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41.
The effectiveness of phosphorus‐containing compounds as gas‐phase combustion inhibitors varies widely with flame type. To understand this behavior, experiments are performed with dimethyl methylphosphonate (DMMP) added to the oxidizer stream of methane–air co‐flow diffusion flames (cup‐burner configuration). At low volume fraction, phosphorus (via DMMP addition) is shown to be about four times as effective as bromine (via Br2 addition) at reducing the amount of CO2 required for extinguishment; however, above about 3000 μL/L to 6000 μL/L, the marginal effectiveness of DMMP is approximately zero. In contrast, the diminished effectiveness does not occur for Br2 addition. To explore the role of condensation of active phosphorus‐containing compounds to the particles, laser‐scattering measurements are performed. Finally, to examine the behavior of the flame stabilization region (which is responsible for extinguishment), premixed burning velocity simulations with detailed kinetics are performed for DMMP addition to methane–air flames. Analyses of the numerical results are performed to understand the variation in the inhibition mechanism with temperature, agent loading, and stoichiometry, to interpret the loss of effectiveness for DMMP in the present experiments. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
42.
The characteristics of low temperature-grown GaAs photoconductive antenna (PCA) terahertz detectors probed by 1.56 μm laser pulses are investigated. The influence of TM and TE polarized probe, as well as the saturation characteristics are studied for 2 μm- and 5 μm-gap PCA’s. Different polarization characteristics at low probe powers and at the saturation regimes were observed. Results are explained in terms of the polarization-dependent photocarrier distribution at the PCA gap arising from tight focusing. This work also demonstrates using a 1.56 μm probe for a GaAs PCA to achieve ~60 dB SNR; matching its performance characteristics for above-bandgap probes.  相似文献   
43.
Mesoscopic crystalline anatase particles of titanium(IV) oxide (titania) with decahedral morphology and with octahedral morphology were synthesized by gas-phase reaction of titanium(IV) chloride with oxygen and hydrothermal reaction of titanate nanowires in an alkaline medium, respectively, and their photocatalytic activities in relation with their crystal morphology were investigated.  相似文献   
44.
Several agents are under consideration to replace CF3Br for use in suppressing fires in aircraft cargo bays. In a Federal Aviation Administration performance test simulating the explosion of an aerosol can, however, the replacements, when added at sub-inerting concentrations, have all been found to create higher pressure rise than with no agent, hence failing the test. Thermodynamic equilibrium calculations as well as perfectly-stirred reactor simulations with detailed reaction kinetics, are performed to understand the reasons for the unexpected enhanced combustion rather than suppression. The high pressure rise with added C2HF5 or C3H2F3Br is shown to be dependent upon the amount of added agent, and can only occur if a large fraction of the available oxidizer in the chamber is consumed, corresponding to stoichiometric proportions of fuel, oxygen, and agent. Conversely, due to the unique stoichiometry of CF3Br, this agent is predicted to cause no increase in pressure, even in the absence of chemical inhibition. The stirred-reactor simulations predict that the inhibition effectiveness of CF3Br is highly dependent upon the mixing conditions of the reactants (which affects the local stoichiometry and hence the overall reaction rate). For C2HF5, however, the overall reaction rate was only weakly dependent upon stoichiometry, so the fuel–oxidizer mixing state has less effect on the suppression effectiveness.  相似文献   
45.
Oxidative steam reforming of n-C4H10 over MgO-supported Ni catalysts is described. The Ni/MgO catalysts were prepared by the impregnation method from aqueous Ni(NO3)2 precursor solutions at two pH values. Ni/MgO prepared at pH 7 exhibited considerably higher activity than Ni/MgO prepared from a conventional acidic aqueous precursor solution (pH 3.5). The H2 formation rate for the modified Ni/MgO was up to 2.3 times that for conventional Ni/MgO under a high space velocity of 1660 L(h g)−1. Furthermore, after reduction at high temperature (1273 K), the modified Ni/MgO showed a higher H2 formation rate than did Rh/MgO. The superior performance of the modified Ni/MgO was ascribed to stronger resistance to oxidation of Ni0 due to the formation of relatively large Ni0 particles.  相似文献   
46.
