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Solute effects on high-entropy alloys of equiatomic proportions are scientifically intriguing because there is no such well-defined “solute” and “solvent” atoms compared to those of conventional single principal element alloys. To date, most of the face-centered cubic alloys exhibit solid solution strengthening rather than softening due to the interactions between dislocations and solute atoms. Here, we present the careful experimental measurements and demonstrate solid solution softening, albeit weak, in a single phase CoCrFeMnNi through the minor addition of 2. at.% Al. This softening effect is mostly related to the decreased Peierl's stress by Al addition.

The 2xxx series Al alloys have been widely used in aerospace industry owing to their high strength, good plasticity and superior formability. To ensure a good control of shape, the quenched alloy sheets require a small pre-deformation before artificial aging. However, this pre-deformation considerably deteriorates the mechanical strength of the Al–3.0Cu–1.8Mg–0.5Si (wt%) alloys due to the formation of unfavorable large-sized precipitates at dislocations. To tackle this issue, we designed a pre-aging process prior to the pre-deformation. The thermal–mechanical treatment, involving pre-aging, pre-deformation and subsequent aging, markedly enhanced the ultimate tensile strength up to 521 MPa compared to that (448 MPa) of the alloy without pre-aging. Microstructure characterization revealed that the fine precipitates (~ 2 nm) with a uniform dispersion were promoted within the Al matrix, which in turn partly suppressed the formation of the unfavorable large-sized precipitate (~ 100 nm). Our findings provide a new clue for designing stronger Al alloys with age-hardenability.

We investigated the influence of Ti addition on the coercivity and microstructure of Ga-doped R-Fe-B (R = Nd + Pr) based sintered magnets. Detailed microstructure observations of the 0.5 at.%Ti-doped sample with the highest coercivity of 2.38 T revealed a near-complete grain isolation through the formation of thick (0.5–1.0 μm) grain boundary (GB) phases such as the R6(Fe,Ga)14 and the double hexagonal close-packed (DHCP) Nd. This suggests that these GB phases are non-ferromagnetic and decouple intergrain exchange. The formation of the R6(Fe,Ga)14 phase is found to be triggered by the formation of hexagonal TiB2 at high temperatures, which leads to a B-lean composition of GB phases that fall into a narrow compositional region, in which the R6(Fe,Ga)14 forms during post-sinter annealing at intermediate temperatures. Despite the high coercivity, the interface between the R6(Fe,Ga)14 and R2Fe14B phases in the post-sinter annealed 0.5 at.%Ti sample exhibits zig-zag morphology which is expected to deteriorate the coercivity with local demagnetizing field. Thus, further efforts to improve interfacial roughness should lead to further improve coercivity.

The use of retired batteries from electric vehicles as a second-life battery energy storage system has been recognized as a way to break the high investment cost limitation of battery energy storage systems with the associated cost reduction of a park-level integrated energy system. The battery degradation and replacements should be further considered in the planning period, especially compared with new battery energy storage systems. Additionally, there is a lack of discussion on utilizing thermal energy storage systems in coordination with second-life battery to reduce degradation. For this reason, an electric/thermal hybrid energy storage system planning method for park-level integrated energy systems with second-life battery utilization is proposed. A cumulative battery life loss calculation model is developed. A bi-level optimal planning model of electric/thermal hybrid energy storage system using second-life batteries, including an upper-level planning model and a lower-level operating model, is proposed. At the upper level, to maximize the net present value during the planning stage, the capacity of the hybrid energy storage system as well as when the second-life battery energy storage system needs to be replaced are optimized. At the lower level, the operation schemes are optimized to obtain the minimum annual operating cost, which are fed back to the upper level. The proposed method considers continuous capacity degradation of second-life batteries and mutually beneficial relationships between thermal energy storage and second-life batteries. Finally, a case study demonstrates the economic effectiveness and battery service life improvement of the proposed planning method.

The flexibility of energy systems in industrial plants will play an important role in helping bulk energy systems to deal with the various challenges brought by the net-zero carbon transition. The emerging digital twins, which have attracted rapidly increasing interests with some industrial applications, have the potential to facilitate the flexibility service provision from industrial energy systems. This potential is identified in this paper by matching the key features of digital twins and key issues and needs of providing flexibility services from industrial energy systems. The study presented in this paper preliminarily frames this new research area, with potential aspects and directions identified for future research.

