Uniform Square Research Articles

Unexpectedly high degradation efficiency for MB on Bi3O4Br photocatalyst obtained from bismuth citrate

For the first time, pure Bi3O4Br with a uniform square sheet-like structure was synthesized using a hydrothermal method at 180 °C and pH of 12.5 by employing bismuth citrate as the bismuth source without any surfactant. The photocatalytic activity of Bi3O4Br for the degradation of methylene blue (MB), tetracycline (TC), methyl violet (MV), and rhodamine B (RhB) was evaluated under visible light illumination and the results showed that the as-prepared Bi3O4Br exhibited excellent photodegradation efficiency for MB with an apparent rate constant (ka) of 0.02676 min−1, superior to TC, MV and RhB with ka = 0.00899 min−1, 0.00073 min−1 and 0.00409 min−1, respectively. Since the direct oxidation of the holes predominates in the degradation process, the study on the photocatalytic mechanism suggested that a more positive valence band (VB) potential of Bi3O4Br than HOMO orbital position of MB was prerequisite and also, the smaller the difference between VB potential of a photocatalyst and HOMO energy level of a pollutant, the faster the migration of the holes and subsequent oxidation of pollutant.

DFT based investigations on inherent CO2 adsorption and direct dissociation capability of Ti2C and Nb2C mxenes

Transition metal carbide MXenes, specifically Ti2C and Nb2C, have been investigated for their ability to efficiently adsorb and dissociate CO2 using First Principles Calculations based on Density Functional Theory (FPS-DFT). Pure Ti2C and Nb2C sheets were studied with the adsorption of 1 to 4 CO2 molecules, and the results were analyzed for each case. For 4 CO2 molecules adsorbed on Ti2C and Nb2C sheets, the weight percentage (wt%) ratio was found to be 21.39% and 14.33%, respectively. The Density of States (DOS) analysis revealed that, upon CO2 adsorption, the CO2 molecule dissociates into CO and O atoms on the MXene surface. The CO molecule showed no significant hybridization with the host sheet atoms, whereas the O atom exhibited strong hybridization with the MXene surface. Transition State (TS) profiles illustrated the dissociation steps on both Ti2C and Nb2C surfaces. Phonon calculations confirmed the dynamic stability of both pure and CO2 adsorbed MXenes. Molecular Dynamics (MD) simulations conducted at 900 K indicated uniform temperature and Mean Square displacement (MSD) profiles, suggesting the stability of both pure and CO2 adsorbed MXenes at elevated temperatures, as well as uniform CO2 adsorption behavior. The adsorption energies for Ti2C and Nb2C sheets were calculated to be in the range of -1.89 to -2.77eV, suggesting that the adsorption process is favorable, spontaneous, and predominantly involves chemisorption. These findings indicate that Ti2C and Nb2C MXenes, in their intrinsic forms, are promising candidates for CO2 adsorption and dissociation technologies.

The optical properties of nano-structural α-Fe2O3 dependence on the shape.

Three different crystal morphologies of α-Fe2O3, including uniform hexagonal, square, and rhombic shapes, were prepared according to the aqueous-thermal reaction. The hexagonal-shaped α-Fe2O3 was enclosed by the 104 plane, while the square and rhombic structures were enclosed by the 110 plane. Two absorption peaks at 455 and 532 cm-1 were found for the perpendicular (⊥) modes, and one absorption peak at 650 cm-1 appeared for the parallel (||) mode for hexagon-shaped α-Fe2O3 during analysis by Fourier-transform infrared spectroscopy. However, the peaks of square- and rhombic-shaped α-Fe2O3 for perpendicular (⊥) mode blueshifted, and the former two peaks merged together forming a broad band at approximately 480 cm-1. For Raman spectra determination, the peaks arose from the Brillouin zone center, and two additional peaks were observed at 660 and 1320 cm-1, belonging to 1 longitudinal optical (1LO) and 2 longitudinal optical (2LO) modes. All three materials exhibited higher intensities when excited at a wavelength of 633 cm-1. Furthermore, in the polarization state, the centers of all peak positions slightly shifted for hexagon-shaped α-Fe2O3, but all peak positions for square-shaped and rhombic-shaped α-Fe2O3 exhibited a significant blueshift. The structure of hexagon-shaped α-Fe2O3 was relatively tolerant regarding the polarization properties of vibration modes; however, the symmetry of crystal square-shaped and rhombic-shaped α-Fe2O3 changed, subsequently revealing different optical properties. RESEARCH HIGHLIGHTS: The hexagon-shaped, square-shaped, and rhombic-shaped α-Fe2O3 enclosed by different planes were synthesized. The Fourier Transform Infrared spectrometer peaks of α-Fe2O3 depended on their hexagon, square and rhombic shapes. Compared with hexagon-shaped α-Fe2O3, the Raman peaks for square and rhombi ones significantly shifted. The hexagon-shaped α-Fe2O3 is relatively tolerant regarding the polarization properties.

