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Compared to buildings constructed in situ, prefabricated buildings (PBs) offer many environmental benefits in terms of carbon emissions, energy consumption, material consumption, and waste generati...

In this paper, an efficient nonstandard finite difference scheme for the numerical solution of chaotic fractional-order Chen system is developed. In the new method, an appropriate nonlocal framework in conjunction with the Grünwald-Letnikov approximation are applied for the discretization of fractional differential system. By constructing the discretization with the nonstandard finite difference scheme, high resolution of the system can be obtained, and the numerical instabilities of the nonlinear fractional-order Chen chaotic system can be also addressed to some extent. In addition, a new fractional derivative of the Caputo type is employed in the context of fractional-order Chen system to further decrease the computational complexity in the long-term treatment of fractional model. Numerical simulations demonstrate the applicability, accuracy and efficiency of the developed method.

Load conductive component onto textiles via coating method is a simple and facile fabrication process to prepare flexible smart wearable device. However, this functional textile will suffer a significant damage after washing or mechanical wear, which hindered its application. In this study, polydopamine (PDA) was used as an interfacial agent to enhance the combination between carbon nanotubes (CNTs) and cotton fiber to fabricated a highly conductive fabric. Furthermore, a hydrophobic material 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) was introduced to the conductive fabric via dip-coating process, which effectively fixed the CNTs and simultaneously realize the water resistance of the composite fabric, as the contact angle for the fabric was up to 138°. Owning to the formation of a stable conductive path, the composite conductive fabric always possessed a surface resistance lower than 110 Ω/sq. Even after going through the repeated mechanical deformation or multiple stripping cycles, this conductive pathway of the composite fabric was still well maintained. Benefit from the excellent stability and high electrical conductivity, this fabric shows an attractive electromagnetic (EMI) shielding performance, as its EMI shielding effectiveness was 22 dB under 6.57–9.99 GHz and 23 dB under 11.9–18 GHz. Furthermore, the fabric exhibited an outstanding electric heating performance with the heating temperature reaches more than 85 °C at 6 V. Along with the facile preparation technique and stable functional performance, we expect that this hydrophobic conductive cotton fabric can be used as wearable electronics and for the design of various smart flexible devices.

A selective liquation process to extract Al from a coarse Al–Si alloy, produced by carbothermal reduction, was investigated on the laboratory scale. The products obtained by selective liquation–vacuum distillation were analyzed by X-ray diffraction, inductively coupled plasma optical emission spectrometry and scanning electron microscopy. During the selective liquation process with the use of zinc as the solvent, the pure aluminum in the coarse Al–Si alloy dissolved in the zinc melt to form an α-solid solution with zinc, and most of the silicon and iron-rich phases and Al–Si–Fe intermetallics precipitated and grew into massive grains that entered into the slag and separated with the Zn–Al alloy melt. However, some fine silicon particles remained in the Zn–Al alloy. Thus, Al–Si alloys conforming to industrial application standards were obtained when the Zn–Al alloys were separated by a distillation process.

An effective method is proposed in this paper for calculating the transient magnetic field and induced voltage in the photovoltaic bracket system under lightning stroke. Considering the need for the lightning current responses on various branches of the photovoltaic bracket system, a brief outline is given to the equivalent circuit model of the photovoltaic bracket system. The analytic formulas of the transient magnetic field are derived from the vector potential for the tilted, vertical and horizontal branches in the photovoltaic bracket system. With a time–space discretization scheme put forward for theses formulas, the magnetic field distribution in an assigned spatial domain is determined on the basis of the lightning current responses. The magnetic linkage passing through a conductor loop is evaluated by the surface integral of the magnetic flux density and the induced voltage is obtained from the time derivative of the magnetic linkage. In order to check the validity of the proposed method, an experiment is made on a reduced-scale photovoltaic bracket system. Then, the proposed method is applied to an actual photovoltaic bracket system. The calculations are performed for the magnetic field distributions and induced voltages under positive and negative lightning strokes.

NaF-KF-LiF-AlF3-based low-temperature electrolytes have attracted great interest because of their potential to optimize and improve current industrial aluminum production methods. In the present study, the saturated alumina solubility in quaternary NaF-KF-LiF-AlF3-based melts (total cryolite molar ratio $$ {\text{CR}} = \left( {n_{\text{NaF}} + n_{\text{KF}} + n_{\text{LiF}} } \right)/n_{{{\text{AlF}}_{3} }} $$ of 1.3) with both KF and LiF content of 0 mol.% to 20 mol.% were evaluated by measuring the weight loss of a rotating corundum disk over the temperature range of 800–920°C. The effects of the KF content, LiF content, and temperature on alumina solubility are discussed in detail. The results fit well with the following empirical equation within the temperature of 830–890°C: ω(Al2O3)sat = A × (t/1000)B, where A = 0.3101[KF] − 0.1254[LiF] − 0.0057[KF]2 + 0.0028[LiF]2 + 4.486, B = 0.3839[KF] + 0.0368[LiF] − 0.0140[KF]2 + 0.0057[LiF]2 + 4.913, and t is the temperature in Celsius. Alumina solubility diagrams at various temperatures are illustrated based on the empirical regression equation obtained. Finally, some problems and challenges preventing the application of these low-temperature melts in industry are discussed.

