Journal articles: 'Periodic patches'

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GEORGESCU, PAUL, GABRIEL DIMITRIU, and ROBERT SINCLAIR. "IMPULSIVE CONTROL OF AN INTEGRATED PEST MANAGEMENT MODEL WITH DISPERSAL BETWEEN PATCHES." Journal of Biological Systems 18, no. 03 (September 2010): 535–69. http://dx.doi.org/10.1142/s0218339010003561.

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We consider a two-patch SI model of integrated pest management with dispersal of both susceptible and infective pests between patches. A biological control, consisting of the periodic release of infective pests and a chemical control, consisting of periodic and impulsive pesticide spraying, are employed in order to maintain the size of the pest population below an economically acceptable level. It is assumed that the spread of the disease which is inflicted on the pest population through the use of the biological control is characterized by a nonlinear force of infection expressed in an abstract form. A sufficient condition for the local stability of the susceptible pest-eradication periodic solution is found using Floquet theory for periodic systems of ordinary differential equations, an analysis of the influence of dispersal between patches being performed for several particular cases. Our numerical simulations indicate that an increase in the amount but not in the frequency of pesticide use may not result in control. We also show that patches which are stable in isolation can be destabilized by dispersal between patches.

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Franović, Igor, and Sebastian Eydam. "Patched patterns and emergence of chaotic interfaces in arrays of nonlocally coupled excitable systems." Chaos: An Interdisciplinary Journal of Nonlinear Science 32, no. 9 (September 2022): 091102. http://dx.doi.org/10.1063/5.0111507.

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We disclose a new class of patterns, called patched patterns, in arrays of non-locally coupled excitable units with attractive and repulsive interactions. The self-organization process involves the formation of two types of patches, majority and minority ones, characterized by uniform average spiking frequencies. Patched patterns may be temporally periodic, quasiperiodic, or chaotic, whereby chaotic patterns may further develop interfaces comprised of units with average frequencies in between those of majority and minority patches. Using chaos and bifurcation theory, we demonstrate that chaos typically emerges via a torus breakup and identify the secondary bifurcation that gives rise to chaotic interfaces. It is shown that the maximal Lyapunov exponent of chaotic patched patterns does not decay, but rather converges to a finite value with system size. Patched patterns with a smaller wavenumber may exhibit diffusive motion of chaotic interfaces, similar to that of the incoherent part of chimeras.

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JANG, HONG-KYU, YEON-GWAN LEE, JAE-HWAN SHIN, and CHUN-GON KIM. "ELECTROMAGNETIC WAVE ABSORBING TECHNIQUE USING PERIODIC PATTERNS FOR LOW RCS PATCH ARRAY ANTENNA." International Journal of Modern Physics B 27, no. 17 (July 3, 2013): 1350094. http://dx.doi.org/10.1142/s021797921350094x.

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This paper presents an electromagnetic wave absorbing technique to reduce a radar cross-section (RCS) of a patch array antenna without compromising their antenna performance. The technique is based on periodic patterns, which is made of resistive materials. The 2×2 patch array antenna with a resonance frequency of 3.0 GHz was designed and fabricated. To reduce the RCS of the patch array antenna, the periodic patterns using a square patch element were proposed and applied to the surface between the four antenna patches. The printed lossy periodic patterns have radar absorbing performance at 12.0 GHz frequency. The measured results show that the lossy periodic patterns have no significant effect on the antenna radiation performance. On the other hand, the RCS is reduced by more than 98% compared to the conventional antenna at the target frequency.

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Mokrani, Bilal, Renaud Bastaits, Mihaita Horodinca, Iulian Romanescu, Ioanica Burda, Régis Viguié, and André Preumont. "Parallel Piezoelectric Shunt Damping of Rotationally Periodic Structures." Advances in Materials Science and Engineering 2015 (2015): 1–12. http://dx.doi.org/10.1155/2015/162782.

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This paper considers the RL shunt damping of rotationally periodic structures with an array of regularly spaced piezoelectric patches. The technique is targeted to the damping of a specific mode withnnodal diameters. For this particular case, one can take advantage of the shape of the targeted mode to organize the piezoelectric patches as a modal filter (in parallel loops) which reduces the demand on the inductors of the tuned inductive shunt. In the case of a perfectly rotationally periodic structure, it is possible to organize 4npiezoelectric transducers (PZT patches) in two parallel loops of 2npatches each. In this way, the demand on the inductors is reduced by4n2as compared to independent loops, which may allow a fully passive integration of the RL shunt in a turbomachinery application. The method is first illustrated experimentally on a circular plate; it is then applied to a prototype of an industrial bladed drum. The influence of blade mistuning is investigated.

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ZHANG, LONG, and ZHIDONG TENG. "PERMANENCE IN A PERIODIC PREDATOR–PREY SYSTEM WITH PREY DISPERSAL AND PREDATOR DENSITY-INDEPENDENT." Journal of Biological Systems 14, no. 04 (December 2006): 491–507. http://dx.doi.org/10.1142/s0218339006001933.

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In this paper, we study two-species predator–prey Lotka–Volterra-type dispersal system with periodic coefficients, in which the prey species can disperse among n-patches, but the predator species which is density-independent is confined to some patches and cannot disperse. By utilizing the analytic method, sufficient and realistic conditions on the boundedness, permanence, extinction, and the existence of positive periodic solution are established. The theoretical results are confirmed by a special example and numerical simulations.

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Hamilton, J. K., I. R. Hooper, and C. R. Lawrence. "Exploring microwave absorption by non-periodic metasurfaces." Advanced Electromagnetics 10, no. 3 (October 14, 2021): 1–6. http://dx.doi.org/10.7716/aem.v10i3.1803.

