低温热处理对鲕状赤铁矿助磨效果的试验研究

采用SRJX4-13型箱式电阻炉对鲕状赤铁矿进行低温热处理,从磨矿细度,平均粒度,孔隙率以及磨矿能耗几个方面,考察了低温热处理对鲕状赤铁矿的助磨效果。研究结果表明,矿石在400℃的温度下热处理90min,水淬冷却,孔隙率由3.6901%提高到4.0816%,磨矿产品-0.038mm含量由50.25%增大到60.88%;平均粒径由68.72μm减小为36.57μm;达到相同的磨矿细度,经热处理后的矿石所需要的磨矿时间更短。由此可知,低温热处理改善了鲕状赤铁矿的细磨效果,一定程度上降低了磨矿的能耗,对矿石的细磨起到了一定的辅助作用。     

Evaluation of SCC susceptibility of supermartensitic stainless steel using slow strain rate tests

Abstract

The susceptibility to chloride stress corrosion cracking (Cl-SCC) of supermartensitic stainless steel (SMSS) was evaluated at different temperatures through slow strain rate tests. In order to evaluate the Cl-SCC susceptibility the reduction in area and the time to failure ratio were considered. It is clear that all specimens tested in the chloride solution exhibited a generally high resistance to chloride SCC. However, according to the slow strain rate tests results, at lower temperature (5°C) the susceptibility to Cl-SCC increases compared to the other temperatures studied; also an increase in the corrosion rate was observed as the temperature decreased according to electrochemical impedance spectroscopy measurement. The corrosion mechanism observed on the material under dynamic stress was a combination of high activation resistivity with a diffusive process on the metallic interface given by a thin film from a protector layer of chromium oxides. This mechanism generates a high corrosion resistance and therefore good performance to chloride induced SCC.     

延长混凝土工程寿命的简易途径

古代混凝土工程之所以耐久,除了它的化学组成和现代混凝土有所不同外,古代混凝土强度低、施工进度慢也是成就耐久的原因之一。现代混凝土工程短命的主要原因是施工进度过快。由于赶工期使许多工序被简化,使混凝土体内原始互不相通的微裂缝和微空隙数量增加、提前连通并延伸到混凝土表面,使大气中的冷热、干湿循环进入混凝土体内和钢筋表面,从...     

大都市低碳交通策略的国际案例比较分析

本文从城市交通规划和城市交通政策作为切入点,旨在探索国内外大都市的低碳交通策略.通过对12个国际大都市在推行低碳交通方面的实践经验总结归纳出当前大都市交通的五种低碳化策略,并对每一类策略的利弊和适用条件进行分析.在此基础上,提出在规划战略层面探索城市土地利用与交通一体规划策略,在实施层面构建公共交通和慢行交通并重的缘色出行结构,在管理层面完善交通需求管理体系应是现阶段我国大都市主要的低碳交通策略.     

南京市鼓楼片区慢行单元规划

慢行交通主要包括步行和自行车交通,在中短距离出行中具有一定的优势。针对慢行交通中的系统缺乏、设施配套不足和场所缺乏等问题,南京市鼓楼片区慢行单元规划通过打造自然休闲慢行单元、轨道交通接驳单元、历史文化慢行单元、商业活力慢行单元和人文高校慢行单元,并以慢行路线将各个单元串联起来,构建起较完整的慢行交通系统,进而推动片区整体系统的健康发展。     

CRTSⅢ型轨道板气液联动同步放张器的优化与改进

基于气液联动同步放张器在实际运用中出现的新型放张工艺要求,深入了解现场钢筋放张工艺和放张器实际使用时出现的问题,进行针对性的完善和改进。优化其结构尺寸,克服钢筋或放张器断裂现象;严格控制液压油流过环形间隙的流量和时间,实现缓慢动态同步放张;设计回油单向阀,达到油液迅速自动复位的目的。优化和完善了气液联动同步放张器,并以有限元分析数据为参考,证实了放张器的可行性。     

非洲某铜电炉渣的浮选试验研究

对赞比亚某电炉渣进行光谱分析、物相分析及多元素分析。结果表明,该电炉渣含铜3.5%,铜主要以金属铜和硫化铜形式产出。根据该电炉渣的矿物学特征,采用一粗两扫两精的选别流程,实验室闭路试验可获得,铜精矿品位34.01%、回收率92.57%的选别指标,达到了该电炉渣综合回收铜的目的。     

A fracture mechanics concept for the accelerated characterization of creep crack growth in PE-HD pipe grades

For the lifetime prediction of pressurized polyethylene (PE) pipes based on methods of the linear elastic fracture mechanics the knowledge of the crack resistance and the kinetics of creep crack growth (CCG) is essential. In the present work a rather brittle nonpipe material was used to develop a methodology for an accelerated measurement of crack kinetics in fatigue tests on cracked round bar (CRB) specimens at ambient temperatures of 23 °C. A material and specimen specific compliance calibration curve was generated to detect the crack kinetics with only one single CRB test. Based on an already proposed concept the kinetics at different R-ratios (minimum/maximum load) was measured and extrapolated to the case of CCG. To demonstrate the transferability of this concept to pipe materials a PE 80 pipe grade was used. Although the necessary testing time increased considerably the concept still has the potential to reduce the overall testing time for new pipe materials to be certified significantly. With the presented procedure a characterization of CCG in modern PE pipe grades at room temperature and without the use of stress cracking liquids is possible within a few months.     

SLOWING DOWN NUTRIENT FLOWS — ECOLOGICAL DESIGN OF THE FENGXIANG PARK ON THE MEISHE RIVER IN HAIKOU

Haikou is a coastal tourist city in Hainan Province of South China with beautiful natural landscapes. During the rapid urbanization in the past decades, the role of natural rivers as city’s water ecological infrastructure has been long-time neglected, resulting in a sharp deterioration of urban ecological resilience and security. Fengxiang Park, sitting at the middle reaches of the Meishe River, is a key ecological node in the watershed, which however had suffered from severe ecological problems. In this demonstrative project, the site was envisioned as an urban park which mitigates urban flooding and water pollution and provides citizens a quality waterfront with pleasant, slow living environment through a substantial ecosystem improvement with means of Design Ecology. Techniques of green sponge construction and the reinforced constructed wetland system deployed in the park have effectively slowed down the flow of water and nutrients, restored habitats for fauna and flora, and increased biodiversity; the introduction of a diversity of slow traffic system has brought vitality to the city by encouraging green traffic modes among citizens and tourists, creating a new tourism, recreational, and cultural destination for the city. More importantly, in view of increasingly severe issues such as water pollution and shortage around the globe, this project shows an obvious reference significance to other practices in urban water quality improvement, flooding control, and the creation of public spaces to provide social and cultural services.     

Crystal growth, thermal and optical studies on a metalorganic nonlinear optical material dipotassium boro maleate (DKBM)

A single crystal of dipotassium boro maleate (DKBM) was grown using slow evaporation method. The solubility of DKBM was determined for various temperatures. The structure of the grown crystal was confirmed by single crystal X-ray diffraction (SXRD) and powder X-ray diffraction (PXRD) techniques. The Fourier transform infrared (FT-IR) study reveals the various functional groups present in the grown crystal. The UV-Vis-NIR spectra revealed the transmission properties of the grown crystal. Thermal stability of the crystal was investigated using thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The nonlinear optical (NLO) property of the crystal was confirmed by powder second harmonic generation (SHG) test.