Effects of asymmetry on the dynamic stability of aircraft

The oblique wing concept for transonic aircraft was proposed to reduce drag. The dynamic stability of the aircraft was investigated by analytically determining the stability derivatives at angles of skew ranging from 0 and 45 deg and using these stability derivatives in a linear analysis of the coupled aircraft behavior. The stability derivatives were obtained using a lifting line aerodynamic theory and found to give reasonable agreement with derivatives developed in a previous study for the same aircraft. In the dynamic analysis, no instability or large changes occurred in the root locations for skew angles varying from 0 to 45 deg with the exception of roll convergence. The damping in roll, however, decreased by an order of magnitude. Rolling was a prominent feature of all the oscillatory mode shapes at high skew angles

On the solution of Lambert’s problem by regularization

Lambert’s problem is the two-point boundary-value problem resulting from a two-body orbital transfer between two position vectors in a given time. It lies at the very heart of several fundamental astrodynamics and space engineering problems and, as such, it has attracted the interest of scientists over centuries. In this work, we revisit the solution of Lambert’s problem based on Levi-Civita regularization developed by Carles Simó in 1973. We offer an exhaustive derivation of the theory, including proofs of all the results and the formulae employed, and we extend the algorithm to deal with multi-revolution transfers. Then, after investigating a range of initial guess search techniques and testing different numerical methods to approximate the solution, we propose a procedure in which the initial guess is assigned very efficiently by querying a pre-defined interpolating table. Then, in order to achieve both speed and robustness, we combine Newton-Raphson with safety checks to avoid out of boundary deviations to approximate the solution. We validate the method through several tests and applications, and we assess its convergence and performance. The algorithm presents no singularities, converges in all realistic scenarios and its computational cost is comparable with state of the art algorithms

On Nichols algebras over PGL(2,q) and PSL(2,q)

We compute necessary conditions on Yetter-Drinfeld modules over the groups \mathbf{PGL}(2,q)=\mathbf{PGL}(2,\FF_q) and \mathbf{PSL}(2,q)=\mathbf{PSL}(2,\FF_q) to generate finite dimensional Nichols algebras. This is a first step towards a classification of pointed Hopf algebras with group of group-likes isomorphic to one of these groups. As a by-product of the techniques developed in this work, we prove that there is no non-trivial finite-dimensional pointed Hopf algebra over the Mathieu groups $M_{20}$ and $M_{21}=\mathbf{PSL}(3,4)$.Comment: Minor change

El Papel de Estímulos Discriminativos en el Efecto de Costo Hundido

Se empleó un análogo analítico-conductual del efecto de costo hundido, enel cual todos los ensayos iniciaron con una razón esperada corta respectoa una recompensa monetaria imaginaria, pero algunos ensayos adquirieron una razón esperada más larga durante parte del ensayo. Los sujetos teníanla opción (preferible) de “escapar” del ensayo si la razón esperada más largaestaba en efecto, para iniciar un nuevo ensayo que de nuevo tuviera unarazón esperada corta. Con un diseño entre sujetos, se probó si la presenciade estímulos discriminativos correlacionados con las razones esperadasafectarían la conducta de escapar. En una condición, tales estímulos estabanpresentes; en la otra condición, estaban ausentes. Los sujetos persistieronsignificativamente más en la condición en la cual los estímulos discriminativosestaban ausentes

An Automatic Tree Search Algorithm for the Tisserand Graph

The Tisserand graph (TG) is a graphical tool commonly employed in the preliminary design of gravity-assisted trajectories. The TG is a two-dimensional map showing essential orbital information regarding the Keplerian orbits resulting from the close passage by one or more massive bodies, given the magnitude of the hyperbolic excess speed ($v_{\infty}$) and the minimum allowed pericenter height for each passage. Contours of constant $v_{\infty}$ populate the TG. Intersections between contours allow to link consecutive flybys and build sequences of encounters en route to a selected destination. When the number of perturbing bodies is large and many $v_{\infty}$ levels are considered, the identification of all the possible sequences of encounters through the visual inspection of the TG becomes a laborious task. Besides, if the sequences are used as input for a numerical code for trajectory design and optimization, an automated examination of the TG is desirable. This contribution describes an automatic technique to explore the TG and find all the encounter paths. The technique is based on a tree search method, and the intersections between contours are found using the regula-falsi scheme. The method is validated through comparisons with solutions available in the open literature. Examples are given of application to interplanetary mission scenarios, including the coupling with a trajectory optimizer

Efecto de los parámetros del proceso de extracción por prensado sobre el rendimiento y la calidad de aceite de Pistacho

