AIM:To propose a novel glaucoma surgery for rebalancing translaminar pressure difference.METHODS:Three non-human primates with normal eyes and two with laser-induced glaucoma underwent the novel surgical procedure.Can...AIM:To propose a novel glaucoma surgery for rebalancing translaminar pressure difference.METHODS:Three non-human primates with normal eyes and two with laser-induced glaucoma underwent the novel surgical procedure.Cannulation of the subarachnoid space was performed after completion of routine vitrectomy steps.An XEN 45 implant was inserted into the created puncture to communicate between the vitreous body and subarachnoid space.Intraocular pressure(IOP),fundus photography,and spectral-domain optical coherence tomography were assessed at baseline and regular intervals during follow-up.RESULTS:All operated eyes showed IOP reduction in the first postoperative month.Two(2/3)normal eyes and one(1/2)glaucomatous eye maintained lower IOP until 18mo after operation.The XEN 45 implant remained positioned through the lamina cribrosa in all normal eyes but was not detected in two glaucomatous eyes.Complications observed in this study included retinal vascular bleeding in 1/3 normal eyes and XEN implant dislocation in all 2 glaucomatous eyes.CONCLUSION:Subarachnoid space cannulation and mini-shunt implantation may contribute to IOP reduction,possibly by rebalancing translaminar pressure difference and enhancing aqueous humor drainage.The development of a suitable mini-shunt requires further investigation.展开更多
An autonomous altitude adjustment system for a stratospheric satellite(StratoSat)platform is proposed.This platform consists of a helium balloon,a ballonet,and a two-way blower.The helium balloon generates lift to bal...An autonomous altitude adjustment system for a stratospheric satellite(StratoSat)platform is proposed.This platform consists of a helium balloon,a ballonet,and a two-way blower.The helium balloon generates lift to balance the platform gravity.The two-way blower inflates and deflates the ballonet to regulate the buoyancy.Altitude adjustment is achieved by tracking the differential pressure difference(DPD),and a threshold switching strategy is used to achieve blower flow control.The vertical acceleration regulation ability is decided not only by the blower flow rate,but also by the designed margin of pressure difference(MPD).Pressure difference is a slow-varying variable compared with altitude,and it is adopted as the control variable.The response speed of the actuator to disturbance can be delayed,and the overshoot caused by the large inertia of the platform is inhibited.This method can maintain a high tracking accuracy and reduce the complexity of model calculation,thus improving the robustness of controller design.展开更多
Background: Pressure measurement in total cavopulmonary connection (TCPC) patients is a domain of cardiaccatheterization. 4D velocity encoded cardiovascular magnetic resonance (4D–flow MRI) offers an alternative fora...Background: Pressure measurement in total cavopulmonary connection (TCPC) patients is a domain of cardiaccatheterization. 4D velocity encoded cardiovascular magnetic resonance (4D–flow MRI) offers an alternative forassessment of even minor pressure differences. The scope of this study was to measure even minor pressure differencesin the anastomosis of TCPC patients, who are clinically uncompromised. Methods: Twenty-four patients(median 15 years [8;34]) with TCPC were studied prospectively by 4D-flow MRI. Pressure differences betweensuperior vena cava (SVC) and extracardiac conduit (C) to both right pulmonary artery (RPA) and left pulmonaryartery (LPA) were assessed. Small fluid obstructions as vortices within the anastomosis were detected by flowpathlines from 4D-flow MRI. In two patients pressure differences were calculated also by computational flowdynamics (CFD) as a plausibility check for the order of magnitude. Results: Median values of pressure differencesin the anastomosis between SVC and RPA were 0.63 (0.21–2.1) mmHg, between C and RPA 0.67 (0.3–2.2)mmHg, between SVC and LPA 0.8 (0.3–2.4) mmHg and between C and LPA 0.7 (0.2–1.9) mmHg. Patients withpotential flow obstruction (stents, occluder, vortices) had significantly higher gradients at the anastomosis (p <0.05) than patients without potential obstructions, although the absolute values were small. CFD- and measurement-based pressure difference showed good agreement. Conclusion: 4D-flow MRI is able to detect minor pressuredifferences within the Fontan circuit even in patients with apparently satisfactory TCPC. Slightly higherpressure differences are due to the presence of small flow obstruction.展开更多
This paper aims to design an optimized blade for Horizontal Axis Wind Turbine(HWAT).Since airfoil is a basic component of blade design,an optimized airfoil(referred as SJX)was proposed based on the line theory through...This paper aims to design an optimized blade for Horizontal Axis Wind Turbine(HWAT).Since airfoil is a basic component of blade design,an optimized airfoil(referred as SJX)was proposed based on the line theory through the weight analogy to pressure distribution of air flow.Its lift,drag,lift⁃to⁃drag ratio were compared with those NACA2409⁃34,NACA2410,and RK40 airfoils by using Profili software at fixed wind velocity and under different angles of attack.The NACA2409⁃34 airfoil was found to be greatly similar with the SJX airfoil.Based on the Wilson method,blades using SJX and NACA2490⁃34 airfoils were developed and different performance parameters such as velocity distribution,pressure distribution,and power were compared under variable wind velocities and different angles of attack ranging from-4°to 6°at different radius from the center of rotor using computational fluid dynamics(CFD)in ANSYS FLUENT.Results of the study suggested that the performance of the SJX based airfoil and blade was much more optimized.展开更多
Background: In new outpatients, blood pressure should be measured in both arms. A previous study reported that an inter-arm systolic blood pressure difference (ΔSBP) of ≥10 mm Hg is associated with an increased risk...Background: In new outpatients, blood pressure should be measured in both arms. A previous study reported that an inter-arm systolic blood pressure difference (ΔSBP) of ≥10 mm Hg is associated with an increased risk of mortality. Aim: The aim was to identify the associations with absolute values of ΔSBP (|ΔSBP|) ≥10 mm Hg. Subjects and Methods: This study included 2481 patients. Patients with a body mass index ≥25 kg/m<sup>2</sup> were defined as obese. The group of A was defined as following: ankle-brachial index (ABI) was <0.9 or ≥1.3. ΔSBP was expressed as right arm BP minus left arm BP. |ΔSBP| ≥10 mm Hg were analyzed using multivariate logistic analysis. Results: |ΔSBP| ≥10 mm Hg was found in 6.0% of patients and |ΔSBP| < 5 mm Hg in 80.4%. In multivariate analysis, the odds ratios (ORs) of the associations with |ΔSBP| ≥10 mm Hg were significantly associated with abnormal ABI and obesity regardless of sex and age. Moreover, the OR of the combined effects of abnormal ABI and obesity was higher than that of abnormal ABI and obesity alone. Conclusion: |ΔSBP| ≥10 mm Hg was associated with abnormal ABI and obesity. In a primary care setting, blood pressure should be actively measured in both arms. This study suggests that the associations with |ΔSBP| ≥10 mm Hg may be a useful part of screening for abnormal ABI.展开更多
