1,721,027 research outputs found
Evaluating the taxonomy of macrofossils used in macroevolution: a case study of Artemisia (Asteraceae)
No full textJiao, Bo-Han, Lu, Li-Li, Chen, Chen, Wei, Meng, Shen, Jia-Hao, Yuan, Yuan, Wang, Yu-Fei, Gao, Tian-Gang (2022): Evaluating the taxonomy of macrofossils used in macroevolution: a case study of Artemisia (Asteraceae). Phytotaxa 572 (1): 107-114, DOI: 10.11646/phytotaxa.572.1.8, URL: http://dx.doi.org/10.11646/phytotaxa.572.1.
The Applications of Hypersingular Meshless Method for Waveguide and Electromagnetic Wave Problems
No full text在本文中，提出並且實作了一個用來求解電磁波波導管、空腔共振器或電磁波散射問題的數值方法，其中牽涉到求解二維以及三維的赫姆霍茲方程式。在基本解法數值方法中，為避開奇異性將源點佈在離開邊界的虛擬邊界上是必要的。而在本文中提出的數值方法，使用了雙層勢能核函數替代傳統的基本解法中的單層勢能核函數，並且將源點直接佈在物理邊界上，使源點和邊界點重合，導致在矩陣中發生超強奇異性。這麼作的目的是在於藉由去除奇異性技術將含奇異性以及超強奇異性的格林函數正規化，以推導出係數矩陣中的對角線項。如此本數值方法保留了傳統基本解法的無網格特色，且應用本數值方法可以得到可靠的答案。本文中完成了包括電磁波波導管、空腔共振器以及三維的聲波散射問題的數值模擬，並且藉由跟解析解以及其他數值方法的結果比較來證明本方法是可行而且精確的。In this thesis, a numerical algorithm for solving the ElectroMagnetic (EM) waveguide, EM resonator and electromagnetic wave scattering problems, involving 2-D and 3-D Helmholtz equation, is described and implemented. In the Method of Fundamental Solutions (MFS), seeding location of the source points on a fictitious boundary off-setting from the real boundary is necessary. However, in the proposed method the double-layer potential kernel functions are employed as the alternative radial basis functions (RBFs) in the conventional MFS which uses the fundamental solutions, seeding the source points on the real boundary, and the source points coincide with the boundary points, causing hypersingularity occurs. The purpose of above-mentioned statements is to derive the diagonal terms of the influence matrices by using a desingularization technique to regularize the singularity and hypersingularity of the Green’s functions. Applying the proposed method in which the meshless features of the MFS are maintained yields a reliable solution. Numerical simulations consist of the solutions of electromagnetic waveguide, resonator and 3-D electromagnetic wave scattering problems. Numerical examples are performed, and compared the present numerical results with the analytical solutions, results of conventional MFS and other numerical methods. The validity and accuracy of the proposed method are well demonstrated.中文摘要(I)
Abstract(II)
Table Caption(V)
Figure Caption(VI)
Chapter 1. Introduction(1)
1.1 Motivation(1)
1.2 Literature Review(3)
1.3 Scope of the Thesis(4)
References(5)
Chapter 2. Electromagnetism Preliminaries(8)
2.1 Maxwell’s Equations(8)
2.2 Wave Equations and Helmholtz Equations(9)
2.3 Boundary Conditions(11)
2.4 Waveguide and Resonator(12)
2.5 Derivation of Analytical Solutions(15)
References(21)
Chapter 3. Hypersingular Meshless Method (HMM)(23)
3.1 Theory of the HMM(23)
3.2 Conventional Method of Fundamental Solutions(24)
3.3 Single and Double Layer potentials(25)
3.4 HMM for Helmholtz Equation(27)
3.5 Derivation of the Diagonal Coefficients of Influence Matrix(30)
References(35)
Chapter 4. HMM for Waveguide and Resonator Problems(37)
4.1 Frequency Analysis by the SVD Technique(37)
4.2 Waveguide Problems(40)
4.3 Resonator Problems(42)
References(44)
Chapter 5. HMM for Wave Scattering Problems(46)
5.1 Formulations(46)
5.2 Numerical Results(49)
References(53)
Chapter 6. Conclusions and Further Researches(54)
6.1 Conclusions(54)
6.2 Further Researches(55)
Appendix A The Detail Derivations of Equations for both Laplace Equation and Helmholtz Equation(57)
Appendix B The HMM for Interior Wave Scattering Problems(58
FIGURE S1 in Evaluating the taxonomy of macrofossils used in macroevolution: a case study of Artemisia (Asteraceae)
No full textFIGURE S1. Morphological comparison of Artemisia and its three closely related genera in the phylogenetic tree. The phylogenetic tree was summarized from Malik et al. (2017), Mei et al. (2016) and Sanz et al. (2008). The pictures in black boxes are A. A. igniaria; B. A. tridentata; C. A. chinensis; D. A. maritima; E. A. annua; F. A. stechmanniana; G. A. frigida; H. A. scoparia; and I. Kaschgaria komarovii; J. Chrysanthemum indicum; K. Ajania pallasiana; L1. fossil leaf (redrawn from Zazula et al. 2003); L2. fossil leaf (redrawn from Zazula et al. 2007); and L3. fossil corolla (redrawn from Zazula et al. 2003).Published as part of Jiao, Bo-Han, Lu, Li-Li, Chen, Chen, Wei, Meng, Shen, Jia-Hao, Yuan, Yuan, Wang, Yu-Fei & Gao, Tian-Gang, 2022, Evaluating the taxonomy of macrofossils used in macroevolution: a case study of Artemisia (Asteraceae), pp. 107-114 in Phytotaxa 572 (1) on page 114, DOI: 10.11646/phytotaxa.572.1.8, http://zenodo.org/record/730573
