126 research outputs found
Fast inverse nonlinear Fourier transform
No full textThis paper considers the non-Hermitian Zakharov-Shabat scattering problem which forms the basis for defining the SU(2)-nonlinear Fourier transform (NFT). The theoretical underpinnings of this generalization of the conventional Fourier transform is quite well established in the Ablowitz-Kaup-Newell-Segur formalism; however, efficient numerical algorithms that could be employed in practical applications are still unavailable. In this paper, we present two fast inverse NFT algorithms with O(KN+Nlog2N) complexity and a convergence rate of O(N-2), where N is the number of samples of the signal and K is the number of eigenvalues. These algorithms are realized using a new fast layer-peeling (LP) scheme [O(Nlog2N)] together with a new fast Darboux transformation (FDT) algorithm [O(KN+Nlog2N)] previously developed by V. Vaibhav [Phys. Rev. E 96, 063302 (2017)2470-004510.1103/PhysRevE.96.063302]. The proposed fast inverse NFT algorithm proceeds in two steps: The first step involves computing the radiative part of the potential using the fast LP scheme for which the input is synthesized under the assumption that the radiative potential is nonlinearly bandlimited, i.e., the continuous spectrum has a compact support. The second step involves addition of bound states using the FDT algorithm. Finally, the performance of these algorithms is demonstrated through exhaustive numerical tests.</p
FluProCAD: a computational screening workflow for fluorescent protein variants
No full textFluorescent proteins are the backbone of modern high-resolution microscopy, but natural variants often require optimisation to perform effectively. While directed evolution is commonly used for such optimisation, predicting mutation effects requires a deep understanding of photophysics and photochemistry at the atomic scale. Computational chemistry provides a route to obtain such insights from first principles but requires significant expertise. To address this, we developed FluProCAD, a command-line-based workflow that automates system setup and computation of key properties of fluorescent protein mutants using established atomistic models, without the need for prior modeling experience. We applied FluProCAD to two case studies. First, we evaluated the optical and thermodynamic properties of Aequorea victoria Green Fluorescent Protein (avGFP) mutants, successfully reproducing changes in optical responses and folding and dimerisation free energies for five variants. Second, we predicted structural changes in 14 rsGreen0.7 protein variants and validated these models against experimental crystal structures. These results demonstrate the potential of FluProCAD to streamline the optimisation of fluorescent proteins, and expand the computational toolkit for advancing their performance
BARON: Base-Station Authentication Through Core Network for Mobility Management in 5G Networks
Get PDFFifth-generation (5G) cellular communication networks are being deployed on applications beyond mobile devices, including vehicular networks and industry automation. Despite their increasing popularity, 5G networks, as defined by the Third Generation Partnership Project (3GPP), have been shown to be vulnerable against fake base station (FBS) attacks. An adversary carrying out an FBS attack emulates a legitimate base station by setting up a rogue base station. This enables the adversary to control the connection of any user equipment that (inadvertently) connects with the rogue base station. Such an adversary can gather sensitive information belonging to the user. While there is a large body of work focused on the development of tools to detect FBSs, the user equipment will continue to remain vulnerable to an FBS attack. In this paper, we propose BARON, a defense methodology to enable user equipment to determine whether a target base station that it is connecting to is legitimate or rogue. BARON accomplishes this by ensuring that the user receives an authentication token from the target base station which can be computed only by a legitimate and trusted entity. As a consequence, receiving such an authentication token from a base station ensures legitimacy of the base station. We evaluate BARON through extensive experiments on the handover process between base stations in 5G networks. Our experimental results show that BARON introduces an overhead of less than 1% during handover completion, which is 10000× lower than the overhead reported by a state-of-the-art method. BARON is also effective in thwarting an FBS attack and quickly recovering connection to a legitimate base station. Cyber Securit
Higher order convergent fast nonlinear Fourier transform
