Browsing by Issue Date, starting with "2010-01-12"

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Morphologies of Self-Organizing Regioregular Conjugated Polymer/Fullerene Aggregates in Thin Film Solar Cells
(2010-01-12)
Chiu, Mao-Yuan
;
Jeng, U-Ser
;
Su, Ming-Shin
;
Wei, Kung-Hwa
;
材料科學與工程學系
In this study, We used simultaneous synchrotron grazing incidence X-ray scattering and diffraction to elucidate the overall morphologies of bulk heterojunction (BHJ) thin film (ca. 100 nm) solar cells containing phase-separated poly(3-hexylthiophene) (P3HT) and [6,6]-phertyl-C(61)-butyric acid methyl ester (PCBM) domains. Specifically, the dimensions and orientation of the P3HT crystallites and the sizes of the PCBM aggregates in BHJ thin films were determined. The appropriate PCBM aggregate size and density required for all optimum performance of the film in the photovoltaics device resulted in deteriorated ordering in the out-of-plane direction, but improved the in-plane packing of the P3HT lamellae. When the P3HT crystallites and PCBM aggregates had comparable domain sizes and number densities, the interpercolated networks for electron- and hole-transport were optimized in the film. This new understanding of the underlying mechanism of carrier mobility in BHJ thin films might be crucial in improving the efficiency of future solar cells.
Identification of the mokH Gene Encoding Transcription Factor for the Upregulation of Monacolin K Biosynthesis in Monascus pilosus
(2010-01-13)
Chen, Yi-Pei
;
Yuan, Gwo-Fang
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Hsieh, Sung-Yuan
;
Lin, Yu-Shan
;
Wang, Wei-Yi
Monacolin K is a secondary metabolite synthesized by polyketide synthases (PKS) from Monascus. The monacolin K biosynthetic gene cluster, mokA-mokI, has been characterized in Monascus pilosus. The mokH gene encoding Zn(II)2Cys6 binuclear DNA binding protein is assumed to be an activator for monacolin K production. In this study, the mokH gene was cloned and driven by the glyceraldehyde-3-phosphate dehydrogenase (gpd) promoter for overexpression in M. pilosus. The transformants containing an extra copy of the mokH gene were obtained and verified by PCR and Southern hybridization. The transcripts of mokH in the transformants were expressed significantly higher than those of the wild-type strain. The transformants were stably inherited through the next generation, as determined by observation of the enhanced green fluorescent protein (EGFP). The transformant T-mokH1 also showed a 1.7-fold higher production of monacolin K than the wild-type strain in a time course analysis. Analysis of the RT-PCR products demonstrated that the monacolin K biosynthetic genes in the transformant were expressed to a greater extent than those in the wildtype strain. These results indicated that mokH upregulated the transcription of monacolin K biosynthetic genes and increased monacolin K production.
Optical access system for dual service network
(2010-01-14)
Chen, Jyehong
;
Lin, Chun-Ting
;
Shih, Po-Tsung
;
Peng, Peng-Chun
;
Dai, Sheng-Peng
The present invention relates to an optical access system for dual service network, which mainly comprises an optical modulation device which is used to receive on-off keying (OOK) signal from cable network and radio frequency (RF) signal from wireless network, the optical modulation device then modulates the OOK signal and the RF signal to an optical signal and send out an output optical signal. Lastly, the output optical signal is being delivered to an optical receiving device through an optical fiber transmission channel, and the optical receiving device can access the OOK signal and RF signal from the output optical signal. In addition, the present invention does not require remote nodes (receiver side) to use any optical filter to discern on-off keying signal from cable network and RF signal from wireless network. The present invention can also apply to the field of wavelength-division multiplexing system.
