Browsing by Author "Yang, Yi-Chun"

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Ability of an alkali-tolerant mutant strain of the microalga Chlorella sp AT1 to capture carbon dioxide for increasing carbon dioxide utilization efficiency
(2017-11-01)
Kuo, Chiu-Mei
;
Lin, Tsung-Hsien
;
Yang, Yi-Chun
;
Zhang, Wen-Xin
;
Lai, Jinn-Tsyy
An alkali-tolerant Chlorella sp. AT1 mutant strain was screened by NTG mutagenesis. The strain grew well in pH 6-11 media, and the optimal pH for growth was 10. The CO2 utilization efficiencies of Chlorella sp. AT1 cultured with intermittent 10% CO2 aeration for 10, 20 and 30 min at 3-h intervals were approximately 80, 42 and 30%, respectively. In alkaline medium (pH = 11) with intermittent 10% CO2 aeration for 30 min at 3-, 6- and 12-h intervals, the medium pH gradually changed to 10, and the biomass productivities of Chlorella sp. AT1 were 0.987, 0.848 and 0.710 g L-1 d(-1), respectively. When Chlorella sp. AT1 was aerated with 10% CO2 intermittently for 30 min at 3-h intervals in semi-continuous cultivation for 21 days, the biomass concentration and biomass productivity were 4.35 g L-1 and 0.726 g L-1 d(-1), respectively. Our results show that CO2 utilization efficiency can be markedly increased by intermittent CO2 aeration and alkaline media as a CO2-capturing strategy for alkali-tolerant microalga cultivation.
An efficient Photobioreactors/Raceway circulating system combined with alkaline-CO2 capturing medium for microalgal cultivation
(2018-10-01)
Kuo, Chiu-Mei
;
Jian, Jhong-Fu
;
Sun, Yu-Ling
;
Lin, Tsung-Hsien
;
Yang, Yi-Chun
High efficiency of microalgal growth and CO2 fixation in a Photobioreactors (PBRs)/Raceway circulating (PsRC) system combined with alkaline-CO2 capturing medium and operation was established and investigated. Compared with a pH 6 medium, the average biomass productivity of Chlorella sp. AT1 cultured in a pH 11 medium at 2L min(-1) circulation rate for 7 days increased by about 2-fold to 0.346g L-1 d(-1). The maximum amount of CO2 fixation and CO2 utilization efficiency of Chlorella sp. AT1 could be obtained at a PBRs to Raceway ratio of 1:10 in an indoor-simulated PsRC system. A similar result was also shown in an outdoor PsRC system with a 10-ton scale for microalgal cultivation. Under the appropriate circulation rate, the stable growth performance of Chlorella sp. AT1 cultured by long-term semi-continuous operation in the 10-ton outdoor PsRC system was observed, and the total amount of CO2 fixation was approximately 1.2kg d(-1) with 50% CO2 utilization efficiency.
Efficient Heat Dissipation of Photonic Crystal Microcavity by Mono layer Graphene
(2013-12-01)
Shih, Min-Hsiung
;
Li, Lain-Jong
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Yang, Yi-Chun
;
Chou, Hsiang-Yu
;
Lin, Cheng-Te
Graphene, which exhibits excellent thermal conductivity, is a potential heat dissipation medium for compact optoelectronic devices. Photonic devices normally produce large-quantity of unwanted heat, and thus, a heat dissipation strategy is urgently needed. In this study, single-layer graphene (SLG) grown by chemical vapor deposition (CVD) is used to cover the surface of a photonic crystal (PhC) cavity, where the heat flux produced by the PhC cavity can be efficiently dissipated along the in-plane direction of the SLG. The thermal properties of the graphene-capped PhC cavity were characterized by experiments and theoretical calculations. The thermal resistance of the SLG-capped PhC cavity obtained from experiments is lower than half of that of a bare PhC cavity. The temperature of a SLG-capped PhC cavity is 45 K lower than that without SLG capping under an optical power of 100 mu W. Our simulation results indicate that SLG receives the majority of the heat fluxes from the device, leading to the efficient heat dissipation. Both the experimental and simulation results suggest that the SLG is a promising material to enhance the heat dissipation efficiency for optoelectronic applications.
Light Emission Enhancement of GaN-Based Photonic Crystal With Ultraviolet AlN/AlGaN Distributed Bragg Reflector
(2010-11-15)
Chen, Cheng-Chang
;
Chen, Jun-Rong
;
Yang, Yi-Chun
;
Shih, M. -H.
;
Kuo, Hao-Chung
In this study, we demonstrated two-dimensional (2-D) photonic crystal band-edge coupling operation in the ultraviolet wavelength range. The light extraction enhancement was obtained from the photonic crystal structure with an ultraviolet AlN/AlGaN distributed Bragg reflector (UVDBR). The DBR provides a high reflectivity of 85% with 15-nm stopband width. A fivefold enhancement in photoluminescence emission was also achieved compared with the emission from the unpatterned area on the same sample at 374 nm wavelength. We also study the photonic crystal band-edge coupling with finite-difference time-domain and plane-wave expansion methods.
