雷电的形成威力及预防

雷电灾害严重危及生命和财产的安全。因此，了解雷电成因，既有助于认识雷电的危害性，又可加强人类对雷电的防护。     

Regression quantiles for unstable autoregressive models

This paper investigates regression quantiles (RQ) for unstable autoregressive models. The uniform Bahadur representation of the RQ process is obtained. The joint asymptotic distribution of the RQ process is derived in a unified manner for all types of characteristic roots on or outside the unit circle. It involves stochastic integrals in terms of a sequence of independent and identically distributed multivariate Brownian motions with correlated components. The related L-estimator is also discussed. The asymptotic distributions of the RQ and the L-estimator corresponding to the nonstationary componentwise arguments can be transformed into a function of a normal random variable and a sequence of i.i.d. univariate Brownian motions. This is different from the analysis based on the LSE in the literature. As an auxiliary theorem, a weak convergence of a randomly weighted residual empirical process to the stochastic integral of a Kiefer process is established. The results obtained in this paper provide an asymptotic theory for nonstationary time series processes, which can be used to construct robust unit root tests.     

Some New uniform frames with block size four and index one or three

In this paper, some new uniform frames with block size four and index one or three are obtained. The known existence results for (4,1)‐frames and (4,3)‐frames are both improved to the extent that only a finite number of possible exceptions remain. © 2003 Wiley Periodicals, Inc.     

热喷涂技术的现状和发展

介绍了热喷涂工艺的特点，喷涂方法的种类及其技术以及热喷涂技术的应用概况，并对热喷涂技术的发展方向给予了展望。     

Study on a Cross Diffusion Parabolic System

This paper considers a kind of strongly coupled cross diffusion parabolic system,which can be usedas the multi-dimensional Lyumkis energy transport model in semiconductor science.The global existence andlarge time behavior are obtained for smooth solution to the initial boundary value problem.When the initialdata are a small perturbation of an isothermal stationary solution,the smooth solution of the problem under theinsulating boundary condition,converges to that stationary solution exponentially fast as time goes to infinity.     

Asymmetric hydrogenation of alkyl(vinyl)thioethers: a promising approach to α-chiral thioethers

This paper describes the enantioselective hydrogenation of vinylthioethers. We show that thioether derivatives of maleic esters can be hydrogenated with full conversion and up to 60% ee, and that α-thioether cinnamic acids can be hydrogenated in 51% ee with modest conversion.     

Cluster and periodic DFT calculations of adsorption and activation of CO2 on the Cu(hkl) surfaces

The adsorption behavior and thermal activation of carbon dioxide on the Cu(1 1 1), Cu(1 0 0), and Cu(1 1 0) surfaces have been investigated by means of density functional theory calculations and cluster models and periodic slabs. According to the cluster models, the optimized results indicate that the basis set of C and O atoms has a distinct effect on the adsorption energy, but an indistinct one on the equilibrium geometry. For the CO₂/Cu(hkl) adsorption systems studied here, the final structure of adsorbed CO₂ is near linear and the preferred modes for the adsorption of CO₂ onto the Cu(1 1 1), Cu(1 0 0), and Cu(1 1 0) surfaces are the side-on adsorption at the cross bridge site with an adsorption energy of 13.06 kJ/mol, the side-on adsorption at the short bridge site (13.54 kJ/mol), and the end-on adsorption on the on-top site with C–O bonds located along the short bridge site (26.01 kJ/mol), respectively. However, the calculated adsorption energies from periodic slabs are lower as compared to the experimental data as well as the cluster model data, indicating that the periodic slab approach of generalized gradient approximation in the density function theory may be not suitable to obtain quantitative information on the interaction of CO₂ with Cu(hkl) surfaces.     

应用马尔科夫状态转移链的作战航空综合体效能评估

文章阐述了作战航空综合体的相关概念及组成,应用马尔科夫状态转移链建立了作战航空综合体完成典型作战任务时的数学模型,确定了作战效能的评估指标,最后通过具体算例检验了模型的正确性和可行性.     

Crosslinked epoxy materials exhibiting thermal remendablility and removability from multifunctional maleimide and furan compounds

Crosslinked polymeric materials, which exhibit thermal remendability and removability through Diels–Alder (DA) and retro‐DA reactions, were obtained from using multifunctional maleimide and furan compounds as monomers. The synthesized monomers possess low melting points and good solubility in organo solvents to show excellent processing properties. The performance of DA and retro‐DA reactions were demonstrated with DSC and FTIR measurements. High performance of thermal remendablility and removability of the crosslinked materials were observed with SEM and solvent tests. These materials were applicable in advanced encapsulants and structural materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 905–913, 2006     

Sulfonated poly(aryl ether ether ketone ketone)s containing fluorinated moieties as proton exchange membrane materials

A series of sulfonated poly(aryl ether ether ketone ketone)s statistical copolymers with high molecular weights were synthesized via an aromatic nucleophilic substitution polymerization. The sulfonation content (SC), defined as the number of sulfonic acid groups contained in an average repeat unit, could be controlled by the feed ratios of monomers. Flexible and strong membranes in sodium sulfonate form could be prepared by the solution casting method, and readily transformed to their proton forms by treating them in 2 N sulfuric acid. The polymers showed high T_gs, which increased with an increase in SC. Membranes prepared from the present sulfonated poly(ether ether ketone ketone) copolymers containing the hexafluoroisopropylidene moiety (SPEEKK‐6F) and copolymers containing the pendant 3,5‐ditrifluoromethylphenyl moiety (SPEEKK‐6FP) had lower water uptakes and lower swelling ratios in comparison with previously prepared copolymers containing 6F units. All of the polymers possessed proton conductivities higher than 1 × 10^?2 S/cm at room temperature, and proton conductivity values of several polymers were comparable to that of Nafion at high relative humidity. Their thermal stability, oxidative stability, and mechanical properties were also evaluated. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2299–2310, 2006