• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.249-254
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• 1997

ABA-type block copolymers composed of poly(L-leucine)(PLL) as the A component and poly(ethylene glycol)(PEG) as the B component were synthesized by ring-opening polymerization of L-leucine N-carboxyanhydride initiated by primary amino group located at both ends of PEG chain. A silver sulfadiazine(AgSD)-impregnated wound dressing of sponge-type was prepared by the lyophilization method. Morphological structure of this wound dressing obtained by scanning electron microscopy(SEM) was composed of a dense skin layer and a macroporous inner sponge layer. Equilibrium water content(EWC) of wound dressing was above 10%. It increased with an increased of PEO content in the block copolymer due to the hydrophilicity of PEO. AgSD release from AgSD- impregnated wound dressing in PBS buffer(pH=7.4) was dependent on PEG composition in the block copolymer. Therefore, EWC and release of AgSD can be control by PEG composition. Antibacterial capacity of AgSD-impregnated wound dressing was examined in agar plate against Pseudmonas aeruginosa and Stapplococus aruous. Cytotoxicity of the wound dressing was evaluated by studing mouse skin fibroblast(L929). From the behavior of antimicrobial releasing and the investigation of the suppression of bacterial proliferation, it was supposed that the wound dressing containing antibiotics could protect the wound surfaces from bacterial invasion to suppress the bacterial proliferation effectively. In cytotoxicity observation, cellular damage was reduced by the control led released of AgSD from the LEL sponge matrix of AgSD-medicated wound dressing. In vivo test, granulous tissue formation and wound contraction or the AgSD and DHEA impregnated wound dressing were aster than any other groups.

• Progress in Medical Physics
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• v.9 no.1
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• pp.29-35
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• 1998

There has been necessity of an air free ionization chamber using the gold-crystal-aluminium plates, henceforth called the crystal chamber. The crystal chamber formed of parallel plates is very small in size and has more response for absorbed dose of therapeutic radiation beams. The gold plate on the crystal facing the photon and electron beam acts as an intensifier of signals and crystal plate as an ionization medium respectively. Both the copper guard ring and the aluminum collecting electrode are connected to an electrometer. Using high energy photon (6, 15 MV) and electron (9, 12, 15, 18 MeV) beams, the responses of the crystal chamber are evaluated against a PTW Farmer-type chamber at a field size of 10${\times}$10cm$^2$ and 100 cm SSD. The responses of crystal chamber for therapeutic radiation electron and photon beams are greater in magnitude by several order than Farmer. The crystal chamber has good linearity without correction factor C$\_$t,p/ with respect to the signals, a reading reproduction with good accuracy and precision less than 0.5%, and has other useful functions in measuring radiation beams.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.21-26
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• 2008

A multi-geophysical surveys were carried out at Hwasan caldera which is located in Euisung Sub-basin. In order to overcome the limitation of the previous studies, dense gravity data and magnetotelluric (MT) data were obtained and integrated. In this study, the independent inversion models from gravity and MT method were integrated using a correlation and classification approaches to map geologic structure. The results of integration analysis indicated followings; 1) pyroclastic rocks around the central area of Hwasan caldera have lower density and resistivity when compared with those of neighborhood regions and are extended to around 1 km in depth, 2) the high resistivity and density intrusive igneous rocks are imaged around the ring fault boundary, and 3) the basement structure, which has low resistivity and high density, 5 km deep inferred by integration analysis. Also, for integration analysis, we suggested Structure Index method. This method is analyzed using Type Angle and Type Intensity, which are calculated by the spatial correlation of the physical properties. In this study, we can perform the integration analysis effectively using Structure Index method.

• Journal of the Ergonomics Society of Korea
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• v.32 no.6
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• pp.511-516
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• 2013

Objective: The objective of this study is designing an optimal hand tool through maximum grip force study accordance to the hand grip span. Background: In order to prevent musculoskeletal diseases, studies on hand tool design are proceeding based on grip strength, finger force, and contribution of individual finger force on total grip strength. However, experimental apparatus using a tool that is actually used in work place was almost non-existent. Method: 19 males were participated in an experiment. Using the load cell inserted real plier, finger force, grip strength, and subjective discomfort rate of both hands (dominant and non-dominant) were measured in 5 different hand grip span(45mm, 50mm, 60mm, 70mm, and 80mm). Results: There was significant difference(p<0.001) of total grip strength, individual finger force and subjective discomfort rating according to various hand grip span(45, 50, 60, 70, and 80mm). Also, statistically significant different(p<0.001) was shown between the dominant hand and non-dominant hand. In addition, individual finger force in maximum grip was in order of middle finger, ring finger, index finger, and little finger. Conclusion: Optimal grip span of pliers that exerting maximum grip strength is 50~60mm. Application: This finding is expected to be used for designing proper pliers.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.2
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• pp.120-126
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• 2010

This paper propose analysis and examination of the melting characteristic of fuse elements by repeating overcurrent as a depletion factor of high pressure current limiting fuse through test following existence and nonexistence of extinction material and various configuration of elements. To examine deterioration progress rate by repeating overcurrent we analyzed heat for various element notching configuration, designed plate type, ring type element and estimated the relationship with life span by analyzing breaking characteristic through repeating overcurrent test with adjusting load factor at Silicon Dioxide(SiO2) filled state or in air. A Crack by repeat stress, decrease of section and transformation by friction with extinction material by repeating overcurrent causes a problem which shortens life span based on fuse repeating frequency. Since the contents of this paper might be useful to research the correlation between friction of materials and repeating life span based on load factor of repeating current, the quality of product would be improved through solution of the problem.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.1
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• pp.1-6
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• 2016

