35293254
Quasi-complements of the cappable degrees
Say that a nonzero c. e. degree b is a quasi-complement of a c. e. degree a if a ∩ b = 0 and a ∪ b is high. It is well-known (due to Shore) that each cappable degree has a high quasi-complement. However, by the existence of the almost deep degrees, there are nonzero cappable degrees having no low quasi-complements. In this paper, we prove that any nonzero cappable degree has a low2 quasi-complement. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
6081408
Universal Cupping Degrees
Cupping nonzero computably enumerable (c.e. for short) degrees to 0′ in various structures has been one of the most important topics in the development of classical computability theory. An incomplete c.e. degree a is cuppable if there is an incomplete c.e. degree b such that a∪b=0′, and noncuppable if there is no such degree b. Sacks splitting theorem shows the existence of cuppable degrees. However, Yates(unpublished) and Cooper [3] proved that there are noncomputable noncuppable degrees. After that, Harrington and Shelah were able to employ the cupping/noncupping properties to show that the theory of the c.e. degrees under relation ≤ is undecidable. Cuppable and noncuppable degrees were further studied later. See Harrington [7], Miller [10], Fejer and Soare [6], Ambos-Spies, Lachlan and Soare [1], etc..
7723209
1-Generic splittings of computably enumerable degrees
Say a set G⊆ω is 1-generic if for any e∈ω, there is a string σ⊂G such that {e}σ(e)↓ or ∀τ⊇σ({e}τ(e)↑). It is known that 0′ can be split into two 1-generic degrees. In this paper, we generalize this and prove that any nonzero computably enumerable degree can be split into two 1-generic degrees. As a corollary, no two computably enumerable degrees bound the same class of 1-generic degrees.
9638835
Isolation and Lattice Embeddings
1961392
Degrees of Weakly Computable Reals
This paper studies the degrees of weakly computable reals. It is shown that certain types of limit-recursive reals are Turing incomparable to all weakly computable reals except the recursive and complete ones. Furthermore, it is shown that an r.e. Turing degree is array-recursive iff every real in it is weakly computable.
1638130
Bounding computably enumerable degrees in the Ershov hierarchy
Nanyang Technol Univ, Sch Math & Phys Sci, Div Math Sci, Singapore 639798, Singapore. Chinese Acad Sci, Inst Software, Beijing 100080, Peoples R China. Natl Univ Singapore, Dept Math, Singapore 119260, Singapore.
8499708
Cooperation models for service oriented multi-agent system
In the paper, the cooperation models for service oriented multi-agent system are formally and rigorously investigated and put forward. According to the service request forces and service offer manners, a number of elementary cooperation models and their atomic communication acts are identified. The rigorous semantics of the communication acts and the cooperation models and their constraints are formally defined and analyzed.
4178545
Data placement and query processing based on RPE parallelisms
The basic idea behind parallel database systems is to perform operations in parallel to reduce the response time and improve the system throughput. Data placement is a key factor on the performance of parallel database systems. This paper proposes two data partition strategies to decluster XML documents with very large size, path schema based path instance balancing (PSPIB) strategy, in which all path instances with the same path schema in a data tree are declustered evenly over all sites, and node schema based node round-robin (NSNRR) strategy, in which all node objects with the same node schema in a data tree are declustered over all sites in a round-robin way. Accordingly, two query processing algorithms are proposed based on the two partition methods, parallel path merge (PPM) algorithm and parallel pipelining path join (PPPJ) algorithm. The performance analysis and evaluation on the two data placement strategies and corresponding query processing algorithms are given in this paper.
1432738
SGDB: a database of synthetic genes re-designed for optimizing protein over-expression
Here we present the Synthetic Gene Database (SGDB): a relational database that houses sequences and associated experimental information on synthetic (artificially engineered) genes from all peer-reviewed studies published to date. At present, the database comprises information from more than 200 published experiments. This resource not only provides reference material to guide experimentalists in designing new genes that improve protein expression, but also offers a dataset for analysis by bioinformaticians who seek to test ideas regarding the underlying factors that influence gene expression. The SGDB was built under MySQL database management system. We also offer an XML schema for standardized data description of synthetic genes. Users can access the database at , or batch downloads all information through XML files. Moreover, users may visually compare the coding sequences of a synthetic gene and its natural counterpart with an integrated web tool at , and discuss questions, findings and related information on an associated e-forum at .
5979296
A Lookahead Branch-and-Bound Algorithm for the Maximum Quartet Consistency Problem
A lookahead branch-and-bound algorithm (LBnB) is proposed for solving the Maximum Quartet Consistency (MQC) Problem where the input is a complete set of quartets on the taxa and the goal is to construct a phylogeny that satisfies the maximum number of given quartets. It integrates a number of previous efforts on exact algorithms, heuristics, and approximation algorithms for the NP-hard MQC problem, and a few improved search techniques, especially a lookahead scheme, to solve the problem optimally. The theoretical running time analysis of the LBnB algorithm is provided, and an extensive simulation study has been well designed to compare the algorithm to previous existing exact algorithms and a best heuristic Hypercleaning. The experimental results on both synthetic and real datasets show that LBnB outperformed other exact algorithms, and it was competitive to Hypercleaning on many datasets.
6594297
Generic Universal Switch Blocks
A switch block M with W terminals on each side is said to be universal if every set of nets satisfying the dimension constraint (i.e., the number of nets on each side of M is at most W) is simultaneously routable through M. In this paper, we present an algorithm to construct N-sided universal switch blocks with W terminals on each side. Each of our universal switch blocks has (/sub 2//sup N/) W switches and switch-block flexibility N-1 (i.e., F/sub S/=N-1). We prove that no switch block with less than (/sub 2//sup N/)W switches can be universal. We also compare our universal switch blocks with others of the topology associated with Xilinx XC4000-type FPGAs. To explore the area performance of the universal switch blocks, we develop a detailed router for hierarchical FPGAs (HFPGAs) with 5-sided switch blocks. Experimental results demonstrate that our universal switch blocks improve routability at the chip level. Based on extensive experiments, we also provide key insights into the interactions between switch-block architectures and routing.