Aircraft control system

An aircraft control system is described which is particularly suited to rotary wing aircraft. Longitudinal acceleration and course rate commands are derived from a manual control stick to control translational velocity of the aircraft along a flight path. In the collective channel the manual controls provide vertical velocity commands. In the yaw channel the manual controls provide sideslip or heading rate commands at high or low airspeeds, respectively. The control system permits pilots to fly along prescribed flight paths in a precise manner with relatively low work load

Fixed-base simulation evaluation of various low-visibility landing systems for helicopters

Fixed base simulation evaluation of one fully automatic and six manual low visibility landing systems for helicopter

Observation of new quantum interference effect in solids

In order to achieve quantum interference of free electrons inside a solid, we have modified the geometry of the solid so that de Broglie waves interfere destructively inside the solid. Quantum interference of de Broglie waves leads to a reduction in the density of possible quantum states of electrons inside the solid and increases the Fermi energy level. This effect was studied theoretically within the limit of the quantum theory of free electrons inside the metal. It has been shown that if a metal surface is modified with patterned indents, the Fermi energy level will increase and consequently the electron work function will decrease. This effect was studied experimentally in both Au and SiO2 thin films of special geometry and structure. Work function reductions of 0.5 eV in Au films and 0.2 eV in SiO2 films were observed. Comparative measurements of work function were made using the Kelvin Probe method based on compensation of internal contact potential difference. Electron emission from the same thin films was studied by two independent research groups using Photoelectron Emission Microscopy (PEEM).Comment: 11 pages, 5 figure

Upper ocean vertical supply: A neglected primary factor controlling the distribution of neodymium concentrations of open ocean surface waters?

Neodymium (Nd) isotopes are an important geochemical tool to trace the present and past water mass mixing as well as continental inputs. The distribution of Nd concentrations in open ocean surface waters (0–100 m) is generally assumed to be controlled by lateral mixing of Nd from coastal surface currents and by removal through reversible particle scavenging. However, using 228Ra activity as an indicator of coastal water mass influence, surface water Nd concentration data available on key oceanic transects as a whole do not support the above scenario. From a global compilation of available data, we find that more stratified regions are generally associated with low surface Nd concentrations. This implies that upper ocean vertical supply may be an as yet neglected primary factor in determining the basin-scale variations of surface water Nd concentrations. Similar to the mechanism of nutrients supply, it is likely that stratification inhibits vertical supply of Nd from the subsurface thermocline waters and thus the magnitude of Nd flux to the surface layer. Consistently, the estimated required input flux of Nd to the surface layer to maintain the observed concentrations could be nearly two orders of magnitudes larger than riverine/dust flux, and also larger than the model-based estimation on shelf-derived coastal flux. In addition, preliminary results from modeling experiments reveal that the input from shallow boundary sources, riverine input, and release from dust are actually not the primary factors controlling Nd concentrations most notably in the Pacific and Southern Ocean surface waters

Proper Orthogonal Decomposition Closure Models For Turbulent Flows: A Numerical Comparison

This paper puts forth two new closure models for the proper orthogonal decomposition reduced-order modeling of structurally dominated turbulent flows: the dynamic subgrid-scale model and the variational multiscale model. These models, which are considered state-of-the-art in large eddy simulation, together with the mixing length and the Smagorinsky closure models, are tested in the numerical simulation of a 3D turbulent flow around a circular cylinder at Re = 1,000. Two criteria are used in judging the performance of the proper orthogonal decomposition reduced-order models: the kinetic energy spectrum and the time evolution of the POD coefficients. All the numerical results are benchmarked against a direct numerical simulation. Based on these numerical results, we conclude that the dynamic subgrid-scale and the variational multiscale models perform best.Comment: 28 pages, 6 figure

Poloidal-toroidal decomposition in a finite cylinder. II. Discretization, regularization and validation

The Navier-Stokes equations in a finite cylinder are written in terms of poloidal and toroidal potentials in order to impose incompressibility. Regularity of the solutions is ensured in several ways: First, the potentials are represented using a spectral basis which is analytic at the cylindrical axis. Second, the non-physical discontinuous boundary conditions at the cylindrical corners are smoothed using a polynomial approximation to a steep exponential profile. Third, the nonlinear term is evaluated in such a way as to eliminate singularities. The resulting pseudo-spectral code is tested using exact polynomial solutions and the spectral convergence of the coefficients is demonstrated. Our solutions are shown to agree with exact polynomial solutions and with previous axisymmetric calculations of vortex breakdown and of nonaxisymmetric calculations of onset of helical spirals. Parallelization by azimuthal wavenumber is shown to be highly effective

Dynamically Correct Formulations of the Linearised Navier-Stokes Equations

Motivated by the need to efficiently obtain low-order models of fluid flows around complex geometries for the purpose of feedback control system design, this paper considers the effect on system dynamics of basing plant models on different formulations of the linearised Navier-Stokes equations. We consider the dynamics of a single computational node formed by spatial discretisation of the governing equations in both primitive variables (momentum equation & continuity equation) and pressure Poisson equation (PPE) formulations. This reveals fundamental numerical differences at the nodal level, whose effects on the system dynamics at the full system level are exemplified by considering the corresponding formulations of a two-dimensional (2D) channel flow, subjected to a variety of different boundary conditions

Deceiving, Fraudulent, and Seductive: The Discourses of Money in US Novels of the Early Republic

This thesis focuses on the importance of money and the representations of its various physical manifestations (such as coin, paper money) in American fiction of the 1790s. My project traces the transition from the colonies\u27 financial dependency on Britain to their independency, relating to the monetary union created after the passage of the constitution. I argue that this shift from financial dependency to independency influences books such as Charlotte Temple by Susanna Rowson, Kelroy by Rebecca Rush, Ormond or the Secret Witness and Arthur Mervyn by Charles Brockden Brown. My project highlights, on the one hand, the importance of such a transition as it demonstrated a form of independence from the Crown; yet, on the other hand, this independence created issues among the colonists particularly as periodic financial crises or shortages of circulating money led to great uncertainty. These uncertainties emerge in the fiction of the day, especially in anxiety over the monetary union and paper currency. The transition toward a monetary union created social and commercial problems for merchants, businessmen, and families. Within this system, money seemingly becomes a traumatic object that deceives, seduces, and betrays people. Characters in the novels perceive money as treacherous, tricking people into believing in its arbitrary, imaginary, and socially constructed power. Money is anthropomorphized insofar as it seems to have intentions. Building on thing theory, I consider paper money a hyperobject, imbued with an apparent agency. In my thesis, I explore the implications of this widespread reaction to this strange power of paper currency. In this regard, paper money\u27s hyperobjectivity is revealed by examining the notion of commodification, closely exploring instantaneous changes that occur in the novels in relationship to economic changes, and money\u27s ephemerality