Single Sphere Research Articles

Analysis of glory phenomena created by retroreflecting microspheres

Light fields from localized light sources create a variety of interesting glory phenomena when reflected by small glass spheres (microbeads). Starting with single glass spheres, the interplay of the underlying optical phenomena, i.e., refraction, reflection, diffraction, and dispersion, have been studied both theoretically and experimentally. In a second step, we considered retroreflecting screens formed by flat arrays of tiny glass spheres when exposed to divergent illumination. The arising glories show a specific ring pattern and appear freely floating around the light source as their blurred real image. The investigated glory structures will have numerous applications in sophisticated lamp and illumination designs, as demonstration tools in optical education or advertising, and artistic installations, in particular when appearing as three-dimensional objects by stereoscopic observation.

Simple Qualitative Modelling of Particle Size Analysis using Ray Tracing Method

Understanding particle size analysis is essential for pharmaceutical, mining, environmental, coatings, and other industries. Although there are numerous technologies that can be utilized to take particle size measurements, the results of those measurements are presented automatically and are sometimes difficult to understand. In this study, using the ray-tracing method, simple qualitative modelling of particle size analysers can be developed. The laser is positioned as the initial position of the light source in x and y directions. The cell is pictured by cuvettes with four surfaces clear, and the particle is modelled as a sphere. Reflection of a single ray of the laser beam on many spheres can be performed using single ray reflection on a single sphere consecutively until the beam leaving the observation region or arriving at a light sensor. Then with vector formulation of ray direction after reflection on many spheres system we can define with n = 1,2,3,… where . As a test of the particle size analysis model, the results are compared with measurements of the monodisperse polystyrene latex. Interesting patterns in FFT and autocorrelation function results are found. Unfortunately, this finding is still considered inconclusive, due to the pattern obtained is not completely like the experimental results.

Growth Pattern Control and Nanoarchitecture Engineering of Metal-Organic Framework Single Crystals by Confined Space Synthesis.

The nanoarchitecture engineering of metal–organic frameworks (MOFs) is a fascinating but intellectually challenging concept that opens up avenues for both tailoring the properties of MOFs and expanding their applications. Herein, we report the confined growth of ZIF-8 single crystals in a three-dimensionally ordered (3DO) macroporous polystyrene replica and reveal that their growth patterns, morphologies, and nanoarchitectures can be highly engineered using the concentration of the precursor. Impressively, the favorable in situ confined growth enables the successful fabrication of 3DO sphere-assembled ZIF-8 single crystals or 3DO single-crystalline ZIF-8 sphere arrays when a low- or high-concentration precursor solution, respectively, is used as the feedstock. Furthermore, our strategy can be extended to the preparation of other 3DO MOF single crystals, including ZIF-67 and HKUST-1, with similar controllable hierarchical nanoarchitectures. With the successful preparation of a series of diameter-tunable ZIF-8 single-crystalline spheres, we further unravel their interesting size–performance relationship in the Knoevenagle reaction between benzaldehyde and malononitrile, wherein the smallest spheres show the fastest first-order reaction kinetics. This study not only develops a general strategy for engineering the nanoarchitectures of MOF single crystals but also provides fundamental knowledge of the mechanism for the growth of hierarchical single crystals under confined spaces.

Drag correlations for flow past monodisperse arrays of spheres and porous spheres based on symbolic regression: Effects of permeability

An accurate drag correlation accounting for multiscale heterogeneous porous structures is a prerequisite for reliable CFD simulation of fluidized beds. Though particle clusters in fluidized beds are usually modeled as porous particles, particle-resolved direct numerical simulation (PR-DNS), in which monodisperse arrays of spheres are taken as model systems, has been widely used as a first-principle approach to derive drag correlations. This work is to bridge the gap of drag correlations for monodisperse arrays of spheres and porous spheres by considering permeability effects and derive new drag correlations using symbolic regression (SR) methods. Firstly, experimental porous spheres settling data were utilized to identify the most important features affecting drag force using Support Vector Machine (SVM), in which the permeability β was packed up in addition to the solid fraction ϕ and Reynolds numbers Re. A new drag correlation for porous spheres based on ϕ,Re, and β, which has physical terms, high prediction accuracy and correct limiting cases, is automatically generated using SR method. Then, PR-DNS data from open sources were used to distill drag correlations for monodisperse arrays of spheres by incorporating the extra permeability parameter by SR method, demonstrating solid physical basis with high accuracy. It is further shown the SR based on drag correlations for porous spheres and monodisperse arrays of spheres can be reduced to limiting cases of a single solid sphere and Stokes flow. The proposed new drag correlations not only provide a way to use permeability as a simple yet physically sounded parameter to quantify heterogeneous structures in fluidized beds, but also open a venue for directly validating drag correlations obtained purely from PR-DNS simulations with experimental data of flow around porous spheres.

