Nonlinear Dynamics - This paper focuses on the problem of nonlinear system identification by proposing an improved approach for existing frequency-domain nonlinear identification through feedback... 相似文献
Nonlinear Dynamics - Investigation of the dynamic characteristics of linear guideway is essential for enhancing structural performance of machine tools. However, few mechanical models are... 相似文献
Collagen is the most abundant protein in mammals, and there has been long-standing interest in understanding and controlling collagen assembly in the design of new materials. Collagen-like peptides (CLPs), also known as collagen-mimetic peptides (CMPs) or collagen-related peptides (CRPs), have thus been widely used to elucidate collagen triple helix structure as well as to produce higher-order structures that mimic natural collagen fibers. This mini-review provides an overview of recent progress on these topics, in three broad topical areas. The first focuses on reported developments in deciphering the chemical basis for collagen triple helix stabilization, which we review not with the intent of describing the basic structure and biological function of collagen, but to summarize different pathways for designing collagen-like peptides with high thermostability. Various approaches for producing higher-order structures via CLP self-assembly, via various types of intermolecular interaction, are then discussed. Finally, recent developments in a new area, the production of polymer–CLP bioconjugates, are summarized. Biological applications of collagen contained hydrogels are also included in this section. The topics may serve as a guide for the design of collagen-like peptides and their bioconjugates for targeted application in the biomedical arena. 相似文献
Human motion induced vibration has very low frequency, ranging from 2 Hz to 5 Hz. Traditional vibration isolators are not effective in low-frequency regions due to the trade-off between the low natural frequency and the high load capacity. In this paper, inspired by the human spine, we propose a novel bionic human spine inspired quasi-zero stiffness (QZS) vibration isolator which consists of a cascaded multi-stage negative stiffness structure. The force and stiffness characteristics are investigated first, the dynamic model is established by Newton’s second law, and the isolation performance is analyzed by the harmonic balance method (HBM). Numerical results show that the bionic isolator can obtain better low-frequency isolation performance by increasing the number of negative structure stages, and reducing the damping values and external force values can obtain better low-frequency isolation performance. In comparison with the linear structure and existing traditional QZS isolator, the bionic spine isolator has better vibration isolation performance in low-frequency regions. It paves the way for the design of bionic ultra-low-frequency isolators and shows potential in many engineering applications.
In this study, a novel kinetic model is established to investigate the dynamic characteristic of the ball screw feed system by considering the thermal deformation of bearing joints, screw-nut joints and screw shaft. Based on the Hertz contact theory, the relationship between elastic restoring force and axial deformation of bearing joints and screw-nut joints is obtained, respectively. Then the dynamic characteristics of the kinetic equation are analyzed by Runge–Kutta method. The vibration characteristics of the feed system with and without thermal deformation are analyzed, and the results indicate that the amplitude becomes larger when thermal deformation is considered. The motion state of the feed system at different frequencies is analyzed, and the results show that with the change of frequency, the motion state of the system will appear period-doubling motion, quasi-periodic motion and chaotic motion. Finally, the influence of different parameters on the vibration characteristics of the system is discussed.
Three anthracen- or pyrene-based coumarin derivatives have been successfully synthesized and characterized by EA, IR and 1H NMR. The photophysical properties of all derivatives were investigated by UV-Vis and photoluminescence spectroscopic analysis. Their thermal stabilities were demonstrated by TGA. These compounds exhibit strong blue mission under ultraviolet light excitation and have potential possible to explore organic electroluminescent materials. The vacuum-processed doped devices with a configuration of ITO/TAPC (20 nm)/TBADN: b1 (x wt%, 30 nm)/TPBi (50 nm)/Liq (2 nm)/Al (150 nm) was fabricated, in which the devices based on b1 exhibited the best electroluminescence performance with a maximum brightness of 8165 cd/m2 and a maximum luminous efficiencies of 6.13 cd/A and a maximum external quantum efficiency (EQE) of 2.75%. 相似文献
Nonlinear Dynamics - In this paper, a nonlinear energy sink and a negative stiffness element are integrated for achieving enhanced, passive, and adaptive vibration suppression for a pipe conveying... 相似文献
Two mononuclear Pt(II) complexes, Pt(dbbpy)Cl2 (1) and [Pt(dbbpy)2](PF6)2 (2) (dbbpy?=?4,4′-ditertbutyl-2,2′-biyridine) were synthesized and characterized by single-crystal X-ray diffraction analysis, elemental analysis, 1H NMR, and ESI–MS. Their binding affinities for both double-stranded (DS) calf thymus DNA (ct-DNA) and G-quadruplex DNA (HT21 and BCL-2) were investigated. In addition to structural differences, complex 1 displayed higher binding affinity for DS ct-DNA, whereas positively charged complex 2 was selective for binding to G-quadruplex DNA over DS DNA. The time-dependent cleavage of supercoiled circular plasmid pBR322 DNA by 1 was observed using agarose gel electrophoresis, whereas complex 2 hardly cleaved DS DNA. Stabilization of G-quadruplex HT21 DNA by both complexes was assessed by PCR stop assays. Both complexes exhibited moderate activities for inhibition of topoisomerase I as well as modest antiproliferation activities toward cancer cells in CKK-8 assays. 相似文献