Test of Einstein Equivalence Principle for 0-spin and half-integer-spin atoms: Search for spin-gravity coupling effects

We report on a conceptually new test of the equivalence principle performed by measuring the acceleration in Earth's gravity field of two isotopes of strontium atoms, namely, the bosonic $^{88}$Sr isotope which has no spin vs the fermionic $^{87}$Sr isotope which has a half-integer spin. The effect of gravity upon the two atomic species has been probed by means of a precision differential measurement of the Bloch frequency for the two atomic matter waves in a vertical optical lattice. We obtain the values $\eta = (0.2\pm 1.6)\times10^{-7}$ for the E\"otv\"os parameter and $k=(0.5\pm1.1)\times10^{-7}$ for the coupling between nuclear spin and gravity. This is the first reported experimental test of the equivalence principle for bosonic and fermionic particles and opens a new way to the search for the predicted spin-gravity coupling effects.Comment: 5 pages, 4 figures. New spin-gravtity coupling analysis on the data added to the manuscrip

Generation and Structure of Solitary Rossby Vortices in Rotating Fluids

The formation of zonal flows and vortices in the generalized Charney-Hasegawa-Mima equation is studied. We focus on the regime when the size of structures is comparable to or larger than the deformation (Rossby) radius. Numerical simulations show the formation of anticyclonic vortices in unstable shear flows and ring-like vortices with quiescent cores and vorticity concentrated in a ring. Physical mechanisms that lead to these phenomena and their relevance to turbulence in planetary atmospheres are discussed.Comment: 3 pages in REVTeX, 5 postscript figures separately, submitted to Phys. Rev.

Optical frequency fiber dissemination at 10^−19 uncertainty level in Italy

We describe the realization of a coherent optical fiber link for the metrological frequency dissemination on the national scale. This infrastructure will improve the frequency references used in radio-astronomy and in atomic physics and will benefit several laboratories in Italy involved in high resolution spectroscopy, matter physics and radioastronomy. The present infrastructure will be part of a forthcoming European network of optical links. This paper describes the haul implementation, the characterization and the future applications of this backbone. © 2014 AEIT

Vortex merger near a topographic slope in a homogeneous rotating fluid

This work is a contribution to the PHYSINDIEN research program. It was supported by CNRS-RFBR contract PRC 1069/16-55-150001.The effect of a bottom slope on the merger of two identical Rankine vortices is investigated in a two dimensional, quasi-geostrophic, incompressible fluid. When two cyclones initially lie parallel to the slope, and more than two vortex diameters away from the slope, the critical merger distance is unchanged. When the cyclones are closer to the slope, they can merge at larger distances, but they lose more mass into filaments, thus weakening the efficiency of merger. Several effects account for this: the topographic Rossby wave advects the cyclones, reduces their mutual distance and deforms them. This along shelf wave breaks into filaments and into secondary vortices which shear out the initial cyclones. The global motion of fluid towards the shallow domain and the erosion of the two cyclones are confirmed by the evolution of particles seeded both in the cyclone sand near the topographic slope. The addition of tracer to the flow indicates that diffusion is ballistic at early times. For two anticyclones, merger is also facilitated because one vortex is ejected offshore towards the other, via coupling with a topographic cyclone. Again two anticyclones can merge at large distance but they are eroded in the process. Finally, for taller topographies, the critical merger distance is again increased and the topographic influence can scatter or completely erode one of the two initial cyclones. Conclusions are drawn on possible improvements of the model configuration for an application to the ocean.PostprintPeer reviewe

Complex Analysis of the Strength of Semi-Submersible Drilling Platform Structures

This paper presents the results of experimental and model strength analysis (by finite elements method, FEM) for water drilling platform structures. The validity of this analysis is supported by some examples

Пути повышения эффективности инженерного анализа корпусов судов с применением пространственных конечно-элементных моделей // Three-dimensional finite-element models for more efficient hull design

Abstract: Объект и цель научной работы. Рассматриваются расчетные модели судовых корпусных конструкций, сформированные по методу конечных элементов (КЭ) и предназначенные для решения задач поддержки жизненного цикла. Большой порядок разрешающих систем уравнений актуализирует проблему повышения эффективности расчета. Анализируются подходы к решению указанной проблемы. Приводятся примеры расчетного анализа напряженного состояния реального корпуса судна, находящегося в условиях длительной эксплуатации. Материалы и методы. Повышение эффективности расчета конструкции корпуса судна обеспечивается применением метода структуризации. При этом реализуется системный подход к расчетным исследованиям больших механических систем, алгоритмической основой которого служат методы подконструкций (Substructures) и суперэлементов (Super Elements), изложенные в работах Пржеменицкого (Przemienitcki), Аргириса (Argiris), Мейснера (Meissner) и ряда других исследователей. Метод структуризации позволяет эффективно мобилизовать коллективные усилия инженеров. Каждый из них может не только сформировать модель подконструкции, но и осуществить ее анализ и конструирование с учетом смежных подсистем без пересчета системы в целом. Комплексные расчетные исследования прочности и устойчивости выделенных фрагментов выполняются с точными граничными условиями и различными конструктивными схемами. Основные результаты. Получены обобщенные граничные условия для конструктивных отсеков корпуса судна, позволяющие оценить их напряженно- деформированное состояние (НДС) в зависимости от ряда конструктивно-технологических факторов. Дана расчетная прогнозная оценка влияния износов связей на НДС корпуса судна в различные периоды его эксплуатации. Приводится оценка влияния технологических схем ремонта корпуса методом замены на устойчивость конструкции надстройки судна. Заключение. Предложенные подходы обеспечивают полноту, эффективность и комплексность инженерного анализа судового корпуса как большой механической системы. Они позволяют существенно сократить общее расчетное время, уменьшить трудоемкость формирования и анализа расчетных КЭ-моделей судовых корпусов, а также повысить эффективность коллективной работы специалистов, занимающихся проектированием, эксплуатацией и ремонтом судовых корпусных конструкций. Предложенные подходы можно рекомендовать к применению для решения инженерных задач поддержки жизненного цикла объектов морской техники. Object and purpose of research. This paper discusses FE models of hull structures for lifecycle support applications involving highly complex equation systems, which makes calculation efficiency an urgent and relevant challenge. The paper contains several case studies of hull stress calculation for a ship in long-term service. Materials and methods. The efficiency of hull analysis is improved by the method of structurization implementing a system approach to the calculations of large mechanical systems. The algorithms of this approach are based on the methods of substructures and superelements suggested by Przemienitcki, Argiris, Meissner and a number of other researchers. Structurization methods enables efficient coordination of engineering efforts, when each expert can not only generate a model of substructure, but also analyse and engineer it with consideration of neighbouring subsystems and without the necessity to recalculate the system as a whole. Comprehensive strength and stability calculations for given fragments are performed with accurate boundary conditions and various design layouts. Main results. Generalized boundary conditions for hull compartments yielded by this study made it possible to estimate their stress-strain state depending on a number of design and technological factors, as well as to predict structural wear effect upon hull stresses and strains at different stages of service life. The study also estimated the effect of various superstructure replacement techniques during ship repair upon structural stability of hull. Conclusion. The approaches suggested in this paper offer comprehensive, efficient and integrated analysis of hull as large mechanical system, considerably reducing the total time of calculations and man-hours required to generate and analyse FE-based hull models, as well as making the collective efforts of hull design, operation and repair experts more coordinated and efficient. These approaches may be recommended for life cycle support applications in marine industry