An attempt is made to elaborate the definition of the coefficient of strain-rate sensitivity, which is a fundamental concept for macroscopic dynamic plasticity and dislocation dynamics. Since a solid subjected to larg...An attempt is made to elaborate the definition of the coefficient of strain-rate sensitivity, which is a fundamental concept for macroscopic dynamic plasticity and dislocation dynamics. Since a solid subjected to large dynamic loading usually undergoes dynamic response with finite deformation, therefore, the definition of this coefficient is also put forward to the case of large dynamic plastic deformation. The analogy between internal friction increment and overstress due to strain-rate sensitivity is clarified.展开更多
In this paper, the diffraction of water waves by a vertically floating cylinder in a two-layer fluid of a finite depth is studied. Analytical expressions for the hydrodynamic loads on the vertically floating cylinder ...In this paper, the diffraction of water waves by a vertically floating cylinder in a two-layer fluid of a finite depth is studied. Analytical expressions for the hydrodynamic loads on the vertically floating cylinder are obtained by use of the method of eigenfunction expansions. The hydrodynamic loads on the vertically floating cylinder in a two-layer fluid inelude not only the surge, heave and pitch exciting forces due to the incident wave of the surface-wave mode, but also those due to the incident wave of the internal-wave mode. This is different from the case of a homogenous fluid. Some given examples show that, for a two-layer fluid system with a small density difference, the hydrodynamic loads for the surface-wave mode do not differ significantly from those due to surface waves in a single-layer fluid, but the hydrodynamic loads for the internal-wave mode are important over a wide range of frequencies. Moreover, also considered are the free surface and interface elevations generated by the diffraction wave due to the incident wave of the surface-wave and interhal-wave modes, and transfer of energy between modes.展开更多
With the large-scale density stratified tank and the numerical flume proposed,series of numerical cases in line with the experiments are carried out to investigate the interaction between the tension leg platforms(TLP...With the large-scale density stratified tank and the numerical flume proposed,series of numerical cases in line with the experiments are carried out to investigate the interaction between the tension leg platforms(TLPs)and the internal solitary waves(ISWs).The waveforms,and the loads and the torques on the TLP obtained by the experiments and the simulations agree well with each other.Experimental results show that the amplitudes of the dimensionless horizontal force and torque linearly increase with the dimensionless amplitude,while that of the vertical force increases in a parabolic curve.Besides,the numerical results indicate that the horizontal and vertical forces on the TLP due to the ISWs can be divided into three components,namely,the wave pressure-difference forces,the viscous pressure-difference forces,and the frictional force that is negligible.The wave pressure-difference forces are always the major constituents.However the viscous pressure-difference component is unimportant,it is negligible as compared with the vertical forces.展开更多
According to the established prediction model of internal solitary wave loads on FPSO in the previous work,the lumped mass model and the movement equations of finite displacement in time domain,the dynamic response mo...According to the established prediction model of internal solitary wave loads on FPSO in the previous work,the lumped mass model and the movement equations of finite displacement in time domain,the dynamic response model of interaction between internal solitary waves and FPSO with mooring lines were established.Through calculations and analysis,time histories of dynamic loads of FPSO exerted by internal solitary waves,FPSO’s motion and dynamic tension of mooring line were obtained.The effects of the horizontal pretension of mooring line,the amplitude of internal solitary wave and layer fluid depth on dynamic response behavior of FPSO were mastered.It was shown that the internal solitary waves had significant influence on FPSO,such as the large magnitude horizontal drift and a sudden tension increment.With internal solitary wave of −170 m amplitude in the ocean with upper and lower layer fluid depth ratio being 60:550,the dynamic loads reached 991.132 kN(horizontal force),18067.3 kN(vertical force)and−5042.92 kN·m(pitching moment).Maximum of FPSO’s horizontal drift was 117.56 m.Tension increment of upstream mooring line approached 401.48 kN and that of backflow mooring line was−140 kN.Moreover,the loads remained nearly constant with different pretension but increased obviously with the changing amplitude and layer fluid depth ratio.Tension increments of mooring lines also changed little with the pretension but increased rapidly when amplitude and layer fluid depth ratio increased.However,FPSO’s motion increased quickly with not only the horizontal pretension but also the amplitude of internal solitary wave and layer fluid depth ratio.展开更多
