Letteratura scientifica selezionata sul tema "Membranes suspendues"
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Articoli di riviste sul tema "Membranes suspendues"
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Jugade, Sanket S., Anuj Aggarwal e Akshay K. Naik. "Nanomechanical spectroscopy of ultrathin silicon nitride suspended membranes". European Physical Journal Applied Physics 94, n. 2 (maggio 2021): 20301. http://dx.doi.org/10.1051/epjap/2021210068.
Testo completoAbstract (sommario):
Mechanical properties of a nanomechanical resonator significantly impact the performance of a resonant Nano-electromechanical system (NEMS) device. We study the mechanical properties of suspended membranes fabricated out of low-pressure chemical vapor deposited silicon nitride thin films. We fabricated doubly-clamped membranes of silicon nitride with thickness less than 50 nm and length varying from 5 to 60 μm. The elastic modulus and stress in the suspended membranes were measured using Atomic Force Microscope (AFM)-based nanomechanical spectroscopy. The elastic moduli of the suspended membranes are significantly higher than those of corresponding on-substrate thin films. We observed a reduction in net stress after the fabrication of suspended membrane, which is explained by estimating the thermal stress and intrinsic stress. We also use a mathematical model to study the stress and thickness-dependent elastic modulus of the ultrathin membranes. Lastly, we study the capillary force-gradient between the SiNx suspended membrane-Si substrate that could collapse the suspended membrane.
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Mahmud, Mahmud, Muthia Elma, Rahmat Subkhan, Aulia Rahma, Rhafiq Abdul Ghani, Rendy Muhamad Iqbal e Mohd Hafiz Dzarfan Othman. "Comparison of Hollow Fiber and Flat Sheet Membranes for Removing TDS and Turbidity of Palm Oil Mill Effluent Wastewater". Diffusion Foundations and Materials Applications 36 (6 novembre 2024): 15–26. http://dx.doi.org/10.4028/p-5wccge.
Testo completoAbstract (sommario):
The most significant pollutant produced from agricultural industry in Kalimantan, Indonesia is Palm Oil Mill Effluent (POME). Due to the high levels of suspended particles and organic matter, POME has become a brownish color with high turbidity, color, chemical oxygen demand, and oil and grease content. To recycle the POME wastewater as clean water, these pollutants must be eliminated. In this study, we compare the effectiveness of hollow fiber (HF) and flat sheet (FS) membrane to remove total dissolved solid (TDS) and turbidity from POME with varied filtration pressure. HF and FS membrane were prepared from PVDF and nylon66 polymer, respectively. The PVDF HF membrane was modified using TiO2 and SBE (spent bleaching earth) to improve HF membrane properties to maintaining fouling. Meanwhile, FS membrane was added by pectin to increase the hydrophilic properties. Overall membrane’s morphology was determined by Scanning Electron Microscopy (SEM) to investigate the membrane structure. Both of HF and FS membrane were operated via ultrafiltration (UF) under cross flow system. The filtration pressures were varied at 1-3 bar and followed by flux and rejection evaluation. The results show both HF and FS membranes has stability flux. In addition, TDS rejection up to 25% while turbidity is excellent high over 95% for all membranes. The fabrication HF membrane has finger like-sponge structure and FS membrane exhibits sponge asymmetric structure. Overall, all membranes perform highest water flux (FS membrane) while highest rejection conducted by HF membrane for POME wastewater treatment.
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Makisha, Nikolay A. "Research of performance characteristics of membrane modules for wastewater treatment". Stroitel stvo nauka i obrazovanie [Construction Science and Education], n. 1 (31 marzo 2020): 6. http://dx.doi.org/10.22227/2305-5502.2020.1.6.
Testo completoAbstract (sommario):
Introduction. The study focuses on the operation of a standalone membrane bioreactor applicable as an alternative to submerged membrane modules widely used as part of small capacity wastewater treatment facilities. Materials and methods. An ultra-filtration membrane was used to perform the research in a laboratory environment. The liquid, exposed to research, represented synthetic wastewater, whose composition was similar to the one of urban wastewaters, and it had varied concentrations of suspended solids (MLSS). The membrane element, produced by Raifil (Republic of Korea), that has capillary ultra-filtration membranes, was used in the experiments. The membrane pore size is 1 micron. The total membrane filter area is one square meter. This membrane module has standard characteristics (pore size, material), typical for ultra-filtration membranes; therefore, we can assume that any further results will not demonstrate any substantial discrepancies, if ultra-filtration membranes made by other manufacturers are used to conduct experiments. Results. The author describes a methodology for the optimization of pressure and MLSS values used in the process of membrane treatment. The author obtained the pressure values at which the amount of suspended solids in the filtered material shows a sharp rise, which means a slip of suspended solids into the filtrate, or a slip of contaminants. The author also identified the operating parameters that ensure maximal capacity. Conclusions. These findings help to outline a roadmap for further research into the optimization of membrane bioreactors (both standalone and submerged units) used in wastewater treatment.
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Subaer, Subaer, Hamzah Fansuri, Abdul Haris, Misdayanti Misdayanti, Imam Ramadhan, Teguh Wibawa, Yulprista Putri, Harlyenda Ismayanti e Agung Setiawan. "Pervaporation Membranes for Seawater Desalination Based on Geo–rGO–TiO2 Nanocomposites: Part 2—Membranes Performances". Membranes 12, n. 11 (26 ottobre 2022): 1046. http://dx.doi.org/10.3390/membranes12111046.
Testo completoAbstract (sommario):
This is part 2 of the research on pervaporation membranes for seawater desalination based on Geo–rGO–TiO2 nanocomposite. The quality of the Geo–rGO–TiO2 pervaporation membranes (PV), as well as the suitability of the built pervaporation system, is thoroughly discussed. The four membranes described in detail in the first article were tested for their capabilities using the parameters turbidity, salinity, total suspended solids (TSS), and electrical conductivity (EC). The membranes’ flux permeate was measured as a function of temperature, and salt rejection was calculated using the electrical conductivity values of the feed and permeate. Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) techniques were used to investigate changes in the chemical composition and internal structure of the membranes after use in pervaporation systems. The morphology of the membrane’s surfaces was examined by means of scanning electron microscopy (SEM), and the elemental distribution was observed by using X-ray mapping and energy dispersive spectroscopy (EDS). The results showed that the pervaporation membrane of Geo–rGO–TiO2 (1, 3) achieved a permeate flux as high as 2.29 kg/m2·h with a salt rejection of around 91%. The results of the FTIR and XRD measurements did not show any changes in the functional group and chemical compositions of the membrane after the pervaporation process took place. Long-term pressure and temperature feed cause significant cracking in geopolymer and Geo–TiO2 (3) membranes. SEM results revealed that the surface of all membranes is leached out, and elemental distribution based on X-ray mapping and EDS observations revealed the addition of Na+ ions on the membrane surface. The study’s findings pave the way for more research and development of geopolymers as the basic material for inorganic membranes, particularly with the addition of rGO–TiO2 nanocomposites.
