Second-order Behavior Research Articles

Hexagonal diameter in cadmium sulfide/anodic alumina nanoporous bi-layer membrane by a sol–gel spin coating and their sensing application

Cadmium sulfide/anodic alumina nanoporous bi-layer film was designed for the first time by two-step anodization followed by a sol–gel spin coating method. The chemical composition, morphological, electrical and structural properties of the AA and Cd/AA nanoporous membranes have been examined. The morphological investigation of AA layer demonstrates the development of an exceptionally ordered hexagonal exhibit of nanoporous anodic alumina of pore diameter ~ 55 nm and inter-pore distance ~ 125 nm. Though, CdS/AA demonstrated the deposition of nanoporous CdS layer from agglomerated CdS nanoparticles on the surface of the membrane of AA. The energy-dispersive X-ray spectrum of CdS/AA outlined signs of O, Al, Cd, and S, which shows its high purity. The X-ray diffraction affirmed the development of cubic-phase CdS in the favored (220) orientation with normal ~ 86.2 nm crystallite size. The present voltage and resistance–concentration attributes of the CdS/AA layer as a glucose biosensor are fitted well with second-order polynomial behavior (correlation coefficient = 0.981). The glucose concentration changed from 0 to 400 mg/dl. In light of the upsides of the fabrication approach, this new age of minimal effort biosensors can be utilized as a guarantee building block for nanophotonic and nanoelectronic gadgets.

A deep learning method for bearing fault diagnosis based on Cyclic Spectral Coherence and Convolutional Neural Networks

Accurate fault diagnosis is critical to ensure the safe and reliable operation of rotating machinery. Data-driven fault diagnosis techniques based on Deep Learning (DL) have recently gained increasing attention due to theirs powerful feature learning capacity. However, one of the critical challenges lies in how to embed domain diagnosis knowledge into DL to obtain suitable features that correlate well with the health conditions and to generate better predictors. In this paper, a novel DL-based fault diagnosis method, based on 2D map representations of Cyclic Spectral Coherence (CSCoh) and Convolutional Neural Networks (CNN), is proposed to improve the recognition performance of rolling element bearing faults. Firstly, the 2D CSCoh maps of vibration signals are estimated by cyclic spectral analysis to provide bearing discriminative patterns for specific type of faults. The motivation for using CSCoh-based preprocessing scheme is that the valuable health condition information can be revealed by exploiting the second-order cyclostationary behavior of bearing vibration signals. Thus, the difficulty of feature learning in deep diagnosis model is reduced by leveraging domain-related diagnosis knowledge. Secondly, a CNN model is constructed to learn high-level feature representations and conduct fault classification. More specifically, Group Normalization (GN) is employed in CNN to normalize the feature maps of network, which can reduce the internal covariant shift induced by data distribution discrepancy. The proposed method is tested and evaluated on two experimental datasets, including data category imbalances and data collected under different operating conditions. Experimental results demonstrate that the proposed method can achieve high diagnosis accuracy under different datasets and present better generalization ability, compared to state-of-the-art fault diagnosis techniques.

Heme-FeIII Superoxide, Peroxide and Hydroperoxide Thermodynamic Relationships: FeIII-O2•- Complex H-Atom Abstraction Reactivity.

Establishing redox and thermodynamic relationships between metal-ion-bound O2 and its reduced (and protonated) derivatives is critically important for a full understanding of (bio)chemical processes involving dioxygen processing. Here, a ferric heme peroxide complex, [(F8)FeIII-(O22-)]- (P) (F8 = tetrakis(2,6-difluorophenyl)porphyrinate), and a superoxide complex, [(F8)FeIII-(O2•-)] (S), are shown to be redox interconvertible. Using Cr(η-C6H6)2, an equilibrium state where S and P are present is established in tetrahydrofuran (THF) at -80 °C, allowing determination of the reduction potential of S as -1.17 V vs Fc+/0. P could be protonated with 2,6-lutidinium triflate, yielding the low-spin ferric hydroperoxide species, [(F8)FeIII-(OOH)] (HP). Partial conversion of HP back to P using a derivatized phosphazene base gave a P/HP equilibrium mixture, leading to the determination of pKa = 28.8 for HP (THF, -80 °C). With the measured reduction potential and pKa, the O-H bond dissociation free energy (BDFE) of hydroperoxide species HP was calculated to be 73.5 kcal/mol, employing the thermodynamic square scheme and Bordwell relationship. This calculated O-H BDFE of HP, in fact, lines up with an experimental demonstration of the oxidizing ability of S via hydrogen atom transfer (HAT) from TEMPO-H (2,2,6,6-tetramethylpiperdine-N-hydroxide, BDFE = 66.5 kcal/mol in THF), forming the hydroperoxide species HP and TEMPO radical. Kinetic studies carried out with TEMPO-H(D) reveal second-order behavior, kH = 0.5, kD = 0.08 M-1 s-1 (THF, -80 °C); thus, the hydrogen/deuterium kinetic isotope effect (KIE) = 6, consistent with H-atom abstraction by S being the rate-determining step. This appears to be the first case where experimentally derived thermodynamics lead to a ferric heme hydroperoxide OO-H BDFE determination, that FeIII-OOH species being formed via HAT reactivity of the partner ferric heme superoxide complex.

