A multi-collection latent topic model for federated search     

Mark Baillie  Mark Carman  Fabio Crestani 《Information Retrieval》2011,14(4):390-412

Collection selection is a crucial function, central to the effectiveness and efficiency of a federated information retrieval system. A variety of solutions have been proposed for collection selection adapting proven techniques used in centralised retrieval. This paper defines a new approach to collection selection that models the topical distribution in each collection. We describe an extended version of latent Dirichlet allocation that uses a hierarchical hyperprior to enable the different topical distributions found in each collection to be modelled. Under the model, resources are ranked based on the topical relationship between query and collection. By modelling collections in a low dimensional topic space, we can implicitly smooth their term-based characterisation with appropriate terms from topically related samples, thereby dealing with the problem of missing vocabulary within the samples. An important advantage of adopting this hierarchical model over current approaches is that the model generalises well to unseen documents given small samples of each collection. The latent structure of each collection can therefore be estimated well despite imperfect information for each collection such as sampled documents obtained through query-based sampling. Experiments demonstrate that this new, fully integrated topical model is more robust than current state of the art collection selection algorithms.  相似文献   

Energy: Learning from the Past     

Fabio Bevilacqua 《Science & Education》2014,23(6):1231-1243

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Electronic systems design: An experiment of project-based learning on network     

Domenico Ponta  Giuliano Donzellini  Hannu Markkanen 《European Journal of Engineering Education》2001,26(4):375-390

The NetPro project creates models, methods, tools and materials for network-based project learning in engineering education. This new environment is a distributed system that facilitates sharing and peer reviewing of project deliverables and interaction in special interest group discussions. The paper presents as an example the pilot course on Electronic Systems Design and its preliminary evaluation.  相似文献   

The effects of alcohol use on academic achievement in high school     

Balsa AI  Giuliano LM  French MT 《Economics of Education Review》2011,30(1):1-15

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Psychometric Properties of the ECERS-R Among an Epidemiological Sample of Preschools     

Marília Mariano  Sheila C. Caetano  Anderson Ribeiro da Silva  Pamela J. Surkan  Silvia S. Martins  Hugo Cogo-Moreira 《Early education and development》2019,30(4):511-521

Research Findings: The Early Childhood Environment Rating Scale–Revised (ECERS-R) is widely used to evaluate the quality of early childhood education and its association with child development. However, the psychometric properties of the ECERS-R are not well established. Consequently, in this study we tested 3 different factor solutions of the ECERS-R using models sourced from the existing literature (featuring 1-, 2-, and 3-correlated-factor solutions) and applying confirmatory factor analysis to data from the epidemiological sample of the Embu Pre-school Mental Health Study (n = 1,292 children). Alternative measures of child education quality (such as teacher-to-child ratio) were also analyzed. The confirmatory factor analysis returned good fit indices for both the unidimensional and 3-correlated-factor solution models. Practice or Policy: This study showcases different applications of the ECERS-R, both the full and shortened versions. These findings are particularly important for improving ECERS-R guidelines for researchers, professionals, and policymakers.  相似文献   

Long-term correlations in short,non-stationary time series: An application to international R&D collaborations     

Lorenzo Righetto  Alessandro Spelta  Emanuele Rabosio  Fabio Pammolli 《Journal of Informetrics》2019,13(2):583-592

Within the perimeter of patent collaboration networks, the average distance of collaborations and the number of countries involved per each collaboration have been shown to have increased steadily in time. Less attention, though, has been devoted to assessing whether this growth of cross-country collaborations is stable in time. To address this scientific question we focus on the identification of long-term correlations (i.e. temporal persistence). Our data set consists of time series of yearly average collaboration radii and of cross-border links in the Euro-American subsystem of the global collaboration network for the period 1978–2014. To investigate the fundamental persistence properties of these time series, we use Detrended Fluctuation Analysis, a method that allows us to measure long-term correlations in detrended signals. Also, we devise a general and original procedure to assess the statistical significance of results for short time series. Our results, showing that long-term correlations do exist in the majority of our signals, reinforce the hypothesis of a diminishing role of geographical distance in technological collaborations. Results at national level show that a significant degree of heterogeneity in persistence parameters can be detected within Europe, irrespectively of the efforts towards the set-up of an integrated European Research Area.  相似文献   

