Photothermal catalysis is a promising technology primarily utilized the solar energy to produce photogenerated e^(-)/h^(+) pairs together with the production of heat energy.However,the inefficient separation of charge...Photothermal catalysis is a promising technology primarily utilized the solar energy to produce photogenerated e^(-)/h^(+) pairs together with the production of heat energy.However,the inefficient separation of charge carriers and inadequate response to near-infrared(NIR)light usually leads to the unsatisfactory photocatalytic efficiency,hindering their application potentials.In this work,a significantly enhanced photothermal catalytic hydrogen evolution reaction over the lead-free perovskite Cs_(3)Bi_(2)Br_(9)/FeS_(2)(CBB/FS)heterostructure is simultaneously verified,where the CBB/FS Z-scheme heterojunctions display the strong stability and superb photothermal catalytic activity.Under the simulated solar irradiation(AM 1.5G),the optimized CBB/FS-5 achieves a photocatalytic hydrogen evolution rate of 31.5 mmol g^(-1)h^(-1),which is 112.6 and 77.1 times higher than that of FS and CBB,respectively,together with an apparent quantum yield of 29.5%at 420 nm.This significantly improved photocatalytic H_(2)evolution can be mainly attributed to the Z-scheme charge transfer and photothermal-assisted synergistically enhanced photocatalytic H_(2)production,and the potential mechanism of the enhanced photocatalytic H_(2)evolution is also proposed by photoelectrochemical characterizations,in situ XPS,EPR spectra,and the DFT calculations.This work provides new insights to the design of high-efficient photothermal catalysts,leading to the sustainable and efficient solutions towards the energy and environmental challenges.展开更多
All-solid-state batteries(ASSBs)with sulfide-type solid electrolytes(SEs)are gaining significant attention due to their potential for the enhanced safety and energy density.In the slurry-coating process for ASSBs,nitr...All-solid-state batteries(ASSBs)with sulfide-type solid electrolytes(SEs)are gaining significant attention due to their potential for the enhanced safety and energy density.In the slurry-coating process for ASSBs,nitrile rubber(NBR)is primarily used as a binder due to its moderate solubility in non-polar solvents,which exhibites minimal chemical reactivity with sulfide SEs.However,the NBR binder,composed of butadiene and acrylonitrile units with differing polarities,exhibits different chemical compatibility depending on the subtle differences in polarity of solvents.Herein,we systematically demonstrate how the chemical compatibility of solvents with the NBR binder influences the performance of ASSBs.Anisole is found to activate the acrylonitrile units,inducing an elongated polymer chain configuration in the binder solution,which gives an opportunity to strongly interact with the solid components of the electrode and the current collector.Consequently,selecting anisole as a solvent for the NBR binder enables the fabrication of a mechanically robust graphite-silicon anode,allowing ASSBs to operate at a lower stacking pressure of 16 MPa.This approach achieves an initial capacity of 480 mAh g^(-1),significantly higher than the 390 mAh g^(-1)achieved with the NBR/toluene binder that has less chemical compatibility.Furthermore,internal stress variations during battery operation are monitored,revealing that the enhanced mechanical properties,achieved through acrylonitrile activation,effectively mitigate internal stress in the graphite/silicon composite anode.展开更多
Systematic optimization of the photocatalyst and investigation of the role of each component is important to maximizing catalytic activity and comprehending the photocatalytic conversion of CO_(2) reduction to solar f...Systematic optimization of the photocatalyst and investigation of the role of each component is important to maximizing catalytic activity and comprehending the photocatalytic conversion of CO_(2) reduction to solar fuels.A surface-modified Ag@Ru-P25 photocatalyst with H_(2)O_(2) treatment was designed in this study to convert CO_(2) and H_(2)O vapor into highly selective CH4.Ru doping followed by Ag nanoparticles(NPs)cocatalyst deposition on P25(TiO_(2))enhances visible light absorption and charge separation,whereas H_(2)O_(2) treatment modifies the surface of the photocatalyst with hydroxyl(–OH)groups and promotes CO_(2) adsorption.High-resonance transmission electron microscopy,X-ray photoelectron spectroscopy,X-ray absorption near-edge structure,and extended X-ray absorption fine structure techniques were used to analyze the surface and chemical composition of the photocatalyst,while thermogravimetric analysis,CO_(2) adsorption isotherm,and temperature programmed desorption study were performed to examine the significance of H_(2)O_(2) treatment in increasing CO_(2) reduction activity.The optimized Ag1.0@Ru1.0-P25 photocatalyst performed excellent CO_(2) reduction activity into CO,CH4,and C2H6 with a~95%selectivity of CH4,where the activity was~135 times higher than that of pristine TiO_(2)(P25).For the first time,this work explored the effect of H_(2)O_(2) treatment on the photocatalyst that dramatically increases CO_(2) reduction activity.展开更多
Understanding the mechanical and transport behavior of thin(i.e.small aperture)cracks slipping under supercritical carbon dioxide(sc-CO_(2))conditions is essential to evaluate the integrity of sealing formations with ...Understanding the mechanical and transport behavior of thin(i.e.small aperture)cracks slipping under supercritical carbon dioxide(sc-CO_(2))conditions is essential to evaluate the integrity of sealing formations with buoyant sc-CO_(2)below and the success of waterless fracturing.The two major items of interest in this work are frictional strength and permeability change of the crack.We used a triaxial cell that permits in situ visualization to conduct and monitor slippage along the faces of narrow cracks subjected to triaxial stresses.Such cracks are analogs to small geological faults.We tested carbonate-rich,1-inch diameter Wolfcamp shale samples that are saw cut 30to vertical to create a thin crack.Friction coefficients ranged from about 0.6 to 0.8 consistent with expectations for brittle rocks.The sc-CO_(2)generally did not alter friction coefficient over the time scale of experiments.From a transport perspective,saturating cracks with sc-CO_(2)substantially decreased permeability of the crack by 26%e52%,while slip resulted in a variety of permeability responses.Overall,the combined impact of sc-CO_(2)saturation and slip reduced fault permeability for all tests.Our observations support the notion that the sealing capacity of some caprocks improves when saturated with sc-CO_(2)and that some slip of small fractures is not necessarily detrimental to caprock integrity.展开更多
