3-D Full-Vectorial Analysis of Strong Optical Waveguide Discontinuities Using Pade Approximants

A full-vectorial 3-D numerical method applicable to high-index contrast optical waveguide discontinuities is presented. Rigorous treatment of the longitudinal boundary condition is incorporated in the formulation. The square root of the characteristic matrix is approximated using Padeacute approximants which results in an efficient implementation. The biconjugate gradient stabilized method is utilized to iteratively calculate the reflected and transmitted fields. A preconditioner is proposed which results in reduced number of iterations. The proposed method is applied to various optical waveguide facets exhibiting strong transverse and longitudinal refractive index discontinuities. In all cases, the modal reflectivities of the fundamental TE-Like and TM-Like modes are calculated for both the full-vectorial and the semi-vectorial formulations. Significant difference in the calculated modal reflectivity is seen between the full and semi-vectorial models. The error in the power balance remains low in the full-vectorial case irrespective of the waveguide dimensions. However, in the semi-vectorial case, the error in the power balance is found to increase when the waveguide width is reduced     

Multi-User Opportunistic Scheduling using Power Controlled Hierarchical Constellations

In this letter, we study an application of hierarchical constellations (known also as embedded, multi-resolution, or asymmetrical constellations) for multi-user opportunistic scheduling. The key idea is to rely on hierarchical constellations to transmit information to two or more best users simultaneously in each transmission. The transmit power as well as the constellation parameter is changed according to the link qualities of the selected users in a way that a given target bit error rate (BER) is satisfied. The expressions for the average transmit power, and the outage probability with truncated channel inversion power control are presented. We also analyze and compare buffer distribution, average buffer occupancy, and packet loss probability of different; schemes via queuing analysis. We finally compare the hierarchical scheme for multi-user scheduling with a uniform constellation-based time-slotted scheme     

Graphene oxide-coated microbottle resonators for relative humidity sensing

Graphene oxide (GO) is a 2D coating material used to improve fiber optics sensors’ response to relative humidity. Microbottle resonators (MBRs) have garnered more attention as sensing media structures. An MBR with a 190 µm diameter was coated with GO. Then, tapered fiber light coupling was used to investigate the relative humidity sensing performance in the range of 35—70%RH at 25 °C. The MBR showed a higher Q factor before and after GO coating. The sensitivity of 0.115 dB/%RH was recorded with the 190 µm GO-coated MBR sample compared to a sensitivity of 0.022 dB/%RH for the uncoated MBR sample. These results show that the MBR can be used in fiber optic sensing applications for environmental sensing.     

Physico-chemical characteristics of palm-based oil blends for the production of reduced fat spreads

The effect of blending and interesterification on the physicochemical characteristics of fat blends containing palm oil products was studied. The characteristics of the palm-based blends were tailored to resemble oil blends extracted from commercial reduced fat spreads (RFS). The commercial products were found to contain up to 20.4% trans fatty acids, whereas the palm-based blends were free of trans fatty acids. Slip melting point of the blends varied from 26.0–32.0°C for tub, and 30.0–33.0°C for block RFS. Solid fat content at 5 and 10°C (refrigeration temperature), respectively, varied from 10.9–19.7% and 8.5–17.6% for tub, and 28.2–38.6% and 20.8–33.5% for block RFS. Melting enthalpy of the tub RFS varied from 35.0–54.3 J/g and that of block RFS varied from 58.0–75.4 J/g. To produce block RFS, 65% palm oil (PO) and 18% palm kernel olein (PKOo) could be added in a ternary blend with sunflower oil (SFO), but only 47% PO and 10% PKOo are suggested for tub RFS. Higher proportion of PO, i.e., 72% for block RFS and 65% for tub RFS, could be used after the ternary blend was interesterified. Although a ternary blend of palm olein (POo)/SFO/PKOo was not suitable for RFS formulation, after interesterification as much as 90% POo and 26% PKOo could be used in the block RFS formulation. For tub RFS a maximum of 30% POo was found suitable.     

Improvement of thermal conductivity and dielectric constant of graphene-filled epoxy nanocomposites using colloidal polymerization approach

Polymer Bulletin - The effect of the polymeric cross-link density on the thermal conductivity of an oxidized graphene (OG)-filled epoxy nanocomposite was investigated by two different fabrication...     

Adhesion of cornstarch-g-poly (2-hydroxyethyl acrylate) to cotton fibers in sizing

Abstract

A range of starch-g-poly (2-hydroxyethyl acrylate) (S-g-PHEA) with different grafting ratio was prepared by graft copolymerization of 2-hydroxyethyl acrylate (HEA) onto granular cornstarch using ammonium cerium nitrate as initiator. The adhesive ability of the sizes to cotton fibers, film properties, and desizing ability of HEA branch grafted onto starch were investigated. The effects of grafting conditions (such as reaction time, temperature, HEA and initiator concentration, etc.) on grafting ratio and efficiency were investigated. Fourier transformed infrared spectroscopy (FTIR) and Thermogravimetric analysis (TGA) was employed to characterize the complexes of S-g-PHEA. The effect of grafting ratio on the sizing properties of grafted starch was studied by testing the ability of the grafted starch to adhere to cotton fiber and film properties. It was confirmed that the HEA branch can effectively improve the adhesion ability of starch to cotton fibers, improves the flexibility of the starch film while reduces the brittleness, and enhances the abrasion resistance of the yarns (the highest enhancement ratio up to 225.71%). An increase in the grafting ratio facilitates the adhesion to the cotton fibers while making the desizing difficult. The desizing efficiency was high when the grafting ratio was less than 10%, which lead to easy access to desizing and then fewer residues have remained, and at the same time, good sizing performance is maintained, which indicates that the S-g-PHEA possesses the application potential of cotton warp sizing.     

Development of a three-part time-of-day electrical energy tariff

This paper presents an analytical technique for determining peak, offpeak and midpeak hours tariffs for various durations of these three periods. The technique considers the existing flat rate tariff, an hourly generation scenario of a utility on an average yearly demand day, the weighted average life time, annutised capital cost and fuel cost of base and peak load plants, and a break even point condition in the utility's revenue. The developed tariff has been applied to 30 representative industrial consumers served by the Bangladesh Power Development Board (BPDB) to estimate the minimum possible shift in consumption pattern and hence corresponding reduction in peak generation capacity requirement as well as peak time load shedding by BPDB. © 1998 John Wiley & Sons, Ltd.