Collective modes of a harmonically trapped one-dimensional Bose gas: the effects of finite particle number and nonzero temperature

Following the idea of the density functional approach, we develop a generalized Bogoliubov theory of an interacting Bose gas confined in a one-dimensional harmonic trap, by using a local chemical potential - calculated with the Lieb-Liniger exact solution - as the exchange energy. At zero temperature, we use the theory to describe collective modes of a finite-particle system in all interaction regimes from the ideal gas limit, to the mean-field Thomas-Fermi regime, and to the strongly interacting Tonks-Girardeau regime. At finite temperature, we investigate the temperature dependence of collective modes in the weak-coupling regime by means of a Hartree-Fock-Bogoliubov theory with Popov approximation. By emphasizing the effects of finite particle number and nonzero temperature on collective mode frequencies, we make comparisons of our results with the recent experimental measurement [E. Haller et al., Science 325, 1224 (2009)] and some previous theoretical predictions. We show that the experimental data are still not fully explained within current theoretical framework.Comment: 10 pages, 8 figure

Broadband enhancement of light harvesting in luminescent solar concentrator

Luminescent solar concentrator (LSC) can absorb large-area incident sunlight, then emit luminescence with high quantum efficiency, which finally be collected by a small photovoltaic (PV) system. The light-harvesting area of the PV system is much smaller than that of the LSC system, potentially improving the efficiency and reducing the cost of solar cells. Here, based on Fermi-golden rule, we present a theoretical description of the luminescent process in nanoscale LSCs where the conventional ray-optics model is no longer applicable. As an example calculated with this new model, we demonstrate that a slot waveguide consisting of a nanometer-sized low-index slot region sandwiched by two high-index regions provides a broadband enhancement of light harvesting by the luminescent centers in the slot region. This is because the slot waveguide can (1) greatly enhance the spontaneous emission due to the Purcell effect, (2) dramatically increase the effective absorption cross-section of luminescent centers, and (3) strongly improve the quantum efficiency of luminescent centers. It is found that about 80% solar photons can be ultimately converted to waveguide-coupled luminescent photons even for a low luminescent quantum efficiency of 0.5. This LSC is potential to construct a tandem structure which can absorb nearly full-spectrum solar photons, and also may be of special interest for building integrated nano-PV applications

A Research on Sexual Difference in the Resident Space

Being the existence of human’ life and activities; Space has been in close relationship between the gender and the society classes based on it. After the thoughts of feminism being introduced to the research on urban space in 1970s for the first time, gender difference in space environment is widely focused on and the research extends to the field of architecture. The establishment of “the Lab on the sexuality and space” indicates that there is more foucus on the subject. The present study is insufficient for an objective and systematic study about the gender difference and living space in special environment. Having “Wuhan Baubuting Block” and some ancient settlements in the southeast in Hubei as a case study, having carrying on the preceding literature research, exploring the theory behind the data, analyzing the transformation trend, in the perspective of humanism I suggest that eliminating the sexual difference in the living space is a way to improve the space arrangements. Key words: the sexual difference, the habitation, the space environment, humanism Résumé: Being the existence of human’ life and activities; Space has been in close relationship between the gender and the society classes based on it. After the thoughts of feminism being introduced to the research on urban space in 1970s for the first time, gender difference in space environment is widely focused on and the research extends to the field of architecture. The establishment of “the Lab on the sexuality and space” indicates that there is more focus on the subject. The present study is insufficient for an objective and systematic study about the gender difference and living space in special environment. Having “Wuhan Baubuting Block” and some ancient settlements in the southeast in Hubei as a case study, having carrying on the preceding literature research, exploring the theory behind the data, analyzing the transformation trend, in the perspective of humanism I suggest that eliminating the sexual difference in the living space is a way to improve the space arrangements. Mots-Clés: the sexual difference, the habitation, the space environment, humanis

Ten years of MIREX: reflections, challenges and opportunities

The Music Information Retrieval Evaluation eXchange (MIREX) has been run annually since 2005, with the October 2014 plenary marking its tenth iteration. By 2013, MIREX has evaluated approximately 2000 individual music information retrieval (MIR) algorithms for a wide range of tasks over 37 different test collections. MIREX has involved researchers from over 29 different contrives with a median of 109 individual participants per year. This pater summarizes the history of MIREX form its earliest planning meeting in 2001 to the present. It reflects upon the administrative, financial, and technological challenges MIREX has faced and describes how those challenges have been surmounted. We propose new funding models, a distributed evaluation framework, and more holistic user experience evaluation tasks-some evolutionary, some revolutionary-for the continued success of MIREX. We hope that this paper will inspire MIR community members to contribute their ideas so MIREX can have many more successful years to come