TA32钛合金板成形性能与电磁辅助弯曲成形实验研究

由于TA32钛合金板室温成形性差、精度难以保证,开展了电磁辅助弯曲成形方法的实验研究,通过拉伸和电磁成形实验探究了TA32钛合金的力学性能和成形性能,获得了TA32钛合金板在准静态和动态拉伸下的应力、应变关系,给出了在电磁成形状态下的成形极限应变,阐明了电磁成形作用下的TA32钛合金的增塑机制。采用匀压式电磁辅助弯曲成形的方法对TA32钛合金板开展实验研究,结果表明:电磁辅助弯曲成形方法能够有效地提高弯曲件的成形精度,并且在一定条件下,放电能量越高,贴模效果越好、成形精度越高。带压紧翼的弯曲件的变形区外层过度伸长而产生减薄并开裂,不带压紧翼的弯曲件通过合理地控制放电电压能够获得较好的成形效果。     

FGSC-23：面向深度学习精细识别的高分辨率光学遥感图像舰船目标数据集

目的 基于光学遥感图像的舰船目标识别研究广受关注,但是目前公开的光学遥感图像舰船目标识别数据集存在规模小、目标类别少等问题,难以训练出具有较高舰船识别精度的深度学习模型。为此,本文面向基于深度学习的舰船目标精细识别任务研究需求,搜集公开的包含舰船目标的高分辨率谷歌地球和GF-2卫星水面场景遥感图像,构建了一个高分辨率光学遥感图像舰船目标精细识别数据集（fine-grained ship collection-23,FGSC-23）。方法 将图像中的舰船目标裁剪出来,制作舰船样本切片,人工对目标类别进行标注,并在每个切片中增加舰船长宽比和分布方向两类属性标签,最终形成包含23个类别、4 052个实例的舰船目标识别数据集。结果 按1：4比例将数据集中各类别图像随机划分为测试集和训练集,并展开验证实验。实验结果表明,在通用识别模型识别效果验证中,VGG16（Visual Geometry Group 16-layer net）、ResNet50、Inception-v3、DenseNet121、MobileNet和Xception等经典卷积神经网络（convolutional neural network,CNN）模型的整体测试精度分别为79.88%、81.33%、83.88%、84.00%、84.24%和87.76%;在舰船目标精细识别的模型效果验证中,以VGG16和ResNet50模型为基准网络,改进模型在测试集上的整体测试精度分别为93.58%和93.09%。结论 构建的FGSC-23数据集能够满足舰船目标识别算法的验证任务。     

Effect of Signature Sequence on the Performance of an Asynchronous Multiple-Chip-Rate DS/CDMA System

The effects of signature sequence on the performance of an asynchronousmultiple-chip-rate (MCR)-DS/CDMA system are considered.The equations for the multiple access interference (MAI)and the variance of the MAI are developed.The bit error rate is derived by using the Gaussianapproximation.The deterministic signature sequences such as maximal-lengthsequences and Gold sequences are compared with random signature sequencesin terms of the variance of the MAI and bit error rate.We find that the performance of signature sequences in an asynchronousMCR-DS/CDMA system depends not onlyon the crosscorrelation properties of sequences but also on the carrierfrequencyseparation between the interfering and desired users.     

Chromosomal localization of mouse Cenpa gene

Using a previously isolated mouse centromere protein A (Cenpa) probe, we have localized the gene to the proximal region of mouse Chromosome 5, between the known Il6 and Yes1 loci near [Adra2C-D5H4S43-Hdh]. Comparison of this localization with that of human CENPA, which maps to chromosome 2, is consistent with the presence of a new region of conserved synteny between the two species.     

Regularization parameter estimation for feedforward neural networks

Under the framework of the Kullback-Leibler (KL) distance, we show that a particular case of Gaussian probability function for feedforward neural networks (NNs) reduces into the first-order Tikhonov regularizer. The smooth parameter in kernel density estimation plays the role of regularization parameter. Under some approximations, an estimation formula is derived for estimating regularization parameters based on training data sets. The similarity and difference of the obtained results are compared with other work. Experimental results show that the estimation formula works well in sparse and small training sample cases.     

Inhibitory effect of Asparagus cochinchinensis on tumor necrosis factor-alpha secretion from astrocytes

We investigated whether an aqueous extract of Asparagus cochinchinensis Merrill (Liliaceae) roots (ACAE) inhibits secretion of tumor necrosis factor-alpha (TNF-alpha) from primary cultures of mouse astrocytes. ACAE dose-dependently inhibited the TNF-alpha secretion by astrocytes stimulated with substance P (SP) and lipopolysaccharide (LPS). IL-1 has been shown to elevate TNF-alpha secretion from LPS-stimulated astrocytes while having no effect on astrocytes in the absence of LPS. We therefore investigated whether IL-1 mediated inhibition of TNF-alpha secretion from astrocytes by ACAE. Treatment of ACAE to astrocytes stimulated with both LPS and SP decreased IL-1 secretion. Moreover, incubation of astrocytes with IL-1 antibody abolished the synergistic cooperative effect of LPS and SP. These results suggest that ACAE may inhibit TNF-alpha secretion by inhibiting IL-1 secretion and that ACAE has a antiinflammatory activity in the central nervous system.     

高温合金激光表面熔掺Y_2O_3质点的研究

本文通过激光辐照的方法,研究了在高温合金试样表面掺杂Y_2O_3质点的可能性、均匀程度与激光辐照参数的关系。结果表明,当预涂粉末数量为0.035g/cm~2和0.059g/cm~2时,选择功率密度为1.76×10~4w/cm~2,扫描速度为0.36m/min时,可获得Y_2O_3质点在熔掺区中宏观上的均匀分布,其氧化钇的含量达1.2～2.0Wt％。     

System reliability analysis of an N-version programming application

This paper presents a quantitative reliability analysis of a system designed to tolerate both hardware and software faults. The system achieves integrated fault tolerance by implementing N-version programming (NVP) on redundant hardware. The system analysis considers unrelated software faults, related software faults, transient hardware faults, permanent hardware faults, and imperfect coverage. The overall model is Markov in which the states of the Markov chain represent the long-term evolution of the system-structure. For each operational configuration, a fault-tree model captures the effects of software faults and transient hardware faults on the task computation. The software fault model is parameterized using experimental data associated with a recent implementation of an NVP system using the current design paradigm. The hardware model is parameterized by considering typical failure rates associated with hardware faults and coverage parameters. The authors results show that it is important to consider both hardware and software faults in the reliability analysis of an NVP system, since these estimates vary with time. Moreover, the function for error detection and recovery is extremely important to fault-tolerant software. Several orders of magnitude reduction in system unreliability can be observed if this function is provided promptly     

Effect of MoS2-based composite coatings on tribological behavior and efficiency of gear

MoS₂-based Ti composite coatings were deposited on the SCM420 alloy and gears using an RF magnetron sputtering (RFMS) system. While MoS₂ coating had been coated on the silicon substrate. The coatings structures were compared to each other to find the effect of Ti. The composite coatings have been tested in a ball-on-disk tribometer to investigate tribological behavior at various conditions. The scratch test was conducted to characterize adhesion force between composite coatings and substrates. The structure of the coatings has been extensively studied by a variety of techniques, including optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM), etc. The composite coatings were also applied to the gears of a reduction gearbox. The efficiency of uncoated and MoS₂-based Ti coated gear was measured and compared at various input rotating speed under absorption oil film condition. It was found that the efficiency of gear had significantly improved after MoS₂-based Ti composite coatings deposition.