• Journal of the Korean Society of Radiology
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• v.13 no.3
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• pp.473-479
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• 2019

PET-CT improves performance and reduces the time by combining PET and CT of spatial resolution, and uses CT scan for attenuation correction. This study analyzed PET image evaluation. The condition of the tube voltage and current of CT will be changed using. Uniformity phantom and resolution phantom were injected with 37 MBq $^{18}F$ (fluorine ; 511 keV, half life - 109.7 min), respectively. PET-CT (Biograph, siemens, US) was used to perform emission scan (30 min) and penetration scan. And then the collected image data were reconstructed in OSEM-3D. The same ROI was set on the image data with a analyzer (Vinci 2.54, Germany) and profile was used to analyze and compare spatial resolution and image quality through FWHM and SI. Analyzing profile with pre-defined ROI in each phantom, PET image was not influenced by the change of tube voltage or exposure dose. However, CT image was influenced by tube voltage, but not by exposure dose. When tube voltage was fixed and exposure dose changed, exposure dose changed too, increasing dose value. When exposure dose was fixed at 150 mA and tube voltage was varied, the result was 10.56, 24.6 and 35.61 mGy in each variables (in resolution phantom). In this study, attenuation image showed no significant difference when exposure dose was changed. However, when exposure dose increased, the amount of dose that patient absorbed increased too, which indicates that CT exposure dose should be decreased to minimum to lower the exposure dose that patient absorbs. Therefore future study needs to discuss the conditions that could minimize exposure dose that gets absorbed by patient during PET-CT scan.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2497-2502
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• 2014

The 5 wt.% Ga-doped zinc oxide (GZO) thin films were fabricated on PES substrates with various RF power 50~80 W by using RF magnetron sputtering in order to investigate the optical and electrical properties of GZO thin films. The XRD measurement showed that GZO thin films exhibit c-axis orientation. At a RF power of 70W, the GZO thin film showed the highest (002) diffraction peak with a Full-Width-Half-Maximum (FWHM) of $0.44^{\circ}$. AFM analysis showed that the lowest surface roughness (0.20 nm) was obtained for the GZO thin film fabricated at 70 W of RF power. The electrical property indicated that the minimum resistivity ($6.93{\times}10^{-4}{\Omega}{\cdot}cm$) and maximum carrier concentration ($7.04{\times}10^{20}cm^{-3}$) and hall mobility ($12.70cm^2/Vs$) were obtained in the GZO thin film fabricated at 70W of RF power. The optical transmittance in the visible region was higher than 80 %, regardless of RF power. The optical band-gap showed the slight blue-shift with increased in carrier concentration which can be explained by the Burstein-Moss effect.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.2
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• pp.122-127
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• 2010

Purpose: The Xpress3.$cardiac^{TM}$ which is a kind of wide beam reconstruction (WBR) method developed by UltraSPECT (Haifa, Israel) enables the acquisition of at quarter time while maintaining image quality. The purpose of this study is to investigate the usefulness of WBR method for decreasing scan times and to compare to it with filtered back projection (FBP), which is the method routinely used. Materials and Methods: Phantom and clinical studies were performed. The anthropomorphic torso phantom was made on an equality with counts from patient's body. The Tl-201 concentrations in the compartments were 74 kBq (2 ${\mu}Ci$)/cc in myocardium, 11.1 kBq (0.3 ${\mu}Ci$)/cc in soft tissue, and 2.59 kBq (0.07 ${\mu}Ci$)/cc in lung. The non-gated Tl-201 myocardial perfusion SPECT data were acquired with the phantom. The former study was scanned for 50 seconds per frame with FBP method, and the latter study was acquired for 13 seconds per frame with WBR method. Using the Xeleris ver. 2.0551, full width at half maximum (FWHM) and average image contrast were compared. In clinical studies, we analyzed the 30 patients who were examined by Tl-201 gated myocardial perfusion SPECT in department of nuclear medicine at Asan Medical Center from January to April 2010. The patients were imaged at full time (50 second per frame) with FBP algorithm and again quarter-time (13 second per frame) with the WBR algorithm. Using the 4D MSPECT (4DM), Quantitative Perfusion SPECT (QPS), and Quantitative Gated SPECT (QGS) software, the summed stress score (SSS), summed rest score (SRS), summed difference score, end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) were analyzed for their correlations and statistical comparison by paired t-test. Results: As a result of the phantom study, the WBR method improved FWHM more than about 30% compared with FBP method (WBR data 5.47 mm, FBP data 7.07 mm). And the WBR method's average image contrast was also higher than FBP method's. However, in result of quantitative indices, SSS, SDS, SRS, EDV, ESV, EF, there were statistically significant differences from WBR and FBP(p<0.01). In the correlation of SSS, SDS, SRS, there were significant differences for WBR and FBP (0.18, 0.34, 0.08). But EDV, ESV, EF showed good correlation with WBR and FBP (0.88, 0.89, 0.71). Conclusion: From phantom study results, we confirmed that the WBR method reduces an acquisition time while improving an image quality compared with FBP method. However, we should consider significant differences in quantitative indices. And it needs to take an evaluation test to apply clinical study to find a cause of differences out between phantom and clinical results.

