Band Suppression Research Articles

Joint suppression of cardiac bSSFP cine banding and flow artifacts using twofold phase-cycling and a dual-encoder neural network

BackgroundCardiac bSSFP cine imaging suffers from banding and flow artifacts induced by off-resonance. The work aimed to develop a twofold phase cycling sequence with a neural network-based reconstruction (2P-SSFP+Network) for a joint suppression of banding and flow artifacts in cardiac cine imaging. MethodsA dual-encoder neural network was trained on 1620 pairs of phase-cycled left ventricular (LV) cine images collected from 18 healthy subjects. Twenty healthy subjects and 25 patients were prospectively scanned using the proposed 2P-SSFP sequence. bSSFP cine of a single RF phase increment (1P-SSFP), bSSFP cine of a single RF phase increment with a network-based artifact reduction (1P-SSFP+Network), the averaging of the two phase-cycled images (2P-SSFP+Average), and the proposed method were mutually compared, in terms of artifact suppression performance in the LV, generalizability over altered scan parameters and scanners, suppression of large-area banding artifacts in the left atrium (LA), and accuracy of downstream segmentation tasks. ResultsIn the healthy subjects, 2P-SSFP+Network showed robust suppressions of artifacts across a range of phase combinations. Compared with 1P-SSFP and 2P-SSFP+Average, 2P-SSFP+Network improved banding artifacts (3.85±0.67 and 4.50±0.45 vs 5.00±0.00, P<0.01 and P=0.02, respectively), flow artifacts (3.35±0.78 and 2.10±0.77 vs 4.90±0.20, both P<0.01), and overall image quality (3.25±0.51 and 2.30±0.60 vs 4.75±0.25, both P<0.01). 1P-SSFP+Network and 2P-SSFP+Network achieved a similar artifact suppression performance, yet the latter had fewer hallucinations (two-chamber, 4.25±0.51 vs 4.85±0.45, P=0.04; four-chamber, 3.45±1.21 vs 4.65±0.50, P=0.03; and LA, 3.35±1.00 vs 4.65±0.45, P<0.01). Furthermore, in the pulmonary veins and LA, 1P-SSFP+Network could not eliminate banding artifacts since they occupied a large area, whereas 2P-SSFP+Network reliably suppressed the artifacts. In the downstream automated myocardial segmentation task, 2P-SSFP+Network achieved more accurate segmentations than 1P-SSFP with different phase increments. Conclusions2P-SSFP+Network jointly suppresses banding and flow artifacts while manifesting a good generalizability against variations of anatomy and scan parameters. It provides a feasible solution for robust suppression of the two types of artifacts in bSSFP cine imaging.

Research on the shear band suppression mechanism in strut-based lattice structures by oblique graded design

Under compressive loads, shear band formation in lattice structures can lead to stress fluctuations, resulting in a decrease in energy absorption capacity. To specifically suppress shear bands, it is necessary to expound the formation mechanisms. This study used theoretical analysis, experiments, and finite element (FE) simulations to elucidate the mechanism underlying shear band formation in strut-based lattice structures. It was determined that stress concentration at strut joints along the 45° diagonal plane induced shear deformation. Shear bands were most pronounced along the four body diagonals, and their existence diminished as the distance from the diagonal increased. Therefore, a design of oblique graded lattice structure (OGLS) was proposed, and quasi-static compression experiments were performed using FE method. The results showed that the main internal stress of OGLS is combined with the original 45° shear stress and the annular staggered stress produced by the oblique graded design, which constrains each other and avoids mutual dislocation deformation, thus realizing shear band suppression. However, an excessively large graded coefficient excessively weakens the 45° shear stress and results in the appearance of an annular compact band. By optimizing the graded coefficient based on the deformation consistency of the outer contour, the optimized OGLS exhibited significant improvements in yield strength, plateau stress, and energy absorption, which are increased by 36.06%, 39.29%, and 34.41%, respectively. This research offers novel perspectives on how lattice structures can attain stable compression deformation and a high energy absorption capacity.

Facile construction of efficient WO3/V2O5 coupled g-C3N4 ternary composite photocatalyst for environmental emergent aqueous pollutant degradation: Stability, degradation reaction pathway and effect of pH evaluation.

