• Journal of Biomedical Engineering Research
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• v.25 no.5
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• pp.329-334
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• 2004

The electronic nose (E-nose) recently finds its applications in medical diagnosis, specifically on detection of diabetes, pulmonary or gastrointestinal problem, or infections by examining odors in the breath or tissues with its odor characterizing ability. The odor recognition performance of E-nose can be improved by manipulating the sensor array responses of vapors in time-profile forms. The different chemical interactions between the sensor materials and the volatile organic compounds (VOC's) leave unique marks in the signal profiles giving more information than collection of the conventional piecemal features, i.e., maximum sensitivity, signal slopes, rising time. In this study, to use them in vapor recognition task conveniently, a novel time-profile method was proposed, which is adopted from digital image pattern matching. The degrees of matching between 8 different vapors were evaluated by using the proposed method. The test vapors are measured by the silicon-based gas sensor array with 16 CB-polymer composites installed in membrane structure. The results by the proposed method showed clear discrimination of vapor species than by the conventional method.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.68.1-68.1
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• 2012

The best part of graphene is - charge-carriers in it are mass less particles which move in near relativistic speeds. Comparing to other materials, electrons in graphene travel much faster - at speeds of $10^8cm/s$. A graphene sheet is pure enough to ensure that electrons can travel a fair distance before colliding. Electronic devices few nanometers long that would be able to transmit charge at breath taking speeds for a fraction of power compared to present day CMOS transistors. Many researches try to check a possibility to make it a perfect replacement for silicon based devices. Graphene has shown high potential to be used as interconnects in the field of high frequency electrical devices. With all those advantages of graphene, we demonstrate characteristics of electrical and optical properties of graphene such as the effect of graphene geometry on the microwave properties using the measurements of S-parameter in range of 500 MHz - 40 GHz at room temperature condition. We confirm that impedance and resistance decrease with increasing the number of graphene layer and w/L ratio. This result shows proper geometry of graphene to be used as high frequency interconnects. This study also presents the optical properties of graphene oxide (GO), which were deposited in different substrate, or influenced by oxygen plasma, were confirmed using different characterization techniques. 4-6 layers of the polycrystalline GO layers, which were confirmed by High resolution transmission electron microscopy (HRTEM) and electron diffraction analysis, were shown short range order of crystallization by the substrate as well as interlayer effect with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups on its layers. X-ray photoelectron Spectroscopy (XPS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation, and Fourier Transform Infrared spectroscopy (FTIR) and XPS analysis shows the changes in oxygen functional groups with nature of substrate. Moreover, the photoluminescent (PL) peak emission wavelength varies with substrate and the broad energy level distribution produces excitation dependent PL emission in a broad wavelength ranging from 400 to 650 nm. The structural and optical properties of oxygen plasma treated GO films for possible optoelectronic applications were also investigated using various characterization techniques. HRTEM and electron diffraction analysis confirmed that the oxygen plasma treatment results short range order crystallization in GO films with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups. In addition, Electron energy loss spectroscopy (EELS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation and XPS analysis shows that epoxy pairs convert to more stable C=O and O-C=O groups with oxygen plasma treatment. The broad energy level distribution resulting from the broad size distribution of the $sp^2$ clusters produces excitation dependent PL emission in a broad wavelength range from 400 to 650 nm. Our results suggest that substrate influenced, or oxygen treatment GO has higher potential for future optoelectronic devices by its various optical properties and visible PL emission.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1927-1934
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• 2016

In this paper, we proposed a I-gate n-MOSFET (n-type Metal Oxide Semiconductors Field Effect Transistor) structure in order to mitigate a radiation-induced leakage current path in an isolation oxide interface of a silicon-based standard n-MOSFET. The proposed I-gate n-MOSFET structure was designed by using a layout modification technology in the standard 0.18um CMOS (Complementary Metal Oxide Semiconductor) process, this structure supplements the structural drawbacks of conventional radiation-tolerant electronic device using layout modification technology such as an ELT (Enclosed Layout Transistor) and a DGA (Dummy Gate-Assisted) n-MOSFET. Thus, in comparison with the conventional structures, it can ensure expandability of a circuit design in a semiconductor-chip fabrication. Also for verification of a radiation-tolerant characteristic, we carried out M&S (Modeling and Simulation) using TCAD 3D (Technology Computer Aided Design 3-dimension) tool. As a results, we had confirmed the radiation-tolerant characteristic of the I-gate n-MOSFET structure.

