A new position regulation strategy for VTOL UAVs using IMU and GPS measurements

We propose a new position regulation strategy for VTOL-UAVs using IMU and GPS measurements. Since there is no sensor that measures the attitude, our approach does not rely on the knowledge (or reconstruction) of the system orientation as usually done in the existing literature. Instead, IMU and GPS measurements are directly incorporated in the control law. An important feature of the proposed strategy, is that the accelerometer is used to measure the apparent acceleration of the vehicle, as opposed to only measuring the gravity vector, which would otherwise lead to unexpected performance when the vehicle is accelerating (i.e. not in a hover configuration).     

GPM: A generic and scalable P2P model that optimizes tree depth for multicast communications

Group communications (real‐time and non‐real‐time) refer to one‐to‐many or many‐to‐many communications. On the one hand, multicast is considered as an appropriate solution for supporting group communication‐oriented applications (we distinguish IP network multicast from application layer multicast). On the other hand, peer‐to‐peer model tends to be a good candidate for supporting today Internet applications (e.g. P2P IPTV, P2P VoIP, etc.). In this context, P2P has attracted significant interest in the recent years. This is mainly due to its properties that also make P2P well adapted to today social networks. In this paper, we propose GPM (Generic P2P Multicast): a novel generic and scalable approach, that optimizes multicast tree depth in P2P networks (structured and unstructured), and contributes to control the network overlay latency. For multicast tree construction, the approach we propose is based on a distributed algorithm using a specific data structures (adjacency and forwarding matrixes). GPM model inherits from P2P attributes such as scalability, flexibility and fault tolerance, while taking into consideration the respective characteristics of one‐to‐many and many‐to‐many type of applications. We also give a performance evaluation for validation and comparison purposes while considering some main existing application layer multicast protocols. Copyright © 2011 John Wiley & Sons, Ltd.     

First-principles DFT study of SO2 and SO3 adsorption on 2PANI: a model for polyaniline response

Interaction of SO_x (x?=?2,3) molecules on active sites of dianiline (as a model for polyaniline, denoted here as 2PANI) was studied using density functional theory at the BLYP-D/6-31+G(d) level of theory. Natural population analysis was used to find out the charge distribution as well as the net transferred charge of SO_x upon adsorption on 2PANI and the result has been compared with Mulliken charge analysis to evaluate the sensing ability of 2PANI. The computed density of states point to the remarkable orbital hybridization between SO_x and 2PANI during the adsorption process. As a consequence, the results of UV–VIS confirm the sensing ability of 2PANI toward SO₂ and SO₃. Based on our results, it can be found that at proper configuration the SO₂ and SO₃ molecules can be adsorbed on 2PANI with adsorption energies (E_ads) of ?18.2 and ?62.9?kJ/mol (BSSE), respectively.     

Bioreactors for heart valve tissue engineering: a review

Bioreactors have great potential in the successful development of tissue‐engineered heart valve replacements, both at the research stage and in commercial platforms. Their ability to mimick the chemical and physiological conditions of the body has allowed researchers to study in vitro cellular responses, and this has helped in the fabrication of better and more efficient tissues in vivo. Use of different bioreactors, such as, rotating, dynamic flexure, cyclic stretch and pulsatile bioreactors, in tissue engineering of heart valves has been widely investigated. However, this research is still at its early stage, and many critical issues need to be resolved to make tissue engineered heart valves sufficiently reliable for clinical applications. In the following article, after a brief introduction to the structure and role of heart valves, the efforts of tissue engineers in designing heart valves using different bioreactors is described. © 2015 Society of Chemical Industry     

Electrical and mechanical properties of BZT − xBCT lead-free piezoceramics

In this study, lead-free (1 − x)Ba(Zr_0.2Ti_0.8)O₃ − x(Ba_0.7Ca_0.3)TiO₃ compositions are synthesized via conventional solid oxide route, and the ceramics are fabricated with normal sintering in air. The effects of composition fluctuations on dielectric, piezoelectric, and mechanical properties are investigated. The phase structure and the microstructure are analyzed with X-ray diffraction and scanning electron microscopy. The best dielectric and piezoelectric properties of ε_r = 11 207 and d₃₃ = 330 pC/N were obtained for BZT−0.35BCT and BZT−0.5BCT ceramics, respectively. The mechanical behavior—in terms of Vickers hardness and compressive and flexural strengths—was investigated, and the best mechanical behavior was found in the vicinity of the phase transition boundary with x values between 0.5 and 0.6.     

The food preservative potential of essential oils: is lemongrass the answer?

Several essential oils of medicinal plants possess proven antimicrobial activity and are suitable for applications on the food industry. The oil from Cymbopogon citratus (lemongrass) has been reported to have a wide range of biological activities. However, there are few controlled studies confirming its antimicrobial activity. The aim of our study was to assess the antimicrobial potential of lemongrass oil against a wide spectrum of food spoilage and pathogenic bacteria and yeast in liquid and vapour phase. The chemical composition of the oil was analyzed by gas chromatography; 14 components were identified and geranial (28.93 %), neral (24.30 %) and myrcene (23.92 %) were the most abundant constituents. Lemongrass oil showed potent antimicrobial activity against Gram positive bacteria and exhibited the strongest antifungal effect against Candida albicans and C. parapsilosis. Minimum inhibitory concentration varied from 0.019 to 1.25 mg mL^?1 for Gram positive bacteria and yeasts, indicating Staphylococcus aureus, S. epidermidis and C. albicans as the most susceptible strains. Moreover, the diameter of inhibition zone (DIZ) increased with increasing essential oil (EO) volume. Considerably superior antimicrobial activity was observed in the vapour phase. The DIZ resulting from the exposure to EO vapour was significantly larger than that from the same volume in the liquid phase. The DIZ varied from 22 to 90 mm for Candida strains. There is growing evidence that EO in vapour phase are effective antimicrobial systems and that they do have advantages over the use of oil in liquid phase. Our results imply that lemongrass oil could be useful for the development of novel types of natural preservatives for food control.     

Influence of annealing temperature on the structural and anti-corrosion characteristics of sol–gel derived,spin-coated thin films

Recently, an aqueous particulate sol–gel process using metallic chloride precursors was introduced to synthesize zirconium titanate. In this paper, the effect of annealing temperature on the structural and corrosion protection characteristics of spin-coated thin films obtained from this sol–gel system was investigated. Based on scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and spectroscopic reflectometry studies, it was found that the flatness and thickness of the thin films were decreased by increasing the annealing temperature. Also, the corrosion protection of stainless steel AISI 316L provided by the prepared coatings, as analyzed by electrochemical potentiodynamic polarization experiments in a simulated body fluid, was improved in this order: 500 °C-annealed sample<900 °C-annealed sample<700 °C-annealed sample, attributed to a compromise between the defect density and the adhesion of the films to the substrate.     

70—THE MECHANICS OF SELF-PLYING STRUCTURES. PART II: MULTIFILAMENT STRANDS

Analyses of the mechanics of self-plying structures are presented for multi-filament component strands, and an account is given of the experimental verification of theoretical predictions, made by means of the use of nylon multifilament model yarns.