Theodoros Tsiboukis

• Aristotle University of Thessaloniki

Electromagnetic (EM) fields triggered by lightning strikes are likely to display non-negligible variability in practice, with an apparent effect on various quantities of interest, such as induced voltages on transmission lines. This paper investigates the stochastic properties of lightning-generated fields, when the latter are affected by random gr...

We present and validate a computational approach that enables the quantification of time-dependent uncertainty in axially-symmetric electromagnetic (EM) problems, in the context of a unique simulation. In essence, the finite-difference time-domain (FDTD) method, adapted to model bodies of revolution (BOR), is combined with truncated polynomial-chao...

The performance of optical filters with resonant waveguide gratings is investigated numerically in a stochastic context, assuming random fluctuations of various design variables. Specifically, we derive stochastic models based on polynomial chaos expansions, whose involved coefficients are obtained by computing spectral projections via sparse-grid...

Purpose Important statistical variations are likely to appear in the propagation of surface plasmon polariton waves atop the surface of graphene sheets, degrading the expected performance of real-life THz applications. It is the objective of this paper to introduce an efficient numerical algorithm that is able to accurately and rapidly predict the...

The development of an accurate convolutional perfectly matched layer for the efficient termination of infinite graphene structures is introduced in this paper. Initially, the popular two-dimensional material receives the appropriate theoretical analysis, which reveals the necessity of a flexible terminating condition that can enhance the performanc...

The performance of optical filters with resonant waveguide gratings is predicted numerically, assuming random fluctuations of various design variables. Specifically, we derive stochastic models based on polynomial-chaos expansions (PCEs), by employing a stochastic collocation (SC) approach that exploits the rigorous coupled-wave analysis (RCWA) det...

The rigorous design of arbitrarily shaped graphene and nanocomposite structures in realistic electromagnetic compatibility applications is presented in this paper by means of a combined finite-volume time-domain methodology. The new 3D formulation proposes a set of adjustable-order derivative approximators in general curvilinear coordinates and an...

The aim of this paper is to investigate the impact of the ground-material uncertainty on the properties of electromagnetic fields generated by lightning strikes. Although several analytical as well as numerical approaches have been proposed throughout previous years for the prediction of lightning-induced fields, these are mostly applied within a f...

An efficient and consistent methodology is developed in this paper for the precise evaluation of unknown dielectric permittivity media parameters involved in the design of 3-D waveguide structures. In essence, the selected configuration is numerically solved for a set of predetermined permittivity values by means of a time-domain (herein, the finit...

A systematic technique for the accurate implementation of electromagnetic resonance-based wireless power transfer (WPT) implementations by means of diverse metamaterials is presented in this paper. To this aim, two distinct resonating elements are selected, i.e. the edge-coupled split ring resonator (EC-SRR) and the E2 SRR. In particular, the macro...

The computation of the reflection/transmission coefficients from normally illuminated bianisotropic metamaterial slabs through a rigorous method is presented in this paper. The bianisotropic particles that compose finite slabs are approximated as electric and magnetic dipoles. Modeling these slabs as a succession of 2D arrays, the interaction of al...

Purpose Metamaterials have been utilised in several exciting configurations such as tuneable reflectors, reconfigurable absorbers, and programmable modulators, triggering intense research efforts. Among them, the ability to steer the radiation pattern of a single antenna component by employing a metamaterial-based superstrate is considered crucial...

The finite-difference time-domain method is herein combined with polynomial-chaos expansions for the study of axially-symmetric structures featuring material uncertainties. By exploiting the problem's periodicity, we reduce the high computational burden of fully 3D simulations, and reliably extract the necessary statistical information from a singl...

An efficient methodology is developed to analyze 3-D waveguide structures when their dielectric permittivity parameters are unknown or under optimization. Mainly, the configuration is numerically solved for a set of predetermined permittivity values through a time-domain (herein the FDTD) technique at least twice, depending on the desired accuracy....

An efficient cloaking-shielding technique based on the use of a double superstrate-layer overlay is developed in this paper for planar microstrips. The metamaterial-inspired formulation reduces considerably the induced on the strip current and the reflected from the microstrip electric field, thus alleviating the electromagnetic susceptibility of m...

