A popular dynamical model for the vortex induced vibration(VIV)of a suspended flexible cable consists of two coupled equations.The first equation is a partial differential equation governing the cable vibration.The se...A popular dynamical model for the vortex induced vibration(VIV)of a suspended flexible cable consists of two coupled equations.The first equation is a partial differential equation governing the cable vibration.The second equation is a wake oscillator that models the lift coefficient acting on the cable.The incoming wind acting on the cable is usually assumed as the uniform wind with a constant velocity,which makes the VIV model be a deterministic one.In the real world,however,the wind velocity is randomly fluctuant and makes the VIV of a suspended flexible cable be treated as a random vibration.In the present paper,the deterministic VIV model of a suspended flexible cable is modified to a random one by introducing the fluctuating wind.Using the normal mode approach,the random VIV system is transformed into an infinite-dimensional modal vibration system.Depending on whether a modal frequency is close to the aeolian frequency or not,the corresponding modal vibration is characterized as a resonant vibration or a non-resonant vibration.By applying the stochastic averaging method of quasi Hamiltonian systems,the response of modal vibrations in the case of resonance or non-resonance can be analytically predicted.Then,the random VIV response of the whole cable can be approximately calculated by superimposing the response of the most influential modal vibrations.Some numerical simulation results confirm the obtained analytical results.It is found that the intensity of the resonant modal vibration is much higher than that of the non-resonant modal vibration.Thus,the analytical results of the resonant modal vibration can be used as a rough estimation for the whole response of a cable.展开更多
BACKGROUND Stapes ankylosis is a rare cause of conductive hearing loss,and stapes suprastructure fixation is extremely rare with fewer than 30 reported cases.Patients usually visit the clinic with non-progressive cond...BACKGROUND Stapes ankylosis is a rare cause of conductive hearing loss,and stapes suprastructure fixation is extremely rare with fewer than 30 reported cases.Patients usually visit the clinic with non-progressive conductive hearing loss that typically began in the early years of life.CASE SUMMARY Herein,we report a case of a 37-year-old female with an isolated stapedial suprastructure fixation.The patient presented with unusual fluctuating auditory symptoms of tinnitus,ear fullness and mixed hearing loss.Pre-operative temporal bone computed tomography findings and operative findings revealed an isolated stapedial suprastructure fixation with monopod stapes caused by elongated pyramidal eminence.The hearing threshold recovered completely,and fluctuating auditory symptoms disappeared after the surgery.CONCLUSION This is the first report of stapedial suprastructure fixation with fluctuating auditory symptoms.Successful results are expected with surgical treatment.展开更多
Biomonitoring using fish has been a popular method of assessing the toxic effects of cadmium concentrations of cadmium in water bodies and has led to bioaccumulation in fish contributing to various morphological alter...Biomonitoring using fish has been a popular method of assessing the toxic effects of cadmium concentrations of cadmium in water bodies and has led to bioaccumulation in fish contributing to various morphological alterations. Among the known effects of these alterations is developmental instability via fluctuating asymmetry (FA). The utilization of FA data is a simple yet effective method to evaluate the toxic effects of cadmium on the stability of development. This study used climbing perch (Anabas testudieneus) to assess the FA in the diameter of the eye because of low-level cadmium exposure. The left and right sides of the traits were measured once every four weeks for 16 weeks. The average measurements from both sides of the traits were used to calculate the FA value. Results found that the highest mean FA for the diameter of the eye was obtained in the highest treatment group, 0.015 mg/L. The results also indicate that increasing concentrations of cadmium exposure had a statistically significant effect on the FA of eye diameter. There was also a statistically significant interaction between the duration of exposure and treatment groups in FA of the diameter of the eye. The results from the study indicate that prolonged exposure to sub-lethal concentrations of cadmium can cause significant effects on the normal development of eyes in Anabas testudineus. This study can add to the body of research regarding fluctuating asymmetry as a tool to study developmental toxicants and assess other bilateral organs.展开更多
A new averaged general dynamic equation(GDE) for nanoparticles in the turbulent flow is derived by considering the combined effect of convection, Brownian diffusion, turbulent diffusion, turbulent coagulation, and flu...A new averaged general dynamic equation(GDE) for nanoparticles in the turbulent flow is derived by considering the combined effect of convection, Brownian diffusion, turbulent diffusion, turbulent coagulation, and fluctuating coagulation. The equation is solved with the Taylor-series expansion moment method in a turbulent pipe flow. The experiments are performed. The numerical results of particle size distribution correlate well with the experimental data. The results show that, for a turbulent nanoparticulate flow, a fluctuating coagulation term should be included in the averaged particle GDE. The larger the Schmidt number is and the lower the Reynolds number is,the smaller the value of ratio of particle diameter at the outlet to that at the inlet is. At the outlet, the particle number concentration increases from the near-wall region to the near-center region. The larger the Schmidt number is and the higher the Reynolds number is, the larger the difference in particle number concentration between the near-wall region and near-center region is. Particle polydispersity increases from the near-center region to the near-wall region. The particles with a smaller Schmidt number and the flow with a higher Reynolds number show a higher polydispersity. The degree of particle polydispersity is higher considering fluctuating coagulation than that without considering fluctuating coagulation.展开更多
