Geometrical Cross Section Research Articles

Numerical Study of Atmospheric Ice Accretion on Various Geometric Cross-Sections

This paper describes the numerical study of atmospheric ice accretion on four different geometric cross sections, circular, parabola, triangle and cube. Most structures are the combination of these four basic geometric cross sections. Understanding of the atmospheric ice accretion physics on these will provide a base for further analyses of ice accretion and its effects on complex structures. CFD based numerical analyses are carried out in this research work to understand the rate and shape of atmospheric ice growth on these cross sections. For constant wind speed and atmospheric temperature, the ice growth is simulated as function of time, where more ice accretion is found on cube as compared to three other cross sections. Parametric study to understand the effect of iced surface roughness showed a significant difference in ice growth, when compared with the case, where no surface roughness was assumed on the cross sections.

The optical, physical and chemical properties of the products of glyoxal uptake on ammonium sulfate seed aerosols

Abstract. The heterogeneous reaction between gas phase glyoxal and ammonium sulfate (AS) aerosols, a proxy for inorganic atmospheric aerosol, was studied in terms of the dependence of the optical, physical and chemical properties of the product aerosols on initial particle size and ambient relative humidity (RH). Our experiments imitate an atmospheric scenario of a dry particle hydration at ambient RH conditions in the presence of glyoxal gas followed by efflorescence due to decrease of the ambient RH. The reactions were studied under different RH conditions, starting from dry conditions (~20% RH) and up to 90% RH, covering conditions prevalent in many atmospheric environments, and followed by consequent drying of the reacted particles before their analysis by the aerosol mass spectrometer (AMS), cavity ring down (CRD) and scanning mobility particle sizer (SMPS) systems. At λ = 355 nm, the reacted aerosols demonstrate a substantial growth in optical extinction cross section, as well as in mobility diameter under a broad range of RH values (35–90%). The ratio of the product aerosol to seed aerosol geometric cross section reached up to ~3.5, and the optical extinction cross-section up to ~250. The reactions show a trend of increasing physical and optical growth with decreasing seed aerosol size, from 100 nm to 300 nm, as well as with decreasing RH values from 90% to ~40%. Optically inactive aerosols, at the limit of the Mie range (100 nm diameter) become optically active as they grow due to the reaction. AMS analyses of the reaction of 300 nm AS at RH values of 50%, 75% and 90% show that the main products of the reaction are glyoxal oligomers, formed by acetal formation in the presence of AS. In addition, imidazole formation, which is a minor channel, is observed for all reactions, yielding a product which absorbs at λ = 290 nm, with possible implications on the radiative properties of the product aerosols. The ratio of absorbing substances (C-N compounds, including imidazoles) increases with increasing RH value. A core/shell model used for the investigation of the optical properties of the reaction products of AS with gas phase glyoxal, shows that the refractive index (RI) of the reaction products are n= 1.68(±0.10)+0.01(±0.02) at 50% RH and n = 1.65(±0.06)+0.02(±0.01) at 75% RH at 355 nm. The observed increase in the ratio of the absorbing substances is not indicated in the imaginary part of the products at RH 50% and 75%. A further increase in the ratio of absorbing substances and a resulting increase in the imaginary part of the RI at higher RH values is expected, and may become even more substantial after longer reaction times, possibly in cloud or fog droplets. This study shows that the reaction of abundant substances present in atmospheric aerosols, such as AS, and gas phase glyoxal alters the aerosols' optical, physical and chemical properties and may have implications on the radiative effect of these aerosols.

