CyberSec Research

Recent studies have applied variational calculus, conformal mapping, and point transformations to generalize the one-dimensional (1D) space-charge limited current density (SCLCD) and electron emission mechanisms to nonplanar geometries; however, these assessments have focused on extending the Child-Langmuir law (CLL) for SCLCD in vacuum. Since the charge in the diode is independent of coordinate system (i.e., covariant), we apply bijective point transformations to extend the Mott-Gurney law (MGL) for the SCLCD in a collisional or semiconductor gap to nonplanar 1D geometries. This yields a modified MGL that replaces the Cartesian gap distance with a canonical gap distance that may be written generally in terms of geometric scale factors that are known for multiple geometries. We tabulate results for common geometries. Such an approach may be applied to any current density, including non-space-charge limited gaps and SCLCD that may fall between the CLL and MGL.

Arrayed Waveguide Gratings (AWGs) are widely used photonic components for splitting and combining different wavelengths of light. They play a key role in wavelength division multiplexing (WDM) systems by enabling efficient routing of multiple data channels over a single optical fiber and as a building block for various optical signal processing, computing, imaging, and spectroscopic applications. Recently, there has been growing interest in integrating AWGs in ferroelectric material platforms, as the platform simultaneously provide efficient electro-optic modulation capability and thus hold the promise for fully integrated WDM transmitters. To date, several demonstrations have been made in the X-cut thin-film lithium niobate ($\mathrm{LiNbO}_3$) platform, yet, the large anisotropy of $\mathrm{LiNbO}_3$ complicates the design and degrades the performance of the AWGs. To address this limitation, we use the recently developed photonic integrated circuits (PICs) based on thin-film lithium tantalate ($\mathrm{LiTaO}_3$), a material with a similar Pockels coefficient as $\mathrm{LiNbO}_3$ but significantly reduced optical anisotropy, as an alternative viable platform. In this work, we manufacture $\mathrm{LiTaO}_3$ AWGs using deep ultraviolet lithography on a wafer-scale. The fabricated AWGs feature a channel spacing of 100 GHz, an insertion loss of < 4 dB and crosstalk of < -14 dB. In addition, we demonstrate a cyclic AWG, as well as a multiplexing and demultiplexing AWG pair for the first time on $\mathrm{LiTaO}_3$ platform. The wafer-scale fabrication of these AWGs not only ensures uniformity and reproducibility, but also paves the way for realizing volume-manufactured integrated WDM transmitters in ferroelectric photonic integrated platforms.

Conventional electronics is founded on a paradigm where shaping perfect electrical elements is done at the fabrication plant, so as to make devices and systems identical, "eternally immutable". In nature, morphogenic evolutions are observed in most living organisms and exploit topological plasticity as a low-resource mechanism for in operando manufacturing and computation. Often fractal, the resulting topologies feature inherent disorder: a property which is never exploited in conventional electronics manufacturing, while necessary for data generation and security in software. In this study, we present how such properties can be exploited to implement long-term and evolvable synaptic plasticity in an electronic hardware. The rich topology of conducting polymer dendrites (CPDs) is exploited to program the non-ideality of their electrochemical capacitances containing constant-phase-elements. Their evolution through structural changes alters the characteristic time constants for them to charge and discharge with the applied voltage stimuli. Under a train of voltage spikes, the evolvable current relaxation of the electrochemical systems promotes short-term plasticity with timescales ranging from milliseconds to seconds. This large window depends on the temporality of the voltage pulses used for reading, but also on the structure of a pair of CPDs on two electrodes, grown by voltage pulses. This study demonstrates how relevant physically transient and non-ideal electrochemical components can be exploited for unconventional electronics, with the aim to mimic a universal property of living organisms which could barely be replicated in a silicon monocrystal.

We report on the design and demonstration of ultra-wide bandgap (UWBG) AlGaN-channel metal-insulator heterostructure field effect transistors (HEFTs) for high-power, high-frequency applications. We find that the integration of gate dielectrics and field plates greatly improves the breakdown field in these devices, with state-of-art average breakdown field of 5.3 MV/cm (breakdown voltage > 260 V) with an associated maximum current density of 342 mA/mm, and cut-off frequency of 9.1 GHz. Furthermore, low trap-related impact was observed from minimal gate and drain lag estimated from pulsed I-V characteristics. The reported results provide the potential of UWBG AlGaN HEFTs for the next generation high-power radio frequency applications.