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Aljlil, Saad A. "Fabrication of Bentonite–Silica Sand/Suspended Waste Palm Leaf Composite Membrane for Water Purification". Membranes 10, n. 10 (16 ottobre 2020): 290. http://dx.doi.org/10.3390/membranes10100290.
Testo completoAbstract (sommario):
In this study, a method for fabricating tubular ceramic membranes via extrusion using economical and locally available bentonite–silica sand and waste palm leaves was developed as a tool for conducting the necessary task of purifying water polluted with oil and suspended solid materials produced via various industrial processes. The developed tubular ceramic membranes were found to be highly efficient at separating the pollutants from water. The properties of the fabricated membrane were evaluated via mechanical testing, pore size distribution analysis, and contact angle measurements. The water contact angle of the fabricated membrane was determined to be 55.5°, which indicates that the membrane surface is hydrophilic, and the average pore size was found to be 66 nm. The membrane was found to demonstrate excellent corrosion resistance under acidic as well as basic conditions, with weight losses of less than 1% in each case. The membrane surface was found to be negatively charged and it could strongly repulse the negatively charged fine bentonite particles and oil droplets suspended in the water, thereby enabling facile purification through backwashing. The obtained ceramic membranes with desirable hydrophilic properties can thus serve as good candidates for use in ultrafiltration processes.
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Ng, T. C. A., e H. Y. Ng. "Physico-chemical characterisation versus in situ micro-structural characterisation of membrane fouling in membrane bioreactors". Water Science and Technology 63, n. 8 (1 aprile 2011): 1781–87. http://dx.doi.org/10.2166/wst.2011.196.
Testo completoAbstract (sommario):
Fouling characteristics of aerobic submerged membrane bioreactors were analysed under two different membrane materials. Polyethersulfone (PES) membranes were found to foul faster at sub-critical flux than polyolefin (PO) membranes. Physico-chemical characterisation, by means of comparison of extracellular polymeric substances (EPS) and soluble microbial products (SMP) concentrations, as well as the mixed liquor suspended solids (MLSS) concentration were unable to explain the differences in membrane fouling of the contrasting membrane materials. The use of confocal laser scanning microscopy (CLSM) to image organic foulants directly on the membrane surface, coupled with image analyses showed that membrane fouling mechanism shifted from a biofilm initiated process on PO membranes to a bio-organic dominated process on PES membranes under sub-critical flux conditions. These results show that physico-chemical characterisation of an MBR process may not effectively distinguish the effectiveness of different membrane materials, so long as operating conditions are identical, and that characterisation of foulants on the membrane surfaces was necessary to elucidate the differences in membrane fouling.
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Park, Jiyeong, Seok-Hong Min, Won-Hee Lee, No-Suk Park, Hyung-Soo Kim e Jong-Oh Kim. "Properties and filtration performance of microporous metal membranes fabricated by rolling process". Journal of Water Reuse and Desalination 7, n. 1 (3 marzo 2016): 11–15. http://dx.doi.org/10.2166/wrd.2016.000.
Testo completoAbstract (sommario):
We evaluated the filtration performance of microporous metal membranes fabricated by the rolling process. Metal wire meshes were rolled with thickness reduction ratios of 10, 20, and 30%. The pore size of the metal wire mesh membrane decreased with increasing rolling ratio, whereas the removal efficiency of the suspended solids and turbidity showed a very slight increase compared to that of an unrolled mesh membrane. The metal powder was dispersed on the surface of the rolled metal wire mesh membrane and bound with polyvinyl alcohol, then dried at 100°C for 1 h, and finally sintered at 1,000°C for 3 h. The mean pore size, suspended solids, and turbidity of the metal powder membrane at a rolling ratio of 30% were approximately 0.7 μm, 84% and 83%, respectively. Therefore, microporous metal membranes successfully fabricated by the rolling process were also sufficiently permeable filters.
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Dada, Saubana Olorunsola, Chidambaram Thamariselvan, Mahmood Jebur e Sumith Ranil Wickramasinghe. "Innovative Approaches to Poultry Processing Wastewater Treatment: The Stainless Steel Ultrafiltration Membrane as a Viable Option". Membranes 13, n. 11 (11 novembre 2023): 880. http://dx.doi.org/10.3390/membranes13110880.
Testo completoAbstract (sommario):
In pursuit of sustainability, we explored replacing conventional dissolved air floatation (DAF) in poultry processing wastewater (PPW) treatment with a precisely tuned 0.02 µm stainless-steel ultrafiltration (SSUF) membrane. SSUF is a robust, homogenously porous membrane with strong chemical resistance, ease of cleaning, and exceptional resistance to organic fouling. Unlike polymeric membranes, it can be regenerated multiple times, making it a cost-effective choice due to its compatibility with harsh chemical cleaning. The PPW used for the study was untreated wastewater from all processing units and post-initial screening. Our study revealed the SSUF membrane’s exceptional efficiency at eliminating contaminants. It achieved an impressive removal rate of up to 99.9% for total suspended solids (TSS), oil, grease, E. coli, and coliform. Additionally, it displayed a notable reduction in chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total Kjeldahl nitrogen (TKN), up to 90%, 76%, and 76%, respectively. Our investigation further emphasized the SSUF membrane’s ability in pathogen removal, affirming its capacity to effectively eradicate up to 99.99% of E. coli and coliform. The measured critical flux of the membrane was 48 Lm−2h−1 at 38 kPa pressure and 1.90 m/s cross-flow velocity. In summary, our study highlights the considerable potential of the SSUF membrane. Its robust performance treating PPW offers a promising avenue for reducing its environmental impact and advocating for sustainable wastewater management practices.
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Fraga, Maria C., Rosa M. Huertas, João G. Crespo e Vanessa J. Pereira. "Novel Submerged Photocatalytic Membrane Reactor for Treatment of Olive Mill Wastewaters". Catalysts 9, n. 9 (13 settembre 2019): 769. http://dx.doi.org/10.3390/catal9090769.
Testo completoAbstract (sommario):
A new hybrid photocatalytic membrane reactor that can easily be scaled-up was designed, assembled and used to test photocatalytic membranes developed using the sol–gel technique. Extremely high removals of total suspended solids, chemical oxygen demand, total organic carbon, phenolic and volatile compounds were obtained when the hybrid photocatalytic membrane reactor was used to treat olive mill wastewaters. The submerged photocatalytic membrane reactor proposed and the modified membranes represent a step forward towards the development of new advanced treatment technology able to cope with several water and wastewater contaminants.
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Lorain, Olivier, Sébastien Marcellino, André Deratani, Sana Gassara, Isabelle Duchemin e Jean-Michel Espenan. "New ultrafiltration (UF) membrane made with a new polymer material for long-lasting rejection performance, Neophil®". Water Practice and Technology 15, n. 2 (19 marzo 2020): 356–64. http://dx.doi.org/10.2166/wpt.2020.022.
