Intrinsic Parameters Research Articles

Lithium-coupled electron transfer reactions of nano-confined WOx within Zr-based metal-organic framework.

Interfacial charge transfer reactions involving cations and electrons are fundamental to (photo/electro) catalysis, energy storage, and beyond. Lithium-coupled electron transfer (LCET) at the electrode-electrolyte interfaces of lithium-ion batteries (LIBs) is a preeminent example to highlight the importance of charge transfer in modern-day society. The thermodynamics of LCET reactions define the minimal energy for charge/discharge of LIBs, and yet, these parameters are rarely available in the literature. Here, we demonstrate the successful incorporation of tungsten oxides (WOx) within a chemically stable Zr-based metal-organic framework (MOF), MOF-808. Cyclic voltammograms (CVs) of the composite, WOx@MOF-808, in Li+-containing acetonitrile (MeCN)-based electrolytes showed an irreversible, cathodic Faradaic feature that shifted in a Nernstian fashion with respect to the Li+ concentration, i.e., ∼59 mV/log [(Li+)]. The Nernstian dependence established 1:1 stoichiometry of Li+ and e-. Using the standard redox potential of Li+/0, the apparent free energy of lithiation of WOx@MOF-808 (ΔGapp,Li) was calculated to be -36 ± 1kcal mol-1. ΔGapp,Li is an intrinsic parameter of WOx@MOF-808, and thus by deriving the similar reaction free energies of other metal oxides, their direct comparisons can be achieved. Implications of the reported measurements will be further contrasted to proton-coupled electron transfer (PCET) reactions on metal oxides.

A Rapid Method for Obtaining Camera Intrinsic Parameters Based on a 3D Calibration Target

A Rapid Method for Obtaining Camera Intrinsic Parameters Based on a 3D Calibration Target

The sensitivity of Prazeres clay – some results on reconstituted samples

Soil’s structure is defined as the issue responsible for the differences observed in the mechanical response of natural soil samples compared to the intrinsic behaviour of reconstituted samples. The parameter that incorporates the differences in microstructure of intact and reconstituted clays is designated by stress sensitivity. The influence of microstructure and fabric on the behaviour of soils has been evaluated by comparing strength and compressibility characteristics of intact and reconstituted samples of the same material. Included on a broad characterization study of Lisbon Miocene Prazeres clay held at Porto University, some oedometer and triaxial tests were undertaken on intact and reconstituted samples. In this paper, the process of preparing reconstituted samples and consolidating them in a large oedometer to the in-situ stress is thoroughly described. The results of oedometer and triaxial tests on reconstituted samples are presented and compared with results for intact samples from the same site. A proposal for parameterisation of the intrinsic characteristics of this clay is established on the basis of test results. Concerning compressibility, oedometer test results show good adjustment to the isotropic compression line (ICL). Triaxial test results for intact samples in the light of critical states soil mechanics are similar to those obtained in s’-t space for the reconstituted samples. The intrinsic parameters show good agreement with those described in the literature for soils of the same nature.

Exploring the Impact of Different Leadership Styles on Job Satisfaction among Primary School Teachers in the Achaia Region, Greece

This study explores the relationship between the transformational style of primary education Principals and the job satisfaction of their primary teachers in the Achaia region of Greece. A survey of primary school teachers in Greece (n = 411) revealed a strong positive association between transformational leadership and job satisfaction, highlighting the critical role of effective leadership in fostering a positive and supportive work environment for teachers. Pearson correlation analysis demonstrated significant correlations between leadership style and job satisfaction, considering both extrinsic and intrinsic parameters. Demographic factors, such as age and work experience, were associated with variations in satisfaction with the freedom to choose how to work, recognition for work, and promotion prospects. Specifically, older teachers expressed lower satisfaction levels in these areas. Moreover, the study highlighted the substantial impact of leadership style on job satisfaction. Age had a negative correlation with satisfaction with the freedom to choose how to work (r = −0.11, p = 0.019) and satisfaction with recognition for work (r = −0.112, p = 0.019), suggesting that older teachers tend to be less satisfied with these aspects of their jobs. Work experience had a negative correlation with satisfaction with promotion prospects (r = −0.14, p < 0.001), suggesting that more experienced teachers tend to be less satisfied with their prospects for career advancement. Transformational and personalized leadership styles were positively correlated with job satisfaction. Transformational leadership exhibited a strong positive correlation with satisfaction from the administration, colleagues, and working conditions (r = 0.785, p < 0.001). Transactional leadership also exhibits significant positive correlations with these aspects of job satisfaction, albeit to a slightly lesser extent. On the other hand, transactional leadership demonstrated a moderate positive correlation with overall job satisfaction (r = 0.301, p < 0.01), while no significant correlation is observed with satisfaction from the administration, colleagues, and working conditions. Passive laissez-faire leadership, in contrast, revealed negative correlations with all dimensions of job satisfaction, indicating a detrimental impact on the satisfaction levels of primary school teachers. These nuanced findings underscore the importance of considering multiple leadership styles in understanding their varied impacts on job satisfaction among teachers.