The present study aims to assess the potential difference of biomechanical response of the optic nerve head to the same level of trans-lamina cribrosa pressure difference(TLCPD) induced by a reduced cerebrospinal flui...The present study aims to assess the potential difference of biomechanical response of the optic nerve head to the same level of trans-lamina cribrosa pressure difference(TLCPD) induced by a reduced cerebrospinal fluid pressure(CSFP) or an elevated intraocular pressure(IOP). A finite element model of optic nerve head tissue(pre-and post-laminar neural tissue, lamina cribrosa, sclera, and pia mater) was constructed. Computed stresses, deformations, and strains were compared at each TLCPD step caused by reduced CSFP or elevated IOP. The results showed that elevating TLCPD increased the strain in optic nerve head,with the largest strains occurring in the neural tissue around the sclera ring. Relative to a baseline TLCPD of 10 mmHg, at a same TLCPD of 18 mmHg, the pre-laminar neural tissue experienced 11.10% first principal strain by reduced CSFP and 13.66% by elevated IOP, respectively. The corresponding values for lamina cribrosa were 6.09% and 6.91%. In conclusion, TLCPD has a significant biomechanical impact on optic nerve head tissue and, more prominently, within the pre-laminar neural tissue and lamina cribrosa. Comparatively, reducing CSFP showed smaller strain than elevating IOP even at a same level of TLCPD on ONH tissue, indicating a different potential role of low CSFP in the pathogenesis of glaucoma.展开更多
To address the control accuracy of large fuel flowrate during pressure fluctuation,a novel electro-hydraulic fuel metering unit(FMU)is constructed for afterburner fuel system of military aeroengine.Different from the ...To address the control accuracy of large fuel flowrate during pressure fluctuation,a novel electro-hydraulic fuel metering unit(FMU)is constructed for afterburner fuel system of military aeroengine.Different from the previous FMU,the proposed FMU can achieve the higher precision opening control by a new metering valve with double control chambers(MVDCC),and realize the lower pressure difference fluctuation regulating by a novel two-stage constant pressure difference compensated valve(CPDCV)with dynamic damping orifice and damping piston.The experimental and AMESim simulation results verify the validity and superiority of the novel FMU.Since the temperature-induced variation in fuel properties and device capabilities may degrade or even impair the properties of novel FMU,the discharge flowrate is analyzed by global sensitivity analysis to research the effect proportion of each factor,the temperature effect is explored to ensure the working reliability in long-span temperature variation.Finally,the optimization of structure parameters for novel CPDCV can further reduce pressure difference fluctuation during pressure regulation,and the overshoot,adjust time and the integral of time multiplied by absolute value of error(ITAE)can be reduced by 24%,30%and 26%,respectively.This paper provides a reference for improving the stability of large flowrate during pressure fluctuation.展开更多
Background Most of endovascular stent-graft modifications to preserve side branch must be customized according to extensive pre-operative assessment, which may not be possible in many hospitals and emergency settings....Background Most of endovascular stent-graft modifications to preserve side branch must be customized according to extensive pre-operative assessment, which may not be possible in many hospitals and emergency settings. The study was to develop a novel stent-grafts system that would allow in situ ＂fenestration＂, with less reliance on preoperative imaging. Methods The magnitude of pressure difference （PD） between left subclavian artery （LSA） and aortic arch were measured in 12 experimental pigs. Changes of PD before and after LSA was covered were analyzed respectively. The novel stent graft was made by multi-dimensional and multiple textiles forming technology. According to the PD measurement in pigs, we evaluated the feasibility of the stent-graft in a mock circulation system. Results In pigs, the blood pressure of aortic arch was significantly higher than that of LSA after it was covered （P 〈0.001） and PD was （42.78±5.17） mmHg. After target vessel was covered and when PD between the LSA and aorta reached the magnitude measured in pigs, contrast media oozed from the cranny of graft to the LSA, which was generated by sliding and deformation of yarns of novel stent-graft. Conclusions The study proposes the design of pressure difference-induced perforation aortic stent-grafts system and verifies that the PD between LSA and aortic arch is high enough to allow in situ ＂fenestration＂ by stent graft made by multi-dimensional and multiple textiles forming technoloav.展开更多
An improved finite difference method （FDM）is described to solve existing problems such as low efficiency and poor convergence performance in the traditional method adopted to derive the pressure distribution of aero...An improved finite difference method （FDM）is described to solve existing problems such as low efficiency and poor convergence performance in the traditional method adopted to derive the pressure distribution of aerostatic bearings. A detailed theoretical analysis of the pressure distribution of the orifice-compensated aerostatic journal bearing is presented. The nonlinear dimensionless Reynolds equation of the aerostatic journal bearing is solved by the finite difference method. Based on the principle of flow equilibrium, a new iterative algorithm named the variable step size successive approximation method is presented to adjust the pressure at the orifice in the iterative process and enhance the efficiency and convergence performance of the algorithm. A general program is developed to analyze the pressure distribution of the aerostatic journal bearing by Matlab tool. The results show that the improved finite difference method is highly effective, reliable, stable, and convergent. Even when very thin gas film thicknesses （less than 2 Win）are considered, the improved calculation method still yields a result and converges fast.展开更多
