A comprehensive numerical analysis of cross-flow vortex-induced vibrations for top tension risers under different flows

In this paper, the cross-flow vortex-induced vibration (VIV) response of a top tension riser under different flow fields are comprehensively studied using a numerical simulation model based on time domain analysis. A semi-empirical time-domain analysis model that considers the fluid-structure interaction problem in the riser vibration process is proposed and verified by comparison with the previous experimental results. The influence of the flow velocity, the spanwise length of the flow field, and other factors on the VIV amplitude and frequency characteristics of the riser is analyzed in detail. The results show that the VIV response of the riser exhibits obvious multi-modal characteristics, which are accompanied by modal transition, lock-in vibration, synchronous vibration, etc., and the region where the lock-in or synchronous vibration occurs is exactly the region where the crest of the amplitude curve locates. Besides, the VIV intensity of the riser in the stepped flow and uniform flow fields show a tendency of fluctuating increase with the increase of the flow velocity and spanwise length of the flow field, while the VIV intensity of the riser in shear flow is positively correlated with the flow velocity and spanwise length of the flow field. The present study may provide a reference for the prediction of VIV of marine riser in the complex current environment

A mini review of recent progress on vortex-induced vibrations of marine risers

© 2019 Elsevier Ltd Marine risers are subject to vortex-induced vibration (VIV) caused by a combination of various external and internal excitations. The external excitations include the current-induced hydrodynamic forces and the wave-induced motions of the floating platform, while the internal excitation refers to the effect of internal flow. With significant increase of the riser aspect ratio, the VIV becomes much more complicated, resulting in more frequent fatigue damages to the risers. Hence, VIV is an important research area in marine engineering. This review surveys the latest progress on the VIV research, including the multi-mode response, VIV response at high Reynolds numbers, flow-induced vibrations between multiple marine risers, VIV of inclined risers and intermittent VIV in oscillatory flow. Particularly, the impacts of the floating platform and internal flow that have not been widely considered in previous studies are discussed to comprehensively understand the VIV of marine risers. Moreover, typical experimental and numerical investigations on the VIV of marine risers are also introduced

Study on the Influencing Factors of Farmers’ Adoption of Conservation Tillage Technology in Black Soil Region in China: A Logistic-ISM Model Approach

The adoption of conservation tillage technology can improve the production efficiency of black soils (mollisols), and it has great significance to ensure the sustainable development of agriculture. This paper takes farmers in the black soil region of Jilin Province as the research object, uses 442 survey data of farmers in seven municipal areas in the black soil region of Jilin Province, constructs a logistic-ISM model, first determines the influencing factors of farmers’ adoption of conservation tillage technology, and then analyzes the hierarchical structure of each influencing factor. The results show that: (1) among the eight significant influencing factors of farmers’ adoption of conservation tillage technology, age, whether they know the government’s subsidies for conservation tillage and the number of labor force are the deep-rooted factors; (2) Education level, whether you know that the government is promoting conservation tillage, and the planting area are intermediate level factors; (3) whether they have received the technical services of conservation tillage and whether the cultivated land is scattered is the direct factors. Based on the significance analysis of the influencing factors of farmers’ adoption of conservation tillage technology and the research on the action mechanism of the influencing factors of farmers’ adoption of conservation tillage technology, this paper puts forward policy suggestions to improve the extension system of conservation tillage technology, improve the implementation of land transfer and subsidy policies, strengthen the ability of rural socialized services, and strengthen the publicity of black soils protection

Study on application of ultrasound microbubbles in the diagnosis of buccal carcinoma and metastatic cervical lymph nodes in mice

Background: This project′s aim was to explore the enhancing effect of contrast media on primary cancer and cervical metastatic lymph nodes of cheek carcinoma by local injection. Materials and Methods: Lymphatic metastasis cheek carcinoma mice models were established, then self-made contrast media was administered into the primary cheek carcinoma and harmonic mode imaging was performed to observe the enhancement of primary lesions and cervical metastatic lymph nodes. Results: The echo intensity (EI) was compared. The detection rate of metastatic lymph nodes and inflammatory lymph nodes was 61% (17/28) and 50% (6/12) before contrast-enhanced ultrasound (CEUS) imaging and 82% (23/28) and 75% (9/12) after CEUS imaging. After CEUS imaging, the EI of primary cancer and cervical metastatic lymph nodes was significantly increased, (P < 0.01). Conclusion: After injection of self-made contrast media via the primary lesion, it can enter the lymph duct and obviously enhance the effect of ultrasonography on cervical metastatic lymph nodes of cheek carcinoma

A Requirement for SOCS-1 and SOCS-3 Phosphorylation in Bcr-Abl-Induced Tumorigenesis

Suppressors of cytokine signaling 1 and 3 (SOCS-1 and SOCS-3) are inhibitors of the Janus tyrosine kinase (JAK)/signal transducers and activators of transcription (STAT) pathway and function in a negative feedback loop during cytokine signaling. Abl transformation is associated with constitutive activation of JAK/STAT-dependent signaling. However, the mechanism by which Abl oncoproteins bypass SOCS inhibitory regulation remains poorly defined. Here, we demonstrate that coexpression of Bcr-Abl with SOCS-1 or SOCS-3 results in tyrosine phosphorylation of these SOCS proteins. Interestingly, SOCS-1 is highly tyrosine phosphorylated in one of five primary chronic myelogenous leukemia samples. Bcr-Abl-dependent tyrosine phosphorylation of SOCS-1 and SOCS-3 occurs mainly on Tyr 155 and Tyr 204 residues of SOCS-1 and on Tyr 221 residue of SOCS-3. We observed that phosphorylation of these SOCS proteins was associated with their binding to Bcr-Abl. Bcr-Abl-dependent phosphorylation of SOCS-1 and SOCS-3 diminished their inhibitory effects on the activation of JAK and STAT5 and thereby enhanced JAK/STAT5 signaling. Strikingly, disrupting the tyrosine phosphorylation of SOCS-1 or SOCS-3 impaired the expression of Bcl-XL protein and sensitized K562 leukemic cells to undergo apoptosis. Moreover, selective mutation of tyrosine phosphorylation sites of SOCS-1 or SOCS-3 significantly blocked Bcr-Abl-mediated tumorigenesis in nude mice and inhibited Bcr-Abl-mediated murine bone marrow transformation. Together, these results reveal a mechanism of how Bcr-Abl may overcome SOCS-1 and SOCS-3 inhibition to constitutively activate the JAK/STAT-dependent signaling, and suggest that Bcr-Abl may critically requires tyrosine phosphorylation of SOCS-1 and SOCS-3 to mediate tumorigenesis when these SOCS proteins are present in cells