• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.12
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• pp.1001-1007
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• 2001

In this study, high dielectric materials, (Pb,La)Ti $O_3$ thin films were fabricated by PLD (Pulsed Laser Deposition) method and investigated in terms of structural and electrical characteristics in order to develope the dielectric materials for the use of new capacitor layers of Giga bit-level DRAM. The deposition conditions were examined in order to fabricate uniform thin films through systematic changes of oxygen pressures and substrate temperature. The uniform thickness and smooth morphology of (P $b_{0.72}$L $a_{0.28}$)Ti $O_3$ thin films were obtained at the conditions of substrate-target distance 5.5[cm], laser energy density 2.1[J/$\textrm{cm}^2$], oxygen pressure 200[mTorr] and substrate temperature 500[$^{\circ}C$]. After the (P $b_{0.72}$L $a_{0.28}$)Ti $O_3$ thin films were fabricated under the above conditions, they were post-annealed by RTA process in order to increase the dielectric constant. The film thickness of 1200 [$\AA$] had dielectric constant 821. Assuming that operating voltage is 2V, leakage current density of (P $b_{0.72}$L $a_{0.28}$)Ti $O_3$ thin films would result into 10$^{-7}$ [A/$\textrm{cm}^2$] and satisfied the specification of 256M DRAM planar capacitor, 4$\times$10$^{-7}$ [A/$\textrm{cm}^2$]m}^2$]

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.238-239
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• 2010

Dimethyl sulphoxide (DMSO) is one of the widely-used secondary dopants in order to enhance the conductivity of poly(3, 4-ethylenedioxy-thiophene):poly(styrene sulfonate) (PEDOT:PSS) film. In this work, we investigated the effect of DMSO doping in to PEDOT:PSS on the electrical performance of the bulk heterojunction photovoltaics consisting of poly(3-hexylthiophene-2, 5-diyl) and phenyl-C61-butyric acid methyl ester. Correlation between the power conversion efficiency and the mechanism of improving conductivity, surface morphology, and contact properties was examined. The PEDOT:PSS films, which contain different concentration of DMSO, have been prepared and annealed at different annealing temperatures. The mixture of DMSO and PEDOT:PSS was prepared with a ratio of 1%, 5%, 15%, 25%, 35%, 45%, 55% by volume of DMSO, respectively. The DMSO-contained PEDOT:PSS solutions were stirred for 1hr at $40^{\circ}C$, then spin-coated on the ultra-sonicated glass. The spin-coated films were baked for 10min at $65^{\circ}C$, $85^{\circ}C$, and $120^{\circ}C$ in air. In order to investigate the electrical performance, P3HT:PCBM blended film was deposited with thickness of 150nm on DMSO-doped PEDOT:PSS layer. After depositing 100nm of Al, the device was post-annealed for 30min at $120^{\circ}C$ in vacuum. The fabricated cells, in this study, have been characterized by using several techniques such as UV-Visible spectrum, 4-point probe, J-V characteristics, and atomic force microscopy (AFM). The power conversion efficiency (AM 1.5G conditions) was increased from 0.91% to 2.35% by tuning DMSO doping ratio and annealing temperature. It is believed that the improved power conversion efficiency of the photovoltaics is attributed to the increased conductivity, leading to increasing short-circuit current in DMSO-doped PEDOT:PSS layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.381-382
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• 2007

IZO/Ag/IZO (IAI) anode films for flexible organic light emitting diodes (OLEDs) were grown on PC (polycarbonate) substrate using DC sputter (IZO) and thermal evaporator (Ag) systems as a function of Ag thickness. To investigate electrical and optical properties of IAI stacked films, 4-point probe and UV/Vis spectrometer were used, respectively. From a IAI stacked film with 12nm-thick Ag, sheet resistance of $6.9\;{\Omega}/{\square}$ and transmittance of above 82 % at a range of 500-550 nm wavelength were obtained. In addition, structural and surface properties of IAI stacked films were analyzed by XRD (X-ray diffraction) and SEM (scanning electron microscopy), respectively. Moreover, IAI stacked films showed dramatically improved mechanical properties when subjected to bending both as a function of number of cycles to a fixed radius. Finally, OLEDs fabricated on both flexible IAI stacked anode and conventional ITO/Glass were fabricated and, J-V-L characteristics of those OLEDs were compared by Keithley 2400.

