PdRhO2 formation during the air oxidation of a Pd-15Rh alloy

The surfaces of air-oxidized Pd-15Rh alloys have been examined by X-ray photoelectron spectroscopy (XPS) and by Raman spectroscopy. The XPS results indicate that the near-surface region of samples oxidized in the temperature range 1075 to 1125 K contains Pd in both the +2 and +1 oxidation states and Rh in the +3 oxidation state. The ratio of Pd (I) to Rh (III) is found to be 11. Raman spectra confirm that two Pd-containing phases, PdO and PdRhO₂, are present in the near-surface region and eliminate the possibility that Rh₂O₃ is present. Also, a resonant Raman effect is observed in anhydrous PdO for exciting wavelengths in the vicinity of 500 nm.     

Nano- and meso-measurement methods in the study of dielectrics

Measurements of the physical form and morphology of dielectrics and of their chemical characteristics and physical properties have become increasingly important at micron and sub-micron length scales. Such length scales are accessible by different forms of microscopy but scanning probe methods allow both chemical and physical measurements to be made, in addition to morphological and typographical imaging, at nanoscopic and mesoscopic length scales. These measurements are described in this paper with examples drawn from many areas of dielectric research and applications, including polymer morphology, surface and subsurface charge measurements along with the dynamics of charge-decay, surface potential and work function, microelectronics, ferroelectrics, photocharging, dielectric response and nanoscopic relaxation and nanoscopic Raman spectroscopy. The future of scanning probe methods for dielectric measurements is assured but more effort is required to both develop and consolidate this form of nano-metrology.     

Adaptive sidelobe nulling using digitally controlled phase-shifters

Adaptive null-steering arrays which use phase-only weights are examined. The optimal phase weightings are developed and the mathematical equations are reduced to a simplified computational form. Approximations for low sidelobe arrays allow more efficient computations and demonstrate the decomposition of the antenna pattern into a sum of patterns which place gain towards each directional emitter. Computer simulations and breadboard array measurements substantiate the mathematical development and indicate the practicality of the method.     

Positive DC Coronas with Arbitrary Outer-Conductor Geometries

The two-dimensional Poisson's equation for a positive dc corona in air with arbitrarily-shaped boundaries-is solved using numerical methods. Solutions to the problem give the potential, electric field, space charge density, ion trajectories, and current density for all points in the field of interest, and the corona current flowing to any boundary. Good agreement is obtained between the theory and experimental measurements.     

Energy — audit and management

The authors, Nigel Isaacs, Michael Donn and Dr George Baird of the School of Architecture, Victoria University of Wellington, present a succinct account of the practical difficulties they encountered when implementing recommendations from energy audits in a defined number of New Zealand schools. It is concluded that these difficulties relate more to funding and personnel than the engineering of the energy savings in themselves.     

Correlates of motorcycle helmet use among recent graduates of a motorcycle training course

Helmets significantly decrease morbidity and mortality from motorcycle crashes, but many areas of the world lack universal helmet laws. To educate motorcyclists in areas without helmet laws, more knowledge of motorcyclists’ helmet beliefs is needed.A web-based survey was therefore designed to assess motorcyclists’ attitudes, norms and behaviors towards helmets in a U.S. state with a limited helmet law. Of 445 survey respondents, 68.4% of respondents reported always wearing a helmet. The not-always-helmeted riders were more likely than the always-helmeted to be male; to bave less education; and to have a history of previous motorcycle crashes and injuries. Although both groups had taken rider training classes, fewer of the not-always-helmeted had learned how to ride in a class. The strongest correlates of being not-always-helmeted (vs. always-helmeted) were attitudes that helmets were not protective and impaired sight/hearing; and the normative belief that they would only wear helmets if forced by law. Because attitudes are often more easily changed than normative beliefs, education may increase helmet use. However, less than half of riders in this state with a mandatory education program learned how to ride from a rider education course, and 44% of non-helmeted said they would only wear a helmet if forced by law. Legislation may therefore be a more efficient and effective strategy than education to increase helmet use.     

Loss of the thalamic nuclei for "head direction" impairs performance on spatial memory tasks in rats.

This study sought to characterize the effects of removing the nuclei of primary importance in relaying the thalamic head direction signal to the hippocampal formation (the anterior dorsal [AD] and lateral dorsal [LD] nuclei) on the performance of a variety of spatial and nonspatial tasks. The results indicate that combined excitotoxic lesions of the AD and LD nuclei produce marked deficits on a variety of spatial tasks. These tasks included T-maze alternation and the ability to locate a hidden platform set at a fixed distance and fixed direction from a beacon in a Morris water maze. Although object recognition appeared unaffected, marked impairments were found in the ability to detect when an object was placed in a novel position (object-in-place memory). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A statistical, nonparametric methodology for document degradation model validation

Printing, photocopying, and scanning processes degrade the image quality of a document. Statistical models of these degradation processes are crucial for document image understanding research. In this paper, we present a statistical methodology that can be used to validate local degradation models. This method is based on a nonparametric, two-sample permutation test. Another standard statistical device, the power function, is then used to choose between algorithm variables such as distance functions. Since the validation and the power function procedures are independent of the model, they can be used to validate any other degradation model. A method for comparing any two models is also described. It uses p-values associated with the estimated models to select the model that is closer to the real world.     

Solidification behavior and recovery kinetics of liquid crystalline polymers

The supercooling behavior of three thermotropic liquid crystalline polymers (TLCP's), 60 mole% p-hydroxybenzoic acid and 40 mole% poly(ethyleneterephthalate), 60/40 PHB/PET, 80 mole% p-hydroxybenzoic acid and 20 mole% poly(ethyleneterephthalate), 80/20 PHB/PET and a copolyester of 73 mole% p-hydroxybenzoic acid and 27 mole% of 2-hydroxy-6-naphthoic acid, Vectra A900, was studied by means of both rheological and thermal methods. 60/40 PHB/PET and Vectra A900 exhibited a degree of supercooling as high as 80°C while there was only 20°C of supercooling for 80/20 PHB/PET. The degree of supercooling for the blends of 60/40 PHB/PET and 80/20 PHB/PET also decreased with the increase in 80/20 PHB/PET content. The increase in G′ as the temperature decreased was more gradual for 60/40 PHB/PET and Vectra A900 than that for 80/20 PHB/PET, which was beneficial from a processing point of view. The solidification of the LCP melt was attributed to both the crystallization and the freezing of the mesophase. The degree of crystallinity for all three TLCP's was very small, less than 5%, as measured by the DSC. It was found that both 60/40 PHB/PET and Vectra A900 showed an induction period of a few minutes during solidification while 80/20 PHB/PET solidified continuously at the test temperature. Therefore, 60/40 PHB/PET and Vectra A900 seem to be more suitable for use in processes such as blow molding and film blowing than 80/20 PHB/PET.     

Effect of sparse long‐chain branching on the step‐strain behavior of a series of well‐defined polyethylenes

The effect of sparse long chain branching, LCB, on the shear step‐strain relaxation modulus is analyzed using a series of eight high‐density polyethylene (HDPE) resins. Strains of 1 to 1250% are imposed on materials with LCB content ranging from zero to 3.33 LCB per 10,000 carbon atoms. All materials are observed to obey time–strain separation beyond some characteristic time, τ_k. The presence of LCB is observed to increase the value of τ_k relative to the linear resin. The behavior of the relaxation modulus at times shorter than τ_k is investigated by an analysis of the enhancement seen in the linear relaxation modulus, G⁰(t), as a function of strain and LCB content. This enhancement is seen to (1) increase with increasing strain in all resins, (2) be significantly larger in the sparsely branched HDPE resins relative to the linear HDPE resin, and (3) increase in magnitude with increasing LCB content. The shape and smoothness of the damping function is also investigated. The finite rise time to impose the desired strain is compared to the Rouse relaxation time of linear HDPE resins studied. Sparse LCB is found to increase the magnitude of the relaxation modulus at short times relative to the linear resin. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers