Browsing by Issue Date, starting with "2016-02-21"

Now showing 1 - 20 of 17940

Atomic and electronic aspects of the coloration mechanism of gasochromic Pt/Mo-modified V2O5 smart films: an in situ X-ray spectroscopic study
(2016-02-21)
Lu, Ying-Rui
;
Hsu, Hsin-Hua
;
Chen, Jeng-Lung
;
Chang, Han-Wei
;
Chen, Chi-Liang
In this work, gasochromic pristine and Mo-modified V2O5 thin films were prepared by the sol-gel spin coating method. Both films exhibit excellent gasochromic coloration. Synchrotron grazing incidence X-ray diffraction reveals that the Mo-modified V2O5 thin film is more amorphous than the pristine V2O5 thin film. X-ray absorption spectroscopy (XAS) was utilized to elucidate the modifications of the local electronic and atomic structures that are caused by Mo. In situ soft-XAS and in situ hard-XAS were performed to monitor the effect of the adsorption of dihydrogen on the charge state of vanadium and local atomic rearrangement in the gasochromic thin films. The gasochromic V2O5 film has a significantly pyramid-like oxygen-coordinated environment. However, the Mo-modified film exhibits mixed pyramid- and octahedral-like structures. Analytic results indicate that upon gasochromic coloration, adsorption of hydrogen adds electrons to the V 3d t(2g) orbital, lowering the charge state of vanadium. The films undergo structural modification before the valence is changed. The Mo-modified V2O5 film exhibits faster coloration because the apical V-O bond differs from that in the pristine V2O5 film. This in situ XAS allows real-time monitoring of changes in the element-specific local atomic structure during the gasochromic reaction and enables the elucidation of the gasochromic mechanism.
Theoretical and experimental studies for high-repetition-rate disordered crystal lasers with harmonic self-mode locking
(2016-02-22)
Sung, C. L.
;
Lee, C. Y.
;
Cho, H. H.
;
Huang, Y. J.
;
Chen, Y. F.
A harmonically self-mode-locked Nd:Sr3Y2(BO3)(4) disordered crystal laser with subpicosecond pulse duration is demonstrated. We exploit the damped harmonic oscillator model to numerically verify that the mode spacing of the laser cavity can be modified to be the harmonics of the free spectral range of the Fabry-Perot cavity when the optical length of the laser cavity is close to a commensurate ratio of the optical length of the FabryPerot cavity. In experiment, the Fabry-Perot cavity can be formed by the pump facet of the disordered crystal and the front mirror. A 110 GHz single-pulse harmonically mode-locked pulse train with pulse duration of 857 fs is experimentally achieved under optical lengths of 27.19 and 4.08 mm for the laser cavity and Fabry-Perot cavity respectively, corresponding to a fractional number of 20/3. A maximum output power of 162 mW is obtained at an incident pump power of 3.1 W. (C)2016 Optical Society of America
Low-Temperature and Ultrafast Synthesis of Patternable Few-Layer Transition Metal Dichacogenides with Controllable Stacking Alignment by a Microwave-Assisted Selenization Process
(2016-02-23)
Chen, Yu-Ze
;
Medina, Henry
;
Wang, Sheng-Wen
;
Su, Teng-Yu
;
Li, Jian-Guang
To date, the chemical vapor deposition (CVD) process is the most popular approach because of its high yield and quality. Nevertheless, the need for a high temperature and the relatively long process time within each cycle hinder the commercial development in terms of production cost. In this work, we demonstrate a fast (<3 min) and feasible approach to synthesizing a few-layers of WSe2 and MoSe2 on arbitrary substrates by a microwave-assisted selenization process. The transition metal dichalcogenides (TMDs) can be patterned by standard photolithography. Furthermore, controllable layered growth from horizontal to vertical alignment can be achieved, leading to an enhanced chemical catalytic activity caused by large edge sites (exposed areas). As a proof, a highly sensitive NO gas sensor based on vertical WSe2 was fabricated. Moreover, our microwave assisted selenization process can be further extended to achieve other two-dimensional TMD materials because of the simplicity of the process.