• Solar Energy
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• v.20 no.2
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• pp.43-54
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• 2000

We prepared and characterized $Cu(In_{1-x}Ga_x)Se_2$(CIGS) films using a elemental co-evaporation method for absorbing layer of high efficiency thin film solar cells. The CIGS films deposited on a soda-lime glass exhibited low resistivity because of higher carrier concentration. Na was accumulated at the CIGS surface and the 0 and Se were also accumulated at the surface, suggesting that oxidation is a driving force of Na accumulation. The structure of CIGS film was modified or a secondary phase was formed in the Cu-poor CIGS bulk films probably due to the incorporation of Na into Cu vacancy sites. As the Ga/(In+Ga) ratio increased, the diffraction peaks of $Cu(In_{1-x}Ga_x)Se_2$ films were shifted to larger angle and splitted, and the grain size of $Cu_{0.91}(In_{1-x}Ga_x)Se_2$ films became smaller. All $Cu_{0.91}(In_{1-x}Ga_x)Se_2$ films showed the p-type conductivity regardless of the Ga/(In+Ga) ratio. Ag/n-ZnO/i-ZnO/CdS/$Cu_{0.91}(In_{0.7}Ga_{0.3})Se_2$/Mo solar cells were fabricated. The currently best efficiency in this study was 14.48% for $0.18cm^2$ area ($V_{oc}=581.5mV,\;J_{sc}=34.88mA$, F.F=0.714).

• Journal of the Korean Electrochemical Society
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• v.4 no.3
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• pp.113-117
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• 2001

Specific capacitance and charge-discharge rate of EDLC using activated carbon electrode were affected by the compositions of electrolytes, the conditions of charge-discharge and physical properties of activated carbon materials. The activated carbon electrode was prepared by dip coating method. Charge-discharge test and electrochemical experiments were carried out for various kinds of organic electrolytes. Effects of charge and discharge current density on the specific capacitance were studied. Characteristics of leakage current, self-discharge and time-voltage curves in optimum conditions of organic electrolytes were compared with conventional $1M-Et_4NBF_4/PC$ electrolyte. The EDLC using MSP-20(specific surface area: $2000m^2/g$) electrode and $1M-LiPF_6/PC-DEC(1:1)$ was exhibited th highest specific capacitance of 130F/g and low polarization resistances. The EDLC using MSP-20 electrode at $1M-LiPF_6/PC-DEC(1:1)$ was small leak current of 0.0004A for 15min, long voltage retention of 0.8V after 100h and linear time-voltage curves with small IR-drop.

• Corrosion Science and Technology
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• v.8 no.2
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• pp.62-67
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• 2009

Ti and Ti-alloys have good biocompatibility, appropriate mechanical properties and excellent corrosion resistance. However, the widely used Ti-6Al-4V is found to release toxic ions (Al and V) into the body, leading to undesirable long-term effects. Ti-6Al-4V has much higher elastic modulus (100 GPa) than cortical bone (20 GPa). Therefore, titanium alloys with low elastic modulus have been developed as biomaterials to minimize stress shielding. The electrochemical behavior of surface-modified and MC3T3-E1 cell-cultured Ti-30(Nb,Ta) alloys with low elastic modulus have been investigated using various electrochemical methods. Surfaces of test samples were treated as follows: $0.3{\mu}m$ polished; $25{\mu}m$, $50{\mu}m$ and $125{\mu}m$ sandblasted. Specimen surfaces were cultured with MC3T3-E1 cells for 2 days. Average surface roughness ($R_a$) and morphology of specimens were determined using a surface profilometer, OM, and FE-SEM. Corrosion behavior was investigated using a potentiostat(EG&G PARSTAT 2273), and electrochemical impedance spectroscopy was performed (10 mHz to 100 kHz) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The microstructures of the Ti-30(Ta,Nb) alloys had a needle-like appearance. The $R_a$ of polished Ti-30Ta and Ti-30Nb alloys was lower than that of the sandblasted Ti alloy. Cultured cells displayed round shapes. For polished alloy samples, cells were well-cultured on all surfaces compared to sandblasted alloy samples. In sandblasted and cell-cultured Ti-30(Nb,Ta) alloy, the pitting potential decreased and passive current density increased as $R_a$ increased. Anodic polarization curves of cell-cultured Ti alloys showed unstable behavior in the passive region compared to non-cell-cultured alloys. From impedance tests of sandblasted and cell-cultured alloys, the polarization resistance decreased as $R_a$ increased, whereas, $R_a$ for cell-cultured Ti alloys increased compared to non-cell-cultured Ti alloys.

