Geometrical Cross Section Research Articles

Experimental and numerical investigations of the octagonal concrete-filled thin-walled tube columns with binding bars (O-CFT-WBB) under compressive pressure and thermal loads

An experimental and theoretical investigation is conducted to evaluate the behavior of CFT columns with a unique geometric cross-section under axial loading and in a thermal environment. In this study, based on previous research on octagonal CFT columns, this geometry was chosen as a favorable option compared to other possible configurations. Additionally, binding bars were employed to enhance these columns' mechanical and thermal behavior. A thermal gradient (temperature changes ranging from 0 to 600 degrees) was applied in the laboratory to replicate extreme environmental conditions. By experimental results, a theoretical investigation was conducted to derive suggested formulas for considering confinement effects in O-CFT-WBB columns, and the results were then compared with experimental results and the closest existing formulas. After examining the experimental results, it was shown that the presented formulas had more accuracy than the existing ones. Additionally, based on the experimental results, the presence of binding bars at different temperatures led to different behaviors in the axial capacity of the columns. According to the results, the binding bars in the O-CFT-WB columns can lead to different behaviors in the axial capacity of the columns. Based on a constitutive model of confined concrete, a method for calculating the maximum strength of L-shaped CFT columns with and without binding bars is proposed. The method is verified with experimental results from this test program and data from other experiments.

Učinak veličine stupa i kuta nagiba pukotina na stabilnost podzemnih prostorija u poroznim vapnencima

Pillars play an essential role in the stability of an underground cavity. Their most important parameters are the dimensions, material parameters, condition, and joint geometry. This research investigates the impact of geometrical horizontal cross section and joint’s dip angle on the stability of the pillar, which affects the stability of cavities. The chosen study site is in a cellar system in Budapest, Hungary. According to the laboratory and on-site investigations, the cellar’s host rock is porous limestone with a low strength but a massive rock mass with few discontinuities. In some of the previously investigated cellar systems the edge of the pillars was cut because of space requirements. Therefore, this study aims to determine the effect of such geometrical changes on the stability of the cellar. A 25 m2 room with a single square-based pillar was used to model the stability. Material parameters were determined through various laboratory tests such as UCS, triaxial, and discontinuity shear strength tests, as well as rock mass classification. Three-dimensional finite element software (RS3) was used to evaluate the stability of the studied pillar. Overall, this study provides valuable insights into the factors that influence stability of pillars in underground cavities and highlights the importance of carefully considering these factors when designing, verifying, and constructing support systems for underground structures.

Effects of surface coating on the shortwave and longwave radiative effects of dust aerosol in comparison with external mixing: A theoretical study

Dust particles can be coated with a surface layer of pollutants such as sulfate and nitrate after mixing with local pollution during long-range transport. Previous studies investigated the effects of surface coating on scattering properties and direct radiative effects (DRE) of dust in the solar shortwave (SW) spectral region. In this research, we carried out a theoretical study of the surface coating effects in both solar SW and the terrestrial longwave (LW) and compared the results with external mixing. Three dust coating schemes were developed to study a hypothetical sulfate-dust coating case, in which the thickness of the coating sulfate layer is proportional to the size, surface area, and mass of the dust core, respectively. We found that at the 0.55 µm the aerosol optical thickness (AOD) of the externally mixed dust-sulfate increases more efficiently with the increasing sulfate mass than the coated dust cases, whereas the opposite is true at the 10 µm. This is because at 0.55 µm the difference in the total geometrical cross section is the dominant factor for the AOD difference, while at the 10 µm the dominant factor is the difference in extinction cross section. The differences in dust DRE at the top of atmosphere and surface between the external mixing and coated dust cases can be largely explained by the differences in AOD. Dust absorption in the SW is found to be significantly enhanced by the surface coating of non-absorptive sulfate due to the so-called “lensing effect”. When SW and LW DREs are combined, the volume- and area-proportional coating schemes have a significantly weaker cooling effect than externally mixed dust-sulfate. This research provides the theoretical understanding of how surface coating affects the SW, LW and total dust DREs.

