A Continuous Local Motion Planning Framework for Unmanned Vehicles in Complex Environments

As the complexity of an unmanned vehicle’s operational environment increases so does the need to consider the obstacle space continually, and this is aided by splitting the motion planning functionality into distinct global and local layers. This paper presents a new continuous local motion planning framework, where the output and control space elements of the traditional receding horizon control problem are separated into distinct layers. This separation reduces the complexity of the local motion trajectory optimisation, enabling faster design and increased horizon length. The focus of this paper is on the output space component of this framework. Bezier polynomial functions are used to describe local motion trajectories which are constrained to vehicle performance limits and optimised to track a global trajectory. Development and testing is in simulation, targeted at a nonlinear model of a quadrotor unmanned air vehicle. The defined framework is used to provide situation-aware tracking of a global trajectory in the presence of static and dynamic obstacles, as well as realistic turbulence and gusts. Also demonstrated is the immediate-term decentralised deconfliction of multiple unmanned vehicles, and multiple formations of unmanned vehicles.     

WLAN and WPAN coexistence in UL band

Wireless local- and personal-area networks provide complimentary services in the same unlicensed (UL) radio frequency band of operation. As the mutual benefits of utilizing these services become increasingly apparent, the likelihood of mutual interference may also increase. A method was developed for examining wireless services coexistence in order to evaluate the impact that interference may have on network performance. The methodology for the analysis was centered on deriving a closed-form solution for the probability of collision Pr[C] in terms of the network and radio propagation parameters. In addition, a set of measures of performance was derived based on Pr[C]. In this fashion, the network performance was investigated in regards to the presence of interference. The approach was then illustrated by examining the coexistence between 802.11b and Bluetooth UL band wireless services and summarizing the impact on network performance     

Microstructures of Simulated Nuclear Waste

The microstructures of simulated tailored ceramic forms for the Idaho Chemical Processing Plant (ICPP) high-level waste were characterized by TEM. The ceramic forms were consolidated from simulated ICPP waste calcines with either silicayttria-based or silica–lithia-based additives by hot isostatic pressing. The hot isostatically pressed ceramic waste forms are composed of cubic CaF₂, monoclinic ZrO₂, stabilized cubic ZrO₂, tetragonal ZrSiO₄, and amorphous silicate phases which can be phase separated. The phaseseparated glass is a result of phase immiscibility in the soda aluminosilicate glass to the compositions of albite and mullite.     

Mechanism for the Radiolytically Induced Decomposition of Soda–Silicate Glasses

A mechanism is proposed for the radiolysis which occurs in soda-silicate glasses when they are irradiated. The mechanism is consistent with the observations of the reaction products which are produced and the rates at which the decomposition proceeds.     

An electron microscopy investigation of the structure of porous silicon by oxide replication

The morphology of porous silicon is studied by scanning electron microscopy (SEM) by making an oxide replica of the pore structure. Highly branched n-type porous silicon samples were prepared and a replica was formed by oxidation of the pores followed by selective removal of the silicon substrate to expose the oxide pores. Scanning and transmission electron microscopy images confirmed many previously held assumptions about porous silicon formation, including the fractal structure and crystallographic propagation; they also provided a clearer understanding of the details of pore formation. The replica procedure also provides a platform for a more facile and comprehensive analysis of the porous silicon morphology.     

A novel technique for the preparation of thin films for cross-sectional transmission electron microscopy

A method is described for the preparation of cross-sectional samples of thin films for transmission electron microscopy. The technique produces larger amounts of thin region as compared with ion milling and eliminates the problems associated with ion beam damage. The requirement is that the films or multilayers must initially be deposited on a water-soluble substrate such as single-crystal NaCl.     

SEM/EDS images from a laser printer

A method for producing hardcopy images with a laser printer from scanned video images is presented. The advantages and limitations of this method are compared to the traditional Polaroid technique used for scanning electron microscopy and some methods of creating artificial grey scales using arrays of dots are discussed.     

Feature-based image reconstruction in three dimensions for electron microscopy Part 2: Image reconstruction

The three-dimensional reconstruction of an electron microscopy specimen from a feature-based representation of the images taken from it is described. The method involves the assembling of the features, their correlation, and the measurement of the disparities between the original images.     

PN acquisition for DS/SS using a preloop parallel binary search phase estimator and a closed-loop selective search subsystem

An acquisition method of long pseudo-noise (PN) sequences in direct-sequence spread spectrum (DS/SS) systems is presented. The concurrent cross correlation of locally generated auxiliary signals with the incoming PN sequence produces binary search estimates leading to an initial approximation of the input signal's PN offset. The PN receiver then uses a closed-loop subsystem to determine the true offset of the incoming PN signal. New phase estimates are generated from successive corrections of likely errors in the binary search. The acquisition scheme's average acquisition time and its variance are analytically determined. Simulation results show that the proposed acquisition scheme is faster than the conventional serial receiver. A hybrid serial/parallel PN acquisition receiver is used for comparing the acquisition performance given similar hardware complexity. The hybrid receiver used the same number of parallel correlators as used in the proposed receiver's input phase estimator. Simulation results show that the proposed system provides an improved performance under normal operating conditions.