Search Results (48)

Accurately detecting coal slime water concentration during coal washing is crucial for optimizing dosing systems and improving separation efficiency. Traditional concentration detection methods are often affected by flow field disturbances. To address these limitations, this paper proposes a pressure differential concentration detection system utilizing interference rectification for a stabilized flow field and improved measurement accuracy. The experimental system comprises a circulating slurry tank, a defoamer, and a turbulence removal measuring tank. Numerical simulations and experimental studies investigated the effects of slurry concentration and inflow velocity on detection accuracy. Through dynamic measurement of pressure difference data under different concentrations and flow rates, the characteristics of a solid–liquid two-phase flow field are simulated using Fluent software. The results demonstrate that for low-concentration (C = 10%) and high-concentration (C = 30%) slurries, a flow velocity of ≥0.7 m/s significantly improves flow uniformity and achieves a stable particle suspension state, maintaining a measurement error within 1% for a flow rate of 0.7 m/s. However, flow rates exceeding 0.7 m/s decrease flow stability, increasing errors. Notably, the combination of sensors at positions No. 2 and No. 4 yields the lowest measurement errors, which verifies the influence of sensor layout on detection accuracy. A 0.7 m/s velocity is identified as the key threshold for flow field stability, and the nonlinear influence of the synergistic effect of flow rate and concentration on the detection stability is revealed. These findings provide valuable insights for optimizing pulp concentration detection systems and enhancing industrial dosing precision. Full article

The authors present an in-depth theoretical study of two nonlinear circuits capable of transient thermal energy harvesting at one temperature. The first circuit has a storage capacitor and diode connected in series. The second circuit has three storage capacitors, and two diodes arranged for full wave rectification. The authors solve both Ito–Langevin and Fokker–Planck equations for both circuits using a large parameter space including capacitance values and diode quality. Surprisingly, using diodes one can harvest thermal energy at a single temperature by charging capacitors. However, this is a transient phenomenon. In equilibrium, the capacitor charge is zero, and this solution alone satisfies the second law of thermodynamics. The authors found that higher quality diodes provide more stored charge and longer lifetimes. Harvesting thermal energy from the ambient environment using diode nonlinearity requires capacitors to be charged but then disconnected from the circuit before they have time to discharge. Full article

Three-phase diode bridge rectifiers are widely employed in various industrial applications because of their inherent simplicity, robustness, low electromagnetic interference and good overall performance. However, their use causes harmonic distortion in the electric power network line currents due to their nonlinear nature, which, in turn, affects the electric power quality. The fundamental approach to limit the line currents’ total harmonic distortion (THD) introduced by the diode bridge rectification systems is based on increasing the number of steps in their waveform per power supply cycle and drawing them closer to the pure-sine waveforms. This can be achieved by employing the conventional twelve-pulse rectification system composed of two parallel connected six-pulse diode bridge rectifiers, in which the DC circuit is expanded on the auxiliary circuit responsible for adequately shaping the line currents’ waveforms per power supply cycle. When the auxiliary circuit is connected to the interphase reactor (IPR) additional (secondary) winding, the ability of the rectification system to reduce the line current THD depends mainly on the auxiliary circuit current waveform and its parameters. This paper provides a space vector analysis of the twelve-pulse diode bridge rectifier operation. It leads to devising a formula for the auxiliary circuit current related to the phase angle of the rectification system line currents’ space vector and the load current, which has been missing in the literature so far. The formula explicitly defines the auxiliary circuit current waveform that guarantees the optimal line currents’ THD for the twelve-pulse diode bridge rectifier which is expanded with the auxiliary circuit connected to the IPR secondary winding. The theoretical studies are validated through experimental investigations. Full article

Biosensors operating in the terahertz (THz) region are gaining substantial interest in biomedical analysis due to their significant potential for high-sensitivity trace-amount solution detection. However, progress in compact, high-sensitivity chips and methods for simple, rapid and trace-level measurements is limited by the spatial resolution of THz waves and their strong absorption in polar solvents. In this work, a compact nonlinear optical crystal (NLOC)-based reflective THz biosensor with a few arrays of asymmetrical meta-atoms was developed. A near-field point THz source was locally generated at a femtosecond-laser-irradiation spot via optical rectification, exciting only the single central meta-atom, thereby inducing Fano resonance. The reflective resonance response demonstrated dependence on several aspects, including structure asymmetricity, geometrical size, excitation point position, thickness and array-period arrangement. DNA samples were examined using 1 μL applied to an effective sensing area of 0.234 mm² (484 μm × 484 μm) for performance evaluation. The developed Fano resonance sensor exhibited nearly double sensitivity compared to that of symmetrical sensors and one-gap split ring resonators. Thus, this study advances liquid-based sensing by enabling easy, rapid and trace-level measurements while also driving the development of compact and highly sensitive THz sensors for biological samples. Full article

