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排序方式: 共有367条查询结果,搜索用时 15 毫秒
31.
Eric Besson Dr. Ahmad Mehdi Prof. Arie Van der Lee Dr. Hervé Chollet Dr. Catherine Reyé Prof. Roger Guilard Prof. Robert J. P. Corriu Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(33):10226-10233
In this paper, we investigate the cation‐exchange properties of a self‐assembled hybrid material towards trivalent ions, lanthanides (La3+, Eu3+, Gd3+, Yb3+) and Fe3+. The bis‐zwitterionic lamellar material was prepared by sol–gel process from only 3‐aminopropyltriethoxysilane (APTES), succinic anhydride, and ethylenediamine. In ethanol heated under reflux, the exchange ethylenediammonium versus Ln3+ proved to be complete by complexometry measurements and elemental analyses, one Cl? ion per one LnIII remaining as expected for charge balance. In aqueous solution at 20 °C, the material was found to be selective towards lanthanide in spite of the similarity of their ionic radii. The cation uptake depends on the nature of the salt, the difference between two lanthanides reaching up to 20 % in some cases. Finally, ion‐exchange reaction with FeCl3 was chosen as a probe to get more information on the material after incorporation of trivalent ions. Based on Mössbauer spectroscopic investigations on the resulting material in conjunction with the XRD analysis of materials containing trivalent ions, a structural model was proposed to describe the incorporation of trivalent ions by exchange reaction within the original zwitterionic material. 相似文献
32.
33.
H. Suchowski B. D. Bruner A. Ganany-Padowicz I. Juwiler A. Arie Y. Silberberg 《Applied physics. B, Lasers and optics》2011,105(4):697-702
A new method for efficient, broadband sum and difference frequency generation of ultrafast pulses is demonstrated. The principles
of the method follow from an analogy between frequency conversion and coherent optical excitation of a two-level system. For
conversion of ultrafast pulses, the concepts of adiabatic conversion are developed further in order to account for dispersion
and group velocity mismatch. The scheme was implemented using aperiodically poled nonlinear crystals and a single step nonlinear
mixing process, leading to conversion of near-IR (∼790 nm) ultrafast pulses into the blue (∼450 nm) and mid-IR (∼3.15 μm)
spectral regions. Conversion bandwidths up to 15 THz FWHM and efficiencies up to 50% are reported. 相似文献
34.
Whereas periodic gratings enable us to couple light into a surface plasmon polariton only at a specific angle and wavelength, we show here that quasiperiodic gratings enable the coupling of light at multiple wavelengths and angles. The quasiperiodic grating can be designed in a systematic manner using the dual-grid method, thereby enabling us to control the coupling strength and grating dimensions. We verified the method experimentally by efficiently coupling light into a surface plasmon from several different illumination angles using a single quasiperiodic grating. 相似文献
35.
We report on a new (to our knowledge) configuration incorporating both birefringence and quasi-phase-matching, enabling efficient phase-matched nonlinear diffraction in one-dimensional periodically poled nonlinear crystals. We demonstrate the method experimentally, showing an efficient nonlinear diffraction to the first few orders in two types of crystals, MgO doped congruent lithium niobate and congruent lithium niobate, and characterize its efficiency dependence on the fundamental power, the propagation angle, and the crystal temperature. This configuration can increase efficiencies observed in nonlinear diffraction experiments, enables ferroelectric domain characterization by nonlinear microscopy, and can be used to determine the duty cycles of periodically poled nonlinear crystals. 相似文献
36.
