分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-02 合作期刊: 《热科学学报》
摘要：To promote the utilization efficiency of coal resources, and to assist with the control of sulphur during gasification and/or downstream processes, it is essential to gain basic knowledge of sulphur transformation associated with gasification performance. In this research we investigated the influence of O-2/C molar ratio both on gasification performance and sulphur transformation of a low rank coal, and the sulphur transformation mechanism was also discussed. Experiments were performed in a circulating fluidized bed gasifier with O-2/C molar ratio ranging from 0.39 to 0.78 mol/mol. The results showed that increasing the O-2/C molar ratio from 0.39 to 0.78 mol/mol can increase carbon conversion from 57.65% to 91.92%, and increase sulphur release ratio from 29.66% to 63.11%. The increase of O-2/C molar ratio favors the formation of H2S, and also favors the retained sulphur transforming to more stable forms. Due to the reducing conditions of coal gasification, H2S is the main form of the released sulphur, which could be formed by decomposition of pyrite and by secondary reactions. Bottom char shows lower sulphur content than fly ash, and mainly exist as sulphates. X-ray photoelectron spectroscopy (XPS) measurements also show that the intensity of pyrite declines and the intensity of sulphates increases for fly ash and bottom char, and the change is more obvious for bottom char. During CFB gasification process, bigger char particles circulate in the system and have longer residence time for further reaction, which favors the release of sulphur species and can enhance the retained sulphur transforming to more stable forms.
分类： 动力与电气工程 >> 工程热物理学 提交时间： 2017-06-22 合作期刊: 《热科学学报》
摘要：Floating zone technique is a crucible-free process for growth of high quality single crystals. Unstable thermocapillary convection is a typical phenomenon during the process under microgravity. Therefore, it is very important to investigate the instability of thermocapillary convection in liquid bridges with deformable free-surface under microgravity. In this works, the Volume of Fluid (VOF) method is employed to track the free-surface movement. The results are presented as the behavior of flow structure and temperature distribution of the molten zone. The impact of Marangoni number (Ma) is also investigated on free-surface deformation as well as the instability of thermocapillary convection. The free-surface exhibits a noticeable axisymmetric (but it is non-centrosymmetric) and elliptical shape along the circumferential direction. This specific surface shape presents a typical narrow 'neck-shaped' structure with convex at two ends of the zone and concave at the mid-plane along the axial direction. At both theta = 0 degrees and theta = 90 degrees, the deformation ratio increases rapidly with Ma at first, and then increases slowly. Moreover, the hydrothermal wave number m and the instability of thermocapillary convection increase with Ma.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-05-02
Chen, AB [Chen, Aibing][ 1 ]
Liu, C [Liu, Chao][ 2 ]
Yu, YF [Yu, Yifeng][ 1 ]
Hu, YQ [Hu, Yongqi][ 1 ]
Lv, HJ [Lv, Haijun][ 1 ]
Zhang, Y [Zhang, Yue][ 1 ]
Shen, SF [Shen, Shufeng][ 1 ]
Zhang, J [Zhang, Jian][ 3 ]
摘要：Nitrogen-doped carbon nanofibers (MCNFs) with an aligned mesoporous structure were synthesized by a co-confined carbonization method using anodic aluminum oxide (AAO) membrane and tetraethy- lorthosilicate (TEOS) as co-confined templates and ionic liquids as the precursor. The as-synthesized MCNFs with the diameter of 80–120 nm possessed a bulk nitrogen content of 5.3 wt% and bimodal meso- porous structure. The nitrogen atoms were mostly bound to the graphitic network in two forms, i.e. pyridinic and pyrrolic nitrogen, providing adsorption sites for acidic gases like SO2 and CO2 . Cyclic exper- iments revealed a considerable stability of MCNFs over 20 runs of SO2 adsorption and 15 runs for CO2 adsorption. The MCNFs also have a preferable adsorption performance for Cd2+.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-05-02
Xu, MW [Xu, Minwei][ 1,2 ]
Sun, HT [Sun, Huiting][ 1 ]
Shen, C [Shen, Cai][ 3 ]
Yang, S [Yang, Sen][ 1 ]
Que, WX [Que, Wenxiu][ 2 ]
Zhang, Y [Zhang, Yin][ 4 ]
Song, XP [Song, Xiaoping][ 1 ]
摘要：A lithium-assisted approach has been developed for the exfoliation of pristine graphite, which allows the large-scale preparation of few-layer graphene nanosheets. The process involves an unexpected physical insertion and exfoliation, and the graphene nanosheets prepared by this method reveal undisturbed sp2-hybridized structures. A possible two-step mechanism, which involves the negative charge being trapped around the edges of the graphite layers and a subsequent lithiation process, is proposed to explain the insertion of lithium inside the graphite interlayers. If necessary, the present exfoliation can be repeated and thinner (single or 2–3 layer) graphene can be achieved on a large scale. This simple process provides an efficient process for the exfoliation of pristine graphite, which might promote the future applications of graphene.
