Salinity Selection for a Low Salinity Water-Low Salinity Surfactant Process

A laboratory selection of salinity for a low salinity water-low salinity surfactant (LS-LSS) process is presented in this paper with systematical investigation on surfactant phase behavior, interfacial tension (IFT), and dynamic retention in porous media with IOS2024 and isoamyl alcohol (IAA) as surfactant system. The results show that 0.4 wt% IOS2024 with 1 wt% IAA can provide ultra-low IFT of 10^?3 mN/m at around 3000–4000 mg/L total dissolved solids, but at that salinity range the surfactant retention is very high. The search for an optimum surfactant formulation has to consider solution properties and retention in addition to the low IFT. The salinity for a LS-LSS process should thus not be focused on either optimal salinity or ultra-low IFT, but instead the best choice could be a compromise between the properties in question. The three-phase region, where ultra-low IFT are found, is also associated with high retention values. However, we show that as salinity is increased from a two-phase region with oil solubilized in a water continuous microemulsion, there is a region close to the three-phase boundary which has potential. This region does not give ultra-low, but fairly low (10^?2 mN/m in this case) interfacial tensions, and also significantly lower retention.      

Counterparty risk valuation on credit-linked notes under a Markov Chain framework

A credit-linked note(CLN) is a note paying an enhanced coupon to investors for bearing the credit risk of a reference entity. In this paper, we study the counterparty risk on CLNs under a Markov chain framework, and introduce a Markov copula model to describe joint defaults between the reference entity underlying the CLN and CLN issuer. Assuming that the respective default intensities are directly and inversely proportional to the interest rate, which follows a CIR process, we obtain the explicit formulae for CLN values through a PDE approach.Finally, credit valuation adjustment(CVA) formula is derived to price counterparty credit risk.     

Ionic association of some tetraheptylammonium and tetraoctylphosphonium salts in methyl isobutyl ketone

The extent of ionic association of (hept)₄NCl, (hept)₄NBr, (hept)₄NI, (hept)₄N(NO₃) and (oct)₄P(NO₃) in methyl isobutyl ketone at 55°C has been measured by vapour pressure osmometry with matched thermistors. From the dependence of the osmotic coefficient on the solute concentration the equilibrium constants for ion-pair formation have been obtained for the five quaternary salts. These equilibrium constants are compared with the predictions of Bjerrum's ionic-association model and the Denison-Ramsay-Fuoss model. The latter model required a correction term for the entropy contribution.     

融资融券交易与A股市场波动相关性实证研究

本文基于A股市场开展融资融券交易以来的实际数据,用Johnson协整检验,误差修正模型和Granger因果关系检验方法,实证研究了融资融券业务的开展对A股市场价格和波动性的影响,结果显示融资融券交易对A股市场的价格和波动性的影响都不显著.     

Facile synthesis of calcium carbonate with an absolutely pure crystal form using 1-butyl-3-methylimidazolium dodecyl sulfate as the modifier

Calcium carbonate (CaCO₃) nanocrystals with controllable polymorph and morphology have been successfully synthesized with the aid of an effective control agent, a halogen-free, low-cost ionic liquid surfactant, 1-butyl-3-methylimidazolium dodecylsulfate ([C₄mim][C₁₂SO₄]) in a supersaturated aqueous solution. For the first time, facile preparation of pure lens-like vaterite, sheet-like calcite, and peanut-like aragonite was all achieved in the [C₄mim][C₁₂SO₄] aqueous solution through changing the concentration, temperature, and initial pH value and adding magnesium ions. Washed by water and ethanol, all the aggregates were free of [C₄mim][C₁₂SO₄] and can be stable at least 1 month in air. The crystal form of the aggregates changed from pure calcite to pure vaterite at room temperature only through increasing [C₄mim][C₁₂SO₄] concentration. Formation of the ordered CaCO₃ structures is mainly ascribed to the aggregation of the primary nanoparticles whose formation mechanism is related to the change of supersaturation. This study can provide a facile and environment-friendly method to fabricate CaCO₃ crystal aggregates with various morphologies and polymorphs and can be used for large-scale industrial production and biomimetic synthesis.     

Crystal growth,structure determination and magnetism of a new m=3, n=1 member of the A3n+3mA′nB3m+nO9m+6n family of oxides: 12R-Ba12Rh9.25Ir1.75O33

Single crystals of a new Ba–Rh–Ir–O oxide were grown from a molten potassium carbonate flux. The new compound, Ba₁₂Rh_9.25Ir_1.75O₃₃, is structurally related to the 2H-hexagonal perovskite structure and contains pseudo one-dimensional chains of alternating units of ten face-sharing (Rh/Ir)O₆ octahedra and one (Rh/Ir)O₆ trigonal prism. The magnetic susceptibility of Ba₁₂Rh_9.25Ir_1.75O₃₃ is featureless, indicating the absence of magnetic order. The oxide is a semiconductor with a room temperature resistance of 280 Ω.     

水下垂向运动目标的海底多基站声定位方法及精度分析

针对水下垂向运动目标具有瞬变运动特性、难以对其轨迹进行高精度和高帧率测量的问题,提出一种有水声信标的海底多基站声定位模型,基于高斯-牛顿法给出求解算法,证明了算法满足局部线性收敛条件。数值仿真和精度分析表明,基站站址误差、声速误差和信号时延估计误差通过测量斜距传播到目标位置参数,误差传播过程受接收基阵几何构型、目标相对位置及水声学约束条件等因素影响。在多个海底基站共面条件下,补充海面基站可改进垂向测量能力。利用该方法对全区域进行精度估计,获取了定位性能在空间分布上的细节特征。以水平范围1 km×1 km、水深60 m的海区计算,对于由13个海底基站和1个海面基站构成的14元测量阵,目标运动深度范围为35~60 m,在x,y,z三个方向的均方根误差(RMSE)平均值分别为0.30 m,1.47 m,0.34 m。本文工作为水下垂向运动目标定位提供了一种技术途径,可为测量系统的论证设计提供参考。     

Recent developments in materials synthesis in surfactant systems

The paper reviews the use of surfactant self-assembly to template the synthesis of polymers, ceramics with extended structures, and nanoparticles. The objective of the review is to highlight newer concepts linking self-assembly to materials nanostructure and to the realization of functional materials.     

Remarks about hysteresis in superconductivity modelling

Hysteresis is not a property of the constitutive laws of superconductors, but an observed macroscopic property of some devices, including superconductive material, which one uses in order to access a key parameter in modelling, namely the critical current density. The paper aims at clarifying these issues, by exposing the relation between the critical current density and the so-called `magnetic moment’ of a superconductive sample.