Chemical exchange saturation transfer magnetic resonance imaging is an advanced imaging technique that enables the detection of compounds at low concentrations with high sensitivity and spatial resolution and has been...Chemical exchange saturation transfer magnetic resonance imaging is an advanced imaging technique that enables the detection of compounds at low concentrations with high sensitivity and spatial resolution and has been extensively studied for diagnosing malignancy and stroke.In recent years,the emerging exploration of chemical exchange saturation transfer magnetic resonance imaging for detecting pathological changes in neurodegenerative diseases has opened up new possibilities for early detection and repetitive scans without ionizing radiation.This review serves as an overview of chemical exchange saturation transfer magnetic resonance imaging with detailed information on contrast mechanisms and processing methods and summarizes recent developments in both clinical and preclinical studies of chemical exchange saturation transfer magnetic resonance imaging for Alzheimer’s disease,Parkinson’s disease,multiple sclerosis,and Huntington’s disease.A comprehensive literature search was conducted using databases such as PubMed and Google Scholar,focusing on peer-reviewed articles from the past 15 years relevant to clinical and preclinical applications.The findings suggest that chemical exchange saturation transfer magnetic resonance imaging has the potential to detect molecular changes and altered metabolism,which may aid in early diagnosis and assessment of the severity of neurodegenerative diseases.Although promising results have been observed in selected clinical and preclinical trials,further validations are needed to evaluate their clinical value.When combined with other imaging modalities and advanced analytical methods,chemical exchange saturation transfer magnetic resonance imaging shows potential as an in vivo biomarker,enhancing the understanding of neuropathological mechanisms in neurodegenerative diseases.展开更多
Hydrogen energy from electrocatalysis driven by sustainable energy has emerged as a solution against the background of carbon neutrality.Proton exchange membrane(PEM)-based electrocatalytic systems represent a promisi...Hydrogen energy from electrocatalysis driven by sustainable energy has emerged as a solution against the background of carbon neutrality.Proton exchange membrane(PEM)-based electrocatalytic systems represent a promising technology for hydrogen production,which is equipped to combine efficiently with intermittent electricity from renewable energy sources.In this review,PEM-based electrocatalytic systems for H2 production are summarized systematically from low to high operating temperature systems.When the operating temperature is below 130℃,the representative device is a PEM water electrolyzer;its core components and respective functions,research status,and design strategies of key materials especially in electrocatalysts are presented and discussed.However,strong acidity,highly oxidative operating conditions,and the sluggish kinetics of the anode reaction of PEM water electrolyzers have limited their further development and shifted our attention to higher operating temperature PEM systems.Increasing the temperature of PEM-based electrocatalytic systems can cause an increase in current density,accelerate reaction kinetics and gas transport and reduce the ohmic value,activation losses,ΔGH*,and power consumption.Moreover,further increasing the operating temperature(120-300℃)of PEM-based devices endows various hydrogen carriers(e.g.,methanol,ethanol,and ammonia)with electrolysis,offering a new opportunity to produce hydrogen using PEM-based electrocatalytic systems.Finally,several future directions and prospects for developing PEM-based electrocatalytic systems for H_(2) production are proposed through devoting more efforts to the key components of devices and reduction of costs.展开更多
This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass ...This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass transfer coefficients and air psychrometric correlations, the model provides insights into the impact of design and operational parameters on the exchanger cooling performance. Validated against an established numerical model, it accurately simulates cooling behavior with a Root Mean Square Deviation of 0.43 - 1.18˚C under varying inlet air conditions. The results show that tube geometry, including equivalent diameter, flatness ratio, and length significantly influences cooling outcomes. Smaller diameters enhance wet-bulb effectiveness but reduce cooling capacity, while increased flatness and length improve both. For example, extending the flatness ratio of a 15 mm diameter, 0.6 m long tube from 1 (circular) to 4 raises the exchange surface area from 0.028 to 0.037 m2, increasing wet-bulb effectiveness from 60% to 71%. Recommended diameters range from 5 mm for tubes under 0.5 m to 1 cm for tubes 0.5 to 1 m in length. Optimal air velocities depend on tube length: 1 m/s for tubes under 0.8 m, 1.5 m/s for lengths of 0.8 to 1.2 m, and up to 2 m/s for longer tubes. This model offers a practical alternative to complex numerical and CFD methods, with potential applications in cooling tower optimization for thermal and nuclear power plants and geothermal heat exchangers.展开更多
Removing copper from nickel electrolysis anode solution has been a major keypoint in the nickel metallurgy industry.In this study,we proposed a novel process flow to promote removing copper from nickel electrolysis an...Removing copper from nickel electrolysis anode solution has been a major keypoint in the nickel metallurgy industry.In this study,we proposed a novel process flow to promote removing copper from nickel electrolysis anode solution.A simulated nickel anode solution was designed,and static and dynamic adsorption experiments were conducted to determine the best of solution pH,adsorption time and temperature,resin dosage and particle size,and stirring speed.The optimal conditions were explored for copper removal from nickel electrolysis anode solution.Based on the optimal experimental conditions and the relevant experimental data,a novel process for copper removal from nickel electrolysis anodes was designed and verified.This novel process of copper removal from nickel electrolysis anodes was confirmed with nickel anolyte solution with nickel 50−60 g/L and copper 0.5 g/L.After finishing the novel process of copper removal,the nickel in the purified nickel anolyte became undetectable and copper concentration was 3 mg/L,the novel process of resin adsorption to remove copper from nickel anode solution through static and dynamic adsorptions has an efficacious copper removal.It is a beneficial supplement to traditional methods.展开更多
