The arsenic(As)release from sediments in great lakes is affected by various factors.In this study,the characteristics of As release fromsediments was investigated,and the As sources and sinks with the strengths in sed...The arsenic(As)release from sediments in great lakes is affected by various factors.In this study,the characteristics of As release fromsediments was investigated,and the As sources and sinks with the strengths in sediments from different areas(grass-type,algae-type,and grass-algae alternation areas)in great shallow lakes(Taihu Lake,China)were analyzed,and the influence of P competition in the process of As release was also studied.The results showed that changing trend of the values of equilibrium As concentration in sediments were consistent with the regional changes(0 to 28.12μg/L),and the sediments from algaetype areas had the higher values.The sediments from western lake and northwest lake bay were a strong As and a weak P source,and the north lake bay had the opposite trend of these two regions.Intense P source competition with As from the sediments occurred in algae-type areas.The grass-type areas had strong As and P retention capacities,indicating a sink role of sediment with high As and P sorption capacities.The degree of As and P saturation had similar trend in sediments,and the grass-type areas had the higher values,18.3%-21.4%and 15.31%-20.34%,respectively.Contribution analysis results showed that most of As release contribution was from the bottom(30-50 cm)sediments,and the surface(0-10 cm)sediments from algae-type areas contributed more to the overlying water than other region.展开更多
In this work,numerical simulations are performed to investigate the influence of combining ribs and triangular cavities on the thermal-hydraulic performance(THP)of MCHS at fluid velocities ranging from1 to 4 m/s(corre...In this work,numerical simulations are performed to investigate the influence of combining ribs and triangular cavities on the thermal-hydraulic performance(THP)of MCHS at fluid velocities ranging from1 to 4 m/s(corresponding to Reynolds numbers(Re)of 129.75 to 519).Specifically,the ribs are positioned on the bottomwall,and the rib width is equal to the mini-channel width,while the triangular cavities are arranged on the two side walls of the MCHS.By analyzing and comparing key parameters such as velocity distribution,streamline patterns,pressure drop,skin friction coefficient(C_(f)),Nusselt number(Nu),friction factor(f),temperature fields,and performance evaluation criterion(PEC),the advantages of rib-cavity coupling configuration in enhancing THP are systematically discussed.Furthermore,the effects of cavity distribution(left,middle,and right),cavity depth(0.04,0.06,and 0.08 mm),and rib height(0.02,0.04,and 0.06 mm)on THP are analyzed to optimize the geometric parameters of the ribs and the cavities.The numerical simulation results indicate that,in comparison to the use of ribs or cavities alone,rib-cavity coupling can further improve the THP ofMCHS without causing a significant increase in pressure drop.The downstreamwall of the cavity is perpendicular to the flow direction which is more favorable for enhancing the heat transfer performance.Increasing the cavity depth improves the heat transfer performance ofMCHS,themaximumNu ratio increase by 35%at a rib height of 0.06 mm.However the increase in the rib height leads to a significant increase in the pressure drop,which in turn exerts a negative impact on THP,a maximumPEC of 1.198 is obtained at a rig height of 0.02 mm.The greatest improvement in THP,reaching 19.8%,is achieved when the cavity depth is 0.08 mm and the rib height is 0.02 mm.展开更多
[Objectives]To assess the carbon sink capacity in seawater suspension cage aquaculture of shellfish in Tianjin from 2015 to 2022.[Methods]The carbon sink capacity of different shellfish species was evaluated using bot...[Objectives]To assess the carbon sink capacity in seawater suspension cage aquaculture of shellfish in Tianjin from 2015 to 2022.[Methods]The carbon sink capacity of different shellfish species was evaluated using both physical and value assessment methods.[Results]The shellfish cultivated in seawater suspension cages in Tianjin exhibited a significant capacity for carbon sinks.The amounts of carbon removed by suspension cage aquaculture of Rapana venosa,Crassostrea gigas,Scapharca subcrenata,Scapharca broughtonii and Argopectens irradias were 448.297,403.398,89.463,40.657,and 106.719 t,respectively.Furthermore,the total volume of shellfish cultivated in seawater exhibited a consistent upward trend over time,correlating with an annual increase in the amount of carbon removed.Among the shellfish cultivated in seawater suspension cages,the order of carbon sink capacity was as follows:C.gigas>R.venosa>A.irradias>S.subcrenata and S.broughtonii.In terms of the carbon sink capacity of soft tissues,the ranking was as follows:A.irradias>R.venosa>C.gigas>S.subcrenata and S.broughtonii.The structural and yield factors associated with seawater suspension cage aquaculture of shellfish significantly influenced the enhancement of the total carbon sink of cultivated shellfish.Notably,structural factors had a greater impact on the increase in the carbon sink of cultivated shellfish compared to total yield factors.[Conclusions]The findings will serve as a reference for enhancing the carbon sink potential of fisheries and achieving sustainable development in seawater aquaculture in Tianjin.展开更多
