具有交易费用和马氏调制的均值-方差组合选择

研究了均值-方差准则下,最优投资组合选择问题.投资者为了增加财富它可以在金融市场上投资.金融市场由一个无风险资产和n个带跳的风险资产组成,并假设金融市场具有马氏调制,买卖风险资产时,考虑交易费用.目标是,在终值财富的均值等于d的限制下,使终值财富的方差最小,即均值-方差组合选择问题.应用随机控制的理论解决该问题,获得了最优的投资策略和有效边界.     

A convergence rate for approximate solutions of Fredholm integral equations of the first kind

We study the convergence rate for solving Fredholm integral equations of the first kind by using the well known collocation method. By constructing an approximate interpolation neural network, we deduce the convergence rate of the approximate solution by only using continuous functions as basis functions for the Fredholm integral equations of the first kind. This convergence rate is bounded in terms of a modulus of smoothness.     

环氧树脂对封端型水性聚氨酯树脂的改性研究

以聚醚多元醇、甲苯二异氰酸酯和二羟甲基丙酸为主要原料,丙烯酸单体封端,加入改性剂环氧树脂E-44,制备出稳定的水性聚氨酯分散体.红外光谱分析表明反应得到了水性聚氨酯结构;随着环氧树脂含量的增加,水性聚氨酯树脂粒径,黏度逐渐增大,乳液贮存稳定性下降,低温柔韧性变差,吸水率逐渐减小;甲基丙烷酸羟乙酯(HEMA)作为封端剂水性聚氨酯乳液高温稳定性优于季戊四醇三丙烯酸酯(PETA)封端剂乳液;环氧树脂改性增加了水性聚氨酯树脂的热稳定性.     

公路隧道太阳光直接增强照明系统的设计

为了利用绿色能源有效解决公路隧道进出口区段的黑洞效应和白洞效应,在阳光输送机研究的基础上,研制一种利用平行太阳光直接实现公路隧道进出口区段增强照明功能的新系统。该系统通过光路变换和反射等措施实现了在无光纤等传输介质条件下高效率、远距离的太阳光输送功能,利用太阳光本身时有时无的性能缺陷改善了隧道增强照明系统亮度自适应隧道外光强的技术要求,针对受光体位置固定不变的系统专门设计了极轴式自动跟踪系统,保证了对太阳光的实时跟踪。实验结果证明,该增强照明系统不但无须光导纤维或者导光管,而且使得传输效率提高40%左右,为隧道等白天也需要增强照明的地下工程直接利用太阳能开辟了一条新路。     

Alcohol-assisted photoetching of silicon carbide with a femtosecond laser

Femtosecond lasers have proved to be effective tools for micromachining silicon carbide material. In the drilling process, however, when the debris around the hole was not removed efficiently, the depth of hole would not increase further. In this paper, alcohol-assisted photoetching of 6H silicon carbide was investigated using a femtosecond laser. Machining in the presence of alcohol was beneficial to the debris ejection from the hole. The alcohol flow and volatilization was also helpful to further carry away the ablation debris and reduce the ablated material redeposition. The experiment showed that photoetching assisted by alcohol produced cleaner ablation effect and deeper hole than in ambient air. Moreover, alcohol assistance would not produce additional thermal damage around the hole. Vias were formed in a 250 μm thick wafer with alcohol-assisted photoetching technique using a femtosecond laser, which demonstrated the potential for this processing technique.     

Phase equilibrium and insulin partitioning in aqueous two-phase systems containing block copolymers and potassium phosphate

In this work, phase diagrams of aqueous two-phase systems (ATPS) containing PEO–PPO–PEO block copolymers and potassium phosphate as well as the partitioning behavior of insulin in these systems are presented. Experiments aimed at the identification of the effects of copolymer structure (by varying the number of EO units per polymer molecule), temperature (283.15 and 298.15 K) and pH (5.0 and 7.0) on the phase behavior of these systems were carried out. The results indicated the enlargement of the two-phase region upon increasing the temperature, pH and copolymer hydrophobicity (expressed as the PO/EO ratio in the copolymer molecule). Experimental measurements of the partitioning of human insulin in these ATPS also indicated the dependency of the partition coefficients on temperature, pH, and copolymer hydrophobicity, with the latter being the most influential factor. Finally, experimental data on the phase behavior and insulin partitioning were correlated using an excess Gibbs energy virial-type model modified in order to account for coulombic interactions and ionization equilibrium between the various forms of the phosphate ion.     

