Hysteresis Parameters Research Articles

Dynamic behavior modelling of a hybrid magnetorheological elastomer with encapsulated fluid for base vibration isolation

Magnetorheological elastomers (MRE) based semi-active isolators utilize MREs whose mechanical properties, such as stiffness and damping, change in response to an external magnetic field. MREs implementation in semi-active isolation remains challenging due to their slow response time caused by the suspension of the magnetic particles inside the elastomeric matrix and limited damping capabilities. Hybrid MREs, a combination of MREs and MRFs, have been developed to improve semi-active isolation's material properties and performance. However, modelling the nonlinear and hysteretic behavior of hybrid MRE-based isolators remains a challenge and needs to be adequately addressed. To bridge the gap, this study presents a parametric model for a hybrid semi-active isolator's nonlinear and hysteretic behavior that utilizes a hybrid MRE (H-MRE). The behavior of conventional and hybrid MRE-based isolators are experimentally tested under varying loading conditions of excitation frequency and input current. Simulation models are created using combinations of three different phenomenological models, Bouc-Wen, Modified-Dahl and LuGre friction. The experimental data are used to optimize and fit the simulated response of each model, and hence optimal values of the MRE and MRF hysteresis parameters are determined. The parameter estimation results indicate that a combination of LuGre friction for the MRE and Bouc-Wen for the MRF improves the accuracy of predicting the dynamic behaviour of the hybrid isolator. The relationship between the model parameters and loading conditions is also investigated and described through polynomial equations of the third order. These findings could provide valuable insights for the system identification and control of hybrid semi-active isolators and pave the way for developing smart base isolation systems utilizing hybrid MREs in future research.

Rock Magnetism and Magnetic Fabric Study of the Icelandite and Rhyodacite Long Volcanic Sequence at Mauna Kuwale, Wai’anae Volcano, Oahu, Hawaii, USA

In order to understand further the emplacement (i.e., volcanic growth) of 22 Icelandite and 3 Rhyodacite cooling units in one of the long volcanic sequences known as Mauna Kuwale of the Wai’anae volcano (ca. 3.3 Ma), Oahu Hawaii we have conducted appropriate rock magnetic experiments described below as well as anisotropy of magnetic susceptibility (AMS) studies of such 25 units. We have undertaken rock magnetic investigations such as continuous and partial thermo-magnetic cycles of low field magnetic susceptibility versus temperature dependence, (k-T) curves experiments. We classified the k-T heating-cooling dependence of susceptibility in three groups A, B and C. Type A: yielded two components of titano-magnetite with a predominat Ti rich phase and occasionally a relevant magnetite component phase. Type B: samples are characterized by Ti poor magnetites. Magnetite dominates as the main magnetic carrier. Type C: k-T curves show one single phase of titanomagnetite, and Ti poor magnetite. The coercivity or remanence, determined by back field magnetization is always <60 mT, which suggest the predominance of magnetic components of low coercivity, like magnetite. Usually, two coercivity components are identified in the specimens. In addition we also conducted magnetic granulometry analyses on 27 specimens to determine the domain state of the flows. The ratio of hysteresis parameters (Mr/Mrs versus Hcr/Hc) show that overall samples fall in the Pseudo-Single Domain (PSD) region with high values of Mr/Mrs and very low values of Hcr/Hc. Only two samples from cooling units 17 and specially 22 show a Single Domain (SD) magnetic behavior and a sample from one unit approaches the SD-MD mixture region. We measured the magnetic susceptibility of all cooling units and we found out that in all analyzed units the magnetic susceptibility is low 13.7 ± 8.8 (10−3 SI). Magnetic anisotropy/magnetic fabric is used as a tool in rock fabric analyses to investigate the preferred orientation of magnetic minerals in rocks. Magnetic anisotropy is low on all (measured) flows from the Icelandite cooling units from 1 to 17 (mean P’ = 1.010), but becomes noticeably distinct and high in rhyodacite cooling units 23, 24 and 25 (mean P’ = 1.074). Four units show a magnetic fabric with k3 axes vertical to sub-vertical which may be denoted as normal for the horizontal to sub horizontal units. Two Icelandite cooling units display oblate shapes and two other cooling units triaxial shapes. K1 axes are horizontal but point in different directions, i.e., NE and NW. Remaining cooling units show different magnetic fabric. Units 17, 23, 24 and 25, despite important variations in anisotropy (low for units 25 and high for units 23 and 24) and shape of ellipsoid (oblate in cooling unit 23, prolate in 24 and triaxial in 25) the k3 axes show the same orientation, SW to SSW dipping around 45° and a very steady magnetic lineation azimuth NW nearly horizontal to sub horizontal. The magnetic mineralogy and magnetic fabric indicate that both the Icelandite and Rhyodacite cooling units the magmatic evolution during the shield stage of the entire Wai’anae volcano and that such growth was not affected by tectonic deformation.

