715438
Non-linear Dimensionality Reduction by Locally Linear Isomaps
Algorithms for nonlinear dimensionality reduction (NLDR) find meaningful hidden low-dimensional structures in a high-dimensional space. Current algorithms for NLDR are Isomaps, Local Linear Embedding and Laplacian Eigenmaps. Isomaps are able to reliably recover low-dimensional nonlinear structures in high-dimensional data sets, but suffer from the problem of short-circuiting, which occurs when the neighborhood distance is larger than the distance between the folds in the manifolds. We propose a new variant of Isomap algorithm based on local linear properties of manifolds to increase its robustness to short-circuiting. We demonstrate that the proposed algorithm works better than Isomap algorithm for normal, noisy and sparse data sets.
5943508
Extracting regions of symmetry
This paper presents an approach for extending the normalized-cut (n-cut) segmentation algorithm to find symmetric regions present in natural images. We use an existing algorithm to quickly detect possible symmetries present in an image. The detected symmetries are then individually verified using the modified n-cut algorithm to eliminate spurious detections. The weights of the n-cut algorithm are modified so as to include both symmetric and spatial affinities. A global parameter is defined to model the tradeoff between spatial coherence and symmetry. Experimental results indicate that symmetric quality measure for a region segmented by our algorithm is a good indicator for the significance of the principal axis of symmetry.
18286724
Watermarking of MPEG-4 Videos
A MPEG-4 compressed domain video watermarking method is proposed and its performance is studied at video bit rates ranging from 64 Kb/s to 900 Kb/s. The watermark is inserted by modifying Discrete Cosine Transformation (DCT) coefficients. The strength of watermark is changed according to local frame characteristics to reduce impact on visual quality. The algorithm’s performance is also studied for watermarking bits in a frame ranging from 1 Kb/frame to 3 Kb/frame. The watermark is attack-free against attacks like scaling, rotation and cropping even if blind-techniques are used.
8374849
Quorum placement in networks to minimize access delays
A quorum system is a family of sets (themselves called quorums), each pair of which intersect. In many distributed algorithms, the basic unit accessed by a client is a quorum of nodes. Such algorithms are used for applications such as mutual exclusion, data replication, and dissemination of information. However, accessing spread-out quorums causes access delays that we would like to minimize. Furthermore, every member of the quorum incurs processing load to handle quorum accesses by clients.In this paper we study the problem of placing quorums in a physical network so as to minimize the delay that clients incur by accessing quorums, and while respecting each physical node's capacity (in terms of the load of client requests it can handle). We provide approximation algorithms for this problem for two natural measures of delay (the max-delay and total-delay). All our algorithms ensure that each node's load is within a constant factor of its capacity, and minimize delay to within a constant factor of the optimal delay for all capacity-respecting solutions. We also provide better approximations for several well-known quorum systems.
209398811
Life Science Research and Data Management.
A distance measuring arrangement for use, for example, in a camera and the like equipped with an automatic focus control system which includes an illuminance intensity detecting portion for detecting the illuminance intensity of a target object and a distance signal correcting portion for correcting the distance signal from a distance measuring portion according to the output of the illuminance intensity detecting portion so as to obtain the distance signal not affected by the illuminance intensity of the target object.
13293366
Improved bandwidth approximation for trees
A linear arrangement of an n-vertex graph G = (V, E) is a one-one mapping f of the vertex set V onto the set In] = {0, 1 , . . . , n 1}. The bandwidth of this linear arrangement is the maximum distance between the images of the endpoints of any edge in E(G). When the input graph G is a tree, the best known approximation algorithm for the minimum bandwidth linear arrangement (which is based on the principle of volume respecting embeddings) outputs a linear arrangement which has bandwidth within O(log 3 n) of the optimal bandwidth. In this paper, we present a simple randomized O(log 2 n lov~-n)-approximation algorithm for bandwidth minimization on trees.
1412337
Simpler and better approximation algorithms for network design
We give simple and easy-to-analyze randomized approximation algorithms for several well-studied NP-hard network design problems. Our algorithms improve over the previously best known approximation ratios. Our main results are the following.We give a randomized 3.55-approximation algorithm for the connected facility location problem. The algorithm requires three lines to state, one page to analyze, and improves the best-known performance guarantee for the problem.We give a 5.55-approximation algorithm for virtual private network design. Previously, constant-factor approximation algorithms were known only for special cases of this problem.We give a simple constant-factor approximation algorithm for the single-sink buy-at-bulk network design problem. Our performance guarantee improves over what was previously known, and is an order of magnitude improvement over previous combinatorial approximation algorithms for the problem.
37922436
Improved Bandwidth Approximation for Trees and Chordal Graphs
A linear arrangement of an n-vertex graph G=(V,E) is a one?one mapping f of the vertex set V onto the set n]={0,1,?,n?1}. The bandwidth of this linear arrangement is the maximum difference between the images of the endpoints of any edge in E(G). When the input graph G is a tree, the best known approximation algorithms for the minimum bandwidth linear arrangement (which are based on the principle of volume respecting embeddings) output a linear arrangement which has bandwidth within O(log3n) of the optimal bandwidth. In this paper, we present a simple randomized O(log2.5n)-approximation algorithm for bandwidth minimization on trees. We also show that a close variant of this algorithm gives a similar performance guarantee for chordal graphs.