Transverse Profile Research Articles

Optimizing proton acceleration using hollow laser pulses and a double-layer target: effects of focal spot position and polarization

Abstract We study the influence of hollow laser pulse settings, specifically adjustments to the focal plane and the phase structure and polarization, on the acceleration of high-energy, low-divergence proton beams from a double-layer target using a feasible laser energy (~ 3.7 J). We investigate the laser's relativistic self-focusing dynamics in the near-critical plasma layer of the target and examine hot electron generation and proton acceleration using three-dimensional particle-in-cell (PIC) simulations. First, we vary the focal spot position of a tightly focused twisted driver, leading to distinct laser beam width evolution that impacts hot electron generation in the near-critical plasma, particularly in the transverse direction. The resulting proton beams differ in maximum longitudinal momentum (0.29-0.35 mi c) and transverse profile. The most efficient acceleration, with a cutoff energy of 40 MeV and ultra-low divergence (~25 mrad), occurs when the driver is focused at the center of the target.
Next, we modify the phase structure and polarization of the laser pulse, transitioning from a linearly polarized twisted beam to cylindrical vector beams with radial and azimuthal polarization, all exhibiting hollow, cylindrically symmetric intensity profiles. This change primarily affects the proton beam's maximum energies, influenced by the ultra-relativistic direct laser-accelerated (DLA) electrons, efficiently generated only by the radially polarized and twisted laser pulses. However, the bulk properties of the proton beam remain similar, as the relativistic mid-energy electrons (< 25 MeV), which sustain a strong sheath field, are the main contributors to proton acceleration in this setup.

Tuning planar transverse domain wall dynamics in bilayer nanostructures using transverse magnetic fields, Rashba, and spin-Hall effects

Abstract This work deals with the tunability of a planar transverse domain wall with an arbitrary azimuthal angle, achieved by applying a transverse magnetic field of tunable strength and fixed orientation. To be precise, we investigate the static and dynamic features of a planar transverse domain wall within a bilayer nanostructure consisting of a ferromagnetic layer and a non-magnetic heavy metal layer, employing the Landau-Lifshitz-Gilbert equation as our theoretical framework. The domain wall dynamics are analyzed through the collective coordinate method and regular perturbation asymptotic approach, accounting for the combined effects of axial and transverse magnetic fields, spin-polarized electric currents, Rashba effect, and spin-Hall effect. Our study comprehensively analyses the planar transverse domain wall profile, characterized by sharply defined boundaries between adjacent domains and a precise distribution of the transverse magnetic field. In addition, we detail the linear polar angle distribution within the domain wall region, the capability to freely tune the domain wall width, and the enhanced domain wall velocity in steady-state regime. The analytical results are further numerically illustrated, offering valuable insights into manipulating and controlling domain wall dynamics.

Irreversible effects for SWCNT‐MWCNT/water based flow with Coriolis force over rotating frame: A numerical study

AbstractIn this study, two different types of nanofluids are used: One is the simple nanofluid consist of single‐wall carbon nanotubes (SWCNT), and the other is the hybrid nanofluid composed of single and multi‐wall carbon nanotubes (SWCNT‐MWCNT). The famous Xue model is incorporated for the thermal energy analysis. An important property related to the nanoparticles is the Brownian motion and thermal‐migration, which is described by using Buongiorno's model. The appropriate similarity transformations are used to convert the governing nonlinear partial differential equations into the nonlinear coupled ordinary differential equations for the both velocity and temperature profiles. The numerical solution is obtained for the present problem by using bvp4c Matlab routine. This code is based on the finite difference method that implements the three‐stage Lobatto IIIa formula. The comparative analysis for the entropy generation in rotating frame due to heat transfer, viscous heating, and mass diffusion is the main focus in this study. The impact of different parameters such as, rotational motion , thermomigration and Brownian motion , volume fractions of SWCNT & SWCNT‐MWCNT ,, Eckert number , Lewis number , chemical reaction parameter , Brinkman number the temperature ratio parameter and concentration difference parameter on axial and transverse velocity, temperature profile, entropy generation, and Bejan number are obtained. The obtained results for these different variables are presented through graphs and tabular form. When the solid volume fraction is enhanced, the flow and heat distribution are observed to increase. The Nusselt and Sherwood numbers for both nanofluids are investigated. The decay in Nusselt number is observed as the values of the heat source/sink parameter, thermophoresis, Brownian motion, and Eckert number are increased. However, in the case of Sherwood enhancement an increment in the value of the chemical reaction parameter, thermophoresis, Brownian motion, and Lewis number is observed. The entropy generation is enhanced as a result of increment in Brinkman number and temperature ratio. However, in the case of Bejan number, opposite trend was seen in the entropy generation. For the hybrid nanofluid, the enhancement in both heat transmission and irreversibility effect is observed as compared to simple nanofluid.

