The transmission of digital signals through random, time-variant, dispersive channels with application to chaff scatter

This paper is a report on the characterization and modeling of a specific dispersive communication channel, a chaff scatter channel. Theoretical and experimental results are given. The basic modeling of the chaff scatter channel as a linear, time-variant, random-parameter filter is given and its salient properties developed. Based on this model, a theoretical analysis of a continuous-phase binary FSK communications system operating over the chaff scatter channel is given. Experimental results obtained in the use of this system on an actual chaff scatter channel are then presented and compared with the theoretical results.     

A control and management network for wireless ATM systems

This paper describes the design of a control and management network (orderwire) for a mobile wireless Asynchronous Transfer Mode (ATM) network. This mobile wireless ATM network is part of the Rapidly Deployable Radio Network (RDRN). The orderwire system consists of a packet radio network which overlays the mobile wireless ATM network. Each network element in this network uses Global Positioning System (GPS) information to control a beamforming antenna subsystem which provides for spatial reuse. This paper also proposes a novel Virtual Network Configuration (VNC) algorithm for predictive network configuration. A mobile ATM Private Network–Network Interface (PNNI) based on VNC is also discussed. Finally, as a prelude to the system implementation, results of a Maisie simulation of the orderwire system are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Computer Modeling of the Local Telephone Network

In this paper, we describe the structure and operation of an innovative computer-based model of the local exchange telephone network known as the HCPM. This model can be used in a variety of regulatory arenas, since it provides a regulatory agency with an independent source of information about the forward-looking costs of providing local telephone service. The model can also be used more broadly by governmental agencies in planning for infrastructure development, expanding telephone service to currently unserved areas, or, as in the case of the U.S., designing an efficient universal service program. The HCPM represents an advance over previous models in its ability to build plant to precise customer locations if data are available, while retaining the flexibility of being able to produce good results even with more highly aggregate location data such as those available from the U.S. Census.     

Structural characterization of drug-like compounds by ion mobility mass spectrometry: comparison of theoretical and experimentally derived nitrogen collision cross sections

We present the use of drug-like molecules as a traveling wave (T-wave) ion mobility (IM) calibration sample set, covering the m/z range of 122.1-609.3, the nitrogen collision cross-section (Ω(N(2))) range of 124.5-254.3 ?(2) and the helium collision cross-section (Ω(He)) range of 63.0-178.8 ?(2). Absolute Ω(N(2)) and Ω(He) values for the drug-like calibrants and two diastereomers were measured using a drift-tube instrument with radio frequency (RF) ion confinement. T-wave drift-times for the protonated diastereomers betamethasone and dexamethasone are reproducibly different. Calibration of these drift-times yields T-wave Ω(N(2)) values of 189.4 and 190.4 ?(2), respectively. These results demonstrate the ability of T-wave IM spectrometry to differentiate diastereomers differing in Ω(N(2)) value by only 1 ?(2), even though the resolution of these IM experiments were ～40 (Ω/ΔΩ). Demonstrated through density functional theory optimized geometries and ionic electrostatic surface potential analysis, the small but measurable mobility difference between the two diastereomers is mainly due to short-range van der Waals interactions with the neutral buffer gas and not long-range charge-induced dipole interactions. The experimental RF-confining drift-tube and T-wave Ω(N(2)) values were also evaluated using a nitrogen based trajectory method, optimized for T-wave operating temperature and pressures, incorporating additional scaling factors to the Lennard-Jones potentials. Experimental Ω(He) values were also compared to the original and optimized helium based trajectory methods.     

Study of the Fate of Lipophilic Wood Extractives During Acid Sulphite Pulping Process by Ultrasonic Solid-Liquid Extraction and Gas Chromatography Mass Spectrometry

Abstract

Lipophilic extractives in dissolving pulp are still a big concern for pulp industries due to their detrimental effect on the quality of pulp. Since lipophilic extractives remaining in pulp are trapped in low-accessible fiber structures, effective extraction methods need to be established for studying their fate in the process. A simple, ultrasonic, solid liquid extraction established in this study was found to be more effective in capturing extractive residues in all “elemental chlorine-free” bleaching stages. Its efficiency was dependent on the extraction temperature, time, and solvent composition. A linearly correlated removal pattern of sterols and unsaturated fatty acids by the bleaching sequence was observed. It was further found that the bleaching combination did not fully remove lipophilic extractives. This study suggests an opportunity to explore ultrasonication-based extraction as an effective extraction procedure prior to gas chromatography mass spectrometry analysis for monitoring extractives in pulp.     

Grain Growth Phenomena in the Interface Region of α-Alumina Bilayer Composites

Microstructural development in the interface region of α-Al₂O₃ bilayer composites has been systematically investigated in terms of the sintering additive CaO–SiO₂, residual impurity level in the starting powders (particularly MgO), and sintering conditions. The interfacial microstructure is strongly related to relative CaO–SiO₂ doping levels in the two constituting layers and to residual impurities in the starting powders. The presence of high levels of impurities in the starting powder can substantially modify the features of CaO–SiO₂-Al₂O₃ liquid at the interface region, thereby strongly influencing α-Al₂O₃ grain growth across the interface. Three grain growth modes in the interface region thus have been identified for different combinations of impurity level and CaO–SiO₂ dopant in the α-Al₂O₃ bilayer. This provides an important mechanism for controlling two-dimensional structures in coatings, films, and layered ceramic materials for various engineering applications.     

Transformations for within-subject designs: A Monte Carlo investigation.

Explored the use of transformations to improve power in within-S designs in which multiple observations are collected for each S in each condition, such as reaction time (RT) and psychophysiological experiments. Often, the multiple measures within a treatment are simply averaged to yield a single number, but other transformations have been proposed. Monte Carlo simulations were used to investigate the influence of those transformations on the probabilities of Type I and Type II errors. With normally distributed data, Z and range correction transformations led to substantial increases in power over simple averages. With highly skewed distributions, the optimal transformation depended on several variables, but Z and range correction performed well across conditions. Correction for outliers was useful in increasing power, and trimming was more effective than eliminating all points beyond a criterion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dielectrophoretically controlled fabrication of single-crystal nickel silicide nanowire interconnects

We report here on applying electric fields and dielectric media to achieve controlled alignment of single-crystal nickel silicide nanowires between two electrodes. Depending on the concentration of nanowire suspension and the distribution of electrical field, various configurations of nanowire interconnects, such as single, chained, and branched nanowires were aligned between the electrodes. Several alignment mechanisms, including the induced charge layer on the electrode surface, nanowire dipole-dipole interactions, and an enhanced local electrical field surrounding the aligned nanowires are proposed to explain these novel dielectrophoretic phenomena of one-dimensional nanostructures. This study demonstrates the promising potential of dielectrophoresis for constructing nanoscale interconnects using metallic nanowires as building blocks.