Values Of Magnetic Field Intensity Research Articles

Design and characterisation of a cell exposure system with high magnetic field homogeneity: RILZ coils.

In vitro studies requiring controlled exposure to low-frequency electromagnetic fields employ exposure systems with different geometries and configurations, the Helmholtz configuration being one of the most widely used. This configuration has limitations in the homogeneity of the spatial distribution of the magnetic field intensity values. We present the design, manufacturing, and characterisation of a new coil system, called RILZ configuration, which improves the distribution of magnetic field intensity values in the three dimensions of space for three different heights in comparison with the traditional circular coils in Helmholtz configuration. In addition, a comparative study of the cellular response in CT2A cultures exposed to a magnetic field of 50 Hz and 100µT for 48hrs is performed with both exposure systems. The results of the study show reduced values of deviation from the central value of magnetic field intensity using the RILZ coil system. These differences are statistically significant compared to the Helmholtz configuration for the three Cartesian directions: x (p < 0.01), y (p < 0.01), z (p < 0.01). In addition, the intensity values for three different heights are statistically significantly correlated using the RILZ coil system (p < 0.01). The differences in cell behaviour are also statistically significant between the two systems (p < 0.01) and may be directly related to the differences found in the distribution of intensity values between the two systems. This study highlights the importance of the homogeneity of the magnetic field intensity generated by the exposure systems used and offers an effective solution to control the magnetic field exposure parameters in vitro assays.

Calculation of Magnetic Fields Generated by Traction Transformers and Busbars in Electric Locomotive Systems by Finite Element Method

Güç sistemi ekipmanlarının etrafında oluşturduğu manyetik alan yoğunluğunun insan sağlığı üzerine olan etkileri çeşitli kuruluşlar tarafından incelenmektedir. İnsanların güç sistemi ekipmanlarının şebeke frekansında oluşturduğu manyetik alan yoğunluğuna maruz kalması durumunda izin verilen sınır değerler International Commission on Non‐Ionizing Radiation Protection (ICNIRP) tarafından belirlenmiştir. Buna göre kamuya açık alanlar ve çalışma ortamları için izin verilen en yüksek manyetik alan yoğunluğu değerleri sırası ile 0,2mT ve 1mT olarak belirtilmiştir. Bu kapsamda lokomotiflerde cer gücünü sağlamak için kullanılan cer transformatörü, bara, sürücü ve motor gibi elemanların oluşturduğu manyetik alan yoğunluklarının önemli bir parametre olduğu görülmektedir. Bu bileşenlerin etrafında oluşan manyetik alan yoğunluklarının yolcuların ve personelin sağlığı için belirlenen sınırların altında kalması önerilmektedir. Bu sebepten dolayı lokomotif sistemlerinin tasarımı aşamasında bileşenlerin etrafında oluşan manyetik alan yoğunluklarının belirlenmesi gerekmektedir. Bu çalışma kapsamında lokomotiflerde kullanılmakta olan bir cer transformatörünün ve örnek bir bara yapısının oluşturduğu manyetik alan yoğunluklarının hesaplanması hedeflenmiştir. Bu amaç ile cer transformatörü, basit bir lokomotif kasası ve bara yapısının geometrik modeli üç boyutlu koordinat sisteminde oluşturulmuş ve Ansys Electronics Suite sonlu elemanlar analizi yazılımına aktarılıp analiz çalışmaları gerçekleştirilmiştir. Analiz sonuçlarına göre belirlenen ölçüm düzlemlerinde manyetik alan yoğunluklarının sınır değerlerin altında kaldığı görülmektedir. Manyetik alan yoğunluğu değerleri modelin geometrik yapısına, malzeme parametrelerine ve işletme durumuna bağlı olarak değiştiğinden dolayı bu analizlerin tasarım aşamasında değerlendirilmesinin gerekliliği çalışma kapsamında vurgulanmıştır.

