Browsing by Issue Date, starting with "2009-12-01"

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Three-Dimensional Greedy Anti-Void Routing for Wireless Sensor Networks
(2009-12-01)
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
Due to the low-cost design nature of greedy-based routing algorithms, it is considered feasible to adopt this type of schemes within the three-dimensional (3D) wireless sensor networks. In the existing research work, the unreachability problem (i.e., the so-called void problem) resulting from the greedy routing algorithms has not been fully resolved, especially under the 3D environment. In this letter, a three-dimensional greedy anti-void routing (3D-GAR) protocol is proposed to solve the 3D void problem by exploiting the boundary finding technique for the unit ball graph (UBG). The proposed 3D rolling-ball UBG boundary traversal (3D-RUT) scheme is employed to guarantee the delivery of packets from the source to the destination node. The correctness proofs, protocol implementation, and performance evaluation for the proposed 3D-GAR protocol are also given in this letter.
Square-Gate AlGaN/GaN HEMTs With Improved Trap-Related Characteristics
(2009-12-01)
Lin, Yu-Syuan
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Wu, Jia-Yi
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Chan, Chih-Yuan
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Hsu, Shawn S. H.
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Huang, Chih-Fang
In this brief, the trap-related characteristics of high-breakdown AlGaN/GaN high-electron-mobility transistors (HEMTs) were investigated. Compared with a conventional multifinger layout, the square-gate design presented reduced the current collapse from 19% to 6% and almost eliminated the gate lag. The flicker noise density and the gate leakage decreased from 1.16 x 10(-10) to 1.17 x 10(-11) 1/Hz (f = 100 Hz) and from 7.36 x 10(-5) to 1.80 x 10(-6) A/mm (V(GS) = -4 V and V(DS) = 100 V), respectively. The breakdown voltage was also improved from 350 to 650 V. With the channel area away from the defects generated by the mesa etching process, the square-gate AlGaN/GaN HEMTs demonstrated excellent performance with much less trapping effects.
All-solution-processed blue small molecular organic light-emitting diodes with multilayer device structure
(2009-12-01)
You, Jia-Da
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Tseng, Shin-Rong
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Meng, Hsin-Fei
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Yen, Feng-Wen
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Lin, I-Feng
All-solution-processed multilayer blue small molecular organic light-emitting diodes are fabricated by blade coating method. Fluorescent blue host, 1-(7 -(9.9'-bianthracen-10-yl)-9,9-dioctyl-9H-fluoren-2-yl)pyrene, and blue dopant, 4,4'-(1E,1'E)-2,2'-(naphthalene-2,6-diyl)bis(ethene-2,1-diyl)bis(N,N-bis(4-hexylphenyl)aniline),are used to achieve good solubility and pinhole-free thin film by solution process. The multilayer device structure with hole/electron transport layer is achieved by blade coating method without the dissolution problem between layers. The efficiency of the all-solution-processed device is 4.8 cd/A at 1200 cd/m(2), close to that by thermal deposition in high vacuum chamber. The device performance is optimized with the annealing temperature of TPBi layer at 50 degrees C. (C) 2009 Elsevier B.V. All rights reserved.
