A two-degree-of-freedom(2DOF)vibration isolation structure with an integrated geometric nonlinear inerter(NI)device is proposed.The device is integrated into an inertial nonlinear energy sink(INES),and its vibration s...A two-degree-of-freedom(2DOF)vibration isolation structure with an integrated geometric nonlinear inerter(NI)device is proposed.The device is integrated into an inertial nonlinear energy sink(INES),and its vibration suppression performance is examined by the Runge-Kutta(RK)method and verified by the harmonic balance method(HBM).The new isolator is compared with a traditional vibration isolator.The results show a significant improvement in the vibration suppression performance.To investigate the effects of the excitation amplitude and initial condition on the dynamics of the system,a series of transmissibility-frequency response analyses are performed based on the displacement transmissibility.The energy flow of the system is analyzed,and numerous calculations reveal a series of ideal values for the energy sink in the NI-INES system.This study provides new insights for the design of vibration isolators.展开更多
A novel vibration absorber is designed to suppress vibrations in fluidconveying pipes subject to varying fluid speeds.The proposed absorber combines the fundamental principles of nonlinear energy sinks(NESs)and nonlin...A novel vibration absorber is designed to suppress vibrations in fluidconveying pipes subject to varying fluid speeds.The proposed absorber combines the fundamental principles of nonlinear energy sinks(NESs)and nonlinear energy harvesters(NEHs).The governing equation is derived,and a second-order discrete system is used to assess the performance of the developed device.The results demonstrate that the proposed absorber achieves significantly enhanced energy dissipation efficiency,reaching up to 95%,over a wider frequency range.Additionally,it successfully harvests additional electric energy.This research establishes a promising avenue for the development of new nonlinear devices aimed at suppressing fluid-conveying pipe vibrations across a broad frequency spectrum.展开更多
RNA interfering(RNAi), mediated by small interfering RNAs and microRNAs, is currently one of the most promising tools of gene therapy. Small RNAs are capable of inducing specific post-transcriptional gene silencing, p...RNA interfering(RNAi), mediated by small interfering RNAs and microRNAs, is currently one of the most promising tools of gene therapy. Small RNAs are capable of inducing specific post-transcriptional gene silencing, providing a potentially effective platform for the treatment of a wide array of diseases. However, similar to other nucleic acid-based drugs,the major hurdle of RNAi therapy is lack of efficient and non-immunogenic delivery vehicles. Currently, viruses, synthetic polymers, and lipid-based carriers are among the most widely studied vehicles for small RNA delivery. However, many drawbacks are reported to be associated with these delivery vehicles. There is a pressing need to replace them with more efficient and better-tolerated approaches. Exosomes secreted from the endocytic compartment of live cells, are a subtype of endogenous extracellular vesicles that transfer genetic and biochemical information among different cells, thus playing an important role in cellcell communication. Recently, accumulating attention has been focused on harnessing exosomes as nanaocarriers for small RNAs delivery. Due to their natural role in shuttling endogenous nucleic acid in our body, exosomes may exhibit higher delivery efficiency, lower immunogenicity, and better compatibility than existing foreign RNA carriers. Importantly,exosomes own intrinsic homing capacity that can guide small RNAs across natural membranous barriers. Moreover, such a capacity can be further improved by adding appropriate targeting moieties. In this manuscript, we briefly review the progress and challenges of RNAi therapy, and discuss the potential of exosomes' applications in small RNA delivery with focus on the most recent advances in exosome-based small RNA delivery for disease therapy.展开更多
The dynamics and stability of fluid-conveying corrugated pipes are investigated. The flow velocity is assumed to harmonically vary along the pipe rather than with time. The dimensionless equation is discretized with t...The dynamics and stability of fluid-conveying corrugated pipes are investigated. The flow velocity is assumed to harmonically vary along the pipe rather than with time. The dimensionless equation is discretized with the differential quadrature method (DQM). Subsequently, the effects of the mean flow velocity and two key parameters of the corrugated pipe, i.e., the amplitude of the corrugations and the total number of the corrugations, are studied. The results show that the corrugated pipe will lose stability by flutter even if it has been supported at both ends. When the total number of the corrugations is sufficient, this flutter instability occurs at a micro flow velocity. These phenomena are verified via the Runge-Kutta method. The critical flow velocity of divergence is analyzed in detail. Compared with uniform pipes, the critical velocity will be reduced due to the corrugations, thus accelerating the divergence instability. Specifically, the critical flow velocity decreases if the amplitude of the corrugations increases. However, the critical flow velocity cannot be monotonously reduced with the increase in the total number of the corrugations. An extreme point appears, which can be used to realize the parameter optimization of corrugated pipes in practical applications.展开更多
The mathematical modeling of a rotating tapered Timoshenko beam with preset and pre-twist angles is constructed. The partial differential equations governing the six degrees, i.e., three displacements in the axial, fl...The mathematical modeling of a rotating tapered Timoshenko beam with preset and pre-twist angles is constructed. The partial differential equations governing the six degrees, i.e., three displacements in the axial, flapwise, and edgewise directions and three cross-sectional angles of torsion, flapwise bending, and edgewise bending, are obtained by the Euler angle descriptions. The power series method is then used to investigate the natural frequencies and the corresponding complex mode functions. It is found that all the natural frequencies are increased by the centrifugal stiffening except the twist frequency, which is slightly decreased. The tapering ratio increases the first transverse,torsional, and axial frequencies, while decreases the second transverse frequency. Because of the pre-twist, all the directions are gyroscopically coupled with the phase differences among the six degrees.展开更多
