Filters
Availability
Publication Year
Resource Type
Faculty
School/Institute
Publication Search Results
Sort
Results per page
1 - 10 of 12
-
(1998)Journal ArticleThe first results obtained using a SOI device for microdosimetry applications are presented. Microbeam and broadbeam spectroscopy methods are used for determining minority carrier lifetime and radiation damage constants. A spectroscopy model is presented which includes the majority of effects that impact spectral resolution. Charge collection statistics were found to substantially affect spectral resolution. Lateral diffusion effects significantly complicate charge collection
-
(1998)Journal ArticleSingle-address-space operating systems (SASOS) are an attractive model for making the best use of the wide address space provided by the latest generations of microprocessors. SASOS remove the address space boundaries which make data sharing between processes difficult and expensive in traditional operating systems. They offer the potential of significant performance advantages for applications where sharing is important, such as object-oriented databases or persistent programming systems. We have built the Mungi system to demonstrate that a SASOS can offer these performance advantages without resorting to special hardware. Mungi is a very `pure` SASOS, featuring an unintrusive protection model based on sparse capabilities, a fast protected procedure call mechanism, and uses shared memory as the exclusive inter-process communication mechanism, as well as for I/O. The simplicity of our model makes it easy to implement it efficiently on conventional architectures. Our implementation of Mungi for the MIPS R4600 64-bit microprocessor is presented, which is based on our port of the L4 microkernel. Mungi is shown to outperform, in some instances by more than an order of magnitude, two UNIX operating systems, Irix and Linux, in several important operations, such as task creation and inter-process communications, and on the OO1 object-oriented database benchmark. As well, we describe how our approach to key issues in SASOS design provides better performance than other systems, such as Opal. Our experience shows that the SASOS concept is viable, and that a well-designed microkernel is an excellent base on which to build high-performance operating systems.
-
-
(1998)Journal ArticleYBa2Cu3O7-y with high grain alignment has been successfully fabricated by a modified powder melting process at a temperature of ~930oC which is near the eutectic point of the starting materials Y2BaCuO5, BaCuO2, and CuO. In terms of the levitation force and YBa2Cu3O7-y grain alignment, the best result was shown in a sample having a Y2BaCuO5:BaCuO2:CuO molecular ratio of 1:3:5. In the present work, the Cu-surplus eutectic liquid was completely absorbed by use of a Y2BaCuO5 substrate, by which the final composition was driven to stoichiometric YBa2Cu3O7-y. The results were comparable to those obtained by the conventional melt-texture-growth process. A new invariant point apparently occurred at ~930-940oC owing to an interfacial reaction between YBa2Cu3O7-y matrix and Y2BaCuO5 substrate.
-
(1999)Journal ArticleUsing near-infrared imaging and spectroscopy, we discuss the discovery of six emission-line sources within 20 pc of Sgr A West but outside of the central parsec. The objects are coincident with stars seen in the J, H, and K images; all have Brγ (2.166 μm) in emission, several also have He i (2.058 and 2.112/3 μm), and some have He ii (2.189 μm) emission lines. Comparison of the H- and K-band spectra of the newly discovered stars with recently published infrared spectral atlases of optically classified stars suggests that most of these stars are similar to massive stars in transition (e.g., Ofpe/WN9, B[e], and LBV), although one is definitely a WN6 star. Two of the potential stars are associated with the radio emission regions A–D near Sgr A East, three are near or within the radio emission regions H1–H8 (nomenclature from Yusef-Zadeh & Morris), the last is near G0.10+0.02 and is likely to be associated with the G0.12+0.02 (Arches) cluster of stars, discussed in a previous paper. The stars are shown to be significant sources of ionization for their associated radio emission regions, with several capable of completely ionizing the regions. These results provide additional support for the idea that these thermal radio regions, and similar such regions in the Galactic center, are indeed photoionized by hot young stars.
-
-
-
-
-