Transcranial magnetic stimulation (TMS) has been proven to be effective in treating many psychiatric disorders. The stimulus in-tensity and focality of the TMS coil are normally used to meas-ure the effect of biological stimulation. In order to improve the performance of the coil, the magnetic core can be added to the existing coils to enhance the stimulus intensity and focality of the local space. However, the core loss caused by the high frequen-cy alternating magnetic field in the core should not be neglected. In this paper, the optimal design of transcranial magnetic stimu-lation thin core coil with the trade-off between stimulation effect and heat energy is proposed. By building multi-objective optimi-zation model and using exhaustive search, the dimensions of the magnetic core is reasonably designed, the stimulation effect of the coil can be significantly improved, the heat energy generated by the core can be reduced compared to other core coils. The fi-nite element method is used to analyze and compare the stimula-tion effect before and after adding the magnetic core. The simu-lation results verify the superiority of the proposed design.

As a novel form of energy storage, large-capacity flywheels offer a promising solution for supporting the efficient operation of new energy grid connection and advanced power system. In order to ensure the stable operation of the flywheel rotor, the introduction of superconducting maglev bearings (SMB), characterized by stable levitation without the need for an origin, low energy losses, and high rotational speeds, can significantly enhance the performance of large-capacity flywheel. This paper focuses on a 100 kWh flywheel energy storage system, where the axial load requirement for the heavy-duty bearing system is set at 8 tonnes. A rotor-excited SMB system is designed, with reference to the stator-excited SMB designed by the Japan Institute of Iron and Steel Technology (ISIT), to investigate the levitation performance of both SMB configurations at different temperatures. Furthermore, the levitation force and stiffness are calculated under optimal parameter combinations to compare the mechanical performances of the two configurations. The mechanical properties of the bearing system are compared. The results reveal that, due to structural differences, the rotor-excited and stator-excited SMBs exhibit distinct levitation characteristics and mechanical properties, each offering specific advantages and disadvantages for the operation of large-capacity flywheels. These findings provide valuable insights and solutions for further performance optimization of such systems.

As a new non-invasive biotechnology, transcranial magnetic stimulation (TMS) is widely used in the treatment of various psychiatric diseases. The stimulation coil of traditional transcranial magnetic stimulator produces a lot of Joule heat during treatment procedures, which leads to low stimulation efficiency. However, discussion about heating problem in TMS is very limited. In this paper, a new transcranial magnetic stimulator which can work continuously is proposed. Its stimulation coil is wound with hollow copper wire and the central hollow part is used to circulate low-temperature deionized water. The cooling deionized water is provided by a small silent chiller. The Joule heat generated during medicals treatment is taken away by the cooling deionized water, so that the temperature of the stimulation coil can be maintained within a safe range. Finite element method is adopted to analyze the intracranial induced electrical field produced by the water-cooling stimulation coil (WSC). Geometric structure of WSC is optimized based on minimum Joule heat. Design of cooling parameters is carried out with coupled multiphysical field analysis. Results prove that the WSC is able to generate the required intracranial induced electrical field. When 3000 pulses are applied, the temperature of the new transcranial magnetic stimulator could be maintained at room temperature, while the temperature rise of the magnetic stimulation without water cooling is 57K.

Transcranial magnetic stimulation (TMS) shows great research potential in human neuroscience. However, when it comes to stimulating deeper brain regions, traditional TMS is restricted by the balance between stimulation focalization and stimulation depth. Temporal interference (TI) stimulation offers a new thought to solve the problem. In this paper, we first discussed the principles of TI-TMS and then established the theoretical model of TI-TMS using the head-surrounded spatial array. Next, we specially designed the parametric characterized spatial array (PCS array) suitable for TI-TMS. The proposed PCS array contains eight special-shaped coils that constitute four sets of difference frequency stimulation pairs and are placed around the human head. Distribution characteristics of the temporally interfering electric fields (E-fields) including stimulation intensity, stimulation focalizations on 1D, 2D, and 3D levels, and attenuation ratios in X, Y, and Z directions were obtained using the finite element analysis method. Our results indicate that the proposed PCS array could form an obvious focusing area with strong stimulation at a stimulation depth of 5 cm below the human scalp while the superficial region is under weak stimulation, which effectively combines the advantages of TMS and TI stimulation. Compared to the traditional TMS systems, the TI-TMS with PCS array can realize selective and focalized stimulation in the deep brain and increase the average attenuation ratio of the induced temporally interfering E-fields by more than 1.93 times. A real human head model containing gray matter was also employed in this paper to verify our results.

