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The relaxation modulus of heterogeneous propellants permits evaluating the structural integrity and life of a solid rocket motor. Its governing factors were investigated by the Voronoi cell finite element method (VCFEM) at the microscopic level. The formula of viscoelastic VCFEM is based on the discrete form of the Prony series viscoelastic constitutive model in the time domain; the iterative procedure is also proposed to obtain the effective modulus at each time step. The random sampling method is adopted to analyze the effect of each microparameter on the effective relaxation modulus. The results show that the matrix modulus and inclusion weight fraction exert a more pronounced effect on the relaxation modulus than the inclusion material constants and particle grain.

This study aims to explore the potential mechanism of Liangfu Pills in the treatment of functional dyspepsia(FD) based on network pharmacology and molecular docking, and verify the mechanism by animal experiment. The active components of Liangfu Pills were screened from Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform(TCMSP), and the targets of Liangfu Pills were predicted by SwissTargetPrediction. The targets of FD were retrieved from GeneCards. On this basis, the common targets of the disease and the pills were yielded and the protein interaction was retrieved based on STRING. The core targets were screened out, followed by Gene Oncology(GO) term enrichment and Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway enrichment analysis with DAVID. Finally, molecular docking was carried out with the help of AutoDock Tools to predict the binding degree between the effective components of Liangfu Pills and core targets. A total of 19 active components of Liangfu Pills and 591 FD-related targets were screened out by network pharmacology, of which 253 were common targets of the disease and the prescription. Liangfu Pills was mainly involved in the biological processes of response to drug, negative regulation of transcription, positive regulation of apoptotic process, and cell surface receptor signaling pathway, and the KEGG pathways of hypoxia-inducible factor-1(HIF-1) signaling pathway, serotonergic synapse, tumor necrosis factor(TNF) signaling pathway, cyclic adenosine monophosphate(cAMP) signaling pathway, calcium signal pathway, and inflammatory mediator regulation of transient receptor potential(TRP) channels. The results of molecular docking showed that the key active components of Liangfu Pills had certain binding activity to the targets mitogen-activated protein kinase 1(MAPK1), protein kinase B(AKT1), transient receptor potential cation channel subfamily V member 1(TRPV1), 5-hydroxytryptamine receptor 1 A(HTR1 A), and 5-hydroxytryptamine receptor 2 A(HTR2 A). FD was induced in rats, and then Liangfu Pills was given to FD rats for 7 days. The results showed that Liangfu Pills could significantly relieve the symptoms of FD rats, significantly increase the expression of 5-hydroxytryptamine(5-HT), and down-regulate the expression of TRPV1. Through network pharmacology, molecular docking, and experimental verification, this study proved that Liangfu Pills improved FD through multiple components and multiple targets. The result lays a basis for further research on the mechanism and clinical application of Liangfu Pills in the treatment of FD.

A new phloroglucinol was isolated from 50% ethanol extract of Dryopteris fragrans by silica gel column chromatography, Sephadex LH-20 gel column chromatography, thin-layer chromatography(TLC), and preparative liquid column chromatography. On the basis of MS, ~1H-NMR, ~(13)C-NMR, and reference materials, compound 1 was identified as 2,5-cyclohexadien-1-one, 2-{[2,6-dihydroxy-4-methoxy-3-methyl-5-(1-isobutyl)phenyl]methyl}-3,5-dihydroxy-4,4-dimethyl-6-(1-oxobutyl)(1), and named disaspidin BB. Compound 1 was evaluated for its antibacterial activity. The experimental results showed that compared with the commonly used topical antibiotics erythromycin or mupirocin, disaspidin BB exhibited significant antibacterial activities against Staphylococcus epidermidis(SEP), S. haemolyticus(SHA), and methicillin-resistant S. aureus(MRSA)(Plt;0.05). Additionally, disaspidin BB was sensitive to ceftazidime-resistant SEP1-SEP4, SHA5-SHA7, MRSA8, and MRSA9. The MIC values of disaspidin BB against SEP and SHA were 1.67-2.71 μg·mL~(-1) and 10.00-33.33 μg·mL~(-1) respectively. Disaspidin BB has good antibacterial activities and deserves development as a new anti-infective drug for external use.

Thermal effect on mass detection sensitivity of double-layered graphene sheet (DLGS) resonators based on their nonlocal vibration is investigated. A rectangular DLGS with a nanoparticle anywhere at the upper sheet is modeled as two nanoplates connected by van der Waals force. Based on the nonlocal Kirchhoff theory of plates which incorporates size effects into the classical theory, Galerkin strip transfer function method (GSTFM), which is a semi-analytical method, is developed to solve the characteristic equations and in settling the semi-analytical solutions of the frequency shift of the mass-plate vibrating system. It can give exact closed-form solutions along the strip longitudinal direction. Obtained results from the semi-analytical solutions are in good agreement with the available data in literature. Parametric studies on the natural frequency shift including the temperature changes, the nonlocal parameter and the location of the attached nanoparticle are discussed. The obtained results show that an increase of the temperature difference yields to reduction of fundamental frequency, and the DLGS-based nanomechanical resonator became more sensitive at a negative temperature change. Those conclusions are helpful to the design and application of GS-based resonator as nanomass sensor.

