Highly ordered anodic alumina nanotemplate with about 14 nm diameter

A novel method for the fabrication of highly ordered nanopore arrays with very small diameter of 14 nm was demonstrated by using low-temperature anodization. Two-step anodization was carried out at 25 V, sulfuric acid concentration of 0.3 M, and electrolyte temperature of −15 °C. After anodization, a regular pore array with mean diameter of 14 nm and interpore distance of 65 nm was formed. The pore diameter and regular arrangement were confirmed by scanning electron microscopy (SEM) and fast Fourier transformation (FFT), respectively. The present results strongly suggest that the diameter of pores in a highly ordered alumina template can be reduced by lowering the anodization temperature.     

用不稳定试井资料研究油藏储集层流动系统模式：以准东油区为例

从不稳定试井Ｈｏｒｎｅｒ曲线形态分类入手，结合油藏动态特征对油藏储集层流动系统进行分类，并初步确定出各类流动系统的特征参数及其相应的开采特点。根据不稳定试井Ｈｏｒｎｅｒ曲线形态，可以把相应的储集层流动系统划分为三大类（孔隙流动系统、双重介质流动系统、裂缝流动系统）五个亚类。特别提出了双重介质孔缝串并流动系统组合模式。这无论对新区开发方案的编制，还是老区开发政策的制定都具有重要的借鉴参考价值。     

Equal Strain Consolidation by Vertical Drains

This paper shows the development of a series of closed-form solutions of equal strain consolidation in the presence of a vertical drain with smear and well resistance. Using an approach that considers the effects of both the radial and vertical drainage in a fully coupled fashion, solutions are obtained for the excess pore pressure and the degree of consolidation in the compressible soil subjected to a step- or ramp-loading situation. The closed-form solutions in the present paper may be evaluated in an electronic spreadsheet on a standard personal computer.     

利用测井资料评价储集层性质的探讨

根据对储集层之简化导电模型的理论分析,提出了一个由电阻率、孔隙度信息表示的、反映储层性质的“孔隙结构参数S”。实际应用表明,S参数在评价储集层性质、计算储层渗透率等方面具有一定的使用价值。     

Pervaporation performance analysis and prediction—using a hybrid solution-diffusion and pore-flow model

A hybrid mathematic model for pervaporation is proposed which incorporates the concepts of solution-diffusion model and pore model. The model allows performance prediction as well as the establishment of the internal concentration and pressure profiles within the membrane. The model parameters specific to the particular membrane and mixture system are determined using liquid sorption and pervaporation experimental data. The model is experimentally examined using ethanol–water mixtures and poly(dimethyl siloxane)–poly(vinyldiene fluoride) (PDMS–PVDF) composite membranes. The characteristics of flux and separation factor predicted using the model are in fair agreement with the experimental data under various feed concentrations and downstream pressures for different membrane arrangements, including single-layer, reverse single-layer and double-layer PDMS–PVDF composite membranes. Internal profiles of pressure, concentration and component mole fraction can be established using the model. Concentration polarization phenomena for ethanol and water are located at membrane interfaces and vapor–liquid interfaces, respectively. Performances of several different membrane designs are compared using the model.     

In situ leaching method for determination of chloride in concrete pore water

In the in situ leaching (ISL) method, pore water ionic content is determined in small cavities drilled in mortar/concrete specimens. Prior investigations have demonstrated the ISL applicability to obtain pH and nitrite ion concentration in concrete/mortar pore water. The application of the method is extended here to determine pore water chloride ion concentration (and pH) within practical test times in mortars and concretes prepared in the laboratory and in concrete cores extracted from a bridge deck in deicing salt service. Spatial resolution for the determination of composition profiles is also illustrated. Modeling of the ISL process indicates that chloride binding accelerates the approach toward a terminal cavity concentration, reducing test duration to practical lengths for moderate permeability concretes. This acceleration can be attributed to maintaining a higher gradient of free chloride near the cavity wall due to the release, during leaching, of previously bound chloride. Consequently, there is a faster chloride buildup in the cavity water compared with the no-binding case. Experimental chloride and pH results obtained by the ISL test in mortar samples show good agreement with those from the pore water expression (PWE) method. Also, examples are presented of application of ISL data to obtain chloride binding isotherms, and pore water chloride to hydroxide ratio relevant to assessing conditions for corrosion of steel reinforcement. The ISL method presents a less costly and less disruptive alternative to PWE for pore water analysis. It is noted, however, that in a few instances ISL could not be implemented because of excessive absorption of cavity water by the surrounding medium.     