• Clean Technology
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• v.22 no.4
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• pp.308-315
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• 2016

$SiO_x/ZnO$ composites were prepared from sol-gel method for excellent cycle life characteristics. The composites were coated by PVC as a carbon precursor. ZnO removal to create a void space therein was able to buffer the volume change during charge and discharge. To determine the crystal structure and the shape of the synthesized composite, XRD, SEM, TEM analysis was performed. The carbon contents in the composites were confirmed by TGA. The pore structure and pore size distribution of the composite was measured with the BET specific surface area analysis and BJH pore size distribution. Enhanced electric conductivity by carbon addition was determined from powder resistance measurement. Electrochemical properties were measured with the AC impedance and the charge and discharge cycle life characteristics. When carbon was coated on the $SiO_x/ZnO$ sample, the electrical conductivity and the discharge capacity were increased. After removal of ZnO with HCl the surface area of the sample was increased, but the discharge capacity was decreased. $SiO_x/ZnO$ sample without acarbon coating showed very low discharge capacity, and after carbon coating the sample showed high discharge capacity. For cycle life characteristics, $C-SiO_x/ZnO$ composite (Zn : Si : C = 1 : 1 : 8) with a capacity of $815mAh\;g^{-1}$ at 50 cycle and 0.2 C has higher capacity than existing graphite-based anode materials.

• Journal of radiological science and technology
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• v.35 no.2
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• pp.109-117
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• 2012

The purpose of this work was to evaluate an amorphous silicon cesium iodide based indirect flat-panel detector (FPD) in terms of their modulation transfer function (MTF), Wiener spectrum (WS, or noise power spectrum, NPS), and detective quantum efficiency (DQE). Measurements were made on flat-panel detector using the International Electrotechnical Commission (IEC) defined RQA3, RQA5, RQA7, and RQA9 radiographic technique. The MTFs of the systems were measured using an edge method. The WS(NPS) of the systems were determined for a range of exposure levels by two-dimensional (2D). Fourier analysis of uniformly exposed radiographs. The DQEs were assessed from the measured MTF, WS(NPS), exposure, and estimated ideal signal-to-noise ratios. Characteristic curve in the RQA3 showed difference in the characteristic curve from RQA5, RQA7, RQA9. MTFs were not differences according to x-ray beam quality. WS(NPS) was reduced with increasing dose, and RQA 3, RQA5, RQA7, RQA9 as the order is reduced. DQE represented the best in the 1mR, RQA 3, RQA5, RQA7, RQA9 decrease in the order. The physical imaging characteristics of FPD may also differ from input beam quality. This study gives an initial motivation that the physical imaging characteristics of FPD is an important issue for the right use of digital radiography system.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.384-391
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• 2005

A polymer optical microring resonator, which is laterally coupled to a straight bus waveguide, has been proposed and demonstrated using a nanoimprint technique. The propagation loss of the ring waveguide and the optical power coupling between the ring and bus waveguides was calculated by using a beam propagation method, then the dependence of the device performance on them was investigated using a transfer matrix method. We have especially introduced an imprint stamp incorporating a smoothing buffer layer made of a silicon nitride thin film. This layer played an efficient role in improving the sidewall roughness of the waveguide pattern engraved on the stamp and thus reducing the scattering loss. As a result the overall Q factor of the resonator was greatly increased. Also it reduced the gap between the ring and bus waveguides effectively to enhance the coupling between them, without relying on the direct writing method based on an e-beam writer. As for the achieved device performance at the wavelength of 1550 nm, the quality factor, the extinction ratio, and the free spectral range were ~103800, ~11 dB, and 1.16 m, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.77-77
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• 2000

Titanium oxide (TiO2) thin films have valuable properties such as a high refractive index, excellent transmittance in the visible and near-IR frequency, and high chemical stability. Therefore it is extensively used in anti-reflection coating, sensor, and photocatalysis as electrical and optical applications. Specially, TiO2 have a high dielectric constant of 180 along the c axis and 90 along the a axis, so it is highlighted in fabricating dielectric capacitors in micro electronic devices. A variety of methods have been used to produce patterned self-assembled monolayers (SAMs), including microcontact printing ($\mu$CP), UV-photolithotgraphy, e-beam lithography, scanned-probe based micro-machining, and atom-lithography. Above all, thin film fabrication on $\mu$CP modified surface is a potentially low-cost, high-throughput method, because it does not require expensive photolithographic equipment, and it produce micrometer scale patterns in thin film materials. The patterned SAMs were used as thin resists, to transfer patterns onto thin films either by chemical etching or by selective deposition. In this study, we deposited TiO2 thin films on Si (1000 substrateds using titanium (IV) isopropoxide ([Ti(O(C3H7)4)] ; TIP as a single molecular precursor at deposition temperature in the range of 300-$700^{\circ}C$ without any carrier and bubbler gas. Crack-free, highly oriented TiO2 polycrystalline thin films with anatase phase and stoichimetric ratio of Ti and O were successfully deposited on Si(100) at temperature as low as 50$0^{\circ}C$. XRD and TED data showed that below 50$0^{\circ}C$, the TiO2 thin films were dominantly grown on Si(100) surfaces in the [211] direction, whereas with increasing the deposition temperature to $700^{\circ}C$, the main films growth direction was changed to be [200]. Two distinct growth behaviors were observed from the Arhenius plots. In addition to deposition of THe TiO2 thin films on Si(100) substrates, patterning of TiO2 thin films was also performed at grown temperature in the range of 300-50$0^{\circ}C$ by MOCVD onto the Si(100) substrates of which surface was modified by organic thin film template. The organic thin film of SAm is obtained by the $\mu$CP method. Alpha-step profile and optical microscope images showed that the boundaries between SAMs areas and selectively deposited TiO2 thin film areas are very definite and sharp. Capacitance - Voltage measurements made on TiO2 films gave a dielectric constant of 29, suggesting a possibility of electronic material applications.

