199,803 research outputs found
Les « Contes » de M. Karl Ewald
No full textPellisson Maurice. Les « Contes » de M. Karl Ewald. In: La revue pédagogique, tome 53, Juillet-Décembre 1908. pp. 51-59
[Johann Ludwig Ewald]
No full textPorträt von Johann Ludwig Ewald (1747-1822), nach einem Gemälde von Ernst von Valentini (1759-1835)E. Valentin del. ; H. Lips sculp.Datierung und Titel gemäss KruseAuf Blatt handschriftliche Notiz "Brun, II, 76"Auf Rückseite des Blattes handschriftliche Notiz "J. D. M. Ewald"Auf Unterlagenblatt handschriftliche Notiz "Ewald"Auf Unterlagenblatt und Rückseite des Blattes Nummerierung nach Lips' Inventarisierung übernommen: Nr. 892, Album I
Application of stochastic differential games and real option theory in environmental economics
No full textThis thesis presents several problems based on papers written jointly by the author and Dr. Christian-Oliver Ewald. Firstly, the author extends the model presented by Fershtman and Nitzan (1991), which studies a deterministic differential public good game. Two types of volatility are considered. In the first case the volatility of the diffusion term is dependent on the current level of public good, while in the second case the volatility is dependent on the current rate of public good provision by the agents. The result in the latter case is qualitatively different from the first one. These results are discussed in detail, along with numerical examples. Secondly, two existing lines of research in game theoretic studies of fisheries are combined and extended. The first line of research is the inclusion of the aspect of predation and the consideration of multi-species fisheries within classical game theoretic fishery models. The second line of research includes continuous time and uncertainty. This thesis considers a two species fishery game and compares the results of this with several cases. Thirdly, a model of a fishery is developed in which the dynamic of the unharvested fish population is given by the stochastic logistic growth equation and it is assumed that the fishery harvests the fish population following a constant effort strategy. Explicit formulas for optimal fishing effort are derived in problems considered and the effects of uncertainty, risk aversion and mean reversion speed on fishing efforts are investigated. Fourthly, a Dixit and Pindyck type irreversible investment problem in continuous time is solved, using the assumption that the project value follows a Cox-Ingersoll- Ross process. This solution differs from the two classical cases of geometric Brownian motion and geometric mean reversion and these differences are examined. The aim is to find the optimal stopping time, which can be applied to the problem of extracting resources
RECOMBINATION DELAYED FLUORESCENCE IN CRYSTALLITES OF SOME ORGANIC MOLECULES
No full textM. Ewald and G. Durocher, J. Chem. Phys., July (1971). M. Ewald, B. Muel and G. Durocher, Chem. Phys. Letters, 5, 83 (1970). M. Ewald and G. Durocher, Chem. Phys. Letters, April (1971). M. Ewald and G. Durocher, to be published.""Author Institution: D\'{e}partment de Chimie, Universit\'{e} de Montrcal B.P. 6128In view of a certain number of photobiological processes for which it has been suggested that the primary action of light is to cause the ionization of some specific molecules, a systematic study has been carried out in our laboratory on the effect of primary U.V. irradiation on the nature of the delayed emission in some compounds like the aromatic , the acridine , the xanthene , and the . It has been shown that the presence of a very small amount of aggregated solute molceules in an ethanol rigid glass matrix is sufficient to produce a delayed fluorescene (DF) with the following characteristics: 1. Shift in the positions of the vibrational peaks or appearance of new low energy components compared to the normal fluorescence spectra. 2. The action spectra of the DF can be correlated with the treshold for intrinsic charge carrier generation in the crystalline state and generally shows “antibatic” relationship with the absorption spectra of the solute molecules. 3. The DF obeys the relationship with n equal to 1.0. 4. The decay with time of the DF generally obeys a double exponential law with time constants varying between 0.3 to 10.0 sec. It has been proposed that the DF originates from electron-hole recombination after the detrapping of charge carriers in the crystallites first generated by the incident U.V. light
Et ukendt digt af Ewald og et velkendt brev i original
No full textErik M. Christensen om Johannes Ewald
Ewald, Glendora (Death, 1892-01-09)
No full textAddress: Wells St.Age at death: 1 day217/Pg.5/1892/F W S/Cinti, Ohio/Dr. Wm. A. Geohegan/Ewald & C.H./Delhi G. Prot.Original record filed in drawer labeled 'ERNST, M.-EWRY'
Molecular simulation of the vapor-liquid equilibria of xylene mixtures: Force field performance, and Wolf vs. Ewald for electrostatic interactions
No full textThis article explores how well vapor-liquid equilibria of pure components and binary mixtures of xylenes can be predicted using different force fields in molecular simulations. The accuracy of the Wolf method and the Ewald summation is evaluated. Monte Carlo simulations in the Gibbs ensemble are performed at conditions comparable to experimental data, using four different force fields. Similar results using the Wolf and the Ewald methods can be obtained for the prediction of densities and the phase compositions of binary mixtures. With the Wolf method, up to 50% less CPU time is used compared to the Ewald method, at the cost of accuracy and additional parameter calibration. The densities of p-xylene and m-xylene can be well estimated using the TraPPE-UA and AUA force fields. The largest differences of VLE with experiments are observed for o-xylene. The p-xylene/o-xylene binary mixtures at 6.66 and 81.3 kPa are simulated, leading to an excellent agreement in the predictions of the composition of the liquid phase compared to experiments. The composition of the vapor phase is dominated by the properties of the component with the largest mole fraction in the liquid phase. The accuracy of the predictions of the phase composition are related to the quality of the density predictions of the pure component systems. The phase composition of the binary system of xylenes is very sensitive to slight differences in vapor phase density of each xylene isomer, and how well the differences are captured by the force fields.Engineering Thermodynamic
The numerical accuracy of truncated Ewald sums for periodic systems with long-range Coulomb interactions
No full textEwald summation is widely used to calculate electrostatic interactions in computer simulations of condensed-matter systems. An analysis is presented of the errors arising from truncating the infinite real- and Fourier-space lattice sums in the Ewald formulation. An optimal choice is derived for the Fourier-space cutoff given a screening parameter η. It is found that the number of vectors in Fourier space required to achieve a given accuracy scales with η3. The proposed method can be used to determine computationally efficient parameters for Ewald sums, to assess the quality of Ewald-sum implementations, and to compare different implementations
Ewald sums for Yukawa potentials in quasi-two-dimensional systems
No full text7 pages, no figure.International audienceIn this note, we derive Ewald sums for Yukawa potential for three dimensional systems with two dimensional periodicity. This sums are derived from the Ewald sums for Yukawa potentials with three dimensional periodicity [G. Salin and J.-M. Caillol, J. Chem. Phys. {\bf 113}, 10459 (2000)] by using the method proposed by Parry for the Coulomb interactions [D.E. Parry, Surf. Sci. {\bf 49}, 433 (1975); {\bf 54}, 195 (1976)]
- …
