1,721,126 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Algorithm and Architecture Design of Eigen-based Doppler Engine in Ultrasound Systems
No full text超音波影像（ultrasonic imaging）因為有低成本、非侵入性（non-invasiveness）、即時成像、與儀器較方便攜帶等優點，所以是一種被廣泛使用的造影方式。而其中彩色都卜勒（color Doppler）影像是一種在醫學界被廣泛使用的超音波成像模式。其主要的價值在於它可以即時（real-time）地呈現出體內流速影像，應用的對象包含血流及心搏等。然而目前超音波系統的可攜性仍明顯不足，不但會使病人必須親自到醫院才能作檢查，造成病人的痛苦，且使這樣的醫療資源難以普及化，尤其在一些需要第一線診斷的情況如救護車或戰場等，大型的醫療設備更無法提供立即的救助。
而傳統的都卜勒引擎需要複雜的參數設定，所以沒有辦法在環境變化的情形下適當的自動調節參數即時成像。所以我們希望可以不僅讓受過訓練的專業人員，使其繁複的操作步驟簡化，且降低儀器的操作介面面積以增加可攜性，這些都有利於可攜式系統之使用便利性與有效性。本論文的研究主題是針對我們正在發展的一套可攜性超音波影像系統，設計並實現智慧型彩色都卜勒的數位訊號處理引擎（Intelligent color Doppler DSP engine）。由於此超音波系統的目標為智慧型、良好的影像品質及高攜帶性。首先，本設計根據智慧型（Intelligent）的特色自動根據處理環境調整參數以及智慧地選擇所需的計算複雜度，其具有的彈性能根據目前環境需求變化動態自行調整係數，方便使用者對各種不同的目標環境都能夠掌握到實用的資訊，並兼顧良好的抗雜訊能力。
在超音波都卜勒信號處理用於顯示血流資訊時，由於血流信號相較於周圍的組織及背景雜訊微弱許多，需要各式的濾波器將雜訊濾除，其中障壁濾波器(clutter filter)便是用以濾除影響最大的組織雜訊，傳統上是以高通濾波器(high-pass filter)實現。近年有以奇異值或特徵值分解理論(eigen-based theory)為基礎的濾波演算法，具有信號可適性(signal-adaptive)特性可隨目前環境調整濾波特性，符合智慧型動態調適的特性，並可大幅增強障壁濾波器之效能，但在實際應用上仍有運算複雜度過高及運算速度受限等問題，在演算法上亦有可改進之處。
本論文的研究主題主要有三個部分，第一部分首先針用於障壁濾波器的特徵值演算法提出改進，利用所收到超音波信號於特徵值與頻率上之特性，使用聯合決策機制改善其效能；同時根據超音波觀測生理部位時其連續變化特性為基礎，提出回溯確認機制進一步增加信號判讀正確性，相較於目前文獻可改善2-5dB的處理效果。在本論文的第二部分中，進一步設計一套非線性軟決策閥值(nonlinear soft-decision thresholding)機制，相較於傳統的硬決策(hard decision)機制，本論文藉由組織與血流在時間與空間上不同的統計特性使用軟決策(soft decision)機制，並使用最大似然(maximum likelihood, ML)以及最大事後機率(maximum a posteriori, MAP)之方法，更準確地判斷血流信號並濾除信號通過障壁濾波器後殘餘的組織及背景雜訊，相較於文獻可改進5-10dB之效能。
本論文的第三部分對目前以奇異值或特徵值分解為基礎的高效能濾波引擎，在實際應用時會遭遇之運算速度較慢及運算複雜度過大之問題，提出一套超線性收斂(superlinear convergence)之快速奇異值分解演算法，同時兼具可快速運算及總運算複雜度低的優點，並以硬體實現其架構。其硬體實現後的吞吐量可達現有文獻之20-40倍，等效的單位面積吞吐量效率也能達到約5倍之多，並能同時支援數種不同大小矩陣之奇異值或特徵值分解運算。Ultrasonic imaging is a well-established imaging modality that has the advantages of cost-effectiveness, non-invasiveness, rapid imaging, and portability. color Doppler imaging is a well-established Doppler ultrasound mode and very valuable for visualizing in the real-time distribution of blood flow in a specific region of interest. The blood velocity can be detected by measuring the Doppler frequency shift of the echoes back-scattered from the moving blood. Nevertheless, the portability of current high-frequency ultrasonic imaging systems is insufficient. This will be more and more unacceptable since it is inconvenient and sometimes harmful for patients to go to the hospital for diagnoses. The high cost also reduces the popularity of such medical devices. Moreover, in ambulances or battlefields, portable devices supporting immediate diagnosis can greatly increase the survival rate.
