New poly(butylene succinate)/layered silicate nanocomposites. II. Effect of organically modified layered silicates on structure,properties, melt rheology,and biodegradability

A series of new poly(butylene succinate) (PBS)/layered silicate nanocomposites were prepared successfully by simple melt extrusion of PBS and organically modified layered silicates (OMLS). Three different types of OMLS were used for the preparation of nanocomposites: two functionalized ammonium salts modified montmorillonite and a phosphonium salt modified saponite. The structure of the nanocomposites in the nanometer scale was characterized with wide-angle X-ray diffraction and transmission electron microscopic observations. With three different types of layered silicates modified with three different types of surfactants, the effect of OMLS in nanocomposites was investigated by focusing on four major aspects: structural analysis, materials properties, melt rheological behavior, and biodegradability. Interestingly, all these nanocomposites exhibited concurrent improvements of material properties when compared with pure PBS. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3160–3172, 2003     

Modified modulation formats using time-varying phase functions

New modulation formats are presented that increase the transmission rate over that of conventional systems, without degrading the bit error rate (BER) and with minimal bandwidth variation. A time-varying function called an "extra phase variation function" (EPVF) is added to the discrete phase of conventional modulation formats such as M-PSK and QAM to transmit additional data bits. A receiver configuration is presented that allows the decoding of information represented by the discrete and extra phases. It is shown that in an additive white Gaussian noise (AWGN) channel, the BER performance of the bits carried by the discrete phase and the extra phase in the modified format improves over the BER of conventional modulation formats.     

Theory of a multiply fed and loaded insulated linear antenna in air

Analytic expressions are derived for the input admittance and the current distribution along the multiply fed and loaded insulated antenna in air which is excited across feed gaps of nonzero widths. The Wiener-Hopf type analysis for a center fed insulated antenna is combined with the axial field discontinuity (AFD) method to develop the current and admittance expression. This AFD method considers the metallic surface of the linear antenna as a series combination of longitudinal, electric-field surface functions that exist due to feeding and/or loading. The analysis, which does not employ superposition of even and odd distributions of sources and loads, yields final expressions in terms of the excitation location, its aperture electric field within the feed gaps, impedance locations, and their values. The current distribution for cases of unity dielectric constant shows an excellent agreement with data based on the moment method. The input admittances and current distributions are reported for different multiple excitations and loads and dielectric constants of the insulator     

Simultaneous Approximation for Generalized Baskakov-Durrmeyer-Type Operators

The present paper deals with the study of a Durrmeyer-type integral modification of certain modified Baskakov operators. Here we study simultaneous approximation properties for these operators by using the iterative combinations. We obtain an asymptotic formula and an error estimation in terms of higher order modulus of continuity for these operators.      

Acousto-optic mode coupling of partially coherent light in two-mode optical fibers

An acoustic pulse propagating on a two-mode fiber can act as a beam splitter in a scanning interferometer. When this device is employed in white-light interferometry, the effects of distributed coupling and dispersive interferometer arms need to be considered. A theory suitable for treating acousto-optic interaction of partially coherent light in a moving interaction region was developed. It was found that differential optical dispersion should be negligible and the acoustic pulse length short. Also the coherence time should be short but long compared to the intermodal group delay difference over a pulse length. Experiments with long acoustic pulses were performed, and fairly good agreement with theory was obtained.