Performance prediction for centrifugal pumps is now mainly based on numerical calculation and most of the studies merely focus on one model.Therefore,the research results are not representative.To make an improvement ...Performance prediction for centrifugal pumps is now mainly based on numerical calculation and most of the studies merely focus on one model.Therefore,the research results are not representative.To make an improvement of numerical calculation method and performance prediction for centrifugal pumps,performance of six centrifugal pump models at design flow rate and off design flow rates,whose specific speed are different,were simulated by using commercial code FLUENT.The standard k-t turbulence model and SIMPLEC algorithm were chosen in FLUENT.The simulation was steady and moving reference frame was used to consider the impeller-volute interaction.Also,how to dispose the gap between impeller and volute was presented and the effect of grid number was considered.The characteristic prediction model for centrifugal pumps is established according to the simulation results.The head and efficiency of the six models at different flow rates are predicted and the prediction results are compared with the experiment results in detail.The comparison indicates that the precision of head and efficiency prediction are all less than 5%.The flow analysis indicates that flow change has an important effect on the location and area of low pressure region behind the blade inlet and the direction of velocity at impeller inlet.The study shows that using FLUENT simulation results to predict performance of centrifugal pumps is feasible and accurate.The method can be applied in engineering practice.展开更多
A unit pump test bench is developed on an in-line pump test platform. The bench is composed of pump adapting assembly, fuel supply subsystem, lubricating subsystem and a control unit. A crank angle domain injection co...A unit pump test bench is developed on an in-line pump test platform. The bench is composed of pump adapting assembly, fuel supply subsystem, lubricating subsystem and a control unit. A crank angle domain injection control method is given out and the control accuracy can be 0.1° crank degree. The bench can test both mechanical unit pump and electronic unit pump. A test model-PLD12 electronic unit pump is tested. Full pump delivery map and some influence factors test is done. Experimental results show that the injection quantity is linear with the delivery angle. The quantity change rate is 15% when fuel temperature increases 30 ℃. The delivery quantity per cycle increases 30 mg at 28 V drive voltage. The average delivery difference for two same type pumps is 5 %. Test results show that the bench can be used for unit pump verification.展开更多
The current research of hydrodynamic bearing in blood pump mainly focuses on the bearing structure design.Compared with the typical plane slider bearing and Rayleigh step bearing,spiral groove bearing has excellent pe...The current research of hydrodynamic bearing in blood pump mainly focuses on the bearing structure design.Compared with the typical plane slider bearing and Rayleigh step bearing,spiral groove bearing has excellent performance in load-carrying capacity.However,the load-carrying capacity would decrease significantly with increasing flow rate in conventional designs.In this paper,the special treatment is made to the upper spiral groove bearing to make sure that both the circulatory flowing and load-carrying capacity are high.Three-dimensional computational fluid dynamics(CFD) models in the space between rotor and shaft are developed by using FLUENT software.Effects of groove number,film height and groove depth on load-carrying capacity of the spiral groove bearings are investigated by orthogonal experiment design.The experimental results show that film height is the most remarkable factor to the load-carrying capacity.The variation tendency of load-carrying capacity reveals that the best combination of geometry is the one with groove number of 8,film height 0.03 mm and groove depth 0.08 mm.The velocity and pressure distributions in spiral groove bearings are also analyzed,and the analysis result shows that the distributions are in conformity with the design of the blood pump based on the principle of hydrodynamic bearing.The displacement of the rotor with the best combination parameters is tested by using laser displacement sensors,the testing result shows that the suspending performance is satisfactory both in axial and radial directions.This research proposes a bearing design method which has sufficient load-carrying capacity to support rotor as an effective passive hydrodynamic bearing.展开更多
A special transparent centrifugal pump is designed. Detailed opticalmeasurements of the flow inside the rotating passages of a five-bladed shroud centrifugal pumpimpeller have been performed by using two-dimensional p...A special transparent centrifugal pump is designed. Detailed opticalmeasurements of the flow inside the rotating passages of a five-bladed shroud centrifugal pumpimpeller have been performed by using two-dimensional particle image velocimetry (PIV). The flow issurveyed at three load conditions q_V/q_(Vd) = 0.4, q_V/q_(Vd) = 1.0, q_V/q_(Vd) = 1.5,respectively. As a result, phase averaged PIV velocity vector maps on three planes between hub andshroud of the impeller are presented. At design load, the mean field of relative velocity ispredominantly vane congruent, showing well-behaved flow without separation. The distributions of therelative velocity on different plane along the pump shaft are very different and there is always alow velocity zone near the pressure-side of the blade at both low and design flow rate, but thelow-velocity-zone at the low flow rate is much larger than that at the design one. The studydemonstrates that the PIV technique is efficient in providing reliable and detailed velocity dataover a full impeller passage.展开更多
Aiming to give some advices on the ground coupled heat pump system design in Siehuan Province, China, a typical ground source heat pump （GSHP） system in Sichuan Province was tested in a whole operational year, and t...Aiming to give some advices on the ground coupled heat pump system design in Siehuan Province, China, a typical ground source heat pump （GSHP） system in Sichuan Province was tested in a whole operational year, and the parameters of temperature and flow rate in different parts of system were measured during this period. The seasonal energy efficiency ratio was calculated and the performance of heat pump system in summer was compared with that in winter. The result shows that the coefficient of performance of the system reaches 3.63 in summer and 3.49 in winter, respectively. The heat balance in underground rock mass is acquired basically throughout the year, and the heat accumulation in the earth tends to be zero.展开更多
