Significant effects of weak gravitational lensing on determinations of the cosmology from Type Ia Supernov\ae

Significant adjustments to the values of the cosmological parameters estimated from high-redshift Type Ia Supernov\ae data are reported, almost an order of magnitude greater than previously found. They arise from the effects of weak gravitational lensing on observations of high-redshift sources. The lensing statistics used have been obtained from computations of the three-dimensional shear in a range of cosmological N-body simulations, from which it is estimated that cosmologies with an underlying deceleration parameter q_0 = -0.51 +0.03/-0.24 may be interpreted as having q_0 = -0.55 (appropriate to the currently popular cosmology with density parameter $\Omega_M = 0.3$ and vacuum energy density parameter $\Omega_{\Lambda} = 0.7$). In addition, the standard deviation expected from weak lensing for the peak magnitudes of Type Ia Supernov\ae at redshifts of 1 is expected to be approximately 0.078 magnitudes, and 0.185 magnitudes at redshift 2. This latter value is greater than the accepted intrinsic dispersion of 0.17 magnitudes. Consequently, the effects of weak lensing in observations of high-redshift sources must be taken properly into account.Comment: 9 pages, LaTeX, 4 figure

Friend or Foe? The Kyoto Protocol and the NZ Greenhouse Industry

The greenhouse sector has reinvented itself as a technologically advanced and relatively environmentally friendly industry over the past 15 years. However it remains a high energy user. Two recent surveys have highlighted the potential impact on greenhouse grower costs of the proposed emissions charge on fossil fuels. Growers may be unable to pass on the extra costs due to competition on domestic and export markets from non-Kyoto countries. It is likely that the emissions charge would accelerate the rationalisation of the industry that has already been occurring, and in addition may lead to more profound changes such as the relocation overseas of larger growers. This paper draws out the likely implications of the proposed charge for the greenhouse sector in the light of the policies which are available to mitigate its impacts, and highlights the policy lessons that can be learned.Agricultural and Food Policy, Community/Rural/Urban Development, Environmental Economics and Policy, Industrial Organization, Institutional and Behavioral Economics, International Relations/Trade, Land Economics/Use, Livestock Production/Industries,

On the estimation of gravity-induced non-Gaussianities from weak lensing surveys

We study various measures of weak lensing distortions in future surveys, taking into account the noise arising from the finite survey size and the intrinsic ellipticity of galaxies. We also consider a realistic redshift distribution of the sources, as expected for the SNAP mission. We focus on the low order moments and the full distribution function (pdf) of the aperture-mass \Map and of the smoothed shear component \gammais. We also propose new unbiased estimators for low-order cumulants which have less scatter than the usual estimators of non-Gaussianity based on the moments themselves. Then, using an analytical model which has already been seen to provide a good description of weak gravitational lensing through comparison against numerical simulations, we study the statistical measures which can be extracted from future surveys like the SNAP experiment. We recover the fact that at small angular scales ($1'<\theta_s<10'$) the variance can be extracted with a few percent level accuracy. Non-Gaussianity can also be measured from the skewness of the aperture-mass (at a 10% level) while the shear kurtosis is more noisy and cannot be easily measured beyond 6'. On the other hand, we find that the pdf of the estimator associated with the aperture-mass can be distinguished both from the Gaussian and the Edgeworth expansion and could provide useful constraints, while this appears to be difficult to realize with the shear component. Finally, we investigate various survey strategies and the possibility to perform a redshift binning of the sample.Comment: 16 pages, final version published in MNRA

AutonoVi: Autonomous Vehicle Planning with Dynamic Maneuvers and Traffic Constraints

We present AutonoVi:, a novel algorithm for autonomous vehicle navigation that supports dynamic maneuvers and satisfies traffic constraints and norms. Our approach is based on optimization-based maneuver planning that supports dynamic lane-changes, swerving, and braking in all traffic scenarios and guides the vehicle to its goal position. We take into account various traffic constraints, including collision avoidance with other vehicles, pedestrians, and cyclists using control velocity obstacles. We use a data-driven approach to model the vehicle dynamics for control and collision avoidance. Furthermore, our trajectory computation algorithm takes into account traffic rules and behaviors, such as stopping at intersections and stoplights, based on an arc-spline representation. We have evaluated our algorithm in a simulated environment and tested its interactive performance in urban and highway driving scenarios with tens of vehicles, pedestrians, and cyclists. These scenarios include jaywalking pedestrians, sudden stops from high speeds, safely passing cyclists, a vehicle suddenly swerving into the roadway, and high-density traffic where the vehicle must change lanes to progress more effectively.Comment: 9 pages, 6 figure

