Littérature scientifique sur le sujet « High-yield reaction »
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Articles de revues sur le sujet "High-yield reaction"
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HART, PETER W. « Enhancing yield through high-kappa pulping ». October 2014 13, no 10 (1 novembre 2014) : 33–35. http://dx.doi.org/10.32964/tj13.10.33.
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Chemical pulping consists of a collection of delignification reactions designed to remove amorphous lignin from the fiber matrix while preserving carbohydrates in a fibrous form. Commercially available cooking processes are relatively nonselective with reagents attaching both lignin and carbohydrates. Generally, the carbohydrates react more slowly than the lignin, so some carbohydrate selectivity does exist for modern pulping processes. However, extended reaction times or excessive reaction temperatures will substantially reduce pulp yield. To date, only a few methods of converting high-kappa pulp into enhanced fiber yield have been demonstrated.
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Wang, Qi, Guo Zheng, Jian Jie Ai et Xue Jing Wei. « The Synthesis of High Yield Diglycerin Borate ». Applied Mechanics and Materials 55-57 (mai 2011) : 312–16. http://dx.doi.org/10.4028/www.scientific.net/amm.55-57.312.
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High yield diglycerin borate(DGB) have been synthesized by the raw materials glycerol and boric acid in this paper. The structure of the products was characterized by FTIR and11B NMR. The yield of the products was discussed by reaction conditions that were material ratio, reaction temperature, reaction pressure etc. and then the optimum process conditions of preparing DGB was decided. In this condition, high yield DGB can be prepared which could reach more than 96%.
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Jin, Shuai Yong, Kang Kang Guo, Hui Min Qi, Ya Ping Zhu et Fan Wang. « High Yield Polyborosilazane Precursor for SiBN Ceramics ». Advanced Materials Research 1004-1005 (août 2014) : 409–14. http://dx.doi.org/10.4028/www.scientific.net/amr.1004-1005.409.
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The processible and high yield polyborosilazane (PBSZ) precursor for SiBN ceramics was prepared by coammonolysis reaction of dichlorosilane and trichloroborazine. The synthesized PBSZ precursor was characterized by Fourier Transform Infrared spectroscopy (FTIR),1H,11B, and29Si Nuclear Magnetic Resonance (NMR), and its ceramic conversion chemistry was investigated by differential scanning calorimetric (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA). The PBSZ precursor is a viscous liquid and changes to an insoluble solid via a cross-linking reaction between the N-H group and Si-H group as post-heated from 60 to 180°C. The insoluble solid is transformed to Si3N4and BN amorphous structures with an approximately 95% ceramic yield after being pyrolyzed to 1000°C.
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Daum, B., et K. Buchholz. « High Yield and High Selectivity of Reactions in the Frozen State--the Acceptor Reaction of Dextransucrase ». Biocatalysis and Biotransformation 20, no 1 (janvier 2002) : 15–21. http://dx.doi.org/10.1080/10242420210156.
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Chuliá-Jordán, Raquel, David Santamaría-Pérez, Tomás Marqueño, Javier Ruiz-Fuertes et Dominik Daisenberger. « Oxidation of High Yield Strength Metals Tungsten and Rhenium in High-Pressure High-Temperature Experiments of Carbon Dioxide and Carbonates ». Crystals 9, no 12 (17 décembre 2019) : 676. http://dx.doi.org/10.3390/cryst9120676.
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The laser-heating diamond-anvil cell technique enables direct investigations of materials under high pressures and temperatures, usually confining the samples with high yield strength W and Re gaskets. This work presents experimental data that evidences the chemical reactivity between these refractory metals and CO2 or carbonates at temperatures above 1300 °Ϲ and pressures above 6 GPa. Metal oxides and diamond are identified as reaction products. Recommendations to minimize non-desired chemical reactions in high-pressure high-temperature experiments are given.
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Wolfe, David R. « Investor reaction to new issuances of U.S. high-yield debt ». Corporate Ownership and Control 5, no 3 (2008) : 358–84. http://dx.doi.org/10.22495/cocv5i3c3p4.
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This paper investigates firms issuing high-yield debt and the impact on their stock price by identifying determinants of the negative abnormal return that surrounds the announcement of an issue in the short-run. It is learned the length, coupon payment and amount of the issue are significant in explaining the CAR as is the age of the firm, first-time issuers and the marketplace where its stock trades. Firm performance ratios including the current and total-asset-turnover ratio also have explanatory power. These determinants of the CAR have an explanatory power approaching 55%
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Duangwang, S., et C. Sangwichien. « Optimization Studies on Acid Hydrolysis of Pretreated Oil Palm Empty Fruit Bunch for Production of Xylose by Application of Response Surface Methodology ». Advanced Materials Research 699 (mai 2013) : 77–82. http://dx.doi.org/10.4028/www.scientific.net/amr.699.77.
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Oil palm empty fruit bunch is a lignocellulosic material from palm oil plantations. It is a potential source of xylose which can be used as a raw material for production of xylitol. Using of lignocellulosic waste for bioconversion to fuels and chemicals is justifiable as these materials are low cost, renewable and widespread sources of sugars. The objective of the present study was to determine the effect of H2SO4 concentration, reaction temperature and reaction time for acid hydrolysis of pretreated OPEFB, pretreated OPEFB with reaction temperature, reaction time and NaOH concentration were 130 °C, 40 min and 15% (w/v), respectively to achieve high xylose yield. Batch reactions were carried out under various reaction temperature, reaction time and H2SO4 concentration. Response Surface Methodology (RSM) was followed to optimize acid hydrolysis in order to obtain high yield of xylose. The optimum reaction temperature, reaction time and H2SO4 concentration were found to be 140 °C, 90 min and 7% (w/v), respectively. The maximum value of xylose was obtained 56.39 g/l by using the above condition. The best result of xylose yield obtained was 126%.
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Kobayashi, Toshiaki, et Keith H. Pannell. « A general, high-yield reaction for the formation of (chloromethyl)oligosilanes ». Organometallics 9, no 8 (août 1990) : 2201–3. http://dx.doi.org/10.1021/om00158a012.
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Mat Radzi, Salina, Nurul Jannah Abd Rahman, Hanina Mohd Noor et Mahiran Basri. « High Yield Synthesis of Kojic Ester Using Dual Enzymes System and their Antibacterial Activity ». Key Engineering Materials 594-595 (décembre 2013) : 362–69. http://dx.doi.org/10.4028/www.scientific.net/kem.594-595.362.
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Enzymatic synthesis of kojic ester, a bio-based whitening agent, was successfully carried out via esterification reaction between oleic acid and kojic acid. Commercial immobilized lipases of Novozym 435 and Lipozyme RM IM were used in combination as biocatalyst in the reaction system. Various reaction parameters were chosen to optimize the reaction in order to obtain a high yield of kojic ester including the best ratio of lipases, reaction time and reaction temperature. The optimum conditions for the synthesis of kojic ester was achieved at reaction time of 12 hours, temperature of 60 οC and equal ratio of lipases to produce more than 70 % yield. Antimicrobial tests of synthesized kojic ester towards several types of bacteria via Minimum inhibitory concentration (MIC) and Minimum bactericidal concentration (MBC) analyses were also examined. The results obtained suggested that kojic ester exhibits a good bactericidal effect towards all bacteria tested such as Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Salmonella typhimurium.
