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排序方式: 共有1625条查询结果,搜索用时 15 毫秒
71.
Pradeep L. Menezes Kishore Satish V. Kailas Michael R. Lovell 《Journal of Materials Engineering and Performance》2011,20(8):1438-1446
In the present investigation, soft materials, such as Al-4Mg alloy, high-purity Al and pure Mg pins were slid against hard
steel plates of various surface textures to study the response of materials during sliding. The experiments were conducted
using an inclined pin-on-plate sliding apparatus under both dry and lubricated conditions in an ambient environment. Two kinds
of frictional response, namely steady-state and stick-slip, were observed during sliding. In general, the response was dependent
on material pair, normal load, lubrication, and surface texture of the harder material. More specifically, for the case of
Al-4Mg alloy, the stick-slip response was absent under both dry and lubricated conditions. For Al, stick-slip was observed
only under lubricated conditions. For the case of Mg, the stick-slip response was seen under both dry and lubricated conditions.
Further, it was observed that the amplitude of stick-slip motion primarily depends on the plowing component of friction. The
plowing component of friction was the highest for the surfaces that promoted plane strain conditions and was the lowest for
the surfaces that promoted plane stress conditions near the surface. 相似文献
72.
Jeremy M. Rathfon Zoha M. AL‐Badri Raja Shunmugam Scott M. Berry Santosh Pabba Robert S. Keynton Robert W. Cohn Gregory N. Tew 《Advanced functional materials》2009,19(5):689-695
The chemical sensing of nerve gas agents has become an increasingly important goal due to the 1995 terrorist attack in a Tokyo subway as well as national security concerns in regard to world affairs. Chemical detection needs to be sensitive and selective while being facile, portable, and timely. In this paper, a sensing approach using a pyrene imine molecule is presented that is fluorimetric in response. The detection of a chloro‐Sarin surrogate is measured at 5 ppmv in less than 1 second and is highly selective towards halogenated organophosphates. The pyrene imine molecule is incorporated into polystyrene films as well as micrometer and sub‐micrometer fibers. Using both a direct drawing approach and electrospinning, micrometer and nanofibers can be easily manufactured. Applications for functional sensing micrometer and nanofibers are envisioned for optical devices and photonics in addition to solution and airflow sensing devices. 相似文献
73.
D.G. Narehood S. Kishore H. Goto J.H. Adair J.A. Nelson H.R. Gutiérrez P.C. Eklund 《International Journal of Hydrogen Energy》2009
In situ X-ray diffraction (XRD) and gravimetric hydrogen uptake measurements of d ∼ 2–3 nm spherical PdHx particles have been studied in the temperature and pressure range of 323 < T < 428 K and 0 < P < 10 bar. The Pd particles were protected from sintering with a hydrogen-permeable carbon coating. While only containing ∼300–1000 atoms, the Pd particles were found to exhibit the same fcc structure and lattice constant as the bulk. Our isothermal studies show that, with increasing x, these highly crystalline PdHx nanoparticles also exhibit a complete transformation from the dilute α solid solution phase to the more concentrated β hydride phase. However, we observed that the character of the α–β phase transition in these nanoparticles is very different from that in the bulk. Indeed, the hydrogen uptake isotherm exhibits a noticeable positive slope in the α + β co-existence region. Furthermore, we also observed a noticeable narrowing of the α + β co-existence region (δx) in the nanoparticles. Also, a significant suppression of the critical temperature Tc for the phase boundary was observed: Tc(nano) ≈ 430 K while Tc(bulk) ≈ 570 K. These results signal a significant change in the thermodynamic behavior of very small hydride nanoparticles that may be common to many other nano-scale metal hydride systems as well. 相似文献
74.
Santhi K Dhanaraj SA Rajendran SD Raja K Ponnusankar S Suresh B 《Drug development and industrial pharmacy》1999,25(4):547-551
The stability of liposomes after introduction into the body is presently being discussed and needs thorough understanding. Hence, as a nonliposomal approach, egg albumin nanospheres were prepared by the pH-coacervation method, and a preliminary study was carried out of the influence of process variables on the size and shape of nanospheres by changing the pH of the albumin solution, concentration of albumin solution, and volume of cross-linking agent. The batch prepared with an albumin medium of pH 9, 2% concentration, and 100 μl of 4% glutaraldehyde-ethanol solution was found to have a spherical uniform shape with an average size of 497.6 nm. The ideal batch was loaded with the systemic antifungal drug amphotericin-B. Drug-loaded nanospheres were evaluated to study their in vitro release. They were found to exhibit a biphasic pattern with a cumulative percentage release of 97.7%. 相似文献
75.