Polymer-liquid crystals(PLCs)are common materials for smart windows.However,PLC smart windows usually require high driving voltage to maintain transparency.We synthesized a novel PLC smart film by doping multi-wall ca...Polymer-liquid crystals(PLCs)are common materials for smart windows.However,PLC smart windows usually require high driving voltage to maintain transparency.We synthesized a novel PLC smart film by doping multi-wall carbon nanotubes(MWCNTs)into a reverse-mode polymer network liquid crystal(R-PNLC).展开更多
Personal conditioning system(PCS)is receiving considerable attention due to its energy-saving potential and the ability to satisfy individual comfort requirements.As a part of PCS,personal heating systems can maintain...Personal conditioning system(PCS)is receiving considerable attention due to its energy-saving potential and the ability to satisfy individual comfort requirements.As a part of PCS,personal heating systems can maintain human thermal comfort in cold environments,which leads to their potential role of important heating mode in cold winter,especially in the Hot Summer and Cold Winter regions of China.In order to better promote the development and application of personal heating systems,this paper reviews the published studies.Personal heating systems can be divided into four types based on the mode of heat transfer:conductive,convective,radiative and combinative type.Characteristics of each category and respective devices are introduced.Furthermore,identifying the effects of personal heating on thermal comfort and the models for predicting or evaluating thermal comfort during local heating.This paper would provide users with a guideline for choosing suitable heating equipment during winter.展开更多
Dynamic control of the absorption frequency and intensity of metamaterial absorbers has attracted considerable attention,and many kinds of tunable metamaterial absorbers have been proposed.Unfortunately,due to the int...Dynamic control of the absorption frequency and intensity of metamaterial absorbers has attracted considerable attention,and many kinds of tunable metamaterial absorbers have been proposed.Unfortunately,due to the integration of separate resonant unit and tunable unit,these designed metamaterial absorbers suffer from complex structure and low sensitivity.We numerically and experimentally demonstrate a tunable metamaterial absorber composed of artificial dielectric atoms as both resonant and tunable unit arrayed periodically in the background matrix on the metallic plate.Polarization insensitive and wide incident angle absorption band with simulated and experimental absorptivity of 99%and 96%at 9.65 GHz are achieved at room temperature.The absorption frequency can be gradually modulated by temperature,however,the absorption intensity at working frequency remains near unity.The dielectric atoms based tunable metamaterial absorbers with simple structure have potential applications as tempe rature sensors and frequency selective thermal emitters.展开更多
The melting process of solid-liquid phase change materials(PCM)has a significant impact on their energy storage performance.To more effectively apply solid-liquid PCM for energy storage,it is crucial to study the regu...The melting process of solid-liquid phase change materials(PCM)has a significant impact on their energy storage performance.To more effectively apply solid-liquid PCM for energy storage,it is crucial to study the regulation of melting process of solid-liquid PCM,which is numerically investigated based on double multiple relaxation time lattice Boltzmann method(MRT-LBM)in this work.In this work we pay more attention to the effects of different Stefan numbers(Ste)and Rayleigh numbers(Ra)on the melting process.The results indicate that the PCM melting is greatly influenced by the Ste number and Ra number,which can be divided into the heat conduction dominant stage and the convection dominant stage,according to the onset time of convection Fo_(C).In order to describe the contribution of the heat conduction dominant stage to the whole melting process quantitatively,we firstly propose the ratio of the heat conduction dominant stage R_(pc),which can be defined as the ratio of Fo_(C)to the complete melting time Fo_(M).R_(pc)gradually decreases as the Ra number increases,and when the Ste number rises:R_(pc)=90.0%when Ste=1.0 and Ra=1×10^(5),R_(pc)=39.6%when Ste=0.1 and Ra=1×10^(5),and R_(pc)=14.0%when Ste=1.0 and Ra=1×10~7.A regime map about the effects of different Ste numbers and Ra numbers on R_(pc)has been further summarized.The discovered findings would be helpful in regulating melting process in the energy storage of solid-liquid PCM.展开更多
In order to solve the problem of imbalance resource allocation and service income in the elderly care service industry,this article establishes three service income models in different situations for a single provider...In order to solve the problem of imbalance resource allocation and service income in the elderly care service industry,this article establishes three service income models in different situations for a single provider and a single integrator while considering the quality as well as government subsidies.The results showed that government subsidies can significantly improve quality efforts and service income with a mutual restriction between quality and service income.Government subsidies would have an impact on the quality,and they are more conducive to the service income of providers.When government subsidies are less than 80% of the service income,the incentive effect is better.展开更多
