A silylated melamine sponge(SMS)was prepared by two simple steps,namely,immersion and dehydration of a melamine sponge coated with methyltrichlorosilane.The silylated structure of SMS was characterized by FT-IR(Fourie...A silylated melamine sponge(SMS)was prepared by two simple steps,namely,immersion and dehydration of a melamine sponge coated with methyltrichlorosilane.The silylated structure of SMS was characterized by FT-IR(Fourier-transform infrared)spectroscopy,SEM(Scanning electron microscopy)and in terms of water contact angles.Its oil-water absorption and separation capacities were measured by FT-IR and UV-visible spectrophoto-metry.The experimental results have shown that oligomeric silanol covalently bonds by Si-N onto the surface of melamine sponge skeletons.SMS has shown superhydrophobicity with a water contact angle exceeding 150°±1°,a better separation efficiency with regard to diesel oil(by 99.31%(wt/wt%)in oil-water mixture and even up to 99.99%(wt/wt%)for diesel oil in its saturated aqueous solution.Moreover,SMS inherited the intrinsicflame retardancy of the melamine sponge.In general,SMS has shown superhydrophobicity,high porosity,excellent selectivity,remarkable recyclability,and better absorption capacity for various oils and organic solvents,and a high separation efficiency for oil in saturated aqueous solutions.展开更多
An effectively mild solvent solution containing NaOH/PEG was employed to dissolve the cellulose extracted from the wheat straw.With further combined regeneration process and freeze-drying,the cellulose aerogel was suc...An effectively mild solvent solution containing NaOH/PEG was employed to dissolve the cellulose extracted from the wheat straw.With further combined regeneration process and freeze-drying,the cellulose aerogel was successfully obtained.Scanning electron microscope,X-ray diffraction technique,Fourier transform infrared spectroscopy,and Brunauer-Emmett-Teller were used to characterize this cellulose aerogel of low density(about 40 mg·cm^(–3))and three-dimensional network with large specific surface area(about 101 m2·g^(–1)).Additionally,with a hydrophobic modification by trimethylchlorosilane,the cellulose aerogel showed a strong absorptive capacity for oil and dye solutions.展开更多
The development of novel absorbents is essential for SO_(2)removal.In this study,a novel ionic liquid(IL,[BHEP][HSO_(4)])was prepared,and water was selected as the co-solvent.The density and viscosity of aqueous[BHEP]...The development of novel absorbents is essential for SO_(2)removal.In this study,a novel ionic liquid(IL,[BHEP][HSO_(4)])was prepared,and water was selected as the co-solvent.The density and viscosity of aqueous[BHEP][HSO_(4)]were measured and the SO_(2)absorption performance was systematically investigated.Furthermore,the thermodynamic properties of SO_(2)in aqueous[BHEP][HSO_(4)]were calculated.Additionally,the mechanism of SO_(2)absorption in aqueous[BHEP][HSO_(4)]was confirmed using Fouriertransform infrared and nuclear magnetic resonance spectroscopy.It showed that[BHEP][HSO_(4)]absorbed0.302 g·g^(-1)(g SO_(2)/g IL)at an SO_(2)partial pressure of 2000μl·L^(-1)at 303.2 K,and the SO_(2)desorption enthalpy was-39.63 k J·mol^(-1).The mechanistic study confirmed the chemical absorption of SO_(2)in aqueous[BHEP][HSO_(4)].展开更多
This work investigated and quantified the physicomechanical properties of flat-pressed wood plastic composites produced with recycled polyethylene terephthalate, recycled polyethylene and sawdust derived from selected...This work investigated and quantified the physicomechanical properties of flat-pressed wood plastic composites produced with recycled polyethylene terephthalate, recycled polyethylene and sawdust derived from selected tropical timbers, namely, Nauclea diderrichii, Brachystegia eurycoma, Erythrophleum suaveolens and Prosopis africana, for possible utilization in the wood industry. The compounding of the polymer blends of the precursor plastics, namely recycled PET (rPET) and recycled PE (rPE) with the sawdust (SD) from the selected timbers to produce the desired wood rPET/rPE composites was carried out via the flat press method. The characterization of the physicomechanical properties of the wood plastic composites (WPCs) produced, such as the density, hardness, flexural strength, ultimate tensile strength, elongation %, thickness swelling and water absorption capacity was carried out using methods based mainly on the European Committee for Standardization (CEN) and the American Society for Testing Materials (ASTM) standards. The results of the investigation on the resultant composites indicated that changes in the SD content affected the density of flat-pressed WPCs in line with literature. Generally, it was observed that as wood dust