Minimum Moment Research Articles

SAR Image Registration Based on ROEWA-Blocks and Multiscale Circle Descriptor

Given the imaging characteristics of synthetic aperture radar (SAR) images and the inherent speckle noise in them, scale-invariant feature transform based algorithms are unable to perform satisfactorily. To improve registration efficiency between SAR images, we propose a robust and efficient registration method with three main contributions. First, considering sudden dark patches appearing in SAR images, we propose the ratio of exponentially weighted average blocks to suppress the sudden dark patches and better adapt to different test images. This new operator called blocks of the ratio of exponentially weighted averages (ROEWA-B) divides the processing windows of ROEWA into blocks, which can not only reduce speckle noise but also retain more edge details compared to ROEWA when sudden dark patches appear. Second, for outlier removal, we present an approach using the minimum moment map to remove erroneous keypoints. Finally, based on the gradient location orientation histogram descriptor, we propose a novel multiscale circle descriptor, which combines scale change information to give weights to feature points at different scales. Experimental results for various thresholds and evaluations demonstrate the advantage and robustness of our method in registration.

Estimation of mechanical parameters for orthodontic retraction loops using finite element analysis

Abstract Forces and moments are the main parameters deciding the safety of many of the engineering as well as biomaterials. Since every material has certain yield or ultimate strength, it is always desirable to work in the safe limits to maintain the integrity of the systems. In the present analysis, five standard loops used in the orthodontic applications (T-Loop, Vertical Loop, Opus70, Mushroom and Helix) were analysed using finite element analysis for a fixed horizontal length of 14 mm and a vertical height of 10 mm. Analysis is carried out using 3D beam elements with an element size of 0.25 mm as the accuracy of finite elements are mainly based on element size. For all the analysis, the load deflection rate, vertical force generation and moment values are recorded with carried out in the nonlinear domain to capture the results better. The results shows that minimum force and moment development when the loop is positioned at centre. It is positioned near any bracket, maximum forces and moments are create near the activation bracket. Higher the elastic modulus, the wire is inducing higher moments and forces which are key to the stability of the orthodontic structure. Finite element analysis is effectively used to estimate the load deflection rate, force and moment generation based on different types of loops, positions and materials.

Segmentation of the Eastern Reelfoot Rift Margin: Reinterpretation of the Northeastern Reelfoot Rift Fault Geometry and Seismic Potential

Abstract The eastern Reelfoot rift margin (ERRM) poses a significant seismic hazard to the city of Memphis, Tennessee, and may be capable of generating moment magnitude 7 earthquakes. The goal of this study is to refine the fault structure and geometry of the ERRM, to improve understanding of the associated seismic hazard. We apply multiple filters (e.g., reduction-to-pole and horizontal-gradient) to aeromagnetic intensity data, to visualize the magnetic signature of ERRM basement rocks. To remove ambiguity in our fault interpretations from the magnetic data, we restrict our interpretations to magnetic gradients that correspond to geologic and geophysical evidence of faulting and rank faults on a confidence scheme. From near Covington, Tennessee, to Dyersburg, Tennessee, we interpret the ERRM to be segmented into nine intersecting faults that trend northeast, north-northeast, and north-northwest (two high confidence, four intermediate confidence, and three low confidence). We calculate the moment magnitude potential of each fault based on the estimated fault length. The minimum moment magnitude potential is 6.0, and the maximum is 7.0.

Numerical Study of the Use of Tyre-Derived-Aggregate (TDA) as the Backfill Above Flexible PVC Pipeline

Tyre Derived Aggregates (TDA), produced by shredding scrap car tyres, show many interesting features, such as: durability, low bulk density, thermal insulation, good drainage properties or ability to damp vibrations, which makes them a useful material for civil engineering. One of the possible applications is the partial filling of excavations with TDA during the construction of underground pipelines in order to decrease the load applied on the pipe. The article presents results of a multivariate numerical study of 2D FEM models of a flexible PVC pipe - soil system, in which the presence of a mixture of sand and TDA (tyre chips - 40% by weight) (STCh) in the backfill was simulated. The models differed in the thickness of the STCh layer (t = 0 – 0.9 m) and inclination of the excavation walls (a trench with vertical walls or open excavations with 3:1 and 1:1 slopes). The main goal of the numerical analyses, performed by means of the Z_Soil.PC program, were to investigate the effect of the presence of the softer STCh layer in the backfill zone on the pipe deformation (relative deflection δ/D) and internal forces in the pipe wall. The soil was simulated with the use of either the Hardening Soil Small (HSS) or Coulomb-Mohr (CM) constitutive model with the parameters’ values estimated based on results of laboratory tests (published by researchers from Wollongong University). The PVC pipe was modelled as linear elastic. The results of the analyses show that, due to enhanced arching, STCh layer of the optimum thickness t = 0.55 m can effectively reduce δ/D when used in the backfill of the trench. It can also decrease the difference between the maximum and minimum bending moment in the pipe wall, leading to less ovalization of the pipe cross-section. This positive effect diminishes if the width of excavation is larger, as the model is gradually transforming towards the positive projecting conduit type. The CM model gives underestimated values of the pipe deformation and internal forces. Though, in the case of lack of all the HSS parameters’ values, it is better to use the CM model with E = E 50 than E = E ur as it gives a better approximation of pipe behaviour.

