Browsing by Issue Date, starting with "2017-08-02"

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Enhanced Performance of GaN-based Ultraviolet Light Emitting Diodes by Photon Recycling Using Graphene Quantum Dots
(2017-08-02)
Lin, Tzu-Neng
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Santiago, Svette Reina Merden
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Yuan, Chi-Tsu
;
Chiu, Kuo-Pin
;
Shen, Ji-Lin
ablation. The synthesized GQDs can improve the optical and electrical properties of InGaN/InAlGaN UV light emitting diodes (LEDs) remarkably. An enhancement of electroluminescence and a decrease of series resistance of LEDs were observed after incorporation of GQDs on the LED surface. As the GQD concentration is increased, the emitted light (series resistance) in the LED increases (decreases) accordingly. The light output power achieved a maximum increase as high as 71% after introducing GQDs with the concentration of 0.9 mg/ml. The improved performance of LEDs after the introduction of GQDs is explained by the photon recycling through the light extraction from the waveguide mode and the carrier transfer from GQDs to the active layer.
Interfacial Investigation on Printable Carbon-Based Mesoscopic Perovskite Solar Cells with NiOx/C Back Electrode
(2017-08-02)
Behrouznejad, Fatemeh
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Tsai, Cheng-Min
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Narra, Sudhakar
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Diau, Eric W. -G.
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Taghavinia, Nima
Solar cells with high efficiency, low cost, and high stability are the target for the new generation of solar cells. A fully printable perovskite (CH3NH3PbI3) solar cell (PSC) with device architecture FTO/TiO2/Al2O3/NiOx/C is fabricated in the current research as a low-cost and relatively stable structure and is investigated to determine how different fabrication factors such as the thickness of the insulating spacer layer (Al2O3) or treatments such as heat and UV-O-3 treatments can affect the interfacial properties of this multilayer mesoporous structure. X-ray photoelectron spectra (XPS) show that UV-O-3 treatment increases the Ni3+ (Ni2O3) phase on the surface of the black nickel oxide layer leading to better charge extraction and increasing open-circuit voltage (V-OC) up to 0.945 V. We observe improved CH3NH3PbI3 formation inside the mesoporous layers by the PbI2 penetration at a higher temperature. Impedance spectral together with current-voltage measurements show the effect of thickness for the insulator layer in the internal and interfacial resistances and photovoltaic characteristics of the cell. The best performance of the carbon-based PSC attains power conversion efficiency of 12.1% with the thickness of the Al2O3 layer at 450 nm.
TAG MEMORY AND CACHE SYSTEM WITH AUTOMATING TAG COMPARISON MECHANISM AND CACHE METHOD THEREOF
(2017-08-03)
Tien-Fu Chen
;
Meng-Fan Chang
;
Keng-Hao Yang
A tag memory and a cache system with automating tag comparison mechanism and a cache method thereof are provided. The tag memory in the cache system includes a memory cell array, sensing amplifiers and a tag comparison circuit. The memory cell array stores cache tags, and outputs row tags of the cache tags according to an index in a memory address. The sensing amplifiers perform signal amplifications on the row tags to serve as comparison tags. The tag comparison circuit performs parallel comparisons between a target tag in the memory address and the row tags. When one of the row tags matches the target tag, the tag comparison circuit outputs a location of the matched row tag to serve as a first column address. The first column address is a column address where the memory address corresponds to a first data memory in the cache system.
A Post-Processing Method for Three-Dimensional Electrical Impedance Tomography
(2017-08-03)
Martin, Sebastien
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Choi, Charles T. M.
