A comparison of two conformal mapping techniques applied to an aerobrake body

Conformal mapping is a classical technique which has been utilized for solving problems in aerodynamics and hydrodynamics. Conformal mapping has been successfully applied in the construction of grids around airfoils, engine inlets and other aircraft configurations. Conformal mapping techniques were applied to an aerobrake body having an axis of symmetry. Two different approaches were utilized: (1) Karman-Trefftz transformation; and (2) Point Wise Schwarz Christoffel transformation. In both cases, the aerobrake body was mapped onto a near circle, and a grid was generated in the mapped plane. The mapped body and grid were then mapped back into physical space and the properties of the associated grids were examined. Advantages and disadvantages of both approaches are discussed

Flow instabilities in circular Couette flow of wormlike micelle solutions with a reentrant flow curve

In this work, we numerically investigate flow instabilities of inertialess circular Couette flow of dilute wormlike micelle solutions. Using the reformulated reactive rod model (RRM-R) [Hommel and Graham, JNNFM 295 (2021) 104606], which treats micelles as rigid Brownian rods undergoing reversible scission and fusion in flow, we study the development and behavior of both vorticity banding and finger-like instabilities. In particular, we focus on solutions that exhibit reentrant constitutive curves, in which there exists some region where the shear stress, $\tau$, has a multivalued relation to shear rate, $\dot{\gamma}$. We find that the radial dependence of the shear stress in circular Couette flow allows for solutions in which parts of the domain lie in the region of the flow curve where $\partial \tau /\partial \dot{\gamma} > 0$, while others lie in the region where $\partial \tau /\partial \dot{\gamma} < 0$; this mixed behavior can lead to complex flow instabilities that manifest as finger-like structures of elongated and anisotropically-oriented micelles. In 3D simulations we find that the initial instability is 2D in origin, and 3D finger-like structures arise through the axial instability of 2D sheets. Finally, we show that the RRM-R can capture vorticity banding in narrow-gap circular Couette flow and that vorticity bands are linearly stable to perturbations.Comment: 42 pages, 27 figures, 5 supplemental movie

Sharing tasks or sharing actions? Evidence from the joint Simon task.

In a joint Simon task, a pair of co-acting individuals divide labors of performing a choice-reaction task in such a way that each actor responds to one type of stimuli and ignores the other type that is assigned to the co-actor. It has been suggested that the actors share the mental representation of the joint task and perform the co-actor’s trials as if they were their own. However, it remains unclear exactly which aspects of co-actor’s task-set the actors share in the joint Simon task. The present study addressed this issue by manipulating the proportions of compatible and incompatible trials for one actor (inducer actor) and observing its influences on the performance of the other actor (diagnostic actor) for whom there were always an equal proportion of compatible and incompatible trials. The design of the present study disentangled the effect of trial proportion from the confounding effect of compatibility on the preceding trial. The results showed that the trial proportions for the inducer actor had strong influences on the inducer actor’s own performance, but it had little influence on the diagnostic actor’s performance. Thus, the diagnostic actor did not represent aspects of the inducer actor’s task-set beyond stimuli and responses of the inducer actor. We propose a new account of the effect of preceding compatibility on the joint Simon effect.Action Contro

Venture capital contracting in theory and practice: Implications for entrepreneurship research

This article provides a comprehensive theoretical and empirical literature review of venture capital contracts. This outlines the differences between theoretical and practical uses of contract designs; that is, (1) how does the choice of securities give rise to different adverse selection problems in terms of attracting different types of entrepreneurial companies; how does the choice of securities in conjunction with cash flow and control rights provisions affect (2) the effort levels by the entrepreneur and the investor; and (3) ultimately affect entrepreneurial outcomes. This article highlights the major discrepancies between theory and practice and points out potential avenues for further research

De linde terug in het bos : verslag veldwerkplaats Droog zandlandschap Doorwerth, 9 mei 2008

Verslag van de veldwerkdag Droog zandlandschap in Doorwerth op 9 mei 2008. Tijdens deze veldwerkdag is in de bossen bij kasteel Doorwerth gekeken naar de 0strooisellaag van verschillende bostypen. Aanplant van lindes in een eikenbeukenbos op een relatief arme bodem geeft een zichtbare verbetering van de strooisellaag. De verzuring die in bossen plaatsvindt kan op deze manier plaatselijk worden bestreden. De aanplant van linde en andere boomsoorten met goed verterend strooisel kan dus een bijdrage leveren aan het oplossen van het verzuringsprobleem. Daarbij leidt de verbeterde strooiselkwaliteit tot een verhoging van biodiversiteit en bloemenpracht in het voorjaar

Band gap bowing of binary alloys: Experimental results compared to theoretical tight-binding supercell calculations for CdZnSe

Compound semiconductor alloys of the type ABC find widespread applications as their electronic bulk band gap varies continuously with x, and therefore a tayloring of the energy gap is possible by variation of the concentration. We model the electronic properties of such semiconductor alloys by a multiband tight-binding model on a finite ensemble of supercells and determine the band gap of the alloy. This treatment allows for an intrinsic reproduction of band bowing effects as a function of the concentration x and is exact in the alloy-induced disorder. In the present paper, we concentrate on bulk CdZnSe as a well-defined model system and give a careful analysis on the proper choice of the basis set and supercell size, as well as on the necessary number of realizations. The results are compared to experimental results obtained from ellipsometric measurements of CdZnSe layers prepared by molecular beam epitaxy (MBE) and photoluminescence (PL) measurements on catalytically grown CdZnSe nanowires reported in the literature.Comment: 7 pages, 6 figure