Вплив конструктивних параметрів термоплати на гістерезис за тепловим навантаженням

The contact heat exchangers designed to remove heat from the cooled devices are used in mechanically pumped two-phase loops of thermal management systems for ground and space applications, a thermoplate (heat sink). After the device is turned on, it may overheat abnormally during the process of reaching a stationary operating mode. Overheating is associated with the phenomenon of thermal load hysteresis during the onset of boiling, the transition from single-phase convection to developed boiling in the evaporator of a heat sink material. This work studied the influence of the construction parameters of thermoplate on the hysteresis phenomenon at the integral level. For this purpose, a thermoplate testing methodology was implemented, which includes experiments with slow (quasi-stationary) and quick heating after turning on the device immediately at full power. Overheating of the device is possible during both "slow" and "quick" heating. The maximum overheating in the experiments performed was ~18 K. Such overheating can pose a danger to the reliability of the device. The study was performed with ammonia as a coolant on 5 models of thermoplate that differ in evaporator channel roughness, length, material, longitudinal thermal conductivity, the heat capacity of the structure, etc. The danger of overheating the device is also determined by the maximum thermal load at which the device is operated. The following conclusions were made: the greatest influence on the hysteresis parameters is the value of the evaporator channel surface roughness. Increasing the roughness reduces the risk of overheating the device, and changes the nature of the "boiling curves" in the thermoplate; an increase in the length and longitudinal thermal conductivity has a favorable effect on reducing the risk of overheating; the evaporator surface is made of aluminum alloy instead of stainless steel, which makes hysteresis impossible; in the case of rapid heating of the thermoplate, the maximum heat flux at steady-state has an ambiguous effect: with its increase, overheating due to hysteresis first increases, and in the case of further increase, it decreases and may disappear altogether. A significant increase in the maximum heat flux compared to the heat flux at the beginning of boiling reduces the danger of hysteresis affecting the overheating of the device. The results of this work provide recommendations on how to avoid the dangerous overheating of the device due to the hysteresis phenomenon.

Magnetic properties of gas hydrate-bearing sediments and their association with iron geochemistry in the Sea of Marmara, Turkey

The anaerobic oxidation of methane, a key geochemical process that is involved in the cycling of sulfate and iron (oxyhydr)oxides in marine sediments, results in the formation of iron sulfides. Although ferrimagnetic iron sulfides have been identified in seepage systems, the link between iron migration and sediment magnetic properties remains poorly understood. Here, we investigate two cores from the Sea of Marmara to evaluate biogeochemical iron cycling and iron sulfide mineralogy in gas hydrate-bearing sediments. Magnetic analyses indicate the presence of greigite and pyrrhotite in a core from a hydrate-rich site with a high hydrocarbon flux, which contrasts with a lack of these minerals in a core characterized by only mild seepage. This is supported by the results of rock magnetic and scanning electron microscope analyses of the sediments. The presence of authigenic greigite is critical for assessing local redox records and together with the occurrence of monoclinic pyrrhotite may suggest specific diagenetic processes in gas hydrate environments. Our analysis demonstrates the usefulness of these ferrimagnetic minerals, with a high saturation isothermal remanent magnetization to magnetic susceptibility ratio (SIRM/χ > 15 kAm−1) and a high index of hysteresis parameters (DJH > 0.2) indicative of magnetic mineralogy changes, for evaluating variability in the intensity of seepage fluxes and for estimating gas hydrate distributions.

