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101.
This study addresses two key issues, stability and efficiency, of polymer solar cells based on blended poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) by demonstrating a film‐forming process that involves low‐temperature drying (?5 °C) and subsequent annealing of the active layer. The low‐temperature process achieves 4.70% power conversion efficiency (PCE) and ~1250 h storage half‐life at 65 °C, which are significant improvements over the 3.39% PCE and ~143 h half‐life of the regular room‐temperature process. The improvements are attributed to the enhanced nucleation of P3HT crystallites as well as the minimized separation of the P3HT and PCBM phases at the low drying temperature, which upon post‐drying annealing results in a morphology consisting of small PCBM‐rich domains interspersed within a densely interconnected P3HT crystal network. This morphology provides ample bulk‐heterojunction area for charge generation while allowing for facile charge transport; moreover, the P3HT crystal network serves as an immobile frame at heating temperatures less than the melting point (Tm) of P3HT, thus preventing PCBM/P3HT phase separation and the corresponding device degradation. 相似文献
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Serotonin [5-hydroxytryptamine(5-HT)] in the paraventricular nucleus (PVN) of rats has a suppressive effect on feeding behavior and causes a selective decrease in carbohydrate ingestion, specifically at the onset of the natural (dark) feeding period. Studies conducted here provide further evidence for this phenomena, showing a similar dose-related decrease in carbohydrate ingestion at dark onset after PVN injection of 5-HT or of the agonists, d-norfenfluramine or fluoxetine, which act through endogenous 5-HT. To further characterize the effects of this indoleamine on the macrostructure of feeding, a computer-automated data acquisition system was used to analyze macronutrient feeding patterns in freely feeding animals maintained on the pure diets of protein, carbohydrate, and fat. Results indicate that PVN administration of 5-HT at dark onset decreases intake of the carbohydrate nutrient by decreasing meal size, feeding time, and feeding rate for this nutrient and increasing the satiating effect of carbohydrate. These effects, which occur specifically during the first meal after injection, are opposite those seen after peripheral administration of the 5-HT receptor antagonist, metergoline. This drug stimulates feeding through a selective increase in carbohydrate intake, characterized by an increase in meal size, percent composition, and feeding time for this nutrient and a decrease in the satiety ratio for carbohydrate. These results implicate the serotonergic system in the termination of carbohydrate-rich meals that are prevalent during the early hours of the natural feeding cycle. 相似文献
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Motivated by the scale and complexity of simulating large-scale networks, recent research has focused on hybrid fluid/packet simulators, where fluid models are combined with packet models in order to reduce simulation complexity as well as to track dynamics of end-sources accurately. However, these simulators still need to track the queuing dynamics of network routers, leading to considerable simulation complexity in a large-scale network model. In this paper, we propose a new hybrid simulator – FluNet – where queueing dynamics are not tracked, but instead, an equivalent rate-based model is used. The FluNet simulator is predicated on a fast-queueing regime at bottleneck routers, where the queue length fluctuates on a faster time-scale than end systems. This allows us to simulate large-scale systems, where the simulation “time step-size” is governed only by the time-scale of the end-systems, and not by that of the intermediate routers; whereas a queue-tracking based fluid simulator would require decreasingly smaller step-sizes as the system scale size increases. We validate our model using a ns-2 based implementation. Our results indicate a good match between packet systems and the associated FluNet system. 相似文献
106.
Applying a critical approach to investigate barriers to digital inclusion and online social networking among young people with disabilities 下载免费PDF全文
Lareen Newman Kathryn Browne‐Yung Parimala Raghavendra Denise Wood Emma Grace 《Information Systems Journal》2017,27(5):559-588
Despite the seeming ubiquity of young people's Internet use, there are still many for whom access to the Internet and online social networking remains inequitable and patterned by disadvantage. The connection between information technology and young people with disabilities is particularly under‐researched. This article contributes to the field of critical information systems research by exposing significant barriers and facilitators to Internet accessibility for young people with disabilities. It uses Bourdieu's critical theory to explore how the unequal distribution of resources shapes processes of digital inclusion for young people with disabilities. It highlights access needs and experiences that are both disability and non‐disability related. The article draws on interviews in South Australia with 18 young people aged 10–18 years with a physical disability (such as cerebral palsy) or acquired brain injury and with 17 of their family members. Interviews evaluated participants' and parents' reflections on the benefits of a home‐based, goal‐oriented intervention to increase the young person's Internet use for social participation purposes. The Bourdieuian analysis demonstrated how varying levels of accrued individual and family offline capital resources are related to digital/online resources and disability‐specific online resources. This revealed how unequal resources of capital can influence technology use and hence digital inclusion for young people with disabilities. Our study demonstrates that young people with particular types of disabilities require intensive, personalised and long‐term support from within and beyond the family to ‘get online’. We conclude that Internet studies need to more frequently adopt critical approaches to investigate the needs of users and barriers to information technology use within sub‐groups, such as young people with disabilities. © 2016 John Wiley & Sons Ltd 相似文献
107.