The Reynolds-averaged general dynamic equation(RAGDE)for the nanoparticle size distribution function is derived,including the contribution to particle coagulation resulting from the fluctuating concentration.The equat...The Reynolds-averaged general dynamic equation(RAGDE)for the nanoparticle size distribution function is derived,including the contribution to particle coagulation resulting from the fluctuating concentration.The equation together with that of a turbulent gas flow is solved numerically in the turbulent flow of a ventilation chamber with a jet on the wall based on the proposed model relating the fluctuating coagulation to the gradient of mean concentration.Some results are compared with the experimental data.The results show that the proposed model relating the fluctuating coagulation to the gradient of mean concentration is reasonable,and it is necessary to consider the contribution to coagulation resulting from the fluctuating concentration in such a flow.The changes of the particle number concentration M_(0) and the geometric mean diameter dg are more obvious in the core area of the jet,but less obvious in other areas.With the increase in the initial particle number concentration m00,the values of M_(0) and the standard deviation of the particle sizeσdecrease,but the value of d_(g) increases.The decrease in the initial particle diameter leads to the reduction of M_(0) andσand the increase in d_(g).With the increase in the Reynolds number,particles have few chances of collision,and hence the coagulation rate is reduced,leading to the increase in M_(0) andσand the decrease in d_(g).展开更多
This article examines the effects of reneging, server breakdown and server vacation on the various states of the batch arrivals queueing system with single server providing service to customers in three fluctuating mo...This article examines the effects of reneging, server breakdown and server vacation on the various states of the batch arrivals queueing system with single server providing service to customers in three fluctuating modes. In this queueing system, any batch arrival joins the queue if the server is busy or on vacation or under repair. However, if the server is free, one customer from the arriving batch joins the service immediately while others join the queue. In case of server breakdown, the customer whose service is interrupted returns back to the head of the queue. As soon as the server has is repaired, the server attends to the customer in mode 1. For this queueing system, customers that are impatient due to breakdown and server vacation may renege (leave the queue without getting service). Due to fluctuating modes of service delivery, the system may provide service with complete or reduced efficiency. Consequently, we construct the mathematical model and derive the probability generating functions of the steady state probabilities of several states of the system including the steady state queue size distribution. Further, we discuss some particular cases of the proposed queueing model. We present numerical examples in order to demonstrate the effects of server vacation and reneging on the various states of the system. The study revealed that an increase in reneging and a decrease in server vacation results in a decrease in server utilization and an increase in server’s idle time provided rates of server breakdown and repair completion are constant. In addition, the probability of server vacation, the probability of system is under repair and the probabilities that the server provides service in three fluctuating modes decreases due to an increase in reneging and a decrease in vacation completion rates.展开更多
Geomagnetic activity is characterized by four solar wind conditions. Each condition has specific impact on ionosphere. This paper review on fluctuating activity effects on ionosphere F2 layer through its critical freq...Geomagnetic activity is characterized by four solar wind conditions. Each condition has specific impact on ionosphere. This paper review on fluctuating activity effects on ionosphere F2 layer through its critical frequency foF2 variations. Under fluctuating wind conditions, we have investigated on annual, diurnal and seasonal variations of foF2 during solar cycles 21 and 22 phases covered by Ouagadougou ionosonde station data (Lat: 12.5°N;Long: 358.5°E;dip: 1.43°). Our investigations show that foF2 annual’ variability is in phase with solar cycle. The diurnal variation is “noon bite out” most of the time except for the solar maximum where we have a morning peak testifying to the fact that the vertical drift E × B is disturbed. The seasonal variations show that the fluctuating activity has no particular effect on certain characteristics of the equatorial ionosphere such as electrojet and vertical drift E × B. However, the increase of the electric field pre-reversal phenomenon in autumn is a characteristic effect observed during the fluctuating activity.展开更多
Experiments on a square section cylinder fixed and forced to oscillate transversely in a uni-form stream were conducted in a water tank.The Reynolds numberof the experiments is in the range of 3·10~3tO 10~4,the a...Experiments on a square section cylinder fixed and forced to oscillate transversely in a uni-form stream were conducted in a water tank.The Reynolds numberof the experiments is in the range of 3·10~3tO 10~4,the amplitude to side length ratio A/D is up to 0.7 and the range of reduced velocity is4.5【Vr【12.This study aims at investigating the lock-in phenomenon,the fluctuating lift and the phaseshift between fluctuating lift and displacement of the oscillating cylinder.The problems on the aeroelastic insta.bility relating to present experimental results have been discussed.The flow visualization clearly shows thatthere are drastic changes of vortex-shedding from cylinder at the resonance point and the upper end of thelock-in range.The results of the flow visualization give better understanding of the physical mechanism of thephase shift.展开更多
