A new type of pressure regulating valve for agriculture irrigation, which used spring to regulate pressure was studied. Through the spring regulating pres-sure test, it concluded that for the pressure regulating valve...A new type of pressure regulating valve for agriculture irrigation, which used spring to regulate pressure was studied. Through the spring regulating pres-sure test, it concluded that for the pressure regulating valve with same spring mod-el, the outer pressure became smal er than the inlet pressure of the system and with the changes of inlet pressure, the outlet pressure remained almost the same, and that when inlet pressure was constant, the valve with smal er spring diameter had lower outlet pressure, indicating that the pressure regulating effect of the spring was more obvious with smal er diameter.展开更多
Based on the simulated laboratory experiment of pressure balance for fire ex- tinguishing,the pressure regulating technology was summarized for the fire district in Meiyukou Coal Mine.The technology includes three mea...Based on the simulated laboratory experiment of pressure balance for fire ex- tinguishing,the pressure regulating technology was summarized for the fire district in Meiyukou Coal Mine.The technology includes three measures for air pressure regulation, namely applying the pressure regulating chamber to balance the air pressure of fire district, increasing the air pressure of the working face,and filling the ground surface fractures.A good effect was obtained to prevent and extinguish the fire.When the measures fail to in- crease the pressure of working face or to regulate that of air chamber,the measure to fill the ground surface fractures will play an important role.展开更多
Most current studies about shield tunneling machine focus on the construction safety and tunnel structure stability during the excavation. Behaviors of the machine itself are also studied, like some tracking control o...Most current studies about shield tunneling machine focus on the construction safety and tunnel structure stability during the excavation. Behaviors of the machine itself are also studied, like some tracking control of the machine. Yet, few works concern about the hydraulic components, especially the pressure and flow rate regulation components. This research focuses on pressure control strategies by using proportional pressure relief valve, which is widely applied on typical shield tunneling machines. Modeling of a commercial pressure relief valve is done. The modeling centers on the main valve, because the dynamic performance is determined by the main valve. To validate such modeling, a frequency-experiment result of the pressure relief valve, whose bandwidth is about 3 Hz, is presented as comparison. The modeling and the frequency experimental result show that it is reasonable to regard the pressure relief valve as a second-order system with two low corner frequencies. PID control, dead band compensation control and adaptive robust control（ARC） are proposed and simulation results are presented. For the ARC, implements by using first order approximation and second order approximation are presented. The simulation results show that the second order approximation implement with ARC can track 4 Hz sine signal very well, and the two ARC simulation errors are within 0.2 MPa. Finally, experiment results of dead band compensation control and adaptive robust control are given. The results show that dead band compensation had about 30° phase lag and about 20% off of the amplitude attenuation. ARC is tracking with little phase lag and almost no amplitude attenuation. In this research, ARC has been tested on a pressure relief valve. It is able to improve the valve＇s dynamic performances greatly, and it is capable of the pressure control of shield machine excavation.展开更多
The current study focuses on the motion-pressure coupled control for a multicapsule stratospheric airship and transforms the path-tracking and heading-hold control of airships into guidance tracking with a time-varyin...The current study focuses on the motion-pressure coupled control for a multicapsule stratospheric airship and transforms the path-tracking and heading-hold control of airships into guidance tracking with a time-varying weighted sum of longitudinal and lateral velocities by the definition of compound speed.Herein,an improved nonlinear predictive control method is provided to reduce the control energy consumption by the rolling optimization of controller parameters based on finite time intervals,ensuring infinite-time path-tracking tasks.Simultaneously,combined with the proposed cyclic regulation process of safe pressure between internal and external capsules,this study can fully reflect the force-thermal coupled rule of airships under the actions of atmospheric environment and maneuvering force,while evaluating the long-endurance capability of airships under the conditions of safe superheating and overpressure.The effectiveness of the motionpressure coupled controller was verified through numerical simulations,which can overcome the influence of environmental wind and achieve a tracking effect for the desired cruise path and compound speed.The airspeed provided during the cyclic circadian time caused the maximum superheating of the helium controlled within 30C.The helium in the internal and external capsules achieved circadian regulation.The equivalent micropore diameter of the capsule of 5 mm can achieve 55 days of long-endurance flight.The controller satisfies the requirements of cruise-flight application modes for multicapsule stratospheric airships with important engineering value.展开更多
The pneumatic vibration isolator(PVI)plays an increasingly important role in precision manufacturing.In this paper,aiming to detect the performance of the pressure regulator in the PVI system,a PVI testing system with...The pneumatic vibration isolator(PVI)plays an increasingly important role in precision manufacturing.In this paper,aiming to detect the performance of the pressure regulator in the PVI system,a PVI testing system with a pressure regulator is designed and developed.Firstly,the structure of the pneumatic spring is presented and analyzed,and the nonlinear stiffness is obtained based on the ideal gas model and material mechanics.Then,according to the working principle and continuity equations of ideal airflow,a dynamic model of the PVI system with a pressure regulator is established.Through the simulation analysis,the vibration isolation performance is improved with the efficient and precise pressure regulator.The average values of both the vibration velocity and transmission rate decrease when the vibration is set to 4,10,20 and 40 Hz,respectively.The experiments demonstrate the reliability and effectiveness of the pressure regulator.This achievement will become an important basis for future research concerning precision manufacturing.展开更多