Novel cyclic and linearizing cyclic Pd(II) nanohoop-based cordination complexes achieving nonlinear optical activity transparency trade-off optimization

In this work, we systematically designed and comparatively analyzed the geometric structures, electronic absorption spectra, polarizabilities, first hyperpolarizability (βtot) and dynamic hyper-Rayleigh scattering response of circular Pd(II)-nanohoop complexes with 2,2′-bipyridine-embedded CPPs ligand and curved complexes decorated with alkyl tether accompanied by linear counterparts via quantum chemical calculations. Correlating results demonstrated that in comparison to conventional linear species, nanohoop ligand coordinated with metal Pd(II) can achieve remarkably improved quadratic nonlinear optical (NLO) coefficient, whereas are not accompanied by a certain degree of bathochromic shift in the absorption band. This phenomenon effectively overcomes the trade-off between good transparency and high second-order NLO response. Intriguingly, alkyl tether modified curved complexes own the largest quadratic NLO responses in our case, even the conjugation is broken by alkyl chain modified. Noteworthily, further extending phenylene backbone will not yield any positive effect on the enhancement of their βtot values for circular and linear systems once the number of phenylene reaches a certain degree, suggesting that size-dependent effect can be deemed to an effective approach to obtain the desired NLO response. Additionally, the polarizable environment has a significant influence on second-order NLO behavior, especially an accelerated trend changing from gas phase to solid phase. Overall, we hope these results can enrich the cognition into the NLO structure-function correlations based on metal nanohoop complexes and provide new avenue toward coping with trade-off between good transparency and high NLO performance.

Inelastic second-order analysis of steel columns under minor-axis bending

Abstract The inelastic second-order behavior of steel structural columns under minor-axis bending is presented in this article. To study this behavior, a nonlinear frame element formulation is adopted in which the steel's plasticity process is accompanied at the nodal points of each finite element through the refined plastic-hinge method (RPHM). A tangent modulus approach is employed in order to consider the stiffness degradation in function of the internal forces' variation, and the second-order effects, residual stresses and geometric imperfections are considered in the modeling of column behavior. As a criterium for defining the ultimate limit state of the column cross-section, strength surfaces are adopted. These surfaces describe the interaction between the axial force and bending moment (N-M interaction diagrams). To solve the nonlinear equilibrium equation for the structural system, the Newton-Raphson method is used, coupled with continuation strategies. Columns with different slenderness, boundary and loading conditions are analyzed, and the results obtained are comparable to those found by other researchers. The results lead to the conclusion that the numerical approach adopted in this study can be used for a better behavioral understanding of the steel column under weak-axis bending.