Atomic origin of the spin-polarization of the Co2FeAl Heusler compound
(2016-02-25)
Liang, Jaw-Yeu
;
Lam, Tu-Ngoc
;
Lin, Yan-Cheng
;
Chang, Shu-Jui
;
Lin, Hong-Ji
Using synchrotron x-ray techniques, we studied the Co2FeAl spin-polarization state that generates the half-metallicity of the compound during an A(2) (low-spin) -> B-2 (high-spin) phase transition. Given the advantage of element specificity of x-ray techniques, we could fingerprint the structural and magnetic cross-reactions between Co and Fe within a complex Co2FeAl structure deposited on a MgO (0 0 1) substrate. X-ray diffraction and extended x-ray absorption fine structure investigations determined that the Co atoms preferably populate the (1/4,1/4,1/4) and (3/4,3/4,3/4) sites during the development of the B-2 phase. X-ray magnetic spectroscopy showed that although the two magnetic elements were ferromagnetically coupled, they interacted in a competing manner via a charge-transfer effect, which enhanced Co spin polarization at the expense of Fe spin polarization during the phase transition. This means that the spin-polarization of Co2FeAl was electronically dominated by Fe in A(2) whereas the charge transfer turned the dominance to Co upon B-2 formation. Helicity-dependent x-ray absorption spectra also revealed that only the minority state of Co/Fe was involved in the charge-transfer effect whereas the majority state was independent of it. Despite an overall increase of Co2FeAl magnetization, the charge-transfer effect created an undesired trade-off during the Co-Fe exchange interactions, because of the presence of twice as many X sites (Co) as Y sites (Fe) in the Heusler X(2)YZ formula. This suggests that the spin-polarization of Co2FeAl is unfortunately regulated by compromising the enhanced X (Co) sites and the suppressed Y (Fe) sites, irrespective of the development of the previously known high-spin-polarization phase of B-2. This finding provides a possible cause for the limited half-metallicity of Co2FeAl discovered recently. Electronic tuning between the X and Y sites is necessary to further increase the spin-polarization, and likely the half-metallicity as well, of the compound.
Experimental violation of Bell inequalities for multi-dimensional systems
(2016-02-26)
Lo, Hsin-Pin
;
Li, Che-Ming
;
Yabushita, Atsushi
;
Chen, Yueh-Nan
;
Luo, Chih-Wei
Quantum correlations between spatially separated parts of a d-dimensional bipartite system (d >= 2) have no classical analog. Such correlations, also called entanglements, are not only conceptually important, but also have a profound impact on information science. In theory the violation of Bell inequalities based on local realistic theories for d-dimensional systems provides evidence of quantum nonlocality. Experimental verification is required to confirm whether a quantum system of extremely large dimension can possess this feature, however it has never been performed for large dimension. Here, we report that Bell inequalities are experimentally violated for bipartite quantum systems of dimensionality d=16 with the usual ensembles of polarization-entangled photon pairs. We also estimate that our entanglement source violates Bell inequalities for extremely high dimensionality of d>4000. The designed scenario offers a possible new method to investigate the entanglement of multipartite systems of large dimensionality and their application in quantum information processing.