The aviation oxygen mask,which has a small volume of less than 1L and strong air tightness,imposes extremely high requirements on control performance of the oxygen regulator.Based on analyses of the operation principl...The aviation oxygen mask,which has a small volume of less than 1L and strong air tightness,imposes extremely high requirements on control performance of the oxygen regulator.Based on analyses of the operation principle of oxygen supply system,the dynamic model is established through the combination of mechanism analysis and experimental data.Considering that the traditional fixed-parameter controllers are difficult to meet the control requirements with changes in pulmonary ventilation,this paper presents an online feedback controller based on neural network compensation(NNC),with connection weights that can be updated without pre-training.Then mathematical simulations at different respiratory parameters,such as respiratory rate,are performed to verify the superior lower inspiratory resistance of controller with NNC.In terms of hardware,an embedded AI control platform is to complete the experimental verification.Furthermore,the work may have downward compatibility to achieve stable oxygen supply in civil fields,such as medical ventilators,high-altitude expeditions.展开更多
A novel miniature pressure regulator is fabricated and studied. The regulator can easily be integrated into portable mechatronics or miniature robotic applications because of its lightweight and compact size. An espec...A novel miniature pressure regulator is fabricated and studied. The regulator can easily be integrated into portable mechatronics or miniature robotic applications because of its lightweight and compact size. An especial poppet is designed to minimize its size and to withstand high-pressure. The pressure regulator is designed for a hopping robot which is powered by a combustion system. The hopping robot has great moving capacities such as jumping over big obstacles, wails and dit- ches. The regulator helps the hopping robot to decrease size and weight, and to sustain high pres- sure of oxygen and fuel tank. It will maintain constant output pressure to obtain suitable proportion of oxygen and fuel in the combustion cylinder. Dynamic simulation of the miniature pneumatic pres- sure regulator is performed. Experiments on prototype of miniature pneumatic pressure regulator are also carried out to validate the performance and satisfied performance is obtained.展开更多
The Propellant Feed System(PFS)is a crucial component of Electric Propulsion System(EPS)which is widely used in satellites for its high reliability and specific impulse.The Switching and Proportional Hybrid-controlled...The Propellant Feed System(PFS)is a crucial component of Electric Propulsion System(EPS)which is widely used in satellites for its high reliability and specific impulse.The Switching and Proportional Hybrid-controlled Xenon Feed System(SPHXFS)is a novel type of PFS with high flow regulation precision.This study develops a system-level simulation model with 75 components for the SPHXFS.The accuracy of the model is validated through the comparison with test data,showing an error of less than 3%during the startup phase and less than 0.1%after stabilization.The study analyzes the startup process and finds that the two-stage pressure reduction system avoids two-phase flow interference downstream,achieving a regulation accuracy of±0.1%.A long-term operation simulation of the system is conducted,revealing that pressure fluctuations occur upstream at 4767 s due to Bang-Bang control.However,with proportional control adjustments,these fluctuations do not affect the flow supply.Further research examines the impact of synchronous and asynchronous control modes of the Bang-Bang Valve(TPBBV)under the tank pressures of 6-10 MPa on the system's dynamic characteristics.It is found that the asynchronous control scheme results in a flow supply settling time that is 7.2-10s longer than the synchronous control scheme,with an overshoot increase of 4.1%-4.9%.These insights provide valuable reference and guidance for system optimization design and the formulation of operational strategies.展开更多
Hypertension is a critical health problem and worse other cardiovascular diseases.It is mainly of two types:Primary or essential hypertension and Secondary hypertension.Hypertension is the primary possibility feature ...Hypertension is a critical health problem and worse other cardiovascular diseases.It is mainly of two types:Primary or essential hypertension and Secondary hypertension.Hypertension is the primary possibility feature for coronary heart disease,stroke and renal vascular disease.Herbal medicines have been used for millions of years for the management and treatment of hypertension with minimum side effects.Over aim to write this review is to collect information on the anti-hypertensive effects of natural herbs in animal studies and human involvement as well as to recapitulate the underlying mechanisms,from the bottom of cell culture and ex-vivo tissue data.According to WHO,natural herbs/shrubs are widely used in increasing order to treat almost all the ailments of the human body.Plants are the regular industrial units for the invention of chemical constituents,they used as immunity booster to enhance the natural capacity of the body to fight against different health prob-lems as well as herbal medicines and food products also.Eighty percent population of the world(around 5.6 billion people)consume medicines from natural plants for major health concerns.This review provides a bird’s eye analysis primarily on the traditional utilization,phytochemical constituents and pharmacological values of medicinal herbs used to normalize hypertension i.e.Hibiscus sabdariffa,Allium sativum,Andrographis paniculata,Apium graveolens,Bidenspilosa,Camel-lia sinensis,Coptis chinensis,Coriandrum sativum,Crataegus spp.,Crocus sativus,Cymbopogon citrates,Nigella sativa,Panax ginseng,Salviaemiltiorrhizae,Zingiber officinale,Tribulus terrestris,Rauwolfiaserpentina,Terminalia arjuna etc.展开更多
Characteristic findings in patients with cirrhosis are vasodilatation with low overall systemic vascular resistance, high arterial compliance, increased cardiac output, secondary activation of counter-regulatory syste...Characteristic findings in patients with cirrhosis are vasodilatation with low overall systemic vascular resistance, high arterial compliance, increased cardiac output, secondary activation of counter-regulatory systems （renin-angiotensin-aldosterone system, sympathetic nervous system, release of vasopressin）, and resistance to vasopressors. The vasodilatory state is mediated through adrenomedullin, calcitonin generelated peptide, nitric oxide, and other vasodilators, and is most pronounced in the splanchnic area. This constitutes an effective （although relative） counterbalance to increased arterial blood pressure. This review considers the alterations in systemic hemodynamics in patients with cirrhosis in relation to essential hypertension and arterial hypertension of the renal origin. Subjects with arterial hypertension （essential, secondary） may become normotensive during the development of cirrhosis, and arterial hypertension is rarely manifested in patients with cirrhosis, even in cases with renovascular disease and high circulating renin activity. There is much dispute as to the understanding of homoeostatic regulation in cirrhotic patients with manifest arterial hypertension. This most likely includes the combination of vasodilatation and vasoconstriction in parallel.展开更多
