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RSID: <<2024-12-13T00:31Z MFSK-32 @ 9265000+1500>>
 

Welcome to program 381 of Shortwave Radiogram.

I'm Kim Andrew Elliott in Arlington, Virginia USA.

Here is the lineup for today's program, in MFSK modes as noted:

  1:43 MFSK32: Program preview (now)
  2:53 MFSK32: Mathematician solves the moving sofa problem*
  7:48 MFSK64: Are buildings made of wood sustainable?
13:16 MFSK64: This week's images*
27:52 MFSK32: Closing announcements

* with image(s)


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From Phys.org:

Mathematician solves the moving sofa problem

by Bob Yirka
December 11, 2024

A mathematician at Yonsei University, in Korea, claims to have
solved the moving sofa problem. Jineon Baek has posted a
100+-page proof of the problem on the arXiv preprint server.

Most people who have moved their place of residence have
encountered the the moving sofa problem—it comes up when
attempting to carry a couch around a corner. What is the largest
couch that can be carried around a given corner without getting
stuck? This problem was posited mathematically by mathematician
Leo Moser back in 1966, and until now, has remained unsolved.

Moser's initial thoughts centered on the possibility of
developing a proof showing how mathematics could be used to solve
any such problem using a given shape of a plane as it was moved
around a right-angled corner of an empty space (such as a
hallway) that was one unit in width.

In his work, Baek chose the Gerver sofa as a demonstration shape.
The Gerver sofa is a mathematical construct developed by Joseph
Gerver, a professor at Rutgers University, in 1992. It is
basically a cuboid with a U-shaped front, a flat back with
rounded edges and flat, front-facing arms.

After first, clearly defining the problem, Baek applies
mathematical tools to move through the proof step by step before
eventually arriving at the answer: For a hall of 1 unit, a Gerver
sofa's maximum area can only be 2.2195 units. As part of the
proof, Baek also narrowly defined the shape of the Gerver sofa he
was using. Thus, different interpretations of the sofa shape
would result in different answers.

Because the shape of the sofa is clearly defined at the outset,
the answer Baek found could conceivably be used in the real world
by people attempting to move a couch around a corner—though it
would have to conform to the interpretation of a Gerver sofa as
defined in the proof.

As with all such math proofs, Baek's will have to undergo
scrutiny by other mathematicians to ensure his proof is correct
and actually results in the optimal solution to a given problem.

https://phys.org/news/2024-12-mathematician-sofa-problem.html

Image: The movement of a moving sofa in the perspective of
hallway (top) and sofa (bottom) ...

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From TechXplore.org:

High rises made out of wood? What matters in whether 'mass
timber' buildings are sustainable

by Brent Sohngen
The Conversation
December 11, 2024

A material that's been around since people built shelters—wood—is
increasingly being proposed for low- and mid-rise buildings.

Companies behind these "mass timber" projects say that wood is a
lower-carbon alternative to steel or concrete and brings other
benefits, such as faster construction time and lower cost than
concrete and steel. Advocates say the wood materials, made of
compressed layers of wood with glue, offer good fire safety as
well.

As an economist who studies forestry and natural resources, I
took an interest in this building trend when I heard that a local
bar on campus was going to be replaced by a 13-story building
made out of wood.

I see any increase in the use of wood in buildings as positive
for reducing the substantial carbon footprint of buildings. But
it is critical to consider where wood is sourced and whether
forests are managed sustainably.

The work forests do

One way that researchers assess the environmental footprint of a
product or service is called a life-cycle analysis, which
calculates the cradle-to-grave impact.

One life-cycle analysis found that using mass timber in a
12-story building in Oregon had an 18% lower global warming
impact compared with constructing the building with
steel-reinforced concrete. The carbon emissions benefits are even
greater when comparing timber with steel for low- and mid-rise
buildings. In these studies, the global warming benefits mostly
result from lower emissions in sourcing, transporting and
manufacturing the material for these large wood buildings,
compared with steel or concrete components, rather than
efficiencies in heating or cooling or disposal of the materials
at the end of the building's lifespan.

On a global level, the raw material for mass
timber—forests—absorb large amounts of carbon dioxide from the
atmosphere, making them an important carbon "sink."

Tree cutting is one of the most widespread disturbances in
forests, yet, after accounting for all harvesting, fires, land
use change and other disturbances, forests in the United States
still remove a net 754 million tons of CO2 per year from the
atmosphere, an amount equivalent to 13.5% of U.S. emissions.
Globally, the picture is similar, with forest growth removing 2.6
billion tons of CO2 more from the atmosphere than the combined
effect of all wood harvesting, deforestation, forest fires and
other disturbances.

