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Pollution Prevention Applications
Published in Mary K. Theodore, Louis Theodore, Introduction to Environmental Management, 2021
Mary K. Theodore, Louis Theodore
This equation can be applied to the total mass involved in a process or to a particular species, on either a mole or mass basis. The conservation law for mass can be applied to steady-state or unsteady-state processes and to batch or continuous systems. A steady-state system is one in which there is no change in conditions (e.g., temperature and pressure) or rates of flow with time at any given point in the system; the accumulation term then becomes zero. If there is no chemical reaction, the generation term is zero. All other processes are classified as unsteady state.
Discrete Time Control Systems
Published in Jitendra R. Raol, Ramakalyan Ayyagari, Control Systems, 2020
Jitendra R. Raol, Ramakalyan Ayyagari
The steady-state behavior of a stable control system is measured by the steady error due to step, ramp, or parabolic inputs depending on the system type. One can consider the steady-state error (SSE) at the sampling instants for the following system, see Figure 9.7b: () E(s)=R(s)−H(s)Y(s)
Fundamental concepts
Published in W. John Rankin, Chemical Thermodynamics, 2019
It is possible for systems to be unchanging, and exhibit no tendency to change, but not be at equilibrium. Steady-state and metastable systems are of this type. A steady-state system is one in which all properties are constant despite ongoing processes that strive to change them. For a system to be at steady state there must be a flow of mass or energy through the system. To illustrate a steady-state system, think of a bathtub with the tap open and with the bottom outlet open, as in Figure 2.5. If water flows in and out at the same rate so the water level remains constant this is a steady-state system. In a steady-state system, the values of intensive properties (temperature, density, etc.) may vary from point to point but will remain unchanged with time at any given point. Many natural and industrial processes (those that operate with an approximately constant flow of inputs and outputs) can be considered to be steady-state for some purposes.
Evaluation of the effective length of passing lanes on two-lane highways
Published in Transportation Letters, 2020
Amirhossein Jafari, Ahmed Al-Kaisy, Scott Washburn
A straight, level segment of two-lane highway, including a passing lane of 1.5 miles was created in SwashSim. This length was chosen to represent a typical passing lane in practice. A combination of passing and no-passing segments with a length of 0.5 miles per segment was used. For a %NP of 0, passing is allowed along the entire length of the facility, while for a %NP of 100, passing is not allowed in any part. For a %NP of 20, passing is allowed in four out of five consecutive segments, and so on. The detectors were located in the middle of the segments. One detector was located upstream of the passing lane and multiple detectors were located downstream of the passing lane at 1-mile increments. For lower traffic flow levels, a longer network is required to reach steady state in the platooning level downstream of the passing lane. Therefore, for low traffic flow levels, detectors were installed for a distance of approximately 32 miles downstream of the passing lane, while for higher traffic flow levels, detectors were installed for a distance of approximately 23 miles downstream of the passing lane. Here, steady state refers to the condition where the performance measure becomes nearly constant. The performance measure selected for determining the effective length is follower density, as it accounts for both the percentage of short headways and traffic level. The outputs from the 30 simulation runs were used for each scenario at each detector location and used in this study.
Feedback perimeter control with online estimation of maximum throughput for an incident-affected road network
Published in Journal of Intelligent Transportation Systems, 2021
Jiawen Wang, Xiaozheng He, Srinivas Peeta, Xiaoguang Yang
The goal of the feedback controller is to maintain the system state around the optimal steady state. Around the MNT, according to Equation (11), the following equation can be derived approximately: