A finite element-analytical method for modeling a structure in an infinite fluid

A method is described from which the interaction of an elastic structure with an infinite acoustic fluid is determined. The displacements of the structure and the pressure field of the immediate surrounding fluid are modeled by finite elements, and the remaining pressure field of the infinite fluid region is given by an analytical expression. This method yields a frequency dependent boundary condition for the outer fluid boundary when applied to the frequency response of an elastic beam in contact with an acoustic fluid. The frequency response of the beam is determined using NASTRAN, and compares favorably to the exact solution which is also presented. The effect of the fluid on the response of the structure at low and high frequencies is due to added mass and damping characteristics, respectively

The breakdown flash of Silicon Avalance Photodiodes - backdoor for eavesdropper attacks?

Silicon avalanche photodiodes are the most sensitive photodetectors in the visible to near infrared region. However, when they are used for single photon detection in a Geiger mode, they are known to emit light on the controlled breakdown used to detect a photoelectron. This fluorescence light might have serious impacts on experimental applications like quantum cryptography or single-particle spectroscopy. We characterized the fluorescence behaviour of silicon avalanche photodiodes in the experimentally simple passive quenching configuration and discuss implications for their use in quantum cryptography systems.Comment: 9 pages, 6 figures, submitted to J. Mod. Optic

FEM/SINDA: Combining the strengths of NASTRAN, SINDA, I-DEAS, and PATRAN for thermal and structural analysis

This paper describes the interface/integration between FEM/SINDA, a general purpose geometry driven thermal analysis code, and the FEM software: I-DEAS, PATRAN, and NASTRAN. FEM/SINDA brings together the advantages of the finite element method to model arbitrary geometry and anisotropic materials and SINDA's finite difference capability to model thermal properties, loads, and boundary conditions that vary with time or temperature. I-DEAS and PATRAN thermal entities are directly supported since FEM/SINDA uses the nodes of the FEM model as the point at which the temperature is determined. Output from FEM/SINDA (as well as the FEM/SINDA input deck) can be used directly by NASTRAN for structural analysis

Missing lithotroph identified as new planctomycete

With the increased use of chemical fertilizers in agriculture, many densely populated countries face environmental problems associated with high ammonia emissions. The process of anaerobic ammonia oxidation ('anammox') is one of the most innovative technological advances in the removal of ammonia nitrogen from waste water. This new process combines ammonia and nitrite directly into dinitrogen gas. Until now, bacteria capable of anaerobically oxidizing ammonia had never been found and were known as "lithotrophs missing from nature". Here we report the discovery of this missing lithotroph and its identification as a new, autotrophic member of the order Planctomycetales, one of the major distinct divisions of the Bacteria. The new planctomycete grows extremely slowly, dividing only once every two weeks. At present, it cannot be cultivated by conventional microbiological techniques. The identification of this bacterium as the one responsible for anaerobic oxidation of ammonia makes an important contribution to the problem of unculturability

Experimental demonstration of complementarity with single photons

von Professor Dr. Rudolf Wol

Designing And Optimizing Missiles In An Interactive Environment

Designing missiles is a highly multidisciplinary engineering task. Involved in the design is geometric modeling, aerodynamics, propulsion, thermal analysis, weight estimation, trajectory analysis, lethality, structural analysis, controls analysis, packaging of components, and cost estimation. In the past these disciplines have been separated making it difficult to agree on a design that will satisfy the needs of each of the disciplines. Interactive Missile Design (IMD) is a somftware integrating the disciplinary tools involved in the conceptual design of missiles. With IMD, the designer can concentrate on improving the design instead of spending time on ensuring continuity between the disciplines. IMD will enable better missile designs and also reduce the design cycle time. IMD is built in an object-oriented dependency-tracking webenabled language called AML (Adaptive Modeling Language). With the integration of the disciplinary software optimization has become a natural extension of the capabilities of IMD. This paper will discuss the development of the interactive missile design environment, the optimization functionality integrated with it, as well as a missile optimization example. © 2002 by M. Alexandra Ahlqvist

Strain Energy Function of Red Blood Cell Membranes

The several widely different values of the elastic modulus of the human red blood cell membrane which have been reported in the literature are incorporated into a single strain energy function consisting of two terms. One term gives the small stresses and low elastic modulus which is observed when the red cell membrane is deformed at constant area. The second term contributes a large isotropic stress dependent on the change of area. The strain energy function is applied to the process of sphering of red blood cells in a hypotonic solution. It is shown that a nearly perfect sphere can result even though the red blood cell membrane is homogeneous in all areas of the cell. Results pertinent to sieving and micropipette experiments are also explored

Utilization Of A Dependency-Tracking Language To Reduce Computational Time During Multidisciplinary Design Optimization

Reduction in computational time was desired and achieved in optimizing a multidisciplinary missile design system. The time reduction was realized using an object-oriented, dependency-tracking, demand-driven language called the adaptive modeling language (AML). The features of this language allowing for reduction in computational time are referred to as dependency-tracking and demand-driven computations. The dependency-tracking feature keeps track of the relationship amongst properties and objects within the hierarchy. This feature ensures that only necessary computations be carried out and it also ensures that computations that have previously been performed not be carried out again so long as the input to these computations have not changed. The timesaving features of this language make it an attractive choice when performing optimizations. A computational reduction in time of between 33 and 44% was achieved in the case when the language was used in conjunction with design of experiment and response surface models. The missile design system, interactive missile design and the optimization interface are coded in AML. The efficiency of the language was studied in conjunction with design of experiment, response surface analysis, and gradient-based optimization. The advancement of the missile design software by integrating optimization functionality is also discussed. © 2003 Elsevier Science Ltd. All rights reserved