• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.107-114
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• 2017

A turbocharger is an engine supercharger that is driven by exhaust gas. It improves the output and fuel efficiency by increasing the charging efficiency of the mixture gas, which is achieved by changing the rotatory power of the turbine connected to the exhaust passage. It is important to control the supercharging for this purpose. A nozzle slide joint is one of the core parts. Austenitic stainless steel is currently used as the material for this part, and its excellent mechanical properties include high heat resistance and corrosion resistance. However, because of its poor machinability, there are many difficulties in producing products with complicated shapes. Machining is used in the production of nozzle slide joints for high dimensional accuracy after metal powder injection molding. As design variables in this study, we investigated the sintering temperature, product stress, deformation rate, radius of curvature of the punch, and angle of the chamfer punch, which are related to the strain and shapes. The goal is to suggest a forming process using Nitronic 60 that does not require machining to manufacture a nozzle slide joint for a turbocharger. Accordingly, we determined the best process environment using finite-element analysis, the signal-noise ratio, and the Taguchi method for experiment design. The relative density and hydrostatic pressure of the final product were in accordance with the results of the finite element analysis. Therefore, we conclude that the Taguchi method can be applied to the design process of metal powder injection molding.

• Economic and Environmental Geology
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• v.53 no.3
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• pp.287-296
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• 2020

Mine Reclamation Project is being carried out with the aim of ensuring a sustainable green living and helping to develop eco-friendly mines by analyzing, removing and preventing the harmful factors. Mines developed during the japanese colonial period and mining boom period are still not repaired throughout the country, and from these scattered risks, public safety is worth pursuing as a top priority. The project that is close to public safety in the mine recalmation project is an emergency treatment, and the most widely used method is a filling method similar to the ground subsidence prevention. If dangerous mine cavity or tunnels are located in the mountains, charging with existing materials may not be possible, or unreasonable cases may occur, and new methods of technological development are required. Emergency actions should be carried out safely and efficiently to prevent the loss of precious people's lives on the hiking paths adjacent to dangerous mining sites. In these field conditions, urethane foam materials may be an alternative. In this study, the applicability of urethane foam materials in mining was reviewed through overseas cases. It was also tested on the appropriate depth of top soil for the protection of urethane foam materials through forest fire simulation test. The test result show that approximately 15cm of soil covering (recommended 20cm over) was suitable for maintaining the function of foam materials from forest fires.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.186-186
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• 2000

After LeComber et al. reported the first amorphous hydrogenated silicon (a-Si: H) TFT, many laboratories started the development of an active matrix LCDs using a-Si:H TFTs formed on glass substrate. With increasing the display area and pixel density of TFT-LCD, however, high mobility TFTs are required for pixel driver of TF-LCD in order to shorten the charging time of the pixel electrodes. The most important of these drawbacks is a-Si's electron mobiliy, which is the speed at which electrons can move through each transistor. The problem of low carier mobility for the a-Si:H TFTs can be overcome by introducing polycrystalline silicon (poly-Si) thin film instead of a-Si:H as a semiconductor layer of TFTs. Therefore, poly-Si has gained increasing interest and has been investigated by many researchers. Recnetly, fabrication of such poly-Si TFT-LCD panels with VGA pixel size and monolithic drivers has been reported, . Especially, fabricating poly-Si TFTs at a temperature mach lower than the strain point of glass is needed in order to have high mobility TFTs on large-size glass substrate, and the monolithic drivers will reduce the cost of TFT-LCDs. The conventional methods to fabricate poly-Si films are low pressure chemical vapor deposition (LPCVD0 as well as solid phase crystallization (SPC), pulsed rapid thermal annealing(PRTA), and eximer laser annealing (ELA). However, these methods have some disadvantages such as high deposition temperature over $600^{\circ}C$, small grain size (<50nm), poor crystallinity, and high grain boundary states. Therefore the low temperature and large area processes using a cheap glass substrate are impossible because of high temperature process. In this study, therefore, we have deposited poly-Si thin films on si(100) and glass substrates at growth temperature of below 40$0^{\circ}C$ using newly developed high rate magnetron sputtering method. To improve the sputtering yield and the growth rate, a high power (10~30 W/cm2) sputtering source with unbalanced magnetron and Si ion extraction grid was designed and constructed based on the results of computer simulation. The maximum deposition rate could be reached to be 0.35$\mu$m/min due to a high ion bombardment. This is 5 times higher than that of conventional sputtering method, and the sputtering yield was also increased up to 80%. The best film was obtained on Si(100) using Si ion extraction grid under 9.0$\times$10-3Torr of working pressure and 11 W/cm2 of the target power density. The electron mobility of the poly-si film grown on Si(100) at 40$0^{\circ}C$ with ion extraction grid shows 96 cm2/V sec. During sputtering, moreover, the characteristics of si source were also analyzed with in situ Langmuir probe method and optical emission spectroscopy.

