• Bulletin of the Korean Chemical Society
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• v.35 no.10
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• pp.2995-3000
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• 2014

A sensitive concentration method utilising modified gas-purge microsyringe extraction (GP-MSE) was developed. Concentration (reduction in volume) to a microlitre volume was achieved. PAHs were utilised as semivolatile analytes to optimise the various parameters that affect the concentration efficiency. The injection rate and temperature were the key factors that affected the concentration efficiency. An efficient concentration (75.0-96.1%) of PAHs was obtained under the optimised conditions. The method exhibited good reproducibility (RSD values that ranged from 1.5 to 9.0%). The GP-MSE concentration method enhances the volume reduction (concentration factor), leading to a low method detection limit ($0.5-15ngL^{-1}$). Furthermore, this method offers the advantage of small-volume sampling, enabling even the detection of diurnal hourly changes in the concentration of PAHs in ambient air. Utilising this method in combination with GC-MS, the diurnal hourly flux of PAHs from the gas phase of ambient air was measured. Indeed, the proposed technique is a simple, fast, low-cost and environmentally friendly.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.38-45
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• 2004

This paper studies the effects of intake port configuration on the swirl that is key parameter in the flow field of direct injection diesel engines. In-cylinder flow characteristics is known to have significant effects on fuel air mixing, combustion and emissions. To investigate the swirl flow generated by various intake ports, steady state flow tests were conducted to evaluate the swirl. Helical port geometry, SCV shape and bypass were selected as the design parameters to increase the swirl flow and parametric study was performed to choose the optimal port shape that would generate a high swirl ratio efficiently. The results revealed that a key factor in generating a high swirl ratio was to suitably control the direction of the intake air flow passing through the valve seat. For these purposes, we changed the distance of helical and tangential port as well as installed bypass near the valve seat and the effects of intake port geometry on in-cylinder flow field were visualized by a laser sheet visualization method. From the experimental results, we found that the swirl ratio and mass flow rate had a trade off relation. In addition, the result indicates that the bypass is a effective method to increase the swirl ratio without sacrificing mass flow rate.

• Journal of Ginseng Research
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• v.41 no.4
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• pp.503-512
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• 2017

Background: Chronic heavy alcohol consumption may raise the risk of developing type 2 diabetes mellitus. Saponins inhibit apoptosis of pancreatic islet cells and reduce lipid parameters. The present study was designed to investigate the effect of saponin on chronic ethanol-treated diabetic rats. Methods: Long-Evans Tokushima Fatty (LETO) and Otsuka Long-Evans Tokushima Fatty (OLETF) rats were pair-fed a Lieber-DeCarli diet with and without 5% ethanol for 12 wks. Two weeks after starting the pair-feeding with the Lieber-DeCarli diet, intraperitoneal injection of saponin was performed for 10 wks. To perform the experiments, rats were divided as follows: LETO-Control (LC), LETO-Ethanol (LE), LETO-Ethanol-Saponin (LES), OLETF-Control (OC), OLETF-Ethanol (OE), and OLETF-Ethanol-Saponin (OES). Results: The weights of epididymal and mesenteric fat tissue in LES and OES rats were the lightest from among the LETO and OLETF groups, respectively. The secretion of alanine aminotransferase and cholesterol in OES rats decreased significantly compared to their secretion in OC and OE rats, respectively. The islets of the pancreas in LE and OE rats showed clean, unclear, and smaller morphology compared to those of LC, LES, OC, and OES rats. In addition, the expression of insulin in the islets of the pancreas in LC, LES, OC, and OES rats was higher than in LE and OE rats. Conclusion: Saponin may not only be helpful in alleviating the rapid progress of diabetes due to chronic alcohol consumption in diabetic patients, but may also show potential as an antidiabetic drug candidate for diabetic patients who chronically consume alcohol.