A robust spontaneous exchange bias effect after zero-field cooling was observed in Co_(2)Sn_(1-x)Cr_(x)O_(4)system,which was driven by the transition from superspin-glass to superferromagnetic domain embedded in the f...A robust spontaneous exchange bias effect after zero-field cooling was observed in Co_(2)Sn_(1-x)Cr_(x)O_(4)system,which was driven by the transition from superspin-glass to superferromagnetic domain embedded in the ferrimagnetic matrix.Additionally,the exchange bias effect is gradually pronounced with the positive increase in the cooling field,known as the conventional exchange bias effect.However,as the cooling field gradually decreases and transits from positive to negative,the exchange bias effect can robustly remain positive in the low-negative-field region until the cooling field increases to be sufficiently large in the negative direction.展开更多
Limited models have been devised using Stern theory to obtain the repulsive force from a double layer.Moreover,an elastoplastic model that differentiates various swelling behaviors because of exchangeable cation speci...Limited models have been devised using Stern theory to obtain the repulsive force from a double layer.Moreover,an elastoplastic model that differentiates various swelling behaviors because of exchangeable cation species is yet to be devised.In this study,we introduce a novel multiphysics elastoplastic model for swelling geomaterials that incorporates Stern theory.This model considered the finite size of exchangeable cations and specific adsorption phenomena,which are typically overlooked in existing models.Based on Stern theory,we derived the repulsive force from the double layer and integrated the force into the elastoplastic expansive bedrock model,which addresses electroechemoemechanical phenomena in the interlayer.The proposed model differentiated swelling behaviors based on the type of exchangeable cation species by incorporating these phenomena.To validate the model,a onedimensional(1D)numerical analysis was performed,demonstrating its capability to describe various swelling behaviors due to different exchangeable cation species through comparison with free swelling test results of bentonite.Additionally,a parametric study was conducted to elucidate the effect of the hydrated radius of exchangeable cations and the specific adsorption potential on swelling behavior,analyzed from the perspective of the equilibrium of charge distribution near the mineral surface.展开更多
At present,most quantum secret sharing(QSS)protocols are more or less designed with the incorporation of classical secret sharing schemes.With the increasing maturity of quantum technology,QSS protocols based on pure ...At present,most quantum secret sharing(QSS)protocols are more or less designed with the incorporation of classical secret sharing schemes.With the increasing maturity of quantum technology,QSS protocols based on pure quantum mechanics are becoming more important.Classical secret sharing schemes cannot achieve absolute security,and their involvement can compromise the security of QSS protocols.This paper proposes a QSS scheme based on Greenberger-Horn-Zeilinger(GHZ)basis measurement and quantum entanglement exchange.In this protocol,the secret sender stores the secret information using Pauli operations.Participants obtain their shares by measuring the product state sequentially.Finally,participants complete the secret reconstruction through quantum entanglement exchange and other related quantum operations.In addition,the particles held by participants in the protocol do not contain any secret information.Each participant's particles are in a state of maximum entanglement,and no participant can deduce the particle information of other participants through their own particles.At the same time,the protocol is based on pure quantum mechanics and does not involve classical schemes,which avoids the problem of reduced security of the protocol.Security analysis indicates that the protocol is not vulnerable to retransmission interception and collusion attacks.Moreover,it is capable of detecting and terminating the protocol promptly when facing with attacks from dishonest participants.展开更多
Climate change,rising fuel prices,and fuel security are some challenges that have emerged and have grown worldwide.Therefore,to overcome these obstacles,highly efficient thermodynamic devices and heat recovery systems...Climate change,rising fuel prices,and fuel security are some challenges that have emerged and have grown worldwide.Therefore,to overcome these obstacles,highly efficient thermodynamic devices and heat recovery systems must be introduced.According to reports,much industrial waste heat is lost as flue gas from boilers,heating plants,etc.The primary objective of this study is to investigate and compare unary(Al_(2)O_(3))thermodynamically,binary with three different combinations of nanoparticles namely(Al_(2)O_(3)+TiO_(2),TiO_(2)+ZnO,Al_(2)O_(3)+ZnO)and ternary(Al_(2)O_(3)+TiO_(2)+ZnO)as a heat transfer fluid.Initially,three different types of binary nanofluids were prepared by dispersing two types of nanoparticles in individual trails,such as aluminum oxide,zinc oxide,and titanium dioxide in various combined concentrations(e.g.,2%,4%,and 6%)into the water as the base fluid,using an ultrasonicator to ensure uniform suspension.The operating parameters such as nanoparticle concentration and flow rate are varied to evaluate the performance of various hybrid nanofluids under counterflow configuration.The findings of this research indicate that the binary nanofluid Al_(2)O_(3)+ZnO exhibits the highest thermal performance factor(2.83),followed by the ternary nanofluid Al_(2)O_(3)+TiO_(2)+ZnO(0.828),with the lowest performance observed for the unary nanofluid Al_(2)O_(3)(0.799).This research highlights the need for advancement into novel nanomaterial combinations,optimization of required fluid properties,stability enhancement,and thermal performance to strengthen the utilization of hybrid nanofluids in heat exchangers.展开更多
The purpose of the covert communication scheme is to conceal the communication behavior entirely.In such schemes,the sender and receiver rely on secret keys to establish a covert channel.However,conventional key excha...The purpose of the covert communication scheme is to conceal the communication behavior entirely.In such schemes,the sender and receiver rely on secret keys to establish a covert channel.However,conventional key exchange protocols would expose the key exchange process between them.An adversary who observes the key exchange would be aware of the existence of communication behavior.The keys used in covert communication are not suitable to be generated through conventional key exchange schemes.To address this,we propose a blockchain-based covert elliptic-curve Diffie-Hellman key exchange scheme(BCDH)to conceal the process of the key exchange in blockchain transactions.Following a straightforward setup,BCDH allows the sender and receiver to covertly exchange a secret key on a blockchain without direct communication.Furthermore,we expand the BCDH approach to operate across multiple blockchains,further enhancing its covertness and stability.We analyze BCDH from several perspectives,including covertness,security,randomness,etc.Additionally,we implement a prototype of BCDH on the Ethereum platform to assess its feasibility and performance.Our evaluation demonstrates that BCDH is efficient and well-suited for real-world applications.展开更多
