Browsing by Issue Date, starting with "2010-06-30"

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SECONDARY CONVERGENCE IN FEMTOSECOND LASER TRAPPING
(2010-06-30)
Jiang, Yuqiang
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Ma, Cungen
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Oh, Isamu
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Hosokawa, Yoichiroh
;
Masuhara, Hiroshi
When femtosecond laser pulses pass through a trapped polystyrene bead, water breakdown is induced even though the energy of laser pulse is much lower compared to the threshold value of breakdown when the femtosecond laser directly irradiates in water. This mechanism is assigned to the secondary convergence of the laser by the trapped bead.
A modified support vector machine based prediction model on streamflow at the Shihmen Reservoir, Taiwan
(2010-06-30)
Li, Pei-Hao
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Kwon, Hyun-Han
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Sun, Liqiang
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Lall, Upmanu
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Kao, Jehng-Jung
The uncertainty of the availability of water resources during the boreal winter has led to significant economic losses in recent years in Taiwan. A modified support vector machine (SVM) based prediction framework is thus proposed to improve the predictability of the inflow to Shihmen reservoir in December and January, using climate data from the prior period. Highly correlated climate precursors are first identified and adopted to predict water availability in North Taiwan. A genetic algorithm based parameter determination procedure is implemented to the SVM parameters to learn the non-linear pattern underlying climate systems more flexibly. Bagging is then applied to construct various SVM models to reduce the variance in the prediction by the median of forecasts from the constructed models. The enhanced prediction ability of the proposed modified SVM-based model with respect to a bagged multiple linear regression (MLR), simple SVM, and simple MLR model is also demonstrated. The results show that the proposed modified SVM-based model outperforms the prediction ability of the other models in all of the adopted evaluation scores. Copyright (C) 2009 Royal Meteorological Society
Optical fine structures of highly quantized InGaAs/GaAs self-assembled quantum dots
(2010-06-30)
Ramirez, H. Y.
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Lin, C. H.
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Chao, C. C.
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Hsu, Y.
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You, W. T.
A theoretical model for the electron-hole exchange interaction in three-dimensionally (3D) confining semiconductor nanostructures is presented to explain the observed decreasing tendency of the fine-structure splittings (FSSs) of small InGaAs/GaAs self-assembled quantum dots (QDs) with increasing the emission energies. The experimentally revealed FSS reduction is shown to be highly associated with the significant 3D spreading of electronic orbitals and reduced overlap of electron and hole wave functions in small and/or Ga-diffused QDs. The combination of quantum size and Ga-diffusion effects substantially reduces the averaged e-h exchange interaction and leads to the reduced FSSs in the regime of high emission energy.
Functional imprinting structures on GaN-based light-emitting diodes for light pattern modulation and light extraction efficiency enhancement
(2010-07-01)
Tu, Sheng-Han
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Wu, Shang-Yen
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Lee, Yeeu-Chang
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Pan, Jui-Wen
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Kuo, Cheng-Huang
In this study, we demonstrated a simple method that can be used to simultaneously modulate the far field pattern and enhance the light extraction of GaN-based light-emitting diodes (LEDs). In this method, microstructures were imprinted on a reliable spin-on-glass surface on top of a transparent conductive layer. The far-field pattern was modulated using microoptical structures, and at the same time, the light extraction was enhanced owing to the small refractive index difference and surface roughness. There was no decrease in the electrical performance of these devices. The peak intensity shifted from 0 to 22A degrees in one-dimensional (1D) asymmetrically blazed periodic structures, and a flattened distribution with a uniform intensity within a span of 110A degrees was observed in two-dimensional (2D) symmetrically periodic structures. This method achieved 13 and 40% light enhancements for 1D and 2D structures, respectively.