Direct expansion solar assisted heat pump (DX-SAHP) technology is developed by combining solar energy heat utilization with heat pump energy saving technology. The experimental researches of the DX-SAHP hot water syst...Direct expansion solar assisted heat pump (DX-SAHP) technology is developed by combining solar energy heat utilization with heat pump energy saving technology. The experimental researches of the DX-SAHP hot water system are conducted in this paper, and overall performance of DX-SAHP is analyzed with three different structures of collectors/evaporators, namely a bare-plate collector, a glass-plate collector and double collectors/evaporators (a bare-plate collector and a glass-plate collector). The influence factors and overall performance are studied, which show that the overall performance of the system is mainly influenced by solar irradiation intensity and the collector area. Comparing with glass-plate collector in similar conditions, bare-plate collector system COP is higher. While increasing collector area is conducive to improve the system COP, but will reduce the collector efficiency and increase the workload of the compressor by comparing the bare-plate collector with double-plate collectors.展开更多
Patient-reported outcome measures(PROMs)are essential in orthopedic research and clinical practice,promoting standardized assessments of treatment efficacy and patient well-being.However,their validity across diverse ...Patient-reported outcome measures(PROMs)are essential in orthopedic research and clinical practice,promoting standardized assessments of treatment efficacy and patient well-being.However,their validity across diverse populations depends on rigorous processes of translation,cultural adaptation,and validation.AlMousa et al successfully validated the Arabic version of the American Academy of Orthopedic Surgeons Foot and Ankle Outcomes Questionnaire,demonstrating strong reliability and clinical applicability for Arabic-speaking patients with traumatic foot and ankle injuries.This article highlights the vital role of culturally adapted PROMs in expanding the global scope of orthopedic research,enhancing patient-centered care,and promoting international collaboration.By addressing linguistic and cultural barriers,such adaptations support a more comprehensive and inclusive approach to evidence-based medicine.Future research should aim to optimize the integration of adapted PROMs into clinical practice,evaluate their influences on treatment decision-making,and investigate their functions in largescale multicenter studies to further globally advance orthopedic research.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
BACKGROUND Quality of life(QoL)outcomes are a focal endpoint of cancer treatment strategies.AIM To externally validate the Moroccan Arabic version of the European Organization for Research and Treatment of Cancer(EORT...BACKGROUND Quality of life(QoL)outcomes are a focal endpoint of cancer treatment strategies.AIM To externally validate the Moroccan Arabic version of the European Organization for Research and Treatment of Cancer(EORTC)QoL Questionnaire(QLQ)for colorectal cancer(CRC)patients(CR29).METHODS Both Moroccan Arabic modules of QLQ-CR29 and QLQ-C30 were administered to Moroccan CRC.Psychometric properties were retested by measuring Cronbach’s alpha coefficient for reliability and Intraclass correlation coefficient(ICC)to examine test-retest reproducibility.The multitrait-scaling analysis was performed to demonstrate the validity of the instrument and known-groups comparison was used to test the score’s ability to discriminate between different groups of patients.RESULTS In total,221 patients were included in our study and 34 patients completed the questionnaire twice.The Urinary Frequency scale and Stool Frequency scale had good internal consistency with alpha Cronbach coefficients of 0.79 and 0.83 respectively,while the same coefficients were moderately lower for the Blood and Mucus in Stool scale(0.61)and the Body Image scale(0.67).The ICCs ranged from 0.88 to 1 indicating good to excellent reproducibility.In multitrait scaling analyses,the criterion for item convergent and divergent validity was satisfactory.The known-group comparison showed statistically significant differences between patients according to age,gender,stoma status,tumor location,and radiotherapy.CONCLUSION The Moroccan Arabic version of the EORTC QLQ-CR29 is a valid and reliable tool that can be used safely for research and clinical purposes in Moroccan CRC patients.展开更多
In many civil engineering construction processes, the concrete pump pipe is more and more applicable scope and use scenarios. With the continuous improvement of the quality of concrete pump pipe and the expansion of t...In many civil engineering construction processes, the concrete pump pipe is more and more applicable scope and use scenarios. With the continuous improvement of the quality of concrete pump pipe and the expansion of the type of concrete pump pipe, now in the process of civil engineering construction, the application of concrete pump pipe is increasingly widespread. Pump pipe is one of the important equipment in engineering construction, its role is to transport mixed concrete, pump pipe is particularly important in high-rise buildings, can save labor, while improving the efficiency of engineering building brick. However, when pumping concrete, the pump pipe will produce strong vibration, which may lead to pump pipe rupture and support system instability collapse accident, resulting in casualties, and it is easy to destroy the cross-section size of the formwork and cause the location of the structural reinforcement to deviate, thus affecting the quality of concrete forming. For this purpose, the pump pipe needs to be fixed. The existing fixing method is to reinforce the pump pipe through the well-shaped scaffold, which is mostly rigid structure, and the impact force produced by the pump pipe in the pumping process is easy to damage the pump pipe. Based on the above situation, this paper conducts an experimental study on the impulse force generated by concrete pump pipe in the actual construction process of civil engineering and construction.展开更多
Concrete pump pipe pulse force fixed device is one of the important equipment in engineering construction. Its role is to transport mixed concrete. Concrete pump pipe pulse force fixed device is particularly important...Concrete pump pipe pulse force fixed device is one of the important equipment in engineering construction. Its role is to transport mixed concrete. Concrete pump pipe pulse force fixed device is particularly important in high-rise buildings, because it can save labors, and improve the production efficiency of engineering construction. However, when pumping concrete, the pump pipe will produce strong impulse impact force, which may lead to pump pipe rupture and support system instability collapse accident, resulting in casualties, and it is easy to destroy the cross-section size of the formwork and cause the deviation of the position of the structural reinforcement, affecting the quality of concrete, thereby endangering the safety of the structure. For this purpose, the pump pipe needs to be fixed. The existing fixing method is to reinforce the pump pipe through the well-shaped scaffold, which is mostly rigid structure, and the impact force produced by the pump pipe in the pumping process is easy to damage the pump pipe. Based on the above research, this paper explores the invention of a reusable pulse force fixing device for concrete pump pipe, hoping to be helpful to other workers in the concrete industry.展开更多
AIM: To identify objective and subjective predictors for the reliable diagnosis of gastroesophageal reflux disease (GERD) and the response to proton pump inhibitor (PPI) therapy.
