dimensional formulation along the axial and radial directions is presented based on the first-order shear deformation shell theory. Hamilton's principle is employed for derivation of the governing equations of motion. The solution to formulated boundary value problem is obtained based on a harmonic solution and trigonometric functions for various boundary conditions. The numerical results show influence of significant parameters such as small scale parameter, stiffness of Pasternak foundation, mode number, various boundary conditions, and selected dimensionless geometric parameters on natural frequencies of nanoshell.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.6
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• pp.743-757
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• 2006

Volatile organic compound (VOC) has been well-known to Korea since the end of 1990's however, it has not been well documented until now. In this study, present ambient VOC levels, VOC emission sources, and VOC control technologies were reviewed and discussed. In addition, VOC management strategies to cut down ozone concentrations were suggested based on the present VOC database. For anthropogenic VOC reduction, VOC emitted from painting processes and automobiles should be controlled in the first place in large cities such as Seoul, Daegu, and Incheon. For natural VOC management, low emission trees need to be planted in those cities. It is also very significant to keep updating present and future VOC emission inventories for efficient VOC control strategies. As a conclusion, more systematic VOC control road-map based on BACT (best available control technology) needs to be made up. and more economical and efficient VOC control techniques have to be developed under strong national support in order to lower toxic VOC and photochemical oxidant levels.

• Textile Coloration and Finishing
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• v.9 no.5
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• pp.10-18
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• 1997

In order to study the properties of safflower yellow colors, thermodynamic parameters and dyeing properties on the silk in several dyeing conditions were investigated. The uv-visible spectra of safflower yellow colors in several solvents show hypsochromic shift with the polarity of solvent but bathochromic shift with increasing acidity of solution. The apparent diffusion coefficients and standard affinities of dyeing increased with the increase of dyeing temperature. The standard heat of dyeing(${\Delta}H^0$), entropy change(${\Delta}S^0$) and activation energy($E_{act}$) were calculated to be - 1.144kcal/mol, -7.498(5$0^{\circ}C$)~-3.804(9$0^{\circ}C$)cal/molㆍdeg and 0.123kcal/mol, respectively. The concentration of safflower yellow colors in the silk fiber increased with dyeing temperature, time, concentration of colors and acidity of initial dyebath. Silk fabrics were dyed bright yellow by pre-mordanting with tin chloride. Lightfastness of silk fabrics pre-mordanted by tin chloride was not excellent.

• Design & Manufacturing
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• v.12 no.1
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• pp.31-35
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• 2018

The peltier thermoelectric module are used to cool the heat generated by electronic equipment. In order to increase the efficiency of the peltier thermoelectric module, the heat must be released to the outside. A heat sink is used to discharge such heat to the outside. in this paper, two types of heat sinks with internal tunnels were designed. And the heating and cooling performance of the heat sink with internal tunnel structure was compared and analyzed through ANSYS. The heat sink of the A type had better heat transfer than the heat sink of the B type. Which is about 70% improved.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.1
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• pp.26-30
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• 2010

The present paper studies the thermally-induced vibration phenomenon of the flexible space boom structure. In order to simulate the thermally-induced vibration phenomenon of the flexible thin boom structure of the spacecraft with the attached tip mass in space, the thermally-induced vibration including thermal flutter is experimentally investigated at various thermal environments using a heating lamp in vacuum chamber. In this experimental study, fluctuating characteristics, natural frequency and thermal strains of the thermally-induced vibration are parametrically investigated at various thermal environment conditions. Finally the thermally-induced vibration of the flexible boom structure of the orbiting earth satellite in solar radiation environment from the earth eclipse region including umbra and penumbra is simulated using the power control of the heating lamp in the vacuum chamber.

• Proceedings of the Korean Society for Environmental Edudation Conference
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• 2002.12a
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• pp.79-85
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• 2002

Inquiry activity contents presented at a chapter on natural environment and our lives in 6 science textbooks of the middle school were analyzed based on kinds of the inquiry Loaming classified by textbook. The number of inquiry activity subjects showed severe variation as mean value was 8.3${\times}$3.7 ranged from 4 to 15. Moreover, textbooks had little common point among each other as the percentage of subjects appeared together in the textbooks more than 3 kinds, 50% of total ones investigated, was just 26.3%. Data interpretation occupied significant position in the inquiry activity as 42% of total activity contents, whereas observation and experiment (or survey) did slight part of the activity as 10% and 16%, respectively even though they are main factors of science education. A model for field education based on the reasonable common subjects was prepared in the Gildong ecological park located In the eastern fringe of Seoul as a plan in order to solve the problems.

• Structural Engineering and Mechanics
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• v.15 no.6
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• pp.705-716
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• 2003

Gradient elastic flexural beams are dynamically analysed by analytic means. The governing equation of flexural beam motion is obtained by combining the Bernoulli-Euler beam theory and the simple gradient elasticity theory due to Aifantis. All possible boundary conditions (classical and non-classical or gradient type) are obtained with the aid of a variational statement. A wave propagation analysis reveals the existence of wave dispersion in gradient elastic beams. Free vibrations of gradient elastic beams are analysed and natural frequencies and modal shapes are obtained. Forced vibrations of these beams are also analysed with the aid of the Laplace transform with respect to time and their response to loads with any time variation is obtained. Numerical examples are presented for both free and forced vibrations of a simply supported and a cantilever beam, respectively, in order to assess the gradient effect on the natural frequencies, modal shapes and beam response.