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91.
Mohammad Hammoudeh Robert Newman Christopher Dennett Sarah Mount 《Wireless Communications and Mobile Computing》2013,13(9):809-827
Wireless sensor networks (WSNs) typically gather data at a discrete number of locations. However, it is desirable to be able to design applications and reason about the data in more abstract forms than in points of data. By bestowing the ability to predict inter‐node values upon the network, it is proposed that it will become possible to build applications that are unaware of the concrete reality of sparse data. This interpolation capability is realised as a service of the network. In this paper, the ‘map’ style of presentation has been identified as a suitable sense data visualisation format. Although map generation is essentially a problem of interpolation between points, a new WSN service, called the map generation service, which is based on a Shepard interpolation method, is presented. A modified Shepard method that aims to deal with the special characteristics of WSNs is proposed. It requires small storage, can be localised and integrates the information about the application domain to further reduce the map generation cost and improve the mapping accuracy. Empirical analysis has shown that the map generation service is an accurate, a flexible and an efficient method. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
92.
Caroline Morris Sarah J. Glennie Hon S. Lam Holly E. Baum Dhinushi Kandage Neil A. Williams David J. Morgan Derek N. Woolfson Andrew D. Davidson 《Advanced functional materials》2019,29(8)
Subunit vaccines use delivery platforms to present minimal antigenic components for immunization. The benefits of such systems include multivalency, self‐adjuvanting properties, and more specific immune responses. Previously, the design, synthesis, and characterization of self‐assembling peptide cages (SAGEs) have been reported. In these, de novo peptides are combined to make hubs that assemble into nanoparticles when mixed in aqueous solution. Here it is shown that SAGEs are nontoxic particles with potential as accessible synthetic peptide scaffolds for the delivery of immunogenic components. To this end, SAGEs functionalized with the model antigenic peptides tetanus toxoid632‐651 and ovalbumin323‐339 drive antigen‐specific responses both in vitro and in vivo, eliciting both CD4+ T cell and B cell responses. Additionally, SAGEs functionalized with the antigenic peptide hemagglutinin518‐526 from the influenza virus are also able to drive a CD8+ T cell response in vivo. This work demonstrates the potential of SAGEs to act as a modular scaffold for antigen delivery, capable of inducing and boosting specific and tailored immune responses. 相似文献
93.
Ferroelectric domain configurations in PbTiO3 and Pb(ZrxT1−x)O3 (PZT, x = 0.3 or 0.5) thin films have been studied by transmission electron microscopy. The PbTiOg and PZT thin films have
been deposited by the ionized cluster beam technique and radio frequency sputtering, respectively. The grain size in these
thin films is typically less than 0.5 μm. Lamellar 90°-domain features have been observed in both PbTiO3 and PZT (30/70) samples. The domain walls correspond to the {011} twin boundaries. La-doping and Ca-modification are shown
to affect the microstructure of the PZT films. No clear domain feature occurs in the PZT thin film that has composition near
the morphotropic phase boundary. The effects of grain sizes are briefly discussed. 相似文献
94.
Tina M Geary Peter H Brooks Jane D Beal Alastair Campbell 《Journal of the science of food and agriculture》1999,79(4):633-640
The effect of feeding newly weaned pigs acidified liquid diets was investigated. The control diet was acidified to about pH 4 with lactic acid (LA). A second diet of the same formulation was acidified to about pH 4 by fermentation with Pediococcus acidilactici (PA). Forty‐eight weaner pigs (weight 7 kg±1 kg, age 24±4 days) were allocated to the two dietary treatments according to a randomised block design and fed ad libitum for 28 days. Food intake, daily gain and water intake were recorded, and a microbial assessment of the liquid diet was conducted. Reducing pH<4.0 in either of the liquid diets was effective in eliminating coliform bacteria. There were no significant differences in any of the performance parameters measured. The average daily liveweight gain overall was 474 and 496±17.8 g d−1 for PA and LA, respectively, with a feed conversion ratio overall of 1.15 and 1.11±0.025 for PA and LA, respectively. Fermentation of liquid diets for newly weaned piglets could provide a more cost effective means of acidifying diets than the use of organic acids. Reducing the pH of the liquid diet to 4.00 by fermentation with Pediococcus acidilactici was a cost effective method of eliminating enteropathogens and spoilage organisms from the diet. © 1999 Society of Chemical Industry 相似文献
95.
