rigidity   46

An adaptability limit to climate change due to heat stress
Despite the uncertainty in future climate-change impacts, it is often assumed that humans would be able to adapt to any possible warming. Here we argue that heat stress imposes a robust upper limit to such adaptation. Peak heat stress, quantified by the wet-bulb temperature TW, is surprisingly similar across diverse climates today. TW never exceeds 31 °C. Any exceedence of 35 °C for extended periods should induce hyperthermia in humans and other mammals, as dissipation of metabolic heat becomes impossible. While this never happens now, it would begin to occur with global-mean warming of about 7 °C, calling the habitability of some regions into question. With 11–12 °C warming, such regions would spread to encompass the majority of the human population as currently distributed. Eventual warmings of 12 °C are possible from fossil fuel burning. One implication is that recent estimates of the costs of unmitigated climate change are too low unless the range of possible warming can somehow be narrowed. Heat stress also may help explain trends in the mammalian fossil record.

Trajectories of the Earth System in the Anthropocene: http://www.pnas.org/content/early/2018/07/31/1810141115
We explore the risk that self-reinforcing feedbacks could push the Earth System toward a planetary threshold that, if crossed, could prevent stabilization of the climate at intermediate temperature rises and cause continued warming on a “Hothouse Earth” pathway even as human emissions are reduced. Crossing the threshold would lead to a much higher global average temperature than any interglacial in the past 1.2 million years and to sea levels significantly higher than at any time in the Holocene. We examine the evidence that such a threshold might exist and where it might be.
study  org:nat  environment  climate-change  humanity  existence  risk  futurism  estimate  physics  thermo  prediction  temperature  nature  walls  civilization  flexibility  rigidity  embodied  multi  manifolds  plots  equilibrium  phase-transition  oscillation  comparison  complex-systems  earth 
august 2018 by nhaliday
Uniformitarianism - Wikipedia
Uniformitarianism, also known as the Doctrine of Uniformity,[1] is the assumption that the same natural laws and processes that operate in the universe now have always operated in the universe in the past and apply everywhere.[2][3] It refers to invariance in the principles underpinning science, such as the constancy of causality, or causation, throughout time,[4] but it has also been used to describe invariance of physical laws through time and space.[5] Though an unprovable postulate that cannot be verified using the scientific method, uniformitarianism has been a key first principle of virtually all fields of science.[6]

In geology, uniformitarianism has included the gradualistic concept that "the present is the key to the past" (that events occur at the same rate now as they have always done); many geologists now, however, no longer hold to a strict theory of gradualism.[7] Coined by William Whewell, the word was proposed in contrast to catastrophism[8] by British naturalists in the late 18th century, starting with the work of the geologist James Hutton. Hutton's work was later refined by scientist John Playfair and popularised by geologist Charles Lyell's Principles of Geology in 1830.[9] Today, Earth's history is considered to have been a slow, gradual process, punctuated by occasional natural catastrophic events.
concept  axioms  jargon  homo-hetero  wiki  reference  science  the-trenches  philosophy  invariance  universalism-particularism  time  spatial  religion  christianity  theos  contradiction  noble-lie  thinking  metabuch  reason  rigidity  flexibility  analytical-holistic  systematic-ad-hoc  degrees-of-freedom  absolute-relative  n-factor  explanans  the-great-west-whale  occident  sinosphere  orient  truth  earth  conceptual-vocab  metameta  history  early-modern  britain  anglo  anglosphere  roots  forms-instances  volo-avolo  deep-materialism  new-religion  logos 
january 2018 by nhaliday
Improving the Rigidity of an X2 Mill
Improving the rigidity of an X2 mill by accurately scraping the column mounting bracket and fitting a stiffening plate.
minimill  machining  rigidity  improvement 
january 2018 by adragomir
[1405.0247] Spanning rigid subgraph packing and sparse subgraph covering
Rigidity, arising in discrete geometry, is the property of a structure that does not flex. Laman provides a combinatorial characterization of rigid graphs in the Euclidean plane, and thus rigid graphs in the Euclidean plane have applications in graph theory. We discover a sufficient partition condition of packing spanning rigid subgraphs and spanning trees.As a corollary, we show that a simple graph G contains a packing of k spanning rigid subgraphs and l spanning trees if G is (4k+2l)-edge-connected, and G−Z is essentially (6k+2l−2k|Z|)-edge-connected for every Z⊂V(G). Thus every (4k+2l)-connected and essentially (6k+2l)-connected graph G contains a packing of k spanning rigid subgraphs and l spanning trees. Utilizing it, we show that every 6-connected and essentially 8-connected graph G contains a spanning tree T such that G−E(T) is 2-connected. These improve some previous results. Sparse subgraph covering problems are also studied.
graph-theory  rigidity  classification  proof  feature-construction  rather-interesting  to-write-about  nudge-targets  consider:looking-to-see  consider:rediscovery 
september 2017 by Vaguery
rotational dynamics - Why do non-rigid bodies try to increase their moment of inertia? - Physics Stack Exchange
This happens to isolated rotating system that is not a rigid body.