A High-Performance 30-nm Gate-All-Around Poly-Si Nanowire Thin-Film Transistor With NH(3) Plasma Treatment
(2010-07-01)
Lee, Chen-Ming
;
Tsui, Bing-Yue
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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 novel 30-nm gate-all-around (GAA) polycrystalline-silicon (poly-Si) nanowire (NW) thin-film transistor (TFT) is reported for the first time. Owing to the NW and GAA structure, the channel electric potential is well controlled by the gate electrode. After NH(3) plasma treatment for defects passivation, the values of 0.97 V, 224 mV/dec., and 0.895 V/V of threshold voltage, subthreshold swing, and drain-induced barrier lowering are achieved, respectively. A high driving current of 459 mu A/mu m and an ON-state/OFF-state current ratio of 5 x 10(7) are also obtained. These excellent characteristics indicate that the ultrasmall GAA NW poly-Si TFT would have the potential to be applied in the 3-D integrated-circuit or system-on-panel field.
Structured backward error for palindromic polynomial eigenvalue problems
(2010-07-01)
Li, Ren-Cang
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Lin, Wen-Wei
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Wang, Chern-Shuh
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應用數學系
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Department of Applied Mathematics
A detailed structured backward error analysis for four kinds of palindromic polynomial eigenvalue problems (PPEP) (Sigma(d)(l=0)A(l)lambda(l)) x = 0, A(d-l) = epsilon A(l)(star) for l = 0, 1, ..., left perpendiculard/2right perpendicular, where star is one of the two actions: transpose and conjugate transpose, and epsilon is an element of {+/- 1}. Each of them has its application background with the case star taking transpose and epsilon = 1 attracting a great deal of attention lately because of its application in the fast train modeling. Computable formulas and bounds for the structured backward errors are obtained. The analysis reveals distinctive features of PPEP from general polynomial eigenvalue problems (PEP) investigated by Tisseur (Linear Algebra Appl 309: 339-361, 2000) and by Liu and Wang (Appl Math Comput 165: 405-417, 2005).
Fabrication of Ni Nanostructures on p-Si by Scanning Probe Lithography on Si(3)N(4) Films and Selective Electrodeposition
(2010-07-01)
Lin, Chi-Yuan
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Chang, Chung-Shun
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Chien, Forest S. -S.
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光電工程學系
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Department of Photonics
Ni-Si nano Schottky junctions are fabricated by the combined process of scanning probe lithography and electrodeposition. The Si(3)N(4) film was patterned by probe-induced oxidation and became a mask for selective electrodeposition of Ni on p-Si substrate. The Ni pattern consists of Ni nano dots, whose diameter is less then 60 nm. The composition and ferromagnetism of Ni dots are verified by energy dispersive spectrum and magnetic force microscopy. The schottky barrier of Ni-Si nano contact is 0.52 V determined by the I-V measurement of conducting atomic force microscopy (CAFM). From current mapping images, it shows that chemical impurity at the Ni-Si interfaces can result in the poor conductance of the junctions.
Mining the R&D innovation performance processes for high-tech firms based on rough set theory
(2010-07-01)
Wang, Chun-Hsien
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Chin, Yang-Chieh
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Tzeng, Gwo-Hshiung
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管理科學系
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科技管理研究所
The research and development (R&D) innovation of firms continues to be viewed as an important source of competitive advantage to academics and practitioners. To explore and extract the R&D innovation decision rules, it is important to understand how the R&D innovation rule-base works. However, many studies have not yet adequately induced and extracted the decision rule of R&D innovation and performance based on the characteristics and components of the original data rather than on post-determination models. The analysis of this study is grounded in the taxonomy of induction-related activities using a rough set theory approach or rule-based decision-making technique to infer R&D innovation decision rules and models linking R&D innovation to sales growth. The rules developed using rough set theory can be directly translated into a path-dependent flow network to infer decision paths and parameters. The flow network graph and cause-and-effect relationship of decision rules are heavily exploited in R&D innovation characteristics. In addition, an empirical case of R&D innovation performance will be illustrated to show that the rough sets model and the flow network graph are useful and efficient tools for building R&D innovation decision rules and providing predictions. We will then illustrate that integrating the flow network graph with rough set theory can fully reflect the characteristics of R&D innovation, and, through the established model, we can obtain a more reasonable result than with artificial influence. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.