increased and PET content decreased, the density of composites decreased with some deviations as expected probably due to the anisotropic nature of the wood fillers. The analysis of variance (ANOVA) revealed that there was a statistically significant variation in the wood composites of Nuclea diderichii based on the physicomechanical values as the p-value (0.020) obtained was less than the critical level of α = 0.05. It was also observed that the composite, Wood 1 Sample 5 (W<sub>1</sub>S<sub>5</sub>) which was composed of 40% rPE, 40% rPET and 20% SD (derived from Nuclea diderichii), had the highest percentage elongation (26.84%);the highest flexural strength (14.995 N/mm<sup>2</sup>) and possibly the least carbon footprint in the environment. These properties of W<sub>1</sub>S<sub>5</sub> suggest that it could therefore be the best option for the production of building materials like ceiling boards or floor skirting in the wood plastic composite industry. The results of these investigations have therefore indicated that the fabrication of WPCs from sawdust and rPET/rPE was technically feasible and had prospects for large scale production in the wood industry.展开更多
This work investigated and quantified the physicochemical, structural and morphological properties of four (4) tropical timbers as precursor raw materials for possible utilization in the wood plastic industry. The phy...This work investigated and quantified the physicochemical, structural and morphological properties of four (4) tropical timbers as precursor raw materials for possible utilization in the wood plastic industry. The physicochemical properties of the wood samples such as the bulk and tapped density, moisture content, water absorption capacity at 25°C, volatile content, fixed carbon, ash content, alpha cellulose, hemicellulose, lignin, and extractives contents were determined using standard methods like the European Committee for Standardization and (CEN/TS) and the American Society for Testing Materials (ASTM) standards. The structural and morphological properties of the samples were examined with Fourier Infrared Transform (FTIR) spectroscopy and scanning electron microscope (SEM). Results indicated that the bulk density values of the timbers ranged from 0.34 g/cm<sup>3</sup> in Brachystegia eurycoma (W<sub>3</sub>) to 0.47 g/cm<sup>3</sup> in Erythrophleum suaveolens (W<sub>2</sub>), with the other timbers, Nuclea diderichii (W<sub>1</sub>) and Prosopis africana (W<sub>4</sub>) having the same bulk density of 0.40 g/cm<sup>3</sup>. With respect to their moisture content, W<sub>2</sub> had the highest value (8.38%) while Nauclea diderrichii had the lowest value (6.52%). The water absorption capacities of the woods studied correlated with the cellulose composition of wood in the order of: W<sub>3</sub> > W<sub>1</sub> > W<sub>4</sub> > W<sub>2</sub>. The FTIR results showed that W<sub>2</sub> and W<sub>3</sub> presented a slightly more prominent and broader band than the other woods at 1731 cm<sup>-1</sup>, in agreement with the higher holocellulose content of these species, while W<sub>2</sub> and W<sub>4</sub> presented the most prominent peaks indicating higher lignin content than W<sub>1</sub> and W<sub>3</sub>. The SEM micrographs of the wood flour samples investigated indicated that the surfaces of the woods were rough and heterogeneous with irregular crystal and brick shaped particles. A two-way analysis of variance (ANOVA) carried out with respect to the chemical composition of the wood samples indicated that there was no statistically significant variation in the wood chemical composition between species as the p-value (0.852) obtained was greater than the critical level of α = 0.05.展开更多
An urban traffic ecosystem is a spatial structure composed of air,population,vehicles,roads,green spaces,and regions.Traffic ecological resilience is a critical issue in high-quality urban development.From the perspec...An urban traffic ecosystem is a spatial structure composed of air,population,vehicles,roads,green spaces,and regions.Traffic ecological resilience is a critical issue in high-quality urban development.From the perspective of system optimization,it is important to study the level of urban traffic ecological resilience and analyze its influencing factors.In this study,we evaluated traffic ecological resilience,characterized its spatio-temporal differentiation,and explored its influencing factors by constructing a system of urban traffic ecological resilience and by analyzing the environmental protection and urban construction data in 31 Chinese cities during 2011-2018.By conducting Kernel density analysis,standard deviation ellipse,comprehensive weight determination,panel data regression analysis,andχ2test,we found that traffic ecological resilience was low on the whole and exhibited the temporal trend of“decreasing first and then increasing”and the spatial characteristic of“high in the east,second in the middle,and low in the west”.The cities with high traffic ecological resilience density values were located in Southeast China and tended to move from northwest to southeast.Governance capability,market activity,technological innovation capability,opening degree,and financial resources had significant effects on urban traffic ecological resilience.Finally,we gave some suggestions for improving the urban traffic ecological resilience in Chinese cities as well as other developing countries in the world.展开更多