No full textIt is demonstrated in this letter that linear multistep methods for integrating ordinary differential equations can be used to develop a family of fast forward scattering algorithms with higher orders of convergence. Excluding the cost of computing the discrete eigenvalues, the nonlinear Fourier transform (NFT) algorithm thus obtained has a complexity of O(KN+CpNlog2N) such that the error vanishes as mathop O(N-p) where p ϵ {1,2,3,4} and K is the number of eigenvalues. Such an algorithm can be potentially useful for the recently proposed NFT-based modulation methodology for optical fiber communication. The exposition considers the particular case of the backward differentiation formula (Cp=p3) and the implicit Adams method (Cp=(p-13,p>1) of which the latter proves to be the most accurate family of methods for fast NFT.Accepted Author ManuscriptTeam Raf Van de Pla
Experimental setups for studying homogeneous-isotropic and rotating turbulence in clay suspensions: Preliminary results
Get PDFHomogeneous and isotropic turbulence (HIT) has been at the center of a vast span of research seeking fundamental understanding and insights on the phenomenon of turbulence, which is ubiquitous in nature as well as engineering. The HIT assumption greatly simplifies the analytical treatment of turbulence, however creating truly HIT conditions in experiments has still remained a challenge and most research has focused on Newtonian fluids. Here we uses two different approaches to create HIT in water and aqueous suspension of Laponite clay, a shear-thinning fluid. The first approach involving flow actuators placed symmetrically around an enclosed volume has been used by past studies for creating small regions of HIT in gaseous media. We show using planar particle image velocimetry that our HIT setup is capable of producing low Taylor microscale Reynolds number HIT region of 20 mm x 20 mm in liquid media. Comparison of temporal spectra in water and aqueous clay suspension cases showed that presence of clay significantly alters the scaling of the inertial subrange and increases the Taylor microscale Reynolds number, in addition to suppressing the mean flow. The second approach uses random actuation of jets to stir fluid in a tank, which has been used by past studies to create large HIT regions. We have built a smaller version of this concept with the aim to create high Taylor microscale Reynolds number flow in water and clay suspensions.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2022-05-01The student, Vaibhav Vinay Tipnis, accepted the attached license on 2020-05-08 at 16:14.The student, Vaibhav Vinay Tipnis, submitted this Thesis for approval on 2020-05-08 at 16:39.This Thesis was approved for publication on 2020-05-13 at 07:30.DSpace SAF Submission Ingestion Package generated from Vireo submission #15303 on 2020-08-25 at 17:30:47Made available in DSpace on 2020-08-26T23:58:45Z (GMT). No. of bitstreams: 2
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Pulse de-icing for aircraft applications
Get PDFIce formation and accumulation on aircraft is a major problem in aviation. Icing is directly responsible for fatal aircraft incidents, limiting the safety of air travel and requiring expensive, inefficient, and sometimes ineffective de-icing strategies. In this work, we develop and study electro-thermal pulse deicing capable of ensuring efficient and rapid removal of ice from aircraft during on-ground, takeoff, or flight operation. The pulse approach enables the efficient melting of a thin (<100 µm) ice layer at the aircraft surface in order to limit parasitic heat losses. Only the interface is allowed to melt, with the rest of the ice sliding on the melt lubrication layer due to aerodynamic forces. To study pulse deicing, we develop a transient thermal-hydrodynamic numerical model that accounts for multiple phases and materials, specific and latent heating effects, melt layer hydrodynamics, as well as boundary layer effects. To identify optimal de-icing strategies, we use our model to study the effects of heater thickness (50 µm < t_h < 1 mm), substrate electrical insulation thickness (10 µm < t_i < 1 mm), pulse duration (0.2 s < ∆t_pulse < 4.2 s), and pulse energy (5 KJ < E < 650 KJ). Optimum operating points are identified for large (~100 m, Boeing 747), mid-size (~10 m, Embraer E175) and small (~1 m Cessna 172) aircraft. The scale-dependent thermal-hydraulic model results are used to estimate input conditions required for de-icing and integrated into an electrical model considering energy storage, power electronics, integration, and layout, to achieve overall volumetric and gravimetric power density optimization.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2023-05-01The student, Vaibhav Agarwal, accepted the attached license on 2021-04-26 at 14:24.The student, Vaibhav Agarwal, submitted this Thesis for approval on 2021-04-26 at 14:33.This Thesis was approved for publication on 2021-04-27 at 15:12.DSpace SAF Submission Ingestion Package generated from Vireo submission #16562 on 2021-09-16 at 20:14:22Made available in DSpace on 2021-09-17T04:06:53Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-04-27Embargo set by: Seth Robbins for item 118705
