Investigation of Electrotribological and Arc Erosion Behavior of Cu-15vol.%Cr in situ Composite

Electrotribological and arc erosion behavior of Cu-15vol.%Cr in situ composite was investigated in terms of coefficient of friction, interfacial resistance, bulk temperature, and wear rate as a function of normal pressure, sliding speed, and electrical current. Microstructural change due to electrical sliding was studied to understand wear mechanisms. Cu-15vol.%Cr in situ composite was selected in this research because it exhibits an excellent combination of mechanical strength and electrical/thermal conductivity. It was found that the average coefficient of friction decreased with increasing electrical current under dry electrical sliding. The average coefficient of friction was lower under lubricated electrical sliding than that under dry electrical sliding, but it increased with increasing electrical current. There are no significant effects of normal pressure and sliding speed on coefficient of friction under dry electrical sliding. Under lubricated electrical sliding, the coefficient of friction decreased with increasing normal pressure, but it did not change significantly with sliding speed. Both static and dynamic interfacial resistance decreased slightly with increasing normal pressure and the dynamic interfacial contact resistance decreased with increasing electrical current. The openness of circuit decreased with increasing normal pressure, increased with increasing sliding speed, and electrical current. The bulk temperature increased with increasing electrical current for both dry and lubricated electrical sliding. The non-electrical wear rate of the composite increased with increasing normal pressure and decreased with increasing sliding speed. The electrical wear rate decreased with increasing electrical current under dry electrical sliding, whereas the wear rate increased with increasing electrical current under lubricated electrical sliding. The effects of normal pressure and sliding speed on the wear rate of the composite under both dry and lubricated electrical sliding are dependent upon the level of electrical current. The sliding-induced subsurface deformation occurred not only in the sliding direction but also in the lateral directions perpendicular to the sliding direction. The complex deformation mode was revealed clearly by the morphological change of the ribbon-like filaments. The thickness of the subsurface deformation layer increased with increasing normal pressure and sliding speed under dry non-electrical sliding. The thickness of the subsurface deformation layer decreased with increasing electrical current under dry electrical sliding, whereas the thickness increased with increasing electrical current under lubricated electrical sliding. A hardened surface layer and less damage on the subsurface layer were accounted for reduction in wear rate as electrical current was applied

Investigation of Electrotribological and Arc Erosion Behavior of Cu-15vol.%Cr in situ Composite

Electrotribological and arc erosion behavior of Cu-15vol.%Cr in situ composite was investigated in terms of coefficient of friction, interfacial resistance, bulk temperature, and wear rate as a function of normal pressure, sliding speed, and electrical current. Microstructural change due to electrical sliding was studied to understand wear mechanisms. Cu-15vol.%Cr in situ composite was selected in this research because it exhibits an excellent combination of mechanical strength and electrical/thermal conductivity. It was found that the average coefficient of friction decreased with increasing electrical current under dry electrical sliding. The average coefficient of friction was lower under lubricated electrical sliding than that under dry electrical sliding, but it increased with increasing electrical current. There are no significant effects of normal pressure and sliding speed on coefficient of friction under dry electrical sliding. Under lubricated electrical sliding, the coefficient of friction decreased with increasing normal pressure, but it did not change significantly with sliding speed. Both static and dynamic interfacial resistance decreased slightly with increasing normal pressure and the dynamic interfacial contact resistance decreased with increasing electrical current. The openness of circuit decreased with increasing normal pressure, increased with increasing sliding speed, and electrical current. The bulk temperature increased with increasing electrical current for both dry and lubricated electrical sliding. The non-electrical wear rate of the composite increased with increasing normal pressure and decreased with increasing sliding speed. The electrical wear rate decreased with increasing electrical current under dry electrical sliding, whereas the wear rate increased with increasing electrical current under lubricated electrical sliding. The effects of normal pressure and sliding speed on the wear rate of the composite under both dry and lubricated electrical sliding are dependent upon the level of electrical current. The sliding-induced subsurface deformation occurred not only in the sliding direction but also in the lateral directions perpendicular to the sliding direction. The complex deformation mode was revealed clearly by the morphological change of the ribbon-like filaments. The thickness of the subsurface deformation layer increased with increasing normal pressure and sliding speed under dry non-electrical sliding. The thickness of the subsurface deformation layer decreased with increasing electrical current under dry electrical sliding, whereas the thickness increased with increasing electrical current under lubricated electrical sliding. A hardened surface layer and less damage on the subsurface layer were accounted for reduction in wear rate as electrical current was applied

Development of Space-Time-Controlled Multi-Stage Pulsed Magnetic Field Forming and Manufacturing Technology at the WHMFC*

In November 2011, the Project of Basic Research of Forming by Space-Time-Controlled Multi-Stage Pulsed Magnetic Field (Stic-Must-PMF) was supported by the National Basic Research Program of China (973 Project, 2011.11-2016.08). It is aimed at achieving breakthroughs in manufacturing technology to solve current problems in forming largescale and complex sheet and tube parts and components, imposed by the limitations of existing equipment and materials forming properties. The objective of our research group focuses on the design principles and structural layout optimization of Stic-Must-PMF facility. And this paper will report the development of Stic-Must-PMF forming and manufacturing technology at the Wuhan National High Magnetic Field Center (WHMFC) including numerical modeling, experimental setup and experimental studies

