数字经济对要素市场一体化的影响研究

数字经济的兴起塑造着新的经济形态,而新的经济形态催生要素市场新的变革。本文基于HK模型框架,从理论上证明了数字经济的发展对要素市场一体化进程具有促进作用,并采用2006-2020年我国各省、自治区和直辖市数据,通过构造不完美工具变量实证检验了数字经济对要素市场一体化的影响。研究发现:首先,数字经济能够有效促进本地区要素市场一体化水平的提升,同时对于关联地区具有显著的空间溢出效应。其次,沿海地区间经济关联和地理关联均较为密切,具体表现为该地区两种空间溢出特征均稳健显著,而内陆地区仅仅在经济关联维度表现出数字经济的空间溢出效应。最后,本文进一步考虑了人口流动约束下数字经济与要素市场一体化的关系,发现数字经济对要素市场一体化起促进作用的地区主要为人口流入地区。

Effects of inherent potassium on the catalytic performance of Ni/biochar for steam reforming of toluene as a tar model compound

Biochar supported nickel(Ni/BC)has been widely studied as a cheap and easy-to-prepare catalyst with potential applications in tar reforming during the gasification of low-rank fuels,such as brown coal and biomass.However,the role and behaviors of inherent K species,especially their interactions with Ni particles and the biochar support,are not well understood yet.In this work,three Ni/BC catalysts with varying K amount were prepared from raw,water-washed,and acid-washed biomass.They were used in steam reforming of toluene as a tar model compound to elucidate the effects of inherent K on the catalytic activity and stability.Detailed characterization indicated that K enhanced water adsorption due to its hydroscopicity and lowered the condensation and graphitization degrees of biochar,but the alteration to the electronic state of Ni was not observed.These effects together led to a temperature-dependent role of K.That is,at relatively low temperatures of 450 and 500℃,toluene conversion was increased in the presence of K,due to the increased concentration of adsorbed water around Ni particles.By contrast,at relatively higher temperatures of 550 and 600℃,although initial high activity was achieved,Ni/BC with K deactivated rapidly because of the accelerated consumption of the biochar support.

Visualization on electrified micro-jet instability from Taylor cone in electrohydrodynamic atomization

The cone-jet in electrohydrodynamic atomization has been widely applied into numerous industrial fields owing to micro-sized drops with narrow distribution and high charge.The electrified jet emits from a single capillary sheathed with quartz tube is visualized versus operating parameters and physical properties,and breakup instabilities are also discussed.The range of operating parameters for a steady conejet broadens,as well as the minimum flow rate.Taylor cone angle decreases with an increase in flow rate,while increases as electric potential increasing.The jet breakup length decreases with an increase in flow rate and conductivity,while increases as electric potential increasing.The diffusion angle increases as flow rate increasing,while decrease as electric potential and conductivity increasing.Much clearer whipping instabilities are observed with an increase in“electro-Weber”number and conductivity.The completion in disturbance or/and suppression from axial and radial stresses,drag force dominates the variation.Meanwhile,for a large flow rate,the transition from varicose instabilities to whipping instabilities is found.The whipping instabilities are clearly observed for high conductivity due to much more free ions in liquid.For much higher conductivity,an intermittent electrified jet appears and shows an umbrella plume,and breakup length sharply shortens.

Study of Effect of Boundary Conditions on Patient-Specific Aortic Hemodynamics

Cardiovascular computational fluid dynamics(CFD)based on patient-specific modeling is increasingly used to predict changes in hemodynamic parameters before or after surgery/interventional treatment for aortic dissection(AD).This study investigated the effects of flow boundary conditions(BCs)on patient-specific aortic hemodynamics.We compared the changes in hemodynamic parameters in a type A dissection model and normal aortic model under different BCs:inflow from the auxiliary and truncated structures at aortic valve,pressure control and Windkessel model outflow conditions,and steady and unsteady inflow conditions.The auxiliary entrance remarkably enhanced the physiological authenticity of numerical simulations of flow in the ascending aortic cavity.Thus,the auxiliary entrance can well reproduce the injection flow fromthe aortic valve.In addition,simulations of the aortic model reconstructed with an auxiliary inflow structure and pressure control and the Windkessel model outflow conditions exhibited highly similar flow patterns and wall shear stress distribution in the ascending aorta under steady and unsteady inflow conditions.Therefore,the inflow structure at the valve plays a crucial role in the hemodynamics of the aorta.Under limited time and calculation cost,the steady-state study with an auxiliary inflow valve can reasonably reflect the blood flow state in the ascending aorta and aortic arch.With reasonable BC settings,cardiovascular CFD based on patient-specific ADmodels can aid physicians in noninvasive and rapid diagnosis.

