It is particularly important to explore the response and transmission characteristics of shoe sole when exposed to foot-transmitted vibration(FTV)in daily life.In this study,based on mechanical mobility and vibration ...It is particularly important to explore the response and transmission characteristics of shoe sole when exposed to foot-transmitted vibration(FTV)in daily life.In this study,based on mechanical mobility and vibration transmissibility,the vibration response and transmission characteristics of ordinary sole and multi-cellular structure sole under three excitation modes were analyzed with finite element analysis.The analysis results of the ordinary sole are as follows:The distribution and transmission of vibration energy of ordinary sole are more related to the excitation position and mode-shape;the phalange region is more violent in vibration response to vibration and transmission of vibration.In addition,the analysis results of multi-cellular structure soles show that different types of multi-cellular structure soles have different effects on the equivalent mechanical mobility and the equivalent vibration transmissibility,among which Grid type has the greatest influence.So,this study can help prevent foot injury and provide guidance for the optimal design of the sole.展开更多
This paper carries out a comprehensive and systematic comparison study on the kinematic performance of four six degrees of freedom(6-DOF)parallel mechanisms with different topologies,i.e.,6-UPS,3-(2-UPR)U,3-(2-UCR)U,a...This paper carries out a comprehensive and systematic comparison study on the kinematic performance of four six degrees of freedom(6-DOF)parallel mechanisms with different topologies,i.e.,6-UPS,3-(2-UPR)U,3-(2-UCR)U,and 3-R(2-RPR)U.The research begins by elaborating in detail the similarities and differences among these four parallel mechanisms.By standardizing the definition of the coordinate system for each mechanism,the inverse kinematics and the Jacobian matrix of these four mechanisms are systematically derived.Employing a set of motion/force transmission indices,which are directly obtained from the Jacobian matrix,the kinematic performances of the four mechanisms are thoroughly analyzed and compared within the given workspaces while maintaining the same dimensional parameters for all cases.The comparison study of these four parallel mechanisms extends beyond local transmission indices to also include global transmission indices,covering both position and orientation workspaces,as well as assessments at both the local and global workspace levels.This comprehensive approach ensures a detailed and fair evaluation of their respective kinematic capabilities.The results indicate that the comprehensive kinematic performances of the four parallel mechanisms are similar,and providing a solid theoretical foundation for innovative design and practical guidance for selecting optimal architectures based on specific application requirements.展开更多
H9N2 avian influenza viruses(AIVs)circulate globally in poultry and have become the dominant AIV subtype in China in recent years.Previously,we demonstrated that the H9N2 virus(A/chicken/Eastern China/SDKD1/2015)natur...H9N2 avian influenza viruses(AIVs)circulate globally in poultry and have become the dominant AIV subtype in China in recent years.Previously,we demonstrated that the H9N2 virus(A/chicken/Eastern China/SDKD1/2015)naturally harbors a mammalian-adaptive molecular factor(627K)in the PB2 protein and is weakly pathogenic in mice.Here,we focused on new markers for virulence in mammals.A mouse-adapted H9N2 virus was serially passaged in mice by infecting their lungs.As expected,infected mice showed clinical symptoms and died at passage six.A comparison between the wild-type and mouse-adapted virus sequences identified amino acid substitutions in the hemagglutinin(HA)protein.H9N2 viruses with the T187P t M227L double mutation exhibited an increased affinity to human-type(SAα2,6Gal)receptors and significantly enhanced viral attachment to mouse lung tissues,which contributed to enhancing viral replication and virulence in mice.Additionally,HA with the T187P t M227L mutation enabled H9N2 viral transmission in guinea pigs via direct contact.AIV pathogenicity in mice is a polygenic trait.Our results demonstrated that these HA mutations might be combined with PB2-627K to significantly increase H9N2 virulence in mice,and this enhanced virulence was achieved in other H9N2 AIVs by generating the same combination of mutations.In summary,our study identified novel key elements in the HA protein that are required for H9N2 pathogenicity in mice and provided valuable insights into pandemic preparedness against emerging H_(9)N_(2)strains.展开更多
In the present study, the Volterra series theory is adopted to theoretically investigate the force transmissibility of multiple degrees of freedom （MDOF） structures, in which an isolator with nonlinear anti-symmetri...In the present study, the Volterra series theory is adopted to theoretically investigate the force transmissibility of multiple degrees of freedom （MDOF） structures, in which an isolator with nonlinear anti-symmetric viscous damping is assembled. The results reveal that the anti-symmetric nonlinear viscous damping can significantly reduce the force trans- missibility over all resonance regions for MDOF structures with little effect on the transmissibility over non-resonant and isolation regions. The results indicate that the vibration isolators with an anti-symmetric damping characteristic have great potential to solve the dilemma occurring in the design of linear viscously damped vibration isolators where an increase of the damping level reduces the force transmissibility over resonant frequencies but increases the transmissibility over non-resonant frequency regions. This work is an extension of a previous study in which MDOF structures installed on the mount through an isolator with cubic nonlinear damping are considered. The theoretical analysis results are also verified by simulation studies.展开更多
In order to investigate the nonlinear characteristics of structural joint,the experimental setup with a jointed mass system is established for dynamic characterization analysis and vibration prediction,and a correspon...In order to investigate the nonlinear characteristics of structural joint,the experimental setup with a jointed mass system is established for dynamic characterization analysis and vibration prediction,and a corresponding nonlinearity identification method is studied.First,the sine-sweep vibration test with different baseexcitation levels areapplied to the structural joint system to study the dominant modal of mass rigid motion.Then,based on t e harmonic balance method principle,t e measured vibration transmissibilities a e utilized for nonlinearity identification using different excitation levels.Experimental results show that nonlinear spring and damping force can be represented by a polynomial order approximation.The identified nonlinear stiffness and damping force can predict the system’s response,and they can reveal t e shifts of resonant frequency or damping due to discontinuity of contact mechanisms within a certain range.展开更多
Due to the nonlinearity of breathing crack, cracked structure under excitation of a single frequency always generates higher harmonic components. In this paper, operational deflection shape (ODS) at excitation frequen...Due to the nonlinearity of breathing crack, cracked structure under excitation of a single frequency always generates higher harmonic components. In this paper, operational deflection shape (ODS) at excitation frequency and its higher harmonic components are used to map the deflection pattern of cracked structure. While ODS is sensitive to local variation of structure in nature, a new concept named transmissibility of operational deflection shape (TODS) has been defined for crack localization using beam-like structure. The transmissibility indicates the energy transfer from basic frequency to higher frequency. Then, Teager energy operator (TEO) is employed as a singularity detector to reveal and characterize the features of TODS. Numerical and experimental analysis in cantilever beam show that TODS has strong sensitivity to crack and can locate the crack correctly.展开更多
