Owing to their rolling friction,two-dimensional piston pumps are highly suitable as power components for electro-hydrostatic actuators(EHAs).These pumps are particularly advantageous for applications requiring high ef...Owing to their rolling friction,two-dimensional piston pumps are highly suitable as power components for electro-hydrostatic actuators(EHAs).These pumps are particularly advantageous for applications requiring high efficiency and reliability.However,the ambiguity surrounding the output flow characteristics of individual two-dimensional pumps poses a significant challenge in achieving precise closed-loop control of the EHA positions.To address this issue,this study established a comprehensive numerical model that included gap leakage to analyze the impact of leakage on the output flow characteristics of a two-dimensional piston pump.The validity of the numerical analysis was indirectly confirmed through meticulous measurements of the leakage and volumetric efficiency,ensuring robust results.The research findings indicated that,at lower pump speeds,leakage significantly affected the output flow rate,leading to potential inefficiencies in the system.Conversely,at higher rotational speeds,the impact of leakage was less pronounced,implying that the influence of leakage on the pump outlet flow must be carefully considered and managed for EHAs to perform position servo control.Additionally,the research demonstrates that two-dimensional motion does not have a unique or additional effect on pump leakage,thus simplifying the design considerations.Finally,the study concluded that maintaining an oil-filled leakage environment is beneficial because it helps reduce the impact of leakage and enhances the overall volumetric efficiency of the pump system.展开更多
BACKGROUND Proton pump inhibitors(PPIs)are among the most commonly prescribed medications globally.While concerns exist regarding their association with adverse infection-related outcomes,their impact on coronavirus d...BACKGROUND Proton pump inhibitors(PPIs)are among the most commonly prescribed medications globally.While concerns exist regarding their association with adverse infection-related outcomes,their impact on coronavirus disease 2019(COVID-19)severity remains uncertain.Emerging preclinical data suggest immunomodulatory and antiviral properties of PPIs,yet clinical evidence is conflicting.AIM To investigate whether chronic pre-hospital PPI use is associated with improved outcomes in patients hospitalized with COVID-19.METHODS We conducted a retrospective case-control study of adult inpatients with severe acute respiratory syndrome coronavirus 2 infection admitted to a racially and ethnically diverse communityhospital in Massachusetts from July 2021 to March 2022. Patients were stratified by documented pre-hospital PPIuse. The primary outcomes were intensive care unit (ICU) admission, need for invasive mechanical ventilation, andin-hospital mortality. Multivariable logistic regression was used to adjust for demographics, comorbidities, andtreatment variables. Significance was set at P < 0.05.RESULTSAmong 248 patients, 83 (33.4%) were on PPIs prior to hospitalization. Compared to non-users, PPI users hadsignificantly lower rates of ICU admission (13.3% vs 24.8%, P = 0.034), mechanical ventilation (13.3% vs 25.5%, P =0.027), and in-hospital mortality (6.0% vs 17.6%, P = 0.013). Multivariable analysis confirmed these associations:ICU admission [adjusted odds ratios (aOR): 0.462, 95%CI: 0.223–0.955], mechanical ventilation (aOR: 0.447, 95%CI:0.216–0.923), and mortality (aOR: 0.144, 95%CI: 0.031–0.677). Findings were consistent across demographic andcomorbidity strata.CONCLUSIONIn this diverse, real-world United States cohort, chronic pre-hospital PPI use was independently associated withlower odds of intensive care unit admission, mechanical ventilation, and mortality among COVID-19 inpatients.These findings highlight a potentially protective role of PPIs and support continued therapy in eligible patients.展开更多
To meet the demands for different supply voltage levels on SOC required by digital modules like CPU core and analog modules,a novel dual-output charge pump is proposed. The charge pump can output a step-up and a step-...To meet the demands for different supply voltage levels on SOC required by digital modules like CPU core and analog modules,a novel dual-output charge pump is proposed. The charge pump can output a step-up and a step-down voltage simultaneously with a high driving capability. The multiple gain pair technique was introduced to enhance its efficiency. The proposed co-use technology for capacitors and switch arrays reduced its cost. The charge pump was designed and fabricated in a TSMC 0.35μm mixed-signal CMOS process. A group of analytical equations were derived to model its static characteristics. A state-space model was derived to describe its small-signal dynamic behavior. Analytical predictions were verified by Spectre simulation and testing. The consistency of simulated results as well as test results with analytical predictions demonstrated the high precision of the derived analytical equations and the developed models.展开更多
The limit working parameters and service life of axial piston pump are determined by the carrying ability and lubrication characteristic of its key friction pairs. Therefore, the design and optimization of the key fri...The limit working parameters and service life of axial piston pump are determined by the carrying ability and lubrication characteristic of its key friction pairs. Therefore, the design and optimization of the key friction pairs are always a key and difficult problem in the research on axial piston pump. In the traditional research on piston/cylinder pair, the assembly relationship of piston and cylinder bore is simplified into ideal cylindrical pair, which can not be used to analyze the influences of radial micro-motion of piston on the distribution characteristics of oil-film thickness and pressure in details. In this paper, based on the lubrication theory of the oil film, a numerical simulation model is built, taking the influences of roughness, elastic deformation of piston and pressure-viscosity effect into consideration. With the simulation model, the dynamic characteristics of the radial micro-motion and pressure distribution are analyzed, and the relationships between radial micro-motion and carrying ability, lubrication condition, and abrasion are discussed. Furthermore, a model pump for pressure distribution measurement of oil film between piston and cylinder bore is designed. The comparison of simulation and experimental results of pressure distribution shows that the simulation model has high accuracy. The experiment and simulation results demonstrate that the pressure distribution has peak values that are much higher than the boundary pressure in the piston chamber due to the radial micro-motion, and the abrasion of piston takes place mainly on the hand close to piston ball. In addition, improvement of manufacturing roundness and straightness of piston and cylinder bore is helpful to improve the carrying ability of piston/cylinder pair. The proposed research provides references for designing piston/cylinder pair, and helps to prolong the service life of axial piston pump.展开更多
The existing research of the deep-well centrifugal pump mainly focuses on reduce the manufacturing cost and improve the pump performance, and how to combine above two aspects together is the most difficult and importa...The existing research of the deep-well centrifugal pump mainly focuses on reduce the manufacturing cost and improve the pump performance, and how to combine above two aspects together is the most difficult and important topic. In this study, the performances of the deep-well centrifugal pump with four different impeller outlet widths are studied by the numerical, theoretical and experimental methods in this paper. Two stages deep-well centrifugal pump equipped with different impellers are simulated employing the commercial CFD software to solve the Navier-Stokes equations for three-dimensional incompressible steady flow. The sensitivity analyses of the grid size and turbulence model have been performed to improve numerical accuracy. The flow field distributions are acquired and compared under the design operating conditions, including the static pressure, turbulence kinetic energy and velocity. The prototype is manufactured and tested to certify the numerical predicted performance. The numerical results of pump performance are higher than the test results, but their change trends have an acceptable agreement with each other. The performance results indicted that the oversize impeller outlet width leads to poor pump performances and increasing shaft power. Changing the performance of deep-well centrifugal pump by alter impeller outlet width is practicable and convenient, which is worth popularizing in the engineering application. The proposed research enhances the theoretical basis of pump design to improve the performance and reduce the manufacturing cost of deep-well centrifugal pump.展开更多
Driving a hydraulic cylinder directly by a closed-loop hydraulic pump is currently a key research area in the field of electro-hydraulic control technology,and it is the most direct means to improve the energy efficie...Driving a hydraulic cylinder directly by a closed-loop hydraulic pump is currently a key research area in the field of electro-hydraulic control technology,and it is the most direct means to improve the energy efficiency of an electro-hydraulic control system.So far,this technology has been well applied to the pump-controlled symmetric hydraulic cylinder.However,for the differential cylinder that is widely used in hydraulic technology,satisfactory results have not yet been achieved,due to the asymmetric flow constraint.Therefore,based on the principle of the asymmetric valve controlled asymmetric cylinder in valve controlled cylinder technology,an innovative idea for an asymmetric pump controlled asymmetric cylinder is put forward to address this problem.The scheme proposes to transform the oil suction window of the existing axial piston pump into two series windows.When in use,one window is connected to the rod chamber of the hydraulic cylinder and the other is linked with a low-pressure oil tank.This allows the differential cylinders to be directly controlled by changing the displacement or rotation speed of the pumps.Compared with the loop principle of offsetting the area difference of the differential cylinder through hydraulic valve using existing technology,this method may simplify the circuits and increase the energy efficiency of the system.With the software SimulationX,a hydraulic pump simulation model is set up,which examines the movement characteristics of an individual piston and the compressibility of oil,as well as the flow distribution area as it changes with the rotation angle.The pump structure parameters,especially the size of the unloading groove of the valve plate,are determined through digital simulation.All of the components of the series arranged three distribution-window axial piston pump are designed,based on the simulation analysis of the flow pulse characteristics of the pump,and then the prototype pump is made.The basic characteristics,such as the pressure,flow and noise of the pumps under different rotation speeds,are measured on the test bench.The test results verify the correctness of the principle.The proposed research lays a theoretical foundation for the further development of a new pump-controlled cylinder system.展开更多
Typically,liquid pump and liquids mixer are two separate devices.The invention of piezoelectric pump makes it possible to integrate the two devices.Hower,the existing piezoelectric mixing-pumps are larger because the ...Typically,liquid pump and liquids mixer are two separate devices.The invention of piezoelectric pump makes it possible to integrate the two devices.Hower,the existing piezoelectric mixing-pumps are larger because the need the space outside the chamber,and another shortcome of them is that they cannot adjust the mixing ratio of two liquids.In this paper,a new piezoelectric pump being capable of integrating mixer and pump is presented,based on the theory of the piezoelectric pump with the unsymmetrical slopes element（USE）.Besides the features of two inlets and one outlet,the piezoelectric pump has a rotatable unsymmetrical slopes element（RUSE）.When the pump works,two fluids flow into the inlet channels respectively.Then the RUSE controls the ratio of the two flows by adjusting the flow resistances of the two inlet channels.The fluids form a net flow due to the USE principle,while they are mixed into a homogeneous solution due to strong turbulence flow field and complex vortices generated by RUSE in the chamber.And then the solution flows through the outlet.Firstly,the theoretical analysis on this pump is performed.Meanwhile,the flow field in the chamber is calculated and simulated.And then,the relationship between the flows of the two channels and the rotating angle of the RUSE is set up and analyzed.Finally,experiment with the proposed pump is carried out to verify the numerical results.A RUSE with 20° slope angle is used in the experiment.Four sets of data are tested with the RUSE at the rotating angles of 0°,6°,11°,and 16°,respectively,corresponding to the numerical models.The experimental results show that the empirical data and the theoretical data share the same trend.The maximum error between the theoretical flow and the experimental flow is 11.14%,and the maximum error between the theoretical flow ratio of the two inlets and the experimental one is 2.5%.The experiment verified the theoretical analysis.The proposed research provides a new idea for integration of micro liquids mixer and micro liquids pump.展开更多
A three-dimensional model is used to investigate the mechanism of the South China Sea （SCS） winter counter-current （also known as the SCS Warm Current, or the SCSWC）, which flows against the wind. The model can re...A three-dimensional model is used to investigate the mechanism of the South China Sea （SCS） winter counter-current （also known as the SCS Warm Current, or the SCSWC）, which flows against the wind. The model can reproduce the structure of the band-like currents over the northern shelf of the SCS, including the westward coastal current and slop current, and the SCSWC sandwiched in between. Sensitivity experiments are designed to understand the different roles of Ekman pumping of the SCSWC at different longitude. The results show that the Ekman pumping drives the SCSWC in the west segment. In the east, it is not the Ekman pumping but the intrusion of the Kuroshio that drives the SCSWC.展开更多
Background There is great debate on the possible adverse interaction between proton pump inhibitors （PPIs） and clopidogrel. In ad- dition, whether the use of PPIs affects the clinical efficacy of ticagrelor remains ...Background There is great debate on the possible adverse interaction between proton pump inhibitors （PPIs） and clopidogrel. In ad- dition, whether the use of PPIs affects the clinical efficacy of ticagrelor remains less known. We aimed to determine the impact of concomi- tant administration of PPIs and clopidogrel or ticagrelor on clinical outcomes in patients with acute coronary syndrome （ACS） after percuta- neous coronary intervention （PCI）. Methods We retrospectively analyzed data fi＇om a ＂real world＂, international, multi-center registry between 2003 and 2014 （n = 15,401） and assessed the impact of concomitant administration of PPIs and clopidogrel or ticagrelor on 1-year composite primary endpoint （all-cause death, re-infarction, or severe bleeding） in patients with ACS after PCI. Results Of 9429 patients in the final cohort, 54.8% （n = 5165） was prescribed a PPI at discharge. Patients receiving a PPI were older, more often female, and were more likely to have comorbidities. No association was observed between PPI use and the primary endpoint for patients receiving clopidogrel （ad- justed HR： 1.036; 95% CI： 0.903-1.189） or ticagrelor （adjusted HR： 2.320; 95% CI： 0.875-45.151） （Pinteraction = 0.2004）. Similarly, use of a PPI was not associated with increased risk of all-cause death, re-infarction, or a decreased risk of severe bleeding for patients treated with either clopidogrel or ticagrelor. Conclusions In patients with ACS following PCI, concomitant use of PPIs was not associated with in- creased risk of adverse outcomes in patients receiving either clopidogrel or ticagrelor. Our findings indicate it is reasonable to use a PPI in combination with clopidogrel or ticagrelor, especially in patients with a higher risk of gastrointestinal bleeding.展开更多
The vortex pump is suitable for salt solution transportation.But the salt-out flow mechanism in the pump has not been understood fully.Salt-out layer formation and growth rate are closely related to crystal particle m...The vortex pump is suitable for salt solution transportation.But the salt-out flow mechanism in the pump has not been understood fully.Salt-out layer formation and growth rate are closely related to crystal particle motion and concentration distribution.Study on the particle hydrodynamic characteristics in the pump volute becomes a key problem,because the crystal particles are mainly distributing in this zone after they enter the pump.Phase Doppler particle analyzer(PDPA)is used to measure the two-phase flow field in a model pump volute to get more understanding about the salt-out phenomenon.The crystal particle velocities are obtained in all three peripheral,radial and axial directions.Particle size and particle number density(PND)measurements are also performed in the experiment.Results are presented and discussed along the radial direction under different pump operating conditions,as well as various axial measurement positions.It is found that particle velocity gradient of peripheral component varies with the pump discharge.There is a turning point of relation between peripheral velocity component and discharge.Radial flow velocity curves look like a saddle shape and velocity magnitudes are changing greatly with the discharge.The non-equilibrium velocity feature between liquid and solid phase on this direction is also remarkable.Particles flow into the impeller at radial position R〈I,and the axial velocity component increases in this region.The particle size curve shows an open-up parabola distribution.The largest particles are distributing near the casing peripheral wall.As flow rate increases,accordingly PND increases.It also grows up in the axial-outward direction towards the suction cover.Crystal particle aggregation phenomenon can be revealed from the analysis of particle size and PND distribution,and the aggregation region is determined as well.Research results are helpful for optimal design of this kind of pump preventing salt-out.展开更多
Baoying pumping station is a part of source pumping stations in East Route Project of South-to-North Water Transfer in China. Aiming at the characteristics of head varying, and making use of the function of pump adjus...Baoying pumping station is a part of source pumping stations in East Route Project of South-to-North Water Transfer in China. Aiming at the characteristics of head varying, and making use of the function of pump adjustable blade, mathematical models of pumping station optimal operation are established and solved with genetic algorithm. For different total pumping discharge and total pumping volume of water per day, in order to minimize pumping station operation cost, the number and operation duties of running pump units are respectively determined at different periods of time in a day. The results indicate that the saving of electrical cost is significantly effected by the schemes of adjusting blade angles and time-varying electrical price when pumping certain water volume of water per day, and compared with conventional operation schemes （namely, the schemes of pumping station operation at design blade angles based on certain pumping discharge）, the electrical cost is saved by 4.73%-31.27%. Also, compared with the electrical cost of conventional operation schemes, the electrical cost is saved by 2.03%-5.79% by the schemes of adjusting blade angles when pumping certain discharge.展开更多
Relative roles of Ekman transport and Ekman pumping in driving summer upwelling in the South China Sea （SCS） are examined using QuikSCAT scatterometer wind data. The major upwelling regions in the SCS are the coasta...Relative roles of Ekman transport and Ekman pumping in driving summer upwelling in the South China Sea （SCS） are examined using QuikSCAT scatterometer wind data. The major upwelling regions in the SCS are the coastal regions east and south- east of Vietnam （UESEV）, east and southeast of Hainan Island （UESEH）, and southeast of Guangdong province （USEG）. It is shown that the Ekman transport due to alongshore winds and Ekman pumping due to offshore wind stress curl play different roles in the three upwelling systems. In UESEV, Ekman pumping and Ekman transport are equally important in generating upwelling. The Ek- man transport increases linearly from 0.49 Sv in May to 1.23 Sv in August, while the Ekman pumping increases from 0.36 to 1.22 Sv during the same period. In UESEH, the mean estimates of Ekman transport and Ekman pumping are 0.14 and 0.07 Sv, respectively, indicating that 33% of the total wind-driven upwelling is due to Ekman pumping. In USEC~ the mean Ekman transport is 0.041 Sv with the peak occurring in July, while Ekman pumping is much smaller （0.003 on average）, indicating that the upwelling in this area is primarily driven by Ekman transport. In the summers of 2003 and 2007 following E1 Nifio-Southern Oscillation （ENSO） events, both Ekman transport and Ekman pumping decrease in UESEV due to the abnormally weak southwest monsoon. During the same events, however, Ekman transport is slightly enhanced and Ekman pumping is weakened in UESEH and USEG.展开更多
The flow patterns in the inlet and outlet conduits have a decisive effect on the safe, stable, and highly efficient operation of the pump in a large pumping station with low head. The numerical simulation of three-dim...The flow patterns in the inlet and outlet conduits have a decisive effect on the safe, stable, and highly efficient operation of the pump in a large pumping station with low head. The numerical simulation of three-dimensional （3D） turbulence flow in conduits is an important method to study the hydraulic performance and conduct an optimum hydraulic design for the conduits. With the analyses of the flow patterns in the inlet and outlet conduits, the boundary conditions of the numerical simulation for them can be determined. The main obtained conclusions are as follows： （i） Under normal operation conditions, there is essentially no pre-swirl flow at the impeller chamber inlet of an axial-flow pump system, based on which the boundary condition at the inlet conduit may be defined. （ii） The circulation at the guide vane outlet of an axial-flow pump system has a great effect on the hydraulic performance of the outlet conduit, and there is optimum circulation for the performance. Therefore, it is strongly suggested to design the guide vane according to the optimum circulation. （iii） The residual circulation at the guide vane outlet needs to be considered for the inlet boundary condition of the outlet conduit, and the value of the circulation may be measured in a specially designed test model.展开更多
During transportation of salt aqueous solutions with centrifugal pump,crystallization phenomenon is frequently encountered.For this kind of two-phase flow,it is difficult to be accurately modeled since there are vario...During transportation of salt aqueous solutions with centrifugal pump,crystallization phenomenon is frequently encountered.For this kind of two-phase flow,it is difficult to be accurately modeled since there are various medium properties and phase change characteristics.In view of experiment,several problems are hampering the implementation of precise measurement.Influences of blade outlet angle and medium temperature on crystallization rate were studied.Sodium sulfate solution was applied to simulate practical fluid in chemical industry.Particle image velocimetry(PIV)was employed to measure velocity distributions in rotating impeller.Crystallization processes in three impellers with different blade outlet angles were investigated.Relations among crystallization and flow parameters such as temperature and velocity were obtained.With the same blade wrap angle,when blade outlet angle is larger,diffusion of single flow passage gets stronger,relative velocity at blade outlet decreases and large scale vortex tends to appear near the blade working surface.For the impact of volume effect of particle phase on fluid viscosity,both liquid and solid phase velocities decrease with continual forming and growing of crystal particles.Velocity of solid phase is greater than that of liquid phase and its direction leans more closely to blade working surface.Solid particles tend to move towards blade working surface,as is more obvious in the impeller with large blade outlet angle.Therefore,collision between solid particles with stem part of blade working surface is more intensive in impeller with large blade outlet angle.Concerning transportation of salt aqueous solution,accurate PIV measurement is conducted in centrifugal impellers with different blade outlet angles.The results are useful and instructive in relevant engineering design and operation.展开更多
