Browsing by Issue Date, starting with "2013-08-01"

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A novel approach to collaborative testing in a crowdsourcing environment
(2013-08-01)
Tung, Yuan-Hsin
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Tseng, Shian-Shyong
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資訊工程學系
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Department of Computer Science
Software testing processes are generally labor-intensive and often involve substantial collaboration among testers, developers, and even users. However, considerable human resource capacity exists on the Internet in social networks, expert communities, or internet forums-referred to as crowds. Effectively using crowd resources to support collaborative testing is an interesting and challenging topic. This paper defines the collaborative testing problem in a crowd environment as an NP-Complete job assignment problem and formulates it as an integer linear programming (ILP) problem. Although package tools can be used to obtain the optimal solution to an ILP problem, computational complexity makes these tools unsuitable for solving large-scale problems. This study uses a greedy approach with four heuristic strategies to solve the problem. This is called the crowdsourcing-based collaborative testing approach. This approach includes two phases, training phase and testing phase. The training phase transforms the original problem into an ILP problem. The testing phase solves the ILP using heuristic strategies. A prototype system, called the Collaborative Testing System (COTS), is also implemented. The experiment results show that the proposed heuristic algorithms produce good quality approximate solutions in an acceptable timeframe. (c) 2013 Elsevier Inc. All rights reserved.
Probing Local Ionic Dynamics in Functional Oxides at the Nanoscale
(2013-08-01)
Strelcov, Evgheni
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Kim, Yunseok
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Jesse, Stephen
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Cao, Ye
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Ivanov, Ilia N.
A scanning probe microscopy technique for probing local ionic dynamics in electrochemically active materials based on the first-order reversal curve current-voltage (FORC-IV) method is presented. FORC-IV imaging mode is applied to a Ca-substituted bismuth ferrite (Ca-BFO) system to separate the electronic and ionic phenomena in this material and visualize the spatial variability of these behaviors. The variable-temperature measurements further demonstrate the interplay between the thermally and electric-field-driven resistance changes in Ca-BFO. The FORC-IV is shown to be a simple, powerful, and flexible method for studying electrochemical activity of materials at the nanoscale and, in conjunction with the electrochemical strain microscopy, it can be used for differentiating ferroelectric and ionic behaviors.
Robust MIMO Detection Under Imperfect CSI Based on Bayesian Model Selection
(2013-08)
Cheng, Chien-Chun
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Sezginer, Serdar
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Sari, Hikmet
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Su, Yu T.
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電子工程學系及電子研究所
A robust receiver for multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems is proposed. We are interested in the scenario when only a limited number of observations in both time and frequency domains are available. For this scenario, perfect channel state information is impossible to obtain and the receiver suffers from statistical information mismatch. To overcome this limitation, we first propose the optimum receiver by performing jointly channel and data estimation. For statistical information mismatch, we construct a finite set of covariance matrices and derive a model-selection scheme based on Bayesian Model Selection. Finally, the sliding-window scheme is used in order to enhance the model selection accuracy. Simulation results are presented, showing that the proposed scheme outperforms the conventional scheme under imperfect channel knowledge.
Au Nanostructure-Decorated TiO2 Nanowires Exhibiting Photoactivity Across Entire UV-visible Region for Photoelectrochemical Water Splitting
(2013-08-01)
Pu, Ying-Chih
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Wang, Gongming
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Chang, Kao-Der
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Ling, Yichuan
;
Lin, Yin-Kai
Here we demonstrate that the photoactivity of Au-decorated TiO2 electrodes for photoelectrochemical water oxidation can be effectively enhanced in the entire UV-visible region from 300 to 800 nm by manipulating the shape of the decorated Au nanostructures. The samples were prepared by carefully depositing Au nanoparticles (NPs), Au nanorods (NRs), and a mixture of Au NPs and NRs on the surface of TiO2 nanowire arrays. As compared with bare TiO2, Au NP-decorated TiO2 nanowire electrodes exhibited significantly enhanced photoactivity in both the UV and visible regions. For Au NR-decorated TiO2 electrodes, the photoactivity enhancement was, however, observed in the visible region only, with the largest photocurrent generation achieved at 710 nm. Significantly, TiO2 nanowires deposited with a mixture of Au NPs and NRs showed enhanced photoactivity in the entire UV visible region. Monochromatic incident photon-to-electron conversion efficiency measurements indicated that excitation of surface plasmon resonance of Au is responsible for the enhanced photoactivity of Au nanostructure-decorated TiO2 nanowires. Photovoltage experiment showed that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was attributable to the effective surface passivation of Au NPs. Furthermore, 3D finite-difference time domain simulation was performed to investigate the electrical field amplification at the interface between Au nanostructures and TiO2 upon SPR excitation. The results suggested that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was partially due to the increased optical absorption of TiO2 associated with SPR electrical field amplification. The current study could provide a new paradigm for designing plasmonic metal/semiconductor composite systems to effectively harvest the entire UV visible light for solar fuel production.
