Low-frequency Electromagnetic Radiation Research Articles

Електромагнітна небезпека електро- і гібридного транспорту

The purpose of the article is to determine the impact of electromagnetic radiation from electric vehicles. Hybrid and electric cars emit extremely low-frequency electromagnetic radiation (EMR) or magnetic fields. Studies of EMF levels emitted by cars show that they pose a threat to human health. Measurements of the magnetic induction of internal combustion engine cars, electric cars, and hybrid cars confirm that the magnetic field induction of an electric car is twice as high as that of an internal combustion engine car and does not depend on the speed of movement. The magnetic field induction of a hybrid car is greater than that of an electric car and tends to depend on the speed of movement. The magnetic field induction during external charging of an electric vehicle in the cabin is much lower than when driving. The average value of magnetic field induction in the interior of an electric vehicle is 0.85 ± 0.18 μT; Coverage factor K = 2 at a confidence level of P = 0.95. The magnetic field induction of an electric vehicle is twice as high as that of a car with an internal combustion engine and does not depend on the speed of movement. The average value of magnetic field induction in the interior of a hybrid car is 1.28 ± 0.61 μT; Coverage factor K = 2 at a confidence level of P=0.95. The magnetic field induction of a hybrid car is higher than that of an electric car and tends to depend on the speed of movement.The conducted studies show that electrical equipment in electric vehicles and, in particular, in an electric car and a hybrid car is a source of alternating EMF with strong temporal and spatial heterogeneity in the frequency range from 0 to hundreds of megahertz. This is due to the fact that the MF in an electric vehicle and a hybrid car is a superposition of fields from many sources. The direct sources of MF in electric vehicles are traction motors, rechargeable traction batteries, current-carrying elements, various electrical equipment, such as starting and braking resistance, group switches, rheostat units, electrical circuits for ventilation, lighting, heating, etc. Electronic devices on board are usually higher-frequency than MFs due to changes in the driving mode of electric and hybrid vehicles.

ВПЛИВ НИЗЬКОЧАСТОТНОГО ЕЛЕКТРОМАГНІТНОГО ВИПРОМІНЮВАННЯ НА СИСТЕМУ КОМПЛЕМЕНТУ (ЕКСПЕРИМЕНТАЛЬНЕ ДОСЛІДЖЕННЯ)

Abstract. The article presents the data of an experimental study on determining the state of the complement system under the conditions of exposure to low-frequency electromagnetic radiation (EMR) on the body of rats under the conditions of a subacute experiment. The relevance of the research is dictated by the fact that low-frequency EMR can change the membrane potential and disrupt nerve cell conduction. This can primarily affect the functioning of the hypothalamic-pituitary-adrenal system, which also influences the effectiveness of the immune system functioning. In the conditions of the natural experiment, male rats were exposed to radiation of 600 V/m with a frequency of 70 kHz for 4 hours every day for 30 days. The studies of immunological indices were carried out in the dynamics of the experiment on the 5th, 15th and 30th days. The study showed that under conditions of 30-day exposure to low-frequency EMR, the humoral link of immunity was characterized by suppression of the C4 component in the first half of the study, followed by a compensatory increase in the C4, C5 components. It has been proven that the general effector reactions of activation of the complement system are able to influence the functions of lymphocytes and macrophages. Thus, under the conditions of an anthropogenic factor, a flexible adaptation process takes place in the body of rats, which involves the redistribution of protein functions for the purpose of "economic" functioning of the body under the conditions of stressor action.

Effects of high–low-frequency electromagnetic radiation on vibrational resonance in FitzHugh–Nagumo neuronal systems

Effects of high–low-frequency electromagnetic radiation on vibrational resonance in FitzHugh–Nagumo neuronal systems

Extremely Low Frequency Electromagnetic Field Radiation (50 Hz, 200 µT & 300 µT) to Increase Edamame Productivity and Safety Risks to Health

