• ETRI Journal
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• 제31권6호
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• pp.680-687
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• 2009

This paper reports on an improved piezoelectric microspeaker with a high sound pressure level of 90 dB, a total harmonic distortion of less than 15%, and coherence higher than 0.9. The fabricated Pb(Zr,Ti)$O_3$ (PZT) microspeakers have a thickness of only 1 mm including the speaker frame and an active area of 18 mm${\times}$20 mm. To achieve higher sound pressure and lower distortion, the PZT piezoelectric microspeaker has a well-designed speaker frame and a piezoelectric diaphragm consisting of a tilted PZT membrane and silicone buffer layer. From the simulation and measurement results, we confirmed that the silicon buffer layer can lower the first resonant frequency, which enhances the microspeaker's sound pressure at a low frequency range and can also reduce useless distortion generated by the harmonics. The fabricated PZT piezoelectric microspeakers are implemented on a multichannel speaker array system for personal acoustical space generation. The output sound pressure at a 30 cm distance away from the center of the speaker line array is 15 dB higher than the sound pressure at the neighboring region 30 degrees from the vertical axis.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.419-420
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• 2008

In this study, high quality (Al,N)-codoped p-type ZnO thin films were obtained by DC magnetron sputtering. The film on buffer layer grown in 80% $N_2$ ambient shows highest hole concentration of $2.93\times10^{17}cm^{-3}$. The films show hole concentration in the range of $1.5\times10^{15}$ to $2.93\times10^{17}cm^{-3}$, resistivity of 131.2 to 2.864 $\Omega$cm, mobility of 3.99 to 31.6 $cm^2V^{-1}s^{-1}$. The films on Si show easier p-doping in ZnO than those on buffer layer. The film on Si shows the highest quality of optical photoluminescence (PL) characteristics. The donor energy level $(E_d)$ of (Al,N)-codoped ZnO films is about 50 meV and acceptor energy level $(E_a)$ is in the range of 63 to 71 meV. It will help to improve p-type ZnO films.

• 미생물학회지
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• 제27권4호
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• pp.422-429
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• 1989

Auxotrophic mutant were isolated from wild types by the treatment with NTG as a mutagen, and the conditions of protoplast formation for them were established. The protoplasts of killer yeast Saccharomyces cerevisiae K52 were formed to the level of above 70% when cells grown for 20 hr in PM medium were treated with 200 unit/ml Lyticase 50,000 at $30^{\circ}C$ for 60 min after pretreatment of 50 mM 2-mercaptoethanol in 10mM potassium phosphate buffer (pH 7.5) containing EDTA and 0.6 M sorbitol for 15 min. Also, the protoplast of the recipient S. cerevisiae S 29 were formed to the level of above 85% as it was cultured to the log phase of 24 hr in PM medium under the same conditions. The fusion frequency between the protoplast of killer yeast S. cerevisiae K 52 and the protoplast of recipient S. cerevisiae S 29 was reached to $8.2\times 10^{-6}$ when the hypertonic regeneration medium embeded with the fused protoplasts after mixing the parental protoplasts to 10$^{8}$ cells/ml in SP buffer containing 20 mM $CaCl_{2}$ and 30% PEG 6,000 for 15 min at $30^{\circ}C$ were incubated.

• Journal of Ecology and Environment
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• 제29권4호
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• pp.343-352
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• 2006

This study investigated the relationship between land cover and the water quality variables in the rivers, which are located in the Yamaguchi prefecture of West Japan. The study area included 12 catchments covering $5,809\;Km^2$. pH, dissolved oxygen, suspended solid, E. coli, total nitrogen and total phosphorus were considered as river water quality variables. Satellite data was applied to generate land cover map. For linking alterations in land cover (at whole catchment and buffer zone levels) and the river water quality variables, multiple regression modeling was applied. The results indicated that non-spatial attribute (%) of land cover types (at whole catchment level) consistently explained high amounts of variation in biological oxygen demand (72%), suspended solid (72%) and total nitrogen (87%). At buffer zone-scale, multiple regression models that were developed to represent the linkage between the alterations of land cover and the river water quality variables could also explain high level of total variations in suspended solid (86%) and total nitrogen (91%).

