Values Of Field Strength Research Articles

Assessment of the effect of ferromagnetic liquids on oil recovery of bituminous sands

In Azerbaijan, in addition to natural oil, there are large reserves of it in the form of bituminous rocks. The largest reserves are concentrated in the Balakhani part of the Kirmaki mountain, which are more than 50 million tons. In order to extract oil from bituminous rocks, various methods are used. Including such methods of extracting oil from bituminous rocks (BR): boiling BR with water without additives and with alkaline type additives; extraction method using various solvents; thermal cracking of BR; flotation method and supercritical fluid extraction. In addition to these, methods of influencing bituminous sands with various physical fields are also used, one of which is the use of ferromagnetic fluids (FMF). The use of alkali reactive reagent with iron nanoparticles is an improvement of the method for extracting heavy oil components from bituminous rocks and an environmentally friendly innovative technology. The study of the influence of the magnetic field with tension to 10 A/m on the process of oil extraction from bituminous rocks before and after the use of ferromagnetic fluid showed an increase in oil recovery by 7–8 % and 8–11 %, respectively. Further increase in the external magnetic field strength with the maximum tight bond of the magnetic moment with ferromagnetic particles of nanometer sizes can lead to the appearance of additional tangent stresses caused by the braking of the particle rotation field, the subsequent increase of the effective viscosity of the colloid solution. A numerical method for determining the threshold value of the magnetic field strength has been proposed to analyze this phenomenon, at which the value of the dynamic viscosity of the magnetic fluid is achieved, which is the limit for oil from the field corresponding to the extraction of oil from bituminous rocks.

Investigation of magnetorheological grease flow under the influence of a magnetic field

In this work, we present a novel magnetohydrodynamic flow study using micro-Particle Image Velocimetry (m-PIV) in a rectangular channel under the effect of a uniform transverse magnetic field. This study is the first of its kind to explore the use of magnetorheological grease in machine components such as bearings. Rheological characterisation of grease samples establishes the non-linear relationship between the shear rate and shear stress and thus confirms the non-Newtonian behaviour of the grease. The flow follows a parabolic path away from the magnetic field. Experimental studies reveal that the flow velocities reduce considerably from 11.9 m/s to 1.7 m/s in the vicinity of the magnetic zone due to the formation of strong field-induced chains. These chains are responsible for an increase in localized yield stress of grease thereby causing a surge in the resistance to flow. Further, numerical and analytical models are developed to predict the velocity field under a magnetic field. The analytical model can accurately predict the flow velocity for different magnetic field strengths. It can be deduced that the obtained correlation is a suitable model for estimating the velocity values at different magnetic field strengths for flow in similar configurations. Numerical results predicted by a finite volume method-based solver are in good agreement with the experiments on the upstream side. Flow velocities increase with flow rate and decrease with the onset of the magnetic field. Pressure drop along the channel length shows an abrupt change in the magnetic zone. This is because of the disturbance of the normal flow regime due to the presence of the magnetic field. The grease flow disturbs the distribution of magnetic field lines resulting in flow-induced field strength of B = 0.1 T against an applied external magnetic field strength value of B = 0.3 T. The present study analyses the effects of an external field on the flow patterns of magnetorheological grease. It confirms that magnetorheological grease provides controllability in applications, because flow properties can be varied by tuning the magnetic field strength.

К ОБЪЯСНЕНИЮ ЭФФЕКТА ПОВЕДЕНИЯ Г-ОБРАЗНОЙ РАМКИ В ПРИЗЕМНОМ ЭЛЕКТРИЧЕСКОМ ПОЛЕ

The possibility of determining the zones of the reverse electrode effect in hard-to-reach places using an L-shaped frame is considered. It is shown that joint measurements using instruments and an L-shaped frame with adjustable sensitivity will make it possible to convert the recorded angles of frame movement into physically understandable values of the atmospheric electric field strength.

