Background: To improve railway construction and maintenance, a novel digital twin that helps stakeholders visualize, share data, and monitor the progress and the condition during services is required. Building Information Modelling (BIM) is a digitalization tool, which adopts an interoperable concept that benefits the whole life-cycle assessment (LCA) of the project. BIM’s applications create higher performance on cost efficiency and optimal time schedule, helping to reduce any unexpected consumption and waste over the life cycle of the infrastructure.Methods: The digital twin will be developed using BIM embedded by the lifecycle analysis method. A case study based on Taipei Metro (TM) has been conducted to enhance the performance in operation and maintenance. Life cycles of TM will be assessed and complied with ISO14064. Operation and maintenance activities will be determined from official records provided by TM. Material flows, stocks, and potential risks in the LCA are analyzed using BIM quantification embedded by risk data layer obtained from TM. Greenhouse emission, cost consumption and expenditure will be considered for integration into the BIM.Results: BIM demonstrated strong potential to enable a digital twin for managing railway maintenance and resilience. Based on the case study, a key challenge for BIM in Taiwan is the lack of insights, essential data, and construction standards, and thus the practical adoption of BIM for railway maintenance and resilience management is still in the design phase.Conclusions: This study exhibits a practical paradigm of the digital twin for railway maintenance and resilience improvement. It will assist all stakeholders to engage in the design, construction, and maintenance enhancing the reduction in life cycle cost, energy consumption and carbon footprint. New insight based on the Taipei Mass Rapid Transit system is highly valuable for railway industry globally by increasing the lifecycle sustainability and improving resilience of railway systems. Rapid developments in railway transportation infrastructures enhance the congestion and complexities of the construction so that it becomes difficult to manage the works which consist of many tasks, activities, and components. In addition, the public demand for the improvement of life quality in the metropolitan results in the revolution in railway constructions. In Taiwan, the public has a high dependence on transportation by MRT (Taipei Mass Rapid Transit) in Taipei city. Department of Rapid Transit Systems declared that the average of the annual transport volume in January had greatly increased from 145.45 million to 194.63 million passengers in eight years (2012–2019), which corresponds to an annual average growth rate of approximately 4%.. Becerik-Gerberet al. declared that the consumption of energy, capital, and so on in the maintenance stage are much higher than other stages in the whole life cycle of projects. Therefore, further BIM application for the operation and maintenance phases is necessary. In practice, residual risks and uncertainty  influence the maintainability of infrastructure systems after the construction phase, especially in railway systems, since any omissions of the risk management would increase the possibility of accidents, and can lead to serious casualties. The train route between Chiang Kai-shek Memorial Hall Station and Dongmen Station is used here as a case study to demonstrate the extended application of BIM for LCA of the Mass Rapid Transit (MRT) railway infrastructures. The BIM has been embedded with multiple data layers  to generate a digital twin of the MRT section. As many routes of the MRT are underground tunnels with complex pipelines, operational safety is vital. Railways in underground tunnels can be affected or dislocated by surrounding environmental factors such as earthquakes, floods, etc. This study aims to assess the MRT system using the digital twin to enhance the sustainability of the construction, and help to avoid and mitigate potential accidents that can happen during the operational phase. The digital twin can be valuable in work efficiency, system quality and safety management for construction, maintenance, and operational stages of the MRT.Building Information Modelling (BIM), which is a process to digitise and simulate the built environments, is beneficial to project management, monitoring and operation during the whole life-cycle assessment (LCA) progress in real-time. Relevant parties can access the BIM database to use the information. A study that collected reports from 92 random organizations, stated that in the UK at present, approximately 54.88% of organizations adopt BIM in the design stage for data sharing among stakeholders. The achievement in stakeholder collaboration by BIM is the most significant advantage to firms. Railway infrastructures can be formed by a range of structural assemblies, such as steel rails, sleepers, rail fasteners, concrete slabs, foundations, hydraulically bound, and/or ballast/sub-ballast layers. These assemblies are made from fundamental materials, such as steel, concrete, and rubber. The ballasted track is most-commonly used in traditional railway structures. A ballast bed is usually used to decrease the effective train loads to the ground, and it has an excellent performance in water drainage. The advantages of low consumption and simplicity of ballasted railway track maintenance significantly benefit railway developments, However, the frequency of maintenance works of the ballast layer and the associated vibration and noise causes inconvenience to residents, especially in urban areas. As a result, the consideration for the installation of ballastless tracks (which tend to yield much lesser maintenance activities) gains significant momentum. The standard for ballastless tracks was first developed by the International Union of Railway (UIC) and British Rail’s Paved Concrete Track (PACT). To optimize the quality of life in the city, Floating Slab Track (FST) is often used to better satisfy the requirement of low-noise and low-vibration railways. A test result of the FST application in a light rail at Konya, Turkey demonstrated that the noise levels are about 1.6 times less than before the installation of FST. Non-Ballasted Track with High Isolation (NBHI) could also reduce the vibration by various isolation parameters through multilayers of isolation pads. For the case study in this study, FST and NBHI, which are installed from Chiang Kai-shek Memorial Hall Station to Dongmen Station, have been adopted for demonstrating the digital twin applications to asset maintenance, risk, and resilience management.The construction of railways has increased dramatically in recent years due to the rising density of people who live in urban settings. Taipei City Government stated that the number of passengers traveling by public transportation was 30% in the Taipei metropolitan area in 2001, and by 2005, the mode share for railway had increased to almost 50%. Inaccuracies of information and records happen in the construction stage because the traditional risk assessment lacks up-to-date information, and uncertainties during the operation cause difficulties in comprehensive risk management. The adoption of BIM, which enables a multi-dimensional system, can improve risk identification in real-time. The various natural impacts such as flooding, seismic activity, changes in temperature, and geographic variation, can result in the shortened lifespan of the rail track. Earthquakes can cause instability in the foundations, especially in areas with soft soil. The risk of component failure during the operation stage could lead to a serious derailment situation. Evaluation of wear and tear of railway infrastructures is crucial to operational risk analysis. The risk factors, which are related to resistance reduction in rail infrastructures, should be robustly considered and frequently monitored in the design in order to improve safety and maintenance effectiveness of the railway system.Railway assembly is complex by nature. Risk management and maintenance are important so that any component failure, which could lead to hazardous accidents (such as derailment), does not occur. Moreover, the supply chain of materials and components is one of the key management issues for large-scale projects. It is very difficult to assign, schedule, and update material flows throughout the LCA using the traditional construction and asset management methods. To enhance the sustainability of railway construction, a proper maintenance process is necessary. The design and management of the railway maintenance should consider all potential scenarios of the construction and operations. Three main factors contribute to defects that occur in railway tracks: (1) unexpected situations that occur during operation and maintenance, (2) surrounding environmental impacts, and (3) abrasion and erosion causing damage. In other words, exhaustive risk and hazard management in maintenance is needed through rigorous evaluation in multimeric parameters. In the maintenance phase of the railway system, comprehensive risk analysis is required because it helps to improve sustainability and resilience. According to the European Technology Assessment Group (ETAG), various incidents that can happen regularly in a tunnel include fire, increased temperature, and flooding. These factors can have a serious impact on the railway system, leading to a service breakdown.Maintenance is one of the most important activities in the operational stage over the life cycle of railway systems since detrimental accidents may occur if the track condition is deficient. The rapid development in the urban systems and built environments increases the complexity and interdependence of each mode of transport infrastructure, and this increases the difficulty in risk management among all assets. Earthquakes are also a threat to the railway system which would be affected by vibration or unexpected movement. The maintenance works in the metro railway system in Taiwan currently apply BIM to manage the working schedule, and the BIM is integrated with material inventory and a geographic information system (GIS), which analyzes the consequences that the underground geological structure has on the railway system.Taiwan is located on the circum-pacific seismic belt which results in a high frequency of earthquakes, approximately 40,000 per year, so that the maintenance can be managed in real-time.To improve the quality and efficiency of the maintenance works, integrating all the