双护盾TBM 施工中处理不良地质和设置止浆环的初探

 万家寨引黄工程南干线隧洞, 利用双护盾TBM 施工隧洞, 具有隧洞长、埋深大、地质条件复杂等特点, 有较多不良地质构造, 对工程结构稳定不利, 处理也困难; 另外, 隧洞内豆砾石灌浆时, 如能设置止浆环, 对提高灌浆质量有重要意义。为解决这些问题, 提出了利用空腹管片衬砌技术方案, 针对断层、裂隙处理设置混凝土塞的措施, 对侧壁溶洞建立处理工作面的方法。用此方法还可以在Ⅰ～ Ⅱ围岩中临时安装空腹管片, 在完成对TBM 的支撑作用后拆除管片, 岩壁喷混凝土。     

Investigation of laser consolidation process for metal powder by two-color pyrometer and high-speed video camera

This paper deals with the measurement of surface temperature on metal powder during the laser consolidation process with two-color pyrometer. Additionally, the aspect of selective laser sintering (SLS) and selective laser melting (SLM) of metal powder is visualized with high speed video camera. As a result, the surface temperature during the laser irradiation was ranged 1520–1810 °C and the consolidation phenomena was classified according to the melting point of metal powder. The metal powder at the heating process cohered intermittently to the melt pool although the laser beam was continuously irradiated to the powder surface.     

A Meta-frontier method of decomposing long-term construction productivity components and technological gaps at the firm level: evidence from Malaysia

There is a need for a better approach to measure construction productivity rigorously, multilaterally, longitudinally and decomposed into its components. In response, this paper offers a robust approach to analysing construction productivity at the firm level that has been lacking in the industry to date, by measuring the Total Factor Productivity (TFP) of 37 public-listed Malaysian construction firms over 14 years (2003–2016), based on the Färe-Primont index. In comparing different groups of building, civil and specialist construction firms, this is the first application of a meta-frontier framework to capture the technological gaps involved. Based on the construction firms’ financial data, it is found that TFP improvement generally occurs due to Technical Efficiency (TE) and Scale-Mix Efficiency (SME) (largely scope economies), and significant technological gaps exist among different groups. Moreover, the industry suffered a decline in technologically related production environment over the period – prompting the conclusion that long-term policy engagement should focus on technological improvements. The paper provides a robust approach to analysing construction productivity at the firm level that also can be used for accessing productivity components and technological gaps in construction and other industries.     

修正型斜平面二次包络环面蜗杆修形参数与接触线型

修正型斜平面二次包络环面蜗杆的接触线型要比以往文献记载的更加复杂化,不再是单一的Ⅰ型或Ⅱ型接触线。依据是否存在蜕变点,蜕变点有几个,得到了更多型式的接触线型。得到修形参数,主要是Δa和Δi修形的变化对接触线型式的影响。     

浅谈水泥混凝土路面早期裂缝与预防措施

文章分析了水泥混凝土路面早期出现裂缝的原因以及预防措施.     

利用云南钛铁精矿制备还原铁粉及富钛料的实验研究

针对云南钛铁精矿的物相组成,提出了内配还原剂并辅加添加剂、粘结剂混磨制团进行固态还原,磨选分别获得还原铁粉和尾渣,尾渣酸浸制备富钛料的工艺;重点讨论还原时间、还原剂配比、还原温度、添加剂配比、磁选强度对还原铁粉指标的影响;在固定还原-磨选制度,讨论酸浓度、酸浸时间对富钛料指标的影响。通过试验,获得了最佳的工艺参数:还原剂配比10%、添加剂配比5.0%、粘结剂配比1%,还原温度1210℃,还原时间3 h;磨选工艺参数:磨矿细度为+380μm 10%、150~380μm 60%、150μm 30%,磁选强度64 kA/m;浸出工艺参数:硫酸浓度20%、液固比4:1、浸出温度为95℃、浸出时间为3 h、搅拌速度为250 r/min。在此工艺条件下,还原铁粉全铁为96.01%,富钛料中二氧化钛含量为76.94%。该工艺流程简单,钛铁得到有效利用,还原铁粉可用于湿法冶金的还原剂,富钛料为优质钛白原料,为钛铁精矿综合利用提供借鉴作用。     

