Flux Gate Research Articles

Analysis of orientation errors in triaxial fluxgate sensors and research on their calibration methods

Abstract. Three-axis magnetic flux gate sensors are widely used in Chinese geomagnetic observatories, but due to their directional errors it is necessary to study error correction methods to improve measurement accuracy. Firstly, the mechanism of directional errors produced by three-axis magnetic flux gate sensors is analyzed, followed by the development of measurement tools for conducting directional error measurement experiments on the high-precision three-axis magnetic flux gate sensors of the Chinese FGM-01 series. Experimental results show that correcting the Z-axis and D-axis directional errors is essential. The observation data after error correction, whether in terms of the standard deviation of its all-day baseline values or the relative difference magnitude with the reference instrument, significantly decrease, demonstrating the clear correction effect and proving the effectiveness of this correction method.

Hardware Design and Implementation of a High-Precision Optically Pumped Cesium Magnetometer System Based on the Human-Occupied Vehicle Platform

High-precision magnetometers play a crucial role in ocean exploration, geophysical prospecting, and military and security applications. Installing them on human-occupied vehicle (HOV) platforms can greatly enhance ocean exploration capabilities and efficiency. However, most existing magnetometers suffer from low sensitivity and excessively large size. This study presents a high-sensitivity, miniaturized magnetometer based on cesium optically pumped probes. The designed magnetometer utilizes a three-probe design to eliminate the detection dead zone of the cesium optically pumped probe and enable three-dimensional magnetic detection. The proposed magnetometer uses a flux gate probe to detect the three-axis magnetic field and ensure that the probe does not enter the dead zone. The three probes can automatically switch by measuring the geomagnetic elements and real-time attitude of the HOV platform. This article primarily introduces the cesium three-probe optically pump, flux gate sensor, and automatic switching scheme design of the above-mentioned magnetometer. Moreover, it is proven through testing that the core indicators, such as the accuracy and sensitivity of the cesium three-probe optically pumped and flux gate sensor, reach international standards. Finally, the effectiveness of the automatic switching scheme proposed in this study is demonstrated through drone-mounted experiments.

A comparative study of mass balance in the Lambert Glacier and Amery Ice Shelf along the Chinese inland traverse during 2019–2023 using altimetry, gravity, and in-situ observations

Abstract. The new photon-counting laser altimetry satellite ICESat-2 was successfully launched on September 15, 2018 with an unprecedented ice surface elevation measurement accuracy of 2–4 cm. It is meaningful for accurately estimating volumetric changes in the Antarctic Ice Sheet. Cross-validation of different types of data, especially comparison with in-situ data, is important for the ice sheet mass balance results of a new satellite. This paper proposes an elevation-difference method of grid elevation change rate model, based on ICESat-2 ATL11 elevation time series data, to distinguish the linear change trend of ice sheet surface elevation from the elevation change resulting from periodic precipitation. In order to compare the estimated elevation-change rate with the flux computed from in-situ snow stake velocity measurements and GRACE-FO gravity survey data, we made corrections for firn air content, elastic, and glacier isostatic adjustment. Based on the ATL11 data from 2019 to 2023, our results show that the ice sheet change in Basin 11 along the CHINARE traverse is from ~0.019 m yr−1 to ~0.121 m yr−1, and the mass balance in the upstream of the traverse in Basin 11 is ~1.9±0.2 Gt yr−1. It is comparable to ~2.4±1.2 Gt yr−1 from GRACE-FO during the same time period. Furthermore, the flux across traverse-11.9±1.1 Gt yr−1 is comparable to that of ~-9.7±0.9 Gt yr−1 across the same flux gate during 1997–2009 which is calculated based on GNSS-derived ice velocity observations, considering the time period difference and uncertainties.