Linear regression analysis is one the most common methods for weather-normalizing energy data,where energy versus degree-days is plotted,quantifying the impacts of outside temperature on buildings’energy use.However,...Linear regression analysis is one the most common methods for weather-normalizing energy data,where energy versus degree-days is plotted,quantifying the impacts of outside temperature on buildings’energy use.However,this approach solely con-siders dry-bulb temperature,while other climate variables are ignored.In addition,depending on buildings’internal loads,weather impact can be less influential,making the linear regression method not applicable for energy data normalization in inter-nally driven buildings(such as research laboratory buildings,healthcare facilities,etc.).In this study,several existing buildings from different categories,all located on the University of Massachusetts Amherst campus and exposed to the same weather conditions in a heating-dominated climate,were analyzed.For all cases,regression of monthly steam use on heating degree-days and floor-area normalized steam data were used,investigating applicability of the former when the latter changes.It was found that internal loads can skew steam consumption,depending on the build-ing functionality,making the effect of degree-days negligible.For laboratory-type buildings,besides heating and domestic hot water production,steam is also used for scientific experiments.Here,daily occupancy percentage,even during weekends and holidays,was higher than that of other buildings,indicating the intensity of scientific experiments performed.This significantly impacted steam consumption,resulting in higher floor-area-normalized steam usage.In these cases,steam use did not provide an outstanding correlation to heating degree-days.Whereas,for cases with other func-tionality-types and lower floor-area normalized steam,coefficients of determination in regressions were high.This study concludes that even for buildings located in the same climate,depending on how building functionality and occupancy schedule influ-ence floor-area normalized steam use,multivariate linear regression can provide more accurate analysis,rather than simple linear regression of steam on 展开更多
This study aimed to evaluate the external and internal fluxes of nutrients of an urban eutrophic reservoir （lbirit6 reservoir, SE-Brazil）. External loads were estimated in the tributaries （Pintados and Ibirit6 cre...This study aimed to evaluate the external and internal fluxes of nutrients of an urban eutrophic reservoir （lbirit6 reservoir, SE-Brazil）. External loads were estimated in the tributaries （Pintados and Ibirit6 creeks） through nutrient concentrations and discharge measurements. Using Fick＇s law, internal loads were estimated in the reservoir from fluxes across sediment-water interface from nutrient concentration gradients between the pore water and the water. The Ibirit6 creek （urban sewage recipient） contributes with 72%-47% of ammonium （NH4^＋） and 100%-8% of SRP （soluble reactive phosphorus） of the total quantity entering the reservoir, whereas the Pintados creek （oil refinery effluent recipient） contributions are 20%-19% and 44%-100%, respectively. Despite the high external loads （130 and 2.2 ton-yr^-1 of NH4＋ and SRP, respectively）, internal loads （average flux of 120 and 2 mg·cm^-2yr^-1, respectively） correspond to 25% of the total external loads which may sustain a high productivity in the reservoir for a long time even if the external loads are controlled. The stocks of ammonium and SRP of the interstitial water （100 cm of sediment） would be released to the water in six years and five months, respectively, The release time would be extremely larger （〉 3,000 years） considering the stocks of total N and bioavailable P.展开更多
A stress-strength structural reliability model was proposed with a stochastic strength aging deterioration process. In structural engineering,the deterioration of structure's strength should be the total of the de...A stress-strength structural reliability model was proposed with a stochastic strength aging deterioration process. In structural engineering,the deterioration of structure's strength should be the total of the deterioration owing to continual wear, fatigue,corrosion,etc.,and the abrupt deterioration as a result of randomly variable loads. The deterioration of structure's strength should be influenced by both the internal deterioration owing to direct wear and the external deterioration due to randomly variable loads.Meanwhile,the load process was given as Poisson square wave process. The reliability was derived using stress-strength interference theory. In particular,the reliability was also given when random variables followed the normal distribution.展开更多
基金the NSFC(No.10072068 and No.1992820)the National "973"Program
文摘An attempt is made to elaborate the definition of the coefficient of strain-rate sensitivity, which is a fundamental concept for macroscopic dynamic plasticity and dislocation dynamics. Since a solid subjected to large dynamic loading usually undergoes dynamic response with finite deformation, therefore, the definition of this coefficient is also put forward to the case of large dynamic plastic deformation. The analogy between internal friction increment and overstress due to strain-rate sensitivity is clarified.
