Different operating conditions （e.g. design and off-design） may lead to a significant difference in the hydrodynamics performance of a ship, especially in the total resistance and wake field of ships. This work inve...Different operating conditions （e.g. design and off-design） may lead to a significant difference in the hydrodynamics performance of a ship, especially in the total resistance and wake field of ships. This work investigated the hydrodynamic performance of the well-known KRISO 3600 TEU Container Ship （KCS） under three different operating conditions by means of Particle Image Velocimetry （P/V） and Computational Fluid Dynamics （CFD）. The comparison results show that the use of PIV to measure a ship＇s nominal wake field is an important method which has the advantages of being contactless and highly accurate. Acceptable agreements between the results obtained by the two different methods are achieved. Results indicate that the total resistances of the KCS model under two off-design conditions are 23.88% and 13.92% larger than that under the designed condition, respectively.展开更多
Experimental tests were conducted to evaluate the hydrodynamic performance of an L-type podded propulsor in straight-ahead motion and off-design conditions using an open-water measuring instrument developed by the aut...Experimental tests were conducted to evaluate the hydrodynamic performance of an L-type podded propulsor in straight-ahead motion and off-design conditions using an open-water measuring instrument developed by the authors for podded propulsors, a ship model towing tank, and under water particle image velocimetry （PIV） measurement systems. Under the three types of conditions, the main parameters of an L-type podded propulsor were measured, including the propeller thrust and torque, as well as the thrust, side force, and moment of the whole pod unit.In addition, the flow field on the section between the propeller and the strut was analyzed. Experimental results demonstrate that the dynamic azimuthing rate and direction and the turning direction affect the forces on the propeller and the whole pod unit. Forces are asymmetrically distributed between the left and right azimuthing directions because of the effect of propeller rotation. The findings of this study provide a foundation for further research on L-type podded propulsors.展开更多
Actuator faults can be critical in turbofan engines as they can lead to stall,surge,loss of thrust and failure of speed control.Thus,fault diagnosis of gas turbine actuators has attracted considerable attention,from b...Actuator faults can be critical in turbofan engines as they can lead to stall,surge,loss of thrust and failure of speed control.Thus,fault diagnosis of gas turbine actuators has attracted considerable attention,from both academia and industry.However,the extensive literature that exists on this topic does not address identifying the severity of actuator faults and focuses mainly on actuator fault detection and isolation.In addition,previous studies of actuator fault identification have not dealt with multiple concurrent faults in real time,especially when these are accompanied by sudden failures under dynamic conditions.This study develops component-level models for fault identification in four typical actuators used in high-bypass ratio turbofan engines under both dynamic and steady-state conditions and these are then integrated with the engine performance model developed by the authors.The research results reported here present a novel method of quantifying actuator faults using dynamic effect compensation.The maximum error for each actuator is less than0.06%and 0.07%,with average computational time of less than 0.0058 s and 0.0086 s for steady-state and transient cases,respectively.These results confirm that the proposed method can accurately and efficiently identify concurrent actuator fault for an engine operating under either transient or steady-state conditions,even in the case of a sudden malfunction.The research results emonstrate the potential benefit to emergency response capabilities by introducing this method of monitoring the health of aero engines.展开更多
The potential of 2-amino-1-propanol(AP)as a novel depressant in selectively floating ilmenite from titanaugite under weakly acidic conditions was investigated.Micro-flotation results show that AP significantly reduces...The potential of 2-amino-1-propanol(AP)as a novel depressant in selectively floating ilmenite from titanaugite under weakly acidic conditions was investigated.Micro-flotation results show that AP significantly reduces the recovery of titanaugite while having no evident impact on ilmenite flotation.Subsequent bench-scale flotation tests further confirm a remarkable improvement in separation efficiency upon the introduction of AP.Contact angle and adsorption tests reveal a stronger affinity of AP towards the titanaugite surface in comparison to ilmenite.Zeta potential measurements and X-ray photoelectron spectroscopy(XPS)analyses exhibit favorable adsorption characteristics of AP on titanaugite,resulting from a synergy of electrostatic attraction and chemical interaction.In contrast,electrostatic repulsion hinders any significant interaction between AP and the ilmenite surface.These findings highlight the potential of AP as a highly efficient depressant for ilmenite flotation,paving the way for reduced reliance on sulfuric acid in the industry.展开更多
Although time-dependent deformation of geomaterials underpins slope-failure prediction models,the influence of strain rate on shearing strength and deformation behavior of loess remains unclear.The consolidated undrai...Although time-dependent deformation of geomaterials underpins slope-failure prediction models,the influence of strain rate on shearing strength and deformation behavior of loess remains unclear.The consolidated undrained(CU)and drained(CD)triaxial testing elucidated the impact of strain rate(0.005–0.3 mm/min)on strength envelopes,deformation moduli,pore pressures,and dilatancy characteristics of unsaturated and quasi-saturated loess.Under drained conditions with a controlled matric suction of 50 kPa,increasing strain rates from 0.005 mm/min to 0.011 mm/min induced decreases in failure deviatoric stress(qf),initial deformation modulus(Ei),and cohesion(c),while friction angles remained unaffected.Specimens displayed initial contractive volumetric strains transitioning to dilation across varying confining pressures.Higher rates diminished contractive volumetric strains and drainage volumes,indicating reduced densification and strength in the shear zone.Under undrained conditions,both unsaturated and quasi-saturated(pore pressure coefficient B=0.75)loess exhibited deteriorating mechanical properties with increasing rates from 0.03 mm/min to 0.3 mm/min.For unsaturated loess,reduced contractive volumetric strains at higher rates manifested relatively looser structures in the pre-peak stress phase.The strength decrement in quasi-saturated loess arose from elevated excess porewater pressures diminishing effective stresses.Negative porewater pressures emerged in quasi-saturated loess at lower confining pressures and strain rates.Compared to previous studies,the qf and Ei exhibited rate sensitivity below threshold values before attaining minima with marginal subsequent influence.The underlying mechanism mirrors the transition from creep to accelerated deformation phase of landslides.展开更多