Estimating ice discharge of the Antarctic Peninsula using different ice-thickness datasets

Abstract The Antarctic Peninsula Ice Sheet (APIS) has become a significant contributor to sea-level rise over recent decades. Accurately estimating the ice discharge from the outlet glaciers of the APIS is crucial to quantify the mass balance of the Antarctic Peninsula. We here compute the ice discharge from the outlet glaciers of the APIS north of 70 ${^\circ }$ S for the five most widely used ice-thickness reconstructions, using a common surface velocity field and a common set of flux gates, so the differences in ice discharge can be solely attributed to the differences in ice thickness at the flux gates. The total volumetric ice discharge for 2015–2017 ranges within 45–141 km3 a−1, depending on the ice-thickness model, with a mean of 87 ± 44 km3 a−1. The substantial differences between the ice-discharge results, and a multi-model normalized root-mean-squared deviation of 0.91 for the whole data set, reveal large differences and inconsistencies between the ice-thickness models, giving an indication of the large uncertainty in the current ice-discharge estimates for the APIS. This manifests a fundamental problem of the region: the scarcity of appropriate ice-thickness measurements and the difficulty of the current models to reconstruct the ice-thickness distribution in this complex region.

A thicker Antarctic ice stream during the mid-Pliocene warm period

Ice streams regulate most ice mass loss in Antarctica. Determining ice stream response to warmer conditions during the Pliocene could provide insights into their future behaviour, but this is hindered by a poor representation of subglacial topography in ice-sheet models. We address this limitation using a high-resolution model for Dronning Maud Land (East Antarctica). We show that contrary to dynamic thinning of the region’s ice streams following ice-shelf collapse, the largest ice stream, Jutulstraumen, thickens by 700 m despite lying on a retrograde bed slope. We attribute this counterintuitive thickening to a shallower Pliocene subglacial topography and inherent high lateral stresses at its flux gate. These conditions constrict ice drainage and, combined with increased snowfall, allow ice accumulation upstream. Similar stress balances and increased precipitation projections occur across 27% of present-day East Antarctica, and understanding how lateral stresses regulate ice-stream discharge is necessary for accurately assessing Antarctica’s future sea-level rise contribution.

Basal mass balance and prevalence of ice tongues in the Western ross sea

Ice tongues at the fringes of the Antarctic ice sheet lose mass primarily through both basal melting and calving. They are sensitive to ocean conditions which can weaken the ice both mechanically or through thinning. Ice tongues, which are laterally unconfined, are likely to be particularly sensitive to ocean-induced stresses. Here we examine ice tongues in the Western Ross Sea, by looking into the factors affecting their stability. We calculate the basal mass change of twelve Antarctic ice tongues using a flux gate approach, deriving thickness from ICESat-2 height measurements and ice surface velocities from Sentinel-1 feature-tracking over the same period (October 2018 to December 2021). The basal mass balance ranges between −0.14 ± 0.07 m yr−1 and −1.50 ± 1.2 m yr−1. The average basal mass change for all the ice tongues is −0.82 ± 0.68 m of ice yr−1. Low values of basal melt suggest a stable mass balance condition in this region, with low thermal ocean forcing, as other studies have shown. We found a heterogeneous basal melt pattern with no latitudinal gradient and no clear driver in basal melt indicating that local variables are important in the persistence of ice tongues in the absence of a strong oceanographic melting force. Moreover, thanks to the temporal resolution of the data we were able to resolve the seasonal variability of Drygalski and Aviator Ice Tongues, the two largest ice tongues studied.

Dynamic mass loss from Greenland's marine-terminating peripheral glaciers (1985–2018)

AbstractGlobal glacier mass balance decreased rapidly over the last two decades, exceeding mass loss from the Greenland and Antarctic Ice Sheets. In Greenland, peripheral glaciers and ice caps (GICs) cover only ~5% of Greenland's area but contributed ~20% of the island's ice mass loss between 2000 and 2018. Although Greenland GIC mass loss due to surface meltwater runoff has been estimated using atmospheric models, mass lost to changes in ice discharge into oceans (i.e., dynamic mass loss) remains unquantified. We use the flux gate method to estimate discharge from Greenland's 585 marine-terminating peripheral glaciers between 1985 and 2018, and compute dynamic mass loss as the discharge anomaly relative to the 1985–98 period. Greenland GICs discharged between 2.94 ± 0.23 and 4.03 ± 0.23 Gt a−1from 1985 to 1998, depending on the gap-filling method, and abruptly increased to 5.10 ± 0.21 Gt a−1from 1999 to 2018. The resultant ~1–2 Gt a−1dynamic mass loss was driven by synchronous widespread acceleration around Greenland. The mass loss came predominantly from the southeast region, which contains 39% of the glaciers. Although changes in discharge over time were small relative to surface mass-balance changes, our speed and discharge time series suggest these glaciers may quickly accelerate in response to changes in climate.

New insights in the understanding of TREK-1 channel activation by fatty acids

Among the two-pore domain K+ channels (K2P), TREK-1 channel is one of the most studied K2P channel members due to its involvement in cardio- and neuroprotection but it suffers from a poor specific pharmacological profile. TREK-1 channel is polymodulated by voltage, pH changes, membrane stretch and polyunsaturated fatty acids (PUFAs) and generates an outwardly rectifying current. The PUFAs-mediated activation is supposedly correlated to the length of the carbon chain suggesting a link between FAs membrane insertion and a stretch effect through an increase of membrane tension. The aim of this study is to test the effects of different fatty acids, especially polyunsaturated fatty acids, to delineate a possible mechanism of action to explain the activation of ITREK-1. In this study, using the patch-clamp technique in ruptured whole-cell configuration, we compared the effects of FAs, from stearic acid (C18:0, 18 carbons; 0 double bound) to docosahexaenoic acid (C22:6, 22 carbons; 6 double bounds) on ITREK-1 in a HEK293 cell line overexpressing the human TREK-1 channel. C18:0 and C18:3 failed to activate ITREK-1. Surprisingly, it was the shortest PUFA, linoleic acid (LA C18:2) that produced the largest activated ITREK-1. At 0 mV, ITREK-1 was increased 32.4 ± 5.4 folds by LA (C18:2); DHA(C22:6): 29.7 ± 4.1 and AA(C20:4): 14.7 ± 1.9. Since the activation kinetic was fast (in the range of 1.5 min) and the reversibility immediate when FA solution was washed, we supposed that FAs interact directly with TREK-1 rather than FAs membrane insertion changing membrane tension. Some FAs linearized the current-voltage relationship with a calculated linearization index (LI) greater than 0.9, for C18:2, C22:5w6, C22:6, while the rectifier current was maintained for C20:5, C20:4, C20:5, C22:5w3 FAs (LI < 0.75). We propose that the observed linearization results from an activation process involving a K + -flux gating mechanism. Taken together, all these data suggest that the activation of TREK-1 by PUFAs is not a consequence of change in membrane tension but rather more complex than previously assumed. A better understanding of the TREK-1 channels activation mechanisms will help to develop more efficient activators in the perspective of a use to protect the heart following an infarction.

Method for joint tracking by using magnetic field of the welding current during arc welding

We investigated a possibility to determine electrode deviation from the joint during arc welding by using the strength of the magnetic field from the components of the welding current flowing through the welded parts. Amplitude of the vertical component of the resulting magnetic field is proportionate to the deviation of the electrode from the joint and the sign determines the direction of the deviation. The differential flux gate is utilized as a sensor for the electrode deviation from the joint.

