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Nonlinear dynamics of rub-impact on a rotor-rubber bearing system with the Stribeck friction model
Chunli Hua,Zhushi Rao,Na Ta,Zhencai Zhu 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.8
Recent experiments on rotor-bearing systems have revealed that three or four different responses may occur when the rubbing occurs. In the present study, a mathematical model is established to investigate the dynamic characteristics of a rotor-rubber bearing system. Theadvantage of this model is demonstrated in the nonlinear stiffness of the rubber bearing and the Stribeck friction model, which generatesfriction force depending on the relative velocity. Through numerical calculation, the effects of rotational speed, the decaying factor, thestiffness coefficient, the nonlinear stiffness coefficient, and the imbalance coefficient on the responses of the rotor-rubber bearing systemare investigated in detail using bifurcation diagrams, orbits of the rotor center, phase plane portraits, Poincaré maps, and amplitude spectra. The obtained numerical simulation results improve understanding on the dynamical characteristics of rub-impact on a rotor-rubberbearing system, such as periodic no-rubbing motion, periodic annular rubbing motion, period-multiplying motion, quasi-periodic motion,dry whip, and the jump phenomenon. These results can be effectively used to diagnose rub-impact faults and instabilities in such rotorsystems. This study may contribute to further understanding on the nonlinear dynamical behavior of rub-impact on rotor-bearing systemswith nonlinear stiffness from the rubber bearing and the Stribeck friction model.
Inorganic-organic Hybrid Nanoparticles and Their Application on PET Fabrics for UV Protection
Chunli Li,Rong Li,Xuehong Ren 한국섬유공학회 2020 Fibers and polymers Vol.21 No.2
In this paper, we reported the synthesis of TiO2/γ-(methacryloyloxy)propyltrimethoxysilane (KH570) hybrid nanoparticles with simple and mild condition at room temperature. The as-prepared TiO2/KH570 hybrid nanoparticles were characterized by FT-IR, XRD, SEM, EDS, and XPS. The hybrid nanoparticles were coated onto the surfaces of polyethylene terephthalate (PET) fabrics by pad-dry-cure (PDC) process. The morphology, structural, and chemical composition of the coated fabrics were analyzed by SEM, EDS, and XPS. The ultraviolet protection factor (UPF) was used to evaluate the UV protection property of PET fabrics. The coated PET fabric exhibited good UV resistance abilities with a UPF value of 50+. The air permeability of the coated PET fabrics decreased significantly compared with the original PET fabrics. The coated PET fabrics also showed good washing stability. The coated fabrics had an excellent protective effect against ultraviolet rays after exposure to ultraviolet light for a period of time. The PDC process only caused a small degree loss of the tensile strength of the coated PET fabrics.
Coupled bending and torsional vibration of a rotor system with nonlinear friction
Chunli Hua,Guohua Cao,Zhushi Rao,Na Ta,Zhencai Zhu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.6
Unacceptable vibrations induced by the nonlinear friction in a rotor system seriously affect the health and reliability of the rotating machinery. To find out the basic excitation mechanism and characteristics of the vibrations, a coupled bending and torsional nonlinear dynamic model of rotor system with nonlinear friction is presented. The dynamic friction characteristic is described with a Stribeck curve, which generates nonlinear friction related to relative velocity. The motion equations of unbalance rotor system are established by the Lagrangian approach. Through numerical calculation, the coupled vibration characteristics of a rotor system under nonlinear friction are well investigated. The influence of main system parameters on the behaviors of the system is discussed. The bifurcation diagrams, waterfall plots, the times series, orbit trails, phase plane portraits and Poincaré maps are obtained to analyze dynamic characteristics of the rotor system and the results reveal multiform complex nonlinear dynamic responses of rotor system under rubbing. These analysis results of the present paper can effectively provide a theoretical reference for structural design of rotor systems and be used to diagnose selfexcited vibration faults in this kind of rotor systems. The present research could contribute to further understanding on the self-excited vibration and the bending and torsional coupling vibration of the rotor systems with Stribeck friction model.