Purpose – Wireless power transfer (WPT) is deemed as an emerging technology with exciting applications, like wireless charging devices, and electric vehicles, whereas metamaterials exhibit exceptional properties. For every WPT system that occupies coupled magnetic resonances, it is also mandatory to involve resonators. The purpose of this paper is...

Purpose – Metamaterials are artificially tailored complex media with extraordinary properties, not available in nature. Due to their unique performance, they are considered as a crucial component of modern radio-frequency technology, especially in the THz regime. However, their lack of wide spectral bandwidths introduce constraints for realistic ap...

A family of consistent thin-wire representation models blended with a 3-D optimized vector finite-element time-domain/finite-difference time-domain method is developed in this paper for nanomaterial and graphene devices. Based on a tailored set of telegrapher’s equations, the novel technique approximates traveling waves along the radial direction o...

A reconfigurable THz complex medium, consisting of fundamental piezoelectric micro-devices, is introduced in this paper. By actuating the piezoelectric modules, a controllable metamaterial, presenting enhanced bandwidth tunability, is accomplished. Two diverse polarization topologies are examined, revealing the anisotropic performance of this mater...

Aiming at the minimization of numerical dispersion effects in finite-difference time-domain (FDTD) simulations, we investigate the potential of introducing frequency-dependent coefficients in the approximations of differential operators. The proposed methodology exploits some previous results on optimized finite-differences, but initially avoids th...

The subject of this paper pertains to the construction of finite-difference expressions with minimized, as well as controllable discretization errors, suitable for 3D FDTD simulations in large-scale setups. The proposed spatial approximations are designed to mimic the behavior of the exact operators, when applied to plane-wave trial functions. To e...

Incorporating standard high-order spatial approximations in the alternating-direction implicit (ADI) finite-difference time-domain (FDTD) method does not suffice for improving the technique’s accuracy, as these operators are capable of reducing spatial errors only. We herein develop an alternative design procedure, which results in the construction...

The systematic and accurate design process of realistic nanocomposite applications and finite-sized graphene setups with arbitrary media uncertainties is presented in this paper via a 3-D covariant/contravariant stochastic finite-difference time-domain method. The new technique uses extra nodes pertinent to a convex combination of all obtainable sp...

We develop a methodology that enables the proper introduction of high-order spatial operators in an unconditionally-stable, split-step, finite-difference time-domain scheme. The proposed approach yields spatial approximations that guarantee better balancing of space-time errors, compared to standard fourth-order expressions. The latter are not as e...

The consistent analysis of metallic screens perforated with subwavelength apertures of diverse geometrical patterns (metascreens) by means of a systematic methodology is presented in this paper. The principal concept of the new technique stems from the efficient characterization—via the use of effective surface parameters—of the metascreen’s comple...

A 3-D curvilinear stochastic finite-difference time-domain (S-FDTD) technique on modern graphics processing units (GPUs) is introduced in this paper for complex media with high levels of statistically-variable heterogeneities. The novel accelerated methodology develops a robust covariant/contravariant dual-grid tessellation and estimates the mean v...

A complete computational framework for the efficient study of lightning-induced electromagnetic fields and solution of pertinent problems with uncertainties in realistic environments is presented in this paper. The latter often involve various factors, such as material inhomogeneities, rough terrain surfaces, and irregular lightning channels that m...

In this paper, an efficient integral equation method is developed for the response and scattering characteristics of cloaked two-dimensional planar microstrip receiving antennas. The featured technique combines the Green’s function for the strip-free structure with the decomposition of the strip into cylindrical thin wires and a radiation integral...

The electromagnetic interactions of planar microstrips with their environment are examined in this paper, and a metamaterial-based cloaking process is proposed to diminish the induced current on the strip and the resulting scattered far-field. The featured mathematical analysis employs the Green's function for the strip-free structure, the radiatio...

Purpose – The locally one-dimensional (LOD) finite-difference time-domain (FDTD) method features unconditional stability, yet its low accuracy in time can potentially become detrimental. Regarding the improvement of the method’s reliability, existing solutions introduce high-order spatial operators, which nevertheless cannot deal with the augmented...

Purpose – Stochastic uncertainties in material parameters have a significant impact on the analysis of real-world electromagnetic compatibility (EMC) problems. Conventional approaches via the Monte-Carlo scheme attempt to provide viable solutions, yet at the expense of prohibitively elongated simulations and system overhead, due to the large amount...

