Preparation, structural analysis and dielectric properties of Bi x La1−x FeO3 perovskite

Rare earth element substituted bismuth ferrites (BiFeO₃) are of enormous importance as magnetoelectric materials. The polycrystalline samples of Bi _x La_1−x FeO₃ (x=0, 0.2, 0.4, 0.6, 0.8) were prepared by solid-state reaction using standard ceramic method. The single-phase formation of these compounds was confirmed by X-ray diffraction (XRD) studies. The samples with x=0, 0.2, 0.4, 0.6 are found to be orthorhombic while the sample with x=0.8 is triclinic. The dielectric constant (ε′) and dissipation factor (tan δ) were measured in the frequency range 100 Hz to 1 MHz at room temperature and as a function of temperature at certain fixed frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz). All the samples showed dielectric dispersion. The dielectric constant with temperature shows a broad peak; the peak temperature shifts with frequency which reflects the relaxor-type behavior. The peak above 600 K in the measured temperature range corresponds to antiferromagnetic ordering temperature (Néel temperature). The broadness of the peak changes with composition. The ac conductivity as well as ε′ are found to be maximum for the sample x=0.2 at room temperature.     

Manpower planning procedures for hierarchical manpower systems

In this paper, a model which describes manpower planning procedures for a hierarchical system having certain desired properties to be achieved is presented. These properties will act as constraints on the system. It will be assumed that eventual, desired properties are achieved gradually over a period of time. Promotion policies will be wastagelinked and designed to satisfy vacancy-expansion demands. The model will be applied to data from a group of English County Police Constabularies.     

Impurity analysis of gentamicin bulk samples by improved liquid chromatography-ion trap mass spectrometry

Several gentamicin bulk samples from different origins were investigated using an LC/MS method.LC equipped with ion trap MS with positive ionization was performed on a Capcell Pak C18(AQ) column with the mobile phase containing 50 mM trifluoroacetic(TFA) and methanol.Impurities present in batches of gentamicin bulk samples were elucidated and compared according to their fragmentation behavior.In total seventeen impurities present in samples,five impurities were not elucidated and two compounds were identifi...     

Design of a Franz–Keldysh effect electroabsorption waveguide modulator for millimetre-wave generation

An analysis of the generation of harmonics for millimetre-wave signals using a Franz–Keldysh effect waveguide modulator is presented. The Franz–Keldysh electroabsorption is obtained via a method known to provide accurate results in comparison with experimental data. This is followed by an optimisation of the drive voltage in terms of the d.c. bias for a sinusoidal input. A spectrum rich in harmonics is produced and the fifth is considered in detail for device optimisation. The modulator considered is based on a large core multimode waveguide designed to yield a high coupling efficiency to single-mode fibres. The confinement factor, and hence the length, of the structure are determined via the effective index method. The resulting device could be used for the cost-effective production of millimetre-wave carriers via the harmonics generated whilst enabling the employment of electronics running at the speed of the fundamental.     

On the general theory of (m,n) rings

In this paper, the lattice of congruences of an (m, n) ring is determined, a generalization of the Wedderburn theorem for finite division rings is considered, all (2,n) fields, (2,n) rings of prime order, and all (3,n) rings of prime order are determined. A special class of (2,n) fields, called super-simple (2,n) fields, is characterized. Presented by J. D. Monk.     

Fuzzy control of optical PPM–CDMA with M-ary orthogonal signaling

This paper introduces an incorporated spectral-amplitude coding (SAC) optical code-division multiple-access (OCDMA) scheme. One novel class of optical signature codes based on combinatorial designs is employed with M-ary pulse-position modulation (PPM) signaling to improve the system performance beyond the interference limit. A union upper bound on the bit error rate (BER) is derived and the performance characteristics are then discussed with a variety of system parameters. Furthermore, fuzzy logic (FL) control is proposed to provide tolerance of different degrees of reliability in multirate transmission and to achieve distinct service differentiation for multimedia applications. It is shown that the proposed system can effectively suppress noise effects and offer improved adaptation capabilities for multi-quality network requirements in comparison with systems without optimization.