Preparation and Spectral, Electrochemical, and Photovoltaic Properties of Acene-Modified Zinc Porphyrins
(2010-01-14)
Lin, Ching-Yao
;
Wang, Yu-Chien
;
Hsu, Shun-Ju
;
Lo, Chen-Fu
;
Diau, Eric Wei-Guang
A series of acene-modified zinc porphyrins (benzene to pentacene, denoted as LAC-1 to LAC-5) were prepared to study their absorption spectra, electrochemical properties, and photovoltaic properties. For the absorption spectral changes in THF, porphyrin B bands are red-shifted and broadened from 449 to 501 nm for LAC-I to LAC-3, showing the effect of additional pi-conjugation. In contrast, the B bands of LAC-4 and LAC-5 are blue-shifted. In addition, the tetracenyl group of LAC-4 gives rise to absorption bands in between B and Q bands. On the other hand, the Q bands of LAC-1 to LAC-5 are systematically broadened and red-shifted from 629 to 751 nm. By comparison, the absorption bands of LAC porphyrins on TiO(2) films are broadened and slightly shifted. Fluorescence emission maxima of LAC porphyrins in THF are also systematically red-shifted from LAC-1 to LAC-5. Cyclic voltammetry experiments in THF/TBAP show that the first reductions are systematically positive-shifted from -1.16 to -0.85 V vs SCE for LAC-1 to LAC-5, indicating the effect of increasing pi-conjugation. As for the performance of DSSCs using LAC porphyrins, the overall efficiency are LAC-1 (2.95%), LAC-2 (3.31%), LAC-3 (5.44%), LAC-4 (2.82%), and LAC-5 (0.10%). Overall efficiency of a LAC-3-sensitized solar cell is nearly twice of that of a LAC-1-sensitized solar cell and is about 81% overall efficiency of N719-sensitized solar cells under the same experimental conditions. The conversion efficiency of incident photons to current (IPCE) experiments shows that the broadened absorption bands of LAC-3 effectively minimizes the gap between B and Q bands, contributing to the improved DSSC performance. The very poor performance of LAC-5 is suggested to be caused by rapid nonradiative relaxation of the molecule in the singlet excited state.
Ab Initio Chemical Kinetic Study for Reactions of H Atoms with SiH4 and Si2H6: Comparison of Theory and Experiment
(2010-01-14)
Wu, S. Y.
;
Raghunath, P.
;
Wu, J. S.
;
Lin, M. C.
;
機械工程學系
The reactions of hydrogen atom with silane and disilane are relevant to the understanding of catalytic chemical vapor deposition (Cat-CVD) and plasma enhanced chemical vapor deposition (PECVD) processes. In the present study, these reactions have been investigated by means of A initio molecular-orbital and transition-state theory calculations. In both reactions, the most favorable pathway was found to be the H abstraction leading to the formation of SiH3 and Si2H5 products, with 5.1 and 4.0 kca/mol barriers, respectively. For H + Si2H6, another possible reaction pathway giving SiH3 + SiH4 may take place with two different mechanisms with 4.3 and 6.7 kcal/mol barriers for H-atom attacking side-way and end-on, respectively. To validate the calculated energies of the reactions, two isodesmic reactions, SiH3+CH4 -> SiH4+CH3 and Si2H5+C2H6 -> Si2H6+C2H5 were employed; the predicted heats of the formation for SiH3 (49.0 kcal/mol) and Si2H5 (58.6 kcal/mol) were found to agree well with the experimental data. Finally, rate constants for both H-abstraction reactions predicted in the range of 290-2500 K agree well with experimental data. The result also shows that H+Si2H6 producing H-2+Si2H5 is more favorable than SiH3+SiH4.
Ab Initio Chemical Kinetic Study for Reactions of H Atoms with SiH(4) and Si(2)H(6): Comparison of Theory and Experiment
(2010-01-14)
Wu, S. Y.
;
Raghunath, P.
;
Wu, J. S.
;
Lin, M. C.
;
機械工程學系
The reactions of hydrogen atom with silane and disilane are relevant to the understanding of catalytic chemical vapor deposition (Cat-CVD) and plasma enhanced chemical vapor deposition (PECVD) processes. In the present study, these reactions have been investigated by means of A initio molecular-orbital and transition-state theory calculations. In both reactions, the most favorable pathway was found to be the H abstraction leading to the formation of SiH(3) and Si(2)H(5) products, with 5.1 and 4.0 kca/mol barriers, respectively. For H + Si(2)H(6), another possible reaction pathway giving SiH(3) + SiH(4) may take place with two different mechanisms with 4.3 and 6.7 kcal/mol barriers for H-atom attacking side-way and end-on, respectively. To validate the calculated energies of the reactions, two isodesmic reactions, SiH(3)+CH(4)-> SiH(4)+CH(3) and Si(2)H(5)+C(2)H(6)-> Si(2)H(6)+C(2)H(5) were employed; the predicted heats of the formation for SiH(3) (49.0 kcal/mol) and Si(2)H(5) (58.6 kcal/mol) were found to agree well with the experimental data. Finally, rate constants for both H-abstraction reactions predicted in the range of 290-2500 K agree well with experimental data. The result also shows that H+Si(2)H(6) producing H(2)+Si(2)H(5) is more favorable than SiH(3)+SiH(4).
