Hysteresis Tests Research Articles

Does China's river chief policy improve corporate water disclosure? A quasi-natural experimental

Water resources management has been valued by governments around the world for many years, and different countries have implemented different efforts. To explore the actual impact of water resources management, this study took China's River Chief Policy (CRCP) as an example, adopted the differences in differences method (DID), and used a sample of China's highly water-sensitive listed companies from 2010 to 2017, to study the impact of water management policies on corporate water disclosure. This study found that for companies located by a river, especially state-owned companies and companies with low equity concentration, the CRCP significantly improved the quality of water disclosure. Further research has shown that in regions with low market orientation, the CRCP has had a “spot” or “characteristic” impact on corporate water disclosure; moreover, it is “progressive”. A series of methods (such as a hysteresis test, propensity score matching, and a placebo test) were used to test the robustness of our study, and these tests verified the reliability of our research conclusions.

Influence of prepolymer molecular weight on the rheology and kinetics of HEUR-thickened Latex Suspensions

Hydrophobically Modified Ethoxylated Urethanes (HEURs) were synthesized by a step growth polymerization of polyethylene glycol (PEG, Mn = 4000, 6000, 8000) with isophorone diisocyanate (IPDI). The thickeners were produced with different sizes of the hydrophilic section by changing the molar ratios of reactants. The hydrophobic ends, 1-tetradecanol (C14), was constant for all prepared samples. The structure, molecular weight and polymer dispersity index (PDI) of HEUR were characterized by 1H NMR, IR and GPC respectively. The rheological behavior of the HEUR-thickened latex (Latex/HEUR) was determined by oscillatory and flow experiments. Dramatic increases in viscosity of Latex/HEUR are obtained. Under flow conditions the Latex/HEUR fits the Cross model, showing two regions, a Newtonian and a shear thinning one. Broad thixotropy are observed in hysteresis tests and three interval thixotropy test (3ITT) with decreasing molecular weight of the prepolymer, which was analyzed using a second-order kinetic equation. The results of atomic force microscopy (AFM) and the flow-levelling performance tests for Latex/HEUR films show smoother surface and better levelling with the increase of the hydrophilic component size.

Seismic performance of precast shear wall–slab joint with and without outer longitudinal reinforcement

SummaryComposite slabs without outer longitudinal reinforcement are a new option for assembled shear walls, which are easier to be transported. However, their performance, especially their seismic behavior, which is crucial to assembled structures, is still unclear. Furthermore, the effect of whether an additional reinforcement is incorporated, and its length on seismic behavior is also unclear. Therefore, it is necessary to experimentally investigate the seismic behavior of precast shear wall–slab joints without outer longitudinal reinforcement (PNOJ). Five hysteresis test schemes were designed in detail, including a precast joint with outer longitudinal reinforcement (POJ), three precast joints without outer longitudinal reinforcement (PNOJ), and a cast‐in situ shear wall–slab joint (CJ). Several critical technologies of production, installation, and connection were systematically summarized. The critical indicators of hysteresis and energy dissipation capacity were revealed by analyzing test phenomena and results. The results demonstrated that the PNOJ had great seismic behavior by incorporating additional reinforcement. Meanwhile, the joint seismic behavior was improved by increasing the additional reinforcement length. As compared to the CJ and POJ, the PNOJ demonstrated good seismic behavior and can be used as a reliable wall–slab connection of assembled reinforced concrete structures.

9.05% HTM free perovskite solar cell with negligible hysteresis by introducing silver nanoparticles encapsulated with P4VP polymer

