ESTIMATING SHOPPING DESTINATION CHOICE MODELS FROM TRAVEL DIARY DATA*

This paper examines the issue of modeling dynamic aspects of shopping trip-making behavior using time series data and presents the results of an empirical analysis based on a two-week travel diary survey of households in Hamilton, Ontario. It is concluded that logit models incorporating time dependent variables perform significantly better in terms of both calibrated goodness-of-fit and predictive capabilities than do models which assume no time dependency between choices.     

Changes in Climate Extremes Over the Australian Region and New Zealand During the Twentieth Century

Analyses of high quality data show that there have been some interesting recent changes in the incidence of some climate extremes in the Australian region and New Zealand.     

GPS navigation data bit decoding error during strong equatorial scintillation

Strong equatorial scintillation is often characterized by simultaneous fast phase changes and deep amplitude fading. The combined effect poses a challenge for GNSS receiver carrier tracking performance. One of the consequences of the strong scintillation is increased navigation message data bit decoding error. Understanding the rate of the data bit decoding error under equatorial scintillation is essential for high accuracy and high integrity applications. We present the statistical relationship between the data bit decoding error occurrences and the intensity of amplitude scintillation based on the processing of intermediate frequency GPS scintillation data collected on Ascension Island in March 2013. A third-order phase lock loop (PLL) is implemented to process the data and to access the data bit error typically expected in conventional receivers. A Kalman filter-based PLL is also used to process the same data to demonstrate that the data bit decoding error can be reduced through advanced carrier tracking designs.     

Osmium isotope constraints on the proportion of bolide component in Chicxulub impact melt rocks

Abstract— The spatial distribution and amount of material transferred from the bolide involved in the Cretaceous/Tertiary (K/T) event to the target rocks at Chicxulub is still poorly constrained. In this study, Re‐Os isotopic analyses of impact melt breccias and lithic clasts from the Yaxcopoil‐1 (Yax‐1) borehole were used to determine the distribution and proportion of the bolide component in the target rocks. Because of the much greater concentration of Os in chondritic meteorites compared to the target rocks, little addition of the bolide component would be necessary to greatly perturb the Os concentration and isotopic composition of target rocks. Hence, this is a very sensitive means of examining bolide contributions to the target rocks. For the examined suite of samples, the initial ¹⁸⁷Os/¹⁸⁸Os ratios vary from 0.19 to 2.3. Conservative mixing calculations suggest that the bolide component comprised as much as approximately 0.1%, by mass, of some samples. Most samples, however, have negligible contributions from the bolide. No samples have Os that is dominated by the bolide component, so for this suite of samples, it is impossible to fingerprint the chemical nature of the bolide using relative abundances of siderophile elements. These results suggest that the bolide did not contribute a significant amount of material to the target rocks. This may, in turn, indicate that most of the bolide was vaporized upon impact or otherwise ejected without mixing with the melt from the target.     

A bootstrap based space–time surveillance model with an application to crime occurrences

This study proposes a bootstrap-based space–time surveillance model. Designed to find emerging hotspots in near-real time, the bootstrap based model is characterized by its use of past occurrence information and bootstrap permutations. Many existing space–time surveillance methods, using population at risk data to generate expected values, have resulting hotspots bounded by administrative area units and are of limited use for near-real time applications because of the population data needed. However, this study generates expected values for local hotspots from past occurrences rather than population at risk. Also, bootstrap permutations of previous occurrences are used for significant tests. Consequently, the bootstrap-based model, without the requirement of population at risk data, (1) is free from administrative area restriction, (2) enables more frequent surveillance for continuously updated registry database, and (3) is readily applicable to criminology and epidemiology surveillance. The bootstrap-based model performs better for space–time surveillance than the space–time scan statistic. This is shown by means of simulations and an application to residential crime occurrences in Columbus, OH, year 2000.