• Nuclear Engineering and Technology
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• v.24 no.3
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• pp.274-284
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• 1992

A 1/15-scale CREARE experiment, which simulates the thermal-hydraulic behavior in the reactor pressure vessel of a PWR during a hypothetical Loss Of Coolant Accident, has been analyzed using CATHARE code for the associated model assessment to represent the phenomenon. The key parameters examined in the CREARE experiment were known as ECC water injection rate. ECC water subcooling, system pressure, and steam flow rate coming out from the core bottom. The present CATHARE simulation, however, has been mainly focused on qualitative analysis of a countercurrent flow in the downcomer. The discrepancy of the simulation results with the experimental data is considered arising primarily from an inadequate numerical representation as well as an interfacial friction model. Accordingly it is suggested from the sensitivity studies that either multidimensional approach or further examination of momentum equations at a junction near a volume element in CATHARE be necessary in order to represent the phenomenon more realistically.

• Journal of Korean Medicine Rehabilitation
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• v.26 no.3
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• pp.1-15
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• 2016

Objectives This study was designed to evaluate the anti-inflammatory effects of Seungseup-tang (SST) on the monosodium iodoacetate (MIA)-induced osteoarthritis rats. Methods Osteoarthritis was induced by injection of MIA ($50{\mu}l$ with 80 mg/ml) into knee joint cavity of rats. Rats were divided into 4 groups (normal group, control group, indomethacin treated group, SST treated group, each n=6). Normal group was not injected with MIA and taken normal diet. Control group was injected with MIA and taken with distilled water. Indomethacin treated group was injected with MIA and taken indomethacin 5 mg/kg by oral administration. SST treated group was injected with MIA and taken SST 200 mg/kg by oral administration. We examined the weight-bearing ability of hind paw, biomarkers related to oxidative stress in serum, inflammatory proteins and inflammatory mediators and cytokines. Moreover, histopathological examination of knee joint structure was also performed by Hematoxylin & Eosin (H&E), Safranin-O staining method. Results In the present study, SST treated group showed a similar inhibitory effects alike indomethacin treated group, in most of the studied parameters of inflammation. The increased oxidative stress biomarker such as reactive oxygen species (ROS) and peroxy nitrite ($ONOO^-$) in the serum were reduced with SST. Especially, the level of $ONOO^-$ compared with control group significantly suppressed. Also, the expression of inflammatory mediators and cytokines induced by nuclear factor-kappa B (NF-${\kappa}B$) activation was modulated through inhibition of IkBa phosphorlation. In addition, histological analysis revealed that cartilage damage by MIA repaired markedly in SST treated group. Conclusions According to the results, Seungseup-tang may be effective for preventing the progression of osteoarthritis.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.117-124
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• 2018

Junctionless amorphous InGaZnO thin film transistors with different film thickness have been fabricated. Their device performance parameters were extracted and gate oxide breakdown voltages were analyzed with different film thickness. The device performances were enhanced with increase of film thickness but the gate oxide breakdown voltages were decreased. The device performances were enhanced with increase of temperatures but the gate oxide breakdown voltages were decreased due to the increased drain current. The drain current under illumination was increased due to photo-excited electron-hole pair generation but the gate oxide breakdown voltages were decreased. The reason for decreased breakdown voltage with increase of film thickness, operation temperature and light intensity was due to the increased number of channel electrons and more injection into the gate oxide layer. One should decide the gate oxide thickness with considering the film thickness and operating temperature when one decides to replace the junctionless amorphous InGaZnO thin film transistors as BEOL transistors.

• Transactions on Electrical and Electronic Materials
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• v.16 no.3
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• pp.124-129
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• 2015