Thermal Magnetic Properties Variation of Rock During In-Situ Combustion Process

Summary In-situ combustion (ISC) has been proven as a promising technique for the extraction of heavy oils. It has been used in oil fields since the 1920s; however, it is still not as widely used as steam injection. One of the difficulties limiting its wide application is monitoring and controlling the movement of the combustion front. This work is aimed at studying the change in the properties of rock during the ISC process, which is expected to be used for developing an effective monitoring method of the combustion front movement. Rock samples before and after the ISC process were obtained from the Xinjiang Oil field (China) where an ISC industrial pilot has been implemented. In the temperature range of lower than 500℃, the minerals may only alter slightly. Therefore, it is difficult to determine whether the rock was heated or not during the ISC processes using general mineralogical or geochemical methods, for example, X-ray diffraction. This work takes a comprehensive approach to study the variation of rock properties. Magnetic analysis was chosen as the primary method since a very tiny change in the mineral composition during heating leads to profound changes in the magnetic properties. We analyzed magnetic susceptibility (MS), natural remanent magnetization (NRM), hysteresis parameters and thermomagnetic data. In addition, we performed differential thermomagnetic analysis (DTMA) for tracing magnetic minerals based on their Curie temperatures as well as for monitoring transformations in magnetic minerals during heating. Simultaneously, X-ray diffractometer (XRD), optical microscope for thin-sections, and organic content measurements were used as assistive methods to get a comprehensive evaluation on the variation of rock. We found that there is a big difference in magnetic minerals between the initial samples (not subjected to the ISC process) and burned samples from different wells and depths in the ISC pilot. Several magnetic clusters with different coercive force and domain structure were found in these samples. Based on the difference in magnetic properties, we found that the burned samples were heated to different temperatures during the ISC process. In addition, for some rock samples, the heating temperature during the ISC process was determined, and an analysis was made of the propagation of the combustion front. The thermal magnetic properties variation of rock during the ISC process is obvious, which makes it promising to be used for monitoring the propagation direction of the combustion front. Theoretical calculations of magnetic anomalies that occur due to changes in the magnetic properties of rocks during the ISC process indicate the possibility of the detection of such anomalies from the Earth’s surface through high-precision magnetic surveys. The findings in this work provide a theoretical base and direction for developing combustion front monitoring technologies.

Rockmagnetic Characterization of the Quaternary Fluviolacustrine Sediments of the Thimi Section, Kathmandu Valley, Nepal

The fine-grained silt/clay sediments sampled at 38 levels of a 21 m thick segment at the Thimi outcrop in the Kathmandu valley have been studied for their rockmagnetic properties. These sediments have yielded consistently normal magnetic polarity and 14C ages determined by various workers between 20 and 45 kyrs or even more. They were measured for a set of rock magnetic parameters: low-field magnetic susceptibility, parameters derived from isothermal remanent magnetization (IRM) acquisition and demagnetisation (IRM0.3T, IRM3T, MDFIRM), anhysteretic remanent magnetization (ARM) (ARMtot, ARM(30 mT)/ARMtot, χARM), hysteresis parameters, etc. Several relationships between these parameters have been suggested for the Kathmandu valley sediments. Four rockmagnetic zones, based on the minor variations in magnetic mineral types and grain size parameters, are proposed and their possible relationship to the published pollen data has been discussed.