Assessment of mixed and displacement-based models for static analysis of composite beams of different cross-sections

This paper presents a numerical assessment of different finite element models (FEM) for the static analysis of laminated composite beams of various cross-sections, considering equivalent single layer theories (Classical Lamination Theory – CLT, First-order Shear Deformation Theory – FSDT and Higher-order Shear Deformation Theories – HSDT). New mixed least-squares FEM are developed for all theories and confronted with displacement-based weak form, mixed weak form and mixed weighted residual form FEM, which are derived for comparison purposes. The governing equations consistent with the mixed formulations, derived from the Hellinger–Reissner variation principle, are also presented. A method of transforming the actual geometrical beam cross-section into an equivalent single layer, through transformation matrices and the parallel axis theorem, existing in the literature for the CLT is implemented and extended to the FSDT and HSDT. Validation and assessment of the different FEM involved the implementation of analytical solutions and comparison with numerical and analytical results available in the literature, from which conclusions in terms of accuracy and computational effort are drawn.

Fine structure of high-energy absorption cross sections for black holes

The high-energy absorption cross section of the Schwarzschild black hole is well approximated, in the eikonal regime, by the sum of two terms: the geometrical cross section of the black hole photon sphere and the contribution of a sinc function involving the geometrical characteristics (orbital period and Lyapunov exponent) of the null unstable geodesics lying on this photon sphere. From a numerical analysis, we show that, beyond the eikonal description, this absorption cross section presents a simple fine structure. We then describe it analytically by using Regge pole techniques and interpret it in geometrical terms. We naturally extend our analysis to arbitrary static spherically symmetric black holes endowed with a photon sphere and we then apply our formalism to Schwarzschild–Tangherlini and Reissner–Nordström black holes. Finally, on the example of the Schwarzschild black hole, we show numerically that a complicated hyperfine structure lying beyond the fine structure can also be observed.

In-flight calibration of mesospheric rocket plasma probes

Many effects and factors can influence the efficiency of a rocket plasma probe. These include payload charging, solar illumination, rocket payload orientation and rotation, and dust impact induced secondary charge production. As a consequence, considerable uncertainties can arise in the determination of the effective cross sections of plasma probes and measured electron and ion densities. We present a new method for calibrating mesospheric rocket plasma probes and obtaining reliable measurements of plasma densities. This method can be used if a payload also carries a probe for measuring the dust charge density. It is based on that a dust probe's effective cross section for measuring the charged component of dust normally is nearly equal to its geometric cross section, and it involves the comparison of variations in the dust charge density measured with the dust detector to the corresponding current variations measured with the electron and/or ion probes. In cases in which the dust charge density is significantly smaller than the electron density, the relation between plasma and dust charge density variations can be simplified and used to infer the effective cross sections of the plasma probes. We illustrate the utility of the method by analysing the data from a specific rocket flight of a payload containing both dust and electron probes.

A new transducer receive transfer function calibration method: application to microbubble backscattering cross-section measurements at high frequency

When comparing acoustic scattering experiments with theory, the relationship between the pressure generated by a scatterer at the surface of a transducer and the induced voltage must be known. Methods have been previously proposed to measure the receive transfer function that rely on several assumptions. A new, experimental method for measuring the acoustic response of a spherically-focused transducer, using a hydrophone at twice the focal distance, is proposed that requires a minimum number of assumptions and calculations. The receive transfer function of a spherically-focused, high-frequency transducer was calculated, and found to be within 10% of the receive transfer function calculated assuming reciprocity. Further, using the receive transfer function, the effective backscattering cross-section of bound microbubbles interrogated at 30 MHz was measured to be, on average, 65% of the geometric backscattering cross-section, with significant size-independent variability. These results give insight into selecting the optimal microbubble size distribution for linear microbubble imaging at high frequencies.

A Study on Data Acquisition from Sections of Virtual Coat Profile

Data was obtained through scanning manikin and coats separated by using [TC]2 3D body scanner. The method, using [TC]2 scanner as the experimental method and through double converting the scanned data format to get torso geometric section sets, was analyzed. Main program source code of Torso was provided in this paper. Geometric algorithms of point cloud data and curve data in there sections was provided based on the interception ways of horizontal sections, vertical sections and other random oblique sections toward torso geometric cross section.

