Influence of regenerator flow resistance on stability of pulse tube cooler

Based on the fluid network theory,the possibility of utilizing regenerator flow resistance to suppress the direct current （DC） flow induced by the introduction of a double-inlet in a pulse tube cooler is investigated theoretically. The calculation results show that increasing regenerator flow resistance can lead to a smaller extent of DC flow.Therefore,a better stability performance of the cooler can be realized.On this basis,the stability characteristics of the cooler with various regenerator matrix arrangements are studied by experiments.By replacing 30% space of 247 screens of stainless steel mesh at the cold part of the regenerator by lead balls of 0.25 mm diameter,a long-time stable temperature output at 80 K region is achieved. This achievement provides a new way to obtain stable performance for pulse tube coolers at high temperature and is helpful for its application.

Time to consider the potential role of alternative resistance training methods in cancer management?

Exercise has emerged as fundamental therapeutic medicine in the management of cancer.Exercise improves health-related outcomes,including quality of life,neuromuscular strength,physical function,and body composition,and it is associated with a lower risk of disease recurrence and increased survival.Moreover,exercise during or post cancer treatments is safe,can ameliorate treatment-related side effects,and may enhance the effectiveness of chemotherapy and radiation therapy.To date,traditional resistance training(RT)is the most used RT modality in exercise oncology.However,alternative training modes,such as eccentric,cluster set,and blood flow restriction are gaining increased attention.These training modalities have been extensively investigated in both athletic and clinical populations(e.g.,age-related frailty,cardiovascular disease,type 2 diabetes),showing considerable benefits in terms of neuromuscular strength,hypertrophy,body composition,and physical function.However,these training modes have only been partially or not at all investigated in cancer populations.Thus,this study outlines the benefits of these alternative RT methods in patients with cancer.Where evidence in cancer populations is sparse,we provide a robust rationale for the possible implementation of certain RT methods that have shown positive results in other clinical populations.Finally,we provide clinical insights for research that may guide future RT investigations in patients with cancer and suggest clear practical applications for targeted cancer populations and related benefits.

Flow resistance and its prediction methods in compound channels

A series of experiments was carried out in a large symmetric compound channel composed of a rough main channel and rough floodplains to investigate the resistance characteristics of inbank and overbank flows. The effective Manning, Darcy-Weisbach, Chezy coefficients and the relative Nikuradse roughness height were analyzed. Many different representative methods for predicting the composite roughness were systematically summarized. Besides the measured data, a vast number of laboratory data and field data for compound channels were collected and used to check the validity of these methods for different subsection divisions including the vertical, horizontal, diagonal and bisectional divisions. The computation showed that these methods resulted in big errors in assessing the composite roughness in compound channels, and the reasons were analyzed in detail. The error magnitude is related to the subsection divisions.

Flow Resistance Modeling for Coolant Distribution within Canned Motor Cooling Loops

Taylor–Couette–Poiseuille(TCP)flow dominates the inner water-cooling circulation of canned motor reactor coolant pumps.Current research on TCP flow focuses on torque behaviors and flow regime transitions through experiments and simulations.However,research on axial flow resistance in a large Reynolds number turbulent state is not sufficient,especially for the various flow patterns.This study is devoted to investigating the influence of annular flow on the axial flow resistance of liquid in the coaxial cylinders of the stator and rotor in canned motor reactor coolant pumps,and predicting the coolant flow distribution between the upper coil cooling loop and lower bearing lubricating loop for safe operation.The axial flow resistance,coupled with the annular rotation,is experimentally investigated at a flow rate with an axial Reynolds number,Rea,from 2.6×10~3 to 6.0×10~3 and rotational Reynolds number,Ret,from 1.6×10~4 to 4.0×10~4.It is revealed that the axial flow frictional coe cient varies against the axial flow rate in linear relation sets with logarithmic coordinates,which shift up when the flow has a higher Ret.Further examination of the axial flow resistance,with the Rea extending to 3.5×10~5 and Ret up to 1.6×10~5,by simulation shows gentle variation rates in the axial flow frictional coe cients against the Rea.The relation curves with different Ret values converge when the Rea exceeds 3.5×10~5.A prediction model for TCP flow consisting of a polygonal approximation with logarithmic coordinates is developed to estimate the axial flow resistance against different axial and rotational Reynolds numbers for the evaluation of heat and mass transfer during transition states and the engineering design of the canned motor chamber structure.

