The microstructure evolution and mechanical properties of MgO-C refractories with recycling Si/SiC solid waste from photovoltaic industry

In the present work, the recycling of Si/SiC solid waste from photovoltaic industry for MgO-C refractories preparation has been introduced. The influence of solid waste powders as antioxidant additive on microstructure evolution, mechanical properties and thermal shock resistance of MgO-C refractories has been investigated systematically. With 4?wt% Si/SiC rich solid waste addition, the MgO-C refractories exhibited the highest strength (4.39?MPa) and residual Young's modulus (7.86?GPa) after firing at 1400?°C, compared to only Si or SiC-addition. The presence of iron in the solid waste also promoted the formation of MgO and Mg₂SiO₄ whiskers via catalyst-assisted method. Moreover, a dissolution-saturation-precipitation growth mechanism was used to explain the formation process of the whiskers. The improvements in strength as well as thermal shock resistance can be attributed to the microstructural evolution.     

Formulations and solution algorithms for dynamic assembly routing problem

We study a dynamic version of the assembly routing problem. The assembly lot sizing section deals with decisions concerning the production phase, whereas the routing section organises the collection of raw materials necessary for the production. Traditionally, these two problems are treated separately, and more specifically, in a hierarchical way. We propose three linear programming models: a non-vehicle index model, a two-commodity flow formulation and a logic-based benders decomposition. We develop aggregated rounded capacity constraints for non-vehicle index model and separated them dynamically during the Branch & Cut procedure. Logic-based benders decomposition algorithm solves the Dynamic Assembly Routing Problem iteratively and obtains a feasible solution at each iteration. The numerical tests show that, the two first models are particularly effective at finding the optimal solutions in a reasonable amount of time on instances with up to 50 components and 3 periods.     

Recycling photovoltaic silicon waste for fabricating porous mullite ceramics by low-temperature reaction sintering

In this study, porous mullite ceramics with coral-like structures were fabricated at a low temperature of 900 °C by using photovoltaic silicon waste (PSW) as the silicon source directly. The effects of additive content and sintering temperature on the mullitization reaction of green bodies were studied. The results showed that ammonium molybdate tetrahydrate molybdenum (H₂₄Mo₇N₆O₂₄·4H₂O) as an additive could reduce the reaction temperature for mullitization from 1100 °C to 900 °C. The research on the influence of catalyst on material properties showed that porous mullite ceramics with a flexural strength of 52.83 MPa, a 41.78 % porosity, a sintering expansion rate of 0.49 % and an average pore size of 0.23 μm could be fabricated by introducing 7.5 % H₂₄Mo₇N₆O₂₄·4H₂O at the sintering temperature of 1000 °C. This study develops an environment-friendly recycling method of PSW and provides a new idea for the low-cost preparation of porous mullite ceramics with high purity.     

Partial replacement of metakaolin with red ceramic waste in geopolymer

Metakaolin was incrementally replaced (33.3%, 50% and 66.6%) by red ceramic waste in geopolymer formulation to study the effect on geopolymerisation and its resultant properties. The geopolymer binders composed of two calcined aluminosilicates (viz. Metakaolin and Red ceramic waste), NaOH and sodium silicate. In the experimental compositions, metakaolin was replaced gradually up to 66.6% in the clay fraction, the Si/Al increased from 3.36 to 5.16 and Na/Al increased from 0.93 to 1.38. The FTIR spectroscopic studies of geopolymer pastes along with XRD analysis indicated that the red ceramic waste partly reacts with alkali and takes part in geopolymer formation. Replacement of 33.3% metakaolin by the red ceramic waste in geopolymer binder did not reduce the compressive strength with respect to the pure metakaolin geopolymer here. Additional replacement resulted in a drastic decrease in the compressive strength of the geopolymer binder. However, the compressive strength of geopolymer mortars revealed interesting synergy between the amount of binder and particle packing in the mortar. Despite having a lower amount of binder phase, mortars with 33% and 50% red ceramic waste exhibited maximum compressive strength values. This has been attributed to improved particle packing through incorporation of red ceramic waste particles.     

