Thermal behavior of elastic columns with second-mode imperfections

Pin-ended columns having an initial imperfection in a second buckling mode and subjected to thermal loading have been studied in this paper. Based on a nonlinear relationship between strains and displacements, the buckling equilibrium equations are given with the energy method. Then the formulae for the axial compression and transversal displacement are presented. The relationship between the anti-symmetric imperfection and the axial compression has been studied along with the effect of elevated temperature on the initial imperfection. The response of the column in fire to the modified slenderness ratio is investigated. The proposed method has the potential to provide more detailed information for column designs and thus be deployed in future research to minimize the need for expensive laboratory testing

Mobility analysis of generalized angulated scissor-like elements with the reciprocal screw theory

This paper deals with the planar closed loop linkage consisting of a series of scissor-like elements connected by revolute joints. Because every generalized angulated element (GAE) subtends a constant angle during the motion, every angulated link was assumed as a PRRP linkage which has two prismatic joints and two revolute joints. Therefore, the two PRRP linkages of the GAE are individually movable with a single degree of freedom. The mobility of two types of GAEs was investigated with the method based on the screw theory. It has been proven that both types of GAEs are movable because the terminal constraints exerted to the common joint by the two linkages are equal

Motion analysis of a foldable barrel vault based on regular and irregular Yoshimura Origami

This paper investigates the geometry of a foldable barrel vault with Yoshimura Origami patterns during the motion. On the base of the geometry analysis of the origami unit, the radius, span, rise, and longitudinal length of the foldable barrel vault with regular Yoshimura Origami pattern in all configurations throughout the motion are determined. The results show that the radius of curvature and the span increase during deployment. But the rise increases first, followed by a decrease with increasing fold angle. Furthermore, the influence of the apex angle of the origami unit and the numbers of triangular plates in the span direction on the geometric parameters is also investigated. Finally, the method to obtain the rise and span of the barrel vault with irregular origami pattern is also given

On the Local Discontinuous Galerkin Method for Linear Elasticity

Following Castillo et al. (2000) and Cockburn (2003), a general framework of constructing discontinuous Galerkin (DG) methods is developed for solving the linear elasticity problem. The numerical traces are determined in view of a discrete stability identity, leading to a class of stable DG methods. A particular method, called the LDG method for linear elasticity, is studied in depth, which can be viewed as an extension of the LDG method discussed by Castillo et al. (2000) and Cockburn (2003). The error bounds in L2-norm, H1-norm, and a certain broken energy norm are obtained. Some numerical results are provided to confirm the convergence theory established

The Improvement of 3D Traveltime Tomographic Inversion Method

As 3D high-precision seismic exploration is more and more widely used in seismic data acquisition, traveltime tomographic inversion based on first arrivals is developed from 2D to 3D. However, magnanimity data of 3D traveltime inversion brings about the problem of data storage; the absence of first arrivals with near offset reduces the precision of shallow layer; the utilization of prior information, such as small refraction and micro-logging data, can improve the precision of 3D traveltime inversion. Therefore, we make some improvements in 3D traveltime inversion method. We take compression storage for large and sparse matrix, propose virtual receivers technology, and add prior information to tomographic inversion linear equations. The application in 3D real data indicates that the improvements can effectively improve 3D traveltime tomographic inversion.Key words: 3D seismic exploration; 3D traveltime inversion method; 3D traveltime tomographic inversio

Complex Impacts of Wars on Global Sustainable Development in a Metacoupled World

Wars and armed conflicts have had profound impacts on local and global sustainable development in an interconnected world. However, evidence on the impacts of wars is fragmented and little attention has been paid to the impacts on the 17 UN’s Sustainable Development Goals (SDGs), a unifying framework for achieving global sustainable development. This perspective synthesizes the scattered information to provide a holistic analysis and highlight the applications of remote sensing in assessing the impacts of wars on global sustainable development in a metacoupling world. Wars have complex impacts on all 17 SDGs, which cascade beyond conflict zones and spillover to adjacent and distant countries worldwide. Satellite remote sensing can play a significant role in monitoring environmental and socioeconomic impacts such as crop production, deforestation, pollution, urban damage, and migration. Remote sensing can provide timely, spatiotemporal, large-scale data for sustainable development impact assessment of conflict zones with restricted access. As 2023 is the middle point of the time period (2015-2030) for the 2030 Agenda for Sustainable Development, it is urgent to conduct more quantitative assessments for wars around the world such as the Russia-Ukraine war. Enhancing remote sensing applications in war-related impact assessment with advanced models and frameworks is very helpful and significant. It is also critical to rethink about global governance by incorporating the ripple effects of wars for policy adjustments to achieve SDGs by 2030

First Arrival Time Auto-Picking Method Based on Multi-Time Windows Energy Ratio

First arrival time auto-picking technique plays an important role in seismic exploration. It is widely used in shallow layer tomography and static correction. Conventional method that based on sliding time windows energy ratio is not stable. Here a new method based on multi-time windows energy ratio is proposed. Combining with automatic quality control and phase-domain first arrival estimation technique, our method performs perfectly on seismic records of normal S/N ratio. In the computational process of conventional sliding time windows energy ratio method, first arrivals are often determined by the maximum energy ratio of two adjacent sliding time windows. It is well known that for low S/N ratio data the conventional picking is not effective, and for high S/N ratio data weak reflections are hardly detected. The reason is that first arrival time does not correspond to the maximum energy ratio. Meanwhile conventional method sometime picks local secondary extreme of energy ratio. The new method of multi-time windows energy ratio method takes both maximum and local secondary extreme in consideration. Hence new method promotes the stability and accuracy of first arrival picking. Combined with automatic quality control and phase-domain first arrival estimation, the new method performs well in its application in the middle part of Dzungarian Basin(Northwest China)