Based on diagnostic analysis of reanalysis data for 58-year,the distribution characteristics of decadal variability in diabatic heating,transient eddy heating and transient eddy vorticity forcing related to the sea su...Based on diagnostic analysis of reanalysis data for 58-year,the distribution characteristics of decadal variability in diabatic heating,transient eddy heating and transient eddy vorticity forcing related to the sea surface temperature(SST)anomalies over the North Pacific,as well as their relationship with anomalous atmospheric circulation have been investigated in this paper.A linear baroclinic model(LBM)was used to investigate atmospheric responses to idealized and realistic heat and vorticity forcing anomalies,and then to compare relative roles of different kinds of forcing in terms of geopotential height responses.The results illustrate that the responses of atmospheric height fields to the mid-latitude heating can be either baroclinic or barotropic.The response structure is sensitive to the relative horizontal location of heating with respect to the background jet flow,as well as to the vertical profile of heating.The response to the idealized deep heating over the eastern North Pacific,mimicking the observed heating anomaly,is baroclinic.The atmospheric response to the mid-latitude vorticity forcing is always barotropic,resulting in a geopotential low that is in phase with the forcing.The atmospheric responses to the realistic heat and vorticity forcing show the similar results,suggesting that diabatic heating,transient eddy heating and transient eddy vorticity forcing can all cause atmospheric anomalies and that the vorticity forcing plays a relatively more important role in maintaining the equivalent-barotropic structure of geopotential height anomalies.展开更多
Differential scanning calorimetry(DSC) is a technique extensively applied to analyse precipitation phenomena in Al-Mg-Si alloys, yet the processes occurring during non-isothermal DSC heating, in particular the formati...Differential scanning calorimetry(DSC) is a technique extensively applied to analyse precipitation phenomena in Al-Mg-Si alloys, yet the processes occurring during non-isothermal DSC heating, in particular the formation of clusters in the early stage and their evolution at higher temperatures, remain obscure. Here, we carry out experiments not only to measure heat(via DSC) but also to measure hardness,positron lifetime, electrical resistivity and microstructure of an Al-Mg-Si alloy heated at 3 different rates.Electrical resistivity is measured in situ, the other properties after interrupting the heating process. It is demonstrated that the precipitation process during heating can be divided into various stages, with transition temperatures depending on the heating rate, but the relative behavior of the various measured quantities is connected in the same way. Quenched-in excess vacancies are found to play an important role in cluster formation at lower temperatures, which explains the seeming peculiarity that linear heating at lower temperatures can lead to stronger clustering than isothermal ageing at a higher temperature.These trends are well simulated using a recently developed precipitation model. New aspects about the evolution of these clusters at higher temperatures are revealed by correlating the different measured properties. The methodology applied here could also be extended to investigating more complex nonisothermal heat treatments.展开更多
This paper proposes non-linear autoregressive models with exogenous inputs to model the air temperature ineach room of a Danish school building connected to the local district heating network. To obtain satisfactorymo...This paper proposes non-linear autoregressive models with exogenous inputs to model the air temperature ineach room of a Danish school building connected to the local district heating network. To obtain satisfactorymodels, the authors find it necessary to estimate the solar radiation effect as a function of the time of the dayusing a B-spline basis expansion. Furthermore, this paper proposes a method for estimating the valve positionof the radiator thermostats in each room using modified Hermite polynomials to ensure monotonicity of theestimated curve. The non-linearities require a modification in the estimation procedure: Some parametersare estimated in an outer optimisation, while the usual regression parameters are estimated in an inneroptimisation. The models are able to simulate the temperature 24 h ahead with a root-mean-square-errorof the predictions between 0.25℃ and 0.6℃. The models seem to capture the solar radiation gain in away aligned with expectations. The estimated thermostatic valve functions also seem to capture the importantvariations of the individual room heat inputs.展开更多
In this paper magnetoconvective heat and mass transfer characteristics of a two-dimensional steady flow of a nanofluid over a non-linear stretching sheet in the presence of thermal radiation,Ohmic heating and viscous ...In this paper magnetoconvective heat and mass transfer characteristics of a two-dimensional steady flow of a nanofluid over a non-linear stretching sheet in the presence of thermal radiation,Ohmic heating and viscous dissipation have been investigated numerically.The model used for the nanofluid incorporates the effects of the Brownian motion and the presence of nanopanicles in the base fluid.The governing equations are transformed into a system of nonlinear oidinary differential equations by using similarity transformation.The numerical solutions are obtained by using fifth order Runge-Kutta-Fehlberg method with shooting technique.The non-dimensional parameters on velocity,temperature and concentration profiles and also on local Nusselt number and Sherwood number are discussed.The results indicate that the local skin friction coefficient decreases as the value of the magnetic parameter increases whereas the Nusselt number and Sherwood number increase as the values of the Brownian motion parameter and magnetic parameter increase.展开更多
1 Scope This standard covers the definition, technical requirement, apparatus, specimen, test procedure, calculation and test report on permanent linear change of shaped insulating refractory products.
