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Advances in nanotechnology are impacting biomedicine with the potential to improve disease diagnosis, enhance targeted drug delivery, refine imaging of therapeutic responses, control cell and tissue responses, and guide surgical resection.

This work validates cylindrical IE-GSTC by applying it to physical metasurfaces, i.e. metasurfaces defined by material properties and dimensions rather than by susceptibility tensor components. Previously reported IE-GSTC which was formulated for zero thickness GSTC discontinuity is extended to handle finite thickness of physical metasurfaces. A simple analytical approach is used to extract the bianisotropic susceptibility tensor of concentric, multilayered, magneto-dielectric shell. Plane wave scattering by a physical metasurface constructed of four segments of multilayered, magneto-dielectric metasurface scatterers is used as an example problem to validate cylindrical IEGSTC. A second example considers an opening on the cylindrical metasurface, confirming IE-GSTC can handle metasurfaces with openings. Good agreement is obtained between IE-GSTC results and full wave simulation results for both cases.

This work validates cylindrical IE-GSTC by applying it to physical metasurfaces, i.e. metasurfaces defined by material properties and dimensions rather than by susceptibility tensor components. Previously reported IE-GSTC which was formulated for zero thickness GSTC discontinuity is extended to handle finite thickness of physical metasurfaces. A simple analytical approach is used to extract the bianisotropic susceptibility tensor of concentric, multilayered, magneto-dielectric shell. Plane wave scattering by a physical metasurface constructed of four segments of multilayered, magneto-dielectric metasurface scatterers is used as an example problem to validate cylindrical IEGSTC. A second example considers an opening on the cylindrical metasurface, confirming IE-GSTC can handle metasurfaces with openings. Good agreement is obtained between IE-GSTC results and full wave simulation results for both cases.

Modeling of spherical metasurfaces using generalized sheet transition conditions (GSTCs) and vector wave function (VWF) expansion is presented. The fields internal and external to the metasurface are expanded in terms of spherical VWFs and unknown coefficients. The GSTCs are used to obtain linear relationships between the unknown coefficients. An overdetermined system of equations is then solved by point matching. The method is quasi-analytical, and hence there is no need for meshing, which is encountered in conventional computational electromagnetic methods. This results in the method being extremely fast and hence useful for metasurface optimization. The method is validated by two examples. The formulations presented here can be easily extended to multilayered spherical metasurfaces.

Modeling of circular cylindrical metasurfaces using the method of moments (MoM) based on generalized sheet transition conditions (GSTCs) is presented. GSTCs are used to link the integral equations for fields on the inner and outer contour of the circular cylindrical metasurface. The GSTC-MoM is validated by two examples: 1) anisotropic and gyrotropic metasurface capable of two field transformations; and 2) nongyrotropic metasurface capable of transforming the field generated by an infinite electric line source at origin to the field generated by a displaced electric line source. The formulations presented here can be used as a platform for deriving GSTC-MoM for 3-D spherical and conformal metasurfaces.

A modeling of metasurfaces in the finite-element method (FEM) based on generalized sheet transition conditions (GSTCs) is presented. The discontinuities in electromagnetic fields across a metasurface as represented by the GSTC are modeled by assigning nodes to both the sides of the metasurface. The FEM-GSTC formulation in both 1-D and 2-D domains is derived and implemented. The method is extended to handle more general bianistroptic metasurfaces. The formulations are validated by several illustrative examples.

Conventional strongly coupled magnetic resonance (SCMR) wireless power transfer (WPT) systems have high quality factor ( $Q$ ), leading to limited system bandwidths. In practical applications, especially in human-involved environments, the resonant frequency of SCMR resonators will shift due to the effect of highly dielectric human body. In this letter, a wideband four-coil SCMR WPT system is proposed by improving the coupling between the tx/rx coil and their corresponding resonators. The bandwidth is increased by over 100% compared to a conventional system without sacrificing the efficiency much. The wideband feature is demonstrated by both simulation and measurement. It is analyzed physically and by using an equivalent circuit analysis.