Ultraheavy atomic dark matter freeze-out through rearrangement

Atomic dark matter is usually considered to be produced asymmetrically in the early Universe. In this work, we first propose that the symmetric atomic dark matter can be thermally produced through the freeze-out mechanism. The dominant atom antiatom annihilation channel is the atomic rearrangement. It has a geometrical cross section much larger than that of elementary fermions. After the atomic formation, this annihilation process further depletes dark matter particles and finally freezes out. To give the observed dark matter relic, the dark atoms are naturally ultraheavy, ranging from 106 to 1010 GeV. Published by the American Physical Society 2024

The importance of the local structure of fractal aggregates

The pair correlation function, g(r), is a fundamental descriptor of the inner structure of fractal aggregates of monomers. It provides a natural tool for studying physical properties involving two-point interaction (e.g. optics of aggregates). Several domains of distances between pairs of monomers have been identified. The fractal domain (in which g(r) is a power-law) is generally dominant for large aggregates. We show here that the local behavior of g(r)—involving monomers tangent to a given monomer—is necessary for most of the quantitative applications, even if that local domain is not directly related to fractal morphology. We derive a simple generic pair correlation function for fractal aggregates, depending on three structural parameters only: the fractal dimension, df ; the prefactor, kf ; the local mean coordination number, Zˉ . Unlike the fractal dimension, the prefactor and the mean coordination number are not universal since they depend on many parameters of the generation process. We discuss the impact of the definite shape of g(r) on the aggregate structure factor profile (a measurable quantity through small-angle x-ray scattering). Improvement from the new g(r) shape is also illustrated deriving an analytical expression of the geometric cross section, G, of aggregates for fractal dimension <2 . Accuracy is checked by comparing with numerical data from aggregates of fractal dimension df=1.9 . On the up-to-date analytical expression of G, the contributions of the short- and long-range behaviours of g(r) are well separated, and it is clear that the local behavior of the pair correlation function is required to obtain accurate values of the geometric cross section. Thus, in addition to the fractal structure of aggregates, the local structure of aggregates (to which the prefactor kf and the g(r) divergence at short distances are related) also appears important to accurately describe their physical features.

Classification of Banana Types Based on The Geometrical Attributes using Artificial Neural Network Method

Banana (Musa paradisiaca) is one of the important horticultural commodities. This study aims to measure the physical and geometrical parameters of three different bananas (Muli, Ambon, and Kepok) and to develop prediction equations using an Artificial Neural Network (ANN) model. In this study the backpropagation ANN model with supervised learning method was used. The ANN model had one output node, two hidden layers, and network architecture of 8 inputs, namely fruit weight and volume, projected area and roundness of the fruit, cross section, peel color, and geometric mean fruit cross section diameter. The data for building the model and testing the model were respectively 70% and 30% of the 150 data number in total. The results showed that the best ANN model structure for estimating Muli, Ambon and Kepok bananas was purelin-logsig-logsig with an RMSE value of 0.0077 and an R2 of 0.9999. This shows that the ANN model is highly robust to predict the banana types. Using the built model, the accuracy of the prediction results is 100%. Keywords: Artificial Neural Network, Banana fruits, Geometry attribute.

Numerical study on the impact of geometrical parameters and employing ternary hybrid nanofluid on the hydrothermal performance of mini-channel heat sink

Thermal management and temperature control of the electrical, electronic, and electrochemical devices during their operation have always been a challenge for proper performance and further development of them. In this regard, the utilization of liquid-cooled mini-channel heat sinks (MCHSs) and improving their capability for heat dissipation have been considered an effective method in past decades. The current study aims to improve the hydrothermal performance and temperature uniformity of MCHS. To this end, several channel configurations with novel geometrical cross sections, namely basic case and cases 1–4, are designed to investigate the influence of geometrical parameters on the mini-channel performance and temperature distribution inside the heat sink. Moreover, the hydrothermal improvement of each model in comparison to the basic case is computed through a parameter, namely performance evaluation criteria (PEC). Additionally, the impact of employing water-based ternary hybrid nanofluid (THNF) containing TiO2-MgO-GO ternary hybrid nanoparticles (THNPs) with various volume fractions and shape factors (SFs) instead of distilled water in the mini-channel with optimized hydrothermal behavior is thoroughly scrutinized. the outcomes endorse that in case 3 with trapezoidal geometry and PEC parameter equal to 1.2, the Nusselt number improves by 3.2 and 1.3 times, in comparison to case 2 (lowest values of Nusselt number) and base case, at Reynolds number of 831. Also, this is observed that hydraulic diameter directly impacts the pressure drop, and by decrement of that, the pressure drop heightens. However, case 2 with a rhombus geometry results in better temperature uniformity due to its larger effective heat transfer area. Furthermore, it is observed that the volume fraction and SF of THNP significantly affect the hydrothermal behavior of THNF inside the MCHS. For instance, by employing THNF with volume fractions of 0.03 % and 0.05 %, the average heat transfer coefficient (HTC) improves by 9 % and 17 %, pressure drop increases by 220 Pa and 370 Pa, and thermal resistance reduces by 9 % and 25 %, respectively, at Reynolds number of 1496, compared to distilled water. Further, THNF with a volume fraction of 0.05 %, reduces the maximum temperature of the heat sink by 3 K in comparison to distilled water, at a Reynolds number of 831. In addition, the utilization of disparate types of THNP with various SF, including spherical (sf = 3), platelets (sf = 5.7), blades (sf = 8.6), and lamina (sf = 16.1576) is examined and disclosed with volume fraction of 0.05 % and SF of 16.1576 instead of 3, HTC roughly elevates by 67 % and thermal resistance decreases by 47 %, at a Reynolds number of 831.

