图像动态识别在瞄准设备读数和检定中的应用

瞄准设备是用于初始定向的重要设备,必须对其进行定期计量检定。为了克服瞄准设备读数系统复杂,读数过程繁琐,读数精度受到诸多限制等突出问题,将图像动态识别技术应用到瞄准设备读数和检定中,设计了一种能代替人眼进行瞄准读数或设备检定的计算机判读系统。重点分析了系统软件实现过程中解决的关键环节,即缺陷字符的误识问题的解决、系统的稳定性改善、系统分辨率及精度提高、系统实时性的提高。     

Two problems of two-dimensional steady temperature in a composite semi-infinite plate

Problems of heat conduction in stratiform infinite and semi-infinite bodies form a group of problems which is of interest both from the physical and from the mathematical point of view. The direct solution of a number of such problems, using the corresponding Fourier transform, meets with considerable mathematical difficulties and it is often advantageous to apply a special artifice. The present paper gives an example of such a procedure in the case of a semi-infinite composite plate with a particular arrangement of the different parts.     

On some boundary value problems on a strip in the complex plane

The Sommerfeld integral inversion method for the Helmholtz equation in an angular region with different boundary values leads to boundary value problems in an infinite strip of the complex plane. We investigate a generic system for such boundary value problems and give the existence and uniqueness results with optimal growth estimates on the solution. We also give the solutions of the Dirichlet problem in a strip when the boundary functions grow exponentially.     

Eigenmodes of a compressible liquid drop

The eigenmodes of a non-viscous, compressible liquid drop are investigated. The spectrum is shown to be derivable from two Hermitian eigenvalue problems which are weakly coupled by a non-Hermitian operator. It is shown that both eigenvalue problems admit an asymptotic, lepto-dermous expansion. Their contribution to the entropy of the droplet therefore also allows for such an expansion.     

Applications of the electron backscatter diffraction technique to ceramic materials

A technique with a relatively high spatial resolution is required for an effective analysis of the microstructure of ceramic materials. The recently developed electron backscatter diffraction (EBSD) technique, which works within a scanning electron microscope, enables a spatially highly resolved study of crystallographic orientations while recording Kikuchi patterns on a user-defined grid. However, such an EBSD texture analysis was until now not often performed on ceramic materials – in contrary, the technique is widely employed in the analysis of metallic materials, including the investigation of various types of steels. The use of ceramics possesses a variety of problems for EBSD investigations like: (i) complicated crystal structure, (ii) difficult surface preparation, and (iii) problems arising from a low conductivity of the ceramic materials. Here, we discuss these problems and present solutions in order to obtain high-quality Kikuchi patterns from such ceramics.     

Quantization of an affinely rigid body with constraints

Discussed are some quantization problems of an affinely-rigid body with additional Weyl constraints. We investigate the systems with potential energies for which the variables can be separated. The Sommerfeld polynomial method is used to perform the quantization of such problems.     

Variational approach to three-dimensional inverse problems of potential theory

A method of regularization and solving problems of flow around bodies according to a desired distribution of the characteristics of the fields on the surface of the bodies themselves is described. Examples of solutions of such problems for potential flows are given, and a method of reducing inverse problems of the fluid mechanics of an effectively inviscid liquid to potential problems is presented. Zh. Tekh. Fiz. 67, 8–15 (October 1997)     

Applying backpropagation neural networks to fringe analysis

Advances in image processing and optics technology, allied to the development of algorithmic techniques such as the fast Fourier transform and phase stepping, have allowed automatic fringe analysis to be successfully applied to many problems in visual inspection and noncontact surface measurement. However, when confronted with complicated or noisy images the algorithmic techniques tend to be less successful, implying an alternative approach may be necessary. Neural networks offer such an alternative. They have already been applied with some success to such conceptually similar pattern recognition problems, as the classification of fingerprints, the recognition of facial expressions and the identification of hand-written characters. Here, neural networks are applied to two simple fringe analysis problems. Firstly, to find the radius of a one-dimensional curved surface from its simulated fringe projection intensity distribution and, secondly, to identify four lensshaped objects of different radii of curvature from real fringe patterns obtained under different illumination conditions. In the first experiment, the backpropagation and radial basis function network paradigms are compared. In the second case, backpropagation is compared with the fuzzy-artmap paradigm. Performance criteria are the number of training data presentations, the accuracy of interpolation in the simulation experiment and the classification precision for the real data.     