The nature of the Sulfur-Metallic bonds (Metal = Ni, Pd and Pt) in doped gold nanoclusters: A density functional approach

“Atomically precise gold nanoparticles” that constitute single guest atom doped gold cores besides being protected by ligands, have drawn much attention in the fields of biology, chemistry and physics. To investigate the foundation of organic-metallic interface, metallic alloy- H2S complexes are used to model the core-ligand interactions. In this work, simulation of platinum group doped gold dimers and triangular trimers bonded to H2S, are investigated. To simulate experimental results, features including bond lengths, vibrational frequencies and binding energies were calculated for the dimers of platinum group metals and gold, via DFT. The Au-M dimers have minimum magnetic dipole moments compared to the dimers of two platinum group metals. Among the three platinum group atoms simulated, the relativistic effect prevents Pd from being tightly bonded to other metallic atoms. The “donor-acceptor” model is put forward for the complexes of H2S molecules and dimer/trimers, to explain the interaction of sulfur-metal bonds. The possibility of neighboring metallic atoms affecting the acceptor, Au or platinum group metallic atoms is distinct. A neighboring acceptor may improve the S-M interaction such as S-Ni bond while a neighboring weak donor may reduce the S-M interactions such as S-Pd/Pt bonds. With the isosurface plot of densities of electrons/holes at binding, one can identify that such an interaction involves both electrostatic and covalent features. The complexes having H2S as ligand and cores of the real gold clusters verified the reliability of the donor-acceptor model qualitatively.

Cyclical Changes in the Extraeclipse Brightness and the Period of W UMa-TYPE Close Binary System AM Leo

The results of 14-year photometric monitoring of the contact close binary system (CBS) W UMa-type AM Leo are presented. Low-amplitude cyclic variations in brightness with a period of $$7.6 \pm 0.3$$ years, not associated with the phenomena of eclipses and tidal deformations of the components, as well as low-amplitude cyclic variations of the CBS period with practically the same value of the oscillation period, were found. It is concluded that the mechanism generating such oscillations may be the process of changing the magnetic field of the convective shells of the components. Based on the detected decrease in the depths of both minima of the light curves and the change in their relative values, it was concluded that the system is currently transiting from the W-subtype class to the A-subtype class. The values of seven new values of the moments of minima are given.

People after gluteal tendon repair have gait characteristics which are similar to those of a healthy cohort

BackgroundGluteal-tendon repair is reported to be effective for relieving pain and improving function in patients with gluteal-tendon tears. However, post-operative three-dimensional gait analysis has never been conducted in gluteal-tendon repair patients. Thus, our primary aim was to investigate how biomechanical gait parameters differ between age- and sex-matched participants with and without gluteal-tendon repair. MethodsVicon motion analysis technology was used to measure gait characteristics of 25 gluteal-tendon repair participants and 29 matched healthy comparison group participants. A generalised linear multivariate model was used to compare external hip-adduction moment, range of movement in hip adduction and internal rotation, pelvic obliquity, trunk lean, stride length and velocity of both cohorts throughout stance. FindingsThere were no differences between the groups in external hip adduction moment, pelvic obliquity and range of movement in hip adduction and internal rotation. Gluteal-tendon repair participants had a shorter stride length (P = 0.031) and reduced walking velocity (P = 0.015). Ipsilateral trunk lean was reduced in gluteal-tendon repair participants at the first-peak external hip-adduction moment (P = 0.016), mid-stance minimum external hip-adduction moment (P = 0.029) and second-peak external hip-adduction moment (P = 0.006). InterpretationThere were no differences between the gluteal-tendon repair and comparison groups for external hip-adduction moment and pelvic obliquity. This suggests that gluteal-tendon repair may restore hip control in stance. Slower walking speed, reduced stride length and decreased ipsilateral trunk lean may reflect persistence of pre-operatively developed gait adaptations. Future studies of gait biomechanics before and after gluteal-tendon repair would be needed to substantiate this theory.

A New Feature Descriptor for Multimodal Image Registration Using Phase Congruency.

Images captured by different sensors with different spectral bands cause non-linear intensity changes between image pairs. Classic feature descriptors cannot handle this problem and are prone to yielding unsatisfactory results. Inspired by the illumination and contrast invariant properties of phase congruency, here, we propose a new descriptor to tackle this problem. The proposed descriptor generation mainly involves three steps. (1) Images are convolved with a bank of log-Gabor filters with different scales and orientations. (2) A window of fixed size is selected and divided into several blocks for each keypoint, and an oriented magnitude histogram and the orientation of the minimum moment of a phase congruency-based histogram are calculated in each block. (3) These two histograms are normalized respectively and concatenated to form the proposed descriptor. Performance evaluation experiments on three datasets were carried out to validate the superiority of the proposed method. Experimental results indicated that the proposed descriptor outperformed most of the classic and state-of-art descriptors in terms of precision and recall within an acceptable computational time.

Minimum bending moment distribution in skeletal structures

The research presents skeletal steel structures analysis method according to BIM-based feasibility study tool proposed by Jaakko Haapio. Also in this paper an optimal joint stiffness determination formulae that was obtained. A multi-storey frame with different joint types was analyzed. The frame was modelled with different beams, columns and joints of different finite stiffness including the optimal one (hypothetically the most cost-effective) calculated by the formula. Five models of the frame were compared basing on cost criterion (joint fabrication and overall material costs) with each other and the one with optimal joint stiffness. The method and formula tested is applicable to frames with any number of spans and storeys.

Geotechnical investigations of an earthquake that triggered disastrous landslides in eastern Canada about 1020\u2009cal BP

Geotechnical studies are carried out to investigate the location and magnitude of a prehistoric earthquake in eastern Canada. Previous studies identified 12 sensitive clay landslides of about 1020 cal BP in the Ottawa-Gatineau region, including one of the most disastrous slope failures in eastern Canada. The landslides were hypothesized to have been triggered by an earthquake. In the current study, three of those landslides are investigated to understand their failure mechanisms. The study sites form a triangle of lateral distances of about 38, 38 and 35 km. Micro-seismic surveys, cone penetrometer tests, vane shear tests, soil sampling and laboratory testing are conducted to collect geotechnical data. Slope stability models are constructed to calculate threshold ground accelerations required to trigger the landslides. The ground accelerations are used with Ground-Motion Prediction Equations to triangulate the earthquake. The results indicate an earthquake of a minimum moment magnitude of 5.9 near Eardley, Quebec.

Numerical Simulation of Wave Interaction with Payloads of Different Postures Using OpenFOAM

A three-dimensional numerical wave tank (NWT) is established with Open Source Field Operation and Manipulation (OpenFOAM) software and waves2foam to investigate wave interaction with payloads with different postures in the process of offshore lifting or lowering. Numerical results of regular wave interaction with a vertically suspending cylinder are presented first for validation by comparison with the published data. A series of simulation experiments are carried out, and the forces and the moments exerted by the regular waves on a fixed suspending cylinder payload and a fixed suspending cuboid payload with different postures are presented. It can be concluded from the results that the rotating rectangular payload (cuboid and cylinder) suffers a drastically changed moment when it is initially vertically placed, and the projection area of payload vertical to the force affects the corresponding force. The simulation results also show how the forces and the moments change with different posture angles. With some certain posture, the suspending payload suffers minimum forces and moments. Parametric study for the cuboid payload is done in the case of normal incidence. The influence of the payload’s size and wave parameters on forces and moments are analyzed. All of the numerical simulation results and conclusions provide the fundamentals for further research and safe control of offshore lifting or lowering.

Development of double-stage yielding coupling beam damper

This paper proposes a new type of steel double-stage yielding coupling beam damper (DYCBD), which consists of a shear component and two bending components. Two types of components have different yield displacements. Both DYCBD components are steel dampers with I-shaped cross section. The shear component first yield corresponding to a moderate earthquake, while the bending components do not yield until a major earthquake occurs, which results in the double-stage yielding behavior of the DYCBD. The constitutive model and design method of DYCBD were proposed. Three specimens with different geometries were designed and conducted shear hysteretic tests. The experimental results revealed that specimens exhibited stable hysteretic behavior and double-stage yielding effect. Finite element models (FEMs) were established to explain the deviations between the calculation results and the experimental results, and parameter analysis were carried out. The components stiffness ratio of 0.52 is suggested to achieve the most obvious double-stage yielding effect. A minimum moment of inertia ratio between bending components' flange to total section of 0.83 is also suggested to decrease the deviations between the proposed design method and FEM as a result of parametric study.