Study on a plane grating spectral imaging system with smile and keystone eliminated

Subject of study. For a grating-based imaging spectrometer, a method of using an off-axis lens to correct the smile and keystone is proposed and verified by simulation. Method. In the set coordinate system, the ratios of direction cosines of the refractive rays along the y-axis and z-axis are studied using the spatial ray tracing method. On this basis, the smile characteristics of a single refraction sphere and an off-axis lens have been analyzed. In order to verify the theory, a visible spectral imaging system without an off-axis lens and one with an off-axis lens have been optimized, respectively. Main results. The criterion of the smile sign has been given and discussed. For the spectral imaging system without an off-axis lens, good image quality and high spectral resolution have been achieved, which is less than 1 nm. The modulation transfer functions at the wavelengths of 400, 600, and 800 nm are greater than 0.5 at the Nyquist frequency. However, the maximums of the smile and keystone are greater than 0.07 and 0.06 mm, respectively, which are several times the unit size. For the spectral imaging system with an off-axis lens, the image quality is basically the same as the previous one. The obvious differences between the two systems are the smile and keystone. For the latter, the maximums of smile and keystone at all working wavelengths in all fields are close to 6.24 and 6.40 µm, which are less than half of the unit size. Practical significance. The smile and keystone caused by a plane grating can be corrected by an off-axis lens in a plane-grating-based imaging spectrometer, which provides a universal method for the design of a spectral imaging system.

Interface-resolved simulations of the confinement effect on the sedimentation of a sphere in yield-stress fluids

We perform three-dimensional numerical simulations to investigate the confinement effect on the sedimentation of a single sphere in an otherwise quiescent yield stress fluid, in the presence of finite elasticity and weak inertia. The carrier fluid is modeled using the elastoviscoplastic constitutive laws proposed by Saramito (2009). The additional elastic stress tensor is fully coupled with the flow equation, while the rigid particle is represented by an immersed boundary method. The simulations show the faster relaxation of the fluid velocity and the progressive translation of the location of the negative wake downstream of the sphere as the bounding walls are brought closer to the particle. Moreover, the sphere drag decreases by increasing the particle–wall distance. We show that the confinement ratio (ratio of the gap between rigid confining walls and the sphere radius) reaches a critical value beyond which the wall-effect on the particle and flow dynamics becomes negligible. The key finding here is that the critical confinement ratio and the maximum variation of the Stokes drag with confinement ratio are weakly dependent on the level of material elasticity and plasticity for a certain range of material parameters. Finally, we propose an expression for the Stokes drag coefficient, as a function of material plasticity and confinement ratio.

For the road: calibrated maternal investment in light of extracellular symbiont transmission.

Faithful transmission of beneficial symbionts is critical for the persistence of mutualisms. Many insect groups rely on extracellular routes that require microbial symbionts to survive outside the host during transfer. However, given a prolonged aposymbiotic phase in offspring, how do mothers mitigate the risk of symbiont loss due to unsuccessful transmission? Here, we investigated symbiont regulation and reacquisition during extracellular transfer in the tortoise beetle, Chelymorpha alternans (Coleoptera: Cassidinae). Like many cassidines, C. alternans relies on egg caplets to vertically propagate its obligate symbiont Candidatus Stammera capleta. On average, each caplet is supplied with 12 symbiont-bearing spheres where Stammera is embedded. We observe limited deviation (±2.3) in the number of spheres allocated to each caplet, indicating strict maternal control over symbiont supply. Larvae acquire Stammera 1 day prior to eclosion but are unable to do so after hatching, suggesting that a specific developmental window governs symbiont uptake. Experimentally manipulating the number of spheres available to each egg revealed that a single sphere is sufficient to ensure successful colonization by Stammera relative to the 12 typically packaged within a caplet. Collectively, our findings shed light on a tightly regulated symbiont transmission cycle optimized to ensure extracellular transfer.

Spherical Phaseless Antenna Measurements Experimental Validation of a Two-Antenna-Positions Procedure

The phaseless characterization of antennas enables to reduce the cost and to ease the measurement of radiating systems, especially at high frequencies. The complex near field is retrieved from the acquisition of the antenna radiated field magnitude only, thanks to appropriate phase retrieval algorithms. Thus, a two-scan approach combined to a Gerchberg–Saxton algorithm has proven to lead to accurate phase retrievals. However, instead of measuring the field on two spherical surfaces of different radii as conventionally performed, we propose to measure the magnitude of the field on a single sphere but for two antenna positions. This new strategy is easier to implement in a number of measurement setups. Numerical and experimental validations in a commercial, arch-based, measurement system are shown and discussed.

Dimer of dielectric nanospheres as a generalized Huygens element

We study the conditions of suppressed backward scattering in optical oligomers. Optical oligomers are closely packed clusters of nanoparticles which support multiple resonances, allowing to achieve scattering phase rotation by 2π necessary for metalenses. In this paper we consider the simplest oligomer — a dimer, which is irradiated by a normally-incident plane wave with the magnetic field oriented along the dimer axis. Using the dipole approximation, we have derived analytically the generalized Kerker condition for this system. Similarly to a single sphere case, the electric and magnetic dipole have to be of the same amplitude to suppress the backward scattering. However, due to the inter-particle coupling, the full coupled-dipole problem must be solved to find the wavelength of the backscattering suppression. Using the coupled-dipole and coupled-multipole methods, we have found that the Kerker condition wavelength for the considered dimer is red-shifted compared to a single sphere.

Modeling the Simultaneous Effects of Particle Size and Porosity in Simulating Geo-Materials.

The particle discrete element method (PDEM) is widely used to simulate rock and soil materials to obtain stress and strain. However, there are three shortcomings: (1) Single sphere or ellipsoids directly replace the soil particles; (2) it treats the diameters of spheres or ellipsoids as the soil particle size; (3) the overlapping particle volume is not deducted in calculating the porosity. Hence, it is difficult for the simulation of the geological body to agree with reality. This research found a rotation calculation model and a pixel counting method to make joint soil particles more accurately simulate geological materials to solve the three shortcomings. The model successfully obtained the gradation curve and porosity of the simulated geological body with joint particles. This research will further enrich and broaden the application prospects of PDEM and provide a reference for scientific research and engineering fields in geological engineering, geotechnical engineering, and petroleum engineering.

Revisiting the interaction of highly nonlinear solitary wave with wall: From infinite to finite thickness

The classical reflection of a highly nonlinear solitary wave (HNSW) on an elastic wall has been used to determine the material properties of the wall, but does not work on a plate (a wall with finite thickness). In this paper, by coupling sphere-plate contact with chain dynamics, we revealed that: with the same initial velocity, the energy dissipation of multi-sphere plate impact is different from the single sphere plate impact, but the contact force on the plate performs similarly. Based on this fact, we then developed two universal force models considering the dissipative feature of the plate. These force models (reflection force on the chain and contact force on the plate) can universally connect the signals of the HNSW with the dissipative feature of the plate. With the obtained force models, we proposed a non-destructive evaluation method, which can identify both the plate material and thickness by measuring the two forces: the reflection force on the chain and the contact force on the plate. Agreement with finite element simulations suggests that non-destructive evaluation of thin-walled structure can be realized by using HNSW with the proposed method.

DISCUSSION ON THE ISSUE «OTKUDU EST' POSHLA RUSKAYA ZEMLYA... I OTKUDU RUSKAYA ZEMLYA STALA EST'» IN THE UKRAINIAN EMIGRANT HISTORIOGRAPHY OF THE EARLY 1930s

The article analyzes the discussion on the formation of the Ukrainian nation, which took place at the initiative of the Ukrainian Historical and Philological Society in Prague in the early 1930s and associated with criticism of the views of Miron Korduba. The ideological, not scientific, positions of the opponents of Korduba are revealed. The course of the discussion and its stages have been clarified. It was established that Korduba had supporters among Ukrainian historians, and not just opponents. Ukrainian emigrant historiography, concentrated at that time in Czechoslovakia, Germany and Poland, demonstratively tried to act as a united front with the point of view that the Ukrainian nation was already formed as part of Kievan Rus’ and that the history of the ancient Russian state belongs only to Ukrainians. Korduba's opinion was about an all-Russian state and a single cultural sphere of the Eastern Slavs in antiquity, when the nations had not yet formed. He believed, based on historical facts, that the Ukrainians, as a separate nation, emerged in the XIV century as part of the Lithuanian state.

