First principles study on the structural,electronic and phonon properties of monolayer B2Si

Using first principles density functional theory, we predict a monolayer B₂Si structure with space group Pmm2 in the present work. This structure is confirmed to be dynamically stable. Based on the plane wave pseudopotential approach, the charge density, electron localization function, density of states, energy band, phonon property and thermal conductivity of Pmm2-B₂Si are systematically studied. It is interesting that the sp² hybridization and coordination bond of Si are found in Pmm2-B₂Si, which is the most important factor for its structural stability. The density of states and energy band analysis reveals that Pmm2-B₂Si is metallic because of the partial occupied Si 3pz and B 2pz states. Moreover, the acoustic-optical coupling is important for phonon transport in Pmm2-B₂Si, and the contribution of optical modes to the lattice thermal conductivity along the [100] and [010] directions is 13% and 12%, respectively. This study gives a fundamental understanding of the structural, electronic and phonon properties in Pmm2-B₂Si.     

Component ordering strategies in assembly systems with uncertain capacity and random yield

Sourcing components in a complex global supplier network may lead to a high degree of supply uncertainty. Events, such as unexpected production defects or insufficient supplier capacity, can cause unexpected shortages of required components and halt the assembly of final products. Accordingly, the assembly enterprises must effectively manage various supply uncertainties in their component ordering decisions to avoid such component shortfalls. These issues have guided this research to investigate the optimal ordering strategies of an assembler facing the following two types of supply uncertainty: the uncertain production capacity of a standard component (component 1) and the random production yield of a core component (component 2). The assembler makes the component ordering decisions before these supply uncertainties are realized. We characterize the optimal ordering decision and find that the assembler should order components 1 and 2 according to a fixed ratio, which only depends on the random yield of component 2 and the production cost of component 1, but not on the uncertain capacity of component 1. A case study is presented to further explore the intertwined effects of these two uncertainties in an assembly system. Finally, the model is extended to consider a secondary option of buying additional component 1 s after observing some or all of the supply uncertainties, and this secondary option endows the firm with different capabilities in counteracting the supply uncertainties.     

含硫柔性二苯甲酸及氮杂环配体的Zn(Ⅱ)和Mn(Ⅱ)配合物的合成及晶体结构

以2,2′-二硫代二苯甲酸、2,2′-联吡啶、咪唑、硝酸锌和硝酸锰为原料,使用水热方法合成了配合物[Zn(EBLA)(2,2′-bipy)(H2O)](EBLA=2,2′-二苯甲酸硫醚)(2,2′-bipy=2,2′-联吡啶)(1),自然挥发法制备了配合物[Mn(EBSA)(im)2(H2O)]n(EBSA=2,2′-二硫代二苯甲酸)(im=咪唑)(2)。利用元素分析、红外和热重分析对其进行了表征。利用X-射线单晶衍射对结构进行了测定,并研究了配合物1的荧光性质。配合物1中,2,2′-二苯甲酸硫醚是通过水热方法由2,2′-二硫代二苯甲酸发生原位反应制备,Zn2+离子是五配位的四角锥双核结构;配合物2中,Mn2+离子是六配位的变形八面体一维链状结构。配合物中存在氢键和π-π堆积等弱的分子间作用力。     

Effect of ultrasonic power on the stability of low-molecular-weight oyster peptides functional-nutrition W1/O/W2 double emulsion

Ultrasonic-assisted treatment is an eco-friendly and cost-effective emulsification method, and the acoustic cavitation effect produced by ultrasonic equipment is conducive to the formation of stable emulsion. However, its effect on the underlying stability of low-molecular-weight oyster peptides (LOPs) functional-nutrition W₁/O/W₂ double emulsion has not been reported. The effects of different ultrasonic power (50, 75, 100, 125, and 150 W) on the stability of double emulsions and the ability to mask the fishy odor of LOPs were investigated. Low ultrasonic power (50 W and 75 W) treatment failed to form a well-stabilized double emulsion, and excessive ultrasound treatment (150 W) destroyed its structure. At an ultrasonic power of 125 W, smaller particle-sized double emulsion was formed with more uniform distribution, more whiteness, and a lower viscosity coefficient. Meanwhile, the cavitation effect generated by 125 W ultrasonic power improved storage, and oxidative stabilities, emulsifying properties of double emulsion by reducing the droplet size and improved sensorial acceptability by masking the undesirable flavor of LOPs. The structure of the double emulsion was further confirmed by optical microscopy and confocal laser scanning microscopy. The ultrasonic-assisted treatment is of potential value for the industrial application of double emulsion in functional-nutrition foods.     

A numerical study of rotation effect on the propagation of nonlinear internal solitary waves in the northern South China Sea

In the paper, the rotation effect on the propagation of internal solitary waves (ISWs) in the northern South China Sea (SCS) is studied by applying non-dimensional analysis and a modified two-dimensional regularized long wave equation model. First, the contribution of each term in the model equation with rotation effect is estimated. It is shown that, the rotation effect is important once the scale of the propagating ISWs is larger than 100 km. Then, the model equation is differentiated and set up for the numerical simulation of ISWs in the northern SCS. Several numerical experiments are designed, and it is found that, the rotation effect mainly affects the symmetry of the ISW crestline, the amplitudes of the leading ISW and the north/south-ward extension crestline. With the rotation effect, the ISW crestline is not symmetrical, and the ISW amplitude decreases faster. For an incident depression internal soliton with an amplitude larger than 60 m, after the leading ISW propagates a distance of 330 km, the length of ISW crestline gets larger than 150 km, the contribution of rotation effect on the variation of leading ISW amplitude can reach more than 8%; the rotation effect and the bottom topographic effect on the variation of ISW amplitudes are opposite. The contribution of rotation effect on the variation of leading ISW amplitude decreases with an increase in amplitude of incident soliton, but it increases with the extension distance from the center of ISW crestline for the northern/southern crestlines of propagating ISWs.     