Improve the performance of lattice Boltzmann method for a porous nanoscale transient flow by provide a new modified relaxation time equation

Lattice Boltzmann Method (LBM) is a statistical approach for simulating fluid flow in porous media. LBM is a method based on the kinetic theory of gases and thus is a very powerful tool for simulating such flows. Fluid flow in a nanochannel containing porous media was simulated in this study. The effect of porosity was considered as loss terms in the momentum equations. The flow domain was solved at a high Knudsen number (Kn) of 10 using a new equation for relaxation time to predict increased collisions of molecules to the wall at high Knudsen numbers. No slip condition cannot be applied at high Knudsen numbers due to wall slip. First, the results were calculated at low Knudsen numbers and compared with existing results. Then the results were calculated at high Knudsen numbers. Flow characteristics at different porosities were examined at different inlet to outlet pressure ratios and Knudsen numbers. According to the results, gas permeability and wall slip velocity increased with increasing the Knudsen number, but the maximum axial velocity at the channel center decreased. The wall slip velocity, however, increased by decreasing porosity (increasing barriers). With increasing the Knudsen number at a constant pressure ratio and a certain porosity, the volumetric flow rate decreased at Knudsen numbers below 0.1 and then began to increase at Kn>0.1. The volumetric flow rate increased with increasing porosity. Moreover, the Darcy coefficient increased with increasing the Knudsen number. With an increase in the average pressure along the channel, both permeability and Darcy coefficient decreased. The Darcy coefficient in the slip flow regime varied linearly, but showed a second-order behavior in the transient flow. The results were presented as diagrams including permeability versus Knudsen number, permeability versus porosity and volumetric flow rate as a function of Knudsen number.

Investigating the microstructure and magnetic properties of La-Fe-Si microwires during fabrication and heat treatment process

In this study, the optimized fabrication and evolution of the microstructure and magnetic transition behavior of the melt-extraction LaFe11.2Si1.8 microwires have been studied. After the optimization of extraction technique (heating power 22 KW, feeding rate 30–50 μm/s, rotation velocity 1700 r/min), the content of La(Fe,Si)13 phase in the as-extracted microwires was 54 wt% due to the high solidification velocity, which was increased to 85 wt% via annealing at 1373 K for 20 min. The amount of La(Fe,Si)13 phase was increased and the composition of La(Fe,Si)13 phase became more homogenized through peritectic reaction and short-distance diffusion in the microwires during annealing process. The coexistence of the nanocrystalline and amorphous structures contributed to the broad magnetic transition temperature range of the as-extracted and annealed microwires. The annealed microwires exhibited a second-order magnetic transformation behavior and showed a maximum magnetic entropy change |ΔSM|max of 6.2 J/kg·K and working temperature interval of 36.0 K under a magnetic field of 20 kOe.

Structural Characterization and Second-Order Nonlinear Optical Behavior of Metal Complexes of Ferrocene Derivative

In this manuscript, a ferrocene-linked vic-dioxime ligand (LH2) and its metal complexes [Ni(LH)2, Cu(LH)2, Co(LH)2(H2O)2, Cd(LH)(H2O)(Cl), and Zn(LH)(H2O)(Cl)] are synthesized, and their structures are studied by spectral methods. Redox behavior of the compounds is studied by cyclic voltammetry (CV). For approaching microscopic second-order nonlinear optical (NLO) behavior of the synthesized ligand and its diamagnetic Cd(II), Zn(II), Ni(II) complexes, the electric dipole moment μ, static dipole polarizability α, and first hyperpolarizability β values are computed using ab-initio quantum chemical procedure [finite field (FF)]. The accumulated data indicate that the compounds exhibit non-zero quadratic hyperpolarizability tensor components, implying microscopic NLO phenomena. The HOMOs, LUMOs and the HOMO—LUMO band gaps for first and second frontier orbitals of LH2 ligand and its Cd(II), Zn(II), Ni(II) complexes are evaluated by means of the Hartree-Fock (HF) method.

Semi-analytical orthotropic model for the prediction of the post-buckling behaviour of stiffened cylindrically curved steel panels under uniaxial compression

Stiffened curved steel panels are increasingly used in structural applications in civil, naval and offshore engineering. Due to the incorporation of stiffeners these elements are able to withstand substantial loads with low material usage. However, design provisions to predict the strength of these elements are practically non-existent. The aim of this paper is to present a robust semi-analytical procedure for the prediction of the post-buckling behaviour of stiffened cylindrically curved steel panels under uniform uniaxial compression. The semi-analytical procedure is based on an orthotropic model with the number and geometry of the stiffeners properly taken into account. The procedure is based on nonlinear stability models based on large deflection theory incorporating initial imperfections and geometric nonlinearity. The problem is solved and the equilibrium paths are obtained through the Rayleigh-Ritz method. The validity of these computational models is assessed with the results of finite element analyses for different curvatures, aspect ratios, number and geometry of stiffeners yielding good results. Finally, a design-oriented closed-form expression is derived for the second-order elastic behaviour of the stiffened panels.

