Studying electromagnetic interference spectrum in antenna under aircraft radome using models with artificial charged aerosol clouds

The spectrum of electromagnetic interference that is induced by discharges in an antenna arranged under an aircraft radome in an artificial charged aqueous aerosol cloud has been experimentally studied. It is established that, among different possible variants of lightning-arrest radomes, the minimum level of the spectral density of interference signals in the antenna is provided by vertical stripe electrodes on the radome surface. The maximum characteristic frequencies of signals in a model spherical antenna are several times lower than those in model lightning diverters, while the flat model antennas of disk or rectangular shapes exhibit the opposite trend. It has been suggested that a significant role in determining the characteristics of the electromagnetic interference spectrum in weather radar antennas is played by currents of discharges generated by charges accumulated on the dielectric radome surface.     

Experimental study of the effect of artificial charged aqueous aerosol cloud on model aircraft radome

The effect of artificial clouds of strongly charged aqueous aerosol on model aircraft radomes has been experimentally studied. It is established that the character of discharge development in the “charged aerosol cloud-inner electrode under model radome” gap significantly differs from that observed in the absence of the model radome. The presence of the dielectric radome in the gap between charged cloud and ground can lead to the phenomenon of reversal of the polarity of discharge current from the electrode (modeling antenna). Dependence of the discharge development and its characteristics on the size (volume) of space under radome has been studied. Possible physical mechanisms involved in the interaction of lightning discharges and thunderstorm clouds with radiotrasparent aircraft radomes and equipment arranged inside are considered.     

Effect of model hydrometeors on the development of discharge from an artificial cloud of charged aqueous aerosol

The process of discharge initiation and propagation in clouds of a charged aqueous aerosol in the presence of coarse model hydrometeors has been experimentally studied. It is established that the development of a spark discharge in the gap between a charged aqueous aerosol cloud and a grounded plane depends on the parameters of hydrometeors, the site where a group of hydrometeors is situated, and the electric field strength. A group of conducting cylindrical model hydrometeors most effectively initiates a spark discharge between charged aqueous aerosol clouds. Optimum configurations of such a group for initiating and guiding a discharge are determined. Characteristics of the final stage of discharge from a charged aqueous aerosol cloud in the presence of model hydrometeors are analyzed.     

Universal response in liquid chromatography using charged aerosol detection

A new, empirical approach is introduced to correct for the varying response of aerosol-based detectors with the varying composition of the mobile phase during gradient elution in HPLC. A Corona charged aerosol detector was used in the experiments. The detector is characterized by a nearly universal response at a given, constant mobile-phase composition for sufficiently nonvolatile analytes. A second pump was used to deliver an exactly inverse gradient compared to the analytical HPLC system, and both flows were mixed in a tee piece before introduction to the Corona detector. The approach proposed made it possible to extend the universal response from isocratic to gradient elution conditions in HPLC, vastly improving the usefulness of this detection technique. The constant response of the detector obtained in this way was first demonstrated in flow injection analysis. Very similar calibration curves were obtained for six sulfonamide drugs after mobile-phase compensation. The approach was also applied to gradient elution with excellent results. The data were characterized by good precision ranging from 4% RSD at 10 mg/L to 1.6% RSD at 780 mg/L. The average limit of detection with a 2-microL injection was 0.5 mg/L, corresponding to 1 ng injected on the column. The approach proposed allows quantification of unknown compounds, e.g., in pharmaceutical mixtures. Measurement of analytes at a relative concentration of 0.05% versus the main component is demonstrated.     

Breakdown conduction in thin dielectric films: A bibliographical survey

Interest in the study of thin films has been greatly stimulated in recent years because of thier importance from the point of view of technological and industrial applications. A bibliographical survey limited mainly to breakdown conduction in thin films is presented here. To make the survey a more comprehensive and up-to-date source of information for the workers engaged in this field, the relevant references on some closely related fields, such as electrical conduction and switching phenomena, as well as on some other types of film systems and substances have also been included.The survey covers work published from 1960 onwards (few references appeared before then) and the references have been arranged in roughly chronological order together with the titles of the papers. In addition, a list of books, reviews and monographs has been given. The survey should also prove useful to assess the progress made by the scientific community in the field of breakdown conduction in thin dielectric films.     

Dynamics of a thick-walled dielectric elastomer spherical shell

The nonlinear vibration response of a thick-walled spherical shell subjected to the mechanical pressure and electric field is studied in this paper. When subject to an electric field through the thickness of the spherical shell, the material expands in plane and contracts in thickness. The dielectric elastomer is assumed to be isotropic and neo-Hookean. Based on simple geometrical and spherical capacitor assumptions, we deduce an explicit analytical equation of motion of the dielectric elastomer spherical shell. The dynamic behaviors of the spherical shell under a constant electric loading and periodic electric loading are analyzed. In addition, the critical voltage is calculated in terms of various loading.     