Integration Method of Monitoring Video and Geospatial Data Based on 3D Modeling

The fusion technology of videos has been increasingly applied in various fields such as smart cities and smart agriculture, playing a significant role in enabling real-time scene monitoring and decision-making for surveillance personnel. Currently, conventional methods for integrating geographic data with monitoring videos involve mapping two-dimensional geographic information data onto surveillance videos. However, this method exhibits significant mapping errors in scenarios with large terrain variations and 360 degrees multi-angle real-time previews. To address this issue, this paper proposes a fusion method of monitoring videos and geospatial data based on three-dimensional modeling. This method constructs a virtual scene using digital elevation models and vector geographic data and overlays the images captured under the camera viewport in the virtual scene with each frame of the video images in the monitoring video stream, thereby enhancing the video scene based on geographic data. In practical application scenarios, a system for integrating monitoring videos with geospatial data is designed and implemented. Experimental results demonstrate that this method effectively addresses issues such as unfamiliarity with the geographical environment, ambiguity of location information, inaccuracies in mapping due to terrain variations and changes in camera intrinsic parameters, thus showing superior applicability.

Data-Driven Model Predictive Control for Uncalibrated Visual Servoing

This paper addresses the image-based visual servoing (IBVS) control problem with an uncalibrated camera, unknown dynamics, and constraints. A novel data-driven uncalibrated IBVS (UIBVS) strategy is proposed, incorporated with the Koopman-based model predictive control (KMPC) algorithm and the adaptive robust Kalman filter (ARKF). First, to alleviate the need for calibration of the camera’s intrinsic and extrinsic parameters, the ARKF with an adaptive factor is utilized to estimate the image Jacobian matrix online, thereby eliminating the laborious camera calibration procedures and improving robustness against camera disturbances. Then, a data-driven MPC strategy is proposed, wherein the unknown nonlinear dynamic model is learned using the Koopman operator theory, resulting in a linear Koopman prediction model. Only input–output data are used to construct the prediction model, and hence, the proposed approach is robust against model uncertainties. Furthermore, with a symmetric quadratic cost function, the proposed approach solves the quadratic programming problem online, and visibility constraints as well as joint torque constraints are taken into account. As a result, the proposed KMPC scheme can be implemented in real time, and the UIBVS performance degradation which arises from the control torque constraints can be avoided. Simulations and comparisons for a 2-DOF robotic manipulator demonstrate the feasibility of the proposed approach. Simulation results further validate that the computation time of the proposed approach is comparable to the one of kinematic-based methods.

A comparative study of pose estimation algorithms for visual navigation in autonomous robots

Autonomous navigation is a research field that gives mobile robots the capacity to perform various tasks without human assistance. Autonomous navigation based on visual sensors can be used in GPS denied environments. Vision-based navigation performs feature detection, matching, and pose estimation using camera images. This paper presents a new approach to autonomous navigation for mobile robots using a Color-based Image Segmentation and Centroid Detection algorithm instead of traditional feature detection algorithms. The algorithm intentionally matches features across images using known feature points and uses conventional techniques such as Epipolar Geometry and Perspective-N-Points algorithms for camera pose estimation. The study includes camera calibration to estimate intrinsic parameters and their physical unit conversion ensuring accurate measurements. Experimental datasets are used to analyze the performance of the Epipolar geometry, Perspective-3-Point, and Efficient-Perspective-n-Point based pose estimation algorithms. To enhance accuracy, the P3P algorithm is modified to consider combinations of image points for pose estimation. The paper concludes with a comparative analysis between the original P3P algorithm and the modified version, providing valuable insights into their respective performances. Overall, the paper aims to provide a comparison of different pose estimation algorithms used for visual navigation. Keywords: pose estimation, visual navigation, camera calibration, perspective-n-point, efficient pnp, epipolar geometry Abbreviations PnP, perspective-n-point; P3P, perspective-3-point; EPnP, efficient perspective-n-point; SLAM, simultaneous localization and mapping; VO, visual odometry; GPS, global positioning system; SURF, speeded up robust features; SIFT, scale-invariant feature transform; EKF, extended kalman filter; RGB, red-green-blue; HSV, hue- saturation-value; CNN, convolutional neural network

The pH-Induced Increase of the Rate Constant for HER at Au(111) in Acid Revealed by Combining Experiments and Kinetic Simulation.

Origins of pH effects on the kinetics of electrocatalytic reactions involving the transfer of both protons and electrons, including the hydrogen evolution reaction (HER) considered in this study, are heatedly debated. By taking the HER at Au(111) in acid solutions of different pHs and ionic concentrations as the model systems, herein, we report how to derive the intrinsic kinetic parameters of such reactions and their pH dependence through the measurement of j-E curves and the corresponding kinetic simulation based on the Frumkin-Butler-Volmer theory and the modified Poisson-Nernst-Planck equation. Our study reveals the following: (i) the same set of kinetic parameters, such as the standard activation Gibbs free energy, charge transfer coefficient, and Gibbs adsorption energy for Had at Au(111), can simulate well all the j-E curves measured in solutions with different pH and temperatures; (ii) on the reversible hydrogen electrode scale, the intrinsic rate constant increases with the increase of pH, which is in contrast with the decrease of the HER current with the increase of pH; and (iii) the ratio of the rate constants for HER at Au(111) in x M HClO4 + (0.1 - x) M NaClO4 (pH ≤ 3) deduced before properly correcting the electric double layer (EDL) effects to the ones estimated with EDL correction is in the range of ca. 10 to 40, and even in a solution of x M HClO4 + (1 - x) M NaClO4 (pH ≤ 2) there is a difference of ca. 5× in the rate constants without and with EDL correction. The importance of proper correction of the EDL effects as well as several other important factors on unveiling the intrinsic pH-dependent reaction kinetics are discussed to help converge our analysis of pH effects in electrocatalysis.

Critical effect of exchangeable units distribution on properties of vitrimers: Quantitatively controlling dynamics thus suppressing creep

Vitrimers usually exhibit reprocessability and recyclability due to the reversible crosslinking bonds, thus these materials are expected to be applied as sustainable materials. However, the vitrimer elastomers are susceptible to creep because of their inherent exchange nature, which limits their practical application. The key to improve the creep resistance at service temperature relies on controlling and regulating the intrinsic dynamic properties. Therefore, an in-depth study of the effect of molecular variables on dynamic properties was useful for the design and application of vitrimers. exchangeable units distribution is one of the major molecular variables to tune the dynamics, but it has hardly been studied. Herein, vitrimer elastomers with different uneven degrees of exchangeable units distribution (n) was prepared to study the quantitative relationship between exchangeable units distribution and dynamic behaviors. Due to the uneven exchangeable units distribution, the crosslink-rich and crosslink-poor regions existed simultaneously in networks. The relaxation time of resulting networks increased and then decreased with n due to the combined effects, and samples with moderate uneven distribution showed the longest relaxation time. At the same time, the relaxation times for all samples were short enough to reprocess at elevated temperatures. What is more, the activation energy (Ea) and topology freezing transition temperature (Tv), two important intrinsic parameters for controlling the dynamics, increased linearly with n values. In the meantime, the creep strains and creep rates decreased with n, revealing improved creep resistance. This work provides a strategy to control the dynamics by adjusting the exchangeable units distribution thus enhancing creep resistance. And the proposed strategy and resulting quantitative models might be applied to other vitrimers, which could be utilized to prepare desired vitrimers with exact network designs for various applications.