The experimental analysis takes too much time-consuming process and requires considerable effort,while,the Artificial Neural Network(ANN)algorithms are simple,affordable,and fast,and they allow us to make a relevant a...The experimental analysis takes too much time-consuming process and requires considerable effort,while,the Artificial Neural Network(ANN)algorithms are simple,affordable,and fast,and they allow us to make a relevant analysis in establishing an appropriate relationship between the input and output parameters.This paper deals with the use of back-propagation ANN algorithms for the experimental data of heat transfer coefficient,Nusselt number,and friction factor of water-based Fe_(3)O_(4)-TiO_(2) magnetic hybrid nanofluids in a mini heat sink under magnetic fields.The data considered for the ANN network is at different Reynolds numbers(239 to 1874),different volume concentrations(0%to 2.0%),and different magnetic fields(250 to 1000 G),respectively.Three types of ANN back-propagation algorithms Levenberg-Marquardt(LM),Broyden-Fletcher-Goldfarb-Shanno Quasi Newton(BFGS),and Variable Learning Rate Gradient Descent(VLGD)were used to train the heat transfer coefficient,Nusselt number,and friction factor data,respectively.The ANOVA t-test analysis was also performed to determine the relative accuracy of the three ANN algorithms.The Nusselt number of 2.0%vol.of Fe_(3)O_(4)-TiO_(2) hybrid nanofluid is enhanced by 38.16%without a magnetic field,and it is further enhanced by 88.93%with the magnetic field of 1000 Gauss at a Reynolds number of 1874,with respect to the base fluid.A total of 126 datasets of heat transfer coefficient,Nusselt number,and friction factor were used as input and output data.The three ANN algorithms of LM,BFGS,and VLGD,have shown good acceptance with the experimental data with root-mean-square errors of 0.34883,0.25341,and 1.0202 with correlation coefficients(R2)of 0.99954,0.9967,and 0.94501,respectively,for the Nusselt number data.Moreover,the three ANN algorithms predict root-mean-square errors of 0.001488,0.005041,and 0.006924 with correlation coefficients(R2)of 0.99982,0.99976,and 0.99486,respectively,for the friction factor data.Compared to BFGS and VLGD algorithms,the LM algorithm predicts high accuracy for Nusselt number,and friction factor data.The proposed Nusselt number and friction factor correlations are also discussed.展开更多
Suppressing micro-amplitude vibrations is a critical issue in aerospace engineering.While nonlinear energy sinks(NES)are effective for passive vibration damping,their performance diminishes for micro-amplitude vibrati...Suppressing micro-amplitude vibrations is a critical issue in aerospace engineering.While nonlinear energy sinks(NES)are effective for passive vibration damping,their performance diminishes for micro-amplitude vibrations.This paper introduces a motion-amplified NES(MANES)to address this challenge.The system’s governing equations are derived using Hamilton’s principle,and an approximate analytical solution is validated by numerical methods.The effects of various parameters are explored,with higher vibration reduction efficiency achievable through parameter adjustments.Compared to cubic NES,MANES shows superior vibration suppression and a broader reduction bandwidth for micro-amplitude excitations.Additionally,MANES enters the effective vibration reduction range at lower excitation levels,indicating a reduced threshold for vibration suppression.This study provides insight into the vibration suppression mechanism of MANES,offering a theoretical foundation for mitigating micro-amplitude vibrations in engineering applications.展开更多
As a vital component of the national economic system,the forestry economy plays a significant role in promoting economic and social development.With the increasing emphasis on green and sustainable development,the car...As a vital component of the national economic system,the forestry economy plays a significant role in promoting economic and social development.With the increasing emphasis on green and sustainable development,the carbon sink market has gained widespread attention and experienced rapid expansion,exerting a profound impact on the sustainable development of the forestry economy.In this new stage,deepening the relationship between the carbon sink market and the forestry economy is of great practical significance for enhancing forest coverage,advancing forestry economic growth,and fostering green ecological development.This paper analyzes the impact of the carbon sink market on the sustainable development of the forestry economy and explores specific strategies for its advancement.展开更多
The behavior of single-phase flow and conjugate heat transfer in micro-channel heat sinks(MCHS)subjected to auniform heat flux is investigated by means of numerical simulations.Various geometrical configurations areex...The behavior of single-phase flow and conjugate heat transfer in micro-channel heat sinks(MCHS)subjected to auniform heat flux is investigated by means of numerical simulations.Various geometrical configurations areexamined,particularly,the combinations of rectangular solid and perforated blocks,used to create a disturbancein the flow.The analysis focuses on several key aspects and related metrics,including the temperature distribution,the mean Fanning friction factor,the pressure drop,the Nusselt number,and the overall heat transfer coefficientacross a range of Reynolds numbers(80–870).It is shown that the introduction of such blocks significantlyenhances the heat transfer performances of the MCHS compared to the straight-through flow channel.Specifically,a case is found where the Nusselt number increases by 2.3 times relative to the reference case.The integrationof perforated blocks facilitates the generation of vorticity within the channel,promoting the mixing of coldand hot fluids.Notably,MCHS incorporating perforated rectangular blocks exhibit more pronounced heat transferbenefits at Reynolds numbers smaller than 400.展开更多
The ocean,as the largest carbon sink,and fisheries carbon sinks are the main components of it.Studying fisheries carbon sinks is of great significance for achieving the"dual carbon"goals,addressing global cl...The ocean,as the largest carbon sink,and fisheries carbon sinks are the main components of it.Studying fisheries carbon sinks is of great significance for achieving the"dual carbon"goals,addressing global climate change,and developing the ocean economy.At present,research on fishery carbon sinks is relatively scattered both domestically and internationally.Based on the clarification of scientific concepts related to fishery carbon sinks,a quantitative analysis of the current research statu s and hot trends in the field of fishery carbon sinks has been conducted.The research results show that:(a)the study of fishery carbon sinks has gone through a process from initial proposal to in-depth research,showing a certain degree of volatility.Although the number of publications has surged in recent years,the total amount is still relatively small,reflecting great research value and application prospects.(b)The research institutions are mainly composed of fishery related departments of universities and aquatic research institutions in various regions,with frequent cooperation and less interdisciplinary system cooperation and exchange.(c)The high-frequency keywords are"carbon sink fisheries","carbon sink","marine aquaculture","marine ranching",etc.The emergence of these keywords indicates that"fishery carbon sink"will still be a key area of research in the future.展开更多
