Dependence the Integrated Energy of the Electromagnetic Response from Excitation Pulse Duration for Epoxy Samples With Sand Filler

Results of research of influence of the excitation pulse duration on the parameters of the electromagnetic response of epoxy samples with filler the quartz sand presented in the paper. The electric component of a response was registered by the capacitive sensors using a differential amplifier. Measurements were carried out at two frequencies of the master generator of 65 kHz and 74 kHz. The pulse duration was changing from 10 to 100 microseconds. The stepped sort of dependence of the integrated oscillations energy in the response from duration of the excitation pulse was discovered. The conclusion was made about the determining role of the normal oscillations in formation of such dependence

TG study of the Li[0.4]Fe[2.4]Zn[0.2]O[4] ferrite synthesis

In this paper, the kinetic analysis of Li-Zn ferrite synthesis was studied using thermogravimetry (TG) method through the simultaneous application of non-linear regression to several measurements run at different heating rates (multivariate non-linear regression). Using TG-curves obtained for the four heating rates and Netzsch Thermokinetics software package, the kinetic models with minimal adjustable parameters were selected to quantitatively describe the reaction of Li-Zn ferrite synthesis. It was shown that the experimental TG-curves clearly suggest a two-step process for the ferrite synthesis and therefore a model-fitting kinetic analysis based on multivariate non-linear regressions was conducted. The complex reaction was described by a two-step reaction scheme consisting of sequential reaction steps. It is established that the best results were obtained using the Yander three-dimensional diffusion model at the first stage and Ginstling-Bronstein model at the second step. The kinetic parameters for lithium-zinc ferrite synthesis reaction were found and discussed

Determining the effect of the duration of alternating acoustic excitation on electromagnetic response parameters of the composite

The paper presents the results of the experimental investigation dealing with the effect of the alternating excitation acoustic pulse duration on the parameters of the electromagnetic emission caused by interaction of acoustic vibrations with inhomogeneities in the sample structure, piezoelectric inclusions and media interfaces of different dielectric properties. The model sample was epoxy resin with quartz sand as filler. The electrical component of the response was recorded with a capacitive transducer. The acoustic pulse was generated by piezoelectric transducer at frequencies of 57 kHz, 65 kHz, 74 kHz, 87.5 kHz and 94.5 kHz with the pulse duration varying from 10 ?s to 100 ?s. It is shown that the reduced duration of the acoustic action leads to dominance of the intrinsic frequency in the spectrum. A contribution of tensile pulses to acoustic electromagnetic transformation response generation is revealed

Processing line for industrial radiation-thermal synthesis of doped lithium ferrite powders

The paper considers the issues of industrial production of doped lithium ferrite powders by radiation-thermal method. A technological scheme of the processing line is suggested. The radiation-thermal technological scheme enables production of powders with technical characteristics close to the required ones under relatively low temperature annealing conditions without intermediate mixing. The optimal conditions of the radiation-thermal synthesis are achieved isothermally under irradiation by the electron beam with energy of 2.5 MeV in the temperature range of 700-750 °С within~ 120 min

The Relationship Between the Parameters of the Electric and the Acoustic Signal with the Destruction of Concrete Under Cyclic Freeze-Thaw

The paper presents the research results of the effect of formation crack process on the parameters of the electric and acoustic response to impact excitation. The physical basis of mechanoelectric transformations is described. It was found that with increasing number of freeze-thaw cycles observed increase of the attenuation coefficient of energy of the electric and acoustic response by a linear relationship. Differences in the dynamics of change of attenuation coefficient of energy of the electric and acoustic response associated with differences in formation and registration of electric and acoustic response

Modeling of radiative - conductive heat transfer in compositing materials

A layer of composite material is investigated, which is heated one-sidedly with one-dimensional energy transfer accounting for thermal conductivity and radiation. A mathematical model is suggested for non-stationary coefficient thermophysical problem under radiative-conductive heat transfer in a material layer. Temperature dependencies of thermal capacity and thermal conductivity coefficient of composite radio-transparent material have been determined through numerical modeling by solving the coefficient reverse problem of thermal conductivity

THE ESTIMATION OF RISK FOR DEVELOPMENT OF DISEASES DUE TO WHOLE-BODY VIBRATION EXPOSURE IN THE WORKERS OF TURBINE SHOPS OF THERMAL POWER STATIONS

