排序方式: 共有104条查询结果,搜索用时 0 毫秒
1.
2.
Vicenç Gómez Hilbert J. Kappen Nelly Litvak Andreas Kaltenbrunner 《World Wide Web》2013,16(5-6):645-675
Online discussion threads are conversational cascades in the form of posted messages that can be generally found in social systems that comprise many-to-many interaction such as blogs, news aggregators or bulletin board systems. We propose a framework based on generative models of growing trees to analyse the structure and evolution of discussion threads. We consider the growth of a discussion to be determined by an interplay between popularity, novelty and a trend (or bias) to reply to the thread originator. The relevance of these features is estimated using a full likelihood approach and allows to characterise the habits and communication patterns of a given platform and/or community. We apply the proposed framework on four popular websites: Slashdot, Barrapunto (a Spanish version of Slashdot), Meneame (a Spanish Digg-clone) and the article discussion pages of the English Wikipedia. Our results provide significant insight into understanding how discussion cascades grow and have potential applications in broader contexts such as community management or design of communication platforms. 相似文献
3.
Daniel Campos Frederic Bartumeus Vicen? Méndez Xavier Espadaler 《Journal of the Royal Society Interface》2014,11(90)
We study central-place foraging patterns of Aphaenogaster senilis ants at a population level by video framing individual ant trajectories in a circular arena with a nest connected to its centre. The ants naturally leave and enter the nest and forage generating non-trivial movement patterns around the nest. Our data analysis indicated that the trajectories observed can be classified into two strategies: the risk-averse strategy, which involves wandering around the nest without departing far from it and the risk-prone strategy, which involves long exploration paths with periodic returns to the central region, nearby the nest. We found that both risk-prone and risk-averse strategies exhibit qualitatively the same reorientation patterns, with the time between consecutive reorientations covering a wide range of scales, and fitting a stretched exponential function. Nevertheless, differences in the temporal scales and the time variability of such reorientation events differ, together with other aspects of motion, such as average speed and turns. Our results give experimental evidence that the internal mechanisms driving reorientations in ants tend to favour frequently long relocations, as theory predicts for efficient exploration in patchy landscapes, but ants engaged in central-place foraging can modulate such behaviour to control distances from the nest. Previous works on the species support the idea that risk-prone and risk-averse strategies may reflect actual differences between individuals age and experience; these factors (age and experience) should be then relevant in modulating the internal reorientation clocks. To support the validity of our findings, we develop a random-walk model combining stretched exponential reorientation clocks with klinokinesis that fits the time length and the travelled distance distributions of the observed trajectories. 相似文献
4.
In this paper, we review the role of information fusion in data privacy. To that end, we introduce data privacy, and describe how information and data fusion are used in some fields of data privacy. Our study is focused on the use of aggregation for privacy protections, and record linkage techniques. 相似文献
5.
Marcin Witczak Vicenç Puig Saúl Montes de Oca 《International journal of control》2013,86(10):1788-1799
In this paper, an active fault-tolerant control scheme is proposed in the case of actuator faults. In particular, the general idea of integrating fault identification and control schemes, which takes into account the fault estimation error is first presented in a linear context. As a result, the so-called separation principle for the controller and the fault identification scheme is developed. Subsequently, the proposed approach is extended to a class of non-linear systems. Similarly to the linear case, it is proven that using a suitable control strategy and a faulty identification scheme it is possible to obtain an integrated fault-tolerant control framework, which takes into account the fault identification error. As a result, a non-linear counterpart of the above-mentioned separation principle is developed. Finally, the last part of the paper shows the application results obtained using a twin-rotor system that confirm the high performance of the proposed approach. 相似文献
6.
Pedro Almenar 《Computers & Mathematics with Applications》2012,63(1):310-317
This paper presents an upper bound for the distance between a zero and a critical point of a solution of the second order linear differential equation (p(x)y′)′+q(x)y(x)=0, with p(x),q(x)>0. It also compares it with previous results. 相似文献
7.
International Journal of Information Security - The introduction of advanced metering infrastructure (AMI) smart meters has given rise to fine-grained electricity usage data at different levels of... 相似文献
8.
9.
The broadcast DVB‐T system is an m‐QAM‐OFDM communication system that includes pilot‐symbol‐assisted modulation (PSAM) in order to enhance channel estimation at the receiver. This characteristic makes DVB‐T suitable for a mobile reception, over time‐ and frequency‐selective wireless channels. In this work, a closed‐form expression for the BER as a function of the transmission system, channel model and the channel estimation strategy employed at the receiver is derived. In addition, adjacent channel interference due to Doppler effects is also considered. The results are focused on the DVB‐T system under different scenarios. The channel estimation at the receiver has been shown to be very critical, and the impact of channel estimation errors on the BER is analysed in detail. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
10.
E Fernández Fabrellas M Marín González L Almenar Bonet R Blanquer Olivas 《Canadian Metallurgical Quarterly》1997,52(2):140-141
Swyer-James syndrome, unilateral hyperlucent lung with air entrapment, generally occurs after severe infections during childhood. It is usually diagnosed by its characteristic chest radiographic image film or computed tomography, in patients who are almost asymptomatic. We report a case of Swyer-James syndrome, diagnosed from the study of severe pulmonary hypertension and with a fatal outcome. 相似文献