User's guide to a system of finite-element supersonic panel flutter programs

The utilization and operation of a set of six computer programs for the prediction of panel flutter at supersonic speeds by finite element methods are described. The programs run individually to determine the flutter behavior of a flat panel where the finite elements which model the panel each have four degrees of freedom (DOF), a curved panel where the finite elements each have four DOF, and a curved panel where the finite elements each have six DOF. The panels are assumed to be of infinite aspect ratio and are subjected to either simply-supported or clamped boundary conditions. The aerodynamics used by these programs are based on piston theory. Application of the program is illustrated by sample cases where the number of beam finite elements equals four, the in-plane tension parameter is 0.0, the maximum camber to panel length ratio for a curved panel case is 0.05, and the Mach number is 2.0. This memorandum provides a user's guide for these programs, describes the parameters that are used, and contains sample output from each of the programs

Likely equilibria of stochastic hyperelastic spherical shells and tubes

In large deformations, internally pressurised elastic spherical shells and tubes may undergo a limit-point, or inflation, instability manifested by a rapid transition in which their radii suddenly increase. The possible existence of such an instability depends on the material constitutive model. Here, we revisit this problem in the context of stochastic incompressible hyperelastic materials, and ask the question: what is the probability distribution of stable radially symmetric inflation, such that the internal pressure always increases as the radial stretch increases? For the classic elastic problem, involving isotropic incompressible materials, there is a critical parameter value that strictly separates the cases where inflation instability can occur or not. By contrast, for the stochastic problem, we show that the inherent variability of the probabilistic parameters implies that there is always competition between the two cases. To illustrate this, we draw on published experimental data for rubber, and derive the probability distribution of the corresponding random shear modulus to predict the inflation responses for a spherical shell and a cylindrical tube made of a material characterised by this parameter.Comment: arXiv admin note: text overlap with arXiv:1808.0126

Innovation Policy in Emerging Domains of Activity: First-Mover Advantage or Curse?

Atlanta Conference on Science and Innovation Policy 2009This presentation was part of the session : Policy Actors and RelationshipsThis material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. ©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.Do first-mover advantages exist for public policy? The theory of the first-mover advantage has been well studied in organization theory and marketing science. It is generally accepted that first-mover firms have multiple benefits such as technological leadership, asset preemption, and heightened buyer switching costs. First-mover firms also have the disadvantages of free-ridership, technology uncertainty resolution, enabling new entrants, and incumbent inertia. Previous work has focused on the application of the first-mover theory to firms. However, much can be learned by applying firstmover advantage theory to other areas. Specifically, this study applies the arguments of first-movers to the development of innovation policy in nanotechnology. In addition to the insights provided by this application, additional conditions must be considered when examining the order of entry in innovation policy. The article concludes with a discussion of what follower policies can learn from first-movers. The maximization of laterstage advantages is also discussed.Santa Clara Universit

Likely oscillatory motions of stochastic hyperelastic solids

Stochastic homogeneous hyperelastic solids are characterised by strain-energy densities where the parameters are random variables defined by probability density functions. These models allow for the propagation of uncertainties from input data to output quantities of interest. To investigate the effect of probabilistic parameters on predicted mechanical responses, we study radial oscillations of cylindrical and spherical shells of stochastic incompressible isotropic hyperelastic material, formulated as quasi-equilibrated motions where the system is in equilibrium at every time instant. Additionally, we study finite shear oscillations of a cuboid, which are not quasi-equilibrated. We find that, for hyperelastic bodies of stochastic neo-Hookean or Mooney-Rivlin material, the amplitude and period of the oscillations follow probability distributions that can be characterised. Further, for cylindrical tubes and spherical shells, when an impulse surface traction is applied, there is a parameter interval where the oscillatory and non-oscillatory motions compete, in the sense that both have a chance to occur with a given probability. We refer to the dynamic evolution of these elastic systems, which exhibit inherent uncertainties due to the material properties, as `likely oscillatory motions'

Differences Between Undergraduate and Graduate Students in Self-concept and Depression

Problem. Students have an opportunity for personal growth as they learn about themselves and the world around them. However, their levels of self-concept and depression can influence how they view\u27 themselves, their relationships, and their world. This research compared undergraduate and graduate students with respect to their levels of self-concept and depression. Method A quantitative research design was used for an ex post facto study of 239 students from Andrews University and Western Michigan University. They completed the Demographic Questionnaire, the Tennessee Self-Concept Scale: Second Edition (TSCS:2), and the Beck Depression Inventory-II (BDI-II). Results Using 13 as the B D I-II cut score, the prevalence of depression found for undergraduate and graduate students combined was as follows: a total of 197 (82.4%) were nondepressed, a total of 21 (8.8%) demonstrated mild depressive symptoms, a total of 13 (5.4%) demonstrated moderate depressive symptoms, and a total of 8 (3.3%) demonstrated severe depressive symptoms. The results indicated that undergraduate students demonstrated higher mean depression scores than the graduate students. However, there were no significant differences found between the proportion of undergraduate and graduate students in each BDI-II group. There were no significant differences found in the level of self-concept between undergraduate and graduate students. There were significant differences found between the self-concept of students at different depression groups. For Identity Self-Concept only, the relationship between self-concept and depression was different for undergraduate and graduate students. Conclusions Although the majority of the participants were nondepressed, undergraduate students demonstrated higher mean depression scores than graduate students. Undergraduate and graduate students did not differ in their level of self-concept. There were significant differences found between the self-concept of students at different depression groups. In general, when undergraduate and graduate students were nondepressed or the less depressed they were, then the better they felt about themselves. Conversely, the more depressed they were, then the worse they felt about themselves. The relationship between self-concept and depression was different for undergraduate and graduate students for Identity Self-Concept only. The results of this study suggested that therapeutic goals for students with symptoms of depression, undergraduate or graduate, would be similar

Cooperation of Sperm in Two Dimensions: Synchronization, Attraction and Aggregation through Hydrodynamic Interactions

Sperm swimming at low Reynolds number have strong hydrodynamic interactions when their concentration is high in vivo or near substrates in vitro. The beating tails not only propel the sperm through a fluid, but also create flow fields through which sperm interact with each other. We study the hydrodynamic interaction and cooperation of sperm embedded in a two-dimensional fluid by using a particle-based mesoscopic simulation method, multi-particle collision dynamics (MPC). We analyze the sperm behavior by investigating the relationship between the beating-phase difference and the relative sperm position, as well as the energy consumption. Two effects of hydrodynamic interaction are found, synchronization and attraction. With these hydrodynamic effects, a multi-sperm system shows swarm behavior with a power-law dependence of the average cluster size on the width of the distribution of beating frequencies