Browsing by Issue Date, starting with "2018-05-14"

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Photodissociation of CF2ICF2I in solid para-hydrogen: infrared spectra of anti- and gauche-(C2F4I)-C-center dot radicals
(2018-05-14)
Haupa, Karolina Anna
;
Lim, Manho
;
Lee, Yuan-Pern
;
應用化學系
;
應用化學系分子科學碩博班
The photolysis of 1,2-diiodotetrafluoroethane (CF2ICF2I) has served as a prototypical system in ultrafast reaction dynamics. Even though the intermediates, anti-and gauche-iodotetrafluoroethyl ((C2F4I)-C-center dot) radicals, have been characterized with electron diffraction and X-ray diffraction, their infrared spectra are unreported. We report the formation and infrared identification of these radical intermediates upon ultraviolet photodissociation of CF2ICF2I in solid para-hydrogen (p-H-2) at 3.3 K. Lines at 1364.9/1358.5, 1283.2, 1177.1, 1162.2, 1126.8, 837.3, 658.0, 574.2, and 555.2 cm(-1) are assigned to anti-(C2F4I)-C-center dot, and lines at 1325.9, 1259.7, 1143.4, 1063.4, 921.0, and 765.3 cm(-1) to gauche-(C2F4I)-C-center dot. A secondary photodissociation leading to C2F4 was also observed. The assignments were derived according to behavior on secondary photolysis, comparison of the vibrational wavenumbers and the IR intensities of the observed lines with values predicted with the B3PW91/aug-cc-pVTZ-pp method. This spectral identification provides valuable information for future direct spectral probes of these important intermediates.
Threshold current temperature dependence of quantum-dot photonic crystal surface-emitting lasers with respect to gain-cavity detuning
(2018-05-14)
Hsu, Ming-Yang
;
Lin, Gray
;
Li, Zong-Lin
;
Pan, Po-Chou
;
電機學院
We investigate threshold current temperature dependence of electrically injected quantum-dot (QD) photonic crystal (PC) surface-emitting lasers (SELs) with respect to wavelength detuning between QD gain peak and PC cavity resonance. The lasing emissions cover wavelengths from 1283 nm to 1318 nm. Almost infinite characteristic temperature is realized at certain temperature range for PCSEL with large negative gain-cavity detuning. Moreover, band-edge lasing mode is identified in our "PC slab-on-substrate" structure, and its far-field distribution is characterized as doughnut-shaped beam with azimuthal polarization. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Using advertisement light-panel and CMOS image sensor with frequency-shift-keying for visible light communication
(2018-05-14)
Chow, Chi-Wai
;
Shiu, Ruei-Jie
;
Liu, Yen-Chun
;
Liao, Xin-Lan
;
Lin, Kun-Hsien
A frequency-shift-keying (FSK) visible light communication (VLC) system is proposed and demonstrated using advertisement light-panel as transmitter and mobile-phone image sensor as receiver. The developed application program (APP) in mobile-phone can retrieve the rolling shutter effect (RSE) pattern produced by the FSK VLC signal effectively. Here, we also define noise-ratio value (NRV) to evaluate the contrast of different advertisements displayed on the light-panel. Both mobile-phones under test can achieve success rate > 96% even when the transmission distance is up to 200 cm and the NRVs are low. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Crystal structure and magnetic properties of intermetallic semiconductor FeGa3 lightly doped by Co and Ni
(2018-05-15)
Likhanov, M. S.
;
Verchenko, V. Yu.
;
Nasonova, D. I.
;
Gippius, A. A.
;
Zhurenko, S. V.
We have explored the crystal structure and magnetic properties of two intermetallic solid solutions of the IrIn3 structure type. Although Fe0.95Co0.05Ga3 and Fe0.975Ni0.025Ga3 are isomorphous and possess exactly the same concentration of valence electrons, they display noticeable differences in their crystal structure associated with a different nature of the Fe-Co and Fe-Ni dumbbells. The former contains an odd number of electrons compared to an even number of the latter dumbbell. Responding to localized spins of the Fe-Co dumbbells, the Ga-69 NQR relaxation rate in Fe0.95Co0.05Ga3 is governed by temperature independent spin-lattice relaxation typical for diluted paramagnetic centers at low temperatures. In Fe0.975Ni0.025Ga3 with zero magnetic moment of the dumbbells the Ga-69 spin-lattice relaxation rate is strongly reduced and in-gap states in the energy gap show up as a broad maximum near 70 K. (C) 2018 Elsevier B.V. All rights reserved.
