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排序方式: 共有2261条查询结果,搜索用时 218 毫秒
81.
Lorenzo Spinelli Giovanna Tissoni Luigi A. Lugiato Massimo Brambilla 《Journal of Modern Optics》2013,60(14-15):2413-2422
We introduce here a model which includes the thermal dynamics in the time evolution of a semiconductor multiple quantum well microresonator, driven by a coherent holding beam. The active layer is electrically pumped, in order to obtain population inversion, but it is maintained below the lasing threshold. We show that the inclusion of thermal effects introduces a Hopf instability which may dominate the dynamical behaviour of the system in some operational regimes. In those cases our numerical simulations show that both spatial patterns and cavity solitons perform a drift motion in the transverse direction. This motion develops over the slow time scale which characterizes thermal effects. 相似文献
82.
83.
Tania Martellini Chiara Berlangieri Luigi Dei Emiliano Carretti Saul Santini Angelica Barone Alessandra Cincinelli 《Indoor air》2020,30(5):900-913
Indoor Air Quality monitoring in cultural institutions is of particular concern to protect these places and the cultural heritage content. An indoor monitoring campaign was performed in three museums in Florence (Italy) to determine the occurrence and levels of volatile organic compounds (VOCs). VOCs of interest included BTEX (benzene, toluene, ethylbenzene, xylenes), terpenes, aldehydes, organic acids, and cyclic volatile methyl siloxanes (cVMS). The most abundant VOCs in all samples analyzed were BTEX, which were strictly related to the traffic source, followed by siloxanes and terpenes. Among BTEX, toluene was always the most abundant followed by xylenes, ethylbenzene, and benzene. cVMS in exhibition rooms with the presence of visitors showed higher values compared to samples collected when the museums were closed. Terpenes showed not only the influence of vegetation-biogenic sources surrounding a museum but could also be related to the wood used for the construction of showcases and furniture and the use of cleaning products. Data obtained also showed the presence of organic acids and aldehydes whose source can be traced back to exhibits themselves and wood-based furniture. Assessing the levels of organic acids in museums is important because, over time, it can cause deterioration of the artifacts. 相似文献
84.
Federico Bianchi Simone Formentin Luigi Piroddi 《International Journal of Adaptive Control and Signal Processing》2020,34(1):63-76
Kalman filtering for linear systems is known to provide the minimum variance estimation error, under the assumption that the model dynamics is known. While many system identification tools are available for computing the system matrices from experimental data, estimating the statistics of the output and process noises is still an open problem. Correlation-based approaches are very fast and sufficiently accurate, but there are typically restrictions on the number of noise covariance elements that can be estimated. On the other hand, maximum likelihood methods estimate all elements with high accuracy, but they are computationally expensive, and they require the use of external optimization solvers. In this paper, we propose an alternative solution, tailored for process noise covariance estimation and based on stochastic approximation and gradient-free optimization, that provides a good trade-off in terms of performance and computational load, and is also easy to implement. The effectiveness of the method as compared to the state of the art is shown on a number of recently proposed benchmark examples. 相似文献
85.
Anna Delcampo‐Carda Ana Torres‐Barchino Juan Serra‐Lluch 《Color research and application》2019,44(3):381-395
The impact of the physical environment on individuals has arisen as a growing body of research in population wellbeing. Yet, most of studies in this area do not focus on elderly even though they are particularly susceptible to the characteristics of their interior spaces. It is a well‐known fact that to be old is to acquire a tolerance of disabilities based on the gradual degeneration. A common problem is a dysfunction in visual sensitivity and accordingly, the alteration of their environmental color perception. That is why these impairments need to be understood in order to minimize the elderly spatial difficulties. To know at what point there is a loss in the ability to perceive color is necessary to understand how should we take these facts into consideration. A state‐of‐the‐art literature review of current studies from the last 20 years is carried out. The aim is to analyze existing practices on Evidence‐Based Research through a multidisciplinary approach in order to create knowledge about chromatic built environments for the elderly. Data are identified and considered together with empirical experience about color, perception, built environment and elderly. Thus, the way in which elderly perceive the space is explored. The adjustments in the formulation of these impairments throughout any design strategy to adapt the environment to their physiological changes are determined. This article aims to determine a design interpretation of the various findings, demonstrating that color, as a parameter of the visual performance, influences visual comfort and helps performance in architecture for old people. 相似文献
86.
Traffic geometry is a factor that contributes to cognitive complexity in air traffic control. In conflict‐detection tasks, geometry can affect the attentional effort necessary to correctly perceive and interpret the situation; online measures of situational workload are therefore highly desirable. In this study, we explored whether saccadic movements vary with changes in geometry. We created simple scenarios with two aircraft and simulated a conflict detection task. Independent variables were the conflict angle and the distance to convergence point. We hypothesized lower saccadic peak velocity (and longer duration) for increasing complexity, that is, for increasing conflict angles and for different distances to convergence point. Response times varied accordingly with task complexity. Concerning saccades, there was a decrease of peak velocity (and a related increase of duration) for increased geometry complexity for large saccades (>15°). The data therefore suggest that geometry is able to influence “reaching” saccades and not “fixation” saccades. © 2011 Wiley Periodicals, Inc. 相似文献
87.
Das Internet der Dinge (IoT) bezeichnet die Anbindung von Gegenständen des alltäglichen Gebrauchs an das Internet. Der Fernseher ist als Smart-TV bereits Teil des Internets. Einige Untersuchungen haben hier in jüngster Vergangenheit deutliche Missstände in Bezug auf Datenschutz und Datensicherheit aufgezeigt. Der Beitrag fasst die Ergebnisse einer aktuellen, umfangreichen Untersuchung von fünf Smart-TVs zusammen. 相似文献
88.
89.
Nevio Luigi Tagliamonte Fabrizio Sergi Dino Accoto Giorgio Carpino Eugenio Guglielmelli 《Mechatronics》2012,22(8):1187-1203
Novel compliant actuation systems have been developed in recent years for a variety of possible advantages, such as establishing a safe human–robot interaction, increasing energy efficiency, reducing the effects of impacts and even for the development of neuro-inspired robotic platforms to be used in human motor control studies.In this rapidly growing and transversal research field, systems involving more than one active element (typically motors) for each actuated degree of freedom are being investigated to allow separate position and impedance regulations. Considering the wide range of applications and the large number of different arrangements deriving from the combination of two active elements and passive elastic components, several actuation architectures have been devised.This paper reviews state-of-the-art rotary variable impedance units incorporating two separate motors. Existing devices are grouped in three main categories. A critical and comparative analysis of the most relevant features is carried out, also based on most representative prototypes. Recently proposed methodologies and evaluation criteria for design optimization are illustrated and perspectives on potential applications of double actuation systems are presented. 相似文献
90.
Fuzzy frequency response: definition and analysis for uncertain dynamic systems is proposed in this paper. In terms of transfer function, the uncertain dynamic system is partitioned into several linear sub‐models and organized according to Takagi–Sugeno fuzzy representation. The main contribution of this paper is to demonstrate through the proposal of a Theorem that fuzzy frequency response is a boundary in the magnitude and phase Bode plots. Low‐ and high‐frequency analysis of fuzzy dynamic model is obtained by varying the frequency ω from zero to infinity. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献