Organic electronics are the domain in which the components and circuits are made of organic materials. This new electronics help to realize electronic and optoelectronic devices on flexible substrates. In recent years, organic materials have replaced conventional semiconductors in many electronic components such as, organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic (OPVs). It is well known that organic light emitting diodes (OLEDs) have many advantages in comparison with inorganic light-emitting diodes LEDs. These advantages include the low price of manufacturing, large area of electroluminescent display, uniform emission and lower the requirement for power. The aim of this paper is to model polymer LEDs and OLEDs made with small molecules for studying the electrical and optical characteristics. The purpose of this modeling process is, to obtain information about the running of OLEDs, as well as, the injection and charge transport mechanisms. The first simulation structure used in this paper is a mono layer device; typically consisting of the poly (2-methoxy-5(2'-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) polymer sandwiched between an anode with a high work function, usually an indium tin oxide (ITO) substrate, and a cathode with a relatively low work function, such as Al. Electrons will then be injected from the cathode and recombine with electron holes injected from the anode, emitting light. In the second structure, we replaced MEH-PPV by tris (8-hydroxyquinolinato) aluminum (Alq₃). This simulation uses, the Poole-Frenkel -like mobility model and the Langevin bimolecular recombination model as the transport and recombination mechanism. These models are enabled in ATLAS- SILVACO. To optimize OLED performance, we propose to change some parameters in this device, such as doping concentration, thickness and electrode materials.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.230-235
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• 2005

Reversed-phase high-performance liquid chromatography (RP-HPLC) was used to determine the equilibrium isotherm of single and multi-components of dUrd(2'-deoxyuridine), dGuo(2'-deoxyguanosine), and dAdo(2'-deoxyadenosine) of 2'-deoxyribonucleosides by dynamic method. The composition of mobile phase was 90/10 vol.% (water/MeOH). With an increase in the injection volumes, the retention times were shorter and the peak shapes were triangle-shaped, so Langmuir-type isotherm was assumed. The Langmuir adsorption parameters were estimated by PIM (pulsed-input method), and the competitive Langmuir adsorption isotherm was further utilized. For the sample of the dUrd and dGuo whose retention times were relatively short, the agreement of between the calculated value and experimental data was fairly good in both single and multi-components, but for the dAdo, the last eluting component, some deviations were caused by non-linear and non-ideal properties.

• Investigative Magnetic Resonance Imaging
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• v.19 no.4
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• pp.212-217
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• 2015

Purpose: For a single time-point hyperpolarized $^{13}C$ magnetic resonance spectroscopy imaging (MRSI) of animal models, scan-time window after injecting substrates is critical in terms of signal-to-noise ratio (SNR) of downstream metabolites. Pre-scans of time-resolved magnetic resonance spectroscopy (MRS) can be performed to determine the scan-time window. In this study, based on two-site exchange model, protocol-specific simulation approaches were developed for $^{13}C$ MRSI and the optimal scan-time window was determined to maximize the SNR of downstream metabolites. Materials and Methods: The arterial input function and conversion rate constant from injected substrates (pyruvate) to downstream metabolite (lactate) were precalibrated, based on pre-scans of time-resolved MRS. MRSI was simulated using two-site exchange model with considerations of scan parameters of MRSI. Optimal scan-time window for mapping lactate was chosen from simulated lactate intensity maps. The performance was validated by multiple in vivo experiments of BALB/C nude mice with MDA-MB-231 breast tumor cells. As a comparison, MRSI were performed with other scan-time windows simply chosen from the lactate signal intensities of pre-scan time-resolved MRS. Results: The optimal scan timing for our animal models was determined by simulation, and was found to be 15 s after injection of the pyruvate. Compared to the simple approach, we observed that the lactate peak signal to noise ratio (PSNR) was increased by 230%. Conclusion: Optimal scan timing to measure downstream metabolites using hyperpolarized $^{13}C$ MRSI can be determined by the proposed protocol-specific simulation approaches.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.2
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• pp.40-50
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• 2010

The studies of PMOS transistors in CMOS technologies are reviewed- focusing on the snapback and breakdown behavior of the parasitic PNP BJTs in high current regime. A new failure mechanism of PMOSFET devices under ESD conditions is also analyzed by investigating various I/O structures in a $0.13\;{\mu}m$ CMOS technology. Localized turn-on of the parasitic PNP transistor can be caused by localized charge injection from the adjacent diodes into the body of the PMOSFET, significantly degrading the ESD robustness of PMOSFETs. Based on 2-D device simulations the critical layout parameters affecting this problem are identified. Design guidelines for avoiding this new PMOSFET failure mode are also suggested.