沈阳市苏家屯区耕层土壤养分空间变异性研究

利用地统计学和地理信息系统相结合的方法,研究了沈阳市苏家屯区耕地土壤(0～20 cm)有机质、速效氮、速效磷、速效钾含量的空间变异性特征.结果表明,各变量符合正态分布或经对数转换后符合正态分布,最佳的变异函数理论模型均为球状模型.有机质具有较强的空间相关性(C0与C0+C比值为24.11％),速效氮、速效磷、速效钾具有中度的空间相关性(C0与C0+C比值分别为29.53％、60.77％、58.82％).各变量的空间自相关距离分别为26.051、28.293、15.132和23.813 km.有机质和速效氮的空间变异主要受结构性因子(如成土因子)的影响,速效磷和速效钾主要受随机性因子(如施肥)的影响.Kriging插值绘制出的养分含量空问分布图显示了养分的空间分布格局,它将有助于进一步监测养分动态,为农业和环境管理提供数字地图支持.

基于随机背包的公钥密码

该文构造了一个背包型公钥密码算法。该背包公钥密码具有如下优点:加解密只需要加法和模减法运算,因此加解密速度快;该算法是基于随机背包问题而不是易解背包问题而构造的;证明了在攻击者不掌握私钥信息情况下该密码算法能抵抗直接求解背包问题的攻击,包括低密度攻击和联立丢番图逼近攻击等;证明了攻击者能够恢复私钥信息与攻击者能够分解一个大整数是等价的。分析表明,该算法是一个安全高效的公钥加密算法。

Synthesis and Characterization of Coil-Rod-Coil Triblock Copolymers Comprising Fluorene-Based Mesogenic Monodisperse Conjugated Rod and Poly(ethylene oxide) Coil

A series of coil-rod-coil triblock copolymers (i.e., F3T8EO8, F3T8EO17, F3T8EO45, and F3T8EO125) with a mesogenic monodisperse conjugated oligomer comprising 3 fluorene, 8 thiophene, and 2 phenyl units as the rod and poly(ethylene oxide) (PEO) as the coil were synthesized. A reference compound, that is F3T8ME2, with the identical rod but without PEO was also prepared for comparison. The volume fraction of PEO (f(PEO)) was 0, 0.16, 0.28, 0.50, and 0.73 for F3T8ME2, F3T8EO8, F3T8EO17, F3T8EO45, and F3T8EO125, respectively. It was found that the introduction of PEO into the triblock copolymers encouraged the formation of H-type aggregation and f(PEO)-dependent highly ordered mesophases while f(PEO) < 0.73. For F3T8ME2, only nematic mesophase was observed. In contrast, F3T8EO8 and F3T8EO17, with f(PEO) of 0.16 and 0.28, respectively, are smectic A (SA) mesomorphism.

Structural and Bluish-White Luminescent Properties of Li+-Doped BPO4 as a Potential Environmentally Friendly Phosphor Material

Many efforts have been devoted to exploring novel luminescent materials that not contain expensive or toxic elements, or do not need a mercury vapor plasma source. In this paper, BPO4 and Li+-doped BPO4 powder samples were prepared by the Pechini-type sol-gel (PSG) process. The structure and optical properties of the resulting samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), photoluminescence (PL) excitation and emission spectra, kinetic decay, and X-ray photoelectron spectra (XPS), respectively. It was found that PSG -derived Li+-doped BPO4 annealed at 960 degrees C exhibited bright bluish-white emission centered at 416 nm. The luminescence decay curves analysis indicates that each sample has two kinds of lifetimes (5.9 ns and 0.529 ms) and two types of kinetic decay behaviors which can be fitted into a single-exponential function and a double-exponential function, respectively.

Evolution of the interfacial tension between polydisperse "immiscible" polymers in the absence and in the presence of a compatibilizer

The interfacial tension sigma between two polyisobutylenes (PIB) of dissimilar polydispersity and two polydisperse samples of poly(dimethylsiloxane) (PDMS) was measured as a function of time by means of a pendent drop apparatus at different temperatures ranging from 30 to 110 degreesC. In addition to three of the four possible binary blends, the time evolution of sigma was also determined for one ternary system, where the PIB phase contained 0.03 wt % of a diblock copolymer poly(isobutylene-b-dimethylsiloxane). The pronounced decrease of sigma with advancing time, observed in all cases, is attributed to the migration of the interfacially active lower molecular weight components of the homopolymers and of the compatibilizer into the interphase. Several days are normally required until a becomes constant. These time independent values are not considered as equilibrium data, but accredited to stationary states. A kinetic model is established for sigma(t), which enables a detailed investigation of the rates of transport of the different migrating species of average molar mass of M.

