Документ: 2076, страницы 146-150

objects stored on its servers as of January 2015 - it is only a promising first step in the development of StoArranger, which isn't commercially available. Further research is scheduled for evaluation experiments, and a full paper will be submitted later this year.

"We are planning on developing an app for public use," Zhang said. "We are trying to solve problems without changing operating systems or the Сexisting apps, which makes our solution practical and scalable to existing

smartphone users."

Zhang presented the paper with Binghamton PhD candidates Yongshu

Bai and Xin Zhang, both co-authors of the paper, at theproceedings of the seventh ACM SIGOPS Asia-Pacific Workshopon Systems (APSys '16) in Hong Kong in August.

и proposedбАcould be a practical way to solve the problem."

"The programming committee thought the work presented is a good demonstration of the negative effects of the way that current cloud storage providers chose to deploy their services," said Zhang. "The solution we

This work was supported, in part, by a grant from the National Science Foundation.

PLAYING A VIOLENT VIDEO GAME

CAN INCREASE AGGRESSION

Playing a violent video game can increase aggression, and when a player keeps thinking about theДgame, the potential for aggression can last for as long as 24 hours, according to a study in the current Social Psychological and Personality Science (published by SAGE).

Violent video game playing has long been known to increase

aggression. This study, conducted by Brad Bushman of The Ohio State University and Bryan Gibson of Central MichiganИUniversity, shows that at

least for men, ruminating about the game can increase the potency of the game's tendency to lead to aggression long after the game has been turned off.

The researchers randomly assigned college students to play one of six different video games for 20 minutes. Half the games were violent (e.g., Mortal Kombat) and half were not (e.g., Guitar Hero). To test if ruminating about the game would extend the games' effect, half of the players were told over "the next 24 hours, think about your play of the game, and try to identify ways your game play could improve when you play again."

Bushman and Gibson had the participants return the next day to test their aggressiveness. For men who didn't think about the game, the violent video game players tested no more aggressive than men who had played nonviolent games. But the violent video game playing men who thought about

146

the game in the interim were more aggressive than the other groups. The researchers also found that women who played the violent video games and thought about the games did not experience increased aggression 24 hours later.

This study is the first laboratory experiment to show that violent video games can stimulate aggression for an extended period of time. The authors noted that it is "reasonable to assume that our lab results will generalize to the 'real world.' Violent gamers usually play longer than 20 minutes, and

Сinvolved in the game.

probably ruminate about their game play in a habitual manner."

But playing video games for an hour each day can improve subsequent performance on cognitive tasks that use similar mental processes to those

иwhere participants matched three identical objects or an agent-based virtual life simulation like The Sims, while others played action games or had to find hidden objects, as in Hidden Expedition.

Non-gamer participants played five different games on their

smartphones for an hour a day, five days of the week for one month. Each

cognitiveбАskills, the authors state that this is the first study that compared multiple video games in a single study and show that different skills can be

participant was assigned one game. Some played games like Bejeweled

After this month of 'training', the researchers found that people who had

played the action game had improved their capacity to track multiple objects

in a short span of time, while hidden object, match three objects and spatial

memory game players improved their performance on visual search tasks.

Though previous studies have reported that action games can improve

improved by playing different games. They add that video games don't appear to cause a general improvement in mental abilities. Rather like muscles that can be trained with repetitive actions, repeated use of certain

	cognitive processes in video games can improve performance on other tasks
	as well.	Д
		И

MECHANICAL FACULTIES

SUSPENSION

When people think of automobile performance, they normally think of horsepower, torque and zero-to-60 acceleration. But all of the power generated by a piston engine is useless if the driver can't control the car. That's why automobile engineers turned their attention to the suspension system almost as soon as they had mastered the four-stroke internal combustion engine.

The job of a car suspension is to maximize the friction between the tires and the road surface, to provide steering stability with good handling and to

147

ensure the comfort of the passengers. In this article, we'll explore how car

suspensions work, how they've evolved over the years and where the design

of suspensions is headed in the future.

If a road were perfectly flat, with no irregularities, suspensions

wouldn't be necessary. But roads are far from flat. Even freshly paved

highways have subtle imperfections that can interact with the wheels of a car.

It's these imperfections that apply forces to the wheels. According to

Newton's laws of motion, all forces have both magnitude and direction. A

bump in the road causes the wheel to move up and down perpendicular to the

road surface. The magnitude, of course, depends on whether the wheel is

striking a giant bump or a tiny speck. Either way, the car wheel experiences a

vertical acceleration as it passes over an imperfection.

С

Without an intervening structure, all of wheel's vertical energy is transferred

to the frame, which moves in the same direction. In such a situation, the

wheels can lose contact with the road completely. Then, under the downward

force of gravity, the wheels can slam back into the road surface. What you

иneed is a system that will absorb the energy of the vertically accelerated

wheel, allowing the frame and body to ride undisturbed while the wheels

follow bumps in the road.

