Hysteresis Tests Research Articles

Correlation between nano-scale microstructural behavior and the performance of ZnO thin-film transistors.

Binary ZnO active layers possessing a polycrystalline structure were deposited with various argon/oxygen flow ratios at 250 degrees C via sputtering. Then ZnO thin-film-transistors (TFTs) were fabricated without additional thermal treatments. As the oxygen content increased during the deposition, the preferred orientation along the (0002) was weakened and the rotation of the grains increased, and furthermore, less conducting films were observed. On the other hand, the reduced oxygen flow rate induced the formation of amorphous-like transition layers during the initial growth due to a high growth rate and high energetic bombardment of the adatoms. As a result, the amorphous phases at the gate dielectric/channel interface were responsible for the formation of a hump shape in the subthreshold region of the TFT transfer curve. In addition, the relationship between the crystal properties and the shift in the threshold voltage was experimentally confirmed by a hysteresis test.

Dynamic properties of magnetorheological elastomers based on iron sand and natural rubber

ABSTRACTIn this study, magnetorheological elastomers (MREs) based on iron sand and natural rubber were prepared. The Taguchi method was employed to investigate the effect of a number of factors, namely, the iron sand content, iron sand particle size, and applied magnetic field during curing on the loss tangent (tan δ) and energy dissipated during cyclic loading. Tan δ was measured through dynamic mechanical analysis over a range of frequency (0.01–130 Hz), strain amplitude (0.1–4.5%), and temperature (−100 to 50°C). The energy dissipated was measured with a universal tester under cyclic tensile loading. The data were then statistically analyzed to predict the optimal combination of factors, and finally, experiments were conducted for verification. It was found that the iron sand content had the greatest influence on tan δ when measured over a range of frequency, and the energy dissipated during hysteresis tests. However, none of the factors showed a significant influence on tan δ when measured over a range of strain amplitude. Furthermore, the iron sand content and magnetic field were also found to influence the width of the peak in tan δ as a function of the temperature. The morphological characteristics of the MREs were also examined with scanning electron microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2015,132, 41506.

Damage-free back channel wet-etch process in amorphous indium-zinc-oxide thin-film transistors using a carbon-nanofilm barrier layer.

Amorphous indium-zinc-oxide thin film transistors (IZO-TFTs) with damage-free back channel wet-etch (BCE) process were investigated. A carbon (C) nanofilm was inserted into the interface between IZO layer and source/drain (S/D) electrodes as a barrier layer. Transmittance electron microscope images revealed that the 3 nm-thick C nanofilm exhibited a good corrosion resistance to a commonly used H3PO4-based etchant and could be easily eliminated. The TFT device with a 3 nm-thick C barrier layer showed a saturated field effect mobility of 14.4 cm(2) V(-1) s(-1), a subthreshold swing of 0.21 V/decade, an on-to-off current ratio of 8.3 × 10(10), and a threshold voltage of 2.0 V. The favorable electrical performance of this kind of IZO-TFTs was due to the protection of the inserted C to IZO layer in the back-channel-etch process. Moreover, the low contact resistance of the devices was proved to be due to the graphitization of the C nanofilms after annealing. In addition, the hysteresis and thermal stress testing confirmed that the usage of C barrier nanofilms is an effective method to fabricate the damage-free BCE-type devices with high reliability.

Reinforced Grouting Material Member Force Performance Research

This paper made the same size of reinforced grouting material vertical bending cantilever beam and reinforced concrete ones, respectively for the same static and dynamic load test, the static load for drab one-time loading level, dynamic load as low reversed cyclic loading, observe their cracking and deformation condition, draw the response relationship between the load and displacement hysteresis curves, skeleton curves, Test and data results show that the stress and deformation of the reinforced grouting material member is close to or even better a reinforced concrete member, so it is reliable to replace concrete with grouting material.

