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81.
Lahcen MokniMohamed Belhaq 《Communications in Nonlinear Science & Numerical Simulation》2012,17(4):1980-1985
In Mokni et al. [Mokni L, Belhaq M, Lakrad F. Effect of fast parametric viscous damping excitation on vibration isolation in sdof systems. Commun Nonlinear Sci Numer Simulat 2011;16:1720-1724], it was shown that in a single degree of freedom system a fast nonlinear parametric damping enhances vibration isolation with respect to the case where the nonlinear damping is time-independent. The present work proposes additional enhancement of vibration isolation using delayed nonlinear damping. Attention is focused on assessing the contribution of a delayed nonlinear damping over a fast parametric damping in terms of minimizing transmissibility. The results show that a nonlinear damping with delay greatly improves vibration isolation. 相似文献
82.
以自制的多孔、具柔性亲水手臂的壳聚糖–精氨酸树脂为载体,戊二醛为交联剂固定胰凝乳蛋白酶,确定了酶与载体的最佳比例为20 mg酶/g湿树脂,交联剂的最佳用量为10 mL 1.0%戊二醛/1.5 g湿树脂,交联时间为60 min,所得固定化酶的活力回收率达68.95%。固定化胰凝乳蛋白酶的Km为8.36 mg/mL,比游离酶增大1.52倍,其酶促反应10 min达到最大速率,具有接近游离酶的催化时间进程曲线;其最适温度为70 ℃,比游离酶升高10 ℃;其最适pH值为5.92,比游离酶酸性偏移2个pH值。此外,固定化胰凝乳蛋白酶具有良好的热稳定性和贮存稳定性,75 ℃时的半衰期为8 h,4 ℃时的半衰期为46天。 相似文献
83.
Guo-Ping Cai·Long-Xiang Chen Department of Engineering Mechanics State Key Laboratory of Ocean Engineering Shanghai Jiaotong University Shanghai China 《Acta Mechanica Sinica》2010,26(6):951-965
In recent decades,studies on delayed system dynamics have attracted increasing attention and advances have been achieved in stability,nonlinearity,delay identification, delay elimination and application.However,most of the existing work is on the theoretical basis and little is on the experiment.This paper presents our experimental studies on delayed feedback control conducted in recent years with the focus on the discussion of a DSP-based delayed experiment system.Some phenomena in our delay experiments are discussed and a few topics of interest for further research are brought forward. 相似文献
84.
叶绿体光诱导延迟荧光产生机理的光谱学研究 总被引:1,自引:1,他引:0
研究延迟荧光产生机理对延迟荧光的应用具有重要指导意义。从电荷复合理论出发,对叶绿体光诱导延迟荧光的产生机制进行了简化的理论模拟。得出: 延迟荧光的衰减动力学符合双指数形式;衰减中快相成分对应电子从Q-A上电子回流与P680+的复合产生;慢相成分对电子从Q=B回流与P680+的复合产生。实验结果支持上述理论推理,并证明延迟荧光的更长延时成分来源于PSⅠ中的电子回流到PSⅡ与P680+复合产生激发态的P680*退激发产生。 相似文献
85.
86.
This paper investigates the stability of nonlinear variable-time impulsive differential systems with delayed impulses. By using the comparison principle, the Lyapunov method and inequality techniques, some sufficient conditions for quasi-uniformly asymptotic stability and quasi-exponential stability of a given solution of variable-time impulsive differential systems with delayed impulses are established. 相似文献
87.
Dr. Heli Fan Prof. Dr. Huabing Sun Qi Zhang Prof. Dr. Xiaohua Peng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5215-5224
Two series of 1,1′-biphenyl analogues with various leaving groups (L=OAc, OCH3, OCHCH=CH2, OCH2Ph, SPh, SePh, and Ph3P+) were synthesized. Their reactivity towards DNA and the reaction mechanism were investigated by determining DNA interstrand cross-link (ICL) efficiency, radical and carbocation formation, and the cross-linking reaction sites. All compounds induced DNA ICL formation upon 350 nm irradiation via a carbocation that was generated from oxidation of the corresponding free radicals. The ICL efficiency and the reaction rate strongly depended on the combined effect of the leaving group and the substituent. Among all compounds tested, the high ICL efficiency (30–43 %) and fast reaction rate were observed with compounds carrying a nitrophenyl group and acetate ( 2 a ), ether ( 2 b and 2 c) , or triphenylphosphonium salt ( 2 g ) as leaving groups. Most compounds with a 4-methoxybenzene group showed similar DNA ICL efficiency (≈30 %) with a slow DNA cross-linking reaction rate. Both cation trapping and free radical trapping adducts were detected in the photo activation process of these compounds, which provided direct evidence for the proposed mechanism. Heat stability study in combination with sequence study suggested that these photo-generated benzyl cations alkylate DNA at dG, dA, and dC sites. 相似文献
88.
89.
Unprecedented Acid‐Promoted Polymerization and Gelation of Acrylamide: A Serendipitous Discovery
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Siew Yin Chan Dr. Shermin S. Goh Dr. Qingqing Dou Benjamin Qi Yu Chan Dr. Wee Sim Choo Prof. David James Young Prof. Xian Jun Loh 《化学:亚洲杂志》2018,13(14):1797-1804
Dilute acid polymerizes degassed, aqueous acrylamide with concomitant gelation, without the need for added free radical initiator or cross‐linking agent. This reaction is accelerated by sonication or UV irradiation, but inhibited by adventitious oxygen or the addition of a free radical inhibitor, suggesting an acid‐accelerated free radical process. The resulting hydrogels are thixotropic in nature and partially disrupted by the addition of chaotropic agents, indicating the importance of hydrogen bonding to the 3D network. This discovery was made while trying to prepare pectin‐polyacrylamide hydrogels. We observed that pectin initiated the gelation of acrylamide, but only if the aqueous pectin samples had a pH lower than ca. 5. 相似文献
90.
S. Montserrat P. Cortés Y. Calventus J. M. Hutchinson 《Journal of Thermal Analysis and Calorimetry》1997,49(1):79-85
Structural relaxation in different epoxy-anhydride and epoxy-diamine resins has been investigated by differential scanning calorimetry using annealing and cooling rate experiments. The annealing experiments lead to the determination of enthalpy loss,H, at an equivalent annealing temperatureT
a=T
g-20, and for periods of annealing time, ta, between 1 h and 4 months. The variation ofH with logta, defines a relaxation rate per decade,rrpd, which is very sensitive to changes of the epoxy network. The cooling rate experiments allow the determination of the apparent activation energy,h
*. The effect of the degree of crosslinking, the addition of a reactive diluent, which acts as flexibilizer, and the length of cross-link onrrpd and h* was studied.Financial support has been provided by DGICYT (Project no.PB93/1241). The authors are grateful to CIBA-GEIGY for supplying the epoxies and hardeners, and to HUNTSMAN CORPORATION EUROPE for supplying the JEFFAMINE*, J.M.H. wishes to acknowledge assistance for a sabbatical period from theMinisterio de Education y Ciencia. 相似文献