A novel multispectral smart window has been proposed,which features dynamic modulation of light transmittance and effective shielding against electromagnetic microwave radiation.This design integrates liquid crystal d...A novel multispectral smart window has been proposed,which features dynamic modulation of light transmittance and effective shielding against electromagnetic microwave radiation.This design integrates liquid crystal dynamic scattering and dye doping techniques,enabling the dual regulation of transmittance and scattering within a singlelayer smart window.Additionally,the precise control of conductive film thickness ensures the attainment of robust microwave signal shielding.We present a theoretical model for ion movement in the presence of an alternating electric field,along with a novel approach to manipulate negative dielectric constant.The proposed model successfully enables a rapid transition between light transparent,absorbing and haze states,with an optimum drive frequency adjustable to approximately 300 Hz.Furthermore,the resistive design of the conductive layer effectively mitigates microwave radiation within the 2−18 GHz range.These findings offer an innovative perspective for future advancements in environmental construction.展开更多
Efficient and cost-effective electrocatalysts that can operate across a wide range of pH conditions are essential for green hydrogen production.Inspired by biological systems,Fe_(7)S_(8)nanoparticles incorporated on p...Efficient and cost-effective electrocatalysts that can operate across a wide range of pH conditions are essential for green hydrogen production.Inspired by biological systems,Fe_(7)S_(8)nanoparticles incorporated on polydopamine matrix electrocatalyst were synthesized by co-precipitation and annealing process.The resulting Fe_(7)S_(8)/C electrocatalyst possesses a three-dimensional structure and exhibits enhanced electrocatalytic performance for hydrogen production across various pH conditions.Notably,the Fe_(7)S_(8)/C electrocatalyst demonstrates exceptional activity,achieving low overpotentials of 90.6,45.9,and 107.4 mV in acidic,neutral,and alkaline environments,respectively.Electrochemical impedance spectroscopy reveals that Fe_(7)S_(8)/C exhibits the lowest charge transfer resistance under neutral conditions,indicating an improved proton-coupled electron transfer process.Continuous-wave electron paramagnetic resonance results confirm a change in the valence state of Fe from 3+to 1+during the hydrogen evolution reaction(HER).These findings closely resemble the behavior of natural[FeFe]-hydrogenase,known for its superior hydrogen production in neutral conditions.The remarkable performance of our Fe_(7)S_(8)/C electrocatalyst opens up new possibilities for utilizing bioinspired materials as catalysts for the HER.展开更多
An outliers-free isogeometric modeling method for rotating disk-shaft systems is developed.The Timoshenko beam theory and artificial spring technique are employed for the rotating shaft and elastic boundary conditions...An outliers-free isogeometric modeling method for rotating disk-shaft systems is developed.The Timoshenko beam theory and artificial spring technique are employed for the rotating shaft and elastic boundary conditions.The nonlinear parameterization method is employed for the removal of outliers and three different nonlinear mappings are developed for the discussion of the accuracy of low modes.The energy coupling method between disks and shaft under nonlinear mapping is performed by using the Newton Raphson method.The results show that the isoparametric mapping has better performance in the accuracy of low modes than other nonlinear mapping and the outliers can also be removed,besides,the present method has good convergence rate for different boundary conditions.The accuracy of the proposed method shows good consistency with the Finite Element Method.The time cost of modeling is reduced by 71.4%compared to the traditional rotor model for a multiple disks rotor system,which indicates that the present approach has potential to provide more efficient optimization models of disk-shaft systems.The proposed method can provide a new modeling framework and can be easily extended to the prediction and optimization of vibration characteristics of complex rotor systems with multiple disks and supports.展开更多
Smart windows,capable of dynamically regulating indoor heat,offer a promising avenue for effectively reducing energy consumption.Hydrogel-based smart windows are excellent at thermal modulation and daylighting,but the...Smart windows,capable of dynamically regulating indoor heat,offer a promising avenue for effectively reducing energy consumption.Hydrogel-based smart windows are excellent at thermal modulation and daylighting,but they are difficult to commercialize globally due to problems like winter ice formation,which can affect thermal insulation,daylighting,and structural integrity,as well as an impractical cloud point temperature(t_(cp)).To solve these issues,a ternary anti-freezing system consisting of ethylene glycol(EG),glycerol,and water is proposed.With the t_(cp)regulated at 31.6℃,the system strikes a balance between outstanding daylighting(91.89%)and solar modulation ability(78.32%).Furthermore,the system shows resilience even below-30.0℃and long-term stability,which qualifies it for use in densely populated regions even with severely cold weather.To further illustrate the distinct impacts of EG and glycerol,the optical characteristics and tcpof binary systems containing EG and water as well as glycerol and water were examined.The durability test includes severely cold temperature of-30.0℃ and solar exposure temperature of 60.0℃.This work would offer insights to advance the field's understanding of antifreezing capability modification in smart windows and advance the development of environmentally and energy-efficiently designed buildings.展开更多
With the development of optical technologies,transparent materials that provide protection from light have received considerable attention from scholars.As important channels for external light,windows play a vital ro...With the development of optical technologies,transparent materials that provide protection from light have received considerable attention from scholars.As important channels for external light,windows play a vital role in the regulation of light in buildings,vehicles,and aircrafts.There is a need for windows with switchable optical properties to prevent or attenuate damage or interference to the human eye and light-sensitive instruments by inappropriate optical radiation.In this context,liquid crystals(LCs),owing to their rich responsiveness and unique optical properties,have been considered among the best candidates for advanced light protection materials.In this review,we provide an overview of advances in research on LC-based methods for protection against light.First,we introduce the characteristics of different light sources and their protection requirements.Second,we introduce several classes of light modulation principles based on liquid crystal materials and demonstrate the feasibility of using them for light protection.In addition,we discuss current light protection strategies based on liquid crystal materials for different applications.Finally,we discuss the problems and shortcomings of current strategies.We propose several suggestions for the development of liquid crystal materials in the field of light protection.展开更多
