The next step in nanotechnology

2.B.解析:段落中尚无明确的段落主旨句,
可是段子中冒出了大气反映非凡细节信息的辞藻:20 microwatts(微瓦), 200
nanometers(皮米), hundreds of times smaller than the width of a human
hair, 100 million times more powerful, 225 horsepower(马力),
那么些细节音信贯穿全段, 从质量上它们各自用于描述功率和尺寸大小,
因此可直接判断B(描述了皮米引擎的功率和尺寸大小)是答案。

To start, a jet engine requires pneumatic rotation of the turbine,
AC-electrical fuel pumps, and an AC-electrical “flash” that ignites the
fuel. As the turbine (behind the combustion chamber) is already
rotating, the front inlet fans are also rotating. After the ignition,
both fans and turbine speed up their rotation. As combustion stabilizes,
the engine thereafter only needs the fuel to run at idle. The started
engine can now replace the APU when starting up further engines. During
flight the APU and its generator are not needed.

Let’s imagine a sculptor building a statue, just chipping away with his
chisel. Michelangelo had this elegant way of describing it when he said,
“Every block of stone has a statue inside of it, and it’s the task of
the sculptor to discover it.” But what if he worked in the opposite
direction? Not from a solid block of stone, but from a pile of dust,
somehow gluing millions of these particles together to form a statue.

The auxiliary fuel pump provides fuel under pressure to the fuel/air
control unit for engine starting and/or emergency use. After starting,
the engine-driven fuel pump provides fuel under pressure from the fuel
tank to the fuel/air control unit. This control unit, which essentially
replaces the carburetor, meters fuel based on the mixture control
setting, and sends it to the fuel manifold valve at a rate controlled by
the throttle. After reaching the fuel manifold valve, the fuel is
distributed to the individual fuel discharge nozzles. The discharge
nozzles, which are located in each cylinder head, inject the fuel/air
mixture directly into each cylinder intake port.

A An introduction of a Toyota’s 225 horsepower V6 engine.

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Now, computing is just one example. It’s the one that I’m interested in,
that my group is really invested in, but there are others in renewable
energy, in medicine, in structural materials, where the science is going
to tell you to move towards the nano. That’s where the biggest benefit
is. But if we’re going to do that, the scientists of today and tomorrow
are going to need new tools — tools just like the ones I described. And
they will need chemistry. That’s the point. The beauty of science is
that once you develop these new tools, they’re out there. They’re out
there forever, and anyone anywhere can pick them up and use them, and
help to deliver on the promise of nanotechnology.

In a fuel injection system, the fuel is injected either directly into
the cylinders, or just ahead of the intake valve. A fuel injection
system is considered to be less susceptible to icing than the carburetor
system. Impact icing on the air intake, however, is a possibility in
either system. Impact icing occurs when ice forms on the exterior of the
airplane, and blocks openings such as the air intake for the injection
system.

假设段落中有众所周知的“细节音信词”,
可以考虑拔取那一个细节新闻所展示的主题内容来确认段落主题。

APUs are also used to run accessories while the engines are shut down.
This allows the cabin to be comfortable while the passengers are
boarding before the aircraft’s engines are started. Electrical power is
used to run systems for preflight checks. Some APUs are also connected
to a hydraulic pump, allowing crews to operate hydraulic equipment (such
as flight controls or flaps) prior to engine start. This function can
also be used, on some aircraft, as a backup in flight in case of engine
or hydraulic failure.

I know that’s an absurd notion. It’s probably impossible. The only way
you get a statue from a pile of dust is if the statue built itself — if
somehow we could compel millions of these particles to come together to
form the statue.

Figure 4: Relationship of travel distance and speed of various portions
of propeller blade.

E The working principle of the nanomotor.

APUs providing electricity at 400 Hz are smaller and lighter than their
50/60 Hz counterparts, but are costlier; the drawback being that such
high frequency systems suffer from voltage drops.

But that was 15 years ago, and — fantastic science was done, really
important work. We’ve learned a lot. We were never able to translate
that science into new technologies — into technologies that could
actually impact people. And the reason is, these nanomaterials —
they’re like a double-edged sword. The same thing that makes them so
interesting — their small size — also makes them impossible to work
with. It’s literally like trying to build a statue out of a pile of
dust. And we just don’t have the tools that are small enough to work
with them. But even if we did, it wouldn’t really matter, because we
couldn’t one by one place millions of particles together to build a
technology. So because of that, all of the promise and all of the
excitement has remained just that: promise and excitement. We don’t have
any disease-fighting nanobots, there’s no elevators to space, and the
thing that I’m most interested in, no new types of computing.

