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排序方式: 共有178条查询结果,搜索用时 15 毫秒
1.
The health monitoring has been studied to ensure integrity of design of engine structure by detection, quantification, and prediction of damages. Early detection of faults may allow the downtime of maintenance to be rescheduled, thus preventing sudden shutdown of machines. In cylinder pressure developed, vibrations and noise emissions data provide a rich source of information about condition of engines. Monitoring of vibrations and noise emissions are novel non-intrusive methodologies for which positioning of various transducers are important issue. The presented work shows applicability of these diagnosis methodologies adopted in case of diesel engines. The effects of changing various fuel injection parameters was analyzed. Scope of using non-intrusive technique has been analyzed by changing locations of microphone. Novelty of this worklies in exploring signal processing methods for various locations around the engine test set up. Various frequency ranges of contributing noise and vibration sources were identified. Time-Frequency analysis showed the onset of various cyclic. Based on the identification of various frequency bands, it is possible to device suitable filters in order to extract more information. 相似文献
2.
The output characteristics of a high repetition rate pulsed dye laser has both short-term fluctuations and long-term drift.
In high power high repetition rate lasers flow induced variations dominate over those due to other factors. In this paper
it is shown by dye laser measurements that bandwidth fluctuations can be traced to the effective changes of the resonator
dispersion due to fluctuations in the penetration depth of the pump beam in the dye medium. Short-term wavelength fluctuations
can be traced to instantaneous deflection of the dye laser axis by the refractive index changes due to absorption of the pump
beam. The fluctuations in both the bandwidth and the wavelength decreases with increasing flow rates within a laminar region.
A copper vapor laser operating at 5.6 kHz repetition rate pumped the Rhodamine 6G dye laser used. The wavelength fluctuation
of ±0.0035, 0.0030, 0.0004 nm and the bandwidth fluctuation of ±710, 132, 45 MHz over approx. 60 minutes were observed at
1.2, 3.7, 5.5 lpm flow rates respectively. 相似文献
3.
Aditya M. Vora 《Journal of Non》2008,354(45-46):5022-5032
A well recognized model potential is used to study the superconducting state parameters (SSP) viz. electron–phonon coupling strength λ, Coulomb pseudopotential μ1, transition temperature TC, isotope effect exponent α and effective interaction strength N0V of some binary metallic glasses of simple, non-simple and transition metals. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru–Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used in the present investigation to study the screening influence on the aforesaid properties. Instead of using Vegard’s law, pseudo-alloy-atom model (PAA) in the present investigation is proposed and found successful. The present results of the SSP are found in qualitative agreement with other such earlier reported data wherever exist, which confirms the superconducting phase in the metallic glasses. 相似文献
4.
We present a theoretical analysis of corrugated long-period gratings in planar waveguides. In particular, we calculate the transmission spectra for both the TE and TM polarizations and highlight the polarization-independence conditions. 相似文献
5.
Vipul Dav Wolfgang G. Glasser Garth L. Wilkes 《Journal of Polymer Science.Polymer Physics》1993,31(9):1145-1161
Fibers were spun from isotropic and anisotropic dimethylacetamide solutions of cellulose esters. Take-up speeds of the dry jet/wet spinning process varied. Water served as the coagulant. The mechanical properties of the fibers increased as spinning progressed from the isotropic to the anisotropic state of the solution. A trade-off in solubility and fiber properties was noted as the butyryl acetyl ratio decreased. Whereas high butyryl content enhances both overall solubility and the formation of liquid–crystalline solutions at lower concentration, it results in lower fiber modulus and strength. Morphology of the fibers depended on the coagulation rate which was influenced by the concentration of the sppinning solution. The level of orientation and crystallinity of the fibers increased somewhat when they were spun from liquid-crystalline solutions. © 1993 John Wiley & Sons, Inc. 相似文献
6.
Vora A. Riga A. Dollimore D Alexander K. 《Journal of Thermal Analysis and Calorimetry》2004,75(3):709-717
This study attempts to identify the degradative process which folic acid undergoes in the solid-state under thermal stress.
In order to facilitate the process, the various pieces of the chemical structure, namely, p-amino benzoic acid, pterin and glutamic acid as both its d- and l-isomers were investigated as separate entities. These structured solid-state pieces were then compared to the composite solid
state folic acid degradative curves in order to identify the peaks seen and provide direction for the interpolation of the
degradative mechanism. It was observed that none of the structural pieces could be superimposed as assumed earlier and hence
an attempt was made to identify the decomposition products using various analytical techniques such as infrared spectroscopy,
mass spectroscopy and X-ray diffraction which suggested that the glutamic acid fragment is lost first as evidenced by acid
loss and amide enhancement in the IR spectra. The vitamin was ultimately degrading to carbon fragments and that further identification
was not necessary.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Sanyal A Rautaray D Bansal V Ahmad A Sastry M 《Langmuir : the ACS journal of surfaces and colloids》2005,21(16):7220-7224
We show here that reaction of the fungus, Fusarium oxysporum, with the aqueous heavy-metal ions Pb2+ and Cd2+ results in the one-step formation of the corresponding metal carbonates. The metal carbonates are formed by reaction of the heavy-metal ions with CO2 produced by the fungus during metabolism and thus provide a completely biological method for production of crystals of metal carbonates. The PbCO3 and CdCO3 crystals thus produced have interesting morphologies that are shown to arise because of interaction of the growing crystals with specific proteins secreted by the fungus during reaction. An additional advantage of this approach is that the reaction leads to detoxification of the aqueous solution and could have immense potential for bioremediation of heavy metals. Under conditions of this study, the metal ions are not toxic to the fungus, which readily grows after exposure to the metal ions. 相似文献
8.
Ali M. Emran Th E. Boothe R. D. Finn M. M. Vora P. J. Kothari 《Journal of Radioanalytical and Nuclear Chemistry》1985,91(2):277-284
An analytical technique using reversed-phase liquid chromatography has been developed for the determination of urea at quantities as low as 1 ng to quantitate the amount of non-labelled urea produced during the synthesis of no-carrier-added {11C}urea starting from11CN–. As a result, the specific activity of the {11C} urea thus prepared was calculated to be as high as 3.5±0.8 Ci/mol.Research supported in part by PHS Grant NINCDS 1 PO1 NS 15639. 相似文献
9.
10.