Lumped mass modelling for the dynamic analysis of aircraft structures

Aircraft structures may be modelled by lumping the masses at particular strategic points and the flexibility or stiffness of the structure is obtained with reference to these points. Equivalent moments of inertia for the section at these positions are determined. The lumped masses are calculated based on the assumption that each point will represent the mass spread on one half of the space on each side. Then these parameters are used in the differential equation of motion and the eigen characteristics are determined. A comparison is made with results obtained by other established methods. The lumped mass approach in the dynamic analysis of complicated structures provides an easier means of predicting the dynamic characteristics of these structures. It involves less computer time and avoids computational errors that are inherent in the numerical solution of complicated systems

Applause and Evanescence: An Arts-based Story of Creating and Performing a Choreopoem with Students in an Urban High School

Slope uncertainty predominantly originates from the imperfect analysis model and the inaccuracy and imprecision of the observations. The strength reduction method (SRM) is widely used to attain the safety factor (SF) of the slopes, which is similar to interpretation of the limit state (LS). In this paper, the spectral element method (SEM), using an elasto-plastic Mohr⁻Coulomb failure criterion, is employed to project the plausible LS of the soil slopes. An iterative SRM search method is proposed to evaluate the SF of the slopes regardless of the LS interpretation. The proposed SRM paradigm encompasses the design trigger to trace the uncertain parameters in decision-making. This method is applied to three numerical examples: (1) a homogeneous dry slope, (2) a dry slope with a weak layer, and (3) a partially-wet slope with a weak layer. It is shown that for the case study examples, the proposed SRM reasonably converges to the required precision. Results further are compared and contrasted with some of the conventional and standard techniques in slope stability. This hybrid procedure paves the road for fast and safe stability analysis of man-made and natural slopes.</p

Rational Triumph: or the Dangers of Victory

Full title: Rational triumph: or the dangers of victory : a discourse delivered in the Congregational Church of Shrewsbury, Massachusetts, upon the occasion of the Federal triumphs over the victories of February, 1862, and in view of ultimate victory. by William A. McGinleyhttps://digitalcommons.cedarville.edu/pamphlet_collection/1093/thumbnail.jp

A piecewise continuous Timoshenko beam model for the dynamic analysis of tapered beam-like structures

Distributed parameter modeling offers a viable alternative to the finite element approach for modeling large flexible space structures. The introduction of the transfer matrix method into the continuum modeling process provides a very useful tool to facilitate the distributed parameter model applied to some more complex configurations. A uniform Timoshenko beam model for the estimation of the dynamic properties of beam-like structures has given comparable results. But many aeronautical and aerospace structures are comprised of non-uniform sections or sectional properties, such as aircraft wings and satellite antennas. This paper proposes a piecewise continuous Timoshenko beam model which is used for the dynamic analysis of tapered beam-like structures. A tapered beam is divided into several segments of uniform beam elements. Instead of arbitrarily assumed shape functions used in finite element analysis, the closed-form solution of the Timoshenko beam equation is used. Application of the transfer matrix method relates all the elements as a whole. By corresponding boundary conditions and compatible conditions a characteristic equation for the global tapered beam has been developed, from which natural frequencies can be derived. A computer simulation is shown in this paper, and compared with the results obtained from the finite element analysis. While piecewise continuous Timoshenko beam model decreases the number of elements significantly; comparable results to the finite element method are obtained

Literature Discussions as Mangles of Practice: Sociological Theories of Emergence and/in Dialogic Learning Events

In this report, we argue that some of the most productive and edifying kinds of literature discussions among certain ages/grade levels may be best understood as “mangles of practice” (Pickering, 1995).  Mangles of practice involve the coalescence of planned and contingent forces, and they produce emergent or self-organizing transformations of ongoing social activities, as well as unpredictable outcomes or products.  Indeed, the discussions we studied had these characteristics.  They often involved both planned and contingent actions and reactions by individual, social, cultural, and material agents and agencies.  As such, they were emergent phenomena about which we could seldom predict what precise collections, collisions, and collusions of actions and reactions would occur within them or what the effects of these collections, collisions, and collusions would be.  In spite of (or more likely because of) their unpredictability, these discussions were extremely dynamic knowledge-producing activities.  Given this social fact, we think our findings contribute significantly to understanding the lineaments and potentials of dialogic pedagogy, which deepens students’ learning and development.  More specifically, when teachers successfully prompt and engage students in more robustly dialogic talk that promotes text-to-life connections, life-to text connections, linkages to non-school knowledge (like that of popular culture), etc., then students often reap a wide variety of benefits with respect to their abilities to engage in genuine inquiry, to reason and argue for particular interpretations, to evaluate complex human actions and decisions, and to develop principled social, cultural, and moral equipment for living their own lives.</p

Orbiter Boundary Layer Transition Prediction Tool Enhancements

Updates to an analytic tool developed for Shuttle support to predict the onset of boundary layer transition resulting from thermal protection system damage or repair are presented. The boundary layer transition tool is part of a suite of tools that analyze the local aerothermodynamic environment to enable informed disposition of damage for making recommendations to fly as is or to repair. Using mission specific trajectory information and details of each d agmea site or repair, the expected time (and thus Mach number) of transition onset is predicted to help define proper environments for use in subsequent thermal and stress analysis of the thermal protection system and structure. The boundary layer transition criteria utilized within the tool were updated based on new local boundary layer properties obtained from high fidelity computational solutions. Also, new ground-based measurements were obtained to allow for a wider parametric variation with both protuberances and cavities and then the resulting correlations were calibrated against updated flight data. The end result is to provide correlations that allow increased confidence with the resulting transition predictions. Recently, a new approach was adopted to remove conservatism in terms of sustained turbulence along the wing leading edge. Finally, some of the newer flight data are also discussed in terms of how these results reflect back on the updated correlations

Motorsports Involvement Among Adolescents and Young Adults with Childhood ADHD

Though children with attention-deficit/hyperactivity disorder (ADHD) are at risk for impulsive, health-endangering behavior, few studies have examined non-substance use-related risk-taking behaviors. This study examined whether adolescents and young adults with ADHD histories were more likely than those without ADHD histories to report frequent engagement in motorsports, a collection of risky driving-related activities associated with elevated rates of physical injury. Path analyses tested whether persistent impulsivity, comorbid conduct disorder or antisocial personality disorder (CD/ASP), and heavy alcohol use mediated this association. Analyses also explored whether frequent motorsporting was associated with unsafe and alcohol-influenced driving