In this paper a forward looking (end fire) synthetic aperture radar (SAR) system is described for the Very deep Autonomous Laser-powered Kilowatt-class Yo-yoing Robotic Ice explorer (VALKYRIE) project. Design and analysis of novel conformal log periodic antennas for the radar and the forward looking SAR ambuguity function is presented. Fabrication and laboratory characterization of the antennas system design and in situ testing of the SAR system are discussed in detail.

Transient analysis of dispersive, periodic structures in the case of obliquely incident plane wave is presented in this work. The Laguerre marching-on-in-degree (MoD) is used for the development of an unconditionally stable algorithm. Due to the unconditional stability, Courant-Freidrich-Levy (CFL) temporal discretization limit can be circumvented resulting in less simulation time compared to the conventional dispersive finite difference time domain (FDTD). This is particularly advantageous for multiscale, dispersive structures. The uniaxial perfectly matched layer (UPML) is implemented in the Laguerre domain. By virtue of the Laguerre decomposition, the presented method can simulate general dispersive media compared to conventional dispersive FDTD which can simulate only standard dispersion models such as Debye, Lorentz and Drude. The formulations are validated by estimating the transmission spectra of an infinite double pole Debye slab and comparing the results with analytical results. Further confirmation is obtained by estimating the transmission spectra of zeroth order Floquet mode of a 1D periodic array of dispersive, square cylinders and comparing the results with periodic method of moments solution.

In this paper an algorithm is described for obtaining the response of Power Distribution Networks (PDN) arising in chip, package or pcb during an early design phase. Results are provided for power grids arising in silicon interposers to validate the approach.

In this paper a forward-looking synthetic aperture radar (IceSAR) system is described for the ‘Very deep Autonomous Laser-powered Kilowatt-class Yo-yoing Robotic Ice explorer’ (VALKYRIE) project. Fabrication and laboratory characterization of novel log periodic antennas for IceSAR and system design and in situ testing of the synthetic aperture radar system are presented.

Accurate electromagnetic and thermal analysis is essential for designing wideband radiometer calibration targets as well as for understanding the electromagnetic wave interaction with these highly absorbing structures. To serve this purpose, a three dimensional dispersive finite difference time domain (FDTD) engine has been developed. We present the various aspects associated with this FDTD formulation, including modeling of dispersive lossy media using piecewise linear recursive convolution (PLRC) and application of uniaxial perfectly matched layer (UPML) absorbing boundary condition and symmetry/periodic boundary conditions to provide high accuracy using moderate computational resources. Time domain modeling of the dispersive radar absorbent material is performed by fitting the measured complex permittivity and permeability data to a series of Debye like terms using genetic algorithm (GA) optimization. The broadband reflectivity spectrum of the calibration target is obtained by transient plane wave excitation. The reflectivity spectra of pyramidal calibration targets in the frequency range [6, 200] GHz is obtained and compared to the geometrical optics limit and a finite element solution. The spectrum depends significantly on the height to base ratio and coating thicknesses of the absorbent material.

This paper presents an approach for the fast accurate computation of several useful Mie-based parameters for homogeneous, spherical, liquid water, and ice hydrometeor distributions over a wide range of frequencies, mean hydrometeor diameters, and physical temperatures as occur in the terrestrial atmosphere. The absorption coefficient, scattering coefficient, backscattering coefficient, and phase asymmetry parameters are cast into functions of three independent variables: frequency, temperature, and mean diameter. An exponential drop size distribution with a constant fractional volume of is used to model polydispersed hydrometeors. The ranges used for frequency, temperature, and mean diameter are [1, 1000] GHz, , and [0.002, 20] mm, respectively. The functions are then sampled on a logarithmic grid. Trivariate cubic spline interpolation using nonuniform basis splines (B-splines) is then used to efficiently represent these 3-D functions in a compact library. By using this method, four important criteria are achieved: 1) fast random computability of any of these parameters given the values of frequency, temperature, and mean diameter; 2) minimal memory usage by storage of only B-spline coefficients; 3) representation of parameters using well-behaved functional forms amenable to analytical differentiation for the evaluation of Jacobians, or alternatively, for higher accuracy, B-spline coefficients calculated using true Jacobian values can be used; and 4) negligibly small and bounded error over the entire domain of the library. These procedures result in considerable acceleration of microwave radiative transfer simulations across a broad frequency spectrum, as demonstrated in calculations for both scattering and nonscattering atmospheres. The methods discussed can also be applied to other geophysical problems requiring rapid calculation of series-based functions of several independent variables, where the function evaluation is a time-consuming process, and maximum error bounds are critical.