This paper presents a novel formulation of a cohesive zone model able to effectively approximate the time-and temperature-dependent fracture process along a defined interface. The formulation relies on the assumption that the relaxation behavior of the traction is the origin of the time effects, and time temperature equivalence principle can be introduced in solving the temperature effects. A series basic hypotheses are introduced according to the previous research work and will be complied in the paper. By connecting N Maxwell models in parallel and letting the time-independent traction calculated by PPR cohesive zone model as the input parameter, the time-dependent traction will be output by numerical integration. Reduced time considering the effects of temperature will replace the real time in the numerical integration. With the tool of the user subroutine element, the novel formulation is implemented in FEM code ABAQUS. Typical load cases including constant tensile test and relaxation test are analyzed to illustrate the special properties of the formulation. With three set of input parameters, the proposed model can be utilized in a wide range of applied loading rates and temperatures as validated by the remarkable agreement with the experimental data in the case of the double sandwich cantilever beam made of solid propellant/insulation adherents bonded along the liner interface.

At present, the casting of large-size motors often adopts pressure cure. This technology can effectively reduce the risk of damage to the structural integrity of the grain in the case-bonded casting solid rocket motor. In this paper, ABAQUS is used to establish a finite element model of star-shaped grains. The whole process of pressure cure was simulated and modeled, and the Python script was redeveloped. The Evol evolutionary algorithm was used in ISIGHT to optimize the load parameters such as pressure value, attenuation coefficient of the relief curve, and the attenuation coefficient of the cooling curve. The effects of different pressure values and different cooling and depressurizing rates on the residual stress and strain were analyzed. The optimization results show that the closer the pressure value is to the theoretical pressure, the more significant the effect of pressure cure. However, the effect of stress and strain reduction in different directions is slightly different. The different cooling and pressure relief rates have a great influence on the process quantity. Pressure cure works best when the pressure attenuation coefficient is equal to 6850, and the temperature attenuation coefficient is equal to 8650. The optimization analysis of pressure curing provides a reference for engineering practice.

To explore the prescription patterns of different dosage forms of Chinese herbal medicines (CHMs) for the treatment of rheumatoid arthritis (RA) and their effects on immune-inflammatory indices. Clinical data were collected from patients with RA in 4 hospitals (3 Class A comprehensive hospitals and 1 Class B comprehensive hospital) in Anhui Province, China, from August 2012 to June 2018 via the electronic medical record gathering system. Following extraction of prescription information, each prescribed herb was quantified and standardized according to the knowledge base to establish a database of RA treatment formulae. The medical records were divided into the granules group and decoction pieces group. Core herbs and their combination patterns were obtained from the two groups of cases using Liquorice software. Changes in immune-inflammatory and hepatic and renal function indices were compared between the two groups using SPSS 23.0 software. The Aprior module of SPSS Clementine 11.1 software was applied to analyse the correlation between CHMs and improvement in indices. Finally, the ORACLE 10 g tool was used to evaluate the random walk model of the immune-inflammatory indices between the two groups. (1) We retrospectively analysed 35,898 prescriptions for 6,829 patients with RA who received CHM treatment. There were 3,816 patients in the granules group and 3,013 in the decoction pieces group. (2) The core herbs were Pi (Spleen)-strengthening and dampness-resolving drugs, blood-activating and stasis-resolving drugs, wind/dampness-dispelling drugs and heat-clearing and detoxifying drugs. (3) Both dosage forms could improve immune-inflammatory indices in RA patients, with similar efficacy and no influence on hepatic or renal function. (4) Herba Siegesbeckiae and Oldenlandia had a stronger association with immune-inflammatory indices in the two groups. (5) The immune-inflammatory indices showed obvious improvement after treatment with granules and decoction pieces of CHMs, and there were long range correlations between the comprehensive evaluation indices and interventions. The principal CHM treatment methods for RA in four hospitals in Anhui Province are strengthening Pi and resolving dampness, activating blood and resolving stasis, dispelling wind/dampness and clearing heat. Granules and decoction pieces of CHMs have similar efficacy in improving immune-inflammatory indices in RA patients and could be used as treatment options for RA.