Testo completoAbstract (sommario):
Abstract This paper focuses on the development of a new membrane, named Neophil®, with durable performance using a new amphiphilic nanostructured dibloc-copolymer (BCP) composed of one hydrophilic bloc and one hydrophobic bloc which is anchored deeply and permanently in the polymer matrix (PVDF, Kynar resin Arkema) of the membrane. Compared to conventional membranes, particle rejections (suspended solids, microplastics, bacteria and viruses) have been shown to be maintained through accelerated ageing experiments. In this paper, this new membrane technology is described and its durability is demonstrated and compared with other membranes of the market.
Tesi sul tema "Membranes suspendues"
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Schwarz, Cornelia. "Propriétés optomécaniques, vibrationelles et thermiques de membranes de graphène suspendues". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY024/document.
Testo completoAbstract (sommario):
Le but de la Nano- Opto- Mécanique et Electronic à base de graphène est d'utiliser des membranes de graphène en suspension comme blocs de construction pour aborder le couplage entre l'optique, la mécanique et l'électronique dans ce nouveau matériau. Avec un module d'Young similaire à celui du diamant (1 TPA), le graphène est une membrane extrêmement rigide, légère et mince (epaaisseur de seulement un atome) qui peut supporter son propre poids sans effondrement ou la rupture lorsqu'il est suspendu. Ces membranes, intégrées dans des dispositifs mécaniques, peuvent être actionnés à partir de DC jusqu'à des fréquences de vibration mécaniques très élevées (GHz). En outre, le graphène est un gaz d'électrons 2D exposé pour lequel une porte électrostatique tunes considérablement la densité de porteurs de charge et ses propriétés optiques. Last but not least, il offre une architecture unique pour effectuer la fonctionnalisation physico-chimiques et obtenir des matériaux hybrides combinant les propriétés particulières des espèces chimisorbées avec ceux du graphèneThe aim of the Graphene Nano- Opto- Mechanics and Electronics is to use suspended graphene membranes as building blocks to address the coupling of optics, mechanics and electronics in this novel material. With a Young modulus similar to that of diamond (1 TPa), graphene is an extremely stiff, light and atomically thin membrane that can withstand its own weight without collapsing or breaking when suspended. Such membranes, integrated as mechanical devices, can be actuated from DC up to very high mechanical vibration frequencies (GHz). Moreover, graphene is an exposed 2D electron gas for which an electrostatic gate dramatically tunes the charge carrier density and its optical properties. Last but not least, it provides a unique architecture to perform physico-chemical functionalization and obtain hybrid materials combining the peculiar properties of adsorbed and chemisorbed species with the graphene ones
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Brochard, Cléophanie. "Advanced Nano-Engineering to Transport Heat in Ultra-thin Membranes (2D materials)". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPAST173.
Testo completoAbstract (sommario):
Les travaux de recherche présentés dans cette thèse s'inscrivent dans des travaux menés au C2N. Mon sujet de thèse porte sur le transport de chaleur dans des matériaux dit bidimensionnels. Ces matériaux ont des très fortes liaisons dans deux dimensions de l'espace et de très faibles liaisons (de type Van der Waals) dans la troisième dimension. Cette asymétrie a de fortes conséquences en terme de propriétés thermiques. Tout d'abord, la conductivité thermique de ces matériaux va s'en trouver anisotrope. Dans le plan avec les fortes liaisons, celle-ci va être très élevée tandis que dans la direction perpendiculaire, elle peut atteindre les plus petites valeurs observées dans des solides. En outre, le régime de transport de la chaleur dévie du régime classique suivant la loi de Fourier. Ce sont les raisons qui nous ont poussé à s'intéresser aux propriétés thermiques de ces matériaux. Ma thèse s'est décomposée en deux parties.Dans un premier temps, je me suis intéressée au transport thermique dans du hexagonal Boron Nitride (hBN) qui est un matériau bidimensionel avec une très grande conductivité thermique et une très faible conductivité électrique. J'ai suspendu des matériaux bidimensionnels entre deux poutres chauffantes espacées de 8 microns. À l'aide de mesures de température réalisées avec un spectromètre Raman, j'ai pu déterminer une conductivité thermique de 1650 ±550 W.m⁻¹.K⁻¹ dans une structure de hBN à basse température (aux alentours de -50 °C). Pour ce faire, j'ai comparé les gradients de température expérimentaux mesurés à travers les structures aux gradients de température que j'ai déterminés à l'aide de simulations Comsol. Cette valeur de 1650 ±550 W.m⁻¹.K⁻¹ est une valeur record pour ce matériau et provient du fait que le hBN utilisé est isotopique.J'ai confirmé la procédure expérimentale en réalisant la même expérience sur un échantillon de graphite donnant une conductivité thermique en adéquation avec celles obtenues dans la littérature. Lors de mesures similaires sur un autre échantillon, j'ai observé des gradients de température incohérents avec la loi de Fourier. Cette mesure a été faite autour de la température ambiante. Nous en avons déduit que l'échantillon se trouvait dans un régime où le transport thermique ne suivait plus le modèle classique. Dans un second temps, je me suis intéressée à la possibilité de réaliser de très grands gradients de température à travers des matériaux bidimensionnaux. En fabriquant des hétérostructures de hBN¹¹/MoS₂/WSe₂/hBN¹⁰ chauffées avec un laser de haut en bas, j'ai pu étudier le transport thermique dans la direction des liaisons de type Van der Waals. Une différence en température de 75 °C a été observée sur une distance de 1,5 nm entre le MoS₂ et WSe₂. Cette valeur est extrêmement importante. Cette grande différence en température est à relier à la faible conductance thermique d'interface entre ces deux matériaux et à la forte puissance appliquée à l'échantillon. En utilisant un modèle issu de la littérature comportant une dépendance en conductance thermique d'interface, j'ai pu simuler des gradients de températures au sein de matériaux chauffés par un laser. Ceci m'a permis de simuler des spectres Raman similaires à ceux mesurés. J'en ai déduit des conductances thermiques d'interface environ quatre fois plus faibles entre le MoS₂ et WSe₂ que mesurées dans la littérature (inférieures à 5 MW.m⁻¹.K⁻¹ à opposer à 9 MW.m⁻¹.K⁻¹. J'ai aussi examiné la différence de transport thermique en fonction de l'angle entre ces mêmes matériauxThe research work presented in this manuscript is part of the technological monitoring efforts led at the C2N in the MAT2D team. My subject is about heat transport in so-called two-dimensional materials. These materials have very strong bonds in two dimensions of space and fragile bonds (Van der Waals bonds) in the third dimension. This asymmetry has important thermal property repercussions: the thermal conductivity of these materials is anisotropic. In the strong-bondings plane, the thermal conductivity is very high, whereas