ReLoki: A Light-Weight Relative Localization System Based on UWB Antenna Arrays.

Ultra Wide-Band (UWB) sensing has gained popularity in relative localization applications. Many localization solutions rely on using Time of Flight (ToF) sensing based on a beacon-tag system, which requires four or more beacons in the environment for 3D localization. A lesser researched option is using Angle of Arrival (AoA) readings obtained from UWB antenna pairs to perform relative localization. In this paper, we present a UWB platform called ReLoki that can be used for ranging and AoA-based relative localization in 3D. To enable AoA, ReLoki utilizes the geometry of antenna arrays. In this paper, we present a system design for localization estimates using a Regular Tetrahedral Array (RTA), Regular Orthogonal Array (ROA), and Uniform Square Array (USA). The use of a multi-antenna array enables fully onboard infrastructure-free relative localization between participating ReLoki modules. We also present studies demonstrating sub-50cm localization errors in indoor experiments, achieving performance close to current ToF-based systems, while offering the advantage of not relying on static infrastructure.

Stability Analysis of Steel Columns with Fixed-Free Ends under Axial Compression: Uniform and Non-Uniform Square Hollow Sections

Stability Analysis of Steel Columns with Fixed-Free Ends under Axial Compression: Uniform and Non-Uniform Square Hollow Sections

Uniform stability, boundedness and square integrability for non-autonomous third-order neutral differential equations with delay

Uniform stability, boundedness and square integrability for non-autonomous third-order neutral differential equations with delay

Improvement of Laser-Induced Damage on High-Efficiency Solar Cells via Top-Hat Beam Ablation

An important challenge in industrial laser ablation is laser-induced damage. In this study, reduced damage was achieved through the transition of the laser distribution from a Gaussian beam to a top-hat beam using diffractive optical elements (DOE), which overcome inhomogeneous irradiation. The higher peak fluence of a Gaussian beam far exceeded the ablation threshold and led to severely melted silicon at a higher depth covering the polished texture. The top-hat beam, with uniform irradiation, had a superior ablation characteristic and created a uniform square opening with the shallow melted silicon in the lift-off process. Thus, its effective minor carrier lifetime was 15.35% less at an ablated area fraction of 2% after re-passivation because of the decreased damage. After optimizing the ablation pattern with a top-hat beam, the local contacts improved the average open-circuit voltage (Voc) and short-circuit current (Isc) values of the cells due to the decreased damage and the uniform openings, but the damage induced by a Gaussian beam was too deep and can be partly restored under back surface field (BSF) formation. The overall increment in Isc and Voc enhanced the average efficiency by 0.05% of the absolute value for the PERC cells and 0.03% of the absolute value for bi-facial PERC cells.

Estimation of QTT Ranks of Regular Functions on a Uniform Square Grid

Estimation of QTT Ranks of Regular Functions on a Uniform Square Grid

16QAM optical signal generation scheme based on weighted optimal Euclidean distance.