Application of Laplace transform technique to the solution of certain third-order non-linear systems

A number of papers have appeared on the application of operational methods and in particular the Laplace transform to problems concerning non-linear systems of one kind or other. This, however, has met with only partial success in solving a class of non-linear problems as each approach has some limitations and drawbacks. In this study the approach of Baycura has been extended to certain third-order non-linear systems subjected to non-periodic excitations, as this approximate method combines the advantages of engineering accuracy with ease of application to such problems. Under non-periodic excitations the method provides a procedure for estimating quickly the maximum response amplitude, which is important from the point of view of a designer. Limitations of such a procedure are brought out and the method is illustrated by an example taken from a physical situation.     

CEMS of insulators by use of gas-flow counters

Gas-flow CEMS counters are usually designed in such a manner that the sample to be investigated is inserted into the counter and serves as the backing cathode. If the sample consists of an insulating material, serious problems are expected by charging-up effects similar to those appearing in Maze counters. These problems are discussed in detail. It could be shown by experiments with glass samples that their very low surface conductivity is sufficient to allow a defined operation of such gas-flow CEMS detectors. The electric field strength between the surface of the sample and the anode has to be equal or higher than that between the entrance window and the anode. This can be ensured by an appropriate design of the counter and an excess voltage applied to compensate for the potential drop across the insulating sample.Dedicated to Professor P. Gütlich on the occasion of his 60th birthday.     

Singular solutions of contact problems and block elements

In this work, we consider mixed problems of elasticity theory, in particular, contact problems for cases that are nontraditional. They include mixed problems with discontinuous boundary conditions in which the singularities in the behavior of contact stresses are not studied or the energy of the singularities is unbounded. An example of such mixed problems is contact problems for two rigid stamps approaching each other by rectilinear boundaries up to contact but not merging into one stamp. It has been shown that such problems, which appear in seismology, failure theory, and civil engineering, have singular components with unbounded energy and can be solved by topological methods with pointwise convergence, in particular, by the block element method. Numerical methods that are based on using the energy integral are not applicable to such problems in view of its divergence.     

Laser cleaning of steel for paint removal

Paint removal is an important part of steel processing for marine and offshore engineering. For centuries, a blasting techniques have been widely used for this surface preparation purpose. But conventional blasting always has intrinsic problems, such as noise, explosion risk, contaminant particles, vibration, and dust. In addition, processing wastes often cause environmental problems. In recent years, laser cleaning has attracted much research effort for its significant advantages, such as precise treatment, and high selectivity and flexibility in comparison with conventional cleaning techniques. In the present study, we use this environmentally friendly technique to overcome the problems of conventional blasting. Processed samples are examined with optical microscopes and other surface characterization tools. Experimental results show that laser cleaning can be a good alternative candidate to conventional blasting.     

Anisotropic diffusion in a nematic liquid crystal- An electric field PFG NMR approach

The access to self-diffusion coefficients in anisotropic systems such as thermotropic liquid crystals by means of PFG NMR is complicated by strong dipolar interactions. Additionally, problems arise due to the immediate orientation of low-molar-mass nematic liquid crystals in an external field. The director orientation can be changed by the application of an additional electric field. This can be exploited in order to reduce the dipolar interaction to such an extent that the NMR linewidths change from a solid-state to a liquid-like situation enabling PFG NMR experiments.     

Transient acoustic radiation from impulsively accelerated bodies by the finite element method

Bodies under impulsive motion, immersed in an infinite acoustic fluid, severely put to test any numerical method for the transient exterior acoustic problem. Such problems, in the context of the finite element method (FEM), are not well studied. FE modeling of such problems requires truncation of the infinite fluid domain at a certain distance from the structure. The volume of computation depends upon the extent of this domain as well as the mesh density. The modeling of the fluid truncation boundary is crucial to the economy and accuracy of solution and various boundary dampers have been proposed in the literature for this purpose. The second order damper leads to unsymmetric boundary matrices and this necessitates the use of an unsymmetric equation solver for large problems. The present paper demonstrates the use of FEM with zeroth, first and second order boundary dampers in conjunction with an unsymmetric, out of core, banded equation solver for impulsive motion problems of rigid bodies in an acoustic fluid. The results compare well with those obtained from analytical methods.     

