Browsing by Issue Date, starting with "2016-02-02"

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Strain-Mediated Inverse Photoresistivity in SrRuO3/La0.7Sr0.3MnO3 Superlattices
(2016-02-02)
Liu, Heng-Jui
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Wei, Tzu-Chiao
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Zhu, Yuan-Min
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Liu, Rui-Rui
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Tzeng, Wen-Yen
In the pursuit of novel functionalities by utilizing the lattice degree of freedom in complex oxide heterostructure, the control mechanism through direct strain manipulation across the interfaces is still under development, especially with various stimuli, such as electric field, magnetic field, light, etc. In this study, the superlattices consisting of colossal-magnetoresistive manganites La0.7Sr0.3MnO3 (LSMO) and photostrictive SrRuO3 (SRO) have been designed to investigate the light-dependent controllability of lattice order in the corresponding functionalities and rich interface physics. Two substrates, SrTiO3 (STO) and LaAlO3 (LAO), have been employed to provide the different strain environments to the superlattice system, in which the LSMO sublayers exhibit different orbital occupations. Subsequently, by introducing light, we can modulate the strain state and orbital preference of LSMO sublayers through light-induced expansion of SRO sublayers, leading to surprisingly opposite changes in photoresistivity. The observed photoresistivity decreases in the superlattice grown on STO substrate while increases in the superlattice grown on LAO substrate under light illumination. This work has presented a model system that demonstrates the manipulation of orbital-lattice coupling and the resultant functionalities in artificial oxide superlattices via light stimulus.
Crossover from polariton lasing to exciton lasing in a strongly coupled ZnO microcavity
(2016-02-03)
Lai, Ying-Yu
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Chou, Yu-Hsun
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Lan, Yu-Pin
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Lu, Tien-Chang
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Wang, Shing-Chung
Unlike conventional photon lasing, in which the threshold is limited by the population inversion of the electron-hole plasma, the exciton lasing generated by exciton-exciton scattering and the polariton lasing generated by dynamical condensates have received considerable attention in recent years because of the sub-Mott density and low-threshold operation. This paper presents a novel approach to generate both exciton and polariton lasing in a strongly coupled microcavity (MC) and determine the critical driving requirements for simultaneously triggering these two lasing operation in temperature <140 K and large negative polariton-exciton offset (<-133 meV) conditions. In addition, the corresponding lasing behaviors, such as threshold energy, linewidth, phase diagram, and angular dispersion are verified. The results afford a basis from which to understand the complicated lasing mechanisms in strongly coupled MCs and verify a new method with which to trigger dual laser emission based on exciton and polariton.
Anomalous Electronic Anisotropy Triggered by Ferroelastic Coupling in Multiferroic Heterostructures
(2016-02-03)
Ju, Changcheng
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Yang, Jan-Chi
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Luo, Cheng
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Shafer, Padraic
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Liu, Heng-Jui
Geometrical spin manipulation in Dirac flakes
(2016-02-03)
Kleftogiannis, Ioannis
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Amanatidis, Ilias
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電子物理學系
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Department of Electrophysics
We investigate numerically the spin properties of electrons in flakes made of materials described by the Dirac equation, in the presence of intrinsic spin-orbit coupling (SOC). We show that electrons flowing along the borders of flakes via edge states become helically spin-polarized for strong SOC, for materials with and without a gap at the Fermi energy, corresponding to the massive and massless Dirac equation respectively. The helically spin-polarized electrons create spin-resolved transport, controlled by the flake\'s geometry in a multi-terminal device setup. A simple analytical model containing the basic ingredients of the problem is introduced to get an insight into the helical mechanism, along with our numerical results which are based on an effective tight-binding model.