This research presents a comprehensive study of a Schottky diode fabricated using a gold wafer and a bilayer molybdenum disulfide (${\mathrm{MoS}}_2$) film. Through detailed simulations, we investigated the electric field distribution, potential profile, carrier concentration, and current–voltage characteristics of the device. Our findings confirm the successful formation of a Schottky barrier at the Au/${\mathrm{MoS}}_2$ interface, characterized by a distinct nonlinear I–V relationship. Comparative analysis revealed that the Au/${\mathrm{MoS}}_2$ diode significantly outperforms a traditional W/Si structure in terms of rectification performance. The Au/${\mathrm{MoS}}_2$ diode exhibited a current density of 1.84 × ${10}^{-9}$ A/${\mathrm{cm}}^2$, substantially lower than the 3.62 × ${10}^{-5}$ A/${\mathrm{cm}}^2$ in the W/Si diode. Furthermore, the simulated I–V curves of the Au/${\mathrm{MoS}}_2$ diode closely resembled the ideal diode curve, with a Pearson correlation coefficient of approximately 0.9991, indicating an ideality factor near 1. A key factor contributing to the superior rectification performance of the Au/${\mathrm{MoS}}_2$ diode is its higher Schottky barrier height of 0.9 eV compared to the 0.67 eV of W/Si. This increased barrier height is evident in the band diagram analysis, which further elucidates the underlying physics of Schottky barrier formation in the Au/${\mathrm{MoS}}_2$ junction. This research provides insights into the electronic properties of Schottky contacts based on two-dimensional ${\mathrm{MoS}}_2$, particularly the relationship between electronic barriers, system dimensions, and current flow. The demonstration of high-ideality-factor Au/${\mathrm{MoS}}_2$ diodes contributes to the design and optimization of future electronic and optoelectronic devices based on 2D materials. These findings have implications for advancements in semiconductor technology, potentially enabling the development of smaller, more efficient, and flexible devices. Full article

Biosensors in the Terahertz (THz) region are attracting significant attention in the biomedical and chemical analysis fields owing to their potential for ultra-trace sensing of various solutions with high sensitivity. However, the development of compact, highly sensitive chips and methods for easy, rapid, and trace-amount measurements have been significantly hindered by the limited spatial resolution of THz waves and their strong absorption by water. In this study, we developed a nonlinear optical crystal (NLOC)-based compact THz sensor chip, and a near-field point THz source with a diameter of ~ϕ20 μm was locally generated via optical rectification. Here, only the single central meta-atom was excited. The reflective resonance responses highly depend on the array number and period of the meta-atom structures. The sensing performance was examined with several liquid biological samples, such as mineral water, DNA, and human blood. 1 μL of samples was directly dropped onto the meta-surface with an effective sensing area of 0.32 mm² (564 μm × 564 μm). Obvious resonance frequency shifts were clearly observed. This research holds significance in advancing liquid bio-sample sensing methodologies by facilitating easy, rapid, and trace-amount measurements and promoting the development of compact and highly sensitive THz sensors tailored for liquid biological samples. Full article

The series-type 12-pulse rectifier generates a large amount of harmonics in the AC side current due to the strong nonlinearity of its rectifying diodes, causing serious harmonic pollution to the power grid. This article proposes a series 36-pulse rectifier based on a DC side dual passive frequency-doubling circuit to suppress the AC side current harmonics of a 12-pulse rectifier. The rectifier uses two symmetrical passive pulse multiplication circuits to regulate the circulation in the DC side circuit, increasing the output voltage and current state of the rectifier bridge, thereby increasing the number of pulses in the rectifier from 12 times to 36 times. Firstly, the working principle of the rectifier and the working mode of the dual passive frequency-doubling circuit were analyzed. Secondly, the harmonic suppression mechanism of the rectifier input current was revealed, and the frequency-doubling characteristics of the load voltage were analyzed. Finally, the correctness of the theoretical analysis was verified through a semi-physical platform. The verification and comparison results show that under the optimal conditions of the injecting transformer turns ratio, the DPPC can not only reduce the THD value of the input current by about 1/3 (from 14.87% to 4.78%) but can also increase the fluctuation frequency of the load voltage by 3 times (from 12 to 36), while improving the power quality of the AC/DC side rectifier and achieving the low harmonic operation of the rectifier. The proposed 36-pulse rectifier can effectively suppress harmonics; it has the advantages of simple structure, strong robustness, and high output voltage gain, and it is suitable for medium-voltage and high-voltage high-power rectification applications. Full article

