Dissociation of the 〈001〉 Dislocations and Their Interactions with Dislocation Loops in Tetragonal BaTiO3

Dislocations in pressureless-sintered BaTiO₃ ceramics have been analyzed using transmission electron microscopy. Subjected to effective sintering stresses, dislocations were generated and multiplied in plastically deformed BaTiO₃ crystals by the Frank–Read mechanism from both single- and double-ended sources. This is represented by dislocations encompassing a series of square-like borders that shared a common center. All border dislocations exhibited the characteristic scallop shape. True dislocation line directions ( u ) were determined by trace analysis and Burgers vectors ( b ) by contrast analysis for the dislocations dissociated from b =〈001〉 into two half-partials following the type (I) reaction of     by climb on {001}. Dislocation interactions between the main dislocations created from plastic deformation and dislocation loops of b =〈100〉 or 〈110〉 forming condensation of intrinsic Schottky vacancies were also found to obey the type (IV) reaction of     , the type (V) reactions of     . Migrating dislocations and loops interacting mutually in several stages, illustrated schematically, before arriving at the configuration described by types (IV) and (V) were observed and discussed.     

Mangrove forests as a nature-based solution for coastal flood protection: Biophysical and ecological considerations

Nature-based coastal protection is increasingly recognised as a potentially sustainable and cost-effective solution to reduce coastal flood risk. It uses coastal ecosystems such as mangrove forests to create resilient designs for coastal flood protection. However, to use mangroves effectively as a nature-based measure for flood risk reduction, we must understand the biophysical processes that govern risk reduction capacity through mangrove ecosystem size and structure. In this perspective, we evaluate the current state of knowledge on local physical drivers and ecological processes that determine mangrove functioning as part of a nature-based flood defence. We show that the forest properties that comprise coastal flood protection are well-known, but models cannot yet pinpoint how spatial heterogeneity of the forest structure affects the capacity for wave or surge attenuation. Overall, there is relatively good understanding of the ecological processes that drive forest structure and size, but there is a lack of knowledge on how daily bed-level dynamics link to long-term biogeomorphic forest dynamics, and on the role of combined stressors influencing forest retreat. Integrating simulation models of forest structure under changing physical (e.g. due to sea-level change) and ecological drivers with hydrodynamic attenuation models will allow for better projections of long-term natural coastal protection.     

Study of UAV tracking based on CNN in noisy environment

Multimedia Tools and Applications - Recently, there are lots of tracking methods proposed to improve the performance of visual tracking in videos with challenging situations, such as background...     

微信小程序交互的智能鱼缸设计

随着近年来物联网和智能家居的快速发展,传统家居逐渐转型为智能家居。由于当代生活脚步的加快,许多人因为外出工作或是出游不能保证及时了解自己鱼缸的信息和在合适的时候对鱼进行投喂。为此,本文介绍一款智能鱼缸。该智能鱼缸利用微信小程序及Arduino平台,提供远程控制服务,使养鱼更加方便,用户体验更亲切。     

Phi zeolite synthesized by template-free method for selective catalytic reduction of NO

Nitrogen oxide (NO_x) is one of the major air pollutants. Using a copper-based zeolite with a chabazite structure (CHA) as a catalyst, the selective catalytic reduction (SCR) technology can effectively remove NO_x. This work introduces a low silica CHA type zeolite with structural defects (zeolite Phi, with Si/Al of 4.7). The zeolite Phi is synthesized through a hydrothermal method without adding any template, which is low-cost and environment-friendly. The Cu-exchanged Phi is abundant of surface acidity and isolated Cu²⁺, showing a superior low-temperature activity, a wide work temperature window and a good hydrothermal stability. The presence of Na or Mg decreases the surface acidity and isolated Cu²⁺. The hydrothermally aged Na,Cu/Phi and Mg,Cu/Phi present different levels of framework collapse, which correspondingly induces catalyst deactivation.     

Experimental measurements of the phase and group velocities of body waves in a transversely isotropic medium

In this study, we perform an experimental result for measurements of the body wave phase and group velocities in transversely isotropic media (TIM) by through-transmission technique. After comparing the experimental and theoretical first arrival times of the waves, a difference between the phase velocity and group velocity is observed. When the ratio between propagation distance (d) of the wave and the diameter (D) of transducer is 2.4 for measuring phase velocity and the point probes configuration for measuring group velocity, the accuracy in velocity estimation can reach the limit of system's resolution. However if d/D is 7.8, the wave will propagate with an intermediate velocity between the phase and group velocities. The rapid change of the wave velocity and waveform for qSV-wave propagation with the group velocity has been observed at the propagation direction near the cusps. Therefore, in order to reduce the error in group velocity estimation of qSV-waves, the optimum directions are suggested at 20 and 60°.     

Effects of laser beam energy and incident angle on the pulse laser welding of stainless steel thin sheet

This paper reports an experimental study of laser spot welding on stainless steel sheets. A pulsed Nd:YAG laser was used to weld the stainless steel specimen in the range of laser energy 0.6–1.2 J and incident angle 30–75° (the angle of the laser beam incident direction to the sheet surface). Metallography was applied to measure the cross-sectional size and shape of the welded spot. From the experimental results, it is found that as the laser energy increases, the penetration depth, bead length, and bead width of the welded spot increase. As the laser incident angle increases, the penetration depth and the bead width increase while the bead length decreases. The results illustrate that the shape and size of the welded spot depend not only on the laser energy, but also on the incident angle of laser beam.     

双曲线模型在某残积土地基沉降计算中的应用

对于残积土地基的沉降变形,实践证明采用压缩模量的计算结果往往偏大,应采用现场试验得到的变形模量来进行计算。为此,该文以广州某残积土地基的实测资料为例,对其非线性沉降采用双曲线模型来表示,所需计算参数则根据现场载荷试验来确定,最后将计算结果与试验结果进行对比。结果初步表明,双曲线模型法用于残积土地基的沉降计算是可行的。     

Robust estimation of walking robots velocity and tilt using proprioceptive sensors data fusion

Availability of the instantaneous velocity of a legged robot is usually required for its efficient control. However, estimation of velocity only on the basis of robot kinematics has a significant drawback: the robot is not in touch with the ground all the time, or its feet may twist. In this paper we introduce a method for velocity and tilt estimation in a walking robot. This method combines a kinematic model of the supporting leg and readouts from an inertial sensor. It can be used in any terrain, regardless of the robot’s body design or the control strategy applied, and it is robust in regard to foot twist. It is also immune to limited foot slide and temporary lack of foot contact.