岩土工程勘察设计常见问题与解决对策

勘察数据的准确性关乎建筑架构的稳定性及后期运营周期.分析了目前在岩土勘察设计上的不足之处,分别从技术、管理及人员3个层面来展开,并且列举实例进行分析,从滑动面、物探、电法勘探以及钻探等方面进行研究,提出解决问题的对策,可为类似工程提供借鉴.     

Ni-Foam Structured Ni-Phyllosilicate Ensemble as an Efficient Monolithic Catalyst for CO2 Methanation

This work proposed a new path to synthesize Ni-phyllosilicate through the reaction of nickel hydroxide and silica sol on the surface of Ni-foam to form the monolithic Ni-phyllosilicate/Ni-foam catalyst. Ni-phyllosilicate could reprint the morphology of nickel hydroxid and firmly anchor on the framework of Ni-foam, which obtained fine Ni particles of 2.8 nm after reduction in H₂ at 650 °C, resulting in high catalytic activity for CO₂ methanation. In addition, the Ni-phyllosilicate/Ni-foam catalyst showed high long-term stability in a 100 h-lifetime test owing to the combined effects of surface confinement of Ni-phyllosilicate, firm anchoring between Ni-phyllosilicate and Ni-foam, as well as the high heat transfer property of Ni-foam.

Graphical Abstract

     

失火故障模式下的柴油机信号特征分析

针对一汽锡柴公司某型号柴油机在不同故障模式下的信号特征进行分析,研究了在柴油机典型失火故障下经过小波包分解后的缸盖振动信号特征敏感性,为柴油机的故障模式分析提供参考.     

王家岭选煤厂输送系统提能改造研究

针对当前王家岭选煤厂日均全粒级处理能力远低于矿井提能后的处理能力的问题,对输送系统的提能改造方案进行分析研究,对选煤厂生产能力进行改造.生产实践表明,通过改造后,输送能力完全满足选煤厂10.00 Mt/a的处理能力,同时降低了输送系统设备故障率及维护成本,改造效益显著.     

Common due date assignment scheduling for a no-wait flowshop with convex resource allocation and learning effect

This article addresses the no-wait flowshop scheduling problem with simultaneous consideration of common due date assignment, convex resource allocation and learning effect in a two machine setting. The processing time of each job can be controlled by its position in a sequence and also by allocating extra resource, which is a convex function of the amount of a common continuously divisible resource allocated to the job. The objective is to determine the optimal common due date, the resource allocation and the schedule of jobs such that the total earliness, tardiness and common due date cost (the total resource consumption cost) are minimized under the constraint condition that the total resource consumption cost (the total earliness, tardiness and common due date cost) is limited. Polynomial time algorithms are developed for two versions of the problem.     

Microstructure and Mechanical Properties of Mg–RE–TM Cast Alloys Containing Long Period Stacking Ordered Phases: A Review

Casting magnesium alloys hold the greatest share of magnesium application products due to their short processing period, low cost and near net shape forming. Compared with conventional commercial magnesium alloys or other Mg–RE-based alloys, the novel Mg–RE–TM cast alloys with long period stacking ordered(LPSO) phases usually possess a higher strength and are promising candidates for aluminum alloy applications. Up to now, two ways: alloying design and casting process control(including subsequent heat treatments), have been predominantly employed to further improve the mechanical properties of these alloys. Alloying with other elements or ceramic particles could alter the solidifi cation pattern of alloys, change the morphology of LPSO phases and refi ne the microstructures. Diff erent casting techniques(conventional casting, rapidly solidifi cation, directional solidifi cation, etc.) introduce various microstructure characteristics, such as dendritic structure, nanocrystalline, metastable phase, anisotropy. Further heat treatments could activate the transformation of various LPSO structures and precipitation of diverse precipitates. All these evolutions exert great impacts on the mechanical properties of the LPSO-containing alloys. However, the underlying mechanisms still remain a subject of debate. Therefore, this review mainly provides the state of the art of the casting magnesium alloys research and the accompanying challenges and summarizes some topics that merit future investigation for developing high-performance Mg–RE–TM cast alloys.     

0CrMnTiH齿轮钢的淬透性计算及窄淬透性带控制

采用非线性方程计算法计算20CrMnTiH钢末端淬透性,只需利用生产实际数据加以修正,就能进行精确的淬透性计算和预报,与实测值偏差不超过2HRC。采用化学成分设计和控制,保证20CrMnTiH钢△[C]不超过0.007%,△[Si]波动不超过0.04%,△[Mn]、△[Cr]不超过0.02%,△[Ti]不超过0.01%,△[Alt]不超过0.010%,[Ni]、[Cu]不超过0.05%,[Mo]、[W]、[V]不超过0.03%,[P]、[S]不超过0.020%,[N]和[B]分别不超过0.006 0%和0.0005%,并控制碳偏析指数不超过1.035%,可实现国际先进水平的末端淬透性HRC4带宽控制。     

Rollover crashworthiness analysis and optimization of bus frame for conceptual design

Journal of Mechanical Science and Technology - At the conceptual design stage, utilizing the detailed model to determine the rollover crashworthiness of bus structure would need long design cycle....     

稀土修饰铁碳材料对糖蜜酒精废水处理效果的研究

采用还原铁粉、碳粉、稀土铈及黏结剂等为原料混合制成的Ce-Fe/C复合材料深度处理糖蜜酒精废水,研究了铁碳质量比、稀土铈添加量以及废水处理时间等因素对处理效果的影响。结果表明:以铁碳质量比为5∶1,稀土铈添加质量分数为7%制备的Ce-Fe/C复合材料处理糖蜜酒精废水,当反应时间为150 min时,色度去除率达98%以上,COD去除率达70%以上。对制备的复合材料的表征结果表明,稀土元素Ce有效地掺杂到Fe/C材料的晶格中,提高了Fe/C材料的性能。     

FDM 3D打印工艺参数对PLA制件力学性能的影响

采用五因素四水平正交试验设计,对16组不同工艺参数(打印层厚、填充密度、打印温度、填充速度、外壳厚度)的FDM 3D打印聚乳酸(PLA)制件力学性能进行了测试和结果分析,确定了影响PLA制件力学性能的主要因素,其中,外壳厚度对制件力学性能影响最为明显,打印温度影响最小,同时分析得到了在打印层厚0.15 mm,填充密度40%,打印温度210℃,填充速度60 mm/s,外壳厚度1.6 mm条件下可获得力学性能最佳的制件。最后对试验数据进行回归分析,拟合得到了FDM打印工艺参数与PLA制件力学性能指标的数学模型;通过对不同打印工艺参数的试样进行试验验证,表明该模型拟合误差小(5%以内),可靠性高,可用来对FDM 3D打印制件的加工提供参考。