Hysteresis Areas Research Articles

Numerical Study on Hydrodynamic Performance of a Pitching Hydrofoil with Chordwise and Spanwise Deformation

The hydrofoil plays a crucial role in tidal current energy (TCE) devices, such as horizontal-axis turbines (HATs), vertical-axis turbines (VATs), and oscillating hydrofoils. This study delves into the numerical investigation of passive chordwise and spanwise deformations and the hydrodynamic performance of a deformable hydrofoil. Three-dimensional (3D) coupled fluid–structure interaction (FSI) simulations were conducted using the ANSYS Workbench platform, integrating computational fluid dynamics (CFD) and finite element analysis (FEA). The simulation involved a deformable hydrofoil undergoing pitching motion with varying elastic moduli. The study scrutinizes the impact of elastic modulus on hydrofoil deformation, pressure distribution, flow structure, and hydrodynamic performance. Coefficients of lift, drag, torque, as well as their hysteresis areas and intensities, were defined to assess the hydrodynamic performance. The analysis of the correlation between pressure distribution and deformation elucidates the FSI mechanism. Additionally, the study investigated the 3D effects based on the flow structure around the hydrofoil. Discrepancies in pressure distribution along the spanwise direction result from these 3D effects. Consequently, different chordwise deformations of cross-sections along the spanwise direction were observed, contributing to spanwise deformation. The pressure difference between upper and lower surfaces diminished with increasing deformation. Peak values and fluctuations of lift, drag, and torque decreased. This study provides insights for selecting an appropriate elastic modulus for hydrofoils used in TCE devices.

Critical conditions for ignition of boron particles in chlorine

This paper provides an analysis of ignition and extinction conditions of boron particles (with a diameter of up to 200 μm) in a nitrogen-chlorine gas mixture. The analytical description is carried out in a dimensionless form without using the Frank-Kamenetsky distribution. This makes it possible to more correctly describe extinction conditions of particle. An analytical approach is used to analyze critical conditions, which consists in founding dependencies in the form of parametric functions. It is shown that, depending on the parameters of the gas environment (temperature and proportion of chlorine), there are hysteresis areas, areas of ignition and extinction, and areas of the crisis-free chlorination mode of boron particles.
 The obtained dependencies are compared with experimental results. Their satisfactory agreement allows us to confirm the kinetic parameters of the chlorination reaction of boron particles, namely the activation energy E = 60 kJ/mol and the pre-exponential factor k0 = 4 m/s.

Rheological analysis of wet-mix shotcrete with various viscosity-modifiying admixtures

Shotcrete must be suitable for the process of transport (pumping) and application (spraying) on site. Therefore, it is necessary to obtain a suitable consistency and rheology for its placement. This paper evaluates the influence of various viscosity modifying admixtures (VMAs) on the rheology and thixotropy for application in wet-mix shotcrete. Six VMAs were used and classified into three groups, according to their composition: additives based on silica, phyllosilicates, and polymeric additives. These rheology modifiers were studied in depth in mortars, and the values of the yield stress (τo) and plastic viscosity (μ) of the material were obtained, as well as the thixotropy (hysteresis areas), which represents the energy required for the structural recovery of the fluid. To obtain these parameters, the fluid was tested under dynamic state with a laboratory rheometer, applying a ramp of shear rates. Additionally, the consistency in mortars was determined by obtaining the flow table diameter on the flow table test. This evaluation was carried out in mortars with different contents of superplasticizer (SP). All this information made it possible to evaluate the influence of SP in combination with each of the VMAs, obtaining a workability box, determining the hysteresis areas and verifying which combinations obtained a rheological behaviour superior to the control mix (without VMAs). The results described were correlated with the rebound index obtained in the shotcrete mixes performed on-site. The thixotropy in mortars and the values of the rebound rate on site led to the most accurate correlation that allowed the selection of the most effective VMAs for use in shotcrete. Lastly, both combined results (laboratory and on-site) permitted a process that facilitated analysis of the wet-mix shotcrete to be designed and optimised.