In the present study, the concept of the output frequency response function is applied to theoretically investigate the force transmissibility of multi-degree of freedom (MDOF) structures with a nonlinear anti-symmetr...In the present study, the concept of the output frequency response function is applied to theoretically investigate the force transmissibility of multi-degree of freedom (MDOF) structures with a nonlinear anti-symmetric viscous damping. The results reveal that an anti-symmetric nonlinear viscous damping can significantly reduce the transmissibility over all resonance regions for MDOF structures while it has almost no effect on the transmissibility over non-resonant and isolation regions. The results indicate that the vibration isolators with an anti-symmetric damping characteristic have great potential to overcome the dilemma in the design of linear viscously damped vibration isolators where an increase of the damping level reduces the force transmissibility over resonant region but increases the transmissibility over non-resonant regions.展开更多
A finite element modeling technique is employed in this paper to predict the force transmissibility of tire-cavity-wheel assembly under a free-fixed condition. The tire and wheel force transmissibility is factor in st...A finite element modeling technique is employed in this paper to predict the force transmissibility of tire-cavity-wheel assembly under a free-fixed condition. The tire and wheel force transmissibility is factor in structure borne road noise performance. In order to improve structure borne noise, it is required to lower the 1st peak frequency of force transmissibility. This paper presents an application of finite element analysis modeling along with experimental verification to predict the force transmissibility of tire and wheel assembly. The results of finite element analysis for force transmissibility are shown to be in good agreement with the results from the indoor test. In order to improve structure borne noise, it is required to lower the 1st peak frequency of force transmissibility. And, the effect of the tire design parameters such as the density and modulus of a rubber and the cord stiffness on the force transmissibility is discussed. It is found that the prediction of the force transmissibility model using finite element analysis will be useful for the improvement of the road noise performance of passenger car tire.展开更多
This paper presents a new finite element model updating method for estimating structural parameters and detecting structural damage location and severity based on the structural responses(output-only data).The method ...This paper presents a new finite element model updating method for estimating structural parameters and detecting structural damage location and severity based on the structural responses(output-only data).The method uses the sensitivity relation of transmissibility data through a least-squares algorithm and appropriate normalization of the extracted equations.The proposed transmissibility-based sensitivity equation produces a more significant number of equations than the sensitivity equations based on the frequency response function(FRF),which can estimate the structural parameters with higher accuracy.The abilities of the proposed method are assessed by using numerical data of a two-story two-bay frame model and a plate structure model.In evaluating different damage cases,the number,location,and stiffness reduction of the damaged elements and the severity of the simulated damage have been accurately identified.The reliability and stability of the presented method against measurement and modeling errors are examined using error-contaminated data.The parameter estimation results prove the method’s capabilities as an accurate model updating algorithm.展开更多
A method is proposed based on the transmissibility function and the OnlineSequence Extreme Learning Machine (OS-ELM) algorithm, which is applied to theimpact damage of composite materials. First of all, the transmissi...A method is proposed based on the transmissibility function and the OnlineSequence Extreme Learning Machine (OS-ELM) algorithm, which is applied to theimpact damage of composite materials. First of all, the transmissibility functions of theundamaged signals and the damage signals at different points are calculated. Secondly,the difference between them is taken as the damage index. Finally, principal componentanalysis (PCA) is used to reduce the noise feature. And then, input to the online sequencelimit learning neural network classification to identify damage and confirm the damagelocation. Taking the amplitude of the transmissibility function instead of the accelerationresponse as the signal analysis for structural damage identification cannot be influencedby the excitation amplitude. The OS-ELM algorithm is based on the ELM (ExtremeLearning Machine) algorithm, in-creased training speed also increases the recognitionaccuracy. Experiment in the epoxy board shows that the method can effectively identifythe structural damage accurately.展开更多
The objective of this work was to study the vibration transmissibility characteristics of the undamped and damped smart spring systems. The frequency response characteristics of them were analyzed by using the equival...The objective of this work was to study the vibration transmissibility characteristics of the undamped and damped smart spring systems. The frequency response characteristics of them were analyzed by using the equivalent linearization technique, and the possible types of the system motion were distinguished by using the starting and ending frequencies. The influences of system parameters on the vibration transmissibility characteristics were discussed. The following conclusions may be drawn from the analysis results. The undamped smart spring system may simultaneously have one starting frequency and one ending frequency or only have one starting frequency, and the damped system may simultaneously have two starting frequencies and one ending frequency. There is an optimal control parameter to make the peak value of the vibration transmissibility curve of the system be minimum. When the mass ratio is far away from the stiffness ratio, the vibration transmissibility is small. The effect of the damping ratio on the system vibration transmissibility is significant while the control parameter is less than its optimal value. But the influence of the relative damping ratio on the vibration transmissibility is small.展开更多
In this paper,a novel method is proposed for structural damage detection and localization.The key of the proposed method is the use of the response difference transmissibility(RDT)for damage localization.The RDT is de...In this paper,a novel method is proposed for structural damage detection and localization.The key of the proposed method is the use of the response difference transmissibility(RDT)for damage localization.The RDT is defined to relate response differences of the system to be evaluated and those of the original system.The invariance properties of RDT are also investigated.Based on this,a damage indicator is proposed,and the benefits are verified by a numerical example.Finally,the proposed method is illustrated and validated by finite element simulations and experimental case studies.展开更多
