基于粒子群算法的微纳米铁粉燃烧实验研究

为减少化石燃料的使用,开发清洁、低碳、可再生的新型能源,对微纳米铁粉燃料开展燃烧实验研究。通过微纳米铁粉的比表面积实验、热重分析实验、X射线衍射实验,得到不同粒径铁粉的比表面积、热重曲线以及X射线衍射图谱。分析粒径对比表面积、热重曲线的影响,研究不同粒径铁粉在40 K/min升温速率下的燃烧特性参数和燃烧动力学参数。并用粒子群算法拟合出微纳米铁粉的燃烧速率微分方程,建立微纳米铁粉的燃烧模型。结果表明：除了50 nm铁粉以外,随着粒径增大,铁粉的着火点温度、最高燃烧速率温度、燃尽温度、活化能、指前因子均增大。50 nm铁粉会在高温下发生熔化并凝结,使得燃尽温度上升,燃尽时间延长,不利于反应正常进行。对于粒径在50 nm～2μm范围内的铁粉,可以通过本文建立的铁粉燃烧速率微分方程近似计算不同粒径微纳米铁粉的燃烧特性参数和燃烧动力学参数,误差在允许的范围内。     

基于阴影图的植物阴影算法改进及其绘制

采用帧缓冲区对象(frame buffer object,FBO)技术来改进传统阴影图(shadow Map,SM)算法,即利用FBO技术将场景深度信息直接渲染到纹理中来提高算法的执行效率.依据纹理法线与光源方向的点积来模拟树干及器官几何mesh模型的自阴影,并通过提高分辨率改善投射阴影边缘的锯齿问题.在改进后的SM算法基础上结合方差阴影图(variance shadow map,VSM)算法实现植物软阴影.以植物参数化三维模型为例,采用VS2008、OpenGL图形标准和可编程图形硬件技术,在ParaTree参数化单株木建模工具软件中集成改进后的阴影图算法,实现了植物自阴影边缘的平滑过渡和光源在不同高度角条件下不同阴影亮度的硬阴影和软阴影效果.     

Molecular dynamics simulation and continuum modelling of granular surface flow in rotating drums

Numerical simulations of granular flows in rotating drums operated at medium to high rates (Fr=0.1― 0.2) have been carried out by using a Molecular Dynamics (MD) algorithm that incorporates inelastic particle interactions, sliding friction and rolling friction. The results indicate that the behavior of granular flow in rotating drums can be classified into two distinct zones: a shear active layer at the bed surface and a quasi-static plug flow region adjacent to the wall. The residence time of a tracer particle in the active layer is approximately a third or a half of that in the plug flow region. The thickness of the active layer at mid-chord is about 0.57―0.61 times that of the plug flow region. It is found that all cases simulated in this work are in the rolling-cascading intermediate regime instead of the pure rolling re-gime. The simulated tangential velocity at the mid-chord is also compared with experimental results reported in the literature and good agreement has been obtained. Based on the MD simulations and experimental results, a continuum approach has also been developed. It is shown that the behavior of granular solids in the plug flow region experiences plastic deformation along the radial direction from the wall with the velocity profiles well described by an exponential function, whereas the active layer velocity follows a simple expression for the Couette shear flow. Discussion has also been made on the granular temperature and concentration profiles.     

Flow and heat transfer behaviour of nanofluids in microchannels

Flow and heat transfer of aqueous based silica and alumina nanofluids in microchannels were experimentally investigated. The measured friction factors were higher than conventional model predictions at low Reynolds numbers particularly with high nanoparticle concentrations. A decrease in the friction factor was observed with increasing Reynolds number, possibly due to the augmentation of nanoparticle aggregate shape arising from fluid shear and alteration of local nanoparticle concentration and nanofluid viscosity. Augmentation of the silica nanoparticle morphology by fluid shear may also have affected the friction factor due to possible formation of a core/shell structure of the particles. Measured thermal conductivities of the silica nanofluids were in approximate agreement with the Maxwell-Crosser model, whereas the alumina nanofluids only showed slight enhancements. Enhanced convective heat transfer was observed for both nanofluids, relative to their base fluids (water), at low particle concentrations. Heat transfer enhancement increased with increasing Reynolds number and microchannel hydraulic diameter. However, the majority of experiments showed a larger increase in pumping power requirements relative to heat transfer enhancements, which may hinder the industrial uptake of the nanofluids, particularly in confined environments, such as Micro Electro-Mechanical Systems (MEMS).     