Spectroscopic properties and Stark splitting of Nd3+ ions in different host glasses to obtain pure blue laser

In this study, we investigated the spectroscopic properties and Stark splitting of Nd3+ in several typical host glasses by focusing on the 0.9 μm fluorescence (4F3/2 → 4I9/2). Absorption, emission spectra and decay curves of Nd3+ doped borate, phosphate, fluoride, tellurite, silicate, germanate and fluorophosphate glasses were measured. Judd−Ofelt parameters, Stark splitting and crystal field strength in these glasses were calculated and analyzed. Results demonstrated that broad absorption and emission bands, large Judd−Ofelt parameters (5.14 × 10−20 cm2), strong local field strength (7089.2 cm−1) and high values of fluorescence branching ratio (43.7%) and fluorescence lifetime (542.95 μs) of Nd3+ ions were found in silicate glass. Results indicate that silicate and germanate host glasses show promising potential for pure blue lasers by frequency doubling of 0.9 μm fluorescence.

Mapping of electromagnetic fields of industrial frequency in case of urban area

Repeated detailed mapping of values of electric field strength and magnetic induction on 2 streets in the historic center of St. Petersburg is executed. Measurements were carried out according to the existing methodical requirements and taking into account time of peak loadings of the power supply network. The individual binding of points of measurements naturally increases detail of the final map. Excesses of hygienic standards are not revealed, but the values of magnetic induction exceeding approximate safe levels according to results of foreign researches are widespread. The influence of concrete local sources of electromagnetic fields, such as signs, objects of ventilation, lighting, electrical wiring found reflection is presented by maps. The non-standard sources of electromagnetic fields in the form of large metal designs fixed to facades of buildings and subject to electrization are revealed. Growth of values of electric field strength and magnetic induction from the warm period to cold is noted.

Assessment of Radiofrequency Exposure in the Vicinity of School Environments in Crete Island, South Greece

This study aimed to estimate the radiofrequency exposure levels in the vicinity of nursery and primary schools at the northwest part of Crete island in Greece. Moreover, the compliance with the exposure limits, according to Greek legislation, was investigated. A total of 396 in situ frequency-selective and broadband measurements were conducted around 69 schools, classified in urban and suburban environments, in the range of 27–3000 MHz (subdivided in seven frequency bands). The measured value of the electric field strength (V/m) was recorded and, subsequently, the exposure ratio was calculated. Statistical analysis was performed in order to analyze and evaluate the data. In addition, a worst-case scenario was examined by considering the highest measured exposure level around each school. The statistical tests indicated that the mean and median values of the exposure ratio, even in the worst-case scenario, were found well below 1 for all frequency bands. The calculated distributions of the electric field measurements demonstrated that almost 90% of the latter were below 1 V/m, with the majority of values lying in the range of 0.5–1 V/m. The main contributors to the total exposure were the mobile communication frequencies and broadcasting, while the exposure was greater in urban than in suburban environments.

Electronic properties and behavior of carbon network based on graphene and single-walled carbon nanotubes in strong electrical fields: quantum molecular dynamics study

Using the self-consistent-charge density-functional tight-binding method (SCC-DFTB) and extended lagrangian DFTB-based molecular dynamics, we performed in silico studies of the behavior of graphene–nanotube hybrid structures that are part of a branched 3D carbon network in strong electrical fields. It has been established that strong fields with strength ranging from 5 to 10 V nm−1 cause oscillating deformations of the atomic framework with a frequency in the range from 1.22 to 1.38 THz. It has been revealed that the oscillation frequency is determined primarily by the topology of the atomic framework of graphene–nanotube hybrid, while the electric field strength has an effect within 1%–2%. A further increase in electric field strength reduces the oscillation frequency to 0.7 THz, which accompanies the partial destruction of the atomic framework. The critical value of the electric field strength when the graphene is detached from the nanotube is ∼20 V nm−1.

