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21.
F Javier Benítez Ana I Leal Francisco J Real Juan L Acero Gloria Roldán 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(3):309-316
BACKGROUND: The first stage of the cork industrial process generates great volumes of wastewater with moderate to high organic pollutant content that must be purified using different procedures, such as filtration by membranes. RESULTS: The tangential filtration of these wastewaters was studied using two different laboratory equipments. In the first one, three ultrafiltration (UF) membranes were tested, with molecular weight cut‐off (MWCO) 100 kDa and 30 kDa, and two operating modes were used: total recycling of permeate and retentate streams, and in continuous mode, without recycling both streams. In the total recycling UF experiments, the influence of the operating variables on the permeate flux was first established. The effectiveness of the different membranes was determined by evaluating the rejection coefficients for several parameters that measure the global pollutant content of the effluent. The values found for these rejection coefficients were in the following order: ellagic acid and color > absorbance at 254 nm > tannic content > COD (chemical oxygen demand). In the continuous mode experiments, the fouling mechanism for each membrane was established by fitting the experimental data to various filtration fouling models given in the literature. The operating mode in the second equipment was batch concentration, and additional experiments were carried out with an UF membrane (2 kDa), and with a NF membrane (with MWCO in the range 150–300 Da). CONCLUSIONS: The three operating modes tested provided different rejection levels of organic matter; among them, the most effective procedure tested was batch concentration mode using a NF membrane. Copyright © 2007 Society of Chemical Industry 相似文献
22.
L. M. CRUZ-ORIVE 《Journal of microscopy》2005,219(1):18-28
A new principle is presented to generate isotropic uniform random (IUR) test lines hitting a geometric structure in three-dimensional space (3D). The principle therefore concerns the estimation of surface area, volume, membrane thickness, etc., of arbitrary structures with piecewise smooth boundary. The principle states that a point-sampled test line on an isotropic plane through a fixed point in 3D is effectively an invariant test line in 3D. Particular attention is devoted to the stereology of particles, where an alternative to the surfactor method is obtained to estimate surface area. An interesting case arises when the particle is convex. The methods are illustrated with synthetic examples. 相似文献
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24.
叙述了目前加油站在实行按任意温度下的体积交接,由于未考虑油品体积随温度、压力、密度的变化,出现了零售损耗很大的问题。建议加油站在现阶段采用“准标准体积”交接;在由体积转换为质量计算加油站损溢时,使用油库当月发出的平均密度;当财会核销损溢时,不使用盘存的体积和固定密度进行计算的方法,而使用实际盘点的质量数,以真实反映加油站的当期损溢。 相似文献
25.
应用比较几何的方法研究了完备非紧且具有特定曲率条件的黎曼流形,证明了在一定Pinching条件限制下,流形具有有限拓扑型或者微分同胚于R^n。 相似文献
26.
FANGLiang XIAOFeng TAOZainan KusuhiroMukai 《武汉理工大学学报(材料科学英文版)》2005,20(2):67-70
The density of liquid Ni- Ta alloys was measured by using a modified sessile drop method. It is found that the density of the liquid Ni- Ta alloys decreases with the increasing temperature, but increases with the increase of tantalum concentration in the alloys. The molar volume of liquid Ni- Ta binary alloys increases with the increase of temperature ancl tantalum concentration. 相似文献
27.
S. Matsuo Y. Mizuguchi Y. Tanaka H. Kubota R. Yamamoto 《International Journal of Thermophysics》1996,17(2):441-454
Densities of aqueous of 1,4-dioxane have been measured at temperatures from 298 to 348 K and at pressures up to 40 MPa by a vibrating-tube method. Molar volumes obtained with an estimated uncertainty of ±0.2°,% are correlated with pressure by the Tait equation within the experimental uncertainty. Pressure and composition dependences of the excess molar volume, partial molar volume, and isothermal compressibility are determined and they are compared with those of other aqueous solutions. 相似文献
28.
Three-dimensional (3-D) cell morphology is important for the understanding of cell function and can by quantified in terms of volume and surface area. Differential interference contrast (DIC, or Nomarski) imaging can enable cell edges to be clearly visualized in unstained tissue due to the slight difference in refractive index between aqueous media and cytoplasm. DIC is affected in only one direction - the direction of the optical shear. A 1-D edge detector was used in that direction with a scale length equal to that of an in-focus edge to highlight cell boundaries. By comparison with the signal from the edge detector on an out-of-focus slice, the in-focus slices could be segmented and, after noise suppression, cell outlines obtained. A voxel paradigm was used to calculate cell volume and differential geometry was used for surface area estimation. We applied this approach to obtain 3-D dimensional information by optical sectioning of motile Amoeba proteus. 相似文献
29.
Shiro Matsuoka 《Journal of research of the National Institute of Standards and Technology》1997,102(2):213-228
The high frequency end of the relaxation spectrum for polymer molecules involves the rotation of the segmental bonds. This fast relaxation process, however, cannot take place easily in the condensed state crowded by the densely packed conformers, necessitating the slower cooperatively synchronous relaxation. As the temperature is lowered, the domain of cooperativity grows towards the infinite size at the Kauzmann zero entropy temperature, though actually the system deviates from the equilibrium as the glass transition intervenes typically at 50 K above that temperature. The excess enthalpy and entropy drop faster than predicted by the rotational isomeric states which would reach zero only at 0 K. The real ΔCP is greater than that of the RIS value. The actual volume in excess of the crystalline lattice volume, however, points towards zero at 0 K. Thus, a polymer with higher Tg typically exhibits a lower density and modulus in the glassy state. Since the configurational entropy associated with the free volume is proportional to the logarithm of the latter, the Kauzmann temperature can be scaled by ln M, where M is the algebraic average of the conformer molecular weight. The temperature dependence of the most dominant, i.e., the largest equilibrium domain size will result in the Adam-Gibbs and Vogel equations for the characteristic relaxation time. The cooperative domain distribution leads to the relaxation spectrum that follows a power law. The relationship between the characteristic relaxation time and the rate of physical aging is derived. 相似文献
30.
对经固溶处理的二种Al-Li合金(1.94wt.%Li和2.75wt.%Li)的时效过程进行了研究。结果表明:δ’的生长速率遵从Ostward粗化动力学。1.94wt.%Li合金δ’产生于时效过程中,而2.75wt.%Li合金的δ’产生于时效的前期阶段。前者的表现体积分数明显大于根据相图估算的数伍,真实体积分数则与此值接近;后者的体积分数低于根据相图估算的数值,这可能归咎于δ’固相线的位置、统计学误差及Li更易在时效过程中贫化。 相似文献