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In recent years there has been a large body of work investigating periodic metasurface microwave absorbers. However, surprisingly few investigations have focused on the absorption performance of similar non-periodic designs. In this work, the electromagnetic response of a large area (310 mm x 310 mm) microwave absorber that lacks a global periodicity is experimentally studied. The top metallic layer of the ultra-thin (0.3 mm) absorber is structured with rectangular patches given by a procedurally generated non-periodic pattern, known as the toothpick sequence. The specular reflectivity of both p-polarised and s-polarised incident radiation shows coupling to an additional low frequency mode when compared to a standard square patch periodic absorber. To further explore the coupling efficiency of such non-periodic absorbers, finite element models were used to investigate the influence of increasing sample size.

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Hamilton, J. K., I. R. Hooper, and C. R. Lawrence. "Exploring microwave absorption by non-periodic metasurfaces." Advanced Electromagnetics 10, no. 3 (October 14, 2021): 1–6. http://dx.doi.org/10.7716/aem.v10i3.1803.

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In recent years there has been a large body of work investigating periodic metasurface microwave absorbers. However, surprisingly few investigations have focused on the absorption performance of similar non-periodic designs. In this work, the electromagnetic response of a large area (310 mm x 310 mm) microwave absorber that lacks a global periodicity is experimentally studied. The top metallic layer of the ultra-thin (0.3 mm) absorber is structured with rectangular patches given by a procedurally generated non-periodic pattern, known as the toothpick sequence. The specular reflectivity of both p-polarised and s-polarised incident radiation shows coupling to an additional low frequency mode when compared to a standard square patch periodic absorber. To further explore the coupling efficiency of such non-periodic absorbers, finite element models were used to investigate the influence of increasing sample size.

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8

Lebon, Benoît, Jorge Peixinho, Shun Ishizaka, and Yuji Tasaka. "Subcritical transition to turbulence in a sudden circular pipe expansion." Journal of Fluid Mechanics 849 (June 18, 2018): 340–54. http://dx.doi.org/10.1017/jfm.2018.421.

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The results of experiments on the flow through a circular sudden expansion pipe at moderate Reynolds numbers are presented. At five diameters upstream of the expansion, laminar flow was disturbed by a (constant) cross-flow jet, a suction or a (periodic in–out) synthetic jet from a hole in the wall. When the disturbance exceeded a critical value of the control parameter depending on the Reynolds number, localised turbulent patches formed downstream of the expansion at fixed axial positions. For the cross-flow jet, the onset of turbulent patches is related to the velocity ratio of the mean jet velocity to the mean pipe velocity. At low velocity ratio, turbulent patches formed intermittently. For the suction disturbance, the flow experienced a strong asymmetry of the recirculation region and required a larger velocity ratio before the turbulent patch formed. For the synthetic jet, the amplification of wavy disturbances into turbulent patches and their axial positions are controlled by the driving frequency. Overall, these results suggest the existence of different mechanisms for the development of localised turbulent patches.

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LIU, ZIJIAN, ZHIDONG TENG, and LONG ZHANG. "TWO PATCHES IMPULSIVE DIFFUSION PERIODIC SINGLE-SPECIES LOGISTIC MODEL." International Journal of Biomathematics 03, no. 01 (March 2010): 127–41. http://dx.doi.org/10.1142/s1793524510000842.

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In this paper, we study a periodic single-species logistic system with impulsive diffusion in two patches. By using the iterative method, sufficient and necessary conditions on the existence, uniqueness and global attractivity of positive periodic solution and the extinction of species for this system are established. Two examples and numerical simulations are presented to illustrate the feasibility of our results.

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MARVÁ, M., J. C. POGGIALE, and R. BRAVO DE LA PARRA. "REDUCTION OF SLOW–FAST PERIODIC SYSTEMS WITH APPLICATIONS TO POPULATION DYNAMICS MODELS." Mathematical Models and Methods in Applied Sciences 22, no. 10 (August 13, 2012): 1250025. http://dx.doi.org/10.1142/s021820251250025x.

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This work deals with the approximate reduction of a nonautonomous two time scales ordinary differential equations system with periodic fast dynamics. We illustrate this technique with the analysis of two models belonging to different fields in ecology. On the one hand, we deal with a two patches periodic predator–prey model with a refuge for prey. Considering migrations between patches to be faster than local interaction allows us to study a three-dimensional system by means of a two-dimensional one. On the other hand, a two time scales periodic eco-epidemic model is addressed by considering two competing species, one of them being affected by a periodic SIR epidemic process which is faster than inter-species interactions. The difference between time scales allows us to study the asymptotic behavior of the four-dimensional system by means of a planar, reduced one. Furthermore, we propose a methodology straightforwardly applicable to a very large class of two time scales periodic systems.

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Wen, Luosheng, Bin Long, Xin Liang, and Fengling Zeng. "The Global Behavior of a Periodic Epidemic Model with Travel between Patches." Abstract and Applied Analysis 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/295060.

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We establish an SIS (susceptible-infected-susceptible) epidemic model, in which the travel between patches and the periodic transmission rate are considered. As an example, the global behavior of the model with two patches is investigated. We present the expression of basic reproduction ratioR0and two theorems on the global behavior: ifR0< 1 the disease-free periodic solution is globally asymptotically stable and ifR0> 1, then it is unstable; ifR0> 1, the disease is uniform persistence. Finally, two numerical examples are given to clarify the theoretical results.

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12

Xiang, Li, Yurong Zhang, Dan Zhang, Zhichun Yang, Lingzhi Huang, and Jinliang Wang. "Dynamical Analysis for the Hybrid Network Model of Delayed Predator-Prey Gompertz Systems with Impulsive Diffusion between Two Patches." Discrete Dynamics in Nature and Society 2020 (September 28, 2020): 1–12. http://dx.doi.org/10.1155/2020/5041761.

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In this paper, we consider a hybrid network model of delayed predator-prey Gompertz systems with impulsive diffusion between two patches, in which the patches represent nodes of the network such that the prey population interacts locally in each patch and diffusion occurs along the edges connecting the nodes. Using the discrete dynamical system determined by the stroboscopic map which has a globally stable positive fixed point, we obtain the global attractive condition of predator-extinction periodic solution for the network system. Furthermore, by employing the theory of delay functional and impulsive differential equation, we obtain sufficient condition with time delay for the permanence of the network.