The iron and steel industry discharges large quantities of wastewater. The environmental impact of the wastewater is traditionally assessed from the quantitative aspect. However, the water quality of discharged wastewater plays a more significant role in damaging the natural environment. Moreover, comprehensive assessment of multi-pollutants in wastewater from both quality and quantity is still a gap. In this work, a total environmental impact score (TEIS) is defined to assess the environmental impact of wastewater discharge, by considering the volume of wastewater and the quality of main processes. To implement the comprehensively qualitative and quantitative assessment, a field monitoring and measurement of wastewater discharge volume and the quality is conducted to acquire pH, suspend solids (SS), chemical oxygen demand (COD), total nitrogen (TN), total iron (TFe), and hexavalent chromium (Cr(VI)). The sequence of TEIS values is obtained as steelmaking > ironmaking > sintering > hot rolling > coking > cold rolling and TN > COD > SS > pH > Cr(VI) > TFe. The TEIS of the investigated steel plant is 26.27. The leading process lies in steelmaking with a TEIS of 19.98. The dominant pollutant is TN with a TEIS of 15.00. Finally, a sensitivity analysis is performed to validate the feasibility and generalisability of the TEIS.

We report a detailed analysis of microstructure, magnetic and transport properties of a stoichiometric Mn 2 CoAl Heusler alloy, which has been predicted to be a spin-gapless semiconductor (SGS). Microstructure analysis revealed that the main phase was Mn 1.8 Co 1.4 Al 0.8 rather than Mn 2 CoAl; this stable compound remained even for a Co-rich composition. Along with the Mn 1.8 Co 1.4 Al 0.8 phase, a disk-shaped Mn-rich precipitate phase was observed in both annealed stoichiometric and Co-rich Mn 2 CoAl alloys. Atomically resolved energy-dispersive X-ray spectroscopy mappings revealed that the Mn 1.8 Co 1.4 Al 0.8 phase has a disordered inverse XA Heusler structure with Mn (A) and Al (C) sites partially substituted by Co and Mn, respectively. First-principles calculations based on the observed disordered structure suggest that the Heusler phase is not SGS but half-metallic. However, both annealed stoichiometric and Co-rich Mn 2 CoAl exhibit semiconducting-like resistivity and low anomalous Hall conductivity. These transport properties were regarded as the signatures of SGS in the previous studies; however, it could be due to localization of charged carriers due to the intersection of the Fermi level with Mn 3 d and Co 3 d states in Mn 1.8 Co 1.4 Al 0.8 . This study demonstrates that not only measurements of transport properties but also careful microstructure inspections are essential to validate SGS properties in the theoretically predicted SGS candidates among Heusler compounds.

Community integrated energy system (CIES) couples multiple energy forms and links, it is important to cope with the inadequacy of flexibility for realizing efficient utilization and reliable supply. Based on the detailed modeling of central energy station, district heating network (DHN) and building loads, a unified scheduling model is established by fully considering the coupling characteristics of the sources, the networks, and the loads. Meanwhile, the flexibilities from adjustable capacity of thermal storage device and the indoor temperature on the demand side, as well as the energy storage of DHN, are utilized to improve the economy. Furthermore, a model predictive control (MPC) based robust scheduling strategy is proposed to maintain and utilize CIES flexibility for enhancing the uncertainty adaptability. The scheduling framework consists of rolling optimization and robust constraint generation. The rolling optimization schedules the system with a better adaptation to flexibility demands, and the robust constraints generate adjustable margin for building demands by modifying the upper/lower and ramping limits. After the linearization of nonlinear terms in the model, case studies are conducted based on the data of a typical day in summer. The results show that the unified source-network-load scheduling strategy can give full play to the flexibilities of different energy links with a better operation economy. Additionally, the MPC-based optimization can well adapt to the rolling forecasting uncertainties, and the schedule generated by advance reserving means has stronger robustness for real-time errors.

The anisotropy field of the ThMn12-type Sm(Fe0.8Co0.2)12 compound is high. However, there is an absence of reports on sufficiently high coercivity for anisotropic permanent magnet application. In this study, we employed the grain boundary diffusion process to anisotropic Sm(Fe0.8Co0.2)12 thin films. As-grown (001)-textured nanocrystalline film exhibit a coercivity of only 0.4 T. However, the grain boundary diffusion process via a Cu-Ga capping layer increases coercivity to 0.8 T. The coercivity exhibits relatively low temperature dependence when compared to that of Nd-Fe-B magnets.

