• Korean Journal of Materials Research
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• v.10 no.4
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• pp.290-294
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• 2000

ZnS:Mn TFEL devices were fabricated by electron-beam evaporation method and then the electro-optical properties were investigated. To investigate the capacitance which was due to oxygen vacancy at the $Ta_2O_5$ thin film, AES(Auger Electron Spectroscopy) and C-F(capacitance-frequency) measurements were used. It was found that the capacitance was decreased by annealing the $Ta_2O_5$ film in oxygen ambience. From EL emission measurement, we observed the EL emission spectrum which had the peak range from 550nm and 650nm. This emission is associated with the transition from $^4T_1(^4G)$ first excited state to $^6A_1(^6S)$ ground state in the $3d^5$ energy level configuration of $Mn^{2+}$ occurs. The threshold voltage of EL device with $Ta_2O_5$ insulator layer was found to be 24V~28V. The CIE color coordinates of these emission are X=0.5151, Y=0.4202 which is yellowish orange emitting. The EL device using $Ta_2O_5$ insulator layer can be driven with a low voltage which is beneficial to the practical application.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.8
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• pp.1868-1876
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• 2010

In this paper, we design a 256-bit EEPROM IP using only logic process-based devices. We propose EEPROM core circuits, a control gate (CG) and a tunnel gate (TG) driving circuit, to limit the voltages between the devices within 5.5V; and we propose DC-DC converters : VPP (=+4.75V), VNN (-4.75V), and VNNL (=VNN/3) generation circuit. In addition, we propose switching powers, CG_HV, CG_LV, TG_HV, TG_LV, VNNL_CG, VNNL_TG switching circuit, to be supplied for the CG and TG driving circuit. Simulation results under the typical simulation condition show that the power consumptions in the read, erase, and program mode are $12.86{\mu}W$, $22.52{\mu}W$, and $22.58{\mu}W$ respectively. Furthermore, the manufactured test chip operated normally and generated its target voltages of VPP, VNN, and VNNL as 4.69V, -4.74V, and -1.89V.

• Journal of the Korea Institute of Construction Safety
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• v.1 no.1
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• pp.47-56
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• 2018

In this paper, we analyze various cases of accidents caused by vehicle-mounted MEWPs(mobile elevated work platforms) which are most widely used for the high position level works, review the safety improvement measures for each of them, and propose basic data for the revision of related laws. The accidents by MEWPs were caused by the high level of works, which lead to fatal personnel accidents, so the measures for safety must be thoroughly carried out and the obligatory regulations by the related laws must be strictly observed. In this paper, we classify the cases of accidents at the workshop as 4 representative types and propose measures and remedies for them. According to the current regulations, it is possible to prepare for the accidents such as the wire rope breakage by switching to the all-chain drive method which does not have a daily use time limit instead of the wire rope drive method which is widely used at present. Also, it is suggested to add the daily use timetable to the nameplate attachment duty item according to the driving class.

• Membrane Journal
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• v.29 no.3
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• pp.173-182
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• 2019

Much research has been made for finding new and eco-friendly alternative sources of energy to solve the problems related with the pollution caused by emissions of greenhouse gases such as carbon dioxide as the use of fossil fuels increases worldwide. Among them, fuel cells draws particular interests as an eco-friendly energy generator because only water is obtained as a by-product. Anion exchange membrane-based alkaline fuel cell (AEMFC) that uses anion exchange membrane as an electrolyte is of increased interest recently because of its advantages in using low-cost metal catalyst unlike the PEMFC (potton exchange membrane fuel cell) due to the high-catalyst activity in alkaline conditions. The main properties required as an anion exchange membrane are high hydroxide conductivity and chemical stability at high pH. Recently we reported a chemically crosslinked poly(2-dimethyl-1,4-phenylene oxide) (PPO) by reacting PPO with N,N,N',N'-tetramethyl-1,6-hexanediamine as novel anion exchange membranes. In the current work, we further developed the same crosslinked polymer but having enhanced physicochemical properties, including higher conductivity, increased mechanical and dimensional stabilities by using the PPO with a higher molecular weight and also by increasing the crosslinking density. The obtained polymer membrane also showed a good cell performance.

