环面结导线自感的计算

对一类弯成特殊形状——环面结的导线,利用纽结的Seifert曲面的概念,证明了它的自感也可以应用Neumann公式进行计算,并给出了计算公式以及数值分析.

纽结多项式零点的性质

研究了链环和纽结的Jones多项式性质以及零点分布性质.利用的Jones多项式的某些点取值的性质、微分性质以及三角函数的性质,特别是正弦函数和余弦函数的性质,研究了环面纽结多项式的性质和它们多项式根的性质,同时讨论了单位根的有关性质,讨论了它们之间的内在联系,从而给出某些单位根不是环面纽结多项式的根,证明了当6≤n≤8时,单位根e2p+1/nπi不是环面结Tp,q(其中,(p,q)=1)的琼斯多项式的零点.这些性质的研究将有利于研究整系数多项式与纽结多项式之间的关系.

Microenvironment and electronic state modulation of Pd nanoparticles within MOFs for enhancing low-temperature activity towards DCPD hydrogenation

Precise control of the local environment and electronic state of the guest is an important method of controlling catalytic activity and reaction pathways.In this paper,guest Pd NPs were introduced into a series of host UiO-67 MOFs with different functional ligands and metal nodes,the microenvironment and local electronic structure of Pd is modulated by introducing bipyridine groups and changing metal nodes(Ce_(6)O_(6) or Zr_(6)O_(6)).The bipyridine groups not only promoted the dispersion Pd NPs,but also facilitated electron transfer between Pd and UiO-67 MOFs through the formation of Pd-N bridges.Compared with Zr6 clusters,the tunability and orbital hybridisation of the 4f electronic structure in the Ce_(6) clusters modulate the electronic structure of Pd through the construction of the Ce-O-Pd interfaces.The optimal catalyst Pd/UiO-67(Ce)-bpy presented excellent low-temperature activity towards dicyclopentadiene hydrogenation with a conversion of>99% and a selectivity of>99%(50℃,10 bar).The results show that the synergy of Ce-O-Pd and Pd-N promotes the formation of active Pd^(δ+),which not only enhances the adsorption of H_(2) and electron-rich C=C bonds,but also contributes to the reduction of proton migration distance and improves proton utilization efficiency.These results provide valuable insights for investigating the regulatory role of the host MOFs,the nature of host-guest interactions,and their correlation with catalytic performance.

The Simulations of Annulus-Core Structure in CFB

In this paper, the stochastic particle-trajectory model is proposed for simulating the dynamic behavior of circulating fluidized bed (CFB). In our model, the motion of solid phase is obtained by calculating the individual particle trajectory while gas flow is obtained by solving the Navier-Stokes Equation including two-phase interaction. For the calculation of solid phase, the motion of each particle is decomposed into a collision process and a suspension process. In suspension process, the less important and/or unclear forces are described as a random force considering gravity, drag force and pressure gradient. As a result, the proposed model gives some numerical simulations of CFB. It indicates that the stochastic particle-trajectory model can be used to simulate qualitatively the annulus-core structure of CFB and the influences of stochastic factors cannot be ignored. In a CFB, the coupling of stochastic factors between two phases makes the radial voidage decreased. Moreover, the upward motion of particles is mitigated by both stochastic factors and turbulence between two phases.

Offshore Wind-Parks and Northern Europe＇s Mild Winters： Contribution from Ships, Fishery, et cetera？

The marine environment of North Sea and Baltic is one of the most heavily strained by numerous human activities. Simultaneously water and air temperatures increase more than elsewhere in Europe and globally, which cannot be explained with ＂global warming＂. The climatic change issue would be better understood if this extraordinary regional warming is sufficiently explained. The regional features are unique for in-depth studies due to different summer-winter conditions, shallowness of the seas, geographical structure, and main pathway for maritime weather patterns moving eastwards. The impact of sea activities on the seasonal sea water profile structure is contributing to stronger regional warming, change in growing season, and less severe sea ice conditions. The impact of the man, whether small or large, should be understood very soon and very thoroughly.

纽结Jones多项式根的性质

研究了链环和纽结的Jones多项式性质和根分布.利用环链的Jones多项式的某些性质和正弦、余弦函数的性质给出:当n≤5时,单位根e2p+1/nπi不是环面结T_(p,q)(其中(p,q)=1)的Jones多项式的零点.