Temperature effect on the growth of Au-free InAs and InAs/GaSb heterostructure nanowires on Si substrate by MOCVD
(2018-05-15)
Kakkerla, Ramesh Kumar
;
Anandan, Deepak
;
Hsiao, Chih-Jen
;
Yu, Hung Wei
;
Singh, Sankalp Kumar
We demonstrate the growth of vertically aligned Au-free InAs and InAs/GaSb heterostructure nanowires on Si (1 1 1) substrate by Metal Organic Chemical Vapor Deposition (MOCVD). The effect of growth temperature on the morphology and growth rate of the InAs and InAs/GaSb heterostructure nanowires (NWs) is investigated. Control over diameter and length of the InAs NWs and the GaSb shell thickness was achieved by using growth temperature. As the GaSb growth temperature increase, GaSb radial growth rate increases due to the increase in alkyl decomposition at the substrate surface. Diffusivity of the adatoms increases as the GaSb growth temperature increase which results in tapered GaSb shell growth. Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) measurements revealed that the morphology and shell thickness can be tuned by the growth temperature. Electron microscopy also shows the formation of GaSb both in radial and axial directions outside the InAs NW core can be controlled by the growth temperature. This study demonstrates the control over InAs NWs growth and the GaSb shell thickness can be achieved through proper growth temperature control, such technique is essential for the growth of nanowire for future nano electronic devices, such as Tunnel FET. (C) 2018 Elsevier B.V. All rights reserved.
A least squares augmented immersed interface method for solving Navier-Stokes and Darcy coupling equations
(2018-05-15)
Li, Zhilin
;
Lai, Ming-Chih
;
Peng, Xiaofei
;
Zhang, Zhiyue
;
應用數學系
A new finite difference method based on Cartesian meshes and fast Poisson/Helmholtz solvers is proposed to solve the coupling of a fluid flow modeled by the incompressible Navier-Stokes equations and a porous media modeled by the Darcy's law. The finite difference discretization in time is based on the pressure Poisson equation formulation. At each time step, several augmented variables along the interface between the fluid flow and the porous media are introduced so that the coupled equations can be decoupled into several Poisson/Helmholtz equations with those augmented variables acting as jumps of the unknown solution and some directional derivatives. The augmented variables should be chosen so that the Beavers-Joseph-Saffman (BJS) or Beavers-Joseph (BJ)and other interface conditions are satisfied. It has been tested that a direct extension of the augmented idea in [27] does not work well when the fluid flow is modeled by the Navier-Stokes equations. One of the new ideas of this paper is to enforce the divergence free condition at the interface from the fluid side. In this way, the Schur complement matrix for the augmented variables is over-determined and the least squares solution is used for the coupling problem. The new augmented approach enables us to solve the Navier-Stokes and Darcy coupling efficiently with second order accurate velocity and pressure in the L-infinity norm for tested problems. The proposed new idea in enforcing the divergence free condition at the interface from the fluid side has also been utilized to solve the Stokes and Darcy coupling equations and shown to outperform the original method in [27]. In additional to the detailed accuracy check for the present method, some interesting numerical simulations for Navier-Stokes and Darcy coupling have been conducted in this paper as well. (C) 2018 Elsevier Ltd. All rights reserved.
Fully Integrated Photonic Millimeter-Wave Tracking Generators on the Heterogeneous III-V/Si Platform
(2018-05-15)
Chao, Rui-Lin
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Liang, Linjun
;
Shi, Jin-Wei
;
Komljenovic, Tin
;
Hulme, Jared
Fully integrated photonic microwave/millimeterwave (MMW) tracking generators, which include wavelength-tunable lasers, distributed feedback lasers, phase modulators, and high-speed photodiodes (PDs), are demonstrated on the heterogeneous integrated III-V-on-Si photonic platform. Two on-chip lasers are locked by an external optical phase-locked loop (OPLL), and the two-tone radio-frequency (RF) signals from the on-chip fast PDs can be photonically generated through the heterodyne-beating process between the wavelengthtunable laser and the OPLL output. Furthermore, the frequency spacing between such two-tone RF signals can be tracked by the oscillation frequency in the OPLL with a wide tunability (near dc to 10 GHz). Fast and truly continuous scanning of photo-generated MMW signals thus becomes feasible by simultaneously tuning the OPLL and the central wavelength of the tunable laser in the demonstrated photonic integrated circuit.