In this paper,the Galerkin finite element method(FEM)together with the characteristic-based split(CBS)scheme are applied to study the case of the non-linear Boussinesq approximation within sinusoidal heating inclined ...In this paper,the Galerkin finite element method(FEM)together with the characteristic-based split(CBS)scheme are applied to study the case of the non-linear Boussinesq approximation within sinusoidal heating inclined enclosures filled with a non-Darcy porous media and nanofluids.The enclosure has an inclination angle and its side-walls have varying sinusoidal temperature distributions.The working fluid is a nanofluid that is consisting of water as a based nanofluid and Al2O3 as nanoparticles.The porous medium is modeled using the Brinkman Forchheimer extended Darcy model.The obtained results are analyzed over wide ranges of the non-linear Boussinesq parameter 0≤ζ≤1,the phase deviation 00≤Φ≤1800,the inclination angle 00≤γ≤900,the nanoparticles volume fraction 0%≤φ≤4%,the amplitude ratio 0≤a≤1 and the Rayleigh number 104≤Ra≤106.The results revealed that the average Nusselt number is enhanced by 0.73%,26.46%and 35.42%at Ra=104,105 and 106,respectively,when the non-linearBoussinesq parameter is varied from 0 to 1.In addition,rate of heat transfer in the case of a non-uniformly heating is higher than that of a uniformly heating.Non-linear Boussinesq parameter rises the flow speed and heat transfer in an enclosure.Phase deviation makes clear changes on the isotherms and heat transfer rate on the right wall of an enclosure.An inclination angle varies the flow speed and it has a slight effect on heat transfer in an enclosure.展开更多
冷热电多能联供(combined cooling heating and power,CCHP)型微网具有节能、环保、经济等特点,有良好的发展前景和应用价值。为应对可再生能源的大规模接入及负荷的不确定性,该文提出基于模型预测控制的CCHP型微网动态优化调度策略。...冷热电多能联供(combined cooling heating and power,CCHP)型微网具有节能、环保、经济等特点,有良好的发展前景和应用价值。为应对可再生能源的大规模接入及负荷的不确定性,该文提出基于模型预测控制的CCHP型微网动态优化调度策略。该优化策略首先对设备效率曲线模型进行分段线性化处理,以日前计划联供设备的出力值为参考值,在日内调度下建立可再生能源及负荷预测模型,基于多步滚动优化求解出各联供设备的平滑出力。仿真结果表明:分段线性效率曲线模型不但能更好模拟系统实际运行工况,且计算时间满足在线调度需求;滚动时长选取4h,不仅满足鲁棒性也能满足快速性;所提模型能够有效应对系统不确定性对系统经济调度的影响,实现其经济及安全运行。展开更多
Energy management is facing new challenges due to the increasing supply and demand uncertainties,which is caused by the integration of variable generation resources,inaccurate load forecasts and non-linear efficiency ...Energy management is facing new challenges due to the increasing supply and demand uncertainties,which is caused by the integration of variable generation resources,inaccurate load forecasts and non-linear efficiency curves.To meet these challenges,a robust optimization method incorporating piecewise linear thermal and electrical efficiency curve is proposed to accommodate the uncertainties of cooling,thermal and electrical load,as well as photovoltaic(PV)output power.Case study results demonstrate that the robust optimization model performs better than the deterministic optimization model in terms of the expected operation cost.The fluctuation of net electrical load has greater effect on the dispatching results of the combined cooling,heating and power(CCHP)microgrid than the fluctuation of the cooling and thermal load.The day-ahead schedule is greatly affected by the uncertainty budget of the load demand.The economy of the optimal decision could be achieved by adjusting different uncertainty budget levels according to control the conservatism of the model.展开更多
文摘Based on diagnostic analysis of reanalysis data for 58-year,the distribution characteristics of decadal variability in diabatic heating,transient eddy heating and transient eddy vorticity forcing related to the sea surface temperature(SST)anomalies over the North Pacific,as well as their relationship with anomalous atmospheric circulation have been investigated in this paper.A linear baroclinic model(LBM)was used to investigate atmospheric responses to idealized and realistic heat and vorticity forcing anomalies,and then to compare relative roles of different kinds of forcing in terms of geopotential height