Micro structural design and macro synthesis of aerogel networks with gradient stiffness properties

Conductive aerogels have received extensive attention in a variety of application fields such as structural engineering and electrochemistry due to their lightweight, porous and conductive properties. The stiffness of aerogel is a key factor affecting its performance. So compared with conventional single stiffness aerogels, the preparation of conductive aerogels with gradient stiffness properties is expected to achieve better stiffness matching and greater performance. Here, we develop a theoretical model of the gradient stiffness carbon nanotube (CNT) network and analyze the factors affecting the stiffness of the model from several perspectives, including spatial configuration and intrinsic parameters. Then, according to the guidance of the simulation results, actual CNT aerogels with gradient stiffness properties are successfully synthesized which have an ultra-wide range of stiffness variations. The unique lightweight gradient stiffness conductive aerogels are expected to show outstanding performance in many stiffness-dominated application fields.

Coupled nonlinear Schrödinger (CNLS) equations for two interacting electrostatic wavepackets in a non-Maxwellian fluid plasma model

The nonlinear dynamics of two co-propagating electrostatic wavepackets in a one-dimensional non-magnetized plasma fluid model is considered, from first principles. The coupled waves are characterized by different (carrier) wavenumbers and amplitudes. A plasma consisting of non-thermalized (κ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\kappa $$\\end{document}-distributed) electrons evolving against a cold (stationary) ion background is considered. The original model is reduced, by means of a multiple-scale perturbation method, to a pair of coupled nonlinear Schrödinger (CNLS) equations for the dynamics of the wavepacket envelopes. For arbitrary wavenumbers, the resulting CNLS equations exhibit no known symmetry and thus intrinsically differ from the Manakov system, in general. Exact analytical expressions have been derived for the dispersion, self-modulation (nonlinearity) and cross-modulation (coupling) coefficients involved in the CNLS equations, as functions of the wavenumbers (k1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$k_1$$\\end{document}, k2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$k_2$$\\end{document}) and of the spectral index κ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\kappa $$\\end{document} characterizing the electron profile. An analytical investigation has thus been carried out of the modulational instability (MI) properties of this pair of wavepackets, focusing on the role of the intrinsic (variable) parameters. Modulational instability is shown to occur in most parts of the parameter space. The instability window(s) and the corresponding growth rate are calculated numerically in a number of case studies. Two-wave interaction favors MI by extending its range of occurrence and by enhancing its growth rate. Growth rate patterns obtained for different κ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\kappa $$\\end{document} index (values) suggest that deviation from thermal (Maxwellian) equilibrium, for low κ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\kappa $$\\end{document} values, leads to enhance MI of the interacting wave pair. To the best of our knowledge, the dynamics of two co-propagating wavepackets in a plasma described by a fluid model with κ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\kappa $$\\end{document}-distributed electrons is investigated thoroughly with respect to their MI properties as a function of κ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\kappa $$\\end{document} for the first time, in the framework of an asymmetric CNLS system whose coefficients present no obvious symmetries for arbitrary k1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$k_1$$\\end{document} and k2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$k_2$$\\end{document}. Although we have focused on electrostatic wavepacket propagation in non-thermal (non-Maxwellian) plasma, the results of this study are generic and may be used as basis to model energy localization in nonlinear optics, in hydrodynamics or in dispersive media with Kerr-type nonlinearities where MI is relevant.

Practical Applications of a Set-Based Camera Deployment Methodology.

This work establishes a complete methodology for solving continuous sets of camera deployment solutions for automated machine vision inspection systems in industrial manufacturing facilities. The methods presented herein generate constraints that realistically model cameras and their associated intrinsic parameters and use set-based solving methods to evaluate these constraints over a 3D mesh model of a real part. This results in a complete and certifiable set of all valid camera poses describing all possible inspection poses for a given camera/part pair, as well as how much of the part's surface is inspectable from any pose in the set. These methods are tested and validated experimentally using real cameras and precise 3D tracking equipment and are shown to accurately align with real imaging results according to the hardware they are modelling for a given inspection deployment. In addition, their ability to generate full inspection solution sets is demonstrated on several realistic geometries using realistic factory settings, and they are shown to generate tangible, deployable inspection solutions, which can be readily integrated into real factory settings.