Proton exchange membrane water electrolyzers(PEMWEs)are pivotal for efficient hydrogen production due to their high energy efficiency and ability to operate at high current densities,making them ideally suited for int...Proton exchange membrane water electrolyzers(PEMWEs)are pivotal for efficient hydrogen production due to their high energy efficiency and ability to operate at high current densities,making them ideally suited for integration with renewable energy sources.Cobalt(Co)-based nanomaterials,characterized by diverse oxidation states,tunable electronic spin states,and hybrid orbitals,have emerged as promising non-noble metal alternatives to platinum group catalysts for accelerating the anodic oxygen evolution reaction(OER).Based on their inherent properties,this review provides a comprehensive overview of the latest developments in Co-based nanomaterials for acidic OER.The review begins by introducing the operational principles of PEMWEs,the underlying catalytic mechanisms,and the critical design considerations for OER catalysts.It then explores strategies to enhance the activity and stability of Co-based catalysts for acidic OER in PEMWEs,including the incorporation of corrosion-resistant metals or dispersion on acid-resistant supports to increase active surface area and stability;utilization of geometric structural engineering to improve structural integrity and active site efficiency;the optimization of reaction mechanisms to fine-tune catalytic pathways for enhanced stability and performance.The performance degradation mechanisms and metal leaching analysis for Co-based catalysts in PEMWE are also clarified.Finally,this review not only outlines the key challenges associated with Co-based catalysts for acidic OER but also proposes potential strategies to overcome these limitations,offering a roadmap for future advancements and practical implementation of PEMWE technology.展开更多
The development of alkaline fuel cells is moving forward at an accelerated pace,and the application of ether-free bonded polymers to anion exchange membranes(AEMs)has been widely investigated.However,the question of ...The development of alkaline fuel cells is moving forward at an accelerated pace,and the application of ether-free bonded polymers to anion exchange membranes(AEMs)has been widely investigated.However,the question of the“trade-off”between AEM ionic conductivity and dimensional stability remains difficult.The strategy of inducing microphase separation to improve the performance of AEM has attracted much attention recently,but the design of optimal molecular structures is still being explored.Here,this work introduced different ratios of 3-bromo-1,1,1-trifluoroacetone(x=40,50,and 60)into the main chain of poly(p-terphenylene isatin).Because fluorinated groups have excellent hydrophobicity,hydrophilic hydroxyl-containing side chains are introduced to jointly adjust the formation of phase separation structure.The results show that PTI-PTF_(50)-NOH AEM with the appropriate fluorinated group ratio has the best ionic conductivity and alkali stability under the combined effect of both.It has an ionic conductivity of 133.83 mS cm^(-1)at 80°C.In addition,the OH-conductivity remains at 89%of the initial value at 80°C and 3 M KOH for 1056 h of immersion.The cell polarization curve based on PTI-PTF_(50)-NOH shows a power density of 734.76 mW cm^(-2)at a current density of 1807.7 mA cm^(-2).展开更多
Proton exchange membrane water electrolysis (PEMWE) has garnered significant attention as apivotal technology for converting surplus electricity into hydrogen for long-term storage, as well asfor providing high-purity...Proton exchange membrane water electrolysis (PEMWE) has garnered significant attention as apivotal technology for converting surplus electricity into hydrogen for long-term storage, as well asfor providing high-purity hydrogen for aerospace and high-end manufacturing applications. Withthe ongoing commercialization of PEMWE, advancing iridium-based oxygen evolution reaction(OER) catalysts remains imperative to reconcile stringent requirements for high activity, extendedlongevity, and minimized noble metal loading. The review provides a systematic analysis of theintegrated design of iridium-based catalysts in PEMWE, starting from the fundamentals of OER,including the operation environment of OER catalysts, catalytic performance evaluation withinPEMWE, as well as catalytic and dissolution mechanisms. Subsequently, the catalyst classificationand preparation/characterization techniques are summarized with the focus on the dynamic structure-property relationship. Guided by these understandings, an overview of the design strategiesfor performance enhancement is presented. Specifically, we construct a mathematical frameworkfor cost-performance optimization to offer quantitative guidance for catalyst design. Finally, futureperspectives are proposed, aiming to establish a theoretical framework for rational catalyst design.展开更多
As promising high-temperature proton exchange membranes,phosphoric acid(PA)doped polybenzimidazole(PBI)membranes still face challenges,including excessive PA leaching and limited long-term stability.The preparation of...As promising high-temperature proton exchange membranes,phosphoric acid(PA)doped polybenzimidazole(PBI)membranes still face challenges,including excessive PA leaching and limited long-term stability.The preparation of mixed matrix membranes(MMMs)has emerged as a viable strategy to address these limitations,which can combine the excellent mechanical properties of polymers with the structural advantages of porous fillers.Among various filler materials,nitrogen-containing porous organic polymers(POPs)have shown particular promise because of their excellent compatibility with polymers.Therefore,in this work,a new pyridine-based POP called Py-POP was synthesized.Py-POP was mixed with commercial poly[2,2′-(p-oxidiphenylene)-5,5′-benzimidazole](OPBI)to prepare MMMs.Theoretical calculations indicate that the pyridine groups exhibit strong interactions with PA,significantly enhancing both PA retention and proton conduction efficiency.Remarkably,the PA retention rate of the composite membrane doped with 10 wt%Py-POP is 77.2%at 80/40%RH,which is much higher than that of the OPBI(62.7%).Furthermore,the membrane achieves an outstanding proton conductivity of 0.173 S cm^(-1)at 180℃,which is 4.2 times higher than that of the OPBI membrane.The peak power density of the composite membrane can achieve 915.1 mW cm^(-2) and remains at 891.5 mW cm^(-2) after 80 cycles of testing at 180℃.展开更多