提交时间： 2017-05-02
Sun, Y [Sun, Yan][ 1,2 ]
Yang, SH [Yang, Shenghui][ 1 ]
Zhang, Y [Zhang, Ye][ 1 ]
Jiang, J [Jiang, Jun][ 1 ]
Jiang, HC [Jiang, Haochuan][ 1 ]
摘要：In order to obtain a uniform transparent ceramic scintillator, well-dispersed fine starting powders with high-purity, small grain size, spherical morphology and high sinter-ability are necessary. In this study, Ce3+ doped gadolinium aluminum gallium garne
提交时间： 2017-05-02
Chen, AB [Chen, Aibing][ 1 ]
Yu, YF [Yu, Yifeng][ 1 ]
Zhang, Y [Zhang, Yue][ 1 ]
Zang, WW [Zang, Wenwei][ 1 ]
Yu, YH [Yu, Yunhong][ 1 ]
Zhang, YX [Zhang, Yexin][ 2 ]
Shen, SF [Shen, Shufeng][ 1 ]
Zhang, J [Zhang, Jian][ 2 ]
摘要：Nitrogen-doped ordered mesoporous carbon spheres [N-OMCs] were conveniently produced by using a soluble urea-phenol-formaldehyde resin as the precursor and triblock copolymer F127 as a soft template. The obtained carbon spheres with a mean diameter of aro
分类： 材料科学 >> 材料科学（综合） 提交时间： 2017-03-30
摘要：Cerium doped gadolinium gallium aluminum oxide (GAGG:Ce) nanopowders were prepared by a co-precipitation method with different cation concentrations of the mother salt solution, followed by calcination at different temperatures. The influence of cation co
分类： 材料科学 >> 材料科学（综合） 提交时间： 2017-03-30
摘要：Cerium doped gadolinium gallium aluminum oxide (GAGG:Ce) nanopowders were prepared by a co-precipitation method with different cation concentrations of the mother salt solution, followed by calcination at different temperatures. The influence of cation co
分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：Motivated by the recent LHC hints of a Higgs boson around 125 GeV, we assume a SM-like Higgs with the mass 123-127 GeV and study its implication in low energy SUSY by comparing the MSSM and NMSSM. We consider various experimental constraints at 2-sigma le
分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：We consider the natural supersymmetry scenario in the framework of the R-parity conserving minimal supersymmetric standard model (called natural MSSM) and examine the observability of stop pair production at the LHC. We first scan the parameters of this s
分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：The excess of top quark forward-backward asymmetry (AtFBAFBtA^t_{FB}) reported by the Tevatron and the enhancement of the Higgs decay to diphoton observed by the LHC may point to a same origin of new physics. In this note we examined such anomalies in the
分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：Motivated by the recent progress of direct search for the productions of stop pair and sbottom pair at the LHC, we examine the constraints of the search results on the stop (t ̃ ) mass in natural SUSY. We first scan the parameter space of natural SUSY in the framework of MSSM, considering the constraints from the Higgs mass, B-physics and electroweak precision measurements. Then in the allowed parameter space we perform a Monte Carlo simulation for stop pair production followed by t ̃ → tχ ̃0 or t ̃ → bχ ̃+ and sbottom pair production followed by ̃b → bχ ̃0 or ̃b → tχ ̃−. 1111 1111 Using the combined results of ATLAS with 20.1 fb−1 from the search of l + jets + E/ T , hadronic tt ̄+E/T and 2b+E/T, we find that a stop lighter than 600 GeV can be excluded at 95% CL in this scenario.