Bioequivalence(BE) assessment of topical dermatological products is a long standing challenge. The development of generic topical dermatological products has often been hampered due to the limited number of acceptable...Bioequivalence(BE) assessment of topical dermatological products is a long standing challenge. The development of generic topical dermatological products has often been hampered due to the limited number of acceptable approaches, which are capable of determining the BE between generic products and reference list products. The aim of this manuscript is to review different BE assessment approaches of topical dermatological products. Besides, the advances in BE evaluation and biowaivers are also provided. Currently, except in the case of dermatological corticosteroids, the golden rule to establish the BE of most topical dermatological products still heavily relied on clinical endpoint trials,which are often unreliable, time-consuming and expensive. The regulatory agencies and pharmaceutical industries are forging ahead to the development of new surrogate BE assessment approaches for other topical dermatological products. These promising approaches include dermatopharmacokinetic study(DPK), dermal microdialysis(DMD), in vitro studies, pharmacokinetic study(PK), near-infrared spectrometry(NIR), and confocal Raman spectroscopy(CRS). In addition, the expansion of biowaivers for topical dermatological products has been explored by pharmaceutical scientists. In conclusion, to accelerate the development and approval of topical dermatological products, emphasis should be put on the following areas, i.e., optimizing and standardizing the existing BE assessment methods, exploring novel alternatives of BE assessment approaches, and expanding biowaivers for topical dermatological products.展开更多
The natural dynamic characteristics of a circular cylindrical tube made of three-directional(3 D)functional graded material(FGM)based on the Timoshenko beam theory are investigated.Hamilton’s principle is utilized to...The natural dynamic characteristics of a circular cylindrical tube made of three-directional(3 D)functional graded material(FGM)based on the Timoshenko beam theory are investigated.Hamilton’s principle is utilized to derive the novel motion equations of the tube,considering the interactions among the longitudinal,transverse,and rotation deformations.By dint of the differential quadrature method(DQM),the governing equations are discretized to conduct the analysis of natural dynamic characteristics.The Ritz method,in conjunction with the finite element method(FEM),is introduced to verify the present results.It is found that the asymmetric modes in the tube are controlled by the 3 D FGM,which exhibit more complicated shapes compared with the unidirectional(1 D)and bi-directional(2 D)FGM cases.Numerical examples illustrate the effects of the axial,radial,and circumferential FGM indexes as well as the supported edges on the natural dynamic characteristics in detail.It is notable that the obtained results are beneficial for accurate design of smart structures composed from multi-directional FGM.展开更多
A cationic gene delivery vector, guanidinylated disulfide-containing poly(amido amine)(CARCBA), was synthesized by Michael addition reaction between N,N′-cystaminebisacrylamide(CBA) and guanidine hydrochloride(CAR). ...A cationic gene delivery vector, guanidinylated disulfide-containing poly(amido amine)(CARCBA), was synthesized by Michael addition reaction between N,N′-cystaminebisacrylamide(CBA) and guanidine hydrochloride(CAR). Gel permeation chromatography(GPC) was used to evaluate the molecular weight of synthesized CAR-CBA. Polyethyleneimine(PEI) with molecular weight of 25 kDa was adopted as a reference, and polyethylene glycols(PEG) with different molecular weights were used to establish a standard curve for determining the molecular weight of CAR-CBA. The effects of two critical factors, namely columns and eluents,on the molecular weight measurement of CAR-CBA were investigated to optimize the GPC quantitative method. The results showed that Ultrahydrogel columns(120, 250) and HAc–NaAc(0.5 M, pH 4.5) buffer solution were the optimal column and GPC eluent, respectively.The molecular weight of the synthesized CAR-CBA was analyzed by the optimized GPC method and determined to be 24.66 kDa.展开更多
Cantilevered pipe conveying fluid may become unstable and flutter instability would occur when the velocity of the fluid flow in the pipe exceeds a critical value.In the present study,the theoretical model of a cantil...Cantilevered pipe conveying fluid may become unstable and flutter instability would occur when the velocity of the fluid flow in the pipe exceeds a critical value.In the present study,the theoretical model of a cantilevered fluid-conveying pipe attached by an inerter-based dynamic vibration absorber(IDVA)is proposed and the stability of this dynamical system is explored.Based on linear governing equations of the pipe and the IDVA,the effects of damping coefficient,weight,inerter,location and spring stiffness of the IDVAon the critical flow velocities of the pipe system is examined.It is shown that the stability of the pipe may be significantly affected by the IDVA.In many cases,the stability of the cantilevered pipe can be enhanced by designing the parameter values of the IDVA.By solving nonlinear governing equations of the dynamical system,the nonlinear oscillations of the pipe with IDVA for sufficiently high flow velocity beyond the critical value are determined,showing that the oscillation amplitudes of the pipe can also be suppressed to some extent with a suitable design of the IDVA.展开更多
Phononic crystals(PCs) have recently been developed as effective components for vibration suppression and sound absorption. As a typical design of PCs, wave attenuation occurs in the so-called stop-band. However, the ...Phononic crystals(PCs) have recently been developed as effective components for vibration suppression and sound absorption. As a typical design of PCs, wave attenuation occurs in the so-called stop-band. However, the structural response is still significantly large in the pass-band. In this paper, we combine PCs and acoustic black holes(ABHs) in a unique device, achieving a versatile device that can attenuate vibration in the stop-band, while suppress vibration in the pass-band. This approach provides a versatile platform for controlling vibration in a multiband with a simple design.展开更多