Dynamics of unitarization by classicalization

We study dynamics of the classicalization phenomenon suggested in G. Dvali et al. [1], according to which a class of non-renormalizable theories self-unitarizes at very high-energies via creation of classical configurations (classicalons). We study this phenomenon in an explicit model of derivatively-self-coupled scalar that serves as a prototype for a Nambu–Goldstone–Stückelberg field. We prepare the initial state in form of a collapsing wave-packet of a small occupation number but of very high energy, and observe that the classical configuration indeed develops. Our results confirm the previous estimates, showing that because of self-sourcing the wave-packet forms a classicalon configuration with radius that increases with center of mass energy. Thus, classicalization takes place before the waves get any chance of probing short-distances. The self-sourcing by energy is the crucial point, which makes classicalization phenomenon different from the ordinary dispersion of the wave-packets in other interacting theories. Thanks to this, unlike solitons or other non-perturbative objects, the production of classicalons is not only unsuppressed, but in fact dominates the high-energy scattering. In order to make the difference between classicalizing and non-classicalizing theories clear, we use a language in which the scattering cross section in a generic theory can be universally understood as a geometric cross section set by a classical radius down to which waves can propagate freely, before being scattered. We then show, that in non-classicalizing examples this radius shrinks with increasing energy and becomes microscopic, whereas in classicalizing theories expands and becomes macroscopic. We study analogous scattering in a Galileon system and discover that classicalization also takes place there, although somewhat differently. We thus observe, that classicalization is source-sensitive and that Goldstones pass the first test.

Light absorption and scattering by aggregates: Application to black carbon and snow grains

A geometric-optics surface-wave approach has been developed for the computation of light absorption and scattering by nonspherical particles for application to aggregates and snow grains with external and internal mixing structures. Aggregates with closed- (internal mixing) and open-cell configurations are constructed by means of stochastic procedures using homogeneous and core-shell spheres with smooth or rough surfaces as building blocks. The complex aggregate shape and composition can be accounted for by using the hit-and-miss Monte Carlo geometric photon tracing method. We develop an integral expression for diffraction by randomly oriented aggregates based on Babinet's principle and a photon-number weighted geometric cross section. With reference to surface-wave contributions originally developed for spheres, we introduce a nonspherical correction factor using a non-dimensional volume parameter such that it is 1 for spheres and 0 for elongated particles. The extinction efficiency, single-scattering albedo, and asymmetry factor results for randomly oriented columns and plates compare reasonably well with those determined from the finite-difference time domain (FDTD) and the discrete dipole approximation (DDA) computer codes for size parameters up to about 20. The present theoretical approach covers all size ranges and is particularly attractive from the perspective of efficient light absorption and scattering calculations for complex particle shape and inhomogeneous composition. We show that under the condition of equal volume and mass, the closed-cell configuration has larger absorption than its open-cell counterpart for both ballistic and diffusion-limited aggregates. Because of stronger absorption in the closed-cell case, most of the scattered energy is confined to forward directions, leading to a larger asymmetry factor than the open-cell case. Additionally, light absorption for randomly oriented snowflakes is similar to that of their spherical counterparts under the condition of equal geometrical cross section area for both external and internal mixing states; however, nonspherical snowflakes scatter less light in forward directions than spheres, resulting in a substantial reduction of the asymmetry factor. We further demonstrate that small soot particles on the order of 1 μm internally mixed with snow grains could effectively reduce snow albedo by as much as 5–10%. Indeed, the depositions of black carbon would substantially reduce mountain-snow albedo, which would lead to surface warming and snowmelt, critical to regional climatic surface temperature amplification and feedback.

