Moment Components Research Articles

Experimental investigation of tsunami bore-induced forces and pressures on skewed box section bridges

Tsunamis in Indonesia (2004) and Japan (2011) severely affected communities bordering the Indian Ocean and Japan's east coast. Despite the plausible findings arising from the available studies, the research on the impact of tsunami bore forces applied to bridges of different designs is limited. This is because the estimation methods for tsunami-induced loads presented in the literature have mainly been developed for buildings and require careful adaptation to apply to bridges. The main focus of the present study is to experimentally examine the interaction between a tsunami bore and a box section bridge with different orientations to the direction of the incoming bore, bore strengths, and deck clearances. The experiments were conducted in a 15-m-long, 1.2-m-wide, and 1.2-m-deep wave flume. The forces and pressures applied to the bridge, the bore heights, and the velocities were measured. It was found that the skewed bridge deck is subjected to additional force and moment components, namely the cross-stream force (Fy) and the rolling and yawing moments (Mx and Mz). These components are non-existent for the unskewed bridge deck. Based on the experimental results, equations were proposed for estimating tsunami forces for a box section bridge deck.

Quantized surface magnetism and higher-order topology: Application to the Hopf insulator

We identify topological aspects of the subextensive magnetic moment contributed by the surfaces of a three-dimensional crystallite -- assumed to be insulating in the bulk as well as on all surface facets, with trivial Chern invariants in the bulk. The geometric component of this subextensive moment is given by its derivative with respect to the chemical potential, at zero temperature and zero field, per unit surface area, and hence corresponds to the surface magnetic compressibility. The sum of the surface compressibilities contributed by two opposite facets of a cube-shaped crystallite is quantized to an integer multiple of the fundamental constant $e/h c$; this integer is in one-to-one correspondence with the net chirality of hinge modes on the surface of the crystallite, manifesting a link with higher-order topology. The contribution by a single facet to the magnetic compressibility need not be quantized to integers; however, symmetry and/or Hilbert-space constraints can fix the single-facet compressibility to half-integer multiples of $e/hc$, as will be exemplified by the Hopf insulator.

High-harmonic generation in one-dimensional Mott insulators

We study high-harmonic generation (HHG) in the one-dimensional Hubbard model in order to understand its relation to elementary excitations as well as the similarities and differences to semiconductors. The simulations are based on the infinite time-evolving block decimation (iTEBD) method and exact diagonalization. We clarify that the HHG originates from the doublon-holon recombination, and the scaling of the cutoff frequency is consistent with a linear dependence on the external field. We demonstrate that the subcycle features of the HHG can be reasonably described by a phenomenological three step model for a doublon-holon pair. We argue that the HHG in the one-dimensional Mott insulator is closely related to the dispersion of the doublon-holon pair with respect to its relative momentum, which is not necessarily captured by the single-particle spectrum due to the many-body nature of the elementary excitations. For the comparison to semiconductors, we introduce effective models obtained from the Schrieffer-Wolff transformation, i.e. a strong-coupling expansion, which allows us to disentangle the different processes involved in the Hubbard model: intraband dynamics of doublons and holons, interband dipole excitations, and spin exchanges. These demonstrate the formal similarity of the Mott system to the semiconductor models in the dipole gauge, and reveal that the spin dynamics, which does not directly affect the charge dynamics, can reduce the HHG intensity. We also show that the long-range component of the intraband dipole moment has a substantial effect on the HHG intensity, while the correlated hopping terms for the doublons and holons essentially determine the shape of the HHG spectrum. A new numerical method to evaluate single-particle spectra within the iTEBD method is also introduced.

Reliable method of aerodynamic analysis using computational fluid dynamics and scaled models in the development process of a Very Light Airplane

In past decades a massive improvement of computational fluid dynamics (CFD) methods and the rapid increase of computational resources made it possible to simulate a lot of phenomena appearing during the flow of fluid around objects. In following paper a reliable method of aerodynamic analysis using both CFD and scaled models in the development process of a Very Light Airplane have been presented. A method of preparing a numerical model of an airplane and the aerodynamic analysis methodology have been shown. A numerical calculations using finite volume method implemented in specialized software were performed. What is more important, to perform the aerodynamic tests in wind tunnels, scaled models of an airplane have been prepared using the modern and fast manufacturing technologies, including 3D printing and CNC machining. The results have been shown in the graphs form of aerodynamic force and moment components as function of angle of attack. During research an influence of structural parts of an airplane on aerodynamic characteristics have been analyzed. The qualitative results of a flow around the aircraft body have been presented in form of parameter distribution maps on the airframe surface have been shown. Visualization of pressure distribution have been extended with path lines visualization of the flow. The research described in the paper is an example of professional and innovative approach to the subject matter.

