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261.
262.
Trung-Hien Nguyen Pascal Scalart Mathilde Gay Laurent Bramerie Christophe Peucheret Fausto Gomez-Agis Olivier Sentieys Jean-Claude Simon Michel Joindot 《Photonic Network Communications》2018,36(3):326-337
We report on a simple alternative method for the compensation of quadrature imbalance in optical quadrature phase-shift-keying (QPSK) coherent systems. By introducing a new metric, the phase imbalance can be determined and compensated. The proposed method is theoretically and numerically analyzed. In particular, it is shown that the method exhibits a small bias of estimated phase imbalance value. Thanks to its deterministic property, this bias can be simply compensated by incorporating at the receiver a phase rotator (or phase shift) whose value can be determined based on an analytical analysis. Moreover, the algorithm is also experimentally validated through bit-error-rate and error vector magnitude (EVM) measurements. A good agreement on the performance of the proposed method with that of the Gram–Schmidt orthogonalization procedure is shown in a 20-Gbit/s optical QPSK experiment. The robustness of both methods was verified with up to \(30^\circ \) phase imbalance by comparing the signal with and without phase imbalance compensation. A 10% reduction in EVM is achieved with our method for a high phase imbalance of \(30^\circ \), while the implementation complexity can be reduced owing to the suppression of the use of square-root operators. 相似文献
263.
Margot A. Llosa Tanco Jose A. Medrano Valentina Cechetto Fausto Gallucci David A. Pacheco Tanaka 《International Journal of Hydrogen Energy》2021,46(37):19758-19767
One alternative for the storage and transport of hydrogen is blending a low amount of hydrogen (up to 15 or 20%) into existing natural gas grids. When demanded, hydrogen can be then separated, close to the end users using membranes. In this work, composite alumina carbon molecular sieves membranes (Al-CMSM) supported on tubular porous alumina have been prepared and characterized. Single gas permeation studies showed that the H2/CH4 separation properties at 30 °C are well above the Robeson limit of polymeric membranes. H2 permeation studies of the H2–CH4 mixture gases, containing 5–20% of H2 show that the H2 purity depends on the H2 content in the feed and the operating temperature. In the best scenario investigated in this work, for samples containing 10% of H2 with an inlet pressure of 7.5 bar and permeated pressure of 0.01 bar at 30 °C, the H2 purity obtained was 99.4%. 相似文献
264.
The aim of this study was to study the psychrotrophic microbiota developing during milk creaming of Grana Trentino cheese-making. 138 isolates from raw whole milk, cream and skim milk samples were screened by Randomly amplified polymorphic DNA PCR biotyping and representative strains of each biotype were characterised by partial 16S rRNA gene sequencing and enzymatic activity. Pseudomonadaceae were commonly isolated in cream samples while Streptococcaceae and Enterobacteriaceae in milk samples. Moraxellaceae and Flavobacteriaceae were found in both cream and milk samples.More than 80% of psychrotrophic isolates could grow at 37 °C. All Flavobacteriaceae and half of Pseudomonadaceae biotypes displayed proteolytic activity on milk agar even at low temperatures such as 10 °C. All Streptococcaceae and some of Enterobacteriaceae displayed acidifying activity and almost all Acinetobacter spp. (Moraxellaceae) displayed lipolytic activity towards tributyrin.Even if psychrotrophic bacteria is not the dominant microbial group in raw milk, their total number increases during creaming and becomes one of the most present group together with Lactic Acid Bacteria. Their enzymatic activities may be key players in determining milk quality for cheese making. 相似文献
265.
