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排序方式: 共有9127条查询结果,搜索用时 15 毫秒
961.
Matthias Böhm Marcus Einert Christian Suchomski Bernd M. Smarsly Stephen Mutisya Massimo F. Bertino 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(8):1566-1574
Macroporous TiO2 (anatase) thin films are fabricated by an all low‐temperature process in which substrates are dip‐coated in suspensions of mixed anatase nanoparticles and polystyrene beads, and the templating agents are removed by ultraviolet (UV) irradiation at a temperature below 50 °C. Scanning electron microscopy (SEM) and Raman spectroscopy show that the templating polymer beads are removed by UV irradiation combined with the photocatalytic activity of TiO2. X‐Ray diffraction reveals that nanoparticle growth is negligible in UV irradiated films, while nanoparticle size increases by almost 10 times in calcined films that are prepared for comparison. The macroporous films are prepared on FTO‐(fluorine‐doped tin oxide) coated glass and ITO (indium tin oxide) coated flexible plastics and thereby used as working electrodes. In both cases, the films are electrochemically addressable, and cyclic voltammetry is consistent with the response of bulk TiO2 for calcined films and of nanoscale‐TiO2 for UV‐irradiated films. 相似文献
962.
Jameson L. Toole Carlos Herrera-Yaqüe Christian M. Schneider Marta C. González 《Journal of the Royal Society Interface》2015,12(105)
Studies using massive, passively collected data from communication technologies have revealed many ubiquitous aspects of social networks, helping us understand and model social media, information diffusion and organizational dynamics. More recently, these data have come tagged with geographical information, enabling studies of human mobility patterns and the science of cities. We combine these two pursuits and uncover reproducible mobility patterns among social contacts. First, we introduce measures of mobility similarity and predictability and measure them for populations of users in three large urban areas. We find individuals'' visitations patterns are far more similar to and predictable by social contacts than strangers and that these measures are positively correlated with tie strength. Unsupervised clustering of hourly variations in mobility similarity identifies three categories of social ties and suggests geography is an important feature to contextualize social relationships. We find that the composition of a user''s ego network in terms of the type of contacts they keep is correlated with mobility behaviour. Finally, we extend a popular mobility model to include movement choices based on social contacts and compare its ability to reproduce empirical measurements with two additional models of mobility. 相似文献
963.
In the present article, we analyze a d36-effect piezoelectric torsion transducer following the Saint-Venant torsion theory taking the electrical field into account. A representation of the stress function, the electric potential, and the warping function are derived and solved with finite differences. Then, the one-dimensional governing equations at the structural beam level, including the constitutive relations as well as the balance equations for the dynamics of the transducer, are presented. The axial moment and the total charge are computed as functions of the rate of twist and the applied potential difference. As an example, a cantilevered transducer is studied. 相似文献
964.
Liquid–Liquid Diffusion‐Assisted Crystallization: A Fast and Versatile Approach Toward High Quality Mixed Quantum Dot‐Salt Crystals
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Marcus Adam Zhiyu Wang Aliaksei Dubavik Gordon M. Stachowski Christian Meerbach Zeliha Soran‐Erdem Christin Rengers Hilmi Volkan Demir Nikolai Gaponik Alexander Eychmüller 《Advanced functional materials》2015,25(18):2638-2645
Here, a new, fast, and versatile method for the incorporation of colloidal quantum dots (QDs) into ionic matrices enabled by liquid–liquid diffusion is demonstrated. QDs bear a huge potential for numerous applications thanks to their unique chemical and physical properties. However, stability and processability are essential for their successful use in these applications. Incorporating QDs into a tight and chemically robust ionic matrix is one possible approach to increase both their stability and processability. With the proposed liquid–liquid diffusion‐assisted crystallization (LLDC), substantially accelerated ionic crystallization of the QDs is shown, reducing the crystallization time needed by one order of magnitude. This fast process allows to incorporate even the less stable colloids including initially oil‐based ligand‐exchanged QDs into salt matrices. Furthermore, in a modified two‐step approach, the seed‐mediated LLDC provides the ability to incorporate oil‐based QDs directly into ionic matrices without a prior phase transfer. Finally, making use of their processability, a proof‐of‐concept white light emitting diode with LLDC‐based mixed QD‐salt films as an excellent color‐conversion layer is demonstrated. These findings suggest that the LLDC offers a robust, adaptable, and rapid technique for obtaining high quality QD‐salts. 相似文献
965.
Semiconductor Nanocrystals: Liquid–Liquid Diffusion‐Assisted Crystallization: A Fast and Versatile Approach Toward High Quality Mixed Quantum Dot‐Salt Crystals (Adv. Funct. Mater. 18/2015)
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966.