Furthermore, the traditional Doppler engine needs complex parameter settings, it is inconvenient for the user, and it would not work when the users are not familiar with parameter settings for particular environment. Therefore, we simplify complex operations and enhance the efficiency. These features improve the convenience and efficiency of the portable ultrasound systems. The blood signals are generally much weaker than tissue and background noises, so that various filters are required to mitigate the noises.
The clutter filtering in the Doppler flow imaging is utilized to suppress the great tissue noises. The performance of the clutter filtering will remarkably affect the results of the Doppler flow imaging. Compared with the traditional high-pass filters adopted as clutter filters, singular-value-based or eigenvalue-based filters are proposed for signal-adaptive properties and high de-noising performance. Nevertheless, the high computational complexity and long computational time are still the main limitations for real-time Doppler flow imaging.
There are three main topics in this work. In the first part, the joint-decision mechanism with trace-back verification scheme is proposed to improve the performance of the eigen-based clutter filtering. After receiving the ultrasonic signals of the region of interest, the joint-decision mechanism is proposed to divide the signal spaces as clutter-noise space and blood-signal space according to the properties of eigenvalues and corresponding frequencies. In addition, the trace-back verification scheme is proposed according to the correlation of successive Doppler frames. The performance is 2-5 dB better than that of referenced works.
In the second part of this work, a nonlinear soft-decision thresholding after clutter filtering is proposed. The thresholding scheme is conventionally utilized to eliminate the remaining tissue or background noises after the clutter filters. Compared with the traditional hard-decision thresholding, we use the statistical properties of bloods and tissues for nonlinear thresholding. We use the maximum likelihood (ML) and maximum a posteriori (MAP) tests for decision. There is about 5-10 dB performance improvements compared with that of the referenced works.
In the third part, a superlinear-convergence singular-value-decomposition (SL-SVD) algorithm is proposed with properties of high-speed and low total computational complexity. The SL-SVD may be used to mitigate the problems of computational complexity and processing time in the singular-value-based or eigenvalue-based filters as clutter filters. The hardware is also implemented in 90 nm technology. The implementation results of SL-SVD has 20-40 times throughput compared with that of referenced works. The design is also capable of supporting different sizes of matrixes
VLSI Design Techniques of LDPC Codec for Enhanced Throughput and Efficiency
No full text在新一代的通信標準中，有不少系統都採用低密度奇偶校驗編碼(low-density parity-check, LDPC)，舉凡IEEE 802.16e(mobile WiMAX)、IEEE 802.11n以及百億位元傳輸系統(10GBase-T)皆為此類。對於通道解碼器速度的要求也越來越大，從IEEE 802.16e的每秒數十百萬位元，到IEEE 802.11n的每秒數億位元，甚至是10GBase-T系統的每秒百億位元，都顯示了對速度上更進一步的要求。為了增加傳輸的可靠性，低密度奇偶校驗編碼(low-density parity-check, LDPC)成為通訊系統中極為重要通道編碼(channel coding)的模組，提供更強大的錯誤更正能力。
低密度奇偶校驗編碼最早是由Robert Gallager博士在1962年於其博士論文中發表，並且已被證實具有極為優越的性能。然而當時的科技卻無法實現這種編碼系統，也就逐漸被人們所遺忘。直到三十多年後，隨著超大型積體電路的製程不斷的演進，要實現低密度奇偶校驗編碼已不再是不可能的任務，才再度引起人們廣泛討論與研究。
本論文的目標是在支援單模IEEE 802.11n標準的無線通訊系統下，針對編碼器，利用簡單的邏輯電路來實現硬體；針對解碼器，提出一套有效率的設計流程，透過基本矩陣的行列重排、運算單元的重疊運算和提早結束機制等，設計出具有彈性化的硬體架構，其優點是縮小晶片的面積、提高硬體的使用率、縮短解碼所花費時間、彈性調整解碼的吞吐量和低功率的消耗。
在硬體實作上，透過標準單元的設計流程，利用TSMC 0.13um的先進製程來實現符合IEEE 802.11n單模之低密度奇偶校驗編碼的編解碼器，所實現的晶片面積為2.65mm×2.65mm。In modern communication systems, the low-density parity-check (LDPC) codes are adopted in several ones, such as IEEE 802.16e (mobile WiMAX), IEEE 802.11n, and 10GBase-T system. The demand for speed of the channel decoder grows from the tens of Mbps of IEEE 802.16e standard, hundreds of Mbps of IEEE 802.11n standard, to 10 Gbps of 10GBase-T system. This indicates that the need for the speed of the channel decoder is growing rapidly. To increase the reliability of the transmission, LDPC codes have become an important channel-decoding module in the communication systems.
