Edge enhancement of gravity anomalies and gravity gradient tensors using an improved small sub-domain filtering method

In order to enhance geological body boundary visual effects in images and improve interpretation accuracy using gravity and magnetic field data, we propose an improved small sub-domain filtering method to enhance gravity anomalies and gravity gradient tensors. We discuss the effect of Gaussian white noise on the improved small sub-domain filtering method, as well as analyze the effect of window size on geological body edge recognition at different extension directions. Model experiments show that the improved small sub-domain filtering method is less affected by noise, filter window size, and geological body edge direction so it can more accurately depict geological body edges than the conventional small sub-domain filtering method. It also shows that deeply buried body edges can be well delineated through increasing the filter window size. In application, the enhanced gravity anomalies and calculated gravity gradient tensors of the Hulin basin show that the improved small sub-domain filtering can recognize more horizontal fault locations than the conventional method.

Reliability index algorithm of a sub-domain interconnection large communication network

The normalized weighted capacity reliability index of a sub-domain interconnection large scale communication network is defined and a new algorithm to calculate the reliability index is proposed, The proposed algorithm can be performed using logical or algebraic operation by means of computer-aided programming and the correctness of each key step is validated in detail. This paper takes the sub-domain interconnection symmetrical topologi- cal network for a typical example to calculate the network reliability index and verifies the correctness of the proposed algorithm us- ing the real measured statistical data. The real measured results are well in accordance with the results obtained by the proposed algorithm. The result shows that the proposed algorithm is a valid means to estimate the reliability index of a sub-domain intercon- nection large-scale communication network.

Thermal Fatigue Life Estimation and Fracture Mechanics Studies of Multilayered MEMS Structures Using a Sub-Domain Approach

This paper is concerned with the application of a Physics of Failure (PoF) methodology to assessing the reliability of Micro-Electro-Mechanical-System (MEMS) switches. Numerical simulations, based on the finite element method (FEM) using a sub-domain approach, were performed to examine the damage onset (e.g. yielding) due to temperature variations and to simulated the crack propagation different kind of loading conditions and, in particular, thermal fatigue. In this work remeshing techniques were employed in order to understand the evolution of initial flaws due, for instance, to manufacturing processes or originated after thermal fatigue.

Analysis of a Propeller Wake Flow Field Using Viscous Fluid Mechanics

The computational fluid dynamics （CFD） method is used to numerically simulate a propeller wake flow field in open water. A sub-domain hybrid mesh method was adopted in this paper. The computation domain was separated into two sub-domains, in which tetrahedral elements were used in the inner domain to match the complicated geometry of the propeller, while hexahedral elements were used in the outer domain. The mesh was locally refined on the propeller surface and near the wake flow field, and a size function was used to control the growth rate of the grid. Sections at different axial location were used to study the spatial evolution of the propeller wake in the region ranging from the disc to one propeller diameter （D） downstream. The numerical results show that the axial velocity fluctuates along the wake flow; radial velocity, which is closely related to vortices, attenuates strongly. The trailing vortices interact with the tip vortex at the blades＇ trailing edge and then separate. The strength of the vortex shrinks rapidly, and the radius decreases 20% at one diameter downstream.

Algebraic Method‑Based Point‑to‑Point Trajectory Planning of an Under‑Constrained Cable‑Suspended Parallel Robot with Variable Angle and Height Cable Mast

To avoid impacts and vibrations during the processes of acceleration and deceleration while possessing flexible working ways for cable-suspended parallel robots(CSPRs),point-to-point trajectory planning demands an under-constrained cable-suspended parallel robot(UCPR)with variable angle and height cable mast as described in this paper.The end-effector of the UCPR with three cables can achieve three translational degrees of freedom(DOFs).The inverse kinematic and dynamic modeling of the UCPR considering the angle and height of cable mast are completed.The motion trajectory of the end-effector comprising six segments is given.The connection points of the trajectory segments(except for point P3 in the X direction)are devised to have zero instantaneous velocities,which ensure that the acceleration has continuity and the planned acceleration curve achieves smooth transition.The trajectory is respectively planned using three algebraic methods,including fifth degree polynomial,cycloid trajectory,and double-S velocity curve.The results indicate that the trajectory planned by fifth degree polynomial method is much closer to the given trajectory of the end-effector.Numerical simulation and experiments are accomplished for the given trajectory based on fifth degree polynomial planning.At the points where the velocity suddenly changes,the length and tension variation curves of the planned and unplanned three cables are compared and analyzed.The OptiTrack motion capture system is adopted to track the end-effector of the UCPR during the experiment.The effectiveness and feasibility of fifth degree polynomial planning are validated.

Analytical Modeling of Fluid Sloshing in A 2D Rectangular Container with A Bottom-Mounted T-Shaped Baffle

An analytical procedure is presented to evaluate the fluid sloshing characteristics in a two-dimensional(2D)rectangular container with a bottom-mounted T-shaped baffle.The fluid region is divided into several sub-domains with hypothetical interfaces and the velocities and pressures of the fluid on adjacent interfaces should be identical.The separation of variables in conjunction with the superposition principle is employed to formulate the velocity potential of each sub-domain.The Fourier series expansion is used to derive the eigenvalue equation by substituting the velocity potential solutions into the free surface conditions and the continuity conditions on adjacent interfaces.Under the horizontal base excitation,the total velocity potential of fluid is decomposed of the impulsive and perturbed velocity potentials.The orthogonality of the sloshing modes is demonstrated by implementing Gauss formula.The dynamic response equation is established by incorporating the total velocity potential solution into the surface wave equation.Excellent agreements are achieved between the present results and those from the reported literature and finite element code.Numerical results are exhibited to reveal the effect of the baffle parameters and excitation frequency on sloshing characteristics and responses of liquid.

Improved Genetic Optimization Algorithm with Subdomain Model for Multi-objective Optimal Design of SPMSM

For an optimal design of a surface-mounted permanent magnet synchronous motor(SPMSM),many objective functions should be considered.The classical optimization methods,which have been habitually designed based on magnetic circuit law or finite element analysis(FEA),have inaccuracy or calculation time problems when solving the multi-objective problems.To address these problems,the multi-independent-population genetic algorithm(MGA)combined with subdomain(SD)model are proposed to improve the performance of SPMSM such as magnetic field distribution,cost and efficiency.In order to analyze the flux density harmonics accurately,the accurate SD model is first established.Then,the MGA with time-saving SD model are employed to search for solutions which belong to the Pareto optimal set.Finally,for the purpose of validation,the electromagnetic performance of the new design motor are investigated by FEA,comparing with the initial design and conventional GA optimal design to demonstrate the advantage of MGA optimization method.

Nonlinear semi-analytical modeling of liquid sloshing in rectangular container with horizontal baffles

A nonlinear semi-analytical scheme is proposed for investigating the finiteamplitude nonlinear sloshing in a horizontally baffled rectangular liquid container under the seismic excitation.The sub-domain method is developed to analytically derive the modal behaviors of the baffled linear sloshing.The viscosity dissipation effects from the interior liquid and boundary layers are considered.With the introduction of the generalized time-dependent coordinates,the surface wave elevation and velocity potential are represented by a series of linear modal eigenfunctions.The infinite-dimensional modal system of the nonlinear sloshing is formulated based on the Bateman-Luke variational principle,which is further reduced to the finite-dimensional modal system by using the NarimanovMoiseev asymptotic ordering.The base force and overturning moment induced by the nonlinear sloshing are derived as the functions of the generalized time-dependent coordinates.The present results match well with the available analytical,numerical,and experimental results.The paper examines the surface wave elevation,base force,and overturning moment versus the baffle parameters and excitation amplitude in detail.

