1,720,996 research outputs found
Determinants of Financial M&A Activities among East Asia
No full text自1990年代後，東亞各國在法規上，對於國外直接投資及外國資金進入金融市場漸漸鬆綁，使得區域間金融活動更加頻繁，另一方面，東亞的高經濟成長，吸引各國資金的進入，國外直接投資的增加，促使跨國金融合併與收購活動更加熱絡。 本文關心自1991至2007年，藉由重力理論研究影響東亞各國區域間金融合併與收購的因素，發現國內生產毛額、平均每人生產毛額、 語言、股票市場資本、兩國間貿易與東亞區域內金融合併與收購成正向關係，而距離、通貨膨脹對於東亞區域內金融合併與收購成反向關係，另外，在重力理論加入虛擬變數後，發現近幾年東亞各國區域間合併與收購，相較東亞各國與其他非東亞國家跨國性金融整併活動更加頻繁。此結果意味，一個高收入、高成長、經濟市場開放性越高的市場，越容易吸引其他國家進入該市場進行金融合併與收購，同時，相同的語言，代表著較低的訊息成本，對於跨國整併亦有重要的影響。Since the early 1990s East Asia has reduced its financial restrictions on capital account transactions and barriers to entry by foreign direct investment (FDI), resulting in a rapid increase in the region’s international capital mobility. High levels of economic growth across the region have attracted investment, boosting demand for the limited number of quality assets and increasing cross-border merger and acquisition (M&A) activities, which have driven the flow of FDI. This research studies East Asia’s financial integration analyzing by using a gravity model for the period 1991-2007. Contrary to previous studies, the results showed that the cross-border financial M&A activities between countries in East Asia are more active than those between countries inside and outside of East Asia (e.g., the US and Hong Kong). The paper uses a gravity model, along with some macroeconomic variables, to determine influences on the financial cross-border M&A activities in East Asia. The financial cross-border M&A activity is positively correlated with GDP, GDP per capita, language, stock market capitalization, and trade and negatively correlated with distance and inflation. This suggests that bidder countries that are more likely to international tend to be from larger and more open economies, with high level of income, better macroeconomic policies and a common culture, language.誌謝 II要 IIIBSTRACT IVIST OF TABLES VIIST OF FIGURES VIIHAPTER 1. INTRODUCTION 1.1 ECONOMIC REVIEW OF EAST-ASIA COUNTRIES 2.2 CROSS-BORDER M&A IN EAST ASIA: TRENDS, MOTIVES AND IMPACTS 7HAPTER 2. LITERATURE REVIEW 11.1 FINANCIAL DEEPENING IN EAST ASIA 11.2 FINANCIAL DEEPENING AND CROSS-BORDER M&A METHODS 14HAPTER 3. THE THEORETICAL MODEL AND THE DATA SET 17.1 RESULT 19HAPTER 4. CONCLUSION 23EFERENCE 2
Traitor Tracing for Image Fingerprinting
No full text隨著電腦與網路的普及，產生、修改與傳遞數位資料變得十分容易，如此一來，數位資料面臨被非法散佈的危險。數位指紋嵌入技術利用在資料中置入可茲辨識訊息，以便於使用者非法傳播所購得的版本時，協助追溯洩密來源。
在現存的影像指紋嵌入系統相關研究中，想要同時達到指紋碼短、可以服務的使用者人數多(碼的個數多)、能抵抗的共謀人數多這三個條件，實屬不易。因此衍生出兩個值得研究的方向：一、如何設計浮水印演算法，使得在加強共謀抵抗能力的前提下所造成的長度極長的指紋碼可以嵌入影像而不造成破壞？二、如何建造一個短的指紋碼卻能擁有好的共謀抵抗能力與較多的指紋碼個數。本論文即在影像指紋嵌入系統中作叛徒追蹤的研究上作相關討論，並且試圖解決前述兩個問題，包含：影像指紋嵌入問題上的浮水印技術以及抵抗共謀破壞之指紋碼的設計。
