高温深井通风降温技术的适用条件研究

随着矿山开采深度的不断增加，“三高一扰动”恶劣开采环境问题日益突出，给矿井通风降温工作带来极大困难。对于深井矿山，仅采用通风降温难以满足深部开采的需要，系统研究高温深井矿山通风降温技术的适用性问题，对矿山深部开采具有重要的理论意义和工程适用价值。首先从热力学角度，揭示风流在通风线路中的热交换规律；其次利用差分法原理计算深井筒风流温度，并依此推导出巷道和回采工作面风流温度变化趋势；然后结合采场安全生产允许温度进行反推，最终获取通风降温条件下的可采极限深度计算公式，并选取广西铜坑矿锌多金属矿体作为工程应用试验区进行论证分析。结果表明：基于风流的热交换模型可以推导出风流在井筒、巷道及工作面的温度计算公式，该公式与低温梯度、风流流经路径长度有关；假定工作面温度达到安全开采允许最高温度，可反推出该条件下矿山可采极限深度和巷道通风极限长度（仅采用通风降温措施时）；基于铜坑矿区锌多金属矿的实际条件，代入相关数据，验证计算所得极限开采深度符合实际，即所推导公式是可行的。     

高功率光纤激光器光纤器件封装应力影响研究

高功率激光器无源器件制作过程中封装不当引入的应力,会导致信号光光束质量劣化和光纤温升,为了解决此问题,理论分析了光纤形变对信号光模式分布的影响,利用有限元方法建立包层光导致光纤发热模型,实验研究了不同封装方式对光纤发热情况和信号光光束质量的影响。实验表明,应力导致的光纤形变会造成信号光M2值在受力方向上略微变小而其垂直方向上变大,在输出100 W信号光时,施加应力导致的M2值的变化最高为0.39,与仿真结果相符。在光纤温升方面,相比于使用硬质胶水带来的12 ℃温升,使用硅橡胶封装的剥离器将温升控制在5 ℃以内,且其封装应力引入的M2值的变化在0.05以内。     

基于随机光栅的可调谐随机光纤激光器

提出一种基于随机光栅与高反射布拉格光栅(FBG)相结合的可调谐随机光纤激光器。利用980nm泵浦光源泵浦一段7m长的掺铒光纤(EDF)进行增益放大,由随机光栅提供随机反馈。随机光栅长7cm,具有约10000个折射率修改点,这些点由飞秒激光逐点写入,并沿光纤方向随机分布,两点相邻间隔小于10μm。同时,利用中心波长为1548nm的高反射FBG来组成半开放腔结构,实现了随机激光的输出。实验测得的泵浦阈值功率仅为18mW,斜率效率高达13.2%,并通过改变FBG的中心波长,实现了输出激光波长的可调谐,调谐范围为4.45nm(1548.04~1552.49nm)。得益于半开放式激光腔的设计和EDF的高增益,整个系统具有阈值低、效率高、结构简单等优点。     

基于连续介质损伤力学的7075铝合金高温成形极限理论预测与数值仿真

开展7075铝合金高温单向拉伸试验和成形极限试验，获得了不同温度和应变率的应力-应变曲线和成形极限曲线。结果表明，在较高的温度和应变率时7075铝合金的强度减小、成形性提高。为描述7075铝合金高温损伤演化过程，提出一种改进的连续介质损伤模型，并建立了耦合损伤的多轴统一黏塑性本构模型。基于试验结果，运用NSGAII遗传算法标定了模型中的参数，标定后的本构模型可以很好地预测7075铝合金的高温热力行为和极限应变。通过有限元软件Abaqus的用户材料子程序VUMAT，该本构模型被编入到Abaqus软件中进行数值仿真计算。结果表明，仿真获得的成形极限曲线和应变场分布与试验和理论结果吻合度好，进一步证明了所建立的耦合损伤的多轴本构模型的正确性及其在高温成形极限有限元仿真中的适用性。     

Numerical study of flow distribution uniformity for the optimization of gradient porosity configuration of porous copper fiber sintered felt for hydrogen production through methanol steam reforming micro-reactor

A macroscopic numerical method is proposed to study the flow distribution uniformity of a novel porous copper fiber sintered felt (PCFSF), which has gradient porosities and was developed as the methanol steam reforming micro-reactor catalyst support for hydrogen production for fuel cell applications. The macroscopic porous media developed by the ANSYS/FLUENT software is used to represent the PCFSF. Our results indicate that the gradient porosity can reshape the flow distribution of PCFSFs greatly, thus producing significant influence on their performance. It is further revealed that, for a PCFSF with a determined gradient porosity configuration but different reactant feed directions, the velocity uniformity can be used as a quantitative criterion to evaluate the performance of hydrogen production. Furthermore, new gradient PCFSFs are produced according to the flow distribution of original gradient PCFSFs. The preliminary experimental results of the new gradient PCFSFs of 0.8-0.9-0.7 and 0.7-0.9-0.8 exhibit better methanol conversion and H₂ flow rate. This indicates that the numerical method can be used for the optimization of PCFSFs' gradient porosity configuration, which consists of the shape and position of the interfaces between different porosity portions, the number of interfaces and the porosity distribution in different portions.     

