Pig bedding biochar(PBBC)and Cd-enriched Perilla frutescenswere used for joint remediation of Cd-contaminated soil.Cd-contaminated soil was treated with different concentration of PBBC.The physiological and biochemica...Pig bedding biochar(PBBC)and Cd-enriched Perilla frutescenswere used for joint remediation of Cd-contaminated soil.Cd-contaminated soil was treated with different concentration of PBBC.The physiological and biochemical indicators of P.frutescens was evaluated under different Cd stress,including biomass,antioxidant system.Meanwhile Cd bioavailability,enzyme activity and nutrient bioavailability of the soil were monitored.Results revealed that PBBC at 1%and 5%levels led to decreased diethylenetriaminepentaacetic acid-extractable Cd(DTPA-Cd)content in soil by 19.09%-20.05%and 30.10%-47.08%,respectively.Moreover,PBBC promoted the transformation of exchangeable Cd(EXC-Cd)into a more stable form,enhanced soil enzymes(peroxidase,acid phosphatase,urease,and sucrase)activities,and alleviated P.frutescens's oxidative stress.PBBC increased its biomass,consequently enhancing Cd accumulation in the plant's,thereby improving Phytoextraction rate(PER).1%PBBC showed the best effect,with a total biomass increased 21.42%-26.94%,PERwas enhanced by 39.83%-54.82%.This study justifies that the combining PBBC with P.frutescens enhances Cd removal fromsoil,making the PBBC-P.frutescens a promising choice for treating Cd-polluted soil.展开更多
Ongoing wind energy developments play a key role in mitigating the global effects of climate change and the energy crisis;however,they have complex ecological consequences for many flying animals.The Yellow Sea coast ...Ongoing wind energy developments play a key role in mitigating the global effects of climate change and the energy crisis;however,they have complex ecological consequences for many flying animals.The Yellow Sea coast is considered as an ecological bottleneck for migratory waterbirds along the East Asian–Australasian flyway(EAAF),and is also an important wind farm base in China.However,the effects of large-scale onshore wind farms along the EAAF on multidimensional waterbird diversity,and how to mitigate these effects,remain unclear.Here we examined how wind farms and their surrounding landscapes affected multidimensional waterbird diversity along the Yellow Sea coast.Taxonomic,functional,and phylogenetic diversity of the waterbird assemblages,and mean pairwise distances and nearest taxon distances with null models were quantified in relation to 4 different wind turbine densities.We also measured 6 landscape variables.Multi-dimensional waterbird diversity(taxonomic,functional,and phylogenetic diversity)significantly decreased with increasing wind turbine density.Functional and phylogenetic structures tended to be clustered in waterbird communities,and environmental filtering drove waterbird community assemblages.Furthermore,waterbird diversity was regulated by a combination of wind turbine density and landscape variables,with edge density of aquaculture ponds,in addition to wind turbine density,having the greatest independent contribution to waterbird diversity.These results suggest that attempts to mitigate the impact of wind farms on waterbird diversity could involve the landscape transformation of wind farm regions,for example,by including high-edge-density aquaculture ponds(i.e.,industrial ponds)around wind farms,instead of traditional low-edge-density aquaculture ponds.展开更多
Link flooding attack(LFA)is a type of covert distributed denial of service(DDoS)attack.The attack mechanism of LFAs is to flood critical links within the network to cut off the target area from the Internet.Recently,t...Link flooding attack(LFA)is a type of covert distributed denial of service(DDoS)attack.The attack mechanism of LFAs is to flood critical links within the network to cut off the target area from the Internet.Recently,the proliferation of Internet of Things(IoT)has increased the quantity of vulnerable devices connected to the network and has intensified the threat of LFAs.In LFAs,attackers typically utilize low-speed flows that do not reach the victims,making the attack difficult to detect.Traditional LFA defense methods mainly reroute the attack traffic around the congested link,which encounters high complexity and high computational overhead due to the aggregation of massive attack traffic.To address these challenges,we present an LFA defense framework which can mitigate the attack flows at the border switches when they are small in scale.This framework is lightweight and can be deployed at border switches of the network in a distributed manner,which ensures the scalability of our defense system.The performance of our framework is assessed in an experimental environment.The simulation results indicate that our method is effective in detecting and mitigating LFAs with low time complexity.展开更多
Hydrogen challenge mitigation stands as one of the main objectives in the management of severe accidents at Nuclear Power Plants (NPPs). Key strategies for hydrogen control include atmospheric inertization and hydroge...Hydrogen challenge mitigation stands as one of the main objectives in the management of severe accidents at Nuclear Power Plants (NPPs). Key strategies for hydrogen control include atmospheric inertization and hydrogen removal with Passive Autocatalytic Recombiners (PARs) being a commonly accepted approach. However, an examination of PAR operation specificity reveals potential inefficiencies and reliability issues in certain severe accident scenarios. Moreover, during the in-vessel stage of severe accident development, in some severe accident scenarios PARs can unexpectedly become a source of hydrogen detonation. The effectiveness of hydrogen removal systems depends on various factors, including the chosen strategies, severe accident scenarios, reactor building design, and other influencing factors. Consequently, a comprehensive hydrogen mitigation strategy must effectively incorporate a combination of strategies rather than be based on one strategy, taking into consideration the probabilistic risks and uncertainties associated with the implementation of PARs or other traditional methods. In response to these considerations, within the framework of this research it has been suggested a conceptual strategy to mitigate the hydrogen challenge during the in-vessel stage of severe accident development.展开更多
A novel dual output phase-shift distribution transformer （ DOPSDT ） is proposed based on the electromagnetic filtering theory. First, its structural characteristics, winding connection mode and turn number ratio for...A novel dual output phase-shift distribution transformer （ DOPSDT ） is proposed based on the electromagnetic filtering theory. First, its structural characteristics, winding connection mode and turn number ratio for special phase shifting are investigated. Secondly, the balance formulation of harmonic magneto-motive forces is derived and the electromagnetic filtering principle of the DOPSDT is introduced. The harmonic mitigating performance under different nonlinear load conditions are also analyzed using the field-circuit coupled method, The analysis results show that the DOPSDT can mitigate the primary current distortion even under severe nonlinear load conditions. By applying the zero sequence flux cancellation and phase-shift techniques at their secondary windings, the DOPSDT can significantly reduce the 3rd, 5th, 7th, 9th, 15th, 17th and 19th harmonics within its secondary windings.展开更多
Carbon dioxide(C0_(2))is a major climate forcing factor,closely related to human activities.Quantifying the contribution of C0_(2)emissions to the global radiative forcing(RF)is therefore important to evaluate climate...Carbon dioxide(C0_(2))is a major climate forcing factor,closely related to human activities.Quantifying the contribution of C0_(2)emissions to the global radiative forcing(RF)is therefore important to evaluate climate effects caused by anthropogenic and natural factors.China,the United States(USA),Russia and Canada are the largest countries by land area,at different levels of socio-economic development.In this study,we used data from the Car-bonTracker C0_(2)assimilation model(CT2017 data set)to analyze anthropogenic C0_(2)emissions and terrestrial ecosystem carbon sinks from 2000 to 2016.We derived net RF contributions and showed that anthropogenic C0_(2)emissions had increased significantly from 2000 to 2016,at a rate of 0.125 PgC yr^(-1).Over the same period,carbon uptake by terrestrial ecosystems increased at a rate of 0.003 PgC yr^(-1).Anthropogenic C0_(2)emissions in China and USA accounted for 87.19% of the total,while Russian terrestrial ecosystems were the largest carbon sink and absorbed 14.69 PgC.The resulting cooling effect was-0.013 W m~2 in 2016,representing an offset of-45.06% on climate warming induced by anthropogenic C0_(2).This indicates that net climate warming would be significantly overestimated if terrestrial ecosystems were not included in RF budget analyses.In terms of cumulative effects,we analyzed RFs using reference atmospheres of 1750,at the start of the Industrial Revolution,and 2000,the initial year of this study.Anthropogenic C0_(2)emissions in the study area contributed by+0.42 W m^(-2) and+0.32 W m^(-2) to the global RF,relative to C0_(2)levels of 1750 and 2000,respectively.We also evaluated correlations between global mean atmospheric temperature and net,anthropogenic and natural RFs.We found that the combined(net)RF caused by C0_(2)emissions accounted for 30.3% of global mean temperature variations in 2000-2016.展开更多
The ablative Richtmyer–Meshkov instability(ARMI) is crucial to the successful ignition implosion of the inertial confinement fusion(ICF) because of its action as the seed of the Rayleigh–Taylor instability. In usual...The ablative Richtmyer–Meshkov instability(ARMI) is crucial to the successful ignition implosion of the inertial confinement fusion(ICF) because of its action as the seed of the Rayleigh–Taylor instability. In usual ICF implosions, the first shock driven by various foots of the pulses plays a central role in the ARMI growth. We propose a new scheme for refraining from ARMI with a pulse of successive pickets. With the successive-picket pulse design, a rippled capsule surface is compressed by three successive shocks with sequentially strengthening intensities and ablated stabilization, and the ablative Richtmyer–Meshkov growth is mitigated quite effectively.Our numerical simulations and theoretical analyses identify the validity of this scheme.展开更多
Introduction Mechanotransduction has demonstrated potentials for tissue adaptation in vivo and in vitro. It is well documented that ultrasound,as a mechanical signal,can produce a wide variety of biological effects in...Introduction Mechanotransduction has demonstrated potentials for tissue adaptation in vivo and in vitro. It is well documented that ultrasound,as a mechanical signal,can produce a wide variety of biological effects in vitro and in vivo [1]. As an example,展开更多
The financial cost of disasters in Africa is estimated by the AU to run between 3 and 15 percent of the continent＇s GDR High vulnerability to disaster risk is thus a major challenge undermining Africa＇s accelerated ...The financial cost of disasters in Africa is estimated by the AU to run between 3 and 15 percent of the continent＇s GDR High vulnerability to disaster risk is thus a major challenge undermining Africa＇s accelerated and sustainable structural transformation efforts. But there is a plan in place to build resilience to disasters and reduce the risk impact,展开更多
The need for the mitigation of brown bears has become so severe that many nomads have given up repairing their houses in Maryo Township’s Mendang Village(also named the First Administrative Village),a remote place lo...The need for the mitigation of brown bears has become so severe that many nomads have given up repairing their houses in Maryo Township’s Mendang Village(also named the First Administrative Village),a remote place located in the southwestern section of the Changtang National Nature Reserve(CNNR).Only part of the village belongs to Serling Tso Nature Reserve.展开更多
Milling the free-end of cylindrical parts, which are vertically fixed on the machine table,often suffers from large chatter vibrations. This kind of phenomenon is harmful to the cutting process. Therefore, it is of gr...Milling the free-end of cylindrical parts, which are vertically fixed on the machine table,often suffers from large chatter vibrations. This kind of phenomenon is harmful to the cutting process. Therefore, it is of great importance to develop means to suppress these undesirable chatters.This paper proposes a new idea for designing a tunable mass damper(TMD) to reduce vibrations in milling of cylindrical parts. Frequency response function(FRF) of the milling system is derived to comprehensively reveal the influence of both the dynamic response of the machine tools and the TMD. Critical axial depth of cut, which is usually used to characterize the process stability, is formulated by considering the FRFs of both the milling system itself and the TMD. Maximization of critical axial depth of cut is taken as objective function, while kernel dynamic parameters of TMD,which are involved in the derived expression of critical axial depth of cut, are extracted as designable variables. Optimization procedure is carried out to adjust the parameters of TMD by using sequential quadratic programming algorithm. A series of experiments with a designed passive TMD validate that the design has a good performance in reducing vibrations and improving stability of milling process.展开更多
