Rafael Advanced Defense Systems

About: Rafael Advanced Defense Systems is a company organization based out in Haifa, Israel. It is known for research contribution in the topics: Population & Medicine. The organization has 9989 authors who have published 9429 publications receiving 151171 citations. The organization is also known as: RAFAEL Armament Development Authority & RAFAEL.

Volume rendering

Abstract: A technique for rendering images of volumes containing mixtures of materials is presented. The shading model allows both the interior of a material and the boundary between materials to be colored. Image projection is performed by simulating the absorption of light along the ray path to the eye. The algorithms used are designed to avoid artifacts caused by aliasing and quantization and can be efficiently implemented on an image computer. Images from a variety of applications are shown.

Maximum likelihood localization of multiple sources by alternating projection

Abstract: An algorithm, referred to as APM, for computing the maximum-likelihood estimator of the locations of simple sources in passive sensor arrays is presented. The algorithm is equally applicable to the case of coherent signals and to the case of a single snapshot. The algorithm is iterative; the maximum of the likelihood function is computed by successive approximations. The convergence of the algorithm to the global maximum is demonstrated for a variety of scenarios. The key to this global convergence is the initialization scheme. >

A Reflectance Model for Computer Graphics

Abstract: This paper presents a new reflectance model for rendering computer synthesized images. The model accounts for the relative brightness of different materials and light sources in the same scene. It describes the directional distribution of the reflected light and a color shift that occurs as the reflectance changes with incidence angle. The paper presents a method for obtaining the spectral energy distribution of the light reflected from an object made of a specific real material and discusses a procedure for accurately reproducing the color associated with the spectral energy distribution. The model is applied to the simulation of a metal and a plastic.

Particle Systems—a Technique for Modeling a Class of Fuzzy Objects

Abstract: This paper introduces particle systems--a method for modeling fuzzy objects such as fire, clouds, and water. Particle systems model an object as a cloud of primitive particles that define its volume. Over a period of time, particles are generated into the system, move and change form within the system, and die from the system. The resulting model is able to represent motion, changes of form, and dynamics that are not possible with classical surface-based representations. The particles can easily be motion blurred, and therefore do not exhibit temporal aliasing or strobing. Stochastic processes are used to generate and control the many particles within a particle system. The application of particle systems to the wall of fire element from the Genesis Demo sequence of the film Star Trek H: The Wrath of Khan [10] is presented.

Speculations on the Consequences and Causes of Plate Motions

Abstract: Summary Plate theory has successfully related sea floor spreading to the focal mechanisms of earthquakes and the deep structure of island arcs. It is used here to calculate the temperature distribution in the lithosphere thrust beneath island arcs, and to determine the flow and the stress elsewhere in the mantle. Comparison with observations demonstrates that earthquakes are restricted to those regions of the mantle which are colder than a definite temperature. The flow and the stress heating in the mantle can maintain the high heat flow anomaly observed behind island arcs. Plate theory also suggests a new approach to the convection problem. The most obvious mechanism causing surface motion is the force on the plates due to the sinking lithosphere. This does not appear to be the way in which the motions are maintained. However, the input of large volumes of cold material can control convection and cause general downward movements in the mantle near island arcs. This input of cold lithosphere must cease when the island arc tries to consume a continent, since the light continental crust cannot sink through the denser mantle. Attempts to assimilate continental crust in this way can produce fold mountains, and also permit a rearrangement of convection cells.