On the decay and blow‐up of solution for coupled nonlinear wave equations with nonlinear damping and source terms

In this work, we consider a nonlinear coupled wave equations with initial‐boundary value conditions and nonlinear damping and source terms. Under suitable assumptions on the damping terms and source terms and initial data in the stable set, we obtain that the decay estimates of the energy function is exponential or polynomial by using Nakao's method. By using the energy method, we obtain the blow‐up result of solution with some positive or nonpositive initial energy. Copyright © 2016 John Wiley & Sons, Ltd.     

Control for going from hovering to small speed flight of a model insect

The longitudinal steady-state control for going from hovering to small speed flight of a model insect is studied, using the method of computational fluid dynamics to compute the aerodynamic derivatives and the techniques based on the linear theories of stability and control for determining the non-zero equilibrium points. Morphological and certain kinematical data of droneflies are used for the model insect. A change in the mean stroke angle （δФ） results in a horizontal forward or backward flight; a change in the stroke amplitude （δФ） or a equal change in the down- and upstroke angles of attack （δα1） results in a vertical climb or decent; a proper combination of δФ and δФ controls （or δФ and δα1 controls） can give a flight of any （small） speed in any desired direction.     

Chromatographic and mass spectrometric fingerprinting analyses of Angelica sinensis (Oliv.) Diels-derived dietary supplements

Angelica sinensis (Oliv.) Diels (“Danggui” in Chinese) is one of the most commonly used traditional Chinese medicines. It has been used to invigorate blood circulation for the treatment of anemia, hypertension, chronic bronchitis, asthma, rheumatism, and cardiovascular diseases. There are a number of A. sinensis-derived dietary supplements in the US markets. However, no study have been conducted to investigate the quality of these dietary supplements. In this paper, high-performance liquid chromatographic and flow-injection mass spectrometric fingerprints were both evaluated to assess the consistency of A. sinensis-derived dietary supplements. Similarity analysis was carried out on the high-performance liquid chromatographic (HPLC) fingerprints. Meanwhile, principal component analysis (PCA) was performed on the data obtained from flow-injection mass spectrometric (FIMS) fingerprints, which can analyze each sample in 2 min, compared with 30 min required for the chromatographic fingerprint. Both methods show significant chemical differences between samples that may be due to differences in growing locations, growing conditions, harvesting times, and/or botanical processing. The loading plots obtained from PCA singled out the discriminatory ions that were responsible for chemical differences of A. sinensis-derived dietary supplements.

Energy decay of variable‐coefficient wave equation with nonlinear acoustic boundary conditions and source term

In this paper, we consider a variable‐coefficient wave equation with nonlinear acoustic boundary conditions and source term. Using the Riemannian geometry method, we prove the general energy decay of the system corresponds to the ordinary differential equation (ODE), which certainly is stable under some suitable assumptions.     

HPLC method for the determination and pharmacokinetic studies of four triterpenoids in rat plasma after oral administration of Ganoderma lucidum extract

Four major triterpenoids (ganoderic acids C(2), B, K and H) in rat plasma after oral administration of G. lucidum extract were analyzed quantitatively by high-performance liquid chromatography (HPLC). Plasma samples taken from rats were acidified with hydrochloric acid and extracted with dichloromethane-ethyl acetate (90:10). The chromatographic separation was achieved on an Agilent Zorbax SB-C(18) column (250 x 4.6 mm, 5 microm) at 35 degrees C, with a linear gradient of acetonitrile and 0.03% aqueous phosphoric acid (v/v), at a flow rate of 1.0 mL/min. The four triterpenoids and internal standard (hydrocortisone) were detected at a wavelength 252 nm. All calibration curves showed good linearity (r(2) > 0.99) within test ranges. The relative deviation of this method was less than 10% for intra- and inter-day assays, and the accuracy ranged from 89 to 108%. The extract recovery for the four triterpenoids and internal standard ranged from 95 to 67%, and the QC samples were found to be stable according to the results of the stability study. This is the first report on determination of the major triterpenoids in rat plasma after oral administration of G. lucidum extract and the results provided a firm basis for clarifying the pharmacological effect of G. lucidum and evaluating the clinical applications of this medicinal fungus.     

