ENERGY OPTIMAL GUIDANCE OF UAS IN TIME-VARYING 3-DIMENSIONAL WIND ENVIRONMENTS

Increasing the fuel efficiency of military aircraft provides a tactical advantage to the aircraft operator. Increases in fuel efficiency in turn increase an aircraft’s time on station, allow higher payload capacity, expand operational range, and reduce operating costs. Since the performance increases from fuel-efficiency compound over time, high endurance aircraft, like intelligence, surveillance, and reconnaissance (ISR) unmanned aerial systems (UAS), are a particularly applicable class of aircraft for research. This paper presents an approach for accomplishing these fuel savings through the design of an energy-optimal trajectory planning algorithm. This is done by modeling the performance of a UAS and defining the power required to maintain flight as the cost function in three dimensions and time. The time and location-varying effects of air density and wind are included in this model. Then, using Pontryagin’s Minimum Principle, the problem becomes a boundary value problem, which is then numerically solved, generating the energy-optimal trajectory. This results in an energy-optimal trajectory solution that utilizes favorable atmospheric effects like tailwinds and updrafts, and avoids detrimental atmospheric effects, like headwinds.Approved for public release. Distribution is unlimited.Ensign, United States NavyOperational Energy Offic

Implications of motivation differences in preclinical-clinical transition of dental students:A one-year follow-up study

Background Patient contact and clinical-based learning have been suggested as positive determinants of student motivation. However, few studies have been conducted on how this impacts dental student motivation. Based on the self-determination theory, this study aims to explore differences in the quality of motivation of dental student transition from preclinical (no previous patient contact) to clinical courses. Methods A longitudinal study was conducted with 95 Chilean students who completed the Academic Motivation Scale in two iterations over a one-year period. Results Paired t-test showed a significant increase in relative autonomous motivation as well as in amotivation. Discussions This suggests that while clinical contact supports student self-determination, an abrupt transition might be associated with maladjustment, which could lead to feelings of inadequacy and anxiety. Future research could usefully explore if early and gradual clinical experiences enhance student adaptation to the clinical context, thus increasing relative autonomous motivation and decreasing amotivation in the time

Survey of All Water Treatment Plant Operators Who Fluoridate Drinking Water in Ohio

Author Institution: Department of Community Dentistry, School of Dentistry, and Department of Biology, Case Western Reserve UniversityOhio like several other states in the US is mandated by law to optimally fluoridate all public water systems serving over 5000 people. The purpose of this study was three-fold: 1) to determine if Ohioans on public water supplies are receiving optimally fluoridated water, 2) to determine the knowledge level of water treatment plant operators who fluoridate drinking water, and 3) to compare small and large water treatment plants. A pre-tested survey was sent to all 224 water treatment plants that adjust the fluoride concentration of drinking water in Ohio. A 100% response rate was accomplished, with 93 small and 131 large water treatment plants responding. A z-test was computed to compare proportions between small and large water treatment plants. Significance was assessed at p <0.05. Nearly 90% of water treatment plant operators correctly identified the optimal fluoride level, however almost 30% used incorrect means of determining the optimal level. Approximately three-quarters of the water treatment plant operators were able to maintain the fluoride concentration to within 0.1 mg F/L of their optimal level. A significantly greater proportion of large water treatment plant operators were able to maintain a fluoride concentration to within 0.1 mg F/L of their optimum level when compared to small water treatment plant operators (83.2% vs 60.2%, z = 3.60, p <0.05). Most water treatment plant operators are knowledgeable concerning fluoride levels, however small water treatment plant operators may need additional technical assistance to reach the level attained by large plants

Bottled Water: United States Consumers and Their Perceptions of Water Quality

Consumption of bottled water is increasing worldwide. Prior research shows many consumers believe bottled water is convenient and has better taste than tap water, despite reports of a number of water quality incidents with bottled water. The authors explore the demographic and social factors associated with bottled water users in the U.S. and the relationship between bottled water use and perceptions of the quality of local water supply. They find that U.S. consumers are more likely to report bottled water as their primary drinking water source when they perceive that drinking water is not safe. Furthermore, those who give lower ratings to the quality of their ground water are more likely to regularly purchase bottle water for drinking and use bottle water as their primary drinking water source

A Quantitative Look at Fluorosis, Fluoride Exposure, and Intake in Children Using a Health Risk Assessment Approach

