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Two New Phenolic Compounds from the Fruiting Bodies of Ganoderma tropicum
Li-Li Hu,Qing-Yun Ma,Sheng-Zhuo Huang,Zhi-Kai Guo,Jianchun Guo,Hao Fu Dai,You-Xing Zhao 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.3
Chemical investigation of the fruiting bodies of Ganoderma tropicum led to the isolation of two new phenolic compounds, ganodermatropins A (1) and B (2). Their structures were elucidated by spectroscopic techniques (MS, 1D and 2D NMR). Ganodermatropin A exhibited antimicrobial activity against Staphylococcus aureus.
Overview of the development of smart base isolation system featuring magnetorheological elastomer
Yancheng Li,Jianchun Li 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.24 No.1
Despite its success and wide application, base isolation system has been challenged for its passive nature, i.e., incapable of working with versatile external loadings. This is particularly exaggerated during near-source earthquakes and earthquakes with dominate low-frequency components. To address this issue, many efforts have been explored, including active base isolation system and hybrid base isolation system (with added controllable damping). Active base isolation system requires extra energy input which is not economical and the power supply may not be available during earthquakes. Although with tunable energy dissipation ability, hybrid base isolation systems are not able to alter its fundamental natural frequency to cope with varying external loadings. This paper reports an overview of new adventure with aim to develop adaptive base isolation system with controllable stiffness (thus adaptive natural frequency). With assistance of the feedback control system and the use of smart material technology, the proposed smart base isolation system is able to realize real-time decoupling of external loading and hence provides effective seismic protection against different types of earthquakes.
Analysis and optimization of a typical quasi-zero stiffness vibration isolator
Huan Li,Yang Yu,Jianchun Li,Yancheng Li 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.27 No.3
To isolate vibration at a low-frequency range and at the same time to provide sufficient loading support to the isolated structure impose a challenge in vibration isolation. Quasi-zero stiffness (QZS) vibration isolator, as a potential solution to the challenge, has been widely investigated due to its unique property of high-static & low-dynamic stiffness. This paper provides an in-depth analysis and potential optimization of a typical QZS vibration isolator to illustrate the complexity and importance of design optimization. By carefully examining the governing fundamentals of the QZS vibration isolator, a simplified approximation of force and stiffness relationship is derived to enable the characteristic analysis of the QZS vibration isolator. The explicit formulae of the amplitude-frequency response (AFR) and transmissibility of the QZS vibration isolator are obtained by employing the Harmonic Balance Method. The transmissibility curves under force excitation with different values of nonlinear coefficient, damping ratio, and amplitude of excitation are further investigated. As the result, an optimization of the structural parameter has been demonstrated using a comprehensive objective function with considering multiple dynamic characteristic parameters simultaneously. Finally, the genetic algorithm (GA) is adopted to minimise the objective function to obtain the optimal stiffness ratios under different conditions. General recommendations are provided and discussed in the end.
Microstructure Evolution During Continuous Cooling in Niobium Microalloyed High Carbon Steels
Zhaodong Li,Qilong Yong,Zhengyan Zhang,Xinjun Sun,Jianchun Cao,Haiquan Qi,Zhi Liao 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.5
Effects of microalloyed niobium (Nb) on the austenite decomposition behaviors and microstructure evolutionduring continuous cooling in the near eutectoid steels were investigated. Compared to the Nb freesteel, the Nb microalloyed steel was refined with regard to polygonal ferrite grain, pearlite block and colonysizes. This was because its austenite grain size was smaller. The volume fraction of polygonal ferrite transformedwas more in the Nb microalloyed steels, which indicated the eutectoid carbon content exceededthat of pure carbon steel. The spheroidization of pearlite during continuous cooling was enhanced by Nbmicroalloying, mainly due to a higher critical transformation temperature and the finer pearlite structurewith smaller colony size and narrower interlamellar spacing. Hot deformation right above the equilibriumeutectoid temperature accelerated the spheroidization kinetics of pearlite, especially in the Nb microalloyedsteel.