Sodium titanate (Na 2 Ti 3 O 7 ), as an intermediate product for producing TiO 2 through alkaline process, was used as precursor to prepare Ti metal successfully by FFC Cambridge Process. For the aim to gain insight into the electro-reduction mechanism, the sintered Na 2 Ti 3 O 7 pellets(∼1.83 mm thinkness, open porosity ∼20%) were electrolysed using them as cathodes against graphite counter electrode in the molten CaCl 2 . The experiments were carried out at 900 °C and the applied voltage was 3.1V. Partially reduced samples were prepared by terminating the reduction process after different electrolysis times. The obtained samples were characterised by means of X-ray diffraction analysis, SEM and EDS. The results show that Na 2 Ti 3 O 7 reacts easily with molten CaCl 2 as 2Na 2 Ti 3 O 7 + 2CaCl 2 → Ca 2 Ti 2 O 6 + 4TiO 2 + 4NaCl and Ca 2 Ti 2 O 6 → 2CaTiO 3 . The electrochemical reduction of sodium titanate proceeds via sequential formation of CaTiO 3 , titanium sub-oxides (such as Ti 4 O 7 , Ti 3 O 5 , Ti 2 O 3 and TiO), CaTi 2 O 4 , Ti-O solid solution and Ti. The whole reduction can be divided into three stages: the first stage is that Ca 2+ ions from electrolyte are inserted into Na 2 Ti 3 O 7 particles leading to the formation of titanium sub-oxides and calcium titanates(CaTiO 3 and CaTi 2 O 4 ); the second stage is that calcium titanates are reduced into Ti-O solid solution from outside to inside of the pellets; the third stage is that the formed Ti-O solid solution is further deoxidised to form Ti metal.

In this paper, a new short process integrating carbochlorination and electrolyzation to produce metallic titanium in molten NaCl–CaCl2 electrolyte was presented. This electrochemical experiment was carried out at 1123 K using carbon-doped TiO2 precursors. The electrolysis process of intermediate produced by carbochlorination of carbon-doped TiO2 precursors was studied. The cathodic product was analyzed using X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and scanning electron microscopy (SEM) after electrolysis. The evolved gas was analyzed by a gas chromatograph equipped with a thermal conductivity detector (GC-TCD). Results showed that Ti powder of 98.7% could be obtained as the final product in the cathode by electrolysis for 5 h at 4.0 V using raw pellets with a C/TiO2 mass ratio of 0.15. Furthermore, the electrochemical process of Ti deposition was comprehensively evaluated by cyclic voltammetry and squarewave voltammetry. The electrode reaction mechanisms and particle evolution principles in molten salt during this electrolysis process were discussed. It indicated that titanium chloride in lower valence (TiCl3) with more productive advantage could exist as an intermediate, and Ti3+ ions were reduced to Ti metal by a two-step mechanism corresponding to the pathway: Ti3+ → Ti2+ → Ti.

In the present study, theoretical analysis and electrolysis testing in the laboratory scale demonstrated the potential of Al metal production by electrolysis in a NaF-AlF3-Al2O3 melt with a cryolite ratio (CR; molar ratio of NaF/AlF3) of 1.3. Subsequently, the electrochemical processes of Al deposition on a tungsten cathode in this melt at 860 °C were comprehensively evaluated by cyclic voltammetry, potentiodynamic cathodic polarization, square wave voltammetry, chronopotentiometry, and potentiostatic electrolysis. The results revealed Al deposition on the tungsten cathode, first as an Al4W alloy at approximately − 0.14 V (vs W), and then as liquid metallic Al-containing a co-deposition of metallic Na at − 0.94 V (vs W). The reduction of Al4W alloy and the deposition of metallic Al were both diffusion-controlled and quasi-reversible. The diffusion coefficient of the Al(Ш) ions was calculated to be 1.77 × 10−8 cm2 s−1. The square wave voltammetry curves indicated that the process of AlF4− ion reduction involved both a three-electron transfer reaction resulting in Al deposition (AlF4− → Al), and a two-electron transfer reaction resulting in the formation of monovalent aluminum ions AlF2− (AlF4− → AlF2−). The chronopotentiometry results revealed that the critical cathodic current for Al deposition was approximately 150 mA. X-ray diffraction (XRD) measurements and scanning electron microscope (SEM) observations confirmed that Al4W alloy and metallic Al existed on the electrode surface after potentiostatic electrolysis.

The electrochemical behavior and electrodeposition of cobalt was investigated in the choline chloride-urea deep eutectic solvent containing cobalt chloride. Cyclic voltammetry was used to study the effect of temperature and concentration on the electrochemical behavior of cobalt. Chronoamperometry results show that as the applied potential increases, the electrocrystallization of cobalt on the tungsten electrode gradually tends to three-dimensional instantaneous nucleation. SEM observation of the microstructure of the coating shows that the deposited films obtained in this experimental condition (−0.85 V ∼ −1.0 V; 343 K–373 K) are dense and uniform with fine crystals. As the deposition potential increases, the contours of the particles are become clear and the edges of the particles gradually join. As the temperature rises, the coating particles increase to become gradually uniform, the plush contour gradually disappears, and the particles are no longer connected with the other particles. EDS and XRD analyses show that pure cobalt coating was obtained.

