Parametric study along with selection of optimal solutions in dry wire cut machining of cemented tungsten carbide (WC-Co)

This work deals with parametric study of dry wire EDM (WEDM) process of cemented tungsten carbide. Experiments have been conducted using air as dielectric medium to investigate effects of pulse on time, pulse off time, gap set voltage, discharge current and wire tension on cutting velocity (CV) surface roughness (SR) and oversize (OS). Firstly, a series of exploratory experiments were carried out to identify appropriate gas and its pressure. Afterward, preliminary experiments were conducted to investigate effects of process parameters on dry WEDM characteristics and find appropriate ranges for each factor. Then a central composite rotatable method was employed to design experiments based on response surface methodology (RSM). Empirical models were developed to create relationships between process factors and responses by considering to analysis of variances (ANOVA). To increase the predictability of the process, intelligent models have been developed based on back-propagation neural network (BPNN) and accuracy of these models was compared with mathematical models based on root mean square error (RMSE) and prediction error percent (PEP). In order to select optimal solutions in the cases of single-objective and multi-objectives optimization problems, optimization includes two main approaches. First approach was based on mathematical model and desirability function. Also second approach was designed based on neural network and particle swarm optimization. These approaches were applied in both cases of single-objective and multi-objectives optimization problems and their results were compared with together. Results indicated that selection of air at inlet pressure of 1.5 bar is really appropriate for conducting experiments of next stages. Also, the BPNN creates more accurate prediction rather than mathematical model. Moreover, the BPNN-PSO approach was more efficient in optimization of process rather than mathematical model-desirability function in respect with validation tests.     

Characteristics and anthropogenic sources of carbonyl sulfide in Beijing

Atmospheric mixing ratios of carbonyl sulfide (COS) in Beijing were intensively measured from March 2011 to June 2013. COS mixing ratios exhibited distinct seasonal variation, with a maximum average value of 849 ± 477 pptv in winter and a minimal value of 372 ± 115 pptv in summer. The seasonal variation of COS was mainly ascribed to the combined effects of vegetation uptake and anthropogenic emissions. Two types of significant linear correlations (R² > 0.66) were found between COS and CO during the periods from May to June and from October to March, with slopes (ΔCOS/ΔCO) of 0.72 and 0.14 pptv/ppbv, respectively. Based on the emission ratios of COS/CO from various sources, the dominant anthropogenic sources of COS in Beijing were found to be vehicle tire wear in summer and coal burning in winter. The total anthropogenic emission of COS in Beijing was roughly estimated as 0.53 ± 0.02 Gg/year based on the local CO emission inventory and the ΔCOS/ΔCO ratios.     

钢丝绳产业区重金属对土壤－农产品的复合污染及生态风险评价?

选取钢丝绳行业比较发达的某乡镇为研究区域,对其地区周边土壤及农产品的污染状况进行了野外调查和实验分析研究。结果表明：（1）土壤中铅、锌的含量均有不同程度的污染。（2）土壤中重金属含量与废水灌溉方式有关。（3）废水灌溉的农产品均有不同程度的污染。（4）重金属主要富集在农产品的根部,果实中富集的量很少。     

天维膜处置钢丝绳酸性废液实验中存在的问题

南通地区很多钢丝绳企业采用酸洗磷化工艺,产生大量含铅、铁、锌等重金属离子的酸性废液,造成区域特征性环境污染.选用山东天维膜技术有限公司的扩散渗析阴膜进行钢丝绳酸性废液处置实验.结果表明:该膜能有效地将酸、盐分离,酸的回收率达到90％以上,铅截留率达到70％以上,铁截留率达到80％以上.但实验中出现氯化铅晶体析出,堵塞处...     

南通市钢丝绳行业污泥处置与利用技术方案研究

通过对南通市钢丝绳行业产生污泥的特征进行分析,在总结了国内外重金属污泥控制技术的基础上,结合南通市实际情况,提出了钢丝绳污泥处置方案,并进行了可行性分析.     