Let p be a prime and let $\varphi\in\mathbb{Z}_{p}[x_{1},x_{2},\ldots, x_{p}]$ be a symmetric polynomial, where $\mathbb {Z}_{p}$ is the field of p elements. A sequence T in $\mathbb {Z}_{p}$ of length p is called a φ-zero sequence if φ(T)=0; a sequence in $\mathbb {Z}_{p}$ is called a φ-zero free sequence if it does not contain any φ-zero subsequence. Motivated by the EGZ theorem for the prime p, we consider symmetric polynomials $\varphi\in \mathbb {Z}_{p}[x_{1},x_{2},\ldots, x_{p}]$ , which satisfy the following two conditions: (i) every sequence in $\mathbb {Z}_{p}$ of length 2p?1 contains a φ-zero subsequence, and (ii) the φ-zero free sequences in $\mathbb {Z}_{p}$ of maximal length are all those containing exactly two distinct elements, where each element appears p?1 times. In this paper, we determine all symmetric polynomials in $\mathbb {Z}_{p}[x_{1},x_{2},\ldots, x_{p}]$ of degree not exceeding 3 satisfying the conditions above. 相似文献
37.
Gromov and Piatetski-Shapiro proved existence of finite volume non-arithmetic hyperbolic manifolds of any given dimension. In dimension four and higher, we show that there are about v v such manifolds of volume at most v, considered up to commensurability. Since the number of arithmetic ones tends to be polynomial, almost all hyperbolic manifolds are non-arithmetic in an appropriate sense. Moreover, by restricting attention to non-compact manifolds, our result implies the same growth type for the number of quasi-isometry classes of lattices in SO(n, 1). Our method involves a geometric graph-of-spaces construction that relies on arithmetic properties of certain quadratic forms. 相似文献
38.
S. Acco A. Arie Y. Ben-Aryeh M. Katz P. Blau 《Applied physics. B, Lasers and optics》2011,103(1):89-97
An analytical expression for calculating the signal output power of an optical parametric generator (OPG) configuration was
developed. The model is based on Heisenberg equations in space and radiation mode theory. A simple analytical expression can
be obtained by assuming that all modes within the gain bandwidth of the nonlinear crystal have the same gain and the same
interaction length. Another derivation considers the gain and interaction length of each individual mode. The model predictions
are in excellent agreement with the measured signal power of OPGs based on 25- and 35-mm periodically poled LiNbO3 crystal (with effective quadratic nonlinearity of ∼14.5 pm/V) and 47-mm periodically poled LiTaO3 crystal (with effective quadratic nonlinearity of ∼9 pm/V). In addition, a comparison was made between the summation over
discrete modes approach and the traditional approach of continuous integration over the beam parameters and pump frequency.
We have found that the first approach, which is developed in this paper, predicts more accurately the output power of the
OPG. 相似文献
39.
Arie Hordijk Olaf Passchier Floske Spieksma 《Mathematical Methods of Operations Research》1997,45(2):281-301
In this paper we will consider two-person zero-sum games and derive a general approach for solving them. We apply this approach to a queueing problem. In section 1 we will introduce the model and formulate the Key-theorem. In section 2 we develop the theory that we will use in section 3 to prove the Key-theorem. This includes a general and useful result in Lemma 2.1 on the sufficiency of stationary policies. 相似文献
40.
K. Fradkin-Kashi A. Arie P. Urenski G. Rosenman 《Applied physics. B, Lasers and optics》2000,71(2):251-255
Tunable mid-infrared coherent radiation (3.25-
3.7 μm) is generated by quasi-phase-matched difference frequency generation in a multi-grating periodically-poled RbTiOAsO4 crystal. The spontaneous polarization and coercive field of flux-grown RbTiOAsO4 are determined by polarization switching measurements. The nonlinear interaction enables us to explore the optical and nonlinear
properties of this material in the mid-infrared range, where data is scarce. The measurements are used to derive a mid- infrared
corrected dispersion equation for nz in RbTiOAsO4. This equation is in excellent agreement with previously published measurements of nonlinear interactions in periodically-poled
RbTiOAsO4. The measured wavelength and temperature bandwidths are ≈48 nm cm and ≈29 °C cm, respectively. A relatively high temperature
tuning slope of the phase-matched idler wavelength, -1.27 nm/°C, is measured. This may be useful for realizing temperature-tuned
nonlinear devices.
Received: 30 March 2000 / Revised version: 9 May 2000 / Published online: 30 June 2000 相似文献