排序方式： 共有75条查询结果，搜索用时 15 毫秒
71.
Sugar beet molasses vinasse is a by‐product of ethanol fermentation from sugar beet molasses. Its dark brown colour, which is attributable to the presence of caramels, melanoidins and invert alkaline degradation products, cannot be removed by biological methods. The novelty of this work lies in the use of conventional strongly alkaline ion‐exchange resins for the decolourisation of sugar beet molasses vinasse. The aim of the study was to determine the efficiency of two strong‐base ion‐exchange resins, Dowex 2 and Wofatit ES, when used for the decolourisation of sugar beet molasses vinasse. Optimal conditions and extent of decolourisation were related to the concentration and pH of the vinasse, the time of reaction with the resin, and also to the dose and type of the resin used. The greatest extent of decolourisation (92%) was achieved with Wofatit ES dosed in the amount of 5 g/100 mL of 25% vinasse with an initial pH of 10. The optimal time of reaction with the resin indispensable for attaining the maximal effect of decolourisation was 1.5 h for both resins. The highest extent of reduction in chemical oxygen demand (43%) during decolourisation of 25% vinasse (pH 10) was obtained with Dowex 2. 相似文献
72.
Abstract The main aim of this study is the experimental investigation of friction velocities and shear stresses in rivers under unsteady flow conditions. Special measurements of mean velocities and other hydraulic parameters were made in two small lowland rivers in central Poland. Four controlled flood waves were released and analysed in the selected reaches. The main hydrometric characteristics and the relationship between water level and discharge were established. Friction velocities were obtained directly from the full St Venant equations of motion, as well as from only the steady momentum equation, and their time-dependent forms were established. Both these approaches provided similar results when the unsteadiness parameter was relatively low. It appeared that real friction velocities were much larger than those obtained from the common uniform flow formula. The passing hydrograph influenced the value of the shear velocity significantly. 相似文献
73.
74.
Maria Aldona Augustyniak-Jabłokow Yurii V. Yablokov Bartłomiej Andrzejewski Wojciech Kempiński Szymon Łoś Krzysztof Tadyszak Mikhail Y. Yablokov Valentin A. Zhikharev 《Physics and Chemistry of Minerals》2010,37(4):237-247
The X-band EPR and magnetic susceptibility in the temperature range 4.2–300 K study of the shungite-I, natural nanostructured
material from the deposit of Shunga are reported. Obtained results allow us to assign the EPR signal to conduction electrons,
estimate their number, N
P, and evaluate the Pauli paramagnetism contribution to shungite susceptibility. A small occupation (~5%) of the localized
nonbonding π states in the zigzag edges of the open-ended graphene-like layers and/or on σ (sp
2+x
) orbitals in the curved parts of the shungite globules has been also revealed. The observed temperature dependence of the
EPR linewidth can be explained by the earlier considered interaction of conduction π electrons with local phonon modes associated
with the vibration of peripheral carbon atoms of the open zigzag-type edges and with peripheral carbon atoms cross-linking
different nanostructures. The relaxation time T
2 and diffusion time T
D are found to have comparable values (2.84 × 10−8 and 1.73 × 10−8 s at 5.2 K, respectively), and similar dependence on temperature. The magnetic measurements have revealed the suppression
of orbital diamagnetism due to small amount of large enough fragments of the graphene layers. 相似文献
75.
A knowledge of the quantity of the sand fraction in the sediments deposited in reservoirs makes it easier to determine the bedload transport, which is a rarely measured parameter. The current study discusses the results of investigations into the siltation and physical properties of sediment in two small reservoirs located in the southeastern part of Poland. Also, the quantity of the bedload sand fraction was estimated.The estimation of the reservoir capacity loss after t years of operation was based on hydroacoustic measurements. The sediment density, organic matter content, and granulometric composition were evaluated by means of investigations and analyses of bottom sediment core samples. The interpolation of the parameters describing the sediment properties was done using the Kriging method. The analyses indicate that 10.80 thousand m~3 of sediment were deposited into the Zalew Kielecki Reservoir in the years 2004-2015. Their overall mass was 7320 t, of which sand fraction sediments constituted 39.7%.Between the years 2004 and 2014, the Umer Reservoir retained 11.79 thousand m~3 of sediment having a mass of 7200 t, of which sand fraction constituted 34.6%. 相似文献