• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.184-188
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• 2008

This study presented simple and efficient fabrication of chemical sensors for the detection of acidic gas using 1,3-bisdicyanovinylindane as an indicator because it can be promising materials having property of the rapid color change according to the variation of pH. The dissociation of proton and dye in acidic condition as changing of ion pairs give rise to dramatically change the absorbance intensity of 1,3-bisdicyanovinylindane, which can be easily applied to the development of chemical sensors. In addition, indicator dyes having negatively charge in aqueous phase can be easily fabricated using layer-by-layer (LBL) methods by way of electrostatic interaction. For the proof of concept, we demonstrated the abrupt presentation of skeleton symbol on the chemical sensor, which could be resulted from the reaction of 1,3-bisdicyanovinylindane as background color with acidic gas. Thus, the rapid appearance of symbol will induce user's caution under the emergency condition. The presented chemical gas sensor using 1,3-bisdicyanovinylindane have strong advantages. First, the fabrication process of gas sensor was very simple and low-cost. Secondly, sensors reacted by acidic gas could be reused for several times. Finally, the chemical gas sensor would be environmentally friend, which can be a basic tool for the realization of eco-organic sensor device.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.4
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• pp.533-542
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• 2000

Analytical experiments to determine the line-of-sight temperature distribution is conducted by using spectral radiation intensities. For this study, fourteen narrow bands of $25cm^{-1}$ interval in $CO_2\;4.3{\mu}m$ band ($2,050cm^{-1}$ to $2375cm^{-1}$) are selected. The applied system is a one-dimensional gas slab filled with 100% $CO_2$ gas at 1 atm. Two types of temperature profile are tested; parabolic and boundary layer types. Three kinds of radiation calculation are used in the iteration procedure for the temperature inversion; LBL(Line by Line), SNB(Statistical Narrow Band) and WNB(WSGGM. based Narrow Band) models. The LBL solution shows perfect agreement while some error of temperature prediction is caused by radiation modeling error when using SNB and WNB models. The inversion result shows that the WNB model may be used more accurately in spectral remote sensing techniques than the traditional SNB model.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.186-186
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• 2012

This report investigates a new synthetic route and the size-dependent optical and electrical properties of PbS nanocrystal quantum dots (NQDs) in diameters ranging between 1.5 and 6 nm. Particularly we synthesize ultra-small sized PbS NQDs having extreme quantum confinement with 1.5~2.9 nm in diameter (2.58~1.5 eV in first exciton energy) for the first time by adjusting growth temperature and growth time. In this region, the Stokes shift increases as decreasing size, which is testimony to the highly quantum confinement effect of ultra-small sized PbS NQDs. To find out the electrical properties, we fabricate self-assembled films of PbS NQDs using layer by layer (LBL) spin-coating method and replacing the original ligands with oleic acid to short ligands with 1, 2-ethandithiol (EDT) in the course. The use of capping ligands (EDT) allows us to achieve effective electrical transport in the arrays of solution processed PbS NQDs. These high-quality films apply to Schottky solar cell made in an glass/ITO/PbS/LiF/Al structure and thin-film transistor varying the PbS NQDs diameter 1.5~6 nm. We achieve the highest open-circuit voltage (＜0.6 V) in Schottky solar cell ever using PbS NQDs with first exciton energy 2.58 eV.

• Biomaterials and Biomechanics in Bioengineering
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• v.1 no.1
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• pp.1-12
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• 2014

Polymer multilayered hydrogels were prepared on a titanium alloy (Ti) substrate using a layer-by-layer (LBL) process to load a cell growth factor. Two water-soluble polymers were used to fabricate the multilayered hydrogels, a phospholipid polymer with both N, N-dimethylaminoethyl methacrylate (DMAEMA) units and 4-vinylphenylboronic acid (VPBA) units [poly(MPC-co-DMAEMA-co-VPBA) (PMDV)], and the polysaccharide alginate (ALG). PMDV interacted with ALG through a selective reaction between the VPBA units in PMDV and the hydroxyl groups in ALG and through electrostatic interactions between the DMAEMA units in PMDA and the anionic carboxyl groups in ALG. First, the Ti substrate was covered with photoreactive poly vinyl alcohol, and then the Ti alloy was alternately immersed in the respective polymer solutions to form the PMDV/ALG multilayered hydrogels. In this multilayered hydrogel, vascular endothelial growth factor (VEGF) was introduced in different layers during the LbL process under mild conditions. Release of VEGF from the multilayered hydrogels was dependent on the location; however, release continued for 2 weeks. Endothelial cells adhered to the hydrogel and proliferated, and these corresponded to the VEGF release profile from the hydrogel. We concluded that multilayered hydrogels composed of PMDV and ALG could be loaded with cell growth factors that have high activity and can control cell functions. Therefore, this system provides a cell function controllable substrate based on the controlled release of biologically active proteins.