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13

ARINO, O., and W. V. SMITH. "MIGRATION IN AGE STRUCTURED POPULATION DYNAMICS." Mathematical Models and Methods in Applied Sciences 08, no. 05 (August 1998): 905–25. http://dx.doi.org/10.1142/s021820259800041x.

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We introduce a linear model for age structured populations which migrate between several locations or patches. Birth is allowed in each patch. Existence, uniqueness and positivity of solutions is proved. A certain North Atlantic fishery is given as an example. Asymptotic solutions are characterized in a general system with periodic coefficients by spectral theory techniques and the results are applied to the example.

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Luo, Zhenguo, Liping Luo, Liu Yang, Zhenghui Gao, and Yunhui Zeng. "Existence and Uniqueness of Positive Periodic Solutions for a Delayed Predator-Prey Model with Dispersion and Impulses." Journal of Applied Mathematics 2014 (2014): 1–21. http://dx.doi.org/10.1155/2014/592543.

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An impulsive Lotka-Volterra type predator-prey model with prey dispersal in two-patch environments and time delays is investigated, where we assume the model of patches with a barrier only as far as the prey population is concerned, whereas the predator population has no barriers between patches. By applying the continuation theorem of coincidence degree theory and by means of a suitable Lyapunov functional, a set of easily verifiable sufficient conditions are obtained to guarantee the existence, uniqueness, and global stability of positive periodic solutions of the system. Some known results subject to the underlying systems without impulses are improved and generalized. As an application, we also give two examples to illustrate the feasibility of our main results.

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15

Grooms, Ian, Louis-Philippe Nadeau, and K. Shafer Smith. "Mesoscale Eddy Energy Locality in an Idealized Ocean Model." Journal of Physical Oceanography 43, no. 9 (September 1, 2013): 1911–23. http://dx.doi.org/10.1175/jpo-d-13-036.1.

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Abstract This paper investigates the energy budget of mesoscale eddies in wind-driven two-layer quasigeostrophic simulations. Intuitively, eddy energy can be generated, dissipated, and fluxed from place to place; regions where the budget balances generation and dissipation are “local” and regions that export or import large amounts of eddy energy are “nonlocal.” Many mesoscale parameterizations assume that statistics of the unresolved eddies behave as local functions of the resolved large scales, and studies that relate doubly periodic simulations to ocean patches must assume that the ocean patches have local energetics. This study derives and diagnoses the eddy energy budget in simulations of wind-driven gyres. To more closely approximate the ideas of subgrid-scale parameterization, the authors define the mean and eddies using a spatial filter rather than the more common time average. The eddy energy budget is strongly nonlocal over nearly half the domain in the simulations. In particular, in the intergyre region the eddies lose energy through interactions with the mean, and this energy loss can only be compensated by nonlocal flux of energy from elsewhere in the domain. This study also runs doubly periodic simulations corresponding to ocean patches from basin simulations. The eddy energy level of ocean patches in the basin simulations matches the level in the periodic simulations only in regions with local eddy energy budgets.

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Alotaibi, Hammad, Barry Cox, and Anthony John Roberts. "Couple microscale periodic patches to simulate macroscale emergent dynamics." ANZIAM Journal 59 (April 4, 2018): 313. http://dx.doi.org/10.21914/anziamj.v59i0.11859.

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ALOTAIBI, HAMMAD, BARRY COX, and A. J. ROBERTS. "COUPLE MICROSCALE PERIODIC PATCHES TO SIMULATE MACROSCALE EMERGENT DYNAMICS." ANZIAM Journal 59, no. 3 (January 2018): 313–34. http://dx.doi.org/10.1017/s1446181117000396.

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Macroscale “continuum” level predictions are made by a new way to construct computationally efficient “wrappers” around fine-scale, microscopic, detailed descriptions of dynamical systems, such as molecular dynamics. It is often significantly easier to code a microscale simulator with periodicity: so the challenge addressed here is to develop a scheme that uses only a given periodic microscale simulator; specifically, one for atomistic dynamics. Numerical simulations show that applying a suitable proportional controller within “action regions” of a patch of atomistic simulation effectively predicts the macroscale transport of heat. Theoretical analysis establishes that such an approach will generally be effective and efficient, and also determines good values for the strength of the proportional controller. This work has the potential to empower systematic analysis and understanding at a macroscopic system level when only a given microscale simulator is available.

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Liu, Zijian, Shouming Zhong, Chun Yin, and Wufan Chen. "Two-patches prey impulsive diffusion periodic predator–prey model." Communications in Nonlinear Science and Numerical Simulation 16, no. 6 (June 2011): 2641–55. http://dx.doi.org/10.1016/j.cnsns.2010.09.023.

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Schaich, W. L., G. Schider, J. R. Krenn, A. Leitner, F. R. Aussenegg, I. Puscasu, B. Monacelli, and G. Boreman. "Optical resonances in periodic surface arrays of metallic patches." Applied Optics 42, no. 28 (October 1, 2003): 5714. http://dx.doi.org/10.1364/ao.42.005714.

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NITSCHE, J. C. C. "THE EXISTENCE OF SURFACE PATCHES FOR PERIODIC MINIMAL SURFACES." Le Journal de Physique Colloques 51, no. C7 (December 1990): C7–265—C7–271. http://dx.doi.org/10.1051/jphyscol:1990727.

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Abdulnabi, Hussein A., Refat T. Hussein, and Raad S. Fyath. "UWB Single Port Log Periodic Toothed Terahertz Antenna Design Based on Graphene Artificial Magnetic Conductor." Modern Applied Science 11, no. 3 (January 14, 2017): 86. http://dx.doi.org/10.5539/mas.v11n3p86.

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In this work, a single port exponential tapered toothed log periodic antenna based on graphene artificial magnetic conductor (AMC) is suggested for ultra-wideband (1–10) THz operation. The resonance frequency of the proposed antenna can be tuned by changing the connected DC voltage which leads to variation in the chemical potential of the graphene.The radiating toothed log periodic antenna consists of gold patch placed on 25x25 graphene patches which act as an AMC surface unit. Exponential taper is used to satisfy impedance matching between the antenna and the feeder over the frequency range. The simulation results reveal that 90% of frequency range satisfies when the chemical potential is1eV.

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Mokrani, Bilal, Renaud Bastaits, Iulian Romanescu, Mihaita Horodinca, Ioan Burda, and André Preumont. "Passive Damping of Rotationally Periodic Structures with Tuned Piezoelectric Inductive Shunt." Actuators 7, no. 3 (July 19, 2018): 41. http://dx.doi.org/10.3390/act7030041.

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This paper considers the piezoelectric resistive and inductive RL shunt damping applied to rotationally periodic structures equipped with an array of regularly spaced piezoelectric patches. A method for simplifying the hardware, by reducing the size of the inductors and eliminating the use of synthetic inductors, is described. The paper compares two different ways of using the piezoelectric array: independent loops and parallel loops. It shows that, if a specific mode with n nodal diameters is targeted, mounting 4n piezoelectric patches in two parallel loops is as efficient as mounting them in 4n independent loops, while considerably reducing the demand on the inductors, L, (by 4n2). The method takes advantage of the mode shapes of rotationally periodic structures. The proposed method is validated numerically and experimentally on a rotationally periodic circular plate (nearly axisymmetric). The proposed technique is aimed at turbomachinery applications.

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Eun, Changsun. "Diffusion-Limited Reaction Kinetics of a Reactant with Square Reactive Patches on a Plane." Symmetry 12, no. 10 (October 21, 2020): 1744. http://dx.doi.org/10.3390/sym12101744.

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We present a simple reaction model to study the influence of the size, number, and spatial arrangement of reactive patches on a reactant placed on a plane. Specifically, we consider a reactant whose surface has an N × N square grid structure, with each square cell (or patch) being chemically reactive or inert for partner reactant molecules approaching the cell via diffusion. We calculate the rate constant for various cases with different reactive N × N square patterns using the finite element method. For N = 2, 3, we determine the reaction kinetics of all possible reactive patterns in the absence and presence of periodic boundary conditions, and from the analysis, we find that the dependences of the kinetics on the size, number, and spatial arrangement are similar to those observed in reactive patches on a sphere. Furthermore, using square reactant models, we present a method to significantly increase the rate constant by sequentially breaking the patches into smaller patches and arranging them symmetrically. Interestingly, we find that a reactant with a symmetric patch distribution has a power–law relation between the rate constant and the number of reactive patches and show that this works well when the total reactive area is much less than the total surface area of the reactant. Since our N × N discrete models enable us to examine all possible reactive cases completely, they provide a solid understanding of the surface reaction kinetics, which would be helpful for understanding the fundamental aspects of the competitions between reactive patches arising in real applications.

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Mondal, Sirshendu, Vishnu R. Unni, and R. I. Sujith. "Onset of thermoacoustic instability in turbulent combustors: an emergence of synchronized periodicity through formation of chimera-like states." Journal of Fluid Mechanics 811 (December 15, 2016): 659–81. http://dx.doi.org/10.1017/jfm.2016.770.

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Thermoacoustic systems with a turbulent reactive flow, prevalent in the fields of power and propulsion, are highly susceptible to oscillatory instabilities. Recent studies showed that such systems transition from combustion noise to thermoacoustic instability through a dynamical state known as intermittency, where bursts of large-amplitude periodic oscillations appear in a near-random fashion in between regions of low-amplitude aperiodic fluctuations. However, as these analyses were in the temporal domain, this transition remains still unexplored spatiotemporally. Here, we present the spatiotemporal dynamics during the transition from combustion noise to limit cycle oscillations in a turbulent bluff-body stabilized combustor. To that end, we acquire the pressure oscillations and the field of heat release rate oscillations through high-speed chemiluminescence ($CH^{\ast }$) images of the reaction zone. With a view to get an insight into this complex dynamics, we compute the instantaneous phases between acoustic pressure and local heat release rate oscillations. We observe that the aperiodic oscillations during combustion noise are phase asynchronous, while the large-amplitude periodic oscillations seen during thermoacoustic instability are phase synchronous. We find something interesting during intermittency: patches of synchronized periodic oscillations and desynchronized aperiodic oscillations coexist in the reaction zone. In other words, the emergence of order from disorder happens through a dynamical state wherein regions of order and disorder coexist, resembling a chimera state. Generally, mutually coupled chaotic oscillators synchronize but retain their dynamical nature; the same is true for coupled periodic oscillators. In contrast, during intermittency, we find that patches of desynchronized aperiodic oscillations turn into patches of synchronized periodic oscillations and vice versa. Therefore, the dynamics of local heat release rate oscillations change from aperiodic to periodic as they synchronize intermittently. The temporal variations in global synchrony, estimated through the Kuramoto order parameter, echoes the breathing nature of a chimera state.

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Aris, Mohd Aziz, Mohd Tarmizi Ali, Nurulhuda Abd Rahman, and Idnin Pasya Ibrahim. "Frequency Reconfigurable Antenna Array Using Defected Ground Structure for Outdoor Wireless Communication Systems." International Journal of Electrical & Electronic Systems Research (IEESR) 9, no. 1 (June 24, 2019): 33. http://dx.doi.org/10.24191/ieesr.v9i1.1372.

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This paper proposes frequency reconfigurable antenna for outdoor wireless communication systems, the 4 x 4 array antenna has designed at two resonant frequencies 7.5 GHz and 8.85 GHz. The periodic dumbbell geometry etched on the ground layer newly proposed with dual functionality, to control desired frequency and to couple radiating patches at the top substrate with feeding line at the bottom substrate. The reconfigurability of the patch antenna is controlled by utilizing the copper pad of the feeding network with OPEN and SHORT states. The reconfigurable antenna has been simulated and optimized using Computer Simulation Technology (CST) to get the desired responds. The good agreement between simulation and measured results indicates that the frequency reconfigurable patch array antenna using Periodic Dumbbell Slotted Aperture Structure (FRPDSA) is feasible to support outdoor wireless communication systems.