in the perpendicular direction, it reaches the smallest values observed in solids. Moreover, the heat transport regime deviate from the classical Fourier's Law regime. These are the reasons that drive us to study these properties. The manuscript is constituted of two parts. Firstly, I investigated thermal transport in a two-dimensional material: hexagonal Boron Nitride (hBN). This material is interesting because it is a high thermal conductor and a high electrical insulator. I had to innovate to suspend two-dimensional materials between two heatable cantilevers spaced by 8 microns. Using temperature measurements with a Raman spectrometer, I was able to determine a thermal conductivity of 1650 ±550 W.m⁻¹.K⁻¹ in an suspended hBN structure at low temperature (around -50°C). I used extit{Comsol} simulations to determine temperature gradients across the structure comparable to the experimental results. It allows me to determine the in-plane thermal conductivity of the two-dimensional material. The 1650 ±550 W.m⁻¹.K⁻¹ value is a record value for this material and comes from different parameters. One is the fact that the hBN is isotopic. I confirmed the experimental procedure by doing the same experiment on a sample of Graphite. It gives a thermal conductivity that is coherent with those obtained in the literature. I observed temperature gradients inconsistent with Fourier's law (even around ambient temperature) through similar measurements on another sample. We deduced that the sample was in a non-classical heat regime. Secondly, I investigated the possibility of achieving very large temperature gradients across samples of two-dimensional materials. By heating a thin sample of suspended hBN, I observed a gradient of 210° along 8 microns. By fabricating hBN¹¹/MoS₂/WSe₂/hBN¹⁰ heterostructures heated with a laser, I was also able to study thermal transport in the direction of the Van der Waals bonds. A temperature difference of 75°C was observed within 1.5 nm between MoS₂ and WSe₂. This value is extremely high. This significant temperature difference can be linked to the low thermal conductance at the interface between these two materials and the high optical power applied to the structure. Using a model from the literature with an interface thermal conductance dependence, I could simulate temperature gradients within a material heated by a laser. This enabled me to simulate Raman spectra of MoS₂ similar to those measured. I deduced low interface thermal conductances between MoS₂ and WSe₂ (less than 5 MW.m⁻¹.K⁻¹ whereas in the literature, it was measured equal to 9 MW.m⁻¹.K⁻¹). I also examined the difference in thermal transport as a function of the angle between these same materials and observed a slight difference of temperature of the top material depending of the angle
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Metten, Dominik. "Probing the opto-electronic and mechanical properties of suspended graphene membranes by Raman spectroscopy". Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE002/document.
Testo completoAbstract (sommario):
Ce travail présente une étude par diffusion micro-Raman de membranes de graphène suspendu.La spectroscopie Raman est présentée comme un outil rapide et peu invasif pour estimer les contraintes natives dans du graphène suspendu et est utilisée pour en sonder quantitativement la déflexion, induite soit par une différence de pression d’air soit électrostatiquement. Dans des bulles de graphène pressurisées, une analyse minutieuse des intensités et fréquences des principaux modes Raman permet une détermination tout-op que de la topographie de la bulle, du module de Young et des paramètres de Grüneisen du graphène. Une grille électrostatique offre une manière élégante d’introduire à la fois des contraintes et du dopage dans le graphène. Des mesures Raman permettent une détermination précise de la déflection induite par la force électrostatique (jusqu’à l’effondrement irréversible), en très bon accord avec un modèle électromécaniqueThis work presents a micro-Raman scattering study of undoped suspended graphene membranes. Raman spectroscopy is introduced as a fast and minimally invasive tool to estimate sample dependent built-in strain in suspended graphene, and is further employed to quantatively probe the membrane deflection, which may be induced either by an air pressure difference or electrostatically. In pressurized graphene blisters, an all-optical determination of the blister topography, the Young’s modulus and the Grüneisen parameters of graphene is achieved by a thorough analysis of the intensity and frequency of the main Raman modes. Electrostatic gating offers an elegant way to simultaneously strain and dope graphene. Raman measurements allow an accurate determination of the electrostatically-induced graphene deflection (up to irreversible collapse), in very good agreement with an electromechanical model
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Saadaoui, Mohamed. "Optimisation des circuits passifs micro-ondes suspendus sur membrane diélectrique". Phd thesis, Université Paul Sabatier - Toulouse III, 2005. http://tel.archives-ouvertes.fr/tel-00011358.
Testo completoAbstract (sommario):
Les travaux présentés dans ce mémoire traite du développement et de l'optimisation de nouvelles filières technologiques d'élaboration de circuits micro-ondes suspendus sur membrane diélectrique. Cette élaboration passe par l'étude physique, mécanique et électrique de nouveaux matériaux susceptibles de répondre aux cahiers des charges. Nous proposons la filière technologique basée sur la fabrication de membranes épaisses à partir des dépôts par plasma. L'intérêt majeur de cette technologie est d'améliorer la fiabilité mécanique du composant. Les résultats en terme de caractérisation fréquentielle montre un bon accord avec la filière développée auparavant et qui est dédiée essentiellement à la fabrication de circuits micro-ondes de surface assez faible sur membrane mince. Dans un second volet, nous proposons un banc de test pour la caractérisation mécanique des matériaux. Dans cette optique, un système de gonflement de membrane suspendue sous pression différentielle a permis de tester les propriétés mécaniques du nitrure de silicium. Les contraintes résiduelles et le module d'Young du matériau sont extraits. La dernière partie concerne la réalisation d'une antenne à émission surfacique de type Yagi-Uda sur membrane diélectrique. La miniaturisation et les technologies de micro-usinage volumique du silicium ont permis la réduction des dimensions, et surtout l'utilisation de ce type d'antennes en haute fréquence. Nous décrivons un nouveau procédé de gravure de silicium adapté à la fabrication de ce type d'antenne. La caractérisation électrique des structures fabriquées est en accord avec les résultats de simulation électrique. De plus, des simulations mécaniques des structures fabriquées sont présentées afin de clarifier l'origine des déformations des dispositifs.
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Clark, Nicholas. "Fabrication and applications of suspended graphene membranes". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/fabrication-and-applications-of-suspended-graphene-membranes(c3fffc3a-c487-4ede-92b6-172f1c3f9196).html.