Biological carbon pumping(BCP)is a key process in which dissolved inorganic carbon in terrestrial aquatic ecosystems is utilized by aquatic autotrophs for photosynthesis and transformed into autochthonous organic matt...Biological carbon pumping(BCP)is a key process in which dissolved inorganic carbon in terrestrial aquatic ecosystems is utilized by aquatic autotrophs for photosynthesis and transformed into autochthonous organic matter(AOC).However,the mechanisms underlying BCP and the amount of generated AOC deposited effectively,are still poorly understood.Therefore,we conducted a systematic study combining modern hydrochemical monitoring and a sediment trap experiment in Fuxian Lake(Yunnan,SW China),the second-deepest plateau,oligotrophic freshwater lake in China.Temperature,pH,EC(electrical conductivity),DO(dissolved O2),[HCO3^-],[Ca^2+],SIc,partial CO2(pCO2)pressure,and carbon isotopic compositions of HCO3^-(δ^13CDIc)in water from Fuxian Lake all displayed distinct seasonal and vertical variations.This was especially apparent in an inverse correlation between pCO2 and DO,indicating that variations of hydrochemistry in the lake water were mainly controlled by the metabolism of the aquatic phototrophs.Furthermore,the lowest C/N ratios and highestδ^13Corg were recorded in the trap sediments.Analyses of the C/N ratio demonstrated that the proportions of AOC ranged from 30%to 100%of all OC,indicating that AOC was an important contributor to sedimentary organic matter(OC).It was calculated that the AOC flux in Fuxian Lake was 20.43 t C km^-2 in 2017.Therefore,AOC produced by carbonate weathering and aquatic photosynthesis could potentially be a significant carbon sink and may have an important contribution to solving the lack of carbon sinks in the global carbon cycle.展开更多
To investigate the relation of two different mutations to the outcome of partial external biliary diversion(PEBD)in severe bile salt export pump(BSEP)deficiency.METHODSMutations in the gene encoding BSEP leading to se...To investigate the relation of two different mutations to the outcome of partial external biliary diversion(PEBD)in severe bile salt export pump(BSEP)deficiency.METHODSMutations in the gene encoding BSEP leading to severe BSEP deficiency in two unrelated patients were identified by genomic sequencing.Native liver biopsies and transiently transfected human embryonic kidney(HEK)293 cells expressing either wild-type or mutated BSEP were subjected to immunofluorescence analysis to assess BSEP transporter localization.Bile acid profiles of patient and control bile samples were generated by ultra-performance liquid chromatography-tandem mass spectrometry.Wild-type and mutant BSEP transport of[<sup>3</sup>H]-labeled taurocholate(TC)and taurochenodeoxycholate(TCDC)was assessed by vesicular transport assays.RESULTSA girl(at 2 mo)presented with pruritus,jaundice and elevated serum bile salts(BS).PEBD stabilized liver function and prevented liver transplantation.She was heterozygous for the BSEP deletion p.T919del and the nonsense mutation p.R1235X.At the age of 17 years relative amounts of conjugated BS in her bile were normal,while total BS were less than 3%as compared to controls.An unrelated boy(age 1.5 years)presenting with severe pruritus and elevated serum BS was heterozygous for the same nonsense and another missense mutation,p.G1032R.PEBD failed to alleviate pruritus,eventually necessitating liver transplantation.BS concentration in bile was about 5%of controls.BS were mainly unconjugated with an unusual low amount of chenodeoxycholate derivatives(<5%).The patients’native liver biopsies showed canalicular BSEP expression.Both BSEP p.T919del and p.G1032R were localized in the plasma membrane in HEK293 cells.In vitro transport assays showed drastic reduction of transport by both mutations.Using purified recombinant BSEP as quantifiable reference,per-molecule transport rates for TC and TCDC were determined to be 3 and 2 BS molecules per wild-type BSEP transporter per minute,respectively.CONCLUSIONIn summary,our findings suggest that residual function of BSEP as well as substrate specificity influence the therapeutic effectiveness of PEBD in progressive familial intrahepatic cholestasis type 2(PFIC-2).展开更多
Mud pumping in subgrade beds under ballastless tracks will deteriorate the dynamic performance of infrastructure under railway lines,reduce the smoothness of the railway lines,and seriously affect the comfort and safe...Mud pumping in subgrade beds under ballastless tracks will deteriorate the dynamic performance of infrastructure under railway lines,reduce the smoothness of the railway lines,and seriously affect the comfort and safety of the trains.Due to their good mechanical properties,twocomponent polyurethane materials can be used for grouting to treat the fouling problems caused by ballastless track mud pumping.To develop a polyurethane formula suitable for the treatment of ballastless track mud pumping,we first performed indoor experiments to investigate the mechanical properties and gelation time of polyurethane elastomers synthesized with different raw material composition ratios,to determine an optimal composition ratio of the raw materials.Then,we conducted a dynamic field test to verify the remediation effect of the polyurethane material fabricated according to the design ratio.The results showed that polyurethane grouting material with the selected design ratios improved the contact characteristics between the surface layer of the subgrade bed and the base plate in the area,coordinating the dynamic response between the track structure and the subgrade bed.Thus,the obtained polyurethane grouting material could be used to renovate mud pumping areas of ballastless tracks with a good treatment effect.展开更多
In this paper,an NMOS output-capacitorless low-dropout regulator(OCL-LDO)featuring dual-loop regulation has been proposed,achieving fast transient response with low power consumption.An event-driven charge pump(CP)loo...In this paper,an NMOS output-capacitorless low-dropout regulator(OCL-LDO)featuring dual-loop regulation has been proposed,achieving fast transient response with low power consumption.An event-driven charge pump(CP)loop with the dynamic strength control(DSC),is proposed in this paper,which overcomes trade-offs inherent in conventional structures.The presented design addresses and resolves the large signal stability issue,which has been previously overlooked in the event-driven charge pump structure.This breakthrough allows for the full exploitation of the charge-pump structure's poten-tial,particularly in enhancing transient recovery.Moreover,a dynamic error amplifier is utilized to attain precise regulation of the steady-state output voltage,leading to favorable static characteristics.A prototype chip has been fabricated in 65 nm CMOS technology.The measurement results show that the proposed OCL-LDO achieves a 410 nA low quiescent current(IQ)and can recover within 30 ns under 200 mA/10 ns loading change.展开更多
To study the effect of guide vane outlet angle on pump performance and impeller radial force in an axial-flow heart pump, guide vane outlet angle/34 is considered to be 20°, 15°, 10°, 5° and 3°...To study the effect of guide vane outlet angle on pump performance and impeller radial force in an axial-flow heart pump, guide vane outlet angle/34 is considered to be 20°, 15°, 10°, 5° and 3° respectively. Based on ANSYS Fluent, numerical results of pump head and efficiency are validated by exper/ment results, in which Xanthan gum solutions are used with concentration of 0.06 wt. % as working fluid. Then, the effects of/34 on pump performance and impeller radial force are discussed, the errors of head and efficiency between test and simulation are within 5%. The results a/so indicate that the pump performance and efficiency are much better than those of other angles when guide vane outlet angle/34 is 10°, and the maximum variations in head and efficiency are 1.9% and 2.2%, respectively. With/34 increasing, the pulsation of radial force decreases firstly and then increases, when/34 is 10°, the minimum pulsation is 0. 0392N, which is about 80% of the maximum pulsation amplitude.展开更多
We analyzed the spectroscopic performances of Yb:YAG and developed an efficient room-temperature 20at.% Yb:YAG thin chip (6×6×0.5 mm) laser operating at 1.053μm pumped by Ti-sapphire laser operating at 940n...We analyzed the spectroscopic performances of Yb:YAG and developed an efficient room-temperature 20at.% Yb:YAG thin chip (6×6×0.5 mm) laser operating at 1.053μm pumped by Ti-sapphire laser operating at 940nm. Output power of 356 mW was obtained for an absorbed pump power of 784 mW. The slope efficiency was 69%, and the extrapolated threshold was 273mW. The slope efficiency was as high as 72% with absorbed pump power exceeding 730 mW.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.52205072).
