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Enhanced Toughness and Mechanical Property of Epoxy Resins with Good Shape Memory Behaviors
Longhao Tang,Yanling Wang,Tuo Zhou,Yongfei Li,Qiang Li 한국섬유공학회 2020 Fibers and polymers Vol.21 No.6
Developing shape memory polymers (SMPs) with enough mechanical strength, good toughness and excellentprocessability(mild synthesis conditions) is still a challenge for researchers. Therefore, a series of rigid-flexible epoxy SMPswere prepared based on epoxy resin, trimethylolpropane tris(3-mercaptopropionate) (TMP), and N,N-diglycidyl-4-glycidyloxyaniline (TGE) through thiol-epoxy click-reaction. The effect of sulfide curing agent and modifier on the crosslinknetworks and main features (mechanical strength, toughness, and shape memory performance) of epoxy samples wereinvestigated. Experimental results displayed temperature-dependent modulus and strength with two order of magnitudedifference between room temperature and glass transition temperature (Tg). TGE showed great effect on the improvement ofmechanical properties of the epoxy material, increasing from 724.2 MPa to 1637 MPa, nearly 220 %. Moreover, shapememorytest revealed that prepared epoxy SMPs are capable to fulfil the recovery process within 2 mins as long astemperature elevated to or above Tg, with shape fixity ratio over 99 % and shape recovery ratio above 90 %.
Rongchao Cheng,Xueqi Li,Guoqian Wei,Longhao Yu,Zhendong Su,Li Wei,Xiuping Bai,Jiawei Tian 연세대학교의과대학 2014 Yonsei medical journal Vol.55 No.4
Purpose: Coronary flow reserve (CFR) in the non-infarcted myocardium is often impairedfollowing acute myocardial infarction (AMI). However, the clinical significanceof CFR in the non-infarcted myocardium is not fully understood. The objective of the present study was to assess whether a relationship exists between CFR and left ventricular remodeling following AMI. Materials and Methods: We enrolled 18 consecutive patients undergoing coronary intervention. Heart function was analyzed using real-time myocardial contrast echocardiography at one week and six months aftercoronary angioplasty. Ten subjects were enrolled as the control group and were examinedusing the same method at the same time to assess CFR. Cardiac troponin I (cTnI) levels were routinely analyzed to estimate peak concentration. Results: CFR was 1.55±0.11 in the infarcted zone and 2.05±0.31 in the remote zone (p<0.01) at one week following AMI. According to CFR values in the remote zone, all patients were divided into two groups: Group I (CFR <2.05) and Group II (CFR >2.05). The levels of cTnI were higher in Group I compared to Group II on admission (36.40 vs. 21.38, p<0.05). Furthermore, left ventricular end diastolic volume was higher in Group I compared to Group II at six months following coronary angioplasty. Conclusion: Microvasculardysfunction is commonly observed in the remote myocardium. The CFR value accurately predicts adverse ventricular remodeling following AMI.
Junjie Jiang,Housheng Zhang,Duo Jin,Ao Wang,Longhao Liu 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.2
The existence of load disturbance can lead to the instability of permanent magnet synchronous motor (PMSM) speed control systems. Therefore, a non-singular fast terminal sliding mode control (NFTSMC) strategy based on a disturbance observer is proposed in this paper. First, a new exponential reaching law is presented to relate the rate of convergence to the state error and switching function, which achieves an improvement of the system convergence speed while reducing system jitter. At the same time, to eliminate system jitter, a new smooth saturation function is introduced in place of the symbolic function. Second, a non-singular fast terminal (NFT) sliding surface is generated by combining a nonlinear function with a linear funtion, which makes the state error converge rapidly at different stages. Finally, a disturbance observer is built to boost the robustness of the control system by observing the outside disturbance value and feeding it back to the speed controller. The dependability and effectiveness of the proposed control strategy are confirmed by simulation experiments with MATLAB.