The building shadow problem of airborne lidar
(2009-12-01)
Shih, Peter Tian-Yuan
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Huang, Ching -Mei
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交大名義發表
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National Chiao Tung University
Airborne lidar systems are equipped with a scanning mechanism that produces a swath of 3D coordinated points to form a cloud in each flight strip. The scanning is perpendicular to the direction of flight. The density of the point cloud is one of the major quality measures for the data collected with such systems. Point density, shade (occlusion of the laser beam) and penetration rate are major factors to be considered in the flight design. For practical operations, flight missions may be designed with overlaps ranging from 5 to 50%. Aside from the percentage overlap, the field of view is another important parameter for flight design. An evaluation scheme to assess the percentage overlap between flight strips and the selection of the field of view is proposed in this study. The influences of overlap and field of view are also demonstrated with real data gathered by an airborne lidar system.Resume Les systemes lidar aeroportes sont equipes d'un mecanisme de balayage qui engendre un couloir de nuages de points pour chaque ligne de vol. Le balayage est perpendiculaire la direction de vol. La densite du nuage de point est l'un des principaux criteres de qualite pour les donnees acquises par de tels systemes. La densite des points, l'ombre et le taux de penetration sont les principaux facteurs prendre en compte dans la planification d'un vol. Pour des operations classiques, les missions de vol peuvent etre concues avec des recouvrements compris entre 5 et 50%. De meme que le pourcentage de recouvrement, le champ de vue est un autre parametre important pour la conception du vol. Cette etude propose une methode d'evaluation pour guider le choix du pourcentage de recouvrement entre couloirs de vol et celui du champ de vue. Les influences du recouvrement et du champ de vue sont aussi demontrees avec des donnees reelles issues d'un systeme lidar aeroporte.Zusammenfassung Flugzeuggestutzte Lidarsysteme sind mit einem Scanmechanismus ausgestattet, der fur jeden Flugstreifen eine Punktwolke in Schwadbreite generiert. Die Scanrichtung ist senkrecht zur Flugrichtung. Die Dichte der Punktwolke ist eines der wesentlichen Qualitatsma ss e fur die erfassten Daten. Punktdichte, Abschattung und Durchdringungsrate sind wesentliche Faktoren, die bei der Flugplanung berucksichtigt werden mussen. Fur die Anwendungen in der Praxis werden Uberlappungen von 5 bis 50% bei der Flugplanung vorgesehen. Neben der prozentualen Uberlappung ist aber auch das Sichtfeld ein weiterer wichtiger Parameter fur die Flugplanung. In dieser Studie wird ein Schema zur Bewertung der prozentualen Uberlappung zwischen den Flugstreifen und der Auswahl des Sichtfeldes vorgestellt. Deren Einflusse werden auch an realen Daten eines flugzeuggestutzten Lidarsystems demonstriert.Resumen Los sistemas lidar aerotransportados van equipados con un mecanismo de escaneado que traza una franja de nubes de puntos en cada pasada de vuelo. El escaneado es perpendicular a la direccion de vuelo. La densidad de la nube de puntos es una de las principales medidas de calidad de los datos obtenidos con estos sistemas. La densidad de puntos, la sombra y la tasa de penetracion son los factores mas importantes a tener en cuenta en la planificacion del vuelo. Por razones operativas las misiones de vuelo se disenan con recubrimientos que oscilan entre un 5 y un 50%. Aparte del porcentaje de solapamiento, el angulo de campo es otro parametro importante a tener en cuenta. Este estudio aporta unos procedimientos de evaluacion del recubrimiento entre pasadas y de seleccion del angulo de campo. La influencia de estas dos variables se ha determinado con datos de campo obtenidos mediante un sistema lidar aerotransportado.
【陽明人】賽席爾巡航記（精華篇）
(國立陽明大學牙醫校友會, 2009-12)
徐慕文
Relativistic coupled-cluster calculations of (20)Ne, (40)Ar, (84)Kr, and (129)Xe: Correlation energies and dipole polarizabilities
(2009-12-01)
Mani, B. K.
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Latha, K. V. P.
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Angom, D.
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電子物理學系
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Department of Electrophysics
We have carried out a detailed and systematic study of the correlation energies of inert gas atoms Ne, Ar, Kr, and Xe using relativistic many-body perturbation theory and relativistic coupled-cluster theory. In the relativistic coupled-cluster calculations, we implement perturbative triples and include these in the correlation energy calculations. We then calculate the dipole polarizability of the ground states using perturbed coupled-cluster theory.
EMPIRICAL STUDIES OF STRUCTURAL CREDIT RISK MODELS AND THE APPLICATION IN DEFAULT PREDICTION: REVIEW AND NEW EVIDENCE
(2009-12-01)
Lee, Han-Hsing
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Chen, Ren-Raw
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Lee, Cheng-Few
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資訊管理與財務金融系註：原資管所+財金所
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Department of Information Management and Finance
This paper first reviews empirical evidence and estimation methods of structural credit risk models. Next, an empirical investigation of the performance of default prediction under the down-and-out barrier option framework is provided. In the literature review, a brief overview of the structural credit risk models is provided. Empirical investigations in extant literature papers are described in some detail, and their results are summarized in terms of subject and estimation method adopted in each paper. Current estimation methods and their drawbacks are discussed in detail. In our empirical investigation, we adopt the Maximum Likelihood Estimation method proposed by Duan [Mathematical Finance 10 (1994) 461-462]. This method has been shown by Ericsson and Reneby [Journal of Business 78 (2005) 707-735] through simulation experiments to be superior to the volatility restriction approach commonly adopted in the literature. Our empirical results surprisingly show that the simple Merton model outperforms the Brockman and Turtle [Journal of Financial Economics 67 (2003) 511-529] model in default prediction. The inferior performance of the Brockman and Turtle model may be the result of its unreasonable assumption of the flat barrier.