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Florencio, Rafael, Álvaro Somolinos, Iván González, and Felipe Cátedra. "Method of Moments Based on Equivalent Periodic Problem and FFT with NURBS Surfaces for Analysis of Multilayer Periodic Structures." Electronics 9, no. 2 (January 31, 2020): 234. http://dx.doi.org/10.3390/electronics9020234.

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In this paper, an efficient technique of computation of method of moments (MM) matrix entries for multilayer periodic structures with NURBS surface and Bézier patches modelling is proposed. An approximation in terms of constant pulses of generalized rooftop basis functions (BFs) defined on Bézier patches is proposed. This approximation leads discrete convolutions instead of usual continuous convolution between Green’s functions and BFs obtained by the direct mixed potential integral equation (MPIE) approach. An equivalent periodic problem (EPP) which contains the original problem is proposed to transform the discrete convolutions in discrete cyclic convolutions. The resultant discrete cyclic convolutions are computed by efficiently using the Fast Fourier Transform (FFT) procedure. The performance of the proposed method and direct computation of the MM entries are compared for phases of reflection coefficient. The proposed method is between 9 and 50 times faster than the direct computation for phase errors less than 1 deg. The proposed method exhibits a behaviour of CPU time consumption of O(NbLog10Nb) as the number Nb of BFs increases. This behaviour provides significant CPU time savings with respect to the expected behaviour of O(Nb2) provided by the direct computation of the MM matrix entries.

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Kaipa, Chandra S. R., Alexander B. Yakovlev, Francisco Medina, and Francisco Mesa. "Transmission through stacked 2D periodic distributions of square conducting patches." Journal of Applied Physics 112, no. 3 (August 2012): 033101. http://dx.doi.org/10.1063/1.4740054.

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Luo, Yong, Kazutaka Kikuta, Zhengli Han, Takuya Takahashi, Akira Hirose, and Hiroshi Toshiyoshi. "Programmable leaky‐wave antenna with periodic J‐shaped metamaterial patches." Electronics Letters 51, no. 10 (May 2015): 733–34. http://dx.doi.org/10.1049/el.2015.0206.

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Farooqui, Maaz, Tamer Elnady, and Wael Akl. "Sound attenuation in ducts using locally resonant periodic aluminum patches." Journal of the Acoustical Society of America 139, no. 6 (June 2016): 3277–87. http://dx.doi.org/10.1121/1.4948990.

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Guillot, Vinciane, Arthur Givois, Mathieu Colin, Olivier Thomas, Alireza Ture Savadkoohi, and Claude-Henri Lamarque. "Theoretical and experimental investigation of a 1:3 internal resonance in a beam with piezoelectric patches." Journal of Vibration and Control 26, no. 13-14 (March 5, 2020): 1119–32. http://dx.doi.org/10.1177/1077546320910536.

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Experimental and theoretical results on the nonlinear dynamics of a homogeneous thin beam equipped with piezoelectric patches, presenting internal resonances, are provided. Two configurations are considered: a unimorph configuration composed of a beam with a single piezoelectric patch and a bimorph configuration with two collocated piezoelectric patches symmetrically glued on the two faces of the beam. The natural frequencies and mode shapes are measured and compared with those obtained by theoretical developments. Ratios of frequencies highlight the realization of 1:2 and 1:3 internal resonances, for both configurations, depending on the position of the piezoelectric patches on the length of the beam. Focusing on the 1:3 internal resonance, the governing equations are solved via a numerical harmonic balance method to find the periodic solutions of the system under harmonic forcing. A homodyne detection method is used experimentally to extract the harmonics of the measured vibration signals, on both configurations, and exchanges of energy between the modes in the 1:3 internal resonance are observed. A qualitative agreement is obtained with the model.

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Matekovits, Ladislau, Karu P. Esselle, Mirko Bercigli, and Rodolfo Guidi. "Efficient Numerical Analysis of a Periodic Structure of Multistate Unit Cells." International Journal of Antennas and Propagation 2014 (2014): 1–6. http://dx.doi.org/10.1155/2014/148486.

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Application of the synthetic function expansion (SFX) algorithm to the analysis of active 1- and 2D periodic structures is presented. The single unit cell consisting of a microstrip line loaded by patches positioned below the line is turned into an active structure by inserting a pair of 2 switches to the two ends of each patch; the states of the pair of switches are changed contemporaneously. Variation of the states of the switches modifies the current distribution on the structure. The tunable multistate unit cell is arranged in 24-, 120-, and 9 × 24 element configurations and numerically analyzed. The computational complexity required for the characterization of the large number of possible configurations is lightened by the use of the proposed numerical method.

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He, Jiang, Ruobo Zhou, Zhuhao Wu, Monica A. Carrasco, Peri T. Kurshan, Jonathan E. Farley, David J. Simon, et al. "Prevalent presence of periodic actin–spectrin-based membrane skeleton in a broad range of neuronal cell types and animal species." Proceedings of the National Academy of Sciences 113, no. 21 (May 9, 2016): 6029–34. http://dx.doi.org/10.1073/pnas.1605707113.