Palencia C Rubio J Rubio F Fierro JL Oteo JL 《Journal of nanoscience and nanotechnology》2011,11(5):4142-4152
Carbon nanofibers (CNFs) are considered ideal materials for reinforcing polymers due to their excellent mechanical properties, among others. In order to obtain composites of optimal properties the clue is to enhance the interaction between reinforcement (CNFs) and polymer matrix. Surface modification of CNFs with silane coupling agents (SCAs) has revealed as one of the most interesting methods. The silanization process has been carried out mixing at room temperature and for one minute the hydrolysed silane with CNFs. We have use four different SCAs: 3-aminopropyltriethoxyxilane (APS), 3-aminopropyltrimethoxysilane (AMMO), N-(2-aminoethyl)-3-(aminopropyltrimethoxysilane) (DAMO), and 3-glycidoxypropyltrimethoxysilane (GLYMO), in order to elucidate the SCA-CNFs interaction and the silane structures formed on CNFs surface. XPS and FTIR-ATR techniques have pointed out that each silane adsorbs on CNFs surface through chemical bonding, forming multilayers. Silane nature determines the structure taken on CNFs surface. APS and AMO silanes adsorb taking vertical structures on CNFs surface, while DMO and GMO adsorb on CNFs taking horizontal structures, stabilized by zwitterions formed through H-bonds with hydroxyl groups from CNFs surface. 相似文献
266.
Emilio Vélez-Fort Emiliano Pallecchi Mathieu G. Silly Mounib Bahri Gilles Patriarche Abhay Shukla Fausto Sirotti Abdelkarim Ouerghi 《Nano Research》2014,7(6):835-843
In-plane heteroatom substitution of graphene is a promising strategy to modify its properties. The ability to dope graphene with electron-donor nitrogen heteroatoms is highly important for modulating electrical properties of graphene. Here we demonstrate a transfer-free method to directly grow large area quasi free-standing N-doped graphene bilayers on an insulating substrate (Si3N4). Electron-bombardment heating under nitrogen flux results in simultaneous growth of N-doped graphene and a Si3N4 layer on the SiC surface. The decoupling of N-doped graphene from the substrate and the presence of Si3N4 are identified by X-ray photoemission spectroscopy and low-energy electron diffraction. The substitution of nitrogen atoms in the graphene planes was confirmed using high resolution X-ray photoemission spectroscopy which reveals several atomic configurations for the nitrogen atoms: Graphitic-like, pyridine-like, and pyrrolic- like. Furthermore, we demonstrated for the first time that N-doped graphene could be used to efficiently probe oxygen molecules via nitrogen atom defects. 相似文献
267.
Virgo Collaboration Acernese F Alshourbagy M Amico P Aoudia S Antonucci F Astone P Avino S Babusci D Ballardin G Barone F Barsuglia M Barsotti L Beauville F Bigotta S Birindelli S Bizouard MA Boccara AC Bondu F Bosi L Braccini S Bradaschia C Brillet A Brisson V Brocco L Buskulic D Calloni E Campagna E Cavalier F Carbognani F Cavalieri R Cella G Cesarini E Chassande-Motin E Christensen N Clapson AC Frédéric C Corda C Corsi A Cottone F Coulon JP Cuoco E Dari A Datillo V Davier M del Prete M 《Applied optics》2007,46(17):3466-3484
The Virgo interferometer, aimed at detecting gravitational waves, is now in a commissioning phase. Measurements of its optical properties are needed for the understanding of the instrument. We present the techniques developed for the measurement of the optical parameters of Virgo. These parameters are compared with the Virgo specifications. 相似文献
268.
