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81.
Christoph Bosshard Roland Bouffanais Michel Deville Ralf Gruber Jonas Latt 《Computers & Fluids》2011,44(1):1-8
In this paper, a comprehensive performance review of an MPI-based high-order three-dimensional spectral element method C++ toolbox is presented. The focus is put on the performance evaluation of several aspects with a particular emphasis on the parallel efficiency. The performance evaluation is analyzed with the help of a time prediction model based on a parameterization of the application and the hardware resources. Two tailor-made benchmark cases in computational fluid dynamics (CFD) are introduced and used to carry out this review, stressing the particular interest for clusters with up to thousands of cores. Some problems in the parallel implementation have been detected and corrected. The theoretical complexities with respect to the number of elements, to the polynomial degree, and to communication needs are correctly reproduced. It is concluded that this type of code has a nearly perfect speedup on machines with thousands of cores, and is ready to make the step to next-generation petaFLOP machines. 相似文献
82.
Matthias Jungmann Margarete Kopal Christoph ClauserThomas Berlage 《Computers & Geosciences》2011,37(4):541-553
Electrical borehole wall images represent micro-resistivity measurements at the borehole wall. The lithology reconstruction is often based on visual interpretation done by geologists. This analysis is very time-consuming and subjective. Different geologists may interpret the data differently. In this work, linear discriminant analysis (LDA) in combination with texture features is used for an automated lithology reconstruction of ODP (Ocean Drilling Program) borehole 1203A drilled during Leg 197. Six rock groups are identified by their textural properties in resistivity data obtained by a Formation MircoScanner (FMS). Although discriminant analysis can be used for multi-class classification, non-optimal decision criteria for certain groups could emerge. For this reason, we use a combination of 2-class (binary) classifiers to increase the overall classification accuracy. The generalization ability of the combined classifiers is evaluated and optimized on a testing dataset where a classification rate of more than 80% for each of the six rock groups is achieved. The combined, trained classifiers are then applied on the whole dataset obtaining a statistical reconstruction of the logged formation. Compared to a single multi-class classifier the combined binary classifiers show better classification results for certain rock groups and more stable results in larger intervals of equal rock type. 相似文献
83.
Parametric curved shape surface schemes interpolating vertices and normals of a given triangular mesh with arbitrary topology are widely used in computer graphics for gaming and real-time rendering due to their ability to effectively represent any surface of arbitrary genus. In this context, continuous curved shape surface schemes using only the information related to the triangle corresponding to the patch under construction, emerged as attractive solutions responding to the requirements of resource-limited hardware environments. In this paper we provide a unifying comparison of the local parametric C0 curved shape schemes we are aware of, based on a reformulation of their original constructions in terms of polynomial Bézier triangles. With this reformulation we find a geometric interpretation of all the schemes that allows us to analyse their strengths and shortcomings from a geometrical point of view. Further, we compare the four schemes with respect to their computational costs, their reproduction capabilities of analytic surfaces and their response to different surface interrogation methods on arbitrary triangle meshes with a low triangle count that actually occur in their real-world use. 相似文献
84.
A popular approach in combinatorial optimization is to model problems as integer linear programs. Ideally, the relaxed linear
program would have only integer solutions, which happens for instance when the constraint matrix is totally unimodular. Still,
sometimes it is possible to build an integer solution with the same cost from the fractional solution. Examples are two scheduling
problems (Baptiste and Schieber, J. Sched. 6(4):395–404, 2003; Brucker and Kravchenko, J. Sched. 11(4):229–237, 2008) and the single disk prefetching/caching problem (Albers et al., J. ACM 47:969–986, 2000). We show that problems such as the three previously mentioned can be separated into two subproblems: (1) finding an optimal
feasible set of slots, and (2) assigning the jobs or pages to the slots. It is straigthforward to show that the latter can
be solved greedily. We are able to solve the former with a totally unimodular linear program, from which we obtain simple
combinatorial algorithms with improved worst case running time. 相似文献
85.