Heat transfer enhancement of an impinging synthetic air jet using diffusion-shaped orifice
(2016-02-05)
Liu, Yao-Hsien
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Chang, Tsung-Han
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Wang, Chi-Chuan
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機械工程學系
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Department of Mechanical Engineering
Impingement heat transfer from a synthetic air jet through a diffusion-shaped orifice was investigated in this study. The effect of the opening angle (60 degrees and 90 degrees), orifice thickness (1-3 mm), and driven frequencies (400-800 Hz) were examined. Hot-wire anemometry was used to measure the instantaneous and average flow velocities ejected from the jet holes. At a small jet-to-surface spacing, synthetic jets from a diffusion-shaped orifice produced higher heat transfer than that from a round orifice. The highest heat transfer enhancement from using a diffusion-shaped orifice was approximately 30% compared with the round orifice at an opening angle of 60 degrees. The diffusion-shaped orifice achieved the highest area averaged heat transfer coefficient and Nusslet number of 80 W/m(2).K and 8.9, respectively. When the opening angle increased to 90 degrees, heat transfer enhancement was degraded because of increased flow circulation and reduced ejection flow velocity. The effect of orifice configuration on the heat transfer diminished as the jet-to-surface spacing increased. (C) 2015 Elsevier Ltd. All rights reserved.
Synthesis and Molecular Properties of Two Isomeric Dialkylated Tetrathienonaphthalenes
(2016-02-05)
Chang, Shao-Ling
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Lu, Chih-Wen
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Lai, Yu-Ying
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Hsu, Jhih-Yang
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Cheng, Yen-Ju
Isomeric 2,8-distannyl 5,11-didodecyl alpha/beta-TTN (1, tetrathienonaphthalene = TTN) and 2,8-didodecyl 5,11-distannyl alpha beta-TTN (2) have been designed and successfully synthesized. The naphthalene core structures in alpha beta-TTNs were constructed by a systematic protocol using PtCl2-catalyzed cyclization followed by oxidative Scholl annulation in good yields. Compared to the one-dimensional naphthodithiophene derivatives, the two-dimensional alpha beta-TTN molecules showed good solubility, extended conjugation, strong absorptivity, and highly coplanar structures. Compounds 1 and 2 were polymerized with a 5,5\'-dibromo-2,2\'-bithiophene-based monomer to afford 2,8-alpha beta-PTTNTT and 5,11-alpha beta-PTTNTT copolymers. 2,8-alpha beta-PTTNTT with the alpha-aNDT moiety in the main chain exhibited a higher hole mobility of 1.26 X 10(-2) cm(2) V-1 s(-1).
Excited-state localization and energy transfer in pyrene core dendrimers with fluorene/carbazole as the dendrons and acetylene as the linkages
(2016-02-07)
Yan, Linyin
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Wan, Yan
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Xia, Andong
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Lin, Sheng Hien
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Huang, Ran
A multi-leveled theoretical investigation combining TD-DFT (B3LYP and CAM-B3LYP) methods and a semi-empirical method was conducted to determine the structure-related spectral properties of T-series dendrimers composed of nearly hundreds of atoms, based on a proposed molecular model. Both one-and two-photon absorption spectra of the dendrimer molecules were well reproduced. The "antenna effect" in the dendrimers molecule was theoretically studied. The process of excitation energy localization from chromophores in the branches to the pyrene core before the fluorescence emission was visualized using contours of the charge different density (CDD) between the electronic states. Conclusions based on the theoretical model were drawn about the observed photophysical properties of T-series dendrimers as follows: (a) increasing the generation of a branch would enhance the absorption of photons with a wavelength below 430 nm; (b) enlarging the conjugation of branches would enhance the coupling among the chromophores and would lower the excitation energy; (c) the existence of inter-molecular coupling among the "antenna" chromophores in conjugated branches and the pyrene core would significantly promote two-photon absorption.
