• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.200-200
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• 2012

We investigated a flexible transparent film using the spinning multi-walled carbon nanotubes (MWCNTs). Spin-capable MWCNTs on iron catalyzed on a SiO2 wafer was grown by chemical vapor deposition, which was performed at $780^{\circ}C$ using C2H2 and H2 gas. The average diameter and length of MWCNTs grown on the substrate were ~15 nm and $250{\sim}300{\mu}m$, respectively. The MWCNT sheets were produced by continuously pulling out from well-aligned MWCNTs on a substrate. The MWCNT sheet films were produced simply by direct coating on the flexible film or grass. The thickness of sheet film was remarkably decreased by alcohol spraying on the surface of sheet. The alcohol splay increased transmittance and decreased electrical resistance of MWCNT sheet films. Single and double sheets were produced with sheet resistance of ~699 and ${\sim}349{\Omega}/sq$, respectively, transmittance of 81~85 % and 67~72%, respectively. The MWCNT sheet films were heated through the application of direct current power. The flexible transparent heaters showed a rapid thermal response and uniform distribution of temperature. In addition, MWCNT yarns were prepared by spinning a bundle of MWCNTs from vertically super-aligned MWCNTs on a substrate, and field emission from the tip and side of the yarns was induced in a scanning electron microscope. We found that the field emission behavior from the tip of the yarn was better than the field emission from the side. The field emission turn-on voltages from the tip and side of MWCNT yarns were 1.6 and $1.7V/{\mu}m$, respectively, after the yarn was subjected to an aging process. Both the configuration of the tip end and the body of the yarn were changed remarkably during the field emission. We also performed the field emission of the sheet films. The sheet films showed the turn on voltage of ${\sim}1.45V/{\mu}m$ during the field emission.

• Korean Journal of Materials Research
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• v.34 no.1
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• pp.55-62
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• 2024

Fluorine-doped tin oxide (FTO) has been used as a representative transparent conductive oxide (TCO) in various optoelectronic applications, including light emitting diodes, solar cells, photo-detectors, and electrochromic devices. The FTO plays an important role in providing electron transfer between active layers and external circuits while maintaining high transmittance in the devices. Herein, we report the effects of substrate rotation speed on the electrical and optical properties of FTO films during ultrasonic spray pyrolysis deposition (USPD). The substrate rotation speeds were adjusted to 2, 6, 10, and 14 rpm. As the substrate rotation speed increased from 2 to 14 rpm, the FTO films exhibited different film morphologies, including crystallite size, surface roughness, crystal texture, and film thickness. This FTO film engineering can be attributed to the variable nucleation and growth behaviors of FTO crystallites according to substrate rotation speeds during USPD. Among the FTO films with different substrate rotation speeds, the FTO film fabricated at 6 rpm showed the best optimized TCO characteristics when considering both electrical (sheet resistance of 13.73 Ω/□) and optical (average transmittance of 86.76 % at 400~700 nm) properties with a figure of merit (0.018 Ω^-1).

• Journal of Periodontal and Implant Science
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• v.25 no.1
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• pp.67-75
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• 1995

The progress of periodontal disease and the wound healing process after treatment result in alveolar bone bone change. So, detection of it is very important in the diagnosis and the radiograph of periodontal disease. Various effects have been made to assess the subtle alveolar bone change and digital subtraction radiography (DSR) has been reported to be the best method in evaluating it qualitatively and quantitatively. The present study was performed to estimate the detectable alveolar bone change qualitatively with digital subtraction radiography. For the in vitro study, 10 intraoral standard radiographs were taken from porcine dry mandible which a rectangular cortical bone chip of 0.1mm to 1.0mm thickness with 0.1mm increment was attached on the buccal surface. The radiographs without and with bone plates were reviewed at the same time by 10 observers and requested to detect the presence of cortical bone plates. Digital Subtraction radiograph was reviewed subsequently by using the DSR system(digital converter-256 grey-levels,DT 2851,Data Translation Co., U.S.A;IBM 386 ; CCD camera, FOTOVIX, Tamrom Co., Japan). The detectable thickness of cortical bone plate was O.4mm on the intraoral radiograph and 0.2mm on the subtaction images. For the human study, radiographs were taken from patients by using intraoral film holding device and aluminum reference wedge before and 3 month after bone graft and 1 week after osteoplasty. The grey level change was estimated in the subtraction images and calculated to aluminum equivalent thickness. The grey level of the grafted site was higher that that of healthy controls. Average grey levels of change on healthy controls were O.48mm aluminum equivalent. However, the amount of changes in grafted sites were 1.87mm aluminum thickness equivalent and in the site of osteoplasty were -1.49mm aluminum thickness equivalent. In conclusion, digital subtraction radiography was more effective in detecting as subtle change of alveolar bone than intraoral standard radiography. With the aid of quantitative analysis of digital subtraction radiography, alveolar bone resorption of apposition can be estimated during diagnosis and treatment of periodontally diseased patients.