A hermeneutic defence of the cognitive autonomy of science     

Fabio Gironi 《Metascience》2013,22(2):461-464

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Venture capital financing and the growth of high-tech start-ups: Disentangling treatment from selection effects   总被引：3，自引：0，他引：3  

Fabio Bertoni  Massimo G. ColomboLuca Grilli 《Research Policy》2011,40(7):1028-1043

The financial and innovation literature generally claims that venture capital (VC) investments spur the growth of new technology-based firms (NTBFs). However, it has proved difficult so far to separate the “treatment” effect of the VC investment from the “selection” effect attributable to the ability of the VC investor to screen high growth NTBFs. The aim of this work is to test whether VC investments have a positive treatment effect on the growth of employment and sales of NTBFs. For this purpose we consider a 10-year longitudinal data set for 538 Italian NTBFs, most of which are privately held. The sample includes both VC-backed and non-VC-backed firms. We estimate Gibrat-law-type dynamic panel-data models augmented with time-varying variables that capture the VC status of firms. To control for the endogeneity of VC investments we use several GMM estimators. The econometric results strongly support the view that VC investments positively influence firm growth. The treatment effect of VC investments is of large economic magnitude, especially on growth of employment. Most of it is obtained immediately after the first round of VC finance. Conversely, the selection effect of VC appears to be negligible in the Italian context.  相似文献   

Modelling the joint torques and loadings during squatting at the Smith machine     

Biscarini A  Benvenuti P  Botti F  Mastrandrea F  Zanuso S 《Journal of sports sciences》2011,29(5):457-469

An analytical biomechanical model was developed to establish the relevant properties of the Smith squat exercise, and the main differences from the free barbell squat. The Smith squat may be largely patterned to modulate the distributions of muscle activities and joint loadings. For a given value of the included knee angle (θ(knee)), bending the trunk forward, moving the feet forward in front of the knees, and displacing the weight distribution towards the forefoot emphasizes hip and lumbosacral torques, while also reducing knee torque and compressive tibiofemoral and patellofemoral forces (and vice versa). The tibiofemoral shear force φ(t) displays more complex trends that strongly depend on θ(knee). Notably, for 180° ≥ θ(knee) ≥ 130°, φ(t) and cruciate ligament strain forces can be suppressed by selecting proper pairs of ankle and hip angles. Loading of the posterior cruciate ligament increases (decreases) in the range 180° ≥ θ(knee) ≥ 150° (θ(knee) ≤ 130°) with knee extension, bending the trunk forward, and moving the feet forward in front of the knees. In the range 150° > θ(knee) > 130°, the behaviour changes depending on the foot weight distribution. The conditions for the development of anterior cruciate ligament strain forces are explained. This work enables careful use of the Smith squat in strengthening and rehabilitation programmes.  相似文献   

Multispectral data cube acquisition of aligned images for document analysis by means of a filter-wheel camera provided with focus control     

Gianfranco Bianco  Fabio Bruno  Maurizio Muzzupappa 《Journal of Cultural Heritage》2013,14(3):190-200

Multispectral imaging techniques are widely used to analyse and restore digital images of ancient documents degraded over time. In particular, acquisitions in infrared and ultraviolet bands can reveal information invisible by naked eye, which is not captured by conventional RGB imaging. Multispectral acquisitions are usually performed with filter-wheel cameras that mount a series of interference filters in front of the sensor to select the spectral band in which the document has to be acquired. Due to the use of different filters, the focus of the lens changes and it is necessary to adjust it manually for each filter, because such imaging systems are devoid of automatic focusing. Thus the acquired images may not be perfectly in-focus and have misalignments. In this work we present an automatic solution to acquire a multispectral data cube of aligned images that can be used in document analysis to extract and/or separate information through enhancement techniques. A custom-made motorized autofocus system controlled by software has been installed on a filter-wheel camera, which allows us to acquire in-focus images automatically at each filter changing, and a registration method based on Fourier-Mellin transform aligns these images. A preliminary calibration is performed to set the focusing of each filter with the working distance. As a result, the camera can capture images independently from the contrast of the scene, also in presence of documents with homogeneous texture. The proposed solution reduces considerably the acquisition time and offers a tool to acquire automatically the data cube to be used in further image analysis techniques. The results of experimentations are hereby presented and discussed.  相似文献