Effect of inoculation and nodularisation treatment temperature on recalescence and eutectic undercooling temperature in Spheroidal graphite (SG) cast iron

In this study, the effect of inoculant composition and nodularisation treatment temperature on recalescence temperature (TER) and undercooling temperature (TEU) in SG iron has been studied by using thermal analysis. 0·1, 0·2 and 0·3 wt-% of three types of inoculants Ca,Ce,Al–FeSi, Ca,Sr,Al–FeSi and Ca,Ba,Al–FeSi were used as so called stream inoculation. Ca,Ce,Al–FeSi was found to be the most potent one in reducing both recalescence (?T _r ) and eutectic undercooling (?T). The nodule count has also been found higher in Ca,Ce,Al–FeSi inoculated SG iron samples compared to other two inoculants. It has been observed that higher the nodule count lower is the ?T _r and ?T and vice versa. The recalescence and shrinkage relationship of 24 heats of differential case castings has been established; it was observed that the number of castings containing shrinkage in respective heats increase as the recalescence and nodularisation treatment temperature increases.     

Fabrication of oxide pellets containing lumped Gd2O3 using Y2O3‐stabilized ZrO2 for burnable absorber fuel applications

In this paper, the fabrication of novel burnable absorber fuel concepts with oxide pellets, containing either a lumped Gd₂O₃ rod, a mini‐pellet, or a spherical particle in the centerline of the oxide pellet, is investigated to propose the lumped Gd₂O₃ burnable absorber fuel concept to improve nuclear fuel performance with longer fuel cycle lengths and better fuel utilization. The unique characteristic of the lumped Gd₂O₃ burnable absorber fuel is its high spatial self‐shielding factor that reduces its burnout rate and, therefore, improves the reactivity control. Oxide pellets containing lumped Gd₂O₃ were fabricated by using a combination of cold isostatic pressing and microwave sintering at 1500°C to understand the potential technical issues in the fabrication of duplex burnable absorber fuel. The effect of the sintering temperature on the densification and phase transformation of 8 wt.% yttria‐stabilized zirconia, a surrogate for UO₂, was investigated. Spherical Gd₂O₃ particles were fabricated by the drip casting of a Gd₂O₃‐based Na alginate solution. The fabrication of duplex oxide pellets by using presintered Gd₂O₃ mini‐pellets resulted in internal cracks at the interface between the Gd₂O₃ and 8 wt.% yttria‐stabilized zirconia layers because of the mismatch of their densification. However, the formation of interfacial cracks was eliminated by controlling the initial sintered density of the lumped Gd₂O₃.     

Detection of fresh palm oil adulteration with recycled cooking oil using fatty acid composition and FTIR spectral analysis

There is a growing concern over the food safety issue related to increased incidence of cooking oil adulteration with recycled cooking oil (RCO). The objective of this study was to detect fresh palm olein (FPO) adulteration with RCO using fatty acid composition (FAC) and Fourier-transform infrared spectroscopy (FTIR) spectral analyses combined with chemometrics. RCO prepared in the laboratory was mixed with FPO in the proportion ranged from 1% to 50% (v/v) to obtain the adulterated oil samples (AO). FACs for FPO, RCO, and AO were determined using gas chromatography equipped with a flame ionization detector (GC-FID). The compositions of most fatty acids in RCO lied within the normal ranges of Codex standard, except for C8:0, C10:0, C11:0, C15:0, trans C18:1, and polyunsaturated fatty acids (PUFAs), C20:5. PUFAs showed a consistent decreasing trend with increasing magnitude of change with respect to increasing adulteration level and thus might be a good indicator for detecting FPO adulteration with RCO. The evaluation parameters (coefficient of determination, root mean standard error) of the FTIR-partial least square (PLS) model of palm oil adulteration with recycled oil are R² = 0.995 and 3.25, respectively. For FTIR spectral analysis, the distinct variations in spectral regions and aberrations in characteristic bands between FPO and RCO were observed. The optimized PLS calibration model developed from normal spectral of the combined region at 3602–3398, 3016–2642, and 1845–650 cm^?1 overpredict the adulteration level. On the other hand, the discriminant analysis classification model was able to classify the FPO and AO into two distinct groups. Improvement of the principles of combined techniques in authenticating AO from fresh oil is beneficial as a guideline to detect adulteration in cooking oil.