Agent-based models for first- and second-order emergent collective behaviours of social amoeba Dictyostelium discoideum aggregation and migration phases

Collective behaviour in nature provides a source of inspiration for engineering artificial systems (e.g. robotics, ecosystems of services), due to their inherent mechanisms favouring adaptation to environmental changes and enabling complex emergent behaviour to arise from a relatively simple behaviour of individual entities. The first-order emergence, also referred to as swarm intelligence, is well studied, while higher order levels of emergent behaviour have not received much attention yet. Second-order emergent behaviour arises from the interactions of individuals, which are themselves the result of first-order emergent behaviour. Dictyostelium discoideum provides a compelling case for studying both first- and second-order emergence. Individual cells move around on their own when there is plenty of food. When food is scarce, cells self-aggregate towards a leading center cell (first-order emergent behaviour) to build a super-organism, similar to a slug. The slug displays properties that none of the cells has on its own (e.g. sensitivity to light and heat). It moves as a whole (second-order emergent behaviour) looking for a suitable place to transform into a fruiting body (also known as sporocarp), where later the cells resume their individual behaviour. This paper focuses specifically on the aggregation and migration phases of Dictyostelium discoideum. We present two agent-based models, implemented in Matlab for first order and Python for second order. They display a series of emergent properties, among others homogeneous aggregation territories size (first order) and merging of slugs or new property as sensitivity to light (second order). Future works involve implementing and experimenting both first- and second-order emergence in swarm robotics, and identification of design patterns for engineering higher order emergent behaviour in artificial systems.

Problem-solving behaviour of nurses in a lean environment.

To investigate how the extensiveness of a lean implementation-that is, the extent to which lean as a new practice is adopted across nursing departments-relates to second-order problem solving behaviour of nurses. Lean implementation is expected to stimulate nurses' second-order problem-solving behaviour. We used a vignette-based survey to look for differences in second-order problem-solving behaviour in early-adopter and late-adopter departments at two hospitals with differing degrees of extensiveness of lean implementation. At the hospital with an extensive lean implementation, nurses at the early-adopter department showed 71 second-order problem-solving responses from 50 problem scenarios, as compared with 39 responses from 37 scenarios in the late-adopter department. At the hospital with a less extensive lean implementation, these numbers were 16 from 23 compared with 18 from 19. The nurses in the hospital with an extensive lean implementation show more second-order problem-solving behaviour than those in the hospital with a stand-alone approach in a single department. Extensive lean implementation where management clearly shows its belief in lean is a more favourable environment for changing the problem-solving behaviour of nurses.

Coexisting first- and second-order electronic phase transitions in a correlated oxide

The explanation and control of phase transitions remain cornerstones of contemporary physics. Landau provided an invaluable insight into the thermodynamics of complex systems by formulating their phase transitions in terms of an order parameter. Within this formulation, continuous evolution of the order parameter away from zero classifies the phase transition as second-order, whereas a discontinuous change signals a first-order transition. Here we show that the temperature-tuned insulator–metal transition in the prototypical correlated electron system NdNiO3 defies this established binary classification. By harnessing a nanoscale optical probe of the local electronic conductivity, we reveal two physically distinct yet concurrent phase transitions in epitaxial NdNiO3 films. Whereas the sample bulk exhibits a first-order transition between metal and insulator phases, we resolve anomalous nanoscale domain walls in the insulating state that undergo a distinctly continuous insulator–metal transition, with hallmarks of second-order behaviour. We ascribe these domain walls to boundaries between antiferromagnetically ordered domains within the charge ordered bulk. The close correspondence of these observations to predictions from a Landau theory of coupled charge and magnetic orders highlights the importance of coupled order parameters in driving the complex phase transition in NdNiO3. A phase transition between metallic and insulating states is observed to simultaneously happen in two ways at once. The bulk of the sample shows an instantaneous jump in the conductivity, while 1D domain walls show a slow switching into a metallic state.

