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21.
Romain Carron Enrico Avancini Thomas Feurer Benjamin Bissig Paolo A. Losio Renato Figi 《Science and Technology of Advanced Materials》2018,19(1):396-410
Cu(In,Ga)Se2-based solar cells have reached efficiencies close to 23%. Further knowledge-driven improvements require accurate determination of the material properties. Here, we present refractive indices for all layers in Cu(In,Ga)Se2 solar cells with high efficiency. The optical bandgap of Cu(In,Ga)Se2 does not depend on the Cu content in the explored composition range, while the absorption coefficient value is primarily determined by the Cu content. An expression for the absorption spectrum is proposed, with Ga and Cu compositions as parameters. This set of parameters allows accurate device simulations to understand remaining absorption and carrier collection losses and develop strategies to improve performances. 相似文献
22.
Bertini E Tatu A Keim D 《IEEE transactions on visualization and computer graphics》2011,17(12):2203-2212
In this paper, we present a systematization of techniques that use quality metrics to help in the visual exploration of meaningful patterns in high-dimensional data. In a number of recent papers, different quality metrics are proposed to automate the demanding search through large spaces of alternative visualizations (e.g., alternative projections or ordering), allowing the user to concentrate on the most promising visualizations suggested by the quality metrics. Over the last decade, this approach has witnessed a remarkable development but few reflections exist on how these methods are related to each other and how the approach can be developed further. For this purpose, we provide an overview of approaches that use quality metrics in high-dimensional data visualization and propose a systematization based on a thorough literature review. We carefully analyze the papers and derive a set of factors for discriminating the quality metrics, visualization techniques, and the process itself. The process is described through a reworked version of the well-known information visualization pipeline. We demonstrate the usefulness of our model by applying it to several existing approaches that use quality metrics, and we provide reflections on implications of our model for future research. 相似文献
23.
Giacomo Bucci Laura Carnevali Lorenzo Ridi Enrico Vicario 《International Journal on Software Tools for Technology Transfer (STTT)》2010,12(5):391-403
Oris is a tool for qualitative verification and quantitative evaluation of reactive timed systems, which supports modeling
and analysis of various classes of timed extensions of Petri Nets. As most characterizing features, Oris implements symbolic
state space analysis of preemptive Time Petri Nets, which enable schedulability analysis of real-time systems running under
priority preemptive scheduling; and stochastic Time Petri Nets, which enable an integrated approach to qualitative verification
and quantitative evaluation. In this paper, we present the current version of the tool and we illustrate its application to
two different case studies in the areas of qualitative verification and quantitative evaluation, respectively. 相似文献
24.
Given a set of products each with positive discrete demand, and a set of markets selling products at given prices, the traveling purchaser problem (TPP) looks for a tour visiting a subset of markets such that products demand is satisfied at minimum purchasing and traveling costs. In this paper we analyze a dynamic variant of the problem, where quantities may decrease as time goes on. Complete information is assumed on current state of the world, i.e. decision maker knows quantities available for each product in each market at present time and is informed about any consumption event when it occurs. Nevertheless, planner does not have any information on future events. Two groups of heuristics are described and compared. The first group consists of simplified approaches deciding which market to visit next on the basis of some greedy criteria considering only one of the two objective costs. The second one includes heuristics based on a look-ahead approach taking into account both traveling and purchasing costs and inserting some future prediction. Heuristics behavior has been tested on a large set of randomly generated instances under different levels of dynamism. 相似文献
25.
Alessandro Agnetis Enrico Grande Pitu B. Mirchandani Andrea Pacifici 《Computers & Operations Research》2009
The paper addresses the problem of locating sensors with a circular field of view so that a given line segment is under full surveillance, which is termed as the disc covering problem on a line. The cost of each sensor includes a fixed component f, and a variable component that is a convex function of the diameter of the field-of-view area. When only one type of sensor or, in general, one type of disc, is available, then a simple polynomial algorithm solves the problem. When there are different types of sensors, the problem becomes hard. A branch-and-bound algorithm as well as an efficient heuristic are developed for the special case in which the variable cost component of each sensor is proportional to the square of the measure of the field-of-view area. The heuristic very often obtains the optimal solution as shown in extensive computational testing. 相似文献
26.