文摘Owing to their rolling friction,two-dimensional piston pumps are highly suitable as power components for electro-hydrostatic actuators(EHAs).These pumps are particularly advantageous for applications requiring high efficiency and reliability.However,the ambiguity surrounding the output flow characteristics of individual two-dimensional pumps poses a significant challenge in achieving precise closed-loop control of the EHA positions.To address this issue,this study established a comprehensive numerical model that included gap leakage to analyze the impact of leakage on the output flow characteristics of a two-dimensional piston pump.The validity of the numerical analysis was indirectly confirmed through meticulous measurements of the leakage and volumetric efficiency,ensuring robust results.The research findings indicated that,at lower pump speeds,leakage significantly affected the output flow rate,leading to potential inefficiencies in the system.Conversely,at higher rotational speeds,the impact of leakage was less pronounced,implying that the influence of leakage on the pump outlet flow must be carefully considered and managed for EHAs to perform position servo control.Additionally,the research demonstrates that two-dimensional motion does not have a unique or additional effect on pump leakage,thus simplifying the design considerations.Finally,the study concluded that maintaining an oil-filled leakage environment is beneficial because it helps reduce the impact of leakage and enhances the overall volumetric efficiency of the pump system.
文摘BACKGROUND Proton pump inhibitors(PPIs)are among the most commonly prescribed medications globally.While concerns exist regarding their association with adverse infection-related outcomes,their impact on coronavirus disease 2019(COVID-19)severity remains uncertain.Emerging preclinical data suggest immunomodulatory and antiviral properties of PPIs,yet clinical evidence is conflicting.AIM To investigate whether chronic pre-hospital PPI use is associated with improved outcomes in patients hospitalized with COVID-19.METHODS We conducted a retrospective case-control study of adult inpatients with severe acute respiratory syndrome coronavirus 2 infection admitted to a racially and ethnically diverse communityhospital in Massachusetts from July 2021 to March 2022. Patients were stratified by documented pre-hospital PPIuse. The primary outcomes were intensive care unit (ICU) admission, need for invasive mechanical ventilation, andin-hospital mortality. Multivariable logistic regression was used to adjust for demographics, comorbidities, andtreatment variables. Significance was set at P < 0.05.RESULTSAmong 248 patients, 83 (33.4%) were on PPIs prior to hospitalization. Compared to non-users, PPI users hadsignificantly lower rates of ICU admission (13.3% vs 24.8%, P = 0.034), mechanical ventilation (13.3% vs 25.5%, P =0.027), and in-hospital mortality (6.0% vs 17.6%, P = 0.013). Multivariable analysis confirmed these associations:ICU admission [adjusted odds ratios (aOR): 0.462, 95%CI: 0.223–0.955], mechanical ventilation (aOR: 0.447, 95%CI:0.216–0.923), and mortality (aOR: 0.144, 95%CI: 0.031–0.677). Findings were consistent across demographic andcomorbidity strata.CONCLUSIONIn this diverse, real-world United States cohort, chronic pre-hospital PPI use was independently associated withlower odds of intensive care unit admission, mechanical ventilation, and mortality among COVID-19 inpatients.These findings highlight a potentially protective role of PPIs and support continued therapy in eligible patients.
文摘To meet the demands for different supply voltage levels on SOC required by digital modules like CPU core and analog modules,a novel dual-output charge pump is proposed. The charge pump can output a step-up and a step-down voltage simultaneously with a high driving capability. The multiple gain pair technique was introduced to enhance its efficiency. The proposed co-use technology for capacitors and switch arrays reduced its cost. The charge pump was designed and fabricated in a TSMC 0.35μm mixed-signal CMOS process. A group of analytical equations were derived to model its static characteristics. A state-space model was derived to describe its small-signal dynamic behavior. Analytical predictions were verified by Spectre simulation and testing. The consistency of simulated results as well as test results with analytical predictions demonstrated the high precision of the derived analytical equations and the developed models.
基金supported by National Natural Science Foundation of China(Grant No. 51075360)Doctoral Foundation of Ministry of Education of China(Grant No. 20090101110041)National Key Technology R&D Program of the Twelfth Five-year Plan of China(Grant No. 2011BAF09B03)
文摘The limit working parameters and service life of axial piston pump are determined by the carrying ability and lubrication characteristic of its key friction pairs. Therefore, the design and optimization of the key friction pairs are always a key and difficult problem in the research on axial piston pump. In the traditional research on piston/cylinder pair, the assembly relationship of piston and cylinder bore is simplified into ideal cylindrical pair, which can not be used to analyze the influences of radial micro-motion of piston on the distribution characteristics of oil-film thickness and pressure in details. In this paper, based on the lubrication theory of the oil film, a numerical simulation model is built, taking the influences of roughness, elastic deformation of piston and pressure-viscosity effect into consideration. With the simulation model, the dynamic characteristics of the radial micro-motion and pressure distribution are analyzed, and the relationships between radial micro-motion and carrying ability, lubrication condition, and abrasion are discussed. Furthermore, a model pump for pressure distribution measurement of oil film between piston and cylinder bore is designed. The comparison of simulation and experimental results of pressure distribution shows that the simulation model has high accuracy. The experiment and simulation results demonstrate that the pressure distribution has peak values that are much higher than the boundary pressure in the piston chamber due to the radial micro-motion, and the abrasion of piston takes place mainly on the hand close to piston ball. In addition, improvement of manufacturing roundness and straightness of piston and cylinder bore is helpful to improve the carrying ability of piston/cylinder pair. The proposed research provides references for designing piston/cylinder pair, and helps to prolong the service life of axial piston pump.
基金supported by National Natural Science Foundation of China (Grant Nos. 51279069,51109093)Jiangsu Provincial Natural Science Foundation of China (Grant Nos. BK2011503,BK2011505)
文摘The existing research of the deep-well centrifugal pump mainly focuses on reduce the manufacturing cost and improve the pump performance, and how to combine above two aspects together is the most difficult and important topic. In this study, the performances of the deep-well centrifugal pump with four different impeller outlet widths are studied by the numerical, theoretical and experimental methods in this paper. Two stages deep-well centrifugal pump equipped with different impellers are simulated employing the commercial CFD software to solve the Navier-Stokes equations for three-dimensional incompressible steady flow. The sensitivity analyses of the grid size and turbulence model have been performed to improve numerical accuracy. The flow field distributions are acquired and compared under the design operating conditions, including the static pressure, turbulence kinetic energy and velocity. The prototype is manufactured and tested to certify the numerical predicted performance. The numerical results of pump performance are higher than the test results, but their change trends have an acceptable agreement with each other. The performance results indicted that the oversize impeller outlet width leads to poor pump performances and increasing shaft power. Changing the performance of deep-well centrifugal pump by alter impeller outlet width is practicable and convenient, which is worth popularizing in the engineering application. The proposed research enhances the theoretical basis of pump design to improve the performance and reduce the manufacturing cost of deep-well centrifugal pump.
基金supported by National Natural Science Foundation of China (Grant No. 50775156)Open Fund of The State Key Lab of Fluid Power Transmission and Control of Zhejiang University, China (Grant No. GZKF-2008006)
文摘Driving a hydraulic cylinder directly by a closed-loop hydraulic pump is currently a key research area in the field of electro-hydraulic control technology,and it is the most direct means to improve the energy efficiency of an electro-hydraulic control system.So far,this technology has been well applied to the pump-controlled symmetric hydraulic cylinder.However,for the differential cylinder that is widely used in hydraulic technology,satisfactory results have not yet been achieved,due to the asymmetric flow constraint.Therefore,based on the principle of the asymmetric valve controlled asymmetric cylinder in valve controlled cylinder technology,an innovative idea for an asymmetric pump controlled asymmetric cylinder is put forward to address this problem.The scheme proposes to transform the oil suction window of the existing axial piston pump into two series windows.When in use,one window is connected to the rod chamber of the hydraulic cylinder and the other is linked with a low-pressure oil tank.This allows the differential cylinders to be directly controlled by changing the displacement or rotation speed of the pumps.Compared with the loop principle of offsetting the area difference of the differential cylinder through hydraulic valve using existing technology,this method may simplify the circuits and increase the energy efficiency of the system.With the software SimulationX,a hydraulic pump simulation model is set up,which examines the movement characteristics of an individual piston and the compressibility of oil,as well as the flow distribution area as it changes with the rotation angle.The pump structure parameters,especially the size of the unloading groove of the valve plate,are determined through digital simulation.All of the components of the series arranged three distribution-window axial piston pump are designed,based on the simulation analysis of the flow pulse characteristics of the pump,and then the prototype pump is made.The basic characteristics,such as the pressure,flow and noise of the pumps under different rotation speeds,are measured on the test bench.The test results verify the correctness of the principle.The proposed research lays a theoretical foundation for the further development of a new pump-controlled cylinder system.
基金supported by National Natural Science Foundation of China (Grant No. 50735002, Grant No. 50775109, and Grant No. 51075201)
文摘Typically,liquid pump and liquids mixer are two separate devices.The invention of piezoelectric pump makes it possible to integrate the two devices.Hower,the existing piezoelectric mixing-pumps are larger because the need the space outside the chamber,and another shortcome of them is that they cannot adjust the mixing ratio of two liquids.In this paper,a new piezoelectric pump being capable of integrating mixer and pump is presented,based on the theory of the piezoelectric pump with the unsymmetrical slopes element（USE）.Besides the features of two inlets and one outlet,the piezoelectric pump has a rotatable unsymmetrical slopes element（RUSE）.When the pump works,two fluids flow into the inlet channels respectively.Then the RUSE controls the ratio of the two flows by adjusting the flow resistances of the two inlet channels.The fluids form a net flow due to the USE principle,while they are mixed into a homogeneous solution due to strong turbulence flow field and complex vortices generated by RUSE in the chamber.And then the solution flows through the outlet.Firstly,the theoretical analysis on this pump is performed.Meanwhile,the flow field in the chamber is calculated and simulated.And then,the relationship between the flows of the two channels and the rotating angle of the RUSE is set up and analyzed.Finally,experiment with the proposed pump is carried out to verify the numerical results.A RUSE with 20° slope angle is used in the experiment.Four sets of data are tested with the RUSE at the rotating angles of 0°,6°,11°,and 16°,respectively,corresponding to the numerical models.The experimental results show that the empirical data and the theoretical data share the same trend.The maximum error between the theoretical flow and the experimental flow is 11.14%,and the maximum error between the theoretical flow ratio of the two inlets and the experimental one is 2.5%.The experiment verified the theoretical analysis.The proposed research provides a new idea for integration of micro liquids mixer and micro liquids pump.
基金The Knowledge Innovation Program of the Chinese Academy of Sciences under contract No.KZCX1-YW-12-01the National Science Fund for Distinguished Young Scholars under contract No.40625017+1 种基金the National Natural Science Foundation of China(Key Program)under contract No.40830851the National Program on Key Basic Research Project(973Program)under contract No.2007CB816004
文摘A three-dimensional model is used to investigate the mechanism of the South China Sea （SCS） winter counter-current （also known as the SCS Warm Current, or the SCSWC）, which flows against the wind. The model can reproduce the structure of the band-like currents over the northern shelf of the SCS, including the westward coastal current and slop current, and the SCSWC sandwiched in between. Sensitivity experiments are designed to understand the different roles of Ekman pumping of the SCSWC at different longitude. The results show that the Ekman pumping drives the SCSWC in the west segment. In the east, it is not the Ekman pumping but the intrusion of the Kuroshio that drives the SCSWC.
文摘Background There is great debate on the possible adverse interaction between proton pump inhibitors （PPIs） and clopidogrel. In ad- dition, whether the use of PPIs affects the clinical efficacy of ticagrelor remains less known. We aimed to determine the impact of concomi- tant administration of PPIs and clopidogrel or ticagrelor on clinical outcomes in patients with acute coronary syndrome （ACS） after percuta- neous coronary intervention （PCI）. Methods We retrospectively analyzed data fi＇om a ＂real world＂, international, multi-center registry between 2003 and 2014 （n = 15,401） and assessed the impact of concomitant administration of PPIs and clopidogrel or ticagrelor on 1-year composite primary endpoint （all-cause death, re-infarction, or severe bleeding） in patients with ACS after PCI. Results Of 9429 patients in the final cohort, 54.8% （n = 5165） was prescribed a PPI at discharge. Patients receiving a PPI were older, more often female, and were more likely to have comorbidities. No association was observed between PPI use and the primary endpoint for patients receiving clopidogrel （ad- justed HR： 1.036; 95% CI： 0.903-1.189） or ticagrelor （adjusted HR： 2.320; 95% CI： 0.875-45.151） （Pinteraction = 0.2004）. Similarly, use of a PPI was not associated with increased risk of all-cause death, re-infarction, or a decreased risk of severe bleeding for patients treated with either clopidogrel or ticagrelor. Conclusions In patients with ACS following PCI, concomitant use of PPIs was not associated with in- creased risk of adverse outcomes in patients receiving either clopidogrel or ticagrelor. Our findings indicate it is reasonable to use a PPI in combination with clopidogrel or ticagrelor, especially in patients with a higher risk of gastrointestinal bleeding.
