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951.
Celina M.H. de Figueiredo Guilherme D. da Fonseca Vinicius G.P. de Sa Jeremy Spinrad 《Algorithmica》2006,46(2):149-180
A homogeneous set is a non-trivial module of a graph, i.e. a non-empty,
non-unitary, proper subset of a graph's vertices such that all its elements
present exactly the same outer neighborhood. Given two graphs
the Homogeneous Set Sandwich Problem (HSSP) asks whether there
exists a sandwich graph
which
has a homogeneous set. In 2001 Tang et al. published
an all-fast
algorithm which was recently proven wrong, so that the HSSP's known upper bound would have been reset
thereafter at the former
determined by Cerioli et al. in 1998. We present, notwithstanding, new deterministic
algorithms which have it established at
We give as
well two even faster
randomized algorithms, whose simplicity might
lend them didactic usefulness. We believe that, besides providing efficient
easy-to-implement procedures to solve it, the study of these new approaches
allows a fairly thorough understanding of the problem. 相似文献
952.
Making working memory work: a computational model of learning in the prefrontal cortex and basal ganglia 总被引:1,自引:0,他引:1
The prefrontal cortex has long been thought to subserve both working memory (the holding of information online for processing) and executive functions (deciding how to manipulate working memory and perform processing). Although many computational models of working memory have been developed, the mechanistic basis of executive function remains elusive, often amounting to a homunculus. This article presents an attempt to deconstruct this homunculus through powerful learning mechanisms that allow a computational model of the prefrontal cortex to control both itself and other brain areas in a strategic, task-appropriate manner. These learning mechanisms are based on subcortical structures in the midbrain, basal ganglia, and amygdala, which together form an actor-critic architecture. The critic system learns which prefrontal representations are task relevant and trains the actor, which in turn provides a dynamic gating mechanism for controlling working memory updating. Computationally, the learning mechanism is designed to simultaneously solve the temporal and structural credit assignment problems. The model's performance compares favorably with standard backpropagation-based temporal learning mechanisms on the challenging 1-2-AX working memory task and other benchmark working memory tasks. 相似文献
953.
The efficiency of neuronal encoding in sensory and motor systems has been proposed as a first principle governing response properties within the central nervous system. We present a continuation of a theoretical study presented by Zhang and Sejnowski, where the influence of neuronal tuning properties on encoding accuracy is analyzed using information theory. When a finite stimulus space is considered, we show that the encoding accuracy improves with narrow tuning for one- and two-dimensional stimuli. For three dimensions and higher, there is an optimal tuning width. 相似文献
954.
Slightly modified versions of an early Hebbian/anti-Hebbian neural network are shown to be capable of extracting the sparse, independent linear components of a prefiltered natural image set. An explanation for this capability in terms of a coupling between two hypothetical networks is presented. The simple networks presented here provide alternative, biologically plausible mechanisms for sparse, factorial coding in early primate vision. 相似文献
955.
Making decisions can be hard, but it can also be facilitated. Simple heuristics are fast and frugal but nevertheless fairly accurate decision rules that people can use to compensate for their limitations in computational capacity, time, and knowledge when they make decisions [Gigerenzer, G., Todd, P. M., & the ABC Research Group (1999). Simple Heuristics That Make Us Smart. New York: Oxford University Press.]. These heuristics are effective to the extent that they can exploit the structure of information in the environment in which they operate. Specifically, they require knowledge about the predictive value of probabilistic cues. However, it is often difficult to keep track of all the available cues in the environment and how they relate to any relevant criterion. This problem becomes even more critical if compound cues are considered. We submit that knowledge about the causal structure of the environment helps decision makers focus on a manageable subset of cues, thus effectively reducing the potential computational complexity inherent in even relatively simple decision-making tasks. We review experimental evidence that tested this hypothesis and report the results of a simulation study. We conclude that causal knowledge can act as a meta-cue for identifying highly valid cues, either individual or compound, and helps in the estimation of their validities. 相似文献
956.
Dipl.-Wirtsch.-Ing Michael Klafft Dr. rer. pol. Sarah Spiekermann 《WIRTSCHAFTSINFORMATIK》2006,48(1):36-45
Web-based bid invitation platforms and reverse auctions are increasingly used by consumers for the procurement of goods and
services. An empirical examination shows that with B-2-C these procurement methods generate considerable benefits for the
consumer:
相似文献
– | ⊎ Reverse auctions and bid invitation platforms generate high consumer surplus in the procurement of general and crafts services. |
– | ⊎ The level of this consumer surplus is affected by the number of bidders. The duration of the auction and the starting price are less important. |
– | ⊎ In the painting business prices are considerably lower than with traditional procurement channels. |
– | ⊎ On bid invitation platforms, in most cases (> 55%) the bids with the lowest price are chosen. |
957.
分析化学实验成绩评定软件的开发 总被引:1,自引:0,他引:1
介绍了分析化学实验成绩评定软件的主要内容、设计思想及功能 ,该软件采用VisualFoxPro5 0中文版编程 ,可用于分析化学实验成绩的评定。内容包括 :实验数据输入、实验数据修改、实验数据处理、实验结果查询、实验数据打印、修改学生名单等。本软件具有操作简单、使用方便等特点 相似文献
958.
959.
Metacomputing across intercontinental networks 总被引:1,自引:0,他引:1
S. M. J. M. F. C. Edgar Matthias Michael S. M. 《Future Generation Computer Systems》2001,17(8):911-918
An intercontinental network of supercomputers spanning more than 10 000 miles and running challenging scientific applications was realized at the Supercomputing ’99 (SC99) conference in Portland, OR using PACX-MPI and ATM PVCs. In this paper, we describe how we constructed the heterogeneous cluster of supercomputers, the problems we confronted in terms of multi-architecture and the way several applications handled the specific requirements of a metacomputer. 相似文献
960.
Dimensionality Reduction for Fast Similarity Search in Large Time Series Databases 总被引:36,自引:3,他引:33
Eamonn Keogh Kaushik Chakrabarti Michael Pazzani Sharad Mehrotra 《Knowledge and Information Systems》2001,3(3):263-286
The problem of similarity search in large time series databases has attracted much attention recently. It is a non-trivial
problem because of the inherent high dimensionality of the data. The most promising solutions involve first performing dimensionality
reduction on the data, and then indexing the reduced data with a spatial access method. Three major dimensionality reduction
techniques have been proposed: Singular Value Decomposition (SVD), the Discrete Fourier transform (DFT), and more recently
the Discrete Wavelet Transform (DWT). In this work we introduce a new dimensionality reduction technique which we call Piecewise
Aggregate Approximation (PAA). We theoretically and empirically compare it to the other techniques and demonstrate its superiority.
In addition to being competitive with or faster than the other methods, our approach has numerous other advantages. It is
simple to understand and to implement, it allows more flexible distance measures, including weighted Euclidean queries, and
the index can be built in linear time.
Received 16 May 2000 / Revised 18 December 2000 / Accepted in revised form 2 January 2001 相似文献