Superstructure Model Research Articles

Comprehensive Investigation of the Crystal Structure of Cation-Disordered Li3VO4 as a High-Rate Anode Material: Unveiling the Dichotomy between Order and Disorder.

This study investigates mechanochemical synthesis and cation-disordering mechanism of wurtzite-type Li3VO4 (LVO), highlighting its promise as a high-performance anode material for lithium-ion batteries and hybrid supercapacitors. Mechanochemical treatment of pristine LVO using a high-energy ball mill results in a "pure cation-disordered" LVO phase, allowing for meticulous analysis of cation arrangement. The X-ray and neutron diffraction study demonstrates progressive loss of order in LVO crystal with increasing milling duration. High-resolution transmission electron microscopy reveals disrupted lattice fringes, indicating cationic misalignment. Pair-distribution function analysis confirms loss of cation arrangements and the presence of short-range order. Combination of these multiple analytical techniques achieves a comprehensive understanding of cation regularity and clearly demonstrates order/disorder dichotomy in cation-disordered materials, ranging from short (<8 Å) to middle-long range (8-30 Å), using an integrated superstructure model of the cation-disordered LVO crystals. Electrochemical testing reveals that mechanochemically treated LVO exhibits superior rate capability, with a 70% capacity retention at a high current density of 50C-rate. Lithium diffusion coefficient measurements demonstrate enhanced lithium-ion mobility in the mechanochemically treated LVO, attributed to cation-disordering effect. These findings provide valuable insights into mechanochemical cation-disordering in LVO, presenting its potential as an efficient anode material for lithium-ion-based electrochemical energy storage.

Simultaneous Optimization and Integration of Multiple Process Heat Cascade and Site Utility Selection for the Design of a New Generation of Sugarcane Biorefinery.

Biorefinery plays a crucial role in the decarbonization of the current economic model, but its high investments and costs make its products less competitive. Identifying the best technological route to maximize operational synergies is crucial for its viability. This study presents a new superstructure model based on mixed integer linear programming to identify an ideal biorefinery configuration. The proposed formulation considers the selection and process scale adjustment, utility selection, and heat integration by heat cascade integration from different processes. The formulation is tested by a study where the impact of new technologies on energy efficiency and the total annualized cost of a sugarcane biorefinery is evaluated. As a result, the energy efficiency of biorefinery increased from 50.25% to 74.5% with methanol production through bagasse gasification, mainly due to its high heat availability that can be transferred to the distillery, which made it possible to shift the bagasse flow from the cogeneration to gasification process. Additionally, the production of DME yields outcomes comparable to methanol production. However, CO2 hydrogenation negatively impacts profitability and energy efficiency due to the significant consumption and electricity cost. Nonetheless, it is advantageous for surface power density as it increases biofuel production without expanding the biomass area.

Unraveling the mechanism of vanadium self-intercalation in 1T-VSe2: atomic-scale evidence for phase transition and superstructure model for intercalation compound

Self-intercalation is an efficient strategy for tailoring the property of layer structured materials like transition metal dichalcogenides (TMDCs), while the associated kinetics and mechanism remain scarcely explored. In this study, we investigate the atomic-scale dynamics and mechanism of vanadium (V) self-intercalation in multi-layer 1T-VSe2 using in situ high resolution scanning transmission electron microscopy. The results reveal that the self-intercalation of V induces structural transformation of pristine VSe2 into three V-enrich intercalated compounds, i.e. V5Se8, V3Se4 and VSe. The self-intercalated V follows an ordered arrangement of 2×2 , 2×1 , and 1×1 within the interlayer octahedral sites, corresponding to an intercalation concentration of 25%, 50% and 100% in V5Se8, V3Se4 and VSe, respectively. The V intercalants induced lattice distortions to the host 1T-VSe2 such as the dimerization of neighboring lattice V is observed experimentally, which are further supported by density functional theory (DFT) calculations. Finally, a superstructure model generalizing the possible structures of self-intercalated compounds in layered TMDCs is proposed and then validated by the DFT determined formation energy landscape. This study provides comprehensive insights on the kinetics and mechanism of the self-intercalation in layered TMDC materials, contributing to the precise control for the structure and stoichiometry of self-intercalated TMDC compounds.

Operational strategy of reconfigurable membrane process for bio-based amino acid production

Reconfigurable manufacturing systems can rapidly and economically transform production facilities, allowing for the simultaneous realization of diverse customized product manufacturing and high productivity. In this study, the concept of reconfigurable manufacturing systems was introduced to the counter-current diafiltration membrane process for bio-based amino acid production. A superstructure model adaptable to any counter-current diafiltration cascade configuration was developed. This superstructure model optimizes the objective cost function, minimizing fluctuation costs associated with yield and utility. Case studies such as the production of L-lysine, L-arginine, and L-tryptophan were considered. Sensitivity analysis indicated that when membrane capacity becomes limited due to increased overall feed flow rates and decreased permeate flux, the role of the counter-current diafiltration step grows in importance. Circumstances caused by diverse product manufacturing, natural disturbance in bioprocesses, and shifts in productivity and cost priorities based on market dynamics indicate the promising economic potential of reconfigurable membrane systems. Since scalability, diagnosability, customization, modularity, and integrability are high, the reconfigurable membrane system has proven its capability to flexibly adapt to continuously changing conditions. All superstructure modeling and simulations in this study were executed using in-house graphical user interface software.

Quantitative reliability measures determination of a steel-reinforced concrete beam taking into account fatigue damage accumulation in flexible pin stops

Reliability is one of the most important properties of road bridges due to their degree of responsibility and strategic importance for the transport system. For steel-reinforced concrete bridges, which are widespread nowadays, the question of their overall structure reliability dependence on the element’s condition of steel beam and reinforced concrete slab connection remains not fully studied. The authors have performed fatigue damage accumulation numerical modelling in the conjunction elements of steel-reinforced concrete beam from the cyclic temporary loads influence and analysed this process influence on the overall structure reliability. Based on the previous studies data, a relationship model between the conjunction element shear rigidity and the amount of damage accumulated by it is proposed. The nonlinear finite element calculation algorithm with regard to the conjunction element’s rigidity reduction is proposed and tested on the model of the steel-reinforced concrete superstructure. The selection method of the equivalent time load for modelling the accumulation of fatigue damage process from traffic flow is proposed. In order to optimise the computational resources used it is proposed to use loading process clusterization into enlarged cycles groups and the rational group size is determined. A numerical experiment on the simply supported steel reinforced concrete beam model with different loading cycles number (from 1 loading to 100 million loading cycles) to determine the reliability index β under the assumption of variability of two parameters — design steel resistance and the value of temporary load. FORM (First Order Reliability Method) was used for probabilistic analysis. The study results have shown that the accumulation of fatigue damage in the elements of steel-reinforced concrete superstructures has a significant effect both on the load-bearing capacity of the superstructure beams and on the quantitative indicators of structural reliability (increase in the probability of structural failure, decrease in the reliability index β).

Design and Characterization of Deformable Superstructures Based on Amine-Acrylate Liquid Crystal Elastomers.

Deformable superstructures are man-made materials with large deformation properties that surpass those of natural materials. However, traditional deformable superstructures generally use conventional materials as substrates, limiting their applications in multi-mode reconfigurable robots and space-expandable morphing structures. In this work, amine-acrylate-based liquid crystal elastomers (LCEs) are used as deformable superstructures substrate to provide high driving stress and strain. By changing the molar ratio of amine to acrylate, the thermal and mechanical properties of the LCEs are modified. The LCE with a ratio of 0.9 exhibited improved polymerization degree, elongation at break, and toughness. Besides an anisotropic finite deformation model based on hyperelastic theory is developed for the LCEs to capture the configuration variation under temperature activation. Built upon these findings, an LCE-based paper-cutting structure with negative Poisson's ratio and a 2D lattice superstructure model are combined, processed, and molded by laser cutting. The developed superstructure is pre-programmed to the configuration required for service conditions, and the deformation processes are analyzed using both experimental and finite element methods. This study is expected to advance the application of deformable superstructures and LCEs in the fields of defense and military, aerospace, and bionic robotics.