Lost circulation of drilling fluid is one of the most common engineering problems in the drilling process of fractured formations.In this study,an oil-absorbing polymer gel synthesized using compound monomers with rig...Lost circulation of drilling fluid is one of the most common engineering problems in the drilling process of fractured formations.In this study,an oil-absorbing polymer gel synthesized using compound monomers with rigid and flexible chains was applied to control the oil-based drilling fluid loss while drilling.The microstructure,oil-absorbing performance,and plugging performance the gel was investigated.A large number of dense pores on the surface of the gel were observed,which allowed the oil molecules to enter the internal space of the gel.The initial oil absorption capacity of the gel was fast,and it increased with the increase in the temperature and decrease in the particle size,reaching 20.93 g/g at140℃.At a high temperature of 140℃,the bearing pressure capacity of the gel formula containing particles of different particle sizes reached 7.6 MPa for a fracture of a width of 3 mm,showing that the oil-absorbing gel have excellent plugging performance at high temperature.Plugging mechanism of the gel was investigated through visualized fracture plugging experiments.Results show that the dynamic migratio n,particle-swelling,particle-bridging,particle-aggregation,deformation-filling,and compaction-plugging contribute to the whole lost circulation control process,reflecting that the plugging performance can be effectively enhanced by improving the aggregation and filling degrees of the gel with different particle sizes.展开更多
This review article covers some of the founding literature that helps develop our understandingof the National Innovation System (NIS) concept. Subsequently, several versionsof NIS, including system-functional approac...This review article covers some of the founding literature that helps develop our understandingof the National Innovation System (NIS) concept. Subsequently, several versionsof NIS, including system-functional approaches, are discussed and compared with narrowresearch and development (R&D) and market-based approaches. Finally, the article contendsthat the system-functional and other narrow approaches are limited in application tothe developing low- and middle-income countries (LMICs). Thus, it makes a case for moreinclusive absorptive capacity approaches and explains how they might be more relevant ininvestigating the NIS of an LMIC. Such approaches suggest LMICs be strategic in buildingtheir innovation base and plead for strong local conditions (capacities)to produceknowledge as well as capture and improvise on incoming knowledge from abroad. Theresearch is important as it provides insights into analyzing and capturing innovationprocesses in LMICs, which are prime candidates for development and innovation studiesandpractice.展开更多
Arecoline is an alkaloid with important pharmacological effects in the plant areca nut,which has been demonstrated to be an agonist of muscarinic receptors(M receptor).This study explored the influences of dietary are...Arecoline is an alkaloid with important pharmacological effects in the plant areca nut,which has been demonstrated to be an agonist of muscarinic receptors(M receptor).This study explored the influences of dietary arecoline on growth performance,intestinal digestion and absorption abilities,antioxidant capacity,and the apical junction complex(AJC)of adult grass carp(Ctenopharyngodon idella).Adult grass carp(608to 1512 g)were fed at 6 graded levels of dietary arecoline(0,0.5,1.0,1.5,2.0,and 2.5 mg/kg diet)for 9weeks.The results suggested that appropriate dietary supplementation of arecoline(1.0 mg/kg)increased growth parameters and intestinal growth in adult grass carp(P<0.05),enhanced digestion and absorption capacities(P<0.05),up-regulated muscarinic receptor 3(M3)mRNA level(P<0.05),increased the content of neuropeptide fish substance P(P<0.05),improved antioxidant capacity by activating the Keap1a/Nrf2signaling pathway(P<0.05),reduced intestinal mucosal permeability(P<0.05),and increased m RNA levels of tight junction(TJ)and adherent junction AJ-related proteins in fish by inhibiting the RhoA/ROCK signaling pathway(RhoA/ROCK/MLCK/NMII)(P<0.05).In addition,the appropriate arecoline supplementation for adult grass carp was determined to be 1.20,1.21,1.07,and 1.19 mg/kg based on percentage weight gain,lipase activity,serum diamine oxidase,and protein carbonyl,respectively.Overall,to the best of our knowledge,we investigated for the first time the effects and possible mechanisms of dietary arecoline on intestinal digestive and absorptive capacities and structural integrity in fish and evaluated the appropriate level of supplementation.展开更多
