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The influence of suspended fine particles of differing adsorbing capacity (activated carbon, avicell cellulose, SiO2, and molecular sieves) on the liquid-film mass transfer coefficient κL, was examined experimentally in a stirred cell of well-defined gas-liquid interfacial area by chemical methods. The greatest effect on κL was observed with the activated carbon (about a threefold increase). An addition of glycerine in excess of 2.5 × 10-3 k mol/m3, which was adsorbed on the particles preferentially, removed this increase in κL totally. Amongst other particles, only avicell cellulose showed measureable effects. The increase in κL values was inversely proportional to the temperature and the stirring speed, and the particle loading was found to be immaterial after a certain value. When the reaction rate increased (hence, when the thickness of dissolved gas-rich layer decreased) by gradual addition of a homogeneous catalyst (i.e. Co++ for sulphite oxidation), the effect of particles on κL decreased and eventually it disappeared. 相似文献
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Effect of operating parameters on color and COD removal performance of SBR: sludge age and initial dyestuff concentration 总被引:2,自引:0,他引:2
Effect of sludge and initial dyestuff concentration on color and COD removal performance of anaerobic-aerobic sequential batch reactor was investigated. Remazol Red RR a vinylsulphonyl (VS) and monochlortriazine (MCT), reactive azo dye was used in the study. Sludge age was varied between thetaC=12 days and thetaC=30 days and dyestuff concentration was between D0=50 and D0=500 mg l(-1). The maximum color and COD removal was obtained as 95% and 70% for D0=60 mg l(-1) and COD0=800 mg l(-1) at 15 days sludge retention time, respectively, and no further improvement was observed when sludge age was increased to 30 days. The main color removal phase in this operation system was the anaerobic phase. Because, the color removal efficiency was already above 95% under anaerobic condition and therefore, the contribution of aerobic phase to color removal was negligible. Increasing dyestuff concentration did not significantly affect the decolorization. It was possible to obtain over 90% dyestuff removal even at D0=500 mg l(-1). SBR system reduces 1000 mg l(-1) initial COD concentrations to about 400 mg l(-1) for dyestuff concentration up to 150 mg l(-1). COD removal efficiency decreased from 70% to 60% by increasing initial dyestuff concentration from 100 to 500 mg l(-1). The results indicated that dyestuff and COD are mainly used by anaerobic organisms and aeration does not improve the performance of SBR system. 相似文献
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Ideally, network bandwidth estimation algorithms should be independent of the end system performance. If end system capabilities are involved, then the measurement will be of the system throughput and will not indicate a correct assessment of network bandwidth. Packet dispersion‐based active bandwidth estimation schemes including Pathload, TOPP and pathChirp use delay correlation where the network‐induced delay on packets transmitted at certain rates is translated into bandwidth estimation. Since packet dispersion‐based active measurement schemes use delay correlation, bandwidth estimations are distorted by the host protocol stack‐induced delay variations. Studies revealed that the host protocol stack‐induced delay variations due to context switching are stovepiped in the network‐induced delay variations and impact the measurement process. This study explores the delay variations introduced by the host protocol stack in packet dispersion‐based techniques. The impact of host protocol delay variations and context switching on bandwidth estimation is analyzed and a new active bandwidth estimation tool minimizing the impact of context switching is proposed. Direct Injection Chirp (DIChirp) bypasses the TCP/IP protocol stack and directly interfaces with the network hardware. It uses the kernel for scheduling the outgoing packets, thus achieving more accurate estimation of bandwidth. Experiments revealed that the host protocol and context switching‐induced delay variations can be as high as 800µs and could result in bandwidth estimation errors near 20%. Experiments also revealed that the DIChirp is superior to the pathChirp implementation in performance estimation since the datapath utilized by DIChirp is less prone to delay variations induced by context switching. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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The main scope of this comprehensive study is to investigate the effects of poly(p-benzophenoneoxycarbonylphenyl acrylate), poly(BPOCPA), which presenting as only graft units or both graft and ungrafted units in the matrix, on the fundamental features of isotactic polypropylene (IPP). The graft copolymerization of BPOCPA onto IPP was performed with the aid of bulk melt polymerization at varying monomer content levels ranging from 5% to 40%. The thermal behavior, crystal quality, mechanical performance, and surface morphology of the samples were investigated by means of differential scanning calorimeter, X-ray diffractometer (XRD), universal mechanical test, and scanning electron microscope (SEM) techniques. Thermal analyses depicted that there existed the noteworthy enhancements in both crystalline melting temperatures and percent crystallinities of matrix polymers. Furthermore, according to XRD results, a and b parameters increased significantly at low percentages of the graft units, while the parameter c decreased in all products in consistence with the content. As for the mechanical characterization, the grafting led to remarkable improvements in modulus, tensile and impact strength of the products. SEM micrographs indicated that the samples were completely homogeneous without any phase separation and the products exhibited brittle nature with some ductility. 相似文献
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This study investigates how the preparation and re-pelletization of BSCCO ceramic superconductors affects their structural, magnetic, electrical, and mechanical properties. Samples were prepared using conventional methods including the dry solid state (SS) reaction and wet ammonium nitrate (AN) precipitation, with three variations prepared for each technique. The fabricated samples were then characterized with X-ray powder diffraction (XRD) and scanning electron microscopy. The density, resistance vs. temperature characteristics, AC susceptibility vs. temperature characteristics, and magnetic hysteresis properties were measured. In addition, Vicker's microhardness was measured and revealed that all six samples exhibit the reverse indentation size effect (RISE). Microhardness modeling was also conducted. Calculations with Meyer's law, the Hays and Kendall model, and the proportional sample resistance model indicate that the samples are far from the plateau region, whereas the indentation-induced cracking model was consistent with the experimental results. The elastic modulus, Young's modulus, yield strength, and brittleness index were also calculated for each sample. 相似文献
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