Estimating the electrical conductivity of cement paste pore solutions from OH, K and Na concentrations

A proposed method for estimating the electrical conductivity of cement paste pore solution at 25 °C is based on the concentrations of OH⁻, K⁺ and Na⁺. The approach uses an equation that is a function of the solution ionic strength, and requires a single coefficient for each ionic species. To test the method, the conductivity of solutions containing mixtures of potassium hydroxide and sodium hydroxide with molar ratios of 4:1, 2:1 and 1:1, and having ionic strengths varying from 0.15 to 2.00 mol/l were measured in the laboratory and compared to predicted values. The proposed equation predicts the conductivity of the solutions to within 8% over the concentration range investigated. By comparison, the dilute electrolyte assumption that conductivity is linearly proportional to concentration is in error by 36% at 1 mol/l and in error by 55% at 2 mol/l. The significance and utility of the proposed equation is discussed in the context of predicting ionic transport in cement-based systems.     

Catalyst pore plugging effects on hydrocracking reactions in an Ebullated bed reactor operation

This paper analyzes the deactivation effects of NiMo/Al₂O₃ catalyst during the operation in an Ebullated bed reactor for Heavy residue hydrocracking. The spent catalysts were characterized by chemical analysis, ¹³C NMR, ESM, DRX, and by using thermal programmed oxidation and diffusion studies in a shallow bed micro-reactor. The deactivations were performed in a 5 l continuously stirred tank reactor, while the spent catalysts were tested in a 0.05 l micro-reactor. The study focused on determining the properties of the external layer of the catalyst and on evaluating the internal coke and metal deposition. The results indicated that initial deactivation is mainly due to coke depositions, while its impact on mass transfer reaction control depends on temperature. In long-term deactivation, the metal deposition plays a more important role in blocking the internal micro- and meso-structures and in building up the external layer of the pellets.     

Rehydration and microstructure of cement paste after heating at temperatures up to 300 °C

This paper is concerned with the evolution of the microstructure of cementitious materials subjected to high temperatures and subsequent resaturation in the particular context of long-term storage of radioactive wastes, where diffusive and convective properties are of primary importance. Experimental results obtained by mercury intrusion porosimetry (MIP) are presented concerning the evolution of the pore network of ordinary portland cement (OPC) paste heated at temperatures varying between 80 and 300 °C. The consequences of heating on the macroscopic properties of cement paste are evaluated by measures of the residual gas permeabilities, elastic moduli and Poisson's ratio, obtained by nondestructive methods. Resaturation by direct water absorption and water vapour sorption are used to estimate the reversibility of dehydration. The results provide some evidence of the self-healing capacity of resaturated cement paste after heating at temperatures up to 300 °C.     

Theoretical consideration of the effect of porosity on thermal conductivity of porous materials

The thermal conductivity of porous materials is theoretically studied in connection with nanoporous materials used in recent semiconductor devices. The effects of porosity and pore size on the thermal conductivity are discussed. The thermal conductivity of insulating materials is determined by the heat capacity of phonons, the average phonon velocity and the phonon mean free path. We investigate the porosity dependence of these quantities, especially by taking into account phonon scatterings by pores, and present an expression for the thermal conductivity as a function of porosity. Our model consideration predicts that the thermal conductivity of nanoporous materials depends on the ratio of the pore size R_p to the phonon mean free path for zero-porosity, l₀. The thermal conductivity for l₀/R_p > 1 decreases steeply with increasing porosity because of effective phonon scatterings by pores. On the other hand, the thermal conductivity for l₀/R_p < 0.1 decreases moderately with increasing porosity because phonon scatterings by pores are no longer effective. On the basis of the present theoretical consideration, we discuss the principal factor dominating the porosity dependence of thermal conductivity in nanoporous materials. We also discuss how one can design nanoporous materials with lower or higher thermal conductivity.