J��r?me Schmid Jos�� A. Iglesias?Guiti��n Enrico Gobbetti Nadia Magnenat-Thalmann 《The Visual computer》2011,27(2):85-95
Despite the ability of current GPU processors to treat heavy parallel computation tasks, its use for solving medical image
segmentation problems is still not fully exploited and remains challenging. A lot of difficulties may arise related to, for
example, the different image modalities, noise and artifacts of source images, or the shape and appearance variability of
the structures to segment. Motivated by practical problems of image segmentation in the medical field, we present in this
paper a GPU framework based on explicit discrete deformable models, implemented over the NVidia CUDA architecture, aimed for
the segmentation of volumetric images. The framework supports the segmentation in parallel of different volumetric structures
as well as interaction during the segmentation process and real-time visualization of the intermediate results. Promising
results in terms of accuracy and speed on a real segmentation experiment have demonstrated the usability of the system. 相似文献
27.
We study the problem of guaranteeing correct execution semantics in parallel implementations of logic programming languages in presence of built-in constructs that are sensitive to order
of execution. The declarative semantics of logic programming languages permit execution of various goals in any arbitrary
order (including in parallel). However, goals corresponding to extra-logical built-in constructs should respect the sequential
order of execution to ensure correct semantics. Ensuring this correctness in presence of such built-in constructs, while efficiently
exploiting maximum parallelism, is a difficult problem. In this paper, we propose a formalization of this problem in terms
of operations on dynamic trees. This abstraction enables us to: (i) show that existing schemes to handle order-sensitive computations used in current parallel
systems are sub-optimal; (ii) develop a novel, optimal scheme to handle order-sensitive goals that requires only a constant time overhead per operation. While we present our results in the context of logic programming, they will apply equally well to
most parallel non-deterministic systems.
Received: 20 April 1998 / 3 April 2000 相似文献
28.
Algorithms for Moving Objects Databases 总被引:8,自引:0,他引:8
29.
An interactive system is described for creating and animating deformable 3D characters. By using a hybrid layered model of kinematic and physics-based components together with an immersive 3D direct manipulation interface, it is possible to quickly construct characters that deform naturally when animated and whose behavior can be controlled interactively using intuitive parameters. In this layered construction technique, called the elastic surface layer model, a simulated elastically deformable skin surface is wrapped around a kinematic articulated figure. Unlike previous layered models, the skin is free to slide along the underlying surface layers constrained by geometric constraints which push the surface out and spring forces which pull the surface in to the underlying layers. By tuning the parameters of the physics-based model, a variety of surface shapes and behaviors can be obtained such as more realistic-looking skin deformation at the joints, skin sliding over muscles, and dynamic effects such as squash-and-stretch and follow-through. Since the elastic model derives all of its input forces from the underlying articulated figure, the animator may specify all of the physical properties of the character once, during the initial character design process, after which a complete animation sequence can be created using a traditional skeleton animation technique. Character construction and animation are done using a 3D user interface based on two-handed manipulation registered with head-tracked stereo viewing. In our configuration, a six degree-of-freedom head-tracker and CrystalEyes shutter glasses are used to display stereo images on a workstation monitor that dynamically follow the user head motion. 3D virtual objects can be made to appear at a fixed location in physical space which the user may view from different angles by moving his head. To construct 3D animated characters, the user interacts with the simulated environment using both hands simultaneously: the left hand, controlling a Spaceball, is used for 3D navigation and object movement, while the right hand, holding a 3D mouse, is used to manipulate through a virtual tool metaphor the objects appearing in front of the screen. Hand-eye coordination is made possible by registering virtual space to physical space, allowing a variety of complex 3D tasks necessary for constructing 3D animated characters to be performed more easily and more rapidly than is possible using traditional interactive techniques. 相似文献
30.
Guido Camata Enrico Spacone Riadh Al-Mahaidi Victor Saouma 《Canadian Metallurgical Quarterly》2004,8(6):528-538
The failure mechanisms of reinforced concrete (RC) members change due to the application of externally bonded fiber-reinforced polymer reinforcement. Although an extensive literature is available describing the failure mechanisms of poststrengthened flexural systems, brittle failure modes caused by bond failure, such as midspan debonding and end peeling, need to be further investigated in order to identify and quantify the fracture processes that result in bond failure. Simplified experimental tests have been designed to idealize the bond between the laminate and the RC member. However, it is unclear how the simplified test results can be related to the actual flexural debonding failures. This paper investigates and compares two bond failure tests: a simplified test (or simple shear test) and a recently proposed shear/normal test. After discussing the characteristics of both tests and how they relate to the midspan debonding and end peeling failures, the shear/normal test is studied in more detail using a nonlinear finite-element fracture mechanics program. The program accounts for cohesive localized and distributed concrete crack damage and is capable of describing the geometrical discontinuities that induce different brittle failure mechanisms. The numerical results compare well with available experimental data and help explain the crack formation and propagation pattern up to specimen failure. Parametric studies are presented to elucidate the influence of different material parameters on the failure mechanisms. 相似文献