Effects of Ti on N distribution and diffusion in FeTiN thin films

We studied the distribution and diffusion of N atoms in FeTiN single-layer and bilayer thin films by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). We found that in as-deposited films N atoms are first absorbed by Ti atoms, the rest being dissolved into FeTi lattices. Ti not only directly absorbs N by chemical bonding, but also decreases the energy of the N atoms that are dissolved into FeTi lattices. The diffusion study of N atoms in single layer and bilayer films showed that although the presence of Ti stabilized the /spl alpha/ phase of FeTi lattices during 200/spl deg/C annealing, the diffusion length of dissolved N in FeTi (Ti/spl les/8 at.%) lattices was still comparable to the diffusion length of N in pure Fe. Thus, the addition of a small amount of Ti in /spl alpha/-Fe lattice can not completely stabilize N atoms in the film, and the induced magnetic anisotropy of the films can still be unstable, although the /spl alpha/ phase of FeTiN is stabilized by the addition of Ti. The distribution of N atoms in bilayer films can be fitted by a simple enthalpy model.     

A New Distribution System Reconfiguration Approach Using Optimum Power Flow and Sensitivity Analysis for Loss Reduction

This paper presents a new approach for distribution system reconfiguration (DSR) based on optimum power flow (OPF) in which the branch statuses (open/close) are represented by continuous functions. In the proposed approach, all branches are initially considered closed, and from the OPF results, a heuristic technique is used to determine the next loop to be broken by opening one switch. Then the list of switches that are candidates to be opened is updated, and the above process is repeated until all loops are broken, making the distribution system radial. This paper includes results and comparisons on test systems utilized in three classical papers published in the technical literature, as well as in a previous paper by the authors. Results obtained on a real large-scale distribution system are also presented     

The transistor laser

A research team at the University of Illinois at Urbana-Champaign has developed a new, more powerful kind of device, called the transistor laser. The transistor puts out both electrical signals and a laser beam, which can be directly modulated to send optical signals at the rate of 10 billion bits per second. With some further modification, the transistor laser will eventually send a staggering 100 billion bits per second or more. Instead of using relatively slow wires to connect chips stacked together in packages, transistor lasers can be used as optical interconnects, which would let data flow instantaneously to and from memory chips, graphics processors, and microprocessors. There is much work ahead, but unlike the host of self-assembling, blue-sky nanotechnologies currently being touted as the next big thing in optoelectronics, transistor lasers do not need an entirely new fabrication infrastructure for further development or even to go into production.     

A Comparative Study of High-Field Diamagnetic Fluctuations in Deoxygenated YBa2Cu3O7-x and Polycrystalline (Bi–Pb)2Sr2Ca2Cu3O10

We studied three single crystals of YBa₂Cu₃O_7-x, (Y123) with superconducting transition temperature, T_c=62.5, 52, and 41 K, and a highly textured polycrystalline specimen of (Bi–Pb)₂Sr₂Ca₂Cu₃O₁₀ (Bi2223), with T_c=108K. Isofield magnetization data were obtained as a function of temperature, with the magnetic field applied parallel to the c axis of each sample. The reversible magnetization data for all samples exhibited a rounded transition as magnetization tended toward zero. The reversible data were interpreted in terms of two-dimensional diamagnetic lowest-Landau-level (LLL) fluctuation theory. The LLL scaling analysis yielded consistent values of the superconducting transition temperatures T_c(H) for the various samples. The resulting scaling data were fit well by the two-dimensional LLL expression for magnetization obtained by Tesanovic and colaborators, producing reasonable values of κ but the fitting parameter ∂H_c2/∂T produced values that were larger than the experimentally determined ones. We performed simultaneous scaling of Y123 data and Bi2223, obtaining a single collapsed curve. The single curve was obtained after multiplying the x and y axis of each scaling curve by appropriate sample-dependent scaling factors. An expression for the two-dimensional x-axis LLL scaling was extracted from theory, allowing comparison of theoretical values of the x-axis scaling factors with the experimental values. The comparison between the values of the x-axis produced a deviation of 40% which suggests that the hypothesis of universality of the two-dimensional LLL fluctuations is not supported by the studied samples. We also observe that Y123 magnetization data for temperatures above T_c obbey a universal scaling obtained for the diamagnetic fluctuation magnetization from a theory considering non-local field effects. The same scaling was not obbeyed by the corresponding magnetization calculated from the two-dimensional LLL theory.     

