Simulation of nanofluid natural convection based on single-particle hydrodynamics in energy-conserving dissipative particle dynamics(eDPD)

In the present study,the nanofliud natural convection is investigated by the energy-conserving dissipative particle dynamics(eDPD)method,where the nanoparticles are considered at the single-particle level.The thermal expansion coefficientβand the viscosityμof the simulated system containing nanoparticles are calculated and found to be in close alignment with the previous simulation results.The single-particle hydrodynamics in e DPD enables simulations of nanofluid natural convection with higher Rayleigh numbers and greater nanoparticle volume fractions.Additionally,this approach is utilized to simulate the nanoparticle distribution during the enhanced heat transfer process in the nanofluid natural convection.The localized aggregation of nanoparticles enhances the heat transfer performance of the nanofluid under specific Rayleigh numbers and nanoparticles volume fractions.

Different efficiency toward the biomimetic aerobic oxidation of benzyl alcohol in microchannel and bubble column reactors: Hydrodynamic characteristics and gas–liquid mass transfer

The selective aerobic oxidation of benzyl alcohol to benzaldehyde has attracted considerable attention because benzaldehyde is a high value-added product. The rate of this typical gas–liquid reaction is significantly affected by mass transfer. In this study, CoTPP-mediated(CoTPP: cobalt(II) mesotetraphenylporphyrin) selective benzyl alcohol oxidation with oxygen was conducted in a membrane microchannel(MMC) reactor and a bubble column(BC) reactor, respectively. We observed that 83% benzyl alcohol was converted within 6.5 min in the MMC reactor, but only less than 10% benzyl alcohol was converted in the BC reactor. Hydrodynamic characteristics and gas–liquid mass transfer performances were compared for the MMC and BC reactors. The MMC reactor was assumed to be a plug flow reactor,and the dimensionless variance was 0.29. Compared to the BC reactor, the gas–liquid mass transfer was intensified significantly in MMC reactor. It could be ascribed to the high gas holdup(2.9 times higher than that of BC reactor), liquid film mass transfer coefficient(8.2 times higher than that of BC reactor), and mass transfer coefficient per unit interfacial area(3.8 times higher than that of BC reactor). Moreover,the Hatta number for the MMC reactor reached up to 0.61, which was about 15 times higher than that of the BC reactor. The computational fluid dynamics calculations for mass fractions in both liquid and gas phases were consistent with the experimental data.

A dynamic control structure of liquid-only transfer stream distillation column

The intention of this fundamental work is to explore the manipulation of a mixture of benzene,toluene and o-xylene separated from liquid-only transfer divided-wall column(LTS-DWC).First,two control structures are clearly proposed,including seven component control loops(CS1)and seven temperature control loops(CS2).However,two control structures can handle ±10% feed disturbances rather than larger feed disturbances.Subsequently,an equivalent four-column model by introducing withdraw ratio is developed to discuss the effect of two liquid-only side-stream on the overall reboiler duty.It is indicated that the second liquid-only side-stream withdraw ratio strongly affects the overall energy consumption.Hence,six-component control loops within the fixed second liquid-only side-stream withdraw ratio(CS3)is proposed and the purity of products returns to set value even as facing ±20% feed disturbances.Finally,based on the above results,it is established a temperature control structure(CS4)for controlling fixed second liquid-only side-stream withdraw ratio,which can cope with ±15% disturbances.Inspired by these findings,an insight into the dynamic control of LTS-DWC promotes the industrial implementation of DWC through new liquid-only side-stream configurations.