This study is a follow up to our previously published manuscript on “improved power conversion efficiency in Perovskite solar cell using silver nanoparticles modified photoanode”. Three more photoanodes were fabricated which are: Ag@P4VP NPs mixed with perovskite layer (S2), Ag@P4VP NPs simultaneously mixed both in TiO2 and perovskite films (S3) and P25 NP simultaneously mixed both in TiO2 and perovskite absorber (S4) and their performances were investigated systematically. The performance, especially the photocurrent, and open circuit voltage of PSCs made of Ag@P4VP NPs were significantly affected. The champion device is S3, which shows enhancement in power conversion efficiency (PCE) from 3.80 to 9.05%, short circuit current density (Jsc) from 11.04 to 15.87 mA cm−2, open circuit voltage (Voc) from 0.85 to 0.88 and fill factor (FF) from 0.41 to 0.65, which demonstrates ~ 2.38 times improvement in PCE over the control device (C). When Ag@P4VP NPs was mixed with TiO2, PCE of 5.69%, Jsc of 12.61 mA cm−2, Voc of 0.88 V and FF of 0.51 were achieved, which shows ~ 1.50 times improvement over the performance of the reference cell. Also, when Ag@P4VP NPs was mixed with the perovskite layer, PCE of 8.08%, Jsc of 14.18 mA cm−2, Voc of 0.89 V and FF of 0.64 were achieved, which shows ~ 2.13 times improvement over the performance of the pristine device. The addition of Ag@P4VP NPs enhanced exciton generation and dissociation, encouraging charge separation/transfer, as well as reducing quenching losses. For the hysteresis test, it was found that the devices with Ag@P4VP NPs have almost identical J–V curves with negligible hysteresis, which is attributed to the significant reduction of the trap density of the perovskite film when Ag@P4VP NPs is incorporated to fill the pores with high trapping rate. We however observed hysteretic behavior in devices C and S4, which makes it difficult to estimate the real PCE.

Effects of Pt precursors on Pt/CeO2 to water-gas shift (WGS) reaction activity with Langmuir-Hinshelwood model-based kinetics

The crystallite size effects of Pt nanoparticles on the CeO2 (Pt/CeO2) prepared with four different Pt precursors were investigated in terms of their thermal stability and catalytic activity for a water-gas shift (WGS) reaction using the compositions of reformates after a typical steam reforming of propane. The Pt/CeO2 prepared with a diamine dinitroplatinum (Pt(NO2)2(NH3)3) precursor, which forms the cationic Pt(NH3)22+ species on the negatively-charged CeO2 surfaces, revealed a superior catalytic activity and thermal stability by forming the partially oxidized smaller Pt nanoparticles decorated with metallic Pt surfaces as well as by forming the strongly interacted PtOx-CeO2 interfaces. The stable preservation of the pristine smaller Pt nanoparticles with small aggregations even under the hysteresis test from 250 to 400 °C was mainly attributed to the strong metal-support interactions. The optimized Pt/CeO2 was further studied to obtain kinetic equations derived by Langmuir-Hinshelwood (LH) model, and the optimal operating conditions of WGS reaction were found to be ~280 °C and H2O/CO molar ratio of 9 with the activation energy of ~78.4 kJ/mol.

Effect of quenching media on the properties of TiNi shape memory alloys fabricated by powder metallurgy

Abstract TiNi shape memory alloys (SMAs) are one of the significantly important materials group, which serve in the advanced applications requiring unique characteristics. Although their wide use is well established, further improvement of mechanical properties is still needed. The conventional TiNi SMA is usually manufactured by casting, hot forging and heat treatment processes. In this study, Ti-x at.%Ni alloys, with x equals 50, 51, and 52, were fabricated by powder metallurgy (PM) process through spark plasma sintering, followed by hot extrusion, homogenization, solution, aging and cryogenic quenching treatment. The effects of the compositions, processing conditions, and quenching media on the microstructural and mechanical properties of the alloys were evaluated by XRD, SEM, TEM analyses and tensile hysteresis test. The results showed that hot extrusion could lead to a considerable grain refinement, while the cryogenic quenching lead to a shift in the transformation temperatures and to an improvement of the tensile properties of the alloys such as the tensile strength increment and marginally improved ductility.