Temperature and pressure dependence of phase separation of trans-decahydronaphthalene/polystyrene solution

The cloud-point temperatures (T-c1's) of ti-ans-decahydronaphthalene (TD)/polystyrene (PS, M-w = 270 kg/mol) solutions were determined by fight scattering measurements over a range of temperatures (1-16 degreesC), pressures (100-900 bar), and compositions (4.2-21.6 vol% polymer). The system phase separates upon cooling and the T-c1 was found to increase with the rising pressure for the constant composition. In the absence of special effects this finding indicates positive excess volumes. The special attention was paid to the demixing temperatures as a function of the pressure for the different polymer solutions and the plots in the T-volume fraction plane and P-volume fraction plane. The cloud-point curves of polymer solutions under changing pressures were observed for different compositions, demonstrates that the TD/PS system exhibits UCST (phase separation upon cooling) behavior. With this data the phase diagrams under pressure were calculated applying the Sanchez-Lacombe (SL) lattice fluid theory. Furthermore, the cause of phase separation, i.e., the influence of Flory-Huggins (FH) interaction parameter under pressure was investigated.

Pressure effects on the thermodynamics of trans-decahydronaphthalene/polystyrene polymer solutions: Application of the Sanchez-Lacombe lattice fluid theory

The cloud-point temperatures (T-cl's) of trans-decahydronaphthalene(TD)/polystyrene (PS, (M) over bar (w) = 270 000) solutions were determined by light scattering measurements over a range of temperatures (1-16degreesC), pressures (100-900 bar), and compositions (4.2-21.6 vol.-% polymer). The system phase separates upon cooling and T-cl was found to increase with rising pressure for constant composition. In the absence of special effects, this finding indicates positive excess volume for the mixing. Special attention was paid to the demixing temperatures as a function of pressure for different polymer solutions and the plots in the T-phi plane (where phi signifies volume fractions). The cloud-point curves of polymer solutions under different pressures were observed for different compositions, which demonstrated that pressure has a greater effect on the TD/PS solutions when far from the critical point as opposed to near the critical point. The Sanchez-Lacombe lattice fluid theory (SLLFT) was used to calculate the spinodals, the binodals, the Flory-Huggins (FH) interaction parameter, the enthalpy of mixing, and the volume changes of mixing. The calculated results show that modified PS scaling parameters can describe the thermodynamics of the TD/PS system well. Moreover the SLLFT describes the experimental results well.

Liquid-liquid phase behavior of toluene/polyethylene oxide/poly(ethyleneoxide-b-dimethylsiloxane) polymer-containing ternary mixtures

The experimental data of phase diagrams for both polyethylene oxide/poly(ethylene oxide-b-dimethylsiloxane) binary and toluene/polyethylene oxide/poly(ethylene oxide-b-dimethylsiloxane) ternary polymer-containing systems was obtained at atmosphere pressure by light scattering method. The critical points for some pre-selected compositions and the pressure effect on the phase transition behavior of ternary system were investigated by turbidity measurements. The chosen system is a mixture of ternary which is one of the very few abnormal polymer-containing systems exhibiting pressure-induced both miscibility and immiscibility. This unusual behavior is related to the toluene concentration in the mixtures. The effect of toluene on the phase transition behavior of the ternary polymer-containing mixture was traced. Such behavior can make it possible to process composite materials from incompatible polymers.

Abnormal pressure dependence of the phase boundaries in TL/PEO/P(EO-b-DMS) ternary mixtures

The cloud-point temperatures (T-cl's) of both binary poly(ethylene oxide) (PEO)-poly(ethylene oxide-b-dimethylsiloxane) [P(EO-b-DMS)] and ternary[toluene/PEO/P(EO-b-DMS)] systems were determined by light scattering measurements at atmospheric pressure. The phase separation behavior upon cooling in the ternary system has been investigated at atmospheric pressure and under high pressure and compared to the phase behavior in the binary system. The phase transition temperatures have been obtained for all of the samples. As a result, the pressure induces compatibility in the binary mixtures, but for the ternary system, pressure not only can induce mixing but also can induce phase separation.