基金supported by National Natural Science Foundation of China(Grant No.50476068)Jiangsu Provincial Postgraduate Cultivation Innovation Project of China(Grant No.CX07B_093z)
文摘The vortex pump is suitable for salt solution transportation.But the salt-out flow mechanism in the pump has not been understood fully.Salt-out layer formation and growth rate are closely related to crystal particle motion and concentration distribution.Study on the particle hydrodynamic characteristics in the pump volute becomes a key problem,because the crystal particles are mainly distributing in this zone after they enter the pump.Phase Doppler particle analyzer(PDPA)is used to measure the two-phase flow field in a model pump volute to get more understanding about the salt-out phenomenon.The crystal particle velocities are obtained in all three peripheral,radial and axial directions.Particle size and particle number density(PND)measurements are also performed in the experiment.Results are presented and discussed along the radial direction under different pump operating conditions,as well as various axial measurement positions.It is found that particle velocity gradient of peripheral component varies with the pump discharge.There is a turning point of relation between peripheral velocity component and discharge.Radial flow velocity curves look like a saddle shape and velocity magnitudes are changing greatly with the discharge.The non-equilibrium velocity feature between liquid and solid phase on this direction is also remarkable.Particles flow into the impeller at radial position R〈I,and the axial velocity component increases in this region.The particle size curve shows an open-up parabola distribution.The largest particles are distributing near the casing peripheral wall.As flow rate increases,accordingly PND increases.It also grows up in the axial-outward direction towards the suction cover.Crystal particle aggregation phenomenon can be revealed from the analysis of particle size and PND distribution,and the aggregation region is determined as well.Research results are helpful for optimal design of this kind of pump preventing salt-out.
基金supported by Author Special Foundation of National Excellent Doctoral Dissertation of China (Grant No. 2007B41)Jiangsu Provincial Foundation of "333 Talents Engineering" of ChinaJiangsu Provincial Academic Header Foundation of Qinglan Engineering of China
文摘Baoying pumping station is a part of source pumping stations in East Route Project of South-to-North Water Transfer in China. Aiming at the characteristics of head varying, and making use of the function of pump adjustable blade, mathematical models of pumping station optimal operation are established and solved with genetic algorithm. For different total pumping discharge and total pumping volume of water per day, in order to minimize pumping station operation cost, the number and operation duties of running pump units are respectively determined at different periods of time in a day. The results indicate that the saving of electrical cost is significantly effected by the schemes of adjusting blade angles and time-varying electrical price when pumping certain water volume of water per day, and compared with conventional operation schemes （namely, the schemes of pumping station operation at design blade angles based on certain pumping discharge）, the electrical cost is saved by 4.73%-31.27%. Also, compared with the electrical cost of conventional operation schemes, the electrical cost is saved by 2.03%-5.79% by the schemes of adjusting blade angles when pumping certain discharge.
基金the China Scholarship Council for sponsoring Dakui Wang’svisit to Horn Point Laboratory of University of Marylandthe National Nature Science Foundation of China(Grants Nos.41076011,40531006,41106024 and 40976014)the National Basic Research Program of China(Grant No.2011CB403600)
文摘Relative roles of Ekman transport and Ekman pumping in driving summer upwelling in the South China Sea （SCS） are examined using QuikSCAT scatterometer wind data. The major upwelling regions in the SCS are the coastal regions east and south- east of Vietnam （UESEV）, east and southeast of Hainan Island （UESEH）, and southeast of Guangdong province （USEG）. It is shown that the Ekman transport due to alongshore winds and Ekman pumping due to offshore wind stress curl play different roles in the three upwelling systems. In UESEV, Ekman pumping and Ekman transport are equally important in generating upwelling. The Ek- man transport increases linearly from 0.49 Sv in May to 1.23 Sv in August, while the Ekman pumping increases from 0.36 to 1.22 Sv during the same period. In UESEH, the mean estimates of Ekman transport and Ekman pumping are 0.14 and 0.07 Sv, respectively, indicating that 33% of the total wind-driven upwelling is due to Ekman pumping. In USEC~ the mean Ekman transport is 0.041 Sv with the peak occurring in July, while Ekman pumping is much smaller （0.003 on average）, indicating that the upwelling in this area is primarily driven by Ekman transport. In the summers of 2003 and 2007 following E1 Nifio-Southern Oscillation （ENSO） events, both Ekman transport and Ekman pumping decrease in UESEV due to the abnormally weak southwest monsoon. During the same events, however, Ekman transport is slightly enhanced and Ekman pumping is weakened in UESEH and USEG.
基金Project supported by the Natural Science Foundation of Jiangsu Higher Education Institutions ofChina(No.12KJD570001)
文摘The flow patterns in the inlet and outlet conduits have a decisive effect on the safe, stable, and highly efficient operation of the pump in a large pumping station with low head. The numerical simulation of three-dimensional （3D） turbulence flow in conduits is an important method to study the hydraulic performance and conduct an optimum hydraulic design for the conduits. With the analyses of the flow patterns in the inlet and outlet conduits, the boundary conditions of the numerical simulation for them can be determined. The main obtained conclusions are as follows： （i） Under normal operation conditions, there is essentially no pre-swirl flow at the impeller chamber inlet of an axial-flow pump system, based on which the boundary condition at the inlet conduit may be defined. （ii） The circulation at the guide vane outlet of an axial-flow pump system has a great effect on the hydraulic performance of the outlet conduit, and there is optimum circulation for the performance. Therefore, it is strongly suggested to design the guide vane according to the optimum circulation. （iii） The residual circulation at the guide vane outlet needs to be considered for the inlet boundary condition of the outlet conduit, and the value of the circulation may be measured in a specially designed test model.
基金supported by National Natural Science Foundation of China(Grant No.50476068,Grant No.50776040)Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20060299008)
文摘During transportation of salt aqueous solutions with centrifugal pump,crystallization phenomenon is frequently encountered.For this kind of two-phase flow,it is difficult to be accurately modeled since there are various medium properties and phase change characteristics.In view of experiment,several problems are hampering the implementation of precise measurement.Influences of blade outlet angle and medium temperature on crystallization rate were studied.Sodium sulfate solution was applied to simulate practical fluid in chemical industry.Particle image velocimetry(PIV)was employed to measure velocity distributions in rotating impeller.Crystallization processes in three impellers with different blade outlet angles were investigated.Relations among crystallization and flow parameters such as temperature and velocity were obtained.With the same blade wrap angle,when blade outlet angle is larger,diffusion of single flow passage gets stronger,relative velocity at blade outlet decreases and large scale vortex tends to appear near the blade working surface.For the impact of volume effect of particle phase on fluid viscosity,both liquid and solid phase velocities decrease with continual forming and growing of crystal particles.Velocity of solid phase is greater than that of liquid phase and its direction leans more closely to blade working surface.Solid particles tend to move towards blade working surface,as is more obvious in the impeller with large blade outlet angle.Therefore,collision between solid particles with stem part of blade working surface is more intensive in impeller with large blade outlet angle.Concerning transportation of salt aqueous solution,accurate PIV measurement is conducted in centrifugal impellers with different blade outlet angles.The results are useful and instructive in relevant engineering design and operation.