Enhanced Biomechanical Performance of a Modern Polyester Surgical Mesh for Extensor Mechanism Reconstruction in Total Knee Arthroplasty

BackgroundExtensor mechanism (EM) disruption following total knee arthroplasty is a devastating postoperative complication. Reconstruction with a synthetic mesh is one treatment option, although the optimal mesh material remains unknown. This study sought to compare the mechanical properties of 2 mesh material types that can be used for EM reconstruction. MethodsMechanical properties of a polypropylene mesh (Marlex mesh) and Ligament Advanced Reinforcement System (LARS) mesh were compared using force-displacement data from a material testing machine simulating knee movement during normal human gait. Tension to failure/ultimate tensile load, stiffness coefficients, axial strain, and cyclic hysteresis testing were measured and calculated. ResultsCompared to polypropylene mesh, LARS mesh demonstrated a significantly higher mean ultimate tensile load (2223 N vs 1245 N, P = .002) and stiffness coefficient (255 N/mm vs 14 N/mm, P = .035) in tension to failure testing, and significantly more energy dissipation (hysteresis) in hysteresis testing (771 kJ vs 23 kJ; P ≤ .040). LARS mesh also demonstrated significantly less maximum displacement compared to the polypropylene mesh (9.2 mm vs 90.4 mm; P ≤ .001). ConclusionCompared to polypropylene mesh, LARS mesh showed superior performance related to force-displacement testing. The enhanced mechanical performance of LARS mesh may correlate clinically to fewer failures, increased longevity, and higher resistance to plastic deformation (extensor lag). Future research should evaluate survivorship and clinical outcomes of these meshes when used for EM reconstruction.

Analyzes the effect of temperature on characteristics of crude oil permittivity sensor based on Interdigital Capacitors (IDCs)

This study aims to analyze the effect of temperature on characteristics of crude oil permittivity sensor based on interdigital capacitors (IDCs), including linearity, repeatability and hysteresis. IDCs have been fabricated using the DC Magnetron Sputtering method in three designs with different electrode materials and the same electrode configuration. The electrode materials used silver (Ag), copper (Cu) and molybdenum (Mo) deposited on a FR-4 PCB substrate with a thickness of 1μm. The electrode configuration each design is 15 mm electrode length, 0.5 mm electrode width, 0.5 mm electrode distance and 40 electrodes number. The crude oil was tested at a temperature range of 30 - 70°C. The measurement system uses a PM6303A automatic RCL Meter at a frequency of 1 kHz. The sensor linearity test results showed an increase in the sensitivity value of the IDCs Ag, Mo and Cu sensors when the temperature was more than 50°C. The repeatability sensor test results showed that IDCs made from Ag had the highest measurement precision with a value of %repeatability is 2.5%. The hysteresis test results showed that the design IDCs made from Ag have high stability at high and low temperatures.

Visco-hyperelastic material modeling using nested linkage mechanisms

In this study, basic linear lumped elements such as springs and dashpots are used in nested linkage mechanisms in order to simulate the mechanical behavior of visco-hyperelastic materials. The proposed mechanism model containing two nested linkages can show initial softening followed by hardening response under quasi-static loading, which is commonly displayed by hyperelastic materials. Hence, material nonlinearity is simulated by geometric nonlinearity of the linkage mechanism. The mechanism also displays relaxation, hysteresis, and dynamic stiffness responses of viscoelastic materials with the help of dashpot elements. Visco-hyperelastic material behavior is closely approximated by the proposed mechanism model for the four different test scenarios, i.e., quasi-static loading, ramp-and-hold loading, hysteresis, and dynamic stiffness tests. It is shown that nonlinearity and frequency dependency of visco-hyperelastic materials is successfully captured.

Anti-Icing Performance of a Coating Based on Nano/Microsilica Particle-Filled Amino-Terminated PDMS-Modified Epoxy

Coatings with anti-icing performance possess hydrophobicity and low ice adhesion strength, which delay ice formation and make ice removal easier. In this paper, the anti-icing performance of nano/microsilica particle-filled amino-terminated PDMS (A-PDMS)-modified epoxy coatings was investigated. In the process, the influence of the addition of A-PDMS on the hydrophobicity and ice adhesion strength was investigated. Furthermore, the influences of various weight ratios of nanosilica/microsilica (Rn/m) on the hydrophobicity and ice adhesion strength of the coating were investigated. Hydrophobicity was evaluated by contact angle (CA) and contact angle hysteresis (CAH) tests. Ice adhesion strength was measured by a centrifugal adhesion test. The addition of A-PDMS markedly increased hydrophobicity and decreased ice adhesion. The size combination of particles obviously affects hydrophobicity but has little effect on ice adhesion. Finally, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to reveal the anti-icing mechanism of the coatings.

