• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.8
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• pp.608-613
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• 2013

In this paper, the low-temperature sintering of $TiO_2$ is approached to solve the problem of high temperature sintering which decreases the interconnection between particles or between substrate and particle. $TiO_2$ paste is prepared with Titanium (IV) isopropoxide as the precursor material and calcinate at different conditions (low temperature). In the results, since the changing of temperature and time of sintering, crystalline phase do not change and the intensities of anatase, rutile phase are higher. At $110^{\circ}C$, 7 h sintering condition, crystalline size of anatase and rutile phase are the smallest which are 13.07 and 17.47 nm, respectively. In addition, the highest zeta potential is about 32.77 mV and the repulsive force increases thus leading to the best of the dispersion characteristics between $TiO_2$ particles. Futhermore, DSSCs at that condition exhibits the highest efficiency with the values of $V_{oc}$, $J_{sc}$, FF and ${\eta}$ are 0.69 V, $8.60mA\;cm^{-2}$, 67.93% and 4.06%, respectively.

• Journal of Hydrogen and New Energy
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• v.3 no.2
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• pp.25-33
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• 1992

With the aim to obtain $TiO_2$ films with an increased photorespones and absorbance in the visible region of the solar spectrum, the direct oxidation of titanium alloys were performed. In this study, $Ti-Ga_2O_3$ alloy was prepared by mixing, pressing and arc melting of appropriate amounts of titanium and $Ga_2O_3$ powder. Electrochemical measurements were performed in three electrode cell using electrolyte of 1M NaOH solution. The oxide films on $Ti-Ga_2O_3$ alloy was composed of $Ti_2O$, TiO, $TiO_2$, $Ga_2TiO_5$. The free energy efficiency (${\eta}e$) of $Ti-Ga_2O_3$ oxide films had 0.8~1.3 % and were increased with the increase of $Ga_2O_3$ content up to 10wt %. The onset potential ($V_{on}$) had -0.8V~0.9V ranges and were shifted to anodic direction with the increase of $Ga_2O_3$ content. The spectral response of Ti-$Ga_2O_3$ oxides were similar to the response of the $TiO_2$ and their $E_g$ were observed to 2.90~3.0eV. Variations of onset potential($V_{on}$) associated with electrolyte pH were -59mV/pH. This probably reflects the nature of the bonding of $OH^-$ ion to the $TiO_2$ surface, a common phenomena in the transition-metal oxides.

• Restorative Dentistry and Endodontics
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• v.12 no.1
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• pp.39-49
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• 1986

The purpose of this study was to observe characteristic properties through the polarization curves and SEM images from 4 different types of amalgam obtained by using the potentiostats (Princeton EG & G) & SEM (Jeol/35), and to investigate the degree of corrosion on the oxidation peak of the each phase of amalgam. After each amalgam alloy and Hg was triturated as the direction of the manufacturer by means of the mechanical amalgamator (Shofu Co.), the triturated mass was inserted into the cylindrical metal mold which was 12mm in diameter and 10.0mm in height and was condensed by using routine manner. The specimen was removed from the mold and stored at room temperature for about 24 hours. The standard surface preparation was routinely carried out. Anodic polarization measurement was employed to confirm the corrosion behaviour of the amalgams in a 0.9% saline solution (P.H: 6.8-7.0) at $37^{\circ}C$. The initial rest potential (corrosion potential) was determined after 30 minutes of immersion of specimen in electrolyte, and the potential scan was begun at the point of 100mV cathodic from the corrosion potential. The scan rate was 0.17mV/sec. in the study to observe the degree of corrosion of each phase. SEI and EPMA images on the determined oxidation peaks of each amalgam were observed. The results were as follows: 1. In the four anodic polarization curves, low copper amalgams have three oxidation peaks and high copper amalgams have two oxidation peaks, -270mV, +26mV and +179mV(SEC) in the low copper lathe cut, and -300mV, +39mV and +163mV(SEC) in the low copper spherical. -4mV and +154mV(SEC) in the Dispersalloy, and +17mV and +180mV(SEC) in the Tytin as high copper amalgams. 2. ${\gamma}_2$ phase in the low copper amalgam and ${\eta}$ phase in the high copper amalgam were the most corrodible phases and Ag-Cu eutectic in high copper amalgam was the most slowly corroded phase. 3. Low copper amalgam was more susceptible in corrosion than high copper amalgam.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.2
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• pp.145-154
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• 2013

HNS, including crude oil and products, shipments have increased. The risk analysis of HNS has assumed the importance, especially in maritime transportation area. There are various forms and kinds of HNS and the consequences of an accident are serious. In order to provide practical measures for preventing accidents, this study analyses the potential risks of HNS on maritime transportation accidents at domestic sea by using Event Tree Analysis. This study carries out risk assessment with F-N curve and risk matrix focusing on liquid cargo carriers (Oil and Products Tanker, Chemical Tanker, LPG/LNG Tanker, etc.). Explosion and sinking, suffocation indicate high consequence when on collision represent high probability. Improving human errors should be the main factor to mitigate risk on human lives.

