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991.
Jiasong Zhong Weidong Xiang Zhaoping Chen Haijun Zhao Xiaojuan Liang 《Materials Science and Engineering: B》2013,178(15):998-1003
Cu nanocrystals embedded in sodium borosilicate glass of varied Cu contents from 0.5 to 1.5 wt% have been successfully prepared through a sol–gel process. According to the results of X-ray diffraction (XRD) and the energy dispersive X-ray spectrometry (EDS), the metal Cu nanocrystals in cubic crystal system were well distributed inside glass matrix. Fourier Transform Infrared (FTIR) indicated the sodium borosilicate matrix had no major structural change for gels with different Cu contents. The optical absorption peaks due to the surface plasmon resonance of Cu particles were observed in the wavelength range of 550–600 nm. The absorption peak showed a red-shift trend with increasing Cu contents from 0.5 to 1.5 wt%. Transmission electron microscopy (TEM) revealed the existence of spherical Cu nanocrystals in the matrix. The diameter of Cu nanocrystals varied from 1 to 3.5 nm. Furthermore, the third-order nonlinear optical properties were investigated by Z-scan technique at 800 nm. Experimental results indicated the Cu nanocrystals have obvious positive refractive nonlinearities and reverse saturated absorption performance. 相似文献
992.
993.
A strategy for controlling a fed‐batch Escherichia coli culture is described to maintain the culture at the boundary between oxidative and oxido‐fermentative regimes. A nonlinear predictive controller is designed to regulate the acetate concentration, constraining the feed rate to follow an optimal reference profile which maximizes the biomass growth. For the sake of simplicity and efficiency, the original problem is converted into an unconstrained nonlinear programming problem, solved by control vector parameterization techniques. The robustness of the structure is further improved by explicitly including the difference between system and model prediction. A robustness study based on a Monte Carlo approach is used to evaluate the performance of the proposed controller. This control law is finally compared to the generic model control strategy. 相似文献
994.
The objective of the study was to systematically investigate flavor compounds in Chinese rice wine (CRW) using chromatography technology. In twelve CRW samples, 93 different flavor compounds were detected and identified including 16 alcohols in addition to ethanol, 29 esters, 9 aldehydes, 9 organic acids, 19 amino acids and 11 fatty acids. Statistical analysis by principal component analysis (PCA) indicated that seventeen flavor compounds in Guyue Longshan rice wine made a large contribution to its special flavor. These compounds were benzaldehyde, acetaldehyde, ethyl 2‐hydroxy‐4‐methylvalerate, ethyl butyrate, phenyl ethyl isobutyrate, ethyl benzoate, ethyl phenyl‐acetate, methyl dodecanoate, methyl oleate, ethyl dedecanoate, 1‐butanol, 3‐ethoxyl‐1‐propanol, 1‐enanthol, dodecanol, lactic acid, fumaric acid and lauric acid. 相似文献
995.
《国际计算机数学杂志》2012,89(1):95-104
New L-stable trapezoidal formulas obtained by modifying the nonlinear trapezoidal formulas are presented. Numerical results are presented to confirm the theoretical stability analysis. 相似文献
996.
This paper presents the measurement of the nonlinear mechanical properties of polydimethylsiloxane (PDMS) elastomer based on the mixing ratio of base polymer to curing agent. Strip-type PDMS samples with different mixing ratios were prepared using a simple coating, curing, and cutting process. A cyclic uniaxial tension test with a fixed magnitude of applied strain and a single-pull-to-failure tension test were performed with a micro-tensile tester at room temperature.Our new finding is that when the PDMS is mixed with excessive curing agent, stress softening occurs and residual strain exists in cyclic tension tests when the magnitude of the applied strain increases. For the PDMS-05 samples, in which the mixing ratio of base polymer to curing agent was 5 to 1, there were large differences in the stresses for the same strain level under loading and unloading during the first cycle with a 100% fixed strain amplitude, but the softening effect of the stress in the PDMS dropped rapidly starting from the second cycle.Nonlinear mechanical Neo-Hookean, third-order Mooney, and second-order Ogden models of three different PDMS films were computed from the stress-strain data. The results showed that all models were preferable for the small strain region of PDMS compared with other models. In the nonlinear, large strain region, only the second-order Ogden model properly described the mechanical behavior of the PDMS, while the Neo-Hookean and third-order Mooney-Rivlin models were too stiff or flexible in the measurement range. The bulk modulus of PDMS increased with the amount of curing agent in it. Therefore, the second-order Ogden model is preferable for analyzing the PDMS structure over the entire measurement range. This could provide reasonable mechanical models of PDMS for rapid computational prototyping and for designing active and passive components from PDMS. 相似文献
997.
S.M. Moghimi G. Domairry Soheil SoleimaniE. Ghasemi H. Bararnia 《Advances in Engineering Software》2011,42(3):108-113
The MHD Jeffery-Hamel flows in non-parallel walls are investigated analytically for strongly nonlinear ordinary differential equations using homotopy analysis method (HAM). Results for velocity profiles in divergent and convergent channels are presented for various values of Hartmann and Reynolds numbers. The convergence of the obtained series solutions is explicitly studied and a proper discussion is given for the obtained results. Comparison between HAM and numerical solutions showed excellent agreement. 相似文献
998.
999.
Nonlinear interaction of a monochromatic elastic wave with a low frequency should be a good tool for non-destructive evaluation of existing concrete structures. Nonlinear indicators have already proved efficient in detecting global damage by exhibiting a significant sensitivity regarding classical linear ultrasonic methods like wave speed or attenuation. However, it is necessary to understand the influence of some structural parameters such as porosity, stress state, or water saturation on the nonlinear processes. In this way, a recent model containing all of these potential contributors is presented in this paper. It is sustained by nonlinear interaction experiments in impact mode. This method reveals a great potential for in situ measurements with a low frequency propagating into the whole structure. We make use of a calibrated concrete sample's series, conditioned at different water saturation states, to quantify the influence of water content and porosity on the nonlinear response of concrete. 相似文献
1000.
Hydrogenated amorphous silicon-selenium alloy thin films grown by capacitively coupled radio-frequency glow-discharge are investigated. Nonlinear absorptive effects are evaluated with the help of open aperture z-scan technique in the 525 to 580 nm spectral range. The nonlinear absorption coefficient is found to be very large and reaching the value of 5.14 × 10− 3 cm/W at 525 nm. The origin of the optical nonlinearities is studied and found to be due mainly to two photon absorption in the case of pulsed excitation, whereas thermal effects are thought to be dominant when the sample is excited with a continuous wave laser. Optical limiting potentialities of the thin film are experimentally observed and their thresholds are found to be very low. 相似文献