The lightning transient calculation is carried out in this paper for photovoltaic (PV) bracket systems. The electrical parameters of the conducting branches and earthing electrodes are represented by resistances, capacitances, and inductances. A set of formulas are derived to evaluate the electrical parameters, which are appropriate for the complicated spatial locations of the conducting branches. On the basis of the electrical parameters, the equivalent circuits are constructed for the segmented branches and electrode units in a PV bracket system. By integrating all the equivalent circuits, a complete circuit model is built for the PV bracket system. The lightning transient responses can be obtained from the circuit model. In order to confirm the validity of the circuit model, experimental measurement is made with a reduced-scale PV bracket system and the measured results are compared with the calculated ones. Then, an actual PV bracket system is used as the numerical example. The lightning transient responses are calculated for typical locations of attachment points. The distribution characteristic of lightning transient responses is also explored in the PV bracket system.

A novel cathode with rectangular protrusions has been tested and implemented by Chinese industrial electrolytic aluminum smelters. Measurements of the protrusion wear rate and average cell voltage were conducted. Some experience was acquired with the aim of achieving better current efficiency and longer cathode lifetime. Furthermore, to investigate the influence of the novel cathode after wear down, simulations were carried out to determine the variation of the metal flow for different metal levels and rectangular protrusion heights.

Component factories are experiencing the problems associated with lean production, especially the accuracy of production time prediction and the unnecessary waste in terms of time and resource utilization. In order to solve these problems, a discrete event simulation- (DES-) based lean planning and optimization method for precast component production is proposed by integrating the complexity assessment (CS), discrete event simulation (DES), and lean management (LM). The method includes three submodels: improved production planning, DES, and lean analysis and optimization. In the submodel of improved production planning, a complexity evaluation index system for precast components is established through investigating five component factories, consulting seven domain experts and analysing relevant literature. In the submodel of DES, the DES technique is adopted to simulate and analyse the production activities of precast components. The submodel of lean analysis and optimization provides multidimensional analysis, comparative analysis, and suggestions. Finally, a detailed production case is selected to simulate and test the proposed method. The important findings are as follows: (1) this method can minimize the difference between the processing time of each workstation to avoid bottleneck stations as much as possible; (2) this method can capture the uncertainty during precast component production, and the most likely production time calculated by the method is 12.05 hours instead of the 11.50 hours originally estimated by the component factory; (3) this method can identify some unnecessary waste in the production process of precast components, including less than 50% utilization of workstations and unnecessary equipment purchases; (4) this method also provides some suggestions regarding production optimization. Due to the particularity of precast component production, it further expands the boundary of lean production methodology from the perspective of the construction industry rather than the manufacturing industry. The proposed method assists component factories in planning and optimizing the precast component production when they make detailed production plans.

Efficiency and equity have always been the two points of focus of transport projects. Compared with efficiency, equity is easily overlooked in the evaluation of transport projects. Many studies emphasize that defining and operationalizing costs and benefits and the distributive principle are critical parts in the assessment of transportation equity. However, the scope and time frame of the assessment target are also critical. In this paper, we took China’s fastest urbanizing city, Shenzhen, as a case study to assess transport equity by comparing accessibility among groups. First, the public transport system was divided into bus and subway, and the residents were divided into two groups: urban village and nonurban village. Second, we adopted an enhanced potential opportunity model to measure residents’ bus and subway accessibility and summarized them as transit opportunity. Third, we used the Dagum Gini coefficient decomposition and kernel density estimation method to explore the fair distribution of transit opportunity among groups and districts from 2011 to 2020. Decade-long changes in disparity and distribution of transit opportunity gave us a clear picture. On the one hand, the development of Shenzhen public transport system had a positive effect. All populations are benefiting, and their accessibility is increasing. On the other hand, it also had a negative effect to exacerbate inequality between populations. For the absolute value of the opportunity, Shenzhen’s urban village populations do have fewer transportation opportunities than nonurban villages, and this gap between them will be wider more and more. The public transport system is more inclined to improve the population with high initial opportunity and make them higher. The results illustrated the importance of examining transportation equity over an extended period and could provide information on urban development strategies.

Many design systems are developed in the context of non-prefabricated buildings, and cannot be well suitable for prefabricated buildings which are being popular at present. In order to solve the problem, this paper introduces Design for Manufacture and Assembly (DFMA) into prefabricated building design, and combines it with parametric design of Building Information Modeling (BIM) to develop the concept and process of DFMA-oriented parametric design. For making DFMA-oriented parametric design implemented better, DFMA-oriented architectural design team, precast component creation process based on family template and DFMA, DFMA-oriented BIM re-development process, and optimization process of DFMA-oriented prefabricated building information model are also explored and developed. In the end, some principles of DFMA-oriented parametric design are partially reflected by several examples, and DFMA-oriented parametric design needs to be constantly improved according to its subsequent actual use.

An electrochemical method for the preparation of an Al-Ti master alloy in Al electrolysis melts of Na3AlF6-Al2O3-LiF at 980°C was investigated. The Ti-reducing slag (5.24 wt.% Ti in the Ti-reducing slag) was obtained from the aluminothermic reduction of Na2TiF6. The cold test (i.e., the aluminothermic reduction process without applying any voltages) result revealed the capability of the Al cathode to reduce the Ti slag, and the recovery rate could reach 45.8% at 980°C over 3.5 h with the addition of 10 wt.% Ti-reducing slag. In contrast, the recovery rate of Ti after electrolysis at 3.0 V could reach 99.2%. Thus, the electrochemical treatment for Ti-reducing slag is a cooperative process involving aluminothermic and electrochemical reduction reactions. Electrochemical analysis indicated that the Ti ions are reduced to metallic Ti according to Ti4+ → Ti3+ → Ti. An Al-Ti alloy layer could be prepared on the external surface of the Mo electrode after electrolysis with the addition of 12 wt.% Ti-reducing slag.

A set of analytic formulas are presented to evaluate the circuit parameters of blade, tower, three-phase cable, and monopile foundation. On the basis of the circuit parameters, the circuit model is built and a transient analysis is carried out for the offshore wind turbine (WT) under lightning strikes to multi-blade. The lightning transient responses can be obtained at the different locations of the offshore WT by using the circuit model. An experimental measurement with a reduced-scale WT has been made for checking the validity of the circuit parameter formulas and circuit model. The measured results are compared with the calculated ones and a good agreement is shown between them. The practical feasibility of the circuit model is also examined by a numerical example of an actual Chinese-built offshore WT.

A power law relation between the filtration coefficients of straining and flux through small pores has been reported. The effluent concentrations of the colloidal particles and the exponents derived from the experiment are inconsistent with those obtained from 2D network models simulation in their researches. In this study, a straining-dominant deep bed filtration (DBF) model is proposed based on 3D network simulation. The effects of simulation parameters such as lattice type, lattice coordination number z , pore size distribution (PSD), and particle capture scheme on DBF were investigated. Consistent with the power law formula and the normalized effluent concentrations ( C e/ C 0 ), simulation results indicate that the exponents increase with increasing coordination number z. The change in the PSD parameters alters the flux and weight of path type linked to node, thereby influencing the numerical simulation of staining-dominate DBF on 3D networks. The effects of capture scheme and coordination number on the simulated normalized effluent concentration could be due to variations in the total capture probability for different lattices with the same PSD. The results were obtained from simulation on hexagonal close packing (HCP) and 2D triangular lattices under the optimal conditions. The simulated C e/ C 0 and exponents of the HCP lattice are similar to those of 2D triangular lattice and consistent with the experimental data.

Three-dimensional aluminium electrolytic cells with inclined surface cathodes were simulated in ANSYS and CFX to predict the influence of different side-wall types on the horizontal current and metal flow. The simulated results showed that the ledge thickness decreased with the thermal conductivity of the side wall. The graphitised side wall with the highest thermal conductivity displayed the largest ledge toe extensions of 24.6 cm at the centre of the long side and 28.0 cm at its corner. The long ledge toe extension introduced large inverted horizontal current and increased the maximum metal velocity. Above the largest ledge toe extension, the metal deviation from the equilibrium was 1.6 cm at one quarter of the cell length and 1.8 cm at the cell corner, equal to the metal wave crest in the cell (1.8 cm). With decreasing ledge toe extension, the maximum metal velocity and metal deviation above the ledge toe extension from equilibrium decreased accordingly.

Trapezoidal protrusions were added onto flat cathodes with the objective of enhancing the flow resistance to the metal in aluminum electrolysis cells. This design was tested for 8 months and proved to be effective in reducing cell voltage. Subsequently, trials revealed that when all the protrusions were widened, the energy consumption was barely influenced. Moreover, in the case of flat cathodes alternating with cathodes with widened protrusions, collector bars embedded in the flat cathodes took more current. In this paper, through finite element analysis, protrusions of various arrangements and widths were considered to estimate the current density and velocity in the metal.

In the aluminum reduction cells, gas bubbles are generated at the bottom of the anode which eventually reduces the effective current contact area and the system efficiency. To encourage the removal of gas bubbles, slotted anode has been proposed and increasingly adopted by some industrial aluminum reduction cells. Nonetheless, the exact gas bubble removal mechanisms are yet to be fully understood. A three-dimensional (3D) transient, multiphase flow mathematical model coupled with magnetohydrodynamics has been developed to investigate the effect of slotted anode on the gas bubble movement. The Eulerian volume of fluid approach is applied to track the electrolyte (bath)–molten aluminum (metal) interface. Meanwhile, the Lagrangian discrete particle model is employed to handle the dynamics of gas bubbles with considerations of the buoyancy force, drag force, virtual mass force, and pressure gradient force. The gas bubble coalescence process is also taken into account based on the O’Rourke’s algorithm. The two-way coupling between discrete bubbles and fluids is achieved by the inter-phase momentum exchange. Numerical predictions are validated against the anode current variation in an industrial test. Comparing the results using slotted anode with the traditional one, the time-averaged gas bubble removal rate increases from 36 to 63 pct; confirming that the slotted anode provides more escaping ways and shortens the trajectories for gas bubbles. Furthermore, the slotted anode also reduces gas bubble’s residence time and the probability of coalescence. Moreover, the bubble layer thickness in aluminum cell with slotted anode is reduced about 3.5 mm (17.4 pct), so the resistance can be cut down for the sake of energy saving and the metal surface fluctuation amplitude is significantly reduced for the stable operation due to the slighter perturbation with smaller bubbles.

A novel two-stage method, based on aluminothermic reduction of Na2TiF6, has been proposed to prepare Ti-Al intermetallic alloys in this paper. The entire process of the two-stage aluminothermic reduction was introduced in detail. The result of thermal analysis demonstrated that the aluminothermic reduction reaction was an exothermic process and occurred at approximately 660 °C. Besides Ti-containing cryolite, pure Ti3Al, TiAl and TiAl3 intermetallics could be prepared after the first stage reduction. Further, in secondary reduction, Ti-containing cryolite contained Ti4+, TiOS and Ti-Al intermetallics could be purified completely. As a result, pure cryolite and Al-Ti alloy were obtained. A concept of continuous and cyclic route was proposed. The two-stage aluminothermic reduction process provided a high productivity and pollution-free metallurgical way for preparing Ti-Al intermetallic alloys.

Construction-related environmental impacts have increased with the rapid urbanization in China. Contractors could mitigate the environmental impacts of a building's construction phase by developing an environmentally-friendly construction scheme. However, a construction scheme that performs well on one environmental metric may perform poorly on others. Moreover, it becomes challenging to select the best plan when various construction schemes and diverse environmental metrics need to be considered. This research explores how a multi-objective optimization method can provide Pareto optimal solutions that will help the contractor select a construction scheme that performs well on all environmental metrics. A quantitative environmental assessment and optimization method (EAOM) was established to evaluate and optimize the construction environmental performance using a combination of Life Cycle Assessment (LCA) and Particle Swarm Optimization (PSO). Assessment and optimization were implemented as two integrated and interactively functional modules to complement LCA in multi-objective decision support. In a case of reinforced concrete project, EAOM generated four Pareto construction schemes within 864 possible solutions in a remarkably short time. The results indicate that EAOM is an effective and efficient decision support tool that contractors can implement to improve the environmental performance of construction processes.

Offshore wind turbines are often struck by lightning due to their tall structures and the harsh marine environment. The high transient potential from lightning strike can cause serious damage for the devices of offshore turbines. For analysing the effect of transient potential, a complete transient circuit model is established and an efficient algorithm is also presented to evaluate the circuit parameters of blade, tower, and jacket foundation. On the basis of the circuit model, the transient potential at the different locations of the offshore wind turbine can be carried out during direct lightning strike by PSCAD. Finally, the circuit model is used by a numerical example of an actual Chinese-built offshore wind turbine.

Transit-oriented development (TOD) has been recognised as a sustainable planning approach and that is typically designed for a whole city. Individual land use characteristics and the causations have often been ignored. Therefore, the primary objective of this study was to explore the factors that influence the land use catchment area (LCA) characteristics at a station neighborhood level. First, it contributes a methodology to measure the LCA by introducing a new concept. The density gradient was introduced to generate the scale and compactness degree of each station. Second, it provides a theoretical framework for understanding the causes of different LCAs. The partial least squares (PLS) regression model was employed to explore the accessibility effects. By analysing density gradient curves, it reveals that stations grew to fit the negative exponential function. Regarding the scale and form degree of LCAs, the impact of accessibility before and after a station construction have been corroborated. Moreover, the effects of facilities function before construction, distance from main roads, and elevated stations have been emphasized. The results provide support for a more sophisticated concept of catchment area relating to land use at the level of an individual TOD station, while shedding light on the benefits of those engaged in the future design of TOD with due consideration of the local physical environments.

Construction contractors play a vital role in reducing the environmental impacts during the construction phase. To mitigate these impacts, contractors need to develop environmentally friendly plans that have optimal equipment, materials and labour configurations. However, construction plans with optimal environment may negatively affect the project cost and duration, resulting in dilemma for contractors on adopting low impacts plans. Moreover, the enumeration method that is usually used needs to assess and compare the performances of a great deal of scenarios, which seems to be time consuming for complicated projects with numerous scenarios. This study therefore developed an integrated method to efficiently provide contractors with plans having optimal environment–cost–time performances. Discrete-event simulation (DES) and particle swarm optimisation algorithms (PSO) are integrated through an iterative loop, which remarkably reduces the efforts on optimal scenarios searching. In the integrated method, the simulation module can model the construction equipment and materials consumption, the assessment module can evaluate multi-objective performances, and the optimisation module fast converges on optimal solutions. A prototype is developed and implemented in a hotel building construction. Results show that the proposed method greatly reduced the times of simulation compared with enumeration method. It provides the contractor with a trade-off solution that can average reduce 26.9% of environmental impact, 19.7% of construction cost, and 10.2% of project duration. The method provides contractors with an efficient and practical decision support tool for environmentally friendly planning.

To investigate the electrodeposition mechanism of Ti4+, electrochemistry experiments were conducted using a KF–KCl–K2Ti6O13 molten salt at a Cu electrode at 950 °C. Transient electrochemical techniques such as cyclic voltammetry (CV) and square-wave voltammetry were used in this study. The main phases and compositions of the product were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). The resulting product has the structure of metallic Ti. The results indicate that Ti4+ is reduced to metallic Ti by a two-step mechanism, corresponding to the reduction pathway: Ti4+ → Ti2+ → Ti. Moreover, Cu–Ti alloy could be obtained by the potentiostatic electrolysis at a Cu electrode.

The Pidgeon process currently accounts for 85% of the world’s magnesium production. Although the Pidgeon process has been greatly improved over the past 10 years, such production still consumes much energy and material and creates much pollution. The present study investigates the process of producing magnesium by employing vacuum aluminothermic reduction and by using magnesite as material and obtaining magnesium aluminate spinel as a by-product. The results show that compared with the Pidgeon process, producing magnesium by vacuum aluminothermic reduction can save materials by as much as 50%, increase productivity up to 100%, and save energy by more than 50%. It can also reduce CO2 emission by up to 60% and realize zero discharge of waste residue. Vacuum aluminothermic reduction is a highly efficient, low-energy-consumption, and environmentally friendly method of producing magnesium.

A new route to produce pure Ti powder or TiC nanopowder with diameters of ∼50 nm by electrolysis in molten KCl–NaCl using TiO2 and carbon powder was reported in this paper. This electrochemical experiment was carried out with an innovative equipment unitizing the chlorination and electrolyzation. A fine titanium powder was obtained after electrolysis at 4.0 V for 5 h at 850 °C. TiC nanopowder could be prepared in the anode chamber with the cell voltage up to 4.5 V. Furthermore, the product was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that pure Ti or TiC nanopowder can be prepared after electrolysis. The TiC nanopowder exhibited a polymorphic structure, and it had good thermal stability and oxidation resistance below 345 °C in air investigated by TGA and DSC. Cyclic voltammograms were carried out and the electrode reaction mechanisms during the electrolysis process were discussed in the paper.

Hydrotreatment of heteroatomic model compounds in microalgae-based bio-oils into diesel-like hydrocarbons was carried out over carbon nanotubes (CNTs)-supported β-Mo2C catalyst with superior activity and selectivity under a mild condition (≤200 °C). The results show that stearic acid and hexadecanamide can be completely converted into n-C15–C18 alkanes over β-Mo2C/CNTs catalyst. The β-Mo2C/CNTs favors the pathway of hydrogenation–dehydration–hydrogenation to produce n-octadecane with an optimal yield of 91.24% at a lower temperature of 180 °C during hydrotreating process of stearic acid. The recycle tests demonstrate that the β-Mo2C/CNTs exhibits excellent stability, and can be reused for seven times consecutively without reduction of catalytic stability. Based on the determined products, a brief reaction pathway is proposed. Therefore, a novel approach to produce diesel-like hydrocarbons via catalytic hydrotreatment of microalgae-based bio-oils over β-Mo2C/CNTs is introduced, which provides a basic research as well as technical parameters for its further industrialization.

In order to understand the impact of anode change on heat transfer and magnetohydrodynamic (MHD) flow in aluminum smelting cells, a transient three-dimensional (3D) coupled mathematical model has been developed. The solutions of the mass, momentum and energy conservation equations were simultaneously implemented by the finite volume method with full coupling of the Joule heating and Lorentz force through solving the electrical potential equation. The volume of fluid (VOF) approach was employed to describe the two-phase flow. The phase change of molten electrolyte (bath) as well as molten aluminum (metal) was modeled by an enthalpy — based technique, where the mushy zone is treated as a porous medium with porosity equal to the liquid fraction. The effect of the new anode temperature on recovery time was also analyzed. A reasonable agreement between the test data and simulated results is obtained. The results indicate that the temperature of the bath under cold anodes first decreases reaching the minimal value and rises under the effect of increasing Joule heating, and finally returns to steady state. The colder bath decays the velocity, and the around ledge becomes thicker.

A finite element model was developed to determine the impact of cathode material and shape on current density in an aluminum electrolysis cell. For the cathode material, results show that increased electrical resistivity leads to a higher cathode voltage drop; however, the horizontal current is reduced in the metal. The horizontal current magnitude for six different cathode materials in decreasing order is graphitized, semi-graphitized, full graphitic, 50% anthracite (50% artificial graphite), 70% anthracite (30% artificial graphite), 100% anthracite. The modified cathode shapes with an inclined cathode surface, higher collector bar and cylindrical protrusions are intended to improve horizontal current and flow resistance. Compared to a traditional cathode, modified collector bar sizes of 70 mm × 230 mm and 80 mm × 270 mm can reduce horizontal current density component Jx by 10% and 19%, respectively, due to better conductivity of the steel. The horizontal current in the metal decreases with increase of cathode inclination. The peak value of Jx can be approximately reduced by 20% for a 2° change in inclination. Cylindrical protrusions lead to local horizontal current increase on their tops, but the average current is less affected and the molten metal is effectively slowed down.

Stochastic Brownian dynamics is an extremely powerful way to simulate the polymer dynamics in solutions and melts. Mathematically, these models are described by stochastic differential equations. The most challenging problems are the Monte Carlo algorithm, which simulates the motion of a large number of model particles and hence requires an enormous amount of computer time. It is therefore necessary to develop an efficient numerical method in operational emergency response applications. In this paper, we give an improved multilevel Monte Carlo (improved-MLMC) method based on equilibrium control variables at each level to calculate the propagation of polymers. The improved-MLMC method can be shown to result in asymptotically optimal random errors and reduce total cost when compared to the standard Monte Carlo and MLMC methods. Finally, the effect of the Wi number (dimensionless parameter) on the total cost of the presented MLMC method is also discussed in detail.

Alumina-containing waste can potentially be used to produce a coarse Al–Si alloy by carbothermal reduction and subsequent aluminum metal extraction by soluble anode electrolysis. However, metal impurities in the alloy have important effects on the product purity. In this study, anodic dissolution of the coarse Al–Si alloy and cathodic electrochemical reduction of metal impurity ions in the electrolyte were investigated. The phases, element distributions, and compositions of the anode, electrolyte, and products were investigated by X-ray diffraction, scanning electron microscopy, and inductively coupled plasma atomic emission spectrometry. When using an aluminum wire of diameter 2 mm as reference electrode, the order of anodic metal dissolution is Mg > Ca > Al > Fe > Si > Ti > Mn, and that of metal impurity ion reduction in the electrolyte is Fe > Si > Al > Mg > Ca. Mg and Ca dissolve into the electrolyte before aluminum does, but they have little effect on the product purity because of their high decomposition voltages. Fe and Si in the alloy anode begin to dissolve at electrode potentials of 0.4 and 0.7 V, respectively. If keeping the electrode potential lower than 0.3 V, the Al purity reaches 99.9 %.

A calculating method is proposed for lightning transient analysis in photovoltaic bracket systems. The circuit parameters are evaluated for the conducting branches and grounding electrodes. On the ground of the circuit parameters, the equivalent circuit model is set up for photovoltaic bracket systems. The transient calculation is made by the circuit model and the potential and current responses are obtained in photovoltaic bracket systems. The laboratory-experiment is performed on a reduced-scale photovoltaic bracket system. The results obtained from the measurement are compared with those from the transient calculation to confirm the validity of the circuit model. Then, the probability density function of lightning current is further introduced into the statistical analysis of lightning transients. By means of the transient calculations made in a large interval of lightning current amplitudes, the statistical values of the nodal potential and branch current amplitudes are calculated by probability weights. A numerical example is also given for examining the difference between the statistical and non-statistical values. The proposed method can take account of the actual randomness of lightning discharge and afford a sound basis for lightning protection design of photovoltaic bracket systems.

Diagrams of the equilibrium potential E (relative to the standard chlorine electrode) against the activity of oxide ion ( expressed as its logarithm, pO2−) in systems of Ti-O-Cl-M (M=Li, Na, Mg, Ca, Sr and Ba) were plotted to investigate the electro-deoxidation of porous TiO2 pellets in different chloride molten salts, including LiCl, NaCl, MgCl2, CaCl2, SrCl2 and BaCl2. From the diagrams, the reduction pathways of TiO2 in different molten salts are similar; and the applied potential (vs Cl−/Cl2) on the cathode and O2− ion activity influence greatly on the reduction pathway of TiO2 and the deoxidation limit. To test and verify the results of the thermodynamic analysis, electro-deoxidation experiments in different molten salts were done to determine the actual pathways in the electrochemical reduction of TiO2 and the possible deoxidation limits in the molten salts. The results indicated that the thermodynamic analysis is helpful in predicting and understanding the electrochemical reduction process of titanium oxides though the experimental results differ slightly from the thermodynamic analysis in some systems. Low-oxygen Ti can be obtained only in molten CaCl2.

Underground utility tunnels are crucial for urban areas with high density in both population and number of buildings since they can tremendously improve the utilization of land resources. However, the operation & maintenance (O&M) of such underground tunnels is tedious and challenging, due to the fact that there is a lack of effective information technologies to facilitate O&M of utility tunnels. Although Building information modelling (BIM) technology is asserted to provide a game-changing solution to address the challenges encountered in the AEC industry, the use of BIM for operating and managing utility facilities in an efficient manner is rarely explored in the existing literature. To address this gap, a novel framework is proposed in this research to promote the sustainable O&M of utility tunnels with the support of BIM. Specifically, this framework encompasses three modules, namely, BIM model, O&M database, and monitoring system. A detailed description of each component of the proposed framework, as well as a preliminary user interface design, is presented in this paper. An implementation example is presented to provide the validation of the proposed framework. The preliminary results indicate the feasibility of the proposed framework in facilitating the information integration and communication of utility tunnels. This research contributes to the main body of knowledge by proposing a generic BIM framework for sustainable O&M of utility tunnels and formalizing data requirements as well as management workflow intended for utility tunnel O&M.

The potential of emerging information technology has been proposed by many researchers and practitioners in the construction industry, including smart construction. Meanwhile, emerging information technology acceptance and use is one of the major subjects for current smart construction study and practice. Furthermore, although there are many potential applications for and benefits of emerging information technology in the development of smart construction system, the current issue is that it is unclear why this technology is adopted, and that the factors that enhance its implementation are unknown. Therefore, an emerging information technology acceptance model (EITAM) was proposed, and our hypotheses were tested by structural equation modeling (SEM) based on an open-ended questionnaire survey. This study identified the factors that affect emerging information technology acceptance from engineering construction technology and innovation professionals. The EITAM evaluation results can be used to develop an emerging information technology acceptance strategy that is suitable for continual smart construction promotion. Finally, this study can provide guidance to smart construction developers to establish an effective technological integration plan.