Hua Li,Hongjing Dong,Jianchun Su,Bin Yang 대한약학회 2021 Archives of Pharmacal Research Vol.44 No.9
The influence of phenological stages onchemical composition of Scutellariae Radix (SR), theroot of Scutellaria baicalensis Georgi, was investigated. In order to deal with a large quantity of samples, arapid ultra-performance liquid chromatographic (UPLC)was first developed and validated for the simultaneousquantification of five flavonoids, namely baicalin(baicalein-7-O-b-D-glucuronide, BG), wogonoside(wogonin-7-O-b-D-glucuronide, WG), baicalein (BA),wogonin (WO), oroxylin A (OA) in the samples. Goodlinearity was obtained in the range of 0.742–389 ng(r2[0.9999) and satisfactory recoveries were obtained(101.72–104.56 %) with the RSD value below 5.0 %,for all analytes. Also, extraction conditions were optimizedto obtain maximum extractive contents of thefive flavonoids. Content variations of the five activeingredients in 225 samples from three different originswere investigated in five major phenological periods. Itwas found that the effect of phenology on the contentsof the tested five flavonoids was similar in the threeorigins. The contents of flavone O-glycosides, i.e., BGand WG accumulated to the highest level in leafexpansion period, while flavonoid aglycones, i.e., BA, WO and OA appeared a maximum concentration inflowering period. The UPLC method established in thisstudy was rapid and of good accuracy, repeatability andresolution, and hence can assist in the quality control ofSR.
Semi-active control of smart building-MR damper systems using novel TSK-Inv and max-min algorithms
Mohsen Askari,Jianchun Li,Bijan Samali 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.5
Two novel semi-active control methods for a seismically excited nonlinear benchmark building equipped with magnetorheological dampers are presented and evaluated in this paper. While a primary controller is designed to estimate the optimal control force of a magnetorheological (MR) damper, the required voltage input for the damper to produce such desired control force is achieved using two different methods. The first technique uses an optimal compact Takagi-Sugeno-Kang (TSK) fuzzy inverse model of MR damper to predict the required voltage to actuate the MR dampers (TSKFInv). The other voltage regulator introduced here works based on the maximum and minimum capacities of MR damper at each time-step (MaxMin). Both semi-active algorithms developed here, use acceleration feedback only. The results demonstrate that both TSKFInv and MaxMin algorithms are quite effective in seismic response reduction for wide range of motions from moderate to severe seismic events, compared with the passive systems and performs better than original and Modified clipped optimal controller systems, known as COC and MCOC.
Characterizing nonlinear oscillation behavior of an MRF variable rotational stiffness device
Yang Yu,Yancheng Li,Jianchun Li,Xiaoyu Gu 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.24 No.3
Magneto-rheological fluid (MRF) rotatory dampers are normally used for controlling the constant rotation of machines and engines. In this research, such a device is proposed to act as variable stiffness device to alleviate the rotational oscillation existing in the many engineering applications, such as motor. Under such thought, the main purpose of this work is to characterize the nonlinear torque-angular displacement/angular velocity responses of an MRF based variable stiffness device in oscillatory motion. A rotational hysteresis model, consisting of a rotatory spring, a rotatory viscous damping element and an error function-based hysteresis element, is proposed, which is capable of describing the unique dynamical characteristics of this smart device. To estimate the optimal model parameters, a modified whale optimization algorithm (MWOA) is employed on the captured experimental data of torque, angular displacement and angular velocity under various excitation conditions. In MWOA, a nonlinear algorithm parameter updating mechanism is adopted to replace the traditional linear one, enhancing the global search ability initially and the local search ability at the later stage of the algorithm evolution. Additionally, the immune operation is introduced in the whale individual selection, improving the identification accuracy of solution. Finally, the dynamic testing results are used to validate the performance of the proposed model and the effectiveness of the proposed optimization algorithm.