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排序方式: 共有2518条查询结果,搜索用时 15 毫秒
51.
Marta Alberti Joaquim Ciurana Ciro A. Rodríguez Tugrul Özel 《Journal of Intelligent Manufacturing》2011,22(2):263-277
Economic globalization, together with heightened market competition and increasingly short product life cycles are motivating
companies to use advanced manufacturing technologies. Use of high speed machining is increasingly widespread; however, as
the technology is relatively new, it lacks a deep-rooted knowledge base which would facilitate implementation. One of the
most frequent problems facing companies wishing to adopt this technology is selecting the most appropriate machine tool for
the product in question and own enterprise characteristics. This paper presents a decision support system for high speed milling
machine tool selection based on machine characteristics and performance tests. Profile machining tests are designed and conducted
in participating machining centers. The decision support system is based on product dimension accuracy, process parameters
such as feed rate and interpolation scheme used by CNC and machine characteristics such as machine accuracy and cost. Experimental
data for process error and cycle operation time are obtained from profile machining tests with different geometrical feature
zones that are often used in manufacturing of discrete parts or die/moulds. All those input parameters have direct impact
on productivity and manufacturing cost. Artificial neural network models are utilized for decision support system with reasonable
prediction capability. 相似文献
52.
José Luis Crespo Marta Zorrilla Pilar Bernardos Eduardo Mora 《The Visual computer》2009,25(4):309-323
The objective of this paper is to present an overall approach to forecasting the future position of the moving objects of
an image sequence after processing the images previous to it. The proposed method makes use of classical techniques such as
optical flow to extract objects’ trajectories and velocities, and autoregressive algorithms to build the predictive model.
Our method can be used in a variety of applications, where videos with stationary cameras are used, moving objects are not
deformed and change their position with time. One of these applications is traffic control, which is used in this paper as
a case study with different meteorological conditions to compare with.
相似文献
Marta Zorrilla (Corresponding author)Email: |
53.
In this paper we introduce a method to compute non-dominated bicriteria shortest pairs, each including two disjoint simple paths. The method is based on an algorithm for ranking pairs of disjoint simple paths by non-decreasing order of cost, that is an adaptation of a path ranking algorithm applied to a network obtained from the original one after a suitable modification of the topology. Each path in this new network corresponds to a pair of paths in the former one. Computational results are presented and analysed for randomly generated networks. 相似文献
54.
Marta Gonzlez Llúcia Masip Antoni Granollers Marta Oliva 《Advances in Engineering Software》2009,40(12):1271-1278
In usability context of interactive systems the heuristic evaluation method is widespread. In most applications the results tend to be qualitative, describing such aspects that require some improvement for the benefit of usability. However, these qualitative results do not allow us to determine how usable it is or how it becomes an interactive system. Hence the need for quantitative results may also be very necessary in order to determine the effort that would be needed to get a sufficiently usable system.This article describes, following the idea of the UsabAIPO Project, a new experiment to obtain quantitative results after a heuristic evaluation. This new experimentation has required some variation on the original idea, working with a set of different heuristic categories, while considering the use of the score depending on severity and frequency parameters. 相似文献
55.
Arce-Urriza Marta Cebollada Javier Tarira María Fernanda 《Information Systems and E-Business Management》2017,15(1):69-87
Information Systems and e-Business Management - This study evaluates the differential effect of price promotions on brand choice across the offline and online channels of a grocery retailer. We use... 相似文献
56.
Effects and interactions of temperature and stress-level related damage on permeability of concrete 总被引:5,自引:0,他引:5
The objective of this study is to investigate damage-temperature-stress level-permeability interactions in structural concrete. The tests are performed on hollow cylindrical concrete specimens, subjected to compressive loading and temperature up to 150 °C. The results emphasize that at stress levels lower than 80% of the peak stress, the variation of permeability is small and it is slightly influenced by the stress. As a matter of fact, the permeability under load is smaller than the permeability measured after unloading. As the load exceeds 80% of the peak stress, micro-cracking increases rapidly, causing an increase of the permeability and a greater sensitivity to the applied load, i.e. a noticeable difference between the permeability measured under load and after unloading, the first becoming greater than the latter. In the post-peak phase the increase of permeability is much larger due to significant crack width growth. The increase of permeability with the applied load seems to be greater with temperature, inducing further alterations of concrete and dilation of the porous structure of the material. Finally, the experimental results seem to agree with the format of coupled evolution of the permeability due to damage and temperature assumed by Gawin et al. [D. Gawin, C.E. Majorana, B.A. Schrefler, Numerical analysis of hygro-thermal behaviour and damage of concrete at high temperature, Mechanics of Cohesive-Frictional Materials 4 (1999) 37-74.]. 相似文献
57.