Construction accounts for a considerable number of environmental impacts, especially in countries with rapid urbanization. A predictive environmental assessment method enables a comparison of alternatives in construction operations to mitigate these environmental impacts. Process-based life cycle assessment (pLCA), which is the most widely applied environmental assessment method, requires lots of detailed process information to evaluate. However, a construction project usually operates in uncertain and dynamic project environments, and capturing such process information represents a critical challenge for pLCA. Discrete event simulation (DES) provides an opportunity to include uncertainty and capture the dynamic environments of construction operations. This study proposes a predictive assessment method that integrates DES and pLCA (DES-pLCA) to evaluate the environmental impact of on-site construction operations and supply chains. The DES feeds pLCA with process information that considers the uncertain and dynamic environments of construction, while pLCA guides the comprehensive procedure of environmental assessment. A DES-pLCA prototype was developed and implemented in a case study of an 18-storey building in Northeast China. The results showed that the biggest impact variations on the global warming potential (GWP), acidification potential (AP), eutrophication (EP), photochemical ozone creation potential (POCP), abiotic depletion potential (ADP), and human toxicity potential (HTP) were 5.1%, 4.1%, 4.1%, 4.7%, 0.3%, and 5.9%, respectively, due to uncertain and dynamic factors. Based on the proposed method, an average impact reduction can be achieved for these six indictors of 2.5%, 21.7%, 8.2%, 4.8%, 32.5%, and 0.9%, respectively. The method also revealed that the material wastage rate of formwork installation was the most crucial managing factor that influences global warming performance. The method can support contractors in the development and management of environmentally friendly construction operations that consider the effects of uncertainty and dynamics.

Offsite construction has been identified as an effective approach for enhancing the sustainability of the construction industry. However, due to the fragmented production processes of offsite construction, quality defect control has become a significant challenge in the promotion of offsite construction projects. Offsite construction projects involve multiple interdependent stakeholders in close collaboration. These stakeholders play various roles in quality management and have different degrees of impact on the occurrence of quality defects. To enhance quality defect management in offsite construction projects, it is important to evaluate the different stakeholder impacts on the occurrence of quality defect. Through impact evaluations, critical stakeholders can be identified and their responsibilities clarified with respect to project quality, thereby motivating these key stakeholders to improve their quality defect control. In this study, we developed an evaluation model using the Bayesian network approach to measure stakeholder impacts on defect occurrence in offsite construction projects. Quality defects and stakeholder-related factors that might incur defects were modeled as a Bayesian network and the dependencies among network nodes examined. Then, the stakeholder impacts on the occurrence of quality defects were evaluated using Bayesian analysis. Finally, this Bayesian-network-based evaluation model was applied to a real project in Shenzhen, China. The results indicate that use of precast components with quality defects, misoperations by construction workers, and ineffective quality inspection and testing during onsite assembly and construction were the major factors affecting quality defect control. Additionally, in this case study, we found the contractor to have the highest level of impact on the occurrence of quality defects. This study contributes to the fields of stakeholder impact evaluation and quality defect analysis, and links defect management with key project stakeholders.

Due to more complex structure and increasing prefabrication rate of precast concrete buildings, the assembly order between their constituent components is getting more and more attention. In order to solve the assembly sequence planning and optimization (ASPO) problem in precast concrete buildings, Building Information Modelling (BIM) and Improved Genetic Algorithm (IGA) are organically combined to propose a new method called BIM-IGA-based ASPO method. This method uses BIM for parametric modelling, uses IGA to search for an optimal assembly sequence, and then uses BIM again for visual simulation to further test the assembly sequence. Besides, IGA, which is improved in coding mode, crossover operation and mutation operation, is also used to achieve the dynamic adjustment of assembly sequence in construction process. A full-text example is used to explain the detailed operating principle of BIM-IGA-based ASPO method. The results indicate that the method can effectively find an optimal assembly sequence to reduce the assembly difficulty of a precast concrete building

As an important component of urban construction, the development of the community is of great significance to the sustainable construction of the entire society. The previous studies mainly focused on quantitative research and were limited by the data collectability, affecting the scientificity of the index system. Therefore, based on the theory of sustainable development, through the review of previous literature, combined with relevant experts' opinions and community development goals and other factors, a qualitative evaluation index system for community sustainable development capacity was established. The ANP (analytic network process) method is mainly used to determine the weight of each indicator, and FCE (fuzzy comprehensive evaluation) is proposed to determine every indicator’s membership. Then the hybrid fuzzy evaluation is promoted to evaluate the selected community as the empirical study. In this paper, the indicator selection is not limited by objective factors, and the evaluation system is more accurate; the application of ANP method makes the results of weight more scientific; meanwhile, fuzzy comprehensive evaluation can be suitable for solving various nondeterministic problems. This study transforms qualitative research into quantitative research; it provides an effective evaluation method for local managers and decision makers to carry out community sustainable construction.

The building industry consumes a large amount of nature resources and generates significant environment impacts around the world. To mitigate the resource consumption and associated environmental i ...

Membrane fouling has limited extensive applications for hollow fiber membranes in water treatment. Backwashing and air scouring can effectively solve this problem in the submerged outside-in hollow fiber membrane system. In this study, variation of the fouling layer on the membrane surface during backwashing and the impact of shear stress caused by air scouring on fouling removal were investigated through computational fluid dynamics (CFD) simulation. The backwashing and air scouring process were simulated using CFD and the results were verified by experimental studies. The results of experimental studies are in accordance with the simulation results. During the backwashing process, the velocity profile inside the reactor was presented, and visualization of the particle movement to illustrate the dynamic peeling process of the fouling layer on the membrane surface was also shown. The formation of uneven cleaning reveals that the upper region of the fibers has an excellent cleaning effect during backwashing. After that, the supporting role of air scouring was investigated in the study. It is concluded that the lower part and the middle region of the fibers suffer greater shear stress by analyzing the velocity contours and vectors, and the analysis results indicated that air scouring can further remove membrane fouling.