More and more research results report that exposure to Extremely Low Frequency (ELF) magnetic fields at low intensity can increase cell proliferation. The ELF magnetic field interacts directly with cell membranes, capable of increasing intracellular calcium and under certain conditions affecting cell proliferation. This study wanted to prove the potential of ELF magnetic field radiation with intensity of 200 µT and 300 µT on edamame productivity. The research design used a completely randomized design. The research sample was 250 edamame soybeans of the Ryokkoh-75 variety which were divided into 5 groups. Samples were soaked in warm water for 3 hours and then cured for about 12 hours and exposed to ELF magnetic fields of intensity of 200 µT and 300 µT with variations in exposure time of 60 minutes and 120 minutes. Then it is seeded and planted in the field. Observation of the number of edamame pods and the number of pods was carried out when they were already fruiting, namely day 29 to day 43. The results of the study proved that the number of pods and the number of edamame pods in the group exposed to the 200 µT and 300 µT ELF magnetic fields was higher than the control. It appears that the highest number of fruits and pods occurred in the sample group exposed to the ELF magnetic field intensity of 300 µT. The conclusion is that exposure to the ELF magnetic field intensity of 300 µT has the potential to increase edamame productivity

Effects of Low-Frequency Randomly Polarized Electromagnetic Radiation, as Revealed upon Swelling of Polymer Membrane in Water with Different Isotopic Compositions.

Photoluminescence from the surface of Nafion polymer membrane upon swelling in water under irradiation by electromagnetic waves at a frequency of 100 MHz was studied. In these experiments, natural deionized (DI) water with a deuterium content of 157 ppm and deuterium-depleted water (DDW, deuterium content is 1 ppm) were explored. We have studied for the first time the effect of linearly and randomly polarized low-frequency electromagnetic radiation on the luminescence excitation. To obtain low-frequency electromagnetic radiation with random polarizations, anisotropic solid submicron-sized particles, which result in depolarization effects upon scattering of the initially linearly polarized radiation, were used. We compared two types of colloidal particles: spherically symmetric (isotropic) and elongated (anisotropic). If the radiation is linearly polarized, the intensity of luminescence from the Nafion surface decreases exponentially as the polymer is soaked, and such a behavior is observed both in natural DI water and DDW. When spherically symmetric submicron-sized particles are added to a liquid sample, the luminescence intensity also decreases exponentially upon swelling in both natural DI water and DDW. At the same time, when anisotropic submicron-sized particles are added to DI water, random jumps in the luminescence intensity appear during swelling. At the same time, the exponential decrease in the luminescence intensity is retained upon swelling in DDW. A qualitative theoretical model for the occurrence of random jumps in the luminescence intensity is presented.

Characteristic identification of seismogenic electromagnetic anomalies based on station electromagnetic impedance

The main components of seismo-electromagnetic research are the deep underground electromagnetic seismogenic environment, electromagnetic field changes at different stages of the seismogenic process, and the physical mechanism and change rules of electromagnetic properties of the earth’s interior. Traditional electric and magnetic methods mainly analyze the single field change of the geoelectric field, geomagnetic field, or resistivity at frequencies less than 1 Hz. These do not include the extremely low-frequency band that is sensitive to seismic events, so it is difficult to obtain the characteristics of time-spatial variations and propagation characteristics precursors. In comparison, magnetotelluric stations observe magnetotelluric fields containing seismogenic-induced electromagnetic disturbances, and the observation frequency band is wide. In this paper, the three-dimensional numerical simulation method is used to calculate the magnetotelluric apparent resistivity anomaly generated by resistivity changes in the seismogenic zone, and the forward algorithm of arbitrarily orientated dipole source in layered earth is used to simulate the response of low-frequency pre-earthquake electromagnetic radiation. The magnetotelluric response including seismogenic resistivity anomaly and pre-earthquake electromagnetic radiation is obtained using the field component composition method. The frequency characteristics and spatial distribution characteristics of apparent resistivity anomalies are systematically analyzed, and the results are of important significance for the observation, data processing, and identification and analysis of seismic electromagnetic anomalies in different seismogenic processes.

Effect of extremely low-frequency electromagnetic radiation on pregnancy outcome: A meta-analysis.