A curvilinear stochastic finite-difference time-domain (S-FDTD) methodology is presented in this paper for the systematic analysis of lightning-induced fields over rough terrains with statistical uncertainties. The novel 3-D technique stems from a covariant/contravariant formulation which can profitably handle the variation of specific parameters d...

We present two methodologies that improve the performance of the alternatingdirection-implicit (ADI) finite-difference time-domain (FDTD) scheme. The first one exploits optimized spatial operators and implements an artificial-anisotropy approach, so that errors around a central frequency are minimized. According to the second scheme, a matching-ter...

A tunable THz metamaterial, consisting of fundamental piezoelectric micro-devices, is introduced in this paper. By actuating the piezoelectric components, a controllable complex medium, presenting enhanced bandwidth reconfigurability, is accomplished. The advantages of the proposed structure are sufficiently clarified by means of several numerical...

An elaborate evaluation regarding the efficiency of a novel wireless power transfer (WPT) system, which incorporates spiral split-ring resonators (S-SRRs) as its fundamental blocks, is systematically conducted in this paper. The proposed configuration unveils a remarkable improvement of the power delivered to the load, as verified by several numeri...

An elaborate investigation regarding the efficiency of a novel metamaterial-based wireless power transfer (WPT) system, capable of delivering useful energy to the nodes of a nanonetwork, is systematically pursued in this paper. The WPT apparatus incorporates metamaterial fundamental blocks as its elementary resonators to exploit magnetic resonance...

A complex medium acting as THz modulator for nanonetwork communications, is introduced in this paper. The proposed device stems from the incorporation of a V-beam electrothermal actuator as a tuning apparatus in an electric field driven LC (ELC) resonator. When a suitable actuation voltage is enforced on the electrothermal microelectromechanical sy...

In this paper, bent-beam actuators are exploited to develop novel programmable SRRs, envisaging a THz modulation capability, while simultaneously offering an advanced bandwidth improvement. Extensive numerical simulations through the finite element method (FEM) verify the merits of the proposed configuration.

A systematic investigation concerning the efficiency of a novel wireless power transfer (WPT) system, which utilizes interdigitated split-ring resonators (SRRs) as its elementary blocks, is comprehensively conducted in this paper. The proposed arrangement reveals a noteworthy enhancement of the power delivered to the load as well as a promising tun...

The involvement of piezoelectric micro-electromechanical systems (MEMS) actuators to efficiently implement controllable electric field driven LC (ELC) resonators is introduced in this paper. The new device enables the modification of the structural features of an ELC-based complex medium, unveiling in this manner a significant THz modulation capabi...

A hybrid VFETD/FDTD method is presented for the nondestructive evaluation of 3-D nanoscale components. The new scheme blends a compact stencil process with vector finite elements and divides the space into tightly-coupled blocks. A key asset is that all state-space models are derived via a Krylov-based scheme and scaled Laguerre functions, which de...

The consistent analysis of complex antenna setups with statistically varying media attributes is performed in this paper through a 3-D curvilinear stochastic finite-difference timedomain technique. The new method generalizes the concept of covariant/contravariant metrics for curved structures and derives the mean value and standard deviation of fie...

We present an improved version of the locally-one-dimensional finite-difference time-domain method in 2-D formulation, featuring spatial expressions derived by an error-amending procedure. The latter targets at the balanced treatment of space–time flaws, and assures the efficient exploitation of four-point spatial operators that now depend on the t...

A spectrally optimized stochastic finite-volume time-domain technique is developed in this paper for the consistent analysis of 3-D nanoscale devices with statistically varying media heterogeneities. The novel algorithm is found on a compact block state-space framework and offers single-run evaluations of the mean value and standard deviation, thus...

The development of a robust terminating boundary scheme for the transverse magnetic surface plasmon polaritons, supported on graphene, is introduced in this paper and incorporated in the finite-difference time-domain (FDTD) method. First, the 2-D FDTD algorithm is adjusted to efficiently model the graphene sheet as a surface conductivity, and the e...

A tunable metamaterial, derived from the combination of two-hot-arm electrothermal actuators with a split-ring resonator, is introduced in this paper. Accomplishing a reliable control of the tip displacement, the selected set of radio-frequency microelectromechanical systems (RF-MEMS) circumvent the undesired bandwidth constraints of existing struc...

