introduction: nowadays,  considerable developments  in  the field  of  radiotherapy have  been  achieved.  they  include  the  advances  made  in  the  equipments  and  treatment  planning  techniques  which  require  highly complex calculations. such achievements have made it possible to treat cancer patients not only  with  higher  radiation  dose  but  also  with  higher  precision  and  con...

This work is a short, self-contained introduction to subriemannian geometry with special emphasis on Chow’s Theorem. As an application, a regularity result for the the Poincaré Lemma is presented. At the beginning, the definitions of a subriemannian geometry, horizontal vectorfields and horizontal curves are given. Then the question arises: Can any two points be connected by a horizontal curve?...

Increased emphasis has been placed on improving the explicit role of highway safety in making decisions on highway planning, design, and operations. This can be achieved by quantifying the safety effects of geometric design elements for various highway facilities. While great attention has been directed primarily on rural two-lane highways and to a lesser degree, on urban arterials and rural mu...

The origin of the multiple horizontal charge layers observed in the trailing stratiform region of mesoscale convective systems is explained for the first time on the basis of energy considerations and stability calculations. The latter indicate the presence of a cloud-instability with respect to formation of horizontal polarization layers and associated space charge layers. The author's polariz...

In this paper we report on a curious feature in the V , (U − B) color-magnitude diagrams of globular clusters. In our database, we find that a considerable fraction of blue horizontal branch stars, hotter than the instability strip and cooler than the Grundahl et al. (1999) jump (i.e., 6000 ≤ Teff(K)≤ 10000), have (U − B) colors redder than their red giant progenitors. This red incursion is not...

Background With his classification system, Dr Lenke introduced new parameters in radiographic analysis of idiopathic scoliosis, such as lumbar and thoracic sagittal modifiers [1]. Scoliosis is defined as a 3-dimensional (3D) deformity in the frontal, sagittal and horizontal planes. The spine is considered as a heterogeneous beam and is modeled as a deformable wire, with vertebrae represented by...

The numerical approximation scheme for solving the nonlinear initial value problem ∂tb(v) = ∂xxβ(x, v) + β(x, v) with periodic boundary conditions is presented. Local existence and uniqueness of a solution and convergence of approximations is a consequence of the results of Mikula and Kačur (1996), where the anisotropic curvature driven evolution of plane convex curves is studied. The considere...

Safety on highways is one of the most important subjects in Transportation Engineering. The increasing rate of vehicles and the needs to design or geometrically modify the highways has been emphasized in the safe-design of roadways more than before. Between the constructive components of the highway, due to the increasing occurrences of accidents the horizontal curves are of great importance. T...

The recent advances in computer visualization methods have made it possible to exploit the possibility of applying scientific visualization methods in critical research areas in the field of transportation engineering. In this paper we develop new visualization methods for road design and safety. Typically, roads are designed by combining horizontal and vertical roadway alignments, to allow for...