Inverse problem of pulsed eddy current field of ferromagnetic plates

To determine the wall thickness, conductivity and permeability of a ferromagnetic plate, an inverse problem is established with measured values and calculated values of time-domain induced voltage in pulsed eddy current testing on the plate. From time-domain analytical expressions of the partial derivatives of induced voltage with respect to parameters,it is deduced that the partial derivatives are approximately linearly dependent. Then the constraints of these parameters are obtained by solving a partial linear differential equation. It is indicated that only the product of conductivity and wall thickness, and the product of relative permeability and wall thickness can be determined accurately through the inverse problem with time-domain induced voltage. In the practical testing, supposing the conductivity of the ferromagnetic plate under test is a fixed value, and then the relative variation of wall thickness between two testing points can be calculated via the ratio of the corresponding inversion results of the product of conductivity and wall thickness. Finally, this method for wall thickness measurement is verified by the experiment results of a carbon steel plate.

Univector field method-based multi-agent navigation for pursuit problem in obstacle environments

The pursuit problem is a well-known problem in computer science. In this problem, a group of predator agents attempt to capture a prey agent in an environment with various obstacle types, partial observation, and an infinite grid-world. Predator agents are applied algorithms that use the univector field method to reach the prey agent, strategies for avoiding obstacles and strategies for cooperation between predator agents. Obstacle avoidance strategies are generalized and presented through strategies called hitting and following boundary(HFB); trapped and following shortest path(TFSP); and predicted and following shortest path(PFSP). In terms of cooperation, cooperation strategies are employed to more quickly reach and capture the prey agent. Experimental results are shown to illustrate the efficiency of the method in the pursuit problem.

Generalized variational principles for boundary value problem of electromagnetic field in electrodynamics

An expression of the generalized principle of virtual work for the boundary value problem of the linear and anisotropic electromagnetic field is given. Using Chien＇s method, a pair of generalized variational principles （GVPs） are established, which directly leads to all four Maxwell＇s equations, two intensity-potential equations, two constitutive equations, and eight boundary conditions. A family of constrained variational principles is derived sequentially. As additional verifications, two degenerated forms are obtained, equivalent to two known variational principles. Two modified GVPs are given to provide the hybrid finite element models for the present problem.

A Boundary Integral Formulation of the Plane Problem of Magneto-Elasticity for an Infinite Cylinder in a Transverse Magnetic Field

The objective of this work is to present a boundary integral formulation for the static, linear plane strain problem of uncoupled magneto-elasticity for an infinite magnetizable cylinder in a transverse magnetic field. This formulation allows to obtain analytical solutions in closed form for problems with relatively simple geometries, in addition to being particularly well-adapted to numerical approaches for more complicated cases. As an application, the first fundamental problem of Elasticity for the circular cylinder is investigated.

On the Generalization of Hilbert’s 17th Problem and Pythagorean Fields

The notion of preordering, which is a generalization of the notion of ordering, has been introduced by Serre. On the other hand, the notion of round quadratic forms has been introduced by Witt. Based on these ideas, it is here shown that 1) a field F is formally real n-pythagorean iff the nth radical, RnF is a preordering (Theorem 2), and 2) a field F is n-pythagorean iff for any n-fold Pfister form ρ. There exists an odd integer l(>1) such that l×ρ is a round quadratic form (Theorem 8). By considering upper bounds for the number of squares on Pfister’s interpretation, these results finally lead to the main result (Theorem 10) such that the generalization of pythagorean fields coincides with the generalization of Hilbert’s 17th Problem.

Higher-Order Line Element Analysis of Potential Field with Slender Heterogeneities

Potential field due to line sources residing on slender heterogeneities is involved in various areas,such as heat conduction,potential flow,and electrostatics.Often dipolar line sources are either prescribed or induced due to close interaction with other objects.Its calculation requires a higher-order scheme to take into account the dipolar effect as well as net source effect.In the present work,we apply such a higher-order line element method to analyze the potential field with cylindrical slender heterogeneities.In a benchmark example of two parallel rods,we compare the line element solution with the boundary element solution to show the accuracy as a function in terms of rods distance.Furthermore,we use more complicated examples to demonstrate the capability of the line element technique.

Reconstruction of Current Density Distribution in Weld Area During Resistance Spot Welding of Aluminum Alloy Based on Magnetic Field

Magnetic flux density around the weld area was used to reconstruct the current density distribution during resistance spot welding(RSW) of aluminum alloy according to inverse problem theory. A current-magnetic field model was established and the conjugate gradient method was used to solve this model. The results showed that the current density was low at the center of nugget while high on the edge of nugget. Moreover, the welding time of 30ms—60 ms is a key period for nucleation. The current density distribution can reflect whether the weld nugget is formed or splashed, therefore it has the potential to monitor the weld quality of RSW.

