Peculiar Behavior Research Articles

Flow field analysis of self-sustained flutter of a wide-slotted bridge deck

This study delves into the flutter mechanism of a 5,000 m bridge with a wide-slotted deck, finding that the motion is self-sustained and not violently destructive. The system damping ratio is not fixed, and only one stable orbit exists. High-resolution PIV experiments at an experimental wind speed of 10.5 m/s measured the static and dynamic flow fields on the windward and leeward decks. The static results showed leading-edge separation on the windward deck within the reference range, while separation on the leeward deck was difficult to observe. Dynamic testing identified instantaneous vortices around the windward/leeward deck at each phase, with no signs of vortices in the wind speed vectors at all phases after phase-averaging, indicating that the vortex drift hypothesis is not valid. The analysis of the streamline pattern revealed periodic variations in leading-edge separation size and reattachment length on the windward deck during the vibration process, while the leeward deck showed consistently inconspicuous changes. Further examination uncovered a peculiar behavior in the horizontal wind speed profile on the leeward deck during the vibration process, attributed to dynamic changes in the height difference between the windward and leeward decks during flutter. The study suggests that the unusual wind speed profile on the leeward deck is caused by the dynamic changes in height difference between the windward and leeward decks during the flutter process, resulting in additional wind loading. These findings shed light on the complex dynamics of bridge flutter and have implications for the design and maintenance of long-span bridges.

The Adaptative Modulation of the Phosphinito–Phosphinous Acid Ligand: Computational Illustration Through Palladium-Catalyzed Alcohol Oxidation

The phosphinito–phosphinous acid ligand (PAP) is a singular bidentate-like self-assembled ligand exhibiting dissymmetric but interchangeable electronic properties. This unusual structure has been used for the generation of active palladium hydride through alcohol oxidation. In this paper, we report the first theoretical highlight of the adaptative modulation ability of this ligand within a direct H-abstraction path for Pd and Pt catalyzed alcohol oxidation. A reaction forces study revealed rearrangements in the ligand self-assembling system triggered by a simple proton shift to promote the metal hydride generation via concerted six-center mechanism. We unveil here the peculiar behavior of the phosphinito–phosphinous acid ligand in this catalysis.

Cellulose Acetates in Hydrothermal Carbonization: A Green Pathway to Valorize Residual Bioplastics.

Bioplastics possess the potential to foster a sustainable circular plastic economy, but their end-of-life is still challenging. To sustainably overcome this problem, this work proposes the hydrothermal carbonization (HTC) of residual bioplastics as an alternative green path. The focus is on cellulose acetate - a bioplastic used for eyewear, cigarette filters and other applications - showing the proof of concept and the chemistry behind the conversion, including a reaction kinetics model. HTC of pure and commercial cellulose acetates was assessed under various operating conditions (180-250 °C and 0-6 h), with analyses on the solid and liquid products. Results show the peculiar behavior of these substrates under HTC. At 190-210 °C, the materials almost completely dissolve into the liquid phase, forming 5-hydroxymethylfurfural and organic acids. Above 220 °C, intermediates repolymerize into carbon-rich microspheres (secondary char), achieving solid yields up to 23 %, while itaconic and citric acid form. A comparison with pure substrates and additives demonstrates that the amounts of acetyl groups and derivatives of the plasticizers are crucial in catalyzing HTC reactions, creating a unique environment capable of leading to a total rearrangement of cellulose acetates. HTC can thus represent a cornerstone in establishing a biorefinery for residual cellulose acetate.

Solving the B-SAT Problem Using Quantum Computing: Smaller Is Sometimes Better.

This paper aims to outline the effectiveness of modern universal gate quantum computers when utilizing different configurations to solve the B-SAT (Boolean satisfiability) problem. The quantum computing experiments were performed using Grover's search algorithm to find a valid solution. The experiments were performed under different variations to demonstrate their effects on the results. Changing the number of shots, qubit mapping, and using a different quantum processor were all among the experimental variables. The study also branched into a dedicated experiment highlighting a peculiar behavior that IBM quantum processors exhibit when running circuits with a certain number of shots.

Remembering as an operant: Effects of instructional control and reinforcement on remembering behavior.

