A comparative study of ionospheric IRIEup and ISP assimilative models during some intense and severe geomagnetic storms

Three-dimensional (3-D) electron density matrices, computed in the Mediterranean area by the IRI climatological model and IRIEup and ISP nowcasting models, during some intense and severe geomagnetic-ionospheric storms, were ingested by the ray tracing software tool IONORT, to synthesize quasi-vertical ionograms. IRIEup model was run in different operational modes: (1) assimilating validated autoscaled electron density profiles only from a limited area which, in our case, is the Mediterranean sector (IRIEup_re(V) mode); (2) assimilating electron density profiles from a larger region including several stations spread across Europe: (a) without taking care of validating the autoscaled data in the assimilation process (IRIEup(NV)); (b) validating carefully the autoscaled electron density profiles before their assimilation (IRIEup(V)).The comparative analysis was carried out comparing IRI, IRIEup_re(V), ISP, IRIEup(NV), and IRIEup(V) foF2 synthesized values, with corresponding foF2 measurements autoscaled by ARTIST, and then validated, at the truth sites of Roquetes (40.80°N, 0.50°E, Spain), San Vito (40.60°N, 17.80°E, Italy), Athens (38.00°N, 23.50°E, Greece), and Nicosia, (35.03°N, 33.16°E, Cyprus). The outcomes demonstrate that: (1) IRIEup_re(V), performs better than ISP in the western Mediterranean (around Roquetes); (2) ISP performs slightly better than IRIEup_re(V) in the central part of Mediterranean (around Athens and San Vito); (3) ISP performance is better than the IRIEup_re(V) one in the eastern Mediterranean (around Nicosia); (4) IRIEup(NV) performance is worse than the IRIEup(V) one; (5) in the central Mediterranean area, IRIEup(V) performance is better than the IRIEup_re(V) one, and it is practically the same for the western and eastern sectors.Concerning the overall performance, nowcasting models proved to be considerably more reliable than the climatological IRI model to represent the ionosphere behaviour during geomagnetic-ionospheric storm conditions; ISP and IRIEup(V) provided the best performance, but neither of them has clearly prevailed over the other one.     

Design of a canard configured TransCruiser using CEASIOM

CEASIOM is a multidisciplinary software environment for aircraft design that has been developed as part of the European Framework 6 SimSAC project. It closely integrates discipline-specific tools such as those used for CAD, grid generation, CFD, stability analysis and control system design. The environment allows the user to take an initial design from geometry definition and aerodynamics generation through to full six degrees of freedom simulation and analysis. Key capabilities include variable fidelity aerodynamics tools and aeroelasticity modules. The purpose of this paper is to demonstrate the potential of CEASIOM by presenting the results of a Design, Simulate and Evaluate (DSE) exercise applied to a novel, project specific, transonic cruiser configuration called the TCR. The baseline TCR configuration is first defined using conventional methods, which is then refined and improved within the CEASIOM software environment. A wind tunnel model of this final configuration was then constructed, tested and used to verify the results generated using CEASIOM.     

Time-Optimal Control of a Bounded Phase-Coordinate Process II: High-Order Systems with Multiple Control Inputs

This paper considers the problem arising from the design of an autopilot for a large booster. The motion-controlling actuators of the booster have both position and rate limits. The problem is formulated as a bounded phase-coordinate problem and analyzed by the ``backing out of the target' procedure. A method of constructing the optimal control is presented. An example of an oscillatory system with two control inputs is given, and the optimal control is expressed as an explicit time function.     

Maximum Power Transfer for Full-Wave Rectifier Circuits

An analysis is done to determine the maximum power transfer conditions for full-wave rectifier circuits. Potential applications noted are implanted medical instruments, inductive power transfer to weapons, power transfer using space reflectors, and power generation in space. Three types of series impedances are considered: resistive/inductive (RL), resistive/capacitive (RC), and resistive/inductive/capacitive (RLC). The optimum ratio of ac-to-dc voltage output is determined for each type. For the case that involves all three impedance types, the optimum turning condition is also determined. The differential equations describing the circuits are solved in nondimensional form. The solutions involve partial differential equations, closed-form relationships, and simultaneous equations that are solved by numerical methods. The optimum ratio of peak ac-to-dc voltage ranges from 2.0 to 2.8, depending upon the circuit. The optimum turning differs significantly from the usual resonant conditions, especially for low Q.     

Shaping peace

Soviet General Secretary Gorbachev, in his January 1986 speech, expressed a hope that the level of nuclear weapons would before long be greatly reduced. The Soviet Embassy in Sri Lanka invited Arthur C. Clarke to comment on the General Secretary's speech. This article is his response.     

An experimental study of elastic properties of dragonfly-like flapping wings for use in biomimetic micro air vehicles (BMAVs)

This article studies the elastic properties of several biomimetic micro air vehicle (BMAV) wings that are based on a dragonfly wing. BMAVs are a new class of unmanned micro-sized air vehicles that mimic the flapping wing motion of flying biological organisms (e.g., insects, birds, and bats). Three structurally identical wings were fabricated using different materials: acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), and acrylic. Simplified wing frame structures were fabricated from these materials and then a nanocomposite film was adhered to them which mimics the membrane of an actual dragonfly. These wings were then attached to an electromagnetic actu-ator and passively flapped at frequencies of 10–250 Hz. A three-dimensional high frame rate imag-ing system was used to capture the flapping motions of these wings at a resolution of 320 pixels × 240 pixels and 35000 frames per second. The maximum bending angle, maximum wing tip deflection, maximum wing tip twist angle, and wing tip twist speed of each wing were measured and compared to each other and the actual dragonfly wing. The results show that the ABS wing has considerable flexibility in the chordwise direction, whereas the PLA and acrylic wings show better conformity to an actual dragonfly wing in the spanwise direction. Past studies have shown that the aerodynamic performance of a BMAV flapping wing is enhanced if its chordwise flexibility is increased and its spanwise flexibility is reduced. Therefore, the ABS wing (fabricated using a 3D printer) shows the most promising results for future applications.     

Navier–Stokes solvers in European aircraft design

The paper gives a broad perspective of the progress made during the last 10 years in solving the Navier–Stokes equations and traces how this simulation technique went from being a specialized research topic to a practical engineering tool that design engineers use on a routine basis.

The scope is limited to Navier–Stokes solvers applied to industrial design of airframes with attention focused particularly on developments in Europe. An overview of the different Navier–Stokes codes used in Europe is given, and on-going developments are outlined.

The current state of progress is illustrated by computed steady and unsteady solutions to industrial problems, ranging from airfoil characteristics, flow around an isolated wing, to full aircraft configurations.

A discussion on the future industrial design environment is given, and developments in Europe towards a more integrated design approach with underlying concepts like ‘concurrent engineering (CE)’ and the ‘virtual product (VP)’ are summarized. The paper concludes with a discussion on future challenging applications.