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51.
Borràs J Casanova J Cristea T Gheorghe A Scozzafava A Supuran CT Tudor V 《Metal-Based Drugs》1996,3(3):143-148
Ternary Ni(II) complexes of hydrazine and eight heterocyclic sulfonamides possessing carbonic anhydrase (CA) inhibitory properties, were prepared and characterized by elemental analysis, spectroscopic, magnetic, thermogravimetric, and conductimetric measurements. The complexes behave as strong inhibitors for two isozymes (I and II) of carbonic anhydrase. 相似文献
52.
The problem of computing the chromatic number of a P
5-free graph (a graph which contains no path on 5 vertices as an induced subgraph) is known to be NP-hard. However, we show
that for every fixed integer k, there exists a polynomial-time algorithm determining whether or not a P
5-free graph admits a k-coloring, and finding one, if it does. 相似文献
53.
Maxine M. Denniston Nancy D. Brener Laura Kann Danice K. Eaton Timothy McManus Tonja M. Kyle Alice M. Roberts Katherine H. Flint James G. Ross 《Computers in human behavior》2010
The Youth Risk Behavior Surveillance System (YRBSS) monitors priority health-risk behaviors among US high school students. To better understand the ramifications of changing the YRBSS from paper-and-pencil to Web administration, in 2008 the Centers for Disease Control and Prevention conducted a study comparing these two modes of administration. Eighty-five schools in 15 states agreed to participate in the study. Within each participating school, four classrooms of students in grades 9 or 10 were randomly assigned to complete the Youth Risk Behavior Survey questionnaire in one of four conditions (in-class paper-and-pencil, in-class Web without programmed skip patterns, in-class Web with programmed skip patterns, and “on your own” Web without programmed skip patterns). Findings included less missing data for the paper-and-pencil condition (1.5% vs. 5.3%, 4.4%, 6.4%; p < .001), less perceived privacy and anonymity among respondents for the in-class Web conditions, and a lower response rate for the “on your own” Web condition than for in-class administration by either mode (28.0% vs. 91.2%, 90.1%, 91.4%; p < .001). Although Web administration might be useful for some surveys, these findings do not favor the use of a Web survey for the YRBSS. 相似文献
54.
Maria-Iuliana Dascalu Constanta-Nicoleta Bodea Monica Nastasia Mihailescu Elena Alice Tanase Patricia Ordoñez de Pablos 《Behaviour & Information Technology》2016,35(4):290-297
The almost unlimited access to educational information plethora came with a drawback: finding meaningful material is not a straightforward task anymore. Recommender algorithms can be used to make smart decisions in complex information systems and help the users decide upon useful materials; therefore, they become a promising area in academia and industry. The current paper presents a survey on educational recommender systems (RS): a set of analysis criteria are exposed and the technological specifications and challenges of each analysed system are provided, in the context of the main trends in the development of RS. Also, an ontology-based educational recommendation mechanism is proposed and its application to lifelong learning is highlighted, proving that RS can successfully support new learning paradigms. 相似文献
55.
O. Litany E. Rodolà A. M. Bronstein M. M. Bronstein D. Cremers 《Computer Graphics Forum》2016,35(5):135-143
Shape correspondence is a fundamental problem in computer graphics and vision, with applications in various problems including animation, texture mapping, robotic vision, medical imaging, archaeology and many more. In settings where the shapes are allowed to undergo non‐rigid deformations and only partial views are available, the problem becomes very challenging. To this end, we present a non‐rigid multi‐part shape matching algorithm. We assume to be given a reference shape and its multiple parts undergoing a non‐rigid deformation. Each of these query parts can be additionally contaminated by clutter, may overlap with other parts, and there might be missing parts or redundant ones. Our method simultaneously solves for the segmentation of the reference model, and for a dense correspondence to (subsets of) the parts. Experimental results on synthetic as well as real scans demonstrate the effectiveness of our method in dealing with this challenging matching scenario. 相似文献
56.