Extremely low-frequency electromagnetic radiation (ELF-EMF) are generated by electrical devices and power systems (1 to 300 Hz). Although several studies have demonstrated that ELF-EMF may beassociated with an increased risk of adverse pregnancy outcomes, other studies have shown no evidence of associations. This meta-analysis was conducted to assess the effect of extremely low frequency electromagnetic radiation on pregnancy outcomes. The following electronic bibliographic databases were searched to identify relevant studies: PubMed, Web Of Science, Cochrane library, Embase, EBSCO. In addition, the manual retrieval of relevant references was conducted as a supplement. Select all eligible studies published from Database construction library to March 10, 2021. Search type for queue research on influence of electromagnetic field radiation on pregnancy results. Data were screened and extracted independently by two researchers. Review Manager 5.3 software was used for the meta-analysis. There was no significant increase in the risk of miscarriage, stillbirth, birth defects and preterm delivery in the pregnant women who lived near the electromagnetic fields compared with the control group. Conclusions: No correlation has been found between maternal ELF-EMF exposure and miscarriage, stillbirth, neonatal birth defects and preterm delivery, while the effects on small gestational age and low birth weight are still uncertain. Related research with high-quality large samples and different regions are still needed for further verification.

ИССЛЕДОВАНИЕ ЭЛЕКТРОМАГНИТНОГО ФОНА НА АНТАРКТИЧЕСКОЙ СТАНЦИИ «ВОСТОК»

The electromagnetic background was measured in living quarters of station «Vostok» located on the Antarctic plateau distant from potential sources of technogenic electromagnetic fields. Level of E-radiation in the range from 0.8 to 8 GHz was determined using integral dosimeter MERA. Based on the results of long-term continuous (one to 4 months) measurements, the mean flux density was equal to 1.5 ± 0.8 nwatts/cm2 that is nearly 7 000 times lower than the admissible level for population adopted in Russia. Antarctic station «Vostok» can be considered as a plausible location of biomedical investigations into the effects of low-frequency electromagnetic radiation.

Emotional and behavioral attitudes of Tunisian youth towards childhood leukemia: health education and primary prevention in perspective

BackgroundGiven the increasing blood cancer incidence in Tunisia and recent discoveries proving the involvement of environmental factors, this study examined the environmental health literacy (EHL) of Tunisian secondary school students concerning not only this disease, but also their emotional and behavioral attitudes towards leukemia risks.MethodsA cross-sectional survey was conducted among Tunisian youths (N = 372, 16–20 years; 68% females, 32% males). Data collection took place in four representative public secondary schools in the North, Center, and South of Tunisia. Students completed a paper and pencil questionnaire and described their EHL level of blood cancer, as well as their attitudes and interests in this disease. The statistical software (SPSS, v.25.0) was used to analyze the data collected.ResultsThe results indicated low EHL levels of leukemia. Most youths failed to identify all the leukemogenic (except tobacco and pollution) and non- leukemogenic risk factors. Pesticide use and exposure to low frequency electromagnetic radiation were not considered risk factors. Proximity to heavy-traffic roads and benzene exposure were not perceived by youth as risk factors. Despite these low levels, most participants were interested in having more information about leukemia and cancers in general.ConclusionThis investigation shows a lack of knowledge about leukemia. Low EHL levels will incite educational actors and curriculum designers to optimize content and innovate ICT adapted to this environmental health challenge.

Differentiating between artificial and natural sources of electromagnetic radiation at a seismogenic fault

Ultralow frequency (ULF) to low frequency (LF) electromagnetic radiation represents one of the most promising effects of brittle rock strain and microcracking that might be potentially helpful for short term earthquake forecasting. In this study the results of a six month monitoring campaign are presented from Obir Cave in the eastern Alps. Direct experimental observations of electromagnetic radiation have been made using a customised broadband data logger installed next to the Obir Fault - this seismogenic fault near the Periadriatic Lineament is known to be related to at least three large prehistoric earthquakes. On the basis of these measurements it has been possible to characterise a number of distinct signals: artificial constant narrowband signals at discrete frequencies; short serial broadband impulses; high energy broadband impulses; and low energy broadband impulses. The narrowband artificial signals were removed from the electromagnetic radiation time series analysis so that the natural signals were enhanced and could be compared more easily to meteorological parameters and rock strain indicators. Critically, the high energy broadband impulses show a strong correlation with lightning activity across much of central Europe and the eastern Mediterranean while the low energy broadband impulses appear to be associated with local rock strain in and around Obir Cave. Unfortunately, it seems certain that some of the essential strain related impulses are likely to have been overprinted by the larger lightning related impulses.

Investigation of extremely low-frequency (1Hz-400kHz) pollution frequently encountered in social life: a case study of a shopping mall.