The roles of phosphate and tungstate species in surface acidities of TiO2-ZrO2 binary oxides - A comparison study
(2018-05-15)
Chaudhary, Manchal
;
Shen, Po-fan
;
Chang, Sue-min
;
環境工程研究所
;
Institute of Environmental Engineering
Porous tungstated and phosphated TiO2-ZrO2 (TZ) binary oxides with high and strong acidity were successfully prepared by means of sol-gel or impregnation approaches. In addition, the influences of the two types of modifiers on the microstructures and acidity were systematically examined, compared, and clarified. The TZ oxide derived from a surfactant-templating method exhibited a high surface area of 195 m(2)/g with a pore size of 6.3 nm. Moreover, it had a high acidity of 859 mu mol/g with a density of 4.4 mu mol/nm(2) because of defective surface. Phosphation significantly increased the acidity to 1547 mmol/g and showed the highest acid density of 6.7 mu mol/nm(2) at a surface P density of 22.7P/nm(2). On the other hand, tungstated compounds just showed the highest acidity of 972 mmol/g and the highest acid density of 4.8 mu mol/nm(2) at 4.7 W/nm(2). Compared to tungstate species, phosphate anions are more capable of promoting the acidity because they are able to distort the host network and inhibit elemental rearrangement. While Lewis acidity prevailed in the tungstated compounds, Bronsted acidity was dominant in the phosphated oxides. The W=O and P-OH groups were responsible for strong acidity in the modified compounds. Phosphated compounds formed strong Bronsted acid sites on the P-OH groups with a particular strength, and tungstation produced Lewis acid sites with a continuous strength on the metal ions adjacent to the tungstate moieties. Cyclic NH3 adsorption-desorption processes revealed that the active sites for NH3 adsorption were stable in both the tungstate and phosphate modified compounds, revealing that these solid acids are promising as the adsorbents for removal of base gases. (C) 2018 Elsevier B.V. All rights reserved.
Studying anti-oxidative properties of inclusion complexes of alpha-lipoic acid with gamma-cyclodextrin in single living fission yeast by confocal Raman microspectroscopy
(2018-05-15)
Noothalapati, Hemanth
;
Ikarashi, Ryo
;
Iwasaki, Keita
;
Nishida, Tatsuro
;
Kaino, Tomohiro
alpha-lipoic acid (ALA) is an essential cofactor for many enzyme complexes in aerobic metabolism, especially in mitochondria of eukaryotic cells where respiration takes place. It also has excellent anti-oxidative properties. The acid has two stereo-isomers, R- and S-lipoic acid (R-LA and S-LA), but only the R-LA has biological significance and is exclusively produced in our body. A mutant strain of fission yeast, Delta dpsl, cannot synthesize coenzyme Q10, which is essential during yeast respiration, leading to oxidative stress. Therefore, it shows growth delay in the minimal medium. We studied anti-oxidant properties of ALA in its free form and their inclusion complexes with gamma-cyclodextrin using this mutant yeast model. Both free forms R- and S-LA as well as 1:1 inclusion complexes with gamma-cyclodexhin recovered growth of Delta dps1 depending on the concentration and form. However, it has no effect on the growth of wild type fission yeast strain at all. Raman microspectroscopy was employed to understand the anti-oxidant property at the molecular level. A sensitive Raman band at 1602 cm(-1) was monitored with and without addition of ALAs. It was found that 0.5 mM and 1.0 mM concentrations of ALAs had similar effect in both free and inclusion forms. At 2.5 mM ALAs, free forms inhibited the growth while inclusion complexes helped in recovered. 5.0 mM ALA showed inhibitory effect irrespective of form. Our results suggest that the Raman band at 1602 cm(-1) is a good measure of oxidative stress in fission yeast. (C) 2018 Elsevier B.V. All rights reserved.