The Effect of Sparger Geometry on Gas Bubble Flow Behaviors Using Electrical Resistance Tomography

By electrical resistance tomography (ERT) the cross sectional profiles of gas hold-up in a φ56mm bubble column are obtained with four designs of gas sparger. The effect of sparger geometry on the bubble distribution is re-vealed by applying a sensitivity conjugated gradients reconstruction method (SCG). Experimental results show that over-all hold-up obtained by ERT is generally in good agreement with those measured with the pressure transducer and the ERT system produces informative evidence that the radial profiles of hold-up is very similar to the sparger design in the lower section of bubble column. Meanwhile, the rise velocity of bubble swarm and the Sauter mean bubble size are evaluated using ERT based on dynamic gas disengagement theory. The experimental results are in good agreement with correlations and conventional estimation obtained using pressure transmitter methods.

Flow-resistance analysis of nano-confined fluids inspired from liquid nano-lubrication:A review

How to reduce flow resistance of nano-confined fluids to achieve a high flux is a new challenge for modern chemical engineering applications, such as membrane separation and nanofluidic devices. Traditional models are inapplicable to explain the significant differences in the flow resistance of different liquid–solid systems.On the other hand, friction reduction in liquid nano-lubrication has received considerable attention during the past decades. Both fields are exposed to a common scientific issue regarding friction reduction during liquid–solid relative motion at nanoscale. A promising approach to control the flow resistance of nano-confined fluids is to reference the factors affecting liquid nano-lubrication. In this review, two concepts of the friction coefficient derived from fluid flow and tribology were discussed to reveal their intrinsic relations. Recent progress on low or ultra-low friction coefficients in liquid nano-lubrication was summarized based on two situations. Finally, a new strategy was introduced to study the friction coefficient based on analyzing the intermolecular interactions through an atomic force microscope(AFM), which is a cutting-point to build a new model to study flowresistance at nanoscale.

Effect of Radial Resistance Gap on the Pressure Drop of a Compact Annular-Radial-Orifice Flow Magnetorheological Valve

A compact annular-radial-orifice flow magnetorheological(MR)valve was developed to investigate the effects of radial resistance gap on pressure drop.The fluid flow paths of this proposed MR valve consist of a single annular flow channel,a single radial flow channel and an orifice flow channel through structure design.The finite element modelling and simulation analysis of the MR valve was carried out using ANSYS/Emag software to investigate the changes of the magnetic flux density and yield stress along the fluid flow paths under the four different radial resistance gaps.Moreover,the experimental tests were also conducted to evaluate the pressure drop,showing that the proposed MR valve has significantly improved its pressure drop at 0.5 mm width of the radial resistance gap when the annular resistance gap is fixed at 1 mm.

An adaptive electrical resistance tomography sensor with flow pattern recognition capability

The all traditional electrical resistance tomography (ERT) sensors have a static structure, which cannot satisfy the intelligent requirements for adaptive optimization to ERT sensors that is subject to flow pattern changes during the real-time detection of two-phase flow. In view of this problem, an adaptive ERT sensor with a dynamic structure is proposed. The electrodes of the ERT sensor are arranged in an array structure, the flow pattern recognition technique is introduced into the ERT sensor design and accordingly an ERT flow pattern recognition method based on signal sparsity is proposed. This method uses the sparse representation of the signal to express the sampling voltage of the ERT system as a sparse combination and find its sparse solution to achieve the classification of different flow patterns. With the introduction of flow identification information, the sensor has an intelligent function of adaptively and dynamically adapting the sensor structure according to the real-time flow pattern change. The experimental results show that the sensor can automatically identify four typical flow patterns: core flow, bubble flow, laminar flow and circulation flow with recognition rates of 91%, 93%, 90% and 88% respectively. For different flow patterns, the dynamically optimized sensor can significantly improve the quality of ERT image reconstruction.