Oriented Two‐Dimensional Covalent Organic Framework Membranes with High Ion Flux and Smart Gating Nanofluidic Transport

AbstractNanofluidic ion transport holds high promise in bio‐sensing and energy conversion applications. However, smart nanofluidic devices with high ion flux and modulable ion transport capabilities remain to be realised. Herein, we demonstrate smart nanofluidic devices based on oriented two‐dimensional covalent organic framework (2D COF) membranes with vertically aligned nanochannel arrays that achieved a 2–3 orders of magnitude higher ion flux compared with that of conventional single‐channel nanofluidic devices. The surface‐charge‐governed ion conductance is dominant for electrolyte concentration up to 0.01 M. Moreover, owing to the customisable pH‐responsivity of imine and phenol hydroxyl groups, the COF‐DT membranes attained an actively modulable ion transport with a high pH‐gating on/off ratio of ≈100. The customisable structure and rich chemistry of COF materials will offer a promising platform for manufacturing nanofluidic devices with modifiable ion/molecular transport features.

Oriented Two-Dimensional Covalent Organic Framework Membranes with High Ion Flux and Smart Gating Nanofluidic Transport.

Nanofluidic ion transport holds high promise in bio-sensing and energy conversion applications. However, smart nanofluidic devices with high ion flux and modulable ion transport capabilities remain to be realised. Herein, we demonstrate smart nanofluidic devices based on oriented two-dimensional covalent organic framework (2D COF) membranes with vertically aligned nanochannel arrays that achieved a 2-3 orders of magnitude higher ion flux compared with that of conventional single-channel nanofluidic devices. The surface-charge-governed ion conductance is dominant for electrolyte concentration up to 0.01 M. Moreover, owing to the customisable pH-responsivity of imine and phenol hydroxyl groups, the COF-DT membranes attained an actively modulable ion transport with a high pH-gating on/off ratio of ≈100. The customisable structure and rich chemistry of COF materials will offer a promising platform for manufacturing nanofluidic devices with modifiable ion/molecular transport features.

ESTIMATION OF THE MASS OF CARGO DUMP TRUCK

The article discusses an on-board weighing system for the load of a mining dump truck, which simplifies measurements and, unlike existing systems, does not require the integration of sensors into the structure and electrical circuits of the truck and represents a compact, autonomous device that can be located at any convenient place in the cab. In order to create such a device, it is proposed to use the magnitude of the magnetic field strength generated by DC traction motors as a signal carrying information about the mass of the transported cargo. To measure the magnetic field strength, a flux gate is used, which converts the magnitude of the magnetic field strength into the magnitude of the current. An original circuit for powering the fluxgate excitation winding using a modulated signal generator based on logic elements is proposed. The used power supply scheme allows to exclude the influence of the fluxgate excitation winding on the generator frequency, as well as to increase the fluxgate sensitivity, which makes it possible to install the sensor in any convenient place in the dump truck cabin, and not in the immediate vicinity of the traction motors.

Kir4.1/Kir5.1 channels possess strong intrinsic inward rectification determined by a voltage-dependent K+-flux gating mechanism.

Inwardly rectifying potassium (Kir) channels are broadly expressed in both excitable and nonexcitable tissues, where they contribute to a wide variety of cellular functions. Numerous studies have established that rectification of Kir channels is not an inherent property of the channel protein itself, but rather reflects strong voltage dependence of channel block by intracellular cations, such as polyamines and Mg2+. Here, we identify a previously unknown mechanism of inward rectification in Kir4.1/Kir5.1 channels in the absence of these endogenous blockers. This novel intrinsic rectification originates from the voltage-dependent behavior of Kir4.1/Kir5.1, which is generated by the flux of potassium ions through the channel pore; the inward K+-flux induces the opening of the gate, whereas the outward flux is unable to maintain the gate open. This gating mechanism powered by the K+-flux is convergent with the gating of PIP2 because, at a saturating concentration, PIP2 greatly reduces the inward rectification. Our findings provide evidence of the coexistence of two rectification mechanisms in Kir4.1/Kir5.1 channels: the classical inward rectification induced by blocking cations and an intrinsic voltage-dependent mechanism generated by the K+-flux gating.

