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Academic literature on the topic 'Unstable charge pump'
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Journal articles on the topic "Unstable charge pump"
1
Kumar, Amit, Ruby Gupta, and Jyotsna Sharma. "Effect of dust grains on the parametric coupling of a lower hybrid wave driven ion cyclotron wave in a tokamak plasma." AIP Advances 12, no. 3 (2022): 035026. http://dx.doi.org/10.1063/5.0085062.
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In this article, the effect of dust charge fluctuations on the parametric upconversion of a lower hybrid wave into an ion cyclotron wave and a side band wave in a two-ion species tokamak plasma is studied. When the oscillatory velocity of plasma electrons is a few percent of the sound velocity, the lower hybrid wave becomes unstable and decays into two modes: an ion cyclotron wave mode and a low frequency lower hybrid side band wave. Furthermore, a ponderomotive force by a lower hybrid pump and a side band wave is exerted on the existing electrons, which drives the ion cyclotron decay mode. The presence of negatively charged dust grains and their shape, size, radius, and density influence the instability. The growth rate of instability is calculated by considering typical existing D–T (Deuterium–Tritium) dusty plasma parameters, and it is observed that the growth rate increases with the relative density of dust grains, number density of dust grains, oscillatory velocity of electrons, and amplitude of pump waves. However, the normalized growth rate increases with the unstable wave frequency, and it also increases as we increase the ratio of deuterium to tritium density. Here, the growth rate decreases with the increase in the size of dust grains and electron cyclotron frequency. The theoretical results summarized in the present study are able to efficiently elaborate the complexity produced in plasma properties in a tokamak due to the dust–plasma interactions, which are briefly discussed here.
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Gray, Megan M., Anita A. Thomas, Brian Burns, and Rachel A. Umoren. "Identifying Crucial Equipment and Skills Needed to Evacuate Critically Ill Infants During Disasters: Using Nursing Expertise to Guide Training Targets." Prehospital and Disaster Medicine 34, no. 04 (2019): 370–75. http://dx.doi.org/10.1017/s1049023x19004473.
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AbstractIntroduction:Unexpected disasters, such as earthquakes or fires, require preparation to address knowledge gaps that may negatively affect vulnerable patients. Training programs can promote natural disaster readiness to respond and evacuate patients safely, but also require evidence-based information to guide learning objectives.Problem:There is limited evidence on what skills and bedside equipment are most important to include in disaster training and evacuation programs for critically ill infants.Methods:An expert panel was used to create a 13-item mastery checklist of skills for bedside registered nurses (RNs) required to successfully evacuate a critically ill infant. Expert nurses were surveyed, and the Angoff method was used to determine which of the mastery checklist skills a newly graduated nurse (ie, the “minimally competent” nurse) should be able to do. Participants then rated the importance of 26 commonly available pieces of bedside equipment for use in evacuating a hemodynamically unstable, intubated infant during a disaster.Results:Twenty-three emergency department (ED) and neonatal intensive care unit (NICU) charge RNs responded to the survey with a mean of 19 (SD = 9) years of experience and 30% reporting personal experience with evacuating patients. The skills list scores showed an emphasis on the newly graduated nurse having more complete mastery of skills surrounding thermoregulation, documentation, infection control, respiratory support, and monitoring. Skills for communication, decision making, and anticipating future needs were assessed as less likely for a new nurse to have mastered. On a scale of one (not important) to seven (critically important), the perceived necessity of equipment ranged from a low of 1.6 (breast pump) to a high of 6.9 (face mask). The individual intraclass correlation coefficient (ICC) of 0.55 showed moderate reliability between raters and the average team ICC of 0.97 showed excellent agreement as a group.Conclusion:Experts rated the ability to manage physiological issues, such as thermoregulation and respiratory support, as skills that every nurse should master. Disaster preparedness activities for nurses in training may benefit from checklists of essential equipment and skills to ensure all nurses can independently manage patients’ physiologic needs when they enter the workforce. Advanced nursing training should include education on decision making, communication during emergencies, and anticipation of future issues to ensure that charge and resource nurses can support bedside nurses during evacuation events.
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Luo, Can, Hao Liu, Li Cheng, Chuan Wang, Weixuan Jiao, and Di Zhang. "Unsteady Flow Process in Mixed Waterjet Propulsion Pumps with Nozzle Based on Computational Fluid Dynamics." Processes 7, no. 12 (2019): 910. http://dx.doi.org/10.3390/pr7120910.