For a typical pressurized system with a novel dual-stage gas pressure reducing regulator,a system model is established with modular models of various typical components. The simulation study on the whole working perio...For a typical pressurized system with a novel dual-stage gas pressure reducing regulator,a system model is established with modular models of various typical components. The simulation study on the whole working period shows that the general trends and magnitudes of simulation curves are in agreement with experimental measured curves. As the key component in the pressurized system, the regulator is studied by a series of numerical simulations to reveal the influences of various structure parameters on its stability. Furthermore, the variable ranges which can guarantee the stability of regulator and system are obtained to provide guidance for design. The modeling and analysis approach can be applied to other systems and components.展开更多
The ecosystem-based management of nearshore waters requires integrated assessment of ocean health and scientific guidance on artificial regulations to promote sustainable development. Quantitative approaches were deve...The ecosystem-based management of nearshore waters requires integrated assessment of ocean health and scientific guidance on artificial regulations to promote sustainable development. Quantitative approaches were developed in this paper to assess present and near-term ocean health based on ecosystem services. Results of the case study in the Laizhou Bay of China showed that the index score of ocean health was 0.785 6 out of 1.0 at present and was expected to range from 0.555 1 to 0.804 1 in the near-term future depending on different intensities of artificial regulation of negative pressures. Specifically, the results of ocean health at present mainly indicated that cultural services and provisioning services performed essentially perfectly while supporting services and regulating services functioned less well. It can be concluded that this nearshore ecosystem would partially lose supporting and regulating services in the near-term future if the increasing pressures were not wellregulated but that all of these categories of ecosystem services could be slightly improved if the negative pressures were fully controlled. Additionally, it is recommended that publicity and education on ecosystem services especially on cultural services and regulating services should be further strengthened. The analytical process and resulting quantification provide flexible tools to guide future development of regulations so as to facilitate ecosystem-based management in the coastal zone.展开更多
Objective: to observe the clinical effect of pressure-regulated volume-controlled ventilation (PRVC) combined with Saber c1007 (cardiopulmonary resuscitator) on cardiopulmonary resuscitation in patients with respirato...Objective: to observe the clinical effect of pressure-regulated volume-controlled ventilation (PRVC) combined with Saber c1007 (cardiopulmonary resuscitator) on cardiopulmonary resuscitation in patients with respiratory and cardiac arrest. Methods: a total of 90 patients who received cardiopulmonary resuscitation due to cardiac arrest in the emergency department of our hospital from 2016 to 2020 and were eligible for the study were selected. All patients received standard chest compressions using Sabo c1007 , and the mechanical ventilation mode was selected: The experimental group used PRVC (pressure regulation volume control), control group 1 using VSV (volume support ventilation), control group 2 using PSV (pressure support ventilation), observe the basic conditions of the three groups of patients, the success rate of resuscitation (ROSC success rate), after successful cardiopulmonary resuscitation Respiratory mechanics indexes and blood gas analysis results were analyzed and compared using statistical methods. Results: (1) There was no statistical significance in the comparison of the basic conditions of the patients in each group. (2) The number of successful resuscitations in the experimental group was higher than that in the control group 1 and the control group 2, and the difference was statistically significant (P0.05, χ27.569). (3) The PaO2 and OI of the experimental group were higher than those of the control group 1 and the control group 2, and the differences were statistically significant (F19.604, 103.576, P0.001), and the CVP and PIP of the experimental group were lower than those of the control group 1, There were statistically significant differences between the two control groups (F7.82, 10.731, both P0.05). There was no significant difference in PaCO2 and MAP between the groups (all P>0.05). Conclusion: PRVC can improve the resuscitation success rate of patients with respiratory and cardiac arrest, and the PRVC mode has a good ability to maintain the patients tidal volume and blood oxygen saturation during cardiopulmonary resuscitation. After successful resuscitation, the patients human-machine coordination is good. It has a higher improvement on PaO2 and OI.展开更多
In the process of oilfield water injection volume of injection allocation often appear with the pump displacement situation does not match, the widespread adoption of stator frequency technology allows the pump displa...In the process of oilfield water injection volume of injection allocation often appear with the pump displacement situation does not match, the widespread adoption of stator frequency technology allows the pump displacement and volume of injection allocation phase matching. But the technology in pump class load application speed range is limited, there is still a reflux valve control blind area,＂ turn off undead＂ problem. ＂ One-for-several＂ rotor frequency Technique in water injection station application, solved the control blind area problem, the full realization of the variable frequency close return voltage injection, at the same time, the successful implementation of the slip power efficient feedback. Stable water injection pressure of the system, and the electric energy is saved, satisfy the oilfield high efficiency, fine water needs, has a high application value.展开更多