It is important to periodically measure, analyze, and map electromagnetic radiation levels due to potential risks. This study aims to draw attention to new electromagnetic pollution caused by radio frequencies and extremely low frequencies. For this reason, electric field and magnetic field measurements were carried out in the 1-Hz-400-kHz frequency band in a shopping mall, where electronic devices cause low-frequency electromagnetic radiation intensively. The measurements were performed with the EHP-50F device for 24h a day for a week. The measurements were made at 10 points in the shopping mall, and the measurement results were evaluated over five different sectors: electronics, clothing and accessories (male-female), personal care and cosmetics, supermarket, and the playland for children. Magnetic maps of each sector were produced. In addition, the specific absorption rates (SAR) of male and female customers in these workplaces were determined. This is the first study carried out to find SAR caused by low-frequency radiation. Although the safe limit value of SAR for the whole body is 0.08W/kg, the SAR values calculated in the playland and electronics sectors were obtained to be 0.763 and 0.39W/kg, respectively. Results clearly demonstrate how especially small children are exposed to danger in the long term.

Metal-organic framework-derived Co/CoO nanoparticles with tunable particle size for strong low-frequency microwave absorption in the S and C bands

Nowadays, constructing strong absorption materials addressing the low-frequency electromagnetic radiation (S and C bands) from electronic devices remains a significant challenge. In this work, size-tunable Co/CoO nanoparticles (NPs) are fabricated by decomposing zeolitic imidazolate framework (ZIF-67) precursors and subsequent hydrogen reduction. All samples show obvious low-frequency attenuation in the S and C bands. At a thin thickness of 2.3 mm, the minimum reflection loss (RL) value for the Co/CoO NPs of 30 nm reaches up to −90.3 dB at 4.4 GHz, and the corresponding effective absorption bandwidth (EAB) of RL ≤ −10 dB ranges from 3.8 to 5.4 GHz. Notably, 90 % of the electromagnetic waves can be absorbed in the frequency range of 2.3–13.2 GHz, covering almost the entire S, C, and X bands at a thickness of 1.0–4.0 mm. The strong low-frequency absorption performance is attributed to the nano-porous structure, high conduction loss, tunable dielectric/magnetic loss, as well as optimized impedance matching. These Co/CoO NPs are promising candidates for high-efficient microwave absorbers in the low-frequency application.

A Pursuit of Quantum Neuroscience’s Principles: Coherence Field Theory and the Physics of Mind

Some basic physics of burgeoning quantum neuroscience is described. Anatomy of the neuron suggests that nonsynaptic mechanisms of signal transmittance occur via electric current acceleration and companion electromagnetic field fluctuation. I have named this mechanism of solution chemistry the ebb effect. Phase-locking between neural structure and electric fields that are emergent from cellular EM field fluctuations, in addition to feedback loops within neural networks, are the probable driver of macroscopic oscillation and flow shapes in the brain. CEMI (conscious electromagnetic information) theory is a promising framework for explaining intentionality and the spectrum of arousal as EM field effects. Relatively low frequency electromagnetic radiation is emitted by the accelerating electric currents of neurons. It is hypothesized that this EM radiation superpositions with molecular structure as it spreads to comprise percepts, the hybrid wavelengths of which form subjective images while wavelength vibrations result in subjective feel. These superposition arrays are termed a coherence field, and in combination with the synchronizing influence of quantum entanglement and electromagnetic fluctuations may constitute much of awareness’ substance. If conclusively verified, coherence field theory should have significance ranging from the treatment of perceptual disorders such as anosognosia to advancing foundational constructs like atomic theory.

Low-Frequency Infra-red electromagnetic wave promotes partial nitrification by affecting the community signal system

Ammonia oxidizing bacteria (AOB) are susceptible to environmental factors and compete with nitrite oxidizing bacteria, which seriously limits the stability of partial nitrification (PN). This study investigated the potential of applying low-frequency infra-red electromagnetic radiation to enhance the PN process. The electromagnetic wave (EMW) was evaluated at different intensities, and 0.06 μT EMW was found most effective in enhancing the activity of AOB. The long-term experiment indicated that the application of 0.06 μT EMW shortened the start-up period from over 15 to 10 days, and exhibited more stable to loading rate variation. Through the analysis of the microbial community composition, it was found that Nitrosomonas increased from 0.1% of inoculated sludge to 3.0% of the control reactor and 4.6% of EMW treated reactor. PN metabolic pathway was analyzed through metagenomics sequencing, and a model in which EWM promoted PN activity by affecting the community signal system was proposed: EWM increased the expression of specific genes through a two-component regulatory system and increased the activity of related enzymes by serine-threonine protein kinase. These findings implies that suitable EMW irradiation is efficient and economical for enhancing AOB activity and conducive for rapid start-up and stability of the PN process.

