Scanning/friction force microscopy study of YBa2Cu3O7−δ single crystals grown in BaZrO3 crucibles

Very pure YBa₂Cu₃O_7– (YBCO) single crystals grown in BaZrO₃ crucibles are studied in the as-grown and the oxidized state by scanning force (SFM), friction force (FFM) and scanning tunneling microscopies (STM). The images show clean terraces with step-heights of one unit cell along YBCO(001), i.e. 1.2 nm. Only close to step edges is material contrast observed by FFM indicating traces af flux. Some crystal surfaces exhibit over-layer features, such as star-like, ribbon-like and checkerboard-like structures, which exhibit friction contrast implying the presence of different materials on the surface. Tunneling spectroscopy at 4.7 K in high vacuum reveals a superconducting energy gap of 2 26 me V.     

Fracture of solids by radiation pulses as a method of ensuring safety in space

To determine the optimum conditions of fracturing or altering the trajectory of dangerous space objects (large iron or rock space bodies, threatening to collide with the Earth), and also destroy space debris in the space around the Earth, the author presents a mathematical formulation of the problem of calculating the dynamic strength of solids under the effect of high-energy loading pulses. The results of numerical modeling are compared with the experimental data for the formulation of cupola-shaped swollen areas on the rear surface of a metallic plate subjected to laser radiation. The change in the fracture mechanisms (front and rear spallation) with increasing energy of the effect has been detected. Recommendations are given for optimizing the pulsed laser effect on dangerous space objects to ensure the fragmentation or change their orbit.Expanded form of the document presented at the International Conference Space Protection of the Earth≓ (SPE'94, Snezhinsk, Russian, September 26–30, 1994).Translated from Problemy Prochnosti, No. 3, pp. 31–51, March, 1996.     

A mildly exponential approximation algorithm for the permanent

A new approximation algorithm for the permanent of ann ×n 0,1-matrix is presented. The algorithm is shown to have worst-case time complexity exp(O(n ^1/2 log² n)). Asymptotically, this represents a considerable improvement over the best existing algorithm, which has worst-case time complexity exp((n)).Supported by SERC Grant GR/F 90363; work done in part while visiting DIMACS (Center for Discrete Mathematics and Computer Science).Supported by an NSF PYI grant, with matching equipment grant from the AT&T Foundation; work done in part while visiting DIMACS.     

An application of the technology acceptance model to the level of Internet usage by older adults

In this cross-sectional study, the principles of a technology acceptance model were used to identify variables related to the level of Internet usage by older adults. Community-dwelling older adults aged 60–88 years completed a postal questionnaire survey that elicited responses on the use of the Internet. Out of a sample of 592 older adults (236 males and 356 females), 50.7% used the Internet. A multiple linear regression analysis was carried out on the Internet users sample using the self-reported number of hours of Internet usage per week as the dependent variable. The results indicated that attitude toward using the Internet and good health status were statistically significant predictors of the level of Internet usage. A second multiple regression analysis using Internet activity as the dependent variable showed that attitude, usefulness, good health, and gender (males) were significant predictor variables.     

Mobile multi-view object image search

High user interaction capability of mobile devices can help improve the accuracy of mobile visual search systems. At query time, it is possible to capture multiple views of an object from different viewing angles and at different scales with the mobile device camera to obtain richer information about the object compared to a single view and hence return more accurate results. Motivated by this, we propose a new multi-view visual query model on multi-view object image databases for mobile visual search. Multi-view images of objects acquired by the mobile clients are processed and local features are sent to a server, which combines the query image representations with early/late fusion methods and returns the query results. We performed a comprehensive analysis of early and late fusion approaches using various similarity functions, on an existing single view and a new multi-view object image database. The experimental results show that multi-view search provides significantly better retrieval accuracy compared to traditional single view search.     

An interface finite element for the simulation of localized membrane-bending deformation in shells

The folding of thin shells around localized lines occurs in several situations of engineering interest, such as in buckling induced deformation, as the consequence of crash, in industrial processes like metal forming, in the deployment of folded membranes, in packaging related processes. In this paper an interface element, allowing for displacement and rotation discontinuities, to be placed between two adjacent 4-node Mindlin–Reissner shell finite elements, is developed for a computationally effective simulation of this type of localized deformation. The large displacement and rotation kinematics of the interface element is discussed, arriving at a rigid-rotation free element tangent stiffness matrix. An adaptive dynamic relaxation scheme is proposed for the evolutionary analysis of the quasi-static structural response. To test the element formulation, a simple coupled membrane-bending elastoplastic behavior is assumed. The element is used for the simulation of few examples taken from the literature, where the structural response is characterized by the formation of plastic hinges, exhibiting good accuracy and computational effectiveness.     

A Jacobi-type method for computing balanced realizations

A new numerical scheme for computing balancing coordinate transformations in linear systems theory is presented. The method is closely related to the Jacobi method for diagonalizing symmetric matrices. Here the minimization of the sum of traces of the Gramians by orthogonal and nonorthogonal Jacobi-type rotations is considered. The algorithm is shown to be globally convergent to a balancing transformation that arranges the Hankel singular values in a prescribed ordering. Local quadratic convergence of the algorithm is shown.     

Efficient multitasking in a dual-core CPU system

The paper offers an associative-neural-net method to optimize resource allocation between independent tasks in a multiprocessor system. In the case of a dual-core CPU the method allows the task to be fully solved in O(M) operations. The text was submitted by the authors in English.     

Micromechanical three-axial tactile force sensor for micromaterial characterisation

 A three-axial tactile force sensor for the investigation of micromechanical structures has been developed using silicon micromachining technology. The sensor is capable of performing mechanical micro material characterisation such as the determination of the spring constant of complex micromechanical structures. Another application for this sensor is dimensional metrology where it has been tested as a 3D probe in a test set-up for coordinate measurements.     

On the analysis of stochastic divide and conquer algorithms

This paper develops general tools for the analysis of stochastic divide and conquer algorithms. We concentrate on the average performance and the distribution of the running time of the algorithm. As a special example we analyse the average performance and the running time distribution of the (2k + 1)-median version of Quicksort. Online publication October 13, 2000.