To generate artificial materials with advanced physical and chemical properties and to study phase transition kinetics on submillisecond time scale, an ultrafast nonadiabatic membrane nanocalorimeter was constructed. A set of commercially available membrane gauges for ultrafast nanocalorimetry has been developed. The gauges placed in a thermostat with controlled helium gas pressure and temperature can be utilized as devices for thermal processing and calorimetry with resolution of 1 nJ/K. Controlled ultrafast cooling, as well as heating, up to 10(6) K/s can be attained for nanogram samples. The maximum cooling rate is inversely proportional to the radius of the heated region of the gauge, which was in the range of 10-100 microm depending on the gauge. The minimum addenda heat capacity was 3 nJ/K. The dynamic heat-transfer problem for the temperature distribution in the membrane-gas system at ultrafast processing has been solved. The characteristic rate R(0) corresponding to quasistatic limit of the temperature change in the membrane-gas system has been found to be equal to 10(5) K/s for a 1 microm thick silicon nitride membrane in helium gas. Calorimeter performance at ultrafast rates has been verified by a set of test experiments. The method was applied for thermal processing and calorimetric measurements in a set of linear polymers. It has been established that nearly amorphous polyethylene can be obtained at a cooling rate of 10(6) K/s. 相似文献
86.
Since the various people involved in the design process for a building project tend to hold conflicting views, this inevitably
leads to a range of disparate models for planning and calculation purposes. In order to interpret the relevant geometrical,
topological and semantical data for any given building model, we identify a structural component graph, a graph of room faces,
a room graph and a relational object graph as aids and explain algorithms to derive these relations. We start with a building
model by transferring its geometrical, topological and semantical data into a volume model, decomposing the latter into a
so-called connection model and then extracting all air volume bodies and hulls of the model by means of further decomposition
into elementary cyclic connection components. The technique is demonstrated within the scope of building energy simulation
by deriving both a dimensionally reduced object model required for setting up a thermal multizone model and a geometrical
model for defining single or multiple computational fluid dynamic domains in a building together with incidence matrices correlating
these models. The algorithm is basically applicable to any building energy simulation tool.
相似文献
Ernst RankEmail: |
87.
Emotions should play an important role in the design of interfaces because people interact with machines as if they were social actors. This paper presents a literature review on affective expressions through speech, music and body language. It summarizes the quality and quantity of their parameters and successful examples of synthesis. Moreover, a model for the convincingness of affective expressions, based on Fogg and Hsiang Tseng (1999), was developed and tested. The empirical data did not support the original model and therefore this paper proposes a new model, which is based on appropriateness and intensity of the expressions. Furthermore, the experiment investigated if the type of emotion (happiness, sadness, anger, surprise, fear and disgust), knowledge about the source (human or machine), the level of abstraction (natural face, computer rendered face and matrix face) and medium of presentation (visual, audio/visual, audio) of an affective expression influences its convincingness and distinctness. Only the type of emotion and multimedia presentations had an effect on convincingness. The distinctness of an expression depends on the abstraction and the media through which it is presented. 相似文献
88.
Ordered binary decision diagrams are the state-of-the-art representation of switching functions. In order to keep the sizes of OBDDs tractable, heuristics and dynamic reordering algorithms are applied to optimize the underlying variable order. When finite state machines are represented by OBDDs the state encoding can be used as an additional optimization parameter. In this paper, we analyze local encoding transformations which can be applied dynamically. First, we investigate the potential of re-encoding techniques. We then propose the use of an XOR-transformation and show why this transformation is most suitable among the set of all encoding transformations. The presented theoretical framework establishes a new optimization technique for OBDDs. 相似文献
89.
Analyzing the design of networks for visual information routing is an underconstrained problem due to insufficient anatomical and physiological data. We propose here optimality criteria for the design of routing networks. For a very general architecture, we derive the number of routing layers and the fanout that minimize the required neural circuitry. The optimal fanout l is independent of network size, while the number k of layers scales logarithmically (with a prefactor below 1), with the number n of visual resolution units to be routed independently. The results are found to agree with data of the primate visual system. 相似文献
90.
When artists portray human faces, they generally endow their portraits with properties that render the faces esthetically more pleasing. To obtain insight into the changes introduced by artists, we compared Fourier power spectra in photographs of faces and in portraits by artists. Our analysis was restricted to a large set of monochrome or lightly colored portraits from various Western cultures and revealed a paradoxical result. Although face photographs are not scale-invariant, artists draw human faces with statistical properties that deviate from the face photographs and approximate the scale-invariant, fractal-like properties of complex natural scenes. This result cannot be explained by systematic differences in the complexity of patterns surrounding the faces or by reproduction artifacts. In particular, a moderate change in gamma gradation has little influence on the results. Moreover, the scale-invariant rendering of faces in artists' portraits was found to be independent of cultural variables, such as century of origin or artistic techniques. We suggest that artists have implicit knowledge of image statistics and prefer natural scene statistics (or some other rules associated with them) in their creations. Fractal-like statistics have been demonstrated previously in other forms of visual art and may be a general attribute of esthetic visual stimuli. 相似文献