Characterising the baseband impedance of supply modulators using simple modulated signals

Envelope tracking is one of the promising technologies for 5G power amplifiers, providing high power efficiency over a wide output power range by modulating the supply voltage. Although the baseband impedance, the output impedance of the supply modulator, plays a crucial role in the linearity of the PA, it is often not measured or considered during the modulator design. This paper presents a new, simplified approach to characterising this impedance using a PA with a simple multi-tone modulation as a load. It describes the measurement setup and verifies the results by characterising the baseband impedance of a state-of-the-art buck converter and comparing this to its static model. The results demonstrate that multi-tone signals and complex modulations yield comparable results and are both suitable for measuring and modelling the baseband impedance. This shows that using simple multi-tone measurements and basic equipment, the full static impedance characteristic can be obtained

Sustainable Wireless Services with UAV Swarms Tailored to Renewable Energy Sources

Unmanned Aerial Vehicle (UAV) swarms are often required in off-grid scenarios, such as disaster-struck, war-torn or rural areas, where the UAVs have no access to the power grid and instead rely on renewable energy. Considering a main battery fed from two renewable sources, wind and solar, we scale such a system based on the financial budget, environmental characteristics, and seasonal variations. Interestingly, the source of energy is correlated with the energy expenditure of the UAVs, since strong winds cause UAV hovering to become increasingly energy-hungry. The aim is to maximize the cost efficiency of coverage at a particular location, which is a combinatorial optimization problem for dimensioning of the multivariate energy generation system under non-convex criteria. We have devised a customized algorithm by lowering the processing complexity and reducing the solution space through sampling. Evaluation is done with condensed real-world data on wind, solar energy, and traffic load per unit area, driven by vendor-provided prices. The implementation was tested in four locations, with varying wind or solar intensity. The best results were achieved in locations with mild wind presence and strong solar irradiation, while locations with strong winds and low solar intensity require higher Capital Expenditure (CAPEX) allocation.Comment: To be published in Transactions on Smart Gri

Neighbourhood, Route and Workplace-Related Environmental Characteristics Predict Adults' Mode of Travel to Work

Commuting provides opportunities for regular physical activity which can reduce the risk of chronic disease. Commuters' mode of travel may be shaped by their environment, but understanding of which specific environmental characteristics are most important and might form targets for intervention is limited. This study investigated associations between mode choice and a range of objectively assessed environmental characteristics.Participants in the Commuting and Health in Cambridge study reported where they lived and worked, their usual mode of travel to work and a variety of socio-demographic characteristics. Using geographic information system (GIS) software, 30 exposure variables were produced capturing characteristics of areas around participants' homes and workplaces and their shortest modelled routes to work. Associations between usual mode of travel to work and personal and environmental characteristics were investigated using multinomial logistic regression.Of the 1124 respondents, 50% reported cycling or walking as their usual mode of travel to work. In adjusted analyses, home-work distance was strongly associated with mode choice, particularly for walking. Lower odds of walking or cycling rather than driving were associated with a less frequent bus service (highest versus lowest tertile: walking OR 0.61 [95% CI 0.20–1.85]; cycling OR 0.43 [95% CI 0.23–0.83]), low street connectivity (OR 0.22, [0.07–0.67]; OR 0.48 [0.26–0.90]) and free car parking at work (OR 0.24 [0.10–0.59]; OR 0.55 [0.32–0.95]). Participants were less likely to cycle if they had access to fewer destinations (leisure facilities, shops and schools) close to work (OR 0.36 [0.21–0.62]) and a railway station further from home (OR 0.53 [0.30–0.93]). Covariates strongly predicted travel mode (pseudo r-squared 0.74).Potentially modifiable environmental characteristics, including workplace car parking, street connectivity and access to public transport, are associated with travel mode choice, and could be addressed as part of transport policy and infrastructural interventions to promote active commuting

Estimating deer density and abundance using spatial mark–resight models with camera trap data

Globally, many wild deer populations are actively studied or managed for conservation, hunting, or damage mitigation purposes. These studies require reliable estimates of population state parameters, such as density or abundance, with a level of precision that is fit for purpose. Such estimates can be difficult to attain for many populations that occur in situations that are poorly suited to common survey methods. We evaluated the utility of combining camera trap survey data, in which a small proportion of the sample is individually recognizable using natural markings, with spatial mark–resight (SMR) models to estimate deer density in a variety of situations. We surveyed 13 deer populations comprising four deer species (Cervus unicolor, C. timorensis, C. elaphus, Dama dama) at nine widely separated sites, and used Bayesian SMR models to estimate population densities and abundances. Twelve surveys provided sufficient data for analysis and seven produced density estimates with coefficients of variation (CVs) ≤ 0.25. Estimated densities ranged from 0.3 to 24.6 deer km−2. Camera trap surveys and SMR models provided a powerful and flexible approach for estimating deer densities in populations in which many detections were not individually identifiable, and they should provide useful density estimates under a wide range of conditions that are not amenable to more widely used methods. In the absence of specific local information on deer detectability and movement patterns, we recommend that at least 30 cameras be spaced at 500–1,000 m and set for 90 days. This approach could also be applied to large mammals other than deer