A Comparison of Models for the Fulton-Macpherson Operads

In this thesis we explore the structure of the Fulton-Macpherson operads F_N by providing two new models for them. It is shown in work of Salvatore that these operads are cofibrant by claiming the existence of an isomorphism of operads from WF_N to F_N. Here, W is a functor which, for a large class of topological operads, produces cofibrant replacements. It would be satisfying to be able to write down explicitly what these isomorphisms are. Our new models are an attempt to move towards this. The building blocks of the first model appeared in the Ph.D. thesis of Daniel Singh but they were not assembled into an operad here. This model has a more algebraic feel than others in the literature which gives it technical advantages. We use this to demonstrate many of the well-known properties of the Fulton-Macpherson operads. In particular, we are able to write down explicit isomorphisms between F_1 and the Stasheff operad which we have not seen previously in the literature. This model is isomorphic to other models of the Fulton-Macpherson operads. The second model is a realisation of an operad in posets. This poset operad is built from combinatorial objects called chains of preorders. These objects encode maps from a finite set A to some Euclidean space R^N. In particular, we can impose restrictions to encode injective maps of this type. This model is equivalent up to homotopy to the Fulton-Macpherson operads in a way which we define. It is also homotopy equivalent to the Smith operads, another example of topological operads defined combinatorially. The main advantage of this model is that it has an obvious spine which may pave the way to writing down the desired isomorphisms from WF_N to F_N

Helical Models of the Bidirectional Vortex in a Conical Geometry

This dissertation represents the descriptive and analytical breakdown of two new fluid dynamics solutions for vortex motion. Both solutions model the bidirectional vortex within a conical geometry. The first explored solution satisfies a simple Beltramian characteristic, where the Lamb vector is identically zero. The second solution is of the generalized Beltramian type, which fulfills the condition that the curl of the Lamb vector is equal to zero. The two Beltramian solutions describe the axisymmetric, double helical motion often found in industrial cyclone separators. Other applications include cone-shaped, vortex-driven combustion chambers and the swirling flow through conical devices. Both solutions are derived from first principles and Euler’s equations of motion which showcase the stream function-vorticity relation and ultimately transforms into the Bragg-Hawthorne formulation. The Bragg-Hawthorne equation allows for various implementations of the Bernoulli and swirl functions. The angular momentum equation includes the source term for the Beltramian solution. On the other hand, the Bernoulli relation drives the generalized Beltramian model. Appropriate boundary conditions and assumptions reduce the governing partial differential equation to an ordinary differential equation which is then solved by a separation of variables approach. Resulting velocity, vorticity, and pressure variables are discussed and graphed. The tangential and axial velocities are compared to two experimental and numerical cyclone separator cases. Other features of the conical flow field such as the conical swirl number and dual mantle locations are also explored. The inviscid, incompressible, and rotational models ultimately lay the framework for complementary solutions derived from the Bragg-Hawthorne equation or similar formulation

Food Miles, Carbon Footprinting and their potential impact on trade

To obtain market access for NZ food exports to high value developed country markets exporters are having to comply and consider environmental factors such as carbon footprinting. This growth in demand for environmental attributes is shown in the rise of the food miles debate or concept. Food miles is a concept which has gained traction with the popular press arguing that the further food travels the more energy is used and therefore carbons emissions are greater. This paper assesses, using the same methodology, whether this is the case by comparing NZ production shipped to the UK with a UK source. The study found that due to the different production systems even when shipping was accounted for NZ dairy products used half the energy of their UK counterpart and in the case of lamb a quarter of the energy. In the case of apples the NZ source was 10 per cent more energy efficient. In case of onions whilst NZ used slightly more energy in production the energy cost of shipping was less than the cost of storage in the UK making NZ onions more energy efficient overall. The paper then explores other developments in market access to developed markets especially the rise in demand for products to be carbon footprinted and the introduction of carbon labelling. A review of latest methodology in carbon footprinting the PAS from the UK is reviewed and implications for trade assessed.

A Survey of Gaps, Obstacles, and Technical Challenges for Hypersonic Applications

The object of this study is to canvas the literature for the purpose of identifying and compiling a list of Gaps, Obstacles, and Technological Challenges in Hypersonic Applications (GOTCHA). The significance of GOTCHA related deficiencies is discussed along with potential solutions, promising approaches, and feasible remedies that may be considered by engineers in pursuit of next generation hypersonic vehicle designs and optimizations. Based on the synthesis of several modern surveys and public reports, a cohesive list is formed, consisting of widely accepted areas needing improvement and falling under several general categories. These include: aerodynamics, propulsion, materials, analytical modeling, CFD modeling, and education in high speed flow physics. New methods and lines of research inquiries are suggested such as the homotopy-based analysis (HAM) for the treatment of strong nonlinearities, the use of improved turbulence models and unstructured grids in numerical simulations, the need for accessible validation data, and the refinement of mission objectives for Hypersonic Air-Breathing Propulsion (HABP)