Browsing by Issue Date, starting with "2009-07-01"

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Size-Dependent Strain Relaxation and Optical Characteristics of InGaN/GaN Nanorod LEDs
(2009-07-01)
Wu, Yuh-Renn
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Chiu, Chinghua
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Chang, Cheng-Yu
;
Yu, Peichen
;
Kuo, Hao-Chung
In this paper, InGaN/GaN nanorod LEDs with various sizes are fabricated using self-assembled Ni nanomasks and inductively coupled plasma-reactive ion etching. Photoluminescence (PL) characteristics exhibit size-dependent, wavelength blue shifts of the emission spectra from the nanorod LEDs. Numerical analyses using a valence force field model and a self-consistent Poisson, Schrodinger, and drift-diffusion solver quantitatively describe the correlation between the wavelength blue shifts and the strain relaxation of multiple quantum wells embedded in nanorods with different averaged sizes. Time-resolved PL studies confirm that the array with a smaller size exhibits a shorter carrier lifetime at low temperature, giving rise to a stronger PL intensity. However, the PL intensity deteriorates at room temperature, compared to that of a larger size, possibly due to an increased number of surface states, which decreases the nonradiative lifetime, and hence reduces the internal quantum efficiency.
Wideband LNA Compatible for Differential and Single-Ended Inputs
(2009-07-01)
Kuo, Ming-Ching
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Kuo, Chien-Nan
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Chueh, Tzu-Chan
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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
This letter presents a wideband low-noise amplifier (LNA) that supports both differential and single-ended inputs, while providing differential output. The LNA is implemented in 0.13 mu m. CMOS technology. For sub-1 GHz wideband applications, this LNA achieves 22.5 dB voltage gain, +1 dBrn IIP3, and 2.5 dB NF in the differential receiving mode, while achieving 23 dB voltage gain, -0.5 dB m IIP3, and 2.65 dB NF in the single-ended receiving mode. The LNA core circuit draws 2.5 mA from 1.2 V supply voltage, and occupies a small chip area of 0.06 mm(2).
Astigmatic diffractive optical element for swing-arm-type optical pickup head
(2009-07-01)
Lee, Chi-Hung
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Chiu, Yi
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Shieh, Han-Ping D.
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電控工程研究所
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光電工程學系
Based on a finite-conjugate objective lens with numerical aperture of 0.62 for a 650-nm wavelength, an optical pickup head composed of a multifunction beamsplitter and a diffractive optical element is designed be used in a swing-arm-type optical pickup head. The diffractive optical element is a lens with an elliptical four-level phase profile to provide both focusing and astigmatism. It is also designed with the goal to simplify the overall optical configuration and provide linear characteristics for the focus error signal. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI:10.1117/1.3158944]
Computational identification of riboswitches based on RNA conserved functional sequences and conformations
(2009-07-01)
Chang, Tzu-Hao
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Huang, Hsien-Da
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Wu, Li-Ching
;
Yeh, Chi-Ta
;
Liu, Baw-Jhiune
Riboswitches are cis-acting genetic regulatory elements within a specific mRNA that can regulate both transcription and translation by interacting with their corresponding metabolites. Recently, an increasing number of riboswitches have been identified in different species and investigated for their roles in regulatory functions. Both the sequence contexts and structural conformations are important characteristics of riboswitches. None of the previously developed tools, such as covariance models (CMs), Riboswitch finder, and RibEx, provide a web server for efficiently searching homologous instances of known riboswitches or considers two crucial characteristics of each riboswitch, such as the structural conformations and sequence contexts of functional regions. Therefore, we developed a systematic method for identifying 12 kinds of riboswitches. The method is implemented and provided as a web server, RiboSW, to efficiently and conveniently identify riboswitches within messenger RNA sequences. The predictive accuracy of the proposed method is comparable with other previous tools. The efficiency of the proposed method for identifying riboswitches was improved in order to achieve a reasonable computational time required for the prediction, which makes it possible to have an accurate and convenient web server for biologists to obtain the results of their analysis of a given mRNA sequence. RiboSW is now available on the web at http://RiboSW.mbc.nctu.edu.tw/.
