255 research outputs found
Beyond Lesson Studies and Design Experiments: Using theoretical tools in practice and finding out how they work
Full text linkThis paper aims to illustrate how fruitful insights into the link between school teaching practice and student learning outcomes can be theoretically grounded by the variation theory from the field of phenomenography; and from this framework demonstrate how a 'pedagogy of awareness' can be implemented in the classroom. In this study, five teachers and 162 students at Primary Four level of school education in Hong Kong participated and the practice of the 'learning study' was adopted. By comparing the results of pre- and posttests, a significant gain was observed in the students learning outcomes.
Ferrocenyl ligands for atom transfer radical polymerization
No full textOne of the most effective methods for precision polymer synthesis is controlled radical polymerization, in which atom transfer radical polymerization (ATRP) is an excellent example. A series of ferrocene derivatives were prepared and applied for polymerization of methyl methacrylate (MMA). Formulation by combination of the ferrocenyl ligands and coprous bromide could catalyze ATRP, of which the performance is strongly dependent on the substituents on the Cp rings as well as the reaction condition. The redox potentials of the ferrocene derivatives reveal that the lower E1/2, the better performance on ATRP. The results also showed that the molecular structures of the catalysts determined by X-ray crystallography also play an important role for the performance of the polymerization
Radio transceiver architectures and design issues for wideband cellular systems
No full textAs the era of content driven and rich multimedia mobile applications evolves, the need arises for efficient wideband cellular systems. This paper presents modern radio transceiver architectures used in 3G cellular handsets, such as EDGE, cdma2000, and WCDMA-HSDPA. This includes future ΣΔ-ADC based receiver and mostly all-digital transmitter architectures, which are being enabled by the current aggressive scaling of CMOS technology and the push toward full radio systcm-on-chip (SoC) integration. Furthermore, the paper focuses on discussing some key RF system design issues, and their influence on the choice of architecture used for a specific cellular radio-chipset solution.Elliott MR, 2004, IEEE J SOLID-ST CIRC, V39, P2190, DOI 10.1109-JSSC.2004.836340; KACSMAN D, IEEE RFIC S 2005, P281; MUNKER C, IEEE RFIC S 2005, P265; Neuvo Y., 2004, IEEE INT SOL STAT CI, P32; *QUALC INC, 2001, EC WIR MOB DAT; Razavi B, 1997, IEEE T CIRCUITS-II, V44, P428, DOI 10.1109-82.592569; SCHELL S, 2000, TROP INC PRES FEB 22; Sowlati T, 2004, IEEE J SOLID-ST CIRC, V39, P2179, DOI 10.1109-JSSC.2004.836335; TAMURA M, IEEE RFIC S 2005, P269; van Veldhoven RHM, 2003, IEEE J SOLID-ST CIRC, V38, P2069, DOI 10.1109-JSSC.2003.819165; Waite H, 2004, IEEE J SOLID-ST CIRC, V39, P1175, DOI 10.1109-JSSC.2004.829965; ZHOU J, IEEE RFIC S 2005, P1710
Painted plasters of Malaccan buildings
No full textIn order to characterize pigments and binder used in some painted layers of the external walls of the Cheng Hoon Teng temple (Melaka) some analysis have been carried out such as optical and electron microscopy, XRF and FTIR. Results show that the binder was made mixing calcic lime with milk, while as pigment was used natural ultramarine blue that is “Lapislazuli”. A very expensive pigment that in Europe has been replaced by artificial ultramarine since 1825. Analyses show also that use of a blue pigment was an intentional choice. Furthermore, use of natural ultramarine underline importance of this temple and suggest a symbolic meaning for this color
A CeO <sub>2</sub> (100) surface reconstruction unveiled by in situ STEM and particle swarm optimization techniques
Full text linkThe reconstruction of the polar CeO
(100) surface has been a subject of long-standing debates due to its complexity and the limited availability of experimental data. Herein, we successfully reveal a CeO
(100)–(4 × 6) surface reconstruction by combining in situ spherical aberration–corrected scanning transmission electron microscopy, density functional theory calculations, and a particle swarm optimization–based algorithm for structure searching. We have further elucidated the stabilizing mechanism of the reconstructed structure, which involves the splitting of the filled Ce(4f) states and the mixing of the lower-lying ones with the O(2p) orbitals, as evidenced by the projected density of states. We also reveal that the surface chemisorption properties toward water molecules, an important step in numerous heterogeneous catalytic reactions, are enhanced. These insights into the distinct properties of ceria surface pave the way for performance improvements of ceria in a wide range of applications..W. acknowledges the financial support of the national natural Science Foundationof china (51971202, 52025011, and 92045301), the Key Research and development Programof Zhejiang Province (2021c01003), the Zhejiang Provincial natural Science Foundation ofchina (ld19B030001), the Shanxi- Zheda institute of Advanced Materials and chemicalengineering, and the Fundamental Research Funds for the central Universities. W.Y.acknowledges the financial support of the national natural Science Foundation of china(52171019), the Zhejiang Provincial natural Science Foundation of china (lR23B030004), andthe national Key Research and development Program (2022YFA1505500). Z.