The Effect of Temperature on the Mechanical Properties of Alginate Gels in Water/Alcohol Solutions.

Alginate organohydrogels prepared in water/alcohol mixtures play an important role in electronic and superconductor applications in low-temperature environments. The study deals with the preparation of Ca-alginate organohydrogels and the analysis of their equilibrium swelling and mechanical properties at sub-zero temperatures. It is shown that the equilibrium degree of swelling at room temperature is noticeably affected by the concentration of co-solvents (methanol, ethanol, and 2-propanol) in the mixtures and the number of carbon atoms in the co-solvent molecules. Mechanical properties are studied in small-amplitude oscillatory tests. The data are fitted with a model that involves three material parameters. The influence of temperature is investigated in temperature-sweep oscillatory tests under a cooling-heating program, where a noticeable difference is observed between the storage and loss moduli under cooling and heating (the hysteresis curves). The hysteresis areas are affected by the cooling/heating rate and the number of carbon atoms in the co-solvents.

Hysteresis of lock-in range in a He-Ne ring laser gyroscope.

In this paper, a hysteresis of the lock-in range in a He-Ne ring laser gyroscope is theoretically analyzed. We propose a new model accounting an additional coupling of the counterpropagating waves due to their diffraction on the gratings induced in the cavity mirrors. Numerical simulations in the proposed model show the existence of broad hysteresis areas of a lock-in range. Dependence of hysteresis on the pump excess above the threshold has been studied.

A computationally fast and accurate procedure for the identification of the Chaboche isotropic-kinematic hardening model parameters based on strain-controlled cycles and asymptotic ratcheting rate

The Chaboche isotropic-kinematic hardening (CIKH) model provides a versatile and realistic description of the material stress–strain behavior under generic multiaxial cyclic loadings. However, identifying the backstress parameters is challenging, and can be formulated as an optimization problem using different approaches. Instead of a computationally expensive pointwise search, in this paper the global properties of the cyclic curves are fitted to the experimental data. The conditions introduced are the hysteresis areas, peak stress values and tangent moduli at the extreme points, however the framework can be easily adapted to other target quantities. One linear and two non-linear backstress components of the kinematic hardening model are introduced, although the analytical equations developed can be used to refine the model further, with more components. Two stabilized cycles are required to identify the main kinematic parameters. New analytical expressions for asymptotic ratcheting rates in uniaxial tests are developed and then used to tune the dynamics of the slightly non-linear (hence, slowest) backstress component. After obtaining the kinematic parameters, isotropic hardening laws can also be identified, by considering the evolution of the extreme points of the strain-controlled cycles before stabilization. Practical demonstrations of the procedure are provided by experimental tests carried out on a 7075-T6 aluminum alloy, 42CrMo4+QT steel, and a high-silicon ferritic ductile cast iron. An accurate reproduction of the material behavior is achieved, at a negligible computational cost.

Response Variability and Detraining Effects of Standardized Exercise Programs

Purpose: To compare inter–individual response variability and detraining effects on markers attributed to aerobic and anaerobic performance after shortterm standardized aerobic, strength and mixed training programs. Methods: Thirty–six male students were randomly assigned to either an aerobic, strength, mixed, or control program (9 per group). They performed two consecutive cycling tests (incremental and plateau) to exhaustion at three points: 1 week before training, after 6 weeks of training, and 3 weeks after the training was finished. Maximal oxygen consumption (VO2max), maximal workload (Wmax), and time to exhaustion performed at Wmax (W × time) were compared between groups by repeated–measures ANOVA with Bonferroni post–hoc tests. The inter–subject response variability within each training group was evaluated by comparison with the 95% confidence interval of the control group. Detraining effects were evaluated using the hysteresis areas, which were compared between each training group and the control group by Mann–Whitney U test. Results: Differences were observed in Wmax for the aerobic (F(2,7)=19.562; p=0.001; n²=0.85) and mixed (F(2,7)=13.447; p=0.004; n²=0.99) programs, and in W × time for the mixed program (F(2,7)=15.432; p= 0.016; n²=0.89). There was high inter–subject response variability for all variables and training programs, except for a homogenous positive response to Wmax in the mixed program (X²=6.27; p=0.04). Detraining effects of Wmax were also better maintained after the mixed program. Conclusion: A mixed program of aerobic and strength training demonstrated higher improvements in the studied markers of performance, with lower interindividual response variability, and longer detraining effects compared with aerobic or strength programs.