This study introduces a novel fluxgate current sensor with a compact, ring-shaped configuration that exhibits improved performance through the integration of magnetization residence times and neural networks. The sensor distinguishes itself with a unique magnetization profile, denoted as M waves, which emerge from the interaction between the target signal and ambient magnetic interference, effectively enhancing interference suppression. These M waves highlight the non-linear coupling between the magnetic field and magnetization residence times. Detection of these residence times is accomplished using full-wave rectification circuits and a Schmitt trigger, with a digital output provided by timing sequence detection. A dual-layer feedforward neural network deciphers the target signal, exploiting this non-linear relationship. The sensor achieves a linearity error of $0.054\%$ within a measurement range of 15 A. When juxtaposed with conventional sensors utilizing the residence-time difference strategy, our sensor reduces linearity error by more than 40-fold and extends the effective measurement range by $150\%$. Furthermore, it demonstrates a significant decrease in ambient magnetic interference. Full article

One method of rectifying tilted buildings is by lifting them unevenly using hydraulic jacks. These jacks are loaded both monotonically and cyclically during the rectification process. It has been shown that the change in jack length is the sum of the change in the piston slide out and the change in the jack’s cylinder length, which is supported by a parallelepiped element. Laboratory tests were conducted to investigate the piston slide out and the change in the jack’s cylinder length under both monotonically and cyclically loaded conditions. The results indicated that the piston slide out forms a hysteresis loop. In contrast, the change in the jack’s cylinder length does not exhibit a hysteresis loop and is a non-linear function of the load. A structural model of the jack was proposed, consisting of three components: a linearly elastic component connected in parallel to the component where the frictional force occurs, and a component with non-linear elastic characteristics connected in series with them. Displacements of the linear elastic component, characterized by a constant stiffness, occur as long as the external load exceeds the internal frictional force. The value of the frictional force in this model increases with the load. The stiffness of the non-linear elastic component increases proportionally to the load. Full article

Metal–oxide–semiconductor field-effect transistors (MOSFETs) have proven to be effective devices for rectifying electromagnetic radiation at extremely high frequencies, approximately 1 THz. This paper presents a new interpretation of the THz rectification process in the structure of an MOS transistor. The rectification depends on the nonlinear effect of the carrier dynamics. The paper shows that the so-called self-mixing effect occurs within the interface region between the source and the channel. The basic tool used numerical TCAD simulations, which offer a direct interpretation of different aspects of this interaction. The complex, 2D effect is examined in terms of its basic aspects by comparing the MOS structure with a simplified case study structure. We demonstrate that a contribution to the output-rectified voltage detectable at the drain arises from the charging of the drain well capacitance due to the diffusion of excess electrons from the self-mixing interaction occurring at the source barrier. In addition, the paper provides a quantitative description of the rectification process through the definition of the output equivalent circuit, offering a new perspective for the design of detection systems. Full article

The presence of strong ambient vibrations could have a negative impact on applications such as high precision inertial navigation and tilt measurement due to the vibration rectification error (VRE) of the accelerometer. In this paper, we investigate the origins of the VRE using a self-developed MEMS accelerometer equipped with an area-variation-based capacitive displacement transducer. Our findings indicate that the second-order nonlinearity coefficient is dependent on the frequency but the VRE remains constant when the displacement amplitude of the excitation is maintained at a constant level. This frequency dependence of nonlinearity is a result of several factors coupling with each other during signal conversion from acceleration to electrical output signal. These factors include the amplification of the proof mass’s amplitude as the excitation frequency approaches resonance, the nonlinearity in capacitance-displacement conversion at larger displacements caused by the fringing effect, and the offset of the mechanical suspension’s equilibrium point from the null position of the differential capacitance electrodes. Through displacement transducer and damping optimization, the second-order nonlinearity coefficient is greatly reduced from mg/g${}^2$ to $\mathsf{\mu }$g/g${}^2$. Full article