Guanidinylated bioresponsive poly(amido amine)s polymers, CAR-CBA and CHL-CBA, weresynthesized by Michael-type addition reaction between guanidine hydrochloride(CAR) orchlorhexidine(CHL) and N,N-cystaminebisacrylamide...Guanidinylated bioresponsive poly(amido amine)s polymers, CAR-CBA and CHL-CBA, weresynthesized by Michael-type addition reaction between guanidine hydrochloride(CAR) orchlorhexidine(CHL) and N,N-cystaminebisacrylamide(CBA). Previous studies have shownthat both polymers had high transfection efficiencies as gene delivery carriers. In this study,we investigated the nucleolus localization abilities and cellular internalization pathways ofthese two polymers in gene delivery. Each polymer condensed plasmid DNA(p DNA) andformed nanoparticle complexes, and then their transfection studies were performed inMCF-7 cells. Both complexes were found enriched in nucleolus after cellular transfection,and their transfection efficiencies were significantly improved when transfection was per-formed on MCF-7 cells arrested at M phase. The transfection efficiency of CAR-CBA-pDNAwas inhibited by chlorpromazine, and cell endosomes were disrupted after being exposedto CAR-CBA-pDNA. In regards to CHL-CBA-pDNA, its transfection efficiency was not affected by three types of endocytosis inhibitors used in the study, and CHL-CBA-pDNA showed no effect on endosomes. Cellular lactate dehydrogenase release and membrane morphology were changed after cells were transfected by the two complexes. The results indicated that both CAR-CBA and CHL-CBA polymers demonstrated good nucleolus localization abilities. It was beneficial for transfection when cells were arrested at M phase. CAR-CBA-pDNA cellular internalization was involved with clathrin-mediated endocytosis pathway, and escaping from endosomal entrapment, while the cellular uptake of CHL-CBA-pDNA occurs via clathrin-and caveolae-independent mechanism.展开更多
In the present study,a simple and rapid method was developed to improve the in vitro dissolution of repaglinide,an oral antidiabetic drug,which was based on addition of meglumine in 50%(v/v)ethanol to dissolve repagli...In the present study,a simple and rapid method was developed to improve the in vitro dissolution of repaglinide,an oral antidiabetic drug,which was based on addition of meglumine in 50%(v/v)ethanol to dissolve repaglinide,and the drug dissolved in meglumine/50%ethanol was used directly with a binder to prepare tablets.The mechanism of solubilization of repaglinide by meglumine was studied by using infrared spectrum(IR),ultraviolet(UV)measurement through dual wavelength,differential scanning calorimetry(DSC)and X-ray powder diffraction methods.Dissolution tests of repaglinide tablets were performed in the media with different pH values and the repaglinide concentrations were analyzed by High Performance Liquid Chromatography(HPLC)method.The solubility data showed that with the meglumine concentration increasing,the solubility of repaglinide was increased.Meanwhile,tablets with the molar ratio of repaglinide and meglumine 1:2(n/n)resulted in a significant increase in dissolution compared to the repaglinide tablets without using meglumine,and nearly equal to the commercial preparations of Novo-Norm^(®),which concluded that meglumine had a great role in promoting the dissolution of repaglinide.The results of IR and UV dual wavelength methods suggested the formation of repaglinideemeglumine(REPeMEG)molecular complex.DSC results showed that the melting peak of repaglinide disappeared in the REPeMEG coprecipitate,which indicated that repaglinide was stable when existing at amorphous or molecular state.The experiment of X-ray powder diffraction showed that with the solubilization of meglumine,the crystal diffraction peak of repaglinide disappeared,which further inferred that repaglinide was formed complexes with meglumine.It was demonstrated that the method of improving repaglinide with meglumine was reliable and could be suitable for repaglinide tablets production in industry.This study also provides a feasible way to enhance the dissolution of drugs with low solubility,which will be leading to improved bioavailability of these drugs.展开更多
Most of the newly developed drug candidates are lipophilic and poorly water-soluble. Enhancing the dissolution and bioavailability of these drugs is a major challenge for the pharmaceutical industry. Liquisolid techni...Most of the newly developed drug candidates are lipophilic and poorly water-soluble. Enhancing the dissolution and bioavailability of these drugs is a major challenge for the pharmaceutical industry. Liquisolid technique, which is based on the conversion of the drug in liquid state into an apparently dry, non-adherent, free flowing and compressible powder,is a novel and advanced approach to tackle the issue. The objective of this article is to present an overview of liquisolid technique and summarize the progress of its applications in pharmaceutics. Low cost, simple processing and great potentials in industrial production are main advantages of this approach. In addition to the enhancement of dissolution rate of poorly water-soluble drugs, this technique is also a fairly new technique to effectively retard drug release. Furthermore, liquisolid technique has been investigated as a tool to minimize the effect of pH variation on drug release and as a promising alternative to conventional coating for the improvement of drug photostability in solid dosage forms. Overall, liquisolid technique is a newly developed and promising tool for enhancing drug dissolution and sustaining drug release, and its potential applications in pharmaceutics are still being broadened.展开更多
The linear and nonlinear dynamic responses of a vibratory ring gyroscope are investigated in this study focusing on the response mechanism of such a vibratory gyroscope. It is found that the nonlinear equations govern...The linear and nonlinear dynamic responses of a vibratory ring gyroscope are investigated in this study focusing on the response mechanism of such a vibratory gyroscope. It is found that the nonlinear equations governing the drive and sense directions are coupled through both inertial linear and geometric nonlinear terms. Nonlinear responses are studied based on the full coupled nonlinear dynamic equations. The varying amplitude on the sense direction is analyzed for different input angular rates. The effect of nonlinearity on the ring gyroscope system is performed by comparing the results of nonlinear responses to those of linear responses. The contributions of some parameters to the amplitude responses and gyroscope sensitivity are analyzed, the conclusions of which provide guidelines to improve the sensitivity of the vibratory ring gyroscopes.展开更多
