Longitudinal Disturbances Research Articles

Roles of Social Support and Strain in Predicting Older Adults’ Sleep Disturbances

Sleep disturbances impact the well-being of older adults, but there has been limited research on their longitudinal patterns and how they are affected by the quality of social relationships. This study explored longitudinal sleep disturbance patterns and examined the influence of social support and social strain on sleep disturbances in older adults using data from the Health and Retirement Study (HRS) spanning from 2010 to 2018. Group-based trajectory modeling identified distinct trajectory groups. Multinomial logistic regression and a fixed effects model investigated the relationship between sleep disturbances, social support, social strain, and sociodemographic factors. Three sleep disturbance trajectories were identified: high sleep disturbances, moderate sleep disturbances, and low sleep disturbances. Multinomial logistic regression showed that higher social support decreased the likelihood of classification in the high and moderate sleep disturbance groups. Conversely, higher social strain scores increased the likelihood of belonging to the high and moderate sleep disturbance groups. The fixed effects model confirmed the role of social support in predicting sleep disturbances over time, but social strain was not a significant predictor. These findings suggest the need for tailored interventions addressing social support to reduce sleep disturbances in this population.

Individual-Level Experiences of Structural Inequity and Their Association with Subjective and Objective Sleep Outcomes in the Adolescent Brain Cognitive Development Study

PurposeResearch has documented that adolescent sleep is impacted by various stressors, including interpersonal experiences and structural disadvantage. This study extends existing knowledge by empirically examining interconnected individual experiences of structural inequity and assessing its association with subjective and objective sleep outcomes. MethodsWe utilized data from the Adolescent Brain and Cognitive Development Study to identify seven conceptual domains of structural inequity: perceived discrimination, low school inclusivity, neighborhood safety, unmet medical needs, legal problems, material hardship, and housing insecurity. We operationalized experiences of structural inequity as latent classes, a cumulative exposure, and each domain separately. Sleep disturbances were measured using the Sleep Disturbance Scale, and sleep duration was assessed using Fitbits. Mixed effects linear regression estimated the association between our measures of structural inequity, longitudinal sleep disturbances, and cross-sectional sleep duration. ResultsLatent class analysis revealed common exposure profiles (low risk, interpersonal, and systemic) of experiences of structural inequity across our sample. In longitudinal models, structural inequity was associated with higher Sleep Disturbance Scale scores, whether measured as latent classes, a cumulative exposure, or individual domains. Individuals with interpersonal exposures, those with at least one exposure, and those with legal problems, material hardship, and housing insecurity had lower mean sleep duration. DiscussionResults are consistent with literature that frames structural inequity as a lifelong determinant of sleep disturbance and duration. Adolescence represents a crucial time for interventions aimed at improving sleep and redressing inequities throughout the life course; our work can inform the development of policies and interventions toward this end.

Heat transfer enhancement mechanics of different micro-disturbing structures for transcritical hydrocarbon fuel using 3-D secondary flow intensity analysis

Heat transfer enhancement based upon micro-disturbing structures becomes increasingly important for thermal protection of air-breathing propulsion systems. To explore the influence mechanism of different structures on heat transfer in regenerative cooling channels of scramjet engines, flow structures and heat transfer of supercritical-pressure n-Decane in mini-channels with dimple and micro-rib arrays are numerically investigated. Results indicate effective heat transfer enhancement inside the channels depends more on efficient transverse turbulence disturbance rather than longitudinal or perpendicular turbulence disturbance. Severe thermal stratification generates strong shear layers in channels, where transverse secondary flows bring much intenser flow mixing than longitudinal secondary flows, especially in transcritical temperature region where the best heat transfer enhancement is obtained. With same characteristic dimensions, longitudinal micro-disturbing structures like dimples have lower flow resistance, but transverse micro-disturbing structures like micro-ribs achieve stronger heat transfer enhancement. Besides, the performance of micro-ribs is much more sensitive to the dimensional change. Therefore, micro-ribs have larger working excursion for enhancing performance factor than dimples. With optimal structure parameters: hr = e = 0.3 mm, pr = 3 mm, hd = 0.225 mm, dd = 1.5 mm, overall performance factor in micro-ribbed channel is 1.14 times of that in dimpled channel. Those conclusions provide effective support for optimization design for the regenerative cooling structures.

