527 research outputs found
Ergodicity of certain cocycles over certain interval exchanges
We show that for odd-valued piecewise-constant skew products over a certain
two parameter family of interval exchanges, the skew product is ergodic for a
full-measure choice of parameters
Обеспечение безопасности радиоактивных источников на гипотетическом объекте
Объектом исследования является вопросы организации и функционирования систем физической защиты, учета и контроля ядерных материалов.
Целью работы является создание методического подхода для описания и построения гипотетического объекта и его систем безопасности, с дальнейшем его применением в учебных целях по специальности Безопасность и нераспространение ядерных материалов.The object of research is the organization and functioning of systems of physical protection, accounting and control of nuclear materials.
The aim of the work is to create a methodological approach to the description and construction of a hypothetical object and its security systems, with its further application for educational purposes in the specialty safety and non-proliferation of nuclear materials
Geometry, topology and dynamics of geodesic flows on noncompact polygonal surfaces
We establish the background for the study of geodesics on noncompact
polygonal surfaces. For illustration, we study the recurrence of geodesics on
-periodic polygonal surfaces. We prove, in particular, that almost all
geodesics on a topologically typical -periodic surface with boundary are
recurrent.Comment: 34 pages, 13 figures. To be published in V. V. Kozlov's Festschrif
The development of post-processing algorithm for the ultrasonic evaluation by the application of automated robotic testing systems
The implementation of automated testing systems based on six degrees of freedom (DOF) robotic manipulators is the actual trend in ultrasonic testing equipment development. Such systems are able to provide a fast ultrasonic evaluation with the respect of the surface of the testing object. In this work, the post-processing algorithm based on Synthetic Aperture Focusing Technique (SAFT) is suggested. Such algorithm allows presenting the results in the form of high-resolution imagery of the internal structure of testing objects. The suggested algorithm is applicable in the case of the utilization of automated testing systems based on six DOF robotic manipulators and takes into account all the features conditioned by such equipment application. Performance of the suggested algorithm was tested experimentally
Ergodic infinite group extensions of geodesic flows on translation surfaces
We show that generic infinite group extensions of geodesic flows on square
tiled translation surfaces are ergodic in almost every direction, subject to
certain natural constraints. Recently K. Fr\c{a}czek and C. Ulcigrai have shown
that certain concrete staircases, covers of square-tiled surfaces, are not
ergodic in almost every direction. In contrast we show the almost sure
ergodicity of other concrete staircases. An appendix provides a combinatorial
approach for the study of square-tiled surfaces
New technical approach for the repair of an abdominal wall defect after a transverse rectus abdominis myocutaneous flap: a case report
<p>Abstract</p> <p>Introduction</p> <p>Breast reconstruction with autologous tissue transfer is now a standard operation, but abnormalities of the abdominal wall contour represent a complication which has led surgeons to invent techniques to minimize the morbidity of the donor site.</p> <p>Case presentation</p> <p>We report the case of a woman who had bilateral transverse rectus abdominis myocutaneous flap (TRAM-flap) breast reconstruction. The surgery led to the patient developing an enormous abdominal bulge that caused her disability in terms of abdominal wall and bowel function, pain and contour. In the absence of rectus muscle, the large defect was repaired using a combination of the abdominal wall component separation technique of Ramirez et al and additional mesh augmentation with a lightweight, large-pore polypropylene mesh (Ultrapro<sup>®</sup>).</p> <p>Conclusion</p> <p>The procedure of Ramirez et al is helpful in achieving a tension-free closure of large defects in the anterior abdominal wall. The additional mesh augmentation allows reinforcement of the thinned lateral abdominal wall.</p
Modular Lie algebras and the Gelfand-Kirillov conjecture
Let g be a finite dimensional simple Lie algebra over an algebraically closed
field of characteristic zero. We show that if the Gelfand-Kirillov conjecture
holds for g, then g has type A_n, C_n or G_2.Comment: 20 page
- …