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971.
Quanqing Xu Hengtao Shen Zaiben Chen Bin Cui Xiaofang Zhou Yafei Dai 《Frontiers of Computer Science in China》2009,3(3):381-395
The concept of Peer-to-Peer (P2P) has been introduced into mobile networks, which has led to the emergence of mobile P2P networks,
and originated potential applications in many fields. However,mobile P2P networks are subject to the limitations of transmission
range, and highly dynamic and unpredictable network topology, giving rise to many new challenges for efficient information
retrieval. In this paper, we propose an automatic and economical hybrid information retrieval approach based on cooperative
cache. In this method, the region covered by a mobile P2P network is partitioned into subregions, each of which is identified
by a unique ID and known to all peers. All the subregions then constitute a mobile Kademlia (MKad) network. The proposed hybrid
retrieval approach aims to utilize the floodingbased and Distributed Hash Table (DHT)-based schemes in MKad for indexing and
searching according to the designed utility functions. To further facilitate information retrieval, we present an effective
cache update method by considering all relevant factors. At the same time, the combination of two different methods for cache
update is also introduced. One of them is pull based on time stamp including two different pulls: an on-demand pull and a
periodical pull, and the other is a push strategy using update records. Furthermore, we provide detailed mathematical analysis
on the cache hit ratio of our approach. Simulation experiments in NS-2 showed that the proposed approach is more accurate
and efficient than the existing methods. 相似文献
972.
973.
974.
Liang S Shen G Liu Q Xu Y Zhou L Xiao S Xu Z Gong F You C Wei Y 《Proteomics. Clinical applications》2009,3(6):743-753
Human 14-3-3 proteins have isoform-specific expression and functions in different kinds of normal or tumor cells and tissues. However, the expression profiling of 14-3-3 proteins and isoform-specific biological functions are unclear in human glioma so far. In our study, the expression levels and characterization of 14-3-3 isoforms in human glioma tissues were investigated by a sensitive, accurate stable isotope labeling with amino acids in cell culture-based quantitative proteomic strategy. As a result, except unexpressed 14-3-3σ, the other six isoforms, with different expression levels, were existed in glioma tissues and para-cancerous brain tissues (PBTs). 14-3-3β and η were upregulated, whereas 14-3-3ζ was downregulated in glioma tissues compared with that in PBTs. And the other three isoforms 14-3-3ε, θ, and γ had similar expression levels in human glioma tissues and PBTs. Western blot and immunohistochemistry analysis were both consistent with the quantitative proteomic data. The loss of expression of 14-3-3σ was further discovered due to DNA high methylation in its coding region in glioma by methylation-specific PCR analysis. These results indicated that the four isoforms, including 14-3-3β, η, ζ, and σ, may play important roles in tumorigenesis of human glioma, which is probably used as potential biomarkers for diagnosis and targets for treatment of human gliomas in future. 相似文献
975.
We present two algorithms that are near optimal with respect to the number of inversions present in the input. One of the
algorithms is a variation of insertion sort, and the other is a variation of merge sort. The number of comparisons performed
by our algorithms, on an input sequence of length n that has I inversions, is at most . Moreover, both algorithms have implementations that run in time . All previously published algorithms require at least comparisons for some c > 1.
M. L. Fredman was supported in part by NSF grant CCR-9732689. 相似文献
976.
Ryszard Janicki 《Acta Informatica》2008,45(4):279-320
The paper deals with the foundations of concurrency theory. We show how structurally complex concurrent behaviours can be
modelled by relational structures
(X, ¨, \sqsubset){(X, \diamondsuit, \sqsubset)} , where X is a set (of event occurrences), and ¨{\diamondsuit} (interpreted as commutativity) and
\sqsubset{\sqsubset} (interpreted as weak causality) are binary relations on X. The paper is a continuation of the approach initiated in Gaifman and Pratt (Proceedings of LICS’87, pp 72–85, 1987), Lamport
(J ACM 33:313–326, 1986), Abraham et al. (Semantics for concurrency, workshops in computing. Springer, Heidelberg, pp 311–323,
1990) and Janicki and Koutny (Lect Notes Comput Sci 506:59–74, 1991), substantially developed in Janicki and Koutny (Theoretical
Computer Science 112:5–52, 1993) and Janicki and Koutny (Acta Informatica 34:367–388, 1997), and recently generalized in Guo
and Janicki (Lect Notes Comput Sci 2422:178–191, 2002) and Janicki (Lect Notes Comput Sci 3407:84–98, 2005). For the first
time the full model for the most general case is given. 相似文献
977.
In this paper, the variations of both subunitary polar factors and Hermitian positive semidefinite polar factors in the polar decomposition are studied. New perturbation bounds of both polar factors are given without the restriction that A and its perturbed matrix à have the same rank. These improve recent results. 相似文献
978.
We introduce general sequences of linear operators obtained from classical approximation processes which are useful in the
approximation of the resolvent operators of the generators of suitable C
0-semigroups. The main aim is the representation of the resolvent operators in terms of classical approximation operators.
Work performed under the auspices of PRIN 2006–07 “Kolmogorov equations” (coordinator G. Da Prato) 相似文献
979.
Anti-reflective (AR) boundary conditions (BC) have been introduced recently in connection with fast deblurring algorithms,
both in the case of signals and images. Here we extend such BCs to d dimensions (d ≥ 1) and we study in detail the algebra induced by the AR-BCs, with strongly symmetric point spread functions (PSF), both
from a structural and computational point of view. The use of the re-blurring idea and the computational features of the AR-algebra
allow us to apply Tikhonov-like techniques within O(n
d
log(n)) arithmetic operations, where n
d
is the number of pixels of the reconstructed object. Extensive numerical experimentation concerning 2D images and strongly
symmetric PSFs confirms the effectiveness of our proposal.
相似文献
980.