The single-band high-efficiency light absorption of nanostructures finds extensive applications in var ious fields such as photothermal conversion, optical sensing, and biomedicine. In this paper, a vertically stacked nanohybrid structure is designed with aluminum arsenide (AlAs), indium tin ox ide (ITO) and gallium arsenide (GaAs) stacked, and the photon absorption characteristics of this structure under near-infrared light at a single wavelength of 1240 nm are exploredbased on the finite difference time domain (FDTD) method. When AlAs, ITO, and GaAs are stacked and incident light enters from the GaAs side, a local light enhancement phenomenon occurs. The absorption rate can reach 91.67%, and the temperature change rate reaches 55. 53%, allowing for a wide-range regulation the absorption rate by temperature. In addition, the AlAs/ITO/GaAs sandwich-type hybrid structure also exhibits obvious nonreciprocity. With the change in temperature, the absorption rate of different structural sizes varies differently. The structure can be optimized and designed according to the requirements, providing new ideas for the design of multifunctional optoelectronic devices.

Multigap cavities are used extensively in linear accelerators to achieve velocities up to a few percent of the speed of light, driving nuclear physics research around the world. Unlike for single-gap structures, there is no closed-form expression to calculate the output beam parameters from the cavity voltage and phase. To overcome this, we propose to use a method based on the integration of the first and second moments of the beam distribution through the axially symmetric time-dependent fields of the cavity. A beam-based calibration between the model's electric field scaling and the machine's rf amplitudes is presented, yielding a fast online energy change method, returning cavity amplitude and phase necessary for a desired output beam energy and energy spread. The method is validated with 23Na6+ beam energy measurements.

Parametric arrays (PA) offer exceptional directivity and compactness compared to conventional loudspeakers, facilitating various acoustic applications. However, accurate measurement of audio signals generated by PA remains challenging due to spurious ultrasonic sounds arising from microphone nonlinearities. Existing filtering methods, including Helmholtz resonators, phononic crystals, polymer films, and grazing incidence techniques, exhibit practical constraints such as size limitations, fabrication complexity, or insufficient attenuation. To address these issues, we propose and demonstrate a novel acoustic filter based on the design of a half-wavelength resonator. The developed filter exploits the nodal plane in acoustic pressure distribution, effectively minimizing microphone exposure to targeted ultrasonic frequencies. Fabrication via stereolithography (SLA) 3D printing ensures high dimensional accuracy, which is crucial for high-frequency acoustic filters. Finite element method (FEM) simulations guided filter optimization for suppression frequencies at 40 kHz and 60 kHz, achieving high transmission loss (TL) around 60 dB. Experimental validations confirm the filter's superior performance in significantly reducing spurious acoustic signals, as reflected in frequency response, beam pattern, and propagation curve measurements. The proposed filter ensures stable and precise acoustic characterization, independent of measurement distances and incidence angles. This new approach not only improves measurement accuracy but also enhances reliability and reproducibility in parametric array research and development.

Weconsider Burgers equation on metric graphs for simplest topologies such as star, loops, and tree graphs. Exact traveling wave solutions are obtained for the vertex boundary conditions providing mass conservation and continuity of the solution at the nodes. Constraints for the nonlinearity coefficients ensuring integrability of the Burgers equation are derived. Numerical treatment of the soliton dynamics and their transmission through the graph vertex is presented.

Fibre-reinforced elastomers are lightweight and strong materials that can sustain large deformations. When filled with magnetic particles, their effective mechanical response can be modified by an external magnetic field. In the present study, we propose an effective theory of fibre-reinforced composite, based on a neo-Hookean elastic response and a linear magnetic law in each phase. The theory is shown suitable to describe the motion of composite cylinders. Furthermore, it is found appropriate for the modelling of fibre-reinforced composites subjected to a permanent magnetic field aligned with the fibres. To reach this result, we use the incremental theory ('small on large'), in combination with homogenisation theory and the Bloch-Floquet method. This way, we show that wave directivity is sensitive to the application of a permanent magnetic field, whereas the frequency range in which wave propagation is forbidden is not modified by such a load (the band gaps are invariant). In passing, we describe a method to deduce the total stress in the material based on the measurement of two wave speeds. Furthermore, we propose an effective energy function for the description of nonlinear composites made of Yeoh-type generalised neo-Hookean fibres within a neo-Hookean matrix.

