To improve the resilience of a distribution system against extreme weather,a fuel-based distributed generator(DG)allocation model is proposed in this study.In this model,the DGs are placed at the planning stage.When a...To improve the resilience of a distribution system against extreme weather,a fuel-based distributed generator(DG)allocation model is proposed in this study.In this model,the DGs are placed at the planning stage.When an extreme event occurs,the controllable generators form temporary microgrids(MGs)to restore the load maximally.Simultaneously,a demand response program(DRP)mitigates the imbalance between the power supply and demand during extreme events.To cope with the fault uncertainty,a robust optimization(RO)method is applied to reduce the long-term investment and short-term operation costs.The optimization is formulated as a tri-level defenderattacker-defender(DAD)framework.At the first level,decision-makers work out the DG allocation scheme;at the second level,the attacker finds the optimal attack strategy with maximum damage;and at the third level,restoration measures,namely distribution network reconfiguration(DNR)and demand response are performed.The problem is solved by the nested column and constraint generation(NC&CG)method and the model is validated using an IEEE 33-node system.Case studies validate the effectiveness and superiority of the proposed model according to the enhanced resilience and reduced cost.展开更多
The strain hardening is an effective mode of enhancing mechanical properties in alloys.In this work,the strain hardening behaviors of Mg-xY(x=1,2,and 3 wt%)after extrusion process was investigated using uniaxial tensi...The strain hardening is an effective mode of enhancing mechanical properties in alloys.In this work,the strain hardening behaviors of Mg-xY(x=1,2,and 3 wt%)after extrusion process was investigated using uniaxial tensile tests.Results suggest that the Mg-xY alloys are composed ofα-Mg with a little amount of Mg24Y5 phase.The average grain size reduces from 19.8μm to 12.2μm as the Y content adds from 1 wt%to 2 wt%.Nevertheless,when Y content reaches 3 wt%,the grain size reaches to 12.9μm,which is close to that of Mg-2Y.The strain hardening rate decreases from 883 MPa to 798 MPa at(σ-σ0.2)=40 MPa,and Mg-2Y and Mg-3Y have the similar strain hardening response.Moreover,Mg-1Y shows an obvious ascending stage after the steep decreasing stage,which is mainly caused by the activation of twinning.The strain hardening behavior of Mg-xY is explained based on understanding the roles of the deformation mechanisms via deformation microstructure analysis and Visco-Plastic Self Consistent(VPSC)model.The variation of strain hardening characteristics with increasing Y content is related to the effects of grain size and texture.展开更多
A microcosm system that included river sediment,water and different zeolite capping materials(natural zeolite,surfactant-modified zeolite(SMZ),or aluminum modified zeolite(AMZ))was designed to study the effect of capp...A microcosm system that included river sediment,water and different zeolite capping materials(natural zeolite,surfactant-modified zeolite(SMZ),or aluminum modified zeolite(AMZ))was designed to study the effect of capping on the release of phosphorus and three organic pollutants(phenol,pyridine,and pyrene)from the sediment to the overlying water over the course of three month.For the same amount of the three capping materials,the efficiency of phosphorus inactivation was in the order of SMZ>AMZ>natural zeolite.The inactivation of phosphorus was mainly caused by the covering effect,co-precipitation and adsorption by the capping materials.The different zeolites gave different results for the release of phenol,pyridine,and pyrene from the sediment.When natural zeolite was used as the capping material,there was no effect on the release of pyrene and pyridine,whereas capping the sediment with SMZ or AMZ inhibited the release of pyrene and pyridine but to different extents.However,for controlling the release of phenol from the sediment,aluminum modified zeolite was the most efficient material,whereas no effects were observed when natural zeolite or SMZ were used.The different capabilities of the zeolite materials for controlling the release of different organic pollutants are related to the differences in the electrical properties of these pollutants.展开更多
