177,332 research outputs found
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Sourcing Stone and Ochre Artifacts: A Review of Why It Matters in Australia (and Beyond)
No full textSourcing transported stone and ochre artifacts to their geological origin is popular in archaeology (Andrefsky 2009; Shackley 1998b, 2008, 2011) and a fundamental starting point for understanding the economic and social processes associated with any stone-based technology (Hiscock and Mitchell 1993). Sourcing research has been applied extensively throughout the world: for example, in Africa (e.g., Bernatchez 2008; Nash et al. 2013, 2016; Negash et al. 2006; Shackley and Sahle 2017; Zipkin et al. 2017), Europe (e.g., Andreeva et al. 2014; Brandl et al. 2014; Cavallo et al. 2017; Sánchez de la Torre, Le Bourdonnec, Gratuze et al. 2017; Moreau et al. 2016), South America (e.g., Barberena et al. 2019; Cackler et al. 1999; Cortegoso et al. 2016; Flegenheimer et al. 2003; Méndez et al. 2018; Pintar et al. 2016; Popelka-Filcoff, Lenehan et al. 2007), Oceania (e.g., Allen and Johnson 1997; Clark et al. 2014; Collerson and Weisler 2007; Kirch et al. 2012; McAlister and Allen 2017; Mills et al. 2010; Weisler et al. 2016), North America (e.g., Boulanger et al. 2015; Church 2000; Eiselt et al. 2011; Gauthier et al. 2012; MacDonald et al. 2011; MacDonald et al. 2018; Pitblado, Boeka Cannon, Neff et al. 2013; Popelka-Filcoff, Robertson et al. 2007; ten Bruggencate et al. 2015), and Asia (e.g., Doelman et al. 2008; Doelman et al. 2012; Frahm 2012b; Frahm et al. 2014; Guo et al. 2005; Jia et al. 2010; Kuzmin and Glascock 2007). Such sourcing work should be, and often is, preceded by comprehensive geoarchaeological survey to establish the availability and distribution of both primary (outcropping) and secondary (waterborne) sources (e.g., Borrazzo 2012; Gazzan et al. 2019; MacDonald et al. 2013; Wilson 2007). In this chapter, we explore the application of sourcing techniques to stone and ochre artifacts in Australia.Full Tex
Sequential convex relaxation for convex optimization with bilinear matrix equalities
No full textWe consider the use of the nuclear norm operator, and its tendency to produce low rank results, to provide a convex relaxation of Bilinear Matrix Inequalities (BMIs). The BMI is first written as a Linear Matrix Inequality (LMI) subject to a bi-affine equality constraint and subsequently rewritten into an LMI subject to a rank constraint on a matrix affine in the decision variables. The convex nuclear norm operator is used to relax this rank constraint. We provide an algorithm that iteratively improves on the sum of the objective function and the norm of the equality constraint violation. The algorithm is demonstrated on a controller synthesis example.Accepted Author ManuscriptTeam Raf Van de Pla
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Rank-based optimization techniques for estimation problems in optics
No full textAberrations in optical systems, such as telescopes and microscopes, degrade the quality of the images that can be produced by these systems. For example, an object that is positioned out of focus produces a blurred image on a camera sensor and the turbulent air in the earth’s atmosphere reduces the imaging performance of telescopes. In this thesis we only consider wavefront aberrations. AO can be used to compensate for these wavefront aberrations. The working principle of AO is to quantify by measuring or estimation the wavefront aberration and to dynamically adjust wavefront modulating devices, such as Deformable Mirrors (DMs), to counteract the aberration and thereby improving the optical performance. The estimation of the wavefront aberration based on images of a point source is called phase retrieval, which is a highly nonlinear estimation problem. The success of the estimation usually depends on the (type of) algorithm, the available information on the aberration that is incorporated in the estimate, and the degree to which the model of the optical system corresponds to reality. In this thesis we propose a convex optimization-based method for phase retrieval. The method allows for easy inclusion of many types of prior information on the aberration. Furthermore, we develop an efficient implementation of the optimization. The robustness of the approach against measurement noise is investigated and compared with several other state of the art algorithms. Experimental validation shows the algorithmis well able to estimate aberrations in real-life circumstances. A new type of prior information is