Performance Enhancement of the Flexible Transonic Truss-Braced Wing Aircraft Using Variable-Camber Continuous Trailing-Edge Flaps

Aircraft designers are to a growing extent using vehicle flexibility to optimize performance with objectives such as gust load alleviation and drag minimization. More complex aerodynamically optimized configurations may also require dynamic loads and perhaps eventually flutter suppression. This paper considers an aerodynamically optimized truss-braced wing aircraft designed for a Mach 0.745 cruise. The variable camber continuous trailing edge flap concept with a feedback control system is used to enhance aeroelastic stability. A linearized reduced order aerodynamic model is developed from unsteady Reynolds averaged Navier-Stokes simulations. A static output feedback controller is developed from that model. Closed-loop simulations using the reduced order aerodynamic model show that the controller is effective in stabilizing the vehicle dynamics

Alsophis rijgersmaei

Number of Pages: 3Integrative BiologyGeological Science

Active Flutter Suppression Using Reduced-Order Modeling for Transonic Aeroservoelastic Control Law Development

In this paper, several aerodynamic reduced-order models (ROMs) are generated and coupled with structural models to form aeroelastic ROMs. The aerodynamic ROMs generated here include the effects of control surface motion and are appropriate for use in aeroservoelastic applications. Simple observer-based full-state feedback controllers were designed from these aeroelastic ROMs. Additionally, observer gain matrices were designed from and coupled to the aeroelastic ROMs. Each (linear) observer was then used to estimate the dynamics of a (nonlinear) stand-alone computational fluid-structure dynamics simulation. Then, using the estimated states and the full-state feedback controller, control surface commands were fed back into the computational fluid-structure dynamics simulation to successfully achieve active flutter suppression. The process, as well as some results, are presented in this paper

Reduced Order Modeling for Transonic Aeroservoelastic Control Law Development

As aircraft become more flexible, aeroelastic considerations become increasingly important and complex, particularly for transonic flight where nonlinearities in the flow render linear analysis tools less effective. In order to analyze these aeroelastic interactions between the fluid and the structure efficiently, reduced order models (ROMs) are sometimes generated from and used in place of computational fluid dynamics solutions. In this paper, several aerodynamic ROMs are generated and coupled with structural models to form aeroelastic ROMs. The aerodynamic ROMs generated here include the effects of control surface motion. Hence, the aeroelastic ROMs presented here are appropriate for use in aeroservoelastic applications and are intended to be used for aeroservoelastic control law development. These ROMs are used to simulate a number of test cases with and without control surface involvement. Results show that several of the ROMs generated in the paper are able to predict results similar to solutions of higher-order computational methods

Understanding forest users' participation in participatory forest management (PFM): Insights from Mt. Elgon forest ecosystem, Kenya

Participation of local communities in forest management decision-making has been promoted as a mechanism of improving livelihoods and forest conditions, yet the level of participation in many programs remains low. Using data from a cross-sectional survey of 924 forest-dependent households in Western Kenya, we examine the factors that support or constrain forest dependent people's participation in a Participatory Forest Management (PFM) program. We run a probit model to assess households' choice to join PFM and then compute a Participation Index (PI) for forest users' participation across different stages of the PFM program – planning, implementation and Monitoring and Evaluation (M&E). The determinants of participation are then analyzed using the fractional regression approach. Results show that over half (52%) of the respondents participated in PFM. While vulnerability to shocks, being in a farmers' group, a household's access to the forest within the previous 12 months and access to extension were associated with the likelihood of participating in PFM, the influence of the household head's age and education, access to credit and food insecurity had a negative influence. Our results reveal PIs of 41%, 49%, and 42% at the planning, implementation, and M&E stages respectively, indicating a moderate participation level. The fractional regression model shows that transaction costs associated with access to markets, gender (being male), household expenditure and expected forest benefits positively influence household participation in PFM, while the opportunity costs associated with off-farm income, distance to the forest and lack of extension have a negative influence on participation. These results point to the need to take the household context (gender, education, household expenditure and vulnerability) into consideration during planning and implementation of the forestry programs. The implication is that forest authorities should identify and implement mechanisms to enhance benefits from forests but also reduce costs of participation, especially for women

SPEED: Experimental Design for Policy Evaluation in Linear Heteroscedastic Bandits

In this paper, we study the problem of optimal data collection for policy evaluation in linear bandits. In policy evaluation, we are given a target policy and asked to estimate the expected reward it will obtain when executed in a multi-armed bandit environment. Our work is the first work that focuses on such optimal data collection strategy for policy evaluation involving heteroscedastic reward noise in the linear bandit setting. We first formulate an optimal design for weighted least squares estimates in the heteroscedastic linear bandit setting that reduces the MSE of the value of the target policy. We then use this formulation to derive the optimal allocation of samples per action during data collection. We then introduce a novel algorithm SPEED (Structured Policy Evaluation Experimental Design) that tracks the optimal design and derive its regret with respect to the optimal design. Finally, we empirically validate that SPEED leads to policy evaluation with mean squared error comparable to the oracle strategy and significantly lower than simply running the target policy

Determinants of protected tomato production technologies among smallholder peri-urban producers in Kiambu, Kenya

Climate variability and the rise in incidences of pests and diseases continue to undermine production of high value vegetables among smallholder farmers in sub-Saharan Africa. In order to respond to these challenges, protected farming technologies (PFT) (such as greenhouses) which modify the plant environment and therefore aid in avoiding the harmful eects of climatic factors have been promoted. Greenhouses protect the crops against high solar radiation and heavy rainfall that have the potential of destroying vulnerable crops like tomatoes. Consequently, PFT is associated with better yields and farm incomes. However, the adoption of PFT among smallholder farmers, not least in Kenya is low. Drawing on the Agricultural Household Model (AHM) theoretic framework, this paper assessed the determinants of adoption of PFT among smallholder tomato farmers in Kenya. Tomato is the second most important horticultural vegetable crop in Kenya after potatoes in terms of production volumes and value. Data for the study were collected from a cross sectional multistage random survey of 104 tomato farming households and analysed using maximum likelihood probit model. The probit results revealed that the age of a farmer, educational level, household size, total household income and access to credit positively influenced the likelihood of PFT adoption. The likelihood of adoption was negatively related to distance to input markets and access to the county government extension services. Overall, the results of this study suggest that an integrated promotional strategy that accounts for household heterogeneities and focuses on institutional arrangements that support the accumulation of human and financial capital would enhance PFT adoption

Bacterial Degradation of Plastics

Plastics are not only a major component of societies on Earth but also those in Space. After use, plastics can accumulate and become difficult to recycle or reuse. Finding ways to degrade and recycle synthetic plastics would provide a way to reduce the upmass of Space Travel, create a closed-loop system of resources and even benefit life on Earth. The purpose of this project is to identify and characterize bacterial species that can degrade and recycle plastics. It has been suggested that bacteria can use plastics, like polyethylene and polystyrene, as a carbon source. These plastics are broken down into intermediary molecules which can then be used in the bacterium's metabolism. Environmental samples were collected from various locations rich in plastic waste. These samples are currently being used to culture bacteria in M9 minimal media containing polyethylene and polystyrene beads as the sole carbon source. High Performance Liquid Chromatography (HPLC), Scanning Electron Microscopy (SEM), and DNA sequencing are among the various methods that will be used identify and characterize bacteria that can degrade plastics. The results from these experiments will provide methods to reduce waste of plastics and ultimately improve sustainability for long-term space exploration