Finite element formulation for the large amplitude free vibrations of beams and orthotropic circular plates

A finite element formulation for the large amplitude free oscillations of beams and orthotropic circular plates is presented in this paper. The present formulation does not need the knowledge of longitudinal/inplane forces developed due to large displacements and thus avoids the use of corresponding geometric stiffness matrices, which were used in earlier finite element formulations. The convergence of the results obtained by using the present formulation is very good. Comparison of the present results with the earlier work wherever possible confirms the reliability and effectiveness of the present finite element formulation.     

Preoperative diagnosis of gallbladder perforation by cholescintigraphy

Perforation of the gallbladder in patients with chronic cholecystitis is rarely diagnosed preoperatively. We describe a case in which early cholescintigraphy permitted preoperative diagnosis and, therefore, prompt laparotomy.     

Optimal template matching by nonorthogonal image expansion using restoration

In this paper we present a novel approach for template matching. The basic principle is expansion matching and it entails signal expansion into a set of nonorthogonal templatesimilar basis functions. The coefficients of this expansion signify the presence of the template in the corresponding locations in the image. We demonstrate that this matching technique is robust in conditions of noise, superposition, and severe occlusion. A new and more practical discriminative signal-to-noise ratio (DSNR) for matching is proposed that considers even the filter's off-center response to the template as “noise”. We show that expansion yields the optimal linear operator that maximizes the DSNR and results in a sharp response to the matched template. Theoretical and experimental comparisons of expansion matching and the widely used correlation matching demonstrate the superiority of our approach. Correlation matching (also known as matched filtering) yields broad peaks and spurious responses, both of which hamper good detection. We also show that the special case of expansion with a dense set of self-similar basis functions is equivalent to signal restoration. Expansion matching can be implemented by restoration techniques and also by our recently developed lattice architecture.     

Effects of circuit loss and space charge in gyro-travelling-wave tubes

A modified dispersion relation of a gyro-TWT using a cylindrical waveguide excited in aT E _mn -mode is derived incorporating the effect of the transverse space charge forces. The relation is subsequently studied considering the circuit losses and interpreted for the conventional TWT-type gain equation. The second harmonic operation using theT E ₀₂ cylindrical waveguide mode resonated with the second beam-harmonic mode is found to be more sensitive to the Pierce's loss and space-charge parameters for a gyro-TWT than the fundamental operation using theT E ₀₁ cylindrical waveguide mode resonated with the first beam-harmonic mode. It is established that these parameters substantially influence the device gain and must be considered for the prediction of its accurate value. Furthermore, these parameters when properly controlled can also improve the device bandwidth.     

Gibbs energies of formation of chromium carbides

The carbon potentials corresponding to the two-phase mixtures Cr + Cr₂₃C₆, Cr₂₃C₆ + Cr₇C₃, and Cr₇C₃ + Cr₃C₂ in the binary system Cr-C were measured in the temperature range 973 to 1173 K by using the methane-hydrogen gas equilibration technique. Special precautions were taken to prevent oxidation of the samples and to minimize thermal segregation in the gas phase. The standard Gibbs energies of formation of Cr₂₃C₆, Cr₇C₃, and Cr₃C₂ were derived from the measured carbon potentials. These values are compared with those reported in the literature. The Gibbs energies obtained in this study agree well with those obtained from solid-state cells incorporating CaF₂ and ThO2(Y₂O₃) as solid electrolytes and sealed capsule isopiestic measurements reported in the literature.     

Surface topographical studies of prism faces of barium copper oxalate single crystals

The present paper reports observations made on microstructures of gel-grown barium copper oxalate crystals. Growth spirals, growth layers, liquid inclusions and growth of microcrystallites are described and discussed in relation to the mechanism and conditions of crystal growth.     

Asymmetric convective flows in the high speed rotating frame

Recent experiments have confirmed that heated flows in radial tubes in the high speed rotating frame are asymmetric and non unidirectional.