APPLICATION OF ENTHAIPY METHOD FOR MOVING BOUNDARY PROBLEM IN LASER SURFACE MELTING

A numerical analysis was carried out to study the moving boundary problem in the physical process of pulsed Nd-YAG laser surface melting prior to vaporization.The enthalpy method was applied to solve this two-phase axisymmetrical mehing problem.Computational results of tempera ture fields were obtained,which provide useful information to practical lair treatment processing. The validity of enthalpy method in solving such problems is presented.

Preliminary Study of the Feasibility of Inverse Problem Algorithms Used for Arc Magnetic Measurement Method

Non-contact magnetic measurement method is an effective way to study the air arc behavior experimentally. One of the crucial techniques is to solve an inverse problem for the electromagnetic field. This study is devoted to investigating different algorithms for this kind of inverse problem preliminarily, including the preconditioned conjugate gradient method, penalty function method and genetic algorithm. The feasibility of each algorithm is analyzed. It is shown that the preconditioned conjugate gradient method is valid only for few arc segments, the estimation accuracy of the penalty function method is dependent on the initial conditions, and the convergence of genetic algorithm should be studied further for more segments in an arc current.

ON THE STABILITY ESTIMATION OF ANALYTIC CONTINUATION FOR POTENTIAL FIELD

This paper discusses the stability of solutions to a class of Cauchy problems for Laplace equations under two kinds of nonclassical circumstances. By means of conformal mapping and Tikhonov, Luan Wengui and Yamamoto's methods for solving ill-posed problems respectively, the stability estimations of weighted Holder type and logarithmic type, have been obtained accordingly.

THE INVERSE PROBLEM IN DESIGN OF A MAGNETIC BRUSH BY INTEGRAL EQUATION METHOD

An inverse problem technique with the integral equation method is used to design a kind of magneticbrush made from permanent magnetic bars. Least squares computation and one-dimensional search method areemployed to find the minimum of the object’s function. A method to obtain the initial values of the requiredgeometric parameters is presented. The effectiveness of this technique is illustrated by examples.

Cosmic Continuum Theory: A New Idea on Hilbert’s Sixth Problem

Hilbert’s sixth problem “The mathematical treatment of the axioms of physics” is a century-old problem that still plagues the scientific community. It is a solution necessary to establish a unified axiom of the basic theories of physics according to the characteristics of a mathematical axiomatic system needed to solve this problem. The cosmic continuum hypothesis can make classical theory, quantum theory and relativity have common logical foundation. According to this model, the universe is a continuum formed by the existence continuum and the existence dimension continuum. Their movement and changes can be described by an axiomatic system. The concrete steps are as follows: 1) Construct the axiom system of a cosmic continuum and establish the basic theory of force. 2) Construct the axiom system of action at a distance and establish the basic theory of field. 3) Based on the axiom system of force and field, the axiom system of the branches of physics is established.

The Solution Cosmological Constant Problem

The cosmological constant problem arises because the magnitude of vacuum energy density predicted by the Quantum Field Theory is about 120 orders of magnitude larger then the value implied by cosmological observations of accelerating cosmic expansion. We pointed out that the fractal nature of the quantum space-time with negative Hausdorff-Colombeau dimensions can resolve this tension. The canonical Quantum Field Theory is widely believed to break down at some fundamental high-energy cutoff and therefore the quantum fluctuations in the vacuum can be treated classically seriously only up to this high-energy cutoff. In this paper we argue that the Quantum Field Theory in fractal space-time with negative Hausdorff-Colombeau dimensions gives high-energy cutoff on natural way. We argue that there exists hidden physical mechanism which cancels divergences in canonical QED4, QCD4, Higher-Derivative-Quantum gravity, etc. In fact we argue that corresponding supermassive Pauli-Villars ghost fields really exist. It means that there exists the ghost-driven acceleration of the universe hidden in cosmological constant. In order to obtain the desired physical result we apply the canonical Pauli-Villars regularization up to Λ*. This would fit in the observed value of the dark energy needed to explain the accelerated expansion of the universe if we choose highly symmetric masses distribution between standard matter and ghost matter below the scale Λ*, i.e., The small value of the cosmological constant is explained by tiny violation of the symmetry between standard matter and ghost matter. Dark matter nature is also explained using a common origin of the dark energy and dark matter phenomena.

