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971.
Spectrally efficient backhaul networks are one of the key-factors for the deployment of next generation wireless cellular systems. The ambitious capacity requirements for future broadband wireless networks and the high infrastructure costs for new cell sites pose new challenges in the design of high capacity point-to-point (PtP) wireless microwave links. In this paper we present a study on PtP links that utilize a peculiar form of multiple-input multiple-output configuration, in which a capacity doubling is obtained by exploiting the geometric characteristics of the Line-of-Sight link. The impact of adaptivity on the maximum achievable transmission distance in presence of the main electronic impairments, for typical physical parameters, is discussed in order to reveal the feasibility and the advantages of this class of solutions. 相似文献
972.
Luca Larcher Andrea Padovani Luca VandelliPaolo Pavan 《Microelectronic Engineering》2011,88(7):1168-1173
Charge trapping (CT) memories could be a promising technology option for further NAND Flash scaling. The assessment of the scalability limits and ultimate performances of this technology demands for the comprehensive understanding of the physical mechanisms governing device operation and reliability, which requires accurate physics-based models reproducing the electrical device characteristics. The basic features of the models presented in the literature for CT memory devices are reviewed, underlining their similarities and differences, and highlighting their importance in order to achieve a comprehensive understanding of the physical mechanisms responsible for CT device operation and reliability. A physical model describing the charge transport in nitride and high-κ stacks is also presented, which allows gaining further insights into reliability issues related to charge localization and high-κ tunnel and blocking dielectrics, like the effects of the blocking alumina layer and the band-gap engineered tunnel dielectrics on the TANOS device retention. 相似文献
973.
Luca Pilia Michele Serri Michio M. Matsushita Kunio Awaga Sandrine Heutz Neil Robertson 《Advanced functional materials》2014,24(16):2383-2388
The magnetic, thin‐film structural, conductivity, and magnetoresistance properties of [Ni(quinoline‐8‐thiolate)2] ([Ni(qt)2]) are studied. The conducting and magnetoresistance properties are studied in single crystals and in evaporated thin films through deposition on an interdigitated electrode array. Non‐linear conductivity interpreted through a space‐charge limited conduction mechanism with charges injected from the electrodes is observed. Under applied magnetic field, the material displays giant negative magnetoresistance above 50% at 2 K in both single crystals and in evaporated thin films. The effect can still be observed at 200 K and is interpreted in terms of a double exchange mechanism with the shape of the curve determined by the magnetic anisotropy. The unique observation of giant magnetoresistance (GMR) as an intrinsic effect in an evaporated thin film of paramagnetic molecules opens up new possibilities in organic spintronics. 相似文献
974.
Raffaella Capelli Franco Dinelli Massimo Gazzano Riccardo D'Alpaos Andrea Stefani Gianluca Generali Mauro Riva Monica Montecchi Angelo Giglia Luca Pasquali 《Advanced functional materials》2014,24(35):5603-5613
Herein is described a multidisciplinary approach to understand the performance limitations of small molecule organic light emitting transistors (OLETs) based on a layered architecture, an innovative architecture potentially competitive with the state of the art and more flexible for spectral emission control. The processes of charge injection and field‐effect transport at metal/organic and organic/organic interfaces are analysed using microscopic and spectroscopic techniques in coordination. Atomic force microscopy and ultrasonic force microscopy are employed to characterize the interface morphology and the initial growth stages of organic films where charge transport actually occurs. X‐ray diffraction and near edge X‐ray dichroic absorption with linearly polarised light allow to determine the unit cell packing and the molecular orientation at the active organic interfaces, as well as the amount of non‐ordered domains. Moreover, chemical reactivity at the interfaces is measured by X‐ray photoelectron spectroscopy. It is found that a strong reaction occurs at the metal‐organic interfaces, with molecular fragmentation. Additionally, the transport properties strongly depend on the nature of the materials forming the organic stack. Specifically, amorphous conjugated films as bottom layers can promote an increased molecular disorder in the upper active layer, with a concomitant deterioration of the conduction properties. 相似文献
975.
