• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.625-626
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• 2008

The magnetic domain-refining techniques such as ball scratching, laser irradiation and plasma have been developed to reduce the domain wall spacing and thus iron losses in Fe-3%Si grain-oriented silicon steels. In view point of magnetic properties, it was supposed that the locally residual stresses change the magnetoelastic energy of the material and thus the spacing between $180^{\circ}$ domain walls decreases in order to reduce the magnetostatic energy. The effect of laser irradiation on iron loss and magnetostriction reduction for Fe-3%Si grain-oriented steel were investigated. Since the local tensile stresses were induced at the surface of Fe-3%Si steel by the laser irradiation, the minimum iron loss caused by reducing eddy current loss was obtained in spiete of the decrease of permeability by hindering eddy current loss was obtained in spite of the decrease of permeability by hindering the domain wall movement around the induced stress field. Furthermore, the laser treated 3%Si steel has lower magnetostriction as compared to non laser-treated steel and is less sensitive to applying pre-stresses due to the volume reduction of $90^{\circ}$ domain in materials.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.8 s.227
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• pp.1099-1108
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• 2004

In this paper, a study on the development of expert system for Al matrix composite with shape memory alloy fiber is performed to evaluate termomechanical behavior and mechanical properties. Expert system is very useful computer-based analysis system designed to make analysis technique and knowledge conveniently available to a lot of fabricable condition. In the developed system, it is possible to predict termomechanical behavior and mechanical properties for other composite with shape memory alloy fiber. The smartness of the shape memory alloy is given due to the shape memory effect of the TiNi fiber which generates compressive residual stress in the matrix material when heated after being prestrained. For finite element analysis, an analytical model is assumed two dimensional axisymmetric model compared of one fiber and the matrix. To evaluate the strength of composite using FEM, the concept of smart composite was simulated on computer Thus, in this paper, the FEA was carried out at two critical temperature conditions; room temperature and high temperature(363k). The finite element analysis result was compared with the test result for the analysis validity.

• The Korean Journal of Community Living Science
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• v.14 no.3
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• pp.53-58
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• 2003

This study on the processing of noodles was carried out to increase utilization of Allium fistulosum L., In the areas of total solids in residual liquid, swelling volume, and water absorption, a mixture of 10.0% dried Allium fistulosum L. flour and wheat flour, and a mixture of 25.0% raw Allium fistulosum L. flour and wheat flour both perform similarly to noodles made with just wheat flour. In the area of texture- the gumminess, cutting factor, and chewiness increase as the percentage of dried Allium fistulosum L. flour increases. There is no great difference in these factors between the 10.0% dried and the 25.0% raw mixtures. The color of the noodles with a mixed Allium fistulosum L. flour is green-yellow. As the quantity of Allium fistulosum L. flour increases the color gets darker The over all perception of the noodles made with a mixed Allium fistulosum L. flour was rated higher in color, taste, and smell than regular noodles. This study shows that mixing wheat flour with 10.0% dried Allium fistulosum L. flour or 25.0% raw Allium fistulosum L. flour produces a better noodle product.

• International Journal of Concrete Structures and Materials
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• v.11 no.2
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• pp.365-375
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• 2017

An experimental evaluation of crack propagation and post-cracking behavior in steel fiber reinforced concrete (SFRC) beams, using full-field displacements obtained from the digital image correlation technique is presented. Surface displacements and strains during the fracture test of notched SFRC beams with volume fractions ($V_f$) of steel fibers equal to 0.5 and 0.75% are analyzed. An analysis procedure for determining the crack opening width over the depth of the beam during crack propagation in the flexure test is presented. The crack opening width is established as a function of the crack tip opening displacement and the residual flexural strength of SFRC beams. The softening in the post-peak load response is associated with the rapid surface crack propagation for small increases in crack tip opening displacement. The load recovery in the flexural response of SFRC is associated with a hinge-type behavior in the beam. For the stress gradient produced by flexure, the hinge is established before load recovery is initiated. The resistance provided by the fibers to the opening of the hinge produces the load recovery in the flexural response.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.3
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• pp.499-503
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• 2016

For safety and economy reasons, hazardous waste including radioactive waste is desired to be converted into stable waste forms with a maximum volume reduction. High temperature melting technology using a plasma torch system can effectively treat even the non-flammable waste as desired. By far, one of the most difficult process for melting the non-flammable waste is a tapping of melts because the melting point of a residual slag in the tapping hole is high and because the viscosity of the melt increases sharply when tapping out. In case of a stationary furnace with a slant tapping port on the side of furnace, a certain amount of melts is left in the tapping hole after tapping out. Because of this, at every end of a melting cycle, the tapping hole needs to be opened by tapping device. The developed tapping device of melts based on both a guide electrode and auxiliary electrode is adequate for the application to discharge of melts except that the consumption of the guide electrode is somewhat faster than expected. Melt is collected in the water cooled vessel.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.11
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• pp.1998-2003
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• 2007