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The unsteady flow process of waterjet pumps is related to the comprehensive performance and phenomenon of rotating stall and cavitation. To analyze the unsteady flow process on the unsteady condition, a computational domain containing nozzle, impeller, outlet guide vane (OGV), and shaft is established. The surface vortex of the blade is unstable at the valley point of the hydraulic unstable zone. The vortex core and morphological characteristics of the vortex will change in a small range with time. The flow of the best efficiency point and the start point of the hydraulic unstable zone on each turbo surface is relatively stable. At the valley point of the hydraulic unstable zone, the flow and pressure fields are unstable, which causes the flow on each turbo surface to change with time. The hydraulic performance parameters are measured by establishing the double cycle test loop of a waterjet propulsion device compared with numerical simulated data. The verification results show that the numerical simulation method is credible. In this paper, the outcome is helpful to comprehend the unsteady flow mechanism in the pump of waterjet propulsion devices, and improve and benefit their design and comprehensive performance.
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Han, Feng, Xionghuan Chen, Yang Yang, and Chuan Wang. "Numerical and Experimental Study on the Effect of Rotor–Stator Distance on Rotor–Stator Interaction Strength within Mixed-Flow Centrifugal Pumps." Journal of Marine Science and Engineering 10, no. 8 (2022): 1114. http://dx.doi.org/10.3390/jmse10081114.
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In this article, the influence of rotor–stator distance on the pump performance and rotor–stator interaction strength within mixed-flow centrifugal pump was investigated based on numerical calculation and test verification. Firstly, the performances of mixed-flow centrifugal pumps with two different rotor–stator distances were obtained and compared with the numerical results, which confirms the high accuracy of the numerical simulation. Next, the performances of mixed-flow centrifugal pumps with five different rotor–stator distances were compared and analyzed. It was found that the hydraulic performance of the mixed-flow centrifugal pump varies slightly as the rotor–stator distance increases. The mean values of the standard deviation of the head and efficiency of the mixed-flow centrifugal pump at each rotor–stator distance under full flow conditions are only 0.16 m and 0.11%, respectively. Then, the strengths of the rotor–stator interaction with different rotor–stator distances were analyzed. It was found that the strengths of the shock interaction, the wake interaction, and the potential interaction were all reduced with increasing rotor–stator distance. Moreover, when the rotor–stator distance is 1.5 mm, the pressure distribution in the circumferential direction of the rotor–stator interference zone shows obvious unstable characteristics: the pressure change amplitude is significantly greater than the other rotor–stator distance of the pressure change amplitude, the maximum and minimum pressure amplitude difference being 56.9 kPa, and with the increase in the rotor–stator distance, the maximum and minimum pressure amplitude difference gradually decreases, with an average value of 32.3 kPa. These findings could provide useful insight into prospects for the improvement of the operational stability of mixed-flow centrifugal pumps, and the results of this study can be extended to all centrifugal pumps using diffusers in the form of vanes as the pressure chamber, which has strong practical application and theoretical value.
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Itkin, G. P., A. A. Drobyshev, O. Yu Dmitrieva, A. S. Buchnev, and A. A. Sysoev. "TESTING THE INTERACTION OF HEART LEFT VENTRICLE AND CONTINUOUS-FLOW PUMP ON A MOCK CIRCULATION MODEL UNDER NORMAL AND PATHOLOGICAL CONDITIONS." Russian Journal of Transplantology and Artificial Organs 17, no. 3 (2015): 43–49. http://dx.doi.org/10.15825/1995-1191-2015-3-43-49.
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Introduction. The preliminary study of new developed pumps for circulatory support on the hydrodynamic circulation model is an important step in the process of their designing. Hydrodynamic circulation models that can closely imitate cardio – vascular system are important to defi ne the range of effective functioning of the pumps under normal and heart disease conditions which is of great importance for defi ning the mode of these pumps in real clinical conditions.The aim of study is to create a new hydrodynamic circulation model of the systemic circulation to study the processes of interaction of heart left ventricle and continuous – fl ow pumps.Materials and methods. The main components of the mock circulation model (arterial and venous blocks) are designed as closed reservoirs with an air bag providing the necessary elasticity value of these reservoirs. The heart left ventricle was simulated with an artifi cial heart ventricle with a pneumatic drive Sinus-IS which allows to change its options in a wide range. As a test pump we used the fi rst native implantable axial pump VISH – 1. In the course of research we made the registration and recording of the basic hemodynamic parameters (pressure, fl ow) with a multichannel module Pumpax for the measurement of pressure parameters.Results. The designed circulation model allows to adequately reproduce the main hemodynamic parameters of the circulatory system in normal (arterial pressure – 110/77 mmHg, left atrium pressure – 7 mmHg and cardiac output – 4.2 l/min) and heart failure conditions (arterial pressure – 79/53 mmHg, left atrium pressure – 15 mmHg and cardiac output – 3.1 l/min). On the circulation model the interaction of heart left ventricle and continuous-fl ow pump in heart failure simulation was studied. The dynamics of the main circulation fi gures is shown under conditions of changing of the pump rotor speed. Meanwhile, the conditions of the closing of aortic valve are identifi ed which is important for theclinical use of this pump. Using a special separately fl exible camera on the pump inlet we modeled phenomena of negative pressure leading to unstable pump operation and reduction of pump fl ow.Conclusion. Characteristics of the developed hydrodynamic circulation model allow us to reproduce parameters of systemic circulation in a wide range and to use it in designing of new pumps for circulatory support.