In a viscoelastic material Poisson’s ratio is a function of time and temperature that depends on the time and temperature regime chosen to elicit it. In this paper, new creep constitutive models with the effects of time- and temperature-dependent Poisson’s ratio are proposed and demonstrated. In order to establish a suitable constitutive model, the classical creep constitutive model is improved by the Laplace transform method. The new creep constitutive model is discretized into an incremental model and utilized to deduce the material stiffness matrices and applied to the FEM code MSC.Marc. A fully viscoelastic time and temperature implementation of the constitutive equation in FEM is achieved that allows for elastic and viscoelastic Poisson’s ratio in the calculation. Uniaxial constant rate tensile tests are used to verify the applicability of the proposed creep model. A viscoelastic analysis of the pipe construction is conducted to check the numerical algorithm with the analytical solution. The analytic analysis, creep model solutions, and relaxation model solutions match well. Furthermore, a simplified axisymmetric solid rocket motor (SRM) composed of propellant, insulation, and case is established, and the response of SRM under ignition pressure loading is described.

The evaluation of basic mechanical properties are shown to be of importance for the solid composite propellant development and application. The numerical analysis approach termed the three-phase Voronoi cell finite element method, was proposed to evaluate of the interfacial transition zone effect. Numerical results showed that the performance of the effective modulus could be essentially enhanced by increasing the zone thickness. The module of the composite with the inhomogeneous zone was higher than that of the composite with the homogeneous one. The effect of different zones on volume fractions and matrix moduli was also calculated. The Voronoi method can also be helpful for analyzing the characteristic properties of other three-phase composites.

This paper aims to study the effect of externally applied longitudinal magnetic field on the transverse vibration of viscoelastic double-walled carbon nanotubes (visco-DWCNTs) embedded in a viscoelastic medium. The analyses are carried out based on the nonlocal viscoelastic model and Euler–Bernoulli beam theory. Governing equations are derived for the vibration of the embedded visco-DWCNT subjected to a magnetic field, where the Lorentz magnetic force, the surrounding viscoelastic medium, the intertube van der Waals forces and viscoelasticity of the DWCNT are taken into consideration. In this study, the transfer function method is employed to solve the governing equations, which enables one to obtain the natural frequencies and the corresponding mode shapes in closed form for the DWCNTs with arbitrary boundary conditions. Here the developed mechanics model is first compared with the existing techniques available in the literature in a few particular cases, where excellent agreement is achieved. The validation of the model is followed by a detailed parametric study of the effects of longitudinal magnetic field, nonlocal parameter, boundary conditions, structural damping coefficient and aspect ratio of the DWCNTs on their vibration. The study demonstrates the efficiency of the present technique designed for vibration analysis of a complicated multi-physics system comprising DWCNTs, the viscoelastic medium and a magnetic field in longitudinal direction.

Double-layered graphene sheets (DLGSs) can be applied to the development of a new generation of nanomechanical sensors due to their unique physical properties. A rectangular DLGS with a nanoparticle randomly located in the upper sheet is modeled as two nonlocal Kirchhoff plates connected by van der Waals forces. The Galerkin strip transfer function method which is a semi-analytical method is developed to compute the natural frequencies of the mass-plate vibrating system. It can give exact closed-form solutions along the longitudinal direction of the strip. The results obtained from the semi-analytical method are compared with the previous ones, and the differences between the single-layered graphene sheet (SLGS) and the DLGS mass sensors are also investigated. The results demonstrate the similarity of the in-phase mode between the SLGS and DLGS mass sensors. The sensitivity of the DLGS mass sensor can be increased by decreasing the nonlocal parameter, moving the attached nanoparticle closer to the DLGS center and making the DLGS smaller. These conclusions are helpful for the design and application of graphene-sheet-based resonators as nano-mass sensors.

A new constitutive equation for solid propellant with the effects of aging and viscoelastic Poisson’s ratio is proposed. Effects of thermo-oxidative aging and viscoelastic Poisson’s ratio are considered in this comprehensive constitutive equation with two sets of reduced time system coping with the time and temperature dependence. In order to simulate the single and combined effects of aging and viscoelastic Poisson’s ratio, constitutive equation is rewritten into an incremental form and implemented in the user subroutine UMAT at the platform of finite element code ABAQUS. Detailed procedure for acquiring the parameters in constitutive equation is introduced and conducted for the subsequent applied analysis. Two typical loading cases during the service life of solid rocket motor and four sets of combined constitutive models are simulated. Von Mises strain and stress distribution and their changes versus time are utilized as the main analysis index. The results show that the effects of aging and viscoelastic Poisson’s ratio or their combinations will improve or decrease the level and change the distribution of Von Mises strain and stress in varying degrees.