inspection records with BIM tools can achieve optimum maintenance works. Visualization with a 3D model, coordination of a huge number of data, and powerful simulation in BIM can be applied to a railway system using AutoCAD Revit software. Some research using BIM analyses in different construction showed that the highest cost consumption is in the construction phase. However, there is still a lack of 6D BIM research and application to MRT construction and resilience management. Consequently, this study aims to fill the gap by demonstrating the extended BIM for Taiwan MRT that is capable of dealing with maintenance and resilience management over the life cycle. Depending on various environmental impacts, design parameters (such as radius of curvature which is affected by terrain and design speed) should be considered differently. Time consumption needed for construction and maintenance activities for different types of tracks is also a crucial factor to be embedded in the BIM. The human resource required in railway projects can depend on the amount of work and the size of the project, which can be implemented in the future extension of BIM.The application of BIM from the 1D to 6D approach has been widely used to support the construction of buildings and infrastructures in many projectsNavisworks. Navisworks v.2019 is used in this study to enhance the integration of the virtual model information (in Revit) and the maintenance schedule (e.g. by using multiple data layers and/or using data derived from other software such as MS Excel spreadsheet). Similar packages are also embedded in alternative software such asBentley BIM. After validation with field data obtained via the collaboration with Taiwan MRT , the digital twin has been used to demonstrate new insights on the sensitivity of material flow, hazard management, and lifecycle perspectives.This study adopts Taiwan MRT as a case study to demonstrate new capabilities of digital twins in order to help planning and managing maintenance and resilience in practice. BIM of the Taiwan MRT has been developed using Revit, and multiple layers of datasets have been embedded in the BIM to generate the digital twin. In this study, Revit has been used to establish the BIM. After creating the 3D BIM model through Revit, detailed components and assembly can be verified and the bill of quantities can be determined. The model can then be imported intoThe route. The track route of the Xinyi Line, which is known as the Red Line in Taiwan and has been chosen as a case study, is shown inUtilization of track steel. The steel rail type is UIC 60, which is manufactured according to the European Standard EN 13674-1. The UIC 60 rail steel is adapted to the Xinyi line with a standard track gauge. The route passes through the highly populated Taipei metropolitan area. Reduction of vibration during operation is important to ensure a good quality of life is maintained. Floating slab (FST) and non-ballasted tracks with high isolation (NBHI) have been chosen for the Taipei MRT railway track construction. The total upline length of FST (Red section) and NBHI (Green section) is about 420 m and 866 m, respectively; the total downline length of FST and NBHI is about 400 m and 881 m, respectively.Estimation of Greenhouse Gas Emissions (GHG). Reduction of CO2 and energy consumption is a significant concern to the green construction in value engineering, which means that prediction of GHG emissions is required via the whole LCA. British Standards Institution (BSI) proposed ISO 14064-1 in 2006 and has widely implemented the standards. ISO 14064-1, which is termed an international standard for calculating the total carbon footprint emissions during the production of a product, can be calculated usingI is the activities data,f is the parameter of GHG emissions andGWP is the coefficient of global warming potential which is given by the IPCC2007 report. TheGWP value of carbon dioxide is 1. The total carbon footprint is computed for all the stages of the entire LCA.. The computation of carbon emissions in the operation and maintenance of railways is based on the activities of the maintenance works and carbon emission from the power consumption of facilities, such as offices or maintenance sites. The GHG emission associated with materials is mostly in the manufacturing and processing stage. Railway components, turnouts, and conductor rails are the three main components in the maintenance routine. When the amount of material and energy are known, they are used to calculate the amount of carbon emission by using GHG emission coefficients.Where3D Modelling.. This can be conducted by remodeling the 3D model based on horizontal and vertical alignments, grade, and superelevation, which are available in the design report. The location of the track can also be identified in the design report. When the 3D model is developed, the material of each component can be defined to further used such as quantity take-off, cost estimation, and life cycle assessment. In this study, the model is used for the sustainable and digital maintenance aspects. The quantity of each material is employed to calculate the greenhouse gas emissions. Every component is also considered for the maintenance costs to be demonstrated later on. We have used the free version ofAutoCAD Revit 2020.2 to develop the 3D model of built environments, which is available to students, teachers, and educational institutions. Free, open source alternatives to AutoCAD Revit that can be used to replicate this study areFreeCAD,BIMSpot  can be detected in the clash detection feature. BIM has been used to analyze the material inventory and the flow throughout LCA. The main materials utilized in the railway construction are concrete, steel, and natural rubber, and the environmental risks to the railway construction have been determined using the schedule function that is included in the software. The material management (via BIM volumetric quantification) has been arranged by the bill of quantities, and the detailed information such as dimensions of components; and itemized costs have been input into BIM to achieve comprehensive integration.The frequency of track inspections is one of the critical factors influencing the quality and reliability of the railway infrastructures, since safety is more likely to be compromised if the period between maintenance inspections is much longer. Nevertheless, if the maintenance period is too short, this can increase costs and reduce time efficiency. The railway systems maintenance work has been clarified into two phases: corrective maintenance (CM), and preventative maintenance (PM). When damage has occurred in the construction or during the asset operation, the emergency repair needs to be done immediately, and so it is classified as break-down or CM. If the deterioration is found in construction or operational stages during the track inspection, and the aging parts are repaired or improved before the full damages or failures occur, it is termed PM. The MRT system is designed to be long-term service transportation in the metropolitan area, and so it is important to ascertain its resistance, safety and sustainability by effective maintenance that an appropriate maintenance schedule is required. PM is considered to be more desirable for the sustainability of the rail infrastructures since it gains more financial benefits than corrective maintenance. A comprehensive PM requires a suitable condition-based monitoring system to determine and prioritize risk profiles and the engineering team can promptly respond through adaptive maintenance works. In this study, the life cycle assessments take into account the maintenance schedule, costing and carbon emission in accordance with the preventive maintenance concept.Frequency of maintenance and cost estimation.The material cost has been determined in relation to the maintenance activities tabulated inMaterial usage. The material stock is important to the entire project, and appropriate management to monitor the material flows is vitally needed.Estimation of Greenhouse Gas Emissions (GHG). The GHG emission of the material has been embedded in the manufacturing phase. By using the digital twin of the Taipei MRT track section, the quantity of concrete, steel, rebars and rubbers (including energy consumption in their production) can be determined for the calculation of GHG. The results exhibit that the quantity of concrete, steel and rebars is about 37% (2310.63 tCO2e), 22% (1374.24 tCO2e.) and 41% (2528.21 tCO2e.) respectively (seeUnderlying data).. The power is approximately 5,928,043.234 kWh/ year, multiplied by the GHG emission factor of electricity, the total carbon emission is approximately 3017.37 tCO2e (seeUnderlying data).The carbon emission during the operation and maintenance is computed by using the electricity consumption of the depot, and is approximately 23.8 kWh/car.km3D modeling of the track. The 3D model of the Taipei MRT track section has been established in collaboration with Track Engineering Division of Taipei MRT., the main components to construct a ballastless railway track are rail steel, concrete track slab, fastening systems, and track support systems. FST slab beds, which are made by steel rebar frameworks and concrete, are manufactured off-site. According to a report published by the Department of MRT, the weight of the framework is about 2.5 to 3.5t based on the quantity takeoff using BIM, and the standard dimension of a track slab is 2510 mm × 1450 mm × 280 mm. The bed has 4 circular indentations, and that space is reserved for the bearing pads underneath the slab . The weekly inspection is to ensure that the facilities meet the safety standard, enabling predictive and preventative maintenance concepts. The three main costs in the inspection are thermite welding rail, track alignment abrasion checking, and track and conductor maintenance which are about £563.25 (32%), £480.35 (27%), and £351.36 (20%), respectively.Maintenance schedule and 3D model.Based on the results, it is very clear that, among all of the track components, the majority of GHG emission is derived from the track slabs. This is because track slabs have to redistribute and absorb high-intensity dynamic forces from the train prior to transferring to the track support and tunnel floor. On this ground, the track slabs have been conservatively designed, and then their resultant dimension and volume become overly large, of which the track slabs contribute to much higher consumption of materials (such as concrete and reinforcement), excessive cost and