Large and reliable volumes of water are required to cool thermal power plants. Yet across the world growing demands from society, environmental regulation and climate change impacts are reducing the availability of reliable water supplies. This in turn constrains the capacity and locations of thermal power plants that can be developed. The authors present an integrated and spatially explicit energy systems model that explores optimal capacity expansion planning strategies, taking into account electricity and gas transmission infrastructure and cooling water constraints under climate change. In Great Britain, given the current availability of freshwater, it is estimated that around 32 GW of combined cycle gas turbine capacity can be sustainably and reliably supported by freshwater. However, to maintain the same reliability under a medium climate change scenario, this is halved to 16 GW. The authors also reveal that the current benefit of available freshwater to the power sector is ∼£50 billion between 2010 and 2050. Adapting to expected climate change impacts on the reduced reliability of freshwater resources could add an additional £18–19 billion in system costs to the low-carbon energy transition over the time horizon, as more expensive cooling technologies and locations are required.

We have fabricated a hot-deformed magnet from the Fe77.1Nd11.6Pr3.7B5.1Cu0.1Co1.0Al0.9Ga0.5 alloy composition that was developed for exchange-decoupled sintered magnet. The hot-deformed magnet showed a higher coercivity, μ0Hc = 1.93 T, and better squareness, Hk90/Hc = 0.96, compared to those of the sintered magnet, μ0Hc = 1.48 T and Hk90/Hc = 0.65. Microstructural analyses revealed the higher coercivity in the hot-deformed magnet originates from a larger contribution from the anisotropy term in the Kronmuller formula owing to fine grains, while the better squareness is primarily due to the exchange coupling of the Nd2Fe14B grains through ferromagnetic grain boundary phase, as suggested by atom probe tomography and magneto-optical Kerr effect microscopy.

With the broad application of dry dedusting of blast furnace gas (BFG), the issue of BFG pipeline corrosion comes up because of chlorine in the BFG. Existing methods in preventing the corrosion, such as spraying alkali or installing corrosion-resistant materials, require a significant amount of investment. This paper conducted a novel thermal analysis of the corrosion mechanism to support the study on corrosion prevention without using additional materials. Firstly, thermal models were established to reflect the relationships among the amount of condensation water, the mass transfer rate, the concentration of chloride ion and the ambient temperature. Secondly, the relationship between BFG temperature and the corrosion rate was obtained via a cyclic exposure experiment. Key factors that affect the pipeline corrosion under various BFG temperatures were identified. Finally, a control scheme of the BFG temperature was proposed to avoid the chlorine corrosion.

A single-phase Al0.1CoCrFeNi high-entropy alloy (HEA) with face-centered cubic structure was subjected to cryo-rolling at the liquid N2 temperature and subsequent annealing. Microstructural characterization of post-annealed samples by electron backscattered diffraction and transmission electron microscopy revealed that, the dominant grain boundaries (GBs) are of Σ3 type low energy twin boundaries owing to the low stacking fault energy of the HEA. The resulting ultrafine-grained single-phase HEA with abundant Σ3 twin boundaries shows a high strength above 1.0 GPa and a tensile strain larger than 20%. The quantitative analysis on the grain size dependence of strength suggests that a high lattice friction stress and a high GB strengthening via low energy Σ3 twin boundaries are two major contributions for the excellent strength-ductility balance of the ultra-fine grained HEA.

Controlling the B diffusion in CoFeB-MgO based magnetic tunnel junctions (MTJs) is important to realize the large tunneling magnetoresistance (TMR) ratio, which is required to realize high density magnetic random access memories (MRAMs). Here we investigate the detailed microstructure of the MgO-CoFeB MTJs having W underlayer and overlayer in comparison with well-studied MTJs with Ta underlayer and overlayer. Detailed microstructure analysis based on transmission electron microscopy and electron energy loss spectroscopy revealed that B diffused into Ta under-/overlayers and crystallization of CoFeB to CoFe efficiently occurred upon annealing at 300 °C and 400 °C in MTJs with Ta underlayers. In contrast, B diffused into the [001] tilt grain boundaries of MgO barrier in the case of MTJs with W under-/overlayers. These structural differences well explain the difference in post annealing temperature dependence of TMR ratio and resistance area product (RA) of MTJs with Ta and W under-/overlayers.

