Microscopic Structure Model Research Articles

Advances in Multi‐Scale Biomechanics of Fruits and Vegetables: A Review

ABSTRACTFruits and vegetable (F&V) account for a large proportion of the market output, and reducing mechanical damage can improve economic benefits. During harvesting and storage of F&V, visible mechanical damage and unseen bruises can result from external loads. However, there are relatively few studies on the micro‐damage of F&V, and the micro‐damage changes are reflected in the macro. Therefore, it is necessary to establish macroscopic, mesoscopic, and microscopic mechanical structure models. In this paper, the factors influencing the mechanics of F&V are analyzed, macroscopic, mesoscopic, and microscopic mechanical analysis methods of F&V are reviewed, multi‐scale mechanical relationships are explored, and future research directions of multi‐scale biomechanics of F&V are prospected. The results show that future research direction should mainly focus on the force analysis of microscopic single cell, as it is the basis of mechanical analysis of F&V.

Optimization of mechanical and safety properties by designing interface characteristics within energetic composites

The interfacial structure has an important effect on the mechanical properties and safety of the energetic material. In this work, a mesostructure model reflecting the real internal structure of PBX is established through image digital modeling and vectorization processing technology. The microscopic molecular structure model of PBX is constructed by molecular dynamics, and the interface bonding energy is calculated and transferred to the mesostructure model. Numerical simulations are used to study the influence of the interface roughness on the dynamic compression and impact ignition response of PBX, and to regulate and optimize the mechanical properties and safety of the explosive to obtain the optimal design of the surface roughness of the explosive crystal. The results show that the critical hot spot density of PBX ignition under impact loading is 0.68 mm−2. The improvement of crystal surface roughness can improve the mechanical properties of materials, but at the same time it can improve the impact ignition sensitivity and reduce the safety of materials. The optimal friction coefficient range for the crystal surface that satisfies both the mechanical properties and safety of PBX is 0.06–0.12. This work can provide a reference basis for the formulation design and production processing of energetic materials.

Stereochemically Active Lone Pairs Stabilizing Intrinsic Vacancy Defects in Thermoelectric InTe.

Harvesting waste heat efficiently with thermoelectric energy conversion requires materials with low thermal conductivity. Recently, it was demonstrated how dynamic lone pair expression in thermoelectric InTe is responsible for giant anharmonicity leading to a very low lattice thermal conductivity. InTe also contains correlated disorder of intrinsic defects due to vacancies, and this contributes to additional lowering of the thermal conductivity. Here we use the three-dimensional difference pair distribution function (3D-ΔPDF) to analyze 25 K single crystal diffuse X-ray scattering from InTe to unravel the local defect structure, and propose a microscopic structural model. Extended off-centering of In+ ions induced by vacancies allows for the local expression of stereochemically active lone pairs. The associated electronic stabilization is proposed to be a driving force for the formation of In+ vacancy defects in InTe.

MULTIPHASE TRANSPORT OF FOAM FLUID IN POROUS STRUCTURES FOR ENHANCING OIL RECOVERY

Foams in pores affect the sweep range and oil displacement efficiency for low-permeability reservoir. In this paper, regular porous media with different coordination numbers are constructed to study how the parameters of microscopic pore structure affect foam flooding, and to identify the relationship between foam flooding efficiency and pore size. A two-dimensional microscopic pore structure model is established by computed tomography (CT) and the Imagej software. The sweep range and oil displacement efficiency of foam flooding are compared with that of water flooding. The results show that porous media with low coordination numbers can lead to higher foam flooding efficiency. When the pore size of porous media with a coordination number of 3 is 1 μm, the oil displacement effect is the best. Compared with water, foam can significantly improve oil displacement efficiency. Foam can block the dominant channel and drive out the residual oil in the narrow pore throat with higher efficiency. When the gas-liquid ratio of the foam is 3:1, the residual oil saturation is the lowest, and the flooding effect is the best. The higher contact angle of the wetting wall can produce better efficiency of foam flooding. When the wetting angle is 45°, the oil displacement effect is the best. When the injection rate is 0.5 m/s, the oil displacement effect is the best, but when the injection rate reaches 5 m/s, the residual oil saturation is the smallest. When the coordination number is 4, the oil displacement effect is the best.