A study on in-vitro behaviour of stainless steel 316L subjected to rotational magnetorheological abrasive flow finishing process

In Rotational Magnetorheological Abrasive Flow Finishing (R-MRAFF) process, Magnetic Field Intensity (MFI) is the primary factor for the formation of ferrous chains which is responsible for finishing. Changing the pole distance between magnets to achieve a difference in MFI values will alter the strength of the ferrous chains. In this study, three different MFI values such as 0.34, 0.36, and 0.40 Tesla were chosen for finishing on Stainless Steel 316L (SS 316L). Surface wettability, bio-corrosion, and hemocompatibility studies were conducted to investigate the in-vitro behavior of SS 316L. The wettability of the implants changed from hydrophobic (100.92°) to hydrophilic (83.452°) surface as the MFI value increased. Bio-corrosion studies revealed improved corrosion resistance for R-MRAFF process finished samples, with the corrosion rate reduced from 3.693 to 0.967 μm year−1. Hemocompatibility of SS 316L was improved with reduced platelet adhesion when compared to the pristine sample.

New criteria for selecting reliable Thellier-type paleointensity results from the 1960 Kilauea lava flows, Hawaii

Thellier-type paleointensity experiments associated with partial thermal remanent magnetization checks have been widely used to determine paleointensity values from volcanic and archaeological media. However, previous studies have revealed that a substantial portion of paleointensity results with positive checks for historical lava samples largely fails to predict known Earth magnetic field intensity values. To determine the fidelity of paleointensity values, conventional Thellier-type paleointensity experiments were performed on Kilauea lava flows that erupted in 1960. The positive partial thermal remanent magnetization checks for our results range from 30.28 ± 1.38 µT to 52.94 ± 1.89 µT. This strongly indicates that conventional paleointensity checks cannot guarantee the fidelity of paleointensity results, especially when the unblocking temperatures for the newly formed magnetic particles are higher than the treatment temperature. Therefore, in this study, to check for thermal alteration during heating, the temperature dependence of the hysteresis parameter measured at room temperature for the thermally treated samples was also measured. Our new results show that nearly all biased paleointensity values correspond to a ratio of the coercivity of remanence to the magnetic coercivity of > 3 and a chemical alteration index > ~ 10%, which indicates the strong effect of the domain state and thermal alteration on the fidelity of the paleointensity results. Our study provides feasible criteria to further improve the fidelity of paleointensity estimations.

Non-Uniform Magnetic Field Effects on Ferrofluids Film Boiling: A Numerical Study

In this paper the effect of magnetic field on film boiling of ferrofluids on a horizontal flat plate has been investigated. The obtained results indicate that adding nanoparticles into the base fluid changes vapor film characteristics mainly due to changes in thermophysical properties of the base fluid. Also, ferrofluids enhances film boiling heat transfer on horizontal plate specially at higher volume concentration of nanoparticles. Another important result of this study is the effect of non-uniform magnetic field on horizontal film boiling characteristics. Application of magnetic field changes vapor film behavior mostly at higher values of magnetic field intensity (400) and nanoparticles volume fraction (4 percent).

Effects of different magnetic fields on the freezing parameters of cherry

Magnetic field assisted freezing is a kind of freezing methods that can improve food quality. The objective of this study is to evaluate the effects of various magnetic field type and intensity on cherry during the freezing process. The permanent magnetic field (PMF) ranging from 0 to 20 mT and the alternating magnetic field (AMF) ranging from 0 to 2 mT were applied on the cherry. The final temperature and cooling rate of the frozen environment were −30 °C and 4 °C/min. The freezing parameters, which included the macro indexes and microstructure, were used to evaluate the freezing quality. The results show that the freezing temperature was significantly higher in the presence of AMF compared with the control group (p < 0.05). However, the permanent magnetic field had little influence on the freezing temperature. The phase change time decreased with PMF, whereas it increased with AMF, which may consume more energy. The application of magnetic field could reduce drip loss to some extent. Ice crystals formed homogeneously in the cells when the magnetic field was applied. Compared with the control group, the average ice crystal area achieved a reduction of 67% and 78% with PMF and AMF, respectively. Taking all the evaluation indexes into consideration, the optimum magnetic field intensity values were 10 mT for PMF and 1.26 mT for AMF in this study.

Effect of Gas Metal Arc Welding on Magnetic Response of Ferritic Stainless Steel

The variation of magnetic Barkhausen noise (MBN) response of different regions of the gas metal arc welded ferritic stainless steel SS409L plate in terms of number of pulses and root mean square value with the variation of MBN analysis parameters (magnetic field intensity and magnetizing frequency) have been investigated in the present work. Five different values of magnetic field intensity 250, 500, 750, 1000 and 1250 Oe at the constant magnetizing frequency of 25 Hz and four different values of magnetizing frequency 10, 20, 30 and 40 Hz at a constant magnetic field intensity of 800 Oe were used as MBN analysis parameters. It was found that MBN response depends upon the magnetic field intensity and magnetizing frequency as well on grain size and microhardness of different regions.

