Range Of Field Intensities Research Articles

An ultra-sensitive photonic crystal fiber magnetic field sensor based on Vernier effect using two parallel Sagnac loops

Magnetic field detection is of significant importance in various fields, including military, industrial, and power transmission systems. In this paper, we propose a novel ultra-sensitive photonic crystal fiber (PCF) magnetic field sensor based on the Vernier effect, employing two parallel Sagnac loops. Since magnetic field detection relies on the magneto-optical effect of magnetic fluids, all air holes in the PCF are assumed to filled with magnetic fluids. By inserting two slightly different lengths of PCFs into two parallel Sagnac loops, the Vernier effect can be excited to improve the sensitivity of magnetic field detection. The sensing characteristics of the PCF magnetic field sensor are theoretically studied using the finite element method (FEM). Moreover, the influences of the wavelength and magnetic field intensity on the sensing performance are also analyzed. The results show that the sensitivity and resolution of the PCF magnetic field sensor can reach 11.9 nm Oe−1 and 8.4 × 10−3 Oe, respectively, within the magnetic field intensity range of 80–150 Oe. To our best knowledge, the proposed magnetic field sensor exhibits the highest sensitivity among existing magnetic field sensors based on optical fiber interferometers. The proposed magnetic field sensor possesses ultra-high sensitivity and resolution, which exhibits good application prospects in the field of magnetic field detection.

Enhancing cell separation in a hybrid spiral dielectrophoretic microchannel: Numerical insights and optimal operating conditions.

Reliable separation of circulating tumor cells from blood cells is crucial for early cancer diagnosis and prognosis. Many conventional microfluidic platforms take advantage of the size difference between particles for their separation, which renders them impractical for sorting overlapping-sized cells. To address this concern, a hybrid inertial-dielectrophoretic microfluidic chip is proposed in this work for continuous and single-stage separation of lung cancer cell line A549 cells from white blood cells of overlapping size. The working mechanism of the proposed spiral microchannel embedded with planar interdigitated electrodes is validated against the experimental results. A numerical investigation is carried out over a range of flow conditions and electric field intensity to determine the separation efficiency and migration characteristics of the cell mixture. The results demonstrate the unique capability of the proposed microchannel to achieve high-throughput separation of cells at low applied voltages in both vertical and lateral directions. A significant lateral separation distance between the CTCs and the WBCs has been achieved, which allows for high-resolution and effective separation of cells. The separation resolution can be controlled by adjusting the strength of the applied electric field. Furthermore, the results demonstrate that the lateral separation distance is maximum at a voltage termed the critical voltage, which increases with the increase in the flow rate. The proposed microchannel and the developed technique can provide valuable insight into the development of a tunable and robust medical device for effective and high-throughput separation of cancer cells from the WBCs.

Reflective magnetic field and temperature dual-parameter sensor based on no-core fiber probe

A kind of reflection-type magnetic field and temperature dual-parameter sensor based on surface plasmon resonance (SPR) effect was proposed and investigated. The sensing probe was fabricated with a section of no-core fiber, which was evenly divided into two parts. One part was immersed in magnetic fluid (MF) for magnetic field sensing (Channel 1, referred as CH1). The other part was coated with polydimethylsiloxane (PDMS) for temperature sensing (Channel 2, referred as CH2). The issue of magnetic field and temperature cross-sensitivity was resolved ingeniously. In the magnetic field intensity range of 0–55.1 mT, the maximum magnetic field sensitivity of 122.67 pm/mT was obtained. In the temperature range of 30–70 ℃, the maximum temperature sensitivity was 1662.64 pm/◦C. The sensor has the advantages of simple structure, small size, and potentials for applications in narrow space.

Ampere force fiber optic magnetic field sensor using a Fabry-Perot interferometer.

The paper presents a novel fiber-optic vector magnetic field sensor using a Fabry-Perot interferometer, which consists of an optical fiber end face and a graphene/Au membrane suspended on the ceramic ferrule end face. A pair of gold electrodes are fabricated on the ceramic ferrule by femtosecond laser to transmit electrical current to the membrane. Ampere force is generated when an electrical current flows through the membrane in a perpendicular magnetic field. The change in Ampere force causes a shift in the resonance wavelength in the spectrum. In the magnetic field intensity range of 0 ∼ 180 mT and 0 ∼ -180 mT, the as-fabricated sensor exhibits magnetic field sensitivity of 5.71 pm/mT and 8.07 pm/mT. The proposed sensor has great potential application in weak magnetic field measurements due to its compact structure, cost-effectiveness, ease to manufacture, and good sensing performance.

