Initial Geometric Configuration Research Articles

Improvement on Fourier fundamental mode coefficient for Monte Carlo criticality calculations

Recently, the Fourier fundamental mode coefficient (FFMC) was formulated to advance the existing Monte Carlo fission source stationarity diagnostics. The calculation of FFMC requires a user-defined exterior geometric boundary of the fission source distribution. However, the effect of using different boundary sizes on the reliability of the proposed FFMC indicator is not understood and has never been discussed. This work used different boundaries to investigate their effect on the FFMC results based on a simple homogeneous reactor model. The results show that the choice of FFMC boundaries is also affected by the reactor model's initial source distribution and geometrical configuration. The shortcoming of the abovementioned indicator has been improved by dissociating the indicator into the corresponding Cartesian axes. The new set of indicators is further verified by the checkerboard fuel storage array and the BEAVRS full core cases.

Three-dimensional vibration analysis in extensible pipes conveying fluid with different initial geometrical configurations

In this paper, three-dimensional vibration of fluid-conveying pipes with different initial configurations is investigated. With Green–Lagrange strain tensor, extensible theory, and Plug-flow, governing equations are built by applying Hamiltons principle. The governing partial differential equations are discretized into ordinary differential equations via the differential quadrature method (DQM) and solved numerically to obtain the dynamical character of the different initial configurations. Numerical results show static deflection under different initial geometrical configurations and variation of in-plane and out-of-plane frequencies with increasing fluid velocity. Natural frequency and mode shape are explored under the variation of flow velocity.

The role of edge-driven convection in the generation ofvolcanism – Part 2: Interaction with mantle plumes, applied to the Canary Islands

Abstract. In the eastern Atlantic Ocean, several volcanic archipelagos are located close to the margin of the African continent. This configuration has inspired previous studies to suggest an important role of edge-driven convection (EDC) in the generation of intraplate magmatism. In a companion paper (Manjón-Cabeza Córdoba and Ballmer, 2021), we showed that EDC alone is insufficient to sustain magmatism of the magnitude required to match the volume of these islands. However, we also found that EDC readily develops near a step of lithospheric thickness, such as the oceanic–continental transition (“edge”) along the western African cratonic margin. In this work, we carry out 3D numerical models of mantle flow and melting to explore the possible interactions between EDC and mantle plumes. We find that the stem of a plume that rises close to a lithospheric edge is significantly deflected ocean-ward (i.e., away from the edge). The pancake of ponding hot material at the base of the lithosphere is also deflected by the EDC convection cell (either away or towards the edge). The amount of magmatism and plume deflection depends on the initial geometric configuration, i.e., the distance of the plume from the edge. Plume buoyancy flux and temperature also control the amount of magmatism, and influence the style and extent of plume–EDC interaction. Finally, comparison of model predictions with observations reveals that the Canary plume may be significantly affected and deflected by EDC, accounting for widespread and coeval volcanic activity. Our work shows that many of the peculiar characteristics of eastern Atlantic volcanism are compatible with mantle plume theory once the effects of EDC on plume flow are considered.

Geometric Nonlinear Analysis of the Catenary Cable Element Based on UPFs of ANSYS

The catenary cable element has more advantages than other nonlinear truss elements but is less used in commercial programs. In this paper, the initial geometric configuration of the element is solved iteratively by the dichotomous method. Then the Updated Lagrangian (UL) Formulation for the two-node catenary cable element is combined with the element secondary development tool provided by ANSYS platform-User Programmable Features (UPFs) to develop a three- dimensional cable element—user101. The algorithm and procedure of this paper are verified through examples and a real bridge. The study shows that the developed cable element user101 is more accurate and faster than the ANSYS self-contained element. The method can effectively use the computational theory of nonlinear cable elements with catenary geometry and combine it with ANSYS commercial program, which saves computation time without reducing accuracy and has good practicality.

