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The levels and spectral composition of magnetic fields, generated by equipment for arc welding by different methods were determined, in order to assess their influence on the welder body. Published data on electromagnetic safety of electric arc welding were analyzed. A description of the proposed methodological approaches to determination of magnetic field levels, their measurement methods and methods of assessment of their influence on the welder body is given. Modern standards are characterized as to evaluation of the electromagnetic field impact on man, and their difference from the earlier applied standards. It is shown that new publications began to appear recently, which are devoted to the harmfulness of electromagnetic fields at application of electric production equipment. Hence the need to conduct new studies of electromagnetic fields, in particular their magnetic component (magnetic field intensity, А/m), when using welding equipment. This is required for hygienic assessment of the magnetic fields and development of the respective methods and means of welder protection. For this purpose, it will be necessary to choose new generation instruments for determination of the intensity of the magnetic fields. Proceeding from analysis of the obtained oscillograms and spectrograms of the magnetic fields, evaluation of their levels was performed at application of different arc welding methods. It is shown that the spectral composition of the magnetic field signal is determined, predominantly, by the welding process proper, features of arc burning and mode of electrode metal transfer in the arc gap, as well as output parameters of the welding arc power source. 10 Ref., 5 Tabl., 3 Fig [ABSTRACT FROM AUTHOR]

The levels and spectral composition of magnetic fields, generated by equipment for arc welding by different methods were determined, in order to assess their influence on the welder's body. Published data on electromagnetic safety of electric arc welding were analyzed. A description of the proposed methodological approaches to determination of magnetic field levels, their measurement means and methods of assessment of their influence on the welder's body is given. Modern standards are characterized as to evaluation of the electromagnetic field impact on man, and their difference from the earlier applied standards. It is shown that new publications began to appear recently, which are devoted to the harmfulness of electromagnetic fields at application of electric production equipment. Hence the need to conduct new studies of electromagnetic fields, in particular their magnetic component (magnetic field intensity, A/m), when using welding equipment. This is required for hygienic assessment of the magnetic fields and development of the respective methods and means of welder protection. For this purpose, it was necessary to choose new generation instruments for determination of the intensity of magnetic fields, generated by welding equipment proper. Proceeding from analysis of the obtained oscillograms and spectrograms of the magnetic fields, evaluation of their levels was performed at application of different arc welding methods. It is shown that the spectral composition of the magnetic field signal is determined, predominantly, by the welding process proper, features of arc burning and mode of electrode metal transfer in the arc gap, as well as output parameters of the welding arc power source. [ABSTRACT FROM AUTHOR]

The object of this study is the quantitative characteristics of magnetic fields induced during electric contact welding in various ways: contact point, arc-butt, capacitor point, contact-butt continuous, and pulsating fusion. The problem to be solved is the lack of necessary information regarding the electromagnetic safety of these welding techniques. A description of the proposed methodological approaches to determining the levels of magnetic fields, their measurement tools, and methods for assessing their impact on the welder’s body is given. Based on the analysis and processing of the acquired oscillograms and spectrograms of magnetic fields, their quantitative characteristics were measured. To determine the general level of the polyfrequency magnetic field arising at contact welding, the proposed generalized indicator of the level of the magnetic field was used. It was established that during contact point welding by a stationary machine, the level of the magnetic field exceeds the maximum permissible value at the workplace in the range of 50–1000 Hz at a distance of 0.3 m from the welding electrodes. When manually welding in this way, the magnetic field level exceeds the permissible level in the frequency bands of 5–50, 50–1000 Hz directly near the electrical cable. Capacitor spot welding with direct current is characterized by exceeding the maximum permissible MP at the workplace in the high-frequency range of 1000–10000 Hz. During arc-butt welding, no excess of the maximum permissible levels of the magnetic field was detected at the workplace. It is shown that the spectral composition and magnitude of the magnetic field signal is determined by the welding technique and the initial parameters of power supplies. Orimani results can be used in the field of welding production and labor protection. [ABSTRACT FROM AUTHOR]

Under the mine environment, electromagnetic propagation is polluted by solid particles and noise. For the problem of low accuracy of current prediction of field strength in the mine tunnel, a prediction model based on the least squares support vector machine (LS-SVM) method which was optimized by particle swarm optimization was proposed to predict field intensity in mine tunnel. The measured data of a certain roadway is used as training samples to predict the mine roadway field strength. The influence of training set construction and parameter selection on the prediction effect was analyzed in detail. The simulation results show that the optimized LS-SVM prediction model has a higher prediction accuracy than the dual-slope model and logarithmic correction model. [ABSTRACT FROM AUTHOR]