• Applied Chemistry for Engineering
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• v.30 no.2
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• pp.205-211
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• 2019

Over the past several decades, the polymer dispersed liquid crystal (PDLC) has received particular attention as a material for developing smart window due to their electro-optical switchable properties. In this study, PDLC cells were fabricated using acrylate monomers, namely 2-hydroxyethyl acrylate (2-HEA) and ethylene glycol phenyl ether acrylate (EGPA), and the effect of the monomer composition on their electro-optical properties was investigated. The monomer mixture with a low viscosity (~10 cps) was easily filled between indium tin oxide (ITO) glasses by capillary action at room temperature. PDLC cells prepared using the mixture ratio of 1 : 9 (2-HEA : EGPA) did not show a complete opaque state at a 0 V condition but exhibited unstable electro-optical properties under an electric field. As the LC composition increased in the reaction mixture for PDLC cell preparation, the $V_{th}$ (threshold voltage) and $V_{sat}$ (saturation voltage) values as well as contrast ratio (CR) increased. $V_{th}$ and $V_{sat}$ values also increased with the cell gap thickness. PDLC cells with a $20{\mu}m$ cell gap thickness exhibited higher CR than those with 10 and $40{\mu}m$ cell gap thicknesses. Particularly, PDLC cells prepared using the mixture ratio of 7 : 3 (2-HEA : EGPA) showed excellent electro-optical properties such as a low driving voltage and high contrast ratio.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.107-120
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• 2021

Electric-powered distributed propulsion aircraft possess a complex wake flow and mutual interference with the airframe, due to the use of many propellers. Accordingly, in the early design stage, rapid aerodynamic and load analysis considering the effect of propellers for various configurations and flight conditions are required. In this study, an efficient panel-based aerodynamic analysis method that can take into account the propeller effects is developed and validated. The induced velocity field in the region of propeller wake is calculated based on Actuator Disk Theory (ADT) and is considered as the boundary condition at the vehicle's surface in the three-dimensional steady source-doublet panel method. Analyses are carried out by selecting an isolated propeller of the Korea Aerospace Research Institute (KARI)'s Quad Tilt Propeller (QTP) aircraft and the propeller-wing configuration of the former experimental study as benchmark problems. Through comparisons with the results of computational fluid dynamics (CFD) based on actuator methods, the wake velocity of propeller and the changes in the aerodynamic load distribution of the wing due to the propeller operation are validated. The method is applied to the analysis of the Optional Piloted Personal Aerial Vehicle (OPPAV) and QTP, and the practicality and validity of the method are confirmed through comparison and analysis of the computational time and results with CFD.

• Korean Journal of Optics and Photonics
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• v.33 no.5
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• pp.201-209
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• 2022

The previously developed microspot spectroscopic ellipsometer (SE) is upgraded to a microspot SE compatible with the atomic force microscope (AFM). The focusing optical system of the previous microspot SE is optimized to incorporate an AFM head. In addition, the rotating compensator ellipsometer in polarizer-sample-compensator-analyzer configuration is adopted in order to minimize the negative effects caused by beam wobble. This research leads to the derivation of the expressions needed to get spectro-ellipsometric constants despite the fact that the employed rotating compensator is far from the ideal achromatic quarter-wave plate. The spot size of the developed microspot SE is less than 20 ㎛ while the AFM head is mounted. It operates in the wavelength range of 190-850 nm and has a measurement accuracy of δΔ ≤ 0.05° and δΨ ≤ 0.02°, respectively. Fast measurement of ≤3 s/sp is realized by precisely synchronizing the azimuthal angle of a rotating compensator with the spectrograph. The microspot SE integrated with an AFM is expected to be useful in characterizing the structure and optical properties of finely patterned samples.

• Korean Journal of Plant Resources
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• v.16 no.3
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• pp.264-274
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• 2003