Currently, one of the primary challenges that human society must overcome is the task of decreasing the amount of energy used and the adverse effects that it has on the environment. The daily increase in liquid waste (comprising organic pollutants) is a direct result of the creation and expansion of new companies, causing significant environmental disruption. Water contamination is attributed to several industries such as textile, chemical, poultry, dairy, and pharmaceutical. In this study, we present the successful degradation of methylene blue dye using g-C3N4 (GCN) mixed with WO3 and V2O5 composites (GCN/WO3/V2O5 ternary composite) as a photocatalyst, prepared by a simple mechanochemistry method. The GCN/WO3/V2O5 ternary composite revealed a notable enhancement in photocatalytic performance, achieving around 97% degradation of aqueous methylene blue (MB). This performance surpasses that of the individual photocatalysts, namely pure GCN, GCN/WO3, and GCN/V2O5 composites. Furthermore, the GCN/WO3/V2O5 ternary composite exhibited exceptional stability even after undergoing five consecutive cycles. The exceptional photocatalytic activity of the GCN/WO3/V2O5 ternary composite can be ascribed to the synergistic effect of metal-free GCN and metal oxides, resulting in the alteration of the band gap and suppression of charge recombination in the ternary photocatalyst. This study offers a better platform for understanding the characteristics of materials and their photocatalytic performance under visible light conditions.

Reevaluating soil amplification using multi-spectral HVSR technique in La Chana Neighborhood, Granada, Spain

This work presents a thorough reevaluation of soil amplification in the La Chana neighborhood of Granada through a pioneering application of the horizontal-to-vertical spectral ratio technique on seismic noise data using various spectral approaches. The research recycles old seismic noise data recorded at 34 stations with 2 Hz instruments in the year 2010, supplemented with additional measurements recorded with broadband seismometers at nearby locations in the years 2013 and 2017. Initial traditional processing identifies a narrowband dominant frequency around 1.5 Hz, attributed to artificial or anthropogenic sources. To address this, the Maximum Entropy Algorithm was implemented to smooth the spectral response below 1 Hz, and filter out frequency peaks with very narrow spectral bands, while preserving the narrowband frequency around 1.5 Hz in some records. The Thomson Multitaper method further refined the spectral ratio, emphasizing the detection and suppression of narrow frequency bands that may be related to industrial activity. The results demonstrated the reappearance of the 1.5 Hz frequency, but this time without narrow bandwidths, indicating its possible correlation with the natural ground movement. Fundamental periods, ranging from 0.45 s to 0.88 s, suggest a diverse lithological composition, indicating the presence of layers of sands, clays, conglomerates, and carbonates over a basement that represents the main impedance contrast in the area. The multispectral approach surpasses conventional methods in precision and reliability, providing valuable insights for earthquake risk assessment, urban planning, and engineering decisions in seismically active regions.

Low-frequency vibration reduction of an underwater metamaterial plate excited by a turbulent boundary layer

Flow-induced structural noise is an important component of hydrodynamic noise of underwater structures. Local resonance metamaterials are considered to have excellent performance and enormous potential in the field of low-frequency vibration and noise control. To verify its potential, the paper derived the underwater band gap of a lateral local resonance (LLR) plate through the plane wave expansion (PWE). Then, utilizing the modal superposition approach and Rayleigh integral technique, the vibro-acoustic response of a LLR plate under a turbulent boundary layer (TBL) excitation is obtained. Finite element certification is also conducted through an uncorrelated wall plane wave technique. Parametric study is conducted to analyse the factors which influence the control effects. The result shows that the plate exhibits excellent suppression performance for flow-induced vibration at band gap frequencies. The band gaps and suppression ranges generated by the underwater metamaterial plate, are dramatically narrowed due to the thick fluid load. The paper provides theoretical guidance for the control of flow-induced structural vibration and the application of acoustic metamaterials.

Modulation of the emission spectrum of rare-earth ions using inverse-designed photonic crystals cavities.