Pervaporation Separation and Catalysis Activity of Novel Zirconium Silicalite-1 Zeolite Membrane

Novel zirconium silicalite‐1 zeolite membrane was hydrothermally prepared on the mullite porous support at 150–185°C for 40–72 h by an "in situ" method using tetraethyl orthosilicate (TEOS), zirconium butoxide (ZBOT) and tetrapropylammonium hydroxide (TPAOH) as silica source, zirconium source and organic structure directing agent, respectively. X‐ray diffraction (XRD) patterns, fourier transformed infrared (FT‐IR) spectra, and inductively coupled plasma‐atomic emission spectrometry (ICP) of the accompanying zeolite powder confirmed that the zirconium was isomorphously incorporated into the zeolite framework. The surface chemical compositions of the obtained membrane were measured with an energy‐dispersive X‐ray spectral analyzer (EDS), and the membrane morphologies were observed by a scanning electron microscope (SEM). The results showed that the zeolite crystals growing on the support were zirconium silicalite‐1 zeolites, and the dense membrane layer was composed of the well inter‐growing zeolite crystals. The zirconium silicalite‐1 zeolite membrane, which was derived from the synthesis solution having a molar ratio of 1.00SiO₂:0.01ZrO₂:0.17TPAOH:120H₂O, showed high ethanol permselectivity with a flux of 1.01 kg/(m²·h) accompanied with a separation factor of 73 for ethanol/water (5/95, w/w) system under a pervaporation condition at 60°C. Moreover, this membrane displayed pervaporation‐aided catalysis activity for iso‐propanol oxidation with hydrogen peroxide as oxidant, and the corresponding iso‐propanol conversion was 35%.     

二溴荧光素-N-氯代丁二酰亚胺化学发光体系测定片剂及人血浆中的氢溴酸右美沙芬

研究发现,碱性溶液中,二溴荧光素可吸收N-氯代丁二酰亚胺(NCS)氧化氢溴酸右美沙芬反应的化学能而产生化学发光,从而构建了二溴荧光素-NCS-氢溴酸右美沙芬化学发光体系.利用该体系建立了测定氢溴酸右美沙芬的流动注射化学发光新方法.方法线性范围是9.0×10-10～2.0×10-7 g/mL(r=0.9992),检出限为7.0×10-10 g/mL,对2.0×10-8 g/mL氢溴酸右美沙芬溶液进行11次平行测定的相对标准偏差(RSD)为1.6%.该法已用于片剂及人血浆中氢溴酸右美沙芬含量的测定,结果令人满意.在对有关反应的动力学性质、化学发光光谱及有关物质的紫外吸收光谱和荧光光谱研究的基础上,推断出可能的反应机理.     

Quasinormal Modes of the Schwarzschild Black Hole Surrounded by the Quintessence Field in Rastall Gravity

The quasinormal modes of the Schwarzschild black hole surrounded by the quintessence in Rastall gravity are studied using the sixth-order Wentzel-Kramers-Brillouin approximative approach. The effect of the Rastall parameter on the quasinormal modes of gravitational, electromagnetic and massless scalar perturbations is explored. Compared to the case of Einstein gravity, it is found that, when η < 0, the gravitational field, electromagnetic field as well as massless scalar field damp more rapidly and have larger real frequency of oscillation in Rastall gravity, while when η > 0, the gravitational field, electromagnetic field as well as massless scalar field damp more slowly and have smaller real frequency of oscillation in Rastall gravity. It is also found that the gravitational field, electromagnetic field as well as massless scalar field damp more and more slowly and the real frequency of oscillation for the gravitational perturbation, electromagnetic perturbation as well as massless scalar perturbation becomes smaller and smaller as the Rastall parameter η increases. Compared among the quasinormal frequencies of gravitational, electromagnetic and massless scalar perturbations, I find that, for fixed η, (l, n), ∈ and N_q, the oscillation damps most slowly for the gravitational perturbation, mediate for the electromagnetic perturbation and most rapidly for the massless scalar perturbation, and the real frequency of oscillation is the smallest for the gravitational perturbation, mediate for the electromagnetic perturbation and the largest for the massless scalar perturbation in Rastall gravity.     

Structural and magnetic properties of MoS2 monolayer zigzag nanoribbon doped by Ti,V, Cr,and Mn

In order to find new functions of monolayer MoS₂ in nanoelectronics or spin electronic devices, using spin-polarized density functional theory (DFT) calculations with on-site coulomb interaction (U), we investigated substitutional doping of Mo atoms of monolayer zigzag MoS₂ nanoribbon (ZZ-MoS₂ NR) by transition metals (TM) (where TM = Ti, V, Cr, Mn) at the Mo-edge, S-edge, and the middle of the NRs. The results of this study indicate the NR widened irrespective of the doped TM position and type, and the Mo-edge was found as the easiest substitutional position. For ZZ-MoS₂ NR doped by Mn, Cr or V atoms, the preferred magnetic coupling state is the edge atoms of S at the S-edge, exhibiting the same spin polarization with TM (named the FM1 state), attributing the NR with metallic magnetism. For Ti-doped monolayer ZZ-MoS₂ NR, in addition to the FM1 state, other preferred magnetic coupling state was observed in which the edge atoms of S at the S-edge exhibit the opposite spin polarization with that of Ti (named the FM2 state). Thus, the NR doped by Ti atom possesses metallic (FM1 state) or half-metallic (FM2 state) magnetism. The total magnetic moments of the ZZ-MoS₂ NR doped by TM follows a linear relationship as a function of the TM dopants (Mn, Cr, V, and Ti). Under $>4\text{\%}$ applied strain, the NR doped by Ti atom only presents the characteristics of half-metallic magnetism as the initial one in the FM2 state, and its total magnetic moment always remained 0 μB, i.e., it was not affected by the width of the NR. This study provides a rational route of tuning the magnetic properties of ZZ-MoS₂ NRs for their promising applications in nanoelectronics and spin electronic devices.