Image-based rendering (IBR) involves constructing an image from a new viewpoint, using several input images from different viewpoints. A rendering framework must be flexible enough to handle this kind of data. It must...
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Image-based rendering (IBR) involves constructing an image from a new viewpoint, using several input images from different viewpoints. A rendering framework must be flexible enough to handle this kind of data. It must also be able to handle data extracted from several input images using far less accurate techniques--for example, stereo matching, which introduces a high level of uncertainty. The authors' attempt to define this uncertainty and use it in their rendering framework. When synthesizing new images from real input images, IBR techniques often neglect to take advantage of all the knowledge gathered from computer vision techniques during depth recovery. The authors' image-rendering approach involves three steps: depth extraction, uncertainty estimation, and rendering. Uncertainty is a vague term, which can refer to various aspects of the input images. For example, it can relate to the intrinsic or extrinsic camera parameters. Their technique of rendering depth with uncertainty using ellipsoidal Gaussian kernels is straightforward. They represent each depth uncertainty as an ellipsoid. INSET: Perspective Projection Approximation..
The article describes an approach to explore music collections by navigating through different views. The technique used is called aligned self-organizing maps (SOM). The SOM is an unsupervised neural network with app...
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The article describes an approach to explore music collections by navigating through different views. The technique used is called aligned self-organizing maps (SOM). The SOM is an unsupervised neural network with applications in various domains including audio analysis. As a clustering algorithm, the SOM is very similar to other partitioning algorithms such as K-means. In terms of topology preservation for visualization of high-dimensional data, alternatives include multi-dimensional scaling, Sammon's mapping and generative topographic mapping. The objective of the SOM is to map high-dimensional data into two-dimensional map in such a way that similar items are located near each other. The SOM consists of an ordered set of units that are arranged in two-dimensional visualization called the map. Common choices to arrange the map units are rectangular or hexagonal grids. There are two main parameters for the SOM algorithm. One is the map size the other is the final neighborhood radius. A larger map gives a higher resolution of the mapping but is computationally more expensive. The final neighborhood radius defines the smoothness of the mapping and should be adjusted depending on the noise level in the data. The SOM is a useful tool for exploring a data set according to a given similarity measure. An aligned SOM is an extension to the basic SOM that allows for interactively shifting the focus between different aspects and exploring the resulting gradual changes in the organization of the data.
Selective encryption is a technique to save computational complexity or enable interesting new system functionality by only encrypting a portion of a compressed bitstream while still achieving adequate security. Altho...
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Selective encryption is a technique to save computational complexity or enable interesting new system functionality by only encrypting a portion of a compressed bitstream while still achieving adequate security. Although suggested in a number of specific cases, selective encryption could be much more widely used in consumer electronic applications ranging from mobile multimedia terminals through digital cameras were it subjected to a more thorough security analysis. We describe selective encryption and develop a simple scalar quantizer example to demonstrate the power of the concept, list a number of potential consumer electronics applications, and then describe an appropriate method for developing and analyzing selective encryption for particular compression algorithms. We summarize results from application of this method to the MPEG-2 video compression algorithm.
作者：
Peserico, EMIT
Comp Sci & Artificial Intelligence Lab Cambridge MA 02139 USA
In the context of competitive analysis of online algorithms for the k-server problem, it has been conjectured that every randomized, memoryless online algorithm exhibits the highest competitive ratio against an offlin...
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In the context of competitive analysis of online algorithms for the k-server problem, it has been conjectured that every randomized, memoryless online algorithm exhibits the highest competitive ratio against an offline adversary that is lazy, i.e., that will issue requests forcing it to move one of its own servers only when this is strictly necessary to force a move on the part of the online algorithm. We prove that, in general, this lazy adversary conjecture fails. Moreover, it fails in a very strong sense: there are adversaries which perform arbitrarily better than any other adversary which is even slightly "lazier."
Automatic IP (intellectual property) matching is a key to the reuse of IP cores. A new tabled logic programming-based IP matching algorithm is given that can check whether a given programmable IP can be adapted to mat...
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Automatic IP (intellectual property) matching is a key to the reuse of IP cores. A new tabled logic programming-based IP matching algorithm is given that can check whether a given programmable IP can be adapted to match a given specification. When such adaptation is possible, the algorithm also generates a device driver (an interface) to adapt the IP. Though simulation, refinement and bisimulation algorithms exist, they cannot be used to check the adaptability of an IP, which is the essence of reuse. The IP matching algorithm is based on a formal verification technique called forced simulation. A forced simulation matching algorithm is implemented using a tabled logic programming environment, which provides distinct advantages for encoding such an algorithm. The tool has been used to match several specifications to programmable IN, achieving on an average 12 times speedup and 64% reduction in code size in comparison with previously published algorithms.
