The seismic performance of bridges depends on the ductile behavior of its column, as the deck and other substructural components except pile foundations are normally designed to be elastic to facilitate bridge retrofi...The seismic performance of bridges depends on the ductile behavior of its column, as the deck and other substructural components except pile foundations are normally designed to be elastic to facilitate bridge retrofitting. Codes such as AASHTO, Caltrans, IRC: 112 etc. give guidelines for the seismic performance enhancement of columns through ductile detailing. In the present study, a methodology for the seismic performance enhancement of bridges is discussed by using a "Parameter-Based Influence Factor" (PIF) developed from factorial analysis. The parameters considered in the factorial analysis are: percentage of longitudinal reinforcement (Pt), compressive strength of concrete (f'c), yield strength of steel (fy), spacing of lateral ties (5) and column height (/4). The influence of each parameter and their combination on the limit states considered is estimated. Pushover analysis is used to evaluate the capacity of columns, considering shear failure criteria. A total of 243 (35 combinations) analysis results are compiled to develop 'PIF' used in the performance enhancement process. The study also encompasses other sub-objectives such as evaluating the discrepancies in using the Importance Factor (/) in designing bridges of varied functional importance; and estimating the aspect ratio and slenderness ratio values of bridge columns for its initial sizing.展开更多
The concept of combining metallic honeycomb with folded thin metallic sheets (corrugation) to construct a novel core type for lightweight sandwich structures is proposed. The honeycomb-corrugation hybrid core is man...The concept of combining metallic honeycomb with folded thin metallic sheets (corrugation) to construct a novel core type for lightweight sandwich structures is proposed. The honeycomb-corrugation hybrid core is manufactured by filling the interstices of aluminum corrugations with precision-cut trapezoidal aluminum honeycomb blocks, bonded together using epoxy glue. The performance of such hybrid-cored sandwich panels subjected to out-of-plane compression, transverse shear, and three-point bending is investigated, both experimentally and numerically. The strength and energy absorption of the sandwich are dramatically enhanced, compared to those of a sandwich with either empty corrugation or honeycomb core. The enhancement is induced by the beneficial interaction effects of honeycomb blocks and folded panels on improved buckling resistance as well as altered crushing modes at large plastic deformation. The present approach provides an effective method to further improve the mechanical properties of conventional honeycomb-cored sandwich constructions with low relative densities.展开更多
Ag3PO4 microcrystals with highly enhanced visible light photocatalytic activity are prepared by a facile and simple solid state reaction at room temperature. The composition, morphology and optical properties of the a...Ag3PO4 microcrystals with highly enhanced visible light photocatalytic activity are prepared by a facile and simple solid state reaction at room temperature. The composition, morphology and optical properties of the asprepared Ag3PO4 microcrystMs are characterized by x-ray diffraction, scanning electron microscopy and UV-vis diffuse reflectance spectra. The photocatalytie properties of Ag3PO4 are investigated by the degradation of both methylene blue and methyl orange dyes under visible light irradiation. The as-prepared Ag3PO4 microcrystals possess high photocatalytic oxygen production with the rate of 673μmolh-1g-1. Moreover, the as-prepared Ag3PO4 microcrystals show an enhanced photoelectrochemistry performance under irradiation of visible light.展开更多
A novel benzoxazine-based phenolic resin containing furan groups(PFB) was synthesized via simple two-step reactions and the structure of PFB was confirmed by FTIR and ~1H NMR spectra.Differential scanning calorimetr...A novel benzoxazine-based phenolic resin containing furan groups(PFB) was synthesized via simple two-step reactions and the structure of PFB was confirmed by FTIR and ~1H NMR spectra.Differential scanning calorimetry(DSC) showed that the polybenzoxazine cured from PFB had good heat resistance and lower polymerization temperature compared with that of benzoxazine-based phenolic resins.展开更多
Following the current rapid development of the Internet of Things(IoT)and wireless condition monitoring systems,energy harvesters which use ambient energy have become a key part of achieving an energy-autonomous syste...Following the current rapid development of the Internet of Things(IoT)and wireless condition monitoring systems,energy harvesters which use ambient energy have become a key part of achieving an energy-autonomous system.Miniature wind energy harvesters have attracted widespread attention because of their great potential of power density as well as the rich availability of wind energy in many possible areas of application.This article provides readers with a glimpse into the state-of-the-art of miniature wind energy harvesters.The crucial factors for them to achieve high working efficiency under lower operational wind speed excitation are analyzed.Various potential energy coupling mechanisms are discussed in detail.Design approaches for broadening operational wind-speed-range given a variety of energy coupling mechanisms are also presented,as observed in the literature.Performance enhancement mechanisms including hydrodynamic configuration optimization,and non-linear vibration pick-up structure are reviewed.Conclusions are drawn and the outlook for each coupling mechanisms is presented.展开更多
The nitrogen(N2)-to-ammonia(NH3)fixation driven by renewable energy has an attractive prospect to relieve the global warming and reduce the consumption of fossil fuels.Ideally,photocatalytic,electrochemical,and photoe...The nitrogen(N2)-to-ammonia(NH3)fixation driven by renewable energy has an attractive prospect to relieve the global warming and reduce the consumption of fossil fuels.Ideally,photocatalytic,electrochemical,and photoelectrochemical approaches are developed as the next-generation NH3 synthesis technologies to substitute the Haber–Bosch method.However,the NH3 yield rate of nitrogen reduction reaction(NRR)by green approaches is extremely low,resulting in the current dilemma of NRR and contamination issues.Thus,in this mini review,the past advances on the sustainable NRR are briefly summarized in the three aspects as follows:the selectivity and adjustment of various catalysts,the type of electrolyte/solvent system,and the investigation of reaction conditions.Subsequently,the recent critical activities in the area of sustainable NH3 synthesis are analyzed and discussed deeply,and a perspective for rational and healthy development of this area is provided positively。展开更多
