Rutherford backscattering spectrometry and computer simulation for the in-depth analysis of chemically modified poly(vinylidene fluoride)

The alkaline treatment of poly(vinylidene fluoride) (PVdF), in the presence of phase transfer catalysts (PTCs) has been investigated. Rutherford backscattering spectrometry (RBS) has been used to determine the depth of modification achieved and to provide compositional depth profiles of modified PVdF samples. The complex chemical nature of the modified substrate, and the overlap of the elemental scattering edges within the depths involved (up to 1.4 m), create RBS spectra which are difficult to interpret. The DataFurnace software has been applied to the data, leading to excellent results. Defluorination and oxygenation of PVdF occurs on treatment with NaOH and PTC. Through the use of samples prepared with the aim of establishing the kinetics of the modification, a mechanism concerning elimination of fluorine followed by oxygenation, is shown to occur. The RBS analysis indicates that the kinetics of the defluorination reaction follows the Case 1 (Fickian) diffusion law, and that the depth of treatment is of the order of 1.4 m.     

Generation of terawatt pulses by use of optical parametric chirped pulse amplification

Optical parametric chirped pulse amplifiers offer exciting prospects for generating new extremes in power, intensity, and pulse duration. An experiment is described that was used to investigate the operation of this scheme up to energies approaching a joule, as a step toward its implementation at the petawatt level. The results demonstrate an energy gain of 10(10) with an energy extraction efficiency of 20% and close to diffraction-limited performance. Some spectral narrowing during amplification was shown to be compatible with the time-varying profile of the pump beam and consistent with the measured recompressed pulse durations of 260 and 300 fs before and after amplification, respectively.     

An algorithm for projective point matching in the presence of spurious points

Point matching is the task of finding correspondences between two sets of points such that the two sets of points are aligned with each other. Pure point matching uses only the location of the points to constrain the problem. This is a problem with broad practical applications, but it has only been well studied when the geometric transformation relating the two point sets is of a relatively low order. Here we present a heuristic local search algorithm that can find correspondences between point sets in two dimensions that are related by a projective transform. Point matching is a harder problem when spurious points appear in the sets to be matched. We present a heuristic algorithm which minimizes the effects of spurious points.     

The dimensional nature of disturbed dreaming: Reply to Weiss (2007).

The authors' proposed model of nightmare formation (see record 2007-06095-006) withstands several criticisms raised in an accompanying commentary article (D. S. Weiss, 2007; see record 2007-06095-007). A principal criticism, that the model lacks convergent and divergent validity, appears to stem from the commenter's application of a strong categorical, as opposed to the authors' use of a dimensional, approach to the model/construct of nightmares. Furthermore, ongoing research continues to support the authors' assumptions about the basic relationship between nightmares and affect distress. Other criticisms of the model, including a failure to account for robust epidemiological differences in nightmares and an ambiguity in the concept of affect distress, are also countered by reference to relevant research findings. A robust gender difference in nightmares (women = men) is particularly compatible with studies demonstrating gender differences in emotion among the physiological and cognitive systems that the authors propose are centrally implicated in nightmare formation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gates’ Bidding Model

In evaluating closed-bid competitive procurement auctions, the most crucial issue is to determine the probability of placing a winning bid for a given markup level. There has long been disagreement on how this should be done due to the absence of a mathematical derivation of one of the main evaluation techniques—Gates’ method. Gates’ method is shown in this paper to be valid if, and only if, bids can be described using the proportional hazards family of statistical distributions. When markup values are included in Gates’ method, it is seen that the underlying statistical distribution required for the method to work is closely related to the Weibull distribution. Likelihood based methods are suggested for parameter estimation and an illustrative example is provided by analysis of Shaffer and Micheau's 1971 construction contract bidding data.     

Seeing through dust and water vapor: Millimeter wave radar sensors for mining applications

This paper defines the issues required for the development of successful visualization sensors for use in open cut and underground mines. It examines the mine environment and considers both the reflectivity of the rock and attenuation effects of dust and water droplets. Millimeter wave technology, as an alternative to the more commonly used laser and sonar implementations, is selected due to its superior penetration through adverse atmospheric conditions. Of the available radar techniques, frequency modulated continuous wave (FMCW) is selected as being the most robust. The theoretical performance of a number of 77 and 94 GHz FMCW millimeter wave radar systems is determined and these confirm the capability of these sensors in the mining environment. Implementations of FMCW radar sensors for simple ranging and three‐dimensional surface profiling are discussed before data obtained during field trials in mines is presented to justify the selection of this technology. © 2007 Wiley Periodicals, Inc.     