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Fakeeha, Anis, Ahmed A. Ibrahim, Hesham Aljuraywi, Yazeed Alqahtani, Ahmad Alkhodair, Suliman Alswaidan, Ahmed E. Abasaeed, Samsudeen O. Kasim, Sofiu Mahmud et Ahmed S. Al-Fatesh. « Hydrogen Production by Partial Oxidation Reforming of Methane over Ni Catalysts Supported on High and Low Surface Area Alumina and Zirconia ». Processes 8, no 5 (25 avril 2020) : 499. http://dx.doi.org/10.3390/pr8050499.
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The catalytic activity of the partial oxidation reforming reaction for hydrogen production over 10% Ni supported on high and low surface area alumina and zirconia was investigated. The reforming reactions, under atmospheric pressure, were performed with a feed molar ratio of CH4/O2 = 2.0. The reaction temperature was set to 450–650 °C. The catalytic activity, stability, and carbon formation were determined via TGA, TPO, Raman, and H2 yield. The catalysts were calcined at 600 and 800 °C. The catalysts were prepared via the wet-impregnation method. Various characterizations were conducted using BET, XRD, TPR, TGA, TPD, TPO, and Raman. The highest methane conversion (90%) and hydrogen yield (72%) were obtained at a 650 °C reaction temperature using Ni-Al-H-600, which also showed the highest stability for the ranges of the reaction temperatures investigated. Indeed, the time-on-stream for 7 h of the Ni-Al-H-600 catalyst displayed high activity and a stable profile when the reaction temperature was set to 650 °C.
Thèses sur le sujet "High-yield reaction"
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COGHI, MARIA DONATA. « Samdi mass spectrometry for high yield protein modification reaction development ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2014. http://hdl.handle.net/10281/50887.
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Efficient chemical strategies that attach synthetic molecules to desired positions on protein surfaces are useful tools in the field of chemical biology and represent one major prerequisite for the development of new drugs and materials. Protein modification with polyethylene glycol (PEG) groups is indeed routinely performed on therapeutic proteins to improve serum half-life, or even cytotoxins or imaging agents are efficiently conjugated to cancer-targeting elements. In a typical approach, a synthetic functional group of interest is attached to a uniquely reactive amino acid group introduced by recombinant methods. Most bioconjugation reactions, however, do not reach full conversion. Therefore the development of a straightforward and reliable method to increase the extent of conversion into bioconjugates would be very helpful. In this perspective, we developed a generalizable combinatorial peptide library screening platform suitable for the identification of sequences displaying high levels of reactivity toward a desired bioconjugation reaction. This was achieved by using SAMDI MS technique (Self-Assembled Monolayer and Desorption/Ionization Mass Spectrometry) as a new, efficient and simple method for the evaluation of highly reactive amino acid motifs. The bioconjugation reaction we selected is the oxidative modification of electron-rich tyrosine residues performed using cerium(IV) ammonium nitrate (CAN) as oxidant reagent. The peptides were identified on a 361-member hexapeptide array, wherein the two N- and C-terminal residues to the target residue were varied. The arrays were prepared by immobilizing the peptides to a self-assembled monolayer of alkanethiolates on gold and could therefore be analyzed by mass spectrometry. We found that the most reactive peptides had either a serine N-terminal to the tyrosine residue or another tyrosine in proximity of the reactive site. Conversely, peptides displaying the lowest conversion level contained a positive charged residue: histidine, lysine or arginine, where the lowest relative activity was reached with arginine and leucine as C- and N- terminal residues, respectively. This study provides an important example of how synthetic peptide libraries can accelerate the discovery and optimization of protein bioconjugation strategies.
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Spender, Jonathan. « Photostabilization of High-Yield Pulps Reaction of Thiols and Quinones with Pulp ». Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/SpenderJ2001.pdf.
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Onobun, Emmanuel. « A Novel Method for Synthesis of Hydroxytyrosol ». Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etd/3267.
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Hydroxytyrosol, 3,4-dihydroxyphenolethanol, a naturally occurring polyphenol most common in olive tree (Olea europaea), is one of the most effective member of the polyphenols family, because of its remarkable antioxidant activity, its ability to inhibit oxidation of low density lipids (LDL), and its protection against DNA oxidative damage. Hydroxytyrosol, which is widely used in cosmetics and food supplements industries, can be purchased as an olive oil extract that contains low concentration of hydroxytyrosol besides other polyphenols. The price and low natural abundance of hydroxytyrosol make alternative synthetic sources very attractive. In this research, a novel method for the synthesis of pure hydroxytyrosol from a commercially inexpensive precursor catechol was developed; this can satisfy the increasing market demand and provide a more economical alternative source for this valuable polyphenol.
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Adireddy, Shivaprasad Reddy. « High Yield Solvothermal Synthesis of Hexaniobate Based Nanocomposites via the Capture of Preformed Nanoparticles in Scrolled Nanosheets ». ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/td/1726.
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The ability to encapsulate linear nanoparticle (NP) chains in scrolled nanosheets is an important advance in the formation of nanocomposites.These nanopeapods (NPPs) exhibit interesting properties that may not be achieved by individual entities. Consequently, to fully exploit the potential of NPPs, the fabrication of NPPs must focus on producing composites with unique combinations of morphologically uniform nanomaterials. Various methods can produce NPPs, but expanding these methods to a wide variety of material combinations can be difficult. Recent work in our group has resulted in the in situ formation of peapod-like structures based on chains of cobalt NPs. Building on this initial success, a more versatile approach has been developed that allows for the capture of a series of preformed NPs in NPP composites.
In the following chapters, various synthetic approaches for NPPs of various material combinations will be presented and the key roles of various reaction parameters will be discussed. Also, uniform hexaniobate nanoscrolls were fabricated via a solvothermal method induced by heating up a mixture of TBAOH, hexaniobate crystallites, and oleylamine in toluene. The interlayer spacing of the nanoscrolls was easily tuned by varying the relative amount and chain lengths of the primary alkylamines.
To fabricate NPPs, as-synthesized NPs were treated with hexaniobate crystallite in organic mixtures via solvothermal method. During solvothermal treatment, exfoliated hexaniobate nanosheets scroll around highly ordered chains of NPs to produce the target NPP structures in high yield. Reaction mixtures were held at an aging temperature for a few hours to fabricate various new NPPs (Fe3O4@hexaniobate, Ag@hexaniobate, Au@hexaniobate, Au-Fe3O4@hexaniobate, TiO2@hexaniobate, CdS@hexaniobate, CdSe@hexaniobate, and ZnS@hexaniobate).
This versatile method was first developed for the fabrication of magnetic peapod nanocomposites with preformed nanoparticles (NPs). This approach is effectively demonstrated on a series of ferrite NPs (≤ 14 nm) where Fe3O4@hexaniobate NPPs are rapidly (~ 6 h) generated in high yield. When NP samples with different sizes are reacted, clear evidence for size selectivity is seen. Magnetic dipolar interactions between ferrite NPs within the Fe3O4@hexaniobate samples leads to a significant rise in coercivity, increasing almost four-fold relative to free particles. Other magnetic ferrites NPPs, MFe2O4@hexaniobate (M = Mn, Co, Ni), can also be prepared. This synthetic approach to nanopeapods is quite versatile and should be readily extendable to other, non-ferrite NPs or NP combinations so that cooperative properties can be exploited while the integrity of the NP assemblies is maintained. Further, this approach demonstrated selectivity by encapsulating NPs according to their size.
