• Bulletin of the Korean Chemical Society
• /
• v.27 no.2
• /
• pp.277-280
• /
• 2006

Rapid and highly sensitive determination of nicotine in a PDMS microfluidic channel was investigated using surface enhanced Raman spectroscopy (SERS). A three-dimensional PDMS microfluidic channel was fabricated for this purpose. This channel shows a high mixing efficiency because the transverse and vertical dispersions of the fluid occur simultaneously through the upper and lower zig zag-type blocks. A higher efficiency of mixing could also be obtained by splitting each of the confluent streams into two sub-streams that then joined and recombined. The SERS signal was measured after nicotine molecules were effectively adsorbed onto silver nanoparticles by passing through the three-dimensional channel. A quantitative analysis of nicotine was performed based on the measured peak area at 1030 $cm^{-1}$. The detection limit was estimated to be below 0.1 ppm. In this work, the SERS detection, in combination with a PDMS microfluidic channel, has been applied to the quantitative analysis of nicotine in aqueous solution. Compared to the other conventional analytical methods, the detection sensitivity was enhanced up to several orders of magnitude.

• ETRI Journal
• /
• v.24 no.3
• /
• pp.221-225
• /
• 2002

We performed nonlinear transmission measurements and quantum-chemical calculations on dithienothiophene(DTT)-based molecules to gain insight into the effect of acceptor and donor groups on two-photon absorption(TPA) properties. The TPA intensity showed dispersion characteristics of the single-photon absorption spectrum. When the molecules included an asymmetric donor-acceptor pair, the single- and two-photon absorption maximum wavelengths were red-shifted more than when the molecules had a symmetric donor-donor structure. We interpreted this result as indicating that the $S_2$ state plays the dominating role in the absorption process of molecules with a symmetric structure. The experimental TPA ${\delta}$ values at the absorption peak wavelength showed a dependence on the structural variations. We found the self-consistent force-field theory and Hartree-Fock Hamiltonian with single configuration interaction formalism to be valid for evaluating TPA ${\delta}$. Although the quantum-chemical calculations slightly underestimated the experimental ${\delta}$ values obtained from nonlinear trans -mission measurements, they reasonably predicted the dependence of the ${\delta}$ value on the structural variations. We confirmed the role of molecular symmetry by observing that donor-donor substituted structure gave the highest experimental and theoretical TPA ${\delta}$ values and that the donor-acceptor substituted structure showed a greater red-shift in the TPA absorption maximum wavelength. Overall, the theoretical ${\delta}$ values of DTT-based molecules were in the order of $10^{-46}\;cm^4{\cdot}s{\cdot}photon^{-1}$ and are higher than that of AF-50 by nearly two orders of magnitude.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.57 no.2
• /
• pp.135-139
• /
• 2008

MFISFETs with platinum electrode on the $LiNbO_3$/aluminum nitride/Si(100) structures were successfully fabricated and the properties of the FETs have been discussed. $I_D-V_G$ characteristics of MFISFETs for linear region (that is, 0.1 V of the drain voltage) showed hysteresis loop with a counter-clockwise trace due to the ferroelectric nature of $LiNbO_3$ films. A memory window (i.e., threshold voltage shift) of the fabricated device was about 2[V] for a sweep from -4 to +4[V]. The estimated field-effect electron mobility and transconductance on a linear region were 530[$cm^2/V{\cdot}s$] and 0.16[mS/mm], respectively. The drain current of 27[${\mu}A$] on the "on" state was more than 3 orders of magnitude larger than that of 30[nA] on the "off" state at the same "read" gate voltage of l.5[V], which means the memory operation of the MFISFET.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1998.06a
• /
• pp.63-66
• /
• 1998

Prototype MFSFET′s using ferroelectric oxide LiNbO$_3$ as a gate insulator have been successfully fabricated with the help of 2 sheets of metal masks and demonstrated nonvolatile memory operations of the MFSFET′s. The estimated field-effect electron mobility and transconductance on a linear region of the fabricated FET were 600 $\textrm{cm}^2$/V.s and 0.16 mS/mm, respectively. The drain current of the "on" state was more than 4 orders of magnitude larger than the "off" state current at the same "read" gate voltage of 0.5 V, which means the memory operation of the MFSFET. A write voltage as low as $\pm$3 V, which is applicable to low power integrate circuits, was used for polarization reversal.

