Angle Stability Research Articles

A Meta-Analysis of Surgical Outcomes in 25727 Patients Undergoing Anterior Cervical Discectomy and Fusion or Anterior Cervical Corpectomy and Fusion for Cervical Deformity.

Systematic Review. To evaluate which cervical deformity correction technique between anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF) produces better clinical, radiographic, and operative outcomes. We conducted a meta-analysis comparing studies involving ACDF and ACCF. Adult patients with either original or previously treated cervical spine deformities were included. Two independent reviewers categorized extracted data into clinical, radiographic, and operative outcomes, including complications. Clinical assessments included patient-reported outcomes; radiographic evaluations examined C2-C7 Cobb angle, T1 slope, T1-CL, C2-7 SVA, and graft stability. Surgical measures included surgery duration, blood loss, hospital stay, and complications. 26 studies (25727 patients) met inclusion criteria and were extracted. Of these, 14 studies (19077 patients) with low risk of bias were included in meta-analysis. ACDF and ACCF similarly improve clinical outcomes in terms of JOA and NDI, but ACDF is significantly better at achieving lower VAS neck scores. ACDF is also more advantageous for improving cervical lordosis and minimizing the incidence of graft complications. While there is no significant difference between approaches for most surgical complications, ACDF is favorable for reducing operative time, intraoperative blood loss, and length of hospital stay. While both techniques benefit cervical deformity patients, when both techniques are feasible, ACDF may be superior with respect to VAS neck scores, cervical lordosis, graft complications and certain perioperative outcomes. Further studies are recommended to address outcome variability and refine surgical approach selection.

Study on phase-locked out-of-step fault characteristic analysis and protection of VSPSU

Abstract The variable-speed pumped storage unit (VSPSU) adopts flexible three-phase AC excitation, and the control dominant characteristics of the equipment are significant, which deeply affects the out-of-step (OOS) fault law and stability mechanism of VSPSU. Aiming at the OOS fault of VSPSU, this paper first defines the power angle of VSPSU and analyzes the influence of a phase-locked loop on the power angle stability of the unit. Then, the fault characteristics of the power angle instability of VSPSU are further studied. It is found that the traditional lens impedance protection scheme based on measuring the number of sliding poles has the problem that the phase-locked OOS oscillation cannot be responded to or the response is not timely. Combined with the research on the fault characteristics of power angle instability of VSPSU, an OOS protection method based on a bilateral annular blocker is proposed. The simulation results show that the proposed protection method can quickly and accurately reflect the phase-locked OOS fault of VSPSU, and meet the requirements of VSPSU for the reliability of OOS protection.

[formula omitted] assisted temperature tunable wideband terahertz absorber as a biosensor

In this article, vanadium dioxide (V O2) based tunable wideband terahertz absorber is proposed. It consist of a gold plated ground plane and V O2 based concentric ring resonating geometry on the backside and top surfaces of dielectric material Silicon dioxide (SiO2). Its unit cell has dimension of 30 × 30×9.235μm3. It achieves polarization insensitive absorption A≥90% from 2.279 to 5.699 THz with average absorption >92% and Full Width at Half Maxima (FWHM) of 4.6131 THz. It shows incident angle stability up to θ=20° for A≥90% and up to θ=45° for A≥80%. The proposed absorber’s peak absorption can be tuned from 3% to 94% by changing V O2 conductivity dependent on temperature. As a sensor, it has high sensitivity of 697.7 GHz/RIU for RI sensing, 586.096 GHz/RIU for adrenal gland cell cancer detection and around 650.0 GHz/RIU for urine concentration detection.

Ensuring grid resilience: Voltage stability analysis and contingency ranking in electric power systems

Modern-day power systems are highly stressed and operate close to the stability limit. The bus voltage variation in power systems generally infringes on the researcher's mind about voltage stability. The main focus of this manuscript is the voltage stability problem and voltage security assessment rather than the angle stability problem. Voltage security can be determined by running a full-load AC load flow with contingency analysis. In real-time analysis, running thousands of contingencies in online mode is quite a cumbersome task, so here in this manuscript, we have proposed a functional link-based ANN for voltage security assessment and then predicted the weakest voltage control area by the entropy concept along with the placement of FACTS devices according to the voltage control area weakness factor and contingencies ranking. The novel technique is then tested with IEEE-14 Bus and IEEE-30 Bus systems with voltage stability performance indicators.

