• Tribology and Lubricants
• /
• v.33 no.5
• /
• pp.214-219
• /
• 2017

Abrasive fluidized bed machining (AFBM) is similar to general abrasive fluidized machining (AFM) in that it can perform polishing of the outer and inner surfaces of a 3-dimensional shape by the flow of particles. However, in the case of AFM, the shear force generated by the flow of the particles causes material removal, while in AFBM, the abrasive particles are suspended in the chamber to form a bed. AFBM can be used for deburring, polishing, edge contouring, shot peening, and cleaning of mechanical parts. Most studies on AFBM are limited to metals, and research on application of AFBM to plastic materials has not been performed yet. Therefore, in this study, we investigate the effect of rotating speed of the specimen and the air flow rate on the material removal characteristics during AFBM of polyacetal with a horizontal AFBM machine. The material removal rate (MRR) increases linearly with increase of the rotating speed of the main shaft because of the shear force between the particles of the fluidized bed and the rotation of the workpiece. The reduction in surface roughness tends to increase as the rotating speed of the main shaft increases. As the air flow rate increases, the MRR tends to decrease. At a flow rate of 70 L/min or more, the MRR remains almost constant. The reduction of the surface roughness of the specimen is found to decrease with increasing air flow rate.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.35 no.3
• /
• pp.325-335
• /
• 2011

This study analyzes the current educational curricula in the field of Clothing and Textiles in order to develop appropriate educational methods and courses. We reviewed the curricula offered by 58 Clothing and Textiles Departments at four-year universities in Korea. We analyzed the educational content of each curriculum by dividing all of the courses offered into eight categories. The analysis was based on the information posted on the universities' Internet websites, and the analysis was performed by using descriptive statistics. The results of this study are as follows: First, the educational courses of the Clothing and Textiles Departments are composed of, 36.2% design, 20.4% production, and 14.5% textile categories. In comparison with the results of a similar study conducted in 1999, emphases on the design, distribution, and marketing categories have increased, while the emphases on the production, apparel material, basic knowledge, and consumption science categories have decreased. Second, in the case of the apparel material category, basic knowledge of materials constituted 18.5%, the largest part of the category. The average number of units offered in the area of apparel materials by the 58 Departments was 17 units per year. The curricula were found to vary by regions of the country. The universities located in the Chungcheong region offer more textile material courses, but the universities in the Capital region offer fewer textile material courses than other regions. Departments that are affiliated with universities that emphasize Art and Design have more courses on basic knowledge, dyeing and finishing, and fabric design than other universities.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.4
• /
• pp.309-315
• /
• 2001

Crystallized $LiMn_{2-y}Mg_{y}O_4$ powder was prepared by calcing the mixture of LiOH.$H_2O$, $MnO_2$ and MgO at $800^{\circ}C$ for 36h in an air atmosphere. The structure of $LiMn_{2-y}Mg_{y}O_4$ crystallites was analyzed from powder X-ray diffraction data as a cubic spinel, space group Fd3m. Though all cathode material showed spinel phase based on cubic phase in X-ray diffraction, other peaks gradually exhibited and became intense with increasing y value in $LiMn_{2-y}Mg_{y}O_4$. However, ununiform which calculated by (111) face and (222) face was constant in spite of the increase of y value, except pure $LiMn_2O_4$. AC impedance of Li/$LiMn_{2-y}Mg_{y}O_4$ cells revealed the similar resistance of about $70\Omega$ before cycling. In addition, The impedance of Li/$LiMn_{1.9}Mg_{0.1}O_4$ cell changed during charge and discharge or after cycling.

• Journal of Conservation Science
• /
• v.32 no.4
• /
• pp.449-457
• /
• 2016

A stoneware bottle was recovered from the Incheon Yeongheungdo Shipwreck in 2013. Primary observations showed that this object had a sealed opening and was covered with a foreign material. After it was cleaned via mechanical and chemical methods, wave patterns were observed on the outer surface of the bottle and a yellowish-brown transparent material was found within. In this paper, the process of conserving the stoneware bottle and the analysis conducted on the unknown material found within is explained. The conservation process included steps such as cleaning, desalination and restoration. After of the missing area located at the rim, the original shape of the bottle was made clear. In addition, the unknown inner material was analyzed using FT-IR and GC-MS. Results showed that the material is similar to golden lacquer. It is speculated that the Yeongheungdo Ship had wrecked during the Unified Silla period while carrying a bottle loaded with golden lacquer.

• Journal of the Korean GEO-environmental Society
• /
• v.17 no.6
• /
• pp.5-12
• /
• 2016

This paper deals with the result of thermal resistance test with backfill materials as bottom ash by using backfill material. Bottom ash, one of coal ashes, can be reused to replace sand because of its similar engineering properties. But without considering the thermal property, the abuse of bottom ash resulted in damage for existing structures. To investigate the thermal conductivity of bottom ash, laboratory tests for thermal resistance of that were carried out in this study. Thermal properties of bottom ash was compared with those of in-situ soil, sand, backfill material which can be applied as filling material. The tests were classified by water contents defined as the major influence factor. The beneficial use method of bottom ash was suggested as backfilling material.

