To study the curving performance of trains, 1D and 3D dynamic models of trains were built using nu- merical methods. The 1D model was composed of 210 simple wagons, each allowed only longitudinal motion; whereas the 3...To study the curving performance of trains, 1D and 3D dynamic models of trains were built using nu- merical methods. The 1D model was composed of 210 simple wagons, each allowed only longitudinal motion; whereas the 3D model included three complicated wagons for which longitudinal, lateral, and vertical degrees of freedom were considered. Combined with the calculated results from the 1D model under braking conditions, the behavior of draft gears and brake shoes were added to the 3D model. The assessment of the curving performance of trains was focused on making comparisons between idling and braking conditions. The results indicated the following： when a train brakes on a curved track, the wheel-rail lateral force and derailment factor are greater than under idling conditions. Because the yawing movement of the wheelset is limited by brake shoes, the zone of wheel contact along the wheel tread is wider than under idling conditions. Furthermore, as the curvature becomes tighter, the traction ratio shows a nonlinear increasing trend, whether under idling or braking conditions. By increasing the brake shoe pressure, train steering becomes more difficult.展开更多
Satellite constellation configuration design is a complicated and time-consuming simulation optimization problem. In this paper, a new method called the rapid method for satellite constellation performance calculation...Satellite constellation configuration design is a complicated and time-consuming simulation optimization problem. In this paper, a new method called the rapid method for satellite constellation performance calculation is developed by the Hermite interpolation technique to reduce the computing complication and time. The constellation configuration optimization model is established on the basis of the rapid performance calculation. To reduce the search space and enhance the optimization efficiency, this paper presents a new constellation optimization strategy based on the ordinal optimization （00） theory and expands the algorithm realization for constellation optimization including precise and crude models, ordered performance curves, selection rules and selected subsets. Two experiments about navigation constellation and space based surveillance system （SBSS） are carried out and the analysis of simulation results indicates that the ordinal optimization for satellite constellation configuration design is effective.展开更多
Ectotherms generally demonstrate nonlinear changes in performance （e.g., movement speed, indi- vidual growth, population growth） as a function of temperature that are characterized by thermal performance curves （TP...Ectotherms generally demonstrate nonlinear changes in performance （e.g., movement speed, indi- vidual growth, population growth） as a function of temperature that are characterized by thermal performance curves （TPC）. Predation risk elicits phenotypic and behavioral changes that likewise impact performance measures. We tested whether exposure to predation Orthocyclops modestus impacts the maximum population growth rate （rmax） TPC of the protist Paramecium aurelia. We fit predator and non-predator exposed P. aurelia population growth rates to a function previously shown to best describe Paramecium population growth rate TPC＇s （Lactin-2） and compared subse- quent parameter estimates between curves. For Paramecium exposed to predation risk, maximum population growth increased more rapidly as temperatures rose and decreased more rapidly as temperatures fell compared to the initial temperature. The area under each TPC curve remained ap- proximately the same, consistent with the idea of a trade-off in performance across temperatures. Our results indicate TPCs are flexible given variation in food web context and that trophic inter- actions may play an important role in shaping TPCs. Furthermore, this and other studies illustrate the need for a mechanistic model of TPCs with parameters tied to biologically meaningful properties.展开更多
Environmental temperature variation may play a significant role in the adaptive evolutionary divergence of ectotherm thermal performance curves(TPCs).However,divergence in TPCs may also be constrained due to various c...Environmental temperature variation may play a significant role in the adaptive evolutionary divergence of ectotherm thermal performance curves(TPCs).However,divergence in TPCs may also be constrained due to various causes.Here,we measured TPCs for swimming velocity of temperate and tropical mayflies(Family:Baetidae)and their stonefly predators(Family:Perlidae)from different elevations.We predicted that differences in seasonal climatic regimes would drive divergence in TPCs between temperate and tropical species.Stable tropical temperatures should favor the evolution of"specialists"that perform well across a narrow range of temperatures.Seasonally,variable temperatures in temperate zones,however,should favor"generalists"that perform well across a broad range of temperatures.In phylogenetically paired comparisons of mayflies and stoneflies,swimming speed was generally unaffected by experimental temperature and did not differ among populations between latitudes,suggesting a maintenance of performance breadth across elevation and latitude.An exception was found between temperate and tropical mayflies at low elevation where climatic differences between latitudes are large.In addition,TPCs did not differ between mayflies and their stonefly predators,except at tropical low elevation.Our results indicate that divergence in TPCs may be con strai ned in aquatic in sects except under the most differe nt ther・mal regimes,perhaps because of trade-offs that reduce thermal sensitivity and increase performance breadth.展开更多
