1,720,987 research outputs found
Improved implementation algorithms of the two-dimensional nonseparable linear canonical transform
No full textDiscrete Orthogonal Harmonic Transforms
No full text在數位訊號處理的領域中,離散正交轉換對於信號分析,信號表示,資料壓縮,數位濾波或者是訊號偵測上都是相當重要的工具。然而現有的離散正交轉換,必須要先對轉換的核函數作完整的定義。仍然還有一些連續的正交轉換,並沒有相對應的離散正交轉換。即使我們找到了,離散正交轉換的表達式都相當的複雜,同時也欠缺一般性。
在本篇論文當中,我們提出了一套有系統的方法來計算離散正交轉換。我們首先考慮一維的信號與轉換。先從連續轉換正交轉換的核函數的微分方程式,將其轉換成離散特徵值和特徵向量的問題,最後再用數值方法解此問題。因此,我們探討了一些積分核函數,例如從古典正交多項式多出得正交函數,扁橢圓球波函數以及量子力學中的薛丁格方程式。解出的離散訊號也都用模擬驗證了正確性。同時我們也實作了一些離散正交轉換:例如 chromatic derivatives,Airy 轉換,尺度轉換,一般化分數傅立葉轉換以及線性正則變換。這些離散正交轉換在行為上和常用的類傅立葉轉換有相當大的不同。舉例來說,chromatic derivatives 擁有區域近似的能力,Airy 轉換可以將訊號轉到介於時間和頻率之間的空間上,而尺度轉換對於信號的尺度變化有不變性。我們也探討了一般化的分數傅立葉轉換還有線性正則變換的特徵函數,以及他們的離散實現。這些結果可以直接在離散的角度直接用於訊號的分析。
在高維度的情形下,我們考慮的二維傅立葉轉換的特徵函數,發現不可分離的特徵函數事實上可以寫成 Hermite Gaussian 函數的線性組合。變換組合係數可以得到不同的特徵函數,同時也可以確保正交性。用這樣的概念,我們在離散的角度實作了正交的 gyrator 轉換(和旋轉的 Hermite Gaussian 函數有關)以及正交的Laguerre Gaussian 轉換。gyrator 轉換和 Laguerre Gaussian 轉換都適合用在分析離散的影像信號上。此外,也可以從 Laguerre Gaussian 轉換推導出一個不因旋轉而變的特徵。在三度空間,我們在離散的空間解了球座標簡諧波函數以及球座標簡諧轉換。他們可以用於分析三度空間的訊號,也可以推出不因旋轉而變的特徵。最後我們實做了二維不可分離的線性正則變換。我們提出了一個快速而且準確的演算法,基於分解成許多的步驟,並且套用快速傅立葉演算法。In digital signal processing, the discrete orthogonal transforms are an important tool for signal analysis, signal representation, data compression, digital filtering, and signal detection. However, the existing discrete orthogonal transforms require the explicit definition of the discrete transform kernels. There are still lots of continuous orthogonal transforms, whose corresponding discrete orthogonal transforms are not found. Even they are found, the expressions are very complicated and not general.
In this thesis, a systematic method to computing the discrete orthogonal harmonic transforms is proposed. We first consider the one-dimensional signals and transforms. We can start from the differential equations of the continuous transform kernels, model them as the discrete eigen-problems, and then solve them numerically. As a result, we explore some transform kernels, such as the classical orthogonal functions, derived from the orthogonal polynomials, the prolate spheroidal wave functions, and the Schrodinger equation in quantum mechanics. The discrete equivalents of these functions are all verified by simulations. We also implement some discrete orthogonal harmonic transforms, such as the chromatic derivatives, the Airy transforms, the scale transforms, the generalized fractional Fourier transforms, and the linear canonical transforms. These discrete orthogonal harmonic transforms own different behaviors when they are the conventional Fourier-based transforms. For instance, the chromatic derivatives have the local approximation ability, the Airy transforms convert the signal to the domain which is inbetween the time domain and the frequency domain, the scale transforms are invariant to scale changes of the signals. We also explore the generalized fractional Fourier transforms and the eigenfunctions of the linear canonical transforms, in conjunction with their discrete implementations. These results can be used to analyze the information of the digital signals, directly in the discrete domain.
For the higher dimensional case, we consider the eigenfunctions of the two dimensional Fourier transforms and find a simple linear combination of the Hermite Gaussian functions to express the non-separable eigenfunctions. Changing the combination coefficients results in different eigenfunctions and the orthogonality is guaranteed. With this concept, in the two-dimensional case, the gyrator transforms, which are related to the rotated Hermite Gaussian function, and the Laguerre Gaussian transforms are implemented in the discrete domain and with perfect orthogonality. The gyrator transforms and the Laguerre Gaussian transforms are suitable for analyzing the discrete images. In addition, the rotational invariant features can be derived from the Laguerre Gaussian transforms. In the three-dimensional case, we solve the spherical harmonic oscillator wavefunctions and the spherical harmonic oscillator transforms in the discrete domain. They are suitable for analyzing three-dimensional volume data and for deriving the rotational invariant features. Finally, we also implement the two-dimensional non-separable linear canonical transforms. A fast and accurate algorithm is proposed based on decomposing the linear canonical transforms into many stages and utilizing the fast Fourier transform algorithm
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
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
- …