Study and evaluation of four bar polycentric knee used in the prosthetic limb for transfemoral amputee during the gait cycle

The prosthetic knee is one of the most important parts used in manufacturing of the above knee prostheses limb and it is considered the most important component. Accordingly, it became necessary to conduct a study and evaluate for different types a prosthetic knee. In present work, the mechanism of four bar 3R20 prosthetic knee were evaluated and studied. Virtual model of four bar 3R20 prosthetic knee joint was built using Solid Work 2018 program. The fifty parts of four bar polycentric knee were designed separately and then assembled together. The kinematic analysis of four bar polycentric knee was performed using geometric analysis and Grashof law for double rocket. The results of instant center of rotation (ICR) from analytical solution was estimated using MATLAB program. The kinetic model include data of two components of forces and joint moments which used for transfemoral amputee with (age, height, weight, and stump length) of (28 years, 178 cm, 78 kg, and 29 cm) respectively. The numerical analysis of four bar prosthetic knee involved select the element type in ANSYS Workbench 19.2 program. Quadrilateral and trihedral elements were used in the finite element analysis to generate the mesh. The static analysis was investigated during different segmentation of gait cycle. The results of equivalent (von Mises) stress distribution calculated during stance phase for different loading conditions showed that the maximum stress was printed at the loading response phase with 226.93 Mpa at the root region between prosthetic knee and socket when orientation angles θ 2 = 85.5° and θ 4 = 105.4° and ICR coordinates are −0.560 mm and 77.388 mm for X,Y respectively.

Математичне моделювання впливу шквального вітру на технічні та рослинні структури на урбанізованих територіях

Stormy events in recent years have shown that the destructive effects of wind on urban technical structures and plants pose a special threat. The paper provides an overview of mathematical models and approaches to experimental and theoretical studies of the problems associated with the effects of wind gusts and tornadoes on urban areas. Computer simulations of wind action on standard multistorey buildings in Ukraine are given. The coefficients of normal and shear components of forces and moments of forces acting on the surface of buildings, as well as vortex tracks over the residential complex at different wind speeds from moderate to severe have been computed. The calculations were performed by the finite element method using the model of turbulent air flow in the package AnSys2020. It is shown how with the help of a slight change in shape (roofs, additional passages, shields) the destructive effects of wind on the buildings and plants, as well as the threat to human life can be reduced.

Invariant moment and learning vector quantization (LVQ NN) for images classification

Image classification need two main components, i.e., features and classifier. The feature commonly used for classification of images with different scale is invariant moment; its value is invariant against the spatial transformation dealing with translation, scale and rotation. The classifier that is widely used for classification is LVQ NN. It is shallow network containing only two layers, the initial value of its weight is more fixed so that its output is more stable and its algorithm is relatively simple thus both training and testing process are run fast. Based on these facts, therefore, this research proposed a combination method of invariant moment and LVQ NN (IM-LVQ). The ability of the proposed method would be compared with two other methods. Firstly, the combination method of invariant moment and Euclidean distance (IM-ED). Secondly, the combination of invariant moment and principal component analysis (IM-PCA). The performance of the three methods was evaluated quantitatively with several metrics, viz.: Confusion Matrix, Accuracy, Precision, True Positive Rate, False Positive Rate, ROC graph and training time. The evaluation of the metrics was based upon the changing (reduction) of the scale/size of training image. The results showed that IM-LVQ method outperformed the other two methods in aforementioned metrics.

Extended-body motion in black hole spacetimes: What is possible?

Free-fall is only approximately universal in general relativity. Different extended bodies can fall in different ways, depending on their internal dynamics. Nevertheless, certain aspects of their motion are universal. This paper examines the universal constraints on extended-body motion in vacuum type D spacetimes. Working in the quadrupole approximation, we show that in addition to the (previously-known) constraints imposed by Killing vectors, two components of the gravitational torque must vanish. Furthermore, of the ten components of a body's quadrupole moment, four are found to be irrelevant, two can affect only the force, and the remaining four can affect both forces and torques. As an application, we consider the capabilities of a hypothetical spacecraft which controls its motion by controlling its internal structure. In the Schwarzschild spacetime, such a spacecraft can control its mass, and in doing so, it can stabilize unstable orbits, escape from bound orbits, and more -- all without a rocket.

