水力压裂裂缝几何形态的数值模拟及影响因素分析

本文利用具有最优系数的线性四步法求解了水力压裂裂缝几何形态的数学模型,从而求得了裂缝各截面的高度、宽度和压力。通过大量的计算,对影响裂缝几何形态的因素进行了分析。与此同时,本文给出了比较合理的流量模型和粘度模型。     

Robust performance of the multiloop perturbation compensator

A novel perturbation attenuation method is proposed for robust performance of mechanical systems. First, we give a unified view on a class of existing perturbation observers and define the residual perturbation. In terms of the view and the definition, a new perturbation compensator with multiloop structure is developed. It effectively compensates the perturbation (i.e., model uncertainty and external disturbance) to the plant in a hierarchical and recursive fashion. In the multiloop perturbation compensator (MPEC) proposed, as the number of loops increases, the external disturbance condition for system stability is greatly relaxed and the perturbation attenuation performance is gradually enhanced but the robust stability margin on the modeling error becomes more strict. A recursive algorithm for general n-loop case of the MPEC is derived. By combining the developed robust perturbation compensator with a nominal feedback controller, a robust motion controller is synthesized. Experimental results for XY positioner and 2-DOF robot arms demonstrate the excellent robust tracking performance in spite of arbitrary large perturbation inputs     

Gold and iron supported on Y-type zeolite for carbon monoxide oxidation

Gold and iron supported on Y-type zeolite for carbon monoxide oxidation have been studied. They were prepared by ion exchange of gold(III) compounds with Y-type zeolite, iron-impregnated Y-type zeolite, or iron-exchanged Y-type zeolite in a chloroauric acid solution. The as-prepared gold/Y sample possessed high activity for carbon monoxide oxidation, but it gradually and irreversibly deactivated during the reaction. The deactivation was attributed to the transformation of some gold ions to gold metal. The activities of as-prepared gold/iron/Y samples were poor when compared with that of gold/Y, but their activities were markedly promoted by a high-temperature reduction treatment at 570°C. This is ascribed to the fact that the reduced gold/iron/Y catalyst could catch and release oxygen at low temperature.     

Spin Injection Efficiency at the Source/Channel Interface of Spin Transistors

Almost all spintronic transistors (e.g., spin field-effect transistors, spin bipolar transistors, and spin-enhanced MOSFETs) require high efficiency of spin injection from a ferromagnetic contact into a semiconductor channel for proper operation. In this paper, we calculate the efficiency of spin injection from a realistic nonideal ferromagnetic contact into the semiconductor quantum wire channel of a spintronic transistor, taking into account the presence of an axial magnetic field (caused by either the ferromagnetic contact or external agents) and spin orbit interaction. In our calculations, the temperature is assumed to be low enough that phonon scattering is weak and transport is phase-coherent, although not ballistic because of elastic scattering caused by impurities and defects. We consider a single impurity in the channel and show that the conductance depends strongly on the exact location of this impurity because of quantum mechanical interference effects. This is a nuisance since it exacerbates device variability. The ldquosignrdquo of the impurity potential, i.e., whether it is attractive or repulsive, also influences the channel conductance. Surprisingly, at absolute zero temperature, the spin injection efficiency can reach 100% at certain gate biases, even though the ferromagnetic injector is nonideal. However, this efficiency drops rapidly with increasing temperature.     

焦化蜡油络合脱氮用作催化裂化掺炼进料的研究

采用一种络合物不需分离的络合脱氮剂对焦化蜡油进行脱氮处理，在脱氮剂用量（w）为0.40％时，焦化蜡油碱氮转化率可达到62.00%。在1.0 kg/h小型催化裂化装置上对脱氮后焦化蜡油进行评价的结果表明，单炼焦化蜡油时，与未脱氮的焦化蜡油相比，脱氮后焦化蜡油的轻质油收率提高8.65个百分点；掺炼20％经脱氮处理的焦化蜡油与掺炼20％未脱氮焦化蜡油相比，轻质油收率提高1.77个百分点。     

Estimation of rock mass deformation modulus using variations in transmissivity and RQD with depth

Discontinuity normal stiffness and deformation modulus of large scale rock masses are very difficult to determine. A method for estimation of discontinuity normal stiffness based on the decrease in transmissivity with depth has been proposed by the authors in a former paper. In the current study, the method is further developed by accounting for the changes in both discontinuity aperture and frequency with depth, which are key factors that cause the transmissivity to decrease with depth. The discontinuity frequency can be estimated from RQD measurements, which are readily available in most geotechnical investigations. The transmissivity data from packer tests are usually available in geotechnical investigations for hydropower plants. For a rock mass in a dam site mainly controlled by lithostatic stress, based on transmissivity and RQD data at different depths, the change in discontinuity aperture with depth can be linked to the change in aperture with stress, which defines the normal stiffness of discontinuities. In the case study, the discontinuity normal stiffness is successfully estimated by using transmissivity and RQD data, and the result shows that the normal stiffness increases with stress (depth) and the rate of normal stiffness versus stress (depth) decreases with stress (depth), which is consistent with experimental studies. The estimated normal stiffness has been utilized to calculate the rock mass deformation modulus using an equivalent model. The result of deformation modulus by the proposed method is close to that obtained by using in situ measurements, as well as by using empirical models relating RQD to deformation modulus.     

Aqueous route for mesoporous metal oxides using inorganic metal source and their applications

In this paper, we report a synthetic route for mesoporous metal oxides from inorganic metal sources in aqueous media. This synthesis route offers a versatile, low cost and environmental friendly method to produce mesoporous metal oxides that have very high surface areas. As an example, the synthesis of iron oxide is described in detail. Synthesis conditions including aging time, aging temperature and amount of urea were varied to find the optimal synthesis conditions. We found that recycling the Cetyltrimethylammonium Bromide (CTAB) template is possible when the amount of urea is reduced to stoichiometric. The mesoporous metal oxides made under these conditions are self assemblies of leaf-like single crystal sub-units with randomly distributed mesopores embedded into the crystals. As a result of the crystalline nature, these mesoporous metal oxides have high thermal stabilities and their applications as gas sensors and CO disproportionation catalysts indicate promising aspects of these materials.     

Light and Shape-Memory Polymers: Characterization,Preparation, Stimulation,and Application

Shape-memory polymers (SMPs) are smart materials that change shape when exposed to stimuli and have various applications in different fields due to their unique properties. Light, as a kind of electromagnetic radiation, plays an important role in understanding the structure-property relations of SMPs, preparing original shapes, using them as non-contact stimuli sources, and tuning the optical properties of SMPs. This review provides a comprehensive review of the involvement of light in structure-preparation-stimuli-application of SMPs. The review is divided into four sections. First, applications of optical/spectroscopic approaches that provide information for understanding structure-property relations in SMPs, especially during programming and recovery. Second, describes how to build SMPs with light, including different photochemical reactions and 3D photocuring technologies. Third, discusses how light is used to trigger the shape change of SMPs through both photochemical and photothermal mechanisms. Last, focuses on how to take advantage of the shape-memory effect to tune the optical characteristics of polymers, including various structures of SMP color-changing materials and their synthetic strategies. Future research could focus on developing efficient photothermal fillers, new 3D printing techniques for SMPs, exploring their use in biomedical and wearable devices, and optimizing SMPs for industrial applications.     

广州南沙开发区工业集中供热研究

在分析当地发展集中供热的必要性及供热现状的基础上,认为为适应当地的经济发展,应该发展集中供热;从投资规模、经济效益、环境效益方面论证了该地区发展集中供热的可行性。