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Title:

Algorithms for Non-Negatively Constrained Maximum Penalized Likelihood Reconstruction in Tomographic Imaging

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Image reconstruction is a key component in many medical imaging modalities. The problem of image reconstruction can be viewed as a special inverse problem where the unknown image pixel intensities are estimated from the observed measurements. Since the measurements are usually noise contaminated, statistical reconstruction methods are preferred....

Image reconstruction is a key component in many medical imaging modalities. The problem of image reconstruction can be viewed as a special inverse problem where the unknown image pixel intensities are estimated from the observed measurements. Since the measurements are usually noise contaminated, statistical reconstruction methods are preferred. In this paper we review some non-negatively constrained simultaneous iterative algorithms for maximum penalized likelihood reconstructions, where all measurements are used to estimate all pixel intensities in each iteration. Minimize

Publisher:

Multidisciplinary Digital Publishing Institute

Year of Publication:

2013-03-01T00:00:00Z

Document Type:

article

Language:

English

Subjects:

tomographic imaging ; penalized likelihood ; algorithms ; constrained optimization ; LCC:Mathematics ; LCC:QA1-939 ; LCC:Science ; LCC:Q ; DOAJ:Mathematics ; DOAJ:Mathematics and Statistics ; LCC:Mathematics ; LCC:QA1-939 ; LCC:Science ; LCC:Q ; DOAJ:Mathematics ; DOAJ:Mathematics and Statistics ; LCC:Mathematics ; LCC:QA1-939 ; LCC:Science ; LC...

tomographic imaging ; penalized likelihood ; algorithms ; constrained optimization ; LCC:Mathematics ; LCC:QA1-939 ; LCC:Science ; LCC:Q ; DOAJ:Mathematics ; DOAJ:Mathematics and Statistics ; LCC:Mathematics ; LCC:QA1-939 ; LCC:Science ; LCC:Q ; DOAJ:Mathematics ; DOAJ:Mathematics and Statistics ; LCC:Mathematics ; LCC:QA1-939 ; LCC:Science ; LCC:Q ; LCC:Mathematics ; LCC:QA1-939 ; LCC:Science ; LCC:Q Minimize

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Title:

Algorithms for Non-Negatively Constrained Maximum Penalized Likelihood Reconstruction in Tomographic Imaging

Author:

Description:

Image reconstruction is a key component in many medical imaging modalities. The problem of image reconstruction can be viewed as a special inverse problem where the unknown image pixel intensities are estimated from the observed measurements. Since the measurements are usually noise contaminated, statistical reconstruction methods are preferred....

Image reconstruction is a key component in many medical imaging modalities. The problem of image reconstruction can be viewed as a special inverse problem where the unknown image pixel intensities are estimated from the observed measurements. Since the measurements are usually noise contaminated, statistical reconstruction methods are preferred. In this paper we review some non-negatively constrained simultaneous iterative algorithms for maximum penalized likelihood reconstructions, where all measurements are used to estimate all pixel intensities in each iteration. Minimize

Publisher:

Multidisciplinary Digital Publishing Institute

Year of Publication:

2013-03-12

Source:

Algorithms; Volume 6; Issue 1; Pages 136-160

Algorithms; Volume 6; Issue 1; Pages 136-160 Minimize

Document Type:

Text

Language:

EN

Subjects:

tomographic imaging; penalized likelihood; algorithms; constrained optimization

tomographic imaging; penalized likelihood; algorithms; constrained optimization Minimize

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http://creativecommons.org/licenses/by/3.0/

http://creativecommons.org/licenses/by/3.0/ Minimize

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Title:

A Stochastic Correlation Model with Mean Reversion for Pricing Multi-Asset Options

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Mean reversion, Stochastic correlation, Multi-assetoption

Mean reversion, Stochastic correlation, Multi-assetoption Minimize

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A Closed-Form Asymptotic Variance-Covariance Matrix for the Maximum Likelihood Estimator of the GARCH(1,1) Model

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This paper presents a closed-form asymptotic variance-covariance matrix of the Maximum Likelihood Estimators (MLE) for the GARCH(1,1) model. Starting from the standard asymptotic result, a closed form expression for the information matrix of the MLE is derived via a local approximation. The closed form variance-covariance matrix of MLE for the G...

This paper presents a closed-form asymptotic variance-covariance matrix of the Maximum Likelihood Estimators (MLE) for the GARCH(1,1) model. Starting from the standard asymptotic result, a closed form expression for the information matrix of the MLE is derived via a local approximation. The closed form variance-covariance matrix of MLE for the GARCH(1,1) model can be obtained by inverting the information matrix. The Monte Carlo simulation experiments show that this closed form expression works well in the admissible region of parameters. Minimize

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preprint

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Title:

Consumption Persistence and the Equity Premium Puzzle: A Resolution or Not? (Job Market Paper)

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As first pointed out by Mehra and Prescott (1985), the excess return of equities over the risk-free rate, roughly 6%, is too high to be readily reconciled with a standard intertemporal model. Recently, Bansal and Yaron (2000, 2004) have demonstrated a resolution of the equity premium puzzle when high persistence in the consumption growth process...