Catalysis of black holes/wormholes formation in high energy collisions

The current paradigm suggests that BH/WH formation in particles collisions will happen when a center-mass energy of colliding particles is sufficiently above the Planck scale (the transplanckian region). We confirm the classical geometrical cross section of the BH production reconsidering the process of two transplanckian particles collision in the rest frame of one of incident particles. This consideration permits to use the standard Thorne’s hoop conjecture for a matter compressed into a region to prove a variant of the conjecture dealing with a total amount of compressed energy in the case of colliding particles. We briefly mention that the process of BH formation is catalyzed by the negative cosmological constant and by a particular scalar matter, namely dilaton, while it is relaxed by the positive cosmological constant and at a critical value just turns off.

Penetration of nearby supernova dust in the inner solar system

We investigate the method by which nearby supernovae – within a few tens of pc of the solar system – can penetrate the solar system and deposit live radioactivities on earth. The radioactive isotopic signatures that could potentially leave an observable geological imprint are in the form of refractory metals; consequently, it is likely they would arrive in the form of supernova-produced dust grains. Such grains can penetrate into the solar system more easily than the bulk supernova plasma, which gets stalled and deflected near the solar system due to the solar wind plasma pressure. We therefore examine the motion of charged grains as they decouple from the supernova plasma and are influenced by the solar magnetic, radiation, and gravitational fields. We characterize the dust trajectories with analytical approximations which display the roles of grain size, initial velocity, and surface voltage. These results are verified with full numerical simulations for wide ranges of dust properties. We find that supernova dust grains traverse the inner solar system nearly undeflected, if the incoming grain velocity – which we take to be that of the incident supernova remnant – is comparable to the solar wind speeds and much larger than the escape velocity at 1 AU. Consequently, the dust penetration to 1 AU has essentially 100% transmission probability and the dust capture onto the earth should have a geometric cross section. Our results cast in a new light the terrestrial deposition of radioisotopes from nearby supernovae in the geological past. For explosions beyond ∼10 pc from earth, dust grains can still deliver supernova ejecta to earth, and thus the amount of supernova material deposited is set by the efficiency of dust condensation and survival in supernovae. Turning the problem around, we use observations of live 60Fe in both deep-ocean and lunar samples to infer a conservative lower bound iron condensation efficiency of M dust,Fe/ M tot,Fe ≳ 4 × 10 −4 for the supernova which apparently produced these species 2–3 Myr ago.

Acoustic Sizing of an Ultrasound Contrast Agent

Because the properties of ultrasound contrast agent populations after administration to patients are largely unknown, methods able to study them noninvasively are required. In this study, we acoustically performed a size distribution measurement of the ultrasound contrast agent Definity ®. Single lipid-shelled microbubbles were insonified at 25 MHz, which is considerably higher than their resonance frequency, so that their acoustic responses depended on their geometrical cross sections only. We calculated the size of each microbubble from their measured backscattered pressures. The acoustic size measurements were compared with optical reference size measurements to test their accuracy. Our acoustic sizing method was applied to 88 individual Definity ® bubbles to derive a size distribution of this agent. The size distribution obtained acoustically showed a mean diameter (2.5 μm) and a standard deviation (0.9 μm) in agreement within 8% with the optical reference measurement. At 25 MHz, this method can be applied to bubble sizes larger than 1.2 μm in diameter. It was observed that similar sized bubbles can give different responses (up to a factor 1.5), probably because of shell differences. These limitations should be taken into account when implementing the method in vivo. This acoustic sizing method has potential for estimating the size distribution of an ultrasound contrast agent noninvasively. (E-mail: d.maresca@erasmusmc.nl)

Flow/pressure characteristics and modeling of deformation processes of single-screw extruders

One of the most widespread practical methods of polymer processing is the extrusion method that is based on pressing a polymeric melt through channels of the molding tool which have different geometrical cross sections. The principal technical characteristic of extruders, named flow/pressure balance, and also modeling of deformation processes permit to evaluate their practical output in processing various polymers as a function of the hydraulic resistance which depends on the flow of an extruded polymeric material through the channels of the forming tool. The validity of obtained and presented results permits to recommend them reasonably not only for estimation of extruder output but also for making calculations necessary in extruder equipment design: checking calculation of strength and stability of a screw, calculation of driving power of the equipment being designed, strength calculation of a plasticizing cylinder, etc. POLYM. ENG. SCI., 50:2069–2073, 2010. © 2010 Society of Plastics Engineers