The operation of community integrated energy systems (CIESs) is challenging because it is necessary to couple energy production, conversion and consumption on the end-user side. Multiple energy demands need to be fed simultaneously with the goal of economy and reliability. This paper formulates the optimal scheduling problem based on a real community integrated energy system in China. The system has multiple chillers (i.e. three ground source heat pumps, two conventional water-cooled chillers and two double-duty chillers) and two types of thermal storage devices (i.e. two cold water tanks and an ice-storage tank). Based on detailed device modeling, a community integrated energy system operation strategy considering unit commitment is proposed, and then is transformed into a mixed-integer linear programming model by linearization of nonlinear items. Case studies are conducted based on the data for a typical day in summer. The results show that the proposed strategy can utilize the flexibility of the energy storage devices and realize an economic and reliable operation of the community integrated energy system by coordinating various energy devices. The strategy can also reduce the startup/shutdown frequency of chillers significantly.

Magnetic properties of amorphous and nanocrystalline Fe85.2−xCoxSi0.5B9.5P4Cu0.8 (x = 0, 4, 10, 15, 20, 25, 35, 40, 50 and 57 at%) alloys have been investigated and their detailed structural parameters have been quantitatively investigated by X-ray diffraction, transmission electron microscopy (TEM), small angle X-ray scattering (SAXS) and three dimensional atom probe (3DAP). The nanocrystalline structure that forms by annealing the melt-spun amorphous ribbon at above 400 °C comprises a bcc phase and a residual amorphous phase. Both coercivity and magnetostriction of the nanocrystalline state increase with increasing Co content, from Hc = 4 A m−1 to 29 A m−1 and from λs = 14 ppm–55 ppm, respectively. The saturation polarization Js reaches a maximum of about 1.88 T at a Co-content of about 25 at%. The dependence of magnetic properties on the Co content can be explained by the composite rule of the intrinsic magnetic properties of the constituent phases. We also found the grain size dependence of coercivity to change from the well-known D6 dependence to D3-dependence in the composition range where the magnetocrystalline anisotropy constant vanishes.

In order to meet the required heat supply of each household, save energy, as well as avoid wasting excessive heat, it is necessary to accurately predict the thermal load (TL) in a community. In this paper, we focus on cross-floor prediction over a week for three thermal users located on different floors. Three machine learning methods including Back Propagation Neural Network (BPNN), Extreme Learning Machine (ELM), and Support Vector Machines (SVM) are applied for indoor temperature (Tin) and thermal load prediction. The experimental results show that Extreme Learning Machine outperforms the other two methods in terms of thermal load prediction.

This paper investigates the feasibility of using buildings with heat pumps to support the integration of electric vehicles in electricity distribution networks. Behaviors of buildings with electric vehicles and heat pumps are modelled at a community scale. Based on the model, the on-off state of heat pumps along with buildings are characterized and coordinated with the charging behavior of electric vehicles from two aspects, namely coordination in a single house and coordination of multiple houses at a community scale. A community with 96 houses is used to test the performance of different coordination schemes. The results demonstrate that the new loads from electric vehicle charging would affect the electricity distribution network significantly, while coordination between houses could help mitigate this adverse impact Although the coordination requires new investment in updating IT infrastructure to support the coordination, it is worth to compare it with the cost for reinforcing distribution networks for electric vehicle integration.

This paper studies the protection of digital products under the internet environment. The research object is the website security problem of providing digital products. We try to combine digital watermark and intrusion detection to protect web site and digital products. The first consideration is the security of digital products. Through the use of digital watermarking technology, the digital products provided by the website are added with digital watermark to protect the copyright. The second consideration is the security of digital product websites. we try to realize the security of the website by constructing the intrusion detection system of the website. Through the establishment of a two-tier unified system security architecture, we can better realize the security protection of digital products on the website.

District heating systems (DHS) that generate/consume electricity are increasingly used to provide flexibility to power grids. The quantification of flexibility from a DHS is challenging due to its complex thermal dynamics and time-delay effects. This article proposes a three-stage methodology to quantify the maximum flexibility of a DHS. The DHS is firstly decomposed into multiple parallel subsystems with simpler topological structures. The maximum flexibility of each subsystem is then formulated as an optimal control problem with time delays in state variables. Finally, the available flexibility from the original DHS is estimated by aggregating the flexibility of all subsystems. Numerical results reveal that a DHS with longer pipelines has more flexibility but using this flexibility may lead to extra actions in equipment such as the opening position adjustment of valves, in order to restore the DHS to normal states after providing flexibility. Impacts of the supply temperature of the heat producer, the heat loss coefficient of buildings and the ambient temperature on the available flexibility were quantified.