With the general aim of providing more evidence for considering certain behaviors involved in the act of remembering as operant, two experiments were carried out to verify its sensitivity to differential reinforcement, and to some of the variables upon which it depends. In the first experiment, three children participated, and two variables were manipulated in a "free recall" task: the accuracy of the instructions and the magnitude of the reinforcer applied to the emission of the target words. In the second experiment, 60 was changed to one of comparison between groups. In this case, the response-reinforcer interval (immediate vs. delayed) was manipulated using a "recognition" task. In both experiments, a greater number of remembered items were found in the presence of reinforcement compared to its absence, as well as with a greater magnitude of the reinforcer and with a shorter delay. These results are discussed considering the peculiarities of verbal behavior in humans and provide evidence that operant processes have an important role in traditional human memory tasks.

Peculiar trapping behavior of porous organic nanocage CC1 towards H2S, SF6, SF4, SOCl2 and SO2; A DFT Perspective

The current study explores the trapping of harmful gases using porous organic cage CC1, a covalently bound imine cage with accessible voids. Using WB97XD/6-311G(d, p) theory level, the research computes CC1 and its complexes with pollutants like H2S, SF6, SF4, SOCl2, and SO2. DOS and FMO analyses are performed at DFT/ B3LYP/6-311G(d, p) theoretical level. Interaction energy, NCI, QTAIM, EDD, NBO, charge dissociation, FMO, DOS, and MEP studies provide a detailed insight into the analytes@CC1 complexation. Interaction energies (−4.49 to −0.34 eV) show strong trapping of SOCl2 and SF4 while, slight trapping of H2S within the cavity of CC1. Thermodynamic parameters confirm these findings. Analyses (NCI, QTAIM) indicate strong non-covalent interactions, especially for SOCl2 and SF4. NBO analysis reveals charge transfer from analytes to the cage, except for H2S. EDD analysis is also implemented to verify NBO charge transfer. This study highlights CC1′s peculiar trapping behaviour for the considered analytes.

Periodic information enhancing and controlling stability of complex corporate financial systems

We explore the mechanism and control behavior of how periodic information affects the stability of complex corporate financial systems from two viewpoints: the corporate life cycle and the stability of financial leverage risk. A complex corporate financial system model with correlated noise and periodic driving is proposed. Furthermore, two stability indicators are proposed to measure the stability of the corporate life cycle and the risk of corporate financial leverage. Stochastic simulation results show that enhancing the intensity and frequency of controllable periodic information can improve system stability. The stability of complex corporate life cycles and financial leverage risks exhibits opposite behaviors in terms of noise correlation. In addition, it is observed that there are specific threshold values of system parameters, and the relationship with the intensity of periodic information shows non-monotonic characteristics, manifesting peculiar phenomena and transition behaviors. Finally, by comparing with actual financial data, the proposed model is verified to be superior to the benchmark model.

Step flow mechanism in dissolutive wetting Cu/Ni systems

The Cu-Ni system is a typical dissolutive system due to its mutual dissolution across a wide range of temperatures and compositions. We characterized the effects of Ni dissolution on the wetting behavior of liquid Cu by combining high-temperature wetting experiments, in-situ observation of spreading and solidification, microstructure analysis of the quenched droplets, and computational fluid dynamic (CFD) simulations. In the very early moment, at 1100 °C, when the Cu droplet is brought in contact with the Ni substrate, it oscillates due to capillarity and is dampened by inertial effects, while the significant Ni dissolution at 1150 °C largely reduced the initial oscillations. Later, a peculiar spreading behavior is observed and we propose to describe it through a 4-step mechanism: pinning of the contact line by a newly formed solid solution layer at the interface acting as a physical barrier, driving of liquid towards the solidified edge due to a Ni-concentration induced Marangoni flow, forming of a precursor film ahead of the solidified edge caused by the strong Cu-Ni interactions and Marangoni flow, and finally depinning due to overflow as a result of liquid accumulation at the solidified edge. The formation of a solid solution layer is confirmed by in-situ observation and quenching. The Ni-concentration induced Marangoni flow is characterized experimentally and further investigated by CFD simulations. The proposed step flow mechanism can be potentially relevant to other dissolutive wetting systems (e.g. Bi/Sn, Ag/Cu and Cu/Fe systems), which are crucial for high-temperature processing techniques.