Rechargeable zinc(Zn)-ion batteries(RZIBs) with hydrogel electrolytes(HEs) have gained significant attention in the last decade owing to their high safety, low cost, sufficient material abundance, and superb environme...Rechargeable zinc(Zn)-ion batteries(RZIBs) with hydrogel electrolytes(HEs) have gained significant attention in the last decade owing to their high safety, low cost, sufficient material abundance, and superb environmental friendliness, which is extremely important for wearable energy storage applications. Given that HEs play a critical role in building flexible RZIBs, it is urgent to summarize the recent advances in this field and elucidate the design principles of HEs for practical applications. This review systematically presents the development history, recent advances in the material fundamentals, functional designs, challenges, and prospects of the HEs-based RZIBs. Firstly, the fundamentals, species, and flexible mechanisms of HEs are discussed, along with their compatibility with Zn anodes and various cathodes. Then, the functional designs of hydrogel electrolytes in harsh conditions are comprehensively discussed, including high/low/wide-temperature windows, mechanical deformations(e.g., bending, twisting, and straining), and damages(e.g., cutting, burning, and soaking). Finally, the remaining challenges and future perspectives for advancing HEs-based RZIBs are outlined.展开更多
In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical...In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock.In this paper,freeze-thaw cycles(temperature range of-20℃-20℃)were performed on the sandstones in different water immersion conditions(fully,partially and non-immersed in water).Then,computed tomography(CT)tests were conducted on the sandstones when the freeze-thaw number reached 0,5,10,15,20 and 30.Next,the effects of water immersion conditions on the microstructure deterioration of sandstone under freezethaw cycles were evaluated using CT spatial imaging,porosity and damage factor.Finally,focusing on the partially immersed condition,the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree.The results show that with increasing freeze-thaw number,the porosities and damage factors under fully and partially immersed conditions increase continuously,while those under non-immersed condition first increase and then remain approximately constant.The most severe freeze-thaw damage occurs in fully immersed condition,followed by partially immersed condition and finally non-immersed condition.Interestingly,the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone.For the same freeze-thaw number,the damage factor increases approximately linearly with increasing immersion volume rate,and the increasing immersion degree exacerbates the microstructure deterioration of sandstone.Moreover,the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates.展开更多
Let d(n;r_(1),q_(1),r_(2),q_(2))be the number of factorization n=n_(1)n_(2)satisfying n_i≡r_i(mod q_i)(i=1,2)andΔ(x;r_(1),q_(1),r_(2),q_(2))be the error term of the summatory function of d(n;r_(1),q_(1),r_(2),q_(2))...Let d(n;r_(1),q_(1),r_(2),q_(2))be the number of factorization n=n_(1)n_(2)satisfying n_i≡r_i(mod q_i)(i=1,2)andΔ(x;r_(1),q_(1),r_(2),q_(2))be the error term of the summatory function of d(n;r_(1),q_(1),r_(2),q_(2)).Suppose x≥(q_(1)q_(2))^(1+ε),1≤r_i≤q_i,and(r_i,q_i)=1(i=1,2).This paper studies the power moments and sign changes ofΔ(x;r_(1),q_(1),r_(2),q_(2)).We prove that for sufficiently large constant C,Δ(q_(1)q_(2)x:r_(1),q_(1),r_(2),q_(2))changes sign in the interval[T,T+C√T]for any large T.Meanwhile,we show that for small constants c and c,there exist infinitely many subintervals of length c√log^(-7)T in[T,2T]where±Δ(q_(1)q_(2)x:r_(1),q_(1),r_(2),q_(2))>cx^(1/4)always holds.展开更多
Ti(C,N)-Mo_(2)C-Ni cermet as alternative materials was explored for use in alkaline conditions,replacing the WC-Co cemented carbides,since Co is classified as a potentially carcinogenic substance and there is potentia...Ti(C,N)-Mo_(2)C-Ni cermet as alternative materials was explored for use in alkaline conditions,replacing the WC-Co cemented carbides,since Co is classified as a potentially carcinogenic substance and there is potential hazard of“hard metal disease”under the exposure to cobalt dust.The changes in microstructure,corrosion rate and volumetric loss rate of the two materials were compared under electrochemical corrosion and erosion-corrosion in alkaline environment.The results demonstrates that Ti(C,N)-Mo_(2)C-Ni cermet undergoes passivation when exposed to electrochemical corrosion of NaOH solution,resulting in a significant increase in oxygen content on the corroded surface.The corrosion rate of cermet is approximately one order of magnitude lower than that of the cemented carbide.Under the erosion-corrosion of an alkaline sand-water mixture,both the cermet and cemented carbide experience a gradual increase in volumetric loss rate with prolonging the erosion time.During erosion,the rim phase in cermet is fragile,so cracks easily penetrate it while the core phase remains intact.The medium-grained cemented carbide commonly demonstrates transgranular fracture mode,while in the fine-grained cemented carbide,cracks tend to propagate along phase boundaries.The erosive wear and damage caused by sand particles play a predominant role in the erosion-corrosion process of alkaline sand-water mixtures.This process represents an accelerated destructive phenomenon influenced and intensified by the combined effects of corrosion and erosion.It is confirmed that using cermet as an alternative anti-wear material to cemented carbides is feasible under alkaline conditions,and even better.展开更多
ZnO is a highly significant II-VI semiconductor known for its excellent optoelectronic properties,making it widely applicable and promising for use in light-emitting devices,solar cells,lasers,and photodetectors.The m...ZnO is a highly significant II-VI semiconductor known for its excellent optoelectronic properties,making it widely applicable and promising for use in light-emitting devices,solar cells,lasers,and photodetectors.The methods for preparing ZnO are diverse,and among them,the hydrothermal method is favored for its simplicity,ease of operation,and low cost,making it an optimal choice for ZnO single-crystal growth.Most studies investigating the effects of different hydrothermal experimental parameters on the morphology and performance of ZnO nano-materials typically focus on only 2—3 variable parameters,with few examining the impact of all possible experimental parameter changes on ZnO nano-mate-rials.The principles of the hydrothermal method and its advantages in nano-material preparation were briefly introduced in this article.The detailed discussion on the influence of various experimental parameters on the preparation of ZnO nano-materials was provided,which including reaction materials,Zn^(2+)/OH^(-)ratio,reaction time and temperature,additives,experimental equipment,and annealing conditions.The review co-vers how different experimental parameters affect the morphology and performance of the materials,as well as how different rare earth doping elements influence the performance of ZnO nano-materials.It is hoped that this work will contribute to future research on the hydrothermal synthesis of nano-materials.展开更多
