VHF Boundary Layer Radar and RASS

This thesis describes the refinements, modifications and additions to a prototype Very High Frequency (VHF) Boundary Layer (BL) Spaced Antenna (SA) radar initially installed at the University of Adelaide's Buckland Park field site in 1997. Previous radar observations of the lowest few kilometres of the atmosphere, in particular the Atmospheric Boundary Layer, have used Ultra-High Frequency (UHF) radars. Unlike VHF radars, UHF radars are extremely sensitive to hydro-meteors and have difficulty in distinguishing clear-air echoes from precipitation returns. The advantages and requirements of using a VHF radar to observe the lowest heights is discussed in conjunction with some of the limitations. The successful operation of the system over long periods has enabled in-depth investigation of the performance of the system in a variety of conditions and locations. Observations were made from as low as 300m and as high as 8 km, dependent upon conditions. Comparisons between the radar and alternative wind measuring devices were carried out and examined. The antenna system of the radar is a critical component which was analysed in depth and subsequently re-designed. Through the use of numerical models and mea- surements, evaluation of different designs was accomplished. Further calibration of the remaining components of the full system has enabled estimations of the absolute received power. Additional parameters which can be derived with a calibrated radar were compared with values obtained by other authors, giving favourable results. Full Correlation Analysis (FCA) is the predominant technique used in this work. A brief discussion of the background theory and parameters which can be measured is described. A simple one-dimensional model was developed and combined with a 'radar backscatter model' to investigate potential sources of errors in the parameters determined using FCA with the VHF Boundary Layer Radar. In particular, underes- timations in the wind velocity were examined. The integration of a Radio Acoustic Sounding System (RASS) to obtain tempera- ture profiles is discussed. The theory of RASS measurements including the limitations and considerations which are required for the VHF BL radar are given. The difficulties encountered trying to implement such a system and the subsequent success using a Stratospheric Tropospheric (ST) Profiler in place of the BL radar is presented. Taken as a whole this thesis shows the success of the VHF BL to obtain mea- surements from as low as 300m. The validation of this prototype radar provides an alternative and, in certain situations, a superior device with which to study the lower troposphere.Thesis (Ph.D.)--University of Adelaide, Department of Physics and Mathematical Physics, 2001

Building resilience into Sitka spruce (Picea sitchensis [Bong.] Carr.) forests in Scotland in response to the threat of climate change

Peer reviewedPublisher PD

Carabid beetle communities of Northern heath: their response to management practices

Not availabl

Bending creep of corrugated fibreboard in cycling relative humidity : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Agricultural Engineering at Massey University

Packaging of fresh fruit for export is a major use for corrugated fibreboard manufactured in New Zealand. However the cold and humid conditions used to preserve fruit quality are particularly detrimental to the strength of corrugated packaging. The main objective of this study was to develop a method to measure the performance of corrugated fibreboard in high and cycling relative humidity environments. This method was then used to compare the performance of three corrugated fibre-boards 1 For commercial reasons these will be referred to as 'CB1', 'CB2'and 'CB3' The creep performance of corrugated fibreboard was measured by subjecting samples to four point bending stress under controlled cyclic relative humidity conditions using a computer controlled testing apparatus. A mathematical model by Urbanik (1995) and an empirical exponential model were reviewed before selecting a three term model developed by Pecht (1985) to describe the deflection of the corrugated board. Cyclic relative humidity accelerated the rate of creep compared to a static high humidity environment. The rate of creep in the machine direction was found to be considerably lower than that in the cross machine direction. It was also found that increasing the peak relative humidity from 80% to 90% RH dramatically changed the deflection response. This provides a solution to conflicting data in the literature on relative humidity cycling effects. Isochronous deflection curves were used to compare the creep performance of the corrugated fibreboard samples in an environment cycling between 50% and 90% RH. Corrugated fibreboard sample CB1 had a slightly lower creep stiffness than corrugated boards CB2 (p=0.0580, n=8) and CB3 (p=0.0398, n=8). However a greater number of tests would be required on a wider range of samples to conclusively determine if there were differences in board performance

Design of Geometric Molecular Bonds

An example of a nonspecific molecular bond is the affinity of any positive charge for any negative charge (like-unlike), or of nonpolar material for itself when in aqueous solution (like-like). This contrasts specific bonds such as the affinity of the DNA base A for T, but not for C, G, or another A. Recent experimental breakthroughs in DNA nanotechnology demonstrate that a particular nonspecific like-like bond ("blunt-end DNA stacking" that occurs between the ends of any pair of DNA double-helices) can be used to create specific "macrobonds" by careful geometric arrangement of many nonspecific blunt ends, motivating the need for sets of macrobonds that are orthogonal: two macrobonds not intended to bind should have relatively low binding strength, even when misaligned. To address this need, we introduce geometric orthogonal codes that abstractly model the engineered DNA macrobonds as two-dimensional binary codewords. While motivated by completely different applications, geometric orthogonal codes share similar features to the optical orthogonal codes studied by Chung, Salehi, and Wei. The main technical difference is the importance of 2D geometry in defining codeword orthogonality.Comment: Accepted to appear in IEEE Transactions on Molecular, Biological, and Multi-Scale Communication

Prediction of Debye-Scherrer diffraction patterns in arbitrarily strained samples

The prediction of Debye-Scherrer diffraction patterns from strained samples is typically conducted in the small strain limit. Although valid for small deviations from the hydrostat (such as the conditions of finite strength typically observed in diamond anvil cells) this assertion is likely to fail for the large strain anisotropies (often of order 10% in normal strain) such as those found in uniaixally loaded dynamic compression experiments. In this paper we derive a general form for the (\theta_B, \phi) dependence of the diffraction for an arbitrarily deformed sample in arbitrary geometry. We show that this formula is consistent with ray traced diffraction for highly strained computationally generated polycrystals, and that the formula shows deviations from the small strain solutions previously reported