Software-defined networking is one of the progressive and prominent innovations in Information and Communications Technology.It mitigates the issues that our conventional network was experiencing.However,traffic data ...Software-defined networking is one of the progressive and prominent innovations in Information and Communications Technology.It mitigates the issues that our conventional network was experiencing.However,traffic data generated by various applications is increasing day by day.In addition,as an organization’s digital transformation is accelerated,the amount of information to be processed inside the organization has increased explosively.It might be possible that a Software-Defined Network becomes a bottleneck and unavailable.Various models have been proposed in the literature to balance the load.However,most of the works consider only limited parameters and do not consider controller and transmission media loads.These loads also contribute to decreasing the performance of Software-Defined Networks.This work illustrates how a software-defined network can tackle the load at its software layer and give excellent results to distribute the load.We proposed a deep learning-dependent convolutional neural networkbased load balancing technique to handle a software-defined network load.The simulation results show that the proposed model requires fewer resources as compared to existing machine learning-based load balancing techniques.展开更多
Geothermal energy with abundance and large quantity can partially cover building heating/cooling loads and promote the carbon-neutrality transitions.Shallow geothermal ventilation(SGV)system,with a little initial in-v...Geothermal energy with abundance and large quantity can partially cover building heating/cooling loads and promote the carbon-neutrality transitions.Shallow geothermal ventilation(SGV)system,with a little initial in-vestment cost,is one of promising technologies to partly replace the conventional air-conditioning system for air pre-cooling/pre-heating.This paper reviews applications of SGV system for improving thermal performance over latest two decades,which mainly includes the reclassification of SGV system,coupling with other advanced energy-saving technologies,application potentials for building cooling/heating under various weather conditions.Heat transfer mechanism and mathematical modelling techniques have been reviewed,together with in-depth analysis on current research trends,existing limitations,and recommendations of SGV system.Phase change materials,with considerable latent energy density,can stabilize the thermal performance with high reliability.The review identifies that optimization designs and advanced approaches need to be investigated to address the existing urgent issues of SGV system(e.g.,large land occupation,difficulty in centralized collection of condensate water timely for horizontal buried pipe,bacteria growth,polluted supply air,and high construction cost for ver-tical buried pipe).A plenty of studies show that the SGV system could greatly expand the application scope and improve system energy efficiency by combining with other energy-saving technologies.This paper will provide some guidelines for the scientific researchers and engineers to keep track on recent advancements and research trends of SGV system for the building thermal performance enhancement and pave path for future research works.展开更多
Introduction of asymmetric units into conjugated polymers is an important strategy to regulate the photophysical and electronic properties of polymers,as asymmetric units can not only regulate solubility and energy le...Introduction of asymmetric units into conjugated polymers is an important strategy to regulate the photophysical and electronic properties of polymers,as asymmetric units can not only regulate solubility and energy levels,but also molecular stacking and orientation,thus giving much higher optoelectronic properties.However,very few studies have been reported in this field.The semiconducting properties of conjugated polymers could be regulated through regioregularity adjustment.Here,we took the asymmetric thiophene/pyridine side group DPP as core and developed the regioregular monomer T-Py-DPP through three steps:alkyl chain introduction,tin monomer coupling and NBS double bromination.The T-Py-DPP monomer was polymerized into reg-PPy TDPP-2FBT with a head-to-head structure.The regioregularity of T-Py-DPP unit endowed reg-PPy TDPP-2FBT with backbone planarity,self-assembly orientation,network-like morphology and high crystallinity in films,thus the superior bipolar transport properties.The highest hole and electron mobilities of reg-PPy TDPP-2FBT were 0.93 and 0.57 cm^(2)·V^(-1)·s^(-1),respectively,with 40%improvement relative to the regiorandom polymer.展开更多
Plastic crystal neopentyl glycol(NPG)exhibits colossal barocaloric effect with high entropy changes.However,their application is restricted in several aspects,such as low thermal conductivity,substantial supercooling ...Plastic crystal neopentyl glycol(NPG)exhibits colossal barocaloric effect with high entropy changes.However,their application is restricted in several aspects,such as low thermal conductivity,substantial supercooling effect,and poor springback properties.In this work,multi-walled carbon nanotubes(MWCNTs)with ultra-high thermal conductivity and high mechanical strength were selected for performance enhancement of NPG.The optimal mixing ratio was determined to be NPG with 3 wt%MWCNTs composites,which showed a 6K reduction in supercooling without affecting the phase change enthalpy.Subsequently,comprehensive performance of the composites with optimal mixing ratio was compared with pure NPG At 40 MPa,390J·K^(-1)·kg^(-1)change in entropy and 9.9 K change in temperature were observed.Furthermore,the minimum driving pressure required to achieve reversible barocaloric effect was reduced by 19.2%.In addition,the thermal conductivity of the composite was increased by approximately 28%,significantly reducing the heat exchange time during a barocaloric refrigeration cycle.More importantly,ultra-high pressure release rate resulted in a73.7%reduction in the springback time of the composites,offering new opportunities for the recovery of expansion work.展开更多
Metal-organic framework/organosilica hybrid membranes on tubular ceramic substrates have shown great potential for the implementation of membrane technology in practical gas separation projects due to their higher per...Metal-organic framework/organosilica hybrid membranes on tubular ceramic substrates have shown great potential for the implementation of membrane technology in practical gas separation projects due to their higher permeance compared to commercial polymers.However,the selectivities of the reported membranes are moderate.Here,we have incorporated urea-modulated metal-organic frameworks into organosilica membranes to greatly enhance its separation performance.The urea-modulated metal-organic frameworks exhibit less-defined edges of crystallographic facets and high defect density.They can be well-dispersed in the organosilica layer,which substantially suppresses the interfacial defects between metal-organic frameworks and organosilica,which is beneficial for improving the selectivity of membranes for gas separation.The results have shown that the enhanced ideal selectivity of H_(2)/CH_(4) was 165 and that of CO_(2)/CH_(4) was 43,with H_(2) permeance of about 1.25×10^(−6) mol·m^(−2)·s^(−1)·Pa^(−1) and CO_(2) permeance of 3.27×10^(−7) mol·m^(−2)·s^(−1)·Pa^(−1) at 0.2 MPa and 25℃.In conclusion,the high level of hybrid membranes can be used to separate H_(2)(or CO_(2))from the binary gas mixture H_(2)/CH_(4)(or CO_(2)/CH_(4)),which is important for gas separation in practical applications.Moreover,the simple and feasible modulation of metal-organic framework is a promising strategy to tune different metal-organic frameworks for membranes according to the actual demands.展开更多
