Temporal Precedence Checking for Switched Models and its Application to a Parallel Landing Protocol

This paper presents an algorithm for checking temporal precedence properties of nonlinear switched systems. This class of properties subsume bounded safety and capture requirements about visiting a sequence of predicates within given time intervals. The algorithm handles nonlinear predicates that arise from dynamics-based predictions used in alerting protocols for state-of-the-art transportation systems. It is sound and complete for nonlinear switch systems that robustly satisfy the given property. The algorithm is implemented in the Compare Execute Check Engine (C2E2) using validated simulations. As a case study, a simplified model of an alerting system for closely spaced parallel runways is considered. The proposed approach is applied to this model to check safety properties of the alerting logic for different operating conditions such as initial velocities, bank angles, aircraft longitudinal separation, and runway separation

Effect of H₂S and HCl contaminants on nickel and ceria pattern anode solid oxide fuel cells

In this study, with the motivation of elucidating the effect of H2S and HCl on solid oxide fuel cell anodes, nickel and ceria pattern anodes are prepared on yttrium-stabilized zirconia electrolyte, and the effect of H2S and HCl on their performance is tested using electrochemical impedance spectroscopy. However, it has been found that while H2S adversely impacts both nickel and ceria, the poisoning caused is reversible for nickel and only partially reversible for ceria. Poisoning kinetics are similar and fast for both materials, while recovery kinetics are slower for ceria than nickel. High sulfur coverage is the rate-limiting factor inferred from the elementary kinetic modeling. Unlike H2S, the presence of HCl appeared to be favorable for electrochemical oxidation as the polarization resistance of both pattern electrode cells decreased upon feeding HCl contaminated hydrogen gas. Similar behavior has not been reported previously, and the conclusion regarding underlying mechanisms requires further investigation

A Framework for Smart Distribution of Bio-signal Processing Units in M-Health

This paper introduces the Bio-Signal Processing Unit (BSPU) as a functional component that hosts (part of ) the bio-signal information processing algorithms that are needed for an m-health application. With our approach, the BSPUs can be dynamically assigned to available nodes between the bio-signal source and the application to optimize the use of computation and communication resources. The main contributions of this paper are: (1) it presents the supporting architecture (e.g. components and interfaces) and the mechanism (sequence of interactions) for BSPU distribution; (2) it proposes a coordination mechanism to ensure the correctness of the BSPU distribution; (3) it elaborates the design of smooth transition during BSPU distribution in order to minimize the disturbance to the m-health streaming application

Survey and comparison of petroleum well electrologging tools

The principles used in the design of electrologging tools used in the petroleum industry are reviewed. Examples of tools and methods are taken from Gearhart Industries, Schlumberger Ltd and Western Atlas Ltd who are the three major electrologging companies accounting for 93% of the world market share. The survey and comparison of the tools in each of the category used both during the exploration and development stage of a well and reservoir are made. The results are presented and discussed. Furthermore an insight to the future of this industry is presented

Changing Patterns in the Social Organization of the Coffee Export Sector in Sao Paulo, 1889-1930

http://deepblue.lib.umich.edu/bitstream/2027.42/51040/1/268.pd

NASA-JSC antenna near-field measurement system

Work was completed on the near-field range control software. The capabilities of the data processing software were expanded with the addition of probe compensation. In addition, the user can process the measured data from the same computer terminal used for range control. The design of the laser metrology system was completed. It provides precise measruement of probe location during near-field measurements as well as position data for control of the translation beam and probe cart. A near-field range measurement system was designed, fabricated, and tested

Supermodes of high-repetition-rate passively mode-locked semiconductor lasers

We present a steady-state analysis of high-repetition-rate passively mode-locked semiconductor lasers. The analysis includes effects of amplitude-to-phase coupling in both gain and absorber sections. A many-mode eigenvalue approach is presented to obtain supermode solutions. Using a nearest-neighbor mode coupling approximation, chirp-free pulse generation and electrically chirp-controlled operation are explained for the first time. The presence of a nonzero alpha parameter is found to change the symmetry of the supermode and significantly reduce the mode-locking range over which the lowest order supermode remains the minimum gain solution. An increase in absorber strength tends to lead to downchirped pulses. The effects of individual laser parameters are considered, and agreement with recent experimental results is discussed