Fractal Analysis of Failure Process and Damage Evolution of Jointed Sandstone Based on DIP Technique

The Lannigou gold mine deposit is mainly composed of calcium-bearing sandstone and siltstone, and there are a lot of microdefects such as joints and cracks in the sandstone. The mesostructure of jointed sandstone makes a difference to the fracture process and mechanical properties. The RFPA2D software and Digital Image Processing Technology (DIP) were used to create a real microscopic structural numerical model of jointed sandstone with varied dip angle prefabricated cracks. A digital image-based rock microscopic scale fracture box dimension algorithm was established with MATLAB software. It is used to analyze the fractal characteristics of the acoustic emission field of unique prefabricated fractured sandstone. This study demonstrates that the mechanical parameter of jointed sandstone with different prefabricated cracks have manifest anisotropy, which includes elastic modulus and compressive strength. When the leaning angle of the cracks increases, they all increase linearly. There are three modes of starting-crack under uniaxial compression: from the peak of the prefabricated crack; from the middle of the prefabricated crack; and from the joint. Damage degree and rupture model are quantitatively represented by the fractal dimension. The more fractal dimensions there are, the more serious the damage, and the more complicated the rupture mode becomes. This research offers a novel method for investigating the evolution of rock microscopic scale fractures. This has to have engineering practical value for in-depth studies of rock fracture, instability, and failure, as well as the mechanisms that cause rock engineering disasters.

Self-consistent description of the halo nature of 31Ne with continuum and pairing correlations

Background: A relativistic structure model has previously been used to predict a halo structure for 31Ne (Zhang et al 2014 Phys. Lett. B 730 30), consistent with halo signatures from measured reaction cross sections of Ne isotopes bombarding Carbon targets. However, previous attempts to calculate those cross sections with reaction models were missing contributions from resonances and pairing correlations in their structure input. Purpose: Use a reaction model with our relativistic fully microscopic structure model input to predict these cross sections and momentum distributions and analyze for possible halo signatures. Methods: Structure input for exotic Ne isotopes were obtained via the analytical continuation of the coupling constant (ACCC) method based on the relativistic mean field (RMF) theory with Bardeen–Cooper–Schrieffer (BCS) pairing approximation, the RAB approach. Total reaction cross sections, one-neutron removal cross sections, and momentum distributions of breakup reaction products were calculated with a Glauber model using our relativistic structure input. Results: Our predictions of total reaction and one-neutron removal cross sections of 31Ne on a Carbon target were significantly enhanced compared with those of neighboring Neon isotopes, agreeing with measurements at 240 MeV/nucleon and consistent with a single neutron halo. Furthermore, our calculations of the inclusive longitudinal momentum distribution of the 30Ne and valence neutron residues from the 31Ne breakup reaction indicate a dilute density distribution in coordinate space, another halo signature. Conclusions: We give a full description of the halo nature of 31Ne that includes a self-consistent use of pairing and continuum contributions that makes predictions consistent with reaction cross section measurements. This approach can be utilized to determine the halo structure of other exotic nuclei.

Research on coalbed methane microscopic seepage characteristics of medium and high-rank coal

ABSTRACT In the present study, the microscopic seepage characteristics of coalbed methane (CBM) in medium and high-rank coal are investigated. Moreover, the influence of the coal pore structure on the CBM migration is studied. To this end, X-ray μCT scanning technology is utilized to construct the microscopic pore structure model of medium and high-rank coal. Then, the established model is transformed into a vectorized CAD solid model. Numerical simulation under different working conditions is carried out. The obtained results show that the pore system of coal is in a connected state. However, not all pores can penetrate the entire seepage direction. It is found that pore connectivity is the most important factor determining the CBM seepage performance. As coal metamorphism increases, the corresponding seepage pore connectivity decreases, pore throat radius decreases, seepage channels in coal seams decrease and the coal permeability decreases. Meanwhile, permeability anisotropy and the pore pressure of the coal have different changing laws along different seepage paths. It should be indicated that there is a dominant seepage direction. As the degree of coal metamorphism increases, the permeability in all directions gradually decreases.

