MAV

A comprehensive method is used to design and manufacture a fixed wing micro air vehicle (MAV) with Zimmerman planform. The design process includes four stages which are the specification of the flight mission, determination of the best aspect ratio, identification of the optimum wing loading, and estimation of the weight of the structural components of the MAV. To this end, various statistical and analytical methods are utilized. Based on an aerodynamic analysis, the results show that an optimum aspect ratio that maximizes the performance of the Zimmerman MAV for a well-defined cruise speed is determined. Considering six possible flights, a constraint analysis is performed and an optimum wing loading value is found. Using the 3D panel method, the determination of the shape of the reflexed airfoil for the MAV is successfully done by minimizing the drag force and the angle of attack to use less powerful motor and avoid any stall effect, respectively. During test flight, the results show that the designed Zimmerman MAV satisfies the pre-defined specification. The final characteristics of the manufactured MAV are: wingspan of 44 centimeters, weight of 450 grams, aspect ratio of 1.51, cruise speed of 20m/s, and flight endurance of 20 minutes.

Este trabajo tiene por objetivo analizar cómo las Mipymes colombianas pueden acceder al mercado de valores y beneficiarse así de las ventajas que antes eran exclusivas para las grandes empresas, identificando algunos aspectos de índole legal, normativo, económico y financiero que faciliten el acceso de estas sociedades al mercado bursátil del país, y que a su vez se busque considerar y mitigar aquellos factores que dificultan el acceso de las mismas a crédito de bajo costo con el fin de financiar sus proyectos de corto, mediano y largo plazo.

En este contexto, se entrará a estudiar el Mercado Alternativo Bursátil, tomando como referencia a España, centrándonos entonces, en identificar cómo funciona el mercado de valores de España y Colombia, cómo es la regulación financiera actual en cada país, qué actores se involucran y cuáles son los esfuerzos de los gobiernos para facilitar la entrada de las Pymes en este tipo de mercados y qué tan interesadas y preparadas están las empresas y sus miembros para acceder a este tipo de financiamiento, además de la disposición de los inversores ante el riesgo que presentaría financiar proyectos de sociedades de bajo capital.

Para finalizar, los resultados permitirán determinar principalmente la viabilidad que tienen las empresas pequeñas y medianas en Colombia para acceder al mercado de valores, identificando aquellas experiencias satisfactorias como es el caso del Mercado Alternativo Bursátil en España, haciendo especial énfasis en aquellas medidas que han favorecido a este tipo de empresas para acceder a capital de bajo costo y formulando medidas complementarias para favorecer y estimular el acceso de las Mipymes a la Bolsa de Valores de Colombia.

"The dissertation presents theoretical and numerical studies of unsteady flows relevant to insect flapping flight. Much emphasis is put on the development of a numerical method for modelling incompressible viscous flows past multiple moving solid obstacles. The Navier-Stokes equations are solved using a Fourier pseudo-spectral discretization. Solid obstacles are modelled with the volume penalization method. An original approach is proposed for interpolation of the time-dependent penalization mask function, which takes advantage of the spectral discretization. Two- and three dimensional solvers have been developed, which differ in some implementation aspects. Notably, the three-dimensional code is adapted for massively parallel computers.

The newly-developed numerical method is employed in a study of the Lighthill-Weis-Fogh mechanism, an unsteady aerodynamic mechanism used by some insects. That study begins, however, with the inviscid fluid model first considered by Lighthill. A transition from fling to sweep is analysed, when the connectivity of the domain changes. Then, modifications due to viscosity are explored. Important viscous effects are found near the trailing edges. The flow field near the hinge, observed in numerical simulations, is explained theoretically by local analysis of the Stokes equation.

The importance of the three-dimensional effects is assessed. Numerical simulations are performed at two different values of the Reynolds number, 128 and 1400, typical for insects of different size. The flow during fling is shown to be in reasonable agreement with the two-dimensional approximation. After the wings move apart, three-dimensional effects become essential."

In this work, we present a low-cost, flying research MAV, comparable to common quadcopter platforms. We propose a flyer with only two moving parts (a rotor and a stator) and a single actuator that is capable of hovering flight without active attitude control. The passive stability is analyzed and reduced to two mechanisms that are a function of the relative offset of the center of pressure and center of mass, the angular momentum of rotor and stator and the differential lift of the spinning elements. The design space over these parameters is explored with a dozen models that are unstable and one that is stable. Interestingly, the two stability mechanisms are not compatible requiring opposing design emphasis. Passive stability of this model is verified by Routh Hurwitz criterion, in simulation and a physical prototype. The vehicle has the added benefits of low complexity and favorable size scaling compared to other MAVs. The vehicle design guidelines derived from both theory and experimentation are presented.

Traduzione del volume di A. Wallace-Hadrill (Eng - It).
Nel 79 d.c. il Vesuvio seppellisce Pompei e Ercolano sotto una coltre di cenere e lapilli. Andrew Wallace-Hadrill ricostruisce e decodifica i nessi essenziali, l'identità, la trama di relazioni economiche, sociali, il rilievo straordinario, originale, della civiltà ercolanense: popolazione e provenienze etniche, spazi pubblici e privati, scambi tra città vesuviane e con l'universo romano... ripercorre con rigore evidenze documentarie, problematiche di scavo, di conservazione, di restauro e fruizione. Un'indagine frutto anche dell'impegno decennale del Packard Humanities Institute, nel quadro organico dell'Herculaneum Conservation Project.

This paper discusses a major application of flexible micro actuators in Micro Air Vehicles (MAV). Design, Kinematics, flapping patterns, performance tests of flapping wing mechanism which replicates dragonfly and corresponding results are discussed in this paper. This paper also discusses artificial  foldable wing models by mimicking the unfolding/folding of beetle hind wing in which the actuation is triggered by electrically activated Shape Memory Alloy (SMA) wires.

We consider the effects of chordwise flexibility on the aerodynamic performance of flapping wings using numerical simulation. The two-dimensional Navier–Stokes equations are solved using a Fourier pseudo-spectral method with no-slip boundary conditions imposed by the volume penalization method. The flexible wing is modelled with a non-linear beam equation. Our numerical simulations of heaving plates show that the maximum thrust is achieved at a stroke frequency lower than resonant, which is in agreement with experiments. The oscillatory part of the force only increases in amplitude when the frequency increases. We also consider aerodynamic interactions between two heaving foils.

We compare different models to simulate two-dimensional vortex wakes behind oscillating plates. In particular, we compare solutions using a vortex sheet model and the simpler Brown–Michael model to solutions of the full Navier–Stokes equations obtained using a penalization method. The goal is to determine whether simpler models can be used to obtain good approximations to the form of the wake and the induced forces on the body.

O artigo é uma resposta sistemática e detalhadas às críticas que Luis Felipe Miguel fez em artigo recente à metodologia da análise de valência (MAV). Segundo o autor: (1) a MAV confunde emissor, receptor, pesquisador e objeto do discurso; (2) reduz drasticamente a complexidade do processo comunicativo; (3) reproduz o ideal normativo da imparcialidade jornalística; (4) está sujeita à excessiva subjetividade. Pretendo mostrar que esses argumentos arrolados por Miguel contra a MAV são, quando não equivocados, superficiais. Contra suas críticas argumento que: (1) estudos de valência focam somente o emissor, sem prejuízo para a análise; (2) reduzem complexidade como outras metodologias em ciências sociais; (3) não dependem do pressuposto da imparcialidade para serem feitos; (4) estão menos sujeitos às distorções subjetivas do que metodologias de estudo da mídia como análise de agendamento e de enquadramento, preconizadas por Miguel.