• Clean Technology
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• v.23 no.4
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• pp.378-387
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• 2017

To obtain epoxy resin with permanently attached flame-retardant groups, phosphorus compound containing di-hydroxyl group [10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phospha phenanthrene-10-oxide, DOPO-HQ] and silicone compound containing di-hydroxyl group (polydimethylsiloxane, hydroxyl terminated, PDMS) were reacted with uncured epoxy prepolymer (diglycidyl ether of bisphenol A, DGEBA) and then cured using 4,4-diaminodiphenylmethane (DDM) as a crosslinking agent. The properties of the resulting epoxy materials were characterized using Fourier transform infrared (FTIR) spectrometer, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limiting oxygen index (LOI) test/vertical burning test (UL 94-V test), tensile properties test and impact test. This study examined the effect of phosphorus/silicone compound contents on the thermal/mechanical properties and flame retardancy of cured epoxy resins containing phosphorus and silicone compounds. It was found that the thermal/mechanical properties of epoxy resins containing phosphorus and silicone components were higher than those of simple epoxy resin. The flame-retardancy (LOI: 29.9 ~ 31.8% and UL 94-V: V-0) of all samples containing phosphorus compound and phosphrous compound/silicone compound was found to be passed the flame-retardant requirements (LOI: > 30%, UL 94-V: V-0) of LOI and vertical burning tests. However, the flame-retardancy (LOI: 21.4% and UL 94-V: no rating) of simple epoxy resin was found to be failed the flame-retardant requirements.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.669-676
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• 2020

The purpose of this study was to analyze the changes in the values of Hounsfield Unit (HU) according to the changes in monoenergy (keV) and dilution ratio of the contrast agent, using the spectral CT. Spectral CT was used as the testing device, while 20 cc syringe phantom was used to set a total of six dilution ratios of the contrast agent: 8:2, 7:3, 6:4, 5:5, 4:6, and 3:7. Here, the non-ionic iodine solution (350 mg/ml) was used as a contrast agent. The syringe axial image was reconstructed by adjusting the obtained data on nine MonoE levels; 40 keV, 45 keV, 50 keV, 55 keV, 60 keV, 65 keV, 70 keV, 75 keV, and 80 keV. The HU values were measured at the three points of the reconstructed syringe axial image. The measurements were taken 1,620 times in total. In the analysis of the HU values according to the changes in keV and dilution ratio of the contrast agent, the highest and lowest HU values were obtained from dilution ratio 8:2 and dilution ratio 3:7, respectively, across every MonoE in the comparison of HU according to dilution ratio per MonoE (p<0.05), while the highest and lowest HU values were obtained from 40 keV and 80 keV, respectively, across all dilution ratios in the comparison of HU according to MonoE per dilution ratio (p<0.05). For the correlation per each parameter, a negative correlation of -15.014 ± 0.298 was found for HU per keV (R²=0.519) and a negative correlation of -61.372 ± 3.608 was found for HU per dilution ratio (R²=0.152) (p<0.05). To conclude, an increase in keV or dilution ratio of the contrast agent was shown to decrease the HU, and the findings in this study are anticipated to serve as the basic data in the research of HU-related parameters in Spectral CT.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.53-58
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• 2001

This paper presents a high resolution capacitive microaccelerometer for applications to personal information systems. We reduce the mechanical noise level of the microaccelerometer by increasing the proof-mass based on deep RIE process. We reduce the electrical noise level by increasing the amplitude of an AC sense voltage. The high sense voltage is obtained by DC-to-DC voltage multiplier. In order to solve the nonlinearity problem caused by the high sense voltage, we modify the conventional comb electrode of straight finger type into that of branched finger type, resulting in self force-balancing effects for enhanced detection linearity. The proposed branched finger capacitive microaccelerometer was fabricated by the deep RIE process of an SOI wafer. The fabricated microaccelerometer reduces the electrical noise at the level of $2.4{\mu}g/\sqrt{Hz}$ for the sense voltage of l6.5V, which is 10.1 times smaller than the electrical noise level of $24.3{\mu}g/\sqrt{Hz}$ at 0.9V. For the sense voltage higher than 2V, the electrical noise level of the microaccelerometer became smaller than the constant mechanical noise level of $11{\mu}g/\sqrt{Hz}$. Total noise level, including the electrical noise and the mechanical noise, has been measured as $9{\mu}g/\sqrt{Hz}$ for the sense voltage of 16.5V, which is 3.2 times smaller than the total noise of $28.6{\mu}g/\sqrt{Hz}$ for the sense voltage of 0.9V. The self force-balancing effect results in the increased stiffness of 1.98 N/m at the sense voltage of 17.8V, compared to the stiffness of 1.35 N/m at 0V, thereby generating the additional stiffness at the rate of $0.002N/m/V^{2}$.