Henry Medina Yung‐Chang Lin Chuanhong Jin Chun‐Chieh Lu Chao‐Hui Yeh Kun‐Ping Huang Kazu Suenaga John Robertson Po‐Wen Chiu 《Advanced functional materials》2012,22(10):2123-2128
Conventional methods to prepare large‐area graphene for transparent conducting electrodes involve the wet etching of the metal catalyst and the transfer of the graphene film, which can degrade the film through the creation of wrinkles, cracks, or tears. The resulting films may also be obscured by residual metal impurities and polymer contaminants. Here, it is shown that direct growth of large‐area flat nanographene films on silica can be achieved at low temperature (400 °C) by chemical vapor deposition without the use of metal catalysts. Raman spectroscopy and TEM confirm the formation of a hexagonal atomic network of sp2‐bonded carbon with a domain size of about 3–5 nm. Further spectroscopic analysis reveals the formation of SiC between the nanographene and SiO2, indicating that SiC acts as a catalyst. The optical transmittance of the graphene films is comparable with transferred CVD graphene grown on Cu foils. Despite the fact that the electrical conductivity is an order of magnitude lower than CVD graphene grown on metals, the sheet resistance remains 1–2 orders of magnitude better than well‐reduced graphene oxides. 相似文献
108.
Wang D.X. Yung E.K.N. Chen R.S. Lau P.Y. 《Antennas and Propagation, IEEE Transactions on》2007,55(7):1970-1980
A generalized volume integral equation method is formulated for electromagnetic scattering by arbitrarily shaped complex bodies with inhomogeneous bi-isotropy. Based on the volume equivalence principle, the integral equations are represented in terms of a pair of coupled bi-isotropic polarized volume electric and magnetic flux densities. Reduction of the integral equations into the corresponding matrix equations is obtained using the method of moments (MoM) combined with the tetrahedral mesh. In the MoM solution, the three-dimensional solenoidal function is incorporated as the basis function defined over each tetrahedral element and the details of implementation, particularly the treatment of integral singularities, will be elucidated. The efficiency and accuracy of the proposed method are validated by illustratively supported examples. 相似文献
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Yung‐Pin Tsai Ruey‐an Doong Jhih‐Ci Yang Ying‐Jie Wu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(7):949-956
BACKGROUND: This study compared the removal of aqueous Cr(VI) by multi‐walled carbon nanotubes (CNTs) modified by sulfuric acid, titanium dioxide (TiO2) and composite of CNTs and TiO2. RESULTS: More than 360 h contact time was needed to completely adsorb 3 mg L?1 of Cr(VI) by CNTs, indicating that the rate of adsorption by CNTs alone was slow. The reaction time approaching equilibrium depended on the Cr(VI) concentration. XPS analysis of CNTs after adsorbing Cr(VI) showed that the Cr(VI) on the surface of CNTs was partially reduced to Cr(III). A 3 mg L?1 solution of Cr(VI) was fully photocatalyzed by commercial TiO2 (Degussa P25) in less than 0.5 h under UV irradiation. Unlike P25, reduction by another commercial TiO2 (Hombikat UV100) took 4 h and more than 2 h were necessary for reduction by the composite. Thus the efficiency of Cr(VI) photo‐reduction by the composite was lower than by TiO2, but higher than that by CNTs. XPS analysis of TiO2 and composite showed the existence of both Cr(VI) and Cr(III) on their surfaces. CONCLUSION: In contrast to TiO2, the reduction rate of aqueous Cr(VI) using CNTs as adsorbent was slow. P25 had a markedly higher photocatalytic efficiency than the composite or UV100 alone. Using P25 to reduce aqueous Cr(VI) has a higher potential for practical application. The diameters of TiO2 and CNTs and the ratio of TiO2/CNTs are key problems in the preparation of TiO2/CNTs composite. Copyright © 2011 Society of Chemical Industry 相似文献