共查询到20条相似文献，搜索用时 516 毫秒
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In this paper, we utilize transmission-line matrix simulations to study the electromagnetic properties of hyperbolic metamaterial grids, which are synthesized by arranging unloaded transmission lines over electrical ground planes, such that the unit cells are rectangular in shape. The hyperbolic grids support Bragg and Hyperbolic resonant modes that have rectangular and hyperbolic dispersion surfaces, respectively. We demonstrate the formation of these resonant modes in the hyperbolic grids and their refraction, and spatial scanning properties via circuit simulations. The simulation results are compared with experimental results of a two-layer anisotropic hyperbolic metamaterial. 相似文献
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Enrique A. González-Velasco Emilio Sanvicente 《Journal of The Franklin Institute》1980,310(2):135-142
The analytic representation of band-pass signals, which is extremely useful in information transmission and radar, is usually obtained by first introducing the Hilbert transform of a signal. We consider this procedure artificial, and propose here to follow the opposite path, which leads, in a natural way, to a motivated definition of the Hilbert transform. The key to this procedure is to show how, as a simple application of the Fourier integral, every band-pass signal can be expressed as the real part of a low frequency signal which modulates an exponential. Such a representation, called the analytic signal, is then used to define the Hilbert transform in a natural manner. Finally, we show that the term analytic signal is motivated by the fact that this signal is the restriction to the real axis of a function defined and analytic (holomorphic) in the upper half of the complex plane. 相似文献
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Novica Zarvić Carl Stolze Matthias Boehm Oliver Thomas 《International Journal of Information Management》2012
In an ever more globalised world IT (Information Technology) managers increasingly have to support value creation within inter-organisational collaboration settings. Such organisational forms with their inherent complexity require specific approaches for their IT management within. Especially important for unleashing the chances of networked arrangements is the right form of IT Governance. Choosing the right arrangement for IT Governance is heavily dependent on understanding the concepts on which such business constellations are built. In this paper we provide therefore first a systematically derived, graph-based perspective on the key terms of inter-organisational collaboration. Based on this understanding of concepts and structured representations of inter-organisational dependencies we present interorganisational governance practices for IT. Specifically, we assign accountabilities to top executive roles from both IT and business. By keeping a holistic perspective, the insights gained in this study are highly relevant for strategic information management in terms of Business-IT Alignment as well as monitoring and controlling of inter-organisational information infrastructures in a rapidly changing business environment. 相似文献
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Smartphone use while driving causes car crashes, injuries and high death rates. To date, there is little research into what motivates frequent smartphone use while driving. In this study, we draw on psychological research indicating that personality profiles defined as constellations of multiple personality traits, influence individual beliefs and behaviors. We apply fuzzy-set qualitative comparative analysis (fsQCA) to survey data to derive profiles of drivers who use their smartphone frequently while driving. Our results indicate that personality profiles affect smartphone use behavior while driving and that three equifinal profiles, i.e. distinct constellations of the big five personality traits, influence frequent smartphone use while driving. Interestingly, a single trait can be low in one profile and high in another profile and, depending on the other traits, both profiles might reflect drivers using their smartphone frequently. We contribute to the literature that frequent smartphone use while driving is, to some degree, grounded in personality and that just looking at singular traits can yield misleading results. Complementing these theoretical insights by post-survey interviews, we can reveal distinct measures that reduce frequent smartphone use for each of the three profiles. 相似文献
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《Journal of The Franklin Institute》2023,360(13):10165-10194
