• Current Optics and Photonics
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• v.4 no.3
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• pp.193-199
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• 2020

In this paper we propose a dark-field digital holographic microscopy system based on 360-degree oblique illumination. This setup is constructed without using a dark-field objective. The principle of 360-degree oblique illumination of vortex beam and dark-field digital holographic microscopy are introduced theoretically and experimentally. By analyzing the reconstructed image of a dark-field digital hologram of a USAF 1951 target, it is proved that the imaging resolution can be improved by this method. And also, comparison and analysis are made on the reconstructed image of a bright-dark field digital hologram of a pumpkin stem slice, the result shows that the imaging contrast is also enhanced with this method, and it is effective for dark-field digital holographic microscopy imaging of large transparent biological samples.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.105.1-105.1
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• 2010

바이오디젤 보급 활성화에 따른 식물성 원료유의 가격 상승 및 수급 불안정성 문제를 해결하고자 폐유지를 원료로 바이오디젤을 생산하고자 하는 시도가 이루어지고 있다. 폐유지의 사용은 폐자원 활용 측면에서 의미가 있으며 바이오디젤 생산 단가를 낮출 수 있다. 다양한 폐유지가 산업체로부터 배출되며 이 중에서 dark oil은 식용유 공장에서 식물성 원료유의 정제 과정에서 생기는 부산물로 바이오디젤로 전환 가능한 성분을 포함하고 있다. 본 연구에 사용된 dark oil은 54.9%의 유리지방산과 28.0%의 triglyceride, 4.4%의 diglyceride, 그리고 1% 이하의 monoglyceride를 함유하고 있다. Dark oil의 초기 산가는 109.8 mg KOH/g이었다. 본 연구에서는 dark oil의 유지 부분(triglyceride, diglyceride, monoglyceride)을 유리지방산으로 전환시켜 HAAO(high acid acid oil)을 생산한 후, 고체 산 촉매에 의한 에스테르화 반응을 통하여 바이오디젤을 생산하고자 하였다. 유지 부분의 유리지방산 전환 반응을 위하여 음이온성 계면활성제인 SDBS(sodium dodecyl benzene sulfonate)가 사용되었다. Dark oil:황산:물의 질량비가 10:2:10이고 SDBS가 오일 대비 3%인 조건에서 dark oil의 산가는 190.8 mg KOH/g까지 증가하였고, dark oil:황산:물의 질량비가 10:4:10이고 SDBS가 2%인 조건에서는 산가가 194.2 mg KOH/g까지 증가하였다. 생산된 HAAO을 이용하여 오일 대비 30%의 Amberlyst-15 촉매 하에서 HAAO:메탄올 몰비 1:9인 조건에서 에스테르화 반응을 수행하였을 경우 FAME(fatty acid methyl ester) 함량은 81.3%까지 증가하였다. 고체 산 촉매로써 Amberlyst-15와 가격 면에서 저렴한 PC101을 비교하였을 경우 FAME 함량은 각각 80.7%, 77.9%로 비슷한 효율을 나타내었다. 생산된 바이오디젤의 FAME 함량을 높이기 위해 증류 공정을 필요로 하였다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.5 no.3
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• pp.208-212
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• 2003

Extended light illumination by street lamp and automobile light has provoked problem in farmland. Night break was imposed by incandescent lamp (50∼60 lux) for 10 minutes every three hours during 12 hours dark period increased culm length compared to continuous dark of 12 hours, and decreased the number of grains per spike in rice. However, these characters were increased by 12 hours dark period with and without night break as compared to 9 hours continuous dark condition. Compared to 12 hours continuous dark condition, night break delayed heading by 9 and 26 days and 9 hours continuous dark condition delayed it by 47 and 41 days in Ilpumbyeo and Hwaseongbyeo, respectively. Night break increased stem length and node number, while decreased pods of soybean cultivar Hwanggeumkong. The stem length and node number were increased by 9 hours continuous dark condition compared to 12 hours dark condition with and without night break. Compared to 12 hours continuous dark rendition, night break delayed flowering by 4 days and to 9 hours continuous dark condition by 19 days.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.3
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• pp.247-259
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• 2015

This study was performed to investigate the application of dark $H_2$ fermentation to two-stage bioprocesses for organic waste treatment and energy production. We reviewed information about the two-stage bioprocesses combining dark $H_2$ fermentation with $CH_4$ fermentation, photo $H_2$ fermentation, microbial fuel cells (MFCs), or microbial electrolysis cells (MECs) by using academic information databases and university libraries. Dark fermentative bacteria use organic waste as the sole source of electrons and energy, converting it into $H_2$. The reactions related to dark $H_2$ fermentation are rapid and do not require sunlight, making them useful for treating organic waste. However, the degradation is not complete and organic acids remain. Thus, dark $H_2$ fermentation should be combined with a post-treatment process, such as $CH_4$ fermentation, photo $H_2$ fermentation, MFCs, or MECs. So far, dark $H_2$ fermentation followed by $CH_4$ fermentation is a promising two-stage bioprocess among them. However, if the problems of manufacturing expenses, operational cost, scale-up, and practical applications will be solved, the two-stage bioprocesses combining dark $H_2$ fermentation with photo $H_2$ fermentation, MFCs, or MECs have also infinite potential in organic waste treatment and energy production. This paper demonstrated the feasibility of two-stage bioprocesses combining dark $H_2$ fermentation as a novel system for organic waste treatment and energy production.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.34.1-34.1
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• 2009

