• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.363-367
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• 2022

Transparent ZnO/Ti/ZnO (ZTZ) tri-layered films were prepared with radio frequency (RF) and direct current (DC) magnetron sputtering on the glass substrate. The thickness of the ZnO and Ti films was kept at 50 and 10 nm to consider the effect of the electron irradiation on the crystallization and optoelectrical properties of the films. From the XRD spectra, post-depostion electron irradiated films showed the characteristic peaks of ZnO(002) and Ti(200), respectively. the observed grain size of the ZnO(002) and Ti(200) enlarged up to 18.27 and 12.16 nm at an irradiation condition of 750 eV. In the figure of merit which means an optoelectrical performance of the films, as deposited films show a figure of merit of 2.0×10^-5 𝛺^-1, while the films electron irradiated at 750 eV show a higher figure of merit of 5.7×10^-5 𝛺^-1.

• Current Photovoltaic Research
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• v.11 no.2
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• pp.39-43
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• 2023

Carrier-selective contacts (CSCs) solar cells are considerably attractive on highly efficient crystalline silicon heterojunction (SHJ) solar cells due to their advantages of high thermal tolerance and the simple fabrication process. CSCs solar cells require a hole selective contact (HSC) layer that selectively collects only holes. In order to selectively collect holes, it must have a work function characteristic of 5.0 eV or more when contacted with n-type Si. The VO_x, NiO_x, and CuI_x thin films were fabricated and analyzed respectively to confirm their potential usage as a hole-selective contact (HSC) layer. All thin films showed characteristics of band-gap engergy > 3.0 eV, work function > 5.0 eV and minority carrier lifetime > 1.5 ms.

• Journal of Sensor Science and Technology
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• v.32 no.5
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• pp.290-294
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• 2023

Among various types of harmful gases, hydrogen sulfide is a strong toxic gas that is mainly generated during spillage and wastewater treatment at industrial sites. Hydrogen sulfide can irritate the conjunctiva even at low concentrations of less than 10 ppm, cause coughing, paralysis of smell and respiratory failure at a concentration of 100 ppm, and coma and permanent brain loss at concentrations above 1000 ppm. Therefore, rapid detection of hydrogen sulfide among harmful gases is extremely important for our safety, health, and comfortable living environment. Most hydrogen sulfide gas sensors that have been reported are electrical resistive metal oxide-based semiconductor gas sensors that are easy to manufacture and mass-produce and have the advantage of high sensitivity; however, they have low gas selectivity. In contrast, the electrochemical sensor measures the concentration of hydrogen sulfide using an electrochemical reaction between hydrogen sulfide, an electrode, and an electrolyte. Electrochemical sensors have various advantages, including sensitivity, selectivity, fast response time, and the ability to measure room temperature. However, most electrochemical hydrogen sulfide gas sensors depend on imports. Although domestic technologies and products exist, more research is required on their long-term stability and reliability. Therefore, this study includes the processes from electrode material synthesis to sensor fabrication and characteristic evaluation, and introduces the sensor structure design and material selection to improve the sensitivity and selectivity of the sensor. A sensor case was fabricated using a 3D printer, and an Ag reference electrode, and a Pt counter electrode were deposited and applied to a Polytetrafluoroethylene (PTFE) filter using PVD. The working electrode was also deposited on a PTFE filter using vacuum filtration, and an electrochemical hydrogen sulfide gas sensor capable of measuring concentrations as low as 0.6 ppm was developed.

• Design & Manufacturing
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• v.7 no.1
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• pp.60-63
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• 2013

Recently, Silicone that one of the thermo-sets is used to making optical products such as LED lenses because of excellent thermal properties. LED lenses are required to keep the precise dimensions, so they must be molded to have the minimum deformation. Thermo-sets have the expansion characteristic on the part of thermal property, it is important to optimize the cure condition so that the deformation of the part become minimum. In this study, to investigate the relationship between the shrinkage by the curing and expansion by the thermal properties of the resin, reactive injection experiment was performed by setting the variables such as mold setting temperature, cure time. As a result, it was confirmed that there was a interval while the thermal properties were transferred to more active during the cure process. It is expected to help in determining the reactive injection molding conditions of the thermo-set parts as well as LED lens in order to reduce the amount of deformation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1775-1780
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• 2011

In this paper, it is analyzed about the mechanical characteristics of pedicle screw system which is a artificial implant for surgery to treatment serious lumbar vertebra diseases. The disk of lumbar vertebra to be fixed by pedicle screw system shows regressive phenomena. But if flexible rod, to give a flexibility(under 6 degree) to fixable disk is applied, it can protect against the degeneration of disk. This research is carried out a mechanical characteristic of pedicle screw system used flexible rod through finite elements analysis, and then flexible rod system was verified about safe movement through compression, tension and torsion test which is the pedicle screw system official recognition test(ASTM F 1717).

