Processing investigation and optimization for hybrid thermoplastic composites

A thermoplastic based composite material is suitable for automobile and aerospace applications. The recyclability of thermoplastic and clean processing further enhance its use. The only limitation encountered in using this material is its high-melt viscosity. Various techniques have been developed to overcome this problem. Commingled materials are one of such methods adopted for making proper use of thermoplastic. A major problem observed during the use of a commingled material is its de-commingling, wherein, the uniform distribution of fiber and thermoplastic yam gets disturbed and affects the final quality of the composite. The effects of the braiding process on laminate quality were investigated. Flat plaques were produced by braiding the commingled yam, using a 48- carrier braiding machine. The braids （and control woven samples） were subsequently heated and consolidated in a nonisothermal compression molding operation. Prior to the manufacture of the ＇best quality＇ plaques, a series of moldings were produced under different consolidation conditions, to study the dependence of properties on the process variables. This enabled a processing window to be established for each material and helped to separate the respective effects of yam handling, textile processing, and consolidation on laminate properties.     

Natural radioactivity intake into wheat grown on fertilized farms in two districts of Pakistan

The use of phosphate fertilizers on agricultural farms enhances gamma-ray activity concentration in the farms and therefore absorbed dose rates to the public. The most common natural radionuclides in fertilizer and soil are (40)K, (226)Ra and (232)Th. Agricultural farms at four locations in two districts in Pakistan consisting of saline and normal soils had been under fertilizer treatment for the past 30, 20, 10 and 0 y, therefore, natural radioactivity has been measured in soil samples from these sites to investigate the effect of fertilizers in soil and wheat grown in these sites. Radioactivity measured in soil of the sites under investigation was 550-644, 20-35 and 42-58 Bq kg(-1) for (40)K, (226)Ra and (232)Th, respectively. Wheat was grown in the farms and radioactivity transferred from soil to roots, shoots and grains was also measured. Relatively high natural radioactivity has been observed in the fertilized agricultural farms and in the wheat plants grown in these farms. From the total amount of an element uptaken in a plant, distribution of the element in different parts of the plant has been studied. The distribution of potassium was almost uniform in roots, shoots and grains of wheat; that of radium was different in the three parts of wheat; and that of thorium was almost equal in shoots and grains but quite large in the roots. Soils to grain transfer factors of the natural radionuclides have been determined as 3-4 x 10(-2) for (226)Ra, 2-3 x 10(-2) for (232)Th and 17-20 x 10(-2) for (40)K. Annual doses of (40)K and (226)Ra received by intake of grain products have been estimated to lie within range while the dose received from intake of (232)Th is larger than the range specified in UNSCEAR report 2000.     

A novel word length selection method for a guaranteed $$H_\infty $$ interference rejection performance and overflow oscillation-free realization of 2-D digital filters

This paper examines the problem of the local overflow stability and disturbance attenuation performance analysis of two-dimensional (2-D) Roesser digital filters in the presence of external interferences. In particular, by utilizing the local properties of saturation nonlinearity and Lyapunov stability theory, a novel linear matrix inequality (LMI)-based condition is proposed that not only ensures the nonexistence of overflow oscillations, but also yields the \(H_{\infty }\) interference rejection performance of 2-D digital filters under the overflow constraint. It is worth mentioning here that in contrast to the traditional approaches based on modeling the saturation with a global sector-bound condition, the proposed approach provides a less conservative bound for the attenuation of disturbances and renders the idea of minimum word length for realizing the 2-D (Roesser) filter to eliminate overflow oscillations and attain the specified \(H_{\infty }\) interference attenuation performance index. Finally, a numerical simulation example is also provided, which demonstrates the superiority of the proposed method over the existing techniques.     

All-organic PANI–DBSA/PVDF dielectric composites with unique electrical properties

Novel all-organic polymer high-dielectric permittivity composites of polyaniline (PANI)/poly (vinylidene fluoride) (PVDF) were prepared by solution method and their dielectric and electric properties were studied over the wide ranges of temperatures and frequencies. To improve the interface bonding between two polymers, dodecylbenzenesulfonic acid (DBSA), a bulky molecule containing a polar head and a long non-polar chain was used both as a surfactant and as dopant in polyaniline (PANI) synthesis. Synthesized conducting PANI–DBSA particles were dispersed in poly(vinylidene fluoride) (PVDF) matrix to form an all-organic composite with different PANI–DBSA concentrations. Near the percolation threshold, the dielectric permittivity of the composites at 100 Hz frequency and room temperature was as high as 170, while the dielectric loss tangent value was as low as 0.9. Like typical percolation system, composites experienced high dielectric permittivity at low filler concentrations. However, their dielectric loss tangent was low enough to match with non-percolative ceramic filler-based polymer composites. Maximum electrical conductivity at 24 wt% of PANI–DBSA was mere 10^?6 S/cm, a remarkably low value for percolative-type composites. Increase in the dielectric permittivity of the composites with increase in temperature from 25 to 115 °C for different PANI–DBSA concentrations was always in the same range of 50–60 %. However, the degree of increase in the electrical conductivity with the temperature was more prominent at low filler concentrations compared with high filler concentrations. Distinct electrical and their unique thermal dependence were attributed to an improved interface between the filler and the polymer matrix.     

3D modified unitary matrix pencil method with automatic grouping of unknown parameters of far field signals

In this paper, we propose a 3-dimensional modified unitary matrix pencil (3D MUMP) method for simultaneous estimation of azimuth and elevation angles along with the frequencies of multiple plane wave signals. The unitary transformation is utilized in the 3-dimensional matrix pencil (3D MP) method in order to reduce the computational complexity since it very efficiently converts complex computations into real ones. The proposed method can be considered as an extension to the existing 2-dimensional unitary matrix pencil (2D UMP) method with the following advantages. First, the computationally expensive grouping algorithm is avoided by exploiting the similar eigen-structure property of the matrices (in 3D UMP method) whose eigenvalues yield the required 3D poles. Furthermore, the possibility of wrong groupings is also reduced significantly. Some simulation results are presented at the end to compare the performance of the proposed method with the existing methods.