Channel Thickness Effect on High-Frequency Performance of Poly-Si Thin-Film Transistors
(2013-08-01)
Chen, Kun-Ming
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Tsai, Tzu-I
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Lin, Ting-Yao
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Lin, Horng-Chih
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Chao, Tien-Sheng
In this letter, we present the high-frequency performances of polycrystalline silicon (poly-Si) thin-film transistors (TFTs) with a nominal gate length of 0.22 mu m. Owing to the short gate length and adoption of salicide process, cutoff frequency (f (T)) of 17 GHz and maximum oscillation frequency of similar to 21 GHz are obtained. The result suggests that the poly-Si TFT technology is applicable to RF integrated circuits up to 2 GHz. In addition, we also investigate the effects of channel thickness on the high-frequency characteristics of poly-Si TFTs. We find that the variation of f (T) with channel thickness is mainly due to the change in transconductance.
Crystallized Ohmic Contact Effect in AlGaN/GaN High Electron Mobility Transistor
(2013-08-01)
Liao, Sheng Yu
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Chang, Tsu
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Hsu, Hsiao-Hsuan
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Cheng, Chun-Hu
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Chang, Liann-Be
In this study, we investigate the grain size effect of high electron mobility transistor devices with ohmic contact metals of stacked Ti/Al/Ni/Au and Ti/Al/Mo/Au. In addition to a comparison of electrical characteristics, the ohmic contacts were also examined by a scratch test for the observation of adhesion behavior. The experimental results demonstrate that the metal grain size is strongly dependent on metal adhesion, which may lead to bonding issues. Moreover, the grain-induced lateral stress lowers the drive current and increases the off-state current owing to the degraded gate swing and transconductance of transistor switching characteristics. (C) 2013 The Japan Society of Applied Physics
Holographic photon production with magnetic field in anisotropic plasmas
(2013-08-01)
Wu, Shang-Yu
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Yang, Di-Lun
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物理研究所
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Institute of Physics
We investigate the thermal photon production from constant magnetic field in a strongly coupled and anisotropic plasma via the gauge/gravity duality. The dual geometry with pressure anisotropy is generated from the axion-dilaton gravity action introduced by Mateos and Trancancelli and the magnetic field is coupled to fundamental matters(quarks) through the D3/D7 embeddings. We find that the photon spectra with different quark mass are enhanced at large frequency when the photons are emitted parallel to the anisotropic direction with larger pressure or perpendicular to the magnetic field. However, in the opposite conditions for the emitted directions, the spectra approximately saturate isotropic results in the absence of magnetic field. On the other hand, a resonance emerges at moderate frequency for the photon spectrum with heavy quarks when the photons move perpendicular to the magnetic field. The resonance is more robust when the photons are polarized along the magnetic field. On the contrary, in the presence of pressure anisotropy, the resonance will be suppressed. There exist competing effects of magnetic field and pressure anisotropy on meson melting in the strongly coupled super Yang-Mills plasma, while we argue that the suppression led by anisotropy may not be applied to the quark gluon plasma.
Ambient temperature SNAD process treating anaerobic digester liquor of swine wastewater
(2013-08-01)
Daverey, Achlesh
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Hung, Nien-Tzu
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Dutta, Kasturi
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Lin, Jih-Gaw
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環境工程研究所
In present study, effluent from anaerobic digestion of swine wastewater was treated by the simultaneous partial nitrification, anaerobic ammonium oxidation and denitrification (SNAD) process using a lab scale 5 L sequencing batch reactor (SBR) under ambient temperature. The fluctuation of anaerobic digester liquor quality (COD, 387 +/- 145 mg/L; TKN, 662 +/- 190 mg/L; NH4+-N, 519 +/- 134 mg/L) and temperature created difficulties to develop a stable SNAD process in the SBR (days 1-285). Fed batch feeding strategy was adopted to have a stable condition in the reactor and overcome the negative effects of organic nitrogen. The average total nitrogen, NH4+-N and COD removal efficiencies in the SBR under steady state conditions (days 485-523) were 80%, 96% and 76%, respectively. The results showed that presence of organic nitrogen, mode of feeding and reactor temperature affects the SNAD process. (C) 2013 Elsevier Ltd. All rights reserved.