Magnetic hysteresis loop behaviour of welded ferritic stainless steel 409L with the variation of magnetic field intensity

Hysteresis loop analysis technique, being a non-destructive testing technique is more beneficial than the destructive testing techniques to characterise the welded plate. In this study, the ferritic stainless steel AISI 409L plate was butt welded by gas metal arc welding process. Hysteresis loop analysis technique was used to study the microstructures and microhardness of the base metal region, heat affected zone and weldmetal zone. This study has been carried out at four different values of magnetic field intensity 250, 500, 750 and 1000 Oe. The effect of variation of magnetic field intensity on the hysteresis loop characteristics (average maximum flux density and core loss) has been investigated for base metal, heat affected zone and weldmetal zone. It was found that for each region, the average maximum flux density as well as core loss increases on increasing magnetic field intensity. Also, the variation of average maximum flux density is inversely proportional to the microhardness of the region at each value of magnetic field intensity.

A new method of interface tension measurement of a magnetic fluid drop

A new method for determining the interfacial tension of a magnetic fluid (MF) is proposed on the basis of deformation of a MF drop lying on a liquid substrate and subjected to a vertical uniform magnetic field. The results show that the drop elongates in the direction of the field with an increase of its intensity. As soon as the field strength reaches a certain value, the interface and the free surface of the drop become unstable, which causes the peaks of different height to form. It has been found that the ratio of the corresponding critical values of magnetic field intensity is determined by the ratio of surface tension at the interface to that on the free boundary of the drop. Surface and interfacial tension of liquids used in the experiment were measured with the help of tensiometer by the ring detachment method to verify the experimental data. The presented results on the ferrofluid interface tension measurements can be of interest for the specialists in the field of ferrohydrodynamics.•The magnetic field causes the drop to elongate till the peak instability.•The critical values of the field strength respond to the ferrofluid initial magnetic susceptibility.•The ratio of the critical magnetic field values is determined by the ratio of the interfacial tension.

Effect of pulsed millisecond current magnetic field on the proliferation of C6 rat glioma cells

ABSTRACTIn recent years, using electromagnetic fields as a targeted therapy for tumors has become a new idea. This paper aims to study the response of rat glioma cells (C6) when the external electromagnetic field parameters change and to obtain a complete working range of magnetic field parameters. Four-day, 4-h daily millisecond magnetic field exposure experiments were performed with C6 cells. The peak values of magnetic field intensity were 260 mT, 90 mT, 19 mT and 6 mT. Each day after exposure, cell morphology and cell viability assay (MTT method) were measured. The response of C6 cells shows a significant window effect and time cumulative effect on the cell, and it is non-destructive. The working inhibited magnetic field range of magnetic field increase rate dB/dt (T/s) is [34, 119.5] and [166.75, 527.25], the magnetic field amplitude B (mT) is [6, 260], the magnetic field integral Bt (mT·s) is [0.1649, 0.8085] and the energy integral B2t (mT2·s) is [2.317, 53.328]. Our findings provide the theoretical and experimental basis for clinical applications of electromagnetic fields.

Buckling analysis of graphene oxide powder-reinforced nanocomposite beams subjected to non-uniform magnetic field

Present article deals with the static stability analysis of compositionally graded nanocomposite beams reinforced with graphene oxide powder (GOP) is undertaken once the beam is subjected to an induced force caused by nonuniform magnetic field. The homogenized material properties of the constituent material are approximated through Halpin-Tsai micromechanical scheme. Three distribution types of GOPs are considered, namely uniform, X and O. Also, a higher-order refined beam model is incorporated with the dynamic form of the virtual work\'s principle to derive the partial differential motion equations of the problem. The governing equations are solved via Galerkin\'s method. The introduced mathematical model is numerically validated presenting a comparison between the results of present work with responses obtained from previous articles. New results for the buckling load of GOP reinforced nanocomposites are presented regarding for different values of magnetic field intensity. Besides, other investigations are performed to show the impacts of other variants, such as slenderness ratio, boundary condition, distribution type and so on, on the critical stability limit of beams made from nanocomposites.