Trajectory and determinants of nutritional health in older patients during and six-month post-hospitalisation
(2009-12-01)
Chen, Cheryl C-H
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Tang, Siew T.
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Wang, Charlotte
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Huang, Guan-Hua
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統計學研究所
Aim. The aim of this study was to characterise the trajectory and to identify determinants of nutritional health over time in a sample of older hospitalised patients, using the Generalized Estimating Equation. Background. Nutritional health deteriorates and may fluctuate over time during and post-hospitalisation. To develop a target intervention it is essential that we first have a clear picture of how the nutrition changes and examine the determinants of nutritional health during and post-hospitalisation. Design. A prospective cohort study was conducted on 306 older hospitalised patients aged 65 years and older. Methods. Subjects were recruited from five surgical and medical wards at a tertiary medical center in northern Taiwan and assessed at four points in time: within 48 hours after admission, before discharge and 3-6 months post-discharge. Results. Nutritional health fluctuated significantly over time. The curve dropped during hospitalisation, returned at three months and rose slightly at six months post hospitalisation. After controlling for length of stay and surgical treatment, patients showed decreased cognitive capacity, worsening oral health, increased use of medications, increased functional limitations and raised depressive symptoms, all of which affects their nutritional health over time. The extent of functional status impacting on nutrition varies at different points in time while the predictability of other determinants remained stable. Conclusion. The trajectory of nutritional health is a reflection of the patients' cognitive status, oral health, medication taken, functional status and depressive symptoms. The findings of our study should provide guidance in the development of intervention for the nutritional health of older patients during inpatient as well as transitional care. Relevance to clinical practice. Multi-faceted packages of interventions targeting a range of determinants for managing undernutrition and subsequent decline during and post-hospitalisation need to be tested.
A General Switch-Mode Amplifier Design for Actuators Using MIMO Optimal Feedback Quantization
(2009-12-01)
Hu, Jwu-Sheng
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Chen, Keng-Yuan
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電控工程研究所
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Institute of Electrical and Control Engineering
This paper proposes a novel switch-mode power stage architecture for actuators. For a large number of actuators, the associated power amplifier becomes costly and bulky when each actuator is controlled by an independent amplifier. The proposed architecture allows actuators to share power amplifiers, thereby reducing the number of switching devices. This architecture is mapped into the graph theorem, and acceptable actuation states are analyzed. The switching method is controlled by multiple-input multiple-output optimal feedback quantization, which is designed to minimize a weighted measure of quantization distortion. Simulation and experimental results illustrate the effectiveness of the proposed scheme.
An international comparison of relative contributions to academic productivity
(2009-12-01)
Hung, Wen-Chi
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Lee, Ling-Chu
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Tsai, Min-Hua
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交大名義發表
;
National Chiao Tung University
This paper presents a methodology for measuring the improvements in efficiency and adjustments in the scale of R&D (Research & Development) activities. For this purpose, this study decomposes academic productivity growth into components attributable to (1) world academic frontier change, (2) R&D efficiency change, (3) human capital accumulation, and (4) capital accumulation. The world academic frontier at each point in time is constructed using data envelopment analysis (DEA). This study calculates each of the above four components of academic productivity for 27 countries over 1990-2003, and finds that the components which contribute to academic productivity growth vary with the different countries' characteristics and development stages. Human capital has more weight in terms of the quantity of academic research, and capital accumulation plays a more important role in the citation impact of academic research.
Ultimate Sensitivity for Optically Preamplified Direct-Detected OFDM Systems Using Spectrally Matched Optical Filters
(2009-12-01)
Peng, Wei-Ren
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Feng, Kai-Ming
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Willner, Alan E.
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光電工程學系
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Department of Photonics
We investigate the lower sensitivity bound, in terms of optical signal-to-noise ratio (OSNR), for direct-detected orthogonal frequency-division-multiplexing (DD-OFDM) systems in the presence of optically preamplified receivers. Using the spectrally matched optical filter, which is composed of two parallel filters for the carrier and sideband and has a passband matching to the signal spectrum, the ultimate sensitivity of DD-OFDM is found theoretically to approach that of coherent optical OFDM. We also investigate the effects of the filter's orders and bandwidths to the improved OSNR, and found that these effects could be effectively mitigated via the use of an optical amplifier for the carrier.
Deterministic control of ferroelastic switching in multiferroic materials
(2009-12-01)
Balke, N.
