• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1204-1208
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• 2010

Anion recognition via hydrogen-bonding interactions could be monitored with changes in UV-vis absorption spectra and in some cases easily monitored with naked eye. Urea receptors 1 and 2 connected with both an azo group and a nitrophenyl group as a signaling group for color change proved to be an efficient naked eye receptor for the fluoride ion. The anion recognition phenomena of the receptors 1 and 2 via hydrogen-bonding interactions were investigated through UV-vis absorption and $^1H$ NMR spectra.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.4
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• pp.35-41
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• 1998

The bacterial cellulose has many unique properties that are potentially and commercially beneficial. In order to make opaque product from this cellulose, filling properties by fillers should be known. This study was performed to investigate the effect of filler addition on physical properties of sheets from bacterial cellulose. The effect of filling on its optical properties was also discussed. The apparent density and internal bonding strength of bacterial cellulose sheet are decreasing with the increase of filler contents. Those adversely affect Young's modulus and physical property of the sheet, but these negative phenomena of the bacterial cellulose sheet by filler addition are not so sensitive compared to substantial decreasing of physical properties of ordinary hardwood KP. This strength decrease would be attributed to the decrease of relative bonding sites among pulp fibers. Concerned to optical properties, the bacterial cellulose sheet shows high increase of brightness and opacity according to filler loading, but no significant changes in porosity up to 17.3% loading because of fine and filamentous structure of bacterial cellulose fibers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.11a
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• pp.49-54
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• 1993

This paper discusses the reliability of solder joints of electronic devices on printed circuit board. Solder application is usually done by screen printing method for the bonding between outer leads of devices and thick film(Ag/Pd) pattern on Hybrid IC as wel1 as Cu lands on PCB. As result of thermal stresses generated at the solder joints due to the differences of thermal expansion coefficients between packge body and PCB, Micro cracking often occurs due to thermal fatigue failure at solder joints. The initiation and the propagate of solder joint crack depends on the environmental conditions, such as storage temperature and thermal cycling. The principal mechanisms of the cracking pheno- mana are the formation of kirkendal void caused by the differences in diffusion rate of materials, ant the thermal fatigue effect due to the differences of thermal expansion coefficient between package body and PCB. Finally, This paper experimentally shows a way to supress solder joints cracks by using low-${\alpha}$ PCB and the packages with thin lead frame, and investigates the phenomena of diffusion near the bonding interfaces.

• Journal of Welding and Joining
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• v.21 no.2
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• pp.64-69
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• 2003

The bonding phenomena and mechanical property of duplex stainless steel during brazing have been investigated. The UNS32550 was used for base metal, and the MBF50 was used for insert metal. Brazing was carried out under the various conditions (brazing temperature : 1473K, 1498K, holding time : 0∼1.8ks). There were various microconstituents in the bonded interlayer because of reaction between liquid insert metal and base metal. In the early stage of brazing, BN is formed in the bonded interlayer and base metal near the bonded layer. Cr made is formed in the bonded interlayer. The amount of BN and Cr nitrides decrease with the increase of bonding temperature and holding time. Superior shear strength of 550MPa is obtained by restraining the formation of nitrides. (Received January 17, 2003)

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.161-164
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• 2004

In these days, composite materials are applied to the military field like parts of air crafts, rockets, ammunitions and so on. As high pressure is loaded on the composite body, however, cracks or delamination phenomena can be occurred between layers of laminate. These cracks or delamination usually cause a deterioration of mechanical properties under the complicated loads. In this study, methods for improvement of the inter-laminar bonding strength of thick carbon/epoxy composite structures are suggested and discussed in terms of segment bending test.