The use of polydispersed NP systems is also possible and in this case, evidence for size and shape selectivity was observed. This behavior is significant in that it could be exploited in the purification of inhomogeneous NP samples. Other composite materials containing silver and gold NPs are accessible. Partially filled Fe3O4@hexaniobate NPPs were used as templates for the in situ growth of gold to produce the bi-functional Au- Fe3O4@hexaniobate NPPs. Encapsulation of Ag and Au NP chains with a hexaniobate nanoscroll was shifted the surface plasmon resonance to higher wavelengths.
In these composites NPs can be incorporated to form NPP structures, decorated on nanosheets before scrolling, or attached to the surfaces of the nanoscrolls. The importance of this advancement is the promise it holds for the design and assembly of active nanocomposites. One can create important combinations of nanomaterials for potential applications in a variety of areas including catalysis, solar conversion, thermoelectrics, and multiferroics.
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Butarbutar, Sofia Loren. « Monte Carlo simulation of the radiolysis of water by fast neutrons at elevated temperatures up to 350°C ». Mémoire, Université de Sherbrooke, 2014. http://hdl.handle.net/11143/5887.
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Résumé : Le contrôle de la chimie de l'eau dans un réacteur nucléaire refroidi à l'eau nécessite une compréhension détaillée des effets de la radiolysede l'eau afin de limiter la corrosion et la dégradation des matériaux par oxydation générée par les produits de cette radiolyse. Toutefois, la mesure directe de la chimie dans le cœur des réacteurs est extrêmement difficile, sinon impossible, en raison des conditions extrêmes de haute température et haute pression, et les champs d’irradiation mixtes neutrons/γ, qui ne sont pas compatibles avec l'instrumentation chimique normale. Pour ces raisons,des modèles théoriques et des simulations sur ordinateur sont essentielles pour la prédiction de la chimie sous rayonnement de l'eau de refroidissement dans le cœur et son impact sur les matériaux. Dans ce travail, des simulations Monte Carlo ont été utilisées pour calculer les rendements des principales espèces (e[indice supérieur -][indice inférieur aq], H[indice supérieur •], H[indice inférieur 2], [indice supérieur •]OH et H[indice inférieur 2]O[indice inférieur 2]) formées lors de la radiolyse de l’eau liquide neutre par des neutrons mono-énergétiques de 2 MeV à des températures entre 25 et 350 °C. Le choix des neutrons de 2 MeV comme énergie d'intérêt est représentatif du flux de neutrons rapides dans un réacteur. Pour l'eau légère, la contribution la plus significative à la radiolyse vient des quatre premières collisions des neutrons qui produisent, dans la majorité des cas, des protons avec des énergies de recul de ~1.264, 0.465, 0.171 et 0.063 MeV et des transferts d’énergie linéique (TEL) moyens respectivement de ~22, 43, 69et 76 keV/[micro]m. Par ailleurs, nous avons négligé les effets des radiations dus aux ions de recul de l’oxygène. Les rendements moyens finaux peuvent alors être estimés comme étant la somme des rendements résultant de l’action de ces protons après pondérations en fonction de l’énergie déposée. Les rendements ont été calculés à 10[indice supérieur -7], 10[indice supérieur -6] et 10[indice supérieur -5] s. Les valeurs obtenues sont en accord avec les données expérimentales disponibles. En comparant nos résultats avec les données obtenues pour les rayonnements à faible TEL (rayons γ de [indice supérieur 60]Co ou électrons rapides), nos rendements calculés pour les neutrons rapides ont montré une dépendance en température essentiellement similaire, mais avec des valeurs plus faibles pour les rendements en radicaux libres et des valeurs plus élevées pour les rendements moléculaires. Nous avons également utilisé les simulations Monte Carlo pour étudier l'existence de la chute rapide de la constante de vitesse de réaction de l'électron hydraté (e[indice supérieur -][indice inférieur aq]) sur lui-même – l’une des principales sources de formation de H[indice inférieur 2] – au-dessus de 150 °C. Cette dépendance en température a été observée expérimentalement en milieu alcalin par divers auteurs, mais jamais en milieu neutre. Lorsque cette baisse de la constante de vitesse d’auto-réaction de e[indice supérieur -][indice inférieur aq] est incluse dans nos codes de simulation, tant pour des rayonnements de bas TEL (grappes isolés) que de haut TEL (trajectoires cylindriques), g(H[indice inférieur 2]) montre une discontinuité marquée à la baisse à ~150°C, ce qui n'est pas observée expérimentalement. Les conséquences de la présence de cette discontinuité dans le rendement en H[indice inférieur 2] pour les rayonnements à bas et haut TEL sont discutées. Enfin, nous avons tenté d’expliquer l'augmentation – considérée comme anormale – du rendement en H[indice inférieur 2] en fonction de la température au-dessus de 200 °C par l’intervention de la réaction des atomes H[indice supérieur •] avec l'eau, préalablement proposée par Swiatła-Wojcik et Buxton en 2005. La constante de vitesse de cette réaction est toujours controversée. // Abstract : Controlling the water chemistry in a water-cooled nuclear power reactor requires understanding and mitigating the effects of water radiolysis to limit the corrosion and degradation of materials by oxidizing radiolysis products. However, direct measurement of the chemistry in reactor cores is extremely difficult due to the extreme conditions of high temperature, pressure, and mixed neutron/γ-radiation fields, which are not compatible with normal chemical instrumentation. For these reasons, theoretical models and computer simulations are essential for predicting the detailed radiation chemistry of the cooling water in the core and the impact on materials. Monte Carlo simulations were used to calculate the yields for the primary species (e[superscript -][subscript aq], H[superscript •], H[subscript 2], [superscript •]OH, and H[subscript 2]O[subscript 2]) formed from the radiolysis of neutral liquid water by mono-energetic 2-MeV neutrons and the mechanisms involved at temperatures between 25 and 350 °C. In this work, we chose 2-MeV neutron as our energy of interest since it is known as representative of a fast neutron flux in a nuclear reactor. For light water, for that chosen energy, the most significant contribution to the radiolysis comes from the first four neutron collisions that generate mostly ejected protons with energies of ~1.264, 0.465, 0.171, and 0.063 MeV, which had, at 25 °C, mean linear energy transfers (LETs) of ~22, 43, 69, and 76 keV/[micro]m, respectively. In this work, we simply neglected the radiation effects due to oxygen ion recoils. The average final fast neutron yields could be estimated as the sum of the yields for these protons after allowance was made for the appropriate weightings (by using the Eq (2) in Chapter 4) according to their deposited energy. Yields were calculated at 10[superscript -7], 10[superscript -6] and 10[superscript -5] s. Our computed yield agreed reasonably well with the available experimental data. By comparing our results with data obtained for low-LET radiation ([superscript 60]Co γ-rays or fast electrons), our computed yields for fast neutron radiation showed essentially similar temperature dependences over the range of temperature studied, but with lower values for yields of free radicals and higher values for molecular yields. In this work, we also used our Monte Carlo simulation to investigate the existence of drop of hydrated electron (e[superscript -][subscript aq]) self-reaction rate constant at 150 °C. One of the main sources of H[subscript 2] formation is the self-reaction of hydrated electrons. The temperature dependence of the rate constant of this reaction (k[subscript 1]), measured under alkaline conditions, reveals that the rate constant drops abruptly above ~150 °C. However, when this drop in the e[superscript -][subscript aq] self-reaction rate constant is included in our code for low (isolated spurs) and high (cylindrical tracks) linear energy transfer (LET), g(H[subscript 2]) shows a marked downward discontinuity at ~150 °C which is not observed experimentally. The consequences of the presence of this discontinuity in H[subscript 2] yield for both low and high LET radiation are discussed. Another reaction that might explain the anomalous increasing of H[subscript 2] yield with temperature is the reaction of H[superscript •] atoms with water previously proposed by Swiatla-Wojcik and Buxton (2005) whose rate constant is still in controversial.