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分子醫學與生物工程研究所
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電機工程學系
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Institute of Molecular Medicine and Bioengineering
Electrical impedance tomography is a modern biomedical imaging method. Its goal is to image the electrical properties of human tissues. This approach is safe for the patient's health, is non-invasive and has no known hazards. However, the approach suffers from low accuracy. Linear inverse solvers are commonly used in medical applications, as they are strongly robust to noise. However, linear methods can give only an approximation of the solution that corresponds to a linear perturbation from an initial estimate. This paper proposes a novel reconstruction process. After applying a linear solver, the conductivity distribution is post-processed with a nonlinear algorithm, with the aim of reproducing the abrupt change in conductivity at the boundaries between tissues or organs. The results are used to compare the proposed method with three other widely used methods. The proposed method offers higher quality images and a higher robustness to noise, and significantly reduces the error associated with image reconstruction.
STRUCTURE AND FORMATION METHOD OF SEMICONDUCTOR DEVICE STRUCTURE
(2017-08-03)
Steve S. CHUNG
;
E-Ray HSIEH
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Yi-Hsien LIN
Structures and formation methods of a semiconductor device structure are provided. The semiconductor device structure includes a source structure at least partially in a semiconductor substrate. The semiconductor device structure also includes a channel structure over the semiconductor substrate. The source structure is partially covered by the channel structure. The semiconductor device structure further includes a drain structure covering the channel structure. The drain structure and the source structure have different conductivity types. A portion of the channel structure is sandwiched between the source structure and the drain structure. In addition, the semiconductor device structure includes a gate stack partially covering the channel structure.
Palladium-Catalyzed C-H Bond Activation by Using Iminoquinone as a Directing Group and an Internal Oxidant or a Co-oxidant: Production of Dihydrophenanthridines, Phenanthridines, and Carbazoles
(2017-08-04)
Raju, Selvam
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Annamalai, Pratheepkumar
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Chen, Pei-Ling
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Liu, Yi-Hung
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Chuang, Shih-Ching
A palladium-catalyzed C-H bond activation reaction, via a redox-neutral pathway, for the preparation of dihydrophenanthridine, phenanthridine, and carbazole derivatives from biaryl 2-iminoquinones is developed. The preinstalled iminoquinone was designed to act as a directing group for ortho C-H activation and an internal oxidant or a co-oxidant. This catalysis proceeded through the following sequence: C-H bond activation, coordination and insertion of activated olefins, beta-hydride elimination, H-shift, insertion, and protonation or beta-hydride elimination. using this method without the addition of external oxidants. In addition, carbazoles can be prepared efficiently by
Rewritable ferroelectric vortex pairs in BiFeO3
(2017-08-04)
Li, Yang
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Jin, Yaming
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Lu, Xiaomei
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Yang, Jan-Chi
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Chu, Ying-Hao
Ferroelectric vortex in multiferroic materials has been considered as a promising alternative to current memory cells for the merit of high storage density. However, the formation of regular natural ferroelectric vortex is difficult, restricting the achievement of vortex memory device. Here, we demonstrated the creation of ferroelectric vortex-antivortex pairs in BiFeO3 thin films by using local electric field. The evolution of the polar vortex structure is studied by piezoresponse force microscopy at nanoscale. The results reveal that the patterns and stability of vortex structures are sensitive to the poling position. Consecutive writing and erasing processes cause no influence on the original domain configuration. The Z4 proper coloring vortex-antivortex network is then analyzed by graph theory, which verifies the rationality of artificial vortex-antivortex pairs. This study paves a foundation for artificial regulation of vortex, which provides a possible pathway for the design and realization of non-volatile vortex memory devices and logical devices.
Structural and spectroscopic characterizations of a new near-UV-converting cyan-emitting RbBaScSi3O9:Eu2+ phosphor with robust thermal performance
(2017-08-05)
Ray, Sudeshna
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Tadge, Prachi
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Dhoble, S. J.
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Nair, Govind B.