• Journal of the Korean Ceramic Society
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• v.27 no.6
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• pp.755-762
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• 1990

The tungsten paste was printed on the surface of 92% alumina sheet which was made by type casting process. The printed tungsten was bonded on the Al2O3 by co-firing in reducing atmosphere. During the co-firing, the binder burn-out was easier in wet H2 atmosphere than in dry H2, which affected sintered density. In practically, the use of wet H2 above 100$0^{\circ}C$ was beneficial for density of alumina and bond strength. This phenomena occured more distinctly when atmosphere varied from dry H2 to wet H2 than varied dew point in wet H2. In wet H2, the improvement in bonding strength can be attributed to good glass migration into the metal layer due to inhibition of the tungsten particle growth, with increase of alumina density, at the temperatrue higher than 100$0^{\circ}C$.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.4
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• pp.481-492
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• 1992

Author measured the bonding strength between Dental Porcelain and Nonprecious Dental Alloy and analyzed diffusion Phenomena at the interfaceby by Auger electron spectroscopy and also Electron spectroscopy for Chemical Analysis. The each specimen was sputtered with Al, Cr, In and Sn. 1. Ni whic is the main element of the matris of dental nonprecious alloy diffuse more than the other element and the Ni diffusion rate of each specimen was well coordinated with the bonding strength of each. 2. The Sn thin film suppress the diffusion rate of Ni of matrix into the Dental Porcelain than the In or Cr thin films. 3. The Al thin film suppress the diffusion rate of Ni than the Sn thin film. 4. The main coponent of dental porcelain : Al, Si, Mo diffused into the matrix of alloy. It means that the each element of dental alloy and dental porelain diffused into the each other part.

• ETRI Journal
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• v.17 no.4
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• pp.1-12
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• 1996

A novel body-tied silicon-on-insulator(SOI) n-channel metal-oxide-semiconductor field-effect transistor with grounded body electrode named GBSOI nMOSFET has been developed by wafer bonding and etch-back technology. It has no floating body effect such as kink phenomena on the drain current curves, single-transistor latch and drain current overshoot inherent in a normal SOI device with floating body. We have characterized the interface trap density, kink phenomena on the drain current ($I_{DS}-V_{DS}$) curves, substrate resistance effect on the $I_{DS}-V_{DS}$ curves, subthreshold current characteristics and single transistor latch of these transistors. We have confirmed that the GBSOI structure is suitable for high-speed and low-voltage VLSI circuits.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1126-1131
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• 2007

In 1st Phase Kyeong-Bu High-Speed Line, to lessen the impact in the transition zone between concrete slab track(in tunnel) and ballasted track(on embankment), the ballast bonding method has been adopted. However, in this area, in the beginning of the operation, unsupported sleepers are found, and the track deterioration and damage of concrete sleepers have occurred. In this paper, the status and causes of unsupported sleepers are discussed and several repair measures are proposed.

• Korean Membrane Journal
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• v.2 no.1
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• pp.36-47
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• 2000

This paper deals with the separation of MTBE-methanol mixtures using crosslinked Poly(vinyl alcohol)(PVA) membranes with sulfur-succinic acid(SSA) as a crosslinking agent by pervaporation and vapor permeation technique. The operating temperatures, methanol concentration in feed mixtures, and SSA concentrations in PVA membranes were varied to investigate the separation performance of PVA/SSA membranes and the optimum separation characteristics by pervaporation and vapor permeation. And also, for PVA/SSA membranes, the swelling measurements were carried out to study the transport phenomena. The swelling measurements were carried out for pure MTBE and methanol, and MTBE/methanol=90/10, 80/20 mixtures using PVA/SSA membranes with varying SSA compositions. There are two factors of the membrane network and the hydrogen bonding. In pervaporation separation was also carried out for MTBE/methanol=90/10, 80/20 mixtures at various temperatures. The sulfuric acid group in SSA took an important role in the membrane performance. The crosslinking effect might be over the hydrogen bonding effect due to the sulfuric acid group at 3 and 5% SSA membranes, and this two factors act vice versa on 7% SSA membrane. In this case, the 5% SSA membrane shows the highest separation factor of 2,095 with the flux of 12.79g/㎡$.$hr for MTBE/methanol=80/20 mixtures at 30$^{\circ}C$ which this mixtures show near the azeotopic composition. Compared to pervaporation, vapor permeation showed less flux and similar separation factor. In this case, the flux decreased significantly because of compact structure and the effect of hydrogen bonding. In vapor permeation, density or concentration of methanol in vaporous feed is lower than that of methanol in liquid feed, as a result, the hydrogen bonding portion between the solvent and the hydroxyl group in PVA is reduced in vapor permeation. In this case, the 7% SSA membranes shows the highest separation factor of 2,187 with the flux of 4.84g/㎡$.$hr for MTBE/methanol=80/20 mixtures at 30$^{\circ}C$.