Testo completoAbstract (sommario):
This thesis reports research activity on suspended graphene membranes. Scientific results in the form of peer-reviewed publications are presented, along with supporting information to provide context, detailed experimental procedures, and recommendations of future work. The four papers cover a wide variety of topics, but are linked by common experimental sample fabrication techniques. Understanding the mechanical properties of suspended graphene membranes is crucial to the development of graphene nano-electromechanical devices. In the first presented paper, PeakForce QNM (quantitative nanomechanical mapping) atomic force microscopy imaging was used to rapidly map the nanomechanical properties of a range of suspended graphene membranes. The force-displacement behaviour of monolayer graphene extracted from the peak force imaging map was found to be comparable to that taken using standard nanoindentation. By fitting to a simple elastic model, the two-dimensional elastic modulus was measured at around 350Nm-1, corresponding to a Young's modulus of around 1 TPa. The second paper examines the near-IR light-matter interaction for graphene integrated cavity ring resonators based on silicon-on-insulator (SOI) racetrack waveguides. Fitting of the cavity resonances from the predicted transmission spectra reveal the real part of the effective refractive index for graphene, neff = 2.23 ± 0.02 and linear absorption coefficient, alphagTE = 0.11 ±0.01dB micro metre-1. The evanescent nature of the guided mode coupling to graphene at resonance depends strongly on the height of the graphene above the cavity, which places limits on the cavity length for optical sensing applications. Twisted-bilayer graphene (tBLG) exhibits van Hove singularities in the density of states that can be tuned by changing the twisting angle θ. In the third paper, θ-defined tBLG was produced and characterized using optical reflectivity and resonance Raman scattering. This represents the first reported fabrication of a rationally designed (twist engineered) tBLG structure. The θ-engineered optical response is shown to be consistent with persistent saddlepoint excitons. Separate resonances with Stokes and anti-Stokes Raman scattering components can be achieved due to the sharpness of the two-dimensional saddle-point excitons, similar to what has been previously observed for one-dimensional carbon nanotubes. The excitation power dependence for the Stokes and anti-Stokes emissions indicate that the two processes are correlated and that they share the same phonon. Nano-patterned and suspended graphene membranes find applications in electronic devices, filtration and nano-pore DNA sequencing. However, the fabrication of suspended graphene structures with nanoscale features is challenging. In the fourth and final paper, the direct patterning of suspended membranes consisting of a graphene layer on top of a thin layer of hexagonal boron nitride which acts as a mechanical support is demonstrated for the first time, using a highly focused electron beam to fabricate structures with extremely high resolution within the scanning transmission electron microscope. The boron nitride support enables the fabrication of stable graphene geometries which would otherwise be unachievable, by preventing intrinsic strain in graphene membranes from distorting the patterned features after areas are mechanically separated. Line cuts with widths below 2 nm are reported. It is also demonstrated that the cutting can be monitored in-situ utilising electron energy loss spectroscopy (EELS).
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Northcutt, Robert. "Suspended Polypyrrole Films Supporting Alamethicin Reconstituted Bilayer Membranes". VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2864.
Testo completoAbstract (sommario):
This thesis presents a novel architecture for a sensing element fabricated from a conducting polymer and a bioderived membrane. The thin film device provides controlled, selective ion transport from a chemical concentration and produces measurable electrical signals, ion storage, and small scale actuation. A chemical gradient applied across a bioderived membrane generates ion flow through protein transporters in the presence of a gating signal. A conducting polymer undergoes ion ingress/egress in the presence of an electrical and chemical potential, which causes a change on the polymers conformal backbone. A ligand (or) voltage gated protein in the bioderived membrane results in ion transport through the bioderived membrane. Integrating the two electroactive materials provides a unique architecture which takes advantage of their similarities in ionic function to produce a device with controlled and selective ion transport. The chemoelectromechanical device is one that couples chemical, electrical, and mechanical potentials through number of ions, dielectric displacement, and strain. The prototype consists of a stacked thin conducting polymer film and bioderived membrane which form three aqueous chambers of varying ionic concentrations. The top chamber contains an electrolytic solution, and the bottom chamber contains deionized water adjacent to the conducting polymer. The current that passes through a conducting polymer for an applied electrical signal is based on the level of doping/undoping and therefore can be used as a method of sensing protein function in the sensing element. This architecture results in a sensing element applicable in real time chemical sensors, volatile organic compound detectors, and bioanalytical sensors. The conducting polymer layer is formed from polypyrrole (PPy) doped with sodium dodecylbenzenesulfonate (NaDBS), and the bilayer lipid membrane is formed from 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) reconstituted with the protein alamethicin. The magnitude of current required to span a 175 µm pore was empirically found to be 326.5 A/cm2 and is based on electrode condition, electrode surface area, pyrrole concentration, and electrical potential. A micron-scale pore through a silicon substrate is spanned by a thin PPy(DBS) layer, forming a bridge which supports the bioderived membrane. The bioderived membrane is reconstituted with alamethicin, a voltage-gated protein extracted from trichoderma viride. Ion transport experiments were performed to characterize the PPy(DBS) layer and the bioderived membrane and are represented as electrical equivalents for subsequent analysis. The equivalent impedance of polypyrrole was calculated to be 1.7847±0.1735Ωcm2 and capacitance was calculated to be 1.2673±0.1823µF/cm2. The equivalent impedance of a bioderived membrane was calculated to be 1.654±1.9894MΩcm2, capacitance was calculated to be 1.1221± 0.239µF/cm2, and alamethicin resistance was calculated to be 1.025± 0.7228MΩcm2. Thus, using impedance measurements in the conducting polymer layer, it is proposed that a scaled up sensing element can be fabricated using the suspended polypyrrole supported bioderived membrane.
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Hui, Pui Chuen. "Optomechanics and nonlinear mechanics of suspended photonic crystal membranes". Thesis, Harvard University, 2014. http://nrs.harvard.edu/urn-3:HUL.InstRepos:13068536.
Testo completoAbstract (sommario):
The recent demonstration of strong interactions between optical force and mechanical motion of an optomechanical structure has led to the triumphant result of mechanical ground-state cooling, where the quantum nature of a macroscopic object is revealed. Another intriguing demonstration of quantum physics on a macroscopic level is the measurement of the Casimir force which is a manifestation of the zero- point energy. An interesting aspect of the Casimir effect is that the anharmonicity of the Casimir potential becomes significant when the separation of microscale objects is in the sub-100nm regime. This regime is readily accessible by many of the realized gradient-force-based optomechanical structures. Hence, a new avenue of probing the Casimir effect on-chip all-optically has become available. We propose an integrated optomechanical platform, consisting of a suspended photonic crystal membrane evanescently coupled with a silicon-on-insulator substrate, for (i) measuring the Casimir force gradient and (ii) counteracting the attractive force by exerting a resonantly enhanced repulsive optical gradient force. This thesis first presents the full characterization of the optomechanical properties of the system in vacuo. The interplay of the optical gradient force (optomechanical coupling strength \(g_{om}/2\pi=- 66GHz/nm\)) and the photothermal force manifested in the optical spring effect and dynamic backaction is elucidated. Static displacement by the repulsive force of 1nm/mW is also demonstrated.
In the second part of the thesis, the nonlinear mechanical signatures upon a strong coherent drive are reported. By resonantly driving the photonic crystal membrane with a piezo-actuator and an optical gradient force, we observed mechanical frequency mixing, mechanical bistability and non-trivial interactions of the Brownian peak with the driving signal. Finally we present our recent progress in establishing electro- static control of individual photonic crystal membranes to reduce and calibrate the electrostatic artifact which plagues Casimir measurements.