The external magnetic field is applied to mitigating backward flow jet of molten metal in weld pool so that humping bead may be suppressed during high speed gas metal arc welding（GMAW）. Therefore, the external magne...The external magnetic field is applied to mitigating backward flow jet of molten metal in weld pool so that humping bead may be suppressed during high speed gas metal arc welding（GMAW）. Therefore, the external magnetic field distribution in workpiece is critical to understand the interaction mechanisms of the external magnetic field with molten metal flow. In this study, the steady state external magnetic field induced by excitation device is numerically analyzed by using the the finite element software ANSYS and the three dimensional static magnetic scalar method. The distribution of external transverse magnetic field By in workpiece and arc area is calculated, and the influence of excitation current and air-gap distance on the distribution of transverse magnetic field By has been discussed. The magnetic field distribution in workpiece is measured by using a Tesla-Meter and compared with the simulated result. It is found that both are in good agreement.展开更多
Rapid urbanization has resulted in increased demand for tall buildings in many large and medium-sized cities around the world.Current code-based standards for seismic design are primarily aimed at minimizing life-safe...Rapid urbanization has resulted in increased demand for tall buildings in many large and medium-sized cities around the world.Current code-based standards for seismic design are primarily aimed at minimizing life-safety risks under major earthquakes.While reinforced concrete(RC)high-rise buildings designed following current code requirements are expected to achieve collapse-prevention,the contribution of higher modes of vibrations to the dynamic response of these structures can produce seismic demands significantly larger than those obtained from prescriptive code-based procedures,causing unexpectedly higher structural and non-structural damage to these buildings.These imply considerable costs associated with the loss of residences and business operations as well as the post-earthquake recovery of cities.This paper presents a concise review of the current state-of-the-art and state of research pertaining to the understanding,estimation and mitigation of higher-mode effects on the seismic response of tall and slender RC structures.The paper is organized into four main foci:(1)analytical studies on understanding and quantifying higher-mode effects,(2)available experimental work on this topic,(3)advances in code practices in accounting for higher-mode effects in seismic design of RC tall buildings,and(4)recent developments in innovative systems intended to mitigate higher-mode effects in RC tall buildings.The paper concludes by briefly summarizing future challenges facing the construction of earthquake-resilient RC tall buildings that are essential in building resilient cities of the future.展开更多
The corrosion behavior of a carbon steel covered by sand deposits in the solution containing sulfate-reducing bacteria(SRB)under nitrogen purging conditions was studied by electrochemical measurements and surface anal...The corrosion behavior of a carbon steel covered by sand deposits in the solution containing sulfate-reducing bacteria(SRB)under nitrogen purging conditions was studied by electrochemical measurements and surface analyses,aiming at clarifying the mitigation effects of nitrogen purging on SRB-involved under-deposit corrosion.The electrochemical results show that the variation trend of polarization resistance with immersion time is unchanged,but the corrosion current density is the lowest in the presence of SRB and deposits under nitrogen purging conditions,as compared to that without purging nitrogen,which are confirmed by the cross-sectional corrosion morphology observation after removing the sand deposits.Moreover,it is found that there are no positive synergistic effects between SRB and deposits on corrosion under nitrogen purging conditions,corresponding to the corrosion mitigation.Such mitigation on corrosion can be attributed to the less amount of SRB-produced H2S exhausted by purging nitrogen,which is supported by X-ray photoelectron spectrometry analyses.Therefore,purging nitrogen to the solution could be a practically effective way to mitigate the corrosion of deposit-covered carbon steels in SRB-containing solutions.展开更多
Defending against return-oriented programing(ROP)attacks is extremely challenging for modern operating systems.As the most popular mobile OS running on ARM,Android is even more vulnerable to ROP attacks due to its wea...Defending against return-oriented programing(ROP)attacks is extremely challenging for modern operating systems.As the most popular mobile OS running on ARM,Android is even more vulnerable to ROP attacks due to its weak implementation of ASLR and the absence of effective control-flow integrity enforcement.In this paper,leveraging specific ARM features,an instruction randomization strategy to mitigate ROP attacks in Android even with the threat of single pointer leakage vulnerabilities is proposed.By popping out more registers in functions'epilogue instructions and reallocating registers in function scopes,branch targets in all(direct and indirect)branch instructions potential to be ROP gadgets are changed randomly.Without the knowledge of binaries'runtime instructions layout,adversary's repeated control flow transfer in ROP exploits will be subverted.Furthermore,this instruction randomization idea has been implemented in both Android Dalvik runtime and ART.Corresponding evaluations proved it is capable to introduce enough randomness for more than 99%discovered functions and thwart about 95%ROP gadgets in application's shared libraries and oat file compiled from Dalvik bytecode.Besides,evaluations on real-world exploits also confirmed its effectiveness on mitigating ROP attacks within acceptable performance overhead.展开更多
The climatic, geomorphic, hydrologic and aquifer characteristics of the torrential Gash River across mountainous areas, in far eastern Sudan, were analyzed in order to mitigate its recurring catastrophic impacts. Hydr...The climatic, geomorphic, hydrologic and aquifer characteristics of the torrential Gash River across mountainous areas, in far eastern Sudan, were analyzed in order to mitigate its recurring catastrophic impacts. Hydrologic and climatic data and interpretation of Gash River satellite images were from relevant research works carried out in Gash Basin from 1985 to 2008. The results indicated that the total catchment area of Gash River is about 21,000 km2, and the basin area is 31,000 km2. The total length of Gash River is 450 km and the average slope is 200 cm/km. The width of the catchment varies from 30 m to 90 m and that of the basin is from 100 m to 800 m, and the course of the river is varied. During the period of 1980？2008, the mean annual rainfall was 250 mm and the mean annual discharge was 6.8 ×10~8 m^3, and the flooding is approximately one time per 5 years. Torrential floods measured at Kassala town since 1907 showed that an absolute maximum discharge was 876 m3/s and a mean maximum discharge was 365 m3/s. These characteristics differ widely between catchment and basin areas. The author proposes that, by analyzing the climatic, geomorphic, hydrologic and aquifer characteristics of the Gash River and considering the role of community, a concise database could be provided to formulate the aquifer, geomorphic, hydrologic and climatic （AQUIGEOHYCLIM） regional approach to mitigate Gash River recurring catastrophic impacts.展开更多