We report on the results of numerical simulation based on the Mie theory of the super-resonance effect (the higher-order Fano resonance) for a mesoscale dielectric sphere located in air, since the vacuum environment is an idealization that is almost never encountered in nature. It is first shown using the example of a particle with a refractive index of 1.5 and size parameters of q ∼ 26 and q ∼ 38 that a change in the refractive index of the environment by 2 × 10−4 leads to drop in field intensity in the region of the shadow pole of a sphere by an order of magnitude and a shift in resonance size parameter q to the short-wavelength region. In this case, the relative intensities of the resonance peaks for both the magnetic and electric field in the vicinity of the sphere poles in the optical range can attain these values (106‒107) for a particle in vacuum with an appropriate correction of the resonance size parameter. [ABSTRACT FROM AUTHOR]

This paper reports a study into the levels of magnetic fields induced by arc welding equipment in various ways in order to assess their impact on the body of welders. It is known that welders are exposed to a magnetic field of high intensity. Depending on the welding technique and the type of welding equipment, it may exceed the maximum permissible levels (MPL). Note that new Ukrainian sanitary standards for magnetic fields have been introduced, which regulate their levels depending on the frequency range. Therefore, it became necessary to carry out their hygienic assessment according to the new standards in order to devise appropriate methods for protecting welders. To this end, it was required to choose a new generation of devices to determine the intensity of magnetic fields induced by welding equipment. Based on the analysis of the constructed oscillograms and spectrograms of magnetic fields, it was found that semi-automatic welding with a metal electrode in carbon dioxide is characterized by an increased level of magnetic field in the frequency range of 50‒1000 Hz. With automatic arc welding under the flux, there are no excess of the maximum permissible levels of individual harmonics of the magnetic field but there is an excess of the total value of all harmonic components of the magnetic field. Manual arc welding with direct current involving a non-melting electrode in argon is characterized by a moderate level of magnetic field in workplace. During manual arc welding with coated electrodes, the exceeded level of the magnetic field is observed only on the electrode cable itself. It is shown that the spectral composition of the magnetic field signal is determined mainly by the welding technique itself, the peculiarities of arc combustion, and the nature of the transfer of electrode metal in the arc gap, as well as the initial parameters of the power supplies of the welding arc. [ABSTRACT FROM AUTHOR]

Electromagnetic waves (EMF) are a mixture of electrical and magnetic waves. The energy transmitted by these radiations is absorbed by living tissues. Electromagnetic fields seem to cause infertility in women. Cannabis is annual herbaceous plant grows in tropical areas. This study was conducted to investigate the protective effects of hydroalcoholic extract of Cannabis sativa in various doses of 50, 100 and 150 mg / kg on the damages induced by electromagnetic fields of 50 Hz and 50 Gauss, on the puberty of ovarian follicles and levels of FSH, LH, estradiol and progesterone hormones in NMRI immature mice. In this study, 48 NMRI immature female mice with an approximate age of 16 days and approximate weight of 18 grams were divided into 8 (experimental, sham, positive control and negative control) groups. After the treatment, the ovaries were extracted and weighed, and sections with H& E staining, the number of primordial, primary, secondary, and atretic follicles were counted, and the level of hormones have been done. The results showed that the concentration of 50 mg / kg of cannabis extract after the exposure to electromagnetic field of 50 Gauss could increase the number of follicles and reduce the number of atresia follicles. The group treated with the concentration of 50 mg / kg of cannabis extract after the exposure to electromagnetic field of 50 Gauss showed increased levels of FSH, LH and estradiol hormones (p

To solve the problem of fatigue life prediction of notched 3D woven composites, a novel fatigue life prediction method based on progressive damage and field intensity theory is proposed. By analyzing the initial loading process of 3D woven composite structure based on progressive damage method, the stress field when the fatigue damage develops gently and the dangerous area where the fatigue damage occurs first are obtained. Then combining with the concept of notch field intensity function, the failure criteria of composites and the three-dimensional space vector stress field intensity method, the fatigue damage degree field intensity of the fiber yarns in the dangerous area is analyzed and the most damaged fiber yarn is found. The fatigue life of the structure is calculated with the field intensity equivalent stress and the S-N curve of this fiber yarn. In order to verify the effectiveness of this method, the fatigue life of notched 3D woven composites under several stress levels is predicted and compared with the existing experimental data. The compared results show that the fatigue life prediction values are all within the two-fold error bounds of the experimental data, which are in good agreement with experimental results. Compared with the progressive damage fatigue life prediction method of woven composites, the prediction accuracy of the method proposed in this paper is improved by 31.5% on average, and the calculation efficiency is also greatly improved. [ABSTRACT FROM AUTHOR]