Predicting the Thermal Conductivity of AlSi/Polyester Abradable Coatings: Effects of the Numerical Method 总被引:1,自引:0,他引:1
Rodolphe Bolot Jean-Louis Seichepine Jiang Hao Qiao Christian Coddet 《Journal of Thermal Spray Technology》2011,20(1-2):39-47
The final target of this study is to achieve a better understanding of the behavior of thermally sprayed abradable seals such as AlSi/polyester composites. These coatings are used as seals between the static and the rotating parts in aero-engines. The machinability of the composite coatings during the friction of the blades depends on their mechanical and thermal effective properties. In order to predict these properties from micrographs, numerical studies were performed with different software packages such as OOF developed by NIST and TS2C developed at the UTBM. In 2008, differences were reported concerning predictions of effective thermal conductivities obtained with the two codes. In this article, a particular attention was paid to the mathematical formulation of the problem. In particular, results obtained with a finite difference method using a cell-centered approach or a nodal formulation allow explaining the discrepancies previously noticed. A comparison of the predictions of the computed effective thermal conductivities is thus proposed. This study is part of the NEWAC project, funded by the European Commission within the 6th RTD Framework programm (FP6). 相似文献
967.
A physically based hourly radiation model for inclined planes is presented. The sky diffuse component is derived from typical radiance patterns for clear and overcast conditions, taking anisotropic effects into account. New developments are also proposed for the ground reflected component, in order to supplement the usual isotropic assumption. The proposed radiation model, called CDRS, may be used with different input data combinations, the relative advantages of which are discussed. CDRS outputs are in good agreement with four clear sky sophisticated spectral data sets when wideband as well as spectral irradiances are input. When compared to measured data, CDRS also appears to perform well during clear and overcast sky conditions. Good results from only two cloudy days are also obtained, but more systematic tests should be conducted in this case. All the five other selected engineering models exhibit some degree of inaccuracy for certain slope/azimuth/cloudiness combinations. Particularly, the ASHRAE and DOE-2 models give catastrophic results for southward vertical surfaces during overcast conditions. This unexpected result may lead to important bias in building energy consumption simulations. Finally, some experimental and computational problems are pointed out. These could interfere with models accuracy comparison in validation studies. 相似文献
968.
Vincent Larivière Etienne Vignola-Gagné Christian Villeneuve Pascal Gélinas Yves Gingras 《Scientometrics》2011,87(3):483-498
Using the entire population of professors at universities in the province of Quebec (Canada), this article analyzes the relationship
between sex and research funding, publication rates, and scientific impact. Since age is an important factor in research and
the population pyramids of men and women are different, the role of age is also analyzed. The article shows that, after they
have passed the age of about 38, women receive, on average, less funding for research than men, are generally less productive
in terms of publications, and are at a slight disadvantage in terms of the scientific impact (measured by citations) of their
publications. Various explanations for these differences are suggested, such as the more restricted collaboration networks
of women, motherhood and the accompanying division of labour, women’s rank within the hierarchy of the scientific community
and access to resources as well as their choice of research topics and level of specialization. 相似文献
969.
Christopher J. Stapels Erik B. JohnsonXiao J. Chen Thomas H. PrettymanEric R. Benton James F. Christian 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,652(1):342-346
The compact, robust nature of the CMOS solid-state photomultiplier (SSPM) allows the creation of small, low-power scintillation-based radiation measurement devices. Monitoring space radiation including solar protons and secondary neutrons generated from high-energy protons impinging on spacecraft is required to determine the dose to astronauts. Small size and highly integrated design are desired to minimize consumption of payload resources.RMD is developing prototype radiation measurement and personal dosimeter devices using emerging scintillation materials coupled to CMOS SSPM’s for multiple applications. Spectroscopic measurements of high-energy protons and gamma-rays using tissue-equivalent, inorganic scintillators coupled to SSPM devices demonstrate the ability of an SSPM device to monitor the dose from proton and heavy ion particles, providing real time feedback to astronauts. Measurement of the dose from secondary neutrons introduces additional challenges due to the need to discriminate neutrons from other particle types and to accurately determine their energy deposition. We present strategies for measuring neutron signatures and assessing neutron dose including simulations of relevant environments and detector materials. 相似文献
970.
Mickel McClish Purushottam DokhaleJames Christian Christopher StapelsErik Johnson Frank AugustineKanai S. Shah 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,652(1):264-267
We have designed a 5×5 mm2 position sensitive solid-state photomultiplier (PS-SSPM) using a complementary metal-oxide-semiconductor (CMOS) process that provides imaging capability on the micro-pixel level. The PS-SSPM has 11,664 micro-pixels total, with each having an active area and micro-pixel pitch of 30×30 μm2 and 44.3 μm, respectively. The PS-SSPM was then examined for its performance characteristics such as its energy and spatial resolution, and LYSO scintillator array imaging capabilities. When coupled to 5×5×3 mm3 LYSO, the energy resolution at 511 keV (22Na) was measured as a function of bias, and corrected for the PS-SSPM non-linear output. The resolution is 14% (FWHM) at 511 keV with 30 V bias. The LYSO coincidence timing resolution was 9.4 ns (FWHM) at 511 keV. Spatial resolution studies were conducted using a focused (∼30 μm beam spot diameter) pulsed 635 nm diode laser. Scintillator array imaging studies were conducted at 511 keV using a 6×6 LYSO array, having 500 μm pixels (530 μm pitch) and 5 mm tall. 相似文献