Limiting Spherical Integrals of Bounded Continuous Functions

We use nonstandard analysis to study the limiting behavior of spherical integrals in terms of a Gaussian integral. Peterson and Sengupta proved that if a Gaussian measure $$\mu $$ has full support on a finite-dimensional Euclidean space, then the expected value of a bounded measurable function on that domain can be expressed as a limit of integrals over spheres $$S^{n-1}(\sqrt{n})$$ intersected with certain affine subspaces of $${\mathbb {R}}^n$$ . This allows one to realize the Gaussian Radon transform of such functions as a limit of spherical integrals. We study such limits in terms of Loeb integrals over a single hyperfinite-dimensional sphere. This nonstandard geometric approach generalizes the known limiting result for bounded continuous functions to the case when the Gaussian measure is not necessarily fully supported. We also present an asymptotic linear algebra result needed in the above proof.

Effect of single and hybrid hollow sphere reinforcement on the deformation mechanism of aluminum matrix syntactic foam at a low strain rate

The combination of soft matrix alloys and brittle spheres has gained unceasing demand due to its structural strength and tailored properties to meet industrial and commercial needs. Single sphere aluminum matrix syntactic foams (AMSFs) show poor ductility and fracture strength at high volume fractions of reinforcement. In the present investigation, three different volume fractions of the single sphere (alumina hollow spheres and cenospheres), syntactic foams (SF) and hybrid SF were prepared using a powder metallurgy route with a maximum reinforcement fraction of 30%. The lowest density of 2.17 g cm -3 was produced with no chemical reaction observed between matrix and reinforcement. The quasi-static compression studies have shown a significant effect of particle size and volume fraction with respective mechanical properties (peak stress = 601 MPa (Sample #1), 610 MPa (Sample #4) and 525 MPa (Sample #10)). The densification strain, energy absorption, energy absorption efficiency (EAE) and ideal EAE have been predicated for all the samples. The macroscopic deformation of SFs is in good agreement with stress-strain data. The results show that the slope of the plateau region follows a negative linear trend against the strain hardening exponent.

Methodology and Techniques for Highly-Precise Radar Cross Section Measurements at W-Band

This paper explores the challenges of radar cross section (RCS) measurements at W-band and proposes several techniques to overcome these challenges to obtain an accurate RCS measurement. This paper combines <i>S</i>₁₁ measurements collected using traditional radio frequency (RF) hardware with post-processing algorithms to extract RCS values with a single antenna. Vector background subtraction and time-gating suppress unwanted reflections while increasing the system&#x2019;s dynamic range capability. Experiments are conducted at the University of Oklahoma&#x2019;s mm-Wave Laboratory with a Vector Network Analyzer (VNA) and frequency extender to evaluate the proposed measurement techniques. The setup is calibrated with a metal sphere, and the RCS of a smaller metal sphere and an arrangement of four spheres is extracted. The single sphere&#x2019;s RCS is measured with a 0.304 dBsm average error, and the distributed object under test (OUT) RCS is measured with a 1.60 dBsm average error from 80-90 GHz. Each OUT is placed on a 3D-printed pedestal, and the remainder of the test hardware is part of an existing mm-Wave antenna measurement configuration. The post-processing clutter cancellation techniques enable a flexible test configuration to isolate the OUT RCS without purchasing specialized hardware.

External mass transfer from/to a single sphere in a nonlinear uniaxial extensional creeping flow

This work systematically simulates the external mass transfer from/to a spherical drop and solid particle suspended in a nonlinear uniaxial extensional creeping flow. The mass transfer problem is governed by three dimensionless parameters: the viscosity ratio ( λ ), the Peclet number ( Pe ), and the nonlinear intensity of the flow ( E ). The existing mass transfer theory, valid for very large Peclet numbers only, is expanded, by numerical simulations, to include a much larger range of Peclet numbers (1 ≤ Pe ≤ 10 5 ). The simulation results show that the dimensionless mass transfer rate, expressed as the Sherwood number ( Sh ), agrees well with the theoretical results at the convection-dominated regime ( P e > 10 3 ). Only when E > 5/4, the simulated Sh for a solid sphere in the nonlinear uniaxial extensional flow is larger than theoretical results because the theory neglects the effect of the vortex formed outside the particle on the rate of mass transfer. Empirical correlations are proposed to predict the influence of the dimensionless governing parameters ( λ , Pe , E ) on the Sherwood number ( Sh ). The maximum deviations of all empirical correlations are less than 15% when compared to the numerical simulated results.