Planning trajectories for connected and automated vehicle platoon on curved roads: A two-dimensional cooperative approach

This paper presents a cooperative two-dimensional trajectory planning algorithm for connected and automated vehicle (CAV) platoons. Specifically, the proposed algorithm generates two-dimensional optimal trajectories for CAVs with car-following relationships cooperatively within a complex road geometry. By extending the simplified Newell’s car-following model, we propose a two-dimensional Newell’s car-following model as an equilibrium car-following policy for CAVs. Based on this, a multi-objective constrained optimization is systematically formulated under a Cartesian coordinate. Due to the constraint’s complexity, a new solving algorithm based on the rapid random tree (RRT) technique is proposed. To test the effectiveness of our proposed models and algorithm, numerical simulation experiments with a real-world road geometry are conducted. Results indicate that our proposed method is able to generate trajectories for CAV platoons which are close to the equilibrium condition with smooth controls, while avoiding road obstacles. We further extend the definition of a one-dimensional car-following control string stability to a two-dimensional case. By this definition, we find that the proposed method can achieve empirical two-dimensional string stability, ensuring that both lateral and longitudinal disturbances are attenuated through vehicular strings.

Double-diffusive thermosolutal Hadley–Prats flow: stability analysis

ABSTRACT A mathematical model is formulated to study the onset of double-diffusion fluid flow through an infinite permeable channel with internal heat source and viscous dissipation effects under the influence of convection conditions. Numerically, the dimensionless emerging eigenvalue problem is tackled using the fourth-order Runge–Kutta scheme, specifically applied to longitudinal roll disturbances. Critical values of wave number and vertical thermal Rayleigh number are determined. A higher value of Gebhart number is observed to correlate significantly with the destabilizing phenomena in Hadley–Prats flow. Concentration-based internal heat generation also strongly modifies the critical thermal Rayleigh number. Also, it is found that the horizontal mass flow and viscous dissipation exert a substantial influence on the onset of instability in the flow regime. Linear instability analysis indicates that greater values of Lewis number in the porous medium stabilize the convection process for both values of mass diffusion parameter ( C z ) . Enhancing C z from negative to positive values diminishes the critical thermal Rayleigh ( R z ) value and consequently induces instability in the porous medium. Increased concentration-based internal heat generation generates the destabilization process in the flow region.

Switching Longitudinal and Lateral Semi-decoupled Active Disturbance Rejection Control for Unmanned Ground Vehicles

In this paper, a switching longitudinal and lateral semi-decoupled active disturbance rejection control (ADRC) strategy is proposed for motion control of unmanned ground vehicles (UGVs). To characterize the coupling property between longitudinal and lateral dynamics, a switching longitudinal and lateral semi-coupled model is first developed. By utilizing the switching method, a so-called “two-stage ADRC” strategy is presented. It has two forms before and after the transition instant such that the boundedness premise for the derivative of the total disturbance can be removed. With the designed two-stage ADRC, a longitudinal and lateral semi-decoupled controller is then suggested to solve the motion control problem of UGVs. Finally, both stability analysis and comparison results are given to demonstrate the effectiveness and robustness of the proposed control strategy.

Energy-optimal Speed Regulation for CAVs in Urban Mixed Traffic with Induced Lane Changes

Existing urban energy-optimal vehicle speed regulation (eco-driving) studies were mostly carried out on single-lane roads or did not consider lane changes, delivering overidealized eco-driving results. In addition to lane changes that every vehicle may encounter on roads, the eco-driving connected automated vehicles (CAVs) are subject to induced types of lane changes of manually-driven vehicles (MVs), a cut-in of an MV to the front of a CAV from an adjacent lane, and an escape of an MV from behind a CAV to an adjacent lane. So far, very few studies have considered the impact of lane changes while designing the ecodriving strategies and evaluated the eco-driving performance with respect to lane-changing disturbances in credible simulation environments; and almost no existing work has addressed both lateral and longitudinal disturbances for eco-driving. This paper has developed a generic and deployable eco-driving strategy for CAVs under a unified rolling-horizon optimal control framework that can deal with both longitudinal and lateral disturbances of MVs without assuming communications between CAVs and MVs. The performance of this disturbance-rejection eco-driving strategy was thoroughly evaluated with regard to a multilane urban network, using the microscopic traffic simulator SUMO. The strategy was demonstrated very effective and robust, and similar results were little reported before.

Left ventricular mechanical dispersion as a predictor of the need for pacemaker implantation after transcatheter aortic valve implantation: MeDiPace TAVI study.