The Glauber Model And Flow Analysis with Pb-Pb Collisions at

This work presents data analysis on Pb-Pb collisions with in centrality 40%-50%. Introduction and Monte-Carlo simulation results on the Glauber model are presented, which shed light on the initial geometric configuration of heavy ion collisions. Three-dimensional correlation function is plotted, and Fourier decomposition is carried out in order to obtain elliptic flow. Based on the assumption that non-flow effect is less prominent in long-range area, we separate it from the second Fourier decomposition of two-particle correlation function by making polynomial curve fitting.

Data-Driven Capturability Analysis for Pure Proportional Navigation Guidance Considering Target Maneuver

A data-driven statistical analysis of the missile’s capture region is performed. The capture region is the region of the initial geometric configuration for pursuer missile against a target in which the missile can intercept the target while satisfying specific constraints. The statistical verification approach has advantages over the analytic approach in that it can deal with various guidance algorithms and target maneuver utilizing numerical simulator. In this study, the verification model is constructed using the Gaussian process regression model. The verification model computes the probability distribution of the target capture over the initial configuration space. The data-driven capturability analysis is conducted for the maneuvering target using the Gaussian process regression model. The capture region derived from the statistical model is compared with the analytic model, and the effectiveness of the active sampling algorithm is demonstrated.

MXAN: A new program for ab-initio structural quantitative analysis of XANES experiments

X-ray absorption spectroscopy (XAS) is a powerful method for obtaining electronic and structural information around a well-defined absorbing atom site of different types of matter, from biological systems to condensed materials in almost all possible thermodynamics conditions. The low energy part of the XAS spectrum, from the rising edge up to few hundreds eV, the so called XANES (X-ray absorption near-edge structure) region, is extremely rich of electronic and structural information, like, for example, the oxidation state, overall symmetry, interatomic distances and angles. In this paper we present in details the MXAN method and a new reengineered release of the code proposed in the literature some years ago which allows a complete fit of the XANES energy region in term of well-defined set of structural parameters. This approach is based on the comparison between experimental data and many theoretical calculations performed by varying selected structural parameters starting from a putative structure, i.e. from a well-defined initial geometrical configuration around the absorber. The X-ray photo-absorption cross sections are derived using full multiple-scattering theory, i.e. the scattering path operator is calculated exactly without any series expansion. In this way the analysis can start from the edge without any limitations in the energy range and polarization conditions. Here we present in detail the theoretical background behind the code and new capabilities implemented from theory in this last version of the program as the analysis of XANES data coming from time-dependent spectra. The code is provided with modern technology for rapid deployment of binaries based on Docker runtime so that, without source compiling, its execution reduces to just a command line striking for a full parallel (shared memory) run even using complex construct like memory filesystem in a transparent way to the end-user. Program summaryProgram Title: MXANCPC Library link to program files:https://doi.org/10.17632/4k9363vcvh.1Licensing provisions: GPLv3Programming language: FORTRAN90External routines/libraries: MKL or OpenBLAS libraryNature of problem: In MXAN (Minuit XANES) program we implemented a fitting procedure based on a full Multiple Scattering (MS) theory [1] able to extract local structural information around the absorbing atom from experimental XANES data. The MXAN method has been successfully used for studying many known and unknown molecular systems, yielding structural geometries and metrics comparable to X-ray diffraction and/or EXAFS results [2–4]. The release of this new code paves the route to new possibilities available now in the latest version of the program, as the analysis of XANES data coming from time-dependent and structural disordered systems.Solution method: MXAN program is based on the comparison between experimental data and iterative theoretical calculations performed by varying selected structural parameters starting from a well-defined initial geometrical configuration around the absorber. The calculation of XANES spectra is performed within the so-called full MS approach, i.e. the inverse of the scattering path operator is computed exactly, avoiding any “a-priori” selection of the relevant MS paths [5,6]. The fit procedure is performed in the energy space without the use of any Fourier transform algorithm; polarized spectra can be easily analyzed because the calculation is performed using the full MS approach [1]. The optimization in the space of the parameters is achieved using the CERN-library MINUIT [7] routines minimizing the square residual.Additional comments including restrictions and unusual features: Depending on the molecular system under study and on the operating runtime conditions the program may or may not fit into available host RAM memory. The present release of the code is limited to a single SMP machine by running in parallel using OpenMP and/or the multi-threaded version of MKL or OpenBLAS.