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Spender, Jonathan. « Photostabilization of high-yield pulps : reactions of thiols and quinones with pulp / ». 2001. http://www.library.umaine.edu/theses/theses.asp?Cmd=abstract&ID=CHY2001-003.
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Yeh, Yi-Hsuan, et 葉懿萱. « Synthesis and Characterizations of High-Quantum Yield II -VI Group Core/Shell Quantum Dots Prepared by Successive Ion Layer Adsorption and Reactions ». Thesis, 2016. http://ndltd.ncl.edu.tw/handle/36001899179067212347.
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碩士國立交通大學
應用化學系碩博士班
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Herein, a series of II-VI semiconductor core/shell QDs were synthesized by a two-step method (CdSe/CdS, CdSe/ZnSe, CdSe/CdS/ZnS, CdSe/ZnS,CdZnSe/CdS, and CdSeS/CdS). The reaction conditions were mild by adopting less toxic and less expensive reactants (cadmium oxide, S powder, Se powder, and zinc stearate) and passivating ligands (stearic acid, oleic acid, hexadecylamine,octadecylamine and trioxylphosphine oxide) instead of hazzardous organometallic precursors. Different conditions of various reaction temperatures and feeding ratios of Cd to Se were tested to accomplish the best CdSe cores for further shell decomposition. For shell growth, successive ion layer adsorption and reaction (SILAR) method offered a successful deposition of shell materials onto purified cores to avert homogeneous nucleation. Shell grew under moderate temperature (200 °C) in order to alleviate the alloy formation between the interface of core/shell and abate serious PL emission red-shift. The resulting PL spectra exhibited sharp peaks for most core/shell QDs and FWHM less than 40 nm, indicating satisfactory control of size distribution. After shell growth, the PL QY was significantly enhanced, especially for gradient alloy ternary cores. The resulting cores and core/shell QDs emitted light from yellow-green to red colors. This versatile synthetic methodology providing highly quality, high QY, and low-cost core/shell QDs opens a door to their applications in display and solar cells.
Chapitres de livres sur le sujet "High-yield reaction"
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Zdybał, K., M. R. Malik, A. Coussement, J. C. Sutherland et A. Parente. « Reduced-Order Modeling of Reacting Flows Using Data-Driven Approaches ». Dans Lecture Notes in Energy, 245–78. Cham : Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-16248-0_9.
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AbstractData-driven modeling of complex dynamical systems is becoming increasingly popular across various domains of science and engineering. This is thanks to advances in numerical computing, which provides high fidelity data, and to algorithm development in data science and machine learning. Simulations of multicomponent reacting flows can particularly profit from data-based reduced-order modeling (ROM). The original system of coupled partial differential equations that describes a reacting flow is often large due to high number of chemical species involved. While the datasets from reacting flow simulation have high state-space dimensionality, they also exhibit attracting low-dimensional manifolds (LDMs). Data-driven approaches can be used to obtain and parameterize these LDMs. Evolving the reacting system using a smaller number of parameters can yield substantial model reduction and savings in computational cost. In this chapter, we review recent advances in ROM of turbulent reacting flows. We demonstrate the entire ROM workflow with a particular focus on obtaining the training datasets and data science and machine learning techniques such as dimensionality reduction and nonlinear regression. We present recent results from ROM-based simulations of experimentally measured Sandia flames D and F. We also delineate a few remaining challenges and possible future directions to address them. This chapter is accompanied by illustrative examples using the recently developed Python software, PCAfold. The software can be used to obtain, analyze and improve low-dimensional data representations. The examples provided herein can be helpful to students and researchers learning to apply dimensionality reduction, manifold approaches and nonlinear regression to their problems. The Jupyter notebook with the examples shown in this chapter can be found on GitHub at https://github.com/kamilazdybal/ROM-of-reacting-flows-Springer.
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Pyeon, Cheol Ho. « Neutron Spectrum ». Dans Accelerator-Driven System at Kyoto University Critical Assembly, 125–56. Singapore : Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0344-0_5.
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AbstractThe subcritical multiplication factor is considered an important index for recognizing, in the core, the number of fission neutrons induced by an external neutron source. In this study, the influences of different external neutron sources on core characteristics are carefully monitored. Here, the high-energy neutrons generated by the neutron yield at the location of the target are attained by the injection of 100 MeV protons onto these targets. In actual ADS cores, liquid Pb–Bi has been selected as a material for the target that generates spallation neutrons and for the coolant in fast neutron spectrum cores. The neutron spectrum information is acquired by the foil activation method in the 235U-fueled and Pb–Bi-zoned fuel region of the core, modeling the Pb–Bi coolant core locally around the central region. The neutron spectrum is considered an important parameter for recognizing information on neutron energy at the target. Also, the neutron spectrum evaluated by reliable methodologies could contribute to the accurate prediction of reactor physics parameters in the core through numerical simulations of desired precision. In the present chapter, experimental analyses of high-energy neutrons over 20 MeV are conducted after adequate preparation of experimental settings.
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Yu, Jian-qiang, Qi Li, Yong-lu Wang et Shuai Tao. « Numerical Simulation of Rockburst Characteristics of Tunnel Surrounding Rock Under Dilatancy Effect ». Dans Advances in Frontier Research on Engineering Structures, 163–73. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-8657-4_15.
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AbstractRockburst is one of the most intense reactions in various instability phenomena of underground cavern surrounding rock, which seriously threatens the safety of underground engineering construction personnel and equipment. Based on Mohr–Coulomb strain softening model, the non-associated flow rule is adopted for plastic flow after material yield. By implanting Gu Ming-cheng and Tao Zhen-yu rockburst criterion in the software, the effects of different dilatancy angles on rockburst grade and circumferential stress distribution of surrounding rock of circular tunnel are simulated. The calculation results show that the larger the dilatancy angle is, the more difficult the rock burst pit is to form. The elements of serious rockburst are mainly concentrated in the wall of the tunnel, and the shear bands formed in the high value area of shear strain increment are short. When the dilatancy angle is small, the circumferential stress reaches the maximum at the interface of elastic-plastic zone. With the increase of dilatancy angle, the number of elements entering the plastic state and occurring medium and severe rockburst increases first and then decreases, while the number of elements occurring slight rockburst decreases monotonously. Different dilatancy angles have significant effects on the number of elements occurring rockburst at all levels.
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Berezovets, V., A. Kytsya, Yu Verbovytskyy, I. Zavaliy et V. Yartys. « Hydrolysis of MgH2 in MgCl2 solutions as an effective way for hydrogen generation ». Dans HYDROGEN BASED ENERGY STORAGE : STATUS AND RECENT DEVELOPMENTS, 38–52. Institute for Problems in Materials Science, 2021. http://dx.doi.org/10.15407/materials2021.038.