Palaeomagnetic investigations across Hinlopenstretet border zone: from Caledonian metamorphosed rocks of Ny Friesland to foreland facies of Nordaustlandet (NE Svalbard)

New demagnetization results of 286 palaeomagnetic specimens from 15 sites in Neoproterozoic–Lower Paleozoic sequences of Ny Friesland–Nordaustlandet (the Caledonian Eastern Svalbard Terrane) are presented. New in situ 40 Ar/ 39 Ar ultraviolet mass spectrometry (Uv-MS) age determinations on amphibolites and mylonites from the Ny Friesland cluster in the 340–460 Ma interval correspond broadly to the Caledonian thermal event. Older ages are observed but are more scattered and probably reflect partial resetting or argon gain of Proterozoic micas. Palaeomagnetic, petrological and structural data confirm a west to east decrease in the degree of the Caledonian metamorphism and remagnetization across Hinlopenstretet, which is interpreted here to coincide with the limit of Caledonian east-directed overthrusting. No pre-Caledonian palaeomagnetic record was identified in investigated amphibolites and metacarbonates of Ny Friesland. Pre-folding pre-Caledonian, potentially Neoproterozoic (primary?) magnetization was recognized only in non-metamorphosed Murchisonfjorden (Nordaustlandet) carbonates. However, selective palaeomagnetic palaeopoles from Murchisonfjorden also fall into Caledonian sensu lato and Mesozoic sectors of the Laurussia reference path. This also indicates that regions east of Hinlopenstretet and east of the Caledonian front could be partially subjected to Caledonian remagnetization. Mesozoic palaeomagnetic overprints are potentially related to the injection of Mesozoic dolerites in eastern Svalbard. Here, we discuss two concepts of post-Caledonian rotations that could affect the palaeomagnetic record of the Eastern Svalbard Terrane: rotations around vertical axes related to strike-slip faults and rotations around horizontal axes related to normal listric faults that originated during extension in the Devonian basin and the opening of the Atlantic and Arctic oceans. Supplementary material: (1) A detailed description of applied rock-magnetic and palaeomagnetic procedures, (2) detailed description of investigated geochronological samples, (3) in situ Uv-MS 40 Ar/ 39 Ar isotopic age determination results, (4) mineralogy of ferromagnetic phases, (5) hysteresis parameters, (6) distribution of the NRM components and great circles in palaeomagnetic sites and (7) anisotropy of magnetic susceptibility are available at https://doi.org/10.6084/m9.figshare.c.6132018

Ecological quality of the “Torfowisko pod Węglińcem” nature reserve (SW Poland) based on magnetic and geochemical studies

In this research a combination of magnetic, geochemical and microscopic techniques was used to investigate the ombrothropic peat bog, which covers the “Torfowisko pod Węglińcem” nature reserve, situated in south-western Poland. Hysteresis parameters and measurements of magnetic susceptibility show that the surface layer (∼15 cm) of the protected peat bog area is contaminated by strongly-magnetic materials e.g. low-coercivity magnetite. Geochemical analyses revealed higher concentrations of certain chemical elements (e.g. Li, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Ba and Pb) in the approximately 10 cm surface peat layer. The vertical distribution of the magnetic susceptibility and most of the analyzed chemical elements exhibit strong correlation and this demonstrates that the identified anthropogenic contaminants accumulate via atmospheric deposition. The microscopic analyses of the magnetic material separated from the peat samples identified two types of metal-rich particulates: spherules and irregularly shaped particles including an octahedral magnetic crystals (mean diameter of both types ∼10–300 μm). The magnetic bi-plots show that even finer magnetic grains (<10 μm) may be found at the studied area. The radiocarbon (14C) dating of the surface samples suggests that the formation of the contaminated top peat layer has occurred during last 300 years. In such case the analyzed magnetic material may be the proof of both: historical as well as the present atmospheric deposition.

