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51.
To explore the specimen size effect of mechanical behavior of ultrafine-grained (UFG) materials with different structures, UFG Al sheets processed by equal channel angular pressing (ECAP) were selected as target materials and the dependency of tensile behavior on sheet thickness (t) was systematically investigated. The strength and ductility of ECAPed UFG Al sheets were improved synchronously as t increased from 0.2 to 0.7 mm, and then no apparent change occurred when t reached to 0.7 and 1.0 mm. The corresponding microstructure evolved from dislocation networks in equiaxed grains into the walls and subgrains and finally into the dominated cells in elongated grains or subgrains. Meanwhile, dense shear lines (SLs) and shear bands (SBs) were clearly observed and microvoids and cracks were initiated along SBs with the increase of t. These observations indicated that the plastic deformation of UFG Al sheets was jointly controlled by shear banding, dislocation sliding, and grain-boundary sliding. Furthermore, the propagation of SBs became difficult as t increased. Finally, the obtained results were discussed and compared with those of annealed UFG Al and UFG Cu. 相似文献
52.
Yang Li Peng-fei Du Zhou-hua Jiang Cong-lin Yao Lu Bai Qi Wang Guang Xu Chang-yong Chen Lei Zhang Hua-bing Li 《矿物冶金与材料学报》2019,26(11):1385-1395
The formation mechanism of acicular ferrite and its microstructural characteristics in 430 ferrite stainless steel with TiC additions were studied by theory and experiment. Using an edge-to-edge matching model, a 5.25 mismatch between TiC (FCC structure) and ferritic stainless steel (BCC structure) was identified, which met the mismatch requirement for the heterogeneous nucleation of 430 ferritic stainless steel. TiC was found to be an effective nucleation site for the formation of acicular ferrite in a smelting experiment, as analyzed by metallographic examination, Image-Pro Plus 6.0 analysis software, and SEM-EDS. Furthermore, small inclusions in the size of 2-4 μm increased the probability of acicular ferrite nucleation, and the secondary acicular ferrite would grow sympathetically from the initial acicular ferrite to produce multi-dimensional acicular ferrites. Moreover, the addition of TiC can increase the average microstrain and dislocation density of 430 ferrite stainless steel, as calculated by Williamson-Hall (WH) method, which could play some role in strengthening the dislocation. 相似文献
53.
GAO Aijun 《系统科学与复杂性》1992,(3)
A multidimensional adaptive stochastic approximation procedure trun-cated at randomly varying bounds is studied for the regression function observedwith correlated noise.The algorithm is proved to be asymptotically efficient.Theresult of the paper generalizes the one shown in[1]for the observation noise be-ing i.i.d.random vectors and under other restrictive conditions imposed on theregression function. 相似文献
54.
Fringe is a glycosyltransferase that modifies Notch 总被引:36,自引:0,他引:36
Moloney DJ Panin VM Johnston SH Chen J Shao L Wilson R Wang Y Stanley P Irvine KD Haltiwanger RS Vogt TF 《Nature》2000,406(6794):369-375
Notch receptors function in highly conserved intercellular signalling pathways that direct cell-fate decisions, proliferation and apoptosis in metazoans. Fringe proteins can positively and negatively modulate the ability of Notch ligands to activate the Notch receptor. Here we establish the biochemical mechanism of Fringe action. Drosophila and mammalian Fringe proteins possess a fucose-specific beta1,3 N-acetylglucosaminyltransferase activity that initiates elongation of O-linked fucose residues attached to epidermal growth factor-like sequence repeats of Notch. We obtained biological evidence that Fringe-dependent elongation of O-linked fucose on Notch modulates Notch signalling by using co-culture assays in mammalian cells and by expression of an enzymatically inactive Fringe mutant in Drosophila. The post-translational modification of Notch by Fringe represents a striking example of modulation of a signalling event by differential receptor glycosylation and identifies a mechanism that is likely to be relevant to other signalling pathways. 相似文献
55.