Produção de fitomassa por plantas de cobertura e seus efeitos em atributos do solo

Associated with the positive use of particle formation cover plants and improvement of the differentiating objective effect machining attributes of cover mixes compared to single black sphere impact, in soil structure attributes and in the production of phytomass The experiment was located in Jardim Alegre, PR under a randomized block design with 3 treatments and 7 replications. The treatments consisted of two mixes of cover crops (Mix 1 and Mix 2) and black oat cv. Embrapa 139. After 97 days, the production of wet and dry phytomass was evaluated, and at 100 DAS the total density and porosity of the soil at depths of 0.05 to 0.10 and 010 to 0.15 m. The results indicate that the use of a cover crop mix containing buckwheat, sudan grass and forage radish (Mix 1) results in a greater contribution of plant residues to the soil. The use of cover formed by oat, white oat, rye, Japanese radish and forage radish (Mix 2) mixes a smaller amount of residues, compared to single black oat. Soil density and porosity were not presented in width and depths. of soil. In this sense, it appears that at 100 DAS there are no effects on the physical attributes of a long-term study, demonstrating the need for long-term studies on the effect of coverage for these attributes.

Numerical evaluation of virtual mass force coefficient of single solid particles in acceleration

• Single solid sphere in acceleration is numerically simulated based on the vorticity-stream function formulation. • Particle acceleration changes significantly the surrounding flow field and the stress tensor on the particle surface. • Virtual mass force coefficient is evaluated from the numerical simulation. • A correlation of total drag coefficient with the Reynolds number and acceleration number is proposed for tentative use in particulate flow simulation. Virtual mass force is an indispensable component in the momentum balance involved with dispersed particles in a multiphase system. In this work the accelerating motion of a single solid particle is mathematically formulated and solved using the vorticity-stream function formulation in an orthogonal curvilinear coordinate system. The total drag coefficient was evaluated from the numerical simulation in a range of the Reynolds number ( Re ) from 10 to 200 and the dimensionless acceleration ( A ) between −2.0 to 2.0. The simulation demonstrates that the total drag is heavily correlated with A , and large deceleration even drops the drag force to a negative value. It is found that the value of virtual mass force coefficient ( C V ) of a spherical particle is a variable in a wide range and difficult to be correlated with A and Re. However, the total drag coefficient ( C DV ) is successfully correlated as a function of Re and A , and it increases as A is increased. The proposed correlation of total drag coefficient may be used for simulation of solid–liquid flow with better accuracy.

Self-education of adolescent schoolchildren as a socio-pedagogical necessity

In modern conditions, the question of the need for self-education of students remains relevant. Today it is impossible to find a single sphere of human activity that is not associated with the generally recognized spiritual and material values of society as a whole and of each person. In this regard, the purpose of the article is to consider the need to build pedagogical systems for the actualization of the student's self-education, which are set by the emerging trends of humanization, differentiation of the environmental friendliness of social processes, elevating the function of education in the structure of educational processes and causing the need for a new reading of the concept of education as a synthesis of the processes of learning and learning, upbringing and self-education, development and self-development, maturation and socialization of the individual.

On the problem of interrelation of notions “communication” and “conversation”

Summary. The purpose of the article is to analyze such social problems as communication and communication in the European space in connection with modern integration processes. Methodological basics of the research are logical method, which allows conducting the in-depth interrogation of notions of “communication”, “technical means of communication”, “conversation”, “signal means of connection”. The critical method was applied to reveal the problematic practical borders on interrelation of those notions. Scientific novelty. The importance of research of the notions of ‘communication’ and ‘conversation’ points at a need of exploration and practical preservation of the dialogical form of relations between “I” and another person rooted in the basis of their just and equal treatment in social relations. In this case communication as a form of social interaction allows preserving an autonomous individuality for each person and provides a space to draw the principles from own personal experience and understanding of the world. Conclusions. Development of informational and communicational technologies in XXI century has led to the new communicative situation. On the one hand, it has enhanced the importance of communication in the social, political, cultural spheres of human life; while on the other hand, it revealed the contradiction between possible ways and limits of communication. It can be noted that the messages of communication bear the monologues character, while the conversation possess the dialogical structure. At the same time, communication has an altar-individual character and embraces order, formalization and standardization of social relations and connections. Communication belongs to every single sphere of human life and preconditions the social interaction. At the same time, conversation reveals itself in the process of formation of social and media networks, which aim to monopolize interpersonal communication. Rationality and use of technical means determine the ways of communication as social phenomena nowadays. Thus the main quality of communication is external manifestation of the process of conversation, which is expressed in socially accepted, effective, rationally picked means and forms of information transfer and exchange between the subjects of social interaction.