Hierarchical Identity-based Broadcast Encryption Scheme from LWE
Chunli Yang,Shihui Zheng,Licheng Wang,Xiuhua Lu,Yixian Yang 한국통신학회 2014 Journal of communications and networks Vol.16 No.3
A hierarchical identity-based broadcast encryption (HIBBE)scheme is an identity-based broadcast encryption (IBBE)scheme in a hierarchical environment. In order to obtain secure HIBBEschemes in the quantum era, we propose an H-IBBE schemebased on the learning with errors problemassumption.Our schemeachieves indistinguishability from random under adaptive chosenplaintextand chosen-identity attacks in the random oracle model.
Performance of a modified alkaline lignin towards copper adsorption under different conditions
Chunli Zheng,Qiaorui Wang,Yujie Dai,Bo Zu,Yangyang Zhang,Tian C Zhang 대한환경공학회 2022 Environmental Engineering Research Vol.27 No.3
Polyethyleneimine and carbon disulfide were employed to modify alkaline lignin (AL) in order to introduce -NH, -NH₂ and -CSS- groups. Its adsorption performance towards Cu(II) was evaluated based on the residual concentration (Cr) against the discharge permissible concentration for Cu(II) (2.0 mg/L) established by the World Health Organization. The evaluation was operated under different conditions such as adjusting the solution pH, Cu(II) coexisting with K(I), Na(I), Ca(II) or Mg(II), changing the contact time (t) and initial concentration of Cu(II) (C0), as well as regeneration. When t and C0 equaled to 180 min and 50 mg/L, Cr was less than 2.0 mg/L at pH of 5.03 to 5.65. Under the situation of Cu (II) coexisting with 50 mg/L of K(I), Na(I), Ca(II) or Mg(II), Cr was as low as 1.96, 1.53, 1.97 or 1.55 mg/L (t = 180 min, C0 = 50 mg/L), respectively. Even the modified AL was regenerated and reused four times, Cr was closed to 2 mg/L for each time (t = 180 min, C0 = 51 mg/L). By comparing with other lignin-based materials according to the adsorption equilibrium time, the maximum adsorption capacity, and Cr, the modified AL exhibited higher application potential in copper-loaded water treatment.
Chunli Lu,Longbing Ma,Jian Guan,Zhenlei Liu,Kai Wang,Wanru Duan,Zan Chen,Hao Wu,Fengzeng Jian 대한척추신경외과학회 2022 Neurospine Vol.19 No.4
Objective: Combined with different configuration types of syringomyelia, to analyze the correlation between syrinx resolution and changes in cervical sagittal alignment following Foramen magnum and Magendie dredging (FMMD) for syringomyelia associated with Chiari I malformation (CM-I), and to further explore the respective relationship with clinical outcome. Methods: A consecutive series of 127 patients with CM-I and syringomyelia who underwent FMMD in our center met the inclusion criteria of this study. Their clinical records and radiologic data were retrospectively reviewed. The Japanese Orthopedic Association (JOA) scoring system and the Chicago Chiari Outcome Scale (CCOS) were used to evaluate the surgical efficacy. The phenotypes of syringomyelia and the clinical characteristics of the patients were analyzed according to grouping by cervical curvature at baseline. Results: The preoperative straight or kyphotic cervical alignment is more common in the moniliform syrinx. After surgery, the syrinx resolution and cervical sagittal realignment in the moniliform group are more obvious, and the corresponding prognosis is relatively better. Spearman correlation analysis showed that the ΔS/C ratio (the change ratio of syrinx/cord) was positively correlated with the CCOS (p = 0.001, r = 0.897) and ΔC2–7A (the change of lower cervical angle) (p = 0.002, r = 0.560). There was also a correlation between the ΔJOA score (the change rate of the JOA score) and ΔC2–7A (p = 0.012, r = 0.467). Conclusion: After decompression surgery, syrinx resolution may coexist with the changes in the subaxial lordosis angle, especially for syrinx in moniliform type, and the relationship between syrinx resolution and cervical sagittal realignment might be valuable for evaluating the surgical outcome.