Proton exchange membrane water electrolysis(PEMWE)is a favorable technology for producing highpurity hydrogen under high current density using intermittent renewable energy.The performance of PEMWE is largely determin...Proton exchange membrane water electrolysis(PEMWE)is a favorable technology for producing highpurity hydrogen under high current density using intermittent renewable energy.The performance of PEMWE is largely determined by the oxygen evolution reaction(OER),a sluggish four-electron reaction with a high reaction barrier.Nowadays,iridium(Ir)-based catalysts are the catalysts of choice for OER due to their excellent activity and durability in acidic solution.However,its high price and unsatisfactory electrochemical performance severely restrict the PEMWE’s practical application.In this review,we initiate by introducing the current OER reaction mechanisms,namely adsorbate evolution mechanism and lattice oxygen mechanism,with degradation mechanisms discussed.Optimized strategies in the preparation of advanced Ir-based catalysts are further introduced,with merits and potential problems also discussed.The parameters that determine the performance of PEMWE are then introduced,with unsolved issues and related outlooks summarized in the end.展开更多
This study explores the impact of board diversity on firm performance,with a focus on companies listed on the Singapore Stock Exchange(SGX).Board diversity is examined across various dimensions,including gender,age,et...This study explores the impact of board diversity on firm performance,with a focus on companies listed on the Singapore Stock Exchange(SGX).Board diversity is examined across various dimensions,including gender,age,ethnicity,and professional background,to understand its relationship with key performance indicators such as Return on Assets(ROA)and Return on Equity(ROE).Using a quantitative research approach,the study analyzes data from 90 publicly listed firms,employing descriptive statistics,correlation analysis,and multiple regression techniques.The findings reveal that the direct correlation between board diversity and financial performance,particularly in terms of ROA and ROE,is not statistically significant in the studied sample.Despite the lack of direct significance,the research underscores the nuanced and multifaceted role of diversity in corporate governance,suggesting that its impact may be more complex and influenced by various contextual factors.The study concludes by recommending that companies continue to enhance gender diversity,balance age structures,tailor professional backgrounds to industry needs,and manage board tenure effectively to optimize corporate governance and support sustainable growth.展开更多
ISO releases two standards for textiles.Recently,two international standards,ISO 8159:2025,Textiles-Morphology of fibres and yarns-Vocabulary,and ISO 17971:2025,Textiles-Smart textiles-Test method for determining the ...ISO releases two standards for textiles.Recently,two international standards,ISO 8159:2025,Textiles-Morphology of fibres and yarns-Vocabulary,and ISO 17971:2025,Textiles-Smart textiles-Test method for determining the screen-touch properties of fabrics,were officially released.They are of positive significance for eliminating technical ambiguities in exchanges on textile products and filling the gaps in international standards.展开更多
To prevent server compromise attack and password guessing attacks,an improved and efficient verifier-based key exchange protocol for three-party is proposed,which enables two clients to agree on a common session key w...To prevent server compromise attack and password guessing attacks,an improved and efficient verifier-based key exchange protocol for three-party is proposed,which enables two clients to agree on a common session key with the help of the server.In this protocol,the client stores a plaintext version of the password,while the server stores a verifier for the password.And the protocol uses verifiers to authenticate between clients and the server.The security analysis and performance comparison of the proposed protocol shows that the protocol can resist many familiar attacks including password guessing attacks,server compromise attacks,man-in-the-middle attacks and Denning-Sacco attacks,and it is more efficient.展开更多
Aim To prepare the prolonged-released microspheres of mefformin hydrochloride. Methods Ion-exchange resin-drug mefformin hydrochloride complexes were prepared as core materials, and followed by coating using ethylcell...Aim To prepare the prolonged-released microspheres of mefformin hydrochloride. Methods Ion-exchange resin-drug mefformin hydrochloride complexes were prepared as core materials, and followed by coating using ethylcellulose （EC） by the emulsion solvent diffusion technique. The release rate of mefformin from the microcapsules was highly dependent on the encapsulating formulation, thus being used as an index for formulation screening. Orthogonal experiments were performed to optimize the coating formulation. Results The final chosen formulation for coating of mefformin microcapsules were as follows： （ 1 ） the ratio of EC （20cps） to EC （45cps） was 50：50; （2） the ratio of plasticizer to coating materials was 20% ;and （3） the ratio of resin-mefformin complexes to coating materials was 5 ： 1. Conclusion The prolonged release microspheres of mefformin hydrochloride were successfully prepared.展开更多
Exchange bias effect is observed in the phase separated La0.33Pr0.34Ca0.33MnO3 thin films. High exchange bias field of about 1 kOe is achieved at 4 K. The exchange bias effect in La0.33Pr0.34Ca0.33MnO3 thin films migh...Exchange bias effect is observed in the phase separated La0.33Pr0.34Ca0.33MnO3 thin films. High exchange bias field of about 1 kOe is achieved at 4 K. The exchange bias effect in La0.33Pr0.34Ca0.33MnO3 thin films might originate from the intrinsic phase separation of the La0.33Pr0.34Ca0.33MnO3 or surface effect. The dependence of exchange bias effect on temperature, cooling field, and thickness is also investigated. This work would open an avenue to the application in the magnetic memory devices based on the phase separated manganites.展开更多
基金supported by The University of Hong Kong,China(109000487,109001694,204610401,and 204610519)National Natural Science Foundation of China(82402225)(to JH).
