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The full solenoid over a topological space X is the inverse limit of all finite covers. When X is a compact Hausdorff space admitting a locally path-connected universal cover, we relate the pointed homotopy equivalences of the full solenoid to the abstract commensurator of the fundamental group π1(X). The relationship is an isomorphism when X is an aspherical CW complex. If X is additionally a geodesic metric space and π1(X) is residually finite, we show that this topological model is compatible with the realization of the abstract commensurator as a subgroup of the quasi-isometry group of π1(X) . This is a general topological analog of work of Biswas, Nag, Odden, Sullivan, and others on the universal hyperbolic solenoid, the full solenoid over a closed surface of genus at least two. [ABSTRACT FROM AUTHOR]

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This paper presents an experimental setup of magnetic field taper variations to optimize the efficiency of a Ka-band pulsed gyrotron. Experimental optimization of the gyrotron's efficiency is presented. The efficiency dependence on three input parameters—beam current, magnetic field amplitude, and variations in the magnetic field taper profile—is studied. A gyrotron electron efficiency improvement from 25.4% for a non-tapered magnetic curve to 36.4% for a tapered magnetic curve is measured. The stability of the millimeter wave excitation in the cavity is also affected by the magnetic taper gradient. The magnetic taper is obtained by a practical modification of the solenoid that leads to an 11% electron efficiency improvement. Magnetic tapering can be combined with other types of efficiency enhancement concepts to obtain an overall improved efficiency that can be important for industrial applications. [ABSTRACT FROM AUTHOR]

The article is devoted to the calculation of systems consisting of a solar photovoltaic power source and water pumps. It is noted that such systems can be used both in households or industry, and in agriculture, in particular for irrigation. Several variants of water pumps are shown. An analysis of the operational modes where the photovoltaic power source is connected to the pump has been carried out. The selection of equipment was carried out and the expediency of using a system with an electric energy booster was indicated. A booster for providing current during start-up modes can be a capacitor, a battery of capacitors or an ionistor. Emphasis is placed on the fact that for doing of such systems it is necessary to apply modeling with the use of electrical models. It is shown that for developing of electric models of solenoid-based pumps and pumps based on rotating direct current motors, it is necessary to use the methods of electromechanical analogies. Electrical models of a photovoltaic power source and, based on analogies, a solenoid-based pump and a direct current motor-based pump with permanent magnet excitation and parallel excitation were developed. When developing electrical models, controlled sources of voltage and current were used with mutual influence of the electrical and mechanical parts of the pumps. The need to use direct current motors with parallel excitation is indicated, as they are more stable to emergency modes. It is also stated that in general, the mechanical load of the rotating part of motors is non-linear and depends on the number of revolutions of the shaft. A nonlinear resistance that models a nonlinear mechanical load is shown, and it is noted that the higher-order nonlinearity is insignificant. Conclusions are drawn and further development in the direction of the use of digital technologies is outlined. [ABSTRACT FROM AUTHOR]

A method for optimizing multiple responses in solenoids utilized in a magnetic nozzle assembly for an electric plasma thruster is presented. The primary goal is to minimize power usage while maintaining a sufficiently high magnetic flux density at the coil axis. This is especially critical during testing in a vacuum chamber, where heat dissipation is a challenge, especially for small components and intricate assemblies. This paper presents a method for quickly calculating the magnetic field along the solenoid axis that provides accurate estimates, independent of coil size. Additionally, we present general and concrete results for the employed magnetic nozzle design to illustrate the applied optimization method. The paper details a methodology for optimizing multiple parameters of a solenoid, including its radius, length, current, number of turns, and wire diameter. The aim is to minimize, maximize, or meet specific targets for magnetic flux density, power, or mass. Additional studies could utilize a suitable metric to optimize the homogeneity of the magnetic field of multiple coils. The coils designed using the algorithm have a radius of 17.5 mm, a length of 21 mm, consist of 300 turns with a wire diameter of 1 mm, and operate at a direct current of about 5 A. The potential maximum magnetic field is 40 mT with a power consumption of around 30 W.

Brakes are essential parts of any system that involves motion. A few seconds are spent applying the brake, accumulating enough force to retard a system. In case of emergency stops, we need an efficient braking system that acts quickly and safely to avoid any mishaps. This work aims to develop a prototype of an instantaneous braking system, which can stop the motion of a rotating member. The operating principle of the device is the electromagnetic actuation of a solenoid. The actuation of a solenoid is simple and instantaneous. As a result, we could achieve immediate braking of a rotating member. [ABSTRACT FROM AUTHOR]

Keeping bee colonies is one of the most important sectors of investment in the global agricultural field. Internationally, beekeepers are interested in improving bee feeding methods to maximize the productivity and quality of their products. Whereas the current study aims to develop and evaluate an automatic feeding system that works with solar energy. This technique increases the vertical expansion of beekeeping by designing a multi-shelf mobile apiary for easy transportation as desired. The development process included the inclusion of automated feeders that operate electronically using sensors to provide a nutritional solution for bee colonies without human intervention. Also, the automatic apiary was provided with a sugar solution tank that was equipped with a continuous stirring system that works with a timer. Also, the automatic apiary contains an alarm system and remote mobile contact with the beekeeper in case of depletion of the sugar syrup. The variables under study included three levels of nutritional level volumes of 500, 750, and 1000 ml, respectively, with two stirring periods (3 and 6 times/day) at two concentrations for sugar solution of 50 and 67%. The evaluation process was done during the critical winter period of the year, from December to March. The main results showed that the colonies' strength had an increment ratio over control hives of 30.23% when using the highest variable levels. Also, the seasonal energy consumption ranged from 1.25–2.81 kWh per season. Therefore, beekeepers can benefit from this novel feeding approach. [ABSTRACT FROM AUTHOR]

Brakes are essential parts of any system that involves motion. A few seconds are spent applying the brake, accumulating enough force to retard a system. In case of emergency stops, we need an efficient braking system that acts quickly and safely to avoid any mishaps. This work aims to develop a prototype of an instantaneous braking system, which can stop the motion of a rotating member. The operating principle of the device is the electromagnetic actuation of a solenoid. The actuation of a solenoid is simple and instantaneous. As a result, we could achieve immediate braking of a rotating member.