The impact of a conglomerate merger on its vendors and rivals - a case study of Google\'s acquisition of Motorola
(2016-02-07)
Chiu, Junmao
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Chung, Huimin
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Yang, Yi-Ning
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資訊管理與財務金融系註：原資管所+財金所
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Department of Information Management and Finance
This study explores the valuation effects of the conglomerate merger on an acquiring firm and its stakeholders. We examine Google\'s acquisition of Motorola and the impact that it had on Google\'s vendors and rivals. The empirical results suggest that the announcement of this deal led to positive market reaction among Android\'s vendors, primarily due to Google\'s ability to use Motorola\'s extensive patent portfolio to help protect Android\'s vendors from a potential patent infringement war in the future. Our results also find that when the Open Handset Alliance members obtain help from Motorola\'s patents or get new technology, an increase in shareholder wealth among Android\'s vendors and a decrease in shareholder wealth among Android\'s rivals are likely to occur.
Photonic crystal micropost as a microarray platform
(2016-02-08)
Chang, Chih-Wei
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Huang, Cheng-Sheng
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機械工程學系
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Department of Mechanical Engineering
This study demonstrates a photonic crystal micropost (PCMP) substrate for microarray applications. The substrate comprises an array of circular MPs with a PC on top of these MPs. This substrate enables biomolecule-containing droplets to form a composite contact upon deposition, thus allowing biomolecules to be attached on only the MPs, forming spots. When the device (PC) is excited on resonance, the electric field intensity is enhanced on only the top surface of the MPs. This enables the fluorescence intensities to be enhanced up to 5.50x; principally, this enhancement does not engender an increase in the background (intensity outside MP or spots) and noise intensities. The PCMP substrate enhances the spot intensity and minimizes the background intensity, enabling the detection of lower concentration analytes. (C) 2016 Optical Society of America
High temperature creep properties of directionally solidified CM-247LC Ni-based superalloy
(2016-02-08)
Chiou, Mau-Sheng
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Jian, Sheng-Rui
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Yeh, An-Chou
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Kuo, Chen-Ming
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Juang, Jenh-Yih
This study explores the effects of cooling rate after solution heat treatment on the high temperature/low stress (982 degrees C/200 MPa) creep properties of CM-247LC Nickel base superalloy. Cooling rate was controlled by blowing argon gas, air cooling, and furnace cooling, which, in turn, gave rise to corresponding cooling rates (from 1260 degrees C to 800 degrees C) of 18.7, 7.4, and 0.19 degrees C/s, respectively. The results indicated that higher cooling rate from the solution heat treatment temperature led to finer gamma\' precipitates and much improved tertiary creep as well as rupture life time in high-temperature creep test. The microstructural analyses using both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that finer gamma\' precipitates and narrower gamma channel width could result in denser rafting structure which might have hindered the climb of dislocations across the precipitates rafts. (C) 2015 Elsevier B.V. All rights reserved.
Comparison of thresholding schemes for visible light communication using mobile-phone image sensor
(2016-02-08)
Liu, Yang
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Chow, Chi-Wai
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Liang, Kevin
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Chen, Hung-Yu
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Hsu, Chin-Wei
Based on the rolling shutter effect of the complementary metal-oxide-semiconductor (CMOS) image sensor, bright and dark fringes can be observed in each received frame. By demodulating the bright and dark fringes, the visible light communication (VLC) data logic can be retrieved. However, demodulating the bright and dark fringes is challenging as there is a high data fluctuation and large extinction ratio (ER) variation in each frame due. Hence proper thresholding scheme is needed. In this work, we propose and compare experimentally three thresholding schemes; including third-order polynomial curve fitting, iterative scheme and quick adaptive scheme. The evaluation of these three thresholding schemes is performed. (C) 2016 Optical Society of America
Desorption of Polycyclic Aromatic Hydrocarbons on Mesoporous Sorbents: Thermogravimetric Experiments and Kinetics Study
(2016-02-10)
Li, Ziyi
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Liu, Yingshu
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Yang, Xiong
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Xing, Yi
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Tsa, Chuenjinn
The desorption performances of naphthalene and pyrene on mesoporous MCM-41, SBA-15, and CMK-3 sorbents are studied on the basis of temperature-programmed desorption experiments over the temperature range of 350-800 K at different heating rates. The kinetic parameters for each sorbate sorbent pair are determined with combined model-fitting methods. The data for naphthalene and pyrene are best fitted with the same kinetic models on MCM-41 (with 1D mesopore channels), in contrast to those on SBA-15 and CMK-3, which have micropore mesopore structures, leading to different desorption mechanisms for these two sorbates. SBA-15 with interconnectivity between adjacent mesopores not only shows high sorption capacities but also offers diffusion advantages in desorption, which contributes to the order of the degree of ease in desorption: SBA-15 > MCM-41 > CMK-3. CMK-3, with higher microporosity and hydrophobicity, shows stronger binding with the adsorbates while still benefiting in pyrene desorption from the consecutive mesoporosity.