Electron Field Emission Properties of Nanomaterials on Rough Silicon Rods
(2010-01-14)
Wu, Hung-Chi
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Tsai, Tsung-Yen
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Chu, Fu-Hsuan
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Tai, Nyan-Hwa
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Lin, Heh-Nan
Highly porous, individually separated, and vertically aligned rough silicon rods (r-SiRs) were formed via a modified electroless metal deposition (EMD) approach. Despite inheriting the length of crowded silicon nanowires (NWs) obtained by the conventionally adopted EMD method, the r-SiRs are distributed sparsely, subsequently forming an excellent field emitter substrate. The electron field emission (EFE) of carbon nanotubes (CNTs) grown on r-SiRs can be turned on at (E(0))(CNTs/r-SiRs) = 2.3 V/mu m, yielding a high EFE current density, (J(c))(CNTs/r-SiR) = 3.7 mA/cm(2) in an applied field of 5.1 V/mu m, Additionally, a cactuslike structure consisting of zinc oxide NWs on r-SiRs can be turned on at 2.9 V/mu m. The absence of a high-temperature or expensive photolithographic process makes r-SiRs a promising alternative as a silicon base field emitter substrate.
Optical modulating device with frequency multiplying technique for electrical signals
(2010-01-14)
Chen, Jyehong
;
Lin, Chun-Ting
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Dai, Sheng-Peng
;
Peng, Peng-Chun
;
Shih, Po-Tsung
The present invention relates to an optical modulating device with frequency multiplying technique for electrical signals, which primary comprises a mixer, which generates a mixed data signal from a first electrical signal and a second electrical signal. The mixed data signal is then received by a first phase shift device to have its phase shifted and becomes a first shifted signal. The first electrical signal is further received by a second phase shift device to have its phase shifted and becomes a second shifted signal. The present invention further comprises an integrated electro-optic modulator (Mach-Zehnder modulator), which is used to receive an input optical signal, the mixed data signal, the first shifted signal, the second shifted signal and the first electrical signal mentioned above, the integrated electro-optic modulator will then modulates the input optical signal into a frequency multiplying output optical signal that carries the first electrical signal and the second electrical signal. The present invention can carry and transmit amplitude shift keying signals and vector modulation signals, thereby provides a more advanced optical communication transmission service.
Water permeation analysis on gas diffusion layers of proton exchange membrane fuel cells for Teflon-coating annotation
(2010-01-15)
Chou, Yen-I
;
Siao, Zih-Yuan
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Chen, Yu-Feng
;
Sung, Lung-Yu
;
Yang, Wen-Mei
This study presents an analysis of water permeation of a polytetrafluoroethylene (PTFE)-coated gas diffusion layer (GDL) to determine the influence of hydrophobic treatment on the GDL for diagnosis of water flooding. It is found that the behaviour of water drainage is controlled by the pore configuration instead of the hydrophobicity in GDL. Better water drainage is achieved by the action of the Teflon coating in modulating the GDL pore configuration to give both a larger average pore size and a wider distribution of pore size. The results show that water penetration through the GDL must overcome a threshold surface tension defined by the largest pore range. A 30 wt.% PTFE coating of a GDL is shown to generate a satisfactory pore configuration, explaining the improved cell polarization performance with a lower driven pressure (similar to 1.91 kPa) and a higher rate of water drainage. (C) 2009 Elsevier B. V. All rights reserved.
Generational Differences in the Prevalence of Hearing Impairment in Older Adults
(2010-01-15)
Zhan, Weihai
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Cruickshanks, Karen J.
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Klein, Barbara E. K.
