1,720,954 research outputs found
VR-based Motion Simulator for Ships on Real-time Rendered Dynamic Ocean
No full text這篇論文以物理上的力學系統為架構，探討船在虛擬實境(virtual reality)上的建模以及運動的模擬。我們使用搭載NVIDIA GeForce Go 7400顯示卡的電腦（CPU @2.00GHz）即時的建構一個海洋表面來當做我們的虛擬場景，海浪的大小是根據地心引力及風的方向與強度來產生，在此我們引入海洋學上的波譜理論。另外，為了達到真實與即時的場景繪製，採用圖形處理單元(GPU)來協助並完成著色，同時動態海面上的反射現象與菲涅耳(Fresnel)效應也被我們所考慮。在建構船舶模型上，所受的力與力矩是根據動態海浪的流體力學理論來施予。我們提出一個新的演算法對我們的船身格化成為點，並且依據3D中的數學理論將每個點在世界座摽中定位，並根據浮力去計算船舶在海面下的體積，以及其他流體力學的受力狀況，來模擬船的運動狀態，此外這個場景也可以被我們整合在六自由度的平台上去感知真實的運動情況。This thesis is focused on the construction of physical dynamic system about the ship modeling and motion simulation on virtual reality. We introduce the deep ocean surface constructed as our virtual environment in real-time by personal computer which is mounted NVIDIA GeForce Go 7400 graphics card and 2.00GHz CPU. We introduce an ocean spectrum theorem, so the ocean wave is created by defining the gravity and the wind. Further more, in order to obtain the real-time and realistic rendering ocean scenery, we adopt Graphics Processor Unit (GPU) hardware on shading color. The reflection phenomenon and Fresnel effect are concerned on our dynamic ocean. On ship modeling, the forces and torques are calculated from the generated dynamic waves, which are based on the hydrodynamics and transferred to our ship model. We present a new algorithm to assign points on ship hull, and apply the 3D mathematics theorem to locate each point. According to the calculation of the volume of ship below the ocean surface, we can approach the dynamics of the ship. This simulation can also be integrated with the 6 degree-of-freedom motion platform to generate realistic motion sensation.誌謝 II
摘要 III
Abstract IV
Table of Contents V
List of Figures VII
Chapter 1 Introduction 1
1.1 Background and Motivation 1
1.2 Related Works on Ship and Ocean wave modeling 3
1.3 Thesis Organization 7
Chapter 2 Ocean Dynamics and Rendering 8
2.1 Ocean Waves Modeling 8
2.2 Ocean Wave Parameters 11
2.2.1 Amplitude 11
2.2.2 Wavelength and Pulsation 16
2.2.3 Wave Direction 18
2.3 Ocean Rendering 19
2.3.1 Reflection and Refraction 20
2.3.2 The Fresnel Effect 23
2.3.3 Shading for The Ocean 26
Chapter 3 Ship Modeling and Dynamics 29
3.1 Preliminary Rigid Body Dynamics 29
3.1.1 Position and Orientation 29
3.1.2 The Velocity of a Rigid Body 32
3.1.3 Equations of Motion 33
3.1.4 Forward Euler Integration 35
3.2 The Ship Modeling 36
3.3 Ship Forces and Torques 39
3.3.1 Forces and Torques of Gravity and Sea Wave 41
3.3.2 The Wind Force 48
3.3.3 The Rudder and Propeller Force and Torque 50
Chapter 4 Implementation 52
4.1 Ocean Wave Modeling 52
4.1.1 Wave Modeling 52
4.1.2 Ocean Modeling 56
4.2 GPU Shading 61
4.3 Ship Modeling and Dynamics 64
4.3.1 Ship Modeling 64
4.3.2 Ship Dynamics 69
4.4 Integrated Simulation Loop 73
Chapter 5 Experimental Results 75
5.1 Ocean 75
5.2 Ship 79
5.3 System Integration with 6-dof Motion Platform 81
Chapter 6 Conclusions 84
References 86
Appendix 9
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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