• Journal of Soil and Groundwater Environment
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• v.29 no.4
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• pp.12-20
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• 2024

Diffusive gradients in thin films (DGT) are passive sampling devices used to determine the time-weighted average concentrations (TWAC) of contaminants. To ensure accurate performance in groundwater, it is crucial to identify environmental characteristics and maintain optimal operational conditions. This study examined the deployment time required to reach effective capacity, the thickness of the diffusive boundary layer (DBL) under stagnant water conditions, and biofilm formation on the DGT surface using groundwater samples. When using DGT with Chelex gel (A=3.14 cm²), the effective capacity was 0.7 ㎍ for Cd and 250 ㎍ for Zn, with a deployment time of 24 h. Lower Cd accumulation was due to the competition effect of coexisting ions. The DBL thickness under stagnant conditions was 0.074 cm, 93% of the diffusion gel's thickness (0.08 cm). Neglecting DBL thickness in TWAC calculations led to a 79% decrease in the determined concentration. No biofouling was observed during the 28-d DGT deployment in groundwater. In conclusion, it is essential to consider the appropriate deployment time, DBL thickness, and biofilm formation to ensure accurate DGT performance in determining contaminant levels in groundwater.

• Journal of the Korean Society of Radiology
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• v.10 no.7
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• pp.477-482
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• 2016

This study is tried to determine whether the management of medical radiation is well handled by comparison the guidelines of KFDA(korea food & drug administration) with analysis of dose indicator in mammography. As a method, it is analysed that kVp, exposure time, mAs, compressed breast thickness, average glandular dose and body mass index that were classified in the examination of both breasts by CC(cranio-caudal) and MLO(medio-lateral oblique) with EMR(electronic medical record) and dose report that were sent to the PACS(picture archiving communication system). As a result, in the site inspection according to the age, Compressed breast thickness in CC and MLO were the thickest of 45.6 mm and 49.6 mm in the 50-59 year old respectively. In the overall average compressed breast thickness, CC were 44.2 mm and MLO were 48.9 mm. MLO has more thick by 4.7 mm. In average glandular dose, CC were 1.05 mGy and MLO were 1.14 mGy. MLO has higher by 0.09 mGy than CC. As the compressed breast thickness increases 10mm, CC and MLO increases 0.15 mGy and 0.17 mGy respectively. When it was compared with the average glandular dose of 1.16 mGy per 1 film presented by KFDA, CC was showed 1.05 mGy. However, the 60 mm or more was found to exceed a 1.30 mGy. Also, As the compressed breast thickness was higher, body mass index showed high score. And in the case of 25 or more in the obese body index according to body mass index, it was showed obesity in case of the compressed breast thickness was more than 50mm.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.2
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• pp.307-316
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• 1991

The purpose of this study is to improve the availabilities of radiographic technics as diagnostic method related to mandibular canal in dental clinic. For this study 12 dry mandibles were used and 12 orthopantomograms were taken for measuring the gonial angle and the angle of mandibular canal to inferior border of mandible. 12 sites located between the 1st premolar to the 3rd molar region of 3dry mandibles were selected randomly, for measuring the vertical image magnification rates on three films; intraoral film, orthopantomogram, and computed tomogram, respectively and the thickness of cortical bone, and for observing bucco-lingually and supero-inferiorly location of the mandibular canal. The acquired results were as follows: 1. The means of the gonial angle and the angle of mandibular canal to inferior border of mandible were 123.9° and 143.5° And the two angles of dry mandible in alveolar crest stage were greater than in alveolar socket stage. 2. The vertical image length on intraoral film by paralleling technic was magnified by 3.07% on the average, the length on orthopantomogram by 18.49%, and the length on computed tomogram by 0.27%. 3. Observation of the bucco-lingually positional relationship of the mandibular canal was impossible by occlusal projection with the cross section technic and intraoral standard projection with the Clack's rule, however, possible by computed tomogram. 4. The thickness of the cortical bone of mandible was thickest in inferior border, and thicker by 6.59% at buccal side than at lingual side.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.1
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• pp.68-73
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• 2002