Chlorinating wastewater before it is released into surface water can change the fate of organic pollutants.This transformation is influenced by chlorine residues,bromine-containing wastewater,and solar radiation.Losar...Chlorinating wastewater before it is released into surface water can change the fate of organic pollutants.This transformation is influenced by chlorine residues,bromine-containing wastewater,and solar radiation.Losartan(LOS),one of the earliest sartan antihypertensive drugs produced,is used worldwide and has been found in the environment.However,its transformation mechanisms and environmental risks have not been systematically investigated.This research presents the degradation kinetics,transformation products,and environmental risks of LOS in different scenarios.The results revealed that k_(app),HClO(LOS)ranged from 0.47 to 8.30 L/(mol·s)at pH 5.0-8.0.The k_(app),HBrO(LOS)values at pH 5.0-8.0 ranged from 8.38×10^(3) to 1.55×10^(5) L/(mol·s),revealing a faster bromination reaction than chlorination.LOS degrades through direct photolysis,carbonate radicals(CO3^(•-)),and singlet oxygen(^(1)O_(2))under sunlight exposure.The solar/chlorination process accelerates the reaction rate through radical activity.In addition,chlorination and bromination resulted in halogen addition to the aromatic ring,whereas hydroxylation,hydrogen abstraction,demethylation,ring opening,and hydrolysis reactions were observed across all processes.Some products exhibit high biodegradation resistance and high toxicity,potentially threatening the aquatic environment.This study aims to enhance our understanding of the environmental behavior and resulting risks of LOS by exploring its environmental fate through various transformation processes.展开更多
Si_(3)N_(4)ceramics contain two crystalline phases:a-Si_(3)N_(4)andβ-Si_(3)N_(4),distinguished by their stacking sequences along the c-axis.The equiaxed grains of a-Si_(3)N_(4)with the ABCD stacking sequence show hig...Si_(3)N_(4)ceramics contain two crystalline phases:a-Si_(3)N_(4)andβ-Si_(3)N_(4),distinguished by their stacking sequences along the c-axis.The equiaxed grains of a-Si_(3)N_(4)with the ABCD stacking sequence show high hardness.In contrast,theβ-phase adopts an ABAB stacking pattern and forms elongated columnar grains through preferential growth along the c-axis.展开更多
Electrochemical CO_(2)/CO reduction(CO_(2)/CORR)driven by renewable electricity offers a sustainable strategy to produce high-value-added products like acetate(CH3COOH).However,the difficulties in regulating CO adsorp...Electrochemical CO_(2)/CO reduction(CO_(2)/CORR)driven by renewable electricity offers a sustainable strategy to produce high-value-added products like acetate(CH3COOH).However,the difficulties in regulating CO adsorption geometries remain a major obstacle to achieving high acetate Faradaic efficiency(FE)at industrially relevant current densities.We rationally reason that the CO replenishment rate must match the high turnover rate at high overpotentials so that the optimal ratio between the two*CO configurations could be maintained to promote the critical C-C coupling for acetate production.To address this dilemma,we designed a Cu-BTA(1H-benzotriazole)nanoisland catalyst through in situ reconstruction,combined with elevated CO pressure to create a confined microenvironment for effective*CO configuration modulation.The designed Cu-BTA catalyst exhibits superior CO-to-acetate selectivity with an 80.8%FE and 180 mg h^(−1)cm^(−2)production rate at−400 mA cm^(−2)under 7 bar CO(1 bar=100 kPa),surpassing most Cu-based catalysts.In situ characterizations and density functional theory(DFT)calculations reveal that elevated CO pressure effectively increases the atop-adsorbed CO/bridge-adsorbed CO(*COatop/*COb)ratio,accelerates the rate-determining step(*CO+*CO to*OCCOH),and promotes the formation of key intermediates such as*CCO and*CH_(2)CO,ultimately boosting CH3COOH production.展开更多
Objective: To explore the interventional effects of renal-targeting peptide-modified ginsenoside Rg3 nanomicelle(GRg3@RT-PMs) on hypertension and vascular calcification in patients with long-term renal dialysis, and t...Objective: To explore the interventional effects of renal-targeting peptide-modified ginsenoside Rg3 nanomicelle(GRg3@RT-PMs) on hypertension and vascular calcification in patients with long-term renal dialysis, and to elucidate its potential molecular mechanism, providing a new strategy for the precise treatment of dialysis complications. Methods: GRg3@RT-PMs were prepared using chitosan and ginsenoside Rg3 self-assembly technology modified with a renal-targeted peptide(G3-C12). Their particle size, encapsulation efficiency, and in vitro sustained-release characteristics were characterized. A high-phosphate-induced calcification model of human renal tubular epithelial cells(HK-2) was used to evaluate the targeting ability,biocompatibility, and inhibitory effect of GRg3@RT-PMs on calcification marker proteins(BMP-2, Runx2). A total of 18 dialysis patients were enrolled to assess the effects of oral administration of PMs, GRg3, and GRg3@RT-PMs on blood pressure and arterial calcification. Results: GRg3@RT-PMs had a particle size of(125.3±3.2) nm, an encapsulation efficiency of(89.7±2.3)%, and a cumulative release rate of(82.5±3.1)%over >48 h;GRg3@RT-PMs significantly inhibited the expression of BMP-2 and Runx2 in high-phosphate-induced HK-2 cells(P<0.01);In patients, the systolic blood pressure in the GRg3@RT-PMs group trended toward the normal range and was lower than that in the ginsenoside Rg3 and Rg3/β-CD complex groups, while diastolic blood pressure was more stable(P<0.05);The calcification score in the GRg3@RT-PMs group was lower than that in the Rg3 group after administration(P<0.01). Conclusion: GRg3@RT-PMs effectively alleviated dialysis-related vascular calcification and blood pressure abnormalities through the renal-targeted delivery, demonstrating a potential for clinical translation.展开更多
In view of some of the characteristics of a high-medium pressure gas regulator, such as small fault samples, many fault types and complex fault features etc, in order to improve the accuracy of fault precaution in thi...In view of some of the characteristics of a high-medium pressure gas regulator, such as small fault samples, many fault types and complex fault features etc, in order to improve the accuracy of fault precaution in this paper, a fault diagnosis method based on the combination of the improved wavelet packet and pressure harmonic distortion rate is proposed. On the basis of the harmonic distortion rate of the outlet pressure and the energy value of each frequency band obtained by improved wavelet packet decomposition, the rules for fault data were summarized. Finally, a safety precaution model of the high-medium pressure gas regulator is established.展开更多
文摘A new type of pressure regulating valve for agriculture irrigation, which used spring to regulate pressure was studied. Through the spring regulating pres-sure test, it concluded that for the pressure regulating valve with same spring mod-el, the outer pressure became smal er than the inlet pressure of the system and with the changes of inlet pressure, the outlet pressure remained almost the same, and that when inlet pressure was constant, the valve with smal er spring diameter had lower outlet pressure, indicating that the pressure regulating effect of the spring was more obvious with smal er diameter.