Ultrasonic Wireless Communication Through Metal Barriers

Ultrasound can be used as a carrier to realize wireless communication to and from a metal-enclosed space, which has the characteristics such as immunity to the electromagnetic shielding effect and non-destructive penetration of metal obstacles. This paper firstly reviews the previous studies in the field of ultrasonic wireless communication through metal barriers, and summarizes their achievements and the existing problems. Secondly, an overview of the research methods involved in studying the characteristic of acoustic-electric channel is presented, and the principles are introduced for the actual measurement method, equivalent circuit method, ABCD parameter method, finite element analysis method and time-domain finite difference method. Then, an overview of the communication algorithms are presented such as orthogonal frequency division multiplexing (OFDM), single-carrier frequency domain equalization and multiple input multiple output OFDM. Finally, the potential future study are proposed in light of the trend of development and unsolved problems.     

Solution clustering in random satisfiability

For a large number of random constraint satisfaction problems, such as random k-SAT and random graph and hypergraph coloring, we have very good estimates of the largest constraint density for which solutions exist. All known polynomial-time algorithms for these problems, though, fail to find solutions at much lower densities. To understand the origin of this gap we study how the structure of the space of solutions evolves in such problems as constraints are added. In particular, we show that in random k-SAT for k ≥ 8, much before solutions disappear, they organize into an exponential number of clusters, each of which is relatively small and far apart from all other clusters. Moreover, inside each cluster most variables are frozen, i.e., take only one value.     

Ant colony optimization: Introduction and recent trends

Ant colony optimization is a technique for optimization that was introduced in the early 1990's. The inspiring source of ant colony optimization is the foraging behavior of real ant colonies. This behavior is exploited in artificial ant colonies for the search of approximate solutions to discrete optimization problems, to continuous optimization problems, and to important problems in telecommunications, such as routing and load balancing. First, we deal with the biological inspiration of ant colony optimization algorithms. We show how this biological inspiration can be transfered into an algorithm for discrete optimization. Then, we outline ant colony optimization in more general terms in the context of discrete optimization, and present some of the nowadays best-performing ant colony optimization variants. After summarizing some important theoretical results, we demonstrate how ant colony optimization can be applied to continuous optimization problems. Finally, we provide examples of an interesting recent research direction: The hybridization with more classical techniques from artificial intelligence and operations research.     

Generalized Joseph estimates of stability of plane shear flows with scalar nonlinearity

Possible statements of eigenvalue problems generalizing the classical Orr-Sommerfeld problem are given for incompressible stationary flows of non-Newtonian fluids; these problems are interpreted within the mechanics of a continuum as problems of the shear stability of such flows. A schematic diagram of the integral relation method as applied to these flows is described. In the case of an unperturbed Couette flow, Joseph estimates are generalized for any type of rheological curve and domains of guaranteed stability are constructed on a plane with the axes showing Reynolds numbers corresponding to the tangent and secant dynamic viscosity at one point.     

Solutions to initial value problems by use of finite elements—Unconstrained variational formulations

This paper presents a variational formulation which treats initial value problems and boundary problems in a unified manner. The basic ingredients of this theory are (1) adjoint variable and (2) unconstrained variations. It is an extension of the finite element unconstrained variational formulation used previously in solving several non-conservative stability problems. The technique which makes this extension possible is described. This formulation thus enables one to adapt such numerical techniques as the finite element method, which has had great success and popularity for solution of boundary value problems, for solutions of initial value problems as well. These formulations are given here for a forced vibration problem, a heat (mass) transfer problem and a wave propagation problem. Numerical calculations in conjunction with finite elements for two specific examples are obtained and compared with known exact solutions.     

Boundary Conditions for Coupled Quasilinear Wave Equations with Application to Isolated Systems

We consider the initial-boundary value problem for systems of quasilinear wave equations on domains of the form [0, T] × Σ, where Σ is a compact manifold with smooth boundaries ∂Σ. By using an appropriate reduction to a first order symmetric hyperbolic system with maximal dissipative boundary conditions, well posedness of such problems is established for a large class of boundary conditions on ∂Σ. We show that our class of boundary conditions is sufficiently general to allow for a well posed formulation for different wave problems in the presence of constraints and artificial, nonreflecting boundaries, including Maxwell’s equations in the Lorentz gauge and Einstein’s gravitational equations in harmonic coordinates. Our results should also be useful for obtaining stable finite-difference discretizations for such problems.