74 research outputs found
Fuzzy qualitative approach to address uncertainty in human motion analysis / Lim Chern Hong
No full textHuman motion analysis is one of the most active researches in computer vision society nowadays due to its wide spectrum of applications. Current researchers have been
focused on implementing sophisticated algorithms with the goal to achieve good recognition rate but such work are limited to some constraints or assumptions. As a consequence, these systems are impractical to deploy in real-world environment due to the abounded uncertainties in the human motion analysis pipeline such as human size variation, viewpoint variation, and classification ambiguity. Failing in handling these uncertainties could
affect the overall system performance. In this thesis, fuzzy qualitative reasoning is studied to address the above uncertainties.
Human modelling is the enabling step in the human motion analysis system where the identified person from a video camera will be projected and represented in a better model to ease the latter processes such as feature extraction. Improper care on the variation of human size and camera positions from the ground might results in a defect human
model such as inconsistent human size, and odd human shape. Such defects will hinder the feature extraction process and the error in this step might be cumulated in the rest of
the pipeline and deteriorate the overall system performance. In this thesis, fuzzy qualitative Poisson human model is proposed to generalize the human model in terms of sizes and camera viewpoints.
Besides that, to recognize an action with independent to the human viewpoint is a great challenge in human motion analysis, but remains unsolved due to its inherent
difficulty. Most state-of-the-art methods are found to be impractical where multi camera system is required to serve the purpose. In this context, view specific action recognition framework is proposed to capture and construct the view specific action model for the objective to achieve view invariant human action recognition within single camera. In the framework, a novel human contour namely fuzzy qualitative human contour is proposed for view estimation which helps in the construction of the view specific action model.
Action recognition is the final step in the human motion analysis pipeline where the aim is to infer the action or activity from the video. However, classification ambiguity
could abounded in this step such as the confusion in viewpoint, action, and scene context due to some similarity factors. These cases are denoted as non-mutually cases in the thesis as their results could not be fully distinguished from the others. Hence, a crisp or binary
classifier may not be so effective to deduce the final output for these cases. As a solution, fuzzy qualitative rank classifier is proposed to model the non-mutually exclusive case in the training step and infer with the multi-label and ranking result. This is intuitively
reflecting how human decision is made towards the ambiguous case. In addition, dynamic fuzzy qualitative rank classifier is proposed as the extension to overcome the heuristic method in the learning step. In summary, the collective impact of the above contributions will constitute to achieve a more practical and feasible framework towards the human motion analysis applications. Particular video surveillance system that ensure the public safety and lead to a better and safer society
Scattering Amplitudes of Massive N=2 Gauge Theories in Three Dimensions
No full textWe study the scattering amplitudes of mass-deformed Chern-Simons theories and Yang-Mills-Chern-Simons theories with N=2 supersymmetry in three dimensions. In particular, we derive the on-shell supersymmetry algebras which underlie the scattering matrices of these theories. We then compute various 3 and 4-point on-shell tree-level amplitudes in these theories. For the mass-deformed Chern-Simons theory, odd-point amplitudes vanish and we find that all of the 4-point amplitudes can be encoded elegantly in superamplitudes. For the Yang-Mills-Chern-Simons theory, we obtain all of the 4-point tree-level amplitudes using a combination of perturbative techniques and algebraic constraints and we comment on difficulties related to computing amplitudes with external gauge fields using Feynman diagrams. Finally, we propose a BCFW recursion relation for mass-deformed theories in three dimensions and discuss the applicability of this proposal to mass-deformed N=2 theories
Kähler Ricci flow and Chern Ricci flow on noncompact Hermitian manifolds
