The purpose of our study was to test the hypothesis that the electromagnetic pulse (EMP) is capable of inducing mechanical vibrations in bone ex vivo . A thin segment of human femur diaphysis (from a ...tissue repository) suspended on a tensioned line (range <inline-formula> <tex-math notation="LaTeX">T = </tex-math></inline-formula> 2.2-123 N) was exposed to EMP (mean <inline-formula> <tex-math notation="LaTeX">B =0.64 </tex-math></inline-formula> T, dB / dt = 5877 T/s, and the mean <inline-formula> <tex-math notation="LaTeX">B </tex-math></inline-formula>-field gradient of 127 T/m) from a solenoid with axis orthogonal to tensioning line, forming a harmonic oscillator whose mechanical vibrations were measured using laser Doppler vibrometry (LDV, noise floor 1 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula>/s). Calculated mean Maxwell stress and Lorentz forces acting on a weakly conducting, diamagnetic bone slice point away from the solenoid for maximum sensitivity of LDV measurement. The electromechanical origin of the LDV signal was confirmed by the order-of-magnitude agreement between calculated (range from 12 to 50 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula>/s) and measured initial bone velocity amplitudes (e.g., <inline-formula> <tex-math notation="LaTeX">35.5~\mu \text{m} </tex-math></inline-formula>/s ± <inline-formula> <tex-math notation="LaTeX">7.5~\mu \text{m} </tex-math></inline-formula>/s at <inline-formula> <tex-math notation="LaTeX">T =22.2 </tex-math></inline-formula> N and <inline-formula> <tex-math notation="LaTeX">17.7~\mu \text{m} </tex-math></inline-formula>/s ± <inline-formula> <tex-math notation="LaTeX">2.5~\mu \text{m} </tex-math></inline-formula>/s at <inline-formula> <tex-math notation="LaTeX">T =58.2 </tex-math></inline-formula> N) and the increasing frequency (25-180 Hz) of decaying oscillations with the square root of <inline-formula> <tex-math notation="LaTeX">T </tex-math></inline-formula> over the range of line tensions (<inline-formula> <tex-math notation="LaTeX">r^{2} =0.978 </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">p < 10^{-4} </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">n =17 </tex-math></inline-formula>). Theory and experiment show that magnetic field impulses are capable of exerting measurable mechanical forces on bone ex vivo . The results raise an interesting question if the electromechanical effect could be sufficiently large to contribute to bone remodeling, reportedly sensitive to vibration amplitudes as small as 1 nm, and considering long duration of orthopedic therapy using repetitive EMP (months).
Low‐frequency electromagnetic field (LF‐EMF) stimulation is an emerging neuromodulation tool that is attracting more attention because of its non‐invasive and well‐controlled characteristics. ...However, the effect of different LF‐EMF features including the forms and the time of addition on neuronal activity has not been completely understood. In this study, we used multi‐electrode array (MEA) systems to develop a flexible in vitro magnetic stimulation device with plug‐and‐play features that allows for real‐time delivery of LF‐EMFs to biological tissues. Crucially, the method enables different forms of LF‐EMF to be added at any time to a long‐term potentiation (LTP) experiment without interrupting the process of LTP induction. We demonstrated that the slope of field excitatory postsynaptic potentials (fEPSPs) decreased significantly under post or priming uninterrupted sine LF‐EMFs. The fEPSPs slope would continue to decline significantly when LF‐EMFs were added two times with a 20‐min interval. Paired‐pulse ratio (PPR) was analyzed and the results reflected that LF‐EMFs induced LTP was expressed postsynaptically. The results of pharmacological experiments indicated that AMPA receptor activity was involved in the process of LTP loss caused by post‐LF‐EMFs. Moreover, the effect of priming sine or Quadripulse stimulation (QPS)‐patterned LF‐EMFs depended on the time interval between the end of LF‐EMF and the beginning of baseline recording. Interestingly, the effect of sine LF‐EMFs on LTP would not disappear within 120 min, while the impact of QPS‐patterned LF‐EMFs on LTP might disappear after 90 min. These results indicated that LF‐EMF might have a form‐ and time‐dependent effect on LTP.
In this work, we proposed a flexible in vitro magnetic stimulation method with plug‐and‐play features that allows for real‐time delivery of low‐frequency electromagnetic field (LF‐EMF) to biological tissues. We demonstrate that post and priming LF‐EMF stimulation would cause the loss of electrical stimulation‐induced LTP. The results of pharmacological experiments indicated that AMPA receptor activity was involved in the process of LTP loss caused by LF‐EMFs. The results indicated that LF‐EMF might have a form‐ and time‐dependent effect on LTP.
Nondestructive detection of small fatigue cracks is a critical and challenging task in evaluating the properties of material. This article proposes a novel L-shaped ferrite magnetic open sensing ...structure of the eddy current pulsed thermography system for fatigue crack inspection on metallic materials with anomalistic geometry. The theoretical derivation model of the proposed structure is developed to generate a guided distribution of electromagnetic field for enhancing the weak thermal signal detection. The proposed detection model provides a region of interest that has relatively uniform magnetic field. This significantly enhances the detectability and thermal contrast of omnidirectional microfatigue cracks. In addition, the detection is completely in the open view of the infrared camera, and the configuration has advantages of dramatically increasing portability and efficiency for detecting complex workpiece. Experiments on natural cracks in several samples have been conducted to validate the reliability and efficiency of the proposed system.