Figure 2: The arrows in this illustration indicate the direction of
motion of the crankshaft and piston during the four-stroke cycle.

  1. Paragraph 4 ____.

  2. Although the amount of energy(能量) produced is small — 20
    microwatts( 百卓殊之一瓦) — it is quite impressive( 给人回忆深入的) in
    relation to(与…比较 )the tiny scale of the motor. The whole setup is
    less than 200 nanometers( 飞米) on a side, or hundreds of times smaller
    than the width(宽度) of a human hair. If it could be scaled up to the
    size of an automobile engine, it would be 100 million times more
    powerful(强大的) than a 丰田 Camry’s 225 horsepower(马力) V6
    engine.

If the APU fails before engine start, the engines cannot be started
without an external “start cart” to provide a source of bleed air. If
the APU fails mid-flight, there will be no immediate effect. Even
without the APU, there are two additional ways to restart an aircraft
engine in flight:

Now, as it turns out, this is not that alien of a problem. We just don’t
build anything this way. People don’t build anything this way. But if
you look around — and there’s examples everywhere — Mother Nature
builds everything this way. Everything is built from the bottom up. You
can go to the beach, you’ll find these simple organisms that use
proteins — basically molecules — to template what is essentially sand,
just plucking it from the sea and building these extraordinary
architectures with extreme diversity. And nature’s not crude like us,
just hacking away. She’s elegant and smart, building with what’s
available, molecule by molecule, making structures with a complexity and
a diversity that we can’t even approach. And she’s already at the nano.
She’s been there for hundreds of millions of years. We’re the ones that
are late to the party.

The airplane engine and propeller, often referred to as the aircraft
powerplant, work in combination to produce thrust. The powerplant
propels the airplane and drives the various systems that support the
operation of an airplane.

  1. Paragraph 2

  2. Paragraph 4

  3. Paragraph 5

  4. Paragraph 6

The APU is a small jet engine that is used to start the larger jet
engines. In airliners it’s usually at the very rear of the aircraft,
below the tail. Large engines are heavy and require a lot of torque to
spin up, more than a starter battery can generate. So, the battery spins
up a much smaller APU jet engine. High-speed bleed air from the APU is
used to spin up the main engine.

As an example: if I took the room-sized computer that sent three men to
the moon and back and somehow compressed it — compressed the world’s
greatest computer of its day, so it was the same size as your smartphone
— your actual smartphone, that thing you spent 300 bucks on and just
toss out every two years, would blow this thing away. You would not be
impressed. It couldn’t do anything that your smartphone does. It would
be slow, you couldn’t put any of your stuff on it, you could possibly
get through the first two minutes of a “Walking Dead” episode if you’re
lucky —

Reciprocating engines活塞发动机

F Possible fields of application in the future.

APUs fitted to ***extended-range twin-engine operations (ETOPS)
***aircraft are a critical safety device, as they supply backup
electricity and compressed air in place of the dead engine or failed
main engine generator. While some APUs may not be startable in flight,
ETOPS-compliant APUs must be flight-startable at altitudes up to the
aircraft service ceiling. Recent applications have specified starting up
to 43,000 ft (13,000 m) from a complete cold-soak condition such as the
Hamilton Sundstrand APS5000 for the Boeing 787 Dreamliner. If the APU or
its electrical generator is not available, the aircraft cannot be
released for ETOPS flight and is forced to take a longer non-ETOPS
route.

So we decided that we’re going to use the same tool that nature uses,
and that’s chemistry. Chemistry is the missing tool. And chemistry works
in this case because these nanoscale objects are about the same size as
molecules, so we can use them to steer these objects around, much like a
tool. That’s exactly what we’ve done in our lab. We’ve developed
chemistry that goes into the pile of dust, into the pile of
nanoparticles, and pulls out exactly the ones we need. Then we can use
chemistry to arrange literally billions of these particles into the
pattern we need to build circuits. And because we can do that, we can
build circuits that are many times faster than what anyone’s been able
to make using nanomaterials before. Chemistry’s the missing tool, and
every day our tool gets sharper and gets more precise. And eventually —
and we hope this is within a handful of years — we can deliver on one
of those original promises.

Figure 7: Float-type carburetor.

D Previous inventions of nanoscale(皮米级的) products.

APIC APS3200 APU for Airbus A320 family.
The primary purpose of an aircraft APU is to provide power to start the
main engines. Turbine engines must be accelerated to a high rotational
speed to provide sufficient air compression for self-sustaining
operation. Smaller jet engines are usually started by an electric motor,
while larger engines are usually started by an air turbine motor. Before
the engines are to be turned, the APU is started, generally by a battery
or hydraulic accumulator. Once the APU is running, it provides power
(electric, pneumatic, or hydraulic, depending on the design) to start
the aircraft’s main engines.

(Laughter)

  • Reduction in evaporative icing.
  • Better fuel flow.
  • Faster throttle response.
  • Precise control of mixture.
  • Better fuel distribution.
  • Easier cold weather starts.

提示:

  • It provides cabin air and electric power before the engines are
    started (saving battery power).
  • It provides an emergency source of electric power in the event of
    engine failure.
  • It can start the aircraft engines mid-flight in an emergency.

best365官网,The point is the progress — it’s not gradual. The progress is
relentless. It’s exponential. It compounds on itself year after year, to
the point where if you compare a technology from one generation to the
next, they’re almost unrecognizable. And we owe it to ourselves to keep
this progress going. We want to say the same thing 10, 20, 30 years from
now: look what we’ve done over the last 30 years. Yet we know this
progress may not last forever. In fact, the party’s kind of winding
down. It’s like “last call for alcohol,” right? If you look under the
covers, by many metrics like speed and performance, the progress has
already slowed to a halt. So if we want to keep this party going, we
have to do what we’ve always been able to do, and that is to innovate.

Mixture control

B A description of the nanomotor in terms of power and size.

The APU is normally left off in flight, but may be turned on for certain
long-haul overwater flights as an extra precaution.

So our group’s role and our group’s mission is to innovate by employing
carbon nanotubes, because we think that they can provide a path to
continue this pace. They are just like they sound. They’re tiny, hollow
tubes of carbon atoms, and their nanoscale size, that small size, gives
rise to these just outstanding electronic properties. And the science
tells us if we could employ them in computing, we could see up to a ten
times improvement in performance. It’s like skipping through several
technology generations in just one step.

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The Tiniest Electric Motor in the World

  • a cross-bleed start, where bleed air from a working engine is used
    to start a dead engine, or
  • a windmill start, where the aircraft dives and attains enough speed
    that ram air spins the turbine fast enough to allow a relight.

(Laughter)

The induction system brings in air from the outside, mixes it with fuel,
and delivers the fuel/air mixture to the cylinder where combustion
occurs. Outside air enters the induction system through an intake port
on the front of the engine cowling. This port normally contains an air
filter that inhibits the entry of dust and other foreign objects. Since
the filter may occasionally become clogged, an alternate source of air
must be available. Usually, the alternate air comes from inside the
engine cowling, where it bypasses a clogged air filter. Some alternate
air sources function automatically, while others operate manually.

二零零六年教材上增产了大约17篇小说,词汇选项,阅读判断, 概括大意落成句子,
阅读精晓, 补全短文, 完型填空各种题型上都有新增小说。
理工类和卫生类新增的稿子更展现专业性。新增小说的语言难度和难点考点设置处境在自然水准上显示了08年考题的出题趋势。

Aircraft with APUs can also accept electrical and pneumatic power from
ground equipment when an APU has failed or is not to be used. Some
airports reduce the use of APUs due to noise and pollution, and ground
power is used when possible.

So there we have it. We have this really important problem and we have
what is basically the ideal solution. The science is screaming at us,
“This is what you should be doing to solve your problem.” So, all right,
let’s get started, let’s do this. But you just run right back into that
double-edged sword. This “ideal solution” contains a material that’s
impossible to work with. I’d have to arrange billions of them just to
make one single computer chip. It’s that same conundrum, it’s like this
undying problem.

On a standard day at sea level with the engine shut down, the manifold
pressure gauge will indicate the ambient absolute air pressure of 29.92
in. Hg. Because atmospheric pressure decreases approximately 1 in. Hg
per 1,000 feet of altitude increase, the manifold pressure gauge will
indicate approximately 24.92 in. Hg at an airport that is 5,000 feet
above sea level with standard day conditions.

二〇〇八年课题预测分析

Once the engines are started, the APU is no longer required, but it does
provide a couple of secondary functions:

When I was a graduate student, it was one of the most exciting times to
be working in nanotechnology. There were scientific breakthroughs
happening all the time. The conferences were buzzing, there was tons of
money pouring in from funding agencies. And the reason is when objects
get really small, they’re governed by a different set of physics that
govern ordinary objects, like the ones we interact with. We call this
physics quantum mechanics. And what it tells you is that you can
precisely tune their behavior just by making seemingly small changes to
them, like adding or removing a handful of atoms, or twisting the
material. It’s like this ultimate toolkit. You really felt empowered;
you felt like you could make anything.

At a given altitude, the higher the tachometer reading, the higher the
power output of the engine.