Implementation of nonlinear variable-cost network optimization models for technology assessment in the petrochemicals industry

Innovation in petrochemical technology is ongoing, whether to exploit opportunities, such as increased natural gas liquid supplies, or to face new challenges, including the need to decarbonize and to adapt to a future circular economy. Thus, there is a continuing need for petrochemical technology assessment. We consider methods for implementing optimization-based, superstructure models that assess new technology in the context of the entire hydrocarbon ecosystem, thereby capturing not just first-order, local impacts, but also higher-order, industry-wide impacts. These models are nonlinear, variable-cost, network representations of the industry, incorporating a dominant-producer price leadership approach. They are formulated either as a mixed-integer nonlinear programming problem or as a special-purpose successive linear programming problem. The performance of the different approaches is evaluated based on quality of results and computational efficiency. The comparisons initially use small prototype networks that feature structural properties of the industrial network, followed by application to full-scale, industry-wide problems.

Study on the mechanical characteristics and failure mechanism of the coastal bridge with a box-girder superstructure under the action of breaking solitary waves

Nowadays, bridges with a box-girder superstructure play a crucial role in coastal transportation systems, and many low-lying coastal bridges are severely threatened by breaking waves. However, the study on dynamic characteristics of coastal bridges with a box-girder superstructure under the action of breaking solitary waves is limited, which is crucial for the rational design of these bridges. In this study, a two-dimensional numerical model, including a numerical wave flume and a box-girder superstructure model with a simplified connection system, is developed. The breaking mechanism of solitary waves and the influence of different forms of breaking solitary waves on the box-girder superstructure are investigated in detail in this study. Furthermore, three common failure modes, including the deformation of bearings, sliding between the box-girder superstructure and bearings, and unseating of the box-girder superstructure, and the influence of the damping ratio of bearings on the box-girder superstructure are studied in detail. The results indicate that: (1) The box-girder superstructure is most vulnerable to solitary waves in the breaking state. (2) The unseating and sliding failures of box-girder superstructure under the action of breaking solitary waves are typically accompanied by the deformation and vertical failure of bearings. (3) Increasing the damping ratio of bearings can effectively reduce the lateral displacement and vibration of the box-girder superstructure.

Membrane superstructure optimization for carbon capture from cement plants. Water content influence on optimal solution

A four-membrane superstructure, embedding different connection alternatives and driving force generation options, was extended to consider a four-component wet flue gas mixture. Three case scenarios were assessed for treating a flue gas stream from a cement plant. By minimizing the specific total annual cost (sTAC), each case converged to a distinct local optimal arrangement, achieving the same separation target (90% CO2 recovery and 95% CO2 purity on the concentrated stream), thus highlighting the versatility of the model. In terms of the same superstructure and cost model, the optimal solution for capturing CO2 from wet flue gases is approximately 1.5 times higher than that of a dry mixture. A commonly published optimal two membrane-stage configuration fails to achieve high separation targets, even with low water content. The most cost-effective approach is to eliminate water at the beginning of the process. The energy consumed for CO2 pumping and compression is offset by energy generated during retentate expansion, resulting in a surplus that reduces the overall energy consumption to drive the process.

Smart solutions for clean air: An AI-guided approach to sustainable industrial pollution control in coal-fired power plant

Conventional fossil fuels are relied on heavily to meet the ever-increasing demand for energy required by human activities. However, their usage generates significant air pollutant emissions, such as NOx, SOx, and particulate matter. As a result, a complete air pollutant control system is necessary. However, the intensive operation of such systems is expected to cause deterioration and reduce their efficiency. Therefore, this study evaluates the current air pollutant control configuration of a coal-powered plant and proposes an upgraded system. Using a year-long dataset of air pollutants collected at 30-min intervals from the plant's telemonitoring system, untreated flue gas was reconstructed with a variational autoencoder. Subsequently, a superstructure model with various technology options for treating NOx, SOx, and particulate matter was developed. The most sustainable configuration, which included reburning, desulfurization with seawater, and dry electrostatic precipitator, was identified using an artificial intelligence (AI) model to meet economic, environmental, and reliability targets. Finally, the proposed system was evaluated using a Monte Carlo simulation to assess various scenarios with tightened discharge limits. The untreated flue gas was then evaluated using the most sustainable air pollutant control configuration, which demonstrated a total annual cost, environmental quality index, and reliability indices of 44.1 × 106 USD/year, 0.67, and 0.87, respectively.

