Dynamic characteristic analysis of two-stage quasi-zero stiffness vibration isolation system

A novel two-stage quasi-zero stiffness (QZS) vibration isolator was proposed for the purpose of low-frequency vibration isolation. Firstly, the dynamic model of the vibration isolation system was established; furthermore, the force transmissibility of the system under harmonic force excitation was derived by the averaging method; finally, the effects on the vibration isolation performance caused by excitation amplitude, mass ratio and damping ratio were discussed. Results show that, compared with the corresponding two-stage linear system, two-stage QZS system not only has better isolation performance, but also possesses a wider range of isolation frequency provided that the excitation amplitude, mass ratio and damping ratio is appropriate

Chaotification of Quasi-Zero Stiffness System via Direct Time-delay Feedback Control

This paper presents a chaotification method based on direct time-delay feedback control for a quasi-zero-stiffness isolation system. An analytical function of time-delay feedback control is derived based on differential-geometry control theory. Furthermore, the feasibility and effectiveness of this method was verified by numerical simulations. Numerical simulations show that this method holds the favorable aspects including the advantage of using tiny control gain, the capability of chaotifying across a large range of parametric domain and the high feasibility of the control implement

Janus Monolayer Transition Metal Dichalcogenides

A novel crystal configuration of sandwiched S-Mo-Se structure (Janus SMoSe) at the monolayer limit has been synthesized and carefully characterized in this work. By controlled sulfurization of monolayer MoSe2 the top layer of selenium atoms are substituted by sulfur atoms while the bottom selenium layer remains intact. The peculiar structure of this new material is systematically investigated by Raman, photoluminescence and X-ray photoelectron spectroscopy and confirmed by transmission-electron microscopy and time-of-flight secondary ion mass spectrometry. Density-functional theory calculations are performed to better understand the Raman vibration modes and electronic structures of the Janus SMoSe monolayer, which are found to correlate well with corresponding experimental results. Finally, high basal plane hydrogen evolution reaction (HER) activity is discovered for the Janus monolayer and DFT calculation implies that the activity originates from the synergistic effect of the intrinsic defects and structural strain inherent in the Janus structure.Comment: 22 pages, 12 figure

DETC2005-84187 CHAOS IN THE QUASIPERIODICALLY FORCED HELMHOLTZ-DUFFING OSCILLATOR WITH TWO-WELL POTENTIAL

ABSTRACT The chaotic dynamics of the quasiperiodically excited Helmholtz-Duffing oscillator with two-well potential was investigated. The condition of the existence of homoclinic orbit in the corresponding Hamiltonian system was presented which is asymmetrical resulting from the asymmetry restoring force. It was found that the mechanism for chaos is transverse homoclinic tori and it is illustrated how transverse homoclinic tori give rise to chaos for the Helmholtz-Duffing oscillator with multi-frequency periodic forces. The criterion for the existence of chaos was given utilizing a generalization of the Melnikov's method. The region in parameter space where chaotic dynamics may occur was given. It was also demonstrated that increasing the number of forcing frequencies increases the area in parameter space where chaotic behavior can occur. INTRODUCTION Symmetric Duffing-type oscillators have been widely studied for chaos under both harmonic and parametric excitation

Decision tool of medical endoscope maintenance service in Chinese hospitals: a conjoint analysis

Medical devices are instruments, apparatus, appliances, software, implants, reagents, materials or other articles that are intended for use in the treatment or diagnosis of disease or injury in humans. Concerning medical endoscope devices, which enable doctors to observe and manipulate the area under examination through a puncture hole in the body cavity or organ, hospitals predominantly consider the quality and cost of maintenance services when making their selection. The effective and efficient provision of maintenance services plays a crucial role in ensuring cost-effective and high-quality management of medical devices. In this study, we have developed an innovative decision tool that analyzed key factors impacting the choice of medical devices’ maintenance service. This tool assists hospitals in evaluating and selecting appropriate maintenance services for medical device, specifically endoscopy devices. Moreover, it also serves as a valuable resource for manufacturers and suppliers to enhance their after-sales service offerings

Primary succession of nitrogen cycling microbial communities along the deglaciated forelands of Tianshan Mountain, China