• Korean Journal of Soil Science and Fertilizer
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• v.17 no.2
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• pp.101-107
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• 1984

The suitable paddy soil for application of rice straw under well to moderately well drained soil, the yield and yield components were pronounced more than poorly drained soil. Based on laboratory experiment, application of rice straw promoted the decrease of oxidation-reduction potential in well to moderately well drained soil. This results seems to be enhanced the release of some mineral nutrients such as calcium, potassium, silicon, and increases of availability of soil phosphorus. This explains reason why soil condition became more favorable for the increases of mineral nutrient in rice plant. On the contrary, poorly drained soils, became readily reduced even without application or rice straw, when soil wat submerged. Application of rice straw did not promoted the decrease of oxidation-reduction potential as much as in well drained soil. It was suggested that in this type of soil series, the release of mineral nutrients and the additional increase of available soil phosphorus did not proceed well. It was also suggested that the retardation of root development owing to accumulation of toxic substances such as organic acid, hydrogen sulfide or some other reducing substances formed by the application of rice straw in poorly drained soil series might be considered. In fact, the effect of rice straw on the yield of brown rice became lower.

• Journal of the Korean Society of Radiology
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• v.7 no.4
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• pp.307-311
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• 2013

This study examined the change of artifact volume by analyzing the level of image change associated with the setting of threshold through 3D imaging in scan parameter(slice thickness and helical pitch) and 3D image reconstruction to explore whether the presence of pathology was fully distinguished when CT was taken by lower dose than the existent dose to reduce exposure. Furthermore, this study attempted to investigate Scan Parameter acceptable in CT to reduce exposure dose. For materials and methods, silicon was used to produce samples. Five spherical samples were produced at 10-millimeter intervals(50, 40, 30, 20, and 10 mm) in diameter and were fixed at 120 Kvp of tube voltage and 50 mA of tube current. Varied slab thickness((1.0, 2.0, 3.0, 5.0, and 7.0mm) and Helical Pitch(1.5, 2.0, 3.0) were scanned. The image at an interval of 1.0, 2.0, 3.0, 5.0, and 7.0mm was transmitted to the workstation. Threshold(-200, -50, 50 ~ 1,000) was changed using the volume rendering technique, 3D image was reconstructed, and artifact volume was measured. In conclusion, 1.5 of Helical Pitch showed the least change of volume and 3.0 of helical pitch showed the greatest reduction of volume change. The experiment suggested that as slice thickness was increased, artifact volume was decreased more than actual measurement. Furthermore, in the 3D image reconstruction, when the range of threshold was set as -200 ~1,000, artifact volume was changed the least. Based on the results, it is expected to have an effect of reducing exposure dose.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.111-117
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• 2017

This study examined the material properties of Korean rice husk ash (RHA) according to the manufacturing process, and evaluated the feasibility of its use as a new admixture for high strength concrete. For this purpose, its particle size distribution, chemical composition, and microstructure were analyzed under various parameters, such as calcination temperature ($400^{\circ}C$, $650^{\circ}C$, and $900^{\circ}C$) and the inclusion of a milling process. X-ray fluorescence analysis confirmed that the silicon oxide ($SiO_2$) content of RHA was improved to more than 92% with a calcination process at $650^{\circ}C$ or higher. In addition, microstructural analysis showed that the RHA calcined at $650^{\circ}C$ has a porous structure. Because of this, the absorption capacity of the RHA was improved. On the other hand, when the milling process was applied, the porous structure was destroyed; thus, the absorption capacity tended to decrease further. Based on the analysis results, it was concluded that RHA calcined at $650^{\circ}C$ can be used as an admixture for high strength concrete, which possesses functions of both a shrinkage reducing agent and a pozzolanic activator.