GHG emission. This implies that the next generation of track slabs requires better design and optimization toward net zero GHG emissions. This aspect indicates a new field of transdisciplinary research into more sustainable track slab systems.Surprisingly, the results based on Taipei MRT case study exhibit that, when considering throughout the life cycle, the construction phase of track infrastructures contributes the most GHG emission compared with train operation and asset maintenance phases. This is because Taipei MRT has already exercised green energy grids where the power and electricity used in railway network  are relatively clean (e.g. from solar power) and do not emit significant GHG. This demonstrates a new paradigm for other railway networks globally to learn from.When considering the risks and resilience in asset management, it is found that more frequent and robust track inspection regimes are required when the infrastructure is exposed to uncertain settings such as natura hazards and so on. The case study of real-life MRT has clearly demonstrated that the use of digital twin can significantly improve the efficiency and effectiveness of maintenance responses when defects or damages occur. This is because the digital twin can help (i) locate the defect accurately; (ii) promptly share and visualise information needed by related stakeholders in order to make a robust decision and act on the priority; (iii) create rapid and virtual collaboration that synergizes various expertise from all stakeholders; (iv) rapidly interact with on-side sensors and on-board condition monitoring systems that determine most up-to-date system integrity; (v) link with material stocks to determine the logistics and supply chain capacity of components and materials for repair and/or maintenance actions; and (vi) help engineers, maintainers and technicians to determine lifecyclce costs and GHG in order to make a decision appropriately that can lead to more sustainable construction and maintenance of railway infrastructures.After inputting maintenance records into Revit and Navisworks, and processing them via the schedule function that is included in Revit, examples of the replace and repair activities can be compiled  during the maintenance phase. According to differential damage conditions, the repair methods and maintenance actions can be different, and the required materials can vary during the maintenance phase . The following section presents the causes of damage and the methods to repair such damage found during the inspection(1)Concrete•For the interior attack, the corrosion can result in cracks on concrete when the active anode in the steel bars increase. For the shallow cracks, it can be filled with epoxy mortar after clear fragments and dust are stuck in the cracks. If the crack exceeds the acceptance, the parts should be replaced.•2.Carbonation is one of the main problems for the concrete since it can deteriorate the corrosion of the rebar inside. Epoxy coatings and silane-siloxane sealer cover on the surface of the concrete can decrease the electrochemical reaction with water and CO(2)Metal/ Steel/ Aluminum alloy•The risk of corrosion occurs due to concrete carbonation. The reinforcement inside the concrete is corrosively active especially when exposed to moisture. To stop the chloride contamination from aggressing further, coating the surface of the concrete can pause the degradation; however, the corrosion of the steel bars can be too severe, it should be replaced immediately.•For steel components with little corrosion, appropriate painting could be applied as a protection layer to stop oxidation (reaction between steel and oxygen after removing the rust part).•The steel rail should be replaced depending on the rate of abrasion (wear and tear), fracture, and fatigue failure; if the rail is not within the acceptable wear rate , the rail should be replaced immediately.(3)Rubber•The embrittlement and cracks can occur in the aging rubber and fastener due to residual moisture and ambient heat. Engineers and technicians need to assess the stiffness and damage condition of the elastomers and fasteners, if no cracks appear, the greases, dirt, water, etc should be removed to restore the parts. If cracks occur, the component should be replaced immediately., the flow of material influences the cost consumption and the efficiency of the workflow in the project.According to the different maintenance requirements of components in the MRT constructionSince the CK570H section is underground, the track is barely affected by weather conditions such as wind, rainfall, etc. However, some potential environmental impacts still need to be considered to avoid any unexpected situation causing damages or further risk to the infrastructures.(1)Flood. During 1991 – 2020, the average regional rainfall precipitation in Taipei was 236.85 cm. During the summer, typhoons can still produce significant precipitation such that the flooding leads to a breakdown of the MRT system. Another indirect disaster that causes flooding is an earthquake, the active fault would lead to the displacement of the underground. The breakage of the water pipes and underwater leaking from the cracks can result in serious flooding in the tunnel. The methods to avoid further damages to the railway system is presented below:Although most of MRT track system is the underground section, flooding can still incur if there is a heavy rainfall exceeding the drainage capacity in the area. Generally, the annual average rainfall precipitation over the world is about 100 cm•Installation of full-section floodgates in the underground tunnel is required. The system is then monitored and controlled by operators in the central control room (CCR). When flooding accidents incur, the emergency alarm will rise if the water level is over the acceptable capacity, and the floodgate would be closed to prevent the MRT systems from further damages.•The damage from the water ingress attacks the concrete, which is the key factor leading to material failure due to water contaminates. From the exterior side, a waterproof membrane, which is a cover on the concrete foundation, could be a water-resistant layer. From the interior side, the ingredients of the concrete could be adjusted to be waterproof concrete to improve the strength of the structure. However, they are the temporary protection to decrease the harms from this disaster; thus, detailed inspections must be conducted after the flood as soon as practically and/or reasonably possible.•BIM can be used to evaluate the risk and potential disasters in the future since the design stage. Varied parties can access the enhanced BIM model and jointly evaluate the level of risk through the enhanced BIM model. Then, the protective components and mitigation strategies can be developed, verified, appended, constructed, and estimated. Moreover, related parameters can be included in the enhanced BIM model during the maintenance and operation stages. For example, rainfall can be tracked using the enhanced BIM model in conjunction with field sensors to evaluate the probability of flooding. Then, risk management and inspection/monitoring regimes can be included in the digital twin to establish methodologies to promptly respond to each level of risk. In the case that severe situations and damage cannot be avoided, the repair costs can also be estimated using the digital twin.(2)Earthquake•. Not only could the earthquake indirectly lead to flood, but It could also cause damages to the MRT systems. To avoid any detrimental accidents, the following actions should be taken if the earthquake occurs:Since Taiwan is located on the seismic belt distribution, a high frequency of earthquakes occurs. The seismic monitoring system is used to collect the seismic data, and it is estimated that there are about 20,000 earthquakes s on average annually. Among all earthquakes, around 1,000 times is a classed as a feeble earthquakeThe earthquake could be monitored and controlled in the CCR by the environmental control system in near real time. The sensors, which are installed along the tracks and on-board vehicles, can send the information immediately to the control system. All the systems could be stopped when the alarm is raised in case of any further consequences (such as aftershocks). The seismic warning is categorized into 3 levels depending on the situation, and the CCR could determine whether it is appropriate to resume the operation. The displacement due to an earthquake could damage railway facilities. The inspection of track irregularity should be executed to ensure that geometric parameters of rails are within the tolerance range. If the parameters exceed the acceptance, it needs to be repaired immediately. In practice, railway construction is a mega project that usually involves many stakeholders and companies who can benefit from data integration and sharing. The lack of effectiveness in asset management may lead to serious accidents, especially in the operation and maintenance stage. Digital twin which acts as a powerful information platform (through the integration of BIM and Navisworks), can help to solve these problems. Not only can the digital twin contain a pool of information, but it also enables access to information throughout the whole life cycle of a project. By using the digital twin, all stakeholders relevant to the project can collaborate, co-create, and collect the latest progress in real-time. The database within the digital twin can help to achieve the sustainability goal by enabling efficient asset management and monitoring, and it could determine and control the carbon emission, cost estimation, and time management throughout the whole life-cycle.This study aims to demonstrate how a digital twin (integration of BIM and Navisworks) achieves project sustainability by the information integration in railway construction. Taipei MRT system is one of the main public transportations in Taiwan; and its construction has expanded the development growth of the metropolitan. The case study has demonstrated the ability of the digital twin to implement life cycle assessment, and revealed that the material inventory can be monitored by an interactive BIM model using Revit or equivalent . The case study has also demonstrated that the repair works can be executed smoothly through the digital twin during the maintenance stage. According to the different conditions in various parts/elements of the construction, the proper repair methods should be taken into account in the system design. It is apparent that