The present study performed a numerical investigation to explore the performance enhancement of a co-flow jet(CFJ)airfoil with simple high-lift device configuration,with a specific goal to examine the feasibility and ...The present study performed a numerical investigation to explore the performance enhancement of a co-flow jet(CFJ)airfoil with simple high-lift device configuration,with a specific goal to examine the feasibility and capability of the proposed configuration for low-speed take-off and landing.Computations have been accomplished by an in-house-programmed Reynoldsaveraged Navier-Stokes solver enclosed by k-ωshear stress transport turbulence model.Three crucial geometric parameters,viz.,injection slot location,suction slot location and its angle were selected for the sake of revealing their effects on aerodynamic lift,drag,power consumption and equivalent lift-to-drag ratio.Results show that using simple high-lift devices on CFJ airfoil can significantly augment the aerodynamic associated lift and efficiency which evidences the feasibility of CFJ for short take-off and landing with small angle of attack.The injection and suction slot locations are more influential with respect to the aerodynamic performance of CFJ airfoil compared with the suction slot angle.The injection location is preferable to be located in the downstream of the pressure suction peak on leading edge to reduce the power expenditure of the pumping system for a relative higher equivalent lift-to-drag ratio.Another concluded criterion is that the suction slot should be oriented on the trailing edge flap for achieving more aerodynamic gain,meanwhile,carefully selecting this location is crucial in determining the aerodynamic enhancement of CFJ airfoil with deflected flaps.展开更多
Electrically controlled rotor (ECR) system has the potential to enhance the rotor perfor- mance by applying higher harmonic flap inputs. In order to explore the feasibility and effectiveness for ECR performance enha...Electrically controlled rotor (ECR) system has the potential to enhance the rotor perfor- mance by applying higher harmonic flap inputs. In order to explore the feasibility and effectiveness for ECR performance enhancement using closed-loop control method, firstly, an ECR rotor performance analysis model based on helicopter flight dynamic model is established, which can reflect the performance characteristics of ECR helicopter at high advance ratio. Based on the simulation platform, an active control method named adaptive T-matrix algorithm is adopted to explore the feasibility and effectiveness for ECR performance enhancement. The simulation results verify the effectiveness of this closed-loop control method. For the sample ECR helicopter, about 3% rotor power reduction is obtained with the optimum 2/rev flap inputs at the advance ratio of 0.34. And through analyzing the distributions of attack of angle and drag in rotor disk, the underlying physical essence of ECR power reduction is cleared. Furthermore, the influence of the key control parameters, including convergence factor and weighting matrix, on the effectiveness of closed-loop control for ECR performance enhancement is explored. Some useful results are summarized, which can be used to direct the future active control law design of ECR performance enhancement.展开更多
Considering the issues of energy saving and environment protection,the performance of refrigeration systems requires to be improved.In recent years,nano-fluids have attracted greatly attention from the researchers due...Considering the issues of energy saving and environment protection,the performance of refrigeration systems requires to be improved.In recent years,nano-fluids have attracted greatly attention from the researchers due to their outstanding thermal characteristics.In this work,the published investigations on the preparation and characterization of nano-fluids have been discussed at first.Furthermore,the key thermo-physical properties of nano-fluids,such as thermal conductivity,viscosity,specific heat and density have been summarized.Finally,the performance enhancements in different types of refrigeration systems by using nano-fluids have been reviewed.It is concluded that nano-fluids as refrigerant,lubricant or secondary fluid have wide potential application in refrigeration systems.展开更多
In this article,we review the recent progress and our research activity on the synthesis of inorganic shell nanostructures to enhance the catalytic performance and stability of metal nanoparticles in catalytic applica...In this article,we review the recent progress and our research activity on the synthesis of inorganic shell nanostructures to enhance the catalytic performance and stability of metal nanoparticles in catalytic applications.First,we introduce general synthetic strategies for the fabrication of inorganic nanoscale shell layers,including template-assisted sol-gel coating,hydrothermal(or solvothermal)synthesis and the self-templating process.We also discuss recent examples of metal nanoparticles(NPs)with nanoscale shell layers,namely core-shell,yolk-shell and multiple NPs-embedded nanoscale shell.We then discuss the performance and stability of metal particles in practical catalytic applications.Finally,we conclude with a summary and perspective on the further progress of inorganic nanostructure with nanoscale shell layers for catalytic applications.展开更多
This paper first revisits the previously proposed NSAD (New Self-Adapt DCF) mechanism. Some modifications are presented to further enhance the performance of NSAD in the error-prone environment. Then a new MAC mechani...This paper first revisits the previously proposed NSAD (New Self-Adapt DCF) mechanism. Some modifications are presented to further enhance the performance of NSAD in the error-prone environment. Then a new MAC mechanism is proposed that can realize bandwidth guarantee by assigning different self-adapt parameters to users at different priority levels. The bandwidth guarantee property of this new mechanism is analyzed and the high priority users are found to have bandwidth guaranteed even in heavy contention condition, which is proved true not only by theoretical analysis but also by simulation results. At the same time the new scheme keeps the self-adapt character of NSAD, so the overall system utilization is kept very high in heavy contention condition compared with the previously studied DCF-based QoS mechanisms.展开更多
Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have attracted enormous research interests and efforts towards the development of versatile electronic and optical devices, owing to their extra...Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have attracted enormous research interests and efforts towards the development of versatile electronic and optical devices, owing to their extraordinary and unique fundamental properties and remarkable prospects in nanoelectronic applications. Among the TMDs, tungsten diselenide (WSe2) exhibits tunable ambipolar transport characteristics and superior optical properties such as high quantum efficiency. Herein, we demonstrate significant enhancement in the device performance of WSe2 phototransistor by in situ surface functionalization with cesium carbonate (Cs2CO3). WSe2 was found to be strongly doped with electrons after Cs2CO3 modification. The electron mobility of WSe2 increased by almost one order of magnitude after surface functionalization with 1.6-nm-thick Cs2CO3 decoration. Furthermore, the photocurrent of the WSe2-based phototransistor increased by nearly three orders of magnitude with the deposition of 1.6-nm-thick Cs2CO3. Characterizations by in situ photoelectron spectroscopy techniques confirmed the significant surface charge transfer occurring at the Cs2COB/WSe2 interface. Our findings coupled with the tunable nature of the surface transfer doping method establish WSe2 as a promising candidate for future 2D materials- based optoelectronic devices.展开更多
Hierarchical-structure materials hold great promise for numerous applied domains such as fuel cell,sensor,and optic.However,the developments are significantly impeded by the lack of efficient strategy permitting preci...Hierarchical-structure materials hold great promise for numerous applied domains such as fuel cell,sensor,and optic.However,the developments are significantly impeded by the lack of efficient strategy permitting precise and efficient decoration of specific confined space.Here,an in-situ precise hybridization strategy is proposed to efficiently manipulate the nanostructure of membrane nanochannels.Typically,Nafion ionic nanochannels are impregnated with precursors via heat swelling,followed by microwave-assisted condensation to form polymer quantum dot network.The formation of polymer quantum dot network significantly improves the stability and functionality of ionic nanophase(i.e.,ionic nanochannel).This helps hybrid membrane achieving enhanced proton conduction and methanol barrier properties,resulting in over ten times increase in proton/methanol selectivity.These then impart prominent device performances for both hydrogen and methanol fuel cells with the elevation of~100%.Importantly,such function manipulation of ionic nanochannels is achieved with fully maintaining function of backbone nanophase.Besides,the regulation of physical topology and chemical environment of ionic nanochannel also brings optimization of gas and ion separation properties.This facile and versatile strategy may open up a new avenue for decorating confined space of many hierarchical-structure materials.展开更多
Layered alkali-metal titanate materials are considered as attractive anodes for sodium ion batteries due to their favorable safety and low cost.However,their practical implementation faces major challenges of low elec...Layered alkali-metal titanate materials are considered as attractive anodes for sodium ion batteries due to their favorable safety and low cost.However,their practical implementation faces major challenges of low electronic conductivity and inevitable volume variation during Na^(+)intercalation and de-intercalation,which are generally difficult to conquer by a single modification method.Herein,a synergistic ally enhancing strategy to promote the electrochemical performance of Na_(2)Ti_(2)O_(5)nanowire array anode via simultaneous hydrogenation and carbon coating is developed.Hydrogenation leads to partially reduced titanium;together with conductive carbon layer,it endows Na_(2)Ti_(2)O_(5)with fast electron transport and structural stability.The resulting H-Na_(2)Ti_(2)O_(5)@C anode exhibits enhanced rate capability(8.0C,165 mAh·g^(-1))and stable cycle performance up to 1000 times in sodium-ion half-cells(the capacity of H-Na_(2)Ti_(2)O_(5)without carbon fades drastically after only 100 cycles).In addition,a newcoupling full cell is further designed with graphene hybridized high-voltage Na_(3)(VO_(0.5))_(2)(PO4)_(2)F_(2)as cathode,capable of delivering a high specific energy density of 212.1 Wh·kg^(-1)(based on the mass of both anode and cathode)and good rate and cycling stability.This work may offer inspiration for synergistic optimization of electrode materials for advanced electrochemical energy storage devices.展开更多
A pyridine-anchor co-adsorbent of N,N'-bis((pyridin-2-yl)(methyl) methylene)-o-phenylenediamine(named BPPI) is prepared and employed as co-adsorbent in dye-sensitized solar cells(DSSCs). The prepared co-ads...A pyridine-anchor co-adsorbent of N,N'-bis((pyridin-2-yl)(methyl) methylene)-o-phenylenediamine(named BPPI) is prepared and employed as co-adsorbent in dye-sensitized solar cells(DSSCs). The prepared co-adsorbent could overcome the deficiency of N719 absorption in the low wavelength region of visible spectrum, offset competitive visible light absorption of I_3^-, enhance the spectral responses of the co-adsorbed TiO_2 film in region from 300 nm to 750 nm, suppress charge recombination, prolong electron lifetime, and decrease the total resistance of DSSCs. The optimized cell device co-sensitized by BPPI/N719 dye gives a short circuit current density of 12.98 m A cm^(-2), an open circuit voltage of 0.73 V,and a fill factor of 0.66 corresponding to an overall conversion efficiency of 6.22% under standard global AM 1.5 solar irradiation, which is much higher than that of device solely sensitized by N719(5.29%)under the same conditions. Mechanistic investigations are carried out by various spectral and electrochemical characterizations.展开更多
文摘The seismic performance of bridges depends on the ductile behavior of its column, as the deck and other substructural components except pile foundations are normally designed to be elastic to facilitate bridge retrofitting. Codes such as AASHTO, Caltrans, IRC: 112 etc. give guidelines for the seismic performance enhancement of columns through ductile detailing. In the present study, a methodology for the seismic performance enhancement of bridges is discussed by using a "Parameter-Based Influence Factor" (PIF) developed from factorial analysis. The parameters considered in the factorial analysis are: percentage of longitudinal reinforcement (Pt), compressive strength of concrete (f'c), yield strength of steel (fy), spacing of lateral ties (5) and column height (/4). The influence of each parameter and their combination on the limit states considered is estimated. Pushover analysis is used to evaluate the capacity of columns, considering shear failure criteria. A total of 243 (35 combinations) analysis results are compiled to develop 'PIF' used in the performance enhancement process. The study also encompasses other sub-objectives such as evaluating the discrepancies in using the Importance Factor (/) in designing bridges of varied functional importance; and estimating the aspect ratio and slenderness ratio values of bridge columns for its initial sizing.
基金supported by the National Natural Science Foundation of China(11472208)the National 111 Project of China(B06024)
文摘The concept of combining metallic honeycomb with folded thin metallic sheets (corrugation) to construct a novel core type for lightweight sandwich structures is proposed. The honeycomb-corrugation hybrid core is manufactured by filling the interstices of aluminum corrugations with precision-cut trapezoidal aluminum honeycomb blocks, bonded together using epoxy glue. The performance of such hybrid-cored sandwich panels subjected to out-of-plane compression, transverse shear, and three-point bending is investigated, both experimentally and numerically. The strength and energy absorption of the sandwich are dramatically enhanced, compared to those of a sandwich with either empty corrugation or honeycomb core. The enhancement is induced by the beneficial interaction effects of honeycomb blocks and folded panels on improved buckling resistance as well as altered crushing modes at large plastic deformation. The present approach provides an effective method to further improve the mechanical properties of conventional honeycomb-cored sandwich constructions with low relative densities.
基金Supported by the Beijing Higher Education Young Elite Teacher Project under Grant No YETP1297the Fundamental Research Funds for the Central Universities under Grant No 2014MDLXYZY05+1 种基金the Undergraduate Innovative Test Program of China under Grant Nos GCCX2015110009 and BEIJ2015110024the National Natural Science Foundation of China under Grant Nos11074312 and 11374377
文摘Ag3PO4 microcrystals with highly enhanced visible light photocatalytic activity are prepared by a facile and simple solid state reaction at room temperature. The composition, morphology and optical properties of the asprepared Ag3PO4 microcrystMs are characterized by x-ray diffraction, scanning electron microscopy and UV-vis diffuse reflectance spectra. The photocatalytie properties of Ag3PO4 are investigated by the degradation of both methylene blue and methyl orange dyes under visible light irradiation. The as-prepared Ag3PO4 microcrystals possess high photocatalytic oxygen production with the rate of 673μmolh-1g-1. Moreover, the as-prepared Ag3PO4 microcrystals show an enhanced photoelectrochemistry performance under irradiation of visible light.
基金supported by project of Hubei Provincial Department of Education,China(No.Q20083003)the Innovative Team of Huangshi Institute of Technology.
文摘A novel benzoxazine-based phenolic resin containing furan groups(PFB) was synthesized via simple two-step reactions and the structure of PFB was confirmed by FTIR and ~1H NMR spectra.Differential scanning calorimetry(DSC) showed that the polybenzoxazine cured from PFB had good heat resistance and lower polymerization temperature compared with that of benzoxazine-based phenolic resins.
基金the financial support from National Natural Science Foundation of China Grant No.61604023National Natural Science Foundation of China(Grant No.61804016)。
文摘Following the current rapid development of the Internet of Things(IoT)and wireless condition monitoring systems,energy harvesters which use ambient energy have become a key part of achieving an energy-autonomous system.Miniature wind energy harvesters have attracted widespread attention because of their great potential of power density as well as the rich availability of wind energy in many possible areas of application.This article provides readers with a glimpse into the state-of-the-art of miniature wind energy harvesters.The crucial factors for them to achieve high working efficiency under lower operational wind speed excitation are analyzed.Various potential energy coupling mechanisms are discussed in detail.Design approaches for broadening operational wind-speed-range given a variety of energy coupling mechanisms are also presented,as observed in the literature.Performance enhancement mechanisms including hydrodynamic configuration optimization,and non-linear vibration pick-up structure are reviewed.Conclusions are drawn and the outlook for each coupling mechanisms is presented.
基金The authors are grateful to the National Natural Science Foundation of China(51402100,21573066,21825201,22075075,21805080,and U19A2017)the Provincial Natural Science Foundation of Hunan(2016JJ1006,2020JJ5044,and 2016TP1009)Australian Research Council(DP180100568 and DP180100731)for financial support of this research.
文摘The nitrogen(N2)-to-ammonia(NH3)fixation driven by renewable energy has an attractive prospect to relieve the global warming and reduce the consumption of fossil fuels.Ideally,photocatalytic,electrochemical,and photoelectrochemical approaches are developed as the next-generation NH3 synthesis technologies to substitute the Haber–Bosch method.However,the NH3 yield rate of nitrogen reduction reaction(NRR)by green approaches is extremely low,resulting in the current dilemma of NRR and contamination issues.Thus,in this mini review,the past advances on the sustainable NRR are briefly summarized in the three aspects as follows:the selectivity and adjustment of various catalysts,the type of electrolyte/solvent system,and the investigation of reaction conditions.Subsequently,the recent critical activities in the area of sustainable NH3 synthesis are analyzed and discussed deeply,and a perspective for rational and healthy development of this area is provided positively。
基金supported by Ulsan Metropolitan City-ETRI joint cooperation Project[21AS1600]Development of intelligent technology for key industries and autonomous human-mobile-space autonomous collaboration intelligence technology].
文摘Software-defined networking is one of the progressive and prominent innovations in Information and Communications Technology.It mitigates the issues that our conventional network was experiencing.However,traffic data generated by various applications is increasing day by day.In addition,as an organization’s digital transformation is accelerated,the amount of information to be processed inside the organization has increased explosively.It might be possible that a Software-Defined Network becomes a bottleneck and unavailable.Various models have been proposed in the literature to balance the load.However,most of the works consider only limited parameters and do not consider controller and transmission media loads.These loads also contribute to decreasing the performance of Software-Defined Networks.This work illustrates how a software-defined network can tackle the load at its software layer and give excellent results to distribute the load.We proposed a deep learning-dependent convolutional neural networkbased load balancing technique to handle a software-defined network load.The simulation results show that the proposed model requires fewer resources as compared to existing machine learning-based load balancing techniques.
