Determination of maximum deflection in transverse bending of parallelogram plates using the conformal radiuses ratio

A problem of transverse bending of elastic isotropic parallelogram plates under the action of uniformly distributed load is considered. The plate sides are either pivoted or rigidly restrained. To determine the value of maximum plate deflection, it is proposed that an interpolation technique with respect to form factor be used; and as a geometrical argument, an inner-outer conformal radius ratio can be applied instead of the form factor.     

A working hypothesis for connections between electrically-induced changes in cloud microphysics and storm vorticity,with possible effects on circulation

This paper outlines, and explores the uncertainties in, hypothesized connections between a series of processes that could explain two long-standing puzzles; those of (1) the observed winter storm vorticity responses to atmospheric energy inputs that change the ionosphere–earth current density, J_z, that appear to involve storm invigoration, and (2) changes in anti-cyclonic blocking and circulation that include the observed colder winters in Great Britain and western Europe at solar minima, and especially at extended solar minima. A working hypothesis for the mechanism responsible for (1) is that the flow of J_z through conductivity gradients, as in stratified cloud layers and fog, especially with sea-salt aerosol haze over the high latitude winter oceans, deposits electric changes on droplets and aerosol particles; most importantly on cloud condensation nuclei (CCN). These electric charges modulate scavenging of the particles in clouds and haze layers, increasing the concentration of small CCN and decreasing the concentration of large CCN. When further cloud formation occurs there is increased concentration of small droplets and decreased concentration of large ones, reducing coalescence and the production of rain. Thus updrafts carry more liquid water above the freezing level, and there the increased production of ice releases more latent heat and invigorates the updraft (the Rosenfeld mechanism), leading to increased vorticity. Here we explore the major uncertainties for the reality of the above chain of physical processes. A consequence of cumulative cyclonic vorticity increases is increases in downstream anti-cyclonic blocking. A further working hypothesis for (2) is that the invigoration may be large enough to contribute to the observed increases in blocking in winters at solar minima (high J_z) in the North Atlantic, that result in colder winters in the UK and northern Europe.     

Optimimal control of CNC machine operating regimes

In this paper, a mathematical model of labor-intensity and a method of searching for optimal control of operating conditions in machining arbitrarily configurated parts with the use of CNC machines are considered. Also given is an example of the process optimization..     

Rotational evolution of planetary systems under the action of gravitational and magnetic perturbations

Dynamics of planets around other stars that demonstrate a variety of possible characteristics is of interest from the point of view of realization of new scenarios of evolution which have not been realized in the Solar System. We consider the rotational evolution of exoplanets under the action of gravitational perturbations and magnetic disturbances using the methods of quality analysis and theory of bifurcation of multiparametric differential equations that describe evolution of non-resonant rotation of a dynamically symmetric planet magnetized along its symmetry axis. We analyze 64 phase portraits describing the evolution of angular momentum vector L for all possible values of planet parameters. The values of parameters are determined for the case when the direct rotation of a planet is changed for its retrograde rotation.     

Quantifying the role of solar radiative forcing over the 20th century

The 20th century temperature anomaly record is reproduced using an energy balance model, with a diffusive deep ocean. The model takes into account all the standard radiative forcings, and in addition the possibility of a non-thermal solar component. The model is parameterized and then optimized to produce the most likely values for the climate parameters and radiative forcings which reproduce the 20th century global warming. We find that the best fit is obtained with a negligible net feedback. We also show that a non-thermal solar component is necessarily present, indicating that the total solar contribution to the 20th century global warming, of ΔT_solar = 0.27 ± 0.07 °C, is much larger than can be expected from variation in the total solar irradiance alone. However, we also find that the largest contribution to the 20th century warming comes from anthropogenic sources, with ΔT_man = 0.42 ± 0.11 °C.     

Active debris removal of multiple priority targets

Today’s space debris environment shows major concentrations of objects within distinct orbital regions for nearly all size regimes. The most critical region is found at orbital altitudes near 800 km with high declinations. Within this region many satellites are operated in so called sun-synchronous orbits (SSO). Among those, there are Earth observation, communication and weather satellites. Due to the orbital geometry in SSO, head-on encounters with relative velocities of about 15 km/s are most probable and would thus result in highly energetic collisions, which are often referred to as catastrophic collisions, leading to the complete fragmentation of the participating objects. So called feedback collisions can then be triggered by the newly generated fragments, thus leading to a further population increase in the affected orbital region. This effect is known as the Kessler syndrome.     