A non-local surface susceptibility model for the consistent description of periodic metafilms formed by arbitrarily-shaped, electrically-small, bianisotropic scatterers is developed in this paper. The rigorous scheme is based on the point-dipole approximation technique and is valid for any polarization and propagation direction of an electromagneti...

A reconfigurable THz complex medium, obtained from the embedment of a V-beam electrothermal actuator as a tuning mechanism in a split-ring resonator, is proposed in this paper. When the appropriate actuation voltage is applied on the electrothermal microelectromechanical systems, a controllable metamaterial, presenting enhanced bandwidth tunability...

A programmable THz metamaterial, derived from the utilisation of a piezoelectric controlled microgripper as a split-ring resonator (SRR), is introduced in this paper. By applying the appropriate actuation voltage on the piezoelectric microelectromechanical systems (MEMS), a reconfigurable complex medium, offering enhanced bandwidth tunability, is a...

We present a computational framework for the prediction of electromagnetic fields in lightning problems which, unlike common methodologies, can efficiently incorporate the statistical variations that characterize the ground electric parameters. Our full-wave technique is based on the three-dimensional (3D) extension of the stochastic finite-differe...

A class of nonstandard locally one-dimensional finite-difference time-domain schemes is developed in this paper for the accurate characterization of crosstalk and intermodulation distortions in complicated nanostructured interconnects. The novel 3-D methodology introduces a general curvilinear discretization to consistently treat the rapidly varyin...

A consistent time-domain methodology for the systematic design and broadband assessment of complicated nanostructured EMC devices is introduced in this paper. The novel technique combines a family of nonstandard locally one-dimensional finite-difference time-domain schemes with the advanced features of contemporary graphics processor units in gener...

We present and validate a computational approach for the efficient calculation of lightning-produced electromagnetic fields and solution of pertinent problems in realistic environments. Given that various factors, such as ground-material inhomogeneities and irregular earth surface, may inhibit the utilization of simplified approaches, the finite-di...

The consistent combination of uneven space-time orders in finite-difference time-domain (FDTD) algorithms is the subject of this paper. When low-order time integration is used in conjunction with high-order spatial expressions, the operation of the numerical scheme close to the stability limit causes degraded performance and slow convergence. By ex...

A reduced-order modeling FDTD/vector finite-element time-domain technique is introduced in this paper, for the rigorous and cost-effective study of multiconductor nanoscale structures. The new methodology blends a compact stencil-optimized discretization process with general vector finite elements via the pertinent coupling conditions and divides t...

An efficient 3-D FDTD formulation for the precise analysis of electromagnetic phenomena in graphene structures is presented in this paper. The new concept considers the surface nature of graphene's conductivity and encompasses it directly into the integral form of Maxwell's equations, avoiding the necessity to discretize the material's transverse d...

The most important surface susceptibility models for the electromagnetic characterization of periodic metafilms, based on the dipole approximation method, are systematically analyzed in this paper. Specifically, two well-known techniques, which lead to a set of local effective surface parameters, are investigated along with a new dynamic non-local...

A reconfigurable THz metamaterial, obtained from the exclusive exploitation of a piezoelectric microgripper as a split-ring resonator, is introduced in this paper. By applying the appropriate actuation voltage on the piezoelectric component, a controllable complex medium, presenting enhanced bandwidth tunability, is accomplished. Extensive numerica...

A robust implementation of a stochastic finite-difference time-domain (S-FDTD) technique on modern graphics processing units (GPU) is introduced in this paper for complex media with high levels of statistically-variable heterogeneities. The featured method is compared to the multiple-realisation Monte-Carlo FDTD process, while both schemes are deve...

A programmable THz metamaterial, derived from the utilization of a piezoelectric controlled microgripper as a split-ring resonator (SRR), is introduced in this paper. By applying the appropriate actuation voltage on the piezoelectric microelectromechanical systems (MEMS), a reconfigurable complex medium, offering enhanced bandwidth tunability, is a...

A reconfigurable THz complex medium, obtained from the embedment of a V-beam electrothermal actuator as a tuning mechanism in a split-ring resonator (SRR), is proposed in this paper. When the appropriate actuation voltage is applied on the electrothermal microelectromechanical systems (MEMS), a controllable metamaterial, presenting enhanced bandwid...

