A novel approach to robust radar detection of range-spread targets

This paper proposes a novel approach to robust radar detection of range-spread targets embedded in Gaussian noise with unknown covariance matrix. The idea is to model the useful target echo in each range cell as the sum of a coherent signal plus a random component that makes the signal-plus-noise hypothesis more plausible in presence of mismatches. Moreover, an unknown power of the random components, to be estimated from the observables, is inserted to optimize the performance when the mismatch is absent. The generalized likelihood ratio test (GLRT) for the problem at hand is considered. In addition, a new parametric detector that encompasses the GLRT as a special case is also introduced and assessed. The performance assessment shows the effectiveness of the idea also in comparison to natural competitors.Comment: 28 pages, 8 figure

Improving Weed Management in Flax (Linum usitatissimum L.)

Flax (Linum usitatissimum L.) is a high utility crop that has value in both food and industrial markets. However, because flax is a poor competitor the presence of weeds can negatively influence its growth and development. The objective of this thesis was to evaluate different approaches to help improve weed management in flax, including new herbicide options and investigating integrated weed management (IWM) methodologies. The goal of the IWM experiment was to identify if different combinations of seeding date (early May vs. late May), seeding rate (400 vs. 800 seeds m-2), cultivar height (short vs. tall), and herbicide rate (0X vs. 1X) could improve the competitive ability of flax. Seeding a tall cultivar, at a high seeding rate, in early May, with an in-crop herbicide resulted in the greatest plant population. Factors that improved crop establishment ultimately had a positive influence on the competitive ability of flax by increasing aboveground crop biomass, crop yield, and reducing aboveground weed biomass. In addition, the goal of the herbicide screening trial was to evaluate the tolerance of flax to Group 14 (PPO inhibitors), Group 15 (VLCFA inhibitors), and Group 27 (HPPD inhibitors) herbicides in comparison to registered industry standards. Seven novel modes of action and three registered industry standards were compared to an untreated check to determine the effect that these treatments had on flax growth and development. Flax showed impressive tolerance to most herbicide treatments, with the exception of those containing flumioxazin. Treatments containing topramezone, pyroxasulfone, and fluthiacet-methyl were found to be generally safe. Overall, initial injury caused by these herbicides was transient and did not translate into any reduction in flax yield or thousand seed weight (TSW) at the majority of sites. Results of this study show that flax has acceptable tolerance of several novel herbicides. Moreover, these herbicides can be combined with several cultural factors to improve the competitive ability of flax and ultimately improve how weeds are managed in this crop

Contract specificity and its performance outcomes

Governance theories, such as transaction cost economics, argue that systematic deviations from an attribute–governance alignment should influence performance. This article investigates the performance implications of contract specificity for the procurement of information technology products. The authors argue that parties choose a level of contract specificity that economizes on both the ex ante contracting costs and the ex post transaction costs and that deviations between the observed and the predicted levels of contract specificity are an important determinant of these transaction costs. The authors test the hypotheses using a comprehensive archival data set of information technology transactions and employ a two-step estimation procedure. First, they estimate the “predicted” level of contract specificity, which accounts for key transactional attributes. Second, they study the consequences of deviating from this predicted level of contractual specificity. The results provide the first explicit demonstration of the trade-off between ex ante contracting costs and ex post transaction problems and suggest that parties need to economize jointly on these costs when choosing the governance form

Phytosociology applied to wildlife management - a study on the potentiality for the reintroduction of cervids in the Montemuro-Freita-Arada mountain range

Doutoramento em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de AgronomiaThe aim of the present thesis was to assess the use of phytosociology in wildlife management. In Section II, as a case study, I investigated red deer (Cervus elaphus hispanicus) and roe deer (Capreolus capreolus) free ranging populations occurring in the Natural Park of Montesinho, northeast Portugal, using faecal-pellet counts to assess deer use of semi-natural meadows (lameiros) and forest communities. Phytosociological classification contributed to explain red deer spring selective use of meadows at finer scales and performed better than other clustering criteria for classifying vegetation patches. At the landscape level, composition of the neighbouring vegetation mosaic, topography, and meadow’s characteristics, as management status and dominant phytosociology, produced the best models for deer seasonal use of meadows. The forest use analysis revealed red and roe deer preference for oak forests over pine plantations, and habitat use overlapping between red and roe deer all year round. In Section III, I extrapolated the information gathered in Section II on deer use to build, for the Montemuro-Freita-Arada massif, a predictive map for roe deer use of meadows, showing a generally low use, with exception of isolated meadows closer to oak forest patche

Improving kochia (Kochia scoparia L.) and wild oat (Avena fatua L.) management in cultivated oat (Avena sativa L.)

Saskatchewan is the largest producer of oat (Avena sativa L.) in Canada, producing 54% of Canadian oats. Weeds such as kochia (Kochia scoparia L.) and wild oat (Avena fatua L.) are problematic in oat and require improved chemical and cultural control practices. The objectives of this thesis were two-fold: 1) to determine the tolerance of oat to pre- and post-emergence herbicides and their efficacy for controlling kochia (field study), and 2) to determine the relative effect of seed size and seed treatment on oat competitive ability (greenhouse and phytotron studies). In the field study, fluthiacet-methyl, flumioxazin, florasulam + bromoxynil, acifluorfen, and topramezone were applied POST, while tembotrione and sulfentrazone were applied PRE, to evaluate kochia control and oat tolerance. Pyrasulfotole+ bromoxynil, flumioxazin, tembotrione, and fluthiacet-methyl provided excellent kochia control (>88% biomass reductions). Oat tolerance to pyrasulfotole+ bromoxynil and fluthiacet-methyl was commercially acceptable. In the greenhouse and phytotron studies, two seed sizes (large and small), four seed treatments (pyraclostrobin, pyraclostrobin + thiamethoxam, thiamethoxam, control) and two competitive environments (weed-free and weedy) were evaluated. Under cool growing conditions, seed treatments lead to an increase in shoot production up to 15 and 18%, respectively, for both large and small seeds. Oat plants derived from large seeds produced 23 and 24% more root and shoot biomass, respectively, compared to plants established from small seeds at early developmental stages. The seed size advantage persisted until physiological maturity as plants established from large seeds produced 38% more shoot biomass and 12% more panicles than oat plants derived from small seeds. Regardless of seed size, oat plants produced 78% less shoot biomass and 32% fewer panicles when wild oat competition was present compared with no pots having no wild oat competition. Results presented in this thesis show that pyrasulfotole+ bromoxynil and fluthiacet-methyl are potential herbicides for control of kochia in oat, as they provided excellent control and acceptable crop tolerance. In addition to chemical control, oat producers should consider the use of seed treatments and large seed to improve early season oat vigour and competitive ability

Implementing fire history and fire ecology in fire risk assessment: the study case of Canton Ticino (southern Switzerland)

The understanding of the ecological role of wildfires and the knowledge of its past natural and cultural dynamics in different ecosystems have been recognize as a prerequisite for a sustainable land and ecosystem management. The main objective of this work is to propose a methodological approach for implementing the knowledge derived from studies of fire history, fire ecology, and fire suppression strategies in fire risk analyses in a low-to medium fire-prone region such as the Canton Ticino