The Forward and Inverse Problem Based on Magneto-Acoustic Tomography with Current Injection

The Magneto-acoustic Tomography with Current Injection (MAT-CI) is a new biological electrical impedance imaging technique that combines Electrical Impedance Tomography (EIT) with Ultrasonic Imaging (UI), which possesses the non-invasive and high-contrast of the EIT and the high-resolution of the UI. The MAT-CI is expected to acquire high quality image and embraces a wide application. Its principle is to put the conductive sample in the Static Magnetic Field(SMF) and inject a time-varying current, during which the SMF and the current interact and generate the Lorentz Force that inspire ultrasonic signal received by the ultrasonic transducers positioned around the sample. And then according to related reconstruction algorithm and ultrasonic signal, electrical conductivity image is obtained. In this paper, a forward problem mathematical model of the MAT-CI has been set up to deduce the theoretical equation of the electromagnetic field and solve the sound source distribution by Green’s function. Secondly, a sound field restoration by Wiener filtering and reconstruction of current density by time-rotating method have deduced the Laplace’s equation that caters to the current density to further acquire the electrical conductivity distribution image of the sample through iteration method. In the end, double-loop coils experiments have been conducted to verify its feasibility.

ELECTROELASTIC FIELD FOR AN IMPERMEABLE ANTI-PLANE SHEAR CRACK IN A PIEZOELECTRIC CERAMICS PLATE

Electroelastic behavior of a cracked piezoelectric ceramics plate subjected to four Cases of combined mechanical-electrical loads is analyzed. The integral transform method is applied to convert the problem involving an impermeable anti-plane crack to dual integral equations. Solving the resulting equations, the explicit analytic expressions for electroelastic field along the crack line and the intensity factors of relevant quantities near the crack tip and the mechanical strain energy release rate we obtained, The known results for an infinite piezoelectric ceramics plane containing an impermeable anti-plane crack are recovered from the present results only if the thickness of the plate h --> infinity.

Validity and Accuracy of Eddy Current Field Analysis of Laminations by Introducing Equivalent Conductivities

对于分析叠片铁心中的涡流问题，利用各种等效电导率替代硅钢片实际电导率的匀质化方法是很有应用前景的。为了评估各种电导率模型，该文提出了铁心涡流场分析的二维解析验证方法，并分别基于引入各向异性或各向同性等效电导率的铁心连续体表述和实际叠片表述对涡流场进行了解析计算。通过比较连续体表述下所得到的平均磁通密度和涡流损耗值与相应由实际叠片表述所得到的精确解，对各种电导率模型的有效性和准确性在各种条件下进行了评估。为了进一步考察电导率模型对实际工程问题的适用性，利用有限元法进行了关于TEAM21面向工程基准问题的磁通和杂散场损耗计算。计算结果表明，由该文作者所提出的等效电导率模型优于其他模型。

浅议油气田地面建设工程质量管理DiscussiononQualityManagementofGroundConstructionProjectinOilandGasField

本文以油气田地面工程质量管理为切入点,在概述油气田地面建设工程质量管理应遵守的原则的基础上,分析油气田地面建设工程质量管理中存在的问题,探讨了加强油气田地面建设工程质量管理的策略,旨在说明质量管理在油气田地面建设工程建设中的重要性,以期指导实践。

Fermion field in the vicinity of a brane

A mechanism that enables fermions to live outside of but be localized near a brane is proposed based on the field-theoretical framework. Two types of fermion fields are considered: one is localized to the brane through the Yukawa interaction, and another is localized through the fermion interaction. It is shown that, besides the well-localized zero-mode, there exists a light mode continuum of which oscillating components are delocalized. As a consequence it is possible to assume existence of invisible material particles that live outside the brane on which we reside and beleaguer visible particles. A possible extension to the mind-body problem is discussed.

智慧工地物料配送动态时间窗车辆路径优化

智慧工地物料配送是建筑业提升建造效率的重要环节。为有效解决智慧工地物料配送路径优化问题,依托运筹学理论将其转化为带时间窗的车辆路径规划问题。以总配送路径最短为目标函数,建立动态时间窗车辆路径(VRPDTW)数学模型,构建全局最优理论模型。运用改进人工势场算法分析障碍物和中间节点,再代入基础蚁群算法进行施工现场全局路径规划,对VRPDTW数学模型进行优化。并通过仿真实验对模型进行实证检验。结果表明:改进算法和VRPDTW模型可实现全局优化,能够有效解决智慧工地场景下物料连续配送问题,相较于基础算法,改进算法使路径规划的准确度提高,成本降低,效率提升,具有理论意义和行业应用价值。

Updating the Historical Perspective of the Interaction of Gravitational Field and Orbit in Sun-Planet-Moon System

Studying the two famous old problems that why the moon can move around the Sun and why the orbit of the Moon around the Earth cannot be broken off by the Sun under the condition calculating with F=GMm/R2, the attractive force of the Sun on the Moon is almost 2.2 times that of the Earth, we found that the planet and moon are unified as one single gravitational unit which results in that the Sun cannot have the force of F=GMm/R2 on the moon. The moon is moved by the gravitational unit orbiting around the Sun. It could indicate that the gravitational field of the moon is limited inside the unit and the gravitational fields of both the planet and moon are unified as one single field interacting with the Sun. The findings are further clarified by reestablishing Newton’s repulsive gravity.