This study was carried out in the Burkinabe Sahel aimed at studying contribution of the practice of supplemental irrigation (SI) via excavated rainwater harvesting basin (RWHB) for mitigating effect of rainfall variab...This study was carried out in the Burkinabe Sahel aimed at studying contribution of the practice of supplemental irrigation (SI) via excavated rainwater harvesting basin (RWHB) for mitigating effect of rainfall variability on agricultural production and impact of these RWHB on the dynamics of the water table. This study was conducted during two growing seasons (2013 and 2014) and used a test plot cultivated in corn and fitted out with measuring instruments to analyze water transfer in the soil-plant-atmosphere system on the one hand and the atmosphere-RWHB-water table system on the other hand. Four treatments—one under rainfall regime (T0) and three under SI (T1, T2, and T3)—were used in the experimental design to assess the contribution of the RWHB in improving corn yield. These SI were applied during the mid-season of corn (flowering, pollination, and grain filling). Water flow beneath a partially waterproofed RWHB was assessed using HYDRUS- 2D/3D program. Results showed that water stored in the RWHB allowed applying up to three SI, and increased corn yield up to 24% and 26% respectively in 2013 and 2014. However, SI targeting flowering and grain filling were the best scenarios to mitigate effect of dry spell in rainfed agriculture. Water flow under RWHB during the simulation period showed that dynamic of the saturated front depended on the magnitude of the water depth in the RWHB and the hydrodynamic characteristics of the underlying layers. Deep drainage was observed around 25th day after sowing (DAS) in 2013 and 45th DAS in 2014 according to water profile. This caused the decrease of the infiltration rate in the RWHB that was associated with a significant rise of 4% of the water table level ten days later in 2014. Recharge rate was estimated at 0.5 mm·d-1 during the mid-season and the late season of corn.展开更多
A two-step methodology was used to address and improve the power quality concerns for the PV-integrated microgrid system. First, partial shading was included to deal with the real-time issues. The Improved Jelly Fish ...A two-step methodology was used to address and improve the power quality concerns for the PV-integrated microgrid system. First, partial shading was included to deal with the real-time issues. The Improved Jelly Fish Algorithm integrated Perturb and Obserb (IJFA-PO) has been proposed to track the Global Maximum Power Point (GMPP). Second, the main unit-powered via DC–AC converter is synchronised with the grid. To cope with the wide voltage variation and harmonic mitigation, an auxiliary unit undergoes a novel series compensation technique. Out of various switching approaches, IJFA-based Selective Harmonic Elimination (SHE) in 120° conduction gives the optimal solution. Three switching angles were obtained using IJFA, whose performance was equivalent to that of nine switching angles. Thus, the system is efficient with minimised higher-order harmonics and lower switching losses. The proposed system outperformed in terms of efficiency, metaheuristics, and convergence. The Total Harmonic Distortion (THD) obtained was 1.32%, which is within the IEEE 1547 and IEC tolerable limits. The model was developed in MATLAB/Simulink 2016b and verified with an experimental prototype of grid-synchronised PV capacity of 260 W tested under various loading conditions. The present model is reliable and features a simple controller that provides more convenient and adequate performance.展开更多
This paper examined the causes, effects and measures for mitigating climate change to ensure adequate supply of food through crop production to address the food insecurity which has occupied a central focus of the Nig...This paper examined the causes, effects and measures for mitigating climate change to ensure adequate supply of food through crop production to address the food insecurity which has occupied a central focus of the Nigerian economy. Unfortunately, crop production is fraught with many ecological challenges including climate change. This climate change which occurs as a result of the buildup of Green House Gases (GHGs) occasioned by industrialization, technological modeling and agriculture, exert significant effects on crop yield, water availability, ecosystem disequilibrium resulting in cases of drought, flood earthquake among others. For crop production to be scaled-up to meet the food requirement of the ever growing Nigerian population amidst these challenges, there is need to mitigate these adverse effects of climate change through the adoption of sustainable land management practices that can reduce the atmospheric stock of GHGs such as zero-tillage, appropriate use of fertilizers, avoidance of bush burning, graze land management, improved water management among others. Achieving great success in these areas requires that Nigerian government should be more proactive in their policies that hold promise for sustainable cultures in agricultural production as well as evolving global partnerships on ecological issues.展开更多
We made an evaluation of a suitable mitigation technique for the treatment of drinking water that was artificially enriched with Rn-222 in laboratory by placing a radium rich granite stone (pitchblende) in a closed co...We made an evaluation of a suitable mitigation technique for the treatment of drinking water that was artificially enriched with Rn-222 in laboratory by placing a radium rich granite stone (pitchblende) in a closed container filled with tap water for several days in order to allow Rn-222 concentration to approach its highest possible level. Experiments were designed to investigate the effectiveness of removal of Rn-222 by diffused bubble aeration method at room temperature. The results showed that this method becomes more efficient at higher airto-water ratios. Better aeration depends on the length of travel of bubbles through the water depth. This method is practical and has low capital cost. The removal of Rn-222 from artificially enriched water can be practically achieved by diffused bubble aeration method to greater than 98%.展开更多
基金supported by the Science and Technology Innovation of Fujian Agriculture and Forestry University(Nos.KFB23079 and KFB23065).