Correlating Electrical Resistance Change with Mechanical Damage in Woven SiC/SiC Composites: Experiment and Modeling

Silicon carbide (SiC) fiber‐reinforced SiC matrix composites are inherently multifunctional materials. In addition to their primary function as a structural material, the electric properties of the SiC/SiC composites could be used for the sensing and monitoring of in situ damage nucleation and evolution. To detect damage and use that information to further predict the useful life of a particular component, it is necessary to establish the relationship between damage and electrical resistance change. Here, two typical SiC/SiC composites, melt infiltrated (MI), and chemical vapor infiltrated (CVI) woven SiC/SiC composites, were tested to establish the relationship between the electrical response and mechanical damage in unload–reload tensile hysteresis tests. Compared to the 55% resistance increase seen for CVI composites, the MI SiC/SiC composites exhibit a maximum resistance change in 450% in response to mechanical loading (damage), which is the highest sensitivity known among various composites. An analytic model accounting for fiber breakage and matrix cracks was developed to link the electrical resistance to mechanical damage in the composites. The predictions from the models agree well with the experimental data for both composites with high and low conductive matrices. The residual resistance change after unloading is also correlated to the loading history by the analytical relationship. This study demonstrates that resistance change is sensitive to damage in a predictable manner and can be used to improve the reliability of damage assessment of SiC/SiC composites.

Components interaction effect evaluation of a small-capacity five-component internal balance system

With the development of small unmanned air vehicles, the urge for building the experimental facilities has emerged for the research on the low Reynolds number aerodynamics. In this paper, a five-component internal sting balance with the capacity of 10 N for forces and of 0.5 N·m for moments, which is to be installed in a close-circuit low Reynolds number wind tunnel for small unmanned air vehicle tests, was verified to investigate the interaction effect of its different components. Experimental setups and a sequence of evaluated procedures were designed to implement the application of different range of loads with pitch and roll angle coupled so as to investigate the interaction effect of different components by covering the full load range of sting balance. The sting balance was successfully verified with the designed experimental setups and procedures. Evaluation results showed that the interaction effect between balance components enhanced the measurement error and deteriorated the measurement precision. Moreover, it was also found that both precision and error depended on the loads. Relative error analysis revealed that the average relative error of all components was less than 2.1%. Hysteresis test showed that all balance component exhibited little hysteresis property except that side force component exhibited a mild hysteresis at lower load range.

Stiffness and damping coefficients for rubber mounted hybrid bearing

ABSTRACTA non‐contact passive magnetic bearing has a low friction compared with other passive (journal or ball) bearings. But these bearings have negligible damping due to which even small rotor vibration impacts the bearing magnet. It results in breakage of brittle magnetic materials. To overcome this problem, a hybrid bearing (passive magnet + elastomer) has been proposed in the present manuscript. To select an appropriate rubber, a step‐by‐step approach, using pendulum and hysteresis tests, has been followed. A parametric study on thickness of selected rubber was carried out. Experiments were conducted on three configurations: (i) a stand‐alone magnetic bearing, (ii) magnetic bearing with a butyl rubber having a thickness of 1 mm, and (iii) magnetic bearing with a butyl rubber having a thickness of 1.5 mm. To investigate the effect of rubber Young's modulus on the damping, rubber was made softer by immersing in aromatic liquid, and the experiments were repeated using softer rubber. Copyright © 2014 John Wiley & Sons, Ltd.

Effect of Size on Magnetic Properties of ${\hbox{NdMn}}_2{\hbox{O}}_5$ Nanorods

The effects of size on the magnetic properties of NdMn2O5 nanorods were studied by X-ray diffractometry, transmission electron microscopy, and measurements of magnetic susceptibility and hysteresis. Five types of nanorods with different axial lengths (〈LC〉)×diameters(〈LD〉)-68(36) nm×31(14) nm, 78(30) nm×33(8) nm, 95(36) nm×40(12) nm, 122(48) nm×54(16) nm, 249(46) nm×142(36) nm were made. The axial directions of the five types of nanorod were parallel to the c axis of the crystal. No particular radial direction is found. All samples crystallize with orthorhombic Pbam symmetry. Upon cooling, only the sample with 〈LC〉 = 249 nm occurs in ferrimagnetic and antiferromagnetic ordering at 80 K and 9 K, respectively. Hysteresis testing reveals a ferrimagnetic domain between 10 K and 50 K only in the 〈LC〉 = 249 nm sample. These tests reveal that the magnetic critical size of NdMn2O5 is between 〈LC〉 = 249 nm and 122 nm. For memory storage applications, the estimated maximal capacity of NdMn2O5 nanorods as upstanding pillars is about 32 Gbit/in2.