Progress in 3D‑MXene Electrodes for Lithium/Sodium/Potassium/Magnesium/Zinc/Aluminum‑Ion Batteries

MXenes have attracted increasing attention because of their rich surface functional groups,high electrical conductivity,and outstanding dispersibility in many solvents,and have demonstrated competitive efficiency in energy storage and conversion applications.However,the restacking nature of MXene nanosheets like other two-dimensional(2D)materials through van der Waals forces results in sluggish ionic kinetics,restricted number of active sites,and ultimate deterioration of MXene mate-rial/device performance.The strategy of raising 2D MXenes into three-dimensional(3D)structures has been considered an efficient way for reducing restacking,providing greater porosity,higher surface area,and shorter distances for mass transport of ions,surpassing standard one-dimensional(1D)and 2D structures.In multivalent ion batteries,the positive multivalent ions combine with two or more electrons at the same time,so their capacities are two or three times that of lithium-ion batteries(LIBs)under the same conditions,e.g.,a magnesium ion battery has a high theoretical specific capacity of 2205 mAh g^(−1)and a high volumetric capacity of 3833 mAh cm^(−3).In this review,we summarize the most recent strategies for fabricating 3D MXene architectures,such as assembly,template,3D printing,electrospinning,aerogel,and gas foaming methods.Special consideration has been given to the applications of highly porous 3D MXenes in energy storage devices beyond LIBs,such as sodium ion batteries(SIBs),potassium ion batteries(KIBs),magnesium ion batteries(MIBs),zinc ion batteries(ZIBs),and aluminum ion batteries(AIBs).Finally,the authors provide a summary of the future opportunities and challenges for the construction of 3D MXenes and MXene-based electrodes for applications beyond LIBs.

Superhigh intrinsic proton conductivity in densely carboxylic covalent organic framework

Herein,we developed for the first time two carboxylic acid based intrinsic proton conductors(COOHCOF-1 and COOH-COF-2)via pre-assembly approach.The obtained COOH-COF-1 and COOH-COF-2 not only show outstanding chemical and thermal stabilities,but also exhibit superhigh intrinsic proton conductive behaviors.Especially,the intrinsic proton conductivity of COOH-COF-2 is up to 2.6×10^(−3) S/cm at 353 K and 98%RH,which is the highest value among all the reported acid functionalized COFs.This work lights up the way for the rational design of functional COFs with remarkably intrinsic proton conducting performance and related practical applications.

Assessing Drought Conditions in Cloudy Regions Using Reconstructed Land Surface Temperature