Peculiarities of behavior in “soil–water” environment of radiocesium in contaminated area after the accident at Fukushima Dai-ichi NPP

Peculiarities of behavior in “soil–water” environment of radiocesium in contaminated area after the accident at Fukushima Dai-ichi NPP

Packing properties assessment of cement and alternative powders: Artefacts and protocols

This paper introduces three major recommendations for the assessment of the maximum packing fraction of mineral powders through compressive rheology. First, our results show that a minimum compressive stress is required for the measured solid volume fraction to tend towards a constant jamming fraction. Second, we show that the modification of the particles surface properties, especially their friction coefficient, by polymer adsorption, allows for this jamming fraction to get closer to the particle maximum packing fraction. Finally, we show that a minimal value of the initial solid volume fraction of a sample is necessary to prevent particle size separation during testing. We moreover show that the measured jamming fraction depends on the initial solid volume fraction of cement-based samples. We suggest that such a peculiar behavior finds its origin in the dependency of early hydrates volume or morphology on the initial supersaturation.

Investigation of microstructure and microtexture development and its correlation with mechanical and formability behavior of dissimilar friction stir welded AA6061 and AA5754 sheets

The major attention of the automotive, aerospace, and marine industries currently is towards light-weight structural parts, and this can be achieved by the use of the tailor-welded blanks (TWBs). Using Al alloys as a member of the TWBs lessens the structural weight further, but conventional fusion welding of these alloys is often associated with defects such as porosity, manifestation of segregation and under-fill formation. Friction stir welding (FSW) is a feasible approach not only for producing welds with minimal defects but also for their enhanced formability, which finds extensive applications across industries. Due to its capability of completely negating the rolling directional properties of the as-received sheet, FSW increases the uniformity in the strain distribution during the course of deformation. In the present study, the objective was to perform FSW for dissimilar materials (with advancing side AA6061 and retreating side AA5754 sheets) with a similar thickness of 1.5 mm and to investigate the formability behavior of the TWBs. The effect of different FSW process parameters like rotational speed (950 rpm, 1100 rpm, 1250 rpm, and 1400 rpm) and traverse speed (50 mm/min, 75 mm/min, and 100 mm/min) which were selected based on visual inspection and macrostructure studies of the welds, was investigated on the formability and mechanical behavior of welded AA6061 and AA5754 sheets. Tensile tests were performed for base materials along with the specimens welded at different process parameters according to ASTM E8 standard to evaluate the mechanical properties. Micro-hardness tests were performed at several locations of the cross-section in the transverse direction to the weld in either side. The assessment of formability was executed by deforming the as-received and welded specimens in uniaxial strain paths, plane strain paths, and biaxial strain paths using Limit Dome Height (LDH) tests. Tensile test evaluation of 1250 rpm–50 mm/min, 1250 rpm–75 mm/min, 1400 rpm–50 mm/min, and 1400 rpm–75 mm/min parameter combinations exhibited cracks away from the weld center towards the advancing side (AA6061 side) of the specimens, indicating good quality of the welds, which was in agreement with the stir zone macrostructures. The micro-hardness distribution plots also showed a drop in the hardness in the TMAZ of the advancing side, making it the weakest region of the weld. It has been observed from the LDH test that the formability of all the FSWed specimens was intermediate to the formability of AA5754 (superior formability) and AA6061 (inferior formability), irrespective of the strain paths that might be correlated to their corresponding strain hardening exponents. In the case of uniaxial and plane strain paths in the welded specimens, the failure was towards the advancing side, which was in agreement with the tensile properties, but in the case of biaxial stretching, it was failing at the weld center due to their corresponding microstructural characteristics. An abnormal behavior was witnessed in the equibiaxial stretching, i.e., the minor strain attained for all the welded specimens was significantly less. Comprehensive studies on microstructure and microtexture were performed on the un-deformed and deformed specimens to investigate the peculiar behavior, and it was inferred that the initial local misorientations play a pivotal role in determining the grain orientation spread (GOS) post-deformation. It was further observed that the average GOS values were analogous across all the deformed welded samples in their respective strain paths. It's noteworthy that the presence of the Cube texture component in the biaxial strain path significantly mitigated the impact of the Goss texture, resulting in the peculiar behavior i.e. a notable decrease in the minor strain observed in the deformed welded specimens in the biaxial strain path.

