• Journal of the Korean Society for Nondestructive Testing
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• v.37 no.2
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• pp.99-105
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• 2017

Many composite materials are used in the aerospace industry because of their excellent mechanical properties. However, the nature of aviation exposes these materials to high temperature and high moisture conditions depending on climate, location, and altitude. Therefore, the molecular arrangement chemical properties, and mechanical properties of composite materials can be changed under these conditions. As a result, surface disruptions and cracks can be created. Consequently, moisture-impregnating defects can be induced due to the crack and delamination of composite materials as they are repeatedly exposed to moisture absorption moisture release, fatigue environment, temperature changes, and fluid pressure changes. This study evaluates the possibility of detecting the moisture-impregnating defects of CFRP and GFRP honeycomb structure sandwich composite materials, which are the composite materials in the aircraft structure, by using an active infrared thermography technology among non-destructive testing methods. In all experiments, it was possible to distinguish the area and a number of CFRP composite materials more clearly than those of GFRP composite material. The highest detection rate was observed in the heating duration of 50 mHz and the low detection rate was at the heating duration of over 500 mHz. The reflection method showed a higher detection rate than the transmission method.

• Journal of Korean Library and Information Science Society
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• v.22
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• pp.205-244
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• 1995

Originally the concept of the traditional resource sharing has been discussed in the context of bibliographic materials, and has been labor-intensive and high-cost activities. The technology has had a great impact on such pattern of the resource sharing, and has expanded the limited scope of the traditional concept into the sharing of library information in the levels of local, regional and national systems, and expertise, materials, facilities, equipments and personnels of the library system. While the traditional circulation service as a basic method to share library materials by users can provide the resource to a single person at a time, the electronic resource can be shared, by multi-users at a time anytime anywhere. The maximization of the electronic resource sharing requires that publishing process should be fundamentally changed and articles, books, chapters, speech manuscripts, music scores, maps, sound, and other formats of materials should be prepared in machine readable format. This study examined the positive effects of the technology on the resource sharing, but not investigate the concrete and complex problems as to the cost, guidelines, detailed procedures, design details, and intellectual properties and protection involved in the resource sharing. Some findings extracted from the study can be summarized as follows; (1) ILL will lose its meaning as a method to share the materials if they are all in the electronic format and the phrase 'networked information resource' becomes omnipresent. (2) The technology keeps on changing the concept of resource sharing. Today, the scope of resource sharing not only encompasses the sharing of the primary and secondary materials but also the sharing of the processings(eg. cataloging), expertise, user education, special facilities, and the integrated automated library systems. (3) The sharing of the networked resource will be a method to provide better services for library users in the low cost. (4) The a n.0, pplication of the technology to the resource sharing should be focus on the method which allows an end-users to do the direct access to the needed materials, and to be delivered the primary document as soon as possible.

• International Journal of Advanced Culture Technology
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• v.1 no.2
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• pp.24-32
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• 2013

This paper determined students' ranks of difficulty on the use of materials in terms of 1) understanding the layout of the learning materials, 2) reading comprehension of the learning materials, and 3) realization on relevance to needs of the learning materials. It also determined students' 4) rank and frequency of attitude on the materials. With the data gathered through 128 survey questionnaires, 7 focused group discussions, and 10 interviews, the results were found out that there was an inappropriate assessment procedure set by this particular university. The researcher concludes that: 1) design of four types of classes by just using the two textbooks with their respective workbooks is grammar-based with limited conversation activities; 2) placement for these students in one big class size was implemented without considering their common interest and motivation and language levels; and, 3) qualification of teachers teaching these EFL students did not support students' real needs and the language program itself. Content professors who were made to teach may have the ability to input learning, but their teaching styles may differ from the ones who are real English teachers. This paper then recommends that teachers and school administration should have an appropriate placement exam before students attend the class, especially in a big class size. There could only be a few problems among students in one big class size when students' level of competence is proportioned. With this, topics and conversation activities can even be more flexible with the maneuver of art of questioning, various dimensions of thinking, strategic competence, learning attitude or behavior, etc. to ensure sustenance of communicative mode and level of interest and motivation in the classroom. Grammar-based instruction can only be taught when a need arises. Thus, the course description of each class will be able to transact the objectives ready for developing students' communication competence. Moreover, proper measurement can be utilized to validly assess the amount of students' learning and the progress of language curriculum design in terms of materials selection and teaching approach.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.315-324
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• 2001

Mechanochemical effects that occurred in the fine grinding process of quartz particles using planetary ball mill was investigated. Quartz particles have been frequently utilized for optical materials, semiconductor molding materials. We determined that grinding for a long time can be create amorphous structures from the crystalline quartz by Mechanochemical effects. But, to be produced nano-composite particles that the critical grinding time reached for composite materials in a short time. Henceforth, a qualitative estimation must be conducted on the filler for EMC(Epoxy molding compound) materials. It can be produced mechanochemically treated composite materials and also an integrated grinding efficiency considering of the nano-composite amorphous structured particles. The mechanochemical characteristics were evaluated based on particle morphology, size distribution, specific surface area, density and the amount of amorphous phase materials into the particle surface. The grinding operation in the planetary ball mill can be classified into three stages. During the first stage, initial particle size was reduced for the increase of specific surface area. In the second stage, the specific surface areas increased in spite of the increase in particle size. The final stage as a critical grinding stage, the ground quartz was considered mechanochemically treated particles as a nano- composite amorphous structured particles. The development of amorphous phase on the particle surface was evaluated by X-ray diffractometry, thermal gravity analysis and IR spectrometer. The amount of amorphous phase of particles ground for 2048 minutes was 85.3% and 88.2% by X-ray analysis and thermal gravity analysis, respectively.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.570-574
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• 2010

