Geometrical Cross Section Research Articles

Energy absorption performance of fully clamped curved tubes under transverse loading

Curved tubes are widely used on autobody to suffer the transverse bending loads. This paper studies the energy absorption performance of curved tubes under transverse bending load. Firstly, three-point-bending and fully clamped bending experiments are conducted for three kinds of curved tubes with different radii. It is found that the curvature has a significant impact on the energy absorption effect under the fully clamped condition. However, the influence is limited and it will be easily ignored in the three-point-bending condition. Under fully clamped condition, tubes with large radii have three-plastic-hinges, and curved tubes with small radius have five-plastic-hinges. Due to the participation of axial force, the energy absorption of the curved tubes under fully clamped condition is 2.8–4.1 times that of the three-point-bending condition. Subsequently, FE models of curved tubes with different radii are established to analyze the effect of curvature on the deformation mechanism and energy absorption. It is found that whether the shortening of the plastic hinges can meet the requirements of geometric compatibility determines the deformation modes of curved tubes. The influence of loading (loading direction) and geometric (cross-section and thickness) factors are also discussed. Finally, a theoretical model of curved tubes with three-plastic-hinges mode is proposed to predict the energy absorption performance.

Effect of a “Slight” Curvature of the Axis of a Thin-Walled Nonprismatic Beam on its Free Vibration

This paper presents an analysis of the effect of a “slight” curvature of the axis of a thin-walled beam on its eigenfrequencies and forms. By “slight” we understand such a beam curvature at which no theory of curved beams (arches, horizontally curved girders), but classical beam theory is applied. The subject of the analysis is the open nonprismatic thin-walled beams with any geometrical parameters, and prismatic beams. The thin-walled beam model used in the analysis was derived on the basis of the momentless theory of plates, using the Vlasov assumptions. The free vibrations of the beams were analysed. Calculations were performed for four groups of beams. Each of the groups comprised two beams with the same configuration of flanges and identical geometrical cross section characteristics, but differing in web geometry. One of the beams had a symmetrical web (a beam with a rectilinear axis in the web plane), whereas the web of the other beam was asymmetrical (a beam with its axis curved in the web plane). The algorithm based on Chebyshev polynomials was used to solve the variable coefficient equations describing the model’s vibration. According to this algorithm, solutions are sought in the form of Chebyshev series and the closed analytical recurrence formulas generated by the algorithm are used to calculate the coefficients of the equations. It has been shown that even a “slight” curvature of the beam’s axis has a significant effect on its eigenfrequencies and forms, as confirmed by a comparison of the results with the ones obtained using Finite Element Method (FEM).

Stellar Shocks from Dark Matter Asteroid Impacts.

Macroscopic dark matter is almost unconstrained over a wide "asteroidlike" mass range, where it could scatter on baryonic matter with geometric cross section. We show that when such an object travels through a star, it produces shock waves that reach the stellar surface, leading to a distinctive transient optical, UV, and x-ray emission. This signature can be searched for on a variety of stellar types and locations. In a dense globular cluster, such events occur far more often than flare backgrounds, and an existing UV telescope could probe orders of magnitude in dark matter mass in one week of dedicated observation.

Circular wire-bundle superscatterer

Scattering cross-section is one of the main properties, characterizing an object in wireless applications. Resonant phenomena increase the electromagnetic visibility of a scatterer while keeping its footprint small. However, the single-channel limit or Chu-Harrington limit imposes a tight upper bound on a scattering cross-section of subwavelength objects. Being derived for a dipolar response, this limitation can be bypassed if several resonances of a structure are spectrally co-located and contribute constructively to the scattering. Subwavelength structures, obeying this design concept though hardly achievable in practical implementations, are called superscatterers. Here we demonstrate a superscatterer realization, based on a circular bundle of vertically aligned metal wires, optimized to demonstrate 5 multipoles, resonating at nearly the same frequency. As a result, the scattering cross-section becomes 12 times larger than object's geometrical cross-section. Owing to the multipolar multiplexing within the structure, the scattering is 7 times larger than the dipole single-channel limit. Additionally, as a result of the constructive interference of several multipoles, scattering directivity up to 10 dB is observed. Wire-bundle superscatterers may become an attractive architecture for many applications, including compact directive antennas, radar chaff and beacons, long-range RFID tags, and many others.