在指紋嵌入的浮水印技術上，我們提出了一種可隨著不同影像內容自動調適的浮水印嵌入演算法。先將影像切割成小區塊，根據影像內容的特性，可以利用纇神經網路自動決定出嵌入的強度，而不須費心設計人類視覺模式，並以最佳化能量函數的方法，選擇適合的遷入位置。即使嵌入的指紋碼很長，此方法也能夠維持影像品質與浮水印強度的平衡，更將抵抗共謀破壞納入最佳化過程的考量。
在共謀抵抗指紋碼的設計上，我們提出了一種串接式追溯碼的建造方法，除了理論分析，也提供實作數據。此法可利用外層碼的符號個數的增加來加強追溯能力，並利用二元內層碼來符合”嚴格標記假設”。我們更設計一種利用使用者群組方式的特性來建立追溯碼的方法，來大幅改善追溯能力。根據以上兩種概念，共提出三種追溯碼：群組導向追溯碼、階層式追溯碼以及成員互斥追溯碼。群組導向追溯碼分別利用外層碼與內層碼為群組與組員編碼；階層式追溯碼將指紋碼切割成幾個階層，以樹狀結構來設計碼，而每群分枝僅須一個較為簡單的碼；成員互斥追溯碼則最大化同一群組使用者的指紋碼最短距離。三種碼都能有效將對於碼長、追溯能力與服務人群數量的需求，分散到不同階層各個擊破。實驗結果顯示所提出的方法的確能有效縮短碼長、強化追溯能力、並增加服務人群數。
本論文所提出的指紋碼浮水印嵌入演算法與追溯碼的建造方法，與現存的研究相較，都更為可行而有效，這的確提供一個在影像指紋嵌入系統中作叛徒追溯的一個好的研究方法。The demand of digital data protection is getting stronger dramatically nowadays as more and more digital contents are used on computers and distributed via the Internet. Digital fingerprinting is a technology designed to help protect digital assets and identify security leak sources.
This dissertation addresses the problem of traitor tracing for image fingerprinting, including two major issues: watermarking strategies for image fingerprinting and the design of collusion-secure fingerprinting codes.
In the fingerprint-watermarking, we propose a content-adaptive watermarking strategy, which can adaptively decide watermarking strengths and select suitable embedding positions according to the content based on a neural network and an optimization procedure respectively. It maintains the equilibrium of the robustness and the imperceptibility when embedding long fingerprints without the effort to deal with human visual models. Besides, the collusion-resistance is considered to resist collusion attacks. Experimental results show the feasibility of the proposed watermarking algorithm.
In the fingerprint-designing, we derive a code construction scheme which constructs fingerprint in a concatenated way based on a user grouping policy. The concatenated construction method is analyzed and proven to be efficient in collusion-secure traceability codes: the larger alphabet size of the outer code guarantees the higher tracing ability and the binary inner code makes the fingerprint satisfying the “Strict Marking Assumption”. The group-based fingerprinting scheme can further improve the tracing ability under the concatenated code construction. Based on these two ideas of the fingerprint designing, we propose three collusion-secure traceability codes: the group-oriented traceability code, the hierarchical traceability code, and the member-exclusive traceability code. All of them successfully disperse the decoding efforts over the outer code and the inner code by the grouping structure. Both theoretical analyses and the practical implementation show good performances of error rates and collusion-resiliency.