A solid rocket motor is one of the critical components of solid missiles, and its life and reliability mostly depend on the mechanical behavior of a composite solid propellant (CSP). Effective mechanical properties are critical material constants to analyze the structural integrity of propellant grain. They are estimated by a numerical method that combines the Voronoi cell finite element method (VCFEM) and the homogenization method in the present paper. The correctness of this combined method has been validated by comparing with a standard finite element method and conventional theoretical models. The effective modulus and the effective Poisson’s ratio of a CSP varying with volume fraction and component material properties are estimated. The result indicates that the variations of the volume fraction of inclusions and the properties of the matrix have obvious influences on the effective mechanical properties of a CSP. The microscopic numerical analysis method proposed in this paper can also be used to provide references for the design and the analysis of other large volume fraction composite materials.

The mechanical properties of Composite solid propellant (CSP) are the critical material parameters to analyze the structural integrity of propellant grains, and have a significant influence on the life and reliability of solid rocket motors. A Voronoi cell finite element method using an adaptive algorithm in the time domain is proposed for investigating the linear viscoelasticity of CSP in the present paper. A process is brought forward to produce a Representative volume element (RVE) model, which reflects the microstructural features of CSP. Numerical viscoelastic examples are used for varying the accuracy of this method. In addition, finite element simulations are conducted to understand the effect of microstructural morphology and material properties of inclusion on the effective mechanical properties of CSP using the new method. When this method is applied to the design process of CSP, it can reduce the design cost and shorten the design cycle effectively. The current microscopic numerical analysis method can be used to provide guidance for designing and analyzing the mechanical properties of composite viscoelastic materials.

A semi-analytical method named Galerkin strip distributed transfer function method (GSDTFM) is employed to solve the buckling and vibration of a single-layered graphene sheet (SLGS) nanomechanical resonator subjected to initial in-plane loads within the framework of the nonlocal Kirchhoff plate theory. The buckling load and the frequency shift are obtained by using the GSDTFM. And the effects of the initial in-plane load, the nonlocal parameter as well as the attached nanoparticle location on the frequency shift are investigated. The simulated results show that the buckling load of the SLGS depends on not only the side length of the SLGS, but also the small scale effects. The impact of the initial in-plane load on the fundamental frequency is significant. The frequency shift at an initial tensile load is larger than that at an initial compressive load. These results are consistent with the previously reported ones.

Objectives Aspidin BB, a typical phloroglucinol derivative from Dryopteris fragrans, possesses significant antifungal property. This study aimed to investigate potential mechanism of antifungal activity of Aspidin BB against Trichophyton rubrum which is the most common pathogens responsible for chronic dermatophytosis. Methods The minimum inhibitory concentration (MIC) of Aspidin BB against strains was determined by broth microdilution. The effects of Aspidin BB on ergosterol biosynthesis were investigated by content determination based on UPLC method. Besides, the effects of drugs on squalene epoxidase (SE) in T. rubrum cell membrane were analyzed. Results MIC value of Aspidin BB against T. rubrum was 25.0 μg/mL. Aspidin BB reduced ergosterol content significantly, but no notable effect on squalene epoxidase activity. Conclusion The results suggested that Aspidin BB inhibited ergosterol biosynthesis. However, it was not squalene epoxidase but other components may sever as possible targets in ergosterol biosynthesis pathway.

From the dried root and rhizomes of

From the dried root and rhizomes of Atalantia buxifolia afford 11 compounds, one new compound 1 and ten known compounds 2–11 were isolated and identified. The novel compound 1 was alkaloid glycoside. Its mother nuclear was the acridone, which was relatively rare. The structure of compound 1 was established identified by spectrum and elucidated as β-D-Glu-4,5-dimethoxy-1,6-dihydroxy-10-methyl-acridone. The compound 1 enriched the compound library and laid the material foundation for the subsequent study of pharmacological activities.

The free vibration of a single-layered graphene sheet (SLGS)-based mass sensor is analyzed using the Galerkin strip distributed transfer function method (GSDTFM) based on the nonlocal Kirchhoff plate theory. The dynamic equations of the SLGS-based mass sensor are formulated, and the semi-analytical solutions of the frequency shift are computed with the GSDTFM. The effects of the nonlocal parameter, the attached nanoparticle locations, the plate side length, as well as the boundary conditions, on the frequency shift are studied. The simulated results show that the frequency shift of the SLGS-based mass sensor becomes smaller when the nonlocal parameter increases. The SLGS-based mass sensor is more sensitive when the attached nanoparticle is closer to the SLGS center or the side length of the SLGS becomes smaller. The boundary conditions strongly affect the frequency shift. Stiffer boundary condition causes larger frequency shift.

