Aerospace systems and mission analysis research Status report, 1 Apr. - 31 Dec. 1966

Systems and mission analysis of solar electric propulsion for solar system exploratio

Solar electric space mission analysis Progress report, 1 Jun. - 31 Dec. 1966

Characteristics and trajectory analysis of solar electric propulsion space missions - Mars orbiter and Jupiter flyb

Aerospace systems and mission analysis research - Solar electric space mission analysis Final report

Mission analysis for solar electric propelled spacecraft on Mars Orbiter, Jupiter flyby, and asteroid belt exploration trajectorie

Theoretical and experimental research on parameter tracking systems Final report, 15 Jul. 1964 - Aug. 1965

Parameter tracking systems based on equation error approach for mathematical model of unknown plan

On the representation of chemical ageing of rubber in continuum mechanics

AbstractIn order to represent the chemical ageing behaviour of rubber under finite deformations a three-dimensional theory is proposed. The fundamentals of this approach are different decompositions of the deformation gradient in combination with an additive split of the Helmholtz free energy into three parts. Its first part belongs to the volumetric material behaviour. The second part is a temperature-dependent hyperelasticity model which depends on an additional internal variable to consider the long-term degradation of the primary rubber network. The third contribution is a functional of the deformation history and a further internal variable; it describes the creation of a new network which remains free of stress when the deformation is constant in time. The constitutive relations for the stress tensor and the internal variables are deduced using the Clausius–Duhem inequality. In order to sketch the main properties of the model, expressions in closed form are derived with respect to continuous and intermittent relaxation tests as well as for the compression set test. Under the assumption of near incompressible material behaviour, the theory can also represent ageing-induced changes in volume and their effect on the stress relaxation. The simulations are in accordance with experimental data from literature

Computing the local pressure in molecular dynamics simulations

Computer simulations of inhomogeneous soft matter systems often require accurate methods for computing the local pressure. We present a simple derivation, based on the virial relation, of two equivalent expressions for the local (atomistic) pressure in a molecular dynamics simulation. One of these expressions, previously derived by other authors via a different route, involves summation over interactions between particles within the region of interest; the other involves summation over interactions across the boundary of the region of interest. We illustrate our derivation using simulations of a simple osmotic system; both expressions produce accurate results even when the region of interest over which the pressure is measured is very small.Comment: 11 pages, 4 figure

Volumes transverses aux feuilletages définissables dans des structures o-minimales

Let $\mathcal{F}_\lambda$ be a family of codimension $p$ foliations defined on a family $M_\lambda$ of manifolds and let $X_\lambda$ be a family of compact subsets of $M_\lambda$. Suppose that $\mathcal{F}_\lambda$, $M_\lambda$ and $X_\lambda$ are definable in an o-minimal structure and that all leaves of $\mathcal{F}_\lambda$ are closed. Given a definable family $\Omega_\lambda$ of differential $p$-forms satisfaying $i_Z\Omega_\lambda = 0$ for any vector field $Z$ tangent to $\mathcal{F}_\lambda$, we prove that there exists a constant A >0 such that the integral of $|\Omega_\lambda|$ on any transversal of $\mathcal{F}_\lambda$ intersecting each leaf in at most one point is bounded by $A$. We apply this result to prove that $p$-volumes of transverse sections of $\mathcal{F}_\lambda$ are uniformly bounded

On the total curvatures of a tame function

Given a definable function f, enough differentiable, we study the continuity of the total curvature function t --> K(t), total curvature of the level {f=t}, and the total absolute curvature function t-->|K| (t), total absolute curvature of the level {f=t}. We show they admits at most finitely many discontinuities

Metacognitive computations for information search: Confidence in control

The metacognitive sense of confidence can play a critical role in regulating decision making. In particular, a lack of confidence can justify the explicit, potentially costly, instrumental acquisition of extra information that might resolve uncertainty. Human confidence is highly complex, and recent computational work has suggested a statistically sophisticated tapestry behind the information that governs both the making and monitoring of choices. However, the consequences of the form of such confidence computations for search have yet to be understood. Here, we reveal extra richness in the use of confidence for information seeking by formulating joint models of action, confidence, and information search within a Bayesian and reinforcement learning framework. Through detailed theoretical analysis of these models, we show the intricate normative downstream consequences for search arising from more complex forms of metacognition. For example, our results highlight how the ability to monitor errors or general metacognitive sensitivity impact seeking decisions and can generate diverse relationships between action, confidence, and the optimal search for information. We also explore whether empirical search behavior enjoys any of the characteristics of normatively derived prescriptions. More broadly, our work demonstrates that it is crucial to treat metacognitive monitoring and control as closely linked processes

Redox Proteomics and Platelet Activation: Understanding the Redox Proteome to Improve Platelet Quality for Transfusion.

Blood banks use pathogen inactivation (PI) technologies to increase the safety of platelet concentrates (PCs). The characteristics of PI-treated PCs slightly differ from those of untreated PCs, but the underlying reasons are not well understood. One possible cause is the generation of oxidative stress during the PI process. This is of great interest since reactive oxygen species (ROS) act as second messengers in platelet functions. Furthermore, there are links between protein oxidation and phosphorylation, another mechanism that is critical for cell regulation. Current research efforts focus on understanding the underlying mechanisms and identifying new target proteins. Proteomics technologies represent powerful tools for investigating signaling pathways involving ROS and post-translational modifications such as phosphorylation, while quantitative techniques enable the comparison of the platelet resting state versus the stimulated state. In particular, redox cysteine is a key player in platelet activation upon stimulation by different agonists. This review highlights the experiments that have provided insights into the roles of ROS in platelet function and the implications for platelet transfusion, and potentially in diseases such as inflammation and platelet hyperactivity. The review also describes the implication of redox mechanism in platelet storage considerations