THE EFFECT OF VARIABLE CROSS-SECTION OF PRESTRESSED BEAMS ON THE LOAD-BEARING CAPACITY OF THE STRUCTURE

This paper examines issues related to increasing the load-bearing capacity of span beams of bridge-type cranes by the method of prestressing. A new mathematical model of a bridge crane with prestressed beams has been developed, which is based on the general theory of the stability of elastic systems and allows taking into account the real conditions of the construction of span structures. In this work, the equations of the deflection curve of this beam were obtained, which allow us to consider and analyze the influence of eccentric longitudinal forces on the stressed-deformed state of the span beam, taking into account the variable moment of inertia of its cross-section along the length of the span with a dangerous load combination. The work provides a more detailed calculation coefficient for the critical longitudinal force, which depends on the ratios of the moments of inertia of the cross sections of the span main beam, as well as the length of the support sections of the beam to the length of the beam itself. Based on the results of the obtained equations, a study of the static stiffness of the main beam was conducted depending on the ratio of longitudinal and transverse forces acting on the beam. The analysis of the obtained results revealed the recommended ratio of the lengths of the supporting and middle parts of the bridge, taking into account their geometric cross-section characteristics. The results obtained in this work can be used in the future for the modernization of cranes in order to increase their load capacity, extend their service life without dismantling, as well as for the improvement of existing structures and engineering calculation methods both at the stages of their design and in the conditions of real operation.

A model for predicting two-phase flow patterns transitions in an annulus: Inclinations from horizontal to near-vertical

The concomitant flow of a mixture containing two phases is a complex phenomenon. One of the reasons is that the phases’ interactions depend on the variations of the operational condition imposing the formation of different flow patterns that, in turn, can undergo pattern transition depending on the geometric cross-section change. This paper proposes a model for any annulus inclination, from horizontal to near-vertical, and considers a concentric condition in the particular case of a pipe. The outcome is a generalized, two-phase flow pattern maps function of dimensionless parameters. The influence of the tube inclination is investigated for the transitions: stratified smooth/stratified wavy, stratified wavy/annular dispersed liquid, stratified/intermittent, annular dispersed liquid/intermittent, and intermittent/dispersed bubble. Also, mathematical relations for calculating the shear stress and velocity profile in annuli under inclinations are developed. A new methodology, based on geometric parameters, help obtain the wetted area and perimeters, reducing the classical set of equations.

Outbursts of Comet 67P/Churyumov-Gerasimenko

Abstract We monitored the comet 67P/Churyumov-Gerasimenko close to its perihelion in November 2021 with the GROWTH-India Telescope. We observed two outbursts of this comet on 2021 October 29.940 and November 17.864 UTC, −3.12 days and +15.81 days respectively from the perihelion date. The brightening in the first outburst appears as a compact source, with a radial extent up to 8.″5. The comet brightened by 0.26 ± 0.03 mag in the outburst, with a 27% increase in the effective geometric cross-section and total outburst dust mass of ∼5.3 × 105 kg. The second outburst caused a brightening of 0.49 ± 0.08 mag with effective geometric cross-section and total outburst dust mass 2.5 times larger than the first event. These outbursts are up to an order of magnitude larger than the strongest outburst event observed in situ by the Rosetta spacecraft in 2015.

Direct Detection of Dark Asteroid

Macroscopic dark matter is almost unconstrained over a wide “asteroid-like” mass range, where it could scatter on baryonic matter with geometric cross section. We show that when such an object travels through a star, it produces shock waves which reach the stellar surface, leading to a distinctive transient optical, UV and X-ray emission. This signature can be searched for on a variety of stellar types and locations. In a dense globular cluster, such events occur far more often than flare backgrounds, and an existing UV telescope could probe orders of magnitude in dark matter mass in one week of dedicated observation.

