14,945 research outputs found

    An Improved Oblique Asymptote Method for Parameter Identification of PV Panels

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    A single-diode model is the most important and broadly used tool for PV module design and analysis. The model has 5 parameters to be identified from the I-V characteristics curves. However, due to the lack of explicit form of I or V with the unknown 5 parameters, parameter identification is very difficult. Recent progress in PV model identification are discussed in this paper with the simulation of MATLAB against the measured data from a real PV module. An improved Oblique Asymptote Method is then proposed and compared with existing identification methods. Test results show that the proposed method achieves lower RMSE with less knowledge of I - V data points

    Online language learning to develop english reading and listening skills in university students: a pilot stuy in Hong Kong

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    The range of technological applications in different educational contexts makes it necessary for continued inquiry into online language learning (OLL), especially in relation to its impact on different learner populations whose perception and acceptance of OLL can vary across settings. This pilot study involved 66 Chinese students in a Hong Kong university and examined their OLL experience in online reading and listening activities. Results of the study suggest the easy availability of internet resources can greatly enhance students’ OLL experience, while raising four challenges in the areas of online materials development, student motivation, pedagogy-technology interface, and intercultural communicative competence. Possible ways of tackling such challenges are outlined. The article concludes with a view that successful OLL needs to be predicated on a tripartite framework of hardware, software and humanware

    Solving Linear Coupled Fractional Differential Equations by Direct Operational Method and Some Applications

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    A new direct operational inversion method is introduced for solving coupled linear systems of ordinary fractional differential equations. The solutions so-obtained can be expressed explicitly in terms of multivariate Mittag-Leffler functions. In the case where the multiorders are multiples of a common real positive number, the solutions can be reduced to linear combinations of Mittag-Leffler functions of a single variable. The solutions can be shown to be asymptotically oscillatory under certain conditions. This technique is illustrated in detail by two concrete examples, namely, the coupled harmonic oscillator and the fractional Wien bridge circuit. Stability conditions and simulations of the corresponding solutions are given

    NF-kappaB is essential for induction of CYLD, the negative regulator of NF-kappaB: evidence for a novel inducible autoregulatory feedback pathway

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    The transcription factor NF-κB regulates genes involved in inflammatory and immune responses, tumorigenesis, and apoptosis. In contrast to the pleiotropic stimuli that lead to its positive regulation, the known signaling mechanisms that underlie the negative regulation of NF-κB are very few. Recent studies have identified the tumor suppressor CYLD, loss of which causes a benign human syndrome called cylindromatosis, as a key negative regulator for NF-κB signaling by deubiquitinating tumor necrosis factor (TNF) receptor-associated factor (TRAF) 2, TRAF6, and NEMO (NF-κB essential modulator, also known as IκB kinase γ). However, how CYLD is regulated remains unknown. The present study revealed a novel autoregulatory feedback pathway through which activation of NF-κB by TNF-α and bacterium nontypeable Haemophilus influenzae (NTHi) induces CYLD that in turn leads to the negative regulation of NF-κB signaling. In addition, TRAF2 and TRAF6 appear to be differentially involved in NF-κB-dependent induction of CYLD by TNF-α and NTHi. These findings provide novel insights into the autoregulation of NF-κB activation

    Synthesis of thermochemically stable tetraphenyladamantane-based microporous polymers as gas storage materials

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    In view of environmental pollution control and purification of natural gases, developing ideal porous materials for small gas molecule (hydrogen, methane and carbon dioxide) capture is an important, pressing challenge. Accordingly, herein, three microporous organic polymers (MOP-Ad) have been synthesized by Suzuki coupling polymerization of 1,3,5,7-tetrakis(4-bromophenyl)adamantane “knots” with three phenylboronic acid-type “rods”. Gas adsorption studies of the MOP-Ad materials demonstrated their permanent porosity and good gas storage capabilities (1.07 wt% H2 at 77.3 K and 1.13 bar, 10.3 wt% CO2 and 2.4 wt% CH4 at 273.1 K and 1.13 bar), as well as moderate CO2/CH4 adsorption selectivity. Moreover, high thermal stability (up to 520 °C) and remarkable chemical resistance to strong acids and bases were found in these polymers, making them suitable candidates as gas storage materials in harsh chemical environments

    Ultrafast Nanocrystalline-TiO2(B)/Carbon Nanotube Hyperdispersion Prepared via Combined Ultracentrifugation and Hydrothermal Treatments for Hybrid Supercapacitors

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    Anisotropically grown (b-axis short) single-nano TiO2 (B), uniformly hyper-dispersed on the surface of multiwalled carbon nanotubes (MWCNT), was successfully synthesized via an in situ ultracentrifugation (UC) process coupled with a follow-up hydrothermal treatment. The uc-TiO2 (B)/MWCNT composite materials enable ultrafast Li(+) intercalation especially along the b-axis, resulting in a capacity of 235 mA h g(-1) per TiO2 (B) even at 300C (1C = 335 mA g(-1) )