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排序方式: 共有46条查询结果,搜索用时 15 毫秒
1.
Solvent vapor treatment controls surface wettability in PMMA femtosecond-laser-ablated microchannels
Carmela De Marco Shane M. Eaton Rebeca Martinez-Vazquez Stefano Rampini Giulio Cerullo Marinella Levi Stefano Turri Roberto Osellame 《Microfluidics and nanofluidics》2013,14(1-2):171-176
A solvent vapor treatment was applied to femtosecond-laser-ablated microchannels in PMMA to selectively restore the original hydrophilic wetting behavior of the pristine surface. The hydrophobic surface of the microchannels from the submicron porosity induced by ablation becomes smoother and more transparent after the treatment. This simple and low-cost method, together with suitable masking, can produce wettability patterns that may be exploited to develop passive microfluidic elements such as valves and mixers. 相似文献
2.
J.C. Kuijper X. Raepsaet J.B.M. de Haas W. von Lensa U. Ohlig H.-J. Ruetten H. Brockmann F. Damian F. Dolci W. Bernnat J. Oppe J.L. Kloosterman N. Cerullo G. Lomonaco A. Negrini J. Magill R. Seiler 《Nuclear Engineering and Design》2006,236(5-6):615-2004
The high-temperature gas-cooled reactor (HTGR) appears as a good candidate for the next generation of nuclear power plants. In the “HTR-N” project of the European Union Fifth Framework Program, analyses have been performed on a number of conceptual HTGR designs, derived from reference pebble-bed and hexagonal block-type HTGR types. It is shown that several HTGR concepts are quite promising as systems for the incineration of plutonium and possibly minor actinides.These studies were mainly concerned with the investigation and intercomparison of the plutonium and actinide burning capabilities of a number of HTGR concepts and associated fuel cycles, with emphasis on the use of civil plutonium from spent LWR uranium fuel (first generation Pu) and from spent LWR MOX fuel (second generation Pu). Besides, the “HTR-N” project also included activities concerning the validation of computational tools and the qualification of models. Indeed, it is essential that validated analytical tools are available in the European nuclear community to perform conceptual design studies, industrial calculations (reload calculations and the associated core follow), safety analyses for licensing, etc., for new fuel cycles aiming at plutonium and minor actinide (MA) incineration/transmutation without multi-reprocessing of the discharged fuel.These validation and qualification activities have been centred round the two HTGR systems currently in operation, viz. the HTR-10 and the HTTR. The re-calculation of the HTTR first criticality with a Monte Carlo neutron transport code now yields acceptable correspondence with experimental data. Also calculations by 3D diffusion theory codes yield acceptable results. Special attention, however, has to be given to the modelling of neutron streaming effects. For the HTR-10 the analyses focused on first criticality, temperature coefficients and control rod worth. Also in these studies a good correspondence between calculation and experiment is observed for the 3D diffusion theory codes. 相似文献
3.
Artificial Intelligence (AI) is the science of building computer devices and software applications that mimic many of the characteristics that we associate with human behaviour, such as the ability to reason, see, learn, solve problems, understand languages, and so on. AI systems include natural languages, robotics, expert systems and neural networks. This article focuses on neural networks, which can be designed for problems that arise at any managerial level and may be used to predict the occurrence of fraud. 相似文献
4.
Tetiana Borzda Christoph Gadermaier Natasa Vujicic Peter Topolovsek Milos Borovsak Tomaz Mertelj Daniele Viola Cristian Manzoni Eva A. A. Pogna Daniele Brida Maria Rosa Antognazza Francesco Scotognella Guglielmo Lanzani Giulio Cerullo Dragan Mihailovic 《Advanced functional materials》2015,25(22):3351-3358
The 2D semiconductor MoS2 in its mono‐ and few‐layer form is expected to have a significant exciton binding energy of several 100 meV, suggesting excitons as the primary photoexcited species. Nevertheless, even single layers show a strong photovoltaic effect and work as the active material in high sensitivity photodetectors, thus indicating efficient charge carrier photogeneration. Here, modulation spectroscopy in the sub‐ps and ms time scales is used to study the photoexcitation dynamics in few‐layer MoS2. The results suggest that the primary photoexcitations are excitons that efficiently dissociate into charges with a characteristic time of 700 fs. Based on these findings, simple suggestions for the design of efficient MoS2 photovoltaic and photodetector devices are made. 相似文献
5.
