بطاقات جديدة ومتنوعة
Wednesday, 16 October 2013
Friday, 11 October 2013
Understanding The Moon Phases
The illustration may look a little complex
at first, but it's easy to explain.
Sunlight is shown coming in from the
right. The earth, of course, is at the center of the diagram. The moon is shown
at 8 key stages during its revolution around the earth. The moon phase name is
shown alongside the image. The dotted line from the earth to the moon
represents your line of sight when looking at the moon. The large moon
image shows what you would see at that point in the cycle. For the waning
gibbous, third quarter, and waning crescent phases you have to mentally turn
yourself upside down when imagining the line of sight. When you do this,
you'll "see" that the illuminated portion is on your left, just as
you see in the large image.
One important thing to notice is that
exactly one half of the moon is always illuminated by the sun. Of
course that is perfectly logical, but you need to visualize it in order to
understand the phases. At certain times we see both the sunlit
portion and the shadowed portion -- and that creates the various moon phase
shapes we are all familiar with. Also note that the shadowed part of the moon
is invisible to the naked eye; in the diagram above, it is only shown for
clarification purposes.
So the basic explanation is that the lunar
phases are created by changing angles (relative positions) of the earth, the
moon and the sun, as the moon orbits the earth. If you'd like to examine the
phases of the moon more closely, via computer software, you may be interested
in this moon phases
calendar software.
Moon Phases Simplified:
It's probably easiest to understand the
moon cycle in this order: new moon and full moon, first quarter and third
quarter, and the phases in between. As shown in the above diagram, the new
moon occurs when the moon is positioned between the earth and
sun. The three objects are in approximate alignment (why
"approximate" is explained below). The entire illuminated portion of
the moon is on the back side of the moon, the half that we cannot see. At a full
moon, the earth, moon, and sun are in approximate alignment, just as the new
moon, but the moon is on the opposite side of the earth, so the entire sunlit
part of the moon is facing us. The shadowed portion is entirely hidden from
view. The first quarter and third quarter moons (both often
called a "half moon"), happen when the moon is at a 90 degree angle
with respect to the earth and sun. So we are seeing exactly half of the moon
illuminated and half in shadow.
Once you understand those four key moon
phases, the phases between should be fairly easy to visualize, as the
illuminated portion gradually transitions between them.
An easy way to remember and understand
those "between" lunar phase names is by breaking out and defining 4
words: crescent, gibbous, waxing, and waning. The word crescent refers
to the phases where the moon is less than half illuminated. The word gibbous refers
to phases where the moon is more than half illuminated. Waxing essentially
means "growing" or expanding in illumination, and waning means
"shrinking" or decreasing in illumination.
Thus you can simply combine the two words
to create the phase name, as follows:
After the new moon, the sunlit portion is
increasing, but less than half, so it is waxing crescent. After the first
quarter, the sunlit portion is still increasing, but now it is more than
half, so it iswaxing gibbous. After the full moon (maximum illumination), the
light continually decreases. So the waning gibbous phase occurs next.
Following the third quarter is the waning crescent, which wanes until the
light is completely gone -- a new moon.
Thursday, 10 October 2013
Google Company.
If you don't know what the term Google
means, there's a leading Internet search engine you can use to find
out. Taking its name from "googol" -- the mathematical term for
the value represented by a one followed by 100 zeros -- Google offers targeted
search results from billions of Web pages. Results are based on
a proprietary algorithm; its technology for ranking Web pages is called
PageRank. The firm generates revenue through ad sales. Advertisers
deliver relevant ads targeted to search queries or Web content. The Google
Network is a network of third-party customers that use Google's ad
programs to deliver relevant ads to their own sites. Founders Sergey Brin and Larry
Page each have nearly 30% voting control.
Internet
The Internet is a global
system of interconnected computer
networks that use the standard Internet protocol suite (TCP/IP) to serve several billion
users worldwide. It is a network of networks that consists of
millions of private, public, academic, business, and government networks, of
local to global scope, that are linked by a broad array of electronic, wireless
and optical networking technologies. The Internet carries an extensive range of
information resources and services, such as the inter-linked hypertext documents
of the World Wide Web (WWW), the infrastructure to support email, and peer-to-peer networks.
Most
traditional communications media including telephone, music, film, and
television are being reshaped or redefined by the Internet, giving birth to new
services such as voice over Internet Protocol (VoIP)
and Internet Protocol television (IPTV).
