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11.
Valter Castelvetro Cinzia De Vita Giacomo Giannini Simone Giaiacopi 《应用聚合物科学杂志》2006,102(4):3083-3094
The evolution of the main colloidal parameters in the seeded starved‐feed semi‐continuous emulsion polymerization of butyl methacrylate (BMA) was investigated, with the main purpose of assessing the effectiveness of the semi‐empirical relationship S = K · SS · ΔA/AS as a tool to define the surfactant/monomer feed ratio (∝ K) best suited to achieve a target particle size. In particular, the effect of the type and amount of surfactant [i.e., anionic, sodium dodecyl sulfate (SDS), or nonionic, Brij 58P] added during the semi‐continuous stage was considered. Coagulum formation was never observed under the adopted experimental conditions. To detect the occurrence of secondary nucleation or particle aggregation, or both, the particle size and number of particles, the surface tension and the particle surface coverage ratio were correlated. The best results were obtained with SDS and 0.8 ≤ K ≤ 3. In fact, under the selected experimental conditions, only with SDS did the number of particles remain nearly constant throughout the polymerization at the value defined by the seed latex; the particle size distribution was highly monodisperse, and the final particle diameter closely matched the calculated one (~ 120 nm). The above semi‐empirical relationship based on the adjustable parameter K was validated by running test polymerizations aimed at lattices with well‐defined particle size. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3083–3094, 2006 相似文献
12.
Sascha Stanic Thomas Koch Klaus Schmid Simone Knaus Vasiliki-Maria Archodoulaki 《应用聚合物科学杂志》2021,138(28):50659
The influence of two peroxides (peroxydicarbonate/dilauroyl peroxide) with various concentrations (10–200 mmol/kg PP) and their effective opportunity to introduce long chain branched (LCB) were investigated. The dependence of a single and double extrusion step and the changes of the properties were studied. Experiments were carried out in a single screw extruder at 180°C for the first extrusion step (modification) and at 240°C for the second extrusion step (processing simulation). Melt flow rate and dynamic rheological properties were studied at a measuring temperature of 230°C. For the definitive determination of long chain branched polypropylene (LCB-PP) served the extensional rheology measurements. The mechanical properties were examined via tensile test and impact tensile test. Summarized, LCB (melt strength) could be observed via extensional rheology for all modified specimens and the mechanical properties were maintained or even improved for the modified samples. Particularly, samples containing dilauroyl peroxide display excellent mechanical properties in this study. 相似文献
13.
An empirical analysis was performed to compare the effectiveness of different approaches to training a set of procedural skills to a sample of novice trainees. Sixty-five participants were randomly assigned to one of the following three training groups: (1) learning-by-doing in a 3D desktop virtual environment, (2) learning-by-observing a video (show-and-tell) explanation of the procedures, and (3) trial-and-error. In each group, participants were trained on two car service procedures. Participants were recalled to perform a procedure either 2 or 4 weeks after the training. The results showed that: (1) participants trained through the virtual approach of learning-by-doing performed both procedures significantly better (i.e. p < .05 in terms of errors and time) than people of non-virtual groups, (2) the virtual training group, after a period of non-use, were more effective than non-virtual training (i.e. p < .05) in their ability to recover their skills, (3) after a (simulated) long period from the training—i.e. up to 12 weeks—people who experienced 3D environments consistently performed better than people who received other kinds of training. The results also suggested that independently from the training group, trainees’ visuospatial abilities were a predictor of performance, at least for the complex service procedure, adj R 2 = .460, and that post-training performances of people trained through virtual learning-by-doing are not affected by learning styles. Finally, a strong relationship (p < .001, R 2 = .441) was identified between usability and trust in the use of the virtual training tool—i.e. the more the system was perceived as usable, the more it was perceived as trustable to acquire the competences. 相似文献
14.
Simone Fiori 《Digital Signal Processing》2009,19(4):715-725
Sample averaging is a commonly used way to smooth out irregularities of data and to get rid of random fluctuations in measurements analysis. In adaptive signal processing, where an adaptive system learns its own parameters in order to perform a predefined task, the learnt parameters-pattern may depend on the initial learning state and on the fluctuations of the statistical features of the input signals to the system. In adaptive system learning, averaging may be employed as a method to merge several learnt parameters-patterns in order to get a better representative pattern. Even in the case of scalar parameters, the concept of averaging is not uniquely defined as scalar parameters spaces may exhibit a rich structure to be dealt with. The case of multiple parameter patterns where single parameters are mutually constrained to each other may exhibit an even richer structure. In the present paper, we deal with the case of parameters-patterns belonging to the unit hypersphere and develop an averaging technique based on the differential geometrical structure of such a curved space. Numerical experiments illustrate the behavior of the developed averaging algorithm. 相似文献
15.
This article proposes a new switched adaptive control design for uncertain switched systems with composite (time-driven and state-dependent) switching and shows its applicability in switched impedance control. A composite switched adaptive control design, consisting of the direct switched adaptive control and the indirect switched adaptive control counterpart, is developed to improve the control performance. Specifically, a new stability condition for composite switching is proposed by making use of differential matrix equations and Sylvester matrix equations, which are a generalization of Lyapunov matrix equations. The design results in a time-varying multiple Lyapunov function that is decreasing at the switching instants. From the theoretical point of view, the relevance of this work is the construction of the adaptive laws that guarantee asymptotic tracking error and asymptotic estimation for the direct and indirect switched adaptive control loops, respectively. From the practical point of view, the relevance of this work is validated in a new switched impedance control for the robot interaction with uncertain and discontinuous environments. 相似文献
16.
