Direct Control Research Articles

Alpha Traveling Waves during Working Memory: Disentangling Bottom-up Gating and Top-down Gain Control.

While previous works established the inhibitory role of alpha oscillations during working memory maintenance, it remains an open question whether such an inhibitory control is a top-down process. Here, we attempted to disentangle this issue by considering the spatio-temporal component of waves in the alpha band, i.e., alpha traveling waves. We reanalyzed two pre-existing and open-access EEG datasets (N = 180, 90 males, 80 females, 10 unknown) where participants performed lateralized, visual delayed match-to-sample working memory tasks. In the first dataset, the distractor load was manipulated (2, 4, or 6), whereas in the second dataset, the memory span varied between 1, 3, and 6 items. We focused on the propagation of alpha waves on the anterior-posterior axis during the retention period. Our results reveal an increase in alpha-band forward waves as the distractor load increased, but also an increase in forward waves and a decrease in backward waves as the memory set size increased. Our results also showed a lateralization effect: alpha forward waves exhibited a more pronounced increase in the hemisphere contralateral to the distractors, whereas the reduction in backward waves was stronger in the hemisphere contralateral to the targets. In short, the forward waves were regulated by distractors, whereas targets inversely modulated backward waves. Such a dissociation of goal-related and goal-irrelevant physiological signals suggests the co-existence of bottom-up and top-down inhibitory processes: alpha forward waves might convey a gating effect driven by distractor load, while backward waves may represent direct top-down gain control of downstream visual areas.Significance Statement When exploring the functional role of alpha band neural oscillations during working memory, mostly amplitude modulations have been considered so far, with relatively limited exploration of spatial-temporal dynamics of this rather global brain oscillatory signature. The present study seeks to address this gap by examining the directionality of alpha wave propagation during working memory retention. Our findings offer novel insights into the well-established inhibitory role of alpha waves, demonstrating that this function is manifested differently according to their propagation directions: forward waves seem to facilitate bottom-up gating, while backward waves might mediate top-down gain control.

Selective ion transport through hydrated micropores in polymer membranes.

Ion-conducting polymer membranes are essential in manyseparation processes and electrochemical devices, including electrodialysis1, redox flow batteries2, fuel cells3 and electrolysers4,5. Controlling ion transport and selectivity in these membranes largely hinges on the manipulation of pore size. Although membrane pore structures can be designed in the dry state6, they are redefined upon hydration owing to swelling in electrolyte solutions. Strategies to control pore hydration and a deeper understanding of pore structure evolution are vital for accurate pore size tuning. Here we report polymer membranes containing pendant groups of varying hydrophobicity, strategically positioned near charged groups to regulate theirhydration capacity and pore swelling. Modulation of thehydrated micropore size (less thantwo nanometres) enables direct control over water and ion transport across broad length scales, as quantified by spectroscopic and computational methods. Ion selectivity improves in hydration-restrained pores created by more hydrophobic pendant groups. These highly interconnected ion transport channels, with tuned pore gate sizes, show higher ionic conductivity and orders-of-magnitude lower permeation rates of redox-active species compared with conventional membranes, enabling stable cycling of energy-dense aqueous organic redox flow batteries. This pore size tailoringapproach provides a promising avenue to membranes with precisely controlled ionic and molecular transportfunctions.

Robust direct power control of a three-phase PWM rectifier

This paper presents two robust controls techniques: current control in the dq reference frame and direct power control (DPC) applied to a three-phase PWM rectifier to achieve efficient dc voltage regulation, unit power factor control and harmonic distortion rate reduction. Simulations were performed using Matlab/Simulink software. According to these results, the DPC direct power control seems to be more efficient than the current control in the dq reference frame, which has a lower harmonic distortion rate, and the DC voltage follows its new reference for the two developed controls. However, the response time, overshoot and oscillations of the controlled quantities, as well as the exponential convergence of the errors for the transient regime and the setpoint change, are different. It can be seen that the best values of the latter are those obtained by applying the DPC direct power control, which is considered to be the best performing and most efficient control compared to the other control.