• Journal of Power System Engineering
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• v.17 no.4
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• pp.51-57
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• 2013

The length and position of the inlet port on the double tube heat exchanger is analyzed by CFX ver.11 for studying the characteristic of its flow distribution. When the boundary conditions of the inlet temperature and mass flow rate were each $20^{\circ}C$ and 10 ~ 50 kg/min, 3 models that are based on the distance between the inlet port and the center of the heat exchanger(0, 5.025, 10.05 mm) were analyzed to find the uniformity of the flow rate. Based on the flow rate, 4 lengths (23.723, 33.890, 44.057, 57.274 mm) were used to study the flow distribution according to Reynolds Number. The results show that, when the distance from the inlet to the position of the center of the heat exchanger is 10.05 mm and the length is 57.274 mm, the flow distribution is the most unified.

• Journal of Welding and Joining
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• v.34 no.3
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• pp.40-46
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• 2016

The digital controlled SMA welding power source having the hot start current and short circuit waveform control was developed. The inverter power controller was used an analog circuit and the short circuit waveform controller was developed using a 8-bit MCU. For the evaluation of the developed SMA welding power source it were compared with a domestic welding power sources. Using the high titanium oxide type and low hydrogen type electrodes, the characteristics of hot start and short circuit was evaluated. Developed SMA welding power source shows good start performance. Also, arc stability and low current weldability were improved by the short circuit waveform control.

• Proceedings of the KIPE Conference
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• 2007.11a
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• pp.151-153
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• 2007

Recently study on components for a electric golf car and a utility car driven by a electric motor has been performed actively, and the study on a drive motor, a inverter and a battery focuses on a small, light weight and high power density source to improve fuel efficiency using limited electric energy. Especially, since a utility car such as a golf car performance depends on initial acceleration and maximum speed capability, a drive system requires high power and large and wide operation area, This study therefore investigates on the interior permanent magnet synchronous motor with high power density and wide operation, and is verified with the test result after design and characteristic analysis is performed.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.271-272
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• 2012

Bulk Metallic Glasses (BMGs or amorphous alloy) exhibit high strength and good corrosion resistance. Applications of thin films and micro parts of BMGs have been used a lot since its inception in the research of BMGs. However, Application and fabrication of BMGs are limited to make structural materials. Thin films of BMGs which is sputtered on the surface of structural materials by sputtering process is used to improve limits about application of BMGs. In order to investigate the difference of properties between designed alloys and thin films, we identified that thin films deposited on the surface that have the characteristic of the amorphous films and the composition of designed alloys. Zr-Cu (Cu=30, 35, 38, 40, 50 at.%) and Zr-Cu-Al (Al=10 at.% fixed, Cu=26, 30, 34, 38 at.%) alloys were fabricated with Zr (99.7% purity), Cu (99.997% purity), and Al (99.99% purity) as melting 5 times by arc melting method before rods 2mm in diameter was manufactured. In order to analyze GFA (Glass Forming Ability), rods were observed by Optical Microscopy and SEM and $T_g$, $T_x$, ($T_x$ is crystallization temperature and $T_g$ is the glass transition temperature) and Tm were measured by DTA and DSC. Powder was manufactured by Gas Atomizer and target was sintered using powder in large supercooled liquid region ($=T_x-T_g$) by SPS(Spark Plasma Sintering). Amorphous foil was prepared by RSP process with 5 gram alloy button. The composition of the foil and sputtered thin film was analyzed by EDS and EPMA. In the result of DSC curve, binary alloys ($Zr_{62}Cu_{38}$, $Zr_{60}Cu_{40}$, $Zr_{50}Cu_{50}$) and ternary alloys ($Zr_{64}Al_{10}Cu_{26}$, $Zr_{56}Al_{10}Cu_{34}$, $Zr_{52}Al_{10}Cu_{38}$) have $T_g$ except for $Zr_{70}Cu_{30}$ and $Zr_{60}Al_{10}Cu_{30}$. The compositions with $T_g$ made into powders. Figure shows XRD data of thin film showed similar hollow peak.

• Bulletin of the Korean Mathematical Society
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• v.29 no.2
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• pp.265-275
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• 1992

The characteristic free representation theory of the general linear group has found a wide range of applications, ranging from the theory of free resolutions to the symmetric function theory. Representation theory is used to facilitate the calculation of explicit free resolutions of large classes of ideals (and modules). Recently, K. Akin and D. A. Buchsbaum [2] realized the Jacobi-Trudi identity for a Schur function as a resolution of GL$_{n}$-modules. Over a field of characteristic zero, it was observed by A. Lascoux [6]. T.Jozefiak and J.Weyman [5] used the Koszul complex to realize a formula of D.E. Littlewood as a resolution of schur modules. This leads us to further study resolutions of Schur modules of a particular form. In this article we will describe some new classes of finite free resolutions associated to the Pieri type skew Young diagrams. As a special case of these finite free resolutions we obtain the generalized Koszul complex constructed in [1]. In section 2 we review some of the basic difinitions and properties of Schur modules that we shall use. In section 3 we describe certain exact complexes associated to the Pieri type skew partitions. Throughout this article, unless otherwise specified, R is a commutative ring with an identity element and a mudule F is a finitely generated free R-module.e.