Optimization of the Emitting Coil of a Hardware-Software Complex for Study of Low-Frequency Electromagnetic Radiation’s Shielding Effectiveness

Optimization of the radiation coil of the hardware-software complex for studying the effectiveness of shielding of low-frequency electromagnetic radiation will make it possible to assess the effectiveness of shielding coatings at a higher level. This fact will make it possible to develop coatings with improved characteristics. The purpose of this work was to determine the optimal characteristics of the emitting coil which will ensure its stable operation and magnetic field strength in the frequency range up to 100 kHz.The parameters of the manufactured samples, such as inductance (L), active (R) and total resistance (Z), were obtained using an MNIPI E7-20 emittance meter. In practice, the coils with the optimal parameters calculated theoretically were connected to a current source and amplifier. To detect electromagnetic radiation, a multilayer inductor connected to a UTB-TREND 722-050-5 oscilloscope was used as a signal receiver.The results of measurements showed that the resistance of multilayer coils is approximately 1000 times higher than that of single-layer coils. Also, for multilayer coils, an avalanche-like increase in total resistance is observed starting from a frequency of 10 kHz, while for single-layer coils there is a uniform increase in total resistance over the entire frequency range up to 100 kHz.The paper presents results of research on the correlation of the performance of single-layer and multilayer inductors depending on their parameters in the frequency range from 20 Hz to 100 kHz. Values of the voltage required to provide the magnetic field strength of 1, 5, 20 Oe at 25 Hz and 100 kHz have been calculated. After analyzing the data obtained, the optimal parameters of the inductor were found which ensure stable performance in the frequency range up to 100 kHz.

Does air ionization by radon cause low-frequency atmospheric electromagnetic earthquake precursors?

The aim of this work is to study the relationship between the pre-earthquake emissions of radon and ULF/ELF (1–30 Hz) atmospheric electromagnetic radiation. The problem is considered on the example of the 2011 Tohoku earthquake. Radon, ionizing air, creates ions—centers of condensation of water vapor. As a result of condensation, heat is generated. It results in growth of air temperature and decrease in its humidity. This phenomenon serves as an indicator of air ionization. We used data from 20 Japan Meteorological Agency (JMA) weather stations located on Honshu Island to estimate any changes in temperature and humidity over ± 20 days from the date of the main shock. At the same time, we monitored the intensity and location of the source of ULF/ELF radiation using three induction magnetometers belonging to Chubu University. We compared the times and locations of observed signs of ionization and electromagnetic radiation to find out their relationship. It turned out that they are independent, since their dates and localizations do not match. In addition, we found intense ionization of the air after March 11 over a large area of Honshu Island, caused by radiative radiation from the nuclear disaster at the Fukushima Daiichi nuclear power plant. However, this phenomenon did not cause low-frequency atmospheric electromagnetic radiation either. These suggest that there is no direct relationship between air ionization and ULF/ELF radiation. This is true at least for this case, given the island nature of the land and oceanic EQs.

ISOLATION AND CHARACTERIZATION OF HIGH AMBIENT ELECTROMAGNETIC RADIATION (EMR) BACTERIA

Low-frequency electromagnetic radiation (EMR) exists in our environment and remain unnoticeable. Studies show that EMR exposure may affect human health, animal, plants, and also living microorganisms. Therefore, this study intended to isolate, identify, and characterize bacteria exposed to high ambient EMR as well as to determine the viability and mutagenicity of bacteria exposed to different frequencies. The bacterial samples were collected from two areas with high and low electric field strengths; Universiti Malaysia Terengganu (UMT) hostel (0.14 V/M) and near Lake of UniSZA (Universiti Sultan Zainal Abidin) (0.03 V/M). The bacteria were identified and characterized by several methods. The viability and mutagenicity of each bacterial species were determined by counting the number of colonies formed in the enriched (standard) and minimal media after exposure of 10 MHz and 5 GHz frequencies. The results show that Enterobacter sp., which was isolated in UMT hostel, exhibited non-mutagenic and increased viability after 24 hr of exposure to both EMR frequencies of 10 MHz and 5 GHz. Thus, this bacterial species should be further studied since it has the potential as a bioremediator.