Research On ADCN Method for Damage Detection of Mining Conveyor Belt

Belt conveyor is considered as a momentous component of modern coal mining transportation system, and thus it is an essential task to diagnose and monitor the damage of belt in real time and accurately. Based on the deep learning algorithm, this present study proposes a method of conveyor belt damage detection based on ADCN (Adaptive Deep Convolutional Network). A deep convolution network with unique adaptability is built to extract the different scale features of visible light image of conveyor belt damage, and the target is classified and located in the form of anchor boxes. A data set with data diversity is collected according to the actual working conditions of the conveyor belt. After training and regression, the ADCN model can perfectly capture and classify the damaged target in the video of the conveyor running. Compared with the SVM based method, the method based on ADCN can better meet the real-time and reliability requirements of belt damage detection, and it has the positioning function which SVM does not have.

The microwave spectrum and molecular structure of the gas-phase heterodimer formed between argon and glycidol

The microwave rotational spectrum of the gas-phase heterodimer formed between glycidol and the argon atom is measured from 5.6 to 18.1 GHz. Despite the existence of two low energy conformers for the glycidol molecule, the spectrum of only one argon-glycidol complex is observed, corresponding to the global minimum energy structure. Higher energy isomers, and indeed less abundant isotopologues of the observed species, are presumably not produced with sufficient number density to be detected under the conditions of the experiment. The spectroscopic constants obtained from the analysis of the spectrum are combined with ab initio quantum chemistry predictions for the dipole moment components to determine the structure of the lowest energy arrangement for argon-glycidol. This structure is compared with those previously observed for the argon complexes of analogous fluoromethyloxirane molecules.

Two-step magnetic ordering into a canted state in ferrimagnetic monoclinic Mn3As2

We report the magnetic structure of monoclinic Mn3As2 at 3 ​K and 250 ​K using neutron powder diffraction measurements. From magnetometry data, the Curie temperature of Mn3As2 was confirmed to be around 270 ​K. Calorimetry analysis showed the presence of another transition at 225 ​K. At 270 ​K, Mn3As2 undergoes a k=0 ferrimagnetic ordering in the magnetic space group C2/m (#12.58) with Mn moments pointing along b. Below 225 ​K, there is a canting of Mn moments in the ac plane which produces a multi-k non-collinear magnetic structure in space group C2/c (#15.85). The components of Mn moments along b follow k=0 ordering and the components along a and c have k=[0012] propagation vector. The change in the magnetic ground state with temperature provides a deeper insight into the factors that govern magnetic ordering in Mn–As compounds.

Crocin inhibits the activation of mouse hepatic stellate cells via the lnc-LFAR1/MTF-1/GDNF pathway

ABSTRACT Crocin is the main monomer of saffron, which is a momentous component of traditional Chinese medicine Lang Qing A Ta. Here, we tried to probe into the role of crocin in liver fibrosis. Hematoxylin-eosin staining and Sirius Red staining were used to observe the pathological changes of liver tissues. After hepatic stellate cells (HSCs) were isolated from liver tissues, lnc-LFAR1, MTF-1, GDNF, and α-SMA expressions were detected by qRT-PCR and western blot. Immunohistochemistry and immunofluorescence were used to detect α-SMA expression. Chromatin immunoprecipitation was used to analyze the binding of MTF-1 to the GDNF promoter. Moreover, the dual-luciferase reporter gene, RNA pull-down, and RNA immunoprecipitation were used to clarify the interaction between MTF-1 and GDNF, lnc-LFAR1 and MTF-1. The degree of liver fibrosis was more severe in the mice from the liver fibrosis model, while the liver fibrosis was alleviated by the injection of crocin. lnc-LFAR1, GDNF, and α-SMA were up-regulated, and MTF-1 was down-regulated in liver fibrosis tissues and cells, while these trends were reversed after the injection of crocin. Besides, lnc-LFAR1 negatively regulated MTF-1 expression, and positively regulated GDNF and α-SMA expressions, and MTF-1 was enriched in the promoter region of GDNF. Furthermore, the cellular direct interactions between MTF-1 and GDNF, lnc-LFAR1 and MTF-1 were verified. In vivo experiments confirmed the relief of crocin on liver fibrosis. Our research expounded that crocin restrained the activation of HSCs through the lnc-LFAR1/MTF-1/GDNF axis, thereby ameliorating liver fibrosis.