To sum up, the watermarking and code construction schemes developed in this dissertation provide more flexibility and higher collusion-resiliency than existing solutions, and thus offer a better match for the challenges of the traitor tracing for image fingerprinting.Chapter 1 Introduction 1
1.1. Multimedia Security 1
1.2. Digital Watermarking 2
1.3. Digital Fingerprinting 4
1.4. Goals and Contributions 6
1.5. Structure of Thesis 8
Chapter 2 Watermarking Strategies for Image Fingerprinting 9
2.1. SOM architecture 11
2.2. Adaptive Watermark-Strength Decision 15
2.3. Selection Algorithm for Embedding-Positions 21
2.4. Sequential Detection for Traitor Tracing 25
2.5. The Simulation of the Proposed Watermarking Scheme 28
2.5.1. c-TA Code Construction 28
2.5.2. Experimental Results 33
2.6. Conclusions 41
Chapter 3 Collusion-Secure Codes 42
3.1. Introduction 42
3.2. Combinatorial-designed Codes 42
3.3. Codes with Large Minimum Distances 44
3.3.1. Error Correcting Codes with Larger Relative Minimum Distances 46
3.3.2. Orthogonal Signals 47
3.4. Comparisons of Existing Collusion-Secure Codes 48
Chapter 4 Concatenated Construction of Fingerprinting Codes 55
4.1. Introduction 55
4.2. Concatenated Construction Strategy of Traceability Codes 58
4.3. Analysis of Concatenated Collusion-secure Codes 59
4.3.1. Code-length 60
4.3.2. Type I Errors 60
4.3.3. Type II Errors 61
4.4. The Decoding Algorithm 64
4.5. Examples of Concatenated Traceability Codes 65
Chapter 5 Group-Based Fingerprinting 69
5.1. Scheme 1 - Group-Oriented Traceability Codes 70
5.1.1. The Tracing Algorithm 72
5.1.2. Analysis of Group-Oriented Traceability Codes 73
5.1.3. Experimental Results 74
5.2. Scheme 2 - Hierarchical Traceability Codes 78
5.2.1. Segment-codes 78
5.2.2. Group-codes 80
5.2.3. Constructing Tree-Structured Traceability Codes from Existing Collusion-Secure Codes 83
5.2.4. Experimental Results 85
5.3. Scheme 3 – member-exclusive Traceability Codes 91
5.3.1. The Construction of Member-exclusive Codes 91
5.3.2. Experimental Results 93
5.4. Conclusions 96
Chapter 6 Conclusions 97
Appendix A 100
Reference 10
Characterization of fusC elements in fusidic acid resistant Staphylococcus aureus and Staphylococcus hominis
No full text夫西地酸 (fusidic acid) 為臨床上用於治療葡萄球菌所引起的感染之藥物之一，但細菌可因藥物作用標的基因產生突變或產生保護藥物作用標的的蛋白質 (FusB-protein family) 而產生抗藥性。本實驗收集2008至2010年來臺大醫院細菌室之46株夫西地酸抗藥之抗甲氧西林金黃色葡萄球菌 (methicillin-resistant Staphylococcus aureus, MRSA) 菌株，分析其抗藥基因及分子流行病學。結果顯示，46株夫西地酸抗藥之MRSA菌株中，有19株 (41%) 在fusA基因產生突變，主要以H457Q/L461F及L461K為主，另外有27株 (59%) 帶有fusC基因。帶有fusA基因H457Q/L461F突變之菌株為SCCmec第二型，而帶有其他fusA突變及fusC基因之菌株大多數為SCCmec第三型。另外在PFGE基因分型的結果中顯示，帶有相同抗藥因子的菌株具有較相似的基因型。利用南方墨點法及核酸定序分析MRSA中帶有fusC基因的基因片段結構。結果顯示fusC基因位於一個新SCC基因片段，SCCfusC。SCCfusC，位於rlmH基因的下游及SCCmec片段的上游，並帶有ccrA1B1基因及speG基因。此fusC結構為首次發現，並有可能藉由clonal spread造成對夫西地酸抗藥菌株的增加。 而在凝固酶陰性葡萄球菌中，人葡萄球菌 (S. hominis) 帶有fusC基因的比例較其他菌種來的高。因此，針對人葡萄球菌共蒐集了33株夫西地酸抗藥菌株，其中僅2株帶有fusB基因，而有31株帶有fusC基因。利用PCR偵測其fusC基因的基因片段發現其中14株其fusC基因位於SCCfusC當中，3株位於SCC476。進一步使用核酸定序分析其他位在未知片段之fusC基因上下游序列後得到一個新的SCC基因片段，命名為SCC3390。。除了人葡萄球菌之外，在其他凝固酶陰性葡萄球菌例如表皮葡萄球菌、溶血葡萄球菌及頭狀葡萄球菌中亦偵測到SCCfusC結構，且不同菌種中發現之SCCfusC序列有很高的相似度，推測SCCfusC可於菌種間傳遞。 此外，我們發現有一病人共分離5株菌株，較早收集的3株菌株 (NTUH-9383、NTUH-471及NTUH-1230) 為MRSA，較晚收集的2株菌株 (NTUH-6319及NTUH-7203) 為MSSA (methicillin-susceptible S. aureus)，且2株MSSA對daptomycin及teicoplanin有較高的抗性。