Human motion induced vibration has very low frequency,ranging from 2 Hz to 5 Hz.Traditional vibration isolators are not effective in low-frequency regions due to the trade-off between the low natural frequency and the...Human motion induced vibration has very low frequency,ranging from 2 Hz to 5 Hz.Traditional vibration isolators are not effective in low-frequency regions due to the trade-off between the low natural frequency and the high load capacity.In this paper,inspired by the human spine,we propose a novel bionic human spine inspired quasi-zero stiffness(QZS)vibration isolator which consists of a cascaded multi-stage negative stiffness structure.The force and stiffness characteristics are investigated first,the dynamic model is established by Newton’s second law,and the isolation performance is analyzed by the harmonic balance method(HBM).Numerical results show that the bionic isolator can obtain better low-frequency isolation performance by increasing the number of negative structure stages,and reducing the damping values and external force values can obtain better low-frequency isolation performance.In comparison with the linear structure and existing traditional QZS isolator,the bionic spine isolator has better vibration isolation performance in low-frequency regions.It paves the way for the design of bionic ultra-low-frequency isolators and shows potential in many engineering applications.展开更多
The bandgap,an important characteristic of the periodic structure,is dispersionrelated,which can be designed by tailoring the layout of materials within the periodic microstructures.A typical example of a periodic str...The bandgap,an important characteristic of the periodic structure,is dispersionrelated,which can be designed by tailoring the layout of materials within the periodic microstructures.A typical example of a periodic structure is phononic crystals (PnCs),which are traditionally fabricated from two-phase materials.Herein,we investigate the topologies of periodic three-phase PnCs.The microstructures of the three-phase PnCs are optimized using a two-stage genetic algorithm,and three case studies are proposed to obtain the following:(1)the maximum relative bandgap width,(2)the maximum absolute bandgap width,and (3)the max- imum bandgap at a specified frequency.More importantly,the three-phase material provides significant advantages compared to the typical two-phase materials,such as a low-frequency bandgap.This research is expected to contribute highly to vibration and noise isolation,elastic wave filters,and acoustic devices.展开更多
The fluid-conveying pipes made of polymer-like materials are widely applied in engineering fields. However, the fractional dynamics of fluid-solid interaction remain unknown.In this work, the fractional dynamics of th...The fluid-conveying pipes made of polymer-like materials are widely applied in engineering fields. However, the fractional dynamics of fluid-solid interaction remain unknown.In this work, the fractional dynamics of the pipes subjected to the excitation of supporting foundation are studied. A new nonlinear, fractional-order dynamic model is presented. The method of multiple scales is adopted directly to solve the model for the case of primary resonances.Numerical results are presented to show the effects of fractional order, foundation vibration, and other physical parameters on the steady-state response and stability.展开更多
In this paper,an electrically active,ultra-thin,easy-to-implement,and tunable phononic crystal(PC)-based device is proposed to suppress excessive vibration in pipes conveying fluids.We demonstrate that this device can...In this paper,an electrically active,ultra-thin,easy-to-implement,and tunable phononic crystal(PC)-based device is proposed to suppress excessive vibration in pipes conveying fluids.We demonstrate that this device can be realized by periodic implementation of piezoelectric patches with shunt circuits on the pipe acting as PCs for vibration suppression.The mathematical model of the pipe structure is simplified to the form of the Euler Bernoulli beam,and the transfer matrix method and the finite element method are used to predict the effective bandgap.Conversion between mechanical vibration energy and electrical energy via the piezoelectric effect is observed.As a result,the pipe vibration is suppressed by combined Bragg and electroelastic bandgaps.The comparison with previous literature shows that this ultra-compact device provides a new solution for vibration and noise control in long-distance fluid-conveying pipe systems.展开更多
In this study,the transverse vibration of a traveling beam made of functionally graded material was analyzed.The material gradation was assumed to vary continuously along the thickness direction of the beam in the for...In this study,the transverse vibration of a traveling beam made of functionally graded material was analyzed.The material gradation was assumed to vary continuously along the thickness direction of the beam in the form of power law exponent.The effect of the longitudinally varying tension due to axial acceleration was highlighted,and the dependence of the tension on the finite support rigidity was also considered.A complex governing equation of the functionally graded beam was derived by the Hamilton principle,in which the geometric nonlinearity,material properties and axial load were incorporated.The direct multiscale method was applied to the analysis process of an axially moving functionally graded beam with timedependent velocity,and the natural frequency and solvability conditions were obtained.Based on the conditions,the stability boundaries of subharmonic resonance and combination resonance were obtained.It was found that the dynamic behavior of axial moving beams could be tuned by using the distribution law of the functional gradient parameters.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.12232014 and 12072221)the Fundamental Research Funds for the Central Universities of China(No.2013017)。
文摘A two-degree-of-freedom(2DOF)vibration isolation structure with an integrated geometric nonlinear inerter(NI)device is proposed.The device is integrated into an inertial nonlinear energy sink(INES),and its vibration suppression performance is examined by the Runge-Kutta(RK)method and verified by the harmonic balance method(HBM).The new isolator is compared with a traditional vibration isolator.The results show a significant improvement in the vibration suppression performance.To investigate the effects of the excitation amplitude and initial condition on the dynamics of the system,a series of transmissibility-frequency response analyses are performed based on the displacement transmissibility.The energy flow of the system is analyzed,and numerous calculations reveal a series of ideal values for the energy sink in the NI-INES system.This study provides new insights for the design of vibration isolators.
