Bracket Structure Research Articles

Stochastic Geometric Models with Non-stationary Spatial Correlations in Lagrangian Fluid Flows

Inspired by spatiotemporal observations from satellites of the trajectories of objects drifting near the surface of the ocean in the National Oceanic and Atmospheric Administration’s “Global Drifter Program”, this paper develops data-driven stochastic models of geophysical fluid dynamics (GFD) with non-stationary spatial correlations representing the dynamical behaviour of oceanic currents. Three models are considered. Model 1 from Holm (Proc R Soc A 471:20140963, 2015) is reviewed, in which the spatial correlations are time independent. Two new models, called Model 2 and Model 3, introduce two different symmetry breaking mechanisms by which the spatial correlations may be advected by the flow. These models are derived using reduction by symmetry of stochastic variational principles, leading to stochastic Hamiltonian systems, whose momentum maps, conservation laws and Lie–Poisson bracket structures are used in developing the new stochastic Hamiltonian models of GFD.

Research and analysis on response characteristics of bracket-line coupling system under wind load

In this paper, a three-dimensional finite element model of bracket-line coupling system is established based on ANSYS software. Using the wind velocity time series which is generated by MATLAB as a power input, by comparing and analyzing the influence of different wind speeds and different wind attack angles, it is found that when 0 degree wind acts on the structure, wires have a certain damping effect in the bracket-line coupling system and at the same wind speed, the 90 degree direction is the most unfavorable wind direction for the whole structure according to the three kinds of angle wind calculated at present. In the bracket-line coupling system, the bracket structure is more sensitive to the increase of wind speed while the conductors are more sensitive to the change of wind attack angle.

De Donder–Weyl Hamiltonian formalism of MacDowell–Mansouri gravity

We analyse the behaviour of the MacDowell–Mansouri action with internal symmetry group under the De Donder–Weyl Hamiltonian formulation. The field equations, known in this formalism as the De Donder–Weyl equations, are obtained by means of the graded Poisson–Gerstenhaber bracket structure present within the De Donder–Weyl formulation. The decomposition of the internal algebra allows the symmetry breaking , which reduces the original action to the Palatini action without the topological term. We demonstrate that, in contrast to the Lagrangian approach, this symmetry breaking can be performed indistinctly in the polysymplectic formalism either before or after the variation of the De Donder–Weyl Hamiltonian has been done, recovering Einstein’s equations via the Poisson–Gerstenhaber bracket.

Classical and quantum stochastic models of resistive and memristive circuits

The purpose of this paper is to examine stochastic Markovian models for circuits in phase space for which the drift term is equivalent to the standard circuit equations. In particular, we include dissipative components corresponding to both a resistor and a memristor in series. We obtain a dilation of the problem which is canonical in the sense that the underlying Poisson bracket structure is preserved under the stochastic flow. We do this first of all for standard Wiener noise but also treat the problem using a new concept of symplectic noise, where the Poisson structure is extended to the noise as well as the circuit variables, and in particular where we have canonically conjugate noises. Finally, we construct a dilation which describes the quantum mechanical analogue.

From Koopman\u2013von Neumann theory to quantum theory

Koopman and von Neumann (KvN) extended the Liouville equation by introducing a phase space function S^{(K)}(q,p,t) whose physical meaning is unknown. We show that a different S(q, p, t), with well-defined physical meaning, may be introduced without destroying the attractive “quantum-like” mathematical features of the KvN theory. This new S(q, p, t) is the classical action expressed in phase space coordinates. It defines a mapping between observables and operators which preserves the Lie bracket structure. The new evolution equation reduces to Schrödinger’s equation if functions on phase space are reduced to functions on configuration space. This new kind of “quantization” does not only establish a correspondence between observables and operators, but provides in addition a derivation of quantum operators and evolution equations from corresponding classical entities. It is performed by replacing frac{partial }{partial p} by 0 and p by frac{hbar }{imath } frac{partial }{partial q}, thus providing an explanation for the common quantization rules.

The η–inverted ℝ–motivic sphere

We use an Adams spectral sequence to calculate the R-motivic stable homotopy groups after inverting eta. The first step is to apply a Bockstein spectral sequence in order to obtain h_1-inverted R-motivic Ext groups, which serve as the input to the eta-inverted R-motivic Adams spectral sequence. The second step is to analyze Adams differentials. The final answer is that the Milnor-Witt (4k-1)-stem has order 2^{u+1}, where u is the 2-adic valuation of 4k. This answer is reminiscent of the classical image of J. We also explore some of the Toda bracket structure of the eta-inverted R-motivic stable homotopy groups.