Structural succession and its driving factors for nitrogen (N) cycling microbial communities during the early stages of soil development (0-44 years) were studied along a chronosequence in the glacial forelands of the Tianshan Mountain No.1 glacier in the arid and semi-arid region of central Asia. We assessed the abundance and population of functional genes affiliated with N-fixation (nifH), nitrification (bacterial and archaeal amoA), and denitrification (nirK/S and nosZ) in a glacier foreland using molecular methods. The abundance of functional genes significantly increased with soil development. N cycling community compositions were also significantly shifted within 44 years and were structured by successional age. Cyanobacterial nifH gene sequences were the most dominant N fixing bacteria and its relative abundance increased from 56.8-93.2% along the chronosequence. Ammonia-oxidizing communities shifted from the Nitrososphaera cluster (AOA-amoA) and the Nitrosospira cluster ME (AOB-aomA) in younger soils (0 and 5 years) to communities dominated by soil and sediment 1 (AOA-amoA) and Nitrosospira Cluster 2 Related (AOB-aomA) in older soils (=17 years). Most of the denitrifers closest relatives were potential aerobic denitrifying bacteria, and some other types of denitrifying bacteria (like autotrophic nitrate-reducing, sulfide-oxidizing bacteria and denitrifying phosphorus removing bacteria) were also detected in all soil samples. The regression analysis showed that N cycling microbial communities were dominant in younger soils (0-5 years) and significantly correlated with soil total carbon, while communities that were most abundant in older soils were significantly correlated with soil total nitrogen. These results suggested that the shift of soil C and N contents during the glacial retreat significantly influenced the abundance, composition and diversity of N cycling microbial communities. © 2016 Zeng, Lou, Zhang, Wang, Hu, Shen, Zhang, Han, Zhang, Lin, Chalk and He

MS1, a direct target of MS188, regulates the expression of key sporophytic pollen coat protein genes in Arabidopsis

© 2020 Oxford University Press. All rights reserved. Sporophytic pollen coat proteins (sPCPs) derived from the anther tapetum are deposited into pollen wall cavities and function in pollen-stigma interactions, pollen hydration, and environmental protection. In Arabidopsis, 13 highly abundant proteins have been identified in pollen coat, including seven major glycine-rich proteins GRP14, 16, 17, 18, 19, 20, and GRP-oleosin; two caleosin-related family proteins (AT1G23240 and AT1G23250); three lipase proteins EXL4, EXL5 and EXL6, and ATA27/BGLU20. Here, we show that GRP14, 17, 18, 19, and EXL4 and EXL6 fused with green fluorescent protein (GFP) are translated in the tapetum and then accumulate in the anther locule following tapetum degeneration. The expression of these sPCPs is dependent on two essential tapetum transcription factors, MALE STERILE188 (MS188) and MALE STERILITY 1 (MS1). The majority of sPCP genes are up-regulated within 30 h after MS1 induction and could be restored by MS1 expression driven by the MS188 promoter in ms188, indicating that MS1 is sufficient to activate their expression; however, additional MS1 downstream factors appear to be required for high-level sPCP expression. Our ChIP, in vivo transactivation assay, and EMSA data indicate that MS188 directly activates MS1. Together, these results reveal a regulatory cascade whereby outer pollen wall formation is regulated by MS188 followed by synthesis of sPCPs controlled by MS1

Correlation between serum laminin levels and prognosis of acute myocardial infarction

BackgroundAcute myocardial infarction (AMI) is a critical cardiovascular disease (CVD). Laminin (LN) is involved in the process of myocardial fibrosis and ventricular remodeling observed in AMI; however, there are currently no studies on the correlation between LN and AMI prognosis.PurposeTo explore the predictive value of serum LN levels for major adverse cardiovascular events (MACE) in patients, 6 months after an acute myocardial infarction.MethodsA total of 202 AMI patients who were hospitalized in the Department of Cardiology of the Second Affiliated Hospital of Nantong University between December 2019 and December 2020 were included. The observation endpoint was the occurrence of MACE. Univariate and multivariate logistic analyses were used to evaluate the relationships between the variables and endpoint. The predictive value of LN for MACE in AMI patients was assessed using receiver operating characteristic (ROC) analysis.ResultsA total of 47 patients developed MACE. Univariate logistic analysis showed that smoking, emergency percutaneous coronary intervention (EPCI), age, cardiac troponin I (c-TNI) levels, N-terminal prohormone brain natriuretic peptide (NT-proBNP) levels, and LN levels were associated with the occurrence of MACE (p < 0.05). Multivariate logistic analysis showed that LN was an independent predictor of MACE (odds ratio [OR] = 1.021, 95%CI: 1.014–1.032, p < 0.001). According to the ROC curve, LN can be used as an effective predictor of MACE (AUC = 0.856, 95%CI: 0.794–0.918, p < 0.001). According to the cutoff value, LN>58.80 ng/ml (sensitivity = 83.00%, specificity = 76.80%) or LN>74.15 ng/ml (sensitivity = 76.6%, specificity = 83.2%) indicate a poor prognosis for AMI. Different cut-off values are selected according to the need for higher sensitivity or specificity in clinical applications.ConclusionsLN may be a predictor of MACE following AMI in patients and could be utilized as a novel substitute marker for the prevention and treatment of AMI