18,797 research outputs found
Recommended from our members
Two novel nonlinear companding schemes with iterative receiver to reduce PAPR in multi-carrier modulation systems
Companding transform is an efficient and simple method to reduce the Peak-to-Average Power Ratio (PAPR) for Multi-Carrier Modulation (MCM) systems. But if the MCM signal is only simply operated by inverse companding transform at the receiver, the resultant spectrum may exhibit severe in-band and out-of-band radiation of the distortion components, and considerable peak regrowth by excessive channel noises etc. In order to prevent these problems from occurring, in this paper, two novel nonlinear companding schemes with a iterative receiver are proposed to reduce the PAPR. By transforming the amplitude or power of the original MCM signals into uniform distributed signals, the novel schemes can effectively reduce PAPR for different modulation formats and sub-carrier sizes. Despite moderate complexity increasing at the receiver, but it is especially suitable to be combined with iterative channel estimation. Computer simulation results show that the proposed schemes can offer good system performances without any bandwidth expansion
Micro-displacement sensors based on plastic photonic bandgap Bragg fibers
We demonstrate an amplitude-based micro-displacement sensor that uses a
plastic photonic bandgap Bragg fiber with one end coated with a silver layer.
The reflection intensity of the Bragg fiber is characterized in response to
different displacements (or bending curvatures). We note that the Bragg
reflector of the fiber acts as an efficient mode stripper for the wavelengths
near the edge of the fiber bandgap, which makes the sensor extremely sensitive
to bending or displacements at these wavelengths. Besides, by comparison of the
Bragg fiber sensor to a sensor based on a regular multimode fiber with similar
outer diameter and length, we find that the Bragg fiber sensor is more
sensitive to bending due to presence of mode stripper in the form of the
multilayer reflector. Experimental results show that the minimum detection
limit of the Bragg fiber sensor can be smaller than 5 um for displacement
sensing
Bayesian Speaker Adaptation Based on a New Hierarchical Probabilistic Model
In this paper, a new hierarchical Bayesian speaker adaptation method called HMAP is proposed that combines the advantages of three conventional algorithms, maximum a posteriori (MAP), maximum-likelihood linear regression (MLLR), and eigenvoice, resulting in excellent performance across a wide range of adaptation conditions. The new method efficiently utilizes intra-speaker and inter-speaker correlation information through modeling phone and speaker subspaces in a consistent hierarchical Bayesian way. The phone variations for a specific speaker are assumed to be located in a low-dimensional subspace. The phone coordinate, which is shared among different speakers, implicitly contains the intra-speaker correlation information. For a specific speaker, the phone variation, represented by speaker-dependent eigenphones, are concatenated into a supervector. The eigenphone supervector space is also a low dimensional speaker subspace, which contains inter-speaker correlation information. Using principal component analysis (PCA), a new hierarchical probabilistic model for the generation of the speech observations is obtained. Speaker adaptation based on the new hierarchical model is derived using the maximum a posteriori criterion in a top-down manner. Both batch adaptation and online adaptation schemes are proposed. With tuned parameters, the new method can handle varying amounts of adaptation data automatically and efficiently. Experimental results on a Mandarin Chinese continuous speech recognition task show good performance under all testing conditions
Self-organized criticality in the intermediate phase of rigidity percolation
Experimental results for covalent glasses have highlighted the existence of a
new self-organized phase due to the tendency of glass networks to minimize
internal stress. Recently, we have shown that an equilibrated self-organized
two-dimensional lattice-based model also possesses an intermediate phase in
which a percolating rigid cluster exists with a probability between zero and
one, depending on the average coordination of the network. In this paper, we
study the properties of this intermediate phase in more detail. We find that
microscopic perturbations, such as the addition or removal of a single bond,
can affect the rigidity of macroscopic regions of the network, in particular,
creating or destroying percolation. This, together with a power-law
distribution of rigid cluster sizes, suggests that the system is maintained in
a critical state on the rigid/floppy boundary throughout the intermediate
phase, a behavior similar to self-organized criticality, but, remarkably, in a
thermodynamically equilibrated state. The distinction between percolating and
non-percolating networks appears physically meaningless, even though the
percolating cluster, when it exists, takes up a finite fraction of the network.
We point out both similarities and differences between the intermediate phase
and the critical point of ordinary percolation models without
self-organization. Our results are consistent with an interpretation of recent
experiments on the pressure dependence of Raman frequencies in chalcogenide
glasses in terms of network homogeneity.Comment: 20 pages, 18 figure
Catalytic difunctionalization of unactivated alkenes with unreactive hexamethyldisilane through regeneration of silylium ions
A metalâfree, intermolecular synâaddition of hexamethyldisilane across simple alkenes is reported. The catalytic cycle is initiated and propagated by the transfer of a methyl group from the disilane to a silyliumâionâlike intermediate, corresponding to the (re)generation of the silyliumâion catalyst. The key feature of the reaction sequence is the cleavage of the SiâSi bond in a 1,3âsilyl shift from silicon to carbon. A central intermediate of the catalysis was structurally characterized by Xâray diffraction, and the computed reaction mechanism is fully consistent with the experimental findings.TU Berlin, Open-Access-Mittel - 201
When resources collide: Towards a theory of coincidence in information spaces
This paper is an attempt to lay out foundations for a general theory of coincidence in information spaces such as the World Wide Web, expanding on existing work on bursty structures in document streams and information cascades. We elaborate on the hypothesis that every resource that is published in an information space, enters a temporary interaction with another resource once a unique explicit or implicit reference between the two is found. This thought is motivated by Erwin Shroedingers notion of entanglement between quantum systems. We present a generic information cascade model that exploits only the temporal order of information sharing activities, combined with inherent properties of the shared information resources. The approach was applied to data from the world's largest online citizen science platform Zooniverse and we report about findings of this case study
Supply hubs in industrial parks (SHIP): research perspectives
An industrial park is a cluster of enterprises located in one location to share common infrastructure, service and market opportunities. It has been adopted in many countries as an important tool for promoting the economic and industrial development. However, its further development has been impeded by the shortage of land resources especially for enterprises' construction of warehouses. The supply hub, having been employed by large suppliers to warehouse raw materials near manufacturers provides a promising way of solving such problem. In this paper, it is extended to "Supply Hub in Industrial Park (SHIP)" in the sense that warehouses of individual enterprises could be integrated into a single public warehouse and centrally serves the manufacturing processes of all the enterprises in an industrial park. Through the functioning of SHIP, it is expected that the land utilization and cost savings could be improved. As the initial study of SHIP, this paper focuses on several fundamental research perspectives: conceptual framework, working process, and potential benefits. Despite of the qualitative analysis, a mathematical model of SHIP is formulated. This work will contribute to the further research of logistics solutions in industrial parks.published_or_final_versionThe 40th International Conference on Computers & Industrial Engineering (CIE 2010), Awaji, Japan, 25-28 July 2010. In Proceedings of CIE40, 2010, p. 1-6The 40th International Conference on Computers & Industrial Engineering (CIE 2010), Awaji, Japan, 25-28 July 2010. In Proceedings of CIE40, 2010, p. 1-
- âŠ