Possibility of direct exchange diffusion of hydrogen on the Cl/Si(100)-2X1 surface
(2009-07-01)
Hsieh, Ming-Feng
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Lin, Deng-Sung
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Tsay, Shiow-Fon
;
物理研究所
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Institute of Physics
The diffusion behavior of hydrogen substitutional sites on the chlorine-terminated Si(100) surface was investigated at elevated temperatures using time-lapse scanning tunneling microscopy (STM). STM movies show that each hydrogen atom undergoes Brownian motion within a monochloride dimer row. The position of a hydrogen substitutional site is exchanged directly with that of an immediate neighboring chlorine atom in either the same dimer (intradimer diffusion) or in one of the two adjacent dimers in the same row (intrarow diffusion). Accordingly, conceptual direct exchange diffusion (DED) in a two-dimensional lattice was experimentally observed. Analysis of STM movies at various temperatures yielded rather low attempt frequencies and energy barriers, leading to the suggestion that the diffusion mechanism involves an intermediate low-energy molecular state. Density-functional theory (DFT) calculations were also performed and provided partial support for the proposed diffusion mechanism.
A target-specific approach for the identification of tyrosine-sulfated hemostatic proteins
(2009-07-01)
Liu, Tzu-An
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Yasuda, Shin
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Williams, Frederick E.
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Liu, Ming-Yih
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Suiko, Masahito
A simple methodology for the identification of hemostatic proteins that are subjected to post translational tyrosine sulfation was developed. The procedure involves sequence analysis of members of the three hemostatic pathways using the Sulfinator prediction algorithm, followed by [(35)S]sulfate labeling of cultured HepG2 human hepatoma cells, immunoprecipitation of targeted [(35)S]sulfate-labeled hemostatic proteins, and tyrosine O-[(35)S]sulfate analysis of immunoprecipitated proteins. Three new tyrosine-sulfated hemostatic proteins-protein S. prekallikrein, and plasminogen-were identified. Such a target-specific approach will allow investigation of tyrosine-sulfated proteins of other biochemical/physiological pathways/processes and contribute to a better understanding of the functional role of post-translational tyrosine sulfation. (C) 2009 Elsevier Inc. All rights reserved.
Optimization on MOS-Triggered SCR Structures for On-Chip ESD Protection
(2009-07-01)
Chen, Shih-Hung
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Ker, Ming-Dou
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電機學院
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College of Electrical and Computer Engineering
MOS-triggered silicon-controlled rectifier (SCR) devices have been reported to achieve efficient on-chip electrostatic discharge (ESD) protection in deep-submicrometer CMOS technology. The channel length of the embedded MOS transistor in the MOS-triggered SCR device dominates the trigger mechanism and current distribution to govern the trigger voltage, holding voltage, on resistance, second breakdown current, and ESD robustness of the MOS-triggered SCR device. The embedded MOS transistor in the MOS-triggered SCR device should be optimized to achieve the most efficient ESD protection in advanced CMOS technology. In addition, the layout style of the embedded MOS transistor can be adjusted to improve the MOS-triggered SCR device for ESD protection.
An Effective Scheduling Approach for Maximizing Polyimide Printing Weighted Throughput in Cell Assembly Factories
(2009-07-01)
Chung, S. H.
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Tai, Y. T.
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Pearn, W. L.
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工業工程與管理學系
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Department of Industrial Engineering and Management
Polyimide printing (PI) is an important process operation but also often the cause of bottlenecks in capital-intensive cell assembly factories. Therefore, the development of an effective scheduling method to maximize throughput in this PI process is essential and difficult. In the polyimide printing scheduling problem (PISP), jobs are given weights and clustered by their product types, which must be processed on identical parallel PI machines. The setup times for two consecutive jobs between different product types in the PI machines are sequence-dependent. In this paper, the PISP is formulated as a mixed integer linear programming model. The PISP is also transformed into a multiple tour maximum collection problem (MTMCP), a well-known network problem which has been investigated extensively. Based on this transformation, one can therefore solve the PISP near-optimally using the efficient algorithm.