Auroral radio absorption: The prediction question

The paper summarises key facts and figures about the phenomenon of auroral radio absorption which are relevant to the problem of predicting its occurrence and intensity. The regions most affected are well known in terms of magnetic latitude (or L-value) and local time. The greater difficulty comes from its highly variable character. Exact predictions are never likely to be possible, but statistical forecasts, which would give the likelihood that some critical level will be reached or exceeded, may well be possible. At the present time it is suggested that they might be based on magnetic indices, since their prediction is already well established. Direct measurements of the solar wind, now available in real time, offer another possibility, perhaps to be considered in parallel. The substorm character of the absorption might also be applied, using the observed duration of absorption events and their known dynamics over the Earth’s surface, as an early warning. A comprehensive reference list is included.     

Buckling of composite panels: A criterion for optimum stiffener design

In this paper a linear, closed-form analysis of the buckling behavior of an orthotropic plate with elastic clamping and edge reinforcement under uniform compressive load is presented. This is a typical structural situation found in aerospace engineering for instance as stiffeners in wings or the fuselage. All governing equations are transformed in a dimensionless system using common characteristic quantities to gain good analytical access. The buckling behavior is analyzed and generic buckling diagrams are presented. The solutions show excellent agreement with results from literature and numerical analyses.The minimum bending stiffness of the edge reinforcement needed to withstand buckling is examined and a minimum stiffness criterion is presented. Furthermore an absolute minimum bending stiffness is found which is sufficient to enable the reinforcement to act as a near-rigid support for arbitrarily long plates. These criteria are of interest for optimized lightweight design of stringers and stiffeners.     

The International DORIS Service (IDS): Toward maturity

DORIS is one of the four space-geodetic techniques participating in the Global Geodetic Observing System (GGOS), particularly to maintain and disseminate the Terrestrial Reference Frame as determined by International Earth rotation and Reference frame Service (IERS). A few years ago, under the umbrella of the International Association of Geodesy, a DORIS International Service (IDS) was created in order to foster international cooperation and to provide new scientific products. This paper addresses the organizational aspects of the IDS and presents some recent DORIS scientific results. It is for the first time that, in preparation of the ITRF2008, seven Analysis Centers (AC’s) contributed to derive long-term time series of DORIS stations positions. These solutions were then combined into a homogeneous time series IDS-2 for which a precision of less than 10 mm was obtained. Orbit comparisons between the various AC’s showed an excellent agreement in the radial component, both for the SPOT satellites (e.g. 0.5–2.1 cm RMS for SPOT-2) and Envisat (0.9–2.1 cm RMS), using different software packages, models, corrections and analysis strategies. There is now a wide international participation within IDS that should lead to future improvements in DORIS analysis strategies and DORIS-derived geodetic products.     

Protecting Earth-orbiting spacecraft against micro-meteoroid/orbital debris impact damage using composite structural systems and materials: An overview

Spacecraft that are launched to operate in Earth orbit are susceptible to impacts by meteoroids and pieces of orbital debris (MMOD). The effect of a MMOD particle impact on a spacecraft depends on where the impact occurs, the size, composition, and speed of the impacting object, the function of the impacted system. In order to perform a risk analysis for a particular spacecraft under a specific mission profile, it is important to know whether or not the impacting particle (or its remnants) will exit the rear of an impacted spacecraft wall. A variety of different ballistic limit equations (BLEs) have been developed for many different types of structural wall configurations. BLEs can be used to optimize the design of spacecraft wall parameters so that the resulting configuration is able to withstand the anticipated variety of on-orbit high-speed impact scenarios. While the level of effort exerted in studying the response of metallic multi-wall systems to high speed particle impact is quite substantial, the extent of the effort to study composite material and composite structural systems under similar impact conditions has been much more limited. This paper presents an overview of the activities performed to assess the resiliency of composite structures and materials under high speed projectile impact. The activities reviewed will be those that have been aimed at increasing the level of protection afforded to spacecraft operating in the MMOD environment, and more specifically, on those activities performed to mitigate the mechanical and structural effects of an MMOD impact.