Study on coupled vibration characteristics of a cylindrical container with multiple elastic annular baffles

The coupled vibration characteristics of multiple elastic annular baffles of the same inner radius in a partially liquid-filled rigid cylindrical container were studied. The liquid domain was divided into several simple sub-domains so that the liquid velocity potential in each liquid sub-domain was of class C 1 with continuous boundary conditions. Based on the superposition principle, the general solution of the liquid velocity potential corresponding to each liquid sub-domain was obtained by means of the method of separation of variables. The coupled modes of the multiple elastic annular baffles were expressed in terms of dry-modal functions. The free surface condition, the interface conditions and coupled vibration conditions were expressed in terms of Fourier series along the liquid height and Bessel series in the radial direction, respectively. Stable and fast numerical computations were investigated by the convergence study. Excellent agreements have been achieved in the comparison of re- suits obtained by the proposed approach with those given by the finite element software ADINA. The natural frequencies and mode shapes versus the position, the inner radius and the number of the annular baffles were thoroughly discussed.

A strain smoothing formulation for NURBS-based isogeometric finite element analysis

A strain smoothing formulation for NURBS (non-uniform rational B-splines) based isogeometric finite element analysis is presented. This approach is formulated within the framework of assumed strain methods and strain smoothing operations. The strain smoothing is defined through strain averaging in the element sub-domains which are subsequently used for numerical integration of the Galerkin weak form. This formulation satisfies the orthogonality condition of the assumed strain methods. Meanwhile the present formulation totally avoids the gradient computation of the rational NURBS basis functions in the formulation of stiffness matrix. A transformation method is employed to accurately enforce the displacement boundary conditions. Numerical results demonstrate that the present formation gives very satisfactory solution accuracy simultaneously with improved computational efficiency.

SOME SPECIAL CHARACTERISTICS OF TRACK AND INTENSITY OF TYPHOONS OVER THE WESTERN NORTH PACIFIC

Joint Typhoon Warning Center(JTWC) Best Track data from 1995 to 2014 are processed to examine some specific patterns and trends shown by Typhoons over the Western North Pacific. With a multivariate dataset of 588 TC cases in hand, we carry out a sub-domain analysis by dividing the Western North Pacific region into domains of 2°x2° and find the preferred regions of genesis, favourable direction of movement, steep recurvature, rapid intensification, and rapid decay. The region from longitude 132°E to 134°E and latitude 16°N to 18°N showed the highest number of cases(19) for rapid intensification(RI) and a general pattern is found that the RI systems occurred mostly in the later half of the year with a negative Pacific Decadal Oscillation(PDO) index. Similarly, the domain from longitude 114°E to 116°E and latitude 26°N to 28°N had the highest probability of 0.857 for rapid decay. The probabilities of recurvature for each sub-domain were calculated for angles 30°, 45°, 60°, 90°, 120° and 150°. The sub-domain around longitude 118°E and latitude 12°N had the steepest recurve of 168.69°. It also had a high probability of 0.714 for a recurvature of greater than 90°. The most taken direction of movement of typhoons around the Western North Pacific were analysed in different ways and along the 16 points of compass, the direction from 270° to 292.5° was found to be the most preferred direction of movement.

Kinematic Shakedown Analysis for Strain-Hardening Plates with the C^(1) Nodal Natural Element Method

This paper proposes a novel numerical solution approach for the kinematic shakedown analysis of strain-hardening thin plates using the C^(1)nodal natural element method(C^(1)nodal NEM).Based on Koiter’s theorem and the von Mises and two-surface yield criteria,a nonlinear mathematical programming formulation is constructed for the kinematic shakedown analysis of strain-hardening thin plates,and the C^(1)nodal NEM is adopted for discretization.Additionally,König’s theory is used to deal with time integration by treating the generalized plastic strain increment at each load vertex.A direct iterative method is developed to linearize and solve this formulation by modifying the relevant objective function and equality constraints at each iteration.Kinematic shakedown load factors are directly calculated in a monotonically converging manner.Numerical examples validate the accuracy and convergence of the developed method and illustrate the influences of limited and unlimited strain-hardening models on the kinematic shakedown load factors of thin square and circular plates.