841 research outputs found
Joint Discovery in Synchronous Wireless Networks
No full textGiven a synchronous wireless network with N nodes uniformly located at random on a finite plane, we consider the problem of distributed peer discovery: all nodes want to discover as many other nodes as possible. We assume that there are a total of K physical resources dedicated for the discovery purpose. Each node can pick one resource to transmit its node identifier on, and can receive on the remaining K-1 resources. We assume that node identifiers are broadcast via coded transmission on one single physical resource. This paper addresses link level strategies to increase the average number of discovered devices when N ≅ aK, where a is the degree of density of the network. A classical strategy of discovering one node per resource would lead to a maximum of K-1 nodes being discovered. We focus on a multiple-access channel (MAC) scernario where multiple interferer users are jointly decoded. We propose a scheme to improve the performance. The method, based on iterative belief propagation on factor graph, is called joint iterative decoding (JID). It is shown, through system simulations, that JID may gain by significantly more than 100% over the classical single-user decoding, and by 20-25% over the successive interference cancellation (SIC)
Low Temperature Synthesis of Cubic BaTiO3 Nanoparticles
No full textA new process has been developed to prepare nanocrystalline BaTiO3 at room temperature and atmospheric pressure. The experimental results show that cubic BaTiO3 nanoparticles can be prepared even at room temperature (25 degrees C). These cubic BaTiO3 nanoparticles are irregular quasi-spheres with the size rang from hundreds of nanometers to tens of nanometers as the temperature is increased from 25 to 80 degrees C. Raman spectra of the products obtained at different temperature confirmed that the BaTiO3 were cubic phase. The influence of reactants concentration on the formation of BaTiO3 nanoparticles was also investigated
Cross-sectional UHR-SD-OCT image stack (XZ, full resolution) of porcine left bundle branch fibers
No full textCross-sectional UHR-SD-OCT image stack (XZ, full resolution) of an area of the left ventricular outlet septum in a porcine heart immediately below the membranous septum and below the aortic valve (transition from membranous septum to conduction tissue in left bundle branch
A study of the interface of CeO2/Si heterostructure grown by ion beam deposition
No full textEpitaxial cerium dioxide films on single-crystal silicon substrates (CeO2/Si) have been grown by a dual mass-analyzed low-energy ion beam deposition (IBD) system. By double-crystal X-ray diffraction (XRD), Full Width at Half Maximum (FWHM) are 23' and 33' in the rocking curves for (222) and (111) faces of the CeO2 film, respectively, and the lattice-mismatch Delta a/a with the substrate is about - 0.123%. The results show that the CeO2/Si grown by IBD is of high crystalline quality. In this work, the CeO2/Si heterostructure were investigated by X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) measurements. Especially, XPS and AES depth profiling was used to analyze the compositions and structures in the interface regions of the as-grown and post-annealed CeO2/Si. It was found that there was no silicon oxide in the interface region of the as-grown sample but silicon oxide in the post-annealed sample. The reason for obtaining such high quality heterostructure mainly depends on the absence of silicon oxide in the surface at the beginning of the deposition. (C) 1998 Elsevier Science Ltd. All rights reserved
Cross-sectional UHR-SD-OCT image stack (XZ) of porcine left bundle branch fibers
No full textCross-sectional UHR-SD-OCT image stack (XZ, downsampled due to constraints on video file size) of an area of the left ventricular outlet septum in a porcine heart immediately below the membranous septum and below the aortic valve (transition from membranous septum to conduction tissue in left bundle branch
Deformation twinning in nanocrystalline materials
No full textNanocrystalline (nc) materials can be defined as solids with grain sizes in the range of 1–100 nm. Contrary to coarse-grained metals, which become more difficult to twin with decreasing grain size, nanocrystalline face-centered-cubic (fcc) metals become easier to twin with decreasing grain size, reaching a maximum twinning probability, and then become more difficult to twin when the grain size decreases further, i.e. exhibiting an inverse grain-size effect on twinning. Molecular dynamics simulations and experimental observations have revealed that the mechanisms of deformation twinning in nanocrystalline metals are different from those in their coarse-grained counterparts. Consequently, there are several types of deformation twins that are observed in nanocrystalline materials, but not in coarse-grained metals. It has also been reported that deformation twinning can be utilized to enhance the strength and ductility of nanocrystalline materials. This paper reviews all aspects of deformation twinning in nanocrystalline metals, including deformation twins observed by molecular dynamics simulations and experiments, twinning mechanisms, factors affecting the twinning, analytical models on the nucleation and growth of deformation twins, interactions between twins and dislocations, and the effects of twins on mechanical and other properties. It is the authors’ intention for this review paper to serve not only as a valuable reference for researchers in the field of nanocrystalline metals and alloys, but also as a textbook for the education of graduate students.</p
Deformation Twinning In Bulk Nanocrystalline Metals: Experimental Observations
No full textDeformation twins have been observed in nanocrystalline (nc) fcc metals with medium-to-high stacking fault energies such as aluminum, copper, and nickel. These metals in their coarse-grained states rarely deform by twining at room temperature and low strain rates. Several twinning mechanisms have been reported that are unique to nc metals. This paper reviews experimental evidences on deformation twinning and partial dislocation. emissions from grain boundaries, twinning mechanisms, and twins with zero-macro-strain. Factors that affect the twinning propensity and recent analytical models on the critical grain sizes for twinning are also discussed. The current issues on deformation twinning in nanocrystalline metals are listed
Norm inequalities for cartesian decompositions
No full textAbstractLet the Cartesian decomposition of a complexn × n matrixT beT = A + iB withA, B Hermitian. Letαj andβj be the eigenvalues ofA andB respectively ordered so that|α1|⩾ … ⩾ |αn|and|β1|⩾ … ⩾ |βn|. We prove that∥diag(α1+iβ1,…αn+iβn)∥⩽2∥T∥ for every unitarily invariant norm this settles affirmatively a conjecture of Ando and Bhatia (T. Ando, R. Bhatia, Eigenvalue inequalities associated with the cartesian decomposition, Linear and Multilinear Algebra 22 (1987) 133)
A Smart Frequency Presetting Technique for Fast Lock-in LC-PLL Frequency Synthesizer
No full textThis paper proposes a smart frequency presetting technique for fast lock-in LC-PLL frequency synthesizer. The technique accurately presets the frequency of VCO with small initial frequency error and greatly reduces the lock-in time. It can automatically compensate preset frequency variation with process and temperature. A 2.4GHz synthesizer with 1MHz reference input was implemented in 0.35 mu m CMOS process. The chip core area is 0.4mm(2). Output frequency of VCO ranges from 2390 to 2600MHz. The measured results show that the typical lock-in time is 3 mu s. The phase noise is -112dBc/Hz at 600KHz offset from center frequency. The test chip consumes current of 22mA that includes the consumption of the I/O buffers
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