The goal of this research has been to develop a standardized fast full-Stokes ocean surface emissivity model with Jacobian for a wind-driven ocean surface applicable at arbitrary microwave frequencies, polarizations, and incidence angles. The model is based on the Ohio State University (OSU) two-scale code for surface emission developed by Johnson (2006, IEEE TGRS, 44, 560) as presented in our 2012 URSI talk. A total of five physical tuning parameters for the model were identified, including the spectral strength and the hydrodynamic modulation factor. The short wave part of the sea surface spectrum is also allowed to have an arbitrary ratio relative to the long wave part. The foam fraction is multiplied by a variable correction factor, and also modulated to allow an anisotropic foam fraction with more foam on the leeward side of a wave.

MICROWAVE and millimeter wave remote sensing offer several advantages over infrared and visible observations. This is primarily due to the fact that microwave radiation is transparent to clouds and aerosols, thereby aiding in the accurate determination of temperature and water-vapor profiles. Radiometer calibration is the process by which a relationship is obtained between the output indicator of the radiometer usually voltage or current and the noise temperature at the radiometer input [1]. Microwave radiometer calibration targets are used in radiometer systems to provide a calibration source of known brightness temperature. Precise absolute calibration of radiometers for many Earth remote sensing applications require knowledge of the brightness temperature when viewing a calibration target to within 100 mK or better. The targets are typically periodic array of wedges or pyramids constructed of a thermally-conductive substrate coated with a thin layer of microwave absorbing material. Microwave absorbent materials are electrically dispersive in nature. The ideal radiometer calibration target should be a blackbody radiator with an emissivity of unity at the frequencies of interest. In order to efficiently design wideband calibration targets, an accurate electromagnetic and thermal analysis of these structures is essential [2]. Electromagnetic and thermal analysis of one-dimensional periodic wedge shaped structures has been presented in [3,4]. This work uses the coupled-wave approach for the electromagnetic analysis. However the work is not extended to two dimensionally periodic (doubly periodic) pyramidal structures. In this work, we have used the three dimensional Finite Difference Time Domain (FDTD) method to perform full wave electromagnetic analysis of doubly periodic pyramidal structures with a thin coating of electrically dispersive radar absorbent materials. Due to the higher accuracy required in microwave radiometry than in traditional electromagnetic or optical full wave simulations, we have developed a new precise 3D FDTD code rather than use commercial software packages. The code can be used to optimize presently used calibration targets as well as develop novel target designs.

Inspired by natural swarming and flocking behaviors, in this paper we study a series of problems concerning motion control for autonomous multiagent formations moving in a two dimensional space and avoiding collision with each other as well as obstacles. We give a hierarchical task map and argue that if the formation is kept rigid via implementation of certain distance maintenance constraints, then no inter-agent collision can happen. We outline recently developed procedures based on graph theory for achieving this. We then take the study further by investigating and discussing two strategies for obstacle avoidance by the entire formation. We present some simulation results for the motion of an asymmetrically controlled formation with no global leader, in presence of multiple obstacles on the plane of interest.

This paper presents a set of decentralized control laws for the cohesive motion of 2-dimensional multi-agent formations. We consider rigid and constraint-consistent formations that can be modeled by directed graphs. We analyze both of the two main hierarchical structures for such 2-dimensional formations: The leader-follower and the three-coleader structures. For each structure, we derive a control scheme that moves a given rigid and constraint-consistent formation whose initial position and orientation are specified to a new desired position and orientation cohesively, i.e., without deforming the shape of the formation during the motion. We elaborate our designs considering the path smoothness, chattering, and agent kinematics issues and demonstrate their effectiveness via a set of simulation results. Manuscript received February 15, 2006. This work is supported by National ICT Australia, which is funded by the Australian Government?s Department of Communications, Information Technology and the Arts and the Australian Research Council through the Backing Australia?s Ability Initiative.