基金This project was financially supported by the National Natural Science Foundation of China(Grant No.10572092)the High Technology Research and Development Programof China(863Program,Grant Nos.2006AA09Z352 and 2006AA09196-6)
文摘In this paper, the diffraction of water waves by a vertically floating cylinder in a two-layer fluid of a finite depth is studied. Analytical expressions for the hydrodynamic loads on the vertically floating cylinder are obtained by use of the method of eigenfunction expansions. The hydrodynamic loads on the vertically floating cylinder in a two-layer fluid inelude not only the surge, heave and pitch exciting forces due to the incident wave of the surface-wave mode, but also those due to the incident wave of the internal-wave mode. This is different from the case of a homogenous fluid. Some given examples show that, for a two-layer fluid system with a small density difference, the hydrodynamic loads for the surface-wave mode do not differ significantly from those due to surface waves in a single-layer fluid, but the hydrodynamic loads for the internal-wave mode are important over a wide range of frequencies. Moreover, also considered are the free surface and interface elevations generated by the diffraction wave due to the incident wave of the surface-wave and interhal-wave modes, and transfer of energy between modes.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFC1404202)the National Natural Science Foundation of China(Grant Nos.11972352,11572332)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDB22040203,XDA22000000).
文摘With the large-scale density stratified tank and the numerical flume proposed,series of numerical cases in line with the experiments are carried out to investigate the interaction between the tension leg platforms(TLPs)and the internal solitary waves(ISWs).The waveforms,and the loads and the torques on the TLP obtained by the experiments and the simulations agree well with each other.Experimental results show that the amplitudes of the dimensionless horizontal force and torque linearly increase with the dimensionless amplitude,while that of the vertical force increases in a parabolic curve.Besides,the numerical results indicate that the horizontal and vertical forces on the TLP due to the ISWs can be divided into three components,namely,the wave pressure-difference forces,the viscous pressure-difference forces,and the frictional force that is negligible.The wave pressure-difference forces are always the major constituents.However the viscous pressure-difference component is unimportant,it is negligible as compared with the vertical forces.
基金supported by JUST start-up fund for science research,the Jiangsu Natural Science Foundation(Grant No.BK20210885).
文摘According to the established prediction model of internal solitary wave loads on FPSO in the previous work,the lumped mass model and the movement equations of finite displacement in time domain,the dynamic response model of interaction between internal solitary waves and FPSO with mooring lines were established.Through calculations and analysis,time histories of dynamic loads of FPSO exerted by internal solitary waves,FPSO’s motion and dynamic tension of mooring line were obtained.The effects of the horizontal pretension of mooring line,the amplitude of internal solitary wave and layer fluid depth on dynamic response behavior of FPSO were mastered.It was shown that the internal solitary waves had significant influence on FPSO,such as the large magnitude horizontal drift and a sudden tension increment.With internal solitary wave of −170 m amplitude in the ocean with upper and lower layer fluid depth ratio being 60:550,the dynamic loads reached 991.132 kN(horizontal force),18067.3 kN(vertical force)and−5042.92 kN·m(pitching moment).Maximum of FPSO’s horizontal drift was 117.56 m.Tension increment of upstream mooring line approached 401.48 kN and that of backflow mooring line was−140 kN.Moreover,the loads remained nearly constant with different pretension but increased obviously with the changing amplitude and layer fluid depth ratio.Tension increments of mooring lines also changed little with the pretension but increased rapidly when amplitude and layer fluid depth ratio increased.However,FPSO’s motion increased quickly with not only the horizontal pretension but also the amplitude of internal solitary wave and layer fluid depth ratio.