• Journal of Korean Society of Steel Construction
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• v.20 no.6
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• pp.773-781
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• 2008

As buildings are becoming taller and longer-spanned, the requirements of high-strength and reliable steels are becoming increasingly stringent. Structural steels, however, acquire significantly different mechanical properties when their strength becomes higher. In this study, the mechanical properties, welding characteristics, and conformities of the 600MPa-grade high-strength steel were tested. The 600MPa-grade steel plates exhibited stable criterion strengthvalues and showed low carbon equivalents (${\mathcal{Ceq}}$) and composition (${\mathcal{Pcm}}$) as well as excellent welding hardness. In the tensile strength test, all the specimens were found to have strengths of over 600MPa. In the Sharphy impact test, the impact-absorbed energy of the V-notch specimens was shown to be 47J at the KS limit. Moreover, the maximum hardness of the specimens in the weld-heat-affected zone at a normal temperature was the same as that before welding. Their weld metal properties, however, were found not to be as good as those of high-strength steel. As such, the details of high-strength steel must be determined.

• Geomechanics and Engineering
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• v.17 no.4
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• pp.333-342
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• 2019

Geological dynamic hazards during coal mining can be caused by the failure of a composite system consisting of roof rock and coal layers, subject to different loading rates due to different advancing velocities in the working face. In this paper, the uniaxial compression test simulations on the composite rock-coal layers were performed using $PFC^{2D}$ software and especially the effects of loading rate on the stress-strain behavior, strength characteristics and crack nucleation, propagation and coalescence in a composite layer were analyzed. In addition, considering the composite layer, the mechanisms for the advanced bore decompression in coal to prevent the geological dynamic hazards at a rapid advancing velocity of working face were explored. The uniaxial compressive strength and peak strain are found to increase with the increase of loading rate. After post-peak point, the stress-strain curve shows a steep stepped drop at a low loading rate, while the stress-strain curve exhibits a slowly progressive decrease at a high loading rate. The cracking mainly occurs within coal, and no apparent cracking is observed for rock. While at a high loading rate, the rock near the bedding plane is damaged by rapid crack propagation in coal. The cracking pattern is not a single shear zone, but exhibits as two simultaneously propagating shear zones in a "X" shape. Following this, the coal breaks into many pieces and the fragment size and number increase with loading rate. Whereas a low loading rate promotes the development of tensile crack, the failure pattern shows a V-shaped hybrid shear and tensile failure. The shear failure becomes dominant with an increasing loading rate. Meanwhile, with the increase of loading rate, the width of the main shear failure zone increases. Moreover, the advanced bore decompression changes the physical property and energy accumulation conditions of the composite layer, which increases the strain energy dissipation, and the occurrence possibility of geological dynamic hazards is reduced at a rapid advancing velocity of working face.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.2
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• pp.209-216
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• 2019

