初始浓度对南海珊瑚泥沉积浊液面沉速特性影响试验研究

珊瑚泥是由细粒珊瑚碎屑组成的钙质软泥,在南海岛礁的吹填地基中因颗粒分选以夹层形式分布。在整个吹填场地形成过程中,珊瑚泥的沉积特性会对吹填后形成岛礁的地基稳定性产生一定影响。因此,从影响地基稳定性最初阶段的吹填沉积特性出发,探求初始浓度对珊瑚泥浊液面沉速特性影响。利用扫描电镜观察絮凝体尺寸,根据Stokes定律推得浊液面在等速沉积阶段的理论沉速,并与颗粒组成相近的海相沉积土和同塑性指数的芜湖粉质黏土的沉积特性展开对比分析。试验结果表明:三种土浊液面出现的高度随初始浓度减小而减小;在等速沉积阶段,浊液面沉速随初始浓度增大而减小,其变化逐渐减缓并趋于稳定。区别在于,珊瑚泥浊液面出现时间最早,其沉速远高于其他两种土,等速沉积阶段所用时间仅为其他两种土的1/3,且初始浓度对珊瑚泥等速沉积时间的影响最为明显。最后推导得到了初始浓度与浊液面沉速关系公式,这对于南海海域吹填施工及地基的安全稳定具有一定的现实意义。     

Characterizing cyclic and static moduli and strength of compacted pavement subgrade soils considering moisture variation

Compacted soils are widely used as the subgrade layer for pavements. Knowledge of the mechanical properties of subgrade soils under cyclic and static loading conditions and their variation under the influence of environmental factors is required for the rational design of pavements based on mechanistic methods. This paper presents an experimental investigation of the cyclic and static moduli and the strength properties of seven different compacted Canadian subgrade soils considering the variation in the post-compaction moisture content. Cyclic triaxial tests were performed to reliably determine the resilient modulus (M_R). Unconfined compression tests, which allow an unloading-reloading loop at 1% strain, were performed to determine the deviator stress (S_u1%) at 1% strain, the reloading elastic modulus (E_1%) at 1% strain and the unconfined compressive strength (q_u) at failure. The physical properties, the chemical and mineralogical compositions, and the soil-water characteristics of these soils were also determined. Relationships were developed to predict the M_R from the S_u1%, E_1%, q_u and soil physical properties for the investigated subgrade soils because the experimental determination of M_R is both expensive and time-consuming. The studies presented in this paper provide useful information and approaches that can be used to promote the implementation of mechanistic pavement design methods using simple techniques.     

磁流变材料在现代加工设备中的应用

磁流变(MR)材料是一种新型的智能材料,是由载液、表面活性剂、可磁化分散粒子等组成的一种流体。在外加磁场的控制下磁流变装置能够产生连续可控的阻尼力,从而对振动系统的振动性能进行实时控制。它的特性及应用都处于研究和探索阶段,但从初步实验成果来看磁流变材料有着广阔的应用前景,尤其是在减振降噪方面。简要介绍了磁流变材料的特性,归纳了磁流变材料在现代加工设备中的应用现状,展望了磁流变材料在现代加工设备中的应用前景。     

Influence of filter media depth and vegetation on Faecal Coliform removal by stormwater biofilters

Biofilters are promising technologies that widely applied in the treatment of urban stormwater. However, the microbial removal capacity performance depends greatly on the design of biofilters. Hence, this laboratory study attempts to investigate the influence of filter media depths (i.e. 150, 250, 350 and 450 mm) and the variation of native plants, that is, Cow Grass (Axonopus compressus) and Pearl Grass (Axonopus compressus, dwarf) in removing stormwater microorganism particularly Faecal Coliform (FC). Findings showed that a minimum media depth of 300 mm was required to achieve >1 log FC removal. The mean removal of FC at 450 mm depth filter exceeded 2 log for both Cow and Pearl grass biofilter columns. Results showed that there was no statistically significant difference in vegetation type on the performance of FC removal, however, Cow grass biofilter column revealed higher FC mean log removal compared to Pearl grass biofilter column.     