System capacity and grade of service (GoS) are both important for the rapid growth of cellular communication services. In this paper, we propose a two‐tier TDMA‐based cellular system with macrocell overlaid on microcell clusters by implementing fixed channel assignment (FCA) scheme and fixed reuse partitioning (FRP) scheme in microcell layer and macrocell layer, respectively, named FCA–FRP overlay scheme. Improvement can be achieved in both system capacity and GoS. Theoretical analysis based on the overlay scheme without overflow and with overflow is first presented. It shows that the simulation results are agreed with the analytical results. Then, simulation results, obtained from the overlay scheme with and without overflow, show that the performance in terms of the call blocking probability, the call dropping probability and system capacity of such a system can be greatly improved compared with a conventional one‐tier cellular system deployed with FCA or FRP scheme. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
96.
Sarah Kurtz Daryl Myers W. E. McMahon John Geisz Myles Steiner 《Progress in Photovoltaics: Research and Applications》2008,16(6):537-546
Champion concentrator cell efficiencies have surpassed 40% and now many are asking whether the efficiencies will surpass 50%. Theoretical efficiencies of >60% are described for many approaches, but there is often confusion about “the” theoretical efficiency for a specific structure. The detailed balance approach to calculating theoretical efficiency gives an upper bound that can be independent of material parameters and device design. Other models predict efficiencies that are closer to those that have been achieved. Changing reference spectra and the choice of concentration further complicate comparison of theoretical efficiencies. This paper provides a side‐by‐side comparison of theoretical efficiencies of multi‐junction solar cells calculated with the detailed balance approach and a common one‐dimensional‐transport model for different spectral and irradiance conditions. Also, historical experimental champion efficiencies are compared with the theoretical efficiencies. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
97.
Wei-lun Hung Yuan Xie Narayanan Vijaykrishnan Mahmut Kandemir Mary Jane Irwin 《Journal of Signal Processing Systems》2010,58(2):145-160
Power consumption is a top priority in high performance circuit design today. Many low power techniques have been proposed
to tackle the ever serious, highly pressing power consumption problem, which is composed of both dynamic and static power
in the nanometer era. The static power consumption nowadays receives even more attention than that of dynamic power consumption
when technology scales below 100 nm. In order to mitigate the aggressive power consumption, various existing low power techniques
are often used; however, they are often applied independently or combined with two or at most three different techniques together,
and that is not sufficient to address the escalating power issue. In this paper, we present a power optimization framework
for the minimization of total power consumption in combinational logic through multiple V
dd
assignment, multiple V
th
assignment, device sizing, and stack forcing, while maintaining performance requirements. These four power reduction techniques
are properly encoded into the genetic algorithm and evaluated simultaneously. The overhead imposed by the insertion of level
converters is also taken into account. The effectiveness of each power reduction mechanism is verified, as are the combinations
of different approaches. Experimental results are presented for a number of 65 nm benchmark circuits that span typical circuit
topologies, including inverter chains, SRAM decoders, multiplier, and a 32 bit carry adder. Our experiments show that the
combination of four low power techniques is the effective way to achieve low power budget. The framework is general and can
be easily extended to include other design-time low power techniques, such as multiple gate length or multiple gate oxide
thickness. 相似文献
98.