Drastic change of inelastic scattering dependent on the development of dineutron correlations in Be10

We investigated the development and breaking of the dineutron correlation in $^{10}$Be by analyzing the elastic and inelastic scatterings with a framework combing the microscopic structure and reaction models. For studying the structure, the $^{10}$Be nucleus was constructed under the assumption of a four-body ($\alpha + \alpha + n + n$) cluster model. In this work, we focused on the change in the inner structure for the 0$_1^+$, 2$_1^+$, and 2$_2^+$ states when the strength of the spin-orbit interaction is varied. The inner structure, including various physical quantities such as energy, radius, and transition strength, is drastically influenced by the strength of the spin-orbit interaction. In particular, the development and breaking of the dineutron correlation is governed by the spin-orbit strength. The differences in the inner structure can be manifested by applying the obtained wave functions to elastic and inelastic scatterings with a proton target at $E/A =$ 59.4 and 200 MeV. Although the 0$_1^+$ and 2$_1^+$ states are significantly influenced by the spin-orbit strength of the nuclear structure calculation, the elastic and inelastic cross sections are not much affected. On the other hand, the inelastic cross section of the 2$_2^+$ state depends greatly on the spin-orbit strength of the structure calculation. Thus, we discovered a way to measure the degree of the development of dineutron cluster structure based on its sensitivity to the inelastic cross section of the 2$_2^+$ state of $^{10}$Be.

Global analysis of nuclear cluster structure from the elastic and inclusive electron scattering

Background: Recently, the researches of cluster structure have attracted considerable attention. Many microscopic structure models have been applied to describe the cluster configurations.Purpose: To better analyze the cluster structure and associate with the experimental observations, comparative studies are carried out in this paper by combining the nuclear structure model with the electron scattering theory.Method: The density distributions for candidate nuclei of normal and cluster states are obtained from the deformed relativistic Hartree-Bogoliubov (RHB) model. Using some moderate approximations, the corresponding Coulomb form factors $|{F}_{C}{(q)|}^{2}$ and inclusive cross sections for different configurations are calculated by the distorted wave Born approximation (DWBA) and coherent density fluctuation model (CDFM), respectively.Results: Comparing the $|{F}_{C}{(q)|}^{2}$ and inclusive cross sections of different configurations, the effects of nuclear cluster structure can be revealed, due to the differences of nuclear charge radii ${R}_{C}$ in coordinate space and the discrepancies of Fermi momentum ${k}_{F}$ in momentum space.Conclusions: Results illustrate that the cluster structure can be reflected from the elastic and inclusive electron scattering. The studies conducted in this paper provide a new approach to analyze the cluster configurations, and are also helpful to guide future electron scattering experiments.

Mixed Reality System for Virtual Chemistry Lab

This paper presents a new method for improving teaching aids with the design and development of a chemistry education platform - the Mixed Reality (MR) Chemistry Lab. Our system provides a new educational experience in which students can simulate a chemistry experiment in a virtual lab and interact with objects using Oculus Helmet-Mounted Displays (HMD) and hand controller devices. The proposed system aims to familiarize students with experimental procedures and safety knowledge before conducting actual experiments. Moreover, students will be able to observe microscopic atomic structure models in three dimensions. Our research also includes a five-part, quantitative evaluation system user tests perform using a quantitative questionnaire consisting of five items, including hardware equipment, immersion, education, interaction sense of control, and degree of difficulty. The evaluation results confirm that this system will be helpful to the educational experience of conducting chemistry experiments with scientific evaluation methods, and the proposed system is also expected to have a broad range of applications in many other subjects.

First microscopic coupled-channels calculation of cross sections for inelastic α scattering off O16

The $\alpha$ inelastic scattering on $^{16}$O is investigated with the coupled-channel calculation using the $\alpha$-nucleus coupled-channel potentials, which are microscopically derived by folding the the Melbourne $g$-matrix $NN$ interaction with the $^{16}$O and $\alpha$ densities. The matter and transition densities of $^{16}$O are calculated by a microscopic structure model of the variation after the spin-parity projections combined with the generator coordinate method of $^{12}$C+$\alpha$ in the framework of the antisymmetrized molecular dynamics. The calculation reproduces the observed elastic and inelastic cross sections at incident energies of $E_\alpha$=104 MeV, 130 MeV, 146 MeV, and 386 MeV. The coupled-channel effect on the cross sections is also discussed.

α scattering cross sections on C12 with a microscopic coupled-channels calculation

$\alpha$ elastic and inelastic scattering on $^{12}$C is investigated with the coupled-channel calculation using microscopic $\alpha$-$^{12}$C potentials, which are derived by folding the Melbourne $g$-matrix $NN$ interaction with the matter and transition densities of $^{12}$C. These densities are obtained by a microscopic structure model of the antisymmetrized molecular dynamics combined with and without the $3\alpha$ generator coordinate method. The calculation reproduces satisfactorily well the observed elastic and inelastic cross sections at incident energies of $E_\alpha=130$~MeV, 172.5~MeV, 240~MeV, and 386~MeV with no adjustable parameter. Isoscalar monopole and dipole excitations to the $0^+_2$, $0^+_3$, and $1^-_1$ states in the $\alpha$ scattering are discussed.