Optimization of extrinsic parameters for beneficiation of coal with the help of Cronobacter sp

ABSTRACT Beneficiation increases the calorific value of low-grade coal and extracts environmentally sensitive elements. Bacteria may be used as eco-friendly coal cleaning tool, but the treatment is influenced by several extrinsic and intrinsic factors. This study examined five extrinsic factors, namely particle size of coal, pulp density, bacterial biomass concentration, number of bacterial beads (immobilized bacterial cells) and the duration of treatment. For optimization, the test runs were designed using Taguchi L16 orthogonal array, determining optimal values through S/N ratio analysis and individual parameter contribution using ANOVA. The optimal conditions obtained for sub-bituminous coal beneficiation using Cronobacter sp. are 80–120 mesh particle size, 30% pulp density, 750 mg bacterial biomass/g coal, 25 bacterial beads, and six days of treatment resulting in 13.36% ash yield reduction. Particle size had the highest impact (69.4%), followed by treatment duration (13.1%), pulp density (6.3%), bacterial biomass (6.3%), and bacterial bead number (4.8%). A regression model attributed only 42% influence of these extrinsic factors on inorganic removal from coal. Therefore, further research on other factors, particularly intrinsic ones, in inorganic matter liberation is imperative. These findings can be used for designing experiments that optimize the extraction of cleaner fuel from various types of low-grade coal.

Lattice Oxygen Exchange in Transition Metal Oxyhydroxides and Metal Hydroxide Organic Frameworks Elucidated for the Oxygen Evolution Reaction

To achieve the goal of climate neutrality by 2050, it is essential to increase the use of renewable fuels and carbon-neutral energy.1 The anodic oxygen evolution reaction (OER) is a key reaction not only in electrocatalytic production of many renewable fuels,2 but also for next generation of charge storage devices such as metal-air batteries.3 However, the slow kinetics of the OER process result in high energy losses and costs.4 Therefore, the development of more efficient electrocatalysts is critical for making renewable energy via electrocatalysis a viable option in emerging energy systems.Transition metal (TM) oxides are a promising alternative to expensive noble metals due to their high catalytic OER activity under alkaline conditions and wider earth-abundance. Despite extensive research, establishing structure-activity correlations and understanding mechanistic processes is challenging, given the intricate interplay between external and intrinsic parameters.In this study, we investigate the role of lattice oxygens in electrodeposited Ni-Fe, Co-Fe, and Mn-Fe oxyhydroxide (M(OH)xOy, M = TM) electrocatalysts using surface-enhanced Raman spectroscopy (SERS) in conjunction with secondary ion mass spectroscopy (SIMS). By taking advantage of the Raman shift that results from 16O/18O isotope exchange,5–7 we can track the participation of lattice oxygens in the electrocatalytic cycle. Our investigation reveals that, during OER, all the electrocatalysts display minimal exchange of lattice oxygens with the electrolyte (less than 5%). However, many of these electrocatalysts show partial or complete exchange when exposed to non-catalytic potential when in their more reduced states (see Figure 1).Apart from fully inorganic catalysts, we also present results from Ni-derived metal-hydroxide-organic frameworks (MHOFs), which are analogous to M(OH)xOy catalysts but with organic linkers separating the layers.8 Our findings indicate that MHOFs with linkers that have a high π-π stacking energy (and a high structural stability)8 undergo near complete 16O/18O exchange during OER, while MHOFs employing linkers with a low π-π stacking energy (and thus a low stability) show minor or no lattice exchange during OER.Our study suggests that participation oflattice oxygens is closely linked to the oxidation state of the transition metals rather than to the catalytic process. The work provides a detailed picture of the exchange mechanism and elucidates alternative processes involved in lattice oxygen participation and discusses their relation to the mechanisms of the OER process. References IEA (2023), Energy Technology Perspectives 2023, IEA, Paris https://www.iea.org/reports/energy-technology-perspectives-2023, License: CC BY 4.0.Wei, S. Z. et al. Combining theory and experiment in electrocatalysis: Insights into materials design. Science (80-. ). 355, eaad4998 (2017).Li, Y. & Lu, J. Metal–Air Batteries: Will They Be the Future Electrochemical Energy Storage Device of Choice? ACS Energy Lett. 2, 1370–1377 (2017).Song, F. et al. Transition Metal Oxides as Electrocatalysts for the Oxygen Evolution Reaction in Alkaline Solutions: An Application-Inspired Renaissance. J. Am. Chem. Soc. 140, 7748–7759 (2018).Lee, S., Banjac, K., Lingenfelder, M. & Hu, X. Oxygen Isotope Labeling Experiments Reveal Different Reaction Sites for the Oxygen Evolution Reaction on Nickel and Nickel Iron Oxides. Angew. Chemie Int. Ed. 58, 10295–10299 (2019).Moysiadou, A., Lee, S., Hsu, C.-S., Chen, H. M. & Hu, X. Mechanism of Oxygen Evolution Catalyzed by Cobalt Oxyhydroxide: Cobalt Superoxide Species as a Key Intermediate and Dioxygen Release as a Rate-Determining Step. J. Am. Chem. Soc. 142, 11901–11914 (2020).Diaz-Morales, O., Ferrus-Suspedra, D. & Koper, M. T. M. The importance of nickel oxyhydroxide deprotonation on its activity towards electrochemical water oxidation. Chem. Sci. 7, 2639–2645 (2016).Yuan, S. et al. Tunable metal hydroxide–organic frameworks for catalysing oxygen evolution. Nat. Mater. 21, 673–680 (2022). Figure 1