This paper presents a novel 1T2R three degrees of freedom redundantly actuated and overconstrained ■parallel machining head(■denotes the active prismatic joint), which can construct 5-axis hybrid machine to complete...This paper presents a novel 1T2R three degrees of freedom redundantly actuated and overconstrained ■parallel machining head(■denotes the active prismatic joint), which can construct 5-axis hybrid machine to complete high speed freedom surface milling for large complex structural components in aerospace. Firstly, based on the screw theory, the mobility of the proposed parallel manipulator is briefly analysed. Secondly, the kinematic inverse position and the parasitic motion of the parallel manipulator are explicitly expressed. Furthermore, motion-force transmission performance evaluation indices are derived in detail via an alternative approach based on the screw theory. More importantly, a simple method for quickly solving the maximum virtual power coefficient is proposed, and the motion-force transmission performance evaluation index is greatly improved. To evaluate the kinematic performance, its workspace is calculated. With numerical examples, performance distribution atlases of the manipulator are depicted visually. The corresponding results illustrate that the proposed parallel manipulator has better orientation workspace and superior motion-force transmission performance than the 2 PRU-PRS parallel manipulator, which proves the validity and applicability of applying this manipulator as a machining head.展开更多
Background:As reported by the World Health Organization,a novel coronavirus(2019-nCoV)was identified as the causative virus of Wuhan pneumonia of unknown etiology by Chinese authorities on 7 January,2020.The virus was...Background:As reported by the World Health Organization,a novel coronavirus(2019-nCoV)was identified as the causative virus of Wuhan pneumonia of unknown etiology by Chinese authorities on 7 January,2020.The virus was named as severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)by International Committee on Taxonomy of Viruses on 11 February,2020.This study aimed to develop a mathematical model for calculating the transmissibility of the virus.Methods:In this study,we developed a Bats-Hosts-Reservoir-People transmission network model for simulating the potential transmission from the infection source(probably be bats)to the human infection.Since the Bats-HostsReservoir network was hard to explore clearly and public concerns were focusing on the transmission from Huanan Seafood Wholesale Market(reservoir)to people,we simplified the model as Reservoir-People(RP)transmission network model.The next generation matrix approach was adopted to calculate the basic reproduction number(R0)from the RP model to assess the transmissibility of the SARS-CoV-2.Results:The value of R0 was estimated of 2.30 from reservoir to person and 3.58 from person to person which means that the expected number of secondary infections that result from introducing a single infected individual into an otherwise susceptible population was 3.58.Conclusions:Our model showed that the transmissibility of SARS-CoV-2 was higher than the Middle East respiratory syndrome in the Middle East countries,similar to severe acute respiratory syndrome,but lower than MERS in the Republic of Korea.展开更多
Background:The novel coronavirus,severe acute respiratory syndrome coronavirus 2(SARS-CoV-2,also called 2019-nCoV)causes different morbidity risks to individuals in different age groups.This study attempts to quantify...Background:The novel coronavirus,severe acute respiratory syndrome coronavirus 2(SARS-CoV-2,also called 2019-nCoV)causes different morbidity risks to individuals in different age groups.This study attempts to quantify the age-specific transmissibility using a mathematical model.Methods:An epidemiological model with five compartments(susceptible-exposed-symptomatic-asymptomatic-recovered/removed[SEIAR])was developed based on observed transmission features.Coronavirus disease 2019(COVID-19)cases were divided into four age groups:group 1,those≤14years old;group 2,those 15 to 44years old;group 3,those 45 to 64years old;and group 4,those≥65 years old.The model was initially based on cases(including imported cases and secondary cases)collected in Hunan Province from January 5 to February 19,2020.Another dataset,from Jilin Province,was used to test the model.Results:The age-specific SEIAR model fitted the data well in each age group(P<0.001).In Hunan Province,the highest transmissibility was from age group 4 to 3(median:β43=7.71×10-9;SAR43=3.86×10-8),followed by group 3 to 4(median:β34=3.07×10-9;SAR34=1.53×10-8),group 2 to 2(median:β22=1.24×10-9;SAR22=6.21×10-9),and group 3 to 1(median:β31=4.10×10-10;SAR31=2.08×10-9).The lowest transmissibility was from age group 3 to 3(median:β33=1.64×10-19;SAR33=8.19×10-19),followed by group 4 to 4(median:β44=3.66×10-17;SAR44=1.83×10-16),group 3 to 2(median:β32=1.21×10-16;SAR32=6.06×10-16),and group 1 to 4(median:β14=7.20×10-14;SAR14=3.60×10-13).In Jilin Province,the highest transmissibility occurred from age group 4 to 4(median:β43=4.27×10-8;SAR43=2.13×10-7),followed by group 3 to 4(median:β34=1.81×10-8;SAR34=9.03×10-8).Conclusions:SARS-CoV-2 exhibits high transmissibility between middle-aged(45 to 64 years old)and elderly(≥65 years old)people.Children(≤14 years old)have very low susceptibility to COVID-19.This study will improve our understanding of the transmission feature of SARS-CoV-2 in different age groups and suggest the most prevention measures should be applied to middle-aged and elderly people.展开更多
Decades have passed since the first discovery of H10-subtype avian influenza virus(AIV) in chickens in 1949,and it has been detected in many species including mammals such as minks,pigs,seals and humans.Cases of human...Decades have passed since the first discovery of H10-subtype avian influenza virus(AIV) in chickens in 1949,and it has been detected in many species including mammals such as minks,pigs,seals and humans.Cases of human infections with H10N8viruses identified in China in 2013 have raised widespread attention.Two novel reassortant H10N3 viruses were isolated from chickens in December 2019 in eastern China during routine surveillance for AIVs.The internal genes of these viruses were derived from genotype S(G57) H9N2 and were consistent with H5N6,H7N9 and H10N8,which cause fatal infections in humans.Their viral pathogenicity and transmissibility were further studied in different animal models.The two H10N3 isolates had low pathogenicity in chickens and were transmitted between chickens via direct contact.These viruses were highly pathogenic in mice and could be transmitted between guinea pigs via direct contact and respiratory droplets.More importantly,these viruses can bind to both human-type SAα-2,6-Gal receptors and avian-type SAα-2,3-Gal receptors.Asymptomatic shedding in chickens and good adaptability to mammals of these H10N3 isolates would make it easier to transmit to humans and pose a threat to public health.展开更多
Background The new coronavirus disease COVID-19 began in December 2019 and has spread rapidly by human-to-human transmission.This study evaluated the transmissibility of the infectious disease and analyzed its associa...Background The new coronavirus disease COVID-19 began in December 2019 and has spread rapidly by human-to-human transmission.This study evaluated the transmissibility of the infectious disease and analyzed its association with temperature and humidity to study the propagation pattern of COVID-19.Methods In this study,we revised the reported data in Wuhan based on several assumptions to estimate the actual number of confirmed cases considering that perhaps not all cases could be detected and reported in the complex situation there.Then we used the equation derived from the Susceptible-Exposed-Infectious-Recovered(SEIR)model to calculate R0 from January 24,2020 to February 13,2020 in 11 major cities in China for comparison.With the calculation results,we conducted correlation analysis and regression analysis between R0 and temperature and humidity for four major cities in China to see the association between the transmissibility of COVID-19 and the weather variables.Results It was estimated that the cumulative number of confirmed cases had exceeded 45000 by February 13,2020 in Wuhan.The average R0 in Wuhan was 2.7,significantly higher than those in other cities ranging from 1.8 to 2.4.The inflection points in the cities outside Hubei Province were between January 30,2020 and February 3,2020,while there had not been an obvious downward trend of R0 in Wuhan.R0 negatively correlated with both temperature and humidity,which was significant at the 0.01 level.Conclusions The transmissibility of COVID-19 was strong and importance should be attached to the intervention of its transmission especially in Wuhan.According to the correlation between R0 and weather,the spread of disease will be suppressed as the weather warms.展开更多