Swarm Intelligence Approaches for Grid Load Balancing 总被引:1,自引:0,他引:1
With the rapid growth of data and computational needs, distributed systems and computational Grids are gaining more and more
attention. The huge amount of computations a Grid can fulfill in a specific amount of time cannot be performed by the best
supercomputers. However, Grid performance can still be improved by making sure all the resources available in the Grid are
utilized optimally using a good load balancing algorithm. This research proposes two new distributed swarm intelligence inspired
load balancing algorithms. One algorithm is based on ant colony optimization and the other algorithm is based on particle
swarm optimization. A simulation of the proposed approaches using a Grid simulation toolkit (GridSim) is conducted. The performance
of the algorithms are evaluated using performance criteria such as makespan and load balancing level. A comparison of our
proposed approaches with a classical approach called State Broadcast Algorithm and two random approaches is provided. Experimental
results show the proposed algorithms perform very well in a Grid environment. Especially the application of particle swarm
optimization, can yield better performance results in many scenarios than the ant colony approach. 相似文献
17.
Borkin MA Gajos KZ Peters A Mitsouras D Melchionna S Rybicki FJ Feldman CL Pfister H 《IEEE transactions on visualization and computer graphics》2011,17(12):2479-2488
Heart disease is the number one killer in the United States, and finding indicators of the disease at an early stage is critical for treatment and prevention. In this paper we evaluate visualization techniques that enable the diagnosis of coronary artery disease. A key physical quantity of medical interest is endothelial shear stress (ESS). Low ESS has been associated with sites of lesion formation and rapid progression of disease in the coronary arteries. Having effective visualizations of a patient's ESS data is vital for the quick and thorough non-invasive evaluation by a cardiologist. We present a task taxonomy for hemodynamics based on a formative user study with domain experts. Based on the results of this study we developed HemoVis, an interactive visualization application for heart disease diagnosis that uses a novel 2D tree diagram representation of coronary artery trees. We present the results of a formal quantitative user study with domain experts that evaluates the effect of 2D versus 3D artery representations and of color maps on identifying regions of low ESS. We show statistically significant results demonstrating that our 2D visualizations are more accurate and efficient than 3D representations, and that a perceptually appropriate color map leads to fewer diagnostic mistakes than a rainbow color map. 相似文献
18.
G. Simone G. Perozziello G. Sardella I. Disegna S. Tori N. Manaresi G. Medoro 《Microsystem Technologies》2010,16(7):1269-1276
A hybrid valve for lab on chip applications is presented. The valve is assembled by bonding poly (methyl methacrylate), PMMA,
and silicon-based elastomers. The process used to promote the hybrid bonding includes the deposition of an organosilane (TMSPM)
on the thermoplastic polymer, PMMA to interface PMMA and elastomers. For this study, a membrane in ELASTOSIL? is bonded in correspondence of the end of two microfluidic channels of a fabricated PMMA microfluidic chip. Prior the bonding,
a plasma etching process has been used to remove the TMSPM in a confined circular area. This process made possible to bond
selectively the edge of a membrane leaving free to move its central part. Actuating the membrane with an external positive
pressure or vacuum is possible, respectively, to obstruct or to connect the microfluidic channels. The microvalve may be simply
integrated in microfluidic devices and permits the control of microvolumes of fluid in processes such as transport, separation,
and mixing. The deposition of the TMSPM, the bonding of the valve and its actuation has been characterized and tested. The
flow rate control of liquids through the valve has been characterized. The results have been discussed and commented. The
valve can stand up to 14 psi without showing leakages. 相似文献
19.
This paper discusses the theme of workflow systemadaptability in relation to process modeling. Startingfrom a discussion on the role of formal constructs incooperation, the main claim is that adaptabilityinvolves different dimensions of process modeling.These dimensions concern the possibility to flexiblycombine a rich set of basic categories in order toobtain the most suitable language for modeling thetarget business process and the work practices aroundit; to take into account various levels of visibilityof the contexts of definition and use of a processmodel; and finally to allow for temporary as well aspermanent modifications of the process itself.Ariadne, a notation conceived for the above purpose,is illustrated by means of a working example.Moreover, the paper presents the main designprinciples governing Ariadne's implementation. 相似文献
20.
Julia Andreeva Simone Campana Federica Fanzago Juha Herrala 《Journal of Grid Computing》2008,6(1):3-13
In this paper we present the experience of the ATLAS and CMS High-Energy Physics (HEP) experiments at the Large Hadron Collider
(LHC) with the LCG/EGEE Grid infrastructure. The activity developed around the following two main lines: large-scale physics
and detector simulations and end-user analysis. The LCG/EGEE Grid infrastructure offers a large amount of computing and storage
resources and is growing very rapidly. It provides the natural environment for large-scale physics and detector simulations.
Also, the analysis of these detector simulation data (and in the near future of the reconstructed data from physics collisions)
requires efficient end-users access to Grid resources. In this paper, the main findings and lessons learned in terms of performance,
robustness and scalability of the whole system are discussed in detail. 相似文献