Dear Editor,H_(∞)This letter develops a new framework for the robust stability and performance conditions as well as the relevant controller synthesis with respect to uncertain robot manipulators.There often exist mo...Dear Editor,H_(∞)This letter develops a new framework for the robust stability and performance conditions as well as the relevant controller synthesis with respect to uncertain robot manipulators.There often exist model uncertainties between the nominal model and the real robot manipulator and disturbances. Hence, dealing with their effects plays a crucial role in leading to high tracking performances, as discussed in [1]–[5].展开更多
In addition to the organic matter type,abundance,thermal maturity,and shale reservoir space,the preservation conditions of source rocks play a key factor in affecting the quantity and quality of retained hydrocarbons ...In addition to the organic matter type,abundance,thermal maturity,and shale reservoir space,the preservation conditions of source rocks play a key factor in affecting the quantity and quality of retained hydrocarbons in source rocks of lacustrine shale,yet this aspect has received little attention.This paper,based on the case analysis,explores how preservation conditions influence the enrichment of mobile hydrocarbons in shale oil.Research showns that good preservation conditions play three key roles.(1)Ensure the retention of sufficient light hydrocarbons(C_(1)–C_(13)),medium hydrocarbons(C_(14)–C_(25))and small molecular aromatics(including 1–2 benzene rings)in the formation,which enhances the fluidity and flow of shale oil;(2)Maintain a high energy field(abnormally high pressure),thus facilitating the maximum outflow of shale oil;(3)Ensure that the retained hydrocarbons have the miscible flow condition of multi-component hydrocarbons(light hydrocarbons,medium hydrocarbons,heavy hydrocarbons,and heteroatomic compounds),so that the heavy hydrocarbons(C_(25+))and heavy components(non-hydrocarbons and asphaltenes)have improved fluidity and maximum flow capacity.In conclusion,in addition to the advantages of organic matter type,abundance,thermal maturity,and reservoir space,good preservation conditions of shale layers are essential for the formation of economically viable shale oil reservoirs,which should be incorporated into the evaluation criteria of shale oil-rich areas/segments and considered a necessary factor when selecting favorable exploration targets.展开更多
Based on the environmental conditions for the growth and development of potatoes,the impact of climatic conditions on potato cultivation in Shangdu County was analyzed.Due to significant fluctuations in temperature du...Based on the environmental conditions for the growth and development of potatoes,the impact of climatic conditions on potato cultivation in Shangdu County was analyzed.Due to significant fluctuations in temperature during the seedling stage of potatoes,less precipitation,and uneven temporal and spatial distribution of precipitation,the yield of potatoes is unstable.Therefore,scientific planting suggestions and meteorological service countermeasures were proposed.展开更多
The influences of reaction temperature,duration,pressure,and catalyst concentration on the molecular transformation of residual slurry phase hydrocracking process were investigated.The molecular composition of the het...The influences of reaction temperature,duration,pressure,and catalyst concentration on the molecular transformation of residual slurry phase hydrocracking process were investigated.The molecular composition of the heteroatom compounds in the residue feedstock and its upgrading products were characterized using high-resolution Orbitrap mass spectrometry coupled with multiple ionization methods.The simultaneous promotion of cracking and hydrogenation reactions was observed with increasing of the reaction temperature and time.Specifically,there was a significant increase in the cracking degree of alkyl side chain,while the removal of low-condensation sulfur compounds such as sulfides and benzothiophenes was enhanced.In particular,the cracking reactions were more significantly facilitated by high temperatures,while an appropriately extended reaction time can result in the complete elimination of the aforementioned sulfur compounds with a lower degree of condensation.Under conditions of low hydrogen pressure and catalyst concentration,the products still exhibit a high relative abundance of easily convertible compounds such as sulfoxides,indicating a significant deficiency in the effectiveness of hydrogenation.The hydrogen pressure exhibits an optimal value,beyond which further increments have no effect on the composition and performance of the liquid product but can increase the yield of the liquid product.At significantly high catalyst concentration,the effect of desulfurization and deoxidation slightly diminishes,while the aromatic saturation of highly condensed compounds was notably enhanced.This hydrogenation saturation effect cannot be attained through manipulation of other operational parameters,thereby potentially benefiting subsequent product processing and utilization.This present study demonstrates a profound comprehension of the molecular-level residue slurry phase hydrocracking process,offering not only specific guide for process design and optimization but also valuable fundamental data for constructing reaction models at the molecular level.展开更多
This study investigates pedestrian safety perception in Ho Chi Minh City under mixed traffic conditions by evaluating comfort,crash risk,and injury risk perceptions in two scenarios:walking along and crossing multilan...This study investigates pedestrian safety perception in Ho Chi Minh City under mixed traffic conditions by evaluating comfort,crash risk,and injury risk perceptions in two scenarios:walking along and crossing multilane roads.Using visual experiments with 510 participants,the study identifies how sidewalk quality,obstructions,crossing infrastructure,and traffic conditions shape pedestrian experiences.Statistical modeling reveals that protected sidewalks and comprehensive crossing features significantly enhance perceived safety and comfort.Findings emphasize the need for improved pedestrian infrastructure and traffic calming in dense urban settings to support safer,more inclusive mobility under mixed traffic conditions like Vietnam.展开更多
We used observed concentrations of air pollutants,reanalyzed meteorological parameters,and results from the Goddard Earth Observing System Chemical Transport Model to examine the relationships between concentrations o...We used observed concentrations of air pollutants,reanalyzed meteorological parameters,and results from the Goddard Earth Observing System Chemical Transport Model to examine the relationships between concentrations of maximum daily 8-h average ozone(MDA8 O_(3)),PM_(2.5)(particulate matter with diameter of 2.5μm or less),and PM_(2.5)components and 2-m temperature(T2)or relative humidity(RH),as well as the effectiveness of precursor emission reductions on the control of O_(3) and PM_(2.5) in Beijing–Tianjin–Hebei(BTH)under different summertime temperature and humidity conditions.Both observed(simulated)MDA8 O_(3) and PM_(2.5) concentrations increased as T2 went up,with linear trends of 4.8(3.2)ppb℃^(−1) and 1.9(1.5)μg m^(−3)℃^(−1),respectively.Model results showed that the decreases in MDA8 O_(3) from precursor emission reductions were more sensitive to T2 than to RH.Reducing a larger proportion of volatile organic compound(VOC)emissions at higher T2 was more effective for the control of summertime O_(3) in BTH.For the control of summertime PM_(2.5) in BTH,reducing nitrogen oxides(NOx)combined with a small proportion of VOCs was the best measure.The magnitude of reduction in PM_(2.5) from reducing precursor emissions was more sensitive to RH than to T2,with the best efficiency at high RH.Results from this study are helpful for formulating effective policies to tackle O_(3) and PM_(2.5) pollution in BTH.展开更多
This paper focuses on the direct and inverse problems for a third-order self-adjoint differential operator with non-local potential and anti-periodic boundary conditions.Firstly,we obtain the expressions for the chara...This paper focuses on the direct and inverse problems for a third-order self-adjoint differential operator with non-local potential and anti-periodic boundary conditions.Firstly,we obtain the expressions for the characteristic function and resolvent of this third-order differential operator.Secondly,by using the expression for the resolvent of the operator,we prove that the spectrum for this operator consists of simple eigenvalues and a finite number of eigenvalues with multiplicity 2.Finally,we solve the inverse problem for this operator,which states that the non-local potential function can be reconstructed from four spectra.Specially,we prove the Ambarzumyan theorem and indicate that odd or even potential functions can be reconstructed by three spectra.展开更多
This paper critically re-examines the anthropocentric“Goldilocks Zone”paradigm that has dominated the search for extraterrestrial life.As of 2024,more than 5,500 exoplanets have been identified,yet only about 2%are ...This paper critically re-examines the anthropocentric“Goldilocks Zone”paradigm that has dominated the search for extraterrestrial life.As of 2024,more than 5,500 exoplanets have been identified,yet only about 2%are located within the traditionally defined habitable zone(National Aeronautics and Space Administration(NASA)Exoplanet Archive,2024;Kane et al.,2023).Moreover,the discovery of extremophiles-organisms thriving in high-radiation,extreme heat,or vacuum environments-demonstrates that the boundaries of life far exceed Earth-like conditions(Rothschild&Mancinelli,2001).展开更多
Drains play an important role in seepage control in geotechnical engineering.The enormous number and one-dimensional(1D)geometry of drainage holes make their nature difficult to be accurately modeled in groundwater fl...Drains play an important role in seepage control in geotechnical engineering.The enormous number and one-dimensional(1D)geometry of drainage holes make their nature difficult to be accurately modeled in groundwater flow simulation.It has been well understood that drains function by presenting discharge boundaries,which can be characterized by water head,no-flux,unilateral or mixed water head-unilateral boundary condition.It has been found after years of practices that the flow simulation may become erroneous if the transitions among the drain boundary conditions are not properly considered.For this,a rigorous algorithm is proposed in this study to detect the onset of transitions among the water head,noflux and mixed water head-unilateral boundary conditions for downwards-drilled drainage holes,which theoretically completes the description of drain boundary conditions.After verification against a numerical example,the proposed algorithm is applied to numerical modeling of groundwater flow through a gravity dam foundation.The simulation shows that for hundreds of downwards-drilled drainage holes used to be prescribed with water head boundary condition,56%and 2%of them are transitioned to mixed water head-unilateral and no-flux boundary conditions,respectively.The phreatic surface around the drains will be overestimated by 25e33 m without the use of the mixed boundary condition.For the first time,this study underscores the importance of the mixed water head-unilateral boundary condition and the proposed transition algorithm in drain modeling,which may become more essential for simulation of transient flow because of groundwater dynamics.展开更多
The impacts of lateral boundary conditions(LBCs)provided by numerical models and data-driven networks on convective-scale ensemble forecasts are investigated in this study.Four experiments are conducted on the Hangzho...The impacts of lateral boundary conditions(LBCs)provided by numerical models and data-driven networks on convective-scale ensemble forecasts are investigated in this study.Four experiments are conducted on the Hangzhou RDP(19th Hangzhou Asian Games Research Development Project on Convective-scale Ensemble Prediction and Application)testbed,with the LBCs respectively sourced from National Centers for Environmental Prediction(NCEP)Global Forecast System(GFS)forecasts with 33 vertical levels(Exp_GFS),Pangu forecasts with 13 vertical levels(Exp_Pangu),Fuxi forecasts with 13 vertical levels(Exp_Fuxi),and NCEP GFS forecasts with the vertical levels reduced to 13(the same as those of Exp_Pangu and Exp_Fuxi)(Exp_GFSRDV).In general,Exp_Pangu performs comparably to Exp_GFS,while Exp_Fuxi shows slightly inferior performance compared to Exp_Pangu,possibly due to its less accurate large-scale predictions.Therefore,the ability of using data-driven networks to efficiently provide LBCs for convective-scale ensemble forecasts has been demonstrated.Moreover,Exp_GFSRDV has the worst convective-scale forecasts among the four experiments,which indicates the potential improvement of using data-driven networks for LBCs by increasing the vertical levels of the networks.However,the ensemble spread of the four experiments barely increases with lead time.Thus,each experiment has insufficient ensemble spread to present realistic forecast uncertainties,which will be investigated in a future study.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41176074,51209048,51379043,and 51409063)the High Technology Ship Scientific Research Project of Ministry of Industry and Information Technology of China(Grant No.G014613002)
文摘Different operating conditions （e.g. design and off-design） may lead to a significant difference in the hydrodynamics performance of a ship, especially in the total resistance and wake field of ships. This work investigated the hydrodynamic performance of the well-known KRISO 3600 TEU Container Ship （KCS） under three different operating conditions by means of Particle Image Velocimetry （P/V） and Computational Fluid Dynamics （CFD）. The comparison results show that the use of PIV to measure a ship＇s nominal wake field is an important method which has the advantages of being contactless and highly accurate. Acceptable agreements between the results obtained by the two different methods are achieved. Results indicate that the total resistances of the KCS model under two off-design conditions are 23.88% and 13.92% larger than that under the designed condition, respectively.
基金Foundation item： Supported by the National Natural Science Foundation of China （Grant Nos. 41176074, 51379043 and 51409063）Acknowledgement This project was supported by the National Natural Science Foundation of China （Grant Nos. 41176074,51379043 and 51409063） and was conducted in response to the great support received from a basic research project entitled ＂Multihull Ship Technology Key Laboratory of Fundamental Science for National Defence＂, which was conducted at Harbin Engineering University. The authors would like to extend their sincere gratitude to their colleagues in the towing tank laboratory.
文摘Experimental tests were conducted to evaluate the hydrodynamic performance of an L-type podded propulsor in straight-ahead motion and off-design conditions using an open-water measuring instrument developed by the authors for podded propulsors, a ship model towing tank, and under water particle image velocimetry （PIV） measurement systems. Under the three types of conditions, the main parameters of an L-type podded propulsor were measured, including the propeller thrust and torque, as well as the thrust, side force, and moment of the whole pod unit.In addition, the flow field on the section between the propeller and the strut was analyzed. Experimental results demonstrate that the dynamic azimuthing rate and direction and the turning direction affect the forces on the propeller and the whole pod unit. Forces are asymmetrically distributed between the left and right azimuthing directions because of the effect of propeller rotation. The findings of this study provide a foundation for further research on L-type podded propulsors.
基金support by the National Natural Science Foundation of China(Grant No.52402520)。
文摘Actuator faults can be critical in turbofan engines as they can lead to stall,surge,loss of thrust and failure of speed control.Thus,fault diagnosis of gas turbine actuators has attracted considerable attention,from both academia and industry.However,the extensive literature that exists on this topic does not address identifying the severity of actuator faults and focuses mainly on actuator fault detection and isolation.In addition,previous studies of actuator fault identification have not dealt with multiple concurrent faults in real time,especially when these are accompanied by sudden failures under dynamic conditions.This study develops component-level models for fault identification in four typical actuators used in high-bypass ratio turbofan engines under both dynamic and steady-state conditions and these are then integrated with the engine performance model developed by the authors.The research results reported here present a novel method of quantifying actuator faults using dynamic effect compensation.The maximum error for each actuator is less than0.06%and 0.07%,with average computational time of less than 0.0058 s and 0.0086 s for steady-state and transient cases,respectively.These results confirm that the proposed method can accurately and efficiently identify concurrent actuator fault for an engine operating under either transient or steady-state conditions,even in the case of a sudden malfunction.The research results emonstrate the potential benefit to emergency response capabilities by introducing this method of monitoring the health of aero engines.
基金supported by the National Key Research and Development Program of China(No.2019YFC1803501)the National Natural Science Foundation of China(No.52074357)+2 种基金the Natural Science Foundation of Hunan Province,China(No.2022JJ30713)the Vanadium Titanium Union Foundationthe Project of Technology Innovation Center for Comprehensive Utilization of Strategic Mineral Resources,Ministry of Natural Resources,China。
文摘The potential of 2-amino-1-propanol(AP)as a novel depressant in selectively floating ilmenite from titanaugite under weakly acidic conditions was investigated.Micro-flotation results show that AP significantly reduces the recovery of titanaugite while having no evident impact on ilmenite flotation.Subsequent bench-scale flotation tests further confirm a remarkable improvement in separation efficiency upon the introduction of AP.Contact angle and adsorption tests reveal a stronger affinity of AP towards the titanaugite surface in comparison to ilmenite.Zeta potential measurements and X-ray photoelectron spectroscopy(XPS)analyses exhibit favorable adsorption characteristics of AP on titanaugite,resulting from a synergy of electrostatic attraction and chemical interaction.In contrast,electrostatic repulsion hinders any significant interaction between AP and the ilmenite surface.These findings highlight the potential of AP as a highly efficient depressant for ilmenite flotation,paving the way for reduced reliance on sulfuric acid in the industry.
文摘Although time-dependent deformation of geomaterials underpins slope-failure prediction models,the influence of strain rate on shearing strength and deformation behavior of loess remains unclear.The consolidated undrained(CU)and drained(CD)triaxial testing elucidated the impact of strain rate(0.005–0.3 mm/min)on strength envelopes,deformation moduli,pore pressures,and dilatancy characteristics of unsaturated and quasi-saturated loess.Under drained conditions with a controlled matric suction of 50 kPa,increasing strain rates from 0.005 mm/min to 0.011 mm/min induced decreases in failure deviatoric stress(qf),initial deformation modulus(Ei),and cohesion(c),while friction angles remained unaffected.Specimens displayed initial contractive volumetric strains transitioning to dilation across varying confining pressures.Higher rates diminished contractive volumetric strains and drainage volumes,indicating reduced densification and strength in the shear zone.Under undrained conditions,both unsaturated and quasi-saturated(pore pressure coefficient B=0.75)loess exhibited deteriorating mechanical properties with increasing rates from 0.03 mm/min to 0.3 mm/min.For unsaturated loess,reduced contractive volumetric strains at higher rates manifested relatively looser structures in the pre-peak stress phase.The strength decrement in quasi-saturated loess arose from elevated excess porewater pressures diminishing effective stresses.Negative porewater pressures emerged in quasi-saturated loess at lower confining pressures and strain rates.Compared to previous studies,the qf and Ei exhibited rate sensitivity below threshold values before attaining minima with marginal subsequent influence.The underlying mechanism mirrors the transition from creep to accelerated deformation phase of landslides.
基金supported by the National Natural Science Foundation of China (22379038)Science Research Project of Hebei Education Department (JZX2024015)+4 种基金Shijiazhuang Science and Technology Plan Project (241791357A)Central Guidance for Local Science and Technology Development Funds Project (246Z4408G)Excellent Youth Research Innovation Team of Hebei University (QNTD202410)High-level Talents Research Start-Up Project of Hebei University (521100224223)Hebei Province Innovation Capability Enhancement Plan Project (22567620H)。
文摘Rechargeable zinc(Zn)-ion batteries(RZIBs) with hydrogel electrolytes(HEs) have gained significant attention in the last decade owing to their high safety, low cost, sufficient material abundance, and superb environmental friendliness, which is extremely important for wearable energy storage applications. Given that HEs play a critical role in building flexible RZIBs, it is urgent to summarize the recent advances in this field and elucidate the design principles of HEs for practical applications. This review systematically presents the development history, recent advances in the material fundamentals, functional designs, challenges, and prospects of the HEs-based RZIBs. Firstly, the fundamentals, species, and flexible mechanisms of HEs are discussed, along with their compatibility with Zn anodes and various cathodes. Then, the functional designs of hydrogel electrolytes in harsh conditions are comprehensively discussed, including high/low/wide-temperature windows, mechanical deformations(e.g., bending, twisting, and straining), and damages(e.g., cutting, burning, and soaking). Finally, the remaining challenges and future perspectives for advancing HEs-based RZIBs are outlined.
基金funding support from the National Natural Science Foundation of China(Grant No.12172019).
文摘In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock.In this paper,freeze-thaw cycles(temperature range of-20℃-20℃)were performed on the sandstones in different water immersion conditions(fully,partially and non-immersed in water).Then,computed tomography(CT)tests were conducted on the sandstones when the freeze-thaw number reached 0,5,10,15,20 and 30.Next,the effects of water immersion conditions on the microstructure deterioration of sandstone under freezethaw cycles were evaluated using CT spatial imaging,porosity and damage factor.Finally,focusing on the partially immersed condition,the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree.The results show that with increasing freeze-thaw number,the porosities and damage factors under fully and partially immersed conditions increase continuously,while those under non-immersed condition first increase and then remain approximately constant.The most severe freeze-thaw damage occurs in fully immersed condition,followed by partially immersed condition and finally non-immersed condition.Interestingly,the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone.For the same freeze-thaw number,the damage factor increases approximately linearly with increasing immersion volume rate,and the increasing immersion degree exacerbates the microstructure deterioration of sandstone.Moreover,the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates.
基金supported by the Talent Fund of Beijing Jiaotong University(No.2020RC012)NSFC(No.11871295),supported by NSFC(No.11971476),supported by NSFC(No.12071421)。
文摘Let d(n;r_(1),q_(1),r_(2),q_(2))be the number of factorization n=n_(1)n_(2)satisfying n_i≡r_i(mod q_i)(i=1,2)andΔ(x;r_(1),q_(1),r_(2),q_(2))be the error term of the summatory function of d(n;r_(1),q_(1),r_(2),q_(2)).Suppose x≥(q_(1)q_(2))^(1+ε),1≤r_i≤q_i,and(r_i,q_i)=1(i=1,2).This paper studies the power moments and sign changes ofΔ(x;r_(1),q_(1),r_(2),q_(2)).We prove that for sufficiently large constant C,Δ(q_(1)q_(2)x:r_(1),q_(1),r_(2),q_(2))changes sign in the interval[T,T+C√T]for any large T.Meanwhile,we show that for small constants c and c,there exist infinitely many subintervals of length c√log^(-7)T in[T,2T]where±Δ(q_(1)q_(2)x:r_(1),q_(1),r_(2),q_(2))>cx^(1/4)always holds.
基金Chongqing Light Alloy Materials and Processing Engineering Technology Research Center Open Fund Project(GCZX201903)Yunnan Province Major Science and Technology Special Project Plan(202302AA310038)Sichuan University-Suining Municipal-University Cooperation Project(2023CDSN-12)。
文摘Ti(C,N)-Mo_(2)C-Ni cermet as alternative materials was explored for use in alkaline conditions,replacing the WC-Co cemented carbides,since Co is classified as a potentially carcinogenic substance and there is potential hazard of“hard metal disease”under the exposure to cobalt dust.The changes in microstructure,corrosion rate and volumetric loss rate of the two materials were compared under electrochemical corrosion and erosion-corrosion in alkaline environment.The results demonstrates that Ti(C,N)-Mo_(2)C-Ni cermet undergoes passivation when exposed to electrochemical corrosion of NaOH solution,resulting in a significant increase in oxygen content on the corroded surface.The corrosion rate of cermet is approximately one order of magnitude lower than that of the cemented carbide.Under the erosion-corrosion of an alkaline sand-water mixture,both the cermet and cemented carbide experience a gradual increase in volumetric loss rate with prolonging the erosion time.During erosion,the rim phase in cermet is fragile,so cracks easily penetrate it while the core phase remains intact.The medium-grained cemented carbide commonly demonstrates transgranular fracture mode,while in the fine-grained cemented carbide,cracks tend to propagate along phase boundaries.The erosive wear and damage caused by sand particles play a predominant role in the erosion-corrosion process of alkaline sand-water mixtures.This process represents an accelerated destructive phenomenon influenced and intensified by the combined effects of corrosion and erosion.It is confirmed that using cermet as an alternative anti-wear material to cemented carbides is feasible under alkaline conditions,and even better.
文摘ZnO is a highly significant II-VI semiconductor known for its excellent optoelectronic properties,making it widely applicable and promising for use in light-emitting devices,solar cells,lasers,and photodetectors.The methods for preparing ZnO are diverse,and among them,the hydrothermal method is favored for its simplicity,ease of operation,and low cost,making it an optimal choice for ZnO single-crystal growth.Most studies investigating the effects of different hydrothermal experimental parameters on the morphology and performance of ZnO nano-materials typically focus on only 2—3 variable parameters,with few examining the impact of all possible experimental parameter changes on ZnO nano-mate-rials.The principles of the hydrothermal method and its advantages in nano-material preparation were briefly introduced in this article.The detailed discussion on the influence of various experimental parameters on the preparation of ZnO nano-materials was provided,which including reaction materials,Zn^(2+)/OH^(-)ratio,reaction time and temperature,additives,experimental equipment,and annealing conditions.The review co-vers how different experimental parameters affect the morphology and performance of the materials,as well as how different rare earth doping elements influence the performance of ZnO nano-materials.It is hoped that this work will contribute to future research on the hydrothermal synthesis of nano-materials.
基金support by “R&D Program for Forest Science Technology(RS-2024-0040 3460)” provided by Korea Forest Service(Korea Forestry Promotion Institute)
文摘Dear Editor,H_(∞)This letter develops a new framework for the robust stability and performance conditions as well as the relevant controller synthesis with respect to uncertain robot manipulators.There often exist model uncertainties between the nominal model and the real robot manipulator and disturbances. Hence, dealing with their effects plays a crucial role in leading to high tracking performances, as discussed in [1]–[5].
基金Supported by the National Natural Science Foundation of China(U22B6004)Project of PetroChina Research Institute of Petroleum Exploration and Development(2022yjcq03)Core Technology Key Project of China Petroleum Changqing Oilfield Company(KJZX2023-01).
文摘In addition to the organic matter type,abundance,thermal maturity,and shale reservoir space,the preservation conditions of source rocks play a key factor in affecting the quantity and quality of retained hydrocarbons in source rocks of lacustrine shale,yet this aspect has received little attention.This paper,based on the case analysis,explores how preservation conditions influence the enrichment of mobile hydrocarbons in shale oil.Research showns that good preservation conditions play three key roles.(1)Ensure the retention of sufficient light hydrocarbons(C_(1)–C_(13)),medium hydrocarbons(C_(14)–C_(25))and small molecular aromatics(including 1–2 benzene rings)in the formation,which enhances the fluidity and flow of shale oil;(2)Maintain a high energy field(abnormally high pressure),thus facilitating the maximum outflow of shale oil;(3)Ensure that the retained hydrocarbons have the miscible flow condition of multi-component hydrocarbons(light hydrocarbons,medium hydrocarbons,heavy hydrocarbons,and heteroatomic compounds),so that the heavy hydrocarbons(C_(25+))and heavy components(non-hydrocarbons and asphaltenes)have improved fluidity and maximum flow capacity.In conclusion,in addition to the advantages of organic matter type,abundance,thermal maturity,and reservoir space,good preservation conditions of shale layers are essential for the formation of economically viable shale oil reservoirs,which should be incorporated into the evaluation criteria of shale oil-rich areas/segments and considered a necessary factor when selecting favorable exploration targets.
文摘Based on the environmental conditions for the growth and development of potatoes,the impact of climatic conditions on potato cultivation in Shangdu County was analyzed.Due to significant fluctuations in temperature during the seedling stage of potatoes,less precipitation,and uneven temporal and spatial distribution of precipitation,the yield of potatoes is unstable.Therefore,scientific planting suggestions and meteorological service countermeasures were proposed.
基金supported by the National Key R&D Program of China(2021YFA1501200)the National Natural Science Foundation of China(NSFC U23B20169 and 22021004)the Project of R&D Department of CNPC(2020B-2011)。
文摘The influences of reaction temperature,duration,pressure,and catalyst concentration on the molecular transformation of residual slurry phase hydrocracking process were investigated.The molecular composition of the heteroatom compounds in the residue feedstock and its upgrading products were characterized using high-resolution Orbitrap mass spectrometry coupled with multiple ionization methods.The simultaneous promotion of cracking and hydrogenation reactions was observed with increasing of the reaction temperature and time.Specifically,there was a significant increase in the cracking degree of alkyl side chain,while the removal of low-condensation sulfur compounds such as sulfides and benzothiophenes was enhanced.In particular,the cracking reactions were more significantly facilitated by high temperatures,while an appropriately extended reaction time can result in the complete elimination of the aforementioned sulfur compounds with a lower degree of condensation.Under conditions of low hydrogen pressure and catalyst concentration,the products still exhibit a high relative abundance of easily convertible compounds such as sulfoxides,indicating a significant deficiency in the effectiveness of hydrogenation.The hydrogen pressure exhibits an optimal value,beyond which further increments have no effect on the composition and performance of the liquid product but can increase the yield of the liquid product.At significantly high catalyst concentration,the effect of desulfurization and deoxidation slightly diminishes,while the aromatic saturation of highly condensed compounds was notably enhanced.This hydrogenation saturation effect cannot be attained through manipulation of other operational parameters,thereby potentially benefiting subsequent product processing and utilization.This present study demonstrates a profound comprehension of the molecular-level residue slurry phase hydrocracking process,offering not only specific guide for process design and optimization but also valuable fundamental data for constructing reaction models at the molecular level.
文摘This study investigates pedestrian safety perception in Ho Chi Minh City under mixed traffic conditions by evaluating comfort,crash risk,and injury risk perceptions in two scenarios:walking along and crossing multilane roads.Using visual experiments with 510 participants,the study identifies how sidewalk quality,obstructions,crossing infrastructure,and traffic conditions shape pedestrian experiences.Statistical modeling reveals that protected sidewalks and comprehensive crossing features significantly enhance perceived safety and comfort.Findings emphasize the need for improved pedestrian infrastructure and traffic calming in dense urban settings to support safer,more inclusive mobility under mixed traffic conditions like Vietnam.
基金supported by the National Natural Science Foundation of China(Grant No.91744311).
文摘We used observed concentrations of air pollutants,reanalyzed meteorological parameters,and results from the Goddard Earth Observing System Chemical Transport Model to examine the relationships between concentrations of maximum daily 8-h average ozone(MDA8 O_(3)),PM_(2.5)(particulate matter with diameter of 2.5μm or less),and PM_(2.5)components and 2-m temperature(T2)or relative humidity(RH),as well as the effectiveness of precursor emission reductions on the control of O_(3) and PM_(2.5) in Beijing–Tianjin–Hebei(BTH)under different summertime temperature and humidity conditions.Both observed(simulated)MDA8 O_(3) and PM_(2.5) concentrations increased as T2 went up,with linear trends of 4.8(3.2)ppb℃^(−1) and 1.9(1.5)μg m^(−3)℃^(−1),respectively.Model results showed that the decreases in MDA8 O_(3) from precursor emission reductions were more sensitive to T2 than to RH.Reducing a larger proportion of volatile organic compound(VOC)emissions at higher T2 was more effective for the control of summertime O_(3) in BTH.For the control of summertime PM_(2.5) in BTH,reducing nitrogen oxides(NOx)combined with a small proportion of VOCs was the best measure.The magnitude of reduction in PM_(2.5) from reducing precursor emissions was more sensitive to RH than to T2,with the best efficiency at high RH.Results from this study are helpful for formulating effective policies to tackle O_(3) and PM_(2.5) pollution in BTH.
基金supported by the Tianjin Municipal Science and Technology Program of China(No.23JCZDJC00070)。
文摘This paper focuses on the direct and inverse problems for a third-order self-adjoint differential operator with non-local potential and anti-periodic boundary conditions.Firstly,we obtain the expressions for the characteristic function and resolvent of this third-order differential operator.Secondly,by using the expression for the resolvent of the operator,we prove that the spectrum for this operator consists of simple eigenvalues and a finite number of eigenvalues with multiplicity 2.Finally,we solve the inverse problem for this operator,which states that the non-local potential function can be reconstructed from four spectra.Specially,we prove the Ambarzumyan theorem and indicate that odd or even potential functions can be reconstructed by three spectra.
文摘This paper critically re-examines the anthropocentric“Goldilocks Zone”paradigm that has dominated the search for extraterrestrial life.As of 2024,more than 5,500 exoplanets have been identified,yet only about 2%are located within the traditionally defined habitable zone(National Aeronautics and Space Administration(NASA)Exoplanet Archive,2024;Kane et al.,2023).Moreover,the discovery of extremophiles-organisms thriving in high-radiation,extreme heat,or vacuum environments-demonstrates that the boundaries of life far exceed Earth-like conditions(Rothschild&Mancinelli,2001).
基金Financial support from the National Natural Science Foundation of China(Grant Nos.51925906 and U2340228)the Natural Science Foundation of Hubei Province(Grant No.2022CFA028)is acknowledged.
文摘Drains play an important role in seepage control in geotechnical engineering.The enormous number and one-dimensional(1D)geometry of drainage holes make their nature difficult to be accurately modeled in groundwater flow simulation.It has been well understood that drains function by presenting discharge boundaries,which can be characterized by water head,no-flux,unilateral or mixed water head-unilateral boundary condition.It has been found after years of practices that the flow simulation may become erroneous if the transitions among the drain boundary conditions are not properly considered.For this,a rigorous algorithm is proposed in this study to detect the onset of transitions among the water head,noflux and mixed water head-unilateral boundary conditions for downwards-drilled drainage holes,which theoretically completes the description of drain boundary conditions.After verification against a numerical example,the proposed algorithm is applied to numerical modeling of groundwater flow through a gravity dam foundation.The simulation shows that for hundreds of downwards-drilled drainage holes used to be prescribed with water head boundary condition,56%and 2%of them are transitioned to mixed water head-unilateral and no-flux boundary conditions,respectively.The phreatic surface around the drains will be overestimated by 25e33 m without the use of the mixed boundary condition.For the first time,this study underscores the importance of the mixed water head-unilateral boundary condition and the proposed transition algorithm in drain modeling,which may become more essential for simulation of transient flow because of groundwater dynamics.
基金supported by the Strategic Research and Consulting Project of the Chinese Academy of Engineering[grant number 2024-XBZD-14]the National Natural Science Foundation of China[grant numbers 42192553 and 41922036]the Fundamental Research Funds for the Central Universities–Cemac“GeoX”Interdisciplinary Program[grant number 020714380207]。
文摘The impacts of lateral boundary conditions(LBCs)provided by numerical models and data-driven networks on convective-scale ensemble forecasts are investigated in this study.Four experiments are conducted on the Hangzhou RDP(19th Hangzhou Asian Games Research Development Project on Convective-scale Ensemble Prediction and Application)testbed,with the LBCs respectively sourced from National Centers for Environmental Prediction(NCEP)Global Forecast System(GFS)forecasts with 33 vertical levels(Exp_GFS),Pangu forecasts with 13 vertical levels(Exp_Pangu),Fuxi forecasts with 13 vertical levels(Exp_Fuxi),and NCEP GFS forecasts with the vertical levels reduced to 13(the same as those of Exp_Pangu and Exp_Fuxi)(Exp_GFSRDV).In general,Exp_Pangu performs comparably to Exp_GFS,while Exp_Fuxi shows slightly inferior performance compared to Exp_Pangu,possibly due to its less accurate large-scale predictions.Therefore,the ability of using data-driven networks to efficiently provide LBCs for convective-scale ensemble forecasts has been demonstrated.Moreover,Exp_GFSRDV has the worst convective-scale forecasts among the four experiments,which indicates the potential improvement of using data-driven networks for LBCs by increasing the vertical levels of the networks.However,the ensemble spread of the four experiments barely increases with lead time.Thus,each experiment has insufficient ensemble spread to present realistic forecast uncertainties,which will be investigated in a future study.