Blood flow restriction in human skeletal muscle during rest periods after high-load resistance training down-regulates miR-206 and induces Pax7

Backgroud:Blood flow re striction(BFR) with low-intensity re sistance training has been shown to result in hypertrophy of skeletal muscle.In this study,we tested the hypothesis that BFR during the rest periods between acute,high-intensity resistance exercise sessions(70% of 1 repetition maximum,7 sets with 10 repetitions) enhances the effects of the resistance training.Methods:A total of 7 healthy young men performed squats,and between sets BFR was carried out on one leg while the other leg served as a control.Because BFR was applied during rest periods,even severe occlusion pressure(approximately 230 mmHg),which almost completely blocked blood flow,was well-tolerated by the participants.Five muscle-specific microRNAs were measured from the biopsy samples,which were taken 2 h after the acute training.Results:Doppler data showed that the pattern of blood flow recovery changed significantly between the first and last BFR.microRNA-206 levels significantly decreased in the BFR leg compared to the control.The mRNA levels of RAC-β serine/threonine-protein kinase v22,nuclear re spiratory factor 1,vascular endothelial growth factor,lupus Ku autoantigen protein p70 genes(p <0.05),and paired box 7(p <0.01) increased in the BFR leg.The protein levels of paired box 7,nuclear respiratory factor 1,and peroxisome proliferator-activated receptor y coactivator 1α did not differ between the BFR leg and the control leg.Conclusion:BFR,during the rest periods of high-load resistance training,could lead to mRNA elevation of those proteins that regulate angiogenesis,mitochondrial biogenesis,and muscle hypertrophy and repair.However,BFR also can cause DNA damage,judging from the increase in mRNA levels of lupus Ku autoantigen protein p70.

Effects of simulated submerged and rigid vegetation and grain roughness on hydraulic resistance to simulated overland flow

Better understanding of the role of vegetation and soil on hydraulic resistance of overland flow requires quantitative partition of their interaction. In this paper, a total of 144 hydraulic flume experiments were carried out to investigate the hydraulic characteristics of overland flow. Results show that hydraulic resistance is negatively correlated with Reynolds number on non-simulated vegetated slopes, while positively on vegetated slopes. The law of composite resistance agrees with the dominant resistance, depending on simulated vegetation stem,surface roughness, and discharge. Surface roughness has greater influence on overland flow resistance than vegetation stem when unit discharge is lower than the low-limited critical discharge, while vegetation has a more obvious influence when unit discharge is higher than the upper-limited critical discharge. Combined effects of simulated vegetation and surface roughness are unequal to the sum of the individual effects through t-test, implying the limitation of using linear superposition principle in calculating overland flow resistances under combined effect of roughness elements.

CFD simulation of flow field and resistance in a 19-core tandem ceramic membrane module

CFD simulation of the permeation process of a 19-core tandem ceramic membrane module was established to investigate flow field and resistance and its change in permeate flux to the membrane element position and the channel of each membrane element.The results show that when the volume flow rate changes from26 m3·h-1 to 89 m3·h-1,the resistance of each part of the membrane module increases gradually.The increase in resistance loss in the membrane element is faster than the plates and the bell mouths.In a single ceramic membrane module,the maximum difference in flow rate of each membrane tube is 7.23%.In a single membrane tube,the outer ring channels 3–5,3–6,3–7,3–8 are relatively slow.The maximum mass flow deviation from the mean is 2.7%.This work helps to clarify the flow mechanism within the modules,optimize the structure of the equipment and provide a reliable basis for the improvement of industrial ceramic membrane modules.

