Evaluation of a ground-based sky camera system for use in surface irradiance measurement

This paper describes the evaluation of a ground-based sky camera system for studying the effect of clouds on the level of the ambient ultraviolet radiation. The system has been developed for research in the characterization of the effect of clouds around the sun. It is the first sky camera system to be used for the assessment of cloud conditions in the vicinity of the sun, rather than a whole-sky assessment. The system features a sun-tracking sky camera with an integrated measurement of horizontally received radiation at the same location. The image-processing algorithm uses solar radiation readings to reduce reflections from the sun on the camera system being mistaken for cloud in the images. Cloud amount was estimated in an angular region of between 12.5°and 37.5° around the sun. The algorithm also estimates the amount of solar obstruction by cloud (sun not covered, partially or totally covered). The system was evaluated during September 1997 at Toowoomba, Australia (27.6°S latitude). Compared to manual assessment of 592 images, 76.5% were identified correctly by the algorithm for the degree of solar obstruction and 81.9% for cloud amount. The behavior of ultraviolet radiation levels with cloud conditions is discussed

The Forecasting Capacity of Housing Price Expectations

This study captures the essential elements of the price expectations of market participants in a rising market. Adopting a forward-looking approach, this paper explores the effectiveness of expectations as an indicator of forthcoming housing price changes in Hong Kong. Examination of the quarterly survey data from December 2003 to September 2007 indicates that both homeowners and non-homeowners tend to overestimate the probability of future housing price increases yet underestimate its volatility. This adds weight to the argument that market participants are generally not rational in the prediction of price movement. Homeowners, investors and potential home buyers have more or less the same level of confidence about the future market outlook. Like non-owners, they expect higher prices. The number of correct forecasts exceeds incorrect forecasts, suggesting that overall price expectations are fairly close to realization. It can be broadly concluded that the aggregate price expectations in the long run can be an appropriate forecasting tool for future market performance.Price expectations; Forecastability; Housing market; Hong Kong

Infrared Non-detection of Fomalhaut b -- Implications for the Planet Interpretation

The nearby A4-type star Fomalhaut hosts a debris belt in the form of an eccentric ring, which is thought to be caused by dynamical influence from a giant planet companion. In 2008, a detection of a point-source inside the inner edge of the ring was reported and was interpreted as a direct image of the planet, named Fomalhaut b. The detection was made at ~600--800 nm, but no corresponding signatures were found in the near-infrared range, where the bulk emission of such a planet should be expected. Here we present deep observations of Fomalhaut with Spitzer/IRAC at 4.5 um, using a novel PSF subtraction technique based on ADI and LOCI, in order to substantially improve the Spitzer contrast at small separations. The results provide more than an order of magnitude improvement in the upper flux limit of Fomalhaut b and exclude the possibility that any flux from a giant planet surface contributes to the observed flux at visible wavelengths. This renders any direct connection between the observed light source and the dynamically inferred giant planet highly unlikely. We discuss several possible interpretations of the total body of observations of the Fomalhaut system, and find that the interpretation that best matches the available data for the observed source is scattered light from transient or semi-transient dust cloud.Comment: 12 pages, 4 figures, ApJ 747, 166. V2: updated acknowledgments and reference

Characterization of Wishart–Laplace distributions via Jordan algebra homomorphisms

AbstractFor a real, Hermitian, or quaternion normal random matrix Y with mean zero, necessary and sufficient conditions for a quadratic form Q(Y) to have a Wishart–Laplace distribution (the distribution of the difference of two independent central Wishart Wp(mi,Σ) random matrices) are given in terms of a certain Jordan algebra homomorphism ρ. Further, it is shown that {Qk(Y)} is independent Laplace–Wishart if and only if in addition to the aforementioned conditions, the images ρk(Σ+) of the Moore–Penrose inverse Σ+ of Σ are mutually orthogonal: ρk(Σ+)ρℓ(Σ+)=0 for k≠ℓ

Early Grain Filling Environment and Pre-Maturity α-Amylase Formation in UK Winter Wheat Genotypes

When the UK winter wheat variety Rialto produced unexpected low Hagberg falling numbers that could not be directly linked to sprouting, it was proposed that these reductions in quality could be due to PMAA. The problem was not identified during the selection and commercial development stages. In this project the hypothesis was tested that the variety Rialto is PMAA-susceptible. In addition, the effect of a previously proposed high temperature stimulus for PMAA followed by slow grain drying was assessed on plants grown in a controlled environment, throughout. This was done to eliminate any distorting effects the temperature history of plants grown in field or glasshouse had in previous studies. The identification of an effective and reliable PMAA stimulus could facilitate the development of a screening method for PMAA. Analysis was done on 13 year-location combinations of field grown Rialto. Together, visual and chemical assessments of sprouting and iso-electric focusing of α-amylase isozymes identified several samples with significant α-amylase activity in the apparent absence of sprouting. In addition, tests with α-amylase sensitive Phadebas gel revealed distinctive PMAA discoloration patterns in 10% to 44% of the grain from the 13 samples, leading to the conclusion that Rialto is PMAA-susceptible. Results from a controlled environment experiment confirmed the ability of a high temperature treatment to induce increased amylase production in the grain. However, the increase occurred in low humidity, considered to promote grain drying. Other results suggested that induction transpires during an earlier grain development stage than proposed in previous studies. Further work revealed the potential of a detached tiller technique to be used in a prospective fast and reliable screening method for PMAA