Dirac-like electrons in Bi-Sb alloys are extremely effective in generating spin current and have large spin current mobility., We have studied the charge to spin conversion in Bi1−xSbx/CoFeB heterostructures. The spin Hall conductivity (SHC) of the sputter-deposited heterostructures exhibits a high plateau at Bi-rich compositions, corresponding to the topological insulator phase, followed by a decrease of SHC for Sb-richer alloys, in agreement with the calculated intrinsic spin Hall effect of Bi1−xSbx. The SHC increases with increasing Bi1−xSbx thickness before it saturates, indicating that it is the bulk of the alloy that predominantly contributes to the generation of spin current; the topological surface states, if present, play little role. Unexpectedly, the SHC is found to increase with increasing temperature, following the trend of carrier density. These results suggest that the large SHC at room temperature, with a spin Hall efficiency exceeding 1 and an extremely large spin current mobility, is due to increased number of thermally excited Dirac-like electrons in the L valley of the narrow gap Bi1−xSbx alloy.

This chapter provides an overview of the characteristics of main renewable sources for electrical power generation. First, three forms of renewable sources for electric power generation (wind, solar, and tidal) are reviewed to show their intermittent characteristics. Second, the challenge resulting from high penetration of variable renewable power generation is discussed. Flexibility in the power grid is thus required for balancing electricity supply and demand. Third, the integration of solid oxide fuel cells (SOFCs) with renewable power generation technologies is investigated to show how SOFCs could support the transition to a low-carbon power system. SOFCs have the potential to contribute to achieving a low-carbon power system. This contribution is mainly implemented via two ways: (1) to generate electricity using renewable gases such as hydrogen or biogas and (2) to provide flexibility to the power grid such as through ancillary services. This flexibility is able to facilitate the large-scale integration of renewable power generation technologies in power systems. SOFCs can also play a role as backup generation for local energy systems. The synergies among different energy vectors through coupling components are also discussed. Specifically, the following aspects should be further investigated: – Spatial-temporal modeling tools are required to analyze the interactions and interdependencies among different energy systems and to study the impact of cascading failures affecting the reliability of energy supply. – Assessment methodologies and evaluation criteria are required to quantify the technoeconomic performance of energy system integration.

Due to the increasing use of intermittent renewable generation, the power grid requires more flexible resources to balance supply and demand of electricity. Steam systems with turbine-generators, which are widely used in industries, can be operated flexibly to support the power grid. Yet, the available amount of flexibility of industrial steam systems is still not clearly quantified. This study presents the method to quantify electricity generation flexibility of a typical industrial steam system with a steam turbine-generator and process heat demands. The proposed method is introduced based on a real case of an integrated pulp and paper mill in Austria. An integrated mathematical model representing the combined electricity and steam system is developed to simulate the behaviour of the on-site energy system to quantify the potential flexibility provision. Flexibility is represented as the maximum upward and downward changes in the imported electricity from the public power grid. The results demonstrate that it is possible to aggregate the flexibility of the industrial facility as a lookup table. Also, the results reflect key factors that limit the flexibility at different operating points of the turbine-generator.

We investigated the microstructure of the Dy-free high coercivity sintered magnet that was developed by optimizing the chemical composition of Nd-Fe-B sintered magnet with 0.1 at.%Ga doping in order to understand the reasons for the high coercivity of μ0Hc = 2.0 T and the improved squareness of 0.95 compared to a recently developed 0.5 at. %Ga doped magnet. The as-sintered 0.1Ga sample shows a relatively high coercivity of 1.5 T owing to the finer grain size of ∼3.3 μm and the higher Al concentration up to 1.3 at.% compared to post-sinter annealed 0.5Ga magnet that has a grain size of ∼5.5 μm and Al concentration of 0.9 at. %. The post-sinter annealing leads to a substantial coercivity increase from 1.5 to 2.0 T due to the formation of a thick and crystalline intergranular grain boundary (GB) phase containing 30-60 at.% of Nd. The trace Ga addition of 0.1 at.% improved the wettability of the liquids and facilitated the formation of thick GB phase during the post-sinter annealing. The good squareness is mainly attributed to the ferromagnetic nature of the intergranular GB phase as well as the strong crystal alignment to the easy axis. Finite element micromagnetic simulations of the demagnetization processes of the models incorporating experimentally determined GB thickness and chemistry well explain the simultaneous achievement of the high coercivity and good squareness observed in this magnet in contrast to the very poor squareness observed in the post-sinter annealed 0.5Ga sample.

