Transformation toughened ceramics for the heavy duty diesel engine technology program

The objective of this program is to develop an advanced high temperature oxide structural ceramic for application to the heavy duty diesel engine. The approach is to employ transformation toughening by additions of ZrO.5HfO.5O2 solid solution to the oxide ceramics, mullite (2Al2O3S2SiO2) and alumina (Al2O3). The study is planned for three phases, each 12 months in duration. This report covers Phase 1. During this period, processing techniques were developed to incorporate the ZrO.5HfO.5O2 solid solution in the matrices while retaining the necessary metastable tetragonal phase. Modulus of rupture and of elasticity, coefficient of thermal expansion, fracture toughness by indent technique and thermal diffusivity of representative specimens were measured. In Phase 2, the process will be improved to provide higher mechanical strength and to define the techniques for scale up to component size. In Phase 3, full scale component prototypes will be fabri-]cated

Responses of Three Coral Communities to the 1997–98 El Niño–Southern Oscillation: Galápagos Islands, Ecuador

One deep (13–15 m depth) and two shallow water (1.5 and 7 m) coral communities in the Galápagos Islands, Ecuador were monitored for tissue response (bleaching, paling, morbidity) and secondary responses during and after elevated temperature stress associated with the 1997–98 El Niño–Southern Oscillation (ENSO) event. Between March and May 1998, the fungiid coral Diaseris distorta paled and bleached (up to 88.0% of all individuals bleached) at 13–15 m depth. The small branching colonial coral, Psammocora stellata, paled (79.2% of all colonies) with very little bleaching (11.1%), also at 13–15 m depth. However, by May 1998 colonies of this species in shallower water (7 m depth) suffered high mean mortality (72.4% of colony area, 85.1% decrease in numbers of live colonies). In March 1998, colonies of Pavona clavus, a massive coral species, were 100% bleached at 1.5 m depth and experienced subsequent partial mortality averaging 34.0% per colony. Both Diaseris and Psammocorain deeper water (13–15 m depth) recovered pigment by June 1999. Numbers of Diaseris individuals within permanent transect plots decreased 56.1% from March 1998 through August 2000, but this loss was most likely due to coral displacement by currents and surge rather than temperature-induced mortality. Numbers of Psammocora colonies in deep water did not change appreciably during the survey period (−16.1%). In contrast, surviving shallower water (7 m depth) Psammocora recovered pigment by June 1999, but numbers of live colonies remained low through August 2000 (−83.3% compared to March 1998). Initial recovery of pigmented tissue was evident in Pavona by June 1999, but a decline in live tissue again occurred by August 2000. Sea water temperature at the deeper site reached 28–30°C, but periods of semi-diurnal cooling may have mitigated the bleaching response. Highest temperatures occurred in shallower water (7 m), where Psammocora experienced high mortality and periodic subsurface cooling was suppressed. These data cannot be compared with those from the 1982–83 ENSO because of the lack of quantitative data from the earlier event. However, these observations provide a framework of comparison with other ENSO-affected eastern Pacific coral communities and reefs during the 1997–98 event

The construction of a vocational service rating scale

Thesis (Ed. D.)--Boston University. This item was digitized by the Internet Archive

Deformations and dilations of chaotic billiards, dissipation rate, and quasi-orthogonality of the boundary wavefunctions

We consider chaotic billiards in d dimensions, and study the matrix elements M_{nm} corresponding to general deformations of the boundary. We analyze the dependence of |M_{nm}|^2 on \omega = (E_n-E_m)/\hbar using semiclassical considerations. This relates to an estimate of the energy dissipation rate when the deformation is periodic at frequency \omega. We show that for dilations and translations of the boundary, |M_{nm}|^2 vanishes like \omega^4 as \omega -> 0, for rotations like \omega^2, whereas for generic deformations it goes to a constant. Such special cases lead to quasi-orthogonality of the eigenstates on the boundary.Comment: 4 pages, 3 figure