Energetic analysis of fatigue hysteresis by thermographic and digital image correlation methodologies

AbstractA hysteresis cycle can define the variation in mechanical characteristics of fatigue life and failure response. Traditional analysis is performed using force‐displacement signals derived from the testing equipment, but this approach is prone to large errors due to clearances and slips in the measuring chain. For this reason, the authors here propose a novel setup able to assess accurately the strain status of specimens by digital image correlation (DIC) and a procedure to calculate the hysteresis energy by thermographic analysis in order to measure the damping energy with precision. The results obtained by an experimental investigation on a common austenitic steel (AISI 304) highlight that the hysteresis areas defined by the DIC displacements, and those found by the testing machine outputs have substantial differences in value. The thermal variations and the areas of the hysteresis loops, both linked to the plastic energy, were also compared, showing a reliable correlation.

Cardiorespiratory hysteresis during incremental high-altitude ascent-descent quantifies the magnitude of ventilatory acclimatization.

What is the central question of this study? We assessed the utility of a new metric for quantifying ventilatory acclimatization to high altitude, derived from differential ascent and descent steady-state cardiorespiratory variables (i.e. hysteresis). Furthermore, we aimed to investigate whether the magnitude of cardiorespiratory hysteresis was associated with the development of acute mountain sickness. What is the main finding and its importance? Hysteresis in steady-state cardiorespiratory variables quantifies ventilatory acclimatization to high altitude. The magnitude of cardiorespiratory hysteresis during ascent to and descent from high altitude was significantly related to the development of symptoms of acute mountain sickness. Hysteresis in steady-state chemoreflex drive can provide a simple, non-invasive method of tracking ventilatory acclimatization to high altitude. Maintenance of arterial blood gases is achieved through sophisticated regulation of ventilation, mediated by central and peripheral chemoreflexes. Respiratory chemoreflexes are important during exposure to high altitude owing to the competing influence of hypoxia and hypoxic hyperventilation-mediated hypocapnia on steady-state ventilatory drive. Inter-individual variability exists in ventilatory acclimatization to high altitude, potentially affecting the development of acute mountain sickness (AMS). We aimed to quantify ventilatory acclimatization to high altitude by comparing differential ascent and descent values (i.e. hysteresis) in steady-state cardiorespiratory variables. We hypothesized that: (i)the hysteresis area formed by cardiorespiratory variables during ascent and descent would quantify the magnitude of ventilatory acclimatization; and (ii)larger hysteresis areas would be associated with lower AMS symptom scores during ascent. In 25 healthy, acetazolamide-free trekkers ascending to and descending from 5160m, cardiorespiratory hysteresis was measured in the partial pressure of end-tidal CO2 , peripheral oxygen saturation, minute ventilation, chemoreceptor stimulus index (end-tidal CO2 /peripheral oxygen saturation) and the calculated steady-state chemoreflex drive (SS-CD; minute ventilation/chemoreceptor stimulus index) using portable devices (capnograph, peripheral pulse oximeter and respirometer, respectively). Symptoms of AMS were assessed daily using the Lake Louise questionnaire. We found that: (i)ascent-descent hysteresis was present in all cardiorespiratory variables; (ii)SS-CD is a valid metric for tracking ventilatory acclimatization to high altitude; and (iii)the highest AMS scores during ascent exhibited a significant, moderate and inverse correlation with the magnitude of SS-CD hysteresis (rs =-0.408, P=0.043). We propose that ascent-descent hysteresis is a new and feasible way to quantify ventilatory acclimatization in trekkers during high-altitude exposure.

Establishment of a Synthetic In Vitro Lung Surfactant Model for Particle Interaction Studies on a Langmuir Film Balance.