A flexible but implantable polyimide-based neural implant was fabricated for reliable and stable long-term monitoring of neural activities from brain. The developed neural implant provides 3-dimensional (3D) $3{\times}3$ structure, avoids any hand handling, and makes the insertion more efficient and reliable. Any film curvature caused by residual stress was not observed in the electrode. The 3D flexible polyimide electrode penetrated a dense gel whose stiffness is close to live brain tissue, because a ${\sim}1{\mu}m$ thick nickel was electroplated along the edge of the shank in order to improve the stiffness. The recording sites were positioned at both side of the shank to increase the probability of recording neural signals from a target volume of tissue. Impedance remained stable over 72 hours because of extremely low moisture uptake in the polyimide dielectric layers. At electrical recording test in vitro, the fabricated electrode showed excellent recording performance, suggesting that this electrode has the potential for great recording from neuron firing and long-term implant performance.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.31 no.1
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• pp.46-52
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• 2009

The maxillary posterior edentulous region presents unique and challenging conditions in implant dentistry. The height of the posterior maxilla is reduced greatly as a result of dual resorption from the crest of the ridge and pneumatization of the maxillary sinus after the loss of teeth. Materials previously used for sinus floor grafting include autogenous bone, allogeneic bone, xenogenic bone and alloplastic materials. Autogenous bone is the material of choice, but its use is limited by donor-site morbidity, complications, sparse availability, uncontrolled resorption and marked volume loss. One way to overcome this problem would be to use bone substitutes alone as a osteoconductive scaffold for bone regeneration from the residual bone or in combination with allogeneic bone, which also has osteoinductive properties. The purpose of this article is to describe a double layers technique of demineralized and mineralized bone graft materials instead of autogenous bone in sinus floor augmentation of deficient posterior maxillary alveolar process and to report our experience with this technique. Our results show that maxillary sinus augmentation using mineralized and demineralized bone materials, when installed simultaneously with the implant or not, is good results for bone healing.

• Structural Engineering and Mechanics
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• v.40 no.5
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• pp.595-616
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• 2011

Impact experiments have been carried out on concrete slabs. The first group was traditionally manufactured, densely reinforced concrete targets, and the next were ordinary Portland and calcium aluminate cement based HPSFRC (High performance steel fiber reinforced concrete) and SIFCON (Slurry infiltrated concrete) targets. All specimens were hit by anti-armor tungsten projectiles at a muzzle velocity of over 4 Mach causing destructive perforation. In Part I of this article, production and experimental procedures are described. The first group of specimens were ordinary CEM I 42.5 R cement based targets including only dense reinforcement. In the second and third groups, specimens were produced using CEM I 42.5 R cement and Calcium Aluminate Cement (CAC40) with ordinary reinforcement and steel fibers 2 percent in volume. In the fourth group, SIFCON specimens including 12 percent of steel fibers without reinforcement were tested. A high-speed camera was used to capture impact and residual velocities of the projectile. Sample tests were performed to obtain mechanical properties of the materials. In the companion Part II of this study, numerical investigations and simulations performed will be presented. Few studies exist that examine high-velocity impact effects on CAC40 based HPSFRC targets, so this investigation gives an insight for comparison of their behavior with Portland cement based and SIFCON specimens.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.2
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• pp.115-121
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• 2005

Using a general Saccharomyces cerevisiae as a model strain, continuous ethanol fermentation was carried out in a stirred tank bioreactor with a working volume of 1,500 mL. Three different gravity media containing glucose of 120, 200 and 280 g/L, respectively, supplemented with 5 g/L yeast extract and 3 g/L peptone, were fed into the fermentor at different dilution rates. Although complete steady states developed for low gravity medium containing 120 g/L glucose, quasi-steady states and oscillations of the fermented parameters, including residual glucose, ethanol and biomass were observed when high gravity medium containing 200 g/L glucose and very high gravity medium containing 280 g/L glucose were fed at the designated dilution rate of $0.027\;h^{-1}$. The observed quasi-steady states that incorporated these steady states, quasi-steady states and oscillations were proposed as these oscillations were of relatively short periods of time and their averages fluctuated up and down almost symmetrically. The continuous kinetic models that combined both the substrate and product inhibitions were developed and correlated for these observed quasi-steady states.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.68-71
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• 2013

Reactive Powder Concrete (RPC) is an ultra high strength and high ductility cement-based composite material and has shown some promise as a new generation concrete in construction field. It is characterized by a silica fume-cement mixture with very low water-binder (w/b) ratio and very dense microstructure, which is formed using various powders such as cement, silica fume and very fine quartz sand (0.15~0.4mm) instead of ordinary coarse aggregate. However, the unit weight of cement in RPC is as high as 900~1,000 kg/㎥ due to the use of very fine sand instead of coarse aggregate, and a large volume of relatively expensive silica fume as a high reactivity pozzolan is also used, which is not produced in Korea and thus must be imported. Since the density of RPC has a heavy weight at 2.5~3.0 g/㎤. In this study, the modified RPC was made by the combination of ternary pozzolanic materials such as blast furnace slag and fly ash, silica fume in order to economically and practically feasible for Korea's situation. The fire resistance and structural behavior of the modified RPC exposed to high temperature were investigated.