Elastic Full Waveform Inversion Based on the Trust Region Strategy

In this paper, we investigate the elastic wave full-waveform inversion (FWI) based on the trust region method. The FWI is an optimization problem of minimizing the misfit between the observed data and simulated data. Usually, the line search method is used to update the model parameters iteratively. The line search method generates a search direction first and then finds a suitable step length along the direction. In the trust region method, it defines a trial step length within a certain neighborhood of the current iterate point and then solves a trust region subproblem. The theoretical methods for the trust region FWI with the Newton type method are described. The algorithms for the truncated Newton method with the line search strategy and for the Gauss-Newton method with the trust region strategy are presented. Numerical computations of FWI for the Marmousi model by the L-BFGS method, the Gauss-Newton method and the truncated Newton method are completed. The comparisons between the line search strategy and the trust region strategy are given and show that the trust region method is more efficient than the line search method and both the Gauss-Newton and truncated Newton methods are more accurate than the L-BFGS method.

SUSTAINABLE DESIGN IN PROJECT DELIVERY:A DISCUSSION ON CURRENT AND FUTURE TRENDS

Sustainability principles have become an integral part of the design and construc-tion process for many new construction projects. The selection of the project delivery method (PDM) is extremely important in the effective execution of the project, and plays a critical role in establishing communication and coordination between the key entities: owner, architect, and contractor. The goal of this paper is to hopefully serve as a starting point for further discussion to improve on the AEC industry’s current integration of sustainability principles in PDMs. The first step consists of an assessment of current project delivery systems from a sustainable design perspective. This is followed by a determination of the current limitations, and examination of the various disrup-tions in the industry. Various literature sources are analyzed to form a framework to discuss improvements and optimization strategies beyond the current system. Thereafter, proposed solutions are introduced at both stakeholders, as well as PDM scales. In this paper, the focus for the conducted analysis and proposed method-ologies is predicated on new construction projects instead of retrofits due to the resources available. However, the principles can similarly be applied to retro-fit scenarios as well, depending on the specific requirements of the individual project at play.

Development Strategy and Countermeasures of China's CBM Industry under the Goal of “Carbon Peak and Neutrality”

China’s coalbed methane(CBM) industry is in an extremely important “climbing period” and “strategic opportunity period”,which can be generally characterized by “three low and one small”:low degree of exploration and development,low adaptability of main technology,low return on investment and small development scale.Under the “carbon peak and neutrality” background,the development status of CBM industry is systematically combed.The resources,technology,management problems and reasons are analyzed.Strategies and countermeasures to accelerate the industrial development are put forward according to the factors such as efficient development of resources,major technical breakthrough,talent team training,policy formulation and implementation,return on investment and so on.The existing problems are as follows:(a) The overall occurrence conditions in China are complicated and the development is difficult compared with the other countries.(b) The research precision accuracy of CBM resource conditions is not enough.(c) The adaptability of technology is poor.(d) The management mode is not suitable.In view of these problems,this paper puts forward the “two steps” development strategy and the technical and management countermeasures of “five in one”.The corresponding “five in one” technology and management countermeasures are the formulation and implementation of relevant safeguard measures in accordance with the principle of collaborative innovation in five aspects:resources,technology,talents,policies and investment.Through the above measures,the dream and grand blueprint of CBM industry shall be realized.