The traditional ventilation mode of subway vehicles adopts the form that the inlets and outlets are placed on the upper part of the cabin.The air distribution formed in this mode often cause serious problems of therma...The traditional ventilation mode of subway vehicles adopts the form that the inlets and outlets are placed on the upper part of the cabin.The air distribution formed in this mode often cause serious problems of thermal comfort and energy consumption.In order to solve these problems caused by the traditional ventilation mode,a new hybrid ventilation mode was proposed.The hybrid ventilation mode uses both upper and underside air supply inlets.A method for evaluating the air distribution performance of subway air conditioning was developed.The method applies non-uniformity coefficients,maximum temperature difference,air diffusion performance index,modified energy utilization coefficient and Air short-circuit comprehensive coefficient.Air short-circuit comprehensive coefficient was a new index to evaluate the degree of air short-circuit of supply air.Based on the airflow simulation,the air distribution performance for the hybrid ventilation mode was evaluated using these indexes,and compared with the traditional ventilation mode.The results show that compared with the traditional ventilation mode,the hybrid ventilation mode has more uniform temperature distribution,better thermal comfort,higher energy utilization efficiency and lower degree of air short-circuit of supply air.展开更多
In this study,a turbulent non-premixed(diffusion)methane-air flame has been investigated computationally to analyze the influences of pressure and gravity on flame structure and sooting characteristics between 1 and 1...In this study,a turbulent non-premixed(diffusion)methane-air flame has been investigated computationally to analyze the influences of pressure and gravity on flame structure and sooting characteristics between 1 and 10 atm.The simulation has been conducted in a 2-D axisymmetric computational domain using the finite volume-based computational fluid dynamics(CFD)code.The interaction of turbulence and chemistry is modeled by considering the steady laminar flamelet model(SLFM)and the GRI Mech 3.0 chemical mechanism.The radiative heat transfer calculation is carried out by considering the discrete ordinate(DO)method and the weighted sum grey gas model(WSGGM).The semi-empirical Moss-Brookes model is considered to calculate soot.The impact of gravity on flame and sooting characteristics are evaluated by comparing the normal-gravity flames with the zero-gravity flames.The effect of soot and radiation on flame temperature is also examined.The results show a close agreement with the measurement when both soot and radiation are included in the numerical modeling.The rates of soot formation,surface growth,and oxidation increase with increased operating pressure,regardless of gravity.Zero-gravity flames have a higher soot volume fraction,a wider soot-containing zone,a higher CO mass fraction,and a lower flame temperature than normal-gravity flames while maintaining constant pressure.In normal-gravity flames,the CO mass fraction decreases with pressure,whereas it increases with pressure rise in flames of zero gravity.Flames of zero gravity appear taller and broader compared to the flames of normalgravity for a fixed pressure.An increase in pressure significantly reduces the flame length and width in normal-gravity flames.However,the pressure elevation has little effect on the shape of a zero-gravity flame.The outcomes of the present study will assist in fully understanding the combustion and sooting characteristics of turbulent diffusion flames that will help design and develop high-efficiency,pollutant-free combustion devices and fire suppression systems for space application.展开更多
基金supported by the National Natural Science Foundation of China(No.52172206)the Project of Science&Technology Office of Jiangsu Province(No.KB20181043)the Talent Research Projects of Qilu University of Technology(Shandong Academy of Sciences)(No.2024RCKY018)。
文摘Photothermal catalysis is a promising technology primarily utilized the solar energy to produce photogenerated e^(-)/h^(+) pairs together with the production of heat energy.However,the inefficient separation of charge carriers and inadequate response to near-infrared(NIR)light usually leads to the unsatisfactory photocatalytic efficiency,hindering their application potentials.In this work,a significantly enhanced photothermal catalytic hydrogen evolution reaction over the lead-free perovskite Cs_(3)Bi_(2)Br_(9)/FeS_(2)(CBB/FS)heterostructure is simultaneously verified,where the CBB/FS Z-scheme heterojunctions display the strong stability and superb photothermal catalytic activity.Under the simulated solar irradiation(AM 1.5G),the optimized CBB/FS-5 achieves a photocatalytic hydrogen evolution rate of 31.5 mmol g^(-1)h^(-1),which is 112.6 and 77.1 times higher than that of FS and CBB,respectively,together with an apparent quantum yield of 29.5%at 420 nm.This significantly improved photocatalytic H_(2)evolution can be mainly attributed to the Z-scheme charge transfer and photothermal-assisted synergistically enhanced photocatalytic H_(2)production,and the potential mechanism of the enhanced photocatalytic H_(2)evolution is also proposed by photoelectrochemical characterizations,in situ XPS,EPR spectra,and the DFT calculations.This work provides new insights to the design of high-efficient photothermal catalysts,leading to the sustainable and efficient solutions towards the energy and environmental challenges.
