The experimental investigation of axial-flow pump has been rapidly developed to meet the needs of South-to-North Water Diversion Project of China.Owing to the boundary conditions of hub,blade tip clearance,much of the...The experimental investigation of axial-flow pump has been rapidly developed to meet the needs of South-to-North Water Diversion Project of China.Owing to the boundary conditions of hub,blade tip clearance,much of the physical phenomena and laws involved in this complex flow field can't be fully determined.The flow characteristics of the high efficiency axial-flow pump have been simulated by RNG k-e turbulence model and SIMPLEC arithmetic based on FLUENT software.Numerical results indicate that the data from the prediction show agreement with the experimental results,static pressure on pressure side of blades increases slightly at circumferential direction with radius increasing,and keep almost constant at the same radial while increasing gradually from inlet to exit on the suction side along flow direction at design conditions.The static pressure,total pressure and velocity at inlet,impeller outlet and vane outlet were measured by a five-hole probe,and a contrastive experiment was done to investigate the influence of hub leakage.The experimental results show that inlet flow is almost axial and the prerotation is very small at various conditions.The meridional velocity and circulation distribution are almost identical at impeller outlet at design conditions due to steady flow and high efficiency.The residual circulation exits at downstream of the guide vane,and the circumferential velocity component increases linearly from hub to tip at small flow rate conditions.Hub leakage in adjustable blades results in the decrease of the meridional velocity and circulation at blade exit near hub.The results of numerical simulation and experiments supply important flow structure information for the high-efficiency axial-flow pump.展开更多
The study was carried out in the Tahoua region at the market gardening sites of the Taddis 1 and 2 valley. Small-scale pumping irrigation is one of the most interesting uses of solar energy. The objective of this stud...The study was carried out in the Tahoua region at the market gardening sites of the Taddis 1 and 2 valley. Small-scale pumping irrigation is one of the most interesting uses of solar energy. The objective of this study is to carry out a comparative analysis of two dewatering pumping systems (Solar Kit and GMP) for water mobilization on a certain number of criteria such as sustainable use, economic aspect and performance. To achieve this, the adapted methodology consisted first of all in the development of a data collection tool in the field. Then flow measurements, estimation of fuel consumption, pressure height, etc., were carried out. Thus, the data collection involved a sample of 120 irrigators who had to use the two (2) types of pumping systems. The collected data were analyzed and processed with appropriate software. The results of the study show that the two pumping systems studied have strengths and constraints. Thus, the solar pumping system has a significant investment cost, very low maintenance and a low operating cost. On the other hand, the system with a generator has a relatively low investment cost (25 to 30 times less than solar), but a relatively high operating, upkeep and maintenance cost. He adds that these assets and constraints must be taken into consideration when an investment is made. This study shows that 74% of producers use GMP compared to 26% who use the Solar Kit. But in practice, the Solar Kit is more reliable for producers from the point of view of planted area, environmental management and investment costs, supply of fuel and lubricant. These results indicate better performance of the solar pumping system compared to GMP at the study sites.展开更多
Graphene,owing to its exceptional electronic,optical,thermal,and mechanical properties,has emerged as a highly promising material.Currently,the synthesis of large-area graphene films on metal substrates via chemical v...Graphene,owing to its exceptional electronic,optical,thermal,and mechanical properties,has emerged as a highly promising material.Currently,the synthesis of large-area graphene films on metal substrates via chemical vapor deposition remains the predominant approach for producing high-quality graphene.To realize the potential applications of graphene,it is essential to transfer graphene films to target substrates in a manner that is non-destructive,clean,and efficient,as this significantly affects the performance of graphene devices.This review examines the current methods for graphene transfer from three perspectives:non-destructive transfer,clean transfer,and high-efficiency transfer.It analyzes and compares the advancements and limitations of various transfer techniques.Finally,the review identifies the key challenges faced by current graphene transfer methods and anticipates future developmental prospects.展开更多
Through literature analysis and case study, the introduction history, variety selection (high bush, half high bush, low bush) and regional cultivation techniques of blueberry in China were summarized, and the practica...Through literature analysis and case study, the introduction history, variety selection (high bush, half high bush, low bush) and regional cultivation techniques of blueberry in China were summarized, and the practical effects of precision cultivation (water and fertilizer integration, wild planting) and under-forest economic model (forest-blueberry-fungus system, ecological tourism) were evaluated. It provided a technical reference for expanding the planting scale of blueberry and improving the fruit quality.展开更多
The addition of cold flow improvers(CFIs)is considered as the optimum strategy to improve the cold flow properties(CFPs)of diesel fuels,but this strategy is always limited by the required large dosage.To obtain low-do...The addition of cold flow improvers(CFIs)is considered as the optimum strategy to improve the cold flow properties(CFPs)of diesel fuels,but this strategy is always limited by the required large dosage.To obtain low-dosage and high-efficiency CFIs for diesel,1,2,3,6-tetrahydrophthalic anhydride(THPA)was introduced as a third and polar monomer to enhance the depressive effects of alkyl methacrylatetrans anethole copolymers(C_(14)MC-TA).The terpolymers of alkyl methacrylate-trans anethole-1,2,3,6-tetrahydrophthalic anhydride(C_(14)MC-TA-THPA)were synthesized and compared with the binary copolymers of C_(14)MC-TA and alkyl methacrylate-1,2,3,6-tetrahydrophthalic anhydride(C_(14)MC-THPA).Results showed that C_(14)MC-THPA achieved the best depressive effects on the cold filter plugging point(CFPP)and solid point(SP)by 11℃and 16℃at a dosage of 1250 mg/L and monomer ratio of 6:1,while 1500mg/L C_(14)MC-TA(1:1)reached the optimal depressive effects on the CFPP and SP by 12℃and 18℃.THPA introduction significantly improved the depressive effects of C_(14)MC-TA.Lower dosages of C_(14)MCTA-THPA in diesel exerted better improvement effects on the CFPP and SP than that of C_(14)MC-TA and C_(14)MC-THPA.When the monomer ratio and dosage were 6:0.6:0.4 and 1000 mg/L,the improvement effect of C_(14)MC-TA-THPA on diesel reached the optimum level,and the CFPP and SP were reduced by 13℃and 19℃,respectively.A 3D nonlinear surface diagram fitted by a mathematical model was also used for the first time to better understand the relationships of monomer ratios,dosages,and depressive effects of CFIs in diesel.Surface analysis results showed that C_(14)MC-TA-THPA achieved the optimum depressive effects at a monomer ratio of 6:0.66:0.34 and dosage of 1000 mg/L,and the CFPP and SP decreased by 14℃ and 19℃,respectively.The predicted results were consistent with the actual ones.Additionally,the improvement mechanism of these copolymers in diesel was also explored.展开更多
Coupled-waveguide devices are essential in photonic integrated circuits for coupling,polarization handling,and mode manipulation.However,the performance of these devices usually suffers from high wavelength and struct...Coupled-waveguide devices are essential in photonic integrated circuits for coupling,polarization handling,and mode manipulation.However,the performance of these devices usually suffers from high wavelength and structure sensitivity,which makes it challenging to realize broadband and reliable on-chip optical functions.Recently,topological pumping of edge states has emerged as a promising solution for implementing robust optical couplings.In this paper,we propose and experimentally demonstrate broadband on-chip mode manipulation with very large fabrication tolerance based on the Rice–Mele modeled silicon waveguide arrays.The Thouless pumping mechanism is employed in the design to implement broadband and robust mode conversion and multiplexing.The experimental results prove that various mode-order conversions with low insertion losses and intermodal crosstalk can be achieved over a broad bandwidth of 80 nm ranging from 1500 to 1580 nm.Thanks to such a topological design,the device has a remarkable fabrication tolerance of±70 nm for the structural deviations in waveguide width and gap distance,which is,to the best of our knowledge,the highest among the coupled-waveguide mode-handling devices reported so far.As a proof-of-concept experiment,we cascade the topological mode-order converters to form a four-channel mode-division multiplexer and demonstrate the transmission of a 200-Gb/s 16-quadrature amplitude modulation signal for each mode channel,with the bit error rates below the 7%forward error correction threshold of 3.8×10^(-3).We reveal the possibility of developing new classes of broadband and fabrication-tolerant coupled-waveguide devices with topological photonic approaches,which may find applications in many fields,including optical interconnects,quantum communications,and optical computing.展开更多
This research investigates the design and optimization of a photovoltaic(PV)water pumping system to address seasonal water demands across five locations with varying elevation heads.The systemdraws water froma deep we...This research investigates the design and optimization of a photovoltaic(PV)water pumping system to address seasonal water demands across five locations with varying elevation heads.The systemdraws water froma deep well with a static water level of 30mand a dynamic level of 50m,serving agricultural and livestock needs.The objective of this study is to accurately size a PV system that balances energy generation and demand while minimizing grid dependency.Meanwhile,the study presents a comprehensivemethodology to calculate flowrates,pumping power,daily energy consumption,and system capacity.Therefore,the PV system rating,energy output,and economic performance were evaluated using metrics such as discounted payback period(DPP),net present value(NPV),and sensitivity analysis.The results show that a 2.74 kWp PV system is optimal,producing 4767 kWh/year to meet the system’s annual energy demand of 4686 kWh.In summer,energy demand peaks at 1532.7 kWh,while in winter,it drops to 692.1 kWh.Meanwhile,flow rates range from 11.71 m^(3)/h at 57 m head to 10.49 m^(3)/h at 70 m head,demonstrating the system’s adaptability to diverse hydraulic conditions.Economic analysis reveals that at a 5%interest rate and an electricity price of$0.15/kWh,the NPV is$6981.82 with a DPP of 3.76 years.However,a 30%increase in electricity prices improves the NPV to$10,005.18 and shortens the DPP to 2.76 years,whereas a 20%interest rate reduces the NPV to$1038.79 and extends the DPP to 6.08 years.Nevertheless,the annual PV energy generation exceeds total energy demand by 81 kWh,reducing grid dependency and lowering electricity costs.Additionally,the PV system avoids approximately 3956.6 kg of CO_(2) emissions annually,underscoring its environmental benefits over traditional pumping systems.As a result,this study highlights the economic and environmental viability of PV-powered water pumping systems,offering actionable insights for sustainable energy solutions in agriculture.展开更多
In recent years,S-scheme heterojunctions have garnered significant attention,with their carrier trans-fer mechanism primarily understood as the recombination of less reactive photogenerated carriers while preserving t...In recent years,S-scheme heterojunctions have garnered significant attention,with their carrier trans-fer mechanism primarily understood as the recombination of less reactive photogenerated carriers while preserving the highly reactive ones.However,the detailed interfacial electron transfer process can vary slightly among different S-scheme heterojunctions.Here we design a well-structured S-scheme covalent organic framework(COF)/TiO_(2) heterojunction to explore its microscopic interfacial electron transfer pro-cesses.Notably,we identify a cross-interface secondary electron pumping phenomenon within the S-scheme heterojunction,leading to the formation of high-energy anti-Kasha excited states.This discovery deepens our understanding of the S-scheme charge transfer mechanism and suggests that the redox ca-pabilities of S-scheme heterojunctions exceed traditional expectations.Our findings provide new insights into the origins of the high activity observed in S-scheme heterojunctions and enhance our understanding of their electron transfer processes.展开更多
Background Acute Myocardial Infarction(AMI)is a critical and commonly encountered condition in the field of cardiovascular medicine.When AMI is complicated by cardiogenic shock(CS),the clinical scenario becomes signif...Background Acute Myocardial Infarction(AMI)is a critical and commonly encountered condition in the field of cardiovascular medicine.When AMI is complicated by cardiogenic shock(CS),the clinical scenario becomes significantly more complex and perilous,with a marked increase in patient mortality.Currently,traditional thera-peutic approaches such as intra-aortic balloon pumping(IABP)have demonstrated efficacy in improving myocardi-al perfusion and hemodynamics.However,the supportive capacity of IABP is limited in patients with severe heart failure.In recent years,extracorporeal membrane oxygenation(ECMO),as an advanced extracorporeal circulatory support technology,has been increasingly utilized in clinical practice,offering a novel therapeutic option for pa-tients with severe heart failure.This study aimed to investigate the clinical efficacy of combining IABP and ECMO in patients with AMI complicated by CS,evaluating its impact on myocardial injury,hemodynamic stability,and clinical outcomes.Methods This study retrospectively analyzed the clinical data of 52 patients with AMI compli-cated by CS admitted to our hospital between May 2023 and May 2024.Based on the treatment methods,the pa-tients were divided into an ECMO group(n=26)and a non-ECMO group(n=26).Post-treatment comparisons were made between the two groups regarding myocardial injury markers such as cardiac troponin I,lactate,and creatine kinase-MB,hemodynamic parameters such as mean arterial pressure,cardiac output,and central venous pressure,and the incidence of complications such as acute kidney injury,bleeding,infection.The primary endpoint of this study was the post-treatment mortality rate and the incidence of complications.Secondary endpoints included changes in myocardial injury markers[cardiac troponin I(cTnI),lactic acid(LAC),creatine kinase isoenzymes(CK-MB)]and improvements in hemodynamic parameters[mean arterial pressure(MAP),cardiac output(CO),central venous pressure(CVP)].The results of multivariate regression analyses were used to explore the incidence of EC-MO complications.Results After treatment,the levels of myocardial injury markers such as cTnI,LAC,and CK-MB in ECMO group were significantly lower than non-ECMO group(P<0.05);MAP and CO in ECMO group were significantly higher than non-ECMO group,while CVP was significantly lower(P<0.05);the mortality rate and the incidence of complications in ECMO group were lower than non-ECMO group(P<0.05).Further multivariate re-gression analysis showed that age,smoking,hyperlipidaemia and diabetes could affect the incidence of ECMO complications(P<0.05).Conclusions The combined use of IABP and ECMO exhibits substantial therapeutic benefits,including the mitigation of myocardial injury,enhancement of hemodynamic stability,and improvement in clinical prognosis among patients with AMI complicated by CS.Clinicians applying ECMO therapy should pay particular attention to older patients or those with concomitant diabetes mellitus or hyperlipidemia,as they might re-quire more intensive monitoring and prophylactic measures to mitigate the occurrence of complications.展开更多
A new scheme of coherent mutually pumped phase conjugate(MPPC)reflection that depends on the formation of self-pumped phase conjugate reflection of another beam has been demonstrated in a Cu:KNSBN crystal.The dependen...A new scheme of coherent mutually pumped phase conjugate(MPPC)reflection that depends on the formation of self-pumped phase conjugate reflection of another beam has been demonstrated in a Cu:KNSBN crystal.The dependences of the MPPC reflectivity on the intensity ratio of the two incident beams and on the incident position of the signal beam were measured.We obtain phase conjugate reflectivities of greater than 90%at 488nm.展开更多
The integration of large-scale renewable energy introduces frequency instability challenges due to inherent intermittency.While doubly-fed pumped storage units(DFPSUs)offer frequency regulation potential in pumping mo...The integration of large-scale renewable energy introduces frequency instability challenges due to inherent intermittency.While doubly-fed pumped storage units(DFPSUs)offer frequency regulation potential in pumping mode,conventional strategies fail to address hydraulic-mechanical coupling dynamics and operational constraints,limiting their effectiveness.This paper presents an innovative primary frequency control strategy for double-fed pumped storage units(DFPSUs)operating in pumpingmode,integrating an adaptive parameter calculation method.This method is constrained by operational speed and power limits,addressing key performance factors.A dynamic model that incorporates the reversible pump-turbine characteristics is developed to translate frequency deviations into coordinated adjustments in speed and power during pumping operations.The research thoroughly analyzes the influence of control parameters on the frequency response dynamics.Additionally,the paper introduces a deep reinforcement learning(DRL)-based optimization framework,which enables real-time tuning of control parameters in response to changing rotor speed and frequency states.This method strategicallymanages the utilization of kinetic energy while ensuring compliance with operational safety constraints.The effectiveness of the proposed strategy is validated through simulation studies conducted on a four-machine,two-area DFPSU system.These studies demonstrate the strategy’s potential for improving frequency regulation performance under a variety of operating conditions,highlighting its effectiveness in optimizing energy storage and frequency control in power grids.展开更多
We propose a novel scheme for the population and depletion of nuclear isomers.This scheme combines the γ photons with energiesà 10 keV emitted during the interaction of a contemporary high-intensity laser pulse ...We propose a novel scheme for the population and depletion of nuclear isomers.This scheme combines the γ photons with energiesà 10 keV emitted during the interaction of a contemporary high-intensity laser pulse with a plasma and one or multiple photon beams supplied by intense lasers.Owing to nonlinear effects,two-or multiphoton absorption dominates over the conventional multistep one-photon process for an optimized γ flash.Moreover,this nonlinear effect can be greatly enhanced with the help of externally supplied low-energy photons coming from another laser.These low-energy photons act such that the effective cross-section experienced by the γ photons becomes tunable,growing with the intensity I_(0) of the beam.Assuming I_(0)~10^(18) W·cm^(-2) for the photon beam,an effective cross-section as large as 10^(-21)-10^(-28) cm^(2) for the γ photons can be achieved.Thus,with state-of-the-art 10 PW laser facilities,the yields from two-photon absorption can reach 10^(6)-10^(9) isomers per shot for selected states that are separated from their ground state by E2 transitions.Similar yields for transitions with higher multipolarities can be accommodated by multiphoton absorption with additional photons provided.展开更多
In this paper,we present a high peak power passively Q-switched intracavity frequency-doubled green laser based on an efficient LED-pumped Nd:YAG dual-rod laser module.In quasi-continuous wave(QCW)running operation,th...In this paper,we present a high peak power passively Q-switched intracavity frequency-doubled green laser based on an efficient LED-pumped Nd:YAG dual-rod laser module.In quasi-continuous wave(QCW)running operation,the average output power of the fundamental laser at 1064 nm reaches as high as 20.98 W at a repetition rate of 50 Hz with a maximum single pulse energy of 419.6 mJ,corresponding to a maximum optical conversion efficiency of 38.8%and a slope efficiency of 41%.展开更多
Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback co...Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback control on nuclear spin precession in a metastability exchange optical pumping(MEOP)-based polarized^(3)He system.We analyze the effects of feedback theoretically and validate our predictions experimentally.With optimized feedback parameters,the spin coherence time T_(2)is extended by an order of magnitude.When the feedback strength surpasses a critical threshold,robust maser oscillations are spontaneously excited,demonstrating remarkable resistance to environmental noise and maintaining stable oscillation.This proof-of-principle experiment highlights the viability of MEOP-based^(3)He spin oscillators,especially in low-frequency domains.The operational simplicity and easy integration associated with MEOP-based systems make them particularly promising for fast,high-precision magnetic field measurements.展开更多
During high-speed operation,mixed-flow pumps are susceptible to cavitation,which destabilizes the internal flow,increases energy losses,and degrades hydraulic efficiency.To assess the effectiveness of blade perforatio...During high-speed operation,mixed-flow pumps are susceptible to cavitation,which destabilizes the internal flow,increases energy losses,and degrades hydraulic efficiency.To assess the effectiveness of blade perforation as a cavitation-mitigation strategy,in this study several mixed-flow pump models incorporating perforations were developed.Numerical simulations were performed for configurations with circular holes positioned at different locations along the blade leading edge,and the computational results were validated against experimental measurements.The findings indicate that the location of the perforations plays a decisive role in cavitation suppression.Moving from the blade rim toward the hub along the leading edge,the critical net positive suction head,NPSH_(cr),initially decreases and subsequently increases,while remaining consistently lower than that of the reference non-perforated configuration.The perforations promote the transfer of high-pressure fluid from the pressure side to the suction side of the blade,thereby alleviating local low-pressure regions.This pressure compensation significantly reduces the extent of low-pressure zones in the vicinity of the perforations,leading to a marked suppression of cavitation both locally and downstream of the perforated regions.展开更多
Decarbonising the building sector,particularly residential heating,represents a critical challenge for achieving carbon-neutral energy systems.Efficient solutions must integrate both technological performance and rene...Decarbonising the building sector,particularly residential heating,represents a critical challenge for achieving carbon-neutral energy systems.Efficient solutions must integrate both technological performance and renewable energy sources while considering operational constraints of existing systems.This study investigates a hybrid heating system combining a natural gas boiler(NGB)with an air-to-water heat pump(AWHP),evaluated through a combination of laboratory experiments and dynamic modelling.A prototype developed in the Electrical and Energy Engineering Laboratory enabled the characterization of both heat generators,the collection of experimental data,and the calibration of a MATLAB/Simulink model,including emissions and exhaust analyses.Sensitivity analyses were performed to identify optimal configurations for energy efficiency and system control,accounting for interactions between subsystems.Results highlight that hybridisation significantly improves primary energy efficiency and reduces fuel consumption compared to conventional NGB-only systems.Environmental performance,assessed through CO_(2) and NOx emissions and renewable energy integration,demonstrates the benefits of partial electrification in the residential sector.Economic assessment further quantifies decarbonization costs and fuel savings,illustrating tradeoffs between low-capital,moderate-performance systems and high-efficiency,high-renewable solutions requiring larger investments.The analysis shows that strategic decisions for residential decarbonisation cannot be separated from system-wide considerations,including control strategies,component integration,and economic feasibility.The study underlines the importance of hybrid and renewable-based solutions as pivotal pathways for energy transition in the residential building sector.展开更多
Nuclear reactor coolant pumps require frequent maintenance to ensure operational safety.One critical aspect of this maintenance is verifying the integrity of the mechanical sealing system.Due to the lack of an evaluat...Nuclear reactor coolant pumps require frequent maintenance to ensure operational safety.One critical aspect of this maintenance is verifying the integrity of the mechanical sealing system.Due to the lack of an evaluation criteria and an incomplete understanding of how end-face defects lead to failure,defective mechanical seals are often replaced empirically,which not only contributes to economic losses but also poses risks to reactor safety.To reveal the mechanism by which surface defects affect sealing performance,this study proposes a classification method for end-face defects based on the analysis of approximately one hundred used mechanical seals.A defect characterization model was established by extracting key features of the observed defects.The influence of these defects on sealing performance was analyzed using a liquid-thermal-solid coupling model.Changes in sealing gap,leakage rates,and film stiffness with respect to defect size,location,and other characteristics are discussed.This work contributes to a deeper understanding of defect failure mechanisms.These results can serve as a reference for evaluating defective seals.展开更多
To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-ge...To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-gear type hydraulicmotor pump as the research object.In COMSOL,a coupled heat transfer simulationmodel of themotor pump’s fluid-solid coupling is established,and the internal temperature field characteristics are analyzed.To improve the heat dissipation effect of the motor pump,it is proposed to arrange spoiler in the fan-shaped DC channel of the pump housing to enhance heat dissipation.Three types of spoilers,namely,wing-shaped,inclined rectangle-shaped,and wave-shaped,are designed.The simulation results show that when the motor pump operates under rated conditions,due to the poor heat dissipation environment inside the motor pump,the high-temperature areas of the motor pump are concentrated in the rotor and permanent magnet parts.After arranging the spoiler,the turbulent kinetic energy and vorticity in the fan-shaped DC channel of the pump housing are significantly enhanced.All three spoiler structures can reduce the maximum temperature of each component of the motor.According to the comprehensive performance evaluation criterion(PEC),the inclined rectangle-shaped structure has the best comprehensive heat transfer performance(PEC=1.114),while the wave-shaped structure has higher heat transfer efficiency but greater pressure loss.The wing-shaped structure has relatively limited enhancement effect on heat dissipation.This study systematically quantifies the influence of different spoiler structures on heat dissipation performance and flowresistance characteristics,providing a solution for enhancing the heat dissipation of the motor pump.展开更多
基金supported by National Hi-tech Research and Development Program of China(863 Program,Grant No.2007AA05Z207)National Science and Technology Support Scheme of China(Grant No.2008BAF34B10)Jiangsu Provincial Graduate Student Innovation Foundation of China(Grant No.CX08B_064Z)
文摘The experimental investigation of axial-flow pump has been rapidly developed to meet the needs of South-to-North Water Diversion Project of China.Owing to the boundary conditions of hub,blade tip clearance,much of the physical phenomena and laws involved in this complex flow field can't be fully determined.The flow characteristics of the high efficiency axial-flow pump have been simulated by RNG k-e turbulence model and SIMPLEC arithmetic based on FLUENT software.Numerical results indicate that the data from the prediction show agreement with the experimental results,static pressure on pressure side of blades increases slightly at circumferential direction with radius increasing,and keep almost constant at the same radial while increasing gradually from inlet to exit on the suction side along flow direction at design conditions.The static pressure,total pressure and velocity at inlet,impeller outlet and vane outlet were measured by a five-hole probe,and a contrastive experiment was done to investigate the influence of hub leakage.The experimental results show that inlet flow is almost axial and the prerotation is very small at various conditions.The meridional velocity and circulation distribution are almost identical at impeller outlet at design conditions due to steady flow and high efficiency.The residual circulation exits at downstream of the guide vane,and the circumferential velocity component increases linearly from hub to tip at small flow rate conditions.Hub leakage in adjustable blades results in the decrease of the meridional velocity and circulation at blade exit near hub.The results of numerical simulation and experiments supply important flow structure information for the high-efficiency axial-flow pump.
文摘The study was carried out in the Tahoua region at the market gardening sites of the Taddis 1 and 2 valley. Small-scale pumping irrigation is one of the most interesting uses of solar energy. The objective of this study is to carry out a comparative analysis of two dewatering pumping systems (Solar Kit and GMP) for water mobilization on a certain number of criteria such as sustainable use, economic aspect and performance. To achieve this, the adapted methodology consisted first of all in the development of a data collection tool in the field. Then flow measurements, estimation of fuel consumption, pressure height, etc., were carried out. Thus, the data collection involved a sample of 120 irrigators who had to use the two (2) types of pumping systems. The collected data were analyzed and processed with appropriate software. The results of the study show that the two pumping systems studied have strengths and constraints. Thus, the solar pumping system has a significant investment cost, very low maintenance and a low operating cost. On the other hand, the system with a generator has a relatively low investment cost (25 to 30 times less than solar), but a relatively high operating, upkeep and maintenance cost. He adds that these assets and constraints must be taken into consideration when an investment is made. This study shows that 74% of producers use GMP compared to 26% who use the Solar Kit. But in practice, the Solar Kit is more reliable for producers from the point of view of planted area, environmental management and investment costs, supply of fuel and lubricant. These results indicate better performance of the solar pumping system compared to GMP at the study sites.
基金supported by the National Key R&D Program of China(2020YFB2009002).
文摘Graphene,owing to its exceptional electronic,optical,thermal,and mechanical properties,has emerged as a highly promising material.Currently,the synthesis of large-area graphene films on metal substrates via chemical vapor deposition remains the predominant approach for producing high-quality graphene.To realize the potential applications of graphene,it is essential to transfer graphene films to target substrates in a manner that is non-destructive,clean,and efficient,as this significantly affects the performance of graphene devices.This review examines the current methods for graphene transfer from three perspectives:non-destructive transfer,clean transfer,and high-efficiency transfer.It analyzes and compares the advancements and limitations of various transfer techniques.Finally,the review identifies the key challenges faced by current graphene transfer methods and anticipates future developmental prospects.
文摘Through literature analysis and case study, the introduction history, variety selection (high bush, half high bush, low bush) and regional cultivation techniques of blueberry in China were summarized, and the practical effects of precision cultivation (water and fertilizer integration, wild planting) and under-forest economic model (forest-blueberry-fungus system, ecological tourism) were evaluated. It provided a technical reference for expanding the planting scale of blueberry and improving the fruit quality.
基金supported from the Natural Science Foundation Project of Shanghai(Nos.23ZR1425300 and 22ZR1426100)Experimental Technical Team Construction Project of Shanghai Education Commission(No.10110N230080)+1 种基金National Natural Science Foundation of China(No.22075183)Research and Innovation Project of Shanghai Municipal Education Commission(No.2023ZKZD54).
文摘The addition of cold flow improvers(CFIs)is considered as the optimum strategy to improve the cold flow properties(CFPs)of diesel fuels,but this strategy is always limited by the required large dosage.To obtain low-dosage and high-efficiency CFIs for diesel,1,2,3,6-tetrahydrophthalic anhydride(THPA)was introduced as a third and polar monomer to enhance the depressive effects of alkyl methacrylatetrans anethole copolymers(C_(14)MC-TA).The terpolymers of alkyl methacrylate-trans anethole-1,2,3,6-tetrahydrophthalic anhydride(C_(14)MC-TA-THPA)were synthesized and compared with the binary copolymers of C_(14)MC-TA and alkyl methacrylate-1,2,3,6-tetrahydrophthalic anhydride(C_(14)MC-THPA).Results showed that C_(14)MC-THPA achieved the best depressive effects on the cold filter plugging point(CFPP)and solid point(SP)by 11℃and 16℃at a dosage of 1250 mg/L and monomer ratio of 6:1,while 1500mg/L C_(14)MC-TA(1:1)reached the optimal depressive effects on the CFPP and SP by 12℃and 18℃.THPA introduction significantly improved the depressive effects of C_(14)MC-TA.Lower dosages of C_(14)MCTA-THPA in diesel exerted better improvement effects on the CFPP and SP than that of C_(14)MC-TA and C_(14)MC-THPA.When the monomer ratio and dosage were 6:0.6:0.4 and 1000 mg/L,the improvement effect of C_(14)MC-TA-THPA on diesel reached the optimum level,and the CFPP and SP were reduced by 13℃and 19℃,respectively.A 3D nonlinear surface diagram fitted by a mathematical model was also used for the first time to better understand the relationships of monomer ratios,dosages,and depressive effects of CFIs in diesel.Surface analysis results showed that C_(14)MC-TA-THPA achieved the optimum depressive effects at a monomer ratio of 6:0.66:0.34 and dosage of 1000 mg/L,and the CFPP and SP decreased by 14℃ and 19℃,respectively.The predicted results were consistent with the actual ones.Additionally,the improvement mechanism of these copolymers in diesel was also explored.
基金supported by the National Key R&D Program of China(Grant No.2023YFB2905503)the National Natural Science Foundation of China(Grant Nos.62035016,62105200,62475146,and 62341508).
文摘Coupled-waveguide devices are essential in photonic integrated circuits for coupling,polarization handling,and mode manipulation.However,the performance of these devices usually suffers from high wavelength and structure sensitivity,which makes it challenging to realize broadband and reliable on-chip optical functions.Recently,topological pumping of edge states has emerged as a promising solution for implementing robust optical couplings.In this paper,we propose and experimentally demonstrate broadband on-chip mode manipulation with very large fabrication tolerance based on the Rice–Mele modeled silicon waveguide arrays.The Thouless pumping mechanism is employed in the design to implement broadband and robust mode conversion and multiplexing.The experimental results prove that various mode-order conversions with low insertion losses and intermodal crosstalk can be achieved over a broad bandwidth of 80 nm ranging from 1500 to 1580 nm.Thanks to such a topological design,the device has a remarkable fabrication tolerance of±70 nm for the structural deviations in waveguide width and gap distance,which is,to the best of our knowledge,the highest among the coupled-waveguide mode-handling devices reported so far.As a proof-of-concept experiment,we cascade the topological mode-order converters to form a four-channel mode-division multiplexer and demonstrate the transmission of a 200-Gb/s 16-quadrature amplitude modulation signal for each mode channel,with the bit error rates below the 7%forward error correction threshold of 3.8×10^(-3).We reveal the possibility of developing new classes of broadband and fabrication-tolerant coupled-waveguide devices with topological photonic approaches,which may find applications in many fields,including optical interconnects,quantum communications,and optical computing.
文摘This research investigates the design and optimization of a photovoltaic(PV)water pumping system to address seasonal water demands across five locations with varying elevation heads.The systemdraws water froma deep well with a static water level of 30mand a dynamic level of 50m,serving agricultural and livestock needs.The objective of this study is to accurately size a PV system that balances energy generation and demand while minimizing grid dependency.Meanwhile,the study presents a comprehensivemethodology to calculate flowrates,pumping power,daily energy consumption,and system capacity.Therefore,the PV system rating,energy output,and economic performance were evaluated using metrics such as discounted payback period(DPP),net present value(NPV),and sensitivity analysis.The results show that a 2.74 kWp PV system is optimal,producing 4767 kWh/year to meet the system’s annual energy demand of 4686 kWh.In summer,energy demand peaks at 1532.7 kWh,while in winter,it drops to 692.1 kWh.Meanwhile,flow rates range from 11.71 m^(3)/h at 57 m head to 10.49 m^(3)/h at 70 m head,demonstrating the system’s adaptability to diverse hydraulic conditions.Economic analysis reveals that at a 5%interest rate and an electricity price of$0.15/kWh,the NPV is$6981.82 with a DPP of 3.76 years.However,a 30%increase in electricity prices improves the NPV to$10,005.18 and shortens the DPP to 2.76 years,whereas a 20%interest rate reduces the NPV to$1038.79 and extends the DPP to 6.08 years.Nevertheless,the annual PV energy generation exceeds total energy demand by 81 kWh,reducing grid dependency and lowering electricity costs.Additionally,the PV system avoids approximately 3956.6 kg of CO_(2) emissions annually,underscoring its environmental benefits over traditional pumping systems.As a result,this study highlights the economic and environmental viability of PV-powered water pumping systems,offering actionable insights for sustainable energy solutions in agriculture.
基金financially supported by the National Key Re-search and Development Program of China(No.2022YFB3803600)the National Natural Science Foundation of China(Nos.22202187,22361142704,22238009,U24A2071,and 22411540244)+3 种基金the National Postdoctoral Program for Innovative Talents(No.BX2021275)the Natural Science Foundation of Hubei Province of China(No.2022CFA001)the Project funded by China Postdoctoral Science Foundation(No.2022M712957)the Postdoctoral Funding Program of Hubei Province.
文摘In recent years,S-scheme heterojunctions have garnered significant attention,with their carrier trans-fer mechanism primarily understood as the recombination of less reactive photogenerated carriers while preserving the highly reactive ones.However,the detailed interfacial electron transfer process can vary slightly among different S-scheme heterojunctions.Here we design a well-structured S-scheme covalent organic framework(COF)/TiO_(2) heterojunction to explore its microscopic interfacial electron transfer pro-cesses.Notably,we identify a cross-interface secondary electron pumping phenomenon within the S-scheme heterojunction,leading to the formation of high-energy anti-Kasha excited states.This discovery deepens our understanding of the S-scheme charge transfer mechanism and suggests that the redox ca-pabilities of S-scheme heterojunctions exceed traditional expectations.Our findings provide new insights into the origins of the high activity observed in S-scheme heterojunctions and enhance our understanding of their electron transfer processes.
文摘Background Acute Myocardial Infarction(AMI)is a critical and commonly encountered condition in the field of cardiovascular medicine.When AMI is complicated by cardiogenic shock(CS),the clinical scenario becomes significantly more complex and perilous,with a marked increase in patient mortality.Currently,traditional thera-peutic approaches such as intra-aortic balloon pumping(IABP)have demonstrated efficacy in improving myocardi-al perfusion and hemodynamics.However,the supportive capacity of IABP is limited in patients with severe heart failure.In recent years,extracorporeal membrane oxygenation(ECMO),as an advanced extracorporeal circulatory support technology,has been increasingly utilized in clinical practice,offering a novel therapeutic option for pa-tients with severe heart failure.This study aimed to investigate the clinical efficacy of combining IABP and ECMO in patients with AMI complicated by CS,evaluating its impact on myocardial injury,hemodynamic stability,and clinical outcomes.Methods This study retrospectively analyzed the clinical data of 52 patients with AMI compli-cated by CS admitted to our hospital between May 2023 and May 2024.Based on the treatment methods,the pa-tients were divided into an ECMO group(n=26)and a non-ECMO group(n=26).Post-treatment comparisons were made between the two groups regarding myocardial injury markers such as cardiac troponin I,lactate,and creatine kinase-MB,hemodynamic parameters such as mean arterial pressure,cardiac output,and central venous pressure,and the incidence of complications such as acute kidney injury,bleeding,infection.The primary endpoint of this study was the post-treatment mortality rate and the incidence of complications.Secondary endpoints included changes in myocardial injury markers[cardiac troponin I(cTnI),lactic acid(LAC),creatine kinase isoenzymes(CK-MB)]and improvements in hemodynamic parameters[mean arterial pressure(MAP),cardiac output(CO),central venous pressure(CVP)].The results of multivariate regression analyses were used to explore the incidence of EC-MO complications.Results After treatment,the levels of myocardial injury markers such as cTnI,LAC,and CK-MB in ECMO group were significantly lower than non-ECMO group(P<0.05);MAP and CO in ECMO group were significantly higher than non-ECMO group,while CVP was significantly lower(P<0.05);the mortality rate and the incidence of complications in ECMO group were lower than non-ECMO group(P<0.05).Further multivariate re-gression analysis showed that age,smoking,hyperlipidaemia and diabetes could affect the incidence of ECMO complications(P<0.05).Conclusions The combined use of IABP and ECMO exhibits substantial therapeutic benefits,including the mitigation of myocardial injury,enhancement of hemodynamic stability,and improvement in clinical prognosis among patients with AMI complicated by CS.Clinicians applying ECMO therapy should pay particular attention to older patients or those with concomitant diabetes mellitus or hyperlipidemia,as they might re-quire more intensive monitoring and prophylactic measures to mitigate the occurrence of complications.
基金Supported by the Scioice Foundation of the State Education Commission for the Doctoral Program.
文摘A new scheme of coherent mutually pumped phase conjugate(MPPC)reflection that depends on the formation of self-pumped phase conjugate reflection of another beam has been demonstrated in a Cu:KNSBN crystal.The dependences of the MPPC reflectivity on the intensity ratio of the two incident beams and on the incident position of the signal beam were measured.We obtain phase conjugate reflectivities of greater than 90%at 488nm.
文摘The integration of large-scale renewable energy introduces frequency instability challenges due to inherent intermittency.While doubly-fed pumped storage units(DFPSUs)offer frequency regulation potential in pumping mode,conventional strategies fail to address hydraulic-mechanical coupling dynamics and operational constraints,limiting their effectiveness.This paper presents an innovative primary frequency control strategy for double-fed pumped storage units(DFPSUs)operating in pumpingmode,integrating an adaptive parameter calculation method.This method is constrained by operational speed and power limits,addressing key performance factors.A dynamic model that incorporates the reversible pump-turbine characteristics is developed to translate frequency deviations into coordinated adjustments in speed and power during pumping operations.The research thoroughly analyzes the influence of control parameters on the frequency response dynamics.Additionally,the paper introduces a deep reinforcement learning(DRL)-based optimization framework,which enables real-time tuning of control parameters in response to changing rotor speed and frequency states.This method strategicallymanages the utilization of kinetic energy while ensuring compliance with operational safety constraints.The effectiveness of the proposed strategy is validated through simulation studies conducted on a four-machine,two-area DFPSU system.These studies demonstrate the strategy’s potential for improving frequency regulation performance under a variety of operating conditions,highlighting its effectiveness in optimizing energy storage and frequency control in power grids.
基金supported by the Extreme Light Infrastructure Nuclear Physics(ELI-NP)Phase Ⅱ,a project co-financed by the Romanian Government and the European Union through the European Regional Development Fund—the Competitiveness Operational Programme(1/07.07.2016,COP,ID 1334)the Romanian Ministry of Research and Innovation:PN23210105(Phase 2,the Program Nucleu),ELI-RO grants Proiectul ELI-RO/RDI_2024_AMAP,ELI-RO_RDI_2024_LaLuThe,ELIRO_RDI_2024_SPARC+4 种基金ELI10/01.10.2020 of the Romanian Governmentthe European Union,the Romanian Governmentthe Health Program,within the project“Medical Applications of High-Power Lasers—Dr.LASER”SMIS Code:326475the IOSIN funds for research infrastructures of national interest.
文摘We propose a novel scheme for the population and depletion of nuclear isomers.This scheme combines the γ photons with energiesà 10 keV emitted during the interaction of a contemporary high-intensity laser pulse with a plasma and one or multiple photon beams supplied by intense lasers.Owing to nonlinear effects,two-or multiphoton absorption dominates over the conventional multistep one-photon process for an optimized γ flash.Moreover,this nonlinear effect can be greatly enhanced with the help of externally supplied low-energy photons coming from another laser.These low-energy photons act such that the effective cross-section experienced by the γ photons becomes tunable,growing with the intensity I_(0) of the beam.Assuming I_(0)~10^(18) W·cm^(-2) for the photon beam,an effective cross-section as large as 10^(-21)-10^(-28) cm^(2) for the γ photons can be achieved.Thus,with state-of-the-art 10 PW laser facilities,the yields from two-photon absorption can reach 10^(6)-10^(9) isomers per shot for selected states that are separated from their ground state by E2 transitions.Similar yields for transitions with higher multipolarities can be accommodated by multiphoton absorption with additional photons provided.
基金supported by the Nanjing University of Posts and Telecommunications Foundation,China(Grant Nos.JUH219002 and JUH219007)the Key R&D Program of Shandong Province,China(Grant No.2021CXGC010202)。
文摘In this paper,we present a high peak power passively Q-switched intracavity frequency-doubled green laser based on an efficient LED-pumped Nd:YAG dual-rod laser module.In quasi-continuous wave(QCW)running operation,the average output power of the fundamental laser at 1064 nm reaches as high as 20.98 W at a repetition rate of 50 Hz with a maximum single pulse energy of 419.6 mJ,corresponding to a maximum optical conversion efficiency of 38.8%and a slope efficiency of 41%.
基金supported by the National Natural Science Foundation of China(Grant No.U2230207)。
文摘Achieving long spin coherence times is crucial for quantum precision measurements,and closed-loop control techniques are often employed to accomplish this goal.Here,we demonstrate the impact of closed-loop feedback control on nuclear spin precession in a metastability exchange optical pumping(MEOP)-based polarized^(3)He system.We analyze the effects of feedback theoretically and validate our predictions experimentally.With optimized feedback parameters,the spin coherence time T_(2)is extended by an order of magnitude.When the feedback strength surpasses a critical threshold,robust maser oscillations are spontaneously excited,demonstrating remarkable resistance to environmental noise and maintaining stable oscillation.This proof-of-principle experiment highlights the viability of MEOP-based^(3)He spin oscillators,especially in low-frequency domains.The operational simplicity and easy integration associated with MEOP-based systems make them particularly promising for fast,high-precision magnetic field measurements.
基金the National Key Research and Development Project of China(No.2019YFB 2005300)the Natural Science Foundation of Jiangsu Province(No.BK20220609)the National Natural Science Foundation of China(Grant Nos.52109106,52409122,and 12272187).
文摘During high-speed operation,mixed-flow pumps are susceptible to cavitation,which destabilizes the internal flow,increases energy losses,and degrades hydraulic efficiency.To assess the effectiveness of blade perforation as a cavitation-mitigation strategy,in this study several mixed-flow pump models incorporating perforations were developed.Numerical simulations were performed for configurations with circular holes positioned at different locations along the blade leading edge,and the computational results were validated against experimental measurements.The findings indicate that the location of the perforations plays a decisive role in cavitation suppression.Moving from the blade rim toward the hub along the leading edge,the critical net positive suction head,NPSH_(cr),initially decreases and subsequently increases,while remaining consistently lower than that of the reference non-perforated configuration.The perforations promote the transfer of high-pressure fluid from the pressure side to the suction side of the blade,thereby alleviating local low-pressure regions.This pressure compensation significantly reduces the extent of low-pressure zones in the vicinity of the perforations,leading to a marked suppression of cavitation both locally and downstream of the perforated regions.
基金supported by European Commission and is a part of the HORIZON2020 project RES Heatfunding from the European Union’s Horizon 2020 program in the field of research and innovation on the basis of grant agreement No.956255.
文摘Decarbonising the building sector,particularly residential heating,represents a critical challenge for achieving carbon-neutral energy systems.Efficient solutions must integrate both technological performance and renewable energy sources while considering operational constraints of existing systems.This study investigates a hybrid heating system combining a natural gas boiler(NGB)with an air-to-water heat pump(AWHP),evaluated through a combination of laboratory experiments and dynamic modelling.A prototype developed in the Electrical and Energy Engineering Laboratory enabled the characterization of both heat generators,the collection of experimental data,and the calibration of a MATLAB/Simulink model,including emissions and exhaust analyses.Sensitivity analyses were performed to identify optimal configurations for energy efficiency and system control,accounting for interactions between subsystems.Results highlight that hybridisation significantly improves primary energy efficiency and reduces fuel consumption compared to conventional NGB-only systems.Environmental performance,assessed through CO_(2) and NOx emissions and renewable energy integration,demonstrates the benefits of partial electrification in the residential sector.Economic assessment further quantifies decarbonization costs and fuel savings,illustrating tradeoffs between low-capital,moderate-performance systems and high-efficiency,high-renewable solutions requiring larger investments.The analysis shows that strategic decisions for residential decarbonisation cannot be separated from system-wide considerations,including control strategies,component integration,and economic feasibility.The study underlines the importance of hybrid and renewable-based solutions as pivotal pathways for energy transition in the residential building sector.
基金Supported by National Natural Science Foundation of China(Grant No.51975315)National Science and Technology Major Project of China(Grant No.2019-IV-0020-0088).
文摘Nuclear reactor coolant pumps require frequent maintenance to ensure operational safety.One critical aspect of this maintenance is verifying the integrity of the mechanical sealing system.Due to the lack of an evaluation criteria and an incomplete understanding of how end-face defects lead to failure,defective mechanical seals are often replaced empirically,which not only contributes to economic losses but also poses risks to reactor safety.To reveal the mechanism by which surface defects affect sealing performance,this study proposes a classification method for end-face defects based on the analysis of approximately one hundred used mechanical seals.A defect characterization model was established by extracting key features of the observed defects.The influence of these defects on sealing performance was analyzed using a liquid-thermal-solid coupling model.Changes in sealing gap,leakage rates,and film stiffness with respect to defect size,location,and other characteristics are discussed.This work contributes to a deeper understanding of defect failure mechanisms.These results can serve as a reference for evaluating defective seals.
基金supported by the Henan Provincial Key Research and Development Special Project(251111220200)Natural Science Foundation of Henan Province Project(252300420446).
文摘To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-gear type hydraulicmotor pump as the research object.In COMSOL,a coupled heat transfer simulationmodel of themotor pump’s fluid-solid coupling is established,and the internal temperature field characteristics are analyzed.To improve the heat dissipation effect of the motor pump,it is proposed to arrange spoiler in the fan-shaped DC channel of the pump housing to enhance heat dissipation.Three types of spoilers,namely,wing-shaped,inclined rectangle-shaped,and wave-shaped,are designed.The simulation results show that when the motor pump operates under rated conditions,due to the poor heat dissipation environment inside the motor pump,the high-temperature areas of the motor pump are concentrated in the rotor and permanent magnet parts.After arranging the spoiler,the turbulent kinetic energy and vorticity in the fan-shaped DC channel of the pump housing are significantly enhanced.All three spoiler structures can reduce the maximum temperature of each component of the motor.According to the comprehensive performance evaluation criterion(PEC),the inclined rectangle-shaped structure has the best comprehensive heat transfer performance(PEC=1.114),while the wave-shaped structure has higher heat transfer efficiency but greater pressure loss.The wing-shaped structure has relatively limited enhancement effect on heat dissipation.This study systematically quantifies the influence of different spoiler structures on heat dissipation performance and flowresistance characteristics,providing a solution for enhancing the heat dissipation of the motor pump.