In accordance with the trans-lamina cribrosa pressure difference theory, decreasing the trans-lamina cribrosa pressure difference can re- lieve glaucomatous optic neuropathy. Increased intracranial pressure can also r...In accordance with the trans-lamina cribrosa pressure difference theory, decreasing the trans-lamina cribrosa pressure difference can re- lieve glaucomatous optic neuropathy. Increased intracranial pressure can also reduce optic nerve damage in glaucoma patients, and a safe, effective and noninvasive way to achieve this is by increasing the intra-abdominal pressure. The purpose of this study was to observe the changes in orbital subarachnoid space width and intraocular pressure at elevated intra-abdominal pressure. An inflatable abdominal belt was tied to each of 15 healthy volunteers, aged 22-30 years （12 females and 3 males）, at the navel level, without applying pressure to the abdomen, before they laid in the magnetic resonance imaging machine. The baseline orbital subarachnoid space width around the optic nerve was measured by magnetic resonance imaging at 1, 3, 9, and 15 mm behind the globe. The abdominal belt was inflated to increase the pressure to 40 mmHg （1 mmHg = 0.133 kPa）, then the orbital subarachnoid space width was measured every 10 minutes for 2 hours. After removal of the pressure, the measurement was repeated 10 and 20 minutes later. In a separate trial, the intraocular pressure was measured for all the subjects at the same time points, before, during and after elevated intra-abdominal pressure. Results showed that the baseline mean orbital subarachnoid space width was 0.88 ＋ 0.1 mm （range： 0.77-1.05 mm）, 0.77 ＋ 0.11 mm （range： 0.60-0.94 mm）, 0.70 ＋ 0.08 mm （range： 0.62-0.80 ram）, and 0.68 _＋ 0.08 mm （range： 0.57-0.77 mm） at 1, 3, 9, and 15 mm behind the globe, respectively. During the elevated intra-abdominal pressure, the orbital subarachnoid space width increased from the baseline and dilation of the optic nerve sheath was significant at 1, 3 and 9 mm behind the globe. After decompression of the abdominal pressure, the orbital subarachnoid space width normalized and returned to the baseline value. There was no significant difference in the intraocular pressure before, during and after the intra-abdominal pressure elevation. These results verified that the increased intra-abdominal pressure widens the orbital subarachnoid space in this acute trial, but does not alter the intraocular pressure, indicating that intraocular pressure is not affected by rapid increased in- tra-abdominal pressure. This study was registered in the Chinese Clinical Trial Registry （registration number： ChiCTR-ONRC-14004947）.展开更多
Osmotic pressure can break the fluid balance between intracellular and extracellular solutions.In hypo-osmotic so-lution,water molecules,which transfer into the cell and burst,are driven by the concentration differenc...Osmotic pressure can break the fluid balance between intracellular and extracellular solutions.In hypo-osmotic so-lution,water molecules,which transfer into the cell and burst,are driven by the concentration difference of solute across the semi-permeable membrane.The complicated dynamic processes of intermittent bursts have been previously observed.However,the underlying physical mechanism has yet to be thoroughly explored and analyzed.Here,the intermittent re-lease of inclusion in giant unilamellar vesicles was investigated quantitatively,applying the combination of experimental and theoretical methods in the hypo-osmotic medium.Experimentally,we adopted a highly sensitive electron multiplying charge-coupled device to acquire intermittent dynamic images.Notably,the component of the vesicle phospholipids af-fected the stretch velocity,and the prepared solution of vesicles adjusted the release time.Theoretically,we chose equations and numerical simulations to quantify the dynamic process in phases and explored the influences of physical parameters such as bilayer permeability and solution viscosity on the process.It was concluded that the time taken to achieve the balance of giant unilamellar vesicles was highly dependent on the molecular structure of the lipid.The pore lifetime was strongly related to the internal solution environment of giant unilamellar vesicles.The vesicles prepared in viscous solution were able to visualize long-lived pores.Furthermore,the line tension was measured quantitatively by the release velocity of inclusion,which was of the same order of magnitude as the theoretical simulation.In all,the experimental values well matched the theoretical values.Our investigation clarified the physical regulatory mechanism of intermittent pore forma-tion and inclusion release,which provides an important reference for the development of novel technologies such as gene therapy based on transmembrane transport as well as controlled drug delivery based on liposomes.展开更多
The simulation of the slag discharging process in supercritical water(SCW)fluidized beds is challenging due to the complexity of particle transport in a high-temperature and high-pressure environments.To balance compu...The simulation of the slag discharging process in supercritical water(SCW)fluidized beds is challenging due to the complexity of particle transport in a high-temperature and high-pressure environments.To balance computational efficiency with the need for detailed particle-level information,this study proposes a dynamic three-dimensional numerical model based on computational particle fluid dynamics(CPFD)to investigate the slag discharge process in a SCW fluidized bed reactor.This study presents the dynamic evolution of the flow field,velocity field,and particle phase volume fraction distribution during the slag discharge process,revealing the relationship between the uneven particle distribution and the flow field.Large particles are difficult to be discharged from the bottom of the reactor during the slag discharge process.By increasing the discharging time,the problem of dead zone at the bottom of the reactor can be alleviated effectively.Higher particle velocities and more frequent particle impacts cause more severe wear on the wall near the slag discharge outlet.Reducing the slag discharge differential pressure helps to reduce the wear of the connection.Throughout the entire slag discharge process,the solid holdup remains above 90%,demonstrating the efficiency and rapidity of the slag discharge system.This work aims to provide valuable insights for the design and optimization of slag discharge systems.展开更多