Addressing global warming,a common change today,requires achieving peak carbon dioxide emissions and carbon neutrality(also referred to as the dual carbon goals).Enhancing research on the carbon cycle is urgently need...Addressing global warming,a common change today,requires achieving peak carbon dioxide emissions and carbon neutrality(also referred to as the dual carbon goals).Enhancing research on the carbon cycle is urgently needed as the foundation.Water,a key carrier in the carbon cycle,necessitates investigation into groundwater carbon pools’contribution to atmospheric carbon sinks.This study assessed carbon stocks in the Yinchuan Basin’s soil and groundwater carbon pools.Findings indicate the basin’s surface soils contain approximately 24.16 Tg of organic carbon and a total of 60.01 Tg of carbon.In contrast,the basin’s groundwater holds around 4.90 Tg of carbon,roughly one-fifth of the organic carbon in surface soils.Thus,groundwater and soil carbon pools possess comparable carbon stocks,underscoring the importance of the groundwater carbon pool.Studies on terrestrial carbon balance should incorporate groundwater carbon pools,which deserve increased focus.Evaluating groundwater carbon pools’contributions is vital for achieving the dual carbon goals.展开更多
The purpose of this paper is to study the planning and design of campus plant communities from the perspective of vegetation carbon sink capacity.During the research period,based on literature review and material inve...The purpose of this paper is to study the planning and design of campus plant communities from the perspective of vegetation carbon sink capacity.During the research period,based on literature review and material investigation,the quantitative calculation of the carbon sink capacity of the vegetation of the campus of the case study university was carried out using the i-Tree model,and the shortcomings of the carbon sink level of the campus vegetation community were pointed out based on the calculation results.Subsequently,with the goal of improving the carbon sink capacity,the park is oriented to the planning and design of vegetation communities,and the feasibility of the program is demonstrated with the support of the data on the level of carbon sink capacity after the implementation of the program.It is hoped that this paper can provide technical reference for the managers of universities and urban landscape departments in China,and actively promote the optimization of vegetation communities,enhance the carbon sink capacity,and promote the full implementation of the goal of sustainable development.展开更多
Designing,modeling,and analyzing novel nonlinear elastic elements for the nonlinear energy sink(NES)have long been an attractive research topic.Since gravity is difficult to overcome,previous NES research mainly focus...Designing,modeling,and analyzing novel nonlinear elastic elements for the nonlinear energy sink(NES)have long been an attractive research topic.Since gravity is difficult to overcome,previous NES research mainly focused on horizontal vibration suppression.This study proposes an origami-inspired NES.A stacked Miura-origami(SMO)structure,consisting of two Miura-ori sheets,is adopted to construct a nonlinear elastic element.By adjusting the initial angle and the connecting crease torsional stiffness,the quasi-zero stiffness(QZS)and load-bearing capacity can be customized to match the corresponding mass,establishing the vertical SMO-NES.The dynamic model of the SMO-NES coupled with a linear oscillator(LO)is derived for vibrations in the vertical direction.The approximate analytical solutions of the dynamic equation are obtained by the harmonic balance method(HBM),and the solutions are verified numerically.The parameter design principle of the SMO-NES is provided.Finally,the vibration reduction performance of the SMO-NES is studied.The results show that the proposed SMONES can overcome gravity and achieve quasi-zero nonlinear restoring force.Therefore,the SMO-NES has the ability of wide-frequency vibration reduction,and can effectively suppress vertical vibrations.By adjusting the initial angle and connecting the crease torsional stiffness of the SMO,the SMO-NES can be achieved with different loading weights,effectively suppressing the vibrations with different primary system masses and excitation amplitudes.In conclusion,with the help of popular origami structures,this study proposes a novel NES,and starts the research of combining origami and NES.展开更多
For the estimation of global karst carbon sink,a few conventional methods usually require the parameters that are difficult to measure,resulting in the big cost.Moreover,under the constraints of incomplete and timelin...For the estimation of global karst carbon sink,a few conventional methods usually require the parameters that are difficult to measure,resulting in the big cost.Moreover,under the constraints of incomplete and timeliness issues in the collection of data over a large region,it has remained a challenge for these methods to study global karst carbon sink.Therefore,this paper proposes estimating the global karst carbon sink,and analyzing the suitability of the response surface methodology and the fluctuating variation of karst carbon sink in global karst regions from 1951 to 2050.This paper shows that the proposed method can reduce the time of numerical calculation and is suitable for application in global weathering models;The global karst carbon sink in the future changes not only displays an upward trend but also exposures its fluctuating trend largely.This fluctuation is probably due to global warming.展开更多
With its complex nonlinear dynamic behavior,the tristable system has shown excellent performance in areas such as energy harvesting and vibration suppression,and has attracted a lot of attention.In this paper,an asymm...With its complex nonlinear dynamic behavior,the tristable system has shown excellent performance in areas such as energy harvesting and vibration suppression,and has attracted a lot of attention.In this paper,an asymmetric tristable design is proposed to improve the vibration suppression efficiency of nonlinear energy sinks(NESs)for the first time.The proposed asymmetric tristable NES(ATNES)is composed of a pair of oblique springs and a vertical spring.Then,the three stable states,symmetric and asymmetric,can be achieved by the adjustment of the distance and stiffness asymmetry of the oblique springs.The governing equations of a linear oscillator(LO)coupled with the ATNES are derived.The approximate analytical solution to the coupled system is obtained by the harmonic balance method(HBM)and verified numerically.The vibration suppression efficiency of three types of ATNES is compared.The results show that the asymmetric design can improve the efficiency of vibration reduction through comparing the chaotic motion of the NES oscillator between asymmetric steady states.In addition,compared with the symmetrical tristable NES(TNES),the ATNES can effectively control smaller structural vibrations.In other words,the ATNES can effectively solve the threshold problem of TNES failure to weak excitation.Therefore,this paper reveals the vibration reduction mechanism of the ATNES,and provides a pathway to expand the effective excitation amplitude range of the NES.展开更多
The carbon cycle of terrestrial ecosystems is influenced by global climate change and human activities.Using remote sensing data and land cover products,the spatio-temporal variation characteristics and trends of NEP ...The carbon cycle of terrestrial ecosystems is influenced by global climate change and human activities.Using remote sensing data and land cover products,the spatio-temporal variation characteristics and trends of NEP in the Yangtze River Delta from 2000 to 2020 were analyzed based on the soil respiration model.The driving influences of ecosystem structure evolution,temperature,rainfall,and human activities on NEP were studied.The results show that the NEP shows an overall distribution pattern of high in the southeast and low in the northwest.The area of carbon sinks is larger than that of the carbon sources.NEP spatial heterogeneity is significant.NEP change trend is basically unchanged or significantly better.The future change trend in most areas will be continuous decrease.Compared with temperature,NEP are more sensitive to precipitation.The positive influence of human activities on NEP is mainly observed in north-central Anhui and northern Jiangsu coastal areas,while the negative influence is mainly found in highly urbanized areas.In the process of ecosystem structure,the contribution of unchanged areas to NEP change is greater than that of changed areas.展开更多
Differences in forest attributes and carbon sequestration of each organ and layer between broadleaved and conifer forests of central and outer urban areas are not well-defined,hindering the precise management of urban...Differences in forest attributes and carbon sequestration of each organ and layer between broadleaved and conifer forests of central and outer urban areas are not well-defined,hindering the precise management of urban forests and improvement of function.To clarify the effect of two forest types with different urbanization intensities,we determined differences in vegetation composition and diversity,structural traits,and carbon stocks of 152 plots(20 m×20 m)in urban park forests in Changchun,which had the largest green quantity and carbon density effectiveness.We found that 1.1-fold thicker and healthier trees,and 1.6-to 2.0-fold higher,healthier,denser,and more various shrubs but with sparser trees and herbs occurred in the central urban forests(p<0.05)than in the outer forests.The conifer forests exhibited 30–70%obviously higher tree aboveground carbon sequestration(including stem and leaf)and 20%bigger trees,especially in the outer forests(p<0.05).In contrast,1.1-to 1.5-fold higher branch stocks,healthier and more diverse trees were found in broadleaved forests of both the inner and outer forests(p<0.05).Plant size and dominant species had similarly important roles in carbon stock improvement,especially big-sized woody plants and Pinus tabuliformis.In addition,a higher number of deciduous or needle species positively affected the broadleaved forest of the central urban area and conifer forest of the outer urban area,respectively.These findings can be used to guide precise management and accelerate the improvement of urban carbon function in Northeast China in the future.展开更多
The heat generation of electronic devices is increasing dramatically,which causes a serious bottleneck in the thermal management of electronics,and overheating will result in performance deterioration and even device ...The heat generation of electronic devices is increasing dramatically,which causes a serious bottleneck in the thermal management of electronics,and overheating will result in performance deterioration and even device damage.With the development of micro-machining technologies,the microchannel heat sink(MCHS)has become one of the best ways to remove the considerable amount of heat generated by high-power electronics.It has the advantages of large specific surface area,small size,coolant saving and high heat transfer coefficient.This paper comprehensively takes an overview of the research progress in MCHSs and generalizes the hotspots and bottlenecks of this area.The heat transfer mechanisms and performances of different channel structures,coolants,channel materials and some other influencing factors are reviewed.Additionally,this paper classifies the heat transfer enhancement technology and reviews the related studies on both the single-phase and phase-change flow and heat transfer.The comprehensive review is expected to provide a theoretical reference and technical guidance for further research and application of MCHSs in the future.展开更多
基金supported by the National Natural Science Foundation(Nos.52000024 and 41907335)the Natural Science Foundation of Shanghai(No.23ZR1400700).