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권5호
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• pp.1728-1743
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• 2021

Three-dimensional (3D) video scenes are complex and difficult to control, especially when scene switching occurs. In this paper, we propose two algorithms based on an incremental proportional-integral-derivative (PID) algorithm and a similarity analysis between views to improve the method of bit allocation for multi-view high efficiency video coding (MV-HEVC). Firstly, an incremental PID algorithm is introduced to control the buffer "liquid level" to reduce the negative impact on the target bit allocation of the view layer and frame layer owing to the fluctuation of the buffer "liquid level". Then, using the image similarity between views is used to establish, a bit allocation calculation model for the multi-view video main viewpoint and non-main viewpoint is established. Then, a bit allocation calculation method based on hierarchical B frames is proposed. Experimental simulation results verify that the algorithm ensures a smooth transition of image quality while increasing the coding efficiency, and the PSNR increases by 0.03 to 0.82dB while not significantly increasing the calculation complexity.

• 한국토양비료학회지
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• 제37권4호
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• pp.251-258
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• 2004

밭작물에 대한 규산질 비료의 시용이 널리 이루어지고 있으나 적정시용수준이 밝혀져 있지 못하며 또한 밭토양에서의 유효규산 측정방법이 구명되어있지 못한 실정이다. 본 연구는 참외 시설재배지 토양에 대하여 유효규산 측정방법을 구명하기 위해 수행되었다. 경북 성주지역의 참외 시설재배지,10개소의 토양과 참외 잎 시료를 채취하여 가용성 토양 규산 함량과 잎 중의 총 규산 함량을 분석하였다. 가용성 토양 규산은 0.5 N HCI, 1 N sodium acetate buffer (pH 4.0). citric acid 1%, water, Tris buffer (pH 7.0), 그리고 1주간 담수하는 방법 등으로 추출하였으며, 식물체 규산은 autoclave 방법으로 추출하였다. 추출액중의 가용성 규산은 비색법으로 정량하였다. 각 추출방법별로 가용성 토양규산 함량과 식물체규산 함량과의 관계를 비교하였는데, 1 N sodium acetate buffer 방법이 토양 규산과 식물체 규산 관계를 가장 뚜렷한 포화곡선으로 나타내었다. 포화곡선으로부터 산출된 참외 잎 중의 포화 규산 함량은 약 $14g\;SiO_2\;kg^{-1}$이었고 1 N sodium acetate buffer 방법으로 추출할 경우토양 규산 함량 $120mg\;SiO_2\;kg^{-1}$이 참외에 적정한 수준인 것으로 나타났다. 특히 1 N sodium acetate buffer방법의 경우 참외 잎 중의 규산 함량이 포화되는 수준 이하의 토양 규산 함량 범위에서는 토양 규산 함량과 식물체 규산 함량 사이에 유의성 있는 상관관계가 있었다. 따라서 현재 우리나라에서 논토양의 유효규산 측정방법으로 널리 사용퇴고 있는 1 N sodium acetate buffer를 이용한 유효규산 추출방법이 밭토양에도 적용될 수 있을 것으로 판단되나 앞으로 다양한 작물과 토양을 대상으로 계속적인 연구가 요구된다.

• 한국산림과학회지
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• 제83권3호
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• pp.400-409
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• 1994

본 연구는 다양한 유형의 수림대가 갖는 소음감쇄효과를 측정하기 위하여 수행되었다. 차량통행이 빈번한 도로변 6개 조사지를 대상으로 측정한 결과 수림대의 소음감쇄효과를 확인하였다. 도로로부터 1m와 10m 상의 최대음압도의 차이는 10-15dB로 수림대의 속성에 따라 다소간의 차이를 보이고 있다. 초지를 대조구로 비교하였을 때 조사지 중에서 음압도의 최대차이는 밀생한 관목림에서 보이는 5dB 수준이다. 도로로부터 상향 경사면에 위치하는 조사지의 경우에는 오히려 대조구보다 소음감쇄 정도가 미미하였다. 연구를 통하여 분석된 제한된 정보와 국내외의 이전 연구결과를 토대로 단층 건물 주변의 10m 폭 방음수림대의 적절한 유형을 제시한다면 최소 3m 폭, 2m 수고의 밀식된 관목수림대와 앞뒤로 각각 3m 폭의 부드러운 초지의 조성을 들 수 있다. 위의 처방은 본 연구의 결과로 유추하여 볼 때 소음원인으로부터 발생되는 음압도를 15dB 이상 감소시킬 수 있을 것으로 판단된다.