introduced to estimate dynamic wavefront aberrations. In literature and in practice, the optical path is split between either a wavefront sensor and a camera, or between multiple cameras in order to reliable estimate an aberration. The inherent problem is that between the sensor and cameras the aberration can differ (Non-Common Path (NCP) errors), and a wrong estimate is used in the compensation by the AO system. We propose a method to estimate the aberration from measurements by a single camera, by assuming that the aberration evolves according to (non-specific) model, i.e. the dynamics are contained in a model-set. At the same time that we estimate the aberration, we also identify the dynamics according to which the aberration evolves over time. The estimation of the wavefront aberration based on images of an unknown object is called blind deconvolution if both the aberration and object are estimated. Like phase retrieval, this too is a highly nonlinear estimation problem. We propose the first convexoptimization based estimation method for blind deconvolution problems that estimate aberration and object when the images are acquired using coherent illumination. The method allows for the inclusion of many existing types of prior information on the object and/or aberration. Finally, we analyze controllers for segmented mirrors in large ground-based telescopes. These mirrors consist of many interconnected hexagonal segments. This distributed nature of the system warrants the investigation into whether the controller that keeps the segments aligned can be designed in such a way that it can be distributed over the segments as well, essentially resulting in a distributed controller where local controllers communicate with each other. What complicates the analysis is that the dynamics across segments are not necessarily decoupled: the wind load can be correlated and the flexibility in the supporting structure of the segments can cause dynamic coupling. We investigate the design of a distributed controller that incorporates these global dynamics. Furthermore, we investigate the performance of the distributed controller and howit relates to the communication and interconnection pattern of the local controllers.Team Raf Van de Pla
Simulation of an Artificial Respiratory System: Choosing a New Actuator for Implementation in a Lung Simulator
No full textIt is suspected that instability problems in the current generation of lung simulators are caused by its actuator, a brushless DC motor, in combination with the system configuration. The hypothesis is that these problems can be resolved by replacing the actuator with a backdrivable actuator (that is, an actuator that responds well to external force) in a new system. In this BSc Thesis this hypothesis is researched. The backdrivable actuator (in this particular case, a Voice Coil actuator) in a new system can overcome the instability problems.Electrical EngineeringElectrical Engineering, Mathematics and Computer Scienc
Letter from R. R. Zellick, Assistant Trust Officer, Anglo California National Bank of San Francisco, to Joseph R. Goodman, October 2, 1942
No full textLetter from R. R. Zellick, Assistant Trust Officer at The Anglo California National Bank of San Francisco, to Joseph R. Goodman, regarding property owned by Dave Tatsuno. Zellick mentions a dispute between current tenants and Tatsuno, and that Tatsuno has asked Goodman to help locate trustworthy tenants.Personal correspondence, organizational records, government documents, publications, and other papers created or collected by Joseph R. Goodman documenting the forced removal and incarceration of Japanese Americans during World War II, as well as organized resistance to incarceration. Included in the collection are records of the Japanese Young Men's Christian Association and the Japanese American Citizens' League in San Francisco, including papers of the Japanese YMCA's executive secretary Lincoln Kanai; Sakai family papers; Goodman's correspondence to and from Japanese American incarcerees, organizations opposing forced removal and incarceration of Japanese Americans, the War Relocation Authority, and others; publications, photographs, and ephemera from the Topaz Relocation Center, where Goodman taught high school; War Relocation Authority records and publications; and newspaper clippings, pamphlets, and reports about forced removal and incarceration created by various government, religious, and civic organizations, in California and nationwide
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