• Bulletin of the Korean Chemical Society
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• v.32 no.2
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• pp.467-471
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• 2011

Spin exchange interactions of $(C_2N_2H_{10})[Fe(HPO_3)F_3]$ were examined by performing a spin dimer analysis based on extended Huckel tight binding method and a mapping analysis based on first principles density functional theory. Spin exchange interactions occur through the super-superexchange paths $J_1$ and $J_2$ in $(C_2N_2H_{10})[Fe(HPO_3)F_3]$. In the super-superexchange path $J_2$ magnetic orbital interactions between eg-block levels are much stronger than those from $t_{2g}$-block levels. Both electronic structure calculations show that the spin exchange interaction through the super-superexchange path $J_2$ is much stronger than that of $J_1$.

• Journal of Applied Reliability
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• v.6 no.1
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• pp.51-61
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• 2006

Failure analyses were conducted on a crank shaft and a chock liner by using X-ray diffraction, optical microscopy and SEM/EDS techniques. In the crank shaft, a crack developed where a maximum tensile stress coincided with band structure formed by hot forging. The maximum tensile stress was observed to originate from volume expansion during high frequency induction heat treatment and the band structure to develop between upper and lower dies during hot forging. In the chock liner, the wear mechanism varied with the chemical affinity and hardness of liner material relative to friction pair of housing liner. Brass of low chemical affinity and hardness compared to housing liner showed uniform adhesive wear. STS 304 and STS 420J2 of high chemical affinity showed galling and scoring respectively.

• Journal of the Korean Chemical Society
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• v.24 no.2
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• pp.101-107
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• 1980

Composite ${\pi}$-structure analysis has been proposed for predicting relative isomer stabilities based on nonbonded effects: all the possible crowded ${\pi}$-structures are identified for each isomer, and the systems are represented by abbreviated notation of $(n{\pi}/m)$ : then using simple rules and additivity of the nonbonded effects, the order of stability can be determined. A number of examples are given in support of this analytical procedure.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.547-550
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• 2005

Recently, there has been a intensive social interest for concrete structures with respect to durability by carbonation, chemical attack etc. Specially, the deterioration of concrete due to chemical attack in environments such as Wastewater Treatment Facilities is important factors degrading the durability of concrete structure. The purpose of this paper is to evaluate on deterioration of Wastewater Treatment Facilities concrete to chemical attack through instrumental analysis such as XRD, SEM and EDS. According to the results of this study. Wastewater Treatment Facilities concrete to chemical attack due to $So_{4}^{2-},\;Mg^{2+}$ ions founded out to appear deterioration materials peak : ettringite/thaumasite. gypsum and brucite peak.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.186-190
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• 2011

Periodically ordered mesoporous manganese oxides were synthesized in a single and double replication procedure. Mesoporous SBA-15 and -16 silica and their reverse replica carbons were successively used as hard templates. The silica and carbon pore systems were infiltrated with $Mn(NO_3)_2{\cdot}xH_2O$ or $Mn(AcAc)_2$, which was then converted to $Mn_2O_3$ at 873 K; the silica and carbon matrix were finally removed by NaOH solution or calcinations in air. The structure of the mesoporous $Mn_2O_3$, using a carbon template, corresponds to that of the original SBA-15 and SBA-16 silica. The products consist of hexagonally arranged cylindrical mesopores with crystalline pore walls or cubic mesoporous pores. The structure of replica has been confirmed by XRD, TEM analysis, and its electrochemical properties were tested with cyclic voltammetry. Formation of $Mn_2O_3$ inside the mesoporous carbon pore system showed much improved electrical properties.