文摘Pig bedding biochar(PBBC)and Cd-enriched Perilla frutescenswere used for joint remediation of Cd-contaminated soil.Cd-contaminated soil was treated with different concentration of PBBC.The physiological and biochemical indicators of P.frutescens was evaluated under different Cd stress,including biomass,antioxidant system.Meanwhile Cd bioavailability,enzyme activity and nutrient bioavailability of the soil were monitored.Results revealed that PBBC at 1%and 5%levels led to decreased diethylenetriaminepentaacetic acid-extractable Cd(DTPA-Cd)content in soil by 19.09%-20.05%and 30.10%-47.08%,respectively.Moreover,PBBC promoted the transformation of exchangeable Cd(EXC-Cd)into a more stable form,enhanced soil enzymes(peroxidase,acid phosphatase,urease,and sucrase)activities,and alleviated P.frutescens's oxidative stress.PBBC increased its biomass,consequently enhancing Cd accumulation in the plant's,thereby improving Phytoextraction rate(PER).1%PBBC showed the best effect,with a total biomass increased 21.42%-26.94%,PERwas enhanced by 39.83%-54.82%.This study justifies that the combining PBBC with P.frutescens enhances Cd removal fromsoil,making the PBBC-P.frutescens a promising choice for treating Cd-polluted soil.
基金fnancially supported by the Science and Technology Commission of Shanghai Municipality(No.18DZ1205000)Natural Science Foundation of China(No.31901099)+3 种基金Yangtze Delta Estuarine Wetland Ecosystem Observation and Research Station,Ministry of Education,Shanghai Science and Technology Committee(ECNU-YDEWS-2022)Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering,Institute of Biodiversity Science,Fudan University(2023-FDU-KF-02)Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration(SHUES2023A04)“Pioneer”and“Leading Goose”R&D Program of Zhejiang(2024C02002).
文摘Ongoing wind energy developments play a key role in mitigating the global effects of climate change and the energy crisis;however,they have complex ecological consequences for many flying animals.The Yellow Sea coast is considered as an ecological bottleneck for migratory waterbirds along the East Asian–Australasian flyway(EAAF),and is also an important wind farm base in China.However,the effects of large-scale onshore wind farms along the EAAF on multidimensional waterbird diversity,and how to mitigate these effects,remain unclear.Here we examined how wind farms and their surrounding landscapes affected multidimensional waterbird diversity along the Yellow Sea coast.Taxonomic,functional,and phylogenetic diversity of the waterbird assemblages,and mean pairwise distances and nearest taxon distances with null models were quantified in relation to 4 different wind turbine densities.We also measured 6 landscape variables.Multi-dimensional waterbird diversity(taxonomic,functional,and phylogenetic diversity)significantly decreased with increasing wind turbine density.Functional and phylogenetic structures tended to be clustered in waterbird communities,and environmental filtering drove waterbird community assemblages.Furthermore,waterbird diversity was regulated by a combination of wind turbine density and landscape variables,with edge density of aquaculture ponds,in addition to wind turbine density,having the greatest independent contribution to waterbird diversity.These results suggest that attempts to mitigate the impact of wind farms on waterbird diversity could involve the landscape transformation of wind farm regions,for example,by including high-edge-density aquaculture ponds(i.e.,industrial ponds)around wind farms,instead of traditional low-edge-density aquaculture ponds.
基金supported in part by the National Key R&D Program of China under Grant 2018YFA0701601in part by the National Natural Science Foundation of China(Grant No.62201605,62341110,U22A2002)in part by Tsinghua University-China Mobile Communications Group Co.,Ltd.Joint Institute。
文摘Link flooding attack(LFA)is a type of covert distributed denial of service(DDoS)attack.The attack mechanism of LFAs is to flood critical links within the network to cut off the target area from the Internet.Recently,the proliferation of Internet of Things(IoT)has increased the quantity of vulnerable devices connected to the network and has intensified the threat of LFAs.In LFAs,attackers typically utilize low-speed flows that do not reach the victims,making the attack difficult to detect.Traditional LFA defense methods mainly reroute the attack traffic around the congested link,which encounters high complexity and high computational overhead due to the aggregation of massive attack traffic.To address these challenges,we present an LFA defense framework which can mitigate the attack flows at the border switches when they are small in scale.This framework is lightweight and can be deployed at border switches of the network in a distributed manner,which ensures the scalability of our defense system.The performance of our framework is assessed in an experimental environment.The simulation results indicate that our method is effective in detecting and mitigating LFAs with low time complexity.