A 3-degree of freedom binary search pose estimation technique

This paper describes a novel, binary search pose estimation (BSPE) technique for poses constrained to 3 degrees of freedom (DOF). The technique requires three fiduciary marker points and operates by minimising the angular DOF through a binary search driven algorithm. The technique is less computationally intensive than the standard closed form solutions and quickly converges to a solution which can be verified if additional fiduciary points are available. Evaluation for the technique is presented through a comparison to pose from orthography and scaling with iterations (POSIT) using synthetic data and a real-world application, where the technique is used for pose estimation of a mobile robot with respect to a motor vehicle for inspection purposes.     

Remote sensing of selected water-quality indicators with the hyperspectral imager for the coastal ocean (HICO) sensor

The Hyperspectral Imager for the Coastal Ocean (HICO) offers the coastal environmental monitoring community an unprecedented opportunity to observe changes in coastal and estuarine water quality across a range of spatial scales not feasible with traditional field-based monitoring or existing ocean colour satellites. HICO, an Office of Naval Research-sponsored programme, is the first space-based maritime hyperspectral imaging instrument designed specifically for the coastal ocean. HICO has been operating since September 2009 from the Japanese Experiment Module – Exposed Facility on the International Space Station (ISS). The high pixel resolution (approximately 95 m at nadir) and hyperspectral imaging capability offer a unique opportunity for characterizing a wide range of water colour constituents that could be used to assess environmental condition. In this study, we transform atmospherically corrected ISS/HICO hyperspectral imagery and derive environmental response variables routinely used for evaluating the environmental condition of coastal ecosystem resources. Using atmospherically corrected HICO imagery and a comprehensive field validation programme, three regionally specific algorithms were developed to estimate basic water-quality properties traditionally measured by monitoring agencies. Results indicated that a three-band chlorophyll a algorithm performed best (R² = 0.62) when compared with in situ measurement data collected 2–4 hours of HICO acquisitions. Coloured dissolved organic matter (CDOM) (R² = 0.93) and turbidity (R² = 0.67) were also highly correlated. The distributions of these water-quality indicators were mapped for four estuaries along the northwest coast of Florida from April 2010 to May 2012. However, before the HICO sensor can be transitioned from proof-of-concept to operational status and its data applied to benefit decisions made by coastal managers, problems with vicarious calibration of the sensor need to be resolved and standardized protocols are required for atmospheric correction. Ideally, the sensor should be placed on a polar orbiting platform for greater spatial and temporal coverage as well as for image synchronization with field validation efforts.     

Phenology of vegetation in Southern England from Envisat MERIS terrestrial chlorophyll index (MTCI) data

Given the close association between climate change and vegetation response, there is a pressing requirement to monitor the phenology of vegetation and understand further how its metrics vary over space and time. This article explores the use of the Envisat MERIS terrestrial chlorophyll index (MTCI) data set for monitoring vegetation phenology, via its estimates of chlorophyll content. The MTCI was used to construct the phenological profile of and extract key phenological event dates from woodland and grass/heath land in Southern England as these represented a range of chlorophyll contents and different phenological cycles. The period 2003–2008 was selected as this was known to be a period with temperature and phenological anomalies. Comparisons of the MTCI-derived phenology data were made with ground indicators and climatic proxy of phenology and with other vegetation indices: MERIS global vegetation index (MGVI), MODIS normalized difference vegetation index (NDVI) and MODIS enhanced vegetation index (EVI). Close correspondence between MTCI and canopy phenology as indicated by ground observations and climatic proxy was evident. Also observed was a difference between MTCI-derived phenological profile curves and key event dates (e.g. green-up, season length) and those derived from MERIS MGVI, MODIS NDVI and MODIS EVI. The research presented in this article supports the use of the Envisat MTCI for monitoring vegetation phenology, principally due to its sensitivity to canopy chlorophyll content, a vegetation property that is a useful proxy for the canopy physical and chemical alterations associated with phenological change.