Data mining-based hierarchical cooperative coevolutionary algorithm for TSK-type neuro-fuzzy networks design
(2013-08-01)
Hsu, Chi-Yao
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Lin, Sheng-Fuu
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Chang, Jyun-Wei
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電機工程學系
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Department of Electrical and Computer Engineering
This study proposes a data mining-based hierarchical cooperative coevolutionary algorithm (DMHCCA) for TSK-type neuro-fuzzy networks design. The proposed DMHCCA consists of two-level evolutions: the neuro-level evolution (NULE) and the network-level evolution (NWLE). In NULE, a data mining-based evolutionary learning algorithm is utilized to evolve neurons. The good combinations of neurons evolved in NULE are reserved for being the initial populations of NWLE. In NWLE, the initial population are mated and mutated to produce new structure of networks. Similar to NULE, the good neurons of evolved network in NWLE are inserted into the NULE. Thus, by interactive two-level evolutions, the neurons and structure of network can be evolved locally and globally, respectively. Simulation results using DMHCCA are reported and compared with other existing models. Application of DMHCCA to a three-dimensional (3D) surface alignment task is also described, and experimental results are presented better performance than other alignment systems.
Elimination of high concentration hydrogen sulfide and biogas purification by chemical-biological process
(2013-08-01)
Ho, Kuo-Ling
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Lin, Wei-Chih
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Chung, Ying-Chien
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Chen, Yu-Pei
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Tseng, Ching-Ping
A chemical-biological process was performed to remove a high concentration of H2S in biogas. The high iron concentration tolerance (20 g L-1) of Acidithiobacillus ferrooxidans CP9 provided sufficient ferric iron level for stable and efficient H2S elimination. A laboratory-scale apparatus was setup for a 45 d operation to analyze the optimal conditions. The results reveal that the H2S removal efficiency reached 98% for 1500 ppm H2S. The optimal ferric iron concentration was kept between 9 and 11 g L-1 with a cell density of 10(8) CFU g(-1) granular activated carbon and a loading of 15 g S m(-3) h(-1). In pilot-scale studies for biogas purification, the average inlet H2S concentration was 1645 ppm with a removal efficiency of up to 97% for a 311 d operation and an inlet loading 40.8 g S m(-3) h(-1). When 0.1% glucose was added, the cell density increased twofold under the loading of 65.1 g S m(-3) h(-1) with an H2S removal efficiency still above 96%. The analysis results of the distribution of microorganisms in the biological reactor by DGGE show that microorganism populations of 96.7% and 62.7% were identical to the original strain at day 200 and day 311, respectively. These results clearly demonstrate that ferric iron reduction by H2S and ferrous iron oxidation by A. ferrooxidans CP9 are feasible processes for the removal of H2S from biogas. (C) 2013 Elsevier Ltd. All rights reserved.
An Interframe Prediction Technique Combining Template Matching Prediction and Block-Motion Compensation for High-Efficiency Video Coding
(2013-08-01)
Peng, Wen-Hsiao
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Chen, Chun-Chi
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資訊工程學系
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Department of Computer Science
This paper introduces an interframe prediction technique that combines two motion vectors (MVs) derived respectively from template and block matching for overlapped block motion compensation (OBMC). It has a salient feature of not having to signal the template MV, while achieving a prediction performance close to that of bi-prediction. We begin by studying template matching prediction (TMP) from a theoretical perspective. Based on two signal models, the template MV is shown to approximate the pixel true motion around the template centroid, through which we explain why TMP generally outperforms SKIP prediction but is inferior to block-based motion compensation in terms of prediction performance. We then approach the problem of finding another MV to best complement the template MV from both deterministic and statistical viewpoints, the latter leading to the search of its optimal sampling location in the motion field. The result is a search criterion with OBMC window functions forming a geometry-like motion partitioning when the template area is straddled on the top and to the left of a target block. Generalizations to adaptive template design, multihypothesis prediction and motion merging are made to explore the complexity and performance trade-offs. Extensive experiments based on the HM-6.0 software show that the best of them, in terms of compression performance, achieves 1.7-2.0% BD-rate reductions at a cost of 26% and 39% increases in encoding and decoding times, respectively.
Perceptual Zero-Tree Coding with Efficient Optimization for Embedded Platforms
(2013-08-01)
Wu, B. F.
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Huang, H. Y.
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Wang, J. H.
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Chen, C. J.
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Chen, Y. L.
