Optimal Cross-Wind Towing and Power Generation with Tethered Kites

Non-powered flight vehicles such as kites can provide a means of transmitting wind energy from higher altitudes to the ground via tethers. Although there have been many proposals for systems to extract wind energy from higher altitudes, this paper focuses on the use of a light lifting body at the end of a tether to generate useful power. Two major configurations are studied: 1) the kite is used to tow a ground vehicle in the cross-wind direction, 2) the kite is flown to generate power using a ground generator. In both cases, the useful work done by the kite is transmitted to the ground through the tether. Both applications require automatic control of the kite. A simplified system model is used to study the nature of the optimal trajectories of the system for different wind speeds. Numerical results illustrate that optimal power generation requires complex three-dimensional kite trajectories, whereas cross-wind towing requires much simpler trajectories. A feedback tracking controller is demonstrated for tracking the kite trajectories in the presence of unsteady winds

Use of dry-weight rank multipliers for desert vegetation.

The dry-weight rank technique has been used to measure vegetation in various habitats but has not been evaluated in desert shrub habitats. We sampled browse, forb, and grass in the palo-verde (Cercidium microphylum [Toff.] Rose and Johnston)-saguaro (Carnegiea gigantea [Engelm.) Britt and Rose) mountain slope vegetation association in the Sonoran Desert to determine if rank multipliers derived by 't Mannetje and Haydock differ from mean dry weights from different ranks. Previously derived multipliers were similar to those derived for mountain slope habitat

Diets of desert mule deer.

We studied the diets of desert mule deer (Odocoileus hemionus crooki Mearns) at 3 sites in Arizona and collated this information with that of previous diet studies of desert mule deer across their range in the United States. We documented 96 browse, 69 forbs, 14 succulent, and 6 grass species that each constituted greater than or equal to 1% of the diet during greater or equal to 1 season. The occurrence of individual plant species varied spatially and temporally. Changes in nutrient levels and climatic influence on relative availability and phenology of plant species likely influenced diet. Desert mule deer rely heavily on browse and forbes, which make up the majority of their diet (> 90%). Grasses and succulents were generally < 5% of the diet. Rangeland managers should strive to keep desert rangelands productive with a diversity of forage so animals have opportunities to exercise free choice of diet

Predicting Habitat Suitability of Snow Leopards in the Western Himalayan Mountains, India

The population of snow leopard (Panthera uncia) is declining across their range, due to poaching, habitat fragmentation, retaliatory killing, and a decrease of wild prey species. Obtaining information on rare and cryptic predators living in remote and rugged terrain is important for making conservation and management strategies. We used the Maximum Entropy (MaxEnt) ecological niche modeling framework to predict the potential habitat of snow leopards across the western Himalayan region, India. The model was developed using 34 spatial species occurrence points in the western Himalaya, and 26 parameters including, prey species distribution, temperature, precipitation, land use and land cover (LULC), slope, aspect, terrain ruggedness and altitude. Thirteen variables contributed 98.6% towards predicting the distribution of snow leopards. The area under the curve (AUC) score was high (0.994) for the training data from our model, which indicates predictive ability of the model. The model predicted that there was 42 432 km2 of potential habitat for snow leopards in the western Himalaya region. Protected status was available for 11 247 km2 (26.5%), but the other 31 185 km2 (73.5%) of potential habitat did not have any protected status. Thus, our approach is useful for predicting the distribution and suitable habitats and can focus field surveys in selected areas to save resources, increase survey success, and improve conservation efforts for snow leopards. © 2020, Pleiades Publishing, Inc.12 month embargo; published 13 January 2021This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]