2,181 research outputs found
Why Keep Silent Online? Voices from Stay-at-home Postgraduate Students
Online classroom silence is an overlooked site of research irrespective of the growing popularity of online teaching in today’s education. Against this background, this study showcases why a group of postgraduate students keep silent in their online classes through classroom observation, stimulated recall interviews and in-depth interviews. Reasons found are classified into three categories: the peculiarity of online class, the uniqueness of postgraduate academic lesson, and other general reasons resembling the ones in the traditional classroom. In addition, these factors are found to be interconnected and sometimes exerting both positive and negative effects; unexpectedly, the factor of ‘losing face’, contrary to previous studies, is trivial in contributing to postgraduate students’ online-classroom silence
Spectrum Sharing between Cooperative Relay and Ad-hoc Networks: Dynamic Transmissions under Computation and Signaling Limitations
This paper studies a spectrum sharing scenario between a cooperative relay
network (CRN) and a nearby ad-hoc network. In particular, we consider a dynamic
spectrum access and resource allocation problem of the CRN. Based on sensing
and predicting the ad-hoc transmission behaviors, the ergodic traffic collision
time between the CRN and ad-hoc network is minimized subject to an ergodic
uplink throughput requirement for the CRN. We focus on real-time implementation
of spectrum sharing policy under practical computation and signaling
limitations. In our spectrum sharing policy, most computation tasks are
accomplished off-line. Hence, little real-time calculation is required which
fits the requirement of practical applications. Moreover, the signaling
procedure and computation process are designed carefully to reduce the time
delay between spectrum sensing and data transmission, which is crucial for
enhancing the accuracy of traffic prediction and improving the performance of
interference mitigation. The benefits of spectrum sensing and cooperative relay
techniques are demonstrated by our numerical experiments.Comment: 5 pages, 3 figures, to appear in IEEE International Conference on
Communications (ICC 2011
6,8-Di-tert-butyl-3-(4-nitrophenyl)-2H-chromen-2-one
The title compound, C23H25NO4, was synthesized by the reaction of 2-(4-nitrophenyl)acetonitrile and 3,5-di-tert-butyl-2-hydroxybenzaldehyde. The dihedral angle formed by the benzene ring and the mean plane through the benzopyranone ring system is 35.57 (5)°. The nitro group is almost coplanar with the attached benzene ring [dihedral angle = 5.19 (15)°]. The crystal packing is stabilized by an intermolecular C—H⋯O hydrogen-bond interaction
Optimal Distributed Resource Allocation for Decode-and-Forward Relay Networks
This paper presents a distributed resource allocation algorithm to jointly
optimize the power allocation, channel allocation and relay selection for
decode-and-forward (DF) relay networks with a large number of sources, relays,
and destinations. The well-known dual decomposition technique cannot directly
be applied to resolve this problem, because the achievable data rate of DF
relaying is not strictly concave, and thus the local resource allocation
subproblem may have non-unique solutions. We resolve this non-strict concavity
problem by using the idea of the proximal point method, which adds quadratic
terms to make the objective function strictly concave. However, the proximal
solution adds an extra layer of iterations over typical duality based
approaches, which can significantly slow down the speed of convergence. To
address this key weakness, we devise a fast algorithm without the need for this
additional layer of iterations, which converges to the optimal solution. Our
algorithm only needs local information exchange, and can easily adapt to
variations of network size and topology. We prove that our distributed resource
allocation algorithm converges to the optimal solution. A channel resource
adjustment method is further developed to provide more channel resources to the
bottleneck links and realize traffic load balance. Numerical results are
provided to illustrate the benefits of our algorithm
- …