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"... ARCHEAN greenstonehosted lode gold deposits provide about 13 percent of the world’s gold resources (Jenkins et al., 1997; Goldfarb et al., 2001; Dubé and Gosselin, 2007) and include ..."
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ARCHEAN greenstonehosted lode gold deposits provide about 13 percent of the world’s gold resources (Jenkins et al., 1997; Goldfarb et al., 2001; Dubé and Gosselin, 2007) and include
Convergence Rates of Convex Variational Regularization
"... The aim of this paper is to provide quantitative estimates for the minimizers of nonquadratic regularization problems in terms of the regularization parameter respectively the noise level. As usual for illposed inverse problems, these estimates can be obtained only under additional smoothness a ..."
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Cited by 70 (12 self)
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The aim of this paper is to provide quantitative estimates for the minimizers of nonquadratic regularization problems in terms of the regularization parameter respectively the noise level. As usual for illposed inverse problems, these estimates can be obtained only under additional smoothness assumptions on the data, socalled source conditions, which we identify with the existence of Lagrange multipliers for a limit problem. Under such a source condition, we shall prove a quantitative estimate for the Bregman distance induced by the regularization functional, which turns out to be the natural distance measure to use in this case.
Alternating direction augmented Lagrangian methods for semidefinite programming
, 2009
"... Abstract. We present an alternating direction method based on an augmented Lagrangian framework for solving semidefinite programming (SDP) problems in standard form. At each iteration, the algorithm, also known as a twosplitting scheme, minimizes the dual augmented Lagrangian function sequentially ..."
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Cited by 64 (2 self)
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Abstract. We present an alternating direction method based on an augmented Lagrangian framework for solving semidefinite programming (SDP) problems in standard form. At each iteration, the algorithm, also known as a twosplitting scheme, minimizes the dual augmented Lagrangian function sequentially with respect to the Lagrange multipliers corresponding to the linear constraints, then the dual slack variables and finally the primal variables, while in each minimization keeping the other variables fixed. Convergence is proved by using a fixedpoint argument. A multiplesplitting algorithm is then proposed to handle SDPs with inequality constraints and positivity constraints directly without transforming them to the equality constraints in standard form. Finally, numerical results for frequency assignment, maximum stable set and binary integer quadratic programming problems are presented to demonstrate the robustness and efficiency of our algorithm.
Thirdparty web tracking: Policy and technology
 in IEEE Symposium on Security and Privacy, 2012
"... Abstract—In the early days of the web, content was designed and hosted by a single person, group, or organization. No longer. Webpages are increasingly composed of content from myriad unrelated “thirdparty ” websites in the business of advertising, analytics, social networking, and more. Thirdparty ..."
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Cited by 63 (2 self)
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Abstract—In the early days of the web, content was designed and hosted by a single person, group, or organization. No longer. Webpages are increasingly composed of content from myriad unrelated “thirdparty ” websites in the business of advertising, analytics, social networking, and more. Thirdparty services have tremendous value: they support free content and facilitate web innovation. But thirdparty services come at a privacy cost: researchers, civil society organizations, and policymakers have increasingly called attention to how third parties can track a user’s browsing activities across websites. This paper surveys the current policy debate surrounding thirdparty web tracking and explains the relevant technology. It also presents the FourthParty web measurement platform and studies we have conducted with it. Our aim is to inform researchers with essential background and tools for contributing to public understanding and policy debates about web tracking. KeywordsWeb privacy; thirdparty tracking; Do Not Track. I.
Sparse inverse covariance selection via alternating linearization methods
, 2010
"... Gaussian graphical models are of great interest in statistical learning. Because the conditional independencies between different nodes correspond to zero entries in the inverse covariance matrix of the Gaussian distribution, one can learn the structure of the graph by estimating a sparse inverse co ..."
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Cited by 59 (9 self)
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Gaussian graphical models are of great interest in statistical learning. Because the conditional independencies between different nodes correspond to zero entries in the inverse covariance matrix of the Gaussian distribution, one can learn the structure of the graph by estimating a sparse inverse covariance matrix from sample data, by solving a convex maximum likelihood problem with an ℓ1regularization term. In this paper, we propose a firstorder method based on an alternating linearization technique that exploits the problem’s special structure; in particular, the subproblems solved in each iteration have closedform solutions. Moreover, our algorithm obtains an ϵoptimal solution in O(1/ϵ) iterations. Numerical experiments on both synthetic and real data from gene association networks show that a practical version of this algorithm outperforms other competitive algorithms.
How Did Location Affect adoption of the Commercial Internet? global village, urban density, and identity composition
 University of Chicago
, 2003
"... We provide a framework and evidence to confront two contradictory yet common assertions: (1) new technology such as the Internet favors businesses in urban areas and (2) the Internet reduces the importance of distance for economic activity. Controlling for other factors, we show that participation i ..."