基金The authors will be very thankful for the support from the Hunan University,Central South UniversityThe Hong Kong University of Science and Technology,and University of California.All copyright licenses of have been successfully applied for all cited graphics,images,tables and/or figures。
文摘Geothermal energy with abundance and large quantity can partially cover building heating/cooling loads and promote the carbon-neutrality transitions.Shallow geothermal ventilation(SGV)system,with a little initial in-vestment cost,is one of promising technologies to partly replace the conventional air-conditioning system for air pre-cooling/pre-heating.This paper reviews applications of SGV system for improving thermal performance over latest two decades,which mainly includes the reclassification of SGV system,coupling with other advanced energy-saving technologies,application potentials for building cooling/heating under various weather conditions.Heat transfer mechanism and mathematical modelling techniques have been reviewed,together with in-depth analysis on current research trends,existing limitations,and recommendations of SGV system.Phase change materials,with considerable latent energy density,can stabilize the thermal performance with high reliability.The review identifies that optimization designs and advanced approaches need to be investigated to address the existing urgent issues of SGV system(e.g.,large land occupation,difficulty in centralized collection of condensate water timely for horizontal buried pipe,bacteria growth,polluted supply air,and high construction cost for ver-tical buried pipe).A plenty of studies show that the SGV system could greatly expand the application scope and improve system energy efficiency by combining with other energy-saving technologies.This paper will provide some guidelines for the scientific researchers and engineers to keep track on recent advancements and research trends of SGV system for the building thermal performance enhancement and pave path for future research works.
基金financially supported by the Ministry of Science and Technology of China(Nos.2018YFA0703200 and 2022YFB3603800)the National Natural Science Foundation of China(Nos.21875259,52233010,51725304,61890943,52103245 and 22021002)+2 种基金the CAS Project for Young Scientists in Basic Research(No.YSBR-053)the Youth Innovation Promotion Association of the Chinese Academy of Sciences,the National Program for Support of Top-notch Young Professionals,the Beijing National Laboratory for Molecular Sciences(No.BNLMS-CXXM-202012)the Key Research Program of the Chinese Academy of Sciences(Nos.XDPB13 and 121111KYSB20200004)。
文摘Introduction of asymmetric units into conjugated polymers is an important strategy to regulate the photophysical and electronic properties of polymers,as asymmetric units can not only regulate solubility and energy levels,but also molecular stacking and orientation,thus giving much higher optoelectronic properties.However,very few studies have been reported in this field.The semiconducting properties of conjugated polymers could be regulated through regioregularity adjustment.Here,we took the asymmetric thiophene/pyridine side group DPP as core and developed the regioregular monomer T-Py-DPP through three steps:alkyl chain introduction,tin monomer coupling and NBS double bromination.The T-Py-DPP monomer was polymerized into reg-PPy TDPP-2FBT with a head-to-head structure.The regioregularity of T-Py-DPP unit endowed reg-PPy TDPP-2FBT with backbone planarity,self-assembly orientation,network-like morphology and high crystallinity in films,thus the superior bipolar transport properties.The highest hole and electron mobilities of reg-PPy TDPP-2FBT were 0.93 and 0.57 cm^(2)·V^(-1)·s^(-1),respectively,with 40%improvement relative to the regiorandom polymer.
基金supported by the Basic Research Program of Frontier Leading Technologies in Jiangsu Province(BK20202008)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX23_0240)+3 种基金the key research and demonstration projects of future low-carbon emission buildings(No.BE2022606)Hebei Natural Science Foundation(No.E2022210022)Science and Technology Project of Hebei Education Department(No.BJK2022056)the Introduction Program of Oversea Talents of Hebei Province(No.C20220505)。
文摘Plastic crystal neopentyl glycol(NPG)exhibits colossal barocaloric effect with high entropy changes.However,their application is restricted in several aspects,such as low thermal conductivity,substantial supercooling effect,and poor springback properties.In this work,multi-walled carbon nanotubes(MWCNTs)with ultra-high thermal conductivity and high mechanical strength were selected for performance enhancement of NPG.The optimal mixing ratio was determined to be NPG with 3 wt%MWCNTs composites,which showed a 6K reduction in supercooling without affecting the phase change enthalpy.Subsequently,comprehensive performance of the composites with optimal mixing ratio was compared with pure NPG At 40 MPa,390J·K^(-1)·kg^(-1)change in entropy and 9.9 K change in temperature were observed.Furthermore,the minimum driving pressure required to achieve reversible barocaloric effect was reduced by 19.2%.In addition,the thermal conductivity of the composite was increased by approximately 28%,significantly reducing the heat exchange time during a barocaloric refrigeration cycle.More importantly,ultra-high pressure release rate resulted in a73.7%reduction in the springback time of the composites,offering new opportunities for the recovery of expansion work.
基金supports of this work from“Pioneer”and“Leading Goose”R&D Program of Zhejiang Province(Grant No.2022C01029)National Natural Science Foundation of China(Grant No.21978309)+3 种基金Natural Science Foundation of Zhejiang Province(Grant No.LY21E020008)Youth Innovation Promotion Association,Chinese Acadenry of Sciences(Grant No.2020300)Ningbo Natural Science Foundation(Grant No.2023J354)Ningbo S&T Innovation 2025 Major Special Program(Grant No.2020Z036).
文摘Metal-organic framework/organosilica hybrid membranes on tubular ceramic substrates have shown great potential for the implementation of membrane technology in practical gas separation projects due to their higher permeance compared to commercial polymers.However,the selectivities of the reported membranes are moderate.Here,we have incorporated urea-modulated metal-organic frameworks into organosilica membranes to greatly enhance its separation performance.The urea-modulated metal-organic frameworks exhibit less-defined edges of crystallographic facets and high defect density.They can be well-dispersed in the organosilica layer,which substantially suppresses the interfacial defects between metal-organic frameworks and organosilica,which is beneficial for improving the selectivity of membranes for gas separation.The results have shown that the enhanced ideal selectivity of H_(2)/CH_(4) was 165 and that of CO_(2)/CH_(4) was 43,with H_(2) permeance of about 1.25×10^(−6) mol·m^(−2)·s^(−1)·Pa^(−1) and CO_(2) permeance of 3.27×10^(−7) mol·m^(−2)·s^(−1)·Pa^(−1) at 0.2 MPa and 25℃.In conclusion,the high level of hybrid membranes can be used to separate H_(2)(or CO_(2))from the binary gas mixture H_(2)/CH_(4)(or CO_(2)/CH_(4)),which is important for gas separation in practical applications.Moreover,the simple and feasible modulation of metal-organic framework is a promising strategy to tune different metal-organic frameworks for membranes according to the actual demands.