A Fast-Fractional Flow Reserve Simulation Method in A Patient with Coronary Stenosis Based on Resistance Boundary Conditions

Fractional flow reserve(FFR)is the gold standard to identify individual stenosis causing myocardial ischemia in catheter laboratory.The purpose of this study is to present a fast simulation method to estimate FFR value of a coronary artery,which can evaluate the performance of vascular stenosis,based on resistance boundary conditions.A patient-specific 3-dimensional(3D)model of the left coronary system with intermediate diameter stenosis was reconstructed based on the CTA images.The resistance boundary conditions used to simulate the coronary microcirculation were computed based on anatomical reconstruction of coronary 3D model.This study was performed by coupling the 3D coronary tree model with the lumped parameter model(0D model).The flow rate and pressure of coronary tree were calculated in twenty minutes.In addition,the effect of inlet pressure and myocardial mass on FFRss values has been investigated.The results showed that the effect of myocardial mass was greater than the effect of inlet pressure on FFRss.This FFRss simulation method can quickly and accurately assess the influence of coronary stenosis in aid clinical diagnosis.

Simplified Calculation of Flow Resistance of Suspension Bridge Main Cable Dehumidification System

To calculate the flow resistance of a main cable dehumidification system,this study considers the air flow in the main cable as the flow in a porous medium,and adopts the Hagen–Poiseuille equation by using average hydraulic radius and capillary bundle models.A mathematical derivation is combined with an experimental study to obtain a semi-empirical flow resistance formula.Additionally,Fluent software is used to simulate the flow resistance across the main cable relative to the experimental values.Based on the actual measured results for a Yangtze River bridge,this study verifies the semi-empirical formula,and indicates that it can be applied in actual engineering.

Heart and skeletal muscle insulin resistance but not myocardial blood flow reserve could be related to chronic use of thiazolidione in patients with type-2 diabetes

Heart and skeletal muscle insulin resistance and abnormal myocardial flow reserve (MFR) occurs in patients with type-II diabetes. Improvement of heart and skeletal muscle insulin resistance with rosiglitazone use over 16 weeks have been reported. However, it is not clear whether chronic use of troglitazone can improve heart and skeletal muscle insulin resistance and MFR. Materials and Methods: To test the hypothesis whether effects of troglitazone on heart and skeletal muscle insulin resistance and MFR in patients with type-II diabetes, rest and dipyridamole stress perfusion positron emission tomography (PET) with 13N-ammonia and heart and skeletal muscle 18FDG PET scans under insulin clamping were undertaken before and 12 month after the initiation of troglitazone therapy (400 mg/day) in 23 patients with type-II diabetes. Twenty patients with type-II diabetes without CAD and without medications were served as controls. In controls, any medications were not added from the first PET study and 12 months after the second PET study. Results: Baseline myocardial blood flow (MBF) was comparable before and after the troglitazone group as was the controls. MBF during dipyridamole administration (0.56 mg/min/kg) was not significantly improved in troglitazone group and controls. MFR was not improved in troglitazone group and controls. In troglitazone group, whole body glucose disposal rate (GDR;μmole/min/kg) significantly improved (pre;19.0 ± 9.55, post;28.7 ± 15.3, p as did the skeletal muscle glucose utilization rate (SMGU (μmole/min/kg);pre;20.3 ± 12.0, post;34.8 ± 10.6, p insulin resistance is implicated in patients with type-II diabetes and impaired MFR is uncoupled with insulin resistance in the whole body and heart and skeletal muscle in patients with type-II diabetes.

Resistance characteristics of the ball packed-bed regenerator of the new-type swirl flow hot blast stove

A renovation project of miniaturization and high efficiency is provided for the hot blast stove .The experimental data tested feasibility of the new-type swirl flow hot blast stove. The normal and hot state experiments have been done through changing the angle of gas entering into the regenerator. Factors influencing pressure drop have been studied and analyzed. The experimental results can be formulated in the form of the Ergun equation. The regression equation is obtained. And two modified coefficients are offered to the regenerator pressure drop of the new-type swirl flow hot blast stove.