Usually, the electrical breakdown of dielectric barrier discharge (DBD) at atmo-spheric pressure leads to a filamentary non-homogeneous discharge. However, it is also possible to obtain a diffuse DBD in homogeneous fo...Usually, the electrical breakdown of dielectric barrier discharge (DBD) at atmo-spheric pressure leads to a filamentary non-homogeneous discharge. However, it is also possible to obtain a diffuse DBD in homogeneous form, called atmospheric pressure glow discharge (APGD). We obtained a uniform APGD in helium and in the mixture of argon with alcohol, and studied the electrical characteristics of helium APGD. It is found that the relationship between discharge current and source frequency is different depending on the difference in gas gap when the applied voltage is kept constant. The discharge current shows an increasing trend with the increased frequency when gas gap is 0.8 cm, but the discharge current tends to decrease with the increased frequency when the gas gap increases. The discharge current always increases with the increased applied voltage when the source frequency is kept constant. We also observed a glow-like discharge in nitrogen at atmospheric pressure.展开更多
The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Abla- tion and excitation of the graphite material is performed by using an 1064nm Nd：YAG laser in different a...The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Abla- tion and excitation of the graphite material is performed by using an 1064nm Nd：YAG laser in different ambient pressures. Characteristics of graphite spectra as line intensity variations and signal-to-noise ratio are presented with a main focus on the influence of the ambient pressure on the interaction of laser-induced graphite plasma with an ambient environment. Atomic emission lines are utilized to investigate the dynamical behavior of plasma, such as the excitation temperature and electron density, to describe emission differences under different ambient conditions. The excitation temperature and plasma electron density are the primary factors which contribute to the differences among the atomic carbon emission at different ambient pressures. Reactions between the plasma species and ambient gas, and the total molecular number are the main factors influencing molecular carbon emis- sion. The influence of laser energy on the plasma interaction with environment is also investigated to demonstrate the dynamical behavior of carbon species so that it can be utilized to optimize plasma fluctuations.展开更多
Because ring-stiffened cylindrical shell structures have many merits, they are widely used in many areas. However, as the strength of steel increase continuously, ensuring of the structure stability is becoming more a...Because ring-stiffened cylindrical shell structures have many merits, they are widely used in many areas. However, as the strength of steel increase continuously, ensuring of the structure stability is becoming more and more important. Therefore, it is necessary to carry on a more particular analysis. Based on the understanding and analysis of the characteristics of stability for a ring-stiffened cylindrical shell under uniform external pressure and under external single pressure, the characteristics under different cross uniform external pressures are analyzed, and the regularity of it is also gotten. The curve of stability given various geometrical parameters under different cross uniform external pressures is protracted by the analysis of the theory. The conclusion not only improves the theory structural mechanics, it also was important effects on engineering calculation and design.展开更多
Objective:To analyze the efficacy of hyperbaric oxygen at different pressures in the treatment of sudden deafness.Methods:Eighty-two patients with sudden deafness treated in the Affiliated Hospital of Hebei University...Objective:To analyze the efficacy of hyperbaric oxygen at different pressures in the treatment of sudden deafness.Methods:Eighty-two patients with sudden deafness treated in the Affiliated Hospital of Hebei University from September 2019 to September 2021 were selected as the research subjects.The patients were randomly divided into study group 1 and study group 2,and they were treated with hyperbaric oxygen on the basis of routine treatment,in which the pressure used was 1.8 ATA and 2.2 ATA,respectively.Oxygen was delivered via the pressure stabilizing mask for 60 minutes.The patients received two courses of treatment,each lasting 10 days.The changes in hearing(pure tone audiometry)and the clinical efficacy of both the groups were compared before and after treatment.The data obtained were statistically analyzed using SPSS 19.0.Results:The total effective rate of study group 1 was 90.00%,while that of study group 2 was 76.19%.The differences between the two groups were statistically significant(p<0.05).Conclusion:For patients with sudden deafness treated with hyperbaric oxygen,the clinical efficacy of 1.8 ATA is more significant than that of 2.2 ATA.展开更多
Objective:To observe the efficacy and significance of hyperbaric oxygen at different pressures in the treatment of diffuse axonal injury(DAI).Methods:Sixty patients with DAI were randomly divided into 1.8 ATA group(30...Objective:To observe the efficacy and significance of hyperbaric oxygen at different pressures in the treatment of diffuse axonal injury(DAI).Methods:Sixty patients with DAI were randomly divided into 1.8 ATA group(30 cases)and 2.2 ATA group(30 cases).The routine treatment for each group was the same.The 1.8 ATA.group received hyperbaric oxygen therapy under 1.8 ATA on the basis of routine treatment,whereas the 2.2 ATA group received hyperbaric oxygen therapy under 2.2 ATA.on the basis of routine treatment.The therapy was given once a day over 3 consecutive courses,with each course having 10 sessions.The Glasgow Coma Scale(GCS)on day 10,day 20,and day 30 after treatment,as well as the Glasgow Outcome Scale(GOS)after 6 months were compared between the two groups.Results:The mean GCS on day 10,day 20,and day 30 after treatment,as well as the mean GOS after 6 months of treatment in the 2.2 ATA group were significantly higher than those in the 1.8 ATA group(p<0.05).Conclusion:For patients with dififtise axonal injury,hyperbaric oxygen therapy is more effective with 2.2 ATA.compared with 1.8 ATA.展开更多