Mapping potential areas for finfish mariculture,particularly high-yield regions,is crucial for the proper utilization of marine space and global food security.Physiological models(growth performance models)that consid...Mapping potential areas for finfish mariculture,particularly high-yield regions,is crucial for the proper utilization of marine space and global food security.Physiological models(growth performance models)that consider the spatiotemporal heterogeneity of the marine environment are a potentially effective approach to achieving this goal.In the present study,we developed an integrated model that combines the thermal performance curve and spatiotemporal heterogeneity of the marine environment to map the global high-yield potential mariculture areas for 27 commercial finfish species.Our results showed that the current sizes of the potentially suitable areas(achieving 50% of the maximum growth rate for at least six months annually)and high-yield areas(achieving 75% of the maximum growth rate throughout a year)are(8.00±0.30)×10^(6) and(5.96±0.13)×10^(6) km^(2),respectively.Currently,the sizes of suitable and high-yield areas for warm-water mariculture fish are larger than those for other species.The growth potential of suitable mariculture areas is higher at mid and low latitudes than at high latitudes.Under the two shared socioeconomic pathway scenarios(SSP1-2.6 and SSP5-8.5),the sizes of both suitable and high-yield areas will increase by 2050.However,there is the potential for finfish mariculture to respond differently to climate change among species and regions,and cold-water fish may benefit from global warming.Overall,the global potential for suitable high-yield mariculture areas continues to increase,making finfish mariculture an important contributor to global food security.展开更多
In the evaporation crystallization process system (MVR) of salt making and wastewater treatment, due to the narrow working area of the steam compressor, liquid strike, frequent surge, vehicle trip caused by vibration ...In the evaporation crystallization process system (MVR) of salt making and wastewater treatment, due to the narrow working area of the steam compressor, liquid strike, frequent surge, vehicle trip caused by vibration value exceeding the limit and other conditions are easy to occur.展开更多
A central question in efficient wind farm big-data analytics is how to design an algorithm for autonomously extracting performance curves of wind turbines based on data collected via wind farm supervisory control and ...A central question in efficient wind farm big-data analytics is how to design an algorithm for autonomously extracting performance curves of wind turbines based on data collected via wind farm supervisory control and data acquisition(SCADA)systems.This paper investigates this question systematically,focusing on a challenging setting:the end-to-end autonomous analytics for directly generating mathematical functions of wind turbine performance curves from raw SCADA data.We propose a vision generative modeling(VGM)paradigm for autonomous development of wind turbine performance curve models.We discover that,compared with preva-lently discussed numerical fitting-based performance curve modeling(NFM)methods,VGM directly working on raw data without any data preprocessing and model parameter tuning offers more generalizable and accurate results in deriving performance curves as well as their mathematical forms.The success of VGM is achieved by three computational steps developed in this study.By comparing with a set of state-of-the-art NFM benchmarks in multiple performance curve modeling tasks,we observe that VGM consistently performs more advantageously by achieving a 75.1%accuracy improvement in wind power curve modeling with insufficient SCADA data and an 84.3%improvement in modeling the rotor speed curve based on faulty field data.This work presents a milestone in autonomous wind turbine SCADA data analytics,which possesses a great potential of spanning to autonomous analytics of measured data of other industrial systems.展开更多
Ventilation fans are an important component of any mechanically ventilated building.Poor fan performance could significantly affect the whole building performance metrics.There are several issues such as dirty blades,...Ventilation fans are an important component of any mechanically ventilated building.Poor fan performance could significantly affect the whole building performance metrics.There are several issues such as dirty blades,mechanical wear,aging of fans could impact the fan’s performance.In present work,a novel,indirect and data-driven methodology is introduced to monitor the ventilation fan unit performance.The proposed method is able to perform continuous monitoring of ventilation fan unit in real-time.The real-time performance of 3 Air handling unit(AHU)fans is examined in an academic building.Expected fan performance is modeled with the help of manufacturer data and compared against the real-time performance.Two data-driven models are developed and implemented.The first model is used to compute expected total fan pressure at a given airflow rate while second is a Support Vector Regression(SVR)model,to predict the fan efficiency.The performance monitoring of the ventilation fan unit is determined in terms of expected and actual fan energy consumption.Findings indicated a significant performance gap in three ventilation fan unit in a case building known as OU44,located in city Odense,Denmark.The advantage of this method comprises simplicity,no direct human intervention and scalability to the series of ventilation units.展开更多