• Journal of Climate Change Research
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• v.1 no.2
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• pp.147-161
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• 2010

The temporal and spatial distributions of surface solar radiation were calculated by the one layer solar radiative transfer model(GWNU) which was corrected by multi layer Line-by-Line(LBL) model during 2009 in South Korea. The aerosol optical thickness, ozone amount, cloud fraction and total precipitable water were used as the input data for GWNU model run and they were retrieved from Moderate Resolution Imaging Spectrometer(MODIS), Ozone Monitoring Instrument(OMI), MTSAT-1R satellite data and the Regional Data Assimilation Prediction System(RDAPS) model result, respectively. The surface solar radiation was calculated with 4 km spatial resolution in South Korea region using the GWNU model and the results were compared with surface measurement(by pyranometer) data of 22 KMA solar sites. The maximum values(more than $5,400MJ/m^2$) of model calculated annual solar radiation were found in Andong, Daegu and Jinju regions and these results were corresponded with the MTSAT-1R cloud amount data. However, the spatial distribution of surface measurement data was comparatively different from the model calculation because of the insufficient correction and management problems for the sites instruments(pyranometer).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.5
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• pp.221-226
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• 2010

Quartz crystal microbalance (QCM) gas sensor to detect methyl mercaptan ($CH_3SH$) gas was fabricated by depositing $TiO_2$ nanoparticles and polyelectrolyte on the electrode of QCM. The $TiO_2$/poly(sodium 4-styrenesulfonate) (PSS) thin film fabricated by a layer-by-layer self-assembly (LBL-SA) method showed a high surface area and increased the sensitivity of gas sensor. When the QCM sensors coated with triethanolamine (TEA) or ($TiO_2$/PSS) were exposed to methyl mercaptan gas (1.0 ppm), the frequency shifts of QCM with TEA casting film and $TiO_2$/PSS thin film were ca. 9 Hz and ca. 24 Hz, respectively. As the bilayer number of ($TiO_2$/PSS) increased, the frequency shift of QCM sensor with ($TiO_2$/PSS) thin film was gradually increased. In addition, the frequency shift of QCM sensor was gradually increased as the concentration of methyl mercaptan gas increased from 0.5 ppm to 2.0 ppm. In this study, the surface morphology and sensor property of QCM sensor coated with ($TiO_2$/PSS) thin film were measured.

• Atmosphere
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• v.19 no.4
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• pp.319-329
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• 2009

The intensive dust observation experiment has been performed at Korea Global Atmosphere Watch Center (KGAW) in Anmyeon, Korea during each spring season from 2007 to 2009. Downward and upward hyper-spectral spectrums over the dust condition were measured to understand the hyper-spectral properties of Asian dust using both ground-based Fourier Transform Infrared Spectroscopy (FT-IR) and space-borne AIRS/Aqua. To understand the impact of the Asian dust, a Line-by-Line radiative transfer model runs to calculate the high resolution infrared spectrum over the wave number range of $500-500cm^{-1}$. Furthermore, the radiosonde, a $PM_{10}$ Sampler, a Micro Pulse Lidar (MPL), and an Aerodynamic Particle Sizer (APS) are used to understand the vertical profile of temperature and humidity and the properties of Asian dust like concentration, altitude of dust layer, and size distribution. In this study, we found the Asian dust distributed from surface up to 3-4 km and volume concentration is increased at the size range between 2 and $8{\mu}m$ The observed dust spectrums are larger than the calculated clear sky spectrums by 15~60K for downward and lower by around 2~6K for upward in the wave number range of $800-1200cm^{-1}$. For the characteristics of the spectrum during the Asian dust, the downward spectrum is revealed a positive slope for $800-1000cm^{-1}$ region and negative slope over $1100-1200cm^{-1}$ region. In the upward spectrum, slopes are opposed to the downward one. It is inferred that the difference between measured and calculated spectrum is mostly due to the contribution of emission and/or absorption of the dust particles by the aerosol amount, size distribution, altitude, and composition.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.2
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• pp.161-169
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• 1999

This paper describes the swimming and escaping behavior of amber fish, Seriola aureovittata released in the first bag net of the setnet and observed with telemetry techniques. The setnet used in experiment is composed of a leader, a fish court with a flying net and two bag nets having ramp net. The behavior of the fish attached an ultrasonic depth pinger of 50 KHz is observed using a prototype LBL fish tracking system. The 3-D underwater position ofthe fish is calculated by hyperbolic method with three channels of receiver and the depth of pinger. The results obtained are as follows: 1. The fish released on the sea surface was escaped down to 15 m depth and rised up to near the sea surface during 5 minutes after release. The average swimming speed of the fish during this time was 0.87 m/sec. 2. The swimming speed of the fish is decreased slowly in relation to the time elapsed and the fish showed some escaping behavior forward to the fish court staying 1 to 7 m depth layer near the ramp net. The average speed of the fish during this time was 0.52 m/sec. 3. During 25 minutes after beginning of hauling net, the fish showed a faster swimming speed than before hauling and an escaping behavior repeatedly from the first ramp net to the second one in horizontal. In vertical, the fish moved up and down between the sea surface and 20 m depth. After this time, the fish showed the escaping behavior forward to fish court after come back to the first ramp net in spite of the hauling was continued. It is found that the fish was escaped from the first ramp net to the fish court while the hauling was carried out. The average speed of the fish after beginning of hauling was 0.72 m/sec which increased 38.5 ％ than right before the hauling and showed 0.44 to 0.82 m/see of speed till escaping the first bag net. The average swimming speed during observation was 0.67 m/sec (2.2 times of body length).