The building sector contributes a large ratio of final energy consumption,and improving building energy efficiency is expected to play a significant role in mitigating its carbon dioxide emission.Herein,we collected t...The building sector contributes a large ratio of final energy consumption,and improving building energy efficiency is expected to play a significant role in mitigating its carbon dioxide emission.Herein,we collected the on-site measurement data to investigate the techno-economic performances of different heat pump types that exist in building space heating projects in Qingdao,China.An in-depth analysis revealed the temperature variations of measured low-grade heat sources over the whole heating supply period,and urban sewage water shows high stable heat energy quality compared with seawater and geothermal heat resources.Operational behaviors including cycling inlet and outlet temperature of the selected heat pumps were illustrated,and analysis evaluated detailed effects of operational parameters on energy efficiency performances.Then the relationship between COPs distributions of heat pumps and operational conditions was examined further,and the positive effect of the rising temperature of heat sources on energy efficiency improvement of heat pump is highlighted when the heating supply temperature is higher.Furthermore,we analyzed the economic and carbon emission performance of the heat pump system,and results show that electricity price plays a vital role in the lifespan energy cost saving potential,and the heat pump could serve as a promising approach in reducing CO_(2) related to the building space heating.Finally,we recommended suggestions for improving the overall energy efficiency and cost competitiveness of decentralized heat pump systems for building space heating.展开更多
Performance appraisal is a very important work in the field of human resource management in public institutions. Under the background of the reform of public institutions, how to optimize the performance appraisal sys...Performance appraisal is a very important work in the field of human resource management in public institutions. Under the background of the reform of public institutions, how to optimize the performance appraisal system with the times has become a topic of wide concern. At present, the effect of performance appraisal in many units is not ideal. With the deepening and advancing of unit reform, the original evaluation system has become more and more unsuitable for the development of scientific research institutions. This paper makes a preliminary analysis of the main problems existing in the performance evaluation of scientific research institutions, and briefly expounds the optimization of the assessment form, the establishment of a more scientific evaluation system, and the improvement of the evaluation and incentive mechanism. Some suggestions are put forward for further promoting the reform of scientific research institutions.展开更多
The back-flow of an aortic valvo-pump will re-duce the pumping flow rate but can wash out the gap between the rotor and the stator, and thus can improve the antithrombogenicity of the de-vice. To investigate the regur...The back-flow of an aortic valvo-pump will re-duce the pumping flow rate but can wash out the gap between the rotor and the stator, and thus can improve the antithrombogenicity of the de-vice. To investigate the regurgitation of a 23mm OD aortic valvo-pump, its closed impeller was replaced by a cylinder and hereby the valvo- pump had lost its pumping function. The pres-sure head crossing the aortic valvo-pump was maintained by a locally made pulsatile centrifugal pump, beating rhythmically from 30 to 120mmHg. The back flow from outlet to inlet of valvo-pump via the above-mentioned gap was measured. Results demonstrated that this gap and the pressure head had remarkable effect on back- flow;a larger gap and/or a larger pressure head would lead to a larger back-flow. By 0,20mm gap and 100mmHg pressure head, the valvo-pump had ca. 0,8 l/min back-flow. Instantaneous meas-urement indicated that the back-flow had a pul-satile form with high rate during diastole while low rate during systole of the natural heart imi-tated by pulsatile centrifugal pump. The pump rotated at 12500rpm, 15000rpm and 17500rpm respectively, but it was found the rotating speed had no affection on back-flow. This investigation provides a basis for pump design seeking for both increase of the flow rate and improvement of the compatibility;the former is particularly important for a mini axial pump and the latter is extremely difficult for closed impeller.展开更多
This study explored and reviewed the logistic regression (LR) model, a multivariable method for modeling the relationship between multiple independent variables and a categorical dependent variable, with emphasis on m...This study explored and reviewed the logistic regression (LR) model, a multivariable method for modeling the relationship between multiple independent variables and a categorical dependent variable, with emphasis on medical research. Thirty seven research articles published between 2000 and 2018 which employed logistic regression as the main statistical tool as well as six text books on logistic regression were reviewed. Logistic regression concepts such as odds, odds ratio, logit transformation, logistic curve, assumption, selecting dependent and independent variables, model fitting, reporting and interpreting were presented. Upon perusing the literature, considerable deficiencies were found in both the use and reporting of LR. For many studies, the ratio of the number of outcome events to predictor variables (events per variable) was sufficiently small to call into question the accuracy of the regression model. Also, most studies did not report on validation analysis, regression diagnostics or goodness-of-fit measures;measures which authenticate the robustness of the LR model. Here, we demonstrate a good example of the application of the LR model using data obtained on a cohort of pregnant women and the factors that influence their decision to opt for caesarean delivery or vaginal birth. It is recommended that researchers should be more rigorous and pay greater attention to guidelines concerning the use and reporting of LR models.展开更多