Pistachio nuts have high economical and nutritional value, mostly due to their elevated oil con­tent (50%), which is composed mainly of oleic and linoleic fatty acids. Box-Behnken experimental designs were performed to optimize the oil extraction by response surface analysis. The independent variables measured were seed moisture content (SMC), restriction die (RD), screw press speed (PS) and pressing temperature (PT), while the response variables considered were oil recovery (OR), fine solid contents in the oil (FSC), oil remain­ing in the cake (OC) and parameters related to oil quality (free fatty acid composition (FFAC, mg KOH/g oil), peroxide value (PV, meq O2/kg oil), K232, K270 and pigment contents, mg/kg oil). Given that the chemical quality of pistachio nut oil pressed under different conditions was not affected, the process response was optimized in order to maximize OR under two pressing temperatures. Therefore, at 75 °C, pistachio oil extraction showed a maximum OR (79.61 g/100 g oil) at 8% SMC, 4 mm RD and 20 rpm SP; while, under cold-pressed conditions, the maximum OR (65.97 g/100 g oil) was achieved at 10% SMC, 4mm RD and 20 rpm SP. It is important to highlight that OR values were higher than the results reported previously and the chemical quality parameters from both oils were in the range of Codex standards for virgin (non-refined) oils (FFAC < 0.31 and PV < 0.33).Los frutos de pistacho son altamente nutritivos, principalmente debido a su contenido de aceite (50%), compuesto principalmente por ácidos grasos mono y di-insaturados. Con la finalidad de conocer las condiciones de proceso adecuadas que permitan maximizar la cantidad de aceite extraído preservando la calidad química del mismo se utilizaron dos diseños experimentales de Box-Behnken. Las variables independientes analizadas fueron la humedad de la semilla (HS), el diámetro de reducción (DR), la velocidad y temperatura de prensado (VP y TP, respectivamente), mientras que las variables de respuesta fueron el rendimiento en aceite (RA), el contenido de sólidos finos en el aceite (CFA), el aceite remanente en torta (AT) y parámetros relacionados con la calidad (composición en ácidos grasos libres (CAGL, mg KOH/g aceite), índice de peróxido (IP, meqO2/kg aceite), K232, K270 y pigmentos (mg/kg aceite)). La calidad química de los aceites obtenidos no mostró daño oxidativo y/o hidrolítico significativo bajo las diferentes condiciones del proceso (IP< 0.33 y CAGL< 0.31, respectivamente), por lo tanto, la respuesta se optimizó para maximizar RA a dos TP, 75 y 40 °C. El rendimiento en aceite se maximizó ajustando HS (8% ó 10% b.h.), DR (4 mm), VP (20 rpm) a ambas temperaturas, alcanzando extracciones de aceite de 79.61% y 65.97%, respectivament

THREE-DIMENSIONAL SPORT MOVEMENT ANALYSIS BY MEANS OF FREE FLOATING TV CAMERAS WITH VARIABLE OPTICS

INTRODUCTION: Video analysis and off-line manual digitalization is usually used for 2-D and 3-D studies of human movement in sport science. The main advantage of this approach, with respect to the recourse to opto-electronic automatic motion analyzers, is the high flexibility in system set-up, the avoidance of marking procedures and the possibility of successful operation in a wide range of environmental situations. Such features turn out to be particularly important for recordings to be performed in the frame of high-level competition, when the experimental set-up must be adapted to a pre-defined competitive environment, without interfering with the performances of the athletes. However, when methods proper to conventional close-range photogrammetry are used, most of the advantages offered by the flexibility of video analysis are not obtained. Particularly critical is the restriction of the useful calibrated volume to the field of view made possible by fixed pairs of TV cameras. In this case the useful sequence of images (where the dimension of the acquired subject allows one to limit macroscopic digitalization errors) is often insufficient for the analysis of a complete movement cycle. This limitation hinders a fruitful application of video analysis in the frame of sport activities (alpine and Nordic skiing, swimming, track and field) in which the execution of the particular technical movement is performed within a large physical space. A solution to the problem is proposed based on the use of free moving and zooming cameras. The corresponding dedicated software for repeated calibration based on Direct Linear Transformation (DLT)(Abdel Aziz and Karara, 1971) is described. Results of recording performed in the laboratory are discussed aiming at the validation of the implemented method. The description of the methodology for the recording of sport activities and the presentation of the related results confirm the operational feasibility of the proposed method and the reliability of the resulting quantitative kinematics analysis

An Empirical Study on Collaborative Architecture Decision Making in Software Teams

Architecture decision making is considered one of the most challenging cognitive tasks in software development. The objective of this study is to explore the state of the practice of architecture decision making in software teams, including the role of the architect and the associated challenges. An exploratory case study was conducted in a large software company in Europe and fifteen software architects were interviewed as the primary method of data collection. The results reveal that the majority of software teams make architecture decisions collaboratively. Especially, the consultative decision- making style is preferred as it helps to make decisions efficiently while taking the opinions of the team members into consideration. It is observed that most of the software architects maintain a close relationship with the software teams. Several organisational, process and human related challenges and their impact on architecture decision-making are also identified

"Thermoluminescence dating laboratory improvements tested on an archaeological rescue site in Trino, Vercelli province, Italy"

Thermoluminescence (TL) is a reliable radiation-based technique for the dating and authentication of ceramic objects, allowing the evaluation of the time elapsed since their last exposure to high temperatures (e.g. firing in kiln or later fire events). The TL laboratory developed in the last decade at the Physics Department of the University of Torino, currently operating within the INFN (National Institute of Nuclear Physics) CHNet network, is presented. The 10-years-long experience in the field resulted in the enhancement of the procedures, with the development of customised α and β irradiation systems and the optimisation of sampling approach and chemical pre-treatment. In collaboration with TecnArt S.r.l., the improved procedures were employed for dating two structures from a rescue archaeological site in the Vercelli province (Italy)