Analytical determination of flow resistance characteristic for combination channel inside hydraulic manifold block

Computational fluid dynamics(CFD)was used in conjunction with BP neural network to study theflow resistance characteristic of the combination-channel inside hydraulic manifold block(HMB).The in-put parameters of the combination-channel model were confirmed to have effect on the pressure-drop bythe numerical method,and a BP neural network model was accordingly constructed to predict the channelpressure-drops.The flow resistance characteristic curves of various channels were achieved,and a perfor-mance parameter was given to evaluate the through-flow characteristic of the channel according to thecurves.The predictions are' in agreement with the numerical computation,indicating that the method canbe utilized to accurately determine the flow characteristic of the combination channel with high efficiency.

Sedimentation motion of sand particles in moving water(Ⅰ):The resistance on a small sphere moving in non-uniform flow

In hydraulics,when we deal with the problem of sand particles moving relative to the surrounding water,Stokes'formula of resistance has usually been used to render the velocity of sedimentation of the particles.But such an approach has not been proved rigorously,and its accuracy must be carefully considered.In this paper,we discuss the problem of a sphere moving in a non-uniform flow field,on the basis of the fundamental theory of hydrodynamics.We introduce two assumptions:i)the diameter of the sphere is much smaller than the linear dimension of the flow field,and ii)the velocity of the sphere relative to the surrounding water is very small.Using these two assumptions,we solve the linearized Navier-Stokes equations and equations of continuity by the method of Laplace transform,and finally we obtain a formula for the resistance acting on a sphere moving in a non-uniform flow field.

Resistance Measured by Airflow Perturbation Compared with Standard Pulmonary Function Measures

Background: Routine lung function testing requires expensive equipment, or requires maximum expiratory effort. The airflow perturbation device (APD) is a light handheld device, allowing for serial measures of respiratory resistance noninvasively and effortlessly. Methods: In a convenience sample of 398 patients undergoing pulmonary function testing, we compared routine spirometric indices (forced expired volume in 1 second (FEV1), peak expiratory flow (PEF)), and airways resistance (Raw-272 patients), to measures of respiratory resistance measured with the APD including inspiratory (IR), expiratory (ER) and averaged (AR) resistance. Results: Measures of lung function were significantly correlated (p 0.001). On regression analysis, between 7% - 17% of the variance (R2) for FEV1, PEF, and Raw was explained by APD measurements. Approximately 2/3 of the variance in FEV1 was explained by PEF measurements. Conclusions: APD measurements of lung function correlate with conventional measures. Future studies should be directed at exploring the use of the APD device in serial measures of lung function in patients with lung disease.

Steric hindrance shielding viologen against alkali attack in realizing ultrastable aqueous flow batteries

Viologens known as a kind of promising negolyte materials for aqueous organic redox flow batteries,face a critical stability challenge due to the S_N2 nucleophilic attack by hydroxide ions(OH-)during the battery cycling.In this work,a N-cyclic quaternary ammonium-grafted viologen molecule,viz.1,1'-bis(4,4'-dime thylpiperidiniumyl)-4,4'-bipyridinium tetrachloride((DBPPy)Cl_(4)),is developed by the molecular engineering strategy.The obtained(DBPPy)Cl_(4) molecule shows a decent solubility of 1.84 M and a redox potential of-0.52 V vs.Ag/AgCl,Experimental and theoretical results reveal that the grafted N-cyclic quaternary ammonium groups act as the steric hindrance to prevent nucleophilic attack by OH~-,increasing the alkali resistance of the electroactive molecule.The symmetrical battery with 0.50 M(DBPPy)Cl4shows negligible decay during the 13-day cycling test.As demonstration,the flow battery utilizing 1.0 M(DBPPy)Cl_(4) as the negolyte and 1-(1-oxyl-2,2',6,6'-tetramethylpiperidin-4-yl)-1'-(3-(trimethylammonio)propyl)-4,4'-bipyridinium trichloride as the posolyte exhibits a high capacity retention rate of 99.99%per cycle at 60 mA cm^(-2).

STUDY ON RESISTANCE CHARACTERISTICOF GAS-SOLID DENSE EXTRUSION FLOW

An experimental study is made on the resistance characteristic ofthe dense extrusion flow with pulverized coal and nitrogen as medium in thispaper. Through the analysis of gas compressibility , solids continuity and lam-mar flow of both gas and solids, a