The Critical Influence of Wire Diameter and Bending for Orthodontic Wire Integration—New Insights for Maxillary Movements (In Vitro Study)

Background: Traditional methods for palatal expansion using fixed appliances often face limitations in comfort and aesthetics. In comparison, aligner therapy has limitations, particularly regarding maxillary expansion. The aim of this study is to examine the biomechanical properties regarding the wire diameter and bending of different stainless steel wires to evaluate their potential for incorporation into maxillary aligner therapy. Materials and Methods: Three rectangular stainless steel wires (0.016″ × 0.022″, 0.017″ × 0.025″, and 0.019″ × 0.025″) were tested for mechanical expansion forces in the intermolar region, comparing non-tooth-shaped bent wires (A groups) and tooth-shaped bent wires (B groups). Using a Z010 testing machine (ZwickRoell GmbH and Co. KG, Ulm, Germany), expansion forces were measured at 1 mm intervals over a 5 mm distance, with 15 samples analyzed per group. Statistical analyses included the Shapiro–Wilk test for normal distribution, the Mann–Whitney U test, which revealed significant results (U = 225, p < 0.001), and the Kruskal–Wallis test, which indicated significance (H = 39.130; df = 2; p < 0.001). Results: Tooth-shaped bent wires exhibited significantly lower expansion forces than non-tooth-shaped bent wires for all tested wire types. This difference was most notable in wires with larger transverse profiles (0.019″ × 0.025″), where the tooth-shaped bent wires displayed a marked reduction in mechanical load capacity. Specific force measurements for non-tooth-shaped wires ranged from 760.61 ± 79.51 mN at 1 mm of deformation to 2468.46 ± 66.27 mN at 5 mm of deformation, while tooth-shaped wires ranged from 116.80 ± 3.74 mN to 1979.49 ± 23.23 mN. Conclusions: These findings suggest that non-tooth-shaped bent wires offer a more efficient and uniform expansion potential for maxillary movements due to their stable elastic properties. Clinically, integrating non-tooth-shaped stainless steel wires into aligner therapy may provide a viable method for maxillary expansion, supporting both first- and second-order movements in orthodontic treatment. Further research is needed to explore the integration of such wires for effective maxillary expansion in aligner therapy.

Advances in laser-based bremsstrahlung x-ray sources. II. Laser pulse propagation and guiding in nonuniform plasma media in the presence of self-focusing

An analytic Wentzel–Kramers–Brillouin model is presented of Gaussian laser pulse propagation through plasma with a quadratic transverse density profile and an arbitrarily varying, longitudinal density gradient under conditions of nonlinear self-focusing. From these solutions, it is shown that in the absence of nonlinear self-focusing and transverse nonuniformity, for exponential pre-plasma density profiles, the use of a low density coating of the laser target with electron density n0∼11 ncr (e.g., a CH foam of density 35 mg/cm3 for 1-micron laser light) maximizes laser intensity at best focus. Also, under laser and plasma conditions relevant to recent experiments on high-power laser systems, conditions are obtained for a Gaussian laser pulse to propagate stably through the pre-plasma medium. Such conditions would be expected to enhance the production of relativistic electrons from laser-target coupling, providing a possible explanation for the observed increase in MeV photon dose and enabling applications such as laser-based MeV X-ray radiography.