The wettability of titanium diboride by molten aluminum drops

Titanium diboride is widely accepted to be completely wet by liquid aluminum, yet few published wetting studies demonstrate this behavior, and reported contact angles vary widely. Sessile drop substrates from four different sources were selected and their microstructures and chemistries characterized. The results of sessile drop experiments using four techniques to modify oxide film behavior were compared. The Al-TiB₂ interfaces were examined in metallographic sections or after chemical removal of the Al drop. Al wets a material containing 5.5 wt% Ni in vacuum experiments before the hold temperature of 1025^° C is reached. The other TiB₂ substrates are completely wet by Al at 1025^° C, but only after prolonged holds under vacuum. Elimination of boron oxide from the TiB₂ surface leads to a spreading condition. The role of the substrate microstructure (porosity, grain size, roughness, and carbon content) in altering the wetting kinetics is discussed.     

Virtual private networks: leveraging the Internet

Proponents say virtual private networks could be the wave of the networking future for one very important reason: VPNs transmit data via the Internet, rather than via expensive traditional private networks. Proponents are quick to mention the significant cost savings organizations can realize by using networks that employ the Internet backbone as a data pipeline rather than networks that rely on leased lines, frame-relay technology, and dialup connections for private WANs. However, as with many Internet technologies, potential VPN users are concerned about possible security, reliability, and performance problems. ln addition, a lack of open standards has created concerns about compatibility. The industry is working toward adoption of such standards, but it remains to be seen whether this will lend credibility to VPN technology     

Using a microprocessor-based instrument to predict the incident energy from arc-flash hazards

With better understanding of arc flashes, the electrical safety industry continues to develop new safety procedures for electrical workspaces. To assess the potential arc hazards of a workspace, workers must rely on engineering fault studies to provide vital fault-current data. An instrument, based on a network impedance analyzer, determines the maximum flash-arc incident-energy exposure at a worksite within a few seconds. The digital analyzer measures the power system source impedance, X/R ratio, and the system voltage to predict the bolted fault current and incident energy, while the power distribution system is energized and in normal operation. The instrument computes the incident energy for standard electrical workspaces of an open-air arc and an enclosed box with one open side. Experiments have been conducted to verify the accuracy of the impedance and X/R ratio measurements.     

Calculation of neutron and gamma-ray energy spectra for fusion reactor shield design: Comparison with experiment-II

Measured and calculated neutron and gamma-ray energy spectra resulting from the transport of 14 MeV neutrons through a 0.30-m-thick lithium hydride slab and through a 0.05-m-thick lead slab followed by 0.30 m of lithium hydride are compared. Also reported are comparisons of the measured and calculated neutron energy spectra behind an 0.80-m-thick assembly comprised of stainless steel type 304 and borated polyethylene. The spatial dependence of the gamma-ray energy deposition rate measured using thermoluminescent detectors is compared with calculated data. The calculated data obtained using two-dimensional radiation transport methods and ENDF/B-IV cross-section data are in good agreement for all of the experimental configurations. Calculated integral neutron energy spectra agree with the measured data within 5 to 20% depending on neutron energy for the LiH and Pb plus LiH assemblies. The gamma-ray spectra agree within 20% for these slabs. The measured and calculated neutron energy spectra behind the SS-304-borated polyethylene assembly agree within 5% except at neutron energies below 5 MeV where background radiation influences the measured spectra. The gamma-ray energy deposition rates as a function of depth agree within a factor of two at all detector locations.     

Measuring implementation outcome: beyond success and failure

This paper proposes a framework for measuring the impact of a computer-based application in an organization. Recognizing the complexity of the implementation process, the framework is multi-dimensional: it seeks to measure the outcome of an implementation effort on both the people and tasks affected as separate from user's definition of “success”. The framework can be used to support either the quantitative or case study methodologies used in implementation research. Finally, the authors describe a field test of the framework to demonstrate its usefulness in an organizational setting.     

Uranium Superconductivity Redux

Since the discovery of heavy-fermion superconductivity in uranium compounds in the early 1980s, other uranium compounds have been discovered that are fully as interesting to study. However, as we look forward in the year 2000, we now have higher-purity, single crystals of the element itself. Preliminary resistivity and ac susceptibility measurements show the improved quality of the samples and thus hold the promise of understanding many aspects of its superconductivity, which have remained untouched for almost 25 years.