Investigation on the engineering effects of the geometrical configuration of the jacking rectangular pipe

For rectangular pipe-jacking construction, the primary priorities of smooth construction include minimizing the ground response and designating the appropriate jacking force to achieve the best results in environmental protection and energy conservation. The geometric cross-section design of the jacking rectangular pipe and its engineering performances such as the ground surface displacement, the jacking force consumption, and the stress-bearing state are easy to be ignored in the field construction. In this paper, the ground response characteristics under four kinds of rectangular pipe aspect ratio (H/W) with the same utilization cross-section area were investigated by using the calibrated finite element method (FEM) based on a case study conducted in Japan. The theoretical jacking force of each pipe section design was calculated and compared to provide a reference for long-distance or large-section jacking conditions. The stress-bearing state of each pipe was considered under different buried depths. The results show that the ground surface response decreases while the jacking force increases with increasing the aspect ratios. Thus, a reasonable design of the rectangular pipe section should comprehensively consider the influence of geometric effects on the ground and its stress-bearing state during the jacking construction. The findings of this study provide a practical reference for the safe and economic design of the jacking rectangular pipe and engineering management.

Influence of the Geometrical Cross-Section Design on the Dynamic Cyclic Fatigue Resistance of NiTi Endodontic Rotary Files-An In Vitro Study.

The aim of this study was to analyze and compare the influence of the geometrical cross-section design on the dynamic cyclic fatigue resistance of NiTi endodontic rotary files. Materials and Methods: Forty sterile endodontic rotary files were selected and distributed into the following study groups: A: 25.06 double S-shaped cross-section NiTi alloy endodontic rotary files (Mtwo) (n = 10); B: 20.04 rectangular cross-section NiTi alloy endodontic rotary files (T Pro E1) (n = 10); C: 25.04 convex triangular cross-section NiTi alloy endodontic rotary files (T Pro E2) (n = 10); and D: 25.06 triangular cross-section NiTi alloy endodontic rotary files (T Pro E4) (n = 10). A cyclic fatigue device was used to conduct the static cyclic fatigue tests with stainless steel artificial root canal systems with 200 µm and 250 µm apical diameter, 60° curvature angle, 3 mm radius of curvature, 20 mm length, and 4% and 8% taper. The results were analyzed using the ANOVA test and Weibull statistical analysis. Results: All the pairwise comparisons presented statistically significant differences between the time to failure and number of cycles to failure for the cross-section design study groups (p < 0.001). Conclusions: the double S-shaped cross-section of Mtwo NiTi endodontic files shows higher cyclic fatigue resistance than the rectangular cross-section of T Pro E1 NiTi endodontic files, the convex triangular cross-section of T Pro E2 NiTi endodontic files, and the triangular cross-section of T Pro E4 NiTi endodontic files.

Reinforced Concrete Beam under Support Removal-Parametric Analysis.

This paper investigates the behaviour of a reinforced concrete beam under a support removal. A detailed parametric analysis is carried out, covering the effect of support removal rate on dynamic response. The linear elastic and nonlinear inelastic responses are computed and studied in detail. Critical parameters during the structural response are identified. In order to determine the ultimate load, the vertical pushover analysis is performed. The key parameters driving the beam response are assumed as random variables, and respective reliability study makes it possible to check the overall uncertainty of the dynamic response. In particular, the response spectrum measuring the effect of support removal rate has been computed. It has been demonstrated that the critical vertical response occurs when the time of support removal is up to to 17% of the first natural period. The vertical pushover analysis results in obtaining capacity curves and showed the order in which two plastic hinges occur for various load patterns. Finally, the reliability-based sensitivity analysis indicates the geometric cross-section cover and height are the most sensitive parameters of the beam response.

Evaluation of thermo photovoltaic performance through aluminum-fueled combustor with partially porous medium and different geometric cross-sections

Thermo photovoltaic (TPV) power generation systems have attracted a great deal of attention in the field of portable electronic devices. The high and uniform temperature of TPV combustor plays a decisive role in the improvement of system efficiency. In this study, aluminum is utilized as energy source of TVP. To model the premixed combustion of aluminum-air, an asymptotic model of flame structure including four zones of solid, liquid, and gaseous aluminum and post-flame and three asymptotic fronts of melting, evaporation, and flame is proposed. Then, the conservation equations and boundary conditions are derived and the combustion characteristics of aluminum are obtained. Combustion is evaluated for simple and porous media with trapezoidal, rectangular, triangular, and circular cross-sections. Finally, the influence of parameters on the TVP performance is assessed. The results indicated that in the medium with a porosity factor of 0.8, the total efficiency is higher than the simple medium for all cross-sections. In the medium with a porosity factor of 0.6, however, the triangular and circular cross-sections exhibit lower efficiency compared to the simple medium. In the case with a porosity factor of 0.4, only the efficiency of the channel with a trapezoidal cross-section is higher than the simple medium.