The porous media combustion technology is an effective solution to stable combustion and clean utilization of low heating value gas. For observing the combustion characteristics of porous media burners under various b...The porous media combustion technology is an effective solution to stable combustion and clean utilization of low heating value gas. For observing the combustion characteristics of porous media burners under various back pressures, investigating flame stability and figuring out the distribution laws of combustion gas flow and resistance loss, so as to achieve an optimized design and efficient operation of the devices, a bench of foamed ceramics porous media combustion devices was thus set up to test the cold-state resistance and hot-state combustion characteristic of burners in working conditions without back pressures and with two different back pressures. The following results are achieved from this experimental study. (1) The strong thermal reflux of porous media can preheat the premixed air effectively, so the flame can be kept stable easily, the combustion equivalent ratio of porous media burners is lower than that of traditional burners, and its pollutant content of flue gas is much lower than the national standard value. (2) The friction coefficient of foamed ceramics decreases with the increase of air flow rate, and its decreasing rate slows down gradually. (3) When the flow rate of air is low, viscosity is the dominant flow resistance, and the friction coefficient is in an inverse relation with the flow rate. (4) As the flow rate of air increases, inertia is the dominant flow resistance, and the friction coefficient is mainly influenced by the roughness and cracks of foamed ceramics. (5) After the introduction of secondary air, the minimum equivalent ratio of porous media burners gets much lower and its range of equivalent ratio is much larger than that of traditional burners.展开更多
Elevated translaminar cribrosa pressure difference(TLCPD),namely the difference between intraocular pressure(IOP)and intracranial pressure(ICP),has been widely accepted as an essential pathogenic factor in glaucomatou...Elevated translaminar cribrosa pressure difference(TLCPD),namely the difference between intraocular pressure(IOP)and intracranial pressure(ICP),has been widely accepted as an essential pathogenic factor in glaucomatous neurodegeneration,especially in normal-tension glaucoma(NTG).In 2010,Ningli Wang's team first identified that nearly half of NTG patients exhibit relatively low ICP through a prospective clinical study,opening a novel avenue of TLCPD-related pathophysiological mechanisms in glaucoma(Ren et al.,2010).展开更多
文摘AIM:To propose a novel glaucoma surgery for rebalancing translaminar pressure difference.METHODS:Three non-human primates with normal eyes and two with laser-induced glaucoma underwent the novel surgical procedure.Cannulation of the subarachnoid space was performed after completion of routine vitrectomy steps.An XEN 45 implant was inserted into the created puncture to communicate between the vitreous body and subarachnoid space.Intraocular pressure(IOP),fundus photography,and spectral-domain optical coherence tomography were assessed at baseline and regular intervals during follow-up.RESULTS:All operated eyes showed IOP reduction in the first postoperative month.Two(2/3)normal eyes and one(1/2)glaucomatous eye maintained lower IOP until 18mo after operation.The XEN 45 implant remained positioned through the lamina cribrosa in all normal eyes but was not detected in two glaucomatous eyes.Complications observed in this study included retinal vascular bleeding in 1/3 normal eyes and XEN implant dislocation in all 2 glaucomatous eyes.CONCLUSION:Subarachnoid space cannulation and mini-shunt implantation may contribute to IOP reduction,possibly by rebalancing translaminar pressure difference and enhancing aqueous humor drainage.The development of a suitable mini-shunt requires further investigation.
基金the National Natural Science Foundation of China(No.52175103)。
文摘An autonomous altitude adjustment system for a stratospheric satellite(StratoSat)platform is proposed.This platform consists of a helium balloon,a ballonet,and a two-way blower.The helium balloon generates lift to balance the platform gravity.The two-way blower inflates and deflates the ballonet to regulate the buoyancy.Altitude adjustment is achieved by tracking the differential pressure difference(DPD),and a threshold switching strategy is used to achieve blower flow control.The vertical acceleration regulation ability is decided not only by the blower flow rate,but also by the designed margin of pressure difference(MPD).Pressure difference is a slow-varying variable compared with altitude,and it is adopted as the control variable.The response speed of the actuator to disturbance can be delayed,and the overshoot caused by the large inertia of the platform is inhibited.This method can maintain a high tracking accuracy and reduce the complexity of model calculation,thus improving the robustness of controller design.
基金This work was supported by Deutsche Herzstiftung e.V.
文摘Background: Pressure measurement in total cavopulmonary connection (TCPC) patients is a domain of cardiaccatheterization. 4D velocity encoded cardiovascular magnetic resonance (4D–flow MRI) offers an alternative forassessment of even minor pressure differences. The scope of this study was to measure even minor pressure differencesin the anastomosis of TCPC patients, who are clinically uncompromised. Methods: Twenty-four patients(median 15 years [8;34]) with TCPC were studied prospectively by 4D-flow MRI. Pressure differences betweensuperior vena cava (SVC) and extracardiac conduit (C) to both right pulmonary artery (RPA) and left pulmonaryartery (LPA) were assessed. Small fluid obstructions as vortices within the anastomosis were detected by flowpathlines from 4D-flow MRI. In two patients pressure differences were calculated also by computational flowdynamics (CFD) as a plausibility check for the order of magnitude. Results: Median values of pressure differencesin the anastomosis between SVC and RPA were 0.63 (0.21–2.1) mmHg, between C and RPA 0.67 (0.3–2.2)mmHg, between SVC and LPA 0.8 (0.3–2.4) mmHg and between C and LPA 0.7 (0.2–1.9) mmHg. Patients withpotential flow obstruction (stents, occluder, vortices) had significantly higher gradients at the anastomosis (p <0.05) than patients without potential obstructions, although the absolute values were small. CFD- and measurement-based pressure difference showed good agreement. Conclusion: 4D-flow MRI is able to detect minor pressuredifferences within the Fontan circuit even in patients with apparently satisfactory TCPC. Slightly higherpressure differences are due to the presence of small flow obstruction.
文摘This paper aims to design an optimized blade for Horizontal Axis Wind Turbine(HWAT).Since airfoil is a basic component of blade design,an optimized airfoil(referred as SJX)was proposed based on the line theory through the weight analogy to pressure distribution of air flow.Its lift,drag,lift⁃to⁃drag ratio were compared with those NACA2409⁃34,NACA2410,and RK40 airfoils by using Profili software at fixed wind velocity and under different angles of attack.The NACA2409⁃34 airfoil was found to be greatly similar with the SJX airfoil.Based on the Wilson method,blades using SJX and NACA2490⁃34 airfoils were developed and different performance parameters such as velocity distribution,pressure distribution,and power were compared under variable wind velocities and different angles of attack ranging from-4°to 6°at different radius from the center of rotor using computational fluid dynamics(CFD)in ANSYS FLUENT.Results of the study suggested that the performance of the SJX based airfoil and blade was much more optimized.