This paper compares the strategies for improving the operational flexibility of combined heat and power (CHP) plants to support wind power integration. Four commonly used strategies, namely cutting off low pressure cylinder, installing heat accumulator, installing electric boiler, and utilizing by-pass device are discussed. An integrated model is proposed to quantify the performance of various strategies in improving the flexibility of CHP plants. A 350 MW subcritical extraction condensing turbine in China is used as an example, to compare the performance of the four strategies from the viewpoint of the operating cost of flexibility enhancement. The maximum flexibility and the scope of applicability can be enhanced.

During the heating period in Northeast China, the electricity generated by Combined Heat and Power (CHP) plants has caused a large amount of wind power curtailment. To avoid this curtailment, Heat Storages (HS) and Electric Boilers (EB) are being widely applied to CHP plants. However, the effectiveness of HS and EB on the curtailment of wind power has still not been well evaluated. This paper proposes a new evaluation method consisting of an operation boundary model and an internal coordinated operation model for each flexible CHP plant with HS and EB. Then a system power balance model based on hour-by-hour analysis is established to determine the wind power integration, down-regulation subsidy and the utilization degree of the flexible equipment. The models are validated by using field measured data of a province in China. The results show that the capacity change of the EB has a bigger impact on the down-regulation subsidy than that of the HS, while the EB is more effective when the level of wind power integration is high.

Microstructures of Ga-doped ultra-fine-grained (UFG) Nd-Fe-B magnets processed from press-less sintering of He-jet-milled powder and hydrogenation-disproportionation-desorption-recombination (HDDR) powder have been investigated to understand the large coercivity difference in the two magnets with nearly the same grain size. While the sintered magnet processed from the jet-milled powder showed a very high coercivity of 2.14 T, the sintered magnet made from HDDR powder showed a low coercivity of only 1.31 T regardless of the similar grain size. Microstructure observations by scanning electron microscopy (SEM) and scanning transmission electron microscope (STEM) combined with energy-dispersive X-ray (EDS) analysis revealed that the Nd-rich grain boundary (GB) phase in the magnet produced from HDDR powder exhibits thickness of 1–2 nm with large variations in their chemical compositions, while the Nd-rich GB phase in the magnet made from He-jet-milled powder displays larger thickness variations (1–7 nm) along with significant increase of nonferromagnetic elements (Nd, Pr, Cu, Ga) in the GB phase after optimal annealing. The possible reasons for these differences in GB phases are discussed based on quantitative microstructure characterization results.

In order to determine the optimal day-ahead scheduling schemes of the integrated community energy system (ICES), a two-stage multi-objective scheduling method (TMSM) was proposed, which consists of a multi-objective optimal power flow (MOPF) calculation stage and a multiple attributes decision making (MADM) stage. Firstly, the electric distribution network, the natural gas network and the energy centers (ECs) of the ICES were modelled. Secondly, five typical indices are considered to characterize the operation of ICES, namely the operation cost (OC) and total emission (TE) of ICES, the power loss (PL) and sum of voltage deviation (SVD) of electric distribution network, the sum of pressure deviation (SPD) of natural gas network. In order to tackle the computation problems resulted by the increasing number of objectives, the dimension reduction of objectives is employed. The indices of OC and TE are selected based on the analytic hierarchy process (AHP) method and set as the objectives at the MOPF calculation stage. Thirdly, all the five indices are considered during the MADM stage to determine the final day-ahead scheduling schemes from the alternative solutions obtained in MOPF. Numerical studies demonstrate that the TMSM is able to provide flexibility for the operation of ICES. The determined optimum day-ahead scheduling schemes are capable of satisfying and balancing operational needs in aspects of security, economy and environmental friendliness.

Structural characterization of dislocations and dislocation reactions in a face-centered cubic high entropy alloy was conducted using the state-of-the-art spherical aberration corrected transmission electron microscopy. We experimentally measured the stacking fault energy of the high entropy alloy from the atomic images and diffraction contrast of dislocation cores. The low stacking fault energy results in widely dissociated dislocations and extensive dislocation reactions, which leads to the formation of immobile Lomer and Lomer-Cottrell dislocation locks. These dislocation locks act as both dislocation barriers and sources and are responsible for the significant work hardening with a large hardening rate in the alloy. Based on the atomic-scale characterization and classical dislocation theory, a simple equation was derived to describe the work hardening behavior of the high entropy alloy in the early-stage of plastic deformation.