基金supported by the Technology Innovation Program(00404166,Development of thin-film coating current collector and aqueous binder to enhance the adhesion and conductivity properties on the silicon-rich anode)funded By the Ministry of Trade,Industry&Energy(MOTIE,Korea),the National Research Council of Science&Technology(NST)grant by the Korea government(MSIT)(No.2710024139)the Institute of Civil Military Technology Cooperation funded by the Defense Acquisition Program Administration and Ministry of Trade,Industry and Energy of Korean government under grant No.22-CM-FC-20。
文摘All-solid-state batteries(ASSBs)with sulfide-type solid electrolytes(SEs)are gaining significant attention due to their potential for the enhanced safety and energy density.In the slurry-coating process for ASSBs,nitrile rubber(NBR)is primarily used as a binder due to its moderate solubility in non-polar solvents,which exhibites minimal chemical reactivity with sulfide SEs.However,the NBR binder,composed of butadiene and acrylonitrile units with differing polarities,exhibits different chemical compatibility depending on the subtle differences in polarity of solvents.Herein,we systematically demonstrate how the chemical compatibility of solvents with the NBR binder influences the performance of ASSBs.Anisole is found to activate the acrylonitrile units,inducing an elongated polymer chain configuration in the binder solution,which gives an opportunity to strongly interact with the solid components of the electrode and the current collector.Consequently,selecting anisole as a solvent for the NBR binder enables the fabrication of a mechanically robust graphite-silicon anode,allowing ASSBs to operate at a lower stacking pressure of 16 MPa.This approach achieves an initial capacity of 480 mAh g^(-1),significantly higher than the 390 mAh g^(-1)achieved with the NBR/toluene binder that has less chemical compatibility.Furthermore,internal stress variations during battery operation are monitored,revealing that the enhanced mechanical properties,achieved through acrylonitrile activation,effectively mitigate internal stress in the graphite/silicon composite anode.
基金supported by the Ministry of Science and ICT in Korea(2021R1A2C2009459)X-ray absorption spectra were obtained from Pohang Accelerator Laboratory(PAL)10C beamlinesupported by the US Department of Energy,Office of Science,Office of Advanced Scientific Computing Research,and Scientific Discovery through Advanced Computing(SciDAC)program under Award Number DE-SC0022209.
文摘Systematic optimization of the photocatalyst and investigation of the role of each component is important to maximizing catalytic activity and comprehending the photocatalytic conversion of CO_(2) reduction to solar fuels.A surface-modified Ag@Ru-P25 photocatalyst with H_(2)O_(2) treatment was designed in this study to convert CO_(2) and H_(2)O vapor into highly selective CH4.Ru doping followed by Ag nanoparticles(NPs)cocatalyst deposition on P25(TiO_(2))enhances visible light absorption and charge separation,whereas H_(2)O_(2) treatment modifies the surface of the photocatalyst with hydroxyl(–OH)groups and promotes CO_(2) adsorption.High-resonance transmission electron microscopy,X-ray photoelectron spectroscopy,X-ray absorption near-edge structure,and extended X-ray absorption fine structure techniques were used to analyze the surface and chemical composition of the photocatalyst,while thermogravimetric analysis,CO_(2) adsorption isotherm,and temperature programmed desorption study were performed to examine the significance of H_(2)O_(2) treatment in increasing CO_(2) reduction activity.The optimized Ag1.0@Ru1.0-P25 photocatalyst performed excellent CO_(2) reduction activity into CO,CH4,and C2H6 with a~95%selectivity of CH4,where the activity was~135 times higher than that of pristine TiO_(2)(P25).For the first time,this work explored the effect of H_(2)O_(2) treatment on the photocatalyst that dramatically increases CO_(2) reduction activity.
基金supported as part of the Center for Mechanistic Control of Unconventional Formations(CMC-UF),an Energy Frontier Research Center funded by the U.S.Department of Energy,Of-fice of Science under DOE(BES)Award DE-SC0019165Stanford Nano Shared Facilities(SNSF)with support from NSF under award CMMI-1532224SNSF is additionally supported by the NSF as part of the National Nanotechnology Coordinated Infrastructure under award ECCS-1542152.