Efficiency balance of a light guide plate with microstructures for a see-through head-mounted display
(2016-02-10)
Zhao, Kai-Wei
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Pan, Jui-Wen
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光電系統研究所
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照明與能源光電研究所
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生醫電子轉譯研究中心
The efficiency balance phenomenon for see-through head-mounted displays with different microstructure conditions can be found both theoretically and using optical simulation software. A simple mathematical calculation is used to determine the relationship between the real image (see-through function) energy and the virtual image energy. The simulation is based on factors taken from previous research studies. It is found that the balance value of the optical efficiency remains almost constant (66.63% to 67.38%) under different microstructure conditions. In addition, suitable conditions for the microstructures in see-through head-mounted displays for daily applications can be predicted.
Influence of Phenylethynylene of Push-Pull Zinc Porphyrins on the Photovoltaic Performance
(2016-02-10)
Chou, Hsien-Hsin
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Reddy, Kamani Sudhir K.
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Wu, Hui-Ping
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Guo, Bo-Cheng
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Lee, Hsuan-Wei
A series of zinc porphyrin dyes YD22-YD28 were synthesized and used for dye-sensitized solar cells. Dyes YD26-YD28 consist of zinc porphyrin (ZnP) as core unit, arylamine (Am) as electron-donating group, and p-ethynylbenzoic add (EBA) as an electron-withdrawing/-anchoring group. The dyes YD22-YD25 contain additional phenylethynylene group (PE) bridged between Am and ZnP units. The influence of the PE unit on molecular properties as well as photovoltaic performances were investigated via photophysical and electrochemical studies and density functional calculations. With the insertion of PE unit, the dyes YD22-YD25 possess better light-harvesting properties in terms of significantly red-shifted Q-band absorption. The conversion efficiencies for dyes YD22-YD25 are better than those of dyes YD26-YD28 owing to larger J(SC) output. Natural transition orbitals and Mulliken charge analysis were used to analyze the electron injection efficiency for porphyrin dyes upon time-dependent DFT calculations. The results indicated that insertion of additional PE unit is beneficial to higher J(SC) by means of improved light-harvesting property due to broadened and red-shifted absorption.
Evaluating overall quality of graph visualizations based on aesthetics aggregation
(2016-02-10)
Huang, Weidong
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Huang, Mao Lin
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Lin, Chun-Cheng
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工業工程與管理學系
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Department of Industrial Engineering and Management
Aesthetics are often used to measure the layout quality of graph drawings and it is commonly accepted that drawings with good layout are effective in conveying the embedded data information to end users. However, existing aesthetic criteria are useful only in judging the extents to which a drawing conforms to specific drawing rules. They have limitations in evaluating overall quality. Currently graph visualizations are mainly evaluated based on personal judgments and user studies for their overall quality. Personal judgments are not reliable while user studies can be costly to run. Therefore, there is a need for a direct measure of overall quality. In an attempt to meet this need, we propose a measurement that measures overall quality based on individual aesthetics and gives a single numerical score. We present a user study that validates this measure by demonstrating its sensibility in detecting quality changes and its capacity in predicting the performance of human graph comprehension. The implications of our proposed measure for future research are discussed. (C) 2015 Elsevier Inc. All rights reserved.