We develop computational methods for the study of fluid-structure interactions subject to thermal fluctuations when confined within channels with slit-like geometry. The methods take into account the hydrodynamic coup...We develop computational methods for the study of fluid-structure interactions subject to thermal fluctuations when confined within channels with slit-like geometry. The methods take into account the hydrodynamic coupling and diffusivity of microstructures when influenced by their proximity to no-slip walls. We develop stochastic numerical methods subject to no-slip boundary conditions using a staggered finite volume discretization. We introduce techniques for discretizing stochastic systems in a manner that ensures results consistent with statistical mechanics. We show how an exact fluctuation-dissipation condition can be used for this purpose to discretize the stochastic driving fields and combined with an exact projection method to enforce incompressibility. We demonstrate our computational methods by investigating how the proximity of ellipsoidal colloids to the channel wall affects their active hydrodynamic responses and passive diffusivity. We also study for a large number of interacting particles collective drift-diffusion dynamics and associated correlation functions. We expect the introduced stochastic computational methods to be broadly applicable to applications in which confinement effects play an important role in the dynamics of microstructures subject to hydrodynamic coupling and thermal fluctuations.展开更多
The collective behaviors of two coupled harmonic oscillators with dichotomous fluctuating frequency are investigated,including stability, synchronization, and stochastic resonance(SR). First, the synchronization condi...The collective behaviors of two coupled harmonic oscillators with dichotomous fluctuating frequency are investigated,including stability, synchronization, and stochastic resonance(SR). First, the synchronization condition of the system is obtained. When this condition is satisfied, the mean-field behavior is consistent with any single particle behavior in the system. On this basis, the stability condition and the exact steady-state solution of the system are derived. Comparative analysis shows that, the stability condition is stronger than the synchronization condition, that is to say, when the stability condition is satisfied, the system is both synchronous and stable. Simulation analysis indicates that increasing the coupling strength will reduce the synchronization time. In weak coupling region, there is an optimal coupling strength that maximizes the output amplitude gain(OAG), thus the coupling-induced SR behavior occurs. In strong coupling region, the two particles are bounded as a whole, so that the coupling effect gradually disappears.展开更多
Using the innovative method of the additional Bloch vector,the electron transfer properties of a double quantum dot(DQD) system measured by a quantum point contact(QPC) in a fluctuating environment are investigated.Th...Using the innovative method of the additional Bloch vector,the electron transfer properties of a double quantum dot(DQD) system measured by a quantum point contact(QPC) in a fluctuating environment are investigated.The results show that the environmental noises in transverse and longitudinal directions play different roles in the dynamical evolution of the open quantum systems.Considering the DQD with symmetric energy level,the Fano factor exhibits a slight peak with the increase of transverse noise amplitude σ_(T),which provides a basis for distinguishing dynamical phenomena caused by different directional fluctuation noises in symmetric DQD structures by studying the detector output.In the case of asymmetric DQD,the dependence of a detector current involving the level displacement is distinct when increasing the transverse noise damping coefficient τ_(T) and the longitudinal noise damping coefficient τ_(ε) respectively.Meanwhile,the transverse noise damping coefficient τ_(T) could significantly reduce the Fano factor and enhance the stability of the quantum system compared with the longitudinal one.The Fano factors with stable values as the enhancement of noise amplitudes show different external influences from the detector measurement,and provide a numerical reference for adjusting the noise amplitudes in both transverse and longitudinal directions appropriately in a microscopic experimental process to offset the decoherence effect caused by the measurements.Finally,the research of average waiting time provides unique insights to the development of single electron transfer theory in the short-time limit.展开更多
Underwater reverberation environments that satisfy the conditions of uniformity and isotropy of the diffuse field can be used to measure the acoustic characteristics of underwater targets.This study combines two pract...Underwater reverberation environments that satisfy the conditions of uniformity and isotropy of the diffuse field can be used to measure the acoustic characteristics of underwater targets.This study combines two practical indicators—the standard deviation of the absolute sound pressure field(to indicate uniformity)and the analysis of the wavenumber spectrum in the spherical harmonics domain(to indicate isotropy)—for an accurate evaluation of the diffusion of the sound field in a reverberation tank.A method is proposed that can improve the narrow-band diffusion of the sound field by employing a randomly fluctuating surface.An acoustic experiment was performed in a reverberation water tank(1.2 m×1 m×0.8 m),where a randomly fluctuating surface was generated by making waves.The experimental results show that as the wave motion contributes effectively to the random reflection of sound rays in all directions,the uniformity and isotropy are improved significantly when the surface is fluctuating randomly.This work helps to ensure accurate measurements of the characteristics of underwater targets in reverberation tanks.展开更多