Measurement of Magnetic Hysteresis Loops of the Ni-5at.%W Alloy Substrate as a Function of Temperature in a Stack of 2G HTS-Coated Conductor Annuli

The development of coated conductors with a ferromagnetic substrate and their use in various applications require accurate knowledge of the magnetic properties of the substrate. In this work, we report measurements in the ac regime (30 Hz) of the magnetic hysteresis loops of the Ni-5at.%W alloy ferromagnetic substrate in a stack of second-generation YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> (YBCO) tapes cut in the shape of annuli from 46-mm-wide-coated conductors. The stacked annuli form a closed magnetic circuit, which is the ideal configuration due to the absence of demagnetizing effect. The measurements are carried out at four temperatures between 77 K and 293 K. The peak intensity of the relative permeability is not significantly affected in the range of temperature considered. The coercive field dependence on temperature is also investigated. The hysteresis losses <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> as a function of the amplitude of the flux density <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$B_\text{m}$</tex-math></inline-formula> exhibit a power law behavior ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q\sim B_\text{m}^{n}$</tex-math></inline-formula> ) at the four temperatures. This power law behavior is also studied at low fields under the presence of a dc bias field. Finally, the hysteresis loops can be reproduced with the Jiles–Atherton model, which is used to estimate the hysteresis parameters and to discuss their temperature dependence.

A Deep Learning-Based Approach for the Identification of a Multi-Parameter BWBN Model

A restoring-force model is a versatile mathematical model that can describe the relationship between the restoring force and the deformation obtained from a large number of experiments. Over the past few decades, a large body of work on the development of restoring-force models has been reported in the literature. Under high intensity cyclic loadings or seismic excitations, reinforced concrete (RC) structures undergo a wide range of hysteretic deteriorations such as strength, stiffness and pinching degradations. These characteristic behaviors can be described by the multi-parameter Bouc-Wen-Baber-Noori (BWBN) model, which offers a wide range of applicability. This model has been applied for the response prediction and modeling restoring-force behavior in structural and mechanical engineering systems, by adjusting the distribution range of this model’s parameters. However, a major difficulty in utilizing the multi-parameter BWBN model is the parameters’ identification. In this paper, a deep neural network model is used to estimate the hysteresis parameters of the BWBN model. This model is one of the most versatile and widely used general hysteresis models that can describe the hysteretic behavior of RC columns. The experimental data of the RC columns used in this paper are collected from the database of the Pacific Earthquake Engineering Research Center (PEER). Firstly, the hysteretic loop obtained from a physical experiment is described by the BWBN model, and the parameters of the BWBN model are identified via a genetic optimization algorithm. Then a neural network is established by a backpropagation (BP) algorithm for associating the identified BWBN model parameters with physical parameters of the RC column. Finally, the regression analysis of the identified parameters is carried out to obtain the regression characteristics of the RC columns. The trained neural network model can directly identify the parameters of BWBN model based on the physical parameters of RC columns, and is effective and computationally efficient for multi-parameter BWBN model identification. The proposed approach overcomes the difficult problem of identifying the parameters of BWBN model and provides a promising approach for a wider application of this multi-parameter hysteresis model.

Evaluation of indoor/outdoor urban air pollution by magnetic parameters; preliminary study

The paper presents a comparison of outdoor and indoor air pollution by means of magnetic properties of dust gathered outdoors and indoors on air filters. Outdoor dust (particulate matter smaller than 10 μm, PM10) was collected by means of a PM sampler that was placed in the yard of the building of the Institute of Geophysics, Polish Academy of Sciences (IG PAS), in Warsaw, Poland. Indoor dust samples were collected with the same type of PM sampler, placed inside this building. The magnetic methods were applied for the estimation of concentration and magnetic mineralogy of the magnetic particles present in PM. Magnetic measurements, such as low and high-temperature dependence of volume magnetic susceptibility κ(T), hysteresis parameters, and frequency dependence of mass magnetic susceptibility χfd show that outdoor and indoor PM contain ultra-fine-grained magnetite-like minerals, particularly in a size range < 30 nm. This pointed to the common outdoor sources of pollution intruding inside the building through windows, ventilation systems, and partly carried on dresses by people. The mass of PM10 collected outdoors is of the same range as the mass of PM10 from inside the building. The mass susceptibility of indoor filters, however, is about 1/3 of the mass susceptibility of outdoor filters. The relationship between volume susceptibility and mass indicates a relatively homogenous composition of indoor dust but a varying composition of outdoor dust, with a variable influx of nonmagnetic exogenous particles.