Background:Developing countries exhibit a high disease burden from shigellosis.Owing to the different incidences in males and females,this study aims to analyze the features involved in the transmission of shigellosis...Background:Developing countries exhibit a high disease burden from shigellosis.Owing to the different incidences in males and females,this study aims to analyze the features involved in the transmission of shigellosis among male(subscript m)and female(subscript f)individuals using a newly developed sex-based model.Methods:The data of reported shigellosis cases were collected from the China Information System for Disease Control and Prevention in Hubei Province from 2005 to 2017.A sex-based Susceptible-Exposed-Infectious/Asymptomatic-Recovered(SEIAR)model was applied to explore the dataset,and a sex-age-based SEIAR model was applied in 2010 to explore the sex-and age-specific transmissions.Results:From 2005 to 2017,130770 shigellosis cases(including 73981 male and 56789 female cases)were reported in Hubei Province.The SEIAR model exhibited a significant fitting effect with the shigellosis data(P<0.001).The median values of the shigellosis transmission were 2.3225×10^8 for SARmm(secondary attack rate from male to male),2.5729×10^8 for SARmf 2.7630×10^8 for SARfm,and 2.1061×10^8 for SARff.The top five mean values of the transmission relative rate in 2010(where the subscript 1 was defined as male and age<5 years,2 was male and age 6 to 59 years,3 was male and age>60 years,4 was female and age<5 years,5 was female and age 6 to 59 years,and 6 was male and age>60 years)were 5.76×10^8 forβ61;5.32×10^8 forβ31,4.01×10^8 forβ34,7.52×10^9 forβ62,and 6.04×10^9 for Conclusions:The transmissibility of shigellosis differed among male and female individuals.The transmissibility between the genders was higher than that within the genders,particularly female-to-male transmission.The most important route in children(age<5 years)was transmission from the elderly(age>60 years).Therefore,the greatest interventions should be applied in females and the elderly.展开更多
A mathematical model was developed for a complex nonlinear coupling isolator for attenuating vibration which coupled quadratic damping, viscous damping, Coulomb damping, and nonlinear spring forces. The approximate an...A mathematical model was developed for a complex nonlinear coupling isolator for attenuating vibration which coupled quadratic damping, viscous damping, Coulomb damping, and nonlinear spring forces. The approximate analytical solution for the dynamic transmissibility of the isolator was deduced by combining Fourier transforms and the harmonic balance method with deterministic excitation. The mathematical characteristics of the dynamic transmissibility were analyzed to illustrate the dynamic performance of the isolator. The analytical results show multiple solutions, especially the low-frequency attenuation characteristics below the resonance frequency. The results provide a theoretical basis for the design of nonlinear isolators.展开更多
Space-Based Solar Power(SBSP) presents a promising solution for achieving carbon neutrality and Renewable Electricity 100%(RE100) goals by offering a stable and continuous energy supply. However, its commercialization...Space-Based Solar Power(SBSP) presents a promising solution for achieving carbon neutrality and Renewable Electricity 100%(RE100) goals by offering a stable and continuous energy supply. However, its commercialization faces significant obstacles due to the technical challenges of long-distance microwave Wireless Power Transmission(WPT) from geostationary orbit. Even ground-based kilometer-scale WPT experiments remain difficult because of limited testing infrastructure, high costs, and strict electromagnetic wave regulations. Since the 1975 NASA-Raytheon experiment, which successfully recovered 30 kW of power over 1.55 km, there has been little progress in extending the transmission distance or increasing the retrieved power. This study proposes a cost-effective methodology for conducting long-range WPT experiments in constrained environments by utilizing existing infrastructure. A deep space antenna operating at 2.08 GHz with an output power of 2.3 kW and a gain of 55.3 dBi was used as the transmitter. Two test configurations were implemented: a 1.81 km ground-to-air test using an aerostat to elevate the receiver and a 1.82 km ground-to-ground test using a ladder truck positioned on a plateau. The rectenna consists of a lightweight 3×3 patch antenna array(0.9 m × 0.9 m), accompanied by a steering device and LED indicators to verify power reception. The aerostat-based test achieved a power density of 154.6 mW/m2, which corresponds to approximately 6.2% of the theoretical maximum. The performance gap is primarily attributed to near-field interference, detuning of the patch antenna, rectifier mismatch, and alignment issues. These limitations are expected to be mitigated through improved patch antenna fabrication, a transition from GaN to GaAs rectifiers optimized for lower input power, and the implementation of an automated alignment system. With these enhancements, the recovered power is expected to improve by approximately four to five times. The results demonstrate a practical and scalable framework for long-range WPT experiments under constrained conditions and provide key insights for advancing SBSP technology.展开更多
基金the National Natural Science Foundation of China(No.52175230)Natural Science Foundation of Fujian Province(Nos.2021J01297,2020J011234 and 2020J011227)+3 种基金Technology Program Pilot Project of Fujian Province(No.2020H0015)Xiamen Medical and Health Guidance Project(No.3502720199009)Research Start-Up Fund Project of Huaqiao University(No.11BS412)Subsidized Project for Postgraduates’Innovation Fund in Scientific Research of Huaqiao University(Nos.19013080038 and 20014080038)。
文摘It is particularly important to explore the response and transmission characteristics of shoe sole when exposed to foot-transmitted vibration(FTV)in daily life.In this study,based on mechanical mobility and vibration transmissibility,the vibration response and transmission characteristics of ordinary sole and multi-cellular structure sole under three excitation modes were analyzed with finite element analysis.The analysis results of the ordinary sole are as follows:The distribution and transmission of vibration energy of ordinary sole are more related to the excitation position and mode-shape;the phalange region is more violent in vibration response to vibration and transmission of vibration.In addition,the analysis results of multi-cellular structure soles show that different types of multi-cellular structure soles have different effects on the equivalent mechanical mobility and the equivalent vibration transmissibility,among which Grid type has the greatest influence.So,this study can help prevent foot injury and provide guidance for the optimal design of the sole.