• Journal of the Korean Institute of Gas
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• v.28 no.2
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• pp.93-104
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• 2024

Facility diagnosis is essential for the smooth operation and life extension of rotating equipment used in industrial sites. Compared to other diagnostic methods, vibration diagnosis can find most of the initial defects, such as unbalance, alignment failure, bearing defects and resonance, compared to other diagnostic methods. Therefore, vibration analysis is the most commonly used facility diagnosis method in industrial sites, and is usefully used as a predictive preservation (PdM) technology to manage the condition of the facility. However, since the vibration diagnosis method is performed based on experience based on the standard, it is carried out by experts. Therefore, it is intended to contribute to the reliability of the facility by establishing a system that anyone can easily judge defects by establishing a vibration diagnosis method performed based on experience as a knowledgeable code system. An algorithm was developed based on the ISO-20816 standard for vibration measurement, and the reliability was verified by comparing the results of vibration measurement at various demonstration sites such as petrochemical plant compressors, hydrogen charging stations, and industrial machinery with the results of analysis using a development system. The developed algorithm can contribute to predictive maintenance (PdM) technology that anyone can diagnose the condition of the rotating machine at industrial sites and identify defects early to replace parts at the exact time of replacement. Furthermore, it is expected that it will contribute to reducing maintenance costs and downtime due to the failure of rotating machines when applied to various industrial sites such as oil refining facilities, transportation, production facilities, and aviation facilities.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.3
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• pp.99-105
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• 2014

$LiCoO_2$ thin film have received attention as cathodes of thin-film microbatteries. In this study, $LiCoO_2$ thin films were synthesized on Au substrates by sol-gel spin coating method and electrochemical properties were investigated under annealing temperature and time. The phycochemical properties of $LiCoO_2$ thin film were investigated by X-ray diffraction, scaning electron microscopy and atomic force microscopy. The electrochemical properties were characterized using galvanostatic charging/discharging cycling tests. From X-ray diffraction, as-grown films annealed at $550^{\circ}C$ and $750^{\circ}C$ are presumed to be spinel structure and a single phase of the layered-rock-salt, respectively. The RMS roughness and grain size of the films which annealed at $750^{\circ}C$ has similar values for annealing time 10 and 30 min, while for annealing time 120 min surface roughness, grain size increase and pore appearance were observed. The first discharge capacity of $LiCoO_2$ thin films annealed at $750^{\circ}C$ for 10, 30 and 120 min is about 54.5, 56.8 and $51.87{\mu}Ah/cm^2{\mu}m$, respectively. Corresponding capacity retention at 50th cycle is 97.25, 76.69, 77.19%.

• Journal of the Korean Electrochemical Society
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• v.23 no.1
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• pp.11-17
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• 2020

The Prussian blue analogues of Fe₂(CN)₆ and Na_xFe₂(CN)₆ are prepared by precipitation method and evaluated the electrochemical characteristics as positive electrode materials for lithium-ion batteries (LIBs) because of their low cost. Fe₂(CN)₆ shows a low reversible capacity of 34.6 mAh g^-1, whereas sodium-containing Na_xFe₂(CN)₆ exhibits a reversible capacity of 107.5 mAh g^-1 when the discharge process proceeds first. When charging is first carried out to remove sodium in the structure, the reversible capacity of 114.1 mAh g^-1 is achieved and the cycle performance is further improved. In addition, Na_x-Fe₂(CN)₆ is synthesized at 0℃, room temperature (RT), and 60℃, respectively. Regardless of the synthesis temperature, Na_xFe₂(CN)₆ shows similar initial reversible capacity, but the crystallite size is formed smaller and improved cycle performance when synthetic temperature is lower. The sample synthesized at 0℃ shows a reversible capacity of 86.4 mAh g^-1 at the 120^th cycle and maintains 76.8% of the initial capacity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.15-23
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• 2017

