• Transactions on Electrical and Electronic Materials
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• v.18 no.4
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• pp.207-210
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• 2017

The suspension arrangement of insulators provides flexibility and assists in power transmission in transmission lines. The performance of the insulator string is strongly influenced by the environmental conditions to which it is exposed, its shape and the inherent material properties of suspension-type insulators. The suspension-type insulators are mostly made from glass, porcelain and ceramic material due to their high resistivity. Irregularity in charge distribution throughout the porcelain insulator may lead to accelerated aging and electrical breakdown. A very high and steep lightning impulse voltage may also cause breakdown of suspension-type insulators. We investigated various material characteristics such as alumina addition, surface morphology, x-ray diffraction pattern and relative density of suspension porcelain insulators manufactured in 1989 (36,000 lbs.), 1995 (36,000 lbs.) and 2001 (36,000 lbs.) by the KRI Company for use in 154 kV high power transmission lines. We compared the material characteristics of these porcelain insulators with that of the top-of-the-line porcelain insulators (36,000 lbs.) manufactured by the NGK Company in 2000. These suspension-type porcelain insulators were exposed to arc and flashover tests to examine their electrical and mechanical strength. It was noted that alumina addition (17 wt.%) for K-2001 was one of the major contributors to the enhancement of the performance of the porcelain insulators and to their ability to withstand very high current generation during the arc test. The porcelain insulators manufactured during 2001 also showed the highest relative density of 95.8% as compared to the other insulators manufactured in 1989 and 1995 respectively 94.2% and 91.5%. We also discuss reports of various failure modes of suspension-type porcelain insulators.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.245.2-245.2
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• 2013

Solution processed organic photovoltaic devices have relatively less attention compared to polymer photovoltaic devices even though they have high possibility to be developed because they have both advantages of polymer and organic, such as solution processable, no synthetic batch dependence of photovoltaic performance, high purity and high charge carrier mobility as well as relatively high efficiency (~7%). In addition, solution processed organic photovoltaic devices have an advantage of easiness to study the relationship between the molecular structure and photovoltaic performance due to its simple structure. In this work, five isoindigo based low band gap donor-acceptor-donor (D-A-D) small molecules with different electron donating strength were synthesized for investigating the relationship between the molecular structure and photovoltaic performance, especially, investigating the effects of different electron donating effect of donor group in isoindigo backbone to photovoltaic device performance. The variation of electron donating strength of donor group strongly affected the optical, thermal, electrochemical and photovoltaic device performances of isoindigo organic materials. The highest power conversion efficiency of ~3.2% was realized in bulk heterojuction photovoltaic device consisted of the ID3T as donor and PC70BM as acceptor. This work demonstrates the great potential of isoindigo moieties as electron deficient units as well as guideline for synthesis of donor-acceptor-donor (D-A-D) small molecules for realizing highly efficient solution processed organic photovoltaic devices.

• Korean Journal of Materials Research
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• v.26 no.2
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• pp.73-78
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• 2016

$TiO_2$ nanoparticles were synthesized by a sol-gel process using titanium tetra isopropoxide as a precursor at room temperature. Ag-doped $TiO_2$ nanoparticles were prepared by photoreduction of $AgNO_3$ on $TiO_2$ under UV light irradiation and calcinated at $400^{\circ}C$. Ag-doped $TiO_2$ nanoparticles were characterized for their structural and morphological properties by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The photocatalytic properties of the $TiO_2$ and Ag-doped $TiO_2$ nanoparticles were evaluated according to the degree of photocatalytic degradation of gaseous benzene under UV and visible light irradiation. To estimate the rate of photolysis under UV (${\lambda}=365nm$) and visible (${\lambda}{\geq}410nm$) light, the residual concentration of benzene was monitored by gas chromatography (GC). Both undoped/doped nanoparticles showed about 80 % of photolysis of benzene under UV light. However, under visible light irradiation Ag-doped $TiO_2$ nanoparticles exhibited a photocatalytic reaction toward the photodegradation of benzene more efficient than that of bare $TiO_2$. The enhanced photocatalytic reaction of Ag-doped $TiO_2$ nanoparticles is attributed to the decrease in the activation energy and to the existence of Ag in the $TiO_2$ host lattice, which increases the absorption capacity in the visible region by acting as an electron trapper and promotes charge separation of the photoinduced electrons ($e^-$) and holes ($h^+$). The use of Ag-doped $TiO_2$ nanoparticles preserved the option of an environmentally benign photocatalytic reaction using visible light; These particles can be applicable to environmental cleaning applications.