A modified method for evaluation of critical flux, fouling rate and in situ determination of resistance and compressibility in MBR under different fouling conditions

Identification and quantification of the separate roles of compression and of cake build-up in membranes under different fouling conditions can provide a better understanding of filtration and MBR behavior. A simple and rapid flux-step method for evaluation of critical flux, subcritical and supracritical fouling rates and in situ determination of internal and external irreversible fouling resistance and compressibility, without provoking alteration of the system and without stopping the treatment process is proposed. The main novelty of the modified method is the inclusion of a new stage, termed pre-compression, by means of a flux increase at the beginning of each filtration step. The incorporation of pre-compression phases suppresses the time dependent compression of the irreversible fouling that interferes with the accurate determination of fouling rate, even in highly compressible fouled membranes. Hysteresis tests confirmed that extra fouling due to the pre-compression stages is reversible. The compressibility index of external irreversible fouling rose as high as 0.59, pore blocking compressibility was significantly small and reversible fouling compression effect was not observed in short-term test. A novel method was employed to determine the scouring effect and to measure the efficiency of in situ chemical cleaning methods applied to an AnMBR.

One pot synthesis of opposing ‘rose petal’ and ‘lotus leaf’ superhydrophobic materials with zinc oxide nanorods

The synthesis in one pot1One-pot synthesis indicates that the two-step chemical synthesis on cloth surfaces was accomplished simultaneously for each cloth in one vessel (or one beaker).1 of opposing ‘rose petal’ and ‘lotus leaf’ superhydrophobic materials from commercially available superhydrophilic cloth substrates of varying texture is described for the first time. Surfaces of ‘rough’ textured cloth and ‘smooth’ textured cloth were simultaneously rendered superhydrophobic by growing zinc oxide (ZnO) nanorods by a hydrothermal process in the same chemical bath. Contact angle hysteresis and water pendant drop tests revealed strong water adhesion to ZnO microrod-treated rough cloth. The combination of water contact angle >150° and strong adhesion is indicative of the ‘rose petal effect’ with potential for water pinning. Smooth cloth with ZnO nanorods exhibited no adhesion to water droplets with facilitative roll-off. The combination of water contact angle >150° and weak to no adhesion with water is indicative of the ‘lotus leaf effect’ with potential for self-cleaning. Pendant water drop tests indicated cohesive failure of water on rough cloth coated with ZnO nanorods. Natural rose petals demonstrated adhesive failure between the petal surface and water droplet. A parsimonious explanation is presented. We also describe the development of superhydrophobic clothes without the need for special conditions or further chemical modification.

The mechanical behavior of composite corrugated core coated with elastomer for morphing skins

Coated composite corrugated panels have wide applications in engineering, especially in morphing skins where extreme anisotropic stiffness properties are required. The optimal design of these structures requires high-fidelity models of the panels that would be incorporated into multi-disciplinary system models. Therefore, numerical and experimental investigations are required that retain the dependence on the nonlinear static and dynamic behavior of these structures. Considering the nonlinear effects due to the material properties and mechanism of deformation, the mechanical behavior of composite corrugated laminates with elastomeric coatings is studied in this paper by means of numerical and experimental investigations. The importance of this work is that it provides detailed experimental and numerical models of the panel that can be used for further static and dynamic homogenization and optimization studies. In this regard, an investigation of the manufacturing method and an evaluation of the mechanical characteristics of the materials are presented. Then the tensile, hysteresis and three-point bending tests of the coated corrugated panels are analyzed and the mechanical behavior of the panel is simulated. The comparison studies demonstrate the accuracy of the finite element model to predict the mechanical behavior of the coated corrugated panels. Finally, two concepts to deal with the non-smooth surface of the panel during bending for the morphing skin application are proposed.