Distributed Bragg Reflectors as Broadband and Large-Area Platforms for Light-Coupling Enhancement in 2D Transition-Metal Dichalcogenides
(2018-05-16)
Chen, Yen-Chun
;
Yeh, Han
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Lee, Chien-Ju
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Chang, Wen-Hao
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電子物理學系
Two-dimensional (2D) semiconductors, particularly the direct-gap monolayer transition metal dichalcogenides (TMDs), are currently being developed for various atomically thin optoelectronic devices. However, practical applications are hindered by their low quantum efficiencies in light emissions and absorptions. While photonic cavities and metallic plasmonic structures can significantly enhance the light-matter interactions in TMDs, the narrow spectral resonance and the local hot spots considerably limit the applications when broadband and large area are required. Here, we demonstrate that a properly designed distributed Bragg reflector (DBR) can be an ideal platform for light-coupling enhancement in 2D TMDs. The main idea is based on engineering the amplitude and phase of optical reflection from the DBR to produce optimal substrate-induced interference. We show that the TMDs photoluminescence, Raman, and second harmonic generation signals of monolayer WSe2 can be enhanced by a factor of 26, 34, and 58, respectively. The proposed DBR substrates pave the way for developing a range of 2D optoelectronic devices for broadband and large-area applications.
SELECTIVE CHEMICAL BATH DEPOSITION OF IRIDIUM OXIDE ON THIN FILM FLEXIBLE SUBSTRATES
(2018-05-17)
LIU, Wentai
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CHANG, Chih-Wei
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WU, Pu-Wei
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WU, Chung-Yu
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CHEN, Pu-Chun
A flexible thin film metal oxide electrode fabrication methods and devices are provided and illustrated with thin film polyimide electrode formation and IrOx chemical bath deposition. Growth factors of the deposited film such as film thickness, deposition rate and quality of crystallites can be controlled by varying the solution pH, temperature and component concentrations of the bath. The methods allow for selective deposition of IrOx on a flexible substrate (e.g. polyimide electrode) where the IrOx will only coat onto an exposed metal area but not the entire device surface. This feature enables the bath process to coat the IrOx onto every individual electrode in one batch, and to ensure electrical isolation between channels. The ability to perform selective deposition, pads for external connections will not have IrOx coverage that would otherwise interfere with a soldering/bumping process.
Tunable Spectrum Selectivity for Multiphoton Absorption with Enhanced Visible Light Trapping in ZnO Nanorods
(2018-05-17)
Tan, Kok Hong
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Lim, Fang Sheng
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Toh, Alfred Zhen Yang
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Zheng, Xia-Xi
;
Dee, Chang Fu
Observation of visible light trapping in zinc oxide (ZnO) nanorods (NRs) correlated to the optical and photoelectrochemical properties is reported. In this study, ZnO NR diameter and c-axis length respond primarily at two different regions, UV and visible light, respectively. ZnO NR diameter exhibits UV absorption where large ZnO NR diameter area increases light absorption ability leading to high efficient electron-hole pair separation. On the other hand, ZnO NR c-axis length has a dominant effect in visible light resulting from a multiphoton absorption mechanism due to light reflection and trapping behavior in the free space between adjacent ZnO NRs. Furthermore, oxygen vacancies and defects in ZnO NRs are associated with the broad visible emission band of different energy levels also highlighting the possibility of the multiphoton absorption mechanism. It is demonstrated that the minimum average of ZnO NR c-axis length must satisfy the linear regression model of Z(p,min) = 6.31d to initiate the multiphoton absorption mechanism under visible light. This work indicates the broadening of absorption spectrum from UV to visible light region by incorporating a controllable diameter and c-axis length on vertically aligned ZnO NRs, which is important in optimizing the design and functionality of electronic devices based on light absorption mechanism.