文摘The arsenic(As)release from sediments in great lakes is affected by various factors.In this study,the characteristics of As release fromsediments was investigated,and the As sources and sinks with the strengths in sediments from different areas(grass-type,algae-type,and grass-algae alternation areas)in great shallow lakes(Taihu Lake,China)were analyzed,and the influence of P competition in the process of As release was also studied.The results showed that changing trend of the values of equilibrium As concentration in sediments were consistent with the regional changes(0 to 28.12μg/L),and the sediments from algaetype areas had the higher values.The sediments from western lake and northwest lake bay were a strong As and a weak P source,and the north lake bay had the opposite trend of these two regions.Intense P source competition with As from the sediments occurred in algae-type areas.The grass-type areas had strong As and P retention capacities,indicating a sink role of sediment with high As and P sorption capacities.The degree of As and P saturation had similar trend in sediments,and the grass-type areas had the higher values,18.3%-21.4%and 15.31%-20.34%,respectively.Contribution analysis results showed that most of As release contribution was from the bottom(30-50 cm)sediments,and the surface(0-10 cm)sediments from algae-type areas contributed more to the overlying water than other region.
基金funded by the Sichuan Natural Science Foundation,grant number 2023NSFSC0870.
文摘In this work,numerical simulations are performed to investigate the influence of combining ribs and triangular cavities on the thermal-hydraulic performance(THP)of MCHS at fluid velocities ranging from1 to 4 m/s(corresponding to Reynolds numbers(Re)of 129.75 to 519).Specifically,the ribs are positioned on the bottomwall,and the rib width is equal to the mini-channel width,while the triangular cavities are arranged on the two side walls of the MCHS.By analyzing and comparing key parameters such as velocity distribution,streamline patterns,pressure drop,skin friction coefficient(C_(f)),Nusselt number(Nu),friction factor(f),temperature fields,and performance evaluation criterion(PEC),the advantages of rib-cavity coupling configuration in enhancing THP are systematically discussed.Furthermore,the effects of cavity distribution(left,middle,and right),cavity depth(0.04,0.06,and 0.08 mm),and rib height(0.02,0.04,and 0.06 mm)on THP are analyzed to optimize the geometric parameters of the ribs and the cavities.The numerical simulation results indicate that,in comparison to the use of ribs or cavities alone,rib-cavity coupling can further improve the THP ofMCHS without causing a significant increase in pressure drop.The downstreamwall of the cavity is perpendicular to the flow direction which is more favorable for enhancing the heat transfer performance.Increasing the cavity depth improves the heat transfer performance ofMCHS,themaximumNu ratio increase by 35%at a rib height of 0.06 mm.However the increase in the rib height leads to a significant increase in the pressure drop,which in turn exerts a negative impact on THP,a maximumPEC of 1.198 is obtained at a rig height of 0.02 mm.The greatest improvement in THP,reaching 19.8%,is achieved when the cavity depth is 0.08 mm and the rib height is 0.02 mm.
基金Supported by Science and Technology Commissioner Project of Tianjin Science and Technology Bureau(22ZYCGSN00630).
文摘[Objectives]To assess the carbon sink capacity in seawater suspension cage aquaculture of shellfish in Tianjin from 2015 to 2022.[Methods]The carbon sink capacity of different shellfish species was evaluated using both physical and value assessment methods.[Results]The shellfish cultivated in seawater suspension cages in Tianjin exhibited a significant capacity for carbon sinks.The amounts of carbon removed by suspension cage aquaculture of Rapana venosa,Crassostrea gigas,Scapharca subcrenata,Scapharca broughtonii and Argopectens irradias were 448.297,403.398,89.463,40.657,and 106.719 t,respectively.Furthermore,the total volume of shellfish cultivated in seawater exhibited a consistent upward trend over time,correlating with an annual increase in the amount of carbon removed.Among the shellfish cultivated in seawater suspension cages,the order of carbon sink capacity was as follows:C.gigas>R.venosa>A.irradias>S.subcrenata and S.broughtonii.In terms of the carbon sink capacity of soft tissues,the ranking was as follows:A.irradias>R.venosa>C.gigas>S.subcrenata and S.broughtonii.The structural and yield factors associated with seawater suspension cage aquaculture of shellfish significantly influenced the enhancement of the total carbon sink of cultivated shellfish.Notably,structural factors had a greater impact on the increase in the carbon sink of cultivated shellfish compared to total yield factors.[Conclusions]The findings will serve as a reference for enhancing the carbon sink potential of fisheries and achieving sustainable development in seawater aquaculture in Tianjin.
基金supported by the Recovery and Resilience Plan(PRR)and by European Funds Next Generation EU under the Project“AET—Alliance for Energy Transition,”no.C644914747-00000023,investment project no.56 of the Incentive System“Agendas for Business Innovation”.