The reduction of molecular nitrogen(N_(2))to ammonia(NH_(3))under mild conditions is one of the most promising studies in the energy field due to the important role of NH_(3)in modern industry,production,and life.The ...The reduction of molecular nitrogen(N_(2))to ammonia(NH_(3))under mild conditions is one of the most promising studies in the energy field due to the important role of NH_(3)in modern industry,production,and life.The photocatalytic reduction of N_(2)is expected to achieve clean and sustainable NH_(3)production by using clean solar energy.To date,the new photocatalysts for photocatalytic reduction of N_(2)to NH_(3)at room temperature and atmospheric pressure have not been fully developed.The major challenge is to achieve high light-absorption efficiency,conversion efficiency,and stability of photocatalysts.Herein,the methods for measuring produced NH_(3)are compared,and the problems related to possible NH_(3)pollution in photocatalytic systems are mentioned to provide accurate ideas for measuring photocatalytic efficiency.The recent progress of nitrogen reduction reaction(NRR)photocatalysts at ambient temperature and pressure is summarized by introducing charge transfer,migration,and separation in photocatalytic NRR,which provides a guidance for the selection of future photocatalyst.More importantly,we introduce the latest research strategies of photocatalysts in detail,which can guide the preparation and design of photocatalysts with high NRR activity.展开更多
Purpose： In this contribution we continue our investigations related to the activity index （A/） and its formal analogs. We try to replace the AI by an indicator which is better suited for policy applications. Desig...Purpose： In this contribution we continue our investigations related to the activity index （A/） and its formal analogs. We try to replace the AI by an indicator which is better suited for policy applications. Design/methodology/approach： We point out that fluctuations in the value of the AI for a given country and domain are never the result of that country＇s policy with respect to that domain alone because there are exogenous factors at play. For this reason we introduce the F-measure. This F-measure is nothing but the harmonic mean of the country＇s share in the world＇s publication output in the given domain and the given domain＇s share in the country＇s publication output.Findings： The F-measure does not suffer from the problems the AI does Research limitations： The indicator is not yet fully tested in real cases R＆D policy management： In policy considerations, the AI should better be replaced by the F-measure as this measure can better show the results of science policy measures （which the AI cannot as it depends on exogenous factors）. Originality/value： We provide an original solution for a problem that is not fully realized by policy makers.展开更多
Academic evaluations such as tenure/promotion applications and society fellowship nominations rely heavily on bibliometric measures of each candidate’s research impact, including their research citations. This articl...Academic evaluations such as tenure/promotion applications and society fellowship nominations rely heavily on bibliometric measures of each candidate’s research impact, including their research citations. This article first reviews existing evaluation criteria such as the h-index and<em> q</em>-most-citations, and then proposes a weighted w-index which minimizes shortcomings in existing single-number measures. The w-index consists of three factors<span style="white-space:nowrap;">—</span>3 most cited first-author publications, 3 most cited publications as the corresponding/last author, and 3 additional most cited publications as a co-author, but does not allow double counting of these publications.展开更多
This paper presents the sequence of activities to improve the thermal hydraulic analysis of the IEA-R1 research reactor to operate in safe conditions after power upgrade from 2 to 5 MW and core size reduction from 30 ...This paper presents the sequence of activities to improve the thermal hydraulic analysis of the IEA-R1 research reactor to operate in safe conditions after power upgrade from 2 to 5 MW and core size reduction from 30 to 24 fuel assemblies. A realistic analysis needs the knowledge of the actual operation conditions (heat flow, flow rates) beyond the geometric data and the uncertainties associated with manufacturing and measures. A dummy fuel assembly was designed and constructed to measure the actual flow rate through the core fuel assemblies and its pressure drop. First results showed that the flow distribution over the core is nearly uniform. Nevertheless, the values are below than the calculated ones and the core bypass flow rate is greater than those estimated previously. Based on this, several activities were performed to identify and reduce the bypass flow, such as reduction of the flow rate through the sample irradiators, closing some unnecessary secondary holes on the matrix plate, improvement in the primary flow rate system and better fit of the core components on the matrix plate. A sub-aquatic visual system was used as an important tool to detect some bypass flow path. After these modifications, the fuel assemblies flow rate increased about 13%. Additional tests using the dummy fuel assembly were carried out to measure the internal flow distribution among the rectangular channels. The results showed that the flow rate through the outer channels is 10% - 15% lower than the internal ones. The flow rate in the channel formed between two adjacent fuel assemblies is an estimated parameter and it is difficult to measure because this is an open channel. A new thermal hydraulic analysis of the outermost plates of the fuel assemblies takes into account all this information. Then, a fuel design modification was proposed with the reduction of 50% in the uranium quantity in the outermost fuel plates. In order to avoid the oxidation of the outermost plates by high temperature, low flow rate, a reduction of 50% in the uranium density in the same ones was shown to be adequate to solve the problem.展开更多