Kinetics of Low Molecular Substances Sorption by the Polymer Mixtures

The sorption capacity of polymer blends was analyzed on the basis of absorption kinetics. The study was carried out in an adsorption-active medium with different degrees of deformation. Heptane and butanol were used as adsorption-active media. The influence of the chemical nature of the adsorbate on the sorption process was studied. The free volume fractions for each sample of the composition were calculated. The ability of materials to absorb different amounts of substances allows us to identify the behavior peculiarities of the interfacial regions of different chemical compositions.

A biomimetic chiral auxetic vertebral meta-shell

Abstract The work presents a novel thin-walled biomimetic auxetic meta-shell for patient-specific vertebral orthopedic implants. The proposed design stemmed from the concept of an intrinsically multiple curved auxetic meta-structure, which is created by folding a 2D bio-inspired chiral geometry according to the morphology of human vertebral cortical bones. Through a multi-view stereo Digital Image Correlation (DIC) system, we investigated the mechanical response of a bio-grade titanium (Ti6Al4V ELI) additively manufactured prototype of the meta-structure under compressive loadings. In addition, we analyzed the morphology of the prototype using a scanning electron microscopy (SEM) and an optical image dimension measurement system both before and after compressive tests. An accurate Finite Element model, which exactly reproduced the geometry of the 3D printed meta-shell, was implemented and calibrated against experimental results, obtaining a precise prediction tool of its mechanical response. The findings of this work demonstrate that the designed meta-shell shows a peculiar auxetic behavior, a targeted stiffness matching to that of human vertebral bone tissues and a higher global elastic strain capability compared to those of monolithic traditional vertebral body replacements.


Homogenization of Thermal Properties in Metaplates.

Three-dimensional metamaterials endowed with two-dimensional in-plane periodicity exhibit peculiar thermoelastic behaviour when heated or cooled. By proper design of the unit cell, the equivalent thermal expansion coefficient can be programmed and can also reach negative values. The heterogeneity in the third direction of such metamaterials also causes, in general, a thermal-induced deflection. The prediction of the equivalent thermal properties is important to design the metamaterial suitable for a specific application. Under the hypothesis of small thickness with respect to the global in-plane dimensions, we make use of asymptotic homogenization to describe the thermoelastic behaviour of these metamaterials as that of an equivalent homogenous plate. The method provides explicit expressions for the effective thermal properties, which allow for a cost-effective prediction of the thermoelastic response of these metaplates.

Serotonin deficiency from constitutive SKN-1 activation drives pathogen apathy

When an organism encounters a pathogen, the host innate immune system activates to defend against pathogen colonization and toxic xenobiotics produced. C. elegans employ multiple defense systems to ensure survival when exposed to Pseudomonas aeruginosa including activation of the cytoprotective transcription factor SKN-1/NRF2. Although wildtype C. elegans quickly learn to avoid pathogens, here we describe a peculiar apathy-like behavior towards PA14 in animals with constitutive activation of SKN-1, whereby animals choose not to leave and continue to feed on the pathogen even when a non-pathogenic and healthspan-promoting food option is available. Although lacking the urgency to escape the infectious environment, animals with constitutive SKN-1 activity are not oblivious to the presence of the pathogen and display the typical pathogen-induced intestinal distension and eventual demise. SKN-1 activation, specifically in neurons and intestinal tissues, orchestrates a unique transcriptional program which leads to defects in serotonin signaling that is required from both neurons and non-neuronal tissues. Serotonin depletion from SKN-1 activation limits pathogen defenses capacity, drives the pathogen-associated apathy behaviors and induces a synthetic sensitivity to selective serotonin reuptake inhibitors. Taken together, our work reveals interesting insights into how animals perceive environmental pathogens and subsequently alter behavior and cellular programs to promote survival.

