Browsing by Issue Date, starting with "2008-05-01"

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Variation and mismatch effects of the low-temperature poly-Si TFTs on the circuit for the X-ray active matrix sensor
(2008-05-01)
Tai, Ya-Hsiang
;
Huang, Shih-Che
;
Su, Ko-Ching
;
Tseng, Chen-Yeh
;
顯示科技研究所
The application of the capability of low-temperature poly-Si TFT circuits for high resolution X-ray active matrix sensor is explored. The integration of poly-Si TIFT circuits oil the glass enables an easy connection for the sensor array with fine pixel pitch. A novel charge sensitive amplifier circuit employing poly-Si TFTs is proposed for the readout system of the active matrix sensor. It can considerably increase the circuit's immunity to the unavoidable threshold voltage variations of the poly-Si TFTs.. The V-TH mismatch effect of the TFTs, which results in the offset voltage of the charge amplifier, can also be suppressed by the proposed circuit. However, the noise arisen from the V-TH mismatch can be even larger than that from the V-TH variation after compensation. It reflects that, for higher bit digital X-ray image sensors, the mismatch effect of the devices must be properly taken into consideration. (c) 2007 Elsevier Ltd. All rights reserved.
Surface morphological and nanomechanical properties of PLD-derived ZnO thin films
(2008-05-01)
Jian, Sheng-Rui
;
Teng, I-Ju
;
Yang, Ping-Feng
;
Lai, Yi-Shao
;
Lu, Jian-Ming
This study reports the surface roughness and nanomechanical characteristics of ZnO thin films deposited on the various substrates, obtained by means of atomic force microscopy (AFM), nanoindentation and nanoscratch techniques. ZnO thin films are deposited on (a- and c-axis) sapphires and (0001) 6H-SiC substrates by using the pulsed-laser depositions (PLD) system. Continuous stiffness measurements (CSM) technique is used in the nanoindentation tests to determine the hardness and Young's modulus of ZnO thin films. The importance of the ratio (H/E-film) of elastic to plastic deformation during nanoindentation of ZnO thin films on their behaviors in contact-induced damage during fabrication of ZnO-based devices is considered. In addition, the friction coefficient of ZnO thin films is also presented here.
Adaptive radio resource allocation for downlink OFDMA/SDMA systems with multimedia traffic
(2008-05-01)
Tsai, Chun-Fan
;
Chang, Chung-Ju
;
Ren, Fang-Ching
;
Yen, Chin-Ming
;
電信工程研究所
This paper proposes an adaptive radio resource allocation (ARRA) algorithm for downlink OFDMA/SDMA systems with multimedia traffic. Considering multiple service classes and diverse QoS requirements of multimedia traffic, the ARRA algorithm is designed with the goal to maximize spectrum efficiency and to fulfill quality of service (QoS) requirements. It is composed of two parts, a dynamic priority adjustment (DPA) scheme and a priority-based greedy (PBG) scheme. The DPA adopts a type of time-to-expiration to indicate the degree of user's urgency, and dynamically gives high priorities to urgent users. The PBG allocates the radio resource iteratively, based on a cost value, to maximize the system throughput while allocating enough resource to high-priority users. Simulation results show that the ARRA algorithm outperforms conventional algorithms in terms of system throughput and satisfaction extent of QoS requirements; it can sustain users' QoS requirements up till a traffic load of 0.8, while the conventional algorithms cannot guarantee QoS requirements after a traffic load of 0.3.
High-rate composting of barley dregs with sewage sludge in a pilot scale bioreactor
(2008-05-01)
Lu, Li-An
;
Kumar, Mathava
;
Tsai, Jen-Chleh
;
Lin, Jih-Gaw
;
環境工程研究所
The feasibility of high-rate composting of barley dregs and sewage sludge was examined using a pilot scale bioreactor. A central composite design (CCD) was used to optimize the mix ratio of barley dregs/sewage sludge and moisture content. The performance of the bioreactor was monitored as a function of carbon decomposition rate (CDR) and total volatile solids (TVS) loss rate. The optimum range of mix ratio and moisture content was found to be 35-40% and 55-60%, respectively. High CO2 evolution rate (CER) and TVS loss rate were observed after 3 days of the composting and the compost was matured/stable after 7 days. Cardinal temperature model with inflection (CTMI) was used to analyze the compost stability with respect to CER as a parameter of composting efficiency. After examining the phytotoxicity, the compost can be promoted for land application. (C) 2007 Elsevier Ltd. All rights reserved.
