Two-alternative forced-choice procedures were used to measure the detectability of bright and dark bars at various locations across luminance patterns that produced Mach bands. Detection performance was significantly affected by both dark and bright Mach bands: poor detection performance was observed at locations near, but not in, the Mach bands; relatively good detection performance at locatio...

Mach; UNIX/OSF; HP-PA; virtually addressed cache architecture; PA-RISC; virtual memory Mach shares memory between tasks by virtual address aliasing. This means a physical page can be mapped to more than one virtual page at a time. This works well on hardware architectures that use a physically addressed cache, but can cause some problems for architectures that use a virtually addressed cache re...

From the analysis of a set of airborne images of ship wakes, we show that the wake angles decrease as U(-1) at large velocities, in a way similar to the Mach cone for supersonic airplanes. This previously unnoticed Mach-like regime is in contradiction with the celebrated Kelvin prediction of a constant angle of 19.47° independent of the ship's speed. We propose here a model, confirmed by numeri...

We describe the design and performance of code added to the Mach microkernel (Mach 4.0, version UK02p21) that permits one to build a Mach kernel that includes unmodiied Linux device drivers. We have written emulation code to support all Linux 1.3.35 network and SCSI drivers for the ISA and PCI I/O buses. Emulation increases latency, but very little. The degree depends on both device and operati...

The current CMU Mach 3.0 microkernel exports simple timestamp and delay abstractions through host get time() and a timeout parameter to mach msg(). While this is sufficient for many purposes, it does not provide the precision or generality required for a variety of realtime applications. In this paper we describe extensions to CMU’s Mach 3.0 which provide users with flexible time-based synchron...

We present numerical solutions of the steady and unsteady transonic small disturbance equations that describe the Mach reflection of weak shock waves. The solutions contain a complex structure consisting of a sequence of triple points and tiny supersonic patches directly behind the leading triple point, formed by the reflection of weak shocks and expansion waves between the sonic line and the M...

In order to enrich the modelling of uid ows, we investigate in this paper a coupling between two models dedicated to distinct regimes. More precisely, we focus on the in uence of the Mach number as the low Mach case is known to induce theoretical and numerical issues in a compressible framework. A moving interface is introduced to separate a compressible model (Euler with source term) and its l...

Through a linear analysis, we show how to modify Godunov type schemes applied to the compressible Euler system to make them accurate at any Mach number. This allows to propose all Mach Godunov type schemes. A linear stability result is proposed and a formal asymptotic analysis justifies the construction in the barotropic case when the Godunov type scheme is a Roe scheme. We also underline that ...

Mach-Number Measurement with Laser and Pressure Probes in Humid Supersonic Flow G. C. Herring NASA Langley Research Center, M/S 493 Hampton, VA 23681-2199 Abstract Mach-number measurements using a nonintrusive optical technique, laser-induced thermal acoustics (LITA), are compared to pressure probes in humid supersonic airflow. The two techniques agree well in dry flow (-35 °C dew point), but L...