共查询到20条相似文献，搜索用时 31 毫秒
1.
宋占杰 《天津大学学报(英文版)》2010,16(2)
Szász-type operators can be constructed by a Poisson process. The purpose of this paper is to derive the converse result in connection with Szász-type operators by Steckin-Marchaud-type inequalities and new Ditzian modulus of continuity. The degree of approximation on deterministic signals is also given. 相似文献
2.
As an important type of polynomial approximation, approximation of functions by Bernstein operators is an important topic in approximation theory and computational theory. This paper gives global and pointwise estimates for weighted approximation of functions with singularities by Bernstein operators. The main results are the Jackson＇s estimates of functions f∈ （Wwλ）2 andre Cw, which extends the result of （Della Vecchia et al., 2004）. 相似文献
3.
The relation between composition operators on the Dirichlet spaces in the open unit disk and derivative weighted composition operators on the Bergman spaces in the open unit disk is investigated firstly,and for a combination of several derivative weighted composition operators which acts on classic Bergman space,the lower bound of its essential norm is estimated in terms of the boundary data of the symbols of d-composition operators.Some similar results about composition operators on the Dirichlet space are also presented.A necessary condition is given to determine the compactness of the combination of several derivative weighted composition operators on Bergman spaces. 相似文献
4.
刘水强 《邵阳学院学报(社会科学版)》1998,(2)
The maximally holomorphic functions of a bounded linear operator is introduced and applied to representthe spectrum and characterize the single--valued extension property. The well known results of quasi--nilpo-tent equivalent operators follow easily from the relation of their maximally holomorphie functions. 相似文献
5.
The optimum design for flexible pavement structure is studied by using themethod of mathematical programming.The mathematical model is founded on the basisof“Design Code of Highway Flexible Pavement”issued by the Ministry of Communica-tions of China.The objective function is the cost of pavement structure.The optimal solu-tions of the mathematical model were searched successfully by flexiplex tolerance method.The relevant program has been developed on DPS-8 and IBM-PC computers.And thecalculated results show good convergence and accuracy for engineering applications. 相似文献
6.
The recent two decades have seen a great increase of Original Equipment Manufacturing ("OEM") business in China. OEM products are used exclusively for export purpose and retailed in foreign markets labelled as the purchasing company’s brand. However, whether the use of a trade mark in this circumstance constitutes the "use" in Trade Mark Law and what evidence is needed to justify the "use" in any continuous three-year period have been the focal points of debate regarding the appropriate compass of Trade Mark Law. Looming behind the uncertainty of the legal term -"use" and inconsistent standards adopted by administrative authorities and courts are unidentified risks to be taken by OEM operators. 相似文献
7.
Two-photon Jaynes-Cummimgs model is generalized to the case of Kerr medium in this paper,The field and atom are prepared initially in two-photon superposition state and ground state respectively.Nonlinear coefficient affects the dynamic behaviors of the field and atom.Evolutions of the squeezing for the operators of field and atom and the quantum inversion are discussed.In particular,the higher-order squeezing for atomic dipole and the effects of nonlinearity on it,which have not been studied by other authors,are investigated,Increasing the nonlinear coefficient will decrease the squeezing depth of atomic dipole. 相似文献
8.
向裕民 《重庆大学学报(英文版)》2002,1(2):72-74
For a strip transmission line shielded by rectangular walls,the Green‘s function is helpful to construct the variation expression of the electrostatic energy.Thomson theorem is employed to determine the charge distribution on the strip.The electrostatic force on each side of the rectangular shield wall is achieved by using the principle of virtual work.The results is easy to be obtained by computerized calculation. 相似文献
9.
The two-level atom is described by Pauli sign and environment is described by infinite harmonic particle thermal reservoir.We have studied the entanglement of two-level atoms which are put in the strongly thermal radiation field.The two-level atoms' reducible density rectangular array is obtained.We discuss the properties of entanglement by virtue of concurrence.It is shown that the two two-level atoms initially situated in different coherent superposition states,entanglement of atoms have obvious dissimilarity. 相似文献
10.
The follow-up application of underwater wireless sensor network is influenced by accuracy of self-localization of nodes. The self-localization of nodes is discussed in this paper. First of all, nodes of underwater wireless sensor network are classified into several levels according to the accuracy of position of nodes and the levels are from the first to the fifth in accordance with accuracy of nodes from high to low respectively. Secondly, the level of anchor nodes can be known by those unknown nodes from the information given by the anchor nodes themselves, At the same time the unknown nodes are able to be located in the area controlled by the first level of anchor nodes that are as the aggregation. Then the positioning algorithm is designed correspondingly in accordance with the accuracy level of nodes. Finally, the positioning algorithm is simulated and analyzed. The result shows that the unknown nodes can be located effectively by hierarchical control. 相似文献
11.
A precise micro-location compliant stage with elastics-supported system is enmployed for investigations.The general motion of stage supported by elastic structure is described.The analyses of forward displecement and inverse displacement of stage are formulated.The study of input-output behavior of compliant mechanisms actually belongs to a stress-strain field problem.By using finite element analysis.the compliance coefficients of the stage supported by ring are calculated.Finally,a case is inverstigated to exemplity these formulae. 相似文献
12.
The influence of small organics on the adsorption characteristics of activated carbon produced from industrial pyrolytic tire char（APTC）for malachite green（MG） was investigated by a batch method. Phenol was chosen as the representative of small organics. The effects of phenol on adsorption equilibrium, kinetics and thermodynamics were studied systematically. The results indicate that APTC is a potential adsorbent for MG. The presence of phenol decreases the adsorption capacity of APTC for MG, but improves the rate of adsorption, while the adsorption characteristics, such as equilibrium, kinetics and thermodynamics are not affected by phenol. The adsorption equilibrium data follow Langmuir isotherm and the kinetic data are well described by the pseudo-second-order kinetic model. The adsorption process follows intra-particle diffusion model and the adsorption rate is determined by more than one process. Thermodynamic study shows that the adsorption is an endothermic and spontaneous physisorption process. 相似文献
13.