文摘Hydrogen challenge mitigation stands as one of the main objectives in the management of severe accidents at Nuclear Power Plants (NPPs). Key strategies for hydrogen control include atmospheric inertization and hydrogen removal with Passive Autocatalytic Recombiners (PARs) being a commonly accepted approach. However, an examination of PAR operation specificity reveals potential inefficiencies and reliability issues in certain severe accident scenarios. Moreover, during the in-vessel stage of severe accident development, in some severe accident scenarios PARs can unexpectedly become a source of hydrogen detonation. The effectiveness of hydrogen removal systems depends on various factors, including the chosen strategies, severe accident scenarios, reactor building design, and other influencing factors. Consequently, a comprehensive hydrogen mitigation strategy must effectively incorporate a combination of strategies rather than be based on one strategy, taking into consideration the probabilistic risks and uncertainties associated with the implementation of PARs or other traditional methods. In response to these considerations, within the framework of this research it has been suggested a conceptual strategy to mitigate the hydrogen challenge during the in-vessel stage of severe accident development.
基金The Program for Special Talent in Six Fields of Jiangsu Province (2011-ZBZZ-016)the Postdoctoral Science Foundation of Jiangsu Province (No. 0902038C)
文摘A novel dual output phase-shift distribution transformer （ DOPSDT ） is proposed based on the electromagnetic filtering theory. First, its structural characteristics, winding connection mode and turn number ratio for special phase shifting are investigated. Secondly, the balance formulation of harmonic magneto-motive forces is derived and the electromagnetic filtering principle of the DOPSDT is introduced. The harmonic mitigating performance under different nonlinear load conditions are also analyzed using the field-circuit coupled method, The analysis results show that the DOPSDT can mitigate the primary current distortion even under severe nonlinear load conditions. By applying the zero sequence flux cancellation and phase-shift techniques at their secondary windings, the DOPSDT can significantly reduce the 3rd, 5th, 7th, 9th, 15th, 17th and 19th harmonics within its secondary windings.
基金National Natural Science Foundation of China,No.42071415,No.41671425Outstanding Youth Foundation of Henan Natural Science,No.202300410049National Key Research and Development Program of China,No.2021YFE0106700。
文摘Carbon dioxide(C0_(2))is a major climate forcing factor,closely related to human activities.Quantifying the contribution of C0_(2)emissions to the global radiative forcing(RF)is therefore important to evaluate climate effects caused by anthropogenic and natural factors.China,the United States(USA),Russia and Canada are the largest countries by land area,at different levels of socio-economic development.In this study,we used data from the Car-bonTracker C0_(2)assimilation model(CT2017 data set)to analyze anthropogenic C0_(2)emissions and terrestrial ecosystem carbon sinks from 2000 to 2016.We derived net RF contributions and showed that anthropogenic C0_(2)emissions had increased significantly from 2000 to 2016,at a rate of 0.125 PgC yr^(-1).Over the same period,carbon uptake by terrestrial ecosystems increased at a rate of 0.003 PgC yr^(-1).Anthropogenic C0_(2)emissions in China and USA accounted for 87.19% of the total,while Russian terrestrial ecosystems were the largest carbon sink and absorbed 14.69 PgC.The resulting cooling effect was-0.013 W m~2 in 2016,representing an offset of-45.06% on climate warming induced by anthropogenic C0_(2).This indicates that net climate warming would be significantly overestimated if terrestrial ecosystems were not included in RF budget analyses.In terms of cumulative effects,we analyzed RFs using reference atmospheres of 1750,at the start of the Industrial Revolution,and 2000,the initial year of this study.Anthropogenic C0_(2)emissions in the study area contributed by+0.42 W m^(-2) and+0.32 W m^(-2) to the global RF,relative to C0_(2)levels of 1750 and 2000,respectively.We also evaluated correlations between global mean atmospheric temperature and net,anthropogenic and natural RFs.We found that the combined(net)RF caused by C0_(2)emissions accounted for 30.3% of global mean temperature variations in 2000-2016.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11675026,11875091 and 11575034
文摘The ablative Richtmyer–Meshkov instability(ARMI) is crucial to the successful ignition implosion of the inertial confinement fusion(ICF) because of its action as the seed of the Rayleigh–Taylor instability. In usual ICF implosions, the first shock driven by various foots of the pulses plays a central role in the ARMI growth. We propose a new scheme for refraining from ARMI with a pulse of successive pickets. With the successive-picket pulse design, a rippled capsule surface is compressed by three successive shocks with sequentially strengthening intensities and ablated stabilization, and the ablative Richtmyer–Meshkov growth is mitigated quite effectively.Our numerical simulations and theoretical analyses identify the validity of this scheme.
基金supported by the NIH (R01 AR52379 & R01 AR49286),U S Army Medical Research and NSBRI
文摘Introduction Mechanotransduction has demonstrated potentials for tissue adaptation in vivo and in vitro. It is well documented that ultrasound,as a mechanical signal,can produce a wide variety of biological effects in vitro and in vivo [1]. As an example,
文摘The financial cost of disasters in Africa is estimated by the AU to run between 3 and 15 percent of the continent＇s GDR High vulnerability to disaster risk is thus a major challenge undermining Africa＇s accelerated and sustainable structural transformation efforts. But there is a plan in place to build resilience to disasters and reduce the risk impact,
文摘The need for the mitigation of brown bears has become so severe that many nomads have given up repairing their houses in Maryo Township’s Mendang Village(also named the First Administrative Village),a remote place located in the southwestern section of the Changtang National Nature Reserve(CNNR).Only part of the village belongs to Serling Tso Nature Reserve.