A series of Er~(3+)-activated SrLaGa_3O_7 single crystal fibers for mid-infrared laser application

A multidisciplinary approach for the production and characterization of a series of high concentration Er~(3+)activated SrLaGa_3 O_7(abbreviated as Er:SLGO) crystal fibers is shown to have a great promise for implementation in mid-infrared laser applications.The current approach includes the design and formation of unique layered tetrahedral network structures with several kinds of rare earth(RE) ions including Er ions distributing statistically between layers,such as Er:SLGO,Er,Nd:SLGO,Er,Yb,Ho:SLGO,Er,Eu:SLGO and Er,Ho:SLGO.Five kinds of Er:SLGO crystal fibers were designed to grow via a micropulling down method.Spectroscopic analyses show that Er,Yb,Ho:SLGO and Nd,Er:SLGO crystal fibers were superiorly endowed with inhomogeneous broadening absorption and strong emission.The unique structural components design enables the generation of improved absorption and emission recombination,and the inhibition of self-termination as well.Generally,the use of structural components design may warrant high-efficiency emissions in RE-doped crystal fibers.     

Life history of Plodia interpunctella Hübner on sunflower seeds: Effects of seed qualitative traits and the initial seed damage

Sunflower seeds are regularly infested by Plodia interpunctella during storage. Although this pest prefers damaged seeds, in practice it can infest undamaged seeds as well. This research assessed the influence of the sunflower seed type (oil, protein for human consumption and bird-feed) and the initial seed damage during post-harvest processing (dehulled kernels, 10, 20, 30% of damaged seeds and undamaged seeds) on development of P. interpunctella (larval mortality, larval development, mean developmental duration, adult emergence and fecundity). Biochemical analysis of seeds, kernels and hulls detected the highest content of phenols in the seed and hull and tocopherols in the kernel of the oil type hybrid. The antioxidative activity was the highest in the seed, kernel and hull of the protein type for bird feed. The shortest development (39.5 days) and the highest fecundity (91.3) were on the oil type seeds, while the longest development (42.1 days) and the lowest fecundity (68.1) were on the seeds of the protein type for bird feed. The highest mortality of larvae was on the undamaged seeds of the protein type for bird feed and human consumption (21.3% and 14.0%, respectively). The type of sunflower and the level of initial damage affected larval mortality, developmental duration and fecundity. The mean developmental duration and the number of emerged adults were dependent only on the initial seed damage. Principal component analysis detected strong positive correlation between mortality and development with the tocopherol content on the undamaged seeds while fecundity was associated with the state of kernel and the amount of tannins, proteins and oil content in the seed. The undamaged seeds of the protein type for the bird feed were the least suitable for the development of this pest, while the oil type kernels were the most suitable.     

Multi-hazard loss analysis of tall buildings under wind and seismic loads

This paper presents a framework for life-cycle loss estimation for non-structural damage in tall buildings under wind and seismic loads. Life-cycle cost analysis is a useful design tool for decision- makers, aimed at predicting monetary losses over the lifetime of a structure, accounting for uncertainties involved in the problem definition. For tall buildings, sensitive to dynamic excitations like earthquake and wind, it can be particularly suitable to base design decisions not only on initial cost and performance but also on future repair expenses. The proposed approach harmonises the procedures for intervention costs evaluation of structures subjected to multiple-hazards, taking into account the peculiar differences of wind and earthquake, in terms of load characterisation, type and evolution of damage. Relative effect of the two hazards on damage to drift- and acceleration-sensitive non-structural elements are examined. The influence of uncertainty in structural damping is also taken into account. It is shown that, although it is commonly believed that the design of a given structure is usually dominated by either winds or earthquakes, when LCC-based design is performed, both winds and earthquakes may be important.     

柠条的纤维特性及其双螺杆CMP制浆性能研究

以柠条为原料，分析了其化学组分和纤维形态，并探讨了柠条双螺杆CMP法的制浆工艺以及浆料的纤维形态和成纸的物理性能。研究结果表明：与针、阔叶木相比，柠条原料中纤维素和综纤维素质量分数较低，苯醇抽出物和热水抽出物质量分数较高，柠条纤维长度总体偏短，木质部和皮部的纤维质量平均长度分别为0.621和0.819 mm，还存在部分杂细胞。采用3.5% Na₂SO₃和1.5% NaOH常温预浸12 h、90℃汽蒸1 h后再用双螺杆挤浆机在质量分数35%下进行搓丝，并结合高浓盘磨机磨浆，所得CMP浆得率可达73%。柠条CMP浆基本保持了纤维原有的长度，质量平均长度达0.650 mm，长宽比为32.7，纤维解离较好，但分丝帚化情况不理想，含有部分纤维束和杂细胞。当加拿大游离度为300 mL时，柠条CMP浆成纸的环压强度指数和松厚度较高，分别为8.67（N·m）/g和2.56 cm³/g，抗张指数为19.6（N·m）/g，本色浆白度较高，达50%（ISO）。柠条CMP浆适合配抄瓦楞原纸等包装用纸，漂白后可配抄新闻纸和白板纸。