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排序方式: 共有624条查询结果,搜索用时 15 毫秒
51.
Surdo EM Khan IA Choudhury AA Saleh NB Arnold WA 《Journal of hazardous materials》2011,188(1-3):334-340
Carbon nanotube addition has been shown to improve the mechanical properties of some polymers. Because of their unique adsorptive properties, carbon nanotubes may also improve the barrier performance of polymers used in contaminant containment. This study compares the barrier performance of poly(vinyl alcohol) (PVA) membranes containing single-walled carbon nanotubes (SWCNTs) to that for PVA containing powdered activated carbon (PAC). Raw and surface-functionalized versions of each sorbent were tested for their abilities to adsorb 1,2,4-trichlorobenzene and Cu(2+), representing the important hydrophobic organic and heavy metal contaminant classes, as they diffused across the PVA. In both cases, PAC (for 1,2,4-trichlorobenzene) and functionalized PAC (for Cu(2+)) outperformed SWCNTs on a per mass basis by trapping more of the contaminants within the barrier membrane. Kinetics of sorption are important in evaluating barrier properties, and poor performance of SWCNT-containing membranes as 1,2,4-TCB barriers is attributed to kinetic limitations. 相似文献
52.
A solid state reaction method was used to synthesize barium titanate (BT) and barium cerium titanate (BCT) ceramics at sintering temperature of 1473 K for 4 h. The effect of cerium (Ce) on the structure, microstructure and dielectric properties of BCT was investigated. The scanning electron microscopy (SEM) investigations revealed that the grain size increases with increasing Ce content. The X-ray diffraction (XRD) patterns showed mostly the BT phase, where the lattice parameter decreased with the addition of Ce. The temperature dependence of dielectric constant showed decrease in the phase transition temperature with higher Ce content. The dielectric constant decreased slightly with increasing frequency. The direct current (dc) density-voltage characteristics of the ceramics showed ohmic behavior for both the BT and BCT. As the temperature increased, the dc resistivity of the ceramics decreased. The activation energy increased with increasing Ce content. 相似文献
53.
Galileo Sarasqueta Kaushik Roy Choudhury Jegadesan Subbiah Franky So 《Advanced functional materials》2011,21(1):167-171
A PbSe solution‐processed nanocrystal‐based infrared photodetector incorporating carrier blocking layers is demonstrated, and significant reduction of dark current is achieved. Detectivity values close to 1012 Jones are achieved by using poly[(9,9′‐dioctylfluorenyl‐2,7‐diyl)‐co‐(4,4′‐(N‐(4‐sec‐butyl))diphenylamine)] (TFB) and ZnO nanocrystals (NC) as the electron blocker and hole blocker, respectively. An improvement in lifetime is also observed in the devices with the ZnO NCs hole blocking layer. 相似文献
54.
Nicholas D. Lane Mu Lin Mashfiqui Mohammod Xiaochao Yang Hong Lu Giuseppe Cardone Shahid Ali Afsaneh Doryab Ethan Berke Andrew T. Campbell Tanzeem Choudhury 《Mobile Networks and Applications》2014,19(3):345-359
Smartphone sensing and persuasive feedback design is enabling a new generation of wellbeing apps capable of automatically monitoring multiple aspects of physical and mental health. In this article, we present BeWell+ the next generation of the BeWell smartphone wellbeing app, which monitors user behavior along three health dimensions, namely sleep, physical activity, and social interaction. BeWell promotes improved behavioral patterns via feedback rendered as an ambient display on the smartphone’s wallpaper. With BeWell+, we introduce new mechanisms to address key limitations of the original BeWell app; specifically, (1) community adaptive wellbeing feedback, which generalizes to diverse user communities (e.g., elderly, children) by promoting better behavior yet remains realistic to the user’s lifestyle; and, (2) wellbeing adaptive energy allocation, which prioritizes monitoring fidelity and feedback responsiveness on specific health dimensions (e.g., sleep) where the user needs additional help. We evaluate BeWell+ with a 27 person, 19 day field trial. Our findings show that not only can BeWell+ operate successfully on consumer smartphones; but also users understand feedback and respond by taking steps towards leading healthier lifestyles. 相似文献
55.