Injectable insulin-lysozyme-loaded nanogels with enzymatically-controlled degradation and release for basal insulin treatment: In vitro characterization and in vivo observation
(2016-02-28)
Chou, Hao-Syun
;
Larsson, Mikael
;
Hsiao, Meng-Hsuan
;
Chen, Yi-Chieh
;
Roeding, Magnus
Diabetes is a common global disease that causes immense suffering for individuals and huge costs for the health care system. To minimize complications such as organ degeneration, diabetic patients are required to undergo treatments to maintain the blood glucose level in the normal range, ideally mimicking normal insulin secretion. The normal physiological insulin secretion pattern in healthy individuals consists of a base (basal) level through the day and increased secretion after meals (bolus insulin). Thus effective treatments may combine long acting, low-level insulin therapy with boosts of short acting insulin and/or oral agents. To achieve long term management of basal insulin level, an injectable insulin-loaded gel composed of self-assembled nanoparticles from carboxymethyl-hexanoyl chitosan (CHC) and integrated lysozyme for controlled biodegradation and insulin release was developed. In vitro characterizations and evaluations confirmed that lysozyme was active on CHC and that the amount of lysozyme in a CHC hydrogel determined the degradation and insulin release rate. The degradation products were found to be highly cytocompatible using a cell assay. In vivo evaluation of the system in a diabetic mouse model revealed that the fasted blood glucose level could be maintained in the normal range for 10 days with a single injection of insulin-loaded CHC-lysozyme gel. The insulin-loaded CHC-lysozyme gels clearly show promise for use as a novel injectable long-acting insulin delivery system, with potential to manage the basal insulin level for many days with a single injection. (C) 2015 Elsevier B.V. All rights reserved.
Iterative Symbol Decoding of Variable-Length Codes with Convolutional Codes
(2016-02-29)
Wu, Hung-Tsai
;
Wu, Chun-Feng
;
Chang, Wen-Whei
;
傳播研究所
;
Institute of Communication Studies
In this paper, we present a symbol-level iterative sourcechannel decoding (ISCD) algorithm for reliable transmission of variable-length codes (VLCs). Firstly, an improved source a posteriori probability (APP) decoding approach is proposed for packetized variable-length encoded Markov sources. Also proposed is a recursive implementation based on a three-dimensional joint trellis for symbol decoding of binary convolutional codes. APP channel decoding on this joint trellis is realized by modification of the Bahl-Cocke-Jelinek-Raviv algorithm and adaptation to the non-stationary VLC trellis. Simulation results indicate that the proposed ISCD scheme allows to exchange between its constituent decoders the symbol-level extrinsic information and achieves high robustness against channel noises.
A Rapid Fatigue Test Method on Micro Structures for High-Cycle Fatigue
(2016-03)
Shieh, Yi-Chueh
;
Lin, Hsuan-Yu
;
Hsu, Wensyang
;
Lin, Yu-Hsin
;
機械工程學系
Here, a rapid fatigue test method for micro structure is proposed, where the test sample is excited at its resonant frequency by an external actuator. Due to the scaling effect, a micro cantilever beam has high resonant frequency, so the testing time can be greatly reduced. In addition, no complicated built-in micro actuator is needed; therefore, it is easy to fabricate the test sample. Single-crystal silicon (SCS) beams are fabricated to demonstrate the proposed method here with two types of beams. A notch is designed near the fixed end to have stress concentration effect. The input voltage of the piezoelectric patch is adjusted to excite the cantilever beams at its resonant frequency to have different amplitudes to find the corresponding fatigue life, where a laser Doppler vibrometer is used to monitor displacements of the cantilever beam to control the stress amplitude. Then, the stress-life (S/N) curve of the silicon beam can be obtained. It is found that the fatigue limit of the SCS beam is about 1.33 GPa, and it takes only about 5.2 h to test 1.35 x 10(9) cycles at a resonant frequency of 72 kHz. Comparing with previous fatigue test methods with an external probe, testing 10(9) cycles at a frequency of 20 Hz will need 1.58 years, which indicates that the proposed rapid fatigue test method is particularly suitable for high-cycle fatigue test of micro structure.
