Colloidal Crystalline Arrays of β‐Polymorphic Poly(vinylidene fluoride)

Stable layers of nearly monodisperse spheres of β‐polymorphic poly(vinylidene fluoride) with iridescent properties are prepared. The colloidal crystalline arrays (CCAs) were characterized by optical microscopy, differential scanning calorimetry (DSC), and FT‐IR spectroscopy. FT‐IR spectroscopic and wide‐angle X‐ray scattering (WAXS) studies revealed a β‐polymorphic PVF₂ structure, the DSC study showed that the level of crystallinity in the CCA was much higher than that in the melt‐crystallized sample, and UV‐visible spectroscopy showed extinction peaks at 323 and 510 nm in the CCAs. The β‐polymorphic PVF₂ structure, along with the optical extinction properties of these CCAs, raises the prospect of their application in optical filters and/or piezoelectric sensors.

Optical micrograph of PVF₂ CCA films cast on glass substrates.     

Bispectral and trispectral features for machine condition diagnosis

The application of bispectral and trispectral analysis in condition monitoring is discussed. Higher-order spectral analysis of machine vibrations for the provision of diagnostic features is investigated. Experimental work is based on vibration data collected from a small test rig subjected to bearing faults. The direct use of the entire bispectrum or trispectrum to provide diagnostic features is investigated using a variety of classification algorithms including neural networks, and this is compared with simpler power spectral and statistical feature extraction algorithms. A more detailed investigation of the higher-order spectral structure of the signals is then undertaken. This provides features which can be estimated more easily in practice and could provide diagnostic information about the machines     

A novel approach for broken-rotor-bar detection in cage inductionmotors

In this paper, a new approach is proposed to detect broken rotor bars in induction motors. The motor is disconnected from the supply, and the induced voltage in the stator due to only rotor flux is utilized to detect the fault. If there is any broken bar, it will directly affect the induced voltages in the stator windings. Using this approach, the effects of source nonidealities (such as unbalance, presence of time harmonics, etc.) and nonlinearity of machine magnetizing characteristics due to saturation can be avoided     

Selective Filters and Sinusoidal Oscillators Using CFA Transimpedance Pole

Using a single current feedback amplifier (CFA) device, two new variable frequency sinusoidal RC oscillators are presented. The transadmittance pole of the device (AD-844) has been utilized in the design for generating sine wave signals covering a range of 1 MHz≤f ₀≤31 MHz. Under open-loop conditions, both circuits exhibit resonance characteristics at moderate Q-values (1≤Q≤9). These responses have been experimentally verified with hardware circuit implementation and PSPICE macromodel simulation.     

New ideal active inductance and frequency-dependant negative resistance using d.v.c.c.s./d.v.c.v.s.: applications in sinusoidal-oscillator realisation

A new grounded-capacitor simulation of driving-point impedances of the form as and bs2, corresponding to ideal inductance and frequency-dependent negative resistance (f.d.n.r.) elements, respectively, is presented. The configurations use the minimum of passive components with the d.v.c.c.s./d.v.c.v.s. as the active element. Applications of the active inductance and f.d.n.r. are then proposed in the realisation of some single-resistor-controlled RC oscillators.     

Microbial susceptibility of condensation products of carboxy-terminated polybutadiene and glycerol

Summary Keeping in view the prospects of biodegradable polymers, a polymer was synthesized by the condensation of carboxy-terminated polybutadiene (CTPB) of M_n-5000 with glycerol and tested for its microbial susceptibility. The results of end group estimations and viscosity measurements indicated a quantitative reaction between the two reactants under experimental conditions. The clear-zone method was employed in this investigation to test biodegradability. Two strains of Serratia and three strains of Staphylococcus did show a clear zone surrounding the colony. However, the microbial growth was found to diminish after 4 or 5 days.Presented at the International Conference on Structure-Property Relations of Rubber held at IIT, Kharagpur (India) Dec. 28–31 (1980)