基金Supported by National Natural Science Foundation of China(Grant Nos.52325501,U24B2047).
文摘This paper carries out a comprehensive and systematic comparison study on the kinematic performance of four six degrees of freedom(6-DOF)parallel mechanisms with different topologies,i.e.,6-UPS,3-(2-UPR)U,3-(2-UCR)U,and 3-R(2-RPR)U.The research begins by elaborating in detail the similarities and differences among these four parallel mechanisms.By standardizing the definition of the coordinate system for each mechanism,the inverse kinematics and the Jacobian matrix of these four mechanisms are systematically derived.Employing a set of motion/force transmission indices,which are directly obtained from the Jacobian matrix,the kinematic performances of the four mechanisms are thoroughly analyzed and compared within the given workspaces while maintaining the same dimensional parameters for all cases.The comparison study of these four parallel mechanisms extends beyond local transmission indices to also include global transmission indices,covering both position and orientation workspaces,as well as assessments at both the local and global workspace levels.This comprehensive approach ensures a detailed and fair evaluation of their respective kinematic capabilities.The results indicate that the comprehensive kinematic performances of the four parallel mechanisms are similar,and providing a solid theoretical foundation for innovative design and practical guidance for selecting optimal architectures based on specific application requirements.
基金supported by the National Key Research and Development Project of China:2021YFD1800202by the National Natural Science Foundation of China:31772755,32072892,32072832+1 种基金by the Earmarked Fund for China Agriculture Reasearch System:CARS-40by the Priorty Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘H9N2 avian influenza viruses(AIVs)circulate globally in poultry and have become the dominant AIV subtype in China in recent years.Previously,we demonstrated that the H9N2 virus(A/chicken/Eastern China/SDKD1/2015)naturally harbors a mammalian-adaptive molecular factor(627K)in the PB2 protein and is weakly pathogenic in mice.Here,we focused on new markers for virulence in mammals.A mouse-adapted H9N2 virus was serially passaged in mice by infecting their lungs.As expected,infected mice showed clinical symptoms and died at passage six.A comparison between the wild-type and mouse-adapted virus sequences identified amino acid substitutions in the hemagglutinin(HA)protein.H9N2 viruses with the T187P t M227L double mutation exhibited an increased affinity to human-type(SAα2,6Gal)receptors and significantly enhanced viral attachment to mouse lung tissues,which contributed to enhancing viral replication and virulence in mice.Additionally,HA with the T187P t M227L mutation enabled H9N2 viral transmission in guinea pigs via direct contact.AIV pathogenicity in mice is a polygenic trait.Our results demonstrated that these HA mutations might be combined with PB2-627K to significantly increase H9N2 virulence in mice,and this enhanced virulence was achieved in other H9N2 AIVs by generating the same combination of mutations.In summary,our study identified novel key elements in the HA protein that are required for H9N2 pathogenicity in mice and provided valuable insights into pandemic preparedness against emerging H_(9)N_(2)strains.
基金supported by the EPSRC (UK)the National Science Fund for Distinguished Young Scholars (11125209)the National Natural Science Foundation of China (10902068 and 51121063)
文摘In the present study, the Volterra series theory is adopted to theoretically investigate the force transmissibility of multiple degrees of freedom （MDOF） structures, in which an isolator with nonlinear anti-symmetric viscous damping is assembled. The results reveal that the anti-symmetric nonlinear viscous damping can significantly reduce the force trans- missibility over all resonance regions for MDOF structures with little effect on the transmissibility over non-resonant and isolation regions. The results indicate that the vibration isolators with an anti-symmetric damping characteristic have great potential to solve the dilemma occurring in the design of linear viscously damped vibration isolators where an increase of the damping level reduces the force transmissibility over resonant frequencies but increases the transmissibility over non-resonant frequency regions. This work is an extension of a previous study in which MDOF structures installed on the mount through an isolator with cubic nonlinear damping are considered. The theoretical analysis results are also verified by simulation studies.
基金The Major National Science and Technology Project(No.2012ZX04002032,2013ZX04012032)Graduate Scientific Research Innovation Project of Jiangsu Province(No.KYLX-0096)
文摘In order to investigate the nonlinear characteristics of structural joint,the experimental setup with a jointed mass system is established for dynamic characterization analysis and vibration prediction,and a corresponding nonlinearity identification method is studied.First,the sine-sweep vibration test with different baseexcitation levels areapplied to the structural joint system to study the dominant modal of mass rigid motion.Then,based on t e harmonic balance method principle,t e measured vibration transmissibilities a e utilized for nonlinearity identification using different excitation levels.Experimental results show that nonlinear spring and damping force can be represented by a polynomial order approximation.The identified nonlinear stiffness and damping force can predict the system’s response,and they can reveal t e shifts of resonant frequency or damping due to discontinuity of contact mechanisms within a certain range.