Oxygen Chemisorption on the Surface of an In2O3 (011) Nanocrystal

Density-functional calculations are used to study the structural and electronic properties of stoichiometric and imperfect In2O3 (011) surfaces. We calculate energies of formation of neutral oxygen vacancies on the surface of an indium oxide nanocrystal and analyze the adsorption of an oxygen atom in its ground (triplet) state on a model imperfect surface having O4 vacancies in different charge states. The results indicate that adsorption on a $$V_{{\text{O}}}^{{2 + }}$$ vacancy is the most energetically favorable and that the oxygen atom involved switches from a triplet state to a singlet one. We consider oxygen molecule adsorption from different initial geometric configurations on neutral O1–6 vacancies.

Performance Analysis of Parameter Estimator Based on Closed-Form Newton Method for Ultrawideband Positioning

Ultrawideband (UWB) is considered as a promising technology in indoor positioning due to its accurate time resolution and good penetration through objects. Since the functional model of UWB positioning is nonlinear, iterative algorithms are often considered for solving the nonlinear problem. With a rough initial value, we can obtain the optimal solution by the way of continuous iteration. As an iterative descent method of high efficiency, the Gauss–Newton method is widely used to estimate the position. However, in the UWB indoor positioning, since the location information of the user is rather limited, it is not easy to get a good initial value for iteration. Besides, the positioning system is prone to become ill-posed. These factors make the Gauss–Newton method not easy to converge to a global optimal solution or even diverge, especially under ill-conditioned positioning configuration. Furthermore, the linearization of the positioning functional model results in biased least-squares estimation. The Gauss–Newton method only includes the first-order Taylor expansion of distance equations. The bias comes from neglected higher order terms. In this study, the closed-form Newton method which considers the high order partial derivatives is introduced and proposed. The simulation and measurement experiments are implemented to analyze the performance of the closed-form Newton method in UWB positioning. Both the initial value factor and geometric configuration factor are discussed. Experimental results are given to demonstrate that the closed-form Newton method can converge to the global optimal solution with better convergence and higher efficiency regardless of whether the initial iteration value is reasonable or not. Meanwhile, the closed-form Newton method can improve the accuracy of positioning results, particularly when the anchors are not uniformly and symmetrically distributed, or the ranging error is relatively large. The study shows that closed-form of the Newton method has better convergence and positioning performance than the Gauss–Newton method, especially under ill-conditioned positioning configuration or relatively low measurement precision, even though it adds a little computational cost.

Nonlinear Dynamic Response of Elastically Supported Stiffened Plates with Initial Stresses and Geometric Imperfections Under Impact Loads

This paper deals with the nonlinear dynamic response of elastically supported stiffened plates with initial stresses under impact loads. A stiffened plate is assumed to be composed of a plate with some stiffeners, which are treated separately. The plate is modeled by the thin plate theory, whereas the stiffeners are considered as geometrically nonlinear Euler–Bernoulli beams. First, the equations of both the kinetic energies and strain energies of the plate and stiffeners are established. Then, the dynamic equilibrium equations for the stiffened plate are derived as the Lagrange’s equation of the functional. A parametric analysis is performed to evaluate how initial stresses, initial geometric imperfections, elastic supports, impact loads and configuration of stiffeners affect the time-history responses of the stiffened plates. Some useful nonlinear dynamic properties are obtained, which serve as references for engineering design and application.