Inside such a body (for example, steel chain in free fall) the parts move relatively to each other and there is internal friction that dissipates kinetic energy of the system, while angular momentum is conserved. The dissipation goes on until the parts stop moving with respect to each other, so body rotates as a rigid body, even if it is not rigid by constitution.

The rotating state of the body that has the lowest kinetic energy for given angular momentum is that in which the body has the greatest moment of inertia (with respect to center of mass). For example, a long chain thrown into free fall will twist and turn until it is all straight and rotating as rigid body.

...

If LL is constant (net torque of external forces acting on the system is zero) and the constitution and initial conditions allow it, the system's dissipation will work to diminish energy until it has the minimum value, which happens for maximum IaIa possible.
nibble  q-n-a  overflow  physics  mechanics  tidbits  spatial  rigidity  flexibility  invariance  direction  stylized-facts  dynamical  volo-avolo  street-fighting  yoga 
august 2017 by nhaliday
Tidal locking - Wikipedia
The Moon's rotation and orbital periods are tidally locked with each other, so no matter when the Moon is observed from Earth the same hemisphere of the Moon is always seen. The far side of the Moon was not seen until 1959, when photographs of most of the far side were transmitted from the Soviet spacecraft Luna 3.[12]

never actually thought about this
nibble  wiki  reference  space  mechanics  gravity  navigation  explanation  flux-stasis  marginal  volo-avolo  spatial  direction  invariance  physics  flexibility  rigidity  time  identity  phase-transition  being-becoming 
august 2017 by nhaliday
When Automation Makes Passengers Freight: United Airlines and Seat Assignments
By omitting qualitative research, companies are unable to truly know what they don’t know
unitedairlines  data  algorithm  agency  humanagency  process  automation  rigidity 
april 2017 by benandi
More on Multivariate Gaussians
Fact #1: mean and covariance uniquely determine distribution
Fact #3: closure under sum, marginalizing, and conditioning
covariance of conditional distribution is given by a Schur complement (independent of x_B. is that obvious?)
pdf  exposition  lecture-notes  stanford  nibble  distribution  acm  machine-learning  probability  levers  calculation  ground-up  characterization  rigidity  closure  nitty-gritty  linear-algebra  properties 
february 2017 by nhaliday
ca.analysis and odes - Why do functions in complex analysis behave so well? (as opposed to functions in real analysis) - MathOverflow
Well, real-valued analytic functions are just as rigid as their complex-valued counterparts. The true question is why complex smooth (or complex differentiable) functions are automatically complex analytic, whilst real smooth (or real differentiable) functions need not be real analytic.
q-n-a  overflow  math  math.CA  math.CV  synthesis  curiosity  gowers  oly  mathtariat  tcstariat  comparison  rigidity  smoothness  singularity  regularity  nibble 
january 2017 by nhaliday
Existence of the moment generating function and variance - Cross Validated
This question provides a nice opportunity to collect some facts on moment-generating functions (mgf).

In the answer below, we do the following:
1. Show that if the mgf is finite for at least one (strictly) positive value and one negative value, then all positive moments of X are finite (including nonintegral moments).
2. Prove that the condition in the first item above is equivalent to the distribution of X having exponentially bounded tails. In other words, the tails of X fall off at least as fast as those of an exponential random variable Z (up to a constant).
3. Provide a quick note on the characterization of the distribution by its mgf provided it satisfies the condition in item 1.
4. Explore some examples and counterexamples to aid our intuition and, particularly, to show that we should not read undue importance into the lack of finiteness of the mgf.
q-n-a  overflow  math  stats  acm  probability  characterization  concept  moments  distribution  examples  counterexample  tails  rigidity  nibble  existence  s:null  convergence  series 
january 2017 by nhaliday
pr.probability - When are probability distributions completely determined by their moments? - MathOverflow
Roughly speaking, if the sequence of moments doesn't grow too quickly, then the distribution is determined by its moments. One sufficient condition is that if the moment generating function of a random variable has positive radius of convergence, then that random variable is determined by its moments.
q-n-a  overflow  math  acm  probability  characterization  tidbits  moments  rigidity  nibble  existence  convergence  series 
january 2017 by nhaliday

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