Wave Energy Converters (WECs) are designed to be deployed in arrays, usually in a limited space, to minimize the cost of installation, mooring, and maintenance. Control methods that attempt to maximize the harvested power often lead to power flow from the WEC to the ocean, at times, to maximize the overall harvested power from the ocean over a longer period. The Power Take-Off (PTO) units that can provide power to the ocean (reactive power) are usually more expensive and complex. In this work, an optimal control formulation is presented using Pontryagin’s minimum principle that aims to maximize the harvested energy subject to constraints on the maximum PTO force and power flow direction. An analytical formulation is presented for the optimal control of an array of WECs, assuming irregular wave input. Three variations of the developed control are tested: a formulation without power constraints, a formulation that only allows for positive power, and finally, a formulation that allows for finite reactive power. The control is compared with optimally tuned damping and bang–bang control.

Background. Rubella is a vaccine-preventable disease associated with a significant morbidity and adverse pregnancy outcomes, mainly if acquired in the first trimester of pregnancy with serious consequences to the fetus. Despite increased episodes of rubella epidemics (127 outbreaks in 2009–2015), rubella national vaccination is not yet introduced in Ethiopia. In January 2018, an increase of fever and rash cases was reported in Kuyu District of Oromia. We investigated the outbreak to confirm rubella, determine risk factors, and guide interventions. Methods. We identified rubella cases from health centers and conducted a case-control study (1 case : 2 controls) with 150 participants, from March 12 to 15, 2018. Cases were people who presented with fever and rash or laboratory-confirmed cases. Controls were age matched (<15 yrs) with neighbors selected purposively. We interviewed parents by a structured questionnaire and observed the housing condition. Variables include sex, age, vaccination status, family size, contact history, housing condition, and travel history. Simple logistic regression was used to select the candidate variable at a P value 5 (AOR = 2.4; 95% CI: 1.5–4.11), not well-ventilated living room (AOR = 4.7; 95% CI: 3.43–8.12), history of contact with rash people (AOR = 2.2; 95% CI: 1.6 3.5), no history of diarrhea in the last 14 days (AOR = 0.8; 95% CI: 0.6–0.9), and no history of vitamin A supplementation (AOR = 2.9; 95% CI: 1.7–2.6) were significant factors for rubella infection. Conclusions. We identified rubella outbreak in the rural area. Crowded living condition, large family size, not receiving vitamin A in the last 6 months, and contact with people with symptoms of rubella were factors that drove the outbreak, while not having diarrhea in the last 14 days was the protective factor. We recommended the introduction of rubella immunization national programs and advocated the policy on rubella vaccine and strengthening surveillance for congenital rubella syndrome and rubella.

Unmanned Aerial Vehicles (UAVs), in the form of ornithopters, which emulate avian flight through wing flapping, have been the focus of this investigation. The remarkable maneuverability of birds and insects, often lacking in conventional aircraft, is harnessed to advance the control and stability of flapping wing flight. The need for such exploration is driven by the potential benefits to both scientific inquiry and societal applications. This investigation tackles the task of tailoring the ornithopter's design and component choice to cater to performance expectations derived from the flight attributes of birds, such as superior maneuverability, agility, low-speed flight capabilities, and high propulsive efficiency. The primary goal is to ensure a sustained airborne state through the generation of lift equivalent to the ornithopter's weight. Commonly available materials have been employed in the construction of the ornithopter. SolidWorks flow simulator was utilized to simulate aerodynamics. A 1000mm length of the wing was subjected to a 3m/s air stream at a 5-degree angle of attack for the simulation. The simulated result, which represents a 2kg ornithopter, exhibited a lift force of 0.8N and a drag force of 0.2N. Further simulations were conducted at varying attack angles (from 0 to 35 degrees) to gauge the range of lift and drag coefficients. The investigation concludes that the constructed ornithopter should generate an upward thrust of 2.7N at a speed of 5m/s, even without wing flapping, ensuring controlled and stable flight.