Permanent pacemaker (PM) implantation is common after transcatheter aortic valve implantation (TAVI). Left ventricular mechanical dispersion (MeDi) by speckle tracking echocardiography is a marker of fibrosis that causes alterations in the conduction system. We hypothesized that MeDi can be a predictor of the need for PM implantation after TAVI. Consecutively, 200 TAVI patients were enrolled. Transthoracic echocardiography and electrocardiography examinations were recorded before TAVI to evaluate global longitudinal strain (GLS), MeDi, and conduction disturbances. PM implantation information was obtained 3 months after TAVI. Patients were stratified into PM or no PM group. Mean age was 80 + 7 years (44% women). Twenty-nine patients (16%) received PM. MeDi, QRS duration, existence of right bundle branch abnormality (RBBB), and first-degree atrioventricular (AV) block were significantly different between groups. MeDi was 57 ± 15 ms and 48 ± 12 ms in PM and no PM groups, respectively (P < 0.001). In multivariate analysis, MeDi predicted the need for PM after TAVI independently of GLS, QRS duration, RBBB, and first-degree AV block [odds ratio (OR): 1.73, 95% confidence interval (CI): 1.22-2.45] with an area under the curve (AUC) of 0.68 in receiver operating characteristic (ROC) curves. Moreover, RBBB was an independent predictor of PM need after TAVI (OR: 8.98, 95% CI: 1.78-45.03). When added to RBBB, MeDi had an incremental predictive value with an AUC of 0.73 in ROC curves (P = 0.01). MeDi may be used as an echocardiographic functional predictor of the need for PM after TAVI.

Lean flameout characteristics and unsteady dynamics of swirling non-premixed flame with and without outer flame

The planar laser induced hydroxyl fluorescence (OH-PLIF) technique was used to study three kinds of swirling flame, namely flames I, II, and III, by changing swirl conditions. According to the PLIF results, double structure exists in flames I and II. The inner flame burns in the inner shear layer and is anchored by vortex breakdown, which is similar to the M- or V-shaped flame. The unique outer flame is attached to the inner wall of the air annular nozzle and burns in the outer shear layer. The lean blowout (LBO) equivalent ratio of swirling flame with outer flame is lower than that without outer flame. It is interesting to compare the LBO mechanisms among the three types and the traditional swirling flame, and investigate their unsteady characteristics. Firstly, the flameout process of flames I and II starts from the local extinguishing at the root of the outer flame. However, the LBO process of flame III is consistent with that of traditional swirling flame, that is, it starts with repeated extinguishing and reigniting at the root of the inner recirculation zone (IRZ). Secondly, the unsteady characteristics of the three flames are analyzed by spectral proper orthogonal decomposition. It is found that flame oscillations, asymmetric disturbances, and longitudinal disturbances of different frequencies exist in different combinations under near-LBO conditions. In particular, asymmetric and P-wave disturbances mainly exist in the inner shear layer and jet breaking down, which further indicates the stability and anti-LBO potential of the outer flame.

Carbon Emission Impacts of Longitudinal Disturbance on Low-penetration Connected Automated Vehicle Environments

Carbon Emission Impacts of Longitudinal Disturbance on Low-penetration Connected Automated Vehicle Environments

Modeling of the springed part of a mobile vehicle

During a full-scale invasion, the aggressor country changed the tactics of using mobile fire equipment. These changes led to the creation of highly mobile systems based on wheeled vehicles with an atypical firearm. As a wheeled vehicle, a "Pickup" type car is most often used, since its structural properties have room in the body for installing additional systems with subsequent masking of the selected vehicle. Such wheeled transport bases with an atypical firearm are already used in the Armed Forces of Ukraine both on the line of contact with the enemy and in civilian cities to protect the airspace, depending on the characteristics of the atypical firearm. Analysis of the creation and use of the mentioned systems revealed their certain shortcomings and the corresponding areas of improvement. The article considers the issue of the formation of an oscillating effect in the spring-loaded part of a wheeled vehicle when longitudinal disturbance from the use of a firearm is applied. The work is based on the analysis of requirements for longitudinal and transverse stabilization of the body of a wheeled vehicle. For this, an analysis of the characteristics of the existing types and schemes of the suspension of the "Pickup" type car was carried out. The obtained results are used to calculate the oscillating effect of a wheeled vehicle that occurs as a result of the use of an incendiary agent. The final goal of the work is to create a model of the rigidity of the "vehicle - firearm" system and to use this model to form a control effect of the automatic control system of the stabilization of the firearm. The presence of an automatic control system will increase the efficiency of the installed fire means.

Investigation of the Formation and Further Development of Longitudinal Disturbances and Their Secondary Instability on the Flying Wing Model

Detailed investigation of two-dimensional roughness element influence on the flow behind three-dimensional roughness element was carried out. For the first time studies were conducted on the windward side of the flying wing in the range of free-stream 7,2 – 20 m/s in the favourable gradient region behind roughness elements. Secondary instability mechanisms of disturbances leading to turbulence stage were investigated. It was shown that longitudinal structure forming behind three-dimensional roughness element grows downstream and has its trajectory slightly bend. The longitudinal structure consists of two stationary disturbances different in size. This can be explained by presence of cross flow and secondary disturbances leading to the transition. On the straight wing model, influence of the distributed suction on the stationary disturbance development was investigated and quantitatively determined. It was shown that suction is able to relaminarize the flow and eliminate the separation of the boundary layer.

