HFVS

Acronym	Definition
HFVS	High Fidelity Vibratory Seismic (data acquisition method)
HFVS	High-Frequency Vibratory Sensitive

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Further, attrition appears to be a hallmark of frequent ED use [2], with frequency of ED visits among HFVs often declining from one year to the next [78].

Chronic Pain in the Emergency Department: A Pilot Interdisciplinary Program Demonstrates Improvements in Disability, Psychosocial Function, and Healthcare Utilization

Based on modern control techniques, various flight control systems have been designed to the longitudinal dynamics of HFVs. In [12], the adaptive backstepping method was used to design controllers for HFVs, while fuzzy logic systems (FLSs) and neural networks (NNs) were used to approximate the unknown system dynamics in [13, 14].

However, to our best knowledge, limited attention has been paid to this problem for the controller design of HFVs.

Inspired by the aforementioned discussions, in this paper, we divide the control oriented model (COM) of HFVs into two parts: velocity subsystem and altitude subsystem.

In Section 2, the nonlinear longitudinal dynamics model of HFVs is presented.

In this paper, by functional decomposition, the dynamics of HFVs is decoupled into velocity and altitude subsystem.

The simulation model of HFVs is taken from [18, 21].

The control oriented model (COM) of the longitudinal dynamics of HFV considered in this study is taken form [8,18].

Moreover, as stated in [18], from the model of the HFV, it is easy to check that [g.sub.1](x), [g.sub.2](x), and [g.sub.3](x) are always strictly positive and [g.sub.5](x) is strictly negative since [c.sub.e] is negative.

The COM model of HFV is an MIMO system that has cross-channel coupling.

Neural Networks Approximator Based Robust Adaptive Controller Design of Hypersonic Flight Vehicles Systems Coupled with Stochastic Disturbance and Dynamic Uncertainties