• Textile Coloration and Finishing
• /
• v.32 no.3
• /
• pp.176-183
• /
• 2020

In order to study wearable air cushion materials capable of responding to massive impact in high-altitude fall situation, high tenacity woven fabrics were bonded by heat only depending on various type of thermoplastic films and then mechanical properties were measured. Tensile strength, elongation, and 100% modulus measurement results for 4 types of films show that TPU-2 has higher impact resistance and easier expansion than PET-1. After thermal bonding, the combination with the highest tensile strength was a material with a TPU-2 film for nylon and a PET-2 film for PET, so there was a difference by type of fabric. The tear strength of the bonded materials were increased compared to the fabric alone, which shows that durability against damage such as tearing can be obtained through film adhesion. All of the peel strengths exceeded the values required by automobile airbags by about 5 times, and the TPU-2 bonded fabric showed the highest value. The air permeability was 0 L/dm2 /min. For both the film and the bonded material, which means tightness between the fabric and the film through thermal bonding. It is expected to be applied as a wearable air cushion material by achieving a level of mechanical properties similar to or superior to that of automobile airbags through the method of bonding film and fabric by thermal bonding.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.4
• /
• pp.361-366
• /
• 2002

Spinel $LiMn_{2-y}M_yO_4$ and $LiMn_{2-y}M_yO_4$ (M=Mg, Zn) powders were synthesized by solid-state method at $800^{\circ}C$ for 37h. Crystal structure and electrochemical properties were analyzed by X-ray diffraction, charge-discharge test, cyclic voltammetry and ac impedance to $LiMn_{2-y}M_yO_4$. All cathode material showed spinel structure in X-ray diffraction. Ununiform distortion which calculated by (111) face and (222) face was almost constant in spite of the change of the kind and the substituting ratio of the metal cation in $LiMn_{2-y}M_yO_4$ (M=Mg, Zn). $LiMn_{1.9}Mg_{0.05}Zn_{0.05}O_4/Li$ cell substituted $Mg^{+2}$ and $Zn^{+2}$ showed excellent discharge capacities than other cells, which it presented about 120mAh/g at the 1st cycle and about 73mAh/g at the 250th cycle, respectively. AC impedance of $LiMn_{2-y}M_yO_4/Li$ cells showed the similar resistance of about 65~110$\Omega$ before cycling.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.14 no.3
• /
• pp.152-159
• /
• 2010

Recently, the public interest in eco-friendly material and structure has been increasing and many Hwang-toh researches are being actively performed. Hwang-toh is one of the traditional environment friendly construction materials used as a construction and plastering material. Hwang-toh has many advantages as construction material due to its high heat storage capacity, auto-purification, antibiotic ability, and infrared ray emission characteristics. But, currently it has not been developed into construction material and used in modern construction due to its low strength and dry shrinkage cracking prone characteristics. According to the recent researches and study results, Hwang-toh can be used as a natural pozzolanic material like fly-ash or pozzolan. In this study, mechanical properties and structural flexure behavior experiments of slag, recycled PET fiber, and Hwang-toh added concrete are carried out. The test results showed that drying shrinkage of concrete mixed with Hwang-toh has lower compressive strength and elastic modulus than those of control cement concrete specimen, but it has the similar flexural behavior in reinforced concrete beams.

• Journal of the Korean Geosynthetics Society
• /
• v.17 no.4
• /
• pp.93-102
• /
• 2018

A sprayable waterproofing membrane which is composed of polymer-based material is relatively easy to install due to its construction method comparing with sheet-type membranes. And a sprayable waterproofing membrane has very similar material composition to the TSL which is for a permanent support. In this study, material composition of the sprayable waterproofing membrane was changed to enhance structural properties of membrane while maintaining waterproofing performance. In order to compare with a previous research for the TSL, series of tests were performed according to the performance criteria used for permanent support material (TSL) by EFNARC (2008). From the test result, the structural performance of the sprayable waterproofing membrane considered in this study showed a performance that could be used as a permanent support material.

• Korean Journal of Metals and Materials
• /
• v.48 no.4
• /
• pp.289-296
• /
• 2010

The effects of heat input and different microstructureswere investigated on the tensile-shear properties of an arc-brazed joint of theferritic stainless steel 429EM using a Cu-Si insert alloy. The brazing speed was fixed at 800 mm/min whilethe brazing current varied from 80 to 120A. For abrazing current lower than 100A, fracturing occurred at the joint root in the direction perpendicular to the tensile load. As the brazing current increased to 120A, fracturing occurred at the base metal or the joint root. The joint and the base metal had very similar yield and tensile load values. However, the amount of elongation was decreased considerably compared to when the base metal was used. The fracturing began at the triple point of the root part and was classified into three types. The difference in the tensile-shear properties was closely related to the three fracture types.