We propose a new linear solenoid actuator design to create a solenoid micropump targeting portable microfluidic systems. A novel solenoid actuator design was developed with a unique arrangement of two magnets, which provides a fundamental solution to the inherent problem of force variation in conventional solenoid pumps. Central to the technique is the antisymmetric force distribution of the two magnets in an opposing orientation with a suitable spacing between them. Through a mathematical model and systematic parametric study, we verified that the proposed linear solenoid actuator could provide up to 99.9% constant force source with fast response time and pulsation-free flow in small system size using direct current (DC) power. In addition, the general design rule of the proposed solenoid actuator was found through dimensional analysis. The proposed design is implemented into more practical solenoid micropumps for microfluidic applications such as flow focusing and droplet manipulation in digital microfluidics through our series work. We hope this study will promote the development of various actuators for microfluidics and contribute to the broader application of microfluidics in more fields. [Display omitted] • A novel linear solenoid actuator design for portable microfluidics is proposed. • It fundamentally solves the problem of force variation in a solenoid. • It provides a constant force source without pulsation in a small system size. • General design rules of the proposed solenoid are provided. • The proposed design is implemented into more practical actuators in our series work. [ABSTRACT FROM AUTHOR]

This study comprehensively assesses radiofrequency (RF) volumetric wireless coils utilizing artificial materials for clinical breast MRI. In particular, we evaluated the transmit efficiency, RF safety, and homogeneity of magnetic field amplitude distribution for four structures electromagnetically coupled with a whole-body birdcage coil: extremely high permittivity ceramic coil, solenoid coil, Helmholtz coil, and metamaterial-inspired coil based on periodically coupled split-loop resonators. These coils exhibit favorable attributes, including lightweight construction, compactness, cost-effectiveness, and ease of manufacturing. The results of this study demonstrated that the metamaterial-inspired coil outperforms other wireless coils considered for addressing a specific problem in terms of the set of characteristics. In particular, the metamaterial-inspired coil achieved 85% and 88% homogeneity in magnetic field amplitude distribution at 3 T and 1.5 T MRI, respectively. Also, the 1.5 T metamaterial-inspired coil demonstrated the best performance, increasing the efficiency gain of the birdcage coil by 4.93 times and improving RF safety by 2.96 times. This research explains the limitations and peculiarity of utilizing the volumetric wireless coils in 1.5 and 3 T MRI systems. [Display omitted] • Volumetric wireless coils were compared for a set of electromagnetic characteristics. • Wireless coils enhance the body coil's Tx efficiency and RF safety. • Metasolenoid outperforms other coils in Tx efficiency and RF safety gain. • The Helmholtz coil is the best in terms of Q-factor and ease of manufacture. • Shielding a coil from the body boosts its Tx efficiency and limits the field of view. [ABSTRACT FROM AUTHOR]

A 4 × 4 Butler matrix for millimeter-wave communications is presented in this paper. The circuit takes advantage of a new 3-D Integrated Passive Devices (IPD) process to achieve a performance/compactness trade-off substantially higher than conventional IPD designs. A footprint of 0.84 mm2 is reached by using 3-D transformers and solenoids for designing couplers and phase shifters. Couplers are optimized to maximize the bandwidth of the Butler matrix. Phase variations with frequency are also tuned between phase shifters and crossover for the same purpose. The resulting experimental bandwidth, defined by reflection coefficients at −10 dB, is from 20 GHz to 30.1 GHz, and from 22.1 to 27.5 GHz considering a maximum phase error of 10° for the four states −45°, 135°, −135° and 45°, while insertion losses are measured close to 1.3 dB. Matchings and isolations remain below −17 dB and −12 dB, respectively. [ABSTRACT FROM AUTHOR]

We demonstrate several practical applications of a novel linear solenoid actuator design previously proposed to create a solenoid micropump which can be used in portable microfluidic systems. The proposed solenoid actuator design is extended to a system that can apply a constant force with a longer stroke and apply a higher force. It also demonstrates effective mini-train operation with easy and simple control, a spring-loaded linear servo system that solves the classic non-linear control problem, and droplet dispensing with accurate and fast control, showing its potential as a compact microfluidic solenoid micropump capable of precisely handling small volumes of liquid. Applications to digital microfluidic and flow-focusing microchannel systems have also been successfully demonstrated. We hope that this study will promote the development of various actuators for microfluidics and contribute to the broader application of microfluidics in more fields. [Display omitted] • We demonstrate several practical applications of a novel linear solenoid actuator. • The stroke and force of the proposed linear solenoid actuator are extended. • A spring-loaded linear servo system solves the classic non-linear control problem. • Droplet dispensing shows its potential as a compact microfluidic solenoid micropump. • Application to two real microfluidic systems has been successfully demonstrated. [ABSTRACT FROM AUTHOR]