Optical algorithm for derivative of real-valued functions

The derivation of a function is a fundamental tool for solving problems in calculus. Consequently, the motivations for investigating physical systems capable of performing this task are numerous. Furthermore, the potential to develop an optical computer to replace conventional computers has led us to create an optical algorithm and propose an experimental setup for implementing the derivative of one-dimensional real-valued functions using a paraxial and monochromatic laser beam. To complement the differentiation algorithm, we have experimentally implemented a novel optical algorithm that can transfer a two-dimensional phase-encoded function to the intensity profile of a light beam. Additionally, we demonstrate how to extend the optical algorithm to implement high-order derivatives of two-dimensional real-valued functions encoded in the phase of the transverse profile of photons.

Control of Chemical Waves by Fluid Stretching and Compression.

Oscillatory kinetics coupled to diffusion can produce traveling waves as observed in physical, chemical, and biological systems. We show experimentally that the properties of such waves can be controlled by fluid stretching and compression in a hyperbolic flow. Localized packet waves consisting in a train of parallel waves can develop due to a balance between diffusive broadening and advective compression along the unstable manifold. At a given distance from the stagnation point, the parallel waves transform into planelike waves and smeared waves where the transverse parabolic flow profile disturbs the patterns in the gap width. Once a wave packet has been obtained, it imprints a privileged direction that is maintained even if the compression rate is decreased. The width of the wave packet then scales inversely with the compression rate.

Prediction of steel strip flatness based on the difference in drawing coefficients along its width during steel strip rolling

The paper presents a brief overview of approaches to calculating flat strip shape defects. It is shown that the most important technological factors in forming a flat sheet are the difference in draw bars across the strip width and the inter-roll gap profile, which depends mainly on elastic deformations that are uneven along the barrel length. The elastic deformations of the working roll surface were simulated, which, together with its thermal profile and wear, made it possible to estimate the transverse profile of the rolled product. The process of deformation of a set of rolls in a quarto stand was studied in the ANSYS Mechanic program using the Static Structure module. The results of calculating the elastic deformations of the roll surface in contact with the deformed strip with varying parameters over a wide range of values made it possible to obtain a statistically reliable equation for estimating the roll barrel profile in the deformation zone and the transverse profile of the rolled product. The obtained roll profile was used to study the formation of the flatness defect “waviness” using the DEFORM-3D program. It was carried out by simulating the rolling of a steel strip with a given transverse profile in profiled roll barrels. On the finished strip, the amplitude of the flat shape defect was estimated by comparing the vertical displacements of the strip section at its edge and in its middle at the exit from the rolls. Using a well-known technique, the amplitude of the “wave” and “box” was also calculated. The assessment was carried out on the basis of the difference in the elongation coefficients across the strip width. The results of the assessment and modeling of the rolling process showed very close results, which confirms the possibility of calculating the flatness parameters by the difference in the strip elongations across its width using a well-known formula.

Analysis of heat and mass transfer rates in conducting Casson fluid flow over an expanding surface considering Ohmic heating and Darcy dissipation effects

In a recent scenario, the flow of Casson fluid via porous media has practical applications in various engineering processes, such, as the design of cooling systems for electronic devices, oil recovery in porous reservoirs, and polymer extrusion processes, etc. The proposed investigation illustrates the thermal and solutal transfer rates in a conducting Casson fluid flow over an expanding surface. However, the emphasis goes to the behavior of the Ohmic heating and Darcy dissipation when considering the transverse magnetic field and porous matrix. The governing flow phenomena with their dimensional form are altered into a non-dimensional set of equations with the help of suitable similarity rules. Further, an adequate numerical simulation is adopted to solve the transformed equations using the in-house bvp4c function in MATLAB. The physical parameters involved in the flow problem and their behavior on the governing flow phenomena are presented graphically and described briefly. Prior to this investigation, the conformity of the current numerical output obtained for the heat transfer rate was validated with the earlier work with a good correlation. Moreover, the major outcomes are; the non-Newtonian Casson parameter retards the axial and transverse velocity profile and the shear rate also decreases significantly. The Eckert number caused by the inclusion of the dissipative heat encourages the fluid temperature throughout.

The symmetry change of the transverse modes in ring-LD end-pumped Nd:YVO[formula omitted] laser with an étalon

A straightforward method for converting the symmetry of a diode end-pumped laser with an annular pump beam has been proposed. By introducing an étalon into the cavity, we observed a change in the spatial symmetry of the transverse mode profile from rectangular to cylindrical both in degenerate and non-degenerate ranges. A simulation of the transmittance distribution of the beam through the étalon after filtering is given. Our experimental results indicate that this method of altering the symmetry maintains relative stability during the tilting of the étalon.