Characterization of the polarization fluctuations in gain-switched VCSELs for quantum random number generation

We report a characterization of the polarization fluctuations observed when gain-switching vertical-cavity surface-emitting lasers (VCSELs) for quantum random number generation (QRNG) applications. We compare our experimental measurements with the results obtained from a stochastic rate equations model that incorporates the intrinsic parameters of the VCSEL found using the state-of-the-art experimental techniques. The good agreement obtained between our experiments and simulations can be used to establish a validation process that permits monitoring of the device behavior to detect malicious intrusion or malfunctioning of the QRNG. Simulations of the model are used to look for parameters that maximize the QRNG performance. Along this direction we consider the performance when considering a VCSEL with vanishing values of the amplitude and phase anisotropies. We show that in this system the obtained raw bits have a low bias value that is independent of the sampling time chosen to obtain the random bit and of the parameters of the modulation. We also use the simulations of the model to predict the QRNG performance at high modulation frequencies. We show that random bits obtained at several Gbps rates, after appropriate post-processing, fully pass the NIST statistical test.

Fast monocular visual-inertial calibration and initialization with weak environmental control and motion control

Most existing visual-inertial systems require control of extrinsic environment and extrinsic motion to obtain calibration results and simplify the initialization model. The former limits the usage scenarios of the method, while the latter reduces the estimation accuracy of the state parameters of the navigation system. Therefore, a visual-inertial calibration and initialization method is necessary for weak environmental and motion control conditions. Firstly, to overcome the reliance on environmental control, we establish a motion constraint equation based on the relative consistency of visual-inertial sensing spatial motion and implement a visual-inertial online calibration method. Secondly, to eliminate the reliance on motion control, a dual graph optimization structure is be constructed. The initial optimization outcome serves as the foundation for achieving improved calibration results in the refined optimization. Thirdly, to improve initialization accuracy, a complete initial state model is considered to decouple and calculate the translation extrinsic parameters. These parameters are compensated into subsequent initialization, enhancing the robustness of the initialization process. The proposed method is validated on the EuRoC dataset, and experimental results demonstrate that it achieves more accurate calibration results at a faster rate than VINS-Mono in scenarios without calibration target and with limited vehicle motion. The navigation results of different scenarios demonstrate that our method can more effectively integrate visual-inertial data due to improved calibration and initialization estimates.

On Kinetic Constraints That Catalysis Imposes on Elementary Processes.

Catalysis, the acceleration of product formation by a substance that is left unchanged, typically results from multiple elementary processes, including diffusion of the reactants toward the catalyst, chemical steps, and release of the products. While efforts to design catalysts are often focused on accelerating the chemical reaction on the catalyst, catalysis is a global property of the catalytic cycle that involves all processes. These are controlled by both intrinsic parameters such as the composition and shape of the catalyst and extrinsic parameters such as the concentration of the chemical species at play. We examine here the conditions that catalysis imposes on the different steps of a reaction cycle and the respective role of intrinsic and extrinsic parameters of the system on the emergence of catalysis by using an approach based on first-passage times. We illustrate this approach for various decompositions of a catalytic cycle into elementary steps, including non-Markovian decompositions, which are useful when the presence and nature of intermediate states are a priori unknown. Our examples cover different types of reactions and clarify the constraints on elementary steps and the impact of species concentrations on catalysis.