Systematic exploration of magnetic mechanism of La3Co29Si4B10 by first principles calculation

Rare earth transition metal compounds with intrinsic and high-performance magnetic behaviors have been attractively research topic as a promising permanent magnets material. In particularly, La3Co29Si4B10 is one of typically rare earth ferromagnetism materials with large magnetic moment and high transition temperature. In order to investigate the magnetic origin of sublattice and guide the design of permanent magnet materials with high magnetic moment and high magnetic crystalline anisotropy, we adopt first principles calculations method to investigate the magnetic mechanism of La3Co29Si4B10 combine local coordination environment with density of states. The results show that the magnetic moment mainly comes from the Co atom. According to the different local symmetry and atom hybridization, the Co atoms at different crystal positions can be divided into high spin state with maximum local magnetic moment at 2c position, low spin state with minimum magnetic moment at 8i1 position and medium spin state corresponding moderate magnetic moment size at other positions. Furthermore, the strain-stress of La3Co29Si4B10 will increase the total magnetic moment. Spin orbital coupling calculation indicate that the easy magnetization direction of La3Co29Si4B10 is along in plane with magnetic crystalline anisotropy energy of 0.68 meV/unit cell, which agreement with experimental. Our calculations lay a theoretical foundation for further experimental design of high-performance permanent magnet materials.

Analysis of the dynamic characteristics of salinity intrusion in Shiziyang

This paper studies the law of the salt water intrusion of Shiziyang based on the salinity measurement data in the dry season of Shiziyang, and we can summarize the following characteristics: the salty fresh water in the upstream of Shiziyang is fully mixed, the downstream saltwater belongs to the partial mixed, saltwater is layered obviously during the neap tide, and the mixing effect is the best during the moderate tide. During the neap tide, downstream salt water is layered significantly, and hyperhaline invades rapidly from the bottom, fresh water discharges from the surface; during the moderate tide, salt fresh water mixes well, the salt boundary is the farthest from the estuary at the minimum flood moment; after the spring tide, salt water mixing gradually weakens, forming a salt water wedge.

Proposed Constitutive Law of Uniaxial Compression for Concrete under Deterioration Effects.

In order to study the ductile deformation characteristics and failure process of plain concrete under uniaxial compression, this paper proposes a new constitutive model. The new model was used to fit and analyze the constitutive curve of concrete under uniaxial compressive under various degradation forms and was compared with the traditional constitutive models. Finally, the new model was used to quantitatively analyze and predict the stress–strain curve of concrete in different degradation periods of a set of freeze–thaw measured data. The results show that, compared with the traditional constitutive model, the new model is simple in form and has few parameters, and the numerical value of the parameter can reflect the ductile deformation capacity of concrete. The fitting curve of the new model has the highest fitting degree with the measured stress–strain curve of concrete, and the goodness of fit (R2) is also the largest. The new model is suitable for fitting the stress–strain curve of concrete under uniaxial compression under various deteriorating forms, and the degree of fit between the constitutive prediction curve and the measured curve is high. It can be seen from the fitting results of the new model parameters that the ductile deformation capacity of concrete decreases first and then increases slightly, which is inconsistent with the law of gradual deterioration of strength. There is a minimum moment of ductility deformation capacity of concrete (MDC). The MDC of O-C40 concrete is about 114 freeze–thaw cycles, and the MDC of O-C50 concrete is about 116 freeze–thaw cycles; the degree of fit between the constitutive prediction curve and the measured curve is high. We hope that the improvement mentioned offers valid reference to the study of ductile deformation characteristics and failure process of compressed concrete under different deterioration forms.

Earthquake Source Parameters in Southwestern China and Their Rheological Implications

AbstractEarthquake depth distribution provides key information on rheological behavior of the crust, which usually shows a brittle–ductile transition at a depth of about 10 km. In this study, we use the generalized cut-and-paste method to obtain source parameters of 571 earthquakes in the Sichuan–Yunnan region of China between 2009 and 2017. We were able to successfully determine focal mechanisms, moment magnitudes, and centroid depths of 536 earthquakes with a minimum moment magnitude of 3.2. Our moment magnitudes and centroid depths are systematically smaller than the magnitudes (Ms and mb) and hypocenter depths from the China Earthquake Network Center and International Seismological Centre catalogs for M≥4.0 earthquakes. The earthquake depths in the Sichuan–Yunnan region are mostly in a 5–9 km range, with an average at 7.6 km. About 23% earthquakes have centroid depths <5 km and are concentrated in the southern Sichuan basin. Only very few earthquakes are deeper than 19 km. Compared with the earthquake depth distribution in southern California, the Sichuan–Yunnan region has many shallower earthquakes. The depth distribution suggests that the brittle–ductile transition in the Sichuan–Yunnan region is shallower than the transition beneath southern California, which is probably due to the existence of newborn faults in the Sichuan–Yunnan region.