A two-dimensional signal constellation scheme for binary uniform memoryless source transmission in optical fiber channels is studied in this paper. In geometric shaping (GS), optimization algorithms are usually used to change the overall position of constellation points while maintaining the probability of constellation points unchanged. Different optimization functions are used to allocate the position of constellation symbols, thereby improving constellation performance. A 16 quadrature amplitude modulation (QAM) optical signal generation scheme based on weighted optimal Euclidean distance is proposed in this paper. In order to obtain the best constellation diagram and increase the shaping gain, the weighted optimal Euclidean distance that can minimize the bit error rate (BER) over multiple iterative optimizations is used as the objective function. On the one hand, the proposed 16QAM optical signal generation scheme based on weighted optimal Euclidean distance always outperforms the uniform square 16QAM and the uniform circle 16QAM schemes in the back to back (BTB) transmission. On the other hand, after analyzing the simulation demonstration in a 50GBaud coherent optical communication system over 3000km, results demonstrate that the optical signal to noise ratio (OSNR) performance of this system is better than that of the uniform square 16QAM and the uniform circle 16QAM, which is improved by 0.52dB and 0.85dB, respectively. In addition, the proposed 16QAM system increases the transmission distance by 989km and 741km, respectively, compared to the other two systems. The performance confirms that the proposed novel 16QAM scheme, to the best of our knowledge, can effectively improve the reliability and transmission distance. Therefore, the proposed scheme has a certain development prospect in the future long-distance transmission of high-speed optical fiber communication.

Poster Session: Achromatic biases in noise images.

In a previous study, Winkler et al. (Current Bio 2015) examined the effects of luminance on the perceived color categories selected for uniform square patches. When the square was equiluminant with the background, the patch appeared colored as soon as it was detected, while for increments or decrements, the range of chromaticities that were classified as achromatic was expanded and more strongly along bluish axes. Here we extended these results to examine the color appearance of spatially varying patterns, which contain a wide range of luminance levels. The images were 1/f luminance noise and were briefly alternated with a gray background with the same mean luminance. The noise was shown on each trial with a uniform chromaticity, which was varied across trials over a grid of values spanning the LvsM and SvsLM cone-opponent axes. Observers categorized each noise image as gray or one of the four unique (RGBY) or binary (RB,BG,GY,YR) hues. The perceived achromatic gamut for the noise again tended to vary along bluish-yellowish directions, but was markedly broader compared to the uniform patches. The broadening of the gray category may partly reflect attributions of some of the color to the illuminant, a tendency which may be stronger in the spatially variegated patterns.

Measurements of decaying grid turbulence with various initial conditions

The uniform grid, a tool commonly used to generate homogeneous and isotropic turbulence, has been the subject of many studies. Many studies have primarily focused on how initial conditions of uniform square grids, including the Reynolds number, mesh size, bar size, cross-section of bar, and solidities, affect the statistical characteristics of grid turbulence. However, the influence of mesh shape has not been studied extensively. This study deviates from the norm by examining the influence of different mesh shapes, specifically the uniform nonsquare grid, on grid turbulence. This variation in mesh shape can be easily achieved based on the traditional uniform square grid. The findings reveal that when a uniform nonsquare grid is used, the distance required for turbulence to fully develop decreases. Additionally, there is an increase in the low-frequency components of fluctuating velocity, while high-frequency components decrease. This shift leads to a difference in energy distribution. Moreover, using a uniform nonsquare grid reduces the anisotropies of decaying turbulence to a certain extent. The skewness approaches theoretical value of 0 more closely, while the flatness remains largely unchanged. The mesh shape also affects the decay exponents and power-law coefficients obtained, with the decay exponent potentially getting much closer to 1. Furthermore, larger integral length scales can be achieved at the same downstream position, without significantly modifying the turbulence intensity, by using the uniform nonsquare grid. This could better meet the requirements of large-scale turbulence in certain engineering fields, such as wind engineering, compared to the traditional uniform square grid.

Hydrothermal synthesis of Zr-doped chitosan carbon-shell protected magnetic composites (Zr–Fe3O4@C) for stable removal of Cr(VI) from water: Enhanced adsorption and pH adaptability

