Остроградский──Gauss定理的一个注记     

Xu Jihong 《安徽师范大学学报(自然科学版)》1994,(3)

本文给出在一定条件下，即使在闭曲面围成的空间区域内有奇点公式也同样成立。  相似文献   

一种改进的树形矢量量化编码算法     

梅海泉  郑建宏 《重庆邮电学院学报(自然科学版)》1998,10(2):6-9

矢量量化中的一个最严重的问题是在一本码本中搜索最近码字的高计算复杂度。本文在研究树形矢量量化的基础上提出了一种改进的树形矢量量化编码算法。实验结果表明,本文提出的编码算法相对于树形矢量量化算法可大大改善峰值信噪比（ＰＳＮＲ）。  相似文献   

Construction of High Level Expression Cell Lines of Erythropoietin *     

李文君  张洪齐  丛靖莉  李一勤  刘进元 《清华大学学报》1998,(3)

Ｅｒｙｔｈｒｏｐｏｉｅｔｉｎ（ＥＰＯ）ｉｓｏｎｅｏｆｔｈｅｍｏｓｔｉｍｐｏｒｔａｎｔｒｅｇｕｌａｔｏｒｙｆａｃｔｏｒｓｄｕｒｉｎｇｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｍａｍｍａｌｉａｎｅｒｙｔｈｒｏｃｙｔｅ,ａｃｔｉｎｇｍａｉｎｌｙｏｎｔｈｅｅｒｙｔｈｒ...  相似文献   

    

Deeksha Tripathi;Saroj K. Biswas; 《Journal of forecasting》2024,43(8):3161-3176

Agriculture is facing significant challenges in the development of crop yield forecasts, which are important aspects of decision-making at the international, regional, and local levels. The area of agriculture is attracting growing attention because of increasing the demand for food supplies. To ensure future food supplies, crop yield prediction (CYP) provides the best decision-making to assist farmers in agricultural yield forecasting efficiently. Nevertheless, CYP is a difficult endeavor because of the intricacy of the underlying mechanisms and the effect of numerous factors, including weather patterns, soil characteristics, and crop management techniques. In today's era, ensemble learning (EL) approaches have recently demonstrated significant promise for enhancing the reliability and accuracy of CYP. The success of the EL techniques depends on several facts, including how the base learner models are trained and how these are combined. This study provides important insights into the EL techniques for CYP. This paper proposes an expert system model named precise ensemble expert system for crop yield prediction (PEESCYP) to predict the best crop for agricultural land. The proposed PEESCYP model employs multiple imputation by chained equation (MICE) data imputation technique to treat the missing values of the collected dataset, the isolation forest (IF) technique for outlier detection, the ant colony optimization (ACO) technique to perform feature selection, robust scaling (RS) technique to perform data normalization, and the extra tree (ET) is used for classification to overcome the variance and overfitting problem of the single classifiers. The measurements of the proposed PEESCYP model have been collected by means of accuracy, precision, recall, and F-1 score using a prepared dataset, which is collected from International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), and the proposed model is compared with different single-classifier based ML models, EL models, and various existing models available in the literature. The results of this experiment underline that the proposed PEESCYP model outperforms the others.  相似文献   

掘进机上固定钻探机装置应用     

李云福 《华北科技学院学报》2011,8(3):39-40

ZYJ400／130架柱式回转钻机要改造安装在掘进机上使用,以提高在矿井巷道施工工作中的实用价值。改造后将掘进机与钻探机融为一体。在综掘机的截割部侧,加装架柱式液压回转钻探机。通过改变轨道的方向,调节丝杆的角度,从而改变钻探机的方向,可对工作面的前方、左、右、上、下角度实施打眼探水。改造后的“掘探一体化装置”增加了单位...  相似文献   

大连装备制造业服务化发展路径探讨     

王春芝  严姗姗  金亚南 《大连民族学院学报》2011,13(4):398-401

结合制造业服务化发展的国际化趋势,制造企业服务管理的战略演进及其机理,对大连装备制造业服务化转型中存在的问题及原因进行解析论证;并对大连装备制造业服务化发展策略进行了相应的设计,以期为大连装备制造业的发展提供理论指导。  相似文献   

基于最小二乘支持向量机的交通流量预测模型     

赵亚萍  张和生  周卓楠北京交通大学电气工程学院  杨军  潘成  贾利民 《北京交通大学学报(自然科学版)》2011,(2)

城市交通流具有复杂性、时变性和随机性,实时准确的交通流量预测是实现智能交通诱导及控制的前提.综合分析交通流量影响因素的基础上,进行多路段的交通流量预测研究,提出了基于最小二乘支持向量机的交通流量预测改进模型,并应用平安大街的流量数据进行实例验证.结果表明,该模型具有学习速度快、跟踪性能好及泛化能力强等优点,在交通流预测中更具有实用性和推广性.  相似文献   

基于高维几何特征的孤立点检测算法     

朱玉全  刘晟  孙金津 《江苏大学学报(自然科学版)》2011,32(1):84-88

针对孤立点检测算法不能较好地模拟人工检测过程、未充分考虑待测数据周围样本分布的问题,提出了一种孤立点检测算法DD-SVDD.该算法综合考虑待测样本与目标样本之间的距离,以及待测样本所在区域样本的分布信息,结合距离和平均密度来确定高维特征空间中决策边界附近待测数据的类别.在训练阶段,考虑了决策边界附近目标训练样本的分布,...  相似文献   

指挥艺术和非结构化信息支持     

史越东  王琪 《系统工程理论与实践》1995,(7)

本文首先概括出了“专家型”和“助手型”两种不同的决策思路；继之围绕以有利于发挥指挥艺术的方式进行决策支持这个核心问题，对指挥决策中信息获取和处理方式进行了探讨，并建立了非结构化信息支持的概念；最后提出了基于非结构化数据的智能决策支持系统的设想，并讨论了系统实现的有关技术。  相似文献   

FORECASTING ：EXCHANGE RATES： AN OPTIMAL APPROACH     

BENEKI Christina  YARMOHAMMADI Masoud 《系统科学与复杂性》2014,27(1):21-28

This paper looks at forecasting daily exchange rates for the United Kingdom, European Union, and China. Here, the authors evaluate the forecasting performance of neural networks （NN）, vector singular spectrum analysis （VSSA）, and recurrent singular spectrum analysis （RSSA） for fore casting exchange rates in these countries. The authors find statistically significant evidence based on the RMSE, that both VSSA and RSSA models outperform NN at forecasting the highly unpredictable exchange rates for China. However, the authors find no evidence to suggest any difference between the forecasting accuracy of the three models for UK and EU exchange rates.  相似文献