1,720,982 research outputs found
Theoretical Analysis and Numerical Simulation of Transient Wave in Homogeneous and Nonhomogeneous Multilayered Media
No full text當一均佈動力載荷施加於均質或非均質層狀介質的表面時，本文以拉普拉斯轉換技巧，分析其域內的一維暫態波傳問題。對於均質多層域的暫態響應，採用三種不同的分析及數值計算方式：廣義射線法，Durbin 數值拉普拉斯逆轉換以及有限元素法。由矩陣形式Bromwich展開所組成的廣義射線解為一精確解，展開後級數的每一項代表經過界面相同次數的穿透或反射波。若不執行級數展開，將轉換域下的矩陣解直接採用Durbin 數值逆轉換，所得之結果為一混合解析與數值解，適合計算層狀介質的長時間暫態響應。有限元素解則為一純數值解，可以多點計算並快速分析複雜結構物的暫態響應，但對於高頻或是急遽變化的響應則會出現震盪形式的數值誤差，三種數值計算的結果皆有良好的驗證。
而關於非均質材料的暫態問題，則是使用拉普拉斯轉換技巧配合數值逆轉換的混合解析與數值解，首先探討多項式函數形式的功能性梯度單層域，在雙邊自由與單邊固定的邊界條件，於表面受動力載荷下的應力波傳分析，而與多層均質材料模擬單層功能性梯度板的暫態響應，亦有良好的一致性。本文進一步分析層狀功能性梯度材料，討論其域內的暫態彈性波傳，在數值計算上，則以三層功能性梯度材料為例，將其退化為廣泛應用的雙層相異質材料夾功能性梯度材料之暫態問題，並研究其單邊與雙邊的不連續情況對於暫態響應之影響。
隨機、週期與連續分佈型三種類型的多層均質材料在本文亦有深入研究。文中並以複合材料力學的等效材料方式進行化簡，分析多層域暫態響應並探討等效材料在暫態波傳分析的適用性。In this study, one-dimensional transient wave-propagation in homogeneously and inhomogeneously multilayered media are analyzed by Laplace transform technique. The numerical calculations for homogeneously multilayered media are performed by three methods: generalized ray method, numerical Laplace inversion method (Durbin’s formula), and finite element method (FEM). The analytical result of generalized ray solution for multilayered structures is composed of matrix-form Bromwich expansion in the transform domain. Every term represents a group of waves which is transmitted or reflected through the interface. The numerical inversion of Laplace transform by Durbin’s formula is also used to calculate the transient responses. This numerical Laplace inversion technique has the advantage of calculating the long-time transient responses for complicated multilayered structures. FEM result also agrees well with the calculations by generalized ray method and numerical Laplace inversion.
For the transient-wave problem of inhomogeneously multilayered media, we use Laplace transform technique and the numerical Laplace inversion (Durbin’s formula) to calculate the dynamic behavior of the polynomial FGM (functionally graded material) slab. In addition, the FGM slab is approximated as a multilayered medium with homogeneous material in each layer. The transient responses of FGM formulation and multilayered solution are discussed in detail. Furthermore, transient-wave in inhomogeneously multilayered media is analyzed. In the numerical calculation, three-layered functionally graded media is used for analysis and the degenerative problem of an FGM bounded to two elastic homogeneous materials is discussed.