The results discussed in this thesis point towards an auspicious future of a complete realization of a Casimir optomechanical structure and novel applications with nonlinearity afforded by the Casimir force and the optical gradient force.Engineering and Applied Sciences
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Chance, Gregory Ian. "A suspended-membrane balanced frequency doubler to 200 GHz". Thesis, University of Bath, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419222.
Testo completo
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Lau, Chi Ho. "Process development for the fabrication of suspended membrane with nanoscale through vias on a silicon substrate /". View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?MECH%202009%20LAU.
Testo completo
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Chowdhury, Avishek. "Mechanical nonlinear dynamics of a suspended photonic crystal membrane with integrated actuation". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS284/document.
Testo completoAbstract (sommario):
Les nonlinéarités dans les systèmes nanomécaniques peuvent provenir d’effets dispersif ou dissipatif et ce dans divers systèmes (résistifs, inductifs et capacitifs). Au-delà de l’intérêt fondamental pour tester la réponse dynamique d’un système non-linéaire à plusieurs dégrées de libertés, les nonlinéarités de tels systèmes ouvre la voie vers des capteurs nanomécanique et le traitement du signal. Le résonateur nanomécanique dont la réponse nonlinéaire est étudié, est une membrane suspendue à cristal photonique bidimensionnel utilisée comme miroir déformable. Sa faible masse et sa haute réflectivité en font un candidat idéal pour l’électro-opto-mécanique. L’actuation d’une telle membrane dans le domaine fréquentiel du MHz est rendu possible par des électrodes inter-digitées en dessous de la membrane assurant ainsi l’uniformité de la force d’actuation sur cette dernière. La fabrication de telles structures est basée sur l’intégration hétérogène 3D.La force électrostatique qui s’applique sur la membrane induit des non-linéarités mécaniques avec notamment un effet bistable, des résonances superharmoniques et des résonances stochastiques.La membrane est mise en mouvement par un potentiel électrique V(t) = Vdc + Vac cos(w.t), où Vdc est l’amplitude du courant continu, Vac l’amplitude du courant alternatif à la fréquence d’excitation w;. Le système se comporte alors comme une capacité de sorte que la force qui s’applique sur la membrane varie de manière quadratique avec la tension appliquée. Selon la tension DC ou AC, le comportement de la structure est différent. L’augmentation de la tension DC induit une augmentation de la tension de polarisation sur le matériau qui par conséquent modifie la fréquence propre de la membrane. Tandis que l’augmentation de la tension AC cause l’augmentation de l’amplitude des oscillations de la membrane pouvant aller jusqu’à atteindre le régime non-linéaire.Dans une première série de mesure, la membrane est excitée à la résonance avec une fréquence w; égale à la fréquence du mode mécanique fondamental wm. A partir de la réponse fréquentielle du système, il est possible d’identifier différents modes mécaniques de la membrane sondé optiquement. Pour une excitation plus importante, il est possible d’observer des effets de bistabilité mécanique. Ces non-linéarités sont dues à l’élongation au niveau des points d’ancrage de la membrane.La méthode la plus commune pour agir sur la membrane est l’excitation proche de la résonance fondamentale. Cependant la technique de la résonance superharmonique peut également être utilisée. Cela consiste à appliquer la fréquence d’excitation w; à une fréquence égale à wm/n où n est un entier. La possibilité d’utiliser cette technique est fortement dépendante des nonlinéarités présentes dans le système. Ainsi, l’existence d’une résonance super harmonique à wm/n résulte de la présence d’une nonlinéarité d’ordre n. Dans une seconde série de mesure, un balayage des résonances superharmoniques en fonction de la fréquence et de la puissance a été réalisé en modulant la tension à la fréquence wm/n et en enregistrant la réponse de la membrane autour de wm. Il a été ainsi possible d’observer des résonances superharmoniques allant de n=2 jusqu’à 8. Il a également été possible d’obtenir l’évolution de la phase le long des résonances et ce pour toutes celles observées.Dans une dernière série de mesure, nous utilisons la nonlinéarité présente pour observer des effets de résonance stochastique. L’idée est d’amplifier un signal de faible amplitude (basse fréquence) en injectant du bruit (haute fréquence) dans le système nonlinéaire. Dans le cas de notre système, nous avons été capables d’observer des résonances stochastiques à la fois en amplitude et en phase. Une étude comparative de ces deux régimes est détaillée. Le fait de pouvoir observer la résonance stochastique en phase peut permettre d’envisager la réalisation de communications codées en phaseNonlinearities in nanomechanical systems can arise from various sources such as spring and damping mechanisms and resistive, inductive, and capacitive circuit elements. Beyond fundamental interests for testing the dynamical response of discrete nonlinear systems with many degrees of freedom, non-linearities in nanomechanical devices, open new routes for nanomechanical sensing, and signal processing.The nonlinear response of a nanomechanical resonator consisting in a suspended photonic crystal membrane acting as a deformable mirror has been investigated. The low-mass and high reflectivity of suspended membranes pierced by a two-dimensional photonic crystal, makes them good candidates as electro-optomechanical resonator. Actuation of the membrane motion in the MHz frequency range is achieved via interdigitated electrodes placed underneath the membrane. The choice of these electrodes is due to the fact they are able to uniformly actuate these membranes. The processing of such platforms relies on 3D-heterogenous integration process.The applied electrostatic force induces mechanical non-linearities, in particular bistability, superharmonic resonances and stochastic resonance.The membrane is actuated by an electric load V(t) = Vdc + Vac cos(w.t), where Vdc is the DC polarization voltage, Vac the amplitude of the applied AC voltage, and w; the excitation frequency. The system acts as a capacitive system and thus the force applied on the membrane varies as a quadratic function of the applied voltage. Application of either DC or AC voltages can have different implications. Increasing the DC voltage increases the polarizing voltage on the material which in turn causes modulation of the eigenfrequency of the membranes. While an increase in the periodic AC voltage causes the membrane to oscillate more, pushing the system towards non-linear regime.In a first series of experiments, the membrane is actuated resonantly, with an excitation frequency w; equal to the fundamental mechanical modes frequency wm. From the frequency response spectra of the system it was possible to identify different mechanical modes of these membranes via optical measurements. For increased actuation voltages, bistability effects are observed with two different behaviors (spring hardening or softening). The mechanical nonlinearities due to stretching at the clamping point dominate the resonator dynamics.The most commonly used method to act upon the membrane is the primary-resonance excitation, in which the frequency of the excitation is tuned closed to the fundamental natural frequency of the nanostructure. Superharmonic resonance can also be implemented. It consists in applying an excitation frequency w; equal to wm/n, with n being integer. Existence of these superharmonic resonances is highly dependent on the non-linearity of the system. For example existence of n-th order non-linearity results in presence wm/n superharmonic resonance. In a second series of experiments, frequency-power sweep for superharmonic resonance has been performed, by modulating the electric load at a frequency wm/n and recording the response of the membrane at the fundamental frequency wm. High-order superharmonic resonances are observed with n=2 up to 8. Under superharmonic excitation, the control of the phase across the resonance has been shown for every observed resonance.In the next set of experiments, we used the nonlinearity existing in the system to perform stochastic resonance. The idea of stochastic resonance is amplification of a weak signal (with low frequency) by means of noise injected (higher frequency) in a nonlinear system. For our system we were able to achieve stochastic resonance with both amplitude and phase noise. A comparative study between these two schemes was also done in details. The idea of observing stochastic resonance in phase is very interesting as it opens doors to realize phase encoded communications
Capitoli di libri sul tema "Membranes suspendues"
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Berinskii, Igor, e Anton Krivtsov. "Linear Oscillations of Suspended Graphene". In Shell and Membrane Theories in Mechanics and Biology, 99–107. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-02535-3_5.