This paper empirically investigates the impact of China’s outward foreign direct investment(OFDI)on its export sophistication.Using a provincial-level panel dataset and applying fixed effects and instrumental variabl...This paper empirically investigates the impact of China’s outward foreign direct investment(OFDI)on its export sophistication.Using a provincial-level panel dataset and applying fixed effects and instrumental variable regression techniques,the study finds that,on average,OFDI has no significant impact on China s export sophistication.However,after the full sample is divided into different regions,the study finds that OFDI has a positive and significant impact on export sophistication in the developed coastal region,but no such impact is observed in the less developed inland regions.Further investigation using a panel threshold model reveals that only when GDP,per capita GDP,human capital,and the research and development intensity of a home economy reach a certain level can OFDI promote export sophistication.The findings suggest that accelerating economic development and increasing absorptive capacity can facilitate the contribution of OFDI to China’s export sophistication.展开更多
Innovation is a key stimulus for firms’survival and growth.However,many of Chinese firms fail to make it due to the lack of adequate financial resources.Previous studies have been deeply investigated the relationship...Innovation is a key stimulus for firms’survival and growth.However,many of Chinese firms fail to make it due to the lack of adequate financial resources.Previous studies have been deeply investigated the relationships between financial resources and firms’innovation performance.This paper extends such stream of the literature by focusing on a vital question for entrepreneurs:how to maximize innovation output under resource constraints.Based on an extensive dataset collected at Zhongguancun Science Park(ZSP),Beijing,China,over the period 2011-2014,this paper discusses whether entrepreneurs should pursue extra public funding(control sphere).Besides,this paper also provides empirical evidence for entrepreneurs to make proper choices about resource allocation(entrepreneurial sphere).This paper hypothesizes that enterprises allocating resources by using the entrepreneurial sphere,rather than the control sphere,can advance innovation output.To test our hypothesis,this paper adopts a dynamic panel model estimated by a bootstrapbased bias correction procedure.We find that,in advancing innovative performance,the entrepreneurial sphere is more effective than control.Indeed,at the overall level,the crowding out effect merely offsets the additionality effect when enterprises pursue extra public funding.Therefore,the control sphere does not play an essential role in advancing innovation performance.Thus,extra efforts in that direction will turn out to be in vain.Consequently,as a policy implication we claim that entrepreneurs should spend more time and energy on productive activities rather than lobbying and rent-seeking.In addition,managers should allocate resources properly for internal knowledge creation,external knowledge absorption and S&T activities.展开更多
Considering the serious environmental pollution and economic losses caused by increasing oil spills and chemical leaks,effective and eco-friendly methods of oil/water separation should be urgently developed.Herein,a f...Considering the serious environmental pollution and economic losses caused by increasing oil spills and chemical leaks,effective and eco-friendly methods of oil/water separation should be urgently developed.Herein,a facile strategy(about 20 min)was developed for integrating covalent organic framework(COF)particles with melamine sponges(MS)by covalent bonding,and then a superhydrophobic COF/MS composite(denoted OA-CP@MS)could be further obtained by following modification with a 1-octadecylamine/water dispersion.Specifically,the synthesis process was developed under a mild condition that avoids the need for sealing and high-temperature treatments.It was proven that the fabricated OA-CP@MS presented a prominent absorption capacity for various organic reagents,in which adsorption capacity of chloroform could be up to 173 g/g.Owing to its excellent chemical robustness in strong alkaline and saline environments and in various organic solvents,the prepared OACP@MS showed a great potential to perform oil/water separation in complex practical conditions.Its rapid preparation process,fluorine-free treatment,and water-based modification would extend the application of COF materials in oil/water separation.展开更多
