Synthesis and energy-transfer properties of poly(amidoamine) dendrons modified with naphthyl and dansyl groups

Poly(amidoamine) dendrons of 1-3 generations with naphthyl groups at the periphery and a dansyl group at the focal point were synthesized and carefully characterized. Intramolecular energy-transfer properties of these flexible aliphatic-scaffold light-harvesting dendrons were investigated by UV-vis absorption and fluorescence spectroscopy. Efficient energy transfer from the naphthyl groups to the dansyl group occurred for both the first and the second generation dendrons (the energy-transfer efficiency was 94.3% and 76.9%, respectively), whereas the third generation dendron exhibited a low energy-transfer efficiency of 17.8%. The average donor-acceptor distances between the naphthyl and dansyl groups were calculated for different generation dendrons. Different degrees of the backfolding of dendritic branches were used to interpret the different donor-acceptor distances.     

单摆周期的数值计算

本文从理论上分析了单摆周期随角振幅变化的规律，并给出了数值计算结果     

A complete measurement of spin-observables for intermediate-energy inclusive quasielastic polarized proton scattering from C

The complete set of Wolfenstein parameters, the polarization, the asymmetry of scattering and the unpolarized double-differential cross section are presented for inclusive quasielastic proton scattering from ¹²C at a central momentum transfer of q = 1.9 fm⁻¹ and incident energies of 290 and 420 MeV. The spin observables D₀, D_x, D_y and D_z as well as the longitudinal-to-transverse ratio of spin-flip probabilities are extracted from the data. Across the quasielastic continuum, the experimental data is compared to the variations expected from a single-scattering Fermi-gas approximation using the free NN amplitudes. Medium effects are evident in the pronounced quenching of the polarization parameter relative to the free value.     

X射线衍射仪功能扩展的研究

通过软件实现了用 Ｐ Ｃ 机调用日本 Ｒｉｇａｋｕ 公司生产的 Ｄ／ ｍａｘ 一类 Ｘ 射线衍射仪测量数据，利用 Ｐ Ｃ 机的复杂计算功能，使原有仪器也可以进行新的结构分析工作，扩展了仪器的功能。     

The minimum norm method for the determination of the charge density from elastic electron scattering data

Unphysical behavior in the QR algorithm based least squares determination of the expansion coefficients of the charge density obtained from limited information about the charge form factor occurs when the spread of the singular values in the matrix relating these quantities becomes too large. Setting the smallest singular values equal to zero in the singular value decomposition used in the minimum norm method yields a much more reasonable determination of the charge density. Increasing the size of the basis without increasing the range of the prior information about the charge form factor leads to ambiguities in the determination of the charge density. Numerical results in an analytic model are presented.     

Nonlinear waves generated by a steadily moving line load on an elastic plate

The steady-state response of an infinite plate to a steadily moving line load is studied. The nonlinear plate theory of Herrmann is used. The plate response is governed by a set of nonlinear differential equations and, in addition, must satisfy the “radiation” conditions. Appropriate radiation conditions for the present nonlinear problem are developed. Exact solutions representing nonlinear waves generated by the moving load are constructed.     

Implicit weighted essentially non‐oscillatory schemes for the incompressible Navier–Stokes equations

A class of lower–upper/approximate factorization (LUAF) implicit weighted essentially non‐oscillatory (ENO; WENO) schemes for solving the two‐dimensional incompressible Navier–Stokes equations in a generalized co‐ordinate system is presented. The algorithm is based on the artificial compressibility formulation, and symmetric Gauss–Seidel relaxation is used for computing steady state solutions while symmetric successive overrelaxation is used for treating time‐dependent flows. WENO spatial operators are employed for inviscid fluxes and central differencing for viscous fluxes. Internal and external viscous flow test problems are presented to verify the numerical schemes. The use of a WENO spatial operator not only enhances the accuracy of solutions but also improves the convergence rate for the steady state computation as compared with using the ENO counterpart. It is found that the present solutions compare well with exact solutions, experimental data and other numerical results. Copyright © 1999 John Wiley & Sons, Ltd.     

Two methods for determining impact-force history on elastic plates

Two methods are presented to detect the impact-force history on elastic plates. The first method involves construction of a Greens function to relate the strain responses to an impact force acting axisymmetrically on a circular plate. The classical plate theory and a series of Bessel functions were used to obtain the Greens functions in the time domain. The gradient projection method was employed to search for the optimal force history. Examples using circular plates with free and fixed boundary conditions are demonstrated. On the other hand, the second method is purely experiment-based and involves no Greens function. Thus, this method can be applied to structures of various geometries, boundary conditions and material properties. The very satisfactory agreement between the measured and the detected force histories using both methods shows that they are reliable for impact-force determination purposes.     

On the stability of solutions to quadratic programming problems

We consider the parametric programming problem (Q _p ) of minimizing the quadratic function f(x,p):=x ^T Ax+b ^T x subject to the constraint Cx≤d, where x∈ℝ ⁿ , A∈ℝ ^n×n , b∈ℝ ⁿ , C∈ℝ ^m×n , d∈ℝ ^m , and p:=(A,b,C,d) is the parameter. Here, the matrix A is not assumed to be positive semidefinite. The set of the global minimizers and the set of the local minimizers to (Q _p ) are denoted by M(p) and M ^loc (p), respectively. It is proved that if the point-to-set mapping M ^loc (·) is lower semicontinuous at p then M ^loc (p) is a nonempty set which consists of at most ? _m,n points, where ? _m,n = is the maximal cardinality of the antichains of distinct subsets of {1,2,...,m} which have at most n elements. It is proved also that the lower semicontinuity of M(·) at p implies that M(p) is a singleton. Under some regularity assumption, these necessary conditions become the sufficient ones. Received: November 5, 1997 / Accepted: September 12, 2000?Published online November 17, 2000     

Holder continuity of solutions to a parametric variational inequality

We prove a Hölder continuity property of the locally unique solution to a parametric variational inequality without assuming differentiability of the given data.This research was supported by the World Laboratory (Lausanne).