Phytochemical analysis of traditional Chinese medicine using liquid chromatography coupled with mass spectrometry

Traditional Chinese medicine (TCM) is commonly considered to operate due to the synergistic effects of all the major and minor components in the medicines. Hence sensitive and comprehensive analytical techniques are needed to acquire a better understanding of the pharmacological basis of the herb and to enhance the product quality control. The present review mainly focuses on the phytochemical analysis of TCMs using high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS). Atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) are the two commonly used ion sources. Triple quadrupole, ion trap (IT), Fourier transform ion cyclotron resonance (FTICR) and time-of-flight (TOF) mass spectrometers are used as on-line analyzer. The relationship between structural features and fragmentation patterns should be investigated as thoroughly as possible and hence be applied in the on-line analysis to deduce the structures of detected peaks. Characteristic fragmentation behaviors of the reference standards, as well as information regarding polarity obtained from retention time data, on-line UV spectra, data from the literature and bio-sources of the compounds allowed the identification of the phytochemical constituents in the crude extracts. Although a mass spectrometer is not a universal detector, high-performance liquid chromatography coupled with multistage mass spectrometry (HPLC-MS(n)) technique was still proved to be a rapid and sensitive method to analyze the majority of the many constituents in herbal medicines, particularly for the detection of those present in minor or trace amounts. The methods established using HPLC-MS techniques facilitate the convenient and rapid quality control of traditional medicines and their pharmaceutical preparations. However, the quantitative analysis is not the topic of this review.     

Simultaneous Determination of Six Major Constituents in the Stems of Kadsura heteroclita by LC-DAD

The stem of Kadsura heteroclita is a traditional Chinese medicine with a variety of biological activities. For efficient monitoring of the quality of the herb, a simple, rapid, and accurate HPLC method has been developed for simultaneous determination of five cyclolanostane triterpenoid compounds (schisanlactone E, nigranoic acid, schisandronic acid, and heteroclitalactones A and D) and one tetrahydrofuran lignan (d-epigalbacin) in the stems of K. heteroclita. These six compounds were separated on a C₁₈ column by elution with a mobile-phase gradient prepared from acetonitrile and 0.05% (v/v) aqueous phosphoric acid. The flow rate was 1.0 mL min⁻¹ and the detection wavelength was 210 nm. The recovery of the method was in the range 95.03–102.19% and a good linear relationship (r ² > 0.9999) was obtained between response and compound concentration over a relatively wide range. The method was successfully applied to analysis of the herb collected at different stages of growth.     

Exponential decay of solution to the viscoelastic porous‐thermoelastic system of type III with boundary time‐varying delay

In this paper, we are concerned with a one‐dimensional porous‐thermoelastic system of type III with a viscoelastic damping and boundary time‐varying delay. Under suitable assumptions on relaxation function and time delay, we establish the exponential decay result of the system in which the damping is strong enough to stabilize the thermoelastic system in the presence of time delay. Copyright © 2015 John Wiley & Sons, Ltd.     

三维石墨烯基材料的制备、结构与性能

石墨烯具有单层碳原子组成的六方晶系晶体结构及独特的电学、化学、力学和热学性质。然而,由于石墨烯片层之间较强的π-π键和范德华力,导致易团聚或堆积,使其比表面积大幅减小,严重损害其性能。解决上述问题的最有效方法之一是构建具有多孔结构的三维石墨烯基材料,不仅保留了石墨烯优秀的导电性能和力学性能等本征特性,而且获得密度低、比表面积大、孔隙率高等结构优点,进而满足吸附剂、催化剂载体、生物传感器及电池与超级电容器电极材料等先进功能材料领域的应用需要。因此,开发三维石墨烯基材料的先进制备方法成为本领域研究的热点方向。本文综述了三维石墨烯基材料的现有制备方法,包括自组装法(水热还原法、化学还原法及冷冻干燥法)、模板法(胶体模板法、模板辅助化学气相沉积法及模板辅助水热还原法)和3D打印法(直写成型法、喷墨打印法、熔融沉积成型法、光固化成型法、选区激光烧结法及选区激光熔融法),总结了上述方法的优点及当前存在的主要问题,并且对三维石墨烯基材料制备技术的发展方向进行了展望。