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Hu S.-Y.,Tung Fang Design University | Lee Y.-C.,University of Taipei | Feng Z.-C.,National Taiwan University | Yang S.-H.,National Taiwan Ocean University
Journal of Alloys and Compounds | Year: 2011

Photoluminescence (PL) spectra of a quaternary alloy In 0.014Al0.105Ga0.881N thin film grown by low pressure metalorganic chemical vapor deposition (MOCVD) are studied experimentally in the temperature range of 10-300 K. It is shown that the temperature dependence can be well studied by the Eliseev's model to characterize the scale of the exciton-localization effects for the exciton localization energy. Moreover, the Urbach energy was determined from an analysis of the low-energy side of the PL lineshape. From the temperature dependence of Urbach energy, the value of Urbach energy can be described by the Einstein oscillator model which takes into consideration the contributions from both the thermal and structural disorders. © 2010 Elsevier B.V. All rights reserved.

Lee C.-Y.,National Cheng Kung University | Shiu L.-C.,Nationl Pigtung Institute of Commerce | Lin F.-T.,Tung Fang Design University | Yang C.-S.,National Cheng Kung University
International Journal of Ad Hoc and Ubiquitous Computing | Year: 2013

A Wireless Sensor Network (WSN) must maintain a favourable sensing coverage. In this work, a fast scalable efficient sensor measure is designed for selecting suitable mobile sensors for increasing the coverage ratio and network lifetime of mobile sensor networks. The algorithm, executed on each mobile sensor, is triggered by the event, and then responds to the header with the efficiency factor of the mobile sensor. The header determines which mobile sensors must move to heal the hole. Experiments indicate the superiority of the proposed algorithm in terms of average energy consumption and network lifetime. © 2013 Inderscience Enterprises Ltd.

Guo N.R.,Tung Fang Design University | Li T.-H.S.,National Cheng Kung University
Expert Systems with Applications | Year: 2011

In this paper, a Feature-Extraction Neuron-Fuzzy Classification Model (FENFCM) is proposed that enables the extraction of feature variables and provides the classification results. The proposed classification model synergistically integrates a standard fuzzy inference system and a neural network with supervised learning. The FENFCM automatically generates the fuzzy rules from the numerical data and triangular functions that are used as membership functions both in the feature extraction unit and in the inference unit. To adapt the proposed FENFCM, two modificatory algorithms are applied. First, we utilize Evolutionary Programming (EP) to determine the distribution of fuzzy sets for each feature variable of the feature extraction unit. Second, the Weight Revised Algorithm (WRA) is used to regulate the weight grade of the principal output node of the inference unit. Finally, the proposed FENFCM is validated using two benchmark data sets: the Wine database and the Iris database. Computer simulation results demonstrate that the proposed classification model can provide a sufficiently high classification rate in comparison with that of other models proposed in the literature. © 2010 Elsevier Ltd. All rights reserved.

Hsiao H.-Y.,National Central University | Huang C.-M.,Kun Shan University | Hsu M.-Y.,Tung Fang Design University | Chen H.,National Central University
Separation and Purification Technology | Year: 2011

High-surface-area activated carbon obtained from ultra-thin PAN fibers was evaluated as CO2 adsorbent in a simulated flue gas stream. These carbons were prepared from ultra-thin PAN fibers by means of stabilization, activation, and carbonization. By changing the stabilization temperature, it is possible to control the pore size from supermicropores (0.7-2.0 nm) to mesopores (2-5.5 nm). The surface area of the carbon can be over 2500 m2g -1. Both textural properties and nitrogen functionality influence the CO2 adsorption performance of the adsorbents. The ultra-thin PAN fibers stabilized at 533 K (AC533) achieved the highest CO2 gravimetric equilibrium capacity of 5.53 mmol g-1 in a binary mixture of 15% CO2 in N2 at 323 K, while AC493 had the highest CO2 dynamic adsorption of 2.70 mmol g-1 in a N 2/CO2/H2O mixture (83/10/7% v/v) at 323 K. The textural properties, the micropore surface and micropore volume obtained from micropores below 1.1 nm, have a significant effect on CO2 dynamic adsorption. The stabilization temperature affects the nitrogen group present, as determined by XPS, which enhances the specific adsorbent-adsorbate interaction for CO2. © 2011 Elsevier B.V. All rights reserved.

Hu S.Y.,Tung Fang Design University | Lee Y.C.,Tungnan University | Feng Z.C.,National Taiwan University | Yang S.H.,National Taiwan Ocean University
Journal of Luminescence | Year: 2012

Al xIn yGa 1-x-yN quaternary alloys with different ratios of Al/In were grown by metal-organic chemical vapor deposition on GaN/Al 2O 3 substrates. The structural and emission properties of the as-grown samples were investigated, respectively, by high-resolution X-ray diffraction and photoluminescence (PL) measurements. The PL emission character is related to the two prominent quenching bands, which have been determined to be located at around 1.1 eV and 1.7 eV above the valence band, respectively, by the method of optical quenching of photoconductivity. PL emission is most intense when the Al/In ratio is 7.5 for the Al xIn yGa 1-x-yN layer. In addition, a stronger quenching phenomenon with Al/In ratio of 5.0 in Al xIn yGa 1-x-yN is observed in accordance with a reduction of the intensity of Al xIn yGa 1-x-yN-related emission peak. © 2011 Elsevier B.V. All rights reserved.

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