964 resultados para State of Art


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Mulsemedia—multiple sensorial media—captures a wide variety of research efforts and applications. This article presents a historic perspective on mulsemedia work and reviews current developments in the area. These take place across the traditional multimedia spectrum—from virtual reality applications to computer games—as well as efforts in the arts, gastronomy, and therapy, to mention a few. We also describe standardization efforts, via the MPEG-V standard, and identify future developments and exciting challenges the community needs to overcome.

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We present a modelling study of processes controlling the summer melt of the Arctic sea ice cover. We perform a sensitivity study and focus our interest on the thermodynamics at the ice–atmosphere and ice–ocean interfaces. We use the Los Alamos community sea ice model CICE, and additionally implement and test three new parametrization schemes: (i) a prognostic mixed layer; (ii) a three equation boundary condition for the salt and heat flux at the ice–ocean interface; and (iii) a new lateral melt parametrization. Recent additions to the CICE model are also tested, including explicit melt ponds, a form drag parametrization and a halodynamic brine drainage scheme. The various sea ice parametrizations tested in this sensitivity study introduce a wide spread in the simulated sea ice characteristics. For each simulation, the total melt is decomposed into its surface, bottom and lateral melt components to assess the processes driving melt and how this varies regionally and temporally. Because this study quantifies the relative importance of several processes in driving the summer melt of sea ice, this work can serve as a guide for future research priorities.

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Objective: For the evaluation of the energetic performance of combined renewable heating systems that supply space heat and domestic hot water for single family houses, dynamic behaviour, component interactions, and control of the system play a crucial role and should be included in test methods. Methods: New dynamic whole system test methods were developed based on “hardware in the loop” concepts. Three similar approaches are described and their differences are discussed. The methods were applied for testing solar thermal systems in combination with fossil fuel boilers (heating oil and natural gas), biomass boilers, and/or heat pumps. Results: All three methods were able to show the performance of combined heating systems under transient operating conditions. The methods often detected unexpected behaviour of the tested system that cannot be detected based on steady state performance tests that are usually applied to single components. Conclusion: Further work will be needed to harmonize the different test methods in order to reach comparable results between the different laboratories. Practice implications: A harmonized approach for whole system tests may lead to new test standards and improve the accuracy of performance prediction as well as reduce the need for field tests.

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Due to ubiquitous information requirements, market interest in mobile business intelligence (BI) has grown markedly. However, mobile BI market is a relatively new area that has been driven primarily by the IT industry. Yet, there is a lack of systematic study on the critical success factors for mobile BI. This research reviews the state-of-the-art of mobile BI, and explores the critical success factors based on a rigorous examination of the academic and practitioner literature. The study reveals that critical success factors of mobile BI generally fall into four key dimensions, namely security, mobile technology, system content and quality, and organisational support perspectives. The various research findings will be useful to organisations which are considering or undertaking mobile business intelligence initiatives.

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Due to the increasing world energy demand, renewable energy systems have been significantly applied in the power generation sector. Among the renewable energy options, photovoltaic system is one of the most popular resources which has been experiencing a huge attention during recent decades. The remarkable advantages, such as static and movement free characteristics, low maintenance costs, and longevity are the primary factors for the popularity of solar generation in the late years. Nevertheless, the low PV conversion efficiency in one side and high PV material cost in the other side have made PV generation comparably expensive system. Consequently, a capable maximum power point tracking (MPPT) is all important to elicit the maximum energy from the production of PV systems. Different researches have been conducted to design a fast, simple and robust MPPT technique under uniform conditions. However, due to the series and parallel connection of PV modules and according to the use of bypass diodes, in the structure of PV modules, a conventional techniques are unable to track a true MPP. Recently, several studies have been undertaken to modify these conventional methods and enable them to track the global MPP under rapidly changing environments and partial shading (PS) conditions. This report concentrates on the state of the art of these methods and their evolution to apply under PS conditions. The recent developments and modifications are analyzed through a comparison based on design complexity, cost, speed and the ability to track the MPP under rapid environmental variations and PS conditions.

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Environmental and economical concerns are stimulating research of new materials for construction, furniture, packaging and automotive industries. Particularly attractive are the new materials. This paper presents results about the properties of composites of polyhydroxybutyrate (PHB), polypropylene (PP) and High Density Polyethylene (HDPE) reinforced with natural fibres. The composites were prepared through the extrusion with natural fibres, in an ratio of 30% by weight. The quality of samples was tested utilising injection moulded samples, according to ASTM standards. Results showed that natural fibres can act as an excellent reinforcing material, resulting in low cost composites and improving economical and ecological interests.

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Currently, the major drawback of gene therapy is the gene transfection rate. The two main types of vectors that. are used in gene therapy are based on viral or non-viral gene delivery systems. There are several non-viral systems that can be used to transfer foreign genetic material into the human body. In order to do so, the DNA to be transferred must escape the processes that affect the disposition of macromolecules. These processes include the interaction with blood components, vascular endothelial cells and uptake by the reticuloendothelial system. Furthermore, the degradation of therapeutic DNA by serum nucleases is also a potential obstacle for functional delivery to the target cell. Cationic polymers have a great potential for DNA complexation and may be useful as non-viral vectors for gene therapy applications. The objective of this review was to address the state of the art in gene therapy using synthetic and natural polycations and the latest strategies to improve the efficiency of gene transfer into the cell.

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Embryonic chimerism is generally used in basic research and in vivo diagnosis of undifferentiated embryonic stem cells (ESC), mostly using mice embryos, although there have been reports in the literature on using rat, rabbit, sheep, chicken, primate, bovine, goat and pig embryos. Several techniques can currently be used to produce chimeric embryos, including microinjection, co-culture with ESC, fusion and aggregation. Although microinjection is the most commonly used method in mice, the mere aggregation of embryos with ESC may result in viable chimeras and be as efficient as microinjection. In mice, this chimerism technique has been shown to have the advantage of aggregating embryos in different stages of development with different ploidy, in addition to using ESC in the tetraploid complementation assay. Compared to other techniques for producing chimeras, the aggregation technique is a cheaper, faster and easier methodology to be performed. Moreover, aggregation can be simplified by chemically removing the zona pellucida with pronase or acidic Tyrode’s solution and be enhanced by using the Well of the Well culture system in combination with adhesion molecules, such as phytohemagglutinin. The most commonly used stages for chimerism by aggregation are those that precede the full compaction of the morula. In these stages, embryos have low-tension adherent junctions at the tangential point between two blastomeres. During the embryonic development of mice, the inner cell mass differentiates into epiblast and hypoblast. These layers will originate the fetal tissues and a portion of the extraembryonic tissues (yolk sac, allantois and amnion), whereas the trophectoderm (TE) gives rise to the chorion. A functional TE is essential for the complex molecular communications that occur between the embryo and the uterus. Embryos produced by somatic cell nuclear transfer, such as commercial cattle clones or endangered species, are subject to large fetal and neonatal losses. Hence embryo complementation with heterologous TE could be of assistance to decrease these losses and might as well assist development of high-value embryos in other approaches.