文摘Chemical exchange saturation transfer magnetic resonance imaging is an advanced imaging technique that enables the detection of compounds at low concentrations with high sensitivity and spatial resolution and has been extensively studied for diagnosing malignancy and stroke.In recent years,the emerging exploration of chemical exchange saturation transfer magnetic resonance imaging for detecting pathological changes in neurodegenerative diseases has opened up new possibilities for early detection and repetitive scans without ionizing radiation.This review serves as an overview of chemical exchange saturation transfer magnetic resonance imaging with detailed information on contrast mechanisms and processing methods and summarizes recent developments in both clinical and preclinical studies of chemical exchange saturation transfer magnetic resonance imaging for Alzheimer’s disease,Parkinson’s disease,multiple sclerosis,and Huntington’s disease.A comprehensive literature search was conducted using databases such as PubMed and Google Scholar,focusing on peer-reviewed articles from the past 15 years relevant to clinical and preclinical applications.The findings suggest that chemical exchange saturation transfer magnetic resonance imaging has the potential to detect molecular changes and altered metabolism,which may aid in early diagnosis and assessment of the severity of neurodegenerative diseases.Although promising results have been observed in selected clinical and preclinical trials,further validations are needed to evaluate their clinical value.When combined with other imaging modalities and advanced analytical methods,chemical exchange saturation transfer magnetic resonance imaging shows potential as an in vivo biomarker,enhancing the understanding of neuropathological mechanisms in neurodegenerative diseases.
基金National Key R&D Program of China,Grant/Award Number:2021YFA1500900Basic and Applied Basic Research Foundation of Guangdong Province-Regional Joint Fund Project,Grant/Award Number:2021B1515120024+9 种基金Science Funds of the Education Office of Jiangxi Province,Grant/Award Number:GJJ2201324Science Funds of Jiangxi Province,Grant/Award Numbers:20242BAB25168,20224BAB213018Doctoral Research Start-up Funds of JXSTNU,Grant/Award Number:2022BSQD05China Postdoctoral Science Foundation,Grant/Award Number:2023M741121National Natural Science Foundation of China,Grant/Award Number:22172047Provincial Natural Science Foundation of Hunan,Grant/Award Number:2021JJ30089Shenzhen Science and Technology Program,Grant/Award Number:JCYJ20210324122209025Changsha Municipal Natural Science Foundation,Grant/Award Number:kq2107008Hunan Province of Huxiang Talent project,Grant/Award Number:2023rc3118Natural Science Foundation of Hunan Province,Grant/Award Number:2022JJ10006.
文摘Hydrogen energy from electrocatalysis driven by sustainable energy has emerged as a solution against the background of carbon neutrality.Proton exchange membrane(PEM)-based electrocatalytic systems represent a promising technology for hydrogen production,which is equipped to combine efficiently with intermittent electricity from renewable energy sources.In this review,PEM-based electrocatalytic systems for H2 production are summarized systematically from low to high operating temperature systems.When the operating temperature is below 130℃,the representative device is a PEM water electrolyzer;its core components and respective functions,research status,and design strategies of key materials especially in electrocatalysts are presented and discussed.However,strong acidity,highly oxidative operating conditions,and the sluggish kinetics of the anode reaction of PEM water electrolyzers have limited their further development and shifted our attention to higher operating temperature PEM systems.Increasing the temperature of PEM-based electrocatalytic systems can cause an increase in current density,accelerate reaction kinetics and gas transport and reduce the ohmic value,activation losses,ΔGH*,and power consumption.Moreover,further increasing the operating temperature(120-300℃)of PEM-based devices endows various hydrogen carriers(e.g.,methanol,ethanol,and ammonia)with electrolysis,offering a new opportunity to produce hydrogen using PEM-based electrocatalytic systems.Finally,several future directions and prospects for developing PEM-based electrocatalytic systems for H_(2) production are proposed through devoting more efforts to the key components of devices and reduction of costs.
文摘This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass transfer coefficients and air psychrometric correlations, the model provides insights into the impact of design and operational parameters on the exchanger cooling performance. Validated against an established numerical model, it accurately simulates cooling behavior with a Root Mean Square Deviation of 0.43 - 1.18˚C under varying inlet air conditions. The results show that tube geometry, including equivalent diameter, flatness ratio, and length significantly influences cooling outcomes. Smaller diameters enhance wet-bulb effectiveness but reduce cooling capacity, while increased flatness and length improve both. For example, extending the flatness ratio of a 15 mm diameter, 0.6 m long tube from 1 (circular) to 4 raises the exchange surface area from 0.028 to 0.037 m2, increasing wet-bulb effectiveness from 60% to 71%. Recommended diameters range from 5 mm for tubes under 0.5 m to 1 cm for tubes 0.5 to 1 m in length. Optimal air velocities depend on tube length: 1 m/s for tubes under 0.8 m, 1.5 m/s for lengths of 0.8 to 1.2 m, and up to 2 m/s for longer tubes. This model offers a practical alternative to complex numerical and CFD methods, with potential applications in cooling tower optimization for thermal and nuclear power plants and geothermal heat exchangers.