Gate-Stack Engineering for Self-Organized Ge-dot/SiO2/SiGe-Shell MOS Capacitors
(2016-02-11)
Lai, Wei-Ting
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Yang, Kuo-Ching
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Liao, Po-Hsiang
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George, Tom
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Li, Pei-Wen
We report the first-of-its-kind, self-organized gate-stack heterostructure of Ge-dot/SiO2/SiGe-shell on Si fabricated in a single step through the selective oxidation of a SiGe-nanopatterned pillar over a Si3N4 buffer layer on a Si substrate. Process-controlled tunability of the Ge-dot size (7.5-90 nm), the SiO2 thickness (3-4 nm), and the SiGe-shell thickness (2-15 nm) have been demonstrated, enabling a practically achievable core building block for Ge-based metal-oxide-semiconductor (MOS) devices. Detailed morphologies, structural, and electrical interfacial properties of the SiO2/Ge-dot and SiO2/SiGe interfaces were assessed using transmission electron microscopy, energy dispersive X-ray spectroscopy, and temperature-dependent high/low-frequency capacitance-voltage measurements. Notably, NiGe/SiO2/SiGe and Al/SiO2/Ge-dot/SiO2/SiGe MOS capacitors exhibit low interface trap densities of as low as 3-5 x 10(11) cm(-2) eV(-1) and fixed charge densities of 1-5 x 10(11) cm(-2), suggesting good-quality SiO2/SiGe-shell and SiO2/Ge-dot interfaces. In addition, the advantage of having single-crystalline Si1-xGex shell (x > 0.5) in a compressive stress state in our self-aligned gate-stack heterostructure has great promise for possible SiGe (or Ge) MOS nanoelectronic and nanophotonic applications.
Evaluation and Verification of Channel Transmission Characteristics of Human Body for Optimizing Data Transmission Rate in Electrostatic-Coupling Intra Body Communication System: A Comparative Analysis
(2016-02-11)
Tseng, Yuhwai
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Su, Chauchin
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Ho, Yingchieh
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電控工程研究所
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Institute of Electrical and Control Engineering
Background Intra-body communication is a new wireless scheme for transmitting signals through the human body. Understanding the transmission characteristics of the human body is therefore becoming increasingly important. Electrostatic-coupling intra-body communication system in a ground-free situation that integrate electronic products that are discretely located on individuals, such as mobile phones, PDAs, wearable computers, and biomedical sensors, are of particular interest. Materials and Methods The human body is modeled as a simplified Resistor-Capacitor network. A virtual ground between the transmitter and receiver in the system is represented by a resister-capacitor network. Value of its resistance and capacitance are determined from a system perspective. The system is characterized by using a mathematical unit step function in digital baseband transmission scheme with and without Manchester code. As a result, the signal-to-noise and to-intersymbol-interference ratios are improved by manipulating the load resistor. The data transmission rate of the system is optimized. A battery-powered transmitter and receiver are developed to validate the proposal. Results A ground-free system fade signal energy especially for a low-frequency signal limited system transmission rate. The system transmission rate is maximized by simply manipulating the load resistor. Experimental results demonstrate that for a load resistance of 10k-50k Omega, the high-pass 3 dB frequency of the band-pass channel is 400kHz-2MHz in the worst-case scenario. The system allows a Manchester-coded baseband signal to be transmitted at speeds of up to 20M bit per second with signal-to-noise and signal-to-intersymbol-interference ratio of more than 10 dB. Conclusion The human body can function as a high speed transmission medium with a data transmission rate of 20Mbps in an electrostatic-coupling intra-body communication system. Therefore, a wideband signal can be transmitted directly through the human body with a good signal-to-noise quality of 10 dB if the high-pass 3 dB frequency is suitably selected.