A particle packing method for non-uniform sizes and prescribed filling ratio

This work presents a particle packing method based on a distance minimization procedure with non-uniform sizes and prescribed filling ratio. In the study of engineering problems involving granular systems, like those that employ numerical tools such as the discrete element method, an important modeling task is to produce the initial geometric configuration for a given set of particles. Several methods of particle packing are currently employed for this purpose. In this work, the employed methodology uses the Levenberg–Marquardt minimization strategy and does not require a mesh to generate the initial geometric configuration for the particle set. Also, the technique aims a good approximation for the input parameters of granular media, such as grain size distribution and filling ratio. The proposed methodology is divided into four macro-steps: (a) definition of the initial particle assembly, (b) distance minimization procedure, (c) particle reallocation and d) particle removal. The input data related to the size distribution and filling ratio are used to generate the initial particle assembly, and the following steps are used to eliminate the overlapping between the circles. The packing algorithm presents good computational performance and converges to the input parameters. Granular models generated from real soil data are presented for validation of the proposed strategy.

Clustering structure effect on Hanbury-Brown–Twiss correlation in $$^{12}\hbox {C} {+^{197}}\hbox {Au}$$ collisions at 200 GeV

Through $$^{12}\hbox {C} {+^{197}}\hbox {Au}$$ collisions at $$\sqrt{s_{NN}} = 200\,\hbox {GeV}$$ using a multiphase transport (AMPT) model, the azimuthal angle dependences of the Hanbury Brown–Twiss (HBT) radii relative to the second- and third-order participant plane from $$\pi $$–$$\pi $$ correlations are discussed. Three initial geometric configurations of $$^{12}\hbox {C}$$, namely three-$$\alpha $$-cluster triangle, three-$$\alpha $$-cluster chain and Woods–Saxon distribution of nucleons, are taken into account, and their effects on the correlations are investigated. The ratio of the third- to the second-order HBT radii $$R_{o(s),3}^2/R_{o(s),2}^2$$ is shown to be a clear probe for three configurations. In addition, this work presents the hadronic rescattering time evolution of the azimuthally dependent HBT radii. From the present study, one can learn that the HBT correlation from identical particles at freeze-out is able to provide the information of different initial configurations as collective flow proposed before.

Transverse momentum distribution and elliptic flow of charged hadrons in U+U collisions at sqrt{s_{NN}}=193 GeV using HYDJET++

Recent experimental observations of the charged hadron properties in U+U collisions at 193 GeV contradict many of the theoretical models of particle production including two-component Monte Carlo Glauber model. The experimental results show a small correlation between the charged hadron properties and the initial geometrical configurations (e.g. body–body, tip–tip etc.) of U+U collisions. In this article, we have modified the Monte Carlo HYDJET++ model to study the charged hadron production in U+U collisions at 193 GeV center-of-mass energy in tip–tip and body–body initial configurations. We have modified the hard as well as soft production processes to make this model suitable for U+U collisions. We have calculated the pseudorapidity distribution, transverse momentum distribution and elliptic flow distribution of charged hadrons with different control parameters in various geometrical configurations possible for U+U collision. We find that HYDJET++ model supports a small correlation between the various properties of charged hadrons and the initial geometrical configurations of U+U collision. Further, the results obtained in modified HYDJET++ model regarding dn_{ch}/deta and elliptic flow (v_{2}) suitably matches with the experimental data of U+U collisions in minimum bias configuration.

Strain-dependent elastic properties of graphene oxide and its composite

This paper investigates the effect of hydroxyl groups on elastic properties of graphene oxide (GO) and its composites. A strain-dependent pseudo crease model considering the effects of out-of-plane initial strain and geometric configuration is proposed to predict the elastic modulus of GO, combining with a homogenization method. The results show that the elastic modulus of GO varies from 0.214 TPa to 0.463 TPa as tensile strain increases from 0 to 0.07. Further, considering GO as a rectangular inclusion and using the Mori-Tanaka method, the elastic properties of GO composites are predicted by taking aspect ratio and mass fraction of GO into account. Our study provides an effective method to evaluate the effects of functionalgroups on elastic modulus of GO and to understand the effect of microstructural parameters of GO on elastic properties of GO composites.