Temperature vegetation dryness index(TVDI)in a triangular or trapezoidal feature space can be calculated from the land surface temperature(LST)and normalized difference vegetation index(NDVI),and has been widely applied to regional drought monitoring.However,thermal infrared sensors cannot penetrate clouds to detect surface information of sub-cloud pixels.In cloudy areas,LST data include a large number of cloudy pixels,seriously degrading the spatial and temporal continuity of drought monitoring.In this paper,the Remotely Sensed Daily Land Surface Temperature Reconstruction model(RSDAST)is combined with the LST reconstructed(RLST)by the RSDAST and applied to drought monitoring in a cloudy area.The drought monitoring capability of the reconstructed temperature vegetation drought index(RTVDI)under cloudy conditions is evaluated by comparing the correlation between land surface observations for soil moisture and the TVDI before and after surface temperature reconstruction.Results show that the effective duration and area of the RTVDI in the study area were larger than those of the original TVDI(OTVDI)in 2011.In addition,RLST/NDVI scatter plots cover a wide range of values,with the fitted dry–wet boundaries more representative of real soil moisture conditions.Under continuously cloudy conditions,the OTVDI inverted from the original LST(OLST)loses its drought monitoring capability,whereas RTVDI can completely and accurately reconstruct surface moisture conditions across the entire study area.The correlation between TVDI and soil moisture is stronger for RTVDI(R=-0.45)than that for OTVDI(R=-0.33).In terms of the spatial and temporal distributions,the R value for correlation between RTVDI and soil moisture was higher than that for OTVDI.Hence,in continuously cloudy areas,RTVDI not only expands drought monitoring capability in time and space,but also improves the accuracy of surface soil moisture monitoring and enhances the applicability and reliability of thermal infrared data under extreme conditions.

Retrieval of Aerosol Optical Depth for Chongqing Using the HJ-1 Satellite Data

Aerosol optical depth （AOD） is a common indicator applied in monitoring aerosols in the atmosphere. The hilly landscape and rapid economic growth of the megacity Chongqing have facilitated increased aerosol concentration, and it is meaningful to accurately retrieve AOD over Chongqing. The HJ-1A/B satellite of China carries a sensor/camera called the Charge Coupled Device （CCD）, the spatial resolution of which meets the requirement for re- trieving high resolution AOD. In this paper, analysis of the AOD retrievals from different methods using the H J-1 satellite data revealed the most suitable algorithm. Through comparison with the AOD product of Moderate Resolu- tion Imaging Spectroradiometer （MODIS）, the AOD retrieval results using enhanced vegetation index （EVI） to estim- ate dark pixels showed the highest correlation. The continental aerosol model was used to build a lookup table that was able to facilitate a good AOD retrieval for both city and rural areas. Finally, the algorithm that combined dark pixels, buffer areas, and the deep blue algorithm was found to be most suitable for AOD retrieval. The AOD retrieval results based on the HJ-1 data were consistent with MODIS products, and our algorithm yields reasonable results in most cases. The results were also compared with ground-based PMl0 measurements synchronized with the overpass time of the HJ-1 satellite, and high correlation was found. The findings are relevant to other Chinese satellite data used for retrieving AOD on the same channels.

Extremely Stable Sulfuric Acid Covalent Organic Framework for Highly Effective Ammonia Capture

Ammonia(NH_(3))is one of the most important industrial feedstocks in the fields of fertilizers,drugs,explosives,ordnance,commercial cleanings,and so on.However,the features of ammonia such as high toxicity and corrosivity,and difficulty in handling would inevitably increase the risk of environmental damage and the deterioration of natural/public lands.Although sorts of solid adsorbents such as metal oxides,zeolites,organic polymers,activated carbons,and metal organic frameworks have been applied in NH_(3) capture,they still show low uptake capacity,low affinities,and instability.Herein,we developed the first case of a highly stable sulfuric acid covalent organic framework(COF),namely TpBD-(SO_(3)H)_(2),as NH_(3) capturer,in which sulfonic acid sites can strongly interact with NH_(3) molecules,and enhance the performance of NH_(3) sorption.As a result,TpBD-(SO_(3)H)_(2) shows high chemical stability under strong acid and water conditions,an important merit for the potential application in harsh environment.And it also exhibits high ammonia capacity of 11.5 mmol·g^(−1) at 298 K and 1.0 bar,making it one of the best in all chemically stable NH_(3) adsorbents up to date.This work thus develops sulfuric acid COF materials as a new platform for ammonia capture and storage.