Rare-earth elements play an indispensable role in the optical communication and laser industries, due to their superior luminescent properties. Nevertheless, the selective enhancement and suppression of different emission bands during energy level transitions for multi-band emitting rare-earth ions presents a significant research challenge, which we aim to address. This study explores the potential of leveraging an inverse-designed dual-cavity photonic crystals structure to manipulate the emission spectrum, thereby facilitating the augmentation or suppression of distinct emission bands. We utilized a convolutional neural network model to establish the relationship between geometric parameters and the local density of states, forecasting the optimal cavity geometry parameters for achieving the desired modulation outcomes. This paper delineates the neural network's generalization capabilities, along with the modulation efficacy of the dual-cavity configuration, both confirmed through numerical validation. Our findings highlight the modulatory capacity of Dy3+ ions, which exhibit three emission spectrum in the visible range, to achieve pure color light emission within the devised cavity structure. Notably, our approach yielded enhancements of up to 2.79-fold and 2.81-fold in pure yellow and red light emissions respectively, compared to free space emissions. The single-sided emission enhancement reaches 16.28-fold for yellow light and 30.79-fold for red light. This emphasizes the transformative potential of this methodology in crafting rare-earth-based luminescent materials with meticulously engineered emission attributes.

Photosensitizing CNTs by organotin(IV) compounds: generation of reactive oxygen species and degradation of amoxicillin.

This work is based on probing photosensitization in carbon nanotubes (CNTs) by organotin(IV) compounds to fabricate a hybrid material with excellent photocatalytic activity and generation of reactive oxygen species. Two organotin(IV) compounds (compounds 1 and 2) were synthesized and characterized by spectroscopic and spectrometric studies, elemental analysis and single crystal X-ray diffraction followed by their impregnation inside the CNTs. The so obtained hybrid materials (1@CNT and 2@CNT) were characterized by FTIR, TGA, FE-SEM, HR-TEM, PXRD and XPS analysis, and assessed for photosensitization and generation of reactive oxygen species. The enhanced photocatalytic activity of the fabricated materials in comparison to bare CNTs is attributed to the reduction of band gap and suppression of rapid recombination rates due to the encapsulation of photogenerated electrons. The generation of reactive species in photocatalyst 1@CNT was validated by the degradation of Amoxicillin (AMX) under optimized conditions for catalytic dosage, H2O2 concentration, response time and pH. The material 1@CNT could degrade ca. 83% of AMX by generating free radicals (˙OH and ˙O2-) under visible light irradiation at pH 6 as investigated by UV-visible spectroscopy and supported by EPR and DFT studies. Furthermore, the structural stability and sustained photocatalytic properties of 1@CNT over four cycles highlight its potential as an eco-friendly solution for degrading environmental toxins.

Photocatalytic activity evaluation of polyvinylpyrrolidone K30 assisted synthesis of 1D oxygen-vacancy-rich Bi5O7BrxI1-x nanorod solid solution

The unique layered structure of bismuth halide oxide has led to an extensive application in the degradation of refractory antibiotics from water environments. With the aid of regulating the energy band structure of photocatalytic materials and equilibrating the response towards visible light and redox ability, a novel oxygen-vacancy-rich Bi5O7BrxI1−x nanorod solid solution was synthesized by polyvinylpyrrolidone K30 assisted solvothermal method, and its photocatalytic behavior was investigated for the degradation of antibiotic levofloxacin under visible light. The degradation rate of the optimal Bi5O7Br0.5I0.5 to levofloxacin can reach 82.7% within 30 min, which is 9.22 and 4.74 times higher than those of the monomers Bi5O7Br and Bi5O7I. The catalyst of Bi5O7Br0.5I0.5 shows 99.88% antibacterial activity against Escherichia coli. The efficient photocatalytic ability of the Bi5O7Br0.5I0.5 is resulted from the alteration of energy band structure and suppression of charge recombination due to benign changes in the electronic and crystal structures. Furthermore, both various characterizations and Density Functional Theory calculations reveal that a multitude of oxygen vacancies exist in the Bi5O7Br0.5I0.5. The photocatalytic degradation pathways were explored and the toxicity of the intermediates was also appraised. The present work provides a mild and feasible construction of solid solutions and introduction of oxygen vacancies to eliminate environmentally refractory organic pollutants with photocatalytic technology.