Superstructure optimization models for regional coal industry development considering water resources constraints—A case study of Ordos, China

Optimizing the industrial structure is an important way to address resource constraints, achieve sustainable development. In this study, a planning method that combines the superstructure modeling concept and the mathematical method of mixed integer programming is proposed to investigate the optimized results of the coal industry under given constrained water resources, with 4 major coal application industries and 14 coal technology categories are considered. The results indicate that an increase in available water resources is associated with an increased local utilization rate of coal. Under the Water Rights Replacement Scenario, the local utilization rate of coal reaches 24.9%. Changes in available water resources significantly impact the coal chemical industry. In addition, significant reduction by 25% in carbon dioxide emissions requires 70 percent reduction in IDCL and CTO production. The policy implications for the development of the coal industry are also provided in the end.

Shake-table test on dynamic response of prestressed high-strength concrete pipe piles under Soil–Structure interaction

This paper presents the results of a shake-table test on a superstructure model supported by a prestressed high-strength concrete (PHC) pipe pile in soft soil. The primary objective is to investigate the dynamic response of the PHC pipe pile in soft soil influenced by soil–structure interaction (SSI). Accordingly, a single PHC pipe pile with iron blocks is constructed and embedded in soft soil. First, the production of the physical model of the PHC pipe pile and experimental details are elucidated. Then, the study focuses on the dynamic response of the soil–pile–superstructure system considering different ground motion types and peak ground accelerations (PGAs). Finally, the inertial and kinematic effects on the dynamic response of the PHC pipe pile are analyzed. The results show that the SSI effect can increase the predominant period of the superstructure. With the SSI effect, the seismic design should consider the adverse effects of long-period and pulse-type ground motions on the pile. The SSI effect caused the rate of increase in the pile bending moment to be gradually higher than the increase in PGA. Moreover, the dynamic response of the PHC pipe pile is mainly dominated by the inertial effect.

Matrix Non-Structural Model and Its Application in Heat Exchanger Network without Stream Split

Heat integration by a heat exchanger network (HEN) is an important topic in chemical process system synthesis. From the perspective of optimization, the simultaneous synthesis of HEN belongs to a mixed-integer and nonlinear programming problem. Both the stage-wise superstructure (SWS) model and the chessboard model are the most widely adopted and belong to structural models, in which a framework is assumed for stream matching, and the global optimal solution outside its feasible domain may be defined by the framework. A node-wise non-structural model (NW-NSM) is proposed to find more universal stream matching options, but it requires a mass of structural variables and extra multiple correction strategies. The aim of this paper is to develop a novel matrix non-structural model (M-NSM) for HEN without stream splits from the perspectives of global optimization methods and superstructure models. In the proposed M-NSM, the heat exchanger position order is quantized by matrix elements at each stream, and a HEN structure is initialized by the random generation of matrix elements. An approach for solving HEN problems based on a matrix real-coded genetic algorithm is employed in this model. The results show that M-NSM provides more flexibility to expand the search region for feasible solutions with higher efficiency than previous models.

