考虑渗流效应的深埋海底隧道围岩与衬砌结构应力场研究

深埋海底隧道经常处于高水压工况,地下水渗流对隧道围岩及衬砌结构安全性有较大影响.本文提出了一种含衬砌深埋海底隧道力学模型,研究了海底隧道服役阶段地下水渗流对围岩及衬砌结构稳定性的影响机理.应用保角映射方法将包含海水与围岩弹性区的半无限域映射成圆环域,根据渗流边界条件建立了各界面间极坐标下的渗流方程,得到了海底隧道渗流场解析解.将渗流场以体积力形式作用到应力场中,根据应力边界条件建立了应力平衡方程,基于考虑中间主应力影响的Drucker-Prager （D-P）准则,得到了渗流效应影响下围岩与衬砌结构的弹塑性解析解.以深圳妈湾跨海通道工程为例,将解析解与有限元数值解进行了对比,验证了本文理论解的准确性,研究了渗流效应对隧道围岩与衬砌结构应力场的影响规律.最后,分析了海水深度与内水水头对塑性区半径的影响.研究结果表明:渗流效应对围岩与衬砌结构中的环向应力影响显著,径向应力随ρ增大呈非线性增长;随着海水加深,隧道承受水压不断加大,围岩塑性区范围显著增大;增加内水水头可以有效限制围岩塑性区发展,初始阶段限制效果明显,后续增加内水水头限制效果逐渐减弱.     

Understanding the effects of lignosulfonate on enzymatic saccharification of pure cellulose

The effects of lignosulfonate (LS) on enzymatic saccharification of pure cellulose were studied. Four fractions of LS with different molecular weight (MW) prepared by ultrafiltration of a commercial LS were applied at different loadings to enzymatic hydrolysis of Whatman paper under different pH. Using LS fractions with low MW and high degree of sulfonation can enhance enzymatic cellulose saccharification despite LS can bind to cellulase nonproductively. The enhancing effect varies with LS properties, its loading, and hydrolysis pH. Inhibitive effect on cellulose saccharification was also observed using LS with large MW and low degree of sulfonation. The concept of “LS-cellulase aggregate stabilized and enhanced cellulase binding” was proposed to explain the observed enhancement of cellulose saccharification. The concept was demonstrated by the linear correlation between the measured amount of bound cellulase and saccharification efficiency with and without LS of different MW in a range of pH.     

Enhancing enzymatic hydrolysis of crystalline cellulose and lignocellulose by adding long-chain fatty alcohols

The effects of long-chain fatty alcohols (LFAs) on the enzymatic hydrolysis of crystalline cellulose by two commercial Trichoderma reesei cellulase cocktails (CTec2 and Celluclast 1.5L) were studied. It was found that n-butanol inhibited the enzymatic hydrolysis, but n-octanol, n-decanol and n-dodecanol had strong enhancement on enzymatic hydrolysis of crystalline cellulose in the buffer pH range from 4.0 to 6.0. LFAs can increase the hydrolysis efficiency of crystalline cellulose from 37 to 57 % at Celluclast 1.5L loading of ten filter paper units (FPU)/g glucan. LFAs have similar enhancement on the enzymatic hydrolysis of crystalline cellulose mixed with lignin or xylan. The enhancement of LFAs increased with the decrease of the crystallinity index. LFAs not only enhanced the high-solid enzymatic hydrolysis of lignocellulose, but also improved the rheological properties of high-solid lignocellulosic slurries by decreasing the yield stress and complex viscosity. Meanwhile, LFAs can improve the enzymatic hydrolysis of cellobiose to glucose, especially at low cellulase loading.     

Antibacterial behavior and physical properties of silver nanoparticle-doped ecofriendly nonwoven fabrics

A green approach for forming silver nanoparticles (Ag NPs) on ecofriendly highly absorbent nonwoven fabrics was investigated. The fiber blending ratio of highly absorbent nonwoven fabrics was optimized by simulated body fluid (SBF) and water absorption. SBF and water absorption ratios reached 42 and 42.9 times after addition of 50 wt% highly absorbent fibers. The Ag NPs were characterized by UV-visible spectrometry (UV-Vis), X-ray diffraction (XRD) and transmission electron microscopy (TEM). UV-Vis and XRD images confirmed the presence of Ag NPs. TEM observation revealed that Ag NPs were distributed at 5–10 nm. The results of antimicrobial activity showed that Ag NP dope is effective for producing antimicrobial nonwoven fabrics against E. coli and S. aureus.     