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.27-33
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• 2014

The significance of soil environment is gradually increased due to the soil and underwater contamination caused by petroleum leak accidents. It requires a high cost and long period for the purification of soil compared with other environmental matrix such as water and air. For this reason, it has been embroiled in a legal conflict to find the pollution source and charge of cleanup. In this study, we analyzed the physical properties and typical additives of jet fuel to search a method that can distinguish kerosene and jet fuel contamination. In particular, the chemical marker in kerosene was visualized by the developer and the additives in jet fuel, such as antioxidant and metal deactivator were detected by GC-MS. This study could be used to judge petroleum source at soil contaminant accident sites.

• Journal of Drive and Control
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• v.10 no.4
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• pp.1-6
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• 2013

With aggravation of environmental contamination and energy resource exhaustion, Hybrid Electric Vehicles (HEV) that can be economically operated with low fuel consumption are receiving greater attention. For performance improvement of such HEV, the development of efficient transmission can be seen as one of core technologies such as performance of components and driving strategy. Dual clutch transmission (DCT) is actively studied as a transmission type for HEV due to its advantages of having excellent power transmission efficiency based on manual transmission characteristic, resolving the problem of power interruption, and realizing driving convenience of automatic transmission (AT). In this paper, one diesel HEV equipped with 6-Speed DCT, modelled using MATLAB/Simulink, and a performance simulator developed for this vehicle are introduced. Driving simulation with driving cycles such as FTP75 and NYCC was performed using the developed performance simulator, and the simulated results regarding state of charge and fuel economy, when AT and DCT are applied to this diesel hybrid vehicle respectively, are compared. This performance simulator can be utilized to develop a control algorithm for improving the fuel economy of HEV with DCT.

• Bulletin of the Korean Chemical Society
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• v.15 no.2
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• pp.122-126
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• 1994

Corrosion of brass coated steel cords in the acetonitrile solution of sulfenamide derivatives, N-Cyclohexylbenzothiazole-2-sulfenamide (CBTS), N,N'-Dicyclohexylbenzothiazole-2-sulfenamide (DCBS), N-tert-Butylbenzothiazole-2-sulfenamide (TBBS), N-tert-Amylbenzothiazole-2-sulfenamide (TABS), and N-Oxydiethylbenzothiazole-2-sulfenamide (OBTS) was investigated by potentiostatic anodic and cathodic polarization (Tafel plot), DC polarization resistance, and AC impedance measurements. The corrosion current densities and rates are 1.236 ${\mu}A /cm^2$ and 0.655 MPY for CBTS; 1.881 ${\mu}A/cm^2$ and 0.988 MPY for DCBS; 2.367 ${\mu}A/cm^2$ and 1.257 MPY for TBBS; 3.398 ${\mu}A /cm^2$ and 1.809 MPY for TABS, respectively. OBTS among derivatives under study shows the lowest corrosion density (0.546 ${\mu}A /cm^2$) and the slowest corrosion rate (0.288 MPY). Also, the charge transfer resistances and the double layer capacitances are 275.21 $k{\Omega}{\cdot}cm^2$ and 7.0 ${\mu}F{cdot}cm^{-2}$ for CBTS; 14.24 ${\mu}F{\cdot}cm^2$ and 26 ${\mu}F{\cdot}cm^{-2}$ for DCBS; 54.15 $k{\Omega}{\cdot}cm^2$ and 26 ${\mu}F{\cdot}cm^{-2}$ for TBBS; 0.96$k{\Omega}{\cdot}cm^2$ and 83 ${\mu}F{\cdot}cm^{-2}$ for TABS, respectively. The weaker the electron donating inductive effect of derivatives is and the smaller the effect of steric hindrance is, the more the corrosion of brass coated steel cords in the acetonitrile solution of sulfenamide derivatives is prevented. The above results agree with that observed in the field of tire industry.

