Steady state (disambiguation)

Steady state may refer to:

Steady state

In systems theory, a system in a steady state has numerous properties that are unchanging in time. This means that for those properties p of the system, the partial derivative with respect to time is zero:

The concept of steady state has relevance in many fields, in particular thermodynamics, economics, and engineering. Steady state is a more general situation than dynamic equilibrium. If a system is in steady state, then the recently observed behavior of the system will continue into the future. In stochastic systems, the probabilities that various states will be repeated will remain constant.

In many systems, steady state is not achieved until some time after the system is started or initiated. This initial situation is often identified as a transient state, start-up or warm-up period.

While a dynamic equilibrium occurs when two or more reversible processes occur at the same rate, and such a system can be said to be in steady state, a system that is in steady state may not necessarily be in a state of dynamic equilibrium, because some of the processes involved are not reversible.

Steady state (electronics)

In electronics, steady state is an equilibrium condition of a circuit or network that occurs as the effects of transients are no longer important.

Steady state determination is an important topic, because many design specifications of electronic systems are given in terms of the steady-state characteristics. Periodic steady-state solution is also a prerequisite for small signal dynamic modeling. Steady-state analysis is therefore an indispensable component of the design process.

Calculation methods

Steady state calculation methods can be sorted into time-domain algorithms (time domain sensitivities, shooting) and frequency-domain algorithms (harmonic balance) methods, are the best choice for most microwave circuits excited with sinusoidal signals (e.g. mixers, power amplifiers).

Time domain methods

Time domain methods can be further divided into one step methods (time domain sensitivities) and iterative methods (shooting methods). One step methods require derivatives to compute the steady state; whenever those are not readily available at hand, iterative methods come into focus.

Steady-state economy

A steady-state economy is an economy of relatively stable size. A zero growth economy features stable population and stable consumption that remain at or below carrying capacity. The term typically refers to a national economy, but it can also be applied to the economic system of a city, a region, or the entire planet. Note that Robert Solow and Trevor Swan applied the term steady state a bit differently in their economic growth model. Their steady state occurs when investment equals depreciation, and the economy reaches equilibrium, which may occur during a period of growth.

Physical features

The steady-state economy is an entirely physical concept. Any non-physical components of an economy (e.g. knowledge) can grow indefinitely. But the physical components (e.g. supplies of natural resources, human populations, and stocks of human-built capital) are constrained and endogenously given. An economy could reach a steady state after a period of growth or after a period of downsizing or degrowth. The objective is to establish it at a sustainable scale that does not exceed ecological limits.