Navisworks can help to monitor the schedule execution in real time. Its interaction with BIM can help engineers and infrastructure managers to efficiently arrange the flow of material stocks and effectively respond to the material demand base on the situations considering risks, vulnerability, and maintenance requirements.This study exhibits that digital twin is a technology that benefits project management, condition monitoring, and asset operation throughout the entire life cycle in real-time. In the case study, BIM acts as an integrated database that contains information on the design, construction, operation, maintenance, and decommissioning phases. The quality, efficacy and effectiveness of the operation and maintenance phase are then deeply correlated with the life-cycle assessments. In this study, the workflow and inventory of the material stocks are embedded in the BIM so that the repair methods and maintenance actions can be optimised to decrease the track component and material deterioration. It should be noted that a number of potential risks such as environmental factors can affect the track inspection plan. The integrity of materials and components is critical to operational safety and reliability of Taipei MRT network. Improper asset and maintenance management will lead to unplanned maintenance resulting in excessive cost and time, and potentially a delay of any maintenance task. On this ground, this study unprecedentedly demonstrates the use of digital twin to tackle sustainability and resilience challenges in railway asset management throughout the life cycle under uncertainties . It is noteworthy that this study has already resulted in a new guideline for digital twin adoption in Taipei MRT network for lifecycle asset management and resilience monitoring. The insights from this study can also help engineers, asset managers, infrastructure maintainers and other stakeholders to collaborate and co-create sustainability values for the railway industry globally. https://doi.org/10.5281/zenodo.5034476.Zenodo: Carbon emission and lifecycle costs supporting digital twins for managing railway maintenance and resilience.This project contains the following underlying data:- Project Calculation.xlsx. Creative Commons Attribution 4.0 International license (CC-BY 4.0).Data are available under the terms of the In general, this is a very good paper. It presents a study case of using BIM for Metro LCA. The interesting part is the paper stressed the GHG emissions. Only a few small viewpoints need justification. For example, the noise and vibration of ballasted track disturb residents may not be very precise. Because the noise of slab track in metro is also very big. The noise is mainly from the train braking and starting, especially the parts with rail corrugation. The prediction of CO2 can be very precise, however, predicting the maintenance is quite challenging. It seems the maintenance records of the metro line are not shown in the paper. Maybe, inputting some real maintenance, especially the corrective maintenance. Because it is easy to use the data of PM for analysis, however, including CM will make the study with more accurate prediction.Is the study design appropriate and does the work have academic merit?YesIs the work clearly and accurately presented and does it cite the current literature?YesIf applicable, is the statistical analysis and its interpretation appropriate?YesAre all the source data underlying the results available to ensure full reproducibility?YesAre the conclusions drawn adequately supported by the results?YesAre sufficient details of methods and analysis provided to allow replication by others?YesReviewer Expertise:railway engineering. railway ballast. DEM. Image analysisI confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. https://doi.org/10.5281/zenodo.5034476.The authors wish to thank the reviewer for the valuable comments and commendation. The CO2 data has been archived in European open data platform via Note that the real maintenance data has been adopted throughout this study as part of the collaborative project with Taipei MRT. In this paper, the context of noise and vibration (N&V) is only related to the N&V due to construction and maintenance activities. The use of slab track can yield lesser maintenance activities, which will help improve this issue. The paper is well written and can be accepted for indexing. It presents a case study where track 3D modeling is employed scientifically. The method suggested could be useful in more efficient management of track maintenance. The resilience aspects are also discussed in context of flood and earthquake. However the strategies suggested towards resilience against floods appear to be generic. It could be made more specific in terms of results obtained from BIM. The conclusions can be more focused and specific.Is the study design appropriate and does the work have academic merit?YesIs the work clearly and accurately presented and does it cite the current literature?YesIf applicable, is the statistical analysis and its interpretation appropriate?YesAre all the source data underlying the results available to ensure full reproducibility?No source data requiredAre the conclusions drawn adequately supported by the results?YesAre sufficient details of methods and analysis provided to allow replication by others?YesReviewer Expertise:Geotechnical Engineering, Earthquakes, DRRI confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. More details have added to the methodology part.Flood management aspect has been further discussed in the discussion part.More details have been appended in the result part.The authors wish to thank the reviewer for the valuable and highly constructive comments, which can help significantly improve the quality of the work. All review comments have been adopted in the revision and have been fulfilled in the following details: More detail was added to the methodology part.Flood management was more discussed in the discussion.More detail was included in the result part.The authors wish to thank the reviewer for the valuable comments, which can significantly improve the quality of the work. The comments were fulfilled in the following details:


All anesthesia providers, including nurse anesthetists and anesthesiologists work in a stressful environment with diverse tasks. The profession is characterized by high workload, both dependent and independent job descriptions, and unpredictable conditions. This study was designed and conducted to explain the factors affecting the workplace health of Iranian anesthesia teams.Twenty anesthesia team members including nurse anesthetists and anesthesiologists from 7 different hospitals were enrolled in this phenomenological research. The data were collected in 2022. Semi-structured interviews were used for data collection, and the transcripts were analyzed using qualitative content analysis.The most notable theme emerging from the data which was found to affect workplace health was consistency of anesthesia team. Other themes derived from the data included team tranquility and physical well-being.The participants' emphasis was more on behavioral and managerial factors affecting workplace health, and desirable interpersonal cooperation to create a suitable work environment for them was more prominent. These findings can raise the awareness of chief nurse anesthetists and planners to provide more effective teamwork, modify the job description structure, and reduce staff conflicts. All anesthesia providers, including nurse anesthetists and anesthesiologists work in a stressful environment with diverse tasks. The profession is characterized by high workload, both dependent and independent job descriptions, and unpredictable conditions . StudiesBased on WHO's definition of workplace health, there is an emphasis on the cooperation of employees and managers to create a process of continuous workplace improvement and promotion of health, safety and stability. Also, “Physical work environment”, “Psychosocial work environment”, “Personal health resources” and “Enterprise community involvement” are seriously affected in the anesthesia work environment .In Iran like most other countries, there are two different anesthesia care providers, namely nurse anesthetists and anesthesiologists. A nurse anesthetist has a bachelor's degree in anesthesia. They take care of patients' anesthesia needs before, during, and after surgery with the assistance, advice and supervision of anesthesiologists. When anesthesiologists and nurse anesthetists work together, the nature of their interactions can affect their patient care , 8. Due What is the nurse anesthetist and anesthesiologists' perspectives on health of the workplace in anesthesia environment?What factors  affect the health of work environment of nurse anesthetists and anesthesiologists?A phenomenology design was employed in the study to deepen our understanding of a healthy work environment in a natural setting. Personal interviews were conducted, and qualitative content analysis was performed. By careful examination and constant comparison, qualitative content analysis delves into the depth of individuals' experiences of specific phenomena. Its primary goal is to provide knowledge and understanding of the phenomena under study.via telephone if interested in participating. Thirty-eight employees (32 nurse anesthetists and 6 anesthesiologists) responded of whom 20 were chosen using a purposive sampling method allowing maximum variation in terms of age, gender, and experience to reflect the genuine structure of the anesthesia team in Iran. Sampling continued until data saturation  and they were in almost the same in terms of environmental, managerial, and organizational conditions including employee salaries and benefits. The participants were eligible to participate in the study if they: were anesthesiologists or nurse anesthetists with more than 2 years of clinical experience and had the ability to speak Persian to participate in the interviews. The exclusion criteria was having speech disorder or prior relationship with the research team. The number of staff in each department ranged from 15 to 50. Initial contact with the potential participants was made by written invitations placed in boards of the anesthesia departments in operating rooms explaining the study objectives and asking them to contact the lead researcher turation . To achiThis study was approved by the Ethics Committee of Ahvaz Jundishapur University of Medical Sciences (Ref. ID: IR.AJUMS.REC.1399.702), and an introductory