Investigations on shear band formation in metallic nanolayered composites

While metallic nanolayered composites exhibit ultrahigh strength, they can fail due to shear bands propagation. Shear bands are affected by many factors, such as layer thickness and stacking fault energy. There is a growing demand to simultaneously prevent shear bands while harnessing the high strength potential derived from the dense interface nanostructures. The mechanisms of shear band formation vary among different nanolayered composites, and some of these mechanisms are investigated. The importance of utilizing advanced computational tools to understand shear band formation is highlighted. This review comprehensively addresses the influencing factors of shear band formation, strategies for shear band suppression, and the underlying mechanisms of shear band formation within metallic nanolayered composites.

Wide frequency band oscillation mechanism and suppression measures for grid-interfaced PV inverters based on impedance analysis

With the rapid development of PV and wind power, the energy structure of the power grid is changing dramatically. The dominant power supply role played by conventional power sources such as hydropower and thermal power is gradually replaced by PV and wind power. All the power electronics-based equipment makes the power system stable form more complex, and one of the most significant challenges is wide frequency band oscillation (WFBO). This paper proposes an impedance analysis method for PV inverters in high proportion to new energy-integrated power systems. First, we investigate WFBO mechanism caused by the PV inverter based on its impedance model, and then a detailed impedance model of parallel PV inverters is developed to study WFBOs in PV stations. Finally, the WFBO suppression measure based on active damping control is proposed. Simulation results prove the correctness and feasibility of the active damping control strategy.

On-chip multi-beam frequency shifter through sideband separation.

In this paper, we introduce a novel method to realize a multi-beam optical frequency shifting component for photonic integrated circuits, utilizing an array of parallel optical modulators and a free-propagation region (FPR), such as a slab waveguide-based star coupler. This component generates multiple optical beams with different frequency shifts, making it suitable for various systems, such as multi-beam laser Doppler vibrometry (LDV). We thoroughly elaborate on the working principle of the component through theoretical analysis and demonstrate that by applying periodic wave-like modulation in the modulator array, the discrete harmonic content of the light can be selectively directed to different outputs based on the delay between consecutive modulators. A design comprising a 16-element modulator array and 5 outputs will be presented. Simulations show that this design can generate and collect 5 different harmonics (-2, -1, 0, +1, +2) in the different outputs with a side band suppression ratio of 20 dB to 30 dB for each output. Our proposed design is just one possibility and the component can be modified and optimized for specific applications.

A compact 4 × 4 reconfigurable MIMO antenna design with adjustable suppression of certain frequency bands within the UWB frequency range

This paper introduces a novel 4 × 4 multiple-input multiple-output (MIMO) antenna design with a reconfigurable operating band within the Ultra-Wideband (UWB) range. The antenna consists of four rectangular radiating elements arranged symmetrically and orthogonally on a defected ground plane. The design incorporates switching elements that allow adjustable and reversible suppression of specific bands within the UWB range, enabling the antenna to operate in three different modes: UWB, X-band, and dual-band with sub-6GHz and X-band. Thus, a single UWB antenna can serve as three different antennas, suppressing certain frequencies as required. To mitigate mutual coupling between adjacent antenna elements, four thin stubs are strategically placed at the center of the ground plane, forming a square with open corners. When one of the antenna elements is excited, this structure acts as an insulator, ensuring that the surface current is confined solely to that element and not induced in others. Experimental verification of the proposed design was performed by fabricating and testing the antenna. The results indicated good agreement between simulation and measurement data for various parameters, including S-parameters, radiation patterns, gains, and MIMO parameters such as envelope correlation coefficients (ECC), diversity gain (DG), mean effective gain (MEG), and total active reflection coefficient (TARC).

High Order Harmonic Pass Band Suppression in Microstrip Filter

It is very well understood that filters are backbone of communication system as they are employed in each stage of system design and the key parameters which indicates their performance and suitability to desired application are insertion loss, return loss, group delay etc. Apart from them a very important factor namely high order harmonic pass band which becomes very critical when input of the filter consists of multiple harmonic signal within it and creates interference to succeeding stages of the system. In order to achieve clean frequency spectrum in stop band frequency region, there is need of suppressing the high order harmonic spurious pass bands. In this research work additional microstrip patterns are formed at input/output of the filter schematic to achieve the required goal. In this article concept of the novel technique to eliminate or suppress the high order harmonics is detailed and same is implemented on hairpin type of filter topology.

