The direct-current motor has been widely used in the modern electronic products, such as automatic control system, electronic equipment, home appliances, and electronic toys.The tape recorder, record player, recorder, and computer cannot work without the direct-current motor.So the control of the direct-current motor is a very practical technology.The direct-current motor has good starting performance and speed regulation characteristics, which is characterized by the big starting torque, big maximum torque, the smooth and economical speed regulation in a wide range, easy rotational speed regulation and high efficiency after speed regulation.Compared with AC speed regulation, the direct-current motor is complex in structure, with high production cost and heavy maintenance work.The direct-current regulator is widely applied in CNC machine tools, paper printing, textile printing and dyeing, fiber optic cable equipment, packaging machinery, electrical machinery, food processing machinery, rubber machinery, biological equipment, printed circuit board equipment, experimental equipment, welding and cutting, light industry machinery, logistics and transportation equipment, medical equipment, communication equipment, radar equipment, satellite ground receiving system and other industries.This paper aims at a hand-held speed regulation device, which can make the manual drive of substation maintenance to electric drive, so as to save energy and time.
With the global pursuit of renewable energy and carbon neutrality, hydrogen-based microgrids have also become an important area of research, as ensuring proper design and operation is essential to achieve optimal performance from hybrid systems. This paper proposes a distributed control strategy based on multiagent self-triggered model predictive control (ST-MPC), with the aim of achieving demand-side control of hydrogen-based microgrid systems. This architecture considers a hybrid energy storage system with renewable energy as the main power source, supplemented by fuel cells based on electrolytic hydrogen. The primary objective of this architecture is aiming at the supply and demand balance problem under the supply and demand relationship of microgrid, the service life of hydrogen-based microgrid energy storage equipment can be increased on the basis of realizing demand-side control of hydrogen energy microgrid system. To accomplish this, model predictive controllers are implemented within a self-triggered framework that dynamically adjusts the counting period. The simulation results demonstrate that the ST-MPC architecture significantly reduces the frequency of control action changes while maintaining an acceptable level of set-point tracking. These findings highlight the viability of the proposed solution for microgrids equipped with multiple types of electrochemical storage, which contributes to improved sustainability and efficiency in renewable-based microgrid systems.
The rotor system of a certain type of aerospace transfer pump adopts a SiC-PEEK sliding bearing pair. During operation, the phenomenon of SiC particle shedding from the bearing surface occurs. To investigate the influence of SiC particles on the operating characteristics of sliding bearings, this article sets up a sliding bearing test rig to simulate the working conditions of the aerospace transfer pump, and conducts bearing operation experiments using this platform. Suspensions of SiC particles with different particle sizes and concentrations are injected into the lubricating water used for bearing operation. The current fluctuations during the operation of the sliding bearing are observed, and the changes in bearing morphology before and after the experiment are compared and analyzed. The results show that SiC particles do not affect the bearing operation stability, but increase the operating power. The current at the moment of startup is twice that of stable operation. At the same time, it is found that the addition of SiC particles will aggravate the abrasive wear of the bearing.
Horse head is an important part of Beam pumping unit. Loose connection between the horse head and the walking beam is a common fault, which can cause serious consequences of the horse head cracking or falling off. However, there is currently no research on the characteristics and diagnosis methods of the loose connection of the horse head. We built a proportional test bench of pumping unit to study the dynamic characteristics of the horse head loosening fault. We found that the loose connection may cause the horse head to produce transient vibration at a specific operating angle. And we studied the characteristics of the time, direction and strength of the impulse when the pin is loose. These conclusions provide a certain reference basis for the diagnosis of the fault.
The stress behavior of the reinforced inorganic polymer concrete(IPC) beam was discussed, included the load-deflection curve, craze load and ultimate bearing capacity under the static load function through the method of the experimental study and the non-linear finite element analysis. Compared the data of the experiment with the results of the finite element analysis, it indicates that the reinforced IPC beam owns higher ductility ratio and better deformation capacity on the same loading condition. Meanwhile, the cracks of IPC beam develop more slowly than the normal ones, there were less and smaller cracks on IPC beam. The research results offer the theoretical and experimental references for engineering practice and design index of IPC.
In this paper, we investigate the problem of secure communications in multiple-input-multiple-output interference networks from the perspective of physical layer security.Specifically, the legitimate transmitter-receiver pairs are divided into different categories of active and inactive.To enhance the security performances of active pairs, inactive pairs serve as cooperative jammers and broadcast artificial noises to interfere with the eavesdropper.Besides, active pairs improve their own security by using joint transceivers.The encoding of active pairs and inactive pairs are designed by maximizing the difference of mean-squared errors between active pairs and the eavesdropper.In detail, the transmit precoder matrices of active pairs and inactive pairs are solved according to game theory and linear programming respectively.Experimental results show that the proposed algorithm has fast convergence speed, and the security performances in different scenarios are effectively improved.
Objective To study the cause of death and mechanism after(TACE)in China during the past 14 years.Methods Related repots in Chinese Medical Current Content(CBM)and National Knowledge lnfrastruc ture(CNKI)from January 1994 to June 2008 were retrieved.The cause of death and mechainsm after TACE wer e analyzed.Results A total of 150 patients who died after TACE were reposed in China during the past 14 ye ar s.84%eases were caused by liver lunction failure,upper gastrointestinal bleeding and rupture of liver cancer. 78.7%cases died one month postoperation.Conclusion Liver function failure.upper gastrointestinal bleeding and rupture of liver cancer are the main complications which Can cause death and the majority cases died early.
Key words:
transcatheter hepatic arterial chemoembolization; cause of death; mechanism
An actively cooled and activated cooling approach is proposed and examined in this project in order to deal with the problems associated with methods such as the cryogenic cooling method. It is also aimed to further improve the surface quality of the workpiece after grinding by combining the advantages of the existing cooling methods. Both computational and experimental studies were conducted for grinding the brittle materials with the proposed approach. Optical examinations were used to study the surface morphology. The experimental results show that the surface quality can be improved by up to 23.75% on average in terms of surface roughness Ra. The computational test reveals that the heat can be taken away more effectively by the proposed approach.
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