Observational constraints on the inflaton potential combined with flow-equations in inflaton space

Direct observations provide constraints on the first two derivatives of the inflaton potential in slow roll models. We discuss how present day observations, combined with the flow equations in slow roll parameter space, provide a non-trivial constraint on the third derivative of the inflaton potential. We find a lower bound on the third derivative of the inflaton potential V'''/V > -0.2. We also show that unless the third derivative of the inflaton potential is unreasonably large, then one predicts the tensor to scalar ratio, r, to be bounded from below r > 3 * 10^{-6}.Comment: 4 pages, 2 figures. Important sign mistake corrected. Conclusions, abstract and discussion change

Parental Psychological Control and Autonomy Granting: Distinctions and Associations with Child and Family Functioning

Objective:This study utilized an observational coding scheme to identify parenting behavior reflecting psychological control and autonomy granting, and examined relations between these parenting dimensions and indices of child and family functioning. Design: A community sample of 90 preadolescents (aged 10.5 to 12 years) and both of their parents engaged in a triadic interaction that was coded for parental psychological control and autonomy granting. Participants also completed measures of child adjustment, interparental conflict, and triangulation. Results: Factor analyses indicated that a two-factor model better fit the data than a one-factor model, suggesting that psychological control and autonomy granting are best conceptualized as independent but related constructs. Parental psychological control and autonomy granting exhibited some shared and some unique correlates with indices of child and family functioning. Hierarchical regressions revealed significant interactions between these dimensions, suggesting that the strength of some associations between parents\u27 use of psychological control and youth adjustment problems depends on the level of autonomy granting exhibited by the parent. Conclusions: By examining psychological control and autonomy granting simultaneously as unique constructs, this study identifies patterns of psychological control and autonomy granting that undermine youth adjustment. Findings inform targeted intervention efforts for families of preadolescent youth

Analytical modeling of helicopter static and dynamic induced velocity in GRASP

The methodology used by the General Rotorcraft Aeromechanical Stability Program (GRASP) to model the characteristics of the flow through a helicopter rotor in hovering or axial flight is described. Since the induced flow plays a significant role in determining the aeroelastic properties of rotorcraft, the computation of the induced flow is an important aspect of the program. Because of the combined finite-element/multibody methodology used as the basis for GRASP, the implementation of induced velocity calculations presented an unusual challenge to the developers. To preserve the modelling flexibility and generality of the code, it was necessary to depart from the traditional methods of computing the induced velocity. This is accomplished by calculating the actuator disc contributions to the rotor loads in a separate element called the air mass element, and then performing the calculations of the aerodynamic forces on individual blade elements within the aeroelastic beam element

Low-Complexity Energy-Efficient Broadcasting in One-Dimensional Wireless Networks

In this paper, we investigate the transmission range assignment for N wireless nodes located on a line (a linear wireless network) for broadcasting data from one specific node to all the nodes in the network with minimum energy. Our goal is to find a solution that has low complexity and yet performs close to optimal. We propose an algorithm for finding the optimal assignment (which results in the minimum energy consumption) with complexity O(N^2). An approximation algorithm with complexity O(N) is also proposed. It is shown that, for networks with uniformly distributed nodes, the linear-time approximate solution obtained by this algorithm on average performs practically identical to the optimal assignment. Both the optimal and the suboptimal algorithms require the full knowledge of the network topology and are thus centralized. We also propose a distributed algorithm of negligible complexity, i.e., with complexity O(1), which only requires the knowledge of the adjacent neighbors at each wireless node. Our simulations demonstrate that the distributed solution on average performs almost as good as the optimal one for networks with uniformly distributed nodes.Comment: 17 page

Observational constraint on the fourth derivative of the inflaton potential

We consider the flow-equations for the 3 slow-roll parameters n_S (scalar spectral index), r (tensor to scalar ratio), and dn_S/dlnk (running of the spectral index). We show that the combination of these flow-equations with the observational bounds from cosmic microwave background and large scale structure allows one to put a lower bound on the fourth derivative of the inflationary potential, M_P^4(V''''/V) > -0.02.Comment: 3 pages, 3 figure

Crossing the Phantom Divide

We consider fluid perturbations close to the "phantom divide" characterised by p = -rho and discuss the conditions under which divergencies in the perturbations can be avoided. We find that the behaviour of the perturbations depends crucially on the prescription for the pressure perturbation delta-p. The pressure perturbation is usually defined using the dark energy rest-frame, but we show that this frame becomes unphysical at the divide. If the pressure perturbation is kept finite in any other frame, then the phantom divide can be crossed. Our findings are important for generalised fluid dark energy used in data analysis (since current cosmological data sets indicate that the dark energy is characterised by p ~ -rho so that p < -rho cannot be excluded) as well as for any models crossing the phantom divide, like some modified gravity, coupled dark energy and braneworld models. We also illustrate the results by an explicit calculation for the "Quintom" case with two scalar fields.Comment: 14 pages, 10 figures, v2: updated to agree with published version: more readable figures, slightly expanded discussion on modified gravity models and the interpolation across w=-1, results and conclusions unchange

Vapor chamber fin studies. Operating characteristics of fin models

Operating characteristics and limits of vapor chamber fins or heat pipe