Radiative-conductive heat transfer dynamics in dissipative dispersive anisotropic media

Abstract We develop a self-consistent theoretical formalism to model the dynamics of heat transfer in dissipative, dispersive, anisotropic nanoscale media, such as metamaterials. We employ our envelope dyadic Green’s function method to solve Maxwell’s macroscopic equations for the propagation of fluctuating electromagnetic fields in these media. We assume that the photonic radiative heat transfer mechanism in these media is complemented by dynamic phononic mechanisms of heat storage and conduction, accounting for effects of local heat generation. By employing the Poynting theorem and the fluctuation-dissipation theorem, we derive novel closed-form expressions for the radiative heat flux and the coupling term of photonic and phononic subsystems, which contains the heating rate and the radiative heat power contributions. We apply our formalism to the paraxial heat transfer in uniaxial media and present relevant closed-form expressions. By considering a Gaussian transverse temperature profile, we also obtain and solve a system of integro-differential heat diffusion equations to model the paraxial heat transfer in uniaxial reciprocal media. By applying the developed analytical model to radiative-conductive heat tranfer in nanolayered media constructed by layers of silica and germanium, we compute the temperature profiles for the three first orders of expansion and the total temperature profile as well. The results of this research can be of interest in areas of science and technology related to thermophotovoltaics, energy harvesting, radiative cooling, and thermal management at micro- and nanoscale.

Effects of rail hardness on transverse profile evolution and computed contact conditions in a full-scale wheel-rail test rig evaluation

This paper revisits a comprehensive data set generated in a prior test program using a full-scale wheel-rail test rig. The test program evaluated premium and standard grade rail steels with respect to wear and rolling contact fatigue (RCF). The current work evaluates the evolution of rail profiles throughout the test cases, taking advantage of the database of wheel and rail profiles that were collected. Contact conditions are modelled using the CONTACT library, including recent developments in the handling of conformal geometries and interfacial layers. Observations are made regarding the relative characteristics of rail profiles for each steel type, as they evolve with accumulated wheel passes, on the basis of the computed contact conditions.

Development Characteristics of Single Sand Body of Yan’An Formation in Western Ordos Basin

Abstract The precise characterization of the types and spatial distribution of strongly heterogeneous single sand bodies are a necessary prerequisite for the study of oil and gas reservoir formation. This article takes the Yan’an Formation in the western Ordos Basin as an example to systematically study the internal structure and profile distribution of strongly heterogeneous single sand bodies. The research results indicate that using mud interlayers, physical interlayers, and calcium interlayers as layered interfaces can effectively classify the single sand body types of each small layer in the Yan’an Formation. The drilling rate of a single sand body is between 50% and 85%, and the average number of sand layers is between 3 and 8. When two rivers intersect and are horizontally tangent, due to the mutual erosion of water flow, relatively thick sand bodies can be retained, ultimately resulting in a pattern of relatively thick on both sides and thin in the middle. The single sand body at the bottom is the most developed and has good continuity. In the transverse direction of the river, the continuity of a single sand body is relatively poor, and the extension range of a single sand body is 300m to 1200m. Along the river channel, single sand bodies are developed with good continuity, extending about 2km. The connectivity between the sand body and the well varies with the migration of the river in the transverse river profile of the research area. The lateral contact relationship of a single sand body determines the boundary of the river channel, and the profile characteristics of a single sand body also reflect its planar distribution. The intergranular pores of the Yan’an Formation sand body are relatively developed, and a large number of quartz particles offset the compressive stress of the rock. The corrosion of feldspar particles is relatively strong, retaining a large number of primary intergranular pores. There is a good quantitative relationship between the thickness of sand in a single level channel and the width of the channel. The control of the well network on the sand body is relatively small, and there is room for further densification of drilling. The vertical contact relationship of a single sand body in the Yan’an Formation of the research area can be divided into three modes: separation, stacking, and overlapping. Cut pile sand bodies with good connectivity have good production capacity. The different planar contact relationships reflect the degree of connectivity between channel sand bodies and wells, with lateral cutting type>docking type>isolation type. The side cut sand body has uniform longitudinal water absorption, small water absorption difference, and high-water drive degree. The isolation type has the greatest difference in water absorption rate and the lowest degree of water flooding.