Finally, the numerical calculations of the transient responses for randomly distributed, periodically distributed, and continuously distributed multilayered media are performed to investigate if the effective material concept is suitable for dynamic analysis
Cost Efficient MIMO Equalization Design for MIMO WLAN and FFT/IFFT Hardware Implementation
No full text隨著多媒體應用的快速發展，具有高資料傳輸速率(data rate)的無線網路益加重要。為此，根據多輸入多輸出正交分頻多工(MIMO-OFDM)技術的IEEE 802.11n也應運而生，以提高傳輸速率。本篇論文中提出一個符合IEEE 802.11n 之數位基頻接收器設計，其中包含了符元邊界偵測、同步追蹤迴路設計、快速傅利葉轉換器以及MIMO 等化器。中首先分析二種MIMO 傳輸模式：Alamouti 以及VBLAST，而後更採取並行的方式以兼得高資料傳輸速率與高傳輸品質的優點。如此之模式可達到100Mbps，滿足11n 中資料傳輸速率的基本需求。由簡化的複數乘法器設計， 在本篇論文中提出了一個低複雜度MISO/MIMO 的等化器演算法以供Alamouti 傳輸模式。此演算法包含三個部份：通道估測、MISO/MIMO 信號偵測解碼、以及通道資訊的更新。在一般的狀況下，由此演算法設計之等化器可以減少32%乘法運算的複雜度；而在11n 的系統之中，則可以減少33%的乘法複雜度。利用室內多路徑衰減通道的系統模擬可以得知，運用此演算法之等化器能達到與傳統等化器相同的SER 表現。外，文末呈現一個64 點SISO 的快速傅利葉轉換器晶片，並以FPGA 板驗證之。藉由分析系統需求，可以計算出SDF 管線架構之傅利葉轉換器的各項參數。經過改良後的複數乘法器設計以及適當之記憶體安排，在0.18 μm CMOS製程下，此傅利葉轉換器晶片的核心面積為0.570 mm × 0.565 mm；在40 MHz之工作頻率下，消秏功率為10.8 mW。最後，透過Altera Stradix EP1S80 FPGA板，並以Tektronix TLA 715 邏輯分析儀量測，此傅利葉轉換器功能之正確性得到了驗證。The high data-rate wireless transmission is the demand for many multimedia applications. For this purpose, IEEE 802.11n is the wireless LAN standard to offer higher throughput based on MIMO-OFDM techniques. In this thesis, a digital baseband receiver is presented for IEEE 802.11n, including the initial boundary detection, synchronization tracking loop, FFT, and MIMO equalization.or MIMO transmission schemes, Alamouti and VBLAST are presented here. Furthermore, the combined scheme is taken to achieve both of the advantages, i.e. higher data rate and better quality. The combined scheme can satisfy a 100Mbps requirement of IEEE 802.11n standard.ased on strength-reduced complex multiplication, a cost e cient MISO/MIMO equalization is proposed for Alamouti scheme. The cost efficient MISO/MIMO equalization contains three parts: channel estimation, MISO/MIMO detection and updating process. The overall algorithm can reduce 32 % multiplication complexity in general case compared with 33 % in 11n case. The system performance of this design is the same as the conventional technique evaluated by the uncoded SER simulation over indoor multipath fading channel.inally, a 64-point SISO FFT/IFFT processor is realized in the chip design and evaluated by FPGA board. By analyzing the system performance, the parameters of FFT/IFFT can be derived for SDF pipeline structure. By multiplierless design and memory arrangement, the chip core area occupies 0.570 mm x 0.565 mm and consumes 10.8 mW at operating frequency 40MHz using 0.18 um CMOS technology. The FFT/IFFT functionality is also veri ed by Altera Stradix EP1S80 FPGA board and Tektronix TLA 715.1 Introduction 1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . 1.2 Thesis Overview . . . . . . . . . . . . . . . . . . 3 Principles of MIMO-OFDM 5.1 OFDM technique . . . . . . . . . . . . . . . . . . . 5.1.1 OFDM Signal Model . . . . . . . . . . . . . . . . 5.1.2 Guard interval and Cyclic Prefix . . . . . . . . . 7.2 MIMO technique . . . . . . . . . . . . . . . . . . . 9.2.1 MIMO Signal model . . . . . . . . . . . . . . . . 9.2.2 MIMO Channel Capacity . . . . . . . . . . . . . . 10.2.3 Space Diversity . . . . . . . . . . . . . . . . . 10.2.4 MIMO transmission schemes . . . . . . . . . . . . 11.3 MIMO-OFDM technique . . . . . . . . . . . . . . . . 12 System Speci cation 15.1 An Overview of Wireless LAN . . . . . . . . . . . . 15.2 IEEE 802.11n Speci cation . . . . . . . . . . . . . 17.2.1 Packet Formats . . . . . . . . . . . . . . . . . . 