Axial free vibration of a nanobar carrying a nanoparticle is studied based on the nonlocal elasticity theory and Love’s assumption. By considering inertia of radial motion during longitudinal vibration, a governing equation for a nanobar–mass oscillation system is derived via Hamilton’s principle. An exact frequency equation is obtained and an approximate simple expression for the fundamental-mode resonance frequency is given. The size effect of the resonance frequencies is elucidated. The classical Love bar theory and the nonlocal bar theory can be recovered from two special cases by setting the nonlocal parameter and Poisson’s ratio to zero, respectively. Numerical examples are given to show the influence of the nonlocal scaling parameter and attached mass on the resonance frequencies and frequency shifts. Identification formulas for estimating the mass of an attached nanoparticle and predicting the nonlocal parameter are established through the frequency change.

Digital image correlation methods were used for further studies of the viscoelastic Poisson's ratio of solid propellants. The Poisson's ratio and the Young's relaxation modulus of solid propellants were separately determined in a single stress relaxation test. In addition, the effects of temperature, longitudinal strain, preload and storage time on the Poisson's ratio of solid propellants were discussed. The Poisson's ratio master curve and the Young's relaxation modulus master curve were constructed based on the time-temperature equivalence principle. The obtained results showed that the Poisson's ratio of solid propellants is a monotone non-decreasing function of time, the instantaneous Poisson's ratio increased from 0.3899 to 0.4858 and the time of the equilibrium Poisson's ratio occurred late when the temperature was varied from −30 °C to 70 °C. The Poisson's ratio increased with temperature and longitudinal strain, decreased with preload and storage time, while the amplitude Poisson's ratio increased with preload, decreases with longitudinal strain and storage time. The time of the equilibrium Poisson's ratio occurred in advance with the increase of longitudinal strain, preload and storage time.

This paper studies an axisymmetric problem of a penny-shaped interface crack of a bi-material subjected to compression and radial shear at the crack surfaces in cylindrical coordinate system. The Hankel transform technique is applied to convert the problem to dual integral equations. Closed-form solutions for mode-I and II stress intensity factors are obtained for arbitrary radial shear loading at the crack surfaces. Obtained results indicate that no oscillation singularity occurs. Explicit expressions for the stresses and displacements in the whole bi-material elastic space are derived for constant and linear radial shear stress acting on the crack surfaces, respectively. Under uniform radial shear stress, normal and shear stresses have a usual square-root singularity behind and ahead of the crack front, respectively, and the induced normal stress exhibits a logarithmic singularity at the crack center. Under linearly-distributed radial shear stress, the logarithmic singularity at the crack center disappears, and the square-root singularity is still present for the normal and shear stresses near the crack front. The induced mode-I stress intensity factors depend on Dundurs’ parameter and on applied shear loading. Numerical results for a penny-shaped interface crack in Al2O3/PMMA bi-material are presented to show the influence of the bi-material properties on the stress distribution.

This paper studies an external circular crack at the interface of a bi-material subjected to shear–compressive loading at the crack surfaces. An axisymmetric problem is solved for an external circular crack where radial shear loadings are applied at the smooth crack surfaces. Across the crack surfaces in contact, there are tangential displacement shift and no normal displacement gap. A mixed boundary value problem is reduced to dual integral equations, and a closed-form solution of the interface stresses is given via the Hankel transform technique. Our results indicate that there is no oscillatory singularity near the interface crack front in shear–compression. Both the radial shear stress and the normal stress exhibit a usual square-root singularity ahead of and behind the crack front, respectively. Explicit expressions for the mode-I and II stress intensity factors (SIFs) are obtained for compressive forces applied at the central axis of the bonding part towards to the bonding center. The mode-I SIFs are proportional to mode-II SIFs, and depend on a Dundurs’ parameter. Numerical results of a bi-material Al 2 O 3 /PMMA with an external circular crack subjected to compressive forces are presented to show the influence of the bi-material properties on the stress distribution and the SIFs.

A two-dimensional elastic analysis is made for a crack lying at the interface between two bonded dissimilar homogeneous isotropic media subjected to shear and compression. The Fourier transform technique is applied to reduce the problem to dual integral equations, and the solution is obtained in closed form. Full stress fields at an arbitrary position of the whole bi-material plane induced by a closed mode-II interface crack are explicitly obtained for uniform and linearly distributed shear stress at the crack surface, respectively. The stress intensity factors are gained in closed form. Obtained results indicate that the shear stresses ahead of the crack tip exhibit a usual square-root singularity, rather than oscillatory singularity. Disturbed normal stresses are also singular at the crack surfaces behind the crack tips and depend on a Dundurs’ parameter. Using the maximum tangential stress criterion, the Dundurs’ parameter has an influence on the initiation angle of an interface crack in mixed compression–shear mode.

