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41.
T J Hall E L Madsen J A Zagzebski E J Boote 《The Journal of the Acoustical Society of America》1989,85(6):2410-2416
The accuracy of a method of data reduction for determining acoustic backscatter coefficients was tested using focused transducers and narrow-band pulses. Two phantoms with well-defined scattering properties were the bases of the tests, one having low attenuation and one with tissue-mimicking attenuation. The experimentally determined backscatter coefficients were found to be independent of transducer-to-scattering-volume distance and to agree very well with theoretical values, typically within 10%. 相似文献
42.
43.
The performance of three different functions (penalty, Lagrange–Newton, and projection) used in combination with three different Newton-based optimization algorithms for solving large-scale constrained optimizations is investigated. The test cases correspond to locating minima on seams between two force field energy functions, which can be used to model transitions structures in chemical reactions. The Lagrange–Newton function used in combination with a standard Newton–Raphson optimization is found to be the most efficient for systems up to ~500 atoms, while an iterative algorithm becomes preferable for larger systems. 相似文献
44.
An integral equation formulation for buoyancy-driven convection problems is developed and illustrated. Buoyancy-driven convection in a bounded cylindrical geometry with a free surface is studied for a range of aspect ratios and Nusselt numbers. The critical Rayleigh number, the nature of the cellular motion, and the heat transfer enhancement are computed using linear theory. Green's functions are used to convert the linear problem into linear Fredholm integral equations. Theorems are proved which establish the properties of the eigenvalues and eigenfunctions of the linear integral operator which appears in these equations. 相似文献
45.
46.
Constantin D Davidson P Freyssingeas É Madsen A 《The Journal of chemical physics》2010,133(22):224902
We used x-ray photon correlation spectroscopy to study the dynamics in the lamellar phase of a platelet suspension as a function of the particle concentration. We measured the collective diffusion coefficient along the director of the phase, over length scales down to the interparticle distance, and quantified the hydrodynamic interaction between the particles. This interaction sets in with increasing concentration and can be described qualitatively by a simplified model. No change in the microscopic structure or dynamics is observed at the transition between the fluid and the gel-like lamellar phases. 相似文献
47.
Andresen GB Ashkezari MD Baquero-Ruiz M Bertsche W Bowe PD Butler E Carpenter PT Cesar CL Chapman S Charlton M Fajans J Friesen T Fujiwara MC Gill DR Hangst JS Hardy WN Hayden ME Humphries AJ Hurt JL Hydomako R Jonsell S Madsen N Menary S Nolan P Olchanski K Olin A Povilus A Pusa P Robicheaux F Sarid E Silveira DM So C Storey JW Thompson RI van der Werf DP Wurtele JS Yamazaki Y;ALPHA Collaboration 《Physical review letters》2011,106(2):025002
We demonstrate controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense, and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination. 相似文献
48.
Müller L Waldorf M Gutt C Grübel G Madsen A Finlayson TR Klemradt U 《Physical review letters》2011,107(10):105701
Results of a x-ray photon correlation spectroscopy experiment on the very weakly first order martensitic transformation of a Au50.5Cd49.5 single crystal are presented. Slow non-equilibrium-dynamics are observed in a narrow temperature interval in the direct vicinity of the otherwise athermal phase transformation. These dynamics are associated with the martensite-aging effect. The dynamical aging is accompanied by an avalanchelike behavior which is identified with an incubation-time phenomenon. 相似文献
49.
Jensen BB Ming H Westergaard PG Gunnarsson K Madsen MH Brusch A Hald J Thomsen JW 《Physical review letters》2011,107(11):113001
We present the first experimental determination of the electric-dipole forbidden (3s3p)3P?→(3s2)1S? (M2) transition rate in 2?Mg and compare to state-of-the-art theoretical predictions. Our measurement exploits a magnetic trap isolating the sample from perturbations and a magneto-optical trap as an amplifier converting each 3P?→1S? decay event into millions of photons readily detected. The transition rate is determined to be (4.87 ± 0.3)×10?? s?1 corresponding to a 3P? lifetime of 2050(-110)(+140) sec. This value is in agreement with recent theoretical predictions, and to our knowledge the longest lifetime ever determined in a laboratory environment. 相似文献
50.
Min Wen Gilbert Laporte Oli B G Madsen Anders V Nørrelund Allan Olsen 《The Journal of the Operational Research Society》2014,65(10):1555-1561
Environment-friendly electric vehicles have gained popularity and increased attention in recent years. The deployment of a network of recharging stations is essential given their limited travel range. This paper considers the problem of locating electronic replenishment stations for electric vehicles on a traffic network with flow-based demand. The objective is to optimize the network performance, for example to maximize the flow covered by a prefixed number of stations or to minimize the number of stations needed to cover traffic flows. Two integer linear programming formulations are proposed to model the problem. These models are tested on real-life traffic data collected in Denmark. 相似文献