After SNIa and WMAP observations during the last decade, the discovery of the accelerated expansion of the universe is a major challenge to particle physics and cosmology. There are currently three candidates for the dark energy which results in this accelerated expansion: $\cdot$ a non-zero cosmological constant, $\cdot$ a dynamical cosmological constant (quintessence scalar field), $\cdot$ modifications of Einstein's theory of gravity. The scalar field model like quintessence is a simple model with time-dependent w, which is generally larger than -w1. Because the different w lead to a different expansion history of the universe, the geometrical measurements of cosmic expansion through observations of SNIa, CMB and baryon acoustic oscillations (BAO) can give us tight constraints on w. One of the interesting ways to study the scalar field dark-energy models is to investigate the coupling between the dark energy and the other matter fields. In fact, a number of models which realize the interaction between dark energy and dark matter, or even visible matter, have been proposed so far. Observations of the effects of these interactions will offer an unique opportunity to detect a cosmological scalar field. In this talk, after briefly reviewing the main idea of the three possible candidates for dark energy and their cosmological phenomena, we discuss the interactinng dark-energy model, paying particular attention to the interacting mechanism between dark energy with a hot dark matter (neutrinos). In this so-called mass-varying neutrino (MVN) model, we calculate explicitly the cosmic microwave background (CMB) radiation and large-scale structure (LSS) within cosmological perturbation theory. The evolution of the mass of neutrinos is determined by the quintessence scalar field, which is responsible for the cosmic acceleration today.

• Journal of Astronomy and Space Sciences
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• v.35 no.2
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• pp.67-74
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• 2018

Higgs boson enables the Standard Model (SM) to be established. However, we do not know much about dark matter which occupies approximately six times of the SM particles in universe besides having mass. The interactions of dark matter is much weaker than that of the SM. Further, its mass range is very wide, from the order of eV to PeV. Therefore, many experiments have contributed to search for dark matter by indirect, direct and accelerator research. This paper reviews researches on dark matter using accelerator, especially the $e^+e^-$ collider, from the viewpoint of experimental high energy physicists.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.984-987
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• 2003

유기발광소자 안에 존재하는 비발광영역(dark spot)의 전압에 대한 영향을 근접장 마이크로파 현미경(near-field scanning microwave microscope)을 이용하여 관찰하였다. 유기발광소자는 glass/indiumtin oxide(ITO)/Cu-Pc/tris-(8-hydroquinoline)aluminum(Alq3)/aluminum(Al) 의 기본구조로 제작하였다. Dark spot은 ITO 기판을 부분적으로 에칭하여서 형성시켰다. Dark spot에 $0{\sim}l5 V$ 까지 전압을 인가시키면서 인가 전압에 따른 전기적 특성을 근접장 마이크로파 현미경 image의 변화와 반사계수인 $S_{11}$ 측정을 통하여 연구하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.961-964
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• 2003

This paper presents the temperature annealing effect on the dark current of the InGaAs waveguide photodiodes, which are developed for high-speed optical receivers. The interesting experimental phenomena were observed that the dark current is significantly decreased and the breakdown voltage is slightly increased after annealing at $250^{\circ}C$ whereas the dark current and the breakdown voltage are almost constant after annealing at $200^{\circ}C$. Based on the experimental results, the long-term annealing is more effective for the dark current improvement than the conventional curing process.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.2
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• pp.102-106
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• 2005

A low dark current CMOS image sensor (CIS) pixel without any process modification is developed. Dark current is mainly generated at the interface region of shallow trench isolation (STI) structure. Proposed pixel reduces the dark current effectively by separating the STI region from the photodiode junction using simple layout modification. Test sensor array that has both proposed and conventional pixels is fabricated using 0.18 m CMOS process and the characteristics of the sensor are measured. The result shows that the dark current of the proposed pixel is 0.93fA/pixel that is two times lower than the conventional design.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.3
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• pp.841-847
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• 2016

To study the influence of background color and substratum on hypermelanosis of starry flounder, we compared the daily food intake (DFI), the feed efficiency (FE), the survival, the growth, the ratio of pigmented area on the blind side and the ratio of hypermelanic fish duplicately reared for 180 days in dark-green FRP aquarium (control), white FRP aquarium together with dark-green substratum. The ratio of pigmented area on the blind side was significantly higher at the dark-green group than at the white group. DFI, FE and growth were higher in the dark-green substratum. Pigmented area rate and ratio of hypermelanic fish were significantly higher at the dark green group than at the high dark-green substratum. The results suggest that bright tank color and substratum bottom could inhibit the hypermelanosis.