-K.h.acknowledges the financial support of the national nature Science Foundation of china(22302173). M.v.G.-P. thanks the support of the Grant Pid2021-128915nB- i00 funded by Mcin/Aei/10.13039/501100011033 and by “eRdF A way of making europe.” Author contributions:conceptualization: S.l., Z.-K.h., W.Y.., h.Y., M.v.G.-P., and Y.W. Methodology: K.Z., G.l., S.l.,Z.- K.h., W.Y., and Y.W. investigation: K.Z., G.l., c.Z., S.c., and h.Y. visualization: K.Z., G.l., Z.-K.h.,Y.J., h.Y., and Y.W. Supervision: S.l., Z.-K.h., W.Y., h.Y., M.v.G.-P., and Y.W. Writing—original draft:K.Z. and Y.W. Writing—review and editing: K.Z., G.l., S.d.l., Z.- K.h., Y.J., W.Y., h.Y., M.v.G.- P., andY.W. Funding acquisition: Z.-K.h., W.Y., and Y.W. data curation: W.Y. validation: G.l., S.l., W.Y.,h.Y., and Y.W. Project administration: Z.-K.h., W.Y., and Y.W. Formal analysis: K.Z., G.l., S.l.,Z.- K.h., h.Y. Resources: S.l. and Y.W. Software: S.l
Diabetes promotes an inflammatory macrophage phenotype and atherosclerosis through acyl-CoA synthetase 1
Full text linkAuthor contributions: J.E.K., L.B., C.N.S., and K.E.B. designed research; J.E.K., F.K., S.B., M.M.A., A.V.-G., T.V., L.O.L., L.B., K.R.B., and S.P.-P. performed research; W.Y., A.C., S.S., T.N.W., J.W.H., and R.A.C. contributed new reagents/analytic tools; J.E.K., L.B., S.S., S.P., and K.E.B. analyzed data; and J.E.K. and K.E.B. wrote the paper
Computing the vertical density and seismic velocity profiles from multi-angle reflection data: Error analysis
No full textNumerical models were used to recursively compute the density profile and the seismic velocity profile of three different artificial models of the underground from primary reflection images obtained from multi-angle incident plane wave reflection data. The aim is to investigate the effect of errors in the obtained primary reflection amplitudes on the recursive construction of the vertical density-velocity profiles. The reflection coefficients needed for the computations were obtained by solving the Marchenko equation for different angles of incidence. The recursive computation shows errors occur in every layer, but the error does not necessarily grow with each step. This implies the error does not propagate into the recursive scheme. Adding a random error to the reflection coefficients yielded results in a greater error in each individual layer with respect to the values obtained without an added error. Using a too large angle of incidence can result in too few primary events in the autofocused data, distorting the computed values.Applied Geophysics and PetrophysicsGeoscience & EngineeringCivil Engineering and Geoscience
Investigation on Fault-ride Through Methods for VSC-HVDC Connected Offshore Wind Farms
No full textRecently, there has been a fast development and deployment of wind energy to meet the increasing electrical power demand and to limit the use of fossil fuels. More and more wind farms are planned far from shore because of good wind condition and less visual impact. This is so called offshore wind farm (OWF). In such a situation, high voltage direct current (HVDC) transmission is a favorable option for integrating these OWFs to the onshore grid, because HVDC, compared with high voltage alternating current (HVAC), has lower losses and higher transmission efficiency. For HVDC transmission, voltage source converter (VSC) has some advantages over current source converter (CSC), e.g. independent control of active power and reactive power, bidirectional power transfer for fixed voltage polarity. When a fault occurs at the onshore ac grid which connects OWFs via VSC-HVDC, the active power cannot be fully transmitted to onshore grid, while OWFs still produce active power. The imbalanced power will increase the HVDC-link voltage. This increased dc voltage will lead to high electrical stress for the insulated gate bipolar transistor (IGBT) modules, capacitors as well as cables, and even damage them. There have been different proposed methods to deal with this problem, e.g. chopper controlled resistor, wind turbine generator power setpoint adjustment, wind turbine grid side converter active current reduction, offshore voltage reduction. Chopper resistor method limits dc-link voltage by dissipating the imbalanced power . The second and third method reduce the power output from each wind turbine to limit the dc-link voltage increase. These two methods need communication between HVDC converter and each wind turbine. Offshore voltage reduction method initiates a controlled voltage drop by offshore converter to achieve a fast power reduction. All these four fault ride through (FRT) methods will be implemented in a test system and the effectiveness of these methods are evaluated with simulations made in PSCAD environment. Finally, based on the proposed methods, an enhanced FRT method is developed and its effectiveness is tested with the system. The advantages and disadvantages of different FRT methods are compared and summarized.Electrical Sustainable EnergyElectrical Engineering, Mathematics and Computer Scienc
L‐shaped Connection for Glass Portal Frame: Structural analysis and its application
No full textArchitecture and The Built EnvironmentArchitectural Engineering +TechnologyBuilding Technolog
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