Quantum Dynamics Calculations on Isotope Effects of Hydrogen Transfer Isomerization in Formic Acid Dimer

We present a quantum dynamics study on the isotope effects of hydro-gen transfer isomerization in the formic acid dimer,and this is achieved by multidimensional dy-namics calculations with an efficient quantum mechanical theoretical scheme developed by our group,on a full-dimensional neural network ab initio potential energy surface.The ground-state and fundamental tun-neling splittings for four deuterium isotopologues of formic acid dimer are considered,and the calculated results are in very good general agreement with the avail-able experimental measurements.Strong isotope effects are revealed,the mode-specific funda-mental excitation effects on the tunneling rate are evidently influenced by the deuterium sub-stitution of H atom with the substitution on the OH bond being more effective than on the CH bond.Our studies are helpful for acquiring a better understanding of isotope effects in the double-hydrogen transfer processes.

A priority-based dynamic load transfer algorithm for cellular/WLAN integrated networks

For the integration network of a cellular network and a wireless local area network （WLAN）, a priority-based dynamic load transfer （PDLT） algorithm is proposed. The dynamic vertical handoffs by call admission control are jointly determined by the network conditions and the traffic characteristics in combination with the location-condition of mobile terminals. When there is no bandwidth resource available in the cellular network or WLAN, the proposed PDLT algorithm allows an incoming voice call or data call within the overlapping area of the cellular network and the WLAN to be directed to the spare network; meanwhile, by dynamically computing the occupancy of the bandwidth resource, the proposed PDLT algorithm also allows an ongoing voice call or data communication to be transferred to the network with a sufficient bandwidth resource according to the given threshold to balance the number of voice/data calls in the two networks. The analysis results of a two-dimensional Markov model and the simulation results show that the PDLT algorithm can effectively enhance the whole integrated network＇ s traffic, reduce the blocking probability of new calls and increase the data throughput, and thus decrease the response time for various services.

Discrete time transfer matrix method for dynamics of multibody system with flexible beams moving in space

In this paper, by defining new state vectors and developing new transfer matrices of various elements mov- ing in space, the discrete time transfer matrix method of multi-rigid-flexible-body system is expanded to study the dynamics of multibody system with flexible beams moving in space. Formulations and numerical example of a rigid- flexible-body three pendulums system moving in space are given to validate the method. Using the new method to study the dynamics of multi-rigid-flexible-body system mov- ing in space, the global dynamics equations of system are not needed, the orders of involved matrices of the system are very low and the computational speed is high, irrespec- tive of the size of the system. The new method is simple, straightforward, practical, and provides a powerful tool for multi-rigid-flexible-body system dynamics.

Dynamic Distribution Adaptation Based Transfer Network for Cross Domain Bearing Fault Diagnosis

In machinery fault diagnosis,labeled data are always difficult or even impossible to obtain.Transfer learning can leverage related fault diagnosis knowledge from fully labeled source domain to enhance the fault diagnosis performance in sparsely labeled or unlabeled target domain,which has been widely used for cross domain fault diagnosis.However,existing methods focus on either marginal distribution adaptation(MDA)or conditional distribution adaptation(CDA).In practice,marginal and conditional distributions discrepancies both have significant but different influences on the domain divergence.In this paper,a dynamic distribution adaptation based transfer network(DDATN)is proposed for cross domain bearing fault diagnosis.DDATN utilizes the proposed instance-weighted dynamic maximum mean discrepancy(IDMMD)for dynamic distribution adaptation(DDA),which can dynamically estimate the influences of marginal and conditional distribution and adapt target domain with source domain.The experimental evaluation on cross domain bearing fault diagnosis demonstrates that DDATN can outperformance the state-of-the-art cross domain fault diagnosis methods.

Dynamics Analysis of a Parallel Mill-turn Tool Spindle Head Driven by Dual-linear Motors Using Extended Transfer Matrix Method

