Finite Element Analyses of Single-Edge Bend Specimens for J-R Curve Development

The fracture toughness resistance curve such as the J-integral resistance curve (J-R curve) is widely used in the integrity assessment and strain-based design of energy pipelines with respect to planar defects (i.e. cracks). Two studies about the development of the J-R curve are carried out and reported in this thesis. In the first study, the plastic geometry factor, i.e. the ηpl factor, used to evaluate J in a J-R curve test based on the single-edge bend (SE(B)) specimen is developed based on the three-dimensional (3D) finite element analysis (FEA). The main finding of this study is that besides the crack length, both the thickness and side grooves of the specimens have observable impacts on the ηpl factor. The ηpl factors obtained from 3D FEA are different from those obtained from two-dimensional (2D) FEA. The results of this study can improve the accuracy of the experimentally determined J-R curve and facilitate the use of non-standard (e.g. shallow-cracked) SE(B) specimens for the J-R curves testing. In the second study, 3D FEA is carried out on SE(B) specimens for which the J-R curves have been experimentally determined to develop the constraint-corrected J-R curves for X80 grade pipe steels. The constraint parameters considered in this study include Q, A2, h and Tz. Several different forms of the Q parameter that account for the correction for the load and/or bending stresses are considered. It is observed that three constraint parameters, namely QBM1, Tz and A2, lead to reasonably accurate constraint-corrected J-R curve for a wide range of crack extension compared with the J-R curves experimentally determined from two shallow cracked SE(B) specimens. On the other hand, the constraint-corrected J-R curve based on constraint parameters QHRR, QBM2 and Qm lead to a relatively large error of prediction. The approach for constructing the constrain-corrected J-R curve can be used to develop the structure-specific J-R curve based on those obtained from small-scale test specimens to improve the accuracy of the structural integrity assessment

Evaluating the Legal Issues of Internet Service Providers in China -- A Comparative Copyright Analysis of Chinese ISPs, the U.S. ISPs, and Japanese ISPs

This thesis is motivated by a legal challenge in the area of Chinese copyright protection: Baidu, which was considered a disaster by the copyright owners in China. To solve this legal challenge, the Chinese could learn from the legal experience of Japan and the U.S. regarding this issue. The traditional ISP legal system provides a passive-reactive approach to the secondary copyright liability of ISPs. However, the Baidu issue in China indicates that a passive-reactive ISP model is not able to prevent copyright infringement. Recent cases in China and the U.S. reflect a new trend that the judicial branch adopts an active-preventive approach to ISP issues. This thesis organizes the various legal theories, statutes and cases that may be relevant in an ISP dispute into a framework that may be used to more clearly and effectively evaluate the legal issues of ISPs, with a focus on the proposal for Chinese copyright legal reform. This thesis consists of two parts. The first part examines ISP-related law and cases in the U.S., China and Japan. The second part comparatively analyzes the Baidu issue and suggests possible solutions for Chinese legislature

Evaluating a Unified Intellectual Property System of Internet Service Providers in the Electronic Commerce Law -- A Comparative Research Between China and the U.S.

As the Electronic Commerce Law went into effective in Jan. 1st, 2019, not only did China establish a unified IP protection system of ISPs, but also set up a blueprint for a comprehensive mechanism of ISPs for the future improvement. The question is whether this new law can effectively prevent the serious IP infringement issues of ISPs and therefore successfully improve the IP protection in China. To answerer this question, the dissertation analyzes the development of the mechanism of ISPs in copyright and trademark regimes before the Electronic Commerce Law, and seeks to demonstrate the impact of the Electronic Commerce Law for ISPs in China through a comparatively research. Before the Electronic Commerce Law, China followed a passive-reactive approach of ISPs from the U.S. However, as the online piracy and counterfeit issues continued to grow in the last decade, Chinese legislation decided to shift to an active-preventive approach of ISPs in the Electronic Commerce Law. By comparatively examining the copyright and trademark infringement issues of ISPs between China and the U.S., this dissertation analyzes the benefits and drawbacks of these two approaches, and seeks to demonstrate how an active-preventive approach may prevent infringements more effectively than a passive-reactive approach in China. To conclude a solution for Chinese legislation to improve the unified IP protection system of ISPs, this dissertation examines several active-preventive approaches in different jurisdictions through different cases of ISPs. As a suggestion for the future legal reform, this dissertation explores the possibility of whether Chinese legislation can legally transplant the Blocking Injunction into the unified IP protection system of ISPs, which may improve the mechanism of ISPs and provide a better IP protection in China

