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11.
In the context of IEEE 802.11b network testbeds, we examine the differences between unicast and broadcast link properties, and we show the inherent difficulties in precisely estimating unicast link properties via those of broadcast beacons even if we make the length and transmission rate of beacons be the same as those of data packets. To circumvent the difficulties in link estimation, we propose to estimate unicast link properties directly via data traffic itself without using periodic beacons. To this end, we design a data-driven routing protocol Learn-on-the-Fly (LOF). LOF chooses routes based on ETX/ETT-type metrics, but the metrics are estimated via MAC feedback for unicast data transmission instead of broadcast beacons. Using a realistic sensor network traffic trace and an 802.11b testbed of ~195 Stargates, we experimentally compare the performance of LOF with that of beacon-based protocols, represented by the geography-unaware ETX and the geography-based PRD. We find that LOF reduces end-to-end MAC latency by a factor of 3, enhances energy efficiency by a factor up to 2.37, and improves network throughput by a factor up to 7.78, which demonstrate the feasibility and the potential benefits of data-driven link estimation and routing. 相似文献
12.
When a sensor network is deployed to detect objects penetrating a protected region, it is not necessary to have every point
in the deployment region covered by a sensor. It is enough if the penetrating objects are detected at some point in their
trajectory. If a sensor network guarantees that every penetrating object will be detected by at least k distinct sensors before it crosses the barrier of wireless sensors, we say the network provides k-barrier coverage. In this paper, we develop theoretical foundations for k-barrier coverage. We propose efficient algorithms using which one can quickly determine, after deploying the sensors, whether
the deployment region is k-barrier covered. Next, we establish the optimal deployment pattern to achieve k-barrier coverage when deploying sensors deterministically. Finally, we consider barrier coverage with high probability when
sensors are deployed randomly. The major challenge, when dealing with probabilistic barrier coverage, is to derive critical
conditions using which one can compute the minimum number of sensors needed to ensure barrier coverage with high probability.
Deriving critical conditions for k-barrier coverage is, however, still an open problem. We derive critical conditions for a weaker notion of barrier coverage,
called weak k-barrier coverage. 相似文献
13.
Avijit Mondal Anish Upadhyaya Dinesh Agrawal 《International Journal of Refractory Metals and Hard Materials》2010
Microwave heating is recognized for its various advantages, such as time and energy saving, very rapid heating rates, considerably reduced processing cycle time and temperature, fine microstructures and improved properties. The present paper investigates the feasibility of consolidating tungsten powders through microwave sintering. A comparative analysis has also been attempted between the sintering response of pure tungsten powder compact in a microwave and conventional furnace. 相似文献
14.
Polypyrrole has emerged as one of the highly pursued conducting polymers owing to its high electrical conductivity and good
environmental stability. In spite of its excellent electrical properties, the chemical and thermal stability and processability
are not very satisfactory. The incorporation of a polymer material into an inorganic ion-exchanger provides a high class of
hybrid ion-exchangers with enhanced ion-exchange properties, high reproducibility, high stability, and good selectivity for
heavy metals. A novel organic–inorganic composite-polypyrrole zirconium titanium phosphate has been synthesized using zirconium
titanium phosphate, which is an advanced inorganic ion-exchange material with the qualities listed above. The physicochemical
properties of this composite material are characterized by X-ray, TGA–DTA, AAS, FTIR, SEM, and TEM. The ion-exchange capacity,
pH titrations, elution, and chemical stability were determined to study ion-exchange properties of the material. Distribution
studies for various metal ions revealed that the nano-composite is highly selective for Th(IV). An ion-selective membrane
electrode was fabricated using this material for the determination of Th(IV) ions in solutions. The analytical utility of
this electrode was established by employing it as an indicator electrode in electrometric titrations. 相似文献
15.
Randall M. German Ph.D. Ronald G. Iacocca Ph.D. John L. Johnson Ph.D. Yixiong Liu Ph.D. Anish Upadhyaya B.S. 《JOM Journal of the Minerals, Metals and Materials Society》1995,47(8):46-48
Liquid-phase sintering routinely is used to form dense composite structures. The technique is generally restricted to high solid contents to ensure rigidity of the compact to achieve net shaping. Experimental conditions present during microgravity processing have allowed liquid-phase sintering over a wider range of liquid-solid ratios than possible on Earth. Early results from experiments performed on the space shuttle} Columbia during 1994 are used to show the novel behavior associated with microgravity conditions. 相似文献
16.
