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排序方式： 共有1755条查询结果，搜索用时 15 毫秒
151.
Paula Gregorio‐Godoy Jorge Pérez‐Juste Luis M. Liz‐Marzán Beatriz H. Juárez J. Ricardo Arias‐Gonzalez 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(2):376-384
Temperature changes in the vicinity of a single absorptive nanostructure caused by local heating have strong implications in technologies such as integrated electronics or biomedicine. Herein, the temperature changes in the vicinity of a single optically trapped spherical Au nanoparticle encapsulated in a thermo‐responsive poly(N‐isopropylacrylamide) shell (Au@pNIPAM) are studied in detail. Individual beads are trapped in a counter‐propagating optical tweezers setup at various laser powers, which allows the overall particle size to be tuned through the phase transition of the thermo‐responsive shell. The experimentally obtained sizes measured at different irradiation powers are compared with average size values obtained by dynamic light scattering (DLS) from an ensemble of beads at different temperatures. The size range and the tendency to shrink upon increasing the laser power in the optical trap or by increasing the temperature for DLS agree with reasonable accuracy for both approaches. Discrepancies are evaluated by means of simple models accounting for variations in the thermal conductivity of the polymer, the viscosity of the aqueous solution and the absorption cross section of the coated Au nanoparticle. These results show that these parameters must be taken into account when considering local laser heating experiments in aqueous solution at the nanoscale. Analysis of the stability of the Au@pNIPAM particles in the trap is also theoretically carried out for different particle sizes. 相似文献
152.
Tool management is an important element in the efficiency of flexible manufacturing systems. This paper improves manufacturing flexibility through integrated computer-aided process planning and scheduling with tool management. A new methodology for cutting-tool management is introduced, based on the use of alternative tools. In the methodology proposed, computer-aided process planning singles out all possible tool alternatives for each operation. The tool manager is designed to solve interferences between tool alternatives to make them compatible with scheduling. Interferences occur when the same tools are simultaneously needed in various machining operations. We propose a method to reduce tool alternatives. Thus, interferences disappear, and a collection of tool alternatives compatible with the scheduling of the system is obtained for machining operations. Tool management can use these sets of tools to plan tool changes that are necessary to face tool wear and to react to perturbations in the production system. To prove the response of our proposal, computational experiments are performed on randomly generated test problems. 相似文献
153.
Agustín Jiménez Avello Basil Mohammed Al‐Hadithi Marta Ines Gonzalez Garcia Jose Maria Lopez Rubio 《风能》2014,17(1):57-74
In this paper, a new algorithm, difference equation matrix model (DEMM), in the framework of model predictive control (MPC) is introduced. Instead of the standard dynamic matrix control (DMC), which is based upon step response method that has been used in most research works, we propose a new approach based upon a DEMM for model prediction. It has shown that DEMM has proven to be less computational and thus faster than the original DMC for real time applications. Thus, the drawbacks of DMC for online identification or adaptive design could be avoided. The control of wind turbines is carried out in order to decrease the cost of wind energy by increasing the efficiency, and thus the energy capture, or by reducing structural loading and increasing the lifetimes of the components and turbine structures. Modeling of wind turbine has been carried out. Effect of noise and disturbance on the system has been also studied. The results obtained show that the proposed DEMM minimizes the effect of the disturbance and produces an accurate and smooth control. Significant improvements in the regulation of rotor speed at high wind speeds are obtained from the proposed DEMM, where control set points are obtained ahead of the disturbance, saving the turbine of the negative effects of them and thus increasing its lifetime. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
154.
A. Mahboubi R. Moussavi-Harami R. L. Brenner L. A. Gonzalez 《Journal of Petroleum Geology》2002,25(4):465-484
The Upper Palaeocene (Thanetian) Chehel-Kaman Formation in the Kopet-Dagh Basin of NE Iran is principally composed of carbonates with minor siliciclastics and evaporites. Six stratigraphic sections were measured and more than 1,000 samples were collected for petrographic analysis, together with analyses of carbon and oxygen isotopes and trace element content. Four major carbonate lithofacies (and 13 subfacies) have been identified in previous studies and are interpretd in terms of deposition in a shallow-marine environment.
The petrographic analyses indicate that the Chehel-Kaman Formation carbonates have undergone a complex diagenetic history which includes compaction, cementation, micritization, dissolution, silicification, dolomitization, neomorphism and fracturing. δ18 O and δ13 C values in Chehel-Kaman Formation limestones range between +0.8 and -15.1%0 PDB, and -2.82 and +3.5%0 PDB, respectively. These variations are interpreted to reflect meteoric and burial diagenetic processes. Variations in trace-element concentrations (Fe and Mn increased while Na decreased) also indicated the effects of meteoric flushing. The limestones appear to have been formed at about 28°C.
Chehel-Kaman Formation dolomites were divided into d1 (finely-crystalline) and d2 (coarsely-crystalline) types. Petrographic and geochemical results indicated that the d1 dolomites formed under sabkha conditions from a parental solution at around 26°C, while d2 dolomites formed during burial diagenesis with much hotter pore fluids (around 72°C). The paragenetic sequence indicates that primary porosity decreased during early stages of diagenesis, although secondary porosity was subsequently created improving the reservoir quality of the carbonates. 相似文献
The petrographic analyses indicate that the Chehel-Kaman Formation carbonates have undergone a complex diagenetic history which includes compaction, cementation, micritization, dissolution, silicification, dolomitization, neomorphism and fracturing. δ
Chehel-Kaman Formation dolomites were divided into d1 (finely-crystalline) and d2 (coarsely-crystalline) types. Petrographic and geochemical results indicated that the d1 dolomites formed under sabkha conditions from a parental solution at around 26°C, while d2 dolomites formed during burial diagenesis with much hotter pore fluids (around 72°C). The paragenetic sequence indicates that primary porosity decreased during early stages of diagenesis, although secondary porosity was subsequently created improving the reservoir quality of the carbonates. 相似文献
155.
Jesse Daystar Trevor Treasure Carter Reeb Richard Venditti Ronalds Gonzalez Steve Kelley 《Biofuels, Bioproducts and Biorefining》2015,9(5):484-500
Mandated Environmental Protection Agency biofuel qualifications focused on greenhouse gas (GHG) emissions and fossil fuel use are limited in perspective and have the potential to encourage burden shifting. When a broader host of environmental impacts are examined, environmental trade‐offs often exist when biofuels are compared to gasoline. Multivariate analysis methods examining a wide variety of weighting value systems and methodology assumptions were used to determine process design options with the lowest overall environmental impact. A multivariate environmental analysis was applied to the dilute acid pre‐treatment process followed by enzymatic hydrolysis and the fermentation process for converting loblolly pine, eucalyptus, natural hardwood, switchgrass, and sweet sorghum biomass to ethanol. The influence of co‐product treatment method choices, inclusion of direct land‐use change, and electrical grid assumptions were examined using 16 different weighting methods to create a single score result. Biofuel system rankings based on GHG emissions following the Renewable Fuel Standards 2 (RFS2) methods were very sensitive to the co‐product treatment method, inclusion of land‐use change emissions, and energy grid assumptions. The multivariate analysis ranking was heavily influenced by other environmental impacts resulting from the production of process chemicals used in ethanol conversion. Weighting methods examined had no influence on the environmental preference ranking of the biofuel scenarios. Additionally, the biofuel ranking based on the RFS2 methodology was different than the ranking following the multivariate approach examining additional impacts. These findings demonstrate a robust approach to biofuel life cycle assessment (LCA) scenario analysis and suggest that the limited scope of the RFS2 environmental analysis could result in burden shifting. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd 相似文献
156.
157.
Parameter variations, which are increasing along with advances in process technologies, affect both timing and power. Variability must be considered at both the circuit and microarchitectural design levels to keep pace with performance scaling and to keep power consumption within reasonable limits. This article presents an overview of the main sources of variability and surveys variation-tolerant circuit and microarchitectural approaches 相似文献
158.
A.B. Sifontes G. Gonzalez J.L. Ochoa L.M. Tovar T. Zoltan E. Cañizales 《Materials Research Bulletin》2011,46(11):1794-1799
Cerium oxide (CeO2), nanoparticles were prepared using chitosan as template, cerium nitrate as a starting material and sodium hydroxide as a precipitating agent. The resultant ceria–chitosan spheres were calcined at 350 °C. The synthesized powders were characterized by, XRD, HRTEM, UV–vis, FTIR, and TG-DTA. The average size of the nanoparticles obtained was ∼4 nm and BET specific surface area ∼105 m2 g−1. Blueshifts in the ultraviolet absorption spectra have been observed in cerium oxide nanocrystallites. The band-gap was found to be 4.5 eV. The blueshifts are well explained for diameters down to less than a few nanometers by the change in the electronic band structure. 相似文献
159.
Gustavo Gonzalez María Arévalo Annalisa Chiappone Enrique Martínez Campos Candido Fabrizio Pirri Ignazio Roppolo Paula Bosch 《大分子材料与工程》2023,308(11):2300118
Light- induced polymeric 3D printing is becoming a well-established fabrication method, showing manifold advantages such as control of the local chemistry of the manufactured devices. It can be considered a green technology, since the parts are produced when needed and with minimum amount of materials. In this work 3D printing is combined with another green technology, microwave-assisted reaction, to fabricate objects of complex geometry with controllable surface properties, exploiting the presence of remaining functional groups on the surface of 3D printed specimens. In this context, surface functionalization with different amines is studied, optimizing formulations, reaction times, and avoiding surface deterioration. Then, two different applications are investigated. MW-functionalized filter-type structures have been tested against Staphylococcus aureus bacteria, showing high bactericidal activity on the surface along all areas of the complex-shaped structure. Second, a fluidic chip composed of three separated channels is 3D printed, filled with different amine-reactive dyes (dansyl and eosine derivatives), and made to react simultaneously. Complete and independent functionalization of the surface of the three channels is achieved only after 2 min of irradiation. This study demonstrates that light induced 3D printing and microwave-induced chemistry can be used together effectively, and used to produce functional devices. 相似文献
160.
Qi Zhang Jingguan Liu Qi Wei Xiangru Guo Yan Xu Ruidong Xia Linghai Xie Yan Qian Chen Sun Larry Lüer Juan Cabanillas‐Gonzalez Donal D. C. Bradley Wei Huang 《Advanced functional materials》2018,28(17)
This paper reports state‐of‐the‐art fluorene‐based yellow‐green conjugated polymer blend gain media using Förster resonant‐energy‐transfer from novel blue‐emitting hosts to yield low threshold (≤7 kW cm?2) lasers operating between 540 and 590 nm. For poly(9,9‐dioctylfluorene‐co‐benzothiadiazole) (F8BT) (15 wt%) blended with the newly synthesized 3,6‐bis(2,7‐di([1,1′‐biphenyl]‐4‐yl)‐9‐phenyl‐9H‐fluoren‐9‐yl)‐9‐octyl‐9H–carbazole (DBPhFCz) a highly desirable more than four times increase (relative to F8BT) in net optical gain to 90 cm?1 and 34 times reduction in amplified spontaneous emission threshold to 3 µJ cm?2 is achieved. Detailed transient absorption studies confirm effective exciton confinement with consequent diffusion‐limited polaron‐pair generation for DBPhFCz. This delays formation of host photoinduced absorption long enough to enable build‐up of the spectrally overlapped, guest optical gain, and resolves a longstanding issue for conjugated polymer photonics. The comprehensive study further establishes that limiting host conjugation length is a key factor therein, with 9,9‐dialkylfluorene trimers also suitable hosts for F8BT but not pentamers, heptamers, or polymers. It is additionally demonstrated that the host highest occupied and lowest unoccupied molecular orbitals can be tuned independently from the guest gain properties. This provides the tantalizing prospect of enhanced electron and hole injection and transport without endangering efficient optical gain; a scenario of great interest for electrically pumped amplifiers and lasers. 相似文献