基金supported by the National Natural Science Foundation of China(No.51675440 and 51705427)National Key Research and Development Program of China(No.2017YFB1102800)the Fundamental Research Funds for the Central Universities of China(No.3102018gxc025)
文摘Milling the free-end of cylindrical parts, which are vertically fixed on the machine table,often suffers from large chatter vibrations. This kind of phenomenon is harmful to the cutting process. Therefore, it is of great importance to develop means to suppress these undesirable chatters.This paper proposes a new idea for designing a tunable mass damper(TMD) to reduce vibrations in milling of cylindrical parts. Frequency response function(FRF) of the milling system is derived to comprehensively reveal the influence of both the dynamic response of the machine tools and the TMD. Critical axial depth of cut, which is usually used to characterize the process stability, is formulated by considering the FRFs of both the milling system itself and the TMD. Maximization of critical axial depth of cut is taken as objective function, while kernel dynamic parameters of TMD,which are involved in the derived expression of critical axial depth of cut, are extracted as designable variables. Optimization procedure is carried out to adjust the parameters of TMD by using sequential quadratic programming algorithm. A series of experiments with a designed passive TMD validate that the design has a good performance in reducing vibrations and improving stability of milling process.
基金The authors are grateful to the financial support for this research from the National Natural Science Foundation of China （ Grant No. 51275276） and the Research Fund for the Doctoral Program of Higher Education of China （ Grant No. 20120131130009）.
文摘The external magnetic field is applied to mitigating backward flow jet of molten metal in weld pool so that humping bead may be suppressed during high speed gas metal arc welding（GMAW）. Therefore, the external magnetic field distribution in workpiece is critical to understand the interaction mechanisms of the external magnetic field with molten metal flow. In this study, the steady state external magnetic field induced by excitation device is numerically analyzed by using the the finite element software ANSYS and the three dimensional static magnetic scalar method. The distribution of external transverse magnetic field By in workpiece and arc area is calculated, and the influence of excitation current and air-gap distance on the distribution of transverse magnetic field By has been discussed. The magnetic field distribution in workpiece is measured by using a Tesla-Meter and compared with the simulated result. It is found that both are in good agreement.
基金the financial support of the Nat-ural Sciences and Engineering Research Council of Canada(NSERC).
文摘Rapid urbanization has resulted in increased demand for tall buildings in many large and medium-sized cities around the world.Current code-based standards for seismic design are primarily aimed at minimizing life-safety risks under major earthquakes.While reinforced concrete(RC)high-rise buildings designed following current code requirements are expected to achieve collapse-prevention,the contribution of higher modes of vibrations to the dynamic response of these structures can produce seismic demands significantly larger than those obtained from prescriptive code-based procedures,causing unexpectedly higher structural and non-structural damage to these buildings.These imply considerable costs associated with the loss of residences and business operations as well as the post-earthquake recovery of cities.This paper presents a concise review of the current state-of-the-art and state of research pertaining to the understanding,estimation and mitigation of higher-mode effects on the seismic response of tall and slender RC structures.The paper is organized into four main foci:(1)analytical studies on understanding and quantifying higher-mode effects,(2)available experimental work on this topic,(3)advances in code practices in accounting for higher-mode effects in seismic design of RC tall buildings,and(4)recent developments in innovative systems intended to mitigate higher-mode effects in RC tall buildings.The paper concludes by briefly summarizing future challenges facing the construction of earthquake-resilient RC tall buildings that are essential in building resilient cities of the future.
基金This work is financially supported by the Research on CCUS Integrated Collaborative Technology(kt2022-27-6).
文摘The corrosion behavior of a carbon steel covered by sand deposits in the solution containing sulfate-reducing bacteria(SRB)under nitrogen purging conditions was studied by electrochemical measurements and surface analyses,aiming at clarifying the mitigation effects of nitrogen purging on SRB-involved under-deposit corrosion.The electrochemical results show that the variation trend of polarization resistance with immersion time is unchanged,but the corrosion current density is the lowest in the presence of SRB and deposits under nitrogen purging conditions,as compared to that without purging nitrogen,which are confirmed by the cross-sectional corrosion morphology observation after removing the sand deposits.Moreover,it is found that there are no positive synergistic effects between SRB and deposits on corrosion under nitrogen purging conditions,corresponding to the corrosion mitigation.Such mitigation on corrosion can be attributed to the less amount of SRB-produced H2S exhausted by purging nitrogen,which is supported by X-ray photoelectron spectrometry analyses.Therefore,purging nitrogen to the solution could be a practically effective way to mitigate the corrosion of deposit-covered carbon steels in SRB-containing solutions.
基金supported by the National Natural Science Foundation of China(Grant No.61202387,61332019 and 61373168)the National Basic Research Program of China(“973”Program)(Grant No.2014CB340600)
文摘Defending against return-oriented programing(ROP)attacks is extremely challenging for modern operating systems.As the most popular mobile OS running on ARM,Android is even more vulnerable to ROP attacks due to its weak implementation of ASLR and the absence of effective control-flow integrity enforcement.In this paper,leveraging specific ARM features,an instruction randomization strategy to mitigate ROP attacks in Android even with the threat of single pointer leakage vulnerabilities is proposed.By popping out more registers in functions'epilogue instructions and reallocating registers in function scopes,branch targets in all(direct and indirect)branch instructions potential to be ROP gadgets are changed randomly.Without the knowledge of binaries'runtime instructions layout,adversary's repeated control flow transfer in ROP exploits will be subverted.Furthermore,this instruction randomization idea has been implemented in both Android Dalvik runtime and ART.Corresponding evaluations proved it is capable to introduce enough randomness for more than 99%discovered functions and thwart about 95%ROP gadgets in application's shared libraries and oat file compiled from Dalvik bytecode.Besides,evaluations on real-world exploits also confirmed its effectiveness on mitigating ROP attacks within acceptable performance overhead.