文摘Linear regression analysis is one the most common methods for weather-normalizing energy data,where energy versus degree-days is plotted,quantifying the impacts of outside temperature on buildings’energy use.However,this approach solely con-siders dry-bulb temperature,while other climate variables are ignored.In addition,depending on buildings’internal loads,weather impact can be less influential,making the linear regression method not applicable for energy data normalization in inter-nally driven buildings(such as research laboratory buildings,healthcare facilities,etc.).In this study,several existing buildings from different categories,all located on the University of Massachusetts Amherst campus and exposed to the same weather conditions in a heating-dominated climate,were analyzed.For all cases,regression of monthly steam use on heating degree-days and floor-area normalized steam data were used,investigating applicability of the former when the latter changes.It was found that internal loads can skew steam consumption,depending on the build-ing functionality,making the effect of degree-days negligible.For laboratory-type buildings,besides heating and domestic hot water production,steam is also used for scientific experiments.Here,daily occupancy percentage,even during weekends and holidays,was higher than that of other buildings,indicating the intensity of scientific experiments performed.This significantly impacted steam consumption,resulting in higher floor-area-normalized steam usage.In these cases,steam use did not provide an outstanding correlation to heating degree-days.Whereas,for cases with other func-tionality-types and lower floor-area normalized steam,coefficients of determination in regressions were high.This study concludes that even for buildings located in the same climate,depending on how building functionality and occupancy schedule influ-ence floor-area normalized steam use,multivariate linear regression can provide more accurate analysis,rather than simple linear regression of steam on
文摘This study aimed to evaluate the external and internal fluxes of nutrients of an urban eutrophic reservoir （lbirit6 reservoir, SE-Brazil）. External loads were estimated in the tributaries （Pintados and Ibirit6 creeks） through nutrient concentrations and discharge measurements. Using Fick＇s law, internal loads were estimated in the reservoir from fluxes across sediment-water interface from nutrient concentration gradients between the pore water and the water. The Ibirit6 creek （urban sewage recipient） contributes with 72%-47% of ammonium （NH4^＋） and 100%-8% of SRP （soluble reactive phosphorus） of the total quantity entering the reservoir, whereas the Pintados creek （oil refinery effluent recipient） contributions are 20%-19% and 44%-100%, respectively. Despite the high external loads （130 and 2.2 ton-yr^-1 of NH4＋ and SRP, respectively）, internal loads （average flux of 120 and 2 mg·cm^-2yr^-1, respectively） correspond to 25% of the total external loads which may sustain a high productivity in the reservoir for a long time even if the external loads are controlled. The stocks of ammonium and SRP of the interstitial water （100 cm of sediment） would be released to the water in six years and five months, respectively, The release time would be extremely larger （〉 3,000 years） considering the stocks of total N and bioavailable P.
基金Natural Science Foundation Project of Fujian Province,China(No.2013J01004)
文摘A stress-strength structural reliability model was proposed with a stochastic strength aging deterioration process. In structural engineering,the deterioration of structure's strength should be the total of the deterioration owing to continual wear, fatigue,corrosion,etc.,and the abrupt deterioration as a result of randomly variable loads. The deterioration of structure's strength should be influenced by both the internal deterioration owing to direct wear and the external deterioration due to randomly variable loads.Meanwhile,the load process was given as Poisson square wave process. The reliability was derived using stress-strength interference theory. In particular,the reliability was also given when random variables followed the normal distribution.