基金supported by National Outstanding Young Scientists Founds of China(Grant No.50825902)National Natural Science Foundation of China(Grant No.50509009)
文摘Performance prediction for centrifugal pumps is now mainly based on numerical calculation and most of the studies merely focus on one model.Therefore,the research results are not representative.To make an improvement of numerical calculation method and performance prediction for centrifugal pumps,performance of six centrifugal pump models at design flow rate and off design flow rates,whose specific speed are different,were simulated by using commercial code FLUENT.The standard k-t turbulence model and SIMPLEC algorithm were chosen in FLUENT.The simulation was steady and moving reference frame was used to consider the impeller-volute interaction.Also,how to dispose the gap between impeller and volute was presented and the effect of grid number was considered.The characteristic prediction model for centrifugal pumps is established according to the simulation results.The head and efficiency of the six models at different flow rates are predicted and the prediction results are compared with the experiment results in detail.The comparison indicates that the precision of head and efficiency prediction are all less than 5%.The flow analysis indicates that flow change has an important effect on the location and area of low pressure region behind the blade inlet and the direction of velocity at impeller inlet.The study shows that using FLUENT simulation results to predict performance of centrifugal pumps is feasible and accurate.The method can be applied in engineering practice.
基金the Ministerial Level Advanced Research Foundation (404050301 .4)
文摘A unit pump test bench is developed on an in-line pump test platform. The bench is composed of pump adapting assembly, fuel supply subsystem, lubricating subsystem and a control unit. A crank angle domain injection control method is given out and the control accuracy can be 0.1° crank degree. The bench can test both mechanical unit pump and electronic unit pump. A test model-PLD12 electronic unit pump is tested. Full pump delivery map and some influence factors test is done. Experimental results show that the injection quantity is linear with the delivery angle. The quantity change rate is 15% when fuel temperature increases 30 ℃. The delivery quantity per cycle increases 30 mg at 28 V drive voltage. The average delivery difference for two same type pumps is 5 %. Test results show that the bench can be used for unit pump verification.
基金supported by National Natural Science Foundation of China(Grant No.51275461)Zhejiang Provincial Natural Science Foundation of China(Grant No.Z1110189)+1 种基金National Hi-tech Research and Development Program of China(863 ProgramGrant No.2009AA045401)
文摘The current research of hydrodynamic bearing in blood pump mainly focuses on the bearing structure design.Compared with the typical plane slider bearing and Rayleigh step bearing,spiral groove bearing has excellent performance in load-carrying capacity.However,the load-carrying capacity would decrease significantly with increasing flow rate in conventional designs.In this paper,the special treatment is made to the upper spiral groove bearing to make sure that both the circulatory flowing and load-carrying capacity are high.Three-dimensional computational fluid dynamics(CFD) models in the space between rotor and shaft are developed by using FLUENT software.Effects of groove number,film height and groove depth on load-carrying capacity of the spiral groove bearings are investigated by orthogonal experiment design.The experimental results show that film height is the most remarkable factor to the load-carrying capacity.The variation tendency of load-carrying capacity reveals that the best combination of geometry is the one with groove number of 8,film height 0.03 mm and groove depth 0.08 mm.The velocity and pressure distributions in spiral groove bearings are also analyzed,and the analysis result shows that the distributions are in conformity with the design of the blood pump based on the principle of hydrodynamic bearing.The displacement of the rotor with the best combination parameters is tested by using laser displacement sensors,the testing result shows that the suspending performance is satisfactory both in axial and radial directions.This research proposes a bearing design method which has sufficient load-carrying capacity to support rotor as an effective passive hydrodynamic bearing.
基金This project is supported by National Natural Science Foundation of China(No.50136030) Opening Research Work from Key Laboratory of Jiangsu Province on Hydro-Dynamics Engineering in Yangzhou University, China.
文摘A special transparent centrifugal pump is designed. Detailed opticalmeasurements of the flow inside the rotating passages of a five-bladed shroud centrifugal pumpimpeller have been performed by using two-dimensional particle image velocimetry (PIV). The flow issurveyed at three load conditions q_V/q_(Vd) = 0.4, q_V/q_(Vd) = 1.0, q_V/q_(Vd) = 1.5,respectively. As a result, phase averaged PIV velocity vector maps on three planes between hub andshroud of the impeller are presented. At design load, the mean field of relative velocity ispredominantly vane congruent, showing well-behaved flow without separation. The distributions of therelative velocity on different plane along the pump shaft are very different and there is always alow velocity zone near the pressure-side of the blade at both low and design flow rate, but thelow-velocity-zone at the low flow rate is much larger than that at the design one. The studydemonstrates that the PIV technique is efficient in providing reliable and detailed velocity dataover a full impeller passage.
基金Project(50838009) supported by the National Science Key Foundation 1 tem
文摘Aiming to give some advices on the ground coupled heat pump system design in Siehuan Province, China, a typical ground source heat pump （GSHP） system in Sichuan Province was tested in a whole operational year, and the parameters of temperature and flow rate in different parts of system were measured during this period. The seasonal energy efficiency ratio was calculated and the performance of heat pump system in summer was compared with that in winter. The result shows that the coefficient of performance of the system reaches 3.63 in summer and 3.49 in winter, respectively. The heat balance in underground rock mass is acquired basically throughout the year, and the heat accumulation in the earth tends to be zero.
文摘Direct expansion solar assisted heat pump (DX-SAHP) technology is developed by combining solar energy heat utilization with heat pump energy saving technology. The experimental researches of the DX-SAHP hot water system are conducted in this paper, and overall performance of DX-SAHP is analyzed with three different structures of collectors/evaporators, namely a bare-plate collector, a glass-plate collector and double collectors/evaporators (a bare-plate collector and a glass-plate collector). The influence factors and overall performance are studied, which show that the overall performance of the system is mainly influenced by solar irradiation intensity and the collector area. Comparing with glass-plate collector in similar conditions, bare-plate collector system COP is higher. While increasing collector area is conducive to improve the system COP, but will reduce the collector efficiency and increase the workload of the compressor by comparing the bare-plate collector with double-plate collectors.
基金Supported by the Hubei Provincial Natural Science Foundation,No.2025AFB845Graduate Innovation and Entrepreneurship Fund of Wuhan University of Science and Technology,No.JCX2024044.
文摘Patient-reported outcome measures(PROMs)are essential in orthopedic research and clinical practice,promoting standardized assessments of treatment efficacy and patient well-being.However,their validity across diverse populations depends on rigorous processes of translation,cultural adaptation,and validation.AlMousa et al successfully validated the Arabic version of the American Academy of Orthopedic Surgeons Foot and Ankle Outcomes Questionnaire,demonstrating strong reliability and clinical applicability for Arabic-speaking patients with traumatic foot and ankle injuries.This article highlights the vital role of culturally adapted PROMs in expanding the global scope of orthopedic research,enhancing patient-centered care,and promoting international collaboration.By addressing linguistic and cultural barriers,such adaptations support a more comprehensive and inclusive approach to evidence-based medicine.Future research should aim to optimize the integration of adapted PROMs into clinical practice,evaluate their influences on treatment decision-making,and investigate their functions in largescale multicenter studies to further globally advance orthopedic research.
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.
文摘BACKGROUND Quality of life(QoL)outcomes are a focal endpoint of cancer treatment strategies.AIM To externally validate the Moroccan Arabic version of the European Organization for Research and Treatment of Cancer(EORTC)QoL Questionnaire(QLQ)for colorectal cancer(CRC)patients(CR29).METHODS Both Moroccan Arabic modules of QLQ-CR29 and QLQ-C30 were administered to Moroccan CRC.Psychometric properties were retested by measuring Cronbach’s alpha coefficient for reliability and Intraclass correlation coefficient(ICC)to examine test-retest reproducibility.The multitrait-scaling analysis was performed to demonstrate the validity of the instrument and known-groups comparison was used to test the score’s ability to discriminate between different groups of patients.RESULTS In total,221 patients were included in our study and 34 patients completed the questionnaire twice.The Urinary Frequency scale and Stool Frequency scale had good internal consistency with alpha Cronbach coefficients of 0.79 and 0.83 respectively,while the same coefficients were moderately lower for the Blood and Mucus in Stool scale(0.61)and the Body Image scale(0.67).The ICCs ranged from 0.88 to 1 indicating good to excellent reproducibility.In multitrait scaling analyses,the criterion for item convergent and divergent validity was satisfactory.The known-group comparison showed statistically significant differences between patients according to age,gender,stoma status,tumor location,and radiotherapy.CONCLUSION The Moroccan Arabic version of the EORTC QLQ-CR29 is a valid and reliable tool that can be used safely for research and clinical purposes in Moroccan CRC patients.
文摘In many civil engineering construction processes, the concrete pump pipe is more and more applicable scope and use scenarios. With the continuous improvement of the quality of concrete pump pipe and the expansion of the type of concrete pump pipe, now in the process of civil engineering construction, the application of concrete pump pipe is increasingly widespread. Pump pipe is one of the important equipment in engineering construction, its role is to transport mixed concrete, pump pipe is particularly important in high-rise buildings, can save labor, while improving the efficiency of engineering building brick. However, when pumping concrete, the pump pipe will produce strong vibration, which may lead to pump pipe rupture and support system instability collapse accident, resulting in casualties, and it is easy to destroy the cross-section size of the formwork and cause the location of the structural reinforcement to deviate, thus affecting the quality of concrete forming. For this purpose, the pump pipe needs to be fixed. The existing fixing method is to reinforce the pump pipe through the well-shaped scaffold, which is mostly rigid structure, and the impact force produced by the pump pipe in the pumping process is easy to damage the pump pipe. Based on the above situation, this paper conducts an experimental study on the impulse force generated by concrete pump pipe in the actual construction process of civil engineering and construction.
