Effects of neighboring transitions on electromagnetically induced absorption (EIA), electromagnetically induced transmission (EIT), and switching between EIA and EIT of a degenerate two-level system ...(DTLS) in 85Rb atoms have been investigated on the basis of the angle (θR) between the polarization axes of the coupling and probe beams. Measured spectral profiles are compared with the calculated absorption profiles by considering the effects of the neighboring states. The results match well with observed spectra. EIT, instead of EIA, occurs at smaller θR for the upper hyperfine ground state of 85Rb, and the amplitude of the EIA increases as the angle increases for all transitions of Fg=3→Fe=2,3, and 4 after the transformation from EIT to EIA. Transitions from the lower ground hyperfine level, such as Fg=2→Fe=1,2, and 3, appear as EIT for all values of θR, and the amplitude increases as θR is increased. Theoretical critical θR, in which EIT is converted to EIA, matches well with the experimental ones.
Abstract
Electrical impedance tomography can reconstruct the complex conductivity distribution by injecting a current or voltage at a specific frequency into the target domain. The complex ...conductivity spectroscopy of numerous biological tissues is frequency-dependent. A suitable excitation frequency is vital to high-quality imaging over a wide frequency range. This paper investigates the relationship between the parameters of the biological tissue impedance model and the impedance spectroscopy. A frequency selection method based on the impedance spectroscopy is proposed, in which the impedance spectroscopy on a specific electrode at the domain boundary to be measured is first scanned. In TD-EIT, the difference between the target’s impedance spectroscopy and the null field is calculated, and the frequency corresponding to its extreme value is used as the excitation signal for TD-EIT. The excitation frequency in FD-EIT is the frequency corresponding to the extreme point in the target impedance spectroscopy, and we have also used this method to image the interior of the maize ear. This study provides a quick and efficient method for determining the excitation frequency for EIT, allowing researchers to find the best excitation frequency for high-quality imaging during actual measurements.
Abstract
The current medical imaging techniques can only be used in a few diagnostic scenarios after the development of qualitative lesions, and they frequently include the use of radiation, among ...other things. Electrical impedance tomography, in contrast, uses no radiation and is non-invasive. Electric impedance tomography (EIT), which has these benefits, is frequently utilized for the early stages of disease detection and treatment. This study discusses the research advancements, image reconstruction methods, hardware system design, and clinical applications of EIT in the treatment of lung disorders for the application of EIT in the treatment of lung lesions. The intricacy of EIT systems and their solutions is explained by looking at and introducing a few key components of EIT technology. This provides research ideas for future studies and confirms the technology’s extensive development prospects. The outcome demonstrates that EIT is still in a relatively early stage of development and that image reconstruction algorithms are now being utilized to improve imaging resolution. The accuracy of data collection and processing is increasing, and hardware technology is also advancing quickly. EIT is also employed in clinical settings for pathology in the bladder, brain, and lungs. Future uses of EIT in medicine have a lot of potential for real-time, long-term monitoring and early diagnosis.
Strain measurements have traditionally been accomplished by connecting many gauges to crucial spots on structures. Installing strain gauges can be costly and limited in providing comprehensive data ...for large surface areas or complex structures, posing significant challenges. This work explores the use of piezoresistive nanocomposite sensors as a cost-effective and informative solution for wide surface area strain detection. Piezoresistive sensors are created using two methodologies: film-coated and pellet-fed 3D printing technique (PF3DP), with variable gauge factors achieved by using 6 and 10 wt% multi-wall carbon nanotubes (MWCNTs), respectively. An electrical impedance tomography (EIT) setup is utilized to analyze electrical changes with respect to strain and predict the conductivity distribution across the sensor’s surface. This study employs two efficient machine learning (ML) techniques, artificial neural networks (ANN) and convolutional neural networks (CNN), to analyze and compare image reconstruction resolution at different loads. The machine learning models are designed to reconstruct images quickly and reliably. The study demonstrates that the hybrid-ML model, which combines ANN and CNN models, achieves high-resolution image construction with minimal errors compared to outcomes obtained through EIT for the experimental measurements. Sensors created using 3D printing provide higher image resolution and data stability than film-coated sensors. This technology has the potential for accurate strain sensing and measuring the structural health of complex surfaces.
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•Piezoresistive nanocomposite sensors for wide strain detection.•Solution mixing and 3D printing sensors, with 6 and 10 wt% MWCNTs respectively.•An EIT setup to predict the conductivity distribution across the sensor’s surface.•3D printing sensor provide higher image resolution and conductivity data stability.•Hybrid-ML model, combines ANNs and CNNs model, achieves minimal errors in outcomes.
In this article, a multicircle planar electrical impedance tomography (EIT) sensor is proposed for three-dimensional (3-D) miniature imaging. There are two problems in 3-D miniature EIT imaging: 1) ...the spatial resolution is low since the number of electrodes is limited and 2) contact impedance influences image reconstruction quality severely. The proposed EIT sensor made by a printed circuit board (PCB) adopts a multicircle structure and tackles the two problems. Driven electrodes are distributed on the outermost two circles, while measurement electrodes are distributed on the innermost circle. Contact impedance is reduced since the area of driven electrodes could be larger than traditional ones by using the multicircle structure, and it is also owning to gold that is deposited on the surface of the electrodes. Moreover, a new driven-measurement pattern of the EIT sensor is proposed to improve the spatial resolution as well as image reconstruction quality. The proposed EIT sensor is verified by both simulation and experiment. The average image correlation coefficient (ICC) is as high as 0.8475 in simulation. Compared with the 16-electrode EIT sensor, ICC is improved by 39.16%. In the experiment, the average ICC of four standard objects is 0.8389. The proposed 3-D EIT sensor is good at miniature imaging.