The main topic of this book chapter is the introduction and analysis of complex materials with programmable nature, derived from the combination of double two-hot-arm electrothermal actuators with a split-ring resonator (SRR). The proposed design allows transition between conventional and mu-negative (MNG) performance, along with bandwidth tunabili...

A reconfigurable THz complex medium, presenting epsilon-negative (ENG) performance, is introduced in this paper. The proposed device exploits piezoelectric actuators to control the structural characteristics of an electric field driven LC (ELC) resonator. By setting the appropriate actuation voltage on the piezoelectric microelectromechanical syste...

A systematic method for the efficient design of narrowband filters founded on the extraordinary transmission via single fishnet structures (SFSs) is presented in this paper. Essentially, due to its strong resonant behavior, this phenomenon is proven suitable for the implementation of high-Q devices. The new design formulas are derived through the c...

In this paper, analytical expressions for the co- and cross-polarized scattering coefficients of periodic metafilms comprising arbitrary meta-atoms are systematically derived. These formulas are obtained under the assumption that the metafilm is characterized via a suitable surface susceptibility model. The novel results are successfully employed f...

A novel surface susceptibility model for periodic metafilms of electrically-small bianisotropic meta-atoms is analytically derived in this paper. The featured algorithm results in a matrix of non-local surface effective parameters, unlike most of the existing characterization techniques. The accuracy of the proposed methodology is verified by the e...

An efficient technique for the electromagnetic modelling of metallic screens perforated with subwavelength apertures of various geometrical shapes is introduced in this paper. The proposed method is based on the characterisation – in terms of effective surface parameters – of the complementary array of scatterers and the Babinet duality principle....

In the above titled paper (ibid., vol. 60, no. 12, pp. 5753-5767, Dec. 2012), the implementation of the retrieval algorithm introduced in [2], [3] (therein numbered as [18, [22]) was incorrect. The corrected results are presented here.

A class of volume-optimized pyramidal log-periodic antennas (PLPAs) with an adjustable ultra wideband performance is introduced in this paper. To this aim, a parametric analysis is initially conducted to decrease the total size of the prototype Euclidean-toothed PLPA. The new structures are based on the concept of meander curves, which leads to eff...

In this paper, a computational methodology for the capacitance extraction of metamaterial resonators, like the edge-coupled split ring resonator (EC-SRR), is introduced. Initially, the new algorithm treats the EC-SRR as an open two-conductor system and determines its capacitance matrix via a static finite difference solver. This matrix is then util...

In this paper, a new method for the consistent analysis of periodic metasurfaces with bianisotropic particles is introduced. The proposed technique combines a microscopic modeling approach at the level of the constituting meta-atoms with a macroscopic equivalent surface characterization, to unambiguously determine a set of surface susceptibilities...

In this paper, a family of 3-D finite-difference time-domain schemes is developed in order to investigate electromagnetic wave interactions in graphene arrangements. The novel algorithm excites the computational space through a modified total-field/scattered-field formulation with a focused wideband pulse of oblique incidence. In particular, the ar...

A complex material with programmable nature, derived from the combination of double two-hot-arm electrothermal actuators with a split-ring resonator (SRR), is introduced. The proposed design allows transition between conventional and mu-negative performance, along with bandwidth tunability. Several numerical results support its controllable behavio...

A bianisotropic matrix technique is presented for the development of a homogenized surface susceptibility model of metasurfaces with arbitrary uniaxially mono-anisotropic scatterers, illuminated by obliquely incident TE waves. Based on the sole assumption that the scatterers can be described by point-dipoles, the proposed formulation establishes a...

An efficient method for the characterization of metasurfaces formed by bianisotropic particles is introduced in this paper. The new algorithm properly considers the microscopic polarizabilities of the individual scatterers and associates the scattered fields from the metasurface with the equivalent surface polarization distributions induced on it v...

A generalized conformal time-domain method with adjustable spectral accuracy is introduced in this paper for the consistent analysis of large-scale electromagnetic compatibility problems. The novel 3-D hybrid schemes blend a stenciloptimized finite-volume time-domain and a multimodal Fourier-Chebyshev pseudo-spectral time-domain algorithm that spli...

An efficient technique for the design of millimeter-wave, graphene-loaded waveguides that prevent the propagation of selected higher-order modes and do not allow a significant energy portion to be reflected back to the source plane, is developed in this paper. The optimal location of graphene films is obtained via the theoretical calculation of the...