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Magnesium hydride (MgH2) has a high hydrogen storage capacity (7.6 wt%) and the Mg element is abundant on the earth. Due to its strong reduction ability, even at room temperature it can provide the hydrogen yield reaching 15.2 wt% H (1703 mL/g) when interacting with water, which makes it very attractive for the application in supplying hydrogen for autonomous H energy systems. However, the hydrolysis reaction is rapidly inhibited by the Mg(OH)2 passivation layer formed on the surface of MgH2. In order to remove the passivation film and improve the efficiency of the MgH2 hydrolysis process, several methods including alloying, ball milling, changing the aqueous solution, have been successfully utilized. In this paper the process of hydrolysis of magnesium hydride in aqueous solutions of MgCl2 used as a promotor of the interaction has been studied in detail. It was found that the initial hydrolysis rate, pH of the reaction mixture, and overall reaction yield are all linearly dependent of the logarithm of MgCl2 concentration. It has been shown that pH of the reaction mixture in the presence of MgCl2 is well described by considering a system “weak base and its salt with strong acid” type buffer solution. Reference data for this hydrolysis reaction were also carefully analyzed. The mechanism and the kinetic model of the process of MgH2 hydrolysis in water solutions involved passivation of the MgH2 surface by the formed Mg(OH)2 precipitate followed by its repassivation have been proposed. The obtained after the hydrolysis reactions precipitates were studied using XRD and EDS. It was found also that the final products of reaction consist of Mg(OH)2 (brucsite type) and remaining MgH2. This fact shows that the formation of solid species such as MgCl2 xMgO yH2O at the studied conditions is unlikely and decreasing of pH the reaction mixture has a different nature.
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« Reactive Urothelial Atypia ». Dans High-Yield Uropathology, 170–71. Elsevier, 2012. http://dx.doi.org/10.1016/b978-1-4377-2523-0.00080-2.
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« Urothelial Carcinoma with Unusual Stromal Reactions ». Dans High-Yield Uropathology, 211. Elsevier, 2012. http://dx.doi.org/10.1016/b978-1-4377-2523-0.00103-0.
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Ranjith, Pamirelli, et Madasu Srinivasa Rao. « Breeding for Drought Resistance ». Dans Plant Breeding - Current and Future Views. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97276.
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Drought is the most severe abiotic stresses in many parts of the world and is one of the major problems in present-day climatic scenario. Drought tolerant varieties are with high demand which seems to be a great challenging task to plant breeders however difficulties are combined by the difficulty of crop yield on the genetic and physiological bases. Drought resistance may be defined as the mechanism(s) causing minimum loss of the yield in a drought environment relative to the maximum yield in a constant-free of optimal environment for the crop. Several researchers explained the plant reaction to drought through drought escape, dehydration avoidance, and/or dehydration tolerance mechanisms. Drought stress decreases size of the leaves, stem extension and root proliferation inside the soil, it also disturbs plant water relations and reduces water-use efficiency ultimately reduces the yielding ability of the plant so, breeding for Drought resistance is a good approach, following different breeding strategies and approaches to develop a drought resistant variety combining both conventional and molecular approaches. Considering the parameters like root morphology studies, proline estimation, leaf rolling etc., Selection based on a comprehensive approach of testing might be more effective in breeding better drought-tolerant cultivars.
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Pophaly, Sarang Dilip, Manorama Chauhan, Jitesh Tarak, Shekhar Banala Bashetty, Tejinder Pal Singh et Sudhir Kumar Tomar. « Aerobic Respiration in Lactic Acid Bacteria ». Dans Microbial Cultures and Enzymes in Dairy Technology, 87–100. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-5363-2.ch005.
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Lactic acid bacteria (LAB) are used as food-grade microorganisms for production of a variety of fermented milk products. They are also the most common probiotic organisms used for making functional foods. Lactic acid bacteria are well known for their fermentative metabolism wherein they convert simple carbohydrates to organic acids and other end products. Fermentation helps the bacteria to generate ATP required for various cellular activities via substrate level phosphorylation reaction. Fermentation results in incomplete oxidation of substrate and hence is an inefficient process with a low ATP yield. However, some LAB are genetically capable of activating an auxiliary respiratory metabolism in which a quinol oxidase serves as the final electron acceptor and high ATP production is achieved due to oxidative phosphorylation. The respiratory process is associated with high biomass production of LAB and more robust bacterial cells, which are essentially required for manufacture of high viability starter culture. This chapter explores LAB's current and future applications in dairy starter cultures.
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K. M., Sandhya, Litty Thomas Manamel et Bikas C. Das. « Doping of Semiconductors at Nanoscale with Microwave Heating (Overview) ». Dans Microwave Heating - Electromagnetic Fields Causing Thermal and Non-Thermal Effects. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95558.
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Incorporation of dopants efficiently in semiconductors at the nanoscale is an open challenge and is also essential to tune the conductivity. Typically, heating is a necessary step during nanomaterials’ solution growth either as pristine or doped products. Usually, conventional heating induces the diffusion of dopant atoms into host nanocrystals towards the surface at the time of doped sample growth. However, the dielectric heating by microwave irradiation minimizes this dopant diffusion problem and accelerates precursors’ reaction, which certainly improves the doping yield and reduces processing costs. The microwave radiation provides rapid and homogeneous volumetric heating due to its high penetration depth, which is crucial for the uniform distribution of dopants inside nanometer-scale semiconducting materials. This chapter discusses the effective uses of microwave heating for high-quality nanomaterials synthesis in a solution where doping is necessary to tune the electronic and optoelectronic properties for various applications.
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Calvert, Jack, Abdelwahid Mellouki, John Orlando, Michael Pilling et Timothy Wallington. « Rate Coefficients and Mechanisms for the Atmospheric Oxidation of the N-Atom-Containing Oxygenates ». Dans Mechanisms of Atmospheric Oxidation of the Oxygenates. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199767076.003.0011.
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The many different nitrogen-containing oxygenated volatile organic compounds that are present in the troposphere play important roles in the chemistry of our atmosphere. They can be emitted directly into the atmosphere, such as in the case of amides that are widely used as organic solvents, starting materials, or intermediates in different industries (e.g., synthetic polymers, manufacture of dyes, and synthesis of pesticides). Amides are formed in situ as intermediate products in the degradation of amines (e.g., see Tuazon et al., 1994; Finlayson-Pitts and Pitts, 2000). Nitrogen-containing oxygenated organic compounds are formed in the atmosphere also via reactions of alkoxy (RO) and alkyl peroxy radicals (RO2) with NO or NO2 leading to alkyl nitrates, alkyl nitrites, and peroxy acetyl nitrates. However, primary sources of these organic species have also been suggested such as diesel and other engines and biomass burning (e.g., see Simpson et al., 2002). Alkyl nitrates (RONO2) have been detected in both the urban and the remote troposphere (e.g., see Roberts, 1990; Walega et al., 1992; Atlas et al., 1992; Ridley et al., 1997; and Stroud et al., 2001; see also section I-D). Nitrates are formed as minor products in the reaction of peroxy radicals with NO. The nitrate yield increases with the size of peroxy radicals and can be as high as 20–30% for large (>C6) radicals (Calvert et al., 2008). Peroxyacyl nitrates (RC(O)O2NO2) are important constituents of urban air pollution. They have been identified in ambient air (e.g., see Bertman and Roberts, 1991; Williams et al., 1997, 2000; Nouaime et al., 1998; Hansel and Wisthaler, 2000; also see section I-D). They are formed from photochemical reactions via RC(O)O2 + NO2. A major role of these compounds is their capacity to act as a reservoir for NOx that can be transported from polluted urban to remote regions that are poor NOx regions and where their presence can increase NOx levels (Roberts, 1990). As with other volatile organic compounds (VOCs), once released to the atmosphere, nitrogen-containing organic compounds are expected to undergo degradation primarily via reaction with hydroxyl and nitrate radicals, reaction with ozone, and photolysis. Thermal decomposition is an important loss process for the peroxyacyl nitrates.
