14944633
On Exact and Approximation Algorithms for Distinguishing Substring Selection
The NP-complete Distinguishing Substring Selection problem (DSSS for short) asks, given a set of “good” strings and a set of “bad” strings, for a solution string which is, with respect to Hamming metric, “away” from the good strings and “close” to the bad strings.
14019711
Fixed-parameter tractability and data reduction for multicut in trees
We study an NP-complete (and MaxSNP-hard) communication problem on tree networks, the so-called Multicut in Trees: given an undirected tree and some pairs of nodes of the tree, find out whether there is a set of at most k tree edges whose removal separates all given pairs of nodes. Multicut has been intensively studied for trees as well as for general graphs mainly from the viewpoint of polynomialtime approximation algorithms. By way of contrast, we provide a simple fixed-parameter algorithm for Multicut in Trees showing ∗Supported by the Deutsche Forschungsgemeinschaft (DFG), Emmy Noether research group PIAF (fixed-parameter algorithms), NI 369/4. Parts of this work have been done while the authors were at the Universität Tübingen.
6020472
Compression-based fixed-parameter algorithms for feedback vertex set and edge bipartization
We show that the NP-complete Feedback Vertex Set problem, which asks for the smallest set of vertices to remove from a graph to destroy all cycles, is deterministically solvable in O(c^[email protected]?m) time. Here, m denotes the number of graph edges, k denotes the size of the feedback vertex set searched for, and c is a constant. We extend this to an algorithm enumerating all solutions in O(d^[email protected]?m) time for a (larger) constant d. As a further result, we present a fixed-parameter algorithm with runtime O(2^[email protected]?m^2) for the NP-complete Edge Bipartization problem, which asks for at most k edges to remove from a graph to make it bipartite.
75279
Error Compensation in Leaf Power Problems
AbstractThe k-Leaf Power recognition problem is a particular case of graph
 power problems: For a given graph it asks whether there exists an
 unrooted tree—the k-leaf root—with leaves one-to-one labeled by
 the graph vertices and where the leaves have distance at most k iff their corresponding vertices in the graph are connected by an
 edge. Here we study "error correction" versions of k-Leaf
 Power recognition—that is, adding or deleting at most l
 edges to generate a graph that has a k-leaf root. We provide
 several NP-completeness results in this context, and we show that
 the NP-complete Closest 3-Leaf Power problem (the error
 correction version of 3-Leaf Power) is fixed-parameter
 tractable with respect to the number of edge modifications or vertex
 deletions in the given graph. Thus, we provide the seemingly first
 nontrivial positive algorithmic results in the field of error
 compensation for leaf power problems with k > 2. To this end, as a
 result of independent interest, we develop a forbidden subgraph
 characterization of graphs with 3-leaf roots.
8805498
Bounded Degree Closest k-Tree Power Is NP-Complete
An undirected graph G=V,E is the k-power of an undirected tree T=V,E' if u,v∈ E iff u andi¾?v are connected by a path of length at mosti¾?k ini¾?T. The treei¾?T is called the tree root ofi¾?G. Tree powers can be recognized in polynomial time. The thus naturally arising question is whether a graphi¾?G can be modified by adding or deleting a specified number of edges such thati¾?G becomes a tree power. This problem becomes NP-complete for ki¾? 2. Strengthening this result, we answer the main open question of Tsukiji and Chen [COCOON 2004] by showing that the problem remains NP-complete when additionally demanding that the tree roots must have bounded degree.
9767043
The Computational Complexity of Avoiding Forbidden Submatrices by Row Deletions
We initiate a systematic study of the ROW DELETION(B) problem on matrices: Given an input matrix A and a fixed "forbidden submatrix" B, the task is to remove a minimum number of rows from A such that no row or column permutation of B occurs as a submatrix in the resulting matrix. An application of this problem can be found, for instance, in the construction of perfect phylogenies. Establishing a strong connection to variants of the NP-complete HITTING SET problem, we describe and analyze structural properties of B that make ROW DELETION(B)NP-complete. On the positive side, the close relation with HITTING SET problems yields constant-factor polynomial-time approximation algorithms and fixed-parameter tractability results.