The constrained two-dimensional guillotine cutting problem with defects: an ILP formulation,a Benders decomposition and a CP-based algorithm

This paper addresses a variant of two-dimensional cutting problems in which rectangular small pieces are obtained by cutting a rectangular object through guillotine cuts. The characteristics of this variant are (i) the object contains some defects, and the items cut must be defective-free; (ii) there is an upper bound on the number of times an item type may appear in the cutting pattern; (iii) the number of guillotine stages is not restricted. This problem commonly arises in industrial settings that deal with defective materials, e.g. either by intrinsic characteristics of the object as in the cutting of wooden boards with knotholes in the wood industry, or by the manufacturing process as in the production of flat glass in the glass industry. We propose a compact integer linear programming (ILP) model for this problem based on the discretisation of the defective object. As solution methods for the problem, we develop a Benders decomposition algorithm and a constraint-programming (CP) based algorithm. We evaluate these approaches through computational experiments, using benchmark instances from the literature. The results show that the methods are effective on different types of instances and can find optimal solutions even for instances with dimensions close to real-size.     

ZL109铝合金车削表面完整性实验研究

设计了三因素四水平正交车削实验,综合运用极差分析、方差分析等方法,研究了切削参数对硅铝合金ZL109车削表面完整性的影响规律,得到了切削参数对于表面粗糙度、残余应力和显微硬度的影响程度和趋势,分析了ZL109车削表面完整性的形成机理,以期为切削参数优选提供实验和理论基础。研究结果表明,进给量f对表面粗糙度具有显著影响,切削速度v和进给量f增加会导致表面残余拉应力增大,显微硬度受切削参数的影响较小。     

Synergic effect of various amino acids and ferric oxide on hydrogen production

To overcome nitrogen and iron deficiency in the organic fraction of municipal solid waste, amino acids and ferric oxide were separately added in the feedstock to evaluate their effect on hydrogen production. Furthermore, synergic effect of amino acids and ferric oxide on hydrogen production was evaluated. The co-culture of E. coli and Enterobacter aerogenes was used in the present study. The amino acids were applied in the concentration range of 1.0, 2.5, 5.0, 7.5 and 10.0 g/L while ferric oxide was used in the concentration range of 10, 20, 30, 40, 50, 100, 150, 200 and 500 mg/L. Modified Gompertz model was used to analyze cumulative hydrogen production (P), maximum hydrogen production rate (Rmax) and lag phases (λ). The results exhibited that the hydrogen production was positively affected by each amino acid at every concentration applied. Application of alanine resulted in the highest cumulative and volumetric hydrogen production of 685.4 ± 10.1 mL and 1.9561L_H2/L_substrate respectively which increased to 872.5 ± 10.1 mL and 2.492L_H2/L_substrate for ferric oxide addition along with alanine. COD removal and VFA generation were positively affected by the synergic effect of amino acid and ferric oxide.     

前刀面槽型结构对D型刀片车削球墨铸铁性能的影响

通过切削力、磨损和冲击切削试验,研究了前刀面槽型结构对D型刀片车削球墨铸铁切削性能的影响。试验结果显示,刀具的第一前角对切削力的影响最大;在10°~15°范围内,刀具前角越大,切削力越低;棱带宽度大的刀片具有更加优异的耐磨损性能;具有正刃倾角的刀片显示出更优异的耐冲击性能。     

超精密平面飞切机床关键技术研究

研制了一种用于KDP晶体加工的平面飞切机床,该机床直线轴基于直线电动机驱动、液体静压导轨支承;刀具旋转轴采用高刚度气浮主轴+高刚度主轴旋转机构。基于高精度分辨率位置反馈+线性驱动器+PID控制算法,直线轴获得了1 mm/min速度下,0.018 mm/min的低速波动以及±0.01μm的位置精度;刀具微进给装置采用差动螺纹进给来实现,最终获得了进给分辨率1μm、锁紧后位置移动量小于1μm高精度进给。在优化工艺参数后,金刚石飞切机床加工100 mm×100 mm×10mm的KDP晶体后获得表面粗糙度Rq优于2 nm高精度指标;加工400 mm×400 mm×30 mm的铝镜后获得面形PV值优于3μm的高精度指标。