• Korean Journal of Materials Research
• /
• v.32 no.1
• /
• pp.23-29
• /
• 2022

Fly ash is a by-product of coal fired electrical power plants and used as a material for cement and concrete; particularly, imported fly ash is mainly applied for cement production. Main objectives of this article are to replace domestic fly ash with an imported source. To verify the possibility of domestic fly ash as a material for cement from the aspect of chemical composition and physical properties, we manufactured various kinds of cement, such as using only natural raw material, shale, and partial replacement with domestic and imported fly ash. When we used the domestic and imported fly ash, there were no specific problems in terms of clinker synthesis or cement manufacturing in relation to the natural material, shale. In conclusion, domestic fly ash has been confirmed as an alternative raw material for cement because 7 days and 28 days compressive strength values were better than those of reference cement using natural raw material, on top of the process issue.

• International Journal of Korean Welding Society
• /
• v.1 no.2
• /
• pp.30-35
• /
• 2001

Nowadays, repair welding on in-service natural gas pipeline is a matter of primary concern of gas company. The main purpose of this study is to investigate the effects of welding conditions on the allowable heat input for crack-free welds and welds without burn-through onto in-service natural gas pipeline. First of all, single pass weld bead on plates of the various thickness was deposited to evaluate the penetration of weld metal, the depth of heat affected zone and the hardness of repair weld under various welding conditions. Also, finite element analysis has been conducted to validate experimental results of bead-on plate welds and to develop appropriate model for repair welding. The welding experiments of bead-on-plate weld confirmed the influence of plate thickness, heat input and welding process on safety. And, the finite element model was demonstrated by comparing experimental results. The agreement between the computed and measured values was shown to be generally good. Therefore, It is possible to predict the safety of repair welding under various welding conditions with experimental results and finite element analysis model.

• Carbon letters
• /
• v.16 no.3
• /
• pp.135-146
• /
• 2015

Graphite can be classified into natural graphite from mines and artificial graphite. Due to its outstanding properties such as light weight, thermal resistance, electrical conductivity, thermal conductivity, chemical stability, and high-temperature strength, artificial graphite is used across various industries in powder form and bulk form. Artificial graphite of powder form is usually used as anode materials for secondary cells, while artificial graphite of bulk form is used in steelmaking electrode bars, nuclear reactor moderators, silicon ingots for semiconductors, and manufacturing equipment. This study defines artificial graphite as bulk graphite, and provides an overview of bulk graphite manufacturing, including isotropic and anisotropic materials, molding methods, and heat treatment.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2003.04a
• /
• pp.206-210
• /
• 2003

Machining of deep holes with conventional boring bars frequently induce chatter vibration because of their low dynamic stiffness which is defined as the product of static stiffness and damping of conventional boring bar materials. In addition, the specific stiffness ($E/{\rho}g$) of boring bars is more important than the static stiffness to increase the fundamental natural frequency of boring bars in high speed machining. Therefore, boring bar materials should have high static stiffness and high damping as well as high specific stiffness. The best way to meet requirements is to employ fiber reinforced composite materials for high speed boring bars because composite materials have high static stiffness, high damping and high specific stiffness compared to conventional boring bar materials. In this study, the dynamic characteristics of carbon fiber epoxy composite boring bars were investigated. From the metal cutting test, it was found that the chatter was not initiated up to the ratio of length to diameter of 10.7 at the rotating speed of 2,500 rpm.

• Journal of the Korea Furniture Society
• /
• v.16 no.2 s.30
• /
• pp.27-36
• /
• 2005

Surface materials of furnitures are continuously studied and marketed with new patterns and new technology so as to create designs and fashions but even professionals are also difficult in distinguishing natural materials from artificial materials. Like this, furniture industry is required for rapid coping with the preference of customers which requires high grade of consumption pattern and is rapidly changed; it is intended to review the current situation of our furniture industry. The purpose of this thesis is to activate furniture industry and elevate the importance of surface materials in assumption of continuous R&D based on systemic data analysis of the kinds and colors of surface materials used in the companies within rank five of sales volume in domestic furniture companies.

