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1.
本文对以十字形板与焊接空心球相连的网架节点用有限元的方法进行了受力分析与试验研究,摸清了球面及十字形板内的应力分布规律。分析指出,影响球面应力大小的决定因素是板宽及球厚,板厚及球的直径对球面应力的影响很小。 相似文献
2.
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
3.
The deep-sea clams Calyptogena nautilei and C. tsubasa, which live in the cold-seep area at a depth of 3570 m in the Nankai Trough, Japan, have abundant hemoglobins (Hbs) in erythrocytes, similar to other Calyptogena species. We determined the cDNA-derived amino acid sequences of Hbs from two Calyptogena species. C. tsubasa was found to contain two dimeric Hbs, Hb I consisting of 145 amino acid residues and Hb II with 137 residues, similar to known Hbs from C. soyoae and C. kaikoi. Sequence identity was over 90% among the orthologous chains of Calyptogena Hbs. On the other hand, surprisingly, C. nautilei contained two monomeric Hbs, Hb III containing 141 residues and Hb IV with 134 residues. In addition, Hbs III and IV showed only 33–42% sequence identity with Hbs I and II from other Calyptogena species. The distal (E7) histidine, one of the functionally important residues of the heme protein, is replaced by glutamine in all Hb chains of Calyptogena species. A phylogenetic analysis indicated that C. nautilei Hb III is closer to Hb I from other Calyptogena species. We suppose that a Hb gene was duplicated at least three times in an immediate ancestor of Calyptogena and, presumably depending on physiological conditions different Hb sets are being expressed: dimeric Hbs I and II in C. soyoae, C. kaikoi and C. tsubasa, and monomeric Hbs III and IV in C. nautilei.
Received 13 May 2003; received after revision 5 June 2003; accepted 12 June 2003 相似文献
4.
水电站水库调度计算机模拟教学系统是为提高水库调度、水利水能规划课程的教学效果，为提高实际指导水库调度水平，而设计的CAI系统。根据模拟调度的具体要求，本系统以交互式为主组织教学过程；设计了多种题目类型，其中既有单选题、多选题、是非判断题等客观性题型，又有填空题、简答题、问答题、多问题等非客观性题型，重点设计了为生产调度服务的模拟演示题型。这些题目类型，按循序渐进的原则，逐步覆盖水库调度的各个方面；每道题都包含灵活生动的帮助提示机制，使学员能够主动地理解调度管理的各方面知识。 相似文献
5.
分析了对低成本非破坏性扫描仪的需求,比较了现有图书扫描仪的应用现状,提出以书本表面形态曲线作为扫描路径的三维平板扫描仪,为各图书馆特色资源数字化工作提供了一种低成本无破坏的扫描设备。 相似文献
6.
采用气相色谱法(GC)建立蜂胶超临界CO2萃取物(SEP)的指纹图谱,用于鉴别市售超临界CO2萃取的蜂胶类产品.研究发现来自9省份的16批蜂胶样品超临界CO2萃取物的GC图谱具有9个共有峰,其图谱信息构成蜂胶超临界CO2萃取物的指纹图谱,与所得对照图谱的相似度均大于0.8.方法学考察结果表明,精密性试验、重现性试验和稳... 相似文献
7.
采用钻孔法测定了长纤维局部增强的铝合金试样中增强区与非增强区之间的宏观残余应力,利用有限元法对此进行了模拟计算.结果表明:增强区与非增强区之间存在着明显的宏观残余应力,但分布很不均匀.在增强区和非增强区大部分区域,残余应力并不大,而宏观边界附近的非增强区以及增强区的局部存在高残余拉应力微区.在50%纤维局部增强的试样中... 相似文献
8.
Wen Zhou;Wei Chen;Zhanzhao Wang;Yonghong Ma 《系统科学与信息学报》2015,3(5):434-450
University-industry collaboration networks consist of heterogeneous subjects; in fact, the interactions among these subjects lead to the emergence of the complex characteristics of university-industry collaboration networks and even to the emergence of the networks themselves. Thus, understanding the behavior that generates university-industry collaboration networks is essential to their construction and optimization. To more fully comprehend this generating behavior, we considered a university-industry collaboration network in the ocean energy industry in China as a case study. Employing the motif analysis method, we analyze the network’s generating behavior from four perspectives: motif characteristics, motif classification, motif combination and motif clustering. Furthermore, we explore agents’ modes of adaptive collaboration — and the causes of such collaborations — and summarize the characteristics and modes of networks’ generating behavior. The results indicate that universities and industries tend to form highly stable and close cooperative relationships. The constraints of the network’s generating behavior — which influences the subjects’ interactions through relational and structural embeddedness — include asymmetric information, resource and cost constraints, risk aversion and geographical constraints. Our research presents the benefits of using the motif analysis method to study the network’s generating behavior and its implications in constructing and optimizing a university-industry collaboration network. 相似文献
9.
10.
马振武 《郑州大学学报(理学版)》2004,36(3):22-24
提出了一类新的安全广播加密系统,说明了它与密钥预分配系统的关系,获得在某一安全水平下各用户应掌握的秘密信息量.该系统具有广泛的适用性. 相似文献