CT-based generation of synthetic-pseudo MR images with different weightings for human knee

Synthetic MR images are generated for their high soft-tissue contrast avoiding the discomfort by the long acquisition time and placing claustrophobic patients in the MR scanner's confined space. The aim of this study is to generate synthetic pseudo-MR images from a real CT image for the knee region in vivo. 19 healthy subjects were scanned for model training, while 13 other healthy subjects were imaged for testing. The approach used in this work is novel such that the registration was performed between the MR and CT images, and the femur bone, patella, and the surrounding soft tissue were segmented on the CT image. The tissue type was mapped to its corresponding mean and standard deviation values of the CT# of a window moving on each pixel in the reconstructed CT images, which enabled the remapping of the tissue to its MRI intrinsic parameters: T1, T2, and proton density (ρ). To generate the synthetic MR image of a knee slice, a classic spin-echo sequence was simulated using proper intrinsic and contrast parameters. Results showed that the synthetic MR images were comparable to the real images acquired with the same TE and TR values, and the average slope between them (for all knee segments) was 0.98, while the average percentage root mean square difference (PRD) was 25.7%. In conclusion, this study has shown the feasibility and validity of accurately generating synthetic MR images of the knee region in vivo with different weightings from a single real CT image.

On the surface area per volumetric loading: Its pronounced improvement in densely-packed SWCNT by double-function purification

Volumetric loading is often a critical parameter in process design rather than weight. In this work, we have assessed the volumetric textural parameters of purified single-walled carbon nanotube materials (SWCNT). Purification is a necessary step in the SWCNT manufacturing process as they contain a metal residue inherent to their synthesis. Nitric acid treatment was applied for both metal removal and carbon structural/textural modification. Results show that the volumetric BET area is enhanced in ca. 500% with respect to the non-purified SWCNT (ca. 160% per mass), where both volumetric microporosity and external surfaces are enhanced. For such optimal material, the SWCNT structure remains well-defined though changes are observed (densification, more interstitial space, cutting of the tubes and amorphous carbon being formed). Three intrinsic factors contribute to the volumetric BET's enhancement: the bulk density and the mass-based surface parameters; microporous and external surfaces. The bulk density is enhanced due to a structural densification, thus more carbon is available per volume despite heavier metals (Ni, Y) being removed. One indirect factor, the MOx-removal effect, affects both intrinsic surface parameters. After studying this effect in depth, it was found that the microporosity is truly and largely enhanced due to newly-formed interstitial space. The external surface area is slightly improved but to a much lesser extent than microporosity. Overall, the factors dominating the volumetric BET for our system and applied experimental conditions are the bulk density, microporosity and MOx-removal effect. Concerning the conventional mass-based BET, microporosity and MOx-removal effect are the dominating factors. The study also reveals that mesoporosity control in these materials is possible, in comparison to previous studies.

Optical switching beyond a million cycles of low-loss phase change material Sb2Se3

The development of the next generation of optical phase change technologies for integrated photonic and free-space platforms relies on the availability of materials that can be switched repeatedly over large volumes and with low optical losses. In recent years, the antimony-based chalcogenide phase-change material Sb2Se3 has been identified as particularly promising for a number of applications owing to good optical transparency in the near-infrared part of the spectrum and a high refractive index close to silicon. The crystallization temperature of Sb2Se3 of around 460 K allows switching to be achieved at moderate energies using optical or electrical control signals while providing sufficient data retention time for non-volatile storage. Here, we investigate the parameter space for optical switching of films of Sb2Se3 for a range of film thicknesses relevant to optical applications. By identifying optimal switching conditions, we demonstrate endurance of up to 107 cycles at reversible switching rates of 20 kHz. Our work demonstrates that the combination of intrinsic film parameters with pumping conditions is particularly critical for achieving high endurance in optical phase change applications.