排序方式: 共有75条查询结果,搜索用时 15 毫秒
1.
Nima Taghipour Mariona Dalmases Guy L. Whitworth Miguel Dosil Andreas Othonos Sotirios Christodoulou Shanti Maria Liga Gerasimos Konstantatos 《Advanced materials (Deerfield Beach, Fla.)》2023,35(1):2207678
The use of colloidal quantum dots (CQDs) as a gain medium in infrared laser devices has been underpinned by the need for high pumping intensities, very short gain lifetimes, and low gain coefficients. Here, PbS/PbSSe core/alloyed-shell CQDs are employed as an infrared gain medium that results in highly suppressed Auger recombination with a lifetime of 485 ps, lowering the amplified spontaneous emission (ASE) threshold down to 300 µJ cm−2, and showing a record high net modal gain coefficient of 2180 cm−1. By doping these engineered core/shell CQDs up to nearly filling the first excited state, a significant reduction of optical gain threshold is demonstrated, measured by transient absorption, to an average-exciton population-per-dot 〈Nth〉g of 0.45 due to bleaching of the ground state absorption. This in turn have led to a fivefold reduction in ASE threshold at 〈Nth〉ASE = 0.70 excitons-per-dot, associated with a gain lifetime of 280 ps. Finally, these heterostructured QDs are used to achieve near-infrared lasing at 1670 nm at a pump fluences corresponding to sub-single-exciton-per-dot threshold (〈Nth〉Las = 0.87). This work brings infrared CQD lasing thresholds on par to their visible counterparts, and paves the way toward solution-processed infrared laser diodes. 相似文献
2.
Panagiotis Vlachos Adamantia Kampioti Michael Kornaros Gerasimos Lyberatos 《European Food Research and Technology》2007,225(5-6):653-663
Cork taint, one of the most known off-flavours in wine, is usually attributed to the presence of the aromatic compound 2,4,6-trichloroanisole
(2,4,6-TCA) in cork stoppers made from the bark of the cork oak, Quercus suber. There are many major chemical/biochemical pathways through which 2,4,6-TCA can be formed during cork production. The estimated
incidence of cork-tainted wine bottles ranges from 2–to 7%, costing global wine industry approximately US$ 10 billion annually.
During this study, a laboratory-scale system was designed and constructed, to efficiently treat cork bark and stopper samples
using ozone and/or other sterilizing gases, such as steam, via sequential application of pulsed vacuum–pressure cycles. The
developed physicochemical processes were studied and evaluated in order to achieve both sterilization conditions and 2,4,6-TCA
removal without affecting the mechanical and bottling properties of cork. According to the results, the application of ozone
alone seems to be a promising treatment method for cork barks. However, the pulsed treatment ensures both sufficient removal
(99%) of both bacteria and moulds from cork stoppers when combined with ozone or steam and satisfactory deodorization of cork
stoppers achieving high percentages (90%) of 2,4,6-TCA removal when combined with steam. The operating cost of each alternative
process (plain or pulsed, with or without ozone and/or steam) was estimated and compared, in laboratory scale, for the selection
of the most efficient process, taking into account technicoeconomical aspects. 相似文献
3.
Djamel Mostefa Nicolas Moreau Khalid Choukri Gerasimos Potamianos Stephen M. Chu Ambrish Tyagi Josep R. Casas Jordi Turmo Luca Cristoforetti Francesco Tobia Aristodemos Pnevmatikakis Vassilis Mylonakis Fotios Talantzis Susanne Burger Rainer Stiefelhagen Keni Bernardin Cedrick Rochet 《Language Resources and Evaluation》2007,41(3-4):389-407
4.
5.
Georgia Antonopoulou Hariklia N. Gavala Ioannis V. Skiadas Gerasimos Lyberatos 《International Journal of Hydrogen Energy》2012,37(1):191-208
The Anaerobic digestion model 1 (ADM1) framework can be used to predict fermentative hydrogen production, since the latter is directly related to the acidogenic stage of the anaerobic digestion process. In this study, the ADM1 model framework was used to simulate and predict the process of fermentative hydrogen production from the extractable sugars of sweet sorghum biomass. Kinetic parameters for sugars’ consumption and yield coefficients of acetic, propionic and butyric acid production were estimated using the experimental data obtained from the steady states of a CSTR. Batch experiments were used for kinetic parameter validation. Since the ADM1 does not account for metabolic products such as lactic acid and ethanol that are crucial during the fermentative hydrogen production process, the structure of the model was modified to include lactate and ethanol among the metabolites and to improve the predictions. The modified ADM1 simulated satisfactorily batch experiments although further modifications could be made in order to further improve the predictions for the hydrogenogenic process. 相似文献
6.