三元內容可定址記憶體漏電流截斷裝置
(2009-07-01)
黃柏蒼
;
劉文彥
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黃威
一種應用於三元內容可定址記憶體漏電流截斷裝置。三元內容可定址記憶體之儲存記憶胞區分為運轉模式、待機模式及截止模式,本發明利用多模式閘極電源控制裝置降低三元電晶體可定址記憶體之儲存記憶胞在待機模式及截止模式之漏電流並維持運轉模式執行效能。
A Comparative Study of Carrier Transport for Overlapped and Nonoverlapped Multiple-Gate SOI MOSFETs
(2009-07-01)
Lee, Wei
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Su, Pin
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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
This paper provides a comparative study of carrier transport characteristics for multiple-gate silicon-on-insulator MOSFETs with and without the nonoverlapped source/drain structure. For the overlapped devices, we observed Boltzmann law in subthreshold characteristics and phonon-limited behavior in the inversion regime. For the nonoverlapped devices, however, we found insensitive temperature dependence for drain current in both subthreshold and inversion regimes. Our low-temperature measurements indicate that the intersubband scattering is the dominant carrier transport mechanism for narrow overlapped multigate field-effect transistors (MuGFETs). For the nonoverlapped MuGFETs, the voltage-controlled potential barriers in the nonoverlapped regions may give rise to the weak localization effect (conductance reduction) and the quantum interference fluctuations.
Low-Complexity ICI Mitigation Methods for High-Mobility SISO/MIMO-OFDM Systems
(2009-07-01)
Hsu, Chao-Yuan
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Wu, Wen-Rong
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電信工程研究所
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Institute of Communications Engineering
In orthogonal frequency-division multiplexing (OFDM) systems, it is generally assumed that the channel response is static in an OFDM symbol period. However, the assumption does not hold in high-mobility environments. As a result, intercarrier interference (ICI) is induced, and system performance is degraded. A simple remedy for this problem is the application of the zero-forcing (ZF) equalizer. Unfortunately, the direct ZF method requires the inversion of an N x N ICI matrix, where N is the number of subcarriers. When N is large, the computational complexity can become prohibitively high. In this paper, we first propose a low-complexity ZF method to solve the problem in single-input-single-output (SISO) OFDM systems. The main idea is to explore the special structure inherent in the ICI matrix and apply Newton's iteration for matrix inversion. With our formulation, fast Fourier transforms (FFTs) can be used in the iterative process, reducing the complexity from O(N(3)) to O( N log(2) N). Another feature of the proposed algorithm is that it can converge very fast, typically in one or two iterations. We also analyze the convergence behavior of the proposed method and derive the theoretical output signal-to-interference-plus-noise ratio (SINR). For a multiple-input-multiple-output (MIMO) OFDM system, the complexity of the ZF method becomes more intractable. We then extend the method proposed for SISO-OFDM systems to MIMO-OFDM systems. It can be shown that the computational complexity can be reduced even more significantly. Simulations show that the proposed methods perform almost as well as the direct ZF method, while the required computational complexity is reduced dramatically.
REGIONAL INEQUALITY IN CHINA'S HEALTH CARE EXPENDITURES
(2009-07-01)
Chou, Win Lin
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Wang, Zijun
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交大名義發表
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National Chiao Tung University
This paper has two parts. The first part examines the regional health expenditure inequality in China by testing two hypotheses on health expenditure convergence. Cross-section regressions and cluster analysis are used to study the health expenditure convergence and to identify convergence Clusters. We find no single nationwide convergence, only convergence by Cluster. In the second part of the paper, we investigate the long-run relationship between health expenditure inequality, income inequality, and provincial government budget deficits (1313) by using new panel cointegration tests with health expenditure data in China's urban and rural areas. We find that the income inequality and real provincial government BID are useful in explaining the disparity in health expenditure prevailing between urban and rural areas. In order to reduce health-spending inequality, one long-run policy suggestion from our findings is for the government to implement more rapid economic development and stronger financing schemes in poorer rural areas. Copyright (C) 2009 John Wiley & Sons, Ltd.
10 Gb/s TDM passive optical networks using four wavelengths multiplexed channels
(2009-07-01)
Wang, C. H.
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Shih, F. Y.
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Yeh, C. H.
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Chow, C. W.
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Chi, S.
We propose a new architecture for 10 Gb/s upstream traffic in TDM-PON using externally injection-locked Fabry-Perot laser diodes (FP-LDs) in each optical network unit (ONU). Four directly modulated 2.5 Gb/s FP-LDs were injection-locked by continuous wave (CW) carriers distributed from the optical line terminal (OLT). Hence, a total of 10 Gb/s upstream traffic can be achieved. Experimental results show negligible power penalty at a transmission of 25 km standard single mode fiber (SMF) without dispersion compensation. The performance of the injection-locked FP-LD is also studied. (C) 2009 Elsevier B.V. All rights reserved.
