1,721,141 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
An implementation of nDGP gravity in Pinocchio
Get PDFIn this paper we investigate dark matter structure formation in the normal branch of the Dvali-Gabadadze-Porrati (nDGP) model using the PINOCCHIO algorithm. We first present 2nd order Lagrangian perturbation theory for the nDGP model, which shows that the 1st- and 2nd-order growth functions in nDGP are larger than those in ΛCDM. We then examine the dynamics of ellipsoidal collapse in nDGP, which is accelerated compared to ΛCDM due to enhanced gravitational interactions. Running the nDGP-PINOCCHIO code with a box size of 512 Mpc/h and 1024*1024*1024 particles, we analyze the statistical properties of the output halo catalogs, including the halo power spectrum and halo mass function. The calibrated PINOCCHIO halo power spectrum agrees with N-body simulations within 5% in the comoving wavenumber range k < 0.3 (h/Mpc) at redshift z = 0. The agreement is extended to smaller scales for higher redshifts. For the cumulative halo mass function, the agreement between N-body and PINOCCHIO is also within the simulation scatter.18 pages, 3 figure
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
New Reduced-Complexity Receiver Designs for DS-CDMA Downlink Systems
No full text近年來，直序分碼多工已成為最廣為使用的行動通訊系統之一，隨著使用者對於數據通訊需求的增加，勢必得使用更大的頻寬進行無線傳輸，因此多路徑通道的效應變得更為顯著。無線通訊中的其中一項挑戰即為對抗多路徑通道所產生的影響。
在直序分碼多工下鏈系統中，廣義耙狀接收機能夠非常有效的抵抗由多路徑通道所引入的干擾，但廣義耙狀接收機必須求解一個大維度的反矩陣。在本篇論文中，我們提出一個使用最大比率結合-最小方均誤差的新型耙狀接收機。我們提出的新型耙狀接收機是傳統耙狀接收機和廣義耙狀接收機的一個折衷。此新型耙狀接收機中的訊號耙指以最大比率進行結合，並且擺放額外的雜訊耙指用來估計訊號耙指當中的雜訊和干擾成分並加以消除。我們也提出了一個高效率的耙指選擇演算法，期望夠有效率地找出有用的雜訊耙指。此外，我們將各種耙狀接收機推廣到接收端分集技術以及多輸入輸出的系統當中。模擬結果顯示此新型耙狀接收機有可能只需要較低的複雜度便能夠超越廣義耙狀接收機的效能，並且證明高效率耙指選擇演算法確實能夠選擇出有用的耙指。
另一方面，我們也針對最小方均誤差等化器當中的反矩陣問題進行討論。在本篇論文中，我們提出利用紐曼級數近似法和量子力學當中的雷利-薛丁格微擾理論，以修正快速傅利葉轉換近似法所求解出的近似反矩陣。此外，我們利用離散希伯特轉換導出一個求雷利-薛丁格微擾修正項的快速演算法。藉由分析訊號-干擾及雜訊比的分布情形，我們發現雷利-薛丁格微擾理論可以有效的降低訊號遭受嚴重衰減的機率，並且進一步提出兩種方法使得訊號-干擾及雜訊比有更理想的統計特性。對於一個最小方均誤差等化器，模擬的結果對於顯示紐曼級數微擾法無法有效修正快速傅利葉轉換近似法的結果，但雷利-薛丁格微擾法能夠極為有效的改善快速傅利葉轉換近似法的數值誤差，並且以極低的複雜度逼近理論的最佳效能。In recent years, DS-CDMA systems have gained its popularity and become the most widely used mobile communication systems. However, as the transmission bandwidth increases, one of the primary challenges in wireless communication is to overcome the effect of multipath channel.