E The working principle of the nanomotor.


And we were doing it — and by we I mean my whole generation of graduate
students. We were trying to make blazing fast computers using
nanomaterials. We were constructing quantum dots that could one day go
in your body and find and fight disease. There were even groups trying
to make an elevator to space using carbon nanotubes. You can look that
up, that’s true. Anyways, we thought it was going to affect all parts of
science and technology, from computing to medicine. And I have to admit,
I drank all of the Kool-Aid. I mean, every last drop.

  1. by cylinder arrangement with respect to the crankshaft—radial,
    in-line, v-type or opposed, or
  2. by the method of cooling—liquid or air-cooled.

365娱乐场体育投注,指定的多个段落都未曾分明的段落大旨句(二〇〇七年理工类A/B级概括大意题中三个指定段落都尚未明了段落宗旨句),考生方可因此通读指定段落的不经意来概括出段落主旨,
或倚靠一些实用的答题技巧肯定段落大旨。以确认段落第4段的段落主旨为例分析答题技巧:

延伸阅读:
An auxiliary power unit (APU) is a device on a vehicle that provides
energy for functions other than propulsion. They are commonly found on
large aircraft and naval ships as well as some large land vehicles.
Aircraft APUs generally produce 115 V alternating current (AC) at 400 Hz
(rather than 50/60 Hz in mains supply), to run the electrical systems of
the aircraft; others can produce 28 V direct current (DC). APUs can
provide power through single- or three-phase systems.
APU Function

Now that last one, that’s a really important one. We just have come to
expect the pace of computing advancements to go on indefinitely. We’ve
built entire economies on this idea. And this pace exists because of our
ability to pack more and more devices onto a computer chip. And as those
devices get smaller, they get faster, they consume less power and they
get cheaper. And it’s this convergence that gives us this incredible
pace.

Therefore, at an outside air temperature of 100°F, a temperature drop of
70°F results in an air temperature in the carburetor of 30°F.

C [u]Surface tension[/u](表面张力).

But Michael — he puts it off. Fine, I get it. Their mother’s still
alive, it would make her upset. We just said, “What’s the Fredo in our
problem?” What are we not dealing with? What are we not doing, but needs
to be done to make this a success?” And the answer is that the statue
has to build itself. We have to find a way, somehow, to compel, to
convince billions of these particles to assemble themselves into the
technology. We can’t do it for them. They have to do it for themselves.
And it’s the hard way, and this is not trivial, but in this case, it’s
the only way.

Some airplanes are equipped with a carburetor air temperature gauge,
which is useful in detecting potential icing conditions. Usually, the
face of the gauge is calibrated in degrees Celsius (°C), with a yellow
arc indicating the carburetor air temperatures where icing may occur.
This yellow arc typically ranges between -15°C and +5°C (5°F and 41°F).
If the air temperature and moisture content of the air are such that
carburetor icing is improbable, the engine can be operated with the
indicator in the yellow range with no adverse effects. However, if the
atmospheric conditions are conducive to carburetor icing, the indicator
must be kept outside the yellow arc by application of carburetor heat.

(难度B/A级/二零零六年理工类教材新增文章)

At this point, we said, “Let’s just stop. Let’s not go down that same
road. Let’s just figure out what’s missing. What are we not dealing
with? What are we not doing that needs to be done?” It’s like in “The
Godfather,” right? When Fredo betrays his brother Michael, we all know
what needs to be done. Fredo’s got to go.

Most airplanes also are equipped with an outside air temperature (OAT)
gauge calibrated in both degrees Celsius and Fahrenheit. It provides the
outside or ambient air temperature for calculating true airspeed, and
also is useful in detecting potential icing conditions.

B A description of the nanomotor in terms of power and size.

Thank you so much for your time. I appreciate it.

The fuel/air mixture is then drawn through the intake manifold and into
the combustion chambers, where it is ignited. The “float-type
carburetor” acquires its name from a float, which rests on fuel within
the float chamber. A needle attached to the float opens and closes an
opening at the bottom of the carburetor bowl.

  1. Scientists recently made public the tiniest electric motor ever
    built. You could stuff hundreds of them into the period at the end of
    this sentence. One day a similar engine might power a tiny mechanical
    doctor that would travel through your body to remove your disease.

  2. The motor works by shuffling(来回运动) atoms(原子) between two
    molten metal droplets(小滴) in a carbon nanotube(纳米管). One
    droplet is even smaller than the other. When a small electric current is
    applied to the droplets, atoms slowly get out of the larger droplet and
    join the smaller one. The small droplet grows – but never gets as big as
    the other droplet – and eventually bumps into the large droplet. As they
    touch, the large droplet rapidly sops up (吸入)the atoms it had
    previously lost. This quick shift in energy produces a power
    stroke(动力行程).