High temperature during sprout emergence period of potato (Solanum tuberosum L.) is a major limitation to the yield of fall-grown potato in Korea. To explore the possibility of improving the yield of fall-grown potato through recycled paper mulching, the changes of soil environment and the growth and yield of potato cv. Daeji as affected by three mulching treatments of non-mulched control, recycled paper mulching (RPM), and black polyethylene film-mulching (BPFM) were examined over two fall seasons at Suwon, Korea. The mulching materials were a recycled mulch paper with 110 g/$m^2$ and a thickness of 0.1 mm, which was manufactured from old corrugated containers for this experiment and a commercial black polyethylene film with a thickness of 0.01mm. On an average throughout the growing period, the soil temperature with RPM at the 5-cm depth was lower by 0.4-1.1$^{\circ}C$ than that of the control. The maximum temperature during daytime in RPM was lowered by approximately 1 to 5$^{\circ}C$ according to the weather condition during emergence period, the difference being great on a fine day. The soil temperature with BPFM was much higher than the control. The effect of the mulching treatments diminished as the canopy became developed. The mulching treatments were more advantageous than the control in the conservation of soil water. Moreover, RPM and BPFM efficiently suppressed the occurrence of weeds until the potato harvest. RPM improved the emergence significantly due to lower soil temperature, whereas BPFM showed much poorer emergence than the control. Growth after emergence and yield were significantly higher in RPM than in the control and BPFM. It was concluded that the significantly improved yield in RPM compared to that in the control was mainly due to the improvement of the sprout emergence and tuber growth accompanied by lower soil temperature and better conservation of soil water.

• Journal of the Korean Electrochemical Society
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• v.6 no.4
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• pp.236-241
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• 2003

Magnetic CoW thin film alloys were electrodeposited from citrate baths to investigate the resulting microstructure and magnetic properties. Deposit tungsten (W) content in the films electrodeposited at $70^{\circ}C$ were independent of current density, while coercivity decreased from hard $(H_{c,//}\~150\;Oe\;and\;H_{c.{\bot}}\;\~240\;Oe)$ to soft magnetic properties $(H_{c,//}\~20\;Oe\;and\;H_{c.{\bot}}\;\~30\;Oe)$ with increasing current densities from $10\;to\;100mA{\cdot}cm^2$, with deposit W content $(\~40\%)$ relatively unaffected by the applied current density. X-ray diffraction analysis indicated that hcp $Co_3W$ phases [(200), (201) and (220) planes] in the CoW films electrodeposited at $70^{\circ}C\;and\;10mA{\cdot}cm^{-2}$ were dominant, whereas amorphous CoW phases with small amount of hcp $Co_3W$ [(002) planes] were dominant with deposition at $70^{\circ}C\;and\;100mA{\cdot}cm^{-2}$. At intermediate current densities $(25\;and\;50mA{\cdot}cm^{-2}),\;hop\;Co_3W$ phases [(200), (002), (201) and (220)] were observed. The average grain size was measured to be 30 nm from Sheller formula. It is suggested that the change of the deposit coercivities in the CoW thin films electrodeposited at $70^{\circ}C$ is attributed to the change of microstructures with varying the current density. Nanostructured $Co_3W/amorphous-CoW$ multilayers were fabricated by alternating current density between 10 and $100 mA{\cdot}cm^{-2}$, varying the individual layer thickness. The magnetic properties of $Co_3W/amorphous-CoW$ multilayers were strongly dependent on the thickness of the alternating hard and soft magnetic thin films. The nanostructured $Co_3W/amorphous-CoW$ multilayers exhibited a shift from low to high coercivities suggesting a strong coupling effect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.201-202
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• 2009

ZnO:Al transparent conductive films for solar cells were deposited on the glass substrates at room temperature by facing target sputtering (FTS) method. The sputtering targets were 100 mm diameter disks of 2w.t..%. AZO and Zn metal. ZnO:Al thin films were deposited as a function film thickness. A base pressure was $2{\times}10^{-6}$torr, and a working pressure was 1mTorr. The properties of thin films on the structural, electrical and optical properties of the deposited films were investigated using a four-point probe (Chang-min), an X-ray diffraction (Rigaku), a Hall Effect measurement (Ecopia), an UV/VIS spectrometer (HP) and a $\alpha$-step (Tencor). The lowest resistivity of film was $5.67{\times}10^{-4}[{\Omega}-cm]$ at 500nm. The average transmittance of over 80% was seen in the visible range.

• Journal of the Korean Electrochemical Society
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• v.15 no.3
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• pp.149-153
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• 2012

The $Cu_2O/TiO_2$ inverse opal heterojunction arrays were developed by electrochemical deposition of $Cu_2O$ nanoparticles on $TiO_2$ inverse opal arrays. The $Cu_2O$ nanoparticles completely filled the inner pores of $TiO_2$ inverse opal film (prepared by liquid phase deposition with an average thickness of 400 nm) and covered the entire area; exhibiting high crystalline properties of anatase and cubic phase from $TiO_2$ and $Cu_2O$, respectively. From asymmetric current-voltage profile, it was noticeable that a heterojunction was well formed for charge transport from $Cu_2O$ to $TiO_2$ film resulting from the enhanced charge separation yield. In addition, increased photocurrent of 0.19 $mA/cm^2$ (versus 0.08 $mA/cm^2$ under dark condition) was obtained at -0.35 V from the heterojunction structure in the 0.5M $Na_2SO_4$ solution.