The continuous and excessive emission of CO_(2)into the atmosphere presents a pressing challenge for global sustainable development.In response,researchers have been devoting significant efforts to develop methods for...The continuous and excessive emission of CO_(2)into the atmosphere presents a pressing challenge for global sustainable development.In response,researchers have been devoting significant efforts to develop methods for converting CO_(2)into valuable chemicals and fuels.These conversions have the potential to establish a closed artificial carbon cycle and provide an alternative resource to depleting fossil fuels.Among the various conversion routes,thermochemical CO_(2)reduction stands out as a promising candidate for industrialization.Within the realm of heterogeneous catalysis,single atom catalysts(SACs)have garnered significant attention.The utilization of SACs offers tremendous potential for enhancing catalytic performance.To achieve optimal activity and selectivity of SACs in CO_(2)thermochemical reduction reactions,a comprehensive understanding of key factors such as single atom metal-support interactions,chemical coordination,and accessibility of active sites is crucial.Despite extensive research in this field,the atomic-scale reaction mechanisms in different chemical environments remain largely unexplored.While SACs have been found successful applications in electrochemical and photochemical CO_(2)reduction reactions,their implementation in thermochemical CO_(2)reduction encounters challenges due to the sintering and/or agglomeration effects that occur at elevated temperatures.In this review,we present a unique approach that combines theoretical understanding with experimental strategies to guide researchers in the design of controlled and thermally stable SACs.By elucidating the underlying principles,we aim to enable the creation of SACs that exhibit stable and efficient catalytic activity for thermochemical CO_(2)reduction reactions.Subsequently,we provide a comprehensive overview of recent literature on noble metal-and transition metal-based SACs for thermochemical CO_(2)reduction.The current review is focused on certain CO_(2)-derived products involving one step reduction only for simplicity and for better understanding the SACs enhancement mechanism.We emphasize various synthesis methods employed and highlight the catalytic activity of these SACs.Finally,we delve into the perspectives and challenges associated with SACs in the context of thermochemical CO_(2)reduction reactions,providing valuable insights for future research endeavor.Through this review,we aim to contribute to the advancement of SACs in the field of thermochemical CO_(2)reduction,shedding light on their potential as effective catalysts and addressing the challenges that need to be overcome for their successful implementation as paradigm shift in catalysis.展开更多
This study presents the multifunctional characteristics of multi-walled carbon nanotube(MWCNT)/polypropylene random copolymer(PPR) composites enabled via fused filament fabrication(FFF) under monotonic and quasi-stati...This study presents the multifunctional characteristics of multi-walled carbon nanotube(MWCNT)/polypropylene random copolymer(PPR) composites enabled via fused filament fabrication(FFF) under monotonic and quasi-static cyclic compression. Utilizing in-house MWCNT-engineered PPR filament feedstocks, both bulk and cellular composites were realized. The morphological features of nanocomposites were examined via scanning electron microscopy, which reveals that MWCNTs are uniformly dispersed. The uniformly dispersed MWCNTs forms an electrically conductive network within the PPR matrix, and the resulting nanocomposite shows good electrical conductivity(~10^(-1)S/cm), improved mechanical performance(modulus increases by 125% and compressive strength increases by 25% for 8 wt% MWCNT loading) and pronounced piezoresistive response(gauge factor of 27.9-8.5 for bulk samples)under compression. The influence of strain rate on the piezoresistive response of bulk samples(4 wt% of MWCNT) under compression was also measured. Under repeated cyclic compression(2% constant strain amplitude), the nanocomposite exhibited stable piezoresistive performance up to 100 cycles. The piezoresistive response under repeated cyclic loading with increasing strain amplitude of was also assessed.The gauge factor of BCC and FCC cellular composites(4 wt% of MWCNT) with a relative density of 30%was observed to be 46.4 and 30.2 respectively, under compression. The higher sensitivity of the BCC plate-lattice could be attributed to its higher degree of stretching-dominated deformation behavior than the FCC plate-lattice, which exhibits bending-dominated behavior. The 3D printed cellular PPR/MWCNT composites structures were found to show excellent piezoresistive self-sensing characteristics and open new avenues for in situ structural health monitoring in various applications.展开更多
Biopolymers are promising environmentally benign materials applicable in multifarious applications.They are especially favorable in implantable biomedical devices thanks to their excellent unique properties,including ...Biopolymers are promising environmentally benign materials applicable in multifarious applications.They are especially favorable in implantable biomedical devices thanks to their excellent unique properties,including bioactivity,renewability,bioresorbability,biocompatibility,biodegradability and hydrophilicity.Additive manufacturing(AM)is a flexible and intricate manufacturing technology,which is widely used to fabricate biopolymer-based customized products and structures for advanced healthcare systems.Three-dimensional(3D)printing of these sustainable materials is applied in functional clinical settings including wound dressing,drug delivery systems,medical implants and tissue engineering.The present review highlights recent advancements in different types of biopolymers,such as proteins and polysaccharides,which are employed to develop different biomedical products by using extrusion,vat polymerization,laser and inkjet 3D printing techniques in addition to normal bioprinting and four-dimensional(4D)bioprinting techniques.It also incorporates the influence of nanoparticles on the biological and mechanical performances of 3D-printed tissue scaffolds,and addresses current challenges as well as future developments of environmentally friendly polymeric materials manufactured through the AMtechniques.Ideally,there is a need for more focused research on the adequate blending of these biodegradable biopolymers for achieving useful results in targeted biomedical areas.We envision that biopolymer-based 3D-printed composites have the potential to revolutionize the biomedical sector in the near future.展开更多