Freshwater mussels in an urban watershed: Impacts of anthropogenic inputs and habitat alterations on populations

The substantial increase in urbanization worldwide has resulted in higher emissions of wastewater to riverine systems near urban centers, which often impairs aquatic populations and communities. This study examined the effect of urbanization on freshwater mussel populations, including Species at Risk in two rivers receiving wastewater. The influence of anthropogenic activities was assessed in a watershed in the Laurentian Great Lakes basin, one that historically supported one of the most diverse mussel faunas in Canada. In the Grand River (ON), four sites along a 60km reach spanning from an upstream reference site to an urban-impacted downstream area were examined. In the Speed River, mussel populations at six sites along a 10km reach, selected to bracket specific anthropogenic inputs and structures were assessed. A semi-quantitative visual search method revealed that catch per unit effort in the Grand River declined by >60% from the upstream reference site to the area downstream of an urban center. The size (length) frequency distribution of the most abundant species, Lasmigona costata, was significantly (p≤0.008) different upstream of the majority of urban inputs (45–130mm) compared to downstream of the cities (85–115mm). In the Speed River, impoundments and wastewater treatment plants (WWTP) reduced both the diversity and catch per effort. Most striking were 84 and 95% changes in the number of mussels found on either side of two impoundments, and a 98% drop in mussels immediately downstream of a WWTP outfall. These population level effects of decreased abundance and underrepresentation of smaller mussels downstream of the urban area correspond to previously documented impacts at the biochemical and whole organism level of biological organization in wild mussels at this location. Our results demonstrate that poor water quality and physical barriers in urban environments continue to impair susceptible populations and communities of aquatic animals.

New approach to nonrelativistic ideal magnetohydrodynamics

We provide a novel action principle for nonrelativistic ideal magnetohydrodynamics in the Eulerian scheme exploiting a Clebsch-type parametrisation. Both Lagrangian and Hamiltonian formulations have been considered. Within the Hamiltonian framework, two complementary approaches have been discussed using Dirac's constraint analysis. In one case the Hamiltonian is canonical involving only physical variables but the brackets have a noncanonical structure, while the other retains the canonical structure of brackets by enlarging the phase space. The special case of incompressible magnetohydrodynamics is also considered where, again, both the approaches are discussed in the Hamiltonian framework. The conservation of the stress tensor reveals interesting aspects of the theory.

Strength Analysis and Process Simulation of Subway Contact Rail Support Bracket of Composite Materials

An application of composites for construction of subway brackets is a very effective approach to extend their lifetime. However, this approach involves the necessity to prevent process-induced distortions of the bracket due to thermal deformation and chemical shrinkage. At present study, a process simulation has been carried out to support the design of the production tooling. The simulation was based on the application of viscoelastic model for the resin. Simulation results were verified by comparison with results of manufacturing experiments. To optimize the bracket structure the strength analysis was carried out as well.

Luggage Impact and Structure Optimization for Rear Seat Frame of Automobile

It is essential that the back seat of a vehicle has to be designed safely and reliably and at the same time meet the ECE R17, as to reduce the back seat casualties in accidents caused by luggage impact. This paper studies a sample of back seat frame and establishes its precise CAD model. It adopts nonlinear finite element methodology to simulate the object under the ECE R17. The results reflect two problems. One is the force absorption and anti-deformation of the split seat frame is too weak; the other is the fixed connections linking the frame to the holder is not tight enough causing easy fall-off if being shocked. The test and simulation results suggest the following alterations, respectively to substitute the previous split seat frame for a one-piece seat frame as to improve the overall stiffness and anti-deformation, to adopt one-piece structure on the center support bracket and increases its thickness by 0.5mm, keep the remaining mounting bracket structure unchanged. The analyses of the improved program demonstrate its superior anti-deformation under the regulations.

