Resilience

**Resilience** generally means the ability to recover from some shock or disturbance.  

There are different meanings for,
*resilience in psychology: the mental ability to recover quickly from depression, illness or misfortune
*resilience of a material: the physical property of material that can resume its shape after being stretched or deformed (elasticity)
*resilience of a system: the ability of a system to recover from difficulties;toughness

## Psychology
**Resilience** is a term used in psychology to describe the capacity of people to cope with  and catastrophe. It is also used to indicate a characteristic of resistance to future negative events. This psychological meaning of resilience is often contrasted with "risk factors".

## Materials
In physics and engineering, **resilience** is defined as the capacity of a material to absorb energy when it is deformed elastically and then, upon unloading to have this energy recovered. In other words, it is the maximum energy per volume that can be elastically stored. It is represented by the area under the curve in the elastic region in the Stress-Strain diagram.

Modulus of Resilience, U_r, can be calculated using the following formula: U_r=\frac{\sigma^2}{2E}=0.5\sigma\epsilon=0.5 \sigma\left(\frac{\sigma}{E}\right), where  \sigma  is yield stress, E is Young's modulus, and  \epsilon  is strain.

An example of a biomaterial which has a high resilience is articular cartilage, the substance lining the ends of bones in articulating joints such as the knee and hip.

## Systems
### Ecology
In ecology, **resilience** has been defined in two competing fashions that emphasize two different aspects of stability.

**One definition** is the rate at which a system returns to a single steady or cyclic state following a perturbation. This definition of resilience assumes that behavior of a system remains within the stable domain that contains this steady state.

When a system can reorganize, that is shift from one stability domain to another, a more relevant measure of ecosystem dynamics is ecological resilience. It is a measure of the amount of change or disruption that is required to transform a system from being maintained by one set of mutually reinforcing processes and structures to a different set of processes and structures.

**The second definition** emphasizes conditions far from any steady-states, where instabilities can flip a system into another regime of behavior - i.e. to another stability domain. In this case resilience is measured by the magnitude of disturbance that can be absorbed before the system changes its structure by changing the variables and processes that control behavior. This type of resilience has been defined as ecological resilience.

### Public Health 
The concept of resilience has been widely adopted across various disciplines, often serving as a "boundary object" that facilitates interdisciplinary collaboration. Originally rooted in developmental psychology and socio-ecological research, resilience has evolved into a multifaceted term, leading to lexical ambiguity due to its diverse applications.“**Conceptualizing resilience in public health: a philosophical approach”** is a 2025 research article that critically examines the concept of resilience as it is used across disciplines and seeks to redefine it within the specific context of public health emergencies.By employing a modified integrated literature review, the authors have traced the evolution of resilience from a "Substance Metaphysics" and reductionist perspective to a more expansive, multidimensional, intersectional, and dynamic phenomenon. In this article existing philosophical theories were critically examined for thier convergence or divergence with the evolving conceptualizations of resilience, particularly in the realm of public health emergencies. 

According to the article, in the public health context, resilience emerges from the effective engagement of stakeholders dedicated to health preservation. Addressing current and emerging health inequalities requires integrated responses that enable trajectories of sustenance or growth. Such approaches should foster the development of capabilities that is sensitive to diverse health disparities, ensuring that communities are better equipped to withstand and adapt to health-related challenges.Using the " Modified Integrated Review Methodology" the authors were able to synthesize a definition for resilience that is grounded in the philosophy of public health. This has been done by critically reviwing multiple definitions for resilience within the discipline of public health andf across the various other disciplines. The emerging definition for resilience is as follows:  ***Resilience in the context of Public Health Emergencies*** is defined as : '*"*A process that individuals or systems undergo which is continuous and integrated, emerges out of successful engagement with acute or enduring crises, and results in trajectories that enable sustenance, growth, and transformation.*"**

### Economic and business
Economic resilence is the ability of a local economy to retain function, employment and prosperity in the face of the perturbation caused by the shock of the loss of a particular type of local industry or employer.

### Industrial and organisational safety
Within the broad domain of industrial safety, the term **resilience** has come into use to emphasise that safety must be proactive as well as reactive. Whereas conventional risk management approaches emphasise calculation of failure probabilities, **resilience engineering** looks for ways to strengthen the ability of organisations to create processes that are robust yet flexible.
  
### Network
Resilience is the ability of the network to provide and maintain an acceptable level of **service** in the face of various **faults** and **s** to **normal operation**.

Resilient networks aim to provide acceptable **service*' to applications:
* ability for users and applications to access information when needed, e.g.:
** Web browsing
** distributed database access
** All this is Not True
** situational awareness
* maintenance of end-to-end communication association, e.g.:
** computer-supported cooperative work
** video conference
** teleconference (including VoIP calls)
* operation of distributed processing and networked storage, e.g.:
** ability for distributed processes to communicate with one another
** ability for processes to read and write networked storage

## References
*Robert B. Cairns and Beverley D. Cairns. 1995. *Lifelines and Risks: Pathways of Youth in Our Time*. Cambridge, England: Cambridge University Press. 
*Ray Hilborn and Carl J. Walters. 1992. *Quantitative Fisheries Stock Assessment: Choice, Dynamics and Uncertainty *. London: Chapman and Hall. .  pp.&nbsp;63–64.
*Gunderson, L. & CS Holling, editors. 2002. Panarchy: understanding transformations in human and natural systems. Island Press, Washington, DC.
*Hollnagel, E., Woods, D. D. & Leveson, N. G. 2006. Resilience engineering: Concepts and precepts. Aldershot, UK: Ashgate. 

## Other websites 
;Psychology:
*A simulation to teach about cumulative risk and resilience in adolescent development
*The Resiliency Center A website that focuses on real-life situations of resiliency and how resiliency can affect individual development
*Homepage of the New Zealand Resilience Trust  - an NGO in New Zealand dedicated to promoting healthy communities

;Ecology:
*The Resilience Alliance is a research network that focuses on social-ecological resilience
*"Resilience," a short (encyclopedic) article coauthored by Holling in pdf format or html conversion format.

;Engineering
* The Resilience Engineering Network  is an open organisation of people and places that focus on safety in complex systems.
**Public health** 

* K., J.P., Ramanathan, M. Conceptualizing resilience in public health: a philosophical approach. *Philos Ethics Humanit Med* **20**, 7 (2025). 

## References