MRC를 이용한 비례압력제어밸브의 강인한 제어에 관한 연구

The proportional pressure control valve that was used to relief valve has different dynamic characteristics on each case. Because this valve has different assembling or processing error and environmental condition. However, a customer who used the relief valve wants to have a steadily performance even if the dynamic characteristics of valve was changed. For this reason, the manufacturer try to make the robust controller that has simple structure. This paper concerns about the design of robust controller that didn't affected by plant parameter's changing. The control strategy is a model reference control that conducted by on line identification problem, gradient method and Lyapunov equation. This adaptvie control law's validity that this paper deal with was confirmed by an results of step response test or hysteresis test.

A comparison of the diagnostic performance of the ST/HR hysteresis with cardiopulmonary stress testing parameters in detecting exercise-induced myocardial ischemia

Because ST segment depression has limited diagnostic performance at exercise electrocardiography (ECG), ST segment depression/heart rate (ST/HR) hysteresis and cardiopulmonary exercise test (CPET)-derived parameters have been proposed as alternatives to diagnose exercise-induced myocardial ischemia. We compared the diagnostic performance of such parameters. We studied 56 subjects (45 men, 11 women, age 59.7 ± 13.6 years) referred for suspected exercise-induced myocardial ischemia with an equivocal ECG exercise test. All subjects serially underwent CPET and a myocardial single-photon emission computerized tomography (SPECT) perfusion imaging (as the gold standard for ischemia). Maximum ST depression at peak exercise (ST-max), the ST/HR hysteresis, ΔVO2/ΔWR b-b1 slope, ΔVO2/ΔWR (aa1-bb1), VO2/HR flattening duration and other CPET parameters were derived in all subjects. On the basis of SPECT, 23 subjects (41%) were considered ischemic and 33 subjects (59%) non-ischemic. ST/HR hysteresis was higher (0.026 mV; 95% CI: 0.003 to 0.049 vs -0.016 mV; 95% CI: -0.031 to -0.001 mV) and ST-max was lower (-0.105 mV; 95% CI: -0.158 to -0.052 vs 0.032 mV; 95% CI: -0.001 to -0.066 mV) in ischemic vs non-ischemic subjects (P=0.004 and P=0.001, respectively). Among CPET parameters, ΔVO2/ΔWR b-b(1) slope was lower (9.4 ± 3.8) and ΔVO2/ΔWR (aa(1)-bb(1)) was higher (2.1 ± 2.6) in ischemic vs non-ischemic subjects (11.4 ± 2.3, P=0.005, and 1.1 ± 1.5, P=0.001, respectively). The ST/HR hysteresis had the highest area under the curve value, better (P<0.05) than any other parameters tested, thus showing the highest overall diagnostic performance. The ST/HR hysteresis is superior to CPET-derived parameters for detecting exercise-induced myocardial ischemia in patients with equivocal ECG exercise test results.

Focus on materials

Focus on materials

Fabrication of superhydrophobic coatings based on nanoparticles and fluoropolyurethane

AbstractHydrophobic nanosilica or nanofluoric particles were mixed with fluoropolyurethane resin to fabricate superhydrophobic coatings that have contact angles higher than 145°. These coatings were prepared from the simple mixing of nanoparticles in fluoropolymer and were cured at room temperature. Different fractions of nanosilica, nanofluoric particles, and the combination of them were used to find the best formulations of superhydrophobic coatings. Contact angle, contact angle hysteresis, sliding angle, hardness, and UV durability tests were conducted to find the effectiveness of these coatings. The results showed that only fluoropolyurethane coatings containing nanosilica or the combination of it and fluoric particles were superhydrophobic. Also, the hardness of coatings was increased by raising nanoparticle concentrations. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Thermal and dynamic mechanical analyses on Bi0.5Na0.5TiO3–BaTiO3 ceramics synthesized with citrate method

Bi0.5Na0.5TiO3–xBaTiO3 (BNT–xBT) nano-powders are successfully synthesized by a modified citrate method. The as-prepared BNT-BT powders and the sintered ceramics are homogeneous with a pure perovskite crystal structure. The effects of Ba2+ substitutions for (Bi0.5Na0.5)2+ in the A-sites of Bi0.5Na0.5TiO3 on its phase transformations are explored. The transformations among ferroelectric (FE), anti-ferroelectric (AFE) and paraelectric (PE) states in these ceramics are characterized using ferroelectric hysteresis tests, modulated differential scanning calorimetry and dynamic mechanical analysis. The FE-AFE transition in BNT–xBT with 0≤x≤0.15 is found to relate with a structural transformation which is a first-order phase transition. The mechanical and thermal analyses provide evidence that AFE state (0≤x≤0.15) could be associated with the incommensurate modulation of rhombohedral structures while the mechanisms of forming AFE state in BNT–xBT (x>0.15) could be different.