基于介电常数调制的曲面雷达罩蜂窝积水传感器设计

研制了一种基于介电常数调制的曲面雷达罩的蜂窝积水传感器。介电常数表示电介质在电场中贮存静电能的相对能力,而水的介电常数又远远大于空气和雷达罩材料的介电常数,因此可以利用介电常数调制法来检测雷达罩的蜂窝积水。为保证测试灵敏度,设计的传感器极板必须贴紧被测结构,而雷达罩外形决定了极板应该采用柔性的、可以贴合曲面的探头结构形状。采用多极片之间用铜条焊接的方法构成传感器探头,并利用ANSYS仿真分析对结构进行了设计优化。通过对蜂窝结构的曲面雷达罩积水实验验证,结果证明该传感器可以实现雷达罩蜂窝积水的检测,具有较高的测试灵敏度和重复性。     

Electrophoresis of a charged droplet in a dielectric liquid for droplet actuation

Electrophoretic motion of a charged droplet in a dielectric fluid under an electric field has been investigated experimentally for use as a microdroplet actuation method. The effects of the droplet size, electric field strength, and electrolyte concentration and ion species on the charging of an aqueous droplet have been examined. The amount of electrical charging has been measured by two different methods: indirect measurement using the image analysis of droplet motion and direct measurement using the electrometer. Quantitative comparison of the droplet charge measured experimentally and the theoretical value of a perfectly conductive sphere shows that an aqueous droplet is less charged than the corresponding perfectly conductive sphere. The limiting effect on electrical charging is more significant for an electrolyte droplet, and the effect is positively correlated to the electrolyte concentration rather than the ion species. This implies that the low electrical conductivity of water is not a major cause of the limiting effect. The scaling law of the charging amount for a deionized water droplet nearly follows that of the perfect conductor, whereas for an electrolyte droplet, the scaling law exponent is slightly higher. Some advantages and potentials of the current droplet actuation method are also discussed in comparison with the conventional ones.     

Stability of a charged bubble in a dielectric liquid against radial perturbations

It is shown that the critical conditions for instability of a charged vapor-gas bubble in a dielectric liquid against virtual radially symmetric volume perturbations are substantially less stringent than the critical conditions for it to be unstable against virtual distortions of the shape. Pis’ma Zh. Tekh. Fiz. 25, 25–29 (January 12, 1999)     

Parametric optimisation of composite shell structures for an aircraft Krueger flap

This paper details the conceptual design optimisation of the configuration and composite lay-ups used to replace the conventional honeycomb stiffened structure of a Krueger flap. The multiple composite laminates selected for redesigning the lay-ups within an initial symmetrical quasi-isotropic ply configuration of [0/45/−45/90]_s, had to demonstrate full orthotropic characteristics. In order to construct a numerical process to optimise the required multi-layered composite shells, a commercial finite element code, Ansys, was used to develop a parametric analysis file. This analysis subroutine was then integrated into an Ansys Parametric Design Language code embedding the objective of the optimisation process––mass minimisation––as well as all the constraints and the allowable domains of the parameters. The paper, in its conclusion, presents a comparison between the original product and the optimal design, and reviews the advantages of the future implementation of this design.     

Dispersion of a charged bubble in a liquid dielectric in a electrostatic field

It is predicted that the size and charge of daughter bubbles emitted in an electrostatic field from different tips of a charged parent bubble will differ. Pis’ma Zh. Tekh. Fiz. 24, 30–35 (December 26, 1998)     

Anomalous dielectric and optical properties in perovskite-type artificial superlattices

Perovskite-type BaTiO₃/SrTiO₃ (BTO/STO) artificial superlattices were fabricated by molecular beam epitaxy process and their dielectric properties and refractive indices were measured. A large leakage current was observed in the films on Nb-doped STO substrate. Dielectric permittivity was therefore measured using planer interdigital electrodes. Fine planer electrodes were necessary to reduce the penetration of electric flux into the substrate. Interdigital electrodes were formed by electron-beam lithography. Dielectric permittivity of superlattices along the film surface was determined using electromagnetic field analysis. It was found that the dielectric permittivity of the BTO/STO superlattice with the period of 10 unit cells showed a maximum value above 30,000, which was almost independent from frequency up to 110 MHz. The refractive index of superlattices measured with a spectroscopic ellipsometer also showed the highest value when the period was 10 unit cells. This indicated that the structure of superlattices affected not only the ionic polarization but also the electric polarization. The origin of anomalous properties observed in superlattices may be interpreted by the strains induced into the film.     

Anomalous dielectric and optical properties in perovskite-type artificial superlattices

Perovskite-type BaTiO₃/SrTiO₃ (BTO/STO) artificial superlattices were fabricated by molecular beam epitaxy process and their dielectric properties and refractive indices were measured. A large leakage current was observed in the films on Nb-doped STO substrate. Dielectric permittivity was therefore measured using planer interdigital electrodes. Fine planer electrodes were necessary to reduce the penetration of electric flux into the substrate. Interdigital electrodes were formed by electron-beam lithography. Dielectric permittivity of superlattices along the film surface was determined using electromagnetic field analysis. It was found that the dielectric permittivity of the BTO/STO superlattice with the period of 10 unit cells showed a maximum value above 30,000, which was almost independent from frequency up to 110 MHz. The refractive index of superlattices measured with a spectroscopic ellipsometer also showed the highest value when the period was 10 unit cells. This indicated that the structure of superlattices affected not only the ionic polarization but also the electric polarization. The origin of anomalous properties observed in superlattices may be interpreted by the strains induced into the film.     