Newspaper, book and other print publishing are adapting to website technology,
or are reshaped into blogging and web feeds.
The Internet has enabled and accelerated new forms of human interactions
through instant messaging, Internet forums, and social networking. Online
shopping has boomed both for major retail outlets and small artisans and
traders. Business-to-business and financial services on the Internet
affect supply chains across entire industries.
Soil Pollution
Definition:
Soil pollution is defined as the build-up in soils of persistent toxic compounds, chemicals, salts,
radioactive materials, or disease causing agents, which have adverse effects on plant growth and animal
health.
Click link to more read.
Mosquitoes.
There are over 2500 different species of mosquitoes throughout the
world of which 150 species occur in the United States. 52 species occur in
California, and 19 species occur in Alameda County. In the course of the
District's operation about 10 species are commonly found in the County. Eight
of the species account for over 99% of complaints from the public.
Each of the species has a scientific name that is latin, such as Culex
tarsalis. These names are used in a descriptive manner so that the
name tells something about this particular mosquito. Some species have what is
called "common names" as well as scientific names, such as Anopheles
freeborni, the "Western malaria mosquito".
All mosquitoes must have water in which to complete their life
cycle. This water can range in quality from melted snow water to sewage
effluent and it can be in any container imaginable. The type of water in which
the mosquito larvae is found can be an aid to the identification of which
species it may be. Also, the adult mosquitoes show a very distinct preference
for the types of sources in which to lay their eggs. They lay their eggs in
such places such as tree holes that periodically hold water, tide water pools
in salt marshes, sewage effluent ponds, irrigated pastures, rain water ponds,
etc. Each species therefore has unique environmental requirements for the
maintenance of its life cycle.
The feeding habits of mosquitoes are quite unique in that it is
only the adult females that bite man and other animals. The male mosquitoes
feed only on plant juices. Some female mosquitoes prefer to feed on only one
type of animal or they can feed on a variety of animals. Female mosquitoes feed
on man, domesticated animals, such as cattle, horses, goats, etc; all types of
birds including chickens; all types of wild animals including deer, rabbits;
and they also feed on snakes, lizards, frogs, and toads.
Most female mosquitoes have to feed on an animal and get a
sufficient blood meal before she can develop eggs. If they do not get this
blood meal, then they will die without laying viable eggs. However, some
species of mosquitoes have developed the means to lay viable eggs without
getting a blood meal.
The flight habits of mosquitoes depend again on the species with
which we are dealing. Most domestic species remain fairly close to their point
of origin while some species known for their migration habits are often an
annoyance far from their breeding place. The flight range for females is
usually longer than that of males. Many times wind is a factor in the dispersal
or migration of mosquitoes. Most mosquitoes stay within a mile or two of their
source. However, some have been recorded as far as 75 miles from their breeding
source.
The length of life of the adult
mosquito usually depends on several factors: temperature, humidity, sex of the
mosquito and time of year. Most males live a very short time, about a week; and
females live about a month depending on the above factors.
Electricity from Natural Gas
Natural gas is a fossil fuel formed when layers of buried plants and animals are exposed to intense heat and pressure over thousands of years. The energy that the plants and animals originally obtained from the sun is stored in the form of carbon in natural gas. Natural gas is combusted to generate electricity, enabling this stored energy to be transformed into usable power. Natural gas is a nonrenewable resource because it cannot be replenished on a human time frame.
The natural gas power production process begins with the extraction of natural gas, continues with its treatment and transport to the power plants, and ends with its combustion in boilers and turbines to generate electricity.
Initially, wells are drilled into the ground to remove the natural gas. After the natural gas is extracted, it is treated at gas plants to remove impurities such as hydrogen sulfide, helium, carbon dioxide, hydrocarbons, and moisture. Pipelines then transport the natural gas from the gas plants to power plants.
Power plants use several methods to convert gas to electricity. One method is to burn the gas in a boiler to produce steam, which is then used by a steam turbine to generate electricity. A more common approach is to burn the gas in a combustion turbine to generate electricity.
Power plants use several methods to convert gas to electricity. One method is to burn the gas in a boiler to produce steam, which is then used by a steam turbine to generate electricity. A more common approach is to burn the gas in a combustion turbine to generate electricity.
Another technology, that is growing in popularity is to burn the natural gas in a combustion turbine and use the hot combustion turbine exhaust to make steam to drive a steam turbine. This technology is called "combined cycle" and achieves a higher efficiency by using the same fuel source twice.
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