Analysis of Contacts in Friction Damped Turbine Blades Using Dimensionless Numbers

Abstract A novel design approach for friction hysteresis measurements is introduced to simplify the characterization of turbine blade contact dynamics. It makes use of dimensionless numbers of a metallic friction contact undergoing small, periodic displacements. Such contacts are used in turbine blades to lower resonance amplitudes by energy dissipation through friction. Nonetheless, this approach is not limited to this field. The dimensionless numbers for characterization of the contact are derived based on a generic contact that is typical for applications in turbine blades. A dimensionless number can be found that characterizes the contact extensively. Several friction hysteresis measurements are conducted on a special test rig in a systematic manner exploring a large parameter space for the derived dimensionless number. Based on the experiments, it is concluded that the normalized measured friction hysteresis loops show similitude despite being measured with parameters spanning a wide range. It results in the possibility to design friction hysteresis tests for friction damped turbine blades in a simple and representative way.

Synthesis of nickel nanothorn particles by the hydrothermal method

In this study, an investigation was performed of the preparation of nickel nanothorn particles by the hydrothermal synthesis method. The effects of parameters were investigated on the particle shape and size, which were determined by scanning electron microscope (SEM) analysis. The synthesis parameters were hydrazine concentration, heating temperature in autoclave, heating time in autoclave, nickel sulfate concentration, pH, NaCl concentration. The phases contained in the synthesized samples were analyzed by X-ray powder diffraction (XRD) analysis, nickel purity of samples were analyzed by X-ray fluorescence (XRF), and the magnetic properties of the nickel particles were measured by a magnetic hysteresis test. The results showed that nickel nanothorn particles were successfully produced without any surfactant by simple hydrothermal synthesis. As the hydrazine concentration was increased, the thorn length of the nickel particles also increased.

The behaviour of Nitinol Wire Bundles for Structural Applications

Shape memory alloys (SMA) belong to a family of smart materials, which undergo diffusionless phase transformations when subjected to thermo-mechanical changes making them ideally suitable for utilization in several structural engineering applications. Within this class of materials, Ni-Ti (Nickel-Titanium) alloys are predominantly used due to their non-linear behaviour. Nitinol, one of the Ni-Ti alloys, possesses unique properties such as super-elasticity and shape- memory effect, which makes it suitable for damping vibrations transmitted to structures like buildings and bridges during high wind and seismic events. This paper presents selected results obtained from a series of tests conducted on Nitinol 55 wires and bundles made from wires having diameters of 0.25, 0.5, 0.55, and 1 mm. The tests conducted include microstructure analyses, static tensile tests, hysteresis tests, and cyclic dynamic tests performed on wire bundles of various diameters. It is demonstrated that wires having small diameters (0.25 and 0.5 mm) exhibit greater ultimate strength compared with the ones having a larger diameter (1 mm). The bundles produced from these wires displayed hysteretic behaviour under cyclic-dynamic testing conditions confirming their suitability in structural engineering applications.

Numerical modeling of elastomeric seismic isolators for determining force\u2013displacement curve from cyclic loading

The ideal performance of seismic isolating systems during the past earthquakes has proved them to be very useful in protecting structures against earthquakes. The cyclic loading experimental tests are an important part in the process of completing the design of the isolators, yet they are very expensive and time consuming. Using the accurate analytical modeling of hysteresis tests and knowing the limitations and the amount of error of the finite elements model and its effect on designing the isolated structure make it possible to reduce the financial and time expenses involved in designing seismic isolators along with experimental tests. In the present study, the cyclic loading of two different isolating systems, namely, the high damping rubber bearing (HDRB) and lead rubber bearing (LRB) have been modeled and analyzed in ABAQUS and the outcomes were compared with the experimental results attained by other researchers. Regarding the fact that the most important and complicated component of the elastomeric isolating system is rubber, it was modeled using various strain energy functions. Other factors affecting the finite elements models of elastomeric isolators were also studied. After comparing the effective stiffness of the experimental sample with the analytical model of HDRB, the Yeoh function had the best performance in determining the effective stiffness of the isolating system with an error of less than 7%. In studying LRBs, too, three types of bearings with different dimensions and lateral strain values were studied; the polynomial function in shear strain value of 150% had the best performance in estimating effective stiffness and damping with errors of less than 3% and 18%, respectively.

