A design of multi‐layered location registration areas in microcellular systems

Multi‐layered location registration areas are considered to minimize the control signals at boundary cells in the microcellular systems. The decision of multi‐layered location registration (LR) areas is formulated as an integer programming problem by examining the regional subscriber densities, traffic flows and call arrival rates. By relaxing the constraints of forward and reverse control channels the problem is decomposed into a number of subproblems each of which corresponds to a layer. Each subproblem is solved via a modified graph partitioning algorithm. Feasible LR areas are obtained by considering the two relaxed constraints. Computational experiments are performed in a system with 80 microcells to investigate the performance of the proposed multi‐layer scheme. The simulation results indicate that the two‐layer scheme generally outperforms the one‐layer and three‐layer methods in view of control signals. This revised version was published online in August 2006 with corrections to the Cover Date.     

Simultaneous removal of organic and strong nitrogen from sewage in a pilot-scale BNR process supplemented with food waste.

As the sewerage system is incomplete, sewage in Korea lacks easily biodegradable organics for nutrient removal. In this country, about 11,400 tons of food waste of high organic materials is produced daily. Therefore, the potential of food waste as an external carbon source was examined in a pilot-scale BNR (biological nutrient removal) process for a half year. It was found that as the supply of the external carbon increased, the average removal efficiencies of T-N (total nitrogen) and T-P (total phosphorus) increased from 53% and 55% to 97% and 93%, respectively. VFAs (volatile fatty acids) concentration of the external carbon source strongly affected denitrification efficiency and EBPR (enhanced biological phosphorus removal) activity. Biological phosphorus removal was increased to 93% when T-N removal efficiency increased from 78% to 97%. In this study, several kinds of PHAs (poly-hydroxyalkanoates) in cells were observed. The observed PHAs was composed of 37% 3HB (poly-3-hydroxybutyrate), 47% 3HV (poly-3-hydroxyvalerate), 9% 3HH (poly-3-hydroxyhexanoate), 5% 3HO (poly-3-hydroxyoctanoate), and 2% 3HD (poly-3-hydroxydecanoate).     

Effects of shearing and comonomer content on the crystallization behavior of poly(butylene succinate‐co‐butylene 2‐ethyl‐2‐methyl succinate)

Poly(butylene succinate‐co‐butylene 2‐ethyl‐2‐methyl succinate) (PBSEMS) random copolymers were prepared with different comonomer compositions. The effects of shearing and comonomer content on the crystallization behavior of these copolymers were investigated at 80 °C. The thermal and morphological properties of the resulting samples were also discussed. The copolymers showed a longer induction time and a slower crystallization rate with increasing comonomer content. The promoting effect of shear on the overall crystallization behavior was more notable for those copolymers containing more 2‐ethyl‐2‐methyl succinic acid (EMSA) units. The melting temperature of ‘as‐prepared’ poly(butylene succinate) (PBS) was ca. 115 °C, while that of the copolymers varied from 112 to 102 °C. Higher comonomer contents in the copolymers gave rise to lower melting temperatures and broader melting peaks. In addition, the isothermally crystallized samples showed multiple melting endothermic behavior, the extent of which depended on the comonomer content. The copolymers showed different wide‐angle X‐ray diffraction (WAXD) patterns from that of neat PBS, depending on the comonomer content and shear applied during crystallization. With increasing comonomer content, the copolymers crystallized without shearing, showing the shifting of a diffraction peak to a higher angle, while those crystallized under shear did not show any peak shift. Copyright © 2004 Society of Chemical Industry     

Effect of electron- and hole-transporting materials on the performance of FIrpic-doped PVK phosphorescent devices

PVK-based phosphorescent FIrpic-doped devices have been fabricated and the effect of carrier transporting materials on the device performance has been investigated. We have fabricated the single-layer and double-layer devices to investigate the role of electron- and hole-transporting materials both when they are mixed in the single- and separated from the emissive layer. We have studied NPB as a hole-transporting material, OXD-7 and PBD as electron-transporting materials. Even though PBD had been well known to be unsuitable as an electron-transporting material for FIrpic-doped PVK devices, it was found in this study that the separate utilization of PBD from PVK:FIrpic layer instead of mixing it with the emissive layer could enhance the device performance significantly. Nevertheless, the OXD-7 was found not only superior to PBD as the electron-transporting material for FIrpic-doped PVK devices but also suitable as an electron-transporting material for the single-layer devices.     

Design of Scannable Non‐uniform Planar Array Structure for Maximum Side‐Lobe Reduction

In this letter, we propose a novel design scheme for an optimal non‐uniform planar array geometry in view of maximum side‐lobe reduction. This is implemented by a thinned array using a genetic algorithm. We show that the proposed method can maintain a low side‐lobe level without pattern distortion during beam steering.     

Experimental investigations of three-dimensional effects near a crack tip using computer vision

An experimental study of the near tip deformation fields for a Single Edge-Cracked specimen (SEC) has been completed. The surface deformation fields for a thin SEC plexiglas specimen have been obtained in the region 0.15 <- r/t <- 0.60, where r is radial distance from the crack tip and t is the specimen thickness, by using a novel computer vision method. The results of the study indicate that the value of the J-Integral obtained from the measured surface deformation, and under the assumption of plane stress linearly elastic behavior, is essentially path independent over a region that is considered to be within the crack tip three-dimensional zone by researchers who have performed tests on other materials.However, the near-tip, in-plane displacement field does show a deviation from the traditional linear elastic crack tip singularity over the same region, suggesting the need for further studies to address this inconsistency.