As big data,Artificial Intelligence,and Vehicle-to-Everything(V2X)communication have advanced,Intelligent Transportation Systems(ITS)are being developed to enable efficient and safe transportation systems.Electronic T...As big data,Artificial Intelligence,and Vehicle-to-Everything(V2X)communication have advanced,Intelligent Transportation Systems(ITS)are being developed to enable efficient and safe transportation systems.Electronic Toll Collection(ETC),which is one of the services included in ITS systems,is an automated system that allows vehicles to pass through toll plazas without stopping for manual payment.The ETC system is widely deployed on highways due to its contribution to stabilizing the overall traffic system flow.To ensure secure and efficient toll payments,designing a distributed model for sharing toll payment information among untrusted toll service providers is necessary.However,the current ETC system operates under a centralized model.Additionally,both toll service providers and toll plazas know the toll usage history of vehicles.It raises concerns about revealing the entire driving routes and patterns of vehicles.To address these issues,blockchain technology,suitable for secure data management and data sharing in distributed systems,is being applied to the ETC system.Blockchain enables efficient and transparent management of ETC information.Nevertheless,the public nature of blockchain poses a challenge where users’usage records are exposed to all participants.To tackle this,we propose a blockchain-based toll ticket model named AnonymousTollPass that considers the privacy of vehicles.The proposed model utilizes traceable ring signatures to provide unlinkability between tickets used by a vehicle and prevent the identity of the vehicle using the ticket from being identified among the ring members for the ticket.Furthermore,malicious vehicles’identities can be traced when they attempt to reuse tickets.By conducting simulations,we show the effectiveness of the proposed model and demonstrate that gas fees required for executing the proposed smart contracts are only 10%(when the ring size is 50)of the fees required in previous studies.展开更多
A significant fraction of the conventional oil reserves globally is in carbonate formations which contain a substantial amount of residual oil. Since primary and secondary recovery methods fail to yield above 20%-40%o...A significant fraction of the conventional oil reserves globally is in carbonate formations which contain a substantial amount of residual oil. Since primary and secondary recovery methods fail to yield above 20%-40%of original oil in place from these reserves, the need for enhanced oil recovery(EOR) techniques for incremental oil recovery has become imperative. With the challenges presented by the highly heterogeneous carbonate rocks,evaluation of tertiary-stage recovery techniques including chemical EOR(c EOR) has been a high priority for researchers and oil producers. In this review, the latest developments in the surfactant-based c EOR techniques applied in carbonate formations are discussed, contemplating the future direction of existing methodologies. In connection with this, the characteristics of heterogeneous carbonate reservoirs are outlined. Detailed discussion on surfactant-led oil recovery mechanisms and related processes, such as wettability alteration, interfacial tension reduction, microemulsion phase behavior, surfactant adsorption and mitigation, and foams and their applications is presented. Laboratory experiments, as well as field study data obtained using several surfactants, are also included.This extensive discussion on the subject aims to help researchers and professionals in the field to understand the current situation and plan future enterprises accordingly.展开更多
The merits of CO2 capture and storage to the environmental stability of our world should not be underestimated as emissions of greenhouse gases cause serious problems.It represents the only technology that might rid o...The merits of CO2 capture and storage to the environmental stability of our world should not be underestimated as emissions of greenhouse gases cause serious problems.It represents the only technology that might rid our atmosphere of the main anthropogenic gas while allowing for the continuous use of the fossil fuels which still power today’s world.Underground storage of CO2 involves the injection of CO2 into suitable geological formations and the monitoring of the injected plume over time,to ensure containment.Over the last two or three decades,attention has been paid to technology developments of carbon capture and sequestration.Therefore,it is high time to look at the research done so far.In this regard,a high-level review article is required to provide an overview of the status of carbon capture and sequestration research.This article presents a review of CO2 storage technologies which includes a background of essential concepts in storage,the physical processes involved,modeling procedures and simulators used,capacity estimation,measuring monitoring and verification techniques,risks and challenges involved and field-/pilot-scale projects.It is expected that the present review paper will help the researchers to gain a quick knowledge of CO2 sequestration for future research in this field.展开更多
Recent advancements in perovskites’ application as a solar energy harvester have been astonishing. The power conversion efficiency(PCE) of perovskite solar cells(PSCs) is currently reaching parity(>25 percent), an...Recent advancements in perovskites’ application as a solar energy harvester have been astonishing. The power conversion efficiency(PCE) of perovskite solar cells(PSCs) is currently reaching parity(>25 percent), an accomplishment attained over past decades. PSCs are seen as perovskites sandwiched between an electron transporting material(ETM) and a hole transporting material(HTM). As a primary component of PSCs, HTM has been shown to have a considerable effect on solar energy harvesting, carrier extraction and transport, crystallization of perovskite, stability, and price. In PSCs, it is still necessary to use a HTM.While perovskites are capable of conducting holes, they are present in trace amounts, necessitating the use of an HTM layer for efficient charge extraction. In this review, we provide an understanding of the significant forms of HTM accessible(inorganic, polymeric and small molecule-based HTMs), to motivate further research and development of such materials. The identification of additional criteria suggests a significant challenge to high stability and affordability in PSC.展开更多
In high-temperature applications,like exhaust manifolds,cast irons with a ferritic matrix are mostly used.However,the increasing demand for higher-temperature applications has led manufacturers to use additional expen...In high-temperature applications,like exhaust manifolds,cast irons with a ferritic matrix are mostly used.However,the increasing demand for higher-temperature applications has led manufacturers to use additional expensive materials such as stainless steels and Ni-resist austenitic ductile cast irons.Thus,in order to meet the demand while using low-cost materials,new alloys with improved high-temperature strength and oxidation resistance must be developed.In this study,thermodynamic calculations with Thermo-Calc software were applied to study a novel ductile cast iron with a composition of 3.5wt%C,4wt%Si,1wt%Nb,0‒4wt%Al.The designed compositions were cast,and thermal analysis and microstructural characterization were performed to validate the calculations.The lowest critical temperature of austenite to pearlite eutectoid transformation,i.e.,A1,was calculated,and the solidification sequence was determined.Both calculations and experimental data revealed the importance of aluminum addition,as the A1 increased by increasing the aluminum content in the alloys,indicating the possibility of utilizing the alloys at higher temperature.The experimental data validated the transformation temperature during solidification and at the solid state and confirmed the equilibrium phases at room temperature as ferrite,graphite,and MC-type carbides.展开更多
Turbulent swirling flow inside a short pipe interacting with a conical bluff body was simulated using the commercial CFD code Fluent.The geometry used is a simplified version of a novel liquid/gas separator used in mu...Turbulent swirling flow inside a short pipe interacting with a conical bluff body was simulated using the commercial CFD code Fluent.The geometry used is a simplified version of a novel liquid/gas separator used in multiphase flow metering.Three turbulence models,belonging to the Reynolds averaged Navier-Stokes(RANS)equations framework,are used.These are,RNG k-ε,SST k-ωand the full Reynolds stress model(RSM)in their steady and unsteady versions.Steady and unsteady RSM simulations show similar behavior.Compared to other turbulence models,they yield the best predictions of the mean velocity profiles though they exhibit some discrepancies in the core region.The influence of the Reynolds number on velocity profiles,swirl decay,and wall pressure on the bluff body are also presented.For Reynolds numbers generating a Rankine-like velocity profile,the width and magnitude of flow reversal zone decreases along the pipe axis disappearing downstream for lower Reynolds numbers.The tangential velocity peaks increase with increasing Reynolds number.The swirl decay rate follows an exponential form in accordance with the existing literature.These flow features would affect the performance of the real separator and,thus,the multiphase flow meter,noticeably.展开更多
Layered double hydroxide(LDH),a kind of 2D layered materials,has been recognized as the promising anticorrosion materials for metal and its alloy.The microstructure,physical/chemical properties,usage in corrosion inhi...Layered double hydroxide(LDH),a kind of 2D layered materials,has been recognized as the promising anticorrosion materials for metal and its alloy.The microstructure,physical/chemical properties,usage in corrosion inhibition and inhibition performance of LDH have been studied separately in open literature.However,there is a lack of a complete review to summarize the status of LDH technology and the potential R&D opportunities in the field of corrosion inhibition.In addition,the challenges for LDH in corrosion inhibition of metal-based system have not been summarized systematically.Herein,we review recent advances in the rational design of LDH for corrosion inhibition of metal-based system(i.e.Mg alloy,Al alloy,steel and concrete)and high-throughput anticorrosion materials development.By evaluating the physical/chemical properties,usage in metal-based system and the corrosion inhibition mechanism of LDH,we highlight several important factors of LDH for anticorrosion performance and common features of LDH in applying different metal alloys.Finally,we provide our perspective and recommendation in this field,including high-throughput techiniques for combinatorial compositional design and rapid synthesis of anticorrosion alloys,with the goal of accelerating the development and application of LDH in corrosion inhibition of metal-based system.展开更多
The effects of trapping number on enhanced oil recovery by schizophyllan biopolymer flooding in carbonate reservoirs were investigated by running several 1D simulations using measured reservoir rock and fluid data.Sen...The effects of trapping number on enhanced oil recovery by schizophyllan biopolymer flooding in carbonate reservoirs were investigated by running several 1D simulations using measured reservoir rock and fluid data.Sensitivity analysis was performed on different uncertain parameters to history match the oil recovery obtained in the core flooding experiment.These parameters include inaccessible pore volume(IPV),biopolymer adsorption,permeability reduction factor,shear rate coefficient,hardness of injection water,and trapping number.The IPV,biopolymer adsorption,permeability reduction factor,shear rate coefficient and hardness of injection water have negligible effects on oil recovery by biopolymer flooding.Also,history matching of oil recovery data was not possible when these parameters were varied within their typical range of values.When trapping number effect was considered through capillary desaturation curve(CDC),residual oil saturation was reduced from 25.1%without considering its effect or under low trapping number to 10.0%,and the fitting effect for recovery was better.Therefore,we can’t neglect the trapping number effect during biopolymer flooding simulation in the carbonate reservoirs.展开更多
Mechanical models of residually stressed fibre-reinforced solids,which do not resist bending,have been developed in the literature.However,in some residually stressed fibre-reinforced elastic solids,resistance to fibr...Mechanical models of residually stressed fibre-reinforced solids,which do not resist bending,have been developed in the literature.However,in some residually stressed fibre-reinforced elastic solids,resistance to fibre bending is significant,and the mechanical behavior of such solids should be investigated.Hence,in this paper,we model the mechanical aspect of residually stressed elastic solids with bending stiffness due to fibre curvature,which up to the authors’knowledge has not been mechanically modeled in the past.The proposed constitutive equation involves a nonsymmetric stress and a couple-stress tensor.Spectral invariants are used in the constitutive equation,where each spectral invariant has an intelligible physical meaning,and hence they are useful in experiment and analysis.A prototype strain energy function is proposed.Moreover,we use this prototype to give results for some cylindrical boundary value problems.展开更多
The present study aims to make a thermodynamic analysis of an ethylene cascade re-liquefaction system that consists of the following two subsystems: a liquefaction cycle using ethylene as the working fluid and a refri...The present study aims to make a thermodynamic analysis of an ethylene cascade re-liquefaction system that consists of the following two subsystems: a liquefaction cycle using ethylene as the working fluid and a refrigeration cycle operating with a hydrocarbon refrigerant. The hydrocarbon refrigerants considered are propane(R290), butane(R600), isobutane(R600a), and propylene(R1270). A computer program written in FORTRAN is developed to compute parameters for characteristic points of the cycles and the system's performance, which is determined and analyzed using numerical solutions for the refrigerant condensation temperature, temperature in tank, and temperature difference in the cascade condenser. Results show that R600 a gives the best performance, followed by(in order) R600, R290, and R1270. Furthermore, it is found that an increase in tank temperature improves system performance but that an increase in refrigerant condensation temperature causes deterioration. In addition, it is found that running the system at a low temperature difference in the cascade condenser is advantageous.展开更多
Advancements in manufacturing technology,including the rapid development of additive manufacturing(AM),allow the fabrication of complex functionally graded material(FGM)sectioned beams.Portions of these beams may be m...Advancements in manufacturing technology,including the rapid development of additive manufacturing(AM),allow the fabrication of complex functionally graded material(FGM)sectioned beams.Portions of these beams may be made from different materials with possibly different gradients of material properties.The present work proposes models to investigate the free vibration of FGM sectioned beams based on onedimensional(1D)finite element analysis.For this purpose,a sample beam is divided into discrete elements,and the total energy stored in each element during vibration is computed by considering either the Timoshenko or Euler-Bernoulli beam theory.Then,Hamilton’s principle is used to derive the equations of motion for the beam.The effects of material properties and dimensions of FGM sections on the beam’s natural frequencies and their corresponding mode shapes are then investigated based on a dynamic Timoshenko model(TM).The presented model is validated by comparison with three-dimensional(3D)finite element simulations of the first three mode shapes of the beam.展开更多
Group key security protocols play an important role in today’s communication systems. Their verification, however, remains a great challenge because of the dynamic characteristics of group key construction and distri...Group key security protocols play an important role in today’s communication systems. Their verification, however, remains a great challenge because of the dynamic characteristics of group key construction and distribution protocols. Security properties that are well defined in normal two-party protocols have different meanings and different interpretations in group key distribution protocols, specifically, secrecy properties, such as group secrecy, forward secrecy, backward secrecy, and key independence. In this paper, we present a method to verify forward secrecy properties for group-oriented protocols. The method is based on a correct semantical link between group key protocols and event-B models and also uses the refinement process in the B method to model and verify group and forward secrecy. We use an event-B first-order theorem proving system to provide invariant checking for these secrecy properties. We illustrate our approach on the Tree based Group Diffie-Hellman protocol as case study.展开更多
Preparation and process optimization of porous carbons using different carbon sources and activating agents are frequently and commonly reported in open literature. However, only scanty references are made on utilizat...Preparation and process optimization of porous carbons using different carbon sources and activating agents are frequently and commonly reported in open literature. However, only scanty references are made on utilization of petroleum coke for conversion to high surface area porous carbon using KOH as the activating agent. Hence, the present work attempts a process optimization exercise to prepare high surface area porous carbon from Petroleum coke using chemical activation (KOH) utilizing design of experiments. The effect of activation temperature, petroleum coke to KOH ratio (KPR) and activation duration were assessed on the surface area and yield of the porous carbon. The process optimization was performed covering experimental parameters in the range of 500?C - 800?C, 2 - 5 and 30 - 120 min. The optimal process conditions for maximizing the yield and BET surface area was identified to be an activation temperature of 639?C, KPR of 4.5 and activation duration of 43 min, having BET surface area 1765 m2/g and yield of 89.8%. However, an attempt to maximize only the BET surface area, ignoring yield has resulted with a porous carbon with maximum surface area of 2061 m2/g, with the optimal process conditions being an activation temperature of 688?C, KPR of 3.8 and activation duration of 74 min, with the corresponding yield of only 77%. The characterization of porous carbon was performed using nitrogen adsorption isotherm, FT-IR and SEM analysis.展开更多
With the advent of the wide-spread use of smart phones, video streaming over mobile wireless networks has suddenly taken a huge surge in recent years. Considering its enormous potential, mobile WiMAX is emerging as a ...With the advent of the wide-spread use of smart phones, video streaming over mobile wireless networks has suddenly taken a huge surge in recent years. Considering its enormous potential, mobile WiMAX is emerging as a viable technology for mobile TV which is expected to become of key importance in the future of mobile industry. In this paper, a simulation performance study of Mobile TV over mobile WiMAX is conducted with different types of adaptive modulation and coding taking into account key system and environment parameters which include the variation in the speed of the mobile, path-loss, scheduling service classes with the fixed type of modulations. Our simulation has been conducted using OPNET simulation. Simulation results show that dynamic adaptation of modulation and coding schemes based on channel conditions can offer considerably more enhanced QoS and at the same time reduce the overall bandwidth of the system.展开更多
<span style="font-family:Verdana;">Let <img alt="" src="Edit_1798cf4c-b9a5-4ada-b2d4-9fbf535a6d28.png" />be the partial symmetric semigroup on <img alt="" src=&qu...<span style="font-family:Verdana;">Let <img alt="" src="Edit_1798cf4c-b9a5-4ada-b2d4-9fbf535a6d28.png" />be the partial symmetric semigroup on <img alt="" src="Edit_86c31e58-0588-44fc-8ff3-78c73dc14be6.png" />and let <img alt="" src="Edit_09f7ec2a-49d1-463d-952e-93fbe00740cd.png" />and <img alt="" src="Edit_4aca07c1-9a36-44b6-83af-46fdd6278ca4.png" />be its subsemigroups of order-preserving contractions and order-preserving, order-decreasing contractions mappings of <img alt="" src="Edit_72d2bbdf-2b96-4812-a993-f49640bb98c9.png" />, respectively. In this paper we investigate the cardinalities of <img alt="" src="Edit_95038cdc-5496-495f-bfb9-29c817ba2df4.png" />and <img alt="" src="Edit_f8d3d782-ff8c-43b3-84af-d21a3f4291d5.png" />, the set idempotents of <img alt="" src="Edit_ac8237f8-83ec-4767-9029-b546377bf106.png" />and <img alt="" src="Edit_8b1bf8bf-7472-453c-965d-7308da5b4f4c.png" />, respectively. We also investigate the cardinalities of certain equivalences on <img alt="" src="Edit_e5f7aec4-67c1-48ba-8d03-ea6ceb2e7627.png" />and <img alt="" src="Edit_42a31943-fe9d-4ea8-8999-3aadb705fb38.png" />.</span>展开更多