No full textPh.D.In this thesis, we will investigate the short-time existence of the Chern-Ricci flow and Kähler Ricci flow on complete noncompact manifolds together with its local curvature estimate and global behaviour.In the first part, we will generalize the characterization of maximal existence time of the Chern-Ricci flow shown by Tosatti and Weinkove in [54] to complete noncompact Hermitian manifolds with possibly unbounded curvature. To con struct a flow, we construct a approximating sequence of Hermitian manifolds by conformally blowing up the metric in a neighbourhood of the boundary of a compact exhaustion. After derivation of local a priori estimates, a Chern-Ricci flow can be constructed with an estimate on lifespan.In the second part, we will derive local curvature estimates of Kähler-Ricci flow. When the bisectional curvature BKg(t) is bounded from below along the flow and the original metric is noncollapsing, a global curvature bound can be obtained. We also establish the preservation of nonnegative BK under curvature bound at⁻θ for some θ < 2. We will also discuss under what circumstances this curvature bound may hold.Finally, we will apply the existence of the Chern-Ricci flow to construct a Kähler Ricci flow starting from a non-collapsing complete noncompact K¨ahler manifold with nonnegative bisectional curvature. An application on Yau’s uniformization conjecture will be discussed.在這篇畢業論文中，我們將研究陳里奇流及凱勒里奇流在非緊流形上的短時間存在性，並且我地將討論其曲率的局部估計以及整體特性。在第一部分中，我們先推廣Tosatti和Weinkove[54]對陳里奇流在緊複流形上的最大存在時間描述至非緊複流形上。透過窮舉集上的共形改動，我們可以構作出一串非緊厄米特流形序列，並且流形序列的曲率有限。透過得出對其導數的局部先驗估計，我們能夠構作出一序列的陳里奇流。而且其解的時間區間和局部幾何與其窮舉集無關。由此，我們可以求得在整個複流形上的陳里奇流解。而在第二部分中，我們將求出凱勒里奇流的局部曲率估計。當凱勒里奇流其二分曲率的下界有限並且以初度量g量度的單位球體積有下界時，則能夠得到整個流形上的曲率控制。我們亦探討非負二分曲率在非緊凱勒里奇流上，曲率上界為at⁻ᵖ，p<2 時的保持性。我們亦會討論在此曲率上界的可能性。最後，我們將利用陳里奇流的存在性及上述的局部估計以構作備有非負二分曲率的凱勒里奇流。並且我們將該凱勒里奇流解應用在丘的一致化猜想問題上。Lee, Man Chun.Thesis Ph.D. Chinese University of Hong Kong 2018.Includes bibliographical references (leaves 85-91).Abstracts also in Chinese.Title from PDF title page (viewed on …)
How do foreign currency derivatives impact firm value: empirical evidence from industrial firms in Asian countries
No full textEmpirical research has shown that derivatives have significant impact on firm value. However, the relationship between use of derivatives and firm value is still vague as some studies have indicated a positive relationship while other studies have indicated otherwise. This empirical study aims to contribute to the literature of derivative use by further examining how derivatives impact firm value. The research design behind this investigation employs a hand-collected dataset encompassing a sample of 130 industrial firms from Hong Kong, Singapore, Malaysia and Taiwan from the period of 2008 to 2017. By examining how firms hedge long-term and short term foreign currency exposures with foreign currency derivatives, a clearer picture can be obtained regarding the hedging strategies on Asian firms. This study also examined the effectiveness of derivative usage through comparing the derivative assets and derivative liabilities of firms. This empirical research also studied the impact of utilising foreign currency derivatives in general, as well as different types of foreign currency derivatives, on firm values. The findings in this study are also compared between developed and developing markets to assess the difference and similarities of hedging strategies and firm characteristics of sample firms in both markets. The main findings of this study are as follows. Forward foreign currency contracts are the preferred foreign currency derivative to hedge both short-term and long term foreign currency exposures. Findings also indicate that with the exception of Hong Kong firms, firms from the other countries are experiencing effective derivative hedging on currency exposures. As for the impact of foreign currency derivatives, only coefficients for Hong Kong sample firms are statistically positive and significant. As for the type of derivative contract, foreign options are the only contract which is significant in affecting firm value. However, options are viewed negatively by market participants as evidenced by the hedging discount on firm value
How do foreign currency derivatives impact firm value: empirical evidence from industrial firms in Asian countries
No full textEmpirical research has shown that derivatives have significant impact on firm value. However, the relationship between use of derivatives and firm value is still vague as some studies have indicated a positive relationship while other studies have indicated otherwise. This empirical study aims to contribute to the literature of derivative use by further examining how derivatives impact firm value. The research design behind this investigation employs a hand-collected dataset encompassing a sample of 130 industrial firms from Hong Kong, Singapore, Malaysia and Taiwan from the period of 2008 to 2017. By examining how firms hedge long-term and short term foreign currency exposures with foreign currency derivatives, a clearer picture can be obtained regarding the hedging strategies on Asian firms. This study also examined the effectiveness of derivative usage through comparing the derivative assets and derivative liabilities of firms. This empirical research also studied the impact of utilising foreign currency derivatives in general, as well as different types of foreign currency derivatives, on firm values. The findings in this study are also compared between developed and developing markets to assess the difference and similarities of hedging strategies and firm characteristics of sample firms in both markets. The main findings of this study are as follows. Forward foreign currency contracts are the preferred foreign currency derivative to hedge both short-term and long term foreign currency exposures. Findings also indicate that with the exception of Hong Kong firms, firms from the other countries are experiencing effective derivative hedging on currency exposures. As for the impact of foreign currency derivatives, only coefficients for Hong Kong sample firms are statistically positive and significant. As for the type of derivative contract, foreign options are the only contract which is significant in affecting firm value. However, options are viewed negatively by market participants as evidenced by the hedging discount on firm value
Quantum SU(N) Invariants: Introduction, Physical Interpretation and Asymptotic Behavior
No full text本文旨在介紹紐結以及三維流形的量子SU(N) 不變量及其在Chern-Simons 理論下的物理意義。我們首先使用Skein 理論定義Jones 多項式以及把其推廣為Colored Jones 多項式。然後透過對Temperley-Lieb 代數的研究，我們製作出Jones-Wenzl Idempotent。其特別之處在於它在包括Kirby Moves 的多種變換下有良好的性質。由此我們製作出Reshetikhin-Turaev(RTr，或另一標準化的Wr) 和Turaev- Viro(TVr) 三維流形不變量。它們兩者之間有著不平凡的代數關係:jWrj2 = TV .有了以上背景知識，設G 為一李群，我們從量子群Uq(G) 的表示理論來定義Jones 多項式。上一段所討論的不變量正是Uq(SU(2)) 量子不變量。這個方法與前一個的等價關係將會在正文中證明。我們並提供一套Uq(SU(N)) 量子不變量的Skein 理論作為一種推廣。它給出的正是HOMFLY-PT 多項式以及其Colored 版本。另外在這裡我們將提供一份關於SU(N) 的表示論的摘要。文章第三部分的目的在於把上述紐結以及三維流形的不變量以Chern-Simons 理論統一起來。Chern-Simons 理論能夠描述量子不變量的漸近狀態。最後，我們將利用其物理解釋，淺述量子不變量的經典體積猜想和其各種推廣。具體地我們以八字結的計算來驗證以上猜想有多可信。This thesis aims to provide a self-contained introduction to the theory of quantum SU(N) invariant for knot and 3-manifold together with physical interpretation, under the framework of Chern-Simons theory.By using skein-theoretic approach, we first define the classical Jones polynomial and its generalization, the colored Jones polynomial. After that, by studying the Temperley-Lieb algebra, we construct an element called Jones-Wenzl idempotent which is well-behaved under several operations, such as Kirby moves. In particular, it can be used to construct the Reshetihkin-Turaev invariant (RTr, or Wr after normalization) and Turaev-Viro invariant (TVr) for closed oriented 3-manifolds. It turns out that two invariants satisfy a non-trivial relation: jWrj2 = TV .Having the basic knowledge discussed above, we start to define the colored Jones polynomial using the representation theory of the quantum group Uq(G), where G is a Lie group. It turns out that the theory discussed above corresponds nicely to the Uq(SU(2)) quantum invariant.The equivalence of the two approaches will also be proved. As a generalization, we provide a skein theoretic approach of the Uq(SU(N)) quantum invariants. This gives the classical HOMFLY-PT polynomial and its colored version. A brief summary on representation theory of SU(N) will also be given.The third part of this thesis is to unify all these invariants for knots and 3-manifolds under a physical theory called Chern-Simons theory. The Chern-Simons theory can be used to predict the asymptotic behavior of the quantum invariants. We will finally talk about the volume conjecture and its generalizations for the quantum invariants with the help of the physical interpretation. In particular, we will use figure-eight knot to illustrate the validity of the conjectures.Wong, Ka Ho.Thesis M.Phil. Chinese University of Hong Kong 2016.Includes bibliographical references (leaves ).Abstracts also in Chinese.Title from PDF title page (viewed on …).Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only
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