Static Control Research Articles

Uniform stabilization in Besov spaces with arbitrary decay rates of the magnetohydrodynamic system by finite-dimensional interior localized static feedback controllers

We consider the d-dimensional MagnetoHydroDynamics (MHD) system defined on a sufficiently smooth bounded domain, d=2,3 with homogeneous boundary conditions, and subject to external sources assumed to cause instability. The initial conditions for both fluid and magnetic equations are taken of low regularity. We then seek to uniformly stabilize such MHD system in the vicinity of an unstable equilibrium pair, in the critical setting of correspondingly low regularity spaces, by means of explicitly constructed, static, feedback controls, which are localized on an arbitrarily small interior subdomain. In additional, they will be minimal in number. The resulting space of well-posedness and stabilization is a suitable product space B~q,p2-2/p(Ω)×B~q,p2-2/p(Ω),1<p<2q2q-1,q>d, d,$$\\end{document}]]> of tight Besov spaces for the fluid velocity component and the magnetic field component (each “close” to L3(Ω) for d=3). Showing maximal Lp-regularity up to T=∞ for the feedback stabilized linear system is critical for the analysis of well-posedness and stabilization of the feedback nonlinear problem.

Design of a Suspension Controller with Human Body Model for Ride Comfort Improvement and Motion Sickness Mitigation

This paper presents a method to design a suspension controller with a human body model for ride comfort improvement and motion sickness mitigation. Generally, it has been known that the vertical acceleration of a sprung mass should be reduced for ride comfort. On the other hand, recent studies have shown that, combined, the vertical acceleration and pitch rate of a sprung mass are key factors that cause motion sickness. However, those variables have been considered with respect to the center of gravity of a sprung mass. For motion sickness mitigation, the vertical acceleration of a human head should be also considered. In this paper, the vertical accelerations and pitch rates of a sprung mass and a human head are controlled by a suspension controller for ride comfort improvement and motion sickness mitigation. For the controller design, a half-car and human body models are adopted. With those models, several types of static output feedback suspension controller are designed with linear quadratic optimal control methodology. To reduce the pitch rate of the sprung mass and the vertical acceleration of the head, a filtered-X LMS algorithm is adopted as an adaptive feedforward algorithm and combined with the static output feedback controllers. A frequency response analysis and simulation are performed with the designed controllers on vehicle simulation software, CarSim®. From the simulation results, it is shown that the proposed controllers can effectively reduce the vertical accelerations and the pitch rate of the sprung mass and the human head.

Monocyte adhesion to and transmigration through endothelium following cardiopulmonary bypass shearing is mediated by IL-8 signaling

IntroductionThe use of cardiopulmonary bypass (CPB) can induce sterile systemic inflammation that contributes to morbidity and mortality, especially in children. Patients have been found to have increased expression of cytokines and transmigration of leukocytes during and after CPB. Previous work has demonstrated that the supraphysiologic shear stresses existing during CPB are sufficient to induce proinflammatory behavior in non-adherent monocytes. The interactions between shear stimulated monocytes and vascular endothelial cells have not been well studied and have important translational implications. With these studies, we tested the hypothesis that non-physiological shear stress experienced by monocytes during CPB affects the integrity and function of the endothelial monolayer.MethodsWe have used an in vitro CPB model to study the interaction between THP-1 monocyte-like cells and human neonatal dermal microvascular endothelial cells (HNDMVECs). THP-1 cells were sheared in polyvinyl chloride (PVC) tubing at 2.1 Pa, twice of the physiological shear stress, for 2 h. ELISA, adhesion and transmigration assays, qPCR, and RNA silencing were used to assess the interactions between THP-1 cells and HNDMVECs were characterized after co-culture.ResultsWe found that sheared THP-1 cells adhered to and transmigrated through the HNDMVEC monolayer more readily than static THP-1 controls. Sheared THP-1 cells disrupted the VE-cadherin and led to the reorganization of cytoskeletal F-actin of HNDMVECs. A higher level of IL-8 was detected in the sheared THP-1 and HNDMVEC co-culture medium compared to the static THP-1 and HNDMVEC medium. Further, treating HNDMVECs with IL-8 resulted in increased adherence of non-sheared THP-1 cells, and upregulation in HNDMVECs of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1). Finally, inhibition of HNDMVECs CXCR2/IL-8 receptor with Reparixin and of IL-8 expression with siRNA blocked sheared THP-1 cell adhesion to the endothelial monolayer.ConclusionsThese results suggest that CPB-like sheared monocytes promote IL-8 production followed by increased endothelium permeability, and monocyte adhesion and transmigration. This study revealed a novel mechanism of post-CPB inflammation and will contribute to the development of targeted therapeutics to prevent and repair the damage to neonatal patients.

The interference effect of low-relevant animated elements on digital picturebook comprehension in preschoolers: An eye-movement study.

Digital picture-book (DPB) with animated elements can enhance children's engagement, but irrelevant animations may interfere with their comprehension. To determine the effect of the relevance of animated elements on preschoolers' comprehension, an experimental study was conducted. Thirtythree preschoolers between the aged 4-5 years engaged with DPB in three conditions: high- and lowrelevant animations and a static control while listening to the story; their eye movements were recorded simultaneously. The study found that preschoolers had lower comprehension when exposed to low-relevant animation, but had comparable scores to the static condition with high-relevant animation. The results of eye-movement analysis showed that children who focused less on highrelevant or more on low-relevant elements had poorer comprehension. Those exposed to low-relevant animations looked less at high-relevant elements and more at low-relevant elements than those in the static and high-relevant conditions. These results suggested that low-relevant animations in DPB interfered with children's comprehension by directing their visual attention away from crucial, highrelevant elements and more to less relevant elements. Therefore, designers creating DPBs, as well as parents and caregivers selecting DPBs for children, should consider the importance of the relevance of animated elements. And the corresponding mechanism of animation effect in DPB comprehension was discussed.

Cell modeling using frequency modulation.

Computational models of the cell can be used to study the impact of drugs and assess pathological risks. Typically, these models are computationally demanding or challenging to implement in dedicated hardware for real-time emulation. A new Frequency Modulation (FM) model is proposed to address these limitations. This model utilizes a single sine generator with constant amplitude, while phase and frequency are modulated to emulate an action potential (AP). The crucial element of this model is the identification of the modulating signal. Focusing on FPGA implementation, we have employed a piecewise linear polynomial with a fixed number of breakpoints to serve as the modulating signal. The adaptability of this signal permits the emulation of dynamic properties and the coupling of cells. Additionally, we have introduced a state controller that handles both of these requirements. The building blocks of the FM model have direct integer equivalents, making them suitable for implementation on digital platforms like Field Programmable Gate Arrays (FPGA). We have demonstrated wavefront propagation in 1-D and 2-D models of tissue. We have used various parameters to quantify the wavefront propagation in 2-D tissues and emulated specific cellular dysfunctions. The FM model can replicate any detailed cell model and emulate its corresponding tissue model. This model is at its preliminary stage. The FPGA implementation of this model is a work in progress. Overall, the results demonstrate that the FM model has the potential for real-time cell and tissue emulation on an FPGA.

Static Gain Function-Based Adaptive Control for Nonlinear Systems With Unknown Time Delays

Static Gain Function-Based Adaptive Control for Nonlinear Systems With Unknown Time Delays

Energy saving potential of advanced dual-band electrochromic smart windows for office integration

Integrating dynamic transparent technologies into building envelopes is becoming crucial for tackling the challenges posed by climate change, improving energy efficiency, and enhancing occupant comfort. Nowadays, a range of dynamic glazing technologies exists, among which electrochromic glazing is notably effective in contributing to sustainability objectives in building design. This paper presents a comprehensive simulation analysis of the energy efficiency and interior comfort impacts of a novel class of spectrally selective dual-band electrochromic windows, also referred to as “Plasmochromic”. A simplified office model, oriented both south and west, was used to compare the performance of dual-band electrochromic glazing, using experimental data collected from a window-scale prototype, with that of commercially available advanced glazing systems. The comparison was conducted under two different control strategies: a rule-based and a model-based control algorithm. Five European climate zones have been considered to cover most of the continent’s climatic conditions and provide a comprehensive evaluation of the glazing performances. The simulations demonstrate the superior capability of dual-band electrochromic windows, when coupled with an intelligent control strategy, in reducing total annual energy consumption for heating, cooling, and lighting by up to 27% compared to the best-performing static solar control glazing systems. Additionally, they achieve a reduction of up to 32% in visual discomfort, measured by the cumulative value of useful daylight illuminance.