基金Project supported by the National Key Research and Development Program of China(No.2022YFC3002502)。
文摘A novel vibration absorber is designed to suppress vibrations in fluidconveying pipes subject to varying fluid speeds.The proposed absorber combines the fundamental principles of nonlinear energy sinks(NESs)and nonlinear energy harvesters(NEHs).The governing equation is derived,and a second-order discrete system is used to assess the performance of the developed device.The results demonstrate that the proposed absorber achieves significantly enhanced energy dissipation efficiency,reaching up to 95%,over a wider frequency range.Additionally,it successfully harvests additional electric energy.This research establishes a promising avenue for the development of new nonlinear devices aimed at suppressing fluid-conveying pipe vibrations across a broad frequency spectrum.
基金the financial support from the National Natural Science Foundation of China (Grant No.81373335)Liaoning Province Natural Science Foundation (Grant No.20170541025)
文摘RNA interfering(RNAi), mediated by small interfering RNAs and microRNAs, is currently one of the most promising tools of gene therapy. Small RNAs are capable of inducing specific post-transcriptional gene silencing, providing a potentially effective platform for the treatment of a wide array of diseases. However, similar to other nucleic acid-based drugs,the major hurdle of RNAi therapy is lack of efficient and non-immunogenic delivery vehicles. Currently, viruses, synthetic polymers, and lipid-based carriers are among the most widely studied vehicles for small RNA delivery. However, many drawbacks are reported to be associated with these delivery vehicles. There is a pressing need to replace them with more efficient and better-tolerated approaches. Exosomes secreted from the endocytic compartment of live cells, are a subtype of endogenous extracellular vesicles that transfer genetic and biochemical information among different cells, thus playing an important role in cellcell communication. Recently, accumulating attention has been focused on harnessing exosomes as nanaocarriers for small RNAs delivery. Due to their natural role in shuttling endogenous nucleic acid in our body, exosomes may exhibit higher delivery efficiency, lower immunogenicity, and better compatibility than existing foreign RNA carriers. Importantly,exosomes own intrinsic homing capacity that can guide small RNAs across natural membranous barriers. Moreover, such a capacity can be further improved by adding appropriate targeting moieties. In this manuscript, we briefly review the progress and challenges of RNAi therapy, and discuss the potential of exosomes' applications in small RNA delivery with focus on the most recent advances in exosome-based small RNA delivery for disease therapy.
基金Project supported by the National Natural Science Foundation of China(Nos.11872044,11702192,and 11672187)the National Key Research and Development Program of China(No.2018YFB0106200)
文摘The dynamics and stability of fluid-conveying corrugated pipes are investigated. The flow velocity is assumed to harmonically vary along the pipe rather than with time. The dimensionless equation is discretized with the differential quadrature method (DQM). Subsequently, the effects of the mean flow velocity and two key parameters of the corrugated pipe, i.e., the amplitude of the corrugations and the total number of the corrugations, are studied. The results show that the corrugated pipe will lose stability by flutter even if it has been supported at both ends. When the total number of the corrugations is sufficient, this flutter instability occurs at a micro flow velocity. These phenomena are verified via the Runge-Kutta method. The critical flow velocity of divergence is analyzed in detail. Compared with uniform pipes, the critical velocity will be reduced due to the corrugations, thus accelerating the divergence instability. Specifically, the critical flow velocity decreases if the amplitude of the corrugations increases. However, the critical flow velocity cannot be monotonously reduced with the increase in the total number of the corrugations. An extreme point appears, which can be used to realize the parameter optimization of corrugated pipes in practical applications.
基金Project supported by the National Natural Science Foundation of China(Nos.11672007,11402028,11322214,and 11290152)the Beijing Natural Science Foundation(No.3172003)the Key Laboratory of Vibration and Control of Aero-Propulsion System Ministry of Education,Northeastern University(No.VCAME201601)
文摘The mathematical modeling of a rotating tapered Timoshenko beam with preset and pre-twist angles is constructed. The partial differential equations governing the six degrees, i.e., three displacements in the axial, flapwise, and edgewise directions and three cross-sectional angles of torsion, flapwise bending, and edgewise bending, are obtained by the Euler angle descriptions. The power series method is then used to investigate the natural frequencies and the corresponding complex mode functions. It is found that all the natural frequencies are increased by the centrifugal stiffening except the twist frequency, which is slightly decreased. The tapering ratio increases the first transverse,torsional, and axial frequencies, while decreases the second transverse frequency. Because of the pre-twist, all the directions are gyroscopically coupled with the phase differences among the six degrees.