六角柱體微型感測探針及其製法
(2016-03-01)
鄭裕庭
;
陳益祥
;
李元鼎
;
王覺瑋
本發明為一種六角柱體微型感測探針及其製法，係由一片金屬基電阻式溫度感測探針以及氧化銥/氯化銀酸鹼值感測探針覆合壓焊而成，可同時感測溫度及酸鹼值。此外，此微型感測探針之應力測試可達到3牛頓壓應力，可輕易地穿刺人體和動物的心肌或肌肉組織，故可應用於監測心肌狀態或感測肉類食品的新鮮度。
Suppressing Non-Uniform Tunneling in InAs/GaSb TFET With Dual-Metal Gate
(2016-03-01)
Hsu, Ching-Yi
;
Chang, Chun-Yen
;
Chang, Edward Yi
;
Hu, Chenming
;
材料科學與工程學系
Non-uniformity in electric field causes early onset of tunneling near the edge of InAs/GaSb hetero-junction tunneling field-effect transistors. When a small area, often an edge, of the tunneling junction has a lower turn-on voltage, the steep switching characteristic is degraded. Fermi pinning at InAs surface greatly worsen the uniformity. We propose a dual-metal gate structure to address the non-uniformity issue. With proper choice of work functions, the dual-metal gate structure can effectively suppress the early onset of edge tunneling and significantly improve the subthreshold swing.
Bipolar Conduction in Tin-Oxide Semiconductor Channel Treated by Oxygen Plasma for Low-Power Thin-Film Transistor Application
(2016-03)
Chen, Po-Chun
;
Wu, Yung-Hsien
;
Zheng, Zhi-Wei
;
Chiu, Yu-Chien
;
Cheng, Chun-Hu
In this paper, we investigated the bipolar conduction mechanism in thin-film transistors (TFTs) with oxygen plasma treatment on tin-oxide channel. The optimized p-type thin-oxide TFTs showed an on/off ratio of >10(4), a threshold voltage of -1.05 V, and a field-effect mobility of 2.14 cm(2).V-1.s(-1). By increasing the exposure time of oxygen plasma, excess oxygen was incorporated to thin-oxide channel and converted thin monoxide to oxygen-rich n-type thin dioxide, which in turn led to n-type operation. It indicated that oxygen plasma was the critical factor to determine oxygen concentration, oxygen vacancies, metal ions and channel polarity. This proposed oxygen-content tuning through plasma treatment approach shows great promise in simplification of TFT process that can achieve n-type and p-type TFTs under the same device process.
WIRELESS NEAR-INFRARED SPECTROSCOPE TO REAL-TIME QUANTITATIVELY ASSESS DORSAL FOOT PERIPHERAL CIRCULATION IN PATIENTS WITH DIABETES FOOT ULCER: A PILOT STUDY
(2016-03)
Lin, Yen Pin
;
Chang, Chang Cheng
;
Su, Zeng Wei
;
Chang, Yin-Shuo
;
Lin, Borshyh
Face-Based Heart Rate Signal Decomposition and Evaluation Using Multiple Linear Regression
(2016-03-01)
Lin, Kuan-Yi
;
Chen, Duan-Yu
;
Tsai, Wen-Jiin
;
資訊工程學系
;
Department of Computer Science
Contact measurements of the cardiac pulse using the conventional electrocardiogram equipment requires patients to wear adhesive gel patches or chest straps that can cause skin irritation and discomfort. Commercially available pulse oximetry sensors that attach to the fingertips or earlobes also cause inconvenience for patients and the spring-loaded clips can be painful to use. Therefore, a novel robust non-contact technique is developed for the evaluation of heart rate variation. According to the periodic variation of reflectance strength resulting from changes to hemoglobin absorptivity across the visible light spectrum as heartbeats cause changes to blood volume in the blood vessels in the face, a reflectance signal is decomposed from consecutive frames of the green channel of the facial region. Furthermore, ensemble empirical mode decomposition of the Hilbert-Huang transform (HHT) is used to acquire the primary heart rate signal while reducing the effect of ambient light changes. The effective instantaneous frequencies from intrinsic mode functions decomposed by HHT are implemented by the multiple-linear regression model to evaluate heart rates before the frequencies were rectified by maximum likelihood method assuming Poisson distribution, and the minimum elapse time for heart rate evaluation is also evaluated in the estimate process. Experimental results show that our proposed approach provides a convenient non-contact method to evaluate heart rate and outperforms the current state-of-the-art method with higher accuracy and smaller variance.