This study proposes a block-edge-based perceptual zero-tree coding (PZTC) method, which is implemented with efficient optimization on the embedded platform. PZTC combines two novel compression concepts for coding efficiency and quality: block-edge detection (BED) and the low-complexity and low-memory entropy coder (LLEC). The proposed PZTC was implemented as a fixed-point version and optimized on the DSP-based platform based on both the presented platform-independent and platform-dependent optimization technologies. For platform-dependent optimization, this study examines the fixed-point PZTC and analyzes the complexity to optimize PZTC toward achieving an optimal coding efficiency. Furthermore, hardware-based platform-dependent optimizations are presented to reduce the memory size. The performance, such as compression quality and efficiency, is validated by experimental results.
Synthesis, Molecular and Photovoltaic Properties of an Indolo[3,2-b]indole-Based Acceptor-Donor-Acceptor Small Molecule
(2013-08-01)
Lai, Yu-Ying
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Yeh, Jyun-Ming
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Tsai, Che-En
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Cheng, Yen-Ju
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應用化學系
Indolo[3,2-b]indole, containing two fused indole units, is an unexplored but promising electron-rich molecule for constructing donor-acceptor materials due to its planar, symmetric, and extended conjugated structure. We have successfully developed a new synthetic pathway to prepare 2,7-diboronic ester-indolo[3,2-b]indole, which was then reacted with dithienodiketopyrrolo-pyrrole acceptor to afford a new acceptor-donor-acceptor (A-D-A) conjugated molecule, 2,7-bis(dithienodiketopyrrolo-pyrrole)indolo[3,2-b]indole (2,7-DPPIIDPP). II is used to stand for indolo[3,2-b]indole in order to emphasize that this compound is constructed from two indole units. The A-D-A linkage through the 2,7-positions of II not only preserves the phenylene units in the para-conjugation but also renders stronger electron-donating strength. This material exhibited good thermal stability, high crystallinity, and broad UV/Vis absorption. The solution-processed bulk heterojunction device using the configuration of ITO/PEDOT:PSS/2,7-DPPIIDPP:PC71BM/Ca/Al exhibited a V-oc of 0.72 V, a J(sc) of 6.88 mA/cm(2), and an FF of 49.6%, leading to a power conversion efficiency (PCE) of 2.45%.
Space- and Time-Resolved Mapping of Ionic Dynamic and Electroresistive Phenomena in Lateral Devices
(2013-08-01)
Strelcov, Evgheni
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Jesse, Stephen
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Huang, Yen-Lin
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Teng, Yung-Chun
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Kravchenko, Ivan I.
A scanning probe microscopy-based technique for probing local ionic and electronic transport and their dynamic behavior on the 10 ms to 10 s scale is presented. The time-resolved Kelvin probe force microscopy (tr-KPFM) allows mapping of surface potential in both space and time domains, visualizing electronic and ionic charge dynamics and separating underlying processes based on their time responses. Here, tr-KPFM is employed to explore the interplay of the adsorbed surface ions and bulk oxygen vacancies and their role in the resistive switching in a Ca-substituted bismuth ferrite thin film.
Pillar Height Dependence of Field-Emission Properties in an Array of Carbon Nanotube Pillars
(2013-08-01)
Chang, Chia-Tsung
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Juan, Chuan-Ping
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Cheng, Huang-Chung
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Carbon nanotube pillars with optimal field-emission properties, including a high field enhancement factor beta of 5384 and a low turn-on field E-to of 0.84 V/mu m, have been achieved when the ratio of interpillar spacing to pillar height is 2. However, when this ratio exceeds 2, the field enhancement factor increases with increasing pillar height since the field can be enhanced by increasing the aspect ratio. When the ratio is smaller than 2, the field enhancement factor decreases with increasing pillar height owing to the increased field-screening effect. A simulation has been performed to verify the experimental results. (C) 2013 The Japan Society of Applied Physics
Spatially and Temporally Optimized Video Stabilization
(2013-08-01)
Wang, Yu-Shuen
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Liu, Feng
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Hsu, Pu-Sheng
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Lee, Tong-Yee
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資訊工程學系
Properly handling parallax is important for video stabilization. Existing methods that achieve the aim require either 3D reconstruction or long feature trajectories to enforce the subspace or epipolar geometry constraints. In this paper, we present a robust and efficient technique that works on general videos. It achieves high-quality camera motion on videos where 3D reconstruction is difficult or long feature trajectories are not available. We represent each trajectory as a Bezier curve and maintain the spatial relations between trajectories by preserving the original offsets of neighboring curves. Our technique formulates stabilization as a spatial-temporal optimization problem that finds smooth feature trajectories and avoids visual distortion. The Bezier representation enables strong smoothness of each feature trajectory and reduces the number of variables in the optimization problem. We also stabilize videos in a streaming fashion to achieve scalability. The experiments show that our technique achieves high-quality camera motion on a variety of challenging videos that are difficult for existing methods.