The influence of Al alloying on the microstructures and the mechanical properties of Mg–x Al–1 Sn–0.3 Mn alloy sheets was investigated. The microstructure of Mg– x Al–1 Sn–0.3 Mn consisted of α-Mg and Mg 17 Al ...The influence of Al alloying on the microstructures and the mechanical properties of Mg–x Al–1 Sn–0.3 Mn alloy sheets was investigated. The microstructure of Mg– x Al–1 Sn–0.3 Mn consisted of α-Mg and Mg 17 Al 12 precipitates. Alloying with Al increased the amount of Mg17Al12 and the average grain size. Uniaxial tensile tests were carried out along the extrusion direction(ED), the transverse direction(TD) and 45° toward the ED. Mg–5 Al–1 Sn–0.3 Mn alloy sheet exhibited the best combination of mechanical properties along the ED: a yield strength of 142 MPa, an ultimate tensile strength of 282 MPa and an elongation of 23%. The good performance of Mg–5 Al–1 Sn–0.3 Mn sheet was mainly attributed to the large quantity of Mg17Al12 precipitates and a weak basal texture. Annealing caused static dynamic recrystallization, refined the grain size and enhanced the mechanical properties: yield strength of 186 MPa, ultimate tensile strength of 304 MPa, elongation of 21% along ED. Both strength and ductility were enhanced by Al alloying.展开更多
The collusion among various generating units has been a problematic issue affecting the fairness and transparency of electricity markets.Therefore,it is of great significance to assess the potential of such collusion ...The collusion among various generating units has been a problematic issue affecting the fairness and transparency of electricity markets.Therefore,it is of great significance to assess the potential of such collusion in the electricity market.However,the previous assessment studies primarily focused on the bidding behaviors of collusive generating units,without considering the influences of generation flexibility,such as ramp rates.In this paper,a novel assessment method is proposed to evaluate the collusion potential in the electricity market considering generation flexibility.First,a bi-level optimization model is developed to simulate the collusive strategies of dif-ferent generating units,including the withholding of generation capacities and ramp rates,as well as the uplifting of minimum outputs and bidding prices.In the upper-level problem,collusive generating units optimize their offering strategies to optimize the generation profits without violating the regulatory laws.The lower-level problem is a day-ahead economic dispatch model which minimizes the dispatching costs.Based on the optimal collusive strategies determined by the bi-level model,a framework is then proposed to assess the collusion potential in electricity markets.Moreover,price-based and profit-based indices are proposed to quantitatively evaluate the collusion potential of different generating units.Finally,the proposed assessment method is validated on a modified IEEE 39-node system.The numerical results demonstrated that generation flexibility can be exploited collusively for making excessive profits,particularly during load peaks and valleys.Index Terms-Collusionpotential,economic cdispatch,generation flexibility,ramp rates,strategic withholding.展开更多
The influence of Zn on the strain hardening of as-extruded Mg-x Zn(x = 1, 2, 3 and 4 wt%) magnesium alloys was investigated using uniaxial tensile tests at 10^(-3)s^(-1) at room temperature. The strain hardening rate,...The influence of Zn on the strain hardening of as-extruded Mg-x Zn(x = 1, 2, 3 and 4 wt%) magnesium alloys was investigated using uniaxial tensile tests at 10^(-3)s^(-1) at room temperature. The strain hardening rate,the strain hardening exponent and the hardening capacity were obtained from true plastic stress-strain curves. There were almost no second phases in the as-extruded Mg-Zn magnesium alloys. Average grain sizes of the four as-extruded alloys were about 17.8 μm. With increasing Zn content from 1 to 4 wt%, the strain hardening rate increased from 2850 MPa to 6810 MPa at(б-б_(0.2)) = 60 MPa, the strain hardening exponent n increased from 0.160 to 0.203, and the hardening capacity, Hc increased from 1.17 to 2.34.The difference in strain hardening response of these Mg-Zn alloys might be mainly caused by weaker basal texture and more solute atoms in the α-Mg matrix with higher Zn content.展开更多