In this study, zirconium-doped carbon shell-protected magnetic Fe3O4 composite (Zr–Fe3O4@C) was synthesized by hydrothermal method with chitosan assistance. Chitosan as a stabilizer successfully prevented the aggregation of Fe3O4, resulting in approximately a 30.7% increase in the specific surface area of Zr–Fe3O4@C. TEM analysis revealed that Zr–Fe3O4@C exhibited a relatively uniform square shape with a size of about 120 nm. The synergistic effect between iron and zirconium oxides resulted in a nearly 20% increase in the adsorption capacity of Zr–Fe3O4@C (Fe/Zr molar ratio of 3:1) for Cr(VI) compared to Fe3O4. The introduction of zirconium also significantly improved the acid and base resistance (1–9) and environmental adaptability of Zr–Fe3O4@C composites. With good magnetic properties (53.5 emu/g) and separation recycling properties, Zr–Fe3O4@C showed rapid water separation within 20 s. At a pH of 3 and 30 °C, Zr–Fe3O4@C achieved a maximum adsorption capacity of 132.72 mg/g by the Langmuir isotherm. Furthermore, even after six consecutive treatments, the adsorption performance of Zr–Fe3O4@C for Cr(VI) only decreased by about 9.8%. The stable adsorption performance and regeneration ability suggested that Zr–Fe3O4@C would be considered a reliable candidate for Cr(VI) wastewater remediation.

Interactions of ultrashort laser pulses with hemoglobin: Photophysical aspects and potential applications

Hemoglobin (Hb), a life-sustaining and highly abundant erythrocyte protein, is not readily fluorescent. A few studies have already reported Two-Photon Excited Fluorescence (TPEF) of Hb, however, the mechanisms through which Hb becomes fluorescent upon interaction with ultrashort laser pulses are not completely understood. Here, we characterized photophysically this interaction on Hb thin film and erythrocytes using fluorescence spectroscopy upon single-photon/two-photon absorption, and UV-VIS single-photon absorption spectroscopy. A gradual increase of the fluorescence intensity, ending up with saturation, is observed upon prolonged exposure of Hb thin layer and erythrocytes to ultrashort laser pulses at 730 nm. When compared to protoporphyrin IX (PpIX) and oxidized Hb by H2O2, TPEF spectra from a thin Hb film and erythrocytes showed good mutual agreement, broad peaking at 550 nm, supporting hemoglobin undergoes degradation and that same fluorescent specie(s) originating from the heme moiety are generated. The uniform square shaped patterns of the fluorescent photoproduct exhibited the same level of the fluorescence intensity even after 12 weeks from the formation, indicating high photoproduct stability. We finally demonstrated the full potential of the formed Hb photoproduct with TPEF scanning microscopy towards spatiotemporally controlled micropatterning in HTF and single human erythrocyte labelling and tracking in the whole blood.

Spiral Square Nanosheets Assembled from Ru Clusters.

Spiral two-dimensional (2D) nanosheets exhibit unique physical and chemical phenomena due to their twisted structures. While self-assembly of clusters is an ideal strategy to form hierarchical 2D structures, it is challenging to form spiral nanosheets. Herein, we first report a screw dislocation involved assembled method to obtain 2D spiral cluster assembled nanosheets (CANs) with uniform square morphology. The 2D spiral Ru CANs with a length of approximately 4 μm and thickness of 20.7 ± 3.0 nm per layer were prepared via the assembly of 1-2 nm Ru clusters in the presence of molten block copolymer Pluronic F127. Cryo-electron microscopy (cryo-EM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) demonstrate the existence of screw dislocation in the spiral assembled structure. The X-ray absorption fine structure spectrum indicates that Ru clusters are Ru3+ species, and Ru atoms are mainly coordinated with Cl with a coordination number of 6.5. Fourier-transform infrared (FT-IR) spectra and solid-state nuclear magnetic resonance hydrogen spectra (1H NMR) indicate that the assembly process of Ru clusters is formed by noncovalent interactions, including hydrogen bonding and hydrophilic interactions. Additionally, the Ru-F127 CANs exhibit excellent photothermal conversion performance in the near-infrared (NIR) region.

Identifying Suitable Three-Dimensional Bio-Printed Scaffold Architectures to Incubate in a Perfusion Bioreactor: Simulation and Experimental Approaches

