外力作用下管道内表面缺陷处裂纹扩展研究

为提高油气管道安全风险评估的准确性,以含内表面缺陷管道为研究对象,利用ABAQUS软件线弹性及弹塑性分析不同尺寸缺陷对裂纹萌生特征的影响;采用扩展有限元法,建立管道3点弯曲模型与全尺寸静载物理试验,并非线性拟合裂纹扩展尺寸,研究内表面缺陷处裂纹扩展情况。研究结果表明:内表面缺陷中心处极易萌生裂纹,随着缺陷尺寸的增大,裂纹萌生所需外力在缺陷相对长度为0.08、相对深度为0.4时的增长趋势变化较大,且缺陷深度对裂纹萌生的影响更大;对比数值模拟与全尺寸物理试验,发现在小于70 mm位移载荷或147.25 kN外力下裂纹尺寸快速扩展,之后呈变缓的趋势;非线性拟合裂纹尺寸,得到较为准确的裂纹扩展尺寸的预测结果。     

含风电的电力系统低碳经济调度

含风电场的电力系统调度是一个多目标优化问题。运用机会约束方法,建立了包括低碳化和发电成本两个目标函数的调度模型,在充分考虑环境保护效益的同时,提出了风险成本的概念,使得发电成本更切合工程实际。在改进自适应遗传算法的基础上,引入了pareto最优解集方法,充分发挥了遗传算法的全局搜索能力和pareto求解多目标问题的潜力。通过实际调度案例验证了所提算法的合理性。     

Effect of the vent burst pressure on explosion venting of rich methane-air mixtures in a cylindrical vessel

The effect of the vent burst pressure on explosion venting of a rich methane-air mixture was experimentally investigated in a small cylindrical vessel. The experimental results show that Helmholtz oscillation of the internal flame bubble of the methane-air mixture can occur in a vessel with a vent area much smaller than that reported by previous researchers, and the period of Helmholtz oscillation decreases slightly when the vent burst pressure increases. The maximum overpressure in the vessel increases approximately linearly with the increase in the vent burst pressure; however, the pressure peaks induced by Helmholtz oscillation always remain approximately several kilopascals. The external flame reaches its maximum length in a few milliseconds after vent failure and then oscillates in accordance with the pressure oscillation in the vessel. The maximum length of the external flame increases, but its duration time decreases with the increase in the vent burst pressure.     

Experimental evaluation of the possibility of ignition and flame propagation in accumulated difluoromethane (R32) from a kerosene cigarette lighter

The possibility of ignition and flame propagation in accumulated difluoromethane (CH₂F₂, R32) was examined experimentally, simulating a situation in which a service operative uses a kerosene lighter for smoking. To simulate the situation where a kerosene cigarette lighter is used in accumulated R32, electrodes fixed in the windbreak of the lighter were remotely supplied with electricity to generate sparks of various durations but of similar energies to those of actual sparks generated by rubbing a flint to ignite the fuel in the lighter. We identified several cases of ignition and formation of an open flame in the windbreak of the lighter, and the flame propagated to the accumulated R32 when it was supplied with sufficient energy from the spark. Gas chromatographic analyses confirmed that the mixture in the windbreak of the kerosene lighter consisted mainly of vaporized fuel and air, with no R32. Therefore, even if the lighter is located in accumulated R32, an open flame can be generated in the windbreak of the kerosene cigarette lighter through ignition by the spark energy generated by friction between the flint and the flint wheel. Our results confirmed that there is a real possibility of ignition and flame propagation when a kerosene cigarette lighter is used in accumulated R32 under the leak rate conditions of the present experiment.     