A new kind of Mg–2 Zn–0.6 Ca(wt%) alloy was fabricated by casting and hot extrusion as a high-ductility structural material. The extruded alloy exhibits a superior elongation of ～30%, yield strength of 130 MPa and ...A new kind of Mg–2 Zn–0.6 Ca(wt%) alloy was fabricated by casting and hot extrusion as a high-ductility structural material. The extruded alloy exhibits a superior elongation of ～30%, yield strength of 130 MPa and ultimate tensile strength of 280 MPa along the extrusion direction at room temperature. Microstructure, texture and tensile properties of the extruded alloy were investigated in details. The remarkable improvement of ductility is ascribed to the weakened basal texture, refined grains and a small number of second phase in the alloy.展开更多
Due to the lack of in-depth understanding about the folding issues of the electronic materials,it is a huge challenge to pre-pare a super-foldable and highly electrochemical faradic electrode.Here,inspired from from t...Due to the lack of in-depth understanding about the folding issues of the electronic materials,it is a huge challenge to pre-pare a super-foldable and highly electrochemical faradic electrode.Here,inspired from from the fully nimble structures of cuit cocoons and cockscomb petals,with two-level biomimetic design,for the first time we prepared a super-foldable and electrochemically functional freestanding cathode,made of C-fiber@NiS-cockscomb(SFCNi).In virtue of its nimble biomi-metic structures,SFCNi can remarkably sustain over 100,000 times,repeated true-folding without composite fibers fracture,functional matters detachment,conductivity degradation,or electrochemical performance change.The main mechanism behind these behaviors was disclosed by Real-time scanning electron microscopy and mechanical simulations,on the folding process.Results unveil that the cockscomb-like NiS with atomic thickness can deform freely due to the need of bending,and the cuit-cocoon-like SFCNi can generate an“ε-shape”folding structure at the crease.Such a smart self-adaptive deforma-tion capability can effectively reduce the effect of stresses and local excessive deformations,so that the chemical bonds can preserve their interaction,and the material won’t fracture.This subtle and exceptional mechanical behavior realizes a super-foldable property.The two-level biomimetic design strategy is a novel method for fabrication of super-foldable composite electrodes and integrated multi-functional super-foldable devices.展开更多
基金supported by the Technology Project of State Grid Jiangsu Electric Power Co.,Ltd.,China (J2022160,Research on Key Technologies of Distributed Power Dispatching Control for Resilience Improvement of Distribution Networks).
文摘To improve the resilience of a distribution system against extreme weather,a fuel-based distributed generator(DG)allocation model is proposed in this study.In this model,the DGs are placed at the planning stage.When an extreme event occurs,the controllable generators form temporary microgrids(MGs)to restore the load maximally.Simultaneously,a demand response program(DRP)mitigates the imbalance between the power supply and demand during extreme events.To cope with the fault uncertainty,a robust optimization(RO)method is applied to reduce the long-term investment and short-term operation costs.The optimization is formulated as a tri-level defenderattacker-defender(DAD)framework.At the first level,decision-makers work out the DG allocation scheme;at the second level,the attacker finds the optimal attack strategy with maximum damage;and at the third level,restoration measures,namely distribution network reconfiguration(DNR)and demand response are performed.The problem is solved by the nested column and constraint generation(NC&CG)method and the model is validated using an IEEE 33-node system.Case studies validate the effectiveness and superiority of the proposed model according to the enhanced resilience and reduced cost.
基金The authors thank the National Key R&D Program of China(2016YFB0301100)National Natural Science Foundation of China(51571043)+1 种基金Graduate Research and Innovation Foundation of Chongqing,China(Grant No.CYB18004)Fundamental Research Funds for the Central Universities(Nos.2018CDJDCL0019,cqu2018CDHB1A08 and 2018CDGFCL0005).