Six pentasaccharide resin glycosides from Ipomoea cairica, including four new acylated pentasaccharide resin glycosides, namely cairicoside I–IV (1–4) and the two known compounds cairicoside A (5) and cairicoside C (6), were isolated from the aerial parts of Ipomoea cairica. Their structures were established by a combination of spectroscopic, including two dimensional (2D) NMR and chemical methods. The core of the six compounds was simonic acid A, and they were esterfied the same sites, just differing in the substituent groups. The lactonization site of the aglycone was bonded to the second saccharide moiety at C-2 in 1–4, and at C-3 in 5–6. Compounds 1 and 5, 4 and 6 were two pairs of isomers. The absolute configuration of the aglycone in 1–6 which was (11S)-hydroxyhexadecanoic acid (jalapinolic acid) was established by Mosher’s method. Compounds 1–4 have been evaluated for inhibitory activity against α-glucosidase, which all showed inhibitory activities.

This article studies the influence of the nonlocal scale parameter on the deflection of a nonlocal nanobeam and crack growth. Using the Timoshenko hypothesis, a single governing equation is derived and its exact solution can be determined through appropriate end-support conditions. Numerical calculations are carried out for a cantilever microtubule in solution at a given flow speed. The effects of nonlocal scale parameter on the deflection are discussed. Based on the obtained solutions, the double cantilever beam model is utilized to determine energy release rate near a crack tip for an edge crack and a central crack, respectively. It is found that the scale parameter plays different roles in determining stress intensity factors and energy release rates, depending on crack constraints. When neglecting shear deformation, the results for nonlocal Euler-Bernoulli beams can be directly obtained.

The potential of circular graphene sheet (GS) as a mass sensor is explored. A circular GS carrying a nanoparticle at an arbitrary position is modeled as a circular nanoplate with a concentrated micro-mass for clamped and simply supported boundary conditions. Based on the nonlocal Kirchhoff plate theory which incorporates size effects into the classical theory, the natural frequencies of the mass sensor are derived using the Galerkin method. The effects of mass and position of the nanoparticle on the frequencies and frequency shifts are discussed. The frequencies reduce to the results of the classical model for the absence of the small scale effect, which maintain in accordance with those available in literatures. Numerical results show that when the mass of the attached nanoparticle increases or its location is closer to the plate center, the natural frequency decreases, but frequency shift increases. Small scale effect diminishes the frequencies strongly, but has less effect on the frequency shifts. When the radius of the nanoplate decreases, the frequency shift increases. The results are helpful to design circular GS-based resonators as nanomechanical mass sensor.

This paper studies the damage-viscoelastic behavior of composite solid propellants of solid rocket motors (SRM). Based on viscoelastic theories and strain equivalent hypothesis in damage mechanics, a three-dimensional (3-D) nonlinear viscoelastic constitutive model incorporating with damage is developed. The resulting viscoelastic constitutive equations are numerically discretized by integration algorithm, and a stress-updating method is presented by solving nonlinear equations according to the Newton-Raphson method. A material subroutine of stress-updating is made up and embedded into commercial code of Abaqus. The material subroutine is validated through typical examples. Our results indicate that the finite element results are in good agreement with the analytical ones and have high accuracy, and the suggested method and designed subroutine are efficient and can be further applied to damage-coupling structural analysis of practical SRM grain.

A viscoelastic cohesive zone model (CZM) is formulated herein to model the time- and temperature-dependent fracture process of the interface between the solid propellant and insulation. The model is suitable for the simulation of a wide range of problems especially for the relaxation response of the fracture process. Independent control parameters of the Park-Paulino-Roesler (PPR) models are deduced first. By introducing the relaxed critical displacement, cohesive strength and initial slope parameter into the static PPR model, a viscoelastic CZM is established. Numerical time integration about obtaining the reduced time is described considering the change of the temperature. The properties of the proposed model are discussed in detail through the stretch and relaxation test of the double cantilever beam (DCB). Stretch test of the double cantilever sandwich beam (DCSB) under different loading rates and loading temperatures are designed to inverse the time-dependent and temperature-dependent model parameters respectively. To check the effectiveness of the proposed model and the accuracy of the inversed model parameters, three different tests including stretch test, multiple stretch-relaxation test, and creep test are conducted. The agreement is achieved between the numerical and experimental results.

The structural integrity of solid rocket motor(SRM) grain is severely tested owing to the combined action of low temperature and pressure load under the load case of low temperature ignition. The three dimensional finite element model of SRM was created to analyze the structural integrity of the SRM grain subjected to low temperature and ignition pressure based on three dimensional viscoelastic finite element method via MSC.Patran/Marc. Meanwhile, cold pressurization test was applied on certain SRM. The experimental result and numerical result were compared based on uncoupling principal of temperature and pressure. The result show that the safety factor of solid rocket motor grain is 2.46 which can meet the requirement of structural integrity. The experimental results are in good agreement with the simulation results. Relevant research methods and conclusions can provide reference for the design, analysis and test of SRMs.