Role of Interfacial Orbital Hybridization in Spin-Orbit-Torque Generation in Pt -Based Heterostructures

We report a large enhancement of the spin-orbit-torque (SOT) efficiency achieved by inserting an ultrathin $\mathrm{Co}$ layer between a single-crystal $\mathrm{Pt}$ layer and an epitaxial ${\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}$ layer. We attribute this to the strong interfacial orbital hybridization between $\mathrm{Pt}$ and $\mathrm{Co}$. Another effect of this hybridization is the spin-rotation effect based on the out-of-plane component of the magnetic moment, which explains the observation of out-of-plane torques. Our results offer an effective approach to engineer the SOT in a conventional ferromagnet-heavy metal system, which might provide opportunities for spintronic application.

Dynamical diffraction effects in STEM orbital angular momentum resolved electron energy-loss magnetic chiral dichroism

In this work we derive sum rules for orbital angular momentum(OAM) resolved electron magnetic chiral dichroism (EMCD) which enable the evaluation of the strength of spin and orbital components of the atomic magnetic moments in a crystalline sample. We also demonstrate through numerical simulations that these rules appear to be only slightly dependent from the dynamical diffraction of the electron beam in the sample, making possible their application without the need of additional dynamical diffraction calculations.

How do the geometries of the broach handles relate to the distribution of force and moments in a femoral model?

The continuous improvement of minimally invasive hip endoprostheses surgery comes with a change in geometries of surgery instruments like the broach handles. Consequently, depending on the handles’ curvature this results in a deviation between handle and femoral axis. Therefore, this study aimed to prove the influence of different handles’ curvatures on the preparation of implant site and acting forces and moments in this process. Five femoral models attached to different handles (double-curved, single-curved, straight) were locked in a drop-weight device with standardize implantation forces and moments and five strokes were measured for each possible combination. Distribution of force and moment components was dependent on the handle's curvature, where the lowest variation from the standard force values was by the straight one (av:15.2% ± 0.5%) and the strongest discrepancies were exhibit by the double-curved one (av:54.3% ± 0.1%.). Moment values have also shown this trend with the lowest variation (12.4%–23.3%) by the straight one and the highest discrepancies (56,6%-90.9%) by the double-curved one. Results show that unguided axial impact introduces unwanted transverse forces and moments into the femur. Therefore, broach handles should be modified accordingly so that minimally invasive surgery remains feasible but unwanted forces or moments can still be compensated.

Structure, magnetism, and electronic properties in 3d−5d based double perovskite ( Sr1−xCax)2FeIrO6 ( 0≤x≤1 )

The $3d\text{\ensuremath{-}}5d$ based double perovskites offer an ideal playground to study the interplay between electron correlation ($U$) and spin-orbit coupling (SOC) effect, showing exotic physics. The ${\mathrm{Sr}}_{2}{\mathrm{FeIrO}}_{6}$ is an interesting member in this family with ionic distribution of ${\mathrm{Fe}}^{3+}$ ($3{d}^{5}$) and ${\mathrm{Ir}}^{5+}$ ($5{d}^{4}$) where the later is believed to be nonmagnetic under the picture of strong SOC. Here we report a detailed investigation of structural, magnetic, and electronic transport properties along with electronic structure calculations in ${({\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x})}_{2}{\mathrm{FeIrO}}_{6}$ series with $x$ from 0 to 1. While the basic interactions such as $U$ and SOC are unlikely to be modified, a structural modification is expected due to ionic size difference between ${\mathrm{Sr}}^{2+}$ and ${\mathrm{Ca}}^{2+}$ which would influence other properties such as crystal field effect and bandwidths. While nonmonotonic changes in lattice parameters are observed across the series, the spectroscopic investigations reveal that $3+/5+$ charge state of Fe/Ir continue till the end of the series. An analysis of magnetic data suggests similar nonmonotonic evolution of magnetic parameters with doping. Temperature dependent crystal structure as well as low temperature (5 K) magnetic structure have been determined from neutron powder diffraction measurements which further indicate site ordered moments for both Fe and Ir. The whole series shows insulating behavior with a nonmonotonic variation in resistivity where the charge transport follows the three-dimensional variable range hopping model. The electronic structure calculations show, SOC enhanced, a noncollinear antiferromagnetic and a Mott-type insulating state is the stable ground state for the present series with a substantial amount of orbital moment, but less than the spin magnetic moment, at the Ir site and the magnetocrystalline anisotropy. The calculations further show the evolution of the spin and orbital magnetic moment components across the series along with the magnetization density. The obtained results imply that the local structural modification with introduction of lower size ${\mathrm{Ca}}^{2+}$ has a large influence on the magnetic and transport properties, further showing a large agreement between experimental results as well as theoretical calculations.

