Producing persistent, high-current, high-duty-factor H- beams for routine 1 MW operation of Spallation Neutron Source (invited)

Since 2009, the Spallation Neutron Source (SNS) has been producing neutrons with ion beam powers near 1 MW, which requires the extraction of ～50 mA H(-) ions from the ion source with a ～5% duty factor. The 50 mA are achieved after an initial dose of ～3 mg of Cs and heating the Cs collar to ～170 °C. The 50 mA normally persist for the entire 4-week source service cycles. Fundamental processes are reviewed to elucidate the persistence of the SNS H(-) beams without a steady feed of Cs and why the Cs collar temperature may have to be kept near 170 °C.     

Dream patterns in Anglo and Chicano young adults

This study is the conclusion of an exploratory cross-cultural investigation of dream content and organization. Following our report in "Ego Modalities in the Manifest Dreams of Male and Female Chicanos," (Brenneis and Roll, 1975), this paper examines differences in the organization and content of dreams: (1) between Anglo men and women; (2) between Anglo and Chicano men and Anglo and Chicano women; and (3) between Anglos and Chicanos.     

Calculations of diffusion and diffusion-limited processes in Ni3Al using accelerated molecular dynamics

We present a systematic microscopic approach to diffusion and diffusion-limited processes in Ni₃Al. These processes have been identified as controlling the deformation of the material under specific circumstances. The embedded atom method calculations are done using kinetic Monte Carlo combined with the Dimer method of finding saddlepoints. We compute the tracer diffusivities as functions of composition and temperature. The comparison with available experiments is good. We find that at temperatures below about 1000 K, the diffusivity is a sharp function of composition, showing a pronounced dip on the Ni-rich side at 76 at.% Ni. This agrees well with experiment, except that the experiments show this structure setting in a temperatures below about 1300 K. We show that the structure arises from the composition dependence of both the vacancy formation energy and pre-exponential of the diffusivity. We also compute the mobility of an anti-phase boundary perpendicular to its plane, and conclude that vacancy-assistance is very plausible. We conclude that the kMC + Dimer method works well for these problems above 700 K but less effectively below, owing to the presence of short-range, low-energy hops that tend to localize the vacancy and lower the efficiency of the calculation.     

A 3-GHz 70-mb SRAM in 65-nm CMOS technology with integrated column-based dynamic power supply

Column-based dynamic power supply has been integrated into a high-frequency 70-Mb SRAM design that is fabricated on a high-performance 65-nm CMOS technology. The fully synchronized design achieves a 3-GHz operating frequency at 1.1-V power supply. The power supply at SRAM cell array is dynamically switched between two different voltage levels during READ and WRITE operations. Silicon measurement has proven this method to be effective in achieving both good cell READ and WRITE margins, while lowering the overall SRAM leakage power consumption.     

Fabrication of epitaxial III-nitride cantilevers on silicon (1 1 1) substrates

The molecular beam epitaxy of AlGaN/GaN epilayers on silicon (1 1 1) using an aluminum nitride buffer layer, and subsequent fabrication of free standing III-nitride cantilevers on Si(1 1 1) has been investigated. Transmission electron microscopy (TEM) of cross-section samples reveals a columnar structure consisting of the hexagonal gallium nitride polytype. Selected area diffraction indicates an epitaxial relationship between the gallium nitride and silicon substrate which is described by GaN[0 0 0 1]//Si[1 1 1] and GaN(1 1 0 0)//Si(1 1 1). Imaging of the electronic structure of an AlGaN/GaN interface has been investigated by mapping the variation in the plasmon frequency using an electron energy loss spectrometer on a dedicated scanning transmission electron microscope. Cantilevers were fabricated using a combination of etching processes. Nitride etch rates during inductively coupled plasma dry etch processing using a Cl₂/Ar plasma etchant were obtained by monitoring the optical reflectivity of the nitride films in situ. A peak GaN etch rate of 250 nm/min was measured, the etch rate was found to be strongly dependent on the d.c. self-bias. Thin beams of GaN having a length of 7 μm and 0.7 μm thickness, were fabricated and mechanically released from Si(1 1 1) substrates using a combination of two dry ICP etch processes, using Cl₂/Ar and CF₄/Ar/O₂ chemistries, and a potassium hydroxide (KOH) aqueous wet etch.     

Positions of Truthfully Answered Controls on Control Question Tests With the Polygraph.

Students (N = 120) guilty of a mock crime, innocent and informed, or innocent and uninformed of crime details were examined by polygraph with an altered form of Control Question Test (CQT). Ambiguous, lie-engendering control questions were altered to form clear direct questions answered truthfully. When these control questions were positioned before crime-relevant questions, most guilty and innocent participants were correctly classified. Most participants were classed as guilty when crime-relevant questions were positioned before control questions. Lying to crime-relevant questions in the second position resulted in skin resistance, F(2,108) = 8.2, and blood volume, F(2, 108) = 6.1, responses larger than Orienting Responses to initial control questions. Accurate detection depends on the position of control questions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of Clinic Layouts and Patient-Centered Procedural Innovations Using Discrete-Event Simulation

Abstract

Given that healthcare costs in the U.S. continue to climb, engineering managers can help address this situation by identifying designs for cost savings. Using discrete-event simulation, the layout of four different healthcare clinic scenarios considered in a redesign program named Patient Aligned Care Teams were studied. Model 1 is an existing layout in many clinics and Model 2 is staff-centered, while Models 3 and 4 provide additional space including common hallway(s). Our main conclusion is that Model 4 reduces patient travel distances and average queueing waits, while also providing the best privacy in accordance with HIPAA and the most security for the staff.