responses.The results illustrate that the responses of atmospheric height fields to the mid-latitude heating can be either baroclinic or barotropic.The response structure is sensitive to the relative horizontal location of heating with respect to the background jet flow,as well as to the vertical profile of heating.The response to the idealized deep heating over the eastern North Pacific,mimicking the observed heating anomaly,is baroclinic.The atmospheric response to the mid-latitude vorticity forcing is always barotropic,resulting in a geopotential low that is in phase with the forcing.The atmospheric responses to the realistic heat and vorticity forcing show the similar results,suggesting that diabatic heating,transient eddy heating and transient eddy vorticity forcing can all cause atmospheric anomalies and that the vorticity forcing plays a relatively more important role in maintaining the equivalent-barotropic structure of geopotential height anomalies.
基金supported by the Open Research Fund (No. Kfkt2018-01) of the State Key Laboratory of High Performance Complex Manufacturing at the Central South UniversityNational Natural Science Foundation of China (No. U2032117)。
文摘Differential scanning calorimetry(DSC) is a technique extensively applied to analyse precipitation phenomena in Al-Mg-Si alloys, yet the processes occurring during non-isothermal DSC heating, in particular the formation of clusters in the early stage and their evolution at higher temperatures, remain obscure. Here, we carry out experiments not only to measure heat(via DSC) but also to measure hardness,positron lifetime, electrical resistivity and microstructure of an Al-Mg-Si alloy heated at 3 different rates.Electrical resistivity is measured in situ, the other properties after interrupting the heating process. It is demonstrated that the precipitation process during heating can be divided into various stages, with transition temperatures depending on the heating rate, but the relative behavior of the various measured quantities is connected in the same way. Quenched-in excess vacancies are found to play an important role in cluster formation at lower temperatures, which explains the seeming peculiarity that linear heating at lower temperatures can lead to stronger clustering than isothermal ageing at a higher temperature.These trends are well simulated using a recently developed precipitation model. New aspects about the evolution of these clusters at higher temperatures are revealed by correlating the different measured properties. The methodology applied here could also be extended to investigating more complex nonisothermal heat treatments.
基金funding from the following projectsSustainable plus energy neighbourhoods(syn.ikia)(H2020 No.869918)+3 种基金FMEZEN(Research Council of Norway-257660)Top-up(Innovation Fund Denmark 9045-00017B)SCA+(InterregÖresund-Kattegat-Skagerrak)Flexibile Energy Denmark(FED)(IFD 8090-00069B).
文摘This paper proposes non-linear autoregressive models with exogenous inputs to model the air temperature ineach room of a Danish school building connected to the local district heating network. To obtain satisfactorymodels, the authors find it necessary to estimate the solar radiation effect as a function of the time of the dayusing a B-spline basis expansion. Furthermore, this paper proposes a method for estimating the valve positionof the radiator thermostats in each room using modified Hermite polynomials to ensure monotonicity of theestimated curve. The non-linearities require a modification in the estimation procedure: Some parametersare estimated in an outer optimisation, while the usual regression parameters are estimated in an inneroptimisation. The models are able to simulate the temperature 24 h ahead with a root-mean-square-errorof the predictions between 0.25℃ and 0.6℃. The models seem to capture the solar radiation gain in away aligned with expectations. The estimated thermostatic valve functions also seem to capture the importantvariations of the individual room heat inputs.