Properties of water and argon clusters developed in supersonic expansions.

Using adiabatic molecular dynamics coupled with the fluid dynamics equations, we model nucleation in an expanding beam of water vapor and argon on a microsecond scale. The size distribution of clusters, their temperature, and pickup cross sections in dependence on velocity are investigated and compared to the geometric cross sections and the experiment. The clusters are warmer than the expanding gas because of the time scale of relaxation processes. We also suggest that their translational and rotational kinetic energies are modified due to evaporative cooling. The pickup cross sections determined for the final clusters using molecules of the same kind increase with decreasing velocity, still obeying the (a+bN1/3)2 law.

Morphology Engineering for High-Q Plasmonic Surface Lattice Resonances with Large Field Enhancement

Plasmonic surface lattice resonances (SLRs) have endowed plasmonic systems with unprecedently high quality (Q) factors, giving rise to great advantages for light–matter interactions and boosting the developments of nanolaser, photodetector, biosensor and so on. However, it still lacks exploration to develop a strategy for achieving large electric field enhancements (FEs) while maintaining high Q factors of SLRs. Here, we investigate and verify such a strategy by engineering morphologies of plasmonic lattice, in which the influences of geometrical shapes, cross-section areas and structural compositions of particles are investigated. Firstly, we found that the Q factor of a plasmonic SLR is inversely proportional to the square of the cross-section area of the cell particles in the studied cases. Secondly, larger FEs of SLRs appear when the separated cell particles support stronger FEs. By combining these effects of particle morphology, we achieve a plasmonic SLR with Q factor and FE up to 2100 and 592 times, respectively. Additionally, supported by the derived connections between the Q factors and FEs of SLRs and the properties of cell particles, the property optimizations of SLRs can be done by optimizing the separated particles, which are distinctly time-saving in simulations. These results provide a guideline for the design of high-performance optical nanocavities, and can benefit a variety of fields including biosensing, nonlinear optics and quantum information processing.

Analisis Pengendapan Jumlah Volume Sedimen di dalam Saluran Primer D.I Cipicung Kecamatan Cipunagara Kabupaten Subang

This study aims to determine the amount of deposition due to the volume of sediment mixed with solid household waste in the canal which is high enough to become shallow, resulting in a change in the geometric cross-section of the canal in the primary canal and damage to the irrigation network of D.I. Cipicung. The method used in this research activity uses a mathematical analysis technique from Chow and Grag theory in the form of sediment depth and geometric changes in the channel cross section. The results show that the volume of sediment deposited in the primary canal is Vq primary = 16.24 m3 (section length of 50.5 meters from a channel length of 300 meters) and the geometric change in the cross section of the primary channel is A = 1.24 m2. The amount of sediment volume that affects the geometric changes in the cross-section of the primary channel that needs to be repaired is that the canal linings are still alluvial with construction linings, removal of sediment that has been mixed with solid waste, and periodic maintenance.

Ion-Neutral Collision Cross Section as a Function of the Static Dipole Polarizability and the Ionization Energy of the Ion.

Ion mobility spectrometry is becoming more and more popular as a fast, efficient, and sensitive tool for the separation and identification of ionized molecules in the gas phase. An ion traveling through a drift tube at atmospheric pressure under the influence of an electric field collides with the buffer gas molecules. The mobility of the ion depends inversely on the ion-neutral collision cross section. In the simplest hard-sphere approximation, the collision cross section is the area of the conventional geometric cross section. However, deviations are expected because of the physical interactions between the colliding species. More than a century ago, Langevin described a model for the interaction between a point-charge ion and a polarizable atom (molecule). Since then, the model has been modified many times to include better approximations of the interaction potential, usually preserving the point-charge nature of the ion. Although more advanced approaches allow for considering polarizable ions with dissimilar sizes and shapes, still explicit analytical dependencies on the properties of the ion remain elusive. In this work, an extended version of the Langevin model is proposed and solved using algebraic perturbation theory. A simple analytical expression of the collision cross section depending explicitly on both the static dipole polarizability and the ionization energy of the ion is found. The equation is validated using ion mobility data. Surprisingly, even low-level calculations of the polarizability tensors produce results that are consistent with the experimental observations. This fact makes the equation very attractive for helping applications in different areas, such as the deconvolution of mobilograms of protomers, ion-molecule chemical kinetics, and others.