Analytic image unwarping by a systematic calibration method for omni-directional cameras with hyperbolic-shaped mirrors
(2008-05-01)
Jeng, Sheng-Wen
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
Unwarping an orimi-directional image into a perspective-view one is easy for a single-viewpoint (SVP) designed catadioptric omnidirectional camera. But misalignment between the components (such as the mirror and the lens) of this kind of camera creates multiple viewpoints and distorts the unwarped image if the SVP constraint is assumed. The SVP constraint is relaxed in this study and a systematic method is proposed to derive a set of new and general analytic equations for unwarping images taken from an omni-directional camera with a hyperbolic-shaped mirror (called a hypercatadioptric camera). The derivation is made possible by careful investigation on the system configuration and precise calibration of involved system parameters. As a verification of the correctness of the derived equations, some of the system parameters are adjusted to fit the SVP constraint, and unwarped images using the resulting simplified camera model are shown to be of no difference from those obtained by a method based on the SVP model. The generality of the proposed method so has extended the image-unwarping capability of the existing methods for the hypercatadioptric camera to tolerate lens/mirror assembly imprecision, which is difficult to overcome in most real applications. Some experimental results of image unwarping are also included to show the effectiveness of the proposed method. (C) 2007 Elsevier B.V. All rights reserved.
Metamorphic In0.53Ga0.47As Metal-Oxide-Semiconductor Structure on a GaAs Substrate with ZrO2 High-k Dielectrics
(2008-05-01)
Ku, Chien-I
;
Chang, Edward Yi
;
Hsu, Heng-Tung
;
Chen, Chun-Chi
;
Chang, Chia-Yuan
The electrical properties of metamorphic In0.53Ga0.47As metal-oxide-semiconductor capacitors with a 100-angstrom-thick ZrO2 layer as high-k dielectrics were investigated. The In0.53Ga0.47As surface was pretreated by either sulfur passivation or HCl cleaning before the ZrO2 deposition. Owing to the lower interface-state density after sulfidation, the sulfur-passivated capacitor exhibited better accumulation capacitance and strong inversion at capacitance-voltage measurement than the HCl-cleaned capacitor after post deposition annealing at 350 degrees C. On the basis of material analyses, the capacitors that subjected to underwent sulfur treatment were found to acquire a thin sulfur layer on the interface, which protects their surface from air exposure and prevents performance degradation. [DOI: 10.1143/JJAP.47.3441]
ICI mitigation method for high-speed mobile OFDM systems
(2008-05-01)
Wu, Wen-Rong
;
Hsu, Chao-Yuan
In high-speed mobile environments, the channel is time-varying within an OFDM symbol. This time-varying characteristic will destroy the orthogonality among subcarriers. Thus, the intercarrier interference (ICI) will occur and the system performance will be degraded. An ICI mitigation method for high-speed mobile OFDM systems is proposed, which explores the special structure of the ICI channel matrix and applies the Newton's iterative matrix inversion method. With our formulation, fast Fourier transform (FFT) can be used to reduce the computational complexity. The object of canceling the ICI can be accomplished without the need of any extra circuit.
Solid-state structure of the naphthalene-based n-type semiconductor, and performance improved with Mo-based source/drain electrodes
(2008-05-01)
Kao, Chia-Chun
;
Lin, Pang
;
Shen, Yu-Yuan
;
Yan, Jing-Yi
;
Ho, Jia-Chong
The synthesis, single-crystal structures, and device performance of novel naphthalene-diimide are described. The crystal structure has revealed the importance of a withdrawing group on solid-state packing. Metal molybdenum use as source/drain (S/D) electrodes can improve the performance of the bottom-contact device. The bottom-contact device based on a material of N,N'-bis (4-trifluoromethoxybenzyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide has a high mobility of 3.58 x 10(-2) cm(2) V-1 s(-1), a threshold voltage of 1.3 V, and an on/off current ratio of 5.2 x 10(5). (c) 2008 Published by Elsevier B.V.