EFFECT OF VISCOUS DISSIPATION AND INTERNAL HEAT SOURCE ON MONO-DIFFUSIVE THERMOCONVECTIVE STABILITY IN A HORIZONTAL POROUS MEDIUM LAYER

A mathematical model is developed for studying the onset of mono-diffusive convective fluid flow in a horizontal porous layer with temperature gradient, internal heat generation, and viscous dissipation effects. Darcy's model is used for the porous medium, which is considered to be isotropic and homogenous. A linear instability analysis is conducted, and transverse or longitudinal roll disturbances are examined. The dimensionless emerging eigenvalue problem is solved numerically with the Runge-Kutta and shooting methods for both cases of disturbances, i.e,. longitudinal and transverse rolls. Critical wave number and critical vertical thermal Rayleigh number &lt;i&gt;R&lt;sub&gt;z&lt;/sub&gt;&lt;/i&gt; are identified. For higher values of Gebhart number, Ge, a significant destabilizing effect of Hadley-Prats flow is computed. Internal heat generation also strongly modifies the critical vertical Rayleigh number. Extensive interpretation of the solutions related to the onset of convection is provided. The study is relevant to geophysical flows and materials processing systems.

Effects of longitudinal disturbances on two-dimensional detonation waves

We perform simulations of propagation dynamics of cellular detonations in disturbed media. Upstream density variations impose periodic oscillations of the average leading shock pressure and detonation cell scales. Mode-locking of detonation dynamics still occurs in cellular detonations both for regular and irregular detonations under a large disturbance wavelength.

A nonlinearly kinematic model of the asymmetrically turbulent premixed slit flame subjected to two-way harmonic disturbances

Transversal and longitudinal combustion instabilities typically occur in gas turbines and rocket engines. Quantifying the nonlinear flame dynamic response of turbulent premixed flames subjected to the two-way disturbances and mean bulk flows is significant to understand the complex nonlinear combustion instability phenomena. A Two-way Nonlinear Unforced Flame Speed Modeling (2W-NUFSM) approach was proposed in this study. The turbulent effects were accounted for in the flame propagation speed term and the steady flame term in the kinematic equation of the flame front; an expansion method was then used to obtain the nonlinear solutions corresponding to the transverse and longitudinal acoustic disturbances. The turbulent effect on the flame consumption speed was also considered in the heat release rate calculation of the perturbed flame. Validations of this approach were conducted by comparing its results to the former credible results obtained from other methods and good agreements were obtained. The influence of turbulent effects on the flame dynamic response in an asymmetrical premixed flame was investigated in detail. The coupling effect of the turbulence and harmonic flow disturbances on the flame nonlinear dynamic response was also quantified.

Towards longitudinal and lateral coupling control of autonomous vehicles using offset free MPC

Model predictive control (MPC) is widely used in the motion control of autonomous vehicles. However, the conventional MPC relies on an accurate model and cannot achieve offset-free tracking in steady-state when the autonomous vehicle encounters external disturbance and parameter perturbation. Based on our recently designed C++ offset-free MPC (OF-MPC) solver, this paper uses MPC to solve the longitudinal and lateral coupling control problem directly. In the modeling stage, the constraints of the tire friction circle are approximated by the polygon. And then the polygon constraints are mapped into the state and control space. Finally, the tire friction circle constraints are approximated as convex linear inequality constraints, which are used as the vehicle stability boundary condition. Meanwhile, a convex optimization method is used to solve the reference value problem of MPC, and a systematic method that can prevent the reference value from being outside the feasible region is proposed. The real-time simulation and actual vehicle results show that the algorithm can solve both lateral and longitudinal disturbances problems. The algorithm achieves better tracking accuracy and high-speed stability due to consideration of the longitudinal and lateral coupling constraints. Benefiting from the proposed efficient solver, the average time to complete all calculations, including logic processing and input–output processing, is only about 5ms when the horizon length is 50.

