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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Sous-structures de Hodge, anneaux de Chow et action de certains automorphismes

Fu, Lie 03 October 2013 (has links) (PDF)
Cette thèse se compose de trois chapitres. Dans Chapitre 1, en supposant la conjecture standard de Lefschetz, on démontre la conjecture de Hodge généralisée pour une sous-structure de Hodge de convieau 1 qui est le noyau du cup-produit avec une classe de cohomologie grosse. Dans Chapitre 2, nous établissons une décomposition de la petite diagonale de X × X × X pour une intersection complète de type Calabi-Yau X dans un espace projectif. Comme une conséquence, on déduit une propriété de dégénérescence pour le produit d'intersection dans son anneau de Chow des deux cycles algébriques de dimensions complémentaires et strictement positives. Dans Chapitre 3, on démontre qu'un automorphisme symplectique polarisé de la variété des droites d'une hypersurface cubique de dimension 4 agit trivialement sur son groupe de Chow des 0-cycles, comme prédit par la conjecture de Bloch généralisée.
62

Versions of America: Reading American Literature for Identity and Difference

Chetty, Raj G. 02 August 2006 (has links) (PDF)
My paper examines how American authors of the South Asian Diaspora (Indian-American or South Asian American) can be read 1) as simply American and 2) without regard to ethnicity. I develop this argument using American authors Jhumpa Lahiri, a first generation American of Bengali-Indian descent, and Bharati Mukherjee, an American of Bengali-Indian origin. I borrow from Deepika Bahri's materialist aesthetics in postcolonialism (in turn borrowed from members of the Frankfurt School of Critical Theory) and include theoretical insights from Rey Chow, Graham Huggan, and R. Radhakrishnan regarding multiculturalism, identity politics, and diaspora studies. Huggan and Radhakrishnan's insights are especially useful because their work deals with the South Asian diaspora, in England and the United States, respectively. After setting up a theoretical framework, I critique reviews and essays that privilege hyphenated, "Indian," or "South Asian" identity, and the resultant reading paradigm that fixes these authors into an ethnic minority category. I then trace aesthetic and thematic content of short stories from both Lahiri's Interpreter of Maladies and Mukherjee's The Middleman and Other Stories to demonstrate how these stories resist this ethno-cultural pigeonholing. My analysis exposes how ethnic and multicultural identity politics supplant aesthetic criticism and transform ethno-cultural identity into an aesthetic object, even if done as a celebration of hybridity or liminality as a putatively liberating space (hyphenated identity as embodying that space). Though my purpose is not to undermine the meaningful artwork and criticism instantiated in or about the "in-between" spaces of American culture, I demonstrate that an over-emphasis on ethnicity and culture (culture "other" than the majority culture in the U.S.) in fact stifles the opening of the American literary canon. Ethnicity and culture become ways of limiting the hermeneutics available to literary criticism because they become the only ways of reading, instead of one lens through which American literature is read.
63

A Fractional Step Zonal Model and Unstructured Mesh Generation Frame-work for Simulating Cabin Flows

Tarroc Gil, Sergi January 2021 (has links)
The simulation of physical systems in the early stages of conceptual designs has shown to be a key factor for adequate decision making and avoiding big and expensive issues downstream in engineering projects. In the case of aircraft cabin design, taking into account the thermal comfort of the passengers as well as the proper air circulation and renovation can make this difference. However, current numerical fluid simulations (CFD) are too computationally expensive for integrating them in early design stages where extensive comparative studies have to be performed. Instead, Zonal Models (ZM) appear to be a fast-computation approach that can provide coarse simulations for aircraft cabin flows. In this thesis, a Zonal Model solver is developed as well as a geometry-definition and meshing framework, both in Matlab®, for performing coarse, flexible and computationally cheap flow simulations of user-defined cabin designs. On one hand, this solver consists of a Fractional Step approach for coarse unstructured bi-dimensional meshes. On the other, the cabin geometry can be introduced by hand for simple shapes, but also with Computational Aided Design tools (CAD) for more complex designs. Additionally, it can be chosen to generate the meshes from scratch or morph them from previously generated ones. / <p>The presentation was online</p>
64

台指選擇權之市場指標實證分析

吳建民, Wu,Jian-Min Unknown Date (has links)
本研究有系統地收集了2003年8月12日到2005年9月30日止共495個交易日的台指期貨、選擇權市場裡P/C量、P/C倉、隱含波動率(AIV)、不同天數的歷史波動率等收盤資料,進行這些因素與行情走勢間的關係,以及因素彼此的互動性。結果證實分析台指選擇權指標是需要區分金融重大衝擊前後期間,以及區分漲勢、跌勢、盤整的各期間,各期間的選擇權指標均會有不同意涵。 本論文證實使用結構轉換的Chow-ARMA(2,1)模型可能比較符合模擬指數 實況,且GARCH(1,1) 模型也很適合描述台期指貨波動度預測力。在選擇權指標方面:P/C量與AIV與台指期貨呈現負相關,P/C倉與台指期貨正相關。其中以P/C倉對指數漲跌的影響程度最大、P/C量的影響程度次之、AIV影響程度最小。若把隱含波動率區分成買權與賣權之各個波動率更有效地預測行情走勢,在大跌期間的買賣權隱含波動率更能表現出優越的預測能力,其中前兩期的賣權隱含波動率(PIV)更是效率性指標, 實證結果使用20天的歷史波動率比較能貼近選擇權市場的變化,跟過去教 科書慣用的90天不同。若比較歷史波動率與隱含波動率間的關係,結論是當「大跌期」歷史波動率大於買權隱含波動率(CIV)時,買權是會被低估的,其他的各種假設條件均不成立。理由有二:一是市場效率性決定了是否可使用隱含波動率與歷史波動率之間的高低關係。二是「大跌時期」相對於「大漲時期」的市場資訊被反應的更敏銳,而在「大跌時期」的賣權價格反應比買權價格反應更快速敏銳。 本研究推論的Chow-ARMA(2,1) 台指期貨模型、GARCH(1,1) 波動率模型、P/C量-P/C倉-AIV的多變數模型、FMA20/XIV模型等等在研判指數變化上具有參考價值,進一步均可以做為選擇權操作策略參考依據之一。

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