On convergence rate of finite element eigenvalue analysis with mass lumping by nodal quadrature

Error bounds are obtained for the finite element eigenvalue analysis using the diagonal mass matrix lumped by nodal quadrature. Finite element results of various two-dimensional 2nd order eigenvalue problems and a one-dimensional 4th order eigenvalue problem are compared favorably with the theoretical predictions. Estimates of error bounds, particularly those for eigenvalues, are significantly improved over the existing results, and their range of applicability is broadened. Special attention has been focused on the cases where shape functions have incomplete polynomials.     

Recovery of copper,nickel and cobalt from acidic pressure leaching solutions of low-grade sulfide flotation concentrates

Recovery of copper, nickel and cobalt from the acidic pressure leaching solutions of Jinbaoshan (YN Province, PRC) low-grade sulfide flotation concentrates was investigated. The proposed technique includes four major steps: (1) the acidity adjustment of the acidic pressure leaching solutions; (2) solvent extraction (SX) separation of copper by organic reagent XD5640, and then stripped from the loaded organic phase by H₂SO₄ solution for copper recovery; then (3) iron in raffinates after copper extracting is selectively removed by high-temperature hydrolysis precipitation in an autoclave; and lastly (4) nickel and cobalt are selectively precipitated by Na₂S from the final solutions after removing iron. The experimental results for treating 1 L acidic leaching solutions per batch by this new technique were reported, and some evaluation and further comparisons with previous investigations were also carried out. It was reported that the total percent recovery of Cu could reach 95% or more, and that of Ni and Co were all more than 99%. In the processing, the percent removal of impurities, such as Fe, Mg and Ca, were all also near to 99%.     

Roughness of amorphous/crystalline interface in pre-amorphization implantation: Molecular dynamic simulation and modeling

Pre-amorphization implantation has been applied as a shallow junction technology. Roughness at amorphous/crystalline (a/c) interface should be controlled to improve junction characteristics. To understand and model a/c interface roughness, molecular dynamic method is applied in simulating pre-amorphization implantation. A method to reproduce roughness at a/c interface by molecular dynamic simulation is presented. A model of interface roughness is presented. Si and Ge implantation from 2-20 keV at a dose of 1 × 10¹⁵ cm⁻² is simulated. The depth of a/c interface is reproduced. Experimental results of a/c interface roughness are successfully simulated. The interface roughness is well reproduced and interpreted by the model presented.     

Impacts of transit and walking amenities on robust local knowledge economy

As of 2013, knowledge economy has held more than 10% of U.S. employment, generated nearly 20% of national GDP and expect to increase to 25% during the next 20 years. Likewise, Eurostat 2020 aims to increase investment in Knowledge Intensive Business Services (KIBS) to bypass the competitors, Japan and the U.S. As the result, investigating the determinants of robust knowledge economy is a continuing concern between city scholars, planners and leaders. To date, several locational and non-locational factors have been found to be influential. For instance, transit service, walkable street networks and dense neighborhoods that provide walkable access to urban amenities are the location preferences for the creative class. Creative class, in turn, attracts KIBS, and produces innovation which are all contributive to the knowledge-based economic vitality. While such trend is widely supported by the theoretical efforts, there is little empirical evidence on these complex multidimensional relationships and hence this study seeks to investigate both direct and indirect impacts of transit and walking amenities on the robust local knowledge economy. Using Structural Equation Modeling (SEM), we developed a comprehensive model that accounts for KIBS, creative economy and innovation productivity and investigates their locational and non-locational determinants with the particular focus on walking and transit amenities. Our results generally echo the findings of previous studies about the key role of industry clustering, place quality amenities, diversity and tolerance on the three drivers of robust local knowledge economy. We found that among all exogenous variables racial diversity and industry clustering have the most significant direct effect on innovation productivity. We also found that transit service quality and walkability contribute to a robust local knowledge economy through KIBS and creative class, but they have an adverse relationship to the innovation production of the STEM small firms. This might be due to the fact that walkability and transit access increase the property values and, therefore, make them unaffordable for small innovative firms. Our findings on the impacts of walkability and transit access on innovation productivity in vulnerable small firms call for attention to the equity aspects of innovation-supportive urban developments.     

