Hu C.,Shaanxi Normal University |
Hu C.,Qinghai Normal University |
Liu P.,Shaanxi Normal University
Journal of Alloys and Compounds | Year: 2013
Highly reactive amorphous SiO2 nanospheres were successfully synthesized at room temperature in atmosphere with a mean particle size of 174 nm by a Sol-Gel method. SiO2 ceramics were prepared using SiO 2 nanospheres and their microwave dielectric properties were investigated at different temperatures. Phase evolution, sintering characteristics and microstructures were detected by differential thermal analysis (DTA-TG) analysis, X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Excellent microwave properties of εr ∼ 3.52, Q·f ∼ 92400 GHz and τf ∼ -14.5 ppm/°C, were obtained finally. The optimum sintering temperature of SiO2 ceramics was reduced 125 °C by aqueous Sol-Gel process compared to a conventional solid-state method. The Q·f and εr values of SiO2 ceramics are sensitive to the measured temperatures, which was explained by a simple composite dielectric model. © 2012 Elsevier B.V. All rights reserved.
Zhou M.,Peking University |
Chen Q.,Peking University |
Chen Q.,Qinghai Normal University |
Cai Y.L.,Peking University
Journal of Cleaner Production | Year: 2013
An inexact fuzzy multi-objective programming model (IFMOP) is developed in this study for dealing with industrial structure optimization problems under uncertainty. The IFMOP model is formulated based on integration of an inexact linear programming (ILP), fuzzy flexible optimization (FFO), and multi-objective programming (MOP). It improves upon the existing industrial structure optimization model with advantages in uncertainty reflection, model coupling, data availability and computational requirement. The model can deal with uncertainties expressed as discrete intervals and fuzzy sets. Therefore, it can effectively reflect dynamic, interactive complex, and uncertain characteristics of industrial system without unrealistic simplification. Moreover, the model can be used for supporting temporal and spatial optimization of industrial structure under a variety of environmental and socio-economic conditions. The developed model is first applied to a real case of planning industrial structure of South Four Lake watershed in Shandong province, China. Results demonstrated that the model could help decision makers generate stable and balanced industrial structure patterns, gain in-depth insights into effects of the uncertainties, and analyze trade-offs among economical objective, environmental protection and social demand. © 2012 Elsevier Ltd. All rights reserved.
Liu F.,Qinghai Normal University |
Feng Z.,Xinjiang University
Holocene | Year: 2012
Our review of recently published climatic proxy sequences shows that the most dramatic climate tranistion of the mid Holocene (~8500-~3500 cal. yr BP) occurred at the middle- to late-Holocene transition at ~4000 cal. yr BP. In northern China, an abrupt climatic shift at ~4000 cal. yr BP was recorded in the eastern margin of the Tibetan Plateau, in the western part of the Chinese Loess Plateau and in the vast Inner Mongolian Plateau. In southern China, the ~4000 cal. yr BP event was also abrupt, but it is expressed as one of several quasi-cyclic events in most of the records. We propose that the cumulative effects of insolation-dictated declining trend in tropical SST and the geologically documented increasing trend of ENSO activity were the first-order causes of the cooling and the associated drying during the past 6000 years. Superimposed on the first-order causes were the second-order causes, i.e. the additive effects of the 'Bond Event 3'-associated lower insolation and the increasingly drying-resulted negative feedback of 'air-land interactions'. The second-order causes made ~4000 cal. yr BP the tipping point when the resultant drying had destroyed many Chinese Neolithic cultures. Our review of published archaeological literature shows that six of the seven well-documented Chinese Neolithic cultures collapsed at ~4000 cal. yr BP with the exception of the Henan Longshan Culture that evolved to the more advanced Erlitou Culture. The indicators of the cultural collapse include (1) the number of archaeological sites was significantly reduced, (2) the quality of the archaeological artifacts of the succeeding culture is lower than that of the preceding culture, (3) more sophisticated architectures disappeared, and (4) agricultural cultures were replaced by pastoralism or by agro-pastoralism in northern China. © The Author(s) 2012.
Zhang W.Y.,Dalian Jiaotong University |
Gao H.,Dalian Jiaotong University |
Xu Y.,Qinghai Normal University
Journal of the European Ceramic Society | Year: 2011
Diopside-albite glass-ceramics were fabricated by sintering the powder mixtures of crystallization promoters and waste glass. Two kinds of promoters were synthesized using kaolin clay, talc and chemical reagents. The crystalline phases were formed by a reactive crystallization between promoters and glass during sintering. The effect of promoter components, additions and sintering temperatures on the crystallizing and densifying behavior, microstructures and mechanical properties of glass-ceramics was investigated. The results showed that the higher densities and better mechanical properties were obtained for the glass-ceramics with 12-15% crystallization promoters sintered at 950 °C for 2 h © 2011 Elsevier Ltd.
Li D.-C.,Zhejiang Ocean University |
Geng S.-L.,Qinghai Normal University
Information Sciences | Year: 2014
This paper aims to solve the problem of multiple-objective linear optimization model subject to a system of inf-→ composition fuzzy relation equations, where → is R-, S- or QL-implications generated by continuous Archimedean t-norm (s-norm). Since the feasible domain of inf-→ relation equations constraint is nonconvex, these traditional mathematical programming techniques may have difficulty in computing efficient solutions for this problem. Therefore, we firstly investigate the solution sets of a system of inf-→ composition fuzzy relation equations in order to characterize the feasible domain of this problem. And then employing the smallest solution of constraint equation, we yield the optimal values of linear objective functions subject to a system of inf-→ composition fuzzy relation equations. Secondly, the two-phase approach is applied to generate an efficient solution for the problem of multiple-objective linear optimization model subject to a system of inf-→ composition fuzzy relation equations. Finally, a procedure is represented to compute the optimal solution of multiple-objective linear programming with inf-→ composition fuzzy relation equations constraint. In addition, three numerical examples are provided to illustrate the proposed procedure. © 2014 Elsevier Inc. All rights reserved.