Abstract Traditional cell culturing methods are limited in their ability to supply growth medium to cells within scaffolds. To address this, we developed a custom perfusion bioreactor that allows for dynamic medium supply to encapsulated or seeded cells. Our custom-designed bioreactor improves the in vivo stimuli and conditions, which may enhance cell viability and proliferation performance. Some of the efforts include using dual medium tanks to replace the medium without stopping perfusion and a newly designed perfusion chamber that can accommodate an array of cassettes allowing for a wide assortment of scaffold shapes and sizes. In this paper, we explored the response of fluid flow to certain types of scaffold pore geometries and porosities using simulation and experimental approaches. Various pore geometries were considered, such as uniform triangular, square, diamond, circular, and honeycomb having uniform and variable sizes. Finally, bone tissue architecture was mimicked and simulated to identify the impact of fluid flow. Based on the results, optimum pore geometry for scaffolds were determined. We explored real-time fluid flow response on scaffolds fabricated with 8% Alginate, 4% Alginate-4% Carboxymethyl Cellulose (CMC), and 2% Alginate-6% CMC incubated, allowing a constant fluid flow for various periods such as 1, 2, 4, and 8 h. The change of fabricated scaffolds was determined in terms of swelling rate, i.e., change of filament width and material diffusion, i.e., comparison of dry material weight before and after incubation. This comparative study can assist in application-based materials selection suitable for incubating in a perfusion bioreactor.

Single Ultra-High Dose Rate Proton Transmission Beam for Whole Breast FLASH-Irradiation: Quantification of FLASH-Dose and Relation with Beam Parameters.

Healthy tissue-sparing effects of FLASH (≥40 Gy/s, ≥4-8 Gy/fraction) radiotherapy (RT) make it potentially useful for whole breast irradiation (WBI), since there is often a lot of normal tissue within the planning target volume (PTV). We investigated WBI plan quality and determined FLASH-dose for various machine settings using ultra-high dose rate (UHDR) proton transmission beams (TBs). While five-fraction WBI is commonplace, a potential FLASH-effect might facilitate shorter treatments, so hypothetical 2- and 1-fraction schedules were also analyzed. Using one tangential 250 MeV TB delivering 5 × 5.7 Gy, 2 × 9.74 Gy or 1 × 14.32 Gy, we evaluated: (1) spots with equal monitor units (MUs) in a uniform square grid with variable spacing; (2) spot MUs optimized with a minimum MU-threshold; and (3) splitting the optimized TB into two sub-beams: one delivering spots above an MU-threshold, i.e., at UHDRs; the other delivering the remaining spots necessary to improve plan quality. Scenarios 1-3 were planned for a test case, and scenario 3 was also planned for three other patients. Dose rates were calculated using the pencil beam scanning dose rate and the sliding-window dose rate. Various machine parameters were considered: minimum spot irradiation time (minST): 2 ms/1 ms/0.5 ms; maximum nozzle current (maxN): 200 nA/400 nA/800 nA; two gantry-current (GC) techniques: energy-layer and spot-based. For the test case (PTV = 819 cc) we found: (1) a 7 mm grid achieved the best balance between plan quality and FLASH-dose for equal-MU spots; (2) near the target boundary, lower-MU spots are necessary for homogeneity but decrease FLASH-dose; (3) the non-split beam achieved >95% FLASH for favorable (not clinically available) machine parameters (SB GC, low minST, high maxN), but <5% for clinically available settings (EB GC, minST = 2 ms, maxN = 200 nA); and (4) splitting gave better plan quality and higher FLASH-dose (~50%) for available settings. The clinical cases achieved ~50% (PTV = 1047 cc) or >95% (PTV = 477/677 cc) FLASH after splitting. A single UHDR-TB for WBI can achieve acceptable plan quality. Current machine parameters limit FLASH-dose, which can be partially overcome using beam-splitting. WBI FLASH-RT is technically feasible.

Color appearance of spatial patterns compared by direct estimation and conjoint measurement.

Perceptual scales of color saturation obtained by direct estimation (DE) and maximum likelihood conjoint measurement (MLCM) were compared for red checkerboard patterns and uniform red squares. For the DE task, observers were asked to rate the saturation level as a percentage, indicating the chromatic sensation for each pattern and contrast. For the MLCM procedure, observers judged on each trial which of two stimuli that varied in chromatic contrast and/or spatial pattern evoked the most salient color. In separate experiments, patterns varying only in luminance contrast were also tested. The MLCM data confirmed previous results reported with DE indicating that the slope of the checkerboard scale with cone contrast levels is steeper than that for the uniform square. Similar results were obtained with patterns modulated only in luminance. DE methods were relatively more variable within an observer, reflecting observer uncertainty, while MLCM scales showed greater relative variability across observers, perhaps reflecting individual differences in the appearance of the stimuli. MLCM provides a reliable scaling method, based only on ordinal judgments between pairs of stimuli and that provides less opportunity for subject-specific biases and strategies to intervene in perceptual judgements.