Micromagnetic Modeling of a Magnetically Unstable Zone and Its Geological Significances

AbstractRecent micromagnetic simulations have found that particles in the transitional zone between the single domain (SD) and single vortex (SV) zone are prone to thermal and external magnetic field instabilities that could adversely affect the accuracy of interpretations of paleomagnetic recordings. In this study, we attempt to evaluate the internal magnetization characteristics of these magnetically unstable (MU) particles and the influence on paleomagnetic observations by simulating the magnetic behavior of 68–104 nm truncated octahedral magnetite particles using the MERRILL modeling software. We found that: (a) The size region of the “MU zone” for grains of truncated octahedron shape is different from cubic octahedrons and spheres, indicating that the zone may be controlled by the geometry and shape of particles; (b) The MU zone has a range of 79–97 nm region, which is dominated by a hard‐axis aligned single vortex (HSV); and (c) MU particles are unstable as a function of temperature and have low coercive fields. Finally, the numerical fitting of hysteresis parameters for experimental data suggests that the influence of such MU particles in samples should not be ignored, especially for samples with fine‐grained magnetic minerals as the primary magnetic recording carriers. This research has extended our understanding of the behavior of the “MU zone” and its significance on paleomagnetic records.

Rock magnetism and AMS studies in Kondapalle-Pangidi layered complex, Eastern Ghats Belt, India: Remanence carriers and tectonic implications

The present study is an integrated approach towards the rock magnetism and Anisotropy of Magnetic Susceptibility (AMS) of the high-grade metamorphic rocks in the Kondapalle Pangidi Layered Complex (KPLC), Eastern Ghats Belt (EGB), India. Our study aims at determining the petrography, rock magnetic properties and the magnetic fabrics. The rock magnetic properties and the magnetic fabrics from AMS studies are used to determine their tectonic implications. Petrography reveals that the chief remanence carrier mineral is Ti-magnetite. Rock magnetic studies including Isothermal Remanent Magnetization (IRM), back-field IRM, hysteresis loop studies, and thermo-magnetic studies reveals the same. The magnetic hysteresis parameters (remanence and coercivity) are used to determine the magnetic domains from a modified Day plot. The magnetic domains lie within Stable Single Domain and Pseudo Single Domain ranges, thereby explaining their potential to record an ancient magnetic field. Besides the ferrimagnetic remanence carriers, paramagnetic silicates are also dominant which controlled the development of magnetic fabric. The magnetic fabric bears analogy with the regional structures and bear tectonic implications related to the post-rifting closure of the ocean followed by subduction of the ocean basin, accretionary orogeny and felsic magmatism in the Indo-Antarctic continental blocks.

Low-noise second-order gradient SQUID current sensors overlap-coupled with input coils of different inductances