Achieving high-frequency spectral resolution with quantum sensors, while crucial in fields ranging from physical to biological sciences, is challenging due to their finite coherence time. Here, we introduce a novel protocol that achieves this goal by measuring phase correlations of AC magnetic fields using ensembles of NV centers. Our method extends the sensing dynamic range to frequencies higher than the system's Rabi frequency while achieving arbitrary frequency resolution, limited only by the target field coherence time. Moreover, our approach operates more robustly with respect to the magnetic field's amplitude. Thanks to this robustness, our protocol allows the application of more $\pi$-pulses in pulse sequences such as CPMG, enabling the decoupling of a broader range of frequency noise. The higher harmonics generated in this process continue to act as a part of the signal, ultimately improving the frequency resolution. This method paves the way for achieving arbitrary frequency resolution with improved performances, making it highly versatile for quantum sensing applications across diverse scientific fields.

The attitude control of a spacecraft is integral to achieving mission success. However, failures in actuators such as reaction wheels are detrimental and can often lead to an early end of mission. We propose a Lyapunov-based adaptive controller that can estimate and compensate for reaction wheels degradation simultaneously. The controller incorporates an adaptive update control law with a gradient-based term and an integral concurrent learning term that collects input-output data for online estimation of uncertain parameters. The proposed controller guarantees attitude tracking and its performance is tested through numerical simulations.

This work presents a comprehensive study on the aging behavior of 18650-type lithium-ion batteries, focusing on the uneven intercalation of lithium ions during fast charging processes. It introduces a novel approach using color visual recognition technology to analyze color changes in the graphite anode, indicative of lithiation levels. The study employs X-ray diffraction (XRD) and Distribution of Relaxation Time (DRT) techniques to validate and analyze the observations. The study emphasizes the significance of electrode impedance, the positioning of battery tabs, and electrolyte distribution in influencing the aging dynamics of lithium-ion batteries. Furthermore, the paper presents an innovative impedance Transport-Line Model, specifically developed to capture the evolution of polarization impedance over time. This model offers a deeper understanding of the internal mechanisms driving battery aging, providing valuable insights for the design and optimization of lithium-ion batteries. The research represents a significant contribution to the field, shedding light on the complex aging processes in lithium-ion batteries, particularly under the conditions of fast charging. This could lead to improved battery performance, longevity, and safety, which are critical for the wide range of applications that depend on these energy storage systems.

Kidney stones can cause severe pain and complications such as chronic kidney disease or kidney failure. Retrograde intrarenal surgery (RIRS), which uses laser lithotripsy to fragment stones for removal via a ureteroscope, is widely adopted due to its safety and effectiveness. However, conventional fragment removal methods using basketing and vacuum-assisted aspiration are inefficient, as they can capture only 1 to 3 fragments (1--3\,mm in size) per pass, often requiring dozens to hundreds of ureteroscope passes during a single procedure to completely remove the fragments. These limitations lead to prolonged procedures and residual fragments that contribute to high recurrence rates. To address these limitations, we present a novel spinner device that enables ultra-efficient fragment removal through spinning-induced localized suction. The spinner generates a three-dimensional spiral and circulating flow field that dislodges and draws fragments into its cavity even from distances over 20\,mm, eliminating the need to chase fragments. It can capture over 60 fragments (0.5--2\,mm) or over 15 larger fragments (2--3\,mm) in a single pass, significantly improving removal efficiency. In this work, the spinner design is optimized via computational fluid dynamics to maximize suction performance. \textit{In vitro} testing demonstrates near 100\% capture rates for up to 60 fragments in a single operation and superior large-distance capture efficacy compared to vacuum-assisted methods. \textit{Ex vivo} testing of the integrated spinner-ureteroscope system in a porcine kidney confirmed its high performance by capturing 45 fragments in just 4 seconds during a single pass and achieving complete fragment clearance within a few passes.

The recently suggested concept of a polaritonic Fourier crystal (PFC) is based on a harmonically-corrugated mirror substrate for a thin pristine polaritonic crystal layer. The propagating polaritons in PFC experience a harmonic and mode-selective momentum modulation leading to a manifestation of Bloch modes with practically zero inter-mode scattering. PFC was first demonstrated for the hyperbolic phonon-polaritons in hexagonal boron nitride (hBN) within its Type II Reststrahlen band (RB-II) where the in-plane components of the dielectric permittivity tensor are isotropic and negative, while the out-of-plane component is positive. By contrast, a Type I Reststrahlen band (RB-I) is characterized by negative out-of-plane and positive in-plane permittivity components, and consequently, the inversion of field symmetry of phonon-polaritons compared to RB-II. Behavior of such RB-I modes in a polaritonic crystal is yet to be explored. Here, we employ a biaxial crystal alpha-phase molybdenum trioxide ({\alpha}-MoO3) and near-field imaging to study polaritonic Bloch modes in a one-dimensional PFC within the RB-I where the mid-infrared phonon-polaritons in {\alpha}-MoO3 have anomalous dispersion and negative phase velocity. Surprisingly, we observe a manifestation of Bloch waves as a dispersionless near-field pattern across the first Brillouin zone, in contrast to RB-II case demonstrated with in-plane isotropic hBN. We attribute this difference to the opposite field symmetry of the lowest-order phonon-polariton mode in the two RBs, leading to a different momentum modulation regime in the polaritonic Fourier crystal. Our results reveal the importance of mode symmetry for polaritonic crystals in general and for the emerging field of Fourier crystals in particular, which promise new ways to manipulate the nanolight.