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Singh, Akash
To facilitate the next generation of White Light Emitting Diodes (WLEDs) with higher color rendering and warm lighting, the development of inorganic phosphor for efficient conversion of photons from blue/near-UV light to other visible wavelengths is essential. In this regard, we demonstrate a systematic, cost effective, solution-processable, easily scalable and fully controllable synthesis of a series of RbBaScSi3O9:xEu(2+) (x = 0.2, 0.5, 2, 5, 7), a new cyan emitting scandium silicate based phosphor with 79% internal quantum efficiency under n-UV excitation with robust thermal performance. The concept as well as the methodology of using a "Mineral Inspired Approach" emerges as a new blueprint for the rational design of novel phosphor for phosphor converted WLEDs. The structural refinement, electronic structural calculation using "Density Functional Theory", characteristic photoluminescence study, lifetime measurement as well as the thermal quenching properties of the phosphor has been investigated in detail. Owing to the highly efficient cyan emission at lambda(max) similar to 492 nm a full-width at half-maximum of 63 cm(-1) that shows only very low thermal quenching (89.28% relative to the PL intensity at 150 degrees C with respect to that of measured at room temperature), reflects the great potential for the industrial application of this particular phosphor. (C) 2017 Elsevier B.V. All rights reserved.
Fluorescent coumarin-based probe for cysteine and homocysteine with live cell application
(2017-08-05)
Wei, Ling-Fang
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Thirumalaivasan, Natesan
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Liao, Yu-Cheng
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Wu, Shu-Pao
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應用化學系
Cysteine (Cys) and homocysteine (Hcy) are two of important biological thiols and function as important roles in several biological processes. The development of Cys and Hcy probes will help to explore the functions of biothiols in biological systems. In this work, a new coumarin-based probe AC, containing an acryloyl moiety, was developed for Cys and Hcy detection in cells. Cys and Hcy undergo a nucleophilic addition and subsequent cyclization reaction to remove to the acryloyl group and yield a fluorescent product, 7-hydroxylcomuarin. The probe AC showed good selectivity for cysteine and homocysteine over glutathione and other amino acids and had low detection limits of 65 nM for Cys and 79 nM for Hcy, respectively. Additionally, confocal imaging experiments demonstrated that the probe AC can be applied to visualize Cys and Hcy in living cells. (C) 2017 Elsevier B.V. All rights reserved.
Intermediate-Valence Ytterbium Compound Yb4Ga24Pt9: Synthesis, Crystal Structure, and Physical Properties
(2017-08-07)
Sichevych, Olga
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Prots, Yurii
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Utsumi, Yuki
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Akselrud, Lev
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Schmidt, Marcus
The title compound was synthesized by a reaction of the elemental educts in a corundum crucible at 1200 degrees C under an Ar atmosphere. The excess of Ga used in the initial mixture served as a flux for the subsequent crystal growth at 600 degrees C. The crystal structure of Yb4Ga24Pt9 was determined from single-crystal X-ray diffraction data: new prototype of crystal structure, space group C2/m, Pearson symbol mS74, a = 7.4809(1) angstrom, b = 12.9546(2) angstrom, c = 13.2479(2) angstrom, beta = 100.879(1)degrees, V = 1260.82(6) angstrom(3), R-F = 0.039 for 1781 observed reflections and 107 variable parameters. The structure is described as an ABABB stacking of two slabs with trigonal symmetry and compositions Yb4Ga6 (A) and Ga12Pt6 (B). The hard. X-ray photoelectron spectrum (HAXPES) of Yb4Ga24Pt9 shows both Yb2+ and Yb3+ contributions as evidence of an intermediate valence state of ytterbium The evaluated Yb valence of similar to 2.5 is in good agreement with the results obtained from the magnetic susceptibility measurements. The compound is, a bad metallic conductor.