• Korean Journal of Chemical Engineering
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• v.35 no.12
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• pp.2442-2451
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• 2018

Novel highly active visible-light photocatalysts in the form of zinc bismuth oxide ($ZnBi_2O_4$) and graphite hybrid composites were prepared by coupling via a co-precipitation method followed by calcination at $450^{\circ}C$. The asprepared $ZnBi_2O_4$-graphite hybrid composites were tested for the degradation of rhodamine B (RhB) solutions under visible-light irradiation. The existence of strong electronic coupling between the two components within the $ZnBi_2O_4$-graphite heterostructure suppressed the photogenerated recombination of electrons and holes to a remarkable extent. The prepared composite exhibited excellent photocatalytic activity, leading to more than 93% of RhB degradation at an initial concentration of $50mg{\cdot}L^{-1}$ with 1.0 g catalyst per liter in 150 min. The excellent visible-light photocatalytic mineralization of $ZnBi_2O_4-1.0graphite$ in comparison with pristine $ZnBi_2O_4$ could be attributed to synergetic effects, charge transfer between $ZnBi_2O_4$ and graphite, and the separation efficiency of the photogenerated electrons and holes. The photo-induced $h^+$ and the superoxide anion were the major active species responsible for the photodegradation process. The results demonstrate the feasibility of $ZnBi_2O_4-1.0graphite$ as a potential heterogeneous photocatalyst for environmental remediation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.10
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• pp.761-767
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• 2006

In this study, performance of 2 pure hydrocarbons R290 and R1270 was measured in an attempt to substitute R22 under 3 different temperature conditions. They were tested in a refrigerating bench tester with a hermetic rotary compressor. The test bench provided about 3.5 kW capacity and water and water/glycol mixture were employed as the secondary heat transfer fluids. All tests were conducted under the same external conditions resulting in the average saturation temperatures of $7/45^{\circ}C$ and $-7/41^{\circ}C$ and $-21/28^{\circ}C$ in the evaporator and condenser, respectively. Test results show that the coefficient of performance (COP) of these refrigerants is up to 11.54% higher than that of R22 in all temperature conditions. Compressor discharge temperatures were reduced by $14{\sim}31^{\circ}C$ with these fluids. There was no problem with mineral oil since the mixtures were mainly composed of hydrocarbons. The amount of charge was reduced up to 58% as compared to R22. Overall, these fluids provide good performance with reasonable energy savings without any environmental problem and thus can be used as long term alternatives for residential air-conditioning and heat pumping application.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.58-63
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• 2006

In this study, performance of 2 pure hydrocarbons and 3 mixtures was measured in an attempt to substitute R22 under 3 different temperature conditions. The mixtures were composed of R1270(propylene), R290(propane) and R152a. They were tested in a refrigerating bench tester with a hermetic rotary compressor The test bench provided about 3.5 kW capacity and water and water/glycol mixture were employed as the secondary heat transfer fluids. All tests were conducted under the same external conditions resulting in the average saturation temperatures of $7^{\circ}C/45^{\circ}C$ and $-7^{\circ}C/41^{\circ}C$ and $-21^{\circ}C/28^{\circ}C$ in the evaporator and condenser, respectively. Test results show that the coefficient of performance (COP) of these refrigerants is up to 11.54% higher than that of R22 in all temperature conditions. Compressor discharge temperatures were reduced by $14{\sim}31^{\circ}C$ with these fluids. There was no problem with mineral oil since the mixtures were mainly composed of hydrocarbons. The amount of charge was reduced up to 58% as compared to R22. Overall, these fluids provide good performance with reasonable energy savings without any environmental problem and thus can be used as long term alternatives for residential air-conditioning and heat pumping application.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.4
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• pp.312-319
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• 2006

In this study, performance of 2 pure hydrocarbons and 7 mixtures was measured in an attempt to substitute HCFC22 used in air-conditioners and heat pumps. The mixtures were composed of R1270 (propylene), R290 (propane), HFC152a, and RE170 (Dimethyl ether, DME). The pure and mixed refrigerants tested have GWPs of $3{\sim}58$ as compared to that of $CO_2$ and the mixtures are all near-azeotropic showing the gliding temperature difference (GTD) of less than $0.6^{\circ}C$. Thermodynamic cycle analysis was carried out to determine the optimum compositions and actual tests were performed in a laboratory heat pump test bench at the evaporation and condensation temperatures of 7.5 and $45.1^{\circ}C$ respectively. Test results show that the coefficient of performance (COP) of these mixtures is up to 5.7% higher than that of HCFC22. While propane showed 11.5% reduction in capacity, most of the fluids tested had the similar capacity to that of HCFC22. Compressor discharge temperatures were reduced by $11{\sim}17^{\circ}C$ with these fluids. There was no problem with mineral oil since the mixtures were mainly composed of hydrocarbons. The amount of charge was reduced up to 55% as compared to HCFC22. Overall, these fluids provide good performance with reasonable energy savings without any environmental problem and thus can be used as long term alternatives for. residential air-conditioning and heat pumping application.