基金supported by the National Natural Science Foundation of China(No.11672133)the Research Funds for Central Universities(No.kfjj20180104)support from Rotor Aerodynamics Key Laboratory(No.RAL20190202-2)。
文摘The present study performed a numerical investigation to explore the performance enhancement of a co-flow jet(CFJ)airfoil with simple high-lift device configuration,with a specific goal to examine the feasibility and capability of the proposed configuration for low-speed take-off and landing.Computations have been accomplished by an in-house-programmed Reynoldsaveraged Navier-Stokes solver enclosed by k-ωshear stress transport turbulence model.Three crucial geometric parameters,viz.,injection slot location,suction slot location and its angle were selected for the sake of revealing their effects on aerodynamic lift,drag,power consumption and equivalent lift-to-drag ratio.Results show that using simple high-lift devices on CFJ airfoil can significantly augment the aerodynamic associated lift and efficiency which evidences the feasibility of CFJ for short take-off and landing with small angle of attack.The injection and suction slot locations are more influential with respect to the aerodynamic performance of CFJ airfoil compared with the suction slot angle.The injection location is preferable to be located in the downstream of the pressure suction peak on leading edge to reduce the power expenditure of the pumping system for a relative higher equivalent lift-to-drag ratio.Another concluded criterion is that the suction slot should be oriented on the trailing edge flap for achieving more aerodynamic gain,meanwhile,carefully selecting this location is crucial in determining the aerodynamic enhancement of CFJ airfoil with deflected flaps.
基金supported by the National Natural Science Foundation of China (No. 51375229)
文摘Electrically controlled rotor (ECR) system has the potential to enhance the rotor perfor- mance by applying higher harmonic flap inputs. In order to explore the feasibility and effectiveness for ECR performance enhancement using closed-loop control method, firstly, an ECR rotor performance analysis model based on helicopter flight dynamic model is established, which can reflect the performance characteristics of ECR helicopter at high advance ratio. Based on the simulation platform, an active control method named adaptive T-matrix algorithm is adopted to explore the feasibility and effectiveness for ECR performance enhancement. The simulation results verify the effectiveness of this closed-loop control method. For the sample ECR helicopter, about 3% rotor power reduction is obtained with the optimum 2/rev flap inputs at the advance ratio of 0.34. And through analyzing the distributions of attack of angle and drag in rotor disk, the underlying physical essence of ECR power reduction is cleared. Furthermore, the influence of the key control parameters, including convergence factor and weighting matrix, on the effectiveness of closed-loop control for ECR performance enhancement is explored. Some useful results are summarized, which can be used to direct the future active control law design of ECR performance enhancement.
基金National Natural Science Foundation of China(No.51906013)The Pyramid Talent Training Project of Beijing University of Civil Engineering and Architecture,China(JDYC20200316)。
文摘Considering the issues of energy saving and environment protection,the performance of refrigeration systems requires to be improved.In recent years,nano-fluids have attracted greatly attention from the researchers due to their outstanding thermal characteristics.In this work,the published investigations on the preparation and characterization of nano-fluids have been discussed at first.Furthermore,the key thermo-physical properties of nano-fluids,such as thermal conductivity,viscosity,specific heat and density have been summarized.Finally,the performance enhancements in different types of refrigeration systems by using nano-fluids have been reviewed.It is concluded that nano-fluids as refrigerant,lubricant or secondary fluid have wide potential application in refrigeration systems.
基金supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)the Ministry of Trade,Industry and Energy(MOTIE,No.20174010201490)financially supported by the Korea Environment Industry&Technology Institute(KEITI)through"The Chemical Accident Prevention Technology Development Project"granted by the Korea Ministry of Environment(MOE,No.2017001960004)。
文摘In this article,we review the recent progress and our research activity on the synthesis of inorganic shell nanostructures to enhance the catalytic performance and stability of metal nanoparticles in catalytic applications.First,we introduce general synthetic strategies for the fabrication of inorganic nanoscale shell layers,including template-assisted sol-gel coating,hydrothermal(or solvothermal)synthesis and the self-templating process.We also discuss recent examples of metal nanoparticles(NPs)with nanoscale shell layers,namely core-shell,yolk-shell and multiple NPs-embedded nanoscale shell.We then discuss the performance and stability of metal particles in practical catalytic applications.Finally,we conclude with a summary and perspective on the further progress of inorganic nanostructure with nanoscale shell layers for catalytic applications.
文摘This paper first revisits the previously proposed NSAD (New Self-Adapt DCF) mechanism. Some modifications are presented to further enhance the performance of NSAD in the error-prone environment. Then a new MAC mechanism is proposed that can realize bandwidth guarantee by assigning different self-adapt parameters to users at different priority levels. The bandwidth guarantee property of this new mechanism is analyzed and the high priority users are found to have bandwidth guaranteed even in heavy contention condition, which is proved true not only by theoretical analysis but also by simulation results. At the same time the new scheme keeps the self-adapt character of NSAD, so the overall system utilization is kept very high in heavy contention condition compared with the previously studied DCF-based QoS mechanisms.