Theoretical Investigation of Strain-Adjustable Ge0.92Sn0.08 Light-Emitting Diodes With Giant Magnetostrictive Stressor for Short-Wave Infrared Light Source

A new idea was provided by the group-IV GeSn alloys for short-wave infrared light source compatible with CMOS due to the low cost integrated on the Si platform and can be transformed into direct bandgap alloy. More than 7.1% Sn content or strain engineering is used to achieve the direct bandgap GeSn semiconductors and enhance the luminous efficiency of GeSn light-emitting devices. We theoretically investigate a strain-adjustable GeSn light-emitting diode with the giant magnetostrictive stressor. A 0∼0.11% adjustable uniaxial tensile strain is introduced into Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.92</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.08</sub> LED by adjusting the external magnetic field. A continuously adjustable bandgap from 0.543 eV to 0.475 eV of the Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.92</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.08</sub> alloy is achieved in the magnetic field intensity range of 0∼240 kA/m, and the spontaneous emission rate of the strained LED is enhanced about 3.63 times compared with the relaxed device. Besides, an adjustable range of luminous peak is achieved from 2.18 μm to 2.46 μm, which can promote the application of GeSn light source for magnetic field detection and photo-communication in short-wave infrared.

High-Sensitivity Magnetic Field Sensor Based on Long-Period Grating Near the Dispersion Turning Point

We demonstrate the fabrication of a high-sensitivity magnetic field sensor based on the packaged long-period fiber grating (LPFG) with magnetic fluid. The transmission spectra and the surrounding refractive index (SRI) characteristics of the LPFGs near the dispersion turning point (DTP) were investigated theoretically and experimentally. We have studied the influence of mode order and wavelength separation at DTP on the SRI sensitivity of the DTP-LPFG. The experimental results are consistent with the simulation. The LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0,10</sub> mode has the highest SRI sensitivity of 1956.4 nm/RIU in the range of 1.333-1.435 when the wavelength separation at DTP is 89.1 nm. The sensor achieves a magnetic field sensitivity of 1.9 nm/mT in the magnetic field intensity range of 0-20.5 mT, which indicates that the sensor can be used as a high-sensitivity magnetic field sensor.

Reflective fiber-optic magnetic field sensor based on a magnetic-fluid-filled capillary probe structure

A novel reflective magnetic field sensor is presented and experimentally demonstrated. The sensing probe is fabricated by splicing a section of uncoated four-core fiber (FCF) between two sections of no-core fibers (NCFs), and the end face of the last NCF is coated by silver. The sensor structure is sealed in a magnetic fluid (MF)-filled capillary, so that the NCF–FCF–NCF magnetic field sensing probe structure is obtained. The NCF is used to excite the high-order modes of the FCF’s cladding. Combined with the adjustable refractive index of MF, the sensor is sensitive to the magnetic field and temperature. Experimental results indicate that the presented sensor can measure the low magnetic field and high magnetic field. In the low magnetic field ranges of 0–10 mT and 10–18 mT, the wavelength near 1548 nm varies linearly with the magnetic field intensity, and the sensitivities are −7.43 pm mT−1 and −60 pm mT−1, respectively. The sensitivity of the interference intensity is −0.30782 dB mT−1 in the low magnetic field intensity range of 0–18 mT. The sensor under low magnetic field is also affected by temperature. In the temperature range of 20 °C–70 °C, the temperature sensitivity of the wavelength shift around 1548 nm is 62.33 pm °C−1, and the corresponding sensitivities of the interference intensity are −0.03888 dB °C−1 and −0.02076 dB °C−1 in the range of 30 °C–50 °C and 50 °C–70 °C, respectively. However, the effect of temperature on the sensor in the high magnetic field (18–36 mT) can be ignored. Within the high magnetic field intensity range of 26–36 mT, the sensitivity of the interference intensity near 1598 nm is −1.20993 dB mT−1. The dual-parameter matrix is used to eliminate the cross-sensitivity of temperature in the low magnetic field. This sensor, with the advantages of easy fabrication, high sensitivity and low cost, has the potential application in the magnetic field monitoring.

