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排序方式: 共有373条查询结果,搜索用时 15 毫秒
1.
Ahmed Khattab 《Wireless Networks》2011,17(7):1649-1665
In this paper, we demonstrate that multiple concurrent asynchronous and uncoordinated Single-Input Multiple-Output (SIMO) transmissions can successfully take place even though the respective receivers do not explicitly null out interfering signals. Hence, we propose simple modifications to the widely deployed IEEE 802.11 Medium Access Control (MAC) to enable multiple non-spatially-isolated SIMO sender-receiver pairs to share the medium. Namely, we propose to increase the physical carrier sense threshold, disable virtual carrier sensing, and enable message-in-message packet detection. We use experiments to show that while increasing the peak transmission rate, spatial multiplexing schemes such as those employed by the IEEE 802.11n are highly non-robust to asynchronous and uncoordinated interferers. In contrast, we show that the proposed multi-flow SIMO MAC scheme alleviates the severe unfairness resulting from uncoordinated transmissions in 802.11 multi-hop networks. We analytically compute the optimal carrier sense threshold based on different network performance objectives for a given node density and number of receive antennas. 相似文献
2.
PMCNOC: A Pipelining Multi-channel Central Caching Network-on-chip Communication Architecture Design
N. Wang A. Sanusi P. Y. Zhao M. Elgamel M. A. Bayoumi 《Journal of Signal Processing Systems》2010,60(3):315-331
With the de facto transformation of technology into nano-technology, more and more functional components can be embedded on a single silicon die, thus enabling high degree pipelining operations such as those required for multimedia applications. In recent years, system-on-chip designs have migrated from fairly simple single processor and memory designs to relatively complicated systems with multiple processors, on-chip memories, standard peripherals, and other functional blocks. The communication between these IP blocks is becoming the dominant critical system path and performance bottleneck of system-on-chip designs. Network-on-chip architectures, such as Virtual Channel (2004), Black-bus (2004), Pirate (2004), AEthereal (2005), and VICHAR (2006) architectures, emerged as promising solutions for future system-on-chip communication architecture designs. However, these existing architectures all suffer from certain problems, including high area cost and communication latency and/or low network throughput. This paper presents a novel network-on-chip architecture, Pipelining Multi-channel Central Caching, to address the shortcomings of the existing architectures. By embedding a central cache into every switch of the network, blocked head packets can be removed from the input buffers and stored in the caches temporally, thus alleviating the effect of head-of-line and deadlock problems and achieving higher network throughput and lower communication latency without paying the price of higher area cost. Experimental results showed that the proposed architecture exhibits both hardware simplicity and system performance improvement compared to the existing network-on-chip architectures. 相似文献
3.
D. Depan J. Shah R.D.K. Misra 《Materials science & engineering. C, Materials for biological applications》2011,31(7):1305-1312
A novel folate-decorated and graphene mediated drug delivery system was prepared that involves uniquely combining graphene oxide (GO) with anticancer drug for controlled drug release. The nanocarrier system was synthesized by attaching doxorubicin (DOX) to graphene oxide via strong π–π stacking interaction, followed by encapsulation of graphene oxide with folic acid conjugated chitosan. The π–π stacking interaction, simplified as a non-covalent type of functionalization, enables high drug loading and subsequent controlled release of the drug. The encapsulated graphene oxide enhanced the stability of the nanocarrier system in aqueous medium because of the hydrophilicity and cationic nature of chitosan. The loading and release of DOX indicated strong pH dependence and imply hydrogen-bonding interaction between graphene oxide and DOX. The proposed strategy is advantageous in terms of targeted drug delivery and has high potential to address the current challenges in drug delivery. Thus, the prepared nanohybrid system offers a novel formulation that combines the unique properties of a biodegradable material, chitosan, and graphene oxide for biomedical applications. 相似文献
4.
5.
Studies of an industrial low-carbon steel (B450NbRE) suggest that the impact toughness is unexpectedly low under its practical service, probably resulting from the unstable recovery of rare earths (RE) in steelmaking. The purpose of this work is to investigate the effect of RE on the impact toughness in low-carbon steel. The B450NbRE steels with content of 0.0012–0.0180 wt.% RE were produced by vacuum induction furnace. The impact toughness and microstructure were investigated after hot rolled. The Gleeble-1500 thermal simulator was used to validate the effect of RE on the microstructure. The results indicate that the microstructure of hot-rolled steels is characterized by polygonal ferrite, quasi-polygonal ferrite, bainite and pearlite. The impact toughness increases with RE contents reaching the peak with content of 0.0047 wt.% RE, such a change exhibits the same rule as the case of the ferrite amount. However, this improvement in impact toughness is not only due to an increase in ferrite amount, but also the fine grained structure and the cleaner grain boundaries. And content of 0.0180 wt.% RE is excessive. Such an addition of the RE resulted in the martensite precipitates at the grain boundaries, which are extremely detrimental to impact toughness. 相似文献
6.
R. Devesh Kumar Misra Wah‐Wah Thein‐Han Mahesh Chandra Somani L. Pentti Karjalainen 《Advanced Engineering Materials》2009,11(12):B235-B242
Materials science, engineering, and biological sciences have been combined to improve the tissue compatibility of medical devices. In this regard, nano/ultrafine structuring of austenitic stainless steel obtained using an innovative approach of “phase‐reversion” has been evaluated for modulation of cellular activity. The biochemical and morphology study with fibroblasts point toward the improvement of tissue compatibility on comparison with coarse‐grained structures, strengthening the foundation of nanostructured materials for bio‐medical applications. 相似文献
7.