Non-Drude Behavior in Indium-Tin-Oxide Nanowhiskers and Thin Films Investigated by Transmission and Reflection THz Time-Domain Spectroscopy
(2013-08-01)
Yang, Chan-Shan
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Lin, Mao-Hsiang
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Chang, Chia-Hua
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Yu, Peichen
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Shieh, Jia-Min
A comparative study of indium-tin-oxide (ITO) nanowhiskers (NWhs) and thin films as transparent conductors in the terahertz frequency range are conducted. We employ both transmission-type and reflection-type terahertz time-domain spectroscopies (THz-TDTS and THz-TDRS) to explore the far-infrared optical properties of these samples. Their electrical properties, such as plasma frequencies and carrier scattering times, are analyzed and found to be fitted well by the Drude-Smith model over 0.1-1.4 THz. Further, structural and crystalline properties of samples are examined by scanning electron microscopy and X-ray diffraction, respectively. Non-Drude behavior of complex conductivities in ITO NWhs is attributed to carrier scattering from grain boundaries and impurity ions. In ITO thin films, however, the observed non-Drude behavior is ascribed to scattering by impurity ions only. Considering NWhs and thin films with the same height, mobility of the former is similar to 125 cm(2) V-1 s(-1), much larger than those of the ITO thin films, similar to 27 cm(2) V-1 s(-1). This is attributed to the longer carrier scattering time of the NWhs. The dc conductivities (similar to 250 Omega(-1) cm(-1)) or real conductivities in the THz frequency region of ITO NWhs is, however, lower than those of the ITO thin films (similar to 800 Omega(-1) cm(-1)) but adequate for use as electrodes. Partly, this is a reflection of the much higher plasma frequencies of thin films. Significantly, the transmittance of ITO NWhs (congruent to 60%-70%) is much higher (congruent to 13 times) than those of ITO thin films in the THz frequency range. The underneath basic physics is that the THz radiation can easily propagate through the air-space among NWhs. The superb transmittance and adequate electrical properties of ITO NWhs suggest their potential applications as transparent conducting electrodes in THz devices.
Laser dynamics of asynchronous rational harmonic mode-locked fiber soliton lasers
(2013-08-01)
Jyu, Siao-Shan
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Jiang, Guo-Hao
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Lai, Yinchieh
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光電工程學系
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Department of Photonics
Laser dynamics of asynchronous rational harmonic mode-locked (ARHM) fiber soliton lasers are investigated in detail. In particular, based on the unique laser dynamics of asynchronous mode-locking, we have developed a new method for determining the effective active modulation strength in situ for ARHM lasers. By measuring the magnitudes of the slowly oscillating pulse timing position and central frequency, the effective phase modulation strength at the multiplication frequency of rational harmonic mode-locking can be accurately inferred. The method can be a very useful tool for developing ARHM fiber lasers.
Large-scale Stein and Lyapunov equations, Smith method, and applications
(2013-08-01)
Li, Tiexiang
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Weng, Peter Chang-Yi
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Chu, Eric King-wah
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Lin, Wen-Wei
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應用數學系
We consider the solution of large-scale Lyapunov and Stein equations. For Stein equations, the well-known Smith method will be adapted, with A(k) = A(2k) not explicitly computed but in the recursive form A(k) = A(k-1)(2), and the fast growing but diminishing components in the approximate solutions truncated. Lyapunov equations will be first treated with the Cayley transform before the Smith method is applied. For algebraic equations with numerically low-ranked solutions of dimension n, the resulting algorithms are of an efficient O(n) computational complexity and memory requirement per iteration and converge essentially quadratically. An application in the estimation of a lower bound of the condition number for continuous-time algebraic Riccati equations is presented, as well as some numerical results.
A design of liquid crystal lens with low voltage driving
(2013-08-01)
Tang Xian-Zhu
;
Chung Te-Chen
;
Jen T'ing-Hsien
;
Lu Jian-Gang
;
Shieh Han-Ping
Design rules for liquid crystal (LC) lens with low driving voltage are studied in this paper. Many rules are obtained from simulations of five kinds of LC materials. If normalized Delta n(eff) of the LC material is less than 95%, the driving voltage of LC lens will be less than 10 V. On the premise that the performance of LC lens is satisfied and fabrication process is permitted, the smaller the normalized Aneff, the lower the driving voltage of the designed LC lensis. The results in can guide people in this paper designing and preparing the LC lens with high performance.