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Nonlinear Fourier transform of time-limited and one-sided signals
No full textIn this article, we study the properties of the nonlinear Fourier spectrum in order to gain better control of the temporal support of the signals synthesized using the inverse nonlinear Fourier transform. In particular, we provide necessary and sufficient conditions satisfied by the nonlinear Fourier spectrum such that the generated signal has a prescribed support. In our exposition, we assume that the support is a simply connected domain that is either a bounded interval or the half-line, which amounts to studying the class of signals which are either time-limited or one-sided, respectively. Further, it is shown that the analyticity properties of the scattering coefficients of the aforementioned classes of signals can be exploited to improve the numerical conditioning of the differential approach of inverse scattering. Here, we also revisit the integral approach of inverse scattering and provide the correct derivation of the so called Töplitz inner-bordering algorithm. Finally, we conduct extensive numerical tests in order to verify the analytical results presented in the article. These tests also provide us an opportunity to compare the performance of the two aforementioned numerical approaches in terms of accuracy and complexity of computations.Accepted Author ManuscriptTeam Raf Van de Pla
Exact solution of the Zakharov–Shabat scattering problem for doubly-truncated multisoliton potentials
No full textRecent studies have revealed that multisoliton solutions of the nonlinear Schrödinger equation, as carriers of information, offer a promising solution to the problem of nonlinear signal distortions in fiber optic channels. In any nonlinear Fourier transform based transmission methodology seeking to modulate the discrete spectrum of the multisolitons, choice of an appropriate windowing function is an important design issue on account of the unbounded support of such signals. Here, we consider the rectangle function as the windowing function for the multisolitonic signal and provide a recipe for computing the exact solution of the associated Zakharov–Shabat (ZS) scattering problem for the windowed/doubly-truncated multisoliton potential. The idea consists in expressing the Jost solution of the doubly-truncated multisoliton potential in terms of the Jost solution of the original potential. The proposed method allows us to avoid prohibitive numerical computations normally required in order to accurately quantify the effect of time-domain windowing on the nonlinear Fourier spectrum of the multisolitonic signals. Further, the method devised in this work also applies to general type of signals admissible as ZS scattering potential, and, may prove to be a useful tool in the theoretical analysis of such systems.Accepted Author ManuscriptTeam Raf Van de Pla
Efficient Nonlinear Fourier Transform algorithms of orderfFour on equispaced grid
No full textWe explore two classes of exponential integrators, in this letter, to design the nonlinear Fourier transform (NFT) algorithms with a convergence order of four on an equispaced grid. The integrating factor-based method in the class of the Runge-Kutta methods yields algorithms with complexity O(N\log2N) (where N is the number of samples of the signal), which have superior accuracy-complexity tradeoff than any of the fast methods known currently. The integrators based on Magnus series expansion, namely, standard and commutator-free Magnus methods yield the algorithms of complexity O(N2) that have superior error behavior than that of the fast methods.Accepted Author ManuscriptTeam Raf Van de Pla
Molecular Dynamics Simulations on the Elastic Properties of Polypropylene Bionanocomposite Reinforced with Cellulose Nanofibrils
No full textCellulose-reinforced polypropylene bionanocomposites can show improved elastic properties over their pure polypropylene counterparts. We have used equilibrium and non-equilibrium molecular dynamics (MD) simulations to study the elastic properties of polypropylene bionanocomposite systems composed of cellulose nanofibrils (CNF), polypropylene (PP) matrix, and maleic anhydride (MAH) coupling agent. The components of the bionanocomposite were parametrized for compatibility with the AMBER14SB force fields. The elastic properties of pure PP systems converge for the chains with at least 20 monomers. The ratio of cellulose in CNF-PP bionanocomposites strongly affects their elastic properties. The elastic modulus of CNF-PP bionanocomposites shows small improvement when the adhesion between hydrophobic and hydrophilic components is facilitated by a MAH coupling agent. The results demonstrate how fully-atomistic MD simulations can be systematically used to evaluate the elastic properties of CNF-PP bionanocomposites and to make predictions that are in agreement with experiments
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