Anish Kumar K. Laha T. Jayakumar K. Bhanu Sankaro Rao Baldev Raj 《Metallurgical and Materials Transactions A》2002,33(6):1617-1626
Modified 9Cr-1Mo ferritic steel (T91/P91) has been subjected to a series of heat treatments consisting of soaking for 5 minutes
at the selected temperatures, starting from the α-phase region (1073 K) to the γ + δ-phase region (1623 K), followed by oil quenching. Hardness measurements, microstructural features, and grain-size measurements
by the linear-intercept method have been used for correlating them with the ultrasonic parameters. Ultrasonic velocity and
attenuation measurements, and spectral analysis of the first backwall echo have been used for characterization of the microstructures
obtained by various heat treatments. As the soaking temperature increased above Ac
1, the ultrasonic velocity decreased because of the increase in the volume fraction of martensite in the structure. There were
sharp changes in the ultrasonic velocities corresponding to the two critical temperatures, Ac
1 and Ac
3. Ultrasonic longitudinal- and shear-wave velocities were found to be useful in identifying the Ac
1 and Ac
3 temperatures and for the determination of hardness in the intercritical region. However, ultrasonic attenuation and spectral
analysis of the first backwall echo were found to be useful to characterize the variation in the prior-austenitic grain size
and formation of δ ferrite above the Ac
4 temperature. The scattering coefficients have been experimentally determined for various microstructures and compared with
the theoretically calculated value of the scattering coefficients for iron reported in literature. 相似文献
17.
The analysis of heparan sulfate glycosaminoglycans (HSGAGs) variations in human serum at the disaccharide level has a great potential for disease diagnosis and prognosis. However, the lack of available analytical methodology for the compositional analysis of HSGAGs in human serum remains to be addressed to delineate the possible role of HSGAGs on the onset and/or progression of a disease. In this study, we have developed a method for the in-depth compositional analysis of the 12 heparin/HS-derived disaccharides from human serum using a combination of technologies--fractionation, exhaustive digestion, solid phase extraction, and LC-MS/MS. The method exhibits high recovery (72-110%) and good reproducibility (standard deviation of less than 5%) with a low limit of detection and quantification. Errors from the method validation were within 1.1%. Nondetectable non- or low-sulfated disaccharides in human serum were also detected using the optimized protocol. Further applying this method, the comprehensive analysis of HSGAGs compositions in human sera from female donors showed considerable variations in disaccharide patterns and compositions. 相似文献
18.
K. M. Manikandan A. Yelilarasi S. S. Saravanakumar P. Senthamaraikannan Anish Khan Abdullah M. Asiri 《中国化学工程学报》2019,27(11):2807-2814
The exploration of polymer electrolyte in the field of dye sensitized solar cell (DSSC) can contribute to increase the invention of renewable energy applications. In the present work, the influence of imidazole on the poly (vinylidene fluoride) (PVDF)-poly (methyl methacrylate) (PMMA)-Ethylene carbonate (EC)-KI-I2 polymer blend electrolytes has been evaluated. The different weight percentages of imidazole added into polymer blend electrolytes have been prepared by solution casting. The prepared films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), UV-visible spectra, photoluminescence spectra and impedance spectroscopy. The surface roughness texture of the film was analyzed by atomic force microscopy (AFM). The ionic conductivity of the optimized polymer blend electrolyte was determined by impedance measurement, which is 1.95×10-3 S·cm-1 at room temperature. The polymer electrolyte containing 40 wt% of imidazole content exhibits the highest photo-conversion efficiency of 3.04% under the illumination of 100 mW·cm-2. Moreover, a considerable enhancement in the stability of the DSSC device was demonstrated. 相似文献
19.
M. Anish T. Arunkumar B. Kanimozhi J. Jayaprabakar N. Beemkumar V. Jayaprakash 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2019,41(4):451-467
In this study, a combination of thermal conductivity, viscosity, and density characteristics are experimentally probed for attaining maximum heat transfer using MgO-Therminol 55 as nanofluid is reported. Recent studies proved that nanofluids have miserable properties that make them feasibly useful in many applications in heat transfer compared to base fluid.MgO-Therminol 55 nanofluid is synthesized by diffusion of MgO nanoparticles of size 160–190 nm in Therminol 55 at different concentrations (0.05%–0.3%). Thermal conductivity and viscosity are calculated at a temperature range of 30–60°C using kd2 analyzer and Fenske viscometer. Data obtained from the experimental results reveals that when volume concentration is increased with respect to that thermal conductivity increases, viscosity decreases and density decreases at different temperatures. The proposed models were supportive to the experimental data. 相似文献
20.
Wireless Personal Communications - Femtocell deployment is an important strategy when it comes to improvement of QoS metrics in areas of poor cell coverage like indoors in an LTE environment. This,... 相似文献