18.2.2 System Parameters . . . . . . . . . . . . . . . . 19.2.3 HT-LTF Arrangement . . . . . . . . . . . . . . . . 20.2.4 Pilot Structure . . . . . . . . . . . . . . . . . 22.2.5 Constellation Mapping . . . . . . . . . . . . . . 22.2.6 Space-Time Encoder . . . . . . . . . . . . . . . . 23 Wireless Channel Model 25.1 MIMO Channel . . . . . . . . . . . . . . . . . . . . 25.2 Spatial Correlation . . . . . . . . . . . . . . . . 27.3 Multipath Rayleigh Fading . . . . . . . . . . . . . 28.4 Path Loss and Shadowing . . . . . . . . . . . . . . 30.5 Additive White Gaussion Noise . . . . . . . . . . . 31.6 Timing Frequency Offset. . . . . . . . . . . . . . . 31.7 Carrier Frequency Offset . . . . . . . . . . . . . . 32 Receiver Design 33.1 Packet Detection . . . . . . . . . . . . . . . . . . 34.1.1 Coarse Symbol Boundary Detection . . . . . . . . . 34.1.2 Fine Symbol Boundary Detection . . . . . . . . . . 35.2 CFO estimation . . . . . . . . . . . . . . . . . . . 37.2.1 Coarse/Fine CFO Estimation . . . . . . . . . . . . 37.2.2 Residual CFO Tacking Loop . . . . . . . . . . . . 38.3 Phase Compensation . . . . . . . . . . . . . . . . . . . . . . 40 MIMO Equalization Design 43.1 Channel estimation . . . . . . . . . . . . . . . . . 44.2 MIMO Detection . . . . . . . . . . . . . . . . . . . 46.2.1 Alamouti Scheme . . . . . . . . . . . . . . . . . 47.2.2 VBLAST Scheme . . . . . . . . . . . . . . . . . . 49.2.3 Combined scheme of Alamouti and VBLAST . . . . . . 50.2.4 System Simulation Results . . . . . . . . . . . . 54.3 LMS Adaptation for STBC . . . . . . . . . . . . . . 56.4 Cost Effcient MIMO Equalization . . . . . . . . . . 59.4.1 Strength-Reduced Multiplication . . . . . . . . . 59.4.2 Cost Effcient MISO/MIMO Detection . . . . . . . . 59.4.3 Cost Effcient Updating . . . . . . . . . . . . . . 64.4.4 Cost Effcient Channel Estimation . . . . . . . . . 67.4.5 Comparisons and System Simulation . . . . . . . . 69FT/IFFT Hardware Implementation 73FT/IFFT Algorithm . . . . . . . . . . . . . . . . . . . 73FT/IFFT Architecture . . . . . . . . . . . . . . . . . 75ixed-Point Analysis . . . . . . . . . . . . . . . . . . 77ardware Consideration . . . . . . . . . . . . . . . . . 79.4.1 Processing Element . . . . . . . . . . . . . . . . 79.4.2 Memory Arrangement . . . . . . . . . . . . . . . . 80.4.3 Twiddle Factor Design . . . . . . . . . . . . . . 81.4.4 FFT/IFFT Transform . . . . . . . . . . . . . . . . 83PGA Emulation and Chip Implementation . . . . . . . . . 84.5.1 FPGA Emulation Results . . . . . . . . . . . . . . 86.5.2 Gate-Level Simulations and Chip Summary . . . . . 87onclusion 9
The structure of disclosure duty and the suitability principal in Japan Financial Consumer Protection Regulation
No full text為保護投資大眾於金融商品交易之中能獲得相當之保障，我國於民國100 年12 月30 日通過金融消費者保護法之法律，除針對金融業者於金融交易上之「說明義務」及「適合性原則」明文規範構成要件，且亦認定違反之際即產生損害賠償責任。惟我國早期實務上，對於金融商品交易中因金融業者之瑕疵行為造成投資者交易上之損失，是否應擔負相當的損害賠償責任傾向保守認定，似與投資者保護之主旨相互背離，而往後我國實務在金融消費者保護法之「說明義務」及「適合性原則」認定違反之操作上，能否善為考量達成該法規所預期之效果，非無疑義。觀與我國同樣肯認金融業者於金融交易中之「說明義務」、「適合性原則」責任的日本，於其金融商品交易法訴訟之中，如何評價「說明義務」、「適合性原則」之構成要件，甚至各項衍伸義務，如「建言義務」、「顧客情報蒐集義務」等之義務範圍及是否致生損害賠償責任，又投資者本身有過失之際，是否將之論以與有過失之責，且與有過失應以何為限度，因歷經多年實務及學說見解累積，逐漸形成判斷之基準，尚可供我國評斷時參酌。故本文擬就日本對於「說明義務」及「適合性原則」規範和學說、實務見解加以分析比較，以期能透過借鏡日本之現行制度，使我國建構違反「說明義務」及「適合性原則」之損害責任能更臻完整，另亦提出日本法制存在之爭議問題，其我國能以之為鑒，改善現今制度更趨近於「保障金融消費者權益」之宗旨。