Search

Fluxgate magnetometers provide sensitive and stable measurements of the static and low frequency vector magnetic field. Fluxgates form a magnetic field measurement by periodically saturating a ferromagnetic core and the intrinsic magnetic noise of this material can determine the noise floor of the instrument. We present the results of an empirical experiment to understand the physical parameters that influence the intrinsic magnetic noise of fluxgate cores. We compare two permalloy alloys – the historical standard 6 % molybdenum alloy and a new 28 % copper alloy. We examine the influence of geometry using the historical standard 1” diameter spiral wound ring-core and a new stacked washer racetrack design. We evaluate the influence of material thickness by comparing 100 µm and 50 µm foils. Finally, we investigate heat treatments in terms of temperature and ramp rate and their role in both grain size and magnetic noise. The results of these experiments suggest that thinner foils, potentially comprising the copper alloy, manufactured into continuous racetrack geometry washers may provide excellent performance in fluxgate sensors.

Another cosmological redshift mechanism could exist in general relativity, as is differences in the global metric field gμν between the radiation source in the past, and the observer in the present, known as gravitational redshift in massive stars. In this paper, we present a fully conformal global metric model with time scaling that would lead to the above alternative interpretation of the cosmological redshift. It is based on a relatively simple global solution of Einstein's gravitational equations without the cosmological term, and the analysis also shows other interesting astrophysical implications. The model naturally solves the problem of critical density and spatial flatness, as well as the problem of cosmological redshift in the spectra of distant astrophysical sources, and the problem of Olbers' and Seeliger's paradox. At the same time, it replaces the strict causal horizon principle with a much softer formulation-the region of the practically observable universe. Confrontation with astrophysical data provides interesting agreement with the spatial distribution of astrophysical radiation sources such as γ-ray bursts and quasars. However, probably the most important consequence is the new, generalized formulation of Hubble's law z(r) = (exp(Hr/c)-1), which shows good agreement R 2 ≈ 0.9824 with experimental data even for very distant sources. The paper also physically justifies in principle the modification of Newton's law of gravity for infinite space proposed by Seeliger. The modifying exponential term exp(-Hr/c) is uniquely quantified by the Hubble parameter and the speed of light.

Accurate high-precision magnetic field measurements are a significant challenge for many applications including constellation missions studying space plasmas. Instrument stability and orthogonality are essential to enable meaningful comparison between disparate satellites in a constellation without extensive cross-calibration efforts. Here we describe the design and characterization of Tesseract – a fluxgate magnetometer sensor designed for low-noise, high-stability constellation applications. Tesseract’s design takes advantage of recent developments in the manufacturing of custom low noise fluxgate cores. Six of these custom racetrack fluxgate cores are securely and compactly mounted within a single solid three-axis symmetric base. Tesseract’s feedback windings are configured as a four-square Merritt coil to create a large homogenous magnetic null inside the sensor where the fluxgate cores are held in near-zero field, regardless of the ambient magnetic field, to improve the reliability of the core magnetization cycle. A Biot-Savart simulation is used to optimize the homogeneity of field generated by the feedback Merritt Coils and was verified experimentally to be homogeneous within 0.42 percent along the racetrack cores’ axes; an improvement thirteen times that of the traditional ring-core sensor design. The thermal stability of the feedback windings is measured using an insulated container filled with dry ice inside a coil system. The sensitivity over temperature of the feedback windings is found to be between 13 ppm/°C and 17 ppm/°C. The sensor’s three axes maintain orthogonality to within at most 0.015 degrees over a temperature range of -45 °C to 20 °C; an improvement at least six times that of the ring-core sensor design. Tesseract’s cores achieve a magnetic noise floor of 5 pT/√Hz at one Hz. Tesseract will be flight demonstrated on the ACES-II sounding rockets, currently scheduled to launch in late 2022 and again aboard the TRACERS satellite mission as part of the MAGIC technology demonstration which is currently scheduled to launch in 2023.

In the chapter “Interaction Among Nanoparticles” three basic mechanisms of polarization interaction based on van der Waals forces are initially presented. The chapter is then devoted to a detailed derivation of the collective form of van der Waals interactions in Hamaker’s microscopic theory.

In the chapter “Nanoparticles—Their Specific Properties and Origin” the concept of nanoparticles is primarily formulated in terms of the thermodynamic limit of statistical physics and not as an unreasoned agreement, which is still the common practice. Furthermore, the most important chemical, physical and quantum mechanical properties of nanoparticles are described in detail as far as possible in the individual sections. The second part of the chapter is further devoted to the formation of nanoparticles and aspects of their preparation by bottom-up and top-down methods.

At the beginning of the chapter “Lamelary Aggregation of Nanoparticles from Frozen Liquid on the Sublimation Interface—Experimental Preparation and Application of Nanomaterials” the results of model simulation are confronted with the lamellar structure obtained experimentally. The simulation results are morphologically quite identical. Subsequently, a number of experimental results and practical applications of the patented controlled sublimation technology are presented. The nature of these results supports the assumption of a high application potential of the “mentioned” technology. The nature of these results supports the assumption of a high application potential of the mentioned technology.

Fast development of nanotechnology leads to the top-down preparation of nanoparticles by various disintegration techniques taking a major part in the industrial sector. A very promising way seems to be the use of cavitation implosions. In our approach, the main mechanism of this type of disintegration is based on mutual collisions of solid microparticles in dense dispersions, powered by implosions of vapour cavitation bubbles generated between the particles.This paper presents experimental results of the disintegration of silicon microparticles to the sub-micron scale. In our experiments, the primary silicon particles of mean size of 5927 nm were reduced to 160 nm and 736 nm by the ultrasonic disintegration process after 240 minutes and at the ultrasonic frequency of 32 kHz. We also present a phenomenological model of particles erosive disintegration where particle fragments are approximated by spheres of equivalent volume. This model allows us to calculate the energy needed for successful disintegration of primary microparticles by measuring the particle size distribution. Thus, we can estimate the minimal energy conserved in the cavitation bubble alongside with its radius at a normal pressure of the surrounding liquid.

The publication is focused on the problem of nanoparticle aggregation on the sublimation interface between vacuum and rapid frozen liquid dispersion. The main aims are simulation experiments of mathematical modelling of these processes. During lyophilization of rapid frozen liquid dispersion of nanoparticles, a self-organization of nanoparticles occurs. The resulting structure depends on setting the process parameters. According to the current knowledge, they include temperature, vacuum depth, and nanoparticle fraction in the dispersion liquid. On the free sublimation interface, a streamlined flow of dispersion liquid molecules, also referred to as sublimation wind, flows into the vacuum. Lamellar nanoparticle aggregates are formed on the interface surface in this mode, which are gradually torn by the pressure of the sublimation wind. Aggregated materials with very high specific surface area may be formed by these processes. Mathematical modelling of nanoparticle dynamics on two-dimensional sublimation layer is employed to deepen the understanding of basic mechanisms of these aggregation processes. The simulation results are in good agreement with the experimental results of lamellar nanostructure aggregation of bonded globular nanoparticles nC60. Further refinements based on the simulation experiments will allow active control of the process and quality of aggregated nanostructures.

The aim of this article is the concept of modern avionic system and device for non-powered aircrafts - gliders. This topic is very extensive, and the aim of this work is to summarize the issue and to familiarize the reader with the issues related to the equipment of non-powered. We will design the use of state-of-the-art technology to optimize flight and improve search and use of rising thermals. We will define values that change in thermal lifts. We will design sensors that they will monitor those changes. We will design an application that will use sensor information to get flight data. After that we will make a theoretical proposal of this new system.

This paper presents a new method of deposition of photocatalytic sorbent on nanofibers. This deposition uses controlled sublimation of water molecules from the vacuum-gel that is patent-protected. Silica gel nanostructures are precipitated by heterogeneous nucleation on the surface of nanofibres from an aqueous suspension of silicate nanoparticles and semiconductor carbon nitride (C3N4) or graphene nanosheets. After rapid solidification of gel (at least 104K/s), the nanofibers coated with the silica gel dispersion C3N4, or graphene are subjected to controlled sublimation at – 41 °C. This technology produced a nanofibrous material, which is stably coated with a highly porous silicate sorbent including dispersed photocatalytic nanoparticles. This textile material has a total sorption surface area of the order of hundreds m2/g. Unlike conventional sorbents, it is capable due to dispersed photocatalytic nanoparticles to regenerate sorption capacity by the absorption of visible light. The results of the preliminary research confirmed the high application potential of new controlled sublimation technology in the production of regenerable photocatalytic sorption fabrics.