• 전자공학회논문지 IE
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• v.43 no.4
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• pp.1-7
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• 2006

In this paper, two types of blue organic light-emitting device were designed. We have analyzed the characteristics of Type I device without a hole blocking layer, and analyzed the characteristics of Type II device using a hole blocking layer of BCP or BAlq materials with 30 ${\AA}$ thickness. We obtained the ITO having the work function value of 5.02 eV using $N_2$ plasma treatment method with the plasma power 200 W. Type I device structure was ITO/2-TNATA/$\alpha$-NPD/DPVBi/$Alq_3$/LiF/Al:Li, and type II device structure was ITO/2-TNATA/$\alpha$-NPD/DPVBi/HBL/$Alq_3$/LiF/Al:Li. We have analyzed the characteristics of Type I and Type II device. The characteristics of the device were most efficiency on occasion of using a hole blocking layer of BAlq material with 30 ${\AA}$ thickness. Current density was 226.75 $mA/cm^2$, luminance was 10310 $cd/m^2$, Current efficiency was 4.55 cd/A, power efficiency was 1.43 lm/W at an applied voltage of 10V. The maximum EL wavelength of the fabricated blue organic light-emitting device was 456nm. The full-width at half-maximum (FWHM) for the EL spectra was 57nm. CIE color coordinates were x=0.1438 and y=0.1580, which was similar to NTSC deep-blue color with CIE color coordinates of x=0.14 and y=0.08.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.33-35
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• 2008

We have fabricated and evaluated new high efficiency green light emitting phosphorescent devices with an emission layer of $[TCTA_{1/3}TAZ_{2/3}/TAZ]:Ir(ppy)_3$. The whole experimental devices have the basic structure of $2-TNATA(500 {\AA})/NPB(300{\AA})/EML(300{\AA})/BCP(50{\AA})/SFC137(500{\AA})$ between anode and cathode. We have also fabricated conventional phosphorescent devices with emission layers of $(TCTA_{1/3}TAZ_{2/3}):Ir(ppy)_3$ and $(TCTA/TAZ):Ir(ppy)_3$ and compared their electroluminescence characteristics with those of the device with an emission layer of $(TCTA/TCTA_{1/3}TAZ_{2/3}/TAZ):Ir(ppy)_3$. The current density(J), luminance(L), and current efficiency($\eta$) of the device with an emission layer of $(80{\AA}-TCTA/90{\AA}-TCTA_{1/3}TAZ_{2/3}/130{\AA}-TAZ):10%-Ir(ppy)_3$ were 95 $mA/cm^2$, 25000 $cd/m^2$, and 27 cd/A at an applied voltage of 10V, respectively. The maximum current efficiency was 52 cd/A under the luminance of 400 $cd/m^2$. The peak wavelength and FWHM(full width at half maximum) in the electroluminescence spectral were 513nm and 65nm, respectively. The color coordinate was (0.30, 0.62) on the CIE (Commission Internationale de l'Eclairage) chart. Under the luminance of 15000 $cd/m^2$, the current efficiency of the device with an emission layer of $(80{\AA}-TCTA/90{\AA}-TCTA_{1/3}TAZ_{2/3}/130{\AA}-TAZ):10%-Ir(ppy)_3$ was 34 cd/A, which has been improved 1.7 times and 1.4 limes compared to those of the devices with emission layers of $(300{\AA}-TCTA_{1/3}TAZ_{2/3}): 10%-Ir(ppy)_3$ and $(100{\AA}-TCTA/200{\AA}-TAZ):10%-Ir(ppy)_3$, respectively.