A Ag particle-coated and 1-dodecanethiolmodified melamine sponge(Ag-DDT-MS)was prepared through surface roughness by coating silver particles and subsequent grafting of a hydrophobic long hydrocarbon chain.Superhydrop...A Ag particle-coated and 1-dodecanethiolmodified melamine sponge(Ag-DDT-MS)was prepared through surface roughness by coating silver particles and subsequent grafting of a hydrophobic long hydrocarbon chain.Superhydrophobic and 3D porous Ag-DDT-MS was characterized by Fourier transform infrared spectroscopy,scanning electron microscope,energy-dispersive X-ray spectroscopy,and X-ray diffraction.The water contact angle of Ag-DDT-MS reached 159.2°.Ag-DDT-MS exhibited excellent absorption capacity for high viscous oils and organic solvents,ranging from 42.8 to 105.2 g∙g−1.The absorbed oils can be easily collected by the mechanical pressing process,and the oil recovery rate was satisfactory,more than 90%after 20 recycles.Ag-DDT-MS material also demonstrated good stability and excellent compressionrecovery ability,keeping 88.6%of the initial height after ten compression-release cycles.展开更多
基金funded by Qingyang Science and Technology Support Project(KT2019-03)。
文摘A silylated melamine sponge(SMS)was prepared by two simple steps,namely,immersion and dehydration of a melamine sponge coated with methyltrichlorosilane.The silylated structure of SMS was characterized by FT-IR(Fourier-transform infrared)spectroscopy,SEM(Scanning electron microscopy)and in terms of water contact angles.Its oil-water absorption and separation capacities were measured by FT-IR and UV-visible spectrophoto-metry.The experimental results have shown that oligomeric silanol covalently bonds by Si-N onto the surface of melamine sponge skeletons.SMS has shown superhydrophobicity with a water contact angle exceeding 150°±1°,a better separation efficiency with regard to diesel oil(by 99.31%(wt/wt%)in oil-water mixture and even up to 99.99%(wt/wt%)for diesel oil in its saturated aqueous solution.Moreover,SMS inherited the intrinsicflame retardancy of the melamine sponge.In general,SMS has shown superhydrophobicity,high porosity,excellent selectivity,remarkable recyclability,and better absorption capacity for various oils and organic solvents,and a high separation efficiency for oil in saturated aqueous solutions.
基金supported by the National Natural Science Foundation of China(31270590)China Postdoctoral Science Foundation funded project(2013M540263)Doctoral Candidate Innovation Research Support Program of Science&Technology Review(kjdb2012006).
文摘An effectively mild solvent solution containing NaOH/PEG was employed to dissolve the cellulose extracted from the wheat straw.With further combined regeneration process and freeze-drying,the cellulose aerogel was successfully obtained.Scanning electron microscope,X-ray diffraction technique,Fourier transform infrared spectroscopy,and Brunauer-Emmett-Teller were used to characterize this cellulose aerogel of low density(about 40 mg·cm^(–3))and three-dimensional network with large specific surface area(about 101 m2·g^(–1)).Additionally,with a hydrophobic modification by trimethylchlorosilane,the cellulose aerogel showed a strong absorptive capacity for oil and dye solutions.
基金the National Natural Science Foundation of China(22108115,21776123)China Postdoctoral Science Foundation funded project(2021 M691554)Kempe foundation(SMK21-0020)in Sweden。
文摘The development of novel absorbents is essential for SO_(2)removal.In this study,a novel ionic liquid(IL,[BHEP][HSO_(4)])was prepared,and water was selected as the co-solvent.The density and viscosity of aqueous[BHEP][HSO_(4)]were measured and the SO_(2)absorption performance was systematically investigated.Furthermore,the thermodynamic properties of SO_(2)in aqueous[BHEP][HSO_(4)]were calculated.Additionally,the mechanism of SO_(2)absorption in aqueous[BHEP][HSO_(4)]was confirmed using Fouriertransform infrared and nuclear magnetic resonance spectroscopy.It showed that[BHEP][HSO_(4)]absorbed0.302 g·g^(-1)(g SO_(2)/g IL)at an SO_(2)partial pressure of 2000μl·L^(-1)at 303.2 K,and the SO_(2)desorption enthalpy was-39.63 k J·mol^(-1).The mechanistic study confirmed the chemical absorption of SO_(2)in aqueous[BHEP][HSO_(4)].