分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：In some supersymmetric models like split supersymmetry or models with non-universal gaugino mass, bino (LSP) and winos (NLSP) may have rather small mass splitting in order to provide the correct dark matter relic density through bino/wino co-annihilation. Such a scenario with the compressed bino/wino is difficult to explore at the LHC. In this work we propose to probe this scenario from pp → jχ ̃02χ ̃±1 followed by χ ̃02 → γχ ̃01 and χ ̃±1 → W∗χ ̃01 → l±νχ ̃01 (this method is also applicable to the compressed bino/higgsino scenario). Through a detailed Monte Carlo simulation for both the signal and the backgrounds, we find that for a mass splitting ∆M ∼ 5 − 15 GeV between bino (LSP) and wino (NLSP), the 14 TeV LHC with luminosity of 500fb−1 can probe the wino up to 150 GeV (the sensitivity can reach 5σ for ∆M = 5 GeV and 2σ for ∆M = 15 GeV). We also investigate the dark matter detection sensitivities for this scenario and find that the planned XENON-1T(2017) cannot fully cover the parameter space with wino below 150 GeV allowed by relic density and the LUX limits.
分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：Considering the constraints from collider experiments and dark matter detection, we investigate the SUSY effects in the Higgs production channels e(+) e(?) → Zh at an e(+) e(?) collider with a center-of-mass energy above 240 GeV and γγ → h → bb? at a phot
分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：We explore the explanation of the Fermi Galactic Center excess (GCE) in the next-to-minimal supersymmetric Standard Model. We systematically consider various experimental constraints including the dark matter (DM) relic density, DM direct detection result
分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：Recently the ATLAS collaboration reported a 3σ excess in the leptonic-Z + jets + EmissTTmiss_{T}^{miss} channel. This may be interpreted in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) by gluino pair production with the decay chain g~→qq??χ~0
分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：We propose a deflected anomaly mediation scenario from SUSY QCD which can lead to both positive and negative deflection parameters (there is a smooth transition between these two deflection parameter regions by adjusting certain couplings). Such a scenario can naturally give a SUSY spectrum in which all the colored sparticles are heavy while the sleptons are light. As a result, the discrepancy between the Brookheaven gμ − 2 experiment and LHC data can be reconciled in this scenario. We also find that the parameter space for explaining the gμ − 2 anomaly at 1σ level can be fully covered by the future LUX-ZEPLIN 7.2 Ton experiment.
分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：In the Next-to-Minimal Supersymmetric Standard Model (NMSSM), all singlet-dominated particles including one neutralino, one CP-odd Higgs boson and one CP-even Higgs boson can be simultaneously lighter than about 100 GeV. Consequently, dark matter (DM) in the NMSSM can annihilate into multiple final states to explain the galactic center gamma-ray excess (GCE). In this work we take into account the foreground and background uncertainties for the GCE and investigate these explanations. We carry out a sophisticated scan over the NMSSM parameter space by considering various experi- mental constraints such as the Higgs data, B-physics observables, DM relic density, LUX experiment and the dSphs constraints. Then for each surviving parameter point we per- form a fit to the GCE spectrum by using the correlation matrix that incorporates both the statistical and systematic uncertainties of the measured excess. After examining the properties of the obtained GCE solutions, we conclude that the GCE can be well explained by the pure annihilations χ ̃01χ ̃01 → b ̄b and χ ̃01χ ̃01 → A1Hi with A1 being the lighter singlet- dominated CP-odd Higgs boson and Hi denoting the singlet-dominated CP-even Higgs boson or SM-like Higgs boson, and it can also be explained by the mixed annihilation χ ̃01χ ̃01 → W+W−,A1H1. Among these annihilation channels, χ ̃01χ ̃01 → A1Hi can provide the best interpretation with the corresponding p-value reaching 0.55. We also discuss to what extent the future DM direct detection experiments can explore the GCE solutions and conclude that the XENON-1T experiment is very promising in testing nearly all the solutions.
分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：The ATLAS collaboration recently reported a 3σ excess in the leptonic-Z + jets + EmissTTmiss_{T}^{miss} channel. We intend to interpret this excess by squark pair production in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). The decay chain we
分类： 分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-12-28
摘要：The evidence of a new scalar particle X from the 750 GeV diphoton excess, and the absence of any other signal of new physics at the LHC so far suggest the existence of new colored scalars, which may be moderately light and thus can induce sizable Xgg and
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