Actes de conférences sur le sujet "High-yield reaction"
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Vainionpaa, J. H., J. L. Harris, M. A. Piestrup, C. K. Gary, D. L. Williams, M. D. Apodaca, J. T. Cremer, Qing Ji, B. A. Ludewigt et G. Jones. « High yield neutron generators using the DD reaction ». Dans APPLICATION OF ACCELERATORS IN RESEARCH AND INDUSTRY : Twenty-Second International Conference. AIP, 2013. http://dx.doi.org/10.1063/1.4802303.
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Margarone, D., A. Picciotto, A. Velyhan, J. Krasa, M. Kucharik, M. Morrissey, A. Mangione et al. « Advanced scheme for high-yield laser driven proton-boron fusion reaction ». Dans SPIE LASE, sous la direction de Abdul A. S. Awwal et Monya A. Lane. SPIE, 2015. http://dx.doi.org/10.1117/12.2084598.
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Chida, Tsutomu, Aritomo Yamaguchi, Atsushi Takahashi, Kousuke Hiromori, Naoki Mimura et Naomi Shibasaki-Kitakawa. « Process design for efficient production from glycerol into high-value chemicals ». Dans 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/wimj4199.
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There is an urgent need to develop effective methods to use glycerol, a by-product of biodiesel production, by converting it into high-value chemicals. The by-product glycerol is contaminated with strong alkaline as a catalyst, and the environmental loads of the purification process to remove the contaminants has been a bottleneck to its utilization. As one way to solve this problem, it has been reported that glycerol can be converted to glyceric acid (GA), which is used as a pharmaceutical raw material, by partial oxidation of glycerol using an Au catalyst under alkaline condition. However, the GA yield is low because many side reactions proceed simultaneously. To construct a practical process for efficient GA production, it is necessary to both experimentally analyze the reaction mechanism and to develop a kinetic model that can quantitatively predict the reaction behavior under a wide range of conditions.The purpose of this study is to establish a methodology for process design of efficient production of GA from the by-product glycerol. In our previous study, the reaction mechanism including alkaline and the reactive oxygen species OOH, which is formed from O2 and H2O on Au catalyst, in GA formation was clarified and a kinetic model taken it into account was constructed. In present study, the model was additionally taken temperature dependency into account and enabled to predict GA yield in wide range of operating conditions. In order to design the catalysts, the relationship between GA yield and coverages of adsorbed species on active sites was investigated by the model simulation and it was revealed that the affinity between support and H2O greatly affects GA yield, suggesting that the support, which has strong interaction with H2O, increases the GA yield.
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He, Anpeng, Marie Bonvillain, Robert Bennett, Adam Duhon, Victor Lin et Ning Zhang. « Numerical Simulation of the Polymerization Process in Turbulent Reacting Flows ». Dans ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89825.
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The present research entails turbulent reacting flow being simulated inside a low-density polyethylene tubular reactor using computational fluid dynamics techniques. The effects of initiator mass fraction and initiator injection speed on the stability of the reactor have been studied. The reactor and injector should be designed such that the ethylene does not undergo the potential decomposition reaction; this reaction is exothermic and violent. The products of the decomposition must be vented as a safety measure. ANSYS FLUENT has been used to simulate this reacting flow problem. Both decomposition reaction and polymerization reaction are entered into the software along with their kinetic information. A high product yield of polymer without initiating the ethylene decomposition reaction is expected. Optimal mass fraction of initiator and optimal injection velocity were determined in order to maximize product and maintain the stability of the low-density polyethylene tubular reactor.
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Zhang, Bo, Pengfei He et Chao Zhu. « Modeling on Hydrodynamic Coupled FCC Reaction in Gas-Solid Riser Reactor ». Dans ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21368.
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The fluid catalytic cracking (FCC) riser reactor consists of a bottom section of liquid feed injection and vaporization and an upward straight riser of vapor-catalysts transport and reaction. The product yield, obtained at the top of riser, is an accumulative result of liquid feed injection, vaporization by liquid contacting with hot catalysts, and subsequent catalytic cracking of feed vapor while being transported concurrently with catalysts through the riser. The FCC process involves not only these sequential sub-processes but also complicated coupling among multiphase fluid hydrodynamics, heat and mass transfer between phases, and catalytic kinetic reactions of vapor components in each sub-process. It is essential to build up a model covering all sub-processes/mechanisms mentioned above through riser reactor and giving prompt results, especially for real-time online optimization of industrial operation. This paper aims to develop a parametric model, integrated from bottom feed nozzle to top exit of riser, that can quickly predict both hydrodynamic and kinetic characteristics throughout the riser as well as various parametric effects on production yield and selectivity. Highlights of modeling contributions in this integrated model include a mechanistic and spatial-structural model of multiple-nozzle feeding with strong interactions not only among sprays themselves but also with cross-flowing steam and catalysts, a heat transfer model between gaseous and catalyst phases, and a more-rigorously derived model of reactant conservation in the multiphase flow transport. The convective nature dominating the nozzle feeding, riser transport and kinetic reactions allows us to simplify the governing equations in this integrated model to a set of coupled first-order ordinary differential equations whose solutions can be obtained quickly via Runge-Kutta algorithm. Compared to the published plant data, the predicted VGO conversion and gasoline yield from the proposed model shows a much better agreement to those from previous parametric models, which suggests the newly-added sub-models of previously overlooked mechanisms can be quite important. Some parametric effects, such as the effect of catalyst-to-oil ratio and catalyst inlet temperature, on production yield and selectivity are further predicted. The results show that a higher CTO or catalyst temperature normally leads to higher cracking conversion, higher gasoline production and lower coke content. However, a very high inlet temperature of catalysts does cause over-cracking and lower the gasoline selectivity.
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Kumar, Ashutosh, et Robin Marlar Rajendran. « Expediting Chemical Enhanced Oil Recovery Processes with Prediction of Chemical Reaction Yield Using Machine Learning ». Dans ADIPEC. SPE, 2022. http://dx.doi.org/10.2118/211832-ms.
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Abstract Chemical enhanced oil recovery involves enormous combinations of chemicals, surfactants, etc. The reservoir properties such as temperature, capillary pressure, permeability keeps changing, making the process of identification of suitable chemicals even more challenging. Data driven modelling holds solutions for the complexity involved in identification of most suitable parameters for chemical enhanced oil recovery. Over the last decade, Artificial Intelligence has found its numerous applications in different branches of chemistry. From the selection of chemicals to the operating conditions during synthesis all can be estimated by the use of deep learning models. This paper presents yield prediction which is of high economic significance for chemical enhanced oil recovery, because they enable calculation of investment versus return. These models give us the conversion of reaction into products before performing the lab experiment. This will help chemists in selecting high performance chemicals for specific reservoirs without spending time on costly iterative chemical processes. These models require application of deep learning architectures like transformers and natural language processing techniques like tokenization for the prediction task. Encoder models like BERT are used for receiving the information on chemical reactions in text-based form for a reaction which is then combined with a regression extension layer to give us the desired reaction yield. We demonstrate our model on a HTE dataset with an excellent prediction score. Efforts are also made on the USPTO patent dataset which covers a wide variety of chemical reaction space. The USPTO patent dataset consists of almost every chemical reaction published since late 1970s till 2006. Diverse techniques starting with Multi Layer Perceptrons, Sequence to sequence modelling, Long short term memory models and finally transformers are employed for the improvement of accuracy of patent reactions. The paper presents detailed comparative results of predicting chemical reaction yield, and the enhancements that it will bring to Chemical Enhanced Oil Recovery. Reaction yield prediction models receive very little attention in spite of their enormous potential of determining the reaction conversion rates and its contribution to chemical enhanced oil recovery processes . The paper introduces a novel approach of modelling chemical reaction yield with deep learning models to the petroleum community. Unprecedented result of accuracy beyond 90% in predicting chemical reactions yield and its significance in chemical enhanced oil recovery has been proposed in the paper.
