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1.
This paper compares the attitudes about mathematics of students from traditionally taught calculus classes and those from a “reformed” calculus course. The paper is based on three studies, which together present a consistent picture of student attitudes about calculus reform. The reformed course appeared to violate students' deeply held beliefs about the nature of mathematics and how it should be learned. Although during their first months in the reformed course most students disliked it, their attitudes gradually changed. One and 2 years after, reform students felt significantly more than the traditionally taught students that they better understood how math was used and that they had been required to understand math rather than memorize formulas. 相似文献
2.
David P. Dobkin Steven J. Friedman Kenneth J. Supowit 《Discrete and Computational Geometry》1990,5(1):399-407
LetS be any set ofN points in the plane and let DT(S) be the graph of the Delaunay triangulation ofS. For all pointsa andb ofS, letd(a, b) be the Euclidean distance froma tob and let DT(a, b) be the length of the shortest path in DT(S) froma tob. We show that there is a constantc (≤((1+√5)/2) π≈5.08) independent ofS andN such that $$\frac{{DT(a,b)}}{{d(a,b)}}< c.$$ 相似文献
3.
4.
5.
The dam problem with general geometry is considered. Fluid is drawn from the bottomS
1 at a ratek where 0 k N,
S
1
k M; the objective is to minimize the total pressure of the fluid in the dam. A bang-bang principle is established for any optimal controlk
0, that is,k
0 = 0 on a setA andk
0 =N on the complement setS
1
A. In the case of a rectangular dam the structure ofA is determined and the uniqueness of the minimizerk
0 is established.This work is partially supported by National Science Foundation Grants DMS-8501397 and DMS-8420896. 相似文献
6.
R. R. Mendel Kimball A. Milton James H. Reid Mark A. Samuel 《Zeitschrift fur Physik C Particles and Fields》1986,32(4):517-520
Several methods to determine (or set an upper bound on) the mass of the tau neutrino are described. The decay spectrum of \(\tau \to e\bar \nu _e \nu _\tau \) near the high center-of-mass electron-energy end is particularly sensitive to the tau-neutrino mass. It is shown that an upper bound of 20 MeV or lower may be feasible. In addition, improved limits on the mass and mixing angle of a heavy component of the tau-neutrino may be readily obtained. We also discuss the purely leptonic decays of theD andF mesons, and show how measurements of the ratiosB(D→τντ/B(D→μνμ,B(F→τντ/B(D→μνμ can be sensitive to tau-neutrino masses of 30 MeV or greater. 相似文献
7.
We report simultaneous observation of coherent resonance Raman scattering and incoherently broadened resonance fluorescence following excitation of cytochrome c in the α(0, 0) region. The influence of incoherent broadening processes on resonance Raman scattering experiments is considered. 相似文献
8.
L. Margulies N. Friedman M. Sheves Y. Mazur M.E. Lippitsch M. Riegler F.R. Aussenegg 《Tetrahedron》1985,41(1):191-195
Linear dichroism spectra of several retinoids and related polyenes incorporated in stretched polyethylene films were determined. It is suggested that the retinoids are oriented with the plane of the ring parallel to the stretching direction of the film, the long polyene chain being displaced from that direction. 相似文献
9.
Michael Stavola J.M. Friedman R.A. Stepnoski Mark G. Sceats 《Chemical physics letters》1981,80(1):192-194
Cooperative vibronic spectra involving Gd3+ electronic transitions and the vibrational transitions of nearby water molecules are used to determine the stretching spectrum for isotopically dilute OH in a solution of GdCl3 in D2O. The OH stretching spectrum of water molecules in the first hydration sphere is shifted to lower energy than that of the bulk liquid. 相似文献
10.
Friedman LA You F Sabat M Harman WD 《Journal of the American Chemical Society》2003,125(49):14980-14981
The rhenium furan complexes TpRe(CO)(MeIm)(eta2-2-methylfuran) (1) and TpRe(CO)(MeIm)(eta2-2,5-dmethylfuran) (2) undergo Lewis acid-promoted cyclopentannulation reactions with enones and enals to generate 3-acetylcyclopentene complexes. During the reaction, a rearrangement occurs such that the alpha and beta carbons of the enone are incorporated into the new carbocycle. Treatment of these complexes with an oxidant (H2O2 or silver triflate) liberates the acetylcyclopentene. When a resolved form of the rhenium complex is used, the acetylcyclopentenes can be obtained enantioselectively. 相似文献