Deformation of ferrofluid floating drop under the action of magnetic field as method of interface tension measurement

The deformation of a kerosene-based ferrofluid drop lying on a liquid substrate and subjected to a vertical uniform magnetic field has been studied experimentally. In the absence of magnetic field the drop has a shape of two vertical axisymmetric semi-ellipsoids of different height which are joined at the plane of the interface between air and liquid substrate. The results show that the drop elongates in the direction of the field with an increase of its intensity. As soon as the field strength reaches a certain value, the interface and the free surface of the drop become unstable, which causes the peaks of different height to form. It has been found that the ratio of the corresponding critical values of magnetic field intensity is determined by the ratio of surface tension at the interface to that on the free boundary of the drop. Surface and interfacial tension of liquids used in the experiment was measured with the help of tensiometer by the ring detachment method to verify the experimental data. The presented results on the ferrofluid interface tension measurements can be of interest for the specialists in the field of ferrohydrodynamics.

Control of metabolic current through a protein-like nanowire by means of a magnetic field

The possibility of electrons transfer control by a protein-like nanowire, as a component of the metabolic process, was investigated. The research was carried out in order to access the potential for a positive effect of ATP molecules on the synthesis. The correlation of the nanocurrent dependence on a magnetic field was obtained. It makes it possible to determine the conditions which the synthesis of ATP may be blocked. The threshold value of the magnetic field induction and the corresponding value of magnetic field intensity were calculated. The results of calculations are consistent with experimentally observed results.

English

Geoscience prospecting for gold mineralisation was conducted in Kwakuti town located within Latitudes 9.362500°N to 9.387500°N and Longitudes 6.920833°E to 6.945833°E in Northern Nigeria. The deployed geosciences techniques comprise surface geological mapping, processing and analysis of aeromagnetic total magnetic field intensity data using Oasis Montaj software and X-ray fluorescence analysis of soil samples. Migmatites and gneiss dominate the rock outcrops in the area. The migmatites occupy high elevations on the north-eastern and eastern portion of the area, where they display low magnetic field intensity values. The schist occupies moderate to low elevation areas and they display high magnetic field intensity values. The migmatites are dotted with quartz veins which constitute the gold mineralisation zone. Oval shaped high magnetic anomalous zones within the schist indicate basic intrusive into the schist. First derivative map of the magnetic field intensity data reveal NE-SW trending lineaments. They likely conducted hydrothermal fluids from the basic intrusive into the migmatites on the northeast, where gold mineralisation occurred by metasomatic ionic exchange. Spatial concentration of TiO2 and MnO2 are the highest within the oval shaped high magnetic anomalous zones in the southern portion of the study area. This strengthens the inference that basic intrusive underlies the area. Gold concentration distribution pattern in the area is skewed NE-SW, thereby suggesting that the NE-SW structures control the mineralisation. Mining activities will be more efficient if directed along the NE-SW structural trend. Key words: Aeromagnetic data, aero-radiometric data, geologic mapping, gold mineralisation, X-ray fluorescence.

Response of magnetized plasma having linearly varying electron density profile to oblique electromagnetic wave incidence

ABSTRACTThe response of magnetized plasma slab to obliquely incident electromagnetic wave is determined for different incidence angles and magnetic field intensity values in the case of linearly varying electron density profile along the plasma slab. It is shown that plasma slab provides wide-band absorption due to the proper adjustment of the slope of the electron density profile, incidence angle and magnetic field intensity values. Plasma medium providing wide-band absorption performance under oblique incidence is proposed for military stealth and current shielding applications.

Magnetic field intensity effect on electrical conductivity of magnetorheological biosuspensions based on honey, turmeric and carbonyl iron

Magnetorheological biosuspensions (MRSs) are prepared using honey (HB), turmeric powder (nT) and carbonyl iron (CI) microparticles at various concentrations. By impregnating a cotton fabric with MRSs and compressing the whole system between two copper plates, a magnetoresistor (MRs) is obtained. The resistance R and electrical conductivity σ of MRs are measured as a function of time t for various values of magnetic field intensity H. We show that σ increases with H and is sensibly influenced by the volume fraction ΦCI of carbonyl iron. For fixed ΦCI and H, we show that σ increases with concentration ΦnT of turmeric powder.

