Browsing by Issue Date, starting with "2014-08-18"

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Note on symmetric BCJ numerator
(2014-08-18)
Fu, Chih-Hao
;
Du, Yi-Jian
;
Feng, Bo
;
電子物理學系
;
Department of Electrophysics
We present an algorithm that leads to BCJ numerators satisfying manifestly the three properties proposed by Broedel and Carrasco in [42]. We explicitly calculate the numerators at 4, 5 and 6-points and show that the relabeling property is generically satisfied.
Crystal structure and molecular packing of an asymmetric giant amphiphile constructed by one C-60 and two POSSs
(2014-08-18)
Lin, Ming-Champ
;
Hsu, Chih-Hao
;
Sun, Hao-Jan
;
Wang, Chien-Lung
;
Zhang, Wen-Bin
Based on our recent understanding and development of functionalized molecular nanoparticles (MNPs) as building blocks for constructing various giant molecules, we report our efforts on design and synthesis of an asymmetric giant amphiphile, diBPOSS-C-60, composed of one [60]fullerene (C-60) covalently linked with two isobutyl-functionalized polyhedral oligomeric silsesquioxane (BPOSS) MNPs. Its crystal structure and molecular packing were investigated. The compositional asymmetry between C-60 and BPOSS led to a "sandwich-layered" molecular packing scheme, where a single layer of C-60 is sandwiched between double BPOSS layers: a so-called "one-and-half-layered" structure. Within these layers, the molecules further organized into crystalline arrays. Interestingly, this compound can be viewed as size amplification of a class of atomically thin, two-dimensional layered transition metal dichalcogenides with the "one-and-half-layered" structure. 2014 Elsevier Ltd. All rights reserved.
Crystal structure and molecular packing of an asymmetric giant amphiphile constructed by one C-60 and two POSSs
(2014-08-18)
Lin, Ming-Champ
;
Hsu, Chih-Hao
;
Sun, Hao-Jan
;
Wang, Chien-Lung
;
Zhang, Wen-Bin
Based on our recent understanding and development of functionalized molecular nanoparticles (MNPs) as building blocks for constructing various giant molecules, we report our efforts on design and synthesis of an asymmetric giant amphiphile, diBPOSS-C-60, composed of one [60]fullerene (C-60) covalently linked with two isobutyl-functionalized polyhedral oligomeric silsesquioxane (BPOSS) MNPs. Its crystal structure and molecular packing were investigated. The compositional asymmetry between C-60 and BPOSS led to a "sandwich-layered" molecular packing scheme, where a single layer of C-60 is sandwiched between double BPOSS layers: a so-called "one-and-half-layered" structure. Within these layers, the molecules further organized into crystalline arrays. Interestingly, this compound can be viewed as size amplification of a class of atomically thin, two-dimensional layered transition metal dichalcogenides with the "one-and-half-layered" structure. 2014 Elsevier Ltd. All rights reserved.
Effects of threading dislocations on drain current dispersion and slow transients in unpassivated AlGaN/GaN/Si heterostructure field-effect transistors
(2014-08-18)
Ghosh, Saptarsi
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Dinara, Syed Mukulika
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Mukhopadhyay, Partha
;
Jana, Sanjay K.
;
Bag, Ankush
Current transient analysis combined with response to pulsed bias drives have been used to explore the possibilities of threading dislocations affecting the current dispersion characteristics of AlGaN/GaN heterostructure field-effect transistors (HFETs). A growth strategy is developed to modulate the dislocation density among the heterostructures grown on silicon by plasma-assisted molecular-beam epitaxy. Slow pulsed I-V measurements show severe compressions and appear to be significantly dependent on the threading dislocation density. By analyzing the corresponding slow detrapping process, a deep-level trap with emission time constant in the order of seconds was identified as the cause. Among the specimens, both in the epilayers and at the surface, the number of dislocations was found to have a notable influence on the spatial distribution of deep-level trap density. The observations confirm that the commonly observed degraded frequency performance among AlGaN/GaN HFETs in the form of DC-radio frequency dispersions can at least partly be correlated with threading dislocation density. (C) 2014 AIP Publishing LLC.
Toward epitaxially grown two-dimensional crystal hetero-structures: Single and double MoS2/graphene hetero-structures by chemical vapor depositions
(2014-08-18)
Lin, Meng-Yu
;
Chang, Chung-En
;
Wang, Cheng-Hung
;
Su, Chen-Fung
;
Chen, Chi
Uniform large-size MoS2/graphene hetero-structures fabricated directly on sapphire substrates are demonstrated with layer-number controllability by chemical vapor deposition (CVD). The cross-sectional high-resolution transmission electron microscopy (HRTEM) images provide the direct evidences of layer numbers of MoS2/graphene hetero-structures. Photo-excited electron induced Fermi level shift of the graphene channel are observed on the single MoS2/graphene hetero-structure transistors. Furthermore, double hetero-structures of graphene/MoS2/graphene are achieved by CVD fabrication of graphene layers on top of the MoS2, as confirmed by the cross-sectional HRTEM. These results have paved the possibility of epitaxially grown multi-hetero-structures for practical applications. (C) 2014 AIP Publishing LLC.
Double-graded bandgap in Cu(In,Ga)Se-2 thin film solar cells by low toxicity selenization process
(2014-08-18)
Wang, Yi-Chih
;
Shieh, Han-Ping D.
;
交大名義發表
;
光電工程學系
;
顯示科技研究所
A low-toxic selenization with post gallium diffusion (PGD) treatment has been demonstrated to increase the bandgap in the surface Cu(In,Ga)Se-2 (CIGSe) absorbers and to form double-graded bandgap profiles to improve the cell efficiency. The CIGSe absorber with PGD for 5 min increased open-circuit voltage from 0.49 to 0.66V and efficiency from 9.2% to 13.2%, contributed by the enhancement of carrier recombination in the space-charge region. The reduction in short-circuit current from 30.8 to 29.9 mA/cm(2), attributed to the absorption loss in long-wavelength regions, can be potentially improved by further optimization of the minimum bandgap value in gradient valley. (C) 2014 AIP Publishing LLC.
Method to determine fiducial point for holographic data storage
(2014-08-19)
Ou-Yang Mang
;
Chen Yu-Ta
A method to determine a fiducial point for holographic data storage is disclosed, which utilizes a gray-level frame to sequentially retrieve a regional image used as a retrieved image with the size equal to that of the frame from a received gray-level image. The gray-level frame is compared with each retrieved image to obtain a plurality of values and construct a 2D proto-matrix. The 2D proto-matrix is transformed into a 2D matrix via letting the values smaller than 0 be 0. The 2D matrix and a retrieving matrix, which has a dimensionality equal to or smaller than that of the frame, are used to obtain an anchor matrix. A greatest value in the central region of the 2D matrix is found to function as an anchor value according to the anchor matrix, thereby find a fiducial point in the gray-level image.
Phase-locked loop
(2014-08-19)
Chen Wei-Zen
;
Wang Yan-Ting
The PLL includes a voltage-controlled oscillator (VCO), a frequency down conversion circuit, a phase-frequency detector (PFD), and an adjusting circuit. The VCO is configured to generate an output clock signal. The frequency down conversion circuit is configured to receive the output clock signal and an auxiliary clock signal, and to mix the output clock signal and the auxiliary clock signal to generate a feedback clock signal. By detecting the strength of the feedback clock signal, it provides an auxiliary signal to adjust the frequency of the output clock signal. The PFD is configured to compare the frequencies and the phases of the feedback clock signal and a reference clock signal to generate an adjusting signal. The adjusting circuit is configured to receive the adjusting signal, and to adjust the frequency of the output clock signal generated by the VCO according to the adjusting signal.
In Vivo Live Cell Imaging for the Quantitative Monitoring of Lipids by Using Raman Microspectroscopy
(2014-08-19)
Hosokawa, Masahito
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Ando, Masahiro
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Mukai, Shoichiro
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Osada, Kyoko
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Yoshino, Tomoko
A straightforward in vivo monitoring technique for biomolecules would be an advantageous approach for understanding their spatiotemporal dynamics in living cells. However, the lack of adequate probes has hampered the quantitative determination of the chemical composition and metabolomics of cellular lipids at single-cell resolution. Here, we describe a method for the rapid, direct, and quantitative determination of lipid molecules from living cells using single-cell Raman imaging. In vivo localization of lipids in the form of triacylglycerol (TAG) within oleaginous microalga and their molecular compositions are monitored with high spatial resolution in a non-destructive and label-free manner. This method can provide quantitative and real-time information on compositions, chain lengths, and degree of unsaturation of fatty acids in living cells for improving the cultivating parameters or for determining the harvest timing during large-scale cultivations for microalgal lipid accumulation toward biodiesel production. Therefore, this technique is a potential tool for in vivo lipidomics for understanding the dynamics of lipid metabolisms in various organisms.
Effect of grain orientations of Cu seed layers on the growth of < 111 >-oriented nanotwinned Cu
(2014-08-19)
Liu, Chien-Min
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Lin, Han-Wen
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Lu, Chia-Ling
;
Chen, Chih
;
材料科學與工程學系
We investigate the growth of Cu films on two different Cu seed layers: one with regular < 111 >-oriented grains and the other with very strong < 111 >-preferred orientation. It is found that densely-packed nanotwinned Cu (nt-Cu) can be grown by pulsed electroplating on the strong < 111 >-oriented Cu seed layer without a randomly-oriented transition layer between the nt-Cu and the Cu seed layer. The electroplated nt-Cu grow almost epitaxially on the seed layer and formed < 111 >-oriented columnar structures. However, with the regular < 111 >-oriented Cu seed, there is a randomly-oriented transition layer between the nt-Cu and the regular < 111 >-oriented Cu seed. The results indicate that the seed layer plays a crucial role on the regularity of < 111 >-oriented nanotwinned Cu.
交大e-News第169期
(2014-08-20)
Secretariat
;
國立交通大學秘書室
A steganographic method based on tetris games
(2014-08-20)
Ou, Zhan-He
;
Chen, Ling-Hwei
;
資訊工程學系
;
Department of Computer Science
Although various steganographic methods have been proposed that use distinct cover media, using games to hide data remains a recent development. The study presents a steganographic method based on online Tetris games, in which secret messages are embedded using a generated tetrimino sequence. Each time a person plays an online Tetris game, a new tetrimino sequence should be generated. The proposed method meets this requirement, generating a distinct stegoed tetrimino sequence for each game played. In addition, the study presents a scenario and a simulator for the proposed method. Theoretical proof and experimental results are provided to demonstrate that the proposed method is undetectable. (C) 2013 Elsevier Inc. All rights reserved.
Broadband antireflection and field emission properties of TiN-coated Si-nanopillars
(2014-08-21)
Chang, Yuan-Ming
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Ravipati, Srikanth
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Kao, Pin-Hsu
;
Shieh, Jiann
;
Ko, Fu-Hsiang
Broadband antireflection and field emission characteristics of silicon nanopillars (Si-NPs) fabricated by self-masking dry etching in hydrogen-containing plasma were systematically investigated. In particular, the effects of ultrathin (5-20 nm) titanium nitride (TiN) films deposited on Si-NPs by atomic layer deposition (ALD) on the optoelectronic properties were explored. The results showed that by coating the Si-NPs with a thin layer of TiN the antirefiection capability of pristine Si-NPs can be significantly improved, especially in the wavelength range of 1000-1500 nm. The enhanced field emission characteristics of these TiN/Si-NP heterostructures suggest that, in addition to the reflectance suppression in the long wavelength range arising from the strong wavelength-dependent refractive index of TiN, the TiN-coating may have also significantly modified the effective work function at the TiN/Si interface as well.
Wireless EWOD/DEP chips powered and controlled through LC circuits and frequency modulation
(2014-08-21)
Wu, Sung-Yueh
;
Hsu, Wensyang
;
機械工程學系
;
Department of Mechanical Engineering
This paper presents novel wireless EWOD/DEP chips that are wirelessly powered and controlled through LC circuits with one-to-many transmitter-receiver coupling. Each receiving LC circuit connected to the EWOD/DEP electrode is designed to have a different resonant frequency. When the input frequency is close to one of the resonant frequencies of receiving LC circuits, the induced voltage on the corresponding EWOD/DEP electrode will increase due to the resonance. Therefore, electrodes can be selectively and sequentially activated to provide sufficient EWOD or DEP force to manipulate the droplet or liquid by modulating the input frequency. Unlike previously reported wireless EWOD or DEP devices powered through one-to-one transmitter-receiver coupling, the transmitting inductor in the one-to-many transmitter-receiver coupling design proposed here is much larger than the total sizes of receiving inductors. Therefore, receiving inductors can be easily covered and coupled by the transmitting inductor. Here, droplet transport, splitting, and merging are successfully demonstrated using 5 receiving LC circuits at different input frequencies (1210-1920 Hz). Liquid pumping with multiple electrodes by wireless DEP is also demonstrated using 5 receiving LC circuits at higher input frequencies (51.2-76.1 kHz). Furthermore, liquid pumping with a continuous meandered electrode by wireless DEP is demonstrated through the resonant frequency shifting effect. It shows that the liquid pumping distance on a continuous electrode also can be tuned by proper frequency modulation.
掺碳氮化矽薄膜及其製造方法與裝置
(2014-08-21)
呂志鵬
;
凃弘恩
;
邱維剛
本發明提出一種掺碳氮化矽薄膜及其製造方法與裝置。該掺碳氮化矽薄膜係利用具有選自雙(二甲基胺基)二乙基矽烷、N,N-二甲基三甲基矽胺以及具有氮矽鍵結的一環狀結構其中至少之一的前驅物(precursor)所製成。該製造掺碳氮化矽薄膜的方法包含：提供具有選自雙(二甲基胺基)二乙基矽烷、N,N-二甲基三甲基矽胺或具有氮矽鍵結的環狀結構其中至少之一的前驅物來製備掺碳氮化矽薄膜。該製造掺碳氮化矽薄膜的裝置，包含：反應室；以及與該反應室相連接的容器，該容器含有如前所述的該前驅物。
UV absorption spectrum of the C2 Criegee intermediate CH3CHOO
(2014-08-21)
Smith, Mica C.
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Ting, Wei-Lun
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Chang, Chun-Hung
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Takahashi, Kaito
;
Boering, Kristie A.
The UV spectrum of CH3CHOO was measured by transient absorption in a flow cell at 295 K. The absolute absorption cross sections of CH3CHOO were measured by laser depletion in a molecular beam to be (1.06 +/- 0.09) x 10(-17) cm(2) molecule-1 at 308 nm and (9.7 +/- 0.6) x 10(-18) cm(2) molecule-1 at 352 nm. After scaling the UV spectrum of CH3CHOO to the absolute cross section at 308 nm, the peak UV cross section is (1.27 +/- 0.11) x 10(-)1(7) cm(2) molecule-1 at 328 nm. Compared to the simplest Criegee intermediate CH2OO, the UV absorption band of CH3CHOO is similar in intensity but blue shifted by 14 nm, resulting in a 20% slower photolysis rate estimated for CH3CHOO in the atmosphere. (C) 2014 AIP Publishing LLC.
A clustering time series model for the optimal hedge ratio decision making
(2014-08-22)
Hsu, Yu-Chia
;
Chen, An-Pin
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
In this study, a novel procedure combining computational intelligence and statistical methodologies is proposed to improve the accuracy of minimum-variance optimal hedge ratio (OHR) estimation over various hedging horizons. The time series of financial asset returns are clustered hierarchically using a growing hierarchical self-organizing map (GHSOM) based on the dynamic behaviors of market fluctuation extracted by measurement of variances, covariance, price spread, and their first and second differences. Instead of using original observations, observations with similar patterns in the same cluster and weighted by a resample process are collected to estimate the OHR. Four stock market indexes and related futures contracts, including Taiwan Weighted Index (TWI), Standard & Poor\'s 500 Index (S&P 500), Financial Times Stock Exchange 100 Index (FUSE 100), and NIKKEI 255 Index, are adopted in empirical experiments to investigate the correlation between hedging horizon and performance. Results of the experiments demonstrate that the proposed approach can significantly improve OHR decisions for mid-term and long-term hedging compared with traditional ordinary least squares and naive models. (C) 2014 Elsevier B.V. All rights reserved.
