• Journal of Korean Society for Atmospheric Environment
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• v.10 no.1
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• pp.24-31
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• 1994

Hourly variation of gaseous nitrous acid( HNO$_2$) concentration in Seoul air was monitored from Jan. 11 to SeP. 12, Nitrous acid concentration was determined by DS/IC over nine months of observation, HNO$_2$ range from 0.04 ppb to 5.5 ppb. Gor-tex tube as gaseous HNO$_2$generator in this study is thought to be more convenient and reproducible device than previous generator. As a result of NaOH instead of Na$_2$ CO$_3$/NaHCO$_3$ solution as the IC eluent, we could obtain more stable baseline. The concentration of the NaOH eluent was 15 mM . The limit of detection(3$\sigma$) of the liquid- Phase and gas phase nitrous acid of this method are 1.1ng/$m\ell$ , 0.04 n $\ell$ / $\ell$, respectively. The precisions evaluated by 10 replicate analysis of standard solution and standard gas generated are $\pm$1.59, $\pm$2. 89% RSD, respectively. Due to the lack of standard material for air, direct assessment of the accuracy was not possible. This study was applied to the analysis of Seoul ambient air and their results are reported herein.

• Journal of the Korean Applied Science and Technology
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• v.20 no.4
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• pp.316-323
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• 2003

Zinc complexes with bis[2-(o-hydroxyphenyl) naphtol [1,2] oxazolato ligands (ZnPBO-4) and its derivatives (ZnPBO-S) were synthesized, and luminescent properties of these materials were investigated. Both the fluorescent emission band and electroluminescent emission band were discussed based on their ligand structure differences. The emission band found that it strongly depends on the molecular structure of introduced ligand. It was tuned from 446 nm to 491 nm by changing the ligand structures. Spreading of the ${\pi}$-conjugation in 2-(o-hydroxyphenyl) group gives rise to a blue shift. The EL properties also showed good consistency with their differences of ligand structure. Bright-blue EL emission with a maximum luminance of 3,100 $cd/m^2$ at 12V, current density, 575 $mA/m^2$ was obtained from the organic light-emitting diodes (OLEDs) using ZnPBO-4 as emitting layer. It was also found that the newly synthesized materials were suitable to be used as emitting materials in organic EL device.

• Journal of the Semiconductor & Display Technology
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• v.6 no.1 s.18
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• pp.23-26
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• 2007

The effects of plasma treatment on the ITO/glass substrate before deposition of organic materials were investigated in the fabrication of green light emitting organic devices with $Alq_3-C545T$ fluorescent system. In our experiments, the optimum plasma treatment was obtained at the power and time of 150W and 2 minutes under the $Ar(50%)/O_2$ ambient of 1 mTorr. The green OLED with plasma treatment at 150W for 2 minutes showed the luminance and efficiency of $4700\;cd/m^2$ and 8 lm/W at 10V, respectively. On the contrary, the same structured device without plasma treatment showed much lower performance with the luminance of $2600\;cd/m^2$ and the efficiency of 3.6 lm/W at 10 V.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.418-420
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• 2009

The Authors have demonstrated high efficiency hybrid white organic light-emitting diodes (HWOLED) for reduced efficiency roll-off and color stability. It was shown that HWOLED fabricated in this study have the maximum luminance of 46 420 cd/$m^2$ at 8 V (turn-on voltage of 2.7 V), external quantum efficiency of 13.18%, power efficiency of 28.75 lm/W at 1 000 cd/$m^2$, and reduced efficiency roll-off of 2.7 times than control white device. The HWOLED also showed the stable color shift with $\Delta$Commission Internationale de I'Eclairage coordinates coordinates of ${\pm}$ (0.00, 0.00) from 100 to 10000 cd/$m^2$.

• Journal of Multimedia Information System
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• v.5 no.2
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• pp.91-98
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• 2018

We devised a bird-borne transceiver unit for S-band packet radio communications based on the CC2500 transceiver, a device manufactured by Texas Instruments (TI). Our assessments determined the optimal parameters needed to achieve successful bird-to-center communication over a distance of 18 km and bird-to-bird communication over a distance of 200 m. These parameters included optimal modulation methods, transmission rates, and antennas. We equipped the transceiver unit with a modified dipole antenna (collinear antenna), which we tested in a 10 m anechoic chamber. Our experimental assessments and circuit design review identified the following parameters: 2FSK modulation method; 14.28 kHz frequency shift; 101.56 kHz IF reception bandwidth; and Manchester encoding (+). Our assessments showed bird-to-bird communications could be achieved over a distance of 200 m assuming MSK, FEC (+), and 500 kbps. Following tests by an official body, we obtained 28 sets of a type approval license for 2.4 GHz. In cooperation with the Yamashina Institute for Ornithology, we attempted to tag and release six or more swans. This unit gives us the ability to obtain vital data on swans. We expect this data to provide significant benefits, including clues on improving screening for infected individuals.