It is remarked that in magnetophoresis (one form of which is magnetic separation, which is used in different industries, including glass and ceramic) information on the magnetic susceptibility χ of magnetically active particles, which depends on the intensity H of the applied field, is just as fundamental as information on fractional content of the particles. Data obtained on χ for iron-containing impurity particles of quartz sand from measurements of the magnetic susceptibility of their powder samples are presented. It is shown that the parameter χ, which is inversely dependent on H with exponent close to 0.75, significantly suppresses the role of the parameter H appearing in the basic expression for the magnetic force gripping the particles. It is recommended that in developing a magnetophoresis (separation) apparatus attention should be focused on not so much the parameter H but rather the parameter—gradH that characterizes the nonuniformity of the field and plays a more role in the gripping of the particles. [ABSTRACT FROM AUTHOR]

To solve the problem of fatigue life prediction of notched 3D woven composites, a novel fatigue life prediction method based on progressive damage and field intensity theory is proposed. By analyzing the initial loading process of 3D woven composite structure based on progressive damage method, the stress field when the fatigue damage develops gently and the dangerous area where the fatigue damage occurs first are obtained. Then combining with the concept of notch field intensity function, the failure criteria of composites and the three-dimensional space vector stress field intensity method, the fatigue damage degree field intensity of the fiber yarns in the dangerous area is analyzed and the most damaged fiber yarn is found. The fatigue life of the structure is calculated with the field intensity equivalent stress and the S-N curve of this fiber yarn. In order to verify the effectiveness of this method, the fatigue life of notched 3D woven composites under several stress levels is predicted and compared with the existing experimental data. The compared results show that the fatigue life prediction values are all within the two-fold error bounds of the experimental data, which are in good agreement with experimental results. Compared with the progressive damage fatigue life prediction method of woven composites, the prediction accuracy of the method proposed in this paper is improved by 31.5% on average, and the calculation efficiency is also greatly improved. [ABSTRACT FROM AUTHOR]

• The use of magnetic devices for treating water positively affected soil and tomatoes. • Magnetized water reduced soil salinity by up to 44% and enhanced yield by up to 35%. • Device's performance increased as magnetic intensity decreased till 0.0043Tesla. • Senda cultivar was better improved than Dorra cultivar. • Performance of device could be affected by interference between different aspects. The application of magnetic and Electromagnetic fields for irrigation water treatment is still an attractive and promising process for the alleviation of the adverse effects of salinity and the enhancement of crop production. Hence, a study was initiated to test the effectiveness of different commercial magnetic and electromagnetic water. treatment devices on soil and two Tunisian tomato crop cultivars, Senda and Dorra. For this purpose, a field experiment was conducted at the experimental Station of Cherfech, located in the north of Tunisia. A randomized complete design with three replicates was used and five magnetic, GMX (1.2 T), Magiko (1.6 T), Deltawater (1.4 T), and Magnolith (0.62T), and electromagnetic Aqua-4D (0.0043T) treatment devices were applied for the treatment of a moderate saline water (EC = 2.9 dS m–1). Results showed that different magnetic and electromagnetic treatments tended to reduce soil salinity and pH, improve crop growth, yield, and fruit caliber, but decline the total soluble solids (°Brix) and the titratable acidity of both tomato cultivars. The greatest Magnetic effects were shown for Senda cultivar with Aqua 4-D treatment, whereas the least effect was recorded for Dorra cultivar with Magiko treatment. Accordingly, the influence of magnetic and electromagnetic treatment of irrigation water on soil and tomatoes depends on the choice of tomato cultivar and increases with the following trends: Magiko < Deltawater < GMX < Magnolith < Aqua 4-D. Likewise, their influence depends on their field intensity, which increases in the trend of: 1.6 T < 1.4T < 1.2T < 0.62T < 0.0043T, suggesting that the performance of each device increases as magnetic field intensity decreases. This study highlights that an electromagnetic device (Aqua 4-D) with a weak field intensity (<0.5mT) could also have similar effects to that of a magnetic device (Magnolith). [ABSTRACT FROM AUTHOR]

It was found that it is sufficient to have the values of magnetic susceptibility X of a disperse sample containing ferroparticles to obtain the values of magnetic susceptibility Xч of its particles (particularly, in solving many scientific applied tasks of magnetic control and/or magnetophoresis of such particles). It is important that the values of volume fraction (concentration) γ of the ferroparticles be low (feasible), when simple dependence is acceptable for determining Xч values: Xч = X/γ. The question of the criterion value of γ is considered (it is still a discussion question). This value is up to γ=0.02-0.05 (this is evaluated data existing for a long time) for magnetite samples and even up to γ=0.2-0.25 (circumstantial evidence - by determining the demagnetization factor of disperse ferromagnetic samples). Direct experiments based on the ponderomotive Faraday method are realized with the use of a powder sample within the range of volume fraction γ ≤ 0.3 (for disperse phase - magnetite). The results of the experiments show that the linear part of X(γ) relation ends at γ 0.2. This is confirmed by many other consolidate data obtained by using disperse samples of magnetite (powder, colloid). However, at lower values of γ (γ ≤ 0.02-0.05) “individual” linear relation between X and γ is found as the consolidate data show. Taking into account the proportionality coefficient this relation differs from the previous relation by about 18%. This means that it is appropriate to use X values obtained at γ ≤ 0.02-0.05 for obtaining more accurate values of Xч.