• Journal of the Korean Chemical Society
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• v.55 no.5
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• pp.733-740
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• 2011

Multiple regression analysis was used for the calculation of pKa values of 15 substituted benzaldoximes by using various types of descriptors as parameters. These descriptors are based on quantum mechanical treatments. They were derived by employing semi-empirical calculation represented by the PM3 model and an Abinitio method expressed by Hartree-Fock(HF) model performed at the 6-311 G(d, p) level of theory. The parameters tested for their ability to represent the variations observed in the experimental pKa(s) are atomic and structural properties including Muliken charges on the atoms of hydroxyl group and C=N bond, the angle $C_6-C_1-C_7$, and length of O-H bond. Molecular properties are also used like energies of HOMO and LUMO, hardness(${\eta}$), chemical potential(${\mu}$), total energy(TE), dipole of molecule(DM), and electrophilicity index(W). The relation between pKa values and each of these parameters of the studied compounds is investigated. Depending on these relations, two sets of parameters were constructed for comparison between the PM3 and HF methods. The results obtained favor the Abinitio method for such applications although both models proved to have high predictive power and have sufficient reliability to describe the effect of substituents on pKa values of benzaldoxime compounds under consideration which is clear from the values of correlation coefficient $R^2$ obtained and the consistency between the experimental and the calculated values.

• Korean Journal of Materials Research
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• v.20 no.9
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• pp.483-487
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• 2010

To fabricate $TiO_2$ nanoparticle-based dye sensitized solar cells (DSSCs) at a low-temperature, DSSCs were fabricated using hydropolymer and ZnO nanoparticles composites for the electron transport layer around a low-temperature ($200^{\circ}C$). ZnO nanoparticle with 20 nm and 60 nm diameter were used and Pt was deposited as a counter electrode on ITO/glass using an RF magnetron sputtering. We investigate the effect of ZnO nanoparticle concentration in hydropolymer and ZnO nanoparticle solution on the photoconversion performance of the low temperature fabricated ($200^{\circ}C$) DSSCs. Using cis-bis(isothiocyanato)bis(2,20 bipyridy1-4,40 dicarboxylato) ruthenium (II) bis-tetrabutylammonium (N719) dye as a sensitizer, the corresponding device performance and photo-physical characteristics are investigated through conventional physical characterization techniques. The effect of thickness of the ZnO photoelectrode and the morphology of the ZnO nanoparticles with the variations of hydropolymer to ZnO ratio on the photoconversion performance are also investigated. The morphology of the ZnO layer after sintering was examined using a field emission scanning electron microscope (FE-SEM). 60 nm ZnO nanoparticle DSSCs showed an incident photon-to-current conversion efficiency (IPCE) value of about 7% higher than that of 20 nm ZnO nanoparticle DSSCs. The maximum parameters of the short circuit current density ($J_{sc}$), the open circuit potential ($V_{oc}$), fill factor (ff), and efficiency ($\eta$) in the 60 nm ZnO nanoparticle-based DSSC devices were 4.93 mA/$cm^2$, 0.56V, 0.40, and 1.12%, respectively.

• Journal of Microbiology and Biotechnology
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• v.23 no.2
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• pp.161-166
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• 2013

At present, acetylcholinesterase (AChE) inhibitors are the first group of drugs to treat mild to moderate Alzheimer's disease (AD). Although beneficial in improving cognitive and behavioral symptoms, the effectiveness of AChE inhibitors has been questioned since they do not delay or prevent neurodegeneration in AD patients. Therefore, in the present study, in order to develop new and effective anti-AD agents from lichen products, both the AChE inhibitory and the neuroprotective effects were evaluated. The AChE inhibitory assay was performed based on Ellman's reaction, and the neuroprotective effect was evaluated by using the MTT method on injured PC12 cells. One AChE inhibitor ($IC_{50}$ = 27.1 ${\mu}g/ml$) was isolated by means of bioactivity-guided isolation from the extract of lichen-forming fungus Cladonia macilenta, which showed the most potent AChE inhibitory activity in previous screening experiment. It was then identified as biruloquinone by MS, and $^1H$- and $^{13}C$-NMR analyses. The inhibitory kinetic assay suggested that biruloquinone is a mixed-II inhibitor on AChE. Meanwhile, biruloquinone improved the viability of the $H_2O_2$- and ${\beta}$-amyloid-injured PC12 cells at 1 to 25 ${\mu}g/ml$. The protective effects are proposed to be related to the potent antioxidant activities of biruloquinone. These results imply that biruloquinone has the potential to be developed as a multifunctional anti- AD agent.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.388-388
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• 2016