基金supported by the National Natural Science Foundation of China (Nos. 41430753, U1612441)
文摘Biological carbon pumping(BCP)is a key process in which dissolved inorganic carbon in terrestrial aquatic ecosystems is utilized by aquatic autotrophs for photosynthesis and transformed into autochthonous organic matter(AOC).However,the mechanisms underlying BCP and the amount of generated AOC deposited effectively,are still poorly understood.Therefore,we conducted a systematic study combining modern hydrochemical monitoring and a sediment trap experiment in Fuxian Lake(Yunnan,SW China),the second-deepest plateau,oligotrophic freshwater lake in China.Temperature,pH,EC(electrical conductivity),DO(dissolved O2),[HCO3^-],[Ca^2+],SIc,partial CO2(pCO2)pressure,and carbon isotopic compositions of HCO3^-(δ^13CDIc)in water from Fuxian Lake all displayed distinct seasonal and vertical variations.This was especially apparent in an inverse correlation between pCO2 and DO,indicating that variations of hydrochemistry in the lake water were mainly controlled by the metabolism of the aquatic phototrophs.Furthermore,the lowest C/N ratios and highestδ^13Corg were recorded in the trap sediments.Analyses of the C/N ratio demonstrated that the proportions of AOC ranged from 30%to 100%of all OC,indicating that AOC was an important contributor to sedimentary organic matter(OC).It was calculated that the AOC flux in Fuxian Lake was 20.43 t C km^-2 in 2017.Therefore,AOC produced by carbonate weathering and aquatic photosynthesis could potentially be a significant carbon sink and may have an important contribution to solving the lack of carbon sinks in the global carbon cycle.
基金Supported by the German-Research Foun-dation-through the Clin-ical Research Group KFO217“Hepatobiliary tran-sport an-d liver diseases”the Collaborative Research Cen-tre 974“Commun-ication-an-d Systemic Relevan-ce in-Liver Damage an-d Regen-eration-”
文摘To investigate the relation of two different mutations to the outcome of partial external biliary diversion(PEBD)in severe bile salt export pump(BSEP)deficiency.METHODSMutations in the gene encoding BSEP leading to severe BSEP deficiency in two unrelated patients were identified by genomic sequencing.Native liver biopsies and transiently transfected human embryonic kidney(HEK)293 cells expressing either wild-type or mutated BSEP were subjected to immunofluorescence analysis to assess BSEP transporter localization.Bile acid profiles of patient and control bile samples were generated by ultra-performance liquid chromatography-tandem mass spectrometry.Wild-type and mutant BSEP transport of[<sup>3</sup>H]-labeled taurocholate(TC)and taurochenodeoxycholate(TCDC)was assessed by vesicular transport assays.RESULTSA girl(at 2 mo)presented with pruritus,jaundice and elevated serum bile salts(BS).PEBD stabilized liver function and prevented liver transplantation.She was heterozygous for the BSEP deletion p.T919del and the nonsense mutation p.R1235X.At the age of 17 years relative amounts of conjugated BS in her bile were normal,while total BS were less than 3%as compared to controls.An unrelated boy(age 1.5 years)presenting with severe pruritus and elevated serum BS was heterozygous for the same nonsense and another missense mutation,p.G1032R.PEBD failed to alleviate pruritus,eventually necessitating liver transplantation.BS concentration in bile was about 5%of controls.BS were mainly unconjugated with an unusual low amount of chenodeoxycholate derivatives(<5%).The patients’native liver biopsies showed canalicular BSEP expression.Both BSEP p.T919del and p.G1032R were localized in the plasma membrane in HEK293 cells.In vitro transport assays showed drastic reduction of transport by both mutations.Using purified recombinant BSEP as quantifiable reference,per-molecule transport rates for TC and TCDC were determined to be 3 and 2 BS molecules per wild-type BSEP transporter per minute,respectively.CONCLUSIONIn summary,our findings suggest that residual function of BSEP as well as substrate specificity influence the therapeutic effectiveness of PEBD in progressive familial intrahepatic cholestasis type 2(PFIC-2).
基金The authors gratefully acknowledge the financial support for this research by the National Natural Science Foundation of China(Grant Nos.51978588 and 52078434)。
文摘Mud pumping in subgrade beds under ballastless tracks will deteriorate the dynamic performance of infrastructure under railway lines,reduce the smoothness of the railway lines,and seriously affect the comfort and safety of the trains.Due to their good mechanical properties,twocomponent polyurethane materials can be used for grouting to treat the fouling problems caused by ballastless track mud pumping.To develop a polyurethane formula suitable for the treatment of ballastless track mud pumping,we first performed indoor experiments to investigate the mechanical properties and gelation time of polyurethane elastomers synthesized with different raw material composition ratios,to determine an optimal composition ratio of the raw materials.Then,we conducted a dynamic field test to verify the remediation effect of the polyurethane material fabricated according to the design ratio.The results showed that polyurethane grouting material with the selected design ratios improved the contact characteristics between the surface layer of the subgrade bed and the base plate in the area,coordinating the dynamic response between the track structure and the subgrade bed.Thus,the obtained polyurethane grouting material could be used to renovate mud pumping areas of ballastless tracks with a good treatment effect.
基金supported by the National Natural Science Foundation of China under Grant 62274189the Natural Science Foundation of Guangdong Province,China,under Grant 2022A1515011054the Key Area R&D Program of Guangdong Province under Grant 2022B0701180001.
文摘In this paper,an NMOS output-capacitorless low-dropout regulator(OCL-LDO)featuring dual-loop regulation has been proposed,achieving fast transient response with low power consumption.An event-driven charge pump(CP)loop with the dynamic strength control(DSC),is proposed in this paper,which overcomes trade-offs inherent in conventional structures.The presented design addresses and resolves the large signal stability issue,which has been previously overlooked in the event-driven charge pump structure.This breakthrough allows for the full exploitation of the charge-pump structure's poten-tial,particularly in enhancing transient recovery.Moreover,a dynamic error amplifier is utilized to attain precise regulation of the steady-state output voltage,leading to favorable static characteristics.A prototype chip has been fabricated in 65 nm CMOS technology.The measurement results show that the proposed OCL-LDO achieves a 410 nA low quiescent current(IQ)and can recover within 30 ns under 200 mA/10 ns loading change.
基金Supported by the National Natural Science Foundation of China(No.51574161)the Education Science Project of Young and Middle-aged Teachers of Universities in Fujian Province(No.JZ160396)
文摘To study the effect of guide vane outlet angle on pump performance and impeller radial force in an axial-flow heart pump, guide vane outlet angle/34 is considered to be 20°, 15°, 10°, 5° and 3° respectively. Based on ANSYS Fluent, numerical results of pump head and efficiency are validated by exper/ment results, in which Xanthan gum solutions are used with concentration of 0.06 wt. % as working fluid. Then, the effects of/34 on pump performance and impeller radial force are discussed, the errors of head and efficiency between test and simulation are within 5%. The results a/so indicate that the pump performance and efficiency are much better than those of other angles when guide vane outlet angle/34 is 10°, and the maximum variations in head and efficiency are 1.9% and 2.2%, respectively. With/34 increasing, the pulsation of radial force decreases firstly and then increases, when/34 is 10°, the minimum pulsation is 0. 0392N, which is about 80% of the maximum pulsation amplitude.
基金Supported by the National Natural Science Foundation of China under Grant No.69578026,and National 863-416 Foundationof China.
文摘We analyzed the spectroscopic performances of Yb:YAG and developed an efficient room-temperature 20at.% Yb:YAG thin chip (6×6×0.5 mm) laser operating at 1.053μm pumped by Ti-sapphire laser operating at 940nm. Output power of 356 mW was obtained for an absorbed pump power of 784 mW. The slope efficiency was 69%, and the extrapolated threshold was 273mW. The slope efficiency was as high as 72% with absorbed pump power exceeding 730 mW.