Numerical Studies for Improving Fracture Toughness Resistance Curve Testing Using Single-Edge (Notched) Tension Specimens

The fracture toughness resistance curve, i.e. the J-integral resistance curve (J-R curve) or the crack tip opening displacement resistance (CTOD-R) curves, is widely used in the integrity assessment and strain-based design of energy pipelines with respect to planar defects (i.e. cracks). This thesis deals with issues related to the experimental determination of the J(CTOD)-R curves using the newly-developed single-edge (notched) tension (SE(T)) specimens. In the first study, the plastic geometry factor, i.e. the ηpl factor, used to evaluate J in a J-R curve test based on the SE(T) specimen is developed based on the three-dimensional (3D) finite element analysis (FEA). In the second study, 3D FEA is carried out on SE(T) specimens to develop the plastic constraint factor, i.e. the m factor, used to evaluate CTOD from J. The third study reported in this thesis focuses on the compliance equation, which relates the crack length and specimen’s compliance (i.e. inverse of stiffness) in the J(CTOD)-R curves testing. Three-dimensional FEA of clamped SE(T) specimens is performed to examine the accuracy of the crack mouth opening displacement (CMOD) compliance equations reported in the literature. In the fourth study, the impact of the crack front curvature on the J-R curve measured from the SE(T) specimen is investigated through systematic elastic-plastic 3D FEA of SE(T) specimens containing both straight and curved crack fronts. The last study reported in this thesis is focused on developing the effective thickness that takes accounts for the side grooves effects on the estimations of the stress intensity factor (K) and J for SE(T) specimens. The outcomes of these studies will facilitate and improve the evaluation of J(CTOD)-R curves using the side-grooved SE(T) specimens

Rockstar Effect in Distributed Project Management on GitHub Social Networks

The internet has become increasingly social, opening up new space for online collaboration and distributed project management. Decentralized management techniques such as open-source software, distributed development, and software-as-a-service allow software developers to easily connect online and to solve complex problems collaboratively. Online rockstars, who are well-respected in a community and are followed by numerous other users, often influence the decisions of project managers and clients in software development. Understanding the effects of these rockstars can greatly facilitate technology development and adoption in distributed project management. This paper presents a study of the GitHub social network to understand rockstar effect in distributed project management. In GitHub, developers often collaborate in distributed teams and interact in their online social networks, which evolve with the popularity of software repositories and actions of rockstars. To understand how rockstars influence the popularity of software repositories, this research constructed temporal social networks from 2015 to 2017 between 13.5 million software repositories and 2.6 million GitHub users and examined the evolvement of the behavior of 245,501 rockstar followers. The results show that the more followers a rockstar has, the more triadic events there are in his/her participated repository. And the difference of a number of events between top rockstar and other rockstars is much higher in participative events than in contributive events, indicating higher triadic influence from top rockstar in those events for technology development in distributed project management

Patch-based Progressive 3D Point Set Upsampling

We present a detail-driven deep neural network for point set upsampling. A high-resolution point set is essential for point-based rendering and surface reconstruction. Inspired by the recent success of neural image super-resolution techniques, we progressively train a cascade of patch-based upsampling networks on different levels of detail end-to-end. We propose a series of architectural design contributions that lead to a substantial performance boost. The effect of each technical contribution is demonstrated in an ablation study. Qualitative and quantitative experiments show that our method significantly outperforms the state-of-the-art learning-based and optimazation-based approaches, both in terms of handling low-resolution inputs and revealing high-fidelity details.Comment: accepted to cvpr2019, code available at https://github.com/yifita/P3