排序方式: 共有38条查询结果,搜索用时 78 毫秒
31.
32.
为了提高港口货物吞吐量的预测精度,以宁波舟山港为例对灰色马尔可夫组合预测模型进行了优化研究。首先,用中国统计年鉴中宁波舟山港货物吞吐量的历年数据建立灰色GM(1,1)模型;其次,对模拟误差值用一阶马尔可夫链进行修正并确定误差的转移状态,建立复合灰色马尔可夫预测模型;最后,用粒子群算法对该复合模型进行迭代寻优并优化改进,使模型能够根据实际情况对每个灰区间分别进行分析计算,并实时动态更新其区间参数;最终,提高改进后的模型误差精度。结果表明,用粒子群算法改进的灰色马尔可夫模型误差均值下降了37%,预测值与实际值的拟合度更高,预测结果更符合实际情况。 相似文献
33.
为更好地实现主线教学,分析航海教学的现状,依据船舶航次操作流程,结合《STCW公约》的基本要求,设计航海技术专业教学的主线。采用主线式双语教学,按照主线设计的基本原则和教学的目标定位,提出船舶航次操作规律为线的航海技术专业课程主线。这种教学模式能够有效地拉近理论与实际工作的距离,调动学生学习的积极性,提高航海专业的教学水平。 相似文献
35.
36.
37.
Energy dissipater of multi-stage orifice plate, as a kind of effective energy dissipater with characteristics of high energy dissipation ratio and low cavitations risk, has become welcomed more and more by hydraulics researchers. The relationship between the contraction ratio of upper stage orifice plate and the lower one's under the principle of equal-cavitation characteristics, and the reasonable distance between upper stage orifice plate and the lower one under the condition of complying with this principle, are two important factors to be considered for multi~stage energy dissipater design. In the present paper, these two factors were analyzed by theoretical consideration and numerical simulations, and solving methods were put forward. The conclusion in this paper was proved to be reasonable by model experiment. 相似文献
38.