In this study, we developed a series of second-order gradient overlap-coupling octagonal superconducting quantum interference device (SQUID) current sensors for transition edge sensor (TES) applications. According to the requirements of TESs, we designed various parameters of SQUID current sensors, including different Josephson junction (JJ) sizes, different hysteresis and screening parameters, input coils with different inductances. The superconducting loop, input coil, and feedback coil of the SQUID current sensors adopt a second-order gradient structure, which can effectively enhance their anti-interference electromagnetic capability. Further, all the coupling structures between the superconducting loop and input/feedback coil adopt overlap-coupling octagonal structures, which can effectively enhance the coefficient of coupling mutual inductance. A series of second-order gradient SQUID current sensors overlap-coupled with input coils of 1.5, 2.5, and 5.5 turns based on Nb/Al–AlO x /Nb JJs were successfully fabricated on 2 inch silicon wafers by optimising the fabrication processes. From the simulation results, a minimal magnetic coupling factor of 0.02 between the feedback coil and input coil is obtained in the overlapped structure of the SQUID current sensor with an input coil of 1.5 turns; thus the magnetic interference between the feedback coil and input coil in this design is negligible. According to the measurement results at liquid–helium temperatures, SQUID current sensors with second-order gradient overlap-coupling octagonal structures have an excellent capability to weaken environmental electromagnetic interference. The SQUID current sensor with an input coil of 5.5 turns has the smallest current sensitivity, 2.4 μA/Φ0 and lowest current noise, 1 pA (√Hz)−1 compared with those of other input coils of different turns. The SQUID current sensor with an input coil of 2.5 turns has the lowest flux noise, 0.3 μΦ0 (√Hz)−1, and the lowest coupled noise energy, 11 h, among all the three different input coils, which are balanced results between the input inductance and the device noise. SQUID current sensors with second-order gradient overlap-coupling octagonal structures show low flux noise, low current noise, and low coupled noise energy, which can be compared with the state-of-art SQUID current sensor worldwide, and can satisfy the requirements of TES applications.

Development and Study of a Building Model on Lead Rubber Bearings

The building structures on the lead rubber bearings (seismic bearings) require nonlinear dynamic analysis in the time domain. However, in performing such analyses, it is quite difficult to assess the influence of the seismic bearing characteristics on structural dynamic response and quality of seismic isolation in a whole. To solve this problem, it is proposed to study simple nonlinear models with a small number of degrees of freedom. A planar shear model of a three-storey building on lead rubber bearings implemented in the Matlab software is considered. Seismic excitation on the building is given by artificial accelerograms. When subjected to cyclic loads, the building seismic bearings show a significantly nonlinear behavior described by a bilinear deformation diagram with hysteresis. The nonlinear equations of motion for a seismically isolated three-storey building are derived, and procedures for seismic load modeling and numerical integration of the equations of motion are described. The results of numerical simulation for various hysteresis parameters are obtained and analyzed, and conclusions about the seismic protection effectiveness are drawn. The obtained study results may be of interest for design engineers from the viewpoint of elaborating their own simple models for testing seismic isolated building structures and studying the influence of various hysteresis parameters on the seismic isolation quality.

Analytical model of the readout power and SQUID hysteresis parameter dependence of the resonator characteristics of microwave SQUID multiplexers

We report on the development of an analytical model describing the readout power and superconducting quantum interference device (SQUID) hysteresis parameter dependence of the resonator characteristics used for frequency encoding in microwave SQUID multiplexers. Within the context of this model, we derived the different dependencies by analyzing the Fourier components of the non-linear response of the non-hysteretic rf-SQUID. We show that our model contains the existing model as a limiting case, leading to identical analytical expressions for small readout powers. Considering the approximations we made, our model is valid for rf-SQUID hysteresis parameters which fully covers the parameter range of existing multiplexer devices. We conclude our work with an experimental verification of the model. In particular, we demonstrate a very good agreement between measured multiplexer characteristics and predictions based on our model.

A study of Jiles-Atherton and the modified arctangent models for the description of dynamic hysteresis curves

This paper considers the identification of hysteresis parameters for two different hysteresis models, operated in quasi-static and dynamic behaviors. The extended Jiles-Atherton model via the Bertotti approach and the improved arctangent model are tested and compared. The hysteresis measurement was performed via standard Epstein frame on automotive parts for different magnetization levels and frequencies. The robustness of the Levenberg-Marquardt algorithm is assessed via a comparison of measured, modeled hysteresis loops, and relative permeability profiles, at various frequencies.

Evaluation of Tensile Residual Stress in Welded Steel Plates Using Acoustically Stimulated Electromagnetic Response.