Micromanufacturing is a useful system for reducing energy consumption. For micromanufacturing, tool clamping and workpiece clamping are important components to realize the machining process. Therefore, a shape memory alloy (SMA) ring type tool holder is developed. In addition, this holder needs cooling and heating processes to execute the tool clamping process. This study suggests a cooling/heating device based on peltier elements. The device will be applied to the heating/cooling process of an automatic tool changer (ATC) for the SMA tool holder. This study introduces the configuration and operating principle of the proposed ATC system. The description and prototype evaluation of this system were given. Plastic bolt and aluminum block were selected to enhance the cooling performance, and the installed tool was changed in 17 s during the experiments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1158-1161
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• 2004

This paper presents structural characteristics of station class lightning arresters and electrical characteristics of manufactured ZnO varistor blocks which are usable in those arresters. Three types of station class lightning arresters were investigated and those are a ceramic arrester, a FRP tube type polymer arrester, and a FRP rod type polymer arrester. Each arrester has merits and demerits with structural characteristics. In general, polymer arresters were made of silicon rubber for housing materials, FRP tube or rod for mechanical strength, ZnO blocks for electrical characteristics, and metal parts for electrical contact and the silicon rubber, the housing materials, was directly injected to the arrester module which was assembly composed of electrodes, ZnO blocks and FRP tube or rod, and to prevent the nonlinear electric fields distribution on upper parts of arresters, the grade ring was adopted to the upper electrodes. The reference voltage, nonlinear coefficient, residual voltage, and voltage ratio of manufactured ZnO varistors are 4.90kV, 50, 9.54kV, 1.94, respectively. Compared to designed electrical characteristics, the reference voltage was low for 600v and the voltage ratio was slightly high. However, the characteristics of discharge withstand was so excellent that the mechanical destruction does not occur at the impulse current of $8/20{\mu}s$ 10kA for 100 times.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.1
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• pp.120-131
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• 2016

The full results of troubleshooting process related to the flight control system of a tilt-rotor type UAV in the flight tests are described. Flight tests were conducted in helicopter, conversion, and airplane modes. The vehicle was flown using automatic functions, which include speed-hold, altitude-hold, heading-hold, guidance modes, as well as automatic take-off and landing. Many unexpected problems occurred during the envelope expansion tests which were mostly under those automatic functions. The anomalies in helicopter mode include vortex ring state (VRS), long delay in the automatic take-off, and the initial overshoot in the automatic landing. In contrast, the anomalies in conversion mode are untrimmed AOS oscillation and the calibration errors of the air data sensors. The problems of low damping in rotor speed and roll rate responses are found in airplane mode. Once all of the known problems had been solved, the vehicle in airplane mode gradually reached the maximum design speed of 440km/h at the operation altitude of 3km. This paper also presents a comprehensive detailing of the control systems of the tilt-rotor unmanned air vehicle (UAV).

• Journal of Biosystems Engineering
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• v.8 no.2
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• pp.62-68
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• 1983

This study was to examine the drying characteristics of barley and the effect of moisture content of barley on milling performance. A barley variety, Jogang, having 35.0% of initial moisture content was used for this experiment. Thermo-hydrostatic dryer which consists of blower, condensor, heater, humidifier, drying chamber and control box, etc., was used for the drying experiment. The change in the weight of a barley sample was continuously measured by means of the ring type load cell installed inside the drying chamber. Milling test runs the samples having the predetermined moisture content were taken from each drying test run. A laboratory type barley miller was used for the milling test. The results of the study are summarized as follows: 1. The drying constants (k) applied for the thin layer drying model, (M-Me)/(Mo-Me) = $Ae^{-kt}$ were 0.155, 0.259 and 0.548, respectively, at the three levels of drying temperatures, $40^{\circ}C$, $50^{\circ}C$ and $60^{\circ}C$. The drying constants complied with the Arrhenius Equation, K = Ko exp (-C/T), were determined as $Ko=1.901455{\times}10^8$ and C = 6563. 2. The laboratory milling test indicated that the highest milled and head barley recovery was resulted from the sample which was dryed at $40^{\circ}C$. In general, the increase in the drying temperature from $40^{\circ}C$ to $60^{\circ}C$ indicated a negative effect on milling yields. 3. Also, the sample having 15% M.C. presented the highest milled and head barley recovery among the five moisture content levels (12, 15, 18,21 and 24%).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.2
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• pp.110-118
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• 2002

Organic thin film transitors(OTFT) are of interest for use in broad area electronic applications. And recently organic electroluminescent devices(OELD) have been intensively investigated for using in full-color flat-panel display. We have fabricated inverted-staggered structure OTFTs at lower temperature using the fused-ring polycyclic aromatic hydrocarbon pentacene as the active eletronic material and photoacryl as the organic gate insulator. The field effect mobility is 0.039∼0.17 ㎠/Vs, on-off current ratio is 10$\^$6/, and threshold voltage is -7V. And here we report the study of driving emitting, Ir(ppy)$_3$, phosphorescent OELD with all organic thin film transistor and investigated its electrical characteristics. The OELD with a structure of ITO/TPD/8% Ir(ooy)$_3$ doped in BCP/BCP/Alq$_3$/Li:Al/Al and OTFT with a structure of inverted-stagged Al(gate electrode)/photoacry(gate insulator)/pentacene(p-type organic semiconductor)/ Au(source-drain electrode) were fabricated on the ITP patterned glass substrate. The electrical characteristics are turn-on voltage of -10V, and maximum luminance of about 90 cd/㎡. Device characteristics were quite different with that of only OELD.