Educational data mining (EDM) is a research area where the goal is to develop data mining methods to examine data critically from educational environments. Traditionally, EDM has addressed the following problems: clustering, classification, regression, anomaly detection and association rule mining. In this paper, the ordinal regression (OR) paradigm, is introduced in the field of EDM. The goal of OR problems is the classification of items in an ordinal scale. For instance, the prediction of students' performance in categories (where the different grades could be ordered according to A ? B ? C ? D) is a classical example of an OR problem. The EDM community has not yet explored this paradigm (despite the importance of these problems in the field of EDM). Furthermore, an amenable and interpretable OR model based on the concept of gravitation is proposed. The model is an extension of a recently proposed gravitational model that tackles imbalanced nominal classification problems. The model is carefully adapted to the ordinal scenario and validated with four EDM datasets. The results obtained were compared with state‐of‐the‐art OR algorithms and nominal classification ones. The proposed models can be used to better understand the learning–teaching process in higher education environments. 相似文献
57.
Jose Hoyos Flavio Prieto Guillem Alenyà Carme Torras 《Journal of Intelligent and Robotic Systems》2016,82(1):81-99
Programming by demonstration techniques facilitate the programming of robots. Some of them allow the generalization of tasks through parameters, although they require new training when trajectories different from the ones used to estimate the model need to be added. One of the ways to re-train a robot is by incremental learning, which supplies additional information of the task and does not require teaching the whole task again. The present study proposes three techniques to add trajectories to a previously estimated task-parameterized Gaussian mixture model. The first technique estimates a new model by accumulating the new trajectory and the set of trajectories generated using the previous model. The second technique permits adding to the parameters of the existent model those obtained for the new trajectories. The third one updates the model parameters by running a modified version of the Expectation-Maximization algorithm, with the information of the new trajectories. The techniques were evaluated in a simulated task and a real one, and they showed better performance than that of the existent model. 相似文献
58.
Tang L Garvin MK Lee K Alward WL Kwon YH Abràmoff MD 《IEEE transactions on pattern analysis and machine intelligence》2011,33(11):2245-2258
A robust multiscale stereo matching algorithm is proposed to find reliable correspondences between low contrast and weakly textured retinal image pairs with radiometric differences. Existing algorithms designed to deal with piecewise planar surfaces with distinct features and Lambertian reflectance do not apply in applications such as 3D reconstruction of medical images including stereo retinal images. In this paper, robust pixel feature vectors are formulated to extract discriminative features in the presence of noise in scale space, through which the response of low-frequency mechanisms alter and interact with the response of high-frequency mechanisms. The deep structures of the scene are represented with the evolution of disparity estimates in scale space, which distributes the matching ambiguity along the scale dimension to obtain globally coherent reconstructions. The performance is verified both qualitatively by face validity and quantitatively on our collection of stereo fundus image sets with ground truth, which have been made publicly available as an extension of standard test images for performance evaluation. 相似文献
59.
Ana Gàl 《Computational Complexity》2001,10(4):277-296
We give a characterization of span program size by a
combinatorial-algebraic measure. The measure we consider is a generalization
of a measure on covers which has been used to prove lower
bounds on formula size and has also been studied with respect to communication
complexity.?In the monotone case our new methods yield lower bounds for
the monotone span program complexity of explicit Boolean functions in
n variables over arbitrary fields, improving the previous lower bounds
on monotone span program size. Our characterization of span program
size implies that any matrix with superpolynomial separation between
its rank and cover number can be used to obtain superpolynomial lower
bounds on monotone span program size. We also identify a property
of bipartite graphs that is suficient for constructing Boolean functions
with large monotone span program complexity.
Received: September 30, 2000. 相似文献
60.
An effective protection of our environment is largely dependent on the quality of the available information used to make an appropriate decision. Problems arise when the quantities of available information are huge and nonuniform (i.e., coming from many different disciplines or sources) and their quality could not be stated in advance. Another associated issue is the dynamical nature of the problem. Computers are central in contemporary environmental protection in tasks such as monitoring, data analysis, communication, information storage and retrieval, so it has been natural to try to integrate and enhance all these tasks with Artificial Intelligence knowledge-based techniques. This paper presents an overview of the impact of Artificial Intelligence techniques on the definition and development of Environmental Decision Support Systems (EDSS) during the last fifteen years. The review highlights the desirable features that an EDSS must show. The paper concludes with a selection of successful applications to a wide range of environmental problems. 相似文献