文摘The strain hardening is an effective mode of enhancing mechanical properties in alloys.In this work,the strain hardening behaviors of Mg-xY(x=1,2,and 3 wt%)after extrusion process was investigated using uniaxial tensile tests.Results suggest that the Mg-xY alloys are composed ofα-Mg with a little amount of Mg24Y5 phase.The average grain size reduces from 19.8μm to 12.2μm as the Y content adds from 1 wt%to 2 wt%.Nevertheless,when Y content reaches 3 wt%,the grain size reaches to 12.9μm,which is close to that of Mg-2Y.The strain hardening rate decreases from 883 MPa to 798 MPa at(σ-σ0.2)=40 MPa,and Mg-2Y and Mg-3Y have the similar strain hardening response.Moreover,Mg-1Y shows an obvious ascending stage after the steep decreasing stage,which is mainly caused by the activation of twinning.The strain hardening behavior of Mg-xY is explained based on understanding the roles of the deformation mechanisms via deformation microstructure analysis and Visco-Plastic Self Consistent(VPSC)model.The variation of strain hardening characteristics with increasing Y content is related to the effects of grain size and texture.
基金supported by the National Natural Science Foundation of China(Grant Nos.20677031,20737002).
文摘A microcosm system that included river sediment,water and different zeolite capping materials(natural zeolite,surfactant-modified zeolite(SMZ),or aluminum modified zeolite(AMZ))was designed to study the effect of capping on the release of phosphorus and three organic pollutants(phenol,pyridine,and pyrene)from the sediment to the overlying water over the course of three month.For the same amount of the three capping materials,the efficiency of phosphorus inactivation was in the order of SMZ>AMZ>natural zeolite.The inactivation of phosphorus was mainly caused by the covering effect,co-precipitation and adsorption by the capping materials.The different zeolites gave different results for the release of phenol,pyridine,and pyrene from the sediment.When natural zeolite was used as the capping material,there was no effect on the release of pyrene and pyridine,whereas capping the sediment with SMZ or AMZ inhibited the release of pyrene and pyridine but to different extents.However,for controlling the release of phenol from the sediment,aluminum modified zeolite was the most efficient material,whereas no effects were observed when natural zeolite or SMZ were used.The different capabilities of the zeolite materials for controlling the release of different organic pollutants are related to the differences in the electrical properties of these pollutants.
基金the National Key R&D Program of China(No.2016YFB0301100)the National Natural Science Foundation of China(No.51571043)the Graduate Scientific Research and Innovation Foundation of Chongqing,China(Grant No.CYB18004)。
文摘The influence of Al alloying on the microstructures and the mechanical properties of Mg–x Al–1 Sn–0.3 Mn alloy sheets was investigated. The microstructure of Mg– x Al–1 Sn–0.3 Mn consisted of α-Mg and Mg 17 Al 12 precipitates. Alloying with Al increased the amount of Mg17Al12 and the average grain size. Uniaxial tensile tests were carried out along the extrusion direction(ED), the transverse direction(TD) and 45° toward the ED. Mg–5 Al–1 Sn–0.3 Mn alloy sheet exhibited the best combination of mechanical properties along the ED: a yield strength of 142 MPa, an ultimate tensile strength of 282 MPa and an elongation of 23%. The good performance of Mg–5 Al–1 Sn–0.3 Mn sheet was mainly attributed to the large quantity of Mg17Al12 precipitates and a weak basal texture. Annealing caused static dynamic recrystallization, refined the grain size and enhanced the mechanical properties: yield strength of 186 MPa, ultimate tensile strength of 304 MPa, elongation of 21% along ED. Both strength and ductility were enhanced by Al alloying.
基金supported in part by the Science and Technology Project of SGCC Technical report on multi-objective global optimal allocation model and strategy research of power trading in the new era under Grant No.SGZJ0000KXJS1900181.
文摘The collusion among various generating units has been a problematic issue affecting the fairness and transparency of electricity markets.Therefore,it is of great significance to assess the potential of such collusion in the electricity market.However,the previous assessment studies primarily focused on the bidding behaviors of collusive generating units,without considering the influences of generation flexibility,such as ramp rates.In this paper,a novel assessment method is proposed to evaluate the collusion potential in the electricity market considering generation flexibility.First,a bi-level optimization model is developed to simulate the collusive strategies of dif-ferent generating units,including the withholding of generation capacities and ramp rates,as well as the uplifting of minimum outputs and bidding prices.In the upper-level problem,collusive generating units optimize their offering strategies to optimize the generation profits without violating the regulatory laws.The lower-level problem is a day-ahead economic dispatch model which minimizes the dispatching costs.Based on the optimal collusive strategies determined by the bi-level model,a framework is then proposed to assess the collusion potential in electricity markets.Moreover,price-based and profit-based indices are proposed to quantitatively evaluate the collusion potential of different generating units.Finally,the proposed assessment method is validated on a modified IEEE 39-node system.The numerical results demonstrated that generation flexibility can be exploited collusively for making excessive profits,particularly during load peaks and valleys.Index Terms-Collusionpotential,economic cdispatch,generation flexibility,ramp rates,strategic withholding.