VPN Gateways over Network Processors: Implementation and Evaluation
(2010-07-01)
Lin, Yi-Neng
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Lin, Ying-Dar
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Lai, Yuan-Cheng
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Lin, Chuan-Hung
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資訊工程學系
Networking applications, such as VPN and content filtering, demand extra computing power in order to meet the throughput requirement nowadays. In addition to pure ASIC solutions, network processor architecture is emerging as an alternative to scale up data-plane processing while retaining design flexibility. This article, rather than proposing new algorithms, illustrates the experience in developing IPSec-based VPN gateways over network processors, and investigates the performance issues. The external benchmarks reveal that the system can reach 45Mbps for IPSec using 3DES algorithm, which improves by 350% compared to single XScale core processor and parallels the throughput of a PIII 1GHz processor. Through the internal benchmarks, we analyze the turnaround times of the main functional blocks, and identify the core processor as the performance bottleneck for both packet forwarding and IPSec processing.
Delivering Sustainable Infrastructure that Supports the Urban Built Environment
(2010-07-01)
Boyle, Carol
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Mudd, Gavin
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Mihelcic, James R.
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Anastas, Paul
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Collins, Terry
董事會獨立性與企業財務危機關係之研究
(2010-07-01)
李春安
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徐傳瑛
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Chun-An Li
;
Chuan-Ying Hsu
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Institute of Business and Management
本研究以台灣股票上市、櫃公司自2002年引進獨立董事之後的數據，就董事會獨立性觀點，建構2003年至2005年間的各項解釋變數之縱橫資料 (panel data)，透過二元不連續應變數的羅吉斯模型 (panel-logit model)，探討其與企業財務危機發生可能性的關聯。研究結果顯示，在沒有區分財務危機類型的情況下，獨立董事比率的高低、董事長是否兼任總經理、以及控制權對現金流量請求權偏離程度等公司治理機制，確實攸關財務危機發生的可能性。在進一步對曾經發生過被掏空資產的財務危機公司進行分析的結果顯示，獨立董事比率及控制股東的控制權，皆能有效解釋資產掏空案的發生，尤其是獨立董事的比率，不但統計意義上與掏空公司的財務危機顯著相關，在經濟意義上更是影響重大。對非掏空類型的財務危機而言，則是以董事長不兼任總經理及降低控制權與現金流量請求權之間的偏離程度，才會有明顯遏阻危機發生的效果。整體而言，公司治理變數較財務變數更具有解釋力。
Portable electronic nose system with chemiresistor sensors to detect and distinguish chemical warfare agents
(2010-07-01)
Wang, Li-Chun
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Tang, Kea Tiong
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Kuo, Cheng-Tzu
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Ho, Cheng-Long
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Lin, Shiao-Ray
An electronic nose (E-Nose) has been studied as a means to realize artificial olfaction. Electronic nose "instruments" are currently relatively large, since the signal manipulation and classification are still done by a personal computer (PC) or a laptop. For this reason, we have developed a portable electronic nose system based on a handheld machine by using a vapor detection array made of carbon-black polymer composites and a sensor circuit. In an effort to make a portable electronic nose, we used thin-film chemical sensors based on the carbon-black polymer nanocomposite to reliably detect chemical warfare agents. To replace the large volume of PCs, we used a field-programmable gate array to perform system control, signal manipulation, and classification. This E-Nose system was exposed to dimethyl-methyl phosphonate (DMMP) and dichloromethane (DCM) in parts per million concentration levels. DMMP and DCM were considered as simulants of the nerve agent sarin and the incapacitating agent BZ gases, respectively. (c) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3466797]
New Multiband Coupling Matrix Synthesis Technique and Its Microstrip Implementation
(2010-07-01)
Kuo, Yi-Ting
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Lu, Jhe-Ching
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Liao, Ching-Ku
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Chang, Chi-Yang
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電機工程學系
In this paper, we present a novel analytical multiband transversal coupling matrix synthesis technique. By properly combining several single-band filtering functions, the multiband filtering function with flexible transmission zeros and various bandwidth are available. The transversal coupling scheme is then transformed into a practically realizable coupling scheme. To verify the feasibility of the proposed method, two dual-band coupling schemes, both single-path and dual-path, are proposed as examples of the dual-band filter design. Finally, the dual-band filter, based on the coupling matrix corresponding to a specific coupling scheme, can be realized using a microstrip parallel-coupled structure.