Non-Hermitian mode management in periodically modulated waveguide amplifiers

We propose an efficient mode management scheme in active nonlinear multimode fibers based on non-Hermitian potentials in the longitudinal direction with an antisymmetric transverse profile. The proposal takes advantage of the nonlinear saturation toward particular mode configurations, which can be tuned by the non-Hermitian potential. We demonstrate flexible control of the beam profile within the parameter space of the applied potential with various possibilities, such as improving the beam quality by condensing photons to the lowest order Hermite mode, exciting higher order modes, or engineering a desired mode profile as a combination of modes. The effect is also analytically predicted using a mode-expansion approach, showing good agreement with the full model calculations based on the complex Ginzburg–Landau equation. This study was performed for 1D planar guiding structures, yet the results can be extended to 2D fibers and could be very useful in applications of fiber amplifiers and lasers.

ДО ПИТАННЯ РОЗВИТКУ ВЕЛОІНФРАСТРУКТУРИ І ПЛАНУВАННЯ МОБІЛЬНОСТІ У МІСТАХ

The current state of the bicycle infrastructure in Ukraine is being examined based on the definition of ecological and social component of road traffic efficiency. Identified directions of development and proposed measures for planning bike paths, taking into account the existing transport network of cities. The paper provides fundamental principles of individual mobility for the population, which must align with the basic principles of general urban mobility, namely: safety, directness, continuity, connectivity, attractiveness, and convenience. A thorough analysis of the bicycle movement in the city Kharkiv has been conducted, including the determination of respondents’ attitudes towards the creation bike lanes. Based on statistical data on the fluctuation of respondents’ travel distances within the city, a description of this process was provided according to the normal distribution law. This approach allows determining the main parameters of the city’s modern bike structure. Using specialized software STREETMIX, the modeling of technical solutions for the development of infrastructure for active individual mobility at a main street in Kharkiv was carried out. Five possible solutions for changing the transverse profile of the street were simulated, taking into account the paths of connection for active individual mobility. The obtained average daily increase in street capacity by 12,000 passengers per hour allows asserting the effectiveness of the proposed options for the development of infrastructure for active individual mobility on the respective routes of the city of Kharkiv. The expediency of implementing measures for individual mobility of the popu-lation is substantiated based on determining a comprehensive indicator for assessing the quality of road traffic. Keywords: cycling infrastructure, traffic safety, population mobility indicators, planning solutions, transport network.

Energy redistribution in railway transition zones by geometric optimisation of a novel transition structure

Railway transition zones are critical regions in railway infrastructure that are subjected to excessive operation-driven degradation due to energy concentration within these zones. This work presents a heuristic approach to optimise the geometry of the transition structure and investigate its influence on the strain energy distribution in the railway transition zones (RTZs), with a specific focus on embankment-bridge transitions equipped with a newly proposed ’Safe Hull-Inspired Energy Limiting Design (SHIELD)’ transition structure. For this purpose, a number of three-dimensional finite element models are used to analyze different geometric profiles of SHIELD in a systematic manner. By altering SHIELD’s geometry across longitudinal, transversal, and vertical directions, the influence of the different geometric profiles on the total strain energy distribution across the trackbed layers (ballast, embankment, and subgrade) is studied in terms of spatial and temporal variations. The results establish the contribution of geometry to energy redistribution in all three directions and present an optimum geometry for the type of transition under study. It is found that among all the profiles, the longitudinal geometric profile of SHIELD has the most significant impact on the strain energy distribution, while the transversal profile primarily influences the ballast layer, and the alteration of vertical profiles enhance the local redistribution of strain energy in the vicinity of the transition interface. The preliminary optimisation (heuristic approach) presented in this work provides the starting point for full-scale optimisation to obtain tailored shapes of transition structures such that there is neither a concentration of energy nor an obstruction in the flow of energy in RTZs.