7.
Gerasimos T. Soldatos 《Housing Studies》1990,5(1):36-42
This paper derives necessary and sufficient conditions for the existence and occurrence likelihood of competitive equilibria in urban land and housing markets: (i) when there is imperfect information causing costly search trips and (ii) when land and housing are differentiated according to between‐zone and within‐zone heterogeneity. Such competitive equilibria are contingent on the possibility that consumers spill over into the markets of less preferred zones. The main conclusions are that markets tend to be partitioned into homogeneous sub‐groups and when they do not, heterogeneity may hamper the effectiveness of search and hence work against the existence of competitive equilibria. 相似文献
8.
Extended Kalman and Particle Filtering for sensor fusion in motion control of mobile robots 总被引:1,自引:0,他引:1
Gerasimos G. Rigatos 《Mathematics and computers in simulation》2010,81(3):590-607
Motion control of mobile robots and efficient trajectory tracking is usually based on prior estimation of the robots’ state vector. To this end Gaussian and nonparametric filters (state estimators from position measurements) have been developed. In this paper the Extended Kalman Filter which assumes Gaussian measurement noise is compared to the Particle Filter which does not make any assumption on the measurement noise distribution. As a case study the estimation of the state vector of a mobile robot is used, when measurements are available from both odometric and sonar sensors. It is shown that in this kind of sensor fusion problem the Particle Filter has better performance than the Extended Kalman Filter, at the cost of more demanding computations. 相似文献
9.
Gerasimos G. Rigatos 《Neural Processing Letters》2010,32(2):167-199
This paper studies neural structures with weights that follow the model of the quantum harmonic oscillator (Q.H.O.). The proposed neural networks have stochastic weights which are calculated from the solution of Schrödinger’s equation under the assumption of a parabolic (harmonic) potential. These weights correspond to diffusing particles, which interact to each other as the theory of Brownian motion (Wiener process) predicts. The learning of the stochastic weights (convergence of the diffusing particles to an equilibrium) is analyzed. In the case of associative memories the proposed neural model results in an exponential increase of patterns storage capacity (number of attractors). Finally, it is shown that conventional neural networks and learning algorithms based on error gradient can be conceived as a subset of the proposed quantum neural structures. Thus, the complementarity between classical and quantum physics is also validated in the field of neural computation. 相似文献
10.
Zhenqiu Zhang Gerasimos Potamianos Andrew W. Senior Thomas S. Huang 《Signal, Image and Video Processing》2007,1(2):163-178
The paper introduces a novel detection and tracking system that provides both frame-view and world-coordinate human location
information, based on video from multiple synchronized and calibrated cameras with overlapping fields of view. The system
is developed and evaluated for the specific scenario of a seminar lecturer presenting in front of an audience inside a “smart
room”, its aim being to track the lecturer’s head centroid in the three-dimensional (3D) space and also yield two-dimensional
(2D) face information in the available camera views. The proposed approach is primarily based on a statistical appearance
model of human faces by means of well-known AdaBoost-like face detectors, extended to address the head pose variation observed
in the smart room scenario of interest. The appearance module is complemented by two novel components and assisted by a simple
tracking drift detection mechanism. The first component of interest is the initialization module, which employs a spatio-temporal
dynamic programming approach with appropriate penalty functions to obtain optimal 3D location hypotheses. The second is an
adaptive subspace learning based 2D tracking scheme with a novel forgetting mechanism, introduced to reduce tracking drift
and increase robustness. System performance is benchmarked on an extensive database of realistic human interaction in the
lecture smart room scenario, collected as part of the European integrated project “CHIL”. The system consistently achieves
excellent tracking precision, with a 3D mean tracking error of less than 16 cm, and is demonstrated to outperform four alternative
tracking schemes. Furthermore, the proposed system performs relatively well in detecting frontal and near-frontal faces in
the available frame views.
This work was performed while Zhenqiu Zhang was on a summer internship with the Human Language Technology Department at the
IBM T.J. Watson Research Center. 相似文献