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Stimulated Emission with 349-nm Wavelength in GaN/AlGaN MQWs by Optical Pumping
Sung-Bock Kim,Sung-Bum Bae,Young-Ho Ko,Dong Churl Kim,Eun-Soo Nam 한국진공학회(ASCT) 2017 Applied Science and Convergence Technology Vol.26 No.4
The crack-free AlGaN template has been successfully grown by using selective area growth with triangular GaN facet. The triangular GaN stripe structure was obtained by vertical growth rate enhanced mode with low growth temperature of 950℃ and high growth pressure of 500 torr. The lateral growth rate enhanced mode of AlGaN for crackfree and flat surface was also investigated. Low pressure of 30 torr and high V/III ratio of 4400 were favorable for lateral growth of AlGaN. It was confirmed that the 4 μm -thick Al0.2Ga0.8N was crack-free over entire 2-inch wafer. The dislocation density of Al0.2Ga0.8N was as low as ~7.6 × 10<SUP>8</SUP> /cm<SUP>2</SUP> measured by cathodoluminescence. Based on the high quality AlGaN with low dislocation density, the ultraviolet laser diode epitaxy with cladding, waveguide and GaN/AlGaN multiple quantum well (MQW) was grown by metalorganic chemical vapor deposition. The stimulated emission at 349 nm with full width at half maximum of 1.8 nm from the MQW was observed through optical pumping experiment with 193 nm KrF laser. We also have fabricated the deep ridge type ultraviolet laser diode (UV-LD) with 5 μm-wide and 700 μm-long cavity for electrical properties. The turn on voltage was below 5 V and the resistance was ~55 Ω at applied voltage of 10 V. The amplified spontaneous emission spectrum of UV-LD was also observed from pulsed current injection.
Sang Gon Kim,Seonghyu Shin,Hwan Hee Bae,Jin-Seok Lee,Jung-Tae Kim,Min Jung Seo,Beom-Young Son,Jeom Ho Lee,Seong-Bum Baek 한국육종학회 2015 한국육종학회 심포지엄 Vol.2015 No.07
Understanding the response of a crop to water deficiency is the first step towards breeding drought-tolerant varieties. In this study, inbred maize (Zea mays L.) lines KS140 and KS141 were subjected to drought stress by withholding water for 10 days at the V5 or V6 leaf stage. Water-deficient plants experienced a decrease in relative leaf water content, stomatal conductance, net CO2 assimilation rate, and water use efficiency compared to well-watered plants. This was accompanied by a decrease in the relative leaf water content that resulted in severe growth retardation in KS140 and KS141. However, leaf chlorophyll content in KS140 was unchanged. To understand the proteome dynamics during the 10-day drought stress in maize leaves, comparative proteome analysis was carried out between the well-watered and water-withheld leaves. Differential expression was observed for 29 protein spots from KS140 and 14 protein spots from KS141, and these were identified using MALDI-TOF mass spectrometry. Among identified proteins, metabolism and stress related proteins were highly were increased by drought stress. This study provides a protein profile of a Korean maize inbred line during drought stress, which will be valuable for future studies of the molecular mechanisms underlying drought resistance and for development of selective breeding markers for drought tolerance in maize.
Non-Lithographic Growth of Core–Shell GaAs Nanowires on Si for Optoelectronic Applications
Bae, Myung-Ho,Kim, Bum-Kyu,Ha, Dong-Han,Lee, Sang Jun,Sharma, Rahul,Choi, Kyoung Jin,Kim, Ju-Jin,Choi, Won Jun,Shin, Jae Cheol The American Chemical Society 2014 CRYSTAL GROWTH AND DESIGN Vol.14 No.4
<P>We demonstrated a nonlithographic method for integrating GaAs nanowire (NW) array-based light-emitting diodes (LEDs) on silicon (Si) substrates. A sub-100 nm hole array on a deposited SiO<SUB>2</SUB> layer was patterned on an entire 2 in. Si wafer based on a sacrificed self-assembled InAs NW array. Then, a core–shell <I>n</I>–<I>p</I> junction GaAs NW array was grown on exposed Si windows via the selective-area growth method. The electrical properties of the core–shell <I>n</I>–<I>p</I> junction GaAs NW has been measured and compared to those of the core–shell junction NWs formed via the self-assembled growth method. Room temperature electroluminescence was successfully observed from the fabricated GaAs NW array-based LEDs. The core–shell junction III–V NW array epitaxially grown on a ubiquitous Si platform could be applied to future low-cost optical devices.</P><P>We demonstrated a nonlithographic method for integrating GaAs nanowire (NW) array-based light-emitting diodes on Si. For the NW growth, a sub-100 nm SiO<SUB>2</SUB> hole was patterned on a Si wafer based on a sacrificed self-assembled InAs NW array. Then, a core−shell <I>n</I>−<I>p</I> junction GaAs NW array was grown on exposed Si windows via the selective-area growth method.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cgdefu/2014/cgdefu.2014.14.issue-4/cg401520q/production/images/medium/cg-2013-01520q_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cg401520q'>ACS Electronic Supporting Info</A></P>
A Study on Wavelet-based Denoising Algorithm for Signal Reconstruction in Mixed Noise Environments
Bae, Sang-Bum,Kim, Nam-Ho The Korea Institute of Information and Commucation 2007 Journal of information and communication convergen Vol.5 No.1
In the process of the acquisition, storage, transmission of signals, noises are generated by various causes and the degradation phenomenon by noises tends to generate serious errors for the signal with information. So, in order to analyze and remove these noises, studies on numerous mathematical methods such as the Fourier transform have been implemented. And recently there have been many ongoing wavelet-based denoising algorithms representing excellent characteristics in time-frequency localization and multiresolution analysis, but the method to remove additive white Gaussian noise (AWGN) and the impulse noise simultaneously was not given. So, to reconstruct the corrupted signal by noises, in this paper a novel wavelet-based denoising algorithm was proposed and using signal-to-noise ratio (SNR) this method was compared to conventional methods.