Experimental and numerical analysis on interface damage ofslab track under freeze-thaw cycles

The interface of slab track laid in cold regions is prone to debonding under the coupling of freeze-thaw cyclesand temperature loads.Based on the composite specimen tests,the parameters of cohesive zone model were obtained andused in a simulation model of CRTS III prefabricated slab track to study the interlayer damage.The results show that 1)the digital image correlation(DIC)technique can accurately capture the strain field changes on the interface of compositespecimens under splitting and shear loading;2)when the temperature gradient is−40℃/m−60℃/m,the interfacedamage of the slab track is minimal and presents different patterns of expansion under positive and negative temperaturegradients,each corresponding to damage of the cohesive element dominated by shear stress and normal tensile stress,respectively;3)the reduction of the elastic modulus at the concrete base after freeze-thaw inhibits interface damage andleads to a higher starting temperature gradient load,but cracking can occur on the concrete base after 150 freeze-thaws.For this reason,in the light of damage control of both the interface and concrete base,the elastic modulus of the concretebase is 54%or over that without freeze-thaw cycles.

Insights into the selective catalytic reduction of NO by NH_3 over Mn_3O_4(110):a DFT study coupled with microkinetic analysis

Nitric oxide(NO_x), as one of the main pollutants, can contribute to a series of environmental problems, and to date the selective catalytic reduction(SCR) of NO_x with NH_3 in the presence of excess of O_2 over the catalysts has served as one of the most effective methods, in which Mn-based catalysts have been widely studied owing to their excellent low-temperature activity toward NH3-SCR. However, the related structure-activity relation was not satisfactorily explored at the atomic level. By virtue of DFT+U calculations together with microkinetic analysis, we systemically investigate the selective catalytic reduction process of NO with NH_3 over Mn_3 O_4(110), and identify the crucial thermodynamic and kinetic factors that limit the catalytic activity and selectivity.It is found that NH3 prefers to adsorb on the Lewis acid site and then dehydrogenates into NH_2~* assisted by either the two-or three-fold lattice oxygen; NH_2~* would then react with the gaseous NO to form an important intermediate NH_2 NO that prefers to convert into N_2 O rather than N_2 after the sequential dehydrogenation, while the residual H atoms interact with O_2 and left the surface in the form of H_2 O. The rate-determining step is proposed to be the coupling reaction between NH_2~* and gaseous NO.Regarding the complex surface structure of Mn_3 O_4(110),the main active sites are quantitatively revealed to be O_(3 c) and Mn_(4 c).

The Judgment of Torus Knot and Its Genus

An equivalent description for the torus knot is given in this paper, and the classification theorem of the torus knot is proved in an elementary method. Using the circular presentation of torus knot , we showed that the genus of the torus knot Kp,q is 1/2（p-1）（q-1） A knot called as bitorus knot is defined in the paper and showed . special that bitorus knot are all the connected sum of two torus knots.

Wedge Operations and Doubling Operations of Real Toric Manifolds

This paper deals with two things. First, the cohomology of canonical extensions of real topological toric manifolds is computed when coefficient ring G is a commutative ring in which 2 is unit in G. Second, the author focuses on a specific canonical extensions called doublings and presents their various properties. They include existence of infinitely many real topological toric manifolds admitting complex structures, and a way to construct infinitely many real toric manifolds which have an odd torsion in their cohomology groups.Moreover, some questions about real topological toric manifolds related to Halperin's toral rank conjecture are presented.

Recent advances on silica-based nanostructures in photocatalysis

Development of highly efficient photocatalysts has emerged as a research hotspot because of their crucial role in affecting the conversion efficiency of solar energy for applications in resource exploitation and environmental purification.The photocatalytic performance of the photocatalysts basically depends on the behaviors of light absorption,charge generation and separation,surface property and structural stability.Owing to its unique advantages(high surface area,tunable porosity,modifiable surface),porous silica provides an interesting platform to construct well-defined nanostructures such as core-shell,yolk-shell and other specific structures which effectively improved one or more of the above behaviors for photocatalysis.Typically,the structure with hollow morphology favors the light scattering and enlargement of surface area,while coating or binding with silica can modify the surface property of a photocatalyst to enhance the surface adsorption of reactants and physicochemical stability of catalysts.This review discusses the recent advances in the design,synthesis,formation mechanism of well-defined silica-based nanostructures,and the achievements of desired physicochemical properties for regulating the photocatalytic performance.