Biased Brownian motion in a periodic potential with fluctuating temperature of thermal bath is studied.The general expression of stationary probability current is obtained.The necessary condition for biased Brownian m...Biased Brownian motion in a periodic potential with fluctuating temperature of thermal bath is studied.The general expression of stationary probability current is obtained.The necessary condition for biased Brownian motion is the combination of fluctuating temperature and a periodic ratchet potential.展开更多
This paper investigates the chemical reaction and thermal radiation effects on unsteady MHD free convective flow past a vertical porous plate in the presence of heat absorption/generation.The novelty of present invest...This paper investigates the chemical reaction and thermal radiation effects on unsteady MHD free convective flow past a vertical porous plate in the presence of heat absorption/generation.The novelty of present investigation is that the temperature and concentration of the plate are span wise cosinusoidally unsteady with time.The second order perturbation technique is employed to study the non-linear partial differential equations which govern the fluid flow.The effects of magnetic parameter,radiation,Eckert number,Schmidt number and chemical reaction parameters on velocity,temperature and concentration distributions as well as skin friction coefficients,the rate of heat transfer and the rate of mass transfer are discussed through figures and tables.It is noticed that the Nusselt number declines with rising values of Prandtl and Eckert numbers.展开更多
In present paper, an investigation has been made on the fluctuating flow of a non-Newtonian second grade fluid through a porous medium over a semi-infinite porous plate in presence of a transverse magnetic field B0. T...In present paper, an investigation has been made on the fluctuating flow of a non-Newtonian second grade fluid through a porous medium over a semi-infinite porous plate in presence of a transverse magnetic field B0. The governing equations have been solved analytically and the expressions for the velocity and stress fields are obtained. The free stream velocity U(t) fluctuates in time about a non-zero constant mean. The effects of the permeability parameter K and magnetic field parameter M on velocity field have been analyzed quantitatively with the help of figures. It is noticed that the velocity field asymptotically approaches free stream velocity as it goes far away from the plate.展开更多
The technological development of smart devices and Internet of Things(IoT)has brought ever-larger bandwidth and fluctuating traffic to existing networks.The analy⁃sis of network capital expenditure(CAPEX)is extremely ...The technological development of smart devices and Internet of Things(IoT)has brought ever-larger bandwidth and fluctuating traffic to existing networks.The analy⁃sis of network capital expenditure(CAPEX)is extremely important and plays a fundamen⁃tal role in further network optimizing.In this paper,an adaptability analysis is raised for IP switching and optical transport network(OTN)switching in CAPEX when the service bandwidth is fluctuating violently.This paper establishes a multi-layer network architec⁃ture through Clos network model and discusses impacts of maximum allowable blocking rate and service bandwidth standard deviation on CAPEX of IP network and OTN network to find CAPEX demarcation point in different situations.As simulation results show,when the bandwidth deviation mean rate is 0.3 and the maximum allowable blocking rate is 0.01,the hardware cost of OTN switching will exceed IP switching as the average band⁃width is greater than 6100 Mbit/s.When the service bandwidth fluctuation is severe,the hardware cost of OTN switching will increase and exceed IP switching as the single port rate is allowed in optical switching.The increasing of maximum allowable blocking rate can decrease hardware cost of OTN switching.Finally,it is found that Flex Ethernet(FlexE)can be used to decrease CAPEX of OTN switching greatly at this time.展开更多
This paper deals with TEC variability during fluctuating geomagnetic events (FE) during solar cycle 24 at Koudougou station (lat: 12<sup>o</sup>15'N;Geo long: -2<sup>o</sup>20'E). The s...This paper deals with TEC variability during fluctuating geomagnetic events (FE) during solar cycle 24 at Koudougou station (lat: 12<sup>o</sup>15'N;Geo long: -2<sup>o</sup>20'E). The study was done by comparing TEC variations during FE days with those of quiet days (QA). Comparison was made taking into account solar phases’ and seasons’ influences. FE’s and QA’s TEC curves are characterized by dome profiles. All graphs show two troughs, one in the morning (0500 LT) and the second in the evening (around 2000 LT) and a peak around 1400 LT during all solar phases and winter months and around 1500 LT for the remaining seasons. Both troughs are caused by the decrease of the photo ionization and an increase of the recombination phenomena, as well for FE as for QA periods. FE cause positive storms during all solar phases as well as during seasons and some negative storms during spring and summer months and minimum and maximum solar phases.展开更多
A new and computationally efficient version of the immersed boundary method,which is combined with the coarse-graining method,is introduced for modeling inextensible filaments immersed in low-Reynolds number flows.Thi...A new and computationally efficient version of the immersed boundary method,which is combined with the coarse-graining method,is introduced for modeling inextensible filaments immersed in low-Reynolds number flows.This is used to represent actin biopolymers,which are constituent elements of the cytoskeleton,a complex network-like structure that plays a fundamental role in shape morphology.An extension of the traditional immersed boundary method to include a stochastic stress tensor is also proposed in order to model the thermal fluctuations in the fluid at smaller scales.By way of validation,the response of a single,massless,inextensible semiflexible filament immersed in a thermally fluctuating fluid is obtained using the suggested numerical scheme and the resulting time-averaged contraction of the filament is compared to the theoretical value obtained from the worm-like chain model.展开更多