With the intention to provide a robust and economical model that can be used for predicting particle interactions with the pulmonary surfactant, this study was aimed to find an artificial surfactant model that perfectly mimics the properties of the natural pulmonary surfactant. A surfactant model should be reproducible, robust, and able to predict interactions between the pulmonary surfactant and exogenous influences from air and the aqueous site. We compared three synthetic models with the natural bovine surfactant Alveofact. The lung conditions were simulated by spreading the surfactants at the air/aqueous interface on a Langmuir trough with movable barriers. All three artificial surfactant models showed properties very similar to that of Alveofact. Visualization of the monolayers by atomic force microscopy revealed very similar structures with domain formation. The Tanaka lipid mixture has already shown good results in vitro and in vivo in previous studies. The 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)-1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) model has large conformations in the surface pressure isotherms and showed a biomimetic exclusion plateau, indicative of an effective lung surfactant formulation. Also, the equilibrium spreading pressure was similar. DPPC-1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-1'-rac-glycerol (POPG) had the greatest similarities with Alveofact in the hysteresis areas. The kinetic constants of the relaxation experiments during desorption showed that the PCPG model (at 30 mN/m) had almost identical diffusion and dissolution values as Alveofact. As a proof of concept, the interaction of the models with PLGA nanoparticles showed promising results in all experiments for all the three surfactant models. The results show that the choice of components in a model play a crucial role in obtaining reproducible results. The selected models can be used for further studies as synthetic in vitro lung models.

Hysteresis behaviour of psychobiological variables during exercise

ObjectivesThe rating of perceived exertion (RPE) and the heart rate (HR) have been widely studied and monitored during exercise, but their hysteresis behaviour is still unexplored. Our aim was to study the hysteresis behaviour of RPE and HR in triathletes and non-athletes. DesignCross-sectional study. MethodEighteen triathletes at different competitive levels (elite n = 9, non-elite n = 9) and ten students were tested while cycling and running, using a pyramidal protocol (incremental/decremental workloads). The hysteresis area, considered positive when values of the dependent variables (RPE and HR) at the same workload were higher in the decremental phase than in the incremental phase, and vice versa for the negative areas, was calculated in all tests. The Wilcoxon matched-pairs test and Kruskal Wallis ANOVA were applied to detect intra- and inter-group differences, respectively, of RPE and HR values during the incremental and decremental phases, as well as between cycling and running. ResultsThe following results were observed: a) an incoherent relationship of RPE with HR and workload, b) positive hysteresis areas of RPE and HR in all groups during cycling and running, c) a partial negative hysteresis area of RPE, but not of HR, in the triathlete groups, d) larger hysteresis areas of RPE and HR in students than in triathletes, and e) larger hysteresis areas in cycling than in running. Conclusionsthe study of the hysteresis behaviour of RPE and HR reveals the history dependency of both variables, highlights their incoherent or non-unique relationship during a pyramidal exercise, and questions their widely assumed linear association to workload intensity. The hysteresis area is proposed as a new non-invasive marker of exercise stress and tolerance that should be further investigated.

Fully solvable lower dimensional dynamics of Cartesian product of Kuramoto models

Implementing a positive correlation between the natural frequencies of nodes and their connectivity on a single star graph leads to a pronounced explosive transition to synchronization, additionally presenting hysteresis behavior. From the viewpoint of network connectivity, a star has been considered as a building motif to generate a big graph by graph operations. On the other hand, we propose to construct complex synchronization dynamics by applying the Cartesian product of two Kuramoto models on two star networks. On the product model, the lower dimensional equations describing the ensemble dynamics in terms of collective order parameters are fully solved by the Watanabe–Strogatz method. Different graph parameter choices lead to three different interacting scenarios of the hysteresis areas of two individual factor graphs, which further change the basins of attraction of multiple fixed points. Furthermore, we obtain coupling regimes where cluster synchronization states are often present on the product graph and the number of clusters is fully controlled. More specifically, oscillators on one star graph are synchronized while those on the other star are not synchronized, which induces clustered state on the product model. The numerical results agree perfectly with the theoretic predictions.

An easy approach based on textural properties to evaluate catalyst deactivation during heavy oil hydrotreating

Various heavy oils with different amounts of asphaltenes were hydrotreated with a commercial NiMo catalyst in batch reactor at 100 kg/cm2 hydrogen pressure, 400 °C temperature, 750 rpm stirring rate and 4 h reaction time. Fresh, spent and regenerated catalysts were recovered after reaction, washed with toluene, and analyzed by textural properties. Data of adsorption-desorption isotherms were used to calculate hysteresis areas, whereby a semi-quantitative approach to determine the degree of catalyst deactivation is proposed. By comparison of hysteresis areas of spent and fresh catalysts it was confirmed that the higher the asphaltene content in feed, the faster the catalyst deactivation.

Clotrimazole multiple W/O/W emulsion as anticandidal agent: Characterization and evaluation on skin and mucosae.

Clotrimazole (CLT) was formulated in a multiple W/O/W emulsion (ME) with the aim of evaluating its potential as topical anticandidal agent and comparing with marketed products. A previously evaluated CLT-ME was selected and physicochemically characterized. The in vitro release behavior and the ex vivo permeation profiles were assessed using Franz diffusion cells using three different types of biological membranes: human skin and porcine buccal, sublingual and vaginal mucosae. The antifungal activity against Candida strains was also tested. Results showed CLT-MEs sizes of 29.206 and 47.678 μm with skin compatible pH values of 6.47 and 6.42 exhibiting high zeta potential values of -55.13 and -55.59 mV with dependence on the pH variation. The physicochemical stability was kept for a period of 180 days of storage at room temperature. CLT-MEs exhibited pseudoplastic behavior with hysteresis areas and viscosities of 286 and 331 mPa⋅s showing higher spreadability properties than commercial counterparts. An improved CLT release pattern was supplied by the ME system following a hyperbolic model. Likewise, ME system gave higher skin permeation flux of CLT than commercial reference. CLT amounts retained in the skin and mucosae were also higher than commercial references, which coupled with the higher antimycotic efficacy make CLT-MEs a great tool for clinical investigation of topical candidiasis treatments.

Effects of prestretch on stress relaxation and permanent deformation of orthodontic synthetic elastomeric chains.

ObjectiveThis study was performed to investigate an appropriate degree of prestretch for orthodontic synthetic elastomeric chains focusing on time-dependent viscoelastic properties.MethodsOrthodontic synthetic elastomeric chains of two brands were prestretched to 50, 100, 150, and 200% of the original length in one and three cycles, and the hysteresis areas of the obtained stress-strain curves were determined. Acrylic plates were employed to maintain constant strain during the experiment. A total of 180 samples were classified into nine groups according to brand, and their stresses and permanent deformations were measured immediately after prestretch (0 hour), after 1 hour and 24 hours, and after 1, 2, 3, 4, 5, 6, 7, and 8 weeks. The relationship between stress relaxation and permanent deformation was investigated for various degrees of prestretch, and the estimated stress resulting from tooth movement was calculated.ResultsThe degree of prestretch and the stress relaxation ratio exhibited a strong negative correlation, whereas no correlation was found between the degree of prestretch and the average normalized permanent strain. The maximal estimated stress was observed when prestretch was performed in three cycles to 200% of the original length.ConclusionsAlthough prestretch benefited residual stress, it did not exhibit negative effects such as permanent deformation. The maximal estimated stress was observed at the maximal prestretch, but the difference between prestretch and control groups decreased with time. In general, higher residual stresses were observed for product B than for product A, but this difference was not clinically significant.

Low-cycle fatigue hysteresis by thermographic and digital image correlation methodologies: a first approach

The energetic behaviour of the material under low-cycle fatigue (LCF) can be controlled by the hysteresis cycle in order to define the variation of the mechanical characteristics and to forecast the fatigue and the failure response. The traditional analysis is performed using the force-displacement signals derived by the testing machine that can be coupled with other measuring methodologies. In the present paper, the authors have used the Digital Image Correlation (D.I.C.) to better define the specimen displacement, avoiding many errors of the displacement measurement chain. The thermographic analysis (T.A.), able to follow quickly and with great accuracy the energetic variations, was combined with the stress-strain measurements, allowing to calculate the damping energy. The results pointed out a similar behaviour between the hysteresis areas defined basing on the D.I.C. displacements and those found by the testing machine outputs, but substantial differences in terms of values. The thermal variations and the areas of the hysteresis loops, both linked to the plastic energy, were compared, showing a reliable agreement.

Power Generation Performance Analysis of a Hub Dynamo Considering a Magnetic Hysteresis

In this paper, we propose a computation technique to compute the power generation performance of a hub dynamo, which is installed in a bicycle. The output power of the hub dynamo is small, and it is difficult to accurately predict the power generation performance using 3-D finite-element analysis. First, the output voltage of the hub dynamo is computed considering a magnetic hysteresis and imperfect magnetization areas. The influence of the magnetic hysteresis on the output voltage is investigated. Finally, the computed output voltage is verified by carrying out measurements on a real hub dynamo.

Influence of Thermal Diffusion on the Hysteresis Area of Hydrogen Impurities’ Catalytic Combustion on Platinum Wire

A complex investigation of the hysteresis mechanisms of heat and mass exchange and catalytic flameless combustion of hydrogen-air mixtures on platinum’s particles and wires. Thermal diffusion of hydrogen does not affect the critical conditions for self-ignition mixture unlike conditions extinction mixture. Method is proposed the analytical determination of the hysteresis areas heat and mass exchange particles (wires) catalyst. Inside the areas there is a catalytic ignition, and outside - stationary states of oxidation and catalytic combustion of combustible gas in the air.

Voltage Controller for 3 Level NPC-MLI Based HSVM With Grid Connected PV System

Objectives: This paper proposes an improved Neutral Point Clamped 3-Level Inverter (NPC-TLI) that is suitable for transformer-less Photovoltaic (PV) grid connected system. Methods/Analysis: The use of NPC topology guarantees the reduction of shoot-through risk and helps keep common mode voltage in check. The inverter is controlled by Hysteresis Space Vector Modulation algorithm which helps to decrease Total Harmonic Distortion (THD) factor in the output. The proposed system simulation results were verified using MATLAB/SIMULINK. Findings: Furthermore, the use of a split inductor helps to avoid the use of a transformer, hence, reducing the size, leakage current and the voltage stress in the inverter. The input of the system is derived from a PV source whose output can be synchronized with a grid connected system. Novelty/ Improvement: The use of SVVC using hexagonal hysteresis areas ensures reduced THD and improved DC link voltage balancing in the capacitors of the NPC configuration. Reduced common mode voltage, and switching losses are other added benefits of the inverter configuration.

Rheological behaviour of self-compacting micro-concrete

The rheological behaviour of Self-Compacting Micro-Concrete (SCMC) mixtures has been investigated within the scope of this paper. Rheological measurements have been performed using a novel rheometer equipped with a ball measuring system. Three SCMC mixtures with the same water/cement (W/C) ratios (0.44 by weight) and cement/limestone powder (1/1 by weight) with different High Range Water Reducing Admixtures (HRWRA) contents (1, 1.2 and 1.4% by weight of cement) have been tested. For comparison purpose, three conventional cement paste mixtures with varying W/C ratios (0.30, 0.325 and 0.35) were also prepared. Flow parameters such as yield value and plastic viscosity have been measured along with shear thickening or thinning behaviour. Furthermore, thixotropic behaviour of the various mixtures have been measured using hysteresis areas. Finally, advanced rheological properties of micro-concretes and cement pastes have been compared and discussed. While cement pastes investigated in this study possessed high yield values (34–217 Pa) and very low viscosities (5–19 Pa.s), comparatively high viscosities (17–45 Pa.s) and low yield values (0–47 Pa) have been obtained from SCMCs. The high viscosity of micro-concretes improves the solid holding capacity of this composite. According to flow curve analysis, cement paste mixtures and SCMCs exhibited shear thinning and shear thickening characteristics, respectively.