Francesco Bruni Mauro Sassi Marcello Campione Umberto Giovanella Riccardo Ruffo Silvia Luzzati Francesco Meinardi Luca Beverina Sergio Brovelli 《Advanced functional materials》2014,24(47):7410-7419
Small conjugated molecules (SM) are gaining momentum as an alternative to semiconducting polymers for the production of solution‐processed bulk heterojunction (BHJ) solar cells. The major issue with SM‐BHJs is the low carrier mobility due to the scarce control on the phase‐segregation process and consequent lack of preferential percolative pathways for electrons and holes to the extraction electrodes. Here, a new paradigm for fine tuning the phase‐segregation in SM‐BHJs, based on the post‐deposition exploitation of latent hydrogen bonding in binary mixtures of PCBM with suitably functionalized electron donor molecules, is demonstrated. The strategy consist in the chemical protection of the H‐bond forming sites of the donor species with a thermo‐labile functionality whose controlled thermal cleavage leads to the formation of stable, crystalline, phase‐separated molecular aggregates. This approach allows the fine tuning of the nanoscale film connectivity and thereby to simultaneously optimize the generation of geminate carriers at the donor–acceptor interfaces and the extraction of free charges via ordered phase‐separated domains. As a result, the PV efficiency undergoes an over twenty‐fold increase with respect to control devices. This strategy, demonstrated here with mixtures of diketopyrrolopyrrole derivatives with PCBM can be extended to other molecular systems for achieving highly efficient SM‐BHJ solar cells. 相似文献
976.
We consider the problem of trajectory planning and control for an XYnR? Planar robot with the first two joints (rotational or prismatic) actuated and n rotational passive joints, moving both in the presence and the absence of gravity. Under the assumption that each passive link is attached at the center of percussion of the previous passive link, dynamics of the system can be expressed through the behavior of n special points of the plane. These points are called link‐related acceleration points (LRAP) since their instantaneous acceleration is oriented as the axis of the related passive links. Moreover, LRAP dynamics present a backward recursive form which can be exploited to recursively design a dynamic feedback that completely linearizes the system equations. We use this approach to solve trajectory planning and tracking problems and report simulation results obtained for an RR2R? robot having the first two rotational joints actuated. © 2003 Wiley Periodicals, Inc. 相似文献
977.
In the Friuli Venezia Giulia region, in the North East of Italy, a traditional fermented sausage is produced without the use of microbial starters. It is characterized at the end of the ripening period by accentuated acidity, slight sourness and elastic, semi-hard consistency. In this study, three fermentations, carried out in different seasons (winter, spring and summer) were followed analyzing the microbiological, physicochemical and sensory aspects of this product. The sausages were characterized by an important microbial activity of lactic acid bacteria and micro/staphylococci that resulted in a product with a final pH of about 5.6-5.7. An interesting aspect was the high number of fecal enterococci that can play an important role in the definition of the organoleptic profile of the final product. No Listeria monocytogenes, Salmonella spp. and Staphylococcus aureus were ever isolated from the raw materials or the fermented sausages during the maturation, underlining the safety of this product. The final water activity of the product was 0.91-0.92. One hundred and fifty lactic acid bacteria were isolated and identified by molecular methods to understand which species were more predominant in the product. Lactobacillus curvatus and Lactobacillus sakei were the most numerous (54 and 64 strains isolated, respectively) and they were the only species common to all three fermentations. A cluster analysis of the profiles obtained from these strains after RAPD-PCR highlighted a population distribution that was fermentation-specific. 相似文献
978.