基于节约法的村镇生活垃圾收运路线优化研究

为了降低垃圾收运成本,减少垃圾收运过程产生的环境和社会影响,对含有多种级别道路的村镇生活垃圾收运路线进行了优化。综合考虑垃圾收运过程的运输距离、路况、环境污染等因素,利用层次分析法确定了不同级别道路的综合权重,并对实际运输距离进行修正,得到综合运输距离。以节约综合运输距离为目标,使用节约法对收运路线进行优化,得出了节约路程多、发生拥堵少、环境污染小的村镇生活垃圾收运路线。并以蒙城县岳坊镇为例,对该地区的垃圾收运路线进行优化设计,验证了方法的可行性。     

利用智利地震震源分布确定智利地区主震断层面

从历史地震来看,智利及其周边地区的历史强震主要集中在Nazca板块和南美洲板块之间的俯冲带上,该区也是7级以上大震频发的地区,所以对于该地区的断层结构和震源机制的研究就显得十分有必要.大地震发生后,大量余震在断层面上发生.因此余震震源位置的空间分布可以较为精确地勾画出断层面的位置.假定地震的发震断层可以用一个平面来模拟...     

内陆水体后向散射系数模拟研究

在利用半分析方法结合光学闭合原理模拟水体后向散射系数的过程中,参考波长的选择对最终结果有较大影响.为了得出最佳参考波长的影响因子,利用太湖、巢湖和滇池的野外实测数据,对后向散射系数进行模拟,进而分析水体的最佳参考波长与其对应的水质参数浓度之间的变化规律.同时,建立了太湖、巢湖和滇池水体的后向散射系数曲线的幂函数光谱模型,获得的光谱指数分别为2.643±0.317、 2.719±0.242、 1.638±0.534.结果表明：①以整个湖泊为研究对象时,最佳参考波长随着湖泊水体中总颗粒物浓度c_SPM、有机颗粒物浓度c_SPOM和叶绿素浓度c_CHL平均值的增大而向长波方向移动,太湖、巢湖和滇池水体的最佳参考波长分别为695、 720和730 nm;②以单个湖泊的各个样点为研究对象时,由于内陆湖泊光学特性的复杂性,最佳参考波长的影响因子存在一定差异,但c_SPM是一个共同的影响因子.此外,过高的c_CHL将削弱水质参数浓度与最佳参考波长间的规律性;③在以无机颗粒物为主的水体中,后向散射系数与总颗粒物浓度之间存在更好的相关性,如在太湖水体中,R²达到0.852.     

混合物质谱的简单分类算法

有毒化合物质谱分类是以光谱数据的数值特性为基础的。这此数据的计算机分类提供了各种参数,用以确定属于有毒化合物中某一类的对应化合物。质谱数据的简单分类算法常被用于自相关变换质谱的主分量建模。主分量的有效值为相互确认为确定。对环境空气中１１９种被监测的有毒化合物,有色谱－质谱联用的试验和校正数据所得到的４类预报正确率为７６．５％。     

多维公平测度下考虑灾民心理痛苦效应的应急资源调配*

为有效降低灾后初期应急资源短缺情况下灾民生理和心理受到的伤害,提出等待效应和短缺效应衡量救援过程中的灾民心理痛苦效应,同时耦合时间和供需情况2个维度测度救援过程中的公平性指标,构建调度总时间最短、时间攀比最小和灾民心理痛苦效应最低的多目标应急资源调配模型,研究多灾点、多配送中心、多种类物资救援场景下的应急资源分配和路径规划决策选择问题。应用NSGA-Ⅱ算法对模型求解,以新冠疫情下武汉市医疗物资调度为算例分析验证模型的有效性。结果表明:模型和算法能有效减少供不应求情况下的灾民心理痛苦效应,保证救援活动的公平性,能得到不同目标偏好下的应急资源调配方案。     

Numerical model of flow and pollutant transportation in non-orthogonal curvilinear coordinates

The planar 2D k-ε double equations‘ turbulence model was adopted and transformed into non-orthogonal curvilinear coordinates. The concentration convection-diffusion was introduced to planar 2D SIMPLEC algorithm of flow in non-orthogonal curvilinear coordinates. The numerical model of pollutant transportation in non-orthogonal curvilinear coordinates was constructed. The model was applied to simulate the flow and pollutant concentration fields. In the testing concentration field, two optimal operations of contamination discharging both along bank and in the centerline at the first bend of the meandering channel were adopted. Comparison with available data showed the model developed was successful, was valuable to engineering application.