A parallel satisfiability testing algorithm called Parallel Modoc is presented. Parallel Modoc is based on Modoc, which is based on propositional Model Elimination with an added capability to prune away certain branches that cannot lead to a successful subrefutation. The pruning information is encoded in a partial truth assignment called an autarky. Parallel Modoc executes multiple instances of Modoc as separate processes and allows processes to cooperate by sharing lemmas and autarkies as they are found. When a Modoc process finds a new autarky or a new lemma, it makes the information available to other Modoc processes via a “blackboard”. Combining autarkies generally is not straightforward because two autarkies found by two separate processes may have conflicting assignments. The paper presents an algorithm to combine two arbitrary autarkies to form a larger autarky. Experimental results show that for many of the formulas, Parallel Modoc achieves speedup greater than the number of processors. Formulas that could not be solved in an hour by Modoc were often solved by Parallel Modoc in the order of minutes and, in some cases, in seconds. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
47.
Two stability tests of bifidobacteria in powdered formula were conducted. In a strain comparison test, three kinds of bifidobacterial powders; Bifidobacterium longum BB536, Bifidobacterium breve M-16V and Bifidobacterium infantis M-63 powders, admixed in follow-up formula were used. In a commercial product evaluation, powdered formulas for toddlers containing bifidobacteria sold in the Indonesian market were analysed. When the inactivation rate constant of each sample, which was used as an index of the loss rate, was determined from the stability tests, B. longum was the most stable strain. The mean inactivation rate constant of commercial products was significantly lower than those obtained in strain comparison, although the same strains ( B. longum BB536 and B. breve M-16V) were used. A possible reason was the lower water activity of commercial products compared to the follow-up formula. Also, higher storage temperature yielded lower stability in all strains or samples, which obeys the Arrhenius theory.  相似文献   
48.
It is shown that if there equivalently exist the virtual resistive elements in parallel with the inductive elements of the over-normal tree of a given linear active network or in series with the capacitive elements of the corresponding co-tree, an increase in the number of state variables arises. It is also shown that when a virtual resistor equivalently appears in parallel with the distinct resistor in a tree or in series with the distinct resistor in the co-tree, a decrease in the number of state variables may arise. This is, however, a rare case in the usual types of network. Two algebraic methods for obtaining the state equation of linear active networks are presented. One is useful for the networks in which the decrease in the number of state variables does not arise. From the other, the output equation for the required variables is obtained at the same time as the state equation. Further, the initial values are simply determined without iteration in many cases.  相似文献   
49.
The effects of laser peening (LP) on the bending fatigue strength of the 7075‐T651 aluminum alloy were investigated. Accordingly, the defect tolerance of the aluminum alloy subjected to LP is discussed on the basis of fracture mechanics. The results indicate that a deeper compressive residual stress was induced by LP compared with the case of shot peening (SP). The fatigue strengths increased when both peening types were used. Semicircular slits with depths less than 0.4 and 0.1 mm were rendered harmless on the basis of the applications of LP and SP, respectively. The apparent threshold stress intensity factor range ΔKth,ap increased by approximately five and two times owing to LP and SP, respectively. The increase of the ΔKth,ap was caused by the compressive residual stress induced by the peening. The Kitagawa‐Takahashi diagram of the laser‐peened specimens shows that the defect tolerance of the aluminum alloy was improved by LP.  相似文献   
50.
A stable formula using oil-in-water-in-oil (O/W/O) type multiple emulsions was investigated. The components consisted of hydrophilic nonionic surfactant (HCO-60), organophilic montmorillonite, and lipophilic nonionic surfactant (DIS-14). O/W/O emulsions were prepared by a double-step procedure in which an O/W emulsion was prepared in the first step, and then the O/W emulsion was “re-emulsified” in an oil phase with organophilic montmorillonite. The diameter of the innermost oil droplets decreased with increasing HCO-60 content (0.1–3%), while the viscosity showed a maximum at 1% of HCO-60, indicating that the yiel of re-emulsification is highest at this condition. Viscosity of the O/W/O emulsion increased with increasing organophilic montmorillonite and DIS-14. According to the results of a phase ratio study, viscosity and stability of the O/W/O emulsion decreased at high weight fraction of inner oil phase (0.4–0.5), indicating that the excess amount of inner oil phase is absorbed by the outer oil phase. These results revealed that the weight fraction of inner oil phase should be kept below 0.3 for a stable O/W/O emulsion. A similar study on the weight fraction of O/W phase [фO/W)/O] suggested that the O/W/O emulsion is stable at ϕ(O/W)/O=0.65–0.70.  相似文献   
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