The hybrid dynamics of multi-rigid-body and multi-flexible-body system becomes the mainstream of multi-body dynamics.Currently there lacks a compact approach to model the hybrid dynamics,especially in modern machine tool application,due to the difficulty of solving the hybrid equations or the limitation of current software when dealing with the hybrid dynamics.The extended transfer matrix method（E-TMM）,which extends elements in three-dimensional space with higher matrixes,is proposed to simplify the modeling process of the hybrid dynamics.The E-TMM modeling approaches of 3 basic elements including 3D vibrant rigid body,joint and flexible body are studied in details.A parallel mill-turn tool spindle head unit driven by dual-linear motors is chosen as a plant to demonstrate the E-TMM modeling process.By using E-TMM,the spindle head unit is simplified as a topological network consisting of the three types of element,i.e.,3D vibrant rigid body,joint and flexible body,including 11 rigid bodies,14 joints and 1 3D-Timoshenko beam.Then the dynamic model of the system can be easily obtained by deducing the element-network by means of state vector transformation.The dynamic characteristics of the spindle head,such as natural frequencies,dynamic flexibility,etc.can be predicted by solving the obtained model.Experiment verification indicates that the E-TMM is valid with enough accuracy in the dynamic analysis of the parallel mill-turn tool spindle head.The E-TMM is capable of modeling the dynamics of machine tool structure with no requirements of deducing and solving the sophisticated differential equations.Moreover,the E-TMM provides a simple and elegant tool for hybrid dynamic analysis in future dynamic design of machine tools.

Analysis of Vibration of the Euler-Bernoulli Pipe Conveying Fluid by Dynamic Stiffness Method and Transfer Matrix

The dynamic stiffness method and Transfer method is applied to study the vibration characteristics of the Euler-Bernoulli pipe conveying fluid in this paper. According to the dynamics equation of the pipe conveying fluid, the element dynamic stiffness is established. The vibration characteristic of the single-span pipe is analyzed under two kinds of boundary conditions. The results compared with the literature, which has a good consistency. Based on this method, natural frequency and the critical speed of the two types of multi-span pipe are deserved. This paper shows that the dynamic stiffness method and transfer matrix is an effective method to deal with the vibration problem of pipe conveying fluid.

Dynamic Ensemble Multivariate Time Series Forecasting Model for PM2.5

In forecasting real time environmental factors,large data is needed to analyse the pattern behind the data values.Air pollution is a major threat towards developing countries and it is proliferating every year.Many methods in time ser-ies prediction and deep learning models to estimate the severity of air pollution.Each independent variable contributing towards pollution is necessary to analyse the trend behind the air pollution in that particular locality.This approach selects multivariate time series and coalesce a real time updatable autoregressive model to forecast Particulate matter(PM)PM2.5.To perform experimental analysis the data from the Central Pollution Control Board(CPCB)is used.Prediction is car-ried out for Chennai with seven locations and estimated PM’s using the weighted ensemble method.Proposed method for air pollution prediction unveiled effective and moored performance in long term prediction.Dynamic budge with high weighted k-models are used simultaneously and devising an ensemble helps to achieve stable forecasting.Computational time of ensemble decreases with paral-lel processing in each sub model.Weighted ensemble model shows high perfor-mance in long term prediction when compared to the traditional time series models like Vector Auto-Regression(VAR),Autoregressive Integrated with Mov-ing Average(ARIMA),Autoregressive Moving Average with Extended terms(ARMEX).Evaluation metrics like Root Mean Square Error(RMSE),Mean Absolute Error(MAE)and the time to achieve the time series are compared.

Mathematical Simulation of Dynamic Heat Transfer in a Human-Clothing-Environment System

A mathematical model has been developed to describe the dynamic heat transfer in the clothing microclimate under transient wear conditions. This model is solved numerically by the implicit finite difference method. If the physical activity and ambient conditions are specified, the model can predict the thermoregulatory response of the body. Experimental measurements with garments made of fibers with different levels of hygroscopicity are compared with predictions by the model. There is good agreement between prediction and experiment for the temperature of the clothing microclimate.

