An improved linearization strategy for zero-one quadratic programming problems

We present a new linearized model for the zero-one quadratic programming problem, whose size is linear in terms of the number of variables in the original nonlinear problem. Our derivation yields three alternative reformulations, each varying in model size and tightness. We show that our models are at least as tight as the one recently proposed in [7], and examine the theoretical relationship of our models to a standard linearization of the zero-one quadratic programming problem. Finally, we demonstrate the efficacy of solving each of these models on a set of randomly generated test instances.     

Comparison between Eulerian and Lagrangian semi-analytical models to simulate the pollutant dispersion in the PBL

In this work we display a numerical comparison, under statistical and computational point of view, between semi-analytical Eulerian and Lagrangian dispersion models to simulate the ground-level concentration values of a passive pollutant released from a low height source. The Eulerian approach is based on the solution of the advection–diffusion equation by the Laplace transform technique. The Lagrangian approach is based on solution of the Langevin equation through the Picard’s Iterative Method. Turbulence inputs are calculated according to a parameterization capable of generating continuous values in all stability conditions and in all heights of the Planetary Boundary Layer (PBL). Numerical simulations and comparisons show a good agreement between predicted and observed concentrations values. The comparison reveals the main advantages and disadvantages between the models.     

13.5—14.6MeV中子能区锗的同位素反应截面的测量

报道了在13.5—14.6MeV中子能区用活化法测得的⁷⁶Ge(n,2n)⁷⁵Ge, ⁷⁰Ge(n,2n)⁶⁹Ge, ⁷⁰Ge(n, p)⁷⁰Ga, ⁷²Ge(n,p)⁷²Ga, ⁷³Ge(n,p)⁷³Ga, ⁷²Ge(n,α)^69mZn和⁷⁴Ge(n, α)^71mZn的反应截面值. 中子注量用⁹³Nb(n,2n)^92mNb反应截面得到. 单能中子由T(d,n)⁴He反应获得. 同时还列举了已收集到的文献值以作比较.     

Nuclear spin-lattice relaxation mechanisms in kaolinite confirmed by magic-angle spinning

Spin-lattice relaxation mechanisms in kaolinite have been reinvestigated by magic-angle spinning (MAS) of the sample. MAS is useful to distinguish between relaxation mechanisms: the direct relaxation rate caused by the dipole-dipole interaction with electron spins is not affected by spinning while the spin diffusion-assisted relaxation rate is. Spin diffusion plays a dominant role in ¹H relaxation. MAS causes only a slight change in the relaxation behavior, because the dipolar coupling between ¹H spins is strong. ²⁹Si relaxes directly through the dipole-dipole interaction with electron spins under spinning conditions higher than 2 kHz. A spin diffusion effect has been clearly observed in the ²⁹Si relaxation of relatively pure samples under static and slow-spinning conditions. ²⁷Al relaxes through three mechanisms: phonon-coupled quadrupole interaction, spin diffusion and dipole-dipole interaction with electron spins. The first mechanism is dominant, while the last is negligibly small. Spin diffusion between ²⁷Al spins is suppressed completely at a spinning rate of 2.5 kHz. We have analyzed the relaxation behavior theoretically and discussed quantitatively. Concentrations of paramagnetic impurities, electron spin-lattice relaxation times and spin diffusion rates have been estimated.     

From dilute to dense self-avoiding walks on hypercubic lattices

A field-theoretic representation is presented to count the number of configurations of a single self-avoiding walk on a hypercubic lattice ind dimensions with periodic boundary conditions. We evaluate the connectivity constant as a function of the fractionf of sites occupied by the polymer chain. The meanfield approximation is exact in the limit of infinite dimensions, and corrections to it in powers ofd ^–1 can be systematically evaluated. The connectivity constant and the site entropy calculated throughout second order compare well with known results in two and three dimensions. We also find that the entropy per site develops a maximum atf1–(2d)^–1. Ford=2 (d=3), this maximum occurs atf~0.80 (f~0.86) and its value is about 50% (30%) higher than the entropy per site of a Hamiltonian walk (f=1).     

毛细管电色谱研究进展

毛细管电色谱是一种新兴的具有高效，高选择性的微分离技术。本文评述了毛细管电色说的发展状况和相关的技术，并对其发展前景进行了展望，引用文献２４篇 。     

自由基引发马来酸二丁酯熔融接枝低密度聚乙烯的研究

用马来酸二丁酯(DBM)为接枝单体,过氧化二枯基(DCPO)为引发剂,对低密度聚乙烯(LDPE)进行了熔融接枝功能化。样品的红外光谱表明接枝反应确已发生。通过对样品中酯基的皂化水解测定产物的接枝率,对产物进行萃取,用凝胶量间接表征产物的交联程度;用溶液的特性粘度从侧面显示样品的支化或降解情况。实验结果表明,产物的接枝率和凝胶量可以通过选择反应条件(温度、时间及反应混合物的组成)来控制;过量的DCPO是引起交联产生凝胶的主要原因;向体系中添加DMF可阻止交联反应的发生,但产物的接枝率也有所下降,以自由基机理对上述结果进行了讨论。     

LiCoO2中锂离子固相扩散系数随循环次数的变化

The solid diffusion coefficient of lithium-ion in LiCoO₂ cathode material has been investigated by the capacity intermittent titration technique (CITT) at different voltages and at different charge/discharge cycles. By SEM, XRD and FTIR techniques, the structure of LiCoO₂ was studied before and after charge-discharge cycles, and the relationship between solid diffusion coefficient and crystal structure was further discussed. CITT results show that the value of Li⁺ solid diffusion coefficient of LiCoO₂ is about 10^-12 cm²·s^-1. During the whole charge-discharge cycles, the Li⁺ solid diffusion coefficient decreased within the voltage of 4.0～4.3 V, which is attributed to the change of the structure of LiCoO₂.     

溶液酸度和反应温度对CaMoO4薄膜电化学制备的影响

本工作研究了恒电流电化学技术制备CaMoO₄薄膜工艺中，溶液酸度和反应温度对薄膜形成的影响。结果表明，酸度会影响薄膜的生长时间和光致发光特性，在较低酸度沉积薄膜时，容易造成薄膜的团簇生长和不确定相的形成；适当升高反应温度会加快晶粒的生长、提高薄膜的纯度、增加薄膜发射光谱的相对强度。在CaMoO₄薄膜电化学制备工艺中，溶液pH值控制在12.0附近和反应温度控制在60 ℃的左右比较好。     

自动化流动注射停流动力学分析仪的研制及其性能测试

本文研制了一套自动化流动注射停流动力学分析仪，该仪器由苹果Ⅱ型微机通过１２位ＡＤ／ＤＡ卡，流动注射停流控制仪及用ＢＡＳＩＣ语言编制的软件控制泵的起动和停止，试样的输送和混合，数据采集和处理，结果显示和打印，通过以铁（Ⅲ）与硫氰酸盐的反应体系采用固定时间法和以钒（Ｖ）的胶束催化反庆体系采用安始速法的现场测试证明，该仪器具有结构简单，操作方便，恒温性能好，通用性强等特点。