Magnetic sensor based on WGM hollow microbubble resonator filled with magnetic fluid

In this work, a magnetic sensing scheme based on whispering gallery mode (WGM) hollow microbubble resonator (HMR) filled with magnetic fluid (MF) is proposed. The HMR is made by the pressure-assisted arc discharge method on the microcapillary. WGM is excited by evanescent fields in HMR. The quality factor of resonator is 4.02×106. Then, the influence of the wall thickness of HMR and the concentration of MF on the sensor is studied both theoretically and experimentally. When MF is infiltrated in the HMR, the refractive index (RI) of the MF increases with the increase of the magnetic field intensity, resulting in the shift of the resonance wavelength. By reducing the wall thickness, the magnetic sensing sensitivity is increased from 2.6 pm/mT to 25.21 pm/mT within the magnetic field intensity range of 2 mT–20 mT. In addition, the increase in the concentration of MF and the clustering phenomenon caused by it have also been observed. This work provides a novel magnetic sensing scheme, and the proposed WGM resonator has great application prospects in optofluidic sensing.

Влияние нелинейности закона намагничивания феррожидкости на неустойчивость Кельвина--Гельмгольца

We study Kelvin-Helmholtz instability which develops when a homogenous gas flow is moving over a horizontal surface of a ferrofluid of given physical properties moving in the same direction, in presence of a homogeneous magnetic field parallel to this direction. Magnetic field intensity range includes the values that correspond to the interval where magnetization curve reaches magnetization saturation level. Stability area is constructed in the “magnetic field intensity – dimensionless relative velocity of fluids” parameter plane.

Interpretation of Aeromagnetic Data over the Nigerian Sector of the Mamfe Basin

Four Aeromagnetic data over a part of the Nigerian Sector of the Mamfa Basin have been analyzed using qualitative approach and spectral analysis. The aeromagnetic maps, its analytic signal amplitude and geological modelling sketch helped in identifying the nature and depth of the magnetic sources in the study region. The qualitative interpretation reveals that the study area is characterized by magnetic lineament trend in NE-SW direction and subordinate E-W direction. The results obtained are in line with the trend of the Benue Trough. The aeromagnetic maps reveal that the sedimentary thickness increases towards the northern parts of the study area. The results also reveal that the total magnetic field intensity range from 7800 to 8290 nanotesla (nT) in the study area. The residual anomaly map reveals that the maximum anomaly value is 160nT which is found around Bansara and Ugep environs while the minimum magnetic value is -140nT towards the Abakiliki and Ikom areas. Results from spectral analysis indicated two magnetic source depths, which account for deeper and shallower sources. The deeper magnetic sources vary from 2.76 km near Abakiliki to 5.37 km near Bansara, whereas the shallow magnetic sources vary from 0.58 km near Ikom to 1.76 km near Ugep. The depth to basement map reveals that the sediment thickness increases towards the northern parts of the study area. The depths to basement are deeper in the northern and central parts trending northwest-southeast direction and shallower in the eastern and southern parts of the study area. The result also shows a linear depression with sedimentary accumulation trending northwest-southeast. The temperatures at depth for each anomaly block were estimated to range between 48.46 and 225.69°C with an average of 117.04°C. Based on the computed sedimentary thickness (2.76-5.37km) and temperature at depth (62-220°C), the possibility of hydrocarbon generation in the northern and central parts of the study area is realistic

Long term sedimentation of an elliptic disc subject to an electrostatic field using smoothed particle hydrodynamics method

A two dimensional incompressible smoothed particle hydrodynamics scheme for long term sedimentation of rising or falling particulates (bubbles, drops or rigid particles) in Newtonian fluids is presented and validated by simulating the sedimentation of a single elliptic disc. The proposed method is then used to simulate the sedimentation of an elliptic disc subject to an external electric field parallel to the gravitational field. A range of electric field intensities, permittivity ratios, blockage ratios and density ratios are covered in this study. The results show that for given blockage and density ratios, the final sedimentation orientation of the ellipse is dependent on a combination of permittivity ratio and electric field intensity, ranging from horizontal to vertical. Compared to non-electrified sedimentation, an increase in electric field intensity and permittivity ratio lead to vertical sedimentation. As the channels grow wider, the presence of electric field leads to faster ellipse descent, regardless of its initial orientation.