文摘Concrete pump pipe pulse force fixed device is one of the important equipment in engineering construction. Its role is to transport mixed concrete. Concrete pump pipe pulse force fixed device is particularly important in high-rise buildings, because it can save labors, and improve the production efficiency of engineering construction. However, when pumping concrete, the pump pipe will produce strong impulse impact force, which may lead to pump pipe rupture and support system instability collapse accident, resulting in casualties, and it is easy to destroy the cross-section size of the formwork and cause the deviation of the position of the structural reinforcement, affecting the quality of concrete, thereby endangering the safety of the structure. For this purpose, the pump pipe needs to be fixed. The existing fixing method is to reinforce the pump pipe through the well-shaped scaffold, which is mostly rigid structure, and the impact force produced by the pump pipe in the pumping process is easy to damage the pump pipe. Based on the above research, this paper explores the invention of a reusable pulse force fixing device for concrete pump pipe, hoping to be helpful to other workers in the concrete industry.
文摘AIM: To identify objective and subjective predictors for the reliable diagnosis of gastroesophageal reflux disease (GERD) and the response to proton pump inhibitor (PPI) therapy.
基金This research was funded by Development of the Healthy and Low-Carbon Residential House with Smart Home Environment Management System,Grant No.2019GSF110003Research on the energy efficiency and health performance improvement of building operations based on lifecycle carbon emissions reduction Grant No.2018YFE0106100.We gratefully acknowledge the help from ASSURAN International Scholarship Foundation.
文摘The building sector contributes a large ratio of final energy consumption,and improving building energy efficiency is expected to play a significant role in mitigating its carbon dioxide emission.Herein,we collected the on-site measurement data to investigate the techno-economic performances of different heat pump types that exist in building space heating projects in Qingdao,China.An in-depth analysis revealed the temperature variations of measured low-grade heat sources over the whole heating supply period,and urban sewage water shows high stable heat energy quality compared with seawater and geothermal heat resources.Operational behaviors including cycling inlet and outlet temperature of the selected heat pumps were illustrated,and analysis evaluated detailed effects of operational parameters on energy efficiency performances.Then the relationship between COPs distributions of heat pumps and operational conditions was examined further,and the positive effect of the rising temperature of heat sources on energy efficiency improvement of heat pump is highlighted when the heating supply temperature is higher.Furthermore,we analyzed the economic and carbon emission performance of the heat pump system,and results show that electricity price plays a vital role in the lifespan energy cost saving potential,and the heat pump could serve as a promising approach in reducing CO_(2) related to the building space heating.Finally,we recommended suggestions for improving the overall energy efficiency and cost competitiveness of decentralized heat pump systems for building space heating.
文摘Performance appraisal is a very important work in the field of human resource management in public institutions. Under the background of the reform of public institutions, how to optimize the performance appraisal system with the times has become a topic of wide concern. At present, the effect of performance appraisal in many units is not ideal. With the deepening and advancing of unit reform, the original evaluation system has become more and more unsuitable for the development of scientific research institutions. This paper makes a preliminary analysis of the main problems existing in the performance evaluation of scientific research institutions, and briefly expounds the optimization of the assessment form, the establishment of a more scientific evaluation system, and the improvement of the evaluation and incentive mechanism. Some suggestions are put forward for further promoting the reform of scientific research institutions.
文摘The back-flow of an aortic valvo-pump will re-duce the pumping flow rate but can wash out the gap between the rotor and the stator, and thus can improve the antithrombogenicity of the de-vice. To investigate the regurgitation of a 23mm OD aortic valvo-pump, its closed impeller was replaced by a cylinder and hereby the valvo- pump had lost its pumping function. The pres-sure head crossing the aortic valvo-pump was maintained by a locally made pulsatile centrifugal pump, beating rhythmically from 30 to 120mmHg. The back flow from outlet to inlet of valvo-pump via the above-mentioned gap was measured. Results demonstrated that this gap and the pressure head had remarkable effect on back- flow;a larger gap and/or a larger pressure head would lead to a larger back-flow. By 0,20mm gap and 100mmHg pressure head, the valvo-pump had ca. 0,8 l/min back-flow. Instantaneous meas-urement indicated that the back-flow had a pul-satile form with high rate during diastole while low rate during systole of the natural heart imi-tated by pulsatile centrifugal pump. The pump rotated at 12500rpm, 15000rpm and 17500rpm respectively, but it was found the rotating speed had no affection on back-flow. This investigation provides a basis for pump design seeking for both increase of the flow rate and improvement of the compatibility;the former is particularly important for a mini axial pump and the latter is extremely difficult for closed impeller.