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Zhu, Chuanhui, Shubin Yan, Xiaodong Dong, Wei Zhang, Biyi Huang, and Yang Cui. "Exergy Analysis of Phase-Change Heat-Storage Coupled Solar Heat Pump Heating System." Materials 14, no. 19 (2021): 5552. http://dx.doi.org/10.3390/ma14195552.
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With the rapid development of industrialization, the excessive use of fossil fuels has caused problems such as increased greenhouse gas emissions and energy shortages. The development and use of renewable energy has attracted increased attention. In recent years, solar heat pump heating technology that uses clean solar energy combined with high-efficiency heat pump units is the development direction of clean heating in winter in northern regions. However, the use of solar energy is intermittent and unstable. The low-valley electricity policy is a night-time electricity price policy. Heat pump heating has problems such as frosting and low efficiencies in cold northern regions. To solve these problems, an exergy analysis model of each component of a phase-change heat-storage coupled solar heat pump heating system was established. Exergy analysis was performed on each component of the system to determine the direction of optimization and improvement of the phase-change heat-storage coupled solar heat pump heating system. The results showed that optimizing the heating-end heat exchanger of the system can reduce the exergy loss of the system. When the phase-change heat-storage tank meets the heating demand, its volume should be reduced to lower the exergy loss of the tank heat dissipation. Air-type solar collectors can increase the income exergies of solar collectors.
7
Sakai, Kento, Bungo Iwase, Keisuke Matsumoto, Kazuyoshi Miyagawa, and Satoshi Kawasaki. "Investigation on axial thrust behavior of balance piston system for a rocket pump." Journal of Physics: Conference Series 2217, no. 1 (2022): 012029. http://dx.doi.org/10.1088/1742-6596/2217/1/012029.
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Abstract High stability in axial direction is required for rocket pumps operated under extremely low-temperature and high-pressure conditions, turbopumps therefore uses balance piston (BP) system for balancing their axial thrust. The BP system is stable under quasi-static conditions. However, BP system might become dynamically unstable under some condition. Thus it is fundamental for stability evaluation of turbopumps to predict static/dynamic characteristics in axial direction of BP system. Furthermore, we focus on characteristic change by cavitation which often occurs in the pump inlet. In this paper, an experimental study of a model turbopump which had an unshrouded impeller equipped with BP system was carried out. We experimented it with an active magnetic bearing (AMB) test facility in order forcibly to oscillate it with an optional amplitude and frequency. In addition, we examined characteristics of BP system by three-dimensional computational fluid dynamics (3D-CFD) simulations. The results of 3D-CFD simulations were in good agreement with these tendency of BP system, and were effective in predicting its static/dynamic characteristics. Some cases showed that dynamic characteristic of BP system became unstable by growth of cavitation, therefore we suggest that the influence of cavitation must also be considered in the design of turbopump.
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Yang, Yongfei, Wei Li, Weidong Shi, Yuanfeng Ping, Yang Yang, and Lei Wang. "Numerical investigation on the unstable flow at off-design condition in a mixed-flow pump." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 233, no. 7 (2019): 849–65. http://dx.doi.org/10.1177/0957650919833892.
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The mixed-flow pump is wildly used in industrial and agricultural fields, and the requirements for its stability become more and more restricted with the improvement of the capacities. When the pump is operated under part-loading conditions, unstable characteristic like rotating stall happens and brings intensive vibration and noise. To reveal the internal unstable flow characteristics in mixed-flow pump, unsteady numerical simulation is conducted under different flow rates in the current research. The secondary flow and the vortex induced by the unsteady flow in the pump, which vary with the change of the flow rate, are analyzed according to the simulation results. Pressure fluctuation in different parts of the impeller is numerically predicted and correlated to the rotating stall propagation process. With the reduction of the flow discharge, a critical flow rate (0.6 Qdes in the current model pump) is found related to the rotating stall inception. Unstable vortex structure is found in part of the flow passages of the impeller under the stall inception stage; 0.56 Qdes is the flow rate related to the deep rotating stall under which stable stall vortexes are found in each flow passage of the impeller. Three types of pressure fluctuation characteristics representing different flow field pattern in the impeller are found. When the pump is working at designed flow rate, the pressure fluctuation is regular with the dominant frequency being the rotation frequency fs of the rotor. At the stall inception condition, when the stall core appears in the flow passages of the impeller in turn, the amplitude of the pressure fluctuation is increased and the dominant frequency is changed to a low-frequency signal. When the flow rate is reduced below deep stall condition, owning to the reflux from the guide vane and the intensive rotor–stator interaction, the blade passing frequency of the guide vane fb2 becomes the dominant frequency. Finally, unsteady characteristics of the flow field under stall inception condition are analyzed to demonstrate the propagation process of the rotating stall. The stall vortex is found to propagate from the stalled flow passage to the next, through the tip area of the blade leading edge. During the propagation process, the first vortex shrinks and disappears gradually, while the second vortex grows continuously, and the third vortex shows up at the vanishment of the first stall vortex. This research provides detailed information for the unstable flow especially related to rotating stall evolution with the variation of the operating flow rate of the mixed-flow pump with guide vane.
