Changes In Structural Parameters Research Articles

Influence of a double-mixer configuration on the mixing and combustion characteristics of a multibypass combustor for a turbine-based combined cycle engine

The changes in the flow field and combustion characteristics induced by the mode transition process of a turbine-based combined cycle (TBCC) engine may lead to failure of the mode transition. In this paper, the cold mixing characteristics, combustion efficiency, and cold and thermal flow losses of a TBCC multibypass combustor with a double-mixer configuration are investigated through numerical simulations, and the correlations between the thermal mixing efficiency and combustion efficiency is established. The results show that the thermal mixing efficiency of double-lobed mixer combustors is better at low ram inlet Mach numbers, but the ring-plus-lobed mixer combustor has better mixing and combustor characteristics at relatively high Mach numbers. However, the effect of the turbo core inlet Mach number on the combustion efficiency is not regular. The spacing between the double mixers that maximizes the mixing and combustion characteristics of the combustor is 75 mm. With increasing of expansion angle of the lobed mixer, the thermal mixing efficiency and combustion efficiency increase by 31.9 % and 23.3 %, respectively. In addition, the positive correlation coefficient between combustion efficiency and thermal mixing efficiency caused by changes in the inlet Mach number is greater than that caused by changes in structural parameters.

Tuning of thermoelectric performance by modulating vibrational properties in Ni-doped Sb2Te3

Sb2Te3, a binary chalcogenide-based 3D topological insulator, attracts significant attention for its exceptional thermoelectric performance. We report the vibrational properties of magnetically doped Sb2Te3 thermoelectric material. Ni doping induces defect/disorder in the system and plays a positive role in engineering the thermoelectric properties through tuning the vibrational phonon modes. Synchrotron powder x-ray diffraction study confirms good crystalline quality and single-phase nature of the synthesized samples. The change in structural parameters, including B iso and strain, further corroborate with structural disorder. Detailed modification of phonon modes with doping and temperature variation is analysed from temperature-dependent Raman spectroscopic measurement. Compressive lattice strain is observed from the blue shift of Raman peaks owing to Ni incorporation in Sb site. An attempt is made to extract the lattice thermal conductivity from total thermal conductivity estimated through optothermal Raman studies. Hall concentration data support the change in temperature-dependent resistivity and thermopower. Remarkable increase in thermopower is observed after Ni doping. Simulation of the Pisarenko model, indicating the convergence of the valence band, explains the observed enhancement of thermopower in Sb2−x Ni x Te3. The energy gap between the light and heavy valence band at Γ point is found to be 30 meV (for Sb2Te3), which is reduced to 3 meV (in Sb1.98Ni0.02Te3). A significant increase in thermoelectric power factor is obtained from 715 μWm−1K−2 for pristine Sb2Te3 to 2415 μWm−1K−2 for Ni-doped Sb2Te3 sample. Finally, the thermoelectric figure of merit, ZT is found to increase by four times in Sb1.98Ni0.02Te3 than that of its pristine counterpart.

Study on the pore structure characteristics of maize grain piles and their effects on air flow distribution

The airflow in grain piles is affected by the content of broken grains, which causes changes in the pore structure within the grain pile. To investigate the changes in structural parameters at different broken grain contents, CT scanning and image processing were used to study the pore structure characteristics of broken maize grain contents of 0 %, 4 %, 8 % and 15 % respectively. The airflow distribution in the grain pile under different broken grain contents was studied by numerical simulation. The results showed that as the broken kernel content increased from 0 to 15 %, grain pile porosity gradually decreased, with a change rate of 6.97 %. An increase in the content of broken grains causes a decrease in the diameter and volume of the pores in the grain piles. The average value of the pore coordination number in the grain pile decreased as the broken grain content increased. When the content of broken grains is 0–15 %, the rates of change of pore diameter and tortuosity in the grain piles are 14.94 % and 24.94 %, respectively. As the broken grain content increased, the length and diameter of the pore throat in the grain pile decreased, while the fractal dimension and tortuosity increased. The increased broken grain content in the grain piles impedes the flow of air through the pores, thus affecting ventilation efficiency.

Damage detection and model updating of offshore jacket platforms using a direct sensitivity relation based on structural response

One of the challenges of the finite element model updating using time domain data is the lack of a direct relationship between changes in structural parameters and structural responses. Computational techniques, such as the Finite Difference Method (FDM) and Direct Differentiation Method (DDM), are used to calculate the sensitivity of the structural response to variations of structural parameters in the time domain. The use of these methods is time-consuming for large and complex structure. In the present study, an exact sensitivity equation is presented that establishes a direct and linear relationship between changes of structural parameters and structural response variations. The proposed closed form equations, have high computational efficiency in calculating the sensitivity of time domain responses. The measured responses directly contribute to the calculation of the sensitivity matrix, so the finite element model updating procedure is improved in terms of accuracy and reliability. The proposed method updates the finite element model even using a single excitation frequency that distinguishes the presented sensitivity relationship from frequency response-based methods which use wide ranges of excitation frequencies for model updating. To evaluate the effectiveness of the proposed method, different damage scenarios with different intensities have been simulated on two offshore jacket platform models. The performance of the proposed method in identifying the location and severity of induced damages in the presence of measurement and modeling errors confirms the effectiveness of the proposed method.

On formation, annihilation, and evolution of potential wells, and nonlinear phenomena of multi-magnet energy sink system.

This paper investigates the formation, annihilation, and evolution mechanisms of potential energy wells in nonlinear energy sink systems. The nonlinear energy sink system is composed of multiple inner and outer magnets. Two multi-magnet energy sink (MES) architectures are designed: a single-magnet vibrator and a double-magnet vibrator. Multi-stable (bi-, tri-, quad-, penta-, hexa-, and hepta-stable) mechanisms are elaborated by the Poincaré section and bifurcation diagram concerning the magnet length, the link length, and the MES configuration. The results show that the change in the internal structural parameters of the MES system will generate different types of bifurcations (i.e., saddle-node, subcritical, and super pitchfork bifurcations) and phase trajectories and have rich nonlinear response behaviors in the low frequency and wide frequency range, which can be used for damping and vibration reduction of engineering structures, vibration control, and energy source of the microgrid.

Overview of the application of open cell foam heat exchangers

PURPOSE. Review modern highly porous cellular heat exchangers. METHODS. We conducted a broad literature review on highly porous cellular structures used as heat exchangers. We studied both domestic and foreign literature. RESULTS. We analyzed highly porous heat exchangers of various structures: stochastic (foam with open and closed cells) and ordered (honeycombs and lattices). Methods for producing open/closed cell foams and additive technologies for producing honeycomb and lattice structures have been studied. The basic properties of highly porous structures are described. The factors influencing heat transfer and hydrodynamics in highly porous cellular heat exchangers are analyzed. A review of theapplication areas of highly porous metal heat exchangers is carried out. CONCLUSION. Heat transfer and hydrodynamics in highly porous materials depend on structural parameters, such as porosity, cell size and geometry, diameter, and geometry of the strands. Increasing porosity and cell size leads to a decrease in heat transfer coefficient and pressure drop. Changing the cell geometry affects the specific surface area of the heat exchanger and the pressure drop. Cells with complex geometries, such as octet, have a large surface area and provide a high heat transfer coefficient but high resistance to coolant flow. Cells with simple geometries, such as a cube, on the other hand, provide low flow resistance and low heat transfer coefficient. In general, any structural parameter change affects heat transfer and hydrodynamics.

Dual-band infrared metamaterial perfect absorber for narrow-band thermal emitters

Our study introduces a metamaterial with a straightforward disk-like configuration that exhibits two prominent absorption peaks at wavelengths of 3960 and 4197 nm, with absorption of 96.3% and 94.1%, respectively. The design not only proved to be convenient for the practical fabrication, but also revealed a resilience to the changes in structural parameters. Moreover, this offers versatility across a wide range of applications, due to the polarization-independent behavior. Additionally, the investigation on thermal emission by integrating the metasurface on a spiral structured heat source has yielded a promising result. The metasurface emitter reduced the energy consumption by 35%, compared with the blackbody emitter. The emission intensity at the aforementioned wavelength is 1.75 × 109 and 1.8 × 109 W·sr−1·m−3, respectively, indicating that the high potential of structure for the practical deployment in next-generation microheater of CO2 sensors.

Design and analysis of a highly uniform five-band terahertz filter based on frequency selective surface

In this paper, a highly uniform five-band terahertz filter is presented, achieved by deforming two nested square ring structures. The metal pattern layer of the filter comprises a nested square ring structure with an inner and outer opening, and a metal strip connecting the inner and outer rings. Symmetrical openings divide nested square rings, breaking the current path and generating multiple metal bars of different lengths to excite dipole oscillations. Using metal strips to connect the inner and outer rings, the inner and outer resonant structures are integrated. Compared to a single resonant particle, the coupling of different single resonant particles amplifies the resonance of the combined structure, resulting in a wider stopband width and enhanced isolation between multiple passbands. A metal strip is also added to both ends of the outer ring opening to increase the equivalent capacitance of the outer ring, enhance the resonance, and improve out-of-band suppression. The transmission spectrum has five uniform passbands in the range of 1.3807–1.9917 THz, and the maximum passband ratio (MPR) of 3 dB bandwidth is about 1.16, and the ratio of 10 dB is about 1.17. The transmission coefficient of transmission zero is about 0.1, and the peak transmission coefficient of transmission peak is close to 1. The polarization of TE and TM incident waves is stable, and the filtering characteristics are good. Besides, the rectangular coefficients of the five passbands are all less than 1.33, showing excellent band selectivity. The resonance mechanism is explained by the Q value and electric field current distribution. The influence of structural parameter changes on filtering characteristics is also analyzed, and the main control parameters are found by using correlation analysis tools. From the changes in the MPR curve, it is verified that the structure parameters of the designed filter are in good condition. The multi-passband filter designed in this paper has uniform filtering characteristics, which is helpful to the development of terahertz multi-channel communication.

Longitudinal Rates of Change in Structural Parameters of Optical Coherence Tomography in Primary Angle Closure Glaucoma following Laser Iridotomy along with Peripheral Iridoplasty.

This study aimed to investigate longitudinal rates of change (LRCs) of structural parameters from optical coherence tomography (OCT) in patients with primary angle closure glaucoma (PACG) after laser iridotomy (LI) along with laser peripheral iridoplasty (PI). Among 146 patients diagnosed with PACG, thirty-two subjects (32 eyes) who underwent LI plus PI and accomplished more than five times of reliable OCT tests were included in the current retrospective study. Retinal nerve fiber layer (RNFL) and Bruch's membrane opening-minimum rim width (BMO-MRW) were measured by spectral-domain OCT with three month interval. LRCs of global and six Garway-Heath sectors were investigated using the linear mixed-effects model which adjusted BMO area, sex, and age. Imaging of dual Scheimpflug analyzer was performed before and at 1 week after LI with PI and yearly thereafter. The mean follow-up period was 32.28 ± 13.34 months with a mean number of 10.18 ± 3.33 OCT images. Baseline characteristics are as follows: age, 63 ± 7.9 years; female, 62.5%; intraocular pressure(IOP), 15.48 ± 4.79 mmHg; anterior chamber depth, 2.09 ± 0.18 mm; and mean deviation, -7.97 ± 8.48 dB. Global LRC of BMO-MRW was 0.86 ± 1.34 μm/yr and RNFL was -0.64 ± 0.22 μm/yr. IOP decreased significantly to 13.06 ± 2.21 mmHg (p=0.001) while anterior chamber volume (p=0.011) and mean anterior chamber angle (p=0.022) increased significantly after LI along with PI compared to the baseline at the final visit. LRC of a new parameter, BMO-MRW, and LRC of RNFL were relatively low in patients with PACG, following LI along with PI. After widening of the anterior chamber angle and decrease of IOP due to LI plus PI, PACG might show stable structural prognosis assessed by OCT.

Artificial neural network for deciphering the structural transformation of condensed ZnO by extended x-ray absorption fine structure spectroscopy

Pressure-induced structural phase transitions play a pivotal role in unlocking novel material functionalities and facilitating innovations in materials science. Nonetheless, unveiling the mechanisms of densification, which relies heavily on precise and comprehensive structural analysis, remains a challenge. Herein, we investigated the archetypal B4 → B1 phase transition pathway in ZnO by combining x-ray absorption fine structure (XAFS) spectroscopy with machine learning. Specifically, we developed an artificial neural network (NN) to decipher the extended-XAFS spectra by reconstructing the partial radial distribution functions of Zn–O/Zn pairs. This provided us with access to the evolution of the structural statistics for all the coordination shells in condensed ZnO, enabling us to accurately track the changes in the internal structural parameter u and the anharmonic effect. We observed a clear decrease in u and an increased anharmonicity near the onset of the B4 → B1 phase transition, indicating a preference for the iT phase as the intermediate state to initiate the phase transition that can arise from the softening of shear phonon modes. This study suggests that NN-based approach can facilitate a more comprehensive and efficient interpretation of XAFS under complex in-situ conditions, which paves the way for highly automated data processing pipelines for high-throughput and real-time characterizations in next-generation synchrotron photon sources.

Longitudinal changes in diffusion tensor imaging in hemodialysis patients.

Hemodialysis patients have increased white matter and gray matter pathology in the brain relative to controls based on MRI. Diffusion tensor imaging is useful in detecting differences between hemodialysis and controls but has not identified the expected longitudinal decline in hemodialysis patients. In this study we implemented specialized post-processing techniques to reduce noise to detect longitudinal changes in diffusion tensor imaging parameters and evaluated for any association with changes in cognition. We collected anatomical and diffusion MRIs as well as cognitive testing from in-center hemodialysis patients at baseline and 1 year later. Gray matter thickness, white matter volume, and white matter diffusion tensor imaging parameters were measured to identify longitudinal changes. We analyzed the diffusion tensor imaging parameters by averaging the whole white matter and using a pothole analysis. Eighteen hemodialysis patients were included in the longitudinal analysis and 15 controls were used for the pothole analysis. We used the NIH Toolbox Cognition Battery to assess cognitive performance over the same time frame. Over the course of a year on hemodialysis, we found a decrease in white matter fractional anisotropy across the entire white matter (p < 0.01), and an increase in the number of white matter fractional anisotropy voxels below pothole threshold (p = 0.03). We did not find any relationship between changes in whole brain structural parameters and cognitive performance. By employing noise reducing techniques, we were able to detect longitudinal changes in diffusion tensor imaging parameters in hemodialysis patients. The fractional anisotropy declines over the year indicate significant decreases in white matter health. However, we did not find that declines in fractional anisotropy was associated with declines in cognitive performance.

Tabular Two-Dimensional Correlation Analysis for Multifaceted Characterization Data.

We propose tabular two-dimensional correlation spectroscopy analysis for extracting features from multifaceted characterization data, essential for understanding material properties. This method visualizes similarities and phase lags in structural parameter changes through heatmaps, combining hierarchical clustering and asynchronous correlations. We applied the proposed method to data sets of carbon nanotube (CNT) films annealed at various temperatures and revealed the complexity of their hierarchical structures, which include elements such as voids, bundles, and amorphous carbon. Our analysis addresses the challenge of attempting to understand the sequence of structural changes, especially in multifaceted characterization data where 11 structural parameters derived from eight characterization methods interact with complex behavior. The results show how phase lags (asynchronous changes from stimuli), and parameter similarities can illuminate the sequence of structural changes in materials, providing insights into phenomena such as the removal of amorphous carbon and graphitization in annealed CNTs. This approach is beneficial even with limited data and holds promise for a wide range of material analyses, demonstrating its potential in elucidating complex material behaviors and properties.

Composition and structure of tungsten antimony acid

Tungsten antimony acids (TAA) with the composition H(2)Sb(2)WXO6·nH2O (0 &lt; x ≤ 1.45; 0 &lt; n ≤ 2.0) have been synthesized by hydrolysis of antimony trichloride pre-oxidized with nitric acid in the presence of varying amounts of Na2WO4. To obtain TAA protonated forms, the samples were kept in a 96% solution of sulphuric acid, the precipitate was washed until reaction became neutral and dried in air. The amount of tungsten, antimony, and silver ions in TAA was determined using energy dispersive analysis. Changes in structural parameters upon doping of AA with tungsten ions were studied using a Bruker D8 ADVANCE X-ray diffractometer (CuKa1-radiation). The number of oxonium ions in TAA was determined by the substitutionof these ions by silver ions in equivalent amounts (Ag+-TAA forms). All obtained TAA samples and Ag+ TAA forms had a pyrochlore-type structure, space group symmetry Fd3m. Refinement of the arrangement of atoms in the structure using the Rietveld method showed that tungsten ions replace antimony ions and are statistically located in 16c, oxygen anions in 48f, and oxonium ions and water molecules in 16d and 8b positions, respectively. When tungsten ions were introduced into samples, the structural parameters of the resulting phases changed. There was a decrease in the unit cell parameter and the distance between antimony ions and oxygen anions, while an increase in the distance between oxonium ions and oxygen anions located in 48f positions was observed. This allowed the removal of a proton from oxonium molecules and its transport via a system of hydrogen bonds formed by water molecules

A hybrid reliability assessment method for slab track with changing structural parameters

Changes in the dynamic properties of high-speed rail (HSR) slab track structures can have a great impact on train safety and ride quality. However, the dynamic response of wheel–rail systems, which is related to operational safety, has rarely been considered in existing service reliability assessments of track structures. To solve this problem, a hybrid method was developed, with the serviceability limit state (SLS) first defined with respect to the derailment coefficient (DC) and wheel unloading rate (WUR). In calculating the reliability index, the response surface method and the first-order reliability method were used to solve the implicit expression of wheel–rail force in the SLS equation. To reduce the computation cost, a surrogate model expressing the non-linear mapping of the wheel–rail interaction is proposed. The computation efficiency and accuracy of the hybrid method were compared with Monte Carlo simulation and a back-propagation neural network (BPNN). The computation time of the hybrid method was only 1/8.4 of the BPNN method, while the accuracy of the reliability index was 98% for the DC and 97% for the WUR. The hybrid method was used to assess the reliability of a typical slab track structure under changing stiffness and damping coefficients of the fasteners, cement asphalt mortar and foundation. The stiffness and damping of the fasteners had the most impact on wheel–rail dynamics and track reliability. This research provides new insights into reliability assessments for HSR slab track with respect to train operational safety.

Phase-aided online self-correction method for high-accuracy three-dimensional measurement.

The binocular structured light 3D measurement system is widely used in situ industrial inspection and shape measurement, where the system structure is generally unstable due to mechanical loosening or environmental disturbance. Timely corrections to the changing structural parameters thus is an essential task for online high-accuracy measurement, which is difficult for traditional unidirectional fringe projection methods to self-correct the structural change. To this end, we propose an online self-correction method based on the investigation that orthogonal fringe projection can intrinsically relax the constraint on the epipolar geometry relationship and provide bidirectional phases for accurate corresponding point searching. Since orthogonal fringe projection may sacrifice the measurement efficiency, we further design a searching strategy by locally unwrapping one directional phase to reduce the number of projection patterns. Experimental results demonstrate that the proposed method is effective for online self-correction of unstable system structure to achieve high-accuracy 3D measurement under complex measurement environments.

Sensitive Properties of Power Spectral Density Transmissibility (PSDT) to Moving Vehicles and Structural States in Bridge Health Monitoring

Bridge health monitoring confronts a critical challenge in extracting meaningful features that are sensitive to structural damage while remaining nonsensitive to operational environments and loads. Most of structural response features such as power spectral density (PSD) in the long‐term monitored bridge are influenced by operational vehicle loads. The power spectral density transmissibility (PSDT), defined as the power spectral density ratio of two measured output responses at two different structural locations with the same reference output response, converges independently at the system poles of the applied excitations and transferring outputs. Capitalizing on such a unique property of PSDT around the system poles, the PSDT‐based spectral moment is proposed in the paper to establish a robust structural feature in bridge health monitoring taking into account the time‐varying characteristics under operational vehicle loads. Numerical simulations and comparisons with PSD‐based spectral moment analysis reveal that the PSDT‐based spectral moment exhibits an enhanced robustness to traffic flow excitations and heightened sensitivity to changes in structural parameters. Further laboratory experimental results on the beam under moving vehicle confirm that the PSDT‐based spectral moment is less affected by moving vehicle loads, but it demonstrates higher sensitivity to structural parameter changes. Given its robust properties of low sensitivity to operational vehicle loads and sensitivity to changes in structural parameters, the proposed PSDT‐based spectral moment emerges as an ideal structural feature suitable for the effective applications in the long‐term bridge health monitoring, such as structural damage identification, model updating, condition assessment, and safety warning.

Результати модифікації аутотрансплантата після вторинної кісткової пластики альвеолярного відростка у пацієнтів з вродженим незрощенням верхньої губи та піднебіння.

Purpose. This study aimed to evaluate changes in structural parameters of neoformed osseous tissue after the bone grafting alveolar process with different types of autografts. Methods. The analysis of the anthropometric indices of neoformed bone tissue was conducted by multispiral computed tomography scanning. 29 children with congenital clefts of the alveolar process aged from 8-17 years were involved in the survey. The autotransplant was used from the mandibular symphysis (I group) and tibia (²² group). Results. The overall success rate of the formed bone bridge in the I group was 66,6% and 57,9% in ²² group (p = 0,632) according to the Bergland scale of complete regeneration. The average volume of the neoformed osseous tissue constituted in children of the I group stood at 71,0% ± 10,8, in the children of the ²² group the defect filling appeared to be 68,9% ± 3,7 after 1 year. There was a statistically significant loss of bone volume in percentage equivalent between the I (1%) and II (9,9%) groups over the last 6 months (p = 0,008). During a year the density of the neoformed bone of the I group tended to get 526,1 ± 90,4 HU, in the ²² group the average density was 288,0 ± 46,3 HU, this is 1,8 times less than in the I group (p = 0,054). Conclusions. It has been determined that the reparative processes and bone bridge formation of the mandibular symphysis autotransplant occur more rapidly during the first six months following grafting. At the end of the first year, the bone bridge’s volume and height parameters were similar, but the I group’s density remained higher than that of the II group. Key words: Congenital cleft lip and palate; autograft; bone grafting of the alveolar process; bone bridge height; bone bridge density.

Synthesis, Crystal Structures, Photophysical Properties and Antibacterial Activities of Copper(II) Complex Derived from 4-Chloro-2-{[(2,6-dimethylphenyl)imino]methyl}phenol

A new asymmetrical Schiff base ligand, (E)-4-chloro-2-{[(2,6-dimethylphenyl)amino] methyl}phenol(HL), and its mononuclear Cu(Ⅱ) complex have been synthesized. The molecular structures and spectroscopic properties of the ligand and its complex were experimentally characterized by single crystal X-ray diffraction, elemental analysis, FT-IR, NMR and UV-Vis spectroscopic techniques. The analysis confirmed that the Cu atom in complex is generally four-coordinated by one imino N and one phenolic O atoms of a Schiff-base ligand adopting a trans-configuration of N2O2 donor atoms around the metal ion, forming a tetrahedral geometry. Density functional calculation is being carried out on both HL and copper(Ⅱ) complex to investigate changes in structural parameters, energies of the HOMO and LUMO. The results demonstrated that the HOMO and LUMO were effectively separated with the benzene ring of 2,6-dimethylbenzenamine as a donor unit and the benzene ring of 5-chlorosalicylaldehyde as an acceptor unit. The effective HOMO-LUMO separation helps to induce intramolecular charge transfer from the HOMO to the LUMO. The HOMO-LUMO energy gap become smaller when the Schiff base ligand coordinated with Cu(II) ion, most likely due to the interaction of the d-orbitals of copper(Ⅱ) with the HOMO and/or LUMO of the ligand. These theoretical calculations supported the experimentally observed results.The biological assay revealed that both Schiff base and the complex have different antimicrobial activity. The complex has the MIC value of 0.0781 mmol·L-1 against Escherichia coli.

Fast and High Accuracy CSM Control Under Manipulator Actuator Fault Conditions

The dynamic performance metrics of manipulators are decreased when actuator faults happen. To ensure the response speed and improve the tracking accuracy under actuator fault, the complementary sliding mode (CSM) controller is designed in this article. Different from the general sliding mode control (SMC), there are two sliding surfaces in the CSM controller design process, and the mathematical complexity of the controller is simplified through the relationship of the two complementary sliding surfaces, which helps to reduce the response time. Also, the structural parameter changes and disturbance existed in the real manipulator system are also considered in this paper by introducing uncertainty item during modeling, thus the robustness of the controller is improved. In the experimental part, the control effect of the CSM proposed is compared with that of the conventional sliding mode method. Normal conditions and actuator constant deviation fault of the manipulator are studied. The results show that the CSM has superiority in control accuracy and response speed. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —In recent years, the control problem of manipulators under complex conditions has attracted particular attention. The key to the design of the controller lies in its stability while keeping the tracking performance. Many complex auxiliary methods are proposed to guarantee this, but a few can achieve acceptable performance. This article proposed the complementary sliding mode controller design method, in which two sliding surfaces are used to simplify the proof in the controller design. We choose the error variables to construct the sliding surface, so the CSM could handle several actuator faults very well, which enhances the adaptive ability of the algorithm.

Bound states in continuum domain of double resonant ring metal metasurfaces

Metasurfaces have found extensive applications in microwave, terahertz, and optical range, serving different purposes such as filters, sensors, slow light devices, and nonlinear devices due to their distinctive electromagnetic response characteristics. Recent development requires metasurface devices to exhibit enhanced monochromaticity and stronger light interaction. Consequently, there is a growing interest in designing metasurfaces with high-quality factor (&lt;i&gt;Q&lt;/i&gt;-factor) resonances, considering their crucial role in achieving sharp resonances through constructing bound states in the continuum (BIC) mode. The utilization of BIC has emerged as a prominent method of designing metasurfaces with high &lt;i&gt;Q&lt;/i&gt;-factor resonances. Due to the fact that the changes in the structural parameters of metasurfaces can simultaneously affect the resonance of two components of q-BICs, it is difficult to achieve on-demand design of operating frequency, bandwidth, and &lt;i&gt;Q&lt;/i&gt;-factor. In this work, we investigate a novel THz metasurfaces supporting q-BIC resonance. We optimize the geometric parameters of two split ring resonators (SRRs) to tailor the operating frequencies of intrinsic resonance, and tune the coupling between different resonance modes to form the q-BIC mode resonance. The dominant modes are demonstrated by the results of multipolar decomposition calculations of the electromagnetic field distributions and scattered power at different resonant operating frequencies. In &lt;i&gt;x&lt;/i&gt;-polarized and &lt;i&gt;y&lt;/i&gt;-polarized incident electromagnetic wave, the normalized coupling strength ratio between the two modes are calculated by Jaynes-Cummings model to be 0.54% (&lt;i&gt;x-&lt;/i&gt;polarized) and 4.42% (&lt;i&gt;y-&lt;/i&gt;polarized) respectively, which explains the law that the resonant frequency of different modes changes with the structural parameters of SRRs device. In order to analyze the refractive index sensing capabilities of our designed metasurfaces under the incident electromagnetic waves with different polarizations, we investigate the variations of the transmitted spectrum of the metasurface with refractive index of matters. The calculated results show that the sensitivity of the metasurface is 151 GHz/RIU when the incident wave is &lt;i&gt;y&lt;/i&gt;-polarized and 108 GHz/RIU when the incident wave is &lt;i&gt;x&lt;/i&gt;-polarized. We realize the effective control of the operating frequency, bandwidth, and &lt;i&gt;Q&lt;/i&gt;-factor of the q-BIC mode resonance in the transmission spectrum of the metasurface, which provides a new idea for the practical designing of terahertz metasurfaces with high &lt;i&gt;Q&lt;/i&gt;-factor.