Vanadium dioxide-assisted switching of a half-wave and quarter-wave plate to a dual-band absorber for the terahertz wave

In this study, we present a broadband, multi-functional, and switchable metamaterial for terahertz (THz) waves. The metamaterial design achieves high polarization conversion efficiency and can seamlessly transition between a polarization converter (PC) and a dual-band absorber through the phase transition behavior of vanadium dioxide (VO2). Our design facilitates linear to-cross (Half-wave plate) and linear to-circular (Quarter-wave plate) polarization conversion across a bandwidth extending from 0.58 THz to 0.88 THz, and 0.35 THz to 0.50 THz respectively. Near-perfect absorption at 0.35 THz and 0.99 THz was observed when VO2 changed its phase from an insulator to a conductor. These broadband features are realized through a straightforward metamaterial design incorporating only a reflector, a dielectric spacer, and an antenna (meta-atom resonator). Our designed structure demonstrates impressive angular stability for incident angles ranging from 0° to 45°. The proposed switchable metamaterial holds promise for advancing the development of tunable polarization rotating devices and on/off switching LPC devices, offering broad applications in THz detection, sensing, and communications.

A New Spectral Index for Monitoring Leaf Area Index of Winter Oilseed Rape (Brassica napus L.) under Different Coverage Methods and Nitrogen Treatments.

The leaf area index (LAI) is a crucial physiological indicator of crop growth. This paper introduces a new spectral index to overcome angle effects in estimating the LAI of crops. This study quantitatively analyzes the relationship between LAI and multi-angle hyperspectral reflectance from the canopy of winter oilseed rape (Brassica napus L.) at various growth stages, nitrogen application levels and coverage methods. The angular stability of 16 traditional vegetation indices (VIs) for monitoring the LAI was tested under nine view zenith angles (VZAs). These multi-angle VIs were input into machine learning models including support vector machine (SVM), eXtreme gradient boosting (XGBoost), and Random Forest (RF) to determine the optimal monitoring strategy. The results indicated that the back-scattering direction outperformed the vertical and forward-scattering direction in terms of monitoring the LAI. In the solar principal plane (SPP), EVI-1 and REP showed angle stability and high accuracy in monitoring the LAI. Nevertheless, this relationship was influenced by experimental conditions and growth stages. Compared with traditional VIs, the observation perspective insensitivity vegetation index (OPIVI) had the highest correlation with the LAI (r = 0.77-0.85). The linear regression model based on single-angle OPIVI was most accurate at -15° (R2 = 0.71). The LAI monitoring achieved using a multi-angle OPIVI-RF model had the higher accuracy, with an R2 of 0.77 and with a root mean square error (RMSE) of 0.38 cm2·cm-2. This study provides valuable insights for selecting VIs that overcome the angle effect in future drone and satellite applications.

Simulation study on four-wheeled mobile robot mechanisms using various performance criteria

In this paper, the performance criteria for various four-wheeled mobile robots that are crucial for assessing a robot’s fitness for mobility to successfully complete missions are introduced. The seven proposed performance indices, the root mean squared acceleration (RMSA), posture variance index (PVI), static stability margin (SSM), force angle stability margin (FASM), energy stability margin (ESM), friction requirement (μr), and velocity constraint violation (VCV), address the fluctuation, rollover, and slippage problems in four-wheeled mobile robots. The simulations considered a square bump-shaped obstacle, and the dimensions of the robot were based on nine simulation cases in a 3D environment. Additionally, a methodology for evaluating these seven criteria is outlined. To streamline the simulation process, Taguchi’s catalog of orthogonal arrays (OAs) was used for the experimental design, specifically L9 OA with four factors and three levels was used. Analysis of means (ANOM) was applied to assess the influence of each design factor on the seven criteria, leveraging the OA orthogonality. Finally, the sensitivity analysis and potential for evaluating general mobile robots in the future are discussed.

