Analysis of fading statistics in cellular mobile communication systems

Spatial channel models are often proposed for modeling the angular aspects of mobile radio channel in picocell, microcell, and macrocellular environments. These models are validated through comparison with available measurement results. The comparisons are usually based on the fitness of their pdfs of angle of arrival to the histogram of occurrences of the signals over an angular span, given in the measurement data. This paper presents a comparison of the notable scattering models with various spatial channel measurements. The paper suggests criteria for the comparative analysis of the previously proposed spatial channel models and measurements on the basis of their fading statistics. Quantitative analysis of the considered models and the field measurements is also presented using multipath shape factors i.e. angle spread, the angular constriction and direction of maximum fading. Based on the obtained shape factors, fading statistics like level crossing rates, average fade duration, auto-covariance and coherence distance are evaluated. Effect of increasing Doppler spread on the level crossing rates and average fade duration is also elaborated in detail.     

Enzymatic saccharification of canola meal

For the enzymatic saccharification of canola meal by enzyme preparations from Trichoderma reesei as well as by commercially available hemicellulase and multienzyme preparations, a pretreatment consisting of autoclaving is necessary. These enzyme preparations hydrolysed over 20% (w/w) of pretreated canola meal, which constitutes over 70% saccharification of the total polysaccharides present in canola meal. The results show that saccharification of canola meal is mainly brought about by hemicellulases capable of degrading arabinogalactan, arabinoglucan, galactan and galactomannan, while cellulases and xylanases play a minor role. These hemicellulases were found to be more stable at 50°C than cellulases or xylanases. This pretreatment also released water-soluble polysaccharides consisting mainly of arabinose and glucose. Trichoderma reesei was unable to produce enzymes capable of hydrolysing this polysaccharide when cultivated on canola meal as substrate.     

Pressure Fluctuation Analysis of Laboratory Scale Air/Polyethylene Fluidized Beds

Differential pressure fluctuations were studied along the wall of a laboratory scale column filled with a polyethylene resin. Air flow rates to the column were varied in order to examine the changes in wall pressure with respect to superficial gas velocity. Statistical and spectral analysis was used to study the periodic features of column wall pressure measurements in the dense region of a fluidized bed. From the analysis, it is evident that multiple flow regimes exist in the column. These flow regimes are dependent upon the height above the distributor. Results also show a significant peak developing at 1 Hz as superficial gas velocity increases.     

Manufacture of Mesoporous Silicon from Living Plants and Agricultural Waste: An Environmentally Friendly and Scalable Process

We demonstrate a process for realising mesoporous silicon from a range of land-based plants such as common grasses, bamboos, sugarcane and rice. Such plants act as ??natural factories??, converting and concentrating vast quantities of soluble silicon in soil into nanostructured forms of silica in their roots, stems, branches or leaves. This porous biogenic silica is chemically extracted and then thermally reduced to porous silicon using magnesium vapor. Importantly, for larger batch size, an inexpensive thermal moderator such as salt, is added for control of the reaction exotherm and minimization of sintering. Mesoporous silicon of >350?m²/g with 8?nm wide pores has been obtained from a bamboo extract, for example. The same process is applicable to a wide range of ??silicon accumulator plants??. The purity of this ??naturally derived?? porous silicon is likely to be raised to a level acceptable for a wide range of high volume applications outside of electronics and solar cell technology.     

The application of porous silicon to optical waveguiding technology

The porosification of silicon can be achieved by the partial electrochemical dissolution (anodization) of the surface of a silicon wafer. The degree of porosity is dependent on the anodization parameters and can generally be controlled within the constraints imposed by substrate dopant type and concentration. Control of porosity leads to control of refractive index, and therein lies the concept of using porous silicon as an optical waveguide. We discuss porous silicon wavegides, for the visible to the infrared, produced by a number of approaches: 1) epitaxial growth onto porous silicon (where the porous layer acts as a substrate for a higher refractive index waveguide epilayer); 2) ion implantation (where either selective areas of high electrical resistivity can be produced, which act as a barrier against porosification, or where the surface of a porosified layer is amorphised to form a waveguide; 3) porous silicon multilayers (where the anodization parameters are periodically varied to produce alternate layers of different porosity and thus refractive index); and 4) oxidation of porous silicon (where a porosified layer is oxidized to form a graded-index, dense or porous, oxide waveguide)     

A Non‐Invasive Hydrodynamic Study of Gas‐Solid Fluidised Bed of Linear Low Density Polyethylene

There are several non‐invasive techniques used to study the hydrodynamic characteristics of gas‐solid fluidised bed reactors. In this study a two phase, gas‐solid fluidised bed consisting of air and a linear low‐density polyethylene (LLDPE) resin was examined. The polyethylene sample was composed of irregular, non‐monosized particles ranging in size from 165 to 1500 µm. The experimental techniques used were digital fluoroscopy and pressure fluctuations. This study presents a comparison of the two‐phase system experimental results and two‐dimensional CFD simulation results. CFD packages FLUENT and MFIX were used.     

Direct comparison of hydrogen depth distributions and refractive index profiles in annealed proton-exchanged Z-cut LiNbO/sub 3/ waveguides

For the first time, to the authors' knowledge, hydrogen distributions in weakly and strongly annealed proton-exchanged z-cut LiNbO/sub 3/ have been measured using modified secondary ion mass spectrometry and correlated with refractive index profiles determined by optical waveguide measurements.<>     

Stain Etched Nanostructured Porous Silicon: The Role of Morphology on Antibacterial Drug Loading and Release

In this work, nanostructured porous silicon (pSi) prepared by a metal-assisted stain etched route is investigated for its ability to act as a carrier for sustained delivery of the antibacterial drug triclosan. The morphology, analyzed by transmission electron microscopy, reveals a rather different microstructure than traditional anodized porous silicon; as a consequence, such morphology manifests a different loaded drug crystallinity, triclosan release behavior, and associated antibacterial activity versus Staphococcus aureus relative to high porosity anodized porous silicon. In addition to electron microscopies and antibacterial disk diffusion assays, a combination of x-ray diffraction, thermogravimetric analyses, and UV/Vis spectrophotometric analysis of triclosan release are employed to carry out the above investigations.     

Measurement of the increase in the SHG coefficient of proton-exchanged LiNbO/sub 3/ after annealing using a grating diffraction technique

The effect of limited levels of annealing on the second harmonic generation (SHG) coefficient (d/sub 33/) of proton-exchanged LiNbO/sub 3/ has been determined by measuring nonphasematched SHG in a diffraction grating structure. The effect of annealing is to partially restore the intrinsic nonlinearity of the proton-exchanged layer.<>