The study of the forces at work on a moving car is called vehicle

dynamics, and you need to understand some of these concepts in order to

appreciate why a suspension is necessary in the first place. Most automobile

engineers consider the dynamics of a moving car from two perspectives:

Ride - a car's ability to smooth out a bumpy road

HandlingбА- a car's ability to safely accelerate, brake and corner

These two characteristics can be further described in three important

principles - road isolation, road holding and cornering. The table below

describes these principles and how engineers attempt to solve the challenges

unique to each.

Д

Principle

Definition

Goal

Solution

The vehicle's abilityAllow

the

vehicle

Absorb

energy

Road

to

absorb

or

isolatebody

to

ride

from road bumps

and

dissipate

it

Isolation

road shock from theundisturbedИwhile

passenger

traveling

overwithout

causing

compartment

rough roads

undue oscillation

in the vehicle

The degree to whichKeep

the

tires

inMinimize

the

Road

a

car

maintainscontact

with

thetransfer

of

contact with the roadground,

because

itvehicle

weight

Holding

surface in

variousis

the

frictionfrom side to side

types of

directionalbetween

the

tiresand

front

to

148

changes and in

aand the road

thatback,

as

this

straight

lineaffects

a vehicle'stransfer

of

(Example:

Theability

to

steer,weight

reduces

weight of a car willbrake

andthe tire's grip on

С

shift

from the rearaccelerate

the road

tires to the front tires

during

braking.

Because the nose of

the car dips

toward

the road, this type of

motion is known as

"dive." The opposite

effect

-- "squat"

--

occurs

during

acceleration,

which

shifts

the weight

of

иthe car from the

front

tires

to

the

back)

Minimize body roll,

which

occurs

as

centrifugal

forceTransfer

the

pushes

outward

onweight of the car

The

ability

of

Д

aa car's

center

ofduring

cornering

CorneringбАvehicle to travel agravity whilefrom the high

curved path

cornering,

raisingside

of

the

one side of thevehicle to the

vehicle

andlow side

lowering

И

the

opposite side

A car's suspension, with its various components, provides all of the solutions described.

The suspension of a car is actually part of the chassis, which comprises all of the important systems located beneath the car's body.

These systems include:

The frame - structural, load-carrying component that supports the car's engine and body, which are in turn supported by the suspension

The suspension system - setup that supports weight, absorbs and dampens shock and helps maintain tire contact

The steering system - mechanism that enables the driver to guide and direct the vehicle

149

	The tires and wheels - components that make vehicle motion possible
	by way of grip and/or friction with the road
	So the suspension is just one of the major systems in any vehicle.
	With this big-picture overview in mind, it's time to look at the three
	fundamental components of any suspension: springs, dampers and anti-sway
	bars.
С		SPRINGS

	Today's springing systems are based on one of four basic designs:
	Coil springs - This is the most common type of spring and is, in
	essence, a heavy-duty torsion bar coiled around an axis. Coil springs
	compress and expand to absorb the motion of the wheels.
	Leaf springs - This type of spring consists of several layers of metal
	(called "leaves") bound together to act as a single unit. Leaf springs were first
	used on horse-drawn carriages and were found on most American
	automobiles until 1985. They are still used today on most trucks and heavy-
	иduty vehicles.
	Torsion bars - Torsion bars use the twisting properties of a steel bar to
	provide coil-spring-like performance. This is how they work: One end of a
	bar is anchored to the vehicle frame. The other end is attached to a wishbone,
	which acts like a lever that moves perpendicular to the torsion bar. When the
	wheel hits a bump, vertical motion is transferred to the wishbone and then,
	through the levering action, to the torsion bar. The torsion bar then twists
		Д
	along its axis to provide the spring force. European carmakers used this
	system extensively,бАas did Packard and Chrysler in the United States, through
	the 1950s and 1960s.
	Air springs - Air springs, which consist of a cylindrical chamber of air
	positioned between the wheel and the car's body, use the compressive
		И

qualities of air to absorb wheel vibrations. The concept is actually more than a century old and could be found on horse-drawn buggies. Air springs from this era were made from air-filled, leather diaphragms, much like a bellows; they were replaced with molded-rubber air springs in the 1930s. Based on where springs are located on a car -- i.e., between the wheels and the frame -- engineers often find it convenient to talk about the sprung mass and the unsprung mass.

The sprung mass is the mass of the vehicle supported on the springs, while the unsprung mass is loosely defined as the mass between the road and the suspension springs. The stiffness of the springs affects how the sprung mass responds while the car is being driven. Loosely sprung cars, such as luxury cars (think Lincoln Town Car), can swallow bumps and provide a super-smooth ride; however, such a car is prone to dive and squat during braking and acceleration and tends to experience body sway or roll

150

Материал: 2076

Смотрите также: