Considering the difficulty of broadcasting in the small plots and complex terrain in South China,this research aimed to explore a new efficient broadcasting way and figure out advisable operation parameters by using a...Considering the difficulty of broadcasting in the small plots and complex terrain in South China,this research aimed to explore a new efficient broadcasting way and figure out advisable operation parameters by using a hollow 12-axis,rotor-wing Unmanned Aerial Vehicle(UAV)which is typically made up of four groups of solid support structure,with each consisting of three axes and two rotor wings.A 3.7 L reverse pyramid-shape seed hopper with a 60 mm×13 mm rectangular outlet at the bottom was designed to realize self-gravity seeding.Rice seed firstly directly falls on the rotating disc driven by direct-current dynamo before being sown.The disc was located 120 mm above the ground,with a diameter of 350 mm.Under constant flight conditions,parameters of the on-board broadcasting devices(dropping speed referring to speed for the outlet and the broadcasting speed for the disc’s rotation speed)determine the uniformity of air broadcasting.The FUTABA T8FG transmitter and receiver system were employed as the remote control device.When the UAV flies at 3 m/s and 2 m above the ground with an expected seeding of 180 grain/m^(2),the RD(Right Down)knob marked 29 and LD(Left Down)knob marked-24 with a disc rotation speed of 900 r/min,the broadcasting lasts for 15 seconds with a 25%opening(1.95 cm^(2))of rectangular outlet.In order to verify the feasibility of air broadcasting parameters,the project team carried out a field broadcasting test by using a hollow multi-rotor UAV at Zhongluotan Test Base in Guangzhou in July,2014.In the square field plots of 0.09 hm^(2),flying path of air broadcasting operation was designed.The collected sampling data of broadcasting quantity per unit area after the test showed that there were,on average,187.4 grains/m^(2)of the five sampling points with a standard deviation of 22.77,and a coefficient of variation of 12.15%which was far smaller than that of artificial broadcasting.The average yield of field broadcasted by UAV is 7705.5 kg/hm^(2)in 2014,implying that rice air broadcasting by UAV is fea展开更多
Resistance to breast cancer(BCa) chemotherapy severely hampers the patient’s prognosis.MicroRNAs provide a potential therapeutic prospect for BCa.In this study,the reversal function of microRNA34 a(miR34 a) on doxoru...Resistance to breast cancer(BCa) chemotherapy severely hampers the patient’s prognosis.MicroRNAs provide a potential therapeutic prospect for BCa.In this study,the reversal function of microRNA34 a(miR34 a) on doxorubicin(Dox) resistance of BCa and the possible mechanism was investigated.We found that the relative level of miR34 a was significantly decreased in Dox-resistant breast cancer cell MCF-7(MCF-7/A) compared with Dox-sensitive MCF-7 cells.Transfection with miR34 a significantly suppressed the invasion,migration,adhesion of MCF-7/A cells without inhibiting their growth obviously.The combination of miR34 a and Dox could significantly inhibit the proliferation,migration,invasion and induce the apoptosis of MCF-7/A cells.The synergistic effect of this combination on resistant MCF-7/A cells has no obvious relation with the expressions of classical drug-resistant proteins P-GP,MRP and GST-π,while closely related with the down-regulation on TOP2 A and BCRP.Moreover,we found both protein and mRNA expression of Snail were significantly up-regulated in MCF-7/A cells in comparison with MCF-7 cells.Transfection with small interfering RNA(siRNA) of Snail could inhibit the invasion,migration and adhesion of drug-resistant MCF-7/A cells,while highexpression of Snail could remarkably promote the invasion,migration and adhesion of MCF-7 cells,which might be related with regulation of N-cadherin and E-cadherin.Transfection with miR34 a in MCF-7/A cells induced a decrease of Snail expression.The potential binding sites of miR34 a with 3’UTR of Snail were predicted by miRDB target prediction software,which was confirmed by luciferase reporter gene method.Results showed that the relative activity of luciferase was reduced in MCF-7/A cells after co-transfection of miR34 a and wild type(wt)-Snail,while did not change by co-transfection with miR34 a and 3’ UTR mutant type(mut) Snail.Combination of miR34 a and Dox induced a stronger decrease of Snail in MCF-7/A cells in comparison to miR34 a or Dox treatment alone.What’展开更多
Northeast China has been reported as having serious air pollution in China with increasing occurrences of severe haze epi- sodes. Changchun City, as the center of Northeast China, has longstanding industry and is an i...Northeast China has been reported as having serious air pollution in China with increasing occurrences of severe haze epi- sodes. Changchun City, as the center of Northeast China, has longstanding industry and is an important agricultural base. Additionally, Changchun City has a long winter requiring heating of buildings emitting pollution into the air. These factors contribute to the complex- ity of haze pollution in this area. In order to analyze the causes of heavy haze, surface air quality has been monitored from 2013 to 2015. By using satellite and meteorological data, atmospheric pollution status, spatio-temporal variations and formation have been analyzed. Results indicated that the air quality in 88.9% of days exceeding air quality index （AQI） level-1 standard （AQI 〉50） according to the National Ambient Air Quality Standard （NAAQS） of China. Conversely, 33.7% of the days showed a higher level with AQI 〉 100. Ex- treme haze events （AQI 〉 300） occurred frequently during agricultural harvesting period （from October 10 to November 10）, intensive winter heating period （from Late-December to February） and period of spring windblown dust （April and May）. Most daily concentra- tions of gaseous pollutants, i.e., NO2 （43.8 gg/m3）, CO （0.9 mg/m3）, SO2 （37.9 gg/m3）, and 03 （74.9 gg/m3） were evaluated within level-1 concentration limits of NAAQS standards. However, particulate matter （PM2.5 and PMI0） concentrations （67.3 ~tg/m3and 115.2 ~g/m3, respectively） were significantly higher than their level-1 limits. Severe haze in spring was caused by offsite transported dust and windblown surface soil. Heavy haze periods during fall and winter were mainly formed by intensive emissions of atmospheric pollutants and steady weather conditions （i.e., low wind speed and inversion layer）. The overlay emissions of widespread straw burning and coal combustion for heating were the dominant factors contributing to haze in autumn, while intensive coal burning during the col展开更多
In this research, we normalized the character- istics of ocean eddies by using satellite observation of the Sea Level Anomaly （SLA） data to determine the most typical shape of ocean eddies. This normalization is bas...In this research, we normalized the character- istics of ocean eddies by using satellite observation of the Sea Level Anomaly （SLA） data to determine the most typical shape of ocean eddies. This normalization is based on modified analytic functions with nonlinear optimal fitting. The most typical eddy is the Taylor vortex （~50%）, which exhibits a Gaussian-shaped exp（-r2） SLA and a vorticity distribution of （1-rZ）exp（-r2） as a function of the normalized radii r. The larger the amplitude of the eddy, the more likely the eddy is to be Gaussian-shaped. Furthermore, approximately 40% of ocean eddies are combinations of two Gaussian eddies with different parameters, but the composition of these types of eddies is more like a quadratic eddy than a Gaussian one. Only a small portion of oceanic eddies are pure quadratic eddies （ 〈 10%） with the same vorticity distribution as a Rankine vortex. We concluded that the Taylor vortex is a good approximation of the typical shape of ocean eddies.展开更多
The mixer-settler is a core device of solvent extraction for separating rare earth elements. There are some adverse effects like high rare earth accumulation and poor production efficiency during industrial production...The mixer-settler is a core device of solvent extraction for separating rare earth elements. There are some adverse effects like high rare earth accumulation and poor production efficiency during industrial production. Current researches usually focus on changing the structure of the mixer-settler without making a breakthrough towards gravity clarification. In this paper, in order to improve the efficiency of clarification, a mixer-settler with double stirring mode was designed and manufactured by adding a stirring device in the settler after reducing the volume of the settler. The innovation of this research involves adopting the ultraviolet-visible spectrophotometer to investigate the quantity of aqueous phase entrainment at the settler outlet in order to measure the clarification degree. Experimental results show that the clarification effect with stirring is better than that without stirring. The clarification effect is ameliorated as the stirring speed increases. Generally, the clarification effect shows a best condition when the offset distance is 12.5 cm, making the phase entrainment reduced to less than 0.1%. When the clearance over the tank bottom is 7 cm and 10 cm, respectively, the quantity of aqueous phase entrainment is better than the case with a clearance of 4 cm. The results show that the stirring paddle close to the mixed phase zone can better promote the two-phase separation.展开更多
Wireless sensor networks (WSNs) have the trouble of limited battery power, and wireless charging provides apromising solution to this problem, which is not easily affected by the external environment. In this paper, w...Wireless sensor networks (WSNs) have the trouble of limited battery power, and wireless charging provides apromising solution to this problem, which is not easily affected by the external environment. In this paper, we studythe recharging of sensors in wireless rechargeable sensor networks (WRSNs) by scheduling two mobile chargers(MCs) to collaboratively charge sensors. We first formulate a novel sensor charging scheduling problem with theobjective of maximizing the number of surviving sensors, and further propose a collaborative charging schedulingalgorithm(CCSA) for WRSNs. In the scheme, the sensors are divided into important sensors and ordinary sensors.TwoMCs can adaptively collaboratively charge the sensors based on the energy limit ofMCs and the energy demandof sensors. Finally, we conducted comparative simulations. The simulation results show that the proposed algorithmcan effectively reduce the death rate of the sensor. The proposed algorithm provides a solution to the uncertaintyof node charging tasks and the collaborative challenges posed by multiple MCs in practical scenarios.展开更多
Injury to the brain after intracerebral hemorrhage(ICH)results from numerous complex cellular mechanisms.At present,effective therapy for ICH is limited and a better understanding of the mechanisms of brain injury is ...Injury to the brain after intracerebral hemorrhage(ICH)results from numerous complex cellular mechanisms.At present,effective therapy for ICH is limited and a better understanding of the mechanisms of brain injury is necessary to improve prognosis.There is increasing evidence that ion channel dysregulation occurs at multiple stages in primary and secondary brain injury following ICH.Ion channels such as TWIK-related K+channel 1,sulfonylurea 1 transient receptor potential melastatin 4 and glutamate-gated channels affect ion homeostasis in ICH.They in turn participate in the formation of brain edema,disruption of the blood-brain barrier,and the generation of neurotoxicity.In this review,we summarize the interaction between ions and ion channels,the effects of ion channel dysregulation,and we discuss some therapeutics based on ion-channel modulation following ICH.展开更多
Although single-atom catalysts(SACs)have attracted enormous attention for their applications in the electrochemical reduction of CO_(2)(CO_(2)RR)due to their extraordinary catalytic activity and well-defined active ce...Although single-atom catalysts(SACs)have attracted enormous attention for their applications in the electrochemical reduction of CO_(2)(CO_(2)RR)due to their extraordinary catalytic activity and well-defined active centers,neighboring effects and their influence on the electrochemical performance of SACs have not been well investigated.In this review,we present a summary of the neighboring effects on SACs for the CO_(2)RR process,where the surrounding atoms not only induce electronic modulation of the metal atom but also participate in the CO_(2)RR.Both theoretical and experimental studies have pointed out that the neighboring sites of the anchored metal center can provide second active/adsorption locations during the catalytic process,enhancing CO_(2)RR performance tremendously.This review supplies advanced insights into the significant roles and impacts of neighboring effects on the catalytic process,which also benefit the development of advanced SACs to achieve efficient electrocatalysis.展开更多
Horizontal well drilling and multi-stage hydraulic fracturing technologies are at the root of commercial shale gas development and exploitation.During these processes,typically,a large amount of working fluid enters t...Horizontal well drilling and multi-stage hydraulic fracturing technologies are at the root of commercial shale gas development and exploitation.During these processes,typically,a large amount of working fluid enters the formation,resulting in widespread water-rock interaction.Deeply understanding such effects is required to optimize the production system.In this study,the mechanisms of water-rock interaction and the associated responses of shale fabric are systematically reviewed for working fluids such as neutral fluids,acid fluids,alkali fluids and oxidative fluids.It is shown that shale is generally rich in water-sensitive components such as clay minerals,acidsensitive components(like carbonate minerals),alkali-sensitive components(like quartz),oxidative-sensitive components(like organic matter and pyrite),which easily lead to change of rock fabric and mechanical properties owing to water-rock interaction.According to the results,oxidizing acid fluids and oxidizing fracturing fluids should be used to enhance shale gas recovery.This study also indicates that an aspect playing an important role in increasing cumulative gas production is the optimization of the maximum shut-in time based on the change point of the wellhead pressure drop rate.Another important influential factor to be considered is the control of the wellhead pressure considering the stress sensitivity and creep characteristics of the fracture network.展开更多
Timing newly discovered pulsars requires gradually building up a timing model that connects observations taken days to months apart.This sometimes can be challenging when our initial knowledge of the pulsar’s positio...Timing newly discovered pulsars requires gradually building up a timing model that connects observations taken days to months apart.This sometimes can be challenging when our initial knowledge of the pulsar’s position is arcminutes off from its true position.Such a position error leads to significant arrival time shifts as a result of the Earth’s orbital motion.Traditional down-hill fitting timing algorithms become ineffective when our model predicts the wrong pulse rotations for our next observation.For some pulsars whose model prediction is not too far off,the correct rotation number could be found by trial-and-error methods.For the remaining challenging pulsars,a more generalized method is called for.This paper proposes a GPU-based algorithm that could exhaustively search a large area of trail positions for probable timing solutions.This could help find phase-connected timing solutions for new pulsars using brute force.展开更多
Based on the wave attack task planning method in static complex environment and the rolling optimization framework, an online task planning method in dynamic complex environment based on rolling optimization is propos...Based on the wave attack task planning method in static complex environment and the rolling optimization framework, an online task planning method in dynamic complex environment based on rolling optimization is proposed. In the process of online task planning in dynamic complex environment,online task planning is based on event triggering including target information update event, new target addition event, target failure event, weapon failure event, etc., and the methods include defense area reanalysis, parameter space update, and mission re-planning. Simulation is conducted for different events and the result shows that the index value of the attack scenario after re-planning is better than that before re-planning and according to the probability distribution of statistical simulation method, the index value distribution after re-planning is obviously in the region of high index value, and the index value gap before and after re-planning is related to the degree of posture change.展开更多
Supercritical water gasification is a clean technology for biomass conversion and utilization.In supercritical water gasification systems,H_(2)O is often used as the transport medium.Decreases in the reaction temperat...Supercritical water gasification is a clean technology for biomass conversion and utilization.In supercritical water gasification systems,H_(2)O is often used as the transport medium.Decreases in the reaction temperature at the gasification area and in the heating rate of biomass may limit the gasification rate and efficiency.In this paper,CO_(2)is used as the transport medium due to its relatively low critical point and specific heat capacity.Moreover,a corn stalk gasification system with different transport media is established in this paper,and the influences of various operating parameters,such as temperature,pressure and feedstock concentration,are investigated.The results show that the gas yield in the CO_(2)-transport system decreases by no more than 5 wt%.In addition,thermodynamic analysis reveals that a system with CO_(2)as transport medium consumes approximately 25%less electricity than a system with H_(2)O as the transport medium.In addition,the reaction heat absorption decreases.The results show the superiority of CO_(2)to H_(2)O as a transport medium.展开更多
In order to develop new basic light-weight refractory raw materials,natural forsterite(<0.045 mm)and magnesite(<0.045 mm)were batched according to the chemical composition of forsterite(2MgO·SiO_(2)),wet mi...In order to develop new basic light-weight refractory raw materials,natural forsterite(<0.045 mm)and magnesite(<0.045 mm)were batched according to the chemical composition of forsterite(2MgO·SiO_(2)),wet milled,semi-dry molded and calcined at different temperatures.Then cylinder samples with diameter of 36 mm were prepared.The effects of the wet milling jar rotation speed,the calcination temperature and the anthracite addition on the properties of the samples were researched.The results show that:when the calcination temperature exceeds 1300℃,all the mineral phases have converted to the desired phases;with the increase of the rotation speed and the calcination temperature,the bulk density of the samples increases,the apparent porosity decreases and the compressive strength improves.By comprehensive consideration,400 r·min^(-1) and 1450℃ are taken as the optimal scheme.High addition of anthracite makes the samples light,so series of light-weight raw materials with uniformly distributed micro-pores can be gained.The light-weight raw materials achieved were used for insulation refractory castables,obtaining good application.展开更多
The cause–effect relationship between meso-γ-scale rotation and extreme short-term precipitation events remains elusive in mesoscale meteorological research.We aimed to elucidate this relationship by analyzing a rai...The cause–effect relationship between meso-γ-scale rotation and extreme short-term precipitation events remains elusive in mesoscale meteorological research.We aimed to elucidate this relationship by analyzing a rainstorm over the Pearl River Delta during the nocturnal hours of 15 May 2017 based on 6-min radar observations and 1-min rain gauge data.This rainstorm had a maximum hourly rainfall of 100.1 mm,with 26 stations recording hourly rainfall>60 mm h^(−1) in 5 h.Extreme heavy precipitation was produced in association with a convergence zone along the southern side of a synoptic low-level shear line,where southwesterly warm,humid airflows with precipitable water of>60 mm,little convection inhibition(<10 J kg^(−1)),and a low lifting condensation level(about 300 m)dominated.A meso-γ-scale vortex was quantitatively identified during the hour with the largest number of gauges observing extreme hourly rainfall.The vortex had a mean diameter of 6.1 km and a peak intensity of 3.1×10^(−3) s^(−1) during its lifetime of 54 min.The vortex initialized and remained inside the region of extreme rain rates(radar-retrieved rain rates>100 mm h^(−1)),reached its peak intensity after the peak of the collocated 6-min rainfall accumulation,and then weakened rapidly after the extreme rainfall region moved away.The radar-retrieved liquid water path was about five to seven times the ice water path and the specific differential phase(Kdp)below 0°C increased sharply downward during the lifetime of the vortex,suggesting the presence of active warm rain microphysical processes.These results indicate that the release of the latent heat of condensation induced by extreme rainfall could have contributed to the formation of the vortex in an environment with a weak 0–1-km vertical wind shear(about 4–5 m s^(−1))through enhanced lowlevel convergence,although the strengthening of low-level updrafts by rotational dynamic effects and short-term rainfall cannot be ruled out.展开更多
Chemical upcycling of end-of-life poly(lactide) plastics to lactide,lactate ester and new poly(lactide)has been achieved by using magnesium bis[bis(trimethylsilyl)amide][Mg(HMDS)_(2)]as promoter.Mg(HMDS)2 showed high ...Chemical upcycling of end-of-life poly(lactide) plastics to lactide,lactate ester and new poly(lactide)has been achieved by using magnesium bis[bis(trimethylsilyl)amide][Mg(HMDS)_(2)]as promoter.Mg(HMDS)2 showed high efficiency in L-lactide polymerization and poly(lactide) depolymerization.Mg(HMDS)_(2)/Ph_(2) CHOH catalytic system displayed high ring-opening selectivity and the characteristic of immortal polymerization.Taking advantage of transesterification,depolymerizations of end-oflife poly(lactide) plastics to lactate ester (polymer to value-added chemicals) and lactide (polymer to monomer) were achieved with high yields.Besides,a new“depolymerization-repolymerization”strategy was proposed to directly transform poly(lactide) into new poly(lactide).This work provides a theoretical basis for the design of polymerization and depolymerization catalysts and promotes the development of degradable polymers.展开更多
With the development of the service-oriented computing(SOC),web service has an important and popular solution for the design of the application system to various enterprises.Nowadays,the numerous web services are prov...With the development of the service-oriented computing(SOC),web service has an important and popular solution for the design of the application system to various enterprises.Nowadays,the numerous web services are provided by the service providers on the network,it becomes difficult for users to select the best reliable one from a large number of services with the same function.So it is necessary to design feasible selection strategies to provide users with the reliable services.Most existing methods attempt to select services according to accurate predictions for the quality of service(QoS)values.However,because the network and user needs are dynamic,it is almost impossible to accurately predict the QoS values.Furthermore,accurate prediction is generally time-consuming.This paper proposes a service decision tree based post-pruning prediction approach.This paper first defines the five reliability levels for measuring the reliability of services.By analyzing the quality data of service from the network,the proposed method can generate the training set and convert them into the service decision tree model.Using the generated model and the given predicted services,the proposed method classifies the service to the corresponding reliability level after discretizing the continuous attribute of service.Moreover,this paper applies the post-pruning strategy to optimize the generated model for avoiding the over-fitting.Experimental results show that the proposed method is effective in predicting the service reliability.展开更多
Magnesium and its alloy have good mechanical properties and biodegradability,and have become the hotspot of the next-generation biodegradable vascular stent materials.However,their rapid degradation in vivo and poor b...Magnesium and its alloy have good mechanical properties and biodegradability,and have become the hotspot of the next-generation biodegradable vascular stent materials.However,their rapid degradation in vivo and poor biocompatibility are still the bottlenecks of clinical applications for the cardiovascular stents.In particular,how to induce the repair and regeneration of the vascular endothelial with normal physiological functions on the surface of the magnesium alloy stent materials represents the key to its clinical application in the field of cardiovascular stents.It has been believed that it is an ideal way to completely solve the postoperative complications through constructing the multifunctional anti-corrosive bioactive coating on the magnesium alloy surface to induce the formation of vascular endothelium with normal physiological functions.However,how to construct a corrosion-resistant multifunctional bioactive coating with the good endothelial regeneration abilities on the magnesium alloy surface still faces a great challenge.This paper mainly focused on highlighting and summarizing the recent advances in the surface endothelialization of the magnesium alloy materials for the vascular stent,including the bio-inert coating,in-situ immobilization of bioactive molecules on the surface,polymer coating loaded with bioactive factors,novel multifunctional polymer coating,bioactive micropatterns,bioactive layer with glycocalyx-like structure,NO-releasing coating and bioactive sol-gel coating.The advantages and disadvantages of these strategies were discussed and analyzed.Finally,in the senses of future development and clinical application,this paper analyzed and summarized the development direction and prospect of surface endothelialization of the magnesium alloy vascular stents.It is anticipated that this review can give the new cues to the surface endothelialization of the cardiovascular magnesium alloy stents and promote future advancements in this field.展开更多
High-rate battery-type cathode materials have attracted wide attention for advanced battery-supercapacitor hybrid(BSH)devices.Herein,a core-shell structure of the hollow mesoporous carbon spheres(HMCS)supported NiSe2 ...High-rate battery-type cathode materials have attracted wide attention for advanced battery-supercapacitor hybrid(BSH)devices.Herein,a core-shell structure of the hollow mesoporous carbon spheres(HMCS)supported NiSe2 nanosheets(HMCS/NiSe2)is constructed through two-step reactions.The HMCS/NiSe_(2)shows a max specific capacity of 1,153.5 C·g^(-1) at the current density of 1 A·g^(-1),and can remain at 774.5 C·g^(-1) even at 40 A·g^(-1)(the retention rate as high as 67.1%)and then the HMCS/NiSe_(2) electrode can keep 80.5%specific capacity after 5,000 cycles at a current density of 10 A·g^(-1).Moreover,the density functional theory(DFT)calculation confirmed that the introduction HMCS into NiSe_(2) made adsorption/desorption of OH-easier,which can achieve higher rate capability.The HMCS/NiSe_(2)//6 M KOH//HMCS hybrid device has energy density of 47.15 Wh·kg^(-1) and power density of 801.8 W·kg^(-1).This work provides a feasible electrode material with a high rate and its preparation method for high energy density and power density energy storage devices.展开更多
Porous particle flow is universal in nature and industry.However,in previous numerical simulations,porous particles have usually been assumed to be solid.It is necessary to study the flow and heat-transfer characteris...Porous particle flow is universal in nature and industry.However,in previous numerical simulations,porous particles have usually been assumed to be solid.It is necessary to study the flow and heat-transfer characteristics around porous particles because they are greatly different from those of impermeable particles.In this study,two-dimensional steady flow and heat transfer around and through a porous particle with a constant temperature placed in a cold fluid were numerically investigated.The effects of the Reynolds number(Re)and Darcy number(Da)on the flow and heat-transfer characteristics were investigated in detail.The investigated ranges of the parameters were 10≤Re≤40 and 10^(−6)≤Da≤10^(−2).It is sophisticated to simulate porous particles with traditional simulation methods because of their complicated structure.Therefore,the lattice Boltzmann method was used to solve the generalized macroscopic governing equations because of its simplicity.The drag coefficient decreased with increasing Re or Da,but the decrease was not prominent in the range 10^(−6)≤Da≤10^(−4).The heat-transfer efficiency of the front surface was much stronger than that of the rear surface.The heat-transfer efficiency between the particle and the fluid increased with increasing Re or Da.However,for 10^(−6)≤Da≤10^(−4),the increase was not prominent and the heat-transfer enhancement ratio was slightly larger than one.Furthermore,the effect of Da became more prominent at larger Re.In addition,new correlations for the drag coefficient and surface-averaged Nusselt number were obtained based on the simulated results.展开更多
A rotating axisymmetric circular nanoplate is modeled by the Mindlin plate theory.The Mindlin plate theory incorporates the nonlocal scale and strain gradient effects.The shear deformation of the circular nanoplate is...A rotating axisymmetric circular nanoplate is modeled by the Mindlin plate theory.The Mindlin plate theory incorporates the nonlocal scale and strain gradient effects.The shear deformation of the circular nanoplate is considered and the nonlocal strain gradient theory is utilized to derive the governing differential equation of motion that describes the out-of-plane free vibration behaviors of the nanoplate.The differential quadrature method is used to solve the governing equation numerically,and the natural frequencies of the out-of-plane vibration of rotating nanoplates are obtained accordingly.Two kinds of boundary conditions are commonly used in practical engineering,namely the fixed and simply supported constraints,and are considered in numerical examples.The variations of natural frequencies with respect to the thickness to radius ratio,the angular velocity,the nonlocal characteristic scale and the material characteristic scale are analyzed in detail.In particular,the critical angular velocity that measures whether the rotating circular nanoplate is stable or not is obtained numerically.The presented study has reference significance for the dynamic design and control of rotating circular nanostructures in current nano-technologies and nano-devices.展开更多
基金the grants of National Key Research and Development Plan(2016YF0200700)Innovation project of modern agricultural equipment and technology in Jiangsu Province(NZXT01201403)+1 种基金Guangdong Natural Science Foundation of China(2015A030313420)National Sparking Plan Project(2015GA780039)。
文摘Considering the difficulty of broadcasting in the small plots and complex terrain in South China,this research aimed to explore a new efficient broadcasting way and figure out advisable operation parameters by using a hollow 12-axis,rotor-wing Unmanned Aerial Vehicle(UAV)which is typically made up of four groups of solid support structure,with each consisting of three axes and two rotor wings.A 3.7 L reverse pyramid-shape seed hopper with a 60 mm×13 mm rectangular outlet at the bottom was designed to realize self-gravity seeding.Rice seed firstly directly falls on the rotating disc driven by direct-current dynamo before being sown.The disc was located 120 mm above the ground,with a diameter of 350 mm.Under constant flight conditions,parameters of the on-board broadcasting devices(dropping speed referring to speed for the outlet and the broadcasting speed for the disc’s rotation speed)determine the uniformity of air broadcasting.The FUTABA T8FG transmitter and receiver system were employed as the remote control device.When the UAV flies at 3 m/s and 2 m above the ground with an expected seeding of 180 grain/m^(2),the RD(Right Down)knob marked 29 and LD(Left Down)knob marked-24 with a disc rotation speed of 900 r/min,the broadcasting lasts for 15 seconds with a 25%opening(1.95 cm^(2))of rectangular outlet.In order to verify the feasibility of air broadcasting parameters,the project team carried out a field broadcasting test by using a hollow multi-rotor UAV at Zhongluotan Test Base in Guangzhou in July,2014.In the square field plots of 0.09 hm^(2),flying path of air broadcasting operation was designed.The collected sampling data of broadcasting quantity per unit area after the test showed that there were,on average,187.4 grains/m^(2)of the five sampling points with a standard deviation of 22.77,and a coefficient of variation of 12.15%which was far smaller than that of artificial broadcasting.The average yield of field broadcasted by UAV is 7705.5 kg/hm^(2)in 2014,implying that rice air broadcasting by UAV is fea
基金supported by Natural Science Foundation of Shandong Province(ZR2020MH419,China)Key Research and Development Program of Shandong Province(2017CXGC1401,China)+1 种基金Chinae Australia Centre for Health Sciences Research(CACHSR No.2019GJ01)Major Basic Research Projects of Shandong Province(ZR2018ZC0233,China)
文摘Resistance to breast cancer(BCa) chemotherapy severely hampers the patient’s prognosis.MicroRNAs provide a potential therapeutic prospect for BCa.In this study,the reversal function of microRNA34 a(miR34 a) on doxorubicin(Dox) resistance of BCa and the possible mechanism was investigated.We found that the relative level of miR34 a was significantly decreased in Dox-resistant breast cancer cell MCF-7(MCF-7/A) compared with Dox-sensitive MCF-7 cells.Transfection with miR34 a significantly suppressed the invasion,migration,adhesion of MCF-7/A cells without inhibiting their growth obviously.The combination of miR34 a and Dox could significantly inhibit the proliferation,migration,invasion and induce the apoptosis of MCF-7/A cells.The synergistic effect of this combination on resistant MCF-7/A cells has no obvious relation with the expressions of classical drug-resistant proteins P-GP,MRP and GST-π,while closely related with the down-regulation on TOP2 A and BCRP.Moreover,we found both protein and mRNA expression of Snail were significantly up-regulated in MCF-7/A cells in comparison with MCF-7 cells.Transfection with small interfering RNA(siRNA) of Snail could inhibit the invasion,migration and adhesion of drug-resistant MCF-7/A cells,while highexpression of Snail could remarkably promote the invasion,migration and adhesion of MCF-7 cells,which might be related with regulation of N-cadherin and E-cadherin.Transfection with miR34 a in MCF-7/A cells induced a decrease of Snail expression.The potential binding sites of miR34 a with 3’UTR of Snail were predicted by miRDB target prediction software,which was confirmed by luciferase reporter gene method.Results showed that the relative activity of luciferase was reduced in MCF-7/A cells after co-transfection of miR34 a and wild type(wt)-Snail,while did not change by co-transfection with miR34 a and 3’ UTR mutant type(mut) Snail.Combination of miR34 a and Dox induced a stronger decrease of Snail in MCF-7/A cells in comparison to miR34 a or Dox treatment alone.What’
基金Under the auspices of National Key Research and Development Project(No.2017YFC0212300)Youth Innovation Promotion Association CAS(No.2017275)Frontier Science Research Plan CAS(No.QYZDB-SSW-DQC045)
文摘Northeast China has been reported as having serious air pollution in China with increasing occurrences of severe haze epi- sodes. Changchun City, as the center of Northeast China, has longstanding industry and is an important agricultural base. Additionally, Changchun City has a long winter requiring heating of buildings emitting pollution into the air. These factors contribute to the complex- ity of haze pollution in this area. In order to analyze the causes of heavy haze, surface air quality has been monitored from 2013 to 2015. By using satellite and meteorological data, atmospheric pollution status, spatio-temporal variations and formation have been analyzed. Results indicated that the air quality in 88.9% of days exceeding air quality index （AQI） level-1 standard （AQI 〉50） according to the National Ambient Air Quality Standard （NAAQS） of China. Conversely, 33.7% of the days showed a higher level with AQI 〉 100. Ex- treme haze events （AQI 〉 300） occurred frequently during agricultural harvesting period （from October 10 to November 10）, intensive winter heating period （from Late-December to February） and period of spring windblown dust （April and May）. Most daily concentra- tions of gaseous pollutants, i.e., NO2 （43.8 gg/m3）, CO （0.9 mg/m3）, SO2 （37.9 gg/m3）, and 03 （74.9 gg/m3） were evaluated within level-1 concentration limits of NAAQS standards. However, particulate matter （PM2.5 and PMI0） concentrations （67.3 ~tg/m3and 115.2 ~g/m3, respectively） were significantly higher than their level-1 limits. Severe haze in spring was caused by offsite transported dust and windblown surface soil. Heavy haze periods during fall and winter were mainly formed by intensive emissions of atmospheric pollutants and steady weather conditions （i.e., low wind speed and inversion layer）. The overlay emissions of widespread straw burning and coal combustion for heating were the dominant factors contributing to haze in autumn, while intensive coal burning during the col
文摘In this research, we normalized the character- istics of ocean eddies by using satellite observation of the Sea Level Anomaly （SLA） data to determine the most typical shape of ocean eddies. This normalization is based on modified analytic functions with nonlinear optimal fitting. The most typical eddy is the Taylor vortex （~50%）, which exhibits a Gaussian-shaped exp（-r2） SLA and a vorticity distribution of （1-rZ）exp（-r2） as a function of the normalized radii r. The larger the amplitude of the eddy, the more likely the eddy is to be Gaussian-shaped. Furthermore, approximately 40% of ocean eddies are combinations of two Gaussian eddies with different parameters, but the composition of these types of eddies is more like a quadratic eddy than a Gaussian one. Only a small portion of oceanic eddies are pure quadratic eddies （ 〈 10%） with the same vorticity distribution as a Rankine vortex. We concluded that the Taylor vortex is a good approximation of the typical shape of ocean eddies.
基金supported by Hi-Tech Research and Development Program(863)of China(2010AA03A405)the National Natural Science Foundation of China(No.50974035,No.51004033)
文摘The mixer-settler is a core device of solvent extraction for separating rare earth elements. There are some adverse effects like high rare earth accumulation and poor production efficiency during industrial production. Current researches usually focus on changing the structure of the mixer-settler without making a breakthrough towards gravity clarification. In this paper, in order to improve the efficiency of clarification, a mixer-settler with double stirring mode was designed and manufactured by adding a stirring device in the settler after reducing the volume of the settler. The innovation of this research involves adopting the ultraviolet-visible spectrophotometer to investigate the quantity of aqueous phase entrainment at the settler outlet in order to measure the clarification degree. Experimental results show that the clarification effect with stirring is better than that without stirring. The clarification effect is ameliorated as the stirring speed increases. Generally, the clarification effect shows a best condition when the offset distance is 12.5 cm, making the phase entrainment reduced to less than 0.1%. When the clearance over the tank bottom is 7 cm and 10 cm, respectively, the quantity of aqueous phase entrainment is better than the case with a clearance of 4 cm. The results show that the stirring paddle close to the mixed phase zone can better promote the two-phase separation.
基金Hubei Provincial Natural Science Foundation of China under Grant No.2017CKB893Wuhan Polytechnic University Reform Subsidy Project Grant No.03220153.
文摘Wireless sensor networks (WSNs) have the trouble of limited battery power, and wireless charging provides apromising solution to this problem, which is not easily affected by the external environment. In this paper, we studythe recharging of sensors in wireless rechargeable sensor networks (WRSNs) by scheduling two mobile chargers(MCs) to collaboratively charge sensors. We first formulate a novel sensor charging scheduling problem with theobjective of maximizing the number of surviving sensors, and further propose a collaborative charging schedulingalgorithm(CCSA) for WRSNs. In the scheme, the sensors are divided into important sensors and ordinary sensors.TwoMCs can adaptively collaboratively charge the sensors based on the energy limit ofMCs and the energy demandof sensors. Finally, we conducted comparative simulations. The simulation results show that the proposed algorithmcan effectively reduce the death rate of the sensor. The proposed algorithm provides a solution to the uncertaintyof node charging tasks and the collaborative challenges posed by multiple MCs in practical scenarios.
基金supported by the National Natural Science Foundation of China(82071331,81870942,and 81520108011)the National Key Research and Development Program of China(2018YFC1312200)the Canadian Institutes of Health Research(VWY).
文摘Injury to the brain after intracerebral hemorrhage(ICH)results from numerous complex cellular mechanisms.At present,effective therapy for ICH is limited and a better understanding of the mechanisms of brain injury is necessary to improve prognosis.There is increasing evidence that ion channel dysregulation occurs at multiple stages in primary and secondary brain injury following ICH.Ion channels such as TWIK-related K+channel 1,sulfonylurea 1 transient receptor potential melastatin 4 and glutamate-gated channels affect ion homeostasis in ICH.They in turn participate in the formation of brain edema,disruption of the blood-brain barrier,and the generation of neurotoxicity.In this review,we summarize the interaction between ions and ion channels,the effects of ion channel dysregulation,and we discuss some therapeutics based on ion-channel modulation following ICH.
基金the support from the National Natural Science Foundation of China Grant Council of Hong Kong Joint Research Scheme(N_PolyU502/21)the funding for Projects of Strategic Importance of The Hong Kong Polytechnic University(Project Code:1-ZE2V)+2 种基金Shenzhen Fundamental Research Scheme-General Program(JCYJ20220531090807017)the Natural Science Foundation of Guangdong Province(2023A1515012219)Departmental General Research Fund(Project Code:ZVUL)from Department of Applied Biology and Chemical Technology of Hong Kong Polytechnic University.
文摘Although single-atom catalysts(SACs)have attracted enormous attention for their applications in the electrochemical reduction of CO_(2)(CO_(2)RR)due to their extraordinary catalytic activity and well-defined active centers,neighboring effects and their influence on the electrochemical performance of SACs have not been well investigated.In this review,we present a summary of the neighboring effects on SACs for the CO_(2)RR process,where the surrounding atoms not only induce electronic modulation of the metal atom but also participate in the CO_(2)RR.Both theoretical and experimental studies have pointed out that the neighboring sites of the anchored metal center can provide second active/adsorption locations during the catalytic process,enhancing CO_(2)RR performance tremendously.This review supplies advanced insights into the significant roles and impacts of neighboring effects on the catalytic process,which also benefit the development of advanced SACs to achieve efficient electrocatalysis.
基金Lijun,You,Innovative Research Project for Sichuan Youth Scientific and Technological Innovation(Grants No.2016TD0016)Qiuyang Cheng,Postdoctoral Research Project of Petrochina Southwest Oil and Gas Field Company(Grants No.20230304-13).
文摘Horizontal well drilling and multi-stage hydraulic fracturing technologies are at the root of commercial shale gas development and exploitation.During these processes,typically,a large amount of working fluid enters the formation,resulting in widespread water-rock interaction.Deeply understanding such effects is required to optimize the production system.In this study,the mechanisms of water-rock interaction and the associated responses of shale fabric are systematically reviewed for working fluids such as neutral fluids,acid fluids,alkali fluids and oxidative fluids.It is shown that shale is generally rich in water-sensitive components such as clay minerals,acidsensitive components(like carbonate minerals),alkali-sensitive components(like quartz),oxidative-sensitive components(like organic matter and pyrite),which easily lead to change of rock fabric and mechanical properties owing to water-rock interaction.According to the results,oxidizing acid fluids and oxidizing fracturing fluids should be used to enhance shale gas recovery.This study also indicates that an aspect playing an important role in increasing cumulative gas production is the optimization of the maximum shut-in time based on the change point of the wellhead pressure drop rate.Another important influential factor to be considered is the control of the wellhead pressure considering the stress sensitivity and creep characteristics of the fracture network.
基金supported by the National Natural Science Foundation of China(12041303)the National SKA Program of China(2020SKA0120200)+2 种基金the CAS Project for Young Scientists in Basic Research YSBR-063the National Natural Science Foundation of China(NSFC grant Nos.12203070 and Nos.12203072)the CAS-MPG LEGACY project。
文摘Timing newly discovered pulsars requires gradually building up a timing model that connects observations taken days to months apart.This sometimes can be challenging when our initial knowledge of the pulsar’s position is arcminutes off from its true position.Such a position error leads to significant arrival time shifts as a result of the Earth’s orbital motion.Traditional down-hill fitting timing algorithms become ineffective when our model predicts the wrong pulse rotations for our next observation.For some pulsars whose model prediction is not too far off,the correct rotation number could be found by trial-and-error methods.For the remaining challenging pulsars,a more generalized method is called for.This paper proposes a GPU-based algorithm that could exhaustively search a large area of trail positions for probable timing solutions.This could help find phase-connected timing solutions for new pulsars using brute force.
文摘Based on the wave attack task planning method in static complex environment and the rolling optimization framework, an online task planning method in dynamic complex environment based on rolling optimization is proposed. In the process of online task planning in dynamic complex environment,online task planning is based on event triggering including target information update event, new target addition event, target failure event, weapon failure event, etc., and the methods include defense area reanalysis, parameter space update, and mission re-planning. Simulation is conducted for different events and the result shows that the index value of the attack scenario after re-planning is better than that before re-planning and according to the probability distribution of statistical simulation method, the index value distribution after re-planning is obviously in the region of high index value, and the index value gap before and after re-planning is related to the degree of posture change.
基金National Key R&D Program of China(Grant No.2020YFA0714400).
文摘Supercritical water gasification is a clean technology for biomass conversion and utilization.In supercritical water gasification systems,H_(2)O is often used as the transport medium.Decreases in the reaction temperature at the gasification area and in the heating rate of biomass may limit the gasification rate and efficiency.In this paper,CO_(2)is used as the transport medium due to its relatively low critical point and specific heat capacity.Moreover,a corn stalk gasification system with different transport media is established in this paper,and the influences of various operating parameters,such as temperature,pressure and feedstock concentration,are investigated.The results show that the gas yield in the CO_(2)-transport system decreases by no more than 5 wt%.In addition,thermodynamic analysis reveals that a system with CO_(2)as transport medium consumes approximately 25%less electricity than a system with H_(2)O as the transport medium.In addition,the reaction heat absorption decreases.The results show the superiority of CO_(2)to H_(2)O as a transport medium.
基金The work was supported by Student Research Training Program of Henan University of Science and Technology in 2020(No.2020029).
文摘In order to develop new basic light-weight refractory raw materials,natural forsterite(<0.045 mm)and magnesite(<0.045 mm)were batched according to the chemical composition of forsterite(2MgO·SiO_(2)),wet milled,semi-dry molded and calcined at different temperatures.Then cylinder samples with diameter of 36 mm were prepared.The effects of the wet milling jar rotation speed,the calcination temperature and the anthracite addition on the properties of the samples were researched.The results show that:when the calcination temperature exceeds 1300℃,all the mineral phases have converted to the desired phases;with the increase of the rotation speed and the calcination temperature,the bulk density of the samples increases,the apparent porosity decreases and the compressive strength improves.By comprehensive consideration,400 r·min^(-1) and 1450℃ are taken as the optimal scheme.High addition of anthracite makes the samples light,so series of light-weight raw materials with uniformly distributed micro-pores can be gained.The light-weight raw materials achieved were used for insulation refractory castables,obtaining good application.
基金Supported by the National Natural Science Foundation of China(42030610)National Key Research and Development Program of China for Intergovernmental Cooperation(2019YFE0110100).
文摘The cause–effect relationship between meso-γ-scale rotation and extreme short-term precipitation events remains elusive in mesoscale meteorological research.We aimed to elucidate this relationship by analyzing a rainstorm over the Pearl River Delta during the nocturnal hours of 15 May 2017 based on 6-min radar observations and 1-min rain gauge data.This rainstorm had a maximum hourly rainfall of 100.1 mm,with 26 stations recording hourly rainfall>60 mm h^(−1) in 5 h.Extreme heavy precipitation was produced in association with a convergence zone along the southern side of a synoptic low-level shear line,where southwesterly warm,humid airflows with precipitable water of>60 mm,little convection inhibition(<10 J kg^(−1)),and a low lifting condensation level(about 300 m)dominated.A meso-γ-scale vortex was quantitatively identified during the hour with the largest number of gauges observing extreme hourly rainfall.The vortex had a mean diameter of 6.1 km and a peak intensity of 3.1×10^(−3) s^(−1) during its lifetime of 54 min.The vortex initialized and remained inside the region of extreme rain rates(radar-retrieved rain rates>100 mm h^(−1)),reached its peak intensity after the peak of the collocated 6-min rainfall accumulation,and then weakened rapidly after the extreme rainfall region moved away.The radar-retrieved liquid water path was about five to seven times the ice water path and the specific differential phase(Kdp)below 0°C increased sharply downward during the lifetime of the vortex,suggesting the presence of active warm rain microphysical processes.These results indicate that the release of the latent heat of condensation induced by extreme rainfall could have contributed to the formation of the vortex in an environment with a weak 0–1-km vertical wind shear(about 4–5 m s^(−1))through enhanced lowlevel convergence,although the strengthening of low-level updrafts by rotational dynamic effects and short-term rainfall cannot be ruled out.
基金support by the National Natural Science Foundation of China (No. 21901249)Taishan Scholars Program of Shandong Province (No. tsqn201812112)the Scientific Research and Innovation Fund Project of Shandong Energy Research Institute (No. SEI I202004)。
文摘Chemical upcycling of end-of-life poly(lactide) plastics to lactide,lactate ester and new poly(lactide)has been achieved by using magnesium bis[bis(trimethylsilyl)amide][Mg(HMDS)_(2)]as promoter.Mg(HMDS)2 showed high efficiency in L-lactide polymerization and poly(lactide) depolymerization.Mg(HMDS)_(2)/Ph_(2) CHOH catalytic system displayed high ring-opening selectivity and the characteristic of immortal polymerization.Taking advantage of transesterification,depolymerizations of end-oflife poly(lactide) plastics to lactate ester (polymer to value-added chemicals) and lactide (polymer to monomer) were achieved with high yields.Besides,a new“depolymerization-repolymerization”strategy was proposed to directly transform poly(lactide) into new poly(lactide).This work provides a theoretical basis for the design of polymerization and depolymerization catalysts and promotes the development of degradable polymers.
基金This paper is partially supported by the National Natural Science Foundation of China under Grant No.61972053 and No.61603054by the Scientific Research Foundation of Liaoning Education Department under Grant No.LQ2019016,No.LJ2019015by the Natural Science Foundation of Liaoning Province,China under Grant No.2019-ZD-0505.
文摘With the development of the service-oriented computing(SOC),web service has an important and popular solution for the design of the application system to various enterprises.Nowadays,the numerous web services are provided by the service providers on the network,it becomes difficult for users to select the best reliable one from a large number of services with the same function.So it is necessary to design feasible selection strategies to provide users with the reliable services.Most existing methods attempt to select services according to accurate predictions for the quality of service(QoS)values.However,because the network and user needs are dynamic,it is almost impossible to accurately predict the QoS values.Furthermore,accurate prediction is generally time-consuming.This paper proposes a service decision tree based post-pruning prediction approach.This paper first defines the five reliability levels for measuring the reliability of services.By analyzing the quality data of service from the network,the proposed method can generate the training set and convert them into the service decision tree model.Using the generated model and the given predicted services,the proposed method classifies the service to the corresponding reliability level after discretizing the continuous attribute of service.Moreover,this paper applies the post-pruning strategy to optimize the generated model for avoiding the over-fitting.Experimental results show that the proposed method is effective in predicting the service reliability.
基金financially supported by the National Natural Science Foundation of China(31870952)Natural Science Foundation of Jiangsu Province of China(BK20181480)。
文摘Magnesium and its alloy have good mechanical properties and biodegradability,and have become the hotspot of the next-generation biodegradable vascular stent materials.However,their rapid degradation in vivo and poor biocompatibility are still the bottlenecks of clinical applications for the cardiovascular stents.In particular,how to induce the repair and regeneration of the vascular endothelial with normal physiological functions on the surface of the magnesium alloy stent materials represents the key to its clinical application in the field of cardiovascular stents.It has been believed that it is an ideal way to completely solve the postoperative complications through constructing the multifunctional anti-corrosive bioactive coating on the magnesium alloy surface to induce the formation of vascular endothelium with normal physiological functions.However,how to construct a corrosion-resistant multifunctional bioactive coating with the good endothelial regeneration abilities on the magnesium alloy surface still faces a great challenge.This paper mainly focused on highlighting and summarizing the recent advances in the surface endothelialization of the magnesium alloy materials for the vascular stent,including the bio-inert coating,in-situ immobilization of bioactive molecules on the surface,polymer coating loaded with bioactive factors,novel multifunctional polymer coating,bioactive micropatterns,bioactive layer with glycocalyx-like structure,NO-releasing coating and bioactive sol-gel coating.The advantages and disadvantages of these strategies were discussed and analyzed.Finally,in the senses of future development and clinical application,this paper analyzed and summarized the development direction and prospect of surface endothelialization of the magnesium alloy vascular stents.It is anticipated that this review can give the new cues to the surface endothelialization of the cardiovascular magnesium alloy stents and promote future advancements in this field.
基金supported by the National Natural Science Foundation of China(No.52002122)the Science and Technology Department of Hubei Province(No.2019AAA038)+1 种基金the Wuhan Yellow Crane Talent Program(No.2017-02)received funding from the European Unions Horizon 2020 research and innovation programme under grant agreement No.823717-ESTEEM3.
文摘High-rate battery-type cathode materials have attracted wide attention for advanced battery-supercapacitor hybrid(BSH)devices.Herein,a core-shell structure of the hollow mesoporous carbon spheres(HMCS)supported NiSe2 nanosheets(HMCS/NiSe2)is constructed through two-step reactions.The HMCS/NiSe_(2)shows a max specific capacity of 1,153.5 C·g^(-1) at the current density of 1 A·g^(-1),and can remain at 774.5 C·g^(-1) even at 40 A·g^(-1)(the retention rate as high as 67.1%)and then the HMCS/NiSe_(2) electrode can keep 80.5%specific capacity after 5,000 cycles at a current density of 10 A·g^(-1).Moreover,the density functional theory(DFT)calculation confirmed that the introduction HMCS into NiSe_(2) made adsorption/desorption of OH-easier,which can achieve higher rate capability.The HMCS/NiSe_(2)//6 M KOH//HMCS hybrid device has energy density of 47.15 Wh·kg^(-1) and power density of 801.8 W·kg^(-1).This work provides a feasible electrode material with a high rate and its preparation method for high energy density and power density energy storage devices.
基金supported by the National Natural Science Foundation of China(grant No.51922086).
文摘Porous particle flow is universal in nature and industry.However,in previous numerical simulations,porous particles have usually been assumed to be solid.It is necessary to study the flow and heat-transfer characteristics around porous particles because they are greatly different from those of impermeable particles.In this study,two-dimensional steady flow and heat transfer around and through a porous particle with a constant temperature placed in a cold fluid were numerically investigated.The effects of the Reynolds number(Re)and Darcy number(Da)on the flow and heat-transfer characteristics were investigated in detail.The investigated ranges of the parameters were 10≤Re≤40 and 10^(−6)≤Da≤10^(−2).It is sophisticated to simulate porous particles with traditional simulation methods because of their complicated structure.Therefore,the lattice Boltzmann method was used to solve the generalized macroscopic governing equations because of its simplicity.The drag coefficient decreased with increasing Re or Da,but the decrease was not prominent in the range 10^(−6)≤Da≤10^(−4).The heat-transfer efficiency of the front surface was much stronger than that of the rear surface.The heat-transfer efficiency between the particle and the fluid increased with increasing Re or Da.However,for 10^(−6)≤Da≤10^(−4),the increase was not prominent and the heat-transfer enhancement ratio was slightly larger than one.Furthermore,the effect of Da became more prominent at larger Re.In addition,new correlations for the drag coefficient and surface-averaged Nusselt number were obtained based on the simulated results.
基金supported by the Natural Science Foundation of China(No.11972240)the China Postdoctoral Science Foundation(No.2020M671574)the University Natural Science Research Project of Anhui Province(No.KJ2018A0481).
文摘A rotating axisymmetric circular nanoplate is modeled by the Mindlin plate theory.The Mindlin plate theory incorporates the nonlocal scale and strain gradient effects.The shear deformation of the circular nanoplate is considered and the nonlocal strain gradient theory is utilized to derive the governing differential equation of motion that describes the out-of-plane free vibration behaviors of the nanoplate.The differential quadrature method is used to solve the governing equation numerically,and the natural frequencies of the out-of-plane vibration of rotating nanoplates are obtained accordingly.Two kinds of boundary conditions are commonly used in practical engineering,namely the fixed and simply supported constraints,and are considered in numerical examples.The variations of natural frequencies with respect to the thickness to radius ratio,the angular velocity,the nonlocal characteristic scale and the material characteristic scale are analyzed in detail.In particular,the critical angular velocity that measures whether the rotating circular nanoplate is stable or not is obtained numerically.The presented study has reference significance for the dynamic design and control of rotating circular nanostructures in current nano-technologies and nano-devices.
