Computer model of the trapping media in micro FLASH® memory cells

A computer model for the dielectric trapping layer in the microFLASH memory transistor is developed. Due to local trapping of injected charges in corresponding devices the problem of lateral charge migration in the plane parallel to the transistor channel becomes of principal importance. Molecular Dynamics method was used to design a cluster of atoms with dielectric properties and to perform computer simulation of the redistribution of the injected charges in the program/erase processes. The charge distributions obtained on the basis of proposed model are strongly influenced by Coulomb repulsion between the trapped charge carriers. This effect leads to non-Gaussian discrete space distribution of trapped charges and significantly influences the endurance of the memory device. We demonstrate that large densities of traps and injected carriers are strongly correlated, limiting the amount of charge that can be accumulated in the programming process. The model allows select optimum parameters of the trapping layer to ensure high retention properties of the memory cells.     

High-Throughput Screening of Nanoparticle-Stabilizing Ligands: Application to Preparing Antimicrobial Curcumin Nanoparticles by Antisolvent Precipitation

Nano-Micro Letters - Water-dispersible curcumin nanoparticles were prepared by bottom-up antisolvent precipitation approach. A new high-throughput screening technique was developed for selecting...     

Effect of processing and density on morphology and creep behavior of linear low‐density polyethylene

Creep behavior of 40‐ and 80‐μm‐thick films of linear low‐density polyethylene with four different densities produced by blowing and casting processes was investigated at room temperature (RT) and 70°C. As a criterion for ductile creep failure, strain‐to‐failure was chosen, which amounts to the maximum elongation characterized by necking of the whole sample. At RT under the stress of 8 MPa, strain‐to‐failure increases by one order of magnitude (from 0.08 to 0.80) with a decrease in density from 0.930 to 0.902 g/cm³. Processing effects creep deformation much less significantly in comparison with density. It is found that under loading at RT, some amount of orthorhombic phase in films with the densities of 0.902 and 0.912 g/cm³ transforms into the monocline phase. The intensity of a peak of this phase near the angle 2θ of 19.5° does not depend on the test duration. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

A dynamically generated fuzzy neural network and its application to torsional vibration control of tandem cold rolling mill spindles

Based on the model of Higgins and Goodman, we describe a dynamically generated fuzzy neural network (DGFNN) approach to control, from input–output data, using on-line learning. The DGFNN is complete with the following powerful features drawn or modified from the existing literature: (1) a small FNN is created from scratch—there is no need to specify initial network architecture, initial membership functions, or initial weights, (2) fuzzy rules are constantly combined and pruned to minimize the size of the network while maintaining accuracy, irrelevant inputs are detected and deleted; and (3) membership functions and network weights are trained with a backpropagation-type algorithm. We apply the DGFNN controller to a real-world application of controlling the torsional vibration of tandem cold-rolling mill spindles with a simulated plant. The results of the DGFNN controller are compared with the performances of a conventional proportional-integral controller and a neural controller using recurrent cascade correlation with quickpropagation through time. We show that while both neural approaches increase the control precision and robustness, the DGFNN controller gives the best results for reducing the speed deviation and suppressing the torsional vibration of the spindles, as well as is more computationally efficient.     

Computer model of the trapping media in micro FLASH? memory cells

A computer model for the dielectric trapping layer in the microFLASH memory transistor is developed. Due to local trapping of injected charges in corresponding devices the problem of lateral charge migration in the plane parallel to the transistor channel becomes of principal importance. Molecular Dynamics method was used to design a cluster of atoms with dielectric properties and to perform computer simulation of the redistribution of the injected charges in the program/erase processes. The charge distributions obtained on the basis of proposed model are strongly influenced by Coulomb repulsion between the trapped charge carriers. This effect leads to non-Gaussian discrete space distribution of trapped charges and significantly influences the endurance of the memory device. We demonstrate that large densities of traps and injected carriers are strongly correlated, limiting the amount of charge that can be accumulated in the programming process. The model allows select optimum parameters of the trapping layer to ensure high retention properties of the memory cells.     

