The Bauhaus movement and its influence today
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Monday, 24 October 2022
The Bauhaus movement and its influence today
Monday, 10 October 2022
What may this year's Nobel Prizes in Physics mean?
What
may this year's Nobel Prizes in Physics mean?
Who and why were
they awarded?
Have you heard? The 2022 Nobel Prize in Physics
was awarded jointly to Alain Aspect, John F. Clauser and Anton Zeilinger.
All three laureates received the prize because
of their fundamental contributions to quantum mechanics, relating to
experiments with entangled/coupled, photons. These experiments showed that
information can be transmitted directly over infinite distances, known as
quantum teleportation.
What is Bell's
theorem?
The prize winners' experiments follow what is
known as Bell's theorem. In simple terms, according to this theorem, what is
attempted is to measure whether quantum mechanics approximates Newtonian mechanics,
which is based on events that occur on a local scale (e.g. two balls colliding,
after the collision they only affect each other) or whether, for example, the
particles used in an experiment can be influenced by other particles that may
be located at extremely large distances.
Bell's theorem argues that if certain
predictions of quantum theory are correct, then our world is non-local.
"Non-local" means that there are interactions between events that are
far apart in space and very close together in time. What does this mean? Quite
simply it means that if the quantum approximation is correct then events are
connected even by signals moving at the speed of light. This theorem was proved
in 1964 by John Stewart Bell and over the last few decades has been the subject
of extensive analysis, debate and development by both experimental and
theoretical physicists. The relevant predictions of quantum theory were first
convincingly confirmed by the experiment of Aspect and his collaborators in
1982. Since then they have been confirmed many times. In the context of the
predictions of Bell's theorem, the experiments prove that our world is
non-local. This conclusion is very surprising, given that non-locality seems -
without being 100% sure - not to be predicted by Einstein's theory ofrelativity.
Is quantum
non-locality incompatible with Einstein's relativity?
Here is an important issue, then! Is
non-locality incompatible with fundamental relativity? To attempt to answer
this question one has to face a significant difficulty: What does it mean that
a theory can be characterized as fundamentally relativistic? It may seem
strange that such a difficulty exists for scientists today. For example, one
might think that Maxwell's Einsteinian electromagnetism is a fundamentally
relativistic theory, whereas Newtonian mechanics is not. Obviously, for many
theories of physics it is indeed straightforward to label them as fundamentally
relativistic or not. However, there is a way to show that it is not easy to
precisely formulate the notion of a "fundamentally relativistic
theory", and as far as theories of quantum phenomena are concerned things
are not clear; no scientist today seems to know what a fundamentally
relativistic theory should look like in the quantum world.
Conclusion
We may summarily say that it remains unclear
exactly what "fundamental relativity" means or requires. Therefore,
whether Bell's theorem and related experiments can be compatible with
fundamental relativity remains largely an open question and no one, even after
this year's Nobel Prizes in Physics, could say with certainty that non-locality
is incompatible with Einsteinian relativity.
Friday, 7 October 2022
Why one-way streets are not a good solution
Why
one-way streets are not a good solution
The Served Trips Capacity "STC" is
increased when two-way streets are acquired in the street network
Based on the established transport planning
mentality of the past decades, when it was considered that one-way streets were
a solution in order to improve mobility, the trend towards two-way streets in
cities one could say that it would have puzzled some people - even experts scientists,
traffic engineers!
In the USA, the UK and elsewhere, cities such
as Dallas, Denver, Sacramento, Tampa, London, Sheffield, etc. have already
converted one-way streets into two-way streets in recent years. This shift in
transport planning in areas where a network of two-way roads was implemented
led to the achievement of:
·
Revitalisation, as traffic flow ιn one-way streets is continuous, making
it difficult for cyclists and pedestrians in the area where the one-way streets
are located.
·
Facilitation for commuters, as the one-way streets networks on
the one hand cause confusion for drivers, which ultimately leads to more
vehicle-kilometres travelled, on the other hand, they make it more difficult
for bus passengers to locate stops for a return trip
·
Improved safety, as speeds tend to be higher on the
one-way streets and some studies show that drivers pay less attention while
using them because there is in fact no traffic flow in the opposite direction
·
Economic upgrading of these areas, as local businesses
are more visible when driving in two-way streets
When the transport planning of cities, in
previous decades, was oriented towards one-way streets in order to facilitate
traffic flow there was, in fact, some substance to it. Indeed, to a large
extent, with one-way streets the difficult left turns, which create a conflict
with the opposing traffic, are eliminated. It is also true that any way of
avoiding this conflict because of left turns on two-way streets, creates
traffic congestion, as the establishment of separate left-turn lanes causes
space to be taken up while traffic signal control causes time to be wasted.
It was, because now it is no longer the
dominant view, as there is a shift in the against one-way approach, as the
trend now is for one-way streets to be converted into two-way streets in order
for cities to benefit from the above mentioned advantages of areas with two-way
streets. In addition to these advantages, two-way streets lead to the improvement
of:
·
traffic
congestion
·
the
Served Trips Capacity "STC"
In order to understand these beneficial effects
of areas with two-way streets, it should be borne in mind that the traditional
traffic flow measurement, with which most people are familiar, offers no more
than the information of how many vehicles pass in front of the measurement
point. It is reasonable and predictable that the flow is high on one-way
streets because there is no reason for vehicles to slow down. However, traffic
flow is a quantity that does not take into account the fact that moving through
one-way systems often means that a circuitous route through the area must be
followed in order to get to the desired destination. This detour adds distance
travelled to each trip.
However, by introducing the quantity of the Served
Trips Capacity "STC" and measuring it on a street network, one can
have a realistic estimate of the serving capacity of the network. The STC is
the ratio of two quantities:
·
the
traffic flow capacity, which is determined by the number of vehicles that can
pass through an intersection during a signal cycle, and
·
the
average trip length
Well, research shows that two-way street
networks can serve more trips per time unit than one-way street networks when
the average trip length is short. This is because STC takes into account both
traffic flow and additional travelled distance. A comparison of one-way streets
with different types of two-way streets (e.g., full left-turn lanes, with
left-turn pockets and streets where left turns are banned) is illustrated in
the graph below.
What the graph shows is that, for short trips
(origin-destination), two-way streets perform about as good or better than
one-way streets, whose traffic flow cannot compensate for the additional trip
distance. In the case of longer trip distances, one-way streets start to
perform better, but never reach the STC of two-way streets with banned left
turns (see the dotted red line). The particularity of this type of system (two-way
streets with banned left turns) is that it combines the traffic flow of a
one-way street with the directness of a two-way street. Such streets provide
the higher speeds that a one-way street would have, but with less trip distance
than a one-way street.
Conclusion
Cities wishing to improve the "STC" Served Mobility Capacity in some of their areas should:
·
Increase the number of two-way streets regarding areas with short trip lengths
· Increase the number of two-way streets by banning left turns or at least
providing some options for left turns regarding areas with long trip lengths
Thus, in any case, one-way streets are not
appropriate, and it is advisable to reduce their number in order to
increase the commuters serving capacity.