• The Korean Journal of Nuclear Medicine Technology
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• v.17 no.2
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• pp.59-66
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• 2013

Purpose: Recently, there is an increase of the number of hospitals using auto dispenser to reduce occupational radiation exposure when drawing up of the $^{18}F-FDG$ dose (5.18 MBq/kg) in a syringe from the dramatic high activity of $^{18}F-FDG$ multidose vial. The aim of this study is to confirm that using auto dispenser actually reduces the radiation exposure for technologists. Also we analyzed the reproducibility of auto dispenser to find optimized dispensing method for the device. Materials and Methods: We conducted three experiments. Comparison of radiation exposure on chest and hands: The chest and hands exposure dose received by technologists during the injection were measured by electronic personal dosimeter (EPD) and ring TLD respectively. Reproducibility of dispensed volume: We draw up the normal saline into 5 and 2 mL syringe using auto dispenser by changing the volume from 1 to 15 mm for 5 times in the same setting of the volume. The weight of 5 normal saline dispensed from the device at same volume was measured using micro balance and calculated standard deviation and coefficient of variation. Reproducibility of dispensed radioactivity: We dispensed 362.6 $MBq{\pm}10%$ of $^{18}F-FDG$ in 5 and 2 mL syringes from the multidose vial of different specific activity. In the same setting of volume, we repeated dispensing for 4 times and compared standard deviation and coefficient of variation of radioactivity between 5 syringes. Results: There was significant difference in the average of chest exposure dose according to the dispensing methods (P<0.05). Also, when dispensing $^{18}F-FDG$ in manual method, exposure dose was 11.5 times higher in right hand and 4.8 times higher in left hand than in auto method. In the result of reproducibility of dispensed volume, standard deviation and coefficient of variation shows decline as the dispensing volume increases. As a result of reproducibility of dispensed radioactivity, standard deviation and coefficient of variation increases as the specific activity increases. Conclusion: We approved that the occupational radiation exposure dose of technologists were reduced when dispensing $^{18}F-FDG$ using auto dose dispenser. Secondly, using small syringes helps to increase reproducibility of auto dose dispense. And also, if you lower the specific activity of $^{18}F-FDG$ in multidose vial below 915-1,020 MBq/mL, you can use auto dispenser more effectively keeping the coefficient of variation lower than 10%.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.04a
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• pp.133-134
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• 2014

이동통신망 내에서 셀룰러 주파수를 공유하여 사용하는 D2D(Device-to-Device) 단말들이 밀집한 지역에서는 D2D 단말이 대부분의 자원을 점유하므로 셀룰러 단말이 통신을 할 수 없는 문제점이 있다. 본 논문에서는 이러한 환경에서 셀룰러 통신을 보장하기 위해 셀룰러 단말과 인접한 범위에 있는 일부 D2D 단말에 대한 모드 선택기법을 제안한다. 제안기법은 밀집된 D2D 단말들로 인해 가용자원이 없는 셀룰러 단말의 주변에 있는 D2D 단말을 셀룰러 모드로 전환한다. 이를 통해 셀룰러 단말은 D2D 단말이 밀집한 지역에서 셀룰러 통신에 사용할 자원을 확보하여 셀룰러 통신을 할 수 있다. 시뮬레이션을 통해 이동통신망에서 D2D 밀집지역에 있는 셀룰러 통신의 성능이 향상되었음을 확인하였다.

• Journal of radiological science and technology
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• v.28 no.2
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• pp.137-144
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• 2005