Universal Fast-Flux Control of a Coherent, Low-Frequency Qubit

The \textit{heavy-fluxonium} circuit is a promising building block for superconducting quantum processors due to its long relaxation and dephasing time at the half-flux frustration point. However, the suppressed charge matrix elements and low transition frequency have made it challenging to perform fast single-qubit gates using standard protocols. We report on new protocols for reset, fast coherent control, and readout, that allow high-quality operation of the qubit with a 14 MHz transition frequency, an order of magnitude lower in energy than the ambient thermal energy scale. We utilize higher levels of the fluxonium to initialize the qubit with $97$\% fidelity, corresponding to cooling it to $190~\mathrm{\mu K}$. We realize high-fidelity control using a universal set of single-cycle flux gates, which are comprised of directly synthesizable fast pulses, while plasmon-assisted readout is used for measurements. On a qubit with $T_1, T_{2e}\sim$~300~$\mathrm{\mu s}$, we realize single-qubit gates in $20-60$~ns with an average gate fidelity of $99.8\%$ as characterized by randomized benchmarking.

Пристрій розмагнічування установки магнітної дефектоскопії осі колісної пари

У статті показана необхідність та визначені і проаналізовані основні способи розмагнічування деталей і виробів, виконаних з феромагнітних матеріалів. За результатами порівняльного аналізу обрано і обґрунтовано спосіб розмагнічування осі колісної пари, заснований на циклічному перемагнічуванні синусоїдальним постійно змінюваним магнітним полем з плавно спадною до нуля амплітудою. Запропоновано пристрій розмагнічування, що реалізує даний спосіб і забезпечує якісне розмагнічування осі на підставі визначення її магнітного стану з подальшим коректуванням величини поля, що розмагнічує.

ФЕРРОЗОНДОВЫЕ МАГНИТОМЕТРЫ С НОВЫМ СПОСОБОМ ВОЗБУЖДЕНИЯ НА ОСНОВЕ МАГНИТОЭЛЕКТРИЧЕСКОГО ВЗАИМОДЕЙСТВИЯ

The analysis of the functional peculiarities of the known flux gates has shown that the constructive and technological methods used to increase their operational characteristics within the framework of traditional so-lutions have basically exhausted themselves. The paper proposes a method for exciting flux gates based on a new physical principle relying on the effect of magnetoelectric interaction. The possibility of obtaining a magnetoelectric effect in local inhomogeneities of solid-state structures of ferrite elements of flux-gates when exposed to an alternating electric field is analyzed and substantiated. In this case, in the entire volume of the fer-romagnetic core at the same frequencies of electromechanical and magnetic resonances, a modulating physical process is excited in the form of a standing magnetoelectric wave. This creates a corresponding magnetic modu-lation structure in the entire volume of the ferromagnetic system of the flux gate. The considered design of a fluxgate modulator implements a new method of exciting flux gates, containing a ferromagnetic rod system in the form of two ferrite rod half-elements, located coaxially and joined together by a ferrite permanent magnet with magnetization along the axis of the rods. The authors have experimentally studies a new method for exci¬ting flux gates. The proposed method for exciting flux gates opens up wide opportunities for research in a new direction in science – spintronics, in particular, the applied use of magnetoelectric interaction, which can be effectively used to create various options for flux gates based on new physical principles of operation.

Experimental Research on Over-Range Measurement Method Based on Quasi-Digital Direct-Current Leakage Current Sensor

As for the direct-current (DC) power systems, the DC leakage current sensor is indispensable for positioning insulation faults. And in this paper, a quasi-digital flux gate sensor was designed based on duty ratio model, and the mathematical model between the excitation voltage period and the measured current which exceeded the measurement range was built by analyzing the working principles of the duty-ratio model digital sensor. In this way, the measurement range of the original sensor could be expanded to 1.5 times of its original. Meanwhile, without changing the hardware, the solution provided in this paper also solved the measurement failure problem of part of sensors when the any overcurrent situations happen in the system, such as overload or short-circuit. Besides, the sensor designed in this paper could achieve Level-0.1 measurement accuracy within range, and reach Level-2 over-range measurement accuracy, satisfying the demands of DC power supply system on leakage current measurement.