基金financially supported by the National Key R&D Program of China(No.2016YFB0301100)the National Natural Science Foundation of China(Nos.51571043 and 51531002)the Fundamental Research Funds for the Central Universities(Nos.2018CDJDCL0019 and cqu2018CDHB1A08)
文摘The influence of Zn on the strain hardening of as-extruded Mg-x Zn(x = 1, 2, 3 and 4 wt%) magnesium alloys was investigated using uniaxial tensile tests at 10^(-3)s^(-1) at room temperature. The strain hardening rate,the strain hardening exponent and the hardening capacity were obtained from true plastic stress-strain curves. There were almost no second phases in the as-extruded Mg-Zn magnesium alloys. Average grain sizes of the four as-extruded alloys were about 17.8 μm. With increasing Zn content from 1 to 4 wt%, the strain hardening rate increased from 2850 MPa to 6810 MPa at(б-б_(0.2)) = 60 MPa, the strain hardening exponent n increased from 0.160 to 0.203, and the hardening capacity, Hc increased from 1.17 to 2.34.The difference in strain hardening response of these Mg-Zn alloys might be mainly caused by weaker basal texture and more solute atoms in the α-Mg matrix with higher Zn content.
基金financially supported by the National Key R&D Program of China (No. 2016YFB0301100)the National Natural Science Foundation of China (Nos. 51571043 and 51531002)
文摘A new kind of Mg–2 Zn–0.6 Ca(wt%) alloy was fabricated by casting and hot extrusion as a high-ductility structural material. The extruded alloy exhibits a superior elongation of ～30%, yield strength of 130 MPa and ultimate tensile strength of 280 MPa along the extrusion direction at room temperature. Microstructure, texture and tensile properties of the extruded alloy were investigated in details. The remarkable improvement of ductility is ascribed to the weakened basal texture, refined grains and a small number of second phase in the alloy.
基金We appreciate the financial support of the National Natural Science Foundation of China(No.22176145,51771138)the Fundamental Research Funds for the Central Universities(22120210137)the State Key Laboratory of Fine Chemicals,Dalian University of Technology(KF 2001).
文摘Due to the lack of in-depth understanding about the folding issues of the electronic materials,it is a huge challenge to pre-pare a super-foldable and highly electrochemical faradic electrode.Here,inspired from from the fully nimble structures of cuit cocoons and cockscomb petals,with two-level biomimetic design,for the first time we prepared a super-foldable and electrochemically functional freestanding cathode,made of C-fiber@NiS-cockscomb(SFCNi).In virtue of its nimble biomi-metic structures,SFCNi can remarkably sustain over 100,000 times,repeated true-folding without composite fibers fracture,functional matters detachment,conductivity degradation,or electrochemical performance change.The main mechanism behind these behaviors was disclosed by Real-time scanning electron microscopy and mechanical simulations,on the folding process.Results unveil that the cockscomb-like NiS with atomic thickness can deform freely due to the need of bending,and the cuit-cocoon-like SFCNi can generate an“ε-shape”folding structure at the crease.Such a smart self-adaptive deforma-tion capability can effectively reduce the effect of stresses and local excessive deformations,so that the chemical bonds can preserve their interaction,and the material won’t fracture.This subtle and exceptional mechanical behavior realizes a super-foldable property.The two-level biomimetic design strategy is a novel method for fabrication of super-foldable composite electrodes and integrated multi-functional super-foldable devices.