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Cited by 53 (17 self)
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We provide a framework and evidence to confront two contradictory yet common assertions: (1) new technology such as the Internet favors businesses in urban areas and (2) the Internet reduces the importance of distance for economic activity. Controlling for other factors, we show that participation in the Internet is more likely in rural areas than in urban areas. Use of frontier technologies also arises in rural areas for interfirm technologies, which are associated with ending economic isolation. Nevertheless, talk of the dissolution of cities is premature. Frontier Internet technologies for intrafirm communication and advanced computing appear more often at establishments in urban areas, even with industry controls. Major urban areas also contain many establishments from information technologyintensive industries, whose presence could reinforce the concentration of frontier Internet technologies in these areas. (JEL classification L63, L86, R0).
Of time and space: The contemporary relevance of the Chicago School. Social Forces 75(4
, 1997
"... This essay argues that sociology's major current problems are intellectual. It traces these problems to the exhaustion of the current "variables paradigm " and considers the Chicago School's "contextualist paradigm " as an alternative. Examples of new methodologies foun ..."
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Cited by 56 (0 self)
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This essay argues that sociology's major current problems are intellectual. It traces these problems to the exhaustion of the current "variables paradigm " and considers the Chicago School's "contextualist paradigm " as an alternative. Examples of new methodologies founded on contextual thinking are considered. Anniversaries are often valedictions. A centennial sometimes shows an association to be moribund, just as a diamond jubilee may reveal a queen's irrelevance and a golden anniversary finds many a marriage dead. By contrast, living social relations celebrate themselves daily. Anniversaries merely punctuate their excitement. What then are we to make of this centennial year of sociology at the University of Chicago? Is it simply a time for eulogy? After all, Chicago dominance of sociology is half a century gone. And while the Chicago tradition renewed itself after the war in Goffman, Becker, Janowitz, and their like, many of Chicago's most distinguished alumni since its dominant years belong more to the mainstream than to the Chicago tradition proper: methodologists like Stouffer and Duncan, demographers like Hauser and Keyfitz, macrosociologists like Bendix and Wilensky. Nonetheless, at the heart of the Chicago tradition he insights central to the advancement of contemporary sociology. Therefore, I do not today eulogize the Chicago tradition. One eulogizes only the dead. 1 * This article sparked a lot of commentary. Surprisingly, helpful comments came not only from people I knew well, but also from relative strangers. I have therefore had more help with this article than with virtually anything else I have written. The following all
DC optimal power flow formulation and solution using QuadProgJ
 Economics Department, Iowa State University
, 2006
"... Nonlinear AC Optimal Power Flow (OPF) problems are commonly approximated by linearized DC OPF problems to obtain real power solutions for restructured wholesale power markets. We first present a standard DC OPF problem, which has the numerically desirable form of a strictly convex quadratic programm ..."
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Cited by 22 (8 self)
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injections and branch flows. We then show how this augmented DC OPF problem can be solved using QuadProgJ, an opensource Java SCQP solver newly developed by the authors that implements the wellknown dual activeset SCQP algorithm by Goldfarb and Idnani (1983). To demonstrate the accuracy of Quad
Recovering Probability Distributions from Contemporaneous Security Prices
 Journal of Finance
, 1996
"... Probability distributions of stock market returns have typically been estimated from historical time series. The possibility of extreme events such as the stock market crash of 1987 makes this a perilous enterprise. Alternative parametric and nonparametric approaches use contemporaneously observed o ..."
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Cited by 54 (1 self)
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Probability distributions of stock market returns have typically been estimated from historical time series. The possibility of extreme events such as the stock market crash of 1987 makes this a perilous enterprise. Alternative parametric and nonparametric approaches use contemporaneously observed option prices to recover their underlying riskneutral probability distribution. Parametric methods assume an option pricing formula which is inverted to obtain parameters of the distribution. The nonparametric methods pursued here choose probabilities to minimize an objective function subject to requiring that the chosen probabilities are consistent with observed option and underlying asset prices. This paper examines alternative specifications of the minimization criterion using historically observed S&P 500 index option prices over an eightyear period. With the exception of the lower lefthand tail of the distribution, alternative optimization specifications typically produce approximately the same implied distributions. Most prominently, the paper introduces a new optimization technique for estimating expirationdate riskneutral probability distributions based on maximizing the smoothness of the resulting probability distribution. Since an "almost closedform" solution for this case is available, the smoothness method is computationally orders of magnitude faster than the alternatives. Considerable care is taken to specify such parameters as interest rates, dividends, and synchronous index levels, as well as to filter for general arbitrage violations and to use time aggregation to correct for unrealistic persistent jaggedness of implied volatility smiles. While time patterns of skewness and kurtosis exhibit a discontinuity across the divide of the 1987 market crash, they ...
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