John J. A. Barry Marta M. C. G. Silva Sarah H. Cartmell Robert E. Guldberg Colin A. Scotchford Steven M. Howdle 《Journal of Materials Science》2006,41(13):4197-4204
Porous scaffold structures are used in tissue engineering to provide structural guidance for regenerating tissues. The use
of carbon dioxide (CO2) to create such scaffolds has received some attention in the past but many researchers believe that although CO2 processing of polymers can lead to porous scaffolds there is limited interconnectivity between the pores. In this study,
highly porous (greater than 85%) and well interconnected scaffolds were obtained in which the size, distribution and number
of pores could be controlled. This control was achieved by altering the rate of venting from polymer discs saturated with
CO2 under modest temperature and pressure. The polymer used is a blend of poly (ethyl methacrylate) and tetrahydrofurfuryl methacrylate
(PEMA/THFMA). This polymer system has shown promise for potential applications in cartilage repair. 相似文献
58.
The aim of this work is to provide a high performance air quality simulation using the sulphur transport Eulerian model 2 (STEM-II) program. First of all we optimize the sequential program with the aim of increasing data locality. Then, the optimized program is parallelized using OpenMP shared-memory directives. Experimental results on a 32-processor SGI Origin 2000 show that the parallel program achieves important reductions in the execution times. 相似文献
59.
Pettarin Valeria Frontini Patricia Eliçabe Guillermo Rink Marta Pavan Andrea 《Mechanics of Time-Dependent Materials》2004,8(3):269-288
This paper deals with the influence of the testing equipment on impact load measurements. A previously developed method of analysis and processing of the experimental data based on a refined analogical model of the impact event and inverse problem techniques is used. This method makes it possible to obtain the mechanical response of the material, notwithstanding the disturbance of the dynamic effects associated to the test. Results from tests carried out both on falling weight and swing pendulum instrumented testing machines are compared. It is shown that this method can give an accurate estimation of the actual bending force in impact testing independent of the testing equipment. 相似文献
60.
Marta Oliveira Susana Casal Simone Morais Cláudia Alves Filipa Dias Sandra Ramos Eulália Mendes Cristina Delerue-Matos M. Beatriz P.P. Oliveira 《Food chemistry》2012,130(3):702-709
The present paper reports the amount and estimated daily mineral intake of nine elements (Ca, Mg, K, Na, P, Fe, Mn, Cr and Ni) in commercial instant coffees and coffee substitutes (n = 49). Elements were quantified by high-resolution continuum source flame (HR-CS-FAAS) and graphite furnace (HR-CS-GFAAS) atomic absorption spectrometry, while phosphorous was evaluated by a standard vanadomolybdophosphoric acid colorimetric method.Instant coffees and coffee substitutes are rich in K, Mg and P (>100 mg/100 g dw), contain Na, Ca and Fe in moderate amounts (>1 mg/100 g), and trace levels of Cr and Ni. Among the samples analysed, plain instant coffees are richer in minerals (p < 0.001), except for Na and Cr. Blends of coffee substitutes (barley, malt, chicory and rye) with coffee (20–66%) present intermediate amounts, while lower quantities are found in substitutes without coffee, particularly in barley.From a nutritional point of view the results indicate that the mean ingestion of two instant beverages per day (total of 4 g instant powder), either with or without coffee, cannot be regarded as important sources of minerals to the human diet, although providing a supplementation of some minerals, particularly Mg and Mn in instant coffees. Additionally, and for authentication purposes, the correlations observed between some elements and the coffee percentage in the blends, with particular significance for Mg amounts, provides a potential tool for the estimation of coffee in substitute blends. 相似文献