Scalar models for the generalized Chaplygin gas and the structure formation constraints

The generalized Chaplygin gas model represents an attempt to unify dark matter and dark energy. It is characterized by a fluid with the equation of state p = −A/ρ ^α . It can be obtained from a generalization of the Dirac-Born-Infeld (DBI) action for a scalar, tachyonic field. At a background level, this model gives very good results, but it suffers from many drawbacks at the perturbative level. We show that, while for background analysis it is possible to consider any value of α, the perturbative analysis must be restricted to positive values of α. This restriction can be circumvented if the origin of the generalized Chaplygin gas is traced back to a self-interacting scalar field, instead of the DBI action. But, in doing so, the predictions coming from formation of large-scale structures reduce the generalized Chaplygin gas model to a kind of quintessence model, and the unification scenario is lost if the scalar field is the canonical one. However, if the unification condition is imposed from the beginning as a prior, the model may remain competitive. More interesting results concerning the unification program are obtained if a non-canonical self-interacting scalar field, inspired by Rastall’s theory of gravity, is invoked. In this case, an agreement with the background tests is possible.     

Multiscale study of the structure and hydrogen storage capacity of an aluminum metal-organic framework

First-principles calculations based on density functional theory and Grand Canonical Monte Carlo (GCMC) simulations are carried out to study the structure of a new Aluminum Metal-Organic Framework, MOF-519, and the possibility of storing molecular hydrogen therein. The optimized structure of the inorganic secondary building unit (SBU) of MOF-519 formed by eight octahedrally coordinated aluminum atoms is presented. The different storage sites of H₂ inside the SBU and the BTB ligand are explored. Our results reveal that the SBU exhibits two different favorable physisorption sites with adsorption energies of ?12.2 kJ/mol and ?1.2 kJ/mol per hydrogen molecule. We have also shown that each phenyl group of BTB has three stable H₂ adsorption sites with adsorption energies between ?6.7 kJ/mol and ?11.37 kJ/mol. Using GCMC simulations; we calculated the molecular hydrogen (H₂) gravimetric and volumetric uptake for the SBU and MOF-519. At 77 K and 100 bar pressure, the hydrogen uptake capacity of SBU is considerably enhanced, reaching 16 wt.%. MOF-519 has a high gravimetric uptake, 10 wt.% at 77 K and 4.9 wt.% at 233 K. It has also a high volumetric capacity of 65 g/L at 77 K and 20.3 g/L at 233 K, indicating the potential of this MOF for hydrogen storage applications.     

东鞍山烧结厂含菱铁矿浮选中矿焙烧机制研究

东鞍山烧结厂含菱铁矿浮选中矿经700 ℃还原焙烧-磁选工艺处理,可以得到品位为60.43%,回收率为83.59%的铁精矿。利用X射线衍射分析和扫描电镜分析手段着重对焙烧过程中铁矿物的转化机制进行了研究,结果表明,随着焙烧温度的改变,焙烧过程将经历菱铁矿分解、赤铁矿还原和铁矿物过反应3个阶段,其中赤铁矿还原阶段对应的焙烧温度正是700 ℃,此时焙烧产品中的铁矿物以磁铁矿为主,最有利于弱磁选。     

东鞍山含碳酸盐铁矿石分步浮选中矿的试验研究

针对东鞍山含碳酸盐铁矿石优先分离出的以菱铁矿为主的中矿产品,采用管式炉还原焙烧-弱磁-再磨-弱磁的工艺,用煤做还原剂时,可获得铁品位60.31%,回收率87.49%的铁精矿.     

东鞍山难选铁矿石中菱铁矿的综合利用试验研究

分步浮选法成功解决了东鞍山含菱铁矿铁矿石的分选.本文针对分选出的含菱铁矿中矿,进行了中性焙烧-返回分步浮选的试验研究.通过优化浮选药剂制度,获得了精矿品位为67.80％、回收率为73.98％、尾矿品位为20.73％、回收率为26.02％良好结果,并用SEM探讨了其对赤铁矿浮选过程的影响.