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91.
Stephen J.H. Yang Jia Zhang Leon Lin Jeffrey J.P. Tsai 《Expert systems with applications》2009,36(7):10312-10324
As a large amount of information is added onto the Internet on a daily basis, the efficiency of peer-to-peer (P2P) search has become increasingly important. However, how to quickly discover the right resource in a large-scale P2P network without generating too much network traffic remains highly challenging. In this paper, we propose a novel P2P search method, by applying the concept of social grouping and intelligent social search; we derive peers into social groups in a P2P network to improve search performance. Through a super-peer-based architecture, we establish and maintain virtual social groups on top of a P2P network. The interactions between the peers in the P2P network are used to incrementally build the social relationships between the peers in the associated social groups. In such a P2P network, a search query is propagated along the social groups in the overlay social network. Our preliminary experiments have demonstrated that our method can significantly shorten search routes and result in a higher peer search performance. In addition, our method also enhances the trustworthiness of search results because searches go through trusted peers. 相似文献
92.
Edward Farhi Jeffrey Goldstone David Gosset Harvey B. Meyer 《Computer Physics Communications》2011,(8):1663-1673
In this paper we explore ways to study the zero temperature limit of quantum statistical mechanics using Quantum Monte Carlo simulations. We develop a Quantum Monte Carlo method in which one fixes the ground state energy as a parameter. The Hamiltonians we consider are of the form H=H0+λV with ground state energy E. For fixed H0 and V, one can view E as a function of λ whereas we view λ as a function of E. We fix E and define a path integral Quantum Monte Carlo method in which a path makes no reference to the times (discrete or continuous) at which transitions occur between states. For fixed E we can determine λ(E) and other ground state properties of H. 相似文献
93.
Using ICESat's Geoscience Laser Altimeter System (GLAS) to assess large-scale forest disturbance caused by hurricane Katrina 总被引:1,自引:0,他引:1
Katelyn A. Dolan George C. Hurtt Jeffrey Q. Chambers Ralph O. Dubayah Jeffrey G. Masek 《Remote sensing of environment》2011,115(1):86-96
In 2005, hurricane Katrina resulted in a large disturbance to U.S. forests. Recent estimates of damage from hurricane Katrina have relied primarily on optical remote sensing and field data. This paper is the first large-scale study to use satellite-based lidar data to quantify changes in forest structure from that event. GLAS data for the years prior to and following hurricane Katrina were compared to wind speed, forest cover, and damage data to assess the adequacy of sensor sampling, and to estimate changes in Mean Canopy Height (MCH) over all areas that experienced tropical force winds and greater. Statistically significant decreases in MCH post-Katrina were found to increase with wind intensity: Tropical Storm ?MCH = − 0.5 m, Category 1 ?MCH = − 2 m, and Category 2 ?MCH = − 4 m. A strong relationship was also found between changes in non-photosynthetic vegetation (?NPV), a metric previously shown to be related to storm damage, and post-storm MCH. The season of data acquisition was shown to influence calculations of MCH and MCH loss, but did not preclude the detection of major large-scale patterns of damage. Results from this study show promise for using space-borne lidar for large-scale assessments of forest disturbance, and highlight the need for future data on vegetation structure from space. 相似文献
94.
Hanxiong Chen Jianquan Liu Kazutaka Furuse Jeffrey Xu Yu Nobuo Ohbo 《Knowledge and Information Systems》2011,27(2):165-192
Similarity search is important in information retrieval applications where objects are usually represented as vectors of high
dimensionality. This leads to the increasing need for supporting the indexing of high-dimensional data. On the other hand,
indexing structures based on space partitioning are powerless because of the well-known “curse of dimensionality”. Linear
scan of the data with approximation is more efficient in the high-dimensional similarity search. However, approaches so far
have concentrated on reducing I/O, and ignored the computation cost. For an expensive distance function such as L
p
norm with fractional p, the computation cost becomes the bottleneck. We propose a new technique to address expensive distance functions by “indexing
the function” by pre-computing some key values of the function once. Then, the values are used to develop the upper/lower
bounds of the distance between a data vector and the query vector. The technique is extremely efficient since it avoids most
of the distance function computations; moreover, it does not involve any extra secondary storage because no index is constructed
and stored. The efficiency is confirmed by cost analysis, as well as experiments on synthetic and real data. 相似文献
95.
K. J. Mattias Sandstr m Jeffrey Newman Anna-Lena Sunesson Jan-Olof Levin Anthony P. F. Turner 《Sensors and actuators. B, Chemical》2000,70(1-3):182-187
The possibility of developing a simple, inexpensive and specific personal passive “real-time” air sampler incorporating a biosensor for formic acid was investigated. The sensor is based on the enzymatic reaction between formic acid and formate dehydrogenase (FDH) with nicotinamide adenine dinucleotide (NAD+) as a co-factor and Meldola's blue as mediator. An effective way to immobilise the enzyme, co-factor and Meldola's blue on screen-printed, disposable, electrodes was found to be in a mixture of glycerol and phosphate buffer covered with a gas-permeable membrane. Steady-state current was reached after 4–15 min and the limit of detection was calculated to be below 1 mg/m3. However, the response decreased by 50% after storage at −15°C for 1 day. 相似文献
96.