基金Acknowledgements W. C. acknowledges the financial support from Singapore MOE Grant R143-000-652-112, National Natural Science Foundation of China (No. 21573156) and the technical support from Centre for Advanced 2D Materials and Graphene Research Centre for the device fabrication. G. E. acknowledges Singapore National Research Foundation, Prime Minister's Office, Singapore, for funding the research under its Medium-sized Centre program as well as NRF Research Fellowship (No. NRF-NRFF2011-02). G. E. also acknowledges financial support from Singapore MOE (No. MOE2015-T2-2-123).
文摘Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have attracted enormous research interests and efforts towards the development of versatile electronic and optical devices, owing to their extraordinary and unique fundamental properties and remarkable prospects in nanoelectronic applications. Among the TMDs, tungsten diselenide (WSe2) exhibits tunable ambipolar transport characteristics and superior optical properties such as high quantum efficiency. Herein, we demonstrate significant enhancement in the device performance of WSe2 phototransistor by in situ surface functionalization with cesium carbonate (Cs2CO3). WSe2 was found to be strongly doped with electrons after Cs2CO3 modification. The electron mobility of WSe2 increased by almost one order of magnitude after surface functionalization with 1.6-nm-thick Cs2CO3 decoration. Furthermore, the photocurrent of the WSe2-based phototransistor increased by nearly three orders of magnitude with the deposition of 1.6-nm-thick Cs2CO3. Characterizations by in situ photoelectron spectroscopy techniques confirmed the significant surface charge transfer occurring at the Cs2COB/WSe2 interface. Our findings coupled with the tunable nature of the surface transfer doping method establish WSe2 as a promising candidate for future 2D materials- based optoelectronic devices.
基金The authors would like to acknowledge the financial support from the National Natural Science Foundation of China(No.U2004199)the Excellent Youth Foundation of Henan Province(No.202300410373)+2 种基金China Postdoctoral Science Foundation(Nos.2021T140615 and 2020M672281)the Natural Science Foundation of Henan Province(No.212300410285)the Young Talent Support Project of Henan Province(No.2021HYTP028).
文摘Hierarchical-structure materials hold great promise for numerous applied domains such as fuel cell,sensor,and optic.However,the developments are significantly impeded by the lack of efficient strategy permitting precise and efficient decoration of specific confined space.Here,an in-situ precise hybridization strategy is proposed to efficiently manipulate the nanostructure of membrane nanochannels.Typically,Nafion ionic nanochannels are impregnated with precursors via heat swelling,followed by microwave-assisted condensation to form polymer quantum dot network.The formation of polymer quantum dot network significantly improves the stability and functionality of ionic nanophase(i.e.,ionic nanochannel).This helps hybrid membrane achieving enhanced proton conduction and methanol barrier properties,resulting in over ten times increase in proton/methanol selectivity.These then impart prominent device performances for both hydrogen and methanol fuel cells with the elevation of~100%.Importantly,such function manipulation of ionic nanochannels is achieved with fully maintaining function of backbone nanophase.Besides,the regulation of physical topology and chemical environment of ionic nanochannel also brings optimization of gas and ion separation properties.This facile and versatile strategy may open up a new avenue for decorating confined space of many hierarchical-structure materials.
基金financially supported by the National Natural Science Foundation of China(Nos.52072136,51872104,51972257 and 52172229)the National Key R&D Program of China(No.2016YFA0202602)the Fundamental Research Funds for the Central Universities(No.WUT:2021IVA115)
文摘Layered alkali-metal titanate materials are considered as attractive anodes for sodium ion batteries due to their favorable safety and low cost.However,their practical implementation faces major challenges of low electronic conductivity and inevitable volume variation during Na^(+)intercalation and de-intercalation,which are generally difficult to conquer by a single modification method.Herein,a synergistic ally enhancing strategy to promote the electrochemical performance of Na_(2)Ti_(2)O_(5)nanowire array anode via simultaneous hydrogenation and carbon coating is developed.Hydrogenation leads to partially reduced titanium;together with conductive carbon layer,it endows Na_(2)Ti_(2)O_(5)with fast electron transport and structural stability.The resulting H-Na_(2)Ti_(2)O_(5)@C anode exhibits enhanced rate capability(8.0C,165 mAh·g^(-1))and stable cycle performance up to 1000 times in sodium-ion half-cells(the capacity of H-Na_(2)Ti_(2)O_(5)without carbon fades drastically after only 100 cycles).In addition,a newcoupling full cell is further designed with graphene hybridized high-voltage Na_(3)(VO_(0.5))_(2)(PO4)_(2)F_(2)as cathode,capable of delivering a high specific energy density of 212.1 Wh·kg^(-1)(based on the mass of both anode and cathode)and good rate and cycling stability.This work may offer inspiration for synergistic optimization of electrode materials for advanced electrochemical energy storage devices.
基金supported by National Natural Science Foundation of China (Nos. 21171044 and 21371040)the National Key Basic Research Program of China (973 Program, No. 2013CB632900)+1 种基金the Fundamental Research Funds for the Central Universities (No. HIT. IBRSEM. A201409)Program for Innovation Research of Science in Harbin Institute of Technology (PIRS of HIT Nos. A201418, A201416 and B201414)
文摘A pyridine-anchor co-adsorbent of N,N'-bis((pyridin-2-yl)(methyl) methylene)-o-phenylenediamine(named BPPI) is prepared and employed as co-adsorbent in dye-sensitized solar cells(DSSCs). The prepared co-adsorbent could overcome the deficiency of N719 absorption in the low wavelength region of visible spectrum, offset competitive visible light absorption of I_3^-, enhance the spectral responses of the co-adsorbed TiO_2 film in region from 300 nm to 750 nm, suppress charge recombination, prolong electron lifetime, and decrease the total resistance of DSSCs. The optimized cell device co-sensitized by BPPI/N719 dye gives a short circuit current density of 12.98 m A cm^(-2), an open circuit voltage of 0.73 V,and a fill factor of 0.66 corresponding to an overall conversion efficiency of 6.22% under standard global AM 1.5 solar irradiation, which is much higher than that of device solely sensitized by N719(5.29%)under the same conditions. Mechanistic investigations are carried out by various spectral and electrochemical characterizations.