文摘This work investigated and quantified the physicomechanical properties of flat-pressed wood plastic composites produced with recycled polyethylene terephthalate, recycled polyethylene and sawdust derived from selected tropical timbers, namely, Nauclea diderrichii, Brachystegia eurycoma, Erythrophleum suaveolens and Prosopis africana, for possible utilization in the wood industry. The compounding of the polymer blends of the precursor plastics, namely recycled PET (rPET) and recycled PE (rPE) with the sawdust (SD) from the selected timbers to produce the desired wood rPET/rPE composites was carried out via the flat press method. The characterization of the physicomechanical properties of the wood plastic composites (WPCs) produced, such as the density, hardness, flexural strength, ultimate tensile strength, elongation %, thickness swelling and water absorption capacity was carried out using methods based mainly on the European Committee for Standardization (CEN) and the American Society for Testing Materials (ASTM) standards. The results of the investigation on the resultant composites indicated that changes in the SD content affected the density of flat-pressed WPCs in line with literature. Generally, it was observed that as wood dust increased and PET content decreased, the density of composites decreased with some deviations as expected probably due to the anisotropic nature of the wood fillers. The analysis of variance (ANOVA) revealed that there was a statistically significant variation in the wood composites of Nuclea diderichii based on the physicomechanical values as the p-value (0.020) obtained was less than the critical level of α = 0.05. It was also observed that the composite, Wood 1 Sample 5 (W<sub>1</sub>S<sub>5</sub>) which was composed of 40% rPE, 40% rPET and 20% SD (derived from Nuclea diderichii), had the highest percentage elongation (26.84%);the highest flexural strength (14.995 N/mm<sup>2</sup>) and possibly the least carbon footprint in the environment. These properties of W<sub>1</sub>S<sub>5</sub> suggest that it could therefore be the best option for the production of building materials like ceiling boards or floor skirting in the wood plastic composite industry. The results of these investigations have therefore indicated that the fabrication of WPCs from sawdust and rPET/rPE was technically feasible and had prospects for large scale production in the wood industry.
文摘This work investigated and quantified the physicochemical, structural and morphological properties of four (4) tropical timbers as precursor raw materials for possible utilization in the wood plastic industry. The physicochemical properties of the wood samples such as the bulk and tapped density, moisture content, water absorption capacity at 25°C, volatile content, fixed carbon, ash content, alpha cellulose, hemicellulose, lignin, and extractives contents were determined using standard methods like the European Committee for Standardization and (CEN/TS) and the American Society for Testing Materials (ASTM) standards. The structural and morphological properties of the samples were examined with Fourier Infrared Transform (FTIR) spectroscopy and scanning electron microscope (SEM). Results indicated that the bulk density values of the timbers ranged from 0.34 g/cm<sup>3</sup> in Brachystegia eurycoma (W<sub>3</sub>) to 0.47 g/cm<sup>3</sup> in Erythrophleum suaveolens (W<sub>2</sub>), with the other timbers, Nuclea diderichii (W<sub>1</sub>) and Prosopis africana (W<sub>4</sub>) having the same bulk density of 0.40 g/cm<sup>3</sup>. With respect to their moisture content, W<sub>2</sub> had the highest value (8.38%) while Nauclea diderrichii had the lowest value (6.52%). The water absorption capacities of the woods studied correlated with the cellulose composition of wood in the order of: W<sub>3</sub> > W<sub>1</sub> > W<sub>4</sub> > W<sub>2</sub>. The FTIR results showed that W<sub>2</sub> and W<sub>3</sub> presented a slightly more prominent and broader band than the other woods at 1731 cm<sup>-1</sup>, in agreement with the higher holocellulose content of these species, while W<sub>2</sub> and W<sub>4</sub> presented the most prominent peaks indicating higher lignin content than W<sub>1</sub> and W<sub>3</sub>. The SEM micrographs of the wood flour samples investigated indicated that the surfaces of the woods were rough and heterogeneous with irregular crystal and brick shaped particles. A two-way analysis of variance (ANOVA) carried out with respect to the chemical composition of the wood samples indicated that there was no statistically significant variation in the wood chemical composition between species as the p-value (0.852) obtained was greater than the critical level of α = 0.05.
文摘An urban traffic ecosystem is a spatial structure composed of air,population,vehicles,roads,green spaces,and regions.Traffic ecological resilience is a critical issue in high-quality urban development.From the perspective of system optimization,it is important to study the level of urban traffic ecological resilience and analyze its influencing factors.In this study,we evaluated traffic ecological resilience,characterized its spatio-temporal differentiation,and explored its influencing factors by constructing a system of urban traffic ecological resilience and by analyzing the environmental protection and urban construction data in 31 Chinese cities during 2011-2018.By conducting Kernel density analysis,standard deviation ellipse,comprehensive weight determination,panel data regression analysis,andχ2test,we found that traffic ecological resilience was low on the whole and exhibited the temporal trend of“decreasing first and then increasing”and the spatial characteristic of“high in the east,second in the middle,and low in the west”.The cities with high traffic ecological resilience density values were located in Southeast China and tended to move from northwest to southeast.Governance capability,market activity,technological innovation capability,opening degree,and financial resources had significant effects on urban traffic ecological resilience.Finally,we gave some suggestions for improving the urban traffic ecological resilience in Chinese cities as well as other developing countries in the world.
