A simple permanent deformation model of rockfill materials

Existing experimental results have shown that using a semi-log linear relationship between the permanent volumetric strain and cyclic number underestimates the volumetric deformation of rockfill materials with a large cyclic number, and that the error increases with the confining pressure. The existing permanent deformation models are not suitable for the seismic safety analysis of high dams during strong earthquakes. In this study, a series of large-scale triaxial cyclic loading tests of rockfill materials were performed, and a new permanent deformation model of rockfill materials was developed and validated with three kinds of rockfill materials. The results show that the proposed model can properly reflect the general features of the permanent deformation of rockfill materials. The main features of the model are as follows: (1) relations between the cyclic number and permanent volumetric/shear strain are described by hyperbolic functions, which can avoid underestimating the volumetric deformation occurring during strong earthquakes; (2) the model can capture the effect of the mean effective stress on the permanent volumetric strain, with greater confining pressure correlating to greater permanent volumetric deformation, and the permanent volumetric strain under low confining pressure near the dam crest can be well represented; and (3) the model can reflect the effect of the consolidation stress ratio on the permanent shear strain.     

网络流水印安全威胁及对策综述

与基于流量特性的被动流关联技术相比,基于流水印的主动流关联技术在跳板攻击溯源和匿名用户追踪等方面准确率更高、误报率更低,观测时间也更短.首先介绍基于包载荷、流速率、包时间等载体的典型流水印技术;然后阐述流水印技术所面临的多流攻击、均方自相关攻击、K-S(Kolmogorov-Simirnov)测试、PNR(Peng Ning Reeves)攻击、时延规范化攻击、BACKLIT检测、已知流攻击、输出检测和复制攻击等安全威胁;接着分析流水印技术在抵御多流攻击、均方自相关攻击、K-S测试和BACKLIT检测等各类安全威胁时所主要采取的嵌入位置随机化、水印信息重排序、“一流一印”、“一流一码”、嵌入延迟最小化等方法和手段;最后对流水印安全威胁与对策的研究热点及发展趋势进行总结和展望,认为现有流水印技术的抗攻击能力有待进一步加强、流水印隐蔽性的统一评价体系与指标缺乏、其他载体及多重载体流水印技术的攻击手段亟待研究.     

颤振征兆早期识别的模糊信息融合法

基于切削试验探讨颤振征兆早期识别的模糊信息融合方法。试验中在同一个测量区内使用了功率传感器和加速度传感器,利用模糊数学与Dempster-Shafer证据论相结合的方法对两种传感器信息进行了分析融合,对切削状态进行了描述。试验证实:利用证据理论与模糊推理相结合的信息融合方法进行颤振征兆的早期模糊识别得出的目标切削状态的隶属度介于单一征兆隶属度之间,对过于敏感的传感器,会考虑其他传感器的信息予以修正,降低其评价隶属度;对于不敏感传感器,会考虑其他传感器的信息予以补偿。这种方法弥补了最大隶属度原则的缺陷,即在模糊推理中,系统对某一状态的隶属程度实际上是由模式特征集中贡献最大的那个特征决定的,而没有用到其他特征提供的信息,这说明证据理论与模糊推理相结合的信息融合方法在进行颤振征兆早期识别时具有更高的可靠度。     

中碳锰铁矿中锰和铁的连续测定研究

文章就中锰矿中锰和铁的测定进行了研究。在pH为5．4的六亚甲基四胺-盐酸缓冲介质中,以Cu＋EDTA—PAN-6S作混合指示剂,用EDTA络合滴定锰;在pH为5．0的HAc-NaAc缓冲介质中,以PAN-6S为指示刺,甩EDTA络合滴定铁;终点变色敏锐,准确度高,锰、铁比例在1：10～10：1范围之间相互无影响。此方法可用于中锰矿中锰和铁的连续测定,结果令人满意。     

Thyroxine Regulates the Opening of the Organ of Corti through Affecting P-Cadherin and Acetylated Microtubule

Different serum thyroxine levels may influence the morphology of the inner ear during development. A well-developed organ of Corti (OC) is considered to be critical to the function of hearing. In our study, we treated mice with triiodothyronine (T3) and found that the opening of the OC occurred sooner than in control mice. We also observed an increased formation of acetylated microtubules and a decrease in the adhesion junction molecule P-cadherin the during opening of the OC. Our investigation indicates that thyroxin affects P-cadherin expression and microtubule acetylation to influence the opening of the OC.     