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Actin, spectrin, and associated molecules form a periodic, submembrane cytoskeleton in the axons of neurons. For a better understanding of this membrane-associated periodic skeleton (MPS), it is important to address how prevalent this structure is in different neuronal types, different subcellular compartments, and across different animal species. Here, we investigated the organization of spectrin in a variety of neuronal- and glial-cell types. We observed the presence of MPS in all of the tested neuronal types cultured from mouse central and peripheral nervous systems, including excitatory and inhibitory neurons from several brain regions, as well as sensory and motor neurons. Quantitative analyses show that MPS is preferentially formed in axons in all neuronal types tested here: Spectrin shows a long-range, periodic distribution throughout all axons but appears periodic only in a small fraction of dendrites, typically in the form of isolated patches in subregions of these dendrites. As in dendrites, we also observed patches of periodic spectrin structures in a small fraction of glial-cell processes in four types of glial cells cultured from rodent tissues. Interestingly, despite its strong presence in the axonal shaft, MPS is disrupted in most presynaptic boutons but is present in an appreciable fraction of dendritic spine necks, including some projecting from dendrites where such a periodic structure is not observed in the shaft. Finally, we found that spectrin is capable of adopting a similar periodic organization in neurons of a variety of animal species, including Caenorhabditis elegans, Drosophila, Gallus gallus, Mus musculus, and Homo sapiens.

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Umair, Hassan, Tarik Bin Abdul Latef, Yoshihide Yamada, Wan Nor Liza Binti Wan Mahadi, Mohamadariff Othman, Kamilia Kamardin, Mousa I. Hussein, and Ali Imran Najam. "Tilted Beam Fabry–Perot Antenna with Enhanced Gain and Broadband Low Backscattering." Electronics 10, no. 3 (January 23, 2021): 267. http://dx.doi.org/10.3390/electronics10030267.

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Communication with low radar signature platforms requires antennas with low backscatter, to uphold the low observability attribute of the platforms. In this work, we present the design for a Fabry–Perot (F-P) cavity antenna with low monostatic radar cross section (RCS) and enhanced gain. In addition, peak radiation is tilted inthe elevation plane. This is achieved by incorporating phase gradient metasurface (PGM) with absorptive frequency selective surface (FSS). The periodic surface of metallic square loops with lumped resistors forms the absorptive surface, placed on top of a partially reflecting surface (PRS) with an intervening air gap. The double-sided PRS consists of uniform metallic patches etched in a periodic fashion on its upper side. The bottom surface consists of variable-sized metallic patches, to realize phase gradient. The superstrate assembly is placed at about half free space wavelength above the patch antenna resonating at 6.6 GHz. The antenna’s ground plane and PRS together construct the F-P cavity. A peak gain of 11.5 dBi is achieved at 13° tilt of the elevation plane. Wideband RCS reduction is achieved, spanning 5.6–16 GHz, for x- and y-polarizations of normally incident plane wave. The average RCS reduction is 13 dB. Simulation results with experimental verifications are presented.

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Shah, Preyas N., and Eric S. G. Shaqfeh. "Heat/mass transport in shear flow over a heterogeneous surface with first-order surface-reactive domains." Journal of Fluid Mechanics 782 (October 8, 2015): 260–99. http://dx.doi.org/10.1017/jfm.2015.528.

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Surfaces that include heterogeneous mass transfer at the microscale are ubiquitous in nature and engineering. Many such media are modelled via an effective surface reaction rate or mass transfer coefficient employing the conventional ansatz of kinetically limited transport at the microscale. However, this assumption is not always valid, particularly when there is strong flow. We are interested in modelling reactive and/or porous surfaces that occur in systems where the effective Damköhler number at the microscale can be $O(1)$ and the local Péclet number may be large. In order to expand the range of the effective mass transfer surface coefficient, we study transport from a uniform bath of species in an unbounded shear flow over a flat surface. This surface has a heterogeneous distribution of first-order surface-reactive circular patches (or pores). To understand the physics at the length scale of the patch size, we first analyse the flux to a single reactive patch. We use both analytic and boundary element simulations for this purpose. The shear flow induces a 3-D concentration wake structure downstream of the patch. When two patches are aligned in the shear direction, the wakes interact to reduce the per patch flux compared with the single-patch case. Having determined the length scale of the interaction between two patches, we study the transport to a periodic and disordered distribution of patches again using analytic and boundary integral techniques. We obtain, up to non-dilute patch area fraction, an effective boundary condition for the transport to the patches that depends on the local mass transfer coefficient (or reaction rate) and shear rate. We demonstrate that this boundary condition replaces the details of the heterogeneous surfaces at a wall-normal effective slip distance also determined for non-dilute patch area fractions. The slip distance again depends on the shear rate, and weakly on the reaction rate, and scales with the patch size. These effective boundary conditions can be used directly in large-scale physics simulations as long as the local shear rate, reaction rate and patch area fraction are known.

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35

Miranda, Edson J. P. de, Edilson D. Nobrega, Leopoldo P. R. de Oliveira, and José M. C. Dos Santos. "Elastic wave propagation in metamaterial rods with periodic shunted piezo-patches." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 2 (August 1, 2021): 4303–11. http://dx.doi.org/10.3397/in-2021-2657.

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The wave propagation attenuation in low frequencies by using piezoelectric elastic metamaterials has been developed in recent years. These piezoelectric structures exhibit abnormal properties, different from those found in nature, through the artificial design of the topology or exploring the shunt circuit parameters. In this study, the wave propagation in a 1-D elastic metamaterial rod with periodic arrays of shunted piezo-patches is investigated. This piezoelectric metamaterial rod is capable of filtering the propagation of longitudinal elastic waves over a specified range of frequency, called band gaps. The complex dispersion diagrams are obtained by the extended plane wave expansion (EPWE) and wave finite element (WFE) approaches. The comparison between these methods shows good agreement. The Bragg-type and locally resonant band gaps are opened up. The shunt circuits influence significantly the propagating and the evanescent modes. The results can be used for elastic wave attenuation using piezoelectric periodic structures.

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Shengbing, Chen, Wen Jihong, Wang Gang, Yu Dianlong, and Wen Xisen. "Improved modeling of rods with periodic arrays of shunted piezoelectric patches." Journal of Intelligent Material Systems and Structures 23, no. 14 (June 7, 2012): 1613–21. http://dx.doi.org/10.1177/1045389x12448445.