Recent developments in antibiotic agents for the treatment of complicated intra-abdominal infections
(2016-02-11)
Lin, Shang-Yi
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Huang, Chung-Hao
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Ko, Wen-Chien
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Chen, Yen-Hsu
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Hsueh, Po-Ren
Introduction: Treatment of complicated intra-abdominal infections (cIAIs) is becoming increasingly difficult because of the widespread emergence of multidrug-resistant organisms.Areas covered: In this review, we discuss the effectiveness of several new antibiotics for the treatment of cIAIs, including new -lactamase inhibitor combinations (BLICs) and tetracycline-class drugs, recently developed aminoglycosides and quinolones, and novel lipoglycopeptides and oxazolidinones.Expert opinion: Of the new BLICs, ceftolozane/tazobactam is associated with adequate clinical cure rates in patients with cIAIs. Currently, two new -lactamase inhibitors, namely avibactam and MK-7655, are under development for clinical use in the treatment of cIAIs. Eravacycline, a novel, fully synthetic tetracycline-class drug, has been shown in Phase II and III clinical trials to be more potent than tigecycline against a significant number of multidrug-resistant organisms causing cIAIs. Plazomicin, a next-generation aminoglycoside, is a promising agent for treatment of cIAIs due to multidrug-resistant pathogens. Of the recently developed quinolones, delafloxacin and finafloxacin have been shown to be effective against pathogens that survive and multiply in mildly acidic environments, although further clinical studies examining their clinical utility in the treatment of cIAIs are warranted. Oritavancin, a new semisynthetic lipoglycopeptide agent, has been demonstrated to be a potent antibiotic in the treatment of cIAIs due to drug-resistant Gram-positive organisms. Several other new antibiotics in development also show promise and will hopefully broaden the possibilities for treatment of complicated intra-abdominal infections due to MDR pathogens.
Measurement of the Reactor Antineutrino Flux and Spectrum at Daya Bay
(2016-02-12)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
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Bishai, M.
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Blyth, S.
This Letter reports a measurement of the flux and energy spectrum of electron antineutrinos from six 2.9 GW(th) nuclear reactors with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls in the Daya Bay experiment. Using 217 days of data, 296 721 and 41 589 inverse beta decay (IBD) candidates were detected in the near and far halls, respectively. The measured IBD yield is (1.55 +/- 0.04) x 10(-18) cm(2) GW(-1) day(-1) or (5.92 +/- 0.14) x 10(-43) cm(2) fission(-1). This flux measurement is consistent with previous short-baseline reactor antineutrino experiments and is 0.946 +/- 0.022 (0.991 +/- 0.023) relative to the flux predicted with the Huber-Mueller (ILL-Vogel) fissile antineutrino model. The measured IBD positron energy spectrum deviates from both spectral predictions by more than 2 sigma over the full energy range with a local significance of up to similar to 4 sigma between 4-6 MeV. A reactor antineutrino spectrum of IBD reactions is extracted from the measured positron energy spectrum for model-independent predictions.
Host-only solid-state near-infrared light-emitting electrochemical cells based on interferometric spectral tailoring
(2016-02-14)
Hsu, Jia-Hong
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Su, Hai-Ching
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照明與能源光電研究所
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Institute of Lighting and Energy Photonics
Solid-state near-infrared (NIR) light-emitting electrochemical cells (LECs) possess great potential in applications of NIR light sources due to their simple device structure, compatibility with large area and flexible substrates and low operating voltage. However, common host-guest NIR LECs suffer from the problem of significantly enhanced residual host emission upon increasing the bias voltage to achieve a higher NIR light output. A higher NIR light output can only be obtained at the expense of spectral purity in host-guest NIR LECs. To enhance the NIR light output of LECs without sacrificing the spectral purity significantly, a novel approach to generate NIR EL from host-only red-emitting LECs by adjusting the device thickness to modify the microcavity effect is proposed. NIR EL from host-only red-emitting LECs can be realized by adjusting the device thickness to shift the peak wavelength for constructive interference at the NIR spectral region. NIR EL resulting from the microcavity effect is relatively insensitive to bias voltage. Therefore, without losing spectral purity significantly, a 20x enhancement in the NIR output has been obtained in comparison to the previously reported value from host-guest NIR LECs. These results reveal that tailoring the EL spectra of host-only red-emitting LECs via modifying the microcavity effect would be a promising way to generate a higher NIR light output without suffering from the residual host emission problem of host-guest NIR LECs.