Fabrication and Characterization of Mg-Doped ZnO Nanorod Arrays
(2010-07-01)
Liao, Hung-Chou
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Chen, San-Yuan
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Peng, Cheng-Hsiung
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Lin, Chin-Ching
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Cheng, Syh-Yuh
Photoelectronic characteristics are investigated in well-aligned MgO-coated ZnO nanorods (MgO/ZnO nanocables) grown on Si substrates buffered with ZnO film at a low temperature by solution techniques. Transmission electron microscopy shows that a rough surface was observed for the MgO-coated ZnO nanorods due to deposition of MgO nanoparticles on the surface of the ZnO nanorods. However, after annealed at high temperatures, the surface of the MgO-coated ZnO nanorods was flattened to form Mg-doped ZnO nanorods. Photoluminescence spectra of Mg-doped ZnO nanorods displayed a blue shift of the near-band-edge emission with increasing annealing temperature indicative of an increase in the band gap of the MgZnO alloy due to diffusion of the Mg atoms into the ZnO nanorods. In contrast, no blue shift was detected for the samples annealed in H(2)/N(2) (5%/95%) reduction atmosphere but a blue emission was detected at 800 degrees C, indicating that MgO diffusion process may produce a new luminescent center to emit the blue emission in H(2)/N(2) reduction atmosphere.
Increasing trust in mobile commerce through design aesthetics
(2010-07-01)
Li, Yung-Ming
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Yeh, Yung-Shao
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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
The growth of mobile commerce (m-commerce) has motivated a better understanding of how trust can be built on a mobile device. Researchers have previously examined design aesthetics (or visual aesthetics) of mobile website and incorporated a hedonic component of enjoyment in m-commerce domain, but the relationship between design aesthetics of mobile website design and customer trust in m-commerce has been rarely investigated. In this study, design aesthetics was enhanced to include a website characteristics component as important to trust development on the mobile Internet. This model was examined through an empirical study involving 200 subjects using structural equation modeling techniques. Our research found that design aesthetics did significantly impact website characteristics component, especially customization, perceived usefulness and ease of use, all of which were ultimately shown to have significant explanatory power in affecting customer trust. (C) 2010 Elsevier Ltd. All rights reserved.
Failure and degradation mechanisms of high-power white light emitting diodes
(2010-07-01)
Yang, Shih-Chun
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Lin, Pang
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Wang, Chien-Ping
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Huang, Sheng Bang
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Chen, Chiu-Ling
The investigation explores the factors that influence the long-term performance of high-power 1 W white light emitting diodes (LEDs). LEDs underwent an aging test in which they were exposed to various temperatures and electrical currents, to identify both their degradation mechanisms and the limitations of the LED chip and package materials. The degradation rates of luminous flux increased with electrical and thermal stresses. High electric stress induced surface and bulk defects in the LED chip during short-term aging, which rapidly increased the leakage current. Yellowing and cracking of the encapsulating lens were also important in package degradation at 0.7 A/85 degrees C and 0.7 A/55 degrees C. This degradation reduced the light extraction efficiency to an extent that is strongly related to junction temperature and the period of aging. junction temperatures were measured at various stresses to determine the thermal contribution and the degradation mechanisms. The results provided a complete understanding of the degradation mechanisms of both chip and package, which is useful in designing highly reliable and long-lifetime LEDs. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.