Genetic Diversity Analysis Reveals Potential of the Green Peach Aphid (Myzus persicae) Resistance in Ethiopian Mustard

Brassica carinata (BBCC, 2n = 34) is commonly known as Ethiopian mustard, Abyssinian mustard, or carinata. Its excellent agronomic traits, including resistance to biotic and abiotic stresses, make it a potential genetic donor for interspecific hybridization. Myzus persicae (green peach aphid, GPA) is one of the most harmful pests of Brassica crops, significantly effecting the yield and quality. However, few aphid-resistant Brassica crop germplasms have been utilized in breeding practices, while the underlying biochemical basis of aphid resistance still remains poorly understood. In this study, we examined the genetic diversity of 75 B. carinata accessions and some plant characteristics that potentially contribute to GPA resistance. Initially, the morphological characterization showed abundant diversity in the phenotypic traits, with the dendrogram indicating that the genetic variation of the 75 accessions ranged from 0.66 to 0.98. A population structure analysis revealed that these accessions could be grouped into two main subpopulations and one admixed group, with the majority of accessions (86.67%) clustering in one subpopulation. Subsequently, there were three GPA-resistant B. carinata accessions, BC13, BC47, and BC51. The electrical penetration graph (EPG) assay detected resistance factors in the leaf mesophyll tissue and xylem. The result demonstrated that the Ethiopian mustard accessions were susceptible when the phloem probing time, the first probe time, and the G-wave time were 20.51–32.51 min, 26.36–55.54 s, and 36.18–47.84 min, respectively. In contrast, resistance of the Ethiopian mustard accessions was observed with the phloem probing time, the first probe time, and G-wave time of 41.18–70.78 min, 181.07–365.85 s, and 18.03–26.37 min, respectively. In addition, the epidermal characters, leaf anatomical structure, glucosinolate composition, defense-related enzyme activities, and callose deposition were compared between the resistant and susceptible accessions. GPA-resistant accessions had denser longitudinal leaf structure, higher wax content on the leaf surface, higher indole glucosinolate level, increased polyphenol oxidase (PPO) activity, and faster callose deposition than the susceptible accessions. This study validates that inherent physical and chemical barriers are evidently crucial factors in the resistance against GPA infestation. This study not only provide new insights into the biochemical basis of GPA resistance but also highlights the GPA-resistant B. carinata germplasm resources for the future accurate genetic improvement of Brassica crops.     

基于感兴趣区域的螺栓位姿及尺寸检测研究

为了提高工业生产中螺栓定位抓取的效率和准确性,提出基于感兴趣区域的螺栓位姿及尺寸检测方法。首先利用YOLOv5目标识别算法对螺栓目标进行识别,将识别出的目标区域截取为感兴趣区域。再利用中值滤波和二值化方法对ROI进行预处理,采用Canny改进算法检测目标轮廓。通过最优拟合直线算法获取螺栓的倾斜角度,并用矩特征算法求解出螺栓重心位置。最后采用霍夫两直线段最短距离算法检测螺栓直径。经过实验验证采用YOLOv5目标识别算法的识别准确率达到92.7%,螺栓倾斜角度的检查误差为±1.2°,螺栓直径的检测误差率为±5.5%,实现了对螺栓位姿和尺寸的识别。     

基于UG Open C的FANUC M-16iB/20工业机器人动态仿真

采用UG和其二次开发接口Open C API,对日本FANUC公司生产的M-16iB/20型机器人建立了三维运动仿真模型.采用Denavit-Hartenberg方法建立了连杆坐标系下的机器人运动学模型,并采用Open C编写了运动学正、逆解的程序,阐述了模型的建立方法及过程,实现了在UG环境下的机器人按指定路径的运动仿真.最后总结了该仿真系统的主要特点,为机器人动力学及离线编程技术的研究打下了基础.     

基于Turbo PMAC的平面受控五杆机构PID控制分析

对平面受控五杆机构建立PID控制系统.通过分析PMAC控制算法流程,对控制系统进行了参数整定.整定曲线表明,PMAC PID控制平面受控五杆机构具有很好的稳定性和响应性,能够满足高速度、高精度的工况要求.     

R407C组分分离特性实验研究

针对H407C三元混合工质的非共沸特性,在组分分离实验台上进行了相应的分离实验。结果表明：不同的分离器在不同的加热功率下的分离效果不同;经过组分分离实验,R407C的组分有明显的改变,并且在一定的实验工况下可以得到较好的分离效果。经分离后,轻、重组分最高比例可达48．71％和98．23％。