Method for numerical simulation of the temperature of granule with internal heat release in a medium with random temperature fluctuations is proposed. The method utilized the solution of a system of ordinary stochasti...Method for numerical simulation of the temperature of granule with internal heat release in a medium with random temperature fluctuations is proposed. The method utilized the solution of a system of ordinary stochastic differential equations describing temperature fluctuations of the surrounding and granule. Autocorrelation function of temperature fluctuations has a finite decay time. The suggested method is verified by the comparison with exact analytical results. Random temperature behavior of granule with internal heat release qualitatively differs from the results obtained in the deterministic approach. Mean first passage time of granules temperature intersecting critical temperature is estimated at different regime parameters.展开更多
Fluctuations of the measured parameters of the investigated electric and non-electric systems are considered on the thermodynamics basis.We have defined that entropy of the investigated system in relation to environme...Fluctuations of the measured parameters of the investigated electric and non-electric systems are considered on the thermodynamics basis.We have defined that entropy of the investigated system in relation to environment depends on the correlation between measuring durationТmeas of the system’s fluctuation parameter and the system’s relaxation timeτ.Decrement of the energy spectrum of fluctuations with the decrease of frequency is explained byТmeas>τ.WhenТmeas≈Nmaxτ(where Nmax is the number of possible ways to create the balanced state of the system),entropy of investigated system tends to zero in relation to the environment,and the measurement error caused by fluctuations becomes the minimal.展开更多
基金Project supported by the State Grid Science and Technology Project(No.SGZJJXI0SYJS2101112)。
文摘A popular dynamical model for the vortex induced vibration(VIV)of a suspended flexible cable consists of two coupled equations.The first equation is a partial differential equation governing the cable vibration.The second equation is a wake oscillator that models the lift coefficient acting on the cable.The incoming wind acting on the cable is usually assumed as the uniform wind with a constant velocity,which makes the VIV model be a deterministic one.In the real world,however,the wind velocity is randomly fluctuant and makes the VIV of a suspended flexible cable be treated as a random vibration.In the present paper,the deterministic VIV model of a suspended flexible cable is modified to a random one by introducing the fluctuating wind.Using the normal mode approach,the random VIV system is transformed into an infinite-dimensional modal vibration system.Depending on whether a modal frequency is close to the aeolian frequency or not,the corresponding modal vibration is characterized as a resonant vibration or a non-resonant vibration.By applying the stochastic averaging method of quasi Hamiltonian systems,the response of modal vibrations in the case of resonance or non-resonance can be analytically predicted.Then,the random VIV response of the whole cable can be approximately calculated by superimposing the response of the most influential modal vibrations.Some numerical simulation results confirm the obtained analytical results.It is found that the intensity of the resonant modal vibration is much higher than that of the non-resonant modal vibration.Thus,the analytical results of the resonant modal vibration can be used as a rough estimation for the whole response of a cable.
文摘BACKGROUND Stapes ankylosis is a rare cause of conductive hearing loss,and stapes suprastructure fixation is extremely rare with fewer than 30 reported cases.Patients usually visit the clinic with non-progressive conductive hearing loss that typically began in the early years of life.CASE SUMMARY Herein,we report a case of a 37-year-old female with an isolated stapedial suprastructure fixation.The patient presented with unusual fluctuating auditory symptoms of tinnitus,ear fullness and mixed hearing loss.Pre-operative temporal bone computed tomography findings and operative findings revealed an isolated stapedial suprastructure fixation with monopod stapes caused by elongated pyramidal eminence.The hearing threshold recovered completely,and fluctuating auditory symptoms disappeared after the surgery.CONCLUSION This is the first report of stapedial suprastructure fixation with fluctuating auditory symptoms.Successful results are expected with surgical treatment.
文摘Biomonitoring using fish has been a popular method of assessing the toxic effects of cadmium concentrations of cadmium in water bodies and has led to bioaccumulation in fish contributing to various morphological alterations. Among the known effects of these alterations is developmental instability via fluctuating asymmetry (FA). The utilization of FA data is a simple yet effective method to evaluate the toxic effects of cadmium on the stability of development. This study used climbing perch (Anabas testudieneus) to assess the FA in the diameter of the eye because of low-level cadmium exposure. The left and right sides of the traits were measured once every four weeks for 16 weeks. The average measurements from both sides of the traits were used to calculate the FA value. Results found that the highest mean FA for the diameter of the eye was obtained in the highest treatment group, 0.015 mg/L. The results also indicate that increasing concentrations of cadmium exposure had a statistically significant effect on the FA of eye diameter. There was also a statistically significant interaction between the duration of exposure and treatment groups in FA of the diameter of the eye. The results from the study indicate that prolonged exposure to sub-lethal concentrations of cadmium can cause significant effects on the normal development of eyes in Anabas testudineus. This study can add to the body of research regarding fluctuating asymmetry as a tool to study developmental toxicants and assess other bilateral organs.