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Choudhury, S.
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Jesse, S.
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Huijben, M.
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Chu, Y. H.
Multiferroic materials showing coupled electric, magnetic and elastic orderings provide a platform to explore complexity and new paradigms for memory and logic devices. Until now, the deterministic control of non-ferroelectric order parameters in multiferroics has been elusive. Here, we demonstrate deterministic ferroelastic switching in rhombohedral BiFeO(3) by domain nucleation with a scanning probe. We are able to select among final states that have the same electrostatic energy, but differ dramatically in elastic or magnetic order, by applying voltage to the probe while it is in lateral motion. We also demonstrate the controlled creation of a ferrotoroidal order parameter. The ability to control local elastic, magnetic and torroidal order parameters with an electric field will make it possible to probe local strain and magnetic ordering, and engineer various magnetoelectric, domain-wall-based and strain-coupled devices.
Thermal Properties of 12-Fold Quasi-Photonic Crystal Microcavity Laser With Size-Controlled Nano-Post for Electrical Driving
(2009-12-01)
Ho, Wei-De
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Lu, Tsan-Wen
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Hsiao, Yi-Hua
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Lee, Po-Tsung
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光電工程學系
In this report, we investigate the fabrication process of 12-fold quasi-photonic crystal microcavity with size-controlled nano-post beneath for electrically-driven structure by fine-tuning the wet-etching time. By finite-element method, we simulate and analyze the heat transfer behaviors of microcavities with different nano-post sizes and shapes. From the real devices, we obtain whispering-gallery (WG) single-mode lasing action with high measured quality factor of 8 250 and low threshold of 0.6 mW when the nano-post size is as large as 830 nm in diameter. By varying the substrate temperature, WG single-mode lasing action is still obtained when the substrate temperature is as high as 70 C. Besides, the lasing wavelength red-shift rate is also improved compared with the microcavity without nano-post beneath. By varying the pump condition, lasing action is still observed at room temperature when the pump duty cycle increases to 16.0%. Thus, for electrically-driven photonic crystal microcavity lasers, this nano-post can serve as current injection pathway and heat sink at the same time.
Investigating Silica Nanoparticle Effect on Dynamic and Quasi-static Compressive Strengths of Glass Fiber/Epoxy Nanocomposites
(2009-12-01)
Tsai, Jia-Lin
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Cheng, Yi-Lieh
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機械工程學系
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Department of Mechanical Engineering
The research is aimed to investigate the compressive strengths of glass/epoxy nanocomposites, containing various loadings of spherical silica nanoparticles. Through a sol-gel technique, the silica particles with a diameter of 25 nm were exfoliated uniformly into the epoxy resin. Subsequently, by inserting the silica-epoxy mixture into the unidirectional glass fiber through a vacuum hand lay-up process, the glass fiber/epoxy composite laminates with 10, 20, and 30wt% of silica nanoparticles were fabricated. Quasi-static and dynamic compression tests were conducted on the brick composite specimens with fiber orientations of 0 degrees, 5 degrees, 10 degrees, 15 degrees, and 90 degrees using a hydraulic MTS machine and a split Hopkinson pressure bar, respectively. Observations on the failure specimens indicated that for fiber orientations less than 15 degrees, the fiber microbuckling is the dominant failure mechanism. On the other hand, for the 90 degrees samples, the out-of-plane shear failure is the main failure mechanism. In addition, it was denoted that as the silica contents increase, the compressive strengths of the glass/epoxy composites are improved accordingly. The enhancing mechanism in the compressive strengths can be properly explicated using the microbuckling model.
TCAD/Physics-Based Analysis of High-Density Dual-BOX FD/SOI SRAM Cell With Improved Stability
(2009-12-01)
Kim, Keunwoo
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Kuang, Jente B.
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Gebara, Fadi H.
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Ngo, Hung C.
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Chuang, Ching-Te
This paper presents a new SRAM cell using a global back-gate bias scheme in dual buried-oxide (BOX) FD/SOI CMOS technologies. The scheme uses a single global back-gate bias for all cells in the entire columns or subarray, thereby reducing the area penalty. The scheme improves 6T SRAM standby leakage, read stability, write ability, and read/write performance. The basic concept of the proposed scheme is discussed based on physical analysis/equation to facilitate device parameter optimization for SRAM cell design in back-gated FD/SOI technologies. Numerical 2-D mixed-mode device/circuit simulation results validate the merits and advantages of the proposed scheme.