The main function of conventional insulation materials is only to block the heat transfer and reduce heat loss from the building. On the other hand, thermal storage materials can work as an energy saver by absorbing or emitting heat within a specific temperature range. Thermal storage materials for building can maintain a constant temperature by effectively regulating the cycle of indoor temperature. As a result, we can enhance the performance of a cooling and heating system efficiently. In this study, phase change materials (PCMs) were added as thermal storage materials into gypsum boards which are extensively used for building material and we found out the thermal environmental characteristics. In addition, we checked out some problems when applying the thermal storage materials to buildings. Finally, This study set out to examine the degree of environmental-friendly characteristics of thermal storage building materials by analyzing the amount of TVOC and HCHO contents with the possibility of pollutants emission.

• Metals and materials international
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• v.24 no.6
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• pp.1394-1402
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• 2018

This study investigates the mechanism of MnS precipitation on $Al_2O_3-SiO_2$ inclusions during the solidification of non-oriented silicon steel, especially the influence of the phase structures and sizes of the oxides on the MnS precipitation, by scanning electron microscopy and transmission electron microscopy coupled with energy dispersive spectrometry. The investigation results show that MnS tends to nucleate on submicron-sized $Al_2O_3-SiO_2$ inclusions formed by interdendritic segregation and that it covers the oxides completely. In addition, MnS can precipitate on micron-sized oxides and its precipitation behavior is governed by the phase structure of the oxides. The MnS embryo formed in a MnO-containing oxide can act as a substrate for MnS precipitation, thus permitting further growth via diffusion of solute atoms from the matrix. MnS also precipitates in a MnO-free oxide by the heterogeneous nucleation mechanism. Furthermore, MnS is less prone to precipitation in the $Al_2O_3$-rich regions of the $Al_2O_3-SiO_2$ inclusions; this can be explained by the high lattice disregistry between MnS and $Al_2O_3$.

• Particle and aerosol research
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• v.19 no.3
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• pp.63-76
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• 2023

An electrostatic precipitator (ESP) has a low pressure drop and a high collection efficiency but its collection efficiency can be reduced due to dust accumulation on the collection plates during long-term operations. In order to maintain the initial dust collection efficiency, it is necessary to periodically clean the collection plates. The common cleaning methods are using physical impacts or water sprays. These cleaning methods can lead to damage to the collection plate or generate wastewater. Herein, we implemented an electrodynamic screen (EDS) for ESP cleaning and evaluated its surface cleaning performance of particles. The EDS is an electrostatic system that can electrostatically repel particles on surfaces, allowing it to clean the ESP without causing damage and wastewater generation. Our evaluation included the analysis of the effects of AC voltage characteristics, electrode configuration and environmental conditions on the cleaning performance of the EDS with the aim of achieving effective surface cleaning. It has been demonstrated that activating the EDS cleans up to 65% of the particles on the surface, which indicates about 94% of our target cleaning zone.

• Journal of Electrochemical Science and Technology
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• v.7 no.2
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• pp.115-131
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• 2016

Though battery chemistry and technology had been developed for over a hundred years back, increase in demand for storage energy, in the computer accessories, cell phones, automobile industries for future battery car and uninterrupted power supply, has made, the development of existing and new battery, as an emerging areas of research. With innovation of high energetic inexpensive Nano structure materials, a more energy efficient battery with lower cost can be competitive with the present primary and rechargeable batteries. Materials electrochemistry of electrode materials, their synthesis and testing have been explained in the present paper to find new high efficient battery materials. The paper discusses fundamental of electrochemistry in finding true cell potential, overvoltages, current, specific energy of various combinations of anode-cathode system. It also describes of finding the performance of new electrode materials by various experiments viz. i. Cyclic Voltammetry ii. Chronoamperometry iii. Potentiodynamic Polarization iv. Electrochemical Impedance Spectroscopy (EIS). Research works of different battery materials scientists are discussed for the development of existing battery materials and new nano materials for high energetic electrodes. Problems and prospects of a few promising future batteries are explained.

• Korean Journal of Materials Research
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• v.16 no.7
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• pp.439-444
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• 2006

An apparatus capable of melting and solidifying various materials containerlessly in high vacuum via electrostatic levitation (ESL) has been developed for finding materials with new or improved properties and further building a database for processing materials in microgravity. Containerless solidification of semiconductors, metals, and alloys such as Si, Zr, Nb, Mo, $V_3Si$, and boron carbides has been carried out to test how various materials at how high temperatures can be processed by ESL. The materials in levitation became spherical at melting by their own surface tensions which were ideal for measuring intrinsic thermophysical properties of materials in the liquid state. Multiple cycles of melting and cooling were reproducibly repeated and radiative cooling curves were recorded.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1613-1618
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• 2007

Mechanical characteristics of composite materials containing NiTi shape memory alloy(SMA) have been analyzed in this study by conducting tensile, photo-elasticity and impact tests for the specimens. From the test results, the SMA composite materials can be considered as one of possible ways in detecting and controlling damages in the materials.