Temperature dependence of dielectric permittivity of perovskite-type artificial superlattices

Perovskite-type BaTiO(3)/SrTiO(3) (BTO/STO) artificial superlattices were fabricated by the molecular beam epitaxy method. The X-Ray diffraction (XRD) profiles and reflection, high-energy, electron diffraction (RHEED) oscillations during the growth of superlattices indicated that crystalline orientation toward [001] direction and two-dimensional layer-by-layer growth were achieved. The capacitance, dielectric loss tangent, and complex admittance were measured up to 145 degrees C and up to the frequency of 100 MHz with the microplaner interdigital electrodes. Dielectric permittivity of superlattices was evaluated from the complex admittance with an electromagnetic field analysis as a function of temperature. The [BTO(10)/STO(10)](4) superlattice showed the enormous relative permittivity of 19,000 at room temperature and the dielectric relaxation was observed. The linear relations in the charge versus voltage curves were observed in these superlattices, and the shape of Q-V curves were not changed as a function of temperature. Temperature dependence of dielectric properties of the BTO/STO superlattices was evaluated. It was found that the BTO/STO superlattices did not show a peak in the dielectric permittivity versus temperature curve, which was different from the behavior of BTO-STO bulk ceramics and normal thin films. These results strongly supported that the high permittivity of the superlattices was caused by temperature-stable anisotropic strains induced in the superlattices.     

Breakup of a highly charged bubble in a dielectric liquid into parts of comparable size

An analysis is made of the conditions for instability of a charged gas bubble in a dielectric liquid. It is shown that unlike a charged droplet, the criterion for instability of a bubble is determined by two dimensionless parameters: the Rayleigh parameter and the ratio of the gas pressure in the parent bubble to the Laplace pressure. Pis’ma Zh. Tekh. Fiz. 23, 60–65 (October 12, 1997)     

Deposition of aerosol particles in a model vitreous chamber

The purpose of this study was to assess quantitatively the aerosol deposition in a model eye chamber to identify the mechanism(s) of deposition and delivery efficiency for application in retinal disease treated with vitrectomy. Dry aerosol particles were produced with mixtures of fluorescein and a variable concentration of cesium chloride, which ranged in aerodynamic size from 0.6 to 1.3 μm. The aerosol was injected through a small inlet tube into Teflon chambers that had a vented, spherical cavity (diameter ?"). Two filling times of 60 s and 90 s were used. Although significant loss occurred in the syringe, the mass deposited within the chambers increased with aerosol concentration and ranged from 0.5 to nearly 15 μg. Between 60 and 90% of the mass was deposited on the lower surface of the chamber. The mechanism of deposition was consistent with diffusion through a boundary layer during filling followed by sedimentation of the remaining suspended aerosol particles. Based on these results, an aerosol with a median particle size of 1.3 μm was shown to provide a therapeutically effective dose of 5-fluorouracil. The approach is general and can be applied to the aerosol delivery of other drugs to the vitreous chamber.     

A physical mechanism of dense smoke suppression in a closed room by admitting a charged aqueous aerosol

It is experimentally demonstrated that the rapid suppression of an optically dense aerosol (smoke) by a strongly charged aqueous aerosol is related to acceleration of the volume diffusion and to electrostatic repulsion of the charged agglomerates.     

A simple dynamic model for the formation of debris clouds

A simple model for describing the motion of material in a debris cloud is presented. Motion and distribution of this material are described using three axial velocities, one radial velocity, and the diameter of the projectile. Results of hypervelocity impact tests using copper projectiles and aluminum bumpers are presented. Data from these tests were used to verify several assumptions integral to the development of the model. A method for approximating the pressure-loading history applied to the interior wall of a double sheet structure is also presented.     

Evaluation of the influence of aircraft shielding on the aircrew exposure through an aircraft mathematical model

In order to investigate the influence of aircraft shielding on the galactic component of cosmic rays, an aircraft mathematical model has been developed by the combinatorial geometry package of the Monte-Carlo transport code FLUKA. The isotropic irradiation of the aircraft in the cosmic ray environment has been simulated. Effective dose and ambient dose equivalent rates have been determined inside the aircraft at several locations along the fuselage, at a typical civil aviation altitude (10 580 m), for vertical cut-off rigidity of 0.4 GV (poles) and 17.6 GV (equator) and deceleration potential of 465 MV. The values of both quantities were generally lower than those in the free atmosphere. They depend, in an intricate manner, on the location within the aircraft, quantity of fuel, number of passengers, etc. The position onboard of crew members should be taken into account when assessing individual doses. Likewise due consideration must be taken when positioning detectors which are used to measure H*(10). Care would be needed to avoid ambiguity when comparing the results of calculation with the experimental data.