Analytic expressions for geometric cross-sections of fractal dust aggregates

ABSTRACT In protoplanetary discs and planetary atmospheres, dust grains coagulate to form fractal dust aggregates. The geometric cross-section of these aggregates is a crucial parameter characterizing aerodynamical friction, collision rates, and opacities. However, numerical measurements of the cross-section are often time consuming as aggregates exhibit complex shapes. In this study, we derive a novel analytic expression for geometric cross-sections of fractal aggregates. If an aggregate consists of N monomers of radius R0, its geometric cross-section G is expressed as $G=AN\pi R_0^2/[1+(N-1)\tilde{\sigma }]$, where $\tilde{\sigma }$ is an overlapping efficiency, and A is a numerical factor connecting the analytic expression to the small non-fractal cluster limit. The overlapping efficiency depends on the fractal dimension, fractal prefactor, and N of the aggregate, and its analytic expression is derived as well. The analytic expressions successfully reproduce numerically measured cross-sections of aggregates. We also find that our expressions are compatible with the mean-field light scattering theory of aggregates in the geometrical optics limit. The analytic expressions greatly simplify an otherwise tedious calculation and will be useful in model calculations of fractal grain growth in protoplanetary discs and planetary atmospheres.

Production of X(3872) at high multiplicity

The dependence of the production of the $X(3872)$ meson on the hadron multiplicity in $pp$ collisions has been used as evidence against $X$ being a charm-meson molecule. The argument is based in part on the incorrect assumption that the cross section for the breakup of $X$ by scattering with comovers can be approximated by a geometric cross section inversely proportional to the binding energy of $X$. The breakup cross section should instead be approximated by the probability-weighted sum of the cross sections for the scattering of comoving pions from the charm-meson constituents of $X$, which is insensitive to the binding energy. A simple modification of the comover interaction model gives excellent fits to the data from the LHCb collaboration on the multiplicity dependence of the production of $X$ and $\psi(2S)$ using parameters compatible with $X$ being a loosely bound charm-meson molecule.

Featured Collection Introduction: National Water Model III

Featured Collection Introduction: National Water Model III

A novel contour feature denoising method for real geometrical parameters measurement of multi-core fiber

The multi-core fiber (MCF) plays an important role in expanding capacity. The geometrical parameters and its changes will greatly influence the transmission characteristics of the fiber and the performance of the MCF based devices. The traditional denoising method for analyzing geometrical parameters of the fiber is complex, and the high quality of the fiber image is demanded, which result in poor applicability. In this paper, a novel contour feature denoising method for real geometrical parameters measurement of the fiber is proposed. Compared with the traditional denoising method, the advantage of the proposed method is that denoising the contour image reduces algorithm redundancy, and through the positional relationship between the useful and the pseudo contours, it can effectively remove the influence of noise on the measurement results. The geometrical parameters of two commercial seven-core fibers (SCF) are analyzed by the proposed method, the results show that the real geometrical cross-section of the fiber can be exactly exhibited, and the measurement error of the geometrical parameters is reduced by 4%.

Optimization of the epithermal neutronic beam for BNCT at a 22 MW MTR reactor

The design of an Epithermal Neutronic Beam (ENB) at a 22 MW MTR reactor for the Boron Neutron Capture Therapy (BNCT) is discussed in this paper(Calculations were made for the ETRR-2 reactor). Along the beam a moderator made from the materials: Pb + Al + Cd + Al + FLUENTAL + Al + FLUENTAl + Air + Cd + Bi with Pb was used as reflector. Following the moderator is air + Pb + Air with Bi lined collimator and Li2CO3-Polyethelene at the beam exit. The collimator is surrounded by layers of water, heavy concrete and Pb. The calculated values of the beam at the head phantom were: Фepith = 2.402 х 109 n/cm2.s, Df/Фepith = 1.724 х 10−11 cGy cm2/n and Dγ/Фepith = 0.196 х 10−11 cGy cm2/n, where the head phantom was placed at 5 cm from the beam exit. The obtained values by using the MCNP code of the Advantage Depth (AD), the Advantage Ratio (AR), the Advantage Depth Dose Ratio (ADDR), the treatment time and the therapeutic ratio were: 8.75 cm, 5.62, 36.37 cGy/min, 34.37 and 5.62, respectively.The MCNP geometry plotting resources were used to plot all geometrical cross sections of the simulated reactor.