Effect of temperature and pre-stretch on the dynamic performance of dielectric elastomer minimum energy structure

Dielectric Elastomer Minimum Energy Structures (DEMES) have the ability of actively adjusting their shape to accommodate complex scenarios, understanding the actuation mechanism of DEMES is essential for their effective design and control, which has rendered them a focus of research in the field of soft robotics. The actuation ability of DEMES is usually influenced by external conditions, among which the electromechanical properties of DE materials are highly sensitive to temperature changes, and the pre-stretch ratio of DE materials has a significant impact on the dynamic performance of DEMES. Therefore, it is necessary to study the effects of temperature and pre-stretch ratio on the nonlinear dynamic behavior of DEMES. In this paper, in response to the lack of research on the influence of DE pre-stretch ratio on the actuation characteristics of DEMES, this paper proposes a systematic modeling and analysis framework that comprehensively considers pre-stretch factors, temperature factors, and viscoelastic factors, and establishes the motion control equation of DEMES affected by the coupling effect of DE pre-stretch ratio and temperature. The proposed analytical framework is used to analyze the evolution of the electromechanical response of DEMES under voltage excitation under the coupling of DE pre-stretch ratio and temperature. The results indicate that the bending angle, inelastic deformation, resonant frequency, and dynamic stability of DEMES can be jointly adjusted by the DE pre-stretch ratio and ambient temperature. A low pre-stretch ratio of DE can lead to dynamic instability of DEMES, while appropriate temperature conditions and higher pre-stretch ratios can significantly improve the actuation ability of DEMES. This can provide theoretical guidance for the design and deformation control of DEMES.

Mechanical evaluation of a threaded interference interlocking mechanism for angle-stable intramedullary nailing.

To assess the fatigue and load-to-failure mechanical characteristics of an intramedullary nail with a threaded interference design (TID) in comparison to a commercially available veterinary angle-stable nail with a Morse taper bolt design (I-Loc) of an equivalent size. 10 single interlocking screw/bolt constructs of TID and I-Loc implants were assembled using steel pipe segments and placed through 50,000 cycles of simulated, physiologic axial or torsional loading. Entry torque, postfatigue extraction torque, and 10th, 25,000th, and 50,000th cycle torsional toggle were assessed. Each construct was then loaded to failure in the same respective direction as fatigue testing. Four complete constructs of each design were then assessed using a synthetic bone analog with a 50-mm central defect via nondestructive torsional and axial loading followed by axial load to failure. All constructs were angle stable at all time points and withstood fatigue loading. Median insertional torque, extraction torque-to-insertion torque ratio, and torsional yield load were 33%, 33%, and 72.5% lower, respectively, for the TID interlocking screws. No differences in torsional peak load, torsional stiffness, axial yield load, axial stiffness, or axial peak load were identified. No differences in complete construct angle stability, torsional stiffness, axial peak load, axial stiffness, or axial yield load were identified. The TID had an inferior torsional yield load when compared to I-Loc implants but generated angle stability and sustained simulated physiologic fatigue loading. The TID may be a suitable mechanism for generating angle stability in interlocking nails.

Grid impact analysis on wind power plant interconnection in strengthening electricity systems

The Timor system is one of the large systems in the East Nusa Tenggara region. Based on the general plan for electricity supply for 2021-2030, there is a plan to interconnect a 2x11 MW wind power plant. The addition of wind power plants will pose a considerable threat to the system due to the intermittency nature of renewable energy plants. Therefore, a comprehensive grid impact study is needed to convince network managers that adding wind farms will not cause disruptions to the system either locally or in general and is expected to strengthen the electricity system. The power flow simulation results, installing a 2x11 MW wind farm on the Timor system can improve voltage quality and reduce losses on both 70 and 150 kV systems. For transient stability, the frequency value on the Timor system still meets the grid code requirements. In addition, the simulation results of the intermittency impact of the wind power plant output show that the Timor system is still in a stable condition. The stability of the rotor angle of the existing power plant when the transient stability simulation is carried out shows that it is still in a balanced condition.

