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31.
Investigating factors that influence social presence and learning outcomes in distance higher education 总被引:1,自引:0,他引:1
There are many factors that influence distance learning especially in higher education where collaborative and communicative discourse is necessary for pursuing knowledge. Social presence, among other factors, is an important concept to be facilitated, developed and sustained in distance higher education as it promotes and supports discourse based learning. This study examines the relationship among demographic and other variables, social presence and learning satisfaction. Results showed demographic variables, such as gender, online learning experience and work status were not significant factors in terms of influencing on either social presence or learning satisfaction. While media integration and instructor’s quality teaching were significant predictors of both social presence and learning satisfaction, interactivity among participants was a predictor of social presence but not of learning satisfaction. Along with the study findings, some implications were discussed for online learning practitioners in higher education setting. 相似文献
32.
In sensor networks, a compromised node can either generate fabricated reports with false votes or inject false votes into real reports, which causes severe damage such as false alarms, energy drain and information loss. An interleaved hop-by-hop authentication (IHA) scheme addresses the former attack by detecting and filtering false reports in a deterministic and hop-by-hop fashion. Unfortunately, in IHA, all en-route nodes must join to verify reports while only a few are necessary to the authentication procedure. In this paper, we propose a fuzzy-based interleaved multi-hop authentication scheme based on IHA. In our scheme, the fuzzy logic system only selects some nodes for verification based on the network characteristics. Moreover, we apply a voting method and a hash-based key assignment mechanism to improve network security. Through performance evaluation, the proposed scheme is found to save up to 13% of the energy consumption and to provide more network protection compared to IHA. 相似文献
33.
L. Beirão da Veiga A. Buffa D. Cho G. Sangalli 《Computer Methods in Applied Mechanics and Engineering》2011,200(21-22):1787-1803
We develop optimal approximation estimates for T-splines in the case of geometries obtained by gluing two standard tensor product patches. We derive results both for the T-spline space in the parametric domain and the mapped T-NURBS in the physical one. A set of numerical tests in complete accordance with the theoretical developments is also presented. 相似文献
34.
Homogeneous and nano-sized BPNT [(Ba1-xPbx)Nd2Ti5O14] powders were prepared under various hydrothermal conditions. Crystallinity and homogeneity of the synthetic powders were
investigated. The microwave dielectric properties of the filters prepared with hydrothermal powders were compared with those
of the filters prepared with conventional powders. The microwave dielectric properties of the filter prepared with the hydrothermal
powders were also better than those of the filter manufactured with the conventional powders. The dielectric constant, quality
constant and temperature coefficient of resonance frequency of hydrothermally prepared filter under optimum condition and
measured at 3.5 GHz around were about 93, 6067 and 0 ppm/°C, respectively. 相似文献
35.
Kyung-Hoon Hyun Sangkyu Lee Chae-Woong Cho Ungyu Paik Dae-Hwan Kim Eun-Sang Na Jea-Gun Park 《Journal of Electroceramics》2006,17(2-4):351-354
An attempt was made to improve the conventional lamination process in the multilayered ceramic capacitors (MLCCs) fabrication by adapting a solvent treatment on the BaTiO3 green sheets. During the lamination process, additional particle rearrangement in the BaTiO3 green block was stimulated by solvent treatment. This rearrangement resulted in a more compact structure of the BaTiO3 green sheets compared to that obtained through the conventional lamination process. The overall thickness of BaTiO3/Ni/BaTiO3 laminates was also reduced after solvent treatment. It is suggested that miniaturization in the fabrication of MLCCs can be improved by adapting a solvent treatment during the lamination process. 相似文献
36.
Ki-Won Kim Pyeong-Seok Cho Jong-Heun Lee Seong-Hyeon Hong 《Journal of Electroceramics》2006,17(2-4):895-898
A new method for preparing SnO2 whiskers by the decomposition of SnC2O4 is suggested. A Whisker-like morphology of a SnC2O4 precipitate was attained via the gradual addition of an oxalic acid solution to a hot SnCl2 aqueous solution (T > 50∘C). In comparison, when the solution temperature was either lower than 50∘C or when ethanol was used as the solvent, the SnC2O4 precipitate showed an angular and relatively isotropic morphology. The morphology of the SnC2O4 precipitate remained even after its thermal decomposition into SnO2 at 400∘C indicating that SnC2O4 precipitation is a key step in preparing the whiskers. The formation mechanism of SnO2 whiskers was explained by the supersaturation during the precipitation of SnC2O4. 相似文献
37.
A unique baseband derived RF predistortion system which uses lookup table coefficients extracted at baseband that directly RF envelope modulate a quadrature vector modulator is presented. The primary advantages of this architecture are that it combines the narrowband advantage of envelope predistortion with the accuracy of baseband predistortion. 相似文献
38.
A miniature UWB planar monopole antenna with 5-GHz band-rejection filter and the time-domain characteristics 总被引:2,自引:0,他引:2
Young Jun Cho Ki Hak Kim Dong Hyuk Choi Seung Sik Lee Seong-Ook Park 《Antennas and Propagation, IEEE Transactions on》2006,54(5):1453-1460
A planar monopole antenna with a staircase shape and small volume (25/spl times/26/spl times/1 mm/sup 3/) is proposed in this paper. With the use of a half-bowtie radiating element, the staircase-shape, and a modified ground plane structure, the proposed antenna has a very wide impedance bandwidth measured at about 11.6 GHz (2.9-14.5 GHz, bandwidth ratio about 1:5) below VSWR 2 including the WLAN band notched in the vicinity of 5 GHz. An omnidirectional radiation pattern is obtained. The group delay which is an indication of linearity between two proposed antennas is less than 1 ns. The electrical characteristics in terms of frequency and time domains and physical ones of the proposed antenna make it attractive for use in ultrawideband (UWB) systems. 相似文献
39.
This paper presents an overview on the application of FE simulation as a virtual manufacturing tool in designing manufacturing processes for precision parts. The processes discussed include forging, sheet metal forming and hydroforming. Determination of reliable input parameters to simulate a process is a key element in successful application of process simulation for process design in all the mentioned areas. These issues are discussed in detail. Practical examples of application of FE simulation are presented for improvement of the existing metal forming process and/or designing new metal forming process for manufacturing discrete precision parts in forging, sheet metal forming and hydroforming. 相似文献
40.
Hot band annealing is known to be a prerequisite for good magnetic properties irrespective of manufacturing methods in grain‐oriented Fe‐3 wt.% Si electrical steels. In this study, the effects of hot band annealing on magnetic properties were investigated in 3% grain‐oriented electrical steels of low soluble AI contents and one‐stage cold rolling. Microstructure and precipitate distribution were compared with hot band annealing conditions. Secondary recrystallization behaviour with hot band annealing condition was also discussed. 相似文献