Geometric Parameter Optimization for Axial Modification in Helical Gear Form Grinding

During the axial modification in helical gear form grinding, the contact line between the grinding wheel and the gear constantly changes, and the additional radial motion can cause a “tooth surface twist” phenomenon. An optimization method for tooth surface twist error was proposed to address this. Based on the gear meshing principles, a mathematical model for axial modification in form grinding was established to solve for the instantaneous contact lines at various positions on the actual modified tooth surface. By analyzing the influence of the grinding wheel installation angle on the axial modification contact line, an optimization model was constructed to reduce the twist of the transverse profile, reduce the twist of the flank profile, reduce the helix deviation, and improve the form grinding efficiency. The practical implications of this research are significant, as the Particle Swarm Optimization (PSO) algorithm was employed to optimize the form grinding parameters, leading to a method that effectively reduced tooth surface twist error and improved the form grinding accuracy of the modified tooth surface.

A Cartographic Landscape Analysis of the Geo-Ecological Condition of the Natural Reserve Object—Lake Doshne (Volyn Polissya, Ukraine)

The cartographic landscape analysis of Lake Doshne employs geographic landscape methods, GIS cartographic modeling, and geo-ecological analysis. This study includes hydrochemical analysis of the lake’s water mass, focusing on saline blocks, tropho-saprobiological indicators, and specific toxic action indicators. Three geological sections of anthropogenic and pre-Quaternary complexes, along with a geological–lithological transverse profile of the lake basin, were developed. Additionally, a geographical landscape model of the lake’s natural aquatic complex was presented, distinguishing littoral–sublittoral and profundal aquatic sub-tracts and five types of aquafacies with landscape metric assessments. This approach enables a comprehensive analysis and the creation of cartographic models that can serve as a basis for lake cadastre and optimization of the ecological and landscape conditions in local territories.

An inter-comparison between MCNPX and EGSnrc Monte Carlo codes in grid radiotherapy characterization using beta-emitting radionuclides

IntroductionThe applicability of MCNPX and EGSnrc Monte Carlo codes in dosimetric characterization of spatially fractionated radiotherapy (SFRT or grid radiotherapy, in other words) of superficial tumors using beta-emitting radionuclides has been assessed in the current study. Materials and methodsA grid block including 63 cubic holes was modeled by each Monte Carlo code. Then, the grid block was separately filled by four widely adopted beta-emitting radioisotopes for radionuclide-therapy purposes including 32P, 90Y, 166Ho, and 188Re. Finally, the depth dose distribution and transverse dose profiles at different depths were separately calculated for each radionuclide using both MCNPX and EGSnrc Monte Carlo codes. Obtained results were quantitatively compared by gamma analysis as well as an R-squared statistical test to evaluate the compatibility of acquired dosimetry results by each code. ResultsSimilar dosimetry results were obtained by both Monte Carlo codes, where no significant difference was observed among the obtained data by each code. The uniformity of dose distribution improved with increasing the depth inside the phantom for all radionuclides under investigation. ConclusionFrom the results, it can be concluded that MCNPX and EGSnrc Monte Carlo codes have similar performance in dosimetric characterization of grid radiotherapy using beta-emitting radionuclides. Small differences between the results acquired by employed codes originate from associated statistical uncertainty with the Monte Carlo data as well as differences in considered condense history scheme (CHS) during the electron transport inside the medium.

Inception of Constructional Submarine Conduit by Asymmetry Generated by Turbidity Current

Submarine conduits are features responsible for transporting clastic debris from continents to the deep ocean. While the architecture of conduits has been extensively studied, the process of their inception remains unclear. This study highlights the possibility that some conduits are initiated by depositional processes involving turbidity currents. Here, we present the results of eight experiments where gravity currents were allowed to develop their own pathways. The simulation tank represented natural scales of continental shelves, slopes, and basins. The initial experiments involved sediment-laden flows with low density (1–10% in volume). In first experiment runs (Series I), sediment deposition occurred primarily on the shelf and slope, resulting in an asymmetric transverse profile. This asymmetry facilitated subsequent conservative currents (1034 to 1070 kg/m3 due to salt dissolution) flowing alongside during the second series, resulting in the formation of a constructive submarine conduit. This feature is analogous to gully formations observed in various locations. This study correlates these findings with gully-like features and proposes a model where non-confined density flows can evolve into confined flows through the construction of asymmetric topography. An evolutionary model is proposed to explain the mechanism, which potentially elucidates the formation of many submarine conduits.