Rigid-ion model calculations of phonon dispersion relations, densities of states and partial densities of states of the highT
c
superconductor La2CuO4 and its isostructural compound La2NiO4 have been carried out both in the tetragonal and orthorhombic phases of La2CuO4 and the tetragonal phase of La2NiO4. The calculations are in fair agreement with reported experiments. The computed phonon dispersion in the tetragonal phase
of La2CuO4 reproduces the soft mode behaviour for the lowest Σ4 TO branch which is found to harden in the orthorhombic phase, consistent with experimental data. 相似文献
56.
57.
L Aziz SM Jahangir SN Choudhury K Rahman Y Ohta M Hirakawa 《Canadian Metallurgical Quarterly》1997,85(3):663-666
The priming principle consists of administering a subparalyzing dose of nondepolarizing neuromuscular blocking drug 3-6 min before giving a second dose for tracheal intubation. This study was performed to observe the effects of priming doses of vecuronium and rocuronium on pulmonary function tests and muscular weaknesses in young (25-35 yr of age) and elderly (65-73 yr of age) patients. Ten young and 10 elderly patients were each placed in vecuronium and rocuronium groups. Oxygen saturation and train-of-four (TOF) ratio were determined, and pulmonary function tests were performed. Then 20% of the 95% effective dose (ED95) of the muscle relaxants was given intravenously. All tests were performed again 4 min after vecuronium and 3 min after rocuronium. Other signs of muscular weaknesses were also recorded. Elderly patients showed more signs of muscle weakness in both groups. The TOF ratio was 0.77 and 0.79 in the elderly rocuronium and vecuronium groups, respectively, and 0.89 and 0.90 in the young rocuronium and vecuronium groups, respectively. Dynamic spirometry revealed decreases in forced expiratory volume in 1 s and forced vital capacity in both groups, and no significant changes in peak expiratory flow rate. The expiratory reserve volume was reduced more in the elderly groups. Oxygen saturation decreased in both groups. We conclude that oxygen saturation, pulmonary function, and muscle strength decrease more in the elderly than in their younger counterparts from priming doses of vecuronium or rocuronium. IMPLICATIONS: The priming principle consists of giving a subparalyzing dose of muscle relaxant 3-6 min before giving a second dose for tracheal intubation. We found that priming doses of vecuronium and rocuronium produced greater decreases in oxygen saturation and pulmonary function in the elderly (aged 65-73 yr) than their younger (aged 25-35 yr) counterparts. Priming may not be a safe approach in elderly patients. 相似文献
58.
Epidemiological studies of blood groups in the district of Bankura with special reference to tribals
A Choudhury UK Dutta A Bhattacharyya S Mukherjee 《Canadian Metallurgical Quarterly》1994,92(9):291-292
Distribution of ABO blood groups was studied in 4301 subjects, both tribals and non-tribals of the district of Bankura in West Bengal. It was observed that group 'O' blood was found in most cases and group 'AB' was seen in least number of cases. It was also found that there was no significant difference in distribution of blood groups between the tribals and non-tribals. 相似文献
59.
Although ATM seems to be the wave of the future, one analysis requires that the utilization of the network be quite low. That analysis is based on asymptotic decay rates of steady-state distributions used to develop a concept of effective bandwidths for connection admission control. The present authors have developed an exact numerical algorithm that shows that the effective-bandwidth approximation can overestimate the target small blocking probabilities by several orders of magnitude when there are many sources that are more bursty than Poisson. The bad news is that the appealing simple connection admission control algorithm using effective bandwidths based solely on tail-probability asymptotic decay rates may actually not be as effective as many have hoped. The good news is that the statistical multiplexing gain on ATM networks may actually be higher than some have feared. For one example, thought to be realistic, the analysis indicates that the network actually can support twice as many sources as predicted by the effective-bandwidth approximation. The authors also show that the effective bandwidth approximation is not always conservative. Specifically, for sources less bursty than Poisson, the asymptotic constant grows exponentially in the number of sources (when they are scaled as above) and the effective-bandwidth approximation can greatly underestimate the target blocking probabilities. Finally, they develop new approximations that work much better than the pure effective-bandwidth approximation 相似文献
60.