文摘Due to the nonlinearity of breathing crack, cracked structure under excitation of a single frequency always generates higher harmonic components. In this paper, operational deflection shape (ODS) at excitation frequency and its higher harmonic components are used to map the deflection pattern of cracked structure. While ODS is sensitive to local variation of structure in nature, a new concept named transmissibility of operational deflection shape (TODS) has been defined for crack localization using beam-like structure. The transmissibility indicates the energy transfer from basic frequency to higher frequency. Then, Teager energy operator (TEO) is employed as a singularity detector to reveal and characterize the features of TODS. Numerical and experimental analysis in cantilever beam show that TODS has strong sensitivity to crack and can locate the crack correctly.
基金supported by the National Science Fund for Distinguished Young Scholars (11125209)the National Natural Science Foundation of China (10732060, 10902068)the EPSRC (UK)
文摘In the present study, the concept of the output frequency response function is applied to theoretically investigate the force transmissibility of multi-degree of freedom (MDOF) structures with a nonlinear anti-symmetric viscous damping. The results reveal that an anti-symmetric nonlinear viscous damping can significantly reduce the transmissibility over all resonance regions for MDOF structures while it has almost no effect on the transmissibility over non-resonant and isolation regions. The results indicate that the vibration isolators with an anti-symmetric damping characteristic have great potential to overcome the dilemma in the design of linear viscously damped vibration isolators where an increase of the damping level reduces the force transmissibility over resonant region but increases the transmissibility over non-resonant regions.
文摘A finite element modeling technique is employed in this paper to predict the force transmissibility of tire-cavity-wheel assembly under a free-fixed condition. The tire and wheel force transmissibility is factor in structure borne road noise performance. In order to improve structure borne noise, it is required to lower the 1st peak frequency of force transmissibility. This paper presents an application of finite element analysis modeling along with experimental verification to predict the force transmissibility of tire and wheel assembly. The results of finite element analysis for force transmissibility are shown to be in good agreement with the results from the indoor test. In order to improve structure borne noise, it is required to lower the 1st peak frequency of force transmissibility. And, the effect of the tire design parameters such as the density and modulus of a rubber and the cord stiffness on the force transmissibility is discussed. It is found that the prediction of the force transmissibility model using finite element analysis will be useful for the improvement of the road noise performance of passenger car tire.
文摘This paper presents a new finite element model updating method for estimating structural parameters and detecting structural damage location and severity based on the structural responses(output-only data).The method uses the sensitivity relation of transmissibility data through a least-squares algorithm and appropriate normalization of the extracted equations.The proposed transmissibility-based sensitivity equation produces a more significant number of equations than the sensitivity equations based on the frequency response function(FRF),which can estimate the structural parameters with higher accuracy.The abilities of the proposed method are assessed by using numerical data of a two-story two-bay frame model and a plate structure model.In evaluating different damage cases,the number,location,and stiffness reduction of the damaged elements and the severity of the simulated damage have been accurately identified.The reliability and stability of the presented method against measurement and modeling errors are examined using error-contaminated data.The parameter estimation results prove the method’s capabilities as an accurate model updating algorithm.
文摘A method is proposed based on the transmissibility function and the OnlineSequence Extreme Learning Machine (OS-ELM) algorithm, which is applied to theimpact damage of composite materials. First of all, the transmissibility functions of theundamaged signals and the damage signals at different points are calculated. Secondly,the difference between them is taken as the damage index. Finally, principal componentanalysis (PCA) is used to reduce the noise feature. And then, input to the online sequencelimit learning neural network classification to identify damage and confirm the damagelocation. Taking the amplitude of the transmissibility function instead of the accelerationresponse as the signal analysis for structural damage identification cannot be influencedby the excitation amplitude. The OS-ELM algorithm is based on the ELM (ExtremeLearning Machine) algorithm, in-creased training speed also increases the recognitionaccuracy. Experiment in the epoxy board shows that the method can effectively identifythe structural damage accurately.
基金Project(51375226)supported by the National Natural Science Foundation of ChinaProject(20113218110017)supported by the Doctoral Program Foundation of Institutions of Higher Education of China+2 种基金Project(PAPD)supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,ChinaProject(CXZZ11_0199)supported by the Funding of Jiangsu Innovation Program for Graduate Education,ChinaProject(2014)supported by the the Fundamental Research Funds for the Central Universities,China
文摘The objective of this work was to study the vibration transmissibility characteristics of the undamped and damped smart spring systems. The frequency response characteristics of them were analyzed by using the equivalent linearization technique, and the possible types of the system motion were distinguished by using the starting and ending frequencies. The influences of system parameters on the vibration transmissibility characteristics were discussed. The following conclusions may be drawn from the analysis results. The undamped smart spring system may simultaneously have one starting frequency and one ending frequency or only have one starting frequency, and the damped system may simultaneously have two starting frequencies and one ending frequency. There is an optimal control parameter to make the peak value of the vibration transmissibility curve of the system be minimum. When the mass ratio is far away from the stiffness ratio, the vibration transmissibility is small. The effect of the damping ratio on the system vibration transmissibility is significant while the control parameter is less than its optimal value. But the influence of the relative damping ratio on the vibration transmissibility is small.
基金the National Natural Science Foundation of China(Nos.12141305 and 11902191)the National Key R&D Program of China(Nos.2021YFB3901000 and 2021YFB3901004)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA15021003)。
文摘In this paper,a novel method is proposed for structural damage detection and localization.The key of the proposed method is the use of the response difference transmissibility(RDT)for damage localization.The RDT is defined to relate response differences of the system to be evaluated and those of the original system.The invariance properties of RDT are also investigated.Based on this,a damage indicator is proposed,and the benefits are verified by a numerical example.Finally,the proposed method is illustrated and validated by finite element simulations and experimental case studies.
