• Elastomers and Composites
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• v.46 no.1
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• pp.29-36
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• 2011

The term 'thermal insulating materials' describes a class of materials which can improve the thermal efficiency by reducing the thermal conduction, convention and radiation between the inside and outside of the system. As a thermal insulating material, numerous industrial applications are possible including the automobile, aerospace, aviation, and petrochemical. Especially, the silica aerogel, with their superior thermal insulating behavior, has been widely used as thermal insulating materials. Because the mechanical properties of the silica aerogel cannot meet the industrial demand, use of the silica aerogel is limited. This article aims to review the thermal insulating materials and silica aerogel, and to introduce the silica aerogel/polymer composites.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.12 s.354
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• pp.31-41
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• 2006

Internet access from mobile phones over cellular networks suffer from severe bandwidth limitations and high bit error rates over wireless access links. Tailoring TCP connections to best fit the characteristics of this bottleneck link is thus very important for overall performance improvement. In this work, we propose a simple algorithm in deciding the optimal TCP segment size to maximize the utilization of the bottleneck wireless TCP connection for mobile contents server access, taking the dynamic TCP window variation into account. The proposed algorithm can be used when the product of the access rate and the propagation time is not large. With some numerical examples, it is shown that the optimal TCP segment size becomes a constant value when the TCP window size exceeds a threshold. One can set the maximum segment size of a wireless TCP connection to this optimal segment size for mobile contents server access for maximum efficiency on the expensive wireless link.

• Polymer(Korea)
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• v.37 no.4
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• pp.500-506
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• 2013

The effect of compatibilizer types on the properties of polyphenylene sulfide (PPS)/polyethylene terephthalate (PET) blends was investigated. The blends were extruded by a single screw extruder attached with a Maddock mixing zone and their molded properties were examined. As a basic blend composition, a linear PPS/PET (40/60) blend was selected based on cost efficiency. Three types of compatibilizer, SEBS, modified SEBS, and modified PS were added to the basic blend to improve the properties. The thermal, rheological, mechanical properties and the morphology of the ternary blends were analyzed. The maximum mechanical properties of blends was found at 1 phr of m-SEBS or m-PS content, whose values were almost the same as the theoretical values of miscible blend system. It seemed to by the case that the partial reaction between compatibilizer and the basic blend caused the enhancement of compatibility between linear PPS and PET phases. These ternary blends would be applicable as economic linear PPS alloys.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.164-168
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• 2016

Lean duplex stainless steels with 0.087 wt.% gadolinium (Gd) were inert arc-melted and cast in molds of size $10mm{\times}10mm{\times}20mm$. The micro-hardnesses of the rolling direction (RD), transverse direction (TD) and short transverse (ST) direction were $258.5H_V$, $292.3H_V$, and $314.7H_V$, respectively. A 33% cold rolled specimen had the crystallographic texture that (100) pole was mainly concentrated to the normal direction (ND) and (110) pole was concentrated in the center of ND and RD. The corrosion potential and corrosion rate in artificial seawater and $0.1M\;H_2SO_4$ solution were in the range of $105.6-221.6mV_{SHE}$, $0.59-1.06mA/cm^2$, and $4.75-8.25mV_{SHE}$, $0.69-1.68mA/cm^2$, respectively. The friction coefficient and wear loss of the 0.087 w/o Gd-lean duplex stainless steels in artificial seawater were about 67% and 65% lower than in air, whereas the wear efficiency was 22% higher. The corrosion and wear behaviors of the 0.087 w/o Gd-lean duplex stainless steels significantly depended on the Gd phases.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.5
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• pp.103-115
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• 2014

Mobile-Office is the IT office that enables people handle their business anywhere and anytime without going to head office. It has propagated rapidly in domestic and foreign companies as the users who use mobile terminal such as smartphone have increased sharply. Mobile-Office is emerging as a new way of conducting business. It requires business environment to be changed to improve business efficiency, as fast-growing mobile-based economies emerges. Small and medium-sized companies's utilization ability for advanced IT technology is insufficient, and limitations exist on capacity of building and investment. They need different development methodologies and utilization methods. The purpose of this study is not only to consider the previous business environment problem on accessibility, mobility, effectiveness, complexity and consolidation, but to search more efficient methods for introducing applications to utilize various smart devices and websites with minimum investment in R&D.