The publication is focused on the problem of nanoparticle aggregation on the sublimation interface between vacuum and rapid frozen liquid dispersion. The main aims are simulation experiments of mathematical modelling of these processes. During lyophilization of rapid frozen liquid dispersion of nanoparticles, a self-organization of nanoparticles occurs. The resulting structure depends on setting the process parameters. According to the current knowledge, they include temperature, vacuum depth, and nanoparticle fraction in the dispersion liquid. On the free sublimation interface, a streamlined flow of dispersion liquid molecules, also referred to as sublimation wind, flows into the vacuum. Lamellar nanoparticle aggregates are formed on the interface surface in this mode, which are gradually torn by the pressure of the sublimation wind. Aggregated materials with very high specific surface area may be formed by these processes. Mathematical modelling of nanoparticle dynamics on two-dimensional sublimation layer is employed to deepen the understanding of basic mechanisms of these aggregation processes. The simulation results are in good agreement with the experimental results of lamellar nanostructure aggregation of bonded globular nanoparticles nC

In this work, we describe the model of magnetic Fe2O3 submicroparticles separation during transit of their water dispersion through separation pipe based on matrix of closely organized steel spheres. The fundamental idea originates from detailed field analysis of gradient magnetic field in spheres contacts ambient generated by external magnetic field and its influence on flowing submicroparticles. During the model derivation, the fundamental physical principles have been applied to minimise the influence of the phenomenological members. The determined result formula related to the separation model determines exit dispersion particles concentration and equivalent form of device efficiency. In its fundamental shape, this formula is the function of nine independent physical parameters. In the frame of its experimental verification, most of these parameters have been fixed. The experimental data have been correlated with our model prediction, where only the following three independent variables have been implemented: separation tube length, particles size, and external magnetic field intensity. The theory and experiment comparison have shown that the coefficient of determination R2 is over 0.997. At the same time, the described theoretical model specifies the approach for optimal parameters selection to achieve the requested separation efficiency in concrete conditions.

This paper presents a new method of deposition of photocatalytic sorbent on nanofibers. This deposition uses controlled sublimation of water molecules from the vacuum-gel that is patent-protected. Silica gel nanostructures are precipitated by heterogeneous nucleation on the surface of nanofibres from an aqueous suspension of silicate nanoparticles and semiconductor graphitic carbon nitride or garaphene nanosheets. After gel rapid solidification of at least 104 K/s, the nanofibers coated with the silica gel dispersion gC3N4, or graphene are subjected to controlled sublimation at - 41 oC. This technology has produced a nanofibrous material, which is stably coated with a highly porous silicate sorbent with dispersed photocatalytic nanoparticles. This textile material has a total sorption surface area of the order of hundreds m2/g. Unlike conventional sorbents, it is capable, thanks to dispersed photocatalytic nanoparticles, to regenerate sorption capacity by the absorption of visible light. The results of the preliminary research confirm the high application potential of new controlled sublimation technology in the production of regenerable photocatalytic sorption fabrics.