Two-Stage Transient Control for VSG Considering Fault Current Limitation and Transient Angle Stability

Two-Stage Transient Control for VSG Considering Fault Current Limitation and Transient Angle Stability

Intelligent Power System Stability Assessment and Dominant Instability Mode Identification Using Integrated Active Deep Learning.

Simulation analysis is critical for identifying possible hazards and ensuring secure operation of power systems. In practice, large-disturbance rotor angle stability and voltage stability are two frequently intertwined stability problems. Accurately identifying the dominant instability mode (DIM) between them is important for directing power system emergency control action formulation. However, DIM identification has always relied on human expertise. This article proposes an intelligent DIM identification framework that can discriminate among stable status, rotor angle instability, and voltage instability based on active deep learning (ADL). To reduce human expert efforts required to label the DIM dataset when building DL models, a two-stage batch-mode integrated ADL query strategy (preselection and clustering) is designed for the framework. It samples only the most helpful samples to label in each iteration and considers both information contents and diversity in them to improve query efficiency, significantly reducing the required number of labeled samples. Case studies conducted on a benchmark power system (China Electric Power Research Institute (CEPRI) 36-bus system) and a practical large-area power system (Northeast China Power System) reveal that the proposed approach outperforms conventional methods in terms of accuracy, label efficiency, scalability, and adaptability to operational variability.

Ultra Miniaturization and Transparency Frequency Selective Surface for Dual Band ISM Shielding

This article presents an ultraminiaturized frequency selective surface (FSS) for shielding 2.4 GHz and 5.8 GHz (ISM) signals. The unit cell size is 0.056λ × 0.056λ (λ is the free space wavelength at the first resonant frequency). It has smaller cell size and good transparency compared to previous ISM band studies, and transparency at 54%. The proposed FSS design consists of a wall structure and a compound square loop with 2.4 GHz and 5.8 GHz resonance frequencies for ISM band coverage. This FSS structure was fabricated on float glass with a dielectric constant of 8 by a photolithographic process. The fabricated FSS structure has excellent angular stability and polarization stability, which is further verified by experimentation. An easy optimization method is proposed to tune the independent resonant frequencies by optimizing the geometries individually. This FSS is interpreted by filtering through surface induced currents and equivalent circuit models. A prototype of the proposed FSS is fabricated and measured. The simulation results are in good agreement with the measured results. The proposed FSS has polarization insensitivity and 80∘ angle stability and is suitable for solving the EMI problem in ISM band.

Pattern reconfigurable antenna with specified main lobe deflection and stable bandwidth by using bistable composite laminates

Pattern reconfiguration of antennas has become a very important measure to improve the signal gain and working bandwidth by manipulating beam direction. Developing rational methods to find the reconfigurable structure is a key problem. In this paper, a collaborative optimization method is proposed to comprehensively consider both the geometric parameters of the bistable substrate and the size of the radiation patch. This method enables the design of a pattern reconfigurable antenna with specified main lobe deflection and stable bandwidth. Specifically, by using a two-step process, the log-periodic dipole antenna (LPDA) is conformally mapped from the planar substrate to the bistable substrate. Further investigation reveals that the main lobe deflection angle and bandwidth stability are influenced by the geometric parameters of the bistable substrate and the size of radiation dipoles, respectively. Thus, these parameters are selected as design variables for solving the proposed collaborative optimization model. The transformation between two stable configurations enables the proposed LPDA to deflect the main lobe of the H-plane pattern by 30° while maintaining consistency in the E-plane patterns. Importantly, the resonant frequencies remain unaffected and the bandwidth does not decrease during the pattern reconfiguration. Notably, the pattern reconfigurable mechanism is rooted in that the transformation between the two stable configurations alters the number and position of the dipoles in the radiation region and their current path, thereby changing the radiation direction of electromagnetic waves. The proposed collaborative optimization method has a potential application for other types of antennas and offers opportunities for various applications in the field of wireless communication.

3D-printed multi-material pyramids for broadband electromagnetic wave absorption

Designing and manufacturing broadband electromagnetic wave-absorbing materials represents one of the significant approaches to address electromagnetic pollution issues. This study utilizes three different PLA-based composite absorbing materials to prepare multilayer pyramid structures employing 3D printing technology. Results indicate that with material composition Z1-GT6-N8, material layer height (h) of 6 mm, and pyramid base length (L) of 36 mm, the fabricated structure achieves a minimum reflection loss of −24.19 dB with an effective absorption bandwidth of 14.21 GHz, demonstrating outstanding absorption performance. It is noteworthy that regardless of the incident angle increasing from 0° to 50°, the equivalent absorption bandwidth (EAB) for both transverse electric (TE) and transverse magnetic (TM) polarizations remains greater than 10 GHz, indicating excellent angle stability. The broadband and efficient electromagnetic wave (EMW) absorption characteristics exhibited by this absorber can be attributed to its outstanding impedance matching performance and the integration of multiscale loss mechanisms.

Research on Power Angle Characteristics of One-Machine Infinite-Bus Power Systems of Mixed Gauss and Poisson Stochastic Excitation

Background: A high percentage of renewable energy and a high percentage of power electronic devices are connected to the power system, which leads to the diversification and complexity of stochastic excitation, and the traditional single-excitation stochastic model is no longer applicable. Objective: The study aimed to solve the problem that the high proportion of renewable energy and the high proportion of power electronic equipment are connected to the power system, which leads to the diversification and complexity of stochastic excitation and makes the traditional stochastic model of single excitation no longer applicable. Methods: Firstly, stochastic differential equations for power systems have been modelled with mixed Gaussian white noise and Poisson white noise excitation. Secondly, the Milstein-Euler predictor-corrector method has been developed to solve the stochastic differential equation model of the power system. Finally, the influence of Gauss white noise and Poisson white noise on the power system stability under different excitation intensities has been analyzed. The rationality and correctness of the model have been verified by the simulation of a one-machine infinitebus (OMIB) system. Results: The stochastic differential equation model of a power system with Gauss white noise and Poisson white noise excitation has been established and its angle stability has been analyzed. Increasing the Gaussian white noise and Poisson white noise excitation intensity can lead to an increase in the fluctuation of the power angle curve, as well as an increase in the standard deviation and expected value of the power angle mean curve, which may decrease the stability of the power system. Conclusion: This study provides a reference for stochastic power systems modeling and efficient simulation, and has important application value for power system stability assessment and safety evaluation as well as related patent applications.

Triple band terahertz absorption based fractal ring shaped ultrathin mustard oil adulteration sensor

A tri-band terahertz (THz) absorber for sensing the adulteration percentage in mustard oil is proposed in this paper. It consists of a gold based metallic resonating geometry and metallic ground plane on the top and bottom layers of the dielectric material respectively. It has three absorption peaks with peak absorptivity of 99.74%, 99.96% & 99.94% and Full Width at Half Maxima (FWHM) of 0.57, 0.862 & 1.112 THz at 4.6296, 8.295 & 12.6309 THz respectively. The proposed absorber’s unit cell volume has an overall volume of 10 μm×10μm×1.61μm (0.15432λL×0.15432λL×0.024846λL where λL is wavelength at lowest operating frequency i.e. 4.6296 THz). It has polarization insensitive absorption performance under normal incidence and incident angle (θ∘) stability up to 50° for A≥90%. The proposed structure is simulated through by using CST & HFSS. The results are validated by developing an equivalent circuit model (ECM). The results of CST, HFSS and ECM are found to be in good agreement. A sensitivity varying from ∼0.23 THz/RIU to ∼1.62 THz/RIU is achieved for Refractive Index (RI) sensing case, whereas a high sensitivity in the range of ∼0.4 THz/RIU to ∼2 THz/RIU is achieved for mustard oil adulteration sensing case by mounting the absorber’s top surface with a polyimide based container filled with an analyte (either refractive index material or mustard oil). During the validation, a maximum ∼0.16% error in mustard oil adulteration estimation is achieved. The proposed sensor has advantages of simple & ultra compact dimensions, high sensitivity and minimal error in impurity concentration estimation with respect to other absorber-based sensors.

P‐186: A Novel Liquid Crystal Material for Shortening the UV2 Process of Polymer‐stabilized Vertically Aligned Liquid Crystal Displays

The production of polymer‐stabilized vertically aligned (PSVA) displays requires two UV processes for liquid crystal (LC) alignments. UV1 is usually short for pre‐tilt angle formation, while UV2 takes approximately 90 minutes to consume the remaining reactive monomers (RMs). Therefore, shortening the UV2 process can significantly reduce the power consumption and maintenance costs of UV lamps during LCD fabrication. Herein, we report a novel LC material consisting of fast‐reaction RMs. With the addition of fast‐reaction RMs, the UV2 process can be dramatically decreased from 90 min to 20 min. Furthermore, the reduction of the UV2 process shows competitive optical properties, reliabilities and pre‐tilt angle stabilities compared with the reference. Overall, new fast‐reaction LC materials are beneficial to energy saving and the cost competitiveness of the company.

Small‐signal rotor angle stability of multi‐virtual synchronous machine (n‐VISMA) microgrid

AbstractAutonomous microgrid is known to lack appropriate inertia and damping for grid stabilization. Due to this, virtual synchronous machine (VISMA) has been introduced to provide necessary ancillary services through control of power converters. In a multi‐VISMA (n‐VISMA) microgrid, relative rotor angle stability of the power system is dependent on the active power balance after small perturbation. Thus, the use of relevant analytical models are essential issues for microgrid stability analysis. This paper presents a comprehensive small‐signal stability analysis to study inherent electromechanical oscillations in the virtual rotors. The subsystems of the microgrid consisting of VISMA, network, load and the outer power control were all modelled in Synchronous Reference Frame. The small‐signal model (SSM) was tested on IEEE‐9 bus system with VISMA replacing electromechanical synchronous machines on the network. To validate the developed numerical analytics, dynamic responses of the SSM are compared with those of the non‐linear (NL) system dynamics and the results reveal that the developed linearized SSM is sufficient to accurately characterize behaviour of the VISMA microgrid when operated in autonomous mode. Eigenvalues analysis and parameter sensitivities of the critical modes were investigated. Oscillatory participations of the VISMAs and steady state stability limit of the microgrid have also been investigated.

A Stabilization Control Strategy for Wind Energy Storage Microgrid Based on Improved Virtual Synchronous Generator

In high-penetration renewable-energy grid systems, conventional virtual synchronous generator (VSG) control faces a number of challenges, especially the difficulty of maintaining synchronization during grid voltage drops. This difficulty may lead to current overloads and equipment disconnections, and it has an impact on the security and reliability of the system, as well as limiting the dynamic reactive power support capability of the system. To solve this problem, in this study, a wind–solar hybrid power generation system is designed with a battery energy storage device connected on the DC side, and proposes a low voltage ride-through (LVRT) control strategy for the grid-connected inverter based on an improved VSG. The control strategy employs an integrated current limiting technique combining virtual impedance and vector current limiting to ensure that the VSG exhibits good dynamic power support characteristics during symmetrical faults by adjusting the setpoint value of reactive power. At the same time, it maintains the synchronization and power angle stability of the VSG itself to achieve the goal of LVRT. Simulation results show that the proposed control strategy can effectively suppress the renewable power fluctuations (about 30% reduction in fluctuations compared to the conventional strategy) and ensure the safe and reliable operation of the renewable energy sources and VSGs during grid-side faults. In addition, it provides a given reactive power support and stable grid voltage control (voltage dips reduced by about 20%), which significantly enhances the LVRT capability of the hybrid wind–solar-storage generation system.