New test structure to monitor contact-to-poly leakage in sub-90 nm CMOS technologies
(2008-05-01)
King, Ming-Chu
;
Chin, Albert
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The high leakage or even direct short between contact and gate is a serious problem after the feature sizes are shrunk to 65-nm technology and beyond. However, there is no suitable test structure to effectively monitor the leakage current between them. We have designed a new test structure which can eliminate the drawbacks of existing test structures and effectively monitor the leakage current between contact and gate electrode in state-of-the-art CMOS process technology.
Enhanced light extraction of InGaN-based green LEDs by nano-imprinted 2D photonic crystal pattern
(2008-05-01)
Cheng, B. S.
;
Chiu, C. H.
;
Huang, K. J.
;
Lai, C. F.
;
Kuo, H. C.
In this paper, we propose a simple, low cost and mass producible nanoimprint lithography (NIL) method to texture the surface of GaN-based light emitting diodes (LEDs) with a two-dimensional photonic crystal (2DPC). Such a 2DPC structure not only enhanced the light output power but also changed the far-field pattern simultaneously. Also, a TiO(2)/SiO(2) omnidirectional reflector (ODR) was deposited on the backside of the LEDs to further increase the light output power. Under 350 mA current injection, it was found that forward voltages were 3.35, 3.34 and 3.75 V while the light output powers of the LEDs were 59.5, 92.5 and 112.1 mW for the conventional LED, the PCLED with 20 nm depth, and the PCLED with 120 nm depth all with chip size of 1 mm x 1 mm, respectively. A 88.4% enhancement in light output power of PCLED with a 120 nm depth and ODR on the backside could be achieved when compared to the conventional LED under the driving current of 350 mA. From the measurement results, it was also found that the NIL process does not degrade the electrical properties of the fabricated LEDs.
Reliability mechanisms of LTPS-TFT with HfO2 gate dielectric: PBTI, NBTI, and hot-carrier stress
(2008-05-01)
Ma, Ming-Wen
;
Chen, Chih-Yang
;
Wu, Woei-Cherrig
;
Su, Chun-Jung
;
Kao, Kuo-Hsing
In this paper, a comprehensive study of the reliability mechanisms of high-performance low-temperature polycrystalline-Si thin-film transistor (LTPS-TFT) with HfO2 gate dielectric is reported for the first time. Various bias- and temperature-stress conditions, which correspond to positive-bias stress (PBS), positive-bias temperature instability (PBTI), negative-bias stress (NBS), negative-bias temperature instability (NBTI), and hot-carrier stress, are used to differentiate the distribution and mechanism of trap density states. The generation of deep-trap states of the effective interfacial layer (IL), tail-trap states of poly-Si grain boundaries, and electron trapping of the HfO2 gate dielectric is observed for the PBS and PBTI of the HfO2 LTPS-TFT. In addition, both the deep- and tail-trap states of the effective IL are generated under NBS and NBTI of the HfO2 LTPS-TFT.
A scrambling method for fingerprint positioning based on temporal diversity and spatial dependency
(2008-05-01)
Kuo, Sheng-Po
;
Tseng, Yu-Chee
;
資訊工程學系
;
Department of Computer Science
Signal strength fluctuation is one of the major problems in a fingerprint-based localization system. To alleviate this problem, we propose a scrambling method to exploit temporal diversity and spatial dependency of collected signal samples. We present methods on how these properties can be applied to enhance the positioning accuracy of several existing schemes. Simulation studies and experimental results show that the scrambling method can greatly improve positioning accuracy, especially when the tracked object has some degree of mobility.