Tensile stress enhanced dynamic oxygen vacancies on interlayer stretched Bi_(2)O_(2)CO_(3) as pivotal knobs to promote sustainable selective CO_(2) photoreduction

Surface oxygen vacancies(OVs) with abundant localized electrons on bismuth-oxygen based photocatalysts are proved to have the ability to capture and activate CO_(2).However,the surface OVs are easily filled with oxygen-containing species and destroyed,losing their effects as active sites and hindering the subsequent CO_(2)photoreduction.For realistic and sustainable CO_(2)photoreduction,constructing sustainable and stable surface OVs as active sites on photocatalysts is essential.This work shows the synthesis of interlayer stretched Bi_(2)O_(2)CO_(3) ultrathin nanosheets with tensile stress,which are beneficial to continuously generating light-induced dynamic OVs.With sufficient active sites,excellent,stable,and selective photoreduction of CO_(2)to CO under simulated solar light is achieved.The light-induced OVs can reduce the energy barrier of rate-determining step,resulting in the 100% product selectivity.The results presented herein demonstrate the effect of dynamic OVs induced by interlayer tensile strain on catalysts for the enhanced selective CO_(2)photoreduction process.

Numerical Study of Fluid Dynamics and Heat Transfer Induced by Plasma Discharges

A numerical investigation is conducted to explore the evolution of a plasma discharge and its interaction with the fluid flow based on a self-consistent fluid model which couples the discharge dynamics with the fluid dynamics.The effects of the applied voltage on the distribution of velocity and temperature in initially static air are parainetrically studied.Furthermore,the spatial structure of plasma discharge and the resulting force contours in streamwise and normal directions are discussed in detail.The result shows that the plasma actuator produces a net force that should always be directed away from the exposed electrode,which results in an ionic wind pushing particles into a jet downstream of the actuator.When the energy added by the plasma is taken into account,the ambient air temperature is increased slightly around the electrode,but the velocity is almost not affected.Therefore it is unlikely that the induced flow is buoyancy driven.For the operating voltages considered in this paper,the maximum induced velocity is found to follow a power law,i.e.,it is proportional to the applied voltage to the 3.5 power.This promises an efficient application in the flow control with plasma actuators.

IN RELATION TO CLOTHING COMFORT DYNAMIC MOISTURE TRANSFER THROUGH FABRICS

A sweating apparatus has been developed to permit simultaneous measurement for fabric temperature change and relative humidity change at outer still air layer of fabrics. In this paper, we compared the temperature and relative humidity changes for silk fabrics with polyester fabrics and got GM(1,P) relation models respectively between maximum fabric temperature change, maximum relative humidity change at outer still air layer and relative fabric character parameters. Furthermore, by comparing the objective experiments with subjective wear trials, it is found that the amounts of the change rate of fabric temperature and relative humidity at outer still layer are the most important factors which influence clothing comfort in dynamic moisture transfer condition. The more the changes of temperature and R.H., the more the mugginess and the thermal sensation.

ON THE MECHANISM OF TURBULENT COHERENT STRUCTURE (III)──A STATISTICAL AND DYNAMICALMODEL OF COHERENT STRUCTURE AND ITSHEAT TRANSFER MECHANISM

Following Tsai & Ma[1] and Tsai & Liu[2], a statistical and dynamical near-wall turbulent coherent structural model with separate consideration of two different portions:locally generated and upstream-transported large eddies has been established.With this model, heat transfer in a fully developed open channel in the absence of pressure gradient is numerically simulated. Database of fluctuations of velocity and temperature has also been set. Numerical analysis shows the existence of high-low temperature streak caused by near-wall coherent structure and its swing in the lateral direction.Numerical results are in accordance with the computations and experimental results of other researchers.

Study at Two Dimensions of Thermal Transfer through a Fibers Panel Subjected to Climatic Constraints in Dynamic Frequency Regulations Established

From resolution of two-dimensional equation of heat in dynamic frequency regime, we have plotted evolution curves of temperature according to depth of material or in lateral direction. They will allow us to evaluate thermal behavior of towed material. Aim of study is to use fibers as a thermal insulating material by proposing a method for determining effective thermal insulation layer in dynamic frequency regime.