LDPC codes are first discovered by Dr. Galleger in 1962, and are proved to have great abilities for channel decoding. The technology in 1962 was not advanced enough to support these complex designs of LDPC codes, and it was rediscovered in the late 19 century.
The goal of this thesis is to propose several techniques to improve the throughput, hardware utilization efficiency (HUE), and an early termination scheme to reduce the decoding latency. In hardware implementation, we will construct a simplified LDPC encoder suitable for the IEEE 802.11n standard, and construct the LDPC decoder by using the techniques mentioned in this thesis to prove the feasibility of our algorithms and techniques.
We use the 0.13 technology of the cell-based design flow to implement our LDPC-codec chip suitable for single-mode IEEE 802.11n standard, and the chip area is 2.65mm×2.65mm.List of Figures xi
List of Tables xvi
Chapter 1 Introduction..................................................................1
1.1 Introduction.........................................................................................1
1.2 Motivation & Goal...............................................................................3
1.3 Thesis Overview...................................................................................6
Chapter 2 Low Density Parity-check Codes................................7
2.1 Error Correction Codes......................................................................7
2.1.1 Overview of the Error Correction Codes.......................................7
2.1.2 Block and convolutional codes......................................................9
2.2 Definition of LDPC Codes................................................................10
2.2.1 Encoders of LDPC Codes............................................................12
2.2.2 Decoders of LDPC Codes............................................................15
2.3 Decoding Algorithms.........................................................................17
2.3.1 Sum-Product Algorithm..............................................................17
2.3.2 Min-Sum Algorithm....................................................................20
Chapter 3 VLSI Implementation for LDPC Encoder Design..22
3.1 Parity check matrix in IEEE 802.11n standard..............................22
3.2 Hardware Implementation for Encoding Algorithm.....................23
Chapter 4 Proposed Two Techniques for Enhancing Hardware Efficiency 26
4.1 Matrix Reordering Algorithm..........................................................26
4.1.1 Introduction to LDPC Matrix Reordering...................................26
4.1.2 Proposed Matrix Reordering Algorithms....................................32
4.2 Overlapped Information Passing for Partially-parallel Quasi-Cyclic LDPC Codes...........................................................................................42
4.2.1 Overlapped Message Passing Decoding and State of the Art......42
4.2.2 Proposed Partially-Parallel and Overlapped Message Processing for QC-LDPC Codes....................................................................................................45
Chapter 5 The Early Termination Scheme................................54
5.1 Introduction to the Early Termination............................................54
5.2 Mechanism of Early Termination Schemes....................................55
5.2.1 Conventional Termination Schemes............................................55
5.2.2 Proposed Early Termination Scheme..........................................56
Chapter 6 VLSI Implementation of the LDPC Decoder Design 60
x
6.1 Decision of Word-length and Iteration Number.............................60
6.2 Bit Node Unit Design.........................................................................62
6.3 Check Node Unit Design...................................................................63
6.4 Critical Path Shortening Technique................................................64
6.4.1 The Critical Path in the Conventional Design.............................64
6.4.2 Proposed Structure to Shorten the Critical Path..........................66
6.5 Information Re-allocation for Higher Throughput........................71
6.5.1 Introduction to the Information Allocated in the Memory..........71
6.5.2 Proposed New Information Allocating Method in the Memory..72
Chapter 7 Chip Implementation.................................................75
7.1 Cell-based Design Flow.....................................................................75
7.1.1 C Model and Simulation..............................................................75
7.1.2 RTL Coding.................................................................................75
7.1.3 RTL Simulation...........................................................................76
7.1.4 Synthesis......................................................................................76
7.1.5 Gate-level Simulation..................................................................76
7.1.6 DFT..............................................................................................76
7.1.7 ATPG...........................................................................................77
7.1.8 Scanned Gate-level Simulation....................................................77
7.1.9 Place and Route...........................................................................77
7.1.10 DRC & LVS................................................................................78
7.1.11 Post-layout Gate-level Simulation...............................................78
7.2 Experimental Result..........................................................................78
7.3 Comparison........................................................................................81
Chapter 8 Conclusions.................................................................83
References 8
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Adaptive Channel-Shortened Interpolated Echo and NEXT Canceller Designs Applied to 10GBASE-T Ethernet System
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