• Journal of Chest Surgery
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• v.16 no.1
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• pp.115-120
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• 1983

We implanted pacemakers using screw-in sutureless myocardial electrode in 40 patients between February, 1980 and November, 1982 at Seoul Nation University Hospital. Mean age of total patient who received the pacemaker implantation was 39.9 years, but excluding the patient who received the open heart surgery, mean age was 49.3 years. Cause of pacemaker implantation was complete A-V block in 13 patients, symptomatic sick sinus syndrome in 12 patients, complete A-V block after open heart surgery in 12 patients, second degree A-V block with dizziness in one patient, and atrial fibrillation with slow ventricular response in two patients. In thirty nine cases, electrodes were implanted by subxiphoid approach, on the diaphragmatic surface of right ventricle. I n one case, electrode was implanted through the left anterior thoracotomy. Acute stimulation threshold, measured in 35 patients, varied from 0.1 to 2.5 mA [mean 0.85 mA.], and R-wave amplitude [sensitivity], measured in 19 patients, varied from 2.9 mV to 11.5 mV [mean 7.6 mV]. There was no hospital death. The postoperative complications included wound seroma in two patients [5%], wound hematoma in three patients [7.5%], and pacing failure in one patient [2.5%]. The subxiphoid implantation of the pacemaker using sutureless myocardial lead was valuable in obtaining safe, reliable and long-term impulse generation.

• Progress in Medical Physics
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• v.13 no.2
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• pp.69-73
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• 2002

Exposure measurement data with parallel plate ionization chambers were known to depend on the polarity ($k_{pol}$) effect. In this work, the polarity effect were investigated for three parallel plate ionization chambers with different volume. The ionization chamber was fabricated using acrylic plate for the chamber medium and printed circuit board for electrical configuration. The various sizes of the sensitive volumes designed so far were 0.9, 1.9, and 3.1 co. High voltage generator was fabricated using the conventional 9 V batteries to apply the high voltage (300-500 V) to the electrode of the parallel plate ionization chamber. The gap between two electrodes ranged from 3, 6, and 10mm. As the result of our experiment, the polarity effect was within 0.5% in photon beam and 1% to 3.5% in the electron beams. Among electron beams, 16 MeV beam, which had highest energy, showed less polarity effect than electron beams with other energies.

• Reproductive and Developmental Biology
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• v.35 no.1
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• pp.17-22
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• 2011

This study was designed to determine the effect of electric field strength, duration and fusion buffer in fusion parameters on the rate of membrane fusion between the somatic cell and cytoplast for Korean cattle (HanWoo) somatic cell nuclear transfer (SCNT) procedure. Following electrofusion, effect of 5 or $10\;{\mu}M$ $Ca^{2+}$-ionophore of activation treatment on subsequent development was also evaluated. Cell fusion rates were significantly increased from 23.1% at 20 V/mm to 59.7% at 26 V/mm and 52.9% at 27 V/mm (p<0.05). Due to higher cytoplasmic membrane rupture or cellular lysis, overall efficiency was decreased when the strength was increased to 30 V/mm (18.5%) and 40 V/mm (6.3%) and the fusion rate was also decreased when the strength was at 25 V/mm or below. The optimal duration of electric stimulation was significantly higher in $25\;{\mu}s$ than 20 and $30\;{\mu}s$ (18.5% versus 9.3% and 6.3%, respectively, p<0.05). Two nonelectrolyte fusion buffers, Zimmermann's (0.28 M sucrose) and 0.28 M mannitol solution for cell fusion, were used for donor cell and ooplast fusion and the fusion rate was significantly higher in Zimmermann's cell fusion buffer than in 0.28 M mannitol (91.1% versus 48.4%, respectively, p<0.05). The cleavage and blastocyst formation rates of SCNT bovine embryos activated by $5\;{\mu}M$ $Ca^{2+}$-ionophore was significantly higher than the rates of the embryos activated with $10\;{\mu}M$ of $Ca^{2+}$-ionophore (70.0% versus 42.9% and 22.5% versus 14.3%, respectively; p<0.05). This result is the reverse to that of parthenotes which shows significantly higher cleavage and blastocyst rates in $10\;{\mu}M$ $Ca^{2+}$-ionophore than $5\;{\mu}M$ counterpart (65.6% versus 40.3% and 19.5% versus 9.7%, respectively; p<0.05). In conclusion, SCNT couplet fusion by single pulse of 26 V/mm for $25\;{\mu}s$ in Zimmermann's fusion buffer followed by artificial activation with $5\;{\mu}M$ $Ca^{2+}$-ionophore are suggested as optimal fusion and activation methods in Korean cattle SCNT protocol.