文摘Understanding the mechanical and transport behavior of thin(i.e.small aperture)cracks slipping under supercritical carbon dioxide(sc-CO_(2))conditions is essential to evaluate the integrity of sealing formations with buoyant sc-CO_(2)below and the success of waterless fracturing.The two major items of interest in this work are frictional strength and permeability change of the crack.We used a triaxial cell that permits in situ visualization to conduct and monitor slippage along the faces of narrow cracks subjected to triaxial stresses.Such cracks are analogs to small geological faults.We tested carbonate-rich,1-inch diameter Wolfcamp shale samples that are saw cut 30to vertical to create a thin crack.Friction coefficients ranged from about 0.6 to 0.8 consistent with expectations for brittle rocks.The sc-CO_(2)generally did not alter friction coefficient over the time scale of experiments.From a transport perspective,saturating cracks with sc-CO_(2)substantially decreased permeability of the crack by 26%e52%,while slip resulted in a variety of permeability responses.Overall,the combined impact of sc-CO_(2)saturation and slip reduced fault permeability for all tests.Our observations support the notion that the sealing capacity of some caprocks improves when saturated with sc-CO_(2)and that some slip of small fractures is not necessarily detrimental to caprock integrity.
基金Supported by the China National Key R&D Program during the 14th Five-Year Plan Period(Grant No.2023YFB3811600)the Major Program of Harbin Institute of Technology(Grant No.2023FRFK01002)。
文摘Polymer-liquid crystals(PLCs)are common materials for smart windows.However,PLC smart windows usually require high driving voltage to maintain transparency.We synthesized a novel PLC smart film by doping multi-wall carbon nanotubes(MWCNTs)into a reverse-mode polymer network liquid crystal(R-PNLC).
基金Projects(51978661,51778625)supported by the National Natural Science Foundation of ChinaProject(ACSKL2018KT12)supported by State Key Laboratory of Air-conditioning Equipment and System Energy Conservation,China。
文摘Personal conditioning system(PCS)is receiving considerable attention due to its energy-saving potential and the ability to satisfy individual comfort requirements.As a part of PCS,personal heating systems can maintain human thermal comfort in cold environments,which leads to their potential role of important heating mode in cold winter,especially in the Hot Summer and Cold Winter regions of China.In order to better promote the development and application of personal heating systems,this paper reviews the published studies.Personal heating systems can be divided into four types based on the mode of heat transfer:conductive,convective,radiative and combinative type.Characteristics of each category and respective devices are introduced.Furthermore,identifying the effects of personal heating on thermal comfort and the models for predicting or evaluating thermal comfort during local heating.This paper would provide users with a guideline for choosing suitable heating equipment during winter.
基金financially supported by the Basic Science Center Project of NSFC(No.51788104)the National Natural Science Foundation of China(Nos.51532004,51425401 and 51690161)+3 种基金the Fundamental Research Funds for the Central Universities(Nos.N180903008 and N180912004)the Liaoning PhD start-up Foundation(No.20180540058)the Postdoctoral Science Foundation of China(No.2019M651130)State Key Laboratory of New Ceramic and Fine Processing Tsinghua University(No.KF201804)。
文摘Dynamic control of the absorption frequency and intensity of metamaterial absorbers has attracted considerable attention,and many kinds of tunable metamaterial absorbers have been proposed.Unfortunately,due to the integration of separate resonant unit and tunable unit,these designed metamaterial absorbers suffer from complex structure and low sensitivity.We numerically and experimentally demonstrate a tunable metamaterial absorber composed of artificial dielectric atoms as both resonant and tunable unit arrayed periodically in the background matrix on the metallic plate.Polarization insensitive and wide incident angle absorption band with simulated and experimental absorptivity of 99%and 96%at 9.65 GHz are achieved at room temperature.The absorption frequency can be gradually modulated by temperature,however,the absorption intensity at working frequency remains near unity.The dielectric atoms based tunable metamaterial absorbers with simple structure have potential applications as tempe rature sensors and frequency selective thermal emitters.
基金financially supported by Natural Science Foundation of Heilongjiang Province(Grant No.ZD2021E002)。
文摘The melting process of solid-liquid phase change materials(PCM)has a significant impact on their energy storage performance.To more effectively apply solid-liquid PCM for energy storage,it is crucial to study the regulation of melting process of solid-liquid PCM,which is numerically investigated based on double multiple relaxation time lattice Boltzmann method(MRT-LBM)in this work.In this work we pay more attention to the effects of different Stefan numbers(Ste)and Rayleigh numbers(Ra)on the melting process.The results indicate that the PCM melting is greatly influenced by the Ste number and Ra number,which can be divided into the heat conduction dominant stage and the convection dominant stage,according to the onset time of convection Fo_(C).In order to describe the contribution of the heat conduction dominant stage to the whole melting process quantitatively,we firstly propose the ratio of the heat conduction dominant stage R_(pc),which can be defined as the ratio of Fo_(C)to the complete melting time Fo_(M).R_(pc)gradually decreases as the Ra number increases,and when the Ste number rises:R_(pc)=90.0%when Ste=1.0 and Ra=1×10^(5),R_(pc)=39.6%when Ste=0.1 and Ra=1×10^(5),and R_(pc)=14.0%when Ste=1.0 and Ra=1×10~7.A regime map about the effects of different Ste numbers and Ra numbers on R_(pc)has been further summarized.The discovered findings would be helpful in regulating melting process in the energy storage of solid-liquid PCM.
文摘In order to solve the problem of imbalance resource allocation and service income in the elderly care service industry,this article establishes three service income models in different situations for a single provider and a single integrator while considering the quality as well as government subsidies.The results showed that government subsidies can significantly improve quality efforts and service income with a mutual restriction between quality and service income.Government subsidies would have an impact on the quality,and they are more conducive to the service income of providers.When government subsidies are less than 80% of the service income,the incentive effect is better.
