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The increase in greenhouse gas emissions, as well as the risk of fossil fuel depletion, has prompted a transition to electric transportation. The European Union aims to substantially reduce pollutant emissions by 2035 through the use of renewable energies. In aviation, this transition is particularly challenging, mainly due to the weight of onboard equipment. Traditional electric motors with radial magnetic flux have been replaced by axial magnetic flux motors with reduced weight and volume, high efficiency, power, and torque. These motors were initially developed for electric vehicles with in-wheel motors but have been adapted for aviation without modifications. Worldwide, there are already companies developing propulsion systems for various aircraft categories using such electric motors. One category of aircraft that could benefit from this electric motor development is traditionally constructed training aircraft with significant remaining flight resource. Electric repowering would allow their continued use for pilot training, preparing them for future electrically powered aircraft. This article presents a study on the feasibility of repowering a classic training aircraft with an electric propulsion system. The possibilities of using either a battery or a hybrid source composed of a battery and a fuel cell as an energy source are explored. The goal is to utilize components already in production to eliminate the research phase for specific aircraft components. [ABSTRACT FROM AUTHOR]

Solar UAVs (unmanned aerial vehicles) have experienced important development in recent years. The use of solar free energy is not neglected in the present energy crisis, with the intention to move toward green energies. However, an important problem arises concerning the limited amount of solar energy available on board UAVs. Until now, high-aerodynamic-efficiency configurations have been used. These configurations use high-aspect-ratio wings. However, high-aspect-ratio wings have some disadvantages regarding their excessive elasticity and weak bending resistance in the housing section. Additionally, the aircraft maneuverability is reduced. In this work, a study is proposed on a solar UAV configuration that sacrifices high aerodynamic efficiency for a higher surface area available for solar cells. In this manner, the amount of energy available on board the UAV is increased, and the UAV structure becomes more rigid and robust. The presented UAV fits better with more complex evolutions, is more maneuverable and the wingspan is much reduced. This UAV is more compact, can maneuver better in the take-off and landing phases, and the necessary storage space is considerably reduced. This paper highlights the performances that can be achieved using this kind of UAV and explores whether these performances are enough for some applications. Using an on-board energy balance, the possible performances of this new configuration is studied. As this is a preliminary study, the precision level is not very high, but it offers an image concerning the possibilities of this new configuration. [ABSTRACT FROM AUTHOR]

This paper presents some problems concerning the present trends in the field of aircraft braking systems. New solutions like electro-mechanical or electro-hydrostatic actuators are considered the future, but some big aircraft producers do not renounce yet to classical electro-hydraulic braking systems. New solutions are not generally accepted, they have to prove their reliability and that they bring considerable more advantages than penalties. [ABSTRACT FROM AUTHOR]

This work presents some numerical simulations, performed using AMESim software, for a system composed by two redundant servo-actuators. Certain operating conditions are taken into account for these two electro-hydrostatic servo-actuators, which are coupled to the command surface (aileron) of a transport aircraft. We first considered the situation of slight asymmetries in the construction of the servo-actuators, then a situation in which one servo-actuator fails at maximum flight speed, and then at a medium flight speed, and finally we considered the effect of gusts upon the system. Small differences in the construction of the servo-actuators were taken into consideration by modifying each of the pump displacements, one by +2% and one by −2%, from the nominal value. It is possible that many other asymmetries exist in the construction of servo-actuators, such as different liquid leakages in the cylinders or pumps, small differences in the controller coefficients, and so on. These differences should be taken into account in future works. Our results provide evidence that, under some operation situations of redundant servo-actuators, significant overstresses can appear in one servo-actuator, leading to a decrease in the time for which the system operates correctly. [ABSTRACT FROM AUTHOR]

Fruit formations of Xanthium italicum were gathered from plants, sand and a river bank. They were put in germination conditions to observe how this process takes places and what the seedlings’ growth rate is in the early stages, until the first true leaf appears. Data were processed by variance analysis; using the Duncan test, the correlations between germination and seedlings’ growth in X. italicum and the place of sampling the anthodiums was highlighted. The fruit formations’ harvesting site influences the germination process, the finding being statistically significant; between the length of hypocotyl and cotyledons there is a distinct correlation, statistically significant (r = 0.908) regardless of the place of harvest. [ABSTRACT FROM AUTHOR]

Average composition of household waste in Bucharest has a large variability. The average amount of waste collected is 0.048 m 3/ man. year compared with the U.S. 1m 3 / man. year, South Africa 0.8 m3 / man. year and Australia 0.4 m 3 / man. year. These wastes are sorted, the size which could be sorted and reused according to their composition, remaining part, about 64% of the original composition is subject to biodegradation by composting. The material resulting from the biodegradable composting was analyzed in terms of the physical- chemical and microbiological properties. Physical analyzes aimed material granulometry, humidity and porosity. Chemical analyzes were conducted on fractions and consisted in determining pH, salt content and soluble elements such as Ca, Mg, N, P, K, as well as heavy metals (Cu, Zn, Pb, Cd, Ni, etc.). In order to assess biodegradability of the waste material the breath was determined. The results showed variability in physical characteristics between batches of compost from municipal waste, variability of the chemical characteristics of graded according including especially heavy metals and other hazardous elements. This variation indicates that the coarse fractions have a higher amount of N, P, K and small in high fractions of heavy metals. Determination of breath biodegradable material can be a valuable indicator of degradation phenomenon completion. [ABSTRACT FROM AUTHOR]

As is well known, the airflow speed in a wind tunnel is proportional to the rotation speed of the wind tunnel fan. Thus, the development of an airflow control system to the wind tunnel requires the development of a device able to control the rotation speed of the wind tunnel fan. [ABSTRACT FROM PUBLISHER]