Characterization of viscoelastic behavior of shape memory epoxy systems

AbstractViscoelastic behavior has a remarkable impact on the functional realization of shape memory polymers and their composites. Our previous work reported that a series of shape memory epoxies with varied curing agents and contents were synthesized and exhibited higher shape fixture and recovery rates. The viscoelastic behavior of the materials at different temperatures is experimentally investigated in this study. Stress–strain hysteresis under uniaxial tension, stress relaxation, and creep tests are performed. The energy dissipation factor and residual strain factor as functions of temperatures are presented in the basis of stress–strain hysteresis tests. Moreover, the effects of test temperature, curing‐agent type, and content on the viscoelastic behavior of these materials are discussed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Testing for hysteresis in entrepreneurship in 23 OECD countries

We explore the macrostructure of entrepreneurship rates in a panel of 23 OECD countries over 1972–2006. We find that rates of entrepreneurship in OECD countries exhibit persistence rather than hysteresis. Implications for the design of entrepreneurship policies are discussed.

HYSTERESIS CHARACTERISTICS OF HIGH MODULUS LOW SHRINKAGE POLYESTER TIRE YARN AND CORD

Abstract Hysteresis characteristics of high modulus low shrinkage (HMLS) polyester tire yarn and cord were evaluated to determine “specific work loss,” which indicate its heat generation characteristics. Test parameters were selectively chosen, considering the service conditions of high-speed passenger radial tires in which HMLS polyester tire cords are predominantly used. Specific work loss was found to increase exponentially with the increase in extent of stress relief. Dynamic property of this yarn and cord was also studied to determine “loss tangent (tan δ),” which influences rolling resistance of tires in service. A good correlation has been found between specific work loss of hysteresis test (a slow speed test) and tan δ of dynamic test (a high-speed test). Dynamic property of polyester dipped cord was investigated for a wide range of temperatures (100–180 °C) and frequencies (5–25 Hz). Tan δ at 100 °C was found to be relatively low and its magnitude remained at the same level for a wide range of frequencies. This is a favorable condition for the high-speed passenger radial tires, made out of HMLS polyester tire yarn. Microstructure of HMLS polyester yarn was analyzed. Crystallinity is around 43% (measured by Wide angle x-ray scattering); crystal width and long period are 61 and 142 Å, respectively.

The effect of residence time on the tensile properties of superelastic and thermal activated Ni-Ti orthodontic wires

Since the 1980s, different devices based on superelastic alloys have been developed to fulfill orthodontic applications. Particularly in the last decades several researches have been carried out to evaluate the mechanical behavior of Ni-Ti alloys, including their tensile, torsion and fatigue properties. However, studies regarding the dependence of elastic properties on residence time of Ni-Ti wires in the oral cavity are scarce. Such approach is essential since metallic alloys are submitted to mechanical stresses during orthodontic treatment as well as pH and temperature fluctuations. The goal of the present contribution is to provide elastic stress-strain results to guide the orthodontic choice between martensitic thermal activated and austenitic superelastic Ni-Ti alloys. From the point of view of an orthodontist, the selection of appropriate materials and the correct maintenance of the orthodontic apparatus are essential needs during clinical treatment. The present work evaluated the elastic behavior of Ni-Ti alloy wires with diameters varying from 0.014 to 0.020 inches, submitted to hysteresis tensile tests with 8% strain. Tensile tests were performed after periods of use of 1, 2 and 3 months in the oral cavity of patients submitted to orthodontic treatment. The results from the hysteresis tests allowed to exam the strain range covered by isostress lines upon loading and unloading, as well as the residual strain after unloading for both superelastic and thermal activated Ni-Ti wires. Superelastic Ni-Ti wires exhibited higher load isostress values compared to thermal activated wires. It was found that such differences in the load isostress values can increase with increasing residence time.