We refine the recently introduced "Virtual VNA 3.0" technique to remove the need for coherent detection. The resulting "Virtual VNA 3.1" technique can unambiguously estimate the full scattering matrix of a non-reciprocal, linear, passive, time-invariant device under test (DUT) with $N$ monomodal ports using an $N_\mathrm{A}$-channel coherent wavefront generator and an $N_\mathrm{A}$-channel non-coherent detector, where $N_\mathrm{A}<N$. Waves are injected and received only via a fixed set of $N_\mathrm{A}$ "accessible" DUT ports while the remaining $N_\mathrm{S}$ "not-directly-accessible" DUT ports are terminated by a specific tunable load network. To resolve all ambiguities, an additional modified setup is required in which waves are injected and received via a known $2N_\mathrm{A}$-port system connected to the DUT's accessible ports. We experimentally validate our method for $N_\mathrm{A}=N_\mathrm{S}=4$ considering a non-reciprocal eight-port circuit as DUT. By eliminating the need for coherent detection, our work reduces the hardware complexity which may facilitate applications to large-scale or higher-frequency systems. Additionally, our work provides fundamental insights into the minimal requirements to fully and unambiguously characterize a non-reciprocal DUT.

An activity of the TRIUMF automatic beam tuning program, the Bayesian optimization for Ion Steering, BOIS, method has been developed to perform corrective centroid steering of beams at the TRIUMF ISAC facility. BOIS exclusively controls the steerers for centroid correction after the transverse optics have been set according to theory. The method is fully online, easy to deploy, and has been tested in low energy and postaccelerated beams at ISAC, achieving results comparable to human operators. scaleBOIS and boundBOIS are naive proof of concept solutions to preferably select beam paths with minimal steering. Repeatable and robust automated steering reduces reliance on operator expertise and operational overhead, ensuring reliable beam delivery to the experiments and thereby supporting TRIUMF's scientific mission.

Barely visible impact damage (BVID) can cause serious issue for composite structures, due to sub-surface damage seriously reducing the strength of the material without showing easily detectable surface signs. Dark-field imaging measures ultra-small angle scattering caused by microscopic features within samples. It is sensitive to damage in composite materials which would otherwise be invisible in conventional radiography. Here we demonstrate BVID detection with speckle-based dark-field imaging, a technique requiring only sandpaper (to create the speckle-pattern) in addition to a conventional X-ray imaging setup to extract the dark-field imaging. We demonstrate that the technique is capable of detecting both matrix cracking and delaminations by imaging materials susceptible to these failure mechanisms.

Antiferroelectrics exhibit reversible antipolar-polar phase transitions under electric fields, yielding large electrostrain suitable for electromechanical devices. Nevertheless, in thin-film form, the antiferroelectric behavior is often obscured by competing ferroic orders, resulting in slanted hysteresis loops with undesired remnant polarization, subsequently posing challenges in obtaining ideal antiferroelectricity and understanding their intrinsic electrical behavior. Here, atomistic models for controllable antiferroelectric-ferroelectric phase transition pathways are unveiled along specific crystallographic directions. Guided by the anisotropic phase transition and orientation design, we achieved ideal antiferroelectricity with square double hysteresis loop, large saturated polarization (~60 {\mu}C/cm2), near-zero remnant polarization, fast response time (~75 ns), and near-fatigue-free performance (~10^10 cycles) in (111)P-oriented PbZrO3 epitaxial thin films. Moreover, a bipolar and frequency-independent digital electrostrain (~0.83%) were demonstrated in this architype antiferroelectric system. In-situ X-ray diffraction studies further reveal that the large digital electrostrain results from intrinsic field-induced antiferroelectric-ferroelectric structural transition. This work demonstrates the anisotropic phase transition mechanism and ideal antiferroelectricity with large digital electrostrain in antiferroelectric thin films, offering a new avenue for applications of antiferroelectricity in nanoelectromechanical systems.