Optimal allocation method of electric/air braking force of high-speed train considering axle load transfer

Reasonable distribution of braking force is a factor for a smooth,safe,and comfortable braking of trains.A dynamic optimal allocation strategy of electric-air braking force is proposed in this paper to solve the problem of the lack of consideration of adhesion difference of train wheelsets in the existing high-speed train electric-air braking force optimal allocation strategies.In this method,the braking strategy gives priority to the use of electric braking force.The force model of a single train in the braking process is analyzed to calculate the change of adhesion between the wheel and rail of each wheelset after axle load transfer,and then the adhesion of the train is estimated in real time.Next,with the goal of maximizing the total adhesion utilization ratio of trailer/motor vehicles,a linear programming distribution function is constructed.The proportional coefficient of adhesion utilization ratio of each train and the application upper limit of braking force in the function is updated according to the change time point of wheelset adhesion.Finally,the braking force is dynamically allocated.The simulation results of Matlab/Simulink show that the proposed algorithm not only uses the different adhesion limits of each trailer to reduce the total amount of braking force undertaken by the motor vehicle,but also considers the adhesion difference of each wheelset.The strategy can effectively reduce the risk and time of motor vehicles during the braking process and improve the stability of the train braking.

Accurate Quantum Dynamics of the Simplest Isomerization System Involving Double-H Transfer

We perform accurate quantum dynamcs calculations on the isomerization of vinylidene-acetylene.Large-scale parallel computations are accomplished by an efficient theoretical scheme developed by our group,in which the basis functions are customized for the double-H transfer process.The A_(1)' and B_(2)'' vinylidene and delocalization states are obtained.The peaks recently observed in the cryo-SEVI spectra are analyzed,and very good agreement for the energy levels is achieved between theory and experiment.The discrepancies of energy levels between our calculations and recent experimental cryo-SEVI spectra are of similar magnitudes to the experimental error bars,or≤30 cm^(-1) excluding those involving the excitation of the CCH_(2) scissor mode.A kind of special state,called the isomerization state,is revealed and reported,which is characterized by large probability densities in both vinylidene and acetylene regions.In addition,several states dominated by vinylidene character are reported for the first time.The present work would contribute to the understanding of the double-H transfer.

Discriminated Dimensional Analysis Versus Classical Dimensional Analysis and Applications to Heat Transfer and Fluid Dynamics

In contrast to classical dimensional analysis, discriminated dimensional analysis assumes that spatial coordinates are dimensionally independent of each other and allows other types of geometrical quantity to be used in the dimensional basis, such as surfaces and angles. As a consequence, discriminated dimensional analysis leads to a lower number of dimensional groups, which makes the solution more precise. Besides, these discriminated groups have a clear physical meaning in terms of force and energy balances. The paper introduces this technique and provides dimensional equations for the main quantities and physical parameters of the heat transfer and fluid flow fields. Two applications are presented to demonstrate the efficiency of this method.

Parametric Study by Dynamic Simulation of the Influence of the Air Infiltration Rate and the Convective Thermal Transfer Coefficient on the Thermal Behavior of Residential Buildings Built with Cut Lateritic Blocks

Sustainable building design in dry tropical areas recommends reducing exposure of buildings to solar radiation and/or designing efficient enclosures with satisfactory thermal inertia.We propose in this paper a study of the influence of the infiltration rate in the building and the coefficient of thermal transfer by convection of the walls, on the thermal comfort using TRNSYS software. All the models carried out were validated by recognized scientific criteria, namely correlation （R） and determination （R2） coefficients on the one hand and NBME and CVRMSE coefficients defined by ASHARE, 2002 on the other hand. The results obtained indicate that the modulation of the air infiltration rate allows the simulations on TRNSYS to be compared to in-situ measurements, with an annual average relative difference of 2.86% on the temperature difference. Furthermore, depending on the parameterization of the heat transfer coefficients by convection of the internal and external walls of walls used in the STD, the average annual difference can be reduced by 1% to 4% between the predictions and the measurements.