Seismic behavior of a dolphin-type berth subjected to liquefaction induced lateral spreading: 1g large scale shake table testing and numerical simulations

The effects of liquefaction induced lateral spreading on the piles of a dolphin-type berth were investigated using 1 g large scale shake table testing accompanied by numerical simulations. For this purpose, various aspects of the response of the soil and the pile group to lateral spreading were considered. The results indicated that large bending moments were induced in the piles during lateral spreading and the downslope piles of the group received greater bending moments than the upslope one. The monotonic components of bending moments in the piles were reasonably predicted by the displacement based numerical approach using p-y springs when they were properly tuned for strength reduction in liquefied soil and the pile position in the group. A three dimensional hydro-mechanical finite element analysis was also undertaken in OpenSees which appropriately reproduced the physical model behavior. Lastly, a comprehensive parametric study on the verified finite element model revealed that the relative density of soil and the amplitude of base excitation can profoundly affect the induced bending moments in piles as well as the pile cap displacements while the effect of pile flexibility was comparably smaller in this regard.

TD-DFTB study of optical properties of silver nanoparticle homodimers and heterodimers.

The absorption spectra for face-centered cubic nanoparticle dimers at various interparticle distances are investigated using time-dependent density functional tight binding. Both homodimers and heterodimers are investigated in this work. By studying nanoparticles at various interparticle distances and analyzing their vertical excitations, we found that as the interparticle distance decreases, a red shift arises from contributions of the transition dipole moment that are aligned along the z-axis with nondegenerate features; blue shifts occur for peaks that originate from transition dipole moment components in the x and y directions with double degeneracy. When the nanoparticles are similar in size, the features in the absorption spectra become more sensitive to the interparticle distances. The best-fit curves from vertical excitation energy in the form of AR-b for ΔEredshift/ΔEblueshift vs R are determined. In this way, we determined trends for absorption peak shifts and how these depend on the interparticle distance.

A closed form procedure for the design of longitudinal bars in RC sections subjected to axial load and biaxial bending

AbstractThis paper presents an analytical procedure for the design of the longitudinal reinforcement in reinforced concrete rectangular sections subjected to axial load and biaxial bending moment. The integration of the equilibrium equations is performed in analytical form for the case of uniaxial moment, including the effect of the reinforcement placed on the sides of the section and adopting code‐based constitutive laws for steel and concrete. The strength domain of the section is calculated in closed form for the case of only main steel and in simplified form when including the reinforcement disposed on the side. Additionally, a formulation is proposed for the interaction domain of the two components of the bending moment for constant axial load, in which the uniaxial moment capacities are calculated including all the rebars within the section. The proposed method is adopted for setting a design procedure of the steel bars of rectangular sections subjected to biaxial bending. Comparisons with numerical results and code provisions show the reliability of the approach, which reduces computational costs and give useful indications for practitioners and designers.

Discovering the Elusive Global Minimum in a Ternary Chiral Cluster: Rotational Spectra of Propylene Oxide Trimer

AbstractThe chirality controlled conformational landscape of the trimer of propylene oxide (PO), a prototypical chiral molecule, was investigated using rotational spectroscopy and a range of theoretical tools for conformational searches and for evaluating vibrational contributions to effective structures. Two sets of homochiral (PO)3 rotational transitions were assigned and the associated conformers identified with theoretical support. One set of heterochiral (PO)3 transitions was assigned, but no structures generated by one of the latest, advanced conformational search codes could account for them. With the aid of a Python program, the carbon atom backbone and then the heterochiral (PO)3 structure were generated using 13C isotopic data. Excellent agreement between theoretical and experimental rotational constants and relative dipole moment components of all three conformers was achieved, especially after applying vibrational corrections to the rotational constants.