In Situ Ultrahigh Vacuum Transmission Electron Microscope Investigations of Nanostructures
(2009-07-01)
Chen, L. J.
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Wu, W. W.
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材料科學與工程學系
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Department of Materials Science and Engineering
Passive synchronization between a self-similar pulse and a bound-soliton bunch in a two-color mode-locked fiber laser
(2009-07-01)
Hsiang, Wei-Wei
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Chang, Chia-Hao
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Cheng, Chien-Po
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Lai, Yinchieh
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光電工程學系
We report the first (to our knowledge) experimental observation of passive synchronization between a 1.03 mu m self-similar pulse and a 1.56 mu m bound-soliton bunch in a two-color mode-locked fiber laser. The self-similar pulse can form an effective potential well of several picoseconds to trap the copropagating bound solitons in the shared-fiber section. Such synchronization mechanism is supported by the experimental evidence of smaller time separation between the bound solitons under synchronization, In addition, the self-similar pulse and bound solitons can still remain locked under the periodic collision of another 1.56 mu m unlocked pulse train. (C) 2009 Optical Society of America
All-solution-processed inverted polymer solar cells on granular surface-nickelized polyimide
(2009-07-01)
Hsiao, Yu-Sheng
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Chen, Chih-Ping
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Chao, Ching-Hsun
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Whang, Wha-Tzong
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材料科學與工程學系
In this study, we prepared all-solution-processed inverted polymer solar cells (PSCs) incorporating two solution-processed electrodes-surface-nickelized polyimide films (NiPI films) as cathodes and high-conductivity poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) films as anodes-and an active layer with a bulk heterojunction morphology of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C(61)-buytyric acid methyl ester (PCBM). The granular Ni thin films, which exhibited good adhesion and high-conductivity (ca. 2778 S cm(-1)) on the polyimide (PI) substrates and possessed a work function different from that of pure Ni metal (WF, 5.4 eV). Using ultraviolet photoelectron spectroscopy, we determined that the WF of the NiPI films was ca. 3.9 eV. Prior to the coating of the photoactive layer, the surface of the NiPI films were treated with titanium(diisopropoxide)bis(2,4-pentanedionate) (TIPD) solution to facilitate the deposition of high-quality active layer and further as a hole blocking layer. The solution processed anodes (solvent-modified PEDOT:PSS films) were further coated and subjected to mild oxygen plasma treatment on the active layer. Short exposure (5 s) to the plasma improved the quality of the surface of the active layer for PEDOT:PSS deposition. These inverted PSCs on flexible granular NiPI films provided a power conversion efficiency of 2.4% when illuminated under AM 1.5 conditions (100 mW cm(-2)). The phenomenon of light absorption enhancement in those inverted PSCs was observed as indicated in reflective UV-vis, haze factor and external quantum efficiency (EQE) responses. The resulting fill factor (FF) of 0.43 is still significantly lower than the FF of 0.64 for standard devices. When compared to the planar structure, the improvement of absorbance of light and good haze factors was obtained for granular structure which suggests NiPI as a better back contact electrode through enhancing the light trapping and scattering in inverted PSCs. (C) 2009 Elsevier B.V. All rights reserved.
Determination of global positioning system (GPS) receiver clock errors: impact on positioning accuracy
(2009-07-01)
Yeh, Ta-Kang
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Hwang, Cheinway
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Xu, Guochang
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Wang, Chuan-Sheng
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Lee, Chien-Chih
Enhancing the positioning precision is the primary pursuit of global positioning system (GPS) users. To achieve this goal, most studies have focused on the relationship between GPS receiver clock errors and GPS positioning precision. This study utilizes undifferentiated phase data to calculate GPS clock errors and to compare with the frequency of cesium clock directly, to verify estimated clock errors by the method used in this paper. The frequency stability calculated from this paper (the indirect method) and measured from the National Standard Time and Frequency Laboratory (NSTFL) of Taiwan (the direct method) match to 1.5 x 10(-12) (the value from this study was smaller than that from NSTFL), suggesting that the proposed technique has reached a certain level of quality. The built-in quartz clocks in the GPS receivers yield relative frequency offsets that are 3-4 orders higher than those of rubidium clocks. The frequency stability of the quartz clocks is on average two orders worse than that of the rubidium clock. Using the rubidium clock instead of the quartz clock, the horizontal and vertical positioning accuracies were improved by 26-78% (0.6-3.6 mm) and 20-34% (1.3-3.0 mm), respectively, for a short baseline. These improvements are 7-25% (0.3-1.7 mm) and 11% (1.7 mm) for a long baseline. Our experiments show that the frequency stability of the clock, rather than relative frequency offset, is the governing factor of positioning accuracy.