Chemical mist deposition (CMD) of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was investigated with cavitation frequency f, solvent, flow rate of nitrogen, substrate temperature $T_s$, and substrate dc bias $V_s$ as variables for efficient PEDOT:PSS/crystalline (c-)Si heterojunction solar cells (Fig. 1). The high-speed camera and differential mobility analysis characterizations revealed that average size and flux of PEDOT:PSS mist depend on f, solvent, and $V_s$. The size distribution of mist particles including EG/DI water cosolvent is also shown at three different $V_s$ of 0, 1.5, and 5 kV for a f of 3 MHz (Fig. 2). The size distribution of EG/DI water mist without PEDOT:PSS is also shown at the bottom. A peak maximum shifted from 300-350 to 20-30 nm with a narrow band width of ~150 nm for PEDOT:PSS solution, whose maximum number density increased significantly up to 8000/cc with increasing $V_s$. On the other hand, for EG/water cosolvent mist alone, the peak maximum was observed at a 72.3 nm with a number density of ~700/cc and a band width of ~160 nm and it decreased markedly with increasing $V_s$. These findings were not observed for PEDOT:PSS/EG/DI water mist. In addition, the Mie scattering image of PEDOT:PSS mist under white bias light was not observed at $V_s$ above 5 kV, because the average size of mist became smaller. These results imply that most of solvent is solvated in PEDOT:PSS molecule and/or solvent is vaporized. Thus, higher f and $V_s$ generate preferentially fine mist particle with a narrower band width. Film deposition occurred when $V_s$ was impressed on positive to a c-Si substrate at a Ts of $30-40^{\circ}C$, whereas no deposition of films occurred on negative, implying that negatively charged mist mainly provide the film deposition. The uniform deposition of PEDOT:PSS films occurred on textured c-Si(100) substrate by adjusting $T_s$ and $V_s$. The adhesion of CMD PEDOT:PSS to c-Si enhanced by $V_s$ conspicuously compared to that of spin-coated film. The CMD PEDOT:PSS/c-Si solar cell devices on textured c-Si(100) exhibited a ${\eta}$ of 11.0% with the better uniformity of the solar cell parameters. Furthermore, ${\eta}$ increased to 12.5% with a $J_{sc}$ of $35.6mA/cm^2$, a $V_{oc}$ of 0.53 V, and a FF of 0.67 with an antireflection (AR) coating layer of 20-nm-thick CMD molybdenum oxide $MoO_x$ (n= 2.1) using negatively charged mist of 0.1 wt% 12 Molybdo (VI) phosphoric acid n-Hydrate) $H_3(PMo_{12}O_40){\cdot}nH_2O$ in methanol. CMD. These findings suggest that the CMD with negatively charged mist has a great potential for the uniform deposition of organic and inorganic on textured c-Si substrate by adjusting $T_s$ and $V_s$.

• Fire Science and Engineering
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• v.15 no.1
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• pp.84-92
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• 2001

In today's world, rise in the establishment of social infrastructure resulting from population saturation in large cities has led to more extensive and frequent use of chemical materials on facilities. A result, unexpected and serious accidents, hazards, contingencies and disasters are more prevalent than ever. Such phenomenon calls for more devoted and concerted efforts towards finding ways to reduce the safety hazards that are seen to take place more often than before with the increase in the number of facilities that are prone to bring disaster and hazard coupled with the conventional safety problems that continue to exist even today. In developed countries, such challenge is addressed by various appropriate countermeasures drawn up by local professional committees on industrial facilities, whose members conduct offsite and onsite evaluation un the potential industrial disasters and its seriousness and provide their advice thereof. Against this backdrop, this study aims at identifying a comprehensive safety allowance level (safety acceptable level) when imposing limitation on the development of conventional or new facilities, for the fur pose of establishing a safety allowance level of disastrous and dangerous facilities in Korea. This is done by assessing and applying the level of danger each individual is exposed to in a randomly selected region (disastrous and dangerous areas in Seoul) based on probability of quantitative hazards, as well as simulation and calculation methods which include: i) social disaster evaluation method applying Quantified Risk Assessment of Health & Safety Executive of UK and Matrix of Risk of Evaluated Sources of Hazard; ii) Fault Tree or Event Tree Analysis and etc.