Static Output Feedback Controller Design for Switching Polynomial Fuzzy Time-Varying Delay System

This study focuses on the stability and stabilization problems of a switching polynomial fuzzy system with a time-varying delay. The switching method is based on the operating sub-domains, and the switching polynomial Lyapunov function with a time-varying delay is used to design the switching polynomial static output feedback controller. The switching polynomial Lyapunov function contains a double-integral term for analyzing the upper bound of the time-varying delay. The stabilization of the polynomial system is investigated, using the boundary information of the membership functions and introducing slack polynomial matrices, which can reduce the conservatism of the stability conditions. Subsequently, the sum of squares conditions are obtained, which are convex and can be solved using SOSTOOLS. Finally, the viability and validity of the proposed approach are demonstrated using a numerical example.

Effects of visual disruption on static and dynamic postural control in people with and without chronic ankle instability.

Chronic Ankle Instability (CAI) is a chronic syndrome resulting from repeated ankle sprains that lead to persistent dysfunction.the purpose of this study is to determine whether visual disruption could influence static and dynamic postural control in people with and without chronic ankle instability (CAI), with the objective of gaining a comprehensive understanding of the interactions between visual inputs and postural control. Thirty people with CAI (21 males and 9 females, age = 22.0 ± 1.8years, height = 174.4 ± 10.2cm, body mass = 72.5 ± 15.4kg; Cumberland Ankle Instability Tool (CAIT) score = 19.7 ± 1.8) and twenty-nine without CAI (24 males and 5 females, age = 22.9 ± 1.6years, height = 172.8 ± 8.0cm, body mass = 69.0 ± 11.3kg; CAIT score = 29.0 ± 0.7) were recruited. Their static and dynamic postural control was measured in two conditions with or without visual disruption, simulated using stroboscopic glasses. Static postural control was measured during single-limb standing and represented by root mean square (RMS) of the plantar center of pressure (CoP), dynamic postural control was measured during a Y-balance test and represented by the relative reach distance. Two-way mixed ANOVA (between group: CAI vs non-CAI, within group: normal vision vs visual disruption) was used to analyze data. Significant interactions were detected in the CoP-RMS in the anteroposterior (AP) (p = 0.021, η2 p = 0.090) and mediolateral (ML) (p < 0.001, η2 p = 0.208) directions, and the relative reach distances in the posteromedial (PM) p = 0.023, η2 p = 0.088) and posterolateral (PL) (p = 0.009, η2 p = 0.113) directions, from normal vision to visual disruption. The CoP-RMS in the AP and ML directions significantly increased and the relative reach distances in the PM and PL directions significantly decreased in people with CAI while remaining unchanged in those without CAI. People with CAI are susceptible to visual disruption on postural control, highlighting the importance of visual input in maintaining stable posture in this population.

Wavelength Stabilization of Entangled Biphotons Using Dynamic Temperature Compensation for Quantum Interference Applications

AbstractIn this paper, a dynamic temperature compensation method is presented to stabilize the wavelength of the entangled biphoton source, which is generated on spontaneous parametric down‐conversion from a magnesium oxide doped periodically poled lithium niobate waveguide. Utilizing the dispersive Fourier transformation technique, the photon wavelength variation is monitored in case of conventional static temperature control, revealing a long‐term wavelength drift up to 556.8 pm over a 14‐h measurement period. A Hong‐Ou‐Mandel (HOM) interferometer is constructed to assess the impact on quantum applications, showing a decrease in visibility from 95.5% to 69.4%. To address this issue, a digital proportional‐integral‐differential algorithm is implemented to dynamically compensate the working temperature variation of the waveguide, thereby instantly stabilizing the wavelength to a peak‐to‐peak fluctuation of +138.05 pm/‐127.61 pm with the standard deviation being 30.49 pm. The wavelength stability shows more than a hundredfold enhancement in terms of Allan deviation, reaching at an averaging time of 10000 s. With the dynamic control in operation, the HOM interference visibility turns to stable at 96.1% ± 0.6%. The method provides a simple and accessible solution for precisely controlling and stabilizing the wavelength of entangled biphotons, thus improving performance in various quantum information processing applications.