Bhupendra Girase Jinesh S. Shah R. Devesh K. Misra 《Advanced Engineering Materials》2012,14(4):B101-B111
We describe here favorable modulation of osteoblasts functions and cell–substrate interactions in hybrid silicone elastomers consisting of biocompatible graphene oxide. Pressure induced curing was used to synthesize the hybrid silicone elastomer with high strength–high elongation combination. It was intriguing that the cell–substrate interactions in the hybrid silicone elastomer were observed to be significantly different from those observed in stand alone silicone. The origin of differences in cell–substrate interactions in terms of cell attachment, viability, and proliferation and assessment of proteins actin, vinculin, and fibronectin are addressed and attributed to physico‐chemical properties (topography and hydrophilicity) and to the presence of graphene oxide. The end outcome of the study is a new family of nanostructured polymer composite with desired (enhanced cell functions) and bulk properties (long term stability—high strength‐at‐break). The integration of cellular and molecular biology with material science and engineering described here provides an insight into the ability to modulate cellular and molecular reactions in promoting osteoinductive signaling of surface adherent cells, in the present case, osteoblasts for joint reconstruction. 相似文献
8.
R. Devesh K. Misra Bhupendra Girase Pavan K. C. Venkata Surya Mahesh C. Somani L. Pentti Karjalainen 《Advanced Engineering Materials》2011,13(12):B483-B492
We elucidate here the fundamental principles underlying the modulation of osteoblasts functions in stainless steel biomedical devices achieved by nanoscale/submicron grain structure obtained through the novel concept of phase reversion in a low Ni bearing 15Cr–9Mn–1.7Cu steel. Interestingly, a comparative investigation of nano/submicron (N‐SM) and coarse‐grained (CG) structure under identical conditions indicated that cell attachment, proliferation, and viability are favorably enhanced in N‐SM grained structure and significantly different from the CG structure. These observations were further confirmed by expression levels of vinculin and associated actin cytoskeleton. Computational analysis of immunofluorescence micrographs suggested increased vinculin concentration associated with actin stress fibers in the outer regions of the cells and cellular extensions, implying enhanced cell–substrate interactions on the N‐SM grained substrate. The favorable enhancement of osteoblasts functions and cellular attachment on N‐SM grained surface is attributed to ultrafine grain size, i.e., the availability of greater open lattice in the position of high angle grain boundaries, and high hydrophilicity. The integration of cellular and molecular biology with material science and engineering as described here provides a route to modulate cellular and molecular reactions in promoting osteoinductive signaling of surface adherent cells. The end outcome of the study is that stainless steels with low Ni contents in comparison to the conventionally used bioimplant with 10–13 wt%Ni, as specially processed, exhibit desired, enhanced cell functions, and bulk properties. 相似文献
9.
Jinesh Shah Bhupendra Girase R. Devesh K. Misra 《Advanced Engineering Materials》2011,13(6):B234-B245
Fibroblasts functions in a new family of nanohybrid network elastomers with high strength‐at‐break involving pressure‐induced curing and short chain cross‐links of inorganic nanostructures have been investigated. The concept of chemical design and synthesis involves covalently linking nanometer‐sized titania with a bi‐functional agent, acrylic acid, which has a carboxylic group to coordinate with titania and a vinyl group to form short chain cross‐links as an integral part of the silicone network structure elastomer. Interestingly, the cell–substrate interactions in the hybrid network structure elastomer are significantly different from those observed in stand alone silicone. The origin of intriguing differences in cell–substrate interactions in terms of cell attachment, viability, and proliferation and assessment of proteins actin, vinculin, and fibronectin are addressed and attributed to physico‐chemical properties (topography and hydrophilicity) and to the presence of nanocrystalline titania. The end outcome of the study is a new family of soft tissue implants with desired (enhanced cell functions) and bulk properties (long term stability–high strength‐at‐break). The integration of cellular and molecular biology with material science and engineering described here provides an insight into the ability to modulate cellular and molecular reactions in promoting osteoinductive signaling of surface adherent cells, in the present case, fibroblasts for soft tissue reconstruction. 相似文献
10.
《International Journal of Heat and Mass Transfer》2007,50(21-22):4151-4165
Computational fluid dynamics (CFD) simulations are conducted using the volume-of-fluid (VOF) method to investigate the hydrodynamic characteristics of slug flow and the mechanism of slug flow induced CO2 corrosion. The hydrodynamic characteristics are significantly affected by the viscous, interfacial, and inertial forces. In inertia dominated flows, the velocity of fully developed falling liquid film is increased with increased Taylor bubble rising velocity. The developing falling liquid film is formed at about the length of 0.5 diameter from the Taylor bubble nose, the fully developed falling liquid film is reached at about the length of 1.5–2.1 diameter from the Taylor bubble nose. The average mass transfer coefficient in the falling liquid film is always higher than that in the Taylor bubble wake zone. The iron ion near wall mass transfer coefficient is higher than that of hydrogen ion. The wall shear stress is increased with increased Taylor bubble rising velocity in fully developed falling liquid film zone, and the wall shear stress has a large fluctuation due to the chaotic and turbulent vortexes in Taylor bubble wake zone. The formation and the damage mechanism of the corrosion product scale are proposed for the gas–liquid two-phase vertical upward slug flow induced CO2 corrosion. It is found that the wall shear stress of upward gas–liquid slug flow is alternate with high frequency, which is the key factor resulting in the corrosion product scale fatigue cracking. The CFD simulation results are in satisfactory agreement with previous experimental data and models available in literature. 相似文献