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Klein, Ronald
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Huang, Guan-Hua
There were significant changes in health and lifestyle throughout the 20th century which may have changed temporal patterns of hearing impairment in adults. In this study, the authors aimed to assess the effect of birth cohort on the prevalence of hearing impairment in an adult population aged 45-94 years, using data collected between 1993 and 2008 from 3 cycles of the Epidemiology of Hearing Loss Study (n = 3,753; ages 48-92 years at baseline) and a sample of participants from the Beaver Dam Offspring Study (n = 2,173; ages >= 45 years). Hearing impairment was defined as a pure-tone average of thresholds at 0.5, 1, 2, and 4 kHz greater than 25-dB HL [hearing level]. Descriptive analysis, generalized additive models, and alternating logistic regression models were used to examine the birth cohort effect. Controlling for age, with every 5-year increase in birth year, the odds of having hearing impairment were 13% lower in men (odds ratio = 0.87, 95% confidence interval: 0.83, 0.92) and 6% lower in women (odds ratio = 0.94, 95% confidence interval: 0.89, 0.98). These results suggest that 1) older adults may be retaining good hearing longer than previous generations and 2) modifiable factors contribute to hearing impairment in adults.
Photonic Impulse-Radio Wireless Link at W-Band Using a Near-Ballistic Uni-Traveling-Carrier Photodiode-Based Photonic Transmitter-Mixer
(2010-01-15)
Kuo, F. -M.
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Li, Yu-Tai
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Shi, J. -W.
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Wang, Shao-Ning
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Chen, Nan-Wei
A W-band photonic transmitter-mixer, constructed by integrating a planar quasi-yagi radiator for feeding the WR-10 waveguide-based horn antenna and a near-ballistic uni-travelingcarrier photodiode, is used with a mode-locked fiber laser to obtain 2.5-Gb/s impulse-radio (IR) wireless data transmission at around a center frequency of 100 GHz. The bias-modulation technique provides less jitter and a longer maximum transmission distance compared with the technique of modulating the optical pulse train using an electrooptics modulator. Using the bias-modulation technique, we achieve a 2.5-Gb/s IR wireless data transmission.
Photoluminescence studies of InAs/GaAs quantum dots covered by InGaAs layers
(2010-01-15)
Shu, G. W.
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Wang, J. S.
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Shen, J. L.
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Hsiao, R. S.
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Chen, J. F.
Photoluminescence (PL), PL excitation (PLE), and time-resolved PL were used to study effects of InGaAs layers on the optical properties of InAs/GaAs quantum dots (QDs). A rich fine structure in the excited states of confined excitons (up to n = 4 quantum states) was observed, providing useful information to study the quantum states in the InAs/GaAs QDs. A significant redshift of the PL peak energy for the QDs covered by InGaAs layers was observed, attributing to the decrease of the QD strain and the lowing of the quantum confinement. (C) 2009 Elsevier B.V. All rights reserved.
Synthesis, Electroluminescence, and Photovoltaic Cells of New Vinylene-Copolymers with 4-(Anthracene-10-yl)-2,6-Diphenylpyridine Segments
(2010-01-15)
Mikroyannidis, John A.
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Vellis, Panagiotis D.