• Korean Journal of Materials Research
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• v.18 no.7
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• pp.347-351
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• 2008

We have fabricated and evaluated newNew high high-efficiency green green-light light-emitting phosphorescent devices with an emission layer of [$TCTA/TCTA_{1/3}TAZ_{2/3}/TAZ$] : $Ir(ppy)_3$ were fabricated and evaluated, and compared the electroluminescence characteristics of these devices were compared with the conventional phosphorescent devices with emission layers of ($TCTA_{1/3}TAZ_{2/3}$) : $Ir(ppy)_3$ and (TCTA/TAZ) : $Ir(ppy)_3$. The current density, luminance, and current efficiency of the a device with an emission layer of ($80{\AA}-TCTA/90^{\circ}{\AA}-TCTA_{1/3}TAZ_{2/3}/130{\AA}-TAZ$) : 10%-$Ir(ppy)_3$ were $95\;mA/cm^2$, $25000\;cd/m^2$, and 27 cd/A at an applied voltage of 10 V, respectively. The maximum current efficiency was 52 cd/A under the a luminance value of $400\;cd/m^2$. The peak wavelength and FWHM (FWHM (full width at half maximum) in the electroluminescence spectral were 513 nm and 65 nm, respectively. The color coordinate was (0.30, 0.62) on the CIE (Commission Internationale de I'Eclairage) chart. Under the a luminance of $15000\;cd/m^2$, the current efficiency of the a device with an emission layer of ($80{\AA}-TCTA/90{\AA}-TCTA_{1/3}TAZ_{2/3}/130{\AA}-TAZ$) : 10%-$Ir(ppy)_3$ was 34 cd/A, which has beenshowed an improvement of improved 1.7 and 1.4 times compared to those of the devices with emission layers of ($300{\AA}-TCTA_{1/3}TAZ_{2/3}$) : 10%-$Ir(ppy)_3$ and ($100{\AA}-TCTA/200{\AA}$-TAZ) : 10%-$Ir(ppy)_3$, respectively.

• Journal of the Korean Vacuum Society
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• v.19 no.4
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• pp.281-286
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• 2010

Thickness effects on the structural and optical properties of ZnO thin films fabricated by spin coating method have been carried out. With increase in the thickness of the ZnO thin films, the width and density of striation shape are increased. The ZnO thin film with thickness of 450 nm has a smooth surface morphology. For the ZnO thin film with a smooth surface, orientation factor ${\alpha}_{(002)}$ is sharply increased and FWHM of (002) diffraction peak is decreased compared to the ZnO thin films with a striation shape surface. Thickness and surface morphology of the ZnO thin films hardly affect the NBE peak position. However, the DLE peak position is blue-shifted as the surface morphology is changed from striation to smooth surface. The PL intensity ratio of the NBE to DLE is increased and the FWHM of NBE peak is decreased as the thickness of the ZnO thin films is increased.