Performance Analysis of Digital Video Broadcasting - Second Generation Terrestrial (DVB-T2) Propagation for Fixed Reception in The Central Region of Malaysia

Due to the increasing demand of services and content, Quality of Service (QoS) has become an important aspect in digital broadcasting industry especially with the implementation of Digital Terrestrial Television (DTT) in Malaysia. Thus, the performance of DVB-T2 in Malaysia should be investigated because there are areas which are not in the coverage due to variety of terrain, where some areas received weak DVB-T2 signals. Apart from geological and topographic factors in Malaysia, the selection of DVB-T2 parameters is also an important factor in determining signal strength and coverage This research has proposed to study the performance analysis of DVB-T2 propagation for fixed reception in Malaysia's central region. The Field Strength Measurement (FSM) was set up to evaluate the QoS of DVB-T2 signal such as Field Strength (E), Modulation Error Ratio (MER), and Carrier to Noise Ratio (C/N) at specific test points across Malaysia's central region. The FSM was simulated at the designated test points using CHIRplus_BC software to evaluate the performance of Single Frequency Network (SFN) at three locations of transmitter. The DVB-T2 Modulation and Forward Error Correction (FEC) code rate parameters were simulated in order to evaluate the improvement in terms of coverage area. It can be concluded that the coverage of DTT is reduced with the increase in the distance of the measurement area to the transmitter. The finding also shows that the field strength value obtained from FSM and simulation was comparable. Furthermore, from the simulation results. it can be perceived that the coverage area across the central region of Malaysia could be improved by optimizing the modulation and FEC code rate. However, there is a trade-off between the signal coverage and channel capacity. The greater the signal coverage the less the channel capacity.

Diagnostic value of MRI in the presurgical evaluation of patients with epilepsy: influence of field strength and sequence selection: a systematic review and meta-analysis from the E-PILEPSY Consortium.

MRI is a cornerstone in presurgical evaluation of epilepsy. Despite guidelines, clinical practice varies. In light of the E-PILEPSY pilot reference network, we conducted a systematic review and meta-analysis on the diagnostic value of MRI in the presurgical evaluation of epilepsy patients. We included original research articles on diagnostic value of higher MRI field strength and guideline-recommended and additional MRI sequences in detecting an epileptogenic lesion in adult or paediatric epilepsy surgery candidates. Lesion detection rate was used as a metric in meta-analysis. Eighteen studies were included for MRI field strength and 25 for MRI sequences, none were free from bias. In patients with normal MRI at lower-field strength, 3T improved lesion detection rate by 18% and 7T by 23%. Field strengths higher than 1.5T did not have higher lesion detection rates in patients with hippocampal sclerosis (HS). The lesion detection rate of epilepsy-specific MRI protocols was 83% for temporal lobe epilepsy (TLE) patients. Dedicated MRI protocols and evaluation by an experienced epilepsy neuroradiologist increased lesion detection. For HS, 3DT1, T2, and FLAIR each had a lesion detection rate at around 90%. Apparent diffusion coefficient indices had a lateralizing value of 33% for TLE. DTI fractional anisotropy and mean diffusivity had a localizing value of 8% and 34%. A dedicated MRI protocol and expert evaluation benefits lesion detection rate in epilepsy surgery candidates. If patients remain MRI negative, imaging at higher-field strength may reveal lesions. In HS, apparent diffusion coefficient indices may aid lateralization and localization more than increasing field strength. DTI can add further diagnostic information. For other additional sequences, the quality and number of studies is insufficient to draw solid conclusions. Our findings may be used as evidence base for developing new high-quality MRI studies and clinical guidelines.

Discovery of quasi-periodic oscillations in the persistent X-ray emission of accreting binary X-ray pulsar LMC X-4

