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排序方式: 共有203条查询结果,搜索用时 203 毫秒
81.
Aysegul Askan Volkan Akcelik Jacobo Bielak Omar Ghattas 《Comptes Rendus Mecanique》2010,338(7-8):364-376
In a recent article, we described a seismic inversion method for determining the crustal velocity and attenuation of basins in earthquake-prone regions. We formulated the problem as a constrained nonlinear least-squares optimization problem in which the constraints are the equations that describe the forward wave propagation. Here, we conduct a parametric study to investigate the influence of parameters such as the form of the regularization function, receiver density, preconditioning, noise level of the data, and the multilevel continuation technique on the cost and quality of the inversion. We use the same 2D Los Angeles example as in our earlier study. 相似文献
82.
Alacaoglu Ahmet Malitsky Yura Cevher Volkan 《Computational Optimization and Applications》2021,80(2):321-346
Computational Optimization and Applications - We propose a variance reduced algorithm for solving monotone variational inequalities. Without assuming strong monotonicity, cocoercivity, or... 相似文献
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85.
Burak Guzelturk Pedro Ludwig Hernandez Martinez Qing Zhang Qihua Xiong Handong Sun Xiao Wei Sun Alexander O. Govorov Hilmi Volkan Demir 《Laser \u0026amp; Photonics Reviews》2014,8(1):73-93
In the past two decades, semiconductor quantum dots and wires have developed into new, promising classes of materials for next‐generation lighting and display systems due to their superior optical properties. In particular, exciton–exciton interactions through nonradiative energy transfer in hybrid systems of these quantum‐confined structures have enabled exciting possibilities in light generation. This review focuses on the excitonics of such quantum dot and wire emitters, particularly transfer of the excitons in the complex media of the quantum dots and wires. Mastering excitonic interactions in low‐dimensional systems is essential for the development of better light sources, e.g., high‐efficiency, high‐quality white‐light generation; wide‐range color tuning; and high‐purity color generation. In addition, introducing plasmon coupling provides the ability to amplify emission in specially designed exciton–plasmon nanostructures and also to exceed the Förster limit in excitonic interactions. In this respect, new routes to control excitonic pathways are reviewed in this paper. The review further discusses research opportunities and challenges in the quantum dot and wire excitonics with a future outlook. 相似文献
86.
Effects of flow oscillations on spectrum of Ultrasound Doppler Velocimetry (UDV) signals were investigated theoretically and numerically. A laminar pipe flow with a superimposed oscillating component was considered. Negative impact of oscillation on the ultrasound signal hence on the flow images was observed in the form of spreading of spectral ultrasound signal energy around mean component, leading to image artifacts. Both analytical and numerical results revealed the strong effect of a group of parameters including Doppler frequency, flow oscillation amplitude and frequency. Exceeding a particular value of the group, 1.45, resulted in artifacts in the flow images. Revealing the mechanisms involved in the deteriorations associated with the flow oscillations is potentially useful in UDV studies involving random flow fluctuations such as turbulence. 相似文献
87.
We propose a new law for the deceleration parameter that varies linearly with time and covers Berman’s law where it is constant.
Our law not only allows one to generalize many exact solutions that were obtained assuming constant deceleration parameter,
but also gives a better fit with data (from SNIa, BAO and CMB), particularly concerning the late time behavior of the universe.
According to our law only the spatially closed and flat universes are allowed; in both cases the cosmological fluid we obtain
exhibits quintom like behavior and the universe ends with a big-rip. This is a result consistent with recent cosmological
observations. 相似文献
88.
This paper is concerned with the dynamic assignment of servers to tasks in queueing networks where demand may exceed the capacity
for service. The objective is to maximize the system throughput. We use fluid limit analysis to show that several quantities
of interest, namely the maximum possible throughput, the maximum throughput for a given arrival rate, the minimum arrival
rate that will yield a desired feasible throughput, and the optimal allocations of servers to classes for a given arrival
rate and desired throughput, can be computed by solving linear programming problems. We develop generalized round-robin policies
for assigning servers to classes for a given arrival rate and desired throughput, and show that our policies achieve the desired
throughput as long as this throughput is feasible for the arrival rate. We conclude with numerical examples that illustrate
the points discussed and provide insights into the system behavior when the arrival rate deviates from the one the system
is designed for. 相似文献
89.
Jiao Z Wang X Wang J Ke L Demir HV Koh TW Sun XW 《Chemical communications (Cambridge, England)》2012,48(3):365-367
Plate-like hydrated tungsten trioxide (3WO(3)·H(2)O) films were grown on a fluorine doped tin oxide (FTO) coated transparent conductive substrate via an efficient, facile and template-free hydrothermal method. The film exhibited a fast coloration/bleaching response (t(c90%) = 4.3 s and t(b90%) = 1.4 s) and a high coloration efficiency (112.7 cm(2) C(-1)), which were probably due to a large surface area. 相似文献
90.
A new phenolic ester 2-( p-hydroxyphenyl)ethyl eicosaheptanoic acid ester (1) and a known one hexacosylferulate (2) were isolated from the acetone extract of Salvia microphylla. In addition, two sesquiterpenes beta-eudesmol (3) and 8alpha-hydroxy-beta-eudesmol (4), a diterpene carnosic acid 12-methyl ether (12-methoxycarnosic acid) (5), three triterpenes erithrodiol 3-acetate, oleanolic acid, lupeol and beta-sitosterol were obtained as known compounds from this plant extract. The structures of the isolated compounds were elucidated by spectroscopic methods, including one- and two- dimensional 1H- and 13C-NMR and MS spectroscopies. The selected compounds were tested for antimicrobial activity against standard bacterial strains, and only carnosic acid 12-methyl ether showed antimicrobial activity against S. aureus at 78 microg mL(-1). 相似文献