Growth of crack modeled as double cantilever beam at nanoscale is studied. Using the gradient elasticity theory, the energy of nanocantilevers is calculated. The energy release rate and stress intensity factor of double cantilever nanobeams are obtained. Results indicate that the energy release rates and stress intensity factors exhibit pronounced size effects if the thickness of the nanobeam falls in the same order of the characteristic length. The fracture toughness of the nanostructures is apparently enhanced. The energy release rates and stress intensity factors have little size-dependence if the thickness of the nanobeam is greater much than the characteristic length.

In our previous report (J Pharmaceut Biomed 56 (2011) 443-447), a support vector machine (SVM)-based pharmacodynamic model was established for predicting active fractions of herbal medicines (HMs), where information contents embedded in the chromatograms of the fractions were represented with the peak areas. However, in this representation the global characteristics of the chromatograms were completely missed, which is definitely contrary to the global and holistic views in theories of HMs and undoubtedly reduce the success rate of this model. To deal with the challenge, two chemometrics methods, that is, minimum redundancy maximum relevance (mRMR) and particle swarm optimizer (PSO), were applied in this article for feature selection of the whole chromatograms, and the PSO was also used to tune the SVM parameters. As a case, a sample HM, that is, Xiangdan injection, was investigated. The predictive accuracy was fully evaluated and compared with those by other popular and reported methods. Furthermore, the confirmation on the independent predicting set exhibited that the predicted bioactivities were well consistent with the experimental values. The important potential application of the present model is to be extended to help search active fractions of other HMs.

This paper studies the influence of surface elasticity on crack growth for a nanoscale crack advance. A crack is modeled as a double cantilever beam with consideration of surface stress. Using the Euler-Bernoulli beam theory incorporating with surface effects, a governing equation of static bending is derived and bending solution of a cantilever nanowire is obtained for a concentrated force at the free end. Based on the viewpoint of energy balance, the elastic strain energy is given and energy release rate is determined. The influences of the Surface stress and the surface elasticity on crack growth are discussed. Obtained results indicate that consideration of the surface effects decreases stress intensity factors or energy release rates. The residual surface tension impedes propagation of a nanoscale crack and apparent fracture toughness of nanoscale materials is effectively enhanced.

The potential of single-layered graphene sheet (SLGS) as a nanomechanical sensor is explored. A simply supported SLGS carrying a nanoparticle at any position is modeled as a rectangular nanoplate with a concentrated micro-mass. Based on the nonlocal Kirchhoff theory of plates which incorporates size effects into the classical theory, the natural frequencies of a nanomechanical sensor are derived using the Galerkin method. The effects of the mass and position of the nanoparticle on the frequency shift are discussed. In the absence of the nonlocal parameter, the frequencies reduce to the results of the classical model, in agreement with those using the finite element method. The obtained results show that when the mass of the attached nanoparticle increases or its location is closer to the plate center, the natural frequency decreases, but frequency shift increases. Small scale effect diminishes the frequency shift. Decreasing the plate side length also increases the frequency shift. Obtained results are helpful to the design of SLGS-based resonator as nanomechanical mass sensor.

This paper studies free vibration of double-walled carbon nanotubes (DWCNTs) based nanomechanical sensor under initial axial stress. A bridged DWCNT carrying a nanoparticle at any position of the outer tube is modeled as two clamped nonlocal Euler–Bernoulli beams, and the interaction between two tubes is governed by van der Waals force. For comparison, a bridged single-walled carbon nanotube (SWCNT) based nanomechanical sensor is considered in a similar way. Using the transfer function method, the critical buckling stress and natural frequencies of these nanomechanical sensors are computed. Under small initial stress, the effects of the attached nanoparticle, and the small scale parameter on the frequency shift are discussed. The obtained results show that when the mass of the nanoparticle increases or its location is closed to the beam center, the natural frequency decreases, but frequency shift increases. Initial tensile stress increases the natural frequency, while initial compressive stress decreases the natural frequency. In comparison with SWCNT sensor, DWCNT is more stable, but less sensitive for smaller attached mass. Obtained results are helpful to the design of DWCNT-based resonator as nanomechanical sensor.

This article studies vibration of carbon nanotube (CNT)-based biosensor. A CNT-based biosensor is modeled as a nonlocal Timoshenko beam made of multiwall CNT carrying a spherical nanoscale bio-object at the free end, and the influence of the rotary inertia of the bio-object itself is considered. The fundamental frequencies are computed via the transfer function method. The effects of the attached spherical bio-object's rotary inertia and mass, the length-to-diameter of the CNT on the natural frequencies are discussed. If the nonlocal parameter is neglected, the frequencies for four possible cases are compared. Obtained results show that the rotary inertia decreases the fundamental frequency, while an increase in the diameter of the attached bio-object reduces the natural frequency, but causes frequency shift to rise. The mass sensitivity of biosensor can be improved for short CNTs used. The rotary inertia of the attached bio-object has a strong effect on the natural frequencies and cannot be simply neglected. The nonlocal Timoshenko beam model is more adequate than the nonlocal Euler-Bernoulli beam model for short CNT biosensors. Obtained results are helpful to the design of micro-cantilevered resonator as atomic-resolution mass sensor or biosensor.