Functionalizing Multi-Walled Carbon Nanotubes Using ECR Plasma and a Mild Nitric Acid Treatment
(2009-12-01)
Tseng, Wen-Shou
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Tseng, Chyuan-Yow
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Kuo, Cheng-Tzu
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材料科學與工程學系
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Department of Materials Science and Engineering
In the present work, a two-step process combining electron cyclotron resonance (ECR) plasma and 0.25 M nitric acid treatments is utilized to functionalize multi-walled carbon nanotubes (MWCNTs). In the process, high density and high incident energy hydrogen and oxygen cations generated by using ECR plasma system are used to bombard the MWCNTs for 5 min to break C-C bonds, creating free radical defects on the nanotube surface; the treated nanotubes are subsequently sonicated in the mild acid for 2 h, forming functional groups at the defects. Several characterization techniques, including X-ray photoelectron spectroscopy, scanning electron microscopy, Raman spectroscopy, and thermogravimetric analysis, are utilized to systematically evaluate the effect of the method. The results show that the MWCNTs treated by the presented method can contain a high concentration of oxygen-containing functional groups on the nanotube surface with the added advantage of high thermal stability and minimal destructive effects to the material structure.
Special Issue for SCPDE08: Numerical Methods and Analysis for PDEs and Inverse Problems Preface
(2009-12-01)
Chen, C. S.
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Lai, Ming-Chih
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Ling, Leevan
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Li, Jichun
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Yamamoto, Masahiro
15 GHz High-Isolation Sub-Harmonic Mixer With Delay Compensation
(2009-12-01)
Syu, Jin-Siang
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Meng, Chinchun
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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
A 15-GHz high-isolation sub-harmonic mixer (SHM) with delay compensation is demonstrated in this letter using 0.35 mu m SiGe heterojunction bipolar transistor (HBT) technology. The proposed SHM consisting of two parallel stacked-LO mixer cores with opposite LO I/Q inputs substantially improves port-to-port isolation. A mathematical analysis regarding the isolation properties is also included in this letter. Further, a conventional stacked-LO SHM (w/o compensation) is also implemented with the same device sizes and bias conditions for a fair comparison. SHMs w/ and w/o compensation have similar conversion gain of 9/10 dB and noise figure of 14/13.5 dB when f(LO) = 7.5 GHz. However, the delay compensation technique improves the 2LO-RF/IF isolation by 34/35 dB, the LO-RF/IF isolation by 8/9 dB, and the RF-IF isolation by 22 dB.
Wireless Location Tracking Algorithms for Environments with Insufficient Signal Sources
(2009-12-01)
Tseng, Po-Hsuan
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Feng, Kai-Ten
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Lin, Yu-Chiun
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Chen, Chao-Lin
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電信工程研究所
Location estimation and tracking for the mobile devices have attracted a significant amount of attention in recent years. The network-based location estimation schemes have been widely adopted based on the radio signals between the mobile device and the base stations. The location estimators associated with the Kalman filtering techniques are exploited to both acquire location estimation and trajectory tracking for the mobile devices. However, most of the existing schemes become inapplicable for location tracking due to the deficiency of signal sources. In this paper, two predictive location tracking algorithms are proposed to alleviate this problem. The Predictive Location Tracking (PLT) scheme utilizes the predictive information obtained from the Kalman filter in order to provide the additional signal inputs for the location estimator. Furthermore, the Geometric-assisted PLT (GPLT) scheme incorporates the Geometric Dilution of Precision (GDOP) information into the algorithm design. Persistent accuracy for location tracking can be achieved by adopting the proposed GPLT scheme, especially with inadequate signal sources. Numerical results demonstrate that the GPLT algorithm can achieve better precision in comparison with other network-based location tracking schemes.
A K-Band CMOS Quadrature Frequency Tripler Using Sub-Harmonic Mixer
(2009-12-01)
Kuo, Chien-Nan
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Chen, Huan-Sheng
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Yan, Tzu-Chao
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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
A low-power frequency tripler is designed by using the sub-harmonic mixer configuration for K-band applications. The proposed circuit features quadrature signal generation, applicable to LO signal synthesis in millimeter-wave wireless transceivers. It achieves conversion gain of -5.7 dB at the output frequency of 21 GHz. Implemented in a 0.18 mu m CMOS technology, the circuit consumes power of 7.5 mW with 1.5 V supply voltage. The entire die occupies an area of 1000 x 1050 mu m(2).