Anderson acceleration for electromagnetic nonlinear problems

PurposeThe purpose of this paper is to implement the Anderson acceleration for different formulations of eletromagnetic nonlinear problems and analyze the method efficiency and strategies to obtain a fast convergence.Design/methodology/approachThe paper is structured as follows: the general class of fixed point nonlinear problems is shown at first, highlighting the requirements for convergence. The acceleration method is then shown with the associated pseudo-code. Finally, the algorithm is tested on different formulations (finite element, finite element/boundary element) and material properties (nonlinear iron, hysteresis models for laminates). The results in terms of convergence and iterations required are compared to the non-accelerated case.FindingsThe Anderson acceleration provides accelerations up to 75 per cent in the test cases that have been analyzed. For the hysteresis test case, a restart technique is proven to be helpful in analogy to the restarted GMRES technique.Originality/valueThe acceleration that has been suggested in this paper is rarely adopted for the electromagnetic case (it is normally adopted in the electronic simulation case). The procedure is general and works with different magneto-quasi static formulations as shown in the paper. The obtained accelerations allow to reduce the number of iterations required up to 75 per cent in the benchmark cases. The method is also a good candidate in the hysteresis case, where normally the fixed point schemes are preferred to the Newton ones.

Paleomagnetic evidence for cold emplacement of eruption-fed density current deposits beneath an ancient summit glacier, Tongariro volcano, New Zealand

The thermal structures of eruption-fed, subglacial volcaniclastic deposits are poorly understood because their emplacement is hazardous to observe or obscured by the glacier. Determining deposit emplacement temperature, however, supports improved understanding of the flow dynamics and emplacement processes of volcaniclastic material beneath a glacier. Understanding the emplacement temperatures of ancient volcanic deposits is also important because they can be used, in combination with field studies, to infer the eruptive environment. Here, we use paleomagnetic techniques to quantify the emplacement temperatures of two ancient, proximal, eruption-fed density current deposits at Tongariro volcano, New Zealand. Stepwise thermal demagnetisation of lithic and recycled juvenile block-sized clasts reveal randomly orientated directions of magnetisation, suggesting that the clasts were rotated within the flow but not heated. Additional data from thermomagnetic, hysteresis, and isothermal remanent magnetisation tests indicate that the principal carrier of magnetic remanence is magnetite, and that the magnetisation directions are a primary remanence rather than post-depositional chemical remanent magnetisations. Following systematic removal of any viscous remanent magnetisation, the post-emplacement equilibrium temperatures for the deposits can be estimated at <150°C. The paleomagnetic data support field evidence for rapid cooling of clasts and waterlain deposition. The deposit-forming eruptions took place beneath a summit glacier where the freshly erupted tephra was efficiently cooled by mixing with meltwater. Lithic blocks and recycled juvenile bombs were entrained and remobilised within the cool currents that drained along meltwater channels beneath the ice. This is the first study in which paleomagnetic data have been used to determine the equilibrium temperatures of subglacial density current deposits. The data provide new insight into volcaniclastic flow dynamics beneath a glacier and current-meltwater interactions.