Analysis of the kinetics and current efficiency of pyrrole galvanostatic electropolymerization

We propose a modified kinetic equation for the galvanostatic electropolymerization of pyrrole based on equal rates of monomer disappearance and its galvanostatic electropolymerization associated with applied current (I). The equation is distinguished by a zero‐order kinetic plot and takes into account the effects of the pyrrole initial concentration ([M]₀) and current efficiency (η). We propose a mechanism for obtaining a η of less than 100% and increasing η with increasing [M]₀ and I on the basis of the diffusion of radical cations (M^?+) from the anode surface to the bulk solution after the electroreduction of M^?+ to monomer molecules at the cathode. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1167–1169, 2005     

Biofilm morphology as related to the porous media clogging

Aquifer recharge for the wastewater reuse has been considered and studied as a promising process to cope with the worldwide water scarcity. Soil clogging by an excessive growth of bacteria is often accompanied with the aquifer recharge. In this study, biofilm morphology and hydraulic conductivity were concurrently characterized at two flow rates and two levels of substrate concentrations. The experiments were conducted using a biofilm flow cell that was filled with glass beads. The biofilm images taken by confocal laser scanning microscopy (CLSM) were quantified by textural, areal, and fractal parameters. Hydraulic conductivity was monitored during the experiments. The flow velocity influenced the superficial morphology of biofilms and initial clogging time, while the substrate concentration affected biofilm density and clogging rate. Three different clogging mechanisms were suggested depending on the flow rate and substrate concentration: (1) clogging at a high flow rate can be accelerated by entrapped and accumulated biofilms, and can be easily eliminated by high shear force, (2) clogging at a low flow rate can be delayed for the time of local biofilm growths in the narrow pore necks, but the biofilm is rigid enough not to be sloughed, and (3) clogging in a solution with high substrate concentrations cannot be easily eliminated because of the growth of dense biofilms. The depicted biological clogging mechanisms will play a role in supporting studies about aquifer recharge.     

Development of THz-range Gyrotrons for Detection of Concealed Radioactive Materials

The Center for Applied Electromagnetics (AppEl) at the University of Maryland had started development of a sub-THz gyrotron for detecting concealed radioactive materials. The concept is based on the use of a high-power gyrotron whose power being focused in a small spot with dimensions on the order of a wavelength exceeds the threshold level required for initiating a freely localized microwave breakdown in air. However, in the absence of radioactive materials, the ambient electron density is so small that there is a very small probability to find a free electron in this small volume to trigger the avalanche breakdown process. Therefore the fact that the breakdown was observed would indicate that there is a hidden radioactive material in the vicinity of a focused wave beam. We present the design data for a 200?C300 kW, 670 GHz gyrotron operating with a pulsed solenoid and describe a single-shot pulsed solenoid producing 27?C28 T magnetic fields. Also numerous issues in this specific application are discussed, viz. threshold conditions for initiating the breakdown, production of gamma rays by concealed radioactive materials and their role in producing low energy electrons outside a container, wave beam focusing in a small spot by a limited-size antenna, random walk of energetic electrons which may result in appearance of free electrons in a given volume during the RF pulse and comparison of diffusion time with the time required for competing processes, such as ionization and three-body attachment.     

Effects of 15 years of manure and inorganic fertilizers on soil organic carbon fractions in a wheat-maize system in the North China Plain

Soil organic carbon (SOC) and its labile fractions are strong determinants of chemical, physical, and biological properties, and soil quality. Thus, a 15-year experiment was established to assess how diverse soil fertility management treatments for winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) cropping system affect SOC and total N (TN) concentrations in the North China Plain. The field experiment included three treatments: (1) unfertilized control (CK); (2) inorganic fertilizers (INF); and (3) farmyard manure (FYM). Concentrations of SOC, TN, and different labile SOC fractions were evaluated to 1-m depth. In comparison with INF and CK, FYM significantly increased SOC and TN concentrations in the 0–30 cm depth, and also those of dissolved organic C (DOC), microbial biomass C (MBC), hot-water extractable C (HWC), permanganate oxidizable C (KMnO₄–C), and particulate organic C (POC) in the 0–20 cm depth. Despite the higher crop yields over CK, application of INF neither increased the SOC nor the labile C fractions, suggesting that by itself INF is not a significant factor affecting SOC sequestration. Yet, POC (18.0–45.8% of SOC) and HWC (2.0–2.8%) were the most sensitive fractions affected by applications of FYM. Significantly positive correlations were observed between SOC and labile organic C fractions in the 0–20 cm depth. The data support the conclusion that, wherever feasible and practical, application of FYM is important to soil C sequestration and improving soil quality under a wheat/maize system in the North China Plain.