锌中浸渣还原酸浸试验研究

为了综合回收湿法炼锌过程富集于中浸渣中的有价金属,以高铁闪锌矿为研究对象,开展了中性浸出渣(简称为中浸渣)和锌精矿的联合还原酸浸试验研究。考察了中浸渣和锌精矿质量比、初始硫酸浓度、浸出时间、液固比、温度对锌、铁浸出率的影响。优化条件为:初始硫酸浓度220 g/L,中浸渣与锌精矿质量比1∶0.25,粒度-0.074 mm,液固比6∶1,温度90℃,反应时间3 h。在此条件下,锌和铁的浸出率均在96%以上,浸出液中95%以上的铁为二价铁离子,满足了后续工艺的要求。     

都龙矿区螺旋溜槽尾矿中锡石回收工艺试验研究

都龙矿区新田选矿厂+37μm粗粒级锡石重选工艺中螺旋溜槽尾矿采用摇床重选的作业回收率仅35%左右,难以达到高效回收细粒级锡石的目的。鉴于细粒锡石浮选工艺技术在生产中已获得成功应用,采用浮选工艺回收螺旋溜槽尾矿中锡石可以获得锡粗精矿含锡品位8.03%、作业回收率89.23%的试验指标,相对摇床重选工艺能大幅度提高锡石的回收率。同时将浮锡尾矿尾水回用,在获得相近指标的条件下,可降低药剂耗用量10%~20%,有利于降低药剂成本。     

Markowitz-based portfolio selection with cardinality constraints using improved particle swarm optimization

This work presents particle swarm optimization (PSO), a collaborative population-based meta-heuristic algorithm for solving the Cardinality Constraints Markowitz Portfolio Optimization problem (CCMPO problem). To our knowledge, an efficient algorithmic solution for this nonlinear mixed quadratic programming problem has not been proposed until now. Using heuristic algorithms in this case is imperative. To solve the CCMPO problem, the proposed improved PSO increases exploration in the initial search steps and improves convergence speed in the final search steps. Numerical solutions are obtained for five analyses of weekly price data for the following indices for the period March, 1992 to September, 1997: Hang Seng 31 in Hong Kong, DAX 100 in Germany, FTSE 100 in UK, S&P 100 in USA and Nikkei 225 in Japan. The test results indicate that the proposed PSO is much more robust and effective than existing PSO algorithms, especially for low-risk investment portfolios. In most cases, the PSO outperformed genetic algorithm (GA), simulated annealing (SA), and tabu search (TS).     

An overlooked effect of mandatory audit�Cfirm rotation on investigation strategies

Section 207 of the Sarbanes?COxley Act of 2002 (hereafter, the SOX Act) passed by the US Congress requires a study of mandatory auditor rotation of registered public accounting firms. In the debate over the costs and benefits of mandatory audit?Cfirm rotation, one cost has been overlooked: that of more aggressive monitoring. Because few countries have put such mandatory rotation into practice, there is little empirical evidence available for analysis of its costs and benefits. My research, therefore, uses an analytical approach to demonstrate that, in a firm that has a well-functioning independent board, as required by section 301 of the SOX Act, the board will adopt a more aggressive strategy in investigating the collusion between the manager and the auditor and pay a higher audit fee than it would have done in an environment with no audit?Cfirm rotation requirement. The results of this research alter the balance between the costs and benefits of a mandatory audit?Cfirm rotation requirement and should not be ignored by regulators considering implementing such a requirement.     

高分子混合物pVT关系的计算

用链状流体分子热力学模型分别考查了聚苯乙烯／聚2，6－二甲苯醚（PS／PPO），聚苯乙烯／聚乙烯甲醚（PS／PVME），聚苯乙烯／聚丁二烯（PS／PBD0，聚醚砜／聚氧乙烯（PESP／PEO）等高分子共混物以及聚异丁烯／苯（PIB／B），聚异丁烯／环乙烷（PIB/C），聚二甲基硅氧烷／环已烷（PDMS／C）等高分子溶液的pVT关系，结果显示，用一个与温度无关的二相互作用可调参数可满意关联并预测所选体系的比体积。     

一种高效捕收剂浮选细粒级锡石的试验研究

云南文山都龙以锌锡铟为主的多金属硫化矿使用浮选法回收矿石中的细粒级锡石,浮锡捕收剂先后使用过GY-C3和BY-9,原矿性质变化时两种药剂对稳定生产指标及进一步提升锡回收率的效果不理想。经过试验研究发现JSY-19浮锡捕收剂能很好地适应都龙矿区的原矿性质变化,在流程条件与捕收剂用量相同的条件下,用JSY-19对比工业试验过程中使用的GY-C3、BY-9,其捕收效果更好,可以进一步提升锡回收率,该药剂可以考虑在工业试验以及实际生产中应用。     

One price doesn't fit all: An examination of heterogeneity in price elasticity of residential electricity in India

Although well-designed consumer electricity pricing can improve access, contribute to higher metering, increase penetration of energy efficient technologies, limit extent of the rebound effect, and influence viability of electricity distribution utilities in India, there has been no comprehensive, policy-relevant assessment of price elasticities of electricity demand in the country. The objective of this study is to estimate price elasticity of residential electricity consumption and disaggregate it by state, rural and urban residence, and income categories to provide evidence for electricity tariff setting in India. We combine survey data from five rounds of nationally-representative household consumption expenditure surveys covering the period 2005–2012 with administrative data on electricity deficit and improve on methods applied in previous studies by estimating price elasticities using a quadratic form to account for constraints in electricity supply. We find that while the average price elasticity at the national level is −0.39 (95% confidence interval: −0.46, −0.31), it varies significantly by state, rural and urban residence, and income categories. Our results indicate that a “one ‘price’ fits all” policy may not be an effective approach to electricity tariff setting in India and a data-driven understanding of heterogeneities in price elasticities can better inform residential electricity tariff design in the country.     

间隙碳原子对（Er1—xSmx）2Fe17Cy化合物形成,结构与磁性的影响

用快淬方法制备了单相（Ｅｒ１－ｘＳｍｘ）２Ｆｅ１７ｃｙ（ｘ＝０．２，ｙ≤３．０；ｘ＝０．５，ｙ≤２．０）化合物，研究了它们的形成、结构、稳定性及内禀磁性。结果表明，它们在高温是稳定的，随碳含量的增加，晶体结构由六角的Ｔｈ２Ｎｉ１７型向菱方的Ｔｈ２Ｚｎ１７型转变。间隙碳原子的引入导致了单胞体积的膨胀、室温饱和磁化强度和Ｃｕｒｉｅｉ温度的增加。当ｙ≥１．０时，（Ｅｒ１－ｘＳｍｘ）２Ｆｅ１７Ｃｙ样品在室