15756415
Assembly Sequence Planning
The sequence of mating operations that can be carried out to assemble a group of parts is constrained by the geometric and mechanical properties of the parts, their assembled configuration, and the stability of the resulting subassemblies. An approach to representation and reasoning about these sequences is described here and leads to several alternative explicit and implicit plan representations. The Pleiades system will provide an interactive software environment for designers to evaluate alternative systems and product designs through their impact on the feasibility and complexity of the resulting assembly sequences.
2491447
Unsupervised image segmentation using local homogeneity analysis
In this paper, a novel method is presented for unsupervised image segmentation based on local homogeneity analysis. First, a criterion for homogeneity of a certain pattern is proposed. Applying the criterion to local windows in the original image results in the "H-image". The high and low values of the H-image correspond to possible region boundaries and region interiors respectively. Then, a region growing method is used to segment the image based on the H-image. Finally, visually similar regions are merged together to avoid over-segmentation. Experimental results on real images show the effectiveness and robustness of the method.
16979558
Region-based relevance feedback in image retrieval
Relevance feedback and region-based representation of images are two effective ways to improve accuracy in content-based image retrieval. We propose a novel relevance feedback approach based on region representation. It can be considered as a special case of the query point movement method in region-based image retrieval. By assembling all the segmented regions of positive examples together and resizing the regions to emphasize the latest positive examples, we form a composite image as the optimal query. A region-based image similarity measure is used to calculate the distance between the optimal query and an image in the database. An incremental clustering technique is also considered to improve the retrieval efficiency. Experimental results show that the proposed approach is effective in improving the performance of content-based image retrieval systems.
16669804
An effective region-based image retrieval framework
We present a region-based image retrieval framework that integrates efficient region-based representation in terms of storage and retrieval and effective on-line learning capability. The framework consists of methods for image segmentation and grouping, indexing using modified inverted file, relevance feedback, and continuous learning. By exploiting a vector quantization method, a compact region-based image representation is achieved. Based on this representation, an indexing scheme similar to the inverted file technology is proposed. In addition, it supports relevance feedback based on the vector model with a weighting scheme. A continuous learning strategy is also proposed to enable the system to self improve. Experimental results on a database of 10,000 general-purposed images demonstrate the efficiency and effectiveness of the proposed framework.
14971297
Non-uniform Differential Mesh Deformation
In this paper, we propose a novel mesh deformation approach via manipulating differential properties non-uniformly. Guided by user-specified material properties, our method can deform the surface mesh in a non-uniform way while previous deformation techniques are mainly designed for uniform materials. The non-uniform deformation is achieved by material-dependent gradient field manipulation and Poisson-based reconstruction. Comparing with previous material-oblivious deformation techniques, our method supplies finer control of the deformation process and can generate more realistic results. We propose a novel detail representation that transforms geometric details between successive surface levels as a combination of dihedral angles and barycentric coordinates. This detail representation is similarity-invariant and fully compatible with material properties. Based on these two methods, we implement a multiresolution deformation tool, which allows the user to edit a mesh inside a hierarchy in a material-aware manner. We demonstrate the effectiveness and robustness of our methods by several examples with real-world data.
686393
Accelerated walkthrough of large spline models
CAD and rmimation applications. In this pa-per, we present algorithms for interactive walkthrough ofcomplex NURBS models composed of tens of thousands ofpatches on current graphics systems. Given a spline model,the algorithm precomputes simplification of a collection ofpatches and represents them hierarchically. Given a chang-ing viewpoint, the algorithm combines these simplificationswith dynamic tessellations to generate appropriate levels ofdetail. We also propose a system pipeline for parallel im-plementation on multi-processor configurations. Diiferentcomponents,
6607794
Can an Overlay Compensate for a Careless Underlay?
We investigate the ability of an overlay network to compensate for “careless” routing in the native network layer, i.e., for network-layer routes not optimized for performance. We consider cost/traffic-dependent, overlay routing on top of an underlay routing based on randomly-generated, cost/traffic-independent link weights, and determine the extent to which overlay-overcareless-underlay can achieve performance close to that attainable when underlay routing is performed in an optimal cost/trafficdependent (“careful”) manner. We identify three graph-theoretic metrics that collectively characterize the richness of the underlay network: the tightness (characteristic path length, or CPL), the thickness (cut average) and the weighted sum of node degrees. We find that only when the underlay graph is rich can the overlay compensate for a careless underlay. If network links have linear costs, we prove that overlay cost is a linear increasing function of CPL under some assumptions. Finally, we investigate heuristics (based on the notion of richness) for choosing a set of overlay nodes of fixed size that is likely to result in good overlay performance.
5847118
A self-tuning structure for adaptation in TCP/AQM networks
Congestion control in TCP/AQM networks is expected to perform well for a wide-range of conditions, but recent advances in modeling and analysis indicate that present AQM schemes need an extra dose of adaptability to cope. This paper answers the call and proposes a self-tuning structure wherein AQM parameters are automatically tuned in response to on-line estimation of link capacity and traffic load. This approach is applicable to any AQM scheme that is parameterizable in terms of link capacity and TCP load. In this paper, we will describe this self-tuning structure, illustrate its application to PI and RED AQMs, provide stability analysis, and conduct <tt>ns</tt> simulations to compare with both fixed AQM schemes and the recently proposed adaptive RED.
46427487
The Clar Covering Polynomial of Hexagonal Systems I
Abstract In this paper the Clar covering polynomial of a hexagonal system is introduced. In fact it is a kind of F polynomial [4] of a graph, and can be calculated by recurrence relations. We show that the number of aromatic sextets (in a Clar formula), the number of Clar formulas, the number of Kekule structures and the first Herndon number for any Kekulean hexagonal system can be easily obtained by its Clar covering polynomial. In addition, we give some theorems to calculate the Clar covering polynomial of a hexagonal system. As examples we finally derive the explicit expressions of the Clar covering polynomials for some small hexagonal systems and several types of catacondensed hexagonal systems. A relation between the resonance energy and the Clar covering polynomial of a hexagonal system is considered in the next paper.