Direct Fractional-Order Adaptive Control Design for Cascaded Doubly-Fed Induction Generator (CDFIG) in a Wind Energy System

This paper is devoted to a fractional-order model reference adaptive control (FO-MRAC) synthesis for the independent control of the active and reactive power flows in the cascaded doubly fed induction generator (CDFIG) in wind energy systems. The proposed adaptive control law combines a second-order-like fractional reference model and a direct MIT adaptation law using a fractional order integrator. This generator configuration can be an interesting alternative to standard double-output wound rotor induction generators. It is made up of two identical wound rotor induction motors such that their rotors are mechanically and electrically coupled. Using two cascaded induction machines permits the elimination of the brushes and copper rings in the traditional doubly-fed induction generator DFIG, which makes the system more resistant and reduces maintenance costs. In the first step, we propose a classical PI controller synthesis to regulate the active and reactive power produced by CDFIG. Then, the FO-MRAC design is realized and a comparative study based on numerical simulations is performed between the classical regulators PI, MRAC, and FO- MRAC, to demonstrate the superiority of the proposed fractional-order adaptive controller relative to conventional integer order PI and MRAC controllers. These results illustrate the reliability and efficiency of the proposed adaptive control scheme.

The Relationships Among Proprioception, Balance, and Cognitive Perception of Body Awareness in College Students: A Pilot Study

Introduction: This pilot study examined the relationships among lower extremity proprioception, balance ability, and perception of body awareness. Researchers also evaluated the influence of sex, sport participation, leg dominance, and previous ankle injury. Methods: Eighteen participants (F = 11, M = 7) completed the initial testing, with eight (F = 4, M = 4) repeating the mLEPT one week later. Participant characteristics and mBARQ data were collected using an online survey. Measures included proprioception errors on the mLEPT, utilizing distances of 12 and 22 cm, and the Biodex Balance SystemÔ Limits of Stability Test. Results: For the mLEPT, good reliability was noted for the dominant leg 22 cm distance between trials 1 and 2 for all 18 participants (ICC = 0.83). Moderate test-retest reliability was observed when comparing the averages of day 1 to day 2 for the dominant leg 22 cm distance (ICC = 0.53), and for the overall error when collapsing across conditions (ICC = 0.63). Moderate reliability was also observed for the mBARQ (α = 0.76). Strong inverse relationships between proprioception error and directional control scores were observed, indicating an association between dynamic balance and lower extremity proprioception (r = -0.55-0.54, p = 0.02). Sex, sports participation, leg dominance, and previous ankle injury also influenced proprioception performance. Females displayed better lower extremity proprioception and balance control than males. In addition, participants without previous ankle injury scored higher on the mBARQ, and had better directional control and time to completion, indicating that those without ankle injury had a higher perception of body awareness and better dynamic balance. Conclusions: Both the mLEPT and mBARQ appear to have moderate reliability. mLEPT performance was strongly associated with dynamic balance measures. In addition, lower mBARQ scale scores in those with previous ankle injury were strongly associated with poorer proprioception. While preliminary findings are promising, a larger follow-up study is needed to determine if the mLEPT and mBARQ are potential quick and inexpensive tools to monitor changes in proprioception during rehabilitation post-injury.

Terminal Sliding Mode Control of Microgrid Inverter Systems

ABSTRACTTo enhance the power quality of microgrid inverters and reduce the influence of changes in inductance parameters and external disturbances on the direct power control of the inverter system, a terminal sliding mode control strategy with a variable exponential power reaching law has been proposed. The designed new reaching law comprises a variable exponential term and an enhanced power term. The variable exponential term contains an arctangent function, and the power term coefficient is replaced by a function about the sliding mode. Therefore, the convergence rate can be adaptively adjusted based on different stages of the system, ensuring a faster rate of convergence throughout the process of approaching the sliding mode surface. To weaken the effects of changes in inductance parameters, a power disturbance observer is designed to estimate the internal disturbances induced by the filtered inductance in the system. Subsequently, a sliding mode control law containing disturbance observations is derived. Moreover, a variable exponential terminal sliding surface is designed to adjust the convergence rate of system errors on the sliding surface in stages, thereby enhancing the control performance of the system. The simulation results show that the new reaching law has faster convergence rate and better dynamic performance. The convergence speed of the system error can be accelerated by the designed variable exponential terminal sliding surface. The sliding mode control strategy with the variable exponential power reaching law is applicable to the power control system of three‐phase inverters in microgrids, thereby significantly enhancing the dynamic performance and robustness of the system.

Analisis Efisiensi Biaya Tenaga Kerja Langsung pada PT. Davincy Airindo

This study was conducted with the aim to determine the efficiency of direct labor costs carried out by the company PT Davincy Airindo. In this study using literature review and observation, namely by conducting research in the field through direct interviews and data collection, related documents from the company through internet media. The data obtained is analyzed using the quantitative descriptive analysis method, namely how to compare labor costs that actually occur (actual). The results of the analysis will show whether direct labor costs are used efficiently to produce a product. This shows that Direct Labor Cost Control is in the efficient and stable category (in control).