A Miniaturized Wideband SIR Interdigital Bandpass Filter With High Performance Based on TSV Technology for W-Band Application

In this paper, an ultra-compact wideband stepped impedance resonators (SIR) interdigital bandpass filter (IBPF) is proposed based on through-silicon via (TSV) and three-dimensional integrated circuit (3D IC) technology. SIR structure can achieve higher coupling strength at a small impedance ratio. On this basis, the IBPF is designed by exploiting λ/4 SIR, the proposed filter is realized with compact size and far parasitic passband, and exhibits superior fractional bandwidth and out of band suppression characteristics. Based on the transformation of Chebyshev low-pass circuit model, a seventh-order IBPF centered at 98.5GHz is obtained. An improved method combining TSV technology with coupling coefficient method is proposed, which simplifies the design process and improves the influence of parasitic inductance on the design process. The fractional bandwidth (FBW) of SIR IBPF based on TSV is 40%, the insertion loss is less than 1.3dB, and a reflection of better than 30 dB in the passband. The size of the compact SIR IBPF is only 0.24×0.7mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (0.28 × 0.79 λg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ).

Attentional State-Dependent Peripheral Electrical Stimulation During Action Observation Enhances Cortical Activations in Stroke Patients.

Brain-computer interface (BCI) is a promising technique that enables patients' interaction with computers or machines by analyzing specific brain signal patterns and provides patients with brain state-dependent feedback to assist in their rehabilitation. Action observation (AO) and peripheral electrical stimulation (PES) are conventional methods used to enhance rehabilitation outcomes by promoting neural plasticity. In this study, we assessed the effects of attentional state-dependent feedback in the combined application of BCI-AO with PES on sensorimotor cortical activation in patients after stroke. Our approach involved showing the participants a video with repetitive grasping actions under four different tasks. A mu band suppression (8-13 Hz) corresponding to each task was computed. A topographical representation showed that mu suppression of the dominant (healthy) and affected hemispheres (stroke) gradually became prominent during the tasks. There were significant differences in mu suppression in the affected motor and frontal cortices of the stroke patients. The involvement of both frontal and motor cortices became prominent in the BCI-AO+triggered PES task, in which feedback was given to the patients according to their attentive watching. Our findings suggest that synchronous stimulation according to patient attention is important for neurorehabilitation of stroke patients, which can be achieved with the combination of BCI-AO feedback with PES. BCI-AO feedback combined with PES could be effective in facilitating sensorimotor cortical activation in the affected hemispheres of stroke patients.

A dual-stage partially interpretable neural network for joint suppression of bSSFP banding and flow artifacts in non-phase-cycled cine imaging

PurposeTo develop a partially interpretable neural network for joint suppression of banding and flow artifacts in non-phase-cycled bSSFP cine imaging. MethodsA dual-stage neural network consisting of a voxel-identification (VI) sub-network and artifact-suppression (AS) sub-network is proposed. The VI sub-network provides identification of artifacts, which guides artifact suppression and improves interpretability. The AS sub-network reduces banding and flow artifacts. Short-axis cine images of 12 frequency offsets from 28 healthy subjects were used to train and test the dual-stage network. An additional 77 patients were retrospectively enrolled to evaluate its clinical generalizability. For healthy subjects, artifact suppression performance was analyzed by comparison with traditional phase cycling. The partial interpretability provided by the VI sub-network was analyzed via correlation analysis. Generalizability was evaluated for cine obtained with different sequence parameters and scanners. For patients, artifact suppression performance and partial interpretability of the network were qualitatively evaluated by 3 clinicians. Cardiac function before and after artifact suppression was assessed via left ventricular ejection fraction (LVEF). ResultsFor the healthy subjects, visual inspection and quantitative analysis found a considerable reduction of banding and flow artifacts by the proposed network. Compared with traditional phase cycling, the proposed network improved flow artifact scores (4.57 ± 0.23 vs 3.40 ± 0.38, P = 0.002) and overall image quality (4.33 ± 0.22 vs 3.60 ± 0.38, P = 0.002). The VI sub-network well identified the location of banding and flow artifacts in the original movie and significantly correlated with the change of signal intensities in these regions. Changes of imaging parameters or the scanner did not cause a significant change of overall image quality relative to the baseline dataset, suggesting a good generalizability. For the patients, qualitative analysis showed a significant improvement of banding artifacts (4.01 ± 0.50 vs 2.77 ± 0.40, P < 0.001), flow artifacts (4.22 ± 0.38 vs 2.97 ± 0.57, P < 0.001), and image quality (3.91 ± 0.45 vs 2.60 ± 0.43, P < 0.001) relative to the original cine. The artifact suppression slightly reduced the LVEF (mean bias = -1.25%, P = 0.01). ConclusionsThe dual-stage network simultaneously reduces banding and flow artifacts in bSSFP cine imaging with a partial interpretability, sparing the need for sequence modification. The method can be easily deployed in a clinical setting to identify artifacts and improve cine image quality.