Sarah R. Cowan Wei Lin Leong Natalie Banerji Gilles Dennler Alan J. Heeger 《Advanced functional materials》2011,21(16):3083-3092
Small amounts of impurity, even one part in one thousand, in polymer bulk heterojunction solar cells can alter the electronic properties of the device, including reducing the open circuit voltage, the short circuit current and the fill factor. Steady state studies show a dramatic increase in the trap‐assisted recombination rate when [6,6]‐phenyl C84 butyric acid methyl ester (PC84BM) is introduced as a trap site in polymer bulk heterojunction solar cells made of a blend of the copolymer poly[N‐9″‐hepta‐decanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole) (PCDTBT) and the fullerene derivative [6,6]‐phenyl C61 butyric acid methyl ester (PC60BM). The trap density dependent recombination studied here can be described as a combination of bimolecular and Shockley–Read–Hall recombination; the latter is dramatically enhanced by the addition of the PC84BM traps. This study reveals the importance of impurities in limiting the efficiency of organic solar cell devices and gives insight into the mechanism of the trap‐induced recombination loss. 相似文献
99.
Tahmida N. Huq Lana C. Lee Lissa Eyre Weiwei Li Robert A. Jagt Chaewon Kim Sarah Fearn Vincenzo Pecunia Felix Deschler Judith L. MacManus‐Driscoll Robert L. Z. Hoye 《Advanced functional materials》2020,30(13)
In the search for nontoxic alternatives to lead‐halide perovskites, bismuth oxyiodide (BiOI) has emerged as a promising contender. BiOI is air‐stable for over three months, demonstrates promising early‐stage photovoltaic performance and, importantly, is predicted from calculations to tolerate vacancy and antisite defects. Here, whether BiOI tolerates point defects is experimentally investigated. BiOI thin films are annealed at a low temperature of 100 °C under vacuum (25 Pa absolute pressure). There is a relative reduction in the surface atomic fraction of iodine by over 40%, reduction in the surface bismuth fraction by over 5%, and an increase in the surface oxygen fraction by over 45%. Unexpectedly, the Bi 4f7/2 core level position, Fermi level position, and valence band density of states of BiOI are not significantly changed. Further, the charge‐carrier lifetime, photoluminescence intensity, and the performance of the vacuum‐annealed BiOI films in solar cells remain unchanged. The results show BiOI to be electronically and optoelectronically robust to percent‐level changes in surface composition. However, from photoinduced current transient spectroscopy measurements, it is found that the as‐grown BiOI films have deep traps located ≈0.3 and 0.6 eV from the band edge. These traps limit the charge‐carrier lifetimes of BiOI, and future improvements in the performance of BiOI photovoltaics will need to focus on identifying their origin. Nevertheless, these deep traps are three to four orders of magnitude less concentrated than the surface point defects induced through vacuum annealing. The charge‐carrier lifetimes of the BiOI films are also orders of magnitude longer than if these surface defects were recombination active. This work therefore shows BiOI to be robust against processing conditions that lead to percent‐level iodine‐, bismuth‐, and oxygen‐related surface defects. This will simplify and reduce the cost of fabricating BiOI‐based electronic devices, and stands in contrast to the defect‐sensitivity of traditional covalent semiconductors. 相似文献
100.
Chetana Nagendra Robert Michael Owens Mary Jane Irwin 《The Journal of VLSI Signal Processing》1995,9(3):193-209
In this paper, we present a novel scheme for performing fixed-point arithmetic efficiently on fine-grain, massively parallel,
programmable architectures including both custom and FPGA-based systems. We achieve anO(n) speedup, wheren is the operand precision, over the bit-serial methods of existing fine-grain systems such as the DAP, the MPP and the CM2,
within the constraints of regular, near neighbor communication and only a small amount of on-chip memory. This is possible
by means of digit pipelined algorithms which avoid broadcast and which operate in a fully systolic manner by pipelining at
the digit level. A base 4, signed-digit, fully redundant number system and on-line techniques are used to limit carry propagation
and minimize communication costs. p ]Although our algorithms are digit-serial, we are able to match the performance of the
bit-parallel methods, while retaining low communication complexity. Reconfigurable hardware systems built using field programmable
gate arrays (FPGA's) can share in the speed benefits of these algorithms. By using the organization of logic blocks suggested
in this paper, problems of placement and routing that exist in such systems can be avoided. Since the algorithms are amenable
to pipelining, very high throughput can be obtained. 相似文献