As first pointed out by Mehra and Prescott (1985), the excess return of equities over the risk-free rate, roughly 6%, is too high to be readily reconciled with a standard intertemporal model. Recently, Bansal and Yaron (2000, 2004) have demonstrated a resolution of the equity premium puzzle when high persistence in the consumption growth process is combined with the Generalized Expected Utility (GEU) specification of Epstein and Zin (1989, 1991). However, Nelson and Startz (2006) and Ma, Nelson, and Startz (2006) have shown that standard estimates of persistence are generally spurious in time series models that are weakly identified. This motivates the re-examination of the evidence for resolution of the equity premium puzzle in this paper. Using the valid Anderson-Rubin type test proposed by Ma and Nelson (2006) I show that weak identification may account for the apparent resolution and valid confidence regions and tests reject high persistence in consumption growth. Also, the possibility of integrated expectations is examined using the Median Unbiased Estimator of Stock and Watson (1998) and little supporting evidence is found. Evidently, the equity premium puzzle remains just that. Minimize

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Title:

Is There a Structural Break in the Risk Free Interest Rate Dynamics?

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In this paper, I use the endogenous structural breakpoint tests to empirically search for a potential structural change in the dynamics of risk free interest rate based on the CKLS model (Chan et al. (1992)). To provide a better finite sample performance of this type of test, I bootstrap the critical values. My results indicate a mild evidence o...

In this paper, I use the endogenous structural breakpoint tests to empirically search for a potential structural change in the dynamics of risk free interest rate based on the CKLS model (Chan et al. (1992)). To provide a better finite sample performance of this type of test, I bootstrap the critical values. My results indicate a mild evidence of a structural break during the period of monetary policy change in the 1980s. After this change the volatility of risk free interest rate seems to drop dramatically. Two Monte Carlo experiments are presented to show that bootstrapped critical values reduce the size distortion of asymptotic ones. Minimize

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Macroeconomic management and intergovernmental relations in China

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Over the past 15 years, China has gradually moved from a highly centralized to a decentralized system in almost all aspects of economic management. Decentralization has changed the role of each level of government in economic management, and has greatly complicated the relations between levels of government. The author analyzes three aspects of ...

Over the past 15 years, China has gradually moved from a highly centralized to a decentralized system in almost all aspects of economic management. Decentralization has changed the role of each level of government in economic management, and has greatly complicated the relations between levels of government. The author analyzes three aspects of intergovernmental relations and their impact on macroeconomic management and market development, and suggests the implications for future reform. He addresses three main questions. First, how do fiscal relations between the central and local government affect the central government's ability to use fiscal policy to achieve stabilization and equalization? Localities have controlled effective tax rates and tax bases in two ways: they controlled tax collection by offering tax concessions, and they found ways to shift budgetary funds to extrabudgetary funds, thus avoiding tax-sharing with the central government. As a result, the center has had to resort to ad hoc instruments to influence revenue remittances from local areas, which caused perverse reactions. Second, how do monetary relations between the two levels of government affect the central bank's ability to control the money supply? In the past 14 years, the economy has overheated several times because of an excessive money supply. The author argues that blame for this should be assigned not to the central bank, but to the institutional structure of monetary relations between the central and local governments. The main source of trouble is the central government's inability to commit to a preannounced credit policy. How does the division of regulatory power between the central and local governments affect the functioning of the market system? As the central government relaxed its control over the economy, local governments used the powers transferred to them to restrict market competition. What is needed is a legal framework (including a fair trade commission) that restricts local governments'ability to abuse power. ; Environmental Economics&Policies,Public Sector Economics&Finance,Banks&Banking Reform,Municipal Financial Management,Regional Governance,National Governance,Public Sector Economics&Finance,Environmental Economics&Policies,Banks&Banking Reform,Municipal Financial Management Minimize

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Monetary management and intergovernmental relations in China

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Intergovernmental fiscal transfer in nine countries : lessons for developingcountries

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The author presents an overview of intergovernmental fiscal transfer systems used in nine developing and industrial countries, and draws implications for other developing countries. On the basis of a comparison of these countries, the author classifies equalization transfer formulas into four categories, analyzes the data requirements of each ty...

The author presents an overview of intergovernmental fiscal transfer systems used in nine developing and industrial countries, and draws implications for other developing countries. On the basis of a comparison of these countries, the author classifies equalization transfer formulas into four categories, analyzes the data requirements of each type of formula, discusses the applicability of these formulas in developing countries, and uses illustrative examples to show how the calculations should be carried out. The author also discusses implementation issues, including the transition from an old to a new transfer system. Finally, he presents an illustrative equalization transfer model for China. He concludes that the formula-based equalization transfer system has at least three advantages over the discretionary system prevailing in many countries: 1) It provides the single most important means to address regional disparities; 2) It bases the evaluation of a subnational government's entitlement on objective variables, thus minimizing bargaining and lobbying, and keeping distribution fair; 3) If properly designed, the formula-based system eliminates the disincentive inherent in many discretionary systems that encourages overspending and weak tax collection efforts. ; Public Sector Economics&Finance,Urban Governance and Management,Banks&Banking Reform,Municipal Financial Management,Regional Governance,Public Sector Economics&Finance,Banks&Banking Reform,National Governance,Municipal Financial Management,Regional Governance Minimize

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Title:

Pricing of a reload employee stock option under severance risk

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Since employee stock option grants have some features that do not fulfill the Black-Scholes assumptions, we use a severance incorporating model to capture its main properties that specify the price and reload condition. Generally, the employee is exposed to various severance risks such as termination with cause or without cause. Departure from a...

Since employee stock option grants have some features that do not fulfill the Black-Scholes assumptions, we use a severance incorporating model to capture its main properties that specify the price and reload condition. Generally, the employee is exposed to various severance risks such as termination with cause or without cause. Departure from a firm with or without cause means that the option would be forfeited or exercised immediately, respectively, which gives significant influence to the optimal decision of executing the reload. To compute the reload, we determine the boundary constraint as a free boundary condition and reveal the main features of the impact of severance risk on reload. ; Applied finance, Applied mathematical finance, Asset pricing, Arbitrage relationship Minimize

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