For protecting the investors in a transaction of financial instruments, the ”Financial Consumer Protection Law” was enacted at 30th Dec 2011. The constituent elements of “disclosure duty” and “suitability principal” which financial institution is required in financial transaction is expressly described in this law, and the liability for damages of failing to perform “disclosure duty” and of breach of “suitability principal” is also included in this law. In early practice of law in our country, it’s hard to imagine that financial institutions are liable for their defective conduct in a financial transaction which cause damages to investors, but this conception is not comply with the purpose for protecting investors. After the enactment of the ”Financial Consumer Protection Law”, it’s still doubtful that the implement of the law, especially about the liability for damages of failing to perform “disclosure duty” and of breach of “suitability principal”, will achieve the respected effect of the statute in practice of law in our country. Observing the law of Japan, which is adopting the “disclosure duty” and “suitability principal” that financial institution is required, it has developed, from accumulation of practice and theory of law for a long time, criteria about the constituent elements of “disclosure duty” and “suitability principal”, and criteria about other extended duties such as “duty to advice” or “duty of consumer intelligence gathering”, and even criteria about the comparative negligence of investors. All about that may be a good reference for Taiwan. In order to construct the complete system about liability for damages of failing to perform “disclosure duty” and of breach of “suitability principal”, this article focused on the comparison with the regulations, theory and the conception in practicing law about “disclosure duty” and “suitability principal” in Japan. And this article also pointed out the controversial issues in Japan, for improving the law in our country to be accordant with the purpose of protecting financial consumers
Efficiency Improvement of p-i-n Solar Cell by Embedding Quantum Dots
No full text本論文提出置放量子點於p-i-n 二極體中的本質層，來實現高效率太陽能電池。在選擇適當的量子點材料、量子點尺寸與置入比例下，可於原背景材料的價電帶與傳導帶之間生成一個新的中間能帶，其能階位置由上述條件決定。此一中間能帶可幫助材料吸收不足以跨過原本背景材料之能隙而無法被吸收的入射光子。
本論文先以背景材料及一般p-i-n 架構所能達到的最高能量轉換效率為基準，再置入量子點後以提升轉換效率。本論文中使用砷化鎵為背景材料，使用砷化銦為量子點材料。在選擇適當的參數與更密集的量子點排列下，本論文進一步改善具有同類架構的太陽能電池之能量轉換效率。A model of solar cell embedding quantum dots in the intrinsic layer of a p-i-n solar cell has been presented. With proper selection of material, size and fractional volume, quantum dots can provide an intermediate band between the valence and the conduction bands of the matrix material, which will absorb photons with energy lower than the original bandgap to absorb more incident photons in the otherwise unsed spectral irradiance. The design
approach to acquire the highest efficiency of the conventional p-i-n solar cell is presented as a benchmark. Quantum dots are then embedded in the intrinsic region of the reference solar cell to improve its efficiency. InAs is chosen to implement the quantum dots, to be embedded in the p-i-n solar cell made of GaAs. With a more packed arrangement of QD’s from that in the literatures, the simulation results shows that the efficiency of the conventional GaAs p-i-n solar cell can be increased by 1.05%.Acknowledgment i
Abstract iii
Table of Contents iv
List of Figures vi
List of Tables ix
1 Introduction 1
2 Review of Basic Theories 4
2.1 Solar Cell Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Energy Level of Spherical Quantum Dots . . . . . . . . . . . . . . . . . . . . 6
2.3 Materials Embedding Quantum Dots . . . . . . . . . . . . . . . . . . . . . . 8
2.4 Current Density of Solar Cells . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3 Simulation Results and Discussions 20
4 Conclusions 3
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
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