基金financially supported by the National Natural Science Foundation of China(Grant 52074327,51991361)the Natural Science Foundation of Shandong Province,China(ZR2020QE107)
文摘Lost circulation of drilling fluid is one of the most common engineering problems in the drilling process of fractured formations.In this study,an oil-absorbing polymer gel synthesized using compound monomers with rigid and flexible chains was applied to control the oil-based drilling fluid loss while drilling.The microstructure,oil-absorbing performance,and plugging performance the gel was investigated.A large number of dense pores on the surface of the gel were observed,which allowed the oil molecules to enter the internal space of the gel.The initial oil absorption capacity of the gel was fast,and it increased with the increase in the temperature and decrease in the particle size,reaching 20.93 g/g at140℃.At a high temperature of 140℃,the bearing pressure capacity of the gel formula containing particles of different particle sizes reached 7.6 MPa for a fracture of a width of 3 mm,showing that the oil-absorbing gel have excellent plugging performance at high temperature.Plugging mechanism of the gel was investigated through visualized fracture plugging experiments.Results show that the dynamic migratio n,particle-swelling,particle-bridging,particle-aggregation,deformation-filling,and compaction-plugging contribute to the whole lost circulation control process,reflecting that the plugging performance can be effectively enhanced by improving the aggregation and filling degrees of the gel with different particle sizes.
文摘This review article covers some of the founding literature that helps develop our understandingof the National Innovation System (NIS) concept. Subsequently, several versionsof NIS, including system-functional approaches, are discussed and compared with narrowresearch and development (R&D) and market-based approaches. Finally, the article contendsthat the system-functional and other narrow approaches are limited in application tothe developing low- and middle-income countries (LMICs). Thus, it makes a case for moreinclusive absorptive capacity approaches and explains how they might be more relevant ininvestigating the NIS of an LMIC. Such approaches suggest LMICs be strategic in buildingtheir innovation base and plead for strong local conditions (capacities)to produceknowledge as well as capture and improvise on incoming knowledge from abroad. Theresearch is important as it provides insights into analyzing and capturing innovationprocesses in LMICs, which are prime candidates for development and innovation studiesandpractice.
基金This research was financially supported by the National Key R&D Program of China(2019YFD0900200,2018YFD0900400)National Natural Science Foundation of China for Outstanding Youth Science Foundation(31922086)supported by the earmarked fund for CARS(CARS-45).
文摘Arecoline is an alkaloid with important pharmacological effects in the plant areca nut,which has been demonstrated to be an agonist of muscarinic receptors(M receptor).This study explored the influences of dietary arecoline on growth performance,intestinal digestion and absorption abilities,antioxidant capacity,and the apical junction complex(AJC)of adult grass carp(Ctenopharyngodon idella).Adult grass carp(608to 1512 g)were fed at 6 graded levels of dietary arecoline(0,0.5,1.0,1.5,2.0,and 2.5 mg/kg diet)for 9weeks.The results suggested that appropriate dietary supplementation of arecoline(1.0 mg/kg)increased growth parameters and intestinal growth in adult grass carp(P<0.05),enhanced digestion and absorption capacities(P<0.05),up-regulated muscarinic receptor 3(M3)mRNA level(P<0.05),increased the content of neuropeptide fish substance P(P<0.05),improved antioxidant capacity by activating the Keap1a/Nrf2signaling pathway(P<0.05),reduced intestinal mucosal permeability(P<0.05),and increased m RNA levels of tight junction(TJ)and adherent junction AJ-related proteins in fish by inhibiting the RhoA/ROCK signaling pathway(RhoA/ROCK/MLCK/NMII)(P<0.05).In addition,the appropriate arecoline supplementation for adult grass carp was determined to be 1.20,1.21,1.07,and 1.19 mg/kg based on percentage weight gain,lipase activity,serum diamine oxidase,and protein carbonyl,respectively.Overall,to the best of our knowledge,we investigated for the first time the effects and possible mechanisms of dietary arecoline on intestinal digestive and absorptive capacities and structural integrity in fish and evaluated the appropriate level of supplementation.
基金This research was partially supported by the China Scholarship Council(CSC)and Crawford School of Public Policy,Australian National Univeristy.