The Intellectual Structure of Metacognitive Scaffolding in Science Education: A Co-citation Network Analysis
(2016-03)
Tang, Kai-Yu
;
Wang, Chia-Yu
;
Chang, Hsin-Yi
;
Chen, Sufen
;
Lo, Hao-Chang
The issues of metacognitive scaffolding in science education (MSiSE) have become increasingly popular and important. Differing from previous content reviews, this study proposes a series of quantitative computer-based analyses by integrating document co-citation analysis, social network analysis, and exploratory factor analysis to explore the intellectual structure of the MSiSE literature (i.e. the relationships within and between subfields of MSiSE). Co-citation refers to any two articles that are jointly referenced in other articles. After the computation of co-citation analysis, 27 articles that have been co-cited at least once by follow-up studies as references were identified as the final set of core articles. The whole co-citation profile of 27 cores with the 434 links was then visualized in a network through social network analysis, representing an overview for the intellectual structure of core MSiSE studies. The most cross-referenced underpinnings in the network focused on adaptive scaffolding for self-regulated learning to enhance students\' conceptual understanding and on younger students\' metacognition in online science inquiry learning environments. Furthermore, two emerging topics in the network were identified through an exploratory factor analysis as "non-technological metacognitive scaffolding media," and "behavior patterns & task analysis in technology-infused environments." Overall, the study provides an innovative review method of scholarly communication in the MSiSE literature.
Combining multiple correspondence analysis with association rule mining to conduct user-driven product design of wearable devices
(2016-03)
Wang, Chih-Hsuan
;
Nien, Su-Hau
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
In recent years, the popularity of smart phones has boomed the emergence of wearable devices like wristband, smart watch, and sport watch since these devices are portable to record human body information, synchronize information with smart phones, and conduct real-time monitoring of physical condition. However, a recent survey indicates that near 70% respondents are not interested in buying Apple\'s new iWatch although the marketplace is full of competing alternatives like Samsung\'s Gear fit, LG\'s G watch, and Sony\'s SW3. In this study, a novel framework combining multiple correspondence analysis (MCA), association rule mining (ARM), with K nearest neighbor (KNN) is proposed to help brand companies address the following issues: (1) using MCA to explore the latent relationships between users\' demographic profiles, user perceptions of design attributes, and user preferences for wearable devices, (2) using ARM to identify key design attributes that can best configure a specific alternative to achieve effective product differentiation (positioning), (3) using KNN to accomplish efficient product selection (recommendation). More importantly, hundreds of consumers are surveyed to justify the validity of the presented framework. (C) 2015 Elsevier B.V. All rights reserved.
Epileptic Pattern Recognition and Discovery of the Local Field Potential in Amygdala Kindling Process
(2016-03)
Wang, Yu-Lin
;
Chen, Yin-Lin
;
Su, Alvin Wen-Yu
;
Shaw, Fu-Zen
;
Liang, Sheng-Fu
Epileptogenesis, which occurs in an epileptic brain, is an important focus for epilepsy. The spectral analysis has been popularly applied to study the electrophysiological activities. However, the resolution is dominated by the window function of the algorithm used and the sample size. In this report, a temporal waveform analysis method is proposed to investigate the relationship of electrophysiological discharges and motor outcomes with a kindling process. Wistar rats were subjected to electrical amygdala kindling to induce temporal lobe epilepsy. During the kindling process, different morphologies of afterdischarges (ADs) were found and a recognition method, using template matching techniques combined with morphological comparators, was developed to automatically detect the epileptic patterns. The recognition results were compared to manually labeled results, and 79%-91% sensitivity was found. In addition, the initial ADs (the first 10 s) of different seizure stages were specifically utilized for recognition, and an average of 85% sensitivity was achieved. Our study provides an alternative viewpoint away from frequency analysis and time-frequency analysis to investigate epileptogenesis in an epileptic brain. The recognition method can be utilized as a preliminary inspection tool to identify remarkable changes in a patient\'s electrophysiological activities for clinical use. Moreover, we demonstrate the feasibility of predicting behavioral seizure stages from the early epileptiform discharges.