Steady-State Visual Evoked Potential-Based Brain–Computer Interface System for Enhanced Human Activity Monitoring and Assessment

Advances in brain–computer interfaces (BCIs) have enabled direct and functional connections between human brains and computing systems. Recent developments in artificial intelligence have also significantly improved the ability to detect brain activity patterns. In particular, using steady-state visual evoked potentials (SSVEPs) in BCIs has enabled noticeable advances in human activity monitoring and identification. However, the lack of publicly available electroencephalogram (EEG) datasets has limited the development of SSVEP-based BCI systems (SSVEP-BCIs) for human activity monitoring and assisted living. This study aims to provide an open-access multicategory EEG dataset created under the SSVEP-BCI paradigm, with participants performing forward, backward, left, and right movements to simulate directional control commands in a virtual environment developed in Unity. The purpose of these actions is to explore how the brain responds to visual stimuli of control commands. An SSVEP-BCI system is proposed to enable hands-free control of a virtual target in the virtual environment allowing participants to maneuver the virtual target using only their brain activity. This work demonstrates the feasibility of using SSVEP-BCIs in human activity monitoring and assessment. The preliminary experiment results indicate the effectiveness of the developed system with high accuracy, successfully classifying 89.88% of brainwave activity.

Individual differences in acceptance of direct load control

Consumer acceptance of direct load control is becoming increasingly important as energy systems transition towards greater reliance on intermittent renewable energy sources. The objective of this paper is to better understand the attitudinal and socio-economic determinants of direct load control acceptance. To do so, we collect survey data from participants in 31 European countries (N = 5,970). Regression analyses testing a comprehensive model of attitudinal and socio-economic determinants of direct load control acceptance reveal that attitudes and beliefs specific to direct load control acceptance (social and personal norms, anticipated emotions, and outcome efficacy beliefs) predict acceptance, whereas more general attitudinal variables and socio-economic characteristics play no or only a secondary role. These findings substantially improve our understanding of direct load control acceptance. While European policy documents recognize the importance of individual attitudes for the success of demand response programs, reference to specific factors or processes is often missing due to lack of evidence. The present research helps fill this gap, and can inform the design of novel soft policy measures – highlighting the usefulness of facilitating positive peer influence, of reinforcing perceptions that engaging in demand response is effective, is the responsible thing to do, and also something to be proud of

Synchronous DTC for torque sub-harmonic reduction in low switching frequency induction motor drives

A direct torque control (DTC) algorithm with synchronous modulation for high-power induction motors is presented in this paper. While maintaining the dynamic response and robustness of a PI-based DTC operating in the stationary reference frame, the proposed scheme is able to keep an integer PWM modulation ratio, adjusting the stator flux angle and the switching period at each control step so that the synchronicity condition is always satisfied. In this way, it is possible to achieve an improvement of the very low-frequency harmonic spectrum of the torque, in particular by reducing torque sub-harmonics. These represent one of the main problems associated with low-frequency modulation typical of high-power drives and their reduction allows to avoid drawbacks such as resonance and mechanical stresses. The performance of the proposed algorithm is evaluated with experimental tests on a small-scale test bench.

Enhancing Grid Stability in Distributed Power Systems: A Grid Voltage-modulated Direct Power Control Approach With Super-twisting Sliding Mode Control

Enhancing Grid Stability in Distributed Power Systems: A Grid Voltage-modulated Direct Power Control Approach With Super-twisting Sliding Mode Control

Rare earth doped magnetoelectric composites for enhanced electromagnetic wave absorption

Magnetoelectric electromagnetic wave absorption materials (EWAMs) with multiple loss mechanisms have shown remarkable results in solving electromagnetic (EM) interference and radar stealth. However, due to the Snoek limit, the magnetic properties are affected to some extent. Hence, based on low-cost two-dimensional graphite nanosheets and magnetic ferrite, a rare-earth doping strategy is innovatively proposed, aiming to develop a high-efficiency EWAM. Specifically, taking advantage of the significant differences in magnetic moments and dimensions between Gd and Fe ion, the modified ferrite owns unusual magnetic properties and dielectric capacity. Further, direct control of the EM parameters is achieved by finely tuning the component ratio, which in turn optimizes the response characteristics of EM wave absorption. Experimental results show a maximum reflection loss of −64.04 dB and a wide effective absorption bandwidth covering 4.88 GHz, corresponding to the absorption efficiency of −42.7 dB/mm and 3.25 GHz/mm, respectively. The outstanding performance is related to the synergistic effect of multiple loss management and impedance matching, and further confirmed by the radar cross section (RCS) reduction of 29.15 dBsm. Thus, the novel way opens a new horizon for the next magnetic-based EWAMs.

