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Steady Magnetic Fields
Published in Ahmad Shahid Khan, Saurabh Kumar Mukerji, Electromagnetic Fields, 2020
Ahmad Shahid Khan, Saurabh Kumar Mukerji
The magnetic flux lines shown in Figure 11.1b to 11.3a possess the following properties. These always adopt the path of least reluctance between opposite poles. They form closed loops.The magnetic flux lines neither cross nor even touch one another.They all have the same strength.Their density decreases as they spread out, i.e. when they move from a region of higher permeability to that of lower permeability.Their density reduces with the distance from the poles.They are considered to have direction, the same as the direction of the magnetic flux density vector at various points on the line of force.These lines are directed from the south pole to the north pole within the magnet and from the north pole to the south pole outside the magnet.
Fusion Energy
Published in Geoffrey F. Hewitt, John G. Collier, Introduction to Nuclear Power, 2018
Geoffrey F. Hewitt, John G. Collier
Most effort is therefore being devoted to trying to achieve a fusion reaction using magnetic confinement. The structure of magnetic fields is often indicated by lines of force or field lines the stronger the field, the greater the density of the lines. Within a magnetic field, charged nuclei take a spiral path in the direction of the field lines as illustrated in Figure 9.5a. A magnetic field line causes a charged nudeus to spiral around it (Figure 9.5a). If the field is arranged so as to dose on itself in a circle within a circular chamber (Figure 9.5b), the particles will spiral around the field and remain trapped within the circular chamber, or torus. Unfortunately, this does not always happen in practice due to instabilities that occur in the plasma. Nevertheless, most of the experiments that have tried to achieve controlled fusion reactions make use of this dosed doughnut-shape configuration. Another possibility is to constrict the magnetic field lines at each end of a tube. Particles trying to escape by spiraling along the field lines are reflected back into the central region. This arrangement is called a magnetic mirror or bottle (Figure 9.5c).
Grounding and Interfacing
Published in Douglas Self, Audio Engineering Explained, 2012
Magnetic circuits are similar to electric circuits. Magnetic lines of force always follow a closed path or circuit, from one magnetic pole to the opposite pole, always following the path of least resistance or highest conductivity. The magnetic equivalent of electric current and conductivity are flux density and permeability. High-permeability materials have the ability to concentrate the magnetic force lines or flux. The permeability of air and other nonmagnetic materials such as aluminum, plastic, or wood is 1.00. The permeability of common ferromagnetic materials is about 400 for machine steel, up to 7000 for common 4% silicon transformer steel, and up to 100,000 for special nickel alloys. The permeability of magnetic materials varies with flux density. When magnetic fields become very intense, the material can become saturated, essentially losing its ability to offer an easy path for any additional flux lines. Higher permeability materials also tend to saturate at a lower flux density and to permanently lose their magnetic properties if mechanically stressed.
Research on gas pipeline leakage model identification driven by digital twin
Published in Systems Science & Control Engineering, 2023
Dongmei Wang, Shaoxiong Shi, Jingyi Lu, Zhongrui Hu, Jing Chen
Existing pipeline leakage monitoring technologies include the magnetic leakage detection method, the acoustic system method, the magnetic induction wireless sensor network method, etc. The magnetic leakage detection technology uses tools to magnetize intact pipelines to nearly saturated magnetic flux density and evenly distribute magnetic lines of force in the pipelines. When the pipe wall is damaged due to corrosion and other conditions, the magnetic force line will be deformed and the magnetic flux will leak out, and then the sensor will collect and analyse. However, the environment, the smoothness of the pipeline surface and the degree of corrosion will affect the accuracy of detection results. Acoustic system detection is in the pipeline leakage, because the air pressure difference between the inside and outside of the pipeline will lead to the generation of eddy current, and then the vibration change of sound wave will be generated, the acoustic signal can be installed on the pipeline acoustic sensor capture and then analyse the signals to determine whether the leakage occurs. The acoustic wave method has high sensitivity, but it requires the installation of a large number of sound sensors and is greatly affected by noise, so the effect is not very ideal for long-distance pipelines. The magnetic induction wireless sensor network collects data by setting different sensors inside and around the underground pipeline, and then transmits the data wirelessly by using the magnetic induction waveguide technology, and reports the measurement results to the management centre in real-time. Magnetic induction waveguides can provide accurate real-time information in harsh underground environments, but their measurement performance requires a large number of sensors, so the cost is relatively high. Digital twinning is to create a virtual model for a physical object digitally. By simulating its behaviour in the physical world and perceiving real-time data, it can understand the current state of the system and realize the prediction, analysis and dynamic grasp of the entity according to the current state. The digital twin method has good real-time performance, a virtual model and physical entity interaction, real-time collection of pipeline information for data processing and recognition, and can do timely classification recognition and judgement. Visualization: The visualization model can be updated in real-time according to data interaction, and the information on different working conditions and current pipeline conditions can be obtained directly from the model.