Development of wireless brain computer interface with embedded multitask scheduling and its application on real-time driver's drowsiness detection and warning
(2008-05-01)
Lin, Chin-Teng
;
Chen, Yu-Chieh
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Huang, Teng-Yi
;
Chiu, Tien-Ting
;
Ko, Li-Wei
Biomedical signal monitoring systems have been rapidly advanced with electronic and information technologies in recent years. However, most of the existing physiological signal monitoring systems can only record the signals without the capability of automatic analysis. In this paper, we proposed a novel brain-computer interface (BCI) system that can acquire and analyze electroencephalogram (EEG) signals in real-time to monitor human physiological as well as cognitive states, and, in turn, provide warning signals to the users when needed. The BCI system consists of a four-channel biosignal acquisition/amplification module, a wireless transmission module, a dual-core signal processing unit, and a host system for display and storage. The embedded dual-core processing system with multitask scheduling capability was proposed to acquire and process the input EEG signals in real time. In addition, the wireless transmission module, which eliminates the inconvenience of wiring, can be switched between radio frequency (RF) and Bluetooth according to the transmission distance. Finally, the real-time EEG-based drowsiness monitoring and warning algorithms were implemented and integrated into the system to close the loop of the BCI system. The practical online testing demonstrates the feasibility of using the proposed system with the ability of real-time processing, automatic analysis, and online warning feedback in real-world operation and living environments.
Effects of subcarrier power allocation on an interference avoidance code assignment strategy for multirate MC-DS-CDMA systems
(2008-05-01)
Chang, Chih-Wen
;
Wang, Li-Chun
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, we propose a joint subcarrier power allocation (SPA) and code assignment scheme for the synchronous multirate multicarrier direct-sequence code-division multiple-access (MC-DS-CDMA) system with time- and frequency-domain spreadings. Based on the newly defined metric multiple-access interference (MAI) coefficient, the proposed code assignment strategy can quantitatively predict the incurred MAI before assigning a spreading code. The SPA mechanism aims to maximize the received signal power. In addition to lowering the MAI, the proposed code assignment strategy further considers the compactness of the assigned codes in the entire 2-D tree structure. The simulation results show that the proposed joint SPA and code assignment strategy not only can reach a better received signal quality but can also achieve a high call admission rate.
D類放大器驅動雙聲道負載的方法
(2008-05-01)
胡竹生
;
陳鏗元
本發明提供一種用以驅動一三線雙聲道揚聲器之D類放大器以及方法。該D類放大器包含一第一濾波器、一第二濾波器、一處理器、一二維量化器、一訊號產生器以及一邏輯電路。根據本發明之之D類放大器以及方法能節省製造成本,並且提升效率。並且特別地,根據本發明之D類放大器以及方法係以最佳化回授方式進行,可壓低兩聲道交互影響的效應,也可避免兩個揚聲器之不匹配性。
Synthesis of zirconium dioxide nanotubes, nanowires, and nanocables by concentration dependent solution deposition
(2008-05-01)
Tsai, Min Chiao
;
Lin, Geng Te
;
Chiu, Hsin Tien
;
Lee, Chi Young
;
應用化學系
Nanowires and nanotubes of ZrO(2) were successfully synthesized in this study by concentration dependent solution deposition (CDSD) using Zr[O(CH(2))(3)CH(3)](4) as the precursor and anodic aluminum oxide (AAO) as the substrate. Here, we synthesized one-dimensional zirconium dioxide with a simple and efficient method by sucking the precursor solution though the AAO channels. In these experiments, the key factor in the formation of nanowires and nanotubes is the concentration of the precursor, Zr[O(CH(2))(3)CH(3)](4) butanol solution. Concentrated Zr[O(CH(2))(3)CH(3)](4) solutions cause the formation of solid one-dimensional materials, whereas dilute precursor solutions form hollow nanotubes. The dimensions of the nanomaterials synthesized correspond to the scope of the AAO template are 200-450 nm in diameter and about 60 mu m in length. Furthermore, the cable structures of these nanomaterials, wire-in-tube and tube-in-tube, were synthesized by alternately operating the processes. We are reporting an uncomplicated, fast and versatile method applicable to a wide range of materials, taking advantage of the sol-gel process to prepare a vast variety of nanocomposite full of potential applications, especially cable nanomaterials.
Multiport polarization-independent wavelength-interleaving bidirectional quasicirculator
(2008-05-01)
Hsieh, Po-Jen
;
Su, Der-Chin
;
光電工程學系
;
Department of Photonics
An alternative type of multiport polarization-independent wavelength-interleaving bidirectional quasicirculator is proposed. It contains holographic spatial and polarization modules (HMs), a Lyot-Ohman filter (LOF), a quarterwave plate, and a mirror. Each HM contains a holographic spatial walk-off polarizer, a half-wave plate, and a glass plate. The LOF consists of three half-wave plates and three identical pairs of crystals. The functions of the HM and the LOF are described. Then, the operating principle and the performance of this quasicirculator are described and discussed. In this circulator, the signals in the even and odd channels can circulate with opposite handedness regardless of signal polarizations. It offers a high isolation level, polarization independence, low polarization-mode dispersion, parallel input/output ports and ease of increasing the number of ports.(c) 2008 Society of Photo-Optical Instrumentation Engineers.