文摘Bioequivalence(BE) assessment of topical dermatological products is a long standing challenge. The development of generic topical dermatological products has often been hampered due to the limited number of acceptable approaches, which are capable of determining the BE between generic products and reference list products. The aim of this manuscript is to review different BE assessment approaches of topical dermatological products. Besides, the advances in BE evaluation and biowaivers are also provided. Currently, except in the case of dermatological corticosteroids, the golden rule to establish the BE of most topical dermatological products still heavily relied on clinical endpoint trials,which are often unreliable, time-consuming and expensive. The regulatory agencies and pharmaceutical industries are forging ahead to the development of new surrogate BE assessment approaches for other topical dermatological products. These promising approaches include dermatopharmacokinetic study(DPK), dermal microdialysis(DMD), in vitro studies, pharmacokinetic study(PK), near-infrared spectrometry(NIR), and confocal Raman spectroscopy(CRS). In addition, the expansion of biowaivers for topical dermatological products has been explored by pharmaceutical scientists. In conclusion, to accelerate the development and approval of topical dermatological products, emphasis should be put on the following areas, i.e., optimizing and standardizing the existing BE assessment methods, exploring novel alternatives of BE assessment approaches, and expanding biowaivers for topical dermatological products.
基金Project supported by the National Natural Science Foundation of China(Nos.11902001 and12072221)the China Postdoctoral Science Foundation(No.2018M641643)the Anhui Provincial Natural Science Foundation of China(Nos.1908085QA13 and 1808085ME128)。
文摘The natural dynamic characteristics of a circular cylindrical tube made of three-directional(3 D)functional graded material(FGM)based on the Timoshenko beam theory are investigated.Hamilton’s principle is utilized to derive the novel motion equations of the tube,considering the interactions among the longitudinal,transverse,and rotation deformations.By dint of the differential quadrature method(DQM),the governing equations are discretized to conduct the analysis of natural dynamic characteristics.The Ritz method,in conjunction with the finite element method(FEM),is introduced to verify the present results.It is found that the asymmetric modes in the tube are controlled by the 3 D FGM,which exhibit more complicated shapes compared with the unidirectional(1 D)and bi-directional(2 D)FGM cases.Numerical examples illustrate the effects of the axial,radial,and circumferential FGM indexes as well as the supported edges on the natural dynamic characteristics in detail.It is notable that the obtained results are beneficial for accurate design of smart structures composed from multi-directional FGM.
基金the National Natural Science Foundation of China for financial support(No.81373335)
文摘A cationic gene delivery vector, guanidinylated disulfide-containing poly(amido amine)(CARCBA), was synthesized by Michael addition reaction between N,N′-cystaminebisacrylamide(CBA) and guanidine hydrochloride(CAR). Gel permeation chromatography(GPC) was used to evaluate the molecular weight of synthesized CAR-CBA. Polyethyleneimine(PEI) with molecular weight of 25 kDa was adopted as a reference, and polyethylene glycols(PEG) with different molecular weights were used to establish a standard curve for determining the molecular weight of CAR-CBA. The effects of two critical factors, namely columns and eluents,on the molecular weight measurement of CAR-CBA were investigated to optimize the GPC quantitative method. The results showed that Ultrahydrogel columns(120, 250) and HAc–NaAc(0.5 M, pH 4.5) buffer solution were the optimal column and GPC eluent, respectively.The molecular weight of the synthesized CAR-CBA was analyzed by the optimized GPC method and determined to be 24.66 kDa.
基金The authors gratefully acknowledge the support provided by the National Natural Science Foundation of China(Nos.11622216,11672115 and 11972167).
文摘Cantilevered pipe conveying fluid may become unstable and flutter instability would occur when the velocity of the fluid flow in the pipe exceeds a critical value.In the present study,the theoretical model of a cantilevered fluid-conveying pipe attached by an inerter-based dynamic vibration absorber(IDVA)is proposed and the stability of this dynamical system is explored.Based on linear governing equations of the pipe and the IDVA,the effects of damping coefficient,weight,inerter,location and spring stiffness of the IDVAon the critical flow velocities of the pipe system is examined.It is shown that the stability of the pipe may be significantly affected by the IDVA.In many cases,the stability of the cantilevered pipe can be enhanced by designing the parameter values of the IDVA.By solving nonlinear governing equations of the dynamical system,the nonlinear oscillations of the pipe with IDVA for sufficiently high flow velocity beyond the critical value are determined,showing that the oscillation amplitudes of the pipe can also be suppressed to some extent with a suitable design of the IDVA.
基金Project supported by the National Natural Science Foundation of China(Nos.51575378,11972245,and 11672187)。
文摘Phononic crystals(PCs) have recently been developed as effective components for vibration suppression and sound absorption. As a typical design of PCs, wave attenuation occurs in the so-called stop-band. However, the structural response is still significantly large in the pass-band. In this paper, we combine PCs and acoustic black holes(ABHs) in a unique device, achieving a versatile device that can attenuate vibration in the stop-band, while suppress vibration in the pass-band. This approach provides a versatile platform for controlling vibration in a multiband with a simple design.
