Waste heat recovery from hot steel slag on the production line:Numerical simulation,validation and industrial test

Waste heat recovery from hot steel slag was determined in a granular bed through the combination of numerical simulation and an industrial test method.First,the effective thermal conductivity of the granular bed was calculated.Then,the unsteady-state model was used to simulate the heat recovery under three different flow fields(O-type,S-type,and nonshielding type(Nontype)).Second,the simulation results were validated by in-situ industrial experiments.The two methods confirmed that the heat recovery efficiencies of the flow fields from high to low followed the order of Nontype,S-type,and O-type.Finally,heat recovery was carried out under the Nontype flow field in an industrial test.The heat recovery efficiency increased from~76%and~78%to~81%when the steel slag thickness decreased from 400 and 300 to 200 mm,corresponding to reductions in the steel slag mass from 3.96 and 2.97 to 1.98 t with a blower air volume of 14687 m^(3)/h.Therefore,the research results showed that numerical simulation can not only guide experiments on waste heat recovery but also optimize the flow field.Most importantly,the method proposed in this paper has achieved higher waste heat recovery from hot steel slag in industrial scale.

政治联系会提高企业开工率吗?——基于中国私营企业调查的经验研究

在中国转型发展时期,企业家谋求政治联系是否会繁荣企业的生产?本文使用2012年中国私营企业调查数据,考察政治联系对企业开工率的影响。结果发现:政治联系显著地提升了企业开工率,且对开工率的促进作用因其等级而存在较大差异。此外,政治联系对企业开工率的作用不因外部政治和市场环境的改变而有差异。从影响机制来看,政治联系主要通过抵御企业外部负面冲击和缓解企业内部经营约束两种渠道影响企业开工率。本研究为政治联系影响企业绩效提供了新证据,在一定程度上解释了为何企业家热衷于建立政治联系,并且对建立新型政商关系的政策制定具有重要的参考价值。

县域经济增长能够带来官员的晋升吗?——基于县域卫星灯光数据的新考察

县域经济作为国民经济的基本单元,在中国的经济发展和转型过程中扮演着关键角色,但在大量研究探讨政治晋升是否激励了省市级官员发展经济的背景下,这一层级经济增长的政治动力机制仍然是一个黑箱。本文通过考察经济增长业绩是否能促进官员晋升,分析县级行政区经济增长的动力机制,并以灯光数据衡量的真实增长业绩考察政治晋升动力机制的有效性。基于1998—2013年县域的经济增长及官员晋升数据的实证研究表明:(1)以GDP衡量的增长业绩能够有效促进县委书记的进一步晋升。官员的晋升与任期内GDP平均增长率呈正相关关系;前任官员GDP经济绩效被视为当期县委书记的'标杆',县委书记的晋升与相对于前任任期内GDP平均增长率呈正相关关系。(2)以卫星灯光亮度测算的真实经济业绩并未带来县委书记的晋升。并且,无论是绝对或相对的真实经济增长业绩都未能促进官员的晋升。(3)对晋升机制的研究发现,相对于军队和企业背景,具有学校工作背景的县委书记有更大的概率晋升。此外,无论是以经济效率提升衡量的长期经济发展绩效,还是以固定资本投资提升衡量的短期经济发展绩效,都不是促进县委书记晋升的渠道。上述研究表明,虽然'经济增长驱动晋升'的假说在县级行政区是存在的,但该晋升机制只存在于以GDP为指标的考核体系中,在以卫星灯光亮度测算的真实政绩指标下,经济增长并没有促进官员的晋升。这一研究结果深刻地反映了中国县级行政区层面经济增长与官员晋升之间的关系。

开发区、资源配置与宏观经济效率——基于中国工业企业的实证研究

本文基于资源错配理论,实证检验中国开发区的设立对企业要素配置效率的影响,测算要素配置效率变化产生的宏观经济效应。研究发现,设立开发区的区县,企业资本投入不足的情况得到缓解,但企业劳动过度投入的情况更加严重。从单一投入要素来看,通过影响资本和劳动投入效率带来的总量经济效应分别为1.5%和-1.24%。总体上,开发区通过企业资源配置改善了宏观经济效率,综合二者的影响,开发区的设立使总量生产率年均提升1.52%。

Review on catalytic roles of rare earth elements in ammonia synthesis:Development and perspective

Ammonia(NH3)is mainly produced via the Haber-Bosch process.It was discovered that the performance of a wide variety of catalysts in NH3 synthesis could be considerably enhanced by the addition of rare earth elements(REEs).As a result,catalysts promoted by REEs,especially the Ru-based ones have been extensively investigated.In this review,we summarize the progress of utilizing REEs for ammonia synthesis and outline the prospects of using them in the design and development of highly efficient and stable catalysts for ammonia synthesis.

A theoretical analysis of global characteristics of spread-F

Spread-F is an important ionosphere pheonome-non and it has much effect on radio wave propogation. Taking magnetic inclination and declination into consideration, a theoretical model is deduced for the linear growth-rate of spread-F. It is a generalization of the earlier equatorial model and a relatively complete description o f the spread-F pheonomenon. This theory shows that the magnetic configuration, i.e. the magnetic strength, inclination and declination, affects the occurrence rate greatly, which forms some regional distribution characteristics of the spread-F.

Boosting Efficient Ammonia Synthesis over Atomically Dispersed Co-Based Catalyst via the Modulation of Geometric and Electronic Structures

Ammonia(NH_(3))synthesis at mild conditions is of great significance,while the significant bottleneck of this process is the activation of N_(2) to realize the desired NH_(3) synthesis performance,which requires deep insight and rational design of active sites at the atomic level.Here,were synthesized atomically dispersed Co-based catalysts with different Co-N coordination numbers(CNs)to explore the coordination-sensitive NH_(3) synthesis reaction for the first time.Our studies showed that Co-based catalysts increased the NH_(3) synthesis rate gradually with a decrease in CN.The Co-N_(2) catalyst exhibited the highest NH_(3) synthesis rate of 85.3 mmol gCo^(−1) h^(−1) at 300℃ and 1 MPa,which outperformed most of the previously reported Co-based catalysts.Various characterizations and theoretical calculations demonstrated that atomically dispersed Co catalyst with low CN could generate more unoccupied Co 3d charges and tetrahedral cobalt(Ⅱ)sites.The unoccupied Co 3d charge,in turn,promoted the electron donation from the Co active center to the antibonding π-orbital(π*)of N_(2) and expedites N_(2) hydrogenation.Furthermore,the Co-N_(2) catalyst with more tetrahedral cobalt(II)sites could effectively facilitate the desorption of N-containing intermediate species(such as*NH_(3) and*N_(2)H_(4))to obtain a high NH_(3) synthesis rate.