LOGARITHMIC AMPLIFIERS FOR SOFTWARE HARDWARE MAGNETIC TRACKING SYSTEMS

The work deals with the problem of signal conversion in magnetic tracking devices. Magnetic tracking technology is based on computing the spatial position of an object being tracked upon measuring reference magnetic fields in low-frequency electromagnetic radiation spectrum. Magnetic tracking devices are key components of navigation sensors for virtual and augmented reality. It has been shown that the main problem one faces when developing sensory devices for magnetic tracking is the fact that signals should be measured in a wide measurement range. We have analyzed possible ways to solve the stated problem by digital and combined methods. The latter have proven to be more efficient. They consist in signal amplification due to analog compression, which is performed by logarithmic amplifiers whose negative feedback circuits contain components with non-linear volt-ampere characteristics (typically, diodes or bipo- lar transistors are used). It has been shown that the parameters of logarithmic signal compression can be controlled by modified circuits with auxiliary resistance dividers. The resistance dividers scale the logarithmic volt-ampere characteristics of emitter p-n junctions of bipolar n-p-n and p-n-p transistors. A substantial advantage of circuits with resistance dividers is that they provide the possibility to expand the range of the output voltage of logarithmic amplifiers and optimize the transition between the linear and logarithmic amplification regions. The work presents the results of simulation and experimental investigations into a logarithmic amplifier for a magnetic tracking system. Simulation was carried out using SPICE (Simulation Program with Integrated Circuit Emphasis) models. We applied an integrated approach,which provides collections of transient characteristics of logarithmic amplifiers at different sets of the parameters of resistance dividers. The simulation results have been verified using our own software- firmware magnetic tracking tools – Magnetic Tracking System Integrated Development Environment. The signal converter was built upon a programmable system-on-chip PSoC 5LP by Cypress Semiconductor.

A three-axis antenna to measure near-field low-frequency electromagnetic radiation generated from rock fracture

In general, the generation of electromagnetic radiation initiates with the evolution of the crack in a rockmass. Theoretical observations depict that the low-frequency electromagnetic field excited by a dipole on cracks are directional in the near-field range. Therefore, in this paper, to achieve the measurement of low-frequency near-field, an electromagnetic antenna capabale of simultaneously measuring in directions of three axes is designed. After calibration of the standard alternating field, the antenna is used to monitor electromagnetic signals generated during the uniaxial compression and the Brazilian test. For the same fracture, signals differ in directions at the same position, which are actually components in three coordinate directions. And the three-axis antenna is relatively advantageous in response to low-frequency signals compared with the wide-band loop antenna. The outcomes of this research can provide theoretical as well as a practical basis for characterizing electromagnetic radiations associated with rock fractures.

Early-warning of rock burst in coal mine by low-frequency electromagnetic radiation

Rock burst is one of the major geological hazards in coal mines and is difficult to prevent. Faced with this problem, the low-frequency electromagnetic radiation (EMR) test experiments of coal and rock were conducted to explore the characteristics of low-frequency EMR (1 kHz) signals induced form fractures. The relation between EMR signals and paroxysmal fractures was analyzed theoretically. Time-series extraction method was put forward to represent coal and rock paroxysmal fractures. The research results showed that deformation and fracture of coal and rock is caused by the accumulation of paroxysmal and discrete fractures in the samples. The time series obtained by moving average method shows rather good correlation with interior coal rock fractures, which has more obvious precursory characteristics of coal rock instability and dynamic disasters. When the coal rocks are damaged under uniaxial compression, low-frequency EMR (1 kHz) signals are more sensitive to local fracture with more abundant precursor information than high-frequency EMR (500 kHz) signals. The paroxysmal and discrete low-frequency EMR (1 kHz) signal is quite sensitive to rock burst, and when the signals representing coal rock fractures show an increasing trend and the high signals last for some time, it can be regarded as the precursor of rock burst disaster in coal mine. The separation technology of EMR representing coal rock fractures provided the key scientific basis for the field monitoring and forewarning of EMR technology, and a new method to identify the precursor of dynamic disasters of coal and rock.