基金Project(2019yff0216502)supported by the National Key Research&Development Plan of Ministry of Science and Technology of ChinaProject(2021SK1020-4)supported by the Major Science and Technological Innovation Project of Hunan Province,China。
文摘Removing copper from nickel electrolysis anode solution has been a major keypoint in the nickel metallurgy industry.In this study,we proposed a novel process flow to promote removing copper from nickel electrolysis anode solution.A simulated nickel anode solution was designed,and static and dynamic adsorption experiments were conducted to determine the best of solution pH,adsorption time and temperature,resin dosage and particle size,and stirring speed.The optimal conditions were explored for copper removal from nickel electrolysis anode solution.Based on the optimal experimental conditions and the relevant experimental data,a novel process for copper removal from nickel electrolysis anodes was designed and verified.This novel process of copper removal from nickel electrolysis anodes was confirmed with nickel anolyte solution with nickel 50−60 g/L and copper 0.5 g/L.After finishing the novel process of copper removal,the nickel in the purified nickel anolyte became undetectable and copper concentration was 3 mg/L,the novel process of resin adsorption to remove copper from nickel anode solution through static and dynamic adsorptions has an efficacious copper removal.It is a beneficial supplement to traditional methods.
基金financially supported by the National Natural Science Foundation of China(Nos.11474111 and 11604281)the Young Elite Scientists Sponsorship Program by CAST(No.YESS20220618)the Hundreds of Talents program of Sun Yat-sen University(No.210192)
文摘A robust spontaneous exchange bias effect after zero-field cooling was observed in Co_(2)Sn_(1-x)Cr_(x)O_(4)system,which was driven by the transition from superspin-glass to superferromagnetic domain embedded in the ferrimagnetic matrix.Additionally,the exchange bias effect is gradually pronounced with the positive increase in the cooling field,known as the conventional exchange bias effect.However,as the cooling field gradually decreases and transits from positive to negative,the exchange bias effect can robustly remain positive in the low-negative-field region until the cooling field increases to be sufficiently large in the negative direction.
基金supported by the Japan Tunnelling Association and by JST SPRING(Grant Nos.JTA-R6-G1 and JPMJSP2114).
文摘Limited models have been devised using Stern theory to obtain the repulsive force from a double layer.Moreover,an elastoplastic model that differentiates various swelling behaviors because of exchangeable cation species is yet to be devised.In this study,we introduce a novel multiphysics elastoplastic model for swelling geomaterials that incorporates Stern theory.This model considered the finite size of exchangeable cations and specific adsorption phenomena,which are typically overlooked in existing models.Based on Stern theory,we derived the repulsive force from the double layer and integrated the force into the elastoplastic expansive bedrock model,which addresses electroechemoemechanical phenomena in the interlayer.The proposed model differentiated swelling behaviors based on the type of exchangeable cation species by incorporating these phenomena.To validate the model,a onedimensional(1D)numerical analysis was performed,demonstrating its capability to describe various swelling behaviors due to different exchangeable cation species through comparison with free swelling test results of bentonite.Additionally,a parametric study was conducted to elucidate the effect of the hydrated radius of exchangeable cations and the specific adsorption potential on swelling behavior,analyzed from the perspective of the equilibrium of charge distribution near the mineral surface.
基金Project supported by the National Natural Science Foundation of China(Grant No.62002105)the Key Research and Development Program of Hubei,China(Grant No.2021BEA163)。
文摘At present,most quantum secret sharing(QSS)protocols are more or less designed with the incorporation of classical secret sharing schemes.With the increasing maturity of quantum technology,QSS protocols based on pure quantum mechanics are becoming more important.Classical secret sharing schemes cannot achieve absolute security,and their involvement can compromise the security of QSS protocols.This paper proposes a QSS scheme based on Greenberger-Horn-Zeilinger(GHZ)basis measurement and quantum entanglement exchange.In this protocol,the secret sender stores the secret information using Pauli operations.Participants obtain their shares by measuring the product state sequentially.Finally,participants complete the secret reconstruction through quantum entanglement exchange and other related quantum operations.In addition,the particles held by participants in the protocol do not contain any secret information.Each participant's particles are in a state of maximum entanglement,and no participant can deduce the particle information of other participants through their own particles.At the same time,the protocol is based on pure quantum mechanics and does not involve classical schemes,which avoids the problem of reduced security of the protocol.Security analysis indicates that the protocol is not vulnerable to retransmission interception and collusion attacks.Moreover,it is capable of detecting and terminating the protocol promptly when facing with attacks from dishonest participants.
文摘Climate change,rising fuel prices,and fuel security are some challenges that have emerged and have grown worldwide.Therefore,to overcome these obstacles,highly efficient thermodynamic devices and heat recovery systems must be introduced.According to reports,much industrial waste heat is lost as flue gas from boilers,heating plants,etc.The primary objective of this study is to investigate and compare unary(Al_(2)O_(3))thermodynamically,binary with three different combinations of nanoparticles namely(Al_(2)O_(3)+TiO_(2),TiO_(2)+ZnO,Al_(2)O_(3)+ZnO)and ternary(Al_(2)O_(3)+TiO_(2)+ZnO)as a heat transfer fluid.Initially,three different types of binary nanofluids were prepared by dispersing two types of nanoparticles in individual trails,such as aluminum oxide,zinc oxide,and titanium dioxide in various combined concentrations(e.g.,2%,4%,and 6%)into the water as the base fluid,using an ultrasonicator to ensure uniform suspension.The operating parameters such as nanoparticle concentration and flow rate are varied to evaluate the performance of various hybrid nanofluids under counterflow configuration.The findings of this research indicate that the binary nanofluid Al_(2)O_(3)+ZnO exhibits the highest thermal performance factor(2.83),followed by the ternary nanofluid Al_(2)O_(3)+TiO_(2)+ZnO(0.828),with the lowest performance observed for the unary nanofluid Al_(2)O_(3)(0.799).This research highlights the need for advancement into novel nanomaterial combinations,optimization of required fluid properties,stability enhancement,and thermal performance to strengthen the utilization of hybrid nanofluids in heat exchangers.