One dimensional electron density perturbation is derived by using the cold fluid equation,Possion‘s equation and the continuity equation.The perturbation is generated by a driving laser pulse propagating through a plasma,The upshifting of the frequency of a trailing pulse induced by density perturbation is studide by using optical metric.The results show that it is possible that the photon will gain energy from wht wakefield when assuming photon‘s number to be conserved.i.e..,thd photon will be accelerated. 相似文献
14.
Structure and Magnetic Propoerty of Amorphous Fe—Ni Particles prepared by Mechanical Alloying 总被引：1，自引：0，他引：1
The amorphous Fe67.5 alloy particles have been prepared by mechanical alloying(MA) process of elemental powders.The crystallization is observed at temperature around 405℃ by means of differential thermal analyzer,It is found that the coercivity Hc and the effective magnetic anisotropy value of amorphous phase are not far from that of crystal phase.The magnetization behavior of amorphous and nanocrystalline samples prepared by mechanical alloying and milling process are quite similar,they obey 1/H law at middle-high field and 1/H^2 at higher field.The 1/H field dependence is attributed to a large number of dislocations created during MA process.The studies on the 1/H^2 field dependence reveals that magnetization of Fe-Ni ultrafine particles are governed predominantly by internal stress fields induced by MA process. 相似文献
15.
The methodology of 5-axis cutter selection to avert collision for free-form surface machining by flat-end cutters is presented.The combination of different cutters is adopt aiming at short machining time and high precision.The optimal small cutter is determined based on the geometric information of the points where a cutter most probably collide with the machined surface.Several larger cutters are slected to machine the surface in order to find the interference-free area.The difference of machining time for this area between the optimal small cutter and the large cutters is calculated.The functional relationship between the machining time and the radius of a cutter is established,by which the optimal number of cutters is obtained.The combination of cutters,which possesses the minimum overall machining time,is selected as the optimal cutter sizes.A case study has demonstrated the validity of the proposed methodology and algorithms. 相似文献
16.
The transmission performance of cycloid ball planetary transmission (CBPT) is affected by cycloid tooth undercutting directly, and the design of CBPT can be optimized by the non-undercutting condition. Firstly, the theoretical equation of cycloid tooth is given, and the curvature radius of cycloid tooth profile is derived. Secondly, according to the relationship between the curvature radius and the distribution circle of balls, the non-undercutting condition of cycloid tooth profile is established, and the non-undercutting critical condition is deduced. Finally, the validity of the non-undercutting critical condition is verified by simulation. The result shows that the non-undercutting critical condition can be used to optimize the design of CBPT 相似文献
17.
Xue-ping LI Wei-qiu ZHU Zu-guang YING 《浙江大学学报(A卷英文版)》2008,9(3):330-337
An optimization method for time-delayed feedback control of partially observable linear building structures subjected to seismic excitation is proposed. A time-delayed control problem of partially observable linear building structure under horizontal ground acceleration excitation is formulated and converted into that of completely observable linear structure by using separation principle. The time-delayed control forces are approximately expressed in terms of control forces without time delay. The control system is then governed by Itoe stochastic differential equations for the conditional means of system states and then transformed into those for the conditional means of modal energies by using the stochastic averaging method for quasi-Hamiltonian systems. The control law is assumed to be modal velocity feedback control with time delay and the unknown control gains are determined by the modal performance indices. A three-storey building structure is taken as example to illustrate the proposal method and the numerical results are confirmed by using Monte Carlo simulation. 相似文献
18.
Oil-soluble stannous naphthenate (SN) is synthesized by using naphthenatic acid and SnO. And its molecular structure is confirmed by IR and multielement oil analyzer (MOA). The tribological performances of the organotin as lubricant additive are evaluated with a four-ball friction and wear tester. These experiments indicate that the wear scar diameter (WSD) and friction coefficient are diminished while the load-carrying capability increased by comparison with that of base oil. The elemental composition of the boundary lubricating film is examined by means of Auger electron spectroscopy (AES). Synergistic effect is found in the load-carrying capability of the complex of SN and sulfured olefin. The analytical results of AES indicate that the good performance of stannous naphthenate is attributed to the formation of a boundary lubricating film containing Sn on the rubbed surface. 相似文献
19.
As the classics of Christianity,the Bible has exerted a deep influence on the development of the western culture.The great influence is mostly dedicated to the allusions of the Bible.The cultural connotation reflected by these allusions reveals the source of the western civilization.The paper aims at understanding the essence of the English language and western culture better by illustrating the cultural background on the basis of which the allusions to the Bible is derived. 相似文献
20.
A CO2 laser die-cutting system, which does not need die board any more, is a new technique for manufac-turing packing box. Two optical paths, the galvanometer scanning system and the flying optical system, are used to satisfy different processing needs. The scanning system is composed of galvanometer scanning mirrors and F-θ lens. And the flying optical system is driven by two servo motors. This paper presents the software and hardware design of the laser die-cutting system, the difference between the two optical paths, as well as the relationship among the cutting speed, thickness of wrapping paper and laser power. The cutting speed and thickness of wrapping paper are linearly increased by the incremental laser power, while the cutting speed is hyperbolically decreased by the incremental thickness of wrapping paper when the laser power is constant. The amount of incision is reduced by 20% and the processing time by 40% when tested by a low power RF CO2 laser die-cutting system using the optimized program. This tech- nique is also used for the reference of other rapid laser processing systems. 相似文献