基金support by Khalifa University through CIRA-2020-077 and RC2-2018-024 grants。
文摘The continuous and excessive emission of CO_(2)into the atmosphere presents a pressing challenge for global sustainable development.In response,researchers have been devoting significant efforts to develop methods for converting CO_(2)into valuable chemicals and fuels.These conversions have the potential to establish a closed artificial carbon cycle and provide an alternative resource to depleting fossil fuels.Among the various conversion routes,thermochemical CO_(2)reduction stands out as a promising candidate for industrialization.Within the realm of heterogeneous catalysis,single atom catalysts(SACs)have garnered significant attention.The utilization of SACs offers tremendous potential for enhancing catalytic performance.To achieve optimal activity and selectivity of SACs in CO_(2)thermochemical reduction reactions,a comprehensive understanding of key factors such as single atom metal-support interactions,chemical coordination,and accessibility of active sites is crucial.Despite extensive research in this field,the atomic-scale reaction mechanisms in different chemical environments remain largely unexplored.While SACs have been found successful applications in electrochemical and photochemical CO_(2)reduction reactions,their implementation in thermochemical CO_(2)reduction encounters challenges due to the sintering and/or agglomeration effects that occur at elevated temperatures.In this review,we present a unique approach that combines theoretical understanding with experimental strategies to guide researchers in the design of controlled and thermally stable SACs.By elucidating the underlying principles,we aim to enable the creation of SACs that exhibit stable and efficient catalytic activity for thermochemical CO_(2)reduction reactions.Subsequently,we provide a comprehensive overview of recent literature on noble metal-and transition metal-based SACs for thermochemical CO_(2)reduction.The current review is focused on certain CO_(2)-derived products involving one step reduction only for simplicity and for better understanding the SACs enhancement mechanism.We emphasize various synthesis methods employed and highlight the catalytic activity of these SACs.Finally,we delve into the perspectives and challenges associated with SACs in the context of thermochemical CO_(2)reduction reactions,providing valuable insights for future research endeavor.Through this review,we aim to contribute to the advancement of SACs in the field of thermochemical CO_(2)reduction,shedding light on their potential as effective catalysts and addressing the challenges that need to be overcome for their successful implementation as paradigm shift in catalysis.
基金financial support from the Abu Dhabi National Oil Company (ADNOC), United Arab Emirates under Award No: EX2016-000010。
文摘This study presents the multifunctional characteristics of multi-walled carbon nanotube(MWCNT)/polypropylene random copolymer(PPR) composites enabled via fused filament fabrication(FFF) under monotonic and quasi-static cyclic compression. Utilizing in-house MWCNT-engineered PPR filament feedstocks, both bulk and cellular composites were realized. The morphological features of nanocomposites were examined via scanning electron microscopy, which reveals that MWCNTs are uniformly dispersed. The uniformly dispersed MWCNTs forms an electrically conductive network within the PPR matrix, and the resulting nanocomposite shows good electrical conductivity(~10^(-1)S/cm), improved mechanical performance(modulus increases by 125% and compressive strength increases by 25% for 8 wt% MWCNT loading) and pronounced piezoresistive response(gauge factor of 27.9-8.5 for bulk samples)under compression. The influence of strain rate on the piezoresistive response of bulk samples(4 wt% of MWCNT) under compression was also measured. Under repeated cyclic compression(2% constant strain amplitude), the nanocomposite exhibited stable piezoresistive performance up to 100 cycles. The piezoresistive response under repeated cyclic loading with increasing strain amplitude of was also assessed.The gauge factor of BCC and FCC cellular composites(4 wt% of MWCNT) with a relative density of 30%was observed to be 46.4 and 30.2 respectively, under compression. The higher sensitivity of the BCC plate-lattice could be attributed to its higher degree of stretching-dominated deformation behavior than the FCC plate-lattice, which exhibits bending-dominated behavior. The 3D printed cellular PPR/MWCNT composites structures were found to show excellent piezoresistive self-sensing characteristics and open new avenues for in situ structural health monitoring in various applications.
文摘Biopolymers are promising environmentally benign materials applicable in multifarious applications.They are especially favorable in implantable biomedical devices thanks to their excellent unique properties,including bioactivity,renewability,bioresorbability,biocompatibility,biodegradability and hydrophilicity.Additive manufacturing(AM)is a flexible and intricate manufacturing technology,which is widely used to fabricate biopolymer-based customized products and structures for advanced healthcare systems.Three-dimensional(3D)printing of these sustainable materials is applied in functional clinical settings including wound dressing,drug delivery systems,medical implants and tissue engineering.The present review highlights recent advancements in different types of biopolymers,such as proteins and polysaccharides,which are employed to develop different biomedical products by using extrusion,vat polymerization,laser and inkjet 3D printing techniques in addition to normal bioprinting and four-dimensional(4D)bioprinting techniques.It also incorporates the influence of nanoparticles on the biological and mechanical performances of 3D-printed tissue scaffolds,and addresses current challenges as well as future developments of environmentally friendly polymeric materials manufactured through the AMtechniques.Ideally,there is a need for more focused research on the adequate blending of these biodegradable biopolymers for achieving useful results in targeted biomedical areas.We envision that biopolymer-based 3D-printed composites have the potential to revolutionize the biomedical sector in the near future.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2021R1A2C1095591).