Measurements of Multiparticle Correlations in d+Au Collisions at 200, 62.4, 39, and 19.6GeV and p+Au Collisions at 200GeV and Implications for Collective Behavior.

Recently, multiparticle-correlation measurements of relativistic p/d/^{3}He+Au, p+Pb, and even p+p collisions show surprising collective signatures. Here, we present beam-energy-scan measurements of two-, four-, and six-particle angular correlations in d+Au collisions at sqrt[s_{NN}]=200, 62.4, 39, and 19.6GeV. We also present measurements of two- and four-particle angular correlations in p+Au collisions at sqrt[s_{NN}]=200 GeV. We find the four-particle cumulant to be real valued for d+Au collisions at all four energies. We also find that the four-particle cumulant in p+Au has the opposite sign as that in d+Au. Further, we find that the six-particle cumulant agrees with the four-particle cumulant in d+Au collisions at 200GeV, indicating that nonflow effects are subdominant. These observations provide strong evidence that the correlations originate from the initial geometric configuration, which is then translated into the momentum distribution for all particles, commonly referred to as collectivity.

Effects of organic cations on performance of halide perovskite solar cell

The halide perovskite solar cells employing CH3NH3PbX3 (X=Cl-, Br-, I-) and CH3NH3PbI3-xClx as light absorbers each have shown a rapid rise in power conversion efficiency (PCE) from 3.8% to 22.1% in recent years. The excellent photovoltaic performance is attributed to good optical and electrical properties such as appropriate bandgap, large absorption coefficient, high carrier mobility, long carrier lifetime and long carrier diffusion length. However, the physical mechanism of high PCE for halide perovskite solar cells is still unclear. The Gaussian 09 software is utilized to optimize the geometries of isolated CH3NH3+ and CH3NH3 at a B3 LYP/6-311++G(d, p) level, and the Multiwfn software is used to visualize the electrostatic potentials (ESPs) of CH3NH3+ and CH3NH3. Based on the ESPs of CH3NH3+ and CH3NH3, it is found that the CH3NH3+ has a strong electrophilic character, however, the NH3- side and CH3- side of CH3NH3 have weak nucleophilic and electrophilic character, respectively. So the electrostatic characteristics of CH3NH3+ and CH3NH3 are significantly different. The strong electrostatic repulsive interaction between two neighboring CH3NH3+ radicals plays an important role in structural phase transition of CH3NH3PbI3 material. At room temperature, the CH3NH3+ in the inorganic cage is activated and disordered, and has a strong electrophilic character. Due to these characteristics of CH3NH3+, the interfacial electrons at TiO2/CH3NH3PbI3 heterojunction are combined with CH3NH3+ to form CH3NH3 in the inorganic[PbI3]- framework. The CH3NH3 at the heterojunction under the built-in electric field is more easily oriented than CH3NH3+. Two initial geometrical configurations for CH3NH3+:CH3NH3 and CH3NH3:CH3NH3 dimers are optimized by using Gaussian 09 at an MP2/Aug-cc-PVTZ level. On the basis of the electrostatic characteristic of CH3NH3+:CH3NH3 dimer, the interfacial electrons at TiO2/CH3NH3PbI3 heterojunction are easily injected into the CH3NH3PbI3 material, which leads to the strong polarization of CH3NH3PbI3 material at the heterojunction. From the ESP of optimized CH3NH3:CH3NH3 dimer, it is found that the weak electrostatic field of the inorganic framework, parallel to C-N axis, is induced by the CH3NH3 orientational order, which is made for improving the photogenerated electron-hole pair separation and carrier transport. The TiO2/CH3NH3PbI3 heterojunction has more advantage than traditional p-n junction because of no consumption of carrier for CH3NH3PbI3 material in the process of forming built-in electric field. The physical mechanism is the origin of high PCE for CH3NH3PbI3 solar cells. According to the experimental results and first-principle calculations, we can draw an important conclusion that the electrostatic characteristics of organic CH3NH3+ cations in the inorganic[PbI3]- framework result in the high performances of halide perovskite solar cells.