• Biomaterials and Biomechanics in Bioengineering
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• v.4 no.1
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• pp.1-8
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• 2019

The aim of this study was to investigate the effect of total polymer concentration on the chemical structure, morphology of pores, porosity, swelling ratio, degradation of gelatin-poly (vinyl alcohol) (Gel-PVA) cryogel scaffolds. Porous cryogels were prepared with cryogelation technique by using glutaraldehyde as a crosslinker. Functional group composition of cryogels after crosslinking was investigated by Fourier Transform Infrared (FTIR). The morphology of cryogels was characterized via scanning electron microscopy (SEM) and porosity analysis. All of the cryogels had a porous structure with an average pore size between $45.58{\pm}14.28$ and $50.14{\pm}4.26{\mu}m$. The cryogels were biodegradable and started to degrade in 14 days. As the polymer concentration increased the swelling ratio, the porosity and the degradation rate decreased. Spongy and mechanically stable Gel-PVA cryogels, with tunable properties, can be potential candidates as scaffolds for tissue engineering applications.

• The Korean Journal of Pesticide Science
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• v.8 no.3
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• pp.162-167
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• 2004

In recent years, the diamondback moth (DBM), Plutella xylostella has become one of the most important pests for cruciferous plants in the world. A new type of the thiophosphoryl pyrazole insecticide, called KH502. Its outstanding insecticidal activity could be effective alternative against DBM. We investigated, using the comparative molecular field analysis (CoMPA) method, The structure-activity relationship of various thiophosphorylpyrazole derivatives and structure requirement for insecticidal activity. We found, the key substructures in pyrazole derivatives, the trifluoro-methyl group and the thiophosphoryl group. Both play an important role in insecticidal activity with the binding site. The three dimensional Quantitative Structure Activity Relationship (QSAR) analysis could provide useful information for the structural requirements of pyrazole insecticide as an insecticidal and the design of a new insecticide.

• Proceedings of the KAIS Fall Conference
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• 2011.12a
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• pp.200-203
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• 2011

A copper-based metal organic framework (MOF) named Cu-BTC, also known as HKUST-1, was synthesized by using a solvothermal method at various synthesis temperature, time and pressure. The obtained samples were characterized with Powder X-ray diffraction (XRD) for phase structure, scanning electron microscopy (SEM) for crystal structure, and nitrogen adsorption-desorption for pore textural structure. The Cu-BTC sample was also studied for $CO_2$ adsorption. The analysis results displayed that the sample synthesized at the condition of temperature: $120^{\circ}C$, synthesis time: 12 hours, pressure: 1 bar exhibited a good crystal structure with uniform size of octahedral particles. The BET data revealed a high surface area of 1741.7 $m^2g^{-1}$ and a pore volume of 0.7137 $cm^3g^{-1}$and exhibiteda maximum $CO_2$ adsorption capacity of 170 mg/g of the sorbent at $25^{\circ}C$.

• Journal of the Korean Society of Safety
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• v.35 no.5
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• pp.1-8
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• 2020

Mobile elevating work platforms (MEWPs) consist of a work platform, extending structure, and chassis, and are used to move persons to working positions. MEWPs are useful but are composed of pieces of equipment, and accidents do occur owing to equipment defects. Among these defects, accidents caused by the fracture of bolts fixed to the extension structure and swing system are increasing. This paper presents a failure analysis of the fixing bolts of MEWP. Standard procedure for failure analysis was employed in this investigation. Visual inspection, chemical analysis, tensile strength measurement, microstructural characterization, fractography analysis by Optical Microscope(OM) and Scanning Electron Microscopy(SEM), and finite element analysis (FEA) were used to analyze the failure of the fixing bolts. Using this failure analysis approach, we found the root cause of failure and proposed a means for solving this type of failure in the future. First, the chemical composition of the fixing bolt is obtained by a spectroscopy chemical analysis method, which determined that the chemical composition matched the required standard. The tensile test showed that the tensile and yield strengths were within the required capacity. The stress analysis was carried out at five different boom angles, and it was determined that the fixing bolt of MEWP can withstand the loads at all the boom angles. The outcomes of the fatigue analysis revealed that the fixing bolt fails before reaching the design requirements. The results of the fatigue analysis showed primarily that the failure of the fixing bolt was due to fatigue. A visual inspection of the fractured section of the fixing bolt also confirmed the fatigue failure. We propose a method to prevent failure of the fixing bolt of the MEWP from four different standpoints: the manufacturer, safety certification authority, safety inspection agency, and owner.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.724-724
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• 2003