交大e-News第237期-交大生助「紙飛機計畫」起飛翻譯程式教案供線上下載
(2017-08-07)
國立交通大學秘書室
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Secretariat
Identifying the miRNA signature associated with survival time in patients with lung adenocarcinoma using miRNA expression profiles
(2017-08-08)
Sathipati, Srinivasulu Yerukala
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Ho, Shinn-Ying
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生物科技學系
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生物資訊及系統生物研究所
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Department of Biological Science and Technology
Lung adenocarcinoma is a multifactorial disease. MicroRNA (miRNA) expression profiles are extensively used for discovering potential theranostic biomarkers of lung cancer. This work proposes an optimized support vector regression (SVR) method called SVR-LUAD to simultaneously identify a set of miRNAs referred to the miRNA signature for estimating the survival time of lung adenocarcinoma patients using their miRNA expression profiles. SVR-LUAD uses an inheritable bi-objective combinatorial genetic algorithm to identify a small set of informative miRNAs cooperating with SVR by maximizing estimation accuracy. SVR-LUAD identified 18 out of 332 miRNAs using 10-fold cross-validation and achieved a correlation coefficient of 0.88 +/- 0.01 and mean absolute error of 0.56 +/- 0.03 year between real and estimated survival time. SVR-LUAD performs well compared to some well-recognized regression methods. The miRNA signature consists of the 18 miRNAs which strongly correlates with lung adenocarcinoma: hsa-let-7f-1, hsa-miR-16-1, hsa-miR-152, hsa-miR-217, hsa-miR-18a, hsa-miR- 193b, hsa-miR-3136, hsa-let-7g, hsa-miR-155, hsa-miR-3199-1, hsa-miR-219-2, hsa-miR-1254, hsa-miR-1291, hsa-miR-192, hsa-miR-3653, hsa-miR-3934, hsa-miR-342, and hsa-miR-141. Gene ontology annotation and pathway analysis of the miRNA signature revealed its biological significance in cancer and cellular pathways. This miRNA signature could aid in the development of novel therapeutic approaches to the treatment of lung adenocarcinoma.
Entanglement-free determination of pretilt angles of twisted nematic liquid-crystal cells by phase measurement
(2017-08-10)
Chiang, Che-Wen
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Lin, Ping-Chun
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Yang, Kei-Hsiung
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光電系統研究所
;
影像與生醫光電研究所
The pretilt angle of a twisted nematic (TN) liquid crystal display has a strong effect on viewing angles and response times of the display as well as shifting the light-leaking disclination lines into the black-matrix area within pixels of a thin-film-transistor driven TN panel for a high contrast ratio. In this Letter, we develop an optical method to determine the TN pretilt angle based on heterodyne measurements of the phase versus the incident angle of a thin TN cell subjected to out-of-plane rotations. We believe that our method of measuring phases has advantages of simpler setup and calculations, better stability, and less sensitive to ambient electromagnetic interference than the commonly used method of measuring intensities.
Nano assembly of N-doped graphene quantum dots anchored Fe3O4/halloysite nanotubes for high performance supercapacitor
(2017-08-10)
Ganganboina, Akhilesh Babu
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Chowdhury, Ankan Dutta
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Doong, Ruey-an
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環境工程研究所
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Institute of Environmental Engineering
The development of robust and low cost electrode materials with superior electrochemical properties has been a subject of focus on energy storage devices. Herein, the development of N-doped graphene quantum dots (N-GQDs) deposited on Fe3O4-halloysite nanotubes (Fe3O4-HNTs) as active anode materials has been established for supercapacitor applications. The Fe3O4 nanoparticles synthesised by coprecipitation have been in-situ deposited on HNT surfaces following by the coating of (3-aminopropyl)-triexthoxysilane to anchor 4-10 nm N-GQDs via the formation of amide linkage. The N-GQD@Fe3O4-HNTs exhibits a high specific capacitance of 418 F g(-1) and maintains good rate capability in neutral electrolyte solutions. In addition, the anode materials show excellent electrochemical performance with energy and power densities of 10.4-29 W h kg(-1) and 0.25-5.2 kW kg(-1), respectively. Such excellent electrochemical features can be attributed to the synergistic contribution from individual components. The Fe3O4-HNTs provide 1-dimensional matrix to shorten the diffusion path of electrons and electrolyte ions as well as to absorb the mechanical stress during cycling along with excess sites for charge storage, while N-GQDs offer abundantly accessible electroactive sites for rapid electrons and electrolyte ions transport as well as enhance electrical conductivity of Fe3O4-HNTs. Results obtained in this study clearly demonstrate that metal oxide-HNTs are promising support to anchor N-GQDs nanomaterials as the high performance anode materials for next generation of energy storage devices with high energy and power densities. (C) 2017 Elsevier Ltd. All rights reserved.