Anisotropic programmable metasurfaces with individually controllable 2-bit elements

Programmable metasurfaces capable of manipulating electromagnetic (EM) waves in real time provide new opportunities for various exciting applications. However, most previous programmable metasurfaces only work in a single polarization mode and their elements are controlled in a whole or one-dimensional way, which limits functionality and adaptability to complex environments. Here, an anisotropic programmable metasurface with individually controllable elements is proposed to realize real-time and independent dual-polarized EM control in the two-dimension direction. The anisotropic metasurface element is designed using the ingenious cross-over resonant structure integrated with two sets of varactors to achieve 2-bit phase modulation in the respective polarization direction. As a demonstration, an anisotropic programmable metasurface prototype with 21×20 such elements is simulated, fabricated, and measured. Real-time beam scanning and vortex wave generation are verified respectively under two different polarized wave incidences, which indicates that the realized anisotropic programmable metasurface can achieve totally distinct functionalities for two orthogonal polarizations. Our work could push programmable metasurfaces one step closer towards more advanced information devices and complicated applications in communication and imaging.

Biportal Endoscopic Transforaminal Lumbar Interbody Fusion: The Double-Cage Technique

Biportal endoscopic transforaminal lumbar interbody fusion (BETLIF) is a novel spinal fusion procedure using the unilateral biportal endoscopic technique. The hydrostatic pressure of saline irrigation suppresses bleeding, enabling us to perform delicate surgery in a crystal-clear and magnified surgical field with almost no bleeding. Adequate neural decompression, disc space preparation, and bony endplate preservation can be achieved safely. The sturdy endplate reduces the incidence of cage subsidence and provides good initial stability. We use 2 interbody fusion cages and a large amount of bone graft to promote fusion. Reduction of the spondylolisthesis can also be achieved using a modern pedicle screw system. This article presents a step-by-step demonstration of the BETLIF technique in a 68-year-old patient with degenerative scoliosis and spondylolisthesis at L4-5, including his clinical presentation and treatment results. BETLIF is a safe, effective, and revolutionary minimally invasive solution for spinal fusion. Its advantages include a magnificent surgical field, direct decompression, minimum blood loss, radical discectomy, meticulous endplate preparation, cage insertion under direct visual control, and excellent treatment results with a high fusion rate and few complications.

Plasmonic antennas based on rectangular graphene nanoribbons with controlled polarization of terahertz and infrared radiation

Background. To develop new terahertz wireless communication systems with high throughput and transmission speeds, such as 6G and above, effective control of the polarization direction of emitted terahertz waves is necessary, but most methods are technologically complex and expensive. The implementation of terahertz antennas and devices based on 2D materials such as graphene solves the problem associated with developing effective control. Aim. Study of the possibility of controlling the polarization of terahertz and IR radiation of plasmonic antennas based on rectangular graphene nanoribbons by changing the chemical potential (application of an external electric field). Methods. This important scientific problem related to the design of terahertz antennas can largely be solved by simulation using the electrodynamic simulation program CST MWS 2023. Results. Plasmon terahertz antennas based on rectangular graphene nanoribbons were chosen as the object of analysis and the possibility of emitting waves of two orthogonal polarizations was shown. Methods have been identified for controlling the polarization of terahertz and IR radiation from such antennas, based on the selection of operating frequencies corresponding to the resonances of the modes of surface plasmon-polaritons, and the application of metallization to the dielectric substrate. Conclusion. The ability to control the polarization of terahertz and IR radiation makes it possible to create both new elements of plasmonic antenna arrays and new communication technologies, including future 6G networks.

Shape optimization for high efficiency metasurfaces: theory and implementation

Complex non-local behavior makes designing high efficiency and multifunctional metasurfaces a significant challenge. While using libraries of meta-atoms provide a simple and fast implementation methodology, pillar to pillar interaction often imposes performance limitations. On the other extreme, inverse design based on topology optimization leverages non-local coupling to achieve high efficiency, but leads to complex and difficult to fabricate structures. In this paper, we demonstrate numerically and experimentally a shape optimization method that enables high efficiency metasurfaces while providing direct control of the structure complexity through a Fourier decomposition of the surface gradient. The proposed method provides a path towards manufacturability of inverse-designed high efficiency metasurfaces.