High-sensitivity dual-direction weak magnetic field sensor based on structural modulated ultralong period microfiber grating

A high-sensitivity optical fiber dual-direction weak magnetic field sensor based on a structural modulated ultralong period microfiber grating (SULPMG) is proposed. The SULPMG was fabricated by an electric arc discharge and flame-heating drawing method, and the sensor was fabricated by cascading the SULPMG with a core offset section. By tuning the direction of an applied magnetic field, the refractive index of a magnetic fluid (MF) can be tuned accordingly. The transmission spectral response of the proposed sensor was measured and analyzed. For the weak magnetic field intensity range from 0 mT to 7 mT, the obtained magnetic field sensitivity is −1.759 nm/mT and 1.082 nm/mT when the magnetic field is perpendicular or parallel to the light propagation direction, respectively. Theoretical analysis shows that reducing the waist diameter can further improve the sensitivity of the sensor. The proposed sensor is expected to be applied to weak magnetic field measurements in the aviation, vehicle detection and biomedical fields.

Surface Plasmon-Enhanced Switching Kinetics of Molecular Photochromic Films on Gold Nanohole Arrays.

Diarylethene molecules are discussed as possible optical switches, which can reversibly transition between completely conjugated (closed) and nonconjugated (open) forms with different electrical conductance and optical absorbance, by exposure to UV and visible light. However, in general the opening reaction exhibits much lower quantum yield than the closing process, hindering their usage in optoelectronic devices. To enhance the opening process, which is supported by visible light, we employ the plasmonic field enhancement of gold films perforated with nanoholes. We show that gold nanohole arrays reveal strong optical transmission in the visible range (∼60%) and pronounced enhancement of field intensities, resulting in around 50% faster switching kinetics of the molecular species in comparison with quartz substrates. The experimental UV-vis measurements are verified with finite-difference time-domain simulation that confirm the obtained results. Thus, we propose gold nanohole arrays as transparent and conductive plasmonic material that accelerates visible-light-triggered chemical reactions including molecular switching.

Capillary Instability of a Cylindrical Ferrofluid Jet in a Uniform Longitudinal Magnetic Field

The formulated problem makes it possible to study the influence of magnetic forces on capillary instability of a ferrofluid jet with given physical characteristics in both weak and strong fields. The field intensity range includes values that correspond to the ferrofluid magnetization curve interval in which the curve reaches the value of saturation magnetization. The obtained growth rates and wavelengths of the fastest growing perturbations of the jet surface shape are compared for strong and weak fields.

Electrochemical attack and corrosion of platinum electrodes in dielectrophoretic diagnostic devices.

Though the advances in microelectronic device fabrication have realized new capabilities in integrated analytical and diagnostic platforms, there are still notable limitations in point-of-care sample preparation. AC electrokinetic devices, especially those leveraging dielectrophoresis (DEP), have shown potential to solve these limitations and allow for sample-to-answer in a single point-of-care device. However, when working directly with whole blood or other high conductance (~ 1S/m) biological fluids, the aggressive electrochemical conditions created by the electrode can fundamentally limit the device operation. In this study, platinum wire-based electrode devices spanning circular polytetrafluorethylene (PTFE) wells and a planar microarray device with sputtered platinum electrodes were tested in plasma and PBS buffers of differing concentration across a wide range of frequencies and electric field intensities (AC voltages) to determine their respective safe regions of operation and to gain an understanding about the failure mechanisms of this class of device. At frequencies of 10kHz and below, the upper bound of operation is the degradation of electrodes due to electrochemical attack by chlorine overcoming the native platinum oxide passivation. At higher frequencies, 100kHz and above, the dielectric loss and subsequent heating of the buffer will boil before the electrodes suffer observable damage, due to the slow irreversible reaction kinetics. Effective dielectrophoretic capture of small biological particles at these frequencies is limited, and heat/oxidative denaturation of target material are a major concern. A new class of smaller devices, ones capable of high throughput at voltages low enough to maintain the integrity of the platinum passivation layer, is needed to mitigate these fundamental limitations.