• Proceedings of the KIEE Conference
• /
• 2006.10a
• /
• pp.48-49
• /
• 2006

Highly conductive and transparent films of Ga-doped ZnO have been prepared by pulsed laser deposition using a ZnO target with 3 wt% ${Ga_2}{O_3}$ dopant. Films with the resistivity as low as $3.3{\times}10^{-4}{\Omega}cm$ and the transmittance above 80 % at the wavelength of 400 to 800 nm can be fabricated on glass substrate at room temperature. It is shown that a stable resistivity for the use in oxidation ambient at high temperature can be obtained for the films. Heat treatments were performed to examine the thermal stability of ZnO and GZO films at ptemperature range from $100^{\circ}C$ to $400^{\circ}C$ in $O_2$ ambient for 30 minutes. The resistivity of ZnO film annealed at $400^{\circ}C$ increased by two orders of magnitude, in case of GZO film was relatively stable up to at $400^{\circ}C$. For practical applications at high temperatures the thermal stability of resistivity of GZO thin films might become an advantage for transparent electrodes.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
• /
• 2002.11a
• /
• pp.81-84
• /
• 2002

The effects of the isoelectronic AI-doping of GaN grown by metal organic chemical vapor deposition were investigated for the first time using scanning electron microscopy (SEM), Hall measurements, photoluminescence (PL), and time-resolved PL. When a certain amount of Al was incorporated into the GaN films, the room temperature photoluminescence intensity of the films was approximately two orders larger than that of the undoped GaN. More importantly, the electron mobility significantly increased from 130 for the undoped sample to $500\textrm{cm}^2/Vs$ for the sample grown at a TMAl flow rate of $10{\mu}mol/min$, while the unintentional background concentration only increased slightly relative to the TMAl flow. The incorporation of Al as an isoelectronic dopant into GaN was easy during MOCVD growth and significantly improved the optical and electrical properties of the film. This was believed to result from a reduction in the dislocation-related non-radiative recombination centers or certain other defects due to the isoelectronic Al-doping.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.2
• /
• pp.40.4-41
• /
• 2018

The current 'standard model' of cosmology provides a minimal theoretical framework that can explain the gaussian, nearly scale-invariant density perturbations observed in the CMB to the late time clustering of galaxies. However accepting this framework, requires that we include within our cosmic inventory a vacuum energy that is ~122 orders of magnitude lower than Quantum Mechanical predictions, or alternatively a new scalar field (dark energy) that has negative pressure. An alternative approach to adding extra components to the Universe would be to modify the equations of Gravity. Although GR is supported by many current observations there are still alternative models that can be considered. Recently there have been many works attempting to test for modified gravity using the large scale clustering of galaxies, ISW, cluster abundance, RSD, 21cm observations, and weak lensing. In this work, we compare various modified gravity models using cosmic shear data from the Deep Lens Survey as well as data from CMB, SNe Ia, and BAO. We use the Bayesian Evidence to quantify the comparison robustly, which naturally penalizes complex models with weak data support. In this talk we present our methodology and preliminary results that show f(R) gravity is mildly disfavoured by the data.