文摘The purpose of the covert communication scheme is to conceal the communication behavior entirely.In such schemes,the sender and receiver rely on secret keys to establish a covert channel.However,conventional key exchange protocols would expose the key exchange process between them.An adversary who observes the key exchange would be aware of the existence of communication behavior.The keys used in covert communication are not suitable to be generated through conventional key exchange schemes.To address this,we propose a blockchain-based covert elliptic-curve Diffie-Hellman key exchange scheme(BCDH)to conceal the process of the key exchange in blockchain transactions.Following a straightforward setup,BCDH allows the sender and receiver to covertly exchange a secret key on a blockchain without direct communication.Furthermore,we expand the BCDH approach to operate across multiple blockchains,further enhancing its covertness and stability.We analyze BCDH from several perspectives,including covertness,security,randomness,etc.Additionally,we implement a prototype of BCDH on the Ethereum platform to assess its feasibility and performance.Our evaluation demonstrates that BCDH is efficient and well-suited for real-world applications.
基金financially supported by the National Natural Science Foundation of China(22172063)the Young Taishan Scholars Program(tsqn201812080)+2 种基金the China Scholarship Council(CSC)for scholarship support(202008130132)the Independent Cultivation Program of Innovation Team of Ji’nan City(2021GXRC052)funding from CERCA Programme/Generalitat de Catalunya。
文摘Proton exchange membrane water electrolyzers(PEMWEs)are pivotal for efficient hydrogen production due to their high energy efficiency and ability to operate at high current densities,making them ideally suited for integration with renewable energy sources.Cobalt(Co)-based nanomaterials,characterized by diverse oxidation states,tunable electronic spin states,and hybrid orbitals,have emerged as promising non-noble metal alternatives to platinum group catalysts for accelerating the anodic oxygen evolution reaction(OER).Based on their inherent properties,this review provides a comprehensive overview of the latest developments in Co-based nanomaterials for acidic OER.The review begins by introducing the operational principles of PEMWEs,the underlying catalytic mechanisms,and the critical design considerations for OER catalysts.It then explores strategies to enhance the activity and stability of Co-based catalysts for acidic OER in PEMWEs,including the incorporation of corrosion-resistant metals or dispersion on acid-resistant supports to increase active surface area and stability;utilization of geometric structural engineering to improve structural integrity and active site efficiency;the optimization of reaction mechanisms to fine-tune catalytic pathways for enhanced stability and performance.The performance degradation mechanisms and metal leaching analysis for Co-based catalysts in PEMWE are also clarified.Finally,this review not only outlines the key challenges associated with Co-based catalysts for acidic OER but also proposes potential strategies to overcome these limitations,offering a roadmap for future advancements and practical implementation of PEMWE technology.
基金Natural Science Foundation of China(grant nos 22075031)Jilin Provincial Science&Technology Department(grant nos 20220201105GX)Jilin Provincial Development and Reform Commission(grant nos 2023C034-4)。
文摘The development of alkaline fuel cells is moving forward at an accelerated pace,and the application of ether-free bonded polymers to anion exchange membranes(AEMs)has been widely investigated.However,the question of the“trade-off”between AEM ionic conductivity and dimensional stability remains difficult.The strategy of inducing microphase separation to improve the performance of AEM has attracted much attention recently,but the design of optimal molecular structures is still being explored.Here,this work introduced different ratios of 3-bromo-1,1,1-trifluoroacetone(x=40,50,and 60)into the main chain of poly(p-terphenylene isatin).Because fluorinated groups have excellent hydrophobicity,hydrophilic hydroxyl-containing side chains are introduced to jointly adjust the formation of phase separation structure.The results show that PTI-PTF_(50)-NOH AEM with the appropriate fluorinated group ratio has the best ionic conductivity and alkali stability under the combined effect of both.It has an ionic conductivity of 133.83 mS cm^(-1)at 80°C.In addition,the OH-conductivity remains at 89%of the initial value at 80°C and 3 M KOH for 1056 h of immersion.The cell polarization curve based on PTI-PTF_(50)-NOH shows a power density of 734.76 mW cm^(-2)at a current density of 1807.7 mA cm^(-2).
文摘Proton exchange membrane water electrolysis (PEMWE) has garnered significant attention as apivotal technology for converting surplus electricity into hydrogen for long-term storage, as well asfor providing high-purity hydrogen for aerospace and high-end manufacturing applications. Withthe ongoing commercialization of PEMWE, advancing iridium-based oxygen evolution reaction(OER) catalysts remains imperative to reconcile stringent requirements for high activity, extendedlongevity, and minimized noble metal loading. The review provides a systematic analysis of theintegrated design of iridium-based catalysts in PEMWE, starting from the fundamentals of OER,including the operation environment of OER catalysts, catalytic performance evaluation withinPEMWE, as well as catalytic and dissolution mechanisms. Subsequently, the catalyst classificationand preparation/characterization techniques are summarized with the focus on the dynamic structure-property relationship. Guided by these understandings, an overview of the design strategiesfor performance enhancement is presented. Specifically, we construct a mathematical frameworkfor cost-performance optimization to offer quantitative guidance for catalyst design. Finally, futureperspectives are proposed, aiming to establish a theoretical framework for rational catalyst design.
基金the Natural Science Foundation of Gansu Province(No.24JRRA391).