• Progress in Superconductivity and Cryogenics
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• v.21 no.1
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• pp.18-24
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• 2019

This study was carried out to investigate the effect of milling of boron (B), which is one of raw materials of $MgB_2$, on the critical current density ($J_c$) of $MgB_2$. B powder used in this study is semi-amorphous B (Pavezyum, Turkey, 97% purity, 1 micron). The size of B powder was reduced by planetary milling using $ZrO_2$ balls (a diameter of 2 mm). The B powder and balls with a ratio of 1:20 were charged in a ceramic jar and then the jar was filled with toluene. The milling time was varied from 0 to 8 h. The milled B powders were mixed with Mg powder in the composition of (Mg+2B), and the powder mixtures were uniaxially pressed at 3 tons. The powder compacts were heat-treated at $700^{\circ}C$ for 1 h in flowing argon gas. Powder X-ray diffraction and FWHM (Full width at half maximum) were used to analyze the phase formation and crystallinity of $MgB_2$. The superconducting transition temperature ($T_c$) and $J_c$ of $MgB_2$ were measured using a magnetic property measurement system (MPMS). It was found that $B_2O_3$ was formed by B milling and the subsequent drying process, and the volume fraction of $B_2O_3$ increased as milling time increased. The $T_c$ of $MgB_2$ decreased with increasing milling time, which was explained in terms of the decreased volume fraction of $MgB_2$, the line broadening of $MgB_2$ peaks and the formation of $B_2O_3$. The $J_c$ at 5 K increased with increasing milling time. The $J_c$ increase is more remarkable at the magnetic field higher than 3 T. The $J_c$ at 5 K and 4 T was the highest as $4.37{\times}10^4A/cm^2$ when milling time was 2 h. The $J_c$ at 20 K also increased with increasing milling time. However, The $J_c$ of the samples with the prolonged milling for 6 and 8 h were lower than that of the non-milled sample.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.262-266
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• 2010

ZnO nanostructures were grown on an Au seed layer by a hydrothermal method. The Au seed layer was deposited by ion sputter on a Si (100) substrate, and then the ZnO nanostructures were grown with different precursor concentrations ranging from 0.01 M to 0.3M at $150^{\circ}C$ and different growth temperatures ranging from $100^{\circ}C$ to $250^{\circ}C$ with 0.3 M of precursor concentration. FE-SEM (field-emission scanning electron microscopy), XRD (X-ray diffraction), and PL (photoluminescence) were carried out to investigate the structural and optical properties of the ZnO nanostructures. The different morphologies are shown with different growth conditions by FE-SEM images. The density of the ZnO nanostructures changed significantly as the growth conditions changed. The density increased as the precursor concentration increased. The ZnO nanostructures are barely grown at $100^{\circ}C$ and the ZnO nanostructure grown at $150^{\circ}C$ has the highest density. The XRD pattern shows the ZnO (100), ZnO (002), ZnO (101) peaks, which indicated the ZnO structure has a wurtzite structure. The higher intensity and lower FWHM (full width at half maximum) of the ZnO peaks were observed at a growth temperature of $150^{\circ}C$, which indicated higher crystal quality. A near band edge emission (NBE) and a deep level emission (DLE) were observed at the PL spectra and the intensity of the DLE increased as the density of the ZnO nanostructures increased.

• Journal of the Korean Vacuum Society
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• v.22 no.6
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• pp.327-334
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• 2013

Long-wave infrared detectors using the type-II InAs/GaSb strained superlattice (T2SL) material system with the nBn structure were designed and fabricated. The band gap energy of the T2SL material was calculated as a function of the thickness of the InAs and GaSb layers by the Kronig-Penney model. Growth of the barrier material ($Al_{0.2}Ga_{0.8}Sb$) incorporated Te doping to reduce the dark current. The full width at half maximum (FWHM) of the $1^{st}$ satellite superlattice peak from the X-ray diffraction was around 45 arcsec. The cutoff wavelength of the fabricated device was ${\sim}10.2{\mu}m$ (0.12 eV) at 80 K while under an applied bias of -1.4 V. The measured activation energy of the device was ~0.128 eV. The dark current density was shown to be $1.0{\times}10^{-2}A/cm^2$ at 80 K and with a bias -1.5 V. The responsivity was 0.58 A/W at $7.5{\mu}m$ at 80 K and with a bias of -1.5 V.