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借助CFD专用模拟软件PolyFlow,本文模拟了动态塑化单螺杆挤出机计量段中,聚合物熔体在单螺杆大振幅振动条件下的三维非等温输送流场,研究了大振幅振动力场对挤出产量、功率及螺杆特性的影响。模拟结果显示:振动参数有一个可选范围,当螺杆振动幅值超过该范围而落入横流反向区时,挤出流率将急剧下降,产能比严重降低,螺杆特性变软。 相似文献
44.
Michael Wand Alexander Berner Martin Bokeloh Philipp Jenke Arno Fleck Mark Hoffmann Benjamin Maier Dirk Staneker Andreas Schilling Hans-Peter Seidel 《Computers & Graphics》2008,32(2):204-220
This paper describes a new out-of-core multi-resolution data structure for real-time visualization, interactive editing and externally efficient processing of large point clouds. We describe an editing system that makes use of the novel data structure to provide interactive editing and preprocessing tools for large scanner data sets. Using the new data structure, we provide a complete tool chain for 3D scanner data processing, from data preprocessing and filtering to manual touch-up and real-time visualization. In particular, we describe an out-of-core outlier removal and bilateral geometry filtering algorithm, a toolset for interactive selection, painting, transformation, and filtering of huge out-of-core point-cloud data sets and a real-time rendering algorithm, which all use the same data structure as storage backend. The interactive tools work in real-time for small model modifications. For large scale editing operations, we employ a two-resolution approach where editing is planned in real-time and executed in an externally efficient offline computation afterwards. We evaluate our implementation on example data sets of sizes up to 63 GB, demonstrating that the proposed technique can be used effectively in real-world applications. 相似文献
45.
Greedy scheduling heuristics provide a low complexity and scalable albeit particularly sub-optimal strategy for hardware-based crossbar schedulers. In contrast, the maximum matching algorithm for Bipartite graphs can be used to provide optimal scheduling for crossbar-based interconnection networks with a significant complexity and scalability cost. In this paper, we show how maximum matching can be reformulated in terms of Boolean operations rather than the more traditional formulations. By leveraging the inherent parallelism available in custom hardware design, we reformulate maximum matching in terms of Boolean operations rather than matrix computations and introduce three maximum matching implementations in hardware. Specifically, we examine a Pure Logic Scheduler with three dimensions of parallelism, a Matrix Scheduler with two dimensions of parallelism and a Vector Scheduler with one dimension of parallelism. These designs reduce the algorithmic complexity for an N×N network from O(N3) to O(1), O(K), and O(KN), respectively, where K is the number of optimization steps. While an optimal scheduling algorithm requires K=2N−1 steps, by starting with our hardware-based greedy strategy to generate an initial schedule, our simulation results show that the maximum matching scheduler can achieve 99% of the optimal schedule when K=9. We examine hardware and time complexity of these architectures for crossbar sizes of up to N=1024. Using FPGA synthesis results, we show that a greedy schedule for crossbars, ranging from 8×8 to 256×256, can be optimized in less than 20 ns per optimization step. For crossbars reaching 1024×1024 the scheduling can be completed in approximately 10 μs with current technology and could reach under 90 ns with future technologies. 相似文献
46.
Scanning Depth of Route Panorama Based on Stationary Blur 总被引:1,自引:0,他引:1
This work achieves an efficient acquisition of scenes and their depths along long streets. A camera is mounted on a vehicle
moving along a straight or a mildly curved path and a sampling line properly set in the camera frame scans the 1D images over
scenes continuously to form a 2D route panorama. This paper proposes a method to estimate the depth from the camera path by
analyzing a phenomenon called stationary blur in the route panorama. This temporal blur is a perspective effect in parallel
projection yielded from the sampling slit with a physical width. We analyze the behavior of the stationary blur with respect
to the scene depth, vehicle path, and camera properties. Based on that, we develop an adaptive filter to evaluate the degree
of the blur for depth estimation, which avoids error-prone feature matching or tracking in capturing complex street scenes
and facilitates real time sensing. The method also uses much less data than the structure from motion approach so that it
can extend the sensing area significantly. The resulting route panorama with depth information is useful for urban visualization,
monitoring, navigation, and modeling. 相似文献
47.
Detailed Real-Time Urban 3D Reconstruction from Video 总被引:2,自引:0,他引:2
M. Pollefeys D. Nistér J.-M. Frahm A. Akbarzadeh P. Mordohai B. Clipp C. Engels D. Gallup S.-J. Kim P. Merrell C. Salmi S. Sinha B. Talton L. Wang Q. Yang H. Stewénius R. Yang G. Welch H. Towles 《International Journal of Computer Vision》2008,78(2-3):143-167
The paper presents a system for automatic, geo-registered, real-time 3D reconstruction from video of urban scenes. The system
collects video streams, as well as GPS and inertia measurements in order to place the reconstructed models in geo-registered
coordinates. It is designed using current state of the art real-time modules for all processing steps. It employs commodity
graphics hardware and standard CPU’s to achieve real-time performance. We present the main considerations in designing the
system and the steps of the processing pipeline. Our system extends existing algorithms to meet the robustness and variability
necessary to operate out of the lab. To account for the large dynamic range of outdoor videos the processing pipeline estimates
global camera gain changes in the feature tracking stage and efficiently compensates for these in stereo estimation without
impacting the real-time performance. The required accuracy for many applications is achieved with a two-step stereo reconstruction
process exploiting the redundancy across frames. We show results on real video sequences comprising hundreds of thousands
of frames. 相似文献
48.
Analysis is conducted for slender beams with a varying cross-section under large non-linear elastic deformation. A thickness
variation function is derived to achieve optimal - constant maximum bending stress distribution along the beam for inclined
end load of arbitrary direction. Closed form solutions are derived for the large deflections that correspond to the various
loading conditions. The analysis is repeated for a beam with optimally varying width (for arbitrary end force) and the width
variation function is also determined. 相似文献
49.
Web 2.0 technologies, such as forums and wikis, are enabling an explosion of global knowledge sharing through distributed large-scale conversations, but they seem to be less successful at supporting collaborative deliberation around complex and controversial questions. In order to cope with this limitation, many scholars have proposed to adopt on-line argumentation platforms to improve information visualization, organization and reuse. However, such research has mostly focused on the design of adequate argument-based knowledge formalisms. Less attention has been paid to the empirical analysis of actual interactions mediated by argumentation technology with reasonably large user communities. In this paper, we present an in-depth analysis of the data obtained in the empirical test of an argumentation platform where a 160-member community created, in 3 weeks, what is to our knowledge the largest single online argument map ever built (around 5000 posts). Our results show that (i) users were able to quickly and comprehensively explore and map the debate on the selected discussion topic; (ii) substantial moderation was needed to ensure that the argument map was well-organized and users were confident with the argumentation formalism; (iii) considerable out-of-the map communication occurred, possibly as a way to allow for conversational flows inhibited by the argumentation formalism, (iv) formal rating of contributions favored exploration of the map, understanding the debate structure, and improving the quality of content. 相似文献
50.
我局新建的3500m3/h大型绞吸船新海豚轮运行稳定和施工高效,都离不开变频驱动技术的应用。本文分别对比绞刀的变频和液压驱动、水下泵的变频和高压F-D驱动的性能,分析变频驱动使用中存在的问题以及解决办法,展望了变频驱动在绞吸船上的应用前景。 相似文献