Hydrogen ionization equilibrium in magnetic fields

We assess the partition function and ionization degree of magnetized hydrogen atoms at thermodynamic equilibrium for a wide range of field intensities, B ≈ 105–1012 G. Evaluations include fitting formulae for an arbitrary number of binding energies, the coupling between the internal atomic structure and the center-of-mass motion across the magnetic field, and the formation of the so-called decentered states (bound states with the electron shifted from the Coulomb well). Non-ideal gas effects are treated within the occupational probability method. We also present general mathematical expressions for the bound state correspondence between the limits of zero-field and high-field. This let us evaluate the atomic partition function in a continuous way from the Zeeman perturbative regime to very strong fields. Results are shown for conditions found in atmospheres of magnetic white dwarf (MWD) stars, with temperatures T ≈ 5000–80 000 K and densities ρ ≈ 10−12–10−3 g cm3. Our evaluations show a marked reduction of the gas ionization due to the magnetic field in the atmospheres of strong MWDs. We also found that decentered states could be present in the atmospheres of currently known hot MWDs, giving a significant contribution to the partition function in the strongest magnetized atmospheres.

Analysis of dependence between magnetic properties of granulated ferromagnetic specimens and relation of its length to diameter

Paper studies the problems about experimental determining magnetic parameters of nonuniform granular magnetics. It has been noted that the existing shortage of direct and (or) indirect experimental data on the magnetic properties of granular ferromagnetic specimens with different values of a relative length, in particular, has a negative impact on the validity of the requirements and decisions to create and ensure the performance of relevant functional elements, movable operating elements of various equipments and devices. By the example of cylindrical specimens of balls with the range of relative length 1–16 within the framework of effective medium macromodel the dependences of induction, magnetic permeability, susceptibility, magnetization and field intensity have been obtained. It has been shown that in the range of field intensity 9–47 kA/m values of induction and magnetization of investigating specimens increase, that indicates the absence of magnetic saturation of such granular (as opposed to solid) magnetics. And this is the case at almost stable values of magnetic susceptibility and permeability. Obtained results are useful in designing movable operating elements of various equipments and devices.

Experimental study on the dehydration performance of synergistic effect of electric field and magnetic field

Electromagnetic synergistic oil-water separation is a promising technology for deep dehydration with higher efficiency, shorter dehydration period and flexible control of field parameters. In this paper, non-conductive silicone oil without colloid and asphaltene was used as the continuous phase. The effect of magnetization and Lorentz force on the continuous phase can be excluded to explore the mechanism of the electric field and magnetic field synergistic dehydration. Firstly, the particle size of droplets was characterized. The results showed that the dispersed phase was uniformly distributed and the average particle size was 18.24 um. Then the dehydration performance of different types of outfields was compared. The experimental results showed that the dehydration performance of AC electric field combined with magnetic field was better than that of single AC electric field. The dehydration performance of AC electric field and magnetic field was better than that of DC electric field and magnetic field. On this basis, the theory of AC polarization-electromagnetic force was proposed. Finally, the influence of magnetic field intensity on dehydration performance was explored, including dehydration depth and dehydration speed, and the optimal magnetic field intensity range in this experiment was obtained, and its value was [0.269, 0.355] T.

Observing thermal Schwinger pair production

We study the possibility of observing Schwinger pair production enhanced by a thermal bath of photons. We consider the full range of temperatures and electric field intensities from pure Schwinger production to pure thermal production, and identify the most promising and interesting regimes. In particular, we identify temperatures of $\sim 20~\mathrm{keV}/k_B$ and field intensities of $\sim 10^{23}~\mathrm{Wcm}^{-2}$ where pair production would be observable. In this case, the thermal enhancement over the Schwinger rate is exponentially large and due to effects which are not visible at any finite order in the loop expansion. Pair production in this regime can thus be described as more nonperturbative than the usual Schwinger process, which appears at one loop. Unfortunately, such high temperatures appear to be out of reach of foreseeable technologies, though nonthermal photon distributions with comparable energy densities are possible. We suggest the possibility that similar nonperturbative enhancements may extend out of equilibrium and propose an experimental scheme to test this.

Inactivation and Removal of Micromycetes From Water Using the Electric Field

This study deals with the possibility of inactivation of micromycetes under the influence of electric field with intensity 100–185 V/cm and the temperature increased to 45–65°C. The regularities of the filtration process of Candida albicans micromycetes on the bed of AB-17 anion-exchange granules placed into electric field have been established. The range of field intensity and flow rates of the filtered liquid ensuring the stable purification degree 99–100% are determined.