Experimental research was conducted on the performance curves and the cavity evolution for different flow and geometric parameters in jet pumps for zero flow ratio(ZFR)conditions.New pressure ratio,Pr,flow ratio,qr,we...Experimental research was conducted on the performance curves and the cavity evolution for different flow and geometric parameters in jet pumps for zero flow ratio(ZFR)conditions.New pressure ratio,Pr,flow ratio,qr,were used in place of the conventional performance parameters h,q,to characterize the jet pump flow performance.A super cavitation cavity in the jet pump was observed to fill most of the flow channel,which hindered further increases of the flow rate and increased qr to one,thus,created a critical point on the new P_(r)-q_(r)^(2)curve.Before the critical point,P_(r)was proportional to q_(r)^(2)with a coefficient that was much more sensitive to the area ratio than the relative throat length and the diffusion angle.After the critical point,the flow rate reached its maximum,the limiting flow rate,which only depended on the total inlet pressure and the area ratio.The total inlet pressure was proportional to the square of the limiting flow rate with a flow coefficient that was only a quadratic function of the area ratio.展开更多
More demand-side flexible resources(DFRs)are participating in the frequency regulation of renewable power systems,whose heterogeneous characteristics have a significant impact on the system frequency response.Conseque...More demand-side flexible resources(DFRs)are participating in the frequency regulation of renewable power systems,whose heterogeneous characteristics have a significant impact on the system frequency response.Consequently,selecting suitable DFRs poses a formidable challenge for independent system operators(ISO).In this paper,a reserve allocation methodology for heterogeneous DFRs is proposed to manage the risk of power system frequency.Firstly,a performance curve is developed to describe the cost,capacity,and response speed of DFRs.Moreover,a clustering method for multiple distributed DFRs is conducted to calculate the aggregated performance curves and uncertainty coefficients.Then,the frequency security criterion considering DFRs’performance is constructed,whose linearity makes it can be easily coupled into the system scheduling model and solved.Furthermore,a risk management model for DFRs considering frequency-chance-constraint is proposed to make a trade-off between cost and frequency security.Finally,the model is transformed into mixed integer second-order cone programming(MISOCP)and solved by the commercial solver.The proposed model is validated by the IEEE 30 and IEEE 118 bus systems.展开更多
文摘To study the curving performance of trains, 1D and 3D dynamic models of trains were built using nu- merical methods. The 1D model was composed of 210 simple wagons, each allowed only longitudinal motion; whereas the 3D model included three complicated wagons for which longitudinal, lateral, and vertical degrees of freedom were considered. Combined with the calculated results from the 1D model under braking conditions, the behavior of draft gears and brake shoes were added to the 3D model. The assessment of the curving performance of trains was focused on making comparisons between idling and braking conditions. The results indicated the following： when a train brakes on a curved track, the wheel-rail lateral force and derailment factor are greater than under idling conditions. Because the yawing movement of the wheelset is limited by brake shoes, the zone of wheel contact along the wheel tread is wider than under idling conditions. Furthermore, as the curvature becomes tighter, the traction ratio shows a nonlinear increasing trend, whether under idling or braking conditions. By increasing the brake shoe pressure, train steering becomes more difficult.
文摘Satellite constellation configuration design is a complicated and time-consuming simulation optimization problem. In this paper, a new method called the rapid method for satellite constellation performance calculation is developed by the Hermite interpolation technique to reduce the computing complication and time. The constellation configuration optimization model is established on the basis of the rapid performance calculation. To reduce the search space and enhance the optimization efficiency, this paper presents a new constellation optimization strategy based on the ordinal optimization （00） theory and expands the algorithm realization for constellation optimization including precise and crude models, ordered performance curves, selection rules and selected subsets. Two experiments about navigation constellation and space based surveillance system （SBSS） are carried out and the analysis of simulation results indicates that the ordinal optimization for satellite constellation configuration design is effective.