Evasion Maneuver and Timing Strategy for UAVs Under Direct Force Control

Given the capabilities of modern high-performance missiles, efficient evasion maneuver strategies are crucial for enhancing UAV survivability. This paper addresses the integration of evasion strategies and maneuver timing for targeted UAVs. First, a three-dimensional engagement scenario is modeled using the relative motion mechanism. Subsequently, a fundamental evasion strategy focusing on large roll maneuvers and two-phase acceleration is developed. With the initiation timing of direct force control designated as the control variable, the formulation of a constrained optimization problem to maximize miss distance is fully articulated. While preserving the high fidelity of the established switching model, the feasible timing intervals and the optimal timing are determined through numerical optimization. Finally, simulation experiments are conducted focusing on omnidirectional attacks from the upper hemisphere. The results demonstrate that by implementing specific evasion maneuvers at optimal timing, the target successfully escapes the effective range of the proximity fuse, thus confirming the feasibility of the proposed evasion maneuver and timing strategy.

Protamine administration after catheter ablation of atrial fibrillation using electroporation: a randomized controlled trial

Abstract Background Safety of protamine administration after catheter ablation of atrial fibrillation (AF) using pulse-field system has not been previously described in a prospective randomized trial. Methods Consecutive patients with paroxysmal, persistent or long-standing persistent AF undergoing catheter ablation of AF using Farapulse system were randomly assigned in 1:1 ratio for protamine administration before sheaths removal. All vascular punctions were navigated using a direct ultrasound control. Right femoral vein was used for FaraDrive (16 F) sheath and left femoral vein for ICE (11 F) and decapolar diagnostic catheter (7 F). All sheaths were removed immediately at the end of procedure with subsequent local haemostasis with figure-of-eight suture. Primary endpoint was early and late access site complications. Secondary endpoints were significant bleeding, thromboembolic events and duration of hospital stay. Results 428 consecutive patients were enlisted into the study (213 in protamine group; 215 in control group). Baseline and procedural characteristics were similar between both groups. ACT before venous sheath removal was higher in patients not receiving protamine (330.1 ± 38.6 vs. 189.3 ± 44.7 seconds, P < 0.001). There were no significant differences in both primary and secondary endpoints between both groups: groin hematoma (5 vs 5; p = NS); there were no thromboembolic complications in both groups and no significant differences of hospital stay duration. Conclusion Protamine administration after atrial fibrillation ablation using Farapulse system is not necessary when using ultrasound navigated vascular access and haemostasis with figure of eight suture.

Xenon plasma-focused ion beam milling for fabrication of high-purity, bright single-photon sources operating in the C-band

Electron beam lithography is a standard method for fabricating photonic micro and nanostructures around semiconductor quantum dots (QDs), which are crucial for efficient single and indistinguishable photon sources in quantum information processing. However, this technique is difficult for direct 3D control of the structure shape, complicating the design and enlarging the 2D footprint to suppress in-plane photon leakage while directing photons into the collecting lens aperture. Here, we present an alternative approach to employ xenon plasma-focused ion beam (Xe-PFIB) technology as a reliable method for the 3D shaping of photonic structures containing low-density self-assembled InAs/InP quantum dots emitting in the C-band range of the 3rd telecommunication window. The method is optimized to minimize the possible ion-beam-induced material degradation, which allows exploration of both non-deterministic and deterministic fabrication approaches, resulting in photonic structures naturally shaped as truncated cones. As a demonstration, we fabricate mesas using a heterogeneously integrated structure with a QD membrane atop an aluminum mirror and silicon substrate. Finite-difference time-domain simulations show that the angled sidewalls significantly increase the emission collection efficiency to approx. 0.9 for NA = 0.65. We demonstrate experimentally a high purity of pulsed single-photon emission (∼99%) and a superior extraction efficiency value reported in the C-band of η = 24 ± 4%.

On the Large-x Asymptotic of the Classical Solutions to the Non-Linear Benjamin Equation in Fractional Sobolev Spaces

In this work, we study the large-x asymptotic of classical solutions to the non-linear Benjamin equation modeling propagation of small amplitude internal waves in a two fluid system. In our analysis, we extend known Hs-well-posedness results to the case of the variable-weight Sobolev spaces. The spaces provide a direct control over the asymptotics of classical solutions and their weak derivatives, and permit us to compute the bulk large-x asymptotic of classical solutions explicitly in terms of input data. The asymptotic formula provides a precise description of the qualitative behaviour of classical solutions in weighted spaces and yields a number of weighted persistence and continuation results automatically.