The origin and mitigation of volcano-like morphologies in micron-thick AlGaN/AlN heteroepitaxy
(2017-08-14)
Huang, Chia-Yen
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Chang, Kai-Shiang
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Huang, Cheng-Yao
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Lin, Yun-Hsiang
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Peng, Wei-Chih
We investigated the origin of morphological instability in 2 mu m thick Al0.6Ga0.4N/AlN heteroepitaxy. The primary morphology was driven by the residual epitaxial strain, forming hill-like morphologies via surface diffusion. The secondary morphology was driven by the interaction between the primary morphology and dislocation clusters in the epitaxial layers. The difference in the local growth rate yields volcano-like morphologies centering on deep pits. Insertion of multi-stack superlattice transition layers between AlGaN and GaN effectively suppressed the secondary morphologies by simultaneously pre-relaxing the template and filtering treading dislocations. Published by AIP Publishing.
Direct measurement of site-specific rates of reactions of H with C3H8, i-C4H10, and n-C4H10
(2017-08-14)
Lin, Chia-Chieh
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Chen, Wei-Yu
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Matsui, Hiroyuki
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Wang, Niann-Shiah
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應用化學系
We measured the rates of abstraction of a hydrogen atom from specific sites in propane C3H8, 2-methyl propane (i-C4H10), and butane (n-C4H10); the sites are a primary hydrogen of C3H8 and i-C4H10 and a secondary hydrogen of n-C4H10. The excellent reproducibility of conditions of a diaphragm-less shock tube enabled us to conduct comparative measurements of the evolution of H atoms in three mixtures-(i) 0.5 ppm C2H5I + Ar, (ii) 0.5 ppm C2H5I + 50-100 ppm alkane as C3H8 or i-C4H10 or n-C4H10 + Ar, and (iii) the same concentrations of alkane + Ar without C2H5I-in the temperature range 1000-1200 K and at a pressure of 2.0 bars. The net profile of rise and decay of H atoms in the C2H5I + alkane mixture was derived on subtracting the absorbance of (iii) from that of (ii). Measurements of the mixture (iii) are important because the absorption of alkanes at 121.6 nm is not negligible. In the temperature range 1000-1100 K, the rate of decomposition of C2H5I was evaluated directly on analyzing the exponential growth of H atoms in the mixture (i). The rate of decomposition of C2H5I is summarized as ln(k/s(-1)) = (33.12 +/- 1.4) - (25.23 +/- 1.5) 10(3)/T (T = 1000-1100 K, P = 2.0 bars); the broadening factor F(T) in the Lindemann-Hinshelwood formula was evaluated in the fall-off region. The site-specific rates of H + (C-3-C-4) alkanes are summarized as follows: H + C3H8 -> H-2 + 1-C3H7, ln(k(1a)) = -(21.34 +/- 0.86) - (5.39 +/- 0.93) 10(3)/T, H + i-C4H10 -> H-2 + i-C4H9, ln(k(2a)) = -(20.50 +/- 1.36) - (6.14 +/- 0.13) 10(3)/T, H + n-C4H10 -> H-2 + 2-C4H9, ln(k(3b)) = - (21.37 +/- 1.15) - (4.83 +/- 1.26) 10(3)/T. The present experimental results are compared with published results from quantum-chemical calculations of potential-energy surfaces and transition-state theory. The present experiments are consistent with those calculations for the reaction rates for the attack at the primary site for H + C3H8 and H + i-C4H10, but for the attack at the secondary site of n-C4H10, our results are substantially smaller than the computational prediction, which might indicate a hindrance by the C-H bonds of the primary sites that serves to decrease the rate of abstraction from the secondary site of n-C4H10. The influence on the total rates of reactions H + alkane and the group additivity rule are discussed. Published by AIP Publishing.