This paper reports a SOC(State-of-Charge) estimation method using the extended Kalman filter(EKF) algorithm, which can allow real-time implementation and reduce the error of the model and be robust against noise, to accurately estimate and evaluate the charging/discharging state of the EV(Electric Vehicle) battery. The battery was modeled as the first order Thevenin model for the EKF algorithm and the parameters were derived through experiments. This paper proposes the changed method, which can have the SOC to 0% ~ 100% regardless of the aging of the battery by replacing the rated capacity specified in the battery with the maximum chargeable capacity. In addition, This paper proposes the EKF algorithm to estimate the non-linearity interval of the battery and simulation result based on Ah-counting shows that the proposed algorithm reduces the estimation error to less than 5% in all intervals of the SOC.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.1045-1051
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• 2005

We developed an orofacial pains diagnosis/therapy system which can enlarge a therapy effect through a new stimulation. Contrary to its established method, this therapy system(DDTS-1) is a treating method which absorbs a surplus ion charge- the cause of an outbreak of a pain-of the human body using a capacitor. Absorbing a surplus ion charge of the human body with effect, it obtained optimal parameters which is control signal to control charging/discharging a capacitor to be 6Hz, and capacitance to be $0.1\~0.33{\mu}F.$ Through clinical demonstration, experimented on among patients-namely dental pain patients, joint disorders patients, and trigeminal neuralgia patients to verification of system. In result, an EAST stimulater had a very low change of abnormal potential against normal potential before/after being placed under medical care. DDTS-1 showed obvious differences that two potentials are one and the same potential or one potential is similar to the other one. DDTS-1 comparing with EAST showed the remedial value of the comparative advantage in all the medical treatment of pains. Therefore, stimulation of DDTS-1 is more effective than the existing electric stimulation. We verified its validity of ion charge absorption in the human body using capacitor which presented the present thesis. That is, we verified theoretical adequacy of control action in a pain, and its efficiency as well as confidence.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.81-88
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• 2021

In general, a non-explosive nylon wire cutting-based holding and release mechanism has been used to store and deploy deployable solar panels of CubeSat. However, with this method, accessing the solar panel's access port for charging the cube satellite's battery and electrical inspection and testing of the PCB and payloads while the solar panel is in storage is difficult. Additionally, the mechanism must have a reliable release function in an in-orbit environment, and reusability for stow and deploy of the solar panel, which is a hassle for the operator and difficult to maintain a consistent nylon wire fastening process. In this study, we proposed a pin-puller-based solar panel holding and release mechanism that can easily deploy a solar panel without cutting nylon wires by separating constraining pins. The proposed mechanism's release function and performance were verified through a solar panel deployment test and a maximum separation load measurement test. Through this, we also verified the design feasibility and effectiveness of the pin-puller-based separation device.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.184-192
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• 2022

Porous NiO synthesized via hydrothermal synthesis was used in the electrodes of lithium-sulfur batteries to inhibit the elution of lithium polysulfide. The electrode of the lithium-sulfur battery was manufactured as a freestanding flexible electrode using an economical and simple vacuum filtration method without a current collector and a binder. The porous NiO-added S/CNT/NiO electrode exhibited a high initial discharge capacity of 877 mA h g^-1 (0.2 C), which was 125 mA h g^-1 higher than that of S/CNT, and also showed excellent retention of 84% (S/CNT: 66%). This is the result of suppressing the dissolution of lithium polysulfide into the electrolyte by the strong chemical bond between NiO and lithium polysulfide during the charging and discharging process. In addition, for the flexibility test of the S/CNT/NiO electrode, the 1.6 × 4 cm² pouch cell was prepared and exhibited stable cycle characteristics of 620 mA h g^-1 in both the unfolded and folded state.