Virtual instruments used for LPG pipeline network monitoring

The paper presents a pipeline liquefied petroleum gas network (PLPGN) monitoring system based upon the virtual instrument architecture. Starting from the introduction of development requirements and environment for the monitoring system, the paper discusses its hardware configuration and software functionalities, in detail. Practical application has demonstrated that the virtual instrument-based structure is very effective and the obtained monitoring system is highly flexible.     

Developing a visual component library for a graphical programmingplatform using object orientation

The development of virtual instruments (VIs) is bringing a great revolution to the fields of automated testing and measurement. It is accelerating the integration of measurement systems and is promoting instrument standardization, modularization and generalization. A graphical programming platform for automated testing is one of the most important applications of VI technology, and it provides users with an intuitive and friendly programming environment. The visual component library (VCL) is the key part of such graphical programming platforms. The research reported in this paper makes full use of the advantages of the object-oriented methodology to develop the visual VI components for a graphical programming platform. By setting up two base classes for all the VI components, various VIs can be efficiently developed     

Detection of obstacles in the flight path of an aircraft

The National Aeronautics and Space Administration (NASA), along with members of the aircraft industry, recently developed technologies for a new supersonic aircraft. One of the technological areas considered for this aircraft is the use of video cameras and image-processing equipment to aid the pilot in detecting other aircraft in the sky. The detection techniques should provide high detection probability for obstacles that can vary from subpixel to a few pixels in size, while maintaining a low false alarm probability in the presence of noise and severe background clutter. Furthermore, the detection algorithms must be able to report such obstacles in a timely fashion, imposing severe constraints on their execution time. Approaches are described here to detect airborne obstacles on collision course and crossing trajectories in video images captured from an airborne aircraft. In both cases the approaches consist of an image-processing stage to identify possible obstacles followed by a tracking stage to distinguish between true obstacles and image clutter, based on their behavior. For collision course object detection, the image-processing stage uses morphological filter to remove large-sized clutter. To remove the remaining small-sized clutter, differences in the behavior of image translation and expansion of the corresponding features is used in the tracking stage. For crossing object detection, the image-processing stage uses low-stop filter and image differencing to separate stationary background clutter. The remaining clutter is removed in the tracking stage by assuming that the genuine object has a large signal strength, as well as a significant and consistent motion over a number of frames. The crossing object detection algorithm was implemented on a pipelined architecture from DataCube and runs in real time. Both algorithms have been successfully tested on flight tests conducted by NASA.     

Some comments on the F ring-Prometheus–Pandora environment

The system formed by the F ring and two close satellites, Prometheus and Pandora, has been analysed since the time that Voyager visited the planet Saturn. During the ring plane crossing in 1995 the satellites were found in different positions as predicted by the Voyager data. Besides the mutual effects of Prometheus and Pandora, they are also disturbed by a massive F ring. Showalter et al. [Icarus 100 (1992) 394] proposed that, the core of the ring has a mass which corresponds to a moonlet varying in size from 15 to 70 km in radius which can prevent the ring from spreading due to dissipative forces, such as Poynting–Robertson drag and collisions. We have divided this work into two parts. Firstly we analysed the secular interactions between Prometheus–Pandora and a massive F ring using the secular theory. Our results show the variation in eccentricity and inclination of the satellites and the F ring taking into account a massive ring corresponding to a moonlet of different sizes. There is also a population of dust particles in the ring in the company of moonlets at different sizes [Icarus 109 (1997) 304]. We also analysed the behaviour of these particles under the effects of the Poynting–Robertson drag and radiation pressure. Our results show that the time scale proposed for a dust particle to leave the ring is much shorter than predicted before even in the presence of a coorbital moonlet. This result does not agree with the confinement model proposed by Dermott et al. [Nature 284 (1980) 309]. In 2004, Cassini mission will perform repeated observations of the whole system, including observations of the satellites and the F ring environment. These data will help us to better understand this system.     

Geomagnetic transmission disturbances and heavy-ion fluences observed in low Earth orbit during the solar energetic particle events of October 1989.

The large solar energetic particle (SEP) events and simultaneous large geomagnetic disturbances observed during October 1989 posed a significant, rapidly evolving space radiation hazard. Using data from the GOES-7, NOAA-10, IMP-8 and LDEF satellites, we determined the geomagnetic transmission, heavy ion fluences, mean Fe ionic charge state, and effective radiation hazard observed in low Earth orbit (LEO) for these SEPs. We modeled the geomagnetic transmission by tracing particles through the combination of the internal International Geomagnetic Reference Field (IGRF) and the Tsyganenko (1989) magnetospheric field models, extending the modeling to large geomagnetic disturbances. We used our results to assess the radiation hazard such very large SEP events would pose in the anticipated 52 degrees inclination space station orbit.     

Review of unsteady transonic aerodynamics: Theory and applications

Unsteady transonic flow theory is reviewed and classical results from the nonlinear asymptotic theory are combined with new results from computational fluid dynamics. The emphasis is on applications to the field of aeroelasticity and on clarifying the limitations of linearized theories in problems involving mixed subsonic-supersonic flows. The inherent differences between nonlinear transonic aerodynamics and linear subsonic and supersonic aerodynamics are considered from a theoretical and computational standpoint, and the practical implications of these differences in formulating suitable aerodynamic models for aeroelastic stability calculations are discussed. Transonic similarity principles are reviewed and their relevance in understanding flutter, divergence, and control reversal phenomena of transonic aircraft is illustrated through practical examples.     

Perpendicular Shock Reformation and Ion Acceleration

Kinetic simulations of supercritical, quasi-perpendicular shocks yield time-varying solutions that cyclically reform on proton spatio-temporal scales. Whether a shock solution is stationary or reforming depends upon the plasma parameters which, for SNR shocks and the heliospheric termination shock, are ill defined but believed to be within this time-dependent regime. We first review the time-dependent solutions and the acceleration processes of the ions for a proton–electron plasma. We then present recent results for a three-component plasma: background protons, electrons and a second ion population appropriate for SNR (heavy ions) or the termination shock (pickup protons). This ion acceleration generates a suprathermal “injection” population – a seed population for subsequent acceleration at the shock, which may in turn generate ions at cosmic ray energies.