文摘The climatic, geomorphic, hydrologic and aquifer characteristics of the torrential Gash River across mountainous areas, in far eastern Sudan, were analyzed in order to mitigate its recurring catastrophic impacts. Hydrologic and climatic data and interpretation of Gash River satellite images were from relevant research works carried out in Gash Basin from 1985 to 2008. The results indicated that the total catchment area of Gash River is about 21,000 km2, and the basin area is 31,000 km2. The total length of Gash River is 450 km and the average slope is 200 cm/km. The width of the catchment varies from 30 m to 90 m and that of the basin is from 100 m to 800 m, and the course of the river is varied. During the period of 1980？2008, the mean annual rainfall was 250 mm and the mean annual discharge was 6.8 ×10~8 m^3, and the flooding is approximately one time per 5 years. Torrential floods measured at Kassala town since 1907 showed that an absolute maximum discharge was 876 m3/s and a mean maximum discharge was 365 m3/s. These characteristics differ widely between catchment and basin areas. The author proposes that, by analyzing the climatic, geomorphic, hydrologic and aquifer characteristics of the Gash River and considering the role of community, a concise database could be provided to formulate the aquifer, geomorphic, hydrologic and climatic （AQUIGEOHYCLIM） regional approach to mitigate Gash River recurring catastrophic impacts.
文摘This study was carried out in the Burkinabe Sahel aimed at studying contribution of the practice of supplemental irrigation (SI) via excavated rainwater harvesting basin (RWHB) for mitigating effect of rainfall variability on agricultural production and impact of these RWHB on the dynamics of the water table. This study was conducted during two growing seasons (2013 and 2014) and used a test plot cultivated in corn and fitted out with measuring instruments to analyze water transfer in the soil-plant-atmosphere system on the one hand and the atmosphere-RWHB-water table system on the other hand. Four treatments—one under rainfall regime (T0) and three under SI (T1, T2, and T3)—were used in the experimental design to assess the contribution of the RWHB in improving corn yield. These SI were applied during the mid-season of corn (flowering, pollination, and grain filling). Water flow beneath a partially waterproofed RWHB was assessed using HYDRUS- 2D/3D program. Results showed that water stored in the RWHB allowed applying up to three SI, and increased corn yield up to 24% and 26% respectively in 2013 and 2014. However, SI targeting flowering and grain filling were the best scenarios to mitigate effect of dry spell in rainfed agriculture. Water flow under RWHB during the simulation period showed that dynamic of the saturated front depended on the magnitude of the water depth in the RWHB and the hydrodynamic characteristics of the underlying layers. Deep drainage was observed around 25th day after sowing (DAS) in 2013 and 45th DAS in 2014 according to water profile. This caused the decrease of the infiltration rate in the RWHB that was associated with a significant rise of 4% of the water table level ten days later in 2014. Recharge rate was estimated at 0.5 mm·d-1 during the mid-season and the late season of corn.
文摘A two-step methodology was used to address and improve the power quality concerns for the PV-integrated microgrid system. First, partial shading was included to deal with the real-time issues. The Improved Jelly Fish Algorithm integrated Perturb and Obserb (IJFA-PO) has been proposed to track the Global Maximum Power Point (GMPP). Second, the main unit-powered via DC–AC converter is synchronised with the grid. To cope with the wide voltage variation and harmonic mitigation, an auxiliary unit undergoes a novel series compensation technique. Out of various switching approaches, IJFA-based Selective Harmonic Elimination (SHE) in 120° conduction gives the optimal solution. Three switching angles were obtained using IJFA, whose performance was equivalent to that of nine switching angles. Thus, the system is efficient with minimised higher-order harmonics and lower switching losses. The proposed system outperformed in terms of efficiency, metaheuristics, and convergence. The Total Harmonic Distortion (THD) obtained was 1.32%, which is within the IEEE 1547 and IEC tolerable limits. The model was developed in MATLAB/Simulink 2016b and verified with an experimental prototype of grid-synchronised PV capacity of 260 W tested under various loading conditions. The present model is reliable and features a simple controller that provides more convenient and adequate performance.
文摘This paper examined the causes, effects and measures for mitigating climate change to ensure adequate supply of food through crop production to address the food insecurity which has occupied a central focus of the Nigerian economy. Unfortunately, crop production is fraught with many ecological challenges including climate change. This climate change which occurs as a result of the buildup of Green House Gases (GHGs) occasioned by industrialization, technological modeling and agriculture, exert significant effects on crop yield, water availability, ecosystem disequilibrium resulting in cases of drought, flood earthquake among others. For crop production to be scaled-up to meet the food requirement of the ever growing Nigerian population amidst these challenges, there is need to mitigate these adverse effects of climate change through the adoption of sustainable land management practices that can reduce the atmospheric stock of GHGs such as zero-tillage, appropriate use of fertilizers, avoidance of bush burning, graze land management, improved water management among others. Achieving great success in these areas requires that Nigerian government should be more proactive in their policies that hold promise for sustainable cultures in agricultural production as well as evolving global partnerships on ecological issues.
文摘We made an evaluation of a suitable mitigation technique for the treatment of drinking water that was artificially enriched with Rn-222 in laboratory by placing a radium rich granite stone (pitchblende) in a closed container filled with tap water for several days in order to allow Rn-222 concentration to approach its highest possible level. Experiments were designed to investigate the effectiveness of removal of Rn-222 by diffused bubble aeration method at room temperature. The results showed that this method becomes more efficient at higher airto-water ratios. Better aeration depends on the length of travel of bubbles through the water depth. This method is practical and has low capital cost. The removal of Rn-222 from artificially enriched water can be practically achieved by diffused bubble aeration method to greater than 98%.
