Dynamic responses of axially moving telescopic mechanism for truss structure bridge inspection vehicle under moving mass

Dynamic responses of a telescopic mechanism for truss structure bridge inspection vehicle under moving mass are investigated under the assumption of Euler-Bernoulli beam theory. Equations of motion for the telescopic mechanism are derived using the Hamilton’s principle. The equations are transformed into discretized equations by employing the Galerkin’s method. The eigenfunctions of the beams are derived based on the kinetic and dynamic boundary conditions. The time-dependent features of the eigenfunctions are taken into account. The discretized equations are solved utilizing the Newmark-β method. Numerical results are presented to explore the influence of the moving mass on the dynamic responses of the telescopic mechanism and find appropriate mass-moving strategy to avoid large vibration. The results show that the vibrations when the mass doesn’t move synchronously with the telescopic beam are not always the minimum; on the other hand, the mass moving in the same direction of the telescopic beam will bring in stronger vibration

MicroRNA-141-3p mediates epithelial cell proliferation, apoptosis, and epithelial-mesenchymal transition and alleviates pulmonary fibrosis in mice via Spred2

Objective. This study probed the mechanism of microRNA (miR)-141-3p in the progression of pulmonary fibrosis (PF). Methods. Mice were intratracheally administered with bleomycin (BLM) to establish a PF mouse model. To investigate the effects of miR-141-3p/Spred2 on PF in mice, PF mice received tail vein injections with agomir-141-3p and/or adenovirus vectors overexpressing Spred2 one week after BLM treatment. Then, the pathological changes of lung tissues were analyzed with H&E and Masson’s trichrome staining, and hydroxyproline contents in lung tissues were measured. For cell experiments, after loss- and gain-of-function assays, the role of miR-141-3p/Spred2 in the apoptosis and viability of TGF-β1-stimulated MLE-12 cells was examined by flow cytometry and CCK-8 assay, respectively. miR-141-3p, Spred2, COl 1, and α-SMA expression was determined in cells and mice. Then, the binding of miR-141-3p to Spred2 was tested with a dualluciferase reporter assay. Results. There were abnormally upregulated Spred2 and downregulated miR-141-3p in lung tissues of PF mice. TGF-β1 decelerated viability and augmented apoptosis and COl 1 and α-SMA expression in MLE-12 cells. Spred2 knockdown diminished apoptosis and αSMA and COl 1 expression while enhancing proliferation in TGF-β1-treated MLE-12 cells. Mechanistically, Spred2 was a target gene of miR-1413p. miR-141-3p upregulation accelerated proliferation and repressed apoptosis and α-SMA and COl 1 expression in TGF-β1-treated MLE-12 cells, which was nullified by further overexpressing Spred2. miR-141-3p alleviated PF in mice by targeting Spred2. Conclusion. miR-141-3p negatively modulates Spred2 to promote proliferation and repress epithelialmesenchymal transition and apoptosis of epithelial cells, as well as ameliorating PF in mic

Research on Construction Project Management Strategy Based on EPC General Contracting

At present, the rapid development of urban economy in our country and the rise of the construction industry make the contract management model more specialized and standardized. Among them, EPC is a common type of project general contracting mode, which can be divided into design, procurement, construction and other modules according to the requirements and actual conditions of project construction. When carrying out project management of construction projects, the use of EPC general contracting mode can achieve good management results. Therefore, from the perspective of EPC general contracting, this paper discusses the relevant countermeasures of construction project management, aiming to realize the unified and standardizing management of all aspects of engineering construction and improving the level of project management

Room-Temperature Structures of Solid Hydrogen at High Pressures

By employing first-principles metadynamics simulations, we explore the 300 K structures of solid hydrogen over the pressure range 150-300 GPa. At 200 GPa, we find the ambient-pressure disordered hexagonal close-packed (hcp) phase transited into an insulating partially ordered hcp phase (po-hcp), a mixture of ordered graphene-like H2 layers and the other layers of weakly coupled, disordered H2 molecules. Within this phase, hydrogen remains in paired states with creation of shorter intra-molecular bonds, which are responsible for the very high experimental Raman peak above 4000 cm-1. At 275 GPa, our simulations predicted a transformation from po-hcp into the ordered molecular metallic Cmca phase (4 molecules/cell) that was previously proposed to be stable only above 400 GPa. Gibbs free energy calculations at 300 K confirmed the energetic stabilities of the po-hcp and metallic Cmca phases over all known structures at 220-242 GPa and >242 GPa, respectively. Our simulations highlighted the major role played by temperature in tuning the phase stabilities and provided theoretical support for claimed metallization of solid hydrogen below 300 GPa at 300 K.Comment: Accepted in Journal of Chemical Physic

Dynamic behaviors of 2-DOF axially telescopic mechanism for truss structure bridge inspection vehicle