Three-Element Item Selection Procedures for Multiple Forms Assembly: An Item Matching Approach
(2016-03)
Chen, Pei-Hua
;
交大名義發表
;
管理科學系
;
National Chiao Tung University
;
Department of Management Science
In educational measurement, building multiple alternate test forms is usually highly desirable in practice. Test assembly problems are classified as NP-hard (Non-deterministic Polynomial-time hard) problems, and their computation time increases exponentially as the problem size grows. The purpose of this study was to construct parallel forms item-by-item based on a seed test, using two proposed item selection heuristic methods (random item sequence assigned to maximum distance form with content balance [R-MD-B] and random item sequence assigned to random form with content balancing [R-R-B]) incorporating a flexible content balancing method. The results were compared with two modified versions of the Armstrong, Jones, and Wu heuristics (random item sequence assigned to maximum distance form with Armstrong\'s replacement [R-MD-R] and random item sequence assigned to random form with Armstrong\'s replacement [R-R-R]) and two models incorporating mixed integer programming (MIP) methods. The results showed that the R-MD-B and R-R-B methods yielded results comparable with the two MIP methods with less computation time in terms of the item information functions, test characteristic curves, and content coverage. The results also showed that R-MD-B and R-R-B can be extended to handle test assembly constraints in practical settings.
納中華入臺灣的1949創傷癥候，與發明新臺灣的可能：讀《1949禮讚》
(國立陽明交通大學出版社, 2016-03-01)
顏訥
110 GHz hybrid mode-locked fiber laser with enhanced extinction ratio based on nonlinear silicon-on-insulator micro-ring-resonator (SOI MRR)
(2016-03)
Liu, Yang
;
Hsu, Yung
;
Chow, Chi-Wai
;
Yang, Ling-Gang
;
Yeh, Chien-Hung
We propose and experimentally demonstrate a new 110 GHz high-repetition-rate hybrid mode-locked fiber laser using a silicon-on-insulator microring-resonator (SOI MRR) acting as the optical nonlinear element and optical comb filter simultaneously. By incorporating a phase modulator (PM) that is electrically driven at a fraction of the harmonic frequency, an enhanced extinction ratio (ER) of the optical pulses can be produced. The ER of the optical pulse train increases from 3 dB to 10 dB. As the PM is only electrically driven by the signal at a fraction of the harmonic frequency, in this case 22 GHz (110 GHz/5 GHz), a low bandwidth PM and driving circuit can be used. The mode-locked pulse width and the 3 dB spectral bandwidth of the proposed mode-locked fiber laser are measured, showing that the optical pulses are nearly transform limited. Moreover, stability evaluation for an hour is performed, showing that the proposed laser can achieve stable mode-locking without the need for optical feedback or any other stabilization mechanism.
A Visual Attention Monitor Based on Steady-State Visual Evoked Potential
(2016-03)
Lee, Yi-Chieh
;
Lin, Wen-Chieh
;
Cherng, Fu-Yin
;
Ko, Li-Wei
;
生物科技學系
Attention detection is important for many applications. Automatic determination of users\' visual attention state is challenging because attention involves numerous complex and internal human cognitive functions. Behavioral observations, such as eye gaze or response to external stimuli, can provide clues for users\' visual attention state; however, users\' cognitive state cannot be easily known. Conventional electroencephalography-based methods detect attention by observing the dynamic changes in the frontal lobe of the brain, especially in the anterior cingulate cortex (ACC). However, that area in the brain is associated with many functions, some of which correlate with conscious experience but are not directly related to attention. In this paper, we design an attention monitoring system to detect whether the brain experiences a visual stimulus consciously. Our experiments verified the feasibility of our design, and the average classification rate ranged from 72% to 82%.