基金supported by National Natural Science Foundation of China (Grant no. 81373335)
文摘Guanidinylated bioresponsive poly(amido amine)s polymers, CAR-CBA and CHL-CBA, weresynthesized by Michael-type addition reaction between guanidine hydrochloride(CAR) orchlorhexidine(CHL) and N,N-cystaminebisacrylamide(CBA). Previous studies have shownthat both polymers had high transfection efficiencies as gene delivery carriers. In this study,we investigated the nucleolus localization abilities and cellular internalization pathways ofthese two polymers in gene delivery. Each polymer condensed plasmid DNA(p DNA) andformed nanoparticle complexes, and then their transfection studies were performed inMCF-7 cells. Both complexes were found enriched in nucleolus after cellular transfection,and their transfection efficiencies were significantly improved when transfection was per-formed on MCF-7 cells arrested at M phase. The transfection efficiency of CAR-CBA-pDNAwas inhibited by chlorpromazine, and cell endosomes were disrupted after being exposedto CAR-CBA-pDNA. In regards to CHL-CBA-pDNA, its transfection efficiency was not affected by three types of endocytosis inhibitors used in the study, and CHL-CBA-pDNA showed no effect on endosomes. Cellular lactate dehydrogenase release and membrane morphology were changed after cells were transfected by the two complexes. The results indicated that both CAR-CBA and CHL-CBA polymers demonstrated good nucleolus localization abilities. It was beneficial for transfection when cells were arrested at M phase. CAR-CBA-pDNA cellular internalization was involved with clathrin-mediated endocytosis pathway, and escaping from endosomal entrapment, while the cellular uptake of CHL-CBA-pDNA occurs via clathrin-and caveolae-independent mechanism.
基金The work was supported by Shenyang Pharmaceutical University(10163),including the financial support.
文摘In the present study,a simple and rapid method was developed to improve the in vitro dissolution of repaglinide,an oral antidiabetic drug,which was based on addition of meglumine in 50%(v/v)ethanol to dissolve repaglinide,and the drug dissolved in meglumine/50%ethanol was used directly with a binder to prepare tablets.The mechanism of solubilization of repaglinide by meglumine was studied by using infrared spectrum(IR),ultraviolet(UV)measurement through dual wavelength,differential scanning calorimetry(DSC)and X-ray powder diffraction methods.Dissolution tests of repaglinide tablets were performed in the media with different pH values and the repaglinide concentrations were analyzed by High Performance Liquid Chromatography(HPLC)method.The solubility data showed that with the meglumine concentration increasing,the solubility of repaglinide was increased.Meanwhile,tablets with the molar ratio of repaglinide and meglumine 1:2(n/n)resulted in a significant increase in dissolution compared to the repaglinide tablets without using meglumine,and nearly equal to the commercial preparations of Novo-Norm^(®),which concluded that meglumine had a great role in promoting the dissolution of repaglinide.The results of IR and UV dual wavelength methods suggested the formation of repaglinideemeglumine(REPeMEG)molecular complex.DSC results showed that the melting peak of repaglinide disappeared in the REPeMEG coprecipitate,which indicated that repaglinide was stable when existing at amorphous or molecular state.The experiment of X-ray powder diffraction showed that with the solubilization of meglumine,the crystal diffraction peak of repaglinide disappeared,which further inferred that repaglinide was formed complexes with meglumine.It was demonstrated that the method of improving repaglinide with meglumine was reliable and could be suitable for repaglinide tablets production in industry.This study also provides a feasible way to enhance the dissolution of drugs with low solubility,which will be leading to improved bioavailability of these drugs.
文摘Most of the newly developed drug candidates are lipophilic and poorly water-soluble. Enhancing the dissolution and bioavailability of these drugs is a major challenge for the pharmaceutical industry. Liquisolid technique, which is based on the conversion of the drug in liquid state into an apparently dry, non-adherent, free flowing and compressible powder,is a novel and advanced approach to tackle the issue. The objective of this article is to present an overview of liquisolid technique and summarize the progress of its applications in pharmaceutics. Low cost, simple processing and great potentials in industrial production are main advantages of this approach. In addition to the enhancement of dissolution rate of poorly water-soluble drugs, this technique is also a fairly new technique to effectively retard drug release. Furthermore, liquisolid technique has been investigated as a tool to minimize the effect of pH variation on drug release and as a promising alternative to conventional coating for the improvement of drug photostability in solid dosage forms. Overall, liquisolid technique is a newly developed and promising tool for enhancing drug dissolution and sustaining drug release, and its potential applications in pharmaceutics are still being broadened.
基金supported in part by the National Natural Science Foundation of China (11672007, 11672189, and 11290152)the Beijing Natural Science Foundation (3172003)
文摘The linear and nonlinear dynamic responses of a vibratory ring gyroscope are investigated in this study focusing on the response mechanism of such a vibratory gyroscope. It is found that the nonlinear equations governing the drive and sense directions are coupled through both inertial linear and geometric nonlinear terms. Nonlinear responses are studied based on the full coupled nonlinear dynamic equations. The varying amplitude on the sense direction is analyzed for different input angular rates. The effect of nonlinearity on the ring gyroscope system is performed by comparing the results of nonlinear responses to those of linear responses. The contributions of some parameters to the amplitude responses and gyroscope sensitivity are analyzed, the conclusions of which provide guidelines to improve the sensitivity of the vibratory ring gyroscopes.