Transcranial magnetic stimulation (TMS) has been widely used in scientific research and clinical application. In TMS, the stimulation coil generates a focusing induced electrical field in the intracranial target area to achieve neuromodulation. Since different disorders correspond to their specific target areas, in order to avoid non-target tissue being stimulated, the figure-of-eight (FOE) coil with good focusing performance is still the most commonly used magnetic coil. In this paper, the U-shaped coil with multi-parameters is introduced and optimized. The spatial distributions of the intracranial induced electrical field produced by the U-shaped coil are obtained using the finite-element method. Compared to the traditional FOE coil, the U-shaped coil not only has a great advantage in improving focalization but also is beneficial to obtain other improved characteristics. The mathematical relationship between the coil geometric parameters and the intracranial induced electrical field characteristics is analyzed under the constraint of fixed coil power loss. To further improve coil efficiency, the particle swarm optimization (PSO) is adopted to optimize the coil parameters. A real human head modeled as homogeneous and isotropic is occupied in this paper to verify our method, and a traditional FOE coil is used as the reference coil. We also checked the maximum induced charge density on the targeted plane generated by the optimized U-shaped coil to make sure that it will not cause induced neurologic damage.

As a noninvasive neuromodulation technique, transcranial magnetic stimulation (TMS) has important applications both in the exploration of mental disorder causes and the treatment of mental disorders. During the stimulation, the TMS system generates the intracranial time-varying induced E-field (E-field), which alters the membrane potential of neurons and subsequently exerts neural regulatory effects. The temporal waveform of the induced E-fields is directly related to the stimulation effect. To meet the needs of scientific research on diversified stimulation waveforms and flexible adjustable stimulation parameters, a novel efficient pulse magnetic stimulation circuit (the EPMS circuit) design based on asymmetric cascaded multilevel technology is proposed in this paper. Based on the transient analysis of the discharge circuit, this circuit makes it possible to convert the physical quantity (the intracranial induced E-field) that needs to be measured after magnetic stimulation into easily analyzable electrical signals (the discharge voltage at both ends of the stimulation coil in the TMS circuit). This EPMS circuit can not only realize monophasic and biphasic cosine-shaped intracranial induced E-fields, which are widely used in the market, but also realize three types of new intracranial induced E-field stimulation waveform with optional amplitude and adjustable pulse width, including monophasic near-rectangular, biphasic near-rectangular and monophasic/biphasic ladder-shaped stimulation waveform, which breaks through the limitation of the stimulation waveform of traditional TMS systems. Among the new waveforms produced by the EPMS circuit, further research was conducted on the dynamic response characteristics of neurons under the stimulation of the biphasic four-level waveform (the BFL waveform) with controllable parameters. The relationship between TMS circuit parameters (discharge voltage level and duration) and corresponding neural response characteristics (neuron membrane potential change and neuronal polarizability ratio) was explained from a microscopic perspective. Accordingly, the biological physical quantities (neuronal membrane potential) that are difficult to measure can be transformed into easily analyzable electrical signals (the discharge voltage level and duration). Results showed that compared with monophasic and biphasic cosine induced E-fields with the same energy loss, the neuron polarization ratio is decreased by 54.5% and 87.5%, respectively, under the stimulation of BFL waveform, which could effectively enhance the neuromodulation effect and improve the stimulation selectivity.