Cylinder light concentrator and absorber: theoretical description

We present a detailed theoretical description of a broadband omnidirectional light concentrator and absorber with cylinder geometry. The proposed optical "trap" captures nearly all the incident light within its geometric cross-section, leading to a broad range of possible applications--from solar energy harvesting to thermal light emitters and optoelectronic components. We have demonstrated that an approximate lamellar black-hole with a moderate number of homogeneous layers, while giving the desired ray-optical performance, can provide absorption efficiencies comparable to those of ideal devices with a smooth gradient in index.

Numerical analysis of long-range surface plasmon polariton modes in nanoscale plasmonic waveguides

Guiding properties of nanoscale metallic wire waveguides embedded in a semiconductor are discussed. By performing eigenmode numerical simulations of the waveguide and continually varying the geometrical cross-section parameters, we have obtained comprehensive mode characteristics, such as the effective refractive index, effective mode area, and propagation length, that provide full guided mode description. This allows us to gain insight into possible waveguide applications using the figures of merit. Amplification and polarization manipulation of a plasmonic signal in such a waveguide have also been considered.

Perilaku Lentur pada Keadaan Layan dan Batas Balok Beton Bertulang Berlubang Memanjang

I cross-section of reinforced concrete reduces weight and concrete needs, but the reduction in strength is not considerably large. In addition, I section reinforced concrete beam is relatively complicated and takes much longer time for manufacturing. Another geometric cross-section which results in equivalent weight reduction with that of I cross-section concrete beam may be hollow square crosssections of reinforced concrete beams. This research was conducted to identify and compare the behavior of the shear and dynamic effects of hollow core reinforced concrete beam with an I cross-section beam that equivalent with its. The specimens being tested were four reinforced concrete beams, of 2000 mm length, consisted of a T beam with bottom flange as control beam (BK) possessing dimensions of bfa = 600 mm, bw = 125 mm, bfb = 200 mm, h = 300 mm, tf = 100 mm, and three hollow core T beams as tested beam (BB1, BB2 and BB3) possessing dimensions of bf = 600 mm, bw = 200 mm, blubang = 75 mm h = 300 mm, tf = 100 mm. Static loading was applied by means of a hydraulic jack in a four-point loading system, were. Dynamic loading test was carried out by vibrating the beams to obtain the natural frequency, where the vibrating load were produced by a mechanical vibrator. Whilst the data on the static load carrying capacity was recorded at the first crack and at each initial additional crack until the ultimate fracture, those on dynamic loading was recorded on the solid block, at the first crack and at yield. The parameters being used was the magnitude of deflection, strain of the reinforcing steel and concrete, crack pattern and natural frequency. It can be concluded that the hollow core reinforced concrete beam can be used as an alternative to I section reinforced concrete beam. It was noticed that the difference in shear load carrying capacity between control beam (BK) and hollow beam (BB) was not considerably significant, where the difference between BK (299.3 kN) and BB1 (337.6 kN) is 12.79%, that with BB2 (350, 6 kN) or 17.14%, and that with BB3 (289.4 kN) or −3.31%. The natural frequency of BK is 58.594 Hz, 15.769% larger than the natural frequency of BB3 with 49.354 Hz. The natural frequencies of tested beam decreased with the increased of damage to the beam.