文摘Background: In new outpatients, blood pressure should be measured in both arms. A previous study reported that an inter-arm systolic blood pressure difference (ΔSBP) of ≥10 mm Hg is associated with an increased risk of mortality. Aim: The aim was to identify the associations with absolute values of ΔSBP (|ΔSBP|) ≥10 mm Hg. Subjects and Methods: This study included 2481 patients. Patients with a body mass index ≥25 kg/m<sup>2</sup> were defined as obese. The group of A was defined as following: ankle-brachial index (ABI) was <0.9 or ≥1.3. ΔSBP was expressed as right arm BP minus left arm BP. |ΔSBP| ≥10 mm Hg were analyzed using multivariate logistic analysis. Results: |ΔSBP| ≥10 mm Hg was found in 6.0% of patients and |ΔSBP| < 5 mm Hg in 80.4%. In multivariate analysis, the odds ratios (ORs) of the associations with |ΔSBP| ≥10 mm Hg were significantly associated with abnormal ABI and obesity regardless of sex and age. Moreover, the OR of the combined effects of abnormal ABI and obesity was higher than that of abnormal ABI and obesity alone. Conclusion: |ΔSBP| ≥10 mm Hg was associated with abnormal ABI and obesity. In a primary care setting, blood pressure should be actively measured in both arms. This study suggests that the associations with |ΔSBP| ≥10 mm Hg may be a useful part of screening for abnormal ABI.
基金supported by the National Natural Science Foundation of China(81271005,81300767)the Beijing Natural Science Foundation(7122038,7162037)the Basic-Clinical Research Cooperation Funding of Capital Medical University(2016-JLPT-Y03)。
文摘The present study aims to assess the potential difference of biomechanical response of the optic nerve head to the same level of trans-lamina cribrosa pressure difference(TLCPD) induced by a reduced cerebrospinal fluid pressure(CSFP) or an elevated intraocular pressure(IOP). A finite element model of optic nerve head tissue(pre-and post-laminar neural tissue, lamina cribrosa, sclera, and pia mater) was constructed. Computed stresses, deformations, and strains were compared at each TLCPD step caused by reduced CSFP or elevated IOP. The results showed that elevating TLCPD increased the strain in optic nerve head,with the largest strains occurring in the neural tissue around the sclera ring. Relative to a baseline TLCPD of 10 mmHg, at a same TLCPD of 18 mmHg, the pre-laminar neural tissue experienced 11.10% first principal strain by reduced CSFP and 13.66% by elevated IOP, respectively. The corresponding values for lamina cribrosa were 6.09% and 6.91%. In conclusion, TLCPD has a significant biomechanical impact on optic nerve head tissue and, more prominently, within the pre-laminar neural tissue and lamina cribrosa. Comparatively, reducing CSFP showed smaller strain than elevating IOP even at a same level of TLCPD on ONH tissue, indicating a different potential role of low CSFP in the pathogenesis of glaucoma.
基金co-supported by the National Key Basic Research Program of China(No.2014CB046403)the National Science and Technology Major Project(2017-V-0015-0067)。
文摘To address the control accuracy of large fuel flowrate during pressure fluctuation,a novel electro-hydraulic fuel metering unit(FMU)is constructed for afterburner fuel system of military aeroengine.Different from the previous FMU,the proposed FMU can achieve the higher precision opening control by a new metering valve with double control chambers(MVDCC),and realize the lower pressure difference fluctuation regulating by a novel two-stage constant pressure difference compensated valve(CPDCV)with dynamic damping orifice and damping piston.The experimental and AMESim simulation results verify the validity and superiority of the novel FMU.Since the temperature-induced variation in fuel properties and device capabilities may degrade or even impair the properties of novel FMU,the discharge flowrate is analyzed by global sensitivity analysis to research the effect proportion of each factor,the temperature effect is explored to ensure the working reliability in long-span temperature variation.Finally,the optimization of structure parameters for novel CPDCV can further reduce pressure difference fluctuation during pressure regulation,and the overshoot,adjust time and the integral of time multiplied by absolute value of error(ITAE)can be reduced by 24%,30%and 26%,respectively.This paper provides a reference for improving the stability of large flowrate during pressure fluctuation.
基金DENG Guo-yu and ZHOU Jlan contributed equally to this work. This study was supported by the grants from National Natural Science Foundation of China （No. 30972942, No. 81273522, and No. 81270386）.
文摘Background Most of endovascular stent-graft modifications to preserve side branch must be customized according to extensive pre-operative assessment, which may not be possible in many hospitals and emergency settings. The study was to develop a novel stent-grafts system that would allow in situ ＂fenestration＂, with less reliance on preoperative imaging. Methods The magnitude of pressure difference （PD） between left subclavian artery （LSA） and aortic arch were measured in 12 experimental pigs. Changes of PD before and after LSA was covered were analyzed respectively. The novel stent graft was made by multi-dimensional and multiple textiles forming technology. According to the PD measurement in pigs, we evaluated the feasibility of the stent-graft in a mock circulation system. Results In pigs, the blood pressure of aortic arch was significantly higher than that of LSA after it was covered （P 〈0.001） and PD was （42.78±5.17） mmHg. After target vessel was covered and when PD between the LSA and aorta reached the magnitude measured in pigs, contrast media oozed from the cranny of graft to the LSA, which was generated by sliding and deformation of yarns of novel stent-graft. Conclusions The study proposes the design of pressure difference-induced perforation aortic stent-grafts system and verifies that the PD between LSA and aortic arch is high enough to allow in situ ＂fenestration＂ by stent graft made by multi-dimensional and multiple textiles forming technoloav.
基金The National Natural Science Foundation of China(No50475073,50775036)the High Technology Research Program of Jiangsu Province(NoBG2006035)
文摘An improved finite difference method （FDM）is described to solve existing problems such as low efficiency and poor convergence performance in the traditional method adopted to derive the pressure distribution of aerostatic bearings. A detailed theoretical analysis of the pressure distribution of the orifice-compensated aerostatic journal bearing is presented. The nonlinear dimensionless Reynolds equation of the aerostatic journal bearing is solved by the finite difference method. Based on the principle of flow equilibrium, a new iterative algorithm named the variable step size successive approximation method is presented to adjust the pressure at the orifice in the iterative process and enhance the efficiency and convergence performance of the algorithm. A general program is developed to analyze the pressure distribution of the aerostatic journal bearing by Matlab tool. The results show that the improved finite difference method is highly effective, reliable, stable, and convergent. Even when very thin gas film thicknesses （less than 2 Win）are considered, the improved calculation method still yields a result and converges fast.