Active X-ray optics for the next generation of X-ray space telescopes

Described within is the design, manufacture, metrology and X-ray testing of an active X-ray prototype intended for the next generation of X-ray telescopes. One of the challenges faced by the X-ray telescope community is how to combine high resolution and high sensitivity into one system, as weight limitations place constraints on the optics that can be launched. Therefore the mandate of the active X-ray prototype is to provide high sensitivity through the ability of the optics to be nested and to deliver high angular resolution through the active control of the optic’s form. Piezoelectric unimorph actuators provide the active component: it is intended that they will correct for figure errors within the optic and therefore increase the angular resolution capability. The prototype’s design is based upon an ellipsoidal segment which provides point-to-point focussing of an X-ray source. The prototype itself is composed of an electroformed nickel optic where the non-reflective surface is populated with 30 piezoelectric actuators and it is the production of the prototype that is the core of the presented research. Metrology of the actuators’ influence functions is presented and highlight the prototype’s ability to deform its optic surface by microns. In addition, the measured influence functions are compared against finite element models and a distinct similarity between the functions is observed. The prototype was tested at an X-ray beamline facility in November 2008 and the results showed the prototype’s ability to correct the optic to achieve an improved angular resolution: from 0.786 arc-minutes to 0.686 arc-minutes in terms of full width half maximum. Finally, difficulties in the manufacture of the prototype and X-ray testing shall be presented alongside future work in conclusion to this thesis

Analysis of platinum, palladium and rhodium at trace concentrations in lead using the time resolved spark emission technique called SAFT

Includes bibliographical references.The fire assay technique may be used to extract noble metals from platinum bearing ores. It allows for the use of relatively large quantities of ore sample from which trace quantities of noble metals are concentrated. The fire assay with lead as the collector is one such procedure, where preconcentration of the noble metals allows for direct analysis of the noble metals in lead The samples may be prepared by pyrochemically treating the ore sample with a litharge-based flux. These lead buttons require an homogenising remelt and rapid cast before direct determination of the noble metals can be made using a time resolved form of spectroscopy called SAFf, or Spark Analysis for Traces. The unique characteristics of this technique is that inunediately after the electrical spark discharge has taken place radiation from atomic species continues and is termed after-glow. Special electronic techniques are required to observe this phenomenon as it takes place in microseconds. By studying the emission characteristics of various spectral wavelengths it is possible to determine the time at which the photomultiplier measures the atomic radiation. and not the background radiation. The atomic emission line to background ratio is thus improved and hence precision and limits of detection. Initial investigations into the SAFf analysis of platinum. palladium and rhodium using synthetic standards prepared from pure noble metals and lead revealed an analytical method of great promise. However the method failed when applied to real ore samples for several reasons. The SAFf analysis is particularly sensitive to the effects due to changes of the matrix of the lead depending on the type of sample used to prepare the lead buttons. Corrections for these effects could not be applied as preparation of matrix matched standards also failedAnother serious problem experienced with the SAFf technique was the inherent insensitivity of the selected platinum wavelengths together with high background emissions. The platinum atomic emission to background ratio was thus poor, and hence scientifically inappropriate practice to measure platinum in lead under these circumstances. The most sensitive platinum emission wavelength could not be used because corrections for a spectral interference from nickel could not be applied. A certain portion of base metals are collected in the lead buttons along with the noble metals during the fusion process, and since nickel is present in all ore samples associated with platinum group metals the presence of nickel and platinum together in lead after collection is inevitable. Because of the nature of the ore samples used in the investigations, the concentration range of platinum, palladium and rhodium in lead even after preconcentration using fire assay, was very limited, and attempts to create calibrations using only these samples proved unsuccessful. Additional standards prepared from different ore samples were used to extend the concentration ranges of the calibrations, however this also proved to be of no use as the different matrices of these samples detracted from any possibility of defining an accurate calibration curve