  3. The technique exploits the fact that surface tension — the tendency
    of atoms or molecules to resist separating — becomes more important at
    small scales. Surface tension is the same thing that allows some insects
    to walk on water.

  4. Although the amount of energy produced is small — 20
    microwatts(百相当之一瓦) — it is quite impressive(给人记念深切的)
    in relation to(与…相比较) the tiny scale of the motor. The whole setup
    is less than 200 nanometers on a side, or hundreds of times smaller than
    the width of a human hair. If it could be scaled up to the size of an
    automobile engine, it would be 100 million times more powerful than a
    丰田 Camry’s 225 horsepower V6 engine.

  5. In 1988, Professor Richard Muller and colleagues made the first
    operating(工作的, 运行的) micromotor(微型发动机), which was 100
    microns(微米) across, or about the thickness of a human hair. In 2003,
    Zettl’s group created the first nanoscale motor. In 2006, they built a
    nanoconveyor(皮米传送带), which moves tiny particles along like cars
    in a factory.

  6. Nanotechnology(微米技术) engineers try to mimic nature, building
    things atom-by-atom. Among other things, nanomotors could be used in
    optical circuits to redirect light, a process called optical switching.
    Futurists envision(预想) a day when nanomachines(微米机器), powered
    by nanomotors(微米引擎), travel inside your body to find disease and
    repair damaged cells.

Now, as odd as that sounds, that is almost exactly the problem I work on
in my lab. I don’t build with stone, I build with nanomaterials. They’re
these just impossibly small, fascinating little objects. They’re so
small that if this controller was a nanoparticle, a human hair would be
the size of this entire room. And they’re at the heart of a field we
call nanotechnology, which I’m sure we’ve all heard about, and we’ve all
heard how it is going to change everything.

Although some older adjustable-pitch propellers could only be adjusted
on the ground, most modern adjustable-pitch propellers are designed so
that you can change the propeller pitch in flight. The first
adjustable-pitch propeller systems provided only two pitch settings – a
low-pitch setting and a high-pitch setting. Today, however, nearly all
adjustable-pitch propeller systems are capable of a range of pitch
settings.

C [u]Surface tension[/u](表面张力).

This meters the correct amount of fuel into the carburetor, depending
upon the position of the float, which is controlled by the level of fuel
in the float chamber. When the level of the fuel forces the float to
rise, the needle valve closes the fuel opening and shuts off the fuel
flow to the carburetor. The needle valve opens again when the engine
requires additional fuel.

A An introduction of a Toyota’s 225 horsepower V6 engine.

The reason for the twist is to produce uniform lift from the hub to the
tip. As the blade rotates, there is a difference in the actual speed of
the various portions of the blade. The tip of the blade travels faster
than that part near the hub, because the tip travels a greater distance
than the hub in the same length of time.

D Previous inventions of nanoscale(微米级的) products.

When the air flows through the venturi, a low-pressure area is created,
which forces the fuel to flow through a main fuel jet located at the
throat. The fuel then flows into the airstream, where it is mixed with
the flowing air.

从二零零七年考题的出题情形和二〇〇八年教材的编写景况来看,二零零六年职称拉脱维亚语考试如故将可能从教材中摘选一部分试题直接作为考题。二零零六年考题难度应该与二零零七年考题难度相当。

The propeller is a rotating airfoil, subject to induced drag, stalls,
and other aerodynamic principles that apply to any airfoil. It provides
the necessary thrust to pull, or in some cases push, the airplane
through the air.

练习:

The aircraft powerplant part
2/2

F Possible fields of application in the future.

The climb propeller has a lower pitch, therefore less drag. Less drag
results in higher r.p.m. and more horsepower capability, which increases
performance during takeoffs and climbs, but decreases performance during
cruising flight.
The cruise propeller has a higher pitch, therefore more drag. More drag
results in lower r.p.m. and less horsepower capability, which decreases
performance during takeoffs and climbs, but increases efficiency during
cruising flight.
The propeller is usually mounted on a shaft, which may be an extension
of the engine crankshaft. In this case, the r.p.m. of the propeller
would be the same as the crankshaft r.p.m. On some engines, the
propeller is mounted on a shaft geared to the engine crankshaft. In this
type, the r.p.m. of the propeller is different than that of the engine.
In a fixed-pitch propeller, the tachometer is the indicator of engine
power.

The revolutions per minute are regulated by the throttle, which controls
the fuel/air flow to the engine.

Carburetor air temperature gauge

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