Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： The cryosphere is closely related to climate change, human engineering activities and social and economic development. Each element of cryosphere has significantly different influence characteristics on engineering. Disasters by glaciers, snow cover, and sea (river and lake) ice will mainly affect the construction, safe operation, and serviceability of engineering. Frozen soil is a special foundation soil for engineering structures, thus freezing-thawing disasters and thermal and mechanical stability change of frozen soil will directly affect the stability of engineering. As global change, the elements of cryosphere change and its hydrological and ecological environment, surface process changes have significant influence on engineering, thus it is needed to strengthen the relationship research between the engineering construction and safety operation and the environmental factors change. In addition, engineering security technology is also needed to be more comprehensive to consider the influence of climate and environment changes. Therefore, climate and environmental change will become an important factor to be considered in the construction, safe operation, and serviceability of engineering in the regions of cryosphere in the future. At the same time, the Belt and Road infrastructure construction not only brings opportunities to cryosphere engineering, but also faces greater challenges.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： As one of the most promising next generation reactors, the molten salt breeder reactor (MSBR) with excellent inherence security has attracted more and more attentions in recent years due to energy shortage and the security problem of traditional nuclear reactor. The most significant service characteristic of the structural material used in MSBR is the existence of FLiNaK molten salt compared with other nuclear reactors. FLiNaK molten salt is very corrosive to the structural material in the reactor, and affects the safety operation of nuclear power plants. A polycrystalline Ni-Mo-Cr-Fe superalloy was developed and used as an important structural material in MSBR at Oak Ridge National Laboratory (ORNL), but the corrosion mechanism of the alloy in FLiNaK molten salt has not been determined since the study terminated in 1970' s as some politic reasons. Alloy served in harsh environments, often using protective coating to improve the corrosion properties. While few works about the coating corrosion resistance in FLiNaK molten salt were reported at present. Al2O3 and Cr2O3 coatings usually have excellent corrosion resistance in molten salt, such as sulphate, nitrate and halide molten salt. But, whether the oxide film has corrosion resistance in FLiNaK molten salt has not been determined. In this work, the corrosion mechanism of alloy in FLiNaK molten salt was studied by using immersion corrosion experiment through the method of SEM, EDS and XRD. The influence of Al2O3 coating on corrosion resistance in FLiNaK molten salt was also investigated. The results show that the Al2O3 coating does not affect the exsolution corrosion characteristics of Cr and Mo elements in FLiNaK molten salt at 700 ℃ for 400 h. The different is that naked alloy exhibits intergranular corrosion characteristic, and the alloy with Al2O3 coating exhibits spot corrosion characteristic. The Al2O3 coating cannot improve the corrosion resistance of the alloy in FLiNaK molten salt. The Al2O3 film dissolved in molten salt and resulted in the exposure of the alloy surface. The corrosion rate was increased since the formation of corrosion cell between oxide film and the exposed alloy surface.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： The effect of extensometer induced cold-tesile deformation on microstructure and mechanical properties of Ni-based high temperature alloy GH3535 were investigated by means of OM and TEM as well as measurement of true stress-true stain curves. It was found that GH3535 alloy shows characteristics of strong work hardening; cold deformation can result in significant increase of its strength and hardness, whereas decrease of its ductility. With the increase of deformation degree grains were elongated along the deformation direction and twins became profusely lager. The work hardening kinetics of GH3535 alloy is constant with Ludwigson model, dislocation slipping and twin are the main deformation mechanism. With the increase of deformation degree the slip behavior of dislocations changes from single slip to cross slip. When the deformation degree below 30% the work hardening is mainly caused by the dislocation long-range stress field and twin, conversely, for the deformation degree above 30% work hardening is mainly caused by the dislocation short-range stress field and deformation twin.
Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Other Disciplines of Agriculture, Forestry,Livestock & Aquatic Products Science submitted time 2023-02-17 Cooperative journals: 《智慧农业（中英文）》
Abstract： Yield estimation of fruit tree is one of the important works in orchard management. In order to improve the accuracy of in-situ yield estimation of apple trees in orchard, a method for the yield estimation of single apple tree, which includes an improved YOLOv5 fruit detection network and a yield fitting network was proposed. The in-situ images of the apples without bags at different periods were acquired by using an unmanned aerial vehicle and Raspberry Pi camera, formed an image sample data set. For dealing with no attention preference and the parameter redundancy in feature extraction, the YOLOv5 network was improved by two approaches: 1) replacing the depth separable convolution, and 2) adding the attention mechanism module, so that the computation cost was decreased. Based on the improvement, the quantity of fruit was estimated and the total area of the bounding box of apples were respectively obtained as output. Then, these results were used as the input of the yield fitting network and actual yields were applied as the output to train the yield fitting network. The final model of fruit tree production estimation was obtained by combining the improved YOLOv5 network and the yield fitting network. Yield estimation experimental results showed that the improved YOLOv5 fruit detection algorithm could improve the recognition accuracy and the degree of lightweight. Compared with the previous algorithm, the detection speed of the algorithm proposed in this research was increased by up to 15.37%, while the mean of average accuracy (mAP) was raised up to 96.79%. The test results based on different data sets showed that the lighting conditions, coloring time and with white cloth in background had a certain impact on the accuracy of the algorithm. In addition, the yield fitting network performed better on predicting the yield of apple trees. The coefficients of determination in the training set and test set were respectively 0.7967 and 0.7982. The prediction accuracy of different yield samples was generally stable. Meanwhile, in terms of the with/without of white cloth in background, the range of relative error of the fruit tree yield measurement model was respectively within 7% and 13%. The yield estimation method of apple tree based on improved lightweight YOLOv5 had good accuracy and effectiveness, which could achieve yield estimation of apples in the natural environment, and would provide a technical reference for intelligent agricultural equipment in modern orchard environment.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2019-01-03 Cooperative journals: 《计算机应用研究》
Abstract： There exists several issues in traditional collaborative filtering algorithms: a) It has the sparsity of user rating matrix; b) It ignores the relationship between item attributes. Considering all these problems, this paper proposed a novel collaborative filtering algorithm combining score ratio factor and item attribute. The algorithm used the scoring matrix to obtain the ratio matrix of common and non-common score users between items. Therefore, it increased the influence degree of the users of the item common score, and reduced the error caused by the sparsity of the user-item scoring matrix on the item similarity calculation. quantifying the item attribute could obtain the weight of the item similarity, and it also improved the accuracy of the item similarity calculation. According to the above two points, an algorithm combining scoring scale factor and item attribute weight as item similarity weight is proposed. Experimental results show that, it improved the recall rate and accuracy of the algorithm by 5.1% and 4.7% respectively compared with the existing methods. The algorithm is suitable for personalized recommendation of e-commerce websites.
Subjects: Biology >> Bioengineering submitted time 2017-07-24 Cooperative journals: 《中国生物工程杂志》
Abstract：摘要：海藻糖合成是微生物对抗环境逆境的一种重要途径。本文研究10 L发酵罐中的分批、分批补料及分批补料控温三种不同的海藻糖发酵调控策略下酱油风味形成微生物鲁氏酵母CCTCC M2013310的代谢特征。色谱结果表明，乳酸、丙酮酸和α-酮戊二酸受到不同发酵调控模式的显著影响，但谷氨酸和谷氨酰胺总含量在三种发酵调控模式间却无显著差异。这些结果表明细胞还原力平衡途径和碳氮调控代谢均对胞内海藻糖的积累产生影响。本研究结果为鲁氏酵母CCTCC M2013310的高浓度内源性海藻糖细胞代谢工程改造提供了新思路。
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