The estimation of risk for development of diseases due to whole body vibration exposure on the basis of spectral characteristics at the workplaces in turbine shops of thermal power stations was carried out. The highest average equivalent levels of whole-body vibration by speeding up of vibration and. vibration velocity were observed at the workplaces of turbine machinists of Kuznetsk Thermal Power Station and. the Western-Siberian Thermal Power Station; in the machinists-inspectors of turbine equipment the indicators were a little bit lower. At the workplaces of turbine machinists the highest levels of risk for backache in the lower part and autonomic sensory polyneuropathy syndromes development were registered at the Western-Siberian Thermal Power Station and the Southern-Kuzbass Thermal Power Station, little smaller indicators were observed at Tom-Usinsk Thermal Power Station and Kuznetsk Thermal Power Station

SPECTRAL CHARACTERISTICS OF NOISE IN THE WORKERS OF MAIN DEPARTMENTS OF THE ENTERPRISES OF ALUMINIUM AND THERMAL POWER INDUSTRIES

The study of the spectral characteristics of noise levels in the workers of main departments of the enterprises of aluminium and thermal power industries had shown that equivalent sound levels in electrolysis shops at the workplaces of those engaged in electrolysis and anodic production exceeded permissible indicators on 7,1 and 11,8 dBA; in boiler shops of a thermal power station at the workplaces of boiler machinists, machinists-inspectors of boiler equipment and mill machinists the excess in permissible indicators was 22,2 dBA, 21,4 dBA and 29,3 dBA accordingly. It was established that noise in boiler and turbine shops of a thermal power station was broadband and exceeded maximum permissible values in all parts of a spectrum. In the turbine shops of a thermal power station noise levels more often exceeded maximum permissible levels in low- and high-frequency parts of a spectrum

Determination of the probability of the damage to the health of workers in aluminium production due to the exposure to toxic substances

In the electrolytic aluminium production fluorides in the form of hydrogen fluoride and solid fluorides, alumina-containing dust, carbon monoxide, resinous substances and benz(a)pyrene are released into the air of the working zone representing a hazard to the workers' health. The paper presents the results of the researches of the working conditions of the workers employed in the electrolytic aluminium production. The concentrations of toxic substances in the air of working areas of those engaged in anode works and electrolysis, and crane operators are given; on their basis the risks of occupational diseases (fluorosis), of acute toxic effects, of chronic intoxication, and of cancer are calculated. The average-shift concentrations of hydrogen fluoride in the air of working areas of those engaged in electrolysis are 0.40-0.46 MPC, soluble fluorine salts - 0.31-0.38 MPC, insoluble fluorine salts -0.08-0.09 MPC. In the air of the working areas of those engaged in anode works MPC excess is noted for the aerosols of mostly fibrogenic action - in 1.25 times, for resinous substances - in 1.10 times. In the air of the working areas of those engaged in electrolysis MPC excess for resinous substances is registered in 1.06 times. The average-shift concentration of insoluble fluorine salts, and carbon monoxide in the air of the working areas of those engaged in anode works and electrolysis and crane operators are within the MPC. The risk of occupational disease development (fluorosis) due to the air pollution of the working zone in the aluminium production for the workers of the major occupational groups is ranging from 0.045 to 0.0482. Hydrogen fluoride is the most hazardous contaminant in air of the working zone contributing more than 55 % to the risk of fluorosis. The risk of acute toxic effects for the workers of the major occupational groups associated with the achievement of the concentrations of the contaminants in the air of the working areas of their maximum values are ranging from 0.181 to 0.230

LEDs based upon AlGaInP heterostructures with multiple quantum wells: comparison of fast neutrons and gammaquanta irradiation

The paper presents the research results of watt and volt characteristics of LEDs based upon AlGaInP heterostructures with multiple quantum wells in the active region. The research is completed for LEDs (emission wavelengths 624 nm and 590 nm) under irradiation by fast neutron and gamma-quanta in passive powering mode. Watt-voltage characteristics in the average and high electron injection areas are described as a power function of the operating voltage. It has been revealed that the LEDs transition from average electron injection area to high electron injection area occurs by overcoming the transition area. It disappears as it get closer to the limit result of the irradiation LEDs that is low electron injection mode in the entire supply voltage range. It has been established that the gamma radiation facilitates initial defects restructuring only 42% compared to 100% when irradiation is performed by fast neutrons. Ratio between measured on the boundary between low and average electron injection areas current value and the contribution magnitude of the first stage LEDs emissive power reducing is established. It is allows to predict LEDs resistance to irradiation by fast neutrons and gamma rays