文摘The experimental analysis takes too much time-consuming process and requires considerable effort,while,the Artificial Neural Network(ANN)algorithms are simple,affordable,and fast,and they allow us to make a relevant analysis in establishing an appropriate relationship between the input and output parameters.This paper deals with the use of back-propagation ANN algorithms for the experimental data of heat transfer coefficient,Nusselt number,and friction factor of water-based Fe_(3)O_(4)-TiO_(2) magnetic hybrid nanofluids in a mini heat sink under magnetic fields.The data considered for the ANN network is at different Reynolds numbers(239 to 1874),different volume concentrations(0%to 2.0%),and different magnetic fields(250 to 1000 G),respectively.Three types of ANN back-propagation algorithms Levenberg-Marquardt(LM),Broyden-Fletcher-Goldfarb-Shanno Quasi Newton(BFGS),and Variable Learning Rate Gradient Descent(VLGD)were used to train the heat transfer coefficient,Nusselt number,and friction factor data,respectively.The ANOVA t-test analysis was also performed to determine the relative accuracy of the three ANN algorithms.The Nusselt number of 2.0%vol.of Fe_(3)O_(4)-TiO_(2) hybrid nanofluid is enhanced by 38.16%without a magnetic field,and it is further enhanced by 88.93%with the magnetic field of 1000 Gauss at a Reynolds number of 1874,with respect to the base fluid.A total of 126 datasets of heat transfer coefficient,Nusselt number,and friction factor were used as input and output data.The three ANN algorithms of LM,BFGS,and VLGD,have shown good acceptance with the experimental data with root-mean-square errors of 0.34883,0.25341,and 1.0202 with correlation coefficients(R2)of 0.99954,0.9967,and 0.94501,respectively,for the Nusselt number data.Moreover,the three ANN algorithms predict root-mean-square errors of 0.001488,0.005041,and 0.006924 with correlation coefficients(R2)of 0.99982,0.99976,and 0.99486,respectively,for the friction factor data.Compared to BFGS and VLGD algorithms,the LM algorithm predicts high accuracy for Nusselt number,and friction factor data.The proposed Nusselt number and friction factor correlations are also discussed.
基金supported by the China National Funds for Distinguished Young Scholars(Grant No.12025204)the Shanghai Municipal Education Commission(Grant No.2019-01-07-00-09-E00018)。
文摘Suppressing micro-amplitude vibrations is a critical issue in aerospace engineering.While nonlinear energy sinks(NES)are effective for passive vibration damping,their performance diminishes for micro-amplitude vibrations.This paper introduces a motion-amplified NES(MANES)to address this challenge.The system’s governing equations are derived using Hamilton’s principle,and an approximate analytical solution is validated by numerical methods.The effects of various parameters are explored,with higher vibration reduction efficiency achievable through parameter adjustments.Compared to cubic NES,MANES shows superior vibration suppression and a broader reduction bandwidth for micro-amplitude excitations.Additionally,MANES enters the effective vibration reduction range at lower excitation levels,indicating a reduced threshold for vibration suppression.This study provides insight into the vibration suppression mechanism of MANES,offering a theoretical foundation for mitigating micro-amplitude vibrations in engineering applications.
文摘As a vital component of the national economic system,the forestry economy plays a significant role in promoting economic and social development.With the increasing emphasis on green and sustainable development,the carbon sink market has gained widespread attention and experienced rapid expansion,exerting a profound impact on the sustainable development of the forestry economy.In this new stage,deepening the relationship between the carbon sink market and the forestry economy is of great practical significance for enhancing forest coverage,advancing forestry economic growth,and fostering green ecological development.This paper analyzes the impact of the carbon sink market on the sustainable development of the forestry economy and explores specific strategies for its advancement.
基金funded by the Project of the Hubei Provincial Department of Science and Technology(Grant No.2022CFB957)the Project of Hubei Engineering University of Teaching Research(Grant No.JY2024032)+1 种基金Ministry of Education University-Industry Cooperation Collaborative Education Project(Grant No.220903584161245)College Students’Innovation and Entrepreneurship Training Program(Grant Nos.DC2024031,DC2024032).
文摘The behavior of single-phase flow and conjugate heat transfer in micro-channel heat sinks(MCHS)subjected to auniform heat flux is investigated by means of numerical simulations.Various geometrical configurations areexamined,particularly,the combinations of rectangular solid and perforated blocks,used to create a disturbancein the flow.The analysis focuses on several key aspects and related metrics,including the temperature distribution,the mean Fanning friction factor,the pressure drop,the Nusselt number,and the overall heat transfer coefficientacross a range of Reynolds numbers(80–870).It is shown that the introduction of such blocks significantlyenhances the heat transfer performances of the MCHS compared to the straight-through flow channel.Specifically,a case is found where the Nusselt number increases by 2.3 times relative to the reference case.The integrationof perforated blocks facilitates the generation of vorticity within the channel,promoting the mixing of coldand hot fluids.Notably,MCHS incorporating perforated rectangular blocks exhibit more pronounced heat transferbenefits at Reynolds numbers smaller than 400.