A Low Overhead DPA Countermeasure Circuit Based on Ring Oscillators
(2010-07-01)
Liu, Po-Chun
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Chang, Hsie-Chia
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Lee, Chen-Yi
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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
Side-channel attacks, particularly differential power analysis (DPA) attacks, are efficient ways to extract secret keys of the attacked devices by leaked physical information. To resist DPA attacks, hiding and masking methods are commonly used, but it usually resulted in high area overhead and performance degradation. In this brief, a DPA countermeasure circuit based on digital controlled ring oscillators is presented to efficiently resist the first-order DPA attack. The implementation of the critical S-box of the advanced encryption standard (AES) algorithm shows that the area overhead of a single S-box is about 19% without any extra delay in the critical path. Moreover, the countermeasure circuit can be mounted onto different S-box implementations based on composite field or look-up table (LUT). Based on our approach, a DPA-resistant AES chip can be proposed to maintain the same throughput with less than 2K extra gates.
Fast Handoff among IEEE 802.11r Mobility Domains
(2010-07-01)
Chi, Kuang-Hui
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Tseng, Chien-Chao
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Tsai, Ya-Hsuan
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資訊工程學系
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Department of Computer Science
This paper deals with secure fast handoff among access points (APs) of different IEEE 802.11r mobility domains. We leverage standard IEEE 802.11i mechanisms to let a station preauthenticate and establish a pairwise transient key with some target AP beforehand. Upon reassociation, the new AP aware of the preauthenticated station can thus complete handoff sooner than would otherwise be required. In order to resolve target APs timely, we introduce a location server that maintains network topology of an autonomous system covering multiple mobility domains. The location server assesses with which AP(s) the mobile station may reassociate next using its migration tendency. Accordingly the station is instructed to preauthenticate with fewer potential next APs than unnecessary. Performance discussions indicate that our proposal is effective in practice. Our approach is not only complementary to emerging IEEE 802.11r-based techniques but also useful to any network-layer fast handoff schemes for streamlined communication.
動態評分負載平衡裝置與方法
(2010-07-01)
楊智強
;
高靖鈞
;
黃嘉淵
;
陳健
一種動態評分負載平衡裝置與方法。此裝置包含一狀態收集器、一傳遞延遲量測器、一伺服器評分器、及一分數應對器。一旦延伸網域名稱系統伺服器收到一本地網域名稱系統伺服器發出的請求時,便通知伺服器評分器,伺服器評分器向狀態收集器取得多種狀態訊息,也向傳遞延遲量測器取得不同之服務伺服器與此本地網域名稱系統伺服器之間傳遞延遲所量測的資訊,以進行對不同服務伺服器的評分,分數應對器依評分的結果產生一目標評分値,以對應出一服務伺服器,並回報其IP位址給此本地網域名稱系統伺服器。
Autoregressive Modeling of Temporal/Spectral Envelopes With Finite-Length Discrete Trigonometric Transforms
(2010-07-01)
Hsu, Han-Wen
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Liu, Chi-Min
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資訊工程學系
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Department of Computer Science
The theory of autoregressive (AR) modeling, also known as linear prediction, has been established by the Fourier analysis of infinite discrete-time sequences or continuous-time signals. Nevertheless, for various finite-length discrete trigonometric transforms (DTTs), including the discrete cosine and sine transforms of different types, the theory is not well established. Several DTTs have been used in current audio coding, and the AR modeling method can be applied to reduce coding artifacts or exploit data redundancies. This paper systematically develops the AR modeling fundamentals of temporal and spectral envelopes for the sixteen members of the DTTs. This paper first considers the AR modeling in the generalized discrete Fourier transforms (GDFTs). Then, we derive the modeling to all the DTTs by introducing the analytic transforms which convert the real-valued vectors into complex-valued ones. Through the process, we build the compact matrix representations for the AR modeling of the DTTs in both time domain and DTT domain. These compact forms also illustrate that the AR modeling for the envelopes can be performed through the Hilbert envelope and the power envelope. These compact forms can be used to develop new coding technologies or examine the possible defects in the existing AR modeling methods for DTTs, We apply the forms to analyze the current temporal noise shaping (TNS) tool in MPEG-2/4 advanced audio coding (AAC).