1,091 research outputs found

    Effective potential and geodesic motion in Kerr-de Sitter space-time

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    In the present work, geodesic trajectories in Kerr-de Sitter geometry is analyzed. From the mathematical solution of Lagrangian formalism appropriate to motions in the equatorial plane (for which 'theta' = 0 and 'theta' = (constant)= pi/2) can give potential energy of massive and massless particles for rotating axisymetric black hole. From this, for a particular value of cosmological constant, Kerr parameter, mass, angular momentum and impact parameter; variation of potential with distance can be found. Similarly, for a particular value of cosmological constant, mass and Kerr parameter; variation of velocity with distance can be found

    A discourse on entrepreneurial identity : three essays.

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    My dissertation provides theoretical insights on individual level entrepreneurial identity in three inter-related essays, drawing on multiple theories and disciplines. In the first essay, I advance a dual-process model of identity development, contributing to the debates in the broad identity literature. I articulate that the intrinsic prospection of identity is another fundamental process of identity formation, besides the social construction of identity, the prevalent notion in the literature. I propose a comprehensive conceptual framework of entrepreneurial identity. On the basis of this conceptual framework, I explain that there are within-group and between-group variations in the entrepreneurial identity of different types of entrepreneurs – innovators, imitators, and self-employed professionals. In the second essay, I develop and validate an entrepreneurial identity scale with socially constructed and intrinsically prospected identity dimensions. I theorize on the antecedents of entrepreneurial identity, and empirically test a conceptual model. Particularly, I investigate the influence of career related attitudes, personality characteristics, and family background on entrepreneurial identity. In the final essay, I argue that entrepreneurial identity is a missing link in the nascent entrepreneurship literature. Although the centrality of entrepreneurial intentions and entrepreneurial self-efficacy in predicting an individual’s transition to an entrepreneurial career is well established, we do not adequately know what contributes to entrepreneurial intentions and entrepreneurial self-efficacy. To that end, I investigate the impacts of entrepreneurial identity on entrepreneurial intentions and entrepreneurial self-efficacy in a sample of potential entrepreneurs. Therefore, the third essay fills that critical gap

    Searching for an Environmental Kuznets Curve in Carbon Dioxide Pollutant in Latin American Countries

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    This study utilized a semiparametric panel model to estimate environmental Kuznets curves (EKC) for carbon dioxide (CO2) in 15 Latin American countries, using hitherto unused data on forestry acreage in each country. Results showed an N-shaped curve for the region; however, the shape of the curve is sensitive to the removal of some groups of countries. Specification tests support a semiparametric panel model over a parametric quadratic specification.CO2, forest acreage, environmental Kuznets curve, Latin American countries, semiparametric regression model, Agribusiness, Environmental Economics and Policy, Research and Development/Tech Change/Emerging Technologies, C14, C33, Q23, Q53,

    Test of Convergence in Agricultural Factor Productivity: A Semiparametric Approach

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    We tested for club convergence in U.S. agricultural total factory productivity using a sigma convergence test. We used the same club of states as used by McCunn and Huffman as well as different states within 10 clubs identified by the cluster analysis. Results showed convergence was evident only in a few club groups. Clusters group identified using a statistical method identified only converging clubs. Variables affecting total factor productivity among states were identified using parametric, semiparametric and nonparametric methods. Semiparametric and nonparametric methods gave a better fit than a parametric method as indicated by the specification test. Our results indicated that health care expenditure, public research and extension investment, and private expenditure are important variables impacting total factor productivity differences across states.Clubs, sigma convergence, cluster analysis, semiparametric and nonparametric methods, Productivity Analysis, Research Methods/ Statistical Methods,

    3D hand tracking.

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    The hand is often considered as one of the most natural and intuitive interaction modalities for human-to-human interaction. In human-computer interaction (HCI), proper 3D hand tracking is the first step in developing a more intuitive HCI system which can be used in applications such as gesture recognition, virtual object manipulation and gaming. However, accurate 3D hand tracking, remains a challenging problem due to the hand’s deformation, appearance similarity, high inter-finger occlusion and complex articulated motion. Further, 3D hand tracking is also interesting from a theoretical point of view as it deals with three major areas of computer vision- segmentation (of hand), detection (of hand parts), and tracking (of hand). This thesis proposes a region-based skin color detection technique, a model-based and an appearance-based 3D hand tracking techniques to bring the human-computer interaction applications one step closer. All techniques are briefly described below. Skin color provides a powerful cue for complex computer vision applications. Although skin color detection has been an active research area for decades, the mainstream technology is based on individual pixels. This thesis presents a new region-based technique for skin color detection which outperforms the current state-of-the-art pixel-based skin color detection technique on the popular Compaq dataset (Jones & Rehg 2002). The proposed technique achieves 91.17% true positive rate with 13.12% false negative rate on the Compaq dataset tested over approximately 14,000 web images. Hand tracking is not a trivial task as it requires tracking of 27 degreesof- freedom of hand. Hand deformation, self occlusion, appearance similarity and irregular motion are major problems that make 3D hand tracking a very challenging task. This thesis proposes a model-based 3D hand tracking technique, which is improved by using proposed depth-foreground-background ii feature, palm deformation module and context cue. However, the major problem of model-based techniques is, they are computationally expensive. This can be overcome by discriminative techniques as described below. Discriminative techniques (for example random forest) are good for hand part detection, however they fail due to sensor noise and high interfinger occlusion. Additionally, these techniques have difficulties in modelling kinematic or temporal constraints. Although model-based descriptive (for example Markov Random Field) or generative (for example Hidden Markov Model) techniques utilize kinematic and temporal constraints well, they are computationally expensive and hardly recover from tracking failure. This thesis presents a unified framework for 3D hand tracking, using the best of both methodologies, which out performs the current state-of-the-art 3D hand tracking techniques. The proposed 3D hand tracking techniques in this thesis can be used to extract accurate hand movement features and enable complex human machine interaction such as gaming and virtual object manipulation

    Mitigation of artifacts due to isolated acoustic heterogeneities in photoacoustic computed tomography using a variable data truncation-based reconstruction method

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    Photoacoustic computed tomography (PACT) is an emerging computed imaging modality that exploits optical contrast and ultrasonic detection principles to form images of the absorbed optical energy density within tissue. If the object possesses spatially variant acoustic properties that are unaccounted for by the reconstruction method, the estimated image can contain distortions. While reconstruction methods have recently been developed to compensate for this effect, they generally require the object's acoustic properties to be known a priori. To circumvent the need for detailed information regarding an object's acoustic properties, we previously proposed a half-time reconstruction method for PACT. A half-time reconstruction method estimates the PACT image from a data set that has been temporally truncated to exclude the data components that have been strongly aberrated. However, this method can be improved upon when the approximate sizes and locations of isolated heterogeneous structures, such as bones or gas pockets, are known. To address this, we investigate PACT reconstruction methods that are based on a variable data truncation (VDT) approach. The VDT approach represents a generalization of the half-time approach, in which the degree of temporal truncation for each measurement is determined by the distance between the corresponding ultrasonic transducer location and the nearest known bone or gas void location. Computer-simulated and experimental data are employed to demonstrate the effectiveness of the approach in mitigating artifacts due to acoustic heterogeneities

    Assessing the Impacts of Nature-Based Tourism: Host and Guest Perspectives

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    Nature-based tourism is one of the most popular forms and fastest growing sectors of the tourism industry. Tourism could potentially be a boon as well as a burden to nature-based tourism destinations (Newsome, Moore, and Dowling 2012). The impacts of tourism largely depend o