17686470
Inter-enterprise business document exchange
Electronic business document interoperation is the cornerstone of business process integration. An essential issue for business document interoperation is to maintain semantic consistency of the exchanged business documents between any two autonomous business communities, where the document sender and receiver have no misunderstanding in using the exchanged documents. Existing approaches to resolving this issue either adopts document standards to map heterogeneous document elements or applies business ontologies to mediate inconsistent document elements. While these approaches are effective in certain degree, the issues of limited flexibility and evolvability in using standards and the lack of accuracy in using ontologies to mediate document elements must be explored and resolved. This paper proposes a Collaborative Document Exchange (CODEX) approach to resolving the issues. In this approach, structures and concepts of business document are separated and layered in CODEX framework. Structures provide the commonality of business documents through classified concept identifiers while concepts support particularity of business documents through collaboration.
15601163
High Efficiency Digital Halftoning with Two-Element Error Kernel
A high efficiency and good quality error-diffused halftoning is proposed in this paper. An objective halftone image quality evaluation method based on human visual system obtained by least-mean-square is also introduced. The error diffusion algorithm, first introduced by Floyd and Steinberg in 1975, is currently the most popular method of digital halftoning. However, some annoying shortcomings, such as patches of regular textures, worm effect, and computational complexity still need to be improved. Ostromoukhov proposed a three-element error diffusion solving the problems described above, and achieved excellent performance. In this paper, we further reduced the complexity with the proposed two-element error diffusion by cooperating with the proposed LMS-trained quality evaluation. As demonstrated in experiments, the proposed technique further reduced the complexity by 33% compared to Ostromoukhov's method, and it is still comparable in image quality.
37890888
Alibaba International: Building a Global Electronic Marketplace
Alibaba is the largest global electronic marketplace (GEM) in the world in terms of its participated users. It was successful due to the factors of China's foreign trade regime, the image of low product cost of China, Alibaba's contingent adaptation to users' changing requirements and e-commerce environments. Alibaba is not a technically mature GEM platform compared with the ideal functions of GEM. Suggested solution for Alibaba to continuing its success is to adopt a novel GEM connectivity model
13379605
Protein Fold Recognition Through Application of Residual Dipolar Coupling Data
Residual dipolar coupling (RDC) represents one of the most exciting emerging NMR techniques for studying protein structures. However, solving a protein structure using RDC data alone is a highly challenging problem as it often requires that the starting structure model be close to the actual structure of a protein, for the structure calculation procedure to be effective. We report in this paper a computer program, RDC-PROSPECT, for identification of a structural homolog or analog of a target protein in PDB, which best matches the 15N-1H RDC data of the protein recorded in a single ordering medium. The identified structural homolog/analog can then be used as a starting model for RDC-based structure calculation. Since RDC-PROSPECT uses only RDC data and predicted secondary structure information, its performance is virtually independent of sequence similarity between a target protein and its structural homolog/analog, making it applicable to protein targets out of the scope of current protein threading techniques. We have tested RDC-PROSPECT on all 15N-1H RDC data (representing 33 proteins) available in the BMRB database and the literature. The program correctly identified the structural folds for approximately 80% of the target proteins, significantly better than previously reported results, and achieved an average alignment accuracy of 97.9% residues within 4-residue shift. Through a careful algorithmic design, RDC-PROSPECT is at least one order of magnitude faster than previously reported algorithms for principal alignment frame search, making our algorithm fast enough for large-scale applications.
18367158
A distributed database server for continuous media
In our project, we are adopting a new approach for handling video data. We view the video as a well-defined data type with its own description, parameters and applicable methods. The system is based on PREDATOR, an open-source object-relational DBMS. PREDATOR uses Shore as the underlying storage manager. Supporting video operations (storing, searching-by-content and streaming) and new query types (query-by-example and multi-feature similarity searching) requires major changes in many of the traditional system components. More specifically, the storage and buffer manager has to deal with huge volumes of data with real-time constraints. Query processing has to consider the video methods and operators in generating, optimizing and executing the query plans.