Acoustic emission and X-ray computed microtomography characterization of damage accumulation in a woven Cf/SiC composite

The monotonic tensile and unloading-reloading tensile hysteresis tests of the 2D woven Cf/SiC composite were performed to study the damage accumulation, respectively. The acoustic emission (AE)-based technology was used to characterize the damage extent and select the unloading stresses. The damage evolution was characterized by X-ray computed microtomography (μ-CT), optical microscopy and scanning electron microscopy (SEM). The crack density increased most after unloading from 120 MPa, and the cracks were distributed more closely and uniformly, as compared to the raw materials in μ-CT slices. The large cracks formed at stress above 63 MPa under optical microscopy. Four types of cracking, fiber pull-out and interfacial debonding of the failure materials were summarized in the SEM images.

Hierarchical 3D Nanolayered Duplex-Phase Zr with High Strength, Strain Hardening, and Ductility.

Nanolayered, bimetallic composites are receiving increased attention due to an exceptional combination of strength and thermal stability not possible from their coarse-layered counterparts or constituents alone. Yet, due to their 2D planar, unidirectional arrangement, they are highly anisotropic, which results in limited strain hardening and ductility. Therefore, like many high-performance, ultrastrong materials of our time, they succumb to the usual strength-ductility trade-offs. Here we present the formation of a novel hierarchical microstructure, comprised of crystals consisting of 3D nanolayered α/β-Zr networks. By direct comparison with coarse-layered material of the same chemistry, we show that the unusual hierarchical 3D structure gives rise to high strain hardening, high strength, and high ductility. Using TEM analysis and hysteresis testing, we discovered that the 3D randomly oriented biphase boundaries result in progressively dispersive rather than localized slip with increasing strain. Dislocation activity in the α-Zr lamellae transitions from single slip to multislip and eventually to multimodal slip as strain increases. The diffusive slip-promoting properties of 3D layered networks can potentially invoke simultaneous high strength, strain hardening, and ductility, and reveal a new target in the microstructural design of high performance structural materials.

Biocompatible HA@Fe3 O4 @N-CDs hybrids for detecting and absorbing lead ion.

The trinary hydroxyapatite@Fe3 O4 @N-doped carbon dots (HA@Fe3 O4 @N-CDs) hybrids were prepared by one-pot hydrothermal approach and utilized to detect and remove lead ion from aqueous solution. The structures and morphologies of as-obtained nanorod-like HA@Fe3 O4 @N-CDs hybrids were characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy measurements. These HA@Fe3 O4 @N-CDs hybrids possess good magnetism by magnetic hysteresis test and multi-colored fluorescence by the CLSM measurement. Furthermore, the as-obtained hybrids display excellent biocompatibility by MTT assay. Importantly, the trinary magnetic HA@Fe3 O4 @N-CDs hybrids as a green detector and adsorbent of Pb2+ were investigated. The influence of the different pH, the concentration of heavy metal, and the maximum adsorption capacity on removal efficiency was measured in detail. The maximum Pb2+ adsorption capacity on HA@Fe3 O4 @N-CDs hybrids is 450 mg/g. The kinetic mechanism was a pseudo-second order model, and the isotherm data was fitted well by the Langmuir isotherm and Freundlich model. Hence, the nanorod-like HA@Fe3 O4 @N-CDs hybrids could be a multifunctional material with significant potential applications in heavy metal detection and adsorption, bone tissue regeneration, magnetic therapy, and biomedicine. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

Flexible resistive pressure sensor with silver nanowire networks embedded in polymer using natural formation of air gap

A new type of flexible pressure sensor with air gap has been designed based on polydimethylsiloxane (PDMS) and silver nanowires (AgNWs). During fabrication, the interdigitated Ag electrode was fabricated on the bottom PDMS layer by doctor blading and AgNWs were embedded in the top PDMS layer, with a naturally formed air gap between the AgNW layer and the interdigitated electrodes. The thus-formed air gap was controlled by the number of AgNW layers and played an important role in enhancing sensitivity by decreasing the off current in the absence of pressure. The maximum sensitivity of 16.1 kPa−1 was obtained via optimization of the air gap thickness, the AgNW sensing area, and the channel length of the electrodes. The stability of the sensors was confirmed by durability, repeatability, bending, and hysteresis tests. The pressure sensor based on the highly sensitive AgNW network could provide a great opportunity for measuring various types of forces and displacements in wearable devices.