Ultra-low frequency (ULF) magnetic field emissions associated with some major earthquakes occurred in Indian Subcontinent

We have analyzed ULF magnetic field emissions data obtained from identical 3- component search coil magnetometers installed at Indian stations of Agra (Geograph. lat. 27.2°N, long. 78°E), Shillong (25.92oN, 91.88oE), and Kachchh (23.78oN, 71oE) for the months of April 2012 and September 2013 in which three major earthquakes occurred, one of magnitude M = 8.5 in Indonesian region and two of magnitudes M = 7.4 and 6.8 in Pakistan. The results of the analysis show the occurrence of ULF bursts 09-16 days prior to the occurrence of these earthquakes at Agra and Shillong stations. Such bursts are not observed at Kachchh station. Analysis of ULF data obtained from a flux gate magnetometer at a remote station Kakioka in Japan (Geograph. lat. 36.2oN, long. 140.2oE) does not show such burst also. The bursts contain electromagnetic pulses of periods 10–15s (f = 0.06–0.1 Hz). The origins of these bursts in lithospheric sources (earthquakes) are confirmed by polarization parameter analysis of data. These ULF data are not influenced by lightning and magnetic storms. A long period analysis of the ULF data for the same months between the years 2010 and 2017 shows that occurrence of such bursts are characterized by either large magnitude shallow depth earthquakes (M > 6) or multiple shallow depth earthquakes of low magnitudes (M < 6). The precursory periods of the recorded ULF bursts match very well with those reported by Singh et al. (2018) who analyzed very low frequency (VLF) and ionospheric total electron content (TEC) data recorded at Agra station.

Poly(N-isopropylacrylamide)-gelatin hydrogel membranes with thermo-tunable pores for water flux gating and protein separation

Herein, a hybrid hydrogel was prepared by polymerizing N-isopropylacrylamide (NIPAAm) in the presence of gelatin and mixed with 300 nm polystyrene nanospheres (PNs) to cross-link the gelatin. A thermo-responsive polyNIPAAm(PNIPAAm)-gelatin hybrid hydrogel (NGHH) membrane was obtained after removing the lodged PNs from the NGHH. At the PNIPAAm-to-gelatin content ratio of 1, PNIPAAm in the NGHH membrane extended to completely occupy the pores left by PNs below the lower critical solution temperature (LCST), forming a pore-less membrane. Contrarily, above the LCST, phase separation of PNIPAAm occurred, resulting in pores in the membrane. This pore closing and opening below and above the LCST changed the water flux through the NGHH membranes, indicating the excellent water gating efficiency of these membranes. Accordingly, we applied these membranes as protein valves to separate lysozyme (Lys) and bovine serum albumin (BSA) of different sizes. At both 25 and 45 °C, smaller Lys could be transported through the hydrogen bonding channels of the pore-less membrane, whereas larger BSA was blocked by this membrane at 25 °C and transported through the pore-rich membrane at 45 °C. Thus, this biocompatible and stable NGHH membrane functioned as a biological selective valve, allowing protein separation.

Commissioning of the multiparametric geophysical observatory at Shoal Bay, South Andaman and the preliminary results

The Indian Institute of Geomagnetism (IIG) is operating Multiparametric Geophysical Observatory (MPGO) at Port Blair in South Andaman. We report here on the commissioning of MPGO and the quality of data collected by this observatory. The base line values are regularly computed with the aid of the declination inclination magnetometer, in house developed proton precession magnetometer and the flux gate magnetometer. The total field computed by the vector magnetometer is all time compared with direct measurements from the scalar magnetometer. An attempt to co-relate the precursor seismo-electromagnetic emissions of the earthquake event by the induction coil magnetometer is made. The seismic station of the observatory is capable of recording seismic events within the vicinity of ≈200 km. Further MPGO is upgrading and some more experiments are planned for the future.