基金Project supported by the National Natural Science Foundation of China(No.11132008)
文摘A new averaged general dynamic equation(GDE) for nanoparticles in the turbulent flow is derived by considering the combined effect of convection, Brownian diffusion, turbulent diffusion, turbulent coagulation, and fluctuating coagulation. The equation is solved with the Taylor-series expansion moment method in a turbulent pipe flow. The experiments are performed. The numerical results of particle size distribution correlate well with the experimental data. The results show that, for a turbulent nanoparticulate flow, a fluctuating coagulation term should be included in the averaged particle GDE. The larger the Schmidt number is and the lower the Reynolds number is,the smaller the value of ratio of particle diameter at the outlet to that at the inlet is. At the outlet, the particle number concentration increases from the near-wall region to the near-center region. The larger the Schmidt number is and the higher the Reynolds number is, the larger the difference in particle number concentration between the near-wall region and near-center region is. Particle polydispersity increases from the near-center region to the near-wall region. The particles with a smaller Schmidt number and the flow with a higher Reynolds number show a higher polydispersity. The degree of particle polydispersity is higher considering fluctuating coagulation than that without considering fluctuating coagulation.
基金Project supported by the Major Program of the National Natural Science Foundation of China(No.91852102)。
文摘The Reynolds-averaged general dynamic equation(RAGDE)for the nanoparticle size distribution function is derived,including the contribution to particle coagulation resulting from the fluctuating concentration.The equation together with that of a turbulent gas flow is solved numerically in the turbulent flow of a ventilation chamber with a jet on the wall based on the proposed model relating the fluctuating coagulation to the gradient of mean concentration.Some results are compared with the experimental data.The results show that the proposed model relating the fluctuating coagulation to the gradient of mean concentration is reasonable,and it is necessary to consider the contribution to coagulation resulting from the fluctuating concentration in such a flow.The changes of the particle number concentration M_(0) and the geometric mean diameter dg are more obvious in the core area of the jet,but less obvious in other areas.With the increase in the initial particle number concentration m00,the values of M_(0) and the standard deviation of the particle sizeσdecrease,but the value of d_(g) increases.The decrease in the initial particle diameter leads to the reduction of M_(0) andσand the increase in d_(g).With the increase in the Reynolds number,particles have few chances of collision,and hence the coagulation rate is reduced,leading to the increase in M_(0) andσand the decrease in d_(g).
文摘This article examines the effects of reneging, server breakdown and server vacation on the various states of the batch arrivals queueing system with single server providing service to customers in three fluctuating modes. In this queueing system, any batch arrival joins the queue if the server is busy or on vacation or under repair. However, if the server is free, one customer from the arriving batch joins the service immediately while others join the queue. In case of server breakdown, the customer whose service is interrupted returns back to the head of the queue. As soon as the server has is repaired, the server attends to the customer in mode 1. For this queueing system, customers that are impatient due to breakdown and server vacation may renege (leave the queue without getting service). Due to fluctuating modes of service delivery, the system may provide service with complete or reduced efficiency. Consequently, we construct the mathematical model and derive the probability generating functions of the steady state probabilities of several states of the system including the steady state queue size distribution. Further, we discuss some particular cases of the proposed queueing model. We present numerical examples in order to demonstrate the effects of server vacation and reneging on the various states of the system. The study revealed that an increase in reneging and a decrease in server vacation results in a decrease in server utilization and an increase in server’s idle time provided rates of server breakdown and repair completion are constant. In addition, the probability of server vacation, the probability of system is under repair and the probabilities that the server provides service in three fluctuating modes decreases due to an increase in reneging and a decrease in vacation completion rates.
文摘Geomagnetic activity is characterized by four solar wind conditions. Each condition has specific impact on ionosphere. This paper review on fluctuating activity effects on ionosphere F2 layer through its critical frequency foF2 variations. Under fluctuating wind conditions, we have investigated on annual, diurnal and seasonal variations of foF2 during solar cycles 21 and 22 phases covered by Ouagadougou ionosonde station data (Lat: 12.5°N;Long: 358.5°E;dip: 1.43°). Our investigations show that foF2 annual’ variability is in phase with solar cycle. The diurnal variation is “noon bite out” most of the time except for the solar maximum where we have a morning peak testifying to the fact that the vertical drift E × B is disturbed. The seasonal variations show that the fluctuating activity has no particular effect on certain characteristics of the equatorial ionosphere such as electrojet and vertical drift E × B. However, the increase of the electric field pre-reversal phenomenon in autumn is a characteristic effect observed during the fluctuating activity.
基金Project supported by National Natural Science Foundation of China
文摘Experiments on a square section cylinder fixed and forced to oscillate transversely in a uni-form stream were conducted in a water tank.The Reynolds numberof the experiments is in the range of 3·10~3tO 10~4,the amplitude to side length ratio A/D is up to 0.7 and the range of reduced velocity is4.5【Vr【12.This study aims at investigating the lock-in phenomenon,the fluctuating lift and the phaseshift between fluctuating lift and displacement of the oscillating cylinder.The problems on the aeroelastic insta.bility relating to present experimental results have been discussed.The flow visualization clearly shows thatthere are drastic changes of vortex-shedding from cylinder at the resonance point and the upper end of thelock-in range.The results of the flow visualization give better understanding of the physical mechanism of thephase shift.