Extended finite element simulation of fracture network propagation in formation containing frictional and cemented natural fractures

Shale gas reservoirs often need hydraulic fracturing treatments to create complex fracture network to enhance production. Frictional and cemented natural fractures are often contained in shale formations. The interactions between the hydraulic fractures and these two types of pre-existing natural fractures are different. In this study, we established a two-dimensional fluid-solid coupled hydraulic fracturing model using the extended finite element method (XFEM) to simulate the interactions between hydraulic fractures and natural fractures, and further the formation of fracture network. The results show that when a hydraulic fracture intersects with a natural fracture, the hydraulic fracture may be arrested and propagate along the direction of natural fracture, or cross the natural fracture without being affected. For the frictional natural fractures, the intersection angle, frictional coefficient, stress anisotropy and rock tensile strength have a significant influence on creating fracture network. It is found that decreasing stress difference and interfacial friction, or increasing rock tensile strength may lead to more complex fracture network. For the cemented natural fractures, the intersection angle and the ratio of cement toughness and rock toughness play critical roles in the creation of fracture network. Smaller intersection angle and cement toughness of natural fractures and larger rock fracture toughness often lead to more complex fracture network. In addition, for the same initial geometrical configuration of natural fractures, hydraulic fracturing often leads to more complex fracture network in formations containing frictional natural fractures compared with formations containing cemented natural fractures. These findings offer new insights into the nature and degree of fracture complexity, helping to optimize hydraulic fracturing design in shale gas reservoirs.

Anisotropy of low energy direct photons in relativistic heavy ion collisions

Using the Wigner function approach for electromagnetic radiation fields, we investigate the behavior of low energy photons radiated by the deceleration processes of two colliding nuclei in relativistic heavy ion collisions. The angular distribution reveals information of the initial geometric configurations, which is reflected in the anisotropic parameter v2, with an increasing v2 as energy decreases. This behavior is qualitatively different to the v2 from the hadrons produced in the collisions.

Solar sail structural analysis via improved finite element modeling

Despite the existence of many studies about the structural analysis of a square solar sail, the need for obtaining reliable numerical results still poses a number of practical issues to be solved. The aim of this paper is to propose a new method that improves the existing analysis techniques. In this sense, the solar sail is modeled using distributed sail-boom connections, and its structural behavior in free flight is studied, using the inertia relief method, at different incidence angles of the incoming solar radiation. The proposed approach is able to circumvent the onset of numerical convergence problems by means of suitable strategies. A nonlinear analysis is carried out starting from an initial geometrical configuration in which the whole solar sail is perturbed using a linear combination of the first global buckling modes, obtained with a static eigenvalue analysis. Key points of the procedure are the application of a correct sail pre-stress, a clever choice of the type of elements to be used in the finite element analysis and the use of a suitable mesh refinement. The performance of the new approach have been successfully tested on square solar sails with side length varying from relatively small to medium-to-large sizes, in the range of 10–100 m. A detailed analysis is presented for a reference 20 m × 20 m square solar sail, where the paper shows that the suggested procedure is able to guarantee accurate results without the need of additional stabilization technique. In particular, the vibration global mode shapes and frequencies of the solar sail are correctly described even in presence of unsymmetrical loading conditions. In other terms, the numerical analysis is completed without any convergence problem and any disturbing local modes.

Estudo do movimento de um duplo cone sobre uma pista em V

Utilizamos o princípio da conservação de energia mecânica para estudar o movimento de um duplo cone sobre uma pista em V para diferentes condições (condições iniciais e configurações geométricas). Mostramos que, dependendo das configurações geométricas, esse problema apresenta três regimes de movimentos. No mais interessante deles, o duplo cone rola para a parte mais elevada da pista em V, até mesmo se dermos a ele um pequeno impulso na direção oposta. Por fim, apresentamos o aparato experimental que utilizamos para verificar alguns de nossos resultados teóricos.