СРАВНИТЕЛЬНЫЙ АНАЛИЗ РАЗЛИЧНЫХ СИСТЕМ УПРАВЛЕНИЯ РОТОРНОЙ СИСТЕМОЙ

This article provides a comparative analysis of various control systems for a rotor system on fluid friction bearings. The control was carried out on the basis of the criterion of the minimum friction moment, the controlled parameter was the bearing stiffness coefficients. The following control methods were compared in terms of friction torque and rotor eccentricity: STATIC, PID, DQN, DDPG, Q-Learning and SARSA. The control systems were guided by the following observed parameters: the values of coordinates and velocities along the x, y axes, as well as the frictional moment and relative eccentricity.

Building some bridges among various experimental designs

Designing their experiments is the significant problem that experimenters face. Maximin distance designs, supersaturated designs, minimum aberration designs, uniform designs, minimum moment designs and orthogonal arrays are arguably the most exceedingly used designs for many real-life experiments. From different perspectives, several criteria have been proposed for constructing these designs for investigating quantitative or qualitative factors. Each of those criteria has its pros and cons and thus an optimal criterion does not exist, which may confuse investigators searching for a suitable criterion for their experiment. Some logical questions are now arising, such as are these designs consistent, can an optimal design via a specific criterion perform well based on another criterion and can an optimal design for screening quantitative factors be optimal for qualitative factors? Through theoretical justifications, this paper tries to answer these interesting questions by building some bridges among these designs. Some conditions under which these designs agree with each other are discussed. These bridges can be used to select a suitable criterion for studying some hard problems effectively, such as detection of (combinatorial/geometrical) non-isomorphism among designs and construction of optimal designs. Benchmarks for reducing the computational complexity are given.

The Second Waldmeier Rule and the Form of the 11-Year Cycle

It is known that the form of the 11-year solar-activity cycle can be approximately described by its amplitude A and the arrangement of three characteristic moments: the moment of the minimum (Tmin), maximum (Tmax), and the subsequent minimum (Tmin2). According to the classical Waldmeier rule, there is an anticorrelation between the maximum activity value (amplitude) of cycle A and the duration of its ascending branch Tmax – Tmin, while the correlation between A and the length of the downward branch of the cycle Tmin2 – Tmax is much lower. Following Waldmeier, the moment TV can be entered near the end of the downward branch of the cycle, in which the activity falls within a certain (low) specified level V. The relationship between the length of the corresponding phase of cycle TV – Tmax and the amplitude of this cycle is quite strong. We demonstrate that this connection, which can be called the “second Waldmeier rule,” agrees well with the fact that the downward branch of the cycle has a universal appearance. Thus, one parameter, its value is at the maximum, is enough for an approximate qualitative description of the form of a single 11-year cycle that takes into account the two Waldmeier rules.

Calcaneal elongation and bone strength in leaping galagids.

Small-bodied vertical clinging and leaping primates have elongated calcanei which enhance leap performance by optimizing leap velocity, distance, and acceleration, but at the expense of experiencing relatively large forces during takeoff and landing. This study tests the hypothesis that the elongated calcaneus of leaping galagids is adapted to resist larger and more stereotyped bending loads compared to more quadrupedal galagids. The calcanei of 14 individuals of Otolemur and 14 individuals of Galago (three species of each genus) were μCT scanned. Calcaneal cross-sectional properties (maximum and minimum second moments of area and polar section modulus) were obtained from a slice representing the 50% position of bone segment length and dimensionless ratios were created for each variable using calcaneal cuboid facet area as a proxy for body mass. There were no significant differences in size-adjusted bending strength between Galago and Otolemur. Galago exhibited more elliptically shaped calcaneal cross sections, however, suggesting that its calcanei are more adapted to stereotyped loading regimes than those of Otolemur. The results suggest that the calcaneus of specialized leapers is adapted to more stereotyped loading patterns. The lack of predicted bone strength differences between Galago and Otolemur may be related to body size differences between these taxa, or it may indicate that loads encountered by Galago during naturalistic leaping are not reflected in the available experimental force data.