ABSTRACTWe report the discovery of quasi-periodic oscillations (QPOs) in the high-mass X-ray binary (HMXB) pulsar LMC X-4 in its non-flaring (persistent) state using observations with XMM–Newton. In addition to the 74 mHz coherent pulsations, the persistent emission light curve shows a QPO feature in the frequency range of 20–30 mHz. Quasi-periodic flares have been previously observed from LMC X-4 in observations made with Rossi X-ray Timing Explorer (RXTE). However, this is the first time QPOs have been observed in the persistent emission observations of LMC X-4. QPOs in X-ray binaries are generally thought to be related to the rotation of the inhomogeneous matter distribution in the inner accretion disc. In HMXBs such as LMC X-4 where the compact object is a neutron star with a high magnetic field, the radius of the inner accretion disc is determined by the mass accretion rate and the magnetic moment of the neutron star. In such systems, the QPO feature, along with the pulse period and X-ray luminosity measurement, helps us to constrain the magnetic field strength of the neutron star. We use considerations of magnetospheric accretion to have an approximate value of the magnetic field strength of the neutron star in LMC X-4.

Measuring Exposure to High-Frequency Electromagnetic Fields Experienced by a Helicopter Crew During Flight

Abstract High-frequency electromagnetic fields (EMF) can have a negative effect on both the human body and electronic devices. Monitoring and measurement of the electromagnetic field generated by devices is important from the point of view of environmental protection, the human body and electromagnetic compatibility. In this study, we tested the value of the electromagnetic field strength determined by the NHT3DL by Microrad with measurement probes during flights in the Robinson R44 helicopter. The reference point for the results obtained were the normative limits of the electromagnetic field permitted to affect the crew and passengers during flight. The maximum RMS values recorded during the measurements were E = 4.399 V/m in the 100 kHz–6.5 GHz frequency band and for the magnetic component H = 2.829 A/m in the 300 kHz–30 MHz frequency band. These results were passed to the Statistica 13.3 software for a detailed stochastic analysis of the values tested.

Non-linear interaction of laser light with vacuum: contributions to the energy density and pressure in the presence of an intense magnetic field

Recent simulations show that very large electric and magnetic fields near the kilo tesla strength will likely be generated by ultra-intense lasers at existing facilities over distances of hundreds of microns in underdense plasmas. Even stronger ones are expected in the future although some technical difficulties must be overcome. In addition, it has been shown that vacuum exhibits a peculiar non-linear behaviour in the presence of high magnetic and electric field strengths. In this work, we are interested in the analysis of the thermodynamical contributions of vacuum to the energy density and pressure when radiation interacts with it in the presence of an external magnetic field. Using the Euler–Heisenberg formalism in the regime of weak fields i.e. smaller than critical quantum electrodynamics field strength values, we evaluate these magnitudes and analyse the highly anisotropic behaviour we find. Our work has implications for photon–photon scattering with lasers and astrophysically magnetized underdense systems far outside their surface where matter effects are increasingly negligible.

Constraining models of inflationary magnetogenesis with NANOGrav data

Generation of magnetic field during inflation can explain its presence over a wide range of scales in the Universe. In Ref.\cite{sharma2017}, we proposed a model to generate these fields during inflation. These fields have nonzero anisotropic stress which lead to the generation of a stochastic background of gravitational waves (GW) in the early universe. Here we show that for a scenario of magnetogenesis where reheating takes place around QCD epoch, this stochastic GW background lies in the $95\%$ confidence region of the GW signal probed by NANOGrav collaboration. This is the case when the generated electromagnetic field (EM) energy density is $3-10\%$ of the background energy density at the end of reheating. For this case, the values of magnetic field strength $B_0 \sim (3.8-6.9) \times 10^{-11}$G and its coherence length $\sim 30$ kpc at the present epoch. These values are for the models in which EM fields are of nonhelical nature. For the helical nature of the fields, these values are $B_0 \sim (1.1-1.9) \times 10^{-9}$G and its coherence length $\sim 0.8$ Mpc.

Influence of an External Electric Field and Dissipative Tunneling on Recombination Radiation in Quantum Dots.