基金supported by the Fundamental Research Funds for the Central Universities (Nos. 2018JBZ007, 2018YJS136 and 2017YJS158)China Scholarship Council (CSC) (No. 201807090079)National Natural Science Foundation of China (NSFC) (No. 51675037)
文摘This paper presents a novel 1T2R three degrees of freedom redundantly actuated and overconstrained ■parallel machining head(■denotes the active prismatic joint), which can construct 5-axis hybrid machine to complete high speed freedom surface milling for large complex structural components in aerospace. Firstly, based on the screw theory, the mobility of the proposed parallel manipulator is briefly analysed. Secondly, the kinematic inverse position and the parasitic motion of the parallel manipulator are explicitly expressed. Furthermore, motion-force transmission performance evaluation indices are derived in detail via an alternative approach based on the screw theory. More importantly, a simple method for quickly solving the maximum virtual power coefficient is proposed, and the motion-force transmission performance evaluation index is greatly improved. To evaluate the kinematic performance, its workspace is calculated. With numerical examples, performance distribution atlases of the manipulator are depicted visually. The corresponding results illustrate that the proposed parallel manipulator has better orientation workspace and superior motion-force transmission performance than the 2 PRU-PRS parallel manipulator, which proves the validity and applicability of applying this manipulator as a machining head.
基金This study was supported by Xiamen New Coronavirus Prevention and Control Emergency Tackling Special Topic Program(No:3502Z2020YJ03).
文摘Background:As reported by the World Health Organization,a novel coronavirus(2019-nCoV)was identified as the causative virus of Wuhan pneumonia of unknown etiology by Chinese authorities on 7 January,2020.The virus was named as severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)by International Committee on Taxonomy of Viruses on 11 February,2020.This study aimed to develop a mathematical model for calculating the transmissibility of the virus.Methods:In this study,we developed a Bats-Hosts-Reservoir-People transmission network model for simulating the potential transmission from the infection source(probably be bats)to the human infection.Since the Bats-HostsReservoir network was hard to explore clearly and public concerns were focusing on the transmission from Huanan Seafood Wholesale Market(reservoir)to people,we simplified the model as Reservoir-People(RP)transmission network model.The next generation matrix approach was adopted to calculate the basic reproduction number(R0)from the RP model to assess the transmissibility of the SARS-CoV-2.Results:The value of R0 was estimated of 2.30 from reservoir to person and 3.58 from person to person which means that the expected number of secondary infections that result from introducing a single infected individual into an otherwise susceptible population was 3.58.Conclusions:Our model showed that the transmissibility of SARS-CoV-2 was higher than the Middle East respiratory syndrome in the Middle East countries,similar to severe acute respiratory syndrome,but lower than MERS in the Republic of Korea.
基金partly supported by the Open Research Fund of State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics(SKLVD2019KF005)the Bill&Melinda Gates Foundation(INV-005834)+3 种基金the Science and Technology Program of Fujian Province(No:2020Y0002)the Xiamen New Coronavirus Prevention and Control Emergency Tackling Special Topic Program(No:3502Z2020YJ03)the Hunan Provincial Construction of Innovative Provinces Special Social Development Areas Key Research and Development Project(2020SK3012)the Chinese Academy of Medical Sciences Coronavirus Disease 2019 Science and Technology Research Project in 2020(2020HY320003).
文摘Background:The novel coronavirus,severe acute respiratory syndrome coronavirus 2(SARS-CoV-2,also called 2019-nCoV)causes different morbidity risks to individuals in different age groups.This study attempts to quantify the age-specific transmissibility using a mathematical model.Methods:An epidemiological model with five compartments(susceptible-exposed-symptomatic-asymptomatic-recovered/removed[SEIAR])was developed based on observed transmission features.Coronavirus disease 2019(COVID-19)cases were divided into four age groups:group 1,those≤14years old;group 2,those 15 to 44years old;group 3,those 45 to 64years old;and group 4,those≥65 years old.The model was initially based on cases(including imported cases and secondary cases)collected in Hunan Province from January 5 to February 19,2020.Another dataset,from Jilin Province,was used to test the model.Results:The age-specific SEIAR model fitted the data well in each age group(P<0.001).In Hunan Province,the highest transmissibility was from age group 4 to 3(median:β43=7.71×10-9;SAR43=3.86×10-8),followed by group 3 to 4(median:β34=3.07×10-9;SAR34=1.53×10-8),group 2 to 2(median:β22=1.24×10-9;SAR22=6.21×10-9),and group 3 to 1(median:β31=4.10×10-10;SAR31=2.08×10-9).The lowest transmissibility was from age group 3 to 3(median:β33=1.64×10-19;SAR33=8.19×10-19),followed by group 4 to 4(median:β44=3.66×10-17;SAR44=1.83×10-16),group 3 to 2(median:β32=1.21×10-16;SAR32=6.06×10-16),and group 1 to 4(median:β14=7.20×10-14;SAR14=3.60×10-13).In Jilin Province,the highest transmissibility occurred from age group 4 to 4(median:β43=4.27×10-8;SAR43=2.13×10-7),followed by group 3 to 4(median:β34=1.81×10-8;SAR34=9.03×10-8).Conclusions:SARS-CoV-2 exhibits high transmissibility between middle-aged(45 to 64 years old)and elderly(≥65 years old)people.Children(≤14 years old)have very low susceptibility to COVID-19.This study will improve our understanding of the transmission feature of SARS-CoV-2 in different age groups and suggest the most prevention measures should be applied to middle-aged and elderly people.
基金supported by the National Key Research and Development Project of China (2016YFD0500202-1,2016YFD0501601)the National Natural Science Foundation of China(31772755)+3 种基金Jiangsu Provincial Natural Science Fund for Excellent Young Scholars (BK20170068)the Earmarked Fund For China Agriculture Research System (CARS-40)the Open Project Program of Jiangsu Key Laboratory of Zoonosis (R1808)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)。
文摘Decades have passed since the first discovery of H10-subtype avian influenza virus(AIV) in chickens in 1949,and it has been detected in many species including mammals such as minks,pigs,seals and humans.Cases of human infections with H10N8viruses identified in China in 2013 have raised widespread attention.Two novel reassortant H10N3 viruses were isolated from chickens in December 2019 in eastern China during routine surveillance for AIVs.The internal genes of these viruses were derived from genotype S(G57) H9N2 and were consistent with H5N6,H7N9 and H10N8,which cause fatal infections in humans.Their viral pathogenicity and transmissibility were further studied in different animal models.The two H10N3 isolates had low pathogenicity in chickens and were transmitted between chickens via direct contact.These viruses were highly pathogenic in mice and could be transmitted between guinea pigs via direct contact and respiratory droplets.More importantly,these viruses can bind to both human-type SAα-2,6-Gal receptors and avian-type SAα-2,3-Gal receptors.Asymptomatic shedding in chickens and good adaptability to mammals of these H10N3 isolates would make it easier to transmit to humans and pose a threat to public health.