The prevalence of dental fluorosis in the United States has increased during the last 30 years. In this study, we used a mathematical model commonly employed by the U.S. Environmental Protection Agency to estimate average daily intake of fluoride via all applicable exposure pathways contributing to fluorosis risk for infants and children living in hypothetical fluoridated and non-fluoridated communities. We also estimated hazard quotients for each exposure pathway and hazard indices for exposure conditions representative of central tendency exposure (CTE) and reasonable maximum exposure (RME) conditions. The exposure pathways considered were uptake of fluoride via fluoridated drinking water, beverages, cow’s milk, foods, and fluoride supplements for both age groups. Additionally, consumption of infant formula for infants and inadvertent swallowing of toothpaste while brushing and incidental ingestion of soil for children were also considered. The cumulative daily fluoride intake in fluoridated areas was estimated as 0.20 and 0.11 mg/kg-day for RME and CTE scenarios, respectively, for infants. On the other hand, the RME and CTE estimates for children were 0.23 and 0.06 mg/kg-day, respectively. In areas where municipal water is not fluoridated, our RME and CTE estimates for cumulative daily average intake were, respectively, 0.11 and 0.08 mg/kg-day for infants and 0.21 and 0.06 mg/kg-day for children. Our theoretical estimates are in good agreement with measurement-based estimates reported in the literature. Although CTE estimates were within the optimum range for dental caries prevention, the RME estimates were above the upper tolerable intake limit. This suggests that some children may be at risk for fluorosis

Fluorosis risk from early exposure to fluoride toothpaste

Swallowed fluoride toothpaste in the early years of life has been postulated to be a risk factor for fluorosis, but the epidemiological evidence is weakened by the fact that most of the relevant studies were done in developed countries where an individual is exposed to multiple sources of fluoride. Objectives: To quantify the risk of fluorosis from fluoride toothpaste in a population whose only potential source of fluoride was fluoride toothpaste. Methods: Case-control analyses were conducted to test the hypothesis that fluoride toothpaste use before the age of 6 years increased an individual's risk of fluorosis. Data came from a cross-sectional clinical dental examination of schoolchildren and a self-administered questionnaire to their parents. The study was conducted in Goa, India. The study group consisted of 1189 seventh grade children with a mean age of 12.2 years. Results: The prevalence of fluorosis was 12.9% using the TF index. Results of the crude, stratified, and logistic regression analyses showed that use of fluoride toothpaste before the age of 6 years was a risk indicator for fluorosis (OR 1.83, 95% CI 1.05–3.15). Among children with fluorosis, beginning brushing before the age of 2 years increased the severity of fluorosis significantly ( P < 0.001). Other factors associated with the use of fluoride toothpaste, such as eating or swallowing fluoride toothpaste and higher frequency of use, did not show a statistically significant increased risk for prevalence or severity of fluorosis. Conclusions: Fluoride toothpaste use before the age of 6 years is a risk indicator for fluorosis in this study population.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75437/1/j.1600-0528.1998.tb01957.x.pd

Hydrochemical system analysis of public supply well fields, to reveal water-quality patterns and define groundwater bodies:The Netherlands

Hydrochemical system analysis (HCSA) is used to better understand the individual state of and spatial patterns in groundwater quality, by addressing the spatial distribution of groundwater bodies with specific origins (hydrosomes) and characteristic hydrochemical zones within each hydrosome (facies). The origin is determined by environmental tracers or geomorphological and potentiometric maps, the facies by combining age, redox and alkalinity indices. The HCSA method is applied to all 206 active public supply well fields (PSWFs) in The Netherlands, resulting in the distinction of nine hydrosomes and eleven facies parameters-age (young, intermediate, old), redox ((sub)oxic, anoxic, deep anoxic, mixed) and alkalinity (very low, low, intermediate and high). The resulting classification of PSWFs provides a means to (1) predict their vulnerability; (2) optimize groundwater-quality monitoring programs; and (3) better delineate groundwater bodies, by considering groundwater origin and flow. The HCSA translates complex hydrochemical patterns into easily interpretable maps by showing PSWFs, groundwater bodies and hydrochemical facies. Such maps facilitate communication between researchers, water resources managers and policy makers and can help to solve complex groundwater resources management problems at different scales, ranging from a single well(field) or region to the national or European scale. © 2010 Springer-Verlag