文摘As big data,Artificial Intelligence,and Vehicle-to-Everything(V2X)communication have advanced,Intelligent Transportation Systems(ITS)are being developed to enable efficient and safe transportation systems.Electronic Toll Collection(ETC),which is one of the services included in ITS systems,is an automated system that allows vehicles to pass through toll plazas without stopping for manual payment.The ETC system is widely deployed on highways due to its contribution to stabilizing the overall traffic system flow.To ensure secure and efficient toll payments,designing a distributed model for sharing toll payment information among untrusted toll service providers is necessary.However,the current ETC system operates under a centralized model.Additionally,both toll service providers and toll plazas know the toll usage history of vehicles.It raises concerns about revealing the entire driving routes and patterns of vehicles.To address these issues,blockchain technology,suitable for secure data management and data sharing in distributed systems,is being applied to the ETC system.Blockchain enables efficient and transparent management of ETC information.Nevertheless,the public nature of blockchain poses a challenge where users’usage records are exposed to all participants.To tackle this,we propose a blockchain-based toll ticket model named AnonymousTollPass that considers the privacy of vehicles.The proposed model utilizes traceable ring signatures to provide unlinkability between tickets used by a vehicle and prevent the identity of the vehicle using the ticket from being identified among the ring members for the ticket.Furthermore,malicious vehicles’identities can be traced when they attempt to reuse tickets.By conducting simulations,we show the effectiveness of the proposed model and demonstrate that gas fees required for executing the proposed smart contracts are only 10%(when the ring size is 50)of the fees required in previous studies.
文摘A significant fraction of the conventional oil reserves globally is in carbonate formations which contain a substantial amount of residual oil. Since primary and secondary recovery methods fail to yield above 20%-40%of original oil in place from these reserves, the need for enhanced oil recovery(EOR) techniques for incremental oil recovery has become imperative. With the challenges presented by the highly heterogeneous carbonate rocks,evaluation of tertiary-stage recovery techniques including chemical EOR(c EOR) has been a high priority for researchers and oil producers. In this review, the latest developments in the surfactant-based c EOR techniques applied in carbonate formations are discussed, contemplating the future direction of existing methodologies. In connection with this, the characteristics of heterogeneous carbonate reservoirs are outlined. Detailed discussion on surfactant-led oil recovery mechanisms and related processes, such as wettability alteration, interfacial tension reduction, microemulsion phase behavior, surfactant adsorption and mitigation, and foams and their applications is presented. Laboratory experiments, as well as field study data obtained using several surfactants, are also included.This extensive discussion on the subject aims to help researchers and professionals in the field to understand the current situation and plan future enterprises accordingly.
基金support provided by the Department of Petroleum Engineering,Khalifa University of Science and Technology,Sas Al Nakhl Campus,Abu Dhabi,UAE
文摘The merits of CO2 capture and storage to the environmental stability of our world should not be underestimated as emissions of greenhouse gases cause serious problems.It represents the only technology that might rid our atmosphere of the main anthropogenic gas while allowing for the continuous use of the fossil fuels which still power today’s world.Underground storage of CO2 involves the injection of CO2 into suitable geological formations and the monitoring of the injected plume over time,to ensure containment.Over the last two or three decades,attention has been paid to technology developments of carbon capture and sequestration.Therefore,it is high time to look at the research done so far.In this regard,a high-level review article is required to provide an overview of the status of carbon capture and sequestration research.This article presents a review of CO2 storage technologies which includes a background of essential concepts in storage,the physical processes involved,modeling procedures and simulators used,capacity estimation,measuring monitoring and verification techniques,risks and challenges involved and field-/pilot-scale projects.It is expected that the present review paper will help the researchers to gain a quick knowledge of CO2 sequestration for future research in this field.
文摘Recent advancements in perovskites’ application as a solar energy harvester have been astonishing. The power conversion efficiency(PCE) of perovskite solar cells(PSCs) is currently reaching parity(>25 percent), an accomplishment attained over past decades. PSCs are seen as perovskites sandwiched between an electron transporting material(ETM) and a hole transporting material(HTM). As a primary component of PSCs, HTM has been shown to have a considerable effect on solar energy harvesting, carrier extraction and transport, crystallization of perovskite, stability, and price. In PSCs, it is still necessary to use a HTM.While perovskites are capable of conducting holes, they are present in trace amounts, necessitating the use of an HTM layer for efficient charge extraction. In this review, we provide an understanding of the significant forms of HTM accessible(inorganic, polymeric and small molecule-based HTMs), to motivate further research and development of such materials. The identification of additional criteria suggests a significant challenge to high stability and affordability in PSC.
基金financial support given by Scientific Research Projects Coordination Unit of Kocaeli University under the project No. 2017/118
文摘In high-temperature applications,like exhaust manifolds,cast irons with a ferritic matrix are mostly used.However,the increasing demand for higher-temperature applications has led manufacturers to use additional expensive materials such as stainless steels and Ni-resist austenitic ductile cast irons.Thus,in order to meet the demand while using low-cost materials,new alloys with improved high-temperature strength and oxidation resistance must be developed.In this study,thermodynamic calculations with Thermo-Calc software were applied to study a novel ductile cast iron with a composition of 3.5wt%C,4wt%Si,1wt%Nb,0‒4wt%Al.The designed compositions were cast,and thermal analysis and microstructural characterization were performed to validate the calculations.The lowest critical temperature of austenite to pearlite eutectoid transformation,i.e.,A1,was calculated,and the solidification sequence was determined.Both calculations and experimental data revealed the importance of aluminum addition,as the A1 increased by increasing the aluminum content in the alloys,indicating the possibility of utilizing the alloys at higher temperature.The experimental data validated the transformation temperature during solidification and at the solid state and confirmed the equilibrium phases at room temperature as ferrite,graphite,and MC-type carbides.