Comprehensive 3E analyses of a parabolic trough collector equipped with an innovative combined twisted turbulator

The Parabolic trough collector (PTC) is one of the most well-known equipment in renewable energy. Today, it is also a renewable source for refining and transferring power to a low-carbon economy. The present study aims to investigate the effect of the geometrical shape of the Receiver cross-section in the PTC and to investigate the effect of placing the innovative combined twisted turbulator (CTT) in it. The receiver is simulated with three different geometric shapes circular cross-section (CCS), vertical elliptical cross-section (VECS), and horizontal elliptical cross-section (HECS). The PTC contains a two-phase MWCNT-GO/Syltherm 800 hybrid nanofluid (HNF), simulated using the mixture model. In this study, numerical simulations have been conducted for Reynolds numbers (Re) of 5000 to 20,000, volume fractions (ϕ) of 1 and 2% of nanoparticles, and pitch ratios (PR) of 0.5 to 2 of the innovative CTT. The results obtained from the present study show that the geometrical change of the cross-section of the receiver is very effective in the hydrodynamic performance of the PTC. Also, placing the innovative CTT in Receiver has consistently increased thermal performance and energy efficiency. The performance evaluation criteria (PEC) index is always greater than 1 in all numerical simulation modes. Therefore, innovative CTT is always desirable in terms of the PEC index. The maximum exergy efficiency is Re = 10,000, ϕ= 0.02, and PR = 2. Based on the environmental analysis, the amount of carbon dioxide in the PTC equipped with an innovative CTT containing two-phase MWCNT-GO/Syltherm 800 HNF is 0.033 kg/day.

Collisional Growth and Fragmentation of Dust Aggregates. II. Mass Distribution of Icy Fragments

By performing N-body simulations, we investigated the fundamental processes of collisions between dust aggregates composed of submicron-sized icy dust monomers. We examined the mass distribution of fragments in the collisional outcomes in a wide range of the mass ratio and the collision velocity between colliding dust aggregates. We derived analytic expressions of the mass distribution of large remnants and small fragments by numerical fitting to the simulation results. Our analytic formulae for masses of the large remnants can reproduce the contribution of mass transfer from a large target to a small projectile, which occurs for a mass ratio of ≳3 and is shown in a previous study. We found that the power-law index of the cumulative mass distribution of the small fragments is independent of the mass ratio and only weakly dependent on the collision velocity. On the other hand, the mass fraction of fragments of individual dust monomers decreases with an increasing total mass of colliding aggregates for a fixed mass ratio. This tendency implies that multiple hierarchical disruptive collisions (i.e., collisions between fragments, and collisions between fragments of fragments) are required for producing a large number of individual dust monomers via collisional fragmentation. Our fragment model suggests that the total geometric cross section integrated over the fragments is estimated to be about the same order as the geometric cross section of the target.

Mass flow characteristics of CO2 operating in a transcritical cycle flowing through a needle expansion valve in a direct-expansion solar assisted heat pump

An expansion device is one of the key components of heat pump systems. Although in the literature there are several studies that analyze the effect of opening the expansion valve on heat pumps, none of them reported this effect for heat pumps that operate with solar energy. In this study, the mass flow rate characteristics through an expansion device in a direct-expansion solar assisted heat pump (DX-SAHP) operating with CO2 is investigated. With experimental data, a new correlation is proposed. A statistical method is used to determine the dimensionless Π-groups that most influences the mass flow rate. The parameters selected to compose the new correlation are: outlet and inlet pressures of the expansion device, geometric (cross-section area) and fluid viscosity. The proposed correlation shows good agreement with the measured data with average and standard deviations of 0.77% and 10.4%, respectively. The maximum relative deviation of all predictions of mass flow rate is less than ±30% and approximately 90% of mass flow rate experimental data are within ±20% of the predictions. In addition, for a same needle expansion valve opening, the mass flow rate increases with the augment in the solar radiation flux.