文摘This paper empirically investigates the impact of China’s outward foreign direct investment(OFDI)on its export sophistication.Using a provincial-level panel dataset and applying fixed effects and instrumental variable regression techniques,the study finds that,on average,OFDI has no significant impact on China s export sophistication.However,after the full sample is divided into different regions,the study finds that OFDI has a positive and significant impact on export sophistication in the developed coastal region,but no such impact is observed in the less developed inland regions.Further investigation using a panel threshold model reveals that only when GDP,per capita GDP,human capital,and the research and development intensity of a home economy reach a certain level can OFDI promote export sophistication.The findings suggest that accelerating economic development and increasing absorptive capacity can facilitate the contribution of OFDI to China’s export sophistication.
基金supported by the China Postdoctoral Science Foundation(2022T150663)the National Natural Science Foundation of China(71874176,72102222,and 71673261)
文摘Innovation is a key stimulus for firms’survival and growth.However,many of Chinese firms fail to make it due to the lack of adequate financial resources.Previous studies have been deeply investigated the relationships between financial resources and firms’innovation performance.This paper extends such stream of the literature by focusing on a vital question for entrepreneurs:how to maximize innovation output under resource constraints.Based on an extensive dataset collected at Zhongguancun Science Park(ZSP),Beijing,China,over the period 2011-2014,this paper discusses whether entrepreneurs should pursue extra public funding(control sphere).Besides,this paper also provides empirical evidence for entrepreneurs to make proper choices about resource allocation(entrepreneurial sphere).This paper hypothesizes that enterprises allocating resources by using the entrepreneurial sphere,rather than the control sphere,can advance innovation output.To test our hypothesis,this paper adopts a dynamic panel model estimated by a bootstrapbased bias correction procedure.We find that,in advancing innovative performance,the entrepreneurial sphere is more effective than control.Indeed,at the overall level,the crowding out effect merely offsets the additionality effect when enterprises pursue extra public funding.Therefore,the control sphere does not play an essential role in advancing innovation performance.Thus,extra efforts in that direction will turn out to be in vain.Consequently,as a policy implication we claim that entrepreneurs should spend more time and energy on productive activities rather than lobbying and rent-seeking.In addition,managers should allocate resources properly for internal knowledge creation,external knowledge absorption and S&T activities.
基金supported by the National Natural Science Foundation of China(Grant No.21876073)the Natural Science Foundation of Gansu Province,China(Grant No.20JR5RA235)。
文摘Considering the serious environmental pollution and economic losses caused by increasing oil spills and chemical leaks,effective and eco-friendly methods of oil/water separation should be urgently developed.Herein,a facile strategy(about 20 min)was developed for integrating covalent organic framework(COF)particles with melamine sponges(MS)by covalent bonding,and then a superhydrophobic COF/MS composite(denoted OA-CP@MS)could be further obtained by following modification with a 1-octadecylamine/water dispersion.Specifically,the synthesis process was developed under a mild condition that avoids the need for sealing and high-temperature treatments.It was proven that the fabricated OA-CP@MS presented a prominent absorption capacity for various organic reagents,in which adsorption capacity of chloroform could be up to 173 g/g.Owing to its excellent chemical robustness in strong alkaline and saline environments and in various organic solvents,the prepared OACP@MS showed a great potential to perform oil/water separation in complex practical conditions.Its rapid preparation process,fluorine-free treatment,and water-based modification would extend the application of COF materials in oil/water separation.
基金The National Natural Science Foundation of China(Grant Nos.21777143 and 22078296)is appreciated as financial support.
文摘A Ag particle-coated and 1-dodecanethiolmodified melamine sponge(Ag-DDT-MS)was prepared through surface roughness by coating silver particles and subsequent grafting of a hydrophobic long hydrocarbon chain.Superhydrophobic and 3D porous Ag-DDT-MS was characterized by Fourier transform infrared spectroscopy,scanning electron microscope,energy-dispersive X-ray spectroscopy,and X-ray diffraction.The water contact angle of Ag-DDT-MS reached 159.2°.Ag-DDT-MS exhibited excellent absorption capacity for high viscous oils and organic solvents,ranging from 42.8 to 105.2 g∙g−1.The absorbed oils can be easily collected by the mechanical pressing process,and the oil recovery rate was satisfactory,more than 90%after 20 recycles.Ag-DDT-MS material also demonstrated good stability and excellent compressionrecovery ability,keeping 88.6%of the initial height after ten compression-release cycles.