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Al-Raqom, F., J. F. Klausner, D. Hahn, J. Petrasch et S. A. Sherif. « High Temperature Fluidized Bed Reactor Kinetics With Sintering Inhibitors for Iron Oxidation ». Dans ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62808.
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High purity hydrogen is produced through a thermochemical water splitting process that utilizes iron reduction-oxidation (redox) reactions. An iron powder bed is fluidized to improve heat and mass transfer thus improving the reaction kinetics. Inert additives which act as sintering inhibitors, such as silica (SiO2) and zirconia (ZrO2), are added to the iron powder, and their effectiveness in inhibiting sintering in the oxidation step is evaluated. The influence of particle size, composition, mass fraction and bed temperature on reaction kinetics is investigated. Incorporation of zirconia in the powder bed is done by mixing it with iron powder or by coating the iron particles with a mixture of 1–3 μm and 44 μm zirconia particles. Two different batches of silica are used for blending with iron powder. The silica powder batches include particle diameters ranging from 0–45 μm and 200–300 μm. The mixing ratios of silica to iron are 0.33, 0.5, 0.67 and 0.75 by apparent volume. Experimental studies are conducted in a bench scale experimental fluidized bed reactor at bed temperatures of 450, 550, 650, 750 and 850 °C. It is verified that increasing the bed temperature and the steam residence time increases the hydrogen yield. Increasing the iron particle size reduces the specific surface area and reduces the hydrogen yield. It has been found that sintering can be completely inhibited by mixing iron with 0–45 μm silica powder and maintaining the reaction temperature below 650 °C.
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Tamaura, Y., H. Kaneko, Y. Naganuma, S. Taku, K. Ouchi et N. Hasegawa. « Simultaneous Production of H2 and O2 With Rotary-Type Solar Reactor (Tokyo Tech Model) for Solar Hybrid Fuel ». Dans ASME 2008 2nd International Conference on Energy Sustainability collocated with the Heat Transfer, Fluids Engineering, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/es2008-54282.
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The rotary-type solar reactor has been developed for solar hydrogen production with the two-step water splitting process using the reactive ceramic (Ni, Mn-ferrite). The rotary-type reactor has the rotating tubular cylinder covered on a reactive ceramic and dual reaction cells for O2-releasing and H2-generation reactions. The successive evolutions of O2 and H2 gases were observed in the O2 releasing and H2 generation reaction cells, respectively, with the prototype (small) reactor (diameter of cylinder ; 4cm). There is an upper limit for the rate of H2 gas evolution in the case of the prototype reactor because of the slow rotation rate in a small irradiation area. To confirm the practical operation of the rotary-type solar reactor with the two-step water splitting process for the simultaneous production of H2 and O2 gases, a scaled-up rotary-type solar reactor with 400cm2 of the irradiation area was fabricated (diameter; 50cm). The scaled-up reactor made of inner and outer short tubular cylinders (stainless steel) has a quartz glass window for the irradiation of reactive ceramic coated on the inner tubular cylinder (cylindrical rotor) and reaction cells were aligned in the sharing spaces between the inner and outer short tubular cylinders with gas sealing mechanisms. In the reactor, reactive ceramic coated on the inner tubular cylinder was heated up to 1800K by using the infrared imaging lamps (solar simulator) with thermal flux = 600kW/m2. The solid solution between YSZ and Ni-ferrite was used as reactive ceramic for the scaled-up reactor in order to prevent from sintering at a high temperature in the O2-releasing reaction, since the sintering of reactive ceramic resulted in lowering the yield of H2 gas evolution in the H2-generation reaction. The amounts of H2 and O2 gases evolved at the rotation rate of 0.3rpm were evaluated to 64cm3 and 30cm3 for 10min with the scaled-up rotary-type solar reactor, respectively, which were much larger than those with the prototype reactor. The simultaneous evolutions of H2 and O2 gases in the two-step water splitting process were repeated by employing the scaled-up reactor with the solid solution between YSZ and Ni-ferrite.
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Lee, Shinku, Joongmyeon Bae et Sungkwang Lim. « Numerical Thermal and Mass Analyses of Autothermal Reformer ». Dans ASME 2006 4th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2006. http://dx.doi.org/10.1115/fuelcell2006-97158.
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This paper discusses numerical analysis of heat and mass transfer characteristics in autothermal fuel reformer. Assuming local thermal equilibrium between bulk gas and surface of catalyst, one medium approach for energy equation is incorporated. Also, mass transfer between concentrations of bulk gas and near the surface of catalyst is neglected due to relatively low gas mixture velocity. For surface chemical reaction Langmuir-Hinshelwood reaction is incorporated when methane (CH4) is reformed to hydrogen-rich gases by autothermal reforming (ATR) reaction. Complete combustion, steam reforming, water gas shift and direct methane steam reforming reactions are included in the chemical reaction model. Under two operating conditions (O/C and S/C), ATR reactions are estimated from the numerical calculations. Mass, momentum, and energy equations are simultaneously calculated with chemical reactions. From the predicted results, we can estimate optimum operating conditions for high hydrogen yield.
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Burra, K. G., et A. K. Gupta. « Role of Catalyst in Solid Biomass Gasification ». Dans ASME 2016 Power Conference collocated with the ASME 2016 10th International Conference on Energy Sustainability and the ASME 2016 14th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/power2016-59039.
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Energy recovery from biomass is of pinnacle importance for renewable and sustainable energy development. Gasification techniques offer efficient and effective transformation of solid biomass into gas/liquid fuels and value added materials. This technique offers clean energy production with improved efficiency compared to other transformation techniques. Catalysts offer improved reaction efficiency and product yield. However, a robust catalyst for efficient biomass conversion to fuel gases requires close examination. Transitional metals, being inert compared to alkali metals, have shown good catalytic activity in reformation reactions, such as, high temperature and low temperature water-gas shift reactions in ammonia plants with good heat conductivity and catalytic activity. In this study catalytic conversion of pine wood chips using dry (CO2) gasification is investigated. The catalytic effects of CuO/Al2O3-SiO2 (made by wetness impregnation) on the rate of gasification, along with the gaseous species evolved during the gasification at different temperatures (700°C to 900°C) using CO2 are investigated in a semi-batch type reactor. The H2/CO ratio in the syngas and the temporal evolution of various gases evolved, their total yield, and the energy yield are quantified from the analysis of gases evolved. The results reveal significant enhancement in H2 yield and production rate along with selective dry reformation of CH4, while the effect on CO yields were unaffected. Improved yields of H2 and CH4 but no change in CO suggest the catalytic activity of CuO in enhancing the formation of high molecular weight hydrocarbons.
Rapports d'organisations sur le sujet "High-yield reaction"
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Blink, J. A., W. J. Hogam, J. Hovingh, E. R. Meier et J. H. Pitts. High-Yield Lithium-Injection Fusion-Energy (HYLIFE) reactor. Office of Scientific and Technical Information (OSTI), décembre 1985. http://dx.doi.org/10.2172/6124368.
