Analysis of a single-fold deployable truss beam preloaded by extension of selected face diagonal members

A technique for preloading a deployable box truss beam by extension of one face diagonal per bay was studied to determine if it would result in uniform loading of truss joints without causing excessive truss deformations. Results indicate that it is possible to accomplish uniform loading in the beam region way from beam boundaries, whereas in the regions near boundaries the member loading becomes non-uniform with magnitudes greater than those in the uniform load region. Also, the type of deformation which results in the beam depends on the pattern of preloaded members

Development of response models for the Earth Radiation Budget Experiment (ERBE) sensors. Part 2: Analysis of the ERBE integrating sphere ground calibration

An explicit solution of the spectral radiance leaving an arbitrary point on the wall of a spherical cavity with diffuse reflectivity is obtained. The solution is applicable to spheres with an arbitrary number of openings of any size and shape, an arbitrary number of light sources with possible non-diffuse characteristics, a non-uniform sphere wall temperature distribution, non-uniform and non-diffuse sphere wall emissivity and non-uniform but diffuse sphere wall spectral reflectivity. A general measurement equation describing the output of a sensor with a given field of view, angular and spectral response measuring the sphere output is obtained. The results are applied to the Earth Radiation Budget Experiment (ERBE) integrating sphere. The sphere wall radiance uniformity, loading effects and non-uniform wall temperature effects are investigated. It is shown that using appropriate interpretation and processing, a high-accuracy short-wave calibration of the ERBE sensors can be achieved

Cell-level path allocation in a three-stage ATM switch

A method of cell-level path allocation for three-stage ATM switches has previously been proposed by the authors. The performance of ATM switches using this path allocation algorithm has been evaluated by simulation, and is described. Both uniform and non-uniform models of output loading are considered. The algorithm requires knowledge of the number of cells requesting each output module from a given input module. A fast method for counting the number of requests is described

Efficient and robust initialization of a qubit register with fermionic atoms

We show that fermionic atoms have crucial advantages over bosonic atoms in terms of loading in optical lattices for use as a possible quantum computation device. After analyzing the change in the level structure of a non-uniform confining potential as a periodic potential is superimposed to it, we show how this structure combined with the Pauli principle and fermion degeneracy can be exploited to create unit occupancy of the lattice sites with very high efficiency.Comment: 4 pages, 3 figure

Smeared Impedence Model for Variable Depth Liners

Noise from modern aircraft engines has a significant broadband component, which has motivated the need for broadband acoustic engine liners. A promising broadband design, called a variable depth liner, is composed of groups of resonators tuned for different frequencies. The accuracy of commonly used smeared impedance models, however, has not been thoroughly assessed for this type of liner. Therefore, the purpose of this study is to assess, and if necessary develop, semi-analytical impedance models for variable depth designs. The impedance prediction is complicated by the fact that the radiation loading on individual resonators within the array can be different. While the radiation loading can be neglected on conventional engine liners that consist of a dense array of uniform resonators, the same is not true for variable depth liners. To better understand and model this effect, nine liner samples are tested in the NASA Langley normal incidence tube. Comparisons of predicted and measured data for relatively simple non-uniform samples confirm that the radiation loading can be approximated using mass end correction terms. Semi-analytical impedance models that incorporate the proposed end corrections provide favorable comparisons with measured impedance spectra for variable depth liner samples

Evaporation limited loading of an atom trap

Recently, we have experimentally demonstrated a continuous loading mechanism for an optical dipole trap from a guided atomic beam [1]. The observed evolution of the number of atoms and temperature in the trap are consequences of the unusual trap geometry. In the present paper, we develop a model based on a set of rate equations to describe the loading dynamics of such a mechanism. We consider the collision statistics in the non-uniform trap potential that leads to twodimensional evaporation. The comparison between the resulting computations and experimental data allows to identify the dominant loss process and suggests ways to enhance the achievable steady-state atom number. Concerning subsequent evaporative cooling, we find that the possibility of controlling axial and radial confinement independently allows faster evaporation ramps compared to single beam optical dipole traps.Comment: 10 pages, 7 figure

Assessing the Role of Longitudinal Variability of Vertical Track Stiffness in the Long-Term Deterioration

The performance of the railway system in terms of dynamic loading is depending mainly on the track support conditions. Usually, the track stiffness is used as the main parameter to describe the support conditions and is defined as the ratio of the load applied to the rail over the vertical rail deflection. Ideally that parameter is constant, but in reality this condition is very unlikely to happen. Therefore, there is non-uniform track loading and non-uniform track deterioration, generally known as differential settlement, leading to a general increment of maintenance and renewal costs. Even if it plays a major role in the system dynamics, it is very difficult to derive a measure of the actual variability of the track stiffness along the railway. There are many techniques to experimentally acquire those values, for example using the Falling Weight Deflectometer (FWD) equipment or the Swedish Rolling Stiffness Measurement Vehicle (RSDV) measuring train. However, these measures are usually very costly and limited in extension. The measuring data may not be long enough to be statistically representative, and thus it is not possible to have a clear correlation between the physical properties of the railway system and its long-term behaviour without running simulations with extended track data. The main aim of the present study is to assess the role of longitudinal variability of the vertical track stiffness in the long-term behaviour of the track degradation. In particular, new sets of track stiffness data which can appropriately reproduce the statistical properties of the real ones will be simulated. Then, the variability of the outputs of the vehicle dynamic model depending on the variability in the inputs will be statistically analysed. This is inspired in past research that highlighted the role of vertical stiffness in track deterioration, but not looking at the actual longitudinal variability of vertical stiffness as a contributing factor

The tool switching problem revisited.

In this note we study the complexity of the tool switching problem with non-uniform tool sizes. More speci cally, we consider the problem where the job sequence is given as part of the input. We show that the resulting tooling problem is strongly NP-complete, even in case of unit loading and unloading costs. However, we show that if the capacity of the tool magazine is also given as part of the input, the problem is solvable in polynomial time.Research; Studies; Complexity; Job; Costs; Time;