Various disturbances do exist in the image taking process of scanning transmission electron microscopes (STEM), which seriously reduces the resolution and accuracy of STEM images. In this paper, a deep understanding of the scanning distortion influence on the real and reciprocal spaces of STEM images is achieved via theoretical modeling and simulation. A scanning distortion correction algorithm is further developed based on two images scanned along perpendicular directions, which is able to effectively correct scanning distortion induced deviations and significantly increase the signal to noise ratio of STEM images.

We studied the origin of the enhancement of current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) effect by inserting a thin amorphous CoFeBTa (CFBT) underlayer below a Co2(Mn0.6Fe0.4)Ge (CMFG) Heusler alloy ferromagnetic (FM) layer. Large magnetoresistance ratio of ∼25% and resistance change-area product of ∼7.5 mΩ μm2 were obtained at room temperature by inserting a CFBT (1.2 nm) underlayer. X-ray diffraction (XRD) and transmission electron microscope analyses confirmed that the CMFG FM layer deposited on the CFBT underlayer was amorphous in the as-deposited state and crystallized to a B2-ordered polycrystalline film by annealing at 300 °C. The degree of B2 order (SB2) of the CMFG films was estimated by anomalous XRD using x-ray energies around the Co K-absorption edge. SB2 of the CMFG film deposited on the amorphous CFBT (1.2 nm) underlayer was ∼0.76, much larger than that of the CMFG film deposited on a crystalline CoFe underlayer (SB2 ∼0.47). First-principles calculations indicated that the spin polarization of the sp-conduction electrons in CMFG increases with increasing SB2, which accounts for the enhanced CPP-GMR effect in the pseudo spin-valve by inserting an amorphous CFBT underlayer.

To transform the original centralized scheduling framework of integrated community energy systems (ICES), a decentralized scheduling method is proposed for the optimal operation of ICES. Firstly, linearized mathematical models of the electric distribution system and natural gas distribution system are established to eliminate the nonconvexity and nonlinearity of the multi-energy systems. Meanwhile, an improved energy hub model is proposed by introducing the state variable, which is able to obtain the optimal solution with better accuracy and higher efficiency. Secondly, a decentralized scheduling framework is developed via an improved consensus-based alternating direction method of multipliers (ADMM). By introducing several coupling links as consensus variables, the optimal operation of the ICES is decoupled according to the physical interactions among each sub-system, in which the original model can be solved parallelly in a decentralized manner. Only the consensus variables are exchanged among sub-systems so that the privacy and confidential items of each sub-system operated by different entities can be ensured. Finally, two different ICES test cases with different system scales are utilized to demonstrate the effectiveness of the proposed method, which is able to provide scheduling scheme same as the centralized method. Dynamic step size modification is further considered in the consensus-based ADMM. By updating the step size during each iteration, the computation expense of optimization process is reduced with less consuming time, iteration and apparent oscillation, by which the convergence performance of ADMM is improved with higher computation efficiency.

The multicomponent eutectic alloys (MCEAs) have demonstrated great potential applications in industrial fields owing to their excellent castability during solidification. The cast MCEAs can achieve a good strength-ductility synergy. However, they usually suffer from mechanical failure at surface due to high surface residual stress resulting from direct solidification. Here we introduce a surface treatment technique through electromagnetic induction heating (EMIH), by which the stress level at surface (−24 MPa) was significantly reduced compared to that of the base MCEA (+573 MPa) with a chemical composition of AlCrFe2(Ni0.85Co0.15)2. This EMIH treatment not only mitigates surface residual stress but also enhances tensile ductility by 30 % without sacrificing its yield strength. In contrast, surface gradient structure synthesized by surface mechanical grinding treatment (SMGT) exhibited a dual-phase nanostructure, together with a compressive residual stress that is an order of magnitude higher than that of the EMIH-processed MCEA. The SMGT-processed MCEA showed marginal improvement in its tensile ductility because of limited work hardening ability resulting from limited dislocation sources at surface. Our study envisages an approach to process MCEAs by surface treatment with relatively a low cost.

Improving the computational efficiency of reliability assessment is a long-term goal for researchers. Regarding this issue, an impact-increment-based decoupled reliability assessment approach (IID) is proposed in this study. First, a new formulation of reliability indices is derived by decoupling the reliability index of composite systems into two parts: generation adequacy and transmission reliability. Then, an impact-increment-based state enumeration reliability assessment method is implemented to both the parts, which are more efficient than tradition methods. Thereafter, a reduction technique for the higher-order contingency states is developed for the transmission reliability evaluation. With this technique, the number of analysed contingencies can be significantly reduced, which improves the computational speed significantly. Finally, the overall framework of the proposed IID approach is demonstrated. Case studies are performed on the RTS-79, RTS-96 and a provincial system of China. Results indicate that the proposed method has superior performance to the traditional reliability assessment methods in terms of accuracy and computational speed, particularly on large-scale composite systems.