This article proposes a method of enabling users to share the sensation of walking with each other in a virtual environment (VE). Achieving this shared sensation requires physical equipment, with algorithms to control...
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This article proposes a method of enabling users to share the sensation of walking with each other in a virtual environment (VE). Achieving this shared sensation requires physical equipment, with algorithms to control it. As an example of such physical equipment, a new footpad type of locomotion interface (LI), named GaitMaster2, has been developed and physiologically evaluated. An algorithm for the positional control of users' feet has been proposed, enabling the users to share various aspects of the sensation of walking. As an evaluation, two footpad type LIs were connected via a network. Using the proposed control algorithm, there followed the construction of a master-slave walking environment and a synchronized walking environment. These experiments demonstrated that this method is effective for sharing the sensation of walking in a VE.
Tomita's general parsing algorithm is linear on LR(1) grammars but fails to terminate on grammars with hidden left recursion and is not efficient in the presence of epsilon-rules. When Right Nulled (RN) parse tabl...
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Tomita's general parsing algorithm is linear on LR(1) grammars but fails to terminate on grammars with hidden left recursion and is not efficient in the presence of epsilon-rules. When Right Nulled (RN) parse tables are used Tomita style GLR algorithms operate correctly and more efficiently on all context free grammars. However, an RN table may contain more conflicts than the corresponding LR table, making the construction of parts of the internal structure redundant. We show that in certain cases conflicts can be removed from an RN table without compromising the correctness of the associated parser. In particular, all conflicts can be removed if the grammar is LR(1). This improves the performance of the parser and allows resolved RN tables for LR(1) grammars to be used with standard (deterministic) LR stack-based parsing algorithms, adding the 'short-circuiting' of right nullable reductions to the armoury of efficient implementation techniques for such algorithms.
This paper describes the model-based design and the experimental validation of a control system which suppresses the bouncing behavior of Compressed Natural Gas (CNG) fuel injectors. First a detailed model of the syst...
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This paper describes the model-based design and the experimental validation of a control system which suppresses the bouncing behavior of Compressed Natural Gas (CNG) fuel injectors. First a detailed model of the system is developed, including temperature and supply-voltage variation effects. Using an optical position sensor this model is experimentally validated in a second step. Based on this model a feed-forward controller is developed and tested which minimizes the bouncing energy of the system. Since in series applications position sensing would be too expensive to use, an observer-based iterative control algorithm is derived which uses coil current measurements instead of the position information to asymptotically suppress bouncing.
We consider the problem of routing in an asynchronous dynamically changing ring of processors using schemes that minimize the storage space for the routing information. In general, applying static techniques to a dyna...
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We consider the problem of routing in an asynchronous dynamically changing ring of processors using schemes that minimize the storage space for the routing information. In general, applying static techniques to a dynamic network would require significant re-computation. Moreover, the known dynamic techniques applied to the ring lead to inefficient schemes. In this paper we introduce a new technique, Dynamic Interval Routing, and we show tradeoffs between the stretch factor, the adaptation cost, and the size of the update messages used by routing schemes based upon it. We give three algorithms for rings of maximum size N: the first two are deterministic, one with adaptation cost zero but worst case stretch factor [N/2], the other with worst case adaptation cost O (N) update messages of 0 (log N) bits and stretch factor 1. The third algorithm is randomized, uses update messages of size O (k log N), has adaptation cost O (k), and expected stretch factor 1+1/k, for any integer kgreater than or equal to3. All schemes require O (log N) bits per node for the routing information and all messages headers are of O (log N) bits.
The implementation and validation of a 5-GHz wireless LAN modem based on the HIPERLAN/2 standard is presented. In modern wireless communication systems, there is a demand for higher flexibility and more computational ...
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The implementation and validation of a 5-GHz wireless LAN modem based on the HIPERLAN/2 standard is presented. In modern wireless communication systems, there is a demand for higher flexibility and more computational efficiency. Therefore the emphasis of this work is on the hardware-software structure of the developed modem and its processes, in order to offer a good balance of these requirements. In order to efficiently design and validate the behaviour of the modem, a behavioural model was developed in UML (Unified Modelling Language) as a part of the overall HIPERLAN/2 system's model. The processes of the modem were implemented in an instruction-set processor and custom hardware, combining the advantages of both software and hardware implementations. The communication between the software and hardware parts of the modem is achieved through a specialised programmable interface unit. The UML-based model of the actual HIPERLAN/2 system is used in order to validate the modem's behaviour, using scenarios from in-field usage (such as transfer of data using FTP or HTTP). Furthermore, the validation of the algorithms implemented within the modem was based on this system model, and performed through the use of a custom-validation framework. This framework produces patterns for the validation of the modem's algorithms, at three different development phases (algorithmic, HDL, FPGA-based prototyping), derived from the simulation of the system model in a consistent and automatic way. Implementation figures and co-simulation results for the developed wireless LAN modem are also given.
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