To find the personal radiation dose of radiological technologists, a survey was conducted to 623 radiological technologists who had been working at 44 general hospitals in Korea's 16 cities and provinces from 1998 to 2002. A total of 2,624 cases about personal radiological dose that were collected were analyzed by region, year and hospital, the results of which look as follows : 1. The average radiation dose per capita by region and year for the 5 years was 1.61 mSv. By region, Daegu showed the highest amount 4.74 mSv, followed by Gangwon 4.65 mSv and Gyeonggi 2.15 mSv. The lowest amount was recorded in Chungbuk 0.91 mSv, Jeju 0.94 mSv and Busan 0.97 mSv in order. By year, 2000 appeared to be the year showing the highest amount of radiation dose 1.80 mSv, followed by 2002 1.77 mSv, 1999 1.55 mSv, 2001 1.50 mSv and 1998 1.36 mSv. 2. In 1998, Gangwon featured the highest amount of radiological dose per capita 3.28 mSv, followed by Gwangju 2.51 mSv and Daejeon 2.25 mSv, while Jeju 0.86mSv and Chungbuk 0.85 mSv belonged to the area where the radiation dose remained less than 1.0 mSv In 1999, Gangwon also topped the list with 5.67 mSv, followed by Daegu with 4.35 mSv and Gyeonggi with 2.48 mSv. In the same year, the radiation dose was kept below 1.0 mSv. in Ulsan 0.98 mSv, Gyeongbuk 0.95 mSv and Jeju 0.91 mSv. 3. In 2000, Gangwon was again at the top of the list with 5.73 mSv. Ulsan turned out to have less than 1.0 mSv of radiation dose in the years 1998 and 1999 consecutively, whereas the amount increased relatively high to 5.20 mSv. Chungbuk remained below the level of 1.0 mSv with 0.79 mSv. 4. In 2001, Daegu recorded the highest amount of radiation dose among those ever analyzed for 5 years with 9.05 mSv, followed by Gangwon with 4.01 mSv. The area with less than 1.0 mSv included Gyeongbuk 0.99 mSv and Jeonbuk 0.92 mSv. In 2002, Gangwon also led the list with 4.65 mSv while Incheon 0.88 mSv, Jeonbuk 0.96 mSv and Jeju 0.68 mSv belonged to the regions with less than 1.0 mSv of radiation dose. 5. By hospital, KMH in Daegu showed the record high amount of average radiation dose during the period of 5 years 6.82 mSv, followed by GAH 5.88 mSv in Gangwon and CAH 3.66 mSv in Seoul. YSH in Jeonnam 0.36 mSv comes first in the order of the hospitals with least amount of radiation dose, followed by GNH in Gyeongnam 0.39 mSv and DKH in Chungnam 0.51 mSv. There is a limit to the present study in that a focus is laid on the radiological technologists who are working at the 3rd referral hospitals which are regarded to be stable in terms of working conditions while radiological technologists who are working at small-sized hospitals are excluded from the survey. Besides, there are also cases in which hospitals with less than 5 years since establishment are included in the survey and the radiological technologists who have worked for less than 5 years at a hospital are also put to survey. We can't exclude the possibility, either, of assumption that the difference of personal average radiological dose by region, hospital and year might be ascribed to the different working conditions and facilities by medical institutions. It seems therefore desirable to develop standardized instruments to measure working environment objectively and to invent device to compare and analyze them by region and hospital more accurately in the future.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.2
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• pp.69-74
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• 2015

Recently, energy harvesting technology is increasing due to the fossil fuel shortages. Energy harvesting is generating electrical energy from wasted energies as sunlight, wind, waves, pressure, and vibration etc. Energy harvesting is one of the alternatives of fossil fuel. One of the energy harvesting technologies, the piezoelectric energy harvesting has been actively studied. Piezoelectric generating uses a positive piezoelectric effect which produces electrical energy when mechanical vibration is applied to the piezoelectric device. Piezoelectric energy harvesting has an advantage in that it is relatively not affected by weather, area and place. Also, stable and sustainable energy generation is possible. However, the output power is relatively low, so in this paper, newly designed honeycomb shaped piezoelectric energy harvesting device for increasing a generating efficiency. The output characteristics of the piezoelectric harvesting device were analyzed according to the change of parameters by using the finite element method analysis program. One model which has high output voltage was selected and a prototype of the honeycomb shaped piezoelectric harvesting device was fabricated. Experimental results from the fabricated device were compared to the analyzed results. After the AC-DC converting, the power of one honeycomb shaped piezoelectric energy harvesting device was measured 2.3[mW] at road resistance 5.1[$K{\Omega}$]. And output power was increased the number of harvesting device when piezoelectric energy harvesting device were connected in series and parallel.

• ETRI Journal
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• v.24 no.5
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• pp.333-340
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• 2002

We propose a new process technique for fabricating very high-density trench MOSFETs using 3 mask layers with oxide spacers and a self-aligned technique. This technique reduces the device size in trench width, source, and p-body region with a resulting increase in cell density and current driving capability as well as cost-effective production capability. We were able to obtain a higher breakdown voltage with uniform oxide grown along the trench surface. The channel density of the trench DMOSFET with a cell pitch of 2.3-2.4 ${\mu}m$ was 100 Mcell/$in^2$ and a specific on-resistance of 0.41 $m{\Omega}{\cdot}cm^2$ was obtained under a blocking voltage of 43 V.