Pijush K. Mitra Prodyot K. Sarkar Dipti K. As Bimalendu Biswas Aditya B. Chakraborty Krishna Raja 《Fuel》1978,57(10):639-642
A study of the effect of ash yield on the maximum thickness of the plastic layer (MTPL) of some coking coals (as measured by the Sapozhnikov plastometer) has revealed that with an increase in the former the latter in general decre?es. A rectilinear relation approximately exists between the ash percentage (dry basis) and log MTPL values of coals. For the samples studied, a multiple correlation incorporating the rank factor was found to be unnecessary. Higher Fe2O3 and SO3 contents from the coal were found to be associated with higher MTPL values. 相似文献
76.
Muhammad Asif Zahoor Raja Siraj-ul-Islam Ahmad Raza Samar 《Neural computing & applications》2013,23(7-8):2199-2210
In this paper, a stochastic technique is developed to solve 2-dimensional Bratu equations using feed-forward artificial neural networks, optimized with genetic and interior-point algorithms. The 2-dimensional equations are first transformed into a 1-dimensional boundary value problem, and a mathematical model of the transformed equation is then formulated with neural networks using an unsupervised error. Network weights are optimized to minimize the error. Evolutionary computing based on genetic algorithms is used as a tool for global search, integrated with an interior-point method for rapid local convergence. The methodology is applied to solve three cases of boundary value problems for the Bratu equations. The accuracy, convergence and effectiveness of the scheme is validated for a large number of simulations. Comparison of results is made with the exact solution derived using MATHEMATICA, and is found to be in good agreement. 相似文献
77.
Siddarth Shankar Das Karanam Kishore Kumar Subrata Kumar Das Chandrasekharan Vineeth Tarun Kumar Pant Geetha Ramkumar 《International journal of remote sensing》2013,34(14):4634-4647
Two independent methods for deriving mesopause temperature using meteor radar installed at an equatorial station, Thumba (8.5° N, 76.5° E), are discussed in this article. This meteor radar-derived mesopause temperature is then compared with two different types of spaceborne measurement, namely (i) Sounding the Atmosphere using Broadband Emission Radiometry (SABER) and (ii) the Earth Observing System Microwave Limb Sounder (EOS MLS), and a collocated multi-wavelength dayglow photometer (DGPM). The meteor radar-derived temperature is in fairly good agreement with all the three measurement techniques, with an uncertainty of ±10°. This study focuses on a detailed evaluation and inter-comparison of mesopause temperature derived from different measurement techniques. An attempt is also made to compare the suitability of these observations to study planetary waves and other oscillation activities in the mesospheric region. 相似文献
78.
79.
Raja R. A. Issa Robert F. Cox Clifford F. Killingsworth 《Canadian Metallurgical Quarterly》1999,13(4):281-290
Studies measuring and evaluating the impact of the same multimedia-based education on learners in universities and high schools are a relatively new phenomenon. This study provides a summary of the results from research on the effects of multimedia-based safety education conducted by the M. E. Rinker Sr. School of Building Construction at the University of Florida. The findings are presented along with their related statistical test results. The findings indicate multimedia-based, self-paced learning offers very distinct advantages over traditional, instructor-led classroom learning. Overall, both the high-school and university student groups involved in the study exhibited superior retention rates when learning from the multimedia-based materials. Higher scoring students in the classroom showed little difference in either media, while students who tended to score at the low end of the grading scale uniformly scored higher on multimedia-based materials. The reduced variation in student performance based on test scores in the CD-ROM instruction indicates the positive effects of multimedia-based instruction. 相似文献
80.
In 2012, the government of Bihar revived 34 non-functioning public tubewells using solar panels. The performance of 16 of these wells over 12 months was tracked and analyzed using data from tubewell operators and 240 farmers. Access to affordable irrigation from solar pumps led to a 9–10% increase in productivity of rice and wheat. Furthermore, in a severe drought, farmers could grow paddy in the entire area irrigated by solar pumps, when nearly 40% of other land was left fallow. Solar pumps can help increase crop productivity, reduce the cost of irrigation, and make agriculture more resilient to climate change. 相似文献