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991.
Noise degrades the accuracy of sonar systems. We demonstrate a practical method for increasing the effective signal-to-noise ratio (SNR) by fusing time delay information from a burst of multiple sonar pings. This approach can be useful when there is no relative motion between the sonar and the target during the burst of sonar pinging. Otherwise, the relative motion degrades the fusion and therefore, has to be addressed before fusion can be used. In this paper, we present a robust motion estimation algorithm which uses information from multiple receivers to estimate the relative motion between pings in the burst. We then compensate for motion, and show that the fusion of information from the burst of motion compensated pings improves both the resilience to noise and sonar accuracy, consequently increasing the operating range of the sonar system. 相似文献
992.
Using three crystal polymorphs of indomethacin (IMC), we tested two interpretations of the enhanced crystal growth kinetics near the glass transition temperature Tg. This enhancement refers to the stronger temperature dependence of liquid viscosity eta than crystal growth rate (corrected for thermodynamic driving force). This enhancement is attributed in the first interpretation to an increase of the number of preferred interfacial growth sites with decreasing temperature and, in the second interpretation, to the breakdown of the Stokes-Einstein relation in deeply supercooled liquids. We measured the growth rates of the IMC polymorphs (alpha, gamma, and delta) from Tg + 9 K (Tg = 314 K) to near the respective melting points. From Tg + 19 K to Tg + 69 K, the growth rates of the polymorphs changed by 10(4) fold but displayed the same temperature dependence (eta-0.78) after corrections for thermodynamic driving forces. These results argue for a liquid-state origin of the enhanced growth kinetics. Below ca. Tg + 19 K, delta IMC continued to grow in the same spherulite morphology but alpha and gamma IMC grew in different, fiberlike morphologies and, if measured consistently, at faster rates. We conclude that the liquid dynamics of IMC controls its crystal growth kinetics over a wide range of temperatures but changes of growth morphologies near Tg also lead to apparent acceleration of growth of certain polymorphs. This work also extended a previous study of D-sorbitol to lower temperatures to enable a broader analysis of crystal growth kinetics of organic molecules near Tg. 相似文献
993.
Tsuchiya T Wakahara T Lian Y Maeda Y Akasaka T Kato T Mizorogi N Nagase S 《The journal of physical chemistry. B》2006,110(45):22517-22520
A preferential extraction of endohedral metallofullerenes (EMFs) from carbon soot through the use of reduction in the extraction process and a convenient isolation of endohedral metallofullerene anions (EMFs(-)) and empty fullerenes utilizing their difference in solubility are accomplished. EMFs are easily isolated by one-stage high-performance liquid chromatography after chemical oxidation of the extracted endohedral EMFs(-). 相似文献
994.
We demonstrate the receptor directed end-to-end assembly of multisegment Au/Ni/Au nanowires under agitation in ethanol. The gold end-segments were functionalized with biotin-terminated thiol thereby restricting aggregation to end-to-end attachment via an avidin linkage. On mixing biotin-terminated nanowires with avidin-terminated nanowires, the average chain length is shown to increase linearly with time. The rate constant was independent of the nanowire concentration. Kinetic Monte Carlo simulations were used to model the self-assembly process, and we show that the directed end-to-end assembly of nanowires is similar to the polycondensation of linear polymers. 相似文献
995.
A method has been developed for rapidly separating and detecting strychnine and brucine using a poly(dimethysiloxane) (PDMS)
microchip and electrochemical (EC) detection. PDMS microchannels dynamically modified by Brij35 are shown to be more efficient
than native ones. The two analytes are well separated within 90 s in 70 mmol/L acetate buffer (pH 5.5) containing 0.01% (v/v)
Brij35. Detection limits were found to be 1.0 μmol/L for strychnine and 0.2 μmol/L for brucine at S/N=3. The method was used
to determine trace strychnine and brucine in rat serum, and the results obtained correlate well with those obtained via high-performance
liquid chromatography (HPLC).
相似文献
996.
以2-羟基-1-萘醛和2-氨基-4-硝基苯酚为原料,通过缩合反应合成了阴离子识别受体2-羟基-1-萘醛缩2-氨基-4-硝基苯酚亚胺(R),其结构经1H NMR, 13C NMR和IR表征。采用UV-Vis和1H NMR等研究了受体R对阴离子的识别性能。结果表明:受体R在乙腈中对F-、 H2PO4-和AcO-表现出良好的UV0Vis识别能力,且对上述阴离子表现出裸眼识别性能。通过核磁滴定、紫外滴定、络合常数及Job曲线等对受体R的识别机理进行了研究。结果表明:受体R与阴离子通过分子间氢键结合形成主客体配合物,对F-具有更好的结合能力(络合常数为2.503 × 104 L/mol),与阴离子以比例1/1相互结合。 相似文献
997.
998.
999.
1000.
Fabrication and Properties of Double-Side Tl2Ba2CaCu2O8 Thin Film on CeO2 Buffered Sapphire Substrate
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The double-side Tl2Ba2 CaCu2O8 (Tl-2212) superconducting thin films were fabricated on CeO2 buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO2 buffer thin films on sapphire substrates. Making use of the metal cerium as a sputtering source, the depositing rate is much higher compared with the CeO2 target. The Ti-2212 thin films on CeO2 buffered sapphire substrates were fabricated by adc magnetron sputtering and post-annealing process. The x-ray diffraction indicates that the thin film is pure Tl-2212 phase with the e-axis perpendicular to the substrate surfaces, and epitaxially grown on the CeO2 buffered sapphire. The critical transition temperature Tc is around 106K, the critical current density Jc is around 3.5 MA/cm^2 at 77K, and the microwave surface resistance R8 at 77K and 10 CHz of the film is as low as 390μ Ω. 相似文献