New experimental constraints in a new landscape for composite dark matter

Certain strongly interacting dark matter candidates could have evaded detection, and much work has been done on constraining their parameter space. Recently, it was shown theoretically that the scattering cross section for ${m}_{\ensuremath{\chi}}\ensuremath{\gtrsim}1\text{ }\text{ }\mathrm{GeV}$ pointlike dark matter with a nucleus cannot be significantly larger than the geometric cross section of the nucleus. This realization closes the parameter space for pointlike strongly interacting dark matter. However, strongly interacting dark matter is still theoretically possible for composite particles, with much parameter space open. We set new, wide-ranging limits based on data from a novel detector at the University of Chicago. Backgrounds are greatly suppressed by requiring coincidence detection between two spatially separated liquid-scintillator modules. For dark matter ($v\ensuremath{\sim}{10}^{\ensuremath{-}3}\text{ }\text{ }\mathrm{c}$), the time of flight would be $\ensuremath{\sim}2\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$, whereas for cosmic rays, it would be $\ensuremath{\sim}2\text{ }\text{ }\mathrm{ns}$. We outline ways to greatly increase sensitivity at modest costs.

COMPUTER TECHNOLOGIES IN THE CALCULATION OF GEOMETRIC CHARACTERISTICS OF COMPLEX SECTIONS

None of the calculations for machine parts, structure elements and constructions for strength, rigidity and stability can be performed without using the geometric cross-section characteristics. These include: cross-sectional area, axial, centrifugal and polar moments of inertia, radius of gyration, axial and polar resistance moments of cross-section, etc. The article discusses the problem of technical specialties students` training quality improvement with information technologies aids. There is a review and proposed methodology of usage the software for calculating the geometric cross-sections properties. There are two groups of software: 1) software developed by teachers of higher educational institutions to use in the educational process; 2) industrial software for design engineers, which can also be used during the educational process. Using as an example the calculation of the geometric cross-sections properties of a complex section formed from several rolled profiles, it is demonstrated that the usage of programs "Geom 2006", "Compass 3D", "Consul" and "Constructor of sections" has the following advantages: decrease the costs of effort and time for routine mathematical calculations, makes it easier to find and correct errors made by manual calculations during individual study, which has a positive effect on the learning process; the implementation of calculation and graphic tasks using computer software significantly increases the interest of students for the discipline that is being studied and contributes to the better consolidation of theoretical knowledge and practical skills; students acquire skills in creating design schemes, preparing initial data, analyzing the obtained results, which are necessary for their further work with software systems for structures calculations during the course and for diploma design; it is especially useful to use the proposed programs for distance learning as an effective tool to organize individ-ual study.

3D Printing of Plant-Derived Compounds and a Proposed Nozzle Design for the More Effective 3D FDM Printing

Additive manufacturing technology has been developed in the manufacturing industry; however, limited choice of materials and low printing speeds in large-scale production make 3D printing challenging in the industry. Wood and cellulose-based materials have recently drawn a lot of attention for use as 3D printing materials due to their unique properties such as environmental friendliness, cost-effectiveness and abundancy. However, because these compounds are derived from various natural sources, their different particle sizes can result in low 3D printing quality. The objective of this study is to resolve the mentioned deficiencies in the packaging industry by designing a novel 3D printer nozzle based on the material extrusion method (FDM technique), which provides higher printing speed and enhanced quality for wood and cellulose-based materials. The packaging industry can significantly benefit from 3D printing technology for cellulose-based materials by producing high-quality recyclable economical packaging on a large scale according to the clients’ demand. The proposed nozzle design enables selecting different geometrical cross-sections of the nozzle dies and any number of extrusion points along the nozzle die simultaneously during the 3D printing process. These capabilities lead to advanced performance and improved speed of 3D printing in large scale manufacturing. The proposed nozzle design provides a novel technique for 3D printing of plant-derived compounds with remarkable advantages such as providing selective variable extrusion and multiple nozzle dies. Compared to other existing 3D printing techniques, the proposed nozzle abilities make it a promising option with higher speed and better functionality for the packaging industry.