Revising Articles Written on the Land—Commencement Speech at 2022 Graduation Ceremony of the College of Architecture and Landscape,Peking University

This article is the author’s commencement speech at 2022 Graduation Ceremony of the College of Architecture and Landscape, Peking University. Away from the cities, the author observed, experienced, and recorded the changes in vernacular landscapes: pesticide abuse and cutoff and channelized rivers have resulted in soil hardened, loaches, eels, frogs, and other creatures disappeared, and rivers and water sources seriously polluted; while demolishing the vernacular cultural heritage of the ancient town, the reconstructed one is built with a large number of ornamental, ancient-looking structures, and stereotyped symbols, mirroring the shallow understanding of aesthetic, historical, and cultural identities. Metaphorically, the author is so ashamed of these „articles written on the land” and encourages the graduates to revise them in the future with their knowledge of ecology and aesthetics.     

Redline Dystopias: A Dialogue With a Farmer in Qicha

For the field of national territorial planning, to identify and delimit redlines is the primary step to preserve valuable natural and cultural assets from human interventions, harmonizing human-nature and urbanrural relationships. In the reality, however, the dogmatic planning and design concepts, irrational construction standards, and unscientific and rigid management requirements that ignore the diverse localities, market rules, and stakeholders’ needs usually make the implementation outcome runs the opposite to what was wished, leading to “redline dystopias” called by the author that are damaging our homelands. This article presents a dialogue between the author and a farmer in Qicha, Hainan, to reveal how a “capital farmland dystopia,” one of the redline dystopias, comes into being, appealing for a profound re-examination and reflection in the planning and design professions.     

Regional industrial evolution in China

Evolutionary economic geography (EEG) indicates that regional industrial development is path dependent. The empirical studies in EEG however have not paid sufficient attention to the importance of global linkages nor the role of regional institutions in driving industrial dynamics. Based on firm level data of four‐digit manufacturing industries during 1998 to 2008 in China, we find that Chinese regions branch into new industries technologically related to the existing industrial portfolio and related industries are less likely to exit. Further analysis reveals that global linkages, economic liberalization and state involvement not only create favourable conditions to allow a larger role of technological relatedness but also generate opportunities for Chinese regions to create new paths of industrial development.     

稀土金属提纯方法与研究进展

对各种提纯稀土金属方法的机理进行了阐述,包括真空熔炼、电解精炼、真空蒸馏/升华、熔盐萃取、区域熔炼、固态电迁移、电化学脱氧、外吸气剂法、等离子体熔炼(通氢气或通氩气)等。对研究现状和提纯效果进行了总结。杂质去除需采用多种手段结合,同时提升装备水平,以达到提高提纯效果、降低成本、缩短生产周期的目的。     

Preparation and properties of porous ceramic aggregates using electrical insulators waste

In this paper, porous ceramic aggregates were prepared by electrical insulators waste (EIW). Effects of sintering temperature and content of EIW on the aggregates’ properties such as bulk density, and apparent porosity, total porosity, and cold crushing strength were investigated. With increasing sintering temperature and content of EIW, bulk density and cold crushing strength of the aggregates increased, apparent porosity and total porosity decreased. Based on these results, total porosity of specimens in group B sintered at 1200 °C is 62.0%, cold crushing strength is 35.3 N, and thermal conductivity is 0.165 W/(m K) at 300 °C. Comprehensive properties of specimens can be optimized by adjusting sintering temperature. Meanwhile, strength variation resulted from the combined effects of phase transformation and matrix densification under different sintering temperatures.     

热丝化学气相沉积法制备钛基 BDD 电极及苯酚降解性能研究

目的研究硼掺杂对改善金刚石膜的电阻率的影响,制备掺硼金刚石膜。方法采用热丝化学气相沉积系统,以CH4,H2,(CH3O)3B混合气体为反应气,在钛片衬底上沉积制备掺硼金刚石膜电极。对不同生长阶段沉积出的电极进行扫描电镜、EDX光电子能谱、激光Raman光谱、X射线衍射、电化学性能表征及废水降解应用研究。结果制备出的掺硼金刚石膜呈现出均匀的(111)晶面,Raman光谱图中金刚石特征峰与硼原子特征峰峰型显著,具有较低的背景电流和更宽的电位窗口(3.5 V),对苯酚废水COD降解效果显著。结论有机污染物的吸附量与电极表面的粗糙度正相关,实验室制备的BDD/Ti电极表面粗糙度小,不利于析氢和析氧等副反应的发生,能降低直接电化学氧化作用,从而得到更宽的电势窗口。