文摘In accordance with the trans-lamina cribrosa pressure difference theory, decreasing the trans-lamina cribrosa pressure difference can re- lieve glaucomatous optic neuropathy. Increased intracranial pressure can also reduce optic nerve damage in glaucoma patients, and a safe, effective and noninvasive way to achieve this is by increasing the intra-abdominal pressure. The purpose of this study was to observe the changes in orbital subarachnoid space width and intraocular pressure at elevated intra-abdominal pressure. An inflatable abdominal belt was tied to each of 15 healthy volunteers, aged 22-30 years （12 females and 3 males）, at the navel level, without applying pressure to the abdomen, before they laid in the magnetic resonance imaging machine. The baseline orbital subarachnoid space width around the optic nerve was measured by magnetic resonance imaging at 1, 3, 9, and 15 mm behind the globe. The abdominal belt was inflated to increase the pressure to 40 mmHg （1 mmHg = 0.133 kPa）, then the orbital subarachnoid space width was measured every 10 minutes for 2 hours. After removal of the pressure, the measurement was repeated 10 and 20 minutes later. In a separate trial, the intraocular pressure was measured for all the subjects at the same time points, before, during and after elevated intra-abdominal pressure. Results showed that the baseline mean orbital subarachnoid space width was 0.88 ＋ 0.1 mm （range： 0.77-1.05 mm）, 0.77 ＋ 0.11 mm （range： 0.60-0.94 mm）, 0.70 ＋ 0.08 mm （range： 0.62-0.80 ram）, and 0.68 _＋ 0.08 mm （range： 0.57-0.77 mm） at 1, 3, 9, and 15 mm behind the globe, respectively. During the elevated intra-abdominal pressure, the orbital subarachnoid space width increased from the baseline and dilation of the optic nerve sheath was significant at 1, 3 and 9 mm behind the globe. After decompression of the abdominal pressure, the orbital subarachnoid space width normalized and returned to the baseline value. There was no significant difference in the intraocular pressure before, during and after the intra-abdominal pressure elevation. These results verified that the increased intra-abdominal pressure widens the orbital subarachnoid space in this acute trial, but does not alter the intraocular pressure, indicating that intraocular pressure is not affected by rapid increased in- tra-abdominal pressure. This study was registered in the Chinese Clinical Trial Registry （registration number： ChiCTR-ONRC-14004947）.
基金Project supported by the Joint Funds of Xinjiang Natural Science Foundation,China (Grant No.2022D01C336)School Level Key Projects of Yili Normal University (Grant No.2020YSZD003)+1 种基金the National Natural Science Foundation of China (Grant Nos.11904167 and 22163011)the Postgraduate Scientific Research Innovation Project of Xinjiang, China (Grant No.XJ2022G230)
文摘Osmotic pressure can break the fluid balance between intracellular and extracellular solutions.In hypo-osmotic so-lution,water molecules,which transfer into the cell and burst,are driven by the concentration difference of solute across the semi-permeable membrane.The complicated dynamic processes of intermittent bursts have been previously observed.However,the underlying physical mechanism has yet to be thoroughly explored and analyzed.Here,the intermittent re-lease of inclusion in giant unilamellar vesicles was investigated quantitatively,applying the combination of experimental and theoretical methods in the hypo-osmotic medium.Experimentally,we adopted a highly sensitive electron multiplying charge-coupled device to acquire intermittent dynamic images.Notably,the component of the vesicle phospholipids af-fected the stretch velocity,and the prepared solution of vesicles adjusted the release time.Theoretically,we chose equations and numerical simulations to quantify the dynamic process in phases and explored the influences of physical parameters such as bilayer permeability and solution viscosity on the process.It was concluded that the time taken to achieve the balance of giant unilamellar vesicles was highly dependent on the molecular structure of the lipid.The pore lifetime was strongly related to the internal solution environment of giant unilamellar vesicles.The vesicles prepared in viscous solution were able to visualize long-lived pores.Furthermore,the line tension was measured quantitatively by the release velocity of inclusion,which was of the same order of magnitude as the theoretical simulation.In all,the experimental values well matched the theoretical values.Our investigation clarified the physical regulatory mechanism of intermittent pore forma-tion and inclusion release,which provides an important reference for the development of novel technologies such as gene therapy based on transmembrane transport as well as controlled drug delivery based on liposomes.
基金supported by the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(grant No.52488201).
文摘The simulation of the slag discharging process in supercritical water(SCW)fluidized beds is challenging due to the complexity of particle transport in a high-temperature and high-pressure environments.To balance computational efficiency with the need for detailed particle-level information,this study proposes a dynamic three-dimensional numerical model based on computational particle fluid dynamics(CPFD)to investigate the slag discharge process in a SCW fluidized bed reactor.This study presents the dynamic evolution of the flow field,velocity field,and particle phase volume fraction distribution during the slag discharge process,revealing the relationship between the uneven particle distribution and the flow field.Large particles are difficult to be discharged from the bottom of the reactor during the slag discharge process.By increasing the discharging time,the problem of dead zone at the bottom of the reactor can be alleviated effectively.Higher particle velocities and more frequent particle impacts cause more severe wear on the wall near the slag discharge outlet.Reducing the slag discharge differential pressure helps to reduce the wear of the connection.Throughout the entire slag discharge process,the solid holdup remains above 90%,demonstrating the efficiency and rapidity of the slag discharge system.This work aims to provide valuable insights for the design and optimization of slag discharge systems.
基金This work was supported by the National Science Foundation of China No.19835030.
文摘Usually, the electrical breakdown of dielectric barrier discharge (DBD) at atmo-spheric pressure leads to a filamentary non-homogeneous discharge. However, it is also possible to obtain a diffuse DBD in homogeneous form, called atmospheric pressure glow discharge (APGD). We obtained a uniform APGD in helium and in the mixture of argon with alcohol, and studied the electrical characteristics of helium APGD. It is found that the relationship between discharge current and source frequency is different depending on the difference in gas gap when the applied voltage is kept constant. The discharge current shows an increasing trend with the increased frequency when gas gap is 0.8 cm, but the discharge current tends to decrease with the increased frequency when the gas gap increases. The discharge current always increases with the increased applied voltage when the source frequency is kept constant. We also observed a glow-like discharge in nitrogen at atmospheric pressure.