Design of Hollow Horn Based on Four-terminal Network Method

When designing the horn of the ultrasonic transducer for rotary machining, the traditional analytical method cannot consider the complex assembly cross-section of the horn, resulting in a large final simulation error and design error. At the same time, when the design diameter of the transducer is too large, the size of the back mass obtained by the traditional analytical method is too thin. This paper combines the four terminal network method and the finite element method, selects the sandwich piezoelectric transducer, takes the ER spring chuck commonly used in rotary machining as an example, derives the transmission matrix corresponding to the geometric cross-section shape, and then uses the four-terminal network method and the traditional analytical method to design two sets of stepped ultrasonic transducers with the design frequency of 22 kHz for analysis and comparison. Finally, through the analysis, it is verified that the ultrasonic transducer designed by the four-terminal network method has a performance closer to the theoretical design.

Total and partial charge changing cross-sections of 300 A MeV Fe26+ ion beam in different target media

In the present study, the total and partial charge changing cross-sections of 300 A MeV Fe26+ ion beam in CR39 and in combined medium of Al and CR39 were measured. The CR39 nuclear track detectors were used to identify the incident charged particles and their fragments using an automated image analyzing system. The total charge changing cross-section as calculated is (1220 ± 132) mb in CR39 target and (1472 ± 170) mb in combined target of Al and CR39. The total charge changing cross-section was fitted to the Bradt-Peters geometrical cross-section and compared with earlier results. For calculating the partial charge changing cross-sections for ΔZ = -1, −2, −3,….…,–23, the number of events corresponding to each fragment were determined from multiple Gaussian fitting of the diameter distributions within ±2σ confidence levels and the number of incident and survived beam ions were counted within ±3σ confidence levels. Some beam contaminated events were observed and presented.

Current and Future γ-Ray Searches for Dark Matter Annihilation Beyond the Unitarity Limit

For decades, searches for electroweak-scale dark matter (DM) have been performed without a definitive detection. This lack of success may hint that DM searches have focused on the wrong mass range. A proposed candidate beyond the canonical parameter space is ultraheavy DM (UHDM). In this work, we consider indirect UHDM annihilation searches for masses between 30 TeV and 30 PeV—extending well beyond the unitarity limit at ∼100 TeV—and discuss the basic requirements for DM models in this regime. We explore the feasibility of detecting the annihilation signature, and the expected reach for UHDM with current and future very-high-energy (VHE; >100 GeV) γ-ray observatories. Specifically, we focus on three reference instruments: two Imaging Atmospheric Cherenkov Telescope arrays, modeled on VERITAS and CTA-North, and one extended air shower array, motivated by HAWC. With reasonable assumptions on the instrument response functions and background rate, we find a set of UHDM parameters (mass and cross section) for which a γ-ray signature can be detected by the aforementioned observatories. We further compute the expected upper limits for each experiment. With realistic exposure times, the three instruments can probe DM across a wide mass range. At the lower end, it can still have a point-like cross section, while at higher masses the DM could have a geometric cross section, indicative of compositeness.

Research on Geometric Design Standards for Freeways under a Fully Autonomous Driving Environment

The formulation of the current geometric design standard for freeways considers the influence of the “human-vehicles-road-environment” system. In the fully autonomous environment, the driver has been liberated from the system, which means that the influence of “human” will be reduced. The requirements or limitations of the freeway geometric design standard, which consider the driver’s psychological and physical factors in the traditional driving environment, can be more flexible in the fully automatic driving environment. By using the methods of comparative analysis, theoretical analysis, and theoretical calculation, this article researches the geometric design standard for freeways in an autonomous driving environment from four aspects: control elements of geometric design, horizontal alignment, vertical alignment, and cross-section elements. The main contribution of this article is to propose the recommended values of the geometric design standard for freeways in a fully autonomous driving environment, which can provide reference for the formulation of relevant standards or specifications for autonomous driving roads in the future.

Broadband tunable mid-infrared absorber based on conductive strip-like meta-atom elements

A metamaterial composed of thin metallic strips as an efficient broadband absorber in the mid- infrared spectrum is investigated. Here the matching between dielectric and geometrical properties of the individual elements is critical to ensure high absorption. Detailed theoretical analysis based on the electric dipole approximation is performed to characterize the absorption and scattering properties of the individual elements of the unit cell and the results are used to design the metamaterial composed of such configurations. The absorption cross-section of a strip-shaped element can exceed its longitudinal geometrical cross-section area by 17 times. It was shown that the absorptance of the Ni-based metal-insulator-metal (MIM) metamaterial structure can exceed 90% in ~8.2 – 18 µm spectrum. The broadband absorption is associated with the excitation of the low-Q-factor dipole modes of the strips. Such an absorber demonstrates good polarization and incident angle tolerance for transverse-electric (TE) waves. The absorption spectrum can be tuned by varying individual element parameters.

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.