Luca Rolle Fabrizio Torchio Simone Giacosa Vincenzo Gerbi 《Journal of the science of food and agriculture》2009,89(11):1973-1980
BACKGROUND: Among several common drying systems used in the enological sector the dry‐on‐vine (DOV) method assumes particular importance because famous wines such as Sauternes, Tokay and Ice Wines are produced by grapes dried using this system. Knowledge about trends in mechanical properties and phenolic composition during on‐vine grape drying is scarce. The objective of this current study is therefore to increase the knowledge on these aspects. RESULTS: Berry skin break energy (+0.10 N) and berry skin thickness (+69 µm) values increase during grape dehydration, while the peduncle detach force decreases (?0.86 N). Large reductions in the anthocyanin content have also been observed (?40%), but their profile does not show significant changes. Seed hardness (?7.10 N, ?1.40 mJ) decreases during the withering, and higher seed springiness has been observed. Seed proanthocyanidins (+2050 mg kg berry?1) and flavanols vanillin assay (+670 mg kg berry?1) increase progressively throughout the withering. In contrast, a distinct lowering of these substances in the skins was noted. CONCLUSION: Many modifications in the chemical–physical characteristics of berries of Mondeuse winegrapes throughout the DOV process were found. The mechanical characteristics of grapes, in particular the peduncle detachment force, are important parameters in assessing their suitability for the drying‐on‐plant process. Copyright © 2009 Society of Chemical Industry 相似文献
979.
Nizzetto L Lohmann R Gioia R Jahnke A Temme C Dachs J Herckes P Di Guardo A Jones KC 《Environmental science & technology》2008,42(5):1580-1585
Polycyclic aromatic hydrocarbons (PAHs) were simultaneously measured in air and surface seawater between 49 degrees N and 25 degrees S in the open Atlantic Ocean. Elevated concentrations of PAHs (sigma10 PAHs approximately 1.4-2.5 ng m(-3) air, and 0.7-1 ng L(-1) seawater) occurred in the Biscay Bay and off the northwest coast of Africa. The unexpectedly high concentrations off NW Africa were discussed assessing the possible contribution of the emerging oil industry along the African shore, the role of biomass burning and natural sources of PAHs. In the southern Atlantic, concentrations of PAHs were close to detection limits (sigma10 PAHs approximately 0.02-0.5 ng m(-3) air, and 0.06-0.5 ng L(-1) seawater) and showed decreasing trends with increasing latitudes. Correlations of PAHs' partial pressures versus inverse temperature were not significant in contrast to results for polychlorinated biphenyls from the same transect. This could have been due to the importance of ongoing primary sources and the shorter atmospheric life-times of PAHs. Air-water fugacity ratios (fa/fw) were calculated for selected compounds. They were close to 1 for fluoranthene and pyrene in remote open ocean areas suggesting air-water partitioning near equilibrium. Ratios for anthracene and phenanthrene were < 0.3 in the remote tropical Atlantic, suggesting net volatilization. 相似文献
980.
Michele Spina Massimiliano Cuccioloni Luca Sparapani Stefano Acciarri Anna Maria Eleuteri Evandro Fioretti Mauro Angeletti 《Journal of the science of food and agriculture》2008,88(2):294-304
BACKGROUND: Owing to the demand for ‘health foods’, commercial development of wild vegetables may find a sizable market niche if adequate agricultural methods are used to domesticate such species. Available techniques of cultivation (even in traditional farming) may provide many advantages, such as enhancement of the content of active principles in plants and improvement in the quality of the raw material to be processed on an industrial scale. In this context, the flavonoid composition and content of roots and leaves from five varieties of wild herbs (Cichorium intybus, Portulaca oleracea, Tragopogon porrifolius, Urtica dioica and Valerianella eriocarpa) and their cultivated relatives in central Italy were compared. The aims of the study were (i) to reveal the metabolic profile of particular bioactive metabolites present in some unusual food species by using a simple method of analysis, (ii) to quantify and compare the amount of polyphenolic metabolites in wild and cultivated plants and (iii) to evaluate the effect of growing conditions on polyphenolic variability. Data were subjected to statistical analysis. RESULTS: Each herb possessed a specific flavonoid fingerprint as indicated by high‐performance liquid chromatography (HPLC) data. The total phenolic content in cultivated leaves was greater than that in wild leaves for all herbs examined (P < 0.05), with the exception of P. oleracea. CONCLUSION: The results show that the polyphenolic content of the majority of the cultivated herbs (edible parts) is no lower than that of their wild relatives, thus indicating that these species are suitable for cultivation. Copyright © 2007 Society of Chemical Industry 相似文献