Experimental investigations of the response of a cracked rotor to periodic axial excitation

In this paper, the coupling of lateral and longitudinal vibrations due to the presence of transverse surface crack in a rotor is explored. A crack in a rotor is known to introduce coupling between lateral and longitudinal vibrations. Steady state unbalance response of a cracked rotor with a single centrally situated crack subjected to periodic axial impulses is investigated experimentally. The cracked rotor is excited axially using an electrodynamic exciter at a frequency equal to its bending natural frequency in both non-rotating and rotating conditions. The resulting time domain and frequency domain signals of the cracked rotor are studied. Spectral response of the cracked rotor with and without axial excitation is found to be distinctively different. When excited axially, it shows prominent presence of rotor bending natural frequency. However for an uncracked rotor, the response is similar with or without axial excitation. It is thus proposed that the response of the rotor to axial impulse excitation could be used for more reliable diagnosis of rotor cracks.     

Response of thermal source in a transversely isotropic thermoelastic half-space with mass diffusion by finite element method

The two-dimensional problem of generalized thermoelastic diffusion material with thermal and diffusion relaxation times is investigated in the context of Lord-Shulman theory. As an application of the problem, a particular type of thermal source is considered and the problem is solved numerically by using a finite element method. The components of displacement, stress, temperature distribution, chemical potential, and mass concentration are obtained. The resulting quantities are depicted graphically for a special model. Appreciable effect of relaxation times is observed on various resulting quantities.     

The oscillopolarographic determination of uranium and thorium in supporting electrolytes containing cupferron

Uranium(VI and IV) and thorium(IV) give cathodic indentations in supporting electrolytes prepared from 0.1M perchloric acid, 0.5 M ammonium thiocyanate and 5·10^-3M cupferron (solution A) or from 0.1 M succinic-succinate buffer pH 4, 0.1 M sodium chloride, 10^-3M cupferron and 0.05% gelatine (solution B). The uranium indentation on the dE/dt = f(E) curve (Q=0.75 and 0.73) permits its detection at the 3·10^-7M level. The thorium indentation (Q=0.78) permits its detection at the 4·10^-7M level in solution B. Methods for the elimination of interfering ions for the uranium determination are described. In the determination of thorium, Ga(III), Fe(III), Ti(IV) and U(VI) interfere.     

Cosmologies with Variable G and Λ from Action Principle

Cosmologies with variable G and are developed in this paper from an action principle, and some exact cosmological models are presented. These models indicate that the era of variable G and must have occurred, if at all, prior to other possible eras like radiation and dust.     

Studies on lactams—XX Stereochemistry of some penicillin sulfoxides and analogs from lanthanide induced shifts

Lanthanide induced shifts have been shown to provide reliable information on the steric disposition of protons in the vicinity of the sulfoxide group in penicillin derivatives and analogs. Because of its dipolar nature the sulfoxide bond serves as a favored site for complex formation with the lanthanide. The configuration of several penam sulfoxides and the conformation of the thiazolidine ring of one of them have been deduced.     

The Structure of a Non-Symmetric Disordered Tetramer: A Crystallographic and Solid State Multinuclear NMR Study of the Properties of 3(5)-Ethyl-5(3)-Phenyl-1H-Pyrazole

The X-ray structure and the solid-state NMR measurements, mainly ¹⁵N CPMAS of the labelled compound, allow to determine the static and dynamic properties of 3(5)-ethyl-5(3)-phenyl-1H-pyrazole. The compound is a tetramer formed by three 5-ethyl-3-phenyl-1H-pyrazole and one 3-ethyl-5-phenyl-1H-pyrazole tautomers in dynamic equilibrium with the complementary situation.     

Depression in the cloud point of Tween in the presence of glycol additives and triblock polymers

Cloud point (C_P) measurements of Tween 20 and Tween 80 were carried out in the presence of various glycol oligomers and triblock polymers (TBP). The cloud points of both Tween 20 and 80 decrease in the presence of both types of additives. Among the glycol oligomeric additives, ethylene glycol monobutyl ether was found to reduce the C_P maximum. An increase in the repeating units of polymeric glycol additives leads to a decrease in C_P. Reduction in the C_P in the presence of TBP depends upon the increase in hydrophobic/hydrophilic ratio among the polypropylene to polyethylene units.     

Synthesis of novel chromogenic azocalix[4]arenemonoquinones and their binding with alkali metal cations

Five new chromogenic azocalix[4]arenemonoquinones have been synthesized, characterized and examined for their interaction with alkali metal cations (Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺) by UV-visible spectroscopic and cyclic voltammetric techniques. It has been determined that 4a selectively exhibits a significant bathochromic shift in its UV-visible spectrum on interaction with potassium ion in comparison to its treatment with other alkali metal cations. The binding stoichiometry of 4a and potassium ion was established to be 1:1 with an association constant of 3.27 × 10⁴ M^?1. Cyclic voltammetric experiments in 4:1 dichloromethane-acetonitrile also revealed a significant anodic shift (ΔE _(1/1′) = 115 mV) of the original redox waves of 4a on interaction with potassium ion.     

Synthesis of novel cone-configurated hexa-tert-butyl-trimethoxy-calix[6]arenes bearing tris(bipyridyl) pendants and their use in recognition and ionic speciation

A series of novel cone-configurated p-tert-butyl-trimethoxycalix[6]arenes bearing three 2,2′-bipyridyl units at their lower rim have been synthesized. The ¹H NMR and ¹³C NMR spectra of synthesized derivatives revealed that the ring inversion in calix[6]arene could be suppressed by the introduction of three 2,2′-bipyridyl moieties at the lower rim of calix[6]arene scaffold which fixes it into its cone configuration. The complexation ability of the synthesized receptors (5a–d) towards Fe(II) ion was investigated by UV-Visible titration to reveal that the synthesized receptors interact with Fe(II) in a 1:1 binding stoichiometry and respond to a specific oxidation state of the metal ion. The observations have significance for studies directed at the design of molecular receptors for ionic speciation through molecular recognition.