Modelling the Nonlinear Behavior of the Pot Bearings of Railway Bridge KW51

Railway bridge KW51 in Leuven, Belgium, has been monitored since October 2018 with the aim of validating various structural health monitoring techniques. The displacement and strain measurements on the structure show a nonlinear behavior, which is attributed to friction in the pot bearings. This paper describes and validates a methodology that allows the observed nonlinear behavior of the pot bearings to be modeled. This is important for understanding and reproducing the bridge behavior under combined train and thermal loading as in, e.g., virtual sensing applications. To this end, a previously developed detailed linear finite-element model of the bridge superstructure is augmented with nonlinear Bouc–Wen elements, representing the bearings. A comparison between the measured and predicted bearing displacements under train loading shows a significant improvement of the response prediction in comparison with the case where the bearings are modeled as roller supports, as assumed in the design. In addition, it is also shown that the model enables a qualitative description of the thermal bridge response.

Influence of Mn content on the magnetic properties of the hexagonal Mn(Co,Ge)2 phase

Herein, we report on the effect of Mn content on the magnetic properties of the hexagonal Mn(Co,Ge)2 with composition Mn36+xCo49-xGe15.This compound was previously described as Mn2Co3Ge (MgZn2-type structure), but later as Mn(Co,Ge)2 with its own structure type, all samples in this work follow the same superstructure model. Samples were synthesized by induction melting, the crystal structures were evaluated using a combination of X-ray diffraction together with scanning electron microscopy equipped and an energy dispersive X-ray spectroscopy detector. The Curie temperature (TC) is shifted towards lower temperature as the Mn content is increased. On the other hand, the spin reorientation temperature (TSRT) increases and the magnetic moment decreases as the Mn content is increased. The magnetocaloric properties were investigated for the x=1 alloy, Mn37Co48Ge15. It was found that the isothermal entropy change is 2 J kg−1 K−1 at room temperature for an applied field of 5 T.

Seismic Response Analysis of Reinforced Concrete Frame Structures Considering Slope Effects

According to the seismic damage due to past events, buildings located on slopes can present a worse seismic performance. To explore this, this study established a finite element model based on a 6-story RC frame structure and soil models based on a practical slope using OpenSees software. Combining the superstructure model with the soil model through soil spring elements, three soil-structure interaction systems with different slope rates were set up. Twenty near-field seismic actions were used as input loads for dynamic time–history analysis. The analysis shows that in the process of seismic action, the deformation tendency of the structure is affected by the slope. There is a clear tendency for lateral displacement towards the slope, and it is more obvious with a greater slope ratio. Meanwhile, the slope has no impact on the shear force at the base of the structure or at the bottom of the column. In addition, there is no correlation between the degree of impact and the slope gradient on the peak value of internal forces and deformations of structure.

Synchronous Design of Membrane Material and Process for Pre-Combustion CO2 Capture: A Superstructure Method Integrating Membrane Type Selection

Membrane separation technology for CO2 capture in pre-combustion has the advantages of easy operation, minimal land use and no pollution and is considered a reliable alternative to traditional technology. However, previous studies only focused on the H2-selective membrane (HM) or CO2-selective membrane (CM), paying little attention to the combination of different membranes. Therefore, it is hopeful to find the optimal process by considering the potential combination of H2-selective and CO2-selective membranes. For the CO2 capture process in pre-combustion, this paper presents an optimization model based on the superstructure method to determine the best membrane process. In the superstructure model, both CO2-selective and H2-selective commercial membranes are considered. In addition, the changes in optimal membrane performance and capture cost are studied when the selectivity and permeability of membrane change synchronously based on the Robeson upper bound. The results show that when the CO2 purity is 96% and the CO2 recovery rate is 90%, the combination of different membrane types achieves better results. The optimal process is the two-stage membrane process with recycling, using the combination of CM and HM in all situations, which has obvious economic advantages compared with the Selexol process. Under the condition of 96% CO2 purity and 90% CO2 recovery, the CO2 capture cost can be reduced to 11.75$/t CO2 by optimizing the process structure, operating parameters, and performance of membranes.