Fabrication of Antireflective Sub-Wavelength Structures on Silicon Nitride Using Nano Cluster Mask for Solar Cell Application
(2009-07-01)
Sahoo, Kartika Chandra
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Lin, Men-Ku
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Chang, Edward-Yi
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Lu, Yi-Yao
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Chen, Chun-Chi
We have developed a simple and scalable approach for fabricating sub-wavelength structures (SWS) on silicon nitride by means of self-assembled nickel nanoparticle masks and inductively coupled plasma (ICP) ion etching. Silicon nitride SWS surfaces with diameter of 160-200 nm and a height of 140-150 nm were obtained. A low reflectivity below 1% was observed over wavelength from 590 to 680 nm. Using the measured reflectivity data in PC1D, the solar cell characteristics has been compared for single layer anti-reflection (SLAR) coatings and SWS and a 0.8% improvement in efficiency has been seen.
Greedy Routing with Anti-Void Traversal for Wireless Sensor Networks
(2009-07-01)
Liu, Wen-Jiunn
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Feng, Kai-Ten
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電信工程研究所
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Institute of Communications Engineering
The unreachability problem (i.e., the so-called void problem) that exists in the greedy routing algorithms has been studied for the wireless sensor networks. Some of the current research work cannot fully resolve the void problem, while there exist other schemes that can guarantee the delivery of packets with the excessive consumption of control overheads. In this paper, a greedy antivoid routing (GAR) protocol is proposed to solve the void problem with increased routing efficiency by exploiting the boundary finding technique for the unit disk graph (UDG). The proposed rolling-ball UDG boundary traversal (RUT) is employed to completely guarantee the delivery of packets from the source to the destination node under the UDG network. The boundary map (BM) and the indirect map searching (IMS) scheme are proposed as efficient algorithms for the realization of the RUT technique. Moreover, the hop count reduction (HCR) scheme is utilized as a short-cutting technique to reduce the routing hops by listening to the neighbor's traffic, while the intersection navigation (IN) mechanism is proposed to obtain the best rolling direction for boundary traversal with the adoption of shortest path criterion. In order to maintain the network requirement of the proposed RUT scheme under the non-UDG networks, the partial UDG construction (PUC) mechanism is proposed to transform the non-UDG into UDG setting for a portion of nodes that facilitate boundary traversal. These three schemes are incorporated within the GAR protocol to further enhance the routing performance with reduced communication overhead. The proofs of correctness for the GAR scheme are also given in this paper. Comparing with the existing localized routing algorithms, the simulation results show that the proposed GAR-based protocols can provide better routing efficiency.
FMM: a web server for metabolic pathway reconstruction and comparative analysis
(2009-07-01)
Chou, Chih-Hung
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Chang, Wen-Chi
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Chiu, Chih-Min
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Huang, Chih-Chang
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Huang, Hsien-Da
Synthetic Biology, a multidisciplinary field, is growing rapidly. Improving the understanding of biological systems through mimicry and producing bio-orthogonal systems with new functions are two complementary pursuits in this field. A web server called FMM (From Metabolite to Metabolite) was developed for this purpose. FMM can reconstruct metabolic pathways form one metabolite to another metabolite among different species, based mainly on the Kyoto Encyclopedia of Genes and Genomes (KEGG) database and other integrated biological databases. Novel presentation for connecting different KEGG maps is newly provided. Both local and global graphical views of the metabolic pathways are designed. FMM has many applications in Synthetic Biology and Metabolic Engineering. For example, the reconstruction of metabolic pathways to produce valuable metabolites or secondary metabolites in bacteria or yeast is a promising strategy for drug production. FMM provides a highly effective way to elucidate the genes from which species should be cloned into those microorganisms based on FMM pathway comparative analysis. Consequently, FMM is an effective tool for applications in synthetic biology to produce both drugs and biofuels. This novel and innovative resource is now freely available at http://FMM.mbc.nctu.edu.tw/.