Graphene has become an ideal material in the terahertz band, for its excellent properties and its variable carrier density (which can be modified by bias voltage). A compact metamaterial based on ...graphene was proposed here using the nesting of rectangular rings into square rings to produce electromagnetically induced transparency (EIT) in the terahertz frequency band. In this present paper, we investigated the effects of structural parameter changes on EIT phenomena, the electrical tunability of graphene materials, and their sensor performances and slow-light properties. Due to the sensitivity of the EIT window to changes in the surrounding environment, the simulation results show that its sensitivity and FOM(figure of merit) can achieve 2.26 THz/RIU and 6.21 respectively. Therefore, this paper proposed a compact design structure of graphene, which not only has the unique electrical properties of graphene but also has adjustable characteristics. This will lay a good foundation for future refractive index sensors and other miniaturized devices.
•A compact graphene design structure is proposed.•The structure has good sensitivity.•This structure not only has the unique electrical properties of graphene, but also has adjustable characteristics.
•The magnetic field effects on the EIT in the room temperature for the multilevel V-type model using both the 87Rb D1 and D2 line have been studied.•Multiple EIT windows at a moderate magnetic field ...are observed.•When pump laser is tuned to the 87Rb-D2 transition and 87Rb-D1 transition is used as a probe field, the separation between the two splitted EIT peaks gradually increases with the increase in magnetic field.•The effect of pump field power on the splitted EIT peaks at a particular magnetic field has been investigated.•This study of generating multiple EIT windows in a magnetic field may be useful in multi-channel quantum information processing, in optical magnetometry and in precession spectroscopy.
We have studied the effect of an external magnetic field on the electromagnetically induced transparency in a multi-level V-type system of 87Rb using D1 and D2 lines. We apply the magnetic field at room temperature parallel to the direction of co-propagating pump and probe laser beams. Five independent EIT peaks are observed at a moderate magnetic field of 72.5 G, when 87Rb-D1 line is addressed by the pump laser and the probe laser is scanned across the 87Rb-D2 transitions. When the pump laser is tuned to the 87Rb-D2 transition, we could resolve two EIT peaks at the similar magnetic field. The effects of magnetic field and pump field power on the Zeeman split EIT peaks are also investigated. A theoretical model is developed considering the multiple Zeeman sublevel to reproduce the observed spectra.
We present a terahertz metamaterial based on electromagnetically induced transparency (EIT), of which the unit cell is made up of the coupled “bright” circular split-ring resonator (CSRR) and “dark” ...square split-ring resonator (SSRR) with practically equal resonance frequency. With the strong coupling of bright mode and dark mode, a sharply narrow transparency peak is observed at terahertz region. Then, the influences of the physical parameters on EIT-like effect are simulated and analyzed by the electromagnetic simulation software CST. Furthermore it is numerically demonstrated that the EIT-like metamaterial is a promising candidate for sensing with refractive index sensitivity of 96.2 GHz/RIU, which means that the transmission peak of the sensor shifts 96.2 GHz per unit change of refractive index of the surrounding medium. Finally, transmission responses of the sensor based on EIT-like effect are investigated by terahertz time-domain spectroscopy, showing a good perception capability consistent with the simulation results. With the property of high refractive index sensitivity, the metamaterial can play an important role in terahertz sensing and detection technology.
Abstract
The lateral and rotary light-drag effects in a four-level vee+ladder configuration comprising a Rydberg state as the topmost level is theoretically investigated. We found that it is ...difficult to obtain enhanced lateral and rotary light drags accompanied by suppressed absorption in the three-level vee and ladder configurations. However, in the proposed four-level vee+ladder configuration both lateral and rotary light drags are significantly enhanced as well as suppressing the absorption of the weak probe field via electromagnetically induced transparency (EIT). The profound impacts of the intensity of the controlling fields on both the lateral and rotary light drags are discussed. It is demonstrated that intensifying the controlling fields leads to enhancing the lateral and rotary light-drag effects accompanied by negligible probe field absorption. Furthermore, it is shown that light is dragged opposite of the direction of the host medium motion while the superluminal light propagation dominates. Nevertheless, the light is dragged along the same direction of the host medium motion in the subluminal propagation condition. In addition, we present the real quantities of all the parameters used in this study for future empirical investigations.
This paper describes a simple and reproducible method for universal evaluation of the performance of electrical impedance tomography (EIT) systems using reconstructed images. To address the issues ...where common electrical parameters are not directly related to the quality of EIT images, based on objective full reference (FR) image quality assessment, the method provides a visually distinguishable hot colormap and two new FR metrics, the global and the more specific 'region of interest'. A passive 16 electrode EIT system using an application specific integrated circuit front-end was used to evaluate the proposed method. The measured results show, both visually and in terms of the proposed FR metrics, the impact on recorded EIT images with different design parameters and non-idealities. The paper also compares the image results of a passive electrode system with a matched 'single variable' active electrode system and demonstrates the merit of an active electrode system for noise interference. A figure of merit based on the FR metrics is proposed.
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