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Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
immediate addressing an addressing mode where the operand is specified in the instruction itself. The address field in the instruction holds the data required for the operation. immediate operand a data item contained as a literal within an instruction. immersed flow a flow of electrons emitted from an electron gun exposed to the focusing magnetic fields. immittance a response function for which one variable is a voltage and the other a current. Immittance is a general term for both impedance and admittance and is generally used where the distinction is irrelevant. immunity to a distrubance an equipment or systems capability to operate if an electromagnetic disturbance occurs. impact excitation excitation of an atom or molecule resulting from collision by another particle such as an electron, proton, or neutron. IMPATT diode acronym for impact avalanche and transit time diode. Negative resistance device used at high frequencies used to generate microwave power. Typically used in microwave cavity oscillators. impedance (Z) (1) electrical property of a network that measures its ability to conduct electrical AC current for a given AC voltage. Impedance is defined as the ratio of the AC voltage divided by the AC current at a given point in the network. In general, impedance has two parts: a real (resistive) part and an imaginary (inductive or capacitive "reactive") part. Unless the circuit is purely resistive
Microwave Reactor Design and Configurations
Published in Veera Gnaneswar Gude, Microwave-Mediated Biofuel Production, 2017
Unlike the design of single mode applicators, which are designed based on solutions of the electromagnetic field equations for a given applicator geometry, the design of multimode applicators are often based on trial and error, experience, and intuition (Thostenson, Chou 1999). As the size of the microwave cavity increases, the number of possible resonant modes also increase. Consequently, multimode applicators are usually much larger than one wavelength. The presence of different modes results in multiple hot spots within the microwave cavity. Like single mode cavities, local fluctuations in the electromagnetic field result in localized overheating. To reduce the effect of hot spots, several techniques are used to improve the field uniformity. The uniformity of the microwave field can be improved by increasing the size of the cavity. Because the number of modes within a multimode applicator increases rapidly as the dimensions of the cavity increase, the heating patterns associated with the different resonance modes begin to overlap. The rule of thumb to achieve uniformity within an applicator is to have the longest dimension be 100 times greater than the wavelength of the operating frequency (Kimrey and Janney 1988). Since this is not possible, inclusion of a turntable improves the heating patterns. The purpose of the turntable is to reduce the effect of multiple hot spots by passing the food through areas of high and low power and, therefore, achieve time-averaged uniformity. Another technique for improving the field uniformity is through mode stirring. Mode stirrers are reflectors, which resemble fans that rotate within the cavity near the waveguide input. The mode stirrers ‘‘mix up” the modes by reflecting waves off the irregularly shaped blades and continuously redistribute the electromagnetic field. Like turntables, mode stirring creates time-averaged uniformity. In addition, adding multiple microwave inputs within a multimode cavity can further enhance the uniformity. Most techniques for creating uniformity depend on modifying the electromagnetic field within the microwave cavity. Another method developed to achieve more uniform heating is hybrid heating. Hybrid heating can be achieved through combining microwave heating with conventional heat transfer through radiation, convection, or conduction. Figure 5 shows the schematics of multimode microwave reactors suitable for parallel synthesis and single-batch reactor (top view).
Magnetic dipolar modes in magnon-polariton condensates
Published in Journal of Modern Optics, 2021
The coupling of a subwavelength MDM resonator with a bosonic-field microwave cavity is far from a trivial problem. In this paper, we show that magnon polaritons can be realized due to magnon condensation caused by dipole–dipole interaction in a quasi-2D ferrite disk. This is considered as a main mechanism of strong coupling of the MDM with the microwave-cavity photon. The interaction between MDM ferrite particles and an external EM field is analysed based on the notion of an anapole moment [46,50] and helical-mode MS resonances [51], and considering conservation of an angular momentum in an entire microwave structure [48,52]. The topological properties of microwave-cavity fields arise due to the MDM states. The eigenstates of the system of a ferrite disk and microwave radiation field are mixtures of photons and MDM magnons. When a MDM ferrite disk is placed in a microwave cavity, one observes mixing space and time components and the effects of spacetime curvature of the cavity fields. For modelling magnon-polariton condensates in a microwave cavity, we propose the concept of double-helix resonances creates by ME photons. It is important to note that for MDM resonances in magnetic insulators, along with magnon condensation, we also have electric dipole condensation. Electric dipoles in a ferrite disk are described by a vector order parameter and therefore exhibits spontaneous symmetry breaking. In microwave waveguide, we observe rotational superradiant scattering of microwave photons by MDM vortices. In an environment of scattering states of microwave waveguide, EM waves can carry the topological phases of MDM resonances.
Model-free adaptive control for microwave heating process with actuator saturation constraint
Published in Journal of Microwave Power and Electromagnetic Energy, 2019
Shan Liang, Chengyang Ye, Qingyu Xiong, Zhihui Wang, Tong Liu
The simulation results are given based on the simplified mathematical model of microwave heating system. Compared with the actual control system, this model is ideal. On the one hand, it is assumed that the horizontal direction of the electromagnetic field is constant, but once the heating medium is put into the microwave cavity, the original distribution of the electromagnetic field will be destroyed. This will result in uneven temperature field distribution in the medium, so the temperature curve of the experimental results is more volatile. On the other hand, the mathematical model assumes that the heating medium can completely absorb the microwave generated by the microwave source. However, in the actual microwave heating process, the power of the incident microwave and reflected microwave does exist, so microwave will be lost in the transmission line. Meanwhile in the process of simulation, the virtual actuator is much faster than the actual actuator, which is also one of the possible reasons.
Dielectric and thermodynamic studies of n-cyano-biphenyl (nCB) liquid crystals at microwave frequency
Published in Liquid Crystals, 2023
The microwave cavity spectrometer at 9.0 GHz frequency for a fixed magnetic field of 1.3 kG in TM010 mode is used for measurements. Being cited as one of the standard ones for the dielectric characterisation of polar and non-polar materials, the cavity perturbation technique is one of the widely used techniques for dielectric measurements due to higher accuracy of results as compared to transmission techniques especially for dielectric loss. The description of various resonance techniques for dielectric properties measurement and the accuracy of microwave cavity perturbation technique is given elsewhere [28,29].