文摘This study explored and reviewed the logistic regression (LR) model, a multivariable method for modeling the relationship between multiple independent variables and a categorical dependent variable, with emphasis on medical research. Thirty seven research articles published between 2000 and 2018 which employed logistic regression as the main statistical tool as well as six text books on logistic regression were reviewed. Logistic regression concepts such as odds, odds ratio, logit transformation, logistic curve, assumption, selecting dependent and independent variables, model fitting, reporting and interpreting were presented. Upon perusing the literature, considerable deficiencies were found in both the use and reporting of LR. For many studies, the ratio of the number of outcome events to predictor variables (events per variable) was sufficiently small to call into question the accuracy of the regression model. Also, most studies did not report on validation analysis, regression diagnostics or goodness-of-fit measures;measures which authenticate the robustness of the LR model. Here, we demonstrate a good example of the application of the LR model using data obtained on a cohort of pregnant women and the factors that influence their decision to opt for caesarean delivery or vaginal birth. It is recommended that researchers should be more rigorous and pay greater attention to guidelines concerning the use and reporting of LR models.
基金Taishan Scholars Program of Shandong Province,Grant/Award Number:tsqn201812068Higher School Youth Innovation Team of Shandong Province,Grant/Award Number:2019KJA013+1 种基金The Opening Fund of State Key Laboratory of Heavy Oil Processing,Grant/Award Number:SKLOP202002006National Natural Science Foundation of China,Grant/Award Number:51872173。
文摘The reduction of molecular nitrogen(N_(2))to ammonia(NH_(3))under mild conditions is one of the most promising studies in the energy field due to the important role of NH_(3)in modern industry,production,and life.The photocatalytic reduction of N_(2)is expected to achieve clean and sustainable NH_(3)production by using clean solar energy.To date,the new photocatalysts for photocatalytic reduction of N_(2)to NH_(3)at room temperature and atmospheric pressure have not been fully developed.The major challenge is to achieve high light-absorption efficiency,conversion efficiency,and stability of photocatalysts.Herein,the methods for measuring produced NH_(3)are compared,and the problems related to possible NH_(3)pollution in photocatalytic systems are mentioned to provide accurate ideas for measuring photocatalytic efficiency.The recent progress of nitrogen reduction reaction(NRR)photocatalysts at ambient temperature and pressure is summarized by introducing charge transfer,migration,and separation in photocatalytic NRR,which provides a guidance for the selection of future photocatalyst.More importantly,we introduce the latest research strategies of photocatalysts in detail,which can guide the preparation and design of photocatalysts with high NRR activity.
文摘Purpose： In this contribution we continue our investigations related to the activity index （A/） and its formal analogs. We try to replace the AI by an indicator which is better suited for policy applications. Design/methodology/approach： We point out that fluctuations in the value of the AI for a given country and domain are never the result of that country＇s policy with respect to that domain alone because there are exogenous factors at play. For this reason we introduce the F-measure. This F-measure is nothing but the harmonic mean of the country＇s share in the world＇s publication output in the given domain and the given domain＇s share in the country＇s publication output.Findings： The F-measure does not suffer from the problems the AI does Research limitations： The indicator is not yet fully tested in real cases R＆D policy management： In policy considerations, the AI should better be replaced by the F-measure as this measure can better show the results of science policy measures （which the AI cannot as it depends on exogenous factors）. Originality/value： We provide an original solution for a problem that is not fully realized by policy makers.
文摘Academic evaluations such as tenure/promotion applications and society fellowship nominations rely heavily on bibliometric measures of each candidate’s research impact, including their research citations. This article first reviews existing evaluation criteria such as the h-index and<em> q</em>-most-citations, and then proposes a weighted w-index which minimizes shortcomings in existing single-number measures. The w-index consists of three factors<span style="white-space:nowrap;">—</span>3 most cited first-author publications, 3 most cited publications as the corresponding/last author, and 3 additional most cited publications as a co-author, but does not allow double counting of these publications.
文摘This paper presents the sequence of activities to improve the thermal hydraulic analysis of the IEA-R1 research reactor to operate in safe conditions after power upgrade from 2 to 5 MW and core size reduction from 30 to 24 fuel assemblies. A realistic analysis needs the knowledge of the actual operation conditions (heat flow, flow rates) beyond the geometric data and the uncertainties associated with manufacturing and measures. A dummy fuel assembly was designed and constructed to measure the actual flow rate through the core fuel assemblies and its pressure drop. First results showed that the flow distribution over the core is nearly uniform. Nevertheless, the values are below than the calculated ones and the core bypass flow rate is greater than those estimated previously. Based on this, several activities were performed to identify and reduce the bypass flow, such as reduction of the flow rate through the sample irradiators, closing some unnecessary secondary holes on the matrix plate, improvement in the primary flow rate system and better fit of the core components on the matrix plate. A sub-aquatic visual system was used as an important tool to detect some bypass flow path. After these modifications, the fuel assemblies flow rate increased about 13%. Additional tests using the dummy fuel assembly were carried out to measure the internal flow distribution among the rectangular channels. The results showed that the flow rate through the outer channels is 10% - 15% lower than the internal ones. The flow rate in the channel formed between two adjacent fuel assemblies is an estimated parameter and it is difficult to measure because this is an open channel. A new thermal hydraulic analysis of the outermost plates of the fuel assemblies takes into account all this information. Then, a fuel design modification was proposed with the reduction of 50% in the uranium quantity in the outermost fuel plates. In order to avoid the oxidation of the outermost plates by high temperature, low flow rate, a reduction of 50% in the uranium density in the same ones was shown to be adequate to solve the problem.