基金ADNOC Onshore Company(ADCO)for the financial support of this research project.
文摘Turbulent swirling flow inside a short pipe interacting with a conical bluff body was simulated using the commercial CFD code Fluent.The geometry used is a simplified version of a novel liquid/gas separator used in multiphase flow metering.Three turbulence models,belonging to the Reynolds averaged Navier-Stokes(RANS)equations framework,are used.These are,RNG k-ε,SST k-ωand the full Reynolds stress model(RSM)in their steady and unsteady versions.Steady and unsteady RSM simulations show similar behavior.Compared to other turbulence models,they yield the best predictions of the mean velocity profiles though they exhibit some discrepancies in the core region.The influence of the Reynolds number on velocity profiles,swirl decay,and wall pressure on the bluff body are also presented.For Reynolds numbers generating a Rankine-like velocity profile,the width and magnitude of flow reversal zone decreases along the pipe axis disappearing downstream for lower Reynolds numbers.The tangential velocity peaks increase with increasing Reynolds number.The swirl decay rate follows an exponential form in accordance with the existing literature.These flow features would affect the performance of the real separator and,thus,the multiphase flow meter,noticeably.
基金the Graduate Research and innovation of Chongqing,China(Grant No.CYB20005)the project of Technological Innovation and Application Development in Chongqing(cstc2019jscxmsxm0378)+8 种基金the National Natural Science Foundation of China(Grant Nos.51908092)the Joint Funds of the National Natural Science Foundation of China-Guangdong(Grant No.U1801254)the project funded by Chongqing Special Postdoctoral Science Foundation(XmT2018043)Natural Science Foundation Project of Chongqing for Post-doctor(cstc2019jcyjbsh0079)Technological projects of Chongqing Municipal Education Commission(KJZDK201800801)Projects(No.2020CDJXZ001,2020CDCGJ006 and 2020CDCGCL004)the Fundamental Research Funds for the Central Universitiesthe Innovative Research Team of Chongqing(CXTDG201602014)the Innovative technology of New materials and metallurgy(2019CDXYCL0031).
文摘Layered double hydroxide(LDH),a kind of 2D layered materials,has been recognized as the promising anticorrosion materials for metal and its alloy.The microstructure,physical/chemical properties,usage in corrosion inhibition and inhibition performance of LDH have been studied separately in open literature.However,there is a lack of a complete review to summarize the status of LDH technology and the potential R&D opportunities in the field of corrosion inhibition.In addition,the challenges for LDH in corrosion inhibition of metal-based system have not been summarized systematically.Herein,we review recent advances in the rational design of LDH for corrosion inhibition of metal-based system(i.e.Mg alloy,Al alloy,steel and concrete)and high-throughput anticorrosion materials development.By evaluating the physical/chemical properties,usage in metal-based system and the corrosion inhibition mechanism of LDH,we highlight several important factors of LDH for anticorrosion performance and common features of LDH in applying different metal alloys.Finally,we provide our perspective and recommendation in this field,including high-throughput techiniques for combinatorial compositional design and rapid synthesis of anticorrosion alloys,with the goal of accelerating the development and application of LDH in corrosion inhibition of metal-based system.
基金Khalifa University of Science and Technology for funding this research under Award No. [FSU-2018-26]
文摘The effects of trapping number on enhanced oil recovery by schizophyllan biopolymer flooding in carbonate reservoirs were investigated by running several 1D simulations using measured reservoir rock and fluid data.Sensitivity analysis was performed on different uncertain parameters to history match the oil recovery obtained in the core flooding experiment.These parameters include inaccessible pore volume(IPV),biopolymer adsorption,permeability reduction factor,shear rate coefficient,hardness of injection water,and trapping number.The IPV,biopolymer adsorption,permeability reduction factor,shear rate coefficient and hardness of injection water have negligible effects on oil recovery by biopolymer flooding.Also,history matching of oil recovery data was not possible when these parameters were varied within their typical range of values.When trapping number effect was considered through capillary desaturation curve(CDC),residual oil saturation was reduced from 25.1%without considering its effect or under low trapping number to 10.0%,and the fitting effect for recovery was better.Therefore,we can’t neglect the trapping number effect during biopolymer flooding simulation in the carbonate reservoirs.
文摘Mechanical models of residually stressed fibre-reinforced solids,which do not resist bending,have been developed in the literature.However,in some residually stressed fibre-reinforced elastic solids,resistance to fibre bending is significant,and the mechanical behavior of such solids should be investigated.Hence,in this paper,we model the mechanical aspect of residually stressed elastic solids with bending stiffness due to fibre curvature,which up to the authors’knowledge has not been mechanically modeled in the past.The proposed constitutive equation involves a nonsymmetric stress and a couple-stress tensor.Spectral invariants are used in the constitutive equation,where each spectral invariant has an intelligible physical meaning,and hence they are useful in experiment and analysis.A prototype strain energy function is proposed.Moreover,we use this prototype to give results for some cylindrical boundary value problems.
