61 research outputs found
Chief Rabbi Alexander Safran and Queen Mother Elena
No full textInternational audienceThe paper outlines the decisive role played by Chief Rabbi Alexander Safran (1910– 2006) in Engineer Emil Simiu (Moshe Şmilovici)’s initiative to obtain the title of “Righteous among the Nations” for Queen Mother Elena (1896-1982). This initiative was launched on February 26, 1989, with a letter addressed by Emil Simiu to Alexander Safran, and ended up with the favorable decision of the Commission for the Designation of the Righteous among the Nations of Yad Vashem in Jerusalem (of which the late Ytzhak Artzi was a member), which was communicated on March 15, 1993, to Chief Rabbi Alexander Safran. It is published here, together with two letters written by Alexander Safran on February 13 and 17, 1992 (a copy of the French originals can be found in the Alexander Safran Archive in Geneva), which proved decisive for the Commission for the Designation of the Righteous among the Nations
Modern pressure measurement technology and structural design for wind: a new collaborative paradigm for wind and structural engineers
No full textAgainst a brief historical overview, this paper presents the Database-assisted Design (DAD) approach, a conceptually simple, transparent, and rigorous approach to structural design for wind, which fully exploits the potential of modern computational capabilities and pressure measurement technology. A novel collaborative framework between wind and structural engineers assures the effectiveness of this approach and establishes clear lines of responsibility for their respective contributions to the design process. Wind effects with design mean recurrence intervals are determined by DAD more accurately than is possible by using conventional methods for estimating aerodynamic loads, dynamic effects, and wind directionality effects. The DAD approach is consistent with Building Information Modeling (BIM) requirements, and is in principle applicable to most structures for which wind pressures are determined by aerodynamic testing or CFD methods
Estimation of Wind Effects on High-Rise Structures by the Global Load Effects and Database-Assisted Design Methods
No full textStructural wind effects on high-rise buildings subjected to extreme directional winds can be determined by one of three methods: (i) HFB (high frequency balance), used only for buildings with very complex shapes or with many fine-scale features, (ii) GLE (global load effects), commonly used in current commercial wind engineering laboratory practice, and (iii) the DAD (Database Assisted Design) method. The purpose of this paper is to consider the advantages and drawbacks of the GLE and DAD methods, both of which use the multi-channel pressure scanning system. Following these methods’ brief description, it is noted that the GLE method has over DAD the advantage of significantly lower computational time requirements. This is shown to be due to GLE’s basic assumption that the peak Demand-to-Capacity Indexes (DCIs) of all the building’s structural members occur at the same time. It is then shown that this assumption is incorrect, and that it results in the GLE method’s underestimation of all the structural members’ DCIs, inter-story drift ratios, and top floor accelerations. In contrast, the DAD method is shown to satisfy all applicable strength and serviceability performance criteria. However, the computational resources required for DAD’s use exceed the resources typically available to small or mid-sized structural design offices. Recent research results concerning the DAD method are then noted, and various approaches are proposed to the reduction of the DAD method’s computation time requirements by up to two orders of magnitude
Chaotic transitions in deterministic and stochastic dynamical systems: applications of Melnikov processes in engineering, physics, and neuroscience
No full textThe classical Melnikov method provides information on the behavior of deterministic planar systems that may exhibit transitions, i.e. escapes from and captures into preferred regions of phase space. This book develops a unified treatment of deterministic and stochastic systems that extends the applicability of the Melnikov method to physically realizable stochastic planar systems with additive, state-dependent, white, colored, or dichotomous noise. The extended Melnikov method yields the novel result that motions with transitions are chaotic regardless of whether the excitation is deterministic or stochastic. It explains the role in the occurrence of transitions of the characteristics of the system and its deterministic or stochastic excitation, and is a powerful modeling and identification tool. The book is designed primarily for readers interested in applications. The level of preparation required corresponds to the equivalent of a first-year graduate course in applied mathematics. No previous exposure to dynamical systems theory or the theory of stochastic processes is required. The theoretical prerequisites and developments are presented in the first part of the book. The second part of the book is devoted to applications, ranging from physics to mechanical engineering, naval architecture, oceanography, nonlinear control, stochastic resonance, and neurophysiology
Modern pressure measurement technology and structural design for wind: a new collaborative paradigm for wind and structural engineers
No full textAgainst a brief historical overview, this paper presents the Database-assisted Design (DAD) approach, a conceptually simple, transparent, and rigorous approach to structural design for wind, which fully exploits the potential of modern computational capabilities and pressure measurement technology. A novel collaborative framework between wind and structural engineers assures the effectiveness of this approach and establishes clear lines of responsibility for their respective contributions to the design process. Wind effects with design mean recurrence intervals are determined by DAD more accurately than is possible by using conventional methods for estimating aerodynamic loads, dynamic effects, and wind directionality effects. The DAD approach is consistent with Building Information Modeling (BIM) requirements, and is in principle applicable to most structures for which wind pressures are determined by aerodynamic testing or CFD methods
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