文摘Background The new coronavirus disease COVID-19 began in December 2019 and has spread rapidly by human-to-human transmission.This study evaluated the transmissibility of the infectious disease and analyzed its association with temperature and humidity to study the propagation pattern of COVID-19.Methods In this study,we revised the reported data in Wuhan based on several assumptions to estimate the actual number of confirmed cases considering that perhaps not all cases could be detected and reported in the complex situation there.Then we used the equation derived from the Susceptible-Exposed-Infectious-Recovered(SEIR)model to calculate R0 from January 24,2020 to February 13,2020 in 11 major cities in China for comparison.With the calculation results,we conducted correlation analysis and regression analysis between R0 and temperature and humidity for four major cities in China to see the association between the transmissibility of COVID-19 and the weather variables.Results It was estimated that the cumulative number of confirmed cases had exceeded 45000 by February 13,2020 in Wuhan.The average R0 in Wuhan was 2.7,significantly higher than those in other cities ranging from 1.8 to 2.4.The inflection points in the cities outside Hubei Province were between January 30,2020 and February 3,2020,while there had not been an obvious downward trend of R0 in Wuhan.R0 negatively correlated with both temperature and humidity,which was significant at the 0.01 level.Conclusions The transmissibility of COVID-19 was strong and importance should be attached to the intervention of its transmission especially in Wuhan.According to the correlation between R0 and weather,the spread of disease will be suppressed as the weather warms.
文摘Background:Developing countries exhibit a high disease burden from shigellosis.Owing to the different incidences in males and females,this study aims to analyze the features involved in the transmission of shigellosis among male(subscript m)and female(subscript f)individuals using a newly developed sex-based model.Methods:The data of reported shigellosis cases were collected from the China Information System for Disease Control and Prevention in Hubei Province from 2005 to 2017.A sex-based Susceptible-Exposed-Infectious/Asymptomatic-Recovered(SEIAR)model was applied to explore the dataset,and a sex-age-based SEIAR model was applied in 2010 to explore the sex-and age-specific transmissions.Results:From 2005 to 2017,130770 shigellosis cases(including 73981 male and 56789 female cases)were reported in Hubei Province.The SEIAR model exhibited a significant fitting effect with the shigellosis data(P<0.001).The median values of the shigellosis transmission were 2.3225×10^8 for SARmm(secondary attack rate from male to male),2.5729×10^8 for SARmf 2.7630×10^8 for SARfm,and 2.1061×10^8 for SARff.The top five mean values of the transmission relative rate in 2010(where the subscript 1 was defined as male and age<5 years,2 was male and age 6 to 59 years,3 was male and age>60 years,4 was female and age<5 years,5 was female and age 6 to 59 years,and 6 was male and age>60 years)were 5.76×10^8 forβ61;5.32×10^8 forβ31,4.01×10^8 forβ34,7.52×10^9 forβ62,and 6.04×10^9 for Conclusions:The transmissibility of shigellosis differed among male and female individuals.The transmissibility between the genders was higher than that within the genders,particularly female-to-male transmission.The most important route in children(age<5 years)was transmission from the elderly(age>60 years).Therefore,the greatest interventions should be applied in females and the elderly.
基金Supported by the National Defense Science Foundation of China (No. 00J16.2.5.DZ0502), the Natural Science Foundation for Qualified Personnel of Jiangsu University (No. 04JDG027), and the Natural Science Foundation of Guangxi Zhuang Autonomous Region (Nos. 0339037 and 0141042)
文摘A mathematical model was developed for a complex nonlinear coupling isolator for attenuating vibration which coupled quadratic damping, viscous damping, Coulomb damping, and nonlinear spring forces. The approximate analytical solution for the dynamic transmissibility of the isolator was deduced by combining Fourier transforms and the harmonic balance method with deterministic excitation. The mathematical characteristics of the dynamic transmissibility were analyzed to illustrate the dynamic performance of the isolator. The analytical results show multiple solutions, especially the low-frequency attenuation characteristics below the resonance frequency. The results provide a theoretical basis for the design of nonlinear isolators.
文摘Space-Based Solar Power(SBSP) presents a promising solution for achieving carbon neutrality and Renewable Electricity 100%(RE100) goals by offering a stable and continuous energy supply. However, its commercialization faces significant obstacles due to the technical challenges of long-distance microwave Wireless Power Transmission(WPT) from geostationary orbit. Even ground-based kilometer-scale WPT experiments remain difficult because of limited testing infrastructure, high costs, and strict electromagnetic wave regulations. Since the 1975 NASA-Raytheon experiment, which successfully recovered 30 kW of power over 1.55 km, there has been little progress in extending the transmission distance or increasing the retrieved power. This study proposes a cost-effective methodology for conducting long-range WPT experiments in constrained environments by utilizing existing infrastructure. A deep space antenna operating at 2.08 GHz with an output power of 2.3 kW and a gain of 55.3 dBi was used as the transmitter. Two test configurations were implemented: a 1.81 km ground-to-air test using an aerostat to elevate the receiver and a 1.82 km ground-to-ground test using a ladder truck positioned on a plateau. The rectenna consists of a lightweight 3×3 patch antenna array(0.9 m × 0.9 m), accompanied by a steering device and LED indicators to verify power reception. The aerostat-based test achieved a power density of 154.6 mW/m2, which corresponds to approximately 6.2% of the theoretical maximum. The performance gap is primarily attributed to near-field interference, detuning of the patch antenna, rectifier mismatch, and alignment issues. These limitations are expected to be mitigated through improved patch antenna fabrication, a transition from GaN to GaAs rectifiers optimized for lower input power, and the implementation of an automated alignment system. With these enhancements, the recovered power is expected to improve by approximately four to five times. The results demonstrate a practical and scalable framework for long-range WPT experiments under constrained conditions and provide key insights for advancing SBSP technology.
