High-cycle fatigue characterization of titanium 5Al-2.5Sn alloy

High-cycle fatigue behaviour of titanium 5Al-2.5Sn alloy at room temperature has been studied. S-N curve characterization is performed at different stress ratios ranging from 0 to 0.9 on a subsized fatigue specimen. Both two-stress and three-stress level tests are conducted at different stress ratios to study the cumulative fatigue damage. Life prediction techniques of linear damage rule, double linear damage rule and damage curve approaches are applied, and results are compared with the experimental data. The agreement between prediction and experiment is found to be excellent.     

Consideration of measurement of electrostriction in quartz usingBragg reflection of X-rays

Calculation shows that the linear piezoelectric effect should be readily demonstrated in X-cut quartz by Bragg reflection of X-rays, equipment for which is available in every crystal finishing room. Electrostriction should also be observable and measurable in X-cut, Y-cut and Z-cut quartz, and in other cuts having their major surfaces parallel to X-ray diffracting planes of the crystal. Mechanical compression of the quartz due to the charge on the electrodes must be considered     

Principal axes and surface fitting methods for three-dimensional image registration

We evaluated the effect of the image acquisition parameters on the accuracy of the principal axes and surface-fitting techniques for three-dimensional image registration. Using two types of phantom objects, MR brain image and a mathematically defined ellipsoid, we simulated pairs of scans with known acquisition parameters, including longitudinal coverage, magnitude of mis-registration, number of sections and section thickness. Both methods are sensitive to the systematic deformation of contours. The principal axes method is also sensitive to incomplete scan coverage and to the x-axis and y-axis misangulation. Both methods are insensitive to the number of sections, section thickness and the number of points per section. Surface fitting performed well without user supervision. There is no need for routine inclusion of the scaling factors as search parameters. The results confirm the feasibility of three-dimensional multimodality registration of brain scans with accuracy 1-2 mm, with surface fitting being the method of choice.     

Carrier wave frequency multiplication of AM signals

Until now carrier wave frequency multiplication has been applied in CW, PM and FM techniques. However, it has never been considered as applicable to AM signals. This is due to unsupported opinions that it would distort the envelope of AM signals. Theoretical considerations were carried out with the use of the double Fourier series expansion. The results have shown that it is enough to have an uninterrupted flow of the envelope through the amplifier to have a nondistorted envelope in both amplification and frequency multiplication. The results were verified experimentally and by observations of BC and TV stations at their harmonic frequencies. The conclusion has been made on AM signals having two or more frequency fringes, e.g.: single tone DSB, two tone SSB     

Fractal physiology

The nature of fractals and the use of fractals instead of classical scaling concepts to describe the irregular surfaces, structures, and processes exhibited by physiological systems are described. The mathematical development of fractals is reviewed, and examples of natural fractals are cited. Relationships among power laws, noise, and fractal time signals are examined     

Frequency-dependence of myocardial energetics in failing human myocardium as quantified by a new method for the measurement of oxygen consumption in muscle strip preparations

Diastolic dysfunction at high heart rates may be associated with increased myocardial energy consumption. Frequency-dependent changes of isometric force and oxygen consumption (MVO2) were investigated in strip preparations from endstage failing human hearts exhibiting various degrees of diastolic dysfunction. MVO2 was determined by a new method which was validated. When stimulation rate was increased from 40 to 200 min-1 (n=7), developed force decreased from 16.5+/-4.3 to 7.9+/-2.9 mN/mm2 (P<0.01), diastolic force increased from 15.9+/-3.2 to 22.0+/-3.0 mN/mm2 (P<0.01), and total MVO2 increased from 2.6+/-0.6 to 4.7+/-0.9 ml/min/100 g (P<0.025). Resting MVO2 and resting force were 1.8+/-0.4 ml/min/100 g and 15.9+/-3.0 mN/mm2, respectively. After addition of 30 mm 2,3-butanedione monoxime (BDM) to inhibit crossbridges, resting MVO2 and resting force decreased by 46% (P<0.05) and 15% (P<0.01), respectively, indicating the presence of active force generation in unstimulated failing human myocardium. In each muscle preparation, there was a significant correlation between force-time integral (FTI) and total MVO2 (r=0.96+/-0.01). The strength of these correlations did not vary with the contribution of diastolic FTI to total FTI. The ratio of activity related MVO2 to developed FTI, an inverse index of the economy of contraction, increased depending on the rise of diastolic FTI at higher stimulation rates. In conclusion, in failing human myocardium, diastolic force development is occurring at the same energy expenditure as systolic force generation. Therefore, in muscle preparations with disturbed diastolic function economy of contraction decreases with higher stimulation rates, depending on the rise of diastolic force.     

Derivative constrained optimum broad-band antenna arrays

The optimization problem corresponding to the design of a presteered broadband processor with maximally flat second-order spatial response in the look direction is discussed. The constraints corresponding to necessary and sufficient conditions for second-order flatness are presented. The nonlinearly constrained optimization approach is unable to consistently locate the global minimum. An approach to solving this problem that essentially converts the nonconvex optimization problem into a parameterized set of convex problems is presented. In the case of 2-D scenarios, the global optimum is determined by finding the roots of a cubic function. The characteristics of the constraints, including the minimum number required and the dependence on the choice of coordinate systems, are examined     

A new approach to version control

A method for controlling versions of software and other hierarchically structured entities is presented. Using the variant structure principle, a particular version of an entire system is formed by combining the most relevant existing versions of the various components of the system. An algebraic version language that allows histories (numbered series), subversions (or variants), and joins is described. It is shown that the join operation is simply the lattice least upper bound and together with the variant structure principle, provides a systematic framework for recombining divergent variants. The utility of this approach is demonstrated using LEMUR, a programming environment for modular C programs, which was developed using itself. The ways in which this notion of versions is related to the possible world semantics of intensional logic are discussed     

Stress analysis of elastomeric materials at large extensions using the finite element method

The finite element method is applied to stress and strain analyses around rigid spherical particles in elastomers at large extensions. The stress and strain distribution computed agree well with the classical theoretical ones at small strain. At large extension, however, the maximum stress concentration factor increases greatly and the maximum strain concentration factor decreases slightly as strain increases. These tendencies are increased more in carbon black-filled elastomers than in unfilled ones, which can be understood reasonably by considering both the geometric and material non-linearity. Reinforcement of elastomers with rigid spherical particles was also analysed through a numerical computation. The computed results agree with the Guth and Mooney equations at low volume fraction of fillers. In carbon black-filled elastomers, on the other hand, where the modulus is much higher than that given by the above equations, the computations give a good agreement with the experiments, considering the 20% increase in effective diameter of the filler.