The effect of an external electric field and dissipative tunneling on the spectral intensity of recombination radiation in a quantum dot with an A+ + e impurity complex (a hole localized on a neutral acceptor interacting with an electron localized in the ground state of the quantum dot) is studied in the zero-radius potential model in the adiabatic approximation. The probability of dissipative tunneling of a hole is calculated in the one-instanton approximation. A high sensitivity of the recombination radiation intensity to the strength of the external electric field and to such parameters of the surrounding matrix (dissipative tunneling parameters) as temperature, the constant of interaction with the contact medium (or the heat-bath), and the frequency of phonon modes, has been revealed. It is shown that an external electric field leads to a shift of the recombination radiation threshold by several tens of meV, and a change in the parameters of dissipative tunneling has a noticeable effect on the spectral intensity of recombination radiation. It is shown that the resonant tunneling effect manifests itself in the form of “dips” in the field dependence of the spectral intensity of recombination radiation, which occur at certain values of the external electric field strength and temperature. This opens up certain prospects for the use of the considered system “quantum dot—impurity complex A+ + e” under conditions of dissipative tunneling for the study and diagnostics of biological objects.

Data Processing Mechanism and Algorithm Optimization for Radiated Emission Measurement of Electronic and Electrical Equipment

Radiated emission is one of the most important measurement items in the field of electromagnetic compatibility. The measured value of field strength often deviates from the real value to a certain extent. According to the characteristics of typical log-periodic dipole array antenna, the relation between antenna resonance unit and frequency, as well as the position relation between phase center and calibration reference point, the calculation formula of field strength correction factor is derived. The correction factor of field strength in the 30MHz-1GHz is also calculated precisely. The data processing mechanism of radiated emission measurement is clarified. An optimization algorithm for the measurement of radiated emission is obtained eventually. After the test value is optimized by the correction factor, more accurate field strength can be obtained. The optimization interval is within (-0.348, 2.741) dB. As a data processing mechanism of the radiated disturbance, it can not only improve the accuracy of measurement, but also reduce the uncertainty and error.

The joint influence of normal vibrations and electric field on the stability of a two-layer fluid system

The article focuses on the joint influence of normal vibrations and normal electric field on the stability of a system consisting of two flat horizontal fluid layers. Two cases are considered. In the first one, the system is formed by two layers of dielectric fluids (both layers have the same thickness) and, in the second, the system includes a dielectric fluid layer and an ideal electrically conductive fluid layer. The results obtained for these two cases are qualitatively similar. We study two approximations: the low-viscosity approximation and high-frequency vibrations. For the low-viscosity approximation, the so-called electric instability mode and the resonant mode are analyzed. In this case, the short-wavelength and long-wavelength instability modes are considered. In the low viscosity approximation, there occurs a viscous boundary layer, which is analyzed using a fast coordinate. The problem is studied by applying a multiscale method. It is demonstrated that vibrations increase the critical value of the electric field strength for short-wave instability in the presence of an electric mode. In the case of the long-wave instability, vibrations increase the curvature of the neutral curve near the zero value of the wave number. As for the influence of the electric field on resonant modes, it can lead to the splitting of the first resonance into two or three modes, depending on the values of the Weber number. When splitting is absent, the electric field reduces the critical amplitude of the first resonant mode. Otherwise, the effect of the electric field is more complex. In the high-frequency limit, the expressions describing the critical value of the electric field strength are similar to those for the electric mode considered in the low-viscosity approximation for finite vibration frequencies, and no resonant perturbations occur in this case.

Influence of the Magnetic Field on the Diffusion Capacitance of a Serial Vertical Junction Silicon Solar Cell in Frequency Modulation

In this work, a theoretical study of the effect of the magnetic field on the minority charge carrier density and the diffusion capacity of a silicon solar cell with vertical junction in series in dynamic frequency regime, is done. From the relative continuity equation of the minority charge carriers’ density we establish the boundary condition at the junction and the base medium. The expression of the density of minority carriers of charges in the base, allows us to determine the capacity of diffusion of the solar cell according to the magnetic field, the frequency of modulation, the wavelength of illumination and a junction recombination velocity. The profile of the diffusion coefficient allowed us to make a choice on the values of the magnetic field. These values of the magnetic field intensity will be fixed throughout this article. Each value of the magnetic field strength corresponds to a well-defined value of the resonance frequency. We obtained two ranges of illumination wavelengths from the minority charge carrier’ density profile. The influence of the magnetic field on the diffusion coefficient, of the density of minority charge carriers in short-circuit and open-circuit conditions and of the diffusion capacity, for a specific wavelength, is theoretically studied.