letter was given to the lead researcher to conduct the study in the designated centers. Before starting the study, the lead researcher introduced himself to the participants, and they were briefed on the objectives of the study, the voluntary nature of participation in the study, withdrawal from the study at any time, the reason behind voice recording, information confidentiality, and the accessibility of information for all participants. Finally, informed consent was obtained from all participants.Qualitative, intensive, in-depth and semi-structured interviews were used to collect the required data. The interview guide included a number of open questions to allow participants to express their perceptions and experiences in detail. At the beginning of each interview, the participants were asked to discuss their experience of health in relation to their work environment. They were then asked to describe their perceptions and experiences about the factors  that affect the health of anesthesia teams' work environment. Focusing on the anesthesia team structure, the main questions were asked to extract ways to contribute to a better health-promoting work environment. The participants were also asked to give clear and tangible examples of their experiences. The transcript of the audiotaped interviews was written on the same day by the first author and was used as the original data. Data collection was conducted over 6 months from May 2022 to November 2022. Each interview was conducted in one session in a private room at the operating rooms unit after the working shift. Each session lasted from 40 to 90 min. To prevent the negative impact of participants' exhaustion on the interview, the interviews were conducted at the end of a shift when the workload of the participant was low or when the operating room was not active.Data were analyzed through content analysis following Lewis and Malecha . Each st(1) The content of the recorded interviews was transcribed verbatim and reviewed by the researchers several times to reach a general understanding.(2) Words, sentences, or paragraphs that were linked in terms of content were regarded as semantic units. The semantic units were summarized based on their content.(3) The semantic units reached a level of abstraction and conceptualization and were labeled by codes according to the concept underlying them.(4) The codes were compared according to their similarities and differences and classified with specified labels in more abstract classes.(5) Finally, by comparing different classes with deep and careful reflections, data content was introduced as the theme of the study.The Lincoln and Guba  criteriaA total of 20 participants including 14 nurse anesthetists, 3 chief nurse anesthetists and 3 anesthesiologists from 7 different hospitals were interviewed. Of the 20 participants enrolled in this study, 12 were females and 8 were males. From the deep and rich descriptions provided by the participants, 1,084 semantic units were extracted. After several reviews, the semantic units were summarized and classified on the basis of similarity. They were then summarized once again into three main themes and eight conceptual and abstract subthemes. The three main themes included consistency of the anesthesia team, team tranquility, and physical well-being .Participants considered the consistency of anesthesia teams as one of the most important strategies to promote workplace health. The anesthesia team operates in a stressful and unpredictable environment that is influenced by various individual, organizational and managerial factors. Lack of stability and acting based on personal taste on the part of both anesthesiologists and nurse anesthetists will negatively affect the results of their actions and lead to conflicts at workplace. Participants identified three key strategies effective in consistency the anesthesia team, namely perceptive and adaptive management, stability in team composition, and adherence to the defined job description.The main emphasis of most participants was on the management of anesthesia staff. In Iran, every operating room has a chief nurse anesthetist who is responsible for all activities of anesthesia nurses, including allocation of staff into operating rooms, coordination of the anesthesia team, and resolving possible problems and conflicts. Chief nurse anesthetists are on a regular morning shift every day and monitor staff performance. Arranging anesthesia teams in operating rooms according to the type of surgical procedure and assigning anesthesia nurses to the teams of each anesthesiologist are among their important responsibilities.The work of the chief nurse anesthetist is very influential in the structure of our team. It is important how tactfully he distributes the staff in the operating rooms. If the chief nurse anesthetist knows the staff well and knows the capabilities and personality traits of the staff, the most successful teams could be formed.” (Nurse anesthetist No 3)“Experienced and knowledgeable chief nurse anesthetists prevent a lot of conflicts and frustration among staff by properly dividing the workforce.” (Nurse anesthetist No 7)“From the participants' point of view, it was important for chief nurse anesthetists to pay close attention to the details of verbal and non-verbal behaviors of the staff as well as their motivations and abilities, and to have timely intervention when problems arise in promoting workplace health. In order to increase nurse anesthetists' satisfaction with their job, chief nurse anesthetists need to meet their physical and mental needs and establish balance between the newcomers and the experienced staff.Chief nurse anesthetists should not only focus on their routine tasks, but also be meticulous and able to identify the needs of their employees.” (Chief nurse anesthetist No 2)“In this study, the participants were selected from 4 university hospitals and 3 non-university hospitals. In university centers, although nurse anesthetists are fixed members of the anesthesia team, the presence of anesthesia residents as well as anesthesia nursing students in the operating rooms causes frequent changes in the composition of the anesthesia teams. In non-university centers, however, both anesthesiologists and nurse anesthetists are fixed members and are only distributed in different work shifts, leading to more stability in the composition of the members of the teams. This difference allowed the researcher to examine the frequent changes in the composition of the anesthesia team from the participants' point of view. The participants pointed out that when working with the same people in the team for a long period of time, they gain a good understanding of each other's level of theoretical knowledge, practical skills, and personality traits. This leads to an improved communication and greater coordination in the performance of the anesthesia team, making the staff feel less stress.Mutual recognition and trust come from constant collaboration. I have been working with nurse anesthetists here for almost 5 years. We know what to expect from each other and we have a stress-free environment.” (Anesthesiologist No 1)“A common problem for members of the anesthesia team is the overlap between the duties of anesthesiologists and nurse anesthetists. According to the participants, the following were the common problems associated with job description: lack of any precise definition of job descriptions, ineffective briefing of employees on their job description, lack of adequate supervision over proper implementation of job description, and as a result, lack of commitment of most anesthesia staff to their performance. Doing things that are outside the scope of specific job descriptions often leads to neglecting certain tasks, and under such circumstances, everyone waits for someone else to take the initiative and do that task. In addition, other consequences of undefined job description, from the participants' point of view, were conflicts between members of the anesthesia team, which will ultimately lead to increased stress.Here we do not know exactly what is considered as our duty and what counts as the duty of anesthesiologists. We have to adapt ourselves with different anesthesiologists whose expectations are different. This causes confusion and boredom.” (Nurse anesthetist No 6)“The second theme derived from the participants' experiences was Team tranquility. According to the participants, a calm and less stressful environment is a basic condition for the optimal performance of the team and creating a healthy atmosphere in the workplace. They pointed to three important strategies for achieving such an atmosphere: coworker trust, avoiding conflicts, and interpersonal justice.Anesthesia teams are formed by a limited number of members, often including only a nurse and an anesthesiologist. At university centers, anesthesia residents and anesthesia nursing students may be added to these. The team members work together frequently and continuously, and by increasing their knowledge of each other's capabilities and expectations, a feeling of mutual trust is created between them. From the participants' point of view, this trust provides comfort while providing care at the patient's bedside. Of course, there is a degree of distrust when it comes to working with newcomers. Also, a comparison between the experiences of university staff  and the private centers  shows the formation of more trust between team members in the latter.There are far fewer problems when staff work together for long periods of time. They know each other's working style better and can trust each other in certain situations.” (Chief nurse anesthetist No 1)“Here we have both a resident and a nursing student. There isn't such a thing as a fixed anesthesia team, and members change every day. This does not allow for the establishment of appropriate work relationships and mutual trust.” (Anesthesiologist No 3)“Due to the dense and busy nature of the anesthesia work environment, interpersonal and interdisciplinary conflicts are commonplace. According to the participants, the way staff cope with conflicts is different. However, conflict avoidance was introduced as a more successful solution than conflict resolution. They believed that in a situation where the staff are less likely to get involved in an atmosphere of controversy and competition, conflicts along with subsequent discomfort and stress are less likely to occur. The more intra- and inter-team conflicts are controlled, the more tranquility will be created in the