The terahertz (THz) generation efficiency in the Cherenkov optical rectification scheme can be improved significantly if the silicon adaptor, mounted at the lateral surface of a nonlinear crystal, has a convex output surface with proper geometry. We demonstrate and compare with the results of direct experiments a method for theoretically modeling the angular distributions of the spectral power of THz radiation in the case of different Si adaptors, constructed by mounting plano-spherical lenses on a conventional flat Si prism. The applied method of theoretical modeling shows its usefulness in choosing the best Si adapter geometry. Full article

Energy availability especially that derived from renewable sources has sustainable effects on economic progress and environmental rectifications. However, using clean energy in the energy mix has been influenced by several macro fundamentals. The motivation of this study is to gauge the impact of uncertainties, environmental restrictions and innovation on clean energy consumption for the period 1997–2021 by employing the new econometric estimation techniques commonly known as CUP-FM and CUP-BC. Referring to the preliminary assessment with the slope of homogeneity, cross-sectional dependency and panel cointegration test, it is unveiled that research variables have exposed heterogeneity prosperities, cross-sectional dependence, and long-run association in the empirical equation. According to the empirical model output with CUP-FM and CUP-BC, EPU has a native statistically significant connection to clean energy consumption. At the same time, environmental taxation and technological innovation have had beneficial effects on clean energy development. Additionally, the nonlinear estimation disclosed asymmetric linkage between explanatory and explained variables in the long and short run. Directional causality revealed a feedback hypothesis explaining the relationship between EPU, TI and clean energy consumption. The study has offered policy suggestions based on the findings for future development. Full article

Studying the nonlinear photoresponse of different materials, including III-V semiconductors, two-dimensional materials and many others, is attracting burgeoning interest in the terahertz (THz) field. Especially, developing field-effect transistor (FET)-based THz detectors with preferred nonlinear plasma-wave mechanisms in terms of high sensitivity, compactness and low cost is a high priority for advancing performance imaging or communication systems in daily life. However, as THz detectors continue to shrink in size, the impact of the hot-electron effect on device performance is impossible to ignore, and the physical process of THz conversion remains elusive. To reveal the underlying microscopic mechanisms, we have implemented drift-diffusion/hydrodynamic models via a self-consistent finite-element solution to understand the dynamics of carriers at the channel and the device structure dependence. By considering the hot-electron effect and doping dependence in our model, the competitive behavior between the nonlinear rectification and hot electron-induced photothermoelectric effect is clearly presented, and it is found that the optimized source doping concentrations can be utilized to reduce the hot-electron effect on the devices. Our results not only provide guidance for further device optimization but can also be extended to other novel electronic systems for studying THz nonlinear rectification. Full article

In this study, we investigate the charge transport properties of semiconducting armchair graphene nanoribbons (AGNRs) and heterostructures through their topological states (TSs), with a specific focus on the Coulomb blockade region. Our approach employs a two-site Hubbard model that takes into account both intra- and inter-site Coulomb interactions. Using this model, we calculate the electron thermoelectric coefficients and tunneling currents of serially coupled TSs (SCTSs). In the linear response regime, we analyze the electrical conductance ($G_e$), Seebeck coefficient (S), and electron thermal conductance (${\kappa }_e$) of finite AGNRs. Our results reveal that at low temperatures, the Seebeck coefficient is more sensitive to many-body spectra than electrical conductance. Furthermore, we observe that the optimized S at high temperatures is less sensitive to electron Coulomb interactions than $G_e$ and ${\kappa }_e$. In the nonlinear response regime, we observe a tunneling current with negative differential conductance through the SCTSs of finite AGNRs. This current is generated by electron inter-site Coulomb interactions rather than intra-site Coulomb interactions. Additionally, we observe current rectification behavior in asymmetrical junction systems of SCTSs of AGNRs. Notably, we also uncover the remarkable current rectification behavior of SCTSs of 9-7-9 AGNR heterostructure in the Pauli spin blockade configuration. Overall, our study provides valuable insights into the charge transport properties of TSs in finite AGNRs and heterostructures. We emphasize the importance of considering electron–electron interactions in understanding the behavior of these materials. Full article