Anil Nerode Jeffrey B. Remmel 《Annals of Mathematics and Artificial Intelligence》2008,53(1-4):289-311
Blair et al. (2001) developed an extension of logic programming called set based logic programming. In the theory of set based logic programming the atoms represent subsets of a fixed universe X and one is allowed to compose the one-step consequence operator with a monotonic idempotent operator O so as to ensure that the analogue of stable models in the theory are always closed under O. Marek et al. (1992, Ann Pure Appl Logic 96:231–276 1999) developed a generalization of Reiter’s normal default theories that can be applied to both default theories and logic programs which is based on an underlying consistency property. In this paper, we show how to extend the normal logic programming paradigm of Marek, Nerode, and Remmel to set based logic programming. We also show how one can obtain a new semantics for set based logic programming based on a consistency property. 相似文献
97.
Jeffrey Xu Yu Zhiheng Li Guimei Liu 《The VLDB Journal The International Journal on Very Large Data Bases》2008,17(4):947-970
Data mining has attracted a lot of research efforts during the past decade. However, little work has been reported on the
efficiency of supporting a large number of users who issue different data mining queries periodically when there are new needs
and when data is updated. Our work is motivated by the fact that the pattern-growth method is one of the most efficient methods
for frequent pattern mining which constructs an initial tree and mines frequent patterns on top of the tree. In this paper,
we present a data mining proxy approach that can reduce the I/O costs to construct an initial tree by utilizing the trees that have already been resident in memory. The tree we construct
is the smallest for a given data mining query. In addition, our proxy approach can also reduce CPU cost in mining patterns,
because the cost of mining relies on the sizes of trees. The focus of the work is to construct an initial tree efficiently.
We propose three tree operations to construct a tree. With a unique coding scheme, we can efficiently project subtrees from
on-disk trees or in-memory trees. Our performance study indicated that the data mining proxy significantly reduces the I/O cost to construct trees and CPU cost to mine patterns over the trees constructed. 相似文献
98.
Graphical histories for visualization: supporting analysis, communication, and evaluation 总被引:1,自引:0,他引:1
Heer J Mackinlay J Stolte C Agrawala M 《IEEE transactions on visualization and computer graphics》2008,14(6):1189-1196
Interactive history tools, ranging from basic undo and redo to branching timelines of user actions, facilitate iterative forms of interaction. In this paper, we investigate the design of history mechanisms for information visualization. We present a design space analysis of both architectural and interface issues, identifying design decisions and associated trade-offs. Based on this analysis, we contribute a design study of graphical history tools for Tableau, a database visualization system. These tools record and visualize interaction histories, support data analysis and communication of findings, and contribute novel mechanisms for presenting, managing, and exporting histories. Furthermore, we have analyzed aggregated collections of history sessions to evaluate Tableau usage. We describe additional tools for analyzing users’ history logs and how they have been applied to study usage patterns in Tableau. 相似文献
99.
Charles J. Colbourn Jeffrey H. Dinitz Douglas R. Stinson 《Information and Computation》2001,169(2):160
A quorum system is a set system in which any two subsets have nonempty intersection. Quorum systems have been extensively studied as a method of maintaining consistency in distributed systems. Important attributes of a quorum system include the load, balancing ratio, rank (i.e., quorum size), and availability. Many constructions have been presented in the literature for quorum systems in which these attributes take on optimal or otherwise favorable values. In this paper, we point out an elementary connection between quorum systems and the classical covering systems studied in combinatorial design theory. We look more closely at the quorum systems that are obtained from balanced incomplete block designs (BIBDs). We study the properties of these quorum systems and observe that they have load, balancing ratio, and rank that are all within a constant factor of being optimal. We also provide several observations about computing the failure polynomials of a quorum system (failure polynomials are used to measure availability). Asymptotic properties of failure polynomials have previously been analyzed for certain infinite families of quorum systems. We give an explicit formula for the failure polynomials for an easily constructed infinite class of quorum systems. We also develop two algorithms that are useful for computing failure polynomials for quorum systems and prove that computing failure polynomials is #P-hard. Computational results are presented for several “small” quorum systems obtained from BIBDs. 相似文献
100.
We undertake a systematic study of the role of neural architecture in shaping the dynamics of evolved model pattern generators for a walking task. First, we consider the minimum number of connections necessary to achieve high performance on this task. Next, we identify architectural motifs associated with high fitness. We then examine how high-fitness architectures differ in their ability to evolve. Finally, we demonstrate the existence of distinct parameter subgroups in some architectures and show that these subgroups are characterized by differences in neuron excitabilities and connection signs. 相似文献