• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.377-377
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• 2011

Organic solar cells (OSCs) with low cost have been studied to apply on flexible substrate by solution process in low temperature [1]. In previous researches, conventional organic solar cell was composed of metal oxide anode, buffer layer such as PEDOT:PSS, photoactive layer, and metal cathode with low work function. In this structure, indium tin oxide (ITO) and Al was generally used as metal oxide anode and metal cathode, respectively. However, they showed poor reliability, because PEDOT:PSS was sensitive to moisture and air, and the low work function metal cathode was easily oxidized to air, resulting in decreased efficiency in half per day [2]. Inverted organic solar cells (IOSCs) using high work function metal and buffer layer replacing the PEDOT:PSS have focused as a solution in conventional organic solar cell. On the contrary to conventional OSCs, ZnO and TiO2 are required to be used as a buffer layer, since the ITO in IOSC is used as cathode to collect electrons and block holes. The ZnO is expected to be excellent electron transport layer (ETL), because the ZnO has the advantages of high electron mobility, stability in air, easy fabrication at room temperature, and UV absorption. In this study, the IOSCs based on poly [N-900-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)] (PCDTBT) : [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) were fabricated with the ZnO electron-transport layer and MoO3 hole-transport layer. Thickness of the ZnO for electron-transport layer was controlled by rotation speed in spin-coating. The PCDTBT and PC70BM were mixed with a ratio of 1:2 as an active layer. As a result, the highest efficiency of 2.53% was achieved.

• The Journal of Advanced Prosthodontics
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• v.6 no.6
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• pp.491-497
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• 2014

PURPOSE. This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. MATERIALS AND METHODS. Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed. RESULTS. Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (P<.001). CONCLUSION. The abutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.387-387
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• 2013

Currently, the flash memory and the dynamic random access memory (DRAM) have been used in a variety of applications. However, the downsizing of devices and the increasing density of recording medias are now in progress. So there are many demands for development of new semiconductor memory for next generation. Magnetic random access memory (MRAM) is one of the prospective semiconductor memories with excellent features including non-volatility, fast access time, unlimited read/write endurance, low operating voltage, and high storage density. MRAM is composed of magnetic tunnel junction (MTJ) stack and complementary metal-oxide semiconductor (CMOS). The MTJ stack consists of various magnetic materials, metals, and a tunneling barrier layer. Recently, MgO thin films have attracted a great attention as the prominent candidates for a tunneling barrier layer in the MTJ stack instead of the conventional Al2O3 films, because it has low Gibbs energy, low dielectric constant and high tunneling magnetoresistance value. For the successful etching of high density MRAM, the etching characteristics of MgO thin films as a tunneling barrier layer should be developed. In this study, the etch characteristics of MgO thin films have been investigated in various gas mixes using an inductively coupled plasma reactive ion etching (ICPRIE). The Cl2/Ar, CH3OH/Ar, and CH4/Ar gas mix were employed to find an optimized etching gas for MgO thin film etching. TiN thin films were employed as a hard mask to increase the etch selectivity. The etch rates were obtained using surface profilometer and etch profiles were observed by using the field emission scanning electron microscopy (FESEM).

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.117-117
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• 2016

Total ankle replacement (TAR) is a visible option in the surgical treatment of degenerative or inflammatory diseases of ankle joint. it is attributed to the current TAR which has improvements in surgical technique, uncemented implant fixation and minimally constrained articulation. In the clinical result, they can show promised surgical result when compared to earlier attempts in TAR. However, TAR is still not as successful as total knee replacement (TKR) or total hip replacement (THR), it needs to be note that there are limitations in concerning of long term performance of TAR, the high failure rate still associated with wear of the PE (polyethylene) component that has related with their material property and surface roughness. The aim of this study was to introduce the tribology characteristics of total ankle joint prosthesis with one of TDR model which was fabricated to try multi-axis wear test as a region of motion in ankle joint. The wear specimen of TDR was prepared with Ti-6Al-4V alloy and UHMWPE (ultra-high molecular weight polyethylene) for tibia-talus and bearing component, respectively. A wear test was carried out using a Force 5 (AMTI, Massachusetts, US) wear simulator which can be allowed to move in three axis to flexion-extension ($+3^{\circ}{\sim}-6^{\circ}$), internal-external axial rotation (${\pm}5^{\circ}$), as well as sinusoidal compressive load (1.6 kN, R=10). All tests were performed following standard ISO 14243, wear rate was calculated with weight loss of UHMWPE bearing while the specimen has tested at certain cycles. As based on the preliminary results, wear rate of UHMWPE bearing was $7.9{\times}10^{-6}mg/cycles$ ($R^2=0.86$), calculated loss weight until $10^7cycles$ was 79 mg, respectively.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.458-464
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• 2006

The Pd-Ni-Ag alloy composite membrane using modified porous stainless steel (PSS) as a substrate was prepared by a electroless plating technique. In this work, we have introduced the intermediate layer between Pd-based alloy and a metal substrate. As an intermediate layer, the mixtures of nickel powder and inorganic sol such as $SiO_{2}$ sol, $Al_{2}O_{3}$ sol, and $TiO_{2}$ sol were used. The intermediate layers were coated onto a PSS substrate according to various membrane preparation conditions and then $N_{2}$ fluxes through the membranes with different intermediate layers were measured. The surface morphology of the intermediate layer in the mixture of nickel powder and inorganic sol was analyzed using scanning electron microscope (SEM). Finally, the Pd-Ni-Ag alloy composite membrane using the support coated with the mixture of nickel powder and silica as an intermediate layer was fabricated and then the gas permeances for $H_{2}$ and $N_{2}$ through the Pd-based membrane were investigated. The selectivity of $H_2/N_2$ was infinite and the $H_{2}$ flux was $1.39{\times}10^{-2}mol/m^2{\cdot}s$ at the temperature of $500^{\circ}C$ and trans-membrane pressure difference of 1 bar.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.7 s.361
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• pp.9-15
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• 2007

In this paper, we present the design of Schottky diodes and voltage multiplier for UHF-band passive RFID applications. The Schottky diodes were fabricated using Titanium (Ti/Al/Ta/Al)-Silicon (n-type) junction in $0.35\;{\mu}m$ CMOS process. The Schottky diode having $4{\times}10{\times}10\;{\mu}m^{2}$ contact area showed a turn-on voltage of about 150 mV for the forward diode current of $20\;{\mu}A$. The breakdown voltage is about -9 V, which provides sufficient peak inverse voltage necessary for the voltage multiplier in the RFID tag chip. The effect of the size of Schottky diode on the turn-on voltage and the input impedance at 900 MHz was investigated using small-signal equivalent model. Also, the effect or qualify factor of the diode on the input voltage to the tag chip is examined, which indicates that high qualify factor Schottky diode is desirable to minimize loss. The fabricated voltage multiplier resulted in a output voltage of more than 1.3 V for the input RF signal of 200mV, which is suitable for long-range RFID applications.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.2
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• pp.71-80
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• 2001

To understand paleoceanographic environmental changes in the Esat Sea during the transitional period between Holocene and last glacial maximum, geochemical high resolution study was conducted by using a piston core(95PC-1) samples collected from the southernmost part of the Ulleung Basin. Geochemical results reveal that major distinctive paleoceanographic variations in transitional period are prominent. Major elemental concentrations show distinctive variations between glacial and Holocene suggesting changes in sediment supply. $TiO_2/Al_2O_3$ ratio of the sediment indicates different sediment composition between Holocene and glacial period. The content of total organic carbon ranging from 0.5% to 4% during transitional period. These vslues showed 2-4 times and two times higher than those of last glacial and Holocene, respectively. The C/N ratios deduced from organic matters exceed10 during transitional period suggesting terrigenous organic matter are supplied from continent, especially during last glacial maximum. Carbonate contents are relatively stable during Holocene and last glacial maximum with gradual decrease during glacial period with high fluctuation during transitional period. The variations of chemical index of weathering (CIW) also show a distinctive variation between glacial and Holocene, which is coincident with those of carbonate and organic carbon. The grain size distribution indicates that the difference content of silt fraction during Holocene and glacial period is closely related with climatic effect during glacial period. Therefore geochemical differences in sediment composition between Holocene and last glacial maximum is thought to be related to paleoceanographic, sea-level change and local paleoclimatic changes.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.1
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• pp.56-72
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• 1999

Airborne concentrations of welding fumes in which 13 different metals such as Al, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Si, Sn, Ti, and Zn were analyzed were measured at 18 factories including automobile assembly and manufactures, steel heavy industries and shipyards. Air samples were collected by personal sampler at each worker's worksite(n=339). Blood levels of Cd, Cu, Fe, Mn, Pb and Zn were also measured from samples taken from 447 welders by atomic absorption spectrometry and compared with control values obtained from 127 non-exposed workers. The results were as follows ; 1. Among various welding types, $CO_2$ welding 70.2 % were widely used, shielded metal arc welding(SMAW) 22.1 % came next, and rest of them were metal inert gas(MIG) welding, submerged arc welding(SAW), spot welding(SPOT) and tungsten inert gas(TIG) welding. 2. Welding fume concentration was $0.92mg/m^3$($0.02{\sim}15.33mg/m^3$) at automobile assembly and manufactures, $4.10mg/m^3$($0.02{\sim}70.75mg/m^3$) at steel heavy industries and $5.59mg/m^3$($0.30{\sim}91.16mg/m^3$) at shipyards, respectively, showing significant difference among industry types. Workers exposed to high concentration of welding fumes above Korean Permissible Exposure Limit(KPEL) amounted to 7.9 % and 12.5 %, in $CO_2$ welding and in SMAW at automobile assembly and manufactures and 62.7 % in $CO_2$ welding, and 12.5 % in SMAW at shipyards, and 66.2 % in $CO_2$ welding and 70.6 % in SMAW at steel heavy industries. 3. Geometric mean of airborne concentration of each metal released from welding fumes was below one 10th of KPEL in all welding types. Percentage of workers, however, exposed to airborne concentration of metals above KPEL amounted to 16.8 % in Mn and 7.6 % in Fe in $CO_2$ welding; 37.5 % in Cu in SAW, 30 % in Cu in TIG; and 25 % in Pb in SPOT welding. As a whole, 76 Workers(22.4%) were exposed to high concentration of any of the metals above KPEL. 4. There were differences in airborne concentration of metals such as Al, Cd, Cr, Cu. Fe. Mn, Mo, Ni, Pb, Si, Sn, Ti and Zn by industry types. These concentrations were higher in shipyards and steel heavy industries than in automobile assembly and manufactures. Workers exposed to higher concentration of Pb above KPEI amounted to 7.4 % of workers(7/94) in automobile assembly and manufactures. In shipyards, 19.2 % of workers(19/99) were over-exposed to Mn and 7.1 % (7/99) to Fe above KPEL. In steel heavy industries, 14.4 %(21/146), 7.5 %(11/146) and 13 %(19/146) were over-exposed to Mn, Fe and Cu, respectively. As a whole, 76 out of 339 workers(22.4%) were exposed to any of the metals above KPEL. 5. Blood levels of Cd, Cu, Fe, Mn, Pb, and Zn in welders were $0.11{\mu}g/100m{\ell}$, $0.84{\mu}g/m{\ell}$, $424.4{\mu}g/m{\ell}$, $1.26{\mu}g/100m{\ell}$, $5.01{\mu}g/100m{\ell}$ and $5.68{\mu}g/m{\ell}$, respectively, in contrast to $0.09{\mu}g/100m{\ell}$, $0.70{\mu}g/m{\ell}$, $477.2{\mu}g/m{\ell}$, $0.73{\mu}g/100m{\ell}$, $3.14{\mu}g/100m{\ell}$ and $6.15{\mu}g/m{\ell}$ in non-exposed control groups, showing significantly higher values in welders but Fe and Zn.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.07a
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• pp.25-37
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• 2002

The most important industrial application of gamma radiation in characterizing green compacts is the determination of the density. Examples are given where this method is applied in manufacturing technical components in powder metallurgy. The requirements imposed by modern quality management systems and operation by the workforce in industrial production are described. The accuracy of measurement achieved with this method is demonstrated and a comparison is given with other test methods to measure the density. The advantages and limitations of gamma ray densitometry are outlined. The gamma ray densitometer measures the attenuation of gamma radiation penetrating the test parts (Fig. 1). As the capability of compacts to absorb this type of radiation depends on their density, the attenuation of gamma radiation can serve as a measure of the density. The volume of the part being tested is defined by the size of the aperture screeniing out the radiation. It is a channel with the cross section of the aperture whose length is the height of the test part. The intensity of the radiation identified by the detector is the quantity used to determine the material density. Gamma ray densitometry can equally be performed on green compacts as well as on sintered components. Neither special preparation of test parts nor skilled personnel is required to perform the measurement; neither liquids nor other harmful substances are involved. When parts are exhibiting local density variations, which is normally the case in powder compaction, sectional densities can be determined in different parts of the sample without cutting it into pieces. The test is non-destructive, i.e. the parts can still be used after the measurement and do not have to be scrapped. The measurement is controlled by a special PC based software. All results are available for further processing by in-house quality documentation and supervision of measurements. Tool setting for multi-level components can be much improved by using this test method. When a densitometer is installed on the press shop floor, it can be operated by the tool setter himself. Then he can return to the press and immediately implement the corrections. Transfer of sample parts to the lab for density testing can be eliminated and results for the correction of tool settings are more readily available. This helps to reduce the time required for tool setting and clearly improves the productivity of powder presses. The range of materials where this method can be successfully applied covers almost the entire periodic system of the elements. It reaches from the light elements such as graphite via light metals (AI, Mg, Li, Ti) and their alloys, ceramics ($AI_20_3$, SiC, Si_3N_4, $Zr0_2$, ...), magnetic materials (hard and soft ferrites, AlNiCo, Nd-Fe-B, ...), metals including iron and alloy steels, Cu, Ni and Co based alloys to refractory and heavy metals (W, Mo, ...) as well as hardmetals. The gamma radiation required for the measurement is generated by radioactive sources which are produced by nuclear technology. These nuclear materials are safely encapsulated in stainless steel capsules so that no radioactive material can escape from the protective shielding container. The gamma ray densitometer is subject to the strict regulations for the use of radioactive materials. The radiation shield is so effective that there is no elevation of the natural radiation level outside the instrument. Personal dosimetry by the operating personnel is not required. Even in case of malfunction, loss of power and incorrect operation, the escape of gamma radiation from the instrument is positively prevented.