文摘The present study aims to make a thermodynamic analysis of an ethylene cascade re-liquefaction system that consists of the following two subsystems: a liquefaction cycle using ethylene as the working fluid and a refrigeration cycle operating with a hydrocarbon refrigerant. The hydrocarbon refrigerants considered are propane(R290), butane(R600), isobutane(R600a), and propylene(R1270). A computer program written in FORTRAN is developed to compute parameters for characteristic points of the cycles and the system's performance, which is determined and analyzed using numerical solutions for the refrigerant condensation temperature, temperature in tank, and temperature difference in the cascade condenser. Results show that R600 a gives the best performance, followed by(in order) R600, R290, and R1270. Furthermore, it is found that an increase in tank temperature improves system performance but that an increase in refrigerant condensation temperature causes deterioration. In addition, it is found that running the system at a low temperature difference in the cascade condenser is advantageous.
基金Project supported by Khalifa University of Science and Technology(No.CIRA 2019-024)。
文摘Advancements in manufacturing technology,including the rapid development of additive manufacturing(AM),allow the fabrication of complex functionally graded material(FGM)sectioned beams.Portions of these beams may be made from different materials with possibly different gradients of material properties.The present work proposes models to investigate the free vibration of FGM sectioned beams based on onedimensional(1D)finite element analysis.For this purpose,a sample beam is divided into discrete elements,and the total energy stored in each element during vibration is computed by considering either the Timoshenko or Euler-Bernoulli beam theory.Then,Hamilton’s principle is used to derive the equations of motion for the beam.The effects of material properties and dimensions of FGM sections on the beam’s natural frequencies and their corresponding mode shapes are then investigated based on a dynamic Timoshenko model(TM).The presented model is validated by comparison with three-dimensional(3D)finite element simulations of the first three mode shapes of the beam.
文摘Group key security protocols play an important role in today’s communication systems. Their verification, however, remains a great challenge because of the dynamic characteristics of group key construction and distribution protocols. Security properties that are well defined in normal two-party protocols have different meanings and different interpretations in group key distribution protocols, specifically, secrecy properties, such as group secrecy, forward secrecy, backward secrecy, and key independence. In this paper, we present a method to verify forward secrecy properties for group-oriented protocols. The method is based on a correct semantical link between group key protocols and event-B models and also uses the refinement process in the B method to model and verify group and forward secrecy. We use an event-B first-order theorem proving system to provide invariant checking for these secrecy properties. We illustrate our approach on the Tree based Group Diffie-Hellman protocol as case study.
文摘Preparation and process optimization of porous carbons using different carbon sources and activating agents are frequently and commonly reported in open literature. However, only scanty references are made on utilization of petroleum coke for conversion to high surface area porous carbon using KOH as the activating agent. Hence, the present work attempts a process optimization exercise to prepare high surface area porous carbon from Petroleum coke using chemical activation (KOH) utilizing design of experiments. The effect of activation temperature, petroleum coke to KOH ratio (KPR) and activation duration were assessed on the surface area and yield of the porous carbon. The process optimization was performed covering experimental parameters in the range of 500?C - 800?C, 2 - 5 and 30 - 120 min. The optimal process conditions for maximizing the yield and BET surface area was identified to be an activation temperature of 639?C, KPR of 4.5 and activation duration of 43 min, having BET surface area 1765 m2/g and yield of 89.8%. However, an attempt to maximize only the BET surface area, ignoring yield has resulted with a porous carbon with maximum surface area of 2061 m2/g, with the optimal process conditions being an activation temperature of 688?C, KPR of 3.8 and activation duration of 74 min, with the corresponding yield of only 77%. The characterization of porous carbon was performed using nitrogen adsorption isotherm, FT-IR and SEM analysis.
文摘With the advent of the wide-spread use of smart phones, video streaming over mobile wireless networks has suddenly taken a huge surge in recent years. Considering its enormous potential, mobile WiMAX is emerging as a viable technology for mobile TV which is expected to become of key importance in the future of mobile industry. In this paper, a simulation performance study of Mobile TV over mobile WiMAX is conducted with different types of adaptive modulation and coding taking into account key system and environment parameters which include the variation in the speed of the mobile, path-loss, scheduling service classes with the fixed type of modulations. Our simulation has been conducted using OPNET simulation. Simulation results show that dynamic adaptation of modulation and coding schemes based on channel conditions can offer considerably more enhanced QoS and at the same time reduce the overall bandwidth of the system.
文摘<span style="font-family:Verdana;">Let <img alt="" src="Edit_1798cf4c-b9a5-4ada-b2d4-9fbf535a6d28.png" />be the partial symmetric semigroup on <img alt="" src="Edit_86c31e58-0588-44fc-8ff3-78c73dc14be6.png" />and let <img alt="" src="Edit_09f7ec2a-49d1-463d-952e-93fbe00740cd.png" />and <img alt="" src="Edit_4aca07c1-9a36-44b6-83af-46fdd6278ca4.png" />be its subsemigroups of order-preserving contractions and order-preserving, order-decreasing contractions mappings of <img alt="" src="Edit_72d2bbdf-2b96-4812-a993-f49640bb98c9.png" />, respectively. In this paper we investigate the cardinalities of <img alt="" src="Edit_95038cdc-5496-495f-bfb9-29c817ba2df4.png" />and <img alt="" src="Edit_f8d3d782-ff8c-43b3-84af-d21a3f4291d5.png" />, the set idempotents of <img alt="" src="Edit_ac8237f8-83ec-4767-9029-b546377bf106.png" />and <img alt="" src="Edit_8b1bf8bf-7472-453c-965d-7308da5b4f4c.png" />, respectively. We also investigate the cardinalities of certain equivalences on <img alt="" src="Edit_e5f7aec4-67c1-48ba-8d03-ea6ceb2e7627.png" />and <img alt="" src="Edit_42a31943-fe9d-4ea8-8999-3aadb705fb38.png" />.</span>