文摘Ectotherms generally demonstrate nonlinear changes in performance （e.g., movement speed, indi- vidual growth, population growth） as a function of temperature that are characterized by thermal performance curves （TPC）. Predation risk elicits phenotypic and behavioral changes that likewise impact performance measures. We tested whether exposure to predation Orthocyclops modestus impacts the maximum population growth rate （rmax） TPC of the protist Paramecium aurelia. We fit predator and non-predator exposed P. aurelia population growth rates to a function previously shown to best describe Paramecium population growth rate TPC＇s （Lactin-2） and compared subse- quent parameter estimates between curves. For Paramecium exposed to predation risk, maximum population growth increased more rapidly as temperatures rose and decreased more rapidly as temperatures fell compared to the initial temperature. The area under each TPC curve remained ap- proximately the same, consistent with the idea of a trade-off in performance across temperatures. Our results indicate TPCs are flexible given variation in food web context and that trophic inter- actions may play an important role in shaping TPCs. Furthermore, this and other studies illustrate the need for a mechanistic model of TPCs with parameters tied to biologically meaningful properties.
基金National Science Foundation grant nos.DBI-1807694 to A.A.S.and DEB-1046408 to C.K.G.,European Commission's Marie Curie grant no.H2020-MSCA-IF-2018,843094 to J.G.R.,and Colorado State University.
文摘Environmental temperature variation may play a significant role in the adaptive evolutionary divergence of ectotherm thermal performance curves(TPCs).However,divergence in TPCs may also be constrained due to various causes.Here,we measured TPCs for swimming velocity of temperate and tropical mayflies(Family:Baetidae)and their stonefly predators(Family:Perlidae)from different elevations.We predicted that differences in seasonal climatic regimes would drive divergence in TPCs between temperate and tropical species.Stable tropical temperatures should favor the evolution of"specialists"that perform well across a narrow range of temperatures.Seasonally,variable temperatures in temperate zones,however,should favor"generalists"that perform well across a broad range of temperatures.In phylogenetically paired comparisons of mayflies and stoneflies,swimming speed was generally unaffected by experimental temperature and did not differ among populations between latitudes,suggesting a maintenance of performance breadth across elevation and latitude.An exception was found between temperate and tropical mayflies at low elevation where climatic differences between latitudes are large.In addition,TPCs did not differ between mayflies and their stonefly predators,except at tropical low elevation.Our results indicate that divergence in TPCs may be con strai ned in aquatic in sects except under the most differe nt ther・mal regimes,perhaps because of trade-offs that reduce thermal sensitivity and increase performance breadth.
基金supported by the National Natural Science Founda-tion of China(42025604)the Fundamental Research Funds for the Central Universities of the Ocean University of China.
文摘Mapping potential areas for finfish mariculture,particularly high-yield regions,is crucial for the proper utilization of marine space and global food security.Physiological models(growth performance models)that consider the spatiotemporal heterogeneity of the marine environment are a potentially effective approach to achieving this goal.In the present study,we developed an integrated model that combines the thermal performance curve and spatiotemporal heterogeneity of the marine environment to map the global high-yield potential mariculture areas for 27 commercial finfish species.Our results showed that the current sizes of the potentially suitable areas(achieving 50% of the maximum growth rate for at least six months annually)and high-yield areas(achieving 75% of the maximum growth rate throughout a year)are(8.00±0.30)×10^(6) and(5.96±0.13)×10^(6) km^(2),respectively.Currently,the sizes of suitable and high-yield areas for warm-water mariculture fish are larger than those for other species.The growth potential of suitable mariculture areas is higher at mid and low latitudes than at high latitudes.Under the two shared socioeconomic pathway scenarios(SSP1-2.6 and SSP5-8.5),the sizes of both suitable and high-yield areas will increase by 2050.However,there is the potential for finfish mariculture to respond differently to climate change among species and regions,and cold-water fish may benefit from global warming.Overall,the global potential for suitable high-yield mariculture areas continues to increase,making finfish mariculture an important contributor to global food security.
文摘In the evaporation crystallization process system (MVR) of salt making and wastewater treatment, due to the narrow working area of the steam compressor, liquid strike, frequent surge, vehicle trip caused by vibration value exceeding the limit and other conditions are easy to occur.
基金supported in part by the Hong Kong RGC General Research Fund Project under grant 11213124in part by Guangdong Provincial Basic and Applied Basic Research-Offshore Wind Power Joint Fund Project under Grant 2022A1515240066+4 种基金in part by the Hong Kong RGC Collaborative Research Fund Project under grant C1049-24GFin part by the Shenzhen-Hong Kong-Macao Science and Tech-nology Category C Project under grant SGDX20220530111205037in part by the Hong Kong ITC Innovation and Technology Fund Project under grant ITS/034/22MSin part by the National Natural Science Foundation of China under grant 62402384in part by InnoHK initiative,The Government of the HKSAR,and Laboratory for AIPowered Financial Technologies.