Optimization of High-Q Coupled Nanobeam Cavity for Label-Free Sensing
(2015-10-01)
Yaseen, Mohammad Tariq
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Yang, Yi-Chun
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Shih, Min-Hsiung
;
Chang, Yia-Chung
;
光電工程學系
We numerically and experimentally investigated the lateral coupling between photonic crystal (PhC) nanobeam (NB) cavities, pursuing high sensitivity and figure of merit (FOM) label-free biosensor. We numerically carried out 3D finite-difference time-domain (3D-FDTD) and the finite element method (FEM) simulations. We showed that when two PhC NB cavities separated by a small gap are evanescently coupled, the variation in the gap width significantly changes the coupling efficiency between the two coupled NB cavities and the resulting resonant frequencies split. Experimentally, we fabricated laterally-coupled PhC NB cavities using (InGaAsP) layer on the InP substrate. For sensing, we showed that the laterally coupled PhC NB cavities sensor exhibits higher sensitivity than the single PhC NB cavity. The higher sensitivity of laterally coupled PhC NB cavities is due to the strong evanescent coupling between nearby PhC NB cavities, which depends on the gap width and it is attributed to the large confinement of the electromagnetic field in the gap (air or liquid). As a result of the lateral coupling, both even (symmetric) and odd (asymmetric) modes exist. We show that even modes are more sensitive than odd modes. In addition, higher-order modes exhibit higher sensitivity. Hence, we characterized and examined the fabricated PhC NB cavity as a label-free biosensor, and it exhibits high figure of merit due to its high Q-factor. This illustrates a potentially useful method for optical sensing at nanoscale.
Room temperature continuous wave operation and characterization of photonic crystal nanolaser on a sapphire substrate
(2009-05-21)
Shih, M. H.
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Yang, Yi-Chun
;
Liu, Yu-Chen
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Chang, Zi-Chang
;
Hsu, Kung-Shu
A compact photonic crystal defect nanocavity was fabricated on a sapphire substrate. Continuous wave lasing at room temperature was achieved with a low threshold power. We characterized the operated mode, quality factor and radiative efficiency for the compact laser. The thermal properties of the nanolaser were also investigated.
The Influence of the Thermal Effect on CdSe/ZnS Quantum Dots in Light-Emitting Diodes
(2012-07-15)
Chen, Kuo-Ju
;
Chen, Hsin-Chu
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Shih, Min-Hsiung
;
Wang, Chao-Hsun
;
Kuo, Ming-Yen
This study investigates the effect of temperature on CdSe/ZnS quantum dots (QDs) in GaN-based light-emitting diodes (LEDs) using the phosphor conversion efficiency (PCE) and LED junction temperature. In our simulation, the blue chip and CdSe/ZnS QDs temperature are similar because of their minimal thickness. Furthermore, to verify the effect of temperature on CdSe/ZnS QDs, we use continuous wave and pulsed current sources to measure the relationship between the temperature and relative PCE. Higher junction temperatures are observed with greater CdSe/ZnS QD volume in LEDs. This is attributed to the thermal conduction and nonradiative energy between CdSe/ZnS QDs and blue chip. Therefore, if thermal management is improved, CdSe/ZnS QDs are expected to be used as color converting material in LEDs.
THE RELATIONSHIP BETWEEN PERSONALITY TRAITS AND ONLINE SHOPPING MOTIVATIONS
(2010)
Huang, Jen-Hung
;
Yang, Yi-Chun
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管理科學系
;
Department of Management Science
In this study we investigated the relationship between personality traits and online shopping motivations by comparing Big Five model of personality (McCrae & Costa, 1987) and motivations for Internet shopping. Data were collected from 216 participants using a questionnaire. Regression analysis results indicated that openness was positively associated with adventure and idea motivation, and conscientiousness was positively associated with convenience motivation. Furthermore, extraversion was positively associated with sociality motivation, and neuroticism was positively related to lack of sociality motivation. Implications and further research directions are then discussed.
Tunable Light Emission from GaN-Based Photonic Crystal with Ultraviolet AlN/AlGaN Distributed Bragg Reflector
(2011-04-01)
Chen, Cheng-Chang
;
Chiu, Ching-Hsueh
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Yang, Yi-Chun
;
Shih, M. H.
;
Chen, Jun-Rong
In this paper, the characteristics of GaN-based two-dimensional (2D) photonic crystal bandedge coupling operation with an ultraviolet AlN/AlGaN distributed Bragg reflector (DBR) have been investigated and analyzed. The 25-pair AlN/Al(0.2)GaN(0.8) DBR shows a high reflectivity of 85% at 375nm with the stop-band width of 15nm. A strong light emission was observed from GaN photonic crystals within high reflectivity region of DBR. The emission wavelength can be also manipulated by varying the radius to lattice constant ratio. The photonic crystal bandedge mode was also characterized with three-dimensional plane-wave expansion (PWE) and finite-difference time-domain (FDTD) simulation. (C) 2011 The Japan Society of Applied Physics
Ultraviolet GaN-based microdisk laser with AlN/AlGaN distributed Bragg reflector
(2010-04-12)
Chen, Cheng-Chang
;
Shih, M. H.
;
Yang, Yi-Chun
;
Kuo, Hao-Chung
;
光電工程學系
We demonstrated a 4.7 mu m GaN-based microdisk laser with 25-pair AlN/AlGaN distributed Bragg reflector in ultraviolet range without undercut or deeply-etching procedures. The distributed Bragg reflector provides a high reflectivity of 85%, and selects lasing mode around 375 nm wavelength. Under optical pumping conditions, the lasing action was observed with a low threshold power density of 0.03 kW/cm(2). We also characterized the whispering gallery mode profiles of the microdisk with finite-different time-domain simulation.