Klein‐Gordon‐Zakharov system in energy space: Blow‐up profile and subsonic limit

In this paper, we prove finite‐time blowup in energy space for the three‐dimensional Klein‐Gordon‐Zakharov (KGZ) system by modified concavity method. We obtain the blow‐up rates of solutions in local and global space, respectively. In addition, by using the energy convergence, we study the subsonic limit of the Cauchy problem for KGZ system and prove that any finite energy solution converges to the corresponding solution of Klein‐Gordon equation in energy space.     

Well‐conditioned boundary integral formulations for high‐frequency elastic scattering problems in three dimensions

We construct and analyze a family of well‐conditioned boundary integral equations for the Krylov iterative solution of three‐dimensional elastic scattering problems by a bounded rigid obstacle. We develop a new potential theory using a rewriting of the Somigliana integral representation formula. From these results, we generalize to linear elasticity the well‐known Brakhage–Werner and combined field integral equation formulations. We use a suitable approximation of the Dirichlet‐to‐Neumann map as a regularizing operator in the proposed boundary integral equations. The construction of the approximate Dirichlet‐to‐Neumann map is inspired by the on‐surface radiation conditions method. We prove that the associated integral equations are uniquely solvable and possess very interesting spectral properties. Promising analytical and numerical investigations, in terms of spherical harmonics, with the elastic sphere are provided. Copyright © 2014 John Wiley & Sons, Ltd.     

Efficient Synthesis of Aryl Methyl Sulfide Derivatives Using (Methylthio)trimethylsilane as Methylthiolation Reagent

The synthesis of various aryl methyl sulfides has been achieved by treatment of nitroarenes with a combination of (methylthio)trimethylsilane and cesium carbonate in dimethylsulfoxide. This reaction gives access to aryl methyl sulfide derivatives in high yields.     

Application of Ionic Liquids in an Online Ultrasonic Assisted Extraction and Solid-Phase Trapping of Rhodiosin and Rhodionin from Rhodiola rosea for UPLC

Ionic liquid-based online ultrasonic assisted extraction (UAE) and solid-phase trapping (SPT) technique was developed to extract selectively rhodiosin and rhodionin from Rhodiola rosea for rapid determination by ultra-performance liquid chromatography. Ionic liquids with different cations and anions were investigated and 1-ethyl-3-methylimidazolium bromide solution was selected as the optimal extractant at concentration of 2.0 mol/L. Some extraction parameters such as ultrasonic power, extraction time, and extractant flow rate were optimized. The optimum separation conditions were as follows: ultrasonic power 360 W, extraction time 25 min, extractant flow rate 0.8 mL/min. The proposed approach was evaluated in comparison with the conventional maceration extraction and regular ultrasonic assisted extraction. UAE and SPT offered short extraction time, remarkable efficiency and low column pressure. Moreover, the proposed method was validated by the recovery and precision. Mean recoveries for rhodiosin and rhodionin were 98.5 and 98 %, respectively. The intra- and inter-day precision (RSD) was 1.59 and 2.98 % for rhodiosin and 1.78 and 2.05 % for rhodionin. UAE and SPT provided a new alternative for preparation of flavonoids compounds from solid sample.     

Chromic Acid Adsorbed on Kieselguhr: A New Reagent for the Oxidation of Primary Alcohols to Aldehydes

A new reagent, chromic acid adsorbed on kieselguhr, suitable for the oxidation of primary alcohols to the corresponding aldehydes is described.     

New One‐Pot Three‐Component Synthesis of N‐Phenyl α‐Aminophosphonates

New one‐pot three‐component reactions employing aldehydes, triphenylphosphite, and N‐[(phenylamino)carbonyl]glycine ethyl ester in refluxing xylene readily afford N‐phenyl α‐aminophosphonates in low to moderate yields.