• Journal of Soil and Groundwater Environment
• /
• v.27 no.1
• /
• pp.60-70
• /
• 2022

We evaluated the performance of in-situ capping to prevent the release of phenol, one of hazardous chemicals of concern for their impact on sediment. Sediment near the estuary of Hyeongsan River, Korea, and commercially-available sand were collected to evaluate their physical properties and phenol sorption characteristics. Biodegradation kinetics of phenol spiked into the sediment was evaluated under freshwater and estuarine salinity conditions. These experimental measurements were parameterized and used as input parameters for executing CapSim, a software predicting the performance of in-situ capping. The CapSim simulation demonstrated that capping with 50-cm sand reduced the phenol release by several orders of magnitude over 0.25- and 1-year duration for almost all simulation scenarios. The variables tested, i.e., cap thickness, pore-water movement, and biodegradation rate, showed high correlation to each other to influence the extent of phenol release from sediment to the water column. The findings and the framework employed to evaluate the performance of in-situ capping in this study can be adopted to determine whether in-situ capping is appropriate remedial approach at sediment sites impacted by hazardous chemicals due to accidental spills.

• Korean Journal of Environmental Biology
• /
• v.27 no.4
• /
• pp.397-405
• /
• 2009

We assessed the physical habitat conditions of pale chub (Zacco platypus) considering various stream order in the Geum river basin. Field monitoring was conducted for ecological and habitat conditions for 28 sites from October 2007 to October 2008. The number of Z. platypus sampled during this period was 2,362. In more than 3rd stream, water depth and velocity showing the highest number of samples were 0.8 m and $0.8\;m\;s^{-1}$, respectively. In addition, the highest number of samples was observed under the condition of total length (TL) (8~10 cm), velocity ($0.3\;m\;s^{-1}$), water depth (0.4 m), substrate size (send, 0.1~1.0 mm~coarse gravel, 50.0~100.0 mm) and habitat type (run). Based on the monitoring data (n=1059) the relationship between body weight (BW) and TL in male and female were estimated as $BW=0.0068{\times}TL^{3.0274}$ ($r^2=0.9102$) and $BW=0.0075{\times}TL^{2.9995}$ ($r^2=0.8517$), respectively. Growth equations on days after parturition (DAP) to the TL were estimated as TL=0.0108DAP+1.5795 ($r^2=0.9721$). By equations (TL 6.9 cm), BW were 2.7 g (male) and 2.4 g (female), and DAP was about 490 days.

• Journal of the Korean Wood Science and Technology
• /
• v.13 no.2
• /
• pp.35-44
• /
• 1985

The purposes of this study were, first, to investigate retention levels of toxic elements and oxide individual plies for each panel and, second, to examine disproportioning of individual toxic elements Thirty five water gum plywood panels were treated with a copper-chromium-arsenic preservative (CCA) by the soaking process as the treament time were applied. Such individual plies at a distance of 2.5cm, 7.5cm from the edge were assayed for CuO, $CrO_3$, and $As_2O_5$ on the basis of copper, chromium and arsenic content by Atomic Absorption Spectrophotometry. In these experiments, 12mm thickness plywood panels made of water gum, which were selling, were selected for the preservative treatment. Treating solutions were prepared for 10%, dilute solution of copper-chromium-arsenic preservative and then 1, 3, 6, 12 and 24 hours soaking trements in CCA preservative were applied. The results obtained are as follows: 1. The retention of total oxide in the face and back plies (1+7) retained more than the retention of total oxide in the other plies. The total oxide retention for the individual plies except the face and back plies (1+7) was showed in the following orders; cross plies (3+5), cross plies (2+6), core ply (4). 2. The retentions of total oxide increased as the increase of treatment time. The CCA treated plywood retained high levels of total oxide retention in the face and back plies (1+7). 3. All the retentions in the face and back plies (1+7) is over 5Kg/$m^3$, New Zealand Timber Preservation Standards Specification, and after 6 hours, the retentions in the cross plies (3+5) is over 4. The relative penetration of copper, chromium, and arsenic were not affected by the treatment time. The proportion of arsenic decreased in relation to both copper and chromium and the proportion of copper increased in relation to both chromium and arsenic. 5. A disproportioning of copper, chromium occurred with longer distance from edge, and with longer distance from edge the leachability resistance of CCA treated specimens decreased. After 6 hours (soaking time), the proportion of active elements at a distance of 2.5cm from the edge was consistent. And after 24 hours-soaking, the proportion of active elements at a distance of 7.5cm from the edge was consistent.