anesthesia team.Experience has taught me that I should not argue with my co-workers or the anesthesiologists. I'd better get over some issues. That way I feel more relaxed. This is because I am the one to be harmed in conflicts.” (Nurse anesthetist No 11)“Employees are responsible for keeping their work environment healthy. Some are always looking for competition and tension and behave inflexibly. These conflicts make things difficult for all of us.” (Nurse anesthetist No 5)Members of the anesthesia team noted fairness and being fair in behavior as important factors contributing to interpersonal justice. Justice-based behavior was sought by chief nurse anesthetists, colleagues, and the organization. The participants believed that chief nurse anesthetists' observance of equality in patient allocation and distribution of personnel to different shifts and their fair division of tasks and facilities are effective on the well-being of the anesthesia team members.I try to be as fair as possible in allocating nurse anesthetists into operating rooms. If we always leave longer and more difficult surgeries to certain employees, they will be under a lot of pressure. They would compare themselves to their colleagues and this would disturb their peace and lessen their motivation.” (Chief nurse anesthetist No 2)“Our findings showed that another aspect of justice lies in the treatment of anesthesiologists with nurses. They may exhibit different behaviors depending on the level of experience, their intimacy with the nurse anesthetists, or the mental background they have of these nurses.Some anesthesiologists do not treat us all the same. They are too hard on novice nurses and give them less practical help. I can't make sense of this inequality and it upsets me.” (Nurse anesthetist No 12)“Also among the statements of the participants there were hints of dissatisfaction with organizational inequality between them and other nurses. They described the anesthesia workplace as too crowded, busy, and stressful compared to other wards, and believed that they were not appreciated for their efforts.Physical well-being, defined as the feeling of comfort and physical security in the operating room space, was considered as an effective factor in the health of the workplace. According to the participants, the two main aspects of physical health were operating room structure and workplace accommodations.The experiences of the anesthesia team members showed that the structure of the operating room has a significant role in facilitating their activities and controlling their fatigue and exhaustion. For example, proximity of operating rooms to the nursing station and the lounge can reduce frequent staff walking. In their view, sufficient operating room space for anesthesia staff to move around the patient's bed without disturbance, and the availability of anesthesia equipment and drugs, lead to less energy expenditure and more focus on patient care.Architectural design standards must be carefully observed in the structure of the operating room. For example, in some centers, the distance between operating rooms is too great, and on busy days I have to cover two or three rooms at the same time. Frequent walking this route is very tedious and time consuming.” (Anesthesiologist No 2)“Others insisted on providing ample space for rest, meetings, and anesthesia counseling. Due to the restricted space of the operating room and the constant presence of the anesthesia staff during an 8-h shift, the participants noted the importance of effective air conditioning and adequate lighting in reducing fatigue and stress.Our workplace has limited space with a lot of equipment and staff. What's more, there is no opportunity to leave the ward to relieve fatigue and take a breather. It will be very difficult to bear.” (Nurse anesthetist No 8)“Workplace accommodations were identified as any the availability of any equipment which contributes to the well-being of anesthesia staff in the operating room. Long hours of standing on the patient's bedside leads to fatigue and eventually getting bored with the work environment. The participants insisted that they needed to rest and relax between surgeries. This was said to be achieved by providing facilities such as a roomy lounge equipped with facilities for eating and drinking. Also, the use of ergonomic chairs for long sitting on the patient's bedside was a major factor in promoting physical health from the perspective of the interviewed anesthesia staff.Colleagues in each shift find short opportunities between operations to rest, which must be a comfortable room with sufficient facilities. A room with a bed and facilities for serving drinks and watching TV in those few short minutes; this helps a lot to refresh the staff.” (Chief nurse anesthetist No 1)“The most important finding of the present study was the emphasis on maintaining team unity in the promotion of health in the workplace. As nurse anesthetists and anesthesiologists work together to provide anesthesia care, a platform for close and ongoing interdisciplinary collaboration is created. Most of the health threats involve the entire anesthesia team, and health promotion strategies should be sought in the management of the anesthesia team.Consistency of the anesthesia team as one of the main themes of this study means formation of stable anesthesia teams and establishment of interpersonal relationships between their members. While nurse anesthetists are independent professionals, their performance depends largely on the competence, skills and willingness of anesthesiologists to cooperate with them to provide optimal care during anesthesia . To dateIn this study the effective techniques of chief nurse anesthetists in controlling this condition were defined as perceptive and adaptive management. The managerial capabilities of chief nurse anesthetists in a complex and dense anesthesia work environment play a vital role in improving the health of team members. Chief nurse anesthetists' purposeful planning and tactful organization of forces to form anesthesia teams leads to stability in team composition. The distribution of forces and patient allocation should be based on not only their level of knowledge, ability, and experience but also the surgical procedure and anesthesia methods used. This helps to form strong anesthesia teams with the least change in composition. Chief nurse anesthetists have a special responsibility to create opportunities for team members to communicate with each other and thereby enhance patient safety and outcome . By the Another theme of the study was Team tranquility, which generally emphasized an atmosphere of trust, justice, and collaboration in the operating room among anesthesia colleagues. Coworker trust and avoiding conflicts are directly related and largely indicative of the same thing, namely team tranquility. Interpersonal trust is built upon members' knowledge of each other's expectations as well as ensuring each other's professional skills and competence . AnestheFinally, the physical health of the anesthesia workplace was defined by the members as the feeling of comfort and physical security in the operating room. They considered the structure of operating rooms to be the most important cause of fatigue and burnout, and stated that the necessary criteria for the easy travel and settlement of colleagues and their communication with each other were not observed in most surgical places. This seems to be more related to the architectural design of the operating room. Davies et al. stated that the successful performance of anesthesia team members relies on optimization of the ergonomics of the operating room, and if due attention is not paid to these details, their performance will be disrupted. According to their results, temperature, humidity, adequate lighting, and visibility or availability of equipment needed by the anesthesia team member in the operating room are influencing factors in this regard . MoreoveOur study is worthwhile in that it dealt with a little understood phenomenon and came up with important findings. However, there are a number of limitations that should be addressed. First shortcoming of this study is self-selection bias. The greater likelihood of participation of interviewees with good speaking skills may have affected our results. Given the large number of nurse anesthetists participating in this study, there is a possibility of bias in the findings. In fact, more than half of all participants were nurse anesthetists, and this may have skewed the results toward their attitudes as opposed to those of the anesthesiologists. Of course, more anesthesiologists were supposed to be recruited to alleviate this limitation, but due to their OR cases and schedules, this was not possible.Despite these limitations, the present study is worthwhile due to the credibility of data analysis. Credibility was enhanced in this study as only one researcher who had no affiliation with the institutions or the participants conducted the interviews. Also taking field notes to capture information and verification of transcript accuracy enhanced the credibility of this study.In the present study, interviews were conducted with all members of the anesthesia team, including anesthesiologists, nurse anesthetists, and chief nurse anesthetists, in order to explore the factors affecting workplace health from their perspective. Findings showed that the participants' emphasis is more on behavioral and managerial factors and that desirable interpersonal cooperation in creating a suitable work environment for them is more prominent. These findings can raise the awareness of chief nurse anesthetists and planners to provide more effective teamwork, modify the job description structure, and reduce staff conflicts. Further studies should include senior chief nurse anesthetists, including anesthesiologists and nurse anesthetists.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The studies involving human participants were reviewed and approved by Ahvaz Jundishapur University of Medical Sciences. The patients/participants provided their written informed consent to participate in this study.AK: conceptualization, methodology, formal analysis, writing—review and editing, and project administration. NS: conceptualization, methodology, data curation, formal analysis, software, investigation, and writing-original draft. SA: conceptualization, methodology, formal analysis, writing—review and editing, and supervision. All authors contributed to the article and approved the submitted version.


