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41.
Sandra Pérez-Quirce Felicidad Ronda Carmen Melendre Athina Lazaridou Costas G. Biliaderis 《Food and Bioprocess Technology》2016,9(9):1562-1573
The apparent reduction of β-glucan (BG) molecular weight in rice-based gluten-free (GF) breads fortified with cereal BG concentrates reveals the presence of β-glucanase activity in rice flour. Inactivation of endogenous β-glucanase in rice flour thus seems to be a necessary step when developing GF breads enriched with BG of high molecular weight. The aim of this work was to study the thermal inactivation of endogenous β-glucanase in rice flour by means of microwave (MW) processing; rice flours preconditioned at four different moisture levels (13, 16, 19, 25 %) were treated by MW radiation at 900 W and five MW treatment times (ranging from 40 s to 8 min, applied stepwise at 20-s intervals). The effects of microwaves on starch crystallinity, pasting, and thermal properties of MW-treated rice flours were also explored. The β-glucanase activity in rice flours was assessed by the rate of decrease in specific viscosity of a dilute solution of a purified β-glucan preparation, upon addition of flour extracts. MW proved to be a useful alternative for thermal inactivation of endogenous β-glucanase in rice flours when applied to moistened samples. The inactivation process followed a first-order kinetic response and the apparent rate constant of thermal inactivation increased exponentially with the moisture content of the flour, M, according to the equation 0.0146·exp (0.212·M) (R 2?=?0.97). The MW time required for complete β-glucanase inactivation was only 4 min when the initial flour moisture increased to 25 %. Following MW treatment, the starch crystallinity was unaffected (p?>?0.05) and the side effects of the treatment on flour pasting and thermal properties were rather negligible. 相似文献
42.
Thanasis C. Triantafillou Costas P. Antonopoulos 《Canadian Metallurgical Quarterly》2000,4(4):198-205
The present study describes a simple design model for the calculation of the fiber-reinforced polymer (FRP) contribution to the shear capacity of strengthened RC elements according to the design formats of the Eurocode, American Concrete Institute, and Japan Concrete Institute. The key element in the model is the calculation of an effective FRP strain, which is calculated when the element reaches its shear capacity due to concrete diagonal tension. Diagonal tension failure may be combined with FRP debonding or tensile fracture, and the latter also may occur at a stage beyond the ultimate shear capacity. An upper limit (maximum) to the FRP effective strain also is defined and aimed at controlling crack opening. The effective strain, obtained through calibration with >75 experimental data, is shown to decrease with the FRP axial rigidity divided by the concrete shear strength. It also is demonstrated that the contribution of FRP to shear capacity is typically controlled by either the maximum effective strain or by debonding and, for a given concrete strength, it increases linearly with the FRP axial rigidity until the latter reaches a limiting value beyond which debonding controls and the gain in shear capacity is relatively small. However, proper anchoring (e.g., full wrapping) suppresses the debonding mechanism and results in considerable increases in shear capacity with the FRP axial rigidity. Finally it is demonstrated that, when compared with others, the proposed model gives better agreement with most of the test results available. 相似文献
43.
The selective catalytic reduction of NO by H2 under strongly oxidizing conditions (H2-SCR) in the low-temperature range of 100–200 °C has been studied over Pt supported on a series of metal oxides (e.g., La2O3, MgO, Y2O3, CaO, CeO2, TiO2, SiO2 and MgO-CeO2). The Pt/MgO and Pt/CeO2 solids showed the best catalytic behavior with respect to N2 yield and the widest temperature window of operation compared with the other single metal oxide-supported Pt solids. An optimum 50 wt% MgO-50wt% CeO2 support composition and 0.3 wt% Pt loading (in the 0.1–2.0 wt% range) were found in terms of specific reaction rate of N2 production (mols N2/gcat s). High NO conversions (70–95%) and N2 selectivities (80–85%) were also obtained in the 100–200 °C range at a GHSV of 80,000 h−1 with the lowest 0.1 wt% Pt loading and using a feed stream of 0.25 vol% NO, 1 vol% H2, 5 vol% O2 and He as balance gas. Addition of 5 vol% H2O in the latter feed stream had a positive influence on the catalytic performance and practically no effect on the stability of the 0.1 wt% Pt/MgO-CeO2 during 24 h on reaction stream. Moreover, the latter catalytic system exhibited a high stability in the presence of 25–40 ppm SO2 in the feed stream following a given support pretreatment. N2 selectivity values in the 80–85% range were obtained over the 0.1 wt% Pt/MgO-CeO2 catalyst in the 100–200 °C range in the presence of water and SO2 in the feed stream. The above-mentioned results led to the obtainment of patents for the commercial exploitation of Pt/MgO-CeO2 catalyst towards a new NOx control technology in the low-temperature range of 100–200 °C using H2 as reducing agent. Temperature-programmed desorption (TPD) of NO, and transient titration of the adsorbed surface intermediate NOx species with H2 experiments, following reaction, have revealed important information towards the understanding of basic mechanistic issues of the present catalytic system (e.g., surface coverage, number and location of active NOx intermediate species, NOx spillover). 相似文献
44.
45.
This paper analyses horizontal and vertical price dynamics in the EU petroleum markets. The results indicate that the cross-country price differentials have significant impact on the local price adjustments. We investigate the cross-national price spill-overs and find that the extent of the welfare transfer due to asymmetric price transmission, when analysed in a cross-country setting, is less pronounced than claimed in previous contributions in this area. We also find empirical evidence, although indirect, for the politically charged concept of “fuel tourism”, using a pan-European cross-product time series dataset. 相似文献
46.
Farooq A. Khanday Costas Psychalinos Nisar A. Shah 《Circuits, Systems, and Signal Processing》2013,32(3):959-978
Square-root-domain (SRD) CMOS analog realization of a single cell architecture of the complex Temporal Derivative Cellular Neural Networks (TDCNNs) is introduced in this paper. TDCNN initiates time derivative ‘diffusion’ between CNN cells for non-separable spatiotemporal filtering applications, where the input to the CNN is an image that changes over time. The evaluation of the performance of the complex SRD TDCNN cell has been done using the Cadence Orcad software with TSMC 0.18-μm CMOS process model parameters. The provided simulated results confirm the validity of the theory. 相似文献
47.
We consider a finite-state system with a finite number of clocks, where the transitions may depend on the values of the clocks, and may reset some of the clocks. We address the complexity and provide algorithms for the following problems. Suppose that the system starts from a given current state with a given assignment of values to the clocks. Can a given target state ever appear in the history of the system? What is the earliest time it can appear? What is the latest time it can appear? 相似文献
48.
49.
Steam reforming of methanol is investigated numerically considering both heat and mass transfer of the species in a packed bed microreactor. The numerical results are shown to be in good agreement with experimental data [M.T. Lee, R. Greif, C.P. Grigoropoulos, H.G. Park, F.K. Hsu, J. Power Sources Transport in, 166 (2007) 194–201] with a BASF F3-01(CuO/ZnO/Al2O3) catalyst. A correlation for the conversion efficiency of methanol has been obtained as a function of the operating temperature and a dimensionless time parameter which represents the ratio of the characteristic time of the methanol flow to the time for chemical reaction. The results show that for the constant wall temperature condition the steam reforming process of methanol results in a nearly uniform temperature throughout the microreactor over the range of operating conditions. 相似文献
50.