• 방사성폐기물학회지
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• 제13권2호
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• pp.99-112
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• 2015

본 연구에서는 고준위폐기물 처분시 완충재로 사용되는 벤토나이트의 열적 거동을 평가하기 위해 실내실험장치를 제작하였다. 그리고 실험 결과를 검증하기 위해 유한요소해석 프로그램인 ABAQUS를 이용한 열해석을 실시하였다. 그리고 실험기간 동안의 계절변화를 감안하여 외부대기 온도에 따른 벤토나이트의 열적거동을 평가하였다. 해석결과, 스테인리스스틸이 포함된 case3 해석모델의 결과가 실험결과와 1℃ 내외의 오차를 보이며 거의 일치함을 볼 수 있었다. 그리고 계절에 따른 벤토나이트 온도 해석을 수행한 결과, 시간에 따른 온도분포 경향이 일치함을 확인하였다. 이러한 열해석을 통해 완충재를 둘러싸고 있는 물질의 열전도도와 외부대기의 온도가 벤토나이트 완충재의 열적 거동에 큰 영향을 주는 요소임을 확인할 수 있었다. 향후 열원을 포함한 벤토나이트 완충재의 수분 포화 특성 실험이 실시 될 예정이므로, 실험에 대한 검증과 예측을 위해 보다 적합한 수치해석모델 개발에 대한 연구가 필요할 것이다.

• Journal of Microbiology and Biotechnology
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• 제17권1호
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• pp.89-95
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• 2007

Improvements in the dissolution of proteins in two-dimensional gel electrophoresis have greatly advanced the ability to analyze the proteomes of microorganisms under a wide variety of physiological conditions. This study examined the effect of various combinations of chaotropic agents, a reducing agent, and a detergent on the dissolution of the Streptomyces peucetius cytosolic proteins. The use of urea alone in a rehydration buffer as a chaotropic agent gave the proteome a higher solubility than any of the urea and thiourea combinations, and produced the highest resolution and clearest background in two-dimensional gel electrophoresis. Two % CHAPS, as a detergent in a rehydration buffer, improved the protein solubility. After examining the effect of several concentrations of reducing agent, 50 mM DTT in a rehydration buffer was found to be an optimal condition for the proteome analysis of Streptomyces. Using this optimized buffer condition, more than 2,000 distinct and differentially expressed soluble proteins could be resolved using two-dimensional gel electrophoresis with a pI ranging from 4-7. Under this optimized condition, 15 novel small proteins with low-level expression, which could not be analyzed under the non-optimized conditions, were identified. Overall, the optimized condition helped produce a better reference gel for Streptomyces peucetius.

• 방사성폐기물학회지
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• 제18권spc호
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• pp.21-36
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• 2020

With respect to spent nuclear fuels, disposal containers and bentonite buffer blocks in deep geological disposal systems are the primary engineered barrier elements that are required to isolate radioactive toxicity for a long period of time and delay the leakage of radio nuclides such that they do not affect human and natural environments. Therefore, the thermal stability of the bentonite buffer and structural integrity of the disposal container are essential factors for maintaining the safety of a deep geological disposal system. The most important requirement in the design of such a system involves ensuring that the temperature of the buffer does not exceed 100℃ because of the decay heat emitted from high-level wastes loaded in the disposal container. In addition, the disposal containers should maintain structural integrity under loads, such as hydraulic pressure, at an underground depth of 500 m and swelling pressure of the bentonite buffer. In this study, we analyzed the thermal stability and structural integrity in a deep geological disposal environment of the improved deep geological disposal systems for domestic light-water and heavy-water reactor types of spent nuclear fuels, which were considered to be subject to direct disposal. The results of the thermal stability and structural integrity assessments indicated that the improved disposal systems for each type of spent nuclear fuel satisfied the temperature limit requirement (< 100℃) of the disposal system, and the disposal containers were observed to maintain their integrity with a safety ratio of 2.0 or higher in the environment of deep disposal.