Creep modeling of asperities on joint surface and its effect on joint surface stiffness

Creep of the asperities on joint surface will change the stiffness characteristics of joint surface. Based on creep mechanics, a novel creep model of asperities between two rough surfaces is established from a microscopic point of view in this paper. The change of joint stiffness caused by creep of asperities under constant pre-tightening force is analyzed. The results show that the creep of the asperities leads to the increase of the stiffness of the joint surface with the increase of time when the joint force is constant. Moreover, the influence of key parameters of joint surface on creep of asperities is further studied. It is found that the change rate of joint stiffness increases with the increase of initial contact distance and contact area. According to the proposed creep model and the findings in this paper, more accurate stiffness characteristics of joint surface can be achieved for analysis of dynamic and static characteristics of structures with time

Multi-axial creep-fatigue life prediction considering history-dependent damage evolution : a new numerical procedure and experimental validation

In this paper, a new numerical procedure based on a cycle-by-cycle analysis has been constructed for creep-fatigue behavior and life prediction of high-temperature structures under multi-axial stress states. Within this framework, a modified unified viscoplastic constitutive model with isotropic hardening and modified kinematic hardening rules is developed to simulate the cycle-by-cycle stress-strain responses.Moreover, the newly constructed creep-fatigue approach calculates fatigue and creep damage variables using the critical plane method (CPM) and the modified strain energy density exhaustion (SEDE) model, respectively. The multi-axial ductility factor and elastic follow-up factor are also introduced into the modified SEDE model to accommodate the special multi-axial and mixed controlled modes, which are widely existed in practical structures. In order to validate the feasibility of the proposed numerical procedure, a series of creep-fatigue tests of notched specimens made from nickel-based GH4169 superalloy were carried out at 650 °C. The predicted numbers of cycles to crack initiation agree well with the experimental data. Evidence of crack initiation under various loading conditions was observed via the electron backscatter diffraction (EBSD) technique, indicating location-dependent crack initiations depending on loading conditions. In detail, the crack initiation sites shifting from surface to subsurface with increasing hold times can be well simulated by the proposed numerical procedure due to a reasonable description of the creep- fatigue damage evolution

Synergism and rules from combination of Baicalin, Jasminoidin and Desoxycholic acid in refined Qing Kai Ling for treat ischemic stroke mice model.

Refined Qing-Kai-Ling (QKL), a modified Chinese medicine, consists of three main ingredients (Baicalin, Jasminoidin and Desoxycholic acid), plays a synergistic effect on the treatment of the acute stage of ischemic stroke. However, the rules of the combination and synergism are still unknown. Based on the ischemic stroke mice model, all different kinds of combination of Baicalin, Jasminoidin, and Desoxycholic acid were investigated by the methods of neurological examination, microarray, and genomics analysis. As a result, it confirmed that the combination of three drugs offered a better therapeutical effect on ischemic stroke than monotherapy of each drug. Additionally, we used Ingenuity pathway Analysis (IPA) and principal component analysis (PCA) to extract the dominant information of expression changes in 373 ischemia-related genes. The results suggested that 5 principal components (PC1-5) could account for more than 95% energy in the gene data. Moreover, 3 clusters (PC1, PC2+PC5, and PC3+PC4) were addressed with cluster analysis. Furthermore, we matched PCs on the drug-target networks, the findings demonstrated that Baicalin related with PC1 that played the leading role in the combination; Jasminoidin related with PC2+PC5 that played a compensatory role; while Desoxycholic acid had the least performance alone which could relate with PC3+PC4 that played a compatible role. These manifestations were accorded with the principle of herbal formulae of Traditional Chinese Medicine (TCM), emperor-minister-adjuvant-courier. In conclusion, we firstly provided scientific evidence to the classic theory of TCM formulae, an initiating holistic viewpoint of combination therapy of TCM. This study also illustrated that PCA might be an applicable method to analyze the complicated data of drug combination

Isorhamnetin induces apoptosis and suppresses metastasis of human endometrial carcinoma Ishikawa cells via endoplasmic reticulum stress promotion and matrix metalloproteinase-2/9 inhibition in vitro and in vivo

Endometrial cancer (EC) is a very common female cancer which has attracted more and more attention. According to the individual patient’s condition, the current treatment of EC patients is mainly based on surgery, which is supplemented by chemotherapy, radiotherapy, and endocrine intervention. However, these existing treatment strategies also have some inevitable limitations. Therefore, it is particularly important to find an active ingredient with low toxicity and a high safety profile against EC. Isorhamnetin is a flavonoid known to be present in a variety of plants, such as sea buckthorn, dry willow, and wolfberry. In recent years, the anti-tumor effects of isorhamnetin have been reported. In our study, isorhamnetin was shown to induce apoptosis in Ishikawa cells by inducing the endogenous mitochondrial apoptotic pathway and exogenous death receptor pathway, promoting the endoplasmic reticulum stress-related pathway, and activating the corresponding markers of UPR response. In addition, isorhamnetin affected the expression of MMP2 and MMP9-related proteins in vitro and in vivo and eventually repressed metastasis. Therefore, isorhamnetin can be used as a promising medicinal material for the treatment of EC

Berry Curvature and Bulk-Boundary Correspondence from Transport Measurement for Photonic Chern Bands

Berry curvature is a fundamental element to characterize topological quantum physics, while a full measurement of Berry curvature in momentum space was not reported for topological states. Here we achieve two-dimensional Berry curvature reconstruction in a photonic quantum anomalous Hall system via Hall transport measurement of a momentum-resolved wave packet. Integrating measured Berry curvature over the two-dimensional Brillouin zone, we obtain Chern numbers corresponding to -1 and 0. Further, we identify bulk-boundary correspondence by measuring topology-linked chiral edge states at the boundary. The full topological characterization of photonic Chern bands from Berry curvature, Chern number, and edge transport measurements enables our photonic system to serve as a versatile platform for further in-depth study of novel topological physics

Review of CHINARE chemical oceanographic research in the Southern Ocean during 1984–2016

Between 1984 and 2016, China executed 33 Antarctic cruises with the icebreaker R/V Xuelong, which have provided opportunities for Chinese scientists to investigate the status and changes of the Southern Ocean. Research in chemical oceanography constitutes one of the primary missions of the Chinese National Antarctic Research Expedition (CHINARE). This paper reviews nearly 30 years of Chinese Antarctic expeditions, focusing on the major progress achieved in chemical oceanographic research. Specifically, the sea-surface distributions and air–sea fluxes of CO2 and N2O are considered, and the transport, flux, and budget of organic matter are investigated based on isotopes in the Southern Ocean, especially in Prydz Bay. In addition, the nutrient distribution and deep-water particle export in Prydz Bay and the study of aerosol heavy metal characteristics are considered. Finally, the prospects for future Chinese Antarctic chemical oceanographic research are outlined