• KIEAE Journal
• /
• v.7 no.3
• /
• pp.57-62
• /
• 2007

Most of current building materials are made of organic compounds or at least made with chemical treatments. Though easy to use and comparatively pay less, those materials are generally not enviornmentally sound. VOC is one of harmful effects. On contrary, natural materials such as soil are usually eco-friendly, and environmentally sustainable as well if not treated in autoclaves. Acoustica materials made of such environmentally sound and sustainable could be widely used. It is aimed to prove that soil based materials could be effectively used in acoustical fields rather than the other usual materials. Experiments with various types of soil blocks and soil plaster were performed. It is proved that the soil plaster has better apsorption features than cement plaster. Soil blocks have higher absorption cofficients than soil plaster, due to the thickness, and the absorption characteristics can be controlled by the design of the blocks.

• Fashion & Textile Research Journal
• /
• v.19 no.2
• /
• pp.140-151
• /
• 2017

This study researched the status and prospect of the natural dye program in the Gyeongsang region, with a focus on private centers with sufficient infrastructure and abundant human resources available for natural dyes. Metropolitan cities do not own the drying house and the agricultural land for natural dyes as well as have difficulty securing the land; therefore, entire sites are limited and smaller as they are closer to the city. The one-time program of all centers has been researched to help promote and maintain centers rather than generate profit. It is shown that June-August (summer) is preferred over December-February (winter). Natural dye programs for hobby and education are operated as needed because the number of participants are low. This program uses natural indigo and Persimmon Juice for the dyeing raw materials. Programs are often outsourced by other institutes with a private certification registration system the starting of a business after obtaining certification are often found in institutes operating programs directly. Future plans do not include investments in facilities (like the enlargement of experience centers) the prospect of programs and business value is bright for business strategies that include an exhibition shop for natural dye products and program development.

• Journal of the Korean Ceramic Society
• /
• v.53 no.3
• /
• pp.295-300
• /
• 2016

To investigate the thermal conductivity and the structural properties of naturally cooled excimer-laser annealed Si, molecular-dynamics (MD) simulations have been performed. The thermal conductivity of crystalline Si (c-Si) was measured by direct method at 1000 K. Steady-state heat flow was measured using a stationary temperature profile; significant deviations from Fourier's law were not observed. Reliable processes for measuring the thermal conductivity of c-Si were presented. A natural cooling process to admit heat flow from molten Si (l-Si) to c-Si was performed using an MD cell with a size of $48.9{\times}48.9{\times}97.8{\AA}^3$. During the cooling process, the temperature of the bottom $10{\AA}$ of the MD cell was controlled at 300 K. The results suggest that the natural cooling system described the static structural property of amorphous Si (a-Si) well.

• Smart Structures and Systems
• /
• v.16 no.4
• /
• pp.667-681
• /
• 2015

The scour induced by strong currents and wave action decreases the embedded length of monopiles and leads to a decrease of their structural stability. The objective of this study is the development and consideration of scour-monitoring techniques for offshore monopile foundations. Tests on physical models are carried out with a model monopile and geo-materials prepared in a cylindrical tank. A strain gauge, two coupled ultrasonic transducers, and ten electrodes are used for monitoring the scour. The natural frequency, ultrasonic reflection images, and electrical resistivity profiles are obtained at various scour depths. The experimental results show that the natural frequency of the model monopile decreases with an increase in the scour depth and that the ultrasonic reflection images clearly detect the scour shape and scour depth. In addition, the electrical resistivity decreases with an increase in scour depth. This study suggests that natural frequency measurement, ultrasonic reflection imaging, and electrical resistivity profiling may be used as effective tools to monitor the scour around an offshore monopile foundation.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1188-1192
• /
• 2004

Polyamic acid precursors were prepared by mixing various main chain dianhydrides, main chain diamines and side chain diamines. Copolyimide films with alkylcyclohexylbenzene as a side chain were prepared by thermal imidization of polyamic acid precursors. Pretilt angles on rubbed polyimides changed according to the side chain and main chain structures of the polyimide. Consequently, we found that LC pretilt angles of polyimide films with a liquid crystal structure as a side chain showed to be approximately 90$^{\circ}$ when a linear and rigid polyimide main chain and a side chain of suitable length were employed.