;
Yang, Sheng-Hsiung
;
Hsu, Chain-Shu
;
應用化學系
Three new soluble vinylene-copolymers F, C, and P that contain 4-(anthracene-10-y1)-2,6-diphenylpyridine as common segment and fluorene, carbazole, or phenylene, respectively, as alternating segment were prepared by Heck coupling. The glass transition temperature was high for F and C (11.0 and 117 degrees C), whereas was lower than 25 degrees C for P. The polymers were stable up to similar to 300 degrees C. They emitted blue-green light with maximum located at wavelength of 456-550 nm, which was of the order F < C < P. The photoluminescence quantum efficiency in THF solution was similar to 30% for F and P and only 5% for C. All three copolymers were used as active layers for polymer light emitting diodes (PLEDs) and organic photovoltaic cells. The double PLEDs with configuration of indium-tin oxide (ITO)/poly(ethylenedioxythiophene (PEDOT) : poly(styrenesulfonate)(PSS) /Copolymer F, C, or P/TPBI(1,3,5-tris(2-N-phenylbenzimidazolyl)benzene)/Ca/Al were fabricated. Copolymer P emitted green light with maximum brightness of 28 cd/m(2) and a current yield of 0.85 cd/A. Organic photovoltaics with the configuration of ITO/PEDOT : PSS/Copolymer and [6,6]-phenyl-C61-butyric acid methyl ester blend (1 : 1)/Ca/Al were also fabricated. Copolymer P showed the highest power conversion efficiency of 0.034%. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 731-739, 2010
Determination of dissociative fragment-adsorbate interaction energy during chemisorption of the diatomic molecule HCl on Si(100)
(2010-01-15)
Hsieh, Ming-Feng
;
Cheng, Jen-Yin
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Yang, Jenq-Cheng
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Lin, Deng-Sung
;
Morgenstern, Karina
This study investigates the surface chemistry and the ordering characteristics of coadsorbed hydrogen and chlorine atoms, generated by the exposure of the Si(100) surface to gas-phase HCl molecules at various substrate temperatures, by scanning tunneling microscopy (STM), core-level photoemission spectroscopy, and Monte Carlo simulation. Experimental results show that saturation exposure to HCl causes all surface dangling bonds to be terminated by the two fragments H and Cl atoms and that the number of H-terminated sites exceeds that of Cl-terminated ones by more than 10%. This finding suggests that, in addition to the dominant dissociative chemisorption, atomically selective chemisorption or atom abstraction occurs. STM images reveal that some Cl-terminated sites form patches with a local 2 x 2 structure at 110 K and that the degree of ordering is reduced as the substrate temperature increases. Results of Monte Carlo simulations demonstrate the importance of including dissociative fragment-adsorbate interactions during the random adsorption of diatomic molecules. Comparing the correlations between Cl-terminated sites identified from STM images and those predicted by simulation reveals two effective interaction energies of 8.5 +/- 2.0 and 3.5 +/- 2.0 meV between a dissociative fragment Cl atom and a nearest neighboring Cl adsorbates in the same dimer row and in the adjacent row, respectively.
Field emission characteristics of carbon nanotubes post-treated with high-density Ar plasma
(2010-01-15)
Wang, Wen-Pin
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Wen, Hua-Chiang
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Jian, Sheng-Rui
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Cheng, Huy-Zu
;
Jang, Jason Shian-Ching
The field emission characteristics of carbon nanotubes (CNTs) grown by thermal chemical vapor deposition (CVD) and subsequently surface treated by high-density Ar plasma in an inductively coupled plasma reactive ion etching (ICP-RIE) with the various plasma powers were measured. Results indicate that, after treated by Ar plasma with power between 250 and 500 W, the emission current density of the CNTs is enhanced by nearly two orders of magnitude (increased from 0.65 to 48 mA/cm(2)) as compared to that of the as-grown ones. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to investigate the structural features relevant to the modified field emission properties of CNTs. The SEM images of CNTs subjected to a 500 W Ar plasma treatment exhibit obvious damages to the CNTs. Nevertheless, the turn-on fields decreased from 3.6 to 2.2V/mu m, indicating a remarkable field emission enhancement. Our results further suggest that the primary effect of Ar plasma treatment might be to modify the geometrical structures of the local emission region in CNTs. In any case, the Ar plasma treatment appears to be an efficient method to enhance the site density for electron emission and, hence markedly improving the electric characteristics of the CNTs. (C) 2009 Elsevier B.V. All rights reserved.
Seasonal fouling on seawater desalination RO membrane
(2010-01-15)
Yang, Hui Ling
;
Huang, Chihpin
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Lin, Justin Chun-Te
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環境工程研究所
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Institute of Environmental Engineering
A pilot study has been performed to investigate the seasonal characteristic of seawater reverse osmosis (RO) membrane fouling. Two batches of experiment during summer and winter were both performed 18 days to provide a clear picture on microbial population variability. The feed water of the pilot from seawater desalination plant has significant difference in temperature and silica content between the two seasons. In our experiments, scaling and biofouling are more serious in summer. And the permeate flux decline is closely related to the rise in microbial population, and it was dominated by cell multiplication rather than adhesion. In addition, the summer cell multiplication is much more abundant. Moreover, the extracellular polymeric substance (EPS) feature intensity detected by Fourier-transform infrared spectroscopy was also stronger in summer. The abundant EPS was one of the major reasons to cause the inorganic matter adsorption. Si, Al, Fe, Ca and Mg were found as the major inorganic foulants deposited on the Ro membranes. Silica and calcium in summer appeared obvious higher amounts than that in winter, which indicated that they should be affected by microbial action directly or indirectly more than other elements. In summary, there exists a seasonal effect on membrane scaling and fouling, and scaling is associated with biofouling in some degree. Further researches could be focus on actual association between microbial action and inorganic fouling. (C) 2009 Elsevier B.V. All rights reserved.
