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We investigate the computable content of the Uniform Boundedness Theorem which states that a pointwise bounded sequence of bounded linear operators on Banach spaces is also uniformly bounded. But, given the sequence, can we also effectively find the uniform bound? It turns out that the answer depends on how the sequence is “given”. If it is just given with respect to the compact open topology (i.e. if just a sequence of “programs” is given), then we cannot even compute an upper bound of the uniform bound in general. If, however, the pointwise bounds are available as additional input information, then we can effectively compute an upper bound of the uniform bound. Additionally, we prove an effective version of the contraposition of the Uniform Boundedness Theorem: given a sequence of linear bounded operators which is not uniformly bounded, we can effectively find a witness for the fact that the sequence is not pointwise bounded. As an easy application of this theorem we obtain a computable function whose Fourier series does not converge.  相似文献   

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Starting from a heuristic program, the author has tried to develop a timetable program which can be applied to practical cases. In constructing a timetable, conflicts usually arise as to the availability of teachers, classes and classrooms. So we set up a timetable starting from the subjects most likely to lead to conflicts. When a conflict occurs in the heuristic procedure, exchange facilities are provided for the “dead ends” with the aid of certain “alternating subgraphs”. The main procedure is followed by a program that analyses the result and uses the exchange routine for an improvement within certain limits.  相似文献   

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How may we discriminate between the multitude of point-to-point communication facilities currently available? To take just one aspect of communication, how can we assess the fluency of coordination that results from using some communication technology? This paper describes two groups of measures with this general purpose. The measures described have been devised to be used in a particular approach to evaluation for the design of communication systems that borrows from experimental and ethnographic methods. This approach is promoted as a practical and rigorous way of assessing design alternatives.The first group of measures are subjective ratings that assess someone's awareness of the attentional status of their conversational partner, such awareness is necessary for the successful coordination of conversation. The rating scales are shown to be sensitive in that they distinguish between video and audio mediated conversation in a short experiment.The second group are measures derived from video records of communicative behaviour using “activity set” analysis. This can be used to assess coordination in communication directly. An activity set is a mutually exclusive and exhaustive set of behavioural states. A publicly available tool, Action Recorder, makes it possible to score the tapes in near real time. “Simple statistics” are extracted from a single activity set, examples are: the proportion of time spent looking towards the video monitor and the average duration of these glances. “Contingent statistics” are extracted from two or more activity sets, for example, the proportion of time both members of a pair are looking towards their video monitors. A way of assessing the synchronization evident in two people's behaviour is presented that makes use of these contingent statistics. Inter-observer reliabilities are given for all the measures generated.  相似文献   

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Shortest distance and reliability of probabilistic networks   总被引:1,自引:0,他引:1  
When the “length” of a link is not deterministic and is governed by a stochastic process, the “shortest” path between two points in the network is not necessarily always composed of the same links and depends on the state of the network. For example, in communication and transportation networks, the travel time on a link is not deterministic and the fastest path between two points is not fixed. This paper presents an algorithm to compute the expected shortest travel time between two nodes in the network when the travel time on each link has a given independent discrete probability distribution. The algorithm assumes the knowledge of all the paths between two nodes and methods to determine the paths are referenced.In reliability (i.e. the probability that two given points are connected by a path) computations, associated with each link is a probability of “failure” and a probability of “success”. Since “failure” implies infinite travel time, the algorithm simultaneously computes reliability. The paper also discusses the algorithm's capability to simultaneously compute some other performance measures which are useful in the analysis of emergency services operating on a network.  相似文献   

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In labeling pay or money as a “mere” hygiene factor, Frederick Herzberg set off a controversy that has continued up to the present by asking: Does money matter? Our study, involving several hundred I/S graduates over a four-year period, measures the importance of “above-average salaries” to these graduates as they progress through the early months of their I/S careers. Initially, salary is ranked highly; but as time passes, other factors tend to crowd out salary in importance. It loses its role as a motivator; and, as Herzberg suggests, becomes a hygiene factor.  相似文献   

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Katz  Nielsen  Segal 《Algorithmica》2003,36(1):59-73
We show how to maintain efficiently a minimum piercing set for a set S of intervals on the line, under insertions and deletions to/from S. A linear-size dynamic data structure is presented, which enables us to compute a new minimum piercing set following an insertion or deletion in time O(c( S) log |S|), where c (S) is the size of the new minimum piercing set. We also show how to maintain a piercing set for S of size at most (1+?)c (S), for 0 < ? ≤ 1 , in $\bar O$ ((log |S|)/?) amortized time per update. We then apply these results to obtain efficient solutions to the following three problems: (i) the shooter location problem, (ii) computing a minimum piercing set for arcs on a circle, and (iii) dynamically maintaining a box cover for a d -dimensional point set.  相似文献   

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“Walkthrough” and “Jogthrough” techniques are well known expert based methodologies for the evaluation of user interface design. In this paper we describe the use of “Graphical” Jogthrough method for evaluating the interface design of the Network Simulator, an educational simulation program that enables users to virtually build a computer network, install hardware and software components, make the necessary settings and test the functionality of the network. Graphical Jogthrough is a further modification of a typical Jogthrough method, where evaluators' ratings produce evidence in the form of a graph, presenting estimated proportion of users who effectively use the interface versus the time they had to work with it in order to succeed effectiveness. We comment on the question: “What are the possible benefits and limitations of the Graphical Jogthrough method when applied in the case of educational software interface design?” We present the results of the evaluation session, and concluding from our experience we argue that the method could offer designers quantitative and qualitative data for formulating a useful (though rough in some aspects) estimation about the novice–becoming–expert pace that end users might follow when working with the evaluated interface.  相似文献   

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A distance quasi-metric for pattern recognition is presented. The “quasi” modifier distinguishes the metric from “true” distance metrics which obey a set of standard constraints. By relaxing one of the constraints and coupling it with a fast multidimensional search technique, the metric demonstrates improved accuracy and efficiency compared to other metrics in recognizing hand-written digit samples. A high-level design of a fast optical comparator for computing the distance in O( ) is also presented.  相似文献   

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