文摘A central question in efficient wind farm big-data analytics is how to design an algorithm for autonomously extracting performance curves of wind turbines based on data collected via wind farm supervisory control and data acquisition(SCADA)systems.This paper investigates this question systematically,focusing on a challenging setting:the end-to-end autonomous analytics for directly generating mathematical functions of wind turbine performance curves from raw SCADA data.We propose a vision generative modeling(VGM)paradigm for autonomous development of wind turbine performance curve models.We discover that,compared with preva-lently discussed numerical fitting-based performance curve modeling(NFM)methods,VGM directly working on raw data without any data preprocessing and model parameter tuning offers more generalizable and accurate results in deriving performance curves as well as their mathematical forms.The success of VGM is achieved by three computational steps developed in this study.By comparing with a set of state-of-the-art NFM benchmarks in multiple performance curve modeling tasks,we observe that VGM consistently performs more advantageously by achieving a 75.1%accuracy improvement in wind power curve modeling with insufficient SCADA data and an 84.3%improvement in modeling the rotor speed curve based on faulty field data.This work presents a milestone in autonomous wind turbine SCADA data analytics,which possesses a great potential of spanning to autonomous analytics of measured data of other industrial systems.
文摘Ventilation fans are an important component of any mechanically ventilated building.Poor fan performance could significantly affect the whole building performance metrics.There are several issues such as dirty blades,mechanical wear,aging of fans could impact the fan’s performance.In present work,a novel,indirect and data-driven methodology is introduced to monitor the ventilation fan unit performance.The proposed method is able to perform continuous monitoring of ventilation fan unit in real-time.The real-time performance of 3 Air handling unit(AHU)fans is examined in an academic building.Expected fan performance is modeled with the help of manufacturer data and compared against the real-time performance.Two data-driven models are developed and implemented.The first model is used to compute expected total fan pressure at a given airflow rate while second is a Support Vector Regression(SVR)model,to predict the fan efficiency.The performance monitoring of the ventilation fan unit is determined in terms of expected and actual fan energy consumption.Findings indicated a significant performance gap in three ventilation fan unit in a case building known as OU44,located in city Odense,Denmark.The advantage of this method comprises simplicity,no direct human intervention and scalability to the series of ventilation units.
基金supported by the National Natural Science Foundation of China(Grant Nos.12072243,12102308).
文摘Experimental research was conducted on the performance curves and the cavity evolution for different flow and geometric parameters in jet pumps for zero flow ratio(ZFR)conditions.New pressure ratio,Pr,flow ratio,qr,were used in place of the conventional performance parameters h,q,to characterize the jet pump flow performance.A super cavitation cavity in the jet pump was observed to fill most of the flow channel,which hindered further increases of the flow rate and increased qr to one,thus,created a critical point on the new P_(r)-q_(r)^(2)curve.Before the critical point,P_(r)was proportional to q_(r)^(2)with a coefficient that was much more sensitive to the area ratio than the relative throat length and the diffusion angle.After the critical point,the flow rate reached its maximum,the limiting flow rate,which only depended on the total inlet pressure and the area ratio.The total inlet pressure was proportional to the square of the limiting flow rate with a flow coefficient that was only a quadratic function of the area ratio.
基金supported by the Key Science and Technology Project of China Southern Power Grid Corporation(Grant No.090000KK52220020)。
文摘More demand-side flexible resources(DFRs)are participating in the frequency regulation of renewable power systems,whose heterogeneous characteristics have a significant impact on the system frequency response.Consequently,selecting suitable DFRs poses a formidable challenge for independent system operators(ISO).In this paper,a reserve allocation methodology for heterogeneous DFRs is proposed to manage the risk of power system frequency.Firstly,a performance curve is developed to describe the cost,capacity,and response speed of DFRs.Moreover,a clustering method for multiple distributed DFRs is conducted to calculate the aggregated performance curves and uncertainty coefficients.Then,the frequency security criterion considering DFRs’performance is constructed,whose linearity makes it can be easily coupled into the system scheduling model and solved.Furthermore,a risk management model for DFRs considering frequency-chance-constraint is proposed to make a trade-off between cost and frequency security.Finally,the model is transformed into mixed integer second-order cone programming(MISOCP)and solved by the commercial solver.The proposed model is validated by the IEEE 30 and IEEE 118 bus systems.