基金supported by the National modern Agricultural industry technology system(CARS-45-33)Innovation Team of Tianjin Freshwater Aquaculture Industry Technology System(ITTERS2021000-001 and 002)Tianjin Science and Technology Project(24KPHDRC00280,24ZYCGSN00250,23YDTPJC00420)。
文摘The ocean,as the largest carbon sink,and fisheries carbon sinks are the main components of it.Studying fisheries carbon sinks is of great significance for achieving the"dual carbon"goals,addressing global climate change,and developing the ocean economy.At present,research on fishery carbon sinks is relatively scattered both domestically and internationally.Based on the clarification of scientific concepts related to fishery carbon sinks,a quantitative analysis of the current research statu s and hot trends in the field of fishery carbon sinks has been conducted.The research results show that:(a)the study of fishery carbon sinks has gone through a process from initial proposal to in-depth research,showing a certain degree of volatility.Although the number of publications has surged in recent years,the total amount is still relatively small,reflecting great research value and application prospects.(b)The research institutions are mainly composed of fishery related departments of universities and aquatic research institutions in various regions,with frequent cooperation and less interdisciplinary system cooperation and exchange.(c)The high-frequency keywords are"carbon sink fisheries","carbon sink","marine aquaculture","marine ranching",etc.The emergence of these keywords indicates that"fishery carbon sink"will still be a key area of research in the future.
基金supported by the third scientific survey project in Xinjiang(2022xjkk0300)the public welfare geological survey projects initiated by the China Geological Survey(DD20190296,DD20221731).
文摘Addressing global warming,a common change today,requires achieving peak carbon dioxide emissions and carbon neutrality(also referred to as the dual carbon goals).Enhancing research on the carbon cycle is urgently needed as the foundation.Water,a key carrier in the carbon cycle,necessitates investigation into groundwater carbon pools’contribution to atmospheric carbon sinks.This study assessed carbon stocks in the Yinchuan Basin’s soil and groundwater carbon pools.Findings indicate the basin’s surface soils contain approximately 24.16 Tg of organic carbon and a total of 60.01 Tg of carbon.In contrast,the basin’s groundwater holds around 4.90 Tg of carbon,roughly one-fifth of the organic carbon in surface soils.Thus,groundwater and soil carbon pools possess comparable carbon stocks,underscoring the importance of the groundwater carbon pool.Studies on terrestrial carbon balance should incorporate groundwater carbon pools,which deserve increased focus.Evaluating groundwater carbon pools’contributions is vital for achieving the dual carbon goals.
基金Chongqing Municipal Education Commission Science and Technology Research ProjectResearch on Zero-Emission Campus Construction Based on Plant Community Optimization(Project No.KJQN202305605)。
文摘The purpose of this paper is to study the planning and design of campus plant communities from the perspective of vegetation carbon sink capacity.During the research period,based on literature review and material investigation,the quantitative calculation of the carbon sink capacity of the vegetation of the campus of the case study university was carried out using the i-Tree model,and the shortcomings of the carbon sink level of the campus vegetation community were pointed out based on the calculation results.Subsequently,with the goal of improving the carbon sink capacity,the park is oriented to the planning and design of vegetation communities,and the feasibility of the program is demonstrated with the support of the data on the level of carbon sink capacity after the implementation of the program.It is hoped that this paper can provide technical reference for the managers of universities and urban landscape departments in China,and actively promote the optimization of vegetation communities,enhance the carbon sink capacity,and promote the full implementation of the goal of sustainable development.
基金Project supported by the National Science Fund for Distinguished Young Scholars(No.12025204)the China Scholarship Council(No.202206890066)。
文摘Designing,modeling,and analyzing novel nonlinear elastic elements for the nonlinear energy sink(NES)have long been an attractive research topic.Since gravity is difficult to overcome,previous NES research mainly focused on horizontal vibration suppression.This study proposes an origami-inspired NES.A stacked Miura-origami(SMO)structure,consisting of two Miura-ori sheets,is adopted to construct a nonlinear elastic element.By adjusting the initial angle and the connecting crease torsional stiffness,the quasi-zero stiffness(QZS)and load-bearing capacity can be customized to match the corresponding mass,establishing the vertical SMO-NES.The dynamic model of the SMO-NES coupled with a linear oscillator(LO)is derived for vibrations in the vertical direction.The approximate analytical solutions of the dynamic equation are obtained by the harmonic balance method(HBM),and the solutions are verified numerically.The parameter design principle of the SMO-NES is provided.Finally,the vibration reduction performance of the SMO-NES is studied.The results show that the proposed SMONES can overcome gravity and achieve quasi-zero nonlinear restoring force.Therefore,the SMO-NES has the ability of wide-frequency vibration reduction,and can effectively suppress vertical vibrations.By adjusting the initial angle and connecting the crease torsional stiffness of the SMO,the SMO-NES can be achieved with different loading weights,effectively suppressing the vibrations with different primary system masses and excitation amplitudes.In conclusion,with the help of popular origami structures,this study proposes a novel NES,and starts the research of combining origami and NES.
基金supported by the National Natural Science of China[41961065]the Guangxi Innovative Development Grand Program[GuikeAD19254002 and GuikeAA18242048]+3 种基金the Guangxi Natural Science Foundation for Innovation Research Team[2019GXNSFGA245001]the Guilin Research and Development Plan Program[20190210-2]the National Key Research and Development Program of China[2016YFB0502501]the BaGuiScholars program of Guangxi and the Guangxi Key Laboratory of Spatial Information and Geomatics[19-050-11-12].
