• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1368-1370
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• 2003

Conventional methods investigating soil Hg contamination are time-consuming and expensive. A quicker method is developed to predict soil Hg content with convolved HyMap, ASTER, and TM spectra. The prediction accuracy for each sensor is satisfactory and similar. It suggests that low spectral resolution is not a limitation for predicting soil Hg content. Correlation analysis reveals that Hg -sorption by iron oxides is the mechanism by which to predict spectrally featureless Hg with reflectance spectra. Future study with field measurements and remote sensing data is recommended.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.350-351
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• 2006

Thick film mechanical sensors can be categorized into four main areas piezoresistive, piezoelectric, capacitive and mechanic tube. In this areas, the thick film strain gage is the earliest example of a primary sensing element based on the substrates. The latest thick film sensor is used various pastes that have been specifically developed for pressure sensor application. Some elastic materials exhibit a change in bulk resistivity when they are subjected to displacement by an applied pressure. This property is referred to as piezoresistivity and is a major factor influencing the sensitivity of a piezoresistive strain gage. The effect of thick film resistors was first noticed in the early 1970, as described by Holmes in his paper in 1973.

• Journal of Microbiology
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• v.43 no.spc1
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• pp.101-109
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• 2005

To gain maximal benefit in a competitive environment, single-celled bacteria have adopted a community genetic regulatory mechanism, known as quorum sensing (QS). Many bacteria use QS signaling systems to synchronize target gene expression and coordinate biological activities among a local population. N-acylhomoserine lactones (AHLs) are one family of the well-characterized QS signals in Gram-negative bacteria, which regulate a range of important biological functions, including virulence and biofilm formation. Several groups of AHL-degradation enzymes have recently been identified in a range of living organisms, including bacteria and eukaryotes. Expression of these enzymes in AHL-dependent pathogens and transgenic plants efficiently quenches the microbial QS signaling and blocks pathogenic infections. Discovery of these novel quorum quenching enzymes has not only provided a promising means to control bacterial infections, but also presents new challenges to investigate their roles in host organisms and their potential impacts on ecosystems.

• Korean Journal of Materials Research
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• v.32 no.10
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• pp.435-441
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• 2022

We report the synthesis and gas sensing properties of bare and ZnO decorated TeO₂ nanowires (NWs). A catalyst assisted-vapor-liquid-solid (VLS) growth method was used to synthesize TeO₂ NWs and ZnO decoration was performed using an Au-catalyst assisted-VLS growth method followed by a subsequent heat treatment. Structural and morphological analyses using X-ray diffraction (XRD) and scanning/transmission electron microscopies, respectively, demonstrated the formation of bare and ZnO decorated TeO₂ NWs with desired phase and morphology. NO₂ gas sensing studies were performed at different temperatures ranging from 50 to 400 ℃ towards 50 ppm NO₂ gas. The results obtained showed that both sensors had their best optimal sensing temperature at 350 ℃, while ZnO decorated TeO₂ NWs sensor showed much better sensitivity towards NO₂ relative to a bare TeO₂ NWs gas sensor. The reason for the enhanced sensing performance of the ZnO decorated TeO₂ NWs sensor was attributed to the formation of ZnO (n)/ TeO₂ (p) heterojunctions and the high intrinsic gas sensing properties of ZnO.

• Korean Journal of Remote Sensing
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• v.34 no.2_1
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• pp.227-236
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• 2018

The focus control mechanism of the multi-purpose camera can be required for the better quality image acquisition. A good image acquisition through the hardware system including the optics and image sensor, has to be processed before the post correction for improvement of image quality. In the case of the high-resolution satellite camera, the focus control is not a necessity, unlike a normal camera due to a fixed optical system, but may be required due to various reasons. Although there is a basic focus control method using a motor for satellite electronic optical camera, a focus control method using thermal control can be a good alternative because of its various advantages in design, installation, operation, contamination, high reliability and etc. In this paper, we describe the design method and implementation results for the focus control mechanism using the temperature sensor and heater installed in the telescope structure. In the proposed focus control method, the measured temperature information is converted into temperature data by the Kalman filter and the converted temperature data are used in PI controller for the thermal focus control.

• Korean Journal of Remote Sensing
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• v.22 no.6
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• pp.595-600
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• 2006

GOCI is the core paryload of the geostationary satellite COMS(Communication, Ocean and Meteological Satellite) for ocean monitoring. It is scheduled to be launched at the end of 2008. GOCI observes ocean color around the Korean Peninsula over $2500km\times2500km$ area. It used tilted two-axis scan mechanism to observe entire field of view. In this work, the pointing stability of the tilted two-axis method is analyzed and compared with that of gimbal method. The analysis results show that tilted two-axis method gives great stability and it is adequate for geostationary payload. The results can also be used to determine and analyze the mechanism specifications.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.4
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• pp.322-328
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• 2005

Acylhomoserine lactones (AHLs) are known to be the triggering molecules in the quorum sensing mechanism of many gram-negative bacteria. In order to detect AHL inhibitors that are potential biofilm inhibitors, a convenient and sensitive bioassay was developed based on the $\beta$-galactosidase activity ($\beta$-GAL) of a recombinant Agrobacterium tumefaciens strain. A series of commercially available AHLs were tested for inducing $\beta$-GAL at varying concentrations in agar-plate and liquid cultures of the reporter strain. All AHLs tested exhibited a concentration­dependent induction, and octanoyl homoserine lactone (OHL) showed the highest sensitivity with a detection limit of 0.1 nM in the liquid culture assay. When fimbrolide, a known quorum sensing inhibitor, was added, induction of $\beta$-GAL by OHL was repressed. The repression at a constant OHL concentration was dependent on the fimbrolide concentration with the detection limit below 1 ppm, indicating that this assay is a sensitive method for screening AHL inhibitors.

• Ocean Science Journal
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• v.42 no.1
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• pp.49-59
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• 2007

Besides empirical algorithms with the blue-green ratio, the algorithms based on fluorescence are also important and valid methods for retrieving chlorophyll-a concentration in the ocean waters, especially for Case II waters and the sea with algal blooming. This study reviews the history of initial cognitions, investigations and detailed approaches towards chlorophyll fluorescence, and then introduces the biological mechanism of fluorescence remote sensing and main spectral characteristics such as the positive correlation between fluorescence and chlorophyll concentration, the red shift phenomena. Meanwhile, there exist many influence factors that increase complexity of fluorescence remote sensing, such as fluorescence quantum yield, physiological status of various algae, substances with related optical property in the ocean, atmospheric absorption etc. Based on these cognitions, scientists have found two ways to calculate the amount of fluorescence detected by ocean color sensors: fluorescence line height and reflectance ratio. These two ways are currently the foundation for retrieval of chlorophyll-a concentration in the ocean. As the in-situ measurements and synchronous satellite data are continuously being accumulated, the fluorescence remote sensing of chlorophyll-a concentration in Case II waters should be recognized more thoroughly and new algorithms could be expected.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.272-272
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• 2014

SnO thin films, 100 nm in thickness, were deposited on glass substrates by RF magnetron sputtering. A stack structure of $SnO_2/SnO$, where few nanometers of $SnO_2$ were determined on the SnO thin film by X-ray photoelectron spectroscopy. In addition, XPS depth profile analysis of the pristine and heat treated thin films were introduced. The electrical behavior of the as-sputtered films during the annealing was recorded to investigate the working conditions for the SnO sensor. Subsequently, The NH3 sensing properties of the SnO sensor at operating temperature of $50-200^{\circ}C$ were examined, in which the p-type semiconducting sensing properties of the thin film were noted. The sensor shows good sensitivity and repeatability to $NH_3$ vapor. The sensor properties toward several gases like $H_2S$, $CH_4$ and $C_3H_8$ were also introduced. Finally, a sensing mechanism was proposed and discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.315.2-315.2
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• 2014

Pt-functionalized ZnS nanowires were synthesized on Au-deposited c-plane sapphire substrates by thermal evaporation of ZnS powders followed by wet Pt coating and annealing. The $NO_2$ gas sensing properties of multiple-networked Pt-functionalized ZnS nanowire sensors were examined. Scanning electron microscopy showed the nanowires with diameters of 20-80 nm. Transmission electron microscopy and X-ray diffraction showed that the nanowires were wurtzite-structured ZnS single crystals. The Pt-functionalized ZnS nanowire sensors showed enhanced sensing performance to $NO_2$ gas at $150^{\circ}C$ compared to pristine ZnS nanowire sensors. Pristine and Pt-functionalized ZnS nanowire sensors showed responses of 140-211% and 207-488%, respectively, to 1-5 ppm $NO_2$, which are better than or comparable to those of many oxide semiconductor sensors. In addition, the underlying mechanism of the enhancement of the sensing properties of ZnS nanowires by Pt functionalization is discussed.