Prvi teorijski radovi, koji su opisivali stvaranje velike količine mehaničke energije kad kapljice velike brzine udare u čvrstu površinu kao rezultat hidrauličkog udara, poznati su još od 1960-tih. Heymann je pokazao da je maksimalni tlak kod udara loptaste kapljice tekučine nekoliko puta veći od pretpostavljenog maksimalnog u slučaju klasičnog hidrauličkog udara. Spomenuti maksimalni tlak nekoliko je puta veći od tlaka kontinuiranog mlaza u stanju mirovanja. Kod stvaranja uređaja za generiranje pulsirajućeg mlaza, za visoke je tlakove uvedena nova generalizacija klasične teorije hidrauličkog udara. Na tom je temelju zasnovan novi patentirani princip "multiplikacije impulsa". Multiplikator impulsa je izvor visokotlačnih impulsa sa 100 % dubinom modulacije izlazne brzine tekućeg mlaza. Omogućuje značajno povećanje dezintegracijskog učinka mlaza bez dodavanja abraziva., First theoretical papers, summarizing the high mechanical energy cumulation when high-speed drops impact on the solid surface as a result of the water hammer effect, have been known since 1960’s. Heymann has demonstrated that pressure maximum during the impact of a spherical drop of a liquid is several times higher than the presupposed maximum for the classical waterhammer effect. The mentioned maximum pressure exceeds the stagnation pressure of the continuous jet several times over. When developing devices for pulsed jet generation, a new generalization of the classical water hammer theory for high pressures has been introduced. Based on this a new patented principle of "pulse multiplication" has been formulated. The pulse multiplier is the source of high-pressure pulses with 100 % depth of modulation of discharge velocity of a liquid jet. It enables to significantly increase the jet disintegration effect without addition of abrasives.

A physical analysis of cavitation-based implosive breakage of solid particles focusing on practical application during fine particle disintegration in a liquid suspension is submitted in the present paper. The physical source of the cavitation dynamics phenomena involved is an extreme velocity gradient induced by an ultrahigh-energy liquid jet mixing together with a slow liquid suspension of milled particles. Extreme tensile stresses occurring at velocity gradients over 1000 ms −1 mm −1 at the operating temperature of 65 °C generates high-intensity pure vapor cavitation in the degassed water dispersion with extreme values of impact pressure in the final of bubble implosions on particle surfaces. Preparation of silicon nanoparticles with median diameter approximately 148 nm using a newly developed “Water Jet Mill” (WJM) device is demonstrated in the present article as an example of application of the aforementioned disintegration method as well as of theoretical analysis of this method. The disintegration method is characterized by a high potential for milling of submicron particles with high efficiency.

A mathematical model of synthesis and stabilization of ZnS nanoparticles in aqueous solutions of cetyltrimethylammonium bromide (CTAB) is presented. ZnS nanoparticles precipitated by the reaction of sodium sulphide and zinc acetate are significantly influenced by CTAB both in a stage of nucleation and in a stage of growth and stabilization. The suggested model assumes a dominating influence of the nucleation stage on future properties of emerging ZnS nanoparticles. On the basis of a calculated nucleation rate depending on a degree of the ZnS supersaturation, the model adopts an approximate assumption that ZnS nuclei are formed all at one moment.Mathematical formulation of the nucleation model attempts to explain a recently observed relationship between ZnS nanoparticles radii and the CTAB concentration. The dependence of a surface tension of zinc acetate and CTAB aqueous solutions on the CTAB concentration was measured and further applied to obtain the relation between the CTAB monomer concentration and the CTAB total concentration. The nucleation model assumed a key role of CTAB monomers, which were considered as nucleation centres. The predicted radii Web of Science 10 10 392 385

In this work we report on the aerosol synthesis of photocatalytic powder nanostructures of core-shell Si-ZnS particles. Submicron Si particles were prepared in the form of an aqueous dispersion by disintegration of the semiconductor-grade silicon powder in the cavitation Water Jet Mill disintegrator. Adding zinc acetate converted aqueous dispersion medium into a solution of Zn(Ac)2 in various concentrations. The thus prepared liquid dispersion was then transformed into aerosol microdroplets with an average size of 3.5 microns in the Omron NE-U17 nebulizer. These were subsequently transported by flowing gas into the vigorously stirred aqueous solution of sodium sulfide. At impact of these aerosol “microreactors” the two liquid reactants produce zinc sulphide. Due to heterogeneous nucleation the insoluble phase of ZnS is precipitated on the phase surface of the silicon carrier particles contained in the microdroplets. As the amount of Zn(Ac)2 in a microdroplet is limited, so is the extent of the precipitation reaction and the thickness of the container can be regulated by Zn(Ac)2 concentration in the liquid dispersion. The obtained liquid dispersion of core-shell particles of Si-ZnS was dryed by controlled vacuum sublimation and stabilized in the form of lamellar nanoaggregates with a relatively high surface area. The final material enables easy handling and shows significantly higher photocatalytic activity than TiO2 Evonik P25 standard.