基金the Natural Science Foundation of Liaoning Province(20060390)
文摘Based on the simulated laboratory experiment of pressure balance for fire ex- tinguishing,the pressure regulating technology was summarized for the fire district in Meiyukou Coal Mine.The technology includes three measures for air pressure regulation, namely applying the pressure regulating chamber to balance the air pressure of fire district, increasing the air pressure of the working face,and filling the ground surface fractures.A good effect was obtained to prevent and extinguish the fire.When the measures fail to in- crease the pressure of working face or to regulate that of air chamber,the measure to fill the ground surface fractures will play an important role.
基金Supported by National Natural Science Funds of China(Grant No.51275451)National Basic Research Program of China(973 Program,Grant No.2013CB035404)+1 种基金Science Fund for Creative Research Groups of National Natural Science Foundation of China(Grant No.51221004)National Hi-tech Research and Development Program of China(863 Program,Grant No.2013AA040203)
文摘Most current studies about shield tunneling machine focus on the construction safety and tunnel structure stability during the excavation. Behaviors of the machine itself are also studied, like some tracking control of the machine. Yet, few works concern about the hydraulic components, especially the pressure and flow rate regulation components. This research focuses on pressure control strategies by using proportional pressure relief valve, which is widely applied on typical shield tunneling machines. Modeling of a commercial pressure relief valve is done. The modeling centers on the main valve, because the dynamic performance is determined by the main valve. To validate such modeling, a frequency-experiment result of the pressure relief valve, whose bandwidth is about 3 Hz, is presented as comparison. The modeling and the frequency experimental result show that it is reasonable to regard the pressure relief valve as a second-order system with two low corner frequencies. PID control, dead band compensation control and adaptive robust control（ARC） are proposed and simulation results are presented. For the ARC, implements by using first order approximation and second order approximation are presented. The simulation results show that the second order approximation implement with ARC can track 4 Hz sine signal very well, and the two ARC simulation errors are within 0.2 MPa. Finally, experiment results of dead band compensation control and adaptive robust control are given. The results show that dead band compensation had about 30° phase lag and about 20% off of the amplitude attenuation. ARC is tracking with little phase lag and almost no amplitude attenuation. In this research, ARC has been tested on a pressure relief valve. It is able to improve the valve＇s dynamic performances greatly, and it is capable of the pressure control of shield machine excavation.
基金supported by the National Natural Science Foundation of China(Nos.62073019,62227810).
文摘The current study focuses on the motion-pressure coupled control for a multicapsule stratospheric airship and transforms the path-tracking and heading-hold control of airships into guidance tracking with a time-varying weighted sum of longitudinal and lateral velocities by the definition of compound speed.Herein,an improved nonlinear predictive control method is provided to reduce the control energy consumption by the rolling optimization of controller parameters based on finite time intervals,ensuring infinite-time path-tracking tasks.Simultaneously,combined with the proposed cyclic regulation process of safe pressure between internal and external capsules,this study can fully reflect the force-thermal coupled rule of airships under the actions of atmospheric environment and maneuvering force,while evaluating the long-endurance capability of airships under the conditions of safe superheating and overpressure.The effectiveness of the motionpressure coupled controller was verified through numerical simulations,which can overcome the influence of environmental wind and achieve a tracking effect for the desired cruise path and compound speed.The airspeed provided during the cyclic circadian time caused the maximum superheating of the helium controlled within 30C.The helium in the internal and external capsules achieved circadian regulation.The equivalent micropore diameter of the capsule of 5 mm can achieve 55 days of long-endurance flight.The controller satisfies the requirements of cruise-flight application modes for multicapsule stratospheric airships with important engineering value.
基金National Key Research and Development Project(Grant No.2021YFC0122502)Youth Fund of National Natural Science Foundation of China(Grant Nos.52105044,52105046).
文摘The pneumatic vibration isolator(PVI)plays an increasingly important role in precision manufacturing.In this paper,aiming to detect the performance of the pressure regulator in the PVI system,a PVI testing system with a pressure regulator is designed and developed.Firstly,the structure of the pneumatic spring is presented and analyzed,and the nonlinear stiffness is obtained based on the ideal gas model and material mechanics.Then,according to the working principle and continuity equations of ideal airflow,a dynamic model of the PVI system with a pressure regulator is established.Through the simulation analysis,the vibration isolation performance is improved with the efficient and precise pressure regulator.The average values of both the vibration velocity and transmission rate decrease when the vibration is set to 4,10,20 and 40 Hz,respectively.The experiments demonstrate the reliability and effectiveness of the pressure regulator.This achievement will become an important basis for future research concerning precision manufacturing.