Zebrafish VCAP1X2 regulates cardiac contractility and proliferation of cardiomyocytes and epicardial cells
(2018-05-18)
Hsieh, Fang-Chi
;
Lu, Yu-Fen
;
Liau, Ian
;
Chen, Chien-Chang
;
Cheng, Chao-Min
Sarcomeric signaling complexes are important to sustain proper sarcomere structure and function, however, the mechanisms underlying these processes are not fully elucidated. In a gene trap experiment, we found that vascular cell adhesion protein 1 isoform X2 (VCAP1X2) mutant embryos displayed a dilated cardiomyopathy phenotype, including reduced cardiac contractility, enlarged ventricular chamber and thinned ventricular compact layer. Cardiomyocyte and epicardial cell proliferation was decreased in the mutant heart ventricle, as was the expression of pAKT and pERK. Contractile dysfunction in the mutant was caused by sarcomeric disorganization, including sparse myofilament, blurred Z-disc, and decreased gene expression for sarcomere modulators (smyd1b, mypn and fhl2 alpha), sarcomeric proteins (myh6, myh7, vmhcl and tnnt2 alpha) and calcium regulators (ryr2b and slc8a1 alpha). Treatment of PI3K activator restored Z-disc alignment while injection of smyd1b mRNA restored Z-disc alignment, contractile function and cardiomyocyte proliferation in ventricles of VCAP1X2 mutant embryos. Furthermore, injection of VCAP1X2 variant mRNA rescued all phenotypes, so long as two cytosolic tyrosines were left intact. Our results reveal two tyrosine residues located in the VCAP1X2 cytoplasmic domain are essential to regulate cardiac contractility and the proliferation of ventricular cardiomyocytes and epicardial cells through modulating pAKT and pERK expression levels.
Single-fabrication-step Ge nanosphere/SiO2/SiGe heterostructures: a key enabler for realizing Ge MOS devices
(2018-05-18)
Liao, P. H.
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Peng, K. P.
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Lin, H. C.
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George, T.
;
Li, P. W.
We report channel and strain engineering of self-organized, gate-stacking heterostructures comprising Ge-nanosphere gate/SiO2/SiGe-channels. An exquisitely-controlled dynamic balance between the concentrations of oxygen, Si, and Ge interstitials was effectively exploited to simultaneously create these heterostructures in a single oxidation step. Process-controlled tunability of the channel length (5-95 nm diameters for the Ge-nanospheres), gate oxide thickness (2.5-4.8 nm), as well as crystal orientation, chemical composition and strain engineering of the SiGe-channel was achieved. Single-crystalline (100) Si1-xGex shells with Ge content as high as x = 0.85 and with a compressive strain of 3%, as well as (110) Si1-xGex shells with Ge content of x = 0.35 and corresponding compressive strain of 1.5% were achieved. For each crystal orientation, our high Ge-content, highly-stressed SiGe shells feature a high degree of crystallinity and thus, provide a core 'building block' required for the fabrication of Ge-based MOS devices.
彩虹起義　平權公投
(2018-05-20)
嚴銘浩
;
蔡亞融
;
Department of Communication and Technology
;
傳播與科技學系
【彩虹路上】專題

彩虹起義台灣行動大隊第一次公投說明會發起人中苗博雅、法律白話文王鼎棫之影音專訪。
失智照護新趨勢　為高齡化領航
(2018-05-20)
蕭巧昱
;
Department of Communication and Technology
;
傳播與科技學系
【遺忘芳華　丟失在回憶邊境的住民】專題

高齡化已是社會中不可擋的趨勢，伴隨著失智症盛行率增加的問題，本圖標將帶您一探失智照護的發展現況。
僑生大學生活　三大挑戰
(2018-05-20)
關子茵
;
Department of Communication and Technology
;
傳播與科技學系
【僑生面面觀】專題

僑生在大學的生活的如何？又會遇到什麼問題和抉擇呢？有些問題，不只僑生，就連本地學生也會遇到，該如何解決呢？
從業務員變玩具醫生──馮寶安
(2018-05-20)
楊巧柔
;
Department of Communication and Technology
;
傳播與科技學系
【二手玩具物流】專題

玩具也有醫生？玩具醫生馮寶安從圖書業務變為玩具救星！
林端容　突破創業者的窘境
(2018-05-20)
王貞懿
;
Department of Communication and Technology
;
傳播與科技學系
【破繭而出的年輕世代】專題

青年創業潮持續發燒，許多年輕人想自行創業，卻在許多地方遇到阻礙。創辦Changee及Simpany的林端容，根據創業者的需求提供相對應的協助。
彩虹辭典
(2018-05-20)
郭庭芸
;
Department of Communication and Technology
;
傳播與科技學系
【彩虹路上】專題

以互動網頁形式，收錄常見之性別議題相關名詞，用活潑有趣的方式協助讀者熟悉詞意，能夠更加輕鬆地閱讀本專題。