The effect of pyridine modification of Ni–DOBDC on CO<sub>2</sub> capture under humid conditions
Bae, Youn-Sang,Liu, Jian,Wilmer, Christopher E.,Sun, Hahnbi,Dickey, Allison N.,Kim, Min Bum,Benin, Annabelle I.,Willis, Richard R.,Barpaga, Dushyant,LeVan, M. Douglas,Snurr, Randall Q. The Royal Society of Chemistry 2014 Chemical communications Vol.50 No.25
<P>The metal–organic framework Ni–DOBDC was modified with pyridine molecules to make the normally hydrophilic internal surface more hydrophobic. Experiments and molecular simulations show that the pyridine modification reduces H<SUB>2</SUB>O adsorption while retaining substantial CO<SUB>2</SUB> capacity under the conditions of interest for carbon capture from flue gas.</P> <P>Graphic Abstract</P><P>The metal–organic framework Ni–DOBDC was modified with pyridine molecules to make the normally hydrophilic internal surface more hydrophobic. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cc44954h'> </P>
Boussinesq modelling of a rip current at Haeundae Beach in South Korea
Bae, Jae Seok,Yoon, Sung Bum,Choi, Junwoo BioOne (Coastal Education and Research Foundation) 2013 JOURNAL OF COASTAL RESEARCH Vol.65 No.-
<P>The rip current occurring at Haeundae beach in Busan, South Korea was numerically investigated under directional random wave environment. The numerical simulations were performed using a fully nonlinear Boussinesq equation model, FUNWAVE which is capable of resolving phase interaction and simulating nearshore circulation since it includes the effect of wave-induced momentum flux and horizontal turbulent mixing. To examine the modelling, the rip current occurred on the 12th of June, 2011 at Haeundae beach was simulated by using observations. The results of numerical simulation showed the time-dependent evolution of the wave-induced nearshore circulation that was caused by transformation of random waves due to the unique topography of Haeundae beach. And, it was found that the rip current was well generated and developed through the region where relatively lower wave heights were caused by refraction and diffraction of waves due to the topographical characteristics (i.e., submerged shoal). In addition, we found that a narrow-banded spectral wave (i.e., a swell spectrum) close to a regular wave generates stronger rip current than a broad-banded spectral wave under an equivalent wave height and period condition.</P>
Development of Economical Fertilizer-Based Media for Mass Culturing of Nannochloropsis oceanica
Bae, Jean-Hee,Hur, Sung-Bum The Korean Society of Fisheries and Aquatic Scienc 2011 Fisheries and Aquatic Sciences Vol.14 No.4
This study was conducted to develop economical agricultural fertilizer media for the mass culturing of Nannochloropsis oceanica. Specific growth rates of N. oceanica cultured with differing concentrations of commercial compounds, urea fertilizers, and trace elements (Zn, Cu, Co, Mo) were compared with the growth rate in f/2 medium. Among the various added trace elements, $CuSO_4{\cdot}5H_2O$ was most effective for high growth of N. oceanica. The main nitrogen source in the agricultural fertilizers was ammonium, which was unsuitable for the growth of N. oceanica. Thus, the fertilizer at a lower concentration infused with $NaNO_3$ as a nitrogen source was more effective than fertilizer at higher concentrations. In this study, the growth of N. oceanica cultured with an agricultural fertilizer medium composed of compound fertilizer (41.7 mg/L), urea fertilizer (34.4 mg/L), $NaNO_3$ (150 mg/L), and $CuSO_4{\cdot}5H_2O$ (0.0588 mg/L) was similar to that of N. oceanica cultured in f/2 medium.
FC 1-13 : Expression of extracellular superoxide dismutase protein in diabetes
( Bum Joon Ko ),( Han Eul Lee ),( Gang Mo Lee ),( Je Min An ),( You In Bae ),( Sung Yul Lee ),( Moon Kyun Cho ) 대한피부과학회 2013 대한피부과학회 학술발표대회집 Vol.65 No.2
Background: Diabetes is characterized by chronic hyperglycemia, which can increase reactive oxygen species (ROS) production by the mitochondrial electron transport chain. The formation of ROS induces oxidative stress and activates oxidative damage-inducing genes in cells. No research has been published on oxidative damage-related extracellular superoxide dismutase (EC-SOD) protein levels in human diabetic skin. We investigated the expression of EC-SOD in diabetic skin compared with normal skin tissue in vivo. Objectives: To compare the expression of EC-SOD in normal skin versus diabetic skin. Methods: The expression of EC-SOD protein was evaluated by western blotting in 6 diabetic skin tissue samples and 6 normal skin samples. Immunohistochemical staining was also carried out to confirm the EC-SOD expression level in the 6 diabetic skin tissue samples. Results: The western blotting showed significantly lower EC-SOD protein expression in the diabetic skin tissue than in the normal tissue. Immunohistochemical examination of EC-SOD protein expression supported the western blotting analysis. Conclusion: Diabetic skin tissues express a relatively small amount of EC-SOD protein and may not be protected against oxidative stress. We believe that EC-SOD is related to the altered metabolic state in diabetic skin, which elevates ROS production.