Ya-nan Chen Yan-ping Bao Min Wang Xiao-feng Cai Lin-jing Wang Li-hua Zhao 《矿物冶金与材料学报》2016,23(3):276-282
The strategy that replacing part of MnS with BN was proposed in order to decrease the sulfur content in sulfur based free-cutting steel. The effects of BN and MnS inclusions on the microstructure and machinability of the steel were systematically investigated. The results show that most of the BN and MnS inclusions exist individually in the steel and only a small amount of them are in a composite state forming either isolated particles or clusters of particles. In the case of multi-phased steel, the theoretical calculation predicts that the volume of large BN particles should be 0.7 times of the volume of large MnS particles. The machinability of this type of BN and MnS alloy steel over a wide range of cutting speeds ranging from a low speed appropriate for drilling to a high speed appropriate for turning is confirmed as being equal to or superior to that of an MnS reference steel, even though the sulfur content in the composite steel is only half that of the MnS steel. The aptitude for cutting effect of 240 ppm nitrogen and 115 ppm boron in the composite steel is demonstrated to be equivalent or even better than 1000 ppm sulfur in MnS free-cutting steel. 相似文献
56.
Comparison of reduction disintegration characteristics of TiO<Subscript>2</Subscript>-rich burdens prepared with sintering process and composite agglomeration process 下载免费PDF全文
To reveal the impact of the composite agglomeration process (CAP) on the reduction disintegration properties of TiO2-rich ironmaking burden for a blast furnace, the reduction disintegration indices (RDIs), mineral constituents, and microstructure of the products prepared by the CAP and the traditional sintering process (TSP) were investigated. The results showed that, compared to the sinter with a basicity of 2.0 prepared by the TSP, the RDI+6.3 and the RDI+3.15 of the CAP product with the same basicity increased by 28.2wt% and 13.7wt%, respectively, whereas the RDI-0.5 decreased by 2.7wt%. The analysis of the mineral constituents and microstructure of the products indicated that the decreasing titanohematite content decreased the volume expansion during reduction. Meanwhile, the decreasing perovskite content decreased its detrimental effect on the reduction disintegration properties. In addition, the higher silicoferrite of calcium and aluminum (SFCA) content improved the strength of the CAP product. Together, these factors result in an improvement of the RDI of the CAP products. In addition, compared to the sinter, the reduced CAP products clearly contained fewer cracks, which also led to mitigation of reduction disintegration. 相似文献
57.
Numerous privacy-preserving issues have emerged along with the fast development of the Internet of Things. In addressing privacy protection problems in Wireless Sensor Networks(WSN), secure multi-party computation is considered vital, where obtaining the Euclidian distance between two nodes with no disclosure of either side’s secrets has become the focus of location-privacy-related applications. This paper proposes a novel Privacy-Preserving Scalar Product Protocol(PPSPP) for wireless sensor networks. Based on PPSPP, we then propose a Homomorphic-Encryption-based Euclidean Distance Protocol(HEEDP) without third parties. This protocol can achieve secure distance computation between two sensor nodes. Correctness proofs of PPSPP and HEEDP are provided, followed by security validation and analysis. Performance evaluations via comparisons among similar protocols demonstrate that HEEDP is superior; it is most efficient in terms of both communication and computation on a wide range of data types, especially in wireless sensor networks. 相似文献
58.
Classification is an important machine learning problem, and decision tree construction algorithms are an important class of solutions to this problem. Rain Forest is a scalable way to implement decision tree construction algorithms. It consists of several algorithms, of which the best one is a hybrid between a traditional recursive implementation and an iterative implementation which uses more memory but involves less write operations. We propose an optimized algorithm inspired by Rain Forest. By using a more sophisticated switching criterion between the two algorithms, we are able to get a performance gain even when all statistical information fits in memory. Evaluations show that our method can achieve a performance boost of 2.8 times in average than the traditional recursive implementation. 相似文献
59.
<正>To detect the deformation of the tunnel structure based on image sensor networks is the advanced study and application of spatial sensor technology.For the vertical settlement of metro tunnel caused by internal and external stress after its long period operation,the overall scheme and measuring principle of tunnel deformation detection system is introduced. The image data acquisition and processing of detection target are achieved by the cooperative work of image sensor,ARM embedded system.RS485 communication achieves the data transmission between ARM memory and host computer.The database system in station platform analyses the detection data and obtains the deformation state of tunnel inner wall,which makes it possible to early-warn the tunnel deformation and take preventive measures in time. 相似文献
60.
气泡在垂直向上流动液体中的形成 总被引:4,自引:1,他引:4
研究了液体垂直向上流动、气体水平引入时,导管端头处形成的气泡的尺寸大小。考察了液体平均流速、气体流量和导管直径对气泡脱离尺寸大小的影响。在力平衡假设的基础上,获得了预测气泡脱离尺寸的关系式,预测值与测量值比较,结果令人满意。 相似文献