• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.536-542
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• 2018

Tin dioxide, $SnO_2$, is a well-known n-type semiconductor that shows change in resistance in the presence of gas molecules, such as $H_2$, CO, and $CO_2$. Considerable research has been done on $SnO_2$ semiconductors for gas sensor applications due to their noble property. The nanomaterials exhibit a high surface to volume ratio, which means it has an advantage in the sensing of gas molecules. In this study, SnO nanoplatelets were grown densely on Si substrates using a thermal CVD process. The SnO nanostructures grown by the vapor transport method were post annealed to a $SnO_2$ phase by thermal CVD in an oxygen atmosphere at $830^{\circ}C$ and $1030^{\circ}C$. The pressure of the furnace chamber was maintained at 4.2 Torr. The crystallographic properties of the post-annealed SnO nanostructures were investigated by Raman spectroscopy and XRD. The change in morphology was confirmed by scanning electron microscopy. As a result, the SnO nanostructures were transformed to a $SnO_2$ phase by a post-annealing process.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.166-173
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• 2014

A noncontact nondestructive testing (NDT) method is proposed to detect the damage of pipeline structures and to identify the location of the damage. To achieve this goal, a scanning laser source actuation technique is utilized to generate a guided wave and scans a specific area to find damage location more precisely. The ND: YAG pulsed laser is used to generate Lamb wave and a piezoelectric sensor is installed to measure the structural responses. The measured responses are analyzed using three dimensional Fourier transformation (3DFT). The damage-sensitive features are extracted by wavenumber filtering based on the 3D FT. Then, flaw imaging techniques of a pipeline structures is conducted using the damage-sensitive features. Finally, the pipes with notches are investigated to verify the effectiveness and the robustness of the proposed NDT approach.

• Journal of Sensor Science and Technology
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• v.6 no.6
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• pp.500-507
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• 1997

For fine control of operating temperature of shape memory alloy, we investigated the effect of thermal teratment of shape memory alloy with the impurity kind. The martensitic transformation temperature in a Cu-17.25Zn-15Al and Cu-17.25Zn-15Al-1Ag/Fe was measured using electrical resistivity as a function of quenching temperature. Order-disorder phase transition temperatures in parent phase were measured and kind of transition were distinguised by DSC(differential scanning calorimeter) with heating rate variation. And structual changes were studied with XRD. For the Cu-17.25Zn-15Al shape memory alloy, the order-disorder phase transition temperature, $T_{B2}$ and $T_{L21}$ was 809K and 610K and for the Cu-17.25Zn-15Al-1Ag and Cu-17.25Zn-15Al-1Fe specimen $T_{B2}$ and $T_{L21}$ was 794K and 610K, and 803K and 613K, respectively. In all the specimens, quenching from near $T_{B2}$ leads to an increase in martensitic temperature, whereas quenching from near $T_{L21}$ leads to an decrease in martensitic temperature.

• International conference on construction engineering and project management
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• 2024.07a
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• pp.1295-1295
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• 2024

As extreme weather events such as heavy snowfall and typhoon become more frequent, climate change significantly impacts across various worldwide industries. With demands for dealing with this phenomenon, continuous achievements in safety diagnosis have been announced for large structures. Conversely, in agricultural infrastructures having lower risk to human life, there is lack of established safety diagnosis methods. However, considering expansion of high-value smart farm, the importance of plastic greenhouse cannot be overlooked. Therefore, this study aimed to develop on-site diagnosis technique for structural safety of steel structure greenhouse. To build an analysis model, we generated point cloud data of on-site greenhouse using a camera with LiDAR sensor. Subsequently, we extracted points corresponding to pipes using a pre-trained semantic segmentation model, achieving a pipe segmentation accuracy of 78.1%. These points were then converted into 3D frame model, with a location coordinate error of 5.4 cm for nine reference points, as measured by an on-site survey. In FEM structural analysis, nonlinearity of pipe connection was reflected. The loads were determined based on expected wind speed and snow depth in Korea. The structural safety of on-site model was diagnosed more vulnerable with 10.3% higher maximum axial stress, compared with standard model. Through this research, we expect the quantitative safety diagnosis of predicting greenhouse collapse risk. In addition, this technique will enable localized reinforcement strategies within the structure.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.715-719
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• 2009

The phase change electrode board for the bio-information detection through electrical property response of phase change material was developed in this study. We manufactured the electrode board using Aluminum first that is widely used in conventional semiconductor device process. Without further treatment, these aluminum electrodes tend to contain voids in PETEOS(plasma enhanced tetraethyoxysilane) material that are easily detected by cross-sectional SEM(Scanning Electron Microscope). The voids can be easily attacked and transformed into holes in between PETEOS and electrodes after etch back and washing process. In order to resolve this issue of Al electrode board, we developed a electrode board manufacturing method using low resistivity TiN, which has advantages in terms of the step-coverage of phase change($Ge_2Sb_2Te_5$, GST) thin film as well as thermodynamic stability, without etch back and washing process. This TiN material serves as the top and bottom electrode in PRAM(Phase-change Random Access Memory). The good connection between the TiN electrode and GST thin film was confirmed by observing the cross-section of TiN electrode board using SEM. The resistances of amorphous and crystalline GST thin film on TiN electrodes were also measured, and 1000 times difference between the amorphous and crystalline resistance of GST thin film was obtained, which is well enough for the signal detection.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.6
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• pp.282-288
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• 2017

In this paper, GaAs/AlGaAs multi-layer structure was grown by liquid phase epitaxy with graphite sliding boat, which can be used as a device structure of a photocathode image sensor. The multi-layer structure was grown on an n-type GaAs substrate in the sequence as follows: GaAs buffer layer, Zn-doped p-type AlGaAs layer as etching stop layer, Zn-doped p-type GaAs layer, and Zn-doped p-type AlGaAs layer. The Characteristics of GaAs/AlGaAs structures were analyzed by using scanning electron microscope (SEM), secondary ion mass spectrometer (SIMS) and hall measurement. The SEM images shows that the p-AlGaAs/p-GaAs/p-AlGaAs multi-layer structure was grown with a mirror-like surface on a whole ($1.25mm{\times}25mm$) substrate. The Al composition in the AlGaAs layer was approximately 80 %. Also, it was confirmed that the free carrier concentration in the p-GaAs layer can be adjusted to the range of $8{\times}10^{18}/cm^2$ by hall measurement. In the result, it is expected that the p-AlGaAs/p-GaAs/p-AlGaAs multi-layer structure grown by the LPE can be used as a device structure of a photoelectric cathode image sensor.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.142.2-142.2
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• 2018

One-dimensional metal oxide nanostructures have attracted considerable research activities owing to their strong application potential as components for nanosize electronic or optoelectronic devices utilizing superior optical and electrical properties. In which, semiconducting $SnO_2$ material with wide-bandgap Eg = 3.6 eV at room temperature, is one of the attractive candidates for optoelectronic devices operating at room temperature [1, 2], gas sensor [3, 4], and transparent conducting electrodes [5]. The synthesis and gas sensing properties of semiconducting $SnO_2$ nanomaterials have become one of important research issues since the first synthesis of SnO2 nanowires. In this study, $SnO_2$ nanowire networks were synthesized on a basis of a two-step process. In step 1, Sn spheres (30-800 nm in diameter) embedded in $SiO_2$ on a Si substrate was synthesized by a chemical vapor deposition method at $700^{\circ}C$. In step 2, using the source of these Sn spheres, $SnO_2$ nanowire (20-40 nm in diameter; $1-10{\mu}m$ in length) networks on a spherical Sn surface were synthesized by a thermal oxidation method at $800^{\circ}C$. The Au layers were pre-deposited on the surface of Sn spherical and subsequently oxidized Sn surface of Sn spherical formed SnO2 nanowires networks. Field emission scanning electron microscopy and high-resolution transmission electron microscopy images indicated that $SnO_2$ nanowires are single crystalline. In addition, the $SnO_2$ nanowire is also a tetragonal rutile, with the preferred growth directions along [100] and a lattice spacing of 0.237 nm. Subsequently, the $NO_2$ sensing properties of the $SnO_2$ network nanowires sensor at an operating temperature of $50-250^{\circ}C$ were examined, and showed a reversible response to $NO_2$ at various $NO_2$ concentrations. Finally, details of the growth mechanism and formation of Sn spheres and $SnO_2$ nanowire networks are also discussed.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.938-942
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• 2007

The importance of process improvement under construction has arisen from recent issue, lower productivity in the construction site. The various 3D modeling program is utilized in the procedure of construction as an alternative solution. However, it's still shortage of the consideration about a specific technical application. The purpose of the study in this paper is helpful to improve the productivity of construction site using 3D realization of constructing place as one of extensive modeling technologies, which leads to not only efficient management of construction site allowing people to check the real time situation in the place but also the revitalization of information flow about building process control and prgress, Therefore, I research into modeling algorithm and extensive construction site realization technology. 3D realization of building place would reduce the safety concerns by providing the real time information about construction site, and it could help to access easily to similar project through collecting and appling the database of sites. Furthermore it can be an opportunity to develop the procedure of production in construction industry and to upgrade the image of this field.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.458-463
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• 2019

Palladium (Pd) is widely used as a catalyst and noxious gas sensing materials. Especially, various researches of Pd based hydrogen gas sensor have been studied due to the noble property, Pd can be adsorbed hydrogen up to 900 times its own volume. In this study, palladium oxide (PdO) nanostructures were grown on Si substrate ($SiO_2(300nm)/Si$) for 3 to 5 hours at $230^{\circ}C{\sim}440^{\circ}C$ using thermal chemical vapor deposition system. Pd powder (source material) was vaporized at $950^{\circ}C$ and high purity Ar gas (carrier gas) was flown with the 200 sccm. The surface morphology of as-grown PdO nanostructures were characterized by field-emission scanning electron microscopy(FE-SEM). The crystallographic properties were confirmed by Raman spectroscopy. As the results, the as-grown nanostructures exhibit PdO phase. The nano-cube structures of PdO were synthesized at specific substrate temperatures and specific growth duration. Especially, PdO nano-cube structrures were uniformly grown at $370^{\circ}C$ for growth duration of 5 hours. The PdO nano-cube structures are attributed to vapor-liquid-solid process. The nano-cube structures of PdO on graphene nanosheet can be applied to fabricate of high sensitivity hydrogen gas sensor.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.1-6
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• 2022

As the demand for wearable devices increases, many studies have been studied on the development of flexible electrode materials recently. In particular, the development of high-performance flexible electrode materials is very important for wearable sensors for healthcare because it is necessary to continuously monitor and accurately detect body information such as body temperature, heart rate, blood glucose, and oxygen concentration in real time. In this study, we fabricated the nonenzymatic glucose sensor based on polyaniline/carbon nanotube fiber (PANI/CNT fiber) electrode. PANI layer was synthesized on the flexible CNT fiber electrode through electrochemical polymerization process in order to improve the performance of a flexible CNT fiber based electrode material. Surface morphology of the PANI/CNT fiber electrode was observed by scanning electron microscopy. And its electrochemical characteristics were investigated by chronoamperometry, cyclic voltammetry, electrochemical impedance spectroscopy. Compared to bare CNT fiber electrode, this PANI/CNT fiber electrode exhibited small electron transfer resistance, low peak separation potential and large surface area, resulting in enhanced sensing properties for glucose such as wide linear range (0.024~0.39 and 1.56~50 mM), high sensitivity (52.91 and 2.24 ㎂/mM·cm²), low detection limit (2 μM) and good selectivity. Therefore, it is expected that it will be possible to develop high performance CNT fiber based flexible electrode materials using various nanomaterials.