The G-RAKE receiver is capable to mitigate the interference that is introduced by the multipath channel. The main defect of a G-RAKE is that one needs to evaluate a large matrix inversion. In this thesis, we propose a new MRC-MMSE-RAKE receiver which is a compromise between conventional RAKE and G-RAKE receivers. The signal fingers are placed to collect signal energy and combined with MRC. Additional noise fingers are introduced in order to suppress the interference of the MRC output by the MMSE interference estimation. We also propose an efficient finger selection algorithm (EFSA) to select valuable noise fingers. In addition, we extend the RAKE receivers to the receive diversity scheme and the MIMO transmission. From the simulation results, the MRC-MMSE-RAKE may outperform the G-RAKE with lower complexity, and the proposed EFSA can be utilized to select noise fingers effectively.
On the other hand, we also design two types of MMSE equalizers for DS-CDMA downlink systems. We propose using the Neumann series perturbation (NSP) method and the Rayleigh-Schrödinger perturbation (RSP) method to correct the FFT-based approximation in matrix inversion. Besides, an algorithm for finding the RSP correction is also derived. By analyzing the distribution of SINR, it is found that the RSP is able to reduce the probability of the occurrence of deep fading events, whereas the NSP can not be. Several strategies were proposed to enhance the statistical characteristic of SINR in RSP. From the simulation results, the RSP is able to correct the inaccuracy of the FFT-based approximation and it may achieve the performance of the optimal MMSE equalizer.Abstract I
Contents II
List of Figures IV
List of Tables VI
Chapter 1 Introduction 1
1.1 Motivation......................................................................................................1
1.2 Thesis Overview.............................................................................................2
Chapter 2 System Description 5
2.1 Error Control Coding.....................................................................................5
2.1.1 CRC Attachment............................................................................6
2.1.2 Turbo Encoder....................................................................................7
2.1.3 Turbo Decoder....................................................................................9
2.2 Signal Model of the DS-CDMA Downlink System........................................16
2.3 Spreading Code............................................................................................18
2.3.1 Channelization Code........................................................................18
2.3.2 Scrambling Code..............................................................................20
Chapter 3 The RAKE Receivers for the DS-CDMA Downlink System 23
3.1 The Conventional RAKE Receiver..................................................................23
3.2 The G-RAKE Receiver....................................................................................25
3.3 The Proposed MRC-MMSE-RAKE Receiver.................................................29
3.3.1 MRC Combiner................................................................................34
3.3.2 MMSE Interference Estimation........................................................35
3.3.3 The Comparison with G-RAKE and MRC-MMSE-RAKE.............36
3.3.4 Efficient Finger Selection Algorithm...............................................42
3.4 Complexity Analysis....................................................................................46
3.5 The RAKE Receivers with Receive Diversity.................................................50
II
Master Thesis National Taiwan University
3.5.1 The G-RAKE with Receive Diversity.................................................51
3.5.2 The MRC-MMSE-RAKE with Receive Diversity...........................51
3.6 MIMO Extensions of the RAKE Receivers...................................................56
3.6.1 The MIMO DS-CDMA Downlink System..........................................58
3.6.2 The MIMO-G-RAKE Receiver........................................................60
3.6.3 The MIMO-MRC-MMSE-RAKE.......................................................63
3.7 Simulation Results..........................................................................................65
3.7.1 Fixed Multipath Channel..................................................................65
3.7.2 Effects of the Proposed EFSA..........................................................69
3.7.3 Multipath Rayleigh Fading Channel................................................71
3.7.4 MIMO Multipath Rayleigh Fading Channel....................................74
3.7.5 Multipath Rayleigh Fading Channel with Error Control Coding........79
Chapter 4 The MMSE Equalizer for the DS-CDMA Downlink System 81
4.1 The MMSE Equalizer for DS-CDMA Downlink.........................................81
4.2 FFT-Based Approximation...........................................................................84
4.3 Neumann Series Perturbation Method.........................................................89
4.4 Rayleigh-Schrödinger Perturbation Method................................................93
4.4.1 Introduction to Non-Degenerate RSP Theory..................................94
4.4.2 Introduction to Degenerate RSP Theory...........................................98
4.4.3 The Proposed RSP Method..............................................................99
4.5 SINR Analysis..............................................................................................102
4.6 Complexity Analysis..................................................................................108
4.7 Simulation Results......................................................................................110
Chapter 5 Conclusion 113
References 11
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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