Quantum critical point in the superconducting transition on the surface of a topological insulator
(2014-08-25)
Li, Dingping
;
Rosenstein, Baruch
;
Shapiro, B. Ya
;
Shapiro, I.
;
電子物理學系
Pairing in the Weyl semimetal appearing on the surface of a topological insulator is considered. It is shown that due to an "ultrarelativistic" dispersion relation there is a quantum critical point governing the zero-temperature transition to a superconducting state. Starting from the microscopic Hamiltonian with local attraction, we calculated using the Gor'kov equations, the phase diagram of the superconducting transition at arbitrary chemical potential, and its magnetic properties and critical exponents close to the quantum critical point. The Ginzburg-Landau (GL) effective theory is derived for small chemical potential, allowing us to consider effects of spatial dependence of order parameters in a magnetic field. The GL equations are very different from the conventional ones reflecting the chiral universality class of the quantum phase transition. The order-parameter distribution of a single vortex is found to be different as well. The magnetization near the upper critical field is found to be quadratic, not linear as usual. We discuss the application of these results to recent experiments in which surface superconductivity was found for some three-dimensional topological insulators, and we estimate feasibility of the phonon pairing.
Fabrication and characterization of back-side illuminated InGaN/GaN solar cells with periodic via-holes etching and Bragg mirror processes
(2014-08-25)
Chang, Yi-An
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Chen, Fang-Ming
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Tsai, Yu-Lin
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Chang, Ching-Wen
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Chen, Kuo-Ju
In this study, the design and fabrication schemes of back-side illuminated InGaN/GaN solar cells with periodic via-holes etching and Bragg mirror processes are presented. Compared to typical front-side illuminated solar cells, the improvements of open-circuit voltage (V-oc) from 1.88 to 1.94 V and short-circuit current density (J(sc)) from 0.84 to 1.02 mA/cm(2) are observed. Most significantly, the back-side illuminated InGaN/GaN solar cells exhibit an extremely high fill factor up to 85.5%, leading to a conversion efficiency of 1.69% from 0.66% of typical front-side illuminated solar cells under air mass 1.5 global illuminations. Moreover, the effects of bottom Bragg mirrors on the photovoltaic characteristics of back-side illuminated solar cells are studied by an advanced simulation program. The results show that the J(sc) could further be improved with a factor of 10% from the original back-side illuminated solar cell by the structure optimization of bottom Bragg mirrors. (C) 2014 Optical Society of America
Spatial and electrical switching of defect modes in a photonic bandgap device with a polymer-dispersed liquid crystal defect layer
(2014-08-25)
Wu, Po-Chang
;
Yeh, En-Rong
;
Zyryanov, Victor Ya.
;
Lee, Wei
;
影像與生醫光電研究所
This paper investigates the spectral properties of a one-dimensional photonic crystal (PC) containing an inhomogeneous polymer-dispersed liquid crystal (PDLC) as a defect layer. Experimental results indicate that the voltage-induced reorientation of LC molecules between the light-scattering and transparent states in the PDLC enables the electrical tuning of the transmittance of defect-mode peaks in the spectrum of the PC/PDLC cell. Specifically, owing to the unique configuration of the spatial distribution of LC droplet sizes in the defect layer, a concept concerning the spatial switching in the wavelength of defect modes is proposed. As a result, the PC/PDLC hybrid cell is suggested as a potential element for realizing an electrically tunable and spatially switchable photonic bandgap device, which is polarizer-free and requires no alignment layers in the fabrication process. (C) 2014 Optical Society of America