농촌 한옥 표준설계도 연구

This research aimed to suggest a standard design that reflects Hanok design tendency, and present a selective design that can fulfill a building owner's intention beyond the simple function of building permit or report. In addition, this research attempted to become a standard by establishing a criterion in calculating the measurements of section design or primary framework members, in order to be a guideline for designing Hanok in different sizes and forms. The results are as follows. The building area of Hanok standard design was set to be below <TEX>$85m^2$</TEX>, with a straight type of <TEX>$83.16m^2$</TEX> and an L-shape of <TEX>$84.24m^2$</TEX>. By dividing the plane into a straight type and L-shape, two straight types were suggested: 'general type' and 'large living room type.' The upper floor space, along with the main room and small room, was proposed as an option to be changed into a room where an underfloor heating is installed depending on the building owner's intention. In addition, a criterion for side design and calculation of framework measurements was suggested and applied, while a five-girder design without high pillars was suggested for material-assembling structure. Two types of pillars-circumference and square cylinder-were proposed for the building owner to choose from, and a pointed beam house and ikgong(orthogonally-projected bracket) house were suggested for pojak bracket structure so either of them could be chosen according to the building owner's taste and economic condition. Finally, the sectional size of main materials were divided according to the form of pojak bracket structure to be proposed.

A sequential sampling strategy to improve the global fidelity of metamodels in multi-level system design

In engineering design, complex systems that involve a multitude of decision variables and parameters are often decomposed into several submodels (also called subsystems and/or components) with a hierarchical (multi-level) manner to manage complexity. Metamodeling techniques are widely used to replace the original time-consuming computer simulation models to further reduce computational burden in multi-level system performance analysis and design optimization. However, due to the limited samples from simulation models, metamodels may contain metamodeling uncertainties at un-sampled sites. Such metamodeling uncertainties arising from metamodels across the entire hierarchy will propagate from the lower to upper levels and eventually impact the top-level response of interest. With the aim of improving the global fidelity of metamodels for multi-level system performance analysis and design optimization, a new sequential sampling strategy is proposed in this paper. The proposed method contains two basic elements: (1) quantifying metamodeling uncertainty propagated from the lower-level metamodels to the top-level response of interest and (2) seeking a new sample site at which the global fidelity of the multi-level system model can be maximally improved. As exemplified by the two numerical examples and a multi-scale bracket structure example, with the same amount of samples from computer simulation models, the new sequential sampling strategy is superior to existing sequential sampling strategies in terms of improving the global fidelity of the metamodels of multi-level systems.

The Effects of In-Office Reconditioning on the Slot Dimensions and Static Frictional Resistance of Stainless Steel Brackets.

Orthodontists are commonly faced with the decision of what to do with loose brackets, and with inaccurately located brackets that need repositioning during treatment. One solution is to recycle the brackets. The potential effects of reconditioning a bracket are dependent upon many factors which may result in physical changes like alteration in slot tolerance, which may influence sliding mechanics by affecting frictional resistance. To study and compare the dimensional changes in the bracket slot width and depth in reconditioned brackets from unused brackets under scanning electronic microscope and to study and compare any consequent effects on the static frictional resistance of stainless steel brackets after reconditioning and in unused brackets. Dentarum manufactured 90 stainless steel central incisors edgewise brackets of size 0.22 X 0.030″ inch and 0° tip and 0°angulation were taken. 60 samples for measuring frictional resistance and 30 samples for measuring slot dimensions. Ortho organizers manufactured stainless steel arch wires 0.019 X 0.025″ straight lengths 60 in number were considered for measuring static frictional resistance. The mean slot width and depth of new brackets were 0.0251″ and 0.0471″, which exceeded the manufacturers reported nominal size of 0.022″ X 0.030″, by 0.003″ and 0.017″. The reconditioned brackets demonstrated a further increase in mean slot width and depth to 0.028″ and 0.0518″ that is by 0.0035″ and 0.0047″ which is statistically significant (p=0.001, 0.002). The mean static frictional forces of the reconditioned brackets was nearly similar to that of new brackets that is 0.3167N for reconditioned brackets and 0.2613 N for new brackets. Although the reconditioning process results in physical changes to bracket structure this does not appear to result in significant effect on ex-vivo static frictional resistance.

Retraction Note: Bracket Structure Stress Analysis of Rotating Construction Cable-stayed Bridge of Thousands of Tons

The Publisher and Editor have retracted this article [1] in accordance with good ethical practices. After thorough investigations we believe that the peer review process was compromised. The article was published online on 31-12-2014.

Topology optimization of ship bracket structures

Ship structures are conventionally connected by typical triangular brackets, which could cause stress concentration at the connections between ship structures and the bracket. In this paper, a new design method of brackets is proposed, where sub-modeling technologies are employed to conduct the refinement stress analysis of the brackets, while the topology optimization is applied to improve the stress concentration. In this study, the material distribution of the bracket is chosen as the design variable, and the stress of the girder close to the bracket is considered as the constraints, while the stress of the connections between the bracket and the girders is considered as the objective. A new type of bracket structure is proposed once the proper engineering treatment is applied to the topology optimization results of the bracket. The optimized bracket's stress concentration is seen to improve greatly. In brief, the presented method may provide reference for the strength analysis and optimum design of similar structures.