基金Project supported by the Applied Mathematics Program within the Department of Energy(DOE)Office of Advanced Scientific Computing Research(ASCR)as part of the Collaboratory on Mathematics for Mesoscopic Modeling of Materials(CM4)(No.DOE ASCR CM4 DE-SC0009254)the DOE National Laboratory Directed Research Development(No.LDRD69738)the National Science Foudation of the United States(Nos.DMS-0956210,DMS-1616353,DMR-1121053,and NSF CNS-0960316)
文摘We develop computational methods for the study of fluid-structure interactions subject to thermal fluctuations when confined within channels with slit-like geometry. The methods take into account the hydrodynamic coupling and diffusivity of microstructures when influenced by their proximity to no-slip walls. We develop stochastic numerical methods subject to no-slip boundary conditions using a staggered finite volume discretization. We introduce techniques for discretizing stochastic systems in a manner that ensures results consistent with statistical mechanics. We show how an exact fluctuation-dissipation condition can be used for this purpose to discretize the stochastic driving fields and combined with an exact projection method to enforce incompressibility. We demonstrate our computational methods by investigating how the proximity of ellipsoidal colloids to the channel wall affects their active hydrodynamic responses and passive diffusivity. We also study for a large number of interacting particles collective drift-diffusion dynamics and associated correlation functions. We expect the introduced stochastic computational methods to be broadly applicable to applications in which confinement effects play an important role in the dynamics of microstructures subject to hydrodynamic coupling and thermal fluctuations.
基金supported by the National Natural Science Foundation of China for the Youth (Grant Nos. 11501385 and 11801385)。
文摘The collective behaviors of two coupled harmonic oscillators with dichotomous fluctuating frequency are investigated,including stability, synchronization, and stochastic resonance(SR). First, the synchronization condition of the system is obtained. When this condition is satisfied, the mean-field behavior is consistent with any single particle behavior in the system. On this basis, the stability condition and the exact steady-state solution of the system are derived. Comparative analysis shows that, the stability condition is stronger than the synchronization condition, that is to say, when the stability condition is satisfied, the system is both synchronous and stable. Simulation analysis indicates that increasing the coupling strength will reduce the synchronization time. In weak coupling region, there is an optimal coupling strength that maximizes the output amplitude gain(OAG), thus the coupling-induced SR behavior occurs. In strong coupling region, the two particles are bounded as a whole, so that the coupling effect gradually disappears.
基金Project supported by the Natural Science Foundation of Shandong Province,China(Grant No.ZR2014AM030)。
文摘Using the innovative method of the additional Bloch vector,the electron transfer properties of a double quantum dot(DQD) system measured by a quantum point contact(QPC) in a fluctuating environment are investigated.The results show that the environmental noises in transverse and longitudinal directions play different roles in the dynamical evolution of the open quantum systems.Considering the DQD with symmetric energy level,the Fano factor exhibits a slight peak with the increase of transverse noise amplitude σ_(T),which provides a basis for distinguishing dynamical phenomena caused by different directional fluctuation noises in symmetric DQD structures by studying the detector output.In the case of asymmetric DQD,the dependence of a detector current involving the level displacement is distinct when increasing the transverse noise damping coefficient τ_(T) and the longitudinal noise damping coefficient τ_(ε) respectively.Meanwhile,the transverse noise damping coefficient τ_(T) could significantly reduce the Fano factor and enhance the stability of the quantum system compared with the longitudinal one.The Fano factors with stable values as the enhancement of noise amplitudes show different external influences from the detector measurement,and provide a numerical reference for adjusting the noise amplitudes in both transverse and longitudinal directions appropriately in a microscopic experimental process to offset the decoherence effect caused by the measurements.Finally,the research of average waiting time provides unique insights to the development of single electron transfer theory in the short-time limit.
基金supported by the National Natural Science Foundation of China(Grant No.11874131)。
文摘Underwater reverberation environments that satisfy the conditions of uniformity and isotropy of the diffuse field can be used to measure the acoustic characteristics of underwater targets.This study combines two practical indicators—the standard deviation of the absolute sound pressure field(to indicate uniformity)and the analysis of the wavenumber spectrum in the spherical harmonics domain(to indicate isotropy)—for an accurate evaluation of the diffusion of the sound field in a reverberation tank.A method is proposed that can improve the narrow-band diffusion of the sound field by employing a randomly fluctuating surface.An acoustic experiment was performed in a reverberation water tank(1.2 m×1 m×0.8 m),where a randomly fluctuating surface was generated by making waves.The experimental results show that as the wave motion contributes effectively to the random reflection of sound rays in all directions,the uniformity and isotropy are improved significantly when the surface is fluctuating randomly.This work helps to ensure accurate measurements of the characteristics of underwater targets in reverberation tanks.
基金Supported by the Grant for the Key Research Project in Climbing Program from the National Commission of Science and Technology of China.
文摘Biased Brownian motion in a periodic potential with fluctuating temperature of thermal bath is studied.The general expression of stationary probability current is obtained.The necessary condition for biased Brownian motion is the combination of fluctuating temperature and a periodic ratchet potential.