State and Disturbance Observer-Based Controller Design for Fully Actuated Systems

State and Disturbance Observer-Based Controller Design for Fully Actuated Systems

Working memory load increases movement-related alpha and beta desynchronization

Working memory (WM) load has been well-documented to impair selective attention and inhibitory control. However, its effects on motor function remain insufficiently explored. To extend the existing literature, we investigated the impact of WM load on force control and movement-related brain activity. Sixteen healthy young participants performed a visual static force matching task using a pinch grip under varying WM loads. The task included low and high WM load conditions (memorizing one digit or six digits), and the precision level required to control force was adjusted by manipulating visual gain (low vs. high visual gains), with higher visual gain necessitating more precise force control. Peri-movement alpha and beta event-related desynchronization (ERD), along with force accuracy and steadiness, were measured using electroencephalography recorded over the central areas during the force control task. Results indicated that while force accuracy and steadiness significantly improved with higher visual gain, there was no significant effect of WM load on these measures. Alpha and beta ERD were greater under high than low visual gain, and also greater under high than low WM load. These findings suggest that in young adults, increased WM load leads to compensatory increases in sensorimotor cortical activity to mitigate potential declines in static force control performance that may result from the depletion of neural resources caused by WM load. Our findings extend current understanding of the interaction between WM and sensorimotor processes by offering new insights into how movement-related brain activity is influenced by heightened WM load.

A Comparative Analysis of Active Control vs. Folding Wing Tip Technologies for Gust Load Alleviation

As part of the Ultra High Aspect Ratio Wing Advanced Research and Designs (U-HARWARD) project, funded by CS2JU, various gust load alleviation (GLA) technologies have been developed and studied. GLA plays a crucial role in the development of new generation ultra-high aspect ratio wings (UHARWs), as it reduces gust loads, thereby decreasing the structural weight of the wing and, consequently, the entire aircraft. This weight reduction enhances overall aircraft efficiency, enabling a higher aspect ratio. GLA technologies are categorized into passive systems, which require no active intervention, and active systems, where control surfaces redistribute the aerodynamic loads. In this study, passive GLA was implemented using a folding wing tip (FWT) developed by the University of Bristol, while active GLA employed a Static Output Feedback controller developed by Politecnico di Milano. Both approaches were compared against a baseline aircraft configuration. A flutter assessment confirmed that FWT does not introduce aeroelastic instabilities, ensuring the aircraft remains flutter-free across its flight envelope. A thorough comparison of load envelopes, based on nearly 2000 load cases across different flight points and mass configurations, was conducted in compliance with CS25 regulations, examining both positive and negative gust conditions. The results show a possible 15% reduction in the dynamic load envelope for both passive and active solutions. Using NeOPT, a hybrid finite element (FE) model was developed, with a detailed global FEM (GFEM) for the wingbox and stick elements for other components. Linear gust analyses in Nastran, with the hinge locked and released, provided high-fidelity results, comparing wing failure indexes and demonstrating the effectiveness of the FWT solution.

Signed-network-based consensus control for nonlinear multi-agent systems: a dynamic encryption–decryption approach

Abstract This paper is concerned with the bipartite secure control issue for a class of discrete-time nonlinear multi-agent systems under a dynamic encryption–decryption approach. First, the coupling relationships between agents are portrayed through a signed graph topology containing the edges of positive and negative connection weights. Next, the information transmissions between agents and their neighbors are executed via a shared communication network. The dynamic encryption–decryption approach is implemented to transform original signals into ciphertexts. Under the assumption that the signed graph is structurally balanced, a signed-network-based bipartite secure controller is designed to achieve the desired state control for the nonlinear multi-agent system and sufficient conditions are obtained for the existence of the desired signed-network-based state controller. Furthermore, a precise definition of the minimum channel capacity is proposed to understand the factors affecting the minimum channel capacity. Finally, the effectiveness of the proposed approach is illustrated by two simulation examples.

