The power may be increased or decreased, depending upon the relative signs of the two components of pressure. Consequently, its radiated sound power is altered if this additional pressure has a component in phase with the velocity of the element.
The presence of another surface element vibrating at the same frequency induces an additional pressure on the original element. The time-average rate at which the element does work on a contiguous fluid is given by the time-average product of the volume velocity and the component of the fluid reaction force in phase with the velocity. The physics of this phenomenon becomes clear if we consider the mechanics of sound energy production by a small element of a harmonically vibrating surface. Since far field intensity is proportional to the mean square pressure, and the total radiated sound power is equal to the far field surface intensity integrated over a spherical surface, it is evident from the above that the sound power radiated by one elemental source can be influenced by the presence of another correlated source. It appears that the range of applicability of conventional electromagnets is being severely squeezed.įrank Fahy, in Foundations of Engineering Acoustics, 2001 6.7.1 Sound power of a source in the presence of a second source Still, medium-sized electromagnets capital costs tend to dominate cryogenic costs and hence for small systems permanent magnets are best, while for applications requiring fields greater than 2 T, superconducting magnets would be preferred. On comparison of the experimental magnetic separation setup, the performances of HGMS and superconducting devices approximately equal to each other. The bulk samples were cooled to 30 K and then magnetized by feeding currents using the magnetizing pulse coils. For instance, analyzed a face-to-face type superconducting magnet system, which consists of a pair of Sm-Ba-Cu-O bulk samples mounted on the respective cold stages in vacuum vessels. But while the magnetic field is strong, the cost is high, and maintaining the temperature conditions is difficult. Various kinds of the superconducting magnetic have been constructed in order to develop the practical and industrial applications. But although it was frequently observed that the removal efficiency of pollutants improved when the magnetic field intensity increased up to 1 T, the effects of increasing the magnetic field to greater than 1 T, beyond saturation of most magnetic seeds (see Eq. Meanwhile, high gradient magnetic field of more than 10 T can be formed using conventional superconducting coils. Right now, the highest temperature known superconducting material is pressurized hydrogen sulfide, whose working temperature reaches 203 K (− 70☌). Search for room-temperature superconductors is a challenging study in materials science, and pressurization and hydrogenation have been considered as a way to push up the superconducting critical temperature. One such material, called yttrium barium copper oxide (YBCO), has since cornered the market. During the 1980s, it was discovered that some ceramic materials can reach this state at significantly higher temperatures, using liquid nitrogen. And there is some hope for the future: in the beginning, superconductivity was known only in a few metals at temperatures just above absolute zero at minus 273 oC, reachable with the aid of liquid helium. If this complex cooling were no longer necessary, it would mean a breakthrough for magnetic separation. However, one will need to cryogenically cool the coils, making this technology far too expensive. If a current is started in a circuit formed of a superconductor maintained below its critical temperature, it will persist indefinitely without any power input or heat generation. In principle, the technology has shown great energy saving potential because superconductors are dissipation-less. Therefore, the need for fields larger than those obtainable from conventional solenoids is met with superconductors. Carlos Martinez-Boubeta, Konstantinos Simeonidis, in Nanoscale Materials in Water Purification, 2019 4.2.3 High intensity fields with superconductorsįield intensities of order 100 mT demand bulky coils carrying large currents, which in turn, require substantial power supplies and water cooling.
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