Numerical simulations of collapsing air bubbles considering complex and more accurate equations of state (EoS) for estimating the properties of both the liquid and gas are presented. The necessity for utilising such EoSs in bubble collapse simulations is illustrated by the unphysical (spurious) liquid temperature jump formed in the vicinity of the bubble-air interface when simplified EoSs are used. The solved fluid flow equations follow the mechanical equilibrium multiphase method of Kapila. The solver is coded in the AMReX platform, enabling high-performance computation with parallel processing and Adaptive Mesh Refinement for speeding up simulations. It is initially demonstrated that the frequently used Stiffened Gas (SG) EoS overpredicts the liquid temperature at high compression. More sophisticated EoS models, such as the International Association for the Properties of Water and Steam (IAPWS), the Modified Noble Abel Stiffened Gas (MNASG) and a modified Tait EoS introduced here, are also implemented into the flow solver and their differences are highlighted for bubble collapse cases for the first time. Subsequently, application of the developed model to cases of practical interest is showcased. More specifically, simulations of bubble collapse near a solid wall are presented for conditions simulating shock wave lithotripsy (SWL). It is concluded that for such cases, a maximum increase of  For example, experiments show that the cavitation damage to the material is affected by liquid temperature by varying the liquid-jet impact force It should be noted that the surrounding liquid temperature does not remain constant at different collapse stages depending on the settings. For example, it increases during the course of a given HIFU treatment As zero-dimensional bubble dynamics models cannot simulate non-spherical bubble collapses, CFD methods have been used to model the liquid thermal effects; in the vast majority of relevant studies, the liquid is deemed incompressible and further the Ideal Gas (IG) EoS is utilised. For example, Fursenko et al. However, the dynamics of bubble rebound are affected by the incompressibility assumption The above review shows that simplified thermodynamic assumptions that have been utilised in the vast majority of numerical studies, mainly due to the complexities associated with advanced EoS. It also should be noted that the various EoSs exhibit different accuracy in modelling thermal effects. For instance, in Diffuse Interface Methods (DIM) are widely used for CFD simulation of bubbly flows The rest of this paper is organised as follows: the various liquid EoSs utilised are compared and their differences are highlighted in 2The thermodynamic assumptions that affect the materials involved in bubble dynamic cases can play a detrimental role in the temperature distributions and even the dynamics of bubble collapse, although to a much lesser extent. The EoS can play a detrimental role in capturing the aforementioned variations of density during bubble collapse and can shed light on dissipation mechanisms. Further, the formulation of the EoS has a more intrinsic role, as it can affect the predictions of compression heating of the liquid, and thus, consequently influencing the temperature distribution and the heat transfer . In fact, in the former work of the authors 2.1This is a polytropic-type EoS The implication of this equation is that for any EoS written in the form of While common liquids exhibit weak compressibility, the intense conditions during bubble collapse can lead to significant compressions, reaching magnitudes of many GPa. Furthermore, since in reality the liquid density is affected by temperature also, the aforementioned compression will produce heating of the liquid. On the other hand, the simple liquid EoSs that consider density variations of density due to temperature can greatly overestimate this heating. A particular example of such a model, commonly used in bubble dynamics 2.21.The speed of sound should vary with respect to temperature and, at high pressures, decrease with increase of temperature. Here a function in the form of 2.tanh. Hence, a suitable candidate can have the form:The isobaric density variation with respect to temperature should have an inflexion point, due to the presence of the critical point. Naturally, this can be expressed by using a sigmoid function, such as Expressing Eq. The selected functions Apart from density relation to pressure and temperature, thermodynamic relations for the enthalpy, entropy, speed of sound need to be defined. For heat capacity at constant pressure there are constraints to be satisfied for the EoS to be consistent. In particular, from the definition of enthalpy The integral above comes directly from the choice of EoS; the only degree of freedom for adjusting Similarly, entropy can be obtained by integrating:Further, various derivatives of density and enthalpy can be defined, once the respective formulation is obtained, as 2.3The SG EoS involves molecular attractive and agitative forces. The aim of the Noble Abel Stiffened Gas (NASG) is to add repulsive forces to the SG EoS in order to reduce the density error as shown in The NASG coefficients for liquid water are presented in In It is noted that a set of 2.4To demonstrate the applicability of the modified Tait EoS both in terms of temperature and density prediction, isentropic compression of liquid water is examined in It becomes apparent that the above can play an important role in research on heat transfer of collapsing bubbles; over/under-prediction of liquid temperature due to the adopted EoS can affect the heat fluxes to or from the bubble. Furthermore, the overestimation of compression heating can be observed even at passing shock waves, emitted during bubble collapses as will be shown in the results section.Advanced models such as IAPWS come with a larger complexity, which makes them rather cumbersome to implement. Whereas tabulation methods can be applied see  to expedIn the present study, the aforementioned thermodynamic closures, i.e., IAPWS, modified Tait, MNASG, and SG for liquid and RKPR for gas are implemented on a multiphase DIM known as Kapila model outlined in the subsequent section. While MNASG and SG EoSs are applied in their parametric forms, the IAPWS data, modified Tait, and RKPR EoSs are implemented through tabulated format first because of the intricate nature associated with implementation and secondly for faster computation 3There are many multiphase methods developed for compressible flows in the literature. Those with the least restrictive assumptions consider that the phases are in complete disequilibrium where:As the system of Eq. in which:The finite volume cell index in The mixture internal energy The mixture rule for the internal energies is considered as:However, for the more complex equations of state, tabulated or parametric, there is no analytical solution of Eq. At each stage, the mixture pressure is computed using the mixture rule for the internal energy 3.1In the present work, the Kapila model with advanced thermodynamics has been implemented in the open source package AMReX 4In this section, we initially investigate the role of the EoS for a pure water shock tube test case. Following that, a spherical bubble collapse is simulated and the results are compared with our previous work In all simulations, three levels of grid refinement are considered, which lead to the grid-independent results. Moreover, there is a minimum volume fraction 4.1Shock tube problems serve as benchmark tests for the predictive capability of EoSs. Herein, a 3 m long pure water shock tube case has been considered as described in 4.2The purpose of this test case is twofold; firstly, to validate the solver against widely used bubble collapse cases and secondly, to compare the results against those reported in For comparison purposes, the RKPR and SG EoSs have been selected for the gas and liquid phases, respectively, similarly to our former study After presenting the aforementioned benchmark cases, demonstration of the relative errors that can result from the SG EoS will be reported. In this regard, the initialisation of the previous case is slightly modified by replacing the liquid density with its temperature and lowering the initial pressure ratio as shown in Since the IAPWS and the modified Tait fail at higher compressions, a stronger collapse with the initial 4.3One of the diverse applications of ultrasound cavitation in biomedicine is shock wave lithotripsy (SWL). The mechanism of lithotripsy involves producing short focused microsecond pulses that cause shockwave penetrating the body at a target site. During a treatment session, numerous pulses are administered, typically at frequencies ranging between A simplified representation for SWL can be examined as follows. A compressive shock front from the upper boundary depicted in Initially, the pressure is atmospheric in the whole computational domain; the water and air densities are The temporal variation of the bubble volume is initially shown in Further details of the collapse process are illustrated in the following plots. More specifically, the relevant pressure and numerical Schlieren contours from various moments during the collapse are showcased in In order to gain a deeper insight into the dynamic evolution of liquid temperature, temperature contours are presented in According to Finally, the heatmap of the temporal change of the liquid temperature along the rigid wall is depicted in 5In the current study, we expand the Kapila model to incorporate complex EoSs for both the liquid and gas phases. Since real gas effects during bubble collapses were extensively discussed in our former work, the present work has focused on the thermal effects induced in the liquid phase. Particularly, the deficiencies of EoS for the liquid state ought to both the unphysical specific heat ratio and the absence of terms considering repulsive molecular effects was showcased. It was observed that the SG EoS leads to above The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.


Hibiscus syriacus L. flower (HSF) is a food ingredient commonly used for tea, and previous animal studies have reported its sleep-promoting effect. This study aims to test the potential of HSF extract as functional food that improves sleep in humans.Eighty participants with sleep disturbances who meet the inclusion/exclusion criteria will be enrolled in this study. Since the effect of HSF extract on sleep is considered to be that of a functional food rather than a medicine, participants with severe insomnia will be excluded from the study. The enrolled participants will be randomly assigned to the HSF extract or placebo groups in a 1:1 ratio. The HSF extract and placebo capsules will look identical, and participants, investigators, and outcome assessors will be blinded to the allocation. Four capsules of HSF extract or placebo will be orally administered 30–60 min before bedtime for 4 weeks. The primary outcome of this study will be the change in the Pittsburgh Sleep Quality Index (PSQI) global score from the baseline after 4 weeks. The subjective and objective changes in the participants’ sleep will be evaluated using the Insomnia Severity Index (ISI), Epworth Sleep Scale (ESS), sleep diary, and polysomnography (PSG). The occurrence of adverse events will be closely monitored.The results of this trial will provide data on the efficacy and safety of HSF extract in enhancing sleep quality. Based on the results, the potential of HSF extract as a functional food that improves sleep in humans will be evaluated, and the findings of the trial will be submitted to the Korean Ministry of Food and Drug Safety for consideration as a new functional ingredient that may help to improve sleep quality.https://cris.nih.go.kr/cris/search/detailSearch.do/21497.: Clinical Research Information Service: KCT0007314; Registered 19 May 2022,  Sleep is essential factor for maintaining physical and psychological well-being . Poor slSeveral functional foods have been suggested as potential aids for improving sleep quality , 9, 10. Hibiscus syriacus L. flower (HSF) is