Numerical Research on Energy Evolution in Granite under Different Confining Pressures Using Otsu’s Digital Image Processing and PFC2D

Research on energy accumulation and releasing in the rock plays a key role on revealing its failure mechanism. This paper establishes a microscopic structure model of granite using Otsu digital image processing (DIP) technology and particle flow code software (PFC2D). A series of numerical compression tests under different confining pressures were conducted to investigate the macro and micro characteristics of energy evolution in granite. The results showed that the energy evolution of granite is divided into three stages: stable accumulation, slow dissipation, and rapid release. With increasing confining pressure, the strain energy accumulation ratio decreased exponentially and the peak value of strain energy increased linearly. It was found that the energy accumulation speed in the pre-peak stage increased as a linear function, while the energy release speed in the post-peak stage decreased as an exponential function. In addition, the feldspar is the main microstructure which played a major part in accumulating energy in granite. However, the unit mineral energy of mica particles was bigger than that of feldspar and quartz. When subjected to increasing confining pressure, the feldspar’s total energy growth rate was fastest. Meanwhile, the mica’s unit energy growth rate was fastest.

Manifestation of α clustering in Be10 via α -knockout reaction

Background: Proton-induced {\alpha}-knockout reactions empower direct experimental manifestations of {\alpha}-clustering in nuclei. This is obtained by relating the theoretical descriptions of clustering states with experimental reaction observables. It is desired to introduce microscopic structure models into the theoretical frameworks for {\alpha}-knockout reactions. Purpose: Our goal is to probe the {\alpha}-clustering in $^{10}$Be nucleus by proton-induced {\alpha}-knockout reaction observables. Method: We adopt an extended version of the Tohsaki-Horiuchi-Schuck-R\"opke (THSR) wave function of $^{10}$Be and integrate it with the distorted wave impulse approximation (DWIA) framework for the calculation of (p,p{\alpha}) knockout reactions. Results: We make the first calculation for the $^{10}$Be(p,p{\alpha})$^{6}$He reaction at 250 MeV implementing a microscopic {\alpha}-cluster wave function and predict the triple differential cross sections (TDX). Furthermore, by constructing artificial states of the target nucleus $^{10}$Be with compact or dilute spatial distributions, the TDX is found to be highly sensitive to the extent of clustering in the target nuclei. Conclusions: These results provide reliable manifestation of the {\alpha}-clustering in $^{10}$Be.

Electrically modulated optical properties of fluorescent chiral nematic liquid crystals

Due to the superior optical properties and tremendous application prospects in the field of optical devices, both rare earth complex (REC) and chiral nematic liquid crystal (CNLC) have attracted widespread attention in the fields of theoretical research and engineering applications. Among the research on the optical behaviors of CNLC or REC, the controllable modulation of selective reflection of CNLCs and emitted fluorescence of RECs is of great significance to fabricated tunable optical materials. In this study, europium (III) complexes are dissolved and assembled in the chiral matrix of CNLCs to form binary CNLC-REC composites due to excellent compatibility between RECs and CNLCs. The selective reflection combined with the photoluminescence of binary fluorescent CNLCs are investigated, an electrically-controlled microscopic structure model is established to elaborate the dual-mode optical modulation based on the stable CNLC-REC composites. The reflectance of CNLCs can be tuned in the process from planar state with brilliant Bragg reflection to focal conic state with chaotic scattering, the intensity of fluorescence emitted by RECs can be modulated due to the increased scattering of incident UV light on the surface of CNLC-REC composite films. Furthermore, the dual-mode optical modulation can be operated at low voltages and the response time is within 3 ms. This facile and ultrafast methodology can be used to develop state-of-the-art tunable optical devices in the fields of LC display, fluorescent display and optical sensors.

Composite structural modeling and tensile mechanical behavior of graphene reinforced metal matrix composites

Owing to its distinguished mechanical stiffness and strength, graphene has become an ideal reinforcing material in kinds of composite materials. In this work, the graphene (reduced graphene oxide) reinforced aluminum (Al) matrix composites were fabricated by flaky powder metallurgy. Tensile tests of pure Al matrix and graphene/Al composites with bioinspired layered structures are conducted. By means of an independently developed Python-based structural modeling program, three-dimensional microscopic structural models of graphene/Al composites can be established, in which the size, shape, orientation, location and content of graphene can be reconstructed in line with the actual graphene/Al composite structures. Elastoplastic mechanical properties, damaged materials behaviors, graphene-Al interfacial behaviors and reasonable boundary conditions are introduced and applied to perform the simulations. Based on the experimental and numerical tensile behaviors of graphene/Al composites, the effects of graphene morphology, graphene-Al interface, composite configuration and failure behavior within the tensile mechanical deformations of graphene/Al composites can be revealed and indicated, respectively. From the analysis above, a good understanding can be brought to light for the deformation mechanism of graphene/Al composites.