Microbubble characterization through acoustically induced deflation

Ultrasound contrast agents (UCA) populations are typically polydisperse and contain microbubbles with radii over a given range. Although the behavior of microbubbles of certain sizes might be masked by the behavior of others, the acoustic characterization of UCA is typically made on full populations. In this paper, we have combined acoustic and optical methods to investigate the response of isolated lipid-shelled microbubbles to low-pressure (49 and 62 kPa peak negative pressure) ultrasound tone bursts. These bursts induced slow deflation of the microbubbles. The experimental setup included a microscope connected to a fast camera acquiring one frame per pulse transmitted by a single-element transducer. The behavior of each bubble was measured at multiple frequencies, by cyclically changing the transmission frequency over the range of 2 to 4 MHz during subsequent pulse repetition intervals. The bubble echoes were captured by a second transducer and coherently recorded. More than 50 individual microbubbles were observed. Microbubbles with radii larger than 3 mum did not experience any size reduction. Smaller bubbles slowly deflated, generally until the radius reached a value around 1.4 microm, independent of the initial microbubble size. The detected pressure amplitude backscattered at 2.5 cm distance was very low, decreasing from about 5 Pa down to 1 Pa at 2 MHz as the bubbles deflated. The resonant radius was evaluated from the echo amplitude normalized with respect to the geometrical cross section. At 2-MHz excitation, deflating microbubbles showed highest normalized echo when the radius was 2.2 microm while at higher excitation frequencies, the resonant radius was lower. The relative phase shift of the echo during the deflation process was also measured. It was found to exceed pi/2 in all cases. A heuristic procedure based on the analysis of multiple bubbles of a same population was used to estimate the undamped natural frequency. It was found that a microbubble of 1.7 microm has an undamped natural frequency of 2 MHz. The difference between this size and the resonant radius is discussed as indicative of significant damping.

Formation of trapped surfaces in the collision of nonexpanding gravitational shock waves in an AdS4 space-time

We discuss various mechanisms of catalysis of black holes/wormholes (BH/WH) formation in particles collisions. The current paradigm suggests that BH/WH formation in particles collisions will happen when center of mass energies of colliding particles is sufficiently above the Planck scale (the transplanckian region). To estimate the BH/WH production we use the classical geometrical cross section. We confirm the classical geometrical cross section of the BH production reconsidering the process of two transplanckian particles collision in the rest frame of one of incident particles. This consideration permits to use the standard Thorne's hoop conjecture for a matter compressed into a region to prove a variant of the conjecture dealing with a total amount of compressed energy in the case of colliding particles. We calculate geometrical cross sections for different processes and for different background, in particular, for (A)dS. We show that results are in agreement with closed trapped surface (CTS) estimations though there are no general theorems providing that the BH formation follows from CTS's formation. We show that the process of BH formation is catalyzed by the negative cosmological constant and by a particular scalar matter, namely dilaton, while it is relaxed by the positive cosmological constant and at a critical value just turns off. Also we note that the cross section is sensible to the compactification of extra dimensions and to the particular brane model.

Guiding of slow Ne7+-ions through insulating nano-capillaries of various geometrical cross-sections

We have studied guiding of slow highly charged ions through PET, SiO2, Al2O3, and now, for the first time, insulating nano-capillaries of non-circular cross-section. The guiding effect is been explained by self-organized formation of charge patches on the inner capillary walls. We investigate the effects of the geometrical cross-section on the distribution of Ne7+-ions transmitted through nano-capillaries of rhombic cross-section in muscovite mica, using ion beams of different kinetic energies.

Hypersharp Resonant Capture of Neutrinos as a Laboratory Probe of the Planck Length

The 18.6 keV antineutrino (nue) line from the two-body decay of 3H in crystals can be emitted with a natural width because of motional averaging by lattice vibrations despite the very long lifetime of 3H and contrary to commonly held views of linewidths in such a case. It can be resonantly captured in 3He with geometrical cross section sigma approximately 10(-17) cm2. Using its hypersharp sensitivity DeltaE/E approximately 10(-29) and the method of "time-filtered" resonance, the basic energy width approximately 10(-24) eV expected of the 3H state can be measured to test if ultimate nuclear widths are limited by the Planck length rather than time-energy uncertainty.