Wavelength-tunable erbium fiber ring laser in single-frequency operation utilizing Fabry-Perot laser with Sagnac cavity
(2008-05-01)
Yeh, C. H.
;
Shih, F. Y.
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Lee, C. N.
;
Chen, C. T.
;
Chi, S.
We propose and demonstrate experimentally a stabilized and wavelength-selective erbium-doped fiber ring laser in single-longitudinal-mode operation with Fabry-Perot laser diode (FP-LD) and using a tunable bandpass filter (TBF) inside and outside a Sagnac ring cavity. The side-mode suppression ratios of 21 dB and 36.5 dB and the output power of -3.6 dB m and -8.7 dB m in the wavelengths of 1524.45-1562.35 nm and 1531.07-1562.35 nm with the tuning step of 1.4 nm can be achieved when the TBF outside and inside Sagnac loop, respectively. The output wavelength variation of zero and the output power fluctuation of < 0.1 dB are also obtained. Moreover, the transmission efficiency of the ring laser has also been performed experimentally under a 1.25, 2.5 and 10 Gb/s external modulation, respectively. (C) 2008 Elsevier B.V. All rights reserved.
Thermophoretic particle deposition efficiency in turbulent tube flow
(2008-05-01)
Lin, Jyh-Shyan
;
Tsai, Chuen-Jinn
;
Tung, Kuo-Lun
;
Chiang, Hann-Chyuan
;
環境工程研究所
This study investigated the thermophoretic particle deposition efficiency numerically. The critical trajectory was used to calculate thermophoretic particle deposition in turbulent tube flow. The numerical results obtained in turbulent flow regime in this study were validated by particle deposition efficiency measurements with monodisperse particles (particle diameter ranges from 0.038 to 0.498 mu m) in a tube (I. 18 m long, 0.43 cm i.d., stainless-steel tube). The theoretical predictions are found to fit the experimental data of Tsai et al. [Tsai, C. J., J. S. Lin, S. G. Aggarwal, and D. R. Chen, "Thermophoretic Deposition of Particles in Laminar and Turbulent Tube Flows," Aerosol Sci. Technol., 38, 131 (2004)] very well in turbulent flows. In addition, an empirical expression has been developed to predict the thermophoretic deposition efficiency in turbulent tube flow. (c) 2008 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Study of GaN-based light-emitting diodes grown on chemical wet-etching-patterned sapphire substrate with V-shaped pits roughening surfaces
(2008-05-01)
Lee, Ya-Ju
;
Kuo, Hao-Chung
;
Lu, Tien-Chang
;
Wang, Shing-Chung
;
Ng, Kar Wai
We investigate the mechanism responding for performance enhancement of gallium nitride (GaN)-based light-emitting diode (LED) grown on chemical wet-etching-patterned sapphire substrate (CWE-PSS) with V-Shaped pit features on the top surface. According to temperature-dependent photoluminescence (PL) measurement and the measured external quantum efficiency, the structure can simultaneously enhance both internal quantum efficiency and light extraction efficiency. Comparing to devices grown on planar sapphire substrate, the threading dislocation defects of LED grown on CWE-PSS are reduced from 1.28 x10(9)/cm(2) to 3.62 x10(8)/cm(2), leading to a 12.5% enhancement in internal quantum efficiency. In terms of the theoretical computing of radiation patterns, the V-Shaped pits roughening surface can be thought of as a strong diffuser with paraboloidal autocorrelation function, increasing the escape probability of trapped photons and achieving a 20% enhancement in light extraction efficiency. Moreover, according to the measurement of optical diffraction power, CWE-PSS demonstrated superior guided light extraction efficiency than that of planar sapphire substrate, thus an extra 7.8% enhancement in light extraction efficiency was obtained. Therefore, comparing to the conventional LED, an overall 45% enhancement in integrated output power was achieved.