Fault analysis of the 110 KV power grid with one-way power supply

This paper presents simulation-based studies on the 110 kV substations located in the Euro-Arctic region of Russia. Longitudinal and transversal disturbances in the high voltage grid are studied. The influence of the harsh climatic conditions on the rate of occurrence of accidents is shown. The 110-kV section of the Kola power system was considered and the features of this section were analyzed. The simulation model of the investigated section was created in the ATP-EMTP software and a wire break of the overhead transmission line followed by a single phase-to-ground faults of the same phase was simulated. The influence of combined overvoltage on substations electrical equipment is considered. The simulation results show that overvoltages in power grids with one-way power supply can pose a significant threat to insulation of any substation equipment.

Experiment on longitudinal aerodynamic characteristics of flying wing model with plasma flow control

Horizontal tail is eliminated from the flying wing layout for improving the low observable and aerodynamic efficiency, resulting in degrading longitudinal maneuverability and fight stability. The low speed wind tunnel test study of improving the longitudinal aerodynamic characteristics of large aspect ratio flying wing model is carried out by using plasma flow control technology. The flying wing model has a leading-edge sweep angle of 34.5° and an aspect ratio of 5.79. The reasons for deteriorating the static maneuverability and stability of the flying wing model and the mechanism of plasma control of the flow field and longitudinal aerodynamic characteristics are studied by particle image velocimetry (PIV) flow visualization and static force measurement test. The control law of plasma control of the flight maneuverability and stability of the flying wing model is studied through flight test. The fact that the flow separation of the outer wing of the flying wing model occurs earlier than the inner wing and the wing is swept back can result in the forward movement of the aerodynamic center and the deterioration of the longitudinal static stability. The shock disturbance induced by plasma can suppress the flow separation of the suction surface, thereby extending the linear section of the lift curve of the model, preventing the aerodynamic center from moving forward, and improving the longitudinal static stability. When the wind speed is 50 m/s, the plasma control improves the horizontal rudder efficiency at a high angle of attack of the flying wing model, increases the maximum lift coefficient of the model by about 0.1, and postpones the stall angle of attack by more than 4° at different rudder angles. The plasma control allows the flying model to follow the command movement better while flying, increases the flying pitch limit angle from 11.5° to 15.1°, reduces the amplitude of longitudinal disturbance motion by 2°, and reduces the oscillation attenuation time from 15 to 8 s, thereby improving the longitudinal flight maneuverability and stability of the flying wing model. It can be seen that plasma flow control technology has great potential applications in improving the flight quality of flying wing layout.

Nonlinear Models of Laminar Premixed Slit Flame Responses Subjected to Two-Way Perturbations

Transversal and longitudinal combustion instabilities typically present in gas turbines and rocket engines. It is thus important to investigate the flame responses of the two directional disturbances. When the disturbance level remains weak, the flame response can be considered linear. The flame transfer function (FTF) is typically used, and the global FTF can be easily obtained by superposition of the FTFs at the two-directional forcing. However, when the disturbances arise, the flame response becomes nonlinear due to the nonlinear responses at the two directions and their couplings. The present work thus presents nonlinear analytical models (flame describing function [FDF]) of a two-dimensional laminar premixed slit flame subjected to simultaneously longitudinal and transverse bulk mean flows and disturbances. These nonlinear models are derived based on the asymptotic expansion of the -equation model of the dynamic flame front. A velocity perturbation model is proposed by considering the change of disturbance convection speed with forcing frequency. To analyze the nonlinear coupling effect of the two-directional forcing, a partly FDF is introduced by neglecting the coupling term. By comparing the results from the FDF, partly FDF, and the FTF, the nonlinear effects are investigated. As the flame tip movement plays an important role in the FDFs for the slit flame, the global effects of flame tip movement on the FDFs are also quantified.

Experimental study on formation mechanism of main droplets and elimination method of satellite droplets in jet process

In certain industries, such as the Chinese pharmaceutical pill preparation medicines, the occurrence of satellite droplets and the inconsistent diameters of the main droplets lead to wasted resources and affect the normal operation of the production system. So it is necessary to investigate the formation process of main droplets and the elimination method of satellite droplets in the jet process. In this paper, the effects of the liquid level height, dropper inner diameter, and glycerin mass fraction on the formation of the droplets are revealed, and the optimal frequency for eliminating satellite droplets is explored. The results show that the diameter of the main droplets increases as the liquid level height and the dropper inner diameter increase and decreases as the glycerin mass fraction increases. The fracture length has a growing trend as the liquid level, dropper inner diameter, and glycerin mass fraction increase. With the increase in the dropper inner diameter and glycerin mass fraction, the generation period increases. However, the increase in the liquid level height has an opposite influence on the other parameters. The optimal frequency for eliminating satellite droplets increases as the liquid level height and dropper inner diameter increase and decreases as the liquid becomes more viscous. However, the diameter and generation period of the main droplets decrease when a longitudinal disturbance is added to the jet system.