数字图像中照度不均匀校正技术研究

为了消除数字图像中的照度不均匀性，对现有数字图像的照度不均匀校正技术进行了归类和讨论．分析了这些方法在计算误差上的内在原因，并在此基础上提出了基于小波变换的数字图像照度不均匀校正技术．该技术兼顾了数字图像的频域和空域，使得采用本方法校正后的图像具有品质优，计算误差小和时间消耗较少等特点．     

巷道地震波法在金属矿山采空区探测中的应用

采空区是金属矿山作业施工面临的主要灾害风险源之一,准确探明采空区的分布特征是保障矿山安全开采的重要支撑。为探明隶属于鞍钢集团的弓长岭铁矿和眼前山铁矿作业巷道前方的采空区分布情况,采用巷道地震波法(Seismic Ahead-prospecting , SAP)进行远距离探测。通过对震动信号反射波的提取与偏移成像处理,获取了巷道前方120 m范围内的采空区分布情况,揭示了弓长岭铁矿盲斜井54 m深度巷道前方存在的椭球形民采空区和眼前山铁矿中茨采区22-30 m深度主斜坡道前方存在的矿压致采空区探测结果,为作业提供安全支撑。在此基础上,针对弓长岭铁矿巷道非平整边墙,进行了巷道地震波数值模拟与分析,揭示了非平整边墙产生散射波场对探测结果的影响特征,进一步优化采空区探测结果解译。     

浙江近海虾类资源量的初步评估

本文根据１９８６～１９８９年，对浙江近海（２６°３０＇～３１°３０＇Ｎ、１２５°Ｅ以西）拖虾调查资料，根据虾类的分布特点计算了标准拖网船数据，用密度法评估了主要虾类和总体的资源量和可捕量。其结果为：２０～９０米水涂海域的现存资源量为１００．４千吨，可捕量为８０．３千吨，其中哈氏仿对虾和鹰爪虾的数量最大。为合理利用和管理东海区浙江近海的虾类资源提供基础资料。     

脉冲高压水射流工作原理及研究现状

综述了脉冲高压水射流技术的发展过程，指出脉冲水射流是一种有发展前途的新型射流技术。通过对脉冲高压水射流工作原理的分析，显示了脉冲射流切割和破碎材料的潜在优势，详细探讨了振荡脉冲射流、脉冲水炮和电液动脉冲射流的发生机理和脉冲特性，并简要介绍了几种其他型式的脉冲射流。     

磷酸镁水泥固化铜污染土的工程特性

为研究不同水泥固化重金属污染土的处理效果和工程特性,取掺重金属铜的高岭土作为研究对象,考虑磷酸镁水泥(magnesium phosphate cement,MPC)掺量、养护龄期、初始铜离子浓度三种因素,研究了MPC固化后重金属铜污染土的固化效果及特性.基于无侧限抗压强度试验和扫描电镜试验,分析了三种因素对固化铜污染土...     

碳扩散对非真空热轧不锈钢复合板结合性能的影响

采用非真空热轧方法制备304不锈钢/Q235碳钢复合板材,利用OM、SEM、EDS等研究了不同压下率和轧后冷却方式下复合界面夹杂物、界面组织及力学行为的演变,并分析了C扩散对复合板界面组织形成及结合强度的影响。结果表明,随着轧制压下率的增加,界面夹杂物由块状向线型、连续点状乃至弥散点状分布变化。当压下率较低(28%)时,复合板剪切断裂位于结合界面处,随着压下率增加至47%及以上,复合板断裂位置为脱碳铁素体区。另外,热轧复合板经水冷工艺处理后,由于冷却速率较快,要抑制碳钢侧C元素的扩散,避免复合界面处脱碳区域的形成,从而提高了复合界面的结合强度。