Rhinoptera javanica Muller & Henle from Kenya waters (Piscess: Rhinopteridae)

Volume: XXV

The Elopoid and Clupeoid fishes of East Africa Coastal waters

Volume: XXVI

Nonlocal electromagnetic fields near a metal/vacuum interface

A nonlocal formalism is developed to describe the fields at the surface of an electron gas subjected to an incident electromagnetic wave. The electron gas is confined to a semi-infinite half space by an infinite potential barrier; the positive lattice of ions is taken to be a jellium. The response tensor of the electron gas is separated into contributions from the bulk metal and the surface of the metal. A relationship is found between the tensor elements of the bulk contribution to the response and the Lindhard dielectric functions;Specific attention is given to the physical differences in the fieldsresulting from the semi-classical specular scattering model, aRandom Phase Approximation with self-consistent wave functions,and the fully quantum mechanical infinite barrier model. Thesurface-region fields can be understood in terms of elementaryexcitations of the electron gas. The inverse longitudinal dielectric;function and the energy loss function are discussed. Thepossibility of a collective, longitudinal surface mode is presented;(\u271)DOE Report IS-T-1041. This work was performed under ContractNo. W-7405-eng-82 with the Department of Energy

Approche structurée pour les modèles d'index 2 à entrée dérivée

International audienceThis paper reveals a practical manner to deal with the control design of dynamical systems governed by input derivative index-2 first order differential algebraic equations. This class of dynamical model embeds a polynomial which results in a infinite gain in high frequencies. The idea is grounded on the construction of an adequate SISO controller structure to make possible the control design on a model presenting both rational and a first order polynomial parts. The design approach then leads to a controller in a rational form without any algebraic constrain, which can be implemented on a real-time target. Application for gust load control of a complex aeroservoelastic aircraft dynamical model, which naturally embeds an input derivative action, illustrates the approach, using an H∞-norm minimization performance objective

Generative Design In Factory Layout Planning: An Application Of Evolutionary Computing Within The Creation Of Production Logistic Concepts

This paper describes the creation and application of a generative design approach in the production logistics layout concept creation as part of factory planning projects. Production systems evermore are influenced by an increase of product variants during the planning stages as well as shorter replanning cycles due to higher agility requirements to the production system. Thus, requiring the planner to more frequently conduct the highly complex planning procedure of creating layout concepts for the material supply within the assembly line. Currently, mathematical or graphical assignment methods are executed but are often used disjunct and are not used jointly. Furthermore, today’s planning methods are mainly based on manual planning and assignment activities. To address the aforementioned issues, this paper elaborates the application and usability of generative design methods for production logistics planning. As first step the scope and requirements definition for the new production logistics layout application is conducted. Afterwards, generative design, including a multi-objective genetic algorithm, is used to serve as a solution to compile and search through the high-dimensional solution space of all possible logistic layout concepts. Here, layout restrictions and production goals, such as cost and time savings, are reconciled. After the design creation and evaluation by the algorithm, the planner overviews the results and enhances the design parameters until a final concept is reached. This paper concludes with a SWOT analysis of the new planning approach to investigate the used methods, evaluate the impact of the approach on planner’s work and identify additional research potentials of using the generative design for other factory planning domains

Mesoporous carbon nitride-silica composites by a combined sol-gel/thermal condensation approach and their application as photocatalysts

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Mesoporous carbon nitrides, silicas and their composites have been prepared by a combined sol–gel and thermal condensation approach. Precursors for the carbon nitride (cyanamide) and silica (TEOS) are mixed and condensed simultaneously. After condensation and heat treatment it is observed that the carbon nitride and silica formed highly interpenetrating mesophases which leads either to the formation of mesoporous carbon nitride or silica after selective removal of one of the phases. Importantly, the carbon nitride preserves its graphitic stacking even in the spatial confinement introduced by the surrounding silica phase. As both precursors are liquids this approach allows convenient shaping into thin and thick films or monoliths of mesoporous carbon nitrides. Enhanced photocatalytic activity is observed for the production of hydrogen from water when these mesoporous carbon nitrides are applied as photocatalyst in comparison to the bulk, but also to other mesoporous carbon nitrides, prepared by the reported two-step, hard templating approach.BMBF, 03IS2071D, Light2Hydroge

Algebraic characterization of controllability and observability for second order descriptor systems

We analyze controllability and observability conditions for second order descriptor systems and show how the classical conditions for first order systems can be generalized to this case. We show that performing a classical transformation to first order form may destroy some controllability and observability properties. To avoid this, we will derive a canonical form and new first order formulations that do not destroy the controllability and observability properties. As an example, we demonstrate that the loss of impulse controllability in constrained multi-body systems is due to the representation as first order system

Piezo-Polymer-Composite Unimorph Actuators for Active Cancellation of Flow Instabilities Across Airfoils

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.This article presents a smart device for active cancellation of flow instabilities. An array of two piezo unimorph actuators fabricated in piezo-polymer-composite technology is combined with a thin silicone membrane to mimic a movable wall with a closed surface. By locally displacing the thin membrane, a surface wave is generated that interferes with naturally occurring flow instabilities within the boundary layer of an airfoil. Using flow sensors and an intelligent control enables a destructive interference and therefore, an attenuation of natural flow instabilities. This leads to a delay of transition. The boundary layer remains laminar which means drag is reduced. Within the next pages, the setup of the device with actuators, membrane, sensors, and control is introduced. The main focus of this article is on actuator design, modeling, and implementation for wind tunnel experiments. Results of actuator characterization are presented. The non-linear behavior of the piezoactuator (harmonic distortions and impact of high electric fields) is investigated in detail. This study concludes with the results obtained in wind tunnel experiments which prove the functionality of the presented approach. A maximal attenuation of natural occurring flow instabilities of 80% is achieved.DFG, SPP 1207, Strömungsbeeinflussung in der Natur und Techni