基金supported by the National Natural Science Foundation of China(Nos.61973172,62003177,62003175 and 61973175).
文摘The aviation oxygen mask,which has a small volume of less than 1L and strong air tightness,imposes extremely high requirements on control performance of the oxygen regulator.Based on analyses of the operation principle of oxygen supply system,the dynamic model is established through the combination of mechanism analysis and experimental data.Considering that the traditional fixed-parameter controllers are difficult to meet the control requirements with changes in pulmonary ventilation,this paper presents an online feedback controller based on neural network compensation(NNC),with connection weights that can be updated without pre-training.Then mathematical simulations at different respiratory parameters,such as respiratory rate,are performed to verify the superior lower inspiratory resistance of controller with NNC.In terms of hardware,an embedded AI control platform is to complete the experimental verification.Furthermore,the work may have downward compatibility to achieve stable oxygen supply in civil fields,such as medical ventilators,high-altitude expeditions.
文摘A novel miniature pressure regulator is fabricated and studied. The regulator can easily be integrated into portable mechatronics or miniature robotic applications because of its lightweight and compact size. An especial poppet is designed to minimize its size and to withstand high-pressure. The pressure regulator is designed for a hopping robot which is powered by a combustion system. The hopping robot has great moving capacities such as jumping over big obstacles, wails and dit- ches. The regulator helps the hopping robot to decrease size and weight, and to sustain high pres- sure of oxygen and fuel tank. It will maintain constant output pressure to obtain suitable proportion of oxygen and fuel in the combustion cylinder. Dynamic simulation of the miniature pneumatic pres- sure regulator is performed. Experiments on prototype of miniature pneumatic pressure regulator are also carried out to validate the performance and satisfied performance is obtained.
基金supported by the Fundamental Research Funds for the Central Universities,China(No.JKF-2025009442288)the Excellent Youth Team Cultivation Project for Central Universities of the Ministry of Education,China(No.YWF-22/23/24-JT-106)。
文摘The Propellant Feed System(PFS)is a crucial component of Electric Propulsion System(EPS)which is widely used in satellites for its high reliability and specific impulse.The Switching and Proportional Hybrid-controlled Xenon Feed System(SPHXFS)is a novel type of PFS with high flow regulation precision.This study develops a system-level simulation model with 75 components for the SPHXFS.The accuracy of the model is validated through the comparison with test data,showing an error of less than 3%during the startup phase and less than 0.1%after stabilization.The study analyzes the startup process and finds that the two-stage pressure reduction system avoids two-phase flow interference downstream,achieving a regulation accuracy of±0.1%.A long-term operation simulation of the system is conducted,revealing that pressure fluctuations occur upstream at 4767 s due to Bang-Bang control.However,with proportional control adjustments,these fluctuations do not affect the flow supply.Further research examines the impact of synchronous and asynchronous control modes of the Bang-Bang Valve(TPBBV)under the tank pressures of 6-10 MPa on the system's dynamic characteristics.It is found that the asynchronous control scheme results in a flow supply settling time that is 7.2-10s longer than the synchronous control scheme,with an overshoot increase of 4.1%-4.9%.These insights provide valuable reference and guidance for system optimization design and the formulation of operational strategies.
文摘Hypertension is a critical health problem and worse other cardiovascular diseases.It is mainly of two types:Primary or essential hypertension and Secondary hypertension.Hypertension is the primary possibility feature for coronary heart disease,stroke and renal vascular disease.Herbal medicines have been used for millions of years for the management and treatment of hypertension with minimum side effects.Over aim to write this review is to collect information on the anti-hypertensive effects of natural herbs in animal studies and human involvement as well as to recapitulate the underlying mechanisms,from the bottom of cell culture and ex-vivo tissue data.According to WHO,natural herbs/shrubs are widely used in increasing order to treat almost all the ailments of the human body.Plants are the regular industrial units for the invention of chemical constituents,they used as immunity booster to enhance the natural capacity of the body to fight against different health prob-lems as well as herbal medicines and food products also.Eighty percent population of the world(around 5.6 billion people)consume medicines from natural plants for major health concerns.This review provides a bird’s eye analysis primarily on the traditional utilization,phytochemical constituents and pharmacological values of medicinal herbs used to normalize hypertension i.e.Hibiscus sabdariffa,Allium sativum,Andrographis paniculata,Apium graveolens,Bidenspilosa,Camel-lia sinensis,Coptis chinensis,Coriandrum sativum,Crataegus spp.,Crocus sativus,Cymbopogon citrates,Nigella sativa,Panax ginseng,Salviaemiltiorrhizae,Zingiber officinale,Tribulus terrestris,Rauwolfiaserpentina,Terminalia arjuna etc.
文摘Characteristic findings in patients with cirrhosis are vasodilatation with low overall systemic vascular resistance, high arterial compliance, increased cardiac output, secondary activation of counter-regulatory systems （renin-angiotensin-aldosterone system, sympathetic nervous system, release of vasopressin）, and resistance to vasopressors. The vasodilatory state is mediated through adrenomedullin, calcitonin generelated peptide, nitric oxide, and other vasodilators, and is most pronounced in the splanchnic area. This constitutes an effective （although relative） counterbalance to increased arterial blood pressure. This review considers the alterations in systemic hemodynamics in patients with cirrhosis in relation to essential hypertension and arterial hypertension of the renal origin. Subjects with arterial hypertension （essential, secondary） may become normotensive during the development of cirrhosis, and arterial hypertension is rarely manifested in patients with cirrhosis, even in cases with renovascular disease and high circulating renin activity. There is much dispute as to the understanding of homoeostatic regulation in cirrhotic patients with manifest arterial hypertension. This most likely includes the combination of vasodilatation and vasoconstriction in parallel.