Refractory high-entropy alloys are promising high-temperature materials owing to their excellent softening resistance. However, most RHEAs that can withstand softening at 1200 °C usually suffer from apparent brittleness at room temperature. Here, a high strength-ductile matching Re0.5MoNbW(TaC)0.8 eutectic high-entropy composite (HEC) consisting of body-centered-cubic and multi-component carbide phases was fabricated by arc melting. The HEC exhibits a high yield strength (1340 MPa), ultimate compressive strength (2347 MPa) and plasticity (8.90 %), which exceeds those of previously reported RHEAs and HECs. Quantitative calculations based on experimental observations suggest that semi-coherent phase interface plays an essential role for strength enhancement, and interfacial dependent strengthening dominates among the interface strengthening terms. Our study envisages a strategy to design strong and ductile HECs aiming at high-temperature applications.

Compressor stations play a crucial role in natural gas networks to maintain required pressure levels for transporting gas. Centrifugal compressors commonly used in high pressure gas transmission networks could be driven by gas turbines or electric motors. Including compressor units powered via different fuels in a compressor station allows switching between fuels required by compressors to achieve a set outlet pressure and flow throughput. In this paper, an optimisation model of gas network was developed considering reasonably detailed representation of a compressor station to investigate flexibility provision from the compressor station to the power system. The model was formulated as a mixed integer linear programming (MILP) problem by linearising the nonlinear equations governing gas flow along pipes and compressor power consumption. The model was tested on the gas transmission system in South Wales, UK. The operation of compressors was optimised in response to gas and electricity price subject to meeting operational limits of the gas network. The results showed that the compressors can provide flexibility to the power system through shifting their electricity energy consumption in time or switching between gas- and electric-driven compressor units. It was found that the allowable range for variation of linepack plays a key role in the magnitude and duration of flexibility provision from compressor units.

In Northern China, coal-fired power plants play a key role in electricity and heat generation, significantly intensifying air pollution. Meanwhile, a large percentage of wind power is curtailed every year owing to its conflict with heat supplies during the winter period, leading to a huge amount of energy waste. The flexibility of district heating systems has the potential to solve this problem and has attracted considerable attention from electric power system operators, thermal power plant owners, and policy makers. In this paper, a comprehensive survey on the potential of district heating systems in accommodating fluctuating heat supply and demand is proposed. The work first provides an overview of district heating systems in Northern China and how to quantify the flexibility of district heating systems. Next, the flexibility requirements and enhancement strategies of the district heating systems in northern China are thoroughly reviewed. The survey indicates that there is still great potential for the development of a flexible heating system. Moreover, state-of-the-art topics are addressed, including the challenges to be overcome and the status quo of clean heating provision, wind curtailment mitigation, and industrial waste heat utilization. Finally, this paper discusses future directions for deploying the flexibility of district heating systems in northern China, including new heat sources, digitalization, demand-side management, heat market deregulation, and energy policy reform.

We report transmission electron microscope characterization of phase decomposition in a single-phase CoCrFeMnNi high entropy alloy (HEA) subjected to cold rolling and subsequent annealing at intermediate temperatures. It is found that plastic deformation plays a key role in phase destabilization of the HEA during intermediate annealing. The formation of Cr-rich precipitates in recrystallized grains and recovered samples suggests that dislocations generated by cold rolling is one of the critical factor leading to the destabilization of the stable HEA. Atomic-scale characterization of the Cr-rich precipitates reveals a complex crystallographic structure which is comprised of one-dimensional pentagons with selective atomic occupation. This study indicates that the phase stability of HEAs is very fragile at intermediate temperatures at which the multicomponent solid solutions stabilized by high configurational entropy may break down by local chemical disturbance at dislocations and grain boundaries.

The microstructures of a hierarchical-precipitate-strengthened ferritic alloy are characterized, using transmission-electron microscopy (TEM) and atom-probe tomography (APT). The alloy shows duplex precipitates. The primary precipitate with an average edge length of 90 nm consists of NiAl- and Ni2TiAl-type phases, while the secondary precipitate with an average radius of 2 nm is a NiAl-type phase. Based on the APT results, the volume fractions of the primary and secondary precipitates were calculated, using the lever rule to be 17.3 and 2.3%, respectively.