title: On the origin of anisotropy in magnetohydrodynamic turbulence: the role of higher-order correlations

authors: Oughton, Sean

subjects: magnetic fields

abstract: Evolution of magnetohydrodynamic turbulence is often discussed in terms of second-order statistics like the energy spectra, but consideration of the structure of the von K´arm´an–Howarth hierarchy for MHD indicates that higherorder statistical correlations occupy an influential role. Here we show that both spectral anisotropy and energy decay are strongly associated with higher-order statistics. Dynamical emergence of spectral anisotropy must occur at a higher order in the statistical hierarchy, while numerical evidence suggests that strong variations in energy decay are connected with variations in higher-order statistics.

text: On the origin of anisotropy in magnetohydrodynamic turbulence: the role of higher-order correlations Evolution of magnetohydrodynamic turbulence is often discussed in terms of second-order statistics like the energy spectra, but consideration of the structure of the von K´arm´an–Howarth hierarchy for MHD indicates that higherorder statistical correlations occupy an influential role. Here we show that both spectral anisotropy and energy decay are strongly associated with higher-order statistics. Dynamical emergence of spectral anisotropy must occur at a higher order in the statistical hierarchy, while numerical evidence suggests that strong variations in energy decay are connected with variations in higher-order statistics.

year: 2013

title: Network Simulation Cradle

authors: Jansen, Samuel Thomas

subjects: computer

abstract: This thesis proposes the use of real world network stacks instead of protocol
abstractions in a network simulator, bringing the actual code used in
computer systems inside the simulator and allowing for greater simulation
accuracy. Specifically, a framework called the Network Simulation
Cradle is created that supports the kernel source code from FreeBSD, OpenBSD
and Linux to make the network stacks from these systems available to the
popular network simulator ns-2.

Simulating with these real world network stacks reveals situations where the
result differs significantly from ns-2's TCP models. The simulated
network stacks are able to be directly compared to the same operating system
running on an actual machine, making validation simple. When measuring the
packet traces produced on a test network and in simulation the results are
nearly identical, a level of accuracy previously unavailable using traditional
TCP simulation models. The results of simulations run comparing ns-2 TCP
models and our framework are presented in this dissertation along with
validation studies of our framework showing how closely simulation resembles
real world computers.

Using real world stacks to simulate TCP is a complementary approach to using
the existing TCP models and provides an extra level of validation. This way of
simulating TCP and other protocols provides the network researcher or engineer
new possibilities. One example is using the framework as a protocol
development environment, which allows user-level development of protocols with
a standard set of reproducible tests, the ability to test scenarios which are
costly or impossible to build physically, and being able to trace and debug
the protocol code without affecting results.

text: Network Simulation Cradle This thesis proposes the use of real world network stacks instead of protocol
abstractions in a network simulator, bringing the actual code used in
computer systems inside the simulator and allowing for greater simulation
accuracy. Specifically, a framework called the Network Simulation
Cradle is created that supports the kernel source code from FreeBSD, OpenBSD
and Linux to make the network stacks from these systems available to the
popular network simulator ns-2.

Simulating with these real world network stacks reveals situations where the
result differs significantly from ns-2's TCP models. The simulated
network stacks are able to be directly compared to the same operating system
running on an actual machine, making validation simple. When measuring the
packet traces produced on a test network and in simulation the results are
nearly identical, a level of accuracy previously unavailable using traditional
TCP simulation models. The results of simulations run comparing ns-2 TCP
models and our framework are presented in this dissertation along with
validation studies of our framework showing how closely simulation resembles
real world computers.

Using real world stacks to simulate TCP is a complementary approach to using
the existing TCP models and provides an extra level of validation. This way of
simulating TCP and other protocols provides the network researcher or engineer
new possibilities. One example is using the framework as a protocol
development environment, which allows user-level development of protocols with
a standard set of reproducible tests, the ability to test scenarios which are
costly or impossible to build physically, and being able to trace and debug
the protocol code without affecting results.

year: 2008

title: Re-presenting Māori and Indigenous understandings of Being: Deconstructing the notion of mental illness

authors: Southey, Kim Marie

subjects: Maori

abstract: This thesis examines metaphysics in order to re-present Māori and indigenous understandings of Being and deconstruct the notion of mental illness.  A holistic understanding of Being is crucial to Māori and indigenous worldviews and takes priority as a focus for this thesis. Holistic notions of Being allow indigenous peoples to reimagine potentiality in general and the possibility of a renewed experience of being-in-the-world more specifically. Through an exploration of Māori and indigenous (complex) holism, I seek to re-turn to the influence of things in the world that exist outside of the self-contained individual - that is, beyond the cognitive rational agent.  Doing so shifts the concept of well-being to reside not simply within the person (or the individual’s reactions), but within the entire world in which we live.  

It is posited that a dominant Western metaphysics poses a fundamental risk to Māori and indigenous expressions of Being.  This deeper layer of influence – the metaphysics of presence - is examined to expose its structure – one that insists that things in the world will be represented as fully discernible objects.  The implications that a dominant Western metaphysics has for the notion of mental illness are explored within the context of the metaphysics of presence that sets up things in the world as Beings whose essential meaning is identified only through qualities that can be seen, measured, described and defined.  Within this view of the world, the notion of mental illness is solidified, reflected in a focus on the most discernible aspects of Being – the observable and physical parts of a person that can be examined through science.  To counter this, the more mysterious and unthinkable aspects of Being reflected in Māori and indigenous metaphysics are highlighted as a way of re-turning to holism, to the extent that they resist the expectation that things in the world will be reduced to fit the dominant (metaphysical) framework.  

I engage the relational holistic research approach of whaiwhakaaro (a non-method implicating the more-than-human entities that push thinking and characterised by a free-flowing style of reflection), to draw out the possibilities that exist for re-presenting Māori and indigenous metaphysics and the notion of mental illness.  Eleven interviews were conducted with participants from varying professional and community-based backgrounds.  While the participants represent different views on metaphysics and mental illness, each has a passion for exploring the philosophies that shape the experience of being-in-the-world and how we understand ourselves in relation to all other things.  Their responses provide important signals for how human nature, more-than-human nature, and (mental) well-being are re-conceptualised.  

The main ideas that emerged through the interviews and the process of reflecting on participant responses (whaiwhakaaro) provoked thinking about the possibilities of holism in reconsidering the notion of mental illness.  Māori and indigenous understandings of Being were used to re-turn to ideas of well-being as a collective experience. I posit that, if there is illness, then it resides in the world rather than being centred solely on the individual who experiences the world.  If there is a way to talk about illness and well-being, then it need not be restricted to assigned concepts or pre-determined categories that explain behaviour.  Through a re-turn to complex holism – to Māori and indigenous metaphysical premises – I suggest we can engage with people’s experiences on different terms.  These are the terms that carry excessive meaning, that allow for mystery – to break from conventions and categories. These terms support a different view of individualism where the person is free to express their experience of thorough interconnection – of whakapapa.  In its broadest sense, the re-turn to holism is an understanding of the self as part of a thoroughly connected whole.

text: Re-presenting Māori and Indigenous understandings of Being: Deconstructing the notion of mental illness This thesis examines metaphysics in order to re-present Māori and indigenous understandings of Being and deconstruct the notion of mental illness.  A holistic understanding of Being is crucial to Māori and indigenous worldviews and takes priority as a focus for this thesis. Holistic notions of Being allow indigenous peoples to reimagine potentiality in general and the possibility of a renewed experience of being-in-the-world more specifically. Through an exploration of Māori and indigenous (complex) holism, I seek to re-turn to the influence of things in the world that exist outside of the self-contained individual - that is, beyond the cognitive rational agent.  Doing so shifts the concept of well-being to reside not simply within the person (or the individual’s reactions), but within the entire world in which we live.  

It is posited that a dominant Western metaphysics poses a fundamental risk to Māori and indigenous expressions of Being.  This deeper layer of influence – the metaphysics of presence - is examined to expose its structure – one that insists that things in the world will be represented as fully discernible objects.  The implications that a dominant Western metaphysics has for the notion of mental illness are explored within the context of the metaphysics of presence that sets up things in the world as Beings whose essential meaning is identified only through qualities that can be seen, measured, described and defined.  Within this view of the world, the notion of mental illness is solidified, reflected in a focus on the most discernible aspects of Being – the observable and physical parts of a person that can be examined through science.  To counter this, the more mysterious and unthinkable aspects of Being reflected in Māori and indigenous metaphysics are highlighted as a way of re-turning to holism, to the extent that they resist the expectation that things in the world will be reduced to fit the dominant (metaphysical) framework.  

I engage the relational holistic research approach of whaiwhakaaro (a non-method implicating the more-than-human entities that push thinking and characterised by a free-flowing style of reflection), to draw out the possibilities that exist for re-presenting Māori and indigenous metaphysics and the notion of mental illness.  Eleven interviews were conducted with participants from varying professional and community-based backgrounds.  While the participants represent different views on metaphysics and mental illness, each has a passion for exploring the philosophies that shape the experience of being-in-the-world and how we understand ourselves in relation to all other things.  Their responses provide important signals for how human nature, more-than-human nature, and (mental) well-being are re-conceptualised.  

The main ideas that emerged through the interviews and the process of reflecting on participant responses (whaiwhakaaro) provoked thinking about the possibilities of holism in reconsidering the notion of mental illness.  Māori and indigenous understandings of Being were used to re-turn to ideas of well-being as a collective experience. I posit that, if there is illness, then it resides in the world rather than being centred solely on the individual who experiences the world.  If there is a way to talk about illness and well-being, then it need not be restricted to assigned concepts or pre-determined categories that explain behaviour.  Through a re-turn to complex holism – to Māori and indigenous metaphysical premises – I suggest we can engage with people’s experiences on different terms.  These are the terms that carry excessive meaning, that allow for mystery – to break from conventions and categories. These terms support a different view of individualism where the person is free to express their experience of thorough interconnection – of whakapapa.  In its broadest sense, the re-turn to holism is an understanding of the self as part of a thoroughly connected whole.

year: 2020