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排序方式: 共有750条查询结果,搜索用时 218 毫秒
731.
An electrochemical analog of a biofilm was constructed to test the accuracy of oxygen flux measurements using microelectrodes. We used a cathodically polarized graphite felt attached to the bottom of a flat plate open channel reactor as the reactive surface consuming oxygen. The oxygen flux to the felt was calculated from the polarization current. Microelectrodes were used to measure the oxygen profiles above and within the graphite felt. From the shape of the oxygen profile we evaluated the oxygen flux to the graphite felt. This provided us with two sets of data, the true oxygen flux, calculated from polarization current, and the oxygen flux estimated from microelectrode measurements. Comparing these two fluxes, for different flow velocities, showed that the fluxes evaluated from the polarization current were different from those evaluated from the oxygen profiles. The differences were likely caused by the presence of the microelectrode in the mass boundary layer and/or by the simplifying assumptions accepted in computational procedures employed to calculate oxygen fluxes. For low flow velocities, between zero and 1.0 cm s−1, the differences were velocity sensitive; the higher the flow velocity, the bigger the difference. For higher flow velocities, between 1 cm s−1 and 3 cm s−1, the flux of oxygen estimated from the microelectrode measurements was consistently approximately 80% higher than the true oxygen flux estimated from the polarization current. 相似文献
732.
Zbigniew Lewandowski 《Water research》1985,19(4):535-539
The process of nitrification in activated sludge was investigated. As the solid support for nitrifiers' growth a suspension of marble particles has been used. The results proved the possibility of successful nitrification of 100 mg l?1 NH4-N simultaneously with the removal of 600 mg l?1 COD. 相似文献
733.
A new application of the optical vortex birefringence compensator has been presented. Two parameters of elliptically birefringent medium, an ellipticity angle and an optical path difference, can be measured simultaneously in the setup based on the C polarization type singularities generated using two Wollaston compensators. The theory and numerical investigations of the proposed method have been presented as well as some experiments verifying our theoretical predictions. 相似文献
734.
The interaction of NO and O2 with 5 mol.% of vanadia deposited on Ce0.10Zr0.90O2 and Ce0.69Zr0.31O2 supports by wet impregnation was studied by means of EPR and IR. The supports were structurally characterized by XRD and Raman spectroscopy. Influence of the phase composition of the support on vanadium speciation as well as on surface architecture of the oxovanadium entities was discussed. The NO forms adsorbed on vanadium-containing systems were compared to those observed on bare CeO2-ZrO2 supports. The main products appearing on the catalysts surface during the consecutive reaction with NO and O2 were identified and their thermal evolution was observed. Changes in vanadium speciation accompanying redox processes related to NO and O2 activation were also observed and discussed. 相似文献
735.
Piotr Marek Kuś Francesca Congiu Dariusz Teper Zbigniew Sroka Igor Jerković Carlo Ignazio Giovanni Tuberoso 《LWT》2014
Total phenolic content, antioxidant activity (two assays: 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and ferric reducing antioxidant power (FRAP)), and color coordinates (CIE (Commission Internationale de l'Eclairage) L*a*b*) for six Polish unifloral honeys (black locust, rapeseed, lime, goldenrod, heather and buckwheat) were assessed for several batches of the same honey type and statistically evaluated. Total phenolic content (121.6–1173.8 mg GAE/kg) was similar to the values previously reported for other European honeys and it was also correlated with the color parameters as well as antioxidant activity. The honeys' color ranged from pale yellow to dark amber. Dark buckwheat honey with much higher phenolic content (1113.0 mg GAE/kg) exhibited higher antioxidant activity (5.7 mmol Fe2+/kg and 1.2 mmol TEAC/kg). CIE L*a*b* color coordinates can be helpful for identifying and distinguishing between several honey types, such as heather and buckwheat, but almost no differences were found among very light honeys (rapeseed, goldenrod, black locust and lime). High-performance liquid chromatographic (HPLC) analysis revealed general characteristic fingerprints of Polish unifloral honeys with significant differences among the samples of other honey types. 相似文献
736.
Janusz Gill und Zbigniew Jaczewski 《Zeitschrift für Jagdwissenschaft》1956,4(4):168-171
Zusammenfassung An drei Hirschen wurden die Gewichte und Volumina des Verdauungstraktes festgestellt. Die absolute und relative Kaparität, das Verhältnis der Kapazität zum Körpergewicht sowie die Länge und Gewichte der einzelnen Verdauungsabschnitte und deren Inhalt sind in Tabellen angegeben.
Summary In case of three red deer weights and volumes of the digestive tract were stated. Absolute and relative capacity, the relation of capacity to body weights as well as length and weights of different digestive sections and their contents have been stated in tables.
Résumé Sur trios cerfs on déterminait les poids et les volumes de l'appareil de la digestion. La capacité absolue et relative, la rélation de la capacité au poids du corps, ainsi que la longueur et les poids des diffrentes sections digestives et leur contenu sont présentés en tableaux.相似文献
737.