Change of thermophysical parameters of polypropylene-metal oxide nanocomposite (polypropylene + ZrO2) after electric field influence

In this work, the influence of an electric field on thermophysical properties of the PP+ZrO2 nanocomposites has been investigated. Changes in thermograms before and after applying an electric field (EFI) have been studied depending on the filler percentage in the polymer matrix. After EFI a new, weak maximum at the temperature range of 100–130°С of the thermograms for all concentrations of the filler was observed. Thermophysical parameters of the nanocomposite sample have been calculated for different values of electric field strengths that were applied are calculated depending on the effect of the ETP.

Method of parametric analysis of reciprocating electric generators with permanent magnets

A method for the parametric analysis of electric generators of reciprocating motion with permanent magnets has been developed, which allows revealing the values of the parameters of the magnetic circuit (cross-sectional area) and the working winding (number of turns) at a given value of the efficiency, providing a minimum specific gravity of the generator. The method of parametric analysis of electric generators of reciprocating motion with permanent magnets consists of three stages. The first and second stages are the electromagnetic calculation of the generator: at the first stage, the main geometric dimensions of the magnetic system and the parameters of the working winding of the generator are determined; at the second stage, the verification of the electromagnetic calculation of the generator, calculation of the nominal mode, calculation of the efficiency and assessment of the thermal state of the generator are fulfilled. At the third stage, a parametric analysis of electric generators of reciprocating motion with permanent magnets with specified constraints is carried out, as well as the refinement of the geometric dimensions and configuration of the magnetic system of the generator using a two-dimensional finite element model of the magnetic field. As a result, to ensure better use of the electrical steel of the magnetic circuit of the generator and thereby reduce its mass, the most saturated areas and areas, which are characterized by low values of the magnetic field strength, are determined. Distinctive features of the proposed technique are: the use of a minimum specific gravity of electric generators of reciprocating motion with longitudinal, transverse or combined changes in the magnetic flux passing through the working winding as an objective function; combined approach to electromagnetic calculation; taking into account the influence of the operating temperature on the parameters of the permanent magnet, as well as overheating of individual parts of the generator.

Influence of ferrimagnetic resonance on conversion of electromagnetic energy by a YIG resonator into mechanical one

Using the method of physical modeling, an algorithm for calculating the force with which a standing electromagnetic wave acts on a ferrite sphere of arbitrary diameter placed in a constant magnetic field is obtained. The value of constant magnetic field intensity provides appearance of ferrimagnetic resonance. Dependence of the magnetic field of an electromagnetic wave in the middle of a ferrite sphere on the size of its resonant radius and spherical coordinates are studied. In the center of the ferrite sphere, the resonance radius of which is 4.2634 mm, the microwave magnetic field strength is 83796 times greater than the magnetic field strength in the incident plane polarized wave. Mean-square value of the magnetic field strength over the volume of the sphere increases 4.8 times. Standing wave, formed in a free space with power flow density of 622 kW/m2 and wavelength of 3.2 cm, reflects from metallic shield placed at a distance of λo/8 + nλo/2, n = 0, 1, 2, 3… measured from the center of ferrite sphere and impacts with force of 0,12 N on ferrite sphere with resonance radius of 4,2634 mm. The results of the calculated force acting on the YIG – resonator coincide with the experimental results given in the well-known works (the power flux density is 43 kW/m2, the radius of the ferrite sphere is 1.775 mm, the force is 6 ± 0.5 μN) within the measurement error. Application of spatial resonance, standing electromagnetic wave and YIG resonator allows to increase of energy conversion factor of microwave energy conversion into mechanic one 8,6·104 times in compare to application of ferrite cylinder only in known papers. The research results can be used by the developers of converters of microwave energy into mechanical energy.