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排序方式: 共有337条查询结果,搜索用时 46 毫秒
1.
Joaquín Cortés Eliana Valencia Gonzalo Aguila Esteban Orellana Paulo Araya 《Catalysis Letters》2008,126(1-2):63-71
An experimental study is made of the time decay of activity of the CO–NO reaction on a Pd/Al2O3 looking at the effect on reaction order and apparent activation energy. The optimum kinetics parameters fitting the steady state data at moderate pressures are determined. The time decay curves are analyzed through various catalyst deactivation models. 相似文献
2.
Comparisons of Urban Travel Forecasts Prepared with the Sequential Procedure and a Combined Model 总被引:4,自引:1,他引:3
Justin D. Siegel Joaquín De Cea José Enrique Fernández Renán E. Rodriguez David Boyce 《Networks and Spatial Economics》2006,6(2):135-148
Detailed analyses and comparisons of urban travel forecasts prepared by applying the state-of-practice sequential procedure
and the solution of a combined network equilibrium model are presented. The sequential procedure for solving the trip distribution,
mode choice and assignment problems with feedback is the current practice in most transportation planning agencies, although
its important limitations are well known. The solution of a combined model, in contrast, results from a single mathematical
formulation, which ensures a well-converged and consistent result. Using a real network, several methods for solving the sequential
procedure with feedback are compared to the solution of the combined model ESTRAUS. The results of these methods are shown
to have various levels of instability. The paper concludes with a call for a new paradigm of travel forecasting practice based
on an internally consistent model formulation that can be solved to a level of precision suitable for comparing alternative
scenarios. 相似文献
3.
The objective of our research was to develop assistive technology for visually impaired people, with a high appreciation for the human potential to achieve, to learn, and to achieve goals. In this document, we describe a virtual white cane made of a combination of a Smartphone and a laser pointer. In our device, the laser pointer beam reflection is captured by the Smartphone camera. The distance from the virtual white cane to the reflection is computed through active triangulation. Then, a personalized vibration, the magnitude of which corresponds to distance, is generated in the Smartphone. In this way, the users receive information that could prevent collisions with obstacles in the environment. Our contributions include the development of a virtual white cane around a Smartphone and other off-the-shelf accessories and a methodology to provide personalized vibratory feedback to the user. Our experiments show that to navigate, our instrument is better option, in terms of travel time, that the use of the hands. However, the travel time is still better using a traditional white cane than our instrument. 相似文献
4.
In this paper we study a problem of sequencing jobs in a machine with programmed preventive maintenance and sequence-dependent set-up times. The problem combines two NP-hard problems, so we propose a heuristic method for solving it, which hybridizes multi-start strategies with Tabu Search. We compare our method with the only published metaheuristic algorithm for this problem on a set of 420 instances. The comparison favors the method developed in this work, showing that is able to find high quality solutions in very short computational times. 相似文献
5.
Joaquín Abellán 《Information Fusion》2013,14(4):423-430
In this paper, we present an experimental comparison among different strategies for combining decision trees built by means of imprecise probabilities and uncertainty measures. It has been proven that the combination or fusion of the information obtained from several classifiers can improve the final process of the classification. We use previously developed schemes, known as Bagging and Boosting, along with a new one based on the variation of the root node via the information rank of each feature of the class variable. To this end, we applied two different approaches to deal with missing data and continuous variables. We use a set of tests on the performance of the methods analyzed here, to show that, with the appropriate approach, the Boosting scheme constitutes an excellent way to combine this type of decision tree. It should be noted that it provides good results, even compared with a standard Random Forest classifier, a successful procedure very commonly used in the literature. 相似文献
6.
Atrial Fibrillation (AF) is the most common supraventricular tachyarrhythmia. Recently, it has been suggested that AF is partially organized on its onset and termination, thus being more suitable for antiarrhythmia and to avoid unnecessary therapy. Although several invasive and non-invasive AF organization estimators have been proposed, the organization time course in the first and last minutes of AF has not been quantified yet. The aim of this work is to study non-invasively the organization variation within the first and last minutes of paroxysmal AF. The organization was evaluated making use of sample entropy, which can robustly estimate electrical atrial activity organization from surface ECG recordings. This work proves an organization decrease in the first minutes of AF onset and an increase within the last minute before spontaneous AF termination. These results are in agreement with the conclusions reported by other authors who made use of invasive recordings. 相似文献
7.
Fernando Caballero Luis Merino Joaquín Ferruz Aníbal Ollero 《Journal of Intelligent and Robotic Systems》2009,55(4-5):323-343
This paper presents a new approach for vision-based UAV localization, using mosaics as environment representations. Inter-image motions are used to estimate the motion of the UAV. Online mosaicking is applied to reduce the impact of the accumulative errors in UAV position estimation. A new method to build an stochastic mosaic given the image-to-image homographies is detailed. The mosaic consists of a network of inter-image relations, and is used to create a consistent view of the environment of the UAV and hence, to detect the drift in position estimation by using the mosaic as a resource. The technique could be called simultaneous localization and mosaicking. This technique is specially suitable for monitoring and surveillance tasks in which the UAV will repeatedly cover the same area. The paper also shows experimental results with real UAVs where the benefits of the proposed method are evident. 相似文献
8.
Joaquín Nicolás Joaquín Lasheras Ambrosio Toval Francisco J. Ortiz Bárbara Álvarez 《Requirements Engineering》2009,14(1):27-46
Teleoperated systems for ship hull maintenance (TOS) are robotic systems for ship maintenance tasks, such as cleaning or painting
a ship’s hull. The product line paradigm has recently been applied to TOS, and a TOS reference architecture has thus been
designed. However, TOS requirements specifications have not been developed in any rigorous way with reuse in mind. We therefore
believe that an opportunity exists to increase the abstraction level at which stakeholders can reason about this product line.
This paper reports an experience in which this TOS domain was analyzed, including the lessons learned in the construction
and use of the TOS domain model. The experience is based on the application of extensions of well-known domain analysis techniques,
together with the use of quality attribute templates traced to a feature model to deal with non-functional issues. A qualitative
research method (action research) was used to carry out the experience. 相似文献
9.
Alvarez I Carrascal M Canals F Muixí L Abián J Jaraquemada D 《Proteomics. Clinical applications》2007,1(3):286-298
HLA class I molecules present peptides on the cell surface to CD8(+) T cells. The repertoire of peptides that associate to class I molecules represents the cellular proteome. Therefore, cells expressing different proteomes could generate different class I-associated peptide repertoires. A large number of peptides have been sequenced from HLA class I alleles, mostly from lymphoid cells. On the other hand, T cell immunotherapy is a goal in the fight against cancer, but the identification of T cell epitopes is a laborious task. Proteomic techniques allow the definition of putative T cell epitopes by the identification of HLA natural ligands in tumor cells. In this study, we have compared the HLA class I-associated peptide repertoire from the hepatocellular carcinoma (HCC) cell line SK-Hep-1 with that previously described from lymphoid cells. The analysis of the peptide pool confirmed that, as expected, the peptides from SK-Hep-1 derive from proteins localized in the same compartments as in lymphoid cells. Within this pool, we have identified 12 HLA class I peptides derived from HCC-related proteins. This confirms that tumor cell lines could be a good source of tumor associated antigens to be used, together with MS, to define putative epitopes for cytotoxic T cells from cancer patients. 相似文献
10.