Testo completo
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Smith (Retired), Gregory S., e Cyrus R. Safinya. "Structures and Interactions in Freely Suspended Multilayer Membranes and Dilute Lamellar Fluid Membranes from Synchrotron X-Ray Scattering". In Handbook of Lipid Membranes, 33–47. Boca Raton: CRC Press, 2021. http://dx.doi.org/10.1201/9780429194078-2.
Testo completo
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Buisson, A., F. Morel e J. P. Peries. "Petroleum Residue Hydrotreatment: Suspended Catalyst Separation and Recycling Processes Using Membranes". In Optimization of the Production and Utilization of Hydrocarbons, 712–22. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2256-6_42.
Testo completo
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Goedel, Werner A. "From Monolayers of a Tethered Polymer Melt to Freely Suspended Elastic Membranes". In ACS Symposium Series, 10–30. Washington, DC: American Chemical Society, 1998. http://dx.doi.org/10.1021/bk-1998-0695.ch002.
Testo completo
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Zaidi, A., K. Simms, S. Kok e R. Nelson. "Recent Advances in the Application of Membrane Technology for the Removal of Oil and Suspended Solids from Produced Waters". In Produced Water, 489–501. Boston, MA: Springer US, 1992. http://dx.doi.org/10.1007/978-1-4615-2902-6_38.
Testo completo
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Bir, Tanmoy, e Debabrata Mazumder. "Suspended Solids Removal in Combined Carbon Oxidation, Nitrification, and Denitrification of Wastewater by Moving Bed Hybrid Bioreactor: Membrane Bioreactor System". In Springer Proceedings in Earth and Environmental Sciences, 425–35. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-64006-3_31.
Testo completo
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Belaid, Nebil. "Tertiary Treatment for Safely Treated Wastewater Reuse". In Promising Techniques for Wastewater Treatment and Water Quality Assessment. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.94872.
Testo completoAbstract (sommario):
The tertiary treatment of resulting water from a conventional biological treatment process is envisaged in the aim to obtain a high quality of water that can be reused for different purposes. This treatment is based on the integration of the membrane-based technologies in the total process of wastewater treatment. The experimental studies are carried out on a small pilot, equipped with different mineral membranes of micro and ultrafiltration. These membranes are used for the different tested processes (MF, MF-UF and cogulation-MF). The results obtained make it possible to attend a complete elimination of the total flora and an additional reduction of the other parameters such as turbidity, suspended matter, COD and BOD. Tests on a large scale are then carried out on a semi-industrial pilot, equipped with the same type of membranes. The optimization of the operating conditions made allow the obtaining under the conditions of transmembrane pressure 0.85 bar, a cross flow velocity of 2.25m/s and with ambient temperature a filtrate flux of about 200 L/hm 2. The coupling of a stage of coagulation in the membrane process allows the reduction of the effect of the membrane fouling and an improvement of 36% of the filtrate flux.
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Mendoza-Acevedo, Salvador, Mario Alfredo, Edgar Norman, Jos Antonio e Jos Luis. "Release Optimization of Suspended Membranes in MEMS". In Micromachining Techniques for Fabrication of Micro and Nano Structures. InTech, 2012. http://dx.doi.org/10.5772/30909.
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"Advanced Wastewater Treatments". In Advanced Design of Wastewater Treatment Plants, 293–331. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-9441-3.ch005.
Testo completoAbstract (sommario):
Advanced wastewater treatment is the process that reduces the level of impurities in wastewater below that attainable through conventional secondary or biological treatment. It includes the removal of nutrients such as phosphorus and nitrogen and a high percentage of suspended solids. The removal of nitrogen and phosphorus from wastewater has become an emerging worldwide concern because these compounds cause eutrophication in natural water. A post-treatment process is therefore required to remove nitrogen and phosphorus from the effluent. Therefore, the purpose of this chapter is to provide the deeper knowledge of membrane technology, membrane bioreactor, sequential batch reactor, moving bed biofilm reactor, nitrification, denitrification, phosphorus removal from wastewater, carbon adsorption, and provide a design of a sewage treatment plant using moving bed biofilm reactor technology.
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Gesnot, M., L. Perrier e A. Debourg. "Piezoelectric ceramics: a new concept for in-line density measurements". In European Brewery Convention, 655–62. Oxford University PressOxford, 1997. http://dx.doi.org/10.1093/oso/9780199636907.003.0078.
Testo completoAbstract (sommario):
Abstract In-line measurement of wort and beer gravity offers the opportunity of continuous process monitoring. The principle of the gravity sensor developed is based on a dynamic measurement of the resonance frequency between two piezoelectric membranes. The laboratory trials with this sensor have shown that yeast cells, suspended trub and CO2 bubbles do not interfere with specific gravity measurement. The accuracy and reliability of this system allow specific gravity measurement in a range from 1.0000 to 1.3000 with a variability of 0.002. The results were confirmed by trials in industrial fermentation vessels and in-line measurements of wort specific gravity.
Atti di convegni sul tema "Membranes suspendues"
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Liang, Xiaoya, Qi Zhang, Xing Pang, Yulong Zhao e Hongzhong Liu. "NEMS Accelerometer and Force Sensors Based on Suspended Graphene Membranes". In 2024 IEEE 19th International Conference on Nano/Micro Engineered and Molecular Systems (NEMS), 1–4. IEEE, 2024. http://dx.doi.org/10.1109/nems60219.2024.10639897.
Testo completo
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Jung, Alexander, Anastasiia Ciers, André Strittmatter e Witlef Wieczorek. "Optomechanical Microcavity With a Tensile-strained InGaP Membrane". In Quantum 2.0, QTu3A.13. Washington, D.C.: Optica Publishing Group, 2024. http://dx.doi.org/10.1364/quantum.2024.qtu3a.13.