Vibration Thresholds Using Conventional Audiometry are Clinically Useful Indicators of Postural Instability in Older Adults.

Falls are a major health concern with potentially dramatic consequences for people over 65 years of age. One crucial determinant in the risk of falls in older adults is postural control, a complex process that requires the contribution of different sensory modalities, namely visual, vestibular, auditory, and somatosensory. While there are well-established methods to screen for age-related vision, hearing, tactile, and vestibular impairments, there are very few widely available methods to screen for somatosensory function, but studies indicate that ankle audiometry (vibration thresholds) using a common B-71 bone vibrator can serve that purpose. To date, unfortunately, this technique has received little attention as a tool to measure postural instability in older adults. The objective of the present study was to examine postural control in older adults with and without degradation of the somatosensory functions, as determined with ankle audiometry. This was standard group comparison. In total, 36 healthy elderly aged between 65 and 80 years old were divided into two groups (low vibration threshold [n = 18] and high vibration threshold [n = 18]). Standard audiometry, video head impulse test, vibration thresholds (big toe, ankle, and tibia), and static postural control task using a force platform were performed. Greater postural instability in participants with higher (worse) vibration thresholds as compared with participants with lower (better) vibration thresholds was observed even though both groups were comparable on hearing threshold and vestibular function. The results indicate that performing a simple vibration threshold evaluation, using a clinically available B-71 with a cut-off value of 42 dB hearing loss, could be an effective, fast, and easy-to-use procedure for detecting people at risk of falls.

Static output feedback control for positive 2D discrete systems in Roesser model

Abstract This paper investigates the output stabilization problem for multi-input multi-output positive 2D systems described by a linear discrete-time Roesser system. This kind of systems have the property that the horizontal and vertical states take non-negative values whenever the initial boundaries are non-negative. Conditions for the existence of desired static output feedback controllers guaranteeing the resultant closed-loop system to be positive and asymptotically stable are obtained. Also, the synthesis of static output feedback controllers, including the requirement of positivity of the controllers, is solved. These results are then extended to the case of uncertain plants. All of the proposed conditions are expressed in terms of Linear Programming, which can be easily verified by using standard numerical software. Finally, several numerical examples are included to illustrate the validity and the effectiveness of the developed results.

Effects of simulated microgravity on colorectal cancer organoids growth and drug response

Cellular and molecular dynamics of human cells are constantly affected by gravity. Alteration of the gravitational force disturbs the cellular equilibrium, which might modify physiological and molecular characteristics. Nevertheless, biological responses of cancer cells to reduced gravitational force remains obscure. Here, we aimed to comprehend not only transcriptomic patterns but drug responses of colorectal cancer (CRC) under simulated microgravity. We established four organoids directly from CRC patients, and organoids cultured in 3D clinostat were subjected to genome wide expression profiling and drug library screening. Our observations revealed changes in cell morphology and an increase in cell viability under simulated microgravity compared to their static controls. Transcriptomic analysis highlighted a significant dysregulation in the TBC1D3 family of genes. The upregulation of cell proliferation observed under simulated microgravity conditions was further supported by enriched cell cycle processes, as evidenced by the functional clustering of mRNA expressions using cancer hallmark and gene ontology terms. Our drug screening results indicated an enhanced response rate to 5-FU under conditions of simulated microgravity, suggesting potential implications for cancer treatment strategies in simulated microgravity.

Postural control among older adults with fear of falling and chronic low back pain