Transverse vibration of the shear beams containing rotary inertia and with a two-parameter elastic foundation is studied. Using asymptotic analysis of Timoshenko beam theory, we derive explicit characteristic equations of the nonclassical shear beams with Winkler-Pasternak elastic restraint and with both ends linked to translational and rotational springs. The condition of the nonclassical shear beams reducing to the classical ones is found. Natural frequencies of the nonclassical modes are evaluated for free- and pinned-elastically restrained shear beams with or without bracing. The influences of elastic restraint stiffness and rotary inertia on the natural frequencies are discussed. Some extreme cases can be recovered from the present. The obtained results are helpful in the design of a tall frame building.

The potential of single-walled carbon nanotube (SWCNT) as a micro-mass sensor is explored. A clamped-free SWCNT with an attached tip micro-mass is modeled as a microcantilever with a concentrated mass at the free end. Based on the nonlocal Timoshenko theory of beams, the transverse vibration of the SWCNT-based micro-mass sensor is analyzed. Using the transfer function method, the natural frequencies of a nonlocal Timoshenko cantilever with a tip mass are computed. The effects of the attached mass and rotary inertia on the natural frequencies are discussed. When the nonlocal effect is neglected, the frequencies reduce to the classical results, in agreement with those using the finite element method. The obtained results show that with increasing the attached micro-mass, the natural frequency decreases, but frequency shift increases. Decreasing the length-to-diameter ratio also increases the frequency shift. The effect of the nonlocal parameter is significant, especially for higher-order vibration modes. The nonlocal Timoshenko beam model is more adequate than the nonlocal Euler–Bernoulli beam model for short SWCNT sensors. Obtained results are helpful to the design of SWCNT-based resonator as micro-mass sensor.

Pseudoaspidinol is a phloroglucinol derivative with Antifungal activity and is a major active component of Dryopteris fragrans. In our previous work, we studied the total synthesis of pseudoaspidinol belonging to a phloroglucinol derivative and investigated its antifungal activity as well as its intermediates. However, the results showed these compounds have low antifungal activity. In this study, in order to increase antifungal activities of phloroglucinol derivatives, we introduced antifungal pharmacophore allylamine into the methylphloroglucinol. Meanwhile, we remained C1&ndash, C4 acyl group in C-6 position of methylphloroglucinol using pseudoaspidinol as the lead compound to obtain novel phloroglucinol derivatives, synthesized 17 compounds, and evaluated antifungal activities on Trichophyton rubrum and Trichophyton mentagrophytes in vitro. Molecular docking verified their ability to combine the protein binding site. The results indicated that most of the compounds had strong antifungal activity, in which compound 17 were found to be the most active on Trichophyton rubrum with Minimum Inhibitory Concentration (MIC) of 3.05 &mu, g/mL and of Trichophyton mentagrophytes with MIC of 5.13 &mu, g/mL. Docking results showed that compounds had a nice combination with the protein binding site. These researches could lay the foundation for developing antifungal agents of clinical value.

Ethnopharmacological relevance The herbal formula Xiangdan injection and its modifications have been used in traditional Chinese medicine for about hundreds years to alleviate pain and promoting blood. Aim To investigate the anti-hypoxia active fraction of Xiangdan injection. Materials and methods Xiangdan injection was extracted by ligarine, chloroform, acetic ether, n-butanol and water, represented respectively by A, B, C, D and E. Five extractions were group on the L12(2 5 ) orthogonal designed table. NIH mices anti-hypoxia experiment under normal pressure with rats was adopted on the basis of orthogonal design, prediction pharmacodynamics model of TCM prescriptions was established, and the simulation bias was evaluated by combining two scatterplots. The anti-hypoxia active fraction of Xiangdan injection was determined by experiments. Results The prediction model of TCM prescriptions established in this study can predict the drug actions for different formulas, and PE% ≤ 25% was observed in 112 mice (93.3%). Conclusion As indicated in model prediction and experimental confirmation, the pharmacodynamic actions of the 5 formulas are all superior to that of the original formula, and ADE has the best effect.

To against the emergence of drug-resistent candidiasis, the studys of synergism of natural compounds combine with antifungal agents in vitro showed a continuous growth in recent years. The paper reviewed recent progresses to compare the synergetic effect by FICI method, and to conclude the synergetic mechanisms which have been confirmed as a reference for futher study.