文摘This paper investigates the chemical reaction and thermal radiation effects on unsteady MHD free convective flow past a vertical porous plate in the presence of heat absorption/generation.The novelty of present investigation is that the temperature and concentration of the plate are span wise cosinusoidally unsteady with time.The second order perturbation technique is employed to study the non-linear partial differential equations which govern the fluid flow.The effects of magnetic parameter,radiation,Eckert number,Schmidt number and chemical reaction parameters on velocity,temperature and concentration distributions as well as skin friction coefficients,the rate of heat transfer and the rate of mass transfer are discussed through figures and tables.It is noticed that the Nusselt number declines with rising values of Prandtl and Eckert numbers.
文摘In present paper, an investigation has been made on the fluctuating flow of a non-Newtonian second grade fluid through a porous medium over a semi-infinite porous plate in presence of a transverse magnetic field B0. The governing equations have been solved analytically and the expressions for the velocity and stress fields are obtained. The free stream velocity U(t) fluctuates in time about a non-zero constant mean. The effects of the permeability parameter K and magnetic field parameter M on velocity field have been analyzed quantitatively with the help of figures. It is noticed that the velocity field asymptotically approaches free stream velocity as it goes far away from the plate.
基金This work was supported by National Key Research and Development Program(2018YFB1800504)and the ZTE Research Fund,China.
文摘The technological development of smart devices and Internet of Things(IoT)has brought ever-larger bandwidth and fluctuating traffic to existing networks.The analy⁃sis of network capital expenditure(CAPEX)is extremely important and plays a fundamen⁃tal role in further network optimizing.In this paper,an adaptability analysis is raised for IP switching and optical transport network(OTN)switching in CAPEX when the service bandwidth is fluctuating violently.This paper establishes a multi-layer network architec⁃ture through Clos network model and discusses impacts of maximum allowable blocking rate and service bandwidth standard deviation on CAPEX of IP network and OTN network to find CAPEX demarcation point in different situations.As simulation results show,when the bandwidth deviation mean rate is 0.3 and the maximum allowable blocking rate is 0.01,the hardware cost of OTN switching will exceed IP switching as the average band⁃width is greater than 6100 Mbit/s.When the service bandwidth fluctuation is severe,the hardware cost of OTN switching will increase and exceed IP switching as the single port rate is allowed in optical switching.The increasing of maximum allowable blocking rate can decrease hardware cost of OTN switching.Finally,it is found that Flex Ethernet(FlexE)can be used to decrease CAPEX of OTN switching greatly at this time.
文摘This paper deals with TEC variability during fluctuating geomagnetic events (FE) during solar cycle 24 at Koudougou station (lat: 12<sup>o</sup>15'N;Geo long: -2<sup>o</sup>20'E). The study was done by comparing TEC variations during FE days with those of quiet days (QA). Comparison was made taking into account solar phases’ and seasons’ influences. FE’s and QA’s TEC curves are characterized by dome profiles. All graphs show two troughs, one in the morning (0500 LT) and the second in the evening (around 2000 LT) and a peak around 1400 LT during all solar phases and winter months and around 1500 LT for the remaining seasons. Both troughs are caused by the decrease of the photo ionization and an increase of the recombination phenomena, as well for FE as for QA periods. FE cause positive storms during all solar phases as well as during seasons and some negative storms during spring and summer months and minimum and maximum solar phases.
文摘A new and computationally efficient version of the immersed boundary method,which is combined with the coarse-graining method,is introduced for modeling inextensible filaments immersed in low-Reynolds number flows.This is used to represent actin biopolymers,which are constituent elements of the cytoskeleton,a complex network-like structure that plays a fundamental role in shape morphology.An extension of the traditional immersed boundary method to include a stochastic stress tensor is also proposed in order to model the thermal fluctuations in the fluid at smaller scales.By way of validation,the response of a single,massless,inextensible semiflexible filament immersed in a thermally fluctuating fluid is obtained using the suggested numerical scheme and the resulting time-averaged contraction of the filament is compared to the theoretical value obtained from the worm-like chain model.
文摘Method for numerical simulation of the temperature of granule with internal heat release in a medium with random temperature fluctuations is proposed. The method utilized the solution of a system of ordinary stochastic differential equations describing temperature fluctuations of the surrounding and granule. Autocorrelation function of temperature fluctuations has a finite decay time. The suggested method is verified by the comparison with exact analytical results. Random temperature behavior of granule with internal heat release qualitatively differs from the results obtained in the deterministic approach. Mean first passage time of granules temperature intersecting critical temperature is estimated at different regime parameters.
文摘Fluctuations of the measured parameters of the investigated electric and non-electric systems are considered on the thermodynamics basis.We have defined that entropy of the investigated system in relation to environment depends on the correlation between measuring durationТmeas of the system’s fluctuation parameter and the system’s relaxation timeτ.Decrement of the energy spectrum of fluctuations with the decrease of frequency is explained byТmeas>τ.WhenТmeas≈Nmaxτ(where Nmax is the number of possible ways to create the balanced state of the system),entropy of investigated system tends to zero in relation to the environment,and the measurement error caused by fluctuations becomes the minimal.