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Pullammanappallil, Pratap, Haim Kalman et Jennifer Curtis. Investigation of particulate flow behavior in a continuous, high solids, leach-bed biogasification system. United States Department of Agriculture, janvier 2015. http://dx.doi.org/10.32747/2015.7600038.bard.
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Recent concerns regarding global warming and energy security have accelerated research and developmental efforts to produce biofuels from agricultural and forestry residues, and energy crops. Anaerobic digestion is a promising process for producing biogas-biofuel from biomass feedstocks. However, there is a need for new reactor designs and operating considerations to process fibrous biomass feedstocks. In this research project, the multiphase flow behavior of biomass particles was investigated. The objective was accomplished through both simulation and experimentation. The simulations included both particle-level and bulk flow simulations. Successful computational fluid dynamics (CFD) simulation of multiphase flow in the digester is dependent on the accuracy of constitutive models which describe (1) the particle phase stress due to particle interactions, (2) the particle phase dissipation due to inelastic interactions between particles and (3) the drag force between the fibres and the digester fluid. Discrete Element Method (DEM) simulations of Homogeneous Cooling Systems (HCS) were used to develop a particle phase dissipation rate model for non-spherical particle systems that was incorporated in a two-fluid CFDmultiphase flow model framework. Two types of frictionless, elongated particle models were compared in the HCS simulations: glued-sphere and true cylinder. A new model for drag for elongated fibres was developed which depends on Reynolds number, solids fraction, and fibre aspect ratio. Schulze shear test results could be used to calibrate particle-particle friction for DEM simulations. Several experimental measurements were taken for biomass particles like olive pulp, orange peels, wheat straw, semolina, and wheat grains. Using a compression tester, the breakage force, breakage energy, yield force, elastic stiffness and Young’s modulus were measured. Measurements were made in a shear tester to determine unconfined yield stress, major principal stress, effective angle of internal friction and internal friction angle. A liquid fludized bed system was used to determine critical velocity of fluidization for these materials. Transport measurements for pneumatic conveying were also assessed. Anaerobic digestion experiments were conducted using orange peel waste, olive pulp and wheat straw. Orange peel waste and olive pulp could be anaerobically digested to produce high methane yields. Wheat straw was not digestible. In a packed bed reactor, anaerobic digestion was not initiated above bulk densities of 100 kg/m³ for peel waste and 75 kg/m³ for olive pulp. Interestingly, after the digestion has been initiated and balanced methanogenesis established, the decomposing biomass could be packed to higher densities and successfully digested. These observations provided useful insights for high throughput reactor designs. Another outcome from this project was the development of low cost devices to measure methane content of biogas for off-line (US$37), field (US$50), and online (US$107) applications.
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Page, Martin, Bruce MacAllister, Marissa Campobasso, Angela Urban, Catherine Thomas, Clinton Cender, Clint Arnett et al. Optimizing the Harmful Algal Bloom Interception, Treatment, and Transformation System (HABITATS). Engineer Research and Development Center (U.S.), octobre 2021. http://dx.doi.org/10.21079/11681/42223.
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Harmful algal blooms (HABs) continue to affect lakes and waterways across the nation, often resulting in environmental and economic damage at regional scales. The US Army Engineer Research and Development Center (ERDC) and collaborators have continued research on the Harmful Algal Bloom Interception, Treatment, and Transformation System (HABITATS) project to develop a rapidly deployable and scalable system for mitigating large HABs. The second year of the project focused on optimization research, including (1) development of a new organic flocculant formulation for neutralization and flotation of algal cells; (2) testing and initial optimization of a new, high-throughput biomass dewatering system with low power requirements; (3) development, design, assembly, and initial testing of the first shipboard HABITATS prototype; (4) execution of two field pilot studies of interception and treatment systems in coordination with the Florida Department of Environmental Protection and New York State Department of Environmental Conservation; (5) conversion of algal biomass into biocrude fuel at pilot scale with a 33% increase in yield compared to the previous bench scale continuous-flow reactor studies; and (6) refinement of a scalability analysis and optimization model to guide the future development of full-scale prototypes.
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Cohen, Roni, Kevin Crosby, Menahem Edelstein, John Jifon, Beny Aloni, Nurit Katzir, Haim Nerson et Daniel Leskovar. Grafting as a strategy for disease and stress management in muskmelon production. United States Department of Agriculture, janvier 2004. http://dx.doi.org/10.32747/2004.7613874.bard.
Texte intégralRésumé :
The overall objective of this research was to elucidate the horticultural, pathological, physiological and molecular factors impacting melon varieties (scion) grafted onto M. cannonballus resistant melon and squash rootstocks. Specific objectives were- to compare the performance of resistant melon germplasm (grafted and non-grafted) when exposed to M. cannoballus in the Lower Rio Grande valley and the Wintergarden, Texas, and in the Arava valley, Israel; to address inter-species relationships between a Monosporascus resistant melon rootstock and susceptible melon scions in terms of fruit-set, fruit quality and yield; to study the factors which determine the compatibility between the rootstock and the scion in melon; to compare the responses of graft unions of differing compatibilities under disease stress, high temperatures, deficit irrigation, and salinity stress; and to investigate the effect of rootstock on stress related gene expression in the scion. Some revisions were- to include watermelon in the Texas investigations since it is much more economically important to the state, and also to evaluate additional vine decline pathogens Didymella bryoniae and Macrophomina phaseolina. Current strategies for managing vine decline rely heavily on soil fumigation with methyl bromide, but restrictions on its use have increased the need for alternative management strategies. Grafting of commercial melon varieties onto resistant rootstocks with vigorous root systems is an alternative to methyl bromide for Monosporascus root rot/vine decline (MRR/VD) management in melon production. Extensive selection and breeding has already produced potential melon rootstock lines with vigorous root systems and disease resistance. Melons can also be grafted onto Cucurbita spp., providing nonspecific but efficient protection from a wide range of soil-borne diseases and against some abiotic stresses, but compatibility between the scion and the rootstock can be problematic. During the first year experiments to evaluate resistance to the vine decline pathogens Monosporascus cannonballus, Didymella bryoniae, and Macrophomina phaseolina in melon and squash rootstocks proved the efficacy of these grafted plants in improving yield and quality. Sugars and fruit size were better in grafted versus non-grafted plants in both Texas and Israel. Two melons (1207 and 124104) and one pumpkin, Tetsukabuto, were identified as the best candidate rootstocks in Texas field trials, while in Israel, the pumpkin rootstock RS59 performed best. Additionally, three hybrid melon rootstocks demonstrated excellent resistance to both M. cannonballus and D. bryoniae in inoculated tests, suggesting that further screening for fruit quality and yield should be conducted. Experiments with ABA in Uvalde demonstrated a significant increase in drought stress tolerance and concurrent reduction in transplant shock due to reduced transpiration for ‘Caravelle’ plants. In Israel, auxin was implicated in reducing root development and contributing to increased hydrogen peroxide, which may explain incompatibility reactions with some squash rootstocks. However, trellised plants responded favorably to auxin (NAA) application at the time of fruit development. Gene expression analyses in Israel identified several cDNAs which may code for phloem related proteins, cyclins or other factors which impact the graft compatibility. Manipulation of these genes by transformation or traditional breeding may lead to improved rootstock cultivars. Commercial applications of the new melon rootstocks as well as the ABA and TIBA growth regulators have potential to improve the success of grafted melons in both Israel and Texas. The disease resistance, fruit quality and yield data generated by the field trials will help producers in both locations to decide what rootstock/scion combinations will be best.