Inherently Chiral Biscalix[4]arenes: Design and Syntheses
(2010-01-15)
Luo, Jun
;
Shen, Li-Ching
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Chung, Wen-Sheng
;
應用化學系
;
Department of Applied Chemistry
Inherently chiral biscalix[4]arenes have been designed and synthesized by covalently assembling two calix[4]arene building blocks in a 1,3-position linking with 1,2-position pattern at the lower rims via two triethylene glycol bridges
Effect of microstructure on the nanomechanical properties of Zn1-xCdxSe alloys
(2010-01-15)
Wen, Hua-Chiang
;
Yang, Chu-Shou
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Chou, Wu-Ching
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電子物理學系
;
Department of Electrophysics
We present a study of the nanoindentation behavior of Zn1-xCdxSe epilayers grown using molecular beam epitaxy; the surface roughness, microstructure, and crystallinity were analyzed using atomic force microscopy, cross-sectional transmission electron microscopy, and X-ray diffraction; the hardness H and elastic modulus E were studied using nanoindentation techniques. We found that these highly crystalline materials possessed no stacking faults or twins in their microstructures. We observed a very marked increase in the value of H and a significant decrease in the value of E upon increasing the concentration of Cd, presumably because of an increase in the stiffness of the CdSe bond relative to that of the ZnSe bond. We observed a corresponding shrinkage of the contact-induced damage area for those films having a small grain size and a higher value of H. It appears that resistance against contact-induced damage requires a higher Cd concentration. (C) 2009 Elsevier B.V. All rights reserved.
Characteristics of soluble microbial products in membrane bioreactor and its effect on membrane fouling
(2010-01-15)
Pan, Jill Ruhsing
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Su, Yuchun
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Huang, Chihpin
;
環境工程研究所
;
生物科技學系
In this study, the accumulation and characteristics of soluble microbial products (SMP) in the mixed liquor and the effluent of the membrane bioreactor (MBR) were measured and compared. It was found that the concentration of SMP decreased when the SRT was increased from 10 days to 30 days, and then stabilized as SRT was increased to 60 days. The molecular weight (MW) distributions of SMP indicated that the SMP of larger MW (> 30 kDa) was the most abundant fraction in the MBR. The similar MW distributions of SMP in the mixed liquor and effluent implied that membrane fouling due to SMP in the initial slow fouling stage was not due to size sieving. After the MBR was operated for a period of time, only the SMP of relatively large MW (> 30 kDa) was detected in the mixed liquor. The result indicated that size sieving of SMP occurred only after a cake layer was formed on the membrane surface although the effect was not significant and only worked on larger molecules. The accumulation of hydrophilic components of SMP in the mixed liquor of the bioreactor suggested that the hydrophilic fraction (in carbohydrates) could be the major cause for membrane fouling. (C) 2009 Elsevier B.V. All rights reserved.
Ballistic transport in graphene beyond linear response
(2010-01-15)
Rosenstein, B.
;
Lewkowicz, M.
;
Kao, H. C.
;
Korniyenko, Y.
;
電子物理學系
The process of coherent creation of particle-hole excitations by an electric field in graphene is quantitatively described beyond linear response. We calculate the evolution of current density, number of pairs and energy in ballistic regime for electric field E using the tight-binding model. While for ballistic flight times smaller than t(nl)proportional to E(-1/2) current is linear in E and independent of time, for larger ballistic times the current increases after t(nl) as J proportional to E(3/2)t and finally at yet larger times (t > t(B) proportional to E(-1)) Bloch oscillations set in. It is shown that the number of pairs follows the 2D generalization of the Schwinger's creation rate n proportional to E(3/2) only on certain time segments with a prefactor different from that obtained using the asymptotic formula.