According to collapsar models, gamma ray bursts are caused by relativistic jets that expel energy along the rotation axis of a collapsing stellar core. We discuss how the structure and time-dependence of such jets depends on the properties of the stellar envelope and the central engine. It takes a few seconds for the jet to bore its way through the core of the star; most of the energy output du...

Most of the industrial software codes used for the prediction of the radar cross-section (RCS) of aircrafts are based on ray tracing. While ray based methods give useful scattered fields from the skin of the aircraft illuminated by an incident plane wave, they largely fail to predict the returns from cavities onboard. As a possible enhancement to these ray-tracing programs, an auxiliary program...

A procedure is proposed to functionally decompose an already existing integrated mechanical jet engine subsystem. An integrated sub system is a system where the same design object satisfies multiple functions: which is typically the case in aircraft engine sub systems and components. A generic decomposition method will allow implementation and use in automated design systems and will function a...

We describe an effective numerical approach to solving nonlinear 2 or optimal control problems. Our principal goal will be to use this approach to solve the important problem of jet engine compressor control. The technique is demonstrated first with the tutorial example of the control of a pendulum. We then apply the numerical approach to the problem of controlling jet engine compressor stall a...

Published near-field analyses of full-scale jet noise are limited, and the application of observed laboratory-scale phenomena to full-scale jets is not well understood. To obtain a greater understanding of the connection between radiated noise and source characteristics in full-scale, heated, supersonic jets produced by military aircraft, extensive acoustical measurements were made in the geome...

— It is now generally accepted that long gamma-ray bursts are associated with the final evolutionary stages of massive stars. As a consequence, their jets must propagate through the stellar progenitor and break out on their surface, before they can reach the photospheric radius and produce the gamma-ray photons. We investigate the role of the progenitor star in shaping the jet properties. We sh...

I review how polarization signals have been discussed in the research field of Gamma-Ray Bursts (GRBs). I mainly discuss two subjects in which polarimetry enables us to study the nature of relativistic jets. (1) Jet breaks: Gamma-ray bursts are produced in ultra-relativistic jets. Due to the relativistic beaming effect, the emission can be modeled in a spherical model at early times. However, a...