( )
Perfect Continuous , , , .
Present Perfect Past Perfect Future Perfect
Continuous Continuous Continuous
I have been writing I had been writing I shall have been writing
the letter for an hour the letter for an hour the letter for an hour
when he came when he comes
() ()
, () ,
Perfect Continuous ,
for (an hour, a month, a long time) (, ,
lately
since (yesterday, five oclock) ( , )
Since then
Since the time when
forby the time
Present Perfect Continuous ,
I have been waiting for a long time for my brother
Past Perfect Continuous ,
I had been working for a long time when my brother came.
, .
Future Perfect Continuous ( )
I shall begin to work at ten oclock in the morning. When you return home at five oclock, I shall have been working for seven hours.
10 . 5 , .
Exercise. ,
1. 2 , .
a) She was painting the poster when the teacher came in the classroom.
b) She has already painted this poster.
c) She had been painting the poster for two hours already when the teacher came in the classroom.
2. .
a) The student draws diagram for a long time.
b) The student was drawing diagram for a long time.
c) The student has been drawing diagram for a long time.
3. , .
a) I will have written for 3 hours when he comes.
b) I will have been writing for 3 hours when he comes.
c) I will write for 3 hours when he comes.
Radar Types
. .
Continuous, surveillance, saturation, simultaneous, weight, dimension, guide, sequence, precision, gauge, echo, acquire.
Words to be learnt
to divide into-
hardware- ,
software-
|
|
|
to develop- ,
damage assessment- ()
mainly- ,
array-
saturation attack-
jamming- ,
sumiltaneous-
data rate-
resolution-
to meet- (.)
to intercept- (, )
precision-
to observe-
speed gauge-
altimeter-
scatterometer-
to emit-
transponder-
Text
Radar systems may be divided into types based on the designed use. Radars configurations include Monopulse radar, Bistatic radar, Doppler radar, Continuous-wave radar, etc. depending on the types of hardware and software used. It is used in aviation (Primary and secondary radar), sea vessels, law enforcement, weather surveillance, ground mapping, geophysical surveys, and biological research. Radar originally was developed to meet the needs of the military services, and it continues to have critical applications for national defense purposes. For instance, radars are used to detect aircraft, missiles, artillery and mortar projectiles, ships, land vehicles, and satellites. In addition, radar controls and guides weapons; allows one class of target to be distinguished from another; aids in the navigation of aircraft and ships; and assists in reconnaissance and damage assessment. Military radar systems can be divided into three main classes based on platform: land-based, shipborne, and airborne. Within these broad classes, there are several other categories based mainly on the operational use of the radar system.
Multi Function Radars
Active array MultiFunction Radars (MFRs) enable modern weapon systems to cope with saturation attacks of very small radar cross-section missiles in a concentrated jamming environment. Such MFRs have to provide a large number of fire-control channels, simultaneous tracking of both hostile and defending missiles and mid-course guidance commands.
Multi Target Tracking Radar
Operational functions of a MultiTarget Tracking Radar (MTTR) include:
long-range search;
search information with high data rate for low-flying aircraft;
search information with high resolution of close in air targets;
automatic position and height information;
simultaneous tracking of a lot of aircraft targets;
target designation facilities for other systems.
Air Traffic Control Radar Sets
Air traffic control radars are used both at civilian and military airports. Airborne radar is designed especially to meet the strict space and weight limitations that are necessary for all airborne equipment. Even so, airborne radar sets develop the same peak power as shipboard and shore-based sets. In fighter aircraft, the primary mission of radar is to aid in the search, interception, and destruction of enemy aircraft.
Air-Defense Radar
Air-Defense Radars can detect air targets and determine their position, course, and speed in a relatively large area. The maximum range of Air-Defense Radar can exceed 300 miles, and the bearing coverage is a complete 360-degree circle. Air-Defense Radars are usually divided into two categories, based on the amount of position information supplied. Radar sets that provide only range and bearing information are referred to as two-dimensional, or 2D, radars. Radar sets that supply range, bearing, and height are called three-dimensional, or 3D, radars. Air-Defense Radars are used as early-warning devices because they can detect approaching enemy aircraft or missiles at great distances. Another function of the Air-Defense Radar is guiding combat air patrol (CAP) aircraft to a position suitable to intercept an enemy aircraft.
|
|
|
Air Surveillance Radar Sets
This radar equipment is used for the identification of aircrafts, determination of aircrafts approach sequence and for individual aircraft approach controls by Air Traffic Security operators. This radar network could be used under all weather conditions.
Precision Approach Radar Sets
The precision approach radar guide aircraft to safe landing under conditions approaching zero visibility. By means of radar, aircraft are detected and observed
during the final approach and landing sequence. Guidance information is supplied to the pilot in the form of verbal radio instructions, or to the automatic pilot (autopilot) in the form of pulsed control signals.
Weather Radar Sets
The weather data it finds could be used both for approach support and for feeding into the wider weather data concentration systems.Radar in recent years has become an important tool for the measurement of precipitation and the detection of hazardous weather conditions.
Missile Guidance Radar
A radar system that provides information used to guide a missile to a hostile target is called Guidance Radar.
Navigation Radar
Navigation radars are designed for ship navigation and surface surveillance. When weather conditions render visual piloting impossible on a vessel, radar navigation provides a method of fixing a vessels position with sufficient accuracy to allow safe passage.
Imaging Radar / Non-Imaging Radar
An Imaging Radar forms a picture of the observed object or area. Imaging radars have been used to map the Earth, other planets, asteroids, other celestial objects and to categorize targets for military systems. Typically implementations of a Non-Imaging Radar system are speed gauges and radar altimeters. These are also called scatterometers since they measure the scattering properties of the object or region being observed.
Primary Radar
A Primary Radar transmits high-frequency signals which are reflected at targets. The arisen echoes are received and evaluated. This means, unlike secondary radar sets a primary radar unit receive its own emitted signals as an echo again.
Secondary Radar
At these radar sets the airplane must have a transponder (transmitting responder) on board and this transponder responds to interrogation by transmitting a coded reply signal. This response can contain much more information, than a primary
radar unit is able to acquire (E.g. an altitude, an identification code or also any technical problems on board such as a radio contact loss...).
Pulse Radars
Pulse radar sets transmit a high-frequency impulse signal of high power. After this impulse signal, a longer break follows in which the echoes can be received, before a new transmitted signal is sent out. Direction, distance and sometimes if necessary the height or altitude of the target can be determined from the measured antenna position and propagation time of the pulse-signal.
Continuous- Wave Radar
CW radar sets transmit a high-frequency signal continuously. The echo signal is received and processed. The receiver needs not to be mounted at the same place as the transmitter.
Unmodulated CW- Radar
The transmitted signal of these equipments is constant in amplitude and frequency. This equipment is specialized in speed measurings. Distances cannot be measured.
Modulated CW-Radar
The transmitted signal is constant in amplitude but modulated in frequency. It is an advantage of this equipment that an evaluation is carried out without reception break and the measurement result is therefore continuously available. These radar sets are used when the measuring distance isnt too large and its necessary a continuous measuring.
|
|
|
. (. ), , .
Unit 10.
Grammar Revision