Many control methodologies have been applied to the motion control of linear motor drive systems. Compensations of nonlinearities such as frictions and cogging forces have also been carried out to ...obtain better tracking performance. However, the relationship between the driving current and the resulting motor force has been assumed to be linear, which is invalid for high driving coil currents due to the saturating electromagnetic field effect. This paper focuses on the effective compensation of nonlinear electromagnetic field effect so that the system can be operated at even higher acceleration or heavier load without losing achievable control performance. Specifically, cubic polynomials with unknown weights are used for an effective approximation of the unknown nonlinearity between the electromagnetic force and the driving current. The effectiveness of such an approximation is verified by offline identification experiments. An adaptive robust control (ARC) algorithm with online tuning of the unknown weights and other system parameters is then developed to account for various uncertainties. Theoretically, the proposed ARC algorithm achieves a guaranteed transient and steady-state performance for position tracking, as well as zero steady-state tracking error when subjected to parametric uncertainties only. Comparative experiments of ARC with and without compensation of electromagnetic nonlinearity done on both axes of a linear-motor-driven industrial gantry are shown. The results show that the proposed ARC algorithm achieves better tracking performance than existing ones, validating the effectiveness of the proposed approach in practical applications.
In this paper, a new ferrite-less wireless charging pad, called circular nonferrite pad, for roadway applications is introduced. The pad is characterized by having the ability to control leakage flux ...to reduce the electromagnetic fields outside the charging region. In addition, the pad shows low sensitivity to changes in the self-inductance due to secondary pad misalignment. A comparison of this new pad with similar-sized ferrite pads and single spiral couplers is presented. A formal mathematical description of the pad is shown here with finite element method simulations along with lab measurements to verify the validity of the models. The costs, advantages, and limitations of the new pad are also investigated.
Repeated Wi-Fi studies show that Wi-Fi causes oxidative stress, sperm/testicular damage, neuropsychiatric effects including EEG changes, apoptosis, cellular DNA damage, endocrine changes, and calcium ...overload. Each of these effects are also caused by exposures to other microwave frequency EMFs, with each such effect being documented in from 10 to 16 reviews. Therefore, each of these seven EMF effects are established effects of Wi-Fi and of other microwave frequency EMFs. Each of these seven is also produced by downstream effects of the main action of such EMFs, voltage-gated calcium channel (VGCC) activation. While VGCC activation via EMF interaction with the VGCC voltage sensor seems to be the predominant mechanism of action of EMFs, other mechanisms appear to have minor roles. Minor roles include activation of other voltage-gated ion channels, calcium cyclotron resonance and the geomagnetic magnetoreception mechanism. Five properties of non-thermal EMF effects are discussed. These are that pulsed EMFs are, in most cases, more active than are non-pulsed EMFs; artificial EMFs are polarized and such polarized EMFs are much more active than non-polarized EMFs; dose-response curves are non-linear and non-monotone; EMF effects are often cumulative; and EMFs may impact young people more than adults. These general findings and data presented earlier on Wi-Fi effects were used to assess the Foster and Moulder (F&M) review of Wi-Fi. The F&M study claimed that there were seven important studies of Wi-Fi that each showed no effect. However, none of these were Wi-Fi studies, with each differing from genuine Wi-Fi in three distinct ways. F&M could, at most conclude that there was no statistically significant evidence of an effect. The tiny numbers studied in each of these seven F&M-linked studies show that each of them lack power to make any substantive conclusions. In conclusion, there are seven repeatedly found Wi-Fi effects which have also been shown to be caused by other similar EMF exposures. Each of the seven should be considered, therefore, as established effects of Wi-Fi.
•7 effects have each been repeatedly reported following Wi-Fi & other EMF exposures.•Established Wi-Fi effects, include apoptosis, oxidat. stress &:•testis/sperm dysfunct; Neuropsych; DNA impact; hormone change; Ca2+ rise.•Wi-Fi is thought to act via voltage-gated calcium channel activation.•One claim of no Wi-Fi effects was found to be deeply flawed.
In order to study the influence of different cooling mediums on the fluid velocity and the temperature distribution of end parts in the turbogenerator end region, a 330-MW turbogenerator is analyzed. ...Three-dimensional fluid-thermal coupling analysis model of the turbogenerator end region is given. When the different cooling mediums are used, fluid velocity of fan inlet and pressure values of end-region outlet from the flow network calculation are applied to the end region as boundary conditions, and the losses from 3-D transient electromagnetic field calculation are applied to the end parts as heat sources in the fluid-thermal coupling field. The fluid field and temperature field in the turbogenerator end region are calculated using the hydrogen and air as cooling medium, respectively. Fluid velocity and temperature of end parts in the turbogenerator end region are compared when the different cooling mediums are used. When the hydrogen is used as the cooling medium, comparing the calculated temperature results with the test values, the calculated temperature results match well with test values. These will provide a reference for the ventilation cooling design of large turbogenerator.
In this paper, a testbed is designed and constructed for the investigation of DC PD pulses. The testbed is equipped with a 50\ \Omega transmission line (TL) that terminate to an oscilloscope for ...measuring the charge displacement current generated by PD pulses. Besides the oscilloscope measurements, two types of electromagnetic field sensors (D-dot and B-dot) were developed to capture the EM fields of the PD pulses propagating through the TL. The main goal of this paper is to investigate the DC PD pulses through the EM fields and the corresponding discharge current pulses that are considered as calibrating signals for the developed D-dot and B-dot sensors. The results of DC cavity discharge measured by the constructed testbed and the EM field sensors demonstrate close agreement with the reference PD pulses measured via oscilloscope.
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