基金the financial supports from the National Key Research and Development Program of China(Grant No.2023YFB3811600)the National Science Fund for Distinguished Young Scholars(Grant No.51625201)+6 种基金State Key Program of National Natural Science of China(Grant No.52032004)National Youth Science Funds of China(Grant No.52102039)Key Research and Development Program of Heilongjiang Province(Grant No.GA21D001,2022ZX06C05)the Fundamental Research Funds for the Central Universities(Grant No.HIT.OCEF.2022011)the Major Program of Harbin Institute of Technology(Grant NO.2023FRFK01002)the Fundamental Research Funds for the Central Universities(2022FRFK060026)the National Youth Science Funds of China(Grant No.52302172).
文摘A novel multispectral smart window has been proposed,which features dynamic modulation of light transmittance and effective shielding against electromagnetic microwave radiation.This design integrates liquid crystal dynamic scattering and dye doping techniques,enabling the dual regulation of transmittance and scattering within a singlelayer smart window.Additionally,the precise control of conductive film thickness ensures the attainment of robust microwave signal shielding.We present a theoretical model for ion movement in the presence of an alternating electric field,along with a novel approach to manipulate negative dielectric constant.The proposed model successfully enables a rapid transition between light transparent,absorbing and haze states,with an optimum drive frequency adjustable to approximately 300 Hz.Furthermore,the resistive design of the conductive layer effectively mitigates microwave radiation within the 2−18 GHz range.These findings offer an innovative perspective for future advancements in environmental construction.
基金Outsourced R&D Project of Korea Electric Power Corporation(KEPCO),Grant/Award Number:R23XO04National Research Foundation of Korea(NRF)+7 种基金Korean government(MSIT),Grant/Award Numbers:NRF-2021M3H4A6A01045764,2020M3H4A3106313,2021R1C1C1004264,2021R1A4A1032114Korea Institute for Advancement of Technology(KIAT)Ministry of Trade,Industry,and Energy(MOTIE),Korea,Grant/Award Number:P0025273Korea Institute of Energy Technology Evaluation and Planning(KETEP)and the Ministry of Trade,Industry&Energy(MOTIE)of the Republic of Korea,Grant/Award Number:20224000000320KENTECH Research GrantKorea Institute of Energy Technology,Republic of Korea,Grant/Award Number:KRG2022-01-016Regional Innovation Strategy(RIS)through the National Research Foundation of Korea(NRF)Ministry of Education(MOE),Grant/Award Number:2021RIS-002。
文摘Efficient and cost-effective electrocatalysts that can operate across a wide range of pH conditions are essential for green hydrogen production.Inspired by biological systems,Fe_(7)S_(8)nanoparticles incorporated on polydopamine matrix electrocatalyst were synthesized by co-precipitation and annealing process.The resulting Fe_(7)S_(8)/C electrocatalyst possesses a three-dimensional structure and exhibits enhanced electrocatalytic performance for hydrogen production across various pH conditions.Notably,the Fe_(7)S_(8)/C electrocatalyst demonstrates exceptional activity,achieving low overpotentials of 90.6,45.9,and 107.4 mV in acidic,neutral,and alkaline environments,respectively.Electrochemical impedance spectroscopy reveals that Fe_(7)S_(8)/C exhibits the lowest charge transfer resistance under neutral conditions,indicating an improved proton-coupled electron transfer process.Continuous-wave electron paramagnetic resonance results confirm a change in the valence state of Fe from 3+to 1+during the hydrogen evolution reaction(HER).These findings closely resemble the behavior of natural[FeFe]-hydrogenase,known for its superior hydrogen production in neutral conditions.The remarkable performance of our Fe_(7)S_(8)/C electrocatalyst opens up new possibilities for utilizing bioinspired materials as catalysts for the HER.
文摘An outliers-free isogeometric modeling method for rotating disk-shaft systems is developed.The Timoshenko beam theory and artificial spring technique are employed for the rotating shaft and elastic boundary conditions.The nonlinear parameterization method is employed for the removal of outliers and three different nonlinear mappings are developed for the discussion of the accuracy of low modes.The energy coupling method between disks and shaft under nonlinear mapping is performed by using the Newton Raphson method.The results show that the isoparametric mapping has better performance in the accuracy of low modes than other nonlinear mapping and the outliers can also be removed,besides,the present method has good convergence rate for different boundary conditions.The accuracy of the proposed method shows good consistency with the Finite Element Method.The time cost of modeling is reduced by 71.4%compared to the traditional rotor model for a multiple disks rotor system,which indicates that the present approach has potential to provide more efficient optimization models of disk-shaft systems.The proposed method can provide a new modeling framework and can be easily extended to the prediction and optimization of vibration characteristics of complex rotor systems with multiple disks and supports.