基金Supported by the FRGS under Grant No R.J130000.7809.4F519
文摘The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Abla- tion and excitation of the graphite material is performed by using an 1064nm Nd：YAG laser in different ambient pressures. Characteristics of graphite spectra as line intensity variations and signal-to-noise ratio are presented with a main focus on the influence of the ambient pressure on the interaction of laser-induced graphite plasma with an ambient environment. Atomic emission lines are utilized to investigate the dynamical behavior of plasma, such as the excitation temperature and electron density, to describe emission differences under different ambient conditions. The excitation temperature and plasma electron density are the primary factors which contribute to the differences among the atomic carbon emission at different ambient pressures. Reactions between the plasma species and ambient gas, and the total molecular number are the main factors influencing molecular carbon emis- sion. The influence of laser energy on the plasma interaction with environment is also investigated to demonstrate the dynamical behavior of carbon species so that it can be utilized to optimize plasma fluctuations.
文摘Because ring-stiffened cylindrical shell structures have many merits, they are widely used in many areas. However, as the strength of steel increase continuously, ensuring of the structure stability is becoming more and more important. Therefore, it is necessary to carry on a more particular analysis. Based on the understanding and analysis of the characteristics of stability for a ring-stiffened cylindrical shell under uniform external pressure and under external single pressure, the characteristics under different cross uniform external pressures are analyzed, and the regularity of it is also gotten. The curve of stability given various geometrical parameters under different cross uniform external pressures is protracted by the analysis of the theory. The conclusion not only improves the theory structural mechanics, it also was important effects on engineering calculation and design.
基金The Youth Scientific Research Fund of the Affiliated Hospital of Hebei University“Observation on the Efficacy of Different Pressure Hyperbaric Oxygen in the Treatment of Sudden Deafness”(Grant Number:2021Q040).
文摘Objective:To analyze the efficacy of hyperbaric oxygen at different pressures in the treatment of sudden deafness.Methods:Eighty-two patients with sudden deafness treated in the Affiliated Hospital of Hebei University from September 2019 to September 2021 were selected as the research subjects.The patients were randomly divided into study group 1 and study group 2,and they were treated with hyperbaric oxygen on the basis of routine treatment,in which the pressure used was 1.8 ATA and 2.2 ATA,respectively.Oxygen was delivered via the pressure stabilizing mask for 60 minutes.The patients received two courses of treatment,each lasting 10 days.The changes in hearing(pure tone audiometry)and the clinical efficacy of both the groups were compared before and after treatment.The data obtained were statistically analyzed using SPSS 19.0.Results:The total effective rate of study group 1 was 90.00%,while that of study group 2 was 76.19%.The differences between the two groups were statistically significant(p<0.05).Conclusion:For patients with sudden deafness treated with hyperbaric oxygen,the clinical efficacy of 1.8 ATA is more significant than that of 2.2 ATA.
文摘Objective:To observe the efficacy and significance of hyperbaric oxygen at different pressures in the treatment of diffuse axonal injury(DAI).Methods:Sixty patients with DAI were randomly divided into 1.8 ATA group(30 cases)and 2.2 ATA group(30 cases).The routine treatment for each group was the same.The 1.8 ATA.group received hyperbaric oxygen therapy under 1.8 ATA on the basis of routine treatment,whereas the 2.2 ATA group received hyperbaric oxygen therapy under 2.2 ATA.on the basis of routine treatment.The therapy was given once a day over 3 consecutive courses,with each course having 10 sessions.The Glasgow Coma Scale(GCS)on day 10,day 20,and day 30 after treatment,as well as the Glasgow Outcome Scale(GOS)after 6 months were compared between the two groups.Results:The mean GCS on day 10,day 20,and day 30 after treatment,as well as the mean GOS after 6 months of treatment in the 2.2 ATA group were significantly higher than those in the 1.8 ATA group(p<0.05).Conclusion:For patients with dififtise axonal injury,hyperbaric oxygen therapy is more effective with 2.2 ATA.compared with 1.8 ATA.
文摘The porous media combustion technology is an effective solution to stable combustion and clean utilization of low heating value gas. For observing the combustion characteristics of porous media burners under various back pressures, investigating flame stability and figuring out the distribution laws of combustion gas flow and resistance loss, so as to achieve an optimized design and efficient operation of the devices, a bench of foamed ceramics porous media combustion devices was thus set up to test the cold-state resistance and hot-state combustion characteristic of burners in working conditions without back pressures and with two different back pressures. The following results are achieved from this experimental study. (1) The strong thermal reflux of porous media can preheat the premixed air effectively, so the flame can be kept stable easily, the combustion equivalent ratio of porous media burners is lower than that of traditional burners, and its pollutant content of flue gas is much lower than the national standard value. (2) The friction coefficient of foamed ceramics decreases with the increase of air flow rate, and its decreasing rate slows down gradually. (3) When the flow rate of air is low, viscosity is the dominant flow resistance, and the friction coefficient is in an inverse relation with the flow rate. (4) As the flow rate of air increases, inertia is the dominant flow resistance, and the friction coefficient is mainly influenced by the roughness and cracks of foamed ceramics. (5) After the introduction of secondary air, the minimum equivalent ratio of porous media burners gets much lower and its range of equivalent ratio is much larger than that of traditional burners.
基金supported by the National Natural Science Foundation of China(82130029,82401256).
文摘Elevated translaminar cribrosa pressure difference(TLCPD),namely the difference between intraocular pressure(IOP)and intracranial pressure(ICP),has been widely accepted as an essential pathogenic factor in glaucomatous neurodegeneration,especially in normal-tension glaucoma(NTG).In 2010,Ningli Wang's team first identified that nearly half of NTG patients exhibit relatively low ICP through a prospective clinical study,opening a novel avenue of TLCPD-related pathophysiological mechanisms in glaucoma(Ren et al.,2010).