Synthesis of Amorphous Hydrous Ruthenium Dioxide for Electrochemical Capacitors

采用改性的中和反应及热处理工艺合成了电化学电容器用无定形水合二氧化钌材料（RuO2·xH2O）,并以高导电性石墨板作集流体,研究了合成材料的电化学性能。实验中,以自制的喷雾装置和十二烷基磺酸钠（SDS）分别作为反应辅助分散技术和表面分散剂。结果表明,合成材料的前驱体经175 ℃处理后,可获得大比表面积（218 m2/g）、蓬松状、深黑色无定形的高性能电极材料。循环伏安实验（CV）结果表明,该合成材料具有较好的比电容（995 F/g at 1mV/s）和倍率特性;电化学交流阻抗（EIS）实验进一步证明了该材料具有较低的等效串联内阻（～25 mΩ）,同时验证了材料的倍率特性良好。合成材料有望在国防及民用领域电化学电容器中得到潜在应用     

强制性国家标准GB2494—2014《固结磨具 安全要求》解读

最新发布的强制性国家标准GB 2494—2014《固结磨具安全要求》实施日期为2015年1月1日,该标准内容与所代替标准GB 2494—2003《普通磨具安全规则》相比变化很大。本文首先对新旧标准技术内容的差异进行了对比,然后对新标准GB 2494—2014《固结磨具安全要求》的主要技术内容进行了介绍和解读,最后阐述了企业贯彻实施新标准的注意事项。以此指导相关方正确理解和贯彻实施该强制性国家标准。     

Direct synthesis of highly reactive polyisobutylenes via cationic polymerization of isobutylene co‐initiated with TiCl4 in nonpolar hydrocarbon media

Living cationic polymerization of isobutylene (IB) with 1‐chlorine‐2,4,4‐trimethyl pentane (TMPCl)/TiCl₄/isopropanol (iPrOH) or isoamylol (iAmOH) has been achieved in the presence of 2,6‐di‐tert‐butylpyridine (DtBP) at ?80°C. Polyisobutylenes with nearly theoretical M_n based on TMPCl molecules and more than 90% of tert‐chlorine‐end groups could be obtained at high [TMPCl]. The β‐proton elimination from ? CH₃ in growing chain ends increased with increasing polymerization temperature and decreasing solvent polarity. A chain‐transfer‐dominated cationic polymerization process with H₂O/TiCl₄/iAmOH could be achieved in n‐hexane at ?30°C. The monomer conversion and content of exo‐olefin end groups increased while molecular weight decreased with increasing [iAmOH]. To the best of our knowledge, this is the first example to achieve the direct synthesis of highly reactive polyisobutylene with low M_n of 1200～1600, carrying more than 80% of exo‐olefin terminals by a single‐step process via cationic polymerization co‐initiated by TiCl₄ in nonpolar hydrocarbon. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42232.     

Chitosan/silk fibroin composite scaffolds for wound dressing

Three‐dimensional (3D) chitosan/silk fibroin (CS/SF) porous composite scaffolds have been prepared by simply coating a thin layer of CS onto spunlaced SF scaffolds via hydrogen‐bonding assembly technique, and they were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X‐ray diffraction (XRD), and mechanical property measurements. The results show that porous scaffolds have a pore diameter around 50–200 μm, and improved mechanical property compared with SF, resulting from strong intermolecular hydrogen bonding interactions between CS and SF, together with the maintained β‐sheet structure of SF. The medical and biological properties of the composite scaffolds were further evaluated. The results demonstrate that they possess good biocompatibility and a broad spectrum of antimicrobial properties. The in vivo animal experiments show that the composite scaffolds promote skin regeneration of rats without any teratogenic effect and inflection, thus they are very promising in the application of wound dressings. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42503.     

MC劲性复合桩与钻孔灌注桩在某工程项目中应用对比分析

MC劲性复合桩具有高承载力、低压缩性等优点.相较于常规钻孔灌注桩,MC劲性复合桩在一些淤泥、淤泥质土、含砂土或粉土较多土层较厚的土质,有很强的适应性和经济优势.本文主要介绍一实际工程项目上MC劲性复合桩与灌注桩应用对比研究结果,通过试桩及静载检测结果对比分析了两种桩型在该项目上的优劣和适用性.MC劲性复合桩环境污染小,造价较低,施工质量可靠、施工简便、施工速度快,单桩承载力较高,同时大幅度改善了桩间土的软弱状态和承载力参预度等优点,具有较高的经济效益与社会效益.本文提出了施工中应采取的措施及注意事项,并展望了 MC劲性复合桩在未来地基基础中的应用前景.     

MC劲性复合桩与钻孔灌注桩在某工程项目中应用对比分析

MC劲性复合桩具有高承载力、低压缩性等优点.相较于常规钻孔灌注桩,MC劲性复合桩在一些淤泥、淤泥质土、含砂土或粉土较多土层较厚的土质,有很强的适应性和经济优势.本文主要介绍一实际工程项目上MC劲性复合桩与灌注桩应用对比研究结果,通过试桩及静载检测结果对比分析了两种桩型在该项目上的优劣和适用性.MC劲性复合桩环境污染小,造价较低,施工质量可靠、施工简便、施工速度快,单桩承载力较高,同时大幅度改善了桩间土的软弱状态和承载力参预度等优点,具有较高的经济效益与社会效益.本文提出了施工中应采取的措施及注意事项,并展望了 MC劲性复合桩在未来地基基础中的应用前景.