Deformation dynamics of nanopores upon water imbibition

Capillarity-driven transport in nanoporous solids is widespread in nature and crucial for modern liquid-infused engineering materials. During imbibition, curved menisci driven by high negative Laplace pressures exert an enormous contractile load on the porous matrix. Due to the challenge of simultaneously monitoring imbibition and deformation with high spatial resolution, the resulting coupling of solid elasticity to liquid capillarity has remained largely unexplored. Here, we study water imbibition in mesoporous silica using optical imaging, gravimetry, and high-resolution dilatometry. In contrast to an expected Laplace pressure-induced contraction, we find a square-root-of-time expansion and an additional abrupt length increase when the menisci reach the top surface. The final expansion is absent when we stop the imbibition front inside the porous medium in a dynamic imbibition-evaporation equilibrium, as is typical for transpiration-driven hydraulic transport in plants, especially in trees. These peculiar deformation behaviors are validated by single-nanopore molecular dynamics simulations and described by a continuum model that highlights the importance of expansive surface stresses at the pore walls (Bangham effect) and the buildup or release of contractile Laplace pressures as menisci collectively advance, arrest, or disappear. Our model suggests that these observations apply to any imbibition process in nanopores, regardless of the liquid/solid combination, and that the Laplace contribution upon imbibition is precisely half that of vapor sorption, due to the linear pressure drop associated with viscous flow. Thus, simple deformation measurements can be used to quantify surface stresses and Laplace pressures or transport in a wide variety of natural and artificial porous media.

Quantum migration and its local heat impact: Understanding local heat capacity of confined systems.

For noninteracting particles confined in a constant volume, the temperature derivative of the local energy assumes negative values in thermodynamic equilibrium at low temperatures. This peculiar behavior may entail the misleading unphysical conclusion that the local heat capacity is negative. However, we show that temperature-dependent density variations of confined particles induce an energy selective particle transport within the domain, here called temperature-induced quantum migration. This macroscopic quantum phenomenon causes a redistribution of local heat and ensures a non-negative local heat capacity. Moreover, it induces local heating and cooling effects and a massive overshoot in local heat capacity. The quantum migration also builds up the thermal part of confinement energy, manifesting in an excess global heat capacity. Analyzing the local energy fluctuations shows that the linear relationship between heat capacity and fluctuations is broken at the local scale.

The role of the dynamic pressure in the behavior of an oscillating gas bubble

The paper contains a preliminary study on the role that dynamic pressure might play in the dynamics of a gas bubble oscillating in a liquid. To this aim, we introduce a mathematical model, proposed under the homobaricity hypothesis and deduced from the 14-moment theory of rational extended thermodynamics through significant simplifications, that makes the equations easily integrable over long time intervals. In the presence of a gas with high bulk viscosity, relevant effects can be observed in different physical conditions: isothermal or adiabatic regimes, small amplitude oscillations, non-linear oscillations, resonances, and sonoluminescence. To make the study more realistic, we always refer to carbon dioxide gas, which on the one hand could present high values of bulk viscosity and on the other hand is known for its peculiar behaviors in the framework of cavitation and gas bubbles.

On the cutoff, reappearance, and persistence of subsonic leaky A0 Lamb waves

Abstract Subsonic leaky A0 Lamb waves, whose phase speeds are lower than the fluid’s sound speed, exhibit several peculiar behaviours. In this work, we investigate three such behaviours: Cutoff, where the A0 branch cuts off at some point in the subsonic domain, reappearance, where the cut-off A0 branch reappears at lower frequencies, and persistence, where the A0 branch is never cut off at all. From the literature, we take the case of a 1 mm thick aluminium plate immersed in air of varying density. We then analyse its exact leaky A0 wave solutions by means of a sound radiation model that takes energy conservation into account. This analysis explains these peculiar behaviours by connecting them with the conditions that allow sound-radiating subsonic leaky A0 Lamb waves.

Sensitivity analysis of activity scheduling parameters with a parameter optimization framework

Transportation-related activity scheduling is becoming more complex due to the growing number of potential locations and extensive opportunities to visit various places. Throughout the years, in the field of transportation several attempts were made to optimize travelers’ activity chains with different parameters to set, but there is a lack of comprehensive solutions. In this research, the activity chain optimization algorithm is applied, which requires high computational efforts. To provide an adequate calibration of the parameters, a sensitivity analysis is conducted. The aim of the analysis is to reveal how changes in the attribute values modify the final outcomes. The relevant parameters, activity chains, transport modes, optimization algorithms, and fitness functions, are identified and considered. For each parameter, an investigation is conducted to reveal its behavior throughout the runs. For example, changes in the population size and crossover function lead to more reliable results, while alteration in the number of generations and the mutation function have no effects on the outcomes. The analysis presents a peculiar behavior of the parameters related to the activity chains. The results can be useful for transportation planners and service providers in the adaptation of the existing network and transportation services to the travelers’ mobility patterns.