FIGURE 2 in Evaluating the taxonomy of macrofossils used in macroevolution: a case study of Artemisia (Asteraceae)
No full textFIGURE 2. Leaf morphology of the macrofossils and extant Artemisia frigida leaves. A. Fossil leaf (redrawn from Zazula et al. 2003: Fig. 1d); B. Fossil leaf (redrawn from Zazula et al. 2007: Fig. 7i); C. Extant leaf central lobe of A. frigida; D. Extant upper leaf of A. frigida; E. Extant middle leaf of A. frigida; F. Extant lower leaf of A. frigida. Scale bar = 2 mm.Published as part of Jiao, Bo-Han, Lu, Li-Li, Chen, Chen, Wei, Meng, Shen, Jia-Hao, Yuan, Yuan, Wang, Yu-Fei & Gao, Tian-Gang, 2022, Evaluating the taxonomy of macrofossils used in macroevolution: a case study of Artemisia (Asteraceae), pp. 107-114 in Phytotaxa 572 (1) on page 109, DOI: 10.11646/phytotaxa.572.1.8, http://zenodo.org/record/730573
FIGURE 3 in Evaluating the taxonomy of macrofossils used in macroevolution: a case study of Artemisia (Asteraceae)
No full textFIGURE 3. Corolla morphology of disc floret of extant Artemisia, its allies and the fossils. A. A. igniaria; B. A. tridentata; C. A. chinensis; D. A. maritima; E. A. annua; F. A. stechmanniana; G. A. frigida; H. A. scoparia; I. Kaschgaria komarovii; J. Chrysanthemum indicum; K. Ajania pallasiana; L. fossil (redrawn from Zazula et al. 2003: Fig. 1a). Scale bar = 1 mm.Published as part of Jiao, Bo-Han, Lu, Li-Li, Chen, Chen, Wei, Meng, Shen, Jia-Hao, Yuan, Yuan, Wang, Yu-Fei & Gao, Tian-Gang, 2022, Evaluating the taxonomy of macrofossils used in macroevolution: a case study of Artemisia (Asteraceae), pp. 107-114 in Phytotaxa 572 (1) on page 110, DOI: 10.11646/phytotaxa.572.1.8, http://zenodo.org/record/730573
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Asian Summer Monsoon changes the pollen flow on the Tibetan Plateau
No full textAbundant evidence has revealed that the Tibetan Plateau's uplift influenced the evolution of the Asian Summer Monsoon system. Pollen, as fine powdery substance, which can be easily transmitted by wind currents, has great potential to be used as an indicator of the monsoon's intensity and flow direction, and used for the detection and evaluation of the ancient monsoon on the Tibetan Plateau. Hence, it is extremely important (and necessary) to achieve a better understanding of the modern pollen deposition model on the plateau. However, most of the previous studies mainly focused on the coupling of surface pollen deposition and regional vegetation and the establishment of the transfer function between pollen-vegetation-climate on the Tibetan Plateau, but largely neglected the direct correlation of the modern surface pollen deposition and the monsoon's intensity and its current direction.
We have comprehensively analysed a dataset of the surface pollen on the Tibetan Plateau and discovered that 1) the surface pollen assemblage can reflect the alpine meadows, steppe and desert vegetation which means that surface pollen data can be used to assess the deep-time vegetation. 2) most of the exotic pollen are from trees, the spatial distribution trend of these tree pollen's relative abundance is highly coupled with the path of the Asian Summer Monsoon and the extent to which it encroached on the Tibetan Plateau. These results unambiguously demonstrate that tree pollen deposition on the Tibetan Plateau is dominated by the Asian Summer Monsoon, i.e., the upslope movement of the modern Asian Summer Monsoon drives the spread of pollen rain from low-altitude vegetation to high-altitude areas. If a similar scenario happened at different stages of the Asian Summer Monsoon evolution and the Tibetan Plateau uplift, the pollen buried in the sediments have the potential to reflect the current direction and intensity of the Asian Summer Monsoon at that time. Moreover, it would provide a simple and potentially practical proxy for the study of the evolutionary history of the Asian Summer Monsoon, e.g. wind direction and intensity, under the influence of the plateau's uplift
Variations on the Author
Full text link“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
Full text linkWe 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
- …