Virgili T Grancini G Molotokaite E Suarez-Lopez I Rajendran SK Liscio A Palermo V Lanzani G Polli D Cerullo G 《Nanoscale》2012,4(7):2219-2226
This article is devoted to the exploration of the benefits of a new ultrafast confocal pump-probe technique, able to study the photophysics of different structured materials with nanoscale resolution. This tool offers many advantages over standard stationary microscopy techniques because it directly interrogates excited state dynamics in molecules, providing access to both radiative and non-radiative deactivation processes at a local scale. In this paper we present a few different examples of its application to organic semiconductor systems. The first two are focussed on the study of the photophysics of phase-separated polymer blends: (i) a blue-emitting polyfluorene (PFO) in an inert matrix of PMMA and (ii) an electron donor polythiophene (P3HT) mixed with an electron acceptor fullerene derivative (PCBM). The experimental results on these samples demonstrate the capability of the technique to unveil peculiar interfacial dynamics at the border region between phase-segregated domains, which would be otherwise averaged out using conventional pump-probe spectroscopy. The third example is the study of the photophysics of isolated mesoscopic crystals of the PCBM molecule. Our ultrafast microscope could evidence the presence of two distinctive regions within the crystals. In particular, we could pinpoint for the first time areas within the crystals showing photobleaching/stimulated emission signals from a charge-transfer state. 相似文献
6.
Picosecond Capture of Photoexcited Electrons Improves Photovoltaic Conversion in MAPbI3:C70‐Doped Planar and Mesoporous Solar Cells
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Saba Gharibzadeh Franco Valduga de Almeida Camargo Cristina Roldán‐Carmona Grégoire Clément Gschwend Jorge Pascual Ramón Tena‐Zaera Giulio Cerullo Giulia Grancini Mohammad Khaja Nazeeruddin 《Advanced materials (Deerfield Beach, Fla.)》2018,30(40)
In this work, solar cells based on methylammonium lead iodide (MAPbI3) doped in solution with C70 fullerene in a mesoporous as well as planar electron‐transporting layer (ETL)‐free architecture are realized, showcasing in the latter case a record efficiency of 15.7% and an improved open‐circuit voltage (VOC). Contrary to the bulk heterojunction previously reported, the C70 molecules do not phase segregate and they are rather finely dispersed in the perovskite film, possibly infiltrating at the grain boundaries, while assisting the growth of a highly uniform perovskite layer. By means of time‐resolved femtosecond‐to‐nanosecond optical spectroscopy, with an extended spectral coverage, it is observed that electrons photogenerated in the perovskite are transferred to C70 with a time constant of 20 ps. Despite being captured by C70, electrons are not deeply trapped and can potentially bounce back into the perovskite, as suggested by the high fill factor and enhanced VOC of the MAPbI3:C70 solar cells, especially in the case of the ETL‐free device configuration. 相似文献
7.
Giuseppe M. Patern Luca Moretti Alex J. Barker Qiang Chen Klaus Müllen Akimitsu Narita Giulio Cerullo Francesco Scotognella Guglielmo Lanzani 《Advanced functional materials》2019,29(21)
In the last two decades, the three‐beam pump–push–probe (PPP) technique has become a well‐established tool for investigating the multidimensional configurational space of a molecule, as it permits disclosure of precious information about the multiple and often complex deactivation pathways of the excited molecule. From the spectroscopic point of view, such a tool has revealed details about the efficiency of charge pair generation and conformational relaxation in π‐conjugated molecules and macromolecules. In addition, PPP is effectively utilized for modulating the gain signal in conjugated materials by taking advantage of the spectral overlap between stimulated emission and charge absorption in those systems. However, the relatively low stability of conjugated polymers under intense photoexcitation is a crucial limitation for their real employment in plastic optical fibers (POFs) and for signal control applications. Herein, the role of PPP for achieving ultrafast all‐optical switching in π‐conjugated systems is highlighted. Furthermore, new experimental data on optical switching of a newly synthesized nanographene molecule, namely dibenzo[hi,st]ovalene (DBOV), is reported. The superior environmental and photostability of DBOV and, in general, of graphene nanostructures can represent a great advantage for their effective applications in POFs and information and communications technology. 相似文献
8.
9.
We present an ultrafast transient absorption spectroscopy system in the visible combining high-sensitivity broadband detection with extreme temporal resolution. The instrument is based on an ultrabroadband sub-10 fs optical parametric amplifier coupled to an optical multichannel analyzer with fast electronics, enabling single-shot detection at 1 kHz repetition rate. For a given pump-probe delay tau, we achieve a differential transmission (DeltaTT) sensitivity of the order of 10(-4) over the lambda(pr)=490-720 nm probe wavelength range by averaging over 1000 shots, allowing the acquisition of complete two-dimensional DeltaTT (lambda(pr),Tau) maps within a few minute measurement time. We present application examples highlighting the capability of this instrument to observe ultrafast dynamical processes, follow impulsively excited vibrational motions with frequency as high as 3000 cm(-1) (11 fs period), and determine the probe wavelength dependence of amplitude and phase of the oscillations. 相似文献
10.