Abstract ID: 38 Investigating energy deposition in cellular targets using multiscale tissue models

Purpose To investigate energy deposition in subcellular targets, quantify the microdosimetric spread in a population of cells, and determine how these results depend on details of multiscale Monte Carlo tissue models. Methods Multiscale tissue models are developed involving microscopically-detailed regions of interest (ROIs) embedded in bulk tissue phantoms irradiated by photons (20 keV to 1.25 MeV). Each ROI includes >1500 explicitly-modelled cells; specific energy (energy imparted per unit mass) is scored in nuclei and cytoplasm compartments using the EGSnrc user-code egs_chamber. Different cell arrangement methods and cell/nucleus size distributions are investigated. These microscopic tissue structure models are developed using published data on cell elemental compositions, sizes and number densities. Five cancerous/normal human soft tissues and water are considered. Use of egs_chamber at low doses (∼mGy), considering subcellular (∼micron) targets, is validated by comparison with results from the published literature. Results Populations of 1000 cells generate (normalized) specific energy distributions f(z) indistinguishable from those of a larger population, which suggests that 1000 is an adequate population size for statistical analysis. Validation test results are in good agreement with published experimental and computational data. For ∼mGy doses, there is considerable variation in energy deposition (microdosimetric spread) throughout a cell population: considering muscle with 7.5 microns (3 microns) cell (nucleus) radius and a dose of 4 mGy, the standard deviation of specific energy (relative to the mean) for nuclear targets is 177% for 50 keV photons, and 114% for a Cobalt-60 spectrum. If the nuclear radius increases to 6 microns, then the relative standard deviation decreases to 74% and 47% for 50 keV and Cobalt-60, respectively. The mean specific energy for nuclei differs from bulk tissue dose by up to 30%, depending on cellular elemental compositions. Conclusions At low doses, there is considerable variation in energy deposition within a population of cells. Mean nucleus specific energy generally differs from corresponding bulk tissue dose. Results highlight the importance of model validation and microdosimetric considerations at low doses, and indicate that energy deposition within subcellular targets is sensitive to cell morphology and composition, phantom medium, source energy, and dose.

Fingerprint of local disorder in long range ordered isometric pyrochlores

The detailed characterization of local order and disorder in isometric A2B2O7 crystalline pyrochlores is of significant importance in view of their wide range and sensitive technological applications. Nevertheless, much remains to be understood concerning their atomic scale structures. Here we specifically pinpoint local order and disorder in four stoichiometric Ln2Zr2O7 (Ln = La, Nd, Sm and Eu) pyrochlores using a combination of three standard easily available laboratory techniques: XRD, 17O solid-state MAS NMR and Raman spectroscopy. The evolution of the oxygen sub-lattice identifies specific features (extra 17O NMR signals and Raman bands) which undoubtedly reveal local oxygen order and disorder in these stoichiometric long range ordered crystalline pyrochlores. These results complete the understanding of the atomic scale in these stoichiometric pyrochlores necessitating the need for new microscopic structural models.

19pAC-11 微視的核構造反応模型を用いた^ Be原子核の研究

19pAC-11 微視的核構造反応模型を用いた^ Be原子核の研究

Study of similarity and dissimilarity between10Be and9Li nuclei with microscopic structure and reaction models

We apply the microscopic nuclear structure and reaction models to the elastic scattering of the10Be and9Li nuclei. The states of the10Be and9Li nuclei are described as an α + α(t) + n + n four-body system based on the cluster wave function, respectively. The elastic scattering cross section is obtained by the microscopic coupled channel (MCC) calculation with the MPa interaction, which is the latest version of the complex G-matrix interaction derived from the ESC NN interaction model. We compare the channel coupling (CC) effect of the10Be nucleus with that of the9Li nucleus in the elastic scattering cross sections calculated with the same incident energy per nucleon. At the backward angles, the CC effect on the elastic scattering cross section for the incident10Be nucleus is clearly larger than that for the incident9Li nucleus. We investigate the dissimilarity for the CC effect through the dynamical polarization potential.