Axisymmetric oscillations of a cupola-shaped shell

A spectral boundary problem on axisymmetric eigenoscillations of a cupola-shaped shell is considered with emphasis on small shell thickness. The problem deals with a singularly perturbed system of ordinary differential equations. The paper examines analytical properties of the solution and, based on that, constructs an appropriate functional basis for Ritz’ method. Employing this basis provides fast convergence in the C ³-metrics.     

Comparing finite state machine test

To plan testing activities, testers face the challenge of determining a strategy, including a test coverage criterion that offers an acceptable compromise between the available resources and test goals. Known theoretical properties of coverage criteria do not always help and, thus, empirical data are needed. The results of an experimental evaluation of several coverage criteria for finite state machines (FSMs) are presented, namely, state and transition coverage; initialisation fault and transition fault coverage. The first two criteria focus on FSM structure, whereas the other two on potential faults in FSM implementations. The authors elaborate a comparison approach that includes random generation of FSM, construction of an adequate test suite and test minimisation for each criterion to ensure that tests are obtained in a uniform way. The last step uses an improved greedy algorithm.     

Transition covering tests for systems with queues

This paper introduces a method to cover transitions of a concurrent system under test through a context consisting of infinite‐capacity queues. Concurrent systems have many important applications, but they are very difficult and expensive to test. One of the difficulties in testing concurrent systems is caused by the fact that queues in the test context can distort the behaviour of a concurrent system under test and can cause state explosion in test derivation. The proposed method derives transition covering tests directly from the specification of a concurrent system, not its composition with queues. As transition coverage is an important industrial metric of test quality, the results of the paper have practical applications. A case study is presented to illustrate one of the applications. Copyright © 2008 John Wiley & Sons, Ltd.     

Anodic dissolution of electrochemical chromium coatings in electrolytes for electrochemical machining: The dissolution rate and surface roughness

By the example of dissolution under conditions of controlled hydrodynamics (a rotating disk electrode), the distinctions of the surface formation after the anodic dissolution of electrolytic chromium films in electrolytes for electrochemical machining (ECM) (in chlorides and nitrates at current densities of 0.1–15 A/cm²) have been shown. The roughness of the produced surface was not considered intrinsic and correlated with the nature of the solution anion. In the chlorides, it was determined by the fracture formation due to the surface weakening and by the pitting formation, while, in nitrates, actually only by pitting formation. The influence of the current density and the surface heating at high current densities, along with the dimensions of the layers remaining after the chromium film dissolution, on the degree of the surface weakening and its roughness has been shown. The expedience of the nitrate solutions use at the high electrolyte flow rates during the electrochemical microprocessing of such surfaces has been demonstrated.     

A survey of electromagnetic position tracker calibration techniques

This paper is a comprehensive survey of various techniques used to calibrate electromagnetic position tracking systems. A common framework is established to present the calibration problem as the interpolation problem in 3D. All the known calibration techniques are classified into local and global methods and grouped according to their mathematical models. Both the location error and the orientation error correction techniques are surveyed. Data acquisition devices and methods as well as publicly available software implementations are reviewed, too.     

Study of dissolution of cellulose in ionic liquids by computer modeling

Computer modeling of the geometry and electronic structure of the solvent and its complexes with water and cellobiose allowed: explaining the decrease in the dissolving power of an ionic liquid in the presence of water using data on the electronic structure of the molecules; determining the overall mechanism of solvation of cellulose by ionic liquids and other organic solvents; calculating the change in the energy information of a solvate complex of the elementary cellulose unit with 1-butyl-3-methylimidazolium chloride, which was-20.64 kcal/mole. __________ Translated from Khimicheskie Volokna, No. 2, pp. 51–54, March–April, 2007.     

Structural changes during annealing of deformed Pd-25 at % Ni Alloy

X-ray diffraction analysis and residual resistivity measurements are used to study the short-range order and fine crystal structure of the Pd-25 at % Ni solid solution deformed at room temperature and their changes during isochronous annealings. A short-range order was shown to exist in the deformed alloy; the structure of the order does not correspond to the L1₂ superstructure. During the annealing, the character of the order remains unchanged. Possible physical processes that cause the nonmonotonic changes in the short-range order, fine crystal structure parameters, and residual resistivity are considered.