铝包钢丝拉拔工艺设计与试验

选用连续挤压包覆法生产的铝包钢丝毛坯，采用强制润滑拉拔技术进行拉拔试验研究。通过试验、比较筛选了适合铝包铜丝拉拔的耐温耐压润滑剂。在对铝包钢丝拉拔工艺进行合理设计的基础上，拉制出了产品。对产品的机械性能和电性能进行了测试，并对断口进行了扫描电镜的观察。结果表明，双金属的结合性能良好,各项性能指标均达到相关标准。这一试验研究对铝包钢丝的生产有指导意义。     

梁锚结构加固浅埋隧道洞口软弱地层的承载特性研究

针对隧道洞口埋深浅且软弱围岩稳定性差这一问题,提出在地表增设混凝土框架梁,设置扩大头锚杆与框架梁连接并深入软弱围岩,运用数值模拟分析“混凝土框架梁-扩大头锚杆”结构加固软弱地层后的力学特性。研究结果表明：采用“混凝土框架梁-扩大头锚杆”加固隧道洞口软弱地层,k=0.4时,相比于没有加固对照模型,隧道最大拱顶沉降值下降68.7%,隧道最大边墙收敛值下降15.1%,初期支护最大等效应力减小12.7%;建立不同加固区围岩松动压力分散系数k下的数值模型,通过拱顶沉降结果与加固区围岩松动压力分散系数的线性拟合,提出采用加固结构后的隧道拱顶沉降规律与围岩松动压力计算方法。     

时效对高导耐热铝合金导线第二相析出及其性能的影响

目的 开展时效过程中61.5%IACS高导耐热铝合金导线析出第二相特性及其电导率与拉伸力学性能变化规律的研究,评价其热稳定性。方法 经过150~230 ℃长达630 h时效,揭示第二相的组成、形态与分布及其对时效态铝合金导线电导率与拉伸力学性能的影响规律。结果 时效态铝合金导线中,颗粒状及针状A13Zr(Y, Er)、A13(Zr(Y)xErl?x)第二相在Al晶内、晶界析出,A13Fe相颗粒弥散分布于Al晶界。伴随着时效过程,铝合金导线的抗拉强度与伸长率先上升、再逐渐下降;同时,铝合金导线的电导率先增大、后逐渐趋于稳定。该趋势随时效温度的升高而越加明显。结论 第二相的析出、长大是影响时效态铝合金导线力学性能及电导率的主要原因。经230 ℃、1 h时效,铝合金导线的强度保持率高达94%,满足GB/T 30551—2014的要求。所有时效态铝合金导线的电导率均高于其初始值,该高导耐热铝合金导线的热稳定性良好。     

遵义市某小区滑坡治理工程中的几个问题及处理措施

文章以遵义小区某滑坡治理工程为例,介绍了滑坡治理中有效解决坡面防水、护面结构与坡面的粘结等问题的实践经验,提出了锚杆支护、挂网喷砼、坡脚挡墙衬护、喷面边界浇筑连系梁的综合治理措施。该滑坡治理效果良好。     

Characteristics and anthropogenic sources of carbonyl sulfide in Beijing

Atmospheric mixing ratios of carbonyl sulfide(COS) in Beijing were intensively measured from March 2011 to June 2013. COS mixing ratios exhibited distinct seasonal variation, with a maximum average value of 849 ± 477 pptv in winter and a minimal value of 372 ± 115 pptv in summer. The seasonal variation of COS was mainly ascribed to the combined effects of vegetation uptake and anthropogenic emissions. Two types of significant linear correlations(R2 0.66) were found between COS and CO during the periods from May to June and from October to March, with slopes(ΔCOS/ΔCO) of 0.72 and 0.14 pptv/ppbv, respectively. Based on the emission ratios of COS/CO from various sources, the dominant anthropogenic sources of COS in Beijing were found to be vehicle tire wear in summer and coal burning in winter. The total anthropogenic emission of COS in Beijing was roughly estimated as 0.53 ± 0.02 Gg/year based on the local CO emission inventory and the ΔCOS/ΔCO ratios.