Statistical analysis of severe magnetic fluctuations in the near-Earth plasma sheet observed by THEMIS-E

Abstract. We statistically analyzed severe magnetic fluctuations in the nightside near-Earth plasma sheet at 6–12 RE (Earth radii; 1 RE = 6371 km), because they are important for non-magnetohydrodynamics (non-MHD) effects in the magnetotail and are considered to be necessary for current disruption in the inside-out substorm model. We used magnetic field data from 2013 and 2014 obtained by the Time History of Events and Macroscale Interactions during Substorms E (THEMIS-E) satellite (sampling rate: 4 Hz). A total of 1283 severe magnetic fluctuation events were identified that satisfied the criteria σB∕B &gt; 0. 5, where σB and B are the standard deviation and the average value of magnetic field intensity during the time interval of the local proton gyroperiod, respectively. We found that the occurrence rates of severe fluctuation events are 0.00118, 0.00899, and 0.0238 % at 6–8, 8–10, and 10–12 RE, respectively, and most events last for no more than 15 s. From these occurrence rates, we estimated the possible scale sizes of current disruption by severe magnetic fluctuations as 3.83 RE3 by assuming that four substorms with 5 min intervals of current disruption occur every day. The fluctuation events occurred most frequently at the ZGSM (Z distance in the geocentric solar magnetospheric coordinate system) close to the model neutral sheet within 0.2 RE. Most events occur in association with sudden decreases in the auroral electrojet lower (AL) index and magnetic field dipolarization, indicating that they are related to substorms. Sixty-two percent of magnetic fluctuation events were accompanied by ion flow with velocity V &gt; 100 km s−1, indicating that the violation of ion gyromotion tends to occur during high-speed flow in the near-Earth plasma sheet. The superposed epoch analysis also indicated that the flow speed increases before the severe magnetic fluctuations. We discuss how both the inside-out and outside-in substorm models can explain this increase in flow speeds before magnetic fluctuation events.

Energy of coronal mass ejections and large-scale structure of solar magnetic fields

The relationship between variations of the energy and linear velocity of coronal mass ejections (CME) and the typical dimensions of structural elements of the large-scale solar magnetic field structure (LSMFS) is investigated for the period of 1996–2014. It is shown that the maximum linear velocity and maximum energy of CME correspond to the values of the effective solar multipole index n ~ 4.0–4.4. These values determine the maximum size of the complexes of active regions, which, together with the observed maximum values of magnetic field intensity in the complexes, limit the possible maximum CME energy.

Influence of ferrimagnetic resonance on conversion of electromagnetic energy into mechanical one

In this paper it is obtained in zero approximation the algorithm of calculation of the force of electromagnetic wave propagation in rectangular waveguide applied to the ferrite sphere, placed into constant magnetic field by the method of physical modeling. It is researched the dependence of the force on a value of magnetic field intensity near ferromagnetic resonance. Theoretical results of the calculations were compared with experimental ones. At the resonance electromagnetic field with the power of 10W and the wave length of 3.2 cm influences on ferrite sphere with diameter of 3.55mmwith a force of 6 ± 0.5 µN. This force in enough for rotation of the suspension system of the reference ponderomotive wattmeter, fixed attached by means of braces or kerns. It allows to develop high-precision microwave wattmeters with enough mechanic strength for industrial application.

A FEM approach to biomagnetic fluid flow in multiple stenosed channels

The unsteady and laminar biomagnetic fluid flow of a viscous, incompressible, Newtonian and electrically conducting fluid is numerically investigated. Specifically, the two-dimensional flow driven in an infinite channel containing multiple stenosis and subject to a spatially varying external magnetic field is considered. The numerical method is based on the use of finite element method (FEM) in spatial discretization and unconditionally stable backward finite difference scheme for the time integration, for solving coupled nonlinear differential equations in terms of stream function, vorticity and temperature. Due to nonlinearity, an iterative process is employed between the equations. The study focuses on the alteration of the flow and its temperature behaviors due to the irregular constrictions along the channel. Also, the effects of the external magnetic field, its location and its intensity on the biomagnetic fluid flow are analyzed. The numerical results are presented in terms of streamlines, equivorticity and temperature contours for several values of magnetic field intensity in irregularly and multiply stenosed channels. It is shown that the lengths of the vortices appeared due to the stenosis and magnetic source, increase with an increase in the intensity of the magnetic field and the severity of the constriction.