a food ingredient  global score of 5 or higher, Insomnia Severity Index (ISI) score between 8 and 21, and who agree to participate and sign the informed consent form will be included.The exclusion criteria are as follows: participants with severe diseases in cardiovascular system, immune system, respiratory system, gastrointestinal/hepatic and biliary system, kidney and urinary system, nervous system, musculoskeletal system, infectious disease, or malignant tumor; with diseases or symptoms that could affect sleep, such as nocturia; with mental diseases, including alcohol-use disorder, major depressive disorders, generalized anxiety disorders, post-traumatic stress disorders, and obsessive–compulsive disorder; with a past history of or currently suffering from schizophrenia or bipolar disorder; with cognitive decline; with sleep disorders including insomnia, narcolepsy, obstructive sleep apnea, and restless legs syndrome; with irregular sleep patterns due to night-shifts; current smokers, heavy caffeine drinkers, or excessive alcohol drinkers; those taking medications or dietary supplements that could affect sleep within 4 weeks. To exclude participants with clinical depression and anxiety, the Patient Health Questionnaire-9 (PHQ-9) (cut-off: 10 points)  and GeneFour capsules containing HSF extract or placebo will be orally administered 30–60 min before bedtime for 4 weeks. The investigational products are manufactured as brown-colored hard capsules. One HSF extract capsule (500 mg) includes 250 mg of HSF extract as an active ingredient. The participants in the HSF extract group will take 1,000 mg of HSF extract per day. Placebo capsules have an appearance identical to that of the HSF extract capsules and contain maltodextrin and no active ingredients.Discontinuing or modifying the allocated intervention is not planned, except in case of the participant’s refusal. To monitor adherence, the pharmacists will check for compliance at every visit after prescribing the HSF extract or placebo capsules, and all the remaining capsules will be returned to the clinical pharmacies. During the study period, concomitant care or interventions will be prohibited, except in exceptional cases. Only those medications, dietary supplements, and other treatments initiated before participation in this study that will not affect the results of this study can be permitted. Furthermore, even during the course of the study, if the administration of a medicine is required for the transient treatment of other diseases and the medication is considered to not affect the result, it can be permitted.The primary outcome of this study is the change from the baseline of the PSQI , 30 globThe secondary outcomes include the ISI , 32 and The primary objective of this clinical trial is to evaluate the superiority of the PSQI global score improvement in the HSF extract group compared to that in the placebo group. To estimate the mean difference of the PSQI global score between both groups and the pooled standard deviation, the results of a previous randomized trial  will be Adults with sleep disturbance are being recruited based on the outpatients of two university hospitals in Korea. The clinical sites are located in two metropolitan cities in Korea: Seoul and Daegu. A poster regarding this clinical trial is being posted on the bulletin board and internet homepage of both the hospitals. To enhance the recruitment rate, local advertisements can also be conducted at the bus stops near the hospitals.® system (version 9.4). The allocation ratio for the HSF extract and placebo was 1:1, and the block size was concealed from the other investigators. An investigator affiliated with Dongkook Pharmaceutical, who is in charge of the management of the random allocation sequence and packaging of investigational products, packed the HSF extract capsules and placebo capsules according to the allocated random number. The investigational products were packed identically, and each random number was labeled in the package. The investigators in charge of the enrollment of participants were blinded for the allocation sequence and sequentially assigned the random numbers to the enrolled participants.An independent statistician generated the random allocation sequence using the randomization program of the SASThe participants of the trial, investigators, and outcome assessors will be blinded to the group assignment. Placebo and HSF extract capsules have been developed to have an identical appearance. Concealed envelopes containing information on the group assignment of each random number are being managed by the principal investigators at the two sites. These concealed envelopes will not be disclosed until the completion of this clinical trial unless unblinding is inevitable owing to serious adverse drug reactions or important clinical issues. In such cases, the investigators should immediately contact the sponsors and provide detailed information about the situation. The sponsors and investigator, only after thorough examination, will decide whether or not code breaking for the participant is necessary. The process and reason for the unblinding will be recorded, and the unblinded participants will be dropped from the trial.The validated Korean versions of the PSQI , ISI 3232, and EIn the screening process, the PHQ-9  and GAD-The data obtained from the source documents, such as questionnaires, worksheets, and medical records, will be entered into an electronic Case Report Form (eCRF). Using the validation data system of eCRF, data ranges are set for each value, and a query will appear when outlier data are entered. Full Source Data Verification (SDV) for data entered into the eCRF will be conducted during routine monitoring visits. In addition, prior to trial initiation, a data management plan has already been prepared. The system query of the eCRF is planned to be checked bimonthly.The main population to be analyzed for evaluating efficacy is the Per Protocol (PP) set, and Full Analysis (FA) set will be used supplementary. The PP set will include participants who complete the trial without major deviations from the planned protocol. The FA set will include an additional population for evaluating the efficacy and will include participants who are randomized into groups and who complete more than one assessment after the administration of the investigational products. The main analysis population for evaluating safety will be the safety set, which includes participants administered the investigational products more than once. In the primary and secondary outcomes, there will be no missing data in the PP set, and missing data in the FA set will be imputed using the last observation carried forward method.t-test or Wilcoxon rank sum test, according to the normality of data. Additionally, changes in the PSQI global score over time in each group will be compared using a paired t-test. A generalized linear model (GLM) with covariates of caffeine consumption, age, body mass index, smartphone usage time, and drinking habits can also be conducted. In case of significant differences in baseline characteristics between the two groups, these baseline characteristics can be considered as covariates in conducting the GLM.The change from the baseline PSQI global score at 4 weeks between the two groups will be compared using a two-sample The statistical method used for analyzing secondary outcomes is identical to that used to analyze the primary outcome.The estimated risk of the trial is low because the investigational product of this trial is a food. A data monitoring committee is not required and an interim analysis is not planned.A contract research organization hired by sponsors will monitor the clinical trial to verify the process of informed consent acquisition, conduct the trial in compliance with the approved protocol, and obtain accurate and complete trial data. The initial monitoring visits for each site are scheduled within 7 days of the enrollment of the first participant. Routine monitoring will also be conducted 10–11 times at each site.Adverse events will be carefully assessed through non-directive questioning during the trial period. The symptoms and signs of adverse events in participants will be collected at every visit, and their severity and causality will be assessed. Blood and urine tests will be conducted before and after the intervention, and clinically significant abnormal results will be assessed. Owing to the characteristics of the investigational product as a health functional food, product-related severe adverse events are not expected, and mild dyspepsia may occur.This clinical trial aims to test the potential of HSF extract as functional food for sleep improvement in humans. Approximately one-third of the general population has low-quality sleep, whereas approximately 6–15% of the population is diagnosed with insomnia disorders .Regulations governing functional foods differ between countries. In the United States, there are three categories of health-related claims: nutrient content claims, structure/function claims, and health claims . HoweverIn Korea, functional ingredients are divided into two categories: those that have been notified by the Ministry of Food and Drug Safety (MFDS) and those that undergo individually recognized by the MFDS . The forThis study protocol has some limitations. First, this is the first human study on the effect of HSF extract on sleep improvement, and no previous study has calculated the effect size of HSF extracts. Therefore, we estimated the effect size of HSF extract on sleep improvement based on the results of a previous randomized trial with a similar design. Second, there are some limitations to measuring sleep using PSG in the hospital for a single night , 47. AltThis protocol was approved by the Institutional Review Boards (IRB) of Kyunghee University Hospital at Gangdong (IRB No. KHNMC 2021–11-024) and Keimyung University Dongsan Hospital (IRB No. DSMC 2021-11-07). In case protocol amendments are required, before applying the changes, approval from both the IRBs will be obtained for the revised version of the protocol. The current version of the protocol is 1.2 (date: 2022-01-10).Prior to the screening process, investigators delegated by the principal investigators will provide sufficient information on this clinical trial, and participants will have adequate time to decide whether or not to participate in this clinical trial. If a person decides to participate voluntarily, written informed consent will be obtained from them.To protect the confidentiality of participants, the initial and not the name of each participant will be entered into the eCRF, and each participant will be identified by the screening number of this trial. The two sponsoring institutes  will have access to the final trial dataset, and a blind review will be conducted to confirm the analysis set before the data is locked.The research findings will be submitted to and published in peer-reviewed journals. In addition, the efficacy and safety results of this trial will be submitted to the Korean MFDS for individual recognition of the new functional ingredient as one that “may help to improve sleep quality.”The studies involving human participants were reviewed and approved by the Institutional Review Board of Kyunghee University Hospital at Gangdong and the Institutional Review Board of Keimyung University Dongsan Hospital. The patients/participants provided their written informed consent to participate in this study.ML, YP, CY, DK, and KL have made contributions to the conception and design of the work. YC has drafted the manuscript. All authors substantively revised it, read, and approved the final manuscript.This research was supported by a grant from the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (IPET) through the Technology Commercialization Support Program, funded by the Ministry of Agriculture, Food and Rural Affairs (MAFRA) (821020-3).Hibiscus syriacus L. extract on improving sleep disturbance. YP, DK, and KL were employed by Dongkook Pharm. Co., Ltd.ML was holding a patent for The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.