ObjectiveAltered Postural control could increase the risk of falling in older adults. Factors such as low back pain and fear of falling can be contributing factors to postural control instability. This study aimed to investigate the effect of chronic low back pain (CLBP) and fear of falling (FOF) on postural control of older adults.MethodForty-one older adults were included (27 LBP and 14 control). Among the participants, 22 people had high FOF, and 19 had low FOF based on Falls efficacy scale cut-off of ≥ 26. For postural control evaluation Center of pressure parameters (COP) of Standard deviation (Sd) of velocity, Sd of amplitude, path length and mean velocity in both Medial–lateral (ML) and Anterior–Posterior (AP) directions were measured. Mixed-model anova with two between group factor (Health status; with and without CLBP, and with high and low FES-I groups) and one within factor postural condition (four conditions with and without vision and Achill tendon vibration) was used.ResultNo significant interaction between groups (health status and FES-I) and group with condition (health status and condition or FES-I and condition) was observed for all COP parameters in both AP and ML direction. There was main effect of FES-I for all COP parameters in ML direction, with greater Sd of velocity, Sd of amplitude, path length and mean velocity in older adults with high FES-I compared to low FES-I in the ML direction.ConclusionHigh levels of FOF influenced static postural control in the ML direction. Therefore, paying attention to the lateral stability of older adults is of great importance.

Voluntary wheel running exercise rescues behaviorally-evoked acetylcholine efflux in the medial prefrontal cortex and epigenetic changes in ChAT genes following adolescent intermittent ethanol exposure.

Adolescent intermittent ethanol (AIE) exposure, which models heavy binge ethanol intake in adolescence, leads to a variety of deficits that persist into adulthood-including suppression of the cholinergic neuron phenotype within the basal forebrain. This is accompanied by a reduction in acetylcholine (ACh) tone in the medial prefrontal cortex (mPFC). Voluntary wheel running exercise (VEx) has been shown to rescue AIE-induced suppression of the cholinergic phenotype. Therefore, the goal of the current study is to determine if VEx will also rescue ACh efflux in the mPFC during spontaneous alternation, attention set shifting performance, and epigenetic silencing of the cholinergic phenotype following AIE. Male and female rats were subjected to 16 intragastric gavages of 20% ethanol or tap water on a two-day on/two-day off schedule from postnatal day (PD) 25-54, before being assigned to either VEx or stationary control groups. In Experiment 1, rats were tested on a four-arm spontaneous alternation maze with concurrent in vivo microdialysis for ACh in the mPFC. An operant attention set-shifting task was used to measure changes in cognitive and behavioral flexibility. In Experiment 2, a ChIP analysis of choline acetyltransferase (ChAT) genes was performed on basal forebrain tissue. It was found that VEx increased ACh efflux in the mPFC in both AIE and control male and female rats, as well as rescued the AIE-induced epigenetic methylation changes selectively at the Chat promoter CpG island across sexes. Overall, these data support the restorative effects of exercise on damage to the cholinergic projections to the mPFC and demonstrate the plasticity of cholinergic system for recovery after alcohol induced brain damage.

Piezoelectric silk fibroin nanofibers: Structural optimization to enhance piezoelectricity and biostability for neural tissue engineering

Silk fibroin (SF) has garnered significant interest in tissue engineering due to its excellent biocompatibility and bioactivity. Notably, SF exhibits piezoelectric properties that can be harnessed to electrically stimulate cells, enhancing tissue morphogenesis. However, a systematic approach to control SF's piezoelectricity and biodegradation, and its application in neural morphogenesis, has not been fully explored. In this study, SF was electrospun into nanofibers of various sizes and subjected to a post-electrospinning chemical treatment to examine the effects of phase composition, especially the β-sheet formation, on the piezoelectricity and biostability of SF. The optimized SF scaffolds having a nanofiber diameter of 750 nm and a scaffold thickness of 250 µm allowed for the maintenance of nanofibrous structure for at least 6 weeks in aqueous environments while maintaining piezoelectric potential outputs of at least 200 mVp-p. This enabled cell membrane depolarization over an extended cell culture duration, facilitating the functional maturation of human neural stem cells (hNSCs). Specifically, acoustic piezo-activation of the SF scaffolds, resulting in mechano-electrical stimulation (MES) of the cells, accelerated their differentiation into neurons, astrocytes, and especially oligodendrocytes, leading to robust axon myelination within two weeks. Furthermore, MES enhanced neural connectivity and functional maturity, as evidenced by significant increases in excitatory and inhibitory synapse formation (46 % and 58 %, respectively), action potential amplitude (252 %), and velocity (210 %) compared to static control conditions. These findings demonstrate the potential of biodegradable electrospun SF nanofibers with balanced piezoelectricity and biostability for advancing neural tissue engineering.