Abstract We studied four marine sediment records of the Matuyama–Brunhes geomagnetic reversal from four sites located in the Indian, Atlantic and western Pacific oceans. The results combine paleomagnetic, cosmogenic nuclide beryllium (10Be) and oxygen isotope analyses that were performed on the same samples in order to avoid any stratigraphic bias. The three records from the equatorial Indian Ocean and North Atlantic Ocean did not reveal any offset between the authigenic 10Be/9Be ratio (Be-ratio) peak and the interval of low relative paleointensity (RPI) that characterizes the reversal. The lower and upper limits of transitional directions are also concomitant with the increased atmospheric 10Be production that accompanied the geomagnetic dipole intensity decrease. In contrast, the record from western equatorial Pacific Ocean sediments was found 18 cm below the Be-ratio changes as a result of late magnetization acquisition. At all four sites, maximum 10Be production occurred at the same period soon after the maximum of Marine Isotope Stage 19 (MIS 19) and, therefore, indicates its synchronous worldwide character. Such features are effectively observed from the Be-ratio signals and their relationship with the magnetic transition interval, which further confirms the synchronous character of the transition. Taking all dating uncertainties (1.6 ka between sites and 5 ka for the age model) into consideration, our records suggest a mean reversal age of 772.4 ± 6.6 ka. The age of the transition in the Atlantic Ocean record is closer to 774 ka but this difference is within the limit of significance. Highlights • We present Be-ratio, paleomagnetic and δ 18 O records of four marine cores across the B/M reversal. • The maximum of 10Be production occurs soon after the maximum of Marine Isotope Stage 19. • Our astronomical age model indicates that the reversal occurred at 772.4 ± 6.6 ka. [ABSTRACT FROM AUTHOR]

N this article influence is investigated on distribution of radio waves in the municipal terms of height and building closeness. A model over of distribution of radio waves is brought from an aircraft side. Charts over of dependence of probability of arrival of signal are brought from airship from the height of flight and middle number of building.

For problem of low accuracy of current prediction of field intensity in mine tunnel, a prediction model based on the least squares support vector machine method was proposed to predict the field intensity in mine tunnel by taking measured data of a tunnel as training sample. Influence of training set construction and parameters selection on prediction effect were analyzed in details. The simulation results show that the LS-SVM prediction model has higher prediction accuracy than dual-slope model and logarithmic correction model.

Data of a magnetic susceptibility of ferro-and the ferrimagnetic particles of many technogenic, natural, special media are especially demanded for the solution of various tasks connected with purposeful magnetic impact on these particles. One of productive approaches to definition of a magnetic susceptibility χ of these particles consists in receiving experimental data of a susceptibility of disperse samples 〈 χ 〉 with a disperse phase of these particles. The paper expounds and analyses the results of experiments on defining (by Faraday method in a magnetic field with intensity H = 90–730 kA / m ) the magnetic susceptibility 〈 χ 〉 of disperse samples (conglomerates) with a given volume ratio γ of magnetite particles ( γ = 0.0065–0.25). The corresponding families of concentration and field dependences are provided alongside with discussing the applicability of linear and exponential functions to describe these dependences. We consider the possibility of defining single particles susceptibility χ (with simultaneous obtaining field dependence of this susceptibility) by the commonly used relation χ = 〈 χ 〉 / γ both at relatively small (preferable for accuracy reasons) values γ – to γ = 0.02…0.025, as well as at increased values γ – up to γ = 0.25. The data χ are provided depending on H and correlating with known data at H < 90 kA / m ; they are obtained at small values γ when with almost double distance between the neighbouring particles (in comparison with their proper dimensions) the mutual adverse (to determine valid data χ )magnetic impact of particles is practically excluded. The article also gives the data χ received at increased values γ with almost halved distance between the surfaces of the neighbouring particles. It is specified that in the studied (post-extreme) area of H both variants of obtained field dependences χ are functionally identical within the accuracy of a constant, and close to an exponential dependence χ ∼ 1/ H 0.75 . With the account for the defined here value of constant-multiplier (0.8), it provides the grounds for obtaining valid data χ , employing the results of measuring 〈 χ 〉 for conglomerates with not obligatory small values of γ . It is demonstrated that being obtained by data χ, the calculated field dependence of the particle matter magnetic susceptibility χm (for the case when the particles are traditionally likened to balls with the characteristic for them demagnetising factor equalling 1/3) complies with the anticipated inverse function χm ∼ 1/H in the studied area H (where magnetization M expressed as M = χH reaches saturation M = Const). [ABSTRACT FROM AUTHOR]