Damage modelling: the current state and the latest progress on the development of creep damage constitutive equations for high Cr steels

This paper reviews the fundamentals of the development of creep damage constitutive equations for high Cr steels including (1) a concise summary of the characteristics of creep deformation and creep damage evolution and their dependence on the stress level and the importance of cavitation for the final fracture; (2) a critical review of the state of art of creep damage equation for high Cr steels; (3) some discussion and comments on the various approaches; (4) consideration and suggestion for future work. It emphasises the need for better understanding the nucleation, cavity growth and coalesces and the theory for coupling method between creep cavity damage and brittle fracture and generalisatio

An Analysis of Chinese Young People’s Code-Switching in Online Communication from the Perspective of Pragmatic Identity Theory

Existing studies on code-switching have mostly focused on the study of linguistic features and social functions, and few studies have paid attention to the relationship between the use of code-switching and identity construction and psychological states in different contexts. Based on Pragmatic Identity Theory, taking Wechat moments as an example, this study adopts a combination of quantitative and qualitative methods to explore Chinese young people’s use of code-switching to construct multiple pragmatic identities in different contexts and their underlying psychological motivations. By analyzing 216 pieces of the Wechat moments’ data, it is found that code-switching mainly fulfills the three functions of academic communication, hobby exchange and daily sharing. The study found that with strategic code-switching, Chinese young people constructed five non-conventional pragmatic identities in Wechat moments: academic help-seekers, hobby enthusiasts, hobby critics, life sharers and high-end sharers. This study analyzes the role of code-switching in pragmatic identity construction of Chinese young people, thus offering a new research perspective for understanding the social psychology and identity construction of contemporary youth

Using tweets to help sentence compression for news highlights generation

We explore using relevant tweets of a given news article to help sentence com-pression for generating compressive news highlights. We extend an unsupervised dependency-tree based sentence compres-sion approach by incorporating tweet in-formation to weight the tree edge in terms of informativeness and syntactic impor-tance. The experimental results on a pub-lic corpus that contains both news arti-cles and relevant tweets show that our pro-posed tweets guided sentence compres-sion method can improve the summariza-tion performance significantly compared to the baseline generic sentence compres-sion method.

DxFormer: A Decoupled Automatic Diagnostic System Based on Decoder-Encoder Transformer with Dense Symptom Representations

Diagnosis-oriented dialogue system queries the patient's health condition and makes predictions about possible diseases through continuous interaction with the patient. A few studies use reinforcement learning (RL) to learn the optimal policy from the joint action space of symptoms and diseases. However, existing RL (or Non-RL) methods cannot achieve sufficiently good prediction accuracy, still far from its upper limit. To address the problem, we propose a decoupled automatic diagnostic framework DxFormer, which divides the diagnosis process into two steps: symptom inquiry and disease diagnosis, where the transition from symptom inquiry to disease diagnosis is explicitly determined by the stopping criteria. In DxFormer, we treat each symptom as a token, and formalize the symptom inquiry and disease diagnosis to a language generation model and a sequence classification model respectively. We use the inverted version of Transformer, i.e., the decoder-encoder structure, to learn the representation of symptoms by jointly optimizing the reinforce reward and cross entropy loss. Extensive experiments on three public real-world datasets prove that our proposed model can effectively learn doctors' clinical experience and achieve the state-of-the-art results in terms of symptom recall and diagnostic accuracy.Comment: 7 pages, 4 figures, 3 table

Can digitalization improve the equality and equity of food environment? Evidence from greengrocers in central Shanghai

IntroductionOnline food shopping has a profound impact on people’s food acquisition behavior, the current study aims to understand how online food shopping may affect the accessibility of the local food environment and further influence the health equity among different populations.MethodsTaking 8512 traditional and online greengrocers in central Shanghai as an example, this paper uses Gini coefficient, location quotient and spatial clustering method to compare the equality and equity of food environment between physical and digital food outlets.ResultsIt finds that spatial equality is more significantly improved as a result of online food stores than are population equality and social equity of the food environment; older populations are not disadvantaged in terms of healthy food access but lower-income people are; the impact of online stores varies for different regions and different types of stores; depot-based stores have the most positive impact on health equity.DiscussionPolicy implications are discussed to promote the environmental justice of healthy food accessibility

Decentralized Graph Neural Network for Privacy-Preserving Recommendation

Building a graph neural network (GNN)-based recommender system without violating user privacy proves challenging. Existing methods can be divided into federated GNNs and decentralized GNNs. But both methods have undesirable effects, i.e., low communication efficiency and privacy leakage. This paper proposes DGREC, a novel decentralized GNN for privacy-preserving recommendations, where users can choose to publicize their interactions. It includes three stages, i.e., graph construction, local gradient calculation, and global gradient passing. The first stage builds a local inner-item hypergraph for each user and a global inter-user graph. The second stage models user preference and calculates gradients on each local device. The third stage designs a local differential privacy mechanism named secure gradient-sharing, which proves strong privacy-preserving of users' private data. We conduct extensive experiments on three public datasets to validate the consistent superiority of our framework