Sandra Paszkiewicz Konrad Walkowiak Izabela Irska Zbigniew Rozwadowski Jerzy Dryzek 《应用聚合物科学杂志》2024,141(11):e55089
Two series of biobased poly(ether-ester)s comprised of poly(hexamethylene 2,5-furandicarboxylate) (PHF) as the rigid segments and biopolytetrahydrofuran (pTHF) with different molecular masses (1000 and 2000 g/mol) as the flexible segments were synthesized employing polycondensation in the molten state. The study mainly focuses on comparing these two series in terms of the length of the flexible segment. The content of pTHF segments in the copolymer chains varied from 25 to 75 wt.%. The molecular structure and composition, phase structure, and thermal and mechanical properties were characterized by nuclear magnetic resonance (1H NMR) and Fourier-transformed infrared (FTIR) spectroscopies, differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and positron annihilation lifetime spectroscopy (PALS). In addition, mechanical performance and thermo-oxidative and thermal stability have been investigated. Moreover, cyclic tensile properties were studied to evaluate the elastic properties. 1H NMR and FTIR spectroscopies demonstrate that the syntheses were correctly carried out, which made it possible to obtain the desired compositions of the block copolymers with high molecular masses. The decrease in Tm1, Tc1, and XcPHF values was visible, along with the increase in the flexible segment content. Moreover, the characteristic properties measured by PALS and the values of temperatures designated from TGA (inert and oxidizing atmosphere) did not vary between copolymer series PHF-b-F-pTHF1000 and PHF-b-F-pTHF2000. In turn, along with an increase in flexible segment content and the length of the pTHF, the values of tensile modulus, stress at break, and hardness decrease, while the value of elongation at break increases. 相似文献
738.
Zbigniew W. Kundzewicz Yukiko Hirabayashi Shinjiro Kanae 《Water Resources Management》2010,24(11):2633-2646
River flood damages, worldwide, have increased dynamically in the last few decades, so that it is necessary to interpret this
change. River flooding is a complex phenomenon which can be affected by changes coupled to terrestrial, socio-economic and
climate systems. The climate track in the observed changes is likely, even if human encroaching into the harm’s way and increase
in the damage potential in floodplains can be the dominating factors in many river basins. Increase in intense precipitation
has already been observed, with consequences to increasing risk of rain-induced flooding. Projections for the future, based
on climate model simulations, indicate increase of flood risks in many areas, globally. Over large areas, a 100-year flood
in the control period is projected to become much more frequent in the future time horizon. Despite the fact that the degree
of uncertainty in model-based projections is considerable and difficult to quantify, the change in design flood frequency
has obvious relevance to flood risk management practice. The number of flood-affected people is projected to increase with
the amount of warming. For a 4°C warming the number of flood-affected people is over 2.5 times higher than for a 2°C warming.
The present contribution addresses the climate track in an integrated way, tackling issues related to multiple factors, change
detection, projections, and adaptation to floods. 相似文献
739.
Togo F Kiyono K Struzik ZR Yamamoto Y 《IEEE transactions on bio-medical engineering》2006,53(1):28-34
We investigate heart rate variability (HRV) in the very low-frequency (VLF) range (0.003-0.04 Hz) during deep sleep in good sleepers. Spectral analysis of HRV during deep sleep reveals consistent peaks at <0.04 Hz. By using wavelet analysis, we find both stationary and nonstationary periodic patterns in the VLF range, the presence of which has been discussed but has not been fully established to date. Although the mechanism(s) behind the unique VLF oscillations remain to be fully explored, we conjecture that there is an endogenous rhythmic component in human HRV in the VLF range. Further, our results also suggest a need for caution in the interpretation of the VLF spectral power in HRV during deep sleep. 相似文献
740.
Kiyono K Struzik ZR Aoyagi N Yamamoto Y 《IEEE transactions on bio-medical engineering》2006,53(1):95-102
For a detailed characterization of intermittency and non-Gaussianity of human heart rate, we introduce an analysis method to investigate the deformation process of the probability density function (PDF) of detrended increments when going from fine to coarse scales. To characterize the scale dependence of the multiscale PDF, we use two methods: 1) calculation of Kullback-Leibler relative entropy; 2) parameter estimation based on Castaing's equation (B. Castaing et al, 1990). We compare scale-dependence of the increment PDFs between actual heart rate fluctuations and artificially generated Gaussian and non-Gaussian noise, including a widely used autoregressive model and a recently proposed multifractal model based on a random cascade process. Our analysis highlights an essential difference between heart rate fluctuations and those generated by other models. The outstanding feature of human heart rate is the robust scale-invariance of the non-Gaussian PDF, which is preserved not only in a quiescent condition, but also in a dynamic state during waking hours, in which the mean level of heart rate is dramatically changing. Our results strongly suggest the need for revising existing models of heart rate variability to incorporate the scale-invariance in the PDF. 相似文献