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Yang, Mengqi, Xingxing Huang, Qilian He, et al. "Fluid-Structure Coupling Analysis of a Pump-turbine unit during the Pump Shutdown Transient Process." IOP Conference Series: Earth and Environmental Science 1079, no. 1 (2022): 012038. http://dx.doi.org/10.1088/1755-1315/1079/1/012038.
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Abstract Hydropower is a major renewable clean energy and is widely used worldwide. The reversible pump-turbine unit of the pumped-storage power station is able to work in two main operating modes as required by the power grid: turbine-mode for power generation and pump-mode for power storage. In order to absorb unstable energies such as wind and solar energy and improve the quality of the electricity, reversible pump-turbines need to frequently change operating conditions, and experience more start-stops under different operating modes in a short period. The unstable flow during these transient processes will lead to high-level stresses on the structural components of the pump-turbine units. Therefore, it is of great engineering and academic significance to study the flow characteristics and structural characteristics of the unit during the transient processes. This paper has established a numerical calculation model for a prototype reversible pump-turbine unit, has carried out the CFD calculations of the pump-turbine fluid domains during the pump shutdown transient process, and has analysed the corresponding structural dynamic characteristics of the stationary components of the unit with the fluid-structure coupling method. The pressure variation trend of the spiral case outlet during pump shutdown has the same trend as that of the spiral case domain, and the guide vane flow domain. The maximum flow-induced deformation and stress of the stationary structures have a strong correlation with the axial thrust values of the head cover. The maximum deformation occurs at the inner edge of the head cover, and the maximum stress appears in the fillet of the stay vane leading edge. An increase in the number of shutdowns will result in a higher real risk of fatigue damage to the stay vanes. The conclusions obtained are of great value for safe operation, field condition monitoring, fault diagnosis, and predictive maintenance of the pump-turbine units.
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Nejneru, Carmen, Diana-Petronela Burduhos-Nergis, Mihai Axinte, Manuela Cristina Perju, and Costica Bejinariu. "Corrosion Behaviour of Nodular Cast Iron Used for Rotor Manufacturing in Different Wastewaters." Coatings 12, no. 7 (2022): 911. http://dx.doi.org/10.3390/coatings12070911.
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Submersible drainage sump pumps work in a highly corrosive environment, forming films with corrosive reaction products on the surface. Pump rotors are high-demand parts, so they are made of quality materials with good wear and corrosion resistance properties such as nodular graphite cast iron. This paper analyses the corrosion behaviour of cast iron used in the manufacture of rotors in three types of wastewaters, with variable pH. Nodular graphite cast iron samples were immersed in wastewater for 30, 60, and 90 days and tested by linear polarisation and electrochemical impedance spectroscopy (EIS). Also, the layers of reaction products formed on the surface of the material were analysed by SEM and EDS. The results showed that nodular cast-iron immersed in wastewater with acidic pH showed intense corrosion, the oxide layer formed on its surface is unstable. Also, the final structure of the product layer is that of a tri-layer with cations and anions absorbed from the corrosion media: the double-electric layer directly connected to the metal surface, an internal layer consisting of ferrous compounds and ferric compounds that control the diffusion of oxygen, an outer layer, and a compact crust of ferric compounds. The change in the pH of the wastewater has a major influence on the corrosion rate of the cast iron, which increases from 356.4 µm/year in DWW-1 (6.5 pH) to 1440 µm/year in DWW-2 (3 pH) and 1743 µm/year DWWW-3 (11 pH) respectively. As can be seen, the experimental study covers the problem of the corrosion behaviour of the pump rotor in various types of wastewaters this aspect is particularly important for the good use of wastewater pumps and to predict possible deviations for the operation of the equipment within the treatment plants.