Ergodic and mixing properties of the Boussinesq equations with a degenerate random forcing

We establish the existence, uniqueness and attraction properties of an ergodic invariant measure for the Boussinesq equations in the presence of a degenerate stochastic forcing acting only in the temperature equation and only at the largest spatial scales. The central challenge is to establish time asymptotic smoothing properties of the Markovian dynamics corresponding to this system. Towards this aim we encounter a Lie bracket structure in the associated vector fields with a complicated dependence on solutions. This leads us to develop a novel Hörmander-type condition for infinite-dimensional systems. Demonstrating the sufficiency of this condition requires new techniques for the spectral analysis of the Malliavin covariance matrix.

Strength calculation considering structural stiffness coupling of shaft bracket

In this paper, the current specification concerning strength computing theory of shaft bracket is analyzed, and it is seen that structural stiffness coupling is not considered in this theory. In the view of the shaft bracket structural and mechanical features, the reaction force model of shaft brackets considering structural stiffness coupling is established, and the calculation formulas for the internal forces of the shaft brackets are derived, and the parameters of the generalized stiffness ratio describing the structure stiffness coupling effects is defined. Taking shaft brackets of a certain boat as an example, the quantitative calculation on FEM simulation, the computing theory presented in this paper, and the conventional computing theory without considering structural stiffness coupling are applied, respectively. In addition, the computing method on torsional rigidity of shaft brackets is also put forward. The results show that the computing theory of this paper agrees well with the FEM simulation, while the conventional theory deviates far from the FEM simulation performance. Moreover, the conventional theory yields larger result, which further worsens with the enlargement of the generalized stiffness ratio, causing the overly design of the shaft bracket structure strength. In brief, the computing theory proposed in this paper serves as great guidance to the optimization in the strength design of the shaft bracket structure.

Bracket Structure Stress Analysis of Rotating Construction Cable-stayed Bridge of Thousands of Tons

Based on the rotating construction cable-stayed bridge of thousands of tons, dynamic simulation of bracket structure in rotating construction was analyzed with ANSYS finite element software. The result shows that with the common influence of gravity, traction and prestress, the overall bracket structure presents compressive stress mainly of stress state. Traction force of the impact is not big, considering alone effect of traction, the whole stress level of bracket structure is very low. Under the effect of prestress, bracket structure presents a huge pressure stress in horizontal direction to prevent accidental tilt in the rotating process, and parts of the steel bundle should be removed after the rotation.

Irreversible dynamics, Onsager-Casimir symmetry, and an application to turbulence.

Irreversible contributions to the dynamics of nonequilibrium systems can be formulated in terms of dissipative, or irreversible, brackets. We discuss the structure of such irreversible brackets in view of a degeneracy implied by energy conservation, where we consider different types of symmetries of the bracket corresponding to the Onsager and Casimir symmetries of linear irreversible thermodynamics. Slip and turbulence provide important examples of antisymmetric irreversible brackets and offer guidance for the more general modeling of irreversible dynamics without entropy production. Conversely, turbulence modeling could benefit from elucidating thermodynamic structure. The examples suggest constructing antisymmetric irreversible brackets in terms of completely antisymmetric functions of three indices. Irreversible brackets without well-defined symmetry properties can arise for rare events, causing big configurational changes.

Quantization as a Guide to Ontic Structure

The ontic structural realist stance is motivated by a desire to do philosophical justice to the success of science, whilst withstanding the metaphysical undermining generated by the various species of ontological underdetermination. We are, however, as yet in want of general principles to provide a scaffold for the explicit construction of structural ontologies. Here we will attempt to bridge this gap by utilizing the formal procedure of quantization as a guide to ontic structure of modern physical theory. The example of non-relativistic particle mechanics will be considered and, for that case, it will be shown that a viable candidate for an ontic structural realism framework can be constituted in terms of the combination of a state-space with Poisson bracket structure, and a set of observables, with Lie algebra structure. 1 Introduction2 Formulation Underdetermination and Structural Ontologies3 Quantization and Structural Ontologies4 The Case of Non-relativistic Particle Mechanics 4.1 Formulation underdetermination 4.2 The classical ontology 4.3 Quantum theory and the generalized structural ontology 4.4 Interpretation of results5 Conclusion and Prospects