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41.
Daniel Stuparu Manuela Petrescu 《通讯和计算机》2009,6(3):9-15
One of the most recent features in a database is the Common Table Expressions (CTE), introduced by SQL Server 2005. Microsoft SQL Server 2008 is the second version of SQL Server that supports recursive queries and implements a standard recursive CTE. CTEs are new constructs that offer a more readable form of the derived table that can be declared once and referenced multiple times in a query. Moreover, CTEs can be recursively defined, allowing a recursive entity to be enumerated without the need for recursive-stored procedures. This paper proposes an incursion in the world of Common Table Expression, in order to find its features, its advantages and disadvantages. Also, this paper presents a comparison of performance tests performed on different database systems (SQL Server 2005, SQL Server 2008 and PostgreSQL Server 8.4 Development Version) using similar structures. 相似文献
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Cretu AM Payeur P Petriu EM 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2012,42(3):740-753
This paper discusses the design and implementation of a framework that automatically extracts and monitors the shape deformations of soft objects from a video sequence and maps them with force measurements with the goal of providing the necessary information to the controller of a robotic hand to ensure safe model-based deformable object manipulation. Measurements corresponding to the interaction force at the level of the fingertips and to the position of the fingertips of a three-finger robotic hand are associated with the contours of a deformed object tracked in a series of images using neural-network approaches. The resulting model captures the behavior of the object and is able to predict its behavior for previously unseen interactions without any assumption on the object's material. The availability of such models can contribute to the improvement of a robotic hand controller, therefore allowing more accurate and stable grasp while providing more elaborate manipulation capabilities for deformable objects. Experiments performed for different objects, made of various materials, reveal that the method accurately captures and predicts the object's shape deformation while the object is submitted to external forces applied by the robot fingers. The proposed method is also fast and insensitive to severe contour deformations, as well as to smooth changes in lighting, contrast, and background. 相似文献
44.
Luiza Madalina Gradinaru Mihaela Barbalata-Mandru Stelian Vlad Mioara Petrescu 《应用聚合物科学杂志》2021,138(33):50834
The components of the surface free energy (SFE) were determined from static contact angle measurements of five liquids using different methods. The two manufacturing techniques (casting and electrospinning) applied to obtain polyurethane (PU) membranes give surfaces with different wetting properties. The SFE data varied and were strongly dependent on calculations methods and liquids that were used for contact angle measurements. As a whole, the SFE of electrospun PU membrane (PU-N) (~24 mN/m) was slightly higher than that of casting PU membrane (PU-F) (~18 mN/m) with similar chemical compositions. The overall increase in the value of SFE is mainly due to the microstructures with increased surface area and modulations of nanofibers. The results evidence the impact of the PU membrane preparation on the properties of the biomaterial surface. Such structure–properties–function relationship is necessary to lay the groundwork for establishing a set of design criteria to guide the fabrication of synthetic materials. 相似文献
45.
Oren Etzioni Michael Cafarella Doug Downey Ana-Maria Popescu Tal Shaked Stephen Soderland Daniel S. Weld Alexander Yates 《Artificial Intelligence》2005,165(1):91-134
The KnowItAll system aims to automate the tedious process of extracting large collections of facts (e.g., names of scientists or politicians) from the Web in an unsupervised, domain-independent, and scalable manner. The paper presents an overview of KnowItAll's novel architecture and design principles, emphasizing its distinctive ability to extract information without any hand-labeled training examples. In its first major run, KnowItAll extracted over 50,000 class instances, but suggested a challenge: How can we improve KnowItAll's recall and extraction rate without sacrificing precision?This paper presents three distinct ways to address this challenge and evaluates their performance. Pattern Learning learns domain-specific extraction rules, which enable additional extractions. Subclass Extraction automatically identifies sub-classes in order to boost recall (e.g., “chemist” and “biologist” are identified as sub-classes of “scientist”). List Extraction locates lists of class instances, learns a “wrapper” for each list, and extracts elements of each list. Since each method bootstraps from KnowItAll's domain-independent methods, the methods also obviate hand-labeled training examples. The paper reports on experiments, focused on building lists of named entities, that measure the relative efficacy of each method and demonstrate their synergy. In concert, our methods gave KnowItAll a 4-fold to 8-fold increase in recall at precision of 0.90, and discovered over 10,000 cities missing from the Tipster Gazetteer. 相似文献
46.
A three‐layer neural network, based on 192 sets of experimental data obtained by the authors, was built in order to simulate the influence of four main process parameters on the minimum and stationary spouting velocity and on the pressure drop in a spouted bed. The simulations with the neural net are in good agreement with experimental learning data, and the overall average absolute error is 5.43 %. The neural net was used in the framework of a Monte Carlo simulation using CRYSTAL BALL®. The result of 100,000 trials revealed the percentage contributions of the process parameters to the variance of the selected state variables. Since there is significant uncertainty concerning the design equations of spouted beds, the results of this work should be useful for the design of such devices. 相似文献
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48.
Ana-Maria Fuertes 《Computational statistics & data analysis》2007,51(7):3448-3469
Different estimators of rating transition matrices have been proposed in the literature but their behaviour has been studied mainly in the context of corporate ratings. The finite-sample bias and variability of three sovereign credit migration estimators is investigated through bootstrap simulations. These are a discrete multinomial estimator and two continuous-time hazard rate methods, one of which neglects time heterogeneity in the rating process whereas the other accounts for it. Panel logit models and spectral analysis are utilized to study the properties of the rating process. The sample consists of Moody's ratings 1981-2004 for 72 industrialized and emerging economies. Hazard rate estimators yield more accurate default probabilities. The time homogeneity assumption leads to underestimating the default probability and greater migration risk is inferred upon relaxing it. There is evidence of duration dependence and downgrade momentum effects in the rating process. These findings have important implications for economic and regulatory capital allocation and for the pricing of credit sensitive instruments. 相似文献
49.
RL Houghton M Petrescu DR Benson YA Skeiky A Scalone R Badaró SG Reed L Gradoni 《Canadian Metallurgical Quarterly》1998,177(5):1339-1344
Serologic assays using crude antigens for the diagnosis of visceral leishmaniasis in human immunodeficiency virus type 1 (HIV)-seropositive patients have been shown to lack sensitivity and specificity, particularly in AIDS patients. Antibodies to a cloned antigen, recombinant (r) K39, of Leishmania chagasi are specific for members of the Leishmania donovani complex and have been shown to indicate active disease in immunocompetent persons. This study demonstrated that antibodies to rK39 were also detectable in HIV-seropositive patients coinfected with Leishmania infantum. Furthermore, the rK39 ELISA was more sensitive than an IFA for detecting L. infantum infections in patients with AIDS. In addition, antibody titers to rK39 in HIV-negative patients infected with L. infantum or L. chagasi declined during treatment with meglumine antimoniate or liposomal amphotericin B. In contrast, most patients who clinically relapsed showed increased antibody titers to rK39. These data demonstrate the diagnostic and prognostic utility of rK39 in detecting active visceral leishmaniasis. 相似文献
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