This article proposes a control methodology, referred to as the Nonlinear Disturbance Observer-based Incremental Backstepping (NIBS) approach, for the stratospheric airship with model uncertainty and time delay. In particular, a novel tracking differentiator based on the inverse hyperbolic sine function is designed and utilized in a nonlinear disturbance observer to estimate disturbance and sensor noise. The incremental backstepping control theory is further improved, and combined with the proposed nonlinear disturbance observer to overcome the issues of “term explosion” and signal transmission delay, ensuring the system’s robustness. Moreover, the Lyapunov theory is employed to investigate the stability of the NIBS approach. The simulation results validate that the NIBS control strategy can accurately regulate the speed and angular velocity of the stratospheric airship, while effectively mitigating the effects of sensor noise and time delay. 相似文献
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M.G. Pawley 《Journal of The Franklin Institute》1979,307(3):155-173
A large group of closed plane curves may be classified as roulettes, including epicycloids, hypocycloids, and related epitrochoids and hypotrochoids. The equation for the roulette in complex polar form shows that any roulette may be described by the vector sum of two vectors of specified constant magnitudes rotating with constant angular velocities. Methods for plotting, and for electronic display of roulettes are described. An equation is derived for a roulette approximation for an N-sided regular polygon. In particular, an application to two-dimensional potential theory is described and illustrated by consideration of the roulette approximation for a square as an equipotential curve, with derivation of equations for equipotential curves in the field surrounding the square. General equations are derived for given closed plane curves with points whose x and y coordinates may separately be expanded in Fourier series as functions of the polar angle, assuming these expansions are valid. It is shown that, in general, a closed plane curve may be considered as being described by an infinite sum of vectors, each rotating in a circle. Simplifying effects of symmetry about a polar axis and/or about the origin are discussed, and methods for harmonic analysis of a given closed plane curve with aid of an electronic calculator are described. 相似文献
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本文分析了在Rtx环境下用VC调用Matlab来实现对线性调频信号的实时性分析。由于单分量LFM信号的Wigner—Ville分布是冲激线谱,所以用Wigner—Ville分布分析单分量LFM信号是非常合适的。但对于多分量信号,由于交叉项的存在,时频平面就会变得模糊不清。本文就着重分析用在VC环境分析线性调频信号参数的一种方法。 相似文献
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利用入射激光经过转台散射所得信号光与参考光进行混频的方法得出转台的转速。使激光器出射光通过分束器后分成两束同频光,一束作为参考光,另一束经转台散射后即为信号光。参考光和信号光在探测器光敏面上进行混频,随后通过傅里叶变换(FFT)处理数据,计算出转台转动速度并与实际速度进行比较,结果表明该系统用于转台的转速测量是切实可行的,精度可达0.4%。 相似文献
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《Research Policy》2022,51(3):104410
In the most prestigious journals of many disciplines, female researchers are underrepresented. To better understand this phenomenon, we compare the proportions of female authors in all leading management and organization studies (MOS) journals, explore underlying gendered publication patterns, and analyze factors explaining differences between journals. We examine the gendered distribution of authorship in these journals using a complete, original time series. The comprehensive data set includes all articles published in fourteen leading journals in the MOS field, comprising 77,472 cases (authors) and 43,673 articles. The findings show that women have been underrepresented in all leading MOS journals until now. However, our findings reveal significant differences between journals, with some journals lagging far behind their peers. We ask why some journals score much higher than others and show that gendered authorship constellations and research topic specialization consistently explain female representation differences between journals. More specifically, we find a dominance of ‘men's clubs’ when it comes to authorship constellations and thriving ‘male islands’ when it comes to research topics. In contrast, ‘women's clubs’ are far less prevalent and no ‘female island’ exists. Interestingly, female authorship and ‘shared islands’ play a particularly powerful role in narrowing the gender gap in leading journals. Our results provide a benchmark for female representation across leading journals and allow for the formulation of concrete research policy goals and directions for change. 相似文献
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《Journal of The Franklin Institute》2023,360(7):5017-5047
This paper uses the directed communication topology to investigate the finite-time error constraint containment control for multiple Ocean Bottom Flying Node (OBFN) systems with thruster faults. The OBFN is a benthic Autonomous Underwater Vehicle (AUV), which has been used to explore submarine resources. The model uncertainties, velocity error constraint, external disturbances, and thruster faults of OBFNs motivate the design of containment controller. Moreover, some followers could obtain the states of leader OBFNs. We designed the command filter and the input signal is a hyperbolic tangent function. The virtual velocity error command is generated to follow the velocity error. Then the novel velocity error constraint distributed control algorithm is developed. Furthermore, for the problem of input saturation, by designing a stable anti-saturation compensator, an improved containment algorithm is proposed. It is proved that both the proposed approaches can converge the containment errors towards zero through Lyapunov theory in finite time, which means the followers can reach the convex hull formed by leaders in finite time. Finally, simulation results demonstrate the effectiveness of the two strategies. 相似文献