Cortical and Subcortical Grey Matter Abnormalities in White Matter Hyperintensities and Subsequent Cognitive Impairment

Grey matter(GM)alterations may contribute to cognitive decline in individuals with white matter hyperintensities(WMH)but no consensus has yet emerged.Here,we investigated cortical thickness and grey matter volume in 23 WMH patients with mild cognitive impairment(WMH-MCI),43 WMH patients without cognitive impairment,and 55 healthy controls.Both WMH groups showed GM atrophy in the bilateral thalamus,fronto-insular cortices,and several parietal-temporal regions,and the WMH-MCI group showed more extensive and severe GM atrophy.The GM atrophy in the thalamus and fronto-insular cortices was associated with cognitive decline in the WMH-MCI patients and may mediate the relationship between WMH and cognition in WMH patients.Furthermore,the main results were well replicated in an independent dataset from the Alzheimer's Disease Neuroimaging Initiative database and in other control analyses.These comprehensive results provide robust evidence of specific GM alterations underlying WMH and subsequent cognitive impairment.

Phase-modulated mechanical and thermoelectric properties of Ag_(2)S_(1-x)Te_(x)ductile semiconductors

By virtue of the excellent plasticity and tunable transport properties,Ag_(2)S-based materials demonstrate an intriguing prospect for flexible or hetero-shaped thermoelectric applications.Among them,Ag_(2)S_(1-x)Te_(x)exhibits rich and interesting variations in crystal structure,mechanical and thermoelectric transport properties.However,Te alloying obviously introduces extremely large order-disorder distributions of cations and anions,leading to quite complicated crystal structures and thermoelectric properties.Detailed composition-structure-performance correlation of Ag_(2)S_(1-x)Te_(x)still remains to be established.In this work,we designed and prepared a series of Ag_(2)S_(1-x)Te_(x)(x=0-0.3)materials with low Te content.We discovered that the monoclinic-to-cubic phase transition occurs around x=0.16 at room temperature.Te alloying plays a similar role as heating in facilitating this monoclinic-to-cubic phase transition,which is analyzed based on the thermodynamic principles.Compared with the monoclinic counterparts,the cubic-structured phases are more ductile and softer in mechanical properties.In addition,the cubic phases show a degenerately semiconducting behavior with higher thermoelectric performance.A maximum zT=0.8 at 600 K and bending strain larger than 20% at room temperature were obtained in Ag_(2)S_(0.7)Te_(0.3).This work provides a useful guidance for designing Ag_(2)S-based alloys with enhanced plasticity and high thermoelectric performance.

The influence of urban three-dimensional structure and building greenhouse effect on local radiation flux

Accurate measurements of the three-dimensional structure characteristics of urban buildings and their greenhouse effect are important for evaluating the impact of urbanization on the radiation energy budget and research on the urban heat island(UHI)effect.The decrease in evapotranspiration or the increase in sensible heat caused by urbanization is considered to be the main cause of the UHI effect,but little is known about the influence of the main factor“net radiant flux”of the urban surface heat balance.In this study,experimental observation and quantitative model simulation were used to find that with the increase of building surface area after urbanization,the direct solar radiation flux and net radiation flux on building surface areas changed significantly.In order to accurately quantify the relationship between the positive and negative effects,this study puts forward the equivalent calculation principle of“aggregation element”,which is composed of a building’s sunny face and its shadow face,and the algorithm of the contribution of the area to thermal effect.This research clarifies the greenhouse effect of a building with walls of glass windows.Research shows that when the difference between absorption rates of a concrete wall and grass is−0.21,the cooling effect is shown.In the case of concrete walls with glass windows,the difference between absorption rates of a building wall and grass is−0.11,which is also a cooling effect.The greenhouse effect value of a building with glass windows reduces the cooling effect value to 56%of the effect of a building with concrete walls.The simulation of changes in net radiant flux and flux density shows that the greenhouse effect of a 5-story building with windows yields 15.5%less cooling effect than one with concrete walls,and a 30-story building with windows reduces the cooling effect by 23.0%.The simulation results confirmed that the difference in the equivalent absorption rate of the aggregation element is the“director”of cooling and heating effects,and the area of the aggregation element is the“amplifier”of cooling and heating effects.At the same time,the simulation results prove the greenhouse effect of glass windows,which significantly reduces the cold effect of concrete wall buildings.The model reveals the real contribution of optimized urban design to mitigating UHI and building a comfortable environment where there is no atmospheric circulation.