• Journal of the Korean Society of Radiology
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• v.16 no.5
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• pp.513-518
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• 2022

Electron beam quality assurance (QA) should be done regularly for accurate radiation therapy. However, QA tools used in clinical practice are designed mainly for X-rays. So, a dosimeter for electron beam QA is required. Therefore, in this study, the electron beam detection performance was measured by using a thorium bromide material as an electron beam sensor. In addition, it was evaluated whether it could be applied with an electron beam QA dosimeter. Reproducibility, linearity, and dose rate dependence were evaluated at 6 MeV and 9 MeV energies. As a result of reproducibility, it showed a maximum output change of 0.92% at 6 MeV and 1.15% at 9 MeV. The linearity result evaluation and determination coefficient were presented as 0.9998. As a result of dose rate dependence evaluation, relative standard deviation 0.51% at 6 MeV and relative standard deviation 1.07% at 9 MeV were presented. The manufactured TlBr sensor shows the ability to detect radiation that meets the criteria for evaluation of reproducibility, linearity, and dose rate dependence. These results mean that the TlBr dosimeter is applicable as an electron beam QA dosimeter.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.1
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• pp.128-132
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• 1983

The water relations parameters such as original osmotic pressure $(\Pi_0)$, osmotic pressure $(\Pi_p)$, at the incipient plasmolysis, the volume of osmotic water $(V_o)$ at the full turgor, the relative water content $(RWC^*)$ at the incipient plasmolysis, the volume of osmotic water$(V_p)$ at the incipient plasmolysis, the volume of symplasmic and apoplastic water$(w_s)$ at the maximum turgor, $V_pV_o, \; V_oW_s, \; W_sD_w, \; V_oF_w$ and the elastic modulus were measured through the pressure chamber (DIK-PC-40 Model) technique with the Williams and Geumgangdaerip soybean cultivar shoots. The original osmotic pressure$(\P $i_{0}$ )$, of the both cultivars shoots were appeared insignificant differences as 8.1 bar and 7.8 bar respectively. The osmotic pressure($\pi$$_{p}$ ) at the incipient plasmolysis was 9.0 bar in Williams and 10.4 bar in Geumgangdaerip. The relative water content(RW $C^{*}$) at the incipient plasmolysis was 86.0 per cent in Geumgangdaerip and 92.6 per cent in Williams. The ratio of volume of osmotic water( $V_{p}$ ) at the incipient plasmolysis to total symplasmic water$(V_o)$ , i.e., $V_p/V_o$ was 83.4 per cent in Geumgangdaerip and 90.4 per cent in Williams. The elastic modulus of Geumgangdaerip shoots showed higher value than Williams$(8.5 $\times$ 10^2bar)$ as $1.6 \times10^5$ bar.r.

• Korean Journal of Materials Research
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• v.10 no.12
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• pp.807-811
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• 2000

CeO$_2$ and SrBi$_2$Ta$_2$O$_{9}$ (SBT) thin films for MFISFET (Metal-ferroelectric-insulator-semiconductor-field effect transistor) were deposited by r.f. sputtering and pulsed laser ablation method, respectively. The effects of sputtering gas ratio(Ar:O$_2$) during deposition for CeO$_2$ films were investigated. The CeO$_2$ thin films deposited on Si(100) substrate at $600^{\circ}C$ exhibited (200) preferred orientation. The preferred orientation, Brain size and surface roughness of films decreased with increasing oxygen to argon gas ratio. The films deposited under the condition of Ar:O$_2$= 1 : 1 showed the best C- V characteristics. The leakage current of films showed the order of 10$^{-7}$ ~10$^{-8}$ A at 100kV/cm. The SBT thin films on CeO$_2$/Si substrate showed dense microstructure of polycrystalline phase. From the C-V characteristics of MFIS structure with SBT film annealed at 80$0^{\circ}C$, the memory window width was 0.9V at 5V The leakage current density of Pt/SBT/CeO$_2$/Si structure annealed at 80$0^{\circ}C$ was 4$\times$10$^{-7}$ /$\textrm{cm}^2$ at 5V.

• Geophysics and Geophysical Exploration
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• v.17 no.1
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• pp.11-20
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• 2014

To reveal shear-wave velocities ($v_s$) and site characterization of Wonju, Korea, Rayleigh waves were recorded at 78 sites of lower altitude using 12 to 24 4.5-Hz vertical geophones for 20 days during the period of February to September 2013. Dispersion curves of the Rayleigh waves obtained by the extended spatial autocorrelation method were inverted using the damped least-squares method to derive $v_s$ models. From these 1-D models, the average $v_s$ to a depth of 30 m ($v_s30$), $v_s$ of weathered rocks, depths to these basement rocks, and average $v_s$ of the overburden layer were derived to be $16.3{\pm}0.7m$, $576{\pm}8m/s$, $290{\pm}7m/s$, and $418{\pm}13m/s$, respectively, in the 95% confidence range. To determine adequate proxies for $v_s30$, we computed correlation coefficients of $v_s30$ with topographic slope (r = 0.46) and elevation (r = 0.43). An empirical linear relationship is presented as a combination of individually estimated $v_s30$ with weighting factors of 0.45, 0.45, and 0.1 for topographic slope, elevation, and mapped lithology, respectively. Due to a weak correlation between $v_s30$ obtained from inversion of dispersion curves and the proxy-based estimation (r = 0.50), however, the relatively large error range should be considered for applications of this relationship.