Although today forests are a net CO2 sink in the U.S.—taking in
more carbon from the atmosphere than released through
disturbance—before the middle of the last century, they were a
big source of carbon emissions. Back then, farmers converted land
to agriculture, foresters cut old-growth trees to produce lumber,
and forest fires raged. Carbon losses in the U.S. were so large
that land-based emissions around the turn of the 20th century
were on par with emissions from deforestation in tropical regions
today.

Over the past 100 years, the trend has reversed, as forests have
removed far more CO2 from the atmosphere than they have released.
One reason for this transition has been a sustained increase in
crop yields, which has allowed for greater farm output on fewer
acres. As a result, grain prices fell in real terms and farmers
abandoned less productive lands, allowing forests to return.
These regrowing forests, in turn, removed carbon from the
atmosphere.

Abandonment was not the only reason trees regrew in the U.S. Even
as foresters were still sawing their way through old-growth
stocks in the first half of the 1900s, some foresighted forest
landowners began planting trees because timber scarcity was
growing, as evidenced by timber prices rising at 3% to 4% per
year. By the 1950s and 1960s, over a billion acres were being
planted annually in the U.S., and today, the area planted is
double that.

Economics of forest management

To examine whether wood is sustainably sourced, rather than
contributing to higher carbon emissions, it is instructive to
consider the economics of forest management.

A shift toward using wood rather than other materials in low- to
mid-rise building designs will drive demand for wood products,
resulting in both more harvesting and more planting. Any increase
in harvesting carries risk, including an increase in carbon
emissions, habitat loss, and other impacts. Perhaps the most
evident effects happen when surging demand causes logging in
sensitive ecosystems, critical habitats or old-growth forests. If
lost, ecosystem services like biodiversity are often impossible
to replace.

Carbon may be less of a worry because it can be returned to
forests through regrowth. However, some critics maintain that
harvests deposit CO2 in the atmosphere for the period between a
timber harvest and forest regrowth, resulting in a massive CO2
emission.

There is considerable debate about this "excess" emissions
hypothesis. Other research into the effects of increased wood
demand illustrates that both harvesting and regeneration increase
when demand rises. When timber investments are modeled alongside
harvesting, carbon stocks in forested lands increase when wood
demand ratchets up. This finding is not new. The example of the
last century reveals that elevated timber demand and higher wood
product prices strengthen incentives for landowners to
intensively manage commercial forests—plant more acres, improve
varieties, shift species mixes, fertilize, control drainage and
manage competition.

The sustainability of mass timber will also be determined by
which forests supply this new demand. It is unlikely that much of
this new harvesting will happen on the 42% of U.S. forests owned
by various units of government.. Many of these forests are either
administratively protected—for example, as a wilderness area—or
are remote and costly to access. Where cutting is allowed,
logging is slowed by the considerable planning, impact assessment
and public involvement required.

Even many private landowners have gotten into the habit of
protecting for the purpose of environmental services. Today, over
37 million acres of private land in the U.S. are enrolled in
conservation easements, which limit what current and future
owners can do with their land. Not all of these protected lands
are forests, but where they are, new demands for mass timber are
unlikely to result in more harvesting.

Aside from these legally protected lands, forest protection
happens in many private forests simply because many forest owners
are inattentive or they have strong preferences for wildlife and
benefits other than timber revenue. As a result, research has
found that nonindustrial landowners as a whole are unlikely to
expand cutting even if demand does grow substantively.

Full text:
https://techxplore.com/news/2024-12-high-wood-mass-timber-sustainable.html
 

This is Shortwave Radiogram in MFSK64

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This week's images ...



Lake Toolondo Aurora, Australia, part of the Northern Lights
Photographer of the Year collection (in this case Southern
Lights). https://tinyurl.com/29cuvdmn ...

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A light show with Christmas tree at the Grand-Place in Brussels,
November 29. https://tinyurl.com/2ykf4seq ...

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A very red sunset seen from Northwest Washington DC on December
7. https://tinyurl.com/294gy9qb ...

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Red berries bring some color to winter at the Tyler Arboretum
near Philadelphia. https://tinyurl.com/2ahp6fjg ...

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Dogs on the National Mall in foggy Washington DC, with the
Smithsonian Castle in the background, December 10.
https://tinyurl.com/24syvgj9 ...

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"Olive oil and water droplets" from BBC pictorial on the theme of
fluids. https://tinyurl.com/27vjfpxb ...

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Christmas lights on a tree at the Westonbirt Arboretum in
England. https://tinyurl.com/24z34smt ...

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Our painting of the week is "At Close of Day" by Maxfield Parrish
(1941). https://tinyurl.com/25dkw33w ...

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This is Shortwave Radiogram in MFSK32 ...


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I'm Kim Elliott. Please join us for the next Shortwave
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