DECO2—An Open-Source Energy System Decarbonisation Planning Software including Negative Emissions Technologies

The deployment of CO2 capture and storage (CCS) and negative emissions technologies (NETs) are crucial to meeting the net-zero emissions target by the year 2050, as emphasised by the Glasgow Climate Pact. Over the years, several energy planning models have been developed to address the temporal aspects of carbon management. However, limited works have incorporated CCS and NETs for bottom-up energy planning at the individual plant scale, which is considered in this work. The novel formulation is implemented in an open-source energy system software that has been developed in this work for optimal decarbonisation planning. The DECarbonation Options Optimisation (DECO2) software considers multiperiod energy planning with a superstructural model and was developed in Python with an integrated user interface in Microsoft Excel. The software application is demonstrated with two scenarios that differ in terms of the availabilities of mitigation technologies. For the more conservative Scenario 1, in which CCS is only available in later years, and other NETs are assumed not to be available, all coal plants were replaced with biomass. Meanwhile, only 38% of natural gas plants are CCS retrofitted. The remaining natural gas plants are replaced with biogas. For the more aggressive Scenario 2, which includes all mitigation technologies, once again, all coal plants undergo fuel substitution. However, close to half of the natural gas plants are CCS retrofitted. The results demonstrated the potential of fuel substitutions for low-carbon alternatives in existing coal and natural gas power plants. Additionally, once NETs are mature and are available for commercial deployment, their deployment is crucial in aiding CO2 removal in minimal investment costs scenarios. However, the results indicate that the deployment of energy-producing NETs (EP-NETs), e.g., biochar and biomass with CCS, are far more beneficial in CO2 removal versus energy-consuming NETs (EC-NETs), e.g., enhanced weathering. The newly developed open-source software demonstrates the importance of determining the optimal deployment of mitigation technologies in meeting climate change targets for each period, as well as driving the achievement of net-zero emissions by mid-century.

Features of bridge superstructures modeling during the stress-strain state monitoring

The complication of element design performance of artificial structures leads to the need for more detailed superstructure modeling, since simplified models don`t always allow taking into account deformation features of elements. In addition, during the building period, the actual stress-strain state of structures can be significantly influenced by factors that are difficult or impossible to account for at the design stage. Correct modeling of deformation of elements is one of the essential conditions for the prevention of emergencies during construction, maintenance or timely elimination of the consequences of such incidents with minimal losses. When performing this kind of work, attention should be focused on the most significant design parameters, which comprehensively reflect the nature of the structure operation. This will make it possible to effectively carry out control and promptly make appropriate adjustments to the building process, if it is necessary. The article describes an example of the simplified model modernization to more fully match its actual deformation and the experience of eliminating the consequences of emergency that arose during erection of unique bridge. Thus, the importance of adapting the computational model to the actual nature of the engineering design is confirmed.

Analysis of the Dynamic Response as a Basis for the Efficient Protection of Large Structure Health Using Controllable Frequency-Controlled Drives

Continuous earthmoving machines, such as bucket-wheel excavators (BWEs), are the largest mobile terrestrial machines exposed to the working loads of a periodic character. This paper aims to launch a new idea regarding the preservation of the load-carrying structures of these machines by the means of implementing a controllable frequency-controlled drive of the excavating device. Successful implementation of this idea requires a detailed analysis of the dynamic response of the load-carrying structure in order to determine the domains of frequency of revolutions of the bucket-wheel-drive electromotor (FREM) where the dynamic response of the structure is favorable. The main goal of the presented research was the development of a unique three-step method for the identification of the FREM ranges, where the vibroactivity of the load-carrying structure is within the allowed boundaries. A methodologically original study of the dynamic response was conducted on a unique dynamic model of the BWE slewing superstructure that allows for continuous variation of the FREM, i.e., of the frequency of excitation caused by the forces resisting the excavation. Validation of the spatial reduced dynamic model of the slewing superstructure and the corresponding mathematical model, as well as the overall approach to the determination of the dynamic response, were performed by the means of vibrodiagnostics under the real exploitation conditions. Application of the developed method has yielded: (1) the resonant-free FREM domains; (2) the FREM domains, where the structure is not exposed to the excessive dynamic impacts; and (3) the frequency ratio ranges defining the resonant areas. Additionally, the results of the research have pointed out that the resonant-free state represents a necessary but insufficient condition for the proper dynamic behavior of the BWE slewing superstructure.