文摘For the estimation of global karst carbon sink,a few conventional methods usually require the parameters that are difficult to measure,resulting in the big cost.Moreover,under the constraints of incomplete and timeliness issues in the collection of data over a large region,it has remained a challenge for these methods to study global karst carbon sink.Therefore,this paper proposes estimating the global karst carbon sink,and analyzing the suitability of the response surface methodology and the fluctuating variation of karst carbon sink in global karst regions from 1951 to 2050.This paper shows that the proposed method can reduce the time of numerical calculation and is suitable for application in global weathering models;The global karst carbon sink in the future changes not only displays an upward trend but also exposures its fluctuating trend largely.This fluctuation is probably due to global warming.
基金Project supported by the National Science Fund for Distinguished Young Scholars of China(No.12025204)the National Natural Science Foundation of China(No.12202038)。
文摘With its complex nonlinear dynamic behavior,the tristable system has shown excellent performance in areas such as energy harvesting and vibration suppression,and has attracted a lot of attention.In this paper,an asymmetric tristable design is proposed to improve the vibration suppression efficiency of nonlinear energy sinks(NESs)for the first time.The proposed asymmetric tristable NES(ATNES)is composed of a pair of oblique springs and a vertical spring.Then,the three stable states,symmetric and asymmetric,can be achieved by the adjustment of the distance and stiffness asymmetry of the oblique springs.The governing equations of a linear oscillator(LO)coupled with the ATNES are derived.The approximate analytical solution to the coupled system is obtained by the harmonic balance method(HBM)and verified numerically.The vibration suppression efficiency of three types of ATNES is compared.The results show that the asymmetric design can improve the efficiency of vibration reduction through comparing the chaotic motion of the NES oscillator between asymmetric steady states.In addition,compared with the symmetrical tristable NES(TNES),the ATNES can effectively control smaller structural vibrations.In other words,the ATNES can effectively solve the threshold problem of TNES failure to weak excitation.Therefore,this paper reveals the vibration reduction mechanism of the ATNES,and provides a pathway to expand the effective excitation amplitude range of the NES.
基金National Key R&D Program of China,No.2018YFD1100101。
文摘The carbon cycle of terrestrial ecosystems is influenced by global climate change and human activities.Using remote sensing data and land cover products,the spatio-temporal variation characteristics and trends of NEP in the Yangtze River Delta from 2000 to 2020 were analyzed based on the soil respiration model.The driving influences of ecosystem structure evolution,temperature,rainfall,and human activities on NEP were studied.The results show that the NEP shows an overall distribution pattern of high in the southeast and low in the northwest.The area of carbon sinks is larger than that of the carbon sources.NEP spatial heterogeneity is significant.NEP change trend is basically unchanged or significantly better.The future change trend in most areas will be continuous decrease.Compared with temperature,NEP are more sensitive to precipitation.The positive influence of human activities on NEP is mainly observed in north-central Anhui and northern Jiangsu coastal areas,while the negative influence is mainly found in highly urbanized areas.In the process of ecosystem structure,the contribution of unchanged areas to NEP change is greater than that of changed areas.
基金the Youth Growth Technology Project,Science and Technology Department of Jilin Province(20230508130RC)Bureau of Forestry and Landscaping of Changchun.
文摘Differences in forest attributes and carbon sequestration of each organ and layer between broadleaved and conifer forests of central and outer urban areas are not well-defined,hindering the precise management of urban forests and improvement of function.To clarify the effect of two forest types with different urbanization intensities,we determined differences in vegetation composition and diversity,structural traits,and carbon stocks of 152 plots(20 m×20 m)in urban park forests in Changchun,which had the largest green quantity and carbon density effectiveness.We found that 1.1-fold thicker and healthier trees,and 1.6-to 2.0-fold higher,healthier,denser,and more various shrubs but with sparser trees and herbs occurred in the central urban forests(p<0.05)than in the outer forests.The conifer forests exhibited 30–70%obviously higher tree aboveground carbon sequestration(including stem and leaf)and 20%bigger trees,especially in the outer forests(p<0.05).In contrast,1.1-to 1.5-fold higher branch stocks,healthier and more diverse trees were found in broadleaved forests of both the inner and outer forests(p<0.05).Plant size and dominant species had similarly important roles in carbon stock improvement,especially big-sized woody plants and Pinus tabuliformis.In addition,a higher number of deciduous or needle species positively affected the broadleaved forest of the central urban area and conifer forest of the outer urban area,respectively.These findings can be used to guide precise management and accelerate the improvement of urban carbon function in Northeast China in the future.
基金supported by the National Natural Science Foundation of China(Grant Nos.U20A20301,51825601)。
文摘The heat generation of electronic devices is increasing dramatically,which causes a serious bottleneck in the thermal management of electronics,and overheating will result in performance deterioration and even device damage.With the development of micro-machining technologies,the microchannel heat sink(MCHS)has become one of the best ways to remove the considerable amount of heat generated by high-power electronics.It has the advantages of large specific surface area,small size,coolant saving and high heat transfer coefficient.This paper comprehensively takes an overview of the research progress in MCHSs and generalizes the hotspots and bottlenecks of this area.The heat transfer mechanisms and performances of different channel structures,coolants,channel materials and some other influencing factors are reviewed.Additionally,this paper classifies the heat transfer enhancement technology and reviews the related studies on both the single-phase and phase-change flow and heat transfer.The comprehensive review is expected to provide a theoretical reference and technical guidance for further research and application of MCHSs in the future.