Dynamic behaviors of the 2-DOF axially telescopic mechanism for truss structure bridge inspection vehicle is investigated. The telescopic mechanism is a combination of one vertical beam that can move axially, one constant beam perpendicularly fixed at the end of the vertical beam and one telescopic beam that can move along the axial direction of the constant beam during work. The Euler-Bernoulli beam theory is utilized to simplify the beams. The Lagrangian description is adopted to account for the coordinate for the telescopic mechanism. The equations of motion are derived using the Hamilton’s principle and decomposed into a set of ordinary differential equations by employing the Galerkin’s method. The eigenfunctions are acquired based on the boundary conditions by adopting the dichotomy method. The solutions to the equations are acquired using the Newmark-β method. Experiments are carried out to prove the validity of the theoretical model. Numerical examples are simulated to explore whether the vertical beam and telescopic beam can extend or retract synchronously and obtain appropriate beam moving strategy. The results prove that synchronous motion of the vertical beam and telescopic beam will not always lead to pronounced stronger vibration than the separate ones. On the other hand, the beam moving strategies that the telescopic beam moving before the vertical beam when they all extend out or retract back and moving after the vertical beam when one extends out and the other retracts back will effectively reduce the vibration compared with otherwise

Research on dynamic performance and motion control of robot manipulator

Amongst the robotics and autonomous systems, robot manipulators have proven themselves to be of increasing importance and are widely adopted to substitute for human in repetitive and/or hazardous tasks. In this paper, the purpose is to research on dynamic performance and motion control of robot manipulator for the more precise, crucial and critical tasks in industry. Firstly, the forward and inverse kinematics was accurately described by obtaining the link transformation matrices from each joint in robot manipulator. To find admissible solutions along the path, the workspace of the manipulator was determined by joint limit condition and validated by actual measurement. And then, the dynamic performance of robot manipulator is researched by using the forming flexible multi-body system. Furthermore, the frequency response curves are obtained by exciting vibration simulation based on vibration model, which the predicted method was validated by comparing simulation and experimental results. Finally, the control system architecture was given and the grasping process was conducted by gripper based on motion trajectory control in the workspace

Immunosuppression complicated with Legionnaires’ disease after chemotherapy in a lymphoma patient confirmed by blood mNGS: one case report and literature review

Objective To analyze the clinical characteristics of Legionnaires’ disease in immunosuppressive patients， and to explore the significance of blood metagenomic next-generation sequencing （mNGS） in the early diagnosis and treatment of Legionnaires’ disease in immunosuppressive patients. Methods A patient with angioimmunoblastic T-cell lymphoma who developed pulmonary infection after chemotherapy was reported. The diagnosis of Legionella pneumophila infection was confirmed by blood mNGS. Using “Legionella” “blood” “metagenomic next-generation sequencing” and “mNGS” as the keywords in both Chinese and English， relevant studies were searched from CNKI database， Chinese core journals and PubMed database. Clinical data of patients positive for Legionella pneumophila by blood mNGS were analyzed. Results The female patient， aged 50-year-old， was admitted to our hospital due to “the diagnosis of angioimmunoblastic T-cell lymphoma and continuing chemotherapy for more than 10 months”. After twice intravenous chemotherapy， the patient was complicated with myelosuppression， cough and fever. The possibility of pulmonary infection was considered. Conventional antibiotic therapy yielded low efficacy. Blood mNGS confirmed the infection with Legionella pneumophila. After adjusted antibiotic treatment （levofloxacin + tigecycline）， the patient was improved and discharged. According to literature review， two cases with complete clinical data were searched. Both two cases were children with hematological diseases who were complicated with pulmonary infection after stem cell transplantation. After the pathogen was identified by blood mNGS， the disease was mitigated after anti-Legionella treatment. Conclusions Immunosuppressed patients with Legionella pneumophila infection are likely to be complicated with bloodstream infection， and clinical manifestations are non-specific. mNGS contributes to prompt identification of the pathogen. Combined anti-infection treatment should be delivered and the course of treatment should be properly prolonged， aiming to lower the risk of progression into severe pneumonia

Dihydro­cryptopine

In the crystal structure of the title compound [systematic name: 6,7-dimeth­oxy-12-methyl-16,18-dioxa-12-aza­tetra­cyclo­[12.7.0.04,9.015,19]henicosa-1(21),4,6,8,14,19-hexaen-3-ol], C21H25NO5, the benzene rings exhibits a dihedral angle of 14.95 (4)°. In the crystal, mol­ecules are linked by pairs of O—H⋯O hydrogen bonding into inversion dimers. These dimers are further connected by C—H⋯O inter­actions

AutoPCF: Efficient Product Carbon Footprint Accounting with Large Language Models

The product carbon footprint (PCF) is crucial for decarbonizing the supply chain, as it measures the direct and indirect greenhouse gas emissions caused by all activities during the product's life cycle. However, PCF accounting often requires expert knowledge and significant time to construct life cycle models. In this study, we test and compare the emergent ability of five large language models (LLMs) in modeling the 'cradle-to-gate' life cycles of products and generating the inventory data of inputs and outputs, revealing their limitations as a generalized PCF knowledge database. By utilizing LLMs, we propose an automatic AI-driven PCF accounting framework, called AutoPCF, which also applies deep learning algorithms to automatically match calculation parameters, and ultimately calculate the PCF. The results of estimating the carbon footprint for three case products using the AutoPCF framework demonstrate its potential in achieving automatic modeling and estimation of PCF with a large reduction in modeling time from days to minutes