Jos L. Snchez-Gloria Constanza Estefanía Martínez-Olivares Pedro Rojas-Morales Rogelio Hernndez-Pando Roxana Carb Ivan Rubio-Gayosso Abraham S. Arellano-Buendía Karla M. Rada Fausto Snchez-Muoz Horacio Osorio-Alonso 《International journal of molecular sciences》2021,22(16)
Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling. Recent evidence supports that inflammation plays a key role in triggering and maintaining pulmonary vascular remodeling. Recent studies have shown that garlic extract has protective effects in PAH, but the precise role of allicin, a compound derived from garlic, is unknown. Thus, we used allicin to evaluate its effects on inflammation and fibrosis in PAH. Male Wistar rats were divided into three groups: control (CON), monocrotaline (60 mg/kg) (MCT), and MCT plus allicin (16 mg/kg/oral gavage) (MCT + A). Right ventricle (RV) hypertrophy and pulmonary arterial medial wall thickness were determined. IL-1β, IL-6, TNF-α, NFκB p65, Iκβ, TGF-β, and α-SMA were determined by Western blot analysis. In addition, TNF-α and TGF-β were determined by immunohistochemistry, and miR-21-5p and mRNA expressions of Cd68, Bmpr2, and Smad5 were determined by RT-qPCR. Results: Allicin prevented increases in vessel wall thickness due to TNF-α, IL-6, IL-1β, and Cd68 in the lung. In addition, TGF-β, α-SMA, and fibrosis were lower in the MCT + A group compared with the MCT group. In the RV, allicin prevented increases in TNF-α, IL-6, and TGF-β. These observations suggest that, through the modulation of proinflammatory and profibrotic markers in the lung and heart, allicin delays the progression of PAH. 相似文献
269.
Berta Pérez Fausto Rubio Juan Rubio Aitana Tamayo 《International Journal of Applied Ceramic Technology》2023,20(1):94-111
The processing parameters such as the heat treatment temperature, type of preceramic precursor, and post-synthesis treatments are key factors for the development the different microstructures in polymer-derived ceramics. Moreover, doping with different heteroatoms has increased the ability of the polymer-derived ceramics to produce tunable nanostructures with a controlled pore size and distributions. A preceramic precursor containing P has been prepared from a commercial polysiloxane polymer and a phosphate alkoxide. It has been subjected to thermal treatments in N2, NH3, and Cl2 atmospheres in different order sequences to create differentiated microstructures either in the ceramic matrix and the carbon phase. The structural, textural, and spectroscopic characterization revealed that the P atoms play a key role in the evolution of the microstructure during the thermal treatments. If the chlorination is carried out before the treatment in NH3, a silicophosphate matrix is formed and prevents from nitrogen incorporation into the free carbon phase. On contrary, if the NH3 treatment is carried out before the chlorination, the carbon phase is predominantly modified by the incorporation of P atoms within the free carbon network. 相似文献
270.
Solomon A. Wassie Jose A. Medrano Abdelghafour Zaabout Schalk Cloete Jon Melendez D. Alfredo Pacheco Tanaka Shahriar Amini Martin van Sint Annaland Fausto Gallucci 《International Journal of Hydrogen Energy》2018,43(12):6177-6190
This paper presents a new membrane reactor concept for ultra-pure hydrogen production with integrated CO2 capture: the membrane-assisted gas switching reforming (MA-GSR). This concept integrates alternating exothermic and endothermic redox reaction stages in a single fluidized bed consisting of catalytically active oxygen-carrier particles, by switching the feed between air and methane/steam, where the produced hydrogen is selectively removed via Pd-based membranes. This concept results in overall autothermal conditions and allows easier operation at high pressure compared to alternative novel technologies. In this work, the MA-GSR concept is demonstrated at lab scale using four metallic supported membranes (Pd–Ag based) immersed into a fluidized bed consisting of a Ni-based oxygen carrier. The performance of the reactor has been tested under different experimental operating conditions and high methane conversions (>50%) have been obtained, well above the thermodynamic equilibrium conversion of a conventional fluidized bed as a result of the selective H2 extraction, with (ultra-pure) H2 recoveries above 20% at relatively low temperatures (<550 °C). These results could be further improved by working at elevated pressures or by integrating more membranes. Even though the concept has been successfully demonstrated, further research is required to develop suitable membranes since post-mortem membrane characterization has revealed defects in the membrane selective layer as a consequence of the frequent exposure to thermal cycles with alternating oxidative and reducing atmospheres. 相似文献