Convergence of nonlinear filtering for multiscale systems with correlated Lévy noises

The work concerns nonlinear filtering problems of multiscale systems with Lévy noises in two cases-correlated noises and correlated sensor noises. First of all, we prove that the slow part of the origin system converges to the average system in the uniform mean square sense. Then based on the convergence result, in two cases of correlated Lévy noises and correlated Gaussian noises, we prove that the nonlinear filtering of the slow part converges to that of the average system in the weak sense and the [Formula: see text] sense, respectively. Finally, in the case of correlated sensor Gaussian noises, the nonlinear filtering for the slow part is shown to approximate that of the average system in the [Formula: see text] sense.

Swin-textural: A novel textural features-based image classification model for COVID-19 detection on chest computed tomography

BackgroundChest computed tomography (CT) has a high sensitivity for detecting COVID-19 lung involvement and is widely used for diagnosis and disease monitoring. We proposed a new image classification model, swin-textural, that combined swin-based patch division with textual feature extraction for automated diagnosis of COVID-19 on chest CT images. The main objective of this work is to evaluate the performance of the swin architecture in feature engineering. Material and methodWe used a public dataset comprising 2167, 1247, and 757 (total 4171) transverse chest CT images belonging to 80, 80, and 50 (total 210) subjects with COVID-19, other non-COVID lung conditions, and normal lung findings. In our model, resized 420 × 420 input images were divided using uniform square patches of incremental dimensions, which yielded ten feature extraction layers. At each layer, local binary pattern and local phase quantization operations extracted textural features from individual patches as well as the undivided input image. Iterative neighborhood component analysis was used to select the most informative set of features to form ten selected feature vectors and also used to select the 11th vector from among the top selected feature vectors with accuracy >97.5%. The downstream kNN classifier calculated 11 prediction vectors. From these, iterative hard majority voting generated another nine voted prediction vectors. Finally, the best result among the twenty was determined using a greedy algorithm. ResultsSwin-textural attained 98.71% three-class classification accuracy, outperforming published deep learning models trained on the same dataset. The model has linear time complexity. ConclusionsOur handcrafted computationally lightweight swin-textural model can detect COVID-19 accurately on chest CT images with low misclassification rates. The model can be implemented in hospitals for efficient automated screening of COVID-19 on chest CT images. Moreover, findings demonstrate that our presented swin-textural is a self-organized, highly accurate, and lightweight image classification model and is better than the compared deep learning models for this dataset.

Microstructure characteristics of a René N5 Ni-based single-crystal superalloy prepared by laser-directed energy deposition

This work focused on the microstructure and mechanical properties of nickel-based single crystal (SX) superalloy René N5 prepared by laser-directed energy deposition (L-DED) using a flat-top laser beam. A comparison was conducted with the conventional directional solidification technique. Results show that the crack-free single-crystal superalloys with a fraction of low-angle grain boundary (LAGB) higher than 98.5% were obtained by epitaxial growth under different laser powers. The flat fusion line using a flat-top laser beam can suppress the formation of stray grain and high-angle grain boundaries (LAGB) during the L-DED process. Microstructure observation shows the extremely refined dendrites in L-DED SX superalloys with primary dendrite arm spacing (PDAS) values around 20–30 µm, which is significantly lower than as-cast ones (∼350 µm). PDAS increases with the increasing laser power. Segregation of refractory elements of Re, W, and Ta increases with increasing laser power, and the SX specimens with laser power of 1100 W and 1300 W have lower elemental segregation compared with as-cast specimens. The SX specimens exhibit a uniform square γ′ phase at the dendrite core, with an average size of 79–101 nm and a volume fraction of 57–68%. Besides, the carbides with discontinuous and refined shapes show a uniform distribution in the L-DED specimens in comparison with as-cast specimens. The microhardness of as-deposited specimens increases with the increasing laser power, which is higher than that of as-cast ones. This work can provide potential guidance for the microstructure control in the laser additive manufacturing of Ni-based SX superalloys and a further improvement in high-temperature mechanical performance.