• Journal of the Korean Society of Safety
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• v.29 no.4
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• pp.116-122
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• 2014

This study proposes a system reliability analysis of rack storage facilities subjected to forklift colliding events. The proposed system reliability analysis consists of two steps: the first step is to identify dominant failure modes that most contribute to the failure of the whole rack facilities, and the second step is to evaluate the system failure probability. In the first step, dominant failure modes are identified by using a simulation-based selective searching technique where the contribution of a failure mode to the system failure is roughly estimated based on the distance from the origin in the space of the random variables. In the second step, the multi-scale system reliability method is used to compute the system reliability where the first-order reliability method (FORM) is initially used to evaluate the component failure probability (failure probability of one member), and then the probabilities of the identified failure modes and their statistical dependence are evaluated, which is called as the lower-scale reliability analysis. Since the system failure probability is comprised of the probabilities of the failure modes, a higher-scale reliability analysis is performed again based on the results of the lower-scale analyses, and the system failure probability is finally evaluated. The illustrative example demonstrates the results of the system reliability analysis of the rack storage facilities subjected to forklift impact loadings. The numerical efficiency and accuracy of the approach are compared with the Monte Carlo simulations. The results show that the proposed two-step approach is able to provide accurate reliability assessment as well as significant saving of computational time. The results of the identified failure modes additionally let us know the most-critical members and their failure sequence under the complicated configuration of the member connections.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.181-187
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• 2016

Silica is an essential material in the electronics industries of LCDs and OLEDs, which particularly require high purity. This study attempted to find the optimal design of a magnetic separator for silica sand containing iron compounds using CFD simulation. Three designs of magnetic separation were prepared and their efficiency was examined. As a result of the evaluation, the sufficient contact of particulate silica with the surface of magnetic emitters improved the magnetic separation effects. In addition, the loss of $SiO_2$ and the removal rate of $Fe_2O_3$ depended strongly on the particle size, flow rate and magnetic flux density. In addition, magnetic separation is quite effective for a particle size of $10{\mu}m$ with a 0.2 m/s flow rate.

• Journal of Sensor Science and Technology
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• v.6 no.4
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• pp.290-297
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• 1997

In this study, the radiation monitoring system using CsI(TI) scintillation counter is developed for the measurement of radiation distribution in the field of high dose level. When the inner diameter of collimator is 8 mm, we have realized the optimum detecting efficiency and spatial resolution. At that time, the position resolution was 10 cm at 1 m from the system. And experimental results indicated that the energy resolution of the system were 10 % for 662 keV of Cs-137, 7.6 % for 1.17 MeV of Co-60, and 5.8 % for 1.33 MeV of Co-60. Also, we have shown that the real radiation distribution images may be obtained by our measurement system.

• Journal of Microbiology and Biotechnology
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• v.23 no.1
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• pp.7-14
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• 2013

In the Bacillus amyloliquefaciens ${\alpha}$-amylase (BAA), the loop (residues 176-185; region I) that is the part of the calcium-binding site (CaI, II) has two more amino acid residues than the ${\alpha}$-amylase from Bacillus licheniformis (BLA). Arg176 in this region makes an ionic interaction with Glu126 from region II (residues 118-130), but this interaction is lost in BLA owing to substitution of R176Q and E126V. The goal of the present work was to quantitatively estimate the effect of ionic interaction on the overall stability of the enzyme. To clarify the functional and structural significance of the corresponding salt bridge, Glu126 was deleted (${\Delta}$E126) and converted to Val (E126V), Asp (E126D), and Lys (E126K) by site-directed mutagenesis. Kinetic constants, thermodynamic parameters, and structural changes were examined for the wild-type and mutated forms using UV-visible, atomic absoption, and fluorescence emission spectroscopy. Wild-type exhibited higher $k_{cat}$ and $K_m$ but lower catalytic efficiency than the mutant enzymes. A decreased thermostability and an increased flexibility were also found in all of the mutant enzymes when compared with the wild-type. Additionally, the calcium content of the wild-type was more than ${\Delta}E126$. Thus, it may be suggested that ionic interaction could decrease the mobility of the discussed region, prevent the diffusion of cations, and improve the thermostability of the whole enzyme. Based on these observations, the contribution of loop destabilization may be compensated by the formation of a salt bridge that has been used as an evolutionary mechanism or structural adaptation by the mesophilic enzyme.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.3
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• pp.149-154
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• 2012

According to the coagulation tests for PACs with various basicities, the PACB with lower basicity showed higher coagulation efficiencies of organics and phosphorus than the PAC with higher basicity. The PACB contained higher amount of monomeric Al (III) hydrolytic species comparing with PAC. In case of the coagulation for the sewage treated water, the coagulation efficiency by the charge neutralization and sweep floc formation was higher with PACB than with PAC. Accordingly, when $Al_2O_3$ concentration was similar in the coagulant, PACB showed higher removal efficiencies of turbidity, $COD_{Mn}$, TP, and $PO_4$-P comparing with PAC, especially in the lower range of coagulant dose.