Testo completoAbstract (sommario):
We characterize a chip-based optomechanical microcavity that confines light between a crystalline DBR and a suspended InGaP photonic crystal high-Q membrane. In the future this approach could enable nonlinear quantum optomechanics.
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Berdnikov, Y., V. Neplokh, V. Fedorov, A. D. Bolshakov, V. Yu Mikhailovskii, D. Mitin, A. G. Nasibulin et al. "Flexible suspended membranes of GaP nanowires". In 2020 International Conference Laser Optics (ICLO). IEEE, 2020. http://dx.doi.org/10.1109/iclo48556.2020.9285737.
Testo completo
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Tizani, Lina, e Irfan Saadat. "Suspended Graphene Membranes for Strain Sensor Applications". In 2018 IEEE 13th Nanotechnology Materials and Devices Conference (NMDC). IEEE, 2018. http://dx.doi.org/10.1109/nmdc.2018.8605930.
Testo completo
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Hu, Kai-Ming, Bo Peng, Han Yan, Wen-Ming Zhang, Zhong-Yin Xue, Zeng-Feng Di e Ya-Ting Sun. "Tension-Induced Raman Spectrum Enhanced Phenomena of Graphene Membrane". In ASME 2018 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/detc2018-85158.
Testo completoAbstract (sommario):
In the Letter, we reported the tension-induced Raman spectrum enhanced phenomena of graphene membrane. The standard micro-fabrication processes are utilized to fabricate micro-scale holes on Silicon-On-Insulator (SOI) wafers, and suspended graphene membranes are transferred onto target substrates with shallow holes and flat substrates using the dry and wet transfer techniques, respectively. The corrugated graphene near the hole is stretched smoothly due to the built-in strain during the transfer processes, and the intensity ratio between the 2D and G bands I2D/IG>5, which demonstrates the high quality of graphene sheet is obtained under the stretching stress. The intensity ratio between the 2D and G bands would diminish greatly when the graphene membrane is broken. Therefore, the Raman spectrum intensities of graphene membranes can be tuned by the built-in strain. The study can be helpful for further understanding the formation mechanism of corrugated graphene, the suppressing method of the small ripple in graphene, and the way to improve the quality of graphene.
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Yeary, Lucas, Glenn Cunningham, Nagesh Panduga, Corinne Darvennes, Kevin Walsh, Mark Crain, Robert W. Cohn, Steven A. Harfenist e Jeff Frolik. "Design, Analysis, and Testing of Electrostatically Actuated Micromembranes". In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41155.
Testo completoAbstract (sommario):
This paper reports a numerical design analysis of electrostatically actuated micromembranes. We systematically compare membrane performance in terms of natural frequencies, pull-in voltage (the bias voltage at which the membrane contacts the base electrode) and the effects of variable leg lengths for a given membrane size. Some experimental data on membrane deflection profiles versus bias voltage is included along with some experimentally determined pull-in voltages. Polysilicon micromembranes were successfully fabricated using the low cost MUMPs process that limits the user to three structural layers. The devices are designed with an emphasis on the response of the membrane to applied DC bias voltage to allow for variable stiffening. Circular membranes with diameters ranging from 60 to 160 μm, suspended 2 μm over square back plates of side lengths varying from 60 to 140 μm are investigated for voltages up to 90 volts. Three-dimensional electromechanical finite element simulations have been performed. Pull-in voltage values from simulations compare favorably with the measured results. It was observed that, for maximum deflection of the membrane upon application of DC bias voltage, the optimal dimensions for back plate and top membrane should fall within the ranges 80–120 μm and 80–140 μm, respectively.
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Pogosov, A. G., M. V. Budantsev, E. Yu Zhdanov e D. A. Pokhabov. "Ballistic electron transport in structured suspended semiconductor membranes". In THE PHYSICS OF SEMICONDUCTORS: Proceedings of the 31st International Conference on the Physics of Semiconductors (ICPS) 2012. AIP, 2013. http://dx.doi.org/10.1063/1.4848360.
Testo completo
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Miletta, Bryan A., R. S. Amano, Ammar A. T. Alkhalidi e Jin Li. "Study of Air Bubble Formation for Wastewater Treatment". In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-47065.
Testo completoAbstract (sommario):
Aeration, a unit process in which air and water are brought into intimate contact, is an extremely important step in the process of wastewater treatment. The two most common systems of aeration are subsurface and mechanical. A mechanical system agitates the wastewater by various means (e.g. paddles, blades, or propellers) to introduce air from the atmosphere. Subsurface aeration is the release of air, in the form of bubbles, within the tank of wastewater to supply the microorganisms with the required amount of oxygen they need to metabolize and break down the organic material suspended in the wastewater. The bubbles of Air are released from the bottom of the wastewater tank through diffusers. These diffusers have a surface membrane, usually made of punched rubber, to create the fine bubbles with high oxygen transfer efficiency from supplied air to the diffusers. Since the energy crisis in the early 1970’s, there has been increased interest in these systems due to its high oxygen transfer efficiency. This paper covers experimentation of different air diffuser membranes, varying in material, used in the aeration process of wastewater treatment. Rubber, EPDM rubber (ethylene-propylene-diene Monomer) and PTFE Polytetrafluoroethylene membranes coated membranes were tested. Experimental results showed that the rubber membrane produced the smallest bubble size against expectation. This could be a result of the coating being on the top surface only and the bubble starts from inside the punch.
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Ceylan, M., K. Nilsen, H. Misak e R. Asmatulu. "Development of Low Pressure Filter Testing Vessel and Analysis of Electrospun Nanofiber Membranes for Water Treatment". In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62765.
Testo completoAbstract (sommario):
A low-pressure filtration unit incorporated with polymeric electrospun polyvinyl chloride (PVC) fiber membranes was designed and fabricated for the treatment of waste water in order to improve its quality. This custom-made pressure filter was designed according to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC). A scanning electron microscope (SEM) was used to characterize the electrospun membranes. In order to increase the hydrophilicity and filtration rates of PVC membranes, a lower dosage of poly (ethylene oxide) was added to the PVC solution prior to the electrospinning process. The filter was found to be well suited for the reduction of larger suspended solids, turbidity, and odor. It was demonstrated that this type of filtration membrane could be manufactured at a lower cost and not require electricity or any other external power source to achieve high flow rates. This technology could even be used to enhance the quality of tap water in many places, such as Africa. Another application could be a pre-filtration of reverse osmosis (RO) or other ultrafine filtration systems, to increase the life of the primary filter while decreasing fouling and maintenance.
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Smith, A. D., F. Niklaus, S. Vaziri, A. C. Fischer, M. Sterner, F. Forsberg, S. Schroder, M. Ostling e M. C. Lemme. "Biaxial strain in suspended graphene membranes for piezoresistive sensing". In 2014 IEEE 27th International Conference on Micro Electro Mechanical Systems (MEMS). IEEE, 2014. http://dx.doi.org/10.1109/memsys.2014.6765826.
Testo completo