基金supported by the National Natural Science Foundation of China(No.12072221)the Natural Science Foundation of Liaoning Province of China(No.2019-KF-01-09)。
文摘Human motion induced vibration has very low frequency,ranging from 2 Hz to 5 Hz.Traditional vibration isolators are not effective in low-frequency regions due to the trade-off between the low natural frequency and the high load capacity.In this paper,inspired by the human spine,we propose a novel bionic human spine inspired quasi-zero stiffness(QZS)vibration isolator which consists of a cascaded multi-stage negative stiffness structure.The force and stiffness characteristics are investigated first,the dynamic model is established by Newton’s second law,and the isolation performance is analyzed by the harmonic balance method(HBM).Numerical results show that the bionic isolator can obtain better low-frequency isolation performance by increasing the number of negative structure stages,and reducing the damping values and external force values can obtain better low-frequency isolation performance.In comparison with the linear structure and existing traditional QZS isolator,the bionic spine isolator has better vibration isolation performance in low-frequency regions.It paves the way for the design of bionic ultra-low-frequency isolators and shows potential in many engineering applications.
基金National Natural Science Foundation of China (Nos.11672187, 11302135,11502149and 51308357)Natural Science Foundation of Liaoning Province (Nos.201602572,201602573and 201602627)+1 种基金and Program for Liaoning Excellent Talents in University (LNET,No.LJQ2014019)The financial contri- butions are gratefully acknowledged.
文摘The bandgap,an important characteristic of the periodic structure,is dispersionrelated,which can be designed by tailoring the layout of materials within the periodic microstructures.A typical example of a periodic structure is phononic crystals (PnCs),which are traditionally fabricated from two-phase materials.Herein,we investigate the topologies of periodic three-phase PnCs.The microstructures of the three-phase PnCs are optimized using a two-stage genetic algorithm,and three case studies are proposed to obtain the following:(1)the maximum relative bandgap width,(2)the maximum absolute bandgap width,and (3)the max- imum bandgap at a specified frequency.More importantly,the three-phase material provides significant advantages compared to the typical two-phase materials,such as a low-frequency bandgap.This research is expected to contribute highly to vibration and noise isolation,elastic wave filters,and acoustic devices.
基金supported by the National Natural Science Foundation of China (No.11672187)the Natural Science Research Project of the Institutions of Higher Education in Anhui Province (Nos.KJ2017A114,KJ2017A106,TSKJ2016B18)+1 种基金Natural Science Foundation of Liaoning Province (201602573)the Opening fund of Key Laboratory of Mechanics,Anhui Polytechnic University (No.201607)
文摘The fluid-conveying pipes made of polymer-like materials are widely applied in engineering fields. However, the fractional dynamics of fluid-solid interaction remain unknown.In this work, the fractional dynamics of the pipes subjected to the excitation of supporting foundation are studied. A new nonlinear, fractional-order dynamic model is presented. The method of multiple scales is adopted directly to solve the model for the case of primary resonances.Numerical results are presented to show the effects of fractional order, foundation vibration, and other physical parameters on the steady-state response and stability.
基金the Natural Science Foundation of China[Grant Numbers 11972245,11672187,11902001]the China Postdoctoral Science Foundation funded project[Grant Number 2018M641643].
文摘In this paper,an electrically active,ultra-thin,easy-to-implement,and tunable phononic crystal(PC)-based device is proposed to suppress excessive vibration in pipes conveying fluids.We demonstrate that this device can be realized by periodic implementation of piezoelectric patches with shunt circuits on the pipe acting as PCs for vibration suppression.The mathematical model of the pipe structure is simplified to the form of the Euler Bernoulli beam,and the transfer matrix method and the finite element method are used to predict the effective bandgap.Conversion between mechanical vibration energy and electrical energy via the piezoelectric effect is observed.As a result,the pipe vibration is suppressed by combined Bragg and electroelastic bandgaps.The comparison with previous literature shows that this ultra-compact device provides a new solution for vibration and noise control in long-distance fluid-conveying pipe systems.
基金The authors acknowledge the support of National Natural Science Foundation of China(Nos.11672187,11572182)Natural Science Foundation of Liaoning Province(201602573)+2 种基金the Key Research Projects of Shanghai Science and Technology Commission(No.18010500100)Innovation Program of Shanghai Education Commission(No.2017-01-07-00-09-E00019)Beiyang Young Scholars of Tian jin University(2019XRX-0027).
文摘In this study,the transverse vibration of a traveling beam made of functionally graded material was analyzed.The material gradation was assumed to vary continuously along the thickness direction of the beam in the form of power law exponent.The effect of the longitudinally varying tension due to axial acceleration was highlighted,and the dependence of the tension on the finite support rigidity was also considered.A complex governing equation of the functionally graded beam was derived by the Hamilton principle,in which the geometric nonlinearity,material properties and axial load were incorporated.The direct multiscale method was applied to the analysis process of an axially moving functionally graded beam with timedependent velocity,and the natural frequency and solvability conditions were obtained.Based on the conditions,the stability boundaries of subharmonic resonance and combination resonance were obtained.It was found that the dynamic behavior of axial moving beams could be tuned by using the distribution law of the functional gradient parameters.