文摘As promising high-temperature proton exchange membranes,phosphoric acid(PA)doped polybenzimidazole(PBI)membranes still face challenges,including excessive PA leaching and limited long-term stability.The preparation of mixed matrix membranes(MMMs)has emerged as a viable strategy to address these limitations,which can combine the excellent mechanical properties of polymers with the structural advantages of porous fillers.Among various filler materials,nitrogen-containing porous organic polymers(POPs)have shown particular promise because of their excellent compatibility with polymers.Therefore,in this work,a new pyridine-based POP called Py-POP was synthesized.Py-POP was mixed with commercial poly[2,2′-(p-oxidiphenylene)-5,5′-benzimidazole](OPBI)to prepare MMMs.Theoretical calculations indicate that the pyridine groups exhibit strong interactions with PA,significantly enhancing both PA retention and proton conduction efficiency.Remarkably,the PA retention rate of the composite membrane doped with 10 wt%Py-POP is 77.2%at 80/40%RH,which is much higher than that of the OPBI(62.7%).Furthermore,the membrane achieves an outstanding proton conductivity of 0.173 S cm^(-1)at 180℃,which is 4.2 times higher than that of the OPBI membrane.The peak power density of the composite membrane can achieve 915.1 mW cm^(-2) and remains at 891.5 mW cm^(-2) after 80 cycles of testing at 180℃.
基金supported by the National Key Research and Development Program of China(No.2022YFB4004100)National Natural Science Foundation of China(Nos.U22A20396,22209168)+1 种基金Natural Science Foundation of Anhui Province(No.2208085UD04)Liaoning Binhai Laboratory(No.LBLF-2023-04),and Shandong Energy Institute(No.SEI U202307).
文摘Proton exchange membrane water electrolysis(PEMWE)is a favorable technology for producing highpurity hydrogen under high current density using intermittent renewable energy.The performance of PEMWE is largely determined by the oxygen evolution reaction(OER),a sluggish four-electron reaction with a high reaction barrier.Nowadays,iridium(Ir)-based catalysts are the catalysts of choice for OER due to their excellent activity and durability in acidic solution.However,its high price and unsatisfactory electrochemical performance severely restrict the PEMWE’s practical application.In this review,we initiate by introducing the current OER reaction mechanisms,namely adsorbate evolution mechanism and lattice oxygen mechanism,with degradation mechanisms discussed.Optimized strategies in the preparation of advanced Ir-based catalysts are further introduced,with merits and potential problems also discussed.The parameters that determine the performance of PEMWE are then introduced,with unsolved issues and related outlooks summarized in the end.
文摘This study explores the impact of board diversity on firm performance,with a focus on companies listed on the Singapore Stock Exchange(SGX).Board diversity is examined across various dimensions,including gender,age,ethnicity,and professional background,to understand its relationship with key performance indicators such as Return on Assets(ROA)and Return on Equity(ROE).Using a quantitative research approach,the study analyzes data from 90 publicly listed firms,employing descriptive statistics,correlation analysis,and multiple regression techniques.The findings reveal that the direct correlation between board diversity and financial performance,particularly in terms of ROA and ROE,is not statistically significant in the studied sample.Despite the lack of direct significance,the research underscores the nuanced and multifaceted role of diversity in corporate governance,suggesting that its impact may be more complex and influenced by various contextual factors.The study concludes by recommending that companies continue to enhance gender diversity,balance age structures,tailor professional backgrounds to industry needs,and manage board tenure effectively to optimize corporate governance and support sustainable growth.
文摘ISO releases two standards for textiles.Recently,two international standards,ISO 8159:2025,Textiles-Morphology of fibres and yarns-Vocabulary,and ISO 17971:2025,Textiles-Smart textiles-Test method for determining the screen-touch properties of fabrics,were officially released.They are of positive significance for eliminating technical ambiguities in exchanges on textile products and filling the gaps in international standards.
基金The National High Technology Research and Development Program of China(863Program)(No.2001AA115300)the Natural Science Foundation of Liaoning Province(No.20031018,20062023)
文摘To prevent server compromise attack and password guessing attacks,an improved and efficient verifier-based key exchange protocol for three-party is proposed,which enables two clients to agree on a common session key with the help of the server.In this protocol,the client stores a plaintext version of the password,while the server stores a verifier for the password.And the protocol uses verifiers to authenticate between clients and the server.The security analysis and performance comparison of the proposed protocol shows that the protocol can resist many familiar attacks including password guessing attacks,server compromise attacks,man-in-the-middle attacks and Denning-Sacco attacks,and it is more efficient.
文摘Aim To prepare the prolonged-released microspheres of mefformin hydrochloride. Methods Ion-exchange resin-drug mefformin hydrochloride complexes were prepared as core materials, and followed by coating using ethylcellulose （EC） by the emulsion solvent diffusion technique. The release rate of mefformin from the microcapsules was highly dependent on the encapsulating formulation, thus being used as an index for formulation screening. Orthogonal experiments were performed to optimize the coating formulation. Results The final chosen formulation for coating of mefformin microcapsules were as follows： （ 1 ） the ratio of EC （20cps） to EC （45cps） was 50：50; （2） the ratio of plasticizer to coating materials was 20% ;and （3） the ratio of resin-mefformin complexes to coating materials was 5 ： 1. Conclusion The prolonged release microspheres of mefformin hydrochloride were successfully prepared.
基金V. ACKNOWLEDGEMENTS This work was supported by the National Natural Science Foundation of China （No.11374279 and No.11034006）, the National Basic Research Program of China （No.2014CB921102）, the Strategic Priority Research Program of the Chinese Academy of Sciences （No.XDB01020000）, the Specialized Research Fund for the Doctoral Program of Higher Education （No.20113402110046）, and the Fundamental Research Funds for the Central Universities （No.WK2340000035）.
文摘Exchange bias effect is observed in the phase separated La0.33Pr0.34Ca0.33MnO3 thin films. High exchange bias field of about 1 kOe is achieved at 4 K. The exchange bias effect in La0.33Pr0.34Ca0.33MnO3 thin films might originate from the intrinsic phase separation of the La0.33Pr0.34Ca0.33MnO3 or surface effect. The dependence of exchange bias effect on temperature, cooling field, and thickness is also investigated. This work would open an avenue to the application in the magnetic memory devices based on the phase separated manganites.
