Effects of solid retention time on the performance of submerged anoxic/oxic membrane bioreactor.

In this study, four similar bench-scale submerged Anoxic/Oxic Membrane Bioreactors (MBR) were used simultaneously to investigate the effects of solids retention time (SRT) on organic and nitrogen removal in MBR for treating domestic wastewater. COD removal efficiencies in all reactors were consistently above 94% under steady state conditions. Complete conversion of NH(4+)-N to NO(3-)-N was readily achieved over a feed NH(4+)-N concentration range of 30 to 50 mg/L. It was also observed that SRT did not significantly affect the nitrification in the MBR systems investigated. The average denitrification efficiencies for the 3, 5, 10 and 20 days SRT operations were 43.9, 32.6, 47.5 and 66.5%, respectively. In general, the average effluent nitrogen concentrations, which were mainly nitrate, were about 22.2, 27.6, 21.7 and 13.9 mg/L for the 3, 5, 10 and 20 days SRT systems, respectively. The rate of membrane fouling at 3 days SRT operation was more rapid than that observed at 5 days SRT. No fouling was noted in the 10 days and 20 days SRT systems during the entire period of study.     

Production of anti-erythrocyte antibodies by leukemic and nonleukemic B cells in chronic lymphocytic leukemia patients

We have assessed the specificity of antibodies from the leukemic B cells of five patients with both chronic lymphocytic leukemia and autoimmune hemolytic anemia (CLL-AHA). Leukemic cells from one patient displayed surface immunoglobulin with heavy and light chain isotypes identical to that of the patient's anti-red blood cell (RBC) antibodies, and the leukemic cells secreted antibodies in vitro with anti-RBC activity. However, in the remaining patients, the leukemic cells displayed surface immunoglobulin with light chain isotypes different from that of the patient's anti-RBC antibodies and secreted antibodies in vitro with no detectable anti-RBC activity. Thus, there are two distinct classes of CLL-AHA patients, differentiated by the presence or absence of an anti-RBC antibody-producing leukemic B cell clone. The apparent heterogeneity in the source of pathogenic anti-RBC antibodies may impact the treatment response of the two classes of CLL-AHA patients.     

Analysis and measurement of timing error effects in a SAW-basedgroup demodulator

This paper examines the effect of timing errors on QPSK/FDMA signals regenerated by a SAW-based group demodulator. The presence of a timing offset not only degrades the performance of that channel, but also increases the amount of its interference into other channels. Time windowing of the input to the chirp Fourier transform is shown to reduce the impact of the timing errors, but at the cost of an increased output noise variance. Measurements are presented for the bit-error rate (BER) performance of a single channel with a fixed timing offset using a surface acoustic wave (SAW) group demodulator based on the convolve-multiply-convolve (CMC) configuration with Kaiser-Bessel windowing     

The Impacts of an Electronic Marketplace with Multiple Independent Retailers for Smart Grocery Ordering Systems

This study investigates the impacts of an electronic marketplace with multiple independent retailers for a smart grocery ordering system. Apart from replenishing products from suppliers, the system can also purchase/sell products from/to the electronic marketplace through ‘spot shops’. Both static and dynamic pricing models for the electronic marketplace are developed. An extensive numerical experiment is conducted and the results show that under both static and dynamic pricing, (i) the inventory cost of the aggregated supply chain is significantly reduced; (ii) each participant also enjoys significant cost savings from employing the electronic marketplace. Furthermore, the cost savings increase as the lead times from suppliers increase and/or the variability of their demands increases. The participants’ cost savings also increase as more participants employ the electronic marketplace.     

Detailed modeling of sub-100-nm MOSFETs based on Schro/spl uml/dinger DD per subband and experiments and evaluation of the performance gap to ballistic transport

We analyze in detail the requirements for the detailed physical modeling of nanoscale MOSFETs and show that Schro/spl uml/dinger drift-diffusion per subband simulations are adequate for the inverse modeling of bulk-Si MOSFETs with gate length down to 40 nm (channel length down to 26 nm) from their dc electrical characterization. We show that a proper treatment of quantum effects both in the channel and in the polysilicon gate through the direct solution of Schro/spl uml/dinger equation, and a transport model based on two-dimensional subbands are required for accurate and-after calibration-predictive modeling. The model is included in the NANOTCAD2D code (Curatola and Iannaccone, 2003). We also evaluate the performance gap to ballistic transport, by comparing the experiments with simulations based on a fully ballistic transport model on the devices structures extracted with the inverse modeling procedure.     

Conformal array controlled by photonics

A 96-element conformal array controlled by photonics was built and tested for airborne radars. The L-band array consists of 1 km fibre-optic links and a photonic time shift network. There was no beam squint (shift in angle) as the frequency sweeps over the entire band (850-1400 MHz). A nanosecond impulse response was measured to demonstrate a 50% instantaneous bandwidth (550 MHz), corresponding to a 30 cm range resolution     

New Signature Waveforms for Multi-rate QS-CDMA System with QPSK Modulation

This paper presents a multi-rate quasi-synchronous CDMA (QS-CDMA) system with QPSK modulation based on the new signature waveforms, namely GPZ-chip waveforms which are constructed by the generalized pairwise Z-complementary (GPZ) codes and optimal chip waveforms. According to the properties of GPZ-chip waveforms, the multiple access interference of different users can be reduced or eliminated. The interferences among different streams of the same user are handled by an optimal (or suboptimal) multi-stream detector(s). The performance of the proposed system is simulated and analyzed in a cellular communication environment consisting of multipath fading. The result shows that the proposed system has similar performance as compared to the single-rate QS-CDMA system employing GPZ codes with one chip waveform due to the properties of multi-stream detection. Also, the proposed system can achieve a significant interference reduction as compared to the multi-rate system employing concatenated WH/m sequence sets with one chip waveform due to the zero correlation zone properties of the GPZ-chip waveforms, thus resulting better BER performance.     

Porous silicon as an intermediate layer for thin-film solar cell

The potential of porous silicon (PS) with dual porosity structure as an intermediate layer for ultra-thin film solar cells is described. It is shown that a double-layered PS with a porosity of % allows to grow epitaxial Si film at medium temperature (725°–800°C) and at the same time serves as a gettering/diffusion barrier for impurities from potentially contaminated low-cost substrate. A 3.5 μm thin-film cell with reasonable efficiency is realized using such a PS intermediate layer.     

Study of Non-linear Mechanical Behavior of Oil Palm Mesocarp Fibers

This work investigates the non-linear mechanical behavior of oil palm mesocarp fibers (OPMF) using tensile tests, microstructure observation, and finite element models. The micrograph images showed the fiber’s surface with partly embedded silica bodies, while the cross section contained cell wall structures. Viscoelastic behavior was observed when the fibers were relaxed over time after being stretched, whereas the stress--strain curves from the cyclic tests indicated permanent set (plastic strain) due to the fibers’ deformation. Finite element models were developed comprising single particles (2D and 3D) and 2D multi-particle geometries representing silica bodies embedded in a matrix representing the fiber. The modeling results suggested that silica bodies do not contribute much to the integrity of OPMF, highlighting the need to have a more complex model that considers cellular structures of the fibers and a constitutive relationship of cellulose, hemicelluloses, and lignin.