Flow-induced polymer degradation probed by a high throughput microfluidic set-up

A complex fluid submitted to strong flows can endure irreversible changes in its structure. This is the case for long chain polymer additives that are commonly used as viscosity enhancers in industry, notably for oil recovery. These polymers break in solution when submitted to high deformation rates, eventually causing a serious viscosity loss. This problem of practical importance is though difficult to handle from a fundamental point of view given its complexity. We introduce here a new tool, based on microfluidic technology, for the screening of the degradation of solutions in the model situation of the flow through a constriction. We integrate two functions in a single set-up, a micro-fabricated constriction and an on-chip viscosimeter. This tool enables us to probe rapidly the viscosity loss imparted by flowing through the constriction at a given flow rate. Thanks to microfluidics, the sample preparation and measurement time are significantly lower than those implied by classical measurement protocols (reduction by up to two orders of magnitude). In addition, confinement provides control of the flow in terms of inertia. To illustrate the potential of this approach in a screening perspective, we use this tool to study the degradation of a series of semi-dilute aqueous solutions of PEO of varying molecular weights and concentrations. For each solution we identify a threshold flow rate for polymer degradation. The corresponding critical deformation rate decreases with molecular weight and concentration, as expected (the mass dependence is in line with previous reports and theories for dilute solutions). In addition we characterize the viscosity loss for larger deformation rates and find that, despite the polydispersity of our solutions, the observations for the various solutions can be roughly recast on a master curve by renormalization of the imposed deformation rates according to a law $M_w^{?1.7\pm 03}{c}^{?0.7\pm 03}$.     

Thermal degradation of hydroxypropyl trimethyl ammonium chloride chitosan–Cd complexes

Thermal degradation of hydroxypropyl trimethyl ammonium chloride chitosan–Cd complexes (HTCC–Cd) was investigated by thermogravimetric analysis. The results indicate that the degradation of HTCC–Cd in nitrogen atmosphere was two-step reaction. For the first step of degradation, the initial temperature of mass loss (T ₀), the final temperature of mass loss (T _f), and the temperature of maximum mass loss (T _p) increase linearly with the rising of heating rate (B). T _o = 1.241B + 220.3, T _p = 1.111B + 245.8, and T _f = 1.335B + 358.2. Using different methods, the kinetic parameters of the two steps were investigated. The results show that the activation energies of the first step of degradation obtained using Friedman and Flynn–Wall–Ozawa methods are 1.684 × 10⁵ and 1.646 × 10⁵ J mol^?1, and the corresponding activation energies for the second step are 1.165 × 10⁵ J mol^?1 and 1.373 × 10⁵ kJ mol^?1. The results obtained from Phadnis–Deshpande methods indicate that the two degradation processes are both nucleation and growth process, and follow A₄ mechanism with intergral form g(X) = [?ln(1 ? X)]⁴.     

含硫柔性二苯甲酸及氮杂环配体的Zn(Ⅱ)和Mn(Ⅱ)配合物的合成及晶体结构

以2,2'-二硫代二苯甲酸、2,2'-联吡啶、咪唑、硝酸锌和硝酸锰为原料,使用水热方法合成了配合物[Zn(EBLA)(2,2'-bipy)(H₂O)](EBLA=2,2'-二苯甲酸硫醚)(2,2'-bipy=2,2'-联吡啶)(1),自然挥发法制备了配合物[Mn(EBSA)(im)₂(H₂O)]_n(EBSA=2,2'-二硫代二苯甲酸)(im=咪唑)(2).利用元素分析、红外和热重分析对其进行了表征.利用X-射线单晶衍射对结构进行了测定,并研究了配合物1的荧光性质.配合物1中,2,2'-二苯甲酸硫醚是通过水热方法由2,2'-二硫代二苯甲酸发生原位反应制备,Zn²⁺离子是五配位的四角锥双核结构;配合物2中,Mn²⁺离子是六配位的变形八面体一维链状结构.配合物中存在氢键和π-π堆积等弱的分子间作用力.     

两个含3，3'-硫代二丙酸配体的锰和铜配合物的合成、晶体结构与性质

使用3,3''-硫代二丙酸、4,4''-联吡啶和硝酸锰在水热条件下反应合成了1个锰配合物,即{[Mn（DPA）（4,4''-bipy）]·H₂O}_n（1）（DPA=3,3''-硫代二丙酸,4,4''-bipy=4,4''-联吡啶）;然后又利用3,3''-硫代二丙酸、1,3-双（4-吡啶基）丙烷和硝酸铜在水热条件下反应合成了1个铜配合物,即{[Cu（DPA）（bpp）（H₂O）]·H₂O}_n（2）（DPA=3,3''-硫代二丙酸,bpp=1,3-双（4-吡啶基）丙烷）。并对它们分别进行了元素分析、红外光谱、热稳定性、X射线粉末衍射和X射线单晶衍射的表征。结果表明：配合物1和2分别由3,3''-硫代二丙酸配体和不同氮杂环分子以及金属离子构筑,形成了二维层状的结构。氢键和π-π作用进一步将二维结构拓展成三维超分子网络。     

基于纵向数据下连续型单参数指数族参数的经验贝叶斯检验(英文)

本文讨论了在纵向数据下,运用非参数估计方法构造了连续型单参数指数族参数的经验贝叶斯检验函数,证明了所提出的经验贝叶斯检验函数的渐近最优性,并获得了它的收敛速度.