A comparison of lead-based and lead-free bullets for shooting sambar deer (Cervus unicolor) in Australia

Context. In response to the toxic health threats posed by lead (Pb), there is currently a focus on transitioning to lead-free bullets for shooting wild animals. Aim. We aimed to quantify the killing efficiency and animal welfare outcomes of lead-based and lead-free (copper-based) bullets for ground-based shooting of sambar deer (Cervus unicolor) in Victoria, south-eastern Australia. Methods. We used shooter-collected data from recreational diurnal hunting and professional nocturnal culling during 2020–2021. Shooters recorded rifle calibre, cartridge type, bullet mass, bullet type, shooting outcomes (miss, wound or kill), shooting distance, flight distance (the distance between where the animal was shot and where it died) as an assumed positive correlate of time to incapacitation, anatomical zones struck by bullets, and frequency of bullet exit wounds. We used flight distance as our response variable, assuming that it is positively correlated with time to incapacitation. To examine the role of several predictor variables (including bullet type) potentially influencing flight distance, the dataset was reduced to those deer killed with a single thoracic shot. Key results. Our data captured shooting events involving 276 deer, with 124 deer shot at with lead-based bullets and 152 with copper-based bullets. Most (87%) of the deer were killed with a single shot. The frequency of non-fatal wounding was <4% for both bullet types and there was no distinct difference in the probability of a single shot kill for deer shot with either bullet type. For those deer killed with a single thoracic shot (n = 198), there was no evidence that bullet energy or shooting distance influenced flight distance. After accounting for differences in terminal kinetic energy, the mean flight distance of deer shot with lead-free bullets (35 m) was 56% greater than that of deer shot with lead-based bullets (22 m). Conclusions. Lead-based and lead-free bullets produced similar animal welfare outcomes for shooting sambar deer. Implications. A transition to lead-free ammunition for shooting sambar deer would have minimal impact on efficiency or animal welfare outcomes. animal welfare, culling, human dimensions, invasive species, population control, recreational hunting, toxicology, wildlife management.publishedVersio

A comparison of lead-based and lead-free bullets for shooting sambar deer (Cervus unicolor) in Australia

Context: In response to the toxic health threats posed by lead (Pb), there is currently a focus on transitioning to lead-free bullets for shooting wild animals. Aim: We aimed to quantify the killing efficiency and animal welfare outcomes of lead-based and lead-free (copper-based) bullets for ground-based shooting of sambar deer (Cervus unicolor) in Victoria, south-eastern Australia. Methods: We used shooter-collected data from recreational diurnal hunting and professional nocturnal culling during 2020–2021. Shooters recorded rifle calibre, cartridge type, bullet mass, bullet type, shooting outcomes (miss, wound or kill), shooting distance, flight distance (the distance between where the animal was shot and where it died) as an assumed positive correlate of time to incapacitation, anatomical zones struck by bullets, and frequency of bullet exit wounds. We used flight distance as our response variable, assuming that it is positively correlated with time to incapacitation. To examine the role of several predictor variables (including bullet type) potentially influencing flight distance, the dataset was reduced to those deer killed with a single thoracic shot. Key results: Our data captured shooting events involving 276 deer, with 124 deer shot at with lead-based bullets and 152 with copper-based bullets. Most (87%) of the deer were killed with a single shot. The frequency of non-fatal wounding was <4% for both bullet types and there was no distinct difference in the probability of a single shot kill for deer shot with either bullet type. For those deer killed with a single thoracic shot (n = 198), there was no evidence that bullet energy or shooting distance influenced flight distance. After accounting for differences in terminal kinetic energy, the mean flight distance of deer shot with lead-free bullets (35 m) was 56% greater than that of deer shot with lead-based bullets (22 m). Conclusions: Lead-based and lead-free bullets produced similar animal welfare outcomes for shooting sambar deer. Implications: A transition to lead-free ammunition for shooting sambar deer would have minimal impact on efficiency or animal welfare outcomes