In this paper, analytical S-parameters expressions for periodic metasurfaces of uniaxially monoanisotropic scatterers under TE wave incidence, are extracted. Unlike existing formulas, the derived expressions include the effect of off-diagonal terms in the susceptibility matrix, which represent a weak form of spatial dispersion at the lattice level....

A generalized conformal time-domain method with adjustable spectral accuracy is introduced in this paper for the consistent analysis of large-scale electromagnetic compatibility problems. The novel 3-D hybrid schemes blend a stenciloptimized finite-volume time-domain and a multimodal Fourier-Chebyshev pseudo-spectral time-domain algorithm that spli...

An enhanced metamaterial absorber based on the circumscribed-cross resonator is introduced in this paper. The new structure is polarization-independent, due to the symmetry of its unit cell, and is proven efficient for the attenuation of obliquely incident waves. The absorption mechanism is thoroughly investigated and is found to be mainly related...

A systematic three-dimensional (3D) frequency-dependent finite-difference time-domain technique for the consistent and rigorous analysis of infinite graphene layers is developed in this study. The generalised formulation divides the overall geometry into unit cells and applies the appropriate Floquet periodic boundary conditions to their lateral su...

Graphene is a newly fabricated 2-D material that has attracted much interest due to its potential electronic applications. In this paper, a fully 3-D FDTD-based scheme is proposed for the simulation of electromagnetic interactions with graphene sheets. Graphene's 2-D character is accounted for by a subcell technique, while its dispersive nature is...

A generalized methodology for the rigorous characterization of metafilms/metasurfaces through a set of electric and magnetic surface susceptibilities is presented in this paper. According to the novel formulation, the particle polarizabilities of the metafilm are extracted from the -parameters of a normally incident plane wave and are efficiently r...

The accurate and fully 3-D analysis of graphene surface conductivity models by means of a frequency-dependent finite-difference time-domain method is introduced in this paper. For the infinite sheet to be consistently simulated, the novel technique uses a set of periodic boundary conditions that lead to a unit cell excited with a spectral scheme in...

In this book chapter, a class of reconfigurable metamaterials, obtained from the combination of two-hot-arm electro-thermal actuators with a split-ring resonator, is presented and thoroughly investigated. Offering a reliable control of the tip displacement, the selected actuators overcome the undesired bandwidth constraints of existing structures a...

In this paper, the design of planar, double-negative metamaterials using electric and magnetic resonators is presented. The effective parameters of the proposed structures are extracted from the transmission and reflection coefficients by employing the Kramers-Kronig relations to solve the branch problem in the determination of the effective refrac...

An efficient finite-difference time-domain methodology combined with a robust subcell formulation for the precise analysis of infinite graphene sheets is introduced in this paper. The graphene surface conductivity is modeled through a volume conductivity profile, with the pertinent periodic boundary conditions applied to the unit cell's lateral sur...

A class of efficient pyramidal log-periodic antennas (PLPAs) with an adjustable ultra wideband performance is presented in this paper. The proposed structures are thoroughly investigated in terms of their radiation characteristics by means of a 3-D finite-difference time-domain (FDTD) formulation, while a parametric analysis is conducted in an atte...

The concept of folded bowtie wideband antennas is introduced in this paper. To this aim, the design procedure employs a Peano space-filling curve approach which leads to an entire family of combined bowtie-Peano antennas (BPA). The new structures efficiently blend the broadband performance of bowtie antennas with the compactness of Peano forms. In...

The consistent and precise characterization of metafilms/metasurfaces via a set of electric and magnetic surface susceptibilities is presented in this paper by means of a systematic technique. The new method, which can be regarded as an enhanced generalization of existing approaches, offers extra degrees of freedom and leads to very satisfactory so...

The concept of folded bowtie antennas is presented in this paper. To pursue this objective, a Peano space-filling curve approach is utilised. Thus, the combined Bowtie-Peano antenna (BPA) is introduced, exhibiting the broadband performance of the bowtie antennas combined with the compactness of the Peano designs. Numerical results obtained via a Fi...

A reconfigurable metamaterial, obtained from the combination of two-hot-arm electrothermal actuators with a split-ring resonator, is proposed. Offering a reliable control of the tip displacement, the selected actuators overcome the undesired bandwidth constraints of existing structures and establish significant levels of tunability.