基金supported by the Key Research and Development Program-Guidance Project of Heilongjiang Province of China(Grant No.GZ20210150)。
文摘Smart windows,capable of dynamically regulating indoor heat,offer a promising avenue for effectively reducing energy consumption.Hydrogel-based smart windows are excellent at thermal modulation and daylighting,but they are difficult to commercialize globally due to problems like winter ice formation,which can affect thermal insulation,daylighting,and structural integrity,as well as an impractical cloud point temperature(t_(cp)).To solve these issues,a ternary anti-freezing system consisting of ethylene glycol(EG),glycerol,and water is proposed.With the t_(cp)regulated at 31.6℃,the system strikes a balance between outstanding daylighting(91.89%)and solar modulation ability(78.32%).Furthermore,the system shows resilience even below-30.0℃and long-term stability,which qualifies it for use in densely populated regions even with severely cold weather.To further illustrate the distinct impacts of EG and glycerol,the optical characteristics and tcpof binary systems containing EG and water as well as glycerol and water were examined.The durability test includes severely cold temperature of-30.0℃ and solar exposure temperature of 60.0℃.This work would offer insights to advance the field's understanding of antifreezing capability modification in smart windows and advance the development of environmentally and energy-efficiently designed buildings.
基金supported by the following grants:Key Project of National Natural Science Foundation of China(Grant No.52032004)National Natural Science Foundation for Distinguished Young Scholars of China(Grant No.51625201)+4 种基金National Natural Science Funds of China(Grant No.52102039)China Postdoctoral Science Foundation(Grant No.2021M700036)The Open Fund of State Key Laboratory of Advanced Welding and Joining(Grant No.AWJ-22Z04)National Defense Supporting Scientific Research Projects(186)Keypoint Research and Invention Program of Heilongjiang Province(GA21D001).
文摘With the development of optical technologies,transparent materials that provide protection from light have received considerable attention from scholars.As important channels for external light,windows play a vital role in the regulation of light in buildings,vehicles,and aircrafts.There is a need for windows with switchable optical properties to prevent or attenuate damage or interference to the human eye and light-sensitive instruments by inappropriate optical radiation.In this context,liquid crystals(LCs),owing to their rich responsiveness and unique optical properties,have been considered among the best candidates for advanced light protection materials.In this review,we provide an overview of advances in research on LC-based methods for protection against light.First,we introduce the characteristics of different light sources and their protection requirements.Second,we introduce several classes of light modulation principles based on liquid crystal materials and demonstrate the feasibility of using them for light protection.In addition,we discuss current light protection strategies based on liquid crystal materials for different applications.Finally,we discuss the problems and shortcomings of current strategies.We propose several suggestions for the development of liquid crystal materials in the field of light protection.
文摘The traditional ventilation mode of subway vehicles adopts the form that the inlets and outlets are placed on the upper part of the cabin.The air distribution formed in this mode often cause serious problems of thermal comfort and energy consumption.In order to solve these problems caused by the traditional ventilation mode,a new hybrid ventilation mode was proposed.The hybrid ventilation mode uses both upper and underside air supply inlets.A method for evaluating the air distribution performance of subway air conditioning was developed.The method applies non-uniformity coefficients,maximum temperature difference,air diffusion performance index,modified energy utilization coefficient and Air short-circuit comprehensive coefficient.Air short-circuit comprehensive coefficient was a new index to evaluate the degree of air short-circuit of supply air.Based on the airflow simulation,the air distribution performance for the hybrid ventilation mode was evaluated using these indexes,and compared with the traditional ventilation mode.The results show that compared with the traditional ventilation mode,the hybrid ventilation mode has more uniform temperature distribution,better thermal comfort,higher energy utilization efficiency and lower degree of air short-circuit of supply air.
基金Authors(SG,VMR,SKD)would like to acknowledge the support received from the Institute seed grant(ISIRD)project(KNH).
文摘In this study,a turbulent non-premixed(diffusion)methane-air flame has been investigated computationally to analyze the influences of pressure and gravity on flame structure and sooting characteristics between 1 and 10 atm.The simulation has been conducted in a 2-D axisymmetric computational domain using the finite volume-based computational fluid dynamics(CFD)code.The interaction of turbulence and chemistry is modeled by considering the steady laminar flamelet model(SLFM)and the GRI Mech 3.0 chemical mechanism.The radiative heat transfer calculation is carried out by considering the discrete ordinate(DO)method and the weighted sum grey gas model(WSGGM).The semi-empirical Moss-Brookes model is considered to calculate soot.The impact of gravity on flame and sooting characteristics are evaluated by comparing the normal-gravity flames with the zero-gravity flames.The effect of soot and radiation on flame temperature is also examined.The results show a close agreement with the measurement when both soot and radiation are included in the numerical modeling.The rates of soot formation,surface growth,and oxidation increase with increased operating pressure,regardless of gravity.Zero-gravity flames have a higher soot volume fraction,a wider soot-containing zone,a higher CO mass fraction,and a lower flame temperature than normal-gravity flames while maintaining constant pressure.In normal-gravity flames,the CO mass fraction decreases with pressure,whereas it increases with pressure rise in flames of zero gravity.Flames of zero gravity appear taller and broader compared to the flames of normalgravity for a fixed pressure.An increase in pressure significantly reduces the flame length and width in normal-gravity flames.However,the pressure elevation has little effect on the shape of a zero-gravity flame.The outcomes of the present study will assist in fully understanding the combustion and sooting characteristics of turbulent diffusion flames that will help design and develop high-efficiency,pollutant-free combustion devices and fire suppression systems for space application.
