Connectivity analysis of an AUV network with OFDM based communications

Autonomous underwater vehicle (AUV) networks play a crucial role in tactical, commercial, and scientific applications, where reliable and robust communication protocols are needed due to the challenging characteristics of the channel. With this motivation, connectivity of AUV networks in different regions with varying transducer characteristics are analyzed through simulations based on real-life orthogonal frequency division multiplexing (OFDM) based communication experiments over noisy and Doppler-distorted channels. Doppler compensation is performed according to the autocorrelation using the cyclic prefix. Using binary and quadrature phase shift keying (BPSK and QPSK) modulation schemes in conjunction with low density parity check (LDPC) coding, error rate levels are investigated through shallow water pond and at-sea experiments. It is shown that, the utilized transmission scheme is capable of correcting all bit errors among nearly one million bits transmitted up to a distance of 1 km, yielding a payload rate of 15.6 kbps with 4096 subcarriers and QPSK modulation. The simulations provide key parameters that must be taken into account in the design of scalable and connected AUV networks. © 2017 IEEE

Development of a New largely scalable in vitro prion propagation method for the production of infectious recombinant prions for high resolution structural studies.

The resolution of the three-dimensional structure of infectious prions at the atomic level is pivotal to understand the pathobiology of Transmissible Spongiform Encephalopathies (TSE), but has been long hindered due to certain particularities of these proteinaceous pathogens. Difficulties related to their purification from brain homogenates of disease-affected animals were resolved almost a decade ago by the development of in vitro recombinant prion propagation systems giving rise to highly infectious recombinant prions. However, lack of knowledge about the molecular mechanisms of the misfolding event and the complexity of systems such as the Protein Misfolding Cyclic Amplification (PMCA), have limited generating the large amounts of homogeneous recombinant prion preparations required for high-resolution techniques such as solid state Nuclear Magnetic Resonance (ssNMR) imaging. Herein, we present a novel recombinant prion propagation system based on PMCA that substitutes sonication with shaking thereby allowing the production of unprecedented amounts of multi-labeled, infectious recombinant prions. The use of specific cofactors, such as dextran sulfate, limit the structural heterogeneity of the in vitro propagated prions and makes possible, for the first time, the generation of infectious and likely homogeneous samples in sufficient quantities for studies with high-resolution structural techniques as demonstrated by the preliminary ssNMR spectrum presented here. Overall, we consider that this new method named Protein Misfolding Shaking Amplification (PMSA), opens new avenues to finally elucidate the three-dimensional structure of infectious prions

The effect of hydrogen on the mechanical behaviour of duplex stainless steel

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An evaluation of seed spacing accuracy of a vacuum type precision metering unit based on theoretical considerations and experiments [Teorik ve deneysel verilere dayali{dotless} olarak vakumlu tek dane ekim ünitesinin tohum arali{dotless}gi{dotless} düzgünlügünün degerlendirilmesi]

Currently the most widely used machine for precision seeding of cotton and maize seed is vacuum type. The capture of seeds by vacuum plate and the release of seeds from the vacuum plate should be performed precisely without missing or doubling. The physical phenomena should be clarified theoretically to understand how the precision seeding mechanism works. To solve these problems, an attempt was made to develop a nomogram using equations describing the technical characteristics of the seeder used in this study and to describe the seed capture mechanism relying on basic principles of fluid mechanics and aerodynamic properties of seeds. Seed spacing accuracy tests were performed to test the theory on a sticky belt in the laboratory. Quality of feed index, miss and multiple indices, and precision have been taken as a set of criteria for seed spacing accuracy. The regression models developed using the data obtained via sticky band tests showed that 16 seeds s-1 was the upper limit of seed release frequency (SRF) for cotton and maize seeds. The upper limit of vacuum plate peripheral speed was found to be 0.34 m s-1. The use of 72 holes instead of 26 holes in the vacuum plate at 6.3 kPa created a vacuum band in the width of 10 mm around holes and this increased the multiple index and caused a reduction in seeding performance. For this reason, the use of vacuum plates with 60 or 52 holes is recommended for cotton seed. The forward speed of either 1.0 or 1.5 m s-1 was found to be acceptable for the seed spacing of 0.05 and 0.10 m, respectively. Aerodynamic calculations verified that widely used vacuum plates with 26 holes were the appropriate ones for seeding maize seeds. The performance indices, namely the quality of feed, and miss and multiple indices, reduced significantly for cotton and maize seeding when the precision metering unit was run at 20% (11°) slope to the right as compared to the no slope condition. © TÜBİTAK

Optimization of the seed spacing uniformity performance of a precision seeder using spherical materials and response surface methodology

The objective of this study was to optimize the seed spacing uniformity performance of a precision seeder using spherical materials and Response Surface Methodology (RSM) and to verify the optimum levels of the variables. The variables considered in the study included vacuum on seed plate, the diameter of seed holes and peripheral speed of the seed plate. Spherical materials made of plastic were used and experiments based on Central Composite Design (CCD), one of the designs in RSM were carried out in the laboratory. The data obtained were divided into three different groups in order to obtain the values of Multiple Index, Quality of Feed Index, Miss Index. Other performance indicators called root mean square deviation and CP3 were also calculated and evaluated in the study. Prediction functions mostly for quality of feed index in polynomial form allowed the calculation of the optimum level of each independent variable. Optimum levels of the variables obtained for each spherical material were tested and verified