Objective: We compare the effects of three different approved sources of supplemental zilpaterol on growth-performance responses and carcass characteristics of finishing lambs. Methods: Twenty four Pelibuey${\times}$Katahdin lambs ($46.75{\pm}2.43kg$) were used in a 33-day feeding trial. Lambs were fed a dry rolled corn-based finishing diet. Treatments consisted of the non-supplemental basal diet (Control) versus the basal diet supplemented with 125 mg zilpaterol/kg of diet (as fed basis) from three commercial sources marketed in Mexico: Zilmax (ZIL), Grofactor, and Zipamix. Results: Compared to controls, zilpaterol (ZH) supplementation did not affect dry matter intake (DMI), but increased carcass adjusted daily weight gain (ADG, 36.7%), gain efficiency (34.2%), and dietary net energy (26.0%), and decreased (23.4%) the ratio of observed:expected DMI. Compared to controls, supplemental ZH increased hot carcass weight (6.4%), dressing percentage (3.2%), m. longissimus thoracis (LM) area (15.6%), and shoulder muscle:fat ratio (28.7%), but decreased kidney-pelvic-heart fat, and fat thickness. Supplemental ZH increased 10.9% and 14.3% whole cut weight of loin and leg, respectively, and the proportion (as percentage of cold carcass weight) of leg (4.3%). These increases were reflected in greater forequarter and hindquarter weights. Lambs fed ZH increased (4.6%) empty body weight (EBW) and reduced (14.7%) liver/spleen weight (as g/kg EBW). Likewise, ZH supplementation tended (p = 0.08) to lower (8.9%) visceral fat. Growth performance, energetic efficiency, hot carcass weight, dressing percentage, LM area and whole cuts were not different across supplemental ZH sources. However, compared with non-supplemented controls, only ZIL appreciably decreased carcass fat distribution, including fat thickness, percentage kidney pelvic and heart fat, shoulder fat, and visceral fat. Conclusion: Supplemental ZH increases ADG, gain efficiency, carcass dressing percentage, and LM area. The magnitude of these responses was similar among ZH sources. Nevertheless, compared with non-supplemented controls, only ZIL appreciably decreases carcass fat. The basis for this is uncertain, but indicative that some practical differences in zilpaterol bio-equivalency may exist across commercial sources tested.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.6
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• pp.823-829
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• 2016

Eight Holstein steers ($216{\pm}48kg$ body weight) fitted with ruminal and duodenal cannulas were used to evaluate effects of wheat straw processing (ground vs pelleted) at two straw inclusion rates (7% and 14%; dry matter basis) in dry rolled or steam-flaked corn-based finishing diets on characteristics of digestion. The experimental design was a split plot consisting of two simultaneous $4{\times}4$ Latin squares. Increasing straw level reduced ruminal (p<0.01) and total tract (p = 0.03) organic matter (OM) digestion. As expected, increasing wheat straw level from 7% to 14% decreased (p<0.05) ruminal and total tract digestion of OM. Digestion of neutral detergent fiber (NDF) and starch, per se, were not affected (p>0.10) by wheat straw level. Likewise, straw level did not influence ruminal acetate and propionate molar proportions or estimated methane production (p>0.10). Pelleting straw did not affect ($p{\geq}0.48$) ruminal digestion of OM, NDF, and starch, or microbial efficiency. Ruminal feed N digestion was greater (7.4%; p = 0.02) for ground than for pelleted wheat straw diets. Although ruminal starch digestion was not affected by straw processing, post-ruminal (p<0.01), and total-tract starch (p = 0.05) digestion were greater for ground than for pelleted wheat straw diets, resulting in a tendency for increased post-ruminal (p = 0.06) and total tract (p = 0.07) OM digestion. Pelleting wheat straw decreased (p<0.01) ruminal pH, although ruminal volatile fatty acids (VFA) concentration and estimated methane were not affected ($p{\geq}0.27$). Ruminal digestion of OM and starch, and post-ruminal and total tract digestion of OM, starch and N were greater (p<0.01) for steam-flaked than for dry rolled corn-based diets. Ruminal NDF digestion was greater (p = 0.02) for dry rolled than for steam-flaked corn, although total tract NDF digestion was unaffected (p = 0.94). Ruminal microbial efficiency and ruminal degradation of feed N were not affected (p>0.14) by corn processing. However, microbial N flow to the small intestine and ruminal N efficiency (non-ammonia N flow to the small intestine/N intake) were greater (p<0.01) for steam-flaked than for dry rolled corn-based diets. Ruminal pH and total VFA concentration were not affected ($p{\geq}0.16$) by corn processing method. Compared with dry rolled corn, steam-flaked corn-based diets resulted in decreased acetate:propionate molar ratio (p = 0.02). It is concluded that at 7% or 14% straw inclusion rate, changes in physical characteristics of wheat straw brought about by pelleting negatively impact OM digestion of both steam-flaked and dry-rolled corn-based finishing diets. This effect is due to decreased post-ruminal starch digestion. Replacement of ground straw with pelleted straw also may decrease ruminal pH.