Image-Based Visual-Impedance Control of a Dual-Arm Aerial Manipulator

Three new image-based visual-impedance control laws are proposed in this letter allowing physical interaction of a dual-arm unmanned aerial manipulator equipped with a camera and a force/torque sensor. Namely, two first-order impedance behaviors are designed based on the transpose and the inverse of the system Jacobian matrix, respectively, while a second-order impedance behavior is carried out as well. Visual information is employed both to coordinate the camera motion in an eye-in-hand configuration with the assigned task executed by the other robot arm, and to define the elastic wrench component of the proposed hybrid impedance equations directly in the image plane.

Critical scaling near the yielding transition in granular media.

We show that the yielding transition in granular media displays second-order critical-point scaling behavior. We carry out discrete element simulations in the low-inertial-number limit for frictionless, purely repulsive spherical grains undergoing simple shear at fixed nondimensional shear stress Σ in two and three spatial dimensions. To find a mechanically stable (MS) packing that can support the applied Σ, isotropically prepared states with size L must undergo a total strain γ_{ms}(Σ,L). The number density of MS packings (∝γ_{ms}^{-1}) vanishes for Σ>Σ_{c}≈0.11 according to a critical scaling form with a length scale ξ∝|Σ-Σ_{c}|^{-ν}, where ν≈1.7-1.8. Above the yield stress (Σ>Σ_{c}), no MS packings that can support Σ exist in the large-system limit L/ξ≫1. MS packings generated via shear possess anisotropic force and contact networks, suggesting that Σ_{c} is associated with an upper limit in the degree to which these networks can be deformed away from those for isotropic packings.

A TESTING BASED APPROACH TO THE DISCOVERY OF DIFFERENTIALLY CORRELATED VARIABLE SETS.

Given data obtained under two sampling conditions, it is often of interest to identify variables that behave differently in one condition than in the other. We introduce a method for differential analysis of second-order behavior called Differential Correlation Mining (DCM). The DCM method identifies differentially correlated sets of variables, with the property that the average pairwise correlation between variables in a set is higher under one sample condition than the other. DCM is based on an iterative search procedure that adaptively updates the size and elements of a candidate variable set. Updates are performed via hypothesis testing of individual variables, based on the asymptotic distribution of their average differential correlation. We investigate the performance of DCM by applying it to simulated data as well as to recent experimental datasets in genomics and brain imaging.

In situ Raman spectroscopic monitoring of organic dyes and ferric ions in Fenton reactions on sharp-edged gold nanostar surfaces

For this report, we compared interfacial spectroscopic tools to monitor in situ Fenton reactions of organic dyes on ascorbic acid-reduced gold nanostars (AuNSs). Ultraviolet-visible (UV–vis) absorption and Raman spectroscopic tools were introduced to check the hydroxyl radical destruction of ethyl violet (EV), which contains a triarylmethane group. AuNSs with sharp edges, tips, and corners were used as efficient surface-enhanced resonance Raman scattering (SERRS) substrates for in situ Fenton reaction monitoring. The SERRS intensity of the EV showed a first-order decay curve with a reaction rate constant value of 0.0263 min−1, while the decolorization yielded second-order kinetic behavior with a constant value of 0.00430 L/mol min. In addition to the destruction of the organic dyes, the increased number of ferric (III) ions, as a result of the Fenton reactions, was detected via 4-aminobenzo-15-crown-5 (4AB15C5) conjugated with 4-mercaptobenzoic acid (4MBA). We found that the SERRS bands at ∼1500 cm−1 of 4AB15C5 on AuNSs increased after treatment with H2O2 and FeSO4. Real industrial textile wastewater samples were then tested to determine whether this Raman method could be applied to detect increases in ferric ions. Our spectroscopic data used SERRS peaks via Fenton reaction results to calculate an estimated ∼65% destruction of the organic dyes.

A new improved fiber plastic hinge method accounting for lateral-torsional buckling of 3D steel frames

This paper presents a new advanced analysis method, specifically a new improved fiber plastic hinge method, for analyzing the nonlinear inelastic behavior of 3D steel frames accounting for lateral-torsional buckling. The second-order effects are considered by the use of the geometric stiffness matrix and stability functions obtained from the exact solution of beam-columns under axial force and bending moments at two ends. The spread of plasticity along the member length due to both residual stresses and the impact of axial force is considered by utilizing the Column Research Council (CRC) tangent modulus concept, while the gradual yielding due to flexure is represented by two fiber plastic hinges at the ends of the element. The lateral-torsional buckling stiffness matrix is established by the virtual work principle using the updated Lagrangian formulation. The generalized displacement control method is applied to solve the nonlinear equilibrium equations in an incremental-iterative scheme. The nonlinear load-displacement behavior and ultimate load results compare well with those of previous studies. It is concluded that accurately using only one element per member likely predicts the second-order inelastic behavior of 3D steel frames including the effect of lateral-torsional buckling.

