2,274 research outputs found
Structural Optimization of a Distributed Actuation System in a Flexible In-Plane Morphing Wing
Structural weight and efficiency are hurdles for morphing aircraft being realizable on the full-scale level. The optimal distribution and orientation of actuators throughout an in-plane flexible morphing wing structure is investigated. The drive to minimize structural weight causes a wing to be more flexible and the location and orientation of the actuators become more critical as the structure becomes more flexible. NextGen\u27s N-MAS morphing wing is used as a case study. The wing is modeled as a number of unit cells assembled in a scissor-like structure, each comprised of four linkages pinned together and an actuator. The flexible skin of the wing is modeled with a nonlinear material stretched between two opposing vertices. It will be shown that the optimal orientation of the actuators will vary depending on the loading conditions and initial configuration of the wing. Sequential quadratic programming (SQP) optimization techniques are utilized to orient those actuators and effectively size the members of the structure. The goal is to minimize weight while maximizing the geometric advantage and efficiency. The constraints are member stresses and the force transferred to the actuators is not to be greater than the force the actuator is able to produce. Matlab® code is developed to do the SQP optimization while NASTRAN™ is utilized to do the nonlinear finite element analysis required to evaluate the objective function and constraints. The single-cell results are compared to experimental data to validate the finite element model (FEM) and optimization routine. A three-cell experiment is designed by utilizing aeroelastic scaling techniques. Matlab is used to develop the scaling problem while the actual scaling is done as an optimization in NASTRAN. The objective for scaling the wing is to minimize the differences in the non-dimensional displacements and strain energies between the two models, using the element cross-sectional dimensions as design variables
USDLA: An Instructional Media Selection Guide For Distance Learning
Purpose and Use of the Media Selection Guide
Increasingly, educators and trainers are challenged within their respective organizations to provide for the efficient distribution of instructional con-tent using instructional media. The appropriate selection of instructional media to support distance learning is not intuitive and does not occur as a matter of personal preference. On the contrary, instructional media selec-tion is a systematic sequence of qualitative processes based on sound in-structional design principles. Although media selection is often mentioned when studying the discipline of instructional technology or Instructional Systems Design (ISD), it is sometimes overlooked when applying the se-lection process in a distance-learning environment. It is our intent, there-fore, for this guide to highlight the essentials of good media selection. We hope to present an instructionally sound and systematic approach to se-lecting the most appropriate media for the delivery of content at a dis-tance
Comparison of efficacy of Long-Term Oral Treatment with Telmisartan and Benazepril in Cats with Chronic Kidney Disease
Heavy ion collisions: Correlations and Fluctuations in particle production
Correlations and fluctuations (the latter are directly related to the
2-particle correlations) is one of the important directions in analysis of
heavy ion collisions. At the current stage of RHIC exploration, when the
details matter, basically any physics question is addressed with help of
correlation techniques. In this talk I start with a general introduction to the
correlation and fluctuation formalism and discuss weak and strong sides of
different type of observables. In more detail, I discuss the two-particle
correlations/\mpt fluctuations. In spite of not observing any dramatic
changes in the event-by-event fluctuations with energy, which would indicate a
possible phase transition, such correlations measurements remain an interesting
and important subject, bringing valuable information. Lastly, I show how radial
flow can generate characteristic azimuthal, transverse momentum and rapidity
correlations, which could qualitatively explain many of recently observed
phenomena in nuclear collisions.Comment: 8 pages, 8 figures. Invited talk at 5th International Conference on
Physics and Astrophysics of Quark Gluon Plasma, February 8-12, 2005, Salt
Lake City, Kolkata, Indi
Measurement of complex fragments and clues to the entropy production from 42-137-MeV/nucleon Ar + Au
Intermediate-rapidity fragments with A=1-14 emitted from 42-137-MeV/nucleon Ar + Au have been measured. Evidence is presented that these fragments arise from a common moving source. Entropy values are extracted from the mass distributions by use of quantum statistical and Hauser-Feshbach theories. The extracted entropy values of S/A≈2-2.4 are much smaller than the values expected from measured deuteron-to-proton ratios, but are still considerably higher than theoretically predicted values
Differential flow in heavy-ion collisions at balance energies
A strong differential transverse collective flow is predicted for the first
time to occur in heavy-ion collisions at balance energies. We also give a novel
explanation for the disappearance of the total transverse collective flow at
the balance energies. It is further shown that the differential flow especially
at high transverse momenta is a useful microscope capable of resolving the
balance energy's dual sensitivity to both the nuclear equation of state and
in-medium nucleon-nucleon cross sections in the reaction dynamics.Comment: Phys. Rev. Lett. (1999) in pres
Data-driven prediction of vortex-induced vibration response of marine risers subjected to three-dimensional current
Slender marine structures such as deep-water marine risers are subjected to
currents and will normally experience Vortex Induced Vibrations (VIV), which
can cause fast accumulation of fatigue damage. The ocean current is often
three-dimensional (3D), i.e., the direction and magnitude of the current vary
throughout the water column. Today, semi-empirical tools are used by the
industry to predict VIV induced fatigue on risers. The load model and
hydrodynamic parameters in present VIV prediction tools are developed based on
two-dimensional (2D) flow conditions, as it is challenging to consider the
effect of 3D flow along the risers. Accordingly, the current profiles must be
purposely made 2D during the design process, which leads to significant
uncertainty in the prediction results. Further, due to the limitations in the
laboratory, VIV model tests are mostly carried out under 2D flow conditions and
thus little experimental data exist to document VIV response of riser subjected
to varying directions of the current. However, a few experiments have been
conducted with 3D current. We have used results from one of these experiments
to investigate how well 1) traditional and 2) an alternative method based on a
data driven prediction can describe VIV in 3D currents. Data driven modelling
is particularly suited for complicated problems with many parameters and
non-linear relationships. We have applied a data clustering algorithm to the
experimental 3D flow data in order to identify measurable parameters that can
influence responses. The riser responses are grouped based on their statistical
characteristics, which relate to the direction of the flow. Furthermore we fit
a random forest regression model to the measured VIV response and compare its
performance with the predictions of existing VIV prediction tools (VIVANA-FD).Comment: 12 pages, presented at Norwegian AI Society Symposium 2019, accepted
for publication in Springer Conference Proceeding
Nucleon Flow and Fragment Flow in Heavy Ion Reactions
The collective flow of nucleons and that of fragments in the 12C + 12C
reaction below 150 MeV/nucleon are calculated with the antisymmetrized version
of molecular dynamics combined with the statistical decay calculation. Density
dependent Gogny force is used as the effective interaction. The calculated
balance energy is about 100 MeV/nucleon, which is close to the observed value.
Below the balance energy, the absolute value of the fragment flow is larger
than that of nucleon flow, which is also in accordance with data. The
dependence of the flow on the stochastic collision cross section and its origin
are discussed. All the results are naturally understood by introducing the
concept of two components of flow: the flow of dynamically emitted nucleons and
the flow of the nuclear matter which contributes to both the flow of fragments
and the flow of nucleons due to the statistical decay.Comment: 20 pages, PostScript figures, LaTeX with REVTeX and EPSF, KUNS 121
Identifying Needs and Implementing Organizational Change to Improve Retention of Early-Career Agents
Retention of agents is important for the growth and stability of Cooperative Extension. A study of early-career agents in Virginia Cooperative Extension identified specific areas in which organizational change could be made to improve agent fit in the organization and long-term retention. As a result, numerous changes have been made, particularly associated with existing agents but also in work with prospective agents. Although this article relates specifically to Virginia, the challenges and solutions identified may be relevant to other programs and to national professional development organizations
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