文摘In this paper magnetoconvective heat and mass transfer characteristics of a two-dimensional steady flow of a nanofluid over a non-linear stretching sheet in the presence of thermal radiation,Ohmic heating and viscous dissipation have been investigated numerically.The model used for the nanofluid incorporates the effects of the Brownian motion and the presence of nanopanicles in the base fluid.The governing equations are transformed into a system of nonlinear oidinary differential equations by using similarity transformation.The numerical solutions are obtained by using fifth order Runge-Kutta-Fehlberg method with shooting technique.The non-dimensional parameters on velocity,temperature and concentration profiles and also on local Nusselt number and Sherwood number are discussed.The results indicate that the local skin friction coefficient decreases as the value of the magnetic parameter increases whereas the Nusselt number and Sherwood number increase as the values of the Brownian motion parameter and magnetic parameter increase.
文摘1 Scope This standard covers the definition, technical requirement, apparatus, specimen, test procedure, calculation and test report on permanent linear change of shaped insulating refractory products.
基金the Deanship of Scientific Research at King Khalid University for funding this work through research groups program under Grant Number(R.G.P2/72/41).
文摘In this paper,the Galerkin finite element method(FEM)together with the characteristic-based split(CBS)scheme are applied to study the case of the non-linear Boussinesq approximation within sinusoidal heating inclined enclosures filled with a non-Darcy porous media and nanofluids.The enclosure has an inclination angle and its side-walls have varying sinusoidal temperature distributions.The working fluid is a nanofluid that is consisting of water as a based nanofluid and Al2O3 as nanoparticles.The porous medium is modeled using the Brinkman Forchheimer extended Darcy model.The obtained results are analyzed over wide ranges of the non-linear Boussinesq parameter 0≤ζ≤1,the phase deviation 00≤Φ≤1800,the inclination angle 00≤γ≤900,the nanoparticles volume fraction 0%≤φ≤4%,the amplitude ratio 0≤a≤1 and the Rayleigh number 104≤Ra≤106.The results revealed that the average Nusselt number is enhanced by 0.73%,26.46%and 35.42%at Ra=104,105 and 106,respectively,when the non-linearBoussinesq parameter is varied from 0 to 1.In addition,rate of heat transfer in the case of a non-uniformly heating is higher than that of a uniformly heating.Non-linear Boussinesq parameter rises the flow speed and heat transfer in an enclosure.Phase deviation makes clear changes on the isotherms and heat transfer rate on the right wall of an enclosure.An inclination angle varies the flow speed and it has a slight effect on heat transfer in an enclosure.
文摘冷热电多能联供(combined cooling heating and power,CCHP)型微网具有节能、环保、经济等特点,有良好的发展前景和应用价值。为应对可再生能源的大规模接入及负荷的不确定性,该文提出基于模型预测控制的CCHP型微网动态优化调度策略。该优化策略首先对设备效率曲线模型进行分段线性化处理,以日前计划联供设备的出力值为参考值,在日内调度下建立可再生能源及负荷预测模型,基于多步滚动优化求解出各联供设备的平滑出力。仿真结果表明:分段线性效率曲线模型不但能更好模拟系统实际运行工况,且计算时间满足在线调度需求;滚动时长选取4h,不仅满足鲁棒性也能满足快速性;所提模型能够有效应对系统不确定性对系统经济调度的影响,实现其经济及安全运行。
基金supported by the National Science Foundation of China (No.51277027)the National Science and Technology Support Program of China (No.2015BAA01B01)the State Grid Corporation of China (SGTYHT/14-JS-188)
文摘Energy management is facing new challenges due to the increasing supply and demand uncertainties,which is caused by the integration of variable generation resources,inaccurate load forecasts and non-linear efficiency curves.To meet these challenges,a robust optimization method incorporating piecewise linear thermal and electrical efficiency curve is proposed to accommodate the uncertainties of cooling,thermal and electrical load,as well as photovoltaic(PV)output power.Case study results demonstrate that the robust optimization model performs better than the deterministic optimization model in terms of the expected operation cost.The fluctuation of net electrical load has greater effect on the dispatching results of the combined cooling,heating and power(CCHP)microgrid than the fluctuation of the cooling and thermal load.The day-ahead schedule is greatly affected by the uncertainty budget of the load demand.The economy of the optimal decision could be achieved by adjusting different uncertainty budget levels according to control the conservatism of the model.