Bubbling solutions for a skew-symmetric Chern-Simons system in a torus
(2017-08-15)
Han, Xiaosen
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Huang, Hsin-Yuan
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Lin, Chang-Shou
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應用數學系
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Department of Applied Mathematics
We establish the existence of bubbling solutions for the following skew-symmetric Chern Simons system Delta u(1) + 1/epsilon(2) e(u2) (1 - e(u1)) = 4 pi Sigma N-1 i=1 delta p(1/i) { Delta u(2) + 1/epsilon(2) e(u1) (1 - e(u2)) = 4 pi Sigma N-2 i=1 delta p(2/i) over a parallelogram Omega with doubly periodic boundary condition, where epsilon > 0 is a coupling parameter, and delta(p) denotes the Dirac measure concentrated at p. We obtain that if (N-1 - 1)(N-2 - 1) > 1, there exists an epsilon(o) > 0 such that, for any epsilon is an element of(0, epsilon(o)), the above system admits a solution (u(1),(epsilon), u(2),(epsilon)) satisfying u1,(epsilon) and u(2),(epsilon) blow up simultaneously at the point p*, and 1/epsilon(2) e(uj,k) (1 - e(ui,epsilon)) -> 4 pi N-i delta(p*) , 1 <= i, j <= 2 , i not equal j as epsilon -> 0, where the location of the point p* defined by (1.12) satisfies the condition (1.13). (C) 2017 Elsevier: Inc. All rights reserved.
Efficiency Enhancement in InGaN Photovoltaic Cells With Inverted Textured Surface
(2017-08-15)
Wu, Ming-Hsien
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Horng, Ray-Hua
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Liao, Wen-Yih
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Chang, Sheng-Po
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Chang, Shoou-Jinn
We report on the improvement of conversion efficiency of InGaN photovoltaic (PV) cells with inverted textured surface (ITS). InGaN PV cells with ITS showed short-circuit current density and conversion efficiency of 0.63 mA/cm(2) and 1.01%, which are 68.17% and 73.33% higher than the characteristics of conventional InGaN PV cells, respectively. The improvement can be attributed to the reduction of both the shading effect of the electrode contact pad and surface reflection of the incident irradiation under one-sun air-mass 1.5-G illumination (100 mW/cm(2)).
Ammonium chiral borate salt catalyzed asymmetric Friedel-Crafts alkylation of indoles with alpha,beta-disubstituted enals
(2017-08-15)
Ueda, Mitsuhiro
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Yagyu, Yoshitaka
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Ryu, Ilhyong
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應用化學系
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Department of Applied Chemistry
In, the presence of a catalytic amount of ammonium chiral borate salt, asymmetric Friedel-Crafts alkylation of indoles with alpha,beta-disubstituted enals proceeded to give the corresponding 1,4-addition products with moderate enantioselectivities. (C) 2017 Elsevier Ltd. All rights reserved.
Oxygen Passivation Mediated Tunability of Trion and Excitons in MoS2
(2017-08-16)
Gogoi, Pranjal Kumar
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Hu, Zhenliang
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Wang, Qixing
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Carvalho, Alexandra
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Schmidt, Daniel
Using wide spectral range in situ spectroscopic ellipsometry with systematic ultrahigh vacuum annealing and in situ exposure to oxygen, we report the complex dielectric function of MoS2 isolating the environmental effects and revealing the crucial role of unpassivated and passivated sulphur vacancies. The spectral weights of the A (1.92 eV) and B (2.02 eV) exciton peaks in the dielectric function reduce significantly upon annealing, accompanied by spectral weight transfer in a broad energy range. Interestingly, the original spectral weights are recovered upon controlled oxygen exposure. This tunability of the excitonic effects is likely due to passivation and reemergence of the gap states in the band structure during oxygen adsorption and desorption, respectively, as indicated by ab initio density functional theory calculation results. This Letter unravels and emphasizes the important role of adsorbed oxygen in the optical spectra and many-body interactions of MoS2.