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Junyi, Lee, and Daniel Stephen Balint. "Optimal shunt parameters for maximising wave attenuation with periodic piezoelectric patches." Journal of Intelligent Material Systems and Structures 28, no. 1 (July 28, 2016): 108–23. http://dx.doi.org/10.1177/1045389x16645861.

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Elastic metamaterials, which have huge potential in wave guiding and attenuation applications, can be built from structures with periodic piezoelectric patch arrays. Passive shunts offer the benefits of simplicity and low cost. In this paper, the effects of the magnitude and phase angle of the shunt impedance on the attenuation constant of a beam with periodic piezoelectric patch arrays were studied in order to determine the optimal shunt that produces the widest and most effective band gaps. The attenuation constants were found to be large when the phase angle is [Formula: see text] rad and when the magnitude decreases exponentially with the excitation frequency. This corresponds to a negative capacitance circuit, which is the optimal shunt for such systems. The attenuation constant of the system reduces significantly when the impedance deviates from the optimal value suggesting other circuits are less effective. The impedance and band structure of resistive–inductive (R-L), negative capacitance and resistive shunts were investigated. As expected, the negative capacitance circuit produces a large band gap, while the R-L circuit only produces a band gap around its natural frequency. The transmissibilities of a finite system with these circuits demonstrated that vibration transmissions are low within the band gaps. Furthermore, the stability of the negative capacitance circuit built using a dual-output second-generation current conveyor (DO-CCII) was examined by studying the pole diagrams. The system was found to be stable in ideal conditions but unstable when parasitic effects are considered. This suggests that the stability of the system is an important consideration for the implementation of this strategy and the different negative impedance converter designs available in the literature should be studied to find a suitable circuit configuration.

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Hosung Choo, Hao Ling, and C. S. Liang. "On a Class of Planar Absorbers With Periodic Square Resistive Patches." IEEE Transactions on Antennas and Propagation 56, no. 7 (July 2008): 2127–30. http://dx.doi.org/10.1109/tap.2008.924766.

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Yang, H. Y. D., Reonghee Kim, and D. R. Jackson. "Design consideration for modeless integrated circuit substrates using planar periodic patches." IEEE Transactions on Microwave Theory and Techniques 48, no. 12 (2000): 2233–39. http://dx.doi.org/10.1109/22.898969.

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Zang, Yong Ju, Ao Zhuang, Xiang Hui Ou, Qi Xin Geng, Qi Ping Chen, and Qi Lin Wu. "Design of ACF Microwave Absorbing Composites with Triangle Patches and Circular Aperture Elements." Materials Science Forum 789 (April 2014): 163–68. http://dx.doi.org/10.4028/www.scientific.net/msf.789.163.

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The combination element frequency selective surface (FSS) with regular triangle patches and circular aperture elements in activated carbon fiber (ACF) felts were designed. The effects of the structure parameters and periodic arrangement of regular triangle patches on ACF felt composites were investigated. As the regular triangle patches were embedded into circular apertures, the combination element ACF felt screen (ACFFS) composites presented fluctuant absorbing characteristics and showed double-band frequency response characteristic including band pass and band stop. When the regular triangle edge length (L) increased, the effective absorption frequency (the reflection loss below-10 dB) shifted to low frequency, and the effective bandwidth increased without reducing the maximum absorption value. When the regular triangle patches (L = 30 mm) were in staggered rows, the effective absorption frequency drifted by 3.1 GHz, and the effective bandwidth was enhanced from 4.3 GHz to 11.0 GHz. Although the regular triangle patches are not central symmetry, it is proved that the absorption properties can be improved obviously by both horizontal polarization and vertical polarization.

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Bashir, Tahir, Han Xiong, Abdul Aziz, Muhammad Qureshi, Haroon Ahmed, Abdul Wahab, and Muhammad Umaid. "Design and Analysis of Reflectarray Compound Unit Cell for 5G Communication." Applied Computational Electromagnetics Society 35, no. 12 (February 15, 2021): 1513–18. http://dx.doi.org/10.47037/2020.aces.j.351209.

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In this paper, a single-layer compound unit element is proposed for reflectarray antenna design operating in Ka-band (26.5-29.5GHz) at the center frequency of 28GHz. A systematic study on the performance of a compound unit element is examined first. The structure of the proposed unit element is a unique combination of two different shape simple patches i.e. cross dipole and square patches. The desired phase range is achieved due to the multi-resonance of both patch elements with a single layer without any air-gap. The compound unit element is simulated by computer models of CST Microwave studio based on the Floquet approach (infinite periodic approach) and it has achieved 348.589o reflection phase range. Furthermore, the analysis of the reflection phase range, S-curve gradient, reflection magnitude, fabrication tolerance, and surface current density is also simulated and demonstrated. Based on the remarkable performance, the proposed element can be considered as the best element of single-beam or multi-beam reflectarray antenna design for 5G applications.

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Chen, Bin, Xinghua Shi, and Huajian Gao. "Apparent fracture/adhesion energy of interfaces with periodic cohesive interactions." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 464, no. 2091 (December 18, 2007): 657–71. http://dx.doi.org/10.1098/rspa.2007.0240.

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The apparent fracture/adhesion energy of an interface with periodic cohesive interactions is of general interest to understanding adhesion via periodic adhesion patches (e.g. between micro- and nanostructured surfaces). There are two important length scales for this class of problems: one corresponds to the period of cohesive interaction and the other is the size of the cohesive zone near the tip of a crack along the interface. By theoretical considerations and numerical simulations, we show that the apparent fracture/adhesion energy depends on the ratio between the period of cohesive interaction and the cohesive zone size: it is equal to the average cohesive energy of the interface if the former is much smaller than the latter but becomes the peak value of the local cohesive energy when the opposite is true. This prediction has been confirmed by numerical simulations on the peeling of a thin-film/strip adhering on a substrate via periodic discrete adhesion patches. Our analysis also provides explanations for a recent molecular dynamics simulation which showed that the apparent adhesion energy of a single-stranded DNA (ssDNA) adhering on a graphite sheet is equal to the peak, rather than the average, value of the van der Waals interaction energy between the ssDNA and the substrate.

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Pagliuca, Giulio, Salvatore Martellucci, Chiara Rosato, Camilla Gallipoli, and Andrea Gallo. "Posttraumatic Parotid Fistula Treated with Transdermal Scopolamine: A Case Report." Case Reports in Surgery 2012 (2012): 1–3. http://dx.doi.org/10.1155/2012/713148.

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A parotid fistula is a rare and extremely unpleasant condition. In this paper, we present the case of a 53-year-old woman with a diagnosis of posttraumatic fistula of the parotid gland. After exclusion of other therapeutic alternatives, it was decided to use transdermal scopolamine patches at sustained release (Scopoderm TTS). This technique consists in the application every three days of a patch with 1.5 mg of scopolamine in the area of the mastoid apophysis; the patch releases a dose of 0.5 mg of the active substance over each 24-hour period. The patient underwent periodic clinical followup over a period of three years, achieving satisfactory results with no significant adverse effects.

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Ren, Tao, Chunchuan Liu, Fengming Li, and Chuanzeng Zhang. "Active tuning of the vibration band gap characteristics of periodic laminated composite metamaterial beams." Journal of Intelligent Material Systems and Structures 31, no. 6 (January 21, 2020): 843–59. http://dx.doi.org/10.1177/1045389x19898757.

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A novel strategy is proposed to investigate the vibration band-gap and active tuning characteristics of the laminated composite metamaterial beams. The piezoelectric actuator/sensor pairs are periodically placed along the laminated composite beam axis so that the vibration frequency band-gap and active tuning characteristics can be induced. The dynamic equations of the laminated composite metamaterial beams bonded by the piezoelectric actuator/sensor pairs are established based on the Euler–Bernoulli beam theory. The negative proportional feedback control strategy is employed to provide the positive active control stiffness for the piezoelectric actuator/sensor patches. The spectral element method is used to calculate the dynamic responses of the laminated composite metamaterial beams with the periodically placed piezoelectric patches, and the calculation accuracy for the dynamic responses is validated by the finite element method. The results demonstrating the high-performance vibration band-gap properties in the low-frequency ranges can be achieved by properly designing the sizes and the number of the piezoelectric patches. Moreover, the vibration band-gap characteristics, especially the band-gap width and the normalized band-gap width with respect to the considered excitation frequency range, can be significantly changed by tuning the structural parameters of the piezoelectric actuators and sensors. In addition, the cross-ply angle of the laminated composite metamaterial beams has significant influences on the band-gap characteristics and the vibration reduction performance of the laminated composite beam structures.

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El-Maghrabi, H. M., Ahmed Mohamed Attiya, and Essam Abdel Haleem Hashish. "DESIGN OF A PERFECT ELECTROMAGNETIC CONDUCTOR (PEMC) BOUNDARY BY USING PERIODIC PATCHES." Progress In Electromagnetics Research M 16 (2011): 159–69. http://dx.doi.org/10.2528/pierm10112201.

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46

Sze, K. Y., and L. Shafai. "Formulation for reflection coefficient phase of infinite periodic array of microstrip patches." Electronics Letters 37, no. 3 (2001): 142. http://dx.doi.org/10.1049/el:20010108.

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Hosokawa, K., S. Taguchi, and Y. Ogawa. "Periodic creation of polar cap patches from auroral transients in the cusp." Journal of Geophysical Research: Space Physics 121, no. 6 (June 2016): 5639–52. http://dx.doi.org/10.1002/2015ja022221.

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Li, Hong-Li, Long Zhang, Zhidong Teng, and Yao-Lin Jiang. "A periodic single species model with intermittent unilateral diffusion in two patches." Journal of Applied Mathematics and Computing 53, no. 1-2 (December 12, 2015): 223–44. http://dx.doi.org/10.1007/s12190-015-0965-8.

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Zhang, Zhengqiu, and Zhicheng Wang. "Periodic solutions of two-patches predator-prey dispersion models with continuous delays." Mathematische Nachrichten 259, no. 1 (October 2003): 99–108. http://dx.doi.org/10.1002/mana.200310098.

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Yuan, Baoyin, Sanyi Tang, and Robert A. Cheke. "Duality in Phase Space and Complex Dynamics of an Integrated Pest Management Network Model." International Journal of Bifurcation and Chaos 25, no. 08 (July 2015): 1550103. http://dx.doi.org/10.1142/s0218127415501035.

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Fragmented habitat patches between which plants and animals can disperse can be modeled as networks with varying degrees of connectivity. A predator–prey model with network structures is proposed for integrated pest management (IPM) with impulsive control actions. The model was analyzed using numerical methods to investigate how factors such as the impulsive period, the releasing constant of natural enemies and the mode of connections between the patches affect pest outbreak patterns and the success or failure of pest control. The concept of the cluster as defined by Holland and Hastings is used to describe variations in results ranging from global synchrony when all patches have identical fluctuations to n-cluster solutions with all patches having different dynamics. Heterogeneity in the initial densities of either pest or natural enemy generally resulted in a variety of cluster oscillations. Surprisingly, if n > 1, the clusters fall into two groups one with low amplitude fluctuations and the other with high amplitude fluctuations (i.e. duality in phase space), implying that control actions radically alter the system's characteristics by inducing duality and more complex dynamics. When the impulsive period is small enough, i.e. the control strategy is undertaken frequently, the pest can be eradicated. As the period increases, the pest's dynamics shift from a steady state to become chaotic with periodic windows and more multicluster oscillations arise for heterogenous initial density distributions. Period-doubling bifurcation and periodic halving cascades occur as the releasing constant of the natural enemy increases. For the same ecological system with five differently connected networks, as the randomness of the connectedness increases, the transient duration becomes smaller and the probability of multicluster oscillations appearing becomes higher.

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Journal articles on the topic 'Periodic patches'

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