Residual stress is one factor involved in the degradation and damage of industrial products. It is important to understand the magnitude and distribution of residual stress to maintain the integrity of a product. Magnetic measurements are a potential nondestructive method for evaluating residual stress in steel because the hysteresis properties are sensitive to stress. In recent years, spatial mapping of local magnetic hysteresis loop has been performed by using the acoustically stimulated electromagnetic (ASEM) method, which obtains the conversion coefficients from local hysteresis parameters to tensile stress. In this study, we demonstrate the evaluation and spatial imaging of tensile residual stress through local hysteresis parameters using welded steel specimens. We confirm that local coercivity can be used for evaluating residual tensile stress in the high-stress region. In addition, the spatial distribution of residual stress is well visualized by imaging the ASEM response signals due to remanent magnetization.

Bending and Collapse: Magnetic Recording Fidelity of Magnetofossils From Micromagnetic Simulation

AbstractMagnetosome chains produced by magnetotactic bacteria are important paleoenvironmental and paleomagnetic recorders. It has been shown that magnetic properties of magnetosome chains are closely related to their morphology and chain structures; however, the in situ structures of magnetosome chains in sediments (magnetofossils) are not known. Magnetosome chains are subject to various deformations after cell dissolution and are therefore unlikely to be fully intact, obscuring their original magnetic signals. Here, we use finite element micromagnetic simulations to quantify changes in magnetic signals in response to chain deformation, in particular, as a function of variable degrees of bending and collapse. Our results indicate that bending/collapse leads to a significant coercivity reduction and domain state transition of the chain. Therefore, hysteresis parameters can be used to assess the degree of chain bending/collapse in magnetofossil‐rich sediments. Calculations of the contributions of chain bending/collapse to the post‐depositional remanent magnetization (pDRM) of magnetofossils indicate that pDRM remains both faithful to the pre‐bending/collapse natural remanent magnetization, and that the remanence of some structurally deformed magnetofossil assemblages remains thermally stable over billion‐year timescales, suggesting that even strongly deformed magnetosome chains in ancient geological materials retain faithful paleomagnetic records and thus have potentials for tracing ancient geomagnetic field variations and microbial activities on early Earth.

Remagnetization of Carboniferous Limestone in the Zaduo Area, Eastern Qiangtang Terrane, and Its Tectonic Implications

Robust paleomagnetic results through geological time are one of the keys to understand the drift history of the eastern Qiangtang terrane (EQT). Here, we presented comprehensive petrographic observations and rock magnetic and paleomagnetic analyses of the early Carboniferous Upper Zaduo (ZD) limestone Formation (C1z2) from the Sulucun (SLC) section in the Zaduo area, EQT, to investigate its magnetic originality and geological significance. A total of 12 sites (131 samples) were collected. Photomicrograph observations indicate that the limestone samples were characterized by widespread carbonate veinlets. Electron microprobe and energy dispersive spectrometry analyses confirm that authigenic magnetite formed after pyrite. Rock magnetic analyses reveal the dominant magnetic minerals of pyrite and magnetite, with ‘wasp-waisted’ hysteresis loops and close to the “remagnetization trend” hysteresis parameters. Based on both thermal and alternating field demagnetizations, the characteristic remanent magnetization directions for most samples were isolated: Dg = 6.3°, Ig = 50.1°, kg = 54.9, α95 = 6.2° in-situ, and Ds = 330.2°, Is = 58.9°, ks = 5.9, and α95 = 20.5° after 2-step tilt correction. The κ (α95) value decreases (increases) after tilt-correction, and the ChRM directions failed both the McFadden (1990), Watson and Enkin (1993) fold tests, indicating post-folding magnetizations. The 11 site-mean directions yield a mean in-situ paleopole of 84.4°N, 200.3°E, and A95 = 6.8°, which is coincident with the post ∼53 Myr (especially around 40 Ma) paleopoles of the region. We therefore interpreted that these early Carboniferous limestone samples contain remagnetized magnetizations and that they were obtained after 53 Ma, most likely around 40 Ma, due to the far-field effect of the India–Eurasia collision.