基金financially supported by the National Natural Science Foundation of China (No.11101023)the China Scholarship Council (No.201203070237)
文摘For a typical pressurized system with a novel dual-stage gas pressure reducing regulator,a system model is established with modular models of various typical components. The simulation study on the whole working period shows that the general trends and magnitudes of simulation curves are in agreement with experimental measured curves. As the key component in the pressurized system, the regulator is studied by a series of numerical simulations to reveal the influences of various structure parameters on its stability. Furthermore, the variable ranges which can guarantee the stability of regulator and system are obtained to provide guidance for design. The modeling and analysis approach can be applied to other systems and components.
基金The Public Science and Technology Research Funds Projects of Ocean in China under contract Nos 201005008 and201005009the National Natural Science Foundation of China under contract No.41206112
文摘The ecosystem-based management of nearshore waters requires integrated assessment of ocean health and scientific guidance on artificial regulations to promote sustainable development. Quantitative approaches were developed in this paper to assess present and near-term ocean health based on ecosystem services. Results of the case study in the Laizhou Bay of China showed that the index score of ocean health was 0.785 6 out of 1.0 at present and was expected to range from 0.555 1 to 0.804 1 in the near-term future depending on different intensities of artificial regulation of negative pressures. Specifically, the results of ocean health at present mainly indicated that cultural services and provisioning services performed essentially perfectly while supporting services and regulating services functioned less well. It can be concluded that this nearshore ecosystem would partially lose supporting and regulating services in the near-term future if the increasing pressures were not wellregulated but that all of these categories of ecosystem services could be slightly improved if the negative pressures were fully controlled. Additionally, it is recommended that publicity and education on ecosystem services especially on cultural services and regulating services should be further strengthened. The analytical process and resulting quantification provide flexible tools to guide future development of regulations so as to facilitate ecosystem-based management in the coastal zone.
文摘Objective: to observe the clinical effect of pressure-regulated volume-controlled ventilation (PRVC) combined with Saber c1007 (cardiopulmonary resuscitator) on cardiopulmonary resuscitation in patients with respiratory and cardiac arrest. Methods: a total of 90 patients who received cardiopulmonary resuscitation due to cardiac arrest in the emergency department of our hospital from 2016 to 2020 and were eligible for the study were selected. All patients received standard chest compressions using Sabo c1007 , and the mechanical ventilation mode was selected: The experimental group used PRVC (pressure regulation volume control), control group 1 using VSV (volume support ventilation), control group 2 using PSV (pressure support ventilation), observe the basic conditions of the three groups of patients, the success rate of resuscitation (ROSC success rate), after successful cardiopulmonary resuscitation Respiratory mechanics indexes and blood gas analysis results were analyzed and compared using statistical methods. Results: (1) There was no statistical significance in the comparison of the basic conditions of the patients in each group. (2) The number of successful resuscitations in the experimental group was higher than that in the control group 1 and the control group 2, and the difference was statistically significant (P0.05, χ27.569). (3) The PaO2 and OI of the experimental group were higher than those of the control group 1 and the control group 2, and the differences were statistically significant (F19.604, 103.576, P0.001), and the CVP and PIP of the experimental group were lower than those of the control group 1, There were statistically significant differences between the two control groups (F7.82, 10.731, both P0.05). There was no significant difference in PaCO2 and MAP between the groups (all P>0.05). Conclusion: PRVC can improve the resuscitation success rate of patients with respiratory and cardiac arrest, and the PRVC mode has a good ability to maintain the patients tidal volume and blood oxygen saturation during cardiopulmonary resuscitation. After successful resuscitation, the patients human-machine coordination is good. It has a higher improvement on PaO2 and OI.
文摘In the process of oilfield water injection volume of injection allocation often appear with the pump displacement situation does not match, the widespread adoption of stator frequency technology allows the pump displacement and volume of injection allocation phase matching. But the technology in pump class load application speed range is limited, there is still a reflux valve control blind area,＂ turn off undead＂ problem. ＂ One-for-several＂ rotor frequency Technique in water injection station application, solved the control blind area problem, the full realization of the variable frequency close return voltage injection, at the same time, the successful implementation of the slip power efficient feedback. Stable water injection pressure of the system, and the electric energy is saved, satisfy the oilfield high efficiency, fine water needs, has a high application value.
基金supported by the National Key R&D Program of China(No.2023YFE0112100)the Natural Science Foundation of Xiamen(China)(No.3502Z202373008)the National Natural Science Foundation of China(Nos.22476166 and 42376210).
文摘Chlorinating wastewater before it is released into surface water can change the fate of organic pollutants.This transformation is influenced by chlorine residues,bromine-containing wastewater,and solar radiation.Losartan(LOS),one of the earliest sartan antihypertensive drugs produced,is used worldwide and has been found in the environment.However,its transformation mechanisms and environmental risks have not been systematically investigated.This research presents the degradation kinetics,transformation products,and environmental risks of LOS in different scenarios.The results revealed that k_(app),HClO(LOS)ranged from 0.47 to 8.30 L/(mol·s)at pH 5.0-8.0.The k_(app),HBrO(LOS)values at pH 5.0-8.0 ranged from 8.38×10^(3) to 1.55×10^(5) L/(mol·s),revealing a faster bromination reaction than chlorination.LOS degrades through direct photolysis,carbonate radicals(CO3^(•-)),and singlet oxygen(^(1)O_(2))under sunlight exposure.The solar/chlorination process accelerates the reaction rate through radical activity.In addition,chlorination and bromination resulted in halogen addition to the aromatic ring,whereas hydroxylation,hydrogen abstraction,demethylation,ring opening,and hydrolysis reactions were observed across all processes.Some products exhibit high biodegradation resistance and high toxicity,potentially threatening the aquatic environment.This study aims to enhance our understanding of the environmental behavior and resulting risks of LOS by exploring its environmental fate through various transformation processes.
基金financially supported by the National Natural Science Foundation of China(52322207,92163208,and 52494933)the National Key Research and Development Plan of China(2021YFB3701400)the Independent Innovation Projects of the Hubei Longzhong Laboratory(2022ZZ-11)。
文摘Si_(3)N_(4)ceramics contain two crystalline phases:a-Si_(3)N_(4)andβ-Si_(3)N_(4),distinguished by their stacking sequences along the c-axis.The equiaxed grains of a-Si_(3)N_(4)with the ABCD stacking sequence show high hardness.In contrast,theβ-phase adopts an ABAB stacking pattern and forms elongated columnar grains through preferential growth along the c-axis.
基金supported by the National Natural Science Foundation of China(22373080,22402163,22078274,22475075,and 52376187)the Natural Science Foundation of Fujian Province of China(2024J08008 and 2022J05009)+3 种基金Fujian Provincial Science and Technology Program for International Cooperation(2025I0002)the Natural Science Foundation of Xiamen,China(3502Z202472001)the Fundamental Research Funds for the Central Universities,China(20720240054)the Nan-qiang Youth Scholar Program of Xiamen University and Xiaomi Young Talents Program/Xiaomi Foundation,and the National Key Research and Development Program,China(2024YFE0211300).
文摘Electrochemical CO_(2)/CO reduction(CO_(2)/CORR)driven by renewable electricity offers a sustainable strategy to produce high-value-added products like acetate(CH3COOH).However,the difficulties in regulating CO adsorption geometries remain a major obstacle to achieving high acetate Faradaic efficiency(FE)at industrially relevant current densities.We rationally reason that the CO replenishment rate must match the high turnover rate at high overpotentials so that the optimal ratio between the two*CO configurations could be maintained to promote the critical C-C coupling for acetate production.To address this dilemma,we designed a Cu-BTA(1H-benzotriazole)nanoisland catalyst through in situ reconstruction,combined with elevated CO pressure to create a confined microenvironment for effective*CO configuration modulation.The designed Cu-BTA catalyst exhibits superior CO-to-acetate selectivity with an 80.8%FE and 180 mg h^(−1)cm^(−2)production rate at−400 mA cm^(−2)under 7 bar CO(1 bar=100 kPa),surpassing most Cu-based catalysts.In situ characterizations and density functional theory(DFT)calculations reveal that elevated CO pressure effectively increases the atop-adsorbed CO/bridge-adsorbed CO(*COatop/*COb)ratio,accelerates the rate-determining step(*CO+*CO to*OCCOH),and promotes the formation of key intermediates such as*CCO and*CH_(2)CO,ultimately boosting CH3COOH production.
文摘Objective: To explore the interventional effects of renal-targeting peptide-modified ginsenoside Rg3 nanomicelle(GRg3@RT-PMs) on hypertension and vascular calcification in patients with long-term renal dialysis, and to elucidate its potential molecular mechanism, providing a new strategy for the precise treatment of dialysis complications. Methods: GRg3@RT-PMs were prepared using chitosan and ginsenoside Rg3 self-assembly technology modified with a renal-targeted peptide(G3-C12). Their particle size, encapsulation efficiency, and in vitro sustained-release characteristics were characterized. A high-phosphate-induced calcification model of human renal tubular epithelial cells(HK-2) was used to evaluate the targeting ability,biocompatibility, and inhibitory effect of GRg3@RT-PMs on calcification marker proteins(BMP-2, Runx2). A total of 18 dialysis patients were enrolled to assess the effects of oral administration of PMs, GRg3, and GRg3@RT-PMs on blood pressure and arterial calcification. Results: GRg3@RT-PMs had a particle size of(125.3±3.2) nm, an encapsulation efficiency of(89.7±2.3)%, and a cumulative release rate of(82.5±3.1)%over >48 h;GRg3@RT-PMs significantly inhibited the expression of BMP-2 and Runx2 in high-phosphate-induced HK-2 cells(P<0.01);In patients, the systolic blood pressure in the GRg3@RT-PMs group trended toward the normal range and was lower than that in the ginsenoside Rg3 and Rg3/β-CD complex groups, while diastolic blood pressure was more stable(P<0.05);The calcification score in the GRg3@RT-PMs group was lower than that in the Rg3 group after administration(P<0.01). Conclusion: GRg3@RT-PMs effectively alleviated dialysis-related vascular calcification and blood pressure abnormalities through the renal-targeted delivery, demonstrating a potential for clinical translation.
基金supported by Science and technology project of Beijing in 2015 from Beijing Municipal Science&Technology Commission
文摘In view of some of the characteristics of a high-medium pressure gas regulator, such as small fault samples, many fault types and complex fault features etc, in order to improve the accuracy of fault precaution in this paper, a fault diagnosis method based on the combination of the improved wavelet packet and pressure harmonic distortion rate is proposed. On the basis of the harmonic distortion rate of the outlet pressure and the energy value of each frequency band obtained by improved wavelet packet decomposition, the rules for fault data were summarized. Finally, a safety precaution model of the high-medium pressure gas regulator is established.