Many potato genetic resources have been collected and improved for their diverse traits over the years using breeding program in KPGR. To select potential varieties for table and processing in Korea, 58 elite potato breeding lines and several 'Valley' varieties were cultivated and harvested at Korea Alpine area in 2001. The cultivated lines and varieties were evaluated using their cultural adaptability in the environment and tuber characteristics, such as the depth of tuber eye, tuber shape, skin color, flesh color, scab resistance, yield, and the resistance of hollow heart and internal brown spot disease. Additionally, in the selection of potential processing varieties, reducing sugar content (sum of glucose and fructose concentration) of tubers is critically considered, because it mainly influence on the chip color of processing potato tuber. For table stock varieties with white skin color, 'Early Valley', 'Summer Valley', 'Winter Valley', and 'Taebok Valley' were selected. In the aspect of diverse potato tuber color, several varieties were selected such as 'Golden Valley' for its yellow fresh and skin color, 'Gogu Valley', 'Juice Valley', and 'Rose Valley' for their red skin color, and 'Purple Valley' for its purple skin. Compared with world wide known processing cultivar 'Atlantic', 24 lines (or varieties) were selected for the potential potato processing industry due to their low reducing sugar contents (below 0.3％), high yield (above 4.0 ton/ha), and unique chip colors. Selected white chipping varieties were 'Taedong Valley', 'Kangshim Valley', and 'Kangwon Valley', which have 0.23％, 0.27％, and 0.29％ of reducing sugar contents, respectively. 'Bora Valley', having deep purple color in both skin and fresh, was selected for purple chip variety and has 0.26％ of reducing sugar content. Light yellow chip varieties (lines) were 'Rose Valley' and Valley 54, having 0.19％ and 0.269％ of reducing sugar content, respectively. For French frying potatoes, 'Stick Valley' of 0.22％ and Valley 72 of 0.151％ in reducing sugars were selected. All of these selected lines and 'Valley' varieties can be used as parents to improve potato genetic resources and to develop better varieties with unique traits and colors.

• Journal of Korean Society of Forest Science
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• v.97 no.1
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• pp.61-70
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• 2008

This study was conducted to develop a mobile tower-yarder with tractor for agriculture and forestry that is the efficient yarder in steep terrains, thinning operation and small scale logging operation. It was designed and manufactured that the power source of tower-yarder is equiped three hydraulic pump connected to PTO of tractor, and three hydraulic pump is used to operate the four motor for drum, the cylinder for clutch of interlocker, the cylinder for tower expanding and the out-rigger cylinder. It was to adopt the running skyline system and the inter-lock function, and to equip the double capstan drum, the storage drum and the clutch for interlock in the development of tower-yarder. It was to develop the tower-yarder which the winch torque of double-capstan drum, the traction force of double-capstan drum, the number of rotation of double-capstan drum and the line speed is $191kg{\cdot}m$, 1,910 kgf, 220.5 rpm and 138.5 m/min, respectively. And it was known that the optimum flange diameter of the main and haulback storage drum is about 360 mm and about 460 mm in order to storage the main line length of 250m and the haulback line length of 450 m. The carriage was made to adopt the running skyline system and to equip the lock function in order to the convenience of chocking and the fall down preventing of tree. It was provided to develop the wire remote controller for the inter-lock function, the convenience of control and the efficiency of yarding. In development process, this tower-yarder was attached the 3-point linkage hitch equipment and the tire wheel for the traction and moving of tower-yarder. Also, it was equipped that the out-rigger and the guy line in order to raise the safety and efficiency of yarding of tower-yarder.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.86-92
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• 2022

Recently, the bio-healthcare market is enlarging worldwide due to various reasons such as the COVID-19 pandemic. Among them, biometric measurement and analysis technology are expected to bring about future technological innovation and socio-economic ripple effect. Existing systems require a large-capacity battery to drive signal processing, wireless transmission part, and an operating system in the process. However, due to the limitation of the battery capacity, it causes a spatio-temporal limitation on the use of the device. This limitation can act as a cause for the disconnection of data required for the user's health care monitoring, so it is one of the major obstacles of the health care device. In this study, we report the concept of a standalone healthcare monitoring module, which is based on both triboelectric effects and electromagnetic effects, by converting biomechanical energy into suitable electric energy. The proposed system can be operated independently without an external power source. In particular, the wireless foot pressure measurement monitoring system, which is rationally designed triboelectric sensor (TES), can recognize the user's walking habits through foot pressure measurement. By applying the triboelectric effects to the contact-separation behavior that occurs during walking, an effective foot pressure sensor was made, the performance of the sensor was verified through an electrical output signal according to the pressure, and its dynamic behavior is measured through a signal processing circuit using a capacitor. In addition, the biomechanical energy dissipated during walking is harvested as electrical energy by using the electromagnetic induction effect to be used as a power source for wireless transmission and signal processing. Therefore, the proposed system has a great potential to reduce the inconvenience of charging caused by limited battery capacity and to overcome the problem of data disconnection.