Theta/Alpha Band Suppression and Clinical Outcomes During Globus Pallidus Internus Deep Brain Stimulation in Huntington's Disease.

Theta/Alpha Band Suppression and Clinical Outcomes During Globus Pallidus Internus Deep Brain Stimulation in Huntington's Disease.

Оптические спектры фотонно-кристаллической структуры со слоями графена

The transformation of the graphene-containing optical spectra photonic-crystal structure with a change in the chemical potential (μ) of graphene is studied. In the period of the structure, one layer is a graphene-containing periodic medium (SiO2/Gr)n , and the second layer is assumed to be made of pure silicon. In the case of unexcited graphene (μ = 0), the absorption in the structure exceeds the reflection and transmission for frequencies outside the photonic band gaps. Within these zones, most of the incident radiation is reflected, and there is no transmission at all. As μ increases outside the band gaps, the absorption decreases in the low-frequency region, and the transmission increases the stronger, the greater μ. In a structure with an inversion defect inside the band gaps, either suppression or significant rearrangement of the defect mode takes place.

Rectified Bloch oscillations in dynamically modulated waveguide arrays.

We study the dynamics of excitations in dynamically modulated waveguide arrays with an external spatial linear potential. Longitudinally periodic modulation may cause a significant change in the width of the quasi-energy band and leads to the dynamical band suppression with a linear dispersion relation. This substantially affects the Bloch oscillation dynamics. Novel dynamical phenomena with no analogue in ordinary discrete waveguides, named rectified Bloch oscillations, are highlighted. Due to the interplay between directional coupling between adjacent waveguides and diffraction suppression by the introduced onsite energy difference, at odd times of half Bloch oscillations period, the new submodes are continuously excited along two opposite rectification directions and experience same oscillation evolution, and eventually lead to the formation of a diamondlike intensity network. Both the amplitude and direction of the rectified Bloch oscillations strongly depend on the coupling strength. When coupling strength passes the critical value at which dynamical band suppression with a linear dispersion relation occurs, the direction of Bloch oscillations is inverted.

Tunable and reconfigurable bandstop filters enabled by optically controlled switching elements

The authors report a novel approach for designing tunable and reconfigurable bandstop filters by employing bias-free optically-controlled photoconductive radio frequency (RF) switching elements. To verify the effectiveness of the approach, a bandstop filter with two stopbands centred at 4.05 and 4.75 GHz was designed using a split-ring-coupled microstrip transmission line on RO3010 substrates. To enable reconfigurability, a micromachined Si chip with a thickness of ∼73 μm was embedded in the gap of each resonator. The tuning and reconfiguring of the filter are accomplished by selectively illuminating the Si chips using fibre-coupled laser diodes with a wavelength of 808 nm. By turning on and off each laser diode, the filter stop bands can be dynamically reconfigured. In addition, the suppression of each stop band can be continuously and independently tuned by changing the light intensity from 0 to 20 W/cm2. With geometric scaling, this approach is promising for realizing a novel class of compact and high-performance tunable and/or reconfigurable circuits from the microwave to mmW-THz region.