而在表現型上可發現NTUH-7203具有菌落較小的現象。我們針對NTUH-9383及NTUH-7203進行全基因定序，發現兩株菌株在基因序列上共有13處差異，包含SCCmec基因片段、IS256插入（三處）、8個單點突變（包含 mprF, cls2, clpX and fabF）及1個單一核苷酸的插入。在過去文獻中，mprF及cls2突變被報導與S. aureus產生daptomycin抗藥性有關。NTUH-7203與菌落大小相對正常的NTUH-6319在基因上最明顯的差異為與細菌脂質合成有關的fabF，且外加脂質可讓NTUH-7203的菌落大小恢復，因此fabF突變可能為造成NTUH-7203成為小菌落突變株之主要原因。另外，在電子顯微鏡下發現，除了NTUH-7203之外，NTUH-6319也被觀察到小菌落突變株會有的不正常細胞外觀，推測小菌落突變株的形成是一系列改變所造成。Fusidic acid is an antibiotic used in treatment against staphylococcal infection. Resistance to fusidic acid in Staphylococcus aureus is caused by alternation of drug target site or by protection of drug target site. In this study, we analyzed the resistance determinants in 46 fusidic acid-resistant methicillin-resistant S. aureus isolates collected from 2008 to 2010, and performed genotyping. The results showed that fusC (59%) was more common than fusA mutations (41%). The most frequent mutation sites in fusA includes L461K (N = 8) and H457Q/L461F (N = 6). Two major genotypes, spa type t037-ST239-SCCmec type III (83%) and t002-ST5- SCCmec type II (11%), were found. A novel SCC structure, termed SCCfusC, was integrated into the rlmH gene and located upstream of SCCmec and was present in all but one (26/27) fusC-carrying MRSA isolates. The SCCfusC also contained speG, which contributed to the polyamine resistance. This is the first report about MRSA isolates that carry both fusC and speG. The fusC carriage in S. hominis was more frequent than other coagulase-negative staphylococci (CoNS). To understand the flanking region of fusC in S. hominis, 31 fusC-positive S. hominis isolates were collected and analyzed the structure of fusC element. The results showed that 14 isolates carried SCCfusC, 3 carried SCC476 and 8 carried new SCC structure, SCC3390. By PFGE and MLST analysis, the S. hominis population showed a limited clonality. Moreover, the SCCfusC was found in other species of CoNS including S. hominis, S. epidermidis, S. haemolyticus and S. capitis, suggesting that SCCfusC may transfer between different species of staphylococci. In this study, there were 5 vancomycin-intermediate S. aureus (VISA) isolates recovered from a same patient. The first three isolates (NTUH-9383, NTUH-471, and NTUH-1230) were MRSA but the latest two (NTUH-6319 and NTUH-7203) were methicillin-susceptible S. aureus (MSSA) and exhibited the characteristics of small colony variants (SCVs). Two MSSA isolates also displayed resistance to daptomycin. Whole genome sequencing of NTUH-9383 and NTUH-7203 indicated that there were 13 differences, including the presence or loss of SCCmec, 8 point mutations (including mprF, cls2, clpX and fabF), a single nucleotide insertion and three IS256 insertions. The most significant difference between NTUH-6319 and NTUH-7203 was the point mutation in fabF encoding fatty acid synthesis enzyme, which may possibly correspond to small colony of NTUH-7203. By high-resolution micrographs, both NTUH-6319 and NTUH-7203 displayed the features of SCV, abnormal intercellular substance. The overall findings suggested that daptomycin treatment may cause the formation of SCV after steps of a serial of changes
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