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This paper concerns an adaptive fuzzy tracking control problem for a class of switched uncertain nonlinear systems in strict-feedback form via the modified backstepping technique. The unknown nonlinear functions are approximated by the generalized fuzzy hyperbolic model (GFHM). It is shown that if the designed parameters in the controller and adaptive laws are appropriately selected, then all closed-loop signals are bounded and the stability of the system can be kept under average dwell time methods. In the end, simulation studies are presented to illustrate the effectiveness of the proposed method. 相似文献
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RUDENBERG R 《Journal of The Franklin Institute》1948,246(5):377-408
Increasing lens voltage, higher than the incident electron voltage, at first blocks the beam and then converts the electron lens into a curved mirror, the focal properties of which are analyzed.The embodiment of hyperbolic lenses is discussed by means of the boundary conditions which may be rigorously or approximately satisfied in actual designs. The effects of lateral apertures and windows on the imaging qualities of the field are considered in detail.Expressions are derived for velocity-, angular- and aperture-defects, the latter being merely a surface effect of the hyperbolic field. They all depend on a few parameters only of the lens field and are relatively small in magnitude. An experi- mental verification of the field structure with partial compensation of the defects shows favorable imaging qualities.Two-dimensional fields, constituting electron cylinder lenses, are considered in a similar way, leading to analogous formulations for the cardinal properties. 相似文献
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1/4波长的垂直GP天线广泛用于中波广播以及移动无线电通讯等领域。GP天线即地网天线英文全称为Ground Plane antenna可知地网是GP天线的组成部分,地网的性质会对GP天线产生非常重要的影响。本文借助仿真软件HFSS分析了地网的大小形状材料对GP天线阻抗,共振频率,增益,方向图等天线主要参数的影响。这些结果将为GP天线在有限地平面中的设计提供理论支持。 相似文献
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合成孔径雷达土壤水分反演研究进展 总被引：1，自引：0，他引：1
土壤水分作为地表水存储的重要组成部分,直接影响着陆地和大气间的物质和能量交换,成为水文、气象、农业和生态环境等领域的研究热点之一。合成孔径雷达(Synthetic Aperture Radar,SAR)由于其数据的极化特征、后向散射强度及相位特性对土壤水分的敏感性而成为高空间分辨率土壤水分监测中最有效的方法之一。本文首先对可用于土壤水分反演的SAR传感器进行总结;然后,分别对裸露地表和植被覆盖地表的微波散射模型进行介绍;在讨论影响土壤水分监测因素的基础上,分析主要影响因素的校正方法,并探讨当前合成孔径雷达反演土壤水分的主要方法;最后总结土壤水分反演中存在的问题,同时对未来的发展方向进行展望。 相似文献
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Profiting from voluntary information spillovers: how users benefit by freely revealing their innovations 总被引：3，自引：0，他引：3
Empirical studies of innovation have found that end users frequently develop important product and process innovations. Defying conventional wisdom on the negative effects of uncompensated spillovers, innovative users also often openly reveal their innovations to competing users and to manufacturers. Rival users are thus in a position to reproduce the innovation in-house and benefit from using it, and manufacturers are in a position to refine the innovation and sell it to all users, including competitors of the user revealing its innovation. In this paper, we explore the incentives that users might have to freely reveal their proprietary innovations. We then develop a game-theoretic model to explore the effect of these incentives on users’ decisions to reveal or hide their proprietary information. We find that, under realistic parameter constellations, free revealing pays. We conclude by discussing some implications of our findings. 相似文献
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《Journal of The Franklin Institute》2021,358(14):7170-7186
This paper studies the consensus of nonlinear multi-agent systems with periodic disturbances and uncertain dynamics based on matrix theory, adaptive control, neural networks and fourier series expansion. Firstly, fourier series expansion and neural networks are used to describe the unknown periodic time-varying parameter and uncertain nonlinear dynamic, respectively. Secondly, based on adaptive control technology and reparameterization method, two new fully distributed control protocols are designed based on symbolic function and smooth hyperbolic tangent function, respectively, so that all agents can reach asymptotic consensus. Thirdly, a new positive integral bounded function is introduced to compensate for the approximation error caused by the smooth hyperbolic tangent function instead of the symbolic function, so that all network nodes achieve the same consensus effect. Finally, a simulation example is given to verify the effectiveness of the two algorithms and to illustrate their advantages and disadvantages. 相似文献