Restoration of quantum critical behavior by disorder in pressure-tuned (Mn,Fe)Si

In second-order quantum phase transitions from magnetically ordered to paramagnetic states at T = 0, tuned by pressure or chemical substitution, a quantum critical point is expected to appear with critical behavior manifesting in the slowing down of spin fluctuations in the paramagnetic state and a continuous development of the order parameter in the ordered state. Quantum criticality is discussed widely as a possible driving force for unconventional superconductivity and other exotic phenomena in correlated electron systems. In the real world, however, quantum critical points and quantum criticality are often masked by a preceding first-order transition and/or the development of competing states. Pressure tuning of the itinerant-electron helical magnet MnSi is a well-known example of the suppression of a quantum critical point due to a first-order phase transition and resulting destruction of the ordered state. Utilizing muon spin relaxation experiments, here we report that 15% Fe-substituted (Mn,Fe)Si exhibits completely different behavior with pressure tuning, including the restoration of second-order quantum critical behavior and a quantum critical point at pQPC ~ 21–23 kbar, which coincides with the T = 0 crossing point of the extrapolated phase boundary line of pure MnSi. This result is quantitatively consistent with the recent theory of itinerant-electron ferromagnets by Sang, Belitz, and Kirkpatrick, who argued that disorder would restore a quantum critical point which is otherwise hidden by a first-order transition.

Investigation on the bulk growth of $${\upalpha }$$ α - $$\hbox {LiIO}_{3}$$ LiIO 3 single crystals and the influence of pH on its structural, morphological and optical characteristics

\(\upalpha \)-\(\hbox {LiIO}_{3}\) is an excellent optical material exhibiting strong nonlinear optical, piezoelectric and elasto-optic properties. However, its practical applications are limited by the insufficient reproducibility of the mentioned properties caused by the strong influence of the growth conditions, and, in particular, pH of the solution from which \(\upalpha \)-\(\hbox {LiIO}_{3}\) crystal is grown. Herein, we investigate to grow bulk size good quality crystals of \(\upalpha \)-\(\hbox {LiIO}_{3}\) based on the observed problems during its crystallization process. A systematic investigation was carried out to find the effect of pH on solubility, crystal growth, structural, surface and laser damage properties of \(\upalpha \)-\(\hbox {LiIO}_{3}\) single crystals. The structure and phase of \(\hbox {LiIO}_{3}\) were confirmed by powder X-ray diffractometer analysis. The functional groups of the compound were identified using Fourier transform infrared spectroscopy. Surface defects of the grown crystals were studied by etch patterns. The crystal grown at pH 10 showed 10% optical transmission enhancement in comparison to the crystals grown at pH 2. The indirect optical bandgap of the crystal was reinvestigated using ultraviolet–Visible–near-infrared transmittance spectrum. The laser damage threshold studies of the crystals grown at pH 10 reveal the higher optical radiation stability against 532 nm laser. The second-order nonlinear optical behaviour of \(\upalpha \)-\(\hbox {LiIO}_{3}\) crystals grown at different pH conditions have been investigated by using Kurtz and Perry powder technique with Nd:YAG laser pulses at the wavelength of 1064 nm.

On Weighted Depths in Random Binary Search Trees

Following the model introduced by Aguech et al. (Probab Eng Inf Sci 21:133–141, 2007), the weighted depth of a node in a labelled rooted tree is the sum of all labels on the path connecting the node to the root. We analyse weighted depths of nodes with given labels, the last inserted node, nodes ordered as visited by the depth first search process, the weighted path length and the weighted Wiener index in a random binary search tree. We establish three regimes of nodes depending on whether the second-order behaviour of their weighted depths follows from fluctuations of the keys on the path, the depth of the nodes or both. Finally, we investigate a random distribution function on the unit interval arising as scaling limit for weighted depths of nodes with at most one child.