• Journal of Adhesion and Interface
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• v.21 no.3
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• pp.86-92
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• 2020

We confirmed the effects on the device performances and the charge injection characteristics of organic field-effect transistor (OFET) by selectively differently controlling the surface energies on the contact region of the substrate where the source/drain electrodes are located and the channel region between the two electrodes. When the surface energies of the channel and contact regions were kept low and increased, respectively, the field-effect mobility of the OFET devices was 0.063 ㎠/V·s, the contact resistance was 132.2 kΩ·cm, and the subthreshold swing was 0.6 V/dec. They are the results of twice and 30 times improvements compared to the pristine FET device, respectively. As the results of analyzing the interfacial trap density according to the channel length, a major reason of the improved device performances could be anticipated that the pi-pi overlapping direction of polymer semiconductor molecules and the charge injection pathway from electrode is coincided by selective surface treatment in the contact region, which finally induces the decreases of the charge trap density in the polymer semiconducting film. The selective surface treatment method for the contact region between the electrode and the polymer semiconductor used in this study has the potential to maximize the electrical performances of organic electronics by being utilized with various existing processes to lower the interface resistance.

• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.267-276
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• 2020

Poly(epichlorohydrin) copolyol series (PECH copolyols) were synthesized via cationic ring-opening copolymerization (ROCP) of oxirane-based monomers and effects of reaction temperature, solvent type, and initiator were studied. As a comonomer, two types of alkylene oxides were used, and polymerization conditions were conducted both with diethylene glycol (DEG) as an initiator in methylene chloride (MC) solvent and tripropylene glycol (TPG) in toluene solvent. In order to induce the active monomer (AM) mechanism in the ring-opening copolymerization reaction, the monomer was injected by an incremental monomer addition (IMA) method using a syringe pump, and the polymerization was performed at -5 ℃. PECH copolyol, a synthesized ephichorohydrin (ECH)-based copolyol, was converted to glycidyl azide-based energy-containing copolyol (GAP copolyol) by azadizing the ECH unit through a substitution reaction. It was confirmed that the synthesized azide copolyol had little effects on changes of the solvent and the initiator. Also, the molecular weight increased 500 after the azide reaction, thereby the GAP copolyol was polymerized as designed. As the content of the comonomer increased, both the T_g and viscosity tended to decrease due to the influence of the alkyl chain length. It is possible to fundamentally prevent CH₃N₃ amount produced in the azide reaction process, and it is expected that a large-scale process could be achievable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.10
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• pp.4666-4672
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• 2011

Performance of NOx removal in SCR(Selective Catalytic Reduction) process depends on such various factors as catalyst factors (catalyst composition, catalyst form, space velocity, etc.), temperature of exhaust gas, and velocity distribution of exhaust gas. Especially the flow uniformity of gas stream flowing into the catalyst layer is believed to be the most important factor to influence the performance. In this research, the flow characteristics of a SCR process at design stage was simulated, using 3-dimensional numerical analysis method, to confirm the uniformity of the gas stream. In addition, the effects of guide vanes, baffles, and perforated plates on the flow uniformity for the inside and catalyst layer of the reactor were studied in order to optimize the flow uniformity inside the SCR reactor. It was found that the installation of a guide vane at the inlet duct L-tube part and the installation of a baffle at the upper part is very effective in avoiding chaneling inside the reactor. It was also found that additional installation of a perforated plate at the lower part of the potential catalyst layer buffers once more the flow for very uniform distribution of the gas stream.

• The KIPS Transactions:PartA
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• v.17A no.6
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• pp.265-274
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• 2010

As the process technology scales down and integration densities continue to increase, interconnection has become one of the most important factors in performance of recent multi-core processors. Recently, to reduce the delay due to interconnection, 3D architecture has been adopted in designing multi-core processors. In 3D multi-core processors, multiple cores are stacked vertically and each core on different layers are connected by direct vertical TSVs(through-silicon vias). Compared to 2D multi-core architecture, 3D multi-core architecture reduces wire length significantly, leading to decreased interconnection delay and lower power consumption. Despite the benefits mentioned above, 3D design technique cannot be practical without proper solutions for hotspots due to high temperature. In this paper, we propose three floorplan schemes for reducing the peak temperature in 3D multi-core processors. According to our simulation results, the proposed floorplan schemes are expected to mitigate the thermal problems of 3D multi-core processors efficiently, resulting in improved reliability. Moreover, processor performance improves by reducing the performance degradation due to DTM techniques. Power consumption also can be reduced by decreased temperature and reduced execution time.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.965-975
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• 2014

Pretension PSC (Prestressed Concrete) members are subjected to a certain limit of size as they are generally produced in the off-site plant and transferred to the site due to the large scale of the product on system. In this study, a portable pretensioning production system has been developed, which allow us to apply the pretension method on site. Considering that a 50m span PSC girder using the pretension method requires a pressing device to endure a large jacking force, the portable pretension production system has to ensure safety against such a large pretension jacking force. In this study, the portable pretensioning system to produce a 50m span pretension girder was manufactured by using CFT (Concrete Filled steel Tube) members. In order to understand the stability of the system and the behavior of the elements, a static loading test was conducted and the stability of the proposed portable pretensioning production system was confirmed. The developed portable pretension system was applied to several construction sites and was investigated the problems on site. During the pretension girder and slab members that was producted by this pretension system in construction site, it has be found the several advantages such as simple fabrication processes, reduction of prestress-loss, and a decrease of 15% compared with the fabrcation cost of post-tension girder. After due consideration of the problems, this portable pretension system will be improved.

• Journal of Environmental Science International
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• v.26 no.1
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• pp.23-28
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• 2017

This study was aimed at determining the changes in heavy metal removal efficiency at different acid concentrations in a micro-nanobubble soil washing system and pickling process that is used to dispose of heavy metals. For this purpose, the initial and final heavy metal concentrations were measured to calculate the heavy metal removal efficiency 5, 10, 20, 30, 60, and 120 min into the experiment. Soil contaminated by heavy metals and extracted from 0~15 cm below the surface of a vehicle junkyard in the city of U was used in the experiment. The extracted soil was air-dried for 24 h, after which a No. 10 (2 mm) was used as a filter to remove large particles and other substances from the soil as well as to even out the samples. As for the operating conditions, the air inflow rate in the micro-nano bubble soil washing system was fixed at 2 L/min,; with the concentration of hydrogen peroxide being adjusted to 5%, 10%, or 15%. The treatment lasted 120 min. The results showed that when the concentration of hydrogen peroxide was 5%, the efficiency of Zn removal was 27.4%, whereas those of Ni and Pb were 28.7% and 22.8%, respectively. When the concentration of hydrogen peroxide was 10%, the efficiency of Zn removal was 38.7%, whereas those of Ni and Pb were 42.6% and 28.6%, respectively. When the concentration of hydrogen peroxide was 15%, the efficiency of Zn removal was 49.7%, whereas those of Ni and Pb were 57.1% and 42.6%, respectively. Therefore, the efficiency of removal of all three heavy metals was the highest when the hydrogen peroxide concentration was 15%.

• Journal of Life Science
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• v.14 no.1
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• pp.131-140
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• 2004

T7 bacteriophage gp4 is the replicative DNA helicase that unwinds double-stranded DNA by utilizing dTTP hydrolysis energy. The quaternary structure of the active form of T7 helicase is a hexameric ring with a central channel. Single-stranded DNA passes through the central channel of the hexameric ring as the helicase translocates $5'\rightarrow3'$ along the single-stranded DNA. The DNA unwinding was measured by rapid kinetic methods and showed a lag before the single-stranded DNA started to accumulate exponentially. This behavior was analyzed by a kinetic stepping model for the unwinding process. The observed lag phase increased as predicted by the model with increasing double-stranded DNA length. Trap DNA added in the reaction had no effect on the amplitudes of double-stranded DNA unwound, indicating that the $\tau7$ helicase is a highly processive helicase. Global fitting of the kinetic data to the stepping model provided a kinetic step size of 10-11 bp/step with a rate of $3.7 s^{-1}$ per step. Both the mechanism of DNA unwinding and dTTP hydrolysis and the coupling between the two are unaffected by temperature from $4∼37^{\circ}C$. Thus, the kinetic stepping for dsDNA unwinding is an inherent property of tile replicative DNA helicase.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.443-449
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• 2014

To check the characteristics of nuclear fuels during an irradiation test, the nuclear fuel rod needs to be disassembled from the test rig located in the pool of the research reactor. Then, the disassembled fuel rod is delivered to the hot cell for intermediate examination. A fuel rod that passes the intermediate examination is delivered to the reactor pool to be reassembled into the test rig. The irradiation test is resumed with the reassembled test rig. Because nuclear fuel rods irradiated by neutrons are highly radioactive, all the disassembly and reassembly processes should be carried out in the pool of the research reactor to prevent operators being exposed to radiation. In particular, because a test rig is 5.4-m long and the reactor pool of HANARO is 6-m deep, special tools need to be developed for performing the disassembly and reassembly processes. In this study, a new assembly design of nuclear fuel rods for intermediate examination is introduced. Furthermore, tools for treating the irradiated fuel rod assembly are introduced, and their performance is verified by an out pile test.

• Korean Journal of Materials Research
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• v.1 no.1
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• pp.46-53
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• 1991

The stress of PSG (Phosphosilicate glass), USG (Undoped-silicate grass) and SiN films, which are mainly used as passivation layers in semiconductor memory devices, deposited by CVD methods has been studied as a function of film thickness and holding time in air. The stress of the PSG film or the USG film is increased in tensile state with increasing film thickness. On the other hand the stress level of the SiN film in compressive stress does not change as film thickness changes. The stress of PSG film shows the drastic change from the tensile stress to the compressive stress after the film is left 2 days in air. FTIR spectra indicated that the stress variation was due to the penetration of water molecule. It looks possible to recover the stress of about $2.5{\times}{10^9}dyne/cm^2$ by annealing treatment at $300^{\circ}C$ for 20min. The total stress of multi-layered films having the PSG film is determined mainly by the stress variation of PSG layer with holding time. The total stress of multi-layered film appears to have a functional relationship with the stress in the thickness of each film. The resistance against stress-migration of sputtered Al line increases with increasing the tensile stress for the PSG film or the USG film.

• Analytical Science and Technology
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• v.6 no.1
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• pp.9-19
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• 1993

Fatty acid salts derived from soap can be transferred into a typical derivative with p-bromophenacyl bromide using crown ether, a catalizer by the solid-liquid phase transfer reaction in nonpolar, aprotic solvents and separated by the reverse phase high performance liquid Chromatography (RP-HPLC